[apple/xnu.git] / bsd / dev / dtrace / dtrace.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Portions Copyright (c) 2013, 2016, Joyent, Inc. All rights reserved.
 * Portions Copyright (c) 2013 by Delphix. All rights reserved.
 */

/*
 * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*
 * DTrace - Dynamic Tracing for Solaris
 *
 * This is the implementation of the Solaris Dynamic Tracing framework
 * (DTrace).  The user-visible interface to DTrace is described at length in
 * the "Solaris Dynamic Tracing Guide".  The interfaces between the libdtrace
 * library, the in-kernel DTrace framework, and the DTrace providers are
 * described in the block comments in the <sys/dtrace.h> header file.  The
 * internal architecture of DTrace is described in the block comments in the
 * <sys/dtrace_impl.h> header file.  The comments contained within the DTrace
 * implementation very much assume mastery of all of these sources; if one has
 * an unanswered question about the implementation, one should consult them
 * first.
 *
 * The functions here are ordered roughly as follows:
 *
 *   - Probe context functions
 *   - Probe hashing functions
 *   - Non-probe context utility functions
 *   - Matching functions
 *   - Provider-to-Framework API functions
 *   - Probe management functions
 *   - DIF object functions
 *   - Format functions
 *   - Predicate functions
 *   - ECB functions
 *   - Buffer functions
 *   - Enabling functions
 *   - DOF functions
 *   - Anonymous enabling functions
 *   - Process functions
 *   - Consumer state functions
 *   - Helper functions
 *   - Hook functions
 *   - Driver cookbook functions
 *
 * Each group of functions begins with a block comment labelled the "DTrace
 * [Group] Functions", allowing one to find each block by searching forward
 * on capital-f functions.
 */
#include <sys/errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/conf.h>
#include <sys/random.h>
#include <sys/systm.h>
#include <sys/dtrace_impl.h>
#include <sys/param.h>
#include <sys/proc_internal.h>
#include <sys/ioctl.h>
#include <sys/fcntl.h>
#include <miscfs/devfs/devfs.h>
#include <sys/malloc.h>
#include <sys/kernel_types.h>
#include <sys/proc_internal.h>
#include <sys/uio_internal.h>
#include <sys/kauth.h>
#include <vm/pmap.h>
#include <sys/user.h>
#include <mach/exception_types.h>
#include <sys/signalvar.h>
#include <mach/task.h>
#include <kern/zalloc.h>
#include <kern/ast.h>
#include <kern/sched_prim.h>
#include <kern/task.h>
#include <netinet/in.h>
#include <libkern/sysctl.h>
#include <sys/kdebug.h>

#if MONOTONIC
#include <kern/monotonic.h>
#include <machine/monotonic.h>
#endif /* MONOTONIC */

#include "dtrace_xoroshiro128_plus.h"

#include <IOKit/IOPlatformExpert.h>

#include <kern/cpu_data.h>
extern uint32_t pmap_find_phys(void *, uint64_t);
extern boolean_t pmap_valid_page(uint32_t);
extern void OSKextRegisterKextsWithDTrace(void);
extern kmod_info_t g_kernel_kmod_info;
extern void commpage_update_dof(boolean_t enabled);

/* Solaris proc_t is the struct. Darwin's proc_t is a pointer to it. */
#define proc_t struct proc /* Steer clear of the Darwin typedef for proc_t */

#define t_predcache t_dtrace_predcache /* Cosmetic. Helps readability of thread.h */

extern void dtrace_suspend(void);
extern void dtrace_resume(void);
extern void dtrace_early_init(void);
extern int dtrace_keep_kernel_symbols(void);
extern void dtrace_init(void);
extern void helper_init(void);
extern void fasttrap_init(void);

static int  dtrace_lazy_dofs_duplicate(proc_t *, proc_t *);
extern void dtrace_lazy_dofs_destroy(proc_t *);
extern void dtrace_postinit(void);

extern void dtrace_proc_fork(proc_t*, proc_t*, int);
extern void dtrace_proc_exec(proc_t*);
extern void dtrace_proc_exit(proc_t*);

/*
 * DTrace Tunable Variables
 *
 * The following variables may be dynamically tuned by using sysctl(8), the
 * variables being stored in the kern.dtrace namespace.  For example:
 *      sysctl kern.dtrace.dof_maxsize = 1048575        # 1M
 *
 * In general, the only variables that one should be tuning this way are those
 * that affect system-wide DTrace behavior, and for which the default behavior
 * is undesirable.  Most of these variables are tunable on a per-consumer
 * basis using DTrace options, and need not be tuned on a system-wide basis.
 * When tuning these variables, avoid pathological values; while some attempt
 * is made to verify the integrity of these variables, they are not considered
 * part of the supported interface to DTrace, and they are therefore not
 * checked comprehensively.
 */
uint64_t        dtrace_buffer_memory_maxsize = 0;               /* initialized in dtrace_init */
uint64_t        dtrace_buffer_memory_inuse = 0;
int             dtrace_destructive_disallow = 0;
dtrace_optval_t dtrace_nonroot_maxsize = (16 * 1024 * 1024);
size_t          dtrace_difo_maxsize = (256 * 1024);
dtrace_optval_t dtrace_dof_maxsize = (512 * 1024);
dtrace_optval_t dtrace_statvar_maxsize = (16 * 1024);
dtrace_optval_t dtrace_statvar_maxsize_max = (16 * 10 * 1024);
size_t          dtrace_actions_max = (16 * 1024);
size_t          dtrace_retain_max = 1024;
dtrace_optval_t dtrace_helper_actions_max = 32;
dtrace_optval_t dtrace_helper_providers_max = 64;
dtrace_optval_t dtrace_dstate_defsize = (1 * 1024 * 1024);
size_t          dtrace_strsize_default = 256;
dtrace_optval_t dtrace_strsize_min = 8;
dtrace_optval_t dtrace_strsize_max = 65536;
dtrace_optval_t dtrace_cleanrate_default = 990099000;           /* 1.1 hz */
dtrace_optval_t dtrace_cleanrate_min = 20000000;                        /* 50 hz */
dtrace_optval_t dtrace_cleanrate_max = (uint64_t)60 * NANOSEC;  /* 1/minute */
dtrace_optval_t dtrace_aggrate_default = NANOSEC;               /* 1 hz */
dtrace_optval_t dtrace_statusrate_default = NANOSEC;            /* 1 hz */
dtrace_optval_t dtrace_statusrate_max = (hrtime_t)10 * NANOSEC;  /* 6/minute */
dtrace_optval_t dtrace_switchrate_default = NANOSEC;            /* 1 hz */
dtrace_optval_t dtrace_nspec_default = 1;
dtrace_optval_t dtrace_specsize_default = 32 * 1024;
dtrace_optval_t dtrace_stackframes_default = 20;
dtrace_optval_t dtrace_ustackframes_default = 20;
dtrace_optval_t dtrace_jstackframes_default = 50;
dtrace_optval_t dtrace_jstackstrsize_default = 512;
dtrace_optval_t dtrace_buflimit_default = 75;
dtrace_optval_t dtrace_buflimit_min = 1;
dtrace_optval_t dtrace_buflimit_max = 99;
size_t          dtrace_nprobes_default = 4;
int             dtrace_msgdsize_max = 128;
hrtime_t        dtrace_chill_max = 500 * (NANOSEC / MILLISEC);  /* 500 ms */
hrtime_t        dtrace_chill_interval = NANOSEC;                /* 1000 ms */
int             dtrace_devdepth_max = 32;
int             dtrace_err_verbose;
hrtime_t        dtrace_deadman_interval = NANOSEC;
hrtime_t        dtrace_deadman_timeout = (hrtime_t)10 * NANOSEC;
hrtime_t        dtrace_deadman_user = (hrtime_t)30 * NANOSEC;

/*
 * DTrace External Variables
 *
 * As dtrace(7D) is a kernel module, any DTrace variables are obviously
 * available to DTrace consumers via the backtick (`) syntax.  One of these,
 * dtrace_zero, is made deliberately so:  it is provided as a source of
 * well-known, zero-filled memory.  While this variable is not documented,
 * it is used by some translators as an implementation detail.
 */
const char      dtrace_zero[256] = { 0 };       /* zero-filled memory */
unsigned int    dtrace_max_cpus = 0;            /* number of enabled cpus */
/*
 * DTrace Internal Variables
 */
static dev_info_t       *dtrace_devi;           /* device info */
static vmem_t           *dtrace_arena;          /* probe ID arena */
static dtrace_probe_t   **dtrace_probes;        /* array of all probes */
static int              dtrace_nprobes;         /* number of probes */
static dtrace_provider_t *dtrace_provider;      /* provider list */
static dtrace_meta_t    *dtrace_meta_pid;       /* user-land meta provider */
static int              dtrace_opens;           /* number of opens */
static int              dtrace_helpers;         /* number of helpers */
static dtrace_hash_t    *dtrace_strings;
static dtrace_hash_t    *dtrace_byprov;         /* probes hashed by provider */
static dtrace_hash_t    *dtrace_bymod;          /* probes hashed by module */
static dtrace_hash_t    *dtrace_byfunc;         /* probes hashed by function */
static dtrace_hash_t    *dtrace_byname;         /* probes hashed by name */
static dtrace_toxrange_t *dtrace_toxrange;      /* toxic range array */
static int              dtrace_toxranges;       /* number of toxic ranges */
static int              dtrace_toxranges_max;   /* size of toxic range array */
static dtrace_anon_t    dtrace_anon;            /* anonymous enabling */
static kmem_cache_t     *dtrace_state_cache;    /* cache for dynamic state */
static uint64_t         dtrace_vtime_references; /* number of vtimestamp refs */
static kthread_t        *dtrace_panicked;       /* panicking thread */
static dtrace_ecb_t     *dtrace_ecb_create_cache; /* cached created ECB */
static dtrace_genid_t   dtrace_probegen;        /* current probe generation */
static dtrace_helpers_t *dtrace_deferred_pid;   /* deferred helper list */
static dtrace_enabling_t *dtrace_retained;      /* list of retained enablings */
static dtrace_genid_t   dtrace_retained_gen;    /* current retained enab gen */
static dtrace_dynvar_t  dtrace_dynhash_sink;    /* end of dynamic hash chains */

static int              dtrace_dof_mode;        /* See dtrace_impl.h for a description of Darwin's dof modes. */

                        /*
                         * This does't quite fit as an internal variable, as it must be accessed in
                         * fbt_provide and sdt_provide. Its clearly not a dtrace tunable variable either...
                         */
int                     dtrace_kernel_symbol_mode;      /* See dtrace_impl.h for a description of Darwin's kernel symbol modes. */
static uint32_t         dtrace_wake_clients;
static uint8_t      dtrace_kerneluuid[16];      /* the 128-bit uuid */

/*
 * To save memory, some common memory allocations are given a
 * unique zone. For example, dtrace_probe_t is 72 bytes in size,
 * which means it would fall into the kalloc.128 bucket. With
 * 20k elements allocated, the space saved is substantial.
 */

struct zone *dtrace_probe_t_zone;

static int dtrace_module_unloaded(struct kmod_info *kmod);

/*
 * DTrace Locking
 * DTrace is protected by three (relatively coarse-grained) locks:
 *
 * (1) dtrace_lock is required to manipulate essentially any DTrace state,
 *     including enabling state, probes, ECBs, consumer state, helper state,
 *     etc.  Importantly, dtrace_lock is _not_ required when in probe context;
 *     probe context is lock-free -- synchronization is handled via the
 *     dtrace_sync() cross call mechanism.
 *
 * (2) dtrace_provider_lock is required when manipulating provider state, or
 *     when provider state must be held constant.
 *
 * (3) dtrace_meta_lock is required when manipulating meta provider state, or
 *     when meta provider state must be held constant.
 *
 * The lock ordering between these three locks is dtrace_meta_lock before
 * dtrace_provider_lock before dtrace_lock.  (In particular, there are
 * several places where dtrace_provider_lock is held by the framework as it
 * calls into the providers -- which then call back into the framework,
 * grabbing dtrace_lock.)
 *
 * There are two other locks in the mix:  mod_lock and cpu_lock.  With respect
 * to dtrace_provider_lock and dtrace_lock, cpu_lock continues its historical
 * role as a coarse-grained lock; it is acquired before both of these locks.
 * With respect to dtrace_meta_lock, its behavior is stranger:  cpu_lock must
 * be acquired _between_ dtrace_meta_lock and any other DTrace locks.
 * mod_lock is similar with respect to dtrace_provider_lock in that it must be
 * acquired _between_ dtrace_provider_lock and dtrace_lock.
 */


/*
 * APPLE NOTE:
 *
 * For porting purposes, all kmutex_t vars have been changed
 * to lck_mtx_t, which require explicit initialization.
 *
 * kmutex_t becomes lck_mtx_t
 * mutex_enter() becomes lck_mtx_lock()
 * mutex_exit() becomes lck_mtx_unlock()
 *
 * Lock asserts are changed like this:
 *
 * ASSERT(MUTEX_HELD(&cpu_lock));
 *      becomes:
 * LCK_MTX_ASSERT(&cpu_lock, LCK_MTX_ASSERT_OWNED);
 *
 */
static lck_mtx_t        dtrace_lock;            /* probe state lock */
static lck_mtx_t        dtrace_provider_lock;   /* provider state lock */
static lck_mtx_t        dtrace_meta_lock;       /* meta-provider state lock */
static lck_rw_t         dtrace_dof_mode_lock;   /* dof mode lock */

/*
 * DTrace Provider Variables
 *
 * These are the variables relating to DTrace as a provider (that is, the
 * provider of the BEGIN, END, and ERROR probes).
 */
static dtrace_pattr_t   dtrace_provider_attr = {
{ DTRACE_STABILITY_STABLE, DTRACE_STABILITY_STABLE, DTRACE_CLASS_COMMON },
{ DTRACE_STABILITY_PRIVATE, DTRACE_STABILITY_PRIVATE, DTRACE_CLASS_UNKNOWN },
{ DTRACE_STABILITY_PRIVATE, DTRACE_STABILITY_PRIVATE, DTRACE_CLASS_UNKNOWN },
{ DTRACE_STABILITY_STABLE, DTRACE_STABILITY_STABLE, DTRACE_CLASS_COMMON },
{ DTRACE_STABILITY_STABLE, DTRACE_STABILITY_STABLE, DTRACE_CLASS_COMMON },
};

static void
dtrace_provide_nullop(void *arg, const dtrace_probedesc_t *desc)
{
#pragma unused(arg, desc)
}

static void
dtrace_provide_module_nullop(void *arg, struct modctl *ctl)
{
#pragma unused(arg, ctl)
}

static int
dtrace_enable_nullop(void *arg, dtrace_id_t id, void *parg)
{
#pragma unused(arg, id, parg)
    return (0);
}

static void
dtrace_disable_nullop(void *arg, dtrace_id_t id, void *parg)
{
#pragma unused(arg, id, parg)
}

static void
dtrace_suspend_nullop(void *arg, dtrace_id_t id, void *parg)
{
#pragma unused(arg, id, parg)
}

static void
dtrace_resume_nullop(void *arg, dtrace_id_t id, void *parg)
{
#pragma unused(arg, id, parg)
}

static void
dtrace_destroy_nullop(void *arg, dtrace_id_t id, void *parg)
{
#pragma unused(arg, id, parg)
}


static dtrace_pops_t dtrace_provider_ops = {
        .dtps_provide = dtrace_provide_nullop,
        .dtps_provide_module =  dtrace_provide_module_nullop,
        .dtps_enable =  dtrace_enable_nullop,
        .dtps_disable = dtrace_disable_nullop,
        .dtps_suspend = dtrace_suspend_nullop,
        .dtps_resume =  dtrace_resume_nullop,
        .dtps_getargdesc =      NULL,
        .dtps_getargval =       NULL,
        .dtps_usermode =        NULL,
        .dtps_destroy = dtrace_destroy_nullop,
};

static dtrace_id_t      dtrace_probeid_begin;   /* special BEGIN probe */
static dtrace_id_t      dtrace_probeid_end;     /* special END probe */
dtrace_id_t             dtrace_probeid_error;   /* special ERROR probe */

/*
 * DTrace Helper Tracing Variables
 */
uint32_t dtrace_helptrace_next = 0;
uint32_t dtrace_helptrace_nlocals;
char    *dtrace_helptrace_buffer;
size_t  dtrace_helptrace_bufsize = 512 * 1024;

#if DEBUG
int     dtrace_helptrace_enabled = 1;
#else
int     dtrace_helptrace_enabled = 0;
#endif

#if defined (__arm64__)
/*
 * The ioctl for adding helper DOF is based on the
 * size of a user_addr_t.  We need to recognize both
 * U32 and U64 as the same action.
 */
#define DTRACEHIOC_ADDDOF_U32       _IOW('h', 4, user32_addr_t)                                                             
#define DTRACEHIOC_ADDDOF_U64       _IOW('h', 4, user64_addr_t)
#endif  /* __arm64__ */

/*
 * DTrace Error Hashing
 *
 * On DEBUG kernels, DTrace will track the errors that has seen in a hash
 * table.  This is very useful for checking coverage of tests that are
 * expected to induce DIF or DOF processing errors, and may be useful for
 * debugging problems in the DIF code generator or in DOF generation .  The
 * error hash may be examined with the ::dtrace_errhash MDB dcmd.
 */
#if DEBUG
static dtrace_errhash_t dtrace_errhash[DTRACE_ERRHASHSZ];
static const char *dtrace_errlast;
static kthread_t *dtrace_errthread;
static lck_mtx_t dtrace_errlock;
#endif

/*
 * DTrace Macros and Constants
 *
 * These are various macros that are useful in various spots in the
 * implementation, along with a few random constants that have no meaning
 * outside of the implementation.  There is no real structure to this cpp
 * mishmash -- but is there ever?
 */

#define DTRACE_GETSTR(hash, elm)        \
        (hash->dth_getstr(elm, hash->dth_stroffs))

#define DTRACE_HASHSTR(hash, elm)       \
        dtrace_hash_str(DTRACE_GETSTR(hash, elm))

#define DTRACE_HASHNEXT(hash, elm)      \
        (void**)((uintptr_t)(elm) + (hash)->dth_nextoffs)

#define DTRACE_HASHPREV(hash, elm)      \
        (void**)((uintptr_t)(elm) + (hash)->dth_prevoffs)

#define DTRACE_HASHEQ(hash, lhs, rhs)   \
        (strcmp(DTRACE_GETSTR(hash, lhs), \
            DTRACE_GETSTR(hash, rhs)) == 0)

#define DTRACE_AGGHASHSIZE_SLEW         17

#define DTRACE_V4MAPPED_OFFSET          (sizeof (uint32_t) * 3)

/*
 * The key for a thread-local variable consists of the lower 61 bits of the
 * current_thread(), plus the 3 bits of the highest active interrupt above LOCK_LEVEL.
 * We add DIF_VARIABLE_MAX to t_did to assure that the thread key is never
 * equal to a variable identifier.  This is necessary (but not sufficient) to
 * assure that global associative arrays never collide with thread-local
 * variables.  To guarantee that they cannot collide, we must also define the
 * order for keying dynamic variables.  That order is:
 *
 *   [ key0 ] ... [ keyn ] [ variable-key ] [ tls-key ]
 *
 * Because the variable-key and the tls-key are in orthogonal spaces, there is
 * no way for a global variable key signature to match a thread-local key
 * signature.
 */
#if defined (__x86_64__)
/* FIXME: two function calls!! */
#define DTRACE_TLS_THRKEY(where) { \
        uint_t intr = ml_at_interrupt_context(); /* Note: just one measly bit */ \
        uint64_t thr = (uintptr_t)current_thread(); \
        ASSERT(intr < (1 << 3)); \
        (where) = ((thr + DIF_VARIABLE_MAX) & \
            (((uint64_t)1 << 61) - 1)) | ((uint64_t)intr << 61); \
}
#elif defined(__arm__)
/* FIXME: three function calls!!! */
#define DTRACE_TLS_THRKEY(where) { \
        uint_t intr = ml_at_interrupt_context(); /* Note: just one measly bit */ \
        uint64_t thr = (uintptr_t)current_thread(); \
        uint_t pid = (uint_t)dtrace_proc_selfpid(); \
        ASSERT(intr < (1 << 3)); \
        (where) = (((thr << 32 | pid) + DIF_VARIABLE_MAX) & \
            (((uint64_t)1 << 61) - 1)) | ((uint64_t)intr << 61); \
}
#elif defined (__arm64__)
/* FIXME: two function calls!! */
#define DTRACE_TLS_THRKEY(where) { \
        uint_t intr = ml_at_interrupt_context(); /* Note: just one measly bit */ \
        uint64_t thr = (uintptr_t)current_thread(); \
        ASSERT(intr < (1 << 3)); \
        (where) = ((thr + DIF_VARIABLE_MAX) & \
            (((uint64_t)1 << 61) - 1)) | ((uint64_t)intr << 61); \
}
#else
#error Unknown architecture
#endif

#define DT_BSWAP_8(x)   ((x) & 0xff)
#define DT_BSWAP_16(x)  ((DT_BSWAP_8(x) << 8) | DT_BSWAP_8((x) >> 8))
#define DT_BSWAP_32(x)  ((DT_BSWAP_16(x) << 16) | DT_BSWAP_16((x) >> 16))
#define DT_BSWAP_64(x)  ((DT_BSWAP_32(x) << 32) | DT_BSWAP_32((x) >> 32))

#define DT_MASK_LO 0x00000000FFFFFFFFULL

#define DTRACE_STORE(type, tomax, offset, what) \
        *((type *)((uintptr_t)(tomax) + (uintptr_t)offset)) = (type)(what);


#define DTRACE_ALIGNCHECK(addr, size, flags)                            \
        if (addr & (MIN(size,4) - 1)) {                                 \
                *flags |= CPU_DTRACE_BADALIGN;                          \
                cpu_core[CPU->cpu_id].cpuc_dtrace_illval = addr;        \
                return (0);                                             \
        }

#define DTRACE_RANGE_REMAIN(remp, addr, baseaddr, basesz)               \
do {                                                                    \
        if ((remp) != NULL) {                                           \
                *(remp) = (uintptr_t)(baseaddr) + (basesz) - (addr);    \
        }                                                               \
} while (0)


/*
 * Test whether a range of memory starting at testaddr of size testsz falls
 * within the range of memory described by addr, sz.  We take care to avoid
 * problems with overflow and underflow of the unsigned quantities, and
 * disallow all negative sizes.  Ranges of size 0 are allowed.
 */
#define DTRACE_INRANGE(testaddr, testsz, baseaddr, basesz) \
        ((testaddr) - (baseaddr) < (basesz) && \
        (testaddr) + (testsz) - (baseaddr) <= (basesz) && \
        (testaddr) + (testsz) >= (testaddr))

/*
 * Test whether alloc_sz bytes will fit in the scratch region.  We isolate
 * alloc_sz on the righthand side of the comparison in order to avoid overflow
 * or underflow in the comparison with it.  This is simpler than the INRANGE
 * check above, because we know that the dtms_scratch_ptr is valid in the
 * range.  Allocations of size zero are allowed.
 */
#define DTRACE_INSCRATCH(mstate, alloc_sz) \
        ((mstate)->dtms_scratch_base + (mstate)->dtms_scratch_size - \
        (mstate)->dtms_scratch_ptr >= (alloc_sz))

#define RECOVER_LABEL(bits) dtraceLoadRecover##bits:

#if defined (__x86_64__) || (defined (__arm__) || defined (__arm64__))
#define DTRACE_LOADFUNC(bits)                                           \
/*CSTYLED*/                                                             \
uint##bits##_t dtrace_load##bits(uintptr_t addr);                       \
                                                                        \
uint##bits##_t                                                          \
dtrace_load##bits(uintptr_t addr)                                       \
{                                                                       \
        size_t size = bits / NBBY;                                      \
        /*CSTYLED*/                                                     \
        uint##bits##_t rval = 0;                                        \
        int i;                                                          \
        volatile uint16_t *flags = (volatile uint16_t *)                \
            &cpu_core[CPU->cpu_id].cpuc_dtrace_flags;                   \
                                                                        \
        DTRACE_ALIGNCHECK(addr, size, flags);                           \
                                                                        \
        for (i = 0; i < dtrace_toxranges; i++) {                        \
                if (addr >= dtrace_toxrange[i].dtt_limit)               \
                        continue;                                       \
                                                                        \
                if (addr + size <= dtrace_toxrange[i].dtt_base)         \
                        continue;                                       \
                                                                        \
                /*                                                      \
                 * This address falls within a toxic region; return 0.  \
                 */                                                     \
                *flags |= CPU_DTRACE_BADADDR;                           \
                cpu_core[CPU->cpu_id].cpuc_dtrace_illval = addr;        \
                return (0);                                             \
        }                                                               \
                                                                        \
        {                                                               \
        volatile vm_offset_t recover = (vm_offset_t)&&dtraceLoadRecover##bits;          \
        *flags |= CPU_DTRACE_NOFAULT;                                   \
        recover = dtrace_sign_and_set_thread_recover(current_thread(), recover);        \
        /*CSTYLED*/                                                     \
        /*                                                              \
        * PR6394061 - avoid device memory that is unpredictably         \
        * mapped and unmapped                                           \
        */                                                              \
        if (pmap_valid_page(pmap_find_phys(kernel_pmap, addr)))         \
            rval = *((volatile uint##bits##_t *)addr);                  \
        else {                                                          \
                *flags |= CPU_DTRACE_BADADDR;                           \
                cpu_core[CPU->cpu_id].cpuc_dtrace_illval = addr;        \
                return (0);                                             \
        }                                                               \
                                                                        \
        RECOVER_LABEL(bits);                                            \
        (void)dtrace_set_thread_recover(current_thread(), recover);     \
        *flags &= ~CPU_DTRACE_NOFAULT;                                  \
        }                                                               \
                                                                        \
        return (rval);                                                  \
}
#else /* all other architectures */
#error Unknown Architecture
#endif

#ifdef __LP64__
#define dtrace_loadptr  dtrace_load64
#else
#define dtrace_loadptr  dtrace_load32
#endif

#define DTRACE_DYNHASH_FREE     0
#define DTRACE_DYNHASH_SINK     1
#define DTRACE_DYNHASH_VALID    2

#define DTRACE_MATCH_FAIL       -1
#define DTRACE_MATCH_NEXT       0
#define DTRACE_MATCH_DONE       1
#define DTRACE_ANCHORED(probe)  ((probe)->dtpr_func[0] != '\0')
#define DTRACE_STATE_ALIGN      64

#define DTRACE_FLAGS2FLT(flags)                                         \
        (((flags) & CPU_DTRACE_BADADDR) ? DTRACEFLT_BADADDR :           \
        ((flags) & CPU_DTRACE_ILLOP) ? DTRACEFLT_ILLOP :                \
        ((flags) & CPU_DTRACE_DIVZERO) ? DTRACEFLT_DIVZERO :            \
        ((flags) & CPU_DTRACE_KPRIV) ? DTRACEFLT_KPRIV :                \
        ((flags) & CPU_DTRACE_UPRIV) ? DTRACEFLT_UPRIV :                \
        ((flags) & CPU_DTRACE_TUPOFLOW) ?  DTRACEFLT_TUPOFLOW :         \
        ((flags) & CPU_DTRACE_BADALIGN) ?  DTRACEFLT_BADALIGN :         \
        ((flags) & CPU_DTRACE_NOSCRATCH) ?  DTRACEFLT_NOSCRATCH :       \
        ((flags) & CPU_DTRACE_BADSTACK) ?  DTRACEFLT_BADSTACK :         \
        DTRACEFLT_UNKNOWN)

#define DTRACEACT_ISSTRING(act)                                         \
        ((act)->dta_kind == DTRACEACT_DIFEXPR &&                        \
        (act)->dta_difo->dtdo_rtype.dtdt_kind == DIF_TYPE_STRING)


static size_t dtrace_strlen(const char *, size_t);
static dtrace_probe_t *dtrace_probe_lookup_id(dtrace_id_t id);
static void dtrace_enabling_provide(dtrace_provider_t *);
static int dtrace_enabling_match(dtrace_enabling_t *, int *, dtrace_match_cond_t *cond);
static void dtrace_enabling_matchall_with_cond(dtrace_match_cond_t *cond);
static void dtrace_enabling_matchall(void);
static dtrace_state_t *dtrace_anon_grab(void);
static uint64_t dtrace_helper(int, dtrace_mstate_t *,
    dtrace_state_t *, uint64_t, uint64_t);
static dtrace_helpers_t *dtrace_helpers_create(proc_t *);
static void dtrace_buffer_drop(dtrace_buffer_t *);
static intptr_t dtrace_buffer_reserve(dtrace_buffer_t *, size_t, size_t,
    dtrace_state_t *, dtrace_mstate_t *);
static int dtrace_state_option(dtrace_state_t *, dtrace_optid_t,
    dtrace_optval_t);
static int dtrace_ecb_create_enable(dtrace_probe_t *, void *, void *);
static void dtrace_helper_provider_destroy(dtrace_helper_provider_t *);
static int dtrace_canload_remains(uint64_t, size_t, size_t *,
        dtrace_mstate_t *, dtrace_vstate_t *);
static int dtrace_canstore_remains(uint64_t, size_t, size_t *,
        dtrace_mstate_t *, dtrace_vstate_t *);


/*
 * DTrace sysctl handlers
 *
 * These declarations and functions are used for a deeper DTrace configuration.
 * Most of them are not per-consumer basis and may impact the other DTrace
 * consumers.  Correctness may not be supported for all the variables, so you
 * should be careful about what values you are using.
 */

SYSCTL_DECL(_kern_dtrace);
SYSCTL_NODE(_kern, OID_AUTO, dtrace, CTLFLAG_RW | CTLFLAG_LOCKED, 0, "dtrace"); 

static int
sysctl_dtrace_err_verbose SYSCTL_HANDLER_ARGS
{
#pragma unused(oidp, arg2)
        int changed, error;
        int value = *(int *) arg1;

        error = sysctl_io_number(req, value, sizeof(value), &value, &changed);
        if (error || !changed)
                return (error);

        if (value != 0 && value != 1)
                return (ERANGE);

        lck_mtx_lock(&dtrace_lock);
                dtrace_err_verbose = value;
        lck_mtx_unlock(&dtrace_lock);

        return (0);
}

/*
 * kern.dtrace.err_verbose
 *
 * Set DTrace verbosity when an error occured (0 = disabled, 1 = enabld).
 * Errors are reported when a DIFO or a DOF has been rejected by the kernel.
 */
SYSCTL_PROC(_kern_dtrace, OID_AUTO, err_verbose,
        CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_LOCKED,
        &dtrace_err_verbose, 0,
        sysctl_dtrace_err_verbose, "I", "dtrace error verbose");

static int
sysctl_dtrace_buffer_memory_maxsize SYSCTL_HANDLER_ARGS
{
#pragma unused(oidp, arg2, req)
        int changed, error;
        uint64_t value = *(uint64_t *) arg1;

        error = sysctl_io_number(req, value, sizeof(value), &value, &changed);
        if (error || !changed)
                return (error);

        if (value <= dtrace_buffer_memory_inuse)
                return (ERANGE);

        lck_mtx_lock(&dtrace_lock);
                dtrace_buffer_memory_maxsize = value;   
        lck_mtx_unlock(&dtrace_lock);

        return (0);
}

/*
 * kern.dtrace.buffer_memory_maxsize
 *
 * Set DTrace maximal size in bytes used by all the consumers' state buffers.  By default
 * the limit is PHYS_MEM / 3 for *all* consumers.  Attempting to set a null, a negative value
 * or a value <= to dtrace_buffer_memory_inuse will result in a failure.
 */
SYSCTL_PROC(_kern_dtrace, OID_AUTO, buffer_memory_maxsize,
        CTLTYPE_QUAD | CTLFLAG_RW | CTLFLAG_LOCKED,
        &dtrace_buffer_memory_maxsize, 0,
        sysctl_dtrace_buffer_memory_maxsize, "Q", "dtrace state buffer memory maxsize");

/*
 * kern.dtrace.buffer_memory_inuse
 *
 * Current state buffer memory used, in bytes, by all the DTrace consumers.
 * This value is read-only.
 */
SYSCTL_QUAD(_kern_dtrace, OID_AUTO, buffer_memory_inuse, CTLFLAG_RD | CTLFLAG_LOCKED,
        &dtrace_buffer_memory_inuse, "dtrace state buffer memory in-use");

static int
sysctl_dtrace_difo_maxsize SYSCTL_HANDLER_ARGS
{
#pragma unused(oidp, arg2, req)
        int changed, error;
        size_t value = *(size_t*) arg1;

        error = sysctl_io_number(req, value, sizeof(value), &value, &changed);
        if (error || !changed)
                return (error);

        if (value <= 0)
                return (ERANGE);

        lck_mtx_lock(&dtrace_lock);
                dtrace_difo_maxsize = value;
        lck_mtx_unlock(&dtrace_lock);

        return (0);
}

/*
 * kern.dtrace.difo_maxsize
 *
 * Set the DIFO max size in bytes, check the definition of dtrace_difo_maxsize
 * to get the default value.  Attempting to set a null or negative size will
 * result in a failure.
 */
SYSCTL_PROC(_kern_dtrace, OID_AUTO, difo_maxsize,
        CTLTYPE_QUAD | CTLFLAG_RW | CTLFLAG_LOCKED,
        &dtrace_difo_maxsize, 0,
        sysctl_dtrace_difo_maxsize, "Q", "dtrace difo maxsize");

static int
sysctl_dtrace_dof_maxsize SYSCTL_HANDLER_ARGS
{
#pragma unused(oidp, arg2, req)
        int changed, error;
        dtrace_optval_t value = *(dtrace_optval_t *) arg1;

        error = sysctl_io_number(req, value, sizeof(value), &value, &changed);
        if (error || !changed)
                return (error);

        if (value <= 0)
                return (ERANGE);

        if (value >= dtrace_copy_maxsize())
                return (ERANGE);

        lck_mtx_lock(&dtrace_lock);
                dtrace_dof_maxsize = value;
        lck_mtx_unlock(&dtrace_lock);

        return (0);
}

/*
 * kern.dtrace.dof_maxsize
 *
 * Set the DOF max size in bytes, check the definition of dtrace_dof_maxsize to
 * get the default value.  Attempting to set a null or negative size will result
 * in a failure.
 */
SYSCTL_PROC(_kern_dtrace, OID_AUTO, dof_maxsize,
        CTLTYPE_QUAD | CTLFLAG_RW | CTLFLAG_LOCKED,
        &dtrace_dof_maxsize, 0,
        sysctl_dtrace_dof_maxsize, "Q", "dtrace dof maxsize");

static int
sysctl_dtrace_statvar_maxsize SYSCTL_HANDLER_ARGS
{
#pragma unused(oidp, arg2, req)
        int changed, error;
        dtrace_optval_t value = *(dtrace_optval_t*) arg1;

        error = sysctl_io_number(req, value, sizeof(value), &value, &changed);
        if (error || !changed)
                return (error);

        if (value <= 0)
                return (ERANGE);
        if (value > dtrace_statvar_maxsize_max)
                return (ERANGE);

        lck_mtx_lock(&dtrace_lock);
                dtrace_statvar_maxsize = value;
        lck_mtx_unlock(&dtrace_lock);

        return (0);
}

/*
 * kern.dtrace.global_maxsize
 *
 * Set the variable max size in bytes, check the definition of
 * dtrace_statvar_maxsize to get the default value.  Attempting to set a null,
 * too high or negative size will result in a failure.
 */
SYSCTL_PROC(_kern_dtrace, OID_AUTO, global_maxsize,
        CTLTYPE_QUAD | CTLFLAG_RW | CTLFLAG_LOCKED,
        &dtrace_statvar_maxsize, 0,
        sysctl_dtrace_statvar_maxsize, "Q", "dtrace statvar maxsize");


/*
 * kern.dtrace.provide_private_probes
 *
 * Set whether the providers must provide the private probes.  This is
 * kept as compatibility as they are always provided.
 */
SYSCTL_INT(_kern_dtrace, OID_AUTO, provide_private_probes,
        CTLFLAG_RD | CTLFLAG_LOCKED,
        (int *)NULL, 1, "provider must provide the private probes");

/*
 * kern.dtrace.dof_mode
 *
 * Returns the current DOF mode.
 * This value is read-only.
 */
SYSCTL_INT(_kern_dtrace, OID_AUTO, dof_mode, CTLFLAG_RD | CTLFLAG_LOCKED,
        &dtrace_dof_mode, 0, "dtrace dof mode");

/*
 * DTrace Probe Context Functions
 *
 * These functions are called from probe context.  Because probe context is
 * any context in which C may be called, arbitrarily locks may be held,
 * interrupts may be disabled, we may be in arbitrary dispatched state, etc.
 * As a result, functions called from probe context may only call other DTrace
 * support functions -- they may not interact at all with the system at large.
 * (Note that the ASSERT macro is made probe-context safe by redefining it in
 * terms of dtrace_assfail(), a probe-context safe function.) If arbitrary
 * loads are to be performed from probe context, they _must_ be in terms of
 * the safe dtrace_load*() variants.
 *
 * Some functions in this block are not actually called from probe context;
 * for these functions, there will be a comment above the function reading
 * "Note:  not called from probe context."
 */

int
dtrace_assfail(const char *a, const char *f, int l)
{
        panic("dtrace: assertion failed: %s, file: %s, line: %d", a, f, l);

        /*
         * We just need something here that even the most clever compiler
         * cannot optimize away.
         */
        return (a[(uintptr_t)f]);
}

/*
 * Atomically increment a specified error counter from probe context.
 */
static void
dtrace_error(uint32_t *counter)
{
        /*
         * Most counters stored to in probe context are per-CPU counters.
         * However, there are some error conditions that are sufficiently
         * arcane that they don't merit per-CPU storage.  If these counters
         * are incremented concurrently on different CPUs, scalability will be
         * adversely affected -- but we don't expect them to be white-hot in a
         * correctly constructed enabling...
         */
        uint32_t oval, nval;

        do {
                oval = *counter;

                if ((nval = oval + 1) == 0) {
                        /*
                         * If the counter would wrap, set it to 1 -- assuring
                         * that the counter is never zero when we have seen
                         * errors.  (The counter must be 32-bits because we
                         * aren't guaranteed a 64-bit compare&swap operation.)
                         * To save this code both the infamy of being fingered
                         * by a priggish news story and the indignity of being
                         * the target of a neo-puritan witch trial, we're
                         * carefully avoiding any colorful description of the
                         * likelihood of this condition -- but suffice it to
                         * say that it is only slightly more likely than the
                         * overflow of predicate cache IDs, as discussed in
                         * dtrace_predicate_create().
                         */
                        nval = 1;
                }
        } while (dtrace_cas32(counter, oval, nval) != oval);
}

/*
 * Use the DTRACE_LOADFUNC macro to define functions for each of loading a
 * uint8_t, a uint16_t, a uint32_t and a uint64_t.
 */
DTRACE_LOADFUNC(8)
DTRACE_LOADFUNC(16)
DTRACE_LOADFUNC(32)
DTRACE_LOADFUNC(64)

static int
dtrace_inscratch(uintptr_t dest, size_t size, dtrace_mstate_t *mstate)
{
        if (dest < mstate->dtms_scratch_base)
                return (0);

        if (dest + size < dest)
                return (0);

        if (dest + size > mstate->dtms_scratch_ptr)
                return (0);

        return (1);
}

static int
dtrace_canstore_statvar(uint64_t addr, size_t sz, size_t *remain,
    dtrace_statvar_t **svars, int nsvars)
{
        int i;

        size_t maxglobalsize, maxlocalsize;

        maxglobalsize = dtrace_statvar_maxsize + sizeof (uint64_t);
        maxlocalsize = (maxglobalsize) * NCPU;

        if (nsvars == 0)
                return (0);

        for (i = 0; i < nsvars; i++) {
                dtrace_statvar_t *svar = svars[i];
                uint8_t scope;
                size_t size;

                if (svar == NULL || (size = svar->dtsv_size) == 0)
                        continue;

                scope = svar->dtsv_var.dtdv_scope;

                /**
                 * We verify that our size is valid in the spirit of providing
                 * defense in depth:  we want to prevent attackers from using
                 * DTrace to escalate an orthogonal kernel heap corruption bug
                 * into the ability to store to arbitrary locations in memory.
                 */
                VERIFY((scope == DIFV_SCOPE_GLOBAL && size <= maxglobalsize) ||
                        (scope == DIFV_SCOPE_LOCAL && size <= maxlocalsize));

                if (DTRACE_INRANGE(addr, sz, svar->dtsv_data, svar->dtsv_size)) {
                        DTRACE_RANGE_REMAIN(remain, addr, svar->dtsv_data,
                                svar->dtsv_size);
                        return (1);
                }
        }

        return (0);
}

/*
 * Check to see if the address is within a memory region to which a store may
 * be issued.  This includes the DTrace scratch areas, and any DTrace variable
 * region.  The caller of dtrace_canstore() is responsible for performing any
 * alignment checks that are needed before stores are actually executed.
 */
static int
dtrace_canstore(uint64_t addr, size_t sz, dtrace_mstate_t *mstate,
    dtrace_vstate_t *vstate)
{
        return (dtrace_canstore_remains(addr, sz, NULL, mstate, vstate));
}
/*
 * Implementation of dtrace_canstore which communicates the upper bound of the
 * allowed memory region.
 */
static int
dtrace_canstore_remains(uint64_t addr, size_t sz, size_t *remain,
        dtrace_mstate_t *mstate, dtrace_vstate_t *vstate)
{
        /*
         * First, check to see if the address is in scratch space...
         */
        if (DTRACE_INRANGE(addr, sz, mstate->dtms_scratch_base,
            mstate->dtms_scratch_size)) {
                DTRACE_RANGE_REMAIN(remain, addr, mstate->dtms_scratch_base,
                        mstate->dtms_scratch_size);
                return (1);
        }
        /*
         * Now check to see if it's a dynamic variable.  This check will pick
         * up both thread-local variables and any global dynamically-allocated
         * variables.
         */
        if (DTRACE_INRANGE(addr, sz, (uintptr_t)vstate->dtvs_dynvars.dtds_base,
            vstate->dtvs_dynvars.dtds_size)) {
                dtrace_dstate_t *dstate = &vstate->dtvs_dynvars;
                uintptr_t base = (uintptr_t)dstate->dtds_base +
                    (dstate->dtds_hashsize * sizeof (dtrace_dynhash_t));
                uintptr_t chunkoffs;
                dtrace_dynvar_t *dvar;

                /*
                 * Before we assume that we can store here, we need to make
                 * sure that it isn't in our metadata -- storing to our
                 * dynamic variable metadata would corrupt our state.  For
                 * the range to not include any dynamic variable metadata,
                 * it must:
                 *
                 *      (1) Start above the hash table that is at the base of
                 *      the dynamic variable space
                 *
                 *      (2) Have a starting chunk offset that is beyond the
                 *      dtrace_dynvar_t that is at the base of every chunk
                 *
                 *      (3) Not span a chunk boundary
                 *
                 *      (4) Not be in the tuple space of a dynamic variable
                 *
                 */
                if (addr < base)
                        return (0);

                chunkoffs = (addr - base) % dstate->dtds_chunksize;

                if (chunkoffs < sizeof (dtrace_dynvar_t))
                        return (0);

                if (chunkoffs + sz > dstate->dtds_chunksize)
                        return (0);

                dvar = (dtrace_dynvar_t *)((uintptr_t)addr - chunkoffs);

                if (dvar->dtdv_hashval == DTRACE_DYNHASH_FREE)
                        return (0);

                if (chunkoffs < sizeof (dtrace_dynvar_t) +
                        ((dvar->dtdv_tuple.dtt_nkeys - 1) * sizeof (dtrace_key_t)))
                        return (0);

                return (1);
        }

        /*
         * Finally, check the static local and global variables.  These checks
         * take the longest, so we perform them last.
         */
        if (dtrace_canstore_statvar(addr, sz, remain,
            vstate->dtvs_locals, vstate->dtvs_nlocals))
                return (1);

        if (dtrace_canstore_statvar(addr, sz, remain,
            vstate->dtvs_globals, vstate->dtvs_nglobals))
                return (1);

        return (0);
}


/*
 * Convenience routine to check to see if the address is within a memory
 * region in which a load may be issued given the user's privilege level;
 * if not, it sets the appropriate error flags and loads 'addr' into the
 * illegal value slot.
 *
 * DTrace subroutines (DIF_SUBR_*) should use this helper to implement
 * appropriate memory access protection.
 */
int
dtrace_canload(uint64_t addr, size_t sz, dtrace_mstate_t *mstate,
    dtrace_vstate_t *vstate)
{
        return (dtrace_canload_remains(addr, sz, NULL, mstate, vstate));
}

/*
 * Implementation of dtrace_canload which communicates the upper bound of the
 * allowed memory region.
 */
static int
dtrace_canload_remains(uint64_t addr, size_t sz, size_t *remain,
        dtrace_mstate_t *mstate, dtrace_vstate_t *vstate)
{
        volatile uint64_t *illval = &cpu_core[CPU->cpu_id].cpuc_dtrace_illval;

        /*
         * If we hold the privilege to read from kernel memory, then
         * everything is readable.
         */
        if ((mstate->dtms_access & DTRACE_ACCESS_KERNEL) != 0) {
                DTRACE_RANGE_REMAIN(remain, addr, addr, sz);
                return (1);
        }

        /*
         * You can obviously read that which you can store.
         */
        if (dtrace_canstore_remains(addr, sz, remain, mstate, vstate))
                return (1);

        /*
         * We're allowed to read from our own string table.
         */
        if (DTRACE_INRANGE(addr, sz, (uintptr_t)mstate->dtms_difo->dtdo_strtab,
            mstate->dtms_difo->dtdo_strlen)) {
                DTRACE_RANGE_REMAIN(remain, addr,
                        mstate->dtms_difo->dtdo_strtab,
                        mstate->dtms_difo->dtdo_strlen);
                return (1);
        }

        DTRACE_CPUFLAG_SET(CPU_DTRACE_KPRIV);
        *illval = addr;
        return (0);
}

/*
 * Convenience routine to check to see if a given string is within a memory
 * region in which a load may be issued given the user's privilege level;
 * this exists so that we don't need to issue unnecessary dtrace_strlen()
 * calls in the event that the user has all privileges.
 */
static int
dtrace_strcanload(uint64_t addr, size_t sz, size_t *remain,
        dtrace_mstate_t *mstate, dtrace_vstate_t *vstate)
{
        size_t rsize;

        /*
         * If we hold the privilege to read from kernel memory, then
         * everything is readable.
         */
        if ((mstate->dtms_access & DTRACE_ACCESS_KERNEL) != 0) {
                DTRACE_RANGE_REMAIN(remain, addr, addr, sz);
                return (1);
        }

        /*
         * Even if the caller is uninterested in querying the remaining valid
         * range, it is required to ensure that the access is allowed.
         */
        if (remain == NULL) {
                remain = &rsize;
        }
        if (dtrace_canload_remains(addr, 0, remain, mstate, vstate)) {
                size_t strsz;
                /*
                 * Perform the strlen after determining the length of the
                 * memory region which is accessible.  This prevents timing
                 * information from being used to find NULs in memory which is
                 * not accessible to the caller.
                 */
                strsz = 1 + dtrace_strlen((char *)(uintptr_t)addr,
                        MIN(sz, *remain));
                if (strsz <= *remain) {
                        return (1);
                }
        }

        return (0);
}

/*
 * Convenience routine to check to see if a given variable is within a memory
 * region in which a load may be issued given the user's privilege level.
 */
static int
dtrace_vcanload(void *src, dtrace_diftype_t *type, size_t *remain,
        dtrace_mstate_t *mstate, dtrace_vstate_t *vstate)
{
        size_t sz;
        ASSERT(type->dtdt_flags & DIF_TF_BYREF);

        /*
         * Calculate the max size before performing any checks since even
         * DTRACE_ACCESS_KERNEL-credentialed callers expect that this function
         * return the max length via 'remain'.
         */
        if (type->dtdt_kind == DIF_TYPE_STRING) {
                dtrace_state_t *state = vstate->dtvs_state;

                if (state != NULL) {
                        sz = state->dts_options[DTRACEOPT_STRSIZE];
                } else {
                        /*
                         * In helper context, we have a NULL state; fall back
                         * to using the system-wide default for the string size
                         * in this case.
                         */
                        sz = dtrace_strsize_default;
                }
        } else {
                sz = type->dtdt_size;
        }

        /*
         * If we hold the privilege to read from kernel memory, then
         * everything is readable.
         */
        if ((mstate->dtms_access & DTRACE_ACCESS_KERNEL) != 0) {
                DTRACE_RANGE_REMAIN(remain, (uintptr_t)src, src, sz);
                return (1);
        }

        if (type->dtdt_kind == DIF_TYPE_STRING) {
                return (dtrace_strcanload((uintptr_t)src, sz, remain, mstate,
                        vstate));
        }
        return (dtrace_canload_remains((uintptr_t)src, sz, remain, mstate,
                vstate));
}

#define isdigit(ch)     ((ch) >= '0' && (ch) <= '9')
#define islower(ch)     ((ch) >= 'a' && (ch) <= 'z')
#define isspace(ch)     (((ch) == ' ') || ((ch) == '\r') || ((ch) == '\n') || \
                        ((ch) == '\t') || ((ch) == '\f'))
#define isxdigit(ch)    (isdigit(ch) || ((ch) >= 'a' && (ch) <= 'f') || \
                        ((ch) >= 'A' && (ch) <= 'F'))
#define lisalnum(x)     \
        (isdigit(x) || ((x) >= 'a' && (x) <= 'z') || ((x) >= 'A' && (x) <= 'Z'))

#define DIGIT(x)        \
        (isdigit(x) ? (x) - '0' : islower(x) ? (x) + 10 - 'a' : (x) + 10 - 'A')

/*
 * Convert a string to a signed integer using safe loads.
 */
static int64_t
dtrace_strtoll(char *input, int base, size_t limit)
{
        uintptr_t pos = (uintptr_t)input;
        int64_t val = 0;
        int x;
        boolean_t neg = B_FALSE;
        char c, cc, ccc;
        uintptr_t end = pos + limit;

        /*
         * Consume any whitespace preceding digits.
         */
        while ((c = dtrace_load8(pos)) == ' ' || c == '\t')
                pos++;

        /*
         * Handle an explicit sign if one is present.
         */
        if (c == '-' || c == '+') {
                if (c == '-')
                        neg = B_TRUE;
                c = dtrace_load8(++pos);
        }

        /*
         * Check for an explicit hexadecimal prefix ("0x" or "0X") and skip it
         * if present.
         */
        if (base == 16 && c == '0' && ((cc = dtrace_load8(pos + 1)) == 'x' ||
            cc == 'X') && isxdigit(ccc = dtrace_load8(pos + 2))) {
                pos += 2;
                c = ccc;
        }

        /*
         * Read in contiguous digits until the first non-digit character.
         */
        for (; pos < end && c != '\0' && lisalnum(c) && (x = DIGIT(c)) < base;
            c = dtrace_load8(++pos))
                val = val * base + x;

        return (neg ? -val : val);
}


/*
 * Compare two strings using safe loads.
 */
static int
dtrace_strncmp(const char *s1, const char *s2, size_t limit)
{
        uint8_t c1, c2;
        volatile uint16_t *flags;

        if (s1 == s2 || limit == 0)
                return (0);

        flags = (volatile uint16_t *)&cpu_core[CPU->cpu_id].cpuc_dtrace_flags;

        do {
                if (s1 == NULL) {
                        c1 = '\0';
                } else {
                        c1 = dtrace_load8((uintptr_t)s1++);
                }

                if (s2 == NULL) {
                        c2 = '\0';
                } else {
                        c2 = dtrace_load8((uintptr_t)s2++);
                }

                if (c1 != c2)
                        return (c1 - c2);
        } while (--limit && c1 != '\0' && !(*flags & CPU_DTRACE_FAULT));

        return (0);
}

/*
 * Compute strlen(s) for a string using safe memory accesses.  The additional
 * len parameter is used to specify a maximum length to ensure completion.
 */
static size_t
dtrace_strlen(const char *s, size_t lim)
{
        uint_t len;

        for (len = 0; len != lim; len++) {
                if (dtrace_load8((uintptr_t)s++) == '\0')
                        break;
        }

        return (len);
}

/*
 * Check if an address falls within a toxic region.
 */
static int
dtrace_istoxic(uintptr_t kaddr, size_t size)
{
        uintptr_t taddr, tsize;
        int i;

        for (i = 0; i < dtrace_toxranges; i++) {
                taddr = dtrace_toxrange[i].dtt_base;
                tsize = dtrace_toxrange[i].dtt_limit - taddr;

                if (kaddr - taddr < tsize) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_BADADDR);
                        cpu_core[CPU->cpu_id].cpuc_dtrace_illval = kaddr;
                        return (1);
                }

                if (taddr - kaddr < size) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_BADADDR);
                        cpu_core[CPU->cpu_id].cpuc_dtrace_illval = taddr;
                        return (1);
                }
        }

        return (0);
}

/*
 * Copy src to dst using safe memory accesses.  The src is assumed to be unsafe
 * memory specified by the DIF program.  The dst is assumed to be safe memory
 * that we can store to directly because it is managed by DTrace.  As with
 * standard bcopy, overlapping copies are handled properly.
 */
static void
dtrace_bcopy(const void *src, void *dst, size_t len)
{
        if (len != 0) {
                uint8_t *s1 = dst;
                const uint8_t *s2 = src;

                if (s1 <= s2) {
                        do {
                                *s1++ = dtrace_load8((uintptr_t)s2++);
                        } while (--len != 0);
                } else {
                        s2 += len;
                        s1 += len;

                        do {
                                *--s1 = dtrace_load8((uintptr_t)--s2);
                        } while (--len != 0);
                }
        }
}

/*
 * Copy src to dst using safe memory accesses, up to either the specified
 * length, or the point that a nul byte is encountered.  The src is assumed to
 * be unsafe memory specified by the DIF program.  The dst is assumed to be
 * safe memory that we can store to directly because it is managed by DTrace.
 * Unlike dtrace_bcopy(), overlapping regions are not handled.
 */
static void
dtrace_strcpy(const void *src, void *dst, size_t len)
{
        if (len != 0) {
                uint8_t *s1 = dst, c;
                const uint8_t *s2 = src;

                do {
                        *s1++ = c = dtrace_load8((uintptr_t)s2++);
                } while (--len != 0 && c != '\0');
        }
}

/*
 * Copy src to dst, deriving the size and type from the specified (BYREF)
 * variable type.  The src is assumed to be unsafe memory specified by the DIF
 * program.  The dst is assumed to be DTrace variable memory that is of the
 * specified type; we assume that we can store to directly.
 */
static void
dtrace_vcopy(void *src, void *dst, dtrace_diftype_t *type, size_t limit)
{
        ASSERT(type->dtdt_flags & DIF_TF_BYREF);

        if (type->dtdt_kind == DIF_TYPE_STRING) {
                dtrace_strcpy(src, dst, MIN(type->dtdt_size, limit));
        } else {
                dtrace_bcopy(src, dst, MIN(type->dtdt_size, limit));
        }
}

/*
 * Compare s1 to s2 using safe memory accesses.  The s1 data is assumed to be
 * unsafe memory specified by the DIF program.  The s2 data is assumed to be
 * safe memory that we can access directly because it is managed by DTrace.
 */
static int
dtrace_bcmp(const void *s1, const void *s2, size_t len)
{
        volatile uint16_t *flags;

        flags = (volatile uint16_t *)&cpu_core[CPU->cpu_id].cpuc_dtrace_flags;

        if (s1 == s2)
                return (0);

        if (s1 == NULL || s2 == NULL)
                return (1);

        if (s1 != s2 && len != 0) {
                const uint8_t *ps1 = s1;
                const uint8_t *ps2 = s2;

                do {
                        if (dtrace_load8((uintptr_t)ps1++) != *ps2++)
                                return (1);
                } while (--len != 0 && !(*flags & CPU_DTRACE_FAULT));
        }
        return (0);
}

/*
 * Zero the specified region using a simple byte-by-byte loop.  Note that this
 * is for safe DTrace-managed memory only.
 */
static void
dtrace_bzero(void *dst, size_t len)
{
        uchar_t *cp;

        for (cp = dst; len != 0; len--)
                *cp++ = 0;
}

static void
dtrace_add_128(uint64_t *addend1, uint64_t *addend2, uint64_t *sum)
{
        uint64_t result[2];

        result[0] = addend1[0] + addend2[0];
        result[1] = addend1[1] + addend2[1] +
            (result[0] < addend1[0] || result[0] < addend2[0] ? 1 : 0);

        sum[0] = result[0];
        sum[1] = result[1];
}

/*
 * Shift the 128-bit value in a by b. If b is positive, shift left.
 * If b is negative, shift right.
 */
static void
dtrace_shift_128(uint64_t *a, int b)
{
        uint64_t mask;

        if (b == 0)
                return;

        if (b < 0) {
                b = -b;
                if (b >= 64) {
                        a[0] = a[1] >> (b - 64);
                        a[1] = 0;
                } else {
                        a[0] >>= b;
                        mask = 1LL << (64 - b);
                        mask -= 1;
                        a[0] |= ((a[1] & mask) << (64 - b));
                        a[1] >>= b;
                }
        } else {
                if (b >= 64) {
                        a[1] = a[0] << (b - 64);
                        a[0] = 0;
                } else {
                        a[1] <<= b;
                        mask = a[0] >> (64 - b);
                        a[1] |= mask;
                        a[0] <<= b;
                }
        }
}

/*
 * The basic idea is to break the 2 64-bit values into 4 32-bit values,
 * use native multiplication on those, and then re-combine into the
 * resulting 128-bit value.
 *
 * (hi1 << 32 + lo1) * (hi2 << 32 + lo2) =
 *     hi1 * hi2 << 64 +
 *     hi1 * lo2 << 32 +
 *     hi2 * lo1 << 32 +
 *     lo1 * lo2
 */
static void
dtrace_multiply_128(uint64_t factor1, uint64_t factor2, uint64_t *product)
{
        uint64_t hi1, hi2, lo1, lo2;
        uint64_t tmp[2];

        hi1 = factor1 >> 32;
        hi2 = factor2 >> 32;

        lo1 = factor1 & DT_MASK_LO;
        lo2 = factor2 & DT_MASK_LO;

        product[0] = lo1 * lo2;
        product[1] = hi1 * hi2;

        tmp[0] = hi1 * lo2;
        tmp[1] = 0;
        dtrace_shift_128(tmp, 32);
        dtrace_add_128(product, tmp, product);

        tmp[0] = hi2 * lo1;
        tmp[1] = 0;
        dtrace_shift_128(tmp, 32);
        dtrace_add_128(product, tmp, product);
}

/*
 * This privilege check should be used by actions and subroutines to
 * verify that the user credentials of the process that enabled the
 * invoking ECB match the target credentials
 */
static int
dtrace_priv_proc_common_user(dtrace_state_t *state)
{
        cred_t *cr, *s_cr = state->dts_cred.dcr_cred;

        /*
         * We should always have a non-NULL state cred here, since if cred
         * is null (anonymous tracing), we fast-path bypass this routine.
         */
        ASSERT(s_cr != NULL);

        if ((cr = dtrace_CRED()) != NULL &&
            posix_cred_get(s_cr)->cr_uid == posix_cred_get(cr)->cr_uid &&
            posix_cred_get(s_cr)->cr_uid == posix_cred_get(cr)->cr_ruid &&
            posix_cred_get(s_cr)->cr_uid == posix_cred_get(cr)->cr_suid &&
            posix_cred_get(s_cr)->cr_gid == posix_cred_get(cr)->cr_gid &&
            posix_cred_get(s_cr)->cr_gid == posix_cred_get(cr)->cr_rgid &&
            posix_cred_get(s_cr)->cr_gid == posix_cred_get(cr)->cr_sgid)
                return (1);

        return (0);
}

/*
 * This privilege check should be used by actions and subroutines to
 * verify that the zone of the process that enabled the invoking ECB
 * matches the target credentials
 */
static int
dtrace_priv_proc_common_zone(dtrace_state_t *state)
{
        cred_t *cr, *s_cr = state->dts_cred.dcr_cred;
#pragma unused(cr, s_cr, state) /* __APPLE__ */

        /*
         * We should always have a non-NULL state cred here, since if cred
         * is null (anonymous tracing), we fast-path bypass this routine.
         */
        ASSERT(s_cr != NULL);

        return 1; /* APPLE NOTE: Darwin doesn't do zones. */
}

/*
 * This privilege check should be used by actions and subroutines to
 * verify that the process has not setuid or changed credentials.
 */
static int
dtrace_priv_proc_common_nocd(void)
{
        return 1; /* Darwin omits "No Core Dump" flag. */
}

static int
dtrace_priv_proc_destructive(dtrace_state_t *state)
{
        int action = state->dts_cred.dcr_action;

        if (ISSET(current_proc()->p_lflag, P_LNOATTACH))
                goto bad;

        if (dtrace_is_restricted() && !dtrace_can_attach_to_proc(current_proc()))
                goto bad;

        if (((action & DTRACE_CRA_PROC_DESTRUCTIVE_ALLZONE) == 0) &&
            dtrace_priv_proc_common_zone(state) == 0)
                goto bad;

        if (((action & DTRACE_CRA_PROC_DESTRUCTIVE_ALLUSER) == 0) &&
            dtrace_priv_proc_common_user(state) == 0)
                goto bad;

        if (((action & DTRACE_CRA_PROC_DESTRUCTIVE_CREDCHG) == 0) &&
            dtrace_priv_proc_common_nocd() == 0)
                goto bad;

        return (1);

bad:
        cpu_core[CPU->cpu_id].cpuc_dtrace_flags |= CPU_DTRACE_UPRIV;

        return (0);
}

static int
dtrace_priv_proc_control(dtrace_state_t *state)
{
        if (ISSET(current_proc()->p_lflag, P_LNOATTACH))
                goto bad;

        if (dtrace_is_restricted() && !dtrace_can_attach_to_proc(current_proc()))
                goto bad;

        if (state->dts_cred.dcr_action & DTRACE_CRA_PROC_CONTROL)
                return (1);

        if (dtrace_priv_proc_common_zone(state) &&
            dtrace_priv_proc_common_user(state) &&
            dtrace_priv_proc_common_nocd())
                return (1);

bad:
        cpu_core[CPU->cpu_id].cpuc_dtrace_flags |= CPU_DTRACE_UPRIV;

        return (0);
}

static int
dtrace_priv_proc(dtrace_state_t *state)
{
        if (ISSET(current_proc()->p_lflag, P_LNOATTACH))
                goto bad;

        if (dtrace_is_restricted() && !dtrace_are_restrictions_relaxed() && !dtrace_can_attach_to_proc(current_proc()))
                goto bad;

        if (state->dts_cred.dcr_action & DTRACE_CRA_PROC)
                return (1);

bad:
        cpu_core[CPU->cpu_id].cpuc_dtrace_flags |= CPU_DTRACE_UPRIV;

        return (0);
}

/*
 * The P_LNOATTACH check is an Apple specific check.
 * We need a version of dtrace_priv_proc() that omits
 * that check for PID and EXECNAME accesses
 */
static int
dtrace_priv_proc_relaxed(dtrace_state_t *state)
{

        if (state->dts_cred.dcr_action & DTRACE_CRA_PROC)
                return (1);

        cpu_core[CPU->cpu_id].cpuc_dtrace_flags |= CPU_DTRACE_UPRIV;

        return (0);
}

static int
dtrace_priv_kernel(dtrace_state_t *state)
{
        if (dtrace_is_restricted() && !dtrace_are_restrictions_relaxed())
                goto bad;

        if (state->dts_cred.dcr_action & DTRACE_CRA_KERNEL)
                return (1);

bad:
        cpu_core[CPU->cpu_id].cpuc_dtrace_flags |= CPU_DTRACE_KPRIV;

        return (0);
}

static int
dtrace_priv_kernel_destructive(dtrace_state_t *state)
{
        if (dtrace_is_restricted())
                goto bad;

        if (state->dts_cred.dcr_action & DTRACE_CRA_KERNEL_DESTRUCTIVE)
                return (1);

bad:
        cpu_core[CPU->cpu_id].cpuc_dtrace_flags |= CPU_DTRACE_KPRIV;

        return (0);
}

/*
 * Note:  not called from probe context.  This function is called
 * asynchronously (and at a regular interval) from outside of probe context to
 * clean the dirty dynamic variable lists on all CPUs.  Dynamic variable
 * cleaning is explained in detail in <sys/dtrace_impl.h>.
 */
static void
dtrace_dynvar_clean(dtrace_dstate_t *dstate)
{
        dtrace_dynvar_t *dirty;
        dtrace_dstate_percpu_t *dcpu;
        int i, work = 0;

        for (i = 0; i < (int)NCPU; i++) {
                dcpu = &dstate->dtds_percpu[i];

                ASSERT(dcpu->dtdsc_rinsing == NULL);

                /*
                 * If the dirty list is NULL, there is no dirty work to do.
                 */
                if (dcpu->dtdsc_dirty == NULL)
                        continue;

                /*
                 * If the clean list is non-NULL, then we're not going to do
                 * any work for this CPU -- it means that there has not been
                 * a dtrace_dynvar() allocation on this CPU (or from this CPU)
                 * since the last time we cleaned house.
                 */
                if (dcpu->dtdsc_clean != NULL)
                        continue;

                work = 1;

                /*
                 * Atomically move the dirty list aside.
                 */
                do {
                        dirty = dcpu->dtdsc_dirty;

                        /*
                         * Before we zap the dirty list, set the rinsing list.
                         * (This allows for a potential assertion in
                         * dtrace_dynvar():  if a free dynamic variable appears
                         * on a hash chain, either the dirty list or the
                         * rinsing list for some CPU must be non-NULL.)
                         */
                        dcpu->dtdsc_rinsing = dirty;
                        dtrace_membar_producer();
                } while (dtrace_casptr(&dcpu->dtdsc_dirty,
                    dirty, NULL) != dirty);
        }

        if (!work) {
                /*
                 * We have no work to do; we can simply return.
                 */
                return;
        }

        dtrace_sync();

        for (i = 0; i < (int)NCPU; i++) {
                dcpu = &dstate->dtds_percpu[i];

                if (dcpu->dtdsc_rinsing == NULL)
                        continue;

                /*
                 * We are now guaranteed that no hash chain contains a pointer
                 * into this dirty list; we can make it clean.
                 */
                ASSERT(dcpu->dtdsc_clean == NULL);
                dcpu->dtdsc_clean = dcpu->dtdsc_rinsing;
                dcpu->dtdsc_rinsing = NULL;
        }

        /*
         * Before we actually set the state to be DTRACE_DSTATE_CLEAN, make
         * sure that all CPUs have seen all of the dtdsc_clean pointers.
         * This prevents a race whereby a CPU incorrectly decides that
         * the state should be something other than DTRACE_DSTATE_CLEAN
         * after dtrace_dynvar_clean() has completed.
         */
        dtrace_sync();

        dstate->dtds_state = DTRACE_DSTATE_CLEAN;
}

/*
 * Depending on the value of the op parameter, this function looks-up,
 * allocates or deallocates an arbitrarily-keyed dynamic variable.  If an
 * allocation is requested, this function will return a pointer to a
 * dtrace_dynvar_t corresponding to the allocated variable -- or NULL if no
 * variable can be allocated.  If NULL is returned, the appropriate counter
 * will be incremented.
 */
static dtrace_dynvar_t *
dtrace_dynvar(dtrace_dstate_t *dstate, uint_t nkeys,
    dtrace_key_t *key, size_t dsize, dtrace_dynvar_op_t op,
    dtrace_mstate_t *mstate, dtrace_vstate_t *vstate)
{
        uint64_t hashval = DTRACE_DYNHASH_VALID;
        dtrace_dynhash_t *hash = dstate->dtds_hash;
        dtrace_dynvar_t *free, *new_free, *next, *dvar, *start, *prev = NULL;
        processorid_t me = CPU->cpu_id, cpu = me;
        dtrace_dstate_percpu_t *dcpu = &dstate->dtds_percpu[me];
        size_t bucket, ksize;
        size_t chunksize = dstate->dtds_chunksize;
        uintptr_t kdata, lock, nstate;
        uint_t i;

        ASSERT(nkeys != 0);

        /*
         * Hash the key.  As with aggregations, we use Jenkins' "One-at-a-time"
         * algorithm.  For the by-value portions, we perform the algorithm in
         * 16-bit chunks (as opposed to 8-bit chunks).  This speeds things up a
         * bit, and seems to have only a minute effect on distribution.  For
         * the by-reference data, we perform "One-at-a-time" iterating (safely)
         * over each referenced byte.  It's painful to do this, but it's much
         * better than pathological hash distribution.  The efficacy of the
         * hashing algorithm (and a comparison with other algorithms) may be
         * found by running the ::dtrace_dynstat MDB dcmd.
         */
        for (i = 0; i < nkeys; i++) {
                if (key[i].dttk_size == 0) {
                        uint64_t val = key[i].dttk_value;

                        hashval += (val >> 48) & 0xffff;
                        hashval += (hashval << 10);
                        hashval ^= (hashval >> 6);

                        hashval += (val >> 32) & 0xffff;
                        hashval += (hashval << 10);
                        hashval ^= (hashval >> 6);

                        hashval += (val >> 16) & 0xffff;
                        hashval += (hashval << 10);
                        hashval ^= (hashval >> 6);

                        hashval += val & 0xffff;
                        hashval += (hashval << 10);
                        hashval ^= (hashval >> 6);
                } else {
                        /*
                         * This is incredibly painful, but it beats the hell
                         * out of the alternative.
                         */
                        uint64_t j, size = key[i].dttk_size;
                        uintptr_t base = (uintptr_t)key[i].dttk_value;

                        if (!dtrace_canload(base, size, mstate, vstate))
                                break;

                        for (j = 0; j < size; j++) {
                                hashval += dtrace_load8(base + j);
                                hashval += (hashval << 10);
                                hashval ^= (hashval >> 6);
                        }
                }
        }

        if (DTRACE_CPUFLAG_ISSET(CPU_DTRACE_FAULT))
                return (NULL);

        hashval += (hashval << 3);
        hashval ^= (hashval >> 11);
        hashval += (hashval << 15);

        /*
         * There is a remote chance (ideally, 1 in 2^31) that our hashval
         * comes out to be one of our two sentinel hash values.  If this
         * actually happens, we set the hashval to be a value known to be a
         * non-sentinel value.
         */
        if (hashval == DTRACE_DYNHASH_FREE || hashval == DTRACE_DYNHASH_SINK)
                hashval = DTRACE_DYNHASH_VALID;

        /*
         * Yes, it's painful to do a divide here.  If the cycle count becomes
         * important here, tricks can be pulled to reduce it.  (However, it's
         * critical that hash collisions be kept to an absolute minimum;
         * they're much more painful than a divide.)  It's better to have a
         * solution that generates few collisions and still keeps things
         * relatively simple.
         */
        bucket = hashval % dstate->dtds_hashsize;

        if (op == DTRACE_DYNVAR_DEALLOC) {
                volatile uintptr_t *lockp = &hash[bucket].dtdh_lock;

                for (;;) {
                        while ((lock = *lockp) & 1)
                                continue;

                        if (dtrace_casptr((void *)(uintptr_t)lockp,
                            (void *)lock, (void *)(lock + 1)) == (void *)lock)
                                break;
                }

                dtrace_membar_producer();
        }

top:
        prev = NULL;
        lock = hash[bucket].dtdh_lock;

        dtrace_membar_consumer();

        start = hash[bucket].dtdh_chain;
        ASSERT(start != NULL && (start->dtdv_hashval == DTRACE_DYNHASH_SINK ||
            start->dtdv_hashval != DTRACE_DYNHASH_FREE ||
            op != DTRACE_DYNVAR_DEALLOC));

        for (dvar = start; dvar != NULL; dvar = dvar->dtdv_next) {
                dtrace_tuple_t *dtuple = &dvar->dtdv_tuple;
                dtrace_key_t *dkey = &dtuple->dtt_key[0];

                if (dvar->dtdv_hashval != hashval) {
                        if (dvar->dtdv_hashval == DTRACE_DYNHASH_SINK) {
                                /*
                                 * We've reached the sink, and therefore the
                                 * end of the hash chain; we can kick out of
                                 * the loop knowing that we have seen a valid
                                 * snapshot of state.
                                 */
                                ASSERT(dvar->dtdv_next == NULL);
                                ASSERT(dvar == &dtrace_dynhash_sink);
                                break;
                        }

                        if (dvar->dtdv_hashval == DTRACE_DYNHASH_FREE) {
                                /*
                                 * We've gone off the rails:  somewhere along
                                 * the line, one of the members of this hash
                                 * chain was deleted.  Note that we could also
                                 * detect this by simply letting this loop run
                                 * to completion, as we would eventually hit
                                 * the end of the dirty list.  However, we
                                 * want to avoid running the length of the
                                 * dirty list unnecessarily (it might be quite
                                 * long), so we catch this as early as
                                 * possible by detecting the hash marker.  In
                                 * this case, we simply set dvar to NULL and
                                 * break; the conditional after the loop will
                                 * send us back to top.
                                 */
                                dvar = NULL;
                                break;
                        }

                        goto next;
                }

                if (dtuple->dtt_nkeys != nkeys)
                        goto next;

                for (i = 0; i < nkeys; i++, dkey++) {
                        if (dkey->dttk_size != key[i].dttk_size)
                                goto next; /* size or type mismatch */

                        if (dkey->dttk_size != 0) {
                                if (dtrace_bcmp(
                                    (void *)(uintptr_t)key[i].dttk_value,
                                    (void *)(uintptr_t)dkey->dttk_value,
                                    dkey->dttk_size))
                                        goto next;
                        } else {
                                if (dkey->dttk_value != key[i].dttk_value)
                                        goto next;
                        }
                }

                if (op != DTRACE_DYNVAR_DEALLOC)
                        return (dvar);

                ASSERT(dvar->dtdv_next == NULL ||
                    dvar->dtdv_next->dtdv_hashval != DTRACE_DYNHASH_FREE);

                if (prev != NULL) {
                        ASSERT(hash[bucket].dtdh_chain != dvar);
                        ASSERT(start != dvar);
                        ASSERT(prev->dtdv_next == dvar);
                        prev->dtdv_next = dvar->dtdv_next;
                } else {
                        if (dtrace_casptr(&hash[bucket].dtdh_chain,
                            start, dvar->dtdv_next) != start) {
                                /*
                                 * We have failed to atomically swing the
                                 * hash table head pointer, presumably because
                                 * of a conflicting allocation on another CPU.
                                 * We need to reread the hash chain and try
                                 * again.
                                 */
                                goto top;
                        }
                }

                dtrace_membar_producer();

                /*
                 * Now set the hash value to indicate that it's free.
                 */
                ASSERT(hash[bucket].dtdh_chain != dvar);
                dvar->dtdv_hashval = DTRACE_DYNHASH_FREE;

                dtrace_membar_producer();

                /*
                 * Set the next pointer to point at the dirty list, and
                 * atomically swing the dirty pointer to the newly freed dvar.
                 */
                do {
                        next = dcpu->dtdsc_dirty;
                        dvar->dtdv_next = next;
                } while (dtrace_casptr(&dcpu->dtdsc_dirty, next, dvar) != next);

                /*
                 * Finally, unlock this hash bucket.
                 */
                ASSERT(hash[bucket].dtdh_lock == lock);
                ASSERT(lock & 1);
                hash[bucket].dtdh_lock++;

                return (NULL);
next:
                prev = dvar;
                continue;
        }

        if (dvar == NULL) {
                /*
                 * If dvar is NULL, it is because we went off the rails:
                 * one of the elements that we traversed in the hash chain
                 * was deleted while we were traversing it.  In this case,
                 * we assert that we aren't doing a dealloc (deallocs lock
                 * the hash bucket to prevent themselves from racing with
                 * one another), and retry the hash chain traversal.
                 */
                ASSERT(op != DTRACE_DYNVAR_DEALLOC);
                goto top;
        }

        if (op != DTRACE_DYNVAR_ALLOC) {
                /*
                 * If we are not to allocate a new variable, we want to
                 * return NULL now.  Before we return, check that the value
                 * of the lock word hasn't changed.  If it has, we may have
                 * seen an inconsistent snapshot.
                 */
                if (op == DTRACE_DYNVAR_NOALLOC) {
                        if (hash[bucket].dtdh_lock != lock)
                                goto top;
                } else {
                        ASSERT(op == DTRACE_DYNVAR_DEALLOC);
                        ASSERT(hash[bucket].dtdh_lock == lock);
                        ASSERT(lock & 1);
                        hash[bucket].dtdh_lock++;
                }

                return (NULL);
        }

        /*
         * We need to allocate a new dynamic variable.  The size we need is the
         * size of dtrace_dynvar plus the size of nkeys dtrace_key_t's plus the
         * size of any auxiliary key data (rounded up to 8-byte alignment) plus
         * the size of any referred-to data (dsize).  We then round the final
         * size up to the chunksize for allocation.
         */
        for (ksize = 0, i = 0; i < nkeys; i++)
                ksize += P2ROUNDUP(key[i].dttk_size, sizeof (uint64_t));

        /*
         * This should be pretty much impossible, but could happen if, say,
         * strange DIF specified the tuple.  Ideally, this should be an
         * assertion and not an error condition -- but that requires that the
         * chunksize calculation in dtrace_difo_chunksize() be absolutely
         * bullet-proof.  (That is, it must not be able to be fooled by
         * malicious DIF.)  Given the lack of backwards branches in DIF,
         * solving this would presumably not amount to solving the Halting
         * Problem -- but it still seems awfully hard.
         */
        if (sizeof (dtrace_dynvar_t) + sizeof (dtrace_key_t) * (nkeys - 1) +
            ksize + dsize > chunksize) {
                dcpu->dtdsc_drops++;
                return (NULL);
        }

        nstate = DTRACE_DSTATE_EMPTY;

        do {
retry:
                free = dcpu->dtdsc_free;

                if (free == NULL) {
                        dtrace_dynvar_t *clean = dcpu->dtdsc_clean;
                        void *rval;

                        if (clean == NULL) {
                                /*
                                 * We're out of dynamic variable space on
                                 * this CPU.  Unless we have tried all CPUs,
                                 * we'll try to allocate from a different
                                 * CPU.
                                 */
                                switch (dstate->dtds_state) {
                                case DTRACE_DSTATE_CLEAN: {
                                        void *sp = &dstate->dtds_state;

                                        if (++cpu >= (int)NCPU)
                                                cpu = 0;

                                        if (dcpu->dtdsc_dirty != NULL &&
                                            nstate == DTRACE_DSTATE_EMPTY)
                                                nstate = DTRACE_DSTATE_DIRTY;

                                        if (dcpu->dtdsc_rinsing != NULL)
                                                nstate = DTRACE_DSTATE_RINSING;

                                        dcpu = &dstate->dtds_percpu[cpu];

                                        if (cpu != me)
                                                goto retry;

                                        (void) dtrace_cas32(sp,
                                            DTRACE_DSTATE_CLEAN, nstate);

                                        /*
                                         * To increment the correct bean
                                         * counter, take another lap.
                                         */
                                        goto retry;
                                }

                                case DTRACE_DSTATE_DIRTY:
                                        dcpu->dtdsc_dirty_drops++;
                                        break;

                                case DTRACE_DSTATE_RINSING:
                                        dcpu->dtdsc_rinsing_drops++;
                                        break;

                                case DTRACE_DSTATE_EMPTY:
                                        dcpu->dtdsc_drops++;
                                        break;
                                }

                                DTRACE_CPUFLAG_SET(CPU_DTRACE_DROP);
                                return (NULL);
                        }

                        /*
                         * The clean list appears to be non-empty.  We want to
                         * move the clean list to the free list; we start by
                         * moving the clean pointer aside.
                         */
                        if (dtrace_casptr(&dcpu->dtdsc_clean,
                            clean, NULL) != clean) {
                                /*
                                 * We are in one of two situations:
                                 *
                                 *  (a) The clean list was switched to the
                                 *      free list by another CPU.
                                 *
                                 *  (b) The clean list was added to by the
                                 *      cleansing cyclic.
                                 *
                                 * In either of these situations, we can
                                 * just reattempt the free list allocation.
                                 */
                                goto retry;
                        }

                        ASSERT(clean->dtdv_hashval == DTRACE_DYNHASH_FREE);

                        /*
                         * Now we'll move the clean list to the free list.
                         * It's impossible for this to fail:  the only way
                         * the free list can be updated is through this
                         * code path, and only one CPU can own the clean list.
                         * Thus, it would only be possible for this to fail if
                         * this code were racing with dtrace_dynvar_clean().
                         * (That is, if dtrace_dynvar_clean() updated the clean
                         * list, and we ended up racing to update the free
                         * list.)  This race is prevented by the dtrace_sync()
                         * in dtrace_dynvar_clean() -- which flushes the
                         * owners of the clean lists out before resetting
                         * the clean lists.
                         */
                        rval = dtrace_casptr(&dcpu->dtdsc_free, NULL, clean);
                        ASSERT(rval == NULL);
                        goto retry;
                }

                dvar = free;
                new_free = dvar->dtdv_next;
        } while (dtrace_casptr(&dcpu->dtdsc_free, free, new_free) != free);

        /*
         * We have now allocated a new chunk.  We copy the tuple keys into the
         * tuple array and copy any referenced key data into the data space
         * following the tuple array.  As we do this, we relocate dttk_value
         * in the final tuple to point to the key data address in the chunk.
         */
        kdata = (uintptr_t)&dvar->dtdv_tuple.dtt_key[nkeys];
        dvar->dtdv_data = (void *)(kdata + ksize);
        dvar->dtdv_tuple.dtt_nkeys = nkeys;

        for (i = 0; i < nkeys; i++) {
                dtrace_key_t *dkey = &dvar->dtdv_tuple.dtt_key[i];
                size_t kesize = key[i].dttk_size;

                if (kesize != 0) {
                        dtrace_bcopy(
                            (const void *)(uintptr_t)key[i].dttk_value,
                            (void *)kdata, kesize);
                        dkey->dttk_value = kdata;
                        kdata += P2ROUNDUP(kesize, sizeof (uint64_t));
                } else {
                        dkey->dttk_value = key[i].dttk_value;
                }

                dkey->dttk_size = kesize;
        }

        ASSERT(dvar->dtdv_hashval == DTRACE_DYNHASH_FREE);
        dvar->dtdv_hashval = hashval;
        dvar->dtdv_next = start;

        if (dtrace_casptr(&hash[bucket].dtdh_chain, start, dvar) == start)
                return (dvar);

        /*
         * The cas has failed.  Either another CPU is adding an element to
         * this hash chain, or another CPU is deleting an element from this
         * hash chain.  The simplest way to deal with both of these cases
         * (though not necessarily the most efficient) is to free our
         * allocated block and tail-call ourselves.  Note that the free is
         * to the dirty list and _not_ to the free list.  This is to prevent
         * races with allocators, above.
         */
        dvar->dtdv_hashval = DTRACE_DYNHASH_FREE;

        dtrace_membar_producer();

        do {
                free = dcpu->dtdsc_dirty;
                dvar->dtdv_next = free;
        } while (dtrace_casptr(&dcpu->dtdsc_dirty, free, dvar) != free);

        return (dtrace_dynvar(dstate, nkeys, key, dsize, op, mstate, vstate));
}

/*ARGSUSED*/
static void
dtrace_aggregate_min(uint64_t *oval, uint64_t nval, uint64_t arg)
{
#pragma unused(arg) /* __APPLE__ */
        if ((int64_t)nval < (int64_t)*oval)
                *oval = nval;
}

/*ARGSUSED*/
static void
dtrace_aggregate_max(uint64_t *oval, uint64_t nval, uint64_t arg)
{
#pragma unused(arg) /* __APPLE__ */
        if ((int64_t)nval > (int64_t)*oval)
                *oval = nval;
}

static void
dtrace_aggregate_quantize(uint64_t *quanta, uint64_t nval, uint64_t incr)
{
        int i, zero = DTRACE_QUANTIZE_ZEROBUCKET;
        int64_t val = (int64_t)nval;

        if (val < 0) {
                for (i = 0; i < zero; i++) {
                        if (val <= DTRACE_QUANTIZE_BUCKETVAL(i)) {
                                quanta[i] += incr;
                                return;
                        }
                }
        } else {
                for (i = zero + 1; i < DTRACE_QUANTIZE_NBUCKETS; i++) {
                        if (val < DTRACE_QUANTIZE_BUCKETVAL(i)) {
                                quanta[i - 1] += incr;
                                return;
                        }
                }

                quanta[DTRACE_QUANTIZE_NBUCKETS - 1] += incr;
                return;
        }

        ASSERT(0);
}

static void
dtrace_aggregate_lquantize(uint64_t *lquanta, uint64_t nval, uint64_t incr)
{
        uint64_t arg = *lquanta++;
        int32_t base = DTRACE_LQUANTIZE_BASE(arg);
        uint16_t step = DTRACE_LQUANTIZE_STEP(arg);
        uint16_t levels = DTRACE_LQUANTIZE_LEVELS(arg);
        int32_t val = (int32_t)nval, level;

        ASSERT(step != 0);
        ASSERT(levels != 0);

        if (val < base) {
                /*
                 * This is an underflow.
                 */
                lquanta[0] += incr;
                return;
        }

        level = (val - base) / step;

        if (level < levels) {
                lquanta[level + 1] += incr;
                return;
        }

        /*
         * This is an overflow.
         */
        lquanta[levels + 1] += incr;
}

static int
dtrace_aggregate_llquantize_bucket(int16_t factor, int16_t low, int16_t high,
                                   int16_t nsteps, int64_t value)
{
        int64_t this = 1, last, next;
        int base = 1, order;

        for (order = 0; order < low; ++order)
                this *= factor;

        /*
         * If our value is less than our factor taken to the power of the
         * low order of magnitude, it goes into the zeroth bucket.
         */
        if (value < this)
                return 0;
        else
                last = this;

        for (this *= factor; order <= high; ++order) {
                int nbuckets = this > nsteps ? nsteps : this;

                /*
                 * We should not generally get log/linear quantizations
                 * with a high magnitude that allows 64-bits to
                 * overflow, but we nonetheless protect against this
                 * by explicitly checking for overflow, and clamping
                 * our value accordingly.
                 */
                next = this * factor;
                if (next < this) {
                        value = this - 1;
                }

                /*
                 * If our value lies within this order of magnitude,
                 * determine its position by taking the offset within
                 * the order of magnitude, dividing by the bucket
                 * width, and adding to our (accumulated) base.
                 */
                if (value < this) {
                        return (base + (value - last) / (this / nbuckets));
                }

                base += nbuckets - (nbuckets / factor);
                last = this;
                this = next;
        }

        /*
         * Our value is greater than or equal to our factor taken to the
         * power of one plus the high magnitude -- return the top bucket.
         */
        return base;
}

static void
dtrace_aggregate_llquantize(uint64_t *llquanta, uint64_t nval, uint64_t incr)
{
        uint64_t arg    = *llquanta++;
        uint16_t factor = DTRACE_LLQUANTIZE_FACTOR(arg);
        uint16_t low    = DTRACE_LLQUANTIZE_LOW(arg);
        uint16_t high   = DTRACE_LLQUANTIZE_HIGH(arg);
        uint16_t nsteps = DTRACE_LLQUANTIZE_NSTEP(arg);

        llquanta[dtrace_aggregate_llquantize_bucket(factor, low, high, nsteps, nval)] += incr;
}

/*ARGSUSED*/
static void
dtrace_aggregate_avg(uint64_t *data, uint64_t nval, uint64_t arg)
{
#pragma unused(arg) /* __APPLE__ */
        data[0]++;
        data[1] += nval;
}

/*ARGSUSED*/
static void
dtrace_aggregate_stddev(uint64_t *data, uint64_t nval, uint64_t arg)
{
#pragma unused(arg) /* __APPLE__ */
        int64_t snval = (int64_t)nval;
        uint64_t tmp[2];

        data[0]++;
        data[1] += nval;

        /*
         * What we want to say here is:
         *
         * data[2] += nval * nval;
         *
         * But given that nval is 64-bit, we could easily overflow, so
         * we do this as 128-bit arithmetic.
         */
        if (snval < 0)
                snval = -snval;

        dtrace_multiply_128((uint64_t)snval, (uint64_t)snval, tmp);
        dtrace_add_128(data + 2, tmp, data + 2);
}

/*ARGSUSED*/
static void
dtrace_aggregate_count(uint64_t *oval, uint64_t nval, uint64_t arg)
{
#pragma unused(nval, arg) /* __APPLE__ */
        *oval = *oval + 1;
}

/*ARGSUSED*/
static void
dtrace_aggregate_sum(uint64_t *oval, uint64_t nval, uint64_t arg)
{
#pragma unused(arg) /* __APPLE__ */
        *oval += nval;
}

/*
 * Aggregate given the tuple in the principal data buffer, and the aggregating
 * action denoted by the specified dtrace_aggregation_t.  The aggregation
 * buffer is specified as the buf parameter.  This routine does not return
 * failure; if there is no space in the aggregation buffer, the data will be
 * dropped, and a corresponding counter incremented.
 */
static void
dtrace_aggregate(dtrace_aggregation_t *agg, dtrace_buffer_t *dbuf,
    intptr_t offset, dtrace_buffer_t *buf, uint64_t expr, uint64_t arg)
{
#pragma unused(arg)
        dtrace_recdesc_t *rec = &agg->dtag_action.dta_rec;
        uint32_t i, ndx, size, fsize;
        uint32_t align = sizeof (uint64_t) - 1;
        dtrace_aggbuffer_t *agb;
        dtrace_aggkey_t *key;
        uint32_t hashval = 0, limit, isstr;
        caddr_t tomax, data, kdata;
        dtrace_actkind_t action;
        dtrace_action_t *act;
        uintptr_t offs;

        if (buf == NULL)
                return;

        if (!agg->dtag_hasarg) {
                /*
                 * Currently, only quantize() and lquantize() take additional
                 * arguments, and they have the same semantics:  an increment
                 * value that defaults to 1 when not present.  If additional
                 * aggregating actions take arguments, the setting of the
                 * default argument value will presumably have to become more
                 * sophisticated...
                 */
                arg = 1;
        }

        action = agg->dtag_action.dta_kind - DTRACEACT_AGGREGATION;
        size = rec->dtrd_offset - agg->dtag_base;
        fsize = size + rec->dtrd_size;

        ASSERT(dbuf->dtb_tomax != NULL);
        data = dbuf->dtb_tomax + offset + agg->dtag_base;

        if ((tomax = buf->dtb_tomax) == NULL) {
                dtrace_buffer_drop(buf);
                return;
        }

        /*
         * The metastructure is always at the bottom of the buffer.
         */
        agb = (dtrace_aggbuffer_t *)(tomax + buf->dtb_size -
            sizeof (dtrace_aggbuffer_t));

        if (buf->dtb_offset == 0) {
                /*
                 * We just kludge up approximately 1/8th of the size to be
                 * buckets.  If this guess ends up being routinely
                 * off-the-mark, we may need to dynamically readjust this
                 * based on past performance.
                 */
                uintptr_t hashsize = (buf->dtb_size >> 3) / sizeof (uintptr_t);

                if ((uintptr_t)agb - hashsize * sizeof (dtrace_aggkey_t *) <
                    (uintptr_t)tomax || hashsize == 0) {
                        /*
                         * We've been given a ludicrously small buffer;
                         * increment our drop count and leave.
                         */
                        dtrace_buffer_drop(buf);
                        return;
                }

                /*
                 * And now, a pathetic attempt to try to get a an odd (or
                 * perchance, a prime) hash size for better hash distribution.
                 */
                if (hashsize > (DTRACE_AGGHASHSIZE_SLEW << 3))
                        hashsize -= DTRACE_AGGHASHSIZE_SLEW;

                agb->dtagb_hashsize = hashsize;
                agb->dtagb_hash = (dtrace_aggkey_t **)((uintptr_t)agb -
                    agb->dtagb_hashsize * sizeof (dtrace_aggkey_t *));
                agb->dtagb_free = (uintptr_t)agb->dtagb_hash;

                for (i = 0; i < agb->dtagb_hashsize; i++)
                        agb->dtagb_hash[i] = NULL;
        }

        ASSERT(agg->dtag_first != NULL);
        ASSERT(agg->dtag_first->dta_intuple);

        /*
         * Calculate the hash value based on the key.  Note that we _don't_
         * include the aggid in the hashing (but we will store it as part of
         * the key).  The hashing algorithm is Bob Jenkins' "One-at-a-time"
         * algorithm: a simple, quick algorithm that has no known funnels, and
         * gets good distribution in practice.  The efficacy of the hashing
         * algorithm (and a comparison with other algorithms) may be found by
         * running the ::dtrace_aggstat MDB dcmd.
         */
        for (act = agg->dtag_first; act->dta_intuple; act = act->dta_next) {
                i = act->dta_rec.dtrd_offset - agg->dtag_base;
                limit = i + act->dta_rec.dtrd_size;
                ASSERT(limit <= size);
                isstr = DTRACEACT_ISSTRING(act);

                for (; i < limit; i++) {
                        hashval += data[i];
                        hashval += (hashval << 10);
                        hashval ^= (hashval >> 6);

                        if (isstr && data[i] == '\0')
                                break;
                }
        }

        hashval += (hashval << 3);
        hashval ^= (hashval >> 11);
        hashval += (hashval << 15);

        /*
         * Yes, the divide here is expensive -- but it's generally the least
         * of the performance issues given the amount of data that we iterate
         * over to compute hash values, compare data, etc.
         */
        ndx = hashval % agb->dtagb_hashsize;

        for (key = agb->dtagb_hash[ndx]; key != NULL; key = key->dtak_next) {
                ASSERT((caddr_t)key >= tomax);
                ASSERT((caddr_t)key < tomax + buf->dtb_size);

                if (hashval != key->dtak_hashval || key->dtak_size != size)
                        continue;

                kdata = key->dtak_data;
                ASSERT(kdata >= tomax && kdata < tomax + buf->dtb_size);

                for (act = agg->dtag_first; act->dta_intuple;
                    act = act->dta_next) {
                        i = act->dta_rec.dtrd_offset - agg->dtag_base;
                        limit = i + act->dta_rec.dtrd_size;
                        ASSERT(limit <= size);
                        isstr = DTRACEACT_ISSTRING(act);

                        for (; i < limit; i++) {
                                if (kdata[i] != data[i])
                                        goto next;

                                if (isstr && data[i] == '\0')
                                        break;
                        }
                }

                if (action != key->dtak_action) {
                        /*
                         * We are aggregating on the same value in the same
                         * aggregation with two different aggregating actions.
                         * (This should have been picked up in the compiler,
                         * so we may be dealing with errant or devious DIF.)
                         * This is an error condition; we indicate as much,
                         * and return.
                         */
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
                        return;
                }

                /*
                 * This is a hit:  we need to apply the aggregator to
                 * the value at this key.
                 */
                agg->dtag_aggregate((uint64_t *)(kdata + size), expr, arg);
                return;
next:
                continue;
        }

        /*
         * We didn't find it.  We need to allocate some zero-filled space,
         * link it into the hash table appropriately, and apply the aggregator
         * to the (zero-filled) value.
         */
        offs = buf->dtb_offset;
        while (offs & (align - 1))
                offs += sizeof (uint32_t);

        /*
         * If we don't have enough room to both allocate a new key _and_
         * its associated data, increment the drop count and return.
         */
        if ((uintptr_t)tomax + offs + fsize >
            agb->dtagb_free - sizeof (dtrace_aggkey_t)) {
                dtrace_buffer_drop(buf);
                return;
        }

        /*CONSTCOND*/
        ASSERT(!(sizeof (dtrace_aggkey_t) & (sizeof (uintptr_t) - 1)));
        key = (dtrace_aggkey_t *)(agb->dtagb_free - sizeof (dtrace_aggkey_t));
        agb->dtagb_free -= sizeof (dtrace_aggkey_t);

        key->dtak_data = kdata = tomax + offs;
        buf->dtb_offset = offs + fsize;

        /*
         * Now copy the data across.
         */
        *((dtrace_aggid_t *)kdata) = agg->dtag_id;

        for (i = sizeof (dtrace_aggid_t); i < size; i++)
                kdata[i] = data[i];

        /*
         * Because strings are not zeroed out by default, we need to iterate
         * looking for actions that store strings, and we need to explicitly
         * pad these strings out with zeroes.
         */
        for (act = agg->dtag_first; act->dta_intuple; act = act->dta_next) {
                int nul;

                if (!DTRACEACT_ISSTRING(act))
                        continue;

                i = act->dta_rec.dtrd_offset - agg->dtag_base;
                limit = i + act->dta_rec.dtrd_size;
                ASSERT(limit <= size);

                for (nul = 0; i < limit; i++) {
                        if (nul) {
                                kdata[i] = '\0';
                                continue;
                        }

                        if (data[i] != '\0')
                                continue;

                        nul = 1;
                }
        }

        for (i = size; i < fsize; i++)
                kdata[i] = 0;

        key->dtak_hashval = hashval;
        key->dtak_size = size;
        key->dtak_action = action;
        key->dtak_next = agb->dtagb_hash[ndx];
        agb->dtagb_hash[ndx] = key;

        /*
         * Finally, apply the aggregator.
         */
        *((uint64_t *)(key->dtak_data + size)) = agg->dtag_initial;
        agg->dtag_aggregate((uint64_t *)(key->dtak_data + size), expr, arg);
}

/*
 * Given consumer state, this routine finds a speculation in the INACTIVE
 * state and transitions it into the ACTIVE state.  If there is no speculation
 * in the INACTIVE state, 0 is returned.  In this case, no error counter is
 * incremented -- it is up to the caller to take appropriate action.
 */
static int
dtrace_speculation(dtrace_state_t *state)
{
        int i = 0;
        dtrace_speculation_state_t current;
        uint32_t *stat = &state->dts_speculations_unavail, count;

        while (i < state->dts_nspeculations) {
                dtrace_speculation_t *spec = &state->dts_speculations[i];

                current = spec->dtsp_state;

                if (current != DTRACESPEC_INACTIVE) {
                        if (current == DTRACESPEC_COMMITTINGMANY ||
                            current == DTRACESPEC_COMMITTING ||
                            current == DTRACESPEC_DISCARDING)
                                stat = &state->dts_speculations_busy;
                        i++;
                        continue;
                }

                if (dtrace_cas32((uint32_t *)&spec->dtsp_state,
                    current, DTRACESPEC_ACTIVE) == current)
                        return (i + 1);
        }

        /*
         * We couldn't find a speculation.  If we found as much as a single
         * busy speculation buffer, we'll attribute this failure as "busy"
         * instead of "unavail".
         */
        do {
                count = *stat;
        } while (dtrace_cas32(stat, count, count + 1) != count);

        return (0);
}

/*
 * This routine commits an active speculation.  If the specified speculation
 * is not in a valid state to perform a commit(), this routine will silently do
 * nothing.  The state of the specified speculation is transitioned according
 * to the state transition diagram outlined in <sys/dtrace_impl.h>
 */
static void
dtrace_speculation_commit(dtrace_state_t *state, processorid_t cpu,
    dtrace_specid_t which)
{
        dtrace_speculation_t *spec;
        dtrace_buffer_t *src, *dest;
        uintptr_t daddr, saddr, dlimit, slimit;
        dtrace_speculation_state_t current,  new = DTRACESPEC_INACTIVE;
        intptr_t offs;
        uint64_t timestamp;

        if (which == 0)
                return;

        if (which > (dtrace_specid_t)state->dts_nspeculations) {
                cpu_core[cpu].cpuc_dtrace_flags |= CPU_DTRACE_ILLOP;
                return;
        }
        
        spec = &state->dts_speculations[which - 1];
        src = &spec->dtsp_buffer[cpu];
        dest = &state->dts_buffer[cpu];

        do {
                current = spec->dtsp_state;

                if (current == DTRACESPEC_COMMITTINGMANY)
                        break;

                switch (current) {
                case DTRACESPEC_INACTIVE:
                case DTRACESPEC_DISCARDING:
                        return;

                case DTRACESPEC_COMMITTING:
                        /*
                         * This is only possible if we are (a) commit()'ing
                         * without having done a prior speculate() on this CPU
                         * and (b) racing with another commit() on a different
                         * CPU.  There's nothing to do -- we just assert that
                         * our offset is 0.
                         */
                        ASSERT(src->dtb_offset == 0);
                        return;

                case DTRACESPEC_ACTIVE:
                        new = DTRACESPEC_COMMITTING;
                        break;

                case DTRACESPEC_ACTIVEONE:
                        /*
                         * This speculation is active on one CPU.  If our
                         * buffer offset is non-zero, we know that the one CPU
                         * must be us.  Otherwise, we are committing on a
                         * different CPU from the speculate(), and we must
                         * rely on being asynchronously cleaned.
                         */
                        if (src->dtb_offset != 0) {
                                new = DTRACESPEC_COMMITTING;
                                break;
                        }
                        /*FALLTHROUGH*/

                case DTRACESPEC_ACTIVEMANY:
                        new = DTRACESPEC_COMMITTINGMANY;
                        break;

                default:
                        ASSERT(0);
                }
        } while (dtrace_cas32((uint32_t *)&spec->dtsp_state,
            current, new) != current);

        /*
         * We have set the state to indicate that we are committing this
         * speculation.  Now reserve the necessary space in the destination
         * buffer.
         */
        if ((offs = dtrace_buffer_reserve(dest, src->dtb_offset,
            sizeof (uint64_t), state, NULL)) < 0) {
                dtrace_buffer_drop(dest);
                goto out;
        }

        /*
         * We have sufficient space to copy the speculative buffer into the
         * primary buffer.  First, modify the speculative buffer, filling
         * in the timestamp of all entries with the current time.  The data
         * must have the commit() time rather than the time it was traced,
         * so that all entries in the primary buffer are in timestamp order.
         */
        timestamp = dtrace_gethrtime();
        saddr = (uintptr_t)src->dtb_tomax;
        slimit = saddr + src->dtb_offset;
        while (saddr < slimit) {
                size_t size;
                dtrace_rechdr_t *dtrh = (dtrace_rechdr_t *)saddr;

                if (dtrh->dtrh_epid == DTRACE_EPIDNONE) {
                        saddr += sizeof (dtrace_epid_t);
                        continue;
                }

                ASSERT(dtrh->dtrh_epid <= ((dtrace_epid_t) state->dts_necbs));
                size = state->dts_ecbs[dtrh->dtrh_epid - 1]->dte_size;

                ASSERT(saddr + size <= slimit);
                ASSERT(size >= sizeof(dtrace_rechdr_t));
                ASSERT(DTRACE_RECORD_LOAD_TIMESTAMP(dtrh) == UINT64_MAX);

                DTRACE_RECORD_STORE_TIMESTAMP(dtrh, timestamp);

                saddr += size;
        }

        /*
         * Copy the buffer across.  (Note that this is a
         * highly subobtimal bcopy(); in the unlikely event that this becomes
         * a serious performance issue, a high-performance DTrace-specific
         * bcopy() should obviously be invented.)
         */
        daddr = (uintptr_t)dest->dtb_tomax + offs;
        dlimit = daddr + src->dtb_offset;
        saddr = (uintptr_t)src->dtb_tomax;

        /*
         * First, the aligned portion.
         */
        while (dlimit - daddr >= sizeof (uint64_t)) {
                *((uint64_t *)daddr) = *((uint64_t *)saddr);

                daddr += sizeof (uint64_t);
                saddr += sizeof (uint64_t);
        }

        /*
         * Now any left-over bit...
         */
        while (dlimit - daddr)
                *((uint8_t *)daddr++) = *((uint8_t *)saddr++);

        /*
         * Finally, commit the reserved space in the destination buffer.
         */
        dest->dtb_offset = offs + src->dtb_offset;

out:
        /*
         * If we're lucky enough to be the only active CPU on this speculation
         * buffer, we can just set the state back to DTRACESPEC_INACTIVE.
         */
        if (current == DTRACESPEC_ACTIVE ||
            (current == DTRACESPEC_ACTIVEONE && new == DTRACESPEC_COMMITTING)) {
                uint32_t rval = dtrace_cas32((uint32_t *)&spec->dtsp_state,
                    DTRACESPEC_COMMITTING, DTRACESPEC_INACTIVE);
#pragma unused(rval) /* __APPLE__ */

                ASSERT(rval == DTRACESPEC_COMMITTING);
        }

        src->dtb_offset = 0;
        src->dtb_xamot_drops += src->dtb_drops;
        src->dtb_drops = 0;
}

/*
 * This routine discards an active speculation.  If the specified speculation
 * is not in a valid state to perform a discard(), this routine will silently
 * do nothing.  The state of the specified speculation is transitioned
 * according to the state transition diagram outlined in <sys/dtrace_impl.h>
 */
static void
dtrace_speculation_discard(dtrace_state_t *state, processorid_t cpu,
    dtrace_specid_t which)
{
        dtrace_speculation_t *spec;
        dtrace_speculation_state_t current, new = DTRACESPEC_INACTIVE;
        dtrace_buffer_t *buf;

        if (which == 0)
                return;

        if (which > (dtrace_specid_t)state->dts_nspeculations) {
                cpu_core[cpu].cpuc_dtrace_flags |= CPU_DTRACE_ILLOP;
                return;
        }

        spec = &state->dts_speculations[which - 1];
        buf = &spec->dtsp_buffer[cpu];

        do {
                current = spec->dtsp_state;

                switch (current) {
                case DTRACESPEC_INACTIVE:
                case DTRACESPEC_COMMITTINGMANY:
                case DTRACESPEC_COMMITTING:
                case DTRACESPEC_DISCARDING:
                        return;

                case DTRACESPEC_ACTIVE:
                case DTRACESPEC_ACTIVEMANY:
                        new = DTRACESPEC_DISCARDING;
                        break;

                case DTRACESPEC_ACTIVEONE:
                        if (buf->dtb_offset != 0) {
                                new = DTRACESPEC_INACTIVE;
                        } else {
                                new = DTRACESPEC_DISCARDING;
                        }
                        break;

                default:
                        ASSERT(0);
                }
        } while (dtrace_cas32((uint32_t *)&spec->dtsp_state,
            current, new) != current);

        buf->dtb_offset = 0;
        buf->dtb_drops = 0;
}

/*
 * Note:  not called from probe context.  This function is called
 * asynchronously from cross call context to clean any speculations that are
 * in the COMMITTINGMANY or DISCARDING states.  These speculations may not be
 * transitioned back to the INACTIVE state until all CPUs have cleaned the
 * speculation.
 */
static void
dtrace_speculation_clean_here(dtrace_state_t *state)
{
        dtrace_icookie_t cookie;
        processorid_t cpu = CPU->cpu_id;
        dtrace_buffer_t *dest = &state->dts_buffer[cpu];
        dtrace_specid_t i;

        cookie = dtrace_interrupt_disable();

        if (dest->dtb_tomax == NULL) {
                dtrace_interrupt_enable(cookie);
                return;
        }

        for (i = 0; i < (dtrace_specid_t)state->dts_nspeculations; i++) {
                dtrace_speculation_t *spec = &state->dts_speculations[i];
                dtrace_buffer_t *src = &spec->dtsp_buffer[cpu];

                if (src->dtb_tomax == NULL)
                        continue;

                if (spec->dtsp_state == DTRACESPEC_DISCARDING) {
                        src->dtb_offset = 0;
                        continue;
                }

                if (spec->dtsp_state != DTRACESPEC_COMMITTINGMANY)
                        continue;

                if (src->dtb_offset == 0)
                        continue;

                dtrace_speculation_commit(state, cpu, i + 1);
        }

        dtrace_interrupt_enable(cookie);
}

/*
 * Note:  not called from probe context.  This function is called
 * asynchronously (and at a regular interval) to clean any speculations that
 * are in the COMMITTINGMANY or DISCARDING states.  If it discovers that there
 * is work to be done, it cross calls all CPUs to perform that work;
 * COMMITMANY and DISCARDING speculations may not be transitioned back to the
 * INACTIVE state until they have been cleaned by all CPUs.
 */
static void
dtrace_speculation_clean(dtrace_state_t *state)
{
        int work = 0;
        uint32_t rv;
        dtrace_specid_t i;

        for (i = 0; i < (dtrace_specid_t)state->dts_nspeculations; i++) {
                dtrace_speculation_t *spec = &state->dts_speculations[i];

                ASSERT(!spec->dtsp_cleaning);

                if (spec->dtsp_state != DTRACESPEC_DISCARDING &&
                    spec->dtsp_state != DTRACESPEC_COMMITTINGMANY)
                        continue;

                work++;
                spec->dtsp_cleaning = 1;
        }

        if (!work)
                return;

        dtrace_xcall(DTRACE_CPUALL,
            (dtrace_xcall_t)dtrace_speculation_clean_here, state);

        /*
         * We now know that all CPUs have committed or discarded their
         * speculation buffers, as appropriate.  We can now set the state
         * to inactive.
         */
        for (i = 0; i < (dtrace_specid_t)state->dts_nspeculations; i++) {
                dtrace_speculation_t *spec = &state->dts_speculations[i];
                dtrace_speculation_state_t current, new;

                if (!spec->dtsp_cleaning)
                        continue;

                current = spec->dtsp_state;
                ASSERT(current == DTRACESPEC_DISCARDING ||
                    current == DTRACESPEC_COMMITTINGMANY);

                new = DTRACESPEC_INACTIVE;

                rv = dtrace_cas32((uint32_t *)&spec->dtsp_state, current, new);
                ASSERT(rv == current);
                spec->dtsp_cleaning = 0;
        }
}

/*
 * Called as part of a speculate() to get the speculative buffer associated
 * with a given speculation.  Returns NULL if the specified speculation is not
 * in an ACTIVE state.  If the speculation is in the ACTIVEONE state -- and
 * the active CPU is not the specified CPU -- the speculation will be
 * atomically transitioned into the ACTIVEMANY state.
 */
static dtrace_buffer_t *
dtrace_speculation_buffer(dtrace_state_t *state, processorid_t cpuid,
    dtrace_specid_t which)
{
        dtrace_speculation_t *spec;
        dtrace_speculation_state_t current, new = DTRACESPEC_INACTIVE;
        dtrace_buffer_t *buf;

        if (which == 0)
                return (NULL);

        if (which > (dtrace_specid_t)state->dts_nspeculations) {
                cpu_core[cpuid].cpuc_dtrace_flags |= CPU_DTRACE_ILLOP;
                return (NULL);
        }

        spec = &state->dts_speculations[which - 1];
        buf = &spec->dtsp_buffer[cpuid];

        do {
                current = spec->dtsp_state;

                switch (current) {
                case DTRACESPEC_INACTIVE:
                case DTRACESPEC_COMMITTINGMANY:
                case DTRACESPEC_DISCARDING:
                        return (NULL);

                case DTRACESPEC_COMMITTING:
                        ASSERT(buf->dtb_offset == 0);
                        return (NULL);

                case DTRACESPEC_ACTIVEONE:
                        /*
                         * This speculation is currently active on one CPU.
                         * Check the offset in the buffer; if it's non-zero,
                         * that CPU must be us (and we leave the state alone).
                         * If it's zero, assume that we're starting on a new
                         * CPU -- and change the state to indicate that the
                         * speculation is active on more than one CPU.
                         */
                        if (buf->dtb_offset != 0)
                                return (buf);

                        new = DTRACESPEC_ACTIVEMANY;
                        break;

                case DTRACESPEC_ACTIVEMANY:
                        return (buf);

                case DTRACESPEC_ACTIVE:
                        new = DTRACESPEC_ACTIVEONE;
                        break;

                default:
                        ASSERT(0);
                }
        } while (dtrace_cas32((uint32_t *)&spec->dtsp_state,
            current, new) != current);

        ASSERT(new == DTRACESPEC_ACTIVEONE || new == DTRACESPEC_ACTIVEMANY);
        return (buf);
}

/*
 * Return a string.  In the event that the user lacks the privilege to access
 * arbitrary kernel memory, we copy the string out to scratch memory so that we
 * don't fail access checking.
 *
 * dtrace_dif_variable() uses this routine as a helper for various
 * builtin values such as 'execname' and 'probefunc.'
 */
static
uintptr_t
dtrace_dif_varstr(uintptr_t addr, dtrace_state_t *state,
    dtrace_mstate_t *mstate)
{
        uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];
        uintptr_t ret;
        size_t strsz;

        /*
         * The easy case: this probe is allowed to read all of memory, so
         * we can just return this as a vanilla pointer.
         */
        if ((mstate->dtms_access & DTRACE_ACCESS_KERNEL) != 0)
                return (addr);

        /*
         * This is the tougher case: we copy the string in question from
         * kernel memory into scratch memory and return it that way: this
         * ensures that we won't trip up when access checking tests the
         * BYREF return value.
         */
        strsz = dtrace_strlen((char *)addr, size) + 1;

        if (mstate->dtms_scratch_ptr + strsz >
            mstate->dtms_scratch_base + mstate->dtms_scratch_size) {
                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                return (0);
        }

        dtrace_strcpy((const void *)addr, (void *)mstate->dtms_scratch_ptr,
            strsz);
        ret = mstate->dtms_scratch_ptr;
        mstate->dtms_scratch_ptr += strsz;
        return (ret);
}

/*
 * This function implements the DIF emulator's variable lookups.  The emulator
 * passes a reserved variable identifier and optional built-in array index.
 */
static uint64_t
dtrace_dif_variable(dtrace_mstate_t *mstate, dtrace_state_t *state, uint64_t v,
    uint64_t ndx)
{
        /*
         * If we're accessing one of the uncached arguments, we'll turn this
         * into a reference in the args array.
         */
        if (v >= DIF_VAR_ARG0 && v <= DIF_VAR_ARG9) {
                ndx = v - DIF_VAR_ARG0;
                v = DIF_VAR_ARGS;
        }

        switch (v) {
        case DIF_VAR_ARGS:
                ASSERT(mstate->dtms_present & DTRACE_MSTATE_ARGS);
                if (ndx >= sizeof (mstate->dtms_arg) /
                    sizeof (mstate->dtms_arg[0])) {
                        int aframes = mstate->dtms_probe->dtpr_aframes + 2;
                        dtrace_vstate_t *vstate = &state->dts_vstate;
                        dtrace_provider_t *pv;
                        uint64_t val;

                        pv = mstate->dtms_probe->dtpr_provider;
                        if (pv->dtpv_pops.dtps_getargval != NULL)
                                val = pv->dtpv_pops.dtps_getargval(pv->dtpv_arg,
                                    mstate->dtms_probe->dtpr_id,
                                    mstate->dtms_probe->dtpr_arg, ndx, aframes);
                        /* Special case access of arg5 as passed to dtrace_probe_error() (which see.) */
                        else if (mstate->dtms_probe->dtpr_id == dtrace_probeid_error && ndx == 5) {
                                return ((dtrace_state_t *)(uintptr_t)(mstate->dtms_arg[0]))->dts_arg_error_illval;
                        }

                        else
                                val = dtrace_getarg(ndx, aframes, mstate, vstate);

                        /*
                         * This is regrettably required to keep the compiler
                         * from tail-optimizing the call to dtrace_getarg().
                         * The condition always evaluates to true, but the
                         * compiler has no way of figuring that out a priori.
                         * (None of this would be necessary if the compiler
                         * could be relied upon to _always_ tail-optimize
                         * the call to dtrace_getarg() -- but it can't.)
                         */
                        if (mstate->dtms_probe != NULL)
                                return (val);

                        ASSERT(0);
                }

                return (mstate->dtms_arg[ndx]);

        case DIF_VAR_UREGS: {
                thread_t thread;

                if (!dtrace_priv_proc(state))
                        return (0);

                if ((thread = current_thread()) == NULL) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_BADADDR);
                        cpu_core[CPU->cpu_id].cpuc_dtrace_illval = 0;
                        return (0);
                }

                return (dtrace_getreg(find_user_regs(thread), ndx));
        }


        case DIF_VAR_CURTHREAD:
                if (!dtrace_priv_kernel(state))
                        return (0);

                return ((uint64_t)(uintptr_t)current_thread());

        case DIF_VAR_TIMESTAMP:
                if (!(mstate->dtms_present & DTRACE_MSTATE_TIMESTAMP)) {
                        mstate->dtms_timestamp = dtrace_gethrtime();
                        mstate->dtms_present |= DTRACE_MSTATE_TIMESTAMP;
                }
                return (mstate->dtms_timestamp);

        case DIF_VAR_VTIMESTAMP:
                ASSERT(dtrace_vtime_references != 0);
                return (dtrace_get_thread_vtime(current_thread()));

        case DIF_VAR_WALLTIMESTAMP:
                if (!(mstate->dtms_present & DTRACE_MSTATE_WALLTIMESTAMP)) {
                        mstate->dtms_walltimestamp = dtrace_gethrestime();
                        mstate->dtms_present |= DTRACE_MSTATE_WALLTIMESTAMP;
                }
                return (mstate->dtms_walltimestamp);

        case DIF_VAR_MACHTIMESTAMP:
                if (!(mstate->dtms_present & DTRACE_MSTATE_MACHTIMESTAMP)) {
                        mstate->dtms_machtimestamp = mach_absolute_time();
                        mstate->dtms_present |= DTRACE_MSTATE_MACHTIMESTAMP;
                }
                return (mstate->dtms_machtimestamp);

        case DIF_VAR_CPU:
                return ((uint64_t) dtrace_get_thread_last_cpu_id(current_thread()));

        case DIF_VAR_IPL:
                if (!dtrace_priv_kernel(state))
                        return (0);
                if (!(mstate->dtms_present & DTRACE_MSTATE_IPL)) {
                        mstate->dtms_ipl = dtrace_getipl();
                        mstate->dtms_present |= DTRACE_MSTATE_IPL;
                }
                return (mstate->dtms_ipl);

        case DIF_VAR_EPID:
                ASSERT(mstate->dtms_present & DTRACE_MSTATE_EPID);
                return (mstate->dtms_epid);

        case DIF_VAR_ID:
                ASSERT(mstate->dtms_present & DTRACE_MSTATE_PROBE);
                return (mstate->dtms_probe->dtpr_id);

        case DIF_VAR_STACKDEPTH:
                if (!dtrace_priv_kernel(state))
                        return (0);
                if (!(mstate->dtms_present & DTRACE_MSTATE_STACKDEPTH)) {
                        int aframes = mstate->dtms_probe->dtpr_aframes + 2;

                        mstate->dtms_stackdepth = dtrace_getstackdepth(aframes);
                        mstate->dtms_present |= DTRACE_MSTATE_STACKDEPTH;
                }
                return (mstate->dtms_stackdepth);

        case DIF_VAR_USTACKDEPTH:
                if (!dtrace_priv_proc(state))
                        return (0);
                if (!(mstate->dtms_present & DTRACE_MSTATE_USTACKDEPTH)) {
                        /*
                         * See comment in DIF_VAR_PID.
                         */
                        if (DTRACE_ANCHORED(mstate->dtms_probe) &&
                            CPU_ON_INTR(CPU)) {
                                mstate->dtms_ustackdepth = 0;
                        } else {
                                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                                mstate->dtms_ustackdepth =
                                    dtrace_getustackdepth();
                                DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
                        }
                        mstate->dtms_present |= DTRACE_MSTATE_USTACKDEPTH;
                }
                return (mstate->dtms_ustackdepth);

        case DIF_VAR_CALLER:
                if (!dtrace_priv_kernel(state))
                        return (0);
                if (!(mstate->dtms_present & DTRACE_MSTATE_CALLER)) {
                        int aframes = mstate->dtms_probe->dtpr_aframes + 2;

                        if (!DTRACE_ANCHORED(mstate->dtms_probe)) {
                                /*
                                 * If this is an unanchored probe, we are
                                 * required to go through the slow path:
                                 * dtrace_caller() only guarantees correct
                                 * results for anchored probes.
                                 */
                                pc_t caller[2];

                                dtrace_getpcstack(caller, 2, aframes,
                                    (uint32_t *)(uintptr_t)mstate->dtms_arg[0]);
                                mstate->dtms_caller = caller[1];
                        } else if ((mstate->dtms_caller =
                                dtrace_caller(aframes)) == (uintptr_t)-1) {
                                /*
                                 * We have failed to do this the quick way;
                                 * we must resort to the slower approach of
                                 * calling dtrace_getpcstack().
                                 */
                                pc_t caller;

                                dtrace_getpcstack(&caller, 1, aframes, NULL);
                                mstate->dtms_caller = caller;
                        }

                        mstate->dtms_present |= DTRACE_MSTATE_CALLER;
                }
                return (mstate->dtms_caller);

        case DIF_VAR_UCALLER:
                if (!dtrace_priv_proc(state))
                        return (0);

                if (!(mstate->dtms_present & DTRACE_MSTATE_UCALLER)) {
                        uint64_t ustack[3];

                        /*
                         * dtrace_getupcstack() fills in the first uint64_t
                         * with the current PID.  The second uint64_t will
                         * be the program counter at user-level.  The third
                         * uint64_t will contain the caller, which is what
                         * we're after.
                         */
                        ustack[2] = 0;
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                        dtrace_getupcstack(ustack, 3);
                        DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
                        mstate->dtms_ucaller = ustack[2];
                        mstate->dtms_present |= DTRACE_MSTATE_UCALLER;
                }

                return (mstate->dtms_ucaller);

        case DIF_VAR_PROBEPROV:
                ASSERT(mstate->dtms_present & DTRACE_MSTATE_PROBE);
                return (dtrace_dif_varstr(
                    (uintptr_t)mstate->dtms_probe->dtpr_provider->dtpv_name,
                    state, mstate));

        case DIF_VAR_PROBEMOD:
                ASSERT(mstate->dtms_present & DTRACE_MSTATE_PROBE);
                return (dtrace_dif_varstr(
                    (uintptr_t)mstate->dtms_probe->dtpr_mod,
                    state, mstate));

        case DIF_VAR_PROBEFUNC:
                ASSERT(mstate->dtms_present & DTRACE_MSTATE_PROBE);
                return (dtrace_dif_varstr(
                    (uintptr_t)mstate->dtms_probe->dtpr_func,
                    state, mstate));

        case DIF_VAR_PROBENAME:
                ASSERT(mstate->dtms_present & DTRACE_MSTATE_PROBE);
                return (dtrace_dif_varstr(
                    (uintptr_t)mstate->dtms_probe->dtpr_name,
                    state, mstate));

        case DIF_VAR_PID:
                if (!dtrace_priv_proc_relaxed(state))
                        return (0);

                /*
                 * Note that we are assuming that an unanchored probe is
                 * always due to a high-level interrupt.  (And we're assuming
                 * that there is only a single high level interrupt.)
                 */
                if (DTRACE_ANCHORED(mstate->dtms_probe) && CPU_ON_INTR(CPU))
                        /* Anchored probe that fires while on an interrupt accrues to process 0 */
                        return 0; 

                return ((uint64_t)dtrace_proc_selfpid());

        case DIF_VAR_PPID:
                if (!dtrace_priv_proc_relaxed(state))
                        return (0);

                /*
                 * See comment in DIF_VAR_PID.
                 */
                if (DTRACE_ANCHORED(mstate->dtms_probe) && CPU_ON_INTR(CPU))
                        return (0);

                return ((uint64_t)dtrace_proc_selfppid());

        case DIF_VAR_TID:
                /* We do not need to check for null current_thread() */
                return thread_tid(current_thread()); /* globally unique */

        case DIF_VAR_PTHREAD_SELF:
                if (!dtrace_priv_proc(state))
                        return (0);

                /* Not currently supported, but we should be able to delta the dispatchqaddr and dispatchqoffset to get pthread_self */
                return 0;

        case DIF_VAR_DISPATCHQADDR:
                if (!dtrace_priv_proc(state))
                        return (0);

                /* We do not need to check for null current_thread() */
                return thread_dispatchqaddr(current_thread());

        case DIF_VAR_EXECNAME:
        {
                char *xname = (char *)mstate->dtms_scratch_ptr;
                size_t scratch_size = MAXCOMLEN+1;
                
                /* The scratch allocation's lifetime is that of the clause. */
                if (!DTRACE_INSCRATCH(mstate, scratch_size)) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                        return 0;
                }
                        
                if (!dtrace_priv_proc_relaxed(state))
                        return (0);

                mstate->dtms_scratch_ptr += scratch_size;
                proc_selfname( xname, scratch_size );

                return ((uint64_t)(uintptr_t)xname);
        }


        case DIF_VAR_ZONENAME:
        {
                /* scratch_size is equal to length('global') + 1 for the null-terminator. */
                char *zname = (char *)mstate->dtms_scratch_ptr;
                size_t scratch_size = 6 + 1;

                if (!dtrace_priv_proc(state))
                        return (0);

                /* The scratch allocation's lifetime is that of the clause. */
                if (!DTRACE_INSCRATCH(mstate, scratch_size)) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                        return 0;
                }

                mstate->dtms_scratch_ptr += scratch_size;

                /* The kernel does not provide zonename, it will always return 'global'. */
                strlcpy(zname, "global", scratch_size);

                return ((uint64_t)(uintptr_t)zname);
        }

#if MONOTONIC
        case DIF_VAR_CPUINSTRS:
                return mt_cur_cpu_instrs();

        case DIF_VAR_CPUCYCLES:
                return mt_cur_cpu_cycles();

        case DIF_VAR_VINSTRS:
                return mt_cur_thread_instrs();

        case DIF_VAR_VCYCLES:
                return mt_cur_thread_cycles();
#else /* MONOTONIC */
        case DIF_VAR_CPUINSTRS: /* FALLTHROUGH */
        case DIF_VAR_CPUCYCLES: /* FALLTHROUGH */
        case DIF_VAR_VINSTRS: /* FALLTHROUGH */
        case DIF_VAR_VCYCLES: /* FALLTHROUGH */
                return 0;
#endif /* !MONOTONIC */

        case DIF_VAR_UID:
                if (!dtrace_priv_proc_relaxed(state))
                        return (0);

                /*
                 * See comment in DIF_VAR_PID.
                 */
                if (DTRACE_ANCHORED(mstate->dtms_probe) && CPU_ON_INTR(CPU))
                        return (0);

                return ((uint64_t) dtrace_proc_selfruid());

        case DIF_VAR_GID:
                if (!dtrace_priv_proc(state))
                        return (0);

                /*
                 * See comment in DIF_VAR_PID.
                 */
                if (DTRACE_ANCHORED(mstate->dtms_probe) && CPU_ON_INTR(CPU))
                        return (0);

                if (dtrace_CRED() != NULL)
                        /* Credential does not require lazy initialization. */
                        return ((uint64_t)kauth_getgid());
                else {
                        /* proc_lock would be taken under kauth_cred_proc_ref() in kauth_cred_get(). */
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
                        return -1ULL;
                }

        case DIF_VAR_ERRNO: {
                uthread_t uthread = (uthread_t)get_bsdthread_info(current_thread());
                if (!dtrace_priv_proc(state))
                        return (0);

                /*
                 * See comment in DIF_VAR_PID.
                 */
                if (DTRACE_ANCHORED(mstate->dtms_probe) && CPU_ON_INTR(CPU))
                        return (0);

                if (uthread)
                        return (uint64_t)uthread->t_dtrace_errno;
                else {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
                        return -1ULL;
                }
        }

        default:
                DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
                return (0);
        }
}

typedef enum dtrace_json_state {
        DTRACE_JSON_REST = 1,
        DTRACE_JSON_OBJECT,
        DTRACE_JSON_STRING,
        DTRACE_JSON_STRING_ESCAPE,
        DTRACE_JSON_STRING_ESCAPE_UNICODE,
        DTRACE_JSON_COLON,
        DTRACE_JSON_COMMA,
        DTRACE_JSON_VALUE,
        DTRACE_JSON_IDENTIFIER,
        DTRACE_JSON_NUMBER,
        DTRACE_JSON_NUMBER_FRAC,
        DTRACE_JSON_NUMBER_EXP,
        DTRACE_JSON_COLLECT_OBJECT
} dtrace_json_state_t;

/*
 * This function possesses just enough knowledge about JSON to extract a single
 * value from a JSON string and store it in the scratch buffer.  It is able
 * to extract nested object values, and members of arrays by index.
 *
 * elemlist is a list of JSON keys, stored as packed NUL-terminated strings, to
 * be looked up as we descend into the object tree.  e.g.
 *
 *    foo[0].bar.baz[32] --> "foo" NUL "0" NUL "bar" NUL "baz" NUL "32" NUL
 *       with nelems = 5.
 *
 * The run time of this function must be bounded above by strsize to limit the
 * amount of work done in probe context.  As such, it is implemented as a
 * simple state machine, reading one character at a time using safe loads
 * until we find the requested element, hit a parsing error or run off the
 * end of the object or string.
 *
 * As there is no way for a subroutine to return an error without interrupting
 * clause execution, we simply return NULL in the event of a missing key or any
 * other error condition.  Each NULL return in this function is commented with
 * the error condition it represents -- parsing or otherwise.
 *
 * The set of states for the state machine closely matches the JSON
 * specification (http://json.org/).  Briefly:
 *
 *   DTRACE_JSON_REST:
 *     Skip whitespace until we find either a top-level Object, moving
 *     to DTRACE_JSON_OBJECT; or an Array, moving to DTRACE_JSON_VALUE.
 *
 *   DTRACE_JSON_OBJECT:
 *     Locate the next key String in an Object.  Sets a flag to denote
 *     the next String as a key string and moves to DTRACE_JSON_STRING.
 *
 *   DTRACE_JSON_COLON:
 *     Skip whitespace until we find the colon that separates key Strings
 *     from their values.  Once found, move to DTRACE_JSON_VALUE.
 *
 *   DTRACE_JSON_VALUE:
 *     Detects the type of the next value (String, Number, Identifier, Object
 *     or Array) and routes to the states that process that type.  Here we also
 *     deal with the element selector list if we are requested to traverse down
 *     into the object tree.
 *
 *   DTRACE_JSON_COMMA:
 *     Skip whitespace until we find the comma that separates key-value pairs
 *     in Objects (returning to DTRACE_JSON_OBJECT) or values in Arrays
 *     (similarly DTRACE_JSON_VALUE).  All following literal value processing
 *     states return to this state at the end of their value, unless otherwise
 *     noted.
 *
 *   DTRACE_JSON_NUMBER, DTRACE_JSON_NUMBER_FRAC, DTRACE_JSON_NUMBER_EXP:
 *     Processes a Number literal from the JSON, including any exponent
 *     component that may be present.  Numbers are returned as strings, which
 *     may be passed to strtoll() if an integer is required.
 *
 *   DTRACE_JSON_IDENTIFIER:
 *     Processes a "true", "false" or "null" literal in the JSON.
 *
 *   DTRACE_JSON_STRING, DTRACE_JSON_STRING_ESCAPE,
 *   DTRACE_JSON_STRING_ESCAPE_UNICODE:
 *     Processes a String literal from the JSON, whether the String denotes
 *     a key, a value or part of a larger Object.  Handles all escape sequences
 *     present in the specification, including four-digit unicode characters,
 *     but merely includes the escape sequence without converting it to the
 *     actual escaped character.  If the String is flagged as a key, we
 *     move to DTRACE_JSON_COLON rather than DTRACE_JSON_COMMA.
 *
 *   DTRACE_JSON_COLLECT_OBJECT:
 *     This state collects an entire Object (or Array), correctly handling
 *     embedded strings.  If the full element selector list matches this nested
 *     object, we return the Object in full as a string.  If not, we use this
 *     state to skip to the next value at this level and continue processing.
 */
static char *
dtrace_json(uint64_t size, uintptr_t json, char *elemlist, int nelems,
    char *dest)
{
        dtrace_json_state_t state = DTRACE_JSON_REST;
        int64_t array_elem = INT64_MIN;
        int64_t array_pos = 0;
        uint8_t escape_unicount = 0;
        boolean_t string_is_key = B_FALSE;
        boolean_t collect_object = B_FALSE;
        boolean_t found_key = B_FALSE;
        boolean_t in_array = B_FALSE;
        uint32_t braces = 0, brackets = 0;
        char *elem = elemlist;
        char *dd = dest;
        uintptr_t cur;

        for (cur = json; cur < json + size; cur++) {
                char cc = dtrace_load8(cur);
                if (cc == '\0')
                        return (NULL);

                switch (state) {
                case DTRACE_JSON_REST:
                        if (isspace(cc))
                                break;

                        if (cc == '{') {
                                state = DTRACE_JSON_OBJECT;
                                break;
                        }

                        if (cc == '[') {
                                in_array = B_TRUE;
                                array_pos = 0;
                                array_elem = dtrace_strtoll(elem, 10, size);
                                found_key = array_elem == 0 ? B_TRUE : B_FALSE;
                                state = DTRACE_JSON_VALUE;
                                break;
                        }

                        /*
                         * ERROR: expected to find a top-level object or array.
                         */
                        return (NULL);
                case DTRACE_JSON_OBJECT:
                        if (isspace(cc))
                                break;

                        if (cc == '"') {
                                state = DTRACE_JSON_STRING;
                                string_is_key = B_TRUE;
                                break;
                        }

                        /*
                         * ERROR: either the object did not start with a key
                         * string, or we've run off the end of the object
                         * without finding the requested key.
                         */
                        return (NULL);
                case DTRACE_JSON_STRING:
                        if (cc == '\\') {
                                *dd++ = '\\';
                                state = DTRACE_JSON_STRING_ESCAPE;
                                break;
                        }

                        if (cc == '"') {
                                if (collect_object) {
                                        /*
                                         * We don't reset the dest here, as
                                         * the string is part of a larger
                                         * object being collected.
                                         */
                                        *dd++ = cc;
                                        collect_object = B_FALSE;
                                        state = DTRACE_JSON_COLLECT_OBJECT;
                                        break;
                                }
                                *dd = '\0';
                                dd = dest; /* reset string buffer */
                                if (string_is_key) {
                                        if (dtrace_strncmp(dest, elem,
                                            size) == 0)
                                                found_key = B_TRUE;
                                } else if (found_key) {
                                        if (nelems > 1) {
                                                /*
                                                 * We expected an object, not
                                                 * this string.
                                                 */
                                                return (NULL);
                                        }
                                        return (dest);
                                }
                                state = string_is_key ? DTRACE_JSON_COLON :
                                    DTRACE_JSON_COMMA;
                                string_is_key = B_FALSE;
                                break;
                        }

                        *dd++ = cc;
                        break;
                case DTRACE_JSON_STRING_ESCAPE:
                        *dd++ = cc;
                        if (cc == 'u') {
                                escape_unicount = 0;
                                state = DTRACE_JSON_STRING_ESCAPE_UNICODE;
                        } else {
                                state = DTRACE_JSON_STRING;
                        }
                        break;
                case DTRACE_JSON_STRING_ESCAPE_UNICODE:
                        if (!isxdigit(cc)) {
                                /*
                                 * ERROR: invalid unicode escape, expected
                                 * four valid hexidecimal digits.
                                 */
                                return (NULL);
                        }

                        *dd++ = cc;
                        if (++escape_unicount == 4)
                                state = DTRACE_JSON_STRING;
                        break;
                case DTRACE_JSON_COLON:
                        if (isspace(cc))
                                break;

                        if (cc == ':') {
                                state = DTRACE_JSON_VALUE;
                                break;
                        }

                        /*
                         * ERROR: expected a colon.
                         */
                        return (NULL);
                case DTRACE_JSON_COMMA:
                        if (isspace(cc))
                                break;

                        if (cc == ',') {
                                if (in_array) {
                                        state = DTRACE_JSON_VALUE;
                                        if (++array_pos == array_elem)
                                                found_key = B_TRUE;
                                } else {
                                        state = DTRACE_JSON_OBJECT;
                                }
                                break;
                        }

                        /*
                         * ERROR: either we hit an unexpected character, or
                         * we reached the end of the object or array without
                         * finding the requested key.
                         */
                        return (NULL);
                case DTRACE_JSON_IDENTIFIER:
                        if (islower(cc)) {
                                *dd++ = cc;
                                break;
                        }

                        *dd = '\0';
                        dd = dest; /* reset string buffer */

                        if (dtrace_strncmp(dest, "true", 5) == 0 ||
                            dtrace_strncmp(dest, "false", 6) == 0 ||
                            dtrace_strncmp(dest, "null", 5) == 0) {
                                if (found_key) {
                                        if (nelems > 1) {
                                                /*
                                                 * ERROR: We expected an object,
                                                 * not this identifier.
                                                 */
                                                return (NULL);
                                        }
                                        return (dest);
                                } else {
                                        cur--;
                                        state = DTRACE_JSON_COMMA;
                                        break;
                                }
                        }

                        /*
                         * ERROR: we did not recognise the identifier as one
                         * of those in the JSON specification.
                         */
                        return (NULL);
                case DTRACE_JSON_NUMBER:
                        if (cc == '.') {
                                *dd++ = cc;
                                state = DTRACE_JSON_NUMBER_FRAC;
                                break;
                        }

                        if (cc == 'x' || cc == 'X') {
                                /*
                                 * ERROR: specification explicitly excludes
                                 * hexidecimal or octal numbers.
                                 */
                                return (NULL);
                        }

                        /* FALLTHRU */
                case DTRACE_JSON_NUMBER_FRAC:
                        if (cc == 'e' || cc == 'E') {
                                *dd++ = cc;
                                state = DTRACE_JSON_NUMBER_EXP;
                                break;
                        }

                        if (cc == '+' || cc == '-') {
                                /*
                                 * ERROR: expect sign as part of exponent only.
                                 */
                                return (NULL);
                        }
                        /* FALLTHRU */
                case DTRACE_JSON_NUMBER_EXP:
                        if (isdigit(cc) || cc == '+' || cc == '-') {
                                *dd++ = cc;
                                break;
                        }

                        *dd = '\0';
                        dd = dest; /* reset string buffer */
                        if (found_key) {
                                if (nelems > 1) {
                                        /*
                                         * ERROR: We expected an object, not
                                         * this number.
                                         */
                                        return (NULL);
                                }
                                return (dest);
                        }

                        cur--;
                        state = DTRACE_JSON_COMMA;
                        break;
                case DTRACE_JSON_VALUE:
                        if (isspace(cc))
                                break;

                        if (cc == '{' || cc == '[') {
                                if (nelems > 1 && found_key) {
                                        in_array = cc == '[' ? B_TRUE : B_FALSE;
                                        /*
                                         * If our element selector directs us
                                         * to descend into this nested object,
                                         * then move to the next selector
                                         * element in the list and restart the
                                         * state machine.
                                         */
                                        while (*elem != '\0')
                                                elem++;
                                        elem++; /* skip the inter-element NUL */
                                        nelems--;
                                        dd = dest;
                                        if (in_array) {
                                                state = DTRACE_JSON_VALUE;
                                                array_pos = 0;
                                                array_elem = dtrace_strtoll(
                                                    elem, 10, size);
                                                found_key = array_elem == 0 ?
                                                    B_TRUE : B_FALSE;
                                        } else {
                                                found_key = B_FALSE;
                                                state = DTRACE_JSON_OBJECT;
                                        }
                                        break;
                                }

                                /*
                                 * Otherwise, we wish to either skip this
                                 * nested object or return it in full.
                                 */
                                if (cc == '[')
                                        brackets = 1;
                                else
                                        braces = 1;
                                *dd++ = cc;
                                state = DTRACE_JSON_COLLECT_OBJECT;
                                break;
                        }

                        if (cc == '"') {
                                state = DTRACE_JSON_STRING;
                                break;
                        }

                        if (islower(cc)) {
                                /*
                                 * Here we deal with true, false and null.
                                 */
                                *dd++ = cc;
                                state = DTRACE_JSON_IDENTIFIER;
                                break;
                        }

                        if (cc == '-' || isdigit(cc)) {
                                *dd++ = cc;
                                state = DTRACE_JSON_NUMBER;
                                break;
                        }

                        /*
                         * ERROR: unexpected character at start of value.
                         */
                        return (NULL);
                case DTRACE_JSON_COLLECT_OBJECT:
                        if (cc == '\0')
                                /*
                                 * ERROR: unexpected end of input.
                                 */
                                return (NULL);

                        *dd++ = cc;
                        if (cc == '"') {
                                collect_object = B_TRUE;
                                state = DTRACE_JSON_STRING;
                                break;
                        }

                        if (cc == ']') {
                                if (brackets-- == 0) {
                                        /*
                                         * ERROR: unbalanced brackets.
                                         */
                                        return (NULL);
                                }
                        } else if (cc == '}') {
                                if (braces-- == 0) {
                                        /*
                                         * ERROR: unbalanced braces.
                                         */
                                        return (NULL);
                                }
                        } else if (cc == '{') {
                                braces++;
                        } else if (cc == '[') {
                                brackets++;
                        }

                        if (brackets == 0 && braces == 0) {
                                if (found_key) {
                                        *dd = '\0';
                                        return (dest);
                                }
                                dd = dest; /* reset string buffer */
                                state = DTRACE_JSON_COMMA;
                        }
                        break;
                }
        }
        return (NULL);
}

/*
 * Emulate the execution of DTrace ID subroutines invoked by the call opcode.
 * Notice that we don't bother validating the proper number of arguments or
 * their types in the tuple stack.  This isn't needed because all argument
 * interpretation is safe because of our load safety -- the worst that can
 * happen is that a bogus program can obtain bogus results.
 */
static void
dtrace_dif_subr(uint_t subr, uint_t rd, uint64_t *regs,
    dtrace_key_t *tupregs, int nargs,
    dtrace_mstate_t *mstate, dtrace_state_t *state)
{
        volatile uint16_t *flags = &cpu_core[CPU->cpu_id].cpuc_dtrace_flags;
        volatile uint64_t *illval = &cpu_core[CPU->cpu_id].cpuc_dtrace_illval;
        dtrace_vstate_t *vstate = &state->dts_vstate;

#if !defined(__APPLE__)
        union {
                mutex_impl_t mi;
                uint64_t mx;
        } m;

        union {
                krwlock_t ri;
                uintptr_t rw;
        } r;
#else
/* FIXME: awaits lock/mutex work */
#endif /* __APPLE__ */

        switch (subr) {
        case DIF_SUBR_RAND:
                regs[rd] = dtrace_xoroshiro128_plus_next(
                    state->dts_rstate[CPU->cpu_id]);
                break;

#if !defined(__APPLE__)
        case DIF_SUBR_MUTEX_OWNED:
                if (!dtrace_canload(tupregs[0].dttk_value, sizeof (kmutex_t),
                    mstate, vstate)) {
                        regs[rd] = 0;
                        break;
                }

                m.mx = dtrace_load64(tupregs[0].dttk_value);
                if (MUTEX_TYPE_ADAPTIVE(&m.mi))
                        regs[rd] = MUTEX_OWNER(&m.mi) != MUTEX_NO_OWNER;
                else
                        regs[rd] = LOCK_HELD(&m.mi.m_spin.m_spinlock);
                break;

        case DIF_SUBR_MUTEX_OWNER:
                if (!dtrace_canload(tupregs[0].dttk_value, sizeof (kmutex_t),
                    mstate, vstate)) {
                        regs[rd] = 0;
                        break;
                }

                m.mx = dtrace_load64(tupregs[0].dttk_value);
                if (MUTEX_TYPE_ADAPTIVE(&m.mi) &&
                    MUTEX_OWNER(&m.mi) != MUTEX_NO_OWNER)
                        regs[rd] = (uintptr_t)MUTEX_OWNER(&m.mi);
                else
                        regs[rd] = 0;
                break;

        case DIF_SUBR_MUTEX_TYPE_ADAPTIVE:
                if (!dtrace_canload(tupregs[0].dttk_value, sizeof (kmutex_t),
                    mstate, vstate)) {
                        regs[rd] = 0;
                        break;
                }

                m.mx = dtrace_load64(tupregs[0].dttk_value);
                regs[rd] = MUTEX_TYPE_ADAPTIVE(&m.mi);
                break;

        case DIF_SUBR_MUTEX_TYPE_SPIN:
                if (!dtrace_canload(tupregs[0].dttk_value, sizeof (kmutex_t),
                    mstate, vstate)) {
                        regs[rd] = 0;
                        break;
                }

                m.mx = dtrace_load64(tupregs[0].dttk_value);
                regs[rd] = MUTEX_TYPE_SPIN(&m.mi);
                break;

        case DIF_SUBR_RW_READ_HELD: {
                uintptr_t tmp;

                if (!dtrace_canload(tupregs[0].dttk_value, sizeof (uintptr_t),
                    mstate, vstate)) {
                        regs[rd] = 0;
                        break;
                }

                r.rw = dtrace_loadptr(tupregs[0].dttk_value);
                regs[rd] = _RW_READ_HELD(&r.ri, tmp);
                break;
        }

        case DIF_SUBR_RW_WRITE_HELD:
                if (!dtrace_canload(tupregs[0].dttk_value, sizeof (krwlock_t),
                    mstate, vstate)) {
                        regs[rd] = 0;
                        break;
                }

                r.rw = dtrace_loadptr(tupregs[0].dttk_value);
                regs[rd] = _RW_WRITE_HELD(&r.ri);
                break;

        case DIF_SUBR_RW_ISWRITER:
                if (!dtrace_canload(tupregs[0].dttk_value, sizeof (krwlock_t),
                    mstate, vstate)) {
                        regs[rd] = 0;
                        break;
                }

                r.rw = dtrace_loadptr(tupregs[0].dttk_value);
                regs[rd] = _RW_ISWRITER(&r.ri);
                break;
#else
/* FIXME: awaits lock/mutex work */
#endif /* __APPLE__ */

        case DIF_SUBR_BCOPY: {
                /*
                 * We need to be sure that the destination is in the scratch
                 * region -- no other region is allowed.
                 */
                uintptr_t src = tupregs[0].dttk_value;
                uintptr_t dest = tupregs[1].dttk_value;
                size_t size = tupregs[2].dttk_value;

                if (!dtrace_inscratch(dest, size, mstate)) {
                        *flags |= CPU_DTRACE_BADADDR;
                        *illval = regs[rd];
                        break;
                }

                if (!dtrace_canload(src, size, mstate, vstate)) {
                        regs[rd] = 0;
                        break;
                }

                dtrace_bcopy((void *)src, (void *)dest, size);
                break;
        }

        case DIF_SUBR_ALLOCA:
        case DIF_SUBR_COPYIN: {
                uintptr_t dest = P2ROUNDUP(mstate->dtms_scratch_ptr, 8);
                uint64_t size =
                    tupregs[subr == DIF_SUBR_ALLOCA ? 0 : 1].dttk_value;
                size_t scratch_size = (dest - mstate->dtms_scratch_ptr) + size;

                /*
                 * Check whether the user can access kernel memory
                 */
                if (dtrace_priv_kernel(state) == 0) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_KPRIV);
                        regs[rd] = 0;
                        break;
                }
                /*
                 * This action doesn't require any credential checks since
                 * probes will not activate in user contexts to which the
                 * enabling user does not have permissions.
                 */

                /*
                 * Rounding up the user allocation size could have overflowed
                 * a large, bogus allocation (like -1ULL) to 0.
                 */
                if (scratch_size < size ||
                    !DTRACE_INSCRATCH(mstate, scratch_size)) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                        regs[rd] = 0;
                        break;
                }

                if (subr == DIF_SUBR_COPYIN) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                        if (dtrace_priv_proc(state))
                                dtrace_copyin(tupregs[0].dttk_value, dest, size, flags);
                        DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
                }

                mstate->dtms_scratch_ptr += scratch_size;
                regs[rd] = dest;
                break;
        }

        case DIF_SUBR_COPYINTO: {
                uint64_t size = tupregs[1].dttk_value;
                uintptr_t dest = tupregs[2].dttk_value;

                /*
                 * This action doesn't require any credential checks since
                 * probes will not activate in user contexts to which the
                 * enabling user does not have permissions.
                 */
                if (!dtrace_inscratch(dest, size, mstate)) {
                        *flags |= CPU_DTRACE_BADADDR;
                        *illval = regs[rd];
                        break;
                }

                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                if (dtrace_priv_proc(state))
                        dtrace_copyin(tupregs[0].dttk_value, dest, size, flags);
                DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
                break;
        }

        case DIF_SUBR_COPYINSTR: {
                uintptr_t dest = mstate->dtms_scratch_ptr;
                uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];

                if (nargs > 1 && tupregs[1].dttk_value < size)
                        size = tupregs[1].dttk_value + 1;

                /*
                 * This action doesn't require any credential checks since
                 * probes will not activate in user contexts to which the
                 * enabling user does not have permissions.
                 */
                if (!DTRACE_INSCRATCH(mstate, size)) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                        regs[rd] = 0;
                        break;
                }

                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                if (dtrace_priv_proc(state))
                        dtrace_copyinstr(tupregs[0].dttk_value, dest, size, flags);
                DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);

                ((char *)dest)[size - 1] = '\0';
                mstate->dtms_scratch_ptr += size;
                regs[rd] = dest;
                break;
        }

        case DIF_SUBR_MSGSIZE:
        case DIF_SUBR_MSGDSIZE: {
                /* Darwin does not implement SysV streams messages */
                DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
                regs[rd] = 0;
                break;
        }

        case DIF_SUBR_PROGENYOF: {
                pid_t pid = tupregs[0].dttk_value;
                struct proc *p = current_proc();
                int rval = 0, lim = nprocs;

                while(p && (lim-- > 0)) {
                        pid_t ppid;

                        ppid = (pid_t)dtrace_load32((uintptr_t)&(p->p_pid));
                        if (*flags & CPU_DTRACE_FAULT)
                                break;

                        if (ppid == pid) {
                                rval = 1;
                                break;
                        }

                        if (ppid == 0)
                                break; /* Can't climb process tree any further. */

                        p = (struct proc *)dtrace_loadptr((uintptr_t)&(p->p_pptr));
                        if (*flags & CPU_DTRACE_FAULT)
                                break;
                }

                regs[rd] = rval;
                break;
        }

        case DIF_SUBR_SPECULATION:
                regs[rd] = dtrace_speculation(state);
                break;


        case DIF_SUBR_COPYOUT: {
                uintptr_t kaddr = tupregs[0].dttk_value;
                user_addr_t uaddr = tupregs[1].dttk_value;
                uint64_t size = tupregs[2].dttk_value;

                if (!dtrace_destructive_disallow &&
                    dtrace_priv_proc_control(state) &&
                    !dtrace_istoxic(kaddr, size) &&
                    dtrace_canload(kaddr, size, mstate, vstate)) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                        dtrace_copyout(kaddr, uaddr, size, flags);
                        DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
                }
                break;
        }

        case DIF_SUBR_COPYOUTSTR: {
                uintptr_t kaddr = tupregs[0].dttk_value;
                user_addr_t uaddr = tupregs[1].dttk_value;
                uint64_t size = tupregs[2].dttk_value;
                size_t lim;

                if (!dtrace_destructive_disallow &&
                    dtrace_priv_proc_control(state) &&
                    !dtrace_istoxic(kaddr, size) &&
                    dtrace_strcanload(kaddr, size, &lim, mstate, vstate)) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                        dtrace_copyoutstr(kaddr, uaddr, lim, flags);
                        DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
                }
                break;
        }

        case DIF_SUBR_STRLEN: {
                size_t size = state->dts_options[DTRACEOPT_STRSIZE];
                uintptr_t addr = (uintptr_t)tupregs[0].dttk_value;
                size_t lim;

                if (!dtrace_strcanload(addr, size, &lim, mstate, vstate)) {
                        regs[rd] = 0;
                        break;
                }

                regs[rd] = dtrace_strlen((char *)addr, lim);

                break;
        }

        case DIF_SUBR_STRCHR:
        case DIF_SUBR_STRRCHR: {
                /*
                 * We're going to iterate over the string looking for the
                 * specified character.  We will iterate until we have reached
                 * the string length or we have found the character.  If this
                 * is DIF_SUBR_STRRCHR, we will look for the last occurrence
                 * of the specified character instead of the first.
                 */
                uintptr_t addr = tupregs[0].dttk_value;
                uintptr_t addr_limit;
                uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];
                size_t lim;
                char c, target = (char)tupregs[1].dttk_value;

                if (!dtrace_strcanload(addr, size, &lim, mstate, vstate)) {
                        regs[rd] = 0;
                        break;
                }
                addr_limit = addr + lim;

                for (regs[rd] = 0; addr < addr_limit; addr++) {
                        if ((c = dtrace_load8(addr)) == target) {
                                regs[rd] = addr;

                                if (subr == DIF_SUBR_STRCHR)
                                        break;
                        }

                        if (c == '\0')
                                break;
                }

                break;
        }

        case DIF_SUBR_STRSTR:
        case DIF_SUBR_INDEX:
        case DIF_SUBR_RINDEX: {
                /*
                 * We're going to iterate over the string looking for the
                 * specified string.  We will iterate until we have reached
                 * the string length or we have found the string.  (Yes, this
                 * is done in the most naive way possible -- but considering
                 * that the string we're searching for is likely to be
                 * relatively short, the complexity of Rabin-Karp or similar
                 * hardly seems merited.)
                 */
                char *addr = (char *)(uintptr_t)tupregs[0].dttk_value;
                char *substr = (char *)(uintptr_t)tupregs[1].dttk_value;
                uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];
                size_t len = dtrace_strlen(addr, size);
                size_t sublen = dtrace_strlen(substr, size);
                char *limit = addr + len, *orig = addr;
                int notfound = subr == DIF_SUBR_STRSTR ? 0 : -1;
                int inc = 1;

                regs[rd] = notfound;

                if (!dtrace_canload((uintptr_t)addr, len + 1, mstate, vstate)) {
                        regs[rd] = 0;
                        break;
                }

                if (!dtrace_canload((uintptr_t)substr, sublen + 1, mstate,
                    vstate)) {
                        regs[rd] = 0;
                        break;
                }

                /*
                 * strstr() and index()/rindex() have similar semantics if
                 * both strings are the empty string: strstr() returns a
                 * pointer to the (empty) string, and index() and rindex()
                 * both return index 0 (regardless of any position argument).
                 */
                if (sublen == 0 && len == 0) {
                        if (subr == DIF_SUBR_STRSTR)
                                regs[rd] = (uintptr_t)addr;
                        else
                                regs[rd] = 0;
                        break;
                }

                if (subr != DIF_SUBR_STRSTR) {
                        if (subr == DIF_SUBR_RINDEX) {
                                limit = orig - 1;
                                addr += len;
                                inc = -1;
                        }

                        /*
                         * Both index() and rindex() take an optional position
                         * argument that denotes the starting position.
                         */
                        if (nargs == 3) {
                                int64_t pos = (int64_t)tupregs[2].dttk_value;

                                /*
                                 * If the position argument to index() is
                                 * negative, Perl implicitly clamps it at
                                 * zero.  This semantic is a little surprising
                                 * given the special meaning of negative
                                 * positions to similar Perl functions like
                                 * substr(), but it appears to reflect a
                                 * notion that index() can start from a
                                 * negative index and increment its way up to
                                 * the string.  Given this notion, Perl's
                                 * rindex() is at least self-consistent in
                                 * that it implicitly clamps positions greater
                                 * than the string length to be the string
                                 * length.  Where Perl completely loses
                                 * coherence, however, is when the specified
                                 * substring is the empty string ("").  In
                                 * this case, even if the position is
                                 * negative, rindex() returns 0 -- and even if
                                 * the position is greater than the length,
                                 * index() returns the string length.  These
                                 * semantics violate the notion that index()
                                 * should never return a value less than the
                                 * specified position and that rindex() should
                                 * never return a value greater than the
                                 * specified position.  (One assumes that
                                 * these semantics are artifacts of Perl's
                                 * implementation and not the results of
                                 * deliberate design -- it beggars belief that
                                 * even Larry Wall could desire such oddness.)
                                 * While in the abstract one would wish for
                                 * consistent position semantics across
                                 * substr(), index() and rindex() -- or at the
                                 * very least self-consistent position
                                 * semantics for index() and rindex() -- we
                                 * instead opt to keep with the extant Perl
                                 * semantics, in all their broken glory.  (Do
                                 * we have more desire to maintain Perl's
                                 * semantics than Perl does?  Probably.)
                                 */
                                if (subr == DIF_SUBR_RINDEX) {
                                        if (pos < 0) {
                                                if (sublen == 0)
                                                        regs[rd] = 0;
                                                break;
                                        }

                                        if ((size_t)pos > len)
                                                pos = len;
                                } else {
                                        if (pos < 0)
                                                pos = 0;

                                        if ((size_t)pos >= len) {
                                                if (sublen == 0)
                                                        regs[rd] = len;
                                                break;
                                        }
                                }

                                addr = orig + pos;
                        }
                }

                for (regs[rd] = notfound; addr != limit; addr += inc) {
                        if (dtrace_strncmp(addr, substr, sublen) == 0) {
                                if (subr != DIF_SUBR_STRSTR) {
                                        /*
                                         * As D index() and rindex() are
                                         * modeled on Perl (and not on awk),
                                         * we return a zero-based (and not a
                                         * one-based) index.  (For you Perl
                                         * weenies: no, we're not going to add
                                         * $[ -- and shouldn't you be at a con
                                         * or something?)
                                         */
                                        regs[rd] = (uintptr_t)(addr - orig);
                                        break;
                                }

                                ASSERT(subr == DIF_SUBR_STRSTR);
                                regs[rd] = (uintptr_t)addr;
                                break;
                        }
                }

                break;
        }

        case DIF_SUBR_STRTOK: {
                uintptr_t addr = tupregs[0].dttk_value;
                uintptr_t tokaddr = tupregs[1].dttk_value;
                uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];
                uintptr_t limit, toklimit;
                size_t clim;
                char *dest = (char *)mstate->dtms_scratch_ptr;
                uint8_t c='\0', tokmap[32];      /* 256 / 8 */
                uint64_t i = 0;

                /*
                 * Check both the token buffer and (later) the input buffer,
                 * since both could be non-scratch addresses.
                 */
                if (!dtrace_strcanload(tokaddr, size, &clim, mstate, vstate)) {
                        regs[rd] = 0;
                        break;
                }
                toklimit = tokaddr + clim;

                if (!DTRACE_INSCRATCH(mstate, size)) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                        regs[rd] = 0;
                        break;
                }

                if (addr == 0) {
                        /*
                         * If the address specified is NULL, we use our saved
                         * strtok pointer from the mstate.  Note that this
                         * means that the saved strtok pointer is _only_
                         * valid within multiple enablings of the same probe --
                         * it behaves like an implicit clause-local variable.
                         */
                        addr = mstate->dtms_strtok;
                        limit = mstate->dtms_strtok_limit;
                } else {
                        /*
                         * If the user-specified address is non-NULL we must
                         * access check it.  This is the only time we have
                         * a chance to do so, since this address may reside
                         * in the string table of this clause-- future calls
                         * (when we fetch addr from mstate->dtms_strtok)
                         * would fail this access check.
                         */
                        if (!dtrace_strcanload(addr, size, &clim, mstate,
                                vstate)) {
                                regs[rd] = 0;
                                break;
                        }
                        limit = addr + clim;
                }

                /*
                 * First, zero the token map, and then process the token
                 * string -- setting a bit in the map for every character
                 * found in the token string.
                 */
                for (i = 0; i < (int)sizeof (tokmap); i++)
                        tokmap[i] = 0;

                for (; tokaddr < toklimit; tokaddr++) {
                        if ((c = dtrace_load8(tokaddr)) == '\0')
                                break;

                        ASSERT((c >> 3) < sizeof (tokmap));
                        tokmap[c >> 3] |= (1 << (c & 0x7));
                }

                for (; addr < limit; addr++) {
                        /*
                         * We're looking for a character that is _not_
                         * contained in the token string.
                         */
                        if ((c = dtrace_load8(addr)) == '\0')
                                break;

                        if (!(tokmap[c >> 3] & (1 << (c & 0x7))))
                                break;
                }

                if (c == '\0') {
                        /*
                         * We reached the end of the string without finding
                         * any character that was not in the token string.
                         * We return NULL in this case, and we set the saved
                         * address to NULL as well.
                         */
                        regs[rd] = 0;
                        mstate->dtms_strtok = 0;
                        mstate->dtms_strtok_limit = 0;
                        break;
                }

                /*
                 * From here on, we're copying into the destination string.
                 */
                for (i = 0; addr < limit && i < size - 1; addr++) {
                        if ((c = dtrace_load8(addr)) == '\0')
                                break;

                        if (tokmap[c >> 3] & (1 << (c & 0x7)))
                                break;

                        ASSERT(i < size);
                        dest[i++] = c;
                }

                ASSERT(i < size);
                dest[i] = '\0';
                regs[rd] = (uintptr_t)dest;
                mstate->dtms_scratch_ptr += size;
                mstate->dtms_strtok = addr;
                mstate->dtms_strtok_limit = limit;
                break;
        }

        case DIF_SUBR_SUBSTR: {
                uintptr_t s = tupregs[0].dttk_value;
                uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];
                char *d = (char *)mstate->dtms_scratch_ptr;
                int64_t index = (int64_t)tupregs[1].dttk_value;
                int64_t remaining = (int64_t)tupregs[2].dttk_value;
                size_t len = dtrace_strlen((char *)s, size);
                int64_t i = 0;

                if (!dtrace_canload(s, len + 1, mstate, vstate)) {
                        regs[rd] = 0;
                        break;
                }

                if (!DTRACE_INSCRATCH(mstate, size)) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                        regs[rd] = 0;
                        break;
                }

                if (nargs <= 2)
                        remaining = (int64_t)size;

                if (index < 0) {
                        index += len;

                        if (index < 0 && index + remaining > 0) {
                                remaining += index;
                                index = 0;
                        }
                }

                if ((size_t)index >= len || index < 0) {
                        remaining = 0;
                } else if (remaining < 0) {
                        remaining += len - index;
                } else if ((uint64_t)index + (uint64_t)remaining > size) {
                        remaining = size - index;
                }

                for (i = 0; i < remaining; i++) {
                        if ((d[i] = dtrace_load8(s + index + i)) == '\0')
                                break;
                        }

                d[i] = '\0';

                mstate->dtms_scratch_ptr += size;
                regs[rd] = (uintptr_t)d;
                break;
        }

        case DIF_SUBR_GETMAJOR:
                regs[rd] = (uintptr_t)major( (dev_t)tupregs[0].dttk_value );
                break;

        case DIF_SUBR_GETMINOR:
                regs[rd] = (uintptr_t)minor( (dev_t)tupregs[0].dttk_value );
                break;

        case DIF_SUBR_DDI_PATHNAME: {
                /* APPLE NOTE: currently unsupported on Darwin */
                DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
                regs[rd] = 0;
                break;
        }

        case DIF_SUBR_STRJOIN: {
                char *d = (char *)mstate->dtms_scratch_ptr;
                uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];
                uintptr_t s1 = tupregs[0].dttk_value;
                uintptr_t s2 = tupregs[1].dttk_value;
                uint64_t i = 0, j = 0;
                size_t lim1, lim2;
                char c;

                if (!dtrace_strcanload(s1, size, &lim1, mstate, vstate) ||
                    !dtrace_strcanload(s2, size, &lim2, mstate, vstate)) {
                        regs[rd] = 0;
                        break;
                }

                if (!DTRACE_INSCRATCH(mstate, size)) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                        regs[rd] = 0;
                        break;
                }

                for (;;) {
                        if (i >= size) {
                                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                                regs[rd] = 0;
                                break;
                        }
                        c = (i >= lim1) ? '\0' : dtrace_load8(s1++);
                        if ((d[i++] = c) == '\0') {
                                i--;
                                break;
                        }
                }

                for (;;) {
                        if (i >= size) {
                                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                                regs[rd] = 0;
                                break;
                        }
                        c = (j++ >= lim2) ? '\0' : dtrace_load8(s2++);
                        if ((d[i++] = c) == '\0')
                                break;
                }

                if (i < size) {
                        mstate->dtms_scratch_ptr += i;
                        regs[rd] = (uintptr_t)d;
                }

                break;
        }

        case DIF_SUBR_STRTOLL: {
                uintptr_t s = tupregs[0].dttk_value;
                uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];
                size_t lim;
                int base = 10;

                if (nargs > 1) {
                        if ((base = tupregs[1].dttk_value) <= 1 ||
                            base > ('z' - 'a' + 1) + ('9' - '0' + 1)) {
                                *flags |= CPU_DTRACE_ILLOP;
                                break;
                        }
                }

                if (!dtrace_strcanload(s, size, &lim, mstate, vstate)) {
                        regs[rd] = INT64_MIN;
                        break;
                }

                regs[rd] = dtrace_strtoll((char *)s, base, lim);
                break;
        }

        case DIF_SUBR_LLTOSTR: {
                int64_t i = (int64_t)tupregs[0].dttk_value;
                uint64_t val, digit;
                uint64_t size = 65;     /* enough room for 2^64 in binary */
                char *end = (char *)mstate->dtms_scratch_ptr + size - 1;
                int base = 10;

                if (nargs > 1) {
                        if ((base = tupregs[1].dttk_value) <= 1 ||
                             base > ('z' - 'a' + 1) + ('9' - '0' + 1)) {
                                *flags |= CPU_DTRACE_ILLOP;
                                break;
                        }
                }

                val = (base == 10 && i < 0) ? i * -1 : i;

                if (!DTRACE_INSCRATCH(mstate, size)) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                        regs[rd] = 0;
                        break;
                }

                for (*end-- = '\0'; val; val /= base) {
                        if ((digit = val % base) <= '9' - '0') {
                                *end-- = '0' + digit;
                        } else {
                                *end-- = 'a' + (digit - ('9' - '0') - 1);
                        }
                }

                if (i == 0 && base == 16)
                        *end-- = '0';

                if (base == 16)
                        *end-- = 'x';

                if (i == 0 || base == 8 || base == 16)
                        *end-- = '0';

                if (i < 0 && base == 10)
                        *end-- = '-';

                regs[rd] = (uintptr_t)end + 1;
                mstate->dtms_scratch_ptr += size;
                break;
        }

        case DIF_SUBR_HTONS:
        case DIF_SUBR_NTOHS:
#ifdef _BIG_ENDIAN
                regs[rd] = (uint16_t)tupregs[0].dttk_value;
#else
                regs[rd] = DT_BSWAP_16((uint16_t)tupregs[0].dttk_value);
#endif
                break;


        case DIF_SUBR_HTONL:
        case DIF_SUBR_NTOHL:
#ifdef _BIG_ENDIAN
                regs[rd] = (uint32_t)tupregs[0].dttk_value;
#else
                regs[rd] = DT_BSWAP_32((uint32_t)tupregs[0].dttk_value);
#endif
                break;


        case DIF_SUBR_HTONLL:
        case DIF_SUBR_NTOHLL:
#ifdef _BIG_ENDIAN
                regs[rd] = (uint64_t)tupregs[0].dttk_value;
#else
                regs[rd] = DT_BSWAP_64((uint64_t)tupregs[0].dttk_value);
#endif
                break;


        case DIF_SUBR_DIRNAME:
        case DIF_SUBR_BASENAME: {
                char *dest = (char *)mstate->dtms_scratch_ptr;
                uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];
                uintptr_t src = tupregs[0].dttk_value;
                int i, j, len = dtrace_strlen((char *)src, size);
                int lastbase = -1, firstbase = -1, lastdir = -1;
                int start, end;

                if (!dtrace_canload(src, len + 1, mstate, vstate)) {
                        regs[rd] = 0;
                        break;
                }

                if (!DTRACE_INSCRATCH(mstate, size)) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                        regs[rd] = 0;
                        break;
                }

                /*
                 * The basename and dirname for a zero-length string is
                 * defined to be "."
                 */
                if (len == 0) {
                        len = 1;
                        src = (uintptr_t)".";
                }

                /*
                 * Start from the back of the string, moving back toward the
                 * front until we see a character that isn't a slash.  That
                 * character is the last character in the basename.
                 */
                for (i = len - 1; i >= 0; i--) {
                        if (dtrace_load8(src + i) != '/')
                                break;
                }

                if (i >= 0)
                        lastbase = i;

                /*
                 * Starting from the last character in the basename, move
                 * towards the front until we find a slash.  The character
                 * that we processed immediately before that is the first
                 * character in the basename.
                 */
                for (; i >= 0; i--) {
                        if (dtrace_load8(src + i) == '/')
                                break;
                }

                if (i >= 0)
                        firstbase = i + 1;

                /*
                 * Now keep going until we find a non-slash character.  That
                 * character is the last character in the dirname.
                 */
                for (; i >= 0; i--) {
                        if (dtrace_load8(src + i) != '/')
                                break;
                }

                if (i >= 0)
                        lastdir = i;

                ASSERT(!(lastbase == -1 && firstbase != -1));
                ASSERT(!(firstbase == -1 && lastdir != -1));

                if (lastbase == -1) {
                        /*
                         * We didn't find a non-slash character.  We know that
                         * the length is non-zero, so the whole string must be
                         * slashes.  In either the dirname or the basename
                         * case, we return '/'.
                         */
                        ASSERT(firstbase == -1);
                        firstbase = lastbase = lastdir = 0;
                }

                if (firstbase == -1) {
                        /*
                         * The entire string consists only of a basename
                         * component.  If we're looking for dirname, we need
                         * to change our string to be just "."; if we're
                         * looking for a basename, we'll just set the first
                         * character of the basename to be 0.
                         */
                        if (subr == DIF_SUBR_DIRNAME) {
                                ASSERT(lastdir == -1);
                                src = (uintptr_t)".";
                                lastdir = 0;
                        } else {
                                firstbase = 0;
                        }
                }

                if (subr == DIF_SUBR_DIRNAME) {
                        if (lastdir == -1) {
                                /*
                                 * We know that we have a slash in the name --
                                 * or lastdir would be set to 0, above.  And
                                 * because lastdir is -1, we know that this
                                 * slash must be the first character.  (That
                                 * is, the full string must be of the form
                                 * "/basename".)  In this case, the last
                                 * character of the directory name is 0.
                                 */
                                lastdir = 0;
                        }

                        start = 0;
                        end = lastdir;
                } else {
                        ASSERT(subr == DIF_SUBR_BASENAME);
                        ASSERT(firstbase != -1 && lastbase != -1);
                        start = firstbase;
                        end = lastbase;
                }

                for (i = start, j = 0; i <= end && (uint64_t)j < size - 1; i++, j++)
                        dest[j] = dtrace_load8(src + i);

                dest[j] = '\0';
                regs[rd] = (uintptr_t)dest;
                mstate->dtms_scratch_ptr += size;
                break;
        }

        case DIF_SUBR_CLEANPATH: {
                char *dest = (char *)mstate->dtms_scratch_ptr, c;
                uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];
                uintptr_t src = tupregs[0].dttk_value;
                size_t lim;
                size_t i = 0, j = 0;

                if (!dtrace_strcanload(src, size, &lim, mstate, vstate)) {
                        regs[rd] = 0;
                        break;
                }

                if (!DTRACE_INSCRATCH(mstate, size)) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                        regs[rd] = 0;
                        break;
                }

                /*
                 * Move forward, loading each character.
                 */
                do {
                        c = (i >= lim) ? '\0' : dtrace_load8(src + i++);
next:
                        if ((uint64_t)(j + 5) >= size)  /* 5 = strlen("/..c\0") */
                                break;

                        if (c != '/') {
                                dest[j++] = c;
                                continue;
                        }

                        c = (i >= lim) ? '\0' : dtrace_load8(src + i++);

                        if (c == '/') {
                                /*
                                 * We have two slashes -- we can just advance
                                 * to the next character.
                                 */
                                goto next;
                        }

                        if (c != '.') {
                                /*
                                 * This is not "." and it's not ".." -- we can
                                 * just store the "/" and this character and
                                 * drive on.
                                 */
                                dest[j++] = '/';
                                dest[j++] = c;
                                continue;
                        }

                        c = (i >= lim) ? '\0' : dtrace_load8(src + i++);

                        if (c == '/') {
                                /*
                                 * This is a "/./" component.  We're not going
                                 * to store anything in the destination buffer;
                                 * we're just going to go to the next component.
                                 */
                                goto next;
                        }

                        if (c != '.') {
                                /*
                                 * This is not ".." -- we can just store the
                                 * "/." and this character and continue
                                 * processing.
                                 */
                                dest[j++] = '/';
                                dest[j++] = '.';
                                dest[j++] = c;
                                continue;
                        }

                        c = (i >= lim) ? '\0' : dtrace_load8(src + i++);

                        if (c != '/' && c != '\0') {
                                /*
                                 * This is not ".." -- it's "..[mumble]".
                                 * We'll store the "/.." and this character
                                 * and continue processing.
                                 */
                                dest[j++] = '/';
                                dest[j++] = '.';
                                dest[j++] = '.';
                                dest[j++] = c;
                                continue;
                        }

                        /*
                         * This is "/../" or "/..\0".  We need to back up
                         * our destination pointer until we find a "/".
                         */
                        i--;
                        while (j != 0 && dest[--j] != '/')
                                continue;

                        if (c == '\0')
                                dest[++j] = '/';
                } while (c != '\0');

                dest[j] = '\0';
                regs[rd] = (uintptr_t)dest;
                mstate->dtms_scratch_ptr += size;
                break;
        }

        case DIF_SUBR_INET_NTOA:
        case DIF_SUBR_INET_NTOA6:
        case DIF_SUBR_INET_NTOP: {
                size_t size;
                int af, argi, i;
                char *base, *end;

                if (subr == DIF_SUBR_INET_NTOP) {
                        af = (int)tupregs[0].dttk_value;
                        argi = 1;
                } else {
                        af = subr == DIF_SUBR_INET_NTOA ? AF_INET: AF_INET6;
                        argi = 0;
                }

                if (af == AF_INET) {
#if !defined(__APPLE__)
                        ipaddr_t ip4;
#else
                        uint32_t ip4;
#endif /* __APPLE__ */
                        uint8_t *ptr8, val;

                        /*
                         * Safely load the IPv4 address.
                         */
#if !defined(__APPLE__)                 
                        ip4 = dtrace_load32(tupregs[argi].dttk_value);
#else
                        if (!dtrace_canload(tupregs[argi].dttk_value, sizeof(ip4),
                                mstate, vstate)) {
                                regs[rd] = 0;
                                break;
                        }

                        dtrace_bcopy(
                            (void *)(uintptr_t)tupregs[argi].dttk_value,
                            (void *)(uintptr_t)&ip4, sizeof (ip4));
#endif /* __APPLE__ */                  
                        /*
                         * Check an IPv4 string will fit in scratch.
                         */
#if !defined(__APPLE__)
                        size = INET_ADDRSTRLEN;
#else
                        size = MAX_IPv4_STR_LEN;
#endif /* __APPLE__ */
                        if (!DTRACE_INSCRATCH(mstate, size)) {
                                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                                regs[rd] = 0;
                                break;
                        }
                        base = (char *)mstate->dtms_scratch_ptr;
                        end = (char *)mstate->dtms_scratch_ptr + size - 1;

                        /*
                         * Stringify as a dotted decimal quad.
                         */
                        *end-- = '\0';
                        ptr8 = (uint8_t *)&ip4;
                        for (i = 3; i >= 0; i--) {
                                val = ptr8[i];

                                if (val == 0) {
                                        *end-- = '0';
                                } else {
                                        for (; val; val /= 10) {
                                                *end-- = '0' + (val % 10);
                                        }
                                }

                                if (i > 0)
                                        *end-- = '.';
                        }
                        ASSERT(end + 1 >= base);

                } else if (af == AF_INET6) {
#if defined(__APPLE__)
#define _S6_un __u6_addr
#define _S6_u8 __u6_addr8
#endif /* __APPLE__ */
                        struct in6_addr ip6;
                        int firstzero, tryzero, numzero, v6end;
                        uint16_t val;
                        const char digits[] = "0123456789abcdef";

                        /*
                         * Stringify using RFC 1884 convention 2 - 16 bit
                         * hexadecimal values with a zero-run compression.
                         * Lower case hexadecimal digits are used.
                         *      eg, fe80::214:4fff:fe0b:76c8.
                         * The IPv4 embedded form is returned for inet_ntop,
                         * just the IPv4 string is returned for inet_ntoa6.
                         */

                        if (!dtrace_canload(tupregs[argi].dttk_value,
                                sizeof(struct in6_addr), mstate, vstate)) {
                                regs[rd] = 0;
                                break;
                        }

                        /*
                         * Safely load the IPv6 address.
                         */
                        dtrace_bcopy(
                            (void *)(uintptr_t)tupregs[argi].dttk_value,
                            (void *)(uintptr_t)&ip6, sizeof (struct in6_addr));

                        /*
                         * Check an IPv6 string will fit in scratch.
                         */
                        size = INET6_ADDRSTRLEN;
                        if (!DTRACE_INSCRATCH(mstate, size)) {
                                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                                regs[rd] = 0;
                                break;
                        }
                        base = (char *)mstate->dtms_scratch_ptr;
                        end = (char *)mstate->dtms_scratch_ptr + size - 1;
                        *end-- = '\0';

                        /*
                         * Find the longest run of 16 bit zero values
                         * for the single allowed zero compression - "::".
                         */
                        firstzero = -1;
                        tryzero = -1;
                        numzero = 1;
                        for (i = 0; i < (int)sizeof (struct in6_addr); i++) {
                                if (ip6._S6_un._S6_u8[i] == 0 &&
                                    tryzero == -1 && i % 2 == 0) {
                                        tryzero = i;
                                        continue;
                                }

                                if (tryzero != -1 &&
                                    (ip6._S6_un._S6_u8[i] != 0 ||
                                    i == sizeof (struct in6_addr) - 1)) {

                                        if (i - tryzero <= numzero) {
                                                tryzero = -1;
                                                continue;
                                        }

                                        firstzero = tryzero;
                                        numzero = i - i % 2 - tryzero;
                                        tryzero = -1;

                                        if (ip6._S6_un._S6_u8[i] == 0 &&
                                            i == sizeof (struct in6_addr) - 1)
                                                numzero += 2;
                                }
                        }
                        ASSERT(firstzero + numzero <= (int)sizeof (struct in6_addr));

                        /*
                         * Check for an IPv4 embedded address.
                         */
                        v6end = sizeof (struct in6_addr) - 2;
                        if (IN6_IS_ADDR_V4MAPPED(&ip6) ||
                            IN6_IS_ADDR_V4COMPAT(&ip6)) {
                                for (i = sizeof (struct in6_addr) - 1;
                                     i >= (int)DTRACE_V4MAPPED_OFFSET; i--) {
                                        ASSERT(end >= base);

                                        val = ip6._S6_un._S6_u8[i];

                                        if (val == 0) {
                                                *end-- = '0';
                                        } else {
                                                for (; val; val /= 10) {
                                                        *end-- = '0' + val % 10;
                                                }
                                        }

                                        if (i > (int)DTRACE_V4MAPPED_OFFSET)
                                                *end-- = '.';
                                }

                                if (subr == DIF_SUBR_INET_NTOA6)
                                        goto inetout;

                                /*
                                 * Set v6end to skip the IPv4 address that
                                 * we have already stringified.
                                 */
                                v6end = 10;
                        }

                        /*
                         * Build the IPv6 string by working through the
                         * address in reverse.
                         */
                        for (i = v6end; i >= 0; i -= 2) {
                                ASSERT(end >= base);

                                if (i == firstzero + numzero - 2) {
                                        *end-- = ':';
                                        *end-- = ':';
                                        i -= numzero - 2;
                                        continue;
                                }

                                if (i < 14 && i != firstzero - 2)
                                        *end-- = ':';

                                val = (ip6._S6_un._S6_u8[i] << 8) +
                                    ip6._S6_un._S6_u8[i + 1];

                                if (val == 0) {
                                        *end-- = '0';
                                } else {
                                        for (; val; val /= 16) {
                                                *end-- = digits[val % 16];
                                        }
                                }
                        }
                        ASSERT(end + 1 >= base);

#if defined(__APPLE__)
#undef _S6_un
#undef _S6_u8
#endif /* __APPLE__ */
                } else {
                        /*
                         * The user didn't use AH_INET or AH_INET6.
                         */
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
                        regs[rd] = 0;
                        break;
                }

inetout:        regs[rd] = (uintptr_t)end + 1;
                mstate->dtms_scratch_ptr += size;
                break;
        }

        case DIF_SUBR_JSON: {
                uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];
                uintptr_t json = tupregs[0].dttk_value;
                size_t jsonlen = dtrace_strlen((char *)json, size);
                uintptr_t elem = tupregs[1].dttk_value;
                size_t elemlen = dtrace_strlen((char *)elem, size);

                char *dest = (char *)mstate->dtms_scratch_ptr;
                char *elemlist = (char *)mstate->dtms_scratch_ptr + jsonlen + 1;
                char *ee = elemlist;
                int nelems = 1;
                uintptr_t cur;

                if (!dtrace_canload(json, jsonlen + 1, mstate, vstate) ||
                    !dtrace_canload(elem, elemlen + 1, mstate, vstate)) {
                        regs[rd] = 0;
                        break;
                }

                if (!DTRACE_INSCRATCH(mstate, jsonlen + 1 + elemlen + 1)) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                        regs[rd] = 0;
                        break;
                }

                /*
                 * Read the element selector and split it up into a packed list
                 * of strings.
                 */
                for (cur = elem; cur < elem + elemlen; cur++) {
                        char cc = dtrace_load8(cur);

                        if (cur == elem && cc == '[') {
                                /*
                                 * If the first element selector key is
                                 * actually an array index then ignore the
                                 * bracket.
                                 */
                                continue;
                        }

                        if (cc == ']')
                                continue;

                        if (cc == '.' || cc == '[') {
                                nelems++;
                                cc = '\0';
                        }

                        *ee++ = cc;
                }
                *ee++ = '\0';

                if ((regs[rd] = (uintptr_t)dtrace_json(size, json, elemlist,
                    nelems, dest)) != 0)
                        mstate->dtms_scratch_ptr += jsonlen + 1;
                break;
        }

        case DIF_SUBR_TOUPPER:
        case DIF_SUBR_TOLOWER: {
                uintptr_t src = tupregs[0].dttk_value;
                char *dest = (char *)mstate->dtms_scratch_ptr;
                char lower, upper, base, c;
                uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];
                size_t len = dtrace_strlen((char*) src, size);
                size_t i = 0;

                lower = (subr == DIF_SUBR_TOUPPER) ? 'a' : 'A';
                upper = (subr == DIF_SUBR_TOUPPER) ? 'z' : 'Z';
                base  = (subr == DIF_SUBR_TOUPPER) ? 'A' : 'a';

                if (!dtrace_canload(src, len + 1, mstate, vstate)) {
                        regs[rd] = 0;
                        break;
                }

                if (!DTRACE_INSCRATCH(mstate, size)) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                        regs[rd] = 0;
                        break;
                }

                for (i = 0; i < size - 1; ++i) {
                        if ((c = dtrace_load8(src + i)) == '\0')
                                break;
                        if (c >= lower && c <= upper)
                                c = base + (c - lower);
                        dest[i] = c;
                }

                ASSERT(i < size);

                dest[i] = '\0';
                regs[rd] = (uintptr_t) dest;
                mstate->dtms_scratch_ptr += size;

                break;
        }
        case DIF_SUBR_STRIP:
                if (!dtrace_is_valid_ptrauth_key(tupregs[1].dttk_value)) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
                        break;
                }
                regs[rd] = (uint64_t)dtrace_ptrauth_strip(
                    (void*)tupregs[0].dttk_value, tupregs[1].dttk_value);
                break;

#if defined(__APPLE__)
        case DIF_SUBR_VM_KERNEL_ADDRPERM: {
                if (!dtrace_priv_kernel(state)) {
                        regs[rd] = 0;
                } else {
                        regs[rd] = VM_KERNEL_ADDRPERM((vm_offset_t) tupregs[0].dttk_value);
                }

                break;
        }

        case DIF_SUBR_KDEBUG_TRACE: {
                uint32_t debugid;
                uintptr_t args[4] = {0};
                int i;

                if (nargs < 2 || nargs > 5) {
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
                        break;
                }

                if (dtrace_destructive_disallow)
                        return;

                debugid = tupregs[0].dttk_value;
                for (i = 0; i < nargs - 1; i++)
                        args[i] = tupregs[i + 1].dttk_value;

                kernel_debug(debugid, args[0], args[1], args[2], args[3], 0);

                break;
        }

        case DIF_SUBR_KDEBUG_TRACE_STRING: {
                if (nargs != 3) {
                        break;
                }

                if (dtrace_destructive_disallow)
                        return;

                uint64_t size = state->dts_options[DTRACEOPT_STRSIZE];
                uint32_t debugid = tupregs[0].dttk_value;
                uint64_t str_id = tupregs[1].dttk_value;
                uintptr_t src = tupregs[2].dttk_value;
                size_t lim;
                char buf[size];
                char* str = NULL;

                if (src != (uintptr_t)0) {
                        str = buf;
                        if (!dtrace_strcanload(src, size, &lim, mstate, vstate)) {
                                break;
                        }
                        dtrace_strcpy((void*)src, buf, size);
                }

                (void)kernel_debug_string(debugid, &str_id, str);
                regs[rd] = str_id;

                break;
        }
#endif

        }
}

/*
 * Emulate the execution of DTrace IR instructions specified by the given
 * DIF object.  This function is deliberately void of assertions as all of
 * the necessary checks are handled by a call to dtrace_difo_validate().
 */
static uint64_t
dtrace_dif_emulate(dtrace_difo_t *difo, dtrace_mstate_t *mstate,
    dtrace_vstate_t *vstate, dtrace_state_t *state)
{
        const dif_instr_t *text = difo->dtdo_buf;
        const uint_t textlen = difo->dtdo_len;
        const char *strtab = difo->dtdo_strtab;
        const uint64_t *inttab = difo->dtdo_inttab;

        uint64_t rval = 0;
        dtrace_statvar_t *svar;
        dtrace_dstate_t *dstate = &vstate->dtvs_dynvars;
        dtrace_difv_t *v;
        volatile uint16_t *flags = &cpu_core[CPU->cpu_id].cpuc_dtrace_flags;
        volatile uint64_t *illval = &cpu_core[CPU->cpu_id].cpuc_dtrace_illval;

        dtrace_key_t tupregs[DIF_DTR_NREGS + 2]; /* +2 for thread and id */
        uint64_t regs[DIF_DIR_NREGS];
        uint64_t *tmp;

        uint8_t cc_n = 0, cc_z = 0, cc_v = 0, cc_c = 0;
        int64_t cc_r;
        uint_t pc = 0, id, opc = 0;
        uint8_t ttop = 0;
        dif_instr_t instr;
        uint_t r1, r2, rd;

        /*
         * We stash the current DIF object into the machine state: we need it
         * for subsequent access checking.
         */
        mstate->dtms_difo = difo;

        regs[DIF_REG_R0] = 0;           /* %r0 is fixed at zero */

        while (pc < textlen && !(*flags & CPU_DTRACE_FAULT)) {
                opc = pc;

                instr = text[pc++];
                r1 = DIF_INSTR_R1(instr);
                r2 = DIF_INSTR_R2(instr);
                rd = DIF_INSTR_RD(instr);

                switch (DIF_INSTR_OP(instr)) {
                case DIF_OP_OR:
                        regs[rd] = regs[r1] | regs[r2];
                        break;
                case DIF_OP_XOR:
                        regs[rd] = regs[r1] ^ regs[r2];
                        break;
                case DIF_OP_AND:
                        regs[rd] = regs[r1] & regs[r2];
                        break;
                case DIF_OP_SLL:
                        regs[rd] = regs[r1] << regs[r2];
                        break;
                case DIF_OP_SRL:
                        regs[rd] = regs[r1] >> regs[r2];
                        break;
                case DIF_OP_SUB:
                        regs[rd] = regs[r1] - regs[r2];
                        break;
                case DIF_OP_ADD:
                        regs[rd] = regs[r1] + regs[r2];
                        break;
                case DIF_OP_MUL:
                        regs[rd] = regs[r1] * regs[r2];
                        break;
                case DIF_OP_SDIV:
                        if (regs[r2] == 0) {
                                regs[rd] = 0;
                                *flags |= CPU_DTRACE_DIVZERO;
                        } else {
                                regs[rd] = (int64_t)regs[r1] /
                                    (int64_t)regs[r2];
                        }
                        break;

                case DIF_OP_UDIV:
                        if (regs[r2] == 0) {
                                regs[rd] = 0;
                                *flags |= CPU_DTRACE_DIVZERO;
                        } else {
                                regs[rd] = regs[r1] / regs[r2];
                        }
                        break;

                case DIF_OP_SREM:
                        if (regs[r2] == 0) {
                                regs[rd] = 0;
                                *flags |= CPU_DTRACE_DIVZERO;
                        } else {
                                regs[rd] = (int64_t)regs[r1] %
                                    (int64_t)regs[r2];
                        }
                        break;

                case DIF_OP_UREM:
                        if (regs[r2] == 0) {
                                regs[rd] = 0;
                                *flags |= CPU_DTRACE_DIVZERO;
                        } else {
                                regs[rd] = regs[r1] % regs[r2];
                        }
                        break;

                case DIF_OP_NOT:
                        regs[rd] = ~regs[r1];
                        break;
                case DIF_OP_MOV:
                        regs[rd] = regs[r1];
                        break;
                case DIF_OP_CMP:
                        cc_r = regs[r1] - regs[r2];
                        cc_n = cc_r < 0;
                        cc_z = cc_r == 0;
                        cc_v = 0;
                        cc_c = regs[r1] < regs[r2];
                        break;
                case DIF_OP_TST:
                        cc_n = cc_v = cc_c = 0;
                        cc_z = regs[r1] == 0;
                        break;
                case DIF_OP_BA:
                        pc = DIF_INSTR_LABEL(instr);
                        break;
                case DIF_OP_BE:
                        if (cc_z)
                                pc = DIF_INSTR_LABEL(instr);
                        break;
                case DIF_OP_BNE:
                        if (cc_z == 0)
                                pc = DIF_INSTR_LABEL(instr);
                        break;
                case DIF_OP_BG:
                        if ((cc_z | (cc_n ^ cc_v)) == 0)
                                pc = DIF_INSTR_LABEL(instr);
                        break;
                case DIF_OP_BGU:
                        if ((cc_c | cc_z) == 0)
                                pc = DIF_INSTR_LABEL(instr);
                        break;
                case DIF_OP_BGE:
                        if ((cc_n ^ cc_v) == 0)
                                pc = DIF_INSTR_LABEL(instr);
                        break;
                case DIF_OP_BGEU:
                        if (cc_c == 0)
                                pc = DIF_INSTR_LABEL(instr);
                        break;
                case DIF_OP_BL:
                        if (cc_n ^ cc_v)
                                pc = DIF_INSTR_LABEL(instr);
                        break;
                case DIF_OP_BLU:
                        if (cc_c)
                                pc = DIF_INSTR_LABEL(instr);
                        break;
                case DIF_OP_BLE:
                        if (cc_z | (cc_n ^ cc_v))
                                pc = DIF_INSTR_LABEL(instr);
                        break;
                case DIF_OP_BLEU:
                        if (cc_c | cc_z)
                                pc = DIF_INSTR_LABEL(instr);
                        break;
                case DIF_OP_RLDSB:
                        if (!dtrace_canstore(regs[r1], 1, mstate, vstate)) {
                                *flags |= CPU_DTRACE_KPRIV;
                                *illval = regs[r1];
                                break;
                        }
                        /*FALLTHROUGH*/
                case DIF_OP_LDSB:
                        regs[rd] = (int8_t)dtrace_load8(regs[r1]);
                        break;
                case DIF_OP_RLDSH:
                        if (!dtrace_canstore(regs[r1], 2, mstate, vstate)) {
                                *flags |= CPU_DTRACE_KPRIV;
                                *illval = regs[r1];
                                break;
                        }
                        /*FALLTHROUGH*/
                case DIF_OP_LDSH:
                        regs[rd] = (int16_t)dtrace_load16(regs[r1]);
                        break;
                case DIF_OP_RLDSW:
                        if (!dtrace_canstore(regs[r1], 4, mstate, vstate)) {
                                *flags |= CPU_DTRACE_KPRIV;
                                *illval = regs[r1];
                                break;
                        }
                        /*FALLTHROUGH*/
                case DIF_OP_LDSW:
                        regs[rd] = (int32_t)dtrace_load32(regs[r1]);
                        break;
                case DIF_OP_RLDUB:
                        if (!dtrace_canstore(regs[r1], 1, mstate, vstate)) {
                                *flags |= CPU_DTRACE_KPRIV;
                                *illval = regs[r1];
                                break;
                        }
                        /*FALLTHROUGH*/
                case DIF_OP_LDUB:
                        regs[rd] = dtrace_load8(regs[r1]);
                        break;
                case DIF_OP_RLDUH:
                        if (!dtrace_canstore(regs[r1], 2, mstate, vstate)) {
                                *flags |= CPU_DTRACE_KPRIV;
                                *illval = regs[r1];
                                break;
                        }
                        /*FALLTHROUGH*/
                case DIF_OP_LDUH:
                        regs[rd] = dtrace_load16(regs[r1]);
                        break;
                case DIF_OP_RLDUW:
                        if (!dtrace_canstore(regs[r1], 4, mstate, vstate)) {
                                *flags |= CPU_DTRACE_KPRIV;
                                *illval = regs[r1];
                                break;
                        }
                        /*FALLTHROUGH*/
                case DIF_OP_LDUW:
                        regs[rd] = dtrace_load32(regs[r1]);
                        break;
                case DIF_OP_RLDX:
                        if (!dtrace_canstore(regs[r1], 8, mstate, vstate)) {
                                *flags |= CPU_DTRACE_KPRIV;
                                *illval = regs[r1];
                                break;
                        }
                        /*FALLTHROUGH*/
                case DIF_OP_LDX:
                        regs[rd] = dtrace_load64(regs[r1]);
                        break;
/*
 * Darwin 32-bit kernel may fetch from 64-bit user.
 * Do not cast regs to uintptr_t
 * DIF_OP_ULDSB,DIF_OP_ULDSH, DIF_OP_ULDSW, DIF_OP_ULDUB
 * DIF_OP_ULDUH, DIF_OP_ULDUW, DIF_OP_ULDX
 */
                case DIF_OP_ULDSB:
                        regs[rd] = (int8_t)
                            dtrace_fuword8(regs[r1]);
                        break;
                case DIF_OP_ULDSH:
                        regs[rd] = (int16_t)
                            dtrace_fuword16(regs[r1]);
                        break;
                case DIF_OP_ULDSW:
                        regs[rd] = (int32_t)
                            dtrace_fuword32(regs[r1]);
                        break;
                case DIF_OP_ULDUB:
                        regs[rd] =
                            dtrace_fuword8(regs[r1]);
                        break;
                case DIF_OP_ULDUH:
                        regs[rd] =
                            dtrace_fuword16(regs[r1]);
                        break;
                case DIF_OP_ULDUW:
                        regs[rd] =
                            dtrace_fuword32(regs[r1]);
                        break;
                case DIF_OP_ULDX:
                        regs[rd] =
                            dtrace_fuword64(regs[r1]);
                        break;
                case DIF_OP_RET:
                        rval = regs[rd];
                        pc = textlen;
                        break;
                case DIF_OP_NOP:
                        break;
                case DIF_OP_SETX:
                        regs[rd] = inttab[DIF_INSTR_INTEGER(instr)];
                        break;
                case DIF_OP_SETS:
                        regs[rd] = (uint64_t)(uintptr_t)
                            (strtab + DIF_INSTR_STRING(instr));
                        break;
                case DIF_OP_SCMP: {
                        size_t sz = state->dts_options[DTRACEOPT_STRSIZE];
                        uintptr_t s1 = regs[r1];
                        uintptr_t s2 = regs[r2];
                        size_t lim1 = sz, lim2 = sz;

                        if (s1 != 0 &&
                            !dtrace_strcanload(s1, sz, &lim1, mstate, vstate))
                                break;
                        if (s2 != 0 &&
                            !dtrace_strcanload(s2, sz, &lim2, mstate, vstate))
                                break;

                        cc_r = dtrace_strncmp((char *)s1, (char *)s2,
                                MIN(lim1, lim2));

                        cc_n = cc_r < 0;
                        cc_z = cc_r == 0;
                        cc_v = cc_c = 0;
                        break;
                }
                case DIF_OP_LDGA:
                        regs[rd] = dtrace_dif_variable(mstate, state,
                            r1, regs[r2]);
                        break;
                case DIF_OP_LDGS:
                        id = DIF_INSTR_VAR(instr);

                        if (id >= DIF_VAR_OTHER_UBASE) {
                                uintptr_t a;

                                id -= DIF_VAR_OTHER_UBASE;
                                svar = vstate->dtvs_globals[id];
                                ASSERT(svar != NULL);
                                v = &svar->dtsv_var;

                                if (!(v->dtdv_type.dtdt_flags & DIF_TF_BYREF)) {
                                        regs[rd] = svar->dtsv_data;
                                        break;
                                }

                                a = (uintptr_t)svar->dtsv_data;

                                if (*(uint8_t *)a == UINT8_MAX) {
                                        /*
                                         * If the 0th byte is set to UINT8_MAX
                                         * then this is to be treated as a
                                         * reference to a NULL variable.
                                         */
                                        regs[rd] = 0;
                                } else {
                                        regs[rd] = a + sizeof (uint64_t);
                                }

                                break;
                        }

                        regs[rd] = dtrace_dif_variable(mstate, state, id, 0);
                        break;

                case DIF_OP_STGS:
                        id = DIF_INSTR_VAR(instr);

                        ASSERT(id >= DIF_VAR_OTHER_UBASE);
                        id -= DIF_VAR_OTHER_UBASE;

                        VERIFY(id < (uint_t)vstate->dtvs_nglobals);
                        svar = vstate->dtvs_globals[id];
                        ASSERT(svar != NULL);
                        v = &svar->dtsv_var;

                        if (v->dtdv_type.dtdt_flags & DIF_TF_BYREF) {
                                uintptr_t a = (uintptr_t)svar->dtsv_data;
                                size_t lim;

                                ASSERT(a != 0);
                                ASSERT(svar->dtsv_size != 0);

                                if (regs[rd] == 0) {
                                        *(uint8_t *)a = UINT8_MAX;
                                        break;
                                } else {
                                        *(uint8_t *)a = 0;
                                        a += sizeof (uint64_t);
                                }
                                if (!dtrace_vcanload(
                                    (void *)(uintptr_t)regs[rd], &v->dtdv_type,
                                        &lim, mstate, vstate))
                                        break;

                                dtrace_vcopy((void *)(uintptr_t)regs[rd],
                                    (void *)a, &v->dtdv_type, lim);
                                break;
                        }

                        svar->dtsv_data = regs[rd];
                        break;

                case DIF_OP_LDTA:
                        /*
                         * There are no DTrace built-in thread-local arrays at
                         * present.  This opcode is saved for future work.
                         */
                        *flags |= CPU_DTRACE_ILLOP;
                        regs[rd] = 0;
                        break;

                case DIF_OP_LDLS:
                        id = DIF_INSTR_VAR(instr);

                        if (id < DIF_VAR_OTHER_UBASE) {
                                /*
                                 * For now, this has no meaning.
                                 */
                                regs[rd] = 0;
                                break;
                        }

                        id -= DIF_VAR_OTHER_UBASE;

                        ASSERT(id < (uint_t)vstate->dtvs_nlocals);
                        ASSERT(vstate->dtvs_locals != NULL);
                        svar = vstate->dtvs_locals[id];
                        ASSERT(svar != NULL);
                        v = &svar->dtsv_var;

                        if (v->dtdv_type.dtdt_flags & DIF_TF_BYREF) {
                                uintptr_t a = (uintptr_t)svar->dtsv_data;
                                size_t sz = v->dtdv_type.dtdt_size;

                                sz += sizeof (uint64_t);
                                ASSERT(svar->dtsv_size == (int)NCPU * sz);
                                a += CPU->cpu_id * sz;

                                if (*(uint8_t *)a == UINT8_MAX) {
                                        /*
                                         * If the 0th byte is set to UINT8_MAX
                                         * then this is to be treated as a
                                         * reference to a NULL variable.
                                         */
                                        regs[rd] = 0;
                                } else {
                                        regs[rd] = a + sizeof (uint64_t);
                                }

                                break;
                        }

                        ASSERT(svar->dtsv_size == (int)NCPU * sizeof (uint64_t));
                        tmp = (uint64_t *)(uintptr_t)svar->dtsv_data;
                        regs[rd] = tmp[CPU->cpu_id];
                        break;

                case DIF_OP_STLS:
                        id = DIF_INSTR_VAR(instr);

                        ASSERT(id >= DIF_VAR_OTHER_UBASE);
                        id -= DIF_VAR_OTHER_UBASE;
                        VERIFY(id < (uint_t)vstate->dtvs_nlocals);
                        ASSERT(vstate->dtvs_locals != NULL);
                        svar = vstate->dtvs_locals[id];
                        ASSERT(svar != NULL);
                        v = &svar->dtsv_var;

                        if (v->dtdv_type.dtdt_flags & DIF_TF_BYREF) {
                                uintptr_t a = (uintptr_t)svar->dtsv_data;
                                size_t sz = v->dtdv_type.dtdt_size;
                                size_t lim;

                                sz += sizeof (uint64_t);
                                ASSERT(svar->dtsv_size == (int)NCPU * sz);
                                a += CPU->cpu_id * sz;

                                if (regs[rd] == 0) {
                                        *(uint8_t *)a = UINT8_MAX;
                                        break;
                                } else {
                                        *(uint8_t *)a = 0;
                                        a += sizeof (uint64_t);
                                }

                                if (!dtrace_vcanload(
                                    (void *)(uintptr_t)regs[rd], &v->dtdv_type,
                                    &lim, mstate, vstate))
                                        break;

                                dtrace_vcopy((void *)(uintptr_t)regs[rd],
                                    (void *)a, &v->dtdv_type, lim);
                                break;
                        }

                        ASSERT(svar->dtsv_size == (int)NCPU * sizeof (uint64_t));
                        tmp = (uint64_t *)(uintptr_t)svar->dtsv_data;
                        tmp[CPU->cpu_id] = regs[rd];
                        break;

                case DIF_OP_LDTS: {
                        dtrace_dynvar_t *dvar;
                        dtrace_key_t *key;

                        id = DIF_INSTR_VAR(instr);
                        ASSERT(id >= DIF_VAR_OTHER_UBASE);
                        id -= DIF_VAR_OTHER_UBASE;
                        v = &vstate->dtvs_tlocals[id];

                        key = &tupregs[DIF_DTR_NREGS];
                        key[0].dttk_value = (uint64_t)id;
                        key[0].dttk_size = 0;
                        DTRACE_TLS_THRKEY(key[1].dttk_value);
                        key[1].dttk_size = 0;

                        dvar = dtrace_dynvar(dstate, 2, key,
                            sizeof (uint64_t), DTRACE_DYNVAR_NOALLOC,
                            mstate, vstate);

                        if (dvar == NULL) {
                                regs[rd] = 0;
                                break;
                        }

                        if (v->dtdv_type.dtdt_flags & DIF_TF_BYREF) {
                                regs[rd] = (uint64_t)(uintptr_t)dvar->dtdv_data;
                        } else {
                                regs[rd] = *((uint64_t *)dvar->dtdv_data);
                        }

                        break;
                }

                case DIF_OP_STTS: {
                        dtrace_dynvar_t *dvar;
                        dtrace_key_t *key;

                        id = DIF_INSTR_VAR(instr);
                        ASSERT(id >= DIF_VAR_OTHER_UBASE);
                        id -= DIF_VAR_OTHER_UBASE;
                        VERIFY(id < (uint_t)vstate->dtvs_ntlocals);

                        key = &tupregs[DIF_DTR_NREGS];
                        key[0].dttk_value = (uint64_t)id;
                        key[0].dttk_size = 0;
                        DTRACE_TLS_THRKEY(key[1].dttk_value);
                        key[1].dttk_size = 0;
                        v = &vstate->dtvs_tlocals[id];

                        dvar = dtrace_dynvar(dstate, 2, key,
                            v->dtdv_type.dtdt_size > sizeof (uint64_t) ?
                            v->dtdv_type.dtdt_size : sizeof (uint64_t),
                            regs[rd] ? DTRACE_DYNVAR_ALLOC :
                            DTRACE_DYNVAR_DEALLOC, mstate, vstate);

                        /*
                         * Given that we're storing to thread-local data,
                         * we need to flush our predicate cache.
                         */
                        dtrace_set_thread_predcache(current_thread(), 0);

                        if (dvar == NULL)
                                break;

                        if (v->dtdv_type.dtdt_flags & DIF_TF_BYREF) {
                                size_t lim;

                                if (!dtrace_vcanload(
                                    (void *)(uintptr_t)regs[rd],
                                    &v->dtdv_type, &lim, mstate, vstate))
                                        break;

                                dtrace_vcopy((void *)(uintptr_t)regs[rd],
                                    dvar->dtdv_data, &v->dtdv_type, lim);
                        } else {
                                *((uint64_t *)dvar->dtdv_data) = regs[rd];
                        }

                        break;
                }

                case DIF_OP_SRA:
                        regs[rd] = (int64_t)regs[r1] >> regs[r2];
                        break;

                case DIF_OP_CALL:
                        dtrace_dif_subr(DIF_INSTR_SUBR(instr), rd,
                            regs, tupregs, ttop, mstate, state);
                        break;

                case DIF_OP_PUSHTR:
                        if (ttop == DIF_DTR_NREGS) {
                                *flags |= CPU_DTRACE_TUPOFLOW;
                                break;
                        }

                        if (r1 == DIF_TYPE_STRING) {
                                /*
                                 * If this is a string type and the size is 0,
                                 * we'll use the system-wide default string
                                 * size.  Note that we are _not_ looking at
                                 * the value of the DTRACEOPT_STRSIZE option;
                                 * had this been set, we would expect to have
                                 * a non-zero size value in the "pushtr".
                                 */
                                tupregs[ttop].dttk_size =
                                    dtrace_strlen((char *)(uintptr_t)regs[rd],
                                    regs[r2] ? regs[r2] :
                                    dtrace_strsize_default) + 1;
                        } else {
                                if (regs[r2] > LONG_MAX) {
                                        *flags |= CPU_DTRACE_ILLOP;
                                        break;
                                }
                                tupregs[ttop].dttk_size = regs[r2];
                        }

                        tupregs[ttop++].dttk_value = regs[rd];
                        break;

                case DIF_OP_PUSHTV:
                        if (ttop == DIF_DTR_NREGS) {
                                *flags |= CPU_DTRACE_TUPOFLOW;
                                break;
                        }

                        tupregs[ttop].dttk_value = regs[rd];
                        tupregs[ttop++].dttk_size = 0;
                        break;

                case DIF_OP_POPTS:
                        if (ttop != 0)
                                ttop--;
                        break;

                case DIF_OP_FLUSHTS:
                        ttop = 0;
                        break;

                case DIF_OP_LDGAA:
                case DIF_OP_LDTAA: {
                        dtrace_dynvar_t *dvar;
                        dtrace_key_t *key = tupregs;
                        uint_t nkeys = ttop;

                        id = DIF_INSTR_VAR(instr);
                        ASSERT(id >= DIF_VAR_OTHER_UBASE);
                        id -= DIF_VAR_OTHER_UBASE;

                        key[nkeys].dttk_value = (uint64_t)id;
                        key[nkeys++].dttk_size = 0;

                        if (DIF_INSTR_OP(instr) == DIF_OP_LDTAA) {
                                DTRACE_TLS_THRKEY(key[nkeys].dttk_value);
                                key[nkeys++].dttk_size = 0;
                                VERIFY(id < (uint_t)vstate->dtvs_ntlocals);
                                v = &vstate->dtvs_tlocals[id];
                        } else {
                                VERIFY(id < (uint_t)vstate->dtvs_nglobals);
                                v = &vstate->dtvs_globals[id]->dtsv_var;
                        }

                        dvar = dtrace_dynvar(dstate, nkeys, key,
                            v->dtdv_type.dtdt_size > sizeof (uint64_t) ?
                            v->dtdv_type.dtdt_size : sizeof (uint64_t),
                            DTRACE_DYNVAR_NOALLOC, mstate, vstate);

                        if (dvar == NULL) {
                                regs[rd] = 0;
                                break;
                        }

                        if (v->dtdv_type.dtdt_flags & DIF_TF_BYREF) {
                                regs[rd] = (uint64_t)(uintptr_t)dvar->dtdv_data;
                        } else {
                                regs[rd] = *((uint64_t *)dvar->dtdv_data);
                        }

                        break;
                }

                case DIF_OP_STGAA:
                case DIF_OP_STTAA: {
                        dtrace_dynvar_t *dvar;
                        dtrace_key_t *key = tupregs;
                        uint_t nkeys = ttop;

                        id = DIF_INSTR_VAR(instr);
                        ASSERT(id >= DIF_VAR_OTHER_UBASE);
                        id -= DIF_VAR_OTHER_UBASE;

                        key[nkeys].dttk_value = (uint64_t)id;
                        key[nkeys++].dttk_size = 0;

                        if (DIF_INSTR_OP(instr) == DIF_OP_STTAA) {
                                DTRACE_TLS_THRKEY(key[nkeys].dttk_value);
                                key[nkeys++].dttk_size = 0;
                                VERIFY(id < (uint_t)vstate->dtvs_ntlocals);
                                v = &vstate->dtvs_tlocals[id];
                        } else {
                                VERIFY(id < (uint_t)vstate->dtvs_nglobals);
                                v = &vstate->dtvs_globals[id]->dtsv_var;
                        }

                        dvar = dtrace_dynvar(dstate, nkeys, key,
                            v->dtdv_type.dtdt_size > sizeof (uint64_t) ?
                            v->dtdv_type.dtdt_size : sizeof (uint64_t),
                            regs[rd] ? DTRACE_DYNVAR_ALLOC :
                            DTRACE_DYNVAR_DEALLOC, mstate, vstate);

                        if (dvar == NULL)
                                break;

                        if (v->dtdv_type.dtdt_flags & DIF_TF_BYREF) {
                                size_t lim;

                                if (!dtrace_vcanload(
                                    (void *)(uintptr_t)regs[rd], &v->dtdv_type,
                                    &lim, mstate, vstate))
                                        break;

                                dtrace_vcopy((void *)(uintptr_t)regs[rd],
                                    dvar->dtdv_data, &v->dtdv_type, lim);
                        } else {
                                *((uint64_t *)dvar->dtdv_data) = regs[rd];
                        }

                        break;
                }

                case DIF_OP_ALLOCS: {
                        uintptr_t ptr = P2ROUNDUP(mstate->dtms_scratch_ptr, 8);
                        size_t size = ptr - mstate->dtms_scratch_ptr + regs[r1];

                        /*
                         * Rounding up the user allocation size could have
                         * overflowed large, bogus allocations (like -1ULL) to
                         * 0.
                         */
                        if (size < regs[r1] ||
                            !DTRACE_INSCRATCH(mstate, size)) {
                                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                                regs[rd] = 0;
                                break;
                        }

                        dtrace_bzero((void *) mstate->dtms_scratch_ptr, size);
                                mstate->dtms_scratch_ptr += size;
                                regs[rd] = ptr;
                        break;
                }

                case DIF_OP_COPYS:
                        if (!dtrace_canstore(regs[rd], regs[r2],
                            mstate, vstate)) {
                                *flags |= CPU_DTRACE_BADADDR;
                                *illval = regs[rd];
                                break;
                        }

                        if (!dtrace_canload(regs[r1], regs[r2], mstate, vstate))
                                break;

                        dtrace_bcopy((void *)(uintptr_t)regs[r1],
                            (void *)(uintptr_t)regs[rd], (size_t)regs[r2]);
                        break;

                case DIF_OP_STB:
                        if (!dtrace_canstore(regs[rd], 1, mstate, vstate)) {
                                *flags |= CPU_DTRACE_BADADDR;
                                *illval = regs[rd];
                                break;
                        }
                        *((uint8_t *)(uintptr_t)regs[rd]) = (uint8_t)regs[r1];
                        break;

                case DIF_OP_STH:
                        if (!dtrace_canstore(regs[rd], 2, mstate, vstate)) {
                                *flags |= CPU_DTRACE_BADADDR;
                                *illval = regs[rd];
                                break;
                        }
                        if (regs[rd] & 1) {
                                *flags |= CPU_DTRACE_BADALIGN;
                                *illval = regs[rd];
                                break;
                        }
                        *((uint16_t *)(uintptr_t)regs[rd]) = (uint16_t)regs[r1];
                        break;

                case DIF_OP_STW:
                        if (!dtrace_canstore(regs[rd], 4, mstate, vstate)) {
                                *flags |= CPU_DTRACE_BADADDR;
                                *illval = regs[rd];
                                break;
                        }
                        if (regs[rd] & 3) {
                                *flags |= CPU_DTRACE_BADALIGN;
                                *illval = regs[rd];
                                break;
                        }
                        *((uint32_t *)(uintptr_t)regs[rd]) = (uint32_t)regs[r1];
                        break;

                case DIF_OP_STX:
                        if (!dtrace_canstore(regs[rd], 8, mstate, vstate)) {
                                *flags |= CPU_DTRACE_BADADDR;
                                *illval = regs[rd];
                                break;
                        }

                        /*
                        * Darwin kmem_zalloc() called from
                        * dtrace_difo_init() is 4-byte aligned.
                        */
                        if (regs[rd] & 3) {
                                *flags |= CPU_DTRACE_BADALIGN;
                                *illval = regs[rd];
                                break;
                        }
                        *((uint64_t *)(uintptr_t)regs[rd]) = regs[r1];
                        break;
                case DIF_OP_STRIP:
                        regs[rd] = (uint64_t)dtrace_ptrauth_strip(
                            (void*)regs[r1], r2);
                        break;
                }
        }

        if (!(*flags & CPU_DTRACE_FAULT))
                return (rval);

        mstate->dtms_fltoffs = opc * sizeof (dif_instr_t);
        mstate->dtms_present |= DTRACE_MSTATE_FLTOFFS;

        return (0);
}

static void
dtrace_action_breakpoint(dtrace_ecb_t *ecb)
{
        dtrace_probe_t *probe = ecb->dte_probe;
        dtrace_provider_t *prov = probe->dtpr_provider;
        char c[DTRACE_FULLNAMELEN + 80], *str;
        const char *msg = "dtrace: breakpoint action at probe ";
        const char *ecbmsg = " (ecb ";
        uintptr_t mask = (0xf << (sizeof (uintptr_t) * NBBY / 4));
        uintptr_t val = (uintptr_t)ecb;
        int shift = (sizeof (uintptr_t) * NBBY) - 4, i = 0;

        if (dtrace_destructive_disallow)
                return;

        /*
         * It's impossible to be taking action on the NULL probe.
         */
        ASSERT(probe != NULL);

        /*
         * This is a poor man's (destitute man's?) sprintf():  we want to
         * print the provider name, module name, function name and name of
         * the probe, along with the hex address of the ECB with the breakpoint
         * action -- all of which we must place in the character buffer by
         * hand.
         */
        while (*msg != '\0')
                c[i++] = *msg++;

        for (str = prov->dtpv_name; *str != '\0'; str++)
                c[i++] = *str;
        c[i++] = ':';

        for (str = probe->dtpr_mod; *str != '\0'; str++)
                c[i++] = *str;
        c[i++] = ':';

        for (str = probe->dtpr_func; *str != '\0'; str++)
                c[i++] = *str;
        c[i++] = ':';

        for (str = probe->dtpr_name; *str != '\0'; str++)
                c[i++] = *str;

        while (*ecbmsg != '\0')
                c[i++] = *ecbmsg++;

        while (shift >= 0) {
                mask = (uintptr_t)0xf << shift;

                if (val >= ((uintptr_t)1 << shift))
                        c[i++] = "0123456789abcdef"[(val & mask) >> shift];
                shift -= 4;
        }

        c[i++] = ')';
        c[i] = '\0';

        debug_enter(c);
}

static void
dtrace_action_panic(dtrace_ecb_t *ecb)
{
        dtrace_probe_t *probe = ecb->dte_probe;

        /*
         * It's impossible to be taking action on the NULL probe.
         */
        ASSERT(probe != NULL);

        if (dtrace_destructive_disallow)
                return;

        if (dtrace_panicked != NULL)
                return;

        if (dtrace_casptr(&dtrace_panicked, NULL, current_thread()) != NULL)
                return;

        /*
         * We won the right to panic.  (We want to be sure that only one
         * thread calls panic() from dtrace_probe(), and that panic() is
         * called exactly once.)
         */
        panic("dtrace: panic action at probe %s:%s:%s:%s (ecb %p)",
            probe->dtpr_provider->dtpv_name, probe->dtpr_mod,
            probe->dtpr_func, probe->dtpr_name, (void *)ecb);

        /*
         * APPLE NOTE: this was for an old Mac OS X debug feature
         * allowing a return from panic().  Revisit someday.
         */
        dtrace_panicked = NULL;
}

static void
dtrace_action_raise(uint64_t sig)
{
        if (dtrace_destructive_disallow)
                return;

        if (sig >= NSIG) {
                DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
                return;
        }

        /*
         * raise() has a queue depth of 1 -- we ignore all subsequent
         * invocations of the raise() action.
         */

        uthread_t uthread = (uthread_t)get_bsdthread_info(current_thread());

        if (uthread && uthread->t_dtrace_sig == 0) {
                uthread->t_dtrace_sig = sig;
                act_set_astbsd(current_thread());
        }
}

static void
dtrace_action_stop(void)
{
        if (dtrace_destructive_disallow)
                return;

        uthread_t uthread = (uthread_t)get_bsdthread_info(current_thread());
        if (uthread) {
                /*
                 * The currently running process will be set to task_suspend
                 * when it next leaves the kernel.
                */
                uthread->t_dtrace_stop = 1;
                act_set_astbsd(current_thread());
        }
}


/*
 * APPLE NOTE: pidresume works in conjunction with the dtrace stop action.
 * Both activate only when the currently running process next leaves the
 * kernel.
 */
static void
dtrace_action_pidresume(uint64_t pid)
{
        if (dtrace_destructive_disallow)
                return;

        if (kauth_cred_issuser(kauth_cred_get()) == 0) {
                DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);           
                return;
        }
        uthread_t uthread = (uthread_t)get_bsdthread_info(current_thread());

        /*
         * When the currently running process leaves the kernel, it attempts to
         * task_resume the process (denoted by pid), if that pid appears to have
         * been stopped by dtrace_action_stop().
         * The currently running process has a pidresume() queue depth of 1 --
         * subsequent invocations of the pidresume() action are ignored.
         */     

        if (pid != 0 && uthread && uthread->t_dtrace_resumepid == 0) {
                uthread->t_dtrace_resumepid = pid;
                act_set_astbsd(current_thread());
        }
}

static void
dtrace_action_chill(dtrace_mstate_t *mstate, hrtime_t val)
{
        hrtime_t now;
        volatile uint16_t *flags;
        dtrace_cpu_t *cpu = CPU;

        if (dtrace_destructive_disallow)
                return;

        flags = (volatile uint16_t *)&cpu_core[cpu->cpu_id].cpuc_dtrace_flags;

        now = dtrace_gethrtime();

        if (now - cpu->cpu_dtrace_chillmark > dtrace_chill_interval) {
                /*
                 * We need to advance the mark to the current time.
                 */
                cpu->cpu_dtrace_chillmark = now;
                cpu->cpu_dtrace_chilled = 0;
        }

        /*
         * Now check to see if the requested chill time would take us over
         * the maximum amount of time allowed in the chill interval.  (Or
         * worse, if the calculation itself induces overflow.)
         */
        if (cpu->cpu_dtrace_chilled + val > dtrace_chill_max ||
            cpu->cpu_dtrace_chilled + val < cpu->cpu_dtrace_chilled) {
                *flags |= CPU_DTRACE_ILLOP;
                return;
        }

        while (dtrace_gethrtime() - now < val)
                continue;

        /*
         * Normally, we assure that the value of the variable "timestamp" does
         * not change within an ECB.  The presence of chill() represents an
         * exception to this rule, however.
         */
        mstate->dtms_present &= ~DTRACE_MSTATE_TIMESTAMP;
        cpu->cpu_dtrace_chilled += val;
}

static void
dtrace_action_ustack(dtrace_mstate_t *mstate, dtrace_state_t *state,
    uint64_t *buf, uint64_t arg)
{
        int nframes = DTRACE_USTACK_NFRAMES(arg);
        int strsize = DTRACE_USTACK_STRSIZE(arg);
        uint64_t *pcs = &buf[1], *fps;
        char *str = (char *)&pcs[nframes];
        int size, offs = 0, i, j;
        uintptr_t old = mstate->dtms_scratch_ptr, saved;
        uint16_t *flags = &cpu_core[CPU->cpu_id].cpuc_dtrace_flags;
        char *sym;

        /*
         * Should be taking a faster path if string space has not been
         * allocated.
         */
        ASSERT(strsize != 0);

        /*
         * We will first allocate some temporary space for the frame pointers.
         */
        fps = (uint64_t *)P2ROUNDUP(mstate->dtms_scratch_ptr, 8);
        size = (uintptr_t)fps - mstate->dtms_scratch_ptr +
            (nframes * sizeof (uint64_t));

        if (!DTRACE_INSCRATCH(mstate, (uintptr_t)size)) {
                /*
                 * Not enough room for our frame pointers -- need to indicate
                 * that we ran out of scratch space.
                 */
                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
                return;
        }

        mstate->dtms_scratch_ptr += size;
        saved = mstate->dtms_scratch_ptr;

        /*
         * Now get a stack with both program counters and frame pointers.
         */
        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
        dtrace_getufpstack(buf, fps, nframes + 1);
        DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);

        /*
         * If that faulted, we're cooked.
         */
        if (*flags & CPU_DTRACE_FAULT)
                goto out;

        /*
         * Now we want to walk up the stack, calling the USTACK helper.  For
         * each iteration, we restore the scratch pointer.
         */
        for (i = 0; i < nframes; i++) {
                mstate->dtms_scratch_ptr = saved;

                if (offs >= strsize)
                        break;

                sym = (char *)(uintptr_t)dtrace_helper(
                    DTRACE_HELPER_ACTION_USTACK,
                    mstate, state, pcs[i], fps[i]);

                /*
                 * If we faulted while running the helper, we're going to
                 * clear the fault and null out the corresponding string.
                 */
                if (*flags & CPU_DTRACE_FAULT) {
                        *flags &= ~CPU_DTRACE_FAULT;
                        str[offs++] = '\0';
                        continue;
                }

                if (sym == NULL) {
                        str[offs++] = '\0';
                        continue;
                }

                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);

                /*
                 * Now copy in the string that the helper returned to us.
                 */
                for (j = 0; offs + j < strsize; j++) {
                        if ((str[offs + j] = sym[j]) == '\0')
                                break;
                }

                DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);

                offs += j + 1;
        }

        if (offs >= strsize) {
                /*
                 * If we didn't have room for all of the strings, we don't
                 * abort processing -- this needn't be a fatal error -- but we
                 * still want to increment a counter (dts_stkstroverflows) to
                 * allow this condition to be warned about.  (If this is from
                 * a jstack() action, it is easily tuned via jstackstrsize.)
                 */
                dtrace_error(&state->dts_stkstroverflows);
        }

        while (offs < strsize)
                str[offs++] = '\0';

out:
        mstate->dtms_scratch_ptr = old;
}

static void
dtrace_store_by_ref(dtrace_difo_t *dp, caddr_t tomax, size_t size,
    size_t *valoffsp, uint64_t *valp, uint64_t end, int intuple, int dtkind)
{
        volatile uint16_t *flags;
        uint64_t val = *valp;
        size_t valoffs = *valoffsp;

        flags = (volatile uint16_t *)&cpu_core[CPU->cpu_id].cpuc_dtrace_flags;
        ASSERT(dtkind == DIF_TF_BYREF || dtkind == DIF_TF_BYUREF);

        /*
         * If this is a string, we're going to only load until we find the zero
         * byte -- after which we'll store zero bytes.
         */
        if (dp->dtdo_rtype.dtdt_kind == DIF_TYPE_STRING) {
                char c = '\0' + 1;
                size_t s;

                for (s = 0; s < size; s++) {
                        if (c != '\0' && dtkind == DIF_TF_BYREF) {
                                c = dtrace_load8(val++);
                        } else if (c != '\0' && dtkind == DIF_TF_BYUREF) {
                                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                                c = dtrace_fuword8((user_addr_t)(uintptr_t)val++);
                                DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
                                if (*flags & CPU_DTRACE_FAULT)
                                        break;
                        }

                        DTRACE_STORE(uint8_t, tomax, valoffs++, c);

                        if (c == '\0' && intuple)
                                break;
                }
        } else {
                uint8_t c;
                while (valoffs < end) {
                        if (dtkind == DIF_TF_BYREF) {
                                c = dtrace_load8(val++);
                        } else if (dtkind == DIF_TF_BYUREF) {
                                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                                c = dtrace_fuword8((user_addr_t)(uintptr_t)val++);
                                DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
                                if (*flags & CPU_DTRACE_FAULT)
                                        break;
                        }

                        DTRACE_STORE(uint8_t, tomax,
                            valoffs++, c);
                }
        }

        *valp = val;
        *valoffsp = valoffs;
}

/*
 * Disables interrupts and sets the per-thread inprobe flag. When DEBUG is
 * defined, we also assert that we are not recursing unless the probe ID is an
 * error probe.
 */
static dtrace_icookie_t
dtrace_probe_enter(dtrace_id_t id)
{
        thread_t thread = current_thread();
        uint16_t inprobe;

        dtrace_icookie_t cookie;

        cookie = dtrace_interrupt_disable();

        /*
         * Unless this is an ERROR probe, we are not allowed to recurse in
         * dtrace_probe(). Recursing into DTrace probe usually means that a
         * function is instrumented that should not have been instrumented or
         * that the ordering guarantee of the records will be violated,
         * resulting in unexpected output. If there is an exception to this
         * assertion, a new case should be added.
         */
        inprobe = dtrace_get_thread_inprobe(thread);
        VERIFY(inprobe == 0 ||
            id == dtrace_probeid_error);
        ASSERT(inprobe < UINT16_MAX);
        dtrace_set_thread_inprobe(thread, inprobe + 1);

        return (cookie);
}

/*
 * Clears the per-thread inprobe flag and enables interrupts.
 */
static void
dtrace_probe_exit(dtrace_icookie_t cookie)
{
        thread_t thread = current_thread();
        uint16_t inprobe = dtrace_get_thread_inprobe(thread);

        ASSERT(inprobe > 0);
        dtrace_set_thread_inprobe(thread, inprobe - 1);

#if INTERRUPT_MASKED_DEBUG
        ml_spin_debug_reset(thread);
#endif /* INTERRUPT_MASKED_DEBUG */

        dtrace_interrupt_enable(cookie);
}

/*
 * If you're looking for the epicenter of DTrace, you just found it.  This
 * is the function called by the provider to fire a probe -- from which all
 * subsequent probe-context DTrace activity emanates.
 */
void
dtrace_probe(dtrace_id_t id, uint64_t arg0, uint64_t arg1,
    uint64_t arg2, uint64_t arg3, uint64_t arg4)
{
        processorid_t cpuid;
        dtrace_icookie_t cookie;
        dtrace_probe_t *probe;
        dtrace_mstate_t mstate;
        dtrace_ecb_t *ecb;
        dtrace_action_t *act;
        intptr_t offs;
        size_t size;
        int vtime, onintr;
        volatile uint16_t *flags;
        hrtime_t now;

        cookie = dtrace_probe_enter(id);
        probe = dtrace_probes[id - 1];
        cpuid = CPU->cpu_id;
        onintr = CPU_ON_INTR(CPU);

        if (!onintr && probe->dtpr_predcache != DTRACE_CACHEIDNONE &&
            probe->dtpr_predcache == dtrace_get_thread_predcache(current_thread())) {
                /*
                 * We have hit in the predicate cache; we know that
                 * this predicate would evaluate to be false.
                 */
                dtrace_probe_exit(cookie);
                return;
        }

        if (panic_quiesce) {
                /*
                 * We don't trace anything if we're panicking.
                 */
                dtrace_probe_exit(cookie);
                return;
        }

#if !defined(__APPLE__)
        now = dtrace_gethrtime();
        vtime = dtrace_vtime_references != 0;

        if (vtime && curthread->t_dtrace_start)
                curthread->t_dtrace_vtime += now - curthread->t_dtrace_start;
#else
        /*
         * APPLE NOTE:  The time spent entering DTrace and arriving
         * to this point, is attributed to the current thread.
         * Instead it should accrue to DTrace.  FIXME
         */
        vtime = dtrace_vtime_references != 0;

        if (vtime)
        {
                int64_t dtrace_accum_time, recent_vtime;
                thread_t thread = current_thread();

                dtrace_accum_time = dtrace_get_thread_tracing(thread); /* Time spent inside DTrace so far (nanoseconds) */

                if (dtrace_accum_time >= 0) {
                        recent_vtime = dtrace_abs_to_nano(dtrace_calc_thread_recent_vtime(thread)); /* up to the moment thread vtime */

                        recent_vtime = recent_vtime - dtrace_accum_time; /* Time without DTrace contribution */
                
                        dtrace_set_thread_vtime(thread, recent_vtime);
                }
        }

        now = dtrace_gethrtime(); /* must not precede dtrace_calc_thread_recent_vtime() call! */
#endif /* __APPLE__ */

        /*
         * APPLE NOTE: A provider may call dtrace_probe_error() in lieu of
         * dtrace_probe() in some circumstances.   See, e.g. fasttrap_isa.c.
         * However the provider has no access to ECB context, so passes
         * 0 through "arg0" and the probe_id of the overridden probe as arg1.
         * Detect that here and cons up a viable state (from the probe_id).
         */
        if (dtrace_probeid_error == id && 0 == arg0) {
                dtrace_id_t ftp_id = (dtrace_id_t)arg1;
                dtrace_probe_t *ftp_probe = dtrace_probes[ftp_id - 1];
                dtrace_ecb_t *ftp_ecb = ftp_probe->dtpr_ecb;

                if (NULL != ftp_ecb) {
                        dtrace_state_t *ftp_state = ftp_ecb->dte_state;

                        arg0 = (uint64_t)(uintptr_t)ftp_state;
                        arg1 = ftp_ecb->dte_epid;
                        /*
                         * args[2-4] established by caller.
                         */
                        ftp_state->dts_arg_error_illval = -1; /* arg5 */
                }
        }

        mstate.dtms_difo = NULL;
        mstate.dtms_probe = probe;
        mstate.dtms_strtok = 0;
        mstate.dtms_arg[0] = arg0;
        mstate.dtms_arg[1] = arg1;
        mstate.dtms_arg[2] = arg2;
        mstate.dtms_arg[3] = arg3;
        mstate.dtms_arg[4] = arg4;

        flags = (volatile uint16_t *)&cpu_core[cpuid].cpuc_dtrace_flags;

        for (ecb = probe->dtpr_ecb; ecb != NULL; ecb = ecb->dte_next) {
                dtrace_predicate_t *pred = ecb->dte_predicate;
                dtrace_state_t *state = ecb->dte_state;
                dtrace_buffer_t *buf = &state->dts_buffer[cpuid];
                dtrace_buffer_t *aggbuf = &state->dts_aggbuffer[cpuid];
                dtrace_vstate_t *vstate = &state->dts_vstate;
                dtrace_provider_t *prov = probe->dtpr_provider;
                uint64_t tracememsize = 0;
                int committed = 0;
                caddr_t tomax;

                /*
                 * A little subtlety with the following (seemingly innocuous)
                 * declaration of the automatic 'val':  by looking at the
                 * code, you might think that it could be declared in the
                 * action processing loop, below.  (That is, it's only used in
                 * the action processing loop.)  However, it must be declared
                 * out of that scope because in the case of DIF expression
                 * arguments to aggregating actions, one iteration of the
                 * action loop will use the last iteration's value.
                 */
#ifdef lint
                uint64_t val = 0;
#else
                uint64_t val = 0;
#endif

                mstate.dtms_present = DTRACE_MSTATE_ARGS | DTRACE_MSTATE_PROBE;
                *flags &= ~CPU_DTRACE_ERROR;

                if (prov == dtrace_provider) {
                        /*
                         * If dtrace itself is the provider of this probe,
                         * we're only going to continue processing the ECB if
                         * arg0 (the dtrace_state_t) is equal to the ECB's
                         * creating state.  (This prevents disjoint consumers
                         * from seeing one another's metaprobes.)
                         */
                        if (arg0 != (uint64_t)(uintptr_t)state)
                                continue;
                }

                if (state->dts_activity != DTRACE_ACTIVITY_ACTIVE) {
                        /*
                         * We're not currently active.  If our provider isn't
                         * the dtrace pseudo provider, we're not interested.
                         */
                        if (prov != dtrace_provider)
                                continue;

                        /*
                         * Now we must further check if we are in the BEGIN
                         * probe.  If we are, we will only continue processing
                         * if we're still in WARMUP -- if one BEGIN enabling
                         * has invoked the exit() action, we don't want to
                         * evaluate subsequent BEGIN enablings.
                         */
                        if (probe->dtpr_id == dtrace_probeid_begin &&
                            state->dts_activity != DTRACE_ACTIVITY_WARMUP) {
                                ASSERT(state->dts_activity ==
                                    DTRACE_ACTIVITY_DRAINING);
                                continue;
                        }
                }

                if (ecb->dte_cond) {
                        /*
                         * If the dte_cond bits indicate that this
                         * consumer is only allowed to see user-mode firings
                         * of this probe, call the provider's dtps_usermode()
                         * entry point to check that the probe was fired
                         * while in a user context. Skip this ECB if that's
                         * not the case.
                         */
                        if ((ecb->dte_cond & DTRACE_COND_USERMODE) &&
                            prov->dtpv_pops.dtps_usermode &&
                            prov->dtpv_pops.dtps_usermode(prov->dtpv_arg,
                            probe->dtpr_id, probe->dtpr_arg) == 0)
                                continue;

                        /*
                         * This is more subtle than it looks. We have to be
                         * absolutely certain that CRED() isn't going to
                         * change out from under us so it's only legit to
                         * examine that structure if we're in constrained
                         * situations. Currently, the only times we'll this
                         * check is if a non-super-user has enabled the
                         * profile or syscall providers -- providers that
                         * allow visibility of all processes. For the
                         * profile case, the check above will ensure that
                         * we're examining a user context.
                         */
                        if (ecb->dte_cond & DTRACE_COND_OWNER) {
                                cred_t *cr;
                                cred_t *s_cr =
                                    ecb->dte_state->dts_cred.dcr_cred;
                                proc_t *proc;
#pragma unused(proc) /* __APPLE__ */

                                ASSERT(s_cr != NULL);

                        /*
                         * XXX this is hackish, but so is setting a variable
                         * XXX in a McCarthy OR...
                         */
                                if ((cr = dtrace_CRED()) == NULL ||
                                    posix_cred_get(s_cr)->cr_uid != posix_cred_get(cr)->cr_uid ||
                                    posix_cred_get(s_cr)->cr_uid != posix_cred_get(cr)->cr_ruid ||
                                    posix_cred_get(s_cr)->cr_uid != posix_cred_get(cr)->cr_suid ||
                                    posix_cred_get(s_cr)->cr_gid != posix_cred_get(cr)->cr_gid ||
                                    posix_cred_get(s_cr)->cr_gid != posix_cred_get(cr)->cr_rgid ||
                                    posix_cred_get(s_cr)->cr_gid != posix_cred_get(cr)->cr_sgid ||
#if !defined(__APPLE__)
                                    (proc = ttoproc(curthread)) == NULL ||
                                    (proc->p_flag & SNOCD))
#else
                                        1) /* APPLE NOTE: Darwin omits "No Core Dump" flag */
#endif /* __APPLE__ */
                                        continue;
                        }

                        if (ecb->dte_cond & DTRACE_COND_ZONEOWNER) {
                                cred_t *cr;
                                cred_t *s_cr =
                                    ecb->dte_state->dts_cred.dcr_cred;
#pragma unused(cr, s_cr) /* __APPLE__ */

                                ASSERT(s_cr != NULL);

#if !defined(__APPLE__)
                                if ((cr = CRED()) == NULL ||
                                    s_cr->cr_zone->zone_id !=
                                    cr->cr_zone->zone_id)
                                        continue;
#else
                                /* APPLE NOTE: Darwin doesn't do zones. */
#endif /* __APPLE__ */
                        }
                }

                if (now - state->dts_alive > dtrace_deadman_timeout) {
                        /*
                         * We seem to be dead.  Unless we (a) have kernel
                         * destructive permissions (b) have expicitly enabled
                         * destructive actions and (c) destructive actions have
                         * not been disabled, we're going to transition into
                         * the KILLED state, from which no further processing
                         * on this state will be performed.
                         */
                        if (!dtrace_priv_kernel_destructive(state) ||
                            !state->dts_cred.dcr_destructive ||
                            dtrace_destructive_disallow) {
                                void *activity = &state->dts_activity;
                                dtrace_activity_t current;

                                do {
                                        current = state->dts_activity;
                                } while (dtrace_cas32(activity, current,
                                    DTRACE_ACTIVITY_KILLED) != current);

                                continue;
                        }
                }

                if ((offs = dtrace_buffer_reserve(buf, ecb->dte_needed,
                    ecb->dte_alignment, state, &mstate)) < 0)
                        continue;

                tomax = buf->dtb_tomax;
                ASSERT(tomax != NULL);

                /*
                 * Build and store the record header corresponding to the ECB.
                 */
                if (ecb->dte_size != 0) {
                        dtrace_rechdr_t dtrh;

                        if (!(mstate.dtms_present & DTRACE_MSTATE_TIMESTAMP)) {
                                mstate.dtms_timestamp = dtrace_gethrtime();
                                mstate.dtms_present |= DTRACE_MSTATE_TIMESTAMP;
                        }

                        ASSERT(ecb->dte_size >= sizeof(dtrace_rechdr_t));

                        dtrh.dtrh_epid = ecb->dte_epid;
                        DTRACE_RECORD_STORE_TIMESTAMP(&dtrh, mstate.dtms_timestamp);
                        DTRACE_STORE(dtrace_rechdr_t, tomax, offs, dtrh);
                }

                mstate.dtms_epid = ecb->dte_epid;
                mstate.dtms_present |= DTRACE_MSTATE_EPID;

                if (state->dts_cred.dcr_visible & DTRACE_CRV_KERNEL)
                        mstate.dtms_access = DTRACE_ACCESS_KERNEL;
                else
                        mstate.dtms_access = 0;

                if (pred != NULL) {
                        dtrace_difo_t *dp = pred->dtp_difo;
                        uint64_t rval;

                        rval = dtrace_dif_emulate(dp, &mstate, vstate, state);

                        if (!(*flags & CPU_DTRACE_ERROR) && !rval) {
                                dtrace_cacheid_t cid = probe->dtpr_predcache;

                                if (cid != DTRACE_CACHEIDNONE && !onintr) {
                                        /*
                                         * Update the predicate cache...
                                         */
                                        ASSERT(cid == pred->dtp_cacheid);

                                        dtrace_set_thread_predcache(current_thread(), cid);
                                }

                                continue;
                        }
                }

                for (act = ecb->dte_action; !(*flags & CPU_DTRACE_ERROR) &&
                    act != NULL; act = act->dta_next) {
                        size_t valoffs;
                        dtrace_difo_t *dp;
                        dtrace_recdesc_t *rec = &act->dta_rec;

                        size = rec->dtrd_size;
                        valoffs = offs + rec->dtrd_offset;

                        if (DTRACEACT_ISAGG(act->dta_kind)) {
                                uint64_t v = 0xbad;
                                dtrace_aggregation_t *agg;

                                agg = (dtrace_aggregation_t *)act;

                                if ((dp = act->dta_difo) != NULL)
                                        v = dtrace_dif_emulate(dp,
                                            &mstate, vstate, state);

                                if (*flags & CPU_DTRACE_ERROR)
                                        continue;

                                /*
                                 * Note that we always pass the expression
                                 * value from the previous iteration of the
                                 * action loop.  This value will only be used
                                 * if there is an expression argument to the
                                 * aggregating action, denoted by the
                                 * dtag_hasarg field.
                                 */
                                dtrace_aggregate(agg, buf,
                                    offs, aggbuf, v, val);
                                continue;
                        }

                        switch (act->dta_kind) {
                        case DTRACEACT_STOP:
                                if (dtrace_priv_proc_destructive(state))
                                        dtrace_action_stop();
                                continue;

                        case DTRACEACT_BREAKPOINT:
                                if (dtrace_priv_kernel_destructive(state))
                                        dtrace_action_breakpoint(ecb);
                                continue;

                        case DTRACEACT_PANIC:
                                if (dtrace_priv_kernel_destructive(state))
                                        dtrace_action_panic(ecb);
                                continue;

                        case DTRACEACT_STACK:
                                if (!dtrace_priv_kernel(state))
                                        continue;

                                dtrace_getpcstack((pc_t *)(tomax + valoffs),
                                    size / sizeof (pc_t), probe->dtpr_aframes,
                                    DTRACE_ANCHORED(probe) ? NULL :
                                  (uint32_t *)(uintptr_t)arg0);
                                continue;

                        case DTRACEACT_JSTACK:
                        case DTRACEACT_USTACK:
                                if (!dtrace_priv_proc(state))
                                        continue;

                                /*
                                 * See comment in DIF_VAR_PID.
                                 */
                                if (DTRACE_ANCHORED(mstate.dtms_probe) &&
                                    CPU_ON_INTR(CPU)) {
                                        int depth = DTRACE_USTACK_NFRAMES(
                                            rec->dtrd_arg) + 1;

                                        dtrace_bzero((void *)(tomax + valoffs),
                                            DTRACE_USTACK_STRSIZE(rec->dtrd_arg)
                                            + depth * sizeof (uint64_t));

                                        continue;
                                }

                                if (DTRACE_USTACK_STRSIZE(rec->dtrd_arg) != 0 &&
                                    curproc->p_dtrace_helpers != NULL) {
                                        /*
                                         * This is the slow path -- we have
                                         * allocated string space, and we're
                                         * getting the stack of a process that
                                         * has helpers.  Call into a separate
                                         * routine to perform this processing.
                                         */
                                        dtrace_action_ustack(&mstate, state,
                                            (uint64_t *)(tomax + valoffs),
                                            rec->dtrd_arg);
                                        continue;
                                }

                                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                                dtrace_getupcstack((uint64_t *)
                                    (tomax + valoffs),
                                    DTRACE_USTACK_NFRAMES(rec->dtrd_arg) + 1);
                                DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
                                continue;

                        default:
                                break;
                        }

                        dp = act->dta_difo;
                        ASSERT(dp != NULL);

                        val = dtrace_dif_emulate(dp, &mstate, vstate, state);

                        if (*flags & CPU_DTRACE_ERROR)
                                continue;

                        switch (act->dta_kind) {
                        case DTRACEACT_SPECULATE: {
                                dtrace_rechdr_t *dtrh = NULL;

                                ASSERT(buf == &state->dts_buffer[cpuid]);
                                buf = dtrace_speculation_buffer(state,
                                    cpuid, val);

                                if (buf == NULL) {
                                        *flags |= CPU_DTRACE_DROP;
                                        continue;
                                }

                                offs = dtrace_buffer_reserve(buf,
                                    ecb->dte_needed, ecb->dte_alignment,
                                    state, NULL);

                                if (offs < 0) {
                                        *flags |= CPU_DTRACE_DROP;
                                        continue;
                                }

                                tomax = buf->dtb_tomax;
                                ASSERT(tomax != NULL);

                                if (ecb->dte_size == 0)
                                        continue;

                                ASSERT(ecb->dte_size >= sizeof(dtrace_rechdr_t));
                                dtrh = ((void *)(tomax + offs));
                                dtrh->dtrh_epid = ecb->dte_epid;

                                /*
                                 * When the speculation is committed, all of
                                 * the records in the speculative buffer will
                                 * have their timestamps set to the commit
                                 * time.  Until then, it is set to a sentinel
                                 * value, for debugability.
                                 */
                                DTRACE_RECORD_STORE_TIMESTAMP(dtrh, UINT64_MAX);

                                continue;
                        }

                        case DTRACEACT_CHILL:
                                if (dtrace_priv_kernel_destructive(state))
                                        dtrace_action_chill(&mstate, val);
                                continue;

                        case DTRACEACT_RAISE:
                                if (dtrace_priv_proc_destructive(state))
                                        dtrace_action_raise(val);
                                continue;

                        case DTRACEACT_PIDRESUME:   /* __APPLE__ */
                                if (dtrace_priv_proc_destructive(state))
                                        dtrace_action_pidresume(val);
                                continue;

                        case DTRACEACT_COMMIT:
                                ASSERT(!committed);

                                /*
                                 * We need to commit our buffer state.
                                 */
                                if (ecb->dte_size)
                                        buf->dtb_offset = offs + ecb->dte_size;
                                buf = &state->dts_buffer[cpuid];
                                dtrace_speculation_commit(state, cpuid, val);
                                committed = 1;
                                continue;

                        case DTRACEACT_DISCARD:
                                dtrace_speculation_discard(state, cpuid, val);
                                continue;

                        case DTRACEACT_DIFEXPR:
                        case DTRACEACT_LIBACT:
                        case DTRACEACT_PRINTF:
                        case DTRACEACT_PRINTA:
                        case DTRACEACT_SYSTEM:
                        case DTRACEACT_FREOPEN:
                        case DTRACEACT_APPLEBINARY:   /* __APPLE__ */
                        case DTRACEACT_TRACEMEM:
                                break;

                        case DTRACEACT_TRACEMEM_DYNSIZE:
                                tracememsize = val;
                                break;

                        case DTRACEACT_SYM:
                        case DTRACEACT_MOD:
                                if (!dtrace_priv_kernel(state))
                                        continue;
                                break;

                        case DTRACEACT_USYM:
                        case DTRACEACT_UMOD:
                        case DTRACEACT_UADDR: {
                                if (!dtrace_priv_proc(state))
                                        continue;

                                DTRACE_STORE(uint64_t, tomax,
                                    valoffs, (uint64_t)dtrace_proc_selfpid());
                                DTRACE_STORE(uint64_t, tomax,
                                    valoffs + sizeof (uint64_t), val);

                                continue;
                        }

                        case DTRACEACT_EXIT: {
                                /*
                                 * For the exit action, we are going to attempt
                                 * to atomically set our activity to be
                                 * draining.  If this fails (either because
                                 * another CPU has beat us to the exit action,
                                 * or because our current activity is something
                                 * other than ACTIVE or WARMUP), we will
                                 * continue.  This assures that the exit action
                                 * can be successfully recorded at most once
                                 * when we're in the ACTIVE state.  If we're
                                 * encountering the exit() action while in
                                 * COOLDOWN, however, we want to honor the new
                                 * status code.  (We know that we're the only
                                 * thread in COOLDOWN, so there is no race.)
                                 */
                                void *activity = &state->dts_activity;
                                dtrace_activity_t current = state->dts_activity;

                                if (current == DTRACE_ACTIVITY_COOLDOWN)
                                        break;

                                if (current != DTRACE_ACTIVITY_WARMUP)
                                        current = DTRACE_ACTIVITY_ACTIVE;

                                if (dtrace_cas32(activity, current,
                                    DTRACE_ACTIVITY_DRAINING) != current) {
                                        *flags |= CPU_DTRACE_DROP;
                                        continue;
                                }

                                break;
                        }

                        default:
                                ASSERT(0);
                        }

                        if (dp->dtdo_rtype.dtdt_flags & (DIF_TF_BYREF | DIF_TF_BYUREF)) {
                                uintptr_t end = valoffs + size;

                                if (tracememsize != 0 &&
                                    valoffs + tracememsize < end)
                                {
                                        end = valoffs + tracememsize;
                                        tracememsize = 0;
                                }

                                if (dp->dtdo_rtype.dtdt_flags & DIF_TF_BYREF &&
                                    !dtrace_vcanload((void *)(uintptr_t)val,
                                    &dp->dtdo_rtype, NULL, &mstate, vstate))
                                {
                                        continue;
                                }

                                dtrace_store_by_ref(dp, tomax, size, &valoffs,
                                    &val, end, act->dta_intuple,
                                    dp->dtdo_rtype.dtdt_flags & DIF_TF_BYREF ?
                                    DIF_TF_BYREF: DIF_TF_BYUREF);

                                continue;
                        }

                        switch (size) {
                        case 0:
                                break;

                        case sizeof (uint8_t):
                                DTRACE_STORE(uint8_t, tomax, valoffs, val);
                                break;
                        case sizeof (uint16_t):
                                DTRACE_STORE(uint16_t, tomax, valoffs, val);
                                break;
                        case sizeof (uint32_t):
                                DTRACE_STORE(uint32_t, tomax, valoffs, val);
                                break;
                        case sizeof (uint64_t):
                                DTRACE_STORE(uint64_t, tomax, valoffs, val);
                                break;
                        default:
                                /*
                                 * Any other size should have been returned by
                                 * reference, not by value.
                                 */
                                ASSERT(0);
                                break;
                        }
                }

                if (*flags & CPU_DTRACE_DROP)
                        continue;

                if (*flags & CPU_DTRACE_FAULT) {
                        int ndx;
                        dtrace_action_t *err;

                        buf->dtb_errors++;

                        if (probe->dtpr_id == dtrace_probeid_error) {
                                /*
                                 * There's nothing we can do -- we had an
                                 * error on the error probe.  We bump an
                                 * error counter to at least indicate that
                                 * this condition happened.
                                 */
                                dtrace_error(&state->dts_dblerrors);
                                continue;
                        }

                        if (vtime) {
                                /*
                                 * Before recursing on dtrace_probe(), we
                                 * need to explicitly clear out our start
                                 * time to prevent it from being accumulated
                                 * into t_dtrace_vtime.
                                 */

                                /*                                 
                                 * Darwin sets the sign bit on t_dtrace_tracing
                                 * to suspend accumulation to it.
                                 */
                                dtrace_set_thread_tracing(current_thread(), 
                                    (1ULL<<63) | dtrace_get_thread_tracing(current_thread()));

                        }

                        /*
                         * Iterate over the actions to figure out which action
                         * we were processing when we experienced the error.
                         * Note that act points _past_ the faulting action; if
                         * act is ecb->dte_action, the fault was in the
                         * predicate, if it's ecb->dte_action->dta_next it's
                         * in action #1, and so on.
                         */
                        for (err = ecb->dte_action, ndx = 0;
                            err != act; err = err->dta_next, ndx++)
                                continue;

                        dtrace_probe_error(state, ecb->dte_epid, ndx,
                            (mstate.dtms_present & DTRACE_MSTATE_FLTOFFS) ?
                            mstate.dtms_fltoffs : -1, DTRACE_FLAGS2FLT(*flags),
                            cpu_core[cpuid].cpuc_dtrace_illval);

                        continue;
                }

                if (!committed)
                        buf->dtb_offset = offs + ecb->dte_size;
        }

        /* FIXME: On Darwin the time spent leaving DTrace from this point to the rti is attributed
           to the current thread. Instead it should accrue to DTrace. */
        if (vtime) {
                thread_t thread = current_thread();
                int64_t t = dtrace_get_thread_tracing(thread);
                
                if (t >= 0) {
                        /* Usual case, accumulate time spent here into t_dtrace_tracing */
                        dtrace_set_thread_tracing(thread, t + (dtrace_gethrtime() - now));
                } else {
                        /* Return from error recursion. No accumulation, just clear the sign bit on t_dtrace_tracing. */
                        dtrace_set_thread_tracing(thread, (~(1ULL<<63)) & t);
                }
        }

        dtrace_probe_exit(cookie);
}

/*
 * DTrace Probe Hashing Functions
 *
 * The functions in this section (and indeed, the functions in remaining
 * sections) are not _called_ from probe context.  (Any exceptions to this are
 * marked with a "Note:".)  Rather, they are called from elsewhere in the
 * DTrace framework to look-up probes in, add probes to and remove probes from
 * the DTrace probe hashes.  (Each probe is hashed by each element of the
 * probe tuple -- allowing for fast lookups, regardless of what was
 * specified.)
 */
static uint_t
dtrace_hash_str(const char *p)
{
        unsigned int g;
        uint_t hval = 0;

        while (*p) {
                hval = (hval << 4) + *p++;
                if ((g = (hval & 0xf0000000)) != 0)
                        hval ^= g >> 24;
                hval &= ~g;
        }
        return (hval);
}

static const char*
dtrace_strkey_probe_provider(void *elm, uintptr_t offs)
{
#pragma unused(offs)
        dtrace_probe_t *probe = (dtrace_probe_t*)elm;
        return probe->dtpr_provider->dtpv_name;
}

static const char*
dtrace_strkey_offset(void *elm, uintptr_t offs)
{
        return ((char *)((uintptr_t)(elm) + offs));
}

static const char*
dtrace_strkey_deref_offset(void *elm, uintptr_t offs)
{
        return *((char **)((uintptr_t)(elm) + offs));
}

static dtrace_hash_t *
dtrace_hash_create(dtrace_strkey_f func, uintptr_t arg, uintptr_t nextoffs, uintptr_t prevoffs)
{
        dtrace_hash_t *hash = kmem_zalloc(sizeof (dtrace_hash_t), KM_SLEEP);

        hash->dth_getstr = func;
        hash->dth_stroffs = arg;
        hash->dth_nextoffs = nextoffs;
        hash->dth_prevoffs = prevoffs;

        hash->dth_size = 1;
        hash->dth_mask = hash->dth_size - 1;

        hash->dth_tab = kmem_zalloc(hash->dth_size *
            sizeof (dtrace_hashbucket_t *), KM_SLEEP);

        return (hash);
}

/*
 * APPLE NOTE: dtrace_hash_destroy is not used.
 * It is called by dtrace_detach which is not
 * currently implemented.  Revisit someday.
 */
#if !defined(__APPLE__)
static void
dtrace_hash_destroy(dtrace_hash_t *hash)
{
#if DEBUG
        int i;

        for (i = 0; i < hash->dth_size; i++)
                ASSERT(hash->dth_tab[i] == NULL);
#endif

        kmem_free(hash->dth_tab,
            hash->dth_size * sizeof (dtrace_hashbucket_t *));
        kmem_free(hash, sizeof (dtrace_hash_t));
}
#endif /* __APPLE__ */

static void
dtrace_hash_resize(dtrace_hash_t *hash)
{
        int size = hash->dth_size, i, ndx;
        int new_size = hash->dth_size << 1;
        int new_mask = new_size - 1;
        dtrace_hashbucket_t **new_tab, *bucket, *next;

        ASSERT((new_size & new_mask) == 0);

        new_tab = kmem_zalloc(new_size * sizeof (void *), KM_SLEEP);

        for (i = 0; i < size; i++) {
                for (bucket = hash->dth_tab[i]; bucket != NULL; bucket = next) {
                        void *elm = bucket->dthb_chain;

                        ASSERT(elm != NULL);
                        ndx = DTRACE_HASHSTR(hash, elm) & new_mask;

                        next = bucket->dthb_next;
                        bucket->dthb_next = new_tab[ndx];
                        new_tab[ndx] = bucket;
                }
        }

        kmem_free(hash->dth_tab, hash->dth_size * sizeof (void *));
        hash->dth_tab = new_tab;
        hash->dth_size = new_size;
        hash->dth_mask = new_mask;
}

static void
dtrace_hash_add(dtrace_hash_t *hash, void *new)
{
        int hashval = DTRACE_HASHSTR(hash, new);
        int ndx = hashval & hash->dth_mask;
        dtrace_hashbucket_t *bucket = hash->dth_tab[ndx];
        void **nextp, **prevp;

        for (; bucket != NULL; bucket = bucket->dthb_next) {
                if (DTRACE_HASHEQ(hash, bucket->dthb_chain, new))
                        goto add;
        }

        if ((hash->dth_nbuckets >> 1) > hash->dth_size) {
                dtrace_hash_resize(hash);
                dtrace_hash_add(hash, new);
                return;
        }

        bucket = kmem_zalloc(sizeof (dtrace_hashbucket_t), KM_SLEEP);
        bucket->dthb_next = hash->dth_tab[ndx];
        hash->dth_tab[ndx] = bucket;
        hash->dth_nbuckets++;

add:
        nextp = DTRACE_HASHNEXT(hash, new);
        ASSERT(*nextp == NULL && *(DTRACE_HASHPREV(hash, new)) == NULL);
        *nextp = bucket->dthb_chain;

        if (bucket->dthb_chain != NULL) {
                prevp = DTRACE_HASHPREV(hash, bucket->dthb_chain);
                ASSERT(*prevp == NULL);
                *prevp = new;
        }

        bucket->dthb_chain = new;
        bucket->dthb_len++;
}

static void *
dtrace_hash_lookup_string(dtrace_hash_t *hash, const char *str)
{
        int hashval = dtrace_hash_str(str);
        int ndx = hashval & hash->dth_mask;
        dtrace_hashbucket_t *bucket = hash->dth_tab[ndx];

        for (; bucket != NULL; bucket = bucket->dthb_next) {
                if (strcmp(str, DTRACE_GETSTR(hash, bucket->dthb_chain)) == 0)
                        return (bucket->dthb_chain);
        }

        return (NULL);
}

static dtrace_probe_t *
dtrace_hash_lookup(dtrace_hash_t *hash, void *template)
{
        return dtrace_hash_lookup_string(hash, DTRACE_GETSTR(hash, template));
}

static int
dtrace_hash_collisions(dtrace_hash_t *hash, void *template)
{
        int hashval = DTRACE_HASHSTR(hash, template);
        int ndx = hashval & hash->dth_mask;
        dtrace_hashbucket_t *bucket = hash->dth_tab[ndx];

        for (; bucket != NULL; bucket = bucket->dthb_next) {
                if (DTRACE_HASHEQ(hash, bucket->dthb_chain, template))
                        return (bucket->dthb_len);
        }

        return (0);
}

static void
dtrace_hash_remove(dtrace_hash_t *hash, void *elm)
{
        int ndx = DTRACE_HASHSTR(hash, elm) & hash->dth_mask;
        dtrace_hashbucket_t *bucket = hash->dth_tab[ndx];

        void **prevp = DTRACE_HASHPREV(hash, elm);
        void **nextp = DTRACE_HASHNEXT(hash, elm);

        /*
         * Find the bucket that we're removing this elm from.
         */
        for (; bucket != NULL; bucket = bucket->dthb_next) {
                if (DTRACE_HASHEQ(hash, bucket->dthb_chain, elm))
                        break;
        }

        ASSERT(bucket != NULL);

        if (*prevp == NULL) {
                if (*nextp == NULL) {
                        /*
                         * The removed element was the only element on this
                         * bucket; we need to remove the bucket.
                         */
                        dtrace_hashbucket_t *b = hash->dth_tab[ndx];

                        ASSERT(bucket->dthb_chain == elm);
                        ASSERT(b != NULL);

                        if (b == bucket) {
                                hash->dth_tab[ndx] = bucket->dthb_next;
                        } else {
                                while (b->dthb_next != bucket)
                                        b = b->dthb_next;
                                b->dthb_next = bucket->dthb_next;
                        }

                        ASSERT(hash->dth_nbuckets > 0);
                        hash->dth_nbuckets--;
                        kmem_free(bucket, sizeof (dtrace_hashbucket_t));
                        return;
                }

                bucket->dthb_chain = *nextp;
        } else {
                *(DTRACE_HASHNEXT(hash, *prevp)) = *nextp;
        }

        if (*nextp != NULL)
                *(DTRACE_HASHPREV(hash, *nextp)) = *prevp;
}

/*
 * DTrace Utility Functions
 *
 * These are random utility functions that are _not_ called from probe context.
 */
static int
dtrace_badattr(const dtrace_attribute_t *a)
{
        return (a->dtat_name > DTRACE_STABILITY_MAX ||
            a->dtat_data > DTRACE_STABILITY_MAX ||
            a->dtat_class > DTRACE_CLASS_MAX);
}

/*
 * Returns a dtrace-managed copy of a string, and will
 * deduplicate copies of the same string.
 * If the specified string is NULL, returns an empty string
 */
static char *
dtrace_strref(const char *str)
{
        dtrace_string_t *s = NULL;
        size_t bufsize = (str != NULL ? strlen(str) : 0) + 1;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);

        if (str == NULL)
                str = "";

        for (s = dtrace_hash_lookup_string(dtrace_strings, str); s != NULL;
             s = *(DTRACE_HASHNEXT(dtrace_strings, s)))  {
                if (strncmp(str, s->dtst_str, bufsize) != 0) {
                        continue;
                }
                ASSERT(s->dtst_refcount != UINT32_MAX);
                s->dtst_refcount++;
                return s->dtst_str;
        }

        s = kmem_zalloc(sizeof(dtrace_string_t) + bufsize, KM_SLEEP);
        s->dtst_refcount = 1;
        (void) strlcpy(s->dtst_str, str, bufsize);

        dtrace_hash_add(dtrace_strings, s);

        return s->dtst_str;
}

static void
dtrace_strunref(const char *str)
{
        ASSERT(str != NULL);
        dtrace_string_t *s = NULL;
        size_t bufsize = strlen(str) + 1;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);

        for (s = dtrace_hash_lookup_string(dtrace_strings, str); s != NULL;
             s = *(DTRACE_HASHNEXT(dtrace_strings, s)))  {
                if (strncmp(str, s->dtst_str, bufsize) != 0) {
                        continue;
                }
                ASSERT(s->dtst_refcount != 0);
                s->dtst_refcount--;
                if (s->dtst_refcount == 0) {
                        dtrace_hash_remove(dtrace_strings, s);
                        kmem_free(s, sizeof(dtrace_string_t) + bufsize);
                }
                return;
        }
        panic("attempt to unref non-existent string %s", str);
}

#define DTRACE_ISALPHA(c)       \
        (((c) >= 'a' && (c) <= 'z') || ((c) >= 'A' && (c) <= 'Z'))

static int
dtrace_badname(const char *s)
{
        char c;

        if (s == NULL || (c = *s++) == '\0')
                return (0);

        if (!DTRACE_ISALPHA(c) && c != '-' && c != '_' && c != '.')
                return (1);

        while ((c = *s++) != '\0') {
                if (!DTRACE_ISALPHA(c) && (c < '0' || c > '9') &&
                    c != '-' && c != '_' && c != '.' && c != '`')
                        return (1);
        }

        return (0);
}

static void
dtrace_cred2priv(cred_t *cr, uint32_t *privp, uid_t *uidp, zoneid_t *zoneidp)
{
        uint32_t priv;

        if (cr == NULL || PRIV_POLICY_ONLY(cr, PRIV_ALL, B_FALSE)) {
                if (dtrace_is_restricted() && !dtrace_are_restrictions_relaxed()) {
                        priv = DTRACE_PRIV_USER | DTRACE_PRIV_PROC | DTRACE_PRIV_OWNER;
                }
                else {
                        priv = DTRACE_PRIV_ALL;
                }
                *uidp = 0;
                *zoneidp = 0;
        } else {
                *uidp = crgetuid(cr);
                *zoneidp = crgetzoneid(cr);

                priv = 0;
                if (PRIV_POLICY_ONLY(cr, PRIV_DTRACE_KERNEL, B_FALSE))
                        priv |= DTRACE_PRIV_KERNEL | DTRACE_PRIV_USER;
                else if (PRIV_POLICY_ONLY(cr, PRIV_DTRACE_USER, B_FALSE))
                        priv |= DTRACE_PRIV_USER;
                if (PRIV_POLICY_ONLY(cr, PRIV_DTRACE_PROC, B_FALSE))
                        priv |= DTRACE_PRIV_PROC;
                if (PRIV_POLICY_ONLY(cr, PRIV_PROC_OWNER, B_FALSE))
                        priv |= DTRACE_PRIV_OWNER;
                if (PRIV_POLICY_ONLY(cr, PRIV_PROC_ZONE, B_FALSE))
                        priv |= DTRACE_PRIV_ZONEOWNER;
        }

        *privp = priv;
}

#ifdef DTRACE_ERRDEBUG
static void
dtrace_errdebug(const char *str)
{
        int hval = dtrace_hash_str(str) % DTRACE_ERRHASHSZ;
        int occupied = 0;

        lck_mtx_lock(&dtrace_errlock);
        dtrace_errlast = str;
        dtrace_errthread = (kthread_t *)current_thread();

        while (occupied++ < DTRACE_ERRHASHSZ) {
                if (dtrace_errhash[hval].dter_msg == str) {
                        dtrace_errhash[hval].dter_count++;
                        goto out;
                }

                if (dtrace_errhash[hval].dter_msg != NULL) {
                        hval = (hval + 1) % DTRACE_ERRHASHSZ;
                        continue;
                }

                dtrace_errhash[hval].dter_msg = str;
                dtrace_errhash[hval].dter_count = 1;
                goto out;
        }

        panic("dtrace: undersized error hash");
out:
        lck_mtx_unlock(&dtrace_errlock);
}
#endif

/*
 * DTrace Matching Functions
 *
 * These functions are used to match groups of probes, given some elements of
 * a probe tuple, or some globbed expressions for elements of a probe tuple.
 */
static int
dtrace_match_priv(const dtrace_probe_t *prp, uint32_t priv, uid_t uid,
    zoneid_t zoneid)
{
        if (priv != DTRACE_PRIV_ALL) {
                uint32_t ppriv = prp->dtpr_provider->dtpv_priv.dtpp_flags;
                uint32_t match = priv & ppriv;

                /*
                 * No PRIV_DTRACE_* privileges...
                 */
                if ((priv & (DTRACE_PRIV_PROC | DTRACE_PRIV_USER |
                    DTRACE_PRIV_KERNEL)) == 0)
                        return (0);

                /*
                 * No matching bits, but there were bits to match...
                 */
                if (match == 0 && ppriv != 0)
                        return (0);

                /*
                 * Need to have permissions to the process, but don't...
                 */
                if (((ppriv & ~match) & DTRACE_PRIV_OWNER) != 0 &&
                    uid != prp->dtpr_provider->dtpv_priv.dtpp_uid) {
                        return (0);
                }

                /*
                 * Need to be in the same zone unless we possess the
                 * privilege to examine all zones.
                 */
                if (((ppriv & ~match) & DTRACE_PRIV_ZONEOWNER) != 0 &&
                    zoneid != prp->dtpr_provider->dtpv_priv.dtpp_zoneid) {
                        return (0);
                }
        }

        return (1);
}

/*
 * dtrace_match_probe compares a dtrace_probe_t to a pre-compiled key, which
 * consists of input pattern strings and an ops-vector to evaluate them.
 * This function returns >0 for match, 0 for no match, and <0 for error.
 */
static int
dtrace_match_probe(const dtrace_probe_t *prp, const dtrace_probekey_t *pkp,
    uint32_t priv, uid_t uid, zoneid_t zoneid)
{
        dtrace_provider_t *pvp = prp->dtpr_provider;
        int rv;

        if (pvp->dtpv_defunct)
                return (0);

        if ((rv = pkp->dtpk_pmatch(pvp->dtpv_name, pkp->dtpk_prov, 0)) <= 0)
                return (rv);

        if ((rv = pkp->dtpk_mmatch(prp->dtpr_mod, pkp->dtpk_mod, 0)) <= 0)
                return (rv);

        if ((rv = pkp->dtpk_fmatch(prp->dtpr_func, pkp->dtpk_func, 0)) <= 0)
                return (rv);

        if ((rv = pkp->dtpk_nmatch(prp->dtpr_name, pkp->dtpk_name, 0)) <= 0)
                return (rv);

        if (dtrace_match_priv(prp, priv, uid, zoneid) == 0)
                return (0);

        return (rv);
}

/*
 * dtrace_match_glob() is a safe kernel implementation of the gmatch(3GEN)
 * interface for matching a glob pattern 'p' to an input string 's'.  Unlike
 * libc's version, the kernel version only applies to 8-bit ASCII strings.
 * In addition, all of the recursion cases except for '*' matching have been
 * unwound.  For '*', we still implement recursive evaluation, but a depth
 * counter is maintained and matching is aborted if we recurse too deep.
 * The function returns 0 if no match, >0 if match, and <0 if recursion error.
 */
static int
dtrace_match_glob(const char *s, const char *p, int depth)
{
        const char *olds;
        char s1, c;
        int gs;

        if (depth > DTRACE_PROBEKEY_MAXDEPTH)
                return (-1);

        if (s == NULL)
                s = ""; /* treat NULL as empty string */

top:
        olds = s;
        s1 = *s++;

        if (p == NULL)
                return (0);

        if ((c = *p++) == '\0')
                return (s1 == '\0');

        switch (c) {
        case '[': {
                int ok = 0, notflag = 0;
                char lc = '\0';

                if (s1 == '\0')
                        return (0);

                if (*p == '!') {
                        notflag = 1;
                        p++;
                }

                if ((c = *p++) == '\0')
                        return (0);

                do {
                        if (c == '-' && lc != '\0' && *p != ']') {
                                if ((c = *p++) == '\0')
                                        return (0);
                                if (c == '\\' && (c = *p++) == '\0')
                                        return (0);

                                if (notflag) {
                                        if (s1 < lc || s1 > c)
                                                ok++;
                                        else
                                                return (0);
                                } else if (lc <= s1 && s1 <= c)
                                        ok++;

                        } else if (c == '\\' && (c = *p++) == '\0')
                                return (0);

                        lc = c; /* save left-hand 'c' for next iteration */

                        if (notflag) {
                                if (s1 != c)
                                        ok++;
                                else
                                        return (0);
                        } else if (s1 == c)
                                ok++;

                        if ((c = *p++) == '\0')
                                return (0);

                } while (c != ']');

                if (ok)
                        goto top;

                return (0);
        }

        case '\\':
                if ((c = *p++) == '\0')
                        return (0);
                /*FALLTHRU*/

        default:
                if (c != s1)
                        return (0);
                /*FALLTHRU*/

        case '?':
                if (s1 != '\0')
                        goto top;
                return (0);

        case '*':
                while (*p == '*')
                        p++; /* consecutive *'s are identical to a single one */

                if (*p == '\0')
                        return (1);

                for (s = olds; *s != '\0'; s++) {
                        if ((gs = dtrace_match_glob(s, p, depth + 1)) != 0)
                                return (gs);
                }

                return (0);
        }
}

/*ARGSUSED*/
static int
dtrace_match_string(const char *s, const char *p, int depth)
{
#pragma unused(depth) /* __APPLE__ */
        return (s != NULL && s == p);
}

/*ARGSUSED*/
static int
dtrace_match_module(const char *s, const char *p, int depth)
{
#pragma unused(depth) /* __APPLE__ */
        size_t len;
        if (s == NULL || p == NULL)
                return (0);

        len = strlen(p);

        if (strncmp(p, s, len) != 0)
                return (0);

        if (s[len] == '.' || s[len] == '\0')
                return (1);

        return (0);
}

/*ARGSUSED*/
static int
dtrace_match_nul(const char *s, const char *p, int depth)
{
#pragma unused(s, p, depth) /* __APPLE__ */
        return (1); /* always match the empty pattern */
}

/*ARGSUSED*/
static int
dtrace_match_nonzero(const char *s, const char *p, int depth)
{
#pragma unused(p, depth) /* __APPLE__ */
        return (s != NULL && s[0] != '\0');
}

static int
dtrace_match(const dtrace_probekey_t *pkp, uint32_t priv, uid_t uid,
    zoneid_t zoneid, int (*matched)(dtrace_probe_t *, void *, void *), void *arg1, void *arg2)
{
        dtrace_probe_t *probe;
        dtrace_provider_t prov_template = {
                .dtpv_name = (char *)(uintptr_t)pkp->dtpk_prov
        };

        dtrace_probe_t template = {
                .dtpr_provider = &prov_template,
                .dtpr_mod = (char *)(uintptr_t)pkp->dtpk_mod,
                .dtpr_func = (char *)(uintptr_t)pkp->dtpk_func,
                .dtpr_name = (char *)(uintptr_t)pkp->dtpk_name
        };

        dtrace_hash_t *hash = NULL;
        int len, rc, best = INT_MAX, nmatched = 0;
        dtrace_id_t i;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);

        /*
         * If the probe ID is specified in the key, just lookup by ID and
         * invoke the match callback once if a matching probe is found.
         */
        if (pkp->dtpk_id != DTRACE_IDNONE) {
                if ((probe = dtrace_probe_lookup_id(pkp->dtpk_id)) != NULL &&
                    dtrace_match_probe(probe, pkp, priv, uid, zoneid) > 0) {
                        if ((*matched)(probe, arg1, arg2) == DTRACE_MATCH_FAIL)
                               return (DTRACE_MATCH_FAIL);
                        nmatched++;
                }
                return (nmatched);
        }

        /*
         * We want to find the most distinct of the provider name, module name,
         * function name, and name.  So for each one that is not a glob
         * pattern or empty string, we perform a lookup in the corresponding
         * hash and use the hash table with the fewest collisions to do our
         * search.
         */
        if (pkp->dtpk_pmatch == &dtrace_match_string &&
            (len = dtrace_hash_collisions(dtrace_byprov, &template)) < best) {
                best = len;
                hash = dtrace_byprov;
        }

        if (pkp->dtpk_mmatch == &dtrace_match_string &&
            (len = dtrace_hash_collisions(dtrace_bymod, &template)) < best) {
                best = len;
                hash = dtrace_bymod;
        }

        if (pkp->dtpk_fmatch == &dtrace_match_string &&
            (len = dtrace_hash_collisions(dtrace_byfunc, &template)) < best) {
                best = len;
                hash = dtrace_byfunc;
        }

        if (pkp->dtpk_nmatch == &dtrace_match_string &&
            (len = dtrace_hash_collisions(dtrace_byname, &template)) < best) {
                best = len;
                hash = dtrace_byname;
        }

        /*
         * If we did not select a hash table, iterate over every probe and
         * invoke our callback for each one that matches our input probe key.
         */
        if (hash == NULL) {
                for (i = 0; i < (dtrace_id_t)dtrace_nprobes; i++) {
                        if ((probe = dtrace_probes[i]) == NULL ||
                            dtrace_match_probe(probe, pkp, priv, uid,
                            zoneid) <= 0)
                                continue;

                        nmatched++;

                       if ((rc = (*matched)(probe, arg1, arg2)) != DTRACE_MATCH_NEXT) {
                               if (rc == DTRACE_MATCH_FAIL)
                                       return (DTRACE_MATCH_FAIL);
                               break;
                       }
                }

                return (nmatched);
        }

        /*
         * If we selected a hash table, iterate over each probe of the same key
         * name and invoke the callback for every probe that matches the other
         * attributes of our input probe key.
         */
        for (probe = dtrace_hash_lookup(hash, &template); probe != NULL;
            probe = *(DTRACE_HASHNEXT(hash, probe))) {

                if (dtrace_match_probe(probe, pkp, priv, uid, zoneid) <= 0)
                        continue;

                nmatched++;

                if ((rc = (*matched)(probe, arg1, arg2)) != DTRACE_MATCH_NEXT) {
                    if (rc == DTRACE_MATCH_FAIL)
                        return (DTRACE_MATCH_FAIL);
                    break;
                }
        }

        return (nmatched);
}

/*
 * Return the function pointer dtrace_probecmp() should use to compare the
 * specified pattern with a string.  For NULL or empty patterns, we select
 * dtrace_match_nul().  For glob pattern strings, we use dtrace_match_glob().
 * For non-empty non-glob strings, we use dtrace_match_string().
 */
static dtrace_probekey_f *
dtrace_probekey_func(const char *p)
{
        char c;

        if (p == NULL || *p == '\0')
                return (&dtrace_match_nul);

        while ((c = *p++) != '\0') {
                if (c == '[' || c == '?' || c == '*' || c == '\\')
                        return (&dtrace_match_glob);
        }

        return (&dtrace_match_string);
}

static dtrace_probekey_f *
dtrace_probekey_module_func(const char *p)
{
        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);

        dtrace_probekey_f *f = dtrace_probekey_func(p);
        if (f == &dtrace_match_string) {
                dtrace_probe_t template = {
                        .dtpr_mod = (char *)(uintptr_t)p,
                };
                if (dtrace_hash_lookup(dtrace_bymod, &template) == NULL) {
                        return (&dtrace_match_module);
                }
                return (&dtrace_match_string);
        }
        return f;
}

/*
 * Build a probe comparison key for use with dtrace_match_probe() from the
 * given probe description.  By convention, a null key only matches anchored
 * probes: if each field is the empty string, reset dtpk_fmatch to
 * dtrace_match_nonzero().
 */
static void
dtrace_probekey(const dtrace_probedesc_t *pdp, dtrace_probekey_t *pkp)
{

        pkp->dtpk_prov = dtrace_strref(pdp->dtpd_provider);
        pkp->dtpk_pmatch = dtrace_probekey_func(pdp->dtpd_provider);

        pkp->dtpk_mod = dtrace_strref(pdp->dtpd_mod);
        pkp->dtpk_mmatch = dtrace_probekey_module_func(pdp->dtpd_mod);

        pkp->dtpk_func = dtrace_strref(pdp->dtpd_func);
        pkp->dtpk_fmatch = dtrace_probekey_func(pdp->dtpd_func);

        pkp->dtpk_name = dtrace_strref(pdp->dtpd_name);
        pkp->dtpk_nmatch = dtrace_probekey_func(pdp->dtpd_name);

        pkp->dtpk_id = pdp->dtpd_id;

        if (pkp->dtpk_id == DTRACE_IDNONE &&
            pkp->dtpk_pmatch == &dtrace_match_nul &&
            pkp->dtpk_mmatch == &dtrace_match_nul &&
            pkp->dtpk_fmatch == &dtrace_match_nul &&
            pkp->dtpk_nmatch == &dtrace_match_nul)
                pkp->dtpk_fmatch = &dtrace_match_nonzero;
}

static void
dtrace_probekey_release(dtrace_probekey_t *pkp)
{
        dtrace_strunref(pkp->dtpk_prov);
        dtrace_strunref(pkp->dtpk_mod);
        dtrace_strunref(pkp->dtpk_func);
        dtrace_strunref(pkp->dtpk_name);
}

static int
dtrace_cond_provider_match(dtrace_probedesc_t *desc, void *data)
{
        if (desc == NULL)
                return 1;

        dtrace_probekey_f *func = dtrace_probekey_func(desc->dtpd_provider);

        return func((char*)data, desc->dtpd_provider, 0);
}

/*
 * DTrace Provider-to-Framework API Functions
 *
 * These functions implement much of the Provider-to-Framework API, as
 * described in <sys/dtrace.h>.  The parts of the API not in this section are
 * the functions in the API for probe management (found below), and
 * dtrace_probe() itself (found above).
 */

/*
 * Register the calling provider with the DTrace framework.  This should
 * generally be called by DTrace providers in their attach(9E) entry point.
 */
int
dtrace_register(const char *name, const dtrace_pattr_t *pap, uint32_t priv,
    cred_t *cr, const dtrace_pops_t *pops, void *arg, dtrace_provider_id_t *idp)
{
        dtrace_provider_t *provider;

        if (name == NULL || pap == NULL || pops == NULL || idp == NULL) {
                cmn_err(CE_WARN, "failed to register provider '%s': invalid "
                    "arguments", name ? name : "<NULL>");
                return (EINVAL);
        }

        if (name[0] == '\0' || dtrace_badname(name)) {
                cmn_err(CE_WARN, "failed to register provider '%s': invalid "
                    "provider name", name);
                return (EINVAL);
        }

        if ((pops->dtps_provide == NULL && pops->dtps_provide_module == NULL) ||
            pops->dtps_enable == NULL || pops->dtps_disable == NULL ||
            pops->dtps_destroy == NULL ||
            ((pops->dtps_resume == NULL) != (pops->dtps_suspend == NULL))) {
                cmn_err(CE_WARN, "failed to register provider '%s': invalid "
                    "provider ops", name);
                return (EINVAL);
        }

        if (dtrace_badattr(&pap->dtpa_provider) ||
            dtrace_badattr(&pap->dtpa_mod) ||
            dtrace_badattr(&pap->dtpa_func) ||
            dtrace_badattr(&pap->dtpa_name) ||
            dtrace_badattr(&pap->dtpa_args)) {
                cmn_err(CE_WARN, "failed to register provider '%s': invalid "
                    "provider attributes", name);
                return (EINVAL);
        }

        if (priv & ~DTRACE_PRIV_ALL) {
                cmn_err(CE_WARN, "failed to register provider '%s': invalid "
                    "privilege attributes", name);
                return (EINVAL);
        }

        if ((priv & DTRACE_PRIV_KERNEL) &&
            (priv & (DTRACE_PRIV_USER | DTRACE_PRIV_OWNER)) &&
            pops->dtps_usermode == NULL) {
                cmn_err(CE_WARN, "failed to register provider '%s': need "
                    "dtps_usermode() op for given privilege attributes", name);
                return (EINVAL);
        }

        provider = kmem_zalloc(sizeof (dtrace_provider_t), KM_SLEEP);

        provider->dtpv_attr = *pap;
        provider->dtpv_priv.dtpp_flags = priv;
        if (cr != NULL) {
                provider->dtpv_priv.dtpp_uid = crgetuid(cr);
                provider->dtpv_priv.dtpp_zoneid = crgetzoneid(cr);
        }
        provider->dtpv_pops = *pops;

        if (pops->dtps_provide == NULL) {
                ASSERT(pops->dtps_provide_module != NULL);
                provider->dtpv_pops.dtps_provide = dtrace_provide_nullop;
        }

        if (pops->dtps_provide_module == NULL) {
                ASSERT(pops->dtps_provide != NULL);
                provider->dtpv_pops.dtps_provide_module =
                    dtrace_provide_module_nullop;
        }

        if (pops->dtps_suspend == NULL) {
                ASSERT(pops->dtps_resume == NULL);
                provider->dtpv_pops.dtps_suspend = dtrace_suspend_nullop;
                provider->dtpv_pops.dtps_resume = dtrace_resume_nullop;
        }

        provider->dtpv_arg = arg;
        *idp = (dtrace_provider_id_t)provider;

        if (pops == &dtrace_provider_ops) {
                LCK_MTX_ASSERT(&dtrace_provider_lock, LCK_MTX_ASSERT_OWNED);
                LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);

                provider->dtpv_name = dtrace_strref(name);

                ASSERT(dtrace_anon.dta_enabling == NULL);

                /*
                 * We make sure that the DTrace provider is at the head of
                 * the provider chain.
                 */
                provider->dtpv_next = dtrace_provider;
                dtrace_provider = provider;
                return (0);
        }

        lck_mtx_lock(&dtrace_provider_lock);
        lck_mtx_lock(&dtrace_lock);

        provider->dtpv_name = dtrace_strref(name);

        /*
         * If there is at least one provider registered, we'll add this
         * provider after the first provider.
         */
        if (dtrace_provider != NULL) {
                provider->dtpv_next = dtrace_provider->dtpv_next;
                dtrace_provider->dtpv_next = provider;
        } else {
                dtrace_provider = provider;
        }

        if (dtrace_retained != NULL) {
                dtrace_enabling_provide(provider);

                /*
                 * Now we need to call dtrace_enabling_matchall_with_cond() --
                 * with a condition matching the provider name we just added,
                 * which will acquire cpu_lock and dtrace_lock.  We therefore need
                 * to drop all of our locks before calling into it...
                 */
                lck_mtx_unlock(&dtrace_lock);
                lck_mtx_unlock(&dtrace_provider_lock);

                dtrace_match_cond_t cond = {dtrace_cond_provider_match, provider->dtpv_name};
                dtrace_enabling_matchall_with_cond(&cond);

                return (0);
        }

        lck_mtx_unlock(&dtrace_lock);
        lck_mtx_unlock(&dtrace_provider_lock);

        return (0);
}

/*
 * Unregister the specified provider from the DTrace framework.  This should
 * generally be called by DTrace providers in their detach(9E) entry point.
 */
int
dtrace_unregister(dtrace_provider_id_t id)
{
        dtrace_provider_t *old = (dtrace_provider_t *)id;
        dtrace_provider_t *prev = NULL;
        int self = 0;
        dtrace_probe_t *probe, *first = NULL, *next = NULL;
        dtrace_probe_t template = {
                .dtpr_provider = old
        };

        if (old->dtpv_pops.dtps_enable ==
            (int (*)(void *, dtrace_id_t, void *))dtrace_enable_nullop) {
                /*
                 * If DTrace itself is the provider, we're called with locks
                 * already held.
                 */
                ASSERT(old == dtrace_provider);
                ASSERT(dtrace_devi != NULL);
                LCK_MTX_ASSERT(&dtrace_provider_lock, LCK_MTX_ASSERT_OWNED);
                LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);
                self = 1;

                if (dtrace_provider->dtpv_next != NULL) {
                        /*
                         * There's another provider here; return failure.
                         */
                        return (EBUSY);
                }
        } else {
                lck_mtx_lock(&dtrace_provider_lock);
                lck_mtx_lock(&mod_lock);
                lck_mtx_lock(&dtrace_lock);
        }

        /*
         * If anyone has /dev/dtrace open, or if there are anonymous enabled
         * probes, we refuse to let providers slither away, unless this
         * provider has already been explicitly invalidated.
         */
        if (!old->dtpv_defunct &&
            (dtrace_opens || (dtrace_anon.dta_state != NULL &&
            dtrace_anon.dta_state->dts_necbs > 0))) {
                if (!self) {
                        lck_mtx_unlock(&dtrace_lock);
                        lck_mtx_unlock(&mod_lock);
                        lck_mtx_unlock(&dtrace_provider_lock);
                }
                return (EBUSY);
        }

        /*
         * Attempt to destroy the probes associated with this provider.
         */
        if (old->dtpv_ecb_count!=0) {
                /*
                 * We have at least one ECB; we can't remove this provider.
                 */
                if (!self) {
                        lck_mtx_unlock(&dtrace_lock);
                        lck_mtx_unlock(&mod_lock);
                        lck_mtx_unlock(&dtrace_provider_lock);
                }
                return (EBUSY);
        }

        /*
         * All of the probes for this provider are disabled; we can safely
         * remove all of them from their hash chains and from the probe array.
         */
        for (probe = dtrace_hash_lookup(dtrace_byprov, &template); probe != NULL;
            probe = *(DTRACE_HASHNEXT(dtrace_byprov, probe))) {
                if (probe->dtpr_provider != old)
                        continue;

                dtrace_probes[probe->dtpr_id - 1] = NULL;
                old->dtpv_probe_count--;

                dtrace_hash_remove(dtrace_bymod, probe);
                dtrace_hash_remove(dtrace_byfunc, probe);
                dtrace_hash_remove(dtrace_byname, probe);

                if (first == NULL) {
                        first = probe;
                        probe->dtpr_nextmod = NULL;
                } else {
                        /*
                         * Use nextmod as the chain of probes to remove
                         */
                        probe->dtpr_nextmod = first;
                        first = probe;
                }
        }

        for (probe = first; probe != NULL; probe = next) {
                next = probe->dtpr_nextmod;
                dtrace_hash_remove(dtrace_byprov, probe);
        }

        /*
         * The provider's probes have been removed from the hash chains and
         * from the probe array.  Now issue a dtrace_sync() to be sure that
         * everyone has cleared out from any probe array processing.
         */
        dtrace_sync();

        for (probe = first; probe != NULL; probe = next) {
                next = probe->dtpr_nextmod;

                old->dtpv_pops.dtps_destroy(old->dtpv_arg, probe->dtpr_id,
                    probe->dtpr_arg);
                dtrace_strunref(probe->dtpr_mod);
                dtrace_strunref(probe->dtpr_func);
                dtrace_strunref(probe->dtpr_name);
                vmem_free(dtrace_arena, (void *)(uintptr_t)(probe->dtpr_id), 1);
                zfree(dtrace_probe_t_zone, probe);
        }

        if ((prev = dtrace_provider) == old) {
                ASSERT(self || dtrace_devi == NULL);
                ASSERT(old->dtpv_next == NULL || dtrace_devi == NULL);
                dtrace_provider = old->dtpv_next;
        } else {
                while (prev != NULL && prev->dtpv_next != old)
                        prev = prev->dtpv_next;

                if (prev == NULL) {
                        panic("attempt to unregister non-existent "
                            "dtrace provider %p\n", (void *)id);
                }

                prev->dtpv_next = old->dtpv_next;
        }

        dtrace_strunref(old->dtpv_name);

        if (!self) {
                lck_mtx_unlock(&dtrace_lock);
                lck_mtx_unlock(&mod_lock);
                lck_mtx_unlock(&dtrace_provider_lock);
        }

        kmem_free(old, sizeof (dtrace_provider_t));

        return (0);
}

/*
 * Invalidate the specified provider.  All subsequent probe lookups for the
 * specified provider will fail, but its probes will not be removed.
 */
void
dtrace_invalidate(dtrace_provider_id_t id)
{
        dtrace_provider_t *pvp = (dtrace_provider_t *)id;

        ASSERT(pvp->dtpv_pops.dtps_enable !=
            (int (*)(void *, dtrace_id_t, void *))dtrace_enable_nullop);

        lck_mtx_lock(&dtrace_provider_lock);
        lck_mtx_lock(&dtrace_lock);

        pvp->dtpv_defunct = 1;

        lck_mtx_unlock(&dtrace_lock);
        lck_mtx_unlock(&dtrace_provider_lock);
}

/*
 * Indicate whether or not DTrace has attached.
 */
int
dtrace_attached(void)
{
        /*
         * dtrace_provider will be non-NULL iff the DTrace driver has
         * attached.  (It's non-NULL because DTrace is always itself a
         * provider.)
         */
        return (dtrace_provider != NULL);
}

/*
 * Remove all the unenabled probes for the given provider.  This function is
 * not unlike dtrace_unregister(), except that it doesn't remove the provider
 * -- just as many of its associated probes as it can.
 */
int
dtrace_condense(dtrace_provider_id_t id)
{
        dtrace_provider_t *prov = (dtrace_provider_t *)id;
        dtrace_probe_t *probe, *first = NULL;
        dtrace_probe_t template = {
                .dtpr_provider = prov
        };

        /*
         * Make sure this isn't the dtrace provider itself.
         */
        ASSERT(prov->dtpv_pops.dtps_enable !=
          (int (*)(void *, dtrace_id_t, void *))dtrace_enable_nullop);

        lck_mtx_lock(&dtrace_provider_lock);
        lck_mtx_lock(&dtrace_lock);

        /*
         * Attempt to destroy the probes associated with this provider.
         */
        for (probe = dtrace_hash_lookup(dtrace_byprov, &template); probe != NULL;
            probe = *(DTRACE_HASHNEXT(dtrace_byprov, probe))) {

                if (probe->dtpr_provider != prov)
                        continue;

                if (probe->dtpr_ecb != NULL)
                        continue;

                dtrace_probes[probe->dtpr_id - 1] = NULL;
                prov->dtpv_probe_count--;

                dtrace_hash_remove(dtrace_bymod, probe);
                dtrace_hash_remove(dtrace_byfunc, probe);
                dtrace_hash_remove(dtrace_byname, probe);

                prov->dtpv_pops.dtps_destroy(prov->dtpv_arg, probe->dtpr_id,
                    probe->dtpr_arg);
                dtrace_strunref(probe->dtpr_mod);
                dtrace_strunref(probe->dtpr_func);
                dtrace_strunref(probe->dtpr_name);
                if (first == NULL) {
                        first = probe;
                        probe->dtpr_nextmod = NULL;
                } else {
                        /*
                         * Use nextmod as the chain of probes to remove
                         */
                        probe->dtpr_nextmod = first;
                        first = probe;
                }
        }

        for (probe = first; probe != NULL; probe = first) {
                first = probe->dtpr_nextmod;
                dtrace_hash_remove(dtrace_byprov, probe);
                vmem_free(dtrace_arena, (void *)((uintptr_t)probe->dtpr_id), 1);
                zfree(dtrace_probe_t_zone, probe);
        }

        lck_mtx_unlock(&dtrace_lock);
        lck_mtx_unlock(&dtrace_provider_lock);

        return (0);
}

/*
 * DTrace Probe Management Functions
 *
 * The functions in this section perform the DTrace probe management,
 * including functions to create probes, look-up probes, and call into the
 * providers to request that probes be provided.  Some of these functions are
 * in the Provider-to-Framework API; these functions can be identified by the
 * fact that they are not declared "static".
 */

/*
 * Create a probe with the specified module name, function name, and name.
 */
dtrace_id_t
dtrace_probe_create(dtrace_provider_id_t prov, const char *mod,
    const char *func, const char *name, int aframes, void *arg)
{
        dtrace_probe_t *probe, **probes;
        dtrace_provider_t *provider = (dtrace_provider_t *)prov;
        dtrace_id_t id;

        if (provider == dtrace_provider) {
                LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);
        } else {
                lck_mtx_lock(&dtrace_lock);
        }

        id = (dtrace_id_t)(uintptr_t)vmem_alloc(dtrace_arena, 1,
            VM_BESTFIT | VM_SLEEP);

        probe = zalloc(dtrace_probe_t_zone);
        bzero(probe, sizeof (dtrace_probe_t));

        probe->dtpr_id = id;
        probe->dtpr_gen = dtrace_probegen++;
        probe->dtpr_mod = dtrace_strref(mod);
        probe->dtpr_func = dtrace_strref(func);
        probe->dtpr_name = dtrace_strref(name);
        probe->dtpr_arg = arg;
        probe->dtpr_aframes = aframes;
        probe->dtpr_provider = provider;

        dtrace_hash_add(dtrace_byprov, probe);
        dtrace_hash_add(dtrace_bymod, probe);
        dtrace_hash_add(dtrace_byfunc, probe);
        dtrace_hash_add(dtrace_byname, probe);

        if (id - 1 >= (dtrace_id_t)dtrace_nprobes) {
                size_t osize = dtrace_nprobes * sizeof (dtrace_probe_t *);
                size_t nsize = osize * 2;

                probes = kmem_zalloc(nsize, KM_SLEEP);

                dtrace_probe_t **oprobes = dtrace_probes;

                bcopy(oprobes, probes, osize);
                dtrace_membar_producer();
                dtrace_probes = probes;

                dtrace_sync();

                /*
                 * All CPUs are now seeing the new probes array; we can
                 * safely free the old array.
                 */
                kmem_free(oprobes, osize);
                dtrace_nprobes *= 2;

                ASSERT(id - 1 < (dtrace_id_t)dtrace_nprobes);
        }

        ASSERT(dtrace_probes[id - 1] == NULL);
        dtrace_probes[id - 1] = probe;
        provider->dtpv_probe_count++;   

        if (provider != dtrace_provider)
                lck_mtx_unlock(&dtrace_lock);

        return (id);
}

static dtrace_probe_t *
dtrace_probe_lookup_id(dtrace_id_t id)
{
        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);

        if (id == 0 || id > (dtrace_id_t)dtrace_nprobes)
                return (NULL);

        return (dtrace_probes[id - 1]);
}

static int
dtrace_probe_lookup_match(dtrace_probe_t *probe, void *arg1, void *arg2)
{
#pragma unused(arg2)
        *((dtrace_id_t *)arg1) = probe->dtpr_id;

        return (DTRACE_MATCH_DONE);
}

/*
 * Look up a probe based on provider and one or more of module name, function
 * name and probe name.
 */
dtrace_id_t
dtrace_probe_lookup(dtrace_provider_id_t prid, const char *mod,
    const char *func, const char *name)
{
        dtrace_probekey_t pkey;
        dtrace_id_t id;
        int match;

        lck_mtx_lock(&dtrace_lock);

        pkey.dtpk_prov = dtrace_strref(((dtrace_provider_t *)prid)->dtpv_name);
        pkey.dtpk_pmatch = &dtrace_match_string;
        pkey.dtpk_mod = dtrace_strref(mod);
        pkey.dtpk_mmatch = mod ? &dtrace_match_string : &dtrace_match_nul;
        pkey.dtpk_func = dtrace_strref(func);
        pkey.dtpk_fmatch = func ? &dtrace_match_string : &dtrace_match_nul;
        pkey.dtpk_name = dtrace_strref(name);
        pkey.dtpk_nmatch = name ? &dtrace_match_string : &dtrace_match_nul;
        pkey.dtpk_id = DTRACE_IDNONE;

        match = dtrace_match(&pkey, DTRACE_PRIV_ALL, 0, 0,
            dtrace_probe_lookup_match, &id, NULL);

        dtrace_probekey_release(&pkey);

        lck_mtx_unlock(&dtrace_lock);

        ASSERT(match == 1 || match == 0);
        return (match ? id : 0);
}

/*
 * Returns the probe argument associated with the specified probe.
 */
void *
dtrace_probe_arg(dtrace_provider_id_t id, dtrace_id_t pid)
{
        dtrace_probe_t *probe;
        void *rval = NULL;

        lck_mtx_lock(&dtrace_lock);

        if ((probe = dtrace_probe_lookup_id(pid)) != NULL &&
            probe->dtpr_provider == (dtrace_provider_t *)id)
                rval = probe->dtpr_arg;

        lck_mtx_unlock(&dtrace_lock);

        return (rval);
}

/*
 * Copy a probe into a probe description.
 */
static void
dtrace_probe_description(const dtrace_probe_t *prp, dtrace_probedesc_t *pdp)
{
        bzero(pdp, sizeof (dtrace_probedesc_t));
        pdp->dtpd_id = prp->dtpr_id;

        /* APPLE NOTE: Darwin employs size bounded string operation. */
        (void) strlcpy(pdp->dtpd_provider,
            prp->dtpr_provider->dtpv_name, DTRACE_PROVNAMELEN);

        (void) strlcpy(pdp->dtpd_mod, prp->dtpr_mod, DTRACE_MODNAMELEN);
        (void) strlcpy(pdp->dtpd_func, prp->dtpr_func, DTRACE_FUNCNAMELEN);
        (void) strlcpy(pdp->dtpd_name, prp->dtpr_name, DTRACE_NAMELEN);
}

/*
 * Called to indicate that a probe -- or probes -- should be provided by a
 * specfied provider.  If the specified description is NULL, the provider will
 * be told to provide all of its probes.  (This is done whenever a new
 * consumer comes along, or whenever a retained enabling is to be matched.) If
 * the specified description is non-NULL, the provider is given the
 * opportunity to dynamically provide the specified probe, allowing providers
 * to support the creation of probes on-the-fly.  (So-called _autocreated_
 * probes.)  If the provider is NULL, the operations will be applied to all
 * providers; if the provider is non-NULL the operations will only be applied
 * to the specified provider.  The dtrace_provider_lock must be held, and the
 * dtrace_lock must _not_ be held -- the provider's dtps_provide() operation
 * will need to grab the dtrace_lock when it reenters the framework through
 * dtrace_probe_lookup(), dtrace_probe_create(), etc.
 */
static void
dtrace_probe_provide(dtrace_probedesc_t *desc, dtrace_provider_t *prv)
{
        struct modctl *ctl;
        int all = 0;

        LCK_MTX_ASSERT(&dtrace_provider_lock, LCK_MTX_ASSERT_OWNED);

        if (prv == NULL) {
                all = 1;
                prv = dtrace_provider;
        }
                 
        do {
                /*
                 * First, call the blanket provide operation.
                 */
                prv->dtpv_pops.dtps_provide(prv->dtpv_arg, desc);
                
                /*
                 * Now call the per-module provide operation.  We will grab
                 * mod_lock to prevent the list from being modified.  Note
                 * that this also prevents the mod_busy bits from changing.
                 * (mod_busy can only be changed with mod_lock held.)
                 */
                lck_mtx_lock(&mod_lock);
                
                ctl = dtrace_modctl_list;
                while (ctl) {
                        prv->dtpv_pops.dtps_provide_module(prv->dtpv_arg, ctl);
                        ctl = ctl->mod_next;
                }
                
                lck_mtx_unlock(&mod_lock);
        } while (all && (prv = prv->dtpv_next) != NULL);
}

/*
 * Iterate over each probe, and call the Framework-to-Provider API function
 * denoted by offs.
 */
static void
dtrace_probe_foreach(uintptr_t offs)
{
        dtrace_provider_t *prov;
        void (*func)(void *, dtrace_id_t, void *);
        dtrace_probe_t *probe;
        dtrace_icookie_t cookie;
        int i;

        /*
         * We disable interrupts to walk through the probe array.  This is
         * safe -- the dtrace_sync() in dtrace_unregister() assures that we
         * won't see stale data.
         */
        cookie = dtrace_interrupt_disable();

        for (i = 0; i < dtrace_nprobes; i++) {
                if ((probe = dtrace_probes[i]) == NULL)
                        continue;

                if (probe->dtpr_ecb == NULL) {
                        /*
                         * This probe isn't enabled -- don't call the function.
                         */
                        continue;
                }

                prov = probe->dtpr_provider;
                func = *((void(**)(void *, dtrace_id_t, void *))
                    ((uintptr_t)&prov->dtpv_pops + offs));

                func(prov->dtpv_arg, i + 1, probe->dtpr_arg);
        }

        dtrace_interrupt_enable(cookie);
}

static int
dtrace_probe_enable(const dtrace_probedesc_t *desc, dtrace_enabling_t *enab, dtrace_ecbdesc_t *ep)
{
        dtrace_probekey_t pkey;
        uint32_t priv;
        uid_t uid;
        zoneid_t zoneid;
        int err;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);

        dtrace_ecb_create_cache = NULL;

        if (desc == NULL) {
                /*
                 * If we're passed a NULL description, we're being asked to
                 * create an ECB with a NULL probe.
                 */
                (void) dtrace_ecb_create_enable(NULL, enab, ep);
                return (0);
        }

        dtrace_probekey(desc, &pkey);
        dtrace_cred2priv(enab->dten_vstate->dtvs_state->dts_cred.dcr_cred,
            &priv, &uid, &zoneid);

        err = dtrace_match(&pkey, priv, uid, zoneid, dtrace_ecb_create_enable, enab, ep);

        dtrace_probekey_release(&pkey);

        return err;
}

/*
 * DTrace Helper Provider Functions
 */
static void
dtrace_dofattr2attr(dtrace_attribute_t *attr, const dof_attr_t dofattr)
{
        attr->dtat_name = DOF_ATTR_NAME(dofattr);
        attr->dtat_data = DOF_ATTR_DATA(dofattr);
        attr->dtat_class = DOF_ATTR_CLASS(dofattr);
}

static void
dtrace_dofprov2hprov(dtrace_helper_provdesc_t *hprov,
    const dof_provider_t *dofprov, char *strtab)
{
        hprov->dthpv_provname = strtab + dofprov->dofpv_name;
        dtrace_dofattr2attr(&hprov->dthpv_pattr.dtpa_provider,
            dofprov->dofpv_provattr);
        dtrace_dofattr2attr(&hprov->dthpv_pattr.dtpa_mod,
            dofprov->dofpv_modattr);
        dtrace_dofattr2attr(&hprov->dthpv_pattr.dtpa_func,
            dofprov->dofpv_funcattr);
        dtrace_dofattr2attr(&hprov->dthpv_pattr.dtpa_name,
            dofprov->dofpv_nameattr);
        dtrace_dofattr2attr(&hprov->dthpv_pattr.dtpa_args,
            dofprov->dofpv_argsattr);
}

static void
dtrace_helper_provide_one(dof_helper_t *dhp, dof_sec_t *sec, proc_t *p)
{
        uintptr_t daddr = (uintptr_t)dhp->dofhp_dof;
        dof_hdr_t *dof = (dof_hdr_t *)daddr;
        dof_sec_t *str_sec, *prb_sec, *arg_sec, *off_sec, *enoff_sec;
        dof_provider_t *provider;
        dof_probe_t *probe;
        uint32_t *off, *enoff;
        uint8_t *arg;
        char *strtab;
        uint_t i, nprobes;
        dtrace_helper_provdesc_t dhpv;
        dtrace_helper_probedesc_t dhpb;
        dtrace_meta_t *meta = dtrace_meta_pid;
        dtrace_mops_t *mops = &meta->dtm_mops;
        void *parg;

        provider = (dof_provider_t *)(uintptr_t)(daddr + sec->dofs_offset);
        str_sec = (dof_sec_t *)(uintptr_t)(daddr + dof->dofh_secoff +
            provider->dofpv_strtab * dof->dofh_secsize);
        prb_sec = (dof_sec_t *)(uintptr_t)(daddr + dof->dofh_secoff +
            provider->dofpv_probes * dof->dofh_secsize);
        arg_sec = (dof_sec_t *)(uintptr_t)(daddr + dof->dofh_secoff +
            provider->dofpv_prargs * dof->dofh_secsize);
        off_sec = (dof_sec_t *)(uintptr_t)(daddr + dof->dofh_secoff +
            provider->dofpv_proffs * dof->dofh_secsize);

        strtab = (char *)(uintptr_t)(daddr + str_sec->dofs_offset);
        off = (uint32_t *)(uintptr_t)(daddr + off_sec->dofs_offset);
        arg = (uint8_t *)(uintptr_t)(daddr + arg_sec->dofs_offset);
        enoff = NULL;

        /*
         * See dtrace_helper_provider_validate().
         */
        if (dof->dofh_ident[DOF_ID_VERSION] != DOF_VERSION_1 &&
            provider->dofpv_prenoffs != DOF_SECT_NONE) {
                enoff_sec = (dof_sec_t *)(uintptr_t)(daddr + dof->dofh_secoff +
                    provider->dofpv_prenoffs * dof->dofh_secsize);
                enoff = (uint32_t *)(uintptr_t)(daddr + enoff_sec->dofs_offset);
        }

        nprobes = prb_sec->dofs_size / prb_sec->dofs_entsize;

        /*
         * Create the provider.
         */
        dtrace_dofprov2hprov(&dhpv, provider, strtab);

        if ((parg = mops->dtms_provide_proc(meta->dtm_arg, &dhpv, p)) == NULL)
                return;

        meta->dtm_count++;

        /*
         * Create the probes.
         */
        for (i = 0; i < nprobes; i++) {
                probe = (dof_probe_t *)(uintptr_t)(daddr +
                    prb_sec->dofs_offset + i * prb_sec->dofs_entsize);

                dhpb.dthpb_mod = dhp->dofhp_mod;
                dhpb.dthpb_func = strtab + probe->dofpr_func;
                dhpb.dthpb_name = strtab + probe->dofpr_name;
#if !defined(__APPLE__)
                dhpb.dthpb_base = probe->dofpr_addr;
#else
                dhpb.dthpb_base = dhp->dofhp_addr; /* FIXME: James, why? */
#endif
                dhpb.dthpb_offs = (int32_t *)(off + probe->dofpr_offidx);
                dhpb.dthpb_noffs = probe->dofpr_noffs;
                if (enoff != NULL) {
                        dhpb.dthpb_enoffs = (int32_t *)(enoff + probe->dofpr_enoffidx);
                        dhpb.dthpb_nenoffs = probe->dofpr_nenoffs;
                } else {
                        dhpb.dthpb_enoffs = NULL;
                        dhpb.dthpb_nenoffs = 0;
                }
                dhpb.dthpb_args = arg + probe->dofpr_argidx;
                dhpb.dthpb_nargc = probe->dofpr_nargc;
                dhpb.dthpb_xargc = probe->dofpr_xargc;
                dhpb.dthpb_ntypes = strtab + probe->dofpr_nargv;
                dhpb.dthpb_xtypes = strtab + probe->dofpr_xargv;

                mops->dtms_create_probe(meta->dtm_arg, parg, &dhpb);
        }

        /*
         * Since we just created probes, we need to match our enablings
         * against those, with a precondition knowing that we have only
         * added probes from this provider
         */
        char *prov_name = mops->dtms_provider_name(parg);
        ASSERT(prov_name != NULL);
        dtrace_match_cond_t cond = {dtrace_cond_provider_match, (void*)prov_name};

        dtrace_enabling_matchall_with_cond(&cond);
}

static void
dtrace_helper_provide(dof_helper_t *dhp, proc_t *p)
{
        uintptr_t daddr = (uintptr_t)dhp->dofhp_dof;
        dof_hdr_t *dof = (dof_hdr_t *)daddr;
        uint32_t i;

        LCK_MTX_ASSERT(&dtrace_meta_lock, LCK_MTX_ASSERT_OWNED);

        for (i = 0; i < dof->dofh_secnum; i++) {
                dof_sec_t *sec = (dof_sec_t *)(uintptr_t)(daddr +
                    dof->dofh_secoff + i * dof->dofh_secsize);

                if (sec->dofs_type != DOF_SECT_PROVIDER)
                        continue;

                dtrace_helper_provide_one(dhp, sec, p);
        }
}

static void
dtrace_helper_provider_remove_one(dof_helper_t *dhp, dof_sec_t *sec, proc_t *p)
{
        uintptr_t daddr = (uintptr_t)dhp->dofhp_dof;
        dof_hdr_t *dof = (dof_hdr_t *)daddr;
        dof_sec_t *str_sec;
        dof_provider_t *provider;
        char *strtab;
        dtrace_helper_provdesc_t dhpv;
        dtrace_meta_t *meta = dtrace_meta_pid;
        dtrace_mops_t *mops = &meta->dtm_mops;

        provider = (dof_provider_t *)(uintptr_t)(daddr + sec->dofs_offset);
        str_sec = (dof_sec_t *)(uintptr_t)(daddr + dof->dofh_secoff +
            provider->dofpv_strtab * dof->dofh_secsize);

        strtab = (char *)(uintptr_t)(daddr + str_sec->dofs_offset);

        /*
         * Create the provider.
         */
        dtrace_dofprov2hprov(&dhpv, provider, strtab);

        mops->dtms_remove_proc(meta->dtm_arg, &dhpv, p);

        meta->dtm_count--;
}

static void
dtrace_helper_provider_remove(dof_helper_t *dhp, proc_t *p)
{
        uintptr_t daddr = (uintptr_t)dhp->dofhp_dof;
        dof_hdr_t *dof = (dof_hdr_t *)daddr;
        uint32_t i;

        LCK_MTX_ASSERT(&dtrace_meta_lock, LCK_MTX_ASSERT_OWNED);

        for (i = 0; i < dof->dofh_secnum; i++) {
                dof_sec_t *sec = (dof_sec_t *)(uintptr_t)(daddr +
                    dof->dofh_secoff + i * dof->dofh_secsize);

                if (sec->dofs_type != DOF_SECT_PROVIDER)
                        continue;

                dtrace_helper_provider_remove_one(dhp, sec, p);
        }
}

/*
 * DTrace Meta Provider-to-Framework API Functions
 *
 * These functions implement the Meta Provider-to-Framework API, as described
 * in <sys/dtrace.h>.
 */
int
dtrace_meta_register(const char *name, const dtrace_mops_t *mops, void *arg,
    dtrace_meta_provider_id_t *idp)
{
        dtrace_meta_t *meta;
        dtrace_helpers_t *help, *next;
        uint_t i;

        *idp = DTRACE_METAPROVNONE;

        /*
         * We strictly don't need the name, but we hold onto it for
         * debuggability. All hail error queues!
         */
        if (name == NULL) {
                cmn_err(CE_WARN, "failed to register meta-provider: "
                    "invalid name");
                return (EINVAL);
        }

        if (mops == NULL ||
            mops->dtms_create_probe == NULL ||
            mops->dtms_provide_proc == NULL ||
            mops->dtms_remove_proc == NULL) {
                cmn_err(CE_WARN, "failed to register meta-register %s: "
                    "invalid ops", name);
                return (EINVAL);
        }

        meta = kmem_zalloc(sizeof (dtrace_meta_t), KM_SLEEP);
        meta->dtm_mops = *mops;
        meta->dtm_arg = arg;

        lck_mtx_lock(&dtrace_meta_lock);
        lck_mtx_lock(&dtrace_lock);

        if (dtrace_meta_pid != NULL) {
                lck_mtx_unlock(&dtrace_lock);
                lck_mtx_unlock(&dtrace_meta_lock);
                cmn_err(CE_WARN, "failed to register meta-register %s: "
                    "user-land meta-provider exists", name);
                kmem_free(meta, sizeof (dtrace_meta_t));
                return (EINVAL);
        }

        meta->dtm_name = dtrace_strref(name);

        dtrace_meta_pid = meta;
        *idp = (dtrace_meta_provider_id_t)meta;

        /*
         * If there are providers and probes ready to go, pass them
         * off to the new meta provider now.
         */

        help = dtrace_deferred_pid;
        dtrace_deferred_pid = NULL;

        lck_mtx_unlock(&dtrace_lock);

        while (help != NULL) {
                for (i = 0; i < help->dthps_nprovs; i++) {
                        proc_t *p = proc_find(help->dthps_pid);
                        if (p == PROC_NULL)
                                continue;
                        dtrace_helper_provide(&help->dthps_provs[i]->dthp_prov,
                            p);
                        proc_rele(p);
                }

                next = help->dthps_next;
                help->dthps_next = NULL;
                help->dthps_prev = NULL;
                help->dthps_deferred = 0;
                help = next;
        }

        lck_mtx_unlock(&dtrace_meta_lock);

        return (0);
}

int
dtrace_meta_unregister(dtrace_meta_provider_id_t id)
{
        dtrace_meta_t **pp, *old = (dtrace_meta_t *)id;

        lck_mtx_lock(&dtrace_meta_lock);
        lck_mtx_lock(&dtrace_lock);

        if (old == dtrace_meta_pid) {
                pp = &dtrace_meta_pid;
        } else {
                panic("attempt to unregister non-existent "
                    "dtrace meta-provider %p\n", (void *)old);
        }

        if (old->dtm_count != 0) {
                lck_mtx_unlock(&dtrace_lock);
                lck_mtx_unlock(&dtrace_meta_lock);
                return (EBUSY);
        }

        *pp = NULL;

        dtrace_strunref(old->dtm_name);

        lck_mtx_unlock(&dtrace_lock);
        lck_mtx_unlock(&dtrace_meta_lock);

        kmem_free(old, sizeof (dtrace_meta_t));

        return (0);
}


/*
 * DTrace DIF Object Functions
 */
static int
dtrace_difo_err(uint_t pc, const char *format, ...)
{
        if (dtrace_err_verbose) {
                va_list alist;

                (void) uprintf("dtrace DIF object error: [%u]: ", pc);
                va_start(alist, format);
                (void) vuprintf(format, alist);
                va_end(alist);
        }

#ifdef DTRACE_ERRDEBUG
        dtrace_errdebug(format);
#endif
        return (1);
}

/*
 * Validate a DTrace DIF object by checking the IR instructions.  The following
 * rules are currently enforced by dtrace_difo_validate():
 *
 * 1. Each instruction must have a valid opcode
 * 2. Each register, string, variable, or subroutine reference must be valid
 * 3. No instruction can modify register %r0 (must be zero)
 * 4. All instruction reserved bits must be set to zero
 * 5. The last instruction must be a "ret" instruction
 * 6. All branch targets must reference a valid instruction _after_ the branch
 */
static int
dtrace_difo_validate(dtrace_difo_t *dp, dtrace_vstate_t *vstate, uint_t nregs,
    cred_t *cr)
{
        int err = 0;
        uint_t i;

        int (*efunc)(uint_t pc, const char *, ...) = dtrace_difo_err;
        int kcheckload;
        uint_t pc;
        int maxglobal = -1, maxlocal = -1, maxtlocal = -1;

        kcheckload = cr == NULL ||
            (vstate->dtvs_state->dts_cred.dcr_visible & DTRACE_CRV_KERNEL) == 0;

        dp->dtdo_destructive = 0;

        for (pc = 0; pc < dp->dtdo_len && err == 0; pc++) {
                dif_instr_t instr = dp->dtdo_buf[pc];

                uint_t r1 = DIF_INSTR_R1(instr);
                uint_t r2 = DIF_INSTR_R2(instr);
                uint_t rd = DIF_INSTR_RD(instr);
                uint_t rs = DIF_INSTR_RS(instr);
                uint_t label = DIF_INSTR_LABEL(instr);
                uint_t v = DIF_INSTR_VAR(instr);
                uint_t subr = DIF_INSTR_SUBR(instr);
                uint_t type = DIF_INSTR_TYPE(instr);
                uint_t op = DIF_INSTR_OP(instr);

                switch (op) {
                case DIF_OP_OR:
                case DIF_OP_XOR:
                case DIF_OP_AND:
                case DIF_OP_SLL:
                case DIF_OP_SRL:
                case DIF_OP_SRA:
                case DIF_OP_SUB:
                case DIF_OP_ADD:
                case DIF_OP_MUL:
                case DIF_OP_SDIV:
                case DIF_OP_UDIV:
                case DIF_OP_SREM:
                case DIF_OP_UREM:
                case DIF_OP_COPYS:
                        if (r1 >= nregs)
                                err += efunc(pc, "invalid register %u\n", r1);
                        if (r2 >= nregs)
                                err += efunc(pc, "invalid register %u\n", r2);
                        if (rd >= nregs)
                                err += efunc(pc, "invalid register %u\n", rd);
                        if (rd == 0)
                                err += efunc(pc, "cannot write to %%r0\n");
                        break;
                case DIF_OP_NOT:
                case DIF_OP_MOV:
                case DIF_OP_ALLOCS:
                        if (r1 >= nregs)
                                err += efunc(pc, "invalid register %u\n", r1);
                        if (r2 != 0)
                                err += efunc(pc, "non-zero reserved bits\n");
                        if (rd >= nregs)
                                err += efunc(pc, "invalid register %u\n", rd);
                        if (rd == 0)
                                err += efunc(pc, "cannot write to %%r0\n");
                        break;
                case DIF_OP_LDSB:
                case DIF_OP_LDSH:
                case DIF_OP_LDSW:
                case DIF_OP_LDUB:
                case DIF_OP_LDUH:
                case DIF_OP_LDUW:
                case DIF_OP_LDX:
                        if (r1 >= nregs)
                                err += efunc(pc, "invalid register %u\n", r1);
                        if (r2 != 0)
                                err += efunc(pc, "non-zero reserved bits\n");
                        if (rd >= nregs)
                                err += efunc(pc, "invalid register %u\n", rd);
                        if (rd == 0)
                                err += efunc(pc, "cannot write to %%r0\n");
                        if (kcheckload)
                                dp->dtdo_buf[pc] = DIF_INSTR_LOAD(op +
                                    DIF_OP_RLDSB - DIF_OP_LDSB, r1, rd);
                        break;
                case DIF_OP_RLDSB:
                case DIF_OP_RLDSH:
                case DIF_OP_RLDSW:
                case DIF_OP_RLDUB:
                case DIF_OP_RLDUH:
                case DIF_OP_RLDUW:
                case DIF_OP_RLDX:
                        if (r1 >= nregs)
                                err += efunc(pc, "invalid register %u\n", r1);
                        if (r2 != 0)
                                err += efunc(pc, "non-zero reserved bits\n");
                        if (rd >= nregs)
                                err += efunc(pc, "invalid register %u\n", rd);
                        if (rd == 0)
                                err += efunc(pc, "cannot write to %%r0\n");
                        break;
                case DIF_OP_ULDSB:
                case DIF_OP_ULDSH:
                case DIF_OP_ULDSW:
                case DIF_OP_ULDUB:
                case DIF_OP_ULDUH:
                case DIF_OP_ULDUW:
                case DIF_OP_ULDX:
                        if (r1 >= nregs)
                                err += efunc(pc, "invalid register %u\n", r1);
                        if (r2 != 0)
                                err += efunc(pc, "non-zero reserved bits\n");
                        if (rd >= nregs)
                                err += efunc(pc, "invalid register %u\n", rd);
                        if (rd == 0)
                                err += efunc(pc, "cannot write to %%r0\n");
                        break;
                case DIF_OP_STB:
                case DIF_OP_STH:
                case DIF_OP_STW:
                case DIF_OP_STX:
                        if (r1 >= nregs)
                                err += efunc(pc, "invalid register %u\n", r1);
                        if (r2 != 0)
                                err += efunc(pc, "non-zero reserved bits\n");
                        if (rd >= nregs)
                                err += efunc(pc, "invalid register %u\n", rd);
                        if (rd == 0)
                                err += efunc(pc, "cannot write to 0 address\n");
                        break;
                case DIF_OP_CMP:
                case DIF_OP_SCMP:
                        if (r1 >= nregs)
                                err += efunc(pc, "invalid register %u\n", r1);
                        if (r2 >= nregs)
                                err += efunc(pc, "invalid register %u\n", r2);
                        if (rd != 0)
                                err += efunc(pc, "non-zero reserved bits\n");
                        break;
                case DIF_OP_TST:
                        if (r1 >= nregs)
                                err += efunc(pc, "invalid register %u\n", r1);
                        if (r2 != 0 || rd != 0)
                                err += efunc(pc, "non-zero reserved bits\n");
                        break;
                case DIF_OP_BA:
                case DIF_OP_BE:
                case DIF_OP_BNE:
                case DIF_OP_BG:
                case DIF_OP_BGU:
                case DIF_OP_BGE:
                case DIF_OP_BGEU:
                case DIF_OP_BL:
                case DIF_OP_BLU:
                case DIF_OP_BLE:
                case DIF_OP_BLEU:
                        if (label >= dp->dtdo_len) {
                                err += efunc(pc, "invalid branch target %u\n",
                                    label);
                        }
                        if (label <= pc) {
                                err += efunc(pc, "backward branch to %u\n",
                                    label);
                        }
                        break;
                case DIF_OP_RET:
                        if (r1 != 0 || r2 != 0)
                                err += efunc(pc, "non-zero reserved bits\n");
                        if (rd >= nregs)
                                err += efunc(pc, "invalid register %u\n", rd);
                        break;
                case DIF_OP_NOP:
                case DIF_OP_POPTS:
                case DIF_OP_FLUSHTS:
                        if (r1 != 0 || r2 != 0 || rd != 0)
                                err += efunc(pc, "non-zero reserved bits\n");
                        break;
                case DIF_OP_SETX:
                        if (DIF_INSTR_INTEGER(instr) >= dp->dtdo_intlen) {
                                err += efunc(pc, "invalid integer ref %u\n",
                                    DIF_INSTR_INTEGER(instr));
                        }
                        if (rd >= nregs)
                                err += efunc(pc, "invalid register %u\n", rd);
                        if (rd == 0)
                                err += efunc(pc, "cannot write to %%r0\n");
                        break;
                case DIF_OP_SETS:
                        if (DIF_INSTR_STRING(instr) >= dp->dtdo_strlen) {
                                err += efunc(pc, "invalid string ref %u\n",
                                    DIF_INSTR_STRING(instr));
                        }
                        if (rd >= nregs)
                                err += efunc(pc, "invalid register %u\n", rd);
                        if (rd == 0)
                                err += efunc(pc, "cannot write to %%r0\n");
                        break;
                case DIF_OP_LDGA:
                case DIF_OP_LDTA:
                        if (r1 > DIF_VAR_ARRAY_MAX)
                                err += efunc(pc, "invalid array %u\n", r1);
                        if (r2 >= nregs)
                                err += efunc(pc, "invalid register %u\n", r2);
                        if (rd >= nregs)
                                err += efunc(pc, "invalid register %u\n", rd);
                        if (rd == 0)
                                err += efunc(pc, "cannot write to %%r0\n");
                        break;
                case DIF_OP_LDGS:
                case DIF_OP_LDTS:
                case DIF_OP_LDLS:
                case DIF_OP_LDGAA:
                case DIF_OP_LDTAA:
                        if (v < DIF_VAR_OTHER_MIN || v > DIF_VAR_OTHER_MAX)
                                err += efunc(pc, "invalid variable %u\n", v);
                        if (rd >= nregs)
                                err += efunc(pc, "invalid register %u\n", rd);
                        if (rd == 0)
                                err += efunc(pc, "cannot write to %%r0\n");
                        break;
                case DIF_OP_STGS:
                case DIF_OP_STTS:
                case DIF_OP_STLS:
                case DIF_OP_STGAA:
                case DIF_OP_STTAA:
                        if (v < DIF_VAR_OTHER_UBASE || v > DIF_VAR_OTHER_MAX)
                                err += efunc(pc, "invalid variable %u\n", v);
                        if (rs >= nregs)
                                err += efunc(pc, "invalid register %u\n", rd);
                        break;
                case DIF_OP_CALL:
                        if (subr > DIF_SUBR_MAX &&
                           !(subr >= DIF_SUBR_APPLE_MIN && subr <= DIF_SUBR_APPLE_MAX))
                                err += efunc(pc, "invalid subr %u\n", subr);
                        if (rd >= nregs)
                                err += efunc(pc, "invalid register %u\n", rd);
                        if (rd == 0)
                                err += efunc(pc, "cannot write to %%r0\n");

                        if (subr == DIF_SUBR_COPYOUT ||
                            subr == DIF_SUBR_COPYOUTSTR ||
                            subr == DIF_SUBR_KDEBUG_TRACE ||
                            subr == DIF_SUBR_KDEBUG_TRACE_STRING) {
                                dp->dtdo_destructive = 1;
                        }
                        break;
                case DIF_OP_PUSHTR:
                        if (type != DIF_TYPE_STRING && type != DIF_TYPE_CTF)
                                err += efunc(pc, "invalid ref type %u\n", type);
                        if (r2 >= nregs)
                                err += efunc(pc, "invalid register %u\n", r2);
                        if (rs >= nregs)
                                err += efunc(pc, "invalid register %u\n", rs);
                        break;
                case DIF_OP_PUSHTV:
                        if (type != DIF_TYPE_CTF)
                                err += efunc(pc, "invalid val type %u\n", type);
                        if (r2 >= nregs)
                                err += efunc(pc, "invalid register %u\n", r2);
                        if (rs >= nregs)
                                err += efunc(pc, "invalid register %u\n", rs);
                        break;
                case DIF_OP_STRIP:
                        if (r1 >= nregs)
                                err += efunc(pc, "invalid register %u\n", r1);
                        if (!dtrace_is_valid_ptrauth_key(r2))
                                err += efunc(pc, "invalid key\n");
                        if (rd >= nregs)
                                err += efunc(pc, "invalid register %u\n", rd);
                        if (rd == 0)
                                err += efunc(pc, "cannot write to %%r0\n");
                        break;
                default:
                        err += efunc(pc, "invalid opcode %u\n",
                            DIF_INSTR_OP(instr));
                }
        }

        if (dp->dtdo_len != 0 &&
            DIF_INSTR_OP(dp->dtdo_buf[dp->dtdo_len - 1]) != DIF_OP_RET) {
                err += efunc(dp->dtdo_len - 1,
                    "expected 'ret' as last DIF instruction\n");
        }

        if (!(dp->dtdo_rtype.dtdt_flags & (DIF_TF_BYREF | DIF_TF_BYUREF))) {
                /*
                 * If we're not returning by reference, the size must be either
                 * 0 or the size of one of the base types.
                 */
                switch (dp->dtdo_rtype.dtdt_size) {
                case 0:
                case sizeof (uint8_t):
                case sizeof (uint16_t):
                case sizeof (uint32_t):
                case sizeof (uint64_t):
                        break;

                default:
                        err += efunc(dp->dtdo_len - 1, "bad return size\n");
                }
        }

        for (i = 0; i < dp->dtdo_varlen && err == 0; i++) {
                dtrace_difv_t *v = &dp->dtdo_vartab[i], *existing = NULL;
                dtrace_diftype_t *vt, *et;
                uint_t id;
                int ndx;

                if (v->dtdv_scope != DIFV_SCOPE_GLOBAL &&
                    v->dtdv_scope != DIFV_SCOPE_THREAD &&
                    v->dtdv_scope != DIFV_SCOPE_LOCAL) {
                        err += efunc(i, "unrecognized variable scope %d\n",
                            v->dtdv_scope);
                        break;
                }

                if (v->dtdv_kind != DIFV_KIND_ARRAY &&
                    v->dtdv_kind != DIFV_KIND_SCALAR) {
                        err += efunc(i, "unrecognized variable type %d\n",
                            v->dtdv_kind);
                        break;
                }

                if ((id = v->dtdv_id) > DIF_VARIABLE_MAX) {
                        err += efunc(i, "%d exceeds variable id limit\n", id);
                        break;
                }

                if (id < DIF_VAR_OTHER_UBASE)
                        continue;

                /*
                 * For user-defined variables, we need to check that this
                 * definition is identical to any previous definition that we
                 * encountered.
                 */
                ndx = id - DIF_VAR_OTHER_UBASE;

                switch (v->dtdv_scope) {
                case DIFV_SCOPE_GLOBAL:
                        if (maxglobal == -1 || ndx > maxglobal)
                                maxglobal = ndx;

                        if (ndx < vstate->dtvs_nglobals) {
                                dtrace_statvar_t *svar;

                                if ((svar = vstate->dtvs_globals[ndx]) != NULL)
                                        existing = &svar->dtsv_var;
                        }

                        break;

                case DIFV_SCOPE_THREAD:
                        if (maxtlocal == -1 || ndx > maxtlocal)
                                maxtlocal = ndx;

                        if (ndx < vstate->dtvs_ntlocals)
                                existing = &vstate->dtvs_tlocals[ndx];
                        break;

                case DIFV_SCOPE_LOCAL:
                        if (maxlocal == -1 || ndx > maxlocal)
                                maxlocal = ndx;
                        if (ndx < vstate->dtvs_nlocals) {
                                dtrace_statvar_t *svar;

                                if ((svar = vstate->dtvs_locals[ndx]) != NULL)
                                        existing = &svar->dtsv_var;
                        }

                        break;
                }

                vt = &v->dtdv_type;

                if (vt->dtdt_flags & DIF_TF_BYREF) {
                        if (vt->dtdt_size == 0) {
                                err += efunc(i, "zero-sized variable\n");
                                break;
                        }

                        if ((v->dtdv_scope == DIFV_SCOPE_GLOBAL ||
                            v->dtdv_scope == DIFV_SCOPE_LOCAL) &&
                            vt->dtdt_size > dtrace_statvar_maxsize) {
                                err += efunc(i, "oversized by-ref static\n");
                                break;
                        }
                }

                if (existing == NULL || existing->dtdv_id == 0)
                        continue;

                ASSERT(existing->dtdv_id == v->dtdv_id);
                ASSERT(existing->dtdv_scope == v->dtdv_scope);

                if (existing->dtdv_kind != v->dtdv_kind)
                        err += efunc(i, "%d changed variable kind\n", id);

                et = &existing->dtdv_type;

                if (vt->dtdt_flags != et->dtdt_flags) {
                        err += efunc(i, "%d changed variable type flags\n", id);
                        break;
                }

                if (vt->dtdt_size != 0 && vt->dtdt_size != et->dtdt_size) {
                        err += efunc(i, "%d changed variable type size\n", id);
                        break;
                }
        }

        for (pc = 0; pc < dp->dtdo_len && err == 0; pc++) {
                dif_instr_t instr = dp->dtdo_buf[pc];

                uint_t v = DIF_INSTR_VAR(instr);
                uint_t op = DIF_INSTR_OP(instr);

                switch (op) {
                case DIF_OP_LDGS:
                case DIF_OP_LDGAA:
                case DIF_OP_STGS:
                case DIF_OP_STGAA:
                        if (v > (uint_t)(DIF_VAR_OTHER_UBASE + maxglobal))
                                err += efunc(pc, "invalid variable %u\n", v);
                        break;
                case DIF_OP_LDTS:
                case DIF_OP_LDTAA:
                case DIF_OP_STTS:
                case DIF_OP_STTAA:
                        if (v > (uint_t)(DIF_VAR_OTHER_UBASE + maxtlocal))
                                err += efunc(pc, "invalid variable %u\n", v);
                        break;
                case DIF_OP_LDLS:
                case DIF_OP_STLS:
                        if (v > (uint_t)(DIF_VAR_OTHER_UBASE + maxlocal))
                                err += efunc(pc, "invalid variable %u\n", v);
                        break;
                default:
                        break;
                }
        }

        return (err);
}

/*
 * Validate a DTrace DIF object that it is to be used as a helper.  Helpers
 * are much more constrained than normal DIFOs.  Specifically, they may
 * not:
 *
 * 1. Make calls to subroutines other than copyin(), copyinstr() or
 *    miscellaneous string routines
 * 2. Access DTrace variables other than the args[] array, and the
 *    curthread, pid, ppid, tid, execname, zonename, uid and gid variables.
 * 3. Have thread-local variables.
 * 4. Have dynamic variables.
 */
static int
dtrace_difo_validate_helper(dtrace_difo_t *dp)
{
        int (*efunc)(uint_t pc, const char *, ...) = dtrace_difo_err;
        int err = 0;
        uint_t pc;

        for (pc = 0; pc < dp->dtdo_len; pc++) {
                dif_instr_t instr = dp->dtdo_buf[pc];

                uint_t v = DIF_INSTR_VAR(instr);
                uint_t subr = DIF_INSTR_SUBR(instr);
                uint_t op = DIF_INSTR_OP(instr);

                switch (op) {
                case DIF_OP_OR:
                case DIF_OP_XOR:
                case DIF_OP_AND:
                case DIF_OP_SLL:
                case DIF_OP_SRL:
                case DIF_OP_SRA:
                case DIF_OP_SUB:
                case DIF_OP_ADD:
                case DIF_OP_MUL:
                case DIF_OP_SDIV:
                case DIF_OP_UDIV:
                case DIF_OP_SREM:
                case DIF_OP_UREM:
                case DIF_OP_COPYS:
                case DIF_OP_NOT:
                case DIF_OP_MOV:
                case DIF_OP_RLDSB:
                case DIF_OP_RLDSH:
                case DIF_OP_RLDSW:
                case DIF_OP_RLDUB:
                case DIF_OP_RLDUH:
                case DIF_OP_RLDUW:
                case DIF_OP_RLDX:
                case DIF_OP_ULDSB:
                case DIF_OP_ULDSH:
                case DIF_OP_ULDSW:
                case DIF_OP_ULDUB:
                case DIF_OP_ULDUH:
                case DIF_OP_ULDUW:
                case DIF_OP_ULDX:
                case DIF_OP_STB:
                case DIF_OP_STH:
                case DIF_OP_STW:
                case DIF_OP_STX:
                case DIF_OP_ALLOCS:
                case DIF_OP_CMP:
                case DIF_OP_SCMP:
                case DIF_OP_TST:
                case DIF_OP_BA:
                case DIF_OP_BE:
                case DIF_OP_BNE:
                case DIF_OP_BG:
                case DIF_OP_BGU:
                case DIF_OP_BGE:
                case DIF_OP_BGEU:
                case DIF_OP_BL:
                case DIF_OP_BLU:
                case DIF_OP_BLE:
                case DIF_OP_BLEU:
                case DIF_OP_RET:
                case DIF_OP_NOP:
                case DIF_OP_POPTS:
                case DIF_OP_FLUSHTS:
                case DIF_OP_SETX:
                case DIF_OP_SETS:
                case DIF_OP_LDGA:
                case DIF_OP_LDLS:
                case DIF_OP_STGS:
                case DIF_OP_STLS:
                case DIF_OP_PUSHTR:
                case DIF_OP_PUSHTV:
                        break;

                case DIF_OP_LDGS:
                        if (v >= DIF_VAR_OTHER_UBASE)
                                break;

                        if (v >= DIF_VAR_ARG0 && v <= DIF_VAR_ARG9)
                                break;

                        if (v == DIF_VAR_CURTHREAD || v == DIF_VAR_PID ||
                            v == DIF_VAR_PPID || v == DIF_VAR_TID ||
                            v == DIF_VAR_EXECNAME || v == DIF_VAR_ZONENAME ||
                            v == DIF_VAR_UID || v == DIF_VAR_GID)
                                break;

                        err += efunc(pc, "illegal variable %u\n", v);
                        break;

                case DIF_OP_LDTA:
                case DIF_OP_LDTS:
                case DIF_OP_LDGAA:
                case DIF_OP_LDTAA:
                        err += efunc(pc, "illegal dynamic variable load\n");
                        break;

                case DIF_OP_STTS:
                case DIF_OP_STGAA:
                case DIF_OP_STTAA:
                        err += efunc(pc, "illegal dynamic variable store\n");
                        break;

                case DIF_OP_CALL:
                        if (subr == DIF_SUBR_ALLOCA ||
                            subr == DIF_SUBR_BCOPY ||
                            subr == DIF_SUBR_COPYIN ||
                            subr == DIF_SUBR_COPYINTO ||
                            subr == DIF_SUBR_COPYINSTR ||
                            subr == DIF_SUBR_INDEX ||
                            subr == DIF_SUBR_INET_NTOA ||
                            subr == DIF_SUBR_INET_NTOA6 ||
                            subr == DIF_SUBR_INET_NTOP ||
                            subr == DIF_SUBR_JSON ||
                            subr == DIF_SUBR_LLTOSTR ||
                            subr == DIF_SUBR_STRTOLL ||
                            subr == DIF_SUBR_RINDEX ||
                            subr == DIF_SUBR_STRCHR ||
                            subr == DIF_SUBR_STRJOIN ||
                            subr == DIF_SUBR_STRRCHR ||
                            subr == DIF_SUBR_STRSTR ||
                            subr == DIF_SUBR_KDEBUG_TRACE ||
                            subr == DIF_SUBR_KDEBUG_TRACE_STRING ||
                            subr == DIF_SUBR_HTONS ||
                            subr == DIF_SUBR_HTONL ||
                            subr == DIF_SUBR_HTONLL ||
                            subr == DIF_SUBR_NTOHS ||
                            subr == DIF_SUBR_NTOHL ||
                            subr == DIF_SUBR_NTOHLL)
                                break;

                        err += efunc(pc, "invalid subr %u\n", subr);
                        break;

                default:
                        err += efunc(pc, "invalid opcode %u\n",
                            DIF_INSTR_OP(instr));
                }
        }

        return (err);
}

/*
 * Returns 1 if the expression in the DIF object can be cached on a per-thread
 * basis; 0 if not.
 */
static int
dtrace_difo_cacheable(dtrace_difo_t *dp)
{
        uint_t i;

        if (dp == NULL)
                return (0);

        for (i = 0; i < dp->dtdo_varlen; i++) {
                dtrace_difv_t *v = &dp->dtdo_vartab[i];

                if (v->dtdv_scope != DIFV_SCOPE_GLOBAL)
                        continue;

                switch (v->dtdv_id) {
                case DIF_VAR_CURTHREAD:
                case DIF_VAR_PID:
                case DIF_VAR_TID:
                case DIF_VAR_EXECNAME:
                case DIF_VAR_ZONENAME:
                        break;

                default:
                        return (0);
                }
        }

        /*
         * This DIF object may be cacheable.  Now we need to look for any
         * array loading instructions, any memory loading instructions, or
         * any stores to thread-local variables.
         */
        for (i = 0; i < dp->dtdo_len; i++) {
                uint_t op = DIF_INSTR_OP(dp->dtdo_buf[i]);

                if ((op >= DIF_OP_LDSB && op <= DIF_OP_LDX) ||
                    (op >= DIF_OP_ULDSB && op <= DIF_OP_ULDX) ||
                    (op >= DIF_OP_RLDSB && op <= DIF_OP_RLDX) ||
                    op == DIF_OP_LDGA || op == DIF_OP_STTS)
                        return (0);
        }

        return (1);
}

static void
dtrace_difo_hold(dtrace_difo_t *dp)
{
        uint_t i;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);

        dp->dtdo_refcnt++;
        ASSERT(dp->dtdo_refcnt != 0);

        /*
         * We need to check this DIF object for references to the variable
         * DIF_VAR_VTIMESTAMP.
         */
        for (i = 0; i < dp->dtdo_varlen; i++) {
                dtrace_difv_t *v = &dp->dtdo_vartab[i];

                if (v->dtdv_id != DIF_VAR_VTIMESTAMP)
                        continue;

                if (dtrace_vtime_references++ == 0)
                        dtrace_vtime_enable();
        }
}

/*
 * This routine calculates the dynamic variable chunksize for a given DIF
 * object.  The calculation is not fool-proof, and can probably be tricked by
 * malicious DIF -- but it works for all compiler-generated DIF.  Because this
 * calculation is likely imperfect, dtrace_dynvar() is able to gracefully fail
 * if a dynamic variable size exceeds the chunksize.
 */
static void
dtrace_difo_chunksize(dtrace_difo_t *dp, dtrace_vstate_t *vstate)
{
        uint64_t sval = 0;
        dtrace_key_t tupregs[DIF_DTR_NREGS + 2]; /* +2 for thread and id */
        const dif_instr_t *text = dp->dtdo_buf;
        uint_t pc, srd = 0;
        uint_t ttop = 0;
        size_t size, ksize;
        uint_t id, i;

        for (pc = 0; pc < dp->dtdo_len; pc++) {
                dif_instr_t instr = text[pc];
                uint_t op = DIF_INSTR_OP(instr);
                uint_t rd = DIF_INSTR_RD(instr);
                uint_t r1 = DIF_INSTR_R1(instr);
                uint_t nkeys = 0;
                uchar_t scope;

                dtrace_key_t *key = tupregs;

                switch (op) {
                case DIF_OP_SETX:
                        sval = dp->dtdo_inttab[DIF_INSTR_INTEGER(instr)];
                        srd = rd;
                        continue;

                case DIF_OP_STTS:
                        key = &tupregs[DIF_DTR_NREGS];
                        key[0].dttk_size = 0;
                        key[1].dttk_size = 0;
                        nkeys = 2;
                        scope = DIFV_SCOPE_THREAD;
                        break;

                case DIF_OP_STGAA:
                case DIF_OP_STTAA:
                        nkeys = ttop;

                        if (DIF_INSTR_OP(instr) == DIF_OP_STTAA)
                                key[nkeys++].dttk_size = 0;

                        key[nkeys++].dttk_size = 0;

                        if (op == DIF_OP_STTAA) {
                                scope = DIFV_SCOPE_THREAD;
                        } else {
                                scope = DIFV_SCOPE_GLOBAL;
                        }

                        break;

                case DIF_OP_PUSHTR:
                        if (ttop == DIF_DTR_NREGS)
                                return;

                        if ((srd == 0 || sval == 0) && r1 == DIF_TYPE_STRING) {
                                /*
                                 * If the register for the size of the "pushtr"
                                 * is %r0 (or the value is 0) and the type is
                                 * a string, we'll use the system-wide default
                                 * string size.
                                 */
                                tupregs[ttop++].dttk_size =
                                    dtrace_strsize_default;
                        } else {
                                if (srd == 0)
                                        return;

                                if (sval > LONG_MAX)
                                        return;

                                tupregs[ttop++].dttk_size = sval;
                        }

                        break;

                case DIF_OP_PUSHTV:
                        if (ttop == DIF_DTR_NREGS)
                                return;

                        tupregs[ttop++].dttk_size = 0;
                        break;

                case DIF_OP_FLUSHTS:
                        ttop = 0;
                        break;

                case DIF_OP_POPTS:
                        if (ttop != 0)
                                ttop--;
                        break;
                }

                sval = 0;
                srd = 0;

                if (nkeys == 0)
                        continue;

                /*
                 * We have a dynamic variable allocation; calculate its size.
                 */
                for (ksize = 0, i = 0; i < nkeys; i++)
                        ksize += P2ROUNDUP(key[i].dttk_size, sizeof (uint64_t));

                size = sizeof (dtrace_dynvar_t);
                size += sizeof (dtrace_key_t) * (nkeys - 1);
                size += ksize;

                /*
                 * Now we need to determine the size of the stored data.
                 */
                id = DIF_INSTR_VAR(instr);

                for (i = 0; i < dp->dtdo_varlen; i++) {
                        dtrace_difv_t *v = &dp->dtdo_vartab[i];

                        if (v->dtdv_id == id && v->dtdv_scope == scope) {
                                size += v->dtdv_type.dtdt_size;
                                break;
                        }
                }

                if (i == dp->dtdo_varlen)
                        return;

                /*
                 * We have the size.  If this is larger than the chunk size
                 * for our dynamic variable state, reset the chunk size.
                 */
                size = P2ROUNDUP(size, sizeof (uint64_t));

                /*
                 * Before setting the chunk size, check that we're not going
                 * to set it to a negative value...
                 */
                if (size > LONG_MAX)
                        return;

                /*
                 * ...and make certain that we didn't badly overflow.
                 */
                if (size < ksize || size < sizeof (dtrace_dynvar_t))
                        return;

                if (size > vstate->dtvs_dynvars.dtds_chunksize)
                        vstate->dtvs_dynvars.dtds_chunksize = size;
        }
}

static void
dtrace_difo_init(dtrace_difo_t *dp, dtrace_vstate_t *vstate)
{
        int oldsvars, osz, nsz, otlocals, ntlocals;
        uint_t i, id;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);
        ASSERT(dp->dtdo_buf != NULL && dp->dtdo_len != 0);

        for (i = 0; i < dp->dtdo_varlen; i++) {
                dtrace_difv_t *v = &dp->dtdo_vartab[i];
                dtrace_statvar_t *svar;
                dtrace_statvar_t ***svarp = NULL;
                size_t dsize = 0;
                uint8_t scope = v->dtdv_scope;
                int *np = (int *)NULL;

                if ((id = v->dtdv_id) < DIF_VAR_OTHER_UBASE)
                        continue;

                id -= DIF_VAR_OTHER_UBASE;

                switch (scope) {
                case DIFV_SCOPE_THREAD:
                        while (id >= (uint_t)(otlocals = vstate->dtvs_ntlocals)) {
                                dtrace_difv_t *tlocals;

                                if ((ntlocals = (otlocals << 1)) == 0)
                                        ntlocals = 1;

                                osz = otlocals * sizeof (dtrace_difv_t);
                                nsz = ntlocals * sizeof (dtrace_difv_t);

                                tlocals = kmem_zalloc(nsz, KM_SLEEP);

                                if (osz != 0) {
                                        bcopy(vstate->dtvs_tlocals,
                                            tlocals, osz);
                                        kmem_free(vstate->dtvs_tlocals, osz);
                                }

                                vstate->dtvs_tlocals = tlocals;
                                vstate->dtvs_ntlocals = ntlocals;
                        }

                        vstate->dtvs_tlocals[id] = *v;
                        continue;

                case DIFV_SCOPE_LOCAL:
                        np = &vstate->dtvs_nlocals;
                        svarp = &vstate->dtvs_locals;

                        if (v->dtdv_type.dtdt_flags & DIF_TF_BYREF)
                                dsize = (int)NCPU * (v->dtdv_type.dtdt_size +
                                    sizeof (uint64_t));
                        else
                                dsize = (int)NCPU * sizeof (uint64_t);

                        break;

                case DIFV_SCOPE_GLOBAL:
                        np = &vstate->dtvs_nglobals;
                        svarp = &vstate->dtvs_globals;

                        if (v->dtdv_type.dtdt_flags & DIF_TF_BYREF)
                                dsize = v->dtdv_type.dtdt_size +
                                    sizeof (uint64_t);

                        break;

                default:
                        ASSERT(0);
                }

                while (id >= (uint_t)(oldsvars = *np)) {
                        dtrace_statvar_t **statics;
                        int newsvars, oldsize, newsize;

                        if ((newsvars = (oldsvars << 1)) == 0)
                                newsvars = 1;

                        oldsize = oldsvars * sizeof (dtrace_statvar_t *);
                        newsize = newsvars * sizeof (dtrace_statvar_t *);

                        statics = kmem_zalloc(newsize, KM_SLEEP);

                        if (oldsize != 0) {
                                bcopy(*svarp, statics, oldsize);
                                kmem_free(*svarp, oldsize);
                        }

                        *svarp = statics;
                        *np = newsvars;
                }

                if ((svar = (*svarp)[id]) == NULL) {
                        svar = kmem_zalloc(sizeof (dtrace_statvar_t), KM_SLEEP);
                        svar->dtsv_var = *v;

                        if ((svar->dtsv_size = dsize) != 0) {
                                svar->dtsv_data = (uint64_t)(uintptr_t)
                                    kmem_zalloc(dsize, KM_SLEEP);
                        }

                        (*svarp)[id] = svar;
                }

                svar->dtsv_refcnt++;
        }

        dtrace_difo_chunksize(dp, vstate);
        dtrace_difo_hold(dp);
}

static dtrace_difo_t *
dtrace_difo_duplicate(dtrace_difo_t *dp, dtrace_vstate_t *vstate)
{
        dtrace_difo_t *new;
        size_t sz;

        ASSERT(dp->dtdo_buf != NULL);
        ASSERT(dp->dtdo_refcnt != 0);

        new = kmem_zalloc(sizeof (dtrace_difo_t), KM_SLEEP);

        ASSERT(dp->dtdo_buf != NULL);
        sz = dp->dtdo_len * sizeof (dif_instr_t);
        new->dtdo_buf = kmem_alloc(sz, KM_SLEEP);
        bcopy(dp->dtdo_buf, new->dtdo_buf, sz);
        new->dtdo_len = dp->dtdo_len;

        if (dp->dtdo_strtab != NULL) {
                ASSERT(dp->dtdo_strlen != 0);
                new->dtdo_strtab = kmem_alloc(dp->dtdo_strlen, KM_SLEEP);
                bcopy(dp->dtdo_strtab, new->dtdo_strtab, dp->dtdo_strlen);
                new->dtdo_strlen = dp->dtdo_strlen;
        }

        if (dp->dtdo_inttab != NULL) {
                ASSERT(dp->dtdo_intlen != 0);
                sz = dp->dtdo_intlen * sizeof (uint64_t);
                new->dtdo_inttab = kmem_alloc(sz, KM_SLEEP);
                bcopy(dp->dtdo_inttab, new->dtdo_inttab, sz);
                new->dtdo_intlen = dp->dtdo_intlen;
        }

        if (dp->dtdo_vartab != NULL) {
                ASSERT(dp->dtdo_varlen != 0);
                sz = dp->dtdo_varlen * sizeof (dtrace_difv_t);
                new->dtdo_vartab = kmem_alloc(sz, KM_SLEEP);
                bcopy(dp->dtdo_vartab, new->dtdo_vartab, sz);
                new->dtdo_varlen = dp->dtdo_varlen;
        }

        dtrace_difo_init(new, vstate);
        return (new);
}

static void
dtrace_difo_destroy(dtrace_difo_t *dp, dtrace_vstate_t *vstate)
{
        uint_t i;

        ASSERT(dp->dtdo_refcnt == 0);

        for (i = 0; i < dp->dtdo_varlen; i++) {
                dtrace_difv_t *v = &dp->dtdo_vartab[i];
                dtrace_statvar_t *svar;
                dtrace_statvar_t **svarp = NULL;
                uint_t id;
                uint8_t scope = v->dtdv_scope;
                int *np = NULL;

                switch (scope) {
                case DIFV_SCOPE_THREAD:
                        continue;

                case DIFV_SCOPE_LOCAL:
                        np = &vstate->dtvs_nlocals;
                        svarp = vstate->dtvs_locals;
                        break;

                case DIFV_SCOPE_GLOBAL:
                        np = &vstate->dtvs_nglobals;
                        svarp = vstate->dtvs_globals;
                        break;

                default:
                        ASSERT(0);
                }

                if ((id = v->dtdv_id) < DIF_VAR_OTHER_UBASE)
                        continue;

                id -= DIF_VAR_OTHER_UBASE;
                
                ASSERT(id < (uint_t)*np);

                svar = svarp[id];
                ASSERT(svar != NULL);
                ASSERT(svar->dtsv_refcnt > 0);

                if (--svar->dtsv_refcnt > 0)
                        continue;

                if (svar->dtsv_size != 0) {
                        ASSERT(svar->dtsv_data != 0);
                        kmem_free((void *)(uintptr_t)svar->dtsv_data,
                            svar->dtsv_size);
                }

                kmem_free(svar, sizeof (dtrace_statvar_t));
                svarp[id] = NULL;
        }

        kmem_free(dp->dtdo_buf, dp->dtdo_len * sizeof (dif_instr_t));
        kmem_free(dp->dtdo_inttab, dp->dtdo_intlen * sizeof (uint64_t));
        kmem_free(dp->dtdo_strtab, dp->dtdo_strlen);
        kmem_free(dp->dtdo_vartab, dp->dtdo_varlen * sizeof (dtrace_difv_t));

        kmem_free(dp, sizeof (dtrace_difo_t));
}

static void
dtrace_difo_release(dtrace_difo_t *dp, dtrace_vstate_t *vstate)
{
        uint_t i;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);
        ASSERT(dp->dtdo_refcnt != 0);

        for (i = 0; i < dp->dtdo_varlen; i++) {
                dtrace_difv_t *v = &dp->dtdo_vartab[i];

                if (v->dtdv_id != DIF_VAR_VTIMESTAMP)
                        continue;

                ASSERT(dtrace_vtime_references > 0);
                if (--dtrace_vtime_references == 0)
                        dtrace_vtime_disable();
        }

        if (--dp->dtdo_refcnt == 0)
                dtrace_difo_destroy(dp, vstate);
}

/*
 * DTrace Format Functions
 */
static uint16_t
dtrace_format_add(dtrace_state_t *state, char *str)
{
        char *fmt, **new;
        uint16_t ndx, len = strlen(str) + 1;

        fmt = kmem_zalloc(len, KM_SLEEP);
        bcopy(str, fmt, len);

        for (ndx = 0; ndx < state->dts_nformats; ndx++) {
                if (state->dts_formats[ndx] == NULL) {
                        state->dts_formats[ndx] = fmt;
                        return (ndx + 1);
                }
        }

        if (state->dts_nformats == USHRT_MAX) {
                /*
                 * This is only likely if a denial-of-service attack is being
                 * attempted.  As such, it's okay to fail silently here.
                 */
                kmem_free(fmt, len);
                return (0);
        }

        /*
         * For simplicity, we always resize the formats array to be exactly the
         * number of formats.
         */
        ndx = state->dts_nformats++;
        new = kmem_alloc((ndx + 1) * sizeof (char *), KM_SLEEP);

        if (state->dts_formats != NULL) {
                ASSERT(ndx != 0);
                bcopy(state->dts_formats, new, ndx * sizeof (char *));
                kmem_free(state->dts_formats, ndx * sizeof (char *));
        }

        state->dts_formats = new;
        state->dts_formats[ndx] = fmt;

        return (ndx + 1);
}

static void
dtrace_format_remove(dtrace_state_t *state, uint16_t format)
{
        char *fmt;

        ASSERT(state->dts_formats != NULL);
        ASSERT(format <= state->dts_nformats);
        ASSERT(state->dts_formats[format - 1] != NULL);

        fmt = state->dts_formats[format - 1];
        kmem_free(fmt, strlen(fmt) + 1);
        state->dts_formats[format - 1] = NULL;
}

static void
dtrace_format_destroy(dtrace_state_t *state)
{
        int i;

        if (state->dts_nformats == 0) {
                ASSERT(state->dts_formats == NULL);
                return;
        }

        ASSERT(state->dts_formats != NULL);

        for (i = 0; i < state->dts_nformats; i++) {
                char *fmt = state->dts_formats[i];

                if (fmt == NULL)
                        continue;

                kmem_free(fmt, strlen(fmt) + 1);
        }

        kmem_free(state->dts_formats, state->dts_nformats * sizeof (char *));
        state->dts_nformats = 0;
        state->dts_formats = NULL;
}

/*
 * DTrace Predicate Functions
 */
static dtrace_predicate_t *
dtrace_predicate_create(dtrace_difo_t *dp)
{
        dtrace_predicate_t *pred;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);
        ASSERT(dp->dtdo_refcnt != 0);

        pred = kmem_zalloc(sizeof (dtrace_predicate_t), KM_SLEEP);
        pred->dtp_difo = dp;
        pred->dtp_refcnt = 1;

        if (!dtrace_difo_cacheable(dp))
                return (pred);

        if (dtrace_predcache_id == DTRACE_CACHEIDNONE) {
                /*
                 * This is only theoretically possible -- we have had 2^32
                 * cacheable predicates on this machine.  We cannot allow any
                 * more predicates to become cacheable:  as unlikely as it is,
                 * there may be a thread caching a (now stale) predicate cache
                 * ID. (N.B.: the temptation is being successfully resisted to
                 * have this cmn_err() "Holy shit -- we executed this code!")
                 */
                return (pred);
        }

        pred->dtp_cacheid = dtrace_predcache_id++;

        return (pred);
}

static void
dtrace_predicate_hold(dtrace_predicate_t *pred)
{
        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);
        ASSERT(pred->dtp_difo != NULL && pred->dtp_difo->dtdo_refcnt != 0);
        ASSERT(pred->dtp_refcnt > 0);

        pred->dtp_refcnt++;
}

static void
dtrace_predicate_release(dtrace_predicate_t *pred, dtrace_vstate_t *vstate)
{
        dtrace_difo_t *dp = pred->dtp_difo;
#pragma unused(dp) /* __APPLE__ */

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);
        ASSERT(dp != NULL && dp->dtdo_refcnt != 0);
        ASSERT(pred->dtp_refcnt > 0);

        if (--pred->dtp_refcnt == 0) {
                dtrace_difo_release(pred->dtp_difo, vstate);
                kmem_free(pred, sizeof (dtrace_predicate_t));
        }
}

/*
 * DTrace Action Description Functions
 */
static dtrace_actdesc_t *
dtrace_actdesc_create(dtrace_actkind_t kind, uint32_t ntuple,
    uint64_t uarg, uint64_t arg)
{
        dtrace_actdesc_t *act;

        ASSERT(!DTRACEACT_ISPRINTFLIKE(kind) || (arg != 0 &&
            arg >= KERNELBASE) || (arg == 0 && kind == DTRACEACT_PRINTA));

        act = kmem_zalloc(sizeof (dtrace_actdesc_t), KM_SLEEP);
        act->dtad_kind = kind;
        act->dtad_ntuple = ntuple;
        act->dtad_uarg = uarg;
        act->dtad_arg = arg;
        act->dtad_refcnt = 1;

        return (act);
}

static void
dtrace_actdesc_hold(dtrace_actdesc_t *act)
{
        ASSERT(act->dtad_refcnt >= 1);
        act->dtad_refcnt++;
}

static void
dtrace_actdesc_release(dtrace_actdesc_t *act, dtrace_vstate_t *vstate)
{
        dtrace_actkind_t kind = act->dtad_kind;
        dtrace_difo_t *dp;

        ASSERT(act->dtad_refcnt >= 1);

        if (--act->dtad_refcnt != 0)
                return;

        if ((dp = act->dtad_difo) != NULL)
                dtrace_difo_release(dp, vstate);

        if (DTRACEACT_ISPRINTFLIKE(kind)) {
                char *str = (char *)(uintptr_t)act->dtad_arg;

                ASSERT((str != NULL && (uintptr_t)str >= KERNELBASE) ||
                    (str == NULL && act->dtad_kind == DTRACEACT_PRINTA));

                if (str != NULL)
                        kmem_free(str, strlen(str) + 1);
        }

        kmem_free(act, sizeof (dtrace_actdesc_t));
}

/*
 * DTrace ECB Functions
 */
static dtrace_ecb_t *
dtrace_ecb_add(dtrace_state_t *state, dtrace_probe_t *probe)
{
        dtrace_ecb_t *ecb;
        dtrace_epid_t epid;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);

        ecb = kmem_zalloc(sizeof (dtrace_ecb_t), KM_SLEEP);
        ecb->dte_predicate = NULL;
        ecb->dte_probe = probe;

        /*
         * The default size is the size of the default action: recording
         * the header.
         */
        ecb->dte_size = ecb->dte_needed = sizeof (dtrace_rechdr_t);
        ecb->dte_alignment = sizeof (dtrace_epid_t);

        epid = state->dts_epid++;

        if (epid - 1 >= (dtrace_epid_t)state->dts_necbs) {
                dtrace_ecb_t **oecbs = state->dts_ecbs, **ecbs;
                int necbs = state->dts_necbs << 1;

                ASSERT(epid == (dtrace_epid_t)state->dts_necbs + 1);

                if (necbs == 0) {
                        ASSERT(oecbs == NULL);
                        necbs = 1;
                }

                ecbs = kmem_zalloc(necbs * sizeof (*ecbs), KM_SLEEP);

                if (oecbs != NULL)
                        bcopy(oecbs, ecbs, state->dts_necbs * sizeof (*ecbs));

                dtrace_membar_producer();
                state->dts_ecbs = ecbs;

                if (oecbs != NULL) {
                        /*
                         * If this state is active, we must dtrace_sync()
                         * before we can free the old dts_ecbs array:  we're
                         * coming in hot, and there may be active ring
                         * buffer processing (which indexes into the dts_ecbs
                         * array) on another CPU.
                         */
                        if (state->dts_activity != DTRACE_ACTIVITY_INACTIVE)
                                dtrace_sync();

                        kmem_free(oecbs, state->dts_necbs * sizeof (*ecbs));
                }

                dtrace_membar_producer();
                state->dts_necbs = necbs;
        }

        ecb->dte_state = state;

        ASSERT(state->dts_ecbs[epid - 1] == NULL);
        dtrace_membar_producer();
        state->dts_ecbs[(ecb->dte_epid = epid) - 1] = ecb;

        return (ecb);
}

static int
dtrace_ecb_enable(dtrace_ecb_t *ecb)
{
        dtrace_probe_t *probe = ecb->dte_probe;

        LCK_MTX_ASSERT(&cpu_lock, LCK_MTX_ASSERT_OWNED);
        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);
        ASSERT(ecb->dte_next == NULL);

        if (probe == NULL) {
                /*
                 * This is the NULL probe -- there's nothing to do.
                 */
            return(0);
        }

        probe->dtpr_provider->dtpv_ecb_count++;
        if (probe->dtpr_ecb == NULL) {
                dtrace_provider_t *prov = probe->dtpr_provider;

                /*
                 * We're the first ECB on this probe.
                 */
                probe->dtpr_ecb = probe->dtpr_ecb_last = ecb;

                if (ecb->dte_predicate != NULL)
                        probe->dtpr_predcache = ecb->dte_predicate->dtp_cacheid;

                return (prov->dtpv_pops.dtps_enable(prov->dtpv_arg,
                    probe->dtpr_id, probe->dtpr_arg));
        } else {
                /*
                 * This probe is already active.  Swing the last pointer to
                 * point to the new ECB, and issue a dtrace_sync() to assure
                 * that all CPUs have seen the change.
                 */
                ASSERT(probe->dtpr_ecb_last != NULL);
                probe->dtpr_ecb_last->dte_next = ecb;
                probe->dtpr_ecb_last = ecb;
                probe->dtpr_predcache = 0;

                dtrace_sync();
                return(0);
        }
}

static int
dtrace_ecb_resize(dtrace_ecb_t *ecb)
{
        dtrace_action_t *act;
        uint32_t curneeded = UINT32_MAX;
        uint32_t aggbase = UINT32_MAX;

        /*
         * If we record anything, we always record the dtrace_rechdr_t.  (And
         * we always record it first.)
         */
        ecb->dte_size = sizeof (dtrace_rechdr_t);
        ecb->dte_alignment = sizeof (dtrace_epid_t);

        for (act = ecb->dte_action; act != NULL; act = act->dta_next) {
                dtrace_recdesc_t *rec = &act->dta_rec;
                ASSERT(rec->dtrd_size > 0 || rec->dtrd_alignment == 1);

                ecb->dte_alignment = MAX(ecb->dte_alignment, rec->dtrd_alignment);

                if (DTRACEACT_ISAGG(act->dta_kind)) {
                        dtrace_aggregation_t *agg = (dtrace_aggregation_t *)act;

                        ASSERT(rec->dtrd_size != 0);
                        ASSERT(agg->dtag_first != NULL);
                        ASSERT(act->dta_prev->dta_intuple);
                        ASSERT(aggbase != UINT32_MAX);
                        ASSERT(curneeded != UINT32_MAX);

                        agg->dtag_base = aggbase;
                        curneeded = P2ROUNDUP(curneeded, rec->dtrd_alignment);
                        rec->dtrd_offset = curneeded;
                        if (curneeded + rec->dtrd_size < curneeded)
                                return (EINVAL);
                        curneeded += rec->dtrd_size;
                        ecb->dte_needed = MAX(ecb->dte_needed, curneeded);

                        aggbase = UINT32_MAX;
                        curneeded = UINT32_MAX;
                } else if (act->dta_intuple) {
                        if (curneeded == UINT32_MAX) {
                                /*
                                 * This is the first record in a tuple.  Align
                                 * curneeded to be at offset 4 in an 8-byte
                                 * aligned block.
                                 */
                                ASSERT(act->dta_prev == NULL || !act->dta_prev->dta_intuple);
                                ASSERT(aggbase == UINT32_MAX);

                                curneeded = P2PHASEUP(ecb->dte_size,
                                    sizeof (uint64_t), sizeof (dtrace_aggid_t));

                                aggbase = curneeded - sizeof (dtrace_aggid_t);
                                ASSERT(IS_P2ALIGNED(aggbase,
                                    sizeof (uint64_t)));
                        }

                        curneeded = P2ROUNDUP(curneeded, rec->dtrd_alignment);
                        rec->dtrd_offset = curneeded;
                        curneeded += rec->dtrd_size;
                        if (curneeded + rec->dtrd_size < curneeded)
                                return (EINVAL);
                } else {
                        /* tuples must be followed by an aggregation */
                        ASSERT(act->dta_prev == NULL || !act->dta_prev->dta_intuple);
                        ecb->dte_size = P2ROUNDUP(ecb->dte_size, rec->dtrd_alignment);
                        rec->dtrd_offset = ecb->dte_size;
                        if (ecb->dte_size + rec->dtrd_size < ecb->dte_size)
                                return (EINVAL);
                        ecb->dte_size += rec->dtrd_size;
                        ecb->dte_needed = MAX(ecb->dte_needed, ecb->dte_size);
                }
        }

        if ((act = ecb->dte_action) != NULL &&
            !(act->dta_kind == DTRACEACT_SPECULATE && act->dta_next == NULL) &&
            ecb->dte_size == sizeof (dtrace_rechdr_t)) {
                /*
                 * If the size is still sizeof (dtrace_rechdr_t), then all
                 * actions store no data; set the size to 0.
                 */
                ecb->dte_size = 0;
        }

        ecb->dte_size = P2ROUNDUP(ecb->dte_size, sizeof (dtrace_epid_t));
        ecb->dte_needed = P2ROUNDUP(ecb->dte_needed, (sizeof (dtrace_epid_t)));
        ecb->dte_state->dts_needed = MAX(ecb->dte_state->dts_needed, ecb->dte_needed);
        return (0);
}

static dtrace_action_t *
dtrace_ecb_aggregation_create(dtrace_ecb_t *ecb, dtrace_actdesc_t *desc)
{
        dtrace_aggregation_t *agg;
        size_t size = sizeof (uint64_t);
        int ntuple = desc->dtad_ntuple;
        dtrace_action_t *act;
        dtrace_recdesc_t *frec;
        dtrace_aggid_t aggid;
        dtrace_state_t *state = ecb->dte_state;

        agg = kmem_zalloc(sizeof (dtrace_aggregation_t), KM_SLEEP);
        agg->dtag_ecb = ecb;

        ASSERT(DTRACEACT_ISAGG(desc->dtad_kind));

        switch (desc->dtad_kind) {
        case DTRACEAGG_MIN:
                agg->dtag_initial = INT64_MAX;
                agg->dtag_aggregate = dtrace_aggregate_min;
                break;

        case DTRACEAGG_MAX:
                agg->dtag_initial = INT64_MIN;
                agg->dtag_aggregate = dtrace_aggregate_max;
                break;

        case DTRACEAGG_COUNT:
                agg->dtag_aggregate = dtrace_aggregate_count;
                break;

        case DTRACEAGG_QUANTIZE:
                agg->dtag_aggregate = dtrace_aggregate_quantize;
                size = (((sizeof (uint64_t) * NBBY) - 1) * 2 + 1) *
                    sizeof (uint64_t);
                break;

        case DTRACEAGG_LQUANTIZE: {
                uint16_t step = DTRACE_LQUANTIZE_STEP(desc->dtad_arg);
                uint16_t levels = DTRACE_LQUANTIZE_LEVELS(desc->dtad_arg);

                agg->dtag_initial = desc->dtad_arg;
                agg->dtag_aggregate = dtrace_aggregate_lquantize;

                if (step == 0 || levels == 0)
                        goto err;

                size = levels * sizeof (uint64_t) + 3 * sizeof (uint64_t);
                break;
        }

        case DTRACEAGG_LLQUANTIZE: {
                uint16_t factor = DTRACE_LLQUANTIZE_FACTOR(desc->dtad_arg);
                uint16_t low    = DTRACE_LLQUANTIZE_LOW(desc->dtad_arg);
                uint16_t high   = DTRACE_LLQUANTIZE_HIGH(desc->dtad_arg);
                uint16_t nsteps = DTRACE_LLQUANTIZE_NSTEP(desc->dtad_arg);
                int64_t v;

                agg->dtag_initial = desc->dtad_arg;
                agg->dtag_aggregate = dtrace_aggregate_llquantize;

                if (factor < 2 || low >= high || nsteps < factor)
                        goto err;

                /*
                 * Now check that the number of steps evenly divides a power
                 * of the factor.  (This assures both integer bucket size and
                 * linearity within each magnitude.)
                 */
                for (v = factor; v < nsteps; v *= factor)
                        continue;

                if ((v % nsteps) || (nsteps % factor))
                        goto err;

                size = (dtrace_aggregate_llquantize_bucket(factor, low, high, nsteps, INT64_MAX) + 2) * sizeof (uint64_t);
                break;
  }

        case DTRACEAGG_AVG:
                agg->dtag_aggregate = dtrace_aggregate_avg;
                size = sizeof (uint64_t) * 2;
                break;

        case DTRACEAGG_STDDEV:
                agg->dtag_aggregate = dtrace_aggregate_stddev;
                size = sizeof (uint64_t) * 4;
                break;

        case DTRACEAGG_SUM:
                agg->dtag_aggregate = dtrace_aggregate_sum;
                break;

        default:
                goto err;
        }

        agg->dtag_action.dta_rec.dtrd_size = size;

        if (ntuple == 0)
                goto err;

        /*
         * We must make sure that we have enough actions for the n-tuple.
         */
        for (act = ecb->dte_action_last; act != NULL; act = act->dta_prev) {
                if (DTRACEACT_ISAGG(act->dta_kind))
                        break;

                if (--ntuple == 0) {
                        /*
                         * This is the action with which our n-tuple begins.
                         */
                        agg->dtag_first = act;
                        goto success;
                }
        }

        /*
         * This n-tuple is short by ntuple elements.  Return failure.
         */
        ASSERT(ntuple != 0);
err:
        kmem_free(agg, sizeof (dtrace_aggregation_t));
        return (NULL);

success:
        /*
         * If the last action in the tuple has a size of zero, it's actually
         * an expression argument for the aggregating action.
         */
        ASSERT(ecb->dte_action_last != NULL);
        act = ecb->dte_action_last;

        if (act->dta_kind == DTRACEACT_DIFEXPR) {
                ASSERT(act->dta_difo != NULL);

                if (act->dta_difo->dtdo_rtype.dtdt_size == 0)
                        agg->dtag_hasarg = 1;
        }

        /*
         * We need to allocate an id for this aggregation.
         */
        aggid = (dtrace_aggid_t)(uintptr_t)vmem_alloc(state->dts_aggid_arena, 1,
            VM_BESTFIT | VM_SLEEP);

        if (aggid - 1 >= (dtrace_aggid_t)state->dts_naggregations) {
                dtrace_aggregation_t **oaggs = state->dts_aggregations;
                dtrace_aggregation_t **aggs;
                int naggs = state->dts_naggregations << 1;
                int onaggs = state->dts_naggregations;

                ASSERT(aggid == (dtrace_aggid_t)state->dts_naggregations + 1);

                if (naggs == 0) {
                        ASSERT(oaggs == NULL);
                        naggs = 1;
                }

                aggs = kmem_zalloc(naggs * sizeof (*aggs), KM_SLEEP);

                if (oaggs != NULL) {
                        bcopy(oaggs, aggs, onaggs * sizeof (*aggs));
                        kmem_free(oaggs, onaggs * sizeof (*aggs));
                }

                state->dts_aggregations = aggs;
                state->dts_naggregations = naggs;
        }

        ASSERT(state->dts_aggregations[aggid - 1] == NULL);
        state->dts_aggregations[(agg->dtag_id = aggid) - 1] = agg;

        frec = &agg->dtag_first->dta_rec;
        if (frec->dtrd_alignment < sizeof (dtrace_aggid_t))
                frec->dtrd_alignment = sizeof (dtrace_aggid_t);

        for (act = agg->dtag_first; act != NULL; act = act->dta_next) {
                ASSERT(!act->dta_intuple);
                act->dta_intuple = 1;
        }

        return (&agg->dtag_action);
}

static void
dtrace_ecb_aggregation_destroy(dtrace_ecb_t *ecb, dtrace_action_t *act)
{
        dtrace_aggregation_t *agg = (dtrace_aggregation_t *)act;
        dtrace_state_t *state = ecb->dte_state;
        dtrace_aggid_t aggid = agg->dtag_id;

        ASSERT(DTRACEACT_ISAGG(act->dta_kind));
        vmem_free(state->dts_aggid_arena, (void *)(uintptr_t)aggid, 1);

        ASSERT(state->dts_aggregations[aggid - 1] == agg);
        state->dts_aggregations[aggid - 1] = NULL;

        kmem_free(agg, sizeof (dtrace_aggregation_t));
}

static int
dtrace_ecb_action_add(dtrace_ecb_t *ecb, dtrace_actdesc_t *desc)
{
        dtrace_action_t *action, *last;
        dtrace_difo_t *dp = desc->dtad_difo;
        uint32_t size = 0, align = sizeof (uint8_t), mask;
        uint16_t format = 0;
        dtrace_recdesc_t *rec;
        dtrace_state_t *state = ecb->dte_state;
        dtrace_optval_t *opt = state->dts_options;
        dtrace_optval_t nframes=0, strsize;
        uint64_t arg = desc->dtad_arg;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);
        ASSERT(ecb->dte_action == NULL || ecb->dte_action->dta_refcnt == 1);

        if (DTRACEACT_ISAGG(desc->dtad_kind)) {
                /*
                 * If this is an aggregating action, there must be neither
                 * a speculate nor a commit on the action chain.
                 */
                dtrace_action_t *act;

                for (act = ecb->dte_action; act != NULL; act = act->dta_next) {
                        if (act->dta_kind == DTRACEACT_COMMIT)
                                return (EINVAL);

                        if (act->dta_kind == DTRACEACT_SPECULATE)
                                return (EINVAL);
                }

                action = dtrace_ecb_aggregation_create(ecb, desc);

                if (action == NULL)
                        return (EINVAL);
        } else {
                if (DTRACEACT_ISDESTRUCTIVE(desc->dtad_kind) ||
                    (desc->dtad_kind == DTRACEACT_DIFEXPR &&
                    dp != NULL && dp->dtdo_destructive)) {
                        state->dts_destructive = 1;
                }

                switch (desc->dtad_kind) {
                case DTRACEACT_PRINTF:
                case DTRACEACT_PRINTA:
                case DTRACEACT_SYSTEM:
                case DTRACEACT_FREOPEN:
                case DTRACEACT_DIFEXPR:
                        /*
                         * We know that our arg is a string -- turn it into a
                         * format.
                         */
                        if (arg == 0) {
                                ASSERT(desc->dtad_kind == DTRACEACT_PRINTA ||
                                       desc->dtad_kind == DTRACEACT_DIFEXPR);
                                format = 0;
                        } else {
                                ASSERT(arg != 0);
                                ASSERT(arg > KERNELBASE);
                                format = dtrace_format_add(state,
                                    (char *)(uintptr_t)arg);
                        }

                        /*FALLTHROUGH*/
                case DTRACEACT_LIBACT:
                case DTRACEACT_TRACEMEM:
                case DTRACEACT_TRACEMEM_DYNSIZE:
                case DTRACEACT_APPLEBINARY:     /* __APPLE__ */
                        if (dp == NULL)
                                return (EINVAL);

                        if ((size = dp->dtdo_rtype.dtdt_size) != 0)
                                break;

                        if (dp->dtdo_rtype.dtdt_kind == DIF_TYPE_STRING) {
                                if (!(dp->dtdo_rtype.dtdt_flags & DIF_TF_BYREF))
                                        return (EINVAL);

                                size = opt[DTRACEOPT_STRSIZE];
                        }

                        break;

                case DTRACEACT_STACK:
                        if ((nframes = arg) == 0) {
                                nframes = opt[DTRACEOPT_STACKFRAMES];
                                ASSERT(nframes > 0);
                                arg = nframes;
                        }

                        size = nframes * sizeof (pc_t);
                        break;

                case DTRACEACT_JSTACK:
                        if ((strsize = DTRACE_USTACK_STRSIZE(arg)) == 0)
                                strsize = opt[DTRACEOPT_JSTACKSTRSIZE];

                        if ((nframes = DTRACE_USTACK_NFRAMES(arg)) == 0)
                                nframes = opt[DTRACEOPT_JSTACKFRAMES];

                        arg = DTRACE_USTACK_ARG(nframes, strsize);

                        /*FALLTHROUGH*/
                case DTRACEACT_USTACK:
                        if (desc->dtad_kind != DTRACEACT_JSTACK &&
                            (nframes = DTRACE_USTACK_NFRAMES(arg)) == 0) {
                                strsize = DTRACE_USTACK_STRSIZE(arg);
                                nframes = opt[DTRACEOPT_USTACKFRAMES];
                                ASSERT(nframes > 0);
                                arg = DTRACE_USTACK_ARG(nframes, strsize);
                        }

                        /*
                         * Save a slot for the pid.
                         */
                        size = (nframes + 1) * sizeof (uint64_t);
                        size += DTRACE_USTACK_STRSIZE(arg);
                        size = P2ROUNDUP(size, (uint32_t)(sizeof (uintptr_t)));

                        break;

                case DTRACEACT_SYM:
                case DTRACEACT_MOD:
                        if (dp == NULL || ((size = dp->dtdo_rtype.dtdt_size) !=
                            sizeof (uint64_t)) ||
                            (dp->dtdo_rtype.dtdt_flags & DIF_TF_BYREF))
                                return (EINVAL);
                        break;

                case DTRACEACT_USYM:
                case DTRACEACT_UMOD:
                case DTRACEACT_UADDR:
                        if (dp == NULL ||
                            (dp->dtdo_rtype.dtdt_size != sizeof (uint64_t)) ||
                            (dp->dtdo_rtype.dtdt_flags & DIF_TF_BYREF))
                                return (EINVAL);

                        /*
                         * We have a slot for the pid, plus a slot for the
                         * argument.  To keep things simple (aligned with
                         * bitness-neutral sizing), we store each as a 64-bit
                         * quantity.
                         */
                        size = 2 * sizeof (uint64_t);
                        break;

                case DTRACEACT_STOP:
                case DTRACEACT_BREAKPOINT:
                case DTRACEACT_PANIC:
                        break;

                case DTRACEACT_CHILL:
                case DTRACEACT_DISCARD:
                case DTRACEACT_RAISE:
                case DTRACEACT_PIDRESUME:       /* __APPLE__ */
                        if (dp == NULL)
                                return (EINVAL);
                        break;

                case DTRACEACT_EXIT:
                        if (dp == NULL ||
                            (size = dp->dtdo_rtype.dtdt_size) != sizeof (int) ||
                            (dp->dtdo_rtype.dtdt_flags & DIF_TF_BYREF))
                                return (EINVAL);
                        break;

                case DTRACEACT_SPECULATE:
                        if (ecb->dte_size > sizeof (dtrace_rechdr_t))
                                return (EINVAL);

                        if (dp == NULL)
                                return (EINVAL);

                        state->dts_speculates = 1;
                        break;

                case DTRACEACT_COMMIT: {
                        dtrace_action_t *act = ecb->dte_action;

                        for (; act != NULL; act = act->dta_next) {
                                if (act->dta_kind == DTRACEACT_COMMIT)
                                        return (EINVAL);
                        }

                        if (dp == NULL)
                                return (EINVAL);
                        break;
                }

                default:
                        return (EINVAL);
                }

                if (size != 0 || desc->dtad_kind == DTRACEACT_SPECULATE) {
                        /*
                         * If this is a data-storing action or a speculate,
                         * we must be sure that there isn't a commit on the
                         * action chain.
                         */
                        dtrace_action_t *act = ecb->dte_action;

                        for (; act != NULL; act = act->dta_next) {
                                if (act->dta_kind == DTRACEACT_COMMIT)
                                        return (EINVAL);
                        }
                }

                action = kmem_zalloc(sizeof (dtrace_action_t), KM_SLEEP);
                action->dta_rec.dtrd_size = size;
        }

        action->dta_refcnt = 1;
        rec = &action->dta_rec;
        size = rec->dtrd_size;

        for (mask = sizeof (uint64_t) - 1; size != 0 && mask > 0; mask >>= 1) {
                if (!(size & mask)) {
                        align = mask + 1;
                        break;
                }
        }

        action->dta_kind = desc->dtad_kind;

        if ((action->dta_difo = dp) != NULL)
                dtrace_difo_hold(dp);

        rec->dtrd_action = action->dta_kind;
        rec->dtrd_arg = arg;
        rec->dtrd_uarg = desc->dtad_uarg;
        rec->dtrd_alignment = (uint16_t)align;
        rec->dtrd_format = format;

        if ((last = ecb->dte_action_last) != NULL) {
                ASSERT(ecb->dte_action != NULL);
                action->dta_prev = last;
                last->dta_next = action;
        } else {
                ASSERT(ecb->dte_action == NULL);
                ecb->dte_action = action;
        }

        ecb->dte_action_last = action;

        return (0);
}

static void
dtrace_ecb_action_remove(dtrace_ecb_t *ecb)
{
        dtrace_action_t *act = ecb->dte_action, *next;
        dtrace_vstate_t *vstate = &ecb->dte_state->dts_vstate;
        dtrace_difo_t *dp;
        uint16_t format;

        if (act != NULL && act->dta_refcnt > 1) {
                ASSERT(act->dta_next == NULL || act->dta_next->dta_refcnt == 1);
                act->dta_refcnt--;
        } else {
                for (; act != NULL; act = next) {
                        next = act->dta_next;
                        ASSERT(next != NULL || act == ecb->dte_action_last);
                        ASSERT(act->dta_refcnt == 1);

                        if ((format = act->dta_rec.dtrd_format) != 0)
                                dtrace_format_remove(ecb->dte_state, format);

                        if ((dp = act->dta_difo) != NULL)
                                dtrace_difo_release(dp, vstate);

                        if (DTRACEACT_ISAGG(act->dta_kind)) {
                                dtrace_ecb_aggregation_destroy(ecb, act);
                        } else {
                                kmem_free(act, sizeof (dtrace_action_t));
                        }
                }
        }

        ecb->dte_action = NULL;
        ecb->dte_action_last = NULL;
        ecb->dte_size = 0;
}

static void
dtrace_ecb_disable(dtrace_ecb_t *ecb)
{
        /*
         * We disable the ECB by removing it from its probe.
         */
        dtrace_ecb_t *pecb, *prev = NULL;
        dtrace_probe_t *probe = ecb->dte_probe;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);

        if (probe == NULL) {
                /*
                 * This is the NULL probe; there is nothing to disable.
                 */
                return;
        }

        for (pecb = probe->dtpr_ecb; pecb != NULL; pecb = pecb->dte_next) {
                if (pecb == ecb)
                        break;
                prev = pecb;
        }

        ASSERT(pecb != NULL);

        if (prev == NULL) {
                probe->dtpr_ecb = ecb->dte_next;
        } else {
                prev->dte_next = ecb->dte_next;
        }

        if (ecb == probe->dtpr_ecb_last) {
                ASSERT(ecb->dte_next == NULL);
                probe->dtpr_ecb_last = prev;
        }

        probe->dtpr_provider->dtpv_ecb_count--;
        /*
         * The ECB has been disconnected from the probe; now sync to assure
         * that all CPUs have seen the change before returning.
         */
        dtrace_sync();

        if (probe->dtpr_ecb == NULL) {
                /*
                 * That was the last ECB on the probe; clear the predicate
                 * cache ID for the probe, disable it and sync one more time
                 * to assure that we'll never hit it again.
                 */
                dtrace_provider_t *prov = probe->dtpr_provider;

                ASSERT(ecb->dte_next == NULL);
                ASSERT(probe->dtpr_ecb_last == NULL);
                probe->dtpr_predcache = DTRACE_CACHEIDNONE;
                prov->dtpv_pops.dtps_disable(prov->dtpv_arg,
                    probe->dtpr_id, probe->dtpr_arg);
                dtrace_sync();
        } else {
                /*
                 * There is at least one ECB remaining on the probe.  If there
                 * is _exactly_ one, set the probe's predicate cache ID to be
                 * the predicate cache ID of the remaining ECB.
                 */
                ASSERT(probe->dtpr_ecb_last != NULL);
                ASSERT(probe->dtpr_predcache == DTRACE_CACHEIDNONE);

                if (probe->dtpr_ecb == probe->dtpr_ecb_last) {
                        dtrace_predicate_t *p = probe->dtpr_ecb->dte_predicate;

                        ASSERT(probe->dtpr_ecb->dte_next == NULL);

                        if (p != NULL)
                                probe->dtpr_predcache = p->dtp_cacheid;
                }

                ecb->dte_next = NULL;
        }
}

static void
dtrace_ecb_destroy(dtrace_ecb_t *ecb)
{
        dtrace_state_t *state = ecb->dte_state;
        dtrace_vstate_t *vstate = &state->dts_vstate;
        dtrace_predicate_t *pred;
        dtrace_epid_t epid = ecb->dte_epid;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);
        ASSERT(ecb->dte_next == NULL);
        ASSERT(ecb->dte_probe == NULL || ecb->dte_probe->dtpr_ecb != ecb);

        if ((pred = ecb->dte_predicate) != NULL)
                dtrace_predicate_release(pred, vstate);

        dtrace_ecb_action_remove(ecb);

        ASSERT(state->dts_ecbs[epid - 1] == ecb);
        state->dts_ecbs[epid - 1] = NULL;

        kmem_free(ecb, sizeof (dtrace_ecb_t));
}

static dtrace_ecb_t *
dtrace_ecb_create(dtrace_state_t *state, dtrace_probe_t *probe,
    dtrace_enabling_t *enab)
{
        dtrace_ecb_t *ecb;
        dtrace_predicate_t *pred;
        dtrace_actdesc_t *act;
        dtrace_provider_t *prov;
        dtrace_ecbdesc_t *desc = enab->dten_current;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);
        ASSERT(state != NULL);

        ecb = dtrace_ecb_add(state, probe);
        ecb->dte_uarg = desc->dted_uarg;

        if ((pred = desc->dted_pred.dtpdd_predicate) != NULL) {
                dtrace_predicate_hold(pred);
                ecb->dte_predicate = pred;
        }

        if (probe != NULL) {
                /*
                 * If the provider shows more leg than the consumer is old
                 * enough to see, we need to enable the appropriate implicit
                 * predicate bits to prevent the ecb from activating at
                 * revealing times.
                 *
                 * Providers specifying DTRACE_PRIV_USER at register time
                 * are stating that they need the /proc-style privilege
                 * model to be enforced, and this is what DTRACE_COND_OWNER
                 * and DTRACE_COND_ZONEOWNER will then do at probe time.
                 */
                prov = probe->dtpr_provider;
                if (!(state->dts_cred.dcr_visible & DTRACE_CRV_ALLPROC) &&
                    (prov->dtpv_priv.dtpp_flags & DTRACE_PRIV_USER))
                        ecb->dte_cond |= DTRACE_COND_OWNER;

                if (!(state->dts_cred.dcr_visible & DTRACE_CRV_ALLZONE) &&
                    (prov->dtpv_priv.dtpp_flags & DTRACE_PRIV_USER))
                        ecb->dte_cond |= DTRACE_COND_ZONEOWNER;

                /*
                 * If the provider shows us kernel innards and the user
                 * is lacking sufficient privilege, enable the
                 * DTRACE_COND_USERMODE implicit predicate.
                 */
                if (!(state->dts_cred.dcr_visible & DTRACE_CRV_KERNEL) &&
                    (prov->dtpv_priv.dtpp_flags & DTRACE_PRIV_KERNEL))
                        ecb->dte_cond |= DTRACE_COND_USERMODE;
        }

        if (dtrace_ecb_create_cache != NULL) {
                /*
                 * If we have a cached ecb, we'll use its action list instead
                 * of creating our own (saving both time and space).
                 */
                dtrace_ecb_t *cached = dtrace_ecb_create_cache;
                dtrace_action_t *act_if = cached->dte_action;

                if (act_if != NULL) {
                        ASSERT(act_if->dta_refcnt > 0);
                        act_if->dta_refcnt++;
                        ecb->dte_action = act_if;
                        ecb->dte_action_last = cached->dte_action_last;
                        ecb->dte_needed = cached->dte_needed;
                        ecb->dte_size = cached->dte_size;
                        ecb->dte_alignment = cached->dte_alignment;
                }

                return (ecb);
        }

        for (act = desc->dted_action; act != NULL; act = act->dtad_next) {
                if ((enab->dten_error = dtrace_ecb_action_add(ecb, act)) != 0) {
                        dtrace_ecb_destroy(ecb);
                        return (NULL);
                }
        }

        if ((enab->dten_error = dtrace_ecb_resize(ecb)) != 0) {
                dtrace_ecb_destroy(ecb);
                return (NULL);
        }

        return (dtrace_ecb_create_cache = ecb);
}

static int
dtrace_ecb_create_enable(dtrace_probe_t *probe, void *arg1, void *arg2)
{
        dtrace_ecb_t *ecb;
        dtrace_enabling_t *enab = arg1;
        dtrace_ecbdesc_t *ep = arg2;
        dtrace_state_t *state = enab->dten_vstate->dtvs_state;

        ASSERT(state != NULL);

        if (probe != NULL && ep != NULL && probe->dtpr_gen < ep->dted_probegen) {
                /*
                 * This probe was created in a generation for which this
                 * enabling has previously created ECBs; we don't want to
                 * enable it again, so just kick out.
                 */
                return (DTRACE_MATCH_NEXT);
        }

        if ((ecb = dtrace_ecb_create(state, probe, enab)) == NULL)
                return (DTRACE_MATCH_DONE);

        if (dtrace_ecb_enable(ecb) < 0)
               return (DTRACE_MATCH_FAIL);
        
        return (DTRACE_MATCH_NEXT);
}

static dtrace_ecb_t *
dtrace_epid2ecb(dtrace_state_t *state, dtrace_epid_t id)
{
        dtrace_ecb_t *ecb;
#pragma unused(ecb) /* __APPLE__ */

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);

        if (id == 0 || id > (dtrace_epid_t)state->dts_necbs)
                return (NULL);

        ASSERT(state->dts_necbs > 0 && state->dts_ecbs != NULL);
        ASSERT((ecb = state->dts_ecbs[id - 1]) == NULL || ecb->dte_epid == id);

        return (state->dts_ecbs[id - 1]);
}

static dtrace_aggregation_t *
dtrace_aggid2agg(dtrace_state_t *state, dtrace_aggid_t id)
{
        dtrace_aggregation_t *agg;
#pragma unused(agg) /* __APPLE__ */

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);

        if (id == 0 || id > (dtrace_aggid_t)state->dts_naggregations)
                return (NULL);

        ASSERT(state->dts_naggregations > 0 && state->dts_aggregations != NULL);
        ASSERT((agg = state->dts_aggregations[id - 1]) == NULL ||
            agg->dtag_id == id);

        return (state->dts_aggregations[id - 1]);
}

/*
 * DTrace Buffer Functions
 *
 * The following functions manipulate DTrace buffers.  Most of these functions
 * are called in the context of establishing or processing consumer state;
 * exceptions are explicitly noted.
 */

/*
 * Note:  called from cross call context.  This function switches the two
 * buffers on a given CPU.  The atomicity of this operation is assured by
 * disabling interrupts while the actual switch takes place; the disabling of
 * interrupts serializes the execution with any execution of dtrace_probe() on
 * the same CPU.
 */
static void
dtrace_buffer_switch(dtrace_buffer_t *buf)
{
        caddr_t tomax = buf->dtb_tomax;
        caddr_t xamot = buf->dtb_xamot;
        dtrace_icookie_t cookie;
        hrtime_t now;

        ASSERT(!(buf->dtb_flags & DTRACEBUF_NOSWITCH));
        ASSERT(!(buf->dtb_flags & DTRACEBUF_RING));

        cookie = dtrace_interrupt_disable();
        now = dtrace_gethrtime();
        buf->dtb_tomax = xamot;
        buf->dtb_xamot = tomax;
        buf->dtb_xamot_drops = buf->dtb_drops;
        buf->dtb_xamot_offset = buf->dtb_offset;
        buf->dtb_xamot_errors = buf->dtb_errors;
        buf->dtb_xamot_flags = buf->dtb_flags;
        buf->dtb_offset = 0;
        buf->dtb_drops = 0;
        buf->dtb_errors = 0;
        buf->dtb_flags &= ~(DTRACEBUF_ERROR | DTRACEBUF_DROPPED);
        buf->dtb_interval = now - buf->dtb_switched;
        buf->dtb_switched = now;
        buf->dtb_cur_limit = buf->dtb_limit;

        dtrace_interrupt_enable(cookie);
}

/*
 * Note:  called from cross call context.  This function activates a buffer
 * on a CPU.  As with dtrace_buffer_switch(), the atomicity of the operation
 * is guaranteed by the disabling of interrupts.
 */
static void
dtrace_buffer_activate(dtrace_state_t *state)
{
        dtrace_buffer_t *buf;
        dtrace_icookie_t cookie = dtrace_interrupt_disable();

        buf = &state->dts_buffer[CPU->cpu_id];

        if (buf->dtb_tomax != NULL) {
                /*
                 * We might like to assert that the buffer is marked inactive,
                 * but this isn't necessarily true:  the buffer for the CPU
                 * that processes the BEGIN probe has its buffer activated
                 * manually.  In this case, we take the (harmless) action
                 * re-clearing the bit INACTIVE bit.
                 */
                buf->dtb_flags &= ~DTRACEBUF_INACTIVE;
        }

        dtrace_interrupt_enable(cookie);
}

static int
dtrace_buffer_canalloc(size_t size)
{
        if (size > (UINT64_MAX - dtrace_buffer_memory_inuse))
                return (B_FALSE);
        if ((size + dtrace_buffer_memory_inuse) > dtrace_buffer_memory_maxsize)
                return (B_FALSE);

        return (B_TRUE);
}

static int
dtrace_buffer_alloc(dtrace_buffer_t *bufs, size_t limit, size_t size, int flags,
    processorid_t cpu)
{
        dtrace_cpu_t *cp;
        dtrace_buffer_t *buf;
        size_t size_before_alloc = dtrace_buffer_memory_inuse;

        LCK_MTX_ASSERT(&cpu_lock, LCK_MTX_ASSERT_OWNED);
        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);

        if (size > (size_t)dtrace_nonroot_maxsize &&
            !PRIV_POLICY_CHOICE(CRED(), PRIV_ALL, B_FALSE))
                return (EFBIG);

        cp = cpu_list;

        do {
                if (cpu != DTRACE_CPUALL && cpu != cp->cpu_id)
                        continue;

                buf = &bufs[cp->cpu_id];

                /*
                 * If there is already a buffer allocated for this CPU, it
                 * is only possible that this is a DR event.  In this case,
                 * the buffer size must match our specified size.
                 */
                if (buf->dtb_tomax != NULL) {
                        ASSERT(buf->dtb_size == size);
                        continue;
                }

                ASSERT(buf->dtb_xamot == NULL);

                /* DTrace, please do not eat all the memory. */
                if (dtrace_buffer_canalloc(size) == B_FALSE)
                        goto err;
                if ((buf->dtb_tomax = kmem_zalloc(size, KM_NOSLEEP)) == NULL)
                        goto err;
                dtrace_buffer_memory_inuse += size;

                /* Unsure that limit is always lower than size */
                limit = limit == size ? limit - 1 : limit;
                buf->dtb_cur_limit = limit;
                buf->dtb_limit = limit;
                buf->dtb_size = size;
                buf->dtb_flags = flags;
                buf->dtb_offset = 0;
                buf->dtb_drops = 0;

                if (flags & DTRACEBUF_NOSWITCH)
                        continue;

                /* DTrace, please do not eat all the memory. */
                if (dtrace_buffer_canalloc(size) == B_FALSE)
                        goto err;
                if ((buf->dtb_xamot = kmem_zalloc(size, KM_NOSLEEP)) == NULL)
                        goto err;
                dtrace_buffer_memory_inuse += size;
        } while ((cp = cp->cpu_next) != cpu_list);

        ASSERT(dtrace_buffer_memory_inuse <= dtrace_buffer_memory_maxsize);

        return (0);

err:
        cp = cpu_list;

        do {
                if (cpu != DTRACE_CPUALL && cpu != cp->cpu_id)
                        continue;

                buf = &bufs[cp->cpu_id];

                if (buf->dtb_xamot != NULL) {
                        ASSERT(buf->dtb_tomax != NULL);
                        ASSERT(buf->dtb_size == size);
                        kmem_free(buf->dtb_xamot, size);
                }

                if (buf->dtb_tomax != NULL) {
                        ASSERT(buf->dtb_size == size);
                        kmem_free(buf->dtb_tomax, size);
                }

                buf->dtb_tomax = NULL;
                buf->dtb_xamot = NULL;
                buf->dtb_size = 0;
        } while ((cp = cp->cpu_next) != cpu_list);

        /* Restore the size saved before allocating memory */
        dtrace_buffer_memory_inuse = size_before_alloc;

        return (ENOMEM);
}

/*
 * Note:  called from probe context.  This function just increments the drop
 * count on a buffer.  It has been made a function to allow for the
 * possibility of understanding the source of mysterious drop counts.  (A
 * problem for which one may be particularly disappointed that DTrace cannot
 * be used to understand DTrace.)
 */
static void
dtrace_buffer_drop(dtrace_buffer_t *buf)
{
        buf->dtb_drops++;
}

/*
 * Note:  called from probe context.  This function is called to reserve space
 * in a buffer.  If mstate is non-NULL, sets the scratch base and size in the
 * mstate.  Returns the new offset in the buffer, or a negative value if an
 * error has occurred.
 */
static intptr_t
dtrace_buffer_reserve(dtrace_buffer_t *buf, size_t needed, size_t align,
    dtrace_state_t *state, dtrace_mstate_t *mstate)
{
        intptr_t offs = buf->dtb_offset, soffs;
        intptr_t woffs;
        caddr_t tomax;
        size_t total_off;

        if (buf->dtb_flags & DTRACEBUF_INACTIVE)
                return (-1);

        if ((tomax = buf->dtb_tomax) == NULL) {
                dtrace_buffer_drop(buf);
                return (-1);
        }

        if (!(buf->dtb_flags & (DTRACEBUF_RING | DTRACEBUF_FILL))) {
                while (offs & (align - 1)) {
                        /*
                         * Assert that our alignment is off by a number which
                         * is itself sizeof (uint32_t) aligned.
                         */
                        ASSERT(!((align - (offs & (align - 1))) &
                            (sizeof (uint32_t) - 1)));
                        DTRACE_STORE(uint32_t, tomax, offs, DTRACE_EPIDNONE);
                        offs += sizeof (uint32_t);
                }

                if ((uint64_t)(soffs = offs + needed) > buf->dtb_cur_limit) {
                        if (buf->dtb_cur_limit == buf->dtb_limit) {
                                buf->dtb_cur_limit = buf->dtb_size;

                                os_atomic_inc(&state->dts_buf_over_limit, relaxed);
                                /**
                                 * Set an AST on the current processor
                                 * so that we can wake up the process
                                 * outside of probe context, when we know
                                 * it is safe to do so
                                 */
                                minor_t minor = getminor(state->dts_dev);
                                ASSERT(minor < 32);

                                os_atomic_or(&dtrace_wake_clients, 1 << minor, relaxed);
                                ast_dtrace_on();
                        }
                        if ((uint64_t)soffs > buf->dtb_size) {
                                dtrace_buffer_drop(buf);
                                return (-1);
                        }
                }

                if (mstate == NULL)
                        return (offs);

                mstate->dtms_scratch_base = (uintptr_t)tomax + soffs;
                mstate->dtms_scratch_size = buf->dtb_size - soffs;
                mstate->dtms_scratch_ptr = mstate->dtms_scratch_base;

                return (offs);
        }

        if (buf->dtb_flags & DTRACEBUF_FILL) {
                if (state->dts_activity != DTRACE_ACTIVITY_COOLDOWN &&
                    (buf->dtb_flags & DTRACEBUF_FULL))
                        return (-1);
                goto out;
        }

        total_off = needed + (offs & (align - 1));

        /*
         * For a ring buffer, life is quite a bit more complicated.  Before
         * we can store any padding, we need to adjust our wrapping offset.
         * (If we've never before wrapped or we're not about to, no adjustment
         * is required.)
         */
        if ((buf->dtb_flags & DTRACEBUF_WRAPPED) ||
            offs + total_off > buf->dtb_size) {
                woffs = buf->dtb_xamot_offset;

                if (offs + total_off > buf->dtb_size) {
                        /*
                         * We can't fit in the end of the buffer.  First, a
                         * sanity check that we can fit in the buffer at all.
                         */
                        if (total_off > buf->dtb_size) {
                                dtrace_buffer_drop(buf);
                                return (-1);
                        }

                        /*
                         * We're going to be storing at the top of the buffer,
                         * so now we need to deal with the wrapped offset.  We
                         * only reset our wrapped offset to 0 if it is
                         * currently greater than the current offset.  If it
                         * is less than the current offset, it is because a
                         * previous allocation induced a wrap -- but the
                         * allocation didn't subsequently take the space due
                         * to an error or false predicate evaluation.  In this
                         * case, we'll just leave the wrapped offset alone: if
                         * the wrapped offset hasn't been advanced far enough
                         * for this allocation, it will be adjusted in the
                         * lower loop.
                         */
                        if (buf->dtb_flags & DTRACEBUF_WRAPPED) {
                                if (woffs >= offs)
                                        woffs = 0;
                        } else {
                                woffs = 0;
                        }

                        /*
                         * Now we know that we're going to be storing to the
                         * top of the buffer and that there is room for us
                         * there.  We need to clear the buffer from the current
                         * offset to the end (there may be old gunk there).
                         */
                        while ((uint64_t)offs < buf->dtb_size)
                                tomax[offs++] = 0;

                        /*
                         * We need to set our offset to zero.  And because we
                         * are wrapping, we need to set the bit indicating as
                         * much.  We can also adjust our needed space back
                         * down to the space required by the ECB -- we know
                         * that the top of the buffer is aligned.
                         */
                        offs = 0;
                        total_off = needed;
                        buf->dtb_flags |= DTRACEBUF_WRAPPED;
                } else {
                        /*
                         * There is room for us in the buffer, so we simply
                         * need to check the wrapped offset.
                         */
                        if (woffs < offs) {
                                /*
                                 * The wrapped offset is less than the offset.
                                 * This can happen if we allocated buffer space
                                 * that induced a wrap, but then we didn't
                                 * subsequently take the space due to an error
                                 * or false predicate evaluation.  This is
                                 * okay; we know that _this_ allocation isn't
                                 * going to induce a wrap.  We still can't
                                 * reset the wrapped offset to be zero,
                                 * however: the space may have been trashed in
                                 * the previous failed probe attempt.  But at
                                 * least the wrapped offset doesn't need to
                                 * be adjusted at all...
                                 */
                                goto out;
                        }
                }

                while (offs + total_off > (size_t)woffs) {
                        dtrace_epid_t epid = *(uint32_t *)(tomax + woffs);
                        size_t size;

                        if (epid == DTRACE_EPIDNONE) {
                                size = sizeof (uint32_t);
                        } else {
                                ASSERT(epid <= (dtrace_epid_t)state->dts_necbs);
                                ASSERT(state->dts_ecbs[epid - 1] != NULL);

                                size = state->dts_ecbs[epid - 1]->dte_size;
                        }

                        ASSERT(woffs + size <= buf->dtb_size);
                        ASSERT(size != 0);

                        if (woffs + size == buf->dtb_size) {
                                /*
                                 * We've reached the end of the buffer; we want
                                 * to set the wrapped offset to 0 and break
                                 * out.  However, if the offs is 0, then we're
                                 * in a strange edge-condition:  the amount of
                                 * space that we want to reserve plus the size
                                 * of the record that we're overwriting is
                                 * greater than the size of the buffer.  This
                                 * is problematic because if we reserve the
                                 * space but subsequently don't consume it (due
                                 * to a failed predicate or error) the wrapped
                                 * offset will be 0 -- yet the EPID at offset 0
                                 * will not be committed.  This situation is
                                 * relatively easy to deal with:  if we're in
                                 * this case, the buffer is indistinguishable
                                 * from one that hasn't wrapped; we need only
                                 * finish the job by clearing the wrapped bit,
                                 * explicitly setting the offset to be 0, and
                                 * zero'ing out the old data in the buffer.
                                 */
                                if (offs == 0) {
                                        buf->dtb_flags &= ~DTRACEBUF_WRAPPED;
                                        buf->dtb_offset = 0;
                                        woffs = total_off;

                                        while ((uint64_t)woffs < buf->dtb_size)
                                                tomax[woffs++] = 0;
                                }

                                woffs = 0;
                                break;
                        }

                        woffs += size;
                }

                /*
                 * We have a wrapped offset.  It may be that the wrapped offset
                 * has become zero -- that's okay.
                 */
                buf->dtb_xamot_offset = woffs;
        }

out:
        /*
         * Now we can plow the buffer with any necessary padding.
         */
        while (offs & (align - 1)) {
                /*
                 * Assert that our alignment is off by a number which
                 * is itself sizeof (uint32_t) aligned.
                 */
                ASSERT(!((align - (offs & (align - 1))) &
                    (sizeof (uint32_t) - 1)));
                DTRACE_STORE(uint32_t, tomax, offs, DTRACE_EPIDNONE);
                offs += sizeof (uint32_t);
        }

        if (buf->dtb_flags & DTRACEBUF_FILL) {
                if (offs + needed > buf->dtb_size - state->dts_reserve) {
                        buf->dtb_flags |= DTRACEBUF_FULL;
                        return (-1);
                }
        }

        if (mstate == NULL)
                return (offs);

        /*
         * For ring buffers and fill buffers, the scratch space is always
         * the inactive buffer.
         */
        mstate->dtms_scratch_base = (uintptr_t)buf->dtb_xamot;
        mstate->dtms_scratch_size = buf->dtb_size;
        mstate->dtms_scratch_ptr = mstate->dtms_scratch_base;

        return (offs);
}

static void
dtrace_buffer_polish(dtrace_buffer_t *buf)
{
        ASSERT(buf->dtb_flags & DTRACEBUF_RING);
        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);

        if (!(buf->dtb_flags & DTRACEBUF_WRAPPED))
                return;

        /*
         * We need to polish the ring buffer.  There are three cases:
         *
         * - The first (and presumably most common) is that there is no gap
         *   between the buffer offset and the wrapped offset.  In this case,
         *   there is nothing in the buffer that isn't valid data; we can
         *   mark the buffer as polished and return.
         *
         * - The second (less common than the first but still more common
         *   than the third) is that there is a gap between the buffer offset
         *   and the wrapped offset, and the wrapped offset is larger than the
         *   buffer offset.  This can happen because of an alignment issue, or
         *   can happen because of a call to dtrace_buffer_reserve() that
         *   didn't subsequently consume the buffer space.  In this case,
         *   we need to zero the data from the buffer offset to the wrapped
         *   offset.
         *
         * - The third (and least common) is that there is a gap between the
         *   buffer offset and the wrapped offset, but the wrapped offset is
         *   _less_ than the buffer offset.  This can only happen because a
         *   call to dtrace_buffer_reserve() induced a wrap, but the space
         *   was not subsequently consumed.  In this case, we need to zero the
         *   space from the offset to the end of the buffer _and_ from the
         *   top of the buffer to the wrapped offset.
         */
        if (buf->dtb_offset < buf->dtb_xamot_offset) {
                bzero(buf->dtb_tomax + buf->dtb_offset,
                    buf->dtb_xamot_offset - buf->dtb_offset);
        }

        if (buf->dtb_offset > buf->dtb_xamot_offset) {
                bzero(buf->dtb_tomax + buf->dtb_offset,
                    buf->dtb_size - buf->dtb_offset);
                bzero(buf->dtb_tomax, buf->dtb_xamot_offset);
        }
}

static void
dtrace_buffer_free(dtrace_buffer_t *bufs)
{
        int i;

        for (i = 0; i < (int)NCPU; i++) {
                dtrace_buffer_t *buf = &bufs[i];

                if (buf->dtb_tomax == NULL) {
                        ASSERT(buf->dtb_xamot == NULL);
                        ASSERT(buf->dtb_size == 0);
                        continue;
                }

                if (buf->dtb_xamot != NULL) {
                        ASSERT(!(buf->dtb_flags & DTRACEBUF_NOSWITCH));
                        kmem_free(buf->dtb_xamot, buf->dtb_size);

                        ASSERT(dtrace_buffer_memory_inuse >= buf->dtb_size);
                        dtrace_buffer_memory_inuse -= buf->dtb_size;
                }

                kmem_free(buf->dtb_tomax, buf->dtb_size);
                ASSERT(dtrace_buffer_memory_inuse >= buf->dtb_size);
                dtrace_buffer_memory_inuse -= buf->dtb_size;

                buf->dtb_size = 0;
                buf->dtb_tomax = NULL;
                buf->dtb_xamot = NULL;
        }
}

/*
 * DTrace Enabling Functions
 */
static dtrace_enabling_t *
dtrace_enabling_create(dtrace_vstate_t *vstate)
{
        dtrace_enabling_t *enab;

        enab = kmem_zalloc(sizeof (dtrace_enabling_t), KM_SLEEP);
        enab->dten_vstate = vstate;

        return (enab);
}

static void
dtrace_enabling_add(dtrace_enabling_t *enab, dtrace_ecbdesc_t *ecb)
{
        dtrace_ecbdesc_t **ndesc;
        size_t osize, nsize;

        /*
         * We can't add to enablings after we've enabled them, or after we've
         * retained them.
         */
        ASSERT(enab->dten_probegen == 0);
        ASSERT(enab->dten_next == NULL && enab->dten_prev == NULL);

        /* APPLE NOTE: this protects against gcc 4.0 botch on x86 */
        if (ecb == NULL) return;

        if (enab->dten_ndesc < enab->dten_maxdesc) {
                enab->dten_desc[enab->dten_ndesc++] = ecb;
                return;
        }

        osize = enab->dten_maxdesc * sizeof (dtrace_enabling_t *);

        if (enab->dten_maxdesc == 0) {
                enab->dten_maxdesc = 1;
        } else {
                enab->dten_maxdesc <<= 1;
        }

        ASSERT(enab->dten_ndesc < enab->dten_maxdesc);

        nsize = enab->dten_maxdesc * sizeof (dtrace_enabling_t *);
        ndesc = kmem_zalloc(nsize, KM_SLEEP);
        bcopy(enab->dten_desc, ndesc, osize);
        kmem_free(enab->dten_desc, osize);

        enab->dten_desc = ndesc;
        enab->dten_desc[enab->dten_ndesc++] = ecb;
}

static void
dtrace_enabling_addlike(dtrace_enabling_t *enab, dtrace_ecbdesc_t *ecb,
    dtrace_probedesc_t *pd)
{
        dtrace_ecbdesc_t *new;
        dtrace_predicate_t *pred;
        dtrace_actdesc_t *act;

        /*
         * We're going to create a new ECB description that matches the
         * specified ECB in every way, but has the specified probe description.
         */
        new = kmem_zalloc(sizeof (dtrace_ecbdesc_t), KM_SLEEP);

        if ((pred = ecb->dted_pred.dtpdd_predicate) != NULL)
                dtrace_predicate_hold(pred);

        for (act = ecb->dted_action; act != NULL; act = act->dtad_next)
                dtrace_actdesc_hold(act);

        new->dted_action = ecb->dted_action;
        new->dted_pred = ecb->dted_pred;
        new->dted_probe = *pd;
        new->dted_uarg = ecb->dted_uarg;

        dtrace_enabling_add(enab, new);
}

static void
dtrace_enabling_dump(dtrace_enabling_t *enab)
{
        int i;

        for (i = 0; i < enab->dten_ndesc; i++) {
                dtrace_probedesc_t *desc = &enab->dten_desc[i]->dted_probe;

                cmn_err(CE_NOTE, "enabling probe %d (%s:%s:%s:%s)", i,
                    desc->dtpd_provider, desc->dtpd_mod,
                    desc->dtpd_func, desc->dtpd_name);
        }
}

static void
dtrace_enabling_destroy(dtrace_enabling_t *enab)
{
        int i;
        dtrace_ecbdesc_t *ep;
        dtrace_vstate_t *vstate = enab->dten_vstate;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);

        for (i = 0; i < enab->dten_ndesc; i++) {
                dtrace_actdesc_t *act, *next;
                dtrace_predicate_t *pred;

                ep = enab->dten_desc[i];

                if ((pred = ep->dted_pred.dtpdd_predicate) != NULL)
                        dtrace_predicate_release(pred, vstate);

                for (act = ep->dted_action; act != NULL; act = next) {
                        next = act->dtad_next;
                        dtrace_actdesc_release(act, vstate);
                }

                kmem_free(ep, sizeof (dtrace_ecbdesc_t));
        }

        kmem_free(enab->dten_desc,
            enab->dten_maxdesc * sizeof (dtrace_enabling_t *));

        /*
         * If this was a retained enabling, decrement the dts_nretained count
         * and take it off of the dtrace_retained list.
         */
        if (enab->dten_prev != NULL || enab->dten_next != NULL ||
            dtrace_retained == enab) {
                ASSERT(enab->dten_vstate->dtvs_state != NULL);
                ASSERT(enab->dten_vstate->dtvs_state->dts_nretained > 0);
                enab->dten_vstate->dtvs_state->dts_nretained--;
                dtrace_retained_gen++;
        }

        if (enab->dten_prev == NULL) {
                if (dtrace_retained == enab) {
                        dtrace_retained = enab->dten_next;

                        if (dtrace_retained != NULL)
                                dtrace_retained->dten_prev = NULL;
                }
        } else {
                ASSERT(enab != dtrace_retained);
                ASSERT(dtrace_retained != NULL);
                enab->dten_prev->dten_next = enab->dten_next;
        }

        if (enab->dten_next != NULL) {
                ASSERT(dtrace_retained != NULL);
                enab->dten_next->dten_prev = enab->dten_prev;
        }

        kmem_free(enab, sizeof (dtrace_enabling_t));
}

static int
dtrace_enabling_retain(dtrace_enabling_t *enab)
{
        dtrace_state_t *state;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);
        ASSERT(enab->dten_next == NULL && enab->dten_prev == NULL);
        ASSERT(enab->dten_vstate != NULL);

        state = enab->dten_vstate->dtvs_state;
        ASSERT(state != NULL);

        /*
         * We only allow each state to retain dtrace_retain_max enablings.
         */
        if (state->dts_nretained >= dtrace_retain_max)
                return (ENOSPC);

        state->dts_nretained++;
        dtrace_retained_gen++;

        if (dtrace_retained == NULL) {
                dtrace_retained = enab;
                return (0);
        }

        enab->dten_next = dtrace_retained;
        dtrace_retained->dten_prev = enab;
        dtrace_retained = enab;

        return (0);
}

static int
dtrace_enabling_replicate(dtrace_state_t *state, dtrace_probedesc_t *match,
    dtrace_probedesc_t *create)
{
        dtrace_enabling_t *new, *enab;
        int found = 0, err = ENOENT;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);
        ASSERT(strlen(match->dtpd_provider) < DTRACE_PROVNAMELEN);
        ASSERT(strlen(match->dtpd_mod) < DTRACE_MODNAMELEN);
        ASSERT(strlen(match->dtpd_func) < DTRACE_FUNCNAMELEN);
        ASSERT(strlen(match->dtpd_name) < DTRACE_NAMELEN);

        new = dtrace_enabling_create(&state->dts_vstate);

        /*
         * Iterate over all retained enablings, looking for enablings that
         * match the specified state.
         */
        for (enab = dtrace_retained; enab != NULL; enab = enab->dten_next) {
                int i;

                /*
                 * dtvs_state can only be NULL for helper enablings -- and
                 * helper enablings can't be retained.
                 */
                ASSERT(enab->dten_vstate->dtvs_state != NULL);

                if (enab->dten_vstate->dtvs_state != state)
                        continue;

                /*
                 * Now iterate over each probe description; we're looking for
                 * an exact match to the specified probe description.
                 */
                for (i = 0; i < enab->dten_ndesc; i++) {
                        dtrace_ecbdesc_t *ep = enab->dten_desc[i];
                        dtrace_probedesc_t *pd = &ep->dted_probe;

                        /* APPLE NOTE: Darwin employs size bounded string operation. */
                        if (strncmp(pd->dtpd_provider, match->dtpd_provider, DTRACE_PROVNAMELEN))
                                continue;

                        if (strncmp(pd->dtpd_mod, match->dtpd_mod, DTRACE_MODNAMELEN))
                                continue;

                        if (strncmp(pd->dtpd_func, match->dtpd_func, DTRACE_FUNCNAMELEN))
                                continue;

                        if (strncmp(pd->dtpd_name, match->dtpd_name, DTRACE_NAMELEN))
                                continue;

                        /*
                         * We have a winning probe!  Add it to our growing
                         * enabling.
                         */
                        found = 1;
                        dtrace_enabling_addlike(new, ep, create);
                }
        }

        if (!found || (err = dtrace_enabling_retain(new)) != 0) {
                dtrace_enabling_destroy(new);
                return (err);
        }

        return (0);
}

static void
dtrace_enabling_retract(dtrace_state_t *state)
{
        dtrace_enabling_t *enab, *next;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);

        /*
         * Iterate over all retained enablings, destroy the enablings retained
         * for the specified state.
         */
        for (enab = dtrace_retained; enab != NULL; enab = next) {
                next = enab->dten_next;

                /*
                 * dtvs_state can only be NULL for helper enablings -- and
                 * helper enablings can't be retained.
                 */
                ASSERT(enab->dten_vstate->dtvs_state != NULL);

                if (enab->dten_vstate->dtvs_state == state) {
                        ASSERT(state->dts_nretained > 0);
                        dtrace_enabling_destroy(enab);
                }
        }

        ASSERT(state->dts_nretained == 0);
}

static int
dtrace_enabling_match(dtrace_enabling_t *enab, int *nmatched, dtrace_match_cond_t *cond)
{
        int i = 0;
        int total_matched = 0, matched = 0;

        LCK_MTX_ASSERT(&cpu_lock, LCK_MTX_ASSERT_OWNED);
        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);

        for (i = 0; i < enab->dten_ndesc; i++) {
                dtrace_ecbdesc_t *ep = enab->dten_desc[i];

                enab->dten_current = ep;
                enab->dten_error = 0;

                /**
                 * Before doing a dtrace_probe_enable, which is really
                 * expensive, check that this enabling matches the matching precondition
                 * if we have one
                 */
                if (cond && (cond->dmc_func(&ep->dted_probe, cond->dmc_data) == 0)) {
                        continue;
                }
                /*
                 * If a provider failed to enable a probe then get out and
                 * let the consumer know we failed.
                 */
                if ((matched = dtrace_probe_enable(&ep->dted_probe, enab, ep)) < 0)
                        return (EBUSY);

                total_matched += matched;

                if (enab->dten_error != 0) {
                        /*
                         * If we get an error half-way through enabling the
                         * probes, we kick out -- perhaps with some number of
                         * them enabled.  Leaving enabled probes enabled may
                         * be slightly confusing for user-level, but we expect
                         * that no one will attempt to actually drive on in
                         * the face of such errors.  If this is an anonymous
                         * enabling (indicated with a NULL nmatched pointer),
                         * we cmn_err() a message.  We aren't expecting to
                         * get such an error -- such as it can exist at all,
                         * it would be a result of corrupted DOF in the driver
                         * properties.
                         */
                        if (nmatched == NULL) {
                                cmn_err(CE_WARN, "dtrace_enabling_match() "
                                    "error on %p: %d", (void *)ep,
                                    enab->dten_error);
                        }

                        return (enab->dten_error);
                }

                ep->dted_probegen = dtrace_probegen;
        }

        if (nmatched != NULL)
                *nmatched = total_matched;

        return (0);
}

static void
dtrace_enabling_matchall_with_cond(dtrace_match_cond_t *cond)
{
        dtrace_enabling_t *enab;

        lck_mtx_lock(&cpu_lock);
        lck_mtx_lock(&dtrace_lock);

        /*
         * Iterate over all retained enablings to see if any probes match
         * against them.  We only perform this operation on enablings for which
         * we have sufficient permissions by virtue of being in the global zone
         * or in the same zone as the DTrace client.  Because we can be called
         * after dtrace_detach() has been called, we cannot assert that there
         * are retained enablings.  We can safely load from dtrace_retained,
         * however:  the taskq_destroy() at the end of dtrace_detach() will
         * block pending our completion.
         */

        /*
         * Darwin doesn't do zones.
         * Behave as if always in "global" zone."
         */
        for (enab = dtrace_retained; enab != NULL; enab = enab->dten_next) {
                (void) dtrace_enabling_match(enab, NULL, cond);
        }

        lck_mtx_unlock(&dtrace_lock);
        lck_mtx_unlock(&cpu_lock);

}

static void
dtrace_enabling_matchall(void)
{
        dtrace_enabling_matchall_with_cond(NULL);
}



/*
 * If an enabling is to be enabled without having matched probes (that is, if
 * dtrace_state_go() is to be called on the underlying dtrace_state_t), the
 * enabling must be _primed_ by creating an ECB for every ECB description.
 * This must be done to assure that we know the number of speculations, the
 * number of aggregations, the minimum buffer size needed, etc. before we
 * transition out of DTRACE_ACTIVITY_INACTIVE.  To do this without actually
 * enabling any probes, we create ECBs for every ECB decription, but with a
 * NULL probe -- which is exactly what this function does.
 */
static void
dtrace_enabling_prime(dtrace_state_t *state)
{
        dtrace_enabling_t *enab;
        int i;

        for (enab = dtrace_retained; enab != NULL; enab = enab->dten_next) {
                ASSERT(enab->dten_vstate->dtvs_state != NULL);

                if (enab->dten_vstate->dtvs_state != state)
                        continue;

                /*
                 * We don't want to prime an enabling more than once, lest
                 * we allow a malicious user to induce resource exhaustion.
                 * (The ECBs that result from priming an enabling aren't
                 * leaked -- but they also aren't deallocated until the
                 * consumer state is destroyed.)
                 */
                if (enab->dten_primed)
                        continue;

                for (i = 0; i < enab->dten_ndesc; i++) {
                        enab->dten_current = enab->dten_desc[i];
                        (void) dtrace_probe_enable(NULL, enab, NULL);
                }

                enab->dten_primed = 1;
        }
}

/*
 * Called to indicate that probes should be provided due to retained
 * enablings.  This is implemented in terms of dtrace_probe_provide(), but it
 * must take an initial lap through the enabling calling the dtps_provide()
 * entry point explicitly to allow for autocreated probes.
 */
static void
dtrace_enabling_provide(dtrace_provider_t *prv)
{
        int i, all = 0;
        dtrace_probedesc_t desc;
        dtrace_genid_t gen;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);
        LCK_MTX_ASSERT(&dtrace_provider_lock, LCK_MTX_ASSERT_OWNED);

        if (prv == NULL) {
                all = 1;
                prv = dtrace_provider;
        }

        do {
                dtrace_enabling_t *enab;
                void *parg = prv->dtpv_arg;

retry:
                gen = dtrace_retained_gen;
                for (enab = dtrace_retained; enab != NULL;
                    enab = enab->dten_next) {
                        for (i = 0; i < enab->dten_ndesc; i++) {
                                desc = enab->dten_desc[i]->dted_probe;
                                lck_mtx_unlock(&dtrace_lock);
                                prv->dtpv_pops.dtps_provide(parg, &desc);
                                lck_mtx_lock(&dtrace_lock);
                                /*
                                 * Process the retained enablings again if
                                 * they have changed while we weren't holding
                                 * dtrace_lock.
                                 */
                                if (gen != dtrace_retained_gen)
                                        goto retry;
                        }
                }
        } while (all && (prv = prv->dtpv_next) != NULL);

        lck_mtx_unlock(&dtrace_lock);
        dtrace_probe_provide(NULL, all ? NULL : prv);
        lck_mtx_lock(&dtrace_lock);
}

/*
 * DTrace DOF Functions
 */
/*ARGSUSED*/
static void
dtrace_dof_error(dof_hdr_t *dof, const char *str)
{
#pragma unused(dof) /* __APPLE__ */
        if (dtrace_err_verbose)
                cmn_err(CE_WARN, "failed to process DOF: %s", str);

#ifdef DTRACE_ERRDEBUG
        dtrace_errdebug(str);
#endif
}

/*
 * Create DOF out of a currently enabled state.  Right now, we only create
 * DOF containing the run-time options -- but this could be expanded to create
 * complete DOF representing the enabled state.
 */
static dof_hdr_t *
dtrace_dof_create(dtrace_state_t *state)
{
        dof_hdr_t *dof;
        dof_sec_t *sec;
        dof_optdesc_t *opt;
        int i, len = sizeof (dof_hdr_t) +
            roundup(sizeof (dof_sec_t), sizeof (uint64_t)) +
            sizeof (dof_optdesc_t) * DTRACEOPT_MAX;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);

        dof = kmem_zalloc_aligned(len, 8, KM_SLEEP);
        dof->dofh_ident[DOF_ID_MAG0] = DOF_MAG_MAG0;
        dof->dofh_ident[DOF_ID_MAG1] = DOF_MAG_MAG1;
        dof->dofh_ident[DOF_ID_MAG2] = DOF_MAG_MAG2;
        dof->dofh_ident[DOF_ID_MAG3] = DOF_MAG_MAG3;

        dof->dofh_ident[DOF_ID_MODEL] = DOF_MODEL_NATIVE;
        dof->dofh_ident[DOF_ID_ENCODING] = DOF_ENCODE_NATIVE;
        dof->dofh_ident[DOF_ID_VERSION] = DOF_VERSION;
        dof->dofh_ident[DOF_ID_DIFVERS] = DIF_VERSION;
        dof->dofh_ident[DOF_ID_DIFIREG] = DIF_DIR_NREGS;
        dof->dofh_ident[DOF_ID_DIFTREG] = DIF_DTR_NREGS;

        dof->dofh_flags = 0;
        dof->dofh_hdrsize = sizeof (dof_hdr_t);
        dof->dofh_secsize = sizeof (dof_sec_t);
        dof->dofh_secnum = 1;   /* only DOF_SECT_OPTDESC */
        dof->dofh_secoff = sizeof (dof_hdr_t);
        dof->dofh_loadsz = len;
        dof->dofh_filesz = len;
        dof->dofh_pad = 0;

        /*
         * Fill in the option section header...
         */
        sec = (dof_sec_t *)((uintptr_t)dof + sizeof (dof_hdr_t));
        sec->dofs_type = DOF_SECT_OPTDESC;
        sec->dofs_align = sizeof (uint64_t);
        sec->dofs_flags = DOF_SECF_LOAD;
        sec->dofs_entsize = sizeof (dof_optdesc_t);

        opt = (dof_optdesc_t *)((uintptr_t)sec +
            roundup(sizeof (dof_sec_t), sizeof (uint64_t)));

        sec->dofs_offset = (uintptr_t)opt - (uintptr_t)dof;
        sec->dofs_size = sizeof (dof_optdesc_t) * DTRACEOPT_MAX;

        for (i = 0; i < DTRACEOPT_MAX; i++) {
                opt[i].dofo_option = i;
                opt[i].dofo_strtab = DOF_SECIDX_NONE;
                opt[i].dofo_value = state->dts_options[i];
        }

        return (dof);
}

static dof_hdr_t *
dtrace_dof_copyin(user_addr_t uarg, int *errp)
{
        dof_hdr_t hdr, *dof;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_NOTOWNED);

        /*
         * First, we're going to copyin() the sizeof (dof_hdr_t).
         */
        if (copyin(uarg, &hdr, sizeof (hdr)) != 0) {
                dtrace_dof_error(NULL, "failed to copyin DOF header");
                *errp = EFAULT;
                return (NULL);
        }

        /*
         * Now we'll allocate the entire DOF and copy it in -- provided
         * that the length isn't outrageous.
         */
        if (hdr.dofh_loadsz >= (uint64_t)dtrace_dof_maxsize) {
                dtrace_dof_error(&hdr, "load size exceeds maximum");
                *errp = E2BIG;
                return (NULL);
        }

        if (hdr.dofh_loadsz < sizeof (hdr)) {
                dtrace_dof_error(&hdr, "invalid load size");
                *errp = EINVAL;
                return (NULL);
        }

        dof = kmem_alloc_aligned(hdr.dofh_loadsz, 8, KM_SLEEP);

        if (copyin(uarg, dof, hdr.dofh_loadsz) != 0  ||
          dof->dofh_loadsz != hdr.dofh_loadsz) {
            kmem_free_aligned(dof, hdr.dofh_loadsz);
            *errp = EFAULT;
            return (NULL);
        }           

        return (dof);
}

static dof_hdr_t *
dtrace_dof_copyin_from_proc(proc_t* p, user_addr_t uarg, int *errp)
{
        dof_hdr_t hdr, *dof;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_NOTOWNED);

        /*
         * First, we're going to copyin() the sizeof (dof_hdr_t).
         */
        if (uread(p, &hdr, sizeof(hdr), uarg) != KERN_SUCCESS) {
                dtrace_dof_error(NULL, "failed to copyin DOF header");
                *errp = EFAULT;
                return (NULL);
        }

        /*
         * Now we'll allocate the entire DOF and copy it in -- provided
         * that the length isn't outrageous.
         */
        if (hdr.dofh_loadsz >= (uint64_t)dtrace_dof_maxsize) {
                dtrace_dof_error(&hdr, "load size exceeds maximum");
                *errp = E2BIG;
                return (NULL);
        }

        if (hdr.dofh_loadsz < sizeof (hdr)) {
                dtrace_dof_error(&hdr, "invalid load size");
                *errp = EINVAL;
                return (NULL);
        }

        dof = kmem_alloc_aligned(hdr.dofh_loadsz, 8, KM_SLEEP);

        if (uread(p, dof, hdr.dofh_loadsz, uarg) != KERN_SUCCESS) {
                kmem_free_aligned(dof, hdr.dofh_loadsz);
                *errp = EFAULT;
                return (NULL);
        }

        return (dof);
}

static void
dtrace_dof_destroy(dof_hdr_t *dof)
{
        kmem_free_aligned(dof, dof->dofh_loadsz);
}

static dof_hdr_t *
dtrace_dof_property(const char *name)
{
        unsigned int len = 0;
        dof_hdr_t *dof;

        if (dtrace_is_restricted() && !dtrace_are_restrictions_relaxed()) {
                return NULL;
        }

        if (!PEReadNVRAMProperty(name, NULL, &len)) {
                return NULL;
        }

        dof = kmem_alloc_aligned(len, 8, KM_SLEEP);

        if (!PEReadNVRAMProperty(name, dof, &len)) {
                dtrace_dof_destroy(dof);
                dtrace_dof_error(NULL, "unreadable DOF");
                return NULL;
        }

        if (len < sizeof (dof_hdr_t)) {
                dtrace_dof_destroy(dof);
                dtrace_dof_error(NULL, "truncated header");
                return (NULL);
        }

        if (len < dof->dofh_loadsz) {
                dtrace_dof_destroy(dof);
                dtrace_dof_error(NULL, "truncated DOF");
                return (NULL);
        }

        if (len != dof->dofh_loadsz) {
                dtrace_dof_destroy(dof);
                dtrace_dof_error(NULL, "invalid DOF size");
                return (NULL);
        }

        if (dof->dofh_loadsz >= (uint64_t)dtrace_dof_maxsize) {
                dtrace_dof_destroy(dof);
                dtrace_dof_error(NULL, "oversized DOF");
                return (NULL);
        }

        return (dof);
}

/*
 * Return the dof_sec_t pointer corresponding to a given section index.  If the
 * index is not valid, dtrace_dof_error() is called and NULL is returned.  If
 * a type other than DOF_SECT_NONE is specified, the header is checked against
 * this type and NULL is returned if the types do not match.
 */
static dof_sec_t *
dtrace_dof_sect(dof_hdr_t *dof, uint32_t type, dof_secidx_t i)
{
        dof_sec_t *sec = (dof_sec_t *)(uintptr_t)
            ((uintptr_t)dof + dof->dofh_secoff + i * dof->dofh_secsize);

        if (i >= dof->dofh_secnum) {
                dtrace_dof_error(dof, "referenced section index is invalid");
                return (NULL);
        }

        if (!(sec->dofs_flags & DOF_SECF_LOAD)) {
                dtrace_dof_error(dof, "referenced section is not loadable");
                return (NULL);
        }

        if (type != DOF_SECT_NONE && type != sec->dofs_type) {
                dtrace_dof_error(dof, "referenced section is the wrong type");
                return (NULL);
        }

        return (sec);
}

static dtrace_probedesc_t *
dtrace_dof_probedesc(dof_hdr_t *dof, dof_sec_t *sec, dtrace_probedesc_t *desc)
{
        dof_probedesc_t *probe;
        dof_sec_t *strtab;
        uintptr_t daddr = (uintptr_t)dof;
        uintptr_t str;
        size_t size;

        if (sec->dofs_type != DOF_SECT_PROBEDESC) {
                dtrace_dof_error(dof, "invalid probe section");
                return (NULL);
        }

        if (sec->dofs_align != sizeof (dof_secidx_t)) {
                dtrace_dof_error(dof, "bad alignment in probe description");
                return (NULL);
        }

        if (sec->dofs_offset + sizeof (dof_probedesc_t) > dof->dofh_loadsz) {
                dtrace_dof_error(dof, "truncated probe description");
                return (NULL);
        }

        probe = (dof_probedesc_t *)(uintptr_t)(daddr + sec->dofs_offset);
        strtab = dtrace_dof_sect(dof, DOF_SECT_STRTAB, probe->dofp_strtab);

        if (strtab == NULL)
                return (NULL);

        str = daddr + strtab->dofs_offset;
        size = strtab->dofs_size;

        if (probe->dofp_provider >= strtab->dofs_size) {
                dtrace_dof_error(dof, "corrupt probe provider");
                return (NULL);
        }

        (void) strncpy(desc->dtpd_provider,
            (char *)(str + probe->dofp_provider),
            MIN(DTRACE_PROVNAMELEN - 1, size - probe->dofp_provider));

        /* APPLE NOTE: Darwin employs size bounded string operation. */
        desc->dtpd_provider[DTRACE_PROVNAMELEN - 1] = '\0';

        if (probe->dofp_mod >= strtab->dofs_size) {
                dtrace_dof_error(dof, "corrupt probe module");
                return (NULL);
        }

        (void) strncpy(desc->dtpd_mod, (char *)(str + probe->dofp_mod),
            MIN(DTRACE_MODNAMELEN - 1, size - probe->dofp_mod));

        /* APPLE NOTE: Darwin employs size bounded string operation. */
        desc->dtpd_mod[DTRACE_MODNAMELEN - 1] = '\0';

        if (probe->dofp_func >= strtab->dofs_size) {
                dtrace_dof_error(dof, "corrupt probe function");
                return (NULL);
        }

        (void) strncpy(desc->dtpd_func, (char *)(str + probe->dofp_func),
            MIN(DTRACE_FUNCNAMELEN - 1, size - probe->dofp_func));

        /* APPLE NOTE: Darwin employs size bounded string operation. */ 
        desc->dtpd_func[DTRACE_FUNCNAMELEN - 1] = '\0';

        if (probe->dofp_name >= strtab->dofs_size) {
                dtrace_dof_error(dof, "corrupt probe name");
                return (NULL);
        }

        (void) strncpy(desc->dtpd_name, (char *)(str + probe->dofp_name),
            MIN(DTRACE_NAMELEN - 1, size - probe->dofp_name));

        /* APPLE NOTE: Darwin employs size bounded string operation. */ 
        desc->dtpd_name[DTRACE_NAMELEN - 1] = '\0';

        return (desc);
}

static dtrace_difo_t *
dtrace_dof_difo(dof_hdr_t *dof, dof_sec_t *sec, dtrace_vstate_t *vstate,
    cred_t *cr)
{
        dtrace_difo_t *dp;
        size_t ttl = 0;
        dof_difohdr_t *dofd;
        uintptr_t daddr = (uintptr_t)dof;
        size_t max_size = dtrace_difo_maxsize;
        uint_t i;
        int l, n;
                

        static const struct {
                int section;
                int bufoffs;
                int lenoffs;
                int entsize;
                int align;
                const char *msg;
        } difo[] = {
                { DOF_SECT_DIF, offsetof(dtrace_difo_t, dtdo_buf),
                offsetof(dtrace_difo_t, dtdo_len), sizeof (dif_instr_t),
                sizeof (dif_instr_t), "multiple DIF sections" },

                { DOF_SECT_INTTAB, offsetof(dtrace_difo_t, dtdo_inttab),
                offsetof(dtrace_difo_t, dtdo_intlen), sizeof (uint64_t),
                sizeof (uint64_t), "multiple integer tables" },

                { DOF_SECT_STRTAB, offsetof(dtrace_difo_t, dtdo_strtab),
                offsetof(dtrace_difo_t, dtdo_strlen), 0,
                sizeof (char), "multiple string tables" },

                { DOF_SECT_VARTAB, offsetof(dtrace_difo_t, dtdo_vartab),
                offsetof(dtrace_difo_t, dtdo_varlen), sizeof (dtrace_difv_t),
                sizeof (uint_t), "multiple variable tables" },

                { DOF_SECT_NONE, 0, 0, 0, 0, NULL }
        };

        if (sec->dofs_type != DOF_SECT_DIFOHDR) {
                dtrace_dof_error(dof, "invalid DIFO header section");
                return (NULL);
        }

        if (sec->dofs_align != sizeof (dof_secidx_t)) {
                dtrace_dof_error(dof, "bad alignment in DIFO header");
                return (NULL);
        }

        if (sec->dofs_size < sizeof (dof_difohdr_t) ||
            sec->dofs_size % sizeof (dof_secidx_t)) {
                dtrace_dof_error(dof, "bad size in DIFO header");
                return (NULL);
        }

        dofd = (dof_difohdr_t *)(uintptr_t)(daddr + sec->dofs_offset);
        n = (sec->dofs_size - sizeof (*dofd)) / sizeof (dof_secidx_t) + 1;

        dp = kmem_zalloc(sizeof (dtrace_difo_t), KM_SLEEP);
        dp->dtdo_rtype = dofd->dofd_rtype;

        for (l = 0; l < n; l++) {
                dof_sec_t *subsec;
                void **bufp;
                uint32_t *lenp;

                if ((subsec = dtrace_dof_sect(dof, DOF_SECT_NONE,
                    dofd->dofd_links[l])) == NULL)
                        goto err; /* invalid section link */

                if (ttl + subsec->dofs_size > max_size) {
                        dtrace_dof_error(dof, "exceeds maximum size");
                        goto err;
                }

                ttl += subsec->dofs_size;

                for (i = 0; difo[i].section != DOF_SECT_NONE; i++) {

                        if (subsec->dofs_type != (uint32_t)difo[i].section)
                                continue;

                        if (!(subsec->dofs_flags & DOF_SECF_LOAD)) {
                                dtrace_dof_error(dof, "section not loaded");
                                goto err;
                        }

                        if (subsec->dofs_align != (uint32_t)difo[i].align) {
                                dtrace_dof_error(dof, "bad alignment");
                                goto err;
                        }

                        bufp = (void **)((uintptr_t)dp + difo[i].bufoffs);
                        lenp = (uint32_t *)((uintptr_t)dp + difo[i].lenoffs);

                        if (*bufp != NULL) {
                                dtrace_dof_error(dof, difo[i].msg);
                                goto err;
                        }

                        if ((uint32_t)difo[i].entsize != subsec->dofs_entsize) {
                                dtrace_dof_error(dof, "entry size mismatch");
                                goto err;
                        }

                        if (subsec->dofs_entsize != 0 &&
                            (subsec->dofs_size % subsec->dofs_entsize) != 0) {
                                dtrace_dof_error(dof, "corrupt entry size");
                                goto err;
                        }

                        *lenp = subsec->dofs_size;
                        *bufp = kmem_alloc(subsec->dofs_size, KM_SLEEP);
                        bcopy((char *)(uintptr_t)(daddr + subsec->dofs_offset),
                            *bufp, subsec->dofs_size);

                        if (subsec->dofs_entsize != 0)
                                *lenp /= subsec->dofs_entsize;

                        break;
                }

                /*
                 * If we encounter a loadable DIFO sub-section that is not
                 * known to us, assume this is a broken program and fail.
                 */
                if (difo[i].section == DOF_SECT_NONE &&
                    (subsec->dofs_flags & DOF_SECF_LOAD)) {
                        dtrace_dof_error(dof, "unrecognized DIFO subsection");
                        goto err;
                }
        }
        
        if (dp->dtdo_buf == NULL) {
                /*
                 * We can't have a DIF object without DIF text.
                 */
                dtrace_dof_error(dof, "missing DIF text");
                goto err;
        }

        /*
         * Before we validate the DIF object, run through the variable table
         * looking for the strings -- if any of their size are under, we'll set
         * their size to be the system-wide default string size.  Note that
         * this should _not_ happen if the "strsize" option has been set --
         * in this case, the compiler should have set the size to reflect the
         * setting of the option.
         */
        for (i = 0; i < dp->dtdo_varlen; i++) {
                dtrace_difv_t *v = &dp->dtdo_vartab[i];
                dtrace_diftype_t *t = &v->dtdv_type;

                if (v->dtdv_id < DIF_VAR_OTHER_UBASE)
                        continue;

                if (t->dtdt_kind == DIF_TYPE_STRING && t->dtdt_size == 0)
                        t->dtdt_size = dtrace_strsize_default;
        }

        if (dtrace_difo_validate(dp, vstate, DIF_DIR_NREGS, cr) != 0)
                goto err;

        dtrace_difo_init(dp, vstate);
        return (dp);

err:
        kmem_free(dp->dtdo_buf, dp->dtdo_len * sizeof (dif_instr_t));
        kmem_free(dp->dtdo_inttab, dp->dtdo_intlen * sizeof (uint64_t));
        kmem_free(dp->dtdo_strtab, dp->dtdo_strlen);
        kmem_free(dp->dtdo_vartab, dp->dtdo_varlen * sizeof (dtrace_difv_t));

        kmem_free(dp, sizeof (dtrace_difo_t));
        return (NULL);
}

static dtrace_predicate_t *
dtrace_dof_predicate(dof_hdr_t *dof, dof_sec_t *sec, dtrace_vstate_t *vstate,
    cred_t *cr)
{
        dtrace_difo_t *dp;

        if ((dp = dtrace_dof_difo(dof, sec, vstate, cr)) == NULL)
                return (NULL);

        return (dtrace_predicate_create(dp));
}

static dtrace_actdesc_t *
dtrace_dof_actdesc(dof_hdr_t *dof, dof_sec_t *sec, dtrace_vstate_t *vstate,
    cred_t *cr)
{
        dtrace_actdesc_t *act, *first = NULL, *last = NULL, *next;
        dof_actdesc_t *desc;
        dof_sec_t *difosec;
        size_t offs;
        uintptr_t daddr = (uintptr_t)dof;
        uint64_t arg;
        dtrace_actkind_t kind;

        if (sec->dofs_type != DOF_SECT_ACTDESC) {
                dtrace_dof_error(dof, "invalid action section");
                return (NULL);
        }

        if (sec->dofs_offset + sizeof (dof_actdesc_t) > dof->dofh_loadsz) {
                dtrace_dof_error(dof, "truncated action description");
                return (NULL);
        }

        if (sec->dofs_align != sizeof (uint64_t)) {
                dtrace_dof_error(dof, "bad alignment in action description");
                return (NULL);
        }

        if (sec->dofs_size < sec->dofs_entsize) {
                dtrace_dof_error(dof, "section entry size exceeds total size");
                return (NULL);
        }

        if (sec->dofs_entsize != sizeof (dof_actdesc_t)) {
                dtrace_dof_error(dof, "bad entry size in action description");
                return (NULL);
        }

        if (sec->dofs_size / sec->dofs_entsize > dtrace_actions_max) {
                dtrace_dof_error(dof, "actions exceed dtrace_actions_max");
                return (NULL);
        }

        for (offs = 0; offs < sec->dofs_size; offs += sec->dofs_entsize) {
                desc = (dof_actdesc_t *)(daddr +
                    (uintptr_t)sec->dofs_offset + offs);
                kind = (dtrace_actkind_t)desc->dofa_kind;

                if ((DTRACEACT_ISPRINTFLIKE(kind) &&
                    (kind != DTRACEACT_PRINTA || desc->dofa_strtab != DOF_SECIDX_NONE)) ||
                    (kind == DTRACEACT_DIFEXPR && desc->dofa_strtab != DOF_SECIDX_NONE))
                {
                        dof_sec_t *strtab;
                        char *str, *fmt;
                        uint64_t i;

                        /*
                         * The argument to these actions is an index into the
                         * DOF string table.  For printf()-like actions, this
                         * is the format string.  For print(), this is the
                         * CTF type of the expression result.
                         */
                        if ((strtab = dtrace_dof_sect(dof,
                            DOF_SECT_STRTAB, desc->dofa_strtab)) == NULL)
                                goto err;

                        str = (char *)((uintptr_t)dof +
                            (uintptr_t)strtab->dofs_offset);

                        for (i = desc->dofa_arg; i < strtab->dofs_size; i++) {
                                if (str[i] == '\0')
                                        break;
                        }

                        if (i >= strtab->dofs_size) {
                                dtrace_dof_error(dof, "bogus format string");
                                goto err;
                        }

                        if (i == desc->dofa_arg) {
                                dtrace_dof_error(dof, "empty format string");
                                goto err;
                        }

                        i -= desc->dofa_arg;
                        fmt = kmem_alloc(i + 1, KM_SLEEP);
                        bcopy(&str[desc->dofa_arg], fmt, i + 1);
                        arg = (uint64_t)(uintptr_t)fmt;
                } else {
                        if (kind == DTRACEACT_PRINTA) {
                                ASSERT(desc->dofa_strtab == DOF_SECIDX_NONE);
                                arg = 0;
                        } else {
                                arg = desc->dofa_arg;
                        }
                }

                act = dtrace_actdesc_create(kind, desc->dofa_ntuple,
                    desc->dofa_uarg, arg);

                if (last != NULL) {
                        last->dtad_next = act;
                } else {
                        first = act;
                }

                last = act;

                if (desc->dofa_difo == DOF_SECIDX_NONE)
                        continue;

                if ((difosec = dtrace_dof_sect(dof,
                    DOF_SECT_DIFOHDR, desc->dofa_difo)) == NULL)
                        goto err;

                act->dtad_difo = dtrace_dof_difo(dof, difosec, vstate, cr);

                if (act->dtad_difo == NULL)
                        goto err;
        }

        ASSERT(first != NULL);
        return (first);

err:
        for (act = first; act != NULL; act = next) {
                next = act->dtad_next;
                dtrace_actdesc_release(act, vstate);
        }

        return (NULL);
}

static dtrace_ecbdesc_t *
dtrace_dof_ecbdesc(dof_hdr_t *dof, dof_sec_t *sec, dtrace_vstate_t *vstate,
    cred_t *cr)
{
        dtrace_ecbdesc_t *ep;
        dof_ecbdesc_t *ecb;
        dtrace_probedesc_t *desc;
        dtrace_predicate_t *pred = NULL;

        if (sec->dofs_size < sizeof (dof_ecbdesc_t)) {
                dtrace_dof_error(dof, "truncated ECB description");
                return (NULL);
        }

        if (sec->dofs_align != sizeof (uint64_t)) {
                dtrace_dof_error(dof, "bad alignment in ECB description");
                return (NULL);
        }

        ecb = (dof_ecbdesc_t *)((uintptr_t)dof + (uintptr_t)sec->dofs_offset);
        sec = dtrace_dof_sect(dof, DOF_SECT_PROBEDESC, ecb->dofe_probes);

        if (sec == NULL)
                return (NULL);

        ep = kmem_zalloc(sizeof (dtrace_ecbdesc_t), KM_SLEEP);
        ep->dted_uarg = ecb->dofe_uarg;
        desc = &ep->dted_probe;

        if (dtrace_dof_probedesc(dof, sec, desc) == NULL)
                goto err;

        if (ecb->dofe_pred != DOF_SECIDX_NONE) {
                if ((sec = dtrace_dof_sect(dof,
                    DOF_SECT_DIFOHDR, ecb->dofe_pred)) == NULL)
                        goto err;

                if ((pred = dtrace_dof_predicate(dof, sec, vstate, cr)) == NULL)
                        goto err;

                ep->dted_pred.dtpdd_predicate = pred;
        }

        if (ecb->dofe_actions != DOF_SECIDX_NONE) {
                if ((sec = dtrace_dof_sect(dof,
                    DOF_SECT_ACTDESC, ecb->dofe_actions)) == NULL)
                        goto err;

                ep->dted_action = dtrace_dof_actdesc(dof, sec, vstate, cr);

                if (ep->dted_action == NULL)
                        goto err;
        }

        return (ep);

err:
        if (pred != NULL)
                dtrace_predicate_release(pred, vstate);
        kmem_free(ep, sizeof (dtrace_ecbdesc_t));
        return (NULL);
}

/*
 * APPLE NOTE: dyld handles dof relocation.
 * Darwin does not need dtrace_dof_relocate()
 */

/*
 * The dof_hdr_t passed to dtrace_dof_slurp() should be a partially validated
 * header:  it should be at the front of a memory region that is at least
 * sizeof (dof_hdr_t) in size -- and then at least dof_hdr.dofh_loadsz in
 * size.  It need not be validated in any other way.
 */
static int
dtrace_dof_slurp(dof_hdr_t *dof, dtrace_vstate_t *vstate, cred_t *cr,
    dtrace_enabling_t **enabp, uint64_t ubase, int noprobes)
{
#pragma unused(ubase) /* __APPLE__ */
        uint64_t len = dof->dofh_loadsz, seclen;
        uintptr_t daddr = (uintptr_t)dof;
        dtrace_ecbdesc_t *ep;
        dtrace_enabling_t *enab;
        uint_t i;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);
        ASSERT(dof->dofh_loadsz >= sizeof (dof_hdr_t));

        /*
         * Check the DOF header identification bytes.  In addition to checking
         * valid settings, we also verify that unused bits/bytes are zeroed so
         * we can use them later without fear of regressing existing binaries.
         */
        if (bcmp(&dof->dofh_ident[DOF_ID_MAG0],
            DOF_MAG_STRING, DOF_MAG_STRLEN) != 0) {
                dtrace_dof_error(dof, "DOF magic string mismatch");
                return (-1);
        }

        if (dof->dofh_ident[DOF_ID_MODEL] != DOF_MODEL_ILP32 &&
            dof->dofh_ident[DOF_ID_MODEL] != DOF_MODEL_LP64) {
                dtrace_dof_error(dof, "DOF has invalid data model");
                return (-1);
        }

        if (dof->dofh_ident[DOF_ID_ENCODING] != DOF_ENCODE_NATIVE) {
                dtrace_dof_error(dof, "DOF encoding mismatch");
                return (-1);
        }

        /*
         * APPLE NOTE: Darwin only supports DOF_VERSION_3 for now.
         */
        if (dof->dofh_ident[DOF_ID_VERSION] != DOF_VERSION_3) {
                dtrace_dof_error(dof, "DOF version mismatch");
                return (-1);
        }

        if (dof->dofh_ident[DOF_ID_DIFVERS] != DIF_VERSION_2) {
                dtrace_dof_error(dof, "DOF uses unsupported instruction set");
                return (-1);
        }

        if (dof->dofh_ident[DOF_ID_DIFIREG] > DIF_DIR_NREGS) {
                dtrace_dof_error(dof, "DOF uses too many integer registers");
                return (-1);
        }

        if (dof->dofh_ident[DOF_ID_DIFTREG] > DIF_DTR_NREGS) {
                dtrace_dof_error(dof, "DOF uses too many tuple registers");
                return (-1);
        }

        for (i = DOF_ID_PAD; i < DOF_ID_SIZE; i++) {
                if (dof->dofh_ident[i] != 0) {
                        dtrace_dof_error(dof, "DOF has invalid ident byte set");
                        return (-1);
                }
        }

        if (dof->dofh_flags & ~DOF_FL_VALID) {
                dtrace_dof_error(dof, "DOF has invalid flag bits set");
                return (-1);
        }

        if (dof->dofh_secsize < sizeof(dof_sec_t)) {
                dtrace_dof_error(dof, "invalid section header size");
                return (-1);
        }

        /*
         * Check that the section headers don't exceed the amount of DOF
         * data.  Note that we cast the section size and number of sections
         * to uint64_t's to prevent possible overflow in the multiplication.
         */
        seclen = (uint64_t)dof->dofh_secnum * (uint64_t)dof->dofh_secsize;

        if (dof->dofh_secoff > len || seclen > len ||
            dof->dofh_secoff + seclen > len) {
                dtrace_dof_error(dof, "truncated section headers");
                return (-1);
        }

        if (!IS_P2ALIGNED(dof->dofh_secoff, sizeof (uint64_t))) {
                dtrace_dof_error(dof, "misaligned section headers");
                return (-1);
        }

        if (!IS_P2ALIGNED(dof->dofh_secsize, sizeof (uint64_t))) {
                dtrace_dof_error(dof, "misaligned section size");
                return (-1);
        }

        /*
         * Take an initial pass through the section headers to be sure that
         * the headers don't have stray offsets.  If the 'noprobes' flag is
         * set, do not permit sections relating to providers, probes, or args.
         */
        for (i = 0; i < dof->dofh_secnum; i++) {
                dof_sec_t *sec = (dof_sec_t *)(daddr +
                    (uintptr_t)dof->dofh_secoff + i * dof->dofh_secsize);

                if (noprobes) {
                        switch (sec->dofs_type) {
                        case DOF_SECT_PROVIDER:
                        case DOF_SECT_PROBES:
                        case DOF_SECT_PRARGS:
                        case DOF_SECT_PROFFS:
                                dtrace_dof_error(dof, "illegal sections "
                                    "for enabling");
                                return (-1);
                        }
                }

                if (!(sec->dofs_flags & DOF_SECF_LOAD))
                        continue; /* just ignore non-loadable sections */

                if (sec->dofs_align & (sec->dofs_align - 1)) {
                        dtrace_dof_error(dof, "bad section alignment");
                        return (-1);
                }

                if (sec->dofs_offset & (sec->dofs_align - 1)) {
                        dtrace_dof_error(dof, "misaligned section");
                        return (-1);
                }

                if (sec->dofs_offset > len || sec->dofs_size > len ||
                    sec->dofs_offset + sec->dofs_size > len) {
                        dtrace_dof_error(dof, "corrupt section header");
                        return (-1);
                }

                if (sec->dofs_type == DOF_SECT_STRTAB && *((char *)daddr +
                    sec->dofs_offset + sec->dofs_size - 1) != '\0') {
                        dtrace_dof_error(dof, "non-terminating string table");
                        return (-1);
                }
        }

        /*
         * APPLE NOTE: We have no further relocation to perform.
         * All dof values are relative offsets.
         */

        if ((enab = *enabp) == NULL)
                enab = *enabp = dtrace_enabling_create(vstate);

        for (i = 0; i < dof->dofh_secnum; i++) {
                dof_sec_t *sec = (dof_sec_t *)(daddr +
                    (uintptr_t)dof->dofh_secoff + i * dof->dofh_secsize);

                if (sec->dofs_type != DOF_SECT_ECBDESC)
                        continue;

                /*
                 * APPLE NOTE: Defend against gcc 4.0 botch on x86.
                 * not all paths out of inlined dtrace_dof_ecbdesc
                 * are checked for the NULL return value.
                 * Check for NULL explicitly here.
                */
                ep = dtrace_dof_ecbdesc(dof, sec, vstate, cr);
                if (ep == NULL) {
                        dtrace_enabling_destroy(enab);
                        *enabp = NULL;
                        return (-1);
                }
                
                dtrace_enabling_add(enab, ep);
        }

        return (0);
}

/*
 * Process DOF for any options.  This routine assumes that the DOF has been
 * at least processed by dtrace_dof_slurp().
 */
static int
dtrace_dof_options(dof_hdr_t *dof, dtrace_state_t *state)
{
        uint_t i;
        int rval;
        uint32_t entsize;
        size_t offs;
        dof_optdesc_t *desc;

        for (i = 0; i < dof->dofh_secnum; i++) {
                dof_sec_t *sec = (dof_sec_t *)((uintptr_t)dof +
                    (uintptr_t)dof->dofh_secoff + i * dof->dofh_secsize);

                if (sec->dofs_type != DOF_SECT_OPTDESC)
                        continue;

                if (sec->dofs_align != sizeof (uint64_t)) {
                        dtrace_dof_error(dof, "bad alignment in "
                            "option description");
                        return (EINVAL);
                }

                if ((entsize = sec->dofs_entsize) == 0) {
                        dtrace_dof_error(dof, "zeroed option entry size");
                        return (EINVAL);
                }

                if (entsize < sizeof (dof_optdesc_t)) {
                        dtrace_dof_error(dof, "bad option entry size");
                        return (EINVAL);
                }

                for (offs = 0; offs < sec->dofs_size; offs += entsize) {
                        desc = (dof_optdesc_t *)((uintptr_t)dof +
                            (uintptr_t)sec->dofs_offset + offs);

                        if (desc->dofo_strtab != DOF_SECIDX_NONE) {
                                dtrace_dof_error(dof, "non-zero option string");
                                return (EINVAL);
                        }

                        if (desc->dofo_value == (uint64_t)DTRACEOPT_UNSET) {
                                dtrace_dof_error(dof, "unset option");
                                return (EINVAL);
                        }

                        if ((rval = dtrace_state_option(state,
                            desc->dofo_option, desc->dofo_value)) != 0) {
                                dtrace_dof_error(dof, "rejected option");
                                return (rval);
                        }
                }
        }

        return (0);
}

/*
 * DTrace Consumer State Functions
 */
static int
dtrace_dstate_init(dtrace_dstate_t *dstate, size_t size)
{
        size_t hashsize, maxper, min_size, chunksize = dstate->dtds_chunksize;
        void *base;
        uintptr_t limit;
        dtrace_dynvar_t *dvar, *next, *start;
        size_t i;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);
        ASSERT(dstate->dtds_base == NULL && dstate->dtds_percpu == NULL);

        bzero(dstate, sizeof (dtrace_dstate_t));

        if ((dstate->dtds_chunksize = chunksize) == 0)
                dstate->dtds_chunksize = DTRACE_DYNVAR_CHUNKSIZE;

        VERIFY(dstate->dtds_chunksize < (LONG_MAX - sizeof (dtrace_dynhash_t)));

        if (size < (min_size = dstate->dtds_chunksize + sizeof (dtrace_dynhash_t)))
                size = min_size;

        if ((base = kmem_zalloc(size, KM_NOSLEEP)) == NULL)
                return (ENOMEM);

        dstate->dtds_size = size;
        dstate->dtds_base = base;
        dstate->dtds_percpu = kmem_cache_alloc(dtrace_state_cache, KM_SLEEP);
        bzero(dstate->dtds_percpu, (int)NCPU * sizeof (dtrace_dstate_percpu_t));

        hashsize = size / (dstate->dtds_chunksize + sizeof (dtrace_dynhash_t));

        if (hashsize != 1 && (hashsize & 1))
                hashsize--;

        dstate->dtds_hashsize = hashsize;
        dstate->dtds_hash = dstate->dtds_base;

        /*
         * Set all of our hash buckets to point to the single sink, and (if
         * it hasn't already been set), set the sink's hash value to be the
         * sink sentinel value.  The sink is needed for dynamic variable
         * lookups to know that they have iterated over an entire, valid hash
         * chain.
         */
        for (i = 0; i < hashsize; i++)
                dstate->dtds_hash[i].dtdh_chain = &dtrace_dynhash_sink;

        if (dtrace_dynhash_sink.dtdv_hashval != DTRACE_DYNHASH_SINK)
                dtrace_dynhash_sink.dtdv_hashval = DTRACE_DYNHASH_SINK;

        /*
         * Determine number of active CPUs.  Divide free list evenly among
         * active CPUs.
         */
        start = (dtrace_dynvar_t *)
            ((uintptr_t)base + hashsize * sizeof (dtrace_dynhash_t));
        limit = (uintptr_t)base + size;

        VERIFY((uintptr_t)start < limit);
        VERIFY((uintptr_t)start >= (uintptr_t)base);

        maxper = (limit - (uintptr_t)start) / (int)NCPU;
        maxper = (maxper / dstate->dtds_chunksize) * dstate->dtds_chunksize;

        for (i = 0; i < NCPU; i++) {
                dstate->dtds_percpu[i].dtdsc_free = dvar = start;

                /*
                 * If we don't even have enough chunks to make it once through
                 * NCPUs, we're just going to allocate everything to the first
                 * CPU.  And if we're on the last CPU, we're going to allocate
                 * whatever is left over.  In either case, we set the limit to
                 * be the limit of the dynamic variable space.
                 */
                if (maxper == 0 || i == NCPU - 1) {
                        limit = (uintptr_t)base + size;
                        start = NULL;
                } else {
                        limit = (uintptr_t)start + maxper;
                        start = (dtrace_dynvar_t *)limit;
                }

                VERIFY(limit <= (uintptr_t)base + size);

                for (;;) {
                        next = (dtrace_dynvar_t *)((uintptr_t)dvar +
                            dstate->dtds_chunksize);

                        if ((uintptr_t)next + dstate->dtds_chunksize >= limit)
                                break;

                        VERIFY((uintptr_t)dvar >= (uintptr_t)base &&
                            (uintptr_t)dvar <= (uintptr_t)base + size);
                        dvar->dtdv_next = next;
                        dvar = next;
                }

                if (maxper == 0)
                        break;
        }

        return (0);
}

static void
dtrace_dstate_fini(dtrace_dstate_t *dstate)
{
        LCK_MTX_ASSERT(&cpu_lock, LCK_MTX_ASSERT_OWNED);

        if (dstate->dtds_base == NULL)
                return;

        kmem_free(dstate->dtds_base, dstate->dtds_size);
        kmem_cache_free(dtrace_state_cache, dstate->dtds_percpu);
}

static void
dtrace_vstate_fini(dtrace_vstate_t *vstate)
{
        /*
         * Logical XOR, where are you?
         */
        ASSERT((vstate->dtvs_nglobals == 0) ^ (vstate->dtvs_globals != NULL));

        if (vstate->dtvs_nglobals > 0) {
                kmem_free(vstate->dtvs_globals, vstate->dtvs_nglobals *
                    sizeof (dtrace_statvar_t *));
        }

        if (vstate->dtvs_ntlocals > 0) {
                kmem_free(vstate->dtvs_tlocals, vstate->dtvs_ntlocals *
                    sizeof (dtrace_difv_t));
        }

        ASSERT((vstate->dtvs_nlocals == 0) ^ (vstate->dtvs_locals != NULL));

        if (vstate->dtvs_nlocals > 0) {
                kmem_free(vstate->dtvs_locals, vstate->dtvs_nlocals *
                    sizeof (dtrace_statvar_t *));
        }
}

static void
dtrace_state_clean(dtrace_state_t *state)
{
        if (state->dts_activity == DTRACE_ACTIVITY_INACTIVE)
                return;

        dtrace_dynvar_clean(&state->dts_vstate.dtvs_dynvars);
        dtrace_speculation_clean(state);
}

static void
dtrace_state_deadman(dtrace_state_t *state)
{
        hrtime_t now;

        dtrace_sync();

        now = dtrace_gethrtime();

        if (state != dtrace_anon.dta_state &&
            now - state->dts_laststatus >= dtrace_deadman_user)
                return;

        /*
         * We must be sure that dts_alive never appears to be less than the
         * value upon entry to dtrace_state_deadman(), and because we lack a
         * dtrace_cas64(), we cannot store to it atomically.  We thus instead
         * store INT64_MAX to it, followed by a memory barrier, followed by
         * the new value.  This assures that dts_alive never appears to be
         * less than its true value, regardless of the order in which the
         * stores to the underlying storage are issued.
         */
        state->dts_alive = INT64_MAX;
        dtrace_membar_producer();
        state->dts_alive = now;
}

static int
dtrace_state_create(dev_t *devp, cred_t *cr, dtrace_state_t **new_state)
{
        minor_t minor;
        major_t major;
        char c[30];
        dtrace_state_t *state;
        dtrace_optval_t *opt;
        int bufsize = (int)NCPU * sizeof (dtrace_buffer_t), i;
        unsigned int cpu_it;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);
        LCK_MTX_ASSERT(&cpu_lock, LCK_MTX_ASSERT_OWNED);

        /* Cause restart */
        *new_state = NULL;
        
        if (devp != NULL) {
                minor = getminor(*devp);
        }
        else {
                minor = DTRACE_NCLIENTS - 1;
        }

        state = dtrace_state_allocate(minor);
        if (NULL == state) {
                printf("dtrace_open: couldn't acquire minor number %d. This usually means that too many DTrace clients are in use at the moment", minor);
                return (ERESTART);      /* can't reacquire */
        }

        state->dts_epid = DTRACE_EPIDNONE + 1;

        (void) snprintf(c, sizeof (c), "dtrace_aggid_%d", minor);
        state->dts_aggid_arena = vmem_create(c, (void *)1, UINT32_MAX, 1,
            NULL, NULL, NULL, 0, VM_SLEEP | VMC_IDENTIFIER);

        if (devp != NULL) {
                major = getemajor(*devp);
        } else {
                major = ddi_driver_major(dtrace_devi);
        }

        state->dts_dev = makedev(major, minor);

        if (devp != NULL)
                *devp = state->dts_dev;

        /*
         * We allocate NCPU buffers.  On the one hand, this can be quite
         * a bit of memory per instance (nearly 36K on a Starcat).  On the
         * other hand, it saves an additional memory reference in the probe
         * path.
         */
        state->dts_buffer = kmem_zalloc(bufsize, KM_SLEEP);
        state->dts_aggbuffer = kmem_zalloc(bufsize, KM_SLEEP);
        state->dts_buf_over_limit = 0;

        /*
         * Allocate and initialise the per-process per-CPU random state.
         * SI_SUB_RANDOM < SI_SUB_DTRACE_ANON therefore entropy device is
         * assumed to be seeded at this point (if from Fortuna seed file).
         */
        state->dts_rstate = kmem_zalloc(NCPU * sizeof(uint64_t*), KM_SLEEP);
        state->dts_rstate[0] = kmem_zalloc(2 * sizeof(uint64_t), KM_SLEEP);
        (void) read_random(state->dts_rstate[0], 2 * sizeof(uint64_t));
        for (cpu_it = 1; cpu_it < NCPU; cpu_it++) {
                state->dts_rstate[cpu_it] = kmem_zalloc(2 * sizeof(uint64_t), KM_SLEEP);
                /*
                 * Each CPU is assigned a 2^64 period, non-overlapping
                 * subsequence.
                 */
                dtrace_xoroshiro128_plus_jump(state->dts_rstate[cpu_it-1],
                    state->dts_rstate[cpu_it]);
        }

        state->dts_cleaner = CYCLIC_NONE;
        state->dts_deadman = CYCLIC_NONE;
        state->dts_vstate.dtvs_state = state;

        for (i = 0; i < DTRACEOPT_MAX; i++)
                state->dts_options[i] = DTRACEOPT_UNSET;

        /*
         * Set the default options.
         */
        opt = state->dts_options;
        opt[DTRACEOPT_BUFPOLICY] = DTRACEOPT_BUFPOLICY_SWITCH;
        opt[DTRACEOPT_BUFRESIZE] = DTRACEOPT_BUFRESIZE_AUTO;
        opt[DTRACEOPT_NSPEC] = dtrace_nspec_default;
        opt[DTRACEOPT_SPECSIZE] = dtrace_specsize_default;
        opt[DTRACEOPT_CPU] = (dtrace_optval_t)DTRACE_CPUALL;
        opt[DTRACEOPT_STRSIZE] = dtrace_strsize_default;
        opt[DTRACEOPT_STACKFRAMES] = dtrace_stackframes_default;
        opt[DTRACEOPT_USTACKFRAMES] = dtrace_ustackframes_default;
        opt[DTRACEOPT_CLEANRATE] = dtrace_cleanrate_default;
        opt[DTRACEOPT_AGGRATE] = dtrace_aggrate_default;
        opt[DTRACEOPT_SWITCHRATE] = dtrace_switchrate_default;
        opt[DTRACEOPT_STATUSRATE] = dtrace_statusrate_default;
        opt[DTRACEOPT_JSTACKFRAMES] = dtrace_jstackframes_default;
        opt[DTRACEOPT_JSTACKSTRSIZE] = dtrace_jstackstrsize_default;
        opt[DTRACEOPT_BUFLIMIT] = dtrace_buflimit_default;

        /*
         * Depending on the user credentials, we set flag bits which alter probe
         * visibility or the amount of destructiveness allowed.  In the case of
         * actual anonymous tracing, or the possession of all privileges, all of
         * the normal checks are bypassed.
         */
#if defined(__APPLE__)
        if (cr != NULL) {
                kauth_cred_ref(cr);
                state->dts_cred.dcr_cred = cr;
        }
        if (cr == NULL || PRIV_POLICY_ONLY(cr, PRIV_ALL, B_FALSE)) {
                if (dtrace_is_restricted() && !dtrace_are_restrictions_relaxed()) {
                        /*
                         * Allow only proc credentials when DTrace is
                         * restricted by the current security policy
                         */
                        state->dts_cred.dcr_visible = DTRACE_CRV_ALLPROC;
                        state->dts_cred.dcr_action = DTRACE_CRA_PROC | DTRACE_CRA_PROC_CONTROL | DTRACE_CRA_PROC_DESTRUCTIVE_ALLUSER;
                }
                else {
                        state->dts_cred.dcr_visible = DTRACE_CRV_ALL;
                        state->dts_cred.dcr_action = DTRACE_CRA_ALL;
                }
        }

#else
        if (cr == NULL || PRIV_POLICY_ONLY(cr, PRIV_ALL, B_FALSE)) {
                state->dts_cred.dcr_visible = DTRACE_CRV_ALL;
                state->dts_cred.dcr_action = DTRACE_CRA_ALL;
        }
        else {
                /*
                 * Set up the credentials for this instantiation.  We take a
                 * hold on the credential to prevent it from disappearing on
                 * us; this in turn prevents the zone_t referenced by this
                 * credential from disappearing.  This means that we can
                 * examine the credential and the zone from probe context.
                 */
                crhold(cr);
                state->dts_cred.dcr_cred = cr;

                /*
                 * CRA_PROC means "we have *some* privilege for dtrace" and
                 * unlocks the use of variables like pid, zonename, etc.
                 */
                if (PRIV_POLICY_ONLY(cr, PRIV_DTRACE_USER, B_FALSE) ||
                    PRIV_POLICY_ONLY(cr, PRIV_DTRACE_PROC, B_FALSE)) {
                        state->dts_cred.dcr_action |= DTRACE_CRA_PROC;
                }

                /*
                 * dtrace_user allows use of syscall and profile providers.
                 * If the user also has proc_owner and/or proc_zone, we
                 * extend the scope to include additional visibility and
                 * destructive power.
                 */
                if (PRIV_POLICY_ONLY(cr, PRIV_DTRACE_USER, B_FALSE)) {
                        if (PRIV_POLICY_ONLY(cr, PRIV_PROC_OWNER, B_FALSE)) {
                                state->dts_cred.dcr_visible |=
                                    DTRACE_CRV_ALLPROC;

                                state->dts_cred.dcr_action |=
                                    DTRACE_CRA_PROC_DESTRUCTIVE_ALLUSER;
                        }

                        if (PRIV_POLICY_ONLY(cr, PRIV_PROC_ZONE, B_FALSE)) {
                                state->dts_cred.dcr_visible |=
                                    DTRACE_CRV_ALLZONE;

                                state->dts_cred.dcr_action |=
                                    DTRACE_CRA_PROC_DESTRUCTIVE_ALLZONE;
                        }

                        /*
                         * If we have all privs in whatever zone this is,
                         * we can do destructive things to processes which
                         * have altered credentials.
                         *
                         * APPLE NOTE: Darwin doesn't do zones.
                         * Behave as if zone always has destructive privs.
                         */

                        state->dts_cred.dcr_action |=
                                DTRACE_CRA_PROC_DESTRUCTIVE_CREDCHG;
                }

                /*
                 * Holding the dtrace_kernel privilege also implies that
                 * the user has the dtrace_user privilege from a visibility
                 * perspective.  But without further privileges, some
                 * destructive actions are not available.
                 */
                if (PRIV_POLICY_ONLY(cr, PRIV_DTRACE_KERNEL, B_FALSE)) {
                        /*
                         * Make all probes in all zones visible.  However,
                         * this doesn't mean that all actions become available
                         * to all zones.
                         */
                        state->dts_cred.dcr_visible |= DTRACE_CRV_KERNEL |
                            DTRACE_CRV_ALLPROC | DTRACE_CRV_ALLZONE;

                        state->dts_cred.dcr_action |= DTRACE_CRA_KERNEL |
                            DTRACE_CRA_PROC;
                        /*
                         * Holding proc_owner means that destructive actions
                         * for *this* zone are allowed.
                         */
                        if (PRIV_POLICY_ONLY(cr, PRIV_PROC_OWNER, B_FALSE))
                                state->dts_cred.dcr_action |=
                                    DTRACE_CRA_PROC_DESTRUCTIVE_ALLUSER;

                        /*
                         * Holding proc_zone means that destructive actions
                         * for this user/group ID in all zones is allowed.
                         */
                        if (PRIV_POLICY_ONLY(cr, PRIV_PROC_ZONE, B_FALSE))
                                state->dts_cred.dcr_action |=
                                    DTRACE_CRA_PROC_DESTRUCTIVE_ALLZONE;

                        /*
                         * If we have all privs in whatever zone this is,
                         * we can do destructive things to processes which
                         * have altered credentials.
                         *
                         * APPLE NOTE: Darwin doesn't do zones.                  
                         * Behave as if zone always has destructive privs.
                         */                     
                        state->dts_cred.dcr_action |=
                                DTRACE_CRA_PROC_DESTRUCTIVE_CREDCHG;
                }

                /*
                 * Holding the dtrace_proc privilege gives control over fasttrap
                 * and pid providers.  We need to grant wider destructive
                 * privileges in the event that the user has proc_owner and/or
                 * proc_zone.
                 */
                if (PRIV_POLICY_ONLY(cr, PRIV_DTRACE_PROC, B_FALSE)) {
                        if (PRIV_POLICY_ONLY(cr, PRIV_PROC_OWNER, B_FALSE))
                                state->dts_cred.dcr_action |=
                                    DTRACE_CRA_PROC_DESTRUCTIVE_ALLUSER;

                        if (PRIV_POLICY_ONLY(cr, PRIV_PROC_ZONE, B_FALSE))
                                state->dts_cred.dcr_action |=
                                    DTRACE_CRA_PROC_DESTRUCTIVE_ALLZONE;
                }
        }
#endif

        *new_state = state;
        return(0);  /* Success */
}

static int
dtrace_state_buffer(dtrace_state_t *state, dtrace_buffer_t *buf, int which)
{
        dtrace_optval_t *opt = state->dts_options, size;
        processorid_t cpu = 0;
        size_t limit = buf->dtb_size;
        int flags = 0, rval;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);
        LCK_MTX_ASSERT(&cpu_lock, LCK_MTX_ASSERT_OWNED);
        ASSERT(which < DTRACEOPT_MAX);
        ASSERT(state->dts_activity == DTRACE_ACTIVITY_INACTIVE ||
            (state == dtrace_anon.dta_state &&
            state->dts_activity == DTRACE_ACTIVITY_ACTIVE));

        if (opt[which] == DTRACEOPT_UNSET || opt[which] == 0)
                return (0);

        if (opt[DTRACEOPT_CPU] != DTRACEOPT_UNSET)
                cpu = opt[DTRACEOPT_CPU];

        if (which == DTRACEOPT_SPECSIZE)
                flags |= DTRACEBUF_NOSWITCH;

        if (which == DTRACEOPT_BUFSIZE) {
                if (opt[DTRACEOPT_BUFPOLICY] == DTRACEOPT_BUFPOLICY_RING)
                        flags |= DTRACEBUF_RING;

                if (opt[DTRACEOPT_BUFPOLICY] == DTRACEOPT_BUFPOLICY_FILL)
                        flags |= DTRACEBUF_FILL;

                if (state != dtrace_anon.dta_state ||
                    state->dts_activity != DTRACE_ACTIVITY_ACTIVE)
                        flags |= DTRACEBUF_INACTIVE;
        }

        for (size = opt[which]; (size_t)size >= sizeof (uint64_t); size >>= 1) {
                /*
                 * The size must be 8-byte aligned.  If the size is not 8-byte
                 * aligned, drop it down by the difference.
                 */
                if (size & (sizeof (uint64_t) - 1))
                        size -= size & (sizeof (uint64_t) - 1);

                if (size < state->dts_reserve) {
                        /*
                         * Buffers always must be large enough to accommodate
                         * their prereserved space.  We return E2BIG instead
                         * of ENOMEM in this case to allow for user-level
                         * software to differentiate the cases.
                         */
                        return (E2BIG);
                }
                limit = opt[DTRACEOPT_BUFLIMIT] * size / 100;
                rval = dtrace_buffer_alloc(buf, limit, size, flags, cpu);

                if (rval != ENOMEM) {
                        opt[which] = size;
                        return (rval);
                }

                if (opt[DTRACEOPT_BUFRESIZE] == DTRACEOPT_BUFRESIZE_MANUAL)
                        return (rval);
        }

        return (ENOMEM);
}

static int
dtrace_state_buffers(dtrace_state_t *state)
{
        dtrace_speculation_t *spec = state->dts_speculations;
        int rval, i;

        if ((rval = dtrace_state_buffer(state, state->dts_buffer,
            DTRACEOPT_BUFSIZE)) != 0)
                return (rval);

        if ((rval = dtrace_state_buffer(state, state->dts_aggbuffer,
            DTRACEOPT_AGGSIZE)) != 0)
                return (rval);

        for (i = 0; i < state->dts_nspeculations; i++) {
                if ((rval = dtrace_state_buffer(state,
                    spec[i].dtsp_buffer, DTRACEOPT_SPECSIZE)) != 0)
                        return (rval);
        }

        return (0);
}

static void
dtrace_state_prereserve(dtrace_state_t *state)
{
        dtrace_ecb_t *ecb;
        dtrace_probe_t *probe;

        state->dts_reserve = 0;

        if (state->dts_options[DTRACEOPT_BUFPOLICY] != DTRACEOPT_BUFPOLICY_FILL)
                return;

        /*
         * If our buffer policy is a "fill" buffer policy, we need to set the
         * prereserved space to be the space required by the END probes.
         */
        probe = dtrace_probes[dtrace_probeid_end - 1];
        ASSERT(probe != NULL);

        for (ecb = probe->dtpr_ecb; ecb != NULL; ecb = ecb->dte_next) {
                if (ecb->dte_state != state)
                        continue;

                state->dts_reserve += ecb->dte_needed + ecb->dte_alignment;
        }
}

static int
dtrace_state_go(dtrace_state_t *state, processorid_t *cpu)
{
        dtrace_optval_t *opt = state->dts_options, sz, nspec;
        dtrace_speculation_t *spec;
        dtrace_buffer_t *buf;
        cyc_handler_t hdlr;
        cyc_time_t when;
        int rval = 0, i, bufsize = (int)NCPU * sizeof (dtrace_buffer_t);
        dtrace_icookie_t cookie;

        lck_mtx_lock(&cpu_lock);
        lck_mtx_lock(&dtrace_lock);

        if (state->dts_activity != DTRACE_ACTIVITY_INACTIVE) {
                rval = EBUSY;
                goto out;
        }

        /*
         * Before we can perform any checks, we must prime all of the
         * retained enablings that correspond to this state.
         */
        dtrace_enabling_prime(state);

        if (state->dts_destructive && !state->dts_cred.dcr_destructive) {
                rval = EACCES;
                goto out;
        }

        dtrace_state_prereserve(state);

        /*
         * Now we want to do is try to allocate our speculations.
         * We do not automatically resize the number of speculations; if
         * this fails, we will fail the operation.
         */
        nspec = opt[DTRACEOPT_NSPEC];
        ASSERT(nspec != DTRACEOPT_UNSET);

        if (nspec > INT_MAX) {
                rval = ENOMEM;
                goto out;
        }

        spec = kmem_zalloc(nspec * sizeof (dtrace_speculation_t), KM_NOSLEEP);

        if (spec == NULL) {
                rval = ENOMEM;
                goto out;
        }

        state->dts_speculations = spec;
        state->dts_nspeculations = (int)nspec;

        for (i = 0; i < nspec; i++) {
                if ((buf = kmem_zalloc(bufsize, KM_NOSLEEP)) == NULL) {
                        rval = ENOMEM;
                        goto err;
                }

                spec[i].dtsp_buffer = buf;
        }

        if (opt[DTRACEOPT_GRABANON] != DTRACEOPT_UNSET) {
                if (dtrace_anon.dta_state == NULL) {
                        rval = ENOENT;
                        goto out;
                }

                if (state->dts_necbs != 0) {
                        rval = EALREADY;
                        goto out;
                }

                state->dts_anon = dtrace_anon_grab();
                ASSERT(state->dts_anon != NULL);
                state = state->dts_anon;

                /*
                 * We want "grabanon" to be set in the grabbed state, so we'll
                 * copy that option value from the grabbing state into the
                 * grabbed state.
                 */
                state->dts_options[DTRACEOPT_GRABANON] =
                    opt[DTRACEOPT_GRABANON];

                *cpu = dtrace_anon.dta_beganon;

                /*
                 * If the anonymous state is active (as it almost certainly
                 * is if the anonymous enabling ultimately matched anything),
                 * we don't allow any further option processing -- but we
                 * don't return failure.
                 */
                if (state->dts_activity != DTRACE_ACTIVITY_INACTIVE)
                        goto out;
        }

        if (opt[DTRACEOPT_AGGSIZE] != DTRACEOPT_UNSET &&
            opt[DTRACEOPT_AGGSIZE] != 0) {
                if (state->dts_aggregations == NULL) {
                        /*
                         * We're not going to create an aggregation buffer
                         * because we don't have any ECBs that contain
                         * aggregations -- set this option to 0.
                         */
                        opt[DTRACEOPT_AGGSIZE] = 0;
                } else {
                        /*
                         * If we have an aggregation buffer, we must also have
                         * a buffer to use as scratch.
                         */
                        if (opt[DTRACEOPT_BUFSIZE] == DTRACEOPT_UNSET ||
                          (size_t)opt[DTRACEOPT_BUFSIZE] < state->dts_needed) {
                                opt[DTRACEOPT_BUFSIZE] = state->dts_needed;
                        }
                }
        }

        if (opt[DTRACEOPT_SPECSIZE] != DTRACEOPT_UNSET &&
            opt[DTRACEOPT_SPECSIZE] != 0) {
                if (!state->dts_speculates) {
                        /*
                         * We're not going to create speculation buffers
                         * because we don't have any ECBs that actually
                         * speculate -- set the speculation size to 0.
                         */
                        opt[DTRACEOPT_SPECSIZE] = 0;
                }
        }

        /*
         * The bare minimum size for any buffer that we're actually going to
         * do anything to is sizeof (uint64_t).
         */
        sz = sizeof (uint64_t);

        if ((state->dts_needed != 0 && opt[DTRACEOPT_BUFSIZE] < sz) ||
            (state->dts_speculates && opt[DTRACEOPT_SPECSIZE] < sz) ||
            (state->dts_aggregations != NULL && opt[DTRACEOPT_AGGSIZE] < sz)) {
                /*
                 * A buffer size has been explicitly set to 0 (or to a size
                 * that will be adjusted to 0) and we need the space -- we
                 * need to return failure.  We return ENOSPC to differentiate
                 * it from failing to allocate a buffer due to failure to meet
                 * the reserve (for which we return E2BIG).
                 */
                rval = ENOSPC;
                goto out;
        }

        if ((rval = dtrace_state_buffers(state)) != 0)
                goto err;

        if ((sz = opt[DTRACEOPT_DYNVARSIZE]) == DTRACEOPT_UNSET)
                sz = dtrace_dstate_defsize;

        do {
                rval = dtrace_dstate_init(&state->dts_vstate.dtvs_dynvars, sz);

                if (rval == 0)
                        break;

                if (opt[DTRACEOPT_BUFRESIZE] == DTRACEOPT_BUFRESIZE_MANUAL)
                        goto err;
        } while (sz >>= 1);

        opt[DTRACEOPT_DYNVARSIZE] = sz;

        if (rval != 0)
                goto err;

        if (opt[DTRACEOPT_STATUSRATE] > dtrace_statusrate_max)
                opt[DTRACEOPT_STATUSRATE] = dtrace_statusrate_max;

        if (opt[DTRACEOPT_CLEANRATE] == 0)
                opt[DTRACEOPT_CLEANRATE] = dtrace_cleanrate_max;

        if (opt[DTRACEOPT_CLEANRATE] < dtrace_cleanrate_min)
                opt[DTRACEOPT_CLEANRATE] = dtrace_cleanrate_min;

        if (opt[DTRACEOPT_CLEANRATE] > dtrace_cleanrate_max)
                opt[DTRACEOPT_CLEANRATE] = dtrace_cleanrate_max;

        if (opt[DTRACEOPT_STRSIZE] > dtrace_strsize_max)
                opt[DTRACEOPT_STRSIZE] = dtrace_strsize_max;

        if (opt[DTRACEOPT_STRSIZE] < dtrace_strsize_min)
                opt[DTRACEOPT_STRSIZE] = dtrace_strsize_min;

        if (opt[DTRACEOPT_BUFLIMIT] > dtrace_buflimit_max)
                opt[DTRACEOPT_BUFLIMIT] = dtrace_buflimit_max;

        if (opt[DTRACEOPT_BUFLIMIT] < dtrace_buflimit_min)
                opt[DTRACEOPT_BUFLIMIT] = dtrace_buflimit_min;

        hdlr.cyh_func = (cyc_func_t)dtrace_state_clean;
        hdlr.cyh_arg = state;
        hdlr.cyh_level = CY_LOW_LEVEL;

        when.cyt_when = 0;
        when.cyt_interval = opt[DTRACEOPT_CLEANRATE];

        state->dts_cleaner = cyclic_add(&hdlr, &when);

        hdlr.cyh_func = (cyc_func_t)dtrace_state_deadman;
        hdlr.cyh_arg = state;
        hdlr.cyh_level = CY_LOW_LEVEL;

        when.cyt_when = 0;
        when.cyt_interval = dtrace_deadman_interval;

        state->dts_alive = state->dts_laststatus = dtrace_gethrtime();
        state->dts_deadman = cyclic_add(&hdlr, &when);

        state->dts_activity = DTRACE_ACTIVITY_WARMUP;

        /*
         * Now it's time to actually fire the BEGIN probe.  We need to disable
         * interrupts here both to record the CPU on which we fired the BEGIN
         * probe (the data from this CPU will be processed first at user
         * level) and to manually activate the buffer for this CPU.
         */
        cookie = dtrace_interrupt_disable();
        *cpu = CPU->cpu_id;
        ASSERT(state->dts_buffer[*cpu].dtb_flags & DTRACEBUF_INACTIVE);
        state->dts_buffer[*cpu].dtb_flags &= ~DTRACEBUF_INACTIVE;

        dtrace_probe(dtrace_probeid_begin,
            (uint64_t)(uintptr_t)state, 0, 0, 0, 0);
        dtrace_interrupt_enable(cookie);
        /*
         * We may have had an exit action from a BEGIN probe; only change our
         * state to ACTIVE if we're still in WARMUP.
         */
        ASSERT(state->dts_activity == DTRACE_ACTIVITY_WARMUP ||
            state->dts_activity == DTRACE_ACTIVITY_DRAINING);

        if (state->dts_activity == DTRACE_ACTIVITY_WARMUP)
                state->dts_activity = DTRACE_ACTIVITY_ACTIVE;

        /*
         * Regardless of whether or not now we're in ACTIVE or DRAINING, we
         * want each CPU to transition its principal buffer out of the
         * INACTIVE state.  Doing this assures that no CPU will suddenly begin
         * processing an ECB halfway down a probe's ECB chain; all CPUs will
         * atomically transition from processing none of a state's ECBs to
         * processing all of them.
         */
        dtrace_xcall(DTRACE_CPUALL,
            (dtrace_xcall_t)dtrace_buffer_activate, state);
        goto out;

err:
        dtrace_buffer_free(state->dts_buffer);
        dtrace_buffer_free(state->dts_aggbuffer);

        if ((nspec = state->dts_nspeculations) == 0) {
                ASSERT(state->dts_speculations == NULL);
                goto out;
        }

        spec = state->dts_speculations;
        ASSERT(spec != NULL);

        for (i = 0; i < state->dts_nspeculations; i++) {
                if ((buf = spec[i].dtsp_buffer) == NULL)
                        break;

                dtrace_buffer_free(buf);
                kmem_free(buf, bufsize);
        }

        kmem_free(spec, nspec * sizeof (dtrace_speculation_t));
        state->dts_nspeculations = 0;
        state->dts_speculations = NULL;

out:
        lck_mtx_unlock(&dtrace_lock);
        lck_mtx_unlock(&cpu_lock);

        return (rval);
}

static int
dtrace_state_stop(dtrace_state_t *state, processorid_t *cpu)
{
        dtrace_icookie_t cookie;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);

        if (state->dts_activity != DTRACE_ACTIVITY_ACTIVE &&
            state->dts_activity != DTRACE_ACTIVITY_DRAINING)
                return (EINVAL);

        /*
         * We'll set the activity to DTRACE_ACTIVITY_DRAINING, and issue a sync
         * to be sure that every CPU has seen it.  See below for the details
         * on why this is done.
         */
        state->dts_activity = DTRACE_ACTIVITY_DRAINING;
        dtrace_sync();

        /*
         * By this point, it is impossible for any CPU to be still processing
         * with DTRACE_ACTIVITY_ACTIVE.  We can thus set our activity to
         * DTRACE_ACTIVITY_COOLDOWN and know that we're not racing with any
         * other CPU in dtrace_buffer_reserve().  This allows dtrace_probe()
         * and callees to know that the activity is DTRACE_ACTIVITY_COOLDOWN
         * iff we're in the END probe.
         */
        state->dts_activity = DTRACE_ACTIVITY_COOLDOWN;
        dtrace_sync();
        ASSERT(state->dts_activity == DTRACE_ACTIVITY_COOLDOWN);

        /*
         * Finally, we can release the reserve and call the END probe.  We
         * disable interrupts across calling the END probe to allow us to
         * return the CPU on which we actually called the END probe.  This
         * allows user-land to be sure that this CPU's principal buffer is
         * processed last.
         */
        state->dts_reserve = 0;

        cookie = dtrace_interrupt_disable();
        *cpu = CPU->cpu_id;
        dtrace_probe(dtrace_probeid_end,
            (uint64_t)(uintptr_t)state, 0, 0, 0, 0);
        dtrace_interrupt_enable(cookie);

        state->dts_activity = DTRACE_ACTIVITY_STOPPED;
        dtrace_sync();

        return (0);
}

static int
dtrace_state_option(dtrace_state_t *state, dtrace_optid_t option,
    dtrace_optval_t val)
{
        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);

        if (state->dts_activity != DTRACE_ACTIVITY_INACTIVE)
                return (EBUSY);

        if (option >= DTRACEOPT_MAX)
                return (EINVAL);

        if (option != DTRACEOPT_CPU && val < 0)
                return (EINVAL);

        switch (option) {
        case DTRACEOPT_DESTRUCTIVE:
                /*
                 * Prevent consumers from enabling destructive actions if DTrace
                 * is running in a restricted environment, or if actions are
                 * disallowed.
                 */
                if (dtrace_is_restricted() || dtrace_destructive_disallow)
                        return (EACCES);

                state->dts_cred.dcr_destructive = 1;
                break;

        case DTRACEOPT_BUFSIZE:
        case DTRACEOPT_DYNVARSIZE:
        case DTRACEOPT_AGGSIZE:
        case DTRACEOPT_SPECSIZE:
        case DTRACEOPT_STRSIZE:
                if (val < 0)
                        return (EINVAL);

                if (val >= LONG_MAX) {
                        /*
                         * If this is an otherwise negative value, set it to
                         * the highest multiple of 128m less than LONG_MAX.
                         * Technically, we're adjusting the size without
                         * regard to the buffer resizing policy, but in fact,
                         * this has no effect -- if we set the buffer size to
                         * ~LONG_MAX and the buffer policy is ultimately set to
                         * be "manual", the buffer allocation is guaranteed to
                         * fail, if only because the allocation requires two
                         * buffers.  (We set the the size to the highest
                         * multiple of 128m because it ensures that the size
                         * will remain a multiple of a megabyte when
                         * repeatedly halved -- all the way down to 15m.)
                         */
                        val = LONG_MAX - (1 << 27) + 1;
                }
        }

        state->dts_options[option] = val;

        return (0);
}

static void
dtrace_state_destroy(dtrace_state_t *state)
{
        dtrace_ecb_t *ecb;
        dtrace_vstate_t *vstate = &state->dts_vstate;
        minor_t minor = getminor(state->dts_dev);
        int i, bufsize = (int)NCPU * sizeof (dtrace_buffer_t);
        dtrace_speculation_t *spec = state->dts_speculations;
        int nspec = state->dts_nspeculations;
        uint32_t match;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);
        LCK_MTX_ASSERT(&cpu_lock, LCK_MTX_ASSERT_OWNED);

        /*
         * First, retract any retained enablings for this state.
         */
        dtrace_enabling_retract(state);
        ASSERT(state->dts_nretained == 0);

        if (state->dts_activity == DTRACE_ACTIVITY_ACTIVE ||
            state->dts_activity == DTRACE_ACTIVITY_DRAINING) {
                /*
                 * We have managed to come into dtrace_state_destroy() on a
                 * hot enabling -- almost certainly because of a disorderly
                 * shutdown of a consumer.  (That is, a consumer that is
                 * exiting without having called dtrace_stop().) In this case,
                 * we're going to set our activity to be KILLED, and then
                 * issue a sync to be sure that everyone is out of probe
                 * context before we start blowing away ECBs.
                 */
                state->dts_activity = DTRACE_ACTIVITY_KILLED;
                dtrace_sync();
        }

        /*
         * Release the credential hold we took in dtrace_state_create().
         */
        if (state->dts_cred.dcr_cred != NULL)
                kauth_cred_unref(&state->dts_cred.dcr_cred);

        /*
         * Now we can safely disable and destroy any enabled probes.  Because
         * any DTRACE_PRIV_KERNEL probes may actually be slowing our progress
         * (especially if they're all enabled), we take two passes through the
         * ECBs:  in the first, we disable just DTRACE_PRIV_KERNEL probes, and
         * in the second we disable whatever is left over.
         */
        for (match = DTRACE_PRIV_KERNEL; ; match = 0) {
                for (i = 0; i < state->dts_necbs; i++) {
                        if ((ecb = state->dts_ecbs[i]) == NULL)
                                continue;

                        if (match && ecb->dte_probe != NULL) {
                                dtrace_probe_t *probe = ecb->dte_probe;
                                dtrace_provider_t *prov = probe->dtpr_provider;

                                if (!(prov->dtpv_priv.dtpp_flags & match))
                                        continue;
                        }

                        dtrace_ecb_disable(ecb);
                        dtrace_ecb_destroy(ecb);
                }

                if (!match)
                        break;
        }

        /*
         * Before we free the buffers, perform one more sync to assure that
         * every CPU is out of probe context.
         */
        dtrace_sync();

        dtrace_buffer_free(state->dts_buffer);
        dtrace_buffer_free(state->dts_aggbuffer);

        for (i = 0; i < (int)NCPU; i++) {
                kmem_free(state->dts_rstate[i], 2 * sizeof(uint64_t));
        }
        kmem_free(state->dts_rstate, NCPU * sizeof(uint64_t*));

        for (i = 0; i < nspec; i++)
                dtrace_buffer_free(spec[i].dtsp_buffer);

        if (state->dts_cleaner != CYCLIC_NONE)
                cyclic_remove(state->dts_cleaner);

        if (state->dts_deadman != CYCLIC_NONE)
                cyclic_remove(state->dts_deadman);

        dtrace_dstate_fini(&vstate->dtvs_dynvars);
        dtrace_vstate_fini(vstate);
        kmem_free(state->dts_ecbs, state->dts_necbs * sizeof (dtrace_ecb_t *));

        if (state->dts_aggregations != NULL) {
#if DEBUG
                for (i = 0; i < state->dts_naggregations; i++)
                        ASSERT(state->dts_aggregations[i] == NULL);
#endif
                ASSERT(state->dts_naggregations > 0);
                kmem_free(state->dts_aggregations,
                    state->dts_naggregations * sizeof (dtrace_aggregation_t *));
        }

        kmem_free(state->dts_buffer, bufsize);
        kmem_free(state->dts_aggbuffer, bufsize);

        for (i = 0; i < nspec; i++)
                kmem_free(spec[i].dtsp_buffer, bufsize);

        kmem_free(spec, nspec * sizeof (dtrace_speculation_t));

        dtrace_format_destroy(state);

        vmem_destroy(state->dts_aggid_arena);
        dtrace_state_free(minor);
}

/*
 * DTrace Anonymous Enabling Functions
 */

int
dtrace_keep_kernel_symbols(void)
{
        if (dtrace_is_restricted() && !dtrace_are_restrictions_relaxed()) {
                return 0;
        }

        if (dtrace_kernel_symbol_mode == DTRACE_KERNEL_SYMBOLS_ALWAYS_FROM_KERNEL)
                return 1;

        return 0;
}

static dtrace_state_t *
dtrace_anon_grab(void)
{
        dtrace_state_t *state;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);

        if ((state = dtrace_anon.dta_state) == NULL) {
                ASSERT(dtrace_anon.dta_enabling == NULL);
                return (NULL);
        }

        ASSERT(dtrace_anon.dta_enabling != NULL);
        ASSERT(dtrace_retained != NULL);

        dtrace_enabling_destroy(dtrace_anon.dta_enabling);
        dtrace_anon.dta_enabling = NULL;
        dtrace_anon.dta_state = NULL;

        return (state);
}

static void
dtrace_anon_property(void)
{
        int i, rv;
        dtrace_state_t *state;
        dof_hdr_t *dof;
        char c[32];             /* enough for "dof-data-" + digits */

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);
        LCK_MTX_ASSERT(&cpu_lock, LCK_MTX_ASSERT_OWNED);

        for (i = 0; ; i++) {
                (void) snprintf(c, sizeof (c), "dof-data-%d", i);

                dtrace_err_verbose = 1;

                if ((dof = dtrace_dof_property(c)) == NULL) {
                        dtrace_err_verbose = 0;
                        break;
                }

#ifdef illumos
                /*
                 * We want to create anonymous state, so we need to transition
                 * the kernel debugger to indicate that DTrace is active.  If
                 * this fails (e.g. because the debugger has modified text in
                 * some way), we won't continue with the processing.
                 */
                if (kdi_dtrace_set(KDI_DTSET_DTRACE_ACTIVATE) != 0) {
                        cmn_err(CE_NOTE, "kernel debugger active; anonymous "
                            "enabling ignored.");
                        dtrace_dof_destroy(dof);
                        break;
                }
#endif

                /*
                 * If we haven't allocated an anonymous state, we'll do so now.
                 */
                if ((state = dtrace_anon.dta_state) == NULL) {
                        rv = dtrace_state_create(NULL, NULL, &state);
                        dtrace_anon.dta_state = state;
                        if (rv != 0 || state == NULL) {
                                /*
                                 * This basically shouldn't happen:  the only
                                 * failure mode from dtrace_state_create() is a
                                 * failure of ddi_soft_state_zalloc() that
                                 * itself should never happen.  Still, the
                                 * interface allows for a failure mode, and
                                 * we want to fail as gracefully as possible:
                                 * we'll emit an error message and cease
                                 * processing anonymous state in this case.
                                 */
                                cmn_err(CE_WARN, "failed to create "
                                    "anonymous state");
                                dtrace_dof_destroy(dof);
                                break;
                        }
                }

                rv = dtrace_dof_slurp(dof, &state->dts_vstate, CRED(),
                    &dtrace_anon.dta_enabling, 0, B_TRUE);

                if (rv == 0)
                        rv = dtrace_dof_options(dof, state);

                dtrace_err_verbose = 0;
                dtrace_dof_destroy(dof);

                if (rv != 0) {
                        /*
                         * This is malformed DOF; chuck any anonymous state
                         * that we created.
                         */
                        ASSERT(dtrace_anon.dta_enabling == NULL);
                        dtrace_state_destroy(state);
                        dtrace_anon.dta_state = NULL;
                        break;
                }

                ASSERT(dtrace_anon.dta_enabling != NULL);
        }

        if (dtrace_anon.dta_enabling != NULL) {
                int rval;

                /*
                 * dtrace_enabling_retain() can only fail because we are
                 * trying to retain more enablings than are allowed -- but
                 * we only have one anonymous enabling, and we are guaranteed
                 * to be allowed at least one retained enabling; we assert
                 * that dtrace_enabling_retain() returns success.
                 */
                rval = dtrace_enabling_retain(dtrace_anon.dta_enabling);
                ASSERT(rval == 0);

                dtrace_enabling_dump(dtrace_anon.dta_enabling);
        }
}

/*
 * DTrace Helper Functions
 */
static void
dtrace_helper_trace(dtrace_helper_action_t *helper,
    dtrace_mstate_t *mstate, dtrace_vstate_t *vstate, int where)
{
        uint32_t size, next, nnext;
        int i;
        dtrace_helptrace_t *ent;
        uint16_t flags = cpu_core[CPU->cpu_id].cpuc_dtrace_flags;

        if (!dtrace_helptrace_enabled)
                return;

        ASSERT((uint32_t)vstate->dtvs_nlocals <= dtrace_helptrace_nlocals);

        /*
         * What would a tracing framework be without its own tracing
         * framework?  (Well, a hell of a lot simpler, for starters...)
         */
        size = sizeof (dtrace_helptrace_t) + dtrace_helptrace_nlocals *
            sizeof (uint64_t) - sizeof (uint64_t);

        /*
         * Iterate until we can allocate a slot in the trace buffer.
         */
        do {
                next = dtrace_helptrace_next;

                if (next + size < dtrace_helptrace_bufsize) {
                        nnext = next + size;
                } else {
                        nnext = size;
                }
        } while (dtrace_cas32(&dtrace_helptrace_next, next, nnext) != next);

        /*
         * We have our slot; fill it in.
         */
        if (nnext == size)
                next = 0;

        ent = (dtrace_helptrace_t *)&dtrace_helptrace_buffer[next];
        ent->dtht_helper = helper;
        ent->dtht_where = where;
        ent->dtht_nlocals = vstate->dtvs_nlocals;

        ent->dtht_fltoffs = (mstate->dtms_present & DTRACE_MSTATE_FLTOFFS) ?
            mstate->dtms_fltoffs : -1;
        ent->dtht_fault = DTRACE_FLAGS2FLT(flags);
        ent->dtht_illval = cpu_core[CPU->cpu_id].cpuc_dtrace_illval;

        for (i = 0; i < vstate->dtvs_nlocals; i++) {
                dtrace_statvar_t *svar;

                if ((svar = vstate->dtvs_locals[i]) == NULL)
                        continue;

                ASSERT(svar->dtsv_size >= (int)NCPU * sizeof (uint64_t));
                ent->dtht_locals[i] =
                    ((uint64_t *)(uintptr_t)svar->dtsv_data)[CPU->cpu_id];
        }
}

static uint64_t
dtrace_helper(int which, dtrace_mstate_t *mstate,
    dtrace_state_t *state, uint64_t arg0, uint64_t arg1)
{
        uint16_t *flags = &cpu_core[CPU->cpu_id].cpuc_dtrace_flags;
        uint64_t sarg0 = mstate->dtms_arg[0];
        uint64_t sarg1 = mstate->dtms_arg[1];
        uint64_t rval = 0;
        dtrace_helpers_t *helpers = curproc->p_dtrace_helpers;
        dtrace_helper_action_t *helper;
        dtrace_vstate_t *vstate;
        dtrace_difo_t *pred;
        int i, trace = dtrace_helptrace_enabled;

        ASSERT(which >= 0 && which < DTRACE_NHELPER_ACTIONS);

        if (helpers == NULL)
                return (0);

        if ((helper = helpers->dthps_actions[which]) == NULL)
                return (0);

        vstate = &helpers->dthps_vstate;
        mstate->dtms_arg[0] = arg0;
        mstate->dtms_arg[1] = arg1;

        /*
         * Now iterate over each helper.  If its predicate evaluates to 'true',
         * we'll call the corresponding actions.  Note that the below calls
         * to dtrace_dif_emulate() may set faults in machine state.  This is
         * okay:  our caller (the outer dtrace_dif_emulate()) will simply plow
         * the stored DIF offset with its own (which is the desired behavior).
         * Also, note the calls to dtrace_dif_emulate() may allocate scratch
         * from machine state; this is okay, too.
         */
        for (; helper != NULL; helper = helper->dtha_next) {
                if ((pred = helper->dtha_predicate) != NULL) {
                        if (trace)
                                dtrace_helper_trace(helper, mstate, vstate, 0);

                        if (!dtrace_dif_emulate(pred, mstate, vstate, state))
                                goto next;

                        if (*flags & CPU_DTRACE_FAULT)
                                goto err;
                }

                for (i = 0; i < helper->dtha_nactions; i++) {
                        if (trace)
                                dtrace_helper_trace(helper,
                                    mstate, vstate, i + 1);

                        rval = dtrace_dif_emulate(helper->dtha_actions[i],
                            mstate, vstate, state);

                        if (*flags & CPU_DTRACE_FAULT)
                                goto err;
                }

next:
                if (trace)
                        dtrace_helper_trace(helper, mstate, vstate,
                            DTRACE_HELPTRACE_NEXT);
        }

        if (trace)
                dtrace_helper_trace(helper, mstate, vstate,
                    DTRACE_HELPTRACE_DONE);

        /*
         * Restore the arg0 that we saved upon entry.
         */
        mstate->dtms_arg[0] = sarg0;
        mstate->dtms_arg[1] = sarg1;

        return (rval);

err:
        if (trace)
                dtrace_helper_trace(helper, mstate, vstate,
                    DTRACE_HELPTRACE_ERR);

        /*
         * Restore the arg0 that we saved upon entry.
         */
        mstate->dtms_arg[0] = sarg0;
        mstate->dtms_arg[1] = sarg1;

        return (0);
}

static void
dtrace_helper_action_destroy(dtrace_helper_action_t *helper,
    dtrace_vstate_t *vstate)
{
        int i;

        if (helper->dtha_predicate != NULL)
                dtrace_difo_release(helper->dtha_predicate, vstate);

        for (i = 0; i < helper->dtha_nactions; i++) {
                ASSERT(helper->dtha_actions[i] != NULL);
                dtrace_difo_release(helper->dtha_actions[i], vstate);
        }

        kmem_free(helper->dtha_actions,
            helper->dtha_nactions * sizeof (dtrace_difo_t *));
        kmem_free(helper, sizeof (dtrace_helper_action_t));
}

static int
dtrace_helper_destroygen(proc_t* p, int gen)
{
        dtrace_helpers_t *help = p->p_dtrace_helpers;
        dtrace_vstate_t *vstate;
        uint_t i;

        LCK_MTX_ASSERT(&dtrace_meta_lock, LCK_MTX_ASSERT_OWNED);
        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);

        if (help == NULL || gen > help->dthps_generation)
                return (EINVAL);

        vstate = &help->dthps_vstate;

        for (i = 0; i < DTRACE_NHELPER_ACTIONS; i++) {
                dtrace_helper_action_t *last = NULL, *h, *next;

                for (h = help->dthps_actions[i]; h != NULL; h = next) {
                        next = h->dtha_next;

                        if (h->dtha_generation == gen) {
                                if (last != NULL) {
                                        last->dtha_next = next;
                                } else {
                                        help->dthps_actions[i] = next;
                                }

                                dtrace_helper_action_destroy(h, vstate);
                        } else {
                                last = h;
                        }
                }
        }

        /*
         * Interate until we've cleared out all helper providers with the
         * given generation number.
         */
        for (;;) {
                dtrace_helper_provider_t *prov = NULL;

                /*
                 * Look for a helper provider with the right generation. We
                 * have to start back at the beginning of the list each time
                 * because we drop dtrace_lock. It's unlikely that we'll make
                 * more than two passes.
                 */
                for (i = 0; i < help->dthps_nprovs; i++) {
                        prov = help->dthps_provs[i];

                        if (prov->dthp_generation == gen)
                                break;
                }

                /*
                 * If there were no matches, we're done.
                 */
                if (i == help->dthps_nprovs)
                        break;

                /*
                 * Move the last helper provider into this slot.
                 */
                help->dthps_nprovs--;
                help->dthps_provs[i] = help->dthps_provs[help->dthps_nprovs];
                help->dthps_provs[help->dthps_nprovs] = NULL;

                lck_mtx_unlock(&dtrace_lock);

                /*
                 * If we have a meta provider, remove this helper provider.
                 */
                if (dtrace_meta_pid != NULL) {
                        ASSERT(dtrace_deferred_pid == NULL);
                        dtrace_helper_provider_remove(&prov->dthp_prov,
                            p);
                }

                dtrace_helper_provider_destroy(prov);

                lck_mtx_lock(&dtrace_lock);
        }

        return (0);
}

static int
dtrace_helper_validate(dtrace_helper_action_t *helper)
{
        int err = 0, i;
        dtrace_difo_t *dp;

        if ((dp = helper->dtha_predicate) != NULL)
                err += dtrace_difo_validate_helper(dp);

        for (i = 0; i < helper->dtha_nactions; i++)
                err += dtrace_difo_validate_helper(helper->dtha_actions[i]);

        return (err == 0);
}

static int
dtrace_helper_action_add(proc_t* p, int which, dtrace_ecbdesc_t *ep)
{
        dtrace_helpers_t *help;
        dtrace_helper_action_t *helper, *last;
        dtrace_actdesc_t *act;
        dtrace_vstate_t *vstate;
        dtrace_predicate_t *pred;
        int count = 0, nactions = 0, i;

        if (which < 0 || which >= DTRACE_NHELPER_ACTIONS)
                return (EINVAL);

        help = p->p_dtrace_helpers;
        last = help->dthps_actions[which];
        vstate = &help->dthps_vstate;

        for (count = 0; last != NULL; last = last->dtha_next) {
                count++;
                if (last->dtha_next == NULL)
                        break;
        }

        /*
         * If we already have dtrace_helper_actions_max helper actions for this
         * helper action type, we'll refuse to add a new one.
         */
        if (count >= dtrace_helper_actions_max)
                return (ENOSPC);

        helper = kmem_zalloc(sizeof (dtrace_helper_action_t), KM_SLEEP);
        helper->dtha_generation = help->dthps_generation;

        if ((pred = ep->dted_pred.dtpdd_predicate) != NULL) {
                ASSERT(pred->dtp_difo != NULL);
                dtrace_difo_hold(pred->dtp_difo);
                helper->dtha_predicate = pred->dtp_difo;
        }

        for (act = ep->dted_action; act != NULL; act = act->dtad_next) {
                if (act->dtad_kind != DTRACEACT_DIFEXPR)
                        goto err;

                if (act->dtad_difo == NULL)
                        goto err;

                nactions++;
        }

        helper->dtha_actions = kmem_zalloc(sizeof (dtrace_difo_t *) *
            (helper->dtha_nactions = nactions), KM_SLEEP);

        for (act = ep->dted_action, i = 0; act != NULL; act = act->dtad_next) {
                dtrace_difo_hold(act->dtad_difo);
                helper->dtha_actions[i++] = act->dtad_difo;
        }

        if (!dtrace_helper_validate(helper))
                goto err;

        if (last == NULL) {
                help->dthps_actions[which] = helper;
        } else {
                last->dtha_next = helper;
        }

        if ((uint32_t)vstate->dtvs_nlocals > dtrace_helptrace_nlocals) {
                dtrace_helptrace_nlocals = vstate->dtvs_nlocals;
                dtrace_helptrace_next = 0;
        }

        return (0);
err:
        dtrace_helper_action_destroy(helper, vstate);
        return (EINVAL);
}

static void
dtrace_helper_provider_register(proc_t *p, dtrace_helpers_t *help,
    dof_helper_t *dofhp)
{
        LCK_MTX_ASSERT(&dtrace_meta_lock, LCK_MTX_ASSERT_OWNED);
        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_NOTOWNED);

        lck_mtx_lock(&dtrace_lock);

        if (!dtrace_attached() || dtrace_meta_pid == NULL) {
                /*
                 * If the dtrace module is loaded but not attached, or if
                 * there aren't isn't a meta provider registered to deal with
                 * these provider descriptions, we need to postpone creating
                 * the actual providers until later.
                 */

                if (help->dthps_next == NULL && help->dthps_prev == NULL &&
                    dtrace_deferred_pid != help) {
                        help->dthps_deferred = 1;
                        help->dthps_pid = p->p_pid;
                        help->dthps_next = dtrace_deferred_pid;
                        help->dthps_prev = NULL;
                        if (dtrace_deferred_pid != NULL)
                                dtrace_deferred_pid->dthps_prev = help;
                        dtrace_deferred_pid = help;
                }

                lck_mtx_unlock(&dtrace_lock);

        } else if (dofhp != NULL) {
                /*
                 * If the dtrace module is loaded and we have a particular
                 * helper provider description, pass that off to the
                 * meta provider.
                 */

                lck_mtx_unlock(&dtrace_lock);

                dtrace_helper_provide(dofhp, p);

        } else {
                /*
                 * Otherwise, just pass all the helper provider descriptions
                 * off to the meta provider.
                 */

                uint_t i;
                lck_mtx_unlock(&dtrace_lock);

                for (i = 0; i < help->dthps_nprovs; i++) {
                        dtrace_helper_provide(&help->dthps_provs[i]->dthp_prov,
                                p);
                }
        }
}

static int
dtrace_helper_provider_add(proc_t* p, dof_helper_t *dofhp, int gen)
{
        dtrace_helpers_t *help;
        dtrace_helper_provider_t *hprov, **tmp_provs;
        uint_t tmp_maxprovs, i;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);
        help = p->p_dtrace_helpers;
        ASSERT(help != NULL);

        /*
         * If we already have dtrace_helper_providers_max helper providers,
         * we're refuse to add a new one.
         */
        if (help->dthps_nprovs >= dtrace_helper_providers_max)
                return (ENOSPC);

        /*
         * Check to make sure this isn't a duplicate.
         */
        for (i = 0; i < help->dthps_nprovs; i++) {
                if (dofhp->dofhp_addr ==
                    help->dthps_provs[i]->dthp_prov.dofhp_addr)
                        return (EALREADY);
        }

        hprov = kmem_zalloc(sizeof (dtrace_helper_provider_t), KM_SLEEP);
        hprov->dthp_prov = *dofhp;
        hprov->dthp_ref = 1;
        hprov->dthp_generation = gen;

        /*
         * Allocate a bigger table for helper providers if it's already full.
         */
        if (help->dthps_maxprovs == help->dthps_nprovs) {
                tmp_maxprovs = help->dthps_maxprovs;
                tmp_provs = help->dthps_provs;

                if (help->dthps_maxprovs == 0)
                        help->dthps_maxprovs = 2;
                else
                        help->dthps_maxprovs *= 2;
                if (help->dthps_maxprovs > dtrace_helper_providers_max)
                        help->dthps_maxprovs = dtrace_helper_providers_max;

                ASSERT(tmp_maxprovs < help->dthps_maxprovs);

                help->dthps_provs = kmem_zalloc(help->dthps_maxprovs *
                    sizeof (dtrace_helper_provider_t *), KM_SLEEP);

                if (tmp_provs != NULL) {
                        bcopy(tmp_provs, help->dthps_provs, tmp_maxprovs *
                            sizeof (dtrace_helper_provider_t *));
                        kmem_free(tmp_provs, tmp_maxprovs *
                            sizeof (dtrace_helper_provider_t *));
                }
        }

        help->dthps_provs[help->dthps_nprovs] = hprov;
        help->dthps_nprovs++;

        return (0);
}

static void
dtrace_helper_provider_destroy(dtrace_helper_provider_t *hprov)
{
        lck_mtx_lock(&dtrace_lock);

        if (--hprov->dthp_ref == 0) {
                dof_hdr_t *dof;
                lck_mtx_unlock(&dtrace_lock);
                dof = (dof_hdr_t *)(uintptr_t)hprov->dthp_prov.dofhp_dof;
                dtrace_dof_destroy(dof);
                kmem_free(hprov, sizeof (dtrace_helper_provider_t));
        } else {
                lck_mtx_unlock(&dtrace_lock);
        }
}

static int
dtrace_helper_provider_validate(dof_hdr_t *dof, dof_sec_t *sec)
{
        uintptr_t daddr = (uintptr_t)dof;
        dof_sec_t *str_sec, *prb_sec, *arg_sec, *off_sec, *enoff_sec;
        dof_provider_t *provider;
        dof_probe_t *probe;
        uint8_t *arg;
        char *strtab, *typestr;
        dof_stridx_t typeidx;
        size_t typesz;
        uint_t nprobes, j, k;

        ASSERT(sec->dofs_type == DOF_SECT_PROVIDER);

        if (sec->dofs_offset & (sizeof (uint_t) - 1)) {
                dtrace_dof_error(dof, "misaligned section offset");
                return (-1);
        }

        /*
         * The section needs to be large enough to contain the DOF provider
         * structure appropriate for the given version.
         */
        if (sec->dofs_size <
            ((dof->dofh_ident[DOF_ID_VERSION] == DOF_VERSION_1) ?
            offsetof(dof_provider_t, dofpv_prenoffs) :
            sizeof (dof_provider_t))) {
                dtrace_dof_error(dof, "provider section too small");
                return (-1);
        }

        provider = (dof_provider_t *)(uintptr_t)(daddr + sec->dofs_offset);
        str_sec = dtrace_dof_sect(dof, DOF_SECT_STRTAB, provider->dofpv_strtab);
        prb_sec = dtrace_dof_sect(dof, DOF_SECT_PROBES, provider->dofpv_probes);
        arg_sec = dtrace_dof_sect(dof, DOF_SECT_PRARGS, provider->dofpv_prargs);
        off_sec = dtrace_dof_sect(dof, DOF_SECT_PROFFS, provider->dofpv_proffs);

        if (str_sec == NULL || prb_sec == NULL ||
            arg_sec == NULL || off_sec == NULL)
                return (-1);

        enoff_sec = NULL;

        if (dof->dofh_ident[DOF_ID_VERSION] != DOF_VERSION_1 &&
            provider->dofpv_prenoffs != DOF_SECT_NONE &&
            (enoff_sec = dtrace_dof_sect(dof, DOF_SECT_PRENOFFS,
            provider->dofpv_prenoffs)) == NULL)
                return (-1);

        strtab = (char *)(uintptr_t)(daddr + str_sec->dofs_offset);

        if (provider->dofpv_name >= str_sec->dofs_size ||
            strlen(strtab + provider->dofpv_name) >= DTRACE_PROVNAMELEN) {
                dtrace_dof_error(dof, "invalid provider name");
                return (-1);
        }

        if (prb_sec->dofs_entsize == 0 ||
            prb_sec->dofs_entsize > prb_sec->dofs_size) {
                dtrace_dof_error(dof, "invalid entry size");
                return (-1);
        }

        if (prb_sec->dofs_entsize & (sizeof (uintptr_t) - 1)) {
                dtrace_dof_error(dof, "misaligned entry size");
                return (-1);
        }

        if (off_sec->dofs_entsize != sizeof (uint32_t)) {
                dtrace_dof_error(dof, "invalid entry size");
                return (-1);
        }

        if (off_sec->dofs_offset & (sizeof (uint32_t) - 1)) {
                dtrace_dof_error(dof, "misaligned section offset");
                return (-1);
        }

        if (arg_sec->dofs_entsize != sizeof (uint8_t)) {
                dtrace_dof_error(dof, "invalid entry size");
                return (-1);
        }

        arg = (uint8_t *)(uintptr_t)(daddr + arg_sec->dofs_offset);

        nprobes = prb_sec->dofs_size / prb_sec->dofs_entsize;

        /*
         * Take a pass through the probes to check for errors.
         */
        for (j = 0; j < nprobes; j++) {
                probe = (dof_probe_t *)(uintptr_t)(daddr +
                    prb_sec->dofs_offset + j * prb_sec->dofs_entsize);

                if (probe->dofpr_func >= str_sec->dofs_size) {
                        dtrace_dof_error(dof, "invalid function name");
                        return (-1);
                }

                if (strlen(strtab + probe->dofpr_func) >= DTRACE_FUNCNAMELEN) {
                        dtrace_dof_error(dof, "function name too long");
                        return (-1);
                }

                if (probe->dofpr_name >= str_sec->dofs_size ||
                    strlen(strtab + probe->dofpr_name) >= DTRACE_NAMELEN) {
                        dtrace_dof_error(dof, "invalid probe name");
                        return (-1);
                }

                /*
                 * The offset count must not wrap the index, and the offsets
                 * must also not overflow the section's data.
                 */
                if (probe->dofpr_offidx + probe->dofpr_noffs <
                    probe->dofpr_offidx ||
                    (probe->dofpr_offidx + probe->dofpr_noffs) *
                    off_sec->dofs_entsize > off_sec->dofs_size) {
                        dtrace_dof_error(dof, "invalid probe offset");
                        return (-1);
                }

                if (dof->dofh_ident[DOF_ID_VERSION] != DOF_VERSION_1) {
                        /*
                         * If there's no is-enabled offset section, make sure
                         * there aren't any is-enabled offsets. Otherwise
                         * perform the same checks as for probe offsets
                         * (immediately above).
                         */
                        if (enoff_sec == NULL) {
                                if (probe->dofpr_enoffidx != 0 ||
                                    probe->dofpr_nenoffs != 0) {
                                        dtrace_dof_error(dof, "is-enabled "
                                            "offsets with null section");
                                        return (-1);
                                }
                        } else if (probe->dofpr_enoffidx +
                            probe->dofpr_nenoffs < probe->dofpr_enoffidx ||
                            (probe->dofpr_enoffidx + probe->dofpr_nenoffs) *
                            enoff_sec->dofs_entsize > enoff_sec->dofs_size) {
                                dtrace_dof_error(dof, "invalid is-enabled "
                                    "offset");
                                return (-1);
                        }

                        if (probe->dofpr_noffs + probe->dofpr_nenoffs == 0) {
                                dtrace_dof_error(dof, "zero probe and "
                                    "is-enabled offsets");
                                return (-1);
                        }
                } else if (probe->dofpr_noffs == 0) {
                        dtrace_dof_error(dof, "zero probe offsets");
                        return (-1);
                }

                if (probe->dofpr_argidx + probe->dofpr_xargc <
                    probe->dofpr_argidx ||
                    (probe->dofpr_argidx + probe->dofpr_xargc) *
                    arg_sec->dofs_entsize > arg_sec->dofs_size) {
                        dtrace_dof_error(dof, "invalid args");
                        return (-1);
                }

                typeidx = probe->dofpr_nargv;
                typestr = strtab + probe->dofpr_nargv;
                for (k = 0; k < probe->dofpr_nargc; k++) {
                        if (typeidx >= str_sec->dofs_size) {
                                dtrace_dof_error(dof, "bad "
                                    "native argument type");
                                return (-1);
                        }

                        typesz = strlen(typestr) + 1;
                        if (typesz > DTRACE_ARGTYPELEN) {
                                dtrace_dof_error(dof, "native "
                                    "argument type too long");
                                return (-1);
                        }
                        typeidx += typesz;
                        typestr += typesz;
                }

                typeidx = probe->dofpr_xargv;
                typestr = strtab + probe->dofpr_xargv;
                for (k = 0; k < probe->dofpr_xargc; k++) {
                        if (arg[probe->dofpr_argidx + k] > probe->dofpr_nargc) {
                                dtrace_dof_error(dof, "bad "
                                    "native argument index");
                                return (-1);
                        }

                        if (typeidx >= str_sec->dofs_size) {
                                dtrace_dof_error(dof, "bad "
                                    "translated argument type");
                                return (-1);
                        }

                        typesz = strlen(typestr) + 1;
                        if (typesz > DTRACE_ARGTYPELEN) {
                                dtrace_dof_error(dof, "translated argument "
                                    "type too long");
                                return (-1);
                        }

                        typeidx += typesz;
                        typestr += typesz;
                }
        }

        return (0);
}

static int
dtrace_helper_slurp(proc_t* p, dof_hdr_t *dof, dof_helper_t *dhp)
{
        dtrace_helpers_t *help;
        dtrace_vstate_t *vstate;
        dtrace_enabling_t *enab = NULL;
        int i, gen, rv, nhelpers = 0, nprovs = 0, destroy = 1;
        uintptr_t daddr = (uintptr_t)dof;

        LCK_MTX_ASSERT(&dtrace_meta_lock, LCK_MTX_ASSERT_OWNED);
        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);

        if ((help = p->p_dtrace_helpers) == NULL)
                help = dtrace_helpers_create(p);

        vstate = &help->dthps_vstate;

        if ((rv = dtrace_dof_slurp(dof, vstate, NULL, &enab,
            dhp != NULL ? dhp->dofhp_addr : 0, B_FALSE)) != 0) {
                dtrace_dof_destroy(dof);
                return (rv);
        }

        /*
         * Look for helper providers and validate their descriptions.
         */
        if (dhp != NULL) {
                for (i = 0; (uint32_t)i < dof->dofh_secnum; i++) {
                        dof_sec_t *sec = (dof_sec_t *)(uintptr_t)(daddr +
                            dof->dofh_secoff + i * dof->dofh_secsize);

                        if (sec->dofs_type != DOF_SECT_PROVIDER)
                                continue;

                        if (dtrace_helper_provider_validate(dof, sec) != 0) {
                                dtrace_enabling_destroy(enab);
                                dtrace_dof_destroy(dof);
                                return (-1);
                        }

                        nprovs++;
                }
        }

        /*
         * Now we need to walk through the ECB descriptions in the enabling.
         */
        for (i = 0; i < enab->dten_ndesc; i++) {
                dtrace_ecbdesc_t *ep = enab->dten_desc[i];
                dtrace_probedesc_t *desc = &ep->dted_probe;

                /* APPLE NOTE: Darwin employs size bounded string operation. */
                if (!LIT_STRNEQL(desc->dtpd_provider, "dtrace"))
                        continue;

                if (!LIT_STRNEQL(desc->dtpd_mod, "helper"))
                        continue;

                if (!LIT_STRNEQL(desc->dtpd_func, "ustack"))
                        continue;

                if ((rv = dtrace_helper_action_add(p, DTRACE_HELPER_ACTION_USTACK,
                    ep)) != 0) {
                        /*
                         * Adding this helper action failed -- we are now going
                         * to rip out the entire generation and return failure.
                         */
                        (void) dtrace_helper_destroygen(p, help->dthps_generation);
                        dtrace_enabling_destroy(enab);
                        dtrace_dof_destroy(dof);
                        return (-1);
                }

                nhelpers++;
        }

        if (nhelpers < enab->dten_ndesc)
                dtrace_dof_error(dof, "unmatched helpers");

        gen = help->dthps_generation++;
        dtrace_enabling_destroy(enab);

        if (dhp != NULL && nprovs > 0) {
                dhp->dofhp_dof = (uint64_t)(uintptr_t)dof;
                if (dtrace_helper_provider_add(p, dhp, gen) == 0) {
                        lck_mtx_unlock(&dtrace_lock);
                        dtrace_helper_provider_register(p, help, dhp);
                        lck_mtx_lock(&dtrace_lock);

                        destroy = 0;
                }
        }

        if (destroy)
                dtrace_dof_destroy(dof);

        return (gen);
}

/*
 * APPLE NOTE:  DTrace lazy dof implementation
 *
 * DTrace user static probes (USDT probes) and helper actions are loaded
 * in a process by proccessing dof sections. The dof sections are passed
 * into the kernel by dyld, in a dof_ioctl_data_t block. It is rather
 * expensive to process dof for a process that will never use it. There
 * is a memory cost (allocating the providers/probes), and a cpu cost
 * (creating the providers/probes).
 *
 * To reduce this cost, we use "lazy dof". The normal proceedure for
 * dof processing is to copyin the dof(s) pointed to by the dof_ioctl_data_t
 * block, and invoke dof_slurp_helper() on them. When "lazy dof" is
 * used, each process retains the dof_ioctl_data_t block, instead of
 * copying in the data it points to.
 *
 * The dof_ioctl_data_t blocks are managed as if they were the actual
 * processed dof; on fork the block is copied to the child, on exec and
 * exit the block is freed.
 *
 * If the process loads library(s) containing additional dof, the
 * new dof_ioctl_data_t is merged with the existing block.
 *
 * There are a few catches that make this slightly more difficult.
 * When dyld registers dof_ioctl_data_t blocks, it expects a unique
 * identifier value for each dof in the block. In non-lazy dof terms,
 * this is the generation that dof was loaded in. If we hand back
 * a UID for a lazy dof, that same UID must be able to unload the
 * dof once it has become non-lazy. To meet this requirement, the
 * code that loads lazy dof requires that the UID's for dof(s) in
 * the lazy dof be sorted, and in ascending order. It is okay to skip
 * UID's, I.E., 1 -> 5 -> 6 is legal.
 *
 * Once a process has become non-lazy, it will stay non-lazy. All
 * future dof operations for that process will be non-lazy, even
 * if the dof mode transitions back to lazy.
 *
 * Always do lazy dof checks before non-lazy (I.E. In fork, exit, exec.).
 * That way if the lazy check fails due to transitioning to non-lazy, the
 * right thing is done with the newly faulted in dof.
 */

/*
 * This method is a bit squicky. It must handle:
 *
 * dof should not be lazy.
 * dof should have been handled lazily, but there was an error
 * dof was handled lazily, and needs to be freed.
 * dof was handled lazily, and must not be freed.
 *
 * 
 * Returns EACCESS if dof should be handled non-lazily.
 * 
 * KERN_SUCCESS and all other return codes indicate lazy handling of dof.
 * 
 * If the dofs data is claimed by this method, dofs_claimed will be set.
 * Callers should not free claimed dofs.
 */
static int
dtrace_lazy_dofs_add(proc_t *p, dof_ioctl_data_t* incoming_dofs, int *dofs_claimed)
{
        ASSERT(p);
        ASSERT(incoming_dofs && incoming_dofs->dofiod_count > 0);

        int rval = 0;
        *dofs_claimed = 0;

        lck_rw_lock_shared(&dtrace_dof_mode_lock);

        ASSERT(p->p_dtrace_lazy_dofs == NULL || p->p_dtrace_helpers == NULL);
        ASSERT(dtrace_dof_mode != DTRACE_DOF_MODE_NEVER);

        /*
         * Any existing helpers force non-lazy behavior.
         */
        if (dtrace_dof_mode == DTRACE_DOF_MODE_LAZY_ON && (p->p_dtrace_helpers == NULL)) {
                dtrace_sprlock(p);

                dof_ioctl_data_t* existing_dofs = p->p_dtrace_lazy_dofs;
                unsigned int existing_dofs_count = (existing_dofs) ? existing_dofs->dofiod_count : 0;
                unsigned int i, merged_dofs_count = incoming_dofs->dofiod_count + existing_dofs_count;

                /*
                 * Range check...
                 */
                if (merged_dofs_count == 0 || merged_dofs_count > 1024) {
                        dtrace_dof_error(NULL, "lazy_dofs_add merged_dofs_count out of range");
                        rval = EINVAL;
                        goto unlock;
                }
                
                /*
                 * Each dof being added must be assigned a unique generation.
                 */
                uint64_t generation = (existing_dofs) ? existing_dofs->dofiod_helpers[existing_dofs_count - 1].dofhp_dof + 1 : 1;
                for (i=0; i<incoming_dofs->dofiod_count; i++) {
                        /*
                         * We rely on these being the same so we can overwrite dofhp_dof and not lose info.
                         */
                        ASSERT(incoming_dofs->dofiod_helpers[i].dofhp_dof == incoming_dofs->dofiod_helpers[i].dofhp_addr);
                        incoming_dofs->dofiod_helpers[i].dofhp_dof = generation++;
                }

                
                if (existing_dofs) {
                        /*
                         * Merge the existing and incoming dofs
                         */
                        size_t merged_dofs_size = DOF_IOCTL_DATA_T_SIZE(merged_dofs_count);
                        dof_ioctl_data_t* merged_dofs = kmem_alloc(merged_dofs_size, KM_SLEEP);

                        bcopy(&existing_dofs->dofiod_helpers[0],
                              &merged_dofs->dofiod_helpers[0],
                              sizeof(dof_helper_t) * existing_dofs_count);
                        bcopy(&incoming_dofs->dofiod_helpers[0],
                              &merged_dofs->dofiod_helpers[existing_dofs_count],
                              sizeof(dof_helper_t) * incoming_dofs->dofiod_count);

                        merged_dofs->dofiod_count = merged_dofs_count;

                        kmem_free(existing_dofs, DOF_IOCTL_DATA_T_SIZE(existing_dofs_count));

                        p->p_dtrace_lazy_dofs = merged_dofs;
                } else {
                        /*
                         * Claim the incoming dofs
                         */
                        *dofs_claimed = 1;
                        p->p_dtrace_lazy_dofs = incoming_dofs;
                }

#if DEBUG
                dof_ioctl_data_t* all_dofs = p->p_dtrace_lazy_dofs;
                for (i=0; i<all_dofs->dofiod_count-1; i++) {
                        ASSERT(all_dofs->dofiod_helpers[i].dofhp_dof < all_dofs->dofiod_helpers[i+1].dofhp_dof);
                }
#endif /* DEBUG */

unlock:
                dtrace_sprunlock(p);
        } else {
                rval = EACCES;
        }

        lck_rw_unlock_shared(&dtrace_dof_mode_lock);

        return rval;
}

/*
 * Returns:
 *
 * EINVAL: lazy dof is enabled, but the requested generation was not found.
 * EACCES: This removal needs to be handled non-lazily. 
 */
static int
dtrace_lazy_dofs_remove(proc_t *p, int generation)
{
        int rval = EINVAL;

        lck_rw_lock_shared(&dtrace_dof_mode_lock);

        ASSERT(p->p_dtrace_lazy_dofs == NULL || p->p_dtrace_helpers == NULL);
        ASSERT(dtrace_dof_mode != DTRACE_DOF_MODE_NEVER);

        /*
         * Any existing helpers force non-lazy behavior.
         */
        if (dtrace_dof_mode == DTRACE_DOF_MODE_LAZY_ON && (p->p_dtrace_helpers == NULL)) {
                dtrace_sprlock(p);

                dof_ioctl_data_t* existing_dofs = p->p_dtrace_lazy_dofs;
                
                if (existing_dofs) {            
                        int index, existing_dofs_count = existing_dofs->dofiod_count;
                        for (index=0; index<existing_dofs_count; index++) {
                                if ((int)existing_dofs->dofiod_helpers[index].dofhp_dof == generation) {
                                        dof_ioctl_data_t* removed_dofs = NULL;
                                
                                        /*
                                         * If there is only 1 dof, we'll delete it and swap in NULL.
                                         */
                                        if (existing_dofs_count > 1) {
                                                int removed_dofs_count = existing_dofs_count - 1;
                                                size_t removed_dofs_size = DOF_IOCTL_DATA_T_SIZE(removed_dofs_count);
                                        
                                                removed_dofs = kmem_alloc(removed_dofs_size, KM_SLEEP);
                                                removed_dofs->dofiod_count = removed_dofs_count;
                                        
                                                /*
                                                 * copy the remaining data.
                                                 */
                                                if (index > 0) {
                                                        bcopy(&existing_dofs->dofiod_helpers[0],
                                                              &removed_dofs->dofiod_helpers[0],
                                                              index * sizeof(dof_helper_t));
                                                }
                                        
                                                if (index < existing_dofs_count-1) {
                                                        bcopy(&existing_dofs->dofiod_helpers[index+1],
                                                              &removed_dofs->dofiod_helpers[index],
                                                              (existing_dofs_count - index - 1) * sizeof(dof_helper_t));
                                                }
                                        }
                                
                                        kmem_free(existing_dofs, DOF_IOCTL_DATA_T_SIZE(existing_dofs_count));
                                
                                        p->p_dtrace_lazy_dofs = removed_dofs;

                                        rval = KERN_SUCCESS;

                                        break;
                                }
                        }

#if DEBUG
                        dof_ioctl_data_t* all_dofs = p->p_dtrace_lazy_dofs;
                        if (all_dofs) {
                                unsigned int i;
                                for (i=0; i<all_dofs->dofiod_count-1; i++) {
                                        ASSERT(all_dofs->dofiod_helpers[i].dofhp_dof < all_dofs->dofiod_helpers[i+1].dofhp_dof);
                                }
                        }
#endif

                }
                dtrace_sprunlock(p);
        } else {
                rval = EACCES;
        }
        
        lck_rw_unlock_shared(&dtrace_dof_mode_lock);

        return rval;
}

void
dtrace_lazy_dofs_destroy(proc_t *p)
{
        lck_rw_lock_shared(&dtrace_dof_mode_lock);
        dtrace_sprlock(p);
        
        ASSERT(p->p_dtrace_lazy_dofs == NULL || p->p_dtrace_helpers == NULL);

        dof_ioctl_data_t* lazy_dofs = p->p_dtrace_lazy_dofs;
        p->p_dtrace_lazy_dofs = NULL;

        dtrace_sprunlock(p);
        lck_rw_unlock_shared(&dtrace_dof_mode_lock);

        if (lazy_dofs) {
                kmem_free(lazy_dofs, DOF_IOCTL_DATA_T_SIZE(lazy_dofs->dofiod_count));
        }
}

static int
dtrace_lazy_dofs_proc_iterate_filter(proc_t *p, void* ignored)
{
#pragma unused(ignored)
        /*
         * Okay to NULL test without taking the sprlock.
         */
        return p->p_dtrace_lazy_dofs != NULL;
}

static void
dtrace_lazy_dofs_process(proc_t *p) {
        /*
         * It is possible this process may exit during our attempt to
         * fault in the dof. We could fix this by holding locks longer,
         * but the errors are benign.
         */
        dtrace_sprlock(p);


        ASSERT(p->p_dtrace_lazy_dofs == NULL || p->p_dtrace_helpers == NULL);
        ASSERT(dtrace_dof_mode == DTRACE_DOF_MODE_LAZY_OFF);

        dof_ioctl_data_t* lazy_dofs = p->p_dtrace_lazy_dofs;
        p->p_dtrace_lazy_dofs = NULL;

        dtrace_sprunlock(p);
        lck_mtx_lock(&dtrace_meta_lock);
        /*
         * Process each dof_helper_t
         */
        if (lazy_dofs != NULL) {
                unsigned int i;
                int rval;

                for (i=0; i<lazy_dofs->dofiod_count; i++) {
                        /*
                         * When loading lazy dof, we depend on the generations being sorted in ascending order.
                         */
                        ASSERT(i >= (lazy_dofs->dofiod_count - 1) || lazy_dofs->dofiod_helpers[i].dofhp_dof < lazy_dofs->dofiod_helpers[i+1].dofhp_dof);

                        dof_helper_t *dhp = &lazy_dofs->dofiod_helpers[i];

                        /*
                         * We stored the generation in dofhp_dof. Save it, and restore the original value.
                         */
                        int generation = dhp->dofhp_dof;
                        dhp->dofhp_dof = dhp->dofhp_addr;

                        dof_hdr_t *dof = dtrace_dof_copyin_from_proc(p, dhp->dofhp_dof, &rval);

                        if (dof != NULL) {
                                dtrace_helpers_t *help;
                                                                
                                lck_mtx_lock(&dtrace_lock);
                                
                                /*
                                 * This must be done with the dtrace_lock held
                                 */
                                if ((help = p->p_dtrace_helpers) == NULL)
                                        help = dtrace_helpers_create(p);
                                
                                /*
                                 * If the generation value has been bumped, someone snuck in
                                 * when we released the dtrace lock. We have to dump this generation,
                                 * there is no safe way to load it.
                                 */
                                if (help->dthps_generation <= generation) {
                                        help->dthps_generation = generation;
                                        
                                        /*
                                         * dtrace_helper_slurp() takes responsibility for the dof --
                                         * it may free it now or it may save it and free it later.
                                         */
                                        if ((rval = dtrace_helper_slurp(p, dof, dhp)) != generation) {
                                                dtrace_dof_error(NULL, "returned value did not match expected generation");
                                        }
                                }
                                
                                lck_mtx_unlock(&dtrace_lock);
                        }
                }
                lck_mtx_unlock(&dtrace_meta_lock);
                kmem_free(lazy_dofs, DOF_IOCTL_DATA_T_SIZE(lazy_dofs->dofiod_count));
        } else {
                lck_mtx_unlock(&dtrace_meta_lock);
        }
}

static int
dtrace_lazy_dofs_proc_iterate_doit(proc_t *p, void* ignored)
{
#pragma unused(ignored)

        dtrace_lazy_dofs_process(p);

        return PROC_RETURNED;
}

#define DTRACE_LAZY_DOFS_DUPLICATED 1

static int
dtrace_lazy_dofs_duplicate(proc_t *parent, proc_t *child)
{
        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_NOTOWNED);
        LCK_MTX_ASSERT(&parent->p_dtrace_sprlock, LCK_MTX_ASSERT_NOTOWNED);
        LCK_MTX_ASSERT(&child->p_dtrace_sprlock, LCK_MTX_ASSERT_NOTOWNED);

        lck_rw_lock_shared(&dtrace_dof_mode_lock);
        dtrace_sprlock(parent);

        /*
         * We need to make sure that the transition to lazy dofs -> helpers
         * was atomic for our parent
         */
        ASSERT(parent->p_dtrace_lazy_dofs == NULL || parent->p_dtrace_helpers == NULL);
        /*
         * In theory we should hold the child sprlock, but this is safe...
         */
        ASSERT(child->p_dtrace_lazy_dofs == NULL && child->p_dtrace_helpers == NULL);

        dof_ioctl_data_t* parent_dofs = parent->p_dtrace_lazy_dofs;
        dof_ioctl_data_t* child_dofs = NULL;
        if (parent_dofs) {
                size_t parent_dofs_size = DOF_IOCTL_DATA_T_SIZE(parent_dofs->dofiod_count);
                child_dofs = kmem_alloc(parent_dofs_size, KM_SLEEP);
                bcopy(parent_dofs, child_dofs, parent_dofs_size);
        }

        dtrace_sprunlock(parent);

        if (child_dofs) {
                dtrace_sprlock(child);
                child->p_dtrace_lazy_dofs = child_dofs;
                dtrace_sprunlock(child);
                /**
                 * We process the DOF at this point if the mode is set to
                 * LAZY_OFF. This can happen if DTrace is still processing the
                 * DOF of other process (which can happen because the
                 * protected pager can have a huge latency)
                 * but has not processed our parent yet
                 */
                if (dtrace_dof_mode == DTRACE_DOF_MODE_LAZY_OFF) {
                        dtrace_lazy_dofs_process(child);
                }
                lck_rw_unlock_shared(&dtrace_dof_mode_lock);

                return DTRACE_LAZY_DOFS_DUPLICATED;
        }
        lck_rw_unlock_shared(&dtrace_dof_mode_lock);

        return 0;
}

static dtrace_helpers_t *
dtrace_helpers_create(proc_t *p)
{
        dtrace_helpers_t *help;

        LCK_MTX_ASSERT(&dtrace_lock, LCK_MTX_ASSERT_OWNED);
        ASSERT(p->p_dtrace_helpers == NULL);

        help = kmem_zalloc(sizeof (dtrace_helpers_t), KM_SLEEP);
        help->dthps_actions = kmem_zalloc(sizeof (dtrace_helper_action_t *) *
            DTRACE_NHELPER_ACTIONS, KM_SLEEP);

        p->p_dtrace_helpers = help;
        dtrace_helpers++;

        return (help);
}

static void
dtrace_helpers_destroy(proc_t* p)
{
        dtrace_helpers_t *help;
        dtrace_vstate_t *vstate;
        uint_t i;

        lck_mtx_lock(&dtrace_meta_lock);
        lck_mtx_lock(&dtrace_lock);

        ASSERT(p->p_dtrace_helpers != NULL);
        ASSERT(dtrace_helpers > 0);

        help = p->p_dtrace_helpers;
        vstate = &help->dthps_vstate;

        /*
         * We're now going to lose the help from this process.
         */
        p->p_dtrace_helpers = NULL;
        dtrace_sync();

        /*
         * Destory the helper actions.
         */
        for (i = 0; i < DTRACE_NHELPER_ACTIONS; i++) {
                dtrace_helper_action_t *h, *next;

                for (h = help->dthps_actions[i]; h != NULL; h = next) {
                        next = h->dtha_next;
                        dtrace_helper_action_destroy(h, vstate);
                        h = next;
                }
        }

        lck_mtx_unlock(&dtrace_lock);

        /*
         * Destroy the helper providers.
         */
        if (help->dthps_maxprovs > 0) {
                if (dtrace_meta_pid != NULL) {
                        ASSERT(dtrace_deferred_pid == NULL);

                        for (i = 0; i < help->dthps_nprovs; i++) {
                                dtrace_helper_provider_remove(
                                    &help->dthps_provs[i]->dthp_prov, p);
                        }
                } else {
                        lck_mtx_lock(&dtrace_lock);
                        ASSERT(help->dthps_deferred == 0 ||
                            help->dthps_next != NULL ||
                            help->dthps_prev != NULL ||
                            help == dtrace_deferred_pid);

                        /*
                         * Remove the helper from the deferred list.
                         */
                        if (help->dthps_next != NULL)
                                help->dthps_next->dthps_prev = help->dthps_prev;
                        if (help->dthps_prev != NULL)
                                help->dthps_prev->dthps_next = help->dthps_next;
                        if (dtrace_deferred_pid == help) {
                                dtrace_deferred_pid = help->dthps_next;
                                ASSERT(help->dthps_prev == NULL);
                        }

                        lck_mtx_unlock(&dtrace_lock);
                }


                for (i = 0; i < help->dthps_nprovs; i++) {
                        dtrace_helper_provider_destroy(help->dthps_provs[i]);
                }

                kmem_free(help->dthps_provs, help->dthps_maxprovs *
                    sizeof (dtrace_helper_provider_t *));
        }

        lck_mtx_lock(&dtrace_lock);

        dtrace_vstate_fini(&help->dthps_vstate);
        kmem_free(help->dthps_actions,
            sizeof (dtrace_helper_action_t *) * DTRACE_NHELPER_ACTIONS);
        kmem_free(help, sizeof (dtrace_helpers_t));

        --dtrace_helpers;
        lck_mtx_unlock(&dtrace_lock);
        lck_mtx_unlock(&dtrace_meta_lock);
}

static void
dtrace_helpers_duplicate(proc_t *from, proc_t *to)
{
        dtrace_helpers_t *help, *newhelp;
        dtrace_helper_action_t *helper, *new, *last;
        dtrace_difo_t *dp;
        dtrace_vstate_t *vstate;
        uint_t i;
        int j, sz, hasprovs = 0;

        lck_mtx_lock(&dtrace_meta_lock);
        lck_mtx_lock(&dtrace_lock);
        ASSERT(from->p_dtrace_helpers != NULL);
        ASSERT(dtrace_helpers > 0);

        help = from->p_dtrace_helpers;
        newhelp = dtrace_helpers_create(to);
        ASSERT(to->p_dtrace_helpers != NULL);

        newhelp->dthps_generation = help->dthps_generation;
        vstate = &newhelp->dthps_vstate;

        /*
         * Duplicate the helper actions.
         */
        for (i = 0; i < DTRACE_NHELPER_ACTIONS; i++) {
                if ((helper = help->dthps_actions[i]) == NULL)
                        continue;

                for (last = NULL; helper != NULL; helper = helper->dtha_next) {
                        new = kmem_zalloc(sizeof (dtrace_helper_action_t),
                            KM_SLEEP);
                        new->dtha_generation = helper->dtha_generation;

                        if ((dp = helper->dtha_predicate) != NULL) {
                                dp = dtrace_difo_duplicate(dp, vstate);
                                new->dtha_predicate = dp;
                        }

                        new->dtha_nactions = helper->dtha_nactions;
                        sz = sizeof (dtrace_difo_t *) * new->dtha_nactions;
                        new->dtha_actions = kmem_alloc(sz, KM_SLEEP);

                        for (j = 0; j < new->dtha_nactions; j++) {
                                dtrace_difo_t *dpj = helper->dtha_actions[j];

                                ASSERT(dpj != NULL);
                                dpj = dtrace_difo_duplicate(dpj, vstate);
                                new->dtha_actions[j] = dpj;
                        }

                        if (last != NULL) {
                                last->dtha_next = new;
                        } else {
                                newhelp->dthps_actions[i] = new;
                        }

                        last = new;
                }
        }

        /*
         * Duplicate the helper providers and register them with the
         * DTrace framework.
         */
        if (help->dthps_nprovs > 0) {
                newhelp->dthps_nprovs = help->dthps_nprovs;
                newhelp->dthps_maxprovs = help->dthps_nprovs;
                newhelp->dthps_provs = kmem_alloc(newhelp->dthps_nprovs *
                    sizeof (dtrace_helper_provider_t *), KM_SLEEP);
                for (i = 0; i < newhelp->dthps_nprovs; i++) {
                        newhelp->dthps_provs[i] = help->dthps_provs[i];
                        newhelp->dthps_provs[i]->dthp_ref++;
                }

                hasprovs = 1;
        }

        lck_mtx_unlock(&dtrace_lock);

        if (hasprovs)
                dtrace_helper_provider_register(to, newhelp, NULL);

        lck_mtx_unlock(&dtrace_meta_lock);
}

/**
 * DTrace Process functions
 */

void
dtrace_proc_fork(proc_t *parent_proc, proc_t *child_proc, int spawn)
{
        /*
         * This code applies to new processes who are copying the task
         * and thread state and address spaces of their parent process.
         */
        if (!spawn) {
                /*
                 * APPLE NOTE: Solaris does a sprlock() and drops the
                 * proc_lock here. We're cheating a bit and only taking
                 * the p_dtrace_sprlock lock. A full sprlock would
                 * task_suspend the parent.
                 */
                dtrace_sprlock(parent_proc);

                /*
                 * Remove all DTrace tracepoints from the child process. We
                 * need to do this _before_ duplicating USDT providers since
                 * any associated probes may be immediately enabled.
                 */
                if (parent_proc->p_dtrace_count > 0) {
                        dtrace_fasttrap_fork(parent_proc, child_proc);
                }

                dtrace_sprunlock(parent_proc);

                /*
                 * Duplicate any lazy dof(s). This must be done while NOT
                 * holding the parent sprlock! Lock ordering is
                 * dtrace_dof_mode_lock, then sprlock.  It is imperative we
                 * always call dtrace_lazy_dofs_duplicate, rather than null
                 * check and call if !NULL. If we NULL test, during lazy dof
                 * faulting we can race with the faulting code and proceed
                 * from here to beyond the helpers copy. The lazy dof
                 * faulting will then fail to copy the helpers to the child
                 * process. We return if we duplicated lazy dofs as a process
                 * can only have one at the same time to avoid a race between
                 * a dtrace client and dtrace_proc_fork where a process would
                 * end up with both lazy dofs and helpers.
                 */
                if (dtrace_lazy_dofs_duplicate(parent_proc, child_proc) == DTRACE_LAZY_DOFS_DUPLICATED) {
                        return;
                }

                /*
                 * Duplicate any helper actions and providers if they haven't
                 * already.
                 */
#if !defined(__APPLE__)
                 /*
                 * The SFORKING
                 * we set above informs the code to enable USDT probes that
                 * sprlock() may fail because the child is being forked.
                 */
#endif
                /*
                 * APPLE NOTE: As best I can tell, Apple's sprlock() equivalent
                 * never fails to find the child. We do not set SFORKING.
                 */
                if (parent_proc->p_dtrace_helpers != NULL && dtrace_helpers_fork) {
                        (*dtrace_helpers_fork)(parent_proc, child_proc);
                }
        }
}

void
dtrace_proc_exec(proc_t *p)
{
        /*
         * Invalidate any predicate evaluation already cached for this thread by DTrace.
         * That's because we've just stored to p_comm and DTrace refers to that when it
         * evaluates the "execname" special variable. uid and gid may have changed as well.
         */
        dtrace_set_thread_predcache(current_thread(), 0);

        /*
         * Free any outstanding lazy dof entries. It is imperative we
         * always call dtrace_lazy_dofs_destroy, rather than null check
         * and call if !NULL. If we NULL test, during lazy dof faulting
         * we can race with the faulting code and proceed from here to
         * beyond the helpers cleanup. The lazy dof faulting will then
         * install new helpers which no longer belong to this process!
         */
        dtrace_lazy_dofs_destroy(p);


        /*
         * Clean up any DTrace helpers for the process.
         */
        if (p->p_dtrace_helpers != NULL && dtrace_helpers_cleanup) {
                (*dtrace_helpers_cleanup)(p);
        }

        /*
         * Cleanup the DTrace provider associated with this process.
         */
        proc_lock(p);
        if (p->p_dtrace_probes && dtrace_fasttrap_exec_ptr) {
                (*dtrace_fasttrap_exec_ptr)(p);
        }
        proc_unlock(p);
}

void
dtrace_proc_exit(proc_t *p)
{
        /*
         * Free any outstanding lazy dof entries. It is imperative we
         * always call dtrace_lazy_dofs_destroy, rather than null check
         * and call if !NULL. If we NULL test, during lazy dof faulting
         * we can race with the faulting code and proceed from here to
         * beyond the helpers cleanup. The lazy dof faulting will then
         * install new helpers which will never be cleaned up, and leak.
         */
        dtrace_lazy_dofs_destroy(p);

        /*
         * Clean up any DTrace helper actions or probes for the process.
         */
        if (p->p_dtrace_helpers != NULL) {
                (*dtrace_helpers_cleanup)(p);
        }

        /*
         * Clean up any DTrace probes associated with this process.
         */
        /*
         * APPLE NOTE: We release ptss pages/entries in dtrace_fasttrap_exit_ptr(),
         * call this after dtrace_helpers_cleanup()
         */
        proc_lock(p);
        if (p->p_dtrace_probes && dtrace_fasttrap_exit_ptr) {
                (*dtrace_fasttrap_exit_ptr)(p);
        }
        proc_unlock(p);
}

/*
 * DTrace Hook Functions
 */

/*
 * APPLE NOTE:  dtrace_modctl_* routines for kext support.
 * Used to manipulate the modctl list within dtrace xnu.
 */

modctl_t *dtrace_modctl_list;

static void
dtrace_modctl_add(struct modctl * newctl)
{
        struct modctl *nextp, *prevp;

        ASSERT(newctl != NULL);
        LCK_MTX_ASSERT(&mod_lock, LCK_MTX_ASSERT_OWNED);

        // Insert new module at the front of the list,
        
        newctl->mod_next = dtrace_modctl_list;
        dtrace_modctl_list = newctl;

        /*
         * If a module exists with the same name, then that module
         * must have been unloaded with enabled probes. We will move
         * the unloaded module to the new module's stale chain and
         * then stop traversing the list.
         */

        prevp = newctl;
        nextp = newctl->mod_next;
    
        while (nextp != NULL) {
                if (nextp->mod_loaded) {
                        /* This is a loaded module. Keep traversing. */
                        prevp = nextp;
                        nextp = nextp->mod_next;
                        continue;
                }
                else {
                        /* Found an unloaded module */
                        if (strncmp (newctl->mod_modname, nextp->mod_modname, KMOD_MAX_NAME)) {
                                /* Names don't match. Keep traversing. */
                                prevp = nextp;
                                nextp = nextp->mod_next;
                                continue;
                        }
                        else {
                                /* We found a stale entry, move it. We're done. */
                                prevp->mod_next = nextp->mod_next;
                                newctl->mod_stale = nextp;
                                nextp->mod_next = NULL;
                                break;
                        }
                }
        }
}

static modctl_t *
dtrace_modctl_lookup(struct kmod_info * kmod)
{
    LCK_MTX_ASSERT(&mod_lock, LCK_MTX_ASSERT_OWNED);

    struct modctl * ctl;

    for (ctl = dtrace_modctl_list; ctl; ctl=ctl->mod_next) {
        if (ctl->mod_id == kmod->id)
            return(ctl);
    }
    return (NULL);
}

/*
 * This routine is called from dtrace_module_unloaded().
 * It removes a modctl structure and its stale chain
 * from the kext shadow list.
 */
static void
dtrace_modctl_remove(struct modctl * ctl)
{
        ASSERT(ctl != NULL);
        LCK_MTX_ASSERT(&mod_lock, LCK_MTX_ASSERT_OWNED);
        modctl_t *prevp, *nextp, *curp;

        // Remove stale chain first
        for (curp=ctl->mod_stale; curp != NULL; curp=nextp) {
                nextp = curp->mod_stale;
                /* There should NEVER be user symbols allocated at this point */
                ASSERT(curp->mod_user_symbols == NULL); 
                kmem_free(curp, sizeof(modctl_t));
        }

        prevp = NULL;
        curp = dtrace_modctl_list;
        
        while (curp != ctl) {
                prevp = curp;
                curp = curp->mod_next;
        }

        if (prevp != NULL) {
                prevp->mod_next = ctl->mod_next;
        }
        else {
                dtrace_modctl_list = ctl->mod_next;
        }

        /* There should NEVER be user symbols allocated at this point */
        ASSERT(ctl->mod_user_symbols == NULL);

        kmem_free (ctl, sizeof(modctl_t));
}
        
/*
 * APPLE NOTE: The kext loader will call dtrace_module_loaded
 * when the kext is loaded in memory, but before calling the
 * kext's start routine.
 *
 * Return 0 on success
 * Return -1 on failure
 */
        
static int
dtrace_module_loaded(struct kmod_info *kmod, uint32_t flag)
{
        dtrace_provider_t *prv;

        /*
         * If kernel symbols have been disabled, return immediately
         * DTRACE_KERNEL_SYMBOLS_NEVER is a permanent mode, it is safe to test without holding locks
         */
        if (dtrace_kernel_symbol_mode == DTRACE_KERNEL_SYMBOLS_NEVER)
                return 0;
        
        struct modctl *ctl = NULL;
        if (!kmod || kmod->address == 0 || kmod->size == 0)
                return(-1);
                
        lck_mtx_lock(&dtrace_provider_lock);
        lck_mtx_lock(&mod_lock);        
        
        /*
         * Have we seen this kext before?
         */

        ctl = dtrace_modctl_lookup(kmod);

        if (ctl != NULL) {
                /* bail... we already have this kext in the modctl list */
                lck_mtx_unlock(&mod_lock);
                lck_mtx_unlock(&dtrace_provider_lock);
                if (dtrace_err_verbose)
                        cmn_err(CE_WARN, "dtrace load module already exists '%s %u' is failing against '%s %u'", kmod->name, (uint_t)kmod->id, ctl->mod_modname, ctl->mod_id);
                return(-1);
        }
        else {
                ctl = kmem_alloc(sizeof(struct modctl), KM_SLEEP);
                if (ctl == NULL) {
                        if (dtrace_err_verbose)
                                cmn_err(CE_WARN, "dtrace module load '%s %u' is failing ", kmod->name, (uint_t)kmod->id);
                        lck_mtx_unlock(&mod_lock);
                        lck_mtx_unlock(&dtrace_provider_lock);
                        return (-1);
                }
                ctl->mod_next = NULL;
                ctl->mod_stale = NULL;
                strlcpy (ctl->mod_modname, kmod->name, sizeof(ctl->mod_modname));
                ctl->mod_loadcnt = kmod->id;
                ctl->mod_nenabled = 0;
                ctl->mod_address  = kmod->address;
                ctl->mod_size = kmod->size;
                ctl->mod_id = kmod->id;
                ctl->mod_loaded = 1;
                ctl->mod_flags = 0;
                ctl->mod_user_symbols = NULL;

                /*
                 * Find the UUID for this module, if it has one
                 */
                kernel_mach_header_t* header = (kernel_mach_header_t *)ctl->mod_address;
                struct load_command* load_cmd = (struct load_command *)&header[1];
                uint32_t i;
                for (i = 0; i < header->ncmds; i++) {
                        if (load_cmd->cmd == LC_UUID) {
                                struct uuid_command* uuid_cmd = (struct uuid_command *)load_cmd;
                                memcpy(ctl->mod_uuid, uuid_cmd->uuid, sizeof(uuid_cmd->uuid));
                                ctl->mod_flags |= MODCTL_HAS_UUID;
                                break;
                        }
                        load_cmd = (struct load_command *)((caddr_t)load_cmd + load_cmd->cmdsize);
                }
                
                if (ctl->mod_address == g_kernel_kmod_info.address) {
                        ctl->mod_flags |= MODCTL_IS_MACH_KERNEL;
                        memcpy(dtrace_kerneluuid, ctl->mod_uuid, sizeof(dtrace_kerneluuid));
                }
                /*
                 * Static kexts have a UUID that is not used for symbolication, as all their
                 * symbols are in kernel
                 */
                else if ((flag & KMOD_DTRACE_STATIC_KEXT) == KMOD_DTRACE_STATIC_KEXT) {
                        memcpy(ctl->mod_uuid, dtrace_kerneluuid, sizeof(dtrace_kerneluuid));
                        ctl->mod_flags |= MODCTL_IS_STATIC_KEXT;
                }
        }
        dtrace_modctl_add(ctl);
        
        /*
         * We must hold the dtrace_lock to safely test non permanent dtrace_fbt_symbol_mode(s)
         */
        lck_mtx_lock(&dtrace_lock);
        
        /*
         * DTrace must decide if it will instrument modules lazily via
         * userspace symbols (default mode), or instrument immediately via 
         * kernel symbols (non-default mode)
         *
         * When in default/lazy mode, DTrace will only support modules
         * built with a valid UUID.
         *
         * Overriding the default can be done explicitly in one of
         * the following two ways.
         *
         * A module can force symbols from kernel space using the plist key,
         * OSBundleForceDTraceInit (see kmod.h).  If this per kext state is set,
         * we fall through and instrument this module now.
         *
         * Or, the boot-arg, dtrace_kernel_symbol_mode, can be set to force symbols
         * from kernel space (see dtrace_impl.h).  If this system state is set
         * to a non-userspace mode, we fall through and instrument the module now.
         */

        if ((dtrace_kernel_symbol_mode == DTRACE_KERNEL_SYMBOLS_FROM_USERSPACE) &&
            (!(flag & KMOD_DTRACE_FORCE_INIT)))
        {
                /* We will instrument the module lazily -- this is the default */
                lck_mtx_unlock(&dtrace_lock);
                lck_mtx_unlock(&mod_lock);
                lck_mtx_unlock(&dtrace_provider_lock);
                return 0;
        }
        
        /* We will instrument the module immediately using kernel symbols */
        ctl->mod_flags |= MODCTL_HAS_KERNEL_SYMBOLS;
        
        lck_mtx_unlock(&dtrace_lock);
        
        /*
         * We're going to call each providers per-module provide operation
         * specifying only this module.
         */
        for (prv = dtrace_provider; prv != NULL; prv = prv->dtpv_next)
                prv->dtpv_pops.dtps_provide_module(prv->dtpv_arg, ctl); 
        
        /*
         * APPLE NOTE: The contract with the kext loader is that once this function
         * has completed, it may delete kernel symbols at will.
         * We must set this while still holding the mod_lock.
         */
        ctl->mod_flags &= ~MODCTL_HAS_KERNEL_SYMBOLS;
        
        lck_mtx_unlock(&mod_lock);
        lck_mtx_unlock(&dtrace_provider_lock);
        
        /*
         * If we have any retained enablings, we need to match against them.
         * Enabling probes requires that cpu_lock be held, and we cannot hold
         * cpu_lock here -- it is legal for cpu_lock to be held when loading a
         * module.  (In particular, this happens when loading scheduling
         * classes.)  So if we have any retained enablings, we need to dispatch
         * our task queue to do the match for us.
         */
        lck_mtx_lock(&dtrace_lock);
        
        if (dtrace_retained == NULL) {
                lck_mtx_unlock(&dtrace_lock);
                return 0;
        }
        
        /* APPLE NOTE!
         *
         * The cpu_lock mentioned above is only held by dtrace code, Apple's xnu never actually
         * holds it for any reason. Thus the comment above is invalid, we can directly invoke
         * dtrace_enabling_matchall without jumping through all the hoops, and we can avoid
         * the delay call as well.
         */
        lck_mtx_unlock(&dtrace_lock);
        
        dtrace_enabling_matchall();
        
        return 0;
}

/*
 * Return 0 on success
 * Return -1 on failure
 */
static int
dtrace_module_unloaded(struct kmod_info *kmod)
{
        dtrace_probe_t template, *probe, *first, *next;
        dtrace_provider_t *prov;
        struct modctl *ctl = NULL;
        struct modctl *syncctl = NULL;
        struct modctl *nextsyncctl = NULL;
        int syncmode = 0;
        
        lck_mtx_lock(&dtrace_provider_lock);
        lck_mtx_lock(&mod_lock);
        lck_mtx_lock(&dtrace_lock);

        if (kmod == NULL) {
            syncmode = 1;
        }
        else {
            ctl = dtrace_modctl_lookup(kmod);
            if (ctl == NULL)
            {
                lck_mtx_unlock(&dtrace_lock);
                lck_mtx_unlock(&mod_lock);
                lck_mtx_unlock(&dtrace_provider_lock);
                return (-1);
            }
            ctl->mod_loaded = 0;
            ctl->mod_address = 0;
            ctl->mod_size = 0;
        }
        
        if (dtrace_bymod == NULL) {
                /*
                 * The DTrace module is loaded (obviously) but not attached;
                 * we don't have any work to do.
                 */
                 if (ctl != NULL)
                         (void)dtrace_modctl_remove(ctl);
                 lck_mtx_unlock(&dtrace_lock);
                 lck_mtx_unlock(&mod_lock);
                 lck_mtx_unlock(&dtrace_provider_lock);
                 return(0);
        }

        /* Syncmode set means we target and traverse entire modctl list. */
        if (syncmode)
            nextsyncctl = dtrace_modctl_list;

syncloop:
        if (syncmode)
        {
            /* find a stale modctl struct */
            for (syncctl = nextsyncctl; syncctl != NULL; syncctl=syncctl->mod_next) {
                if (syncctl->mod_address == 0)
                    break;
            }
            if (syncctl==NULL)
            {
                /* We have no more work to do */
                lck_mtx_unlock(&dtrace_lock);
                lck_mtx_unlock(&mod_lock);
                lck_mtx_unlock(&dtrace_provider_lock);
                return(0);
            }
            else {
                /* keep track of next syncctl in case this one is removed */
                nextsyncctl = syncctl->mod_next;
                ctl = syncctl;
            }
        }

        template.dtpr_mod = ctl->mod_modname;
        
        for (probe = first = dtrace_hash_lookup(dtrace_bymod, &template);
            probe != NULL; probe = probe->dtpr_nextmod) {
                if (probe->dtpr_ecb != NULL) {
                        /*
                         * This shouldn't _actually_ be possible -- we're
                         * unloading a module that has an enabled probe in it.
                         * (It's normally up to the provider to make sure that
                         * this can't happen.)  However, because dtps_enable()
                         * doesn't have a failure mode, there can be an
                         * enable/unload race.  Upshot:  we don't want to
                         * assert, but we're not going to disable the
                         * probe, either.
                         */


                        if (syncmode) {
                            /* We're syncing, let's look at next in list */
                            goto syncloop;
                        }

                        lck_mtx_unlock(&dtrace_lock);
                        lck_mtx_unlock(&mod_lock);
                        lck_mtx_unlock(&dtrace_provider_lock);
                    
                        if (dtrace_err_verbose) {
                                cmn_err(CE_WARN, "unloaded module '%s' had "
                                    "enabled probes", ctl->mod_modname);
                        }
                        return(-1);
                }
        }

        probe = first;

        for (first = NULL; probe != NULL; probe = next) {
                ASSERT(dtrace_probes[probe->dtpr_id - 1] == probe);

                dtrace_probes[probe->dtpr_id - 1] = NULL;
                probe->dtpr_provider->dtpv_probe_count--;                                       

                next = probe->dtpr_nextmod;
                dtrace_hash_remove(dtrace_byprov, probe);
                dtrace_hash_remove(dtrace_bymod, probe);
                dtrace_hash_remove(dtrace_byfunc, probe);
                dtrace_hash_remove(dtrace_byname, probe);

                if (first == NULL) {
                        first = probe;
                        probe->dtpr_nextmod = NULL;
                } else {
                        probe->dtpr_nextmod = first;
                        first = probe;
                }
        }

        /*
         * We've removed all of the module's probes from the hash chains and
         * from the probe array.  Now issue a dtrace_sync() to be sure that
         * everyone has cleared out from any probe array processing.
         */
        dtrace_sync();

        for (probe = first; probe != NULL; probe = first) {
                first = probe->dtpr_nextmod;
                prov = probe->dtpr_provider;
                prov->dtpv_pops.dtps_destroy(prov->dtpv_arg, probe->dtpr_id,
                    probe->dtpr_arg);
                dtrace_strunref(probe->dtpr_mod);
                dtrace_strunref(probe->dtpr_func);
                dtrace_strunref(probe->dtpr_name);
                vmem_free(dtrace_arena, (void *)(uintptr_t)probe->dtpr_id, 1);

                zfree(dtrace_probe_t_zone, probe);
        }

        dtrace_modctl_remove(ctl);
        
        if (syncmode)
            goto syncloop;

        lck_mtx_unlock(&dtrace_lock);
        lck_mtx_unlock(&mod_lock);
        lck_mtx_unlock(&dtrace_provider_lock);

        return(0);
}

void
dtrace_suspend(void)
{
        dtrace_probe_foreach(offsetof(dtrace_pops_t, dtps_suspend));
}

void
dtrace_resume(void)
{
        dtrace_probe_foreach(offsetof(dtrace_pops_t, dtps_resume));
}

static int
dtrace_cpu_setup(cpu_setup_t what, processorid_t cpu)
{
        LCK_MTX_ASSERT(&cpu_lock, LCK_MTX_ASSERT_OWNED);
        lck_mtx_lock(&dtrace_lock);

        switch (what) {
        case CPU_CONFIG: {
                dtrace_state_t *state;
                dtrace_optval_t *opt, rs, c;

                /*
                 * For now, we only allocate a new buffer for anonymous state.
                 */
                if ((state = dtrace_anon.dta_state) == NULL)
                        break;

                if (state->dts_activity != DTRACE_ACTIVITY_ACTIVE)
                        break;

                opt = state->dts_options;
                c = opt[DTRACEOPT_CPU];

                if (c != DTRACE_CPUALL && c != DTRACEOPT_UNSET && c != cpu)
                        break;

                /*
                 * Regardless of what the actual policy is, we're going to
                 * temporarily set our resize policy to be manual.  We're
                 * also going to temporarily set our CPU option to denote
                 * the newly configured CPU.
                 */
                rs = opt[DTRACEOPT_BUFRESIZE];
                opt[DTRACEOPT_BUFRESIZE] = DTRACEOPT_BUFRESIZE_MANUAL;
                opt[DTRACEOPT_CPU] = (dtrace_optval_t)cpu;

                (void) dtrace_state_buffers(state);

                opt[DTRACEOPT_BUFRESIZE] = rs;
                opt[DTRACEOPT_CPU] = c;

                break;
        }

        case CPU_UNCONFIG:
                /*
                 * We don't free the buffer in the CPU_UNCONFIG case.  (The
                 * buffer will be freed when the consumer exits.)
                 */
                break;

        default:
                break;
        }

        lck_mtx_unlock(&dtrace_lock);
        return (0);
}

static void
dtrace_cpu_setup_initial(processorid_t cpu)
{
        (void) dtrace_cpu_setup(CPU_CONFIG, cpu);
}

static void
dtrace_toxrange_add(uintptr_t base, uintptr_t limit)
{
        if (dtrace_toxranges >= dtrace_toxranges_max) {
                int osize, nsize;
                dtrace_toxrange_t *range;

                osize = dtrace_toxranges_max * sizeof (dtrace_toxrange_t);

                if (osize == 0) {
                        ASSERT(dtrace_toxrange == NULL);
                        ASSERT(dtrace_toxranges_max == 0);
                        dtrace_toxranges_max = 1;
                } else {
                        dtrace_toxranges_max <<= 1;
                }

                nsize = dtrace_toxranges_max * sizeof (dtrace_toxrange_t);
                range = kmem_zalloc(nsize, KM_SLEEP);

                if (dtrace_toxrange != NULL) {
                        ASSERT(osize != 0);
                        bcopy(dtrace_toxrange, range, osize);
                        kmem_free(dtrace_toxrange, osize);
                }

                dtrace_toxrange = range;
        }

        ASSERT(dtrace_toxrange[dtrace_toxranges].dtt_base == 0);
        ASSERT(dtrace_toxrange[dtrace_toxranges].dtt_limit == 0);

        dtrace_toxrange[dtrace_toxranges].dtt_base = base;
        dtrace_toxrange[dtrace_toxranges].dtt_limit = limit;
        dtrace_toxranges++;
}

/*
 * DTrace Driver Cookbook Functions
 */
/*ARGSUSED*/
static int
dtrace_attach(dev_info_t *devi)
{
        dtrace_provider_id_t id;
        dtrace_state_t *state = NULL;
        dtrace_enabling_t *enab;

        lck_mtx_lock(&cpu_lock);
        lck_mtx_lock(&dtrace_provider_lock);
        lck_mtx_lock(&dtrace_lock);

        /* Darwin uses BSD cloning device driver to automagically obtain minor device number. */
        dtrace_devi = devi;

        dtrace_modload = dtrace_module_loaded;
        dtrace_modunload = dtrace_module_unloaded;
        dtrace_cpu_init = dtrace_cpu_setup_initial;
        dtrace_helpers_cleanup = dtrace_helpers_destroy;
        dtrace_helpers_fork = dtrace_helpers_duplicate;
        dtrace_cpustart_init = dtrace_suspend;
        dtrace_cpustart_fini = dtrace_resume;
        dtrace_debugger_init = dtrace_suspend;
        dtrace_debugger_fini = dtrace_resume;

        register_cpu_setup_func((cpu_setup_func_t *)dtrace_cpu_setup, NULL);

        LCK_MTX_ASSERT(&cpu_lock, LCK_MTX_ASSERT_OWNED);

        dtrace_arena = vmem_create("dtrace", (void *)1, UINT32_MAX, 1,
            NULL, NULL, NULL, 0, VM_SLEEP | VMC_IDENTIFIER);

        dtrace_state_cache = kmem_cache_create("dtrace_state_cache",
            sizeof (dtrace_dstate_percpu_t) * (int)NCPU, DTRACE_STATE_ALIGN,
            NULL, NULL, NULL, NULL, NULL, 0);

        LCK_MTX_ASSERT(&cpu_lock, LCK_MTX_ASSERT_OWNED);

        dtrace_nprobes = dtrace_nprobes_default;
        dtrace_probes = kmem_zalloc(sizeof(dtrace_probe_t*) * dtrace_nprobes,
            KM_SLEEP);

        dtrace_byprov = dtrace_hash_create(dtrace_strkey_probe_provider,
            0, /* unused */
            offsetof(dtrace_probe_t, dtpr_nextprov),
            offsetof(dtrace_probe_t, dtpr_prevprov));

        dtrace_bymod = dtrace_hash_create(dtrace_strkey_deref_offset,
            offsetof(dtrace_probe_t, dtpr_mod),
            offsetof(dtrace_probe_t, dtpr_nextmod),
            offsetof(dtrace_probe_t, dtpr_prevmod));

        dtrace_byfunc = dtrace_hash_create(dtrace_strkey_deref_offset,
            offsetof(dtrace_probe_t, dtpr_func),
            offsetof(dtrace_probe_t, dtpr_nextfunc),
            offsetof(dtrace_probe_t, dtpr_prevfunc));

        dtrace_byname = dtrace_hash_create(dtrace_strkey_deref_offset,
            offsetof(dtrace_probe_t, dtpr_name),
            offsetof(dtrace_probe_t, dtpr_nextname),
            offsetof(dtrace_probe_t, dtpr_prevname));

        if (dtrace_retain_max < 1) {
                cmn_err(CE_WARN, "illegal value (%lu) for dtrace_retain_max; "
                    "setting to 1", dtrace_retain_max);
                dtrace_retain_max = 1;
        }

        /*
         * Now discover our toxic ranges.
         */
        dtrace_toxic_ranges(dtrace_toxrange_add);

        /*
         * Before we register ourselves as a provider to our own framework,
         * we would like to assert that dtrace_provider is NULL -- but that's
         * not true if we were loaded as a dependency of a DTrace provider.
         * Once we've registered, we can assert that dtrace_provider is our
         * pseudo provider.
         */
        (void) dtrace_register("dtrace", &dtrace_provider_attr,
            DTRACE_PRIV_NONE, 0, &dtrace_provider_ops, NULL, &id);

        ASSERT(dtrace_provider != NULL);
        ASSERT((dtrace_provider_id_t)dtrace_provider == id);

#if defined (__x86_64__)
        dtrace_probeid_begin = dtrace_probe_create((dtrace_provider_id_t)
            dtrace_provider, NULL, NULL, "BEGIN", 1, NULL);
        dtrace_probeid_end = dtrace_probe_create((dtrace_provider_id_t)
            dtrace_provider, NULL, NULL, "END", 0, NULL);
        dtrace_probeid_error = dtrace_probe_create((dtrace_provider_id_t)
            dtrace_provider, NULL, NULL, "ERROR", 3, NULL);
#elif (defined(__arm__) || defined(__arm64__))
        dtrace_probeid_begin = dtrace_probe_create((dtrace_provider_id_t)
            dtrace_provider, NULL, NULL, "BEGIN", 2, NULL);
        dtrace_probeid_end = dtrace_probe_create((dtrace_provider_id_t)
            dtrace_provider, NULL, NULL, "END", 1, NULL);
        dtrace_probeid_error = dtrace_probe_create((dtrace_provider_id_t)
            dtrace_provider, NULL, NULL, "ERROR", 4, NULL);
#else
#error Unknown Architecture
#endif

        dtrace_anon_property();
        lck_mtx_unlock(&cpu_lock);

        /*
         * If DTrace helper tracing is enabled, we need to allocate the
         * trace buffer and initialize the values.
         */
        if (dtrace_helptrace_enabled) {
                ASSERT(dtrace_helptrace_buffer == NULL);
                dtrace_helptrace_buffer =
                    kmem_zalloc(dtrace_helptrace_bufsize, KM_SLEEP);
                dtrace_helptrace_next = 0;
        }

        /*
         * If there are already providers, we must ask them to provide their
         * probes, and then match any anonymous enabling against them.  Note
         * that there should be no other retained enablings at this time:
         * the only retained enablings at this time should be the anonymous
         * enabling.
         */
        if (dtrace_anon.dta_enabling != NULL) {
                ASSERT(dtrace_retained == dtrace_anon.dta_enabling);

                /*
                 * APPLE NOTE: if handling anonymous dof, switch symbol modes.
                 */
                if (dtrace_kernel_symbol_mode == DTRACE_KERNEL_SYMBOLS_FROM_USERSPACE) {
                        dtrace_kernel_symbol_mode = DTRACE_KERNEL_SYMBOLS_FROM_KERNEL;
                }
                
                dtrace_enabling_provide(NULL);
                state = dtrace_anon.dta_state;

                /*
                 * We couldn't hold cpu_lock across the above call to
                 * dtrace_enabling_provide(), but we must hold it to actually
                 * enable the probes.  We have to drop all of our locks, pick
                 * up cpu_lock, and regain our locks before matching the
                 * retained anonymous enabling.
                 */
                lck_mtx_unlock(&dtrace_lock);
                lck_mtx_unlock(&dtrace_provider_lock);

                lck_mtx_lock(&cpu_lock);
                lck_mtx_lock(&dtrace_provider_lock);
                lck_mtx_lock(&dtrace_lock);

                if ((enab = dtrace_anon.dta_enabling) != NULL)
                        (void) dtrace_enabling_match(enab, NULL, NULL);

                lck_mtx_unlock(&cpu_lock);
        }

        lck_mtx_unlock(&dtrace_lock);
        lck_mtx_unlock(&dtrace_provider_lock);

        if (state != NULL) {
                /*
                 * If we created any anonymous state, set it going now.
                 */
                (void) dtrace_state_go(state, &dtrace_anon.dta_beganon);
        }

        return (DDI_SUCCESS);
}

/*ARGSUSED*/
static int
dtrace_open(dev_t *devp, int flag, int otyp, cred_t *cred_p)
{
#pragma unused(flag, otyp)
        dtrace_state_t *state;
        uint32_t priv;
        uid_t uid;
        zoneid_t zoneid;
        int rv;

        /* APPLE: Darwin puts Helper on its own major device. */

        /*
         * If no DTRACE_PRIV_* bits are set in the credential, then the
         * caller lacks sufficient permission to do anything with DTrace.
         */
        dtrace_cred2priv(cred_p, &priv, &uid, &zoneid);
        if (priv == DTRACE_PRIV_NONE)
                return (EACCES);

        /*
         * APPLE NOTE: We delay the initialization of fasttrap as late as possible.
         * It certainly can't be later than now!
         */
        fasttrap_init();

        /*
         * Ask all providers to provide all their probes.
         */
        lck_mtx_lock(&dtrace_provider_lock);
        dtrace_probe_provide(NULL, NULL);
        lck_mtx_unlock(&dtrace_provider_lock);

        lck_mtx_lock(&cpu_lock);
        lck_mtx_lock(&dtrace_lock);
        dtrace_opens++;
        dtrace_membar_producer();

#ifdef illumos
        /*
         * If the kernel debugger is active (that is, if the kernel debugger
         * modified text in some way), we won't allow the open.
         */
        if (kdi_dtrace_set(KDI_DTSET_DTRACE_ACTIVATE) != 0) {
                dtrace_opens--;
                lck_mtx_unlock(&dtrace_lock);
                lck_mtx_unlock(&cpu_lock);
                return (EBUSY);
        }
#endif

        rv = dtrace_state_create(devp, cred_p, &state);
        lck_mtx_unlock(&cpu_lock);

        if (rv != 0 || state == NULL) {
                if (--dtrace_opens == 0 && dtrace_anon.dta_enabling == NULL) {
#ifdef illumos
                        (void) kdi_dtrace_set(KDI_DTSET_DTRACE_DEACTIVATE);
#endif
                }
                lck_mtx_unlock(&dtrace_lock);
                /* propagate EAGAIN or ERESTART */
                return (rv);
        }
        
        lck_mtx_unlock(&dtrace_lock);

        lck_rw_lock_exclusive(&dtrace_dof_mode_lock);

        /*
         * If we are currently lazy, transition states.
         *
         * Unlike dtrace_close, we do not need to check the
         * value of dtrace_opens, as any positive value (and
         * we count as 1) means we transition states.
         */
        if (dtrace_dof_mode == DTRACE_DOF_MODE_LAZY_ON) {
                dtrace_dof_mode = DTRACE_DOF_MODE_LAZY_OFF;
                /*
                 * We do not need to hold the exclusive lock while processing
                 * DOF on processes. We do need to make sure the mode does not get
                 * changed to DTRACE_DOF_MODE_LAZY_ON during that stage though
                 * (which should not happen anyway since it only happens in
                 * dtrace_close). There is no way imcomplete USDT probes can be
                 * activate by any DTrace clients here since they all have to
                 * call dtrace_open and be blocked on dtrace_dof_mode_lock
                 */
                lck_rw_lock_exclusive_to_shared(&dtrace_dof_mode_lock);
                /*
                 * Iterate all existing processes and load lazy dofs.
                 */
                proc_iterate(PROC_ALLPROCLIST | PROC_NOWAITTRANS,
                             dtrace_lazy_dofs_proc_iterate_doit,
                             NULL,
                             dtrace_lazy_dofs_proc_iterate_filter,
                             NULL);

                lck_rw_unlock_shared(&dtrace_dof_mode_lock);
        }
        else {
                lck_rw_unlock_exclusive(&dtrace_dof_mode_lock);
        }


        /*
         * Update kernel symbol state.
         *
         * We must own the provider and dtrace locks. 
         *
         * NOTE! It may appear there is a race by setting this value so late
         * after dtrace_probe_provide. However, any kext loaded after the
         * call to probe provide and before we set LAZY_OFF will be marked as
         * eligible for symbols from userspace. The same dtrace that is currently
         * calling dtrace_open() (this call!) will get a list of kexts needing
         * symbols and fill them in, thus closing the race window.
         *
         * We want to set this value only after it certain it will succeed, as
         * this significantly reduces the complexity of error exits.
         */
        lck_mtx_lock(&dtrace_lock);
        if (dtrace_kernel_symbol_mode == DTRACE_KERNEL_SYMBOLS_FROM_USERSPACE) {
                dtrace_kernel_symbol_mode = DTRACE_KERNEL_SYMBOLS_FROM_KERNEL;
        }
        lck_mtx_unlock(&dtrace_lock);

        return (0);
}

/*ARGSUSED*/
static int
dtrace_close(dev_t dev, int flag, int otyp, cred_t *cred_p)
{
#pragma unused(flag, otyp, cred_p) /* __APPLE__ */
        minor_t minor = getminor(dev);
        dtrace_state_t *state;

        /* APPLE NOTE: Darwin puts Helper on its own major device. */
        state = dtrace_state_get(minor);

        lck_mtx_lock(&cpu_lock);
        lck_mtx_lock(&dtrace_lock);

        if (state->dts_anon) {
                /*
                 * There is anonymous state. Destroy that first.
                 */
                ASSERT(dtrace_anon.dta_state == NULL);
                dtrace_state_destroy(state->dts_anon);
        }

        dtrace_state_destroy(state);
        ASSERT(dtrace_opens > 0);

        /*
         * Only relinquish control of the kernel debugger interface when there
         * are no consumers and no anonymous enablings.
         */
        if (--dtrace_opens == 0 && dtrace_anon.dta_enabling == NULL) {
#ifdef illumos
                (void) kdi_dtrace_set(KDI_DTSET_DTRACE_DEACTIVATE);
#endif
        }

        lck_mtx_unlock(&dtrace_lock);
        lck_mtx_unlock(&cpu_lock);

        /*
         * Lock ordering requires the dof mode lock be taken before
         * the dtrace_lock.
         */
        lck_rw_lock_exclusive(&dtrace_dof_mode_lock);
        lck_mtx_lock(&dtrace_lock);
        
        if (dtrace_opens == 0) {
                /*
                 * If we are currently lazy-off, and this is the last close, transition to
                 * lazy state.
                 */
                if (dtrace_dof_mode == DTRACE_DOF_MODE_LAZY_OFF) {
                        dtrace_dof_mode = DTRACE_DOF_MODE_LAZY_ON;
                }

                /*
                 * If we are the last dtrace client, switch back to lazy (from userspace) symbols
                 */
                if (dtrace_kernel_symbol_mode == DTRACE_KERNEL_SYMBOLS_FROM_KERNEL) {
                        dtrace_kernel_symbol_mode = DTRACE_KERNEL_SYMBOLS_FROM_USERSPACE;
                }
        }
        
        lck_mtx_unlock(&dtrace_lock);
        lck_rw_unlock_exclusive(&dtrace_dof_mode_lock);
        
        /*
         * Kext probes may be retained past the end of the kext's lifespan. The
         * probes are kept until the last reference to them has been removed.
         * Since closing an active dtrace context is likely to drop that last reference,
         * lets take a shot at cleaning out the orphaned probes now.
         */
        dtrace_module_unloaded(NULL);

        return (0);
}

/*ARGSUSED*/
static int
dtrace_ioctl_helper(u_long cmd, caddr_t arg, int *rv)
{
#pragma unused(rv)
        /*
         * Safe to check this outside the dof mode lock
         */
        if (dtrace_dof_mode == DTRACE_DOF_MODE_NEVER)
                return KERN_SUCCESS;

        switch (cmd) {
#if defined (__arm64__)
        case DTRACEHIOC_ADDDOF_U32:
        case DTRACEHIOC_ADDDOF_U64:
#else
        case DTRACEHIOC_ADDDOF:
#endif /* __arm64__*/
                        {
                        dof_helper_t *dhp = NULL;
                        size_t dof_ioctl_data_size;
                        dof_ioctl_data_t* multi_dof;
                        unsigned int i;
                        int rval = 0;
                        user_addr_t user_address = *(user_addr_t*)arg;
                        uint64_t dof_count;
                        int multi_dof_claimed = 0;
                        proc_t* p = current_proc();

                        /*
                         * If this is a restricted process and dtrace is restricted,
                         * do not allow DOFs to be registered
                         */
                        if (dtrace_is_restricted() &&
                                !dtrace_are_restrictions_relaxed() &&
                                !dtrace_can_attach_to_proc(current_proc())) {
                                return (EACCES);
                        }

                        /*
                         * Read the number of DOF sections being passed in.
                         */
                        if (copyin(user_address + offsetof(dof_ioctl_data_t, dofiod_count),
                                   &dof_count,
                                   sizeof(dof_count))) {
                                dtrace_dof_error(NULL, "failed to copyin dofiod_count");
                                return (EFAULT);
                        }

                        /*
                         * Range check the count.
                         */
                        if (dof_count == 0 || dof_count > 1024) {
                                dtrace_dof_error(NULL, "dofiod_count is not valid");
                                return (EINVAL);
                        }
                        
                        /*
                         * Allocate a correctly sized structure and copyin the data.
                         */
                        dof_ioctl_data_size = DOF_IOCTL_DATA_T_SIZE(dof_count);
                        if ((multi_dof = kmem_alloc(dof_ioctl_data_size, KM_SLEEP)) == NULL) 
                                return (ENOMEM);
                        
                        /* NOTE! We can no longer exit this method via return */
                        if (copyin(user_address, multi_dof, dof_ioctl_data_size) != 0) {
                                dtrace_dof_error(NULL, "failed copyin of dof_ioctl_data_t");
                                rval = EFAULT;
                                goto cleanup;
                        }
                        
                        /*
                         * Check that the count didn't change between the first copyin and the second.
                         */
                        if (multi_dof->dofiod_count != dof_count) {
                                rval = EINVAL;
                                goto cleanup;
                        }

                        /*
                         * Try to process lazily first.
                         */
                        rval = dtrace_lazy_dofs_add(p, multi_dof, &multi_dof_claimed);

                        /*
                         * If rval is EACCES, we must be non-lazy.
                         */
                        if (rval == EACCES) {
                                rval = 0;
                                /*
                                 * Process each dof_helper_t
                                 */
                                i = 0;
                                do {
                                        dhp = &multi_dof->dofiod_helpers[i];
                                        
                                        dof_hdr_t *dof = dtrace_dof_copyin(dhp->dofhp_dof, &rval);
                                        
                                        if (dof != NULL) {                                      
                                                lck_mtx_lock(&dtrace_meta_lock);
                                                lck_mtx_lock(&dtrace_lock);
                                                
                                                /*
                                                 * dtrace_helper_slurp() takes responsibility for the dof --
                                                 * it may free it now or it may save it and free it later.
                                                 */
                                                if ((dhp->dofhp_dof = (uint64_t)dtrace_helper_slurp(p, dof, dhp)) == -1ULL) {
                                                        rval = EINVAL;
                                                }
                                                
                                                lck_mtx_unlock(&dtrace_lock);
                                                lck_mtx_unlock(&dtrace_meta_lock);
                                        }
                                } while (++i < multi_dof->dofiod_count && rval == 0);
                        }

                        /*
                         * We need to copyout the multi_dof struct, because it contains
                         * the generation (unique id) values needed to call DTRACEHIOC_REMOVE
                         *
                         * This could certainly be better optimized.
                         */
                        if (copyout(multi_dof, user_address, dof_ioctl_data_size) != 0) {
                                dtrace_dof_error(NULL, "failed copyout of dof_ioctl_data_t");
                                /* Don't overwrite pre-existing error code */
                                if (rval == 0) rval = EFAULT;
                        }
                        
                cleanup:
                        /*
                         * If we had to allocate struct memory, free it.
                         */
                        if (multi_dof != NULL && !multi_dof_claimed) {
                                kmem_free(multi_dof, dof_ioctl_data_size);
                        }
                        
                        return rval;
                }

                case DTRACEHIOC_REMOVE: {
                        int generation = *(int*)arg;
                        proc_t* p = current_proc();

                        /*
                         * Try lazy first.
                         */
                        int rval = dtrace_lazy_dofs_remove(p, generation);
                        
                        /*
                         * EACCES means non-lazy
                         */
                        if (rval == EACCES) {
                                lck_mtx_lock(&dtrace_meta_lock);
                                lck_mtx_lock(&dtrace_lock);
                                rval = dtrace_helper_destroygen(p, generation);
                                lck_mtx_unlock(&dtrace_lock);
                                lck_mtx_unlock(&dtrace_meta_lock);
                        }

                        return (rval);
                }

                default:
                        break;
        }

        return ENOTTY;
}

/*ARGSUSED*/
static int
dtrace_ioctl(dev_t dev, u_long cmd, user_addr_t arg, int md, cred_t *cr, int *rv)
{
#pragma unused(md)
        minor_t minor = getminor(dev);
        dtrace_state_t *state;
        int rval;

        /* Darwin puts Helper on its own major device. */

        state = dtrace_state_get(minor);

        if (state->dts_anon) {
           ASSERT(dtrace_anon.dta_state == NULL);
           state = state->dts_anon;
        }

        switch (cmd) {
        case DTRACEIOC_PROVIDER: {
                dtrace_providerdesc_t pvd;
                dtrace_provider_t *pvp;

                if (copyin(arg, &pvd, sizeof (pvd)) != 0)
                        return (EFAULT);

                pvd.dtvd_name[DTRACE_PROVNAMELEN - 1] = '\0';
                lck_mtx_lock(&dtrace_provider_lock);

                for (pvp = dtrace_provider; pvp != NULL; pvp = pvp->dtpv_next) {
                        if (strncmp(pvp->dtpv_name, pvd.dtvd_name, DTRACE_PROVNAMELEN) == 0)
                                break;
                }

                lck_mtx_unlock(&dtrace_provider_lock);

                if (pvp == NULL)
                        return (ESRCH);

                bcopy(&pvp->dtpv_priv, &pvd.dtvd_priv, sizeof (dtrace_ppriv_t));
                bcopy(&pvp->dtpv_attr, &pvd.dtvd_attr, sizeof (dtrace_pattr_t));
                if (copyout(&pvd, arg, sizeof (pvd)) != 0)
                        return (EFAULT);

                return (0);
        }

        case DTRACEIOC_EPROBE: {
                dtrace_eprobedesc_t epdesc;
                dtrace_ecb_t *ecb;
                dtrace_action_t *act;
                void *buf;
                size_t size;
                uintptr_t dest;
                int nrecs;

                if (copyin(arg, &epdesc, sizeof (epdesc)) != 0)
                        return (EFAULT);

                lck_mtx_lock(&dtrace_lock);

                if ((ecb = dtrace_epid2ecb(state, epdesc.dtepd_epid)) == NULL) {
                        lck_mtx_unlock(&dtrace_lock);
                        return (EINVAL);
                }

                if (ecb->dte_probe == NULL) {
                        lck_mtx_unlock(&dtrace_lock);
                        return (EINVAL);
                }

                epdesc.dtepd_probeid = ecb->dte_probe->dtpr_id;
                epdesc.dtepd_uarg = ecb->dte_uarg;
                epdesc.dtepd_size = ecb->dte_size;

                nrecs = epdesc.dtepd_nrecs;
                epdesc.dtepd_nrecs = 0;
                for (act = ecb->dte_action; act != NULL; act = act->dta_next) {
                        if (DTRACEACT_ISAGG(act->dta_kind) || act->dta_intuple)
                                continue;

                        epdesc.dtepd_nrecs++;
                }

                /*
                 * Now that we have the size, we need to allocate a temporary
                 * buffer in which to store the complete description.  We need
                 * the temporary buffer to be able to drop dtrace_lock()
                 * across the copyout(), below.
                 */
                size = sizeof (dtrace_eprobedesc_t) +
                        (epdesc.dtepd_nrecs * sizeof (dtrace_recdesc_t));

                buf = kmem_alloc(size, KM_SLEEP);
                dest = (uintptr_t)buf;

                bcopy(&epdesc, (void *)dest, sizeof (epdesc));
                dest += offsetof(dtrace_eprobedesc_t, dtepd_rec[0]);

                for (act = ecb->dte_action; act != NULL; act = act->dta_next) {
                        if (DTRACEACT_ISAGG(act->dta_kind) || act->dta_intuple)
                                continue;

                        if (nrecs-- == 0)
                                break;

                        bcopy(&act->dta_rec, (void *)dest,
                        sizeof (dtrace_recdesc_t));
                        dest += sizeof (dtrace_recdesc_t);
                }

                lck_mtx_unlock(&dtrace_lock);

                if (copyout(buf, arg, dest - (uintptr_t)buf) != 0) {
                        kmem_free(buf, size);
                        return (EFAULT);
                }

                kmem_free(buf, size);
                return (0);
        }

        case DTRACEIOC_AGGDESC: {
                dtrace_aggdesc_t aggdesc;
                dtrace_action_t *act;
                dtrace_aggregation_t *agg;
                int nrecs;
                uint32_t offs;
                dtrace_recdesc_t *lrec;
                void *buf;
                size_t size;
                uintptr_t dest;

                if (copyin(arg, &aggdesc, sizeof (aggdesc)) != 0)
                        return (EFAULT);

                lck_mtx_lock(&dtrace_lock);

                if ((agg = dtrace_aggid2agg(state, aggdesc.dtagd_id)) == NULL) {
                        lck_mtx_unlock(&dtrace_lock);
                        return (EINVAL);
                }

                aggdesc.dtagd_epid = agg->dtag_ecb->dte_epid;

                nrecs = aggdesc.dtagd_nrecs;
                aggdesc.dtagd_nrecs = 0;

                offs = agg->dtag_base;
                lrec = &agg->dtag_action.dta_rec;
                aggdesc.dtagd_size = lrec->dtrd_offset + lrec->dtrd_size - offs;

                for (act = agg->dtag_first; ; act = act->dta_next) {
                        ASSERT(act->dta_intuple ||
                        DTRACEACT_ISAGG(act->dta_kind));

                        /*
                         * If this action has a record size of zero, it
                         * denotes an argument to the aggregating action.
                         * Because the presence of this record doesn't (or
                         * shouldn't) affect the way the data is interpreted,
                         * we don't copy it out to save user-level the
                         * confusion of dealing with a zero-length record.
                         */
                        if (act->dta_rec.dtrd_size == 0) {
                                ASSERT(agg->dtag_hasarg);
                                continue;
                        }

                        aggdesc.dtagd_nrecs++;

                        if (act == &agg->dtag_action)
                                break;
                }

                /*
                 * Now that we have the size, we need to allocate a temporary
                 * buffer in which to store the complete description.  We need
                 * the temporary buffer to be able to drop dtrace_lock()
                 * across the copyout(), below.
                 */
                size = sizeof (dtrace_aggdesc_t) +
                        (aggdesc.dtagd_nrecs * sizeof (dtrace_recdesc_t));

                buf = kmem_alloc(size, KM_SLEEP);
                dest = (uintptr_t)buf;

                bcopy(&aggdesc, (void *)dest, sizeof (aggdesc));
                dest += offsetof(dtrace_aggdesc_t, dtagd_rec[0]);

                for (act = agg->dtag_first; ; act = act->dta_next) {
                        dtrace_recdesc_t rec = act->dta_rec;

                        /*
                         * See the comment in the above loop for why we pass
                         * over zero-length records.
                         */
                        if (rec.dtrd_size == 0) {
                                ASSERT(agg->dtag_hasarg);
                                continue;
                        }

                        if (nrecs-- == 0)
                                break;

                        rec.dtrd_offset -= offs;
                        bcopy(&rec, (void *)dest, sizeof (rec));
                        dest += sizeof (dtrace_recdesc_t);

                        if (act == &agg->dtag_action)
                                break;
                }

                lck_mtx_unlock(&dtrace_lock);

                if (copyout(buf, arg, dest - (uintptr_t)buf) != 0) {
                        kmem_free(buf, size);
                        return (EFAULT);
                }

                kmem_free(buf, size);
                return (0);
        }

        case DTRACEIOC_ENABLE: {
                dof_hdr_t *dof;
                dtrace_enabling_t *enab = NULL;
                dtrace_vstate_t *vstate;
                int err = 0;

                *rv = 0;

                /*
                 * If a NULL argument has been passed, we take this as our
                 * cue to reevaluate our enablings.
                 */
                if (arg == 0) {
                        dtrace_enabling_matchall();

                        return (0);
                }

                if ((dof = dtrace_dof_copyin(arg, &rval)) == NULL)
                        return (rval);

                lck_mtx_lock(&cpu_lock);
                lck_mtx_lock(&dtrace_lock);
                vstate = &state->dts_vstate;

                if (state->dts_activity != DTRACE_ACTIVITY_INACTIVE) {
                        lck_mtx_unlock(&dtrace_lock);
                        lck_mtx_unlock(&cpu_lock);
                        dtrace_dof_destroy(dof);
                        return (EBUSY);
                }

                if (dtrace_dof_slurp(dof, vstate, cr, &enab, 0, B_TRUE) != 0) {
                        lck_mtx_unlock(&dtrace_lock);
                        lck_mtx_unlock(&cpu_lock);
                        dtrace_dof_destroy(dof);
                        return (EINVAL);
                }

                if ((rval = dtrace_dof_options(dof, state)) != 0) {
                        dtrace_enabling_destroy(enab);
                        lck_mtx_unlock(&dtrace_lock);
                        lck_mtx_unlock(&cpu_lock);
                        dtrace_dof_destroy(dof);
                        return (rval);
                }

                if ((err = dtrace_enabling_match(enab, rv, NULL)) == 0) {
                        err = dtrace_enabling_retain(enab);
                } else {
                        dtrace_enabling_destroy(enab);
                }

                lck_mtx_unlock(&dtrace_lock);
                lck_mtx_unlock(&cpu_lock);
                dtrace_dof_destroy(dof);

                return (err);
        }

        case DTRACEIOC_REPLICATE: {
                dtrace_repldesc_t desc;
                dtrace_probedesc_t *match = &desc.dtrpd_match;
                dtrace_probedesc_t *create = &desc.dtrpd_create;
                int err;

                if (copyin(arg, &desc, sizeof (desc)) != 0)
                        return (EFAULT);

                match->dtpd_provider[DTRACE_PROVNAMELEN - 1] = '\0';
                match->dtpd_mod[DTRACE_MODNAMELEN - 1] = '\0';
                match->dtpd_func[DTRACE_FUNCNAMELEN - 1] = '\0';
                match->dtpd_name[DTRACE_NAMELEN - 1] = '\0';

                create->dtpd_provider[DTRACE_PROVNAMELEN - 1] = '\0';
                create->dtpd_mod[DTRACE_MODNAMELEN - 1] = '\0';
                create->dtpd_func[DTRACE_FUNCNAMELEN - 1] = '\0';
                create->dtpd_name[DTRACE_NAMELEN - 1] = '\0';

                lck_mtx_lock(&dtrace_lock);
                err = dtrace_enabling_replicate(state, match, create);
                lck_mtx_unlock(&dtrace_lock);

                return (err);
        }

        case DTRACEIOC_PROBEMATCH:
        case DTRACEIOC_PROBES: {
                dtrace_probe_t *probe = NULL;
                dtrace_probedesc_t desc;
                dtrace_probekey_t pkey;
                dtrace_id_t i;
                int m = 0;
                uint32_t priv;
                uid_t uid;
                zoneid_t zoneid;

                if (copyin(arg, &desc, sizeof (desc)) != 0)
                        return (EFAULT);

                desc.dtpd_provider[DTRACE_PROVNAMELEN - 1] = '\0';
                desc.dtpd_mod[DTRACE_MODNAMELEN - 1] = '\0';
                desc.dtpd_func[DTRACE_FUNCNAMELEN - 1] = '\0';
                desc.dtpd_name[DTRACE_NAMELEN - 1] = '\0';

                /*
                 * Before we attempt to match this probe, we want to give
                 * all providers the opportunity to provide it.
                 */
                if (desc.dtpd_id == DTRACE_IDNONE) {
                        lck_mtx_lock(&dtrace_provider_lock);
                        dtrace_probe_provide(&desc, NULL);
                        lck_mtx_unlock(&dtrace_provider_lock);
                        desc.dtpd_id++;
                }

                dtrace_cred2priv(cr, &priv, &uid, &zoneid);

                lck_mtx_lock(&dtrace_lock);

                if (cmd == DTRACEIOC_PROBEMATCH)  {
                        dtrace_probekey(&desc, &pkey);
                        pkey.dtpk_id = DTRACE_IDNONE;

                        /* Quiet compiler warning */
                        for (i = desc.dtpd_id; i <= (dtrace_id_t)dtrace_nprobes; i++) {
                                if ((probe = dtrace_probes[i - 1]) != NULL &&
                                        (m = dtrace_match_probe(probe, &pkey,
                                        priv, uid, zoneid)) != 0)
                                        break;
                        }

                        if (m < 0) {
                                lck_mtx_unlock(&dtrace_lock);
                                return (EINVAL);
                        }
                        dtrace_probekey_release(&pkey);

                } else {
                        /* Quiet compiler warning */
                        for (i = desc.dtpd_id; i <= (dtrace_id_t)dtrace_nprobes; i++) {
                                if ((probe = dtrace_probes[i - 1]) != NULL &&
                                        dtrace_match_priv(probe, priv, uid, zoneid))
                                        break;
                        }
                }

                if (probe == NULL) {
                        lck_mtx_unlock(&dtrace_lock);
                        return (ESRCH);
                }

                dtrace_probe_description(probe, &desc);
                lck_mtx_unlock(&dtrace_lock);

                if (copyout(&desc, arg, sizeof (desc)) != 0)
                        return (EFAULT);

                return (0);
        }

        case DTRACEIOC_PROBEARG: {
                dtrace_argdesc_t desc;
                dtrace_probe_t *probe;
                dtrace_provider_t *prov;

                if (copyin(arg, &desc, sizeof (desc)) != 0)
                        return (EFAULT);

                if (desc.dtargd_id == DTRACE_IDNONE)
                        return (EINVAL);

                if (desc.dtargd_ndx == DTRACE_ARGNONE)
                        return (EINVAL);

                lck_mtx_lock(&dtrace_provider_lock);
                lck_mtx_lock(&mod_lock);
                lck_mtx_lock(&dtrace_lock);

                /* Quiet compiler warning */
                if (desc.dtargd_id > (dtrace_id_t)dtrace_nprobes) {
                        lck_mtx_unlock(&dtrace_lock);
                        lck_mtx_unlock(&mod_lock);
                        lck_mtx_unlock(&dtrace_provider_lock);
                        return (EINVAL);
                }

                if ((probe = dtrace_probes[desc.dtargd_id - 1]) == NULL) {
                        lck_mtx_unlock(&dtrace_lock);
                        lck_mtx_unlock(&mod_lock);
                        lck_mtx_unlock(&dtrace_provider_lock);
                        return (EINVAL);
                }

                lck_mtx_unlock(&dtrace_lock);

                prov = probe->dtpr_provider;

                if (prov->dtpv_pops.dtps_getargdesc == NULL) {
                /*
                 * There isn't any typed information for this probe.
                 * Set the argument number to DTRACE_ARGNONE.
                 */
                        desc.dtargd_ndx = DTRACE_ARGNONE;
                } else {
                        desc.dtargd_native[0] = '\0';
                        desc.dtargd_xlate[0] = '\0';
                        desc.dtargd_mapping = desc.dtargd_ndx;

                        prov->dtpv_pops.dtps_getargdesc(prov->dtpv_arg,
                        probe->dtpr_id, probe->dtpr_arg, &desc);
                }

                lck_mtx_unlock(&mod_lock);
                lck_mtx_unlock(&dtrace_provider_lock);

                if (copyout(&desc, arg, sizeof (desc)) != 0)
                        return (EFAULT);

                return (0);
        }

        case DTRACEIOC_GO: {
                processorid_t cpuid;
                rval = dtrace_state_go(state, &cpuid);

                if (rval != 0)
                        return (rval);

                if (copyout(&cpuid, arg, sizeof (cpuid)) != 0)
                        return (EFAULT);

                return (0);
        }

        case DTRACEIOC_STOP: {
                processorid_t cpuid;

                lck_mtx_lock(&dtrace_lock);
                rval = dtrace_state_stop(state, &cpuid);
                lck_mtx_unlock(&dtrace_lock);

                if (rval != 0)
                        return (rval);

                if (copyout(&cpuid, arg, sizeof (cpuid)) != 0)
                        return (EFAULT);

                return (0);
        }

        case DTRACEIOC_DOFGET: {
                dof_hdr_t hdr, *dof;
                uint64_t len;

                if (copyin(arg, &hdr, sizeof (hdr)) != 0)
                        return (EFAULT);

                lck_mtx_lock(&dtrace_lock);
                dof = dtrace_dof_create(state);
                lck_mtx_unlock(&dtrace_lock);

                len = MIN(hdr.dofh_loadsz, dof->dofh_loadsz);
                rval = copyout(dof, arg, len);
                dtrace_dof_destroy(dof);

                return (rval == 0 ? 0 : EFAULT);
        }

        case DTRACEIOC_SLEEP: {
                int64_t time;
                uint64_t abstime;
                uint64_t rvalue = DTRACE_WAKE_TIMEOUT;

                if (copyin(arg, &time, sizeof(time)) != 0)
                        return (EFAULT);

                nanoseconds_to_absolutetime((uint64_t)time, &abstime);
                clock_absolutetime_interval_to_deadline(abstime, &abstime);

                if (assert_wait_deadline(state, THREAD_ABORTSAFE, abstime) == THREAD_WAITING) {
                        if (state->dts_buf_over_limit > 0) {
                                clear_wait(current_thread(), THREAD_INTERRUPTED);
                                rvalue = DTRACE_WAKE_BUF_LIMIT;
                        } else {
                                thread_block(THREAD_CONTINUE_NULL);
                                if (state->dts_buf_over_limit > 0) {
                                        rvalue = DTRACE_WAKE_BUF_LIMIT;
                                }
                        }
                }

                if (copyout(&rvalue, arg, sizeof(rvalue)) != 0)
                        return (EFAULT);

                return (0);
        }

        case DTRACEIOC_SIGNAL: {
                wakeup(state);
                return (0);
        }

        case DTRACEIOC_AGGSNAP:
        case DTRACEIOC_BUFSNAP: {
                dtrace_bufdesc_t desc;
                caddr_t cached;
                boolean_t over_limit;
                dtrace_buffer_t *buf;

                if (copyin(arg, &desc, sizeof (desc)) != 0)
                        return (EFAULT);

                if ((int)desc.dtbd_cpu < 0 || desc.dtbd_cpu >= NCPU)
                        return (EINVAL);

                lck_mtx_lock(&dtrace_lock);

                if (cmd == DTRACEIOC_BUFSNAP) {
                        buf = &state->dts_buffer[desc.dtbd_cpu];
                } else {
                        buf = &state->dts_aggbuffer[desc.dtbd_cpu];
                }

                if (buf->dtb_flags & (DTRACEBUF_RING | DTRACEBUF_FILL)) {
                        size_t sz = buf->dtb_offset;

                        if (state->dts_activity != DTRACE_ACTIVITY_STOPPED) {
                                lck_mtx_unlock(&dtrace_lock);
                                return (EBUSY);
                        }

                        /*
                         * If this buffer has already been consumed, we're
                         * going to indicate that there's nothing left here
                         * to consume.
                         */
                        if (buf->dtb_flags & DTRACEBUF_CONSUMED) {
                                lck_mtx_unlock(&dtrace_lock);

                                desc.dtbd_size = 0;
                                desc.dtbd_drops = 0;
                                desc.dtbd_errors = 0;
                                desc.dtbd_oldest = 0;
                                sz = sizeof (desc);

                                if (copyout(&desc, arg, sz) != 0)
                                        return (EFAULT);

                                return (0);
                        }

                        /*
                         * If this is a ring buffer that has wrapped, we want
                         * to copy the whole thing out.
                         */
                        if (buf->dtb_flags & DTRACEBUF_WRAPPED) {
                                dtrace_buffer_polish(buf);
                                sz = buf->dtb_size;
                        }

                        if (copyout(buf->dtb_tomax, (user_addr_t)desc.dtbd_data, sz) != 0) {
                                lck_mtx_unlock(&dtrace_lock);
                                return (EFAULT);
                        }

                        desc.dtbd_size = sz;
                        desc.dtbd_drops = buf->dtb_drops;
                        desc.dtbd_errors = buf->dtb_errors;
                        desc.dtbd_oldest = buf->dtb_xamot_offset;
                        desc.dtbd_timestamp = dtrace_gethrtime();

                        lck_mtx_unlock(&dtrace_lock);

                        if (copyout(&desc, arg, sizeof (desc)) != 0)
                                return (EFAULT);

                        buf->dtb_flags |= DTRACEBUF_CONSUMED;

                        return (0);
                }

                if (buf->dtb_tomax == NULL) {
                        ASSERT(buf->dtb_xamot == NULL);
                        lck_mtx_unlock(&dtrace_lock);
                        return (ENOENT);
                }

                cached = buf->dtb_tomax;
                over_limit = buf->dtb_cur_limit == buf->dtb_size;

                ASSERT(!(buf->dtb_flags & DTRACEBUF_NOSWITCH));

                dtrace_xcall(desc.dtbd_cpu,
                        (dtrace_xcall_t)dtrace_buffer_switch, buf);

                state->dts_errors += buf->dtb_xamot_errors;

                /*
                * If the buffers did not actually switch, then the cross call
                * did not take place -- presumably because the given CPU is
                * not in the ready set.  If this is the case, we'll return
                * ENOENT.
                */
                if (buf->dtb_tomax == cached) {
                        ASSERT(buf->dtb_xamot != cached);
                        lck_mtx_unlock(&dtrace_lock);
                        return (ENOENT);
                }

                ASSERT(cached == buf->dtb_xamot);
                /*
                 * At this point we know the buffer have switched, so we
                 * can decrement the over limit count if the buffer was over
                 * its limit. The new buffer might already be over its limit
                 * yet, but we don't care since we're guaranteed not to be
                 * checking the buffer over limit count  at this point.
                 */
                if (over_limit) {
                        uint32_t old = os_atomic_dec_orig(&state->dts_buf_over_limit, relaxed);
                        #pragma unused(old)

                        /*
                         * Verify that we didn't underflow the value
                         */
                        ASSERT(old != 0);
                }

                /*
                * We have our snapshot; now copy it out.
                */
                if (dtrace_buffer_copyout(buf->dtb_xamot,
                                        (user_addr_t)desc.dtbd_data,
                                        buf->dtb_xamot_offset) != 0) {
                        lck_mtx_unlock(&dtrace_lock);
                        return (EFAULT);
                }

                desc.dtbd_size = buf->dtb_xamot_offset;
                desc.dtbd_drops = buf->dtb_xamot_drops;
                desc.dtbd_errors = buf->dtb_xamot_errors;
                desc.dtbd_oldest = 0;
                desc.dtbd_timestamp = buf->dtb_switched;

                lck_mtx_unlock(&dtrace_lock);

                /*
                 * Finally, copy out the buffer description.
                 */
                if (copyout(&desc, arg, sizeof (desc)) != 0)
                        return (EFAULT);

                return (0);
        }

        case DTRACEIOC_CONF: {
                dtrace_conf_t conf;

                bzero(&conf, sizeof (conf));
                conf.dtc_difversion = DIF_VERSION;
                conf.dtc_difintregs = DIF_DIR_NREGS;
                conf.dtc_diftupregs = DIF_DTR_NREGS;
                conf.dtc_ctfmodel = CTF_MODEL_NATIVE;

                if (copyout(&conf, arg, sizeof (conf)) != 0)
                        return (EFAULT);

                return (0);
        }

        case DTRACEIOC_STATUS: {
                dtrace_status_t stat;
                dtrace_dstate_t *dstate;
                int i, j;
                uint64_t nerrs;

                /*
                * See the comment in dtrace_state_deadman() for the reason
                * for setting dts_laststatus to INT64_MAX before setting
                * it to the correct value.
                */
                state->dts_laststatus = INT64_MAX;
                dtrace_membar_producer();
                state->dts_laststatus = dtrace_gethrtime();

                bzero(&stat, sizeof (stat));

                lck_mtx_lock(&dtrace_lock);

                if (state->dts_activity == DTRACE_ACTIVITY_INACTIVE) {
                        lck_mtx_unlock(&dtrace_lock);
                        return (ENOENT);
                }

                if (state->dts_activity == DTRACE_ACTIVITY_DRAINING)
                        stat.dtst_exiting = 1;

                nerrs = state->dts_errors;
                dstate = &state->dts_vstate.dtvs_dynvars;

                for (i = 0; i < (int)NCPU; i++) {
                        dtrace_dstate_percpu_t *dcpu = &dstate->dtds_percpu[i];

                        stat.dtst_dyndrops += dcpu->dtdsc_drops;
                        stat.dtst_dyndrops_dirty += dcpu->dtdsc_dirty_drops;
                        stat.dtst_dyndrops_rinsing += dcpu->dtdsc_rinsing_drops;

                        if (state->dts_buffer[i].dtb_flags & DTRACEBUF_FULL)
                                stat.dtst_filled++;

                        nerrs += state->dts_buffer[i].dtb_errors;

                        for (j = 0; j < state->dts_nspeculations; j++) {
                                dtrace_speculation_t *spec;
                                dtrace_buffer_t *buf;

                                spec = &state->dts_speculations[j];
                                buf = &spec->dtsp_buffer[i];
                                stat.dtst_specdrops += buf->dtb_xamot_drops;
                        }
                }

                stat.dtst_specdrops_busy = state->dts_speculations_busy;
                stat.dtst_specdrops_unavail = state->dts_speculations_unavail;
                stat.dtst_stkstroverflows = state->dts_stkstroverflows;
                stat.dtst_dblerrors = state->dts_dblerrors;
                stat.dtst_killed =
                        (state->dts_activity == DTRACE_ACTIVITY_KILLED);
                stat.dtst_errors = nerrs;

                lck_mtx_unlock(&dtrace_lock);

                if (copyout(&stat, arg, sizeof (stat)) != 0)
                        return (EFAULT);

                return (0);
        }

        case DTRACEIOC_FORMAT: {
                dtrace_fmtdesc_t fmt;
                char *str;
                int len;

                if (copyin(arg, &fmt, sizeof (fmt)) != 0)
                        return (EFAULT);

                lck_mtx_lock(&dtrace_lock);

                if (fmt.dtfd_format == 0 ||
                        fmt.dtfd_format > state->dts_nformats) {
                        lck_mtx_unlock(&dtrace_lock);
                        return (EINVAL);
                }

                /*
                 * Format strings are allocated contiguously and they are
                 * never freed; if a format index is less than the number
                 * of formats, we can assert that the format map is non-NULL
                 * and that the format for the specified index is non-NULL.
                 */
                ASSERT(state->dts_formats != NULL);
                str = state->dts_formats[fmt.dtfd_format - 1];
                ASSERT(str != NULL);

                len = strlen(str) + 1;

                if (len > fmt.dtfd_length) {
                        fmt.dtfd_length = len;

                        if (copyout(&fmt, arg, sizeof (fmt)) != 0) {
                                lck_mtx_unlock(&dtrace_lock);
                                return (EINVAL);
                        }
                } else {
                        if (copyout(str, (user_addr_t)fmt.dtfd_string, len) != 0) {
                                lck_mtx_unlock(&dtrace_lock);
                                return (EINVAL);
                        }
                }

                lck_mtx_unlock(&dtrace_lock);
                return (0);
        }

        case DTRACEIOC_MODUUIDSLIST: {
                size_t module_uuids_list_size;
                dtrace_module_uuids_list_t* uuids_list;
                uint64_t dtmul_count;

                /*
                 * Security restrictions make this operation illegal, if this is enabled DTrace
                 * must refuse to provide any fbt probes.
                 */
                if (dtrace_fbt_probes_restricted()) {
                        cmn_err(CE_WARN, "security restrictions disallow DTRACEIOC_MODUUIDSLIST");      
                        return (EPERM);
                }

                /*
                 * Fail if the kernel symbol mode makes this operation illegal.
                 * Both NEVER & ALWAYS_FROM_KERNEL are permanent states, it is legal to check
                 * for them without holding the dtrace_lock.
                 */             
                if (dtrace_kernel_symbol_mode == DTRACE_KERNEL_SYMBOLS_NEVER ||
                    dtrace_kernel_symbol_mode == DTRACE_KERNEL_SYMBOLS_ALWAYS_FROM_KERNEL) {
                        cmn_err(CE_WARN, "dtrace_kernel_symbol_mode of %u disallows DTRACEIOC_MODUUIDSLIST", dtrace_kernel_symbol_mode);
                        return (EPERM);
                }
                        
                /*
                 * Read the number of symbolsdesc structs being passed in.
                 */
                if (copyin(arg + offsetof(dtrace_module_uuids_list_t, dtmul_count),
                           &dtmul_count,
                           sizeof(dtmul_count))) {
                        cmn_err(CE_WARN, "failed to copyin dtmul_count");
                        return (EFAULT);
                }
                
                /*
                 * Range check the count. More than 2k kexts is probably an error.
                 */
                if (dtmul_count > 2048) {
                        cmn_err(CE_WARN, "dtmul_count is not valid");
                        return (EINVAL);
                }

                /*
                 * For all queries, we return EINVAL when the user specified
                 * count does not match the actual number of modules we find
                 * available.
                 *
                 * If the user specified count is zero, then this serves as a
                 * simple query to count the available modules in need of symbols.
                 */
                
                rval = 0;

                if (dtmul_count == 0)
                {
                        lck_mtx_lock(&mod_lock);
                        struct modctl* ctl = dtrace_modctl_list;
                        while (ctl) {
                                ASSERT(!MOD_HAS_USERSPACE_SYMBOLS(ctl));
                                if (!MOD_SYMBOLS_DONE(ctl) && !MOD_IS_STATIC_KEXT(ctl)) {
                                        dtmul_count++;
                                        rval = EINVAL;
                                }
                                ctl = ctl->mod_next;
                        }
                        lck_mtx_unlock(&mod_lock);
                        
                        if (copyout(&dtmul_count, arg, sizeof (dtmul_count)) != 0)
                                return (EFAULT);
                        else
                                return (rval);
                }
                
                /*
                 * If we reach this point, then we have a request for full list data.
                 * Allocate a correctly sized structure and copyin the data.
                 */
                module_uuids_list_size = DTRACE_MODULE_UUIDS_LIST_SIZE(dtmul_count);
                if ((uuids_list = kmem_alloc(module_uuids_list_size, KM_SLEEP)) == NULL) 
                        return (ENOMEM);
                
                /* NOTE! We can no longer exit this method via return */
                if (copyin(arg, uuids_list, module_uuids_list_size) != 0) {
                        cmn_err(CE_WARN, "failed copyin of dtrace_module_uuids_list_t");
                        rval = EFAULT;
                        goto moduuidslist_cleanup;
                }
                
                /*
                 * Check that the count didn't change between the first copyin and the second.
                 */
                if (uuids_list->dtmul_count != dtmul_count) {
                        rval = EINVAL;
                        goto moduuidslist_cleanup;
                }
                
                /*
                 * Build the list of UUID's that need symbols
                 */
                lck_mtx_lock(&mod_lock);
                
                dtmul_count = 0;
                
                struct modctl* ctl = dtrace_modctl_list;
                while (ctl) {
                        /*
                         * We assume that userspace symbols will be "better" than kernel level symbols,
                         * as userspace can search for dSYM(s) and symbol'd binaries. Even if kernel syms
                         * are available, add user syms if the module might use them.
                         */
                        ASSERT(!MOD_HAS_USERSPACE_SYMBOLS(ctl));
                        if (!MOD_SYMBOLS_DONE(ctl) && !MOD_IS_STATIC_KEXT(ctl)) {
                                UUID* uuid = &uuids_list->dtmul_uuid[dtmul_count];
                                if (dtmul_count++ < uuids_list->dtmul_count) {
                                        memcpy(uuid, ctl->mod_uuid, sizeof(UUID));
                                }
                        }
                        ctl = ctl->mod_next;
                }
                
                lck_mtx_unlock(&mod_lock);
                
                if (uuids_list->dtmul_count < dtmul_count)
                        rval = EINVAL;
                
                uuids_list->dtmul_count = dtmul_count;
                
                /*
                 * Copyout the symbols list (or at least the count!)
                 */
                if (copyout(uuids_list, arg, module_uuids_list_size) != 0) {
                        cmn_err(CE_WARN, "failed copyout of dtrace_symbolsdesc_list_t");
                        rval = EFAULT;
                }
                
        moduuidslist_cleanup:
                /*
                 * If we had to allocate struct memory, free it.
                 */
                if (uuids_list != NULL) {
                        kmem_free(uuids_list, module_uuids_list_size);
                }
                
                return rval;
        }

        case DTRACEIOC_PROVMODSYMS: {
                size_t module_symbols_size;
                dtrace_module_symbols_t* module_symbols;
                uint64_t dtmodsyms_count;

                /*
                 * Security restrictions make this operation illegal, if this is enabled DTrace
                 * must refuse to provide any fbt probes.
                 */
                if (dtrace_fbt_probes_restricted()) {
                        cmn_err(CE_WARN, "security restrictions disallow DTRACEIOC_MODUUIDSLIST");      
                        return (EPERM);
                }

                /*
                 * Fail if the kernel symbol mode makes this operation illegal.
                 * Both NEVER & ALWAYS_FROM_KERNEL are permanent states, it is legal to check
                 * for them without holding the dtrace_lock.
                 */
                if (dtrace_kernel_symbol_mode == DTRACE_KERNEL_SYMBOLS_NEVER ||
                    dtrace_kernel_symbol_mode == DTRACE_KERNEL_SYMBOLS_ALWAYS_FROM_KERNEL) {
                        cmn_err(CE_WARN, "dtrace_kernel_symbol_mode of %u disallows DTRACEIOC_PROVMODSYMS", dtrace_kernel_symbol_mode);
                        return (EPERM);
                }
                
                /*
                 * Read the number of module symbols structs being passed in.
                 */
                if (copyin(arg + offsetof(dtrace_module_symbols_t, dtmodsyms_count),
                           &dtmodsyms_count,
                           sizeof(dtmodsyms_count))) {
                        cmn_err(CE_WARN, "failed to copyin dtmodsyms_count");
                        return (EFAULT);
                }
                
                /*
                 * Range check the count. How much data can we pass around?
                 * FIX ME!
                 */
                if (dtmodsyms_count == 0 || (dtmodsyms_count > 100 * 1024)) {
                        cmn_err(CE_WARN, "dtmodsyms_count is not valid");
                        return (EINVAL);
                }
                        
                /*
                 * Allocate a correctly sized structure and copyin the data.
                 */
                module_symbols_size = DTRACE_MODULE_SYMBOLS_SIZE(dtmodsyms_count);
                if ((module_symbols = kmem_alloc(module_symbols_size, KM_SLEEP)) == NULL) 
                        return (ENOMEM);
                        
                rval = 0;

                /* NOTE! We can no longer exit this method via return */
                if (copyin(arg, module_symbols, module_symbols_size) != 0) {
                        cmn_err(CE_WARN, "failed copyin of dtrace_module_symbols_t");
                        rval = EFAULT;
                        goto module_symbols_cleanup;
                }
                        
                /*
                 * Check that the count didn't change between the first copyin and the second.
                 */
                if (module_symbols->dtmodsyms_count != dtmodsyms_count) {
                        rval = EINVAL;
                        goto module_symbols_cleanup;
                }
                        
                /*
                 * Find the modctl to add symbols to.
                 */
                lck_mtx_lock(&dtrace_provider_lock);
                lck_mtx_lock(&mod_lock);
                
                struct modctl* ctl = dtrace_modctl_list;
                while (ctl) {
                        ASSERT(!MOD_HAS_USERSPACE_SYMBOLS(ctl));
                        if (MOD_HAS_UUID(ctl) && !MOD_SYMBOLS_DONE(ctl) && memcmp(module_symbols->dtmodsyms_uuid, ctl->mod_uuid, sizeof(UUID)) == 0) {
                                dtrace_provider_t *prv;
                                ctl->mod_user_symbols = module_symbols;

                                /*
                                 * We're going to call each providers per-module provide operation
                                 * specifying only this module.
                                 */
                                for (prv = dtrace_provider; prv != NULL; prv = prv->dtpv_next)
                                        prv->dtpv_pops.dtps_provide_module(prv->dtpv_arg, ctl);
                                /*
                                 * We gave every provider a chance to provide with the user syms, go ahead and clear them
                                 */
                                ctl->mod_user_symbols = NULL; /* MUST reset this to clear HAS_USERSPACE_SYMBOLS */
                        }
                        ctl = ctl->mod_next;
                }

                lck_mtx_unlock(&mod_lock);
                lck_mtx_unlock(&dtrace_provider_lock);

        module_symbols_cleanup:
                /*
                 * If we had to allocate struct memory, free it.
                 */
                if (module_symbols != NULL) {
                        kmem_free(module_symbols, module_symbols_size);
                }
                
                return rval;
        }

        case DTRACEIOC_PROCWAITFOR: {
                dtrace_procdesc_t pdesc = {
                        .p_name = {0},
                        .p_pid  = -1
                };

                if ((rval = copyin(arg, &pdesc, sizeof(pdesc))) != 0)
                        goto proc_waitfor_error;

                if ((rval = dtrace_proc_waitfor(&pdesc)) != 0)
                        goto proc_waitfor_error;

                if ((rval = copyout(&pdesc, arg, sizeof(pdesc))) != 0)
                        goto proc_waitfor_error;

                return 0;

        proc_waitfor_error:
                /* The process was suspended, revert this since the client will not do it. */
                if (pdesc.p_pid != -1) {
                        proc_t *proc = proc_find(pdesc.p_pid);
                        if (proc != PROC_NULL) {
                                task_pidresume(proc->task);
                                proc_rele(proc);
                        }
                }

                return rval;
        }

        default:
                break;
        }

        return (ENOTTY);
}

/*
 * APPLE NOTE:  dtrace_detach not implemented
 */
#if !defined(__APPLE__)
/*ARGSUSED*/
static int
dtrace_detach(dev_info_t *dip, ddi_detach_cmd_t cmd)
{
        dtrace_state_t *state;

        switch (cmd) {
        case DDI_DETACH:
                break;

        case DDI_SUSPEND:
                return (DDI_SUCCESS);

        default:
                return (DDI_FAILURE);
        }

        lck_mtx_lock(&cpu_lock);
        lck_mtx_lock(&dtrace_provider_lock);
        lck_mtx_lock(&dtrace_lock);

        ASSERT(dtrace_opens == 0);

        if (dtrace_helpers > 0) {
                lck_mtx_unlock(&dtrace_lock);
                lck_mtx_unlock(&dtrace_provider_lock);
                lck_mtx_unlock(&cpu_lock);
                return (DDI_FAILURE);
        }

        if (dtrace_unregister((dtrace_provider_id_t)dtrace_provider) != 0) {
                lck_mtx_unlock(&dtrace_lock);
                lck_mtx_unlock(&dtrace_provider_lock);
                lck_mtx_unlock(&cpu_lock);
                return (DDI_FAILURE);
        }

        dtrace_provider = NULL;

        if ((state = dtrace_anon_grab()) != NULL) {
                /*
                 * If there were ECBs on this state, the provider should
                 * have not been allowed to detach; assert that there is
                 * none.
                 */
                ASSERT(state->dts_necbs == 0);
                dtrace_state_destroy(state);

                /*
                 * If we're being detached with anonymous state, we need to
                 * indicate to the kernel debugger that DTrace is now inactive.
                 */
                (void) kdi_dtrace_set(KDI_DTSET_DTRACE_DEACTIVATE);
        }

        bzero(&dtrace_anon, sizeof (dtrace_anon_t));
        unregister_cpu_setup_func((cpu_setup_func_t *)dtrace_cpu_setup, NULL);
        dtrace_cpu_init = NULL;
        dtrace_helpers_cleanup = NULL;
        dtrace_helpers_fork = NULL;
        dtrace_cpustart_init = NULL;
        dtrace_cpustart_fini = NULL;
        dtrace_debugger_init = NULL;
        dtrace_debugger_fini = NULL;
        dtrace_kreloc_init = NULL;
        dtrace_kreloc_fini = NULL;
        dtrace_modload = NULL;
        dtrace_modunload = NULL;

        lck_mtx_unlock(&cpu_lock);

        if (dtrace_helptrace_enabled) {
                kmem_free(dtrace_helptrace_buffer, dtrace_helptrace_bufsize);
                dtrace_helptrace_buffer = NULL;
        }

        kmem_free(dtrace_probes, dtrace_nprobes * sizeof (dtrace_probe_t *));
        dtrace_probes = NULL;
        dtrace_nprobes = 0;

        dtrace_hash_destroy(dtrace_strings);
        dtrace_hash_destroy(dtrace_byprov);
        dtrace_hash_destroy(dtrace_bymod);
        dtrace_hash_destroy(dtrace_byfunc);
        dtrace_hash_destroy(dtrace_byname);
        dtrace_strings = NULL;
        dtrace_byprov = NULL;
        dtrace_bymod = NULL;
        dtrace_byfunc = NULL;
        dtrace_byname = NULL;

        kmem_cache_destroy(dtrace_state_cache);
        vmem_destroy(dtrace_arena);

        if (dtrace_toxrange != NULL) {
                kmem_free(dtrace_toxrange,
                    dtrace_toxranges_max * sizeof (dtrace_toxrange_t));
                dtrace_toxrange = NULL;
                dtrace_toxranges = 0;
                dtrace_toxranges_max = 0;
        }

        ddi_remove_minor_node(dtrace_devi, NULL);
        dtrace_devi = NULL;

        ddi_soft_state_fini(&dtrace_softstate);

        ASSERT(dtrace_vtime_references == 0);
        ASSERT(dtrace_opens == 0);
        ASSERT(dtrace_retained == NULL);

        lck_mtx_unlock(&dtrace_lock);
        lck_mtx_unlock(&dtrace_provider_lock);

#ifdef illumos
        /*
         * We don't destroy the task queue until after we have dropped our
         * locks (taskq_destroy() may block on running tasks).  To prevent
         * attempting to do work after we have effectively detached but before
         * the task queue has been destroyed, all tasks dispatched via the
         * task queue must check that DTrace is still attached before
         * performing any operation.
         */
        taskq_destroy(dtrace_taskq);
        dtrace_taskq = NULL;
#endif

        return (DDI_SUCCESS);
}
#endif  /* __APPLE__ */

d_open_t _dtrace_open, helper_open;
d_close_t _dtrace_close, helper_close;
d_ioctl_t _dtrace_ioctl, helper_ioctl;

int 
_dtrace_open(dev_t dev, int flags, int devtype, struct proc *p)
{
#pragma unused(p)
        dev_t locdev = dev;

        return  dtrace_open( &locdev, flags, devtype, CRED());
}

int
helper_open(dev_t dev, int flags, int devtype, struct proc *p)
{       
#pragma unused(dev,flags,devtype,p)
        return 0;
}

int
_dtrace_close(dev_t dev, int flags, int devtype, struct proc *p)
{
#pragma unused(p)
        return dtrace_close( dev, flags, devtype, CRED());
}

int
helper_close(dev_t dev, int flags, int devtype, struct proc *p)
{
#pragma unused(dev,flags,devtype,p)
        return 0;
}

int
_dtrace_ioctl(dev_t dev, u_long cmd, caddr_t data, int fflag, struct proc *p)
{
#pragma unused(p)
        int err, rv = 0;
    user_addr_t uaddrp;

    if (proc_is64bit(p))
                uaddrp = *(user_addr_t *)data;
        else
                uaddrp = (user_addr_t) *(uint32_t *)data;

        err = dtrace_ioctl(dev, cmd, uaddrp, fflag, CRED(), &rv);
        
        /* Darwin's BSD ioctls only return -1 or zero. Overload errno to mimic Solaris. 20 bits suffice. */
        if (err != 0) {
                ASSERT( (err & 0xfffff000) == 0 );
                return (err & 0xfff); /* ioctl will return -1 and will set errno to an error code < 4096 */
        } else if (rv != 0) {
                ASSERT( (rv & 0xfff00000) == 0 );
                return (((rv & 0xfffff) << 12)); /* ioctl will return -1 and will set errno to a value >= 4096 */
        } else 
                return 0;
}

int
helper_ioctl(dev_t dev, u_long cmd, caddr_t data, int fflag, struct proc *p)
{
#pragma unused(dev,fflag,p)
        int err, rv = 0;
        
        err = dtrace_ioctl_helper(cmd, data, &rv);
        /* Darwin's BSD ioctls only return -1 or zero. Overload errno to mimic Solaris. 20 bits suffice. */
        if (err != 0) {
                ASSERT( (err & 0xfffff000) == 0 );
                return (err & 0xfff); /* ioctl will return -1 and will set errno to an error code < 4096 */
        } else if (rv != 0) {
                ASSERT( (rv & 0xfff00000) == 0 );
                return (((rv & 0xfffff) << 12)); /* ioctl will return -1 and will set errno to a value >= 4096 */
        } else 
                return 0;
}

#define HELPER_MAJOR  -24 /* let the kernel pick the device number */

/*
 * A struct describing which functions will get invoked for certain
 * actions.
 */
static struct cdevsw helper_cdevsw =
{
        helper_open,            /* open */
        helper_close,           /* close */
        eno_rdwrt,                      /* read */
        eno_rdwrt,                      /* write */
        helper_ioctl,           /* ioctl */
        (stop_fcn_t *)nulldev, /* stop */
        (reset_fcn_t *)nulldev, /* reset */
        NULL,                           /* tty's */
        eno_select,                     /* select */
        eno_mmap,                       /* mmap */
        eno_strat,                      /* strategy */
        eno_getc,                       /* getc */
        eno_putc,                       /* putc */
        0                                       /* type */
};

static int helper_majdevno = 0;

static int gDTraceInited = 0;

void
helper_init( void )
{
        /*
         * Once the "helper" is initialized, it can take ioctl calls that use locks
         * and zones initialized in dtrace_init. Make certain dtrace_init was called
         * before us.
         */

        if (!gDTraceInited) {
                panic("helper_init before dtrace_init\n");
        }

        if (0 >= helper_majdevno)
        {
                helper_majdevno = cdevsw_add(HELPER_MAJOR, &helper_cdevsw);
                
                if (helper_majdevno < 0) {
                        printf("helper_init: failed to allocate a major number!\n");
                        return;
                }
                
                if (NULL == devfs_make_node( makedev(helper_majdevno, 0), DEVFS_CHAR, UID_ROOT, GID_WHEEL, 0666, 
                                        DTRACEMNR_HELPER, 0 )) {
                        printf("dtrace_init: failed to devfs_make_node for helper!\n");
                        return;
                }
        } else
                panic("helper_init: called twice!\n");
}

#undef HELPER_MAJOR

static int
dtrace_clone_func(dev_t dev, int action)
{
#pragma unused(dev)

        if (action == DEVFS_CLONE_ALLOC) {
                return dtrace_state_reserve();
        }
        else if (action == DEVFS_CLONE_FREE) {
                return 0;
        }
        else return -1;
}

void dtrace_ast(void);

void
dtrace_ast(void)
{
        int i;
        uint32_t clients = os_atomic_xchg(&dtrace_wake_clients, 0, relaxed);
        if (clients == 0)
                return;
        /**
         * We disable preemption here to be sure that we won't get
         * interrupted by a wakeup to a thread that is higher
         * priority than us, so that we do issue all wakeups
         */
        disable_preemption();
        for (i = 0; i < DTRACE_NCLIENTS; i++) {
                if (clients & (1 << i)) {
                        dtrace_state_t *state = dtrace_state_get(i);
                        if (state) {
                                wakeup(state);
                        }

                }
        }
        enable_preemption();
}


#define DTRACE_MAJOR  -24 /* let the kernel pick the device number */

static struct cdevsw dtrace_cdevsw =
{
        _dtrace_open,           /* open */
        _dtrace_close,          /* close */
        eno_rdwrt,                      /* read */
        eno_rdwrt,                      /* write */
        _dtrace_ioctl,          /* ioctl */
        (stop_fcn_t *)nulldev, /* stop */
        (reset_fcn_t *)nulldev, /* reset */
        NULL,                           /* tty's */
        eno_select,                     /* select */
        eno_mmap,                       /* mmap */
        eno_strat,                      /* strategy */
        eno_getc,                       /* getc */
        eno_putc,                       /* putc */
        0                                       /* type */
};

lck_attr_t* dtrace_lck_attr;
lck_grp_attr_t* dtrace_lck_grp_attr;
lck_grp_t* dtrace_lck_grp;

static int gMajDevNo;

void dtrace_early_init (void)
{
        dtrace_restriction_policy_load();

        /*
         * See dtrace_impl.h for a description of kernel symbol modes.
         * The default is to wait for symbols from userspace (lazy symbols).
         */
        if (!PE_parse_boot_argn("dtrace_kernel_symbol_mode", &dtrace_kernel_symbol_mode, sizeof (dtrace_kernel_symbol_mode))) {
                dtrace_kernel_symbol_mode = DTRACE_KERNEL_SYMBOLS_FROM_USERSPACE;
        }
}

void
dtrace_init( void )
{
        if (0 == gDTraceInited) {
                int i, ncpu;
                size_t size = sizeof(dtrace_buffer_memory_maxsize);

                /*
                 * DTrace allocates buffers based on the maximum number
                 * of enabled cpus. This call avoids any race when finding
                 * that count.
                 */
                ASSERT(dtrace_max_cpus == 0);
                ncpu = dtrace_max_cpus = ml_get_max_cpus();

                /*
                 * Retrieve the size of the physical memory in order to define
                 * the state buffer memory maximal size.  If we cannot retrieve
                 * this value, we'll consider that we have 1Gb of memory per CPU, that's
                 * still better than raising a kernel panic.
                 */
                if (0 != kernel_sysctlbyname("hw.memsize", &dtrace_buffer_memory_maxsize,
                                             &size, NULL, 0))
                {
                        dtrace_buffer_memory_maxsize = ncpu * 1024 * 1024 * 1024;
                        printf("dtrace_init: failed to retrieve the hw.memsize, defaulted to %lld bytes\n",
                               dtrace_buffer_memory_maxsize);
                }

                /*
                 * Finally, divide by three to prevent DTrace from eating too
                 * much memory.
                 */
                dtrace_buffer_memory_maxsize /= 3;
                ASSERT(dtrace_buffer_memory_maxsize > 0);

                gMajDevNo = cdevsw_add(DTRACE_MAJOR, &dtrace_cdevsw);

                if (gMajDevNo < 0) {
                        printf("dtrace_init: failed to allocate a major number!\n");
                        gDTraceInited = 0;
                        return;
                }

                if (NULL == devfs_make_node_clone( makedev(gMajDevNo, 0), DEVFS_CHAR, UID_ROOT, GID_WHEEL, 0666, 
                                        dtrace_clone_func, DTRACEMNR_DTRACE, 0 )) {
                        printf("dtrace_init: failed to devfs_make_node_clone for dtrace!\n");
                        gDTraceInited = 0;
                        return;
                }

                /*
                 * Allocate the dtrace_probe_t zone
                 */
                dtrace_probe_t_zone = zinit(sizeof(dtrace_probe_t),
                                            1024 * sizeof(dtrace_probe_t),
                                            sizeof(dtrace_probe_t),
                                            "dtrace.dtrace_probe_t");

                /*
                 * Create the dtrace lock group and attrs.
                 */
                dtrace_lck_attr = lck_attr_alloc_init();
                dtrace_lck_grp_attr= lck_grp_attr_alloc_init();         
                dtrace_lck_grp = lck_grp_alloc_init("dtrace",  dtrace_lck_grp_attr);

                /*
                 * We have to initialize all locks explicitly
                 */
                lck_mtx_init(&dtrace_lock, dtrace_lck_grp, dtrace_lck_attr);
                lck_mtx_init(&dtrace_provider_lock, dtrace_lck_grp, dtrace_lck_attr);
                lck_mtx_init(&dtrace_meta_lock, dtrace_lck_grp, dtrace_lck_attr);
                lck_mtx_init(&dtrace_procwaitfor_lock, dtrace_lck_grp, dtrace_lck_attr);
#if DEBUG
                lck_mtx_init(&dtrace_errlock, dtrace_lck_grp, dtrace_lck_attr);
#endif
                lck_rw_init(&dtrace_dof_mode_lock, dtrace_lck_grp, dtrace_lck_attr);

                /*
                 * The cpu_core structure consists of per-CPU state available in any context.
                 * On some architectures, this may mean that the page(s) containing the
                 * NCPU-sized array of cpu_core structures must be locked in the TLB -- it
                 * is up to the platform to assure that this is performed properly.  Note that
                 * the structure is sized to avoid false sharing.
                 */
                lck_mtx_init(&cpu_lock, dtrace_lck_grp, dtrace_lck_attr);
                lck_mtx_init(&cyc_lock, dtrace_lck_grp, dtrace_lck_attr);
                lck_mtx_init(&mod_lock, dtrace_lck_grp, dtrace_lck_attr);

                /*
                 * Initialize the CPU offline/online hooks.
                 */
                dtrace_install_cpu_hooks();

                dtrace_modctl_list = NULL;

                cpu_core = (cpu_core_t *)kmem_zalloc( ncpu * sizeof(cpu_core_t), KM_SLEEP );
                for (i = 0; i < ncpu; ++i) {
                        lck_mtx_init(&cpu_core[i].cpuc_pid_lock, dtrace_lck_grp, dtrace_lck_attr);
                }

                cpu_list = (dtrace_cpu_t *)kmem_zalloc( ncpu * sizeof(dtrace_cpu_t), KM_SLEEP );
                for (i = 0; i < ncpu; ++i) {
                        cpu_list[i].cpu_id = (processorid_t)i;
                        cpu_list[i].cpu_next = &(cpu_list[(i+1) % ncpu]);
                        LIST_INIT(&cpu_list[i].cpu_cyc_list);
                        lck_rw_init(&cpu_list[i].cpu_ft_lock, dtrace_lck_grp, dtrace_lck_attr);
                }

                lck_mtx_lock(&cpu_lock);
                for (i = 0; i < ncpu; ++i) 
                        /* FIXME: track CPU configuration */
                        dtrace_cpu_setup_initial( (processorid_t)i ); /* In lieu of register_cpu_setup_func() callback */
                lck_mtx_unlock(&cpu_lock);

                (void)dtrace_abs_to_nano(0LL); /* Force once only call to clock_timebase_info (which can take a lock) */

                dtrace_strings = dtrace_hash_create(dtrace_strkey_offset,
                    offsetof(dtrace_string_t, dtst_str),
                    offsetof(dtrace_string_t, dtst_next),
                    offsetof(dtrace_string_t, dtst_prev));

                dtrace_isa_init();
                /*
                 * See dtrace_impl.h for a description of dof modes.
                 * The default is lazy dof.
                 *
                 * FIXME: Warn if state is LAZY_OFF? It won't break anything, but
                 * makes no sense...
                 */
                if (!PE_parse_boot_argn("dtrace_dof_mode", &dtrace_dof_mode, sizeof (dtrace_dof_mode))) {
#if CONFIG_EMBEDDED
                        /* Disable DOF mode by default for performance reasons */
                        dtrace_dof_mode = DTRACE_DOF_MODE_NEVER;
#else
                        dtrace_dof_mode = DTRACE_DOF_MODE_LAZY_ON;
#endif
                }

                /*
                 * Sanity check of dof mode value.
                 */
                switch (dtrace_dof_mode) {
                        case DTRACE_DOF_MODE_NEVER:
                        case DTRACE_DOF_MODE_LAZY_ON:
                                /* valid modes, but nothing else we need to do */
                                break;

                        case DTRACE_DOF_MODE_LAZY_OFF:
                        case DTRACE_DOF_MODE_NON_LAZY:
                                /* Cannot wait for a dtrace_open to init fasttrap */
                                fasttrap_init();
                                break;

                        default:
                                /* Invalid, clamp to non lazy */
                                dtrace_dof_mode = DTRACE_DOF_MODE_NON_LAZY;
                                fasttrap_init();
                                break;
                }

#if CONFIG_DTRACE
        if (dtrace_dof_mode != DTRACE_DOF_MODE_NEVER)
            commpage_update_dof(true);
#endif

                gDTraceInited = 1;

        } else
                panic("dtrace_init: called twice!\n");
}

void
dtrace_postinit(void)
{
        /*
         * Called from bsd_init after all provider's *_init() routines have been
         * run. That way, anonymous DOF enabled under dtrace_attach() is safe
         * to go.
         */
        dtrace_attach( (dev_info_t *)(uintptr_t)makedev(gMajDevNo, 0)); /* Punning a dev_t to a dev_info_t* */
        
        /*
         * Add the mach_kernel to the module list for lazy processing
         */
        struct kmod_info fake_kernel_kmod;
        memset(&fake_kernel_kmod, 0, sizeof(fake_kernel_kmod));
        
        strlcpy(fake_kernel_kmod.name, "mach_kernel", sizeof(fake_kernel_kmod.name));
        fake_kernel_kmod.id = 1;
        fake_kernel_kmod.address = g_kernel_kmod_info.address;
        fake_kernel_kmod.size = g_kernel_kmod_info.size;

        if (dtrace_module_loaded(&fake_kernel_kmod, 0) != 0) {
                printf("dtrace_postinit: Could not register mach_kernel modctl\n");
        }
        
        (void)OSKextRegisterKextsWithDTrace();
}
#undef DTRACE_MAJOR

/*
 * Routines used to register interest in cpu's being added to or removed
 * from the system.
 */
void
register_cpu_setup_func(cpu_setup_func_t *ignore1, void *ignore2)
{
#pragma unused(ignore1,ignore2)
}

void
unregister_cpu_setup_func(cpu_setup_func_t *ignore1, void *ignore2)
{
#pragma unused(ignore1,ignore2)
}