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 /*
- * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
+ * Copyright (c) 2000-2019 Apple Inc. All rights reserved.
  *
- * @APPLE_LICENSE_HEADER_START@
- * 
- * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
- * 
- * This file contains Original Code and/or Modifications of Original Code
- * as defined in and that are subject to the Apple Public Source License
- * Version 2.0 (the 'License'). You may not use this file except in
- * compliance with the License. Please obtain a copy of the License at
- * http://www.opensource.apple.com/apsl/ and read it before using this
- * file.
- * 
- * The Original Code and all software distributed under the License are
- * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+ * @Apple_LICENSE_HEADER_START@
+ *
+ * The contents of this file constitute Original Code as defined in and
+ * are subject to the Apple Public Source License Version 1.1 (the
+ * "License").  You may not use this file except in compliance with the
+ * License.  Please obtain a copy of the License at
+ * http://www.apple.com/publicsource and read it before using this file.
+ *
+ * This Original Code and all software distributed under the License are
+ * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
- * Please see the License for the specific language governing rights and
- * limitations under the License.
- * 
- * @APPLE_LICENSE_HEADER_END@
+ * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
+ * License for the specific language governing rights and limitations
+ * under the License.
+ *
+ * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  */
 
-#include <machine/spl.h>
+#include <sys/errno.h>
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/proc_internal.h>
+#include <sys/vm.h>
+#include <sys/sysctl.h>
+#include <sys/kdebug.h>
+#include <sys/kauth.h>
+#include <sys/ktrace.h>
+#include <sys/sysproto.h>
+#include <sys/bsdtask_info.h>
+#include <sys/random.h>
 
-#define HZ      100
 #include <mach/clock_types.h>
 #include <mach/mach_types.h>
 #include <mach/mach_time.h>
+#include <mach/mach_vm.h>
+#include <machine/atomic.h>
 #include <machine/machine_routines.h>
 
-#include <sys/kdebug.h>
-#include <sys/errno.h>
-#include <sys/param.h>
-#include <sys/proc.h>
-#include <sys/vm.h>
-#include <sys/sysctl.h>
+#include <mach/machine.h>
+#include <mach/vm_map.h>
+
+#if defined(__i386__) || defined(__x86_64__)
+#include <i386/rtclock_protos.h>
+#include <i386/mp.h>
+#include <i386/machine_routines.h>
+#include <i386/tsc.h>
+#endif
+
+#include <kern/clock.h>
 
 #include <kern/thread.h>
 #include <kern/task.h>
+#include <kern/debug.h>
+#include <kern/kalloc.h>
+#include <kern/cpu_number.h>
+#include <kern/cpu_data.h>
+#include <kern/assert.h>
+#include <kern/telemetry.h>
+#include <kern/sched_prim.h>
 #include <vm/vm_kern.h>
 #include <sys/lock.h>
+#include <kperf/kperf.h>
+#include <pexpert/device_tree.h>
 
-/* trace enable status */
-unsigned int kdebug_enable = 0;
+#include <sys/malloc.h>
+#include <sys/mcache.h>
 
-/* track timestamps for security server's entropy needs */
-uint64_t *               kd_entropy_buffer = 0;
-unsigned int      kd_entropy_bufsize = 0;
-unsigned int      kd_entropy_count  = 0;
-unsigned int      kd_entropy_indx   = 0;
-unsigned int      kd_entropy_buftomem = 0;
-
-/* kd_buf kd_buffer[kd_bufsize/sizeof(kd_buf)]; */
-kd_buf * kd_bufptr;
-unsigned int kd_buftomem=0;
-kd_buf * kd_buffer=0;
-kd_buf * kd_buflast;
-kd_buf * kd_readlast;
-unsigned int nkdbufs = 8192;
-unsigned int kd_bufsize = 0;
-unsigned int kdebug_flags = 0;
-unsigned int kdebug_nolog=1;
-unsigned int kdlog_beg=0;
-unsigned int kdlog_end=0;
-unsigned int kdlog_value1=0;
-unsigned int kdlog_value2=0;
-unsigned int kdlog_value3=0;
-unsigned int kdlog_value4=0;
-
-unsigned long long kd_prev_timebase = 0LL;
-decl_simple_lock_data(,kd_trace_lock);
+#include <sys/vnode.h>
+#include <sys/vnode_internal.h>
+#include <sys/fcntl.h>
+#include <sys/file_internal.h>
+#include <sys/ubc.h>
+#include <sys/param.h>                  /* for isset() */
 
-kd_threadmap *kd_mapptr = 0;
-unsigned int kd_mapsize = 0;
-unsigned int kd_mapcount = 0;
-unsigned int kd_maptomem = 0;
+#include <mach/mach_host.h>             /* for host_info() */
+#include <libkern/OSAtomic.h>
 
-pid_t global_state_pid = -1;       /* Used to control exclusive use of kd_buffer */
+#include <machine/pal_routines.h>
+#include <machine/atomic.h>
 
-#define DBG_FUNC_MASK 0xfffffffc
+extern unsigned int wake_nkdbufs;
+extern unsigned int trace_wrap;
 
-#ifdef ppc
-extern natural_t rtclock_decrementer_min;
-#endif /* ppc */
+/*
+ * IOP(s)
+ *
+ * IOP(s) are auxiliary cores that want to participate in kdebug event logging.
+ * They are registered dynamically. Each is assigned a cpu_id at registration.
+ *
+ * NOTE: IOP trace events may not use the same clock hardware as "normal"
+ * cpus. There is an effort made to synchronize the IOP timebase with the
+ * AP, but it should be understood that there may be discrepancies.
+ *
+ * Once registered, an IOP is permanent, it cannot be unloaded/unregistered.
+ * The current implementation depends on this for thread safety.
+ *
+ * New registrations occur by allocating an kd_iop struct and assigning
+ * a provisional cpu_id of list_head->cpu_id + 1. Then a CAS to claim the
+ * list_head pointer resolves any races.
+ *
+ * You may safely walk the kd_iops list at any time, without holding locks.
+ *
+ * When allocating buffers, the current kd_iops head is captured. Any operations
+ * that depend on the buffer state (such as flushing IOP traces on reads,
+ * etc.) should use the captured list head. This will allow registrations to
+ * take place while trace is in use.
+ */
 
-struct kdebug_args {
-  int code;
-  int arg1;
-  int arg2;
-  int arg3;
-  int arg4;
-  int arg5;
-};
+typedef struct kd_iop {
+       kd_callback_t   callback;
+       uint32_t        cpu_id;
+       uint64_t        last_timestamp; /* Prevent timer rollback */
+       struct kd_iop*  next;
+} kd_iop_t;
 
-/* task to string structure */
-struct tts
-{
-  task_t   *task;            /* from procs task */
-  pid_t     pid;             /* from procs p_pid  */
-  char      task_comm[20];   /* from procs p_comm */
-};
+static kd_iop_t* kd_iops = NULL;
 
-typedef struct tts tts_t;
+/*
+ * Typefilter(s)
+ *
+ * A typefilter is a 8KB bitmap that is used to selectively filter events
+ * being recorded. It is able to individually address every class & subclass.
+ *
+ * There is a shared typefilter in the kernel which is lazily allocated. Once
+ * allocated, the shared typefilter is never deallocated. The shared typefilter
+ * is also mapped on demand into userspace processes that invoke kdebug_trace
+ * API from Libsyscall. When mapped into a userspace process, the memory is
+ * read only, and does not have a fixed address.
+ *
+ * It is a requirement that the kernel's shared typefilter always pass DBG_TRACE
+ * events. This is enforced automatically, by having the needed bits set any
+ * time the shared typefilter is mutated.
+ */
 
-struct krt
-{
-  kd_threadmap *map;    /* pointer to the map buffer */
-  int count;
-  int maxcount;
-  struct tts *atts;
-};
+typedef uint8_t* typefilter_t;
 
-typedef struct krt krt_t;
+static typefilter_t kdbg_typefilter;
+static mach_port_t  kdbg_typefilter_memory_entry;
 
-/* This is for the CHUD toolkit call */
-typedef void (*kd_chudhook_fn) (unsigned int debugid, unsigned int arg1,
-                               unsigned int arg2, unsigned int arg3,
-                               unsigned int arg4, unsigned int arg5);
+/*
+ * There are 3 combinations of page sizes:
+ *
+ *  4KB /  4KB
+ *  4KB / 16KB
+ * 16KB / 16KB
+ *
+ * The typefilter is exactly 8KB. In the first two scenarios, we would like
+ * to use 2 pages exactly; in the third scenario we must make certain that
+ * a full page is allocated so we do not inadvertantly share 8KB of random
+ * data to userspace. The round_page_32 macro rounds to kernel page size.
+ */
+#define TYPEFILTER_ALLOC_SIZE MAX(round_page_32(KDBG_TYPEFILTER_BITMAP_SIZE), KDBG_TYPEFILTER_BITMAP_SIZE)
 
-kd_chudhook_fn kdebug_chudhook = 0;   /* pointer to CHUD toolkit function */
+static typefilter_t
+typefilter_create(void)
+{
+       typefilter_t tf;
+       if (KERN_SUCCESS == kmem_alloc(kernel_map, (vm_offset_t*)&tf, TYPEFILTER_ALLOC_SIZE, VM_KERN_MEMORY_DIAG)) {
+               memset(&tf[KDBG_TYPEFILTER_BITMAP_SIZE], 0, TYPEFILTER_ALLOC_SIZE - KDBG_TYPEFILTER_BITMAP_SIZE);
+               return tf;
+       }
+       return NULL;
+}
 
-/* Support syscall SYS_kdebug_trace */
-kdebug_trace(p, uap, retval)
-     struct proc *p;
-     struct kdebug_args *uap;
-     register_t *retval;
+static void
+typefilter_deallocate(typefilter_t tf)
 {
-  if (kdebug_nolog)
-    return(EINVAL);
-  
-  kernel_debug(uap->code, uap->arg1, uap->arg2, uap->arg3, uap->arg4, 0);
-  return(0);
+       assert(tf != NULL);
+       assert(tf != kdbg_typefilter);
+       kmem_free(kernel_map, (vm_offset_t)tf, TYPEFILTER_ALLOC_SIZE);
 }
 
+static void
+typefilter_copy(typefilter_t dst, typefilter_t src)
+{
+       assert(src != NULL);
+       assert(dst != NULL);
+       memcpy(dst, src, KDBG_TYPEFILTER_BITMAP_SIZE);
+}
 
-void
-kernel_debug(debugid, arg1, arg2, arg3, arg4, arg5)
-unsigned int debugid, arg1, arg2, arg3, arg4, arg5;
+static void
+typefilter_reject_all(typefilter_t tf)
 {
-       kd_buf * kd;
-       struct proc *curproc;
-       int      s;
-       unsigned long long now;
-       mach_timespec_t *tsp;
+       assert(tf != NULL);
+       memset(tf, 0, KDBG_TYPEFILTER_BITMAP_SIZE);
+}
 
-       if (kdebug_enable & KDEBUG_ENABLE_CHUD) {
-             if (kdebug_chudhook)
-                   kdebug_chudhook(debugid, arg1, arg2, arg3, arg4, arg5);
+static void
+typefilter_allow_all(typefilter_t tf)
+{
+       assert(tf != NULL);
+       memset(tf, ~0, KDBG_TYPEFILTER_BITMAP_SIZE);
+}
 
-             if (!((kdebug_enable & KDEBUG_ENABLE_ENTROPY) ||
-                   (kdebug_enable & KDEBUG_ENABLE_TRACE)))
-               return;
-       }
+static void
+typefilter_allow_class(typefilter_t tf, uint8_t class)
+{
+       assert(tf != NULL);
+       const uint32_t BYTES_PER_CLASS = 256 / 8; // 256 subclasses, 1 bit each
+       memset(&tf[class * BYTES_PER_CLASS], 0xFF, BYTES_PER_CLASS);
+}
 
-       s = ml_set_interrupts_enabled(FALSE);
-
-       if (kdebug_enable & KDEBUG_ENABLE_ENTROPY)
-         {
-           if (kd_entropy_indx < kd_entropy_count)
-             {
-               kd_entropy_buffer [ kd_entropy_indx] = mach_absolute_time();
-               kd_entropy_indx++;
-             }
-           
-           if (kd_entropy_indx == kd_entropy_count)
-             {
-               /* Disable entropy collection */
-               kdebug_enable &= ~KDEBUG_ENABLE_ENTROPY;
-             }
-         }
-
-       if (kdebug_nolog)
-         {
-           ml_set_interrupts_enabled(s);
-           return;
-         }
-
-       usimple_lock(&kd_trace_lock);
-       if (kdebug_flags & KDBG_PIDCHECK)
-         {
-           /* If kdebug flag is not set for current proc, return  */
-           curproc = current_proc();
-           if ((curproc && !(curproc->p_flag & P_KDEBUG)) &&
-               ((debugid&0xffff0000) != (MACHDBG_CODE(DBG_MACH_SCHED, 0) | DBG_FUNC_NONE)))
-             {
-               usimple_unlock(&kd_trace_lock);
-               ml_set_interrupts_enabled(s);
-               return;
-             }
-         }
-       else if (kdebug_flags & KDBG_PIDEXCLUDE)
-         {
-           /* If kdebug flag is set for current proc, return  */
-           curproc = current_proc();
-           if ((curproc && (curproc->p_flag & P_KDEBUG)) &&
-               ((debugid&0xffff0000) != (MACHDBG_CODE(DBG_MACH_SCHED, 0) | DBG_FUNC_NONE)))
-             {
-               usimple_unlock(&kd_trace_lock);
-               ml_set_interrupts_enabled(s);
-               return;
-             }
-         }
-
-       if (kdebug_flags & KDBG_RANGECHECK)
-         {
-           if ((debugid < kdlog_beg) || (debugid > kdlog_end) 
-               && (debugid >> 24 != DBG_TRACE))
-             {
-               usimple_unlock(&kd_trace_lock);
-               ml_set_interrupts_enabled(s);
-               return;
-             }
-         }
-       else if (kdebug_flags & KDBG_VALCHECK)
-         {
-           if ((debugid & DBG_FUNC_MASK) != kdlog_value1 &&
-               (debugid & DBG_FUNC_MASK) != kdlog_value2 &&
-               (debugid & DBG_FUNC_MASK) != kdlog_value3 &&
-               (debugid & DBG_FUNC_MASK) != kdlog_value4 &&
-               (debugid >> 24 != DBG_TRACE))
-             {
-               usimple_unlock(&kd_trace_lock);
-               ml_set_interrupts_enabled(s);
-               return;
-             }
-         }
-       kd = kd_bufptr;
-       kd->debugid = debugid;
-       kd->arg1 = arg1;
-       kd->arg2 = arg2;
-       kd->arg3 = arg3;
-       kd->arg4 = arg4;
-       kd->arg5 = (int)current_act();
-        if (cpu_number())
-            kd->arg5 |= KDBG_CPU_MASK;
-                 
-       now = kd->timestamp = mach_absolute_time();
-
-       /* Watch for out of order timestamps */ 
-
-       if (now < kd_prev_timebase)
-         {
-           kd->timestamp = ++kd_prev_timebase;
-         }
-       else
-         {
-           /* Then just store the previous timestamp */
-           kd_prev_timebase = now;
-         }
-
-
-       kd_bufptr++;
-
-       if (kd_bufptr >= kd_buflast)
-               kd_bufptr = kd_buffer;
-       if (kd_bufptr == kd_readlast) {
-               if (kdebug_flags & KDBG_NOWRAP)
-                       kdebug_nolog = 1;
-               kdebug_flags |= KDBG_WRAPPED;
-       }
-       usimple_unlock(&kd_trace_lock);
-       ml_set_interrupts_enabled(s);
+static void
+typefilter_allow_csc(typefilter_t tf, uint16_t csc)
+{
+       assert(tf != NULL);
+       setbit(tf, csc);
 }
 
-void
-kernel_debug1(debugid, arg1, arg2, arg3, arg4, arg5)
-unsigned int debugid, arg1, arg2, arg3, arg4, arg5;
+static bool
+typefilter_is_debugid_allowed(typefilter_t tf, uint32_t id)
 {
-       kd_buf * kd;
-       struct proc *curproc;
-       int      s;
-       unsigned long long now;
-       mach_timespec_t *tsp;
+       assert(tf != NULL);
+       return isset(tf, KDBG_EXTRACT_CSC(id));
+}
 
-       if (kdebug_enable & KDEBUG_ENABLE_CHUD) {
-             if (kdebug_chudhook)
-                   (void)kdebug_chudhook(debugid, arg1, arg2, arg3, arg4, arg5);
+static mach_port_t
+typefilter_create_memory_entry(typefilter_t tf)
+{
+       assert(tf != NULL);
 
-             if (!((kdebug_enable & KDEBUG_ENABLE_ENTROPY) ||
-                   (kdebug_enable & KDEBUG_ENABLE_TRACE)))
-               return;
-       }
+       mach_port_t memory_entry = MACH_PORT_NULL;
+       memory_object_size_t size = TYPEFILTER_ALLOC_SIZE;
 
-       s = ml_set_interrupts_enabled(FALSE);
-
-       if (kdebug_nolog)
-         {
-           ml_set_interrupts_enabled(s);
-           return;
-         }
-
-       usimple_lock(&kd_trace_lock);
-       if (kdebug_flags & KDBG_PIDCHECK)
-         {
-           /* If kdebug flag is not set for current proc, return  */
-           curproc = current_proc();
-           if ((curproc && !(curproc->p_flag & P_KDEBUG)) &&
-               ((debugid&0xffff0000) != (MACHDBG_CODE(DBG_MACH_SCHED, 0) | DBG_FUNC_NONE)))
-             {
-               usimple_unlock(&kd_trace_lock);
-               ml_set_interrupts_enabled(s);
-               return;
-             }
-         }
-       else if (kdebug_flags & KDBG_PIDEXCLUDE)
-         {
-           /* If kdebug flag is set for current proc, return  */
-           curproc = current_proc();
-           if ((curproc && (curproc->p_flag & P_KDEBUG)) &&
-               ((debugid&0xffff0000) != (MACHDBG_CODE(DBG_MACH_SCHED, 0) | DBG_FUNC_NONE)))
-             {
-               usimple_unlock(&kd_trace_lock);
-               ml_set_interrupts_enabled(s);
-               return;
-             }
-         }
-
-       if (kdebug_flags & KDBG_RANGECHECK)
-         {
-           if ((debugid < kdlog_beg) || (debugid > kdlog_end)
-               && (debugid >> 24 != DBG_TRACE))
-             {
-               usimple_unlock(&kd_trace_lock);
-               ml_set_interrupts_enabled(s);
-               return;
-             }
-         }
-       else if (kdebug_flags & KDBG_VALCHECK)
-         {
-           if ((debugid & DBG_FUNC_MASK) != kdlog_value1 &&
-               (debugid & DBG_FUNC_MASK) != kdlog_value2 &&
-               (debugid & DBG_FUNC_MASK) != kdlog_value3 &&
-               (debugid & DBG_FUNC_MASK) != kdlog_value4 &&
-               (debugid >> 24 != DBG_TRACE))
-             {
-               usimple_unlock(&kd_trace_lock);
-               ml_set_interrupts_enabled(s);
-               return;
-             }
-         }
+       mach_make_memory_entry_64(kernel_map,
+           &size,
+           (memory_object_offset_t)tf,
+           VM_PROT_READ,
+           &memory_entry,
+           MACH_PORT_NULL);
 
-       kd = kd_bufptr;
-       kd->debugid = debugid;
-       kd->arg1 = arg1;
-       kd->arg2 = arg2;
-       kd->arg3 = arg3;
-       kd->arg4 = arg4;
-       kd->arg5 = arg5;
-       now = kd->timestamp = mach_absolute_time();
-
-       /* Watch for out of order timestamps */ 
-
-       if (now < kd_prev_timebase)
-         {
-           /* timestamps are out of order -- adjust */
-           kd->timestamp = ++kd_prev_timebase;
-         }
-       else
-         {
-           /* Then just store the previous timestamp */
-           kd_prev_timebase = now;
-         }
-
-       kd_bufptr++;
-
-       if (kd_bufptr >= kd_buflast)
-               kd_bufptr = kd_buffer;
-       if (kd_bufptr == kd_readlast) {
-               if (kdebug_flags & KDBG_NOWRAP)
-                       kdebug_nolog = 1;
-               kdebug_flags |= KDBG_WRAPPED;
-       }
-       usimple_unlock(&kd_trace_lock);
-       ml_set_interrupts_enabled(s);
+       return memory_entry;
 }
 
+static int  kdbg_copyin_typefilter(user_addr_t addr, size_t size);
+static void kdbg_enable_typefilter(void);
+static void kdbg_disable_typefilter(void);
+
+/*
+ * External prototypes
+ */
+
+void task_act_iterate_wth_args(task_t, void (*)(thread_t, void *), void *);
+void commpage_update_kdebug_state(void); /* XXX sign */
+
+extern int log_leaks;
+
+/*
+ * This flag is for testing purposes only -- it's highly experimental and tools
+ * have not been updated to support it.
+ */
+static bool kdbg_continuous_time = false;
 
-kdbg_bootstrap()
+static inline uint64_t
+kdbg_timestamp(void)
 {
-       kd_bufsize = nkdbufs * sizeof(kd_buf);
-       if (kmem_alloc(kernel_map, &kd_buftomem,
-                             (vm_size_t)kd_bufsize) == KERN_SUCCESS) 
-       kd_buffer = (kd_buf *) kd_buftomem;
-       else kd_buffer= (kd_buf *) 0;
-       kdebug_flags &= ~KDBG_WRAPPED;
-       if (kd_buffer) {
-               simple_lock_init(&kd_trace_lock);
-               kdebug_flags |= (KDBG_INIT | KDBG_BUFINIT);
-               kd_bufptr = kd_buffer;
-               kd_buflast = &kd_bufptr[nkdbufs];
-               kd_readlast = kd_bufptr;
-               kd_prev_timebase = 0LL;
-               return(0);
+       if (kdbg_continuous_time) {
+               return mach_continuous_time();
        } else {
-               kd_bufsize=0;
-               kdebug_flags &= ~(KDBG_INIT | KDBG_BUFINIT);
-               return(EINVAL);
-       }
-       
-}
-
-kdbg_reinit()
-{
-    int x;
-    int ret=0;
+               return mach_absolute_time();
+       }
+}
 
-    /* Disable trace collecting */
-    kdebug_enable &= ~KDEBUG_ENABLE_TRACE;
-    kdebug_nolog = 1;
+static int kdbg_debug = 0;
 
-    if ((kdebug_flags & KDBG_INIT) && (kdebug_flags & KDBG_BUFINIT) && kd_bufsize && kd_buffer)
-        kmem_free(kernel_map, (vm_offset_t)kd_buffer, kd_bufsize);
+int kdbg_control(int *, u_int, user_addr_t, size_t *);
 
-    if ((kdebug_flags & KDBG_MAPINIT) && kd_mapsize && kd_mapptr)
-      {
-       kmem_free(kernel_map, (vm_offset_t)kd_mapptr, kd_mapsize);
-       kdebug_flags &= ~KDBG_MAPINIT;
-       kd_mapsize = 0;
-       kd_mapptr = (kd_threadmap *) 0;
-       kd_mapcount = 0;
-      }  
+static int kdbg_read(user_addr_t, size_t *, vnode_t, vfs_context_t, uint32_t);
+static int kdbg_readcpumap(user_addr_t, size_t *);
+static int kdbg_readthrmap_v3(user_addr_t, size_t, int);
+static int kdbg_readcurthrmap(user_addr_t, size_t *);
+static int kdbg_setreg(kd_regtype *);
+static int kdbg_setpidex(kd_regtype *);
+static int kdbg_setpid(kd_regtype *);
+static void kdbg_thrmap_init(void);
+static int kdbg_reinit(bool);
+static int kdbg_bootstrap(bool);
+static int kdbg_test(size_t flavor);
 
-    ret= kdbg_bootstrap();
+static int kdbg_write_v1_header(bool write_thread_map, vnode_t vp, vfs_context_t ctx);
+static int kdbg_write_thread_map(vnode_t vp, vfs_context_t ctx);
+static int kdbg_copyout_thread_map(user_addr_t buffer, size_t *buffer_size);
+static void kdbg_clear_thread_map(void);
 
-    return(ret);
-}
+static bool kdbg_wait(uint64_t timeout_ms, bool locked_wait);
+static void kdbg_wakeup(void);
 
-void kdbg_trace_data(struct proc *proc, long *arg_pid)
-{
-    if (!proc)
-        *arg_pid = 0;
-    else
-       *arg_pid = proc->p_pid;
-    
-    return;
-}
+int kdbg_cpumap_init_internal(kd_iop_t* iops, uint32_t cpu_count,
+    uint8_t** cpumap, uint32_t* cpumap_size);
 
+static kd_threadmap *kdbg_thrmap_init_internal(size_t max_count,
+    vm_size_t *map_size, vm_size_t *map_count);
 
-void kdbg_trace_string(struct proc *proc, long *arg1, long *arg2, long *arg3, long *arg4)
-{
-    int i;
-    char *dbg_nameptr; 
-    int dbg_namelen;
-    long dbg_parms[4];
+static bool kdebug_current_proc_enabled(uint32_t debugid);
+static errno_t kdebug_check_trace_string(uint32_t debugid, uint64_t str_id);
 
-    if (!proc)
-      {
-       *arg1 = 0;
-       *arg2 = 0;
-       *arg3 = 0;
-       *arg4 = 0;
-       return;
-      }
+int kdbg_write_v3_header(user_addr_t, size_t *, int);
+int kdbg_write_v3_chunk_header(user_addr_t buffer, uint32_t tag,
+    uint32_t sub_tag, uint64_t length,
+    vnode_t vp, vfs_context_t ctx);
 
-    /* Collect the pathname for tracing */
-    dbg_nameptr = proc->p_comm;
-    dbg_namelen = strlen(proc->p_comm);
-    dbg_parms[0]=0L;
-    dbg_parms[1]=0L;
-    dbg_parms[2]=0L;
-    dbg_parms[3]=0L;
-  
-    if(dbg_namelen > sizeof(dbg_parms))
-      dbg_namelen = sizeof(dbg_parms);
-    
-    for(i=0;dbg_namelen > 0; i++)
-      {
-       dbg_parms[i]=*(long*)dbg_nameptr;
-       dbg_nameptr += sizeof(long);
-       dbg_namelen -= sizeof(long);
-      }
+user_addr_t kdbg_write_v3_event_chunk_header(user_addr_t buffer, uint32_t tag,
+    uint64_t length, vnode_t vp,
+    vfs_context_t ctx);
 
-    *arg1=dbg_parms[0];
-    *arg2=dbg_parms[1];
-    *arg3=dbg_parms[2];
-    *arg4=dbg_parms[3];
-}
+// Helper functions
 
-kdbg_resolve_map(thread_act_t th_act, krt_t *t)
-{
-  kd_threadmap *mapptr;
+static int create_buffers(bool);
+static void delete_buffers(void);
 
-  if(t->count < t->maxcount)
-    {
-      mapptr=&t->map[t->count];
-      mapptr->thread  = (unsigned int)th_act;
-      (void) strncpy (mapptr->command, t->atts->task_comm,
-                     sizeof(t->atts->task_comm)-1);
-      mapptr->command[sizeof(t->atts->task_comm)-1] = '\0';
+extern int tasks_count;
+extern int threads_count;
+extern void IOSleep(int);
 
-      /*
-       Some kernel threads have no associated pid.
-       We still need to mark the entry as valid.
-      */
-      if (t->atts->pid)
-         mapptr->valid = t->atts->pid;
-      else
-         mapptr->valid = 1;
+/* trace enable status */
+unsigned int kdebug_enable = 0;
 
-      t->count++;
-    }
-}
+/* A static buffer to record events prior to the start of regular logging */
 
-void kdbg_mapinit()
-{
-       struct proc *p;
-       struct krt akrt;
-       int tts_count;    /* number of task-to-string structures */
-       struct tts *tts_mapptr;
-       unsigned int tts_mapsize = 0;
-       unsigned int tts_maptomem=0;
-       int i;
+#define KD_EARLY_BUFFER_SIZE (16 * 1024)
+#define KD_EARLY_BUFFER_NBUFS (KD_EARLY_BUFFER_SIZE / sizeof(kd_buf))
+#if defined(__x86_64__)
+__attribute__((aligned(KD_EARLY_BUFFER_SIZE)))
+static kd_buf kd_early_buffer[KD_EARLY_BUFFER_NBUFS];
+#else /* defined(__x86_64__) */
+/*
+ * On ARM, the space for this is carved out by osfmk/arm/data.s -- clang
+ * has problems aligning to greater than 4K.
+ */
+extern kd_buf kd_early_buffer[KD_EARLY_BUFFER_NBUFS];
+#endif /* !defined(__x86_64__) */
+
+static unsigned int kd_early_index = 0;
+static bool kd_early_overflow = false;
+static bool kd_early_done = false;
+
+#define SLOW_NOLOG  0x01
+#define SLOW_CHECKS 0x02
+
+#define EVENTS_PER_STORAGE_UNIT         2048
+#define MIN_STORAGE_UNITS_PER_CPU       4
+
+#define POINTER_FROM_KDS_PTR(x) (&kd_bufs[x.buffer_index].kdsb_addr[x.offset])
+
+union kds_ptr {
+       struct {
+               uint32_t buffer_index:21;
+               uint16_t offset:11;
+       };
+       uint32_t raw;
+};
+
+struct kd_storage {
+       union   kds_ptr kds_next;
+       uint32_t kds_bufindx;
+       uint32_t kds_bufcnt;
+       uint32_t kds_readlast;
+       bool kds_lostevents;
+       uint64_t  kds_timestamp;
 
+       kd_buf  kds_records[EVENTS_PER_STORAGE_UNIT];
+};
+
+#define MAX_BUFFER_SIZE            (1024 * 1024 * 128)
+#define N_STORAGE_UNITS_PER_BUFFER (MAX_BUFFER_SIZE / sizeof(struct kd_storage))
+static_assert(N_STORAGE_UNITS_PER_BUFFER <= 0x7ff,
+    "shoudn't overflow kds_ptr.offset");
+
+struct kd_storage_buffers {
+       struct  kd_storage      *kdsb_addr;
+       uint32_t                kdsb_size;
+};
 
-        if (kdebug_flags & KDBG_MAPINIT)
-         return;
+#define KDS_PTR_NULL 0xffffffff
+struct kd_storage_buffers *kd_bufs = NULL;
+int n_storage_units = 0;
+unsigned int n_storage_buffers = 0;
+int n_storage_threshold = 0;
+int kds_waiter = 0;
 
-       /* Calculate the sizes of map buffers*/
-       for (p = allproc.lh_first, kd_mapcount=0, tts_count=0; p; 
-            p = p->p_list.le_next)
-         {
-           kd_mapcount += get_task_numacts((task_t)p->task);
-           tts_count++;
-         }
+#pragma pack(0)
+struct kd_bufinfo {
+       union  kds_ptr kd_list_head;
+       union  kds_ptr kd_list_tail;
+       bool kd_lostevents;
+       uint32_t _pad;
+       uint64_t kd_prev_timebase;
+       uint32_t num_bufs;
+} __attribute__((aligned(MAX_CPU_CACHE_LINE_SIZE)));
 
+
+/*
+ * In principle, this control block can be shared in DRAM with other
+ * coprocessors and runtimes, for configuring what tracing is enabled.
+ */
+struct kd_ctrl_page_t {
+       union kds_ptr kds_free_list;
+       uint32_t enabled        :1;
+       uint32_t _pad0          :31;
+       int                     kds_inuse_count;
+       uint32_t kdebug_flags;
+       uint32_t kdebug_slowcheck;
+       uint64_t oldest_time;
        /*
-        * The proc count could change during buffer allocation,
-        * so introduce a small fudge factor to bump up the
-        * buffer sizes. This gives new tasks some chance of 
-        * making into the tables.  Bump up by 10%.
+        * The number of kd_bufinfo structs allocated may not match the current
+        * number of active cpus. We capture the iops list head at initialization
+        * which we could use to calculate the number of cpus we allocated data for,
+        * unless it happens to be null. To avoid that case, we explicitly also
+        * capture a cpu count.
         */
-       kd_mapcount += kd_mapcount/10;
-       tts_count += tts_count/10;
+       kd_iop_t* kdebug_iops;
+       uint32_t kdebug_cpus;
+} kd_ctrl_page = {
+       .kds_free_list = {.raw = KDS_PTR_NULL},
+       .kdebug_slowcheck = SLOW_NOLOG,
+       .oldest_time = 0
+};
 
-       kd_mapsize = kd_mapcount * sizeof(kd_threadmap);
-       if((kmem_alloc(kernel_map, & kd_maptomem,
-                      (vm_size_t)kd_mapsize) == KERN_SUCCESS))
-       {
-           kd_mapptr = (kd_threadmap *) kd_maptomem;
-           bzero(kd_mapptr, kd_mapsize);
-       }
-       else
-           kd_mapptr = (kd_threadmap *) 0;
+#pragma pack()
 
-       tts_mapsize = tts_count * sizeof(struct tts);
-       if((kmem_alloc(kernel_map, & tts_maptomem,
-                      (vm_size_t)tts_mapsize) == KERN_SUCCESS))
-       {
-           tts_mapptr = (struct tts *) tts_maptomem;
-           bzero(tts_mapptr, tts_mapsize);
-       }
-       else
-           tts_mapptr = (struct tts *) 0;
+struct kd_bufinfo *kdbip = NULL;
 
+#define KDCOPYBUF_COUNT 8192
+#define KDCOPYBUF_SIZE  (KDCOPYBUF_COUNT * sizeof(kd_buf))
 
-       /* 
-        * We need to save the procs command string
-        * and take a reference for each task associated
-        * with a valid process
-        */
+#define PAGE_4KB        4096
+#define PAGE_16KB       16384
 
-       if (tts_mapptr) {
-               for (p = allproc.lh_first, i=0; p && i < tts_count; 
-                    p = p->p_list.le_next) {
-                       if (p->p_flag & P_WEXIT)
-                               continue;
-
-                       if (task_reference_try(p->task)) {
-                               tts_mapptr[i].task = p->task;
-                               tts_mapptr[i].pid  = p->p_pid;
-                               (void)strncpy(&tts_mapptr[i].task_comm, p->p_comm, sizeof(tts_mapptr[i].task_comm) - 1);
-                               i++;
-                       }
-               }
-               tts_count = i;
-       }
-
-
-       if (kd_mapptr && tts_mapptr)
-         {
-           kdebug_flags |= KDBG_MAPINIT;
-           /* Initialize thread map data */
-           akrt.map = kd_mapptr;
-           akrt.count = 0;
-           akrt.maxcount = kd_mapcount;
-           
-           for (i=0; i < tts_count; i++)
-             {
-               akrt.atts = &tts_mapptr[i];
-               task_act_iterate_wth_args(tts_mapptr[i].task, kdbg_resolve_map, &akrt);
-               task_deallocate((task_t) tts_mapptr[i].task);
-             }
-           kmem_free(kernel_map, (vm_offset_t)tts_mapptr, tts_mapsize);
-         }
-}
-
-kdbg_clear()
-{
-int x;
-
-        /* Clean up the trace buffer */ 
-        global_state_pid = -1;
-       kdebug_enable &= ~KDEBUG_ENABLE_TRACE;
-       kdebug_nolog = 1;
-       kdebug_flags &= ~KDBG_BUFINIT;
-       kdebug_flags &= (unsigned int)~KDBG_CKTYPES;
-       kdebug_flags &= ~(KDBG_NOWRAP | KDBG_RANGECHECK | KDBG_VALCHECK);
-       kdebug_flags &= ~(KDBG_PIDCHECK | KDBG_PIDEXCLUDE);
-       kmem_free(kernel_map, (vm_offset_t)kd_buffer, kd_bufsize);
-       kd_buffer = (kd_buf *)0;
-       kd_bufsize = 0;
-       kd_prev_timebase = 0LL;
+kd_buf *kdcopybuf = NULL;
 
-       /* Clean up the thread map buffer */
-       kdebug_flags &= ~KDBG_MAPINIT;
-       kmem_free(kernel_map, (vm_offset_t)kd_mapptr, kd_mapsize);
-       kd_mapptr = (kd_threadmap *) 0;
-       kd_mapsize = 0;
-       kd_mapcount = 0;
-}
+unsigned int nkdbufs = 0;
+unsigned int kdlog_beg = 0;
+unsigned int kdlog_end = 0;
+unsigned int kdlog_value1 = 0;
+unsigned int kdlog_value2 = 0;
+unsigned int kdlog_value3 = 0;
+unsigned int kdlog_value4 = 0;
 
-kdbg_setpid(kd_regtype *kdr)
-{
-  pid_t pid;
-  int flag, ret=0;
-  struct proc *p;
+static lck_spin_t * kdw_spin_lock;
+static lck_spin_t * kds_spin_lock;
+
+kd_threadmap *kd_mapptr = 0;
+vm_size_t kd_mapsize = 0;
+vm_size_t kd_mapcount = 0;
 
-  pid = (pid_t)kdr->value1;
-  flag = (int)kdr->value2;
+off_t   RAW_file_offset = 0;
+int     RAW_file_written = 0;
 
-  if (pid > 0)
-    {
-      if ((p = pfind(pid)) == NULL)
-       ret = ESRCH;
-      else
-       {
-         if (flag == 1)  /* turn on pid check for this and all pids */
-           {
-             kdebug_flags |= KDBG_PIDCHECK;
-             kdebug_flags &= ~KDBG_PIDEXCLUDE;
-             p->p_flag |= P_KDEBUG;
-           }
-         else  /* turn off pid check for this pid value */
-           {
-             /* Don't turn off all pid checking though */
-             /* kdebug_flags &= ~KDBG_PIDCHECK;*/   
-             p->p_flag &= ~P_KDEBUG;
-           }
-       }
-    }
-  else
-    ret = EINVAL;
-  return(ret);
+#define RAW_FLUSH_SIZE  (2 * 1024 * 1024)
+
+/*
+ * A globally increasing counter for identifying strings in trace.  Starts at
+ * 1 because 0 is a reserved return value.
+ */
+__attribute__((aligned(MAX_CPU_CACHE_LINE_SIZE)))
+static uint64_t g_curr_str_id = 1;
+
+#define STR_ID_SIG_OFFSET (48)
+#define STR_ID_MASK       ((1ULL << STR_ID_SIG_OFFSET) - 1)
+#define STR_ID_SIG_MASK   (~STR_ID_MASK)
+
+/*
+ * A bit pattern for identifying string IDs generated by
+ * kdebug_trace_string(2).
+ */
+static uint64_t g_str_id_signature = (0x70acULL << STR_ID_SIG_OFFSET);
+
+#define INTERRUPT       0x01050000
+#define MACH_vmfault    0x01300008
+#define BSC_SysCall     0x040c0000
+#define MACH_SysCall    0x010c0000
+
+struct kd_task_name {
+       task_t ktn_task;
+       pid_t ktn_pid;
+       char ktn_name[20];
+};
+
+struct kd_resolver {
+       kd_threadmap *krs_map;
+       vm_size_t krs_count;
+       vm_size_t krs_maxcount;
+       struct kd_task_name *krs_task;
+};
+
+/*
+ * TRACE file formats...
+ *
+ * RAW_VERSION0
+ *
+ * uint32_t #threadmaps
+ * kd_threadmap[]
+ * kd_buf[]
+ *
+ * RAW_VERSION1
+ *
+ * RAW_header, with version_no set to RAW_VERSION1
+ * kd_threadmap[]
+ * Empty space to pad alignment to the nearest page boundary.
+ * kd_buf[]
+ *
+ * RAW_VERSION1+
+ *
+ * RAW_header, with version_no set to RAW_VERSION1
+ * kd_threadmap[]
+ * kd_cpumap_header, with version_no set to RAW_VERSION1
+ * kd_cpumap[]
+ * Empty space to pad alignment to the nearest page boundary.
+ * kd_buf[]
+ *
+ * V1+ implementation details...
+ *
+ * It would have been nice to add the cpumap data "correctly", but there were
+ * several obstacles. Existing code attempts to parse both V1 and V0 files.
+ * Due to the fact that V0 has no versioning or header, the test looks like
+ * this:
+ *
+ * // Read header
+ * if (header.version_no != RAW_VERSION1) { // Assume V0 }
+ *
+ * If we add a VERSION2 file format, all existing code is going to treat that
+ * as a VERSION0 file when reading it, and crash terribly when trying to read
+ * RAW_VERSION2 threadmap entries.
+ *
+ * To differentiate between a V1 and V1+ file, read as V1 until you reach
+ * the padding bytes. Then:
+ *
+ * boolean_t is_v1plus = FALSE;
+ * if (padding_bytes >= sizeof(kd_cpumap_header)) {
+ *     kd_cpumap_header header = // read header;
+ *     if (header.version_no == RAW_VERSION1) {
+ *         is_v1plus = TRUE;
+ *     }
+ * }
+ *
+ */
+
+#define RAW_VERSION3    0x00001000
+
+// Version 3 header
+// The header chunk has the tag 0x00001000 which also serves as a magic word
+// that identifies the file as a version 3 trace file. The header payload is
+// a set of fixed fields followed by a variable number of sub-chunks:
+/*
+ *  ____________________________________________________________________________
+ | Offset | Size | Field                                                    |
+ |  ----------------------------------------------------------------------------
+ |    0   |  4   | Tag (0x00001000)                                         |
+ |    4   |  4   | Sub-tag. Represents the version of the header.           |
+ |    8   |  8   | Length of header payload (40+8x)                         |
+ |   16   |  8   | Time base info. Two 32-bit numbers, numer/denom,         |
+ |        |      | for converting timestamps to nanoseconds.                |
+ |   24   |  8   | Timestamp of trace start.                                |
+ |   32   |  8   | Wall time seconds since Unix epoch.                      |
+ |        |      | As returned by gettimeofday().                           |
+ |   40   |  4   | Wall time microseconds. As returned by gettimeofday().   |
+ |   44   |  4   | Local time zone offset in minutes. ( " )                 |
+ |   48   |  4   | Type of daylight savings time correction to apply. ( " ) |
+ |   52   |  4   | Flags. 1 = 64-bit. Remaining bits should be written      |
+ |        |      | as 0 and ignored when reading.                           |
+ |   56   |  8x  | Variable number of sub-chunks. None are required.        |
+ |        |      | Ignore unknown chunks.                                   |
+ |  ----------------------------------------------------------------------------
+ */
+// NOTE: The header sub-chunks are considered part of the header chunk,
+// so they must be included in the header chunk’s length field.
+// The CPU map is an optional sub-chunk of the header chunk. It provides
+// information about the CPUs that are referenced from the trace events.
+typedef struct {
+       uint32_t tag;
+       uint32_t sub_tag;
+       uint64_t length;
+       uint32_t timebase_numer;
+       uint32_t timebase_denom;
+       uint64_t timestamp;
+       uint64_t walltime_secs;
+       uint32_t walltime_usecs;
+       uint32_t timezone_minuteswest;
+       uint32_t timezone_dst;
+       uint32_t flags;
+} __attribute__((packed)) kd_header_v3;
+
+typedef struct {
+       uint32_t tag;
+       uint32_t sub_tag;
+       uint64_t length;
+} __attribute__((packed)) kd_chunk_header_v3;
+
+#define V3_CONFIG       0x00001b00
+#define V3_CPU_MAP      0x00001c00
+#define V3_THREAD_MAP   0x00001d00
+#define V3_RAW_EVENTS   0x00001e00
+#define V3_NULL_CHUNK   0x00002000
+
+// The current version of all kernel managed chunks is 1. The
+// V3_CURRENT_CHUNK_VERSION is added to ease the simple case
+// when most/all the kernel managed chunks have the same version.
+
+#define V3_CURRENT_CHUNK_VERSION 1
+#define V3_HEADER_VERSION     V3_CURRENT_CHUNK_VERSION
+#define V3_CPUMAP_VERSION     V3_CURRENT_CHUNK_VERSION
+#define V3_THRMAP_VERSION     V3_CURRENT_CHUNK_VERSION
+#define V3_EVENT_DATA_VERSION V3_CURRENT_CHUNK_VERSION
+
+typedef struct krt krt_t;
+
+static uint32_t
+kdbg_cpu_count(bool early_trace)
+{
+       if (early_trace) {
+#if defined(__x86_64__)
+               return max_ncpus;
+#else /* defined(__x86_64__) */
+               return ml_get_cpu_count();
+#endif /* !defined(__x86_64__) */
+       }
+
+#if defined(__x86_64__)
+       host_basic_info_data_t hinfo;
+       mach_msg_type_number_t count = HOST_BASIC_INFO_COUNT;
+       host_info((host_t)1 /* BSD_HOST */, HOST_BASIC_INFO, (host_info_t)&hinfo, &count);
+       assert(hinfo.logical_cpu_max > 0);
+       return hinfo.logical_cpu_max;
+#else /* defined(__x86_64__) */
+       return ml_get_topology_info()->max_cpu_id + 1;
+#endif /* !defined(__x86_64__) */
 }
 
-/* This is for pid exclusion in the trace buffer */
-kdbg_setpidex(kd_regtype *kdr)
+#if MACH_ASSERT
+
+static bool
+kdbg_iop_list_is_valid(kd_iop_t* iop)
 {
-  pid_t pid;
-  int flag, ret=0;
-  struct proc *p;
+       if (iop) {
+               /* Is list sorted by cpu_id? */
+               kd_iop_t* temp = iop;
+               do {
+                       assert(!temp->next || temp->next->cpu_id == temp->cpu_id - 1);
+                       assert(temp->next || (temp->cpu_id == kdbg_cpu_count(false) || temp->cpu_id == kdbg_cpu_count(true)));
+               } while ((temp = temp->next));
+
+               /* Does each entry have a function and a name? */
+               temp = iop;
+               do {
+                       assert(temp->callback.func);
+                       assert(strlen(temp->callback.iop_name) < sizeof(temp->callback.iop_name));
+               } while ((temp = temp->next));
+       }
 
-  pid = (pid_t)kdr->value1;
-  flag = (int)kdr->value2;
+       return true;
+}
 
-  if (pid > 0)
-    {
-      if ((p = pfind(pid)) == NULL)
-       ret = ESRCH;
-      else
-       {
-         if (flag == 1)  /* turn on pid exclusion */
-           {
-             kdebug_flags |= KDBG_PIDEXCLUDE;
-             kdebug_flags &= ~KDBG_PIDCHECK;
-             p->p_flag |= P_KDEBUG;
-           }
-         else  /* turn off pid exclusion for this pid value */
-           {
-             /* Don't turn off all pid exclusion though */
-             /* kdebug_flags &= ~KDBG_PIDEXCLUDE;*/   
-             p->p_flag &= ~P_KDEBUG;
-           }
-       }
-    }
-  else
-    ret = EINVAL;
-  return(ret);
-}
-
-/* This is for setting a minimum decrementer value */
-kdbg_setrtcdec(kd_regtype *kdr)
-{
-  int ret=0;
-  natural_t decval;
-
-  decval = (natural_t)kdr->value1;
-
-  if (decval && decval < KDBG_MINRTCDEC)
-      ret = EINVAL;
-#ifdef ppc
-  else
-      rtclock_decrementer_min = decval;
-#else
-  else
-    ret = EOPNOTSUPP;
-#endif /* ppc */
+#endif /* MACH_ASSERT */
 
-  return(ret);
+static void
+kdbg_iop_list_callback(kd_iop_t* iop, kd_callback_type type, void* arg)
+{
+       while (iop) {
+               iop->callback.func(iop->callback.context, type, arg);
+               iop = iop->next;
+       }
 }
 
-kdbg_setreg(kd_regtype * kdr)
+static lck_grp_t *kdebug_lck_grp = NULL;
+
+static void
+kdbg_set_tracing_enabled(bool enabled, uint32_t trace_type)
 {
-       int i,j, ret=0;
-       unsigned int val_1, val_2, val;
-       switch (kdr->type) {
-       
-       case KDBG_CLASSTYPE :
-               val_1 = (kdr->value1 & 0xff);
-               val_2 = (kdr->value2 & 0xff);
-               kdlog_beg = (val_1<<24);
-               kdlog_end = (val_2<<24);
-               kdebug_flags &= (unsigned int)~KDBG_CKTYPES;
-               kdebug_flags &= ~KDBG_VALCHECK;       /* Turn off specific value check  */
-               kdebug_flags |= (KDBG_RANGECHECK | KDBG_CLASSTYPE);
-               break;
-       case KDBG_SUBCLSTYPE :
-               val_1 = (kdr->value1 & 0xff);
-               val_2 = (kdr->value2 & 0xff);
-               val = val_2 + 1;
-               kdlog_beg = ((val_1<<24) | (val_2 << 16));
-               kdlog_end = ((val_1<<24) | (val << 16));
-               kdebug_flags &= (unsigned int)~KDBG_CKTYPES;
-               kdebug_flags &= ~KDBG_VALCHECK;       /* Turn off specific value check  */
-               kdebug_flags |= (KDBG_RANGECHECK | KDBG_SUBCLSTYPE);
-               break;
-       case KDBG_RANGETYPE :
-               kdlog_beg = (kdr->value1);
-               kdlog_end = (kdr->value2);
-               kdebug_flags &= (unsigned int)~KDBG_CKTYPES;
-               kdebug_flags &= ~KDBG_VALCHECK;       /* Turn off specific value check  */
-               kdebug_flags |= (KDBG_RANGECHECK | KDBG_RANGETYPE);
-               break;
-       case KDBG_VALCHECK:
-               kdlog_value1 = (kdr->value1);
-               kdlog_value2 = (kdr->value2);
-               kdlog_value3 = (kdr->value3);
-               kdlog_value4 = (kdr->value4);
-               kdebug_flags &= (unsigned int)~KDBG_CKTYPES;
-               kdebug_flags &= ~KDBG_RANGECHECK;    /* Turn off range check */
-               kdebug_flags |= KDBG_VALCHECK;       /* Turn on specific value check  */
-               break;
-       case KDBG_TYPENONE :
-               kdebug_flags &= (unsigned int)~KDBG_CKTYPES;
-               kdlog_beg = 0;
-               kdlog_end = 0;
-               break;
-       default :
-               ret = EINVAL;
-               break;
+       /*
+        * Drain any events from IOPs before making the state change.  On
+        * enabling, this removes any stale events from before tracing.  On
+        * disabling, this saves any events up to the point tracing is disabled.
+        */
+       kdbg_iop_list_callback(kd_ctrl_page.kdebug_iops, KD_CALLBACK_SYNC_FLUSH,
+           NULL);
+
+       int s = ml_set_interrupts_enabled(false);
+       lck_spin_lock_grp(kds_spin_lock, kdebug_lck_grp);
+
+       if (enabled) {
+               /*
+                * The oldest valid time is now; reject past events from IOPs.
+                */
+               kd_ctrl_page.oldest_time = kdbg_timestamp();
+               kdebug_enable |= trace_type;
+               kd_ctrl_page.kdebug_slowcheck &= ~SLOW_NOLOG;
+               kd_ctrl_page.enabled = 1;
+               commpage_update_kdebug_state();
+       } else {
+               kdebug_enable &= ~(KDEBUG_ENABLE_TRACE | KDEBUG_ENABLE_PPT);
+               kd_ctrl_page.kdebug_slowcheck |= SLOW_NOLOG;
+               kd_ctrl_page.enabled = 0;
+               commpage_update_kdebug_state();
+       }
+       lck_spin_unlock(kds_spin_lock);
+       ml_set_interrupts_enabled(s);
+
+       if (enabled) {
+               kdbg_iop_list_callback(kd_ctrl_page.kdebug_iops,
+                   KD_CALLBACK_KDEBUG_ENABLED, NULL);
+       } else {
+               kdbg_iop_list_callback(kd_ctrl_page.kdebug_iops,
+                   KD_CALLBACK_KDEBUG_DISABLED, NULL);
        }
-       return(ret);
 }
 
-kdbg_getreg(kd_regtype * kdr)
+static void
+kdbg_set_flags(int slowflag, int enableflag, bool enabled)
 {
-       int i,j, ret=0;
-       unsigned int val_1, val_2, val;
-#if 0  
-       switch (kdr->type) {
-       case KDBG_CLASSTYPE :
-               val_1 = (kdr->value1 & 0xff);
-               val_2 = val_1 + 1;
-               kdlog_beg = (val_1<<24);
-               kdlog_end = (val_2<<24);
-               kdebug_flags &= (unsigned int)~KDBG_CKTYPES;
-               kdebug_flags |= (KDBG_RANGECHECK | KDBG_CLASSTYPE);
-               break;
-       case KDBG_SUBCLSTYPE :
-               val_1 = (kdr->value1 & 0xff);
-               val_2 = (kdr->value2 & 0xff);
-               val = val_2 + 1;
-               kdlog_beg = ((val_1<<24) | (val_2 << 16));
-               kdlog_end = ((val_1<<24) | (val << 16));
-               kdebug_flags &= (unsigned int)~KDBG_CKTYPES;
-               kdebug_flags |= (KDBG_RANGECHECK | KDBG_SUBCLSTYPE);
-               break;
-       case KDBG_RANGETYPE :
-               kdlog_beg = (kdr->value1);
-               kdlog_end = (kdr->value2);
-               kdebug_flags &= (unsigned int)~KDBG_CKTYPES;
-               kdebug_flags |= (KDBG_RANGECHECK | KDBG_RANGETYPE);
-               break;
-       case KDBG_TYPENONE :
-               kdebug_flags &= (unsigned int)~KDBG_CKTYPES;
-               kdlog_beg = 0;
-               kdlog_end = 0;
-               break;
-       default :
-               ret = EINVAL;
-               break;
+       int s = ml_set_interrupts_enabled(false);
+       lck_spin_lock_grp(kds_spin_lock, kdebug_lck_grp);
+
+       if (enabled) {
+               kd_ctrl_page.kdebug_slowcheck |= slowflag;
+               kdebug_enable |= enableflag;
+       } else {
+               kd_ctrl_page.kdebug_slowcheck &= ~slowflag;
+               kdebug_enable &= ~enableflag;
        }
-#endif /* 0 */
-       return(EINVAL);
+
+       lck_spin_unlock(kds_spin_lock);
+       ml_set_interrupts_enabled(s);
 }
 
+/*
+ * Disable wrapping and return true if trace wrapped, false otherwise.
+ */
+static bool
+disable_wrap(uint32_t *old_slowcheck, uint32_t *old_flags)
+{
+       bool wrapped;
+       int s = ml_set_interrupts_enabled(false);
+       lck_spin_lock_grp(kds_spin_lock, kdebug_lck_grp);
+
+       *old_slowcheck = kd_ctrl_page.kdebug_slowcheck;
+       *old_flags = kd_ctrl_page.kdebug_flags;
+
+       wrapped = kd_ctrl_page.kdebug_flags & KDBG_WRAPPED;
+       kd_ctrl_page.kdebug_flags &= ~KDBG_WRAPPED;
+       kd_ctrl_page.kdebug_flags |= KDBG_NOWRAP;
+
+       lck_spin_unlock(kds_spin_lock);
+       ml_set_interrupts_enabled(s);
 
+       return wrapped;
+}
 
-kdbg_readmap(kd_threadmap *buffer, size_t *number)
+static void
+enable_wrap(uint32_t old_slowcheck)
 {
-  int avail = *number;
-  int ret = 0;
-  int count = 0;
+       int s = ml_set_interrupts_enabled(false);
+       lck_spin_lock_grp(kds_spin_lock, kdebug_lck_grp);
 
-  count = avail/sizeof (kd_threadmap);
+       kd_ctrl_page.kdebug_flags &= ~KDBG_NOWRAP;
 
-  if (count && (count <= kd_mapcount))
-    {
-      if((kdebug_flags & KDBG_MAPINIT) && kd_mapsize && kd_mapptr)
-       {
-         if (*number < kd_mapsize)
-           ret=EINVAL;
-         else
-           {
-             if (copyout(kd_mapptr, buffer, kd_mapsize))
-               ret=EINVAL;
-           }
-       }
-      else
-       ret=EINVAL;
-    }
-  else
-    ret=EINVAL;
-
-  if ((kdebug_flags & KDBG_MAPINIT) && kd_mapsize && kd_mapptr)
-    {
-      kmem_free(kernel_map, (vm_offset_t)kd_mapptr, kd_mapsize);
-      kdebug_flags &= ~KDBG_MAPINIT;
-      kd_mapsize = 0;
-      kd_mapptr = (kd_threadmap *) 0;
-      kd_mapcount = 0;
-    }  
-
-  return(ret);
-}
-
-kdbg_getentropy (mach_timespec_t * buffer, size_t *number, int ms_timeout)
-{
-  int avail = *number;
-  int ret = 0;
-  int count = 0;     /* The number of timestamp entries that will fill buffer */
-
-  if (kd_entropy_buffer)
-    return(EBUSY);
-
-  kd_entropy_count = avail/sizeof(mach_timespec_t);
-  kd_entropy_bufsize = kd_entropy_count * sizeof(mach_timespec_t);
-  kd_entropy_indx = 0;
-
-  /* Enforce maximum entropy entries here if needed */
-
-  /* allocate entropy buffer */
-  if (kmem_alloc(kernel_map, &kd_entropy_buftomem,
-                (vm_size_t)kd_entropy_bufsize) == KERN_SUCCESS)
-    {
-      kd_entropy_buffer = (uint64_t *) kd_entropy_buftomem;
-    }
-  else
-    {
-      kd_entropy_buffer = (uint64_t *) 0;
-      kd_entropy_count = 0;
-      kd_entropy_indx = 0;
-      return (EINVAL);
-    }
-
-  if (ms_timeout < 10)
-    ms_timeout = 10;
-
-  /* Enable entropy sampling */
-  kdebug_enable |= KDEBUG_ENABLE_ENTROPY;
-
-  ret = tsleep (kdbg_getentropy, PRIBIO | PCATCH, "kd_entropy", (ms_timeout/(1000/HZ)));
-
-  /* Disable entropy sampling */
-  kdebug_enable &= ~KDEBUG_ENABLE_ENTROPY;
-
-  *number = 0;
-  ret = 0;
-
-  if (kd_entropy_indx > 0)
-    {
-      /* copyout the buffer */
-      if (copyout(kd_entropy_buffer, buffer, kd_entropy_indx * sizeof(mach_timespec_t)))
-         ret = EINVAL;
-      else
-         *number = kd_entropy_indx;
-    }
-
-  /* Always cleanup */
-  kd_entropy_count = 0;
-  kd_entropy_indx = 0;
-  kd_entropy_buftomem = 0;
-  kmem_free(kernel_map, (vm_offset_t)kd_entropy_buffer, kd_entropy_bufsize);
-  kd_entropy_buffer = (uint64_t *) 0;
-  return(ret);
+       if (!(old_slowcheck & SLOW_NOLOG)) {
+               kd_ctrl_page.kdebug_slowcheck &= ~SLOW_NOLOG;
+       }
+
+       lck_spin_unlock(kds_spin_lock);
+       ml_set_interrupts_enabled(s);
 }
 
+static int
+create_buffers(bool early_trace)
+{
+       unsigned int i;
+       unsigned int p_buffer_size;
+       unsigned int f_buffer_size;
+       unsigned int f_buffers;
+       int error = 0;
 
-/*
- * This function is provided for the CHUD toolkit only.
- *    int val:
- *        zero disables kdebug_chudhook function call
- *        non-zero enables kdebug_chudhook function call
- *    char *fn:
- *        address of the enabled kdebug_chudhook function
-*/
-
-void kdbg_control_chud(int val, void *fn)
-{
-        if (val) {
-                /* enable chudhook */
-               kdebug_enable |= KDEBUG_ENABLE_CHUD;
-               kdebug_chudhook = fn;
-       }
-       else {
-               /* disable chudhook */
-                kdebug_enable &= ~KDEBUG_ENABLE_CHUD;
-               kdebug_chudhook = 0;
-       }
-}
-
-       
-kdbg_control(name, namelen, where, sizep)
-int *name;
-u_int namelen;
-char *where;
-size_t *sizep;
-{
-int ret=0;
-int size=*sizep;
-int max_entries;
-unsigned int value = name[1];
-kd_regtype kd_Reg;
-kbufinfo_t kd_bufinfo;
-
-pid_t curpid;
-struct proc *p, *curproc;
-
-       if (name[0] == KERN_KDGETBUF) {
-          /* 
-             Does not alter the global_state_pid
-             This is a passive request.
-          */
-          if (size < sizeof(kd_bufinfo.nkdbufs)) {
-            /* 
-               There is not enough room to return even
-               the first element of the info structure.
-            */
-            return(EINVAL);
-          }
-
-          kd_bufinfo.nkdbufs = nkdbufs;
-          kd_bufinfo.nkdthreads = kd_mapsize / sizeof(kd_threadmap);
-          kd_bufinfo.nolog = kdebug_nolog;
-          kd_bufinfo.flags = kdebug_flags;
-          kd_bufinfo.bufid = global_state_pid;
-          
-          if(size >= sizeof(kbufinfo_t)) {
-            /* Provide all the info we have */
-            if(copyout (&kd_bufinfo, where, sizeof(kbufinfo_t)))
-              return(EINVAL);
-          }
-          else {
-            /* 
-               For backwards compatibility, only provide
-               as much info as there is room for.
-            */
-            if(copyout (&kd_bufinfo, where, size))
-              return(EINVAL);
-          }
-          return(0);
-       }
-       else if (name[0] == KERN_KDGETENTROPY) {
-        if (kd_entropy_buffer)
-          return(EBUSY);
-        else
-          ret = kdbg_getentropy((mach_timespec_t *)where, sizep, value);
-        return (ret);
-       }
-
-        if(curproc = current_proc())
-         curpid = curproc->p_pid;
-       else
-         return (ESRCH);
-
-        if (global_state_pid == -1)
-           global_state_pid = curpid;
-       else if (global_state_pid != curpid)
-         {
-           if((p = pfind(global_state_pid)) == NULL)
-             {
-               /* The global pid no longer exists */
-               global_state_pid = curpid;
-             }
-           else
-             {
-               /* The global pid exists, deny this request */
-               return(EBUSY);
-             }
-         }
-
-       switch(name[0]) {
-               case KERN_KDEFLAGS:
-                       value &= KDBG_USERFLAGS;
-                       kdebug_flags |= value;
-                       break;
-               case KERN_KDDFLAGS:
-                       value &= KDBG_USERFLAGS;
-                       kdebug_flags &= ~value;
-                       break;
-               case KERN_KDENABLE:    /* used to enable or disable */
-                 if (value)
-                   {
-                     /* enable only if buffer is initialized */
-                     if (!(kdebug_flags & KDBG_BUFINIT))
-                       {
-                         ret=EINVAL;
-                         break;
-                       }
-                   }
-
-                 if (value)
-                   kdebug_enable |= KDEBUG_ENABLE_TRACE;
-                 else
-                   kdebug_enable &= ~KDEBUG_ENABLE_TRACE;
-
-                 kdebug_nolog = (value)?0:1;
-
-                 if (kdebug_enable & KDEBUG_ENABLE_TRACE)
-                     kdbg_mapinit();
-                 break;
-               case KERN_KDSETBUF:
-                 /* We allow a maximum buffer size of 25% of either ram or max mapped address, whichever is smaller */
-                 /* 'value' is the desired number of trace entries */
-                       max_entries = (sane_size/4) / sizeof(kd_buf);
-                       if (value <= max_entries)
-                               nkdbufs = value;
-                       else
-                         nkdbufs = max_entries;
-                       break;
-               case KERN_KDSETUP:
-                       ret=kdbg_reinit();
-                       break;
-               case KERN_KDREMOVE:
-                       kdbg_clear();
-                       break;
-               case KERN_KDSETREG:
-                       if(size < sizeof(kd_regtype)) {
-                               ret=EINVAL;
-                               break;
-                       }
-                       if (copyin(where, &kd_Reg, sizeof(kd_regtype))) {
-                               ret= EINVAL;
-                               break;
+       /*
+        * For the duration of this allocation, trace code will only reference
+        * kdebug_iops. Any iops registered after this enabling will not be
+        * messaged until the buffers are reallocated.
+        *
+        * TLDR; Must read kd_iops once and only once!
+        */
+       kd_ctrl_page.kdebug_iops = kd_iops;
+
+       assert(kdbg_iop_list_is_valid(kd_ctrl_page.kdebug_iops));
+
+       /*
+        * If the list is valid, it is sorted, newest -> oldest. Each iop entry
+        * has a cpu_id of "the older entry + 1", so the highest cpu_id will
+        * be the list head + 1.
+        */
+
+       kd_ctrl_page.kdebug_cpus = kd_ctrl_page.kdebug_iops ? kd_ctrl_page.kdebug_iops->cpu_id + 1 : kdbg_cpu_count(early_trace);
+
+       if (kmem_alloc(kernel_map, (vm_offset_t *)&kdbip, sizeof(struct kd_bufinfo) * kd_ctrl_page.kdebug_cpus, VM_KERN_MEMORY_DIAG) != KERN_SUCCESS) {
+               error = ENOSPC;
+               goto out;
+       }
+
+       if (nkdbufs < (kd_ctrl_page.kdebug_cpus * EVENTS_PER_STORAGE_UNIT * MIN_STORAGE_UNITS_PER_CPU)) {
+               n_storage_units = kd_ctrl_page.kdebug_cpus * MIN_STORAGE_UNITS_PER_CPU;
+       } else {
+               n_storage_units = nkdbufs / EVENTS_PER_STORAGE_UNIT;
+       }
+
+       nkdbufs = n_storage_units * EVENTS_PER_STORAGE_UNIT;
+
+       f_buffers = n_storage_units / N_STORAGE_UNITS_PER_BUFFER;
+       n_storage_buffers = f_buffers;
+
+       f_buffer_size = N_STORAGE_UNITS_PER_BUFFER * sizeof(struct kd_storage);
+       p_buffer_size = (n_storage_units % N_STORAGE_UNITS_PER_BUFFER) * sizeof(struct kd_storage);
+
+       if (p_buffer_size) {
+               n_storage_buffers++;
+       }
+
+       kd_bufs = NULL;
+
+       if (kdcopybuf == 0) {
+               if (kmem_alloc(kernel_map, (vm_offset_t *)&kdcopybuf, (vm_size_t)KDCOPYBUF_SIZE, VM_KERN_MEMORY_DIAG) != KERN_SUCCESS) {
+                       error = ENOSPC;
+                       goto out;
+               }
+       }
+       if (kmem_alloc(kernel_map, (vm_offset_t *)&kd_bufs, (vm_size_t)(n_storage_buffers * sizeof(struct kd_storage_buffers)), VM_KERN_MEMORY_DIAG) != KERN_SUCCESS) {
+               error = ENOSPC;
+               goto out;
+       }
+       bzero(kd_bufs, n_storage_buffers * sizeof(struct kd_storage_buffers));
+
+       for (i = 0; i < f_buffers; i++) {
+               if (kmem_alloc(kernel_map, (vm_offset_t *)&kd_bufs[i].kdsb_addr, (vm_size_t)f_buffer_size, VM_KERN_MEMORY_DIAG) != KERN_SUCCESS) {
+                       error = ENOSPC;
+                       goto out;
+               }
+               bzero(kd_bufs[i].kdsb_addr, f_buffer_size);
+
+               kd_bufs[i].kdsb_size = f_buffer_size;
+       }
+       if (p_buffer_size) {
+               if (kmem_alloc(kernel_map, (vm_offset_t *)&kd_bufs[i].kdsb_addr, (vm_size_t)p_buffer_size, VM_KERN_MEMORY_DIAG) != KERN_SUCCESS) {
+                       error = ENOSPC;
+                       goto out;
+               }
+               bzero(kd_bufs[i].kdsb_addr, p_buffer_size);
+
+               kd_bufs[i].kdsb_size = p_buffer_size;
+       }
+       n_storage_units = 0;
+
+       for (i = 0; i < n_storage_buffers; i++) {
+               struct kd_storage *kds;
+               uint16_t n_elements;
+               static_assert(N_STORAGE_UNITS_PER_BUFFER <= UINT16_MAX);
+               assert(kd_bufs[i].kdsb_size <= N_STORAGE_UNITS_PER_BUFFER *
+                   sizeof(struct kd_storage));
+
+               n_elements = kd_bufs[i].kdsb_size / sizeof(struct kd_storage);
+               kds = kd_bufs[i].kdsb_addr;
+
+               for (uint16_t n = 0; n < n_elements; n++) {
+                       kds[n].kds_next.buffer_index = kd_ctrl_page.kds_free_list.buffer_index;
+                       kds[n].kds_next.offset = kd_ctrl_page.kds_free_list.offset;
+
+                       kd_ctrl_page.kds_free_list.buffer_index = i;
+                       kd_ctrl_page.kds_free_list.offset = n;
+               }
+               n_storage_units += n_elements;
+       }
+
+       bzero((char *)kdbip, sizeof(struct kd_bufinfo) * kd_ctrl_page.kdebug_cpus);
+
+       for (i = 0; i < kd_ctrl_page.kdebug_cpus; i++) {
+               kdbip[i].kd_list_head.raw = KDS_PTR_NULL;
+               kdbip[i].kd_list_tail.raw = KDS_PTR_NULL;
+               kdbip[i].kd_lostevents = false;
+               kdbip[i].num_bufs = 0;
+       }
+
+       kd_ctrl_page.kdebug_flags |= KDBG_BUFINIT;
+
+       kd_ctrl_page.kds_inuse_count = 0;
+       n_storage_threshold = n_storage_units / 2;
+out:
+       if (error) {
+               delete_buffers();
+       }
+
+       return error;
+}
+
+static void
+delete_buffers(void)
+{
+       unsigned int i;
+
+       if (kd_bufs) {
+               for (i = 0; i < n_storage_buffers; i++) {
+                       if (kd_bufs[i].kdsb_addr) {
+                               kmem_free(kernel_map, (vm_offset_t)kd_bufs[i].kdsb_addr, (vm_size_t)kd_bufs[i].kdsb_size);
+                       }
+               }
+               kmem_free(kernel_map, (vm_offset_t)kd_bufs, (vm_size_t)(n_storage_buffers * sizeof(struct kd_storage_buffers)));
+
+               kd_bufs = NULL;
+               n_storage_buffers = 0;
+       }
+       if (kdcopybuf) {
+               kmem_free(kernel_map, (vm_offset_t)kdcopybuf, KDCOPYBUF_SIZE);
+
+               kdcopybuf = NULL;
+       }
+       kd_ctrl_page.kds_free_list.raw = KDS_PTR_NULL;
+
+       if (kdbip) {
+               kmem_free(kernel_map, (vm_offset_t)kdbip, sizeof(struct kd_bufinfo) * kd_ctrl_page.kdebug_cpus);
+
+               kdbip = NULL;
+       }
+       kd_ctrl_page.kdebug_iops = NULL;
+       kd_ctrl_page.kdebug_cpus = 0;
+       kd_ctrl_page.kdebug_flags &= ~KDBG_BUFINIT;
+}
+
+void
+release_storage_unit(int cpu, uint32_t kdsp_raw)
+{
+       int s = 0;
+       struct  kd_storage *kdsp_actual;
+       struct kd_bufinfo *kdbp;
+       union kds_ptr kdsp;
+
+       kdsp.raw = kdsp_raw;
+
+       s = ml_set_interrupts_enabled(false);
+       lck_spin_lock_grp(kds_spin_lock, kdebug_lck_grp);
+
+       kdbp = &kdbip[cpu];
+
+       if (kdsp.raw == kdbp->kd_list_head.raw) {
+               /*
+                * it's possible for the storage unit pointed to
+                * by kdsp to have already been stolen... so
+                * check to see if it's still the head of the list
+                * now that we're behind the lock that protects
+                * adding and removing from the queue...
+                * since we only ever release and steal units from
+                * that position, if it's no longer the head
+                * we having nothing to do in this context
+                */
+               kdsp_actual = POINTER_FROM_KDS_PTR(kdsp);
+               kdbp->kd_list_head = kdsp_actual->kds_next;
+
+               kdsp_actual->kds_next = kd_ctrl_page.kds_free_list;
+               kd_ctrl_page.kds_free_list = kdsp;
+
+               kd_ctrl_page.kds_inuse_count--;
+       }
+       lck_spin_unlock(kds_spin_lock);
+       ml_set_interrupts_enabled(s);
+}
+
+bool
+allocate_storage_unit(int cpu)
+{
+       union kds_ptr kdsp;
+       struct kd_storage *kdsp_actual, *kdsp_next_actual;
+       struct kd_bufinfo *kdbp, *kdbp_vict, *kdbp_try;
+       uint64_t oldest_ts, ts;
+       bool retval = true;
+       int s = 0;
+
+       s = ml_set_interrupts_enabled(false);
+       lck_spin_lock_grp(kds_spin_lock, kdebug_lck_grp);
+
+       kdbp = &kdbip[cpu];
+
+       /* If someone beat us to the allocate, return success */
+       if (kdbp->kd_list_tail.raw != KDS_PTR_NULL) {
+               kdsp_actual = POINTER_FROM_KDS_PTR(kdbp->kd_list_tail);
+
+               if (kdsp_actual->kds_bufindx < EVENTS_PER_STORAGE_UNIT) {
+                       goto out;
+               }
+       }
+
+       if ((kdsp = kd_ctrl_page.kds_free_list).raw != KDS_PTR_NULL) {
+               /*
+                * If there's a free page, grab it from the free list.
+                */
+               kdsp_actual = POINTER_FROM_KDS_PTR(kdsp);
+               kd_ctrl_page.kds_free_list = kdsp_actual->kds_next;
+
+               kd_ctrl_page.kds_inuse_count++;
+       } else {
+               /*
+                * Otherwise, we're going to lose events and repurpose the oldest
+                * storage unit we can find.
+                */
+               if (kd_ctrl_page.kdebug_flags & KDBG_NOWRAP) {
+                       kd_ctrl_page.kdebug_slowcheck |= SLOW_NOLOG;
+                       kdbp->kd_lostevents = true;
+                       retval = false;
+                       goto out;
+               }
+               kdbp_vict = NULL;
+               oldest_ts = UINT64_MAX;
+
+               for (kdbp_try = &kdbip[0]; kdbp_try < &kdbip[kd_ctrl_page.kdebug_cpus]; kdbp_try++) {
+                       if (kdbp_try->kd_list_head.raw == KDS_PTR_NULL) {
+                               /*
+                                * no storage unit to steal
+                                */
+                               continue;
+                       }
+
+                       kdsp_actual = POINTER_FROM_KDS_PTR(kdbp_try->kd_list_head);
+
+                       if (kdsp_actual->kds_bufcnt < EVENTS_PER_STORAGE_UNIT) {
+                               /*
+                                * make sure we don't steal the storage unit
+                                * being actively recorded to...  need to
+                                * move on because we don't want an out-of-order
+                                * set of events showing up later
+                                */
+                               continue;
+                       }
+
+                       /*
+                        * When wrapping, steal the storage unit with the
+                        * earliest timestamp on its last event, instead of the
+                        * earliest timestamp on the first event.  This allows a
+                        * storage unit with more recent events to be preserved,
+                        * even if the storage unit contains events that are
+                        * older than those found in other CPUs.
+                        */
+                       ts = kdbg_get_timestamp(&kdsp_actual->kds_records[EVENTS_PER_STORAGE_UNIT - 1]);
+                       if (ts < oldest_ts) {
+                               oldest_ts = ts;
+                               kdbp_vict = kdbp_try;
+                       }
+               }
+               if (kdbp_vict == NULL) {
+                       kdebug_enable = 0;
+                       kd_ctrl_page.enabled = 0;
+                       commpage_update_kdebug_state();
+                       retval = false;
+                       goto out;
+               }
+               kdsp = kdbp_vict->kd_list_head;
+               kdsp_actual = POINTER_FROM_KDS_PTR(kdsp);
+               kdbp_vict->kd_list_head = kdsp_actual->kds_next;
+
+               if (kdbp_vict->kd_list_head.raw != KDS_PTR_NULL) {
+                       kdsp_next_actual = POINTER_FROM_KDS_PTR(kdbp_vict->kd_list_head);
+                       kdsp_next_actual->kds_lostevents = true;
+               } else {
+                       kdbp_vict->kd_lostevents = true;
+               }
+
+               if (kd_ctrl_page.oldest_time < oldest_ts) {
+                       kd_ctrl_page.oldest_time = oldest_ts;
+               }
+               kd_ctrl_page.kdebug_flags |= KDBG_WRAPPED;
+       }
+       kdsp_actual->kds_timestamp = kdbg_timestamp();
+       kdsp_actual->kds_next.raw = KDS_PTR_NULL;
+       kdsp_actual->kds_bufcnt   = 0;
+       kdsp_actual->kds_readlast = 0;
+
+       kdsp_actual->kds_lostevents = kdbp->kd_lostevents;
+       kdbp->kd_lostevents = false;
+       kdsp_actual->kds_bufindx = 0;
+
+       if (kdbp->kd_list_head.raw == KDS_PTR_NULL) {
+               kdbp->kd_list_head = kdsp;
+       } else {
+               POINTER_FROM_KDS_PTR(kdbp->kd_list_tail)->kds_next = kdsp;
+       }
+       kdbp->kd_list_tail = kdsp;
+out:
+       lck_spin_unlock(kds_spin_lock);
+       ml_set_interrupts_enabled(s);
+
+       return retval;
+}
+
+int
+kernel_debug_register_callback(kd_callback_t callback)
+{
+       kd_iop_t* iop;
+       if (kmem_alloc(kernel_map, (vm_offset_t *)&iop, sizeof(kd_iop_t), VM_KERN_MEMORY_DIAG) == KERN_SUCCESS) {
+               memcpy(&iop->callback, &callback, sizeof(kd_callback_t));
+
+               /*
+                * <rdar://problem/13351477> Some IOP clients are not providing a name.
+                *
+                * Remove when fixed.
+                */
+               {
+                       bool is_valid_name = false;
+                       for (uint32_t length = 0; length < sizeof(callback.iop_name); ++length) {
+                               /* This is roughly isprintable(c) */
+                               if (callback.iop_name[length] > 0x20 && callback.iop_name[length] < 0x7F) {
+                                       continue;
+                               }
+                               if (callback.iop_name[length] == 0) {
+                                       if (length) {
+                                               is_valid_name = true;
+                                       }
+                                       break;
+                               }
+                       }
+
+                       if (!is_valid_name) {
+                               strlcpy(iop->callback.iop_name, "IOP-???", sizeof(iop->callback.iop_name));
+                       }
+               }
+
+               iop->last_timestamp = 0;
+
+               do {
+                       /*
+                        * We use two pieces of state, the old list head
+                        * pointer, and the value of old_list_head->cpu_id.
+                        * If we read kd_iops more than once, it can change
+                        * between reads.
+                        *
+                        * TLDR; Must not read kd_iops more than once per loop.
+                        */
+                       iop->next = kd_iops;
+                       iop->cpu_id = iop->next ? (iop->next->cpu_id + 1) : kdbg_cpu_count(false);
+
+                       /*
+                        * Header says OSCompareAndSwapPtr has a memory barrier
+                        */
+               } while (!OSCompareAndSwapPtr(iop->next, iop, (void* volatile*)&kd_iops));
+
+               return iop->cpu_id;
+       }
+
+       return 0;
+}
+
+void
+kernel_debug_enter(
+       uint32_t        coreid,
+       uint32_t        debugid,
+       uint64_t        timestamp,
+       uintptr_t       arg1,
+       uintptr_t       arg2,
+       uintptr_t       arg3,
+       uintptr_t       arg4,
+       uintptr_t       threadid
+       )
+{
+       uint32_t        bindx;
+       kd_buf          *kd;
+       struct kd_bufinfo *kdbp;
+       struct kd_storage *kdsp_actual;
+       union  kds_ptr kds_raw;
+
+       if (kd_ctrl_page.kdebug_slowcheck) {
+               if ((kd_ctrl_page.kdebug_slowcheck & SLOW_NOLOG) || !(kdebug_enable & (KDEBUG_ENABLE_TRACE | KDEBUG_ENABLE_PPT))) {
+                       goto out1;
+               }
+
+               if (kd_ctrl_page.kdebug_flags & KDBG_TYPEFILTER_CHECK) {
+                       if (typefilter_is_debugid_allowed(kdbg_typefilter, debugid)) {
+                               goto record_event;
+                       }
+                       goto out1;
+               } else if (kd_ctrl_page.kdebug_flags & KDBG_RANGECHECK) {
+                       if (debugid >= kdlog_beg && debugid <= kdlog_end) {
+                               goto record_event;
+                       }
+                       goto out1;
+               } else if (kd_ctrl_page.kdebug_flags & KDBG_VALCHECK) {
+                       if ((debugid & KDBG_EVENTID_MASK) != kdlog_value1 &&
+                           (debugid & KDBG_EVENTID_MASK) != kdlog_value2 &&
+                           (debugid & KDBG_EVENTID_MASK) != kdlog_value3 &&
+                           (debugid & KDBG_EVENTID_MASK) != kdlog_value4) {
+                               goto out1;
+                       }
+               }
+       }
+
+record_event:
+       if (timestamp < kd_ctrl_page.oldest_time) {
+               goto out1;
+       }
+
+       disable_preemption();
+
+       if (kd_ctrl_page.enabled == 0) {
+               goto out;
+       }
+
+       kdbp = &kdbip[coreid];
+       timestamp &= KDBG_TIMESTAMP_MASK;
+
+retry_q:
+       kds_raw = kdbp->kd_list_tail;
+
+       if (kds_raw.raw != KDS_PTR_NULL) {
+               kdsp_actual = POINTER_FROM_KDS_PTR(kds_raw);
+               bindx = kdsp_actual->kds_bufindx;
+       } else {
+               kdsp_actual = NULL;
+               bindx = EVENTS_PER_STORAGE_UNIT;
+       }
+
+       if (kdsp_actual == NULL || bindx >= EVENTS_PER_STORAGE_UNIT) {
+               if (allocate_storage_unit(coreid) == false) {
+                       /*
+                        * this can only happen if wrapping
+                        * has been disabled
+                        */
+                       goto out;
+               }
+               goto retry_q;
+       }
+       if (!OSCompareAndSwap(bindx, bindx + 1, &kdsp_actual->kds_bufindx)) {
+               goto retry_q;
+       }
+
+       // IOP entries can be allocated before xnu allocates and inits the buffer
+       if (timestamp < kdsp_actual->kds_timestamp) {
+               kdsp_actual->kds_timestamp = timestamp;
+       }
+
+       kd = &kdsp_actual->kds_records[bindx];
+
+       kd->debugid = debugid;
+       kd->arg1 = arg1;
+       kd->arg2 = arg2;
+       kd->arg3 = arg3;
+       kd->arg4 = arg4;
+       kd->arg5 = threadid;
+
+       kdbg_set_timestamp_and_cpu(kd, timestamp, coreid);
+
+       OSAddAtomic(1, &kdsp_actual->kds_bufcnt);
+out:
+       enable_preemption();
+out1:
+       if ((kds_waiter && kd_ctrl_page.kds_inuse_count >= n_storage_threshold)) {
+               kdbg_wakeup();
+       }
+}
+
+/*
+ * Check if the given debug ID is allowed to be traced on the current process.
+ *
+ * Returns true if allowed and false otherwise.
+ */
+static inline bool
+kdebug_debugid_procfilt_allowed(uint32_t debugid)
+{
+       uint32_t procfilt_flags = kd_ctrl_page.kdebug_flags &
+           (KDBG_PIDCHECK | KDBG_PIDEXCLUDE);
+
+       if (!procfilt_flags) {
+               return true;
+       }
+
+       /*
+        * DBG_TRACE and MACH_SCHED tracepoints ignore the process filter.
+        */
+       if ((debugid & 0xffff0000) == MACHDBG_CODE(DBG_MACH_SCHED, 0) ||
+           (debugid >> 24 == DBG_TRACE)) {
+               return true;
+       }
+
+       struct proc *curproc = current_proc();
+       /*
+        * If the process is missing (early in boot), allow it.
+        */
+       if (!curproc) {
+               return true;
+       }
+
+       if (procfilt_flags & KDBG_PIDCHECK) {
+               /*
+                * Allow only processes marked with the kdebug bit.
+                */
+               return curproc->p_kdebug;
+       } else if (procfilt_flags & KDBG_PIDEXCLUDE) {
+               /*
+                * Exclude any process marked with the kdebug bit.
+                */
+               return !curproc->p_kdebug;
+       } else {
+               panic("kdebug: invalid procfilt flags %x", kd_ctrl_page.kdebug_flags);
+               __builtin_unreachable();
+       }
+}
+
+static void
+kernel_debug_internal(
+       uint32_t debugid,
+       uintptr_t arg1,
+       uintptr_t arg2,
+       uintptr_t arg3,
+       uintptr_t arg4,
+       uintptr_t arg5,
+       uint64_t flags)
+{
+       uint64_t now;
+       uint32_t bindx;
+       kd_buf *kd;
+       int cpu;
+       struct kd_bufinfo *kdbp;
+       struct kd_storage *kdsp_actual;
+       union kds_ptr kds_raw;
+       bool only_filter = flags & KDBG_FLAG_FILTERED;
+       bool observe_procfilt = !(flags & KDBG_FLAG_NOPROCFILT);
+
+       if (kd_ctrl_page.kdebug_slowcheck) {
+               if ((kd_ctrl_page.kdebug_slowcheck & SLOW_NOLOG) ||
+                   !(kdebug_enable & (KDEBUG_ENABLE_TRACE | KDEBUG_ENABLE_PPT))) {
+                       goto out1;
+               }
+
+               if (!ml_at_interrupt_context() && observe_procfilt &&
+                   !kdebug_debugid_procfilt_allowed(debugid)) {
+                       goto out1;
+               }
+
+               if (kd_ctrl_page.kdebug_flags & KDBG_TYPEFILTER_CHECK) {
+                       if (typefilter_is_debugid_allowed(kdbg_typefilter, debugid)) {
+                               goto record_event;
+                       }
+
+                       goto out1;
+               } else if (only_filter) {
+                       goto out1;
+               } else if (kd_ctrl_page.kdebug_flags & KDBG_RANGECHECK) {
+                       /* Always record trace system info */
+                       if (KDBG_EXTRACT_CLASS(debugid) == DBG_TRACE) {
+                               goto record_event;
+                       }
+
+                       if (debugid < kdlog_beg || debugid > kdlog_end) {
+                               goto out1;
+                       }
+               } else if (kd_ctrl_page.kdebug_flags & KDBG_VALCHECK) {
+                       /* Always record trace system info */
+                       if (KDBG_EXTRACT_CLASS(debugid) == DBG_TRACE) {
+                               goto record_event;
+                       }
+
+                       if ((debugid & KDBG_EVENTID_MASK) != kdlog_value1 &&
+                           (debugid & KDBG_EVENTID_MASK) != kdlog_value2 &&
+                           (debugid & KDBG_EVENTID_MASK) != kdlog_value3 &&
+                           (debugid & KDBG_EVENTID_MASK) != kdlog_value4) {
+                               goto out1;
+                       }
+               }
+       } else if (only_filter) {
+               goto out1;
+       }
+
+record_event:
+       disable_preemption();
+
+       if (kd_ctrl_page.enabled == 0) {
+               goto out;
+       }
+
+       cpu = cpu_number();
+       kdbp = &kdbip[cpu];
+
+retry_q:
+       kds_raw = kdbp->kd_list_tail;
+
+       if (kds_raw.raw != KDS_PTR_NULL) {
+               kdsp_actual = POINTER_FROM_KDS_PTR(kds_raw);
+               bindx = kdsp_actual->kds_bufindx;
+       } else {
+               kdsp_actual = NULL;
+               bindx = EVENTS_PER_STORAGE_UNIT;
+       }
+
+       if (kdsp_actual == NULL || bindx >= EVENTS_PER_STORAGE_UNIT) {
+               if (allocate_storage_unit(cpu) == false) {
+                       /*
+                        * this can only happen if wrapping
+                        * has been disabled
+                        */
+                       goto out;
+               }
+               goto retry_q;
+       }
+
+       now = kdbg_timestamp() & KDBG_TIMESTAMP_MASK;
+
+       if (!OSCompareAndSwap(bindx, bindx + 1, &kdsp_actual->kds_bufindx)) {
+               goto retry_q;
+       }
+
+       kd = &kdsp_actual->kds_records[bindx];
+
+       kd->debugid = debugid;
+       kd->arg1 = arg1;
+       kd->arg2 = arg2;
+       kd->arg3 = arg3;
+       kd->arg4 = arg4;
+       kd->arg5 = arg5;
+
+       kdbg_set_timestamp_and_cpu(kd, now, cpu);
+
+       OSAddAtomic(1, &kdsp_actual->kds_bufcnt);
+
+#if KPERF
+       kperf_kdebug_callback(debugid, __builtin_frame_address(0));
+#endif
+out:
+       enable_preemption();
+out1:
+       if (kds_waiter && kd_ctrl_page.kds_inuse_count >= n_storage_threshold) {
+               uint32_t        etype;
+               uint32_t        stype;
+
+               etype = debugid & KDBG_EVENTID_MASK;
+               stype = debugid & KDBG_CSC_MASK;
+
+               if (etype == INTERRUPT || etype == MACH_vmfault ||
+                   stype == BSC_SysCall || stype == MACH_SysCall) {
+                       kdbg_wakeup();
+               }
+       }
+}
+
+__attribute__((noinline))
+void
+kernel_debug(
+       uint32_t        debugid,
+       uintptr_t       arg1,
+       uintptr_t       arg2,
+       uintptr_t       arg3,
+       uintptr_t       arg4,
+       __unused uintptr_t arg5)
+{
+       kernel_debug_internal(debugid, arg1, arg2, arg3, arg4,
+           (uintptr_t)thread_tid(current_thread()), 0);
+}
+
+__attribute__((noinline))
+void
+kernel_debug1(
+       uint32_t        debugid,
+       uintptr_t       arg1,
+       uintptr_t       arg2,
+       uintptr_t       arg3,
+       uintptr_t       arg4,
+       uintptr_t       arg5)
+{
+       kernel_debug_internal(debugid, arg1, arg2, arg3, arg4, arg5, 0);
+}
+
+__attribute__((noinline))
+void
+kernel_debug_flags(
+       uint32_t debugid,
+       uintptr_t arg1,
+       uintptr_t arg2,
+       uintptr_t arg3,
+       uintptr_t arg4,
+       uint64_t flags)
+{
+       kernel_debug_internal(debugid, arg1, arg2, arg3, arg4,
+           (uintptr_t)thread_tid(current_thread()), flags);
+}
+
+__attribute__((noinline))
+void
+kernel_debug_filtered(
+       uint32_t debugid,
+       uintptr_t arg1,
+       uintptr_t arg2,
+       uintptr_t arg3,
+       uintptr_t arg4)
+{
+       kernel_debug_flags(debugid, arg1, arg2, arg3, arg4, KDBG_FLAG_FILTERED);
+}
+
+void
+kernel_debug_string_early(const char *message)
+{
+       uintptr_t arg[4] = {0, 0, 0, 0};
+
+       /* Stuff the message string in the args and log it. */
+       strncpy((char *)arg, message, MIN(sizeof(arg), strlen(message)));
+       KERNEL_DEBUG_EARLY(
+               TRACE_INFO_STRING,
+               arg[0], arg[1], arg[2], arg[3]);
+}
+
+#define SIMPLE_STR_LEN (64)
+static_assert(SIMPLE_STR_LEN % sizeof(uintptr_t) == 0);
+
+void
+kernel_debug_string_simple(uint32_t eventid, const char *str)
+{
+       if (!kdebug_enable) {
+               return;
+       }
+
+       /* array of uintptr_ts simplifies emitting the string as arguments */
+       uintptr_t str_buf[(SIMPLE_STR_LEN / sizeof(uintptr_t)) + 1] = { 0 };
+       size_t len = strlcpy((char *)str_buf, str, SIMPLE_STR_LEN + 1);
+
+       uintptr_t thread_id = (uintptr_t)thread_tid(current_thread());
+       uint32_t debugid = eventid | DBG_FUNC_START;
+
+       /* string can fit in a single tracepoint */
+       if (len <= (4 * sizeof(uintptr_t))) {
+               debugid |= DBG_FUNC_END;
+       }
+
+       kernel_debug_internal(debugid, str_buf[0],
+           str_buf[1],
+           str_buf[2],
+           str_buf[3], thread_id, 0);
+
+       debugid &= KDBG_EVENTID_MASK;
+       int i = 4;
+       size_t written = 4 * sizeof(uintptr_t);
+
+       for (; written < len; i += 4, written += 4 * sizeof(uintptr_t)) {
+               /* if this is the last tracepoint to be emitted */
+               if ((written + (4 * sizeof(uintptr_t))) >= len) {
+                       debugid |= DBG_FUNC_END;
+               }
+               kernel_debug_internal(debugid, str_buf[i],
+                   str_buf[i + 1],
+                   str_buf[i + 2],
+                   str_buf[i + 3], thread_id, 0);
+       }
+}
+
+extern int      master_cpu;             /* MACH_KERNEL_PRIVATE */
+/*
+ * Used prior to start_kern_tracing() being called.
+ * Log temporarily into a static buffer.
+ */
+void
+kernel_debug_early(
+       uint32_t        debugid,
+       uintptr_t       arg1,
+       uintptr_t       arg2,
+       uintptr_t       arg3,
+       uintptr_t       arg4)
+{
+#if defined(__x86_64__)
+       extern int early_boot;
+       /*
+        * Note that "early" isn't early enough in some cases where
+        * we're invoked before gsbase is set on x86, hence the
+        * check of "early_boot".
+        */
+       if (early_boot) {
+               return;
+       }
+#endif
+
+       /* If early tracing is over, use the normal path. */
+       if (kd_early_done) {
+               KDBG_RELEASE(debugid, arg1, arg2, arg3, arg4);
+               return;
+       }
+
+       /* Do nothing if the buffer is full or we're not on the boot cpu. */
+       kd_early_overflow = kd_early_index >= KD_EARLY_BUFFER_NBUFS;
+       if (kd_early_overflow || cpu_number() != master_cpu) {
+               return;
+       }
+
+       kd_early_buffer[kd_early_index].debugid = debugid;
+       kd_early_buffer[kd_early_index].timestamp = mach_absolute_time();
+       kd_early_buffer[kd_early_index].arg1 = arg1;
+       kd_early_buffer[kd_early_index].arg2 = arg2;
+       kd_early_buffer[kd_early_index].arg3 = arg3;
+       kd_early_buffer[kd_early_index].arg4 = arg4;
+       kd_early_buffer[kd_early_index].arg5 = 0;
+       kd_early_index++;
+}
+
+/*
+ * Transfer the contents of the temporary buffer into the trace buffers.
+ * Precede that by logging the rebase time (offset) - the TSC-based time (in ns)
+ * when mach_absolute_time is set to 0.
+ */
+static void
+kernel_debug_early_end(void)
+{
+       if (cpu_number() != master_cpu) {
+               panic("kernel_debug_early_end() not call on boot processor");
+       }
+
+       /* reset the current oldest time to allow early events */
+       kd_ctrl_page.oldest_time = 0;
+
+#if defined(__x86_64__)
+       /* Fake sentinel marking the start of kernel time relative to TSC */
+       kernel_debug_enter(0, TRACE_TIMESTAMPS, 0,
+           (uint32_t)(tsc_rebase_abs_time >> 32), (uint32_t)tsc_rebase_abs_time,
+           tsc_at_boot, 0, 0);
+#endif /* defined(__x86_64__) */
+       for (unsigned int i = 0; i < kd_early_index; i++) {
+               kernel_debug_enter(0,
+                   kd_early_buffer[i].debugid,
+                   kd_early_buffer[i].timestamp,
+                   kd_early_buffer[i].arg1,
+                   kd_early_buffer[i].arg2,
+                   kd_early_buffer[i].arg3,
+                   kd_early_buffer[i].arg4,
+                   0);
+       }
+
+       /* Cut events-lost event on overflow */
+       if (kd_early_overflow) {
+               KDBG_RELEASE(TRACE_LOST_EVENTS, 1);
+       }
+
+       kd_early_done = true;
+
+       /* This trace marks the start of kernel tracing */
+       kernel_debug_string_early("early trace done");
+}
+
+void
+kernel_debug_disable(void)
+{
+       if (kdebug_enable) {
+               kdbg_set_tracing_enabled(false, 0);
+       }
+}
+
+/*
+ * Returns non-zero if debugid is in a reserved class.
+ */
+static int
+kdebug_validate_debugid(uint32_t debugid)
+{
+       uint8_t debugid_class;
+
+       debugid_class = KDBG_EXTRACT_CLASS(debugid);
+       switch (debugid_class) {
+       case DBG_TRACE:
+               return EPERM;
+       }
+
+       return 0;
+}
+
+/*
+ * Support syscall SYS_kdebug_typefilter.
+ */
+int
+kdebug_typefilter(__unused struct proc* p,
+    struct kdebug_typefilter_args* uap,
+    __unused int *retval)
+{
+       int ret = KERN_SUCCESS;
+
+       if (uap->addr == USER_ADDR_NULL ||
+           uap->size == USER_ADDR_NULL) {
+               return EINVAL;
+       }
+
+       /*
+        * The atomic load is to close a race window with setting the typefilter
+        * and memory entry values. A description follows:
+        *
+        * Thread 1 (writer)
+        *
+        * Allocate Typefilter
+        * Allocate MemoryEntry
+        * Write Global MemoryEntry Ptr
+        * Atomic Store (Release) Global Typefilter Ptr
+        *
+        * Thread 2 (reader, AKA us)
+        *
+        * if ((Atomic Load (Acquire) Global Typefilter Ptr) == NULL)
+        *     return;
+        *
+        * Without the atomic store, it isn't guaranteed that the write of
+        * Global MemoryEntry Ptr is visible before we can see the write of
+        * Global Typefilter Ptr.
+        *
+        * Without the atomic load, it isn't guaranteed that the loads of
+        * Global MemoryEntry Ptr aren't speculated.
+        *
+        * The global pointers transition from NULL -> valid once and only once,
+        * and never change after becoming valid. This means that having passed
+        * the first atomic load test of Global Typefilter Ptr, this function
+        * can then safely use the remaining global state without atomic checks.
+        */
+       if (!os_atomic_load(&kdbg_typefilter, acquire)) {
+               return EINVAL;
+       }
+
+       assert(kdbg_typefilter_memory_entry);
+
+       mach_vm_offset_t user_addr = 0;
+       vm_map_t user_map = current_map();
+
+       ret = mach_to_bsd_errno(
+               mach_vm_map_kernel(user_map,                                    // target map
+               &user_addr,                                             // [in, out] target address
+               TYPEFILTER_ALLOC_SIZE,                                  // initial size
+               0,                                                      // mask (alignment?)
+               VM_FLAGS_ANYWHERE,                                      // flags
+               VM_MAP_KERNEL_FLAGS_NONE,
+               VM_KERN_MEMORY_NONE,
+               kdbg_typefilter_memory_entry,                           // port (memory entry!)
+               0,                                                      // offset (in memory entry)
+               false,                                                  // should copy
+               VM_PROT_READ,                                           // cur_prot
+               VM_PROT_READ,                                           // max_prot
+               VM_INHERIT_SHARE));                                     // inherit behavior on fork
+
+       if (ret == KERN_SUCCESS) {
+               vm_size_t user_ptr_size = vm_map_is_64bit(user_map) ? 8 : 4;
+               ret = copyout(CAST_DOWN(void *, &user_addr), uap->addr, user_ptr_size );
+
+               if (ret != KERN_SUCCESS) {
+                       mach_vm_deallocate(user_map, user_addr, TYPEFILTER_ALLOC_SIZE);
+               }
+       }
+
+       return ret;
+}
+
+/*
+ * Support syscall SYS_kdebug_trace. U64->K32 args may get truncated in kdebug_trace64
+ */
+int
+kdebug_trace(struct proc *p, struct kdebug_trace_args *uap, int32_t *retval)
+{
+       struct kdebug_trace64_args uap64;
+
+       uap64.code = uap->code;
+       uap64.arg1 = uap->arg1;
+       uap64.arg2 = uap->arg2;
+       uap64.arg3 = uap->arg3;
+       uap64.arg4 = uap->arg4;
+
+       return kdebug_trace64(p, &uap64, retval);
+}
+
+/*
+ * Support syscall SYS_kdebug_trace64. 64-bit args on K32 will get truncated
+ * to fit in 32-bit record format.
+ *
+ * It is intentional that error conditions are not checked until kdebug is
+ * enabled. This is to match the userspace wrapper behavior, which is optimizing
+ * for non-error case performance.
+ */
+int
+kdebug_trace64(__unused struct proc *p, struct kdebug_trace64_args *uap, __unused int32_t *retval)
+{
+       int err;
+
+       if (__probable(kdebug_enable == 0)) {
+               return 0;
+       }
+
+       if ((err = kdebug_validate_debugid(uap->code)) != 0) {
+               return err;
+       }
+
+       kernel_debug_internal(uap->code, (uintptr_t)uap->arg1,
+           (uintptr_t)uap->arg2, (uintptr_t)uap->arg3, (uintptr_t)uap->arg4,
+           (uintptr_t)thread_tid(current_thread()), 0);
+
+       return 0;
+}
+
+/*
+ * Adding enough padding to contain a full tracepoint for the last
+ * portion of the string greatly simplifies the logic of splitting the
+ * string between tracepoints.  Full tracepoints can be generated using
+ * the buffer itself, without having to manually add zeros to pad the
+ * arguments.
+ */
+
+/* 2 string args in first tracepoint and 9 string data tracepoints */
+#define STR_BUF_ARGS (2 + (9 * 4))
+/* times the size of each arg on K64 */
+#define MAX_STR_LEN  (STR_BUF_ARGS * sizeof(uint64_t))
+/* on K32, ending straddles a tracepoint, so reserve blanks */
+#define STR_BUF_SIZE (MAX_STR_LEN + (2 * sizeof(uint32_t)))
+
+/*
+ * This function does no error checking and assumes that it is called with
+ * the correct arguments, including that the buffer pointed to by str is at
+ * least STR_BUF_SIZE bytes.  However, str must be aligned to word-size and
+ * be NUL-terminated.  In cases where a string can fit evenly into a final
+ * tracepoint without its NUL-terminator, this function will not end those
+ * strings with a NUL in trace.  It's up to clients to look at the function
+ * qualifier for DBG_FUNC_END in this case, to end the string.
+ */
+static uint64_t
+kernel_debug_string_internal(uint32_t debugid, uint64_t str_id, void *vstr,
+    size_t str_len)
+{
+       /* str must be word-aligned */
+       uintptr_t *str = vstr;
+       size_t written = 0;
+       uintptr_t thread_id;
+       int i;
+       uint32_t trace_debugid = TRACEDBG_CODE(DBG_TRACE_STRING,
+           TRACE_STRING_GLOBAL);
+
+       thread_id = (uintptr_t)thread_tid(current_thread());
+
+       /* if the ID is being invalidated, just emit that */
+       if (str_id != 0 && str_len == 0) {
+               kernel_debug_internal(trace_debugid | DBG_FUNC_START | DBG_FUNC_END,
+                   (uintptr_t)debugid, (uintptr_t)str_id, 0, 0, thread_id, 0);
+               return str_id;
+       }
+
+       /* generate an ID, if necessary */
+       if (str_id == 0) {
+               str_id = OSIncrementAtomic64((SInt64 *)&g_curr_str_id);
+               str_id = (str_id & STR_ID_MASK) | g_str_id_signature;
+       }
+
+       trace_debugid |= DBG_FUNC_START;
+       /* string can fit in a single tracepoint */
+       if (str_len <= (2 * sizeof(uintptr_t))) {
+               trace_debugid |= DBG_FUNC_END;
+       }
+
+       kernel_debug_internal(trace_debugid, (uintptr_t)debugid, (uintptr_t)str_id,
+           str[0], str[1], thread_id, 0);
+
+       trace_debugid &= KDBG_EVENTID_MASK;
+       i = 2;
+       written += 2 * sizeof(uintptr_t);
+
+       for (; written < str_len; i += 4, written += 4 * sizeof(uintptr_t)) {
+               if ((written + (4 * sizeof(uintptr_t))) >= str_len) {
+                       trace_debugid |= DBG_FUNC_END;
+               }
+               kernel_debug_internal(trace_debugid, str[i],
+                   str[i + 1],
+                   str[i + 2],
+                   str[i + 3], thread_id, 0);
+       }
+
+       return str_id;
+}
+
+/*
+ * Returns true if the current process can emit events, and false otherwise.
+ * Trace system and scheduling events circumvent this check, as do events
+ * emitted in interrupt context.
+ */
+static bool
+kdebug_current_proc_enabled(uint32_t debugid)
+{
+       /* can't determine current process in interrupt context */
+       if (ml_at_interrupt_context()) {
+               return true;
+       }
+
+       /* always emit trace system and scheduling events */
+       if ((KDBG_EXTRACT_CLASS(debugid) == DBG_TRACE ||
+           (debugid & KDBG_CSC_MASK) == MACHDBG_CODE(DBG_MACH_SCHED, 0))) {
+               return true;
+       }
+
+       if (kd_ctrl_page.kdebug_flags & KDBG_PIDCHECK) {
+               proc_t cur_proc = current_proc();
+
+               /* only the process with the kdebug bit set is allowed */
+               if (cur_proc && !(cur_proc->p_kdebug)) {
+                       return false;
+               }
+       } else if (kd_ctrl_page.kdebug_flags & KDBG_PIDEXCLUDE) {
+               proc_t cur_proc = current_proc();
+
+               /* every process except the one with the kdebug bit set is allowed */
+               if (cur_proc && cur_proc->p_kdebug) {
+                       return false;
+               }
+       }
+
+       return true;
+}
+
+bool
+kdebug_debugid_enabled(uint32_t debugid)
+{
+       /* if no filtering is enabled */
+       if (!kd_ctrl_page.kdebug_slowcheck) {
+               return true;
+       }
+
+       return kdebug_debugid_explicitly_enabled(debugid);
+}
+
+bool
+kdebug_debugid_explicitly_enabled(uint32_t debugid)
+{
+       if (kd_ctrl_page.kdebug_flags & KDBG_TYPEFILTER_CHECK) {
+               return typefilter_is_debugid_allowed(kdbg_typefilter, debugid);
+       } else if (KDBG_EXTRACT_CLASS(debugid) == DBG_TRACE) {
+               return true;
+       } else if (kd_ctrl_page.kdebug_flags & KDBG_RANGECHECK) {
+               if (debugid < kdlog_beg || debugid > kdlog_end) {
+                       return false;
+               }
+       } else if (kd_ctrl_page.kdebug_flags & KDBG_VALCHECK) {
+               if ((debugid & KDBG_EVENTID_MASK) != kdlog_value1 &&
+                   (debugid & KDBG_EVENTID_MASK) != kdlog_value2 &&
+                   (debugid & KDBG_EVENTID_MASK) != kdlog_value3 &&
+                   (debugid & KDBG_EVENTID_MASK) != kdlog_value4) {
+                       return false;
+               }
+       }
+
+       return true;
+}
+
+bool
+kdebug_using_continuous_time(void)
+{
+       return kdebug_enable & KDEBUG_ENABLE_CONT_TIME;
+}
+
+/*
+ * Returns 0 if a string can be traced with these arguments.  Returns errno
+ * value if error occurred.
+ */
+static errno_t
+kdebug_check_trace_string(uint32_t debugid, uint64_t str_id)
+{
+       /* if there are function qualifiers on the debugid */
+       if (debugid & ~KDBG_EVENTID_MASK) {
+               return EINVAL;
+       }
+
+       if (kdebug_validate_debugid(debugid)) {
+               return EPERM;
+       }
+
+       if (str_id != 0 && (str_id & STR_ID_SIG_MASK) != g_str_id_signature) {
+               return EINVAL;
+       }
+
+       return 0;
+}
+
+/*
+ * Implementation of KPI kernel_debug_string.
+ */
+int
+kernel_debug_string(uint32_t debugid, uint64_t *str_id, const char *str)
+{
+       /* arguments to tracepoints must be word-aligned */
+       __attribute__((aligned(sizeof(uintptr_t)))) char str_buf[STR_BUF_SIZE];
+       static_assert(sizeof(str_buf) > MAX_STR_LEN);
+       vm_size_t len_copied;
+       int err;
+
+       assert(str_id);
+
+       if (__probable(kdebug_enable == 0)) {
+               return 0;
+       }
+
+       if (!kdebug_current_proc_enabled(debugid)) {
+               return 0;
+       }
+
+       if (!kdebug_debugid_enabled(debugid)) {
+               return 0;
+       }
+
+       if ((err = kdebug_check_trace_string(debugid, *str_id)) != 0) {
+               return err;
+       }
+
+       if (str == NULL) {
+               if (str_id == 0) {
+                       return EINVAL;
+               }
+
+               *str_id = kernel_debug_string_internal(debugid, *str_id, NULL, 0);
+               return 0;
+       }
+
+       memset(str_buf, 0, sizeof(str_buf));
+       len_copied = strlcpy(str_buf, str, MAX_STR_LEN + 1);
+       *str_id = kernel_debug_string_internal(debugid, *str_id, str_buf,
+           len_copied);
+       return 0;
+}
+
+/*
+ * Support syscall kdebug_trace_string.
+ */
+int
+kdebug_trace_string(__unused struct proc *p,
+    struct kdebug_trace_string_args *uap,
+    uint64_t *retval)
+{
+       __attribute__((aligned(sizeof(uintptr_t)))) char str_buf[STR_BUF_SIZE];
+       static_assert(sizeof(str_buf) > MAX_STR_LEN);
+       size_t len_copied;
+       int err;
+
+       if (__probable(kdebug_enable == 0)) {
+               return 0;
+       }
+
+       if (!kdebug_current_proc_enabled(uap->debugid)) {
+               return 0;
+       }
+
+       if (!kdebug_debugid_enabled(uap->debugid)) {
+               return 0;
+       }
+
+       if ((err = kdebug_check_trace_string(uap->debugid, uap->str_id)) != 0) {
+               return err;
+       }
+
+       if (uap->str == USER_ADDR_NULL) {
+               if (uap->str_id == 0) {
+                       return EINVAL;
+               }
+
+               *retval = kernel_debug_string_internal(uap->debugid, uap->str_id,
+                   NULL, 0);
+               return 0;
+       }
+
+       memset(str_buf, 0, sizeof(str_buf));
+       err = copyinstr(uap->str, str_buf, MAX_STR_LEN + 1, &len_copied);
+
+       /* it's alright to truncate the string, so allow ENAMETOOLONG */
+       if (err == ENAMETOOLONG) {
+               str_buf[MAX_STR_LEN] = '\0';
+       } else if (err) {
+               return err;
+       }
+
+       if (len_copied <= 1) {
+               return EINVAL;
+       }
+
+       /* convert back to a length */
+       len_copied--;
+
+       *retval = kernel_debug_string_internal(uap->debugid, uap->str_id, str_buf,
+           len_copied);
+       return 0;
+}
+
+static void
+kdbg_lock_init(void)
+{
+       static lck_grp_attr_t *kdebug_lck_grp_attr = NULL;
+       static lck_attr_t     *kdebug_lck_attr     = NULL;
+
+       if (kd_ctrl_page.kdebug_flags & KDBG_LOCKINIT) {
+               return;
+       }
+
+       assert(kdebug_lck_grp_attr == NULL);
+       kdebug_lck_grp_attr = lck_grp_attr_alloc_init();
+       kdebug_lck_grp = lck_grp_alloc_init("kdebug", kdebug_lck_grp_attr);
+       kdebug_lck_attr = lck_attr_alloc_init();
+
+       kds_spin_lock = lck_spin_alloc_init(kdebug_lck_grp, kdebug_lck_attr);
+       kdw_spin_lock = lck_spin_alloc_init(kdebug_lck_grp, kdebug_lck_attr);
+
+       kd_ctrl_page.kdebug_flags |= KDBG_LOCKINIT;
+}
+
+int
+kdbg_bootstrap(bool early_trace)
+{
+       kd_ctrl_page.kdebug_flags &= ~KDBG_WRAPPED;
+
+       return create_buffers(early_trace);
+}
+
+int
+kdbg_reinit(bool early_trace)
+{
+       int ret = 0;
+
+       /*
+        * Disable trace collecting
+        * First make sure we're not in
+        * the middle of cutting a trace
+        */
+       kernel_debug_disable();
+
+       /*
+        * make sure the SLOW_NOLOG is seen
+        * by everyone that might be trying
+        * to cut a trace..
+        */
+       IOSleep(100);
+
+       delete_buffers();
+
+       kdbg_clear_thread_map();
+       ret = kdbg_bootstrap(early_trace);
+
+       RAW_file_offset = 0;
+       RAW_file_written = 0;
+
+       return ret;
+}
+
+void
+kdbg_trace_data(struct proc *proc, long *arg_pid, long *arg_uniqueid)
+{
+       if (!proc) {
+               *arg_pid = 0;
+               *arg_uniqueid = 0;
+       } else {
+               *arg_pid = proc->p_pid;
+               /* Fit in a trace point */
+               *arg_uniqueid = (long)proc->p_uniqueid;
+               if ((uint64_t) *arg_uniqueid != proc->p_uniqueid) {
+                       *arg_uniqueid = 0;
+               }
+       }
+}
+
+
+void
+kdbg_trace_string(struct proc *proc, long *arg1, long *arg2, long *arg3,
+    long *arg4)
+{
+       if (!proc) {
+               *arg1 = 0;
+               *arg2 = 0;
+               *arg3 = 0;
+               *arg4 = 0;
+               return;
+       }
+
+       const char *procname = proc_best_name(proc);
+       size_t namelen = strlen(procname);
+
+       long args[4] = { 0 };
+
+       if (namelen > sizeof(args)) {
+               namelen = sizeof(args);
+       }
+
+       strncpy((char *)args, procname, namelen);
+
+       *arg1 = args[0];
+       *arg2 = args[1];
+       *arg3 = args[2];
+       *arg4 = args[3];
+}
+
+/*
+ *
+ * Writes a cpumap for the given iops_list/cpu_count to the provided buffer.
+ *
+ * You may provide a buffer and size, or if you set the buffer to NULL, a
+ * buffer of sufficient size will be allocated.
+ *
+ * If you provide a buffer and it is too small, sets cpumap_size to the number
+ * of bytes required and returns EINVAL.
+ *
+ * On success, if you provided a buffer, cpumap_size is set to the number of
+ * bytes written. If you did not provide a buffer, cpumap is set to the newly
+ * allocated buffer and cpumap_size is set to the number of bytes allocated.
+ *
+ * NOTE: It may seem redundant to pass both iops and a cpu_count.
+ *
+ * We may be reporting data from "now", or from the "past".
+ *
+ * The "past" data would be for kdbg_readcpumap().
+ *
+ * If we do not pass both iops and cpu_count, and iops is NULL, this function
+ * will need to read "now" state to get the number of cpus, which would be in
+ * error if we were reporting "past" state.
+ */
+
+int
+kdbg_cpumap_init_internal(kd_iop_t* iops, uint32_t cpu_count, uint8_t** cpumap, uint32_t* cpumap_size)
+{
+       assert(cpumap);
+       assert(cpumap_size);
+       assert(cpu_count);
+       assert(!iops || iops->cpu_id + 1 == cpu_count);
+
+       uint32_t bytes_needed = sizeof(kd_cpumap_header) + cpu_count * sizeof(kd_cpumap);
+       uint32_t bytes_available = *cpumap_size;
+       *cpumap_size = bytes_needed;
+
+       if (*cpumap == NULL) {
+               if (kmem_alloc(kernel_map, (vm_offset_t*)cpumap, (vm_size_t)*cpumap_size, VM_KERN_MEMORY_DIAG) != KERN_SUCCESS) {
+                       return ENOMEM;
+               }
+               bzero(*cpumap, *cpumap_size);
+       } else if (bytes_available < bytes_needed) {
+               return EINVAL;
+       }
+
+       kd_cpumap_header* header = (kd_cpumap_header*)(uintptr_t)*cpumap;
+
+       header->version_no = RAW_VERSION1;
+       header->cpu_count = cpu_count;
+
+       kd_cpumap* cpus = (kd_cpumap*)&header[1];
+
+       int32_t index = cpu_count - 1;
+       while (iops) {
+               cpus[index].cpu_id = iops->cpu_id;
+               cpus[index].flags = KDBG_CPUMAP_IS_IOP;
+               strlcpy(cpus[index].name, iops->callback.iop_name, sizeof(cpus->name));
+
+               iops = iops->next;
+               index--;
+       }
+
+       while (index >= 0) {
+               cpus[index].cpu_id = index;
+               cpus[index].flags = 0;
+               strlcpy(cpus[index].name, "AP", sizeof(cpus->name));
+
+               index--;
+       }
+
+       return KERN_SUCCESS;
+}
+
+void
+kdbg_thrmap_init(void)
+{
+       ktrace_assert_lock_held();
+
+       if (kd_ctrl_page.kdebug_flags & KDBG_MAPINIT) {
+               return;
+       }
+
+       kd_mapptr = kdbg_thrmap_init_internal(0, &kd_mapsize, &kd_mapcount);
+
+       if (kd_mapptr) {
+               kd_ctrl_page.kdebug_flags |= KDBG_MAPINIT;
+       }
+}
+
+static void
+kd_resolve_map(thread_t thread, void *opaque)
+{
+       struct kd_resolver *resolve = opaque;
+
+       if (resolve->krs_count < resolve->krs_maxcount) {
+               kd_threadmap *map = &resolve->krs_map[resolve->krs_count];
+               struct kd_task_name *task_name = resolve->krs_task;
+               map->thread = (uintptr_t)thread_tid(thread);
+
+               (void)strlcpy(map->command, task_name->ktn_name, sizeof(map->command));
+               /*
+                * Kernel threads should still be marked with non-zero valid bit.
+                */
+               pid_t pid = resolve->krs_task->ktn_pid;
+               map->valid = pid == 0 ? 1 : pid;
+               resolve->krs_count++;
+       }
+}
+
+static vm_size_t
+kd_resolve_tasks(struct kd_task_name *task_names, vm_size_t ntasks)
+{
+       vm_size_t i = 0;
+       proc_t p = PROC_NULL;
+
+       proc_list_lock();
+       ALLPROC_FOREACH(p) {
+               if (i >= ntasks) {
+                       break;
+               }
+               /*
+                * Only record processes that can be referenced and are not exiting.
+                */
+               if (p->task && (p->p_lflag & P_LEXIT) == 0) {
+                       task_reference(p->task);
+                       task_names[i].ktn_task = p->task;
+                       task_names[i].ktn_pid = p->p_pid;
+                       (void)strlcpy(task_names[i].ktn_name, proc_best_name(p),
+                           sizeof(task_names[i].ktn_name));
+                       i++;
+               }
+       }
+       proc_list_unlock();
+
+       return i;
+}
+
+static vm_size_t
+kd_resolve_threads(kd_threadmap *map, struct kd_task_name *task_names,
+    vm_size_t ntasks, vm_size_t nthreads)
+{
+       struct kd_resolver resolver = {
+               .krs_map = map, .krs_count = 0, .krs_maxcount = nthreads,
+       };
+
+       for (int i = 0; i < ntasks; i++) {
+               struct kd_task_name *cur_task = &task_names[i];
+               resolver.krs_task = cur_task;
+               task_act_iterate_wth_args(cur_task->ktn_task, kd_resolve_map,
+                   &resolver);
+               task_deallocate(cur_task->ktn_task);
+       }
+
+       return resolver.krs_count;
+}
+
+static kd_threadmap *
+kdbg_thrmap_init_internal(size_t maxthreads, vm_size_t *mapsize,
+    vm_size_t *mapcount)
+{
+       kd_threadmap *thread_map = NULL;
+       struct kd_task_name *task_names;
+       vm_size_t names_size = 0;
+
+       assert(mapsize != NULL);
+       assert(mapcount != NULL);
+
+       vm_size_t nthreads = threads_count;
+       vm_size_t ntasks = tasks_count;
+
+       /*
+        * Allow 25% more threads and tasks to be created between now and taking the
+        * proc_list_lock.
+        */
+       if (os_add_overflow(nthreads, nthreads / 4, &nthreads) ||
+           os_add_overflow(ntasks, ntasks / 4, &ntasks)) {
+               return NULL;
+       }
+
+       *mapcount = nthreads;
+       if (os_mul_overflow(nthreads, sizeof(kd_threadmap), mapsize)) {
+               return NULL;
+       }
+       if (os_mul_overflow(ntasks, sizeof(task_names[0]), &names_size)) {
+               return NULL;
+       }
+
+       /*
+        * Wait until the out-parameters have been filled with the needed size to
+        * do the bounds checking on the provided maximum.
+        */
+       if (maxthreads != 0 && maxthreads < nthreads) {
+               return NULL;
+       }
+
+       thread_map = kalloc_tag(*mapsize, VM_KERN_MEMORY_DIAG);
+       bzero(thread_map, *mapsize);
+       task_names = kheap_alloc(KHEAP_TEMP, names_size, Z_WAITOK | Z_ZERO);
+       ntasks = kd_resolve_tasks(task_names, ntasks);
+       *mapcount = kd_resolve_threads(thread_map, task_names, ntasks, nthreads);
+       kheap_free(KHEAP_TEMP, task_names, names_size);
+       return thread_map;
+}
+
+static void
+kdbg_clear(void)
+{
+       /*
+        * Clean up the trace buffer
+        * First make sure we're not in
+        * the middle of cutting a trace
+        */
+       kernel_debug_disable();
+       kdbg_disable_typefilter();
+
+       /*
+        * make sure the SLOW_NOLOG is seen
+        * by everyone that might be trying
+        * to cut a trace..
+        */
+       IOSleep(100);
+
+       /* reset kdebug state for each process */
+       if (kd_ctrl_page.kdebug_flags & (KDBG_PIDCHECK | KDBG_PIDEXCLUDE)) {
+               proc_list_lock();
+               proc_t p;
+               ALLPROC_FOREACH(p) {
+                       p->p_kdebug = 0;
+               }
+               proc_list_unlock();
+       }
+
+       kd_ctrl_page.kdebug_flags &= (unsigned int)~KDBG_CKTYPES;
+       kd_ctrl_page.kdebug_flags &= ~(KDBG_NOWRAP | KDBG_RANGECHECK | KDBG_VALCHECK);
+       kd_ctrl_page.kdebug_flags &= ~(KDBG_PIDCHECK | KDBG_PIDEXCLUDE);
+
+       kd_ctrl_page.oldest_time = 0;
+
+       delete_buffers();
+       nkdbufs = 0;
+
+       /* Clean up the thread map buffer */
+       kdbg_clear_thread_map();
+
+       RAW_file_offset = 0;
+       RAW_file_written = 0;
+}
+
+void
+kdebug_reset(void)
+{
+       ktrace_assert_lock_held();
+
+       kdbg_lock_init();
+
+       kdbg_clear();
+       if (kdbg_typefilter) {
+               typefilter_reject_all(kdbg_typefilter);
+               typefilter_allow_class(kdbg_typefilter, DBG_TRACE);
+       }
+}
+
+void
+kdebug_free_early_buf(void)
+{
+#if defined(__x86_64__)
+       /*
+        * Make Intel aware that the early buffer is no longer being used.  ARM
+        * handles this as part of the BOOTDATA segment.
+        */
+       ml_static_mfree((vm_offset_t)&kd_early_buffer, sizeof(kd_early_buffer));
+#endif /* defined(__x86_64__) */
+}
+
+int
+kdbg_setpid(kd_regtype *kdr)
+{
+       pid_t pid;
+       int flag, ret = 0;
+       struct proc *p;
+
+       pid = (pid_t)kdr->value1;
+       flag = (int)kdr->value2;
+
+       if (pid >= 0) {
+               if ((p = proc_find(pid)) == NULL) {
+                       ret = ESRCH;
+               } else {
+                       if (flag == 1) {
+                               /*
+                                * turn on pid check for this and all pids
+                                */
+                               kd_ctrl_page.kdebug_flags |= KDBG_PIDCHECK;
+                               kd_ctrl_page.kdebug_flags &= ~KDBG_PIDEXCLUDE;
+                               kdbg_set_flags(SLOW_CHECKS, 0, true);
+
+                               p->p_kdebug = 1;
+                       } else {
+                               /*
+                                * turn off pid check for this pid value
+                                * Don't turn off all pid checking though
+                                *
+                                * kd_ctrl_page.kdebug_flags &= ~KDBG_PIDCHECK;
+                                */
+                               p->p_kdebug = 0;
+                       }
+                       proc_rele(p);
+               }
+       } else {
+               ret = EINVAL;
+       }
+
+       return ret;
+}
+
+/* This is for pid exclusion in the trace buffer */
+int
+kdbg_setpidex(kd_regtype *kdr)
+{
+       pid_t pid;
+       int flag, ret = 0;
+       struct proc *p;
+
+       pid = (pid_t)kdr->value1;
+       flag = (int)kdr->value2;
+
+       if (pid >= 0) {
+               if ((p = proc_find(pid)) == NULL) {
+                       ret = ESRCH;
+               } else {
+                       if (flag == 1) {
+                               /*
+                                * turn on pid exclusion
+                                */
+                               kd_ctrl_page.kdebug_flags |= KDBG_PIDEXCLUDE;
+                               kd_ctrl_page.kdebug_flags &= ~KDBG_PIDCHECK;
+                               kdbg_set_flags(SLOW_CHECKS, 0, true);
+
+                               p->p_kdebug = 1;
+                       } else {
+                               /*
+                                * turn off pid exclusion for this pid value
+                                * Don't turn off all pid exclusion though
+                                *
+                                * kd_ctrl_page.kdebug_flags &= ~KDBG_PIDEXCLUDE;
+                                */
+                               p->p_kdebug = 0;
+                       }
+                       proc_rele(p);
+               }
+       } else {
+               ret = EINVAL;
+       }
+
+       return ret;
+}
+
+/*
+ * The following functions all operate on the "global" typefilter singleton.
+ */
+
+/*
+ * The tf param is optional, you may pass either a valid typefilter or NULL.
+ * If you pass a valid typefilter, you release ownership of that typefilter.
+ */
+static int
+kdbg_initialize_typefilter(typefilter_t tf)
+{
+       ktrace_assert_lock_held();
+       assert(!kdbg_typefilter);
+       assert(!kdbg_typefilter_memory_entry);
+       typefilter_t deallocate_tf = NULL;
+
+       if (!tf && ((tf = deallocate_tf = typefilter_create()) == NULL)) {
+               return ENOMEM;
+       }
+
+       if ((kdbg_typefilter_memory_entry = typefilter_create_memory_entry(tf)) == MACH_PORT_NULL) {
+               if (deallocate_tf) {
+                       typefilter_deallocate(deallocate_tf);
+               }
+               return ENOMEM;
+       }
+
+       /*
+        * The atomic store closes a race window with
+        * the kdebug_typefilter syscall, which assumes
+        * that any non-null kdbg_typefilter means a
+        * valid memory_entry is available.
+        */
+       os_atomic_store(&kdbg_typefilter, tf, release);
+
+       return KERN_SUCCESS;
+}
+
+static int
+kdbg_copyin_typefilter(user_addr_t addr, size_t size)
+{
+       int ret = ENOMEM;
+       typefilter_t tf;
+
+       ktrace_assert_lock_held();
+
+       if (size != KDBG_TYPEFILTER_BITMAP_SIZE) {
+               return EINVAL;
+       }
+
+       if ((tf = typefilter_create())) {
+               if ((ret = copyin(addr, tf, KDBG_TYPEFILTER_BITMAP_SIZE)) == 0) {
+                       /* The kernel typefilter must always allow DBG_TRACE */
+                       typefilter_allow_class(tf, DBG_TRACE);
+
+                       /*
+                        * If this is the first typefilter; claim it.
+                        * Otherwise copy and deallocate.
+                        *
+                        * Allocating a typefilter for the copyin allows
+                        * the kernel to hold the invariant that DBG_TRACE
+                        * must always be allowed.
+                        */
+                       if (!kdbg_typefilter) {
+                               if ((ret = kdbg_initialize_typefilter(tf))) {
+                                       return ret;
+                               }
+                               tf = NULL;
+                       } else {
+                               typefilter_copy(kdbg_typefilter, tf);
+                       }
+
+                       kdbg_enable_typefilter();
+                       kdbg_iop_list_callback(kd_ctrl_page.kdebug_iops, KD_CALLBACK_TYPEFILTER_CHANGED, kdbg_typefilter);
+               }
+
+               if (tf) {
+                       typefilter_deallocate(tf);
+               }
+       }
+
+       return ret;
+}
+
+/*
+ * Enable the flags in the control page for the typefilter.  Assumes that
+ * kdbg_typefilter has already been allocated, so events being written
+ * don't see a bad typefilter.
+ */
+static void
+kdbg_enable_typefilter(void)
+{
+       assert(kdbg_typefilter);
+       kd_ctrl_page.kdebug_flags &= ~(KDBG_RANGECHECK | KDBG_VALCHECK);
+       kd_ctrl_page.kdebug_flags |= KDBG_TYPEFILTER_CHECK;
+       kdbg_set_flags(SLOW_CHECKS, 0, true);
+       commpage_update_kdebug_state();
+}
+
+/*
+ * Disable the flags in the control page for the typefilter.  The typefilter
+ * may be safely deallocated shortly after this function returns.
+ */
+static void
+kdbg_disable_typefilter(void)
+{
+       bool notify_iops = kd_ctrl_page.kdebug_flags & KDBG_TYPEFILTER_CHECK;
+       kd_ctrl_page.kdebug_flags &= ~KDBG_TYPEFILTER_CHECK;
+
+       if ((kd_ctrl_page.kdebug_flags & (KDBG_PIDCHECK | KDBG_PIDEXCLUDE))) {
+               kdbg_set_flags(SLOW_CHECKS, 0, true);
+       } else {
+               kdbg_set_flags(SLOW_CHECKS, 0, false);
+       }
+       commpage_update_kdebug_state();
+
+       if (notify_iops) {
+               /*
+                * Notify IOPs that the typefilter will now allow everything.
+                * Otherwise, they won't know a typefilter is no longer in
+                * effect.
+                */
+               typefilter_allow_all(kdbg_typefilter);
+               kdbg_iop_list_callback(kd_ctrl_page.kdebug_iops,
+                   KD_CALLBACK_TYPEFILTER_CHANGED, kdbg_typefilter);
+       }
+}
+
+uint32_t
+kdebug_commpage_state(void)
+{
+       if (kdebug_enable) {
+               if (kd_ctrl_page.kdebug_flags & KDBG_TYPEFILTER_CHECK) {
+                       return KDEBUG_COMMPAGE_ENABLE_TYPEFILTER | KDEBUG_COMMPAGE_ENABLE_TRACE;
+               }
+
+               return KDEBUG_COMMPAGE_ENABLE_TRACE;
+       }
+
+       return 0;
+}
+
+int
+kdbg_setreg(kd_regtype * kdr)
+{
+       int ret = 0;
+       unsigned int val_1, val_2, val;
+       switch (kdr->type) {
+       case KDBG_CLASSTYPE:
+               val_1 = (kdr->value1 & 0xff);
+               val_2 = (kdr->value2 & 0xff);
+               kdlog_beg = (val_1 << 24);
+               kdlog_end = (val_2 << 24);
+               kd_ctrl_page.kdebug_flags &= (unsigned int)~KDBG_CKTYPES;
+               kd_ctrl_page.kdebug_flags &= ~KDBG_VALCHECK;       /* Turn off specific value check  */
+               kd_ctrl_page.kdebug_flags |= (KDBG_RANGECHECK | KDBG_CLASSTYPE);
+               kdbg_set_flags(SLOW_CHECKS, 0, true);
+               break;
+       case KDBG_SUBCLSTYPE:
+               val_1 = (kdr->value1 & 0xff);
+               val_2 = (kdr->value2 & 0xff);
+               val = val_2 + 1;
+               kdlog_beg = ((val_1 << 24) | (val_2 << 16));
+               kdlog_end = ((val_1 << 24) | (val << 16));
+               kd_ctrl_page.kdebug_flags &= (unsigned int)~KDBG_CKTYPES;
+               kd_ctrl_page.kdebug_flags &= ~KDBG_VALCHECK;       /* Turn off specific value check  */
+               kd_ctrl_page.kdebug_flags |= (KDBG_RANGECHECK | KDBG_SUBCLSTYPE);
+               kdbg_set_flags(SLOW_CHECKS, 0, true);
+               break;
+       case KDBG_RANGETYPE:
+               kdlog_beg = (kdr->value1);
+               kdlog_end = (kdr->value2);
+               kd_ctrl_page.kdebug_flags &= (unsigned int)~KDBG_CKTYPES;
+               kd_ctrl_page.kdebug_flags &= ~KDBG_VALCHECK;       /* Turn off specific value check  */
+               kd_ctrl_page.kdebug_flags |= (KDBG_RANGECHECK | KDBG_RANGETYPE);
+               kdbg_set_flags(SLOW_CHECKS, 0, true);
+               break;
+       case KDBG_VALCHECK:
+               kdlog_value1 = (kdr->value1);
+               kdlog_value2 = (kdr->value2);
+               kdlog_value3 = (kdr->value3);
+               kdlog_value4 = (kdr->value4);
+               kd_ctrl_page.kdebug_flags &= (unsigned int)~KDBG_CKTYPES;
+               kd_ctrl_page.kdebug_flags &= ~KDBG_RANGECHECK;    /* Turn off range check */
+               kd_ctrl_page.kdebug_flags |= KDBG_VALCHECK;       /* Turn on specific value check  */
+               kdbg_set_flags(SLOW_CHECKS, 0, true);
+               break;
+       case KDBG_TYPENONE:
+               kd_ctrl_page.kdebug_flags &= (unsigned int)~KDBG_CKTYPES;
+
+               if ((kd_ctrl_page.kdebug_flags & (KDBG_RANGECHECK | KDBG_VALCHECK   |
+                   KDBG_PIDCHECK   | KDBG_PIDEXCLUDE |
+                   KDBG_TYPEFILTER_CHECK))) {
+                       kdbg_set_flags(SLOW_CHECKS, 0, true);
+               } else {
+                       kdbg_set_flags(SLOW_CHECKS, 0, false);
+               }
+
+               kdlog_beg = 0;
+               kdlog_end = 0;
+               break;
+       default:
+               ret = EINVAL;
+               break;
+       }
+       return ret;
+}
+
+static int
+kdbg_write_to_vnode(caddr_t buffer, size_t size, vnode_t vp, vfs_context_t ctx, off_t file_offset)
+{
+       assert(size < INT_MAX);
+       return vn_rdwr(UIO_WRITE, vp, buffer, (int)size, file_offset, UIO_SYSSPACE, IO_NODELOCKED | IO_UNIT,
+                  vfs_context_ucred(ctx), (int *) 0, vfs_context_proc(ctx));
+}
+
+int
+kdbg_write_v3_chunk_header(user_addr_t buffer, uint32_t tag, uint32_t sub_tag, uint64_t length, vnode_t vp, vfs_context_t ctx)
+{
+       int ret = KERN_SUCCESS;
+       kd_chunk_header_v3 header = {
+               .tag = tag,
+               .sub_tag = sub_tag,
+               .length = length,
+       };
+
+       // Check that only one of them is valid
+       assert(!buffer ^ !vp);
+       assert((vp == NULL) || (ctx != NULL));
+
+       // Write the 8-byte future_chunk_timestamp field in the payload
+       if (buffer || vp) {
+               if (vp) {
+                       ret = kdbg_write_to_vnode((caddr_t)&header, sizeof(kd_chunk_header_v3), vp, ctx, RAW_file_offset);
+                       if (ret) {
+                               goto write_error;
+                       }
+                       RAW_file_offset  += (sizeof(kd_chunk_header_v3));
+               } else {
+                       ret = copyout(&header, buffer, sizeof(kd_chunk_header_v3));
+                       if (ret) {
+                               goto write_error;
+                       }
+               }
+       }
+write_error:
+       return ret;
+}
+
+static int
+kdbg_write_v3_chunk_to_fd(uint32_t tag, uint32_t sub_tag, uint64_t length, void *payload, uint64_t payload_size, int fd)
+{
+       proc_t p;
+       struct vfs_context context;
+       struct fileproc *fp;
+       vnode_t vp;
+       p = current_proc();
+
+       if (fp_get_ftype(p, fd, DTYPE_VNODE, EBADF, &fp)) {
+               return EBADF;
+       }
+
+       vp = fp->fp_glob->fg_data;
+       context.vc_thread = current_thread();
+       context.vc_ucred = fp->fp_glob->fg_cred;
+
+       if ((vnode_getwithref(vp)) == 0) {
+               RAW_file_offset = fp->fp_glob->fg_offset;
+
+               kd_chunk_header_v3 chunk_header = {
+                       .tag = tag,
+                       .sub_tag = sub_tag,
+                       .length = length,
+               };
+
+               int ret = kdbg_write_to_vnode((caddr_t)  &chunk_header, sizeof(kd_chunk_header_v3), vp, &context, RAW_file_offset);
+               if (!ret) {
+                       RAW_file_offset += sizeof(kd_chunk_header_v3);
+               }
+
+               ret = kdbg_write_to_vnode((caddr_t) payload, (size_t) payload_size, vp, &context, RAW_file_offset);
+               if (!ret) {
+                       RAW_file_offset  += payload_size;
+               }
+
+               fp->fp_glob->fg_offset = RAW_file_offset;
+               vnode_put(vp);
+       }
+
+       fp_drop(p, fd, fp, 0);
+       return KERN_SUCCESS;
+}
+
+user_addr_t
+kdbg_write_v3_event_chunk_header(user_addr_t buffer, uint32_t tag, uint64_t length, vnode_t vp, vfs_context_t ctx)
+{
+       uint64_t future_chunk_timestamp = 0;
+       length += sizeof(uint64_t);
+
+       if (kdbg_write_v3_chunk_header(buffer, tag, V3_EVENT_DATA_VERSION, length, vp, ctx)) {
+               return 0;
+       }
+       if (buffer) {
+               buffer += sizeof(kd_chunk_header_v3);
+       }
+
+       // Check that only one of them is valid
+       assert(!buffer ^ !vp);
+       assert((vp == NULL) || (ctx != NULL));
+
+       // Write the 8-byte future_chunk_timestamp field in the payload
+       if (buffer || vp) {
+               if (vp) {
+                       int ret = kdbg_write_to_vnode((caddr_t)&future_chunk_timestamp, sizeof(uint64_t), vp, ctx, RAW_file_offset);
+                       if (!ret) {
+                               RAW_file_offset  += (sizeof(uint64_t));
+                       }
+               } else {
+                       if (copyout(&future_chunk_timestamp, buffer, sizeof(uint64_t))) {
+                               return 0;
+                       }
+               }
+       }
+
+       return buffer + sizeof(uint64_t);
+}
+
+int
+kdbg_write_v3_header(user_addr_t user_header, size_t *user_header_size, int fd)
+{
+       int ret = KERN_SUCCESS;
+
+       uint8_t* cpumap = 0;
+       uint32_t cpumap_size = 0;
+       uint32_t thrmap_size = 0;
+
+       size_t bytes_needed = 0;
+
+       // Check that only one of them is valid
+       assert(!user_header ^ !fd);
+       assert(user_header_size);
+
+       if (!(kd_ctrl_page.kdebug_flags & KDBG_BUFINIT)) {
+               ret = EINVAL;
+               goto bail;
+       }
+
+       if (!(user_header || fd)) {
+               ret = EINVAL;
+               goto bail;
+       }
+
+       // Initialize the cpu map
+       ret = kdbg_cpumap_init_internal(kd_ctrl_page.kdebug_iops, kd_ctrl_page.kdebug_cpus, &cpumap, &cpumap_size);
+       if (ret != KERN_SUCCESS) {
+               goto bail;
+       }
+
+       // Check if a thread map is initialized
+       if (!kd_mapptr) {
+               ret = EINVAL;
+               goto bail;
+       }
+       if (os_mul_overflow(kd_mapcount, sizeof(kd_threadmap), &thrmap_size)) {
+               ret = ERANGE;
+               goto bail;
+       }
+
+       mach_timebase_info_data_t timebase = {0, 0};
+       clock_timebase_info(&timebase);
+
+       // Setup the header.
+       // See v3 header description in sys/kdebug.h for more inforamtion.
+       kd_header_v3 header = {
+               .tag = RAW_VERSION3,
+               .sub_tag = V3_HEADER_VERSION,
+               .length = (sizeof(kd_header_v3) + cpumap_size - sizeof(kd_cpumap_header)),
+               .timebase_numer = timebase.numer,
+               .timebase_denom = timebase.denom,
+               .timestamp = 0, /* FIXME rdar://problem/22053009 */
+               .walltime_secs = 0,
+               .walltime_usecs = 0,
+               .timezone_minuteswest = 0,
+               .timezone_dst = 0,
+#if defined(__LP64__)
+               .flags = 1,
+#else
+               .flags = 0,
+#endif
+       };
+
+       // If its a buffer, check if we have enough space to copy the header and the maps.
+       if (user_header) {
+               bytes_needed = (size_t)header.length + thrmap_size + (2 * sizeof(kd_chunk_header_v3));
+               if (*user_header_size < bytes_needed) {
+                       ret = EINVAL;
+                       goto bail;
+               }
+       }
+
+       // Start writing the header
+       if (fd) {
+               void *hdr_ptr = (void *)(((uintptr_t) &header) + sizeof(kd_chunk_header_v3));
+               size_t payload_size = (sizeof(kd_header_v3) - sizeof(kd_chunk_header_v3));
+
+               ret = kdbg_write_v3_chunk_to_fd(RAW_VERSION3, V3_HEADER_VERSION, header.length, hdr_ptr, payload_size, fd);
+               if (ret) {
+                       goto bail;
+               }
+       } else {
+               if (copyout(&header, user_header, sizeof(kd_header_v3))) {
+                       ret = EFAULT;
+                       goto bail;
+               }
+               // Update the user pointer
+               user_header += sizeof(kd_header_v3);
+       }
+
+       // Write a cpu map. This is a sub chunk of the header
+       cpumap = (uint8_t*)((uintptr_t) cpumap + sizeof(kd_cpumap_header));
+       size_t payload_size = (size_t)(cpumap_size - sizeof(kd_cpumap_header));
+       if (fd) {
+               ret = kdbg_write_v3_chunk_to_fd(V3_CPU_MAP, V3_CPUMAP_VERSION, payload_size, (void *)cpumap, payload_size, fd);
+               if (ret) {
+                       goto bail;
+               }
+       } else {
+               ret = kdbg_write_v3_chunk_header(user_header, V3_CPU_MAP, V3_CPUMAP_VERSION, payload_size, NULL, NULL);
+               if (ret) {
+                       goto bail;
+               }
+               user_header += sizeof(kd_chunk_header_v3);
+               if (copyout(cpumap, user_header, payload_size)) {
+                       ret = EFAULT;
+                       goto bail;
+               }
+               // Update the user pointer
+               user_header += payload_size;
+       }
+
+       // Write a thread map
+       if (fd) {
+               ret = kdbg_write_v3_chunk_to_fd(V3_THREAD_MAP, V3_THRMAP_VERSION, thrmap_size, (void *)kd_mapptr, thrmap_size, fd);
+               if (ret) {
+                       goto bail;
+               }
+       } else {
+               ret = kdbg_write_v3_chunk_header(user_header, V3_THREAD_MAP, V3_THRMAP_VERSION, thrmap_size, NULL, NULL);
+               if (ret) {
+                       goto bail;
+               }
+               user_header += sizeof(kd_chunk_header_v3);
+               if (copyout(kd_mapptr, user_header, thrmap_size)) {
+                       ret = EFAULT;
+                       goto bail;
+               }
+               user_header += thrmap_size;
+       }
+
+       if (fd) {
+               RAW_file_written += bytes_needed;
+       }
+
+       *user_header_size = bytes_needed;
+bail:
+       if (cpumap) {
+               kmem_free(kernel_map, (vm_offset_t)cpumap, cpumap_size);
+       }
+       return ret;
+}
+
+int
+kdbg_readcpumap(user_addr_t user_cpumap, size_t *user_cpumap_size)
+{
+       uint8_t* cpumap = NULL;
+       uint32_t cpumap_size = 0;
+       int ret = KERN_SUCCESS;
+
+       if (kd_ctrl_page.kdebug_flags & KDBG_BUFINIT) {
+               if (kdbg_cpumap_init_internal(kd_ctrl_page.kdebug_iops, kd_ctrl_page.kdebug_cpus, &cpumap, &cpumap_size) == KERN_SUCCESS) {
+                       if (user_cpumap) {
+                               size_t bytes_to_copy = (*user_cpumap_size >= cpumap_size) ? cpumap_size : *user_cpumap_size;
+                               if (copyout(cpumap, user_cpumap, (size_t)bytes_to_copy)) {
+                                       ret = EFAULT;
+                               }
+                       }
+                       *user_cpumap_size = cpumap_size;
+                       kmem_free(kernel_map, (vm_offset_t)cpumap, cpumap_size);
+               } else {
+                       ret = EINVAL;
+               }
+       } else {
+               ret = EINVAL;
+       }
+
+       return ret;
+}
+
+int
+kdbg_readcurthrmap(user_addr_t buffer, size_t *bufsize)
+{
+       kd_threadmap *mapptr;
+       vm_size_t mapsize;
+       vm_size_t mapcount;
+       int ret = 0;
+       size_t count = *bufsize / sizeof(kd_threadmap);
+
+       *bufsize = 0;
+
+       if ((mapptr = kdbg_thrmap_init_internal(count, &mapsize, &mapcount))) {
+               if (copyout(mapptr, buffer, mapcount * sizeof(kd_threadmap))) {
+                       ret = EFAULT;
+               } else {
+                       *bufsize = (mapcount * sizeof(kd_threadmap));
+               }
+
+               kfree(mapptr, mapsize);
+       } else {
+               ret = EINVAL;
+       }
+
+       return ret;
+}
+
+static int
+kdbg_write_v1_header(bool write_thread_map, vnode_t vp, vfs_context_t ctx)
+{
+       int ret = 0;
+       RAW_header header;
+       clock_sec_t secs;
+       clock_usec_t usecs;
+       char *pad_buf;
+       uint32_t pad_size;
+       uint32_t extra_thread_count = 0;
+       uint32_t cpumap_size;
+       size_t map_size = 0;
+       uint32_t map_count = 0;
+
+       if (write_thread_map) {
+               assert(kd_ctrl_page.kdebug_flags & KDBG_MAPINIT);
+               if (kd_mapcount > UINT32_MAX) {
+                       return ERANGE;
+               }
+               map_count = (uint32_t)kd_mapcount;
+               if (os_mul_overflow(map_count, sizeof(kd_threadmap), &map_size)) {
+                       return ERANGE;
+               }
+               if (map_size >= INT_MAX) {
+                       return ERANGE;
+               }
+       }
+
+       /*
+        * Without the buffers initialized, we cannot construct a CPU map or a
+        * thread map, and cannot write a header.
+        */
+       if (!(kd_ctrl_page.kdebug_flags & KDBG_BUFINIT)) {
+               return EINVAL;
+       }
+
+       /*
+        * To write a RAW_VERSION1+ file, we must embed a cpumap in the
+        * "padding" used to page align the events following the threadmap. If
+        * the threadmap happens to not require enough padding, we artificially
+        * increase its footprint until it needs enough padding.
+        */
+
+       assert(vp);
+       assert(ctx);
+
+       pad_size = PAGE_16KB - ((sizeof(RAW_header) + map_size) & PAGE_MASK);
+       cpumap_size = sizeof(kd_cpumap_header) + kd_ctrl_page.kdebug_cpus * sizeof(kd_cpumap);
+
+       if (cpumap_size > pad_size) {
+               /* If the cpu map doesn't fit in the current available pad_size,
+                * we increase the pad_size by 16K. We do this so that the event
+                * data is always  available on a page aligned boundary for both
+                * 4k and 16k systems. We enforce this alignment for the event
+                * data so that we can take advantage of optimized file/disk writes.
+                */
+               pad_size += PAGE_16KB;
+       }
+
+       /* The way we are silently embedding a cpumap in the "padding" is by artificially
+        * increasing the number of thread entries. However, we'll also need to ensure that
+        * the cpumap is embedded in the last 4K page before when the event data is expected.
+        * This way the tools can read the data starting the next page boundary on both
+        * 4K and 16K systems preserving compatibility with older versions of the tools
+        */
+       if (pad_size > PAGE_4KB) {
+               pad_size -= PAGE_4KB;
+               extra_thread_count = (pad_size / sizeof(kd_threadmap)) + 1;
+       }
+
+       memset(&header, 0, sizeof(header));
+       header.version_no = RAW_VERSION1;
+       header.thread_count = map_count + extra_thread_count;
+
+       clock_get_calendar_microtime(&secs, &usecs);
+       header.TOD_secs = secs;
+       header.TOD_usecs = usecs;
+
+       ret = vn_rdwr(UIO_WRITE, vp, (caddr_t)&header, (int)sizeof(RAW_header), RAW_file_offset,
+           UIO_SYSSPACE, IO_NODELOCKED | IO_UNIT, vfs_context_ucred(ctx), (int *) 0, vfs_context_proc(ctx));
+       if (ret) {
+               goto write_error;
+       }
+       RAW_file_offset += sizeof(RAW_header);
+       RAW_file_written += sizeof(RAW_header);
+
+       if (write_thread_map) {
+               assert(map_size < INT_MAX);
+               ret = vn_rdwr(UIO_WRITE, vp, (caddr_t)kd_mapptr, (int)map_size, RAW_file_offset,
+                   UIO_SYSSPACE, IO_NODELOCKED | IO_UNIT, vfs_context_ucred(ctx), (int *) 0, vfs_context_proc(ctx));
+               if (ret) {
+                       goto write_error;
+               }
+
+               RAW_file_offset += map_size;
+               RAW_file_written += map_size;
+       }
+
+       if (extra_thread_count) {
+               pad_size = extra_thread_count * sizeof(kd_threadmap);
+               pad_buf = kheap_alloc(KHEAP_TEMP, pad_size, Z_WAITOK | Z_ZERO);
+               if (!pad_buf) {
+                       ret = ENOMEM;
+                       goto write_error;
+               }
+
+               assert(pad_size < INT_MAX);
+               ret = vn_rdwr(UIO_WRITE, vp, (caddr_t)pad_buf, (int)pad_size, RAW_file_offset,
+                   UIO_SYSSPACE, IO_NODELOCKED | IO_UNIT, vfs_context_ucred(ctx), (int *) 0, vfs_context_proc(ctx));
+               kheap_free(KHEAP_TEMP, pad_buf, pad_size);
+               if (ret) {
+                       goto write_error;
+               }
+
+               RAW_file_offset += pad_size;
+               RAW_file_written += pad_size;
+       }
+
+       pad_size = PAGE_SIZE - (RAW_file_offset & PAGE_MASK);
+       if (pad_size) {
+               pad_buf = (char *)kheap_alloc(KHEAP_TEMP, pad_size, Z_WAITOK | Z_ZERO);
+               if (!pad_buf) {
+                       ret = ENOMEM;
+                       goto write_error;
+               }
+
+               /*
+                * embed a cpumap in the padding bytes.
+                * older code will skip this.
+                * newer code will know how to read it.
+                */
+               uint32_t temp = pad_size;
+               if (kdbg_cpumap_init_internal(kd_ctrl_page.kdebug_iops, kd_ctrl_page.kdebug_cpus, (uint8_t**)&pad_buf, &temp) != KERN_SUCCESS) {
+                       memset(pad_buf, 0, pad_size);
+               }
+
+               assert(pad_size < INT_MAX);
+               ret = vn_rdwr(UIO_WRITE, vp, (caddr_t)pad_buf, (int)pad_size, RAW_file_offset,
+                   UIO_SYSSPACE, IO_NODELOCKED | IO_UNIT, vfs_context_ucred(ctx), (int *) 0, vfs_context_proc(ctx));
+               kheap_free(KHEAP_TEMP, pad_buf, pad_size);
+               if (ret) {
+                       goto write_error;
+               }
+
+               RAW_file_offset += pad_size;
+               RAW_file_written += pad_size;
+       }
+
+write_error:
+       return ret;
+}
+
+static void
+kdbg_clear_thread_map(void)
+{
+       ktrace_assert_lock_held();
+
+       if (kd_ctrl_page.kdebug_flags & KDBG_MAPINIT) {
+               assert(kd_mapptr != NULL);
+               kfree(kd_mapptr, kd_mapsize);
+               kd_mapptr = NULL;
+               kd_mapsize = 0;
+               kd_mapcount = 0;
+               kd_ctrl_page.kdebug_flags &= ~KDBG_MAPINIT;
+       }
+}
+
+/*
+ * Write out a version 1 header and the thread map, if it is initialized, to a
+ * vnode.  Used by KDWRITEMAP and kdbg_dump_trace_to_file.
+ *
+ * Returns write errors from vn_rdwr if a write fails.  Returns ENODATA if the
+ * thread map has not been initialized, but the header will still be written.
+ * Returns ENOMEM if padding could not be allocated.  Returns 0 otherwise.
+ */
+static int
+kdbg_write_thread_map(vnode_t vp, vfs_context_t ctx)
+{
+       int ret = 0;
+       bool map_initialized;
+
+       ktrace_assert_lock_held();
+       assert(ctx != NULL);
+
+       map_initialized = (kd_ctrl_page.kdebug_flags & KDBG_MAPINIT);
+
+       ret = kdbg_write_v1_header(map_initialized, vp, ctx);
+       if (ret == 0) {
+               if (map_initialized) {
+                       kdbg_clear_thread_map();
+               } else {
+                       ret = ENODATA;
+               }
+       }
+
+       return ret;
+}
+
+/*
+ * Copy out the thread map to a user space buffer.  Used by KDTHRMAP.
+ *
+ * Returns copyout errors if the copyout fails.  Returns ENODATA if the thread
+ * map has not been initialized.  Returns EINVAL if the buffer provided is not
+ * large enough for the entire thread map.  Returns 0 otherwise.
+ */
+static int
+kdbg_copyout_thread_map(user_addr_t buffer, size_t *buffer_size)
+{
+       bool map_initialized;
+       size_t map_size;
+       int ret = 0;
+
+       ktrace_assert_lock_held();
+       assert(buffer_size != NULL);
+
+       map_initialized = (kd_ctrl_page.kdebug_flags & KDBG_MAPINIT);
+       if (!map_initialized) {
+               return ENODATA;
+       }
+
+       map_size = kd_mapcount * sizeof(kd_threadmap);
+       if (*buffer_size < map_size) {
+               return EINVAL;
+       }
+
+       ret = copyout(kd_mapptr, buffer, map_size);
+       if (ret == 0) {
+               kdbg_clear_thread_map();
+       }
+
+       return ret;
+}
+
+int
+kdbg_readthrmap_v3(user_addr_t buffer, size_t buffer_size, int fd)
+{
+       int ret = 0;
+       bool map_initialized;
+       size_t map_size;
+
+       ktrace_assert_lock_held();
+
+       if ((!fd && !buffer) || (fd && buffer)) {
+               return EINVAL;
+       }
+
+       map_initialized = (kd_ctrl_page.kdebug_flags & KDBG_MAPINIT);
+       map_size = kd_mapcount * sizeof(kd_threadmap);
+
+       if (map_initialized && (buffer_size >= map_size)) {
+               ret = kdbg_write_v3_header(buffer, &buffer_size, fd);
+
+               if (ret == 0) {
+                       kdbg_clear_thread_map();
+               }
+       } else {
+               ret = EINVAL;
+       }
+
+       return ret;
+}
+
+static void
+kdbg_set_nkdbufs(unsigned int req_nkdbufs)
+{
+       /*
+        * Only allow allocation up to half the available memory (sane_size).
+        */
+       uint64_t max_nkdbufs = (sane_size / 2) / sizeof(kd_buf);
+       nkdbufs = (req_nkdbufs > max_nkdbufs) ? (unsigned int)max_nkdbufs :
+           req_nkdbufs;
+}
+
+/*
+ * Block until there are `n_storage_threshold` storage units filled with
+ * events or `timeout_ms` milliseconds have passed.  If `locked_wait` is true,
+ * `ktrace_lock` is held while waiting.  This is necessary while waiting to
+ * write events out of the buffers.
+ *
+ * Returns true if the threshold was reached and false otherwise.
+ *
+ * Called with `ktrace_lock` locked and interrupts enabled.
+ */
+static bool
+kdbg_wait(uint64_t timeout_ms, bool locked_wait)
+{
+       int wait_result = THREAD_AWAKENED;
+       uint64_t abstime = 0;
+
+       ktrace_assert_lock_held();
+
+       if (timeout_ms != 0) {
+               uint64_t ns = timeout_ms * NSEC_PER_MSEC;
+               nanoseconds_to_absolutetime(ns, &abstime);
+               clock_absolutetime_interval_to_deadline(abstime, &abstime);
+       }
+
+       bool s = ml_set_interrupts_enabled(false);
+       if (!s) {
+               panic("kdbg_wait() called with interrupts disabled");
+       }
+       lck_spin_lock_grp(kdw_spin_lock, kdebug_lck_grp);
+
+       if (!locked_wait) {
+               /* drop the mutex to allow others to access trace */
+               ktrace_unlock();
+       }
+
+       while (wait_result == THREAD_AWAKENED &&
+           kd_ctrl_page.kds_inuse_count < n_storage_threshold) {
+               kds_waiter = 1;
+
+               if (abstime) {
+                       wait_result = lck_spin_sleep_deadline(kdw_spin_lock, 0, &kds_waiter, THREAD_ABORTSAFE, abstime);
+               } else {
+                       wait_result = lck_spin_sleep(kdw_spin_lock, 0, &kds_waiter, THREAD_ABORTSAFE);
+               }
+
+               kds_waiter = 0;
+       }
+
+       /* check the count under the spinlock */
+       bool threshold_exceeded = (kd_ctrl_page.kds_inuse_count >= n_storage_threshold);
+
+       lck_spin_unlock(kdw_spin_lock);
+       ml_set_interrupts_enabled(s);
+
+       if (!locked_wait) {
+               /* pick the mutex back up again */
+               ktrace_lock();
+       }
+
+       /* write out whether we've exceeded the threshold */
+       return threshold_exceeded;
+}
+
+/*
+ * Wakeup a thread waiting using `kdbg_wait` if there are at least
+ * `n_storage_threshold` storage units in use.
+ */
+static void
+kdbg_wakeup(void)
+{
+       bool need_kds_wakeup = false;
+
+       /*
+        * Try to take the lock here to synchronize with the waiter entering
+        * the blocked state.  Use the try mode to prevent deadlocks caused by
+        * re-entering this routine due to various trace points triggered in the
+        * lck_spin_sleep_xxxx routines used to actually enter one of our 2 wait
+        * conditions.  No problem if we fail, there will be lots of additional
+        * events coming in that will eventually succeed in grabbing this lock.
+        */
+       bool s = ml_set_interrupts_enabled(false);
+
+       if (lck_spin_try_lock(kdw_spin_lock)) {
+               if (kds_waiter &&
+                   (kd_ctrl_page.kds_inuse_count >= n_storage_threshold)) {
+                       kds_waiter = 0;
+                       need_kds_wakeup = true;
+               }
+               lck_spin_unlock(kdw_spin_lock);
+       }
+
+       ml_set_interrupts_enabled(s);
+
+       if (need_kds_wakeup == true) {
+               wakeup(&kds_waiter);
+       }
+}
+
+int
+kdbg_control(int *name, u_int namelen, user_addr_t where, size_t *sizep)
+{
+       int ret = 0;
+       size_t size = *sizep;
+       unsigned int value = 0;
+       kd_regtype kd_Reg;
+       kbufinfo_t kd_bufinfo;
+       proc_t p;
+
+       if (name[0] == KERN_KDWRITETR ||
+           name[0] == KERN_KDWRITETR_V3 ||
+           name[0] == KERN_KDWRITEMAP ||
+           name[0] == KERN_KDWRITEMAP_V3 ||
+           name[0] == KERN_KDEFLAGS ||
+           name[0] == KERN_KDDFLAGS ||
+           name[0] == KERN_KDENABLE ||
+           name[0] == KERN_KDSETBUF) {
+               if (namelen < 2) {
+                       return EINVAL;
+               }
+               value = name[1];
+       }
+
+       kdbg_lock_init();
+       assert(kd_ctrl_page.kdebug_flags & KDBG_LOCKINIT);
+
+       ktrace_lock();
+
+       /*
+        * Some requests only require "read" access to kdebug trace.  Regardless,
+        * tell ktrace that a configuration or read is occurring (and see if it's
+        * allowed).
+        */
+       if (name[0] != KERN_KDGETBUF &&
+           name[0] != KERN_KDGETREG &&
+           name[0] != KERN_KDREADCURTHRMAP) {
+               if ((ret = ktrace_configure(KTRACE_KDEBUG))) {
+                       goto out;
+               }
+       } else {
+               if ((ret = ktrace_read_check())) {
+                       goto out;
+               }
+       }
+
+       switch (name[0]) {
+       case KERN_KDGETBUF:
+               if (size < sizeof(kd_bufinfo.nkdbufs)) {
+                       /*
+                        * There is not enough room to return even
+                        * the first element of the info structure.
+                        */
+                       ret = EINVAL;
+                       break;
+               }
+
+               memset(&kd_bufinfo, 0, sizeof(kd_bufinfo));
+
+               kd_bufinfo.nkdbufs = nkdbufs;
+               kd_bufinfo.nkdthreads = kd_mapcount < INT_MAX ? (int)kd_mapcount :
+                   INT_MAX;
+               if ((kd_ctrl_page.kdebug_slowcheck & SLOW_NOLOG)) {
+                       kd_bufinfo.nolog = 1;
+               } else {
+                       kd_bufinfo.nolog = 0;
+               }
+
+               kd_bufinfo.flags = kd_ctrl_page.kdebug_flags;
+#if defined(__LP64__)
+               kd_bufinfo.flags |= KDBG_LP64;
+#endif
+               {
+                       int pid = ktrace_get_owning_pid();
+                       kd_bufinfo.bufid = (pid == 0 ? -1 : pid);
+               }
+
+               if (size >= sizeof(kd_bufinfo)) {
+                       /*
+                        * Provide all the info we have
+                        */
+                       if (copyout(&kd_bufinfo, where, sizeof(kd_bufinfo))) {
+                               ret = EINVAL;
+                       }
+               } else {
+                       /*
+                        * For backwards compatibility, only provide
+                        * as much info as there is room for.
+                        */
+                       if (copyout(&kd_bufinfo, where, size)) {
+                               ret = EINVAL;
                        }
-                       ret = kdbg_setreg(&kd_Reg);
-                       break;
-               case KERN_KDGETREG:
-                       if(size < sizeof(kd_regtype)) {
+               }
+               break;
+
+       case KERN_KDREADCURTHRMAP:
+               ret = kdbg_readcurthrmap(where, sizep);
+               break;
+
+       case KERN_KDEFLAGS:
+               value &= KDBG_USERFLAGS;
+               kd_ctrl_page.kdebug_flags |= value;
+               break;
+
+       case KERN_KDDFLAGS:
+               value &= KDBG_USERFLAGS;
+               kd_ctrl_page.kdebug_flags &= ~value;
+               break;
+
+       case KERN_KDENABLE:
+               /*
+                * Enable tracing mechanism.  Two types:
+                * KDEBUG_TRACE is the standard one,
+                * and KDEBUG_PPT which is a carefully
+                * chosen subset to avoid performance impact.
+                */
+               if (value) {
+                       /*
+                        * enable only if buffer is initialized
+                        */
+                       if (!(kd_ctrl_page.kdebug_flags & KDBG_BUFINIT) ||
+                           !(value == KDEBUG_ENABLE_TRACE || value == KDEBUG_ENABLE_PPT)) {
                                ret = EINVAL;
                                break;
                        }
-                       ret = kdbg_getreg(&kd_Reg);
-                       if (copyout(&kd_Reg, where, sizeof(kd_regtype))){
-                               ret=EINVAL;
+                       kdbg_thrmap_init();
+
+                       kdbg_set_tracing_enabled(true, value);
+               } else {
+                       if (!kdebug_enable) {
+                               break;
                        }
+
+                       kernel_debug_disable();
+               }
+               break;
+
+       case KERN_KDSETBUF:
+               kdbg_set_nkdbufs(value);
+               break;
+
+       case KERN_KDSETUP:
+               ret = kdbg_reinit(false);
+               break;
+
+       case KERN_KDREMOVE:
+               ktrace_reset(KTRACE_KDEBUG);
+               break;
+
+       case KERN_KDSETREG:
+               if (size < sizeof(kd_regtype)) {
+                       ret = EINVAL;
                        break;
-               case KERN_KDREADTR:
-                       ret = kdbg_read(where, sizep);
+               }
+               if (copyin(where, &kd_Reg, sizeof(kd_regtype))) {
+                       ret = EINVAL;
                        break;
-               case KERN_KDPIDTR:
-                       if (size < sizeof(kd_regtype)) {
-                               ret = EINVAL;
-                               break;
+               }
+
+               ret = kdbg_setreg(&kd_Reg);
+               break;
+
+       case KERN_KDGETREG:
+               ret = EINVAL;
+               break;
+
+       case KERN_KDREADTR:
+               ret = kdbg_read(where, sizep, NULL, NULL, RAW_VERSION1);
+               break;
+
+       case KERN_KDWRITETR:
+       case KERN_KDWRITETR_V3:
+       case KERN_KDWRITEMAP:
+       case KERN_KDWRITEMAP_V3:
+       {
+               struct  vfs_context context;
+               struct  fileproc *fp;
+               size_t  number;
+               vnode_t vp;
+               int     fd;
+
+               if (name[0] == KERN_KDWRITETR || name[0] == KERN_KDWRITETR_V3) {
+                       (void)kdbg_wait(size, true);
+               }
+               p = current_proc();
+               fd = value;
+
+
+               if (fp_get_ftype(p, fd, DTYPE_VNODE, EBADF, &fp)) {
+                       ret = EBADF;
+                       break;
+               }
+
+               vp = fp->fp_glob->fg_data;
+               context.vc_thread = current_thread();
+               context.vc_ucred = fp->fp_glob->fg_cred;
+
+               if ((ret = vnode_getwithref(vp)) == 0) {
+                       RAW_file_offset = fp->fp_glob->fg_offset;
+                       if (name[0] == KERN_KDWRITETR || name[0] == KERN_KDWRITETR_V3) {
+                               number = nkdbufs * sizeof(kd_buf);
+
+                               KDBG_RELEASE(TRACE_WRITING_EVENTS | DBG_FUNC_START);
+                               if (name[0] == KERN_KDWRITETR_V3) {
+                                       ret = kdbg_read(0, &number, vp, &context, RAW_VERSION3);
+                               } else {
+                                       ret = kdbg_read(0, &number, vp, &context, RAW_VERSION1);
+                               }
+                               KDBG_RELEASE(TRACE_WRITING_EVENTS | DBG_FUNC_END, number);
+
+                               *sizep = number;
+                       } else {
+                               number = kd_mapcount * sizeof(kd_threadmap);
+                               if (name[0] == KERN_KDWRITEMAP_V3) {
+                                       ret = kdbg_readthrmap_v3(0, number, fd);
+                               } else {
+                                       ret = kdbg_write_thread_map(vp, &context);
+                               }
+                       }
+                       fp->fp_glob->fg_offset = RAW_file_offset;
+                       vnode_put(vp);
+               }
+               fp_drop(p, fd, fp, 0);
+
+               break;
+       }
+       case KERN_KDBUFWAIT:
+               *sizep = kdbg_wait(size, false);
+               break;
+
+       case KERN_KDPIDTR:
+               if (size < sizeof(kd_regtype)) {
+                       ret = EINVAL;
+                       break;
+               }
+               if (copyin(where, &kd_Reg, sizeof(kd_regtype))) {
+                       ret = EINVAL;
+                       break;
+               }
+
+               ret = kdbg_setpid(&kd_Reg);
+               break;
+
+       case KERN_KDPIDEX:
+               if (size < sizeof(kd_regtype)) {
+                       ret = EINVAL;
+                       break;
+               }
+               if (copyin(where, &kd_Reg, sizeof(kd_regtype))) {
+                       ret = EINVAL;
+                       break;
+               }
+
+               ret = kdbg_setpidex(&kd_Reg);
+               break;
+
+       case KERN_KDCPUMAP:
+               ret = kdbg_readcpumap(where, sizep);
+               break;
+
+       case KERN_KDTHRMAP:
+               ret = kdbg_copyout_thread_map(where, sizep);
+               break;
+
+       case KERN_KDSET_TYPEFILTER: {
+               ret = kdbg_copyin_typefilter(where, size);
+               break;
+       }
+
+       case KERN_KDTEST:
+               ret = kdbg_test(size);
+               break;
+
+       default:
+               ret = EINVAL;
+               break;
+       }
+out:
+       ktrace_unlock();
+
+       return ret;
+}
+
+
+/*
+ * This code can run for the most part concurrently with kernel_debug_internal()...
+ * 'release_storage_unit' will take the kds_spin_lock which may cause us to briefly
+ * synchronize with the recording side of this puzzle... otherwise, we are able to
+ * move through the lists w/o use of any locks
+ */
+int
+kdbg_read(user_addr_t buffer, size_t *number, vnode_t vp, vfs_context_t ctx, uint32_t file_version)
+{
+       size_t count;
+       unsigned int cpu, min_cpu;
+       uint64_t barrier_min = 0, barrier_max = 0, t, earliest_time;
+       int error = 0;
+       kd_buf *tempbuf;
+       uint32_t rcursor;
+       kd_buf lostevent;
+       union kds_ptr kdsp;
+       bool traced_retrograde = false;
+       struct kd_storage *kdsp_actual;
+       struct kd_bufinfo *kdbp;
+       struct kd_bufinfo *min_kdbp;
+       size_t tempbuf_count;
+       uint32_t tempbuf_number;
+       uint32_t old_kdebug_flags;
+       uint32_t old_kdebug_slowcheck;
+       bool out_of_events = false;
+       bool wrapped = false;
+
+       assert(number != NULL);
+       count = *number / sizeof(kd_buf);
+       *number = 0;
+
+       ktrace_assert_lock_held();
+
+       if (count == 0 || !(kd_ctrl_page.kdebug_flags & KDBG_BUFINIT) || kdcopybuf == 0) {
+               return EINVAL;
+       }
+
+       thread_set_eager_preempt(current_thread());
+
+       memset(&lostevent, 0, sizeof(lostevent));
+       lostevent.debugid = TRACE_LOST_EVENTS;
+
+       /*
+        * Request each IOP to provide us with up to date entries before merging
+        * buffers together.
+        */
+       kdbg_iop_list_callback(kd_ctrl_page.kdebug_iops, KD_CALLBACK_SYNC_FLUSH, NULL);
+
+       /*
+        * Capture the current time.  Only sort events that have occured
+        * before now.  Since the IOPs are being flushed here, it is possible
+        * that events occur on the AP while running live tracing.
+        */
+       barrier_max = kdbg_timestamp() & KDBG_TIMESTAMP_MASK;
+
+       /*
+        * Disable wrap so storage units cannot be stolen out from underneath us
+        * while merging events.
+        *
+        * Because we hold ktrace_lock, no other control threads can be playing
+        * with kdebug_flags.  The code that emits new events could be running,
+        * but it grabs kds_spin_lock if it needs to acquire a new storage
+        * chunk, which is where it examines kdebug_flags.  If it is adding to
+        * the same chunk we're reading from, check for that below.
+        */
+       wrapped = disable_wrap(&old_kdebug_slowcheck, &old_kdebug_flags);
+
+       if (count > nkdbufs) {
+               count = nkdbufs;
+       }
+
+       if ((tempbuf_count = count) > KDCOPYBUF_COUNT) {
+               tempbuf_count = KDCOPYBUF_COUNT;
+       }
+
+       /*
+        * If the buffers have wrapped, do not emit additional lost events for the
+        * oldest storage units.
+        */
+       if (wrapped) {
+               kd_ctrl_page.kdebug_flags &= ~KDBG_WRAPPED;
+
+               for (cpu = 0, kdbp = &kdbip[0]; cpu < kd_ctrl_page.kdebug_cpus; cpu++, kdbp++) {
+                       if ((kdsp = kdbp->kd_list_head).raw == KDS_PTR_NULL) {
+                               continue;
+                       }
+                       kdsp_actual = POINTER_FROM_KDS_PTR(kdsp);
+                       kdsp_actual->kds_lostevents = false;
+               }
+       }
+       /*
+        * Capture the earliest time where there are events for all CPUs and don't
+        * emit events with timestamps prior.
+        */
+       barrier_min = kd_ctrl_page.oldest_time;
+
+       while (count) {
+               tempbuf = kdcopybuf;
+               tempbuf_number = 0;
+
+               if (wrapped) {
+                       /*
+                        * Emit a lost events tracepoint to indicate that previous events
+                        * were lost -- the thread map cannot be trusted.  A new one must
+                        * be taken so tools can analyze the trace in a backwards-facing
+                        * fashion.
+                        */
+                       kdbg_set_timestamp_and_cpu(&lostevent, barrier_min, 0);
+                       *tempbuf = lostevent;
+                       wrapped = false;
+                       goto nextevent;
+               }
+
+               /* While space left in merged events scratch buffer. */
+               while (tempbuf_count) {
+                       bool lostevents = false;
+                       int lostcpu = 0;
+                       earliest_time = UINT64_MAX;
+                       min_kdbp = NULL;
+                       min_cpu = 0;
+
+                       /* Check each CPU's buffers for the earliest event. */
+                       for (cpu = 0, kdbp = &kdbip[0]; cpu < kd_ctrl_page.kdebug_cpus; cpu++, kdbp++) {
+                               /* Skip CPUs without data in their oldest storage unit. */
+                               if ((kdsp = kdbp->kd_list_head).raw == KDS_PTR_NULL) {
+next_cpu:
+                                       continue;
+                               }
+                               /* From CPU data to buffer header to buffer. */
+                               kdsp_actual = POINTER_FROM_KDS_PTR(kdsp);
+
+next_event:
+                               /* The next event to be read from this buffer. */
+                               rcursor = kdsp_actual->kds_readlast;
+
+                               /* Skip this buffer if there are no events left. */
+                               if (rcursor == kdsp_actual->kds_bufindx) {
+                                       continue;
+                               }
+
+                               /*
+                                * Check that this storage unit wasn't stolen and events were
+                                * lost.  This must have happened while wrapping was disabled
+                                * in this function.
+                                */
+                               if (kdsp_actual->kds_lostevents) {
+                                       lostevents = true;
+                                       kdsp_actual->kds_lostevents = false;
+
+                                       /*
+                                        * The earliest event we can trust is the first one in this
+                                        * stolen storage unit.
+                                        */
+                                       uint64_t lost_time =
+                                           kdbg_get_timestamp(&kdsp_actual->kds_records[0]);
+                                       if (kd_ctrl_page.oldest_time < lost_time) {
+                                               /*
+                                                * If this is the first time we've seen lost events for
+                                                * this gap, record its timestamp as the oldest
+                                                * timestamp we're willing to merge for the lost events
+                                                * tracepoint.
+                                                */
+                                               kd_ctrl_page.oldest_time = barrier_min = lost_time;
+                                               lostcpu = cpu;
+                                       }
+                               }
+
+                               t = kdbg_get_timestamp(&kdsp_actual->kds_records[rcursor]);
+
+                               if (t > barrier_max) {
+                                       if (kdbg_debug) {
+                                               printf("kdebug: FUTURE EVENT: debugid %#8x: "
+                                                   "time %lld from CPU %u "
+                                                   "(barrier at time %lld, read %lu events)\n",
+                                                   kdsp_actual->kds_records[rcursor].debugid,
+                                                   t, cpu, barrier_max, *number + tempbuf_number);
+                                       }
+                                       goto next_cpu;
+                               }
+                               if (t < kdsp_actual->kds_timestamp) {
+                                       /*
+                                        * This indicates the event emitter hasn't completed
+                                        * filling in the event (becuase we're looking at the
+                                        * buffer that the record head is using).  The max barrier
+                                        * timestamp should have saved us from seeing these kinds
+                                        * of things, but other CPUs might be slow on the up-take.
+                                        *
+                                        * Bail out so we don't get out-of-order events by
+                                        * continuing to read events from other CPUs' events.
+                                        */
+                                       out_of_events = true;
+                                       break;
+                               }
+
+                               /*
+                                * Ignore events that have aged out due to wrapping or storage
+                                * unit exhaustion while merging events.
+                                */
+                               if (t < barrier_min) {
+                                       kdsp_actual->kds_readlast++;
+                                       if (kdbg_debug) {
+                                               printf("kdebug: PAST EVENT: debugid %#8x: "
+                                                   "time %lld from CPU %u "
+                                                   "(barrier at time %lld)\n",
+                                                   kdsp_actual->kds_records[rcursor].debugid,
+                                                   t, cpu, barrier_min);
+                                       }
+
+                                       if (kdsp_actual->kds_readlast >= EVENTS_PER_STORAGE_UNIT) {
+                                               release_storage_unit(cpu, kdsp.raw);
+
+                                               if ((kdsp = kdbp->kd_list_head).raw == KDS_PTR_NULL) {
+                                                       goto next_cpu;
+                                               }
+                                               kdsp_actual = POINTER_FROM_KDS_PTR(kdsp);
+                                       }
+
+                                       goto next_event;
+                               }
+
+                               /*
+                                * Don't worry about merging any events -- just walk through
+                                * the CPUs and find the latest timestamp of lost events.
+                                */
+                               if (lostevents) {
+                                       continue;
+                               }
+
+                               if (t < earliest_time) {
+                                       earliest_time = t;
+                                       min_kdbp = kdbp;
+                                       min_cpu = cpu;
+                               }
                        }
-                       if (copyin(where, &kd_Reg, sizeof(kd_regtype))) {
-                               ret= EINVAL;
+                       if (lostevents) {
+                               /*
+                                * If any lost events were hit in the buffers, emit an event
+                                * with the latest timestamp.
+                                */
+                               kdbg_set_timestamp_and_cpu(&lostevent, barrier_min, lostcpu);
+                               *tempbuf = lostevent;
+                               tempbuf->arg1 = 1;
+                               goto nextevent;
+                       }
+                       if (min_kdbp == NULL) {
+                               /* All buffers ran empty. */
+                               out_of_events = true;
+                       }
+                       if (out_of_events) {
                                break;
                        }
-                       ret = kdbg_setpid(&kd_Reg);
-                       break;
-               case KERN_KDPIDEX:
-                       if (size < sizeof(kd_regtype)) {
-                               ret = EINVAL;
+
+                       kdsp = min_kdbp->kd_list_head;
+                       kdsp_actual = POINTER_FROM_KDS_PTR(kdsp);
+
+                       /* Copy earliest event into merged events scratch buffer. */
+                       *tempbuf = kdsp_actual->kds_records[kdsp_actual->kds_readlast++];
+
+                       if (kdsp_actual->kds_readlast == EVENTS_PER_STORAGE_UNIT) {
+                               release_storage_unit(min_cpu, kdsp.raw);
+                       }
+
+                       /*
+                        * Watch for out of order timestamps (from IOPs).
+                        */
+                       if (earliest_time < min_kdbp->kd_prev_timebase) {
+                               /*
+                                * If we haven't already, emit a retrograde events event.
+                                * Otherwise, ignore this event.
+                                */
+                               if (traced_retrograde) {
+                                       continue;
+                               }
+                               if (kdbg_debug) {
+                                       printf("kdebug: RETRO EVENT: debugid %#8x: "
+                                           "time %lld from CPU %u "
+                                           "(barrier at time %lld)\n",
+                                           kdsp_actual->kds_records[rcursor].debugid,
+                                           t, cpu, barrier_min);
+                               }
+
+                               kdbg_set_timestamp_and_cpu(tempbuf, min_kdbp->kd_prev_timebase, kdbg_get_cpu(tempbuf));
+                               tempbuf->arg1 = tempbuf->debugid;
+                               tempbuf->arg2 = (kd_buf_argtype)earliest_time;
+                               tempbuf->arg3 = 0;
+                               tempbuf->arg4 = 0;
+                               tempbuf->debugid = TRACE_RETROGRADE_EVENTS;
+                               traced_retrograde = true;
+                       } else {
+                               min_kdbp->kd_prev_timebase = earliest_time;
+                       }
+nextevent:
+                       tempbuf_count--;
+                       tempbuf_number++;
+                       tempbuf++;
+
+                       if ((RAW_file_written += sizeof(kd_buf)) >= RAW_FLUSH_SIZE) {
                                break;
                        }
-                       if (copyin(where, &kd_Reg, sizeof(kd_regtype))) {
-                               ret= EINVAL;
+               }
+               if (tempbuf_number) {
+                       /*
+                        * Remember the latest timestamp of events that we've merged so we
+                        * don't think we've lost events later.
+                        */
+                       uint64_t latest_time = kdbg_get_timestamp(tempbuf - 1);
+                       if (kd_ctrl_page.oldest_time < latest_time) {
+                               kd_ctrl_page.oldest_time = latest_time;
+                       }
+                       if (file_version == RAW_VERSION3) {
+                               if (!(kdbg_write_v3_event_chunk_header(buffer, V3_RAW_EVENTS, (tempbuf_number * sizeof(kd_buf)), vp, ctx))) {
+                                       error = EFAULT;
+                                       goto check_error;
+                               }
+                               if (buffer) {
+                                       buffer += (sizeof(kd_chunk_header_v3) + sizeof(uint64_t));
+                               }
+
+                               assert(count >= (sizeof(kd_chunk_header_v3) + sizeof(uint64_t)));
+                               count -= (sizeof(kd_chunk_header_v3) + sizeof(uint64_t));
+                               *number += (sizeof(kd_chunk_header_v3) + sizeof(uint64_t));
+                       }
+                       if (vp) {
+                               size_t write_size = tempbuf_number * sizeof(kd_buf);
+                               error = kdbg_write_to_vnode((caddr_t)kdcopybuf, write_size, vp, ctx, RAW_file_offset);
+                               if (!error) {
+                                       RAW_file_offset += write_size;
+                               }
+
+                               if (RAW_file_written >= RAW_FLUSH_SIZE) {
+                                       error = VNOP_FSYNC(vp, MNT_NOWAIT, ctx);
+
+                                       RAW_file_written = 0;
+                               }
+                       } else {
+                               error = copyout(kdcopybuf, buffer, tempbuf_number * sizeof(kd_buf));
+                               buffer += (tempbuf_number * sizeof(kd_buf));
+                       }
+check_error:
+                       if (error) {
+                               *number = 0;
+                               error = EINVAL;
                                break;
                        }
-                       ret = kdbg_setpidex(&kd_Reg);
+                       count   -= tempbuf_number;
+                       *number += tempbuf_number;
+               }
+               if (out_of_events == true) {
+                       /*
+                        * all trace buffers are empty
+                        */
                        break;
-               case KERN_KDTHRMAP:
-                       ret = kdbg_readmap((kd_threadmap *)where, sizep);
-                       break;
-               case KERN_KDSETRTCDEC:
-                       if (size < sizeof(kd_regtype)) {
-                               ret = EINVAL;
-                               break;
+               }
+
+               if ((tempbuf_count = count) > KDCOPYBUF_COUNT) {
+                       tempbuf_count = KDCOPYBUF_COUNT;
+               }
+       }
+       if (!(old_kdebug_flags & KDBG_NOWRAP)) {
+               enable_wrap(old_kdebug_slowcheck);
+       }
+       thread_clear_eager_preempt(current_thread());
+       return error;
+}
+
+#define KDEBUG_TEST_CODE(code) BSDDBG_CODE(DBG_BSD_KDEBUG_TEST, (code))
+
+/*
+ * A test IOP for the SYNC_FLUSH callback.
+ */
+
+static int sync_flush_iop = 0;
+
+static void
+sync_flush_callback(void * __unused context, kd_callback_type reason,
+    void * __unused arg)
+{
+       assert(sync_flush_iop > 0);
+
+       if (reason == KD_CALLBACK_SYNC_FLUSH) {
+               kernel_debug_enter(sync_flush_iop, KDEBUG_TEST_CODE(0xff),
+                   kdbg_timestamp(), 0, 0, 0, 0, 0);
+       }
+}
+
+static struct kd_callback sync_flush_kdcb = {
+       .func = sync_flush_callback,
+       .iop_name = "test_sf",
+};
+
+static int
+kdbg_test(size_t flavor)
+{
+       int code = 0;
+       int dummy_iop = 0;
+
+       switch (flavor) {
+       case 1:
+               /* try each macro */
+               KDBG(KDEBUG_TEST_CODE(code)); code++;
+               KDBG(KDEBUG_TEST_CODE(code), 1); code++;
+               KDBG(KDEBUG_TEST_CODE(code), 1, 2); code++;
+               KDBG(KDEBUG_TEST_CODE(code), 1, 2, 3); code++;
+               KDBG(KDEBUG_TEST_CODE(code), 1, 2, 3, 4); code++;
+
+               KDBG_RELEASE(KDEBUG_TEST_CODE(code)); code++;
+               KDBG_RELEASE(KDEBUG_TEST_CODE(code), 1); code++;
+               KDBG_RELEASE(KDEBUG_TEST_CODE(code), 1, 2); code++;
+               KDBG_RELEASE(KDEBUG_TEST_CODE(code), 1, 2, 3); code++;
+               KDBG_RELEASE(KDEBUG_TEST_CODE(code), 1, 2, 3, 4); code++;
+
+               KDBG_FILTERED(KDEBUG_TEST_CODE(code)); code++;
+               KDBG_FILTERED(KDEBUG_TEST_CODE(code), 1); code++;
+               KDBG_FILTERED(KDEBUG_TEST_CODE(code), 1, 2); code++;
+               KDBG_FILTERED(KDEBUG_TEST_CODE(code), 1, 2, 3); code++;
+               KDBG_FILTERED(KDEBUG_TEST_CODE(code), 1, 2, 3, 4); code++;
+
+               KDBG_RELEASE_NOPROCFILT(KDEBUG_TEST_CODE(code)); code++;
+               KDBG_RELEASE_NOPROCFILT(KDEBUG_TEST_CODE(code), 1); code++;
+               KDBG_RELEASE_NOPROCFILT(KDEBUG_TEST_CODE(code), 1, 2); code++;
+               KDBG_RELEASE_NOPROCFILT(KDEBUG_TEST_CODE(code), 1, 2, 3); code++;
+               KDBG_RELEASE_NOPROCFILT(KDEBUG_TEST_CODE(code), 1, 2, 3, 4); code++;
+
+               KDBG_DEBUG(KDEBUG_TEST_CODE(code)); code++;
+               KDBG_DEBUG(KDEBUG_TEST_CODE(code), 1); code++;
+               KDBG_DEBUG(KDEBUG_TEST_CODE(code), 1, 2); code++;
+               KDBG_DEBUG(KDEBUG_TEST_CODE(code), 1, 2, 3); code++;
+               KDBG_DEBUG(KDEBUG_TEST_CODE(code), 1, 2, 3, 4); code++;
+               break;
+
+       case 2:
+               if (kd_ctrl_page.kdebug_iops) {
+                       /* avoid the assertion in kernel_debug_enter for a valid IOP */
+                       dummy_iop = kd_ctrl_page.kdebug_iops[0].cpu_id;
+               }
+
+               /* ensure old timestamps are not emitted from kernel_debug_enter */
+               kernel_debug_enter(dummy_iop, KDEBUG_TEST_CODE(code),
+                   100 /* very old timestamp */, 0, 0, 0, 0, 0);
+               code++;
+               kernel_debug_enter(dummy_iop, KDEBUG_TEST_CODE(code),
+                   kdbg_timestamp(), 0, 0, 0, 0, 0);
+               code++;
+               break;
+
+       case 3:
+               if (kd_ctrl_page.kdebug_iops) {
+                       dummy_iop = kd_ctrl_page.kdebug_iops[0].cpu_id;
+               }
+               kernel_debug_enter(dummy_iop, KDEBUG_TEST_CODE(code),
+                   kdbg_timestamp() * 2 /* !!! */, 0, 0, 0, 0, 0);
+               break;
+
+       case 4:
+               if (!sync_flush_iop) {
+                       sync_flush_iop = kernel_debug_register_callback(
+                               sync_flush_kdcb);
+                       assert(sync_flush_iop > 0);
+               }
+               break;
+
+       default:
+               return ENOTSUP;
+       }
+
+       return 0;
+}
+
+#undef KDEBUG_TEST_CODE
+
+void
+kdebug_init(unsigned int n_events, char *filter_desc, enum kdebug_opts opts)
+{
+       assert(filter_desc != NULL);
+
+       if (log_leaks && n_events == 0) {
+               n_events = 200000;
+       }
+
+       kdebug_trace_start(n_events, filter_desc, opts);
+}
+
+static void
+kdbg_set_typefilter_string(const char *filter_desc)
+{
+       char *end = NULL;
+
+       ktrace_assert_lock_held();
+
+       assert(filter_desc != NULL);
+
+       typefilter_reject_all(kdbg_typefilter);
+       typefilter_allow_class(kdbg_typefilter, DBG_TRACE);
+
+       /* if the filter description starts with a number, assume it's a csc */
+       if (filter_desc[0] >= '0' && filter_desc[0] <= '9') {
+               unsigned long csc = strtoul(filter_desc, NULL, 0);
+               if (filter_desc != end && csc <= KDBG_CSC_MAX) {
+                       typefilter_allow_csc(kdbg_typefilter, (uint16_t)csc);
+               }
+               return;
+       }
+
+       while (filter_desc[0] != '\0') {
+               unsigned long allow_value;
+
+               char filter_type = filter_desc[0];
+               if (filter_type != 'C' && filter_type != 'S') {
+                       printf("kdebug: unexpected filter type `%c'\n", filter_type);
+                       return;
+               }
+               filter_desc++;
+
+               allow_value = strtoul(filter_desc, &end, 0);
+               if (filter_desc == end) {
+                       printf("kdebug: cannot parse `%s' as integer\n", filter_desc);
+                       return;
+               }
+
+               switch (filter_type) {
+               case 'C':
+                       if (allow_value > KDBG_CLASS_MAX) {
+                               printf("kdebug: class 0x%lx is invalid\n", allow_value);
+                               return;
                        }
-                       if (copyin(where, &kd_Reg, sizeof(kd_regtype))) {
-                               ret= EINVAL;
-                               break;
+                       printf("kdebug: C 0x%lx\n", allow_value);
+                       typefilter_allow_class(kdbg_typefilter, (uint8_t)allow_value);
+                       break;
+               case 'S':
+                       if (allow_value > KDBG_CSC_MAX) {
+                               printf("kdebug: class-subclass 0x%lx is invalid\n", allow_value);
+                               return;
                        }
-                       ret = kdbg_setrtcdec(&kd_Reg);
+                       printf("kdebug: S 0x%lx\n", allow_value);
+                       typefilter_allow_csc(kdbg_typefilter, (uint16_t)allow_value);
                        break;
-                      
                default:
-                       ret= EINVAL;
+                       __builtin_unreachable();
+               }
+
+               /* advance to next filter entry */
+               filter_desc = end;
+               if (filter_desc[0] == ',') {
+                       filter_desc++;
+               }
+       }
+}
+
+uint64_t
+kdebug_wake(void)
+{
+       if (!wake_nkdbufs) {
+               return 0;
        }
-       return(ret);
+       uint64_t start = mach_absolute_time();
+       kdebug_trace_start(wake_nkdbufs, NULL, trace_wrap ? KDOPT_WRAPPING : 0);
+       return mach_absolute_time() - start;
 }
 
-kdbg_read(kd_buf * buffer, size_t *number)
+/*
+ * This function is meant to be called from the bootstrap thread or kdebug_wake.
+ */
+void
+kdebug_trace_start(unsigned int n_events, const char *filter_desc,
+    enum kdebug_opts opts)
 {
-int avail=*number;
-int count=0;
-int copycount=0;
-int totalcount=0;
-int s;
-unsigned int my_kdebug_flags;
-kd_buf * my_kd_bufptr;
+       if (!n_events) {
+               kd_early_done = true;
+               return;
+       }
+
+       ktrace_start_single_threaded();
+
+       kdbg_lock_init();
+
+       ktrace_kernel_configure(KTRACE_KDEBUG);
+
+       kdbg_set_nkdbufs(n_events);
+
+       kernel_debug_string_early("start_kern_tracing");
+
+       if (kdbg_reinit((opts & KDOPT_ATBOOT))) {
+               printf("error from kdbg_reinit, kernel tracing not started\n");
+               goto out;
+       }
+
+       /*
+        * Wrapping is disabled because boot and wake tracing is interested in
+        * the earliest events, at the expense of later ones.
+        */
+       if (!(opts & KDOPT_WRAPPING)) {
+               uint32_t old1, old2;
+               (void)disable_wrap(&old1, &old2);
+       }
+
+       if (filter_desc && filter_desc[0] != '\0') {
+               if (kdbg_initialize_typefilter(NULL) == KERN_SUCCESS) {
+                       kdbg_set_typefilter_string(filter_desc);
+                       kdbg_enable_typefilter();
+               }
+       }
+
+       /*
+        * Hold off interrupts between getting a thread map and enabling trace
+        * and until the early traces are recorded.
+        */
+       bool s = ml_set_interrupts_enabled(false);
+
+       if (!(opts & KDOPT_ATBOOT)) {
+               kdbg_thrmap_init();
+       }
+
+       kdbg_set_tracing_enabled(true, KDEBUG_ENABLE_TRACE);
+
+       if ((opts & KDOPT_ATBOOT)) {
+               /*
+                * Transfer all very early events from the static buffer into the real
+                * buffers.
+                */
+               kernel_debug_early_end();
+       }
 
-       s = ml_set_interrupts_enabled(FALSE);
-       usimple_lock(&kd_trace_lock);
-       my_kdebug_flags = kdebug_flags;
-       my_kd_bufptr = kd_bufptr;
-       usimple_unlock(&kd_trace_lock);
        ml_set_interrupts_enabled(s);
 
-       count = avail/sizeof(kd_buf);
-       if (count) {
-               if ((my_kdebug_flags & KDBG_BUFINIT) && kd_bufsize && kd_buffer) {
-                       if (count > nkdbufs)
-                               count = nkdbufs;
-                       if (!(my_kdebug_flags & KDBG_WRAPPED) && (my_kd_bufptr > kd_readlast))
-                         {
-                           copycount = my_kd_bufptr-kd_readlast;
-                           if (copycount > count)
-                             copycount = count;
-
-                           if (copyout(kd_readlast, buffer, copycount * sizeof(kd_buf)))
-                             {
-                               *number = 0;
-                               return(EINVAL);
-                             }
-                           kd_readlast += copycount;
-                           *number = copycount;
-                           return(0);
-                         }
-                       else if (!(my_kdebug_flags & KDBG_WRAPPED) && (my_kd_bufptr == kd_readlast))
-                         {
-                           *number = 0;
-                           return(0);
-                         }
-                       else
-                         {
-                           if (my_kdebug_flags & KDBG_WRAPPED)
-                             {
-                               kd_readlast = my_kd_bufptr;
-                               kdebug_flags &= ~KDBG_WRAPPED;
-                             }
-
-                           /* Note that by setting kd_readlast equal to my_kd_bufptr,
-                              we now treat the kd_buffer read the same as if we weren't
-                              wrapped and my_kd_bufptr was less than kd_readlast.
-                           */
-
-                           /* first copyout from readlast to end of kd_buffer */
-                           copycount = kd_buflast - kd_readlast;
-                           if (copycount > count)
-                             copycount = count;
-                           if (copyout(kd_readlast, buffer, copycount * sizeof(kd_buf)))
-                             {
-                               *number = 0;
-                               return(EINVAL);
-                             }
-                           buffer += copycount;
-                           count -= copycount;
-                           totalcount = copycount;
-                           kd_readlast += copycount;
-                           if (kd_readlast == kd_buflast)
-                             kd_readlast = kd_buffer;
-                           if (count == 0)
-                             {
-                               *number = totalcount;
-                               return(0);
-                             }
-
-                            /* second copyout from top of kd_buffer to bufptr */
-                           copycount = my_kd_bufptr - kd_readlast;
-                           if (copycount > count)
-                             copycount = count;
-                           if (copycount == 0)
-                             {
-                               *number = totalcount;
-                               return(0);
-                             }
-                           if (copyout(kd_readlast, buffer, copycount * sizeof(kd_buf)))
-                             {
-                               return(EINVAL);
-                             }
-                           kd_readlast += copycount;
-                           totalcount += copycount;
-                           *number = totalcount;
-                           return(0);
-                         }
-               } /* end if KDBG_BUFINIT */             
-       } /* end if count */
-       return (EINVAL);
-}
-
-unsigned char *getProcName(struct proc *proc);
-unsigned char *getProcName(struct proc *proc) {
-
-       return (unsigned char *) &proc->p_comm; /* Return pointer to the proc name */
+       printf("kernel tracing started with %u events, filter = %s\n", n_events,
+           filter_desc ?: "none");
+
+out:
+       ktrace_end_single_threaded();
+}
+
+void
+kdbg_dump_trace_to_file(const char *filename)
+{
+       vfs_context_t ctx;
+       vnode_t vp;
+       size_t write_size;
+       int ret;
+
+       ktrace_lock();
+
+       if (!(kdebug_enable & KDEBUG_ENABLE_TRACE)) {
+               goto out;
+       }
+
+       if (ktrace_get_owning_pid() != 0) {
+               /*
+                * Another process owns ktrace and is still active, disable tracing to
+                * prevent wrapping.
+                */
+               kdebug_enable = 0;
+               kd_ctrl_page.enabled = 0;
+               commpage_update_kdebug_state();
+               goto out;
+       }
+
+       KDBG_RELEASE(TRACE_WRITING_EVENTS | DBG_FUNC_START);
+
+       kdebug_enable = 0;
+       kd_ctrl_page.enabled = 0;
+       commpage_update_kdebug_state();
+
+       ctx = vfs_context_kernel();
+
+       if (vnode_open(filename, (O_CREAT | FWRITE | O_NOFOLLOW), 0600, 0, &vp, ctx)) {
+               goto out;
+       }
+
+       kdbg_write_thread_map(vp, ctx);
+
+       write_size = nkdbufs * sizeof(kd_buf);
+       ret = kdbg_read(0, &write_size, vp, ctx, RAW_VERSION1);
+       if (ret) {
+               goto out_close;
+       }
+
+       /*
+        * Wait to synchronize the file to capture the I/O in the
+        * TRACE_WRITING_EVENTS interval.
+        */
+       ret = VNOP_FSYNC(vp, MNT_WAIT, ctx);
+
+       /*
+        * Balance the starting TRACE_WRITING_EVENTS tracepoint manually.
+        */
+       kd_buf end_event = {
+               .debugid = TRACE_WRITING_EVENTS | DBG_FUNC_END,
+               .arg1 = write_size,
+               .arg2 = ret,
+               .arg5 = (kd_buf_argtype)thread_tid(current_thread()),
+       };
+       kdbg_set_timestamp_and_cpu(&end_event, kdbg_timestamp(),
+           cpu_number());
+
+       /* this is best effort -- ignore any errors */
+       (void)kdbg_write_to_vnode((caddr_t)&end_event, sizeof(kd_buf), vp, ctx,
+           RAW_file_offset);
+
+out_close:
+       vnode_close(vp, FWRITE, ctx);
+       sync(current_proc(), (void *)NULL, (int *)NULL);
+
+out:
+       ktrace_unlock();
+}
 
+static int
+kdbg_sysctl_continuous SYSCTL_HANDLER_ARGS
+{
+#pragma unused(oidp, arg1, arg2)
+       int value = kdbg_continuous_time;
+       int ret = sysctl_io_number(req, value, sizeof(value), &value, NULL);
+
+       if (ret || !req->newptr) {
+               return ret;
+       }
+
+       kdbg_continuous_time = value;
+       return 0;
 }
+
+SYSCTL_NODE(_kern, OID_AUTO, kdbg, CTLFLAG_RD | CTLFLAG_LOCKED, 0,
+    "kdbg");
+
+SYSCTL_PROC(_kern_kdbg, OID_AUTO, experimental_continuous,
+    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_LOCKED, 0,
+    sizeof(int), kdbg_sysctl_continuous, "I",
+    "Set kdebug to use mach_continuous_time");
+
+SYSCTL_INT(_kern_kdbg, OID_AUTO, debug,
+    CTLFLAG_RW | CTLFLAG_LOCKED,
+    &kdbg_debug, 0, "Set kdebug debug mode");
+
+SYSCTL_QUAD(_kern_kdbg, OID_AUTO, oldest_time,
+    CTLTYPE_QUAD | CTLFLAG_RD | CTLFLAG_LOCKED,
+    &kd_ctrl_page.oldest_time,
+    "Find the oldest timestamp still in trace");