xnu-7195.101.1.tar.gz

[apple/xnu.git] / bsd / kern / kern_newsysctl.c

/*
 * Copyright (c) 2000-2019 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 *
 * 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. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 *
 * 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
 * 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_OSREFERENCE_LICENSE_HEADER_END@
 *
 *
 * Copyright (c) 1982, 1986, 1989, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Mike Karels at Berkeley Software Design, Inc.
 *
 * Quite extensively rewritten by Poul-Henning Kamp of the FreeBSD
 * project, to make these variables more userfriendly.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)kern_sysctl.c       8.4 (Berkeley) 4/14/94
 */


#include <kern/counter.h>
#include <sys/param.h>
#include <sys/buf.h>
#include <sys/kernel.h>
#include <sys/sysctl.h>
#include <sys/malloc.h>
#include <sys/proc_internal.h>
#include <sys/kauth.h>
#include <sys/systm.h>
#include <sys/sysproto.h>

#include <os/atomic_private.h>

#include <security/audit/audit.h>
#include <pexpert/pexpert.h>

#include <IOKit/IOBSD.h>

#if CONFIG_MACF
#include <security/mac_framework.h>
#endif

#if defined(HAS_APPLE_PAC)
#include <os/hash.h>
#include <ptrauth.h>
#endif /* defined(HAS_APPLE_PAC) */

static LCK_GRP_DECLARE(sysctl_lock_group, "sysctl");
static LCK_RW_DECLARE(sysctl_geometry_lock, &sysctl_lock_group);
static LCK_MTX_DECLARE(sysctl_unlocked_node_lock, &sysctl_lock_group);

/*
 * Conditionally allow dtrace to see these functions for debugging purposes.
 */
#ifdef STATIC
#undef STATIC
#endif
#if 0
#define STATIC
#else
#define STATIC static
#endif

/* forward declarations  of static functions */
STATIC void sysctl_sysctl_debug_dump_node(struct sysctl_oid_list *l, int i);
STATIC int sysctl_sysctl_debug(struct sysctl_oid *oidp, void *arg1,
    int arg2, struct sysctl_req *req);
STATIC int sysctl_sysctl_name(struct sysctl_oid *oidp, void *arg1,
    int arg2, struct sysctl_req *req);
STATIC int sysctl_sysctl_next_ls(struct sysctl_oid_list *lsp,
    int *name, u_int namelen, int *next, int *len, int level,
    struct sysctl_oid **oidpp);
STATIC int sysctl_old_kernel(struct sysctl_req *req, const void *p, size_t l);
STATIC int sysctl_new_kernel(struct sysctl_req *req, void *p, size_t l);
STATIC int name2oid(char *name, int *oid, size_t *len);
STATIC int sysctl_sysctl_name2oid(struct sysctl_oid *oidp, void *arg1, int arg2, struct sysctl_req *req);
STATIC int sysctl_sysctl_next(struct sysctl_oid *oidp, void *arg1, int arg2,
    struct sysctl_req *req);
STATIC int sysctl_sysctl_oidfmt(struct sysctl_oid *oidp, void *arg1, int arg2, struct sysctl_req *req);
STATIC int sysctl_old_user(struct sysctl_req *req, const void *p, size_t l);
STATIC int sysctl_new_user(struct sysctl_req *req, void *p, size_t l);

STATIC void sysctl_create_user_req(struct sysctl_req *req, struct proc *p, user_addr_t oldp,
    size_t oldlen, user_addr_t newp, size_t newlen);
STATIC int sysctl_root(boolean_t from_kernel, boolean_t string_is_canonical, char *namestring, size_t namestringlen, int *name, size_t namelen, struct sysctl_req *req);

int     kernel_sysctl(struct proc *p, int *name, size_t namelen, void *old, size_t *oldlenp, void *new, size_t newlen);
int     kernel_sysctlbyname(const char *name, void *oldp, size_t *oldlenp, void *newp, size_t newlen);
int     userland_sysctl(boolean_t string_is_canonical,
    char *namestring, size_t namestringlen,
    int *name, u_int namelen, struct sysctl_req *req,
    size_t *retval);

SECURITY_READ_ONLY_LATE(struct sysctl_oid_list) sysctl__children; /* root list */
__SYSCTL_EXTENSION_NODE();

/*
 * Initialization of the MIB tree.
 *
 * Order by number in each list.
 */

static void
sysctl_register_oid_locked(struct sysctl_oid *new_oidp,
    struct sysctl_oid *oidp)
{
        struct sysctl_oid_list *parent = new_oidp->oid_parent;
        struct sysctl_oid_list *parent_rw = NULL;
        struct sysctl_oid *p, **prevp;

        p = SLIST_FIRST(parent);
        if (p && p->oid_number == OID_MUTABLE_ANCHOR) {
                parent_rw = p->oid_arg1;
        }

        if (oidp->oid_number == OID_AUTO) {
                int n = OID_AUTO_START;

                /*
                 * If this oid has a number OID_AUTO, give it a number which
                 * is greater than any current oid.  Make sure it is at least
                 * OID_AUTO_START to leave space for pre-assigned oid numbers.
                 */

                SLIST_FOREACH_PREVPTR(p, prevp, parent, oid_link) {
                        if (p->oid_number >= n) {
                                n = p->oid_number + 1;
                        }
                }

                if (parent_rw) {
                        SLIST_FOREACH_PREVPTR(p, prevp, parent_rw, oid_link) {
                                if (p->oid_number >= n) {
                                        n = p->oid_number + 1;
                                }
                        }
                }

                /*
                 * Reflect the number in an allocated OID into the template
                 * of the caller for sysctl_unregister_oid() compares.
                 */
                oidp->oid_number = new_oidp->oid_number = n;
        } else {
                /*
                 * Insert the oid into the parent's list in order.
                 */
                SLIST_FOREACH_PREVPTR(p, prevp, parent, oid_link) {
                        if (oidp->oid_number == p->oid_number) {
                                panic("attempting to register a sysctl at previously registered slot : %d",
                                    oidp->oid_number);
                        } else if (oidp->oid_number < p->oid_number) {
                                break;
                        }
                }

                if (parent_rw) {
                        SLIST_FOREACH_PREVPTR(p, prevp, parent_rw, oid_link) {
                                if (oidp->oid_number == p->oid_number) {
                                        panic("attempting to register a sysctl at previously registered slot : %d",
                                            oidp->oid_number);
                                } else if (oidp->oid_number < p->oid_number) {
                                        break;
                                }
                        }
                }
        }

#if defined(HAS_APPLE_PAC)
        if (oidp->oid_handler) {
                /*
                 * Sign oid_handler address-discriminated upon installation to make it
                 * harder to replace with an arbitrary function pointer.  Blend with
                 * a hash of oid_arg1 for robustness against memory corruption.
                 */
                oidp->oid_handler = ptrauth_auth_and_resign(oidp->oid_handler,
                    ptrauth_key_function_pointer,
                    ptrauth_function_pointer_type_discriminator(typeof(oidp->oid_handler)),
                    ptrauth_key_function_pointer,
                    ptrauth_blend_discriminator(&oidp->oid_handler,
                    os_hash_kernel_pointer(oidp->oid_arg1)));
        }
#endif /* defined(HAS_APPLE_PAC) */

        SLIST_NEXT(oidp, oid_link) = *prevp;
        *prevp = oidp;
}

void
sysctl_register_oid(struct sysctl_oid *new_oidp)
{
        struct sysctl_oid *oidp;

        if (new_oidp->oid_number < OID_AUTO) {
                panic("trying to register a node %p with an invalid oid_number: %d",
                    new_oidp, new_oidp->oid_number);
        }
        if (new_oidp->oid_kind & CTLFLAG_PERMANENT) {
                panic("Use sysctl_register_oid_early to register permanent nodes");
        }

        /*
         * The OID can be old-style (needs copy), new style without an earlier
         * version (also needs copy), or new style with a matching version (no
         * copy needed).  Later versions are rejected (presumably, the OID
         * structure was changed for a necessary reason).
         */
        if (!(new_oidp->oid_kind & CTLFLAG_OID2)) {
#if __x86_64__
                /*
                 * XXX: KHEAP_DEFAULT is perhaps not the most apropriate zone, as it
                 * XXX: will subject us to use-after-free by other consumers.
                 */
                oidp = kheap_alloc(KHEAP_DEFAULT, sizeof(struct sysctl_oid),
                    Z_WAITOK | Z_ZERO);
                if (oidp == NULL) {
                        return;         /* reject: no memory */
                }
                /*
                 * Copy the structure only through the oid_fmt field, which
                 * is the last field in a non-OID2 OID structure.
                 *
                 * Note:        We may want to set the oid_descr to the
                 *              oid_name (or "") at some future date.
                 */
                memcpy(oidp, new_oidp, offsetof(struct sysctl_oid, oid_descr));
#else
                panic("Old style sysctl without a version number isn't supported");
#endif
        } else {
                /* It's a later version; handle the versions we know about */
                switch (new_oidp->oid_version) {
                case SYSCTL_OID_VERSION:
                        /* current version */
                        oidp = new_oidp;
                        break;
                default:
                        return;                 /* rejects unknown version */
                }
        }

        lck_rw_lock_exclusive(&sysctl_geometry_lock);
        sysctl_register_oid_locked(new_oidp, oidp);
        lck_rw_unlock_exclusive(&sysctl_geometry_lock);
}

__startup_func
void
sysctl_register_oid_early(struct sysctl_oid *oidp)
{
        assert((oidp->oid_kind & CTLFLAG_OID2) &&
            (oidp->oid_kind & CTLFLAG_PERMANENT) &&
            oidp->oid_version == SYSCTL_OID_VERSION);
        assert(startup_phase < STARTUP_SUB_SYSCTL);

        /*
         * Clear the flag so that callers can use sysctl_register_oid_early
         * again if they wish to register their node.
         */
        if (oidp->oid_kind & CTLFLAG_NOAUTO) {
                oidp->oid_kind &= ~CTLFLAG_NOAUTO;
                return;
        }

        sysctl_register_oid_locked(oidp, oidp);
}

void
sysctl_unregister_oid(struct sysctl_oid *oidp)
{
        struct sysctl_oid *removed_oidp = NULL; /* OID removed from tree */
#if __x86_64__
        struct sysctl_oid *old_oidp = NULL;     /* OID compatibility copy */
#endif
        struct sysctl_oid_list *lsp;

        /* Get the write lock to modify the geometry */
        lck_rw_lock_exclusive(&sysctl_geometry_lock);

        lsp = oidp->oid_parent;
        if (SLIST_FIRST(lsp) && SLIST_FIRST(lsp)->oid_number == OID_MUTABLE_ANCHOR) {
                lsp = SLIST_FIRST(lsp)->oid_arg1;
        }

        if (oidp->oid_kind & CTLFLAG_PERMANENT) {
                panic("Trying to unregister permanent sysctl %p", oidp);
        }

        if (!(oidp->oid_kind & CTLFLAG_OID2)) {
#if __x86_64__
                /*
                 * We're using a copy so we can get the new fields in an
                 * old structure, so we have to iterate to compare the
                 * partial structure; when we find a match, we remove it
                 * normally and free the memory.
                 */
                SLIST_FOREACH(old_oidp, lsp, oid_link) {
                        if (!memcmp(&oidp->oid_number, &old_oidp->oid_number, (offsetof(struct sysctl_oid, oid_descr) - offsetof(struct sysctl_oid, oid_number)))) {
                                break;
                        }
                }
                if (old_oidp != NULL) {
                        SLIST_REMOVE(lsp, old_oidp, sysctl_oid, oid_link);
                        removed_oidp = old_oidp;
                }
#else
                panic("Old style sysctl without a version number isn't supported");
#endif
        } else {
                /* It's a later version; handle the versions we know about */
                switch (oidp->oid_version) {
                case SYSCTL_OID_VERSION:
                        /* We can just remove the OID directly... */
                        SLIST_REMOVE(lsp, oidp, sysctl_oid, oid_link);
                        removed_oidp = oidp;
                        break;
                default:
                        /* XXX: Can't happen; probably tree coruption.*/
                        break;                  /* rejects unknown version */
                }
        }

#if defined(HAS_APPLE_PAC)
        if (removed_oidp && removed_oidp->oid_handler) {
                /*
                 * Revert address-discriminated signing performed by
                 * sysctl_register_oid() (in case this oid is registered again).
                 */
                removed_oidp->oid_handler = ptrauth_auth_and_resign(removed_oidp->oid_handler,
                    ptrauth_key_function_pointer,
                    ptrauth_blend_discriminator(&removed_oidp->oid_handler,
                    os_hash_kernel_pointer(removed_oidp->oid_arg1)),
                    ptrauth_key_function_pointer,
                    ptrauth_function_pointer_type_discriminator(typeof(removed_oidp->oid_handler)));
        }
#endif /* defined(HAS_APPLE_PAC) */

        /*
         * We've removed it from the list at this point, but we don't want
         * to return to the caller until all handler references have drained
         * out.  Doing things in this order prevent other people coming in
         * and starting new operations against the OID node we want removed.
         *
         * Note:        oidp could be NULL if it wasn't found.
         */
        while (removed_oidp && removed_oidp->oid_refcnt) {
                lck_rw_sleep(&sysctl_geometry_lock, LCK_SLEEP_EXCLUSIVE,
                    &removed_oidp->oid_refcnt, THREAD_UNINT);
        }

        /* Release the write lock */
        lck_rw_unlock_exclusive(&sysctl_geometry_lock);

#if __x86_64__
        /* If it was allocated, free it after dropping the lock */
        kheap_free(KHEAP_DEFAULT, old_oidp, sizeof(struct sysctl_oid));
#endif
}

/*
 * Exported in BSDKernel.exports, kept for binary compatibility
 */
#if defined(__x86_64__)
void
sysctl_register_fixed(void)
{
}
#endif

/*
 * New handler interface
 *   If the sysctl caller (user mode or kernel mode) is interested in the
 *   value (req->oldptr != NULL), we copy the data (bigValue etc.) out,
 *   if the caller wants to set the value (req->newptr), we copy
 *   the data in (*pValue etc.).
 */

int
sysctl_io_number(struct sysctl_req *req, long long bigValue, size_t valueSize, void *pValue, int *changed)
{
        int             smallValue;
        int             error;

        if (changed) {
                *changed = 0;
        }

        /*
         * Handle the various combinations of caller buffer size and
         * data value size.  We are generous in the case where the
         * caller has specified a 32-bit buffer but the value is 64-bit
         * sized.
         */

        /* 32 bit value expected or 32 bit buffer offered */
        if (((valueSize == sizeof(int)) ||
            ((req->oldlen == sizeof(int)) && (valueSize == sizeof(long long))))
            && (req->oldptr)) {
                smallValue = (int)bigValue;
                if ((long long)smallValue != bigValue) {
                        return ERANGE;
                }
                error = SYSCTL_OUT(req, &smallValue, sizeof(smallValue));
        } else {
                /* any other case is either size-equal or a bug */
                error = SYSCTL_OUT(req, &bigValue, valueSize);
        }
        /* error or nothing to set */
        if (error || !req->newptr) {
                return error;
        }

        /* set request for constant */
        if (pValue == NULL) {
                return EPERM;
        }

        /* set request needs to convert? */
        if ((req->newlen == sizeof(int)) && (valueSize == sizeof(long long))) {
                /* new value is 32 bits, upconvert to 64 bits */
                error = SYSCTL_IN(req, &smallValue, sizeof(smallValue));
                if (!error) {
                        *(long long *)pValue = (long long)smallValue;
                }
        } else if ((req->newlen == sizeof(long long)) && (valueSize == sizeof(int))) {
                /* new value is 64 bits, downconvert to 32 bits and range check */
                error = SYSCTL_IN(req, &bigValue, sizeof(bigValue));
                if (!error) {
                        smallValue = (int)bigValue;
                        if ((long long)smallValue != bigValue) {
                                return ERANGE;
                        }
                        *(int *)pValue = smallValue;
                }
        } else {
                /* sizes match, just copy in */
                error = SYSCTL_IN(req, pValue, valueSize);
        }
        if (!error && changed) {
                *changed = 1;
        }
        return error;
}

int
sysctl_io_string(struct sysctl_req *req, char *pValue, size_t valueSize, int trunc, int *changed)
{
        int error;
        size_t len = strlen(pValue) + 1;

        if (changed) {
                *changed = 0;
        }

        if (trunc && req->oldptr && req->oldlen && (req->oldlen < len)) {
                /* If trunc != 0, if you give it a too small (but larger than
                 * 0 bytes) buffer, instead of returning ENOMEM, it truncates the
                 * returned string to the buffer size.  This preserves the semantics
                 * of some library routines implemented via sysctl, which truncate
                 * their returned data, rather than simply returning an error. The
                 * returned string is always nul (ascii '\0') terminated. */
                error = SYSCTL_OUT(req, pValue, req->oldlen - 1);
                if (!error) {
                        char c = '\0';
                        error = SYSCTL_OUT(req, &c, 1);
                }
        } else {
                /* Copy string out */
                error = SYSCTL_OUT(req, pValue, len);
        }

        /* error or no new value */
        if (error || !req->newptr) {
                return error;
        }

        /* attempt to set read-only value */
        if (valueSize == 0) {
                return EPERM;
        }

        /* make sure there's room for the new string */
        if (req->newlen >= valueSize) {
                return EINVAL;
        }

        /* copy the string in and force nul termination */
        error = SYSCTL_IN(req, pValue, req->newlen);
        pValue[req->newlen] = '\0';

        if (!error && changed) {
                *changed = 1;
        }
        return error;
}

int
sysctl_io_opaque(struct sysctl_req *req, void *pValue, size_t valueSize, int *changed)
{
        int error;

        if (changed) {
                *changed = 0;
        }

        /* Copy blob out */
        error = SYSCTL_OUT(req, pValue, valueSize);

        /* error or nothing to set */
        if (error || !req->newptr) {
                return error;
        }

        error = SYSCTL_IN(req, pValue, valueSize);

        if (!error && changed) {
                *changed = 1;
        }
        return error;
}

/*
 * SYSCTL_OID enumerators
 *
 * Because system OIDs are immutable, they are composed of 2 lists hanging from
 * a first dummy OID_MUTABLE_ANCHOR node that has an immutable list hanging from
 * its `oid_parent` field and a mutable list hanging from its oid_arg1 one.
 *
 * Those enumerators abstract away the implicit merging of those two lists in
 * two possible order:
 * - oid_number order (which will interleave both sorted lists)
 * - system order which will list the immutable list first,
 *   and the mutable list second.
 */
struct sysctl_oid_iterator {
        struct sysctl_oid *a;
        struct sysctl_oid *b;
};

static struct sysctl_oid_iterator
sysctl_oid_iterator_begin(struct sysctl_oid_list *l)
{
        struct sysctl_oid_iterator it = { };
        struct sysctl_oid *a = SLIST_FIRST(l);

        if (a == NULL) {
                return it;
        }

        if (a->oid_number == OID_MUTABLE_ANCHOR) {
                it.a = SLIST_NEXT(a, oid_link);
                it.b = SLIST_FIRST((struct sysctl_oid_list *)a->oid_arg1);
        } else {
                it.a = a;
        }
        return it;
}

static struct sysctl_oid *
sysctl_oid_iterator_next_num_order(struct sysctl_oid_iterator *it)
{
        struct sysctl_oid *a = it->a;
        struct sysctl_oid *b = it->b;

        if (a == NULL && b == NULL) {
                return NULL;
        }

        if (a == NULL) {
                it->b = SLIST_NEXT(b, oid_link);
                return b;
        }

        if (b == NULL || a->oid_number <= b->oid_number) {
                it->a = SLIST_NEXT(a, oid_link);
                return a;
        }

        it->b = SLIST_NEXT(b, oid_link);
        return b;
}

#define SYSCTL_OID_FOREACH_NUM_ORDER(oidp, l) \
        for (struct sysctl_oid_iterator it = sysctl_oid_iterator_begin(l); \
                ((oidp) = sysctl_oid_iterator_next_num_order(&it)); )

static struct sysctl_oid *
sysctl_oid_iterator_next_system_order(struct sysctl_oid_iterator *it)
{
        struct sysctl_oid *a = it->a;
        struct sysctl_oid *b = it->b;

        if (a) {
                it->a = SLIST_NEXT(a, oid_link);
                return a;
        }

        if (b) {
                it->b = SLIST_NEXT(b, oid_link);
                return b;
        }

        return NULL;
}

#define SYSCTL_OID_FOREACH_SYS_ORDER(oidp, l) \
        for (struct sysctl_oid_iterator it = sysctl_oid_iterator_begin(l); \
                ((oidp) = sysctl_oid_iterator_next_system_order(&it)); )

/*
 * "Staff-functions"
 *
 * These functions implement a presently undocumented interface
 * used by the sysctl program to walk the tree, and get the type
 * so it can print the value.
 * This interface is under work and consideration, and should probably
 * be killed with a big axe by the first person who can find the time.
 * (be aware though, that the proper interface isn't as obvious as it
 * may seem, there are various conflicting requirements.
 *
 * {0,0}        printf the entire MIB-tree.
 * {0,1,...}    return the name of the "..." OID.
 * {0,2,...}    return the next OID.
 * {0,3}        return the OID of the name in "new"
 * {0,4,...}    return the kind & format info for the "..." OID.
 */

/*
 * sysctl_sysctl_debug_dump_node
 *
 * Description: Dump debug information for a given sysctl_oid_list at the
 *              given oid depth out to the kernel log, via printf
 *
 * Parameters:  l                               sysctl_oid_list pointer
 *              i                               current node depth
 *
 * Returns:     (void)
 *
 * Implicit:    kernel log, modified
 *
 * Locks:       Assumes sysctl_geometry_lock is held prior to calling
 *
 * Notes:       This function may call itself recursively to resolve Node
 *              values, which potentially have an inferioer sysctl_oid_list
 *
 *              This function is only callable indirectly via the function
 *              sysctl_sysctl_debug()
 *
 * Bugs:        The node depth indentation does not work; this may be an
 *              artifact of leading space removal by the log daemon itself
 *              or some intermediate routine.
 */
STATIC void
sysctl_sysctl_debug_dump_node(struct sysctl_oid_list *l, int i)
{
        struct sysctl_oid *oidp;
        struct sysctl_oid_list *lp;
        const char *what;

        SYSCTL_OID_FOREACH_SYS_ORDER(oidp, l) {
                switch (oidp->oid_kind & CTLTYPE) {
                case CTLTYPE_NODE:
                        lp = oidp->oid_arg1;
                        what = "Node   ";
                        if (lp && SLIST_FIRST(lp) &&
                            SLIST_FIRST(lp)->oid_number == OID_MUTABLE_ANCHOR) {
                                what = "NodeExt";
                        } else {
                        }
                        break;
                case CTLTYPE_INT:
                        what = "Int    ";
                        break;
                case CTLTYPE_STRING:
                        what = "String ";
                        break;
                case CTLTYPE_QUAD:
                        what = "Quad   ";
                        break;
                case CTLTYPE_OPAQUE:
                        what = "Opaque ";
                        break;
                default:
                        what = "Unknown";
                        break;
                }

                printf("%*s%-3d[%c%c%c%c%c] %s %s\n", i, "", oidp->oid_number,
                    oidp->oid_kind & CTLFLAG_LOCKED ? 'L':' ',
                    oidp->oid_kind & CTLFLAG_RD ? 'R':' ',
                    oidp->oid_kind & CTLFLAG_WR ? 'W':' ',
                    oidp->oid_kind & CTLFLAG_PERMANENT ? ' ':'*',
                    oidp->oid_handler ? 'h' : ' ',
                    what, oidp->oid_name);

                if ((oidp->oid_kind & CTLTYPE) == CTLTYPE_NODE) {
                        if (!oidp->oid_handler) {
                                sysctl_sysctl_debug_dump_node(lp, i + 2);
                        }
                }
        }
}

/*
 * sysctl_sysctl_debug
 *
 * Description: This function implements the "sysctl.debug" portion of the
 *              OID space for sysctl.
 *
 * OID:         0, 0
 *
 * Parameters:  __unused
 *
 * Returns:     ENOENT
 *
 * Implicit:    kernel log, modified
 *
 * Locks:       Acquires and then releases a read lock on the
 *              sysctl_geometry_lock
 */
STATIC int
sysctl_sysctl_debug(__unused struct sysctl_oid *oidp, __unused void *arg1,
    __unused int arg2, __unused struct sysctl_req *req)
{
        lck_rw_lock_shared(&sysctl_geometry_lock);
        sysctl_sysctl_debug_dump_node(&sysctl__children, 0);
        lck_rw_done(&sysctl_geometry_lock);
        return ENOENT;
}

SYSCTL_PROC(_sysctl, 0, debug, CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_LOCKED,
    0, 0, sysctl_sysctl_debug, "-", "");

/*
 * sysctl_sysctl_name
 *
 * Description: Convert an OID into a string name; this is used by the user
 *              space sysctl() command line utility; this is done in a purely
 *              advisory capacity (e.g. to provide node names for "sysctl -A"
 *              output).
 *
 * OID:         0, 1
 *
 * Parameters:  oidp                            __unused
 *              arg1                            A pointer to the OID name list
 *                                              integer array, beginning at
 *                                              adjusted option base 2
 *              arg2                            The number of elements which
 *                                              remain in the name array
 *
 * Returns:     0                               Success
 *      SYSCTL_OUT:EPERM                        Permission denied
 *      SYSCTL_OUT:EFAULT                       Bad user supplied buffer
 *      SYSCTL_OUT:???                          Return value from user function
 *                                              for SYSCTL_PROC leaf node
 *
 * Implict:     Contents of user request buffer, modified
 *
 * Locks:       Acquires and then releases a read lock on the
 *              sysctl_geometry_lock
 *
 * Notes:       SPI (System Programming Interface); this is subject to change
 *              and may not be relied upon by third party applications; use
 *              a subprocess to communicate with the "sysctl" command line
 *              command instead, if you believe you need this functionality.
 *              Preferrably, use sysctlbyname() instead.
 *
 *              Setting of the NULL termination of the output string is
 *              delayed until after the geometry lock is dropped.  If there
 *              are no Entries remaining in the OID name list when this
 *              function is called, it will still write out the termination
 *              byte.
 *
 *              This function differs from other sysctl functions in that
 *              it can not take an output buffer length of 0 to determine the
 *              space which will be required.  It is suggested that the buffer
 *              length be PATH_MAX, and that authors of new sysctl's refrain
 *              from exceeding this string length.
 */
STATIC int
sysctl_sysctl_name(__unused struct sysctl_oid *oidp, void *arg1, int arg2,
    struct sysctl_req *req)
{
        int *name = (int *) arg1;
        u_int namelen = arg2;
        int error = 0;
        struct sysctl_oid *oid;
        struct sysctl_oid_list *lsp = &sysctl__children, *lsp2;
        char tempbuf[10] = {};

        lck_rw_lock_shared(&sysctl_geometry_lock);
        while (namelen) {
                if (!lsp) {
                        snprintf(tempbuf, sizeof(tempbuf), "%d", *name);
                        if (req->oldidx) {
                                error = SYSCTL_OUT(req, ".", 1);
                        }
                        if (!error) {
                                error = SYSCTL_OUT(req, tempbuf, strlen(tempbuf));
                        }
                        if (error) {
                                lck_rw_done(&sysctl_geometry_lock);
                                return error;
                        }
                        namelen--;
                        name++;
                        continue;
                }
                lsp2 = 0;
                SYSCTL_OID_FOREACH_NUM_ORDER(oid, lsp) {
                        if (oid->oid_number != *name) {
                                continue;
                        }

                        if (req->oldidx) {
                                error = SYSCTL_OUT(req, ".", 1);
                        }
                        if (!error) {
                                error = SYSCTL_OUT(req, oid->oid_name,
                                    strlen(oid->oid_name));
                        }
                        if (error) {
                                lck_rw_done(&sysctl_geometry_lock);
                                return error;
                        }

                        namelen--;
                        name++;

                        if ((oid->oid_kind & CTLTYPE) != CTLTYPE_NODE) {
                                break;
                        }

                        if (oid->oid_handler) {
                                break;
                        }

                        lsp2 = (struct sysctl_oid_list *)oid->oid_arg1;
                        break;
                }
                lsp = lsp2;
        }
        lck_rw_done(&sysctl_geometry_lock);
        return SYSCTL_OUT(req, "", 1);
}

SYSCTL_NODE(_sysctl, 1, name, CTLFLAG_RD | CTLFLAG_LOCKED, sysctl_sysctl_name, "");

/*
 * sysctl_sysctl_next_ls
 *
 * Description: For a given OID name value, return the next consecutive OID
 *              name value within the geometry tree
 *
 * Parameters:  lsp                             The OID list to look in
 *              name                            The OID name to start from
 *              namelen                         The length of the OID name
 *              next                            Pointer to new oid storage to
 *                                              fill in
 *              len                             Pointer to receive new OID
 *                                              length value of storage written
 *              level                           OID tree depth (used to compute
 *                                              len value)
 *              oidpp                           Pointer to OID list entry
 *                                              pointer; used to walk the list
 *                                              forward across recursion
 *
 * Returns:     0                               Returning a new entry
 *              1                               End of geometry list reached
 *
 * Implicit:    *next                           Modified to contain the new OID
 *              *len                            Modified to contain new length
 *
 * Locks:       Assumes sysctl_geometry_lock is held prior to calling
 *
 * Notes:       This function will not return OID values that have special
 *              handlers, since we can not tell wheter these handlers consume
 *              elements from the OID space as parameters.  For this reason,
 *              we STRONGLY discourage these types of handlers
 */
STATIC int
sysctl_sysctl_next_ls(struct sysctl_oid_list *lsp, int *name, u_int namelen,
    int *next, int *len, int level, struct sysctl_oid **oidpp)
{
        struct sysctl_oid *oidp;

        *len = level;
        SYSCTL_OID_FOREACH_NUM_ORDER(oidp, lsp) {
                *next = oidp->oid_number;
                *oidpp = oidp;

                if (!namelen) {
                        if ((oidp->oid_kind & CTLTYPE) != CTLTYPE_NODE) {
                                return 0;
                        }
                        if (oidp->oid_handler) {
                                /* We really should call the handler here...*/
                                return 0;
                        }
                        lsp = (struct sysctl_oid_list *)oidp->oid_arg1;

                        if (!SLIST_FIRST(lsp)) {
                                /* This node had no children - skip it! */
                                continue;
                        }

                        if (!sysctl_sysctl_next_ls(lsp, 0, 0, next + 1,
                            len, level + 1, oidpp)) {
                                return 0;
                        }
                        goto next;
                }

                if (oidp->oid_number < *name) {
                        continue;
                }

                if (oidp->oid_number > *name) {
                        if ((oidp->oid_kind & CTLTYPE) != CTLTYPE_NODE) {
                                return 0;
                        }
                        if (oidp->oid_handler) {
                                return 0;
                        }
                        lsp = (struct sysctl_oid_list *)oidp->oid_arg1;
                        if (!sysctl_sysctl_next_ls(lsp, name + 1, namelen - 1,
                            next + 1, len, level + 1, oidpp)) {
                                return 0;
                        }
                        goto next;
                }
                if ((oidp->oid_kind & CTLTYPE) != CTLTYPE_NODE) {
                        continue;
                }

                if (oidp->oid_handler) {
                        continue;
                }

                lsp = (struct sysctl_oid_list *)oidp->oid_arg1;
                if (!sysctl_sysctl_next_ls(lsp, name + 1, namelen - 1, next + 1,
                    len, level + 1, oidpp)) {
                        return 0;
                }
next:
                namelen = 1;
                *len = level;
        }
        return 1;
}

/*
 * sysctl_sysctl_next
 *
 * Description: This is an iterator function designed to iterate the oid tree
 *              and provide a list of OIDs for use by the user space "sysctl"
 *              command line tool
 *
 * OID:         0, 2
 *
 * Parameters:  oidp                            __unused
 *              arg1                            Pointer to start OID name
 *              arg2                            Start OID name length
 *              req                             Pointer to user request buffer
 *
 * Returns:     0                               Success
 *              ENOENT                          Reached end of OID space
 *      SYSCTL_OUT:EPERM                        Permission denied
 *      SYSCTL_OUT:EFAULT                       Bad user supplied buffer
 *      SYSCTL_OUT:???                          Return value from user function
 *                                              for SYSCTL_PROC leaf node
 *
 * Implict:     Contents of user request buffer, modified
 *
 * Locks:       Acquires and then releases a read lock on the
 *              sysctl_geometry_lock
 *
 * Notes:       SPI (System Programming Interface); this is subject to change
 *              and may not be relied upon by third party applications; use
 *              a subprocess to communicate with the "sysctl" command line
 *              command instead, if you believe you need this functionality.
 *              Preferrably, use sysctlbyname() instead.
 *
 *              This function differs from other sysctl functions in that
 *              it can not take an output buffer length of 0 to determine the
 *              space which will be required.  It is suggested that the buffer
 *              length be PATH_MAX, and that authors of new sysctl's refrain
 *              from exceeding this string length.
 */
STATIC int
sysctl_sysctl_next(__unused struct sysctl_oid *oidp, void *arg1, int arg2,
    struct sysctl_req *req)
{
        int *name = (int *) arg1;
        u_int namelen = arg2;
        int i, j, error;
        struct sysctl_oid *oid;
        struct sysctl_oid_list *lsp = &sysctl__children;
        int newoid[CTL_MAXNAME] = {};

        lck_rw_lock_shared(&sysctl_geometry_lock);
        i = sysctl_sysctl_next_ls(lsp, name, namelen, newoid, &j, 1, &oid);
        lck_rw_done(&sysctl_geometry_lock);
        if (i) {
                return ENOENT;
        }
        error = SYSCTL_OUT(req, newoid, j * sizeof(int));
        return error;
}

SYSCTL_NODE(_sysctl, 2, next, CTLFLAG_RD | CTLFLAG_LOCKED, sysctl_sysctl_next, "");

/*
 * name2oid
 *
 * Description: Support function for use by sysctl_sysctl_name2oid(); looks
 *              up an OID name given a string name.
 *
 * Parameters:  name                            NULL terminated string name
 *              oid                             Pointer to receive OID name
 *              len                             Pointer to receive OID length
 *                                              pointer value (see "Notes")
 *
 * Returns:     0                               Success
 *              ENOENT                          Entry not found
 *
 * Implicit:    *oid                            Modified to contain OID value
 *              *len                            Modified to contain OID length
 *
 * Locks:       Assumes sysctl_geometry_lock is held prior to calling
 */
STATIC int
name2oid(char *name, int *oid, size_t *len)
{
        struct sysctl_oid_iterator it;
        struct sysctl_oid *oidp;
        char *p;
        char i;

        if (!*name) {
                return ENOENT;
        }

        p = name + strlen(name) - 1;
        if (*p == '.') {
                *p = '\0';
        }

        *len = 0;

        for (p = name; *p && *p != '.'; p++) {
                ;
        }
        i = *p;
        if (i == '.') {
                *p = '\0';
        }

        it = sysctl_oid_iterator_begin(&sysctl__children);
        oidp = sysctl_oid_iterator_next_system_order(&it);

        while (oidp && *len < CTL_MAXNAME) {
                if (strcmp(name, oidp->oid_name)) {
                        oidp = sysctl_oid_iterator_next_system_order(&it);
                        continue;
                }
                *oid++ = oidp->oid_number;
                (*len)++;

                if (i == '\0') {
                        return 0;
                }

                if ((oidp->oid_kind & CTLTYPE) != CTLTYPE_NODE) {
                        break;
                }

                if (oidp->oid_handler) {
                        break;
                }

                it = sysctl_oid_iterator_begin(oidp->oid_arg1);
                oidp = sysctl_oid_iterator_next_system_order(&it);

                *p = i; /* restore */
                name = p + 1;
                for (p = name; *p && *p != '.'; p++) {
                        ;
                }
                i = *p;
                if (i == '.') {
                        *p = '\0';
                }
        }
        return ENOENT;
}

/*
 * sysctl_sysctl_name2oid
 *
 * Description: Translate a string name to an OID name value; this is used by
 *              the sysctlbyname() function as well as by the "sysctl" command
 *              line command.
 *
 * OID:         0, 3
 *
 * Parameters:  oidp                            __unused
 *              arg1                            __unused
 *              arg2                            __unused
 *              req                             Request structure
 *
 * Returns:     ENOENT                          Input length too short
 *              ENAMETOOLONG                    Input length too long
 *              ENOMEM                          Could not allocate work area
 *      SYSCTL_IN/OUT:EPERM                     Permission denied
 *      SYSCTL_IN/OUT:EFAULT                    Bad user supplied buffer
 *      SYSCTL_IN/OUT:???                       Return value from user function
 *      name2oid:ENOENT                         Not found
 *
 * Implicit:    *req                            Contents of request, modified
 *
 * Locks:       Acquires and then releases a read lock on the
 *              sysctl_geometry_lock
 *
 * Notes:       SPI (System Programming Interface); this is subject to change
 *              and may not be relied upon by third party applications; use
 *              a subprocess to communicate with the "sysctl" command line
 *              command instead, if you believe you need this functionality.
 *              Preferrably, use sysctlbyname() instead.
 *
 *              This function differs from other sysctl functions in that
 *              it can not take an output buffer length of 0 to determine the
 *              space which will be required.  It is suggested that the buffer
 *              length be PATH_MAX, and that authors of new sysctl's refrain
 *              from exceeding this string length.
 */
STATIC int
sysctl_sysctl_name2oid(__unused struct sysctl_oid *oidp, __unused void *arg1,
    __unused int arg2, struct sysctl_req *req)
{
        char *p;
        int error, oid[CTL_MAXNAME] = {};
        size_t len = 0;          /* set by name2oid() */

        if (req->newlen < 1) {
                return ENOENT;
        }
        if (req->newlen >= MAXPATHLEN) { /* XXX arbitrary, undocumented */
                return ENAMETOOLONG;
        }

        p = kheap_alloc(KHEAP_TEMP, req->newlen + 1, Z_WAITOK);
        if (!p) {
                return ENOMEM;
        }

        error = SYSCTL_IN(req, p, req->newlen);
        if (error) {
                kheap_free(KHEAP_TEMP, p, req->newlen + 1);
                return error;
        }

        p[req->newlen] = '\0';

        /*
         * Note:        We acquire and release the geometry lock here to
         *              avoid making name2oid needlessly complex.
         */
        lck_rw_lock_shared(&sysctl_geometry_lock);
        error = name2oid(p, oid, &len);
        lck_rw_done(&sysctl_geometry_lock);

        kheap_free(KHEAP_TEMP, p, req->newlen + 1);

        if (error) {
                return error;
        }

        error = SYSCTL_OUT(req, oid, len * sizeof *oid);
        return error;
}

SYSCTL_PROC(_sysctl, 3, name2oid, CTLFLAG_RW | CTLFLAG_ANYBODY | CTLFLAG_KERN | CTLFLAG_LOCKED, 0, 0,
    sysctl_sysctl_name2oid, "I", "");

/*
 * sysctl_sysctl_oidfmt
 *
 * Description: For a given OID name, determine the format of the data which
 *              is associated with it.  This is used by the "sysctl" command
 *              line command.
 *
 * OID:         0, 4
 *
 * Parameters:  oidp                            __unused
 *              arg1                            The OID name to look up
 *              arg2                            The length of the OID name
 *              req                             Pointer to user request buffer
 *
 * Returns:     0                               Success
 *              EISDIR                          Malformed request
 *              ENOENT                          No such OID name
 *      SYSCTL_OUT:EPERM                        Permission denied
 *      SYSCTL_OUT:EFAULT                       Bad user supplied buffer
 *      SYSCTL_OUT:???                          Return value from user function
 *
 * Implict:     Contents of user request buffer, modified
 *
 * Locks:       Acquires and then releases a read lock on the
 *              sysctl_geometry_lock
 *
 * Notes:       SPI (System Programming Interface); this is subject to change
 *              and may not be relied upon by third party applications; use
 *              a subprocess to communicate with the "sysctl" command line
 *              command instead, if you believe you need this functionality.
 *
 *              This function differs from other sysctl functions in that
 *              it can not take an output buffer length of 0 to determine the
 *              space which will be required.  It is suggested that the buffer
 *              length be PATH_MAX, and that authors of new sysctl's refrain
 *              from exceeding this string length.
 */
STATIC int
sysctl_sysctl_oidfmt(__unused struct sysctl_oid *oidp, void *arg1, int arg2,
    struct sysctl_req *req)
{
        int *name = (int *) arg1;
        int error = ENOENT;             /* default error: not found */
        u_int namelen = arg2;
        u_int indx;
        struct sysctl_oid_iterator it;
        struct sysctl_oid *oid;

        lck_rw_lock_shared(&sysctl_geometry_lock);

        it = sysctl_oid_iterator_begin(&sysctl__children);
        oid = sysctl_oid_iterator_next_system_order(&it);

        indx = 0;
        while (oid && indx < CTL_MAXNAME) {
                if (oid->oid_number == name[indx]) {
                        indx++;
                        if ((oid->oid_kind & CTLTYPE) == CTLTYPE_NODE) {
                                if (oid->oid_handler) {
                                        goto found;
                                }
                                if (indx == namelen) {
                                        goto found;
                                }
                                it = sysctl_oid_iterator_begin(oid->oid_arg1);
                                oid = sysctl_oid_iterator_next_system_order(&it);
                        } else {
                                if (indx != namelen) {
                                        error =  EISDIR;
                                        goto err;
                                }
                                goto found;
                        }
                } else {
                        oid = sysctl_oid_iterator_next_system_order(&it);
                }
        }
        /* Not found */
        goto err;

found:
        if (!oid->oid_fmt) {
                goto err;
        }
        error = SYSCTL_OUT(req,
            &oid->oid_kind, sizeof(oid->oid_kind));
        if (!error) {
                error = SYSCTL_OUT(req, oid->oid_fmt,
                    strlen(oid->oid_fmt) + 1);
        }
err:
        lck_rw_done(&sysctl_geometry_lock);
        return error;
}

SYSCTL_NODE(_sysctl, 4, oidfmt, CTLFLAG_RD | CTLFLAG_LOCKED, sysctl_sysctl_oidfmt, "");


/*
 * Default "handler" functions.
 */

/*
 * Handle an int, signed or unsigned.
 * Two cases:
 *     a variable:  point arg1 at it.
 *     a constant:  pass it in arg2.
 */

int
sysctl_handle_int(__unused struct sysctl_oid *oidp, void *arg1, int arg2,
    struct sysctl_req *req)
{
        return sysctl_io_number(req, arg1? *(int*)arg1: arg2, sizeof(int), arg1, NULL);
}

/*
 * Handle a long, signed or unsigned.  arg1 points to it.
 */

int
sysctl_handle_long(__unused struct sysctl_oid *oidp, void *arg1,
    __unused int arg2, struct sysctl_req *req)
{
        if (!arg1) {
                return EINVAL;
        }
        return sysctl_io_number(req, *(long*)arg1, sizeof(long), arg1, NULL);
}

/*
 * Handle a quad, signed or unsigned.  arg1 points to it.
 */

int
sysctl_handle_quad(__unused struct sysctl_oid *oidp, void *arg1,
    __unused int arg2, struct sysctl_req *req)
{
        if (!arg1) {
                return EINVAL;
        }
        return sysctl_io_number(req, *(long long*)arg1, sizeof(long long), arg1, NULL);
}

/*
 * Expose an int value as a quad.
 *
 * This interface allows us to support interfaces defined
 * as using quad values while the implementation is still
 * using ints.
 */
int
sysctl_handle_int2quad(__unused struct sysctl_oid *oidp, void *arg1,
    __unused int arg2, struct sysctl_req *req)
{
        int error = 0;
        long long val;
        int newval;

        if (!arg1) {
                return EINVAL;
        }
        val = (long long)*(int *)arg1;
        error = SYSCTL_OUT(req, &val, sizeof(long long));

        if (error || !req->newptr) {
                return error;
        }

        error = SYSCTL_IN(req, &val, sizeof(long long));
        if (!error) {
                /*
                 * Value must be representable; check by
                 * casting and then casting back.
                 */
                newval = (int)val;
                if ((long long)newval != val) {
                        error = ERANGE;
                } else {
                        *(int *)arg1 = newval;
                }
        }
        return error;
}

/*
 * Handle our generic '\0' terminated 'C' string.
 * Two cases:
 *      a variable string:  point arg1 at it, arg2 is max length.
 *      a constant string:  point arg1 at it, arg2 is zero.
 */

int
sysctl_handle_string( __unused struct sysctl_oid *oidp, void *arg1, int arg2,
    struct sysctl_req *req)
{
        return sysctl_io_string(req, arg1, arg2, 0, NULL);
}

/*
 * Handle any kind of opaque data.
 * arg1 points to it, arg2 is the size.
 */

int
sysctl_handle_opaque(__unused struct sysctl_oid *oidp, void *arg1, int arg2,
    struct sysctl_req *req)
{
        return sysctl_io_opaque(req, arg1, arg2, NULL);
}

/*
 * Transfer functions to/from kernel space.
 */
STATIC int
sysctl_old_kernel(struct sysctl_req *req, const void *p, size_t l)
{
        size_t i = 0;

        if (req->oldptr) {
                i = l;
                if (i > req->oldlen - req->oldidx) {
                        i = req->oldlen - req->oldidx;
                }
                if (i > 0) {
                        bcopy((const void*)p, CAST_DOWN(char *, (req->oldptr + req->oldidx)), i);
                }
        }
        req->oldidx += l;
        if (req->oldptr && i != l) {
                return ENOMEM;
        }
        return 0;
}

STATIC int
sysctl_new_kernel(struct sysctl_req *req, void *p, size_t l)
{
        if (!req->newptr) {
                return 0;
        }
        if (req->newlen - req->newidx < l) {
                return EINVAL;
        }
        bcopy(CAST_DOWN(char *, (req->newptr + req->newidx)), p, l);
        req->newidx += l;
        return 0;
}

int
kernel_sysctl(struct proc *p, int *name, size_t namelen, void *old, size_t *oldlenp, void *new, size_t newlen)
{
        int error = 0;
        struct sysctl_req req;

        /*
         * Construct request.
         */
        bzero(&req, sizeof req);
        req.p = p;
        if (oldlenp) {
                req.oldlen = *oldlenp;
        }
        if (old) {
                req.oldptr = CAST_USER_ADDR_T(old);
        }
        if (newlen) {
                req.newlen = newlen;
                req.newptr = CAST_USER_ADDR_T(new);
        }
        req.oldfunc = sysctl_old_kernel;
        req.newfunc = sysctl_new_kernel;
        req.lock = 1;

        /* make the request */
        error = sysctl_root(TRUE, FALSE, NULL, 0, name, namelen, &req);

        if (error && error != ENOMEM) {
                return error;
        }

        if (oldlenp) {
                *oldlenp = req.oldidx;
        }

        return error;
}

/*
 * Transfer function to/from user space.
 */
STATIC int
sysctl_old_user(struct sysctl_req *req, const void *p, size_t l)
{
        int error = 0;
        size_t i = 0;

        if (req->oldptr) {
                if (req->oldlen - req->oldidx < l) {
                        return ENOMEM;
                }
                i = l;
                if (i > req->oldlen - req->oldidx) {
                        i = req->oldlen - req->oldidx;
                }
                if (i > 0) {
                        error = copyout((const void*)p, (req->oldptr + req->oldidx), i);
                }
        }
        req->oldidx += l;
        if (error) {
                return error;
        }
        if (req->oldptr && i < l) {
                return ENOMEM;
        }
        return 0;
}

STATIC int
sysctl_new_user(struct sysctl_req *req, void *p, size_t l)
{
        int error;

        if (!req->newptr) {
                return 0;
        }
        if (req->newlen - req->newidx < l) {
                return EINVAL;
        }
        error = copyin((req->newptr + req->newidx), p, l);
        req->newidx += l;
        return error;
}

#define WRITE_EXPERIMENT_FACTORS_ENTITLEMENT "com.apple.private.write-kr-experiment-factors"
/*
 * Is the current task allowed to write to experiment factors?
 * tasks with the WRITE_EXPERIMENT_FACTORS_ENTITLEMENT are always allowed to write these.
 * In the development / debug kernel we also allow root to write them.
 */
STATIC bool
can_write_experiment_factors(__unused struct sysctl_req *req)
{
        if (IOTaskHasEntitlement(current_task(), WRITE_EXPERIMENT_FACTORS_ENTITLEMENT)) {
                return true;
        }
#if DEBUG || DEVELOPMENT
        return !proc_suser(req->p);
#else
        return false;
#endif /* DEBUG || DEVELOPMENT */
}

/*
 * Traverse our tree, and find the right node, execute whatever it points
 * at, and return the resulting error code.
 */

int
sysctl_root(boolean_t from_kernel, boolean_t string_is_canonical,
    char *namestring, size_t namestringlen,
    int *name, size_t namelen, struct sysctl_req *req)
{
        u_int indx;
        int i;
        struct sysctl_oid_iterator it;
        struct sysctl_oid *oid;
        sysctl_handler_t oid_handler = NULL;
        int error;
        boolean_t unlocked_node_found = FALSE;
        boolean_t namestring_started = FALSE;

        /* Get the read lock on the geometry */
        lck_rw_lock_shared(&sysctl_geometry_lock);

        if (string_is_canonical) {
                /* namestring is actually canonical, name/namelen needs to be populated */
                error = name2oid(namestring, name, &namelen);
                if (error) {
                        goto err;
                }
        }

        it = sysctl_oid_iterator_begin(&sysctl__children);
        oid = sysctl_oid_iterator_next_system_order(&it);

        indx = 0;
        while (oid && indx < CTL_MAXNAME) {
                if (oid->oid_number == name[indx]) {
                        if (!from_kernel && !string_is_canonical) {
                                if (namestring_started) {
                                        if (strlcat(namestring, ".", namestringlen) >= namestringlen) {
                                                error = ENAMETOOLONG;
                                                goto err;
                                        }
                                }

                                if (strlcat(namestring, oid->oid_name, namestringlen) >= namestringlen) {
                                        error = ENAMETOOLONG;
                                        goto err;
                                }
                                namestring_started = TRUE;
                        }

                        indx++;
                        if (!(oid->oid_kind & CTLFLAG_LOCKED)) {
                                unlocked_node_found = TRUE;
                        }
                        if (oid->oid_kind & CTLFLAG_NOLOCK) {
                                req->lock = 0;
                        }
                        /*
                         * For SYSCTL_PROC() functions which are for sysctl's
                         * which have parameters at the end of their OID
                         * space, you need to OR CTLTYPE_NODE into their
                         * access value.
                         *
                         * NOTE: For binary backward compatibility ONLY! Do
                         * NOT add new sysctl's that do this!  Existing
                         * sysctl's which do this will eventually have
                         * compatibility code in user space, and this method
                         * will become unsupported.
                         */
                        if ((oid->oid_kind & CTLTYPE) == CTLTYPE_NODE) {
                                if (oid->oid_handler) {
                                        goto found;
                                }
                                if (indx == namelen) {
                                        error = ENOENT;
                                        goto err;
                                }

                                it = sysctl_oid_iterator_begin(oid->oid_arg1);
                                oid = sysctl_oid_iterator_next_system_order(&it);
                        } else {
                                if (indx != namelen) {
                                        error = EISDIR;
                                        goto err;
                                }
                                goto found;
                        }
                } else {
                        oid = sysctl_oid_iterator_next_system_order(&it);
                }
        }
        error = ENOENT;
        goto err;
found:

        /*
         * indx is the index of the first remaining OID name,
         * for sysctls that take them as arguments
         */
        if (!from_kernel && !string_is_canonical && (indx < namelen)) {
                char tempbuf[10];
                u_int indx2;

                for (indx2 = indx; indx2 < namelen; indx2++) {
                        snprintf(tempbuf, sizeof(tempbuf), "%d", name[indx2]);

                        if (namestring_started) {
                                if (strlcat(namestring, ".", namestringlen) >= namestringlen) {
                                        error = ENAMETOOLONG;
                                        goto err;
                                }
                        }

                        if (strlcat(namestring, tempbuf, namestringlen) >= namestringlen) {
                                error = ENAMETOOLONG;
                                goto err;
                        }
                        namestring_started = TRUE;
                }
        }

        /* If writing isn't allowed */
        if (req->newptr && (!(oid->oid_kind & CTLFLAG_WR) ||
            ((oid->oid_kind & CTLFLAG_SECURE) && securelevel > 0))) {
                error = (EPERM);
                goto err;
        }

        /*
         * If we're inside the kernel, the OID must be marked as kernel-valid.
         */
        if (from_kernel && !(oid->oid_kind & CTLFLAG_KERN)) {
                error = (EPERM);
                goto err;
        }

        if (req->newptr && req->p) {
                if (oid->oid_kind & CTLFLAG_EXPERIMENT) {
                        /*
                         * Experiment factors have different permissions since they need to be
                         * writable by procs with WRITE_EXPERIMENT_FACTORS_ENTITLEMENT.
                         */
                        if (!can_write_experiment_factors(req)) {
                                error = (EPERM);
                                goto err;
                        }
                } else {
                        /*
                         * This is where legacy enforcement of permissions occurs.  If the
                         * flag does not say CTLFLAG_ANYBODY, then we prohibit anyone but
                         * root from writing new values down.  If local enforcement happens
                         * at the leaf node, then it needs to be set as CTLFLAG_ANYBODY.  In
                         * addition, if the leaf node is set this way, then in order to do
                         * specific enforcement, it has to be of type SYSCTL_PROC.
                         */
                        if (!(oid->oid_kind & CTLFLAG_ANYBODY) &&
                            (error = proc_suser(req->p))) {
                                goto err;
                        }
                }
        }

        /*
         * sysctl_unregister_oid() may change the handler value, so grab it
         * under the lock.
         */
        oid_handler = oid->oid_handler;
        if (!oid_handler) {
                error = EINVAL;
                goto err;
        }

        /*
         * Reference the OID and drop the geometry lock; this prevents the
         * OID from being deleted out from under the handler call, but does
         * not prevent other calls into handlers or calls to manage the
         * geometry elsewhere from blocking...
         */
        if ((oid->oid_kind & CTLFLAG_PERMANENT) == 0) {
                OSAddAtomic(1, &oid->oid_refcnt);
        }

        lck_rw_done(&sysctl_geometry_lock);

#if CONFIG_MACF
        if (!from_kernel) {
                error = mac_system_check_sysctlbyname(kauth_cred_get(),
                    namestring,
                    name,
                    namelen,
                    req->oldptr,
                    req->oldlen,
                    req->newptr,
                    req->newlen);
                if (error) {
                        goto dropref;
                }
        }
#endif

        /*
         * ...however, we still have to grab the mutex for those calls which
         * may be into code whose reentrancy is protected by it.
         */
        if (unlocked_node_found) {
                lck_mtx_lock(&sysctl_unlocked_node_lock);
        }

#if defined(HAS_APPLE_PAC)
        /*
         * oid_handler is signed address-discriminated by sysctl_register_oid().
         */
        oid_handler = ptrauth_auth_and_resign(oid_handler,
            ptrauth_key_function_pointer,
            ptrauth_blend_discriminator(&oid->oid_handler,
            os_hash_kernel_pointer(oid->oid_arg1)),
            ptrauth_key_function_pointer,
            ptrauth_function_pointer_type_discriminator(typeof(oid_handler)));
#endif /* defined(HAS_APPLE_PAC) */

        if ((oid->oid_kind & CTLTYPE) == CTLTYPE_NODE) {
                i = oid_handler(oid, name + indx, (int)(namelen - indx), req);
        } else {
                i = oid_handler(oid, oid->oid_arg1, oid->oid_arg2, req);
        }
        error = i;

        if (unlocked_node_found) {
                lck_mtx_unlock(&sysctl_unlocked_node_lock);
        }

#if CONFIG_MACF
        /* only used from another CONFIG_MACF block */
dropref:
#endif

        /*
         * This is tricky... we re-grab the geometry lock in order to drop
         * the reference and wake on the address; since the geometry
         * lock is a reader/writer lock rather than a mutex, we have to
         * wake on all apparent 1->0 transitions.  This abuses the drop
         * after the reference decrement in order to wake any lck_rw_sleep()
         * in progress in sysctl_unregister_oid() that slept because of a
         * non-zero reference count.
         *
         * Note:        OSAddAtomic() is defined to return the previous value;
         *              we use this and the fact that the lock itself is a
         *              barrier to avoid waking every time through on "hot"
         *              OIDs.
         */
        lck_rw_lock_shared(&sysctl_geometry_lock);

        if ((oid->oid_kind & CTLFLAG_PERMANENT) == 0) {
                if (OSAddAtomic(-1, &oid->oid_refcnt) == 1) {
                        wakeup(&oid->oid_refcnt);
                }
        }

err:
        lck_rw_done(&sysctl_geometry_lock);
        return error;
}

void
sysctl_create_user_req(struct sysctl_req *req, struct proc *p, user_addr_t oldp,
    size_t oldlen, user_addr_t newp, size_t newlen)
{
        bzero(req, sizeof(*req));

        req->p = p;

        req->oldlen = oldlen;
        req->oldptr = oldp;

        if (newlen) {
                req->newlen = newlen;
                req->newptr = newp;
        }

        req->oldfunc = sysctl_old_user;
        req->newfunc = sysctl_new_user;
        req->lock = 1;

        return;
}

int
sysctl(proc_t p, struct sysctl_args *uap, __unused int32_t *retval)
{
        int error, new_error;
        size_t oldlen = 0, newlen;
        int name[CTL_MAXNAME];
        struct sysctl_req req;
        char *namestring;
        size_t namestringlen = MAXPATHLEN;

        /*
         * all top-level sysctl names are non-terminal
         */
        if (uap->namelen > CTL_MAXNAME || uap->namelen < 2) {
                return EINVAL;
        }
        error = copyin(uap->name, &name[0], uap->namelen * sizeof(int));
        if (error) {
                return error;
        }

        AUDIT_ARG(ctlname, name, uap->namelen);

        if (uap->newlen > SIZE_T_MAX) {
                return EINVAL;
        }
        newlen = (size_t)uap->newlen;

        if (uap->oldlenp != USER_ADDR_NULL) {
                uint64_t        oldlen64 = fuulong(uap->oldlenp);

                /*
                 * If more than 4G, clamp to 4G
                 */
                if (oldlen64 > SIZE_T_MAX) {
                        oldlen = SIZE_T_MAX;
                } else {
                        oldlen = (size_t)oldlen64;
                }
        }

        sysctl_create_user_req(&req, p, uap->old, oldlen, uap->new, newlen);

        /* Guess that longest length for the passed-in MIB, if we can be more aggressive than MAXPATHLEN */
        if (uap->namelen == 2) {
                if (name[0] == CTL_KERN && name[1] < KERN_MAXID) {
                        namestringlen = 32; /* "kern.speculative_reads_disabled" */
                } else if (name[0] == CTL_HW && name[1] < HW_MAXID) {
                        namestringlen = 32; /* "hw.cachelinesize_compat" */
                }
        }

        namestring = kheap_alloc(KHEAP_TEMP, namestringlen, Z_WAITOK);
        if (!namestring) {
                oldlen = 0;
                goto err;
        }

        error = userland_sysctl(FALSE, namestring, namestringlen, name, uap->namelen, &req, &oldlen);

        kheap_free(KHEAP_TEMP, namestring, namestringlen);

        if ((error) && (error != ENOMEM)) {
                return error;
        }

err:
        if (uap->oldlenp != USER_ADDR_NULL) {
                /*
                 * Only overwrite the old error value on a new error
                 */
                new_error = suulong(uap->oldlenp, oldlen);

                if (new_error) {
                        error = new_error;
                }
        }

        return error;
}

// sysctlbyname is also exported as KPI to kexts
// and the syscall name cannot conflict with it
int
sys_sysctlbyname(proc_t p, struct sysctlbyname_args *uap, __unused int32_t *retval)
{
        int error, new_error;
        size_t oldlen = 0, newlen;
        char *name;
        size_t namelen = 0;
        struct sysctl_req req;
        int oid[CTL_MAXNAME];

        if (uap->namelen >= MAXPATHLEN) { /* XXX arbitrary, undocumented */
                return ENAMETOOLONG;
        }
        namelen = (size_t)uap->namelen;

        name = kheap_alloc(KHEAP_TEMP, namelen + 1, Z_WAITOK);
        if (!name) {
                return ENOMEM;
        }

        error = copyin(uap->name, name, namelen);
        if (error) {
                kheap_free(KHEAP_TEMP, name, namelen + 1);
                return error;
        }
        name[namelen] = '\0';

        /* XXX
         * AUDIT_ARG(ctlname, name, uap->namelen);
         */

        if (uap->newlen > SIZE_T_MAX) {
                kheap_free(KHEAP_TEMP, name, namelen + 1);
                return EINVAL;
        }
        newlen = (size_t)uap->newlen;

        if (uap->oldlenp != USER_ADDR_NULL) {
                uint64_t        oldlen64 = fuulong(uap->oldlenp);

                /*
                 * If more than 4G, clamp to 4G
                 */
                if (oldlen64 > SIZE_T_MAX) {
                        oldlen = SIZE_T_MAX;
                } else {
                        oldlen = (size_t)oldlen64;
                }
        }

        sysctl_create_user_req(&req, p, uap->old, oldlen, uap->new, newlen);

        error = userland_sysctl(TRUE, name, namelen + 1, oid, CTL_MAXNAME, &req, &oldlen);

        kheap_free(KHEAP_TEMP, name, namelen + 1);

        if ((error) && (error != ENOMEM)) {
                return error;
        }

        if (uap->oldlenp != USER_ADDR_NULL) {
                /*
                 * Only overwrite the old error value on a new error
                 */
                new_error = suulong(uap->oldlenp, oldlen);

                if (new_error) {
                        error = new_error;
                }
        }

        return error;
}

/*
 * This is used from various compatibility syscalls too.  That's why name
 * must be in kernel space.
 */
int
userland_sysctl(boolean_t string_is_canonical,
    char *namestring, size_t namestringlen,
    int *name, u_int namelen, struct sysctl_req *req,
    size_t *retval)
{
        int error = 0;
        struct sysctl_req req2;

        do {
                /* if EAGAIN, reset output cursor */
                req2 = *req;
                if (!string_is_canonical) {
                        namestring[0] = '\0';
                }

                error = sysctl_root(FALSE, string_is_canonical, namestring, namestringlen, name, namelen, &req2);
        } while (error == EAGAIN);

        if (error && error != ENOMEM) {
                return error;
        }

        if (retval) {
                if (req2.oldptr && req2.oldidx > req2.oldlen) {
                        *retval = req2.oldlen;
                } else {
                        *retval = req2.oldidx;
                }
        }
        return error;
}

/*
 * Kernel versions of the userland sysctl helper functions.
 *
 * These allow sysctl to be used in the same fashion in both
 * userland and the kernel.
 *
 * Note that some sysctl handlers use copyin/copyout, which
 * may not work correctly.
 *
 * The "sysctlbyname" KPI for use by kexts is aliased to this function.
 */

int
kernel_sysctlbyname(const char *name, void *oldp, size_t *oldlenp, void *newp, size_t newlen)
{
        int oid[CTL_MAXNAME];
        int name2mib_oid[2];
        int error;
        size_t oidlen;

        /* look up the OID with magic service node */
        name2mib_oid[0] = 0;
        name2mib_oid[1] = 3;

        oidlen = sizeof(oid);
        error = kernel_sysctl(current_proc(), name2mib_oid, 2, oid, &oidlen, __DECONST(void *, name), strlen(name));
        oidlen /= sizeof(int);
        if (oidlen > UINT_MAX) {
                error = EDOM;
        }

        /* now use the OID */
        if (error == 0) {
                error = kernel_sysctl(current_proc(), oid, (u_int)oidlen, oldp, oldlenp, newp, newlen);
        }
        return error;
}

int
scalable_counter_sysctl_handler SYSCTL_HANDLER_ARGS
{
#pragma unused(arg2, oidp)
        scalable_counter_t counter = *(scalable_counter_t*) arg1;
        uint64_t value = counter_load(&counter);
        return SYSCTL_OUT(req, &value, sizeof(value));
}

#define X(name, T) \
int \
experiment_factor_##name##_handler SYSCTL_HANDLER_ARGS \
{ \
        int error, changed = 0; \
        T *ptr; \
        T new_value, current_value; \
        struct experiment_spec *spec = (struct experiment_spec *) arg1; \
        if (!arg1) { \
                return EINVAL; \
        } \
        ptr = (T *)(spec->ptr); \
        current_value = *ptr; \
        error = sysctl_io_number(req, current_value, sizeof(T), &new_value, &changed); \
        if (error != 0) { \
                return error; \
        } \
        if (changed) { \
                if (new_value < (T) spec->min_value || new_value > (T) spec->max_value) { \
                        return EINVAL; \
                } \
                if (os_atomic_cmpxchg(&spec->modified, false, true, acq_rel)) { \
                        spec->original_value = current_value; \
                } \
                os_atomic_store_wide(ptr, new_value, relaxed); \
        } \
        return 0; \
}

experiment_factor_numeric_types
#undef X