FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_sysctl.c

     /*-
      * SPDX-License-Identifier: BSD-3-Clause
      *
      * 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. 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 <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include "opt_capsicum.h"
    #include "opt_ddb.h"
    #include "opt_ktrace.h"
    #include "opt_sysctl.h"
    
    #include <sys/param.h>
    #include <sys/fail.h>
    #include <sys/systm.h>
    #include <sys/capsicum.h>
    #include <sys/kernel.h>
    #include <sys/limits.h>
    #include <sys/sysctl.h>
    #include <sys/malloc.h>
    #include <sys/priv.h>
    #include <sys/proc.h>
    #include <sys/jail.h>
    #include <sys/kdb.h>
    #include <sys/lock.h>
    #include <sys/mutex.h>
    #include <sys/rmlock.h>
    #include <sys/sbuf.h>
    #include <sys/sx.h>
    #include <sys/sysproto.h>
    #include <sys/uio.h>
    #ifdef KTRACE
    #include <sys/ktrace.h>
    #endif
    
    #ifdef DDB
    #include <ddb/ddb.h>
    #include <ddb/db_lex.h>
    #endif
    
    #include <net/vnet.h>
    
    #include <security/mac/mac_framework.h>
    
    #include <vm/vm.h>
    #include <vm/vm_extern.h>
    
    static MALLOC_DEFINE(M_SYSCTL, "sysctl", "sysctl internal magic");
    static MALLOC_DEFINE(M_SYSCTLOID, "sysctloid", "sysctl dynamic oids");
    static MALLOC_DEFINE(M_SYSCTLTMP, "sysctltmp", "sysctl temp output buffer");
    
    /*
     * The sysctllock protects the MIB tree.  It also protects sysctl
     * contexts used with dynamic sysctls.  The sysctl_register_oid() and
     * sysctl_unregister_oid() routines require the sysctllock to already
     * be held, so the sysctl_wlock() and sysctl_wunlock() routines are
     * provided for the few places in the kernel which need to use that
     * API rather than using the dynamic API.  Use of the dynamic API is
     * strongly encouraged for most code.
     *
     * The sysctlmemlock is used to limit the amount of user memory wired for
     * sysctl requests.  This is implemented by serializing any userland
     * sysctl requests larger than a single page via an exclusive lock.
     *
    * The sysctlstringlock is used to protect concurrent access to writable
    * string nodes in sysctl_handle_string().
    */
   static struct rmlock sysctllock;
   static struct sx __exclusive_cache_line sysctlmemlock;
   static struct sx sysctlstringlock;
   
   #define SYSCTL_WLOCK()          rm_wlock(&sysctllock)
   #define SYSCTL_WUNLOCK()        rm_wunlock(&sysctllock)
   #define SYSCTL_RLOCK(tracker)   rm_rlock(&sysctllock, (tracker))
   #define SYSCTL_RUNLOCK(tracker) rm_runlock(&sysctllock, (tracker))
   #define SYSCTL_WLOCKED()        rm_wowned(&sysctllock)
   #define SYSCTL_ASSERT_LOCKED()  rm_assert(&sysctllock, RA_LOCKED)
   #define SYSCTL_ASSERT_WLOCKED() rm_assert(&sysctllock, RA_WLOCKED)
   #define SYSCTL_ASSERT_RLOCKED() rm_assert(&sysctllock, RA_RLOCKED)
   #define SYSCTL_INIT()           rm_init_flags(&sysctllock, "sysctl lock", \
                                       RM_SLEEPABLE)
   #define SYSCTL_SLEEP(ch, wmesg, timo)                                   \
                                   rm_sleep(ch, &sysctllock, 0, wmesg, timo)
   
   static int sysctl_root(SYSCTL_HANDLER_ARGS);
   
   /* Root list */
   struct sysctl_oid_list sysctl__children = SLIST_HEAD_INITIALIZER(&sysctl__children);
   
   static char*    sysctl_escape_name(const char*);
   static int      sysctl_remove_oid_locked(struct sysctl_oid *oidp, int del,
                       int recurse);
   static int      sysctl_old_kernel(struct sysctl_req *, const void *, size_t);
   static int      sysctl_new_kernel(struct sysctl_req *, void *, size_t);
   
   static struct sysctl_oid *
   sysctl_find_oidname(const char *name, struct sysctl_oid_list *list)
   {
           struct sysctl_oid *oidp;
   
           SYSCTL_ASSERT_LOCKED();
           SYSCTL_FOREACH(oidp, list) {
                   if (strcmp(oidp->oid_name, name) == 0) {
                           return (oidp);
                   }
           }
           return (NULL);
   }
   
   /*
    * Initialization of the MIB tree.
    *
    * Order by number in each list.
    */
   void
   sysctl_wlock(void)
   {
   
           SYSCTL_WLOCK();
   }
   
   void
   sysctl_wunlock(void)
   {
   
           SYSCTL_WUNLOCK();
   }
   
   static int
   sysctl_root_handler_locked(struct sysctl_oid *oid, void *arg1, intmax_t arg2,
       struct sysctl_req *req, struct rm_priotracker *tracker)
   {
           int error;
   
           if (oid->oid_kind & CTLFLAG_DYN)
                   atomic_add_int(&oid->oid_running, 1);
   
           if (tracker != NULL)
                   SYSCTL_RUNLOCK(tracker);
           else
                   SYSCTL_WUNLOCK();
   
           /*
            * Treat set CTLFLAG_NEEDGIANT and unset CTLFLAG_MPSAFE flags the same,
            * untill we're ready to remove all traces of Giant from sysctl(9).
            */
           if ((oid->oid_kind & CTLFLAG_NEEDGIANT) ||
               (!(oid->oid_kind & CTLFLAG_MPSAFE)))
                   mtx_lock(&Giant);
           error = oid->oid_handler(oid, arg1, arg2, req);
           if ((oid->oid_kind & CTLFLAG_NEEDGIANT) ||
               (!(oid->oid_kind & CTLFLAG_MPSAFE)))
                   mtx_unlock(&Giant);
   
           KFAIL_POINT_ERROR(_debug_fail_point, sysctl_running, error);
   
           if (tracker != NULL)
                   SYSCTL_RLOCK(tracker);
           else
                   SYSCTL_WLOCK();
   
           if (oid->oid_kind & CTLFLAG_DYN) {
                   if (atomic_fetchadd_int(&oid->oid_running, -1) == 1 &&
                       (oid->oid_kind & CTLFLAG_DYING) != 0)
                           wakeup(&oid->oid_running);
           }
   
           return (error);
   }
   
   static void
   sysctl_load_tunable_by_oid_locked(struct sysctl_oid *oidp)
   {
           struct sysctl_req req;
           struct sysctl_oid *curr;
           char *penv = NULL;
           char path[96];
           ssize_t rem = sizeof(path);
           ssize_t len;
           uint8_t data[512] __aligned(sizeof(uint64_t));
           int size;
           int error;
   
           path[--rem] = 0;
   
           for (curr = oidp; curr != NULL; curr = SYSCTL_PARENT(curr)) {
                   len = strlen(curr->oid_name);
                   rem -= len;
                   if (curr != oidp)
                           rem -= 1;
                   if (rem < 0) {
                           printf("OID path exceeds %d bytes\n", (int)sizeof(path));
                           return;
                   }
                   memcpy(path + rem, curr->oid_name, len);
                   if (curr != oidp)
                           path[rem + len] = '.';
           }
   
           memset(&req, 0, sizeof(req));
   
           req.td = curthread;
           req.oldfunc = sysctl_old_kernel;
           req.newfunc = sysctl_new_kernel;
           req.lock = REQ_UNWIRED;
   
           switch (oidp->oid_kind & CTLTYPE) {
           case CTLTYPE_INT:
                   if (getenv_array(path + rem, data, sizeof(data), &size,
                       sizeof(int), GETENV_SIGNED) == 0)
                           return;
                   req.newlen = size;
                   req.newptr = data;
                   break;
           case CTLTYPE_UINT:
                   if (getenv_array(path + rem, data, sizeof(data), &size,
                       sizeof(int), GETENV_UNSIGNED) == 0)
                           return;
                   req.newlen = size;
                   req.newptr = data;
                   break;
           case CTLTYPE_LONG:
                   if (getenv_array(path + rem, data, sizeof(data), &size,
                       sizeof(long), GETENV_SIGNED) == 0)
                           return;
                   req.newlen = size;
                   req.newptr = data;
                   break;
           case CTLTYPE_ULONG:
                   if (getenv_array(path + rem, data, sizeof(data), &size,
                       sizeof(long), GETENV_UNSIGNED) == 0)
                           return;
                   req.newlen = size;
                   req.newptr = data;
                   break;
           case CTLTYPE_S8:
                   if (getenv_array(path + rem, data, sizeof(data), &size,
                       sizeof(int8_t), GETENV_SIGNED) == 0)
                           return;
                   req.newlen = size;
                   req.newptr = data;
                   break;
           case CTLTYPE_S16:
                   if (getenv_array(path + rem, data, sizeof(data), &size,
                       sizeof(int16_t), GETENV_SIGNED) == 0)
                           return;
                   req.newlen = size;
                   req.newptr = data;
                   break;
           case CTLTYPE_S32:
                   if (getenv_array(path + rem, data, sizeof(data), &size,
                       sizeof(int32_t), GETENV_SIGNED) == 0)
                           return;
                   req.newlen = size;
                   req.newptr = data;
                   break;
           case CTLTYPE_S64:
                   if (getenv_array(path + rem, data, sizeof(data), &size,
                       sizeof(int64_t), GETENV_SIGNED) == 0)
                           return;
                   req.newlen = size;
                   req.newptr = data;
                   break;
           case CTLTYPE_U8:
                   if (getenv_array(path + rem, data, sizeof(data), &size,
                       sizeof(uint8_t), GETENV_UNSIGNED) == 0)
                           return;
                   req.newlen = size;
                   req.newptr = data;
                   break;
           case CTLTYPE_U16:
                   if (getenv_array(path + rem, data, sizeof(data), &size,
                       sizeof(uint16_t), GETENV_UNSIGNED) == 0)
                           return;
                   req.newlen = size;
                   req.newptr = data;
                   break;
           case CTLTYPE_U32:
                   if (getenv_array(path + rem, data, sizeof(data), &size,
                       sizeof(uint32_t), GETENV_UNSIGNED) == 0)
                           return;
                   req.newlen = size;
                   req.newptr = data;
                   break;
           case CTLTYPE_U64:
                   if (getenv_array(path + rem, data, sizeof(data), &size,
                       sizeof(uint64_t), GETENV_UNSIGNED) == 0)
                           return;
                   req.newlen = size;
                   req.newptr = data;
                   break;
           case CTLTYPE_STRING:
                   penv = kern_getenv(path + rem);
                   if (penv == NULL)
                           return;
                   req.newlen = strlen(penv);
                   req.newptr = penv;
                   break;
           default:
                   return;
           }
           error = sysctl_root_handler_locked(oidp, oidp->oid_arg1,
               oidp->oid_arg2, &req, NULL);
           if (error != 0)
                   printf("Setting sysctl %s failed: %d\n", path + rem, error);
           if (penv != NULL)
                   freeenv(penv);
   }
   
   /*
    * Locate the path to a given oid.  Returns the length of the resulting path,
    * or -1 if the oid was not found.  nodes must have room for CTL_MAXNAME
    * elements and be NULL initialized.
    */
   static int
   sysctl_search_oid(struct sysctl_oid **nodes, struct sysctl_oid *needle)
   {
           int indx;
   
           SYSCTL_ASSERT_LOCKED();
           indx = 0;
           while (indx < CTL_MAXNAME && indx >= 0) {
                   if (nodes[indx] == NULL && indx == 0)
                           nodes[indx] = SLIST_FIRST(&sysctl__children);
                   else if (nodes[indx] == NULL)
                           nodes[indx] = SLIST_FIRST(&nodes[indx - 1]->oid_children);
                   else
                           nodes[indx] = SLIST_NEXT(nodes[indx], oid_link);
   
                   if (nodes[indx] == needle)
                           return (indx + 1);
   
                   if (nodes[indx] == NULL) {
                           indx--;
                           continue;
                   }
   
                   if ((nodes[indx]->oid_kind & CTLTYPE) == CTLTYPE_NODE) {
                           indx++;
                           continue;
                   }
           }
           return (-1);
   }
   
   static void
   sysctl_warn_reuse(const char *func, struct sysctl_oid *leaf)
   {
           struct sysctl_oid *nodes[CTL_MAXNAME];
           char buf[128];
           struct sbuf sb;
           int rc, i;
   
           (void)sbuf_new(&sb, buf, sizeof(buf), SBUF_FIXEDLEN | SBUF_INCLUDENUL);
           sbuf_set_drain(&sb, sbuf_printf_drain, NULL);
   
           sbuf_printf(&sb, "%s: can't re-use a leaf (", __func__);
   
           memset(nodes, 0, sizeof(nodes));
           rc = sysctl_search_oid(nodes, leaf);
           if (rc > 0) {
                   for (i = 0; i < rc; i++)
                           sbuf_printf(&sb, "%s%.*s", nodes[i]->oid_name,
                               i != (rc - 1), ".");
           } else {
                   sbuf_printf(&sb, "%s", leaf->oid_name);
           }
           sbuf_printf(&sb, ")!\n");
   
           (void)sbuf_finish(&sb);
   }
   
   #ifdef SYSCTL_DEBUG
   static int
   sysctl_reuse_test(SYSCTL_HANDLER_ARGS)
   {
           struct rm_priotracker tracker;
   
           SYSCTL_RLOCK(&tracker);
           sysctl_warn_reuse(__func__, oidp);
           SYSCTL_RUNLOCK(&tracker);
           return (0);
   }
   SYSCTL_PROC(_sysctl, OID_AUTO, reuse_test,
       CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE, 0, 0, sysctl_reuse_test, "-",
       "");
   #endif
   
   void
   sysctl_register_oid(struct sysctl_oid *oidp)
   {
           struct sysctl_oid_list *parent = oidp->oid_parent;
           struct sysctl_oid *p;
           struct sysctl_oid *q;
           int oid_number;
           int timeout = 2;
   
           /*
            * First check if another oid with the same name already
            * exists in the parent's list.
            */
           SYSCTL_ASSERT_WLOCKED();
           p = sysctl_find_oidname(oidp->oid_name, parent);
           if (p != NULL) {
                   if ((p->oid_kind & CTLTYPE) == CTLTYPE_NODE) {
                           p->oid_refcnt++;
                           return;
                   } else {
                           sysctl_warn_reuse(__func__, p);
                           return;
                   }
           }
           /* get current OID number */
           oid_number = oidp->oid_number;
   
   #if (OID_AUTO >= 0)
   #error "OID_AUTO is expected to be a negative value"
   #endif  
           /*
            * Any negative OID number qualifies as OID_AUTO. Valid OID
            * numbers should always be positive.
            *
            * NOTE: DO NOT change the starting value here, change it in
            * <sys/sysctl.h>, and make sure it is at least 256 to
            * accommodate e.g. net.inet.raw as a static sysctl node.
            */
           if (oid_number < 0) {
                   static int newoid;
   
                   /*
                    * By decrementing the next OID number we spend less
                    * time inserting the OIDs into a sorted list.
                    */
                   if (--newoid < CTL_AUTO_START)
                           newoid = 0x7fffffff;
   
                   oid_number = newoid;
           }
   
           /*
            * Insert the OID into the parent's list sorted by OID number.
            */
   retry:
           q = NULL;
           SLIST_FOREACH(p, parent, oid_link) {
                   /* check if the current OID number is in use */
                   if (oid_number == p->oid_number) {
                           /* get the next valid OID number */
                           if (oid_number < CTL_AUTO_START ||
                               oid_number == 0x7fffffff) {
                                   /* wraparound - restart */
                                   oid_number = CTL_AUTO_START;
                                   /* don't loop forever */
                                   if (!timeout--)
                                           panic("sysctl: Out of OID numbers\n");
                                   goto retry;
                           } else {
                                   oid_number++;
                           }
                   } else if (oid_number < p->oid_number)
                           break;
                   q = p;
           }
           /* check for non-auto OID number collision */
           if (oidp->oid_number >= 0 && oidp->oid_number < CTL_AUTO_START &&
               oid_number >= CTL_AUTO_START) {
                   printf("sysctl: OID number(%d) is already in use for '%s'\n",
                       oidp->oid_number, oidp->oid_name);
           }
           /* update the OID number, if any */
           oidp->oid_number = oid_number;
           if (q != NULL)
                   SLIST_INSERT_AFTER(q, oidp, oid_link);
           else
                   SLIST_INSERT_HEAD(parent, oidp, oid_link);
   
           if ((oidp->oid_kind & CTLTYPE) != CTLTYPE_NODE &&
   #ifdef VIMAGE
               (oidp->oid_kind & CTLFLAG_VNET) == 0 &&
   #endif
               (oidp->oid_kind & CTLFLAG_TUN) != 0 &&
               (oidp->oid_kind & CTLFLAG_NOFETCH) == 0) {
                   /* only fetch value once */
                   oidp->oid_kind |= CTLFLAG_NOFETCH;
                   /* try to fetch value from kernel environment */
                   sysctl_load_tunable_by_oid_locked(oidp);
           }
   }
   
   void
   sysctl_register_disabled_oid(struct sysctl_oid *oidp)
   {
   
           /*
            * Mark the leaf as dormant if it's not to be immediately enabled.
            * We do not disable nodes as they can be shared between modules
            * and it is always safe to access a node.
            */
           KASSERT((oidp->oid_kind & CTLFLAG_DORMANT) == 0,
               ("internal flag is set in oid_kind"));
           if ((oidp->oid_kind & CTLTYPE) != CTLTYPE_NODE)
                   oidp->oid_kind |= CTLFLAG_DORMANT;
           sysctl_register_oid(oidp);
   }
   
   void
   sysctl_enable_oid(struct sysctl_oid *oidp)
   {
   
           SYSCTL_ASSERT_WLOCKED();
           if ((oidp->oid_kind & CTLTYPE) == CTLTYPE_NODE) {
                   KASSERT((oidp->oid_kind & CTLFLAG_DORMANT) == 0,
                       ("sysctl node is marked as dormant"));
                   return;
           }
           KASSERT((oidp->oid_kind & CTLFLAG_DORMANT) != 0,
               ("enabling already enabled sysctl oid"));
           oidp->oid_kind &= ~CTLFLAG_DORMANT;
   }
   
   void
   sysctl_unregister_oid(struct sysctl_oid *oidp)
   {
           struct sysctl_oid *p;
           int error;
   
           SYSCTL_ASSERT_WLOCKED();
           if (oidp->oid_number == OID_AUTO) {
                   error = EINVAL;
           } else {
                   error = ENOENT;
                   SLIST_FOREACH(p, oidp->oid_parent, oid_link) {
                           if (p == oidp) {
                                   SLIST_REMOVE(oidp->oid_parent, oidp,
                                       sysctl_oid, oid_link);
                                   error = 0;
                                   break;
                           }
                   }
           }
   
           /* 
            * This can happen when a module fails to register and is
            * being unloaded afterwards.  It should not be a panic()
            * for normal use.
            */
           if (error) {
                   printf("%s: failed(%d) to unregister sysctl(%s)\n",
                       __func__, error, oidp->oid_name);
           }
   }
   
   /* Initialize a new context to keep track of dynamically added sysctls. */
   int
   sysctl_ctx_init(struct sysctl_ctx_list *c)
   {
   
           if (c == NULL) {
                   return (EINVAL);
           }
   
           /*
            * No locking here, the caller is responsible for not adding
            * new nodes to a context until after this function has
            * returned.
            */
           TAILQ_INIT(c);
           return (0);
   }
   
   /* Free the context, and destroy all dynamic oids registered in this context */
   int
   sysctl_ctx_free(struct sysctl_ctx_list *clist)
   {
           struct sysctl_ctx_entry *e, *e1;
           int error;
   
           error = 0;
           /*
            * First perform a "dry run" to check if it's ok to remove oids.
            * XXX FIXME
            * XXX This algorithm is a hack. But I don't know any
            * XXX better solution for now...
            */
           SYSCTL_WLOCK();
           TAILQ_FOREACH(e, clist, link) {
                   error = sysctl_remove_oid_locked(e->entry, 0, 0);
                   if (error)
                           break;
           }
           /*
            * Restore deregistered entries, either from the end,
            * or from the place where error occurred.
            * e contains the entry that was not unregistered
            */
           if (error)
                   e1 = TAILQ_PREV(e, sysctl_ctx_list, link);
           else
                   e1 = TAILQ_LAST(clist, sysctl_ctx_list);
           while (e1 != NULL) {
                   sysctl_register_oid(e1->entry);
                   e1 = TAILQ_PREV(e1, sysctl_ctx_list, link);
           }
           if (error) {
                   SYSCTL_WUNLOCK();
                   return(EBUSY);
           }
           /* Now really delete the entries */
           e = TAILQ_FIRST(clist);
           while (e != NULL) {
                   e1 = TAILQ_NEXT(e, link);
                   error = sysctl_remove_oid_locked(e->entry, 1, 0);
                   if (error)
                           panic("sysctl_remove_oid: corrupt tree, entry: %s",
                               e->entry->oid_name);
                   free(e, M_SYSCTLOID);
                   e = e1;
           }
           SYSCTL_WUNLOCK();
           return (error);
   }
   
   /* Add an entry to the context */
   struct sysctl_ctx_entry *
   sysctl_ctx_entry_add(struct sysctl_ctx_list *clist, struct sysctl_oid *oidp)
   {
           struct sysctl_ctx_entry *e;
   
           SYSCTL_ASSERT_WLOCKED();
           if (clist == NULL || oidp == NULL)
                   return(NULL);
           e = malloc(sizeof(struct sysctl_ctx_entry), M_SYSCTLOID, M_WAITOK);
           e->entry = oidp;
           TAILQ_INSERT_HEAD(clist, e, link);
           return (e);
   }
   
   /* Find an entry in the context */
   struct sysctl_ctx_entry *
   sysctl_ctx_entry_find(struct sysctl_ctx_list *clist, struct sysctl_oid *oidp)
   {
           struct sysctl_ctx_entry *e;
   
           SYSCTL_ASSERT_WLOCKED();
           if (clist == NULL || oidp == NULL)
                   return(NULL);
           TAILQ_FOREACH(e, clist, link) {
                   if(e->entry == oidp)
                           return(e);
           }
           return (e);
   }
   
   /*
    * Delete an entry from the context.
    * NOTE: this function doesn't free oidp! You have to remove it
    * with sysctl_remove_oid().
    */
   int
   sysctl_ctx_entry_del(struct sysctl_ctx_list *clist, struct sysctl_oid *oidp)
   {
           struct sysctl_ctx_entry *e;
   
           if (clist == NULL || oidp == NULL)
                   return (EINVAL);
           SYSCTL_WLOCK();
           e = sysctl_ctx_entry_find(clist, oidp);
           if (e != NULL) {
                   TAILQ_REMOVE(clist, e, link);
                   SYSCTL_WUNLOCK();
                   free(e, M_SYSCTLOID);
                   return (0);
           } else {
                   SYSCTL_WUNLOCK();
                   return (ENOENT);
           }
   }
   
   /*
    * Remove dynamically created sysctl trees.
    * oidp - top of the tree to be removed
    * del - if 0 - just deregister, otherwise free up entries as well
    * recurse - if != 0 traverse the subtree to be deleted
    */
   int
   sysctl_remove_oid(struct sysctl_oid *oidp, int del, int recurse)
   {
           int error;
   
           SYSCTL_WLOCK();
           error = sysctl_remove_oid_locked(oidp, del, recurse);
           SYSCTL_WUNLOCK();
           return (error);
   }
   
   int
   sysctl_remove_name(struct sysctl_oid *parent, const char *name,
       int del, int recurse)
   {
           struct sysctl_oid *p, *tmp;
           int error;
   
           error = ENOENT;
           SYSCTL_WLOCK();
           SLIST_FOREACH_SAFE(p, SYSCTL_CHILDREN(parent), oid_link, tmp) {
                   if (strcmp(p->oid_name, name) == 0) {
                           error = sysctl_remove_oid_locked(p, del, recurse);
                           break;
                   }
           }
           SYSCTL_WUNLOCK();
   
           return (error);
   }
   
   /*
    * Duplicate the provided string, escaping any illegal characters.  The result
    * must be freed when no longer in use.
    *
    * The list of illegal characters is ".".
    */
   static char*
   sysctl_escape_name(const char* orig)
   {
           int i, s = 0, d = 0, nillegals = 0;
           char *new;
   
           /* First count the number of illegal characters */
           for (i = 0; orig[i] != '\0'; i++) {
                   if (orig[i] == '.')
                           nillegals++;
           }
   
           /* Allocate storage for new string */
           new = malloc(i + 2 * nillegals + 1, M_SYSCTLOID, M_WAITOK);
   
           /* Copy the name, escaping characters as we go */
           while (orig[s] != '\0') {
                   if (orig[s] == '.') {
                           /* %25 is the hexadecimal representation of '.' */
                           new[d++] = '%';
                           new[d++] = '2';
                           new[d++] = '5';
                           s++;
                   } else {
                           new[d++] = orig[s++];
                   }
           }
   
           /* Finally, nul-terminate */
           new[d] = '\0';
   
           return (new);
   }
   
   static int
   sysctl_remove_oid_locked(struct sysctl_oid *oidp, int del, int recurse)
   {
           struct sysctl_oid *p, *tmp;
           int error;
   
           SYSCTL_ASSERT_WLOCKED();
           if (oidp == NULL)
                   return(EINVAL);
           if ((oidp->oid_kind & CTLFLAG_DYN) == 0) {
                   printf("Warning: can't remove non-dynamic nodes (%s)!\n",
                       oidp->oid_name);
                   return (EINVAL);
           }
           /*
            * WARNING: normal method to do this should be through
            * sysctl_ctx_free(). Use recursing as the last resort
            * method to purge your sysctl tree of leftovers...
            * However, if some other code still references these nodes,
            * it will panic.
            */
           if ((oidp->oid_kind & CTLTYPE) == CTLTYPE_NODE) {
                   if (oidp->oid_refcnt == 1) {
                           SLIST_FOREACH_SAFE(p,
                               SYSCTL_CHILDREN(oidp), oid_link, tmp) {
                                   if (!recurse) {
                                           printf("Warning: failed attempt to "
                                               "remove oid %s with child %s\n",
                                               oidp->oid_name, p->oid_name);
                                           return (ENOTEMPTY);
                                   }
                                   error = sysctl_remove_oid_locked(p, del,
                                       recurse);
                                   if (error)
                                           return (error);
                           }
                   }
           }
           if (oidp->oid_refcnt > 1 ) {
                   oidp->oid_refcnt--;
           } else {
                   if (oidp->oid_refcnt == 0) {
                           printf("Warning: bad oid_refcnt=%u (%s)!\n",
                                   oidp->oid_refcnt, oidp->oid_name);
                           return (EINVAL);
                   }
                   sysctl_unregister_oid(oidp);
                   if (del) {
                           /*
                            * Wait for all threads running the handler to drain.
                            * This preserves the previous behavior when the
                            * sysctl lock was held across a handler invocation,
                            * and is necessary for module unload correctness.
                            */
                           while (oidp->oid_running > 0) {
                                   oidp->oid_kind |= CTLFLAG_DYING;
                                   SYSCTL_SLEEP(&oidp->oid_running, "oidrm", 0);
                           }
                           if (oidp->oid_descr)
                                   free(__DECONST(char *, oidp->oid_descr),
                                       M_SYSCTLOID);
                           if (oidp->oid_label)
                                   free(__DECONST(char *, oidp->oid_label),
                                       M_SYSCTLOID);
                           free(__DECONST(char *, oidp->oid_name), M_SYSCTLOID);
                           free(oidp, M_SYSCTLOID);
                   }
           }
           return (0);
   }
   /*
    * Create new sysctls at run time.
    * clist may point to a valid context initialized with sysctl_ctx_init().
    */
   struct sysctl_oid *
   sysctl_add_oid(struct sysctl_ctx_list *clist, struct sysctl_oid_list *parent,
           int number, const char *name, int kind, void *arg1, intmax_t arg2,
           int (*handler)(SYSCTL_HANDLER_ARGS), const char *fmt, const char *descr,
           const char *label)
   {
           struct sysctl_oid *oidp;
           char *escaped;
   
           /* You have to hook up somewhere.. */
           if (parent == NULL)
                   return(NULL);
           escaped = sysctl_escape_name(name);
           /* Check if the node already exists, otherwise create it */
           SYSCTL_WLOCK();
           oidp = sysctl_find_oidname(escaped, parent);
           if (oidp != NULL) {
                   free(escaped, M_SYSCTLOID);
                   if ((oidp->oid_kind & CTLTYPE) == CTLTYPE_NODE) {
                           oidp->oid_refcnt++;
                           /* Update the context */
                           if (clist != NULL)
                                   sysctl_ctx_entry_add(clist, oidp);
                           SYSCTL_WUNLOCK();
                           return (oidp);
                   } else {
                           sysctl_warn_reuse(__func__, oidp);
                           SYSCTL_WUNLOCK();
                           return (NULL);
                   }
           }
           oidp = malloc(sizeof(struct sysctl_oid), M_SYSCTLOID, M_WAITOK|M_ZERO);
           oidp->oid_parent = parent;
           SLIST_INIT(&oidp->oid_children);
           oidp->oid_number = number;
           oidp->oid_refcnt = 1;
           oidp->oid_name = escaped;
           oidp->oid_handler = handler;
           oidp->oid_kind = CTLFLAG_DYN | kind;
           oidp->oid_arg1 = arg1;
           oidp->oid_arg2 = arg2;
           oidp->oid_fmt = fmt;
           if (descr != NULL)
                   oidp->oid_descr = strdup(descr, M_SYSCTLOID);
           if (label != NULL)
                   oidp->oid_label = strdup(label, M_SYSCTLOID);
           /* Update the context, if used */
           if (clist != NULL)
                   sysctl_ctx_entry_add(clist, oidp);
           /* Register this oid */
           sysctl_register_oid(oidp);
           SYSCTL_WUNLOCK();
           return (oidp);
   }
   
   /*
    * Rename an existing oid.
    */
   void
   sysctl_rename_oid(struct sysctl_oid *oidp, const char *name)
   {
           char *newname;
           char *oldname;
   
           newname = strdup(name, M_SYSCTLOID);
           SYSCTL_WLOCK();
           oldname = __DECONST(char *, oidp->oid_name);
           oidp->oid_name = newname;
           SYSCTL_WUNLOCK();
           free(oldname, M_SYSCTLOID);
   }
   
   /*
    * Reparent an existing oid.
    */
   int
   sysctl_move_oid(struct sysctl_oid *oid, struct sysctl_oid_list *parent)
   {
           struct sysctl_oid *oidp;
   
           SYSCTL_WLOCK();
           if (oid->oid_parent == parent) {
                   SYSCTL_WUNLOCK();
                   return (0);
           }
           oidp = sysctl_find_oidname(oid->oid_name, parent);
           if (oidp != NULL) {
                   SYSCTL_WUNLOCK();
                   return (EEXIST);
           }
           sysctl_unregister_oid(oid);
           oid->oid_parent = parent;
           oid->oid_number = OID_AUTO;
           sysctl_register_oid(oid);
           SYSCTL_WUNLOCK();
           return (0);
   }
   
   /*
    * Register the kernel's oids on startup.
    */
   SET_DECLARE(sysctl_set, struct sysctl_oid);
   
   static void
   sysctl_register_all(void *arg)
   {
           struct sysctl_oid **oidp;
   
           sx_init(&sysctlmemlock, "sysctl mem");
           sx_init(&sysctlstringlock, "sysctl string handler");
           SYSCTL_INIT();
           SYSCTL_WLOCK();
           SET_FOREACH(oidp, sysctl_set)
                   sysctl_register_oid(*oidp);
           SYSCTL_WUNLOCK();
   }
   SYSINIT(sysctl, SI_SUB_KMEM, SI_ORDER_FIRST, sysctl_register_all, NULL);
   
   /*
    * "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.
    *
    * {CTL_SYSCTL, CTL_SYSCTL_DEBUG}               printf the entire MIB-tree.
    * {CTL_SYSCTL, CTL_SYSCTL_NAME, ...}           return the name of the "..."
    *                                              OID.
    * {CTL_SYSCTL, CTL_SYSCTL_NEXT, ...}           return the next OID, honoring
    *                                              CTLFLAG_SKIP.
    * {CTL_SYSCTL, CTL_SYSCTL_NAME2OID}            return the OID of the name in
   *                                              "new"
   * {CTL_SYSCTL, CTL_SYSCTL_OIDFMT, ...}         return the kind & format info
   *                                              for the "..." OID.
   * {CTL_SYSCTL, CTL_SYSCTL_OIDDESCR, ...}       return the description of the
   *                                              "..." OID.
   * {CTL_SYSCTL, CTL_SYSCTL_OIDLABEL, ...}       return the aggregation label of
   *                                              the "..." OID.
   * {CTL_SYSCTL, CTL_SYSCTL_NEXTNOSKIP, ...}     return the next OID, ignoring
   *                                              CTLFLAG_SKIP.
   */
  
  #ifdef SYSCTL_DEBUG
  static void
  sysctl_sysctl_debug_dump_node(struct sysctl_oid_list *l, int i)
  {
          int k;
          struct sysctl_oid *oidp;
  
          SYSCTL_ASSERT_LOCKED();
          SYSCTL_FOREACH(oidp, l) {
                  for (k=0; k<i; k++)
                          printf(" ");
  
                  printf("%d %s ", oidp->oid_number, oidp->oid_name);
  
                  printf("%c%c",
                          oidp->oid_kind & CTLFLAG_RD ? 'R':' ',
                          oidp->oid_kind & CTLFLAG_WR ? 'W':' ');
  
                  if (oidp->oid_handler)
                          printf(" *Handler");
  
                  switch (oidp->oid_kind & CTLTYPE) {
                          case CTLTYPE_NODE:
                                  printf(" Node\n");
                                  if (!oidp->oid_handler) {
                                          sysctl_sysctl_debug_dump_node(
                                              SYSCTL_CHILDREN(oidp), i + 2);
                                  }
                                  break;
                          case CTLTYPE_INT:    printf(" Int\n"); break;
                          case CTLTYPE_UINT:   printf(" u_int\n"); break;
                          case CTLTYPE_LONG:   printf(" Long\n"); break;
                          case CTLTYPE_ULONG:  printf(" u_long\n"); break;
                          case CTLTYPE_STRING: printf(" String\n"); break;
                          case CTLTYPE_S8:     printf(" int8_t\n"); break;
                          case CTLTYPE_S16:    printf(" int16_t\n"); break;
                          case CTLTYPE_S32:    printf(" int32_t\n"); break;
                          case CTLTYPE_S64:    printf(" int64_t\n"); break;
                          case CTLTYPE_U8:     printf(" uint8_t\n"); break;
                          case CTLTYPE_U16:    printf(" uint16_t\n"); break;
                          case CTLTYPE_U32:    printf(" uint32_t\n"); break;
                          case CTLTYPE_U64:    printf(" uint64_t\n"); break;
                          case CTLTYPE_OPAQUE: printf(" Opaque/struct\n"); break;
                          default:             printf("\n");
                  }
          }
  }
  
  static int
  sysctl_sysctl_debug(SYSCTL_HANDLER_ARGS)
  {
          struct rm_priotracker tracker;
          int error;
  
          error = priv_check(req->td, PRIV_SYSCTL_DEBUG);
          if (error)
                  return (error);
          SYSCTL_RLOCK(&tracker);
          sysctl_sysctl_debug_dump_node(&sysctl__children, 0);
          SYSCTL_RUNLOCK(&tracker);
          return (ENOENT);
  }
  
  SYSCTL_PROC(_sysctl, CTL_SYSCTL_DEBUG, debug, CTLTYPE_STRING | CTLFLAG_RD |
      CTLFLAG_MPSAFE, 0, 0, sysctl_sysctl_debug, "-", "");
  #endif
  
  static int
  sysctl_sysctl_name(SYSCTL_HANDLER_ARGS)
  {
          int *name = (int *) arg1;
          u_int namelen = arg2;
          int error;
          struct sysctl_oid *oid;
          struct sysctl_oid_list *lsp = &sysctl__children, *lsp2;
          struct rm_priotracker tracker;
          char buf[10];
  
          error = sysctl_wire_old_buffer(req, 0);
          if (error)
                  return (error);
  
          SYSCTL_RLOCK(&tracker);
          while (namelen) {
                  if (!lsp) {
                          snprintf(buf,sizeof(buf),"%d",*name);
                          if (req->oldidx)
                                  error = SYSCTL_OUT(req, ".", 1);
                          if (!error)
                                  error = SYSCTL_OUT(req, buf, strlen(buf));
                          if (error)
                                  goto out;
                          namelen--;
                          name++;
                          continue;
                  }
                  lsp2 = NULL;
                  SLIST_FOREACH(oid, lsp, oid_link) {
                          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)
                                  goto out;
  
                          namelen--;
                          name++;
  
                          if ((oid->oid_kind & CTLTYPE) != CTLTYPE_NODE) 
                                  break;
  
                          if (oid->oid_handler)
                                  break;
  
                          lsp2 = SYSCTL_CHILDREN(oid);
                          break;
                  }
                  lsp = lsp2;
          }
          error = SYSCTL_OUT(req, "", 1);
   out:
          SYSCTL_RUNLOCK(&tracker);
          return (error);
  }
  
  /*
   * XXXRW/JA: Shouldn't return name data for nodes that we don't permit in
   * capability mode.
   */
  static SYSCTL_NODE(_sysctl, CTL_SYSCTL_NAME, name, CTLFLAG_RD |
      CTLFLAG_MPSAFE | CTLFLAG_CAPRD, sysctl_sysctl_name, "");
  
  enum sysctl_iter_action {
          ITER_SIBLINGS,  /* Not matched, continue iterating siblings */
          ITER_CHILDREN,  /* Node has children we need to iterate over them */
          ITER_FOUND,     /* Matching node was found */
  };
  
  /*
   * Tries to find the next node for @name and @namelen.
   *
   * Returns next action to take. 
   */
  static enum sysctl_iter_action
  sysctl_sysctl_next_node(struct sysctl_oid *oidp, int *name, unsigned int namelen,
      bool honor_skip)
  {
  
          if ((oidp->oid_kind & CTLFLAG_DORMANT) != 0)
                  return (ITER_SIBLINGS);
  
          if (honor_skip && (oidp->oid_kind & CTLFLAG_SKIP) != 0)
                  return (ITER_SIBLINGS);
  
          if (namelen == 0) {
                  /*
                   * We have reached a node with a full name match and are
                   * looking for the next oid in its children.
                   *
                   * For CTL_SYSCTL_NEXTNOSKIP we are done.
                   *
                   * For CTL_SYSCTL_NEXT we skip CTLTYPE_NODE (unless it
                   * has a handler) and move on to the children.
                   */
                  if (!honor_skip)
                          return (ITER_FOUND);
                  if ((oidp->oid_kind & CTLTYPE) != CTLTYPE_NODE) 
                          return (ITER_FOUND);
                  /* If node does not have an iterator, treat it as leaf */
                  if (oidp->oid_handler) 
                          return (ITER_FOUND);
  
                  /* Report oid as a node to iterate */
                  return (ITER_CHILDREN);
          }
  
          /*
           * No match yet. Continue seeking the given name.
           *
           * We are iterating in order by oid_number, so skip oids lower
           * than the one we are looking for.
           *
           * When the current oid_number is higher than the one we seek,
           * that means we have reached the next oid in the sequence and
           * should return it.
           *
           * If the oid_number matches the name at this level then we
           * have to find a node to continue searching at the next level.
           */
          if (oidp->oid_number < *name)
                  return (ITER_SIBLINGS);
          if (oidp->oid_number > *name) {
                  /*
                   * We have reached the next oid.
                   *
                   * For CTL_SYSCTL_NEXTNOSKIP we are done.
                   *
                   * For CTL_SYSCTL_NEXT we skip CTLTYPE_NODE (unless it
                   * has a handler) and move on to the children.
                   */
                  if (!honor_skip)
                          return (ITER_FOUND);
                  if ((oidp->oid_kind & CTLTYPE) != CTLTYPE_NODE)
                          return (ITER_FOUND);
                  /* If node does not have an iterator, treat it as leaf */
                  if (oidp->oid_handler)
                          return (ITER_FOUND);
                  return (ITER_CHILDREN);
          }
  
          /* match at a current level */
          if ((oidp->oid_kind & CTLTYPE) != CTLTYPE_NODE)
                  return (ITER_SIBLINGS);
          if (oidp->oid_handler)
                  return (ITER_SIBLINGS);
  
          return (ITER_CHILDREN);
  }
  
  /*
   * Recursively walk the sysctl subtree at lsp until we find the given name.
   * Returns true and fills in next oid data in @next and @len if oid is found.
   */
  static bool
  sysctl_sysctl_next_action(struct sysctl_oid_list *lsp, int *name, u_int namelen, 
      int *next, int *len, int level, bool honor_skip)
  {
          struct sysctl_oid *oidp;
          bool success = false;
          enum sysctl_iter_action action;
  
          SYSCTL_ASSERT_LOCKED();
          SLIST_FOREACH(oidp, lsp, oid_link) {
                  action = sysctl_sysctl_next_node(oidp, name, namelen, honor_skip);
                  if (action == ITER_SIBLINGS)
                          continue;
                  if (action == ITER_FOUND) {
                          success = true;
                          break;
                  }
                  KASSERT((action== ITER_CHILDREN), ("ret(%d)!=ITER_CHILDREN", action));
  
                  lsp = SYSCTL_CHILDREN(oidp);
                  if (namelen == 0) {
                          success = sysctl_sysctl_next_action(lsp, NULL, 0,
                              next + 1, len, level + 1, honor_skip);
                  } else {
                          success = sysctl_sysctl_next_action(lsp, name + 1, namelen - 1,
                              next + 1, len, level + 1, honor_skip);
                          if (!success) {
  
                                  /*
                                   * We maintain the invariant that current node oid
                                   * is >= the oid provided in @name.
                                   * As there are no usable children at this node,
                                   *  current node oid is strictly > than the requested
                                   *  oid.
                                   * Hence, reduce namelen to 0 to allow for picking first
                                   *  nodes/leafs in the next node in list.
                                   */
                                  namelen = 0;
                          }
                  }
                  if (success)
                          break;
          }
  
          if (success) {
                  *next = oidp->oid_number;
                  if (level > *len)
                          *len = level;
          }
  
          return (success);
  }
  
  static int
  sysctl_sysctl_next(SYSCTL_HANDLER_ARGS)
  {
          int *name = (int *) arg1;
          u_int namelen = arg2;
          int len, error;
          bool success;
          struct sysctl_oid_list *lsp = &sysctl__children;
          struct rm_priotracker tracker;
          int next[CTL_MAXNAME];
  
          len = 0;
          SYSCTL_RLOCK(&tracker);
          success = sysctl_sysctl_next_action(lsp, name, namelen, next, &len, 1,
              oidp->oid_number == CTL_SYSCTL_NEXT);
          SYSCTL_RUNLOCK(&tracker);
          if (!success)
                  return (ENOENT);
          error = SYSCTL_OUT(req, next, len * sizeof (int));
          return (error);
  }
  
  /*
   * XXXRW/JA: Shouldn't return next data for nodes that we don't permit in
   * capability mode.
   */
  static SYSCTL_NODE(_sysctl, CTL_SYSCTL_NEXT, next, CTLFLAG_RD |
      CTLFLAG_MPSAFE | CTLFLAG_CAPRD, sysctl_sysctl_next, "");
  
  static SYSCTL_NODE(_sysctl, CTL_SYSCTL_NEXTNOSKIP, nextnoskip, CTLFLAG_RD |
      CTLFLAG_MPSAFE | CTLFLAG_CAPRD, sysctl_sysctl_next, "");
  
  static int
  name2oid(char *name, int *oid, int *len, struct sysctl_oid **oidpp)
  {
          struct sysctl_oid *oidp;
          struct sysctl_oid_list *lsp = &sysctl__children;
          char *p;
  
          SYSCTL_ASSERT_LOCKED();
  
          for (*len = 0; *len < CTL_MAXNAME;) {
                  p = strsep(&name, ".");
  
                  SYSCTL_FOREACH(oidp, lsp) {
                          if (strcmp(p, oidp->oid_name) == 0)
                                  break;
                  }
                  if (oidp == NULL)
                          return (ENOENT);
                  *oid++ = oidp->oid_number;
                  (*len)++;
  
                  if (name == NULL || *name == '\0') {
                          if (oidpp)
                                  *oidpp = oidp;
                          return (0);
                  }
  
                  if ((oidp->oid_kind & CTLTYPE) != CTLTYPE_NODE)
                          break;
  
                  if (oidp->oid_handler)
                          break;
  
                  lsp = SYSCTL_CHILDREN(oidp);
          }
          return (ENOENT);
  }
  
  static int
  sysctl_sysctl_name2oid(SYSCTL_HANDLER_ARGS)
  {
          char *p;
          int error, oid[CTL_MAXNAME], len = 0;
          struct sysctl_oid *op = NULL;
          struct rm_priotracker tracker;
          char buf[32];
  
          if (!req->newlen) 
                  return (ENOENT);
          if (req->newlen >= MAXPATHLEN)  /* XXX arbitrary, undocumented */
                  return (ENAMETOOLONG);
  
          p = buf;
          if (req->newlen >= sizeof(buf))
                  p = malloc(req->newlen+1, M_SYSCTL, M_WAITOK);
  
          error = SYSCTL_IN(req, p, req->newlen);
          if (error) {
                  if (p != buf)
                          free(p, M_SYSCTL);
                  return (error);
          }
  
          p [req->newlen] = '\0';
  
          SYSCTL_RLOCK(&tracker);
          error = name2oid(p, oid, &len, &op);
          SYSCTL_RUNLOCK(&tracker);
  
          if (p != buf)
                  free(p, M_SYSCTL);
  
          if (error)
                  return (error);
  
          error = SYSCTL_OUT(req, oid, len * sizeof *oid);
          return (error);
  }
  
  /*
   * XXXRW/JA: Shouldn't return name2oid data for nodes that we don't permit in
   * capability mode.
   */
  SYSCTL_PROC(_sysctl, CTL_SYSCTL_NAME2OID, name2oid, CTLTYPE_INT | CTLFLAG_RW |
      CTLFLAG_ANYBODY | CTLFLAG_MPSAFE | CTLFLAG_CAPRW, 0, 0,
      sysctl_sysctl_name2oid, "I", "");
  
  static int
  sysctl_sysctl_oidfmt(SYSCTL_HANDLER_ARGS)
  {
          struct sysctl_oid *oid;
          struct rm_priotracker tracker;
          int error;
  
          error = sysctl_wire_old_buffer(req, 0);
          if (error)
                  return (error);
  
          SYSCTL_RLOCK(&tracker);
          error = sysctl_find_oid(arg1, arg2, &oid, NULL, req);
          if (error)
                  goto out;
  
          if (oid->oid_fmt == NULL) {
                  error = ENOENT;
                  goto out;
          }
          error = SYSCTL_OUT(req, &oid->oid_kind, sizeof(oid->oid_kind));
          if (error)
                  goto out;
          error = SYSCTL_OUT(req, oid->oid_fmt, strlen(oid->oid_fmt) + 1);
   out:
          SYSCTL_RUNLOCK(&tracker);
          return (error);
  }
  
  static SYSCTL_NODE(_sysctl, CTL_SYSCTL_OIDFMT, oidfmt, CTLFLAG_RD |
      CTLFLAG_MPSAFE | CTLFLAG_CAPRD, sysctl_sysctl_oidfmt, "");
  
  static int
  sysctl_sysctl_oiddescr(SYSCTL_HANDLER_ARGS)
  {
          struct sysctl_oid *oid;
          struct rm_priotracker tracker;
          int error;
  
          error = sysctl_wire_old_buffer(req, 0);
          if (error)
                  return (error);
  
          SYSCTL_RLOCK(&tracker);
          error = sysctl_find_oid(arg1, arg2, &oid, NULL, req);
          if (error)
                  goto out;
  
          if (oid->oid_descr == NULL) {
                  error = ENOENT;
                  goto out;
          }
          error = SYSCTL_OUT(req, oid->oid_descr, strlen(oid->oid_descr) + 1);
   out:
          SYSCTL_RUNLOCK(&tracker);
          return (error);
  }
  
  static SYSCTL_NODE(_sysctl, CTL_SYSCTL_OIDDESCR, oiddescr, CTLFLAG_RD |
      CTLFLAG_MPSAFE|CTLFLAG_CAPRD, sysctl_sysctl_oiddescr, "");
  
  static int
  sysctl_sysctl_oidlabel(SYSCTL_HANDLER_ARGS)
  {
          struct sysctl_oid *oid;
          struct rm_priotracker tracker;
          int error;
  
          error = sysctl_wire_old_buffer(req, 0);
          if (error)
                  return (error);
  
          SYSCTL_RLOCK(&tracker);
          error = sysctl_find_oid(arg1, arg2, &oid, NULL, req);
          if (error)
                  goto out;
  
          if (oid->oid_label == NULL) {
                  error = ENOENT;
                  goto out;
          }
          error = SYSCTL_OUT(req, oid->oid_label, strlen(oid->oid_label) + 1);
   out:
          SYSCTL_RUNLOCK(&tracker);
          return (error);
  }
  
  static SYSCTL_NODE(_sysctl, CTL_SYSCTL_OIDLABEL, oidlabel, CTLFLAG_RD |
      CTLFLAG_MPSAFE | CTLFLAG_CAPRD, sysctl_sysctl_oidlabel, "");
  
  /*
   * Default "handler" functions.
   */
  
  /*
   * Handle a bool.
   * Two cases:
   *     a variable:  point arg1 at it.
   *     a constant:  pass it in arg2.
   */
  
  int
  sysctl_handle_bool(SYSCTL_HANDLER_ARGS)
  {
          uint8_t temp;
          int error;
  
          /*
           * Attempt to get a coherent snapshot by making a copy of the data.
           */
          if (arg1)
                  temp = *(bool *)arg1 ? 1 : 0;
          else
                  temp = arg2 ? 1 : 0;
  
          error = SYSCTL_OUT(req, &temp, sizeof(temp));
          if (error || !req->newptr)
                  return (error);
  
          if (!arg1)
                  error = EPERM;
          else {
                  error = SYSCTL_IN(req, &temp, sizeof(temp));
                  if (!error)
                          *(bool *)arg1 = temp ? 1 : 0;
          }
          return (error);
  }
  
  /*
   * Handle an int8_t, signed or unsigned.
   * Two cases:
   *     a variable:  point arg1 at it.
   *     a constant:  pass it in arg2.
   */
  
  int
  sysctl_handle_8(SYSCTL_HANDLER_ARGS)
  {
          int8_t tmpout;
          int error = 0;
  
          /*
           * Attempt to get a coherent snapshot by making a copy of the data.
           */
          if (arg1)
                  tmpout = *(int8_t *)arg1;
          else
                  tmpout = arg2;
          error = SYSCTL_OUT(req, &tmpout, sizeof(tmpout));
  
          if (error || !req->newptr)
                  return (error);
  
          if (!arg1)
                  error = EPERM;
          else
                  error = SYSCTL_IN(req, arg1, sizeof(tmpout));
          return (error);
  }
  
  /*
   * Handle an int16_t, signed or unsigned.
   * Two cases:
   *     a variable:  point arg1 at it.
   *     a constant:  pass it in arg2.
   */
  
  int
  sysctl_handle_16(SYSCTL_HANDLER_ARGS)
  {
          int16_t tmpout;
          int error = 0;
  
          /*
           * Attempt to get a coherent snapshot by making a copy of the data.
           */
          if (arg1)
                  tmpout = *(int16_t *)arg1;
          else
                  tmpout = arg2;
          error = SYSCTL_OUT(req, &tmpout, sizeof(tmpout));
  
          if (error || !req->newptr)
                  return (error);
  
          if (!arg1)
                  error = EPERM;
          else
                  error = SYSCTL_IN(req, arg1, sizeof(tmpout));
          return (error);
  }
  
  /*
   * Handle an int32_t, signed or unsigned.
   * Two cases:
   *     a variable:  point arg1 at it.
   *     a constant:  pass it in arg2.
   */
  
  int
  sysctl_handle_32(SYSCTL_HANDLER_ARGS)
  {
          int32_t tmpout;
          int error = 0;
  
          /*
           * Attempt to get a coherent snapshot by making a copy of the data.
           */
          if (arg1)
                  tmpout = *(int32_t *)arg1;
          else
                  tmpout = arg2;
          error = SYSCTL_OUT(req, &tmpout, sizeof(tmpout));
  
          if (error || !req->newptr)
                  return (error);
  
          if (!arg1)
                  error = EPERM;
          else
                  error = SYSCTL_IN(req, arg1, sizeof(tmpout));
          return (error);
  }
  
  /*
   * Handle an int, signed or unsigned.
   * Two cases:
   *     a variable:  point arg1 at it.
   *     a constant:  pass it in arg2.
   */
  
  int
  sysctl_handle_int(SYSCTL_HANDLER_ARGS)
  {
          int tmpout, error = 0;
  
          /*
           * Attempt to get a coherent snapshot by making a copy of the data.
           */
          if (arg1)
                  tmpout = *(int *)arg1;
          else
                  tmpout = arg2;
          error = SYSCTL_OUT(req, &tmpout, sizeof(int));
  
          if (error || !req->newptr)
                  return (error);
  
          if (!arg1)
                  error = EPERM;
          else
                  error = SYSCTL_IN(req, arg1, sizeof(int));
          return (error);
  }
  
  /*
   * Based on on sysctl_handle_int() convert milliseconds into ticks.
   * Note: this is used by TCP.
   */
  
  int
  sysctl_msec_to_ticks(SYSCTL_HANDLER_ARGS)
  {
          int error, s, tt;
  
          tt = *(int *)arg1;
          s = (int)((int64_t)tt * 1000 / hz);
  
          error = sysctl_handle_int(oidp, &s, 0, req);
          if (error || !req->newptr)
                  return (error);
  
          tt = (int)((int64_t)s * hz / 1000);
          if (tt < 1)
                  return (EINVAL);
  
          *(int *)arg1 = tt;
          return (0);
  }
  
  /*
   * Handle a long, signed or unsigned.
   * Two cases:
   *     a variable:  point arg1 at it.
   *     a constant:  pass it in arg2.
   */
  
  int
  sysctl_handle_long(SYSCTL_HANDLER_ARGS)
  {
          int error = 0;
          long tmplong;
  #ifdef SCTL_MASK32
          int tmpint;
  #endif
  
          /*
           * Attempt to get a coherent snapshot by making a copy of the data.
           */
          if (arg1)
                  tmplong = *(long *)arg1;
          else
                  tmplong = arg2;
  #ifdef SCTL_MASK32
          if (req->flags & SCTL_MASK32) {
                  tmpint = tmplong;
                  error = SYSCTL_OUT(req, &tmpint, sizeof(int));
          } else
  #endif
                  error = SYSCTL_OUT(req, &tmplong, sizeof(long));
  
          if (error || !req->newptr)
                  return (error);
  
          if (!arg1)
                  error = EPERM;
  #ifdef SCTL_MASK32
          else if (req->flags & SCTL_MASK32) {
                  error = SYSCTL_IN(req, &tmpint, sizeof(int));
                  *(long *)arg1 = (long)tmpint;
          }
  #endif
          else
                  error = SYSCTL_IN(req, arg1, sizeof(long));
          return (error);
  }
  
  /*
   * Handle a 64 bit int, signed or unsigned.
   * Two cases:
   *     a variable:  point arg1 at it.
   *     a constant:  pass it in arg2.
   */
  int
  sysctl_handle_64(SYSCTL_HANDLER_ARGS)
  {
          int error = 0;
          uint64_t tmpout;
  
          /*
           * Attempt to get a coherent snapshot by making a copy of the data.
           */
          if (arg1)
                  tmpout = *(uint64_t *)arg1;
          else
                  tmpout = arg2;
          error = SYSCTL_OUT(req, &tmpout, sizeof(uint64_t));
  
          if (error || !req->newptr)
                  return (error);
  
          if (!arg1)
                  error = EPERM;
          else
                  error = SYSCTL_IN(req, arg1, sizeof(uint64_t));
          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(SYSCTL_HANDLER_ARGS)
  {
          char *tmparg;
          size_t outlen;
          int error = 0, ro_string = 0;
  
          /*
           * If the sysctl isn't writable and isn't a preallocated tunable that
           * can be modified by kenv(2), microoptimise and treat it as a
           * read-only string.
           * A zero-length buffer indicates a fixed size read-only
           * string.  In ddb, don't worry about trying to make a malloced
           * snapshot.
           */
          if ((oidp->oid_kind & (CTLFLAG_WR | CTLFLAG_TUN)) == 0 ||
              arg2 == 0 || kdb_active) {
                  arg2 = strlen((char *)arg1) + 1;
                  ro_string = 1;
          }
  
          if (req->oldptr != NULL) {
                  if (ro_string) {
                          tmparg = arg1;
                          outlen = strlen(tmparg) + 1;
                  } else {
                          tmparg = malloc(arg2, M_SYSCTLTMP, M_WAITOK);
                          sx_slock(&sysctlstringlock);
                          memcpy(tmparg, arg1, arg2);
                          sx_sunlock(&sysctlstringlock);
                          outlen = strlen(tmparg) + 1;
                  }
  
                  error = SYSCTL_OUT(req, tmparg, outlen);
  
                  if (!ro_string)
                          free(tmparg, M_SYSCTLTMP);
          } else {
                  if (!ro_string)
                          sx_slock(&sysctlstringlock);
                  outlen = strlen((char *)arg1) + 1;
                  if (!ro_string)
                          sx_sunlock(&sysctlstringlock);
                  error = SYSCTL_OUT(req, NULL, outlen);
          }
          if (error || !req->newptr)
                  return (error);
  
          if (req->newlen - req->newidx >= arg2 ||
              req->newlen - req->newidx < 0) {
                  error = EINVAL;
          } else if (req->newlen - req->newidx == 0) {
                  sx_xlock(&sysctlstringlock);
                  ((char *)arg1)[0] = '\0';
                  sx_xunlock(&sysctlstringlock);
          } else if (req->newfunc == sysctl_new_kernel) {
                  arg2 = req->newlen - req->newidx;
                  sx_xlock(&sysctlstringlock);
                  error = SYSCTL_IN(req, arg1, arg2);
                  if (error == 0) {
                          ((char *)arg1)[arg2] = '\0';
                          req->newidx += arg2;
                  }
                  sx_xunlock(&sysctlstringlock);
          } else {
                  arg2 = req->newlen - req->newidx;
                  tmparg = malloc(arg2, M_SYSCTLTMP, M_WAITOK);
  
                  error = SYSCTL_IN(req, tmparg, arg2);
                  if (error) {
                          free(tmparg, M_SYSCTLTMP);
                          return (error);
                  }
  
                  sx_xlock(&sysctlstringlock);
                  memcpy(arg1, tmparg, arg2);
                  ((char *)arg1)[arg2] = '\0';
                  sx_xunlock(&sysctlstringlock);
                  free(tmparg, M_SYSCTLTMP);
                  req->newidx += arg2;
          }
          return (error);
  }
  
  /*
   * Handle any kind of opaque data.
   * arg1 points to it, arg2 is the size.
   */
  
  int
  sysctl_handle_opaque(SYSCTL_HANDLER_ARGS)
  {
          int error, tries;
          u_int generation;
          struct sysctl_req req2;
  
          /*
           * Attempt to get a coherent snapshot, by using the thread
           * pre-emption counter updated from within mi_switch() to
           * determine if we were pre-empted during a bcopy() or
           * copyout(). Make 3 attempts at doing this before giving up.
           * If we encounter an error, stop immediately.
           */
          tries = 0;
          req2 = *req;
  retry:
          generation = curthread->td_generation;
          error = SYSCTL_OUT(req, arg1, arg2);
          if (error)
                  return (error);
          tries++;
          if (generation != curthread->td_generation && tries < 3) {
                  *req = req2;
                  goto retry;
          }
  
          error = SYSCTL_IN(req, arg1, arg2);
  
          return (error);
  }
  
  /*
   * Based on on sysctl_handle_int() convert microseconds to a sbintime.
   */
  int
  sysctl_usec_to_sbintime(SYSCTL_HANDLER_ARGS)
  {
          int error;
          int64_t tt;
          sbintime_t sb;
  
          tt = *(int64_t *)arg1;
          sb = sbttous(tt);
  
          error = sysctl_handle_64(oidp, &sb, 0, req);
          if (error || !req->newptr)
                  return (error);
  
          tt = ustosbt(sb);
          *(int64_t *)arg1 = tt;
  
          return (0);
  }
  
  /*
   * Based on on sysctl_handle_int() convert milliseconds to a sbintime.
   */
  int
  sysctl_msec_to_sbintime(SYSCTL_HANDLER_ARGS)
  {
          int error;
          int64_t tt;
          sbintime_t sb;
  
          tt = *(int64_t *)arg1;
          sb = sbttoms(tt);
  
          error = sysctl_handle_64(oidp, &sb, 0, req);
          if (error || !req->newptr)
                  return (error);
  
          tt = mstosbt(sb);
          *(int64_t *)arg1 = tt;
  
          return (0);
  }
  
  /*
   * Convert seconds to a struct timeval.  Intended for use with
   * intervals and thus does not permit negative seconds.
   */
  int
  sysctl_sec_to_timeval(SYSCTL_HANDLER_ARGS)
  {
          struct timeval *tv;
          int error, secs;
  
          tv = arg1;
          secs = tv->tv_sec;
  
          error = sysctl_handle_int(oidp, &secs, 0, req);
          if (error || req->newptr == NULL)
                  return (error);
  
          if (secs < 0)
                  return (EINVAL);
          tv->tv_sec = secs;
  
          return (0);
  }
  
  /*
   * Transfer functions to/from kernel space.
   * XXX: rather untested at this point
   */
  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 (req->oldlen <= req->oldidx)
                          i = 0;
                  else
                          if (i > req->oldlen - req->oldidx)
                                  i = req->oldlen - req->oldidx;
                  if (i > 0)
                          bcopy(p, (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((const char *)req->newptr + req->newidx, p, l);
          req->newidx += l;
          return (0);
  }
  
  int
  kernel_sysctl(struct thread *td, int *name, u_int namelen, void *old,
      size_t *oldlenp, void *new, size_t newlen, size_t *retval, int flags)
  {
          int error = 0;
          struct sysctl_req req;
  
          bzero(&req, sizeof req);
  
          req.td = td;
          req.flags = flags;
  
          if (oldlenp) {
                  req.oldlen = *oldlenp;
          }
          req.validlen = req.oldlen;
  
          if (old) {
                  req.oldptr= old;
          }
  
          if (new != NULL) {
                  req.newlen = newlen;
                  req.newptr = new;
          }
  
          req.oldfunc = sysctl_old_kernel;
          req.newfunc = sysctl_new_kernel;
          req.lock = REQ_UNWIRED;
  
          error = sysctl_root(0, name, namelen, &req);
  
          if (req.lock == REQ_WIRED && req.validlen > 0)
                  vsunlock(req.oldptr, req.validlen);
  
          if (error && error != ENOMEM)
                  return (error);
  
          if (retval) {
                  if (req.oldptr && req.oldidx > req.validlen)
                          *retval = req.validlen;
                  else
                          *retval = req.oldidx;
          }
          return (error);
  }
  
  int
  kernel_sysctlbyname(struct thread *td, char *name, void *old, size_t *oldlenp,
      void *new, size_t newlen, size_t *retval, int flags)
  {
          int oid[CTL_MAXNAME];
          size_t oidlen, plen;
          int error;
  
          oid[0] = CTL_SYSCTL;
          oid[1] = CTL_SYSCTL_NAME2OID;
          oidlen = sizeof(oid);
  
          error = kernel_sysctl(td, oid, 2, oid, &oidlen,
              (void *)name, strlen(name), &plen, flags);
          if (error)
                  return (error);
  
          error = kernel_sysctl(td, oid, plen / sizeof(int), old, oldlenp,
              new, newlen, retval, flags);
          return (error);
  }
  
  /*
   * Transfer function to/from user space.
   */
  static int
  sysctl_old_user(struct sysctl_req *req, const void *p, size_t l)
  {
          size_t i, len, origidx;
          int error;
  
          origidx = req->oldidx;
          req->oldidx += l;
          if (req->oldptr == NULL)
                  return (0);
          /*
           * If we have not wired the user supplied buffer and we are currently
           * holding locks, drop a witness warning, as it's possible that
           * write operations to the user page can sleep.
           */
          if (req->lock != REQ_WIRED)
                  WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
                      "sysctl_old_user()");
          i = l;
          len = req->validlen;
          if (len <= origidx)
                  i = 0;
          else {
                  if (i > len - origidx)
                          i = len - origidx;
                  if (req->lock == REQ_WIRED) {
                          error = copyout_nofault(p, (char *)req->oldptr +
                              origidx, i);
                  } else
                          error = copyout(p, (char *)req->oldptr + origidx, i);
                  if (error != 0)
                          return (error);
          }
          if (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);
          WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
              "sysctl_new_user()");
          error = copyin((const char *)req->newptr + req->newidx, p, l);
          req->newidx += l;
          return (error);
  }
  
  /*
   * Wire the user space destination buffer.  If set to a value greater than
   * zero, the len parameter limits the maximum amount of wired memory.
   */
  int
  sysctl_wire_old_buffer(struct sysctl_req *req, size_t len)
  {
          int ret;
          size_t wiredlen;
  
          wiredlen = (len > 0 && len < req->oldlen) ? len : req->oldlen;
          ret = 0;
          if (req->lock != REQ_WIRED && req->oldptr &&
              req->oldfunc == sysctl_old_user) {
                  if (wiredlen != 0) {
                          ret = vslock(req->oldptr, wiredlen);
                          if (ret != 0) {
                                  if (ret != ENOMEM)
                                          return (ret);
                                  wiredlen = 0;
                          }
                  }
                  req->lock = REQ_WIRED;
                  req->validlen = wiredlen;
          }
          return (0);
  }
  
  int
  sysctl_find_oid(int *name, u_int namelen, struct sysctl_oid **noid,
      int *nindx, struct sysctl_req *req)
  {
          struct sysctl_oid_list *lsp;
          struct sysctl_oid *oid;
          int indx;
  
          SYSCTL_ASSERT_LOCKED();
          lsp = &sysctl__children;
          indx = 0;
          while (indx < CTL_MAXNAME) {
                  SLIST_FOREACH(oid, lsp, oid_link) {
                          if (oid->oid_number == name[indx])
                                  break;
                  }
                  if (oid == NULL)
                          return (ENOENT);
  
                  indx++;
                  if ((oid->oid_kind & CTLTYPE) == CTLTYPE_NODE) {
                          if (oid->oid_handler != NULL || indx == namelen) {
                                  *noid = oid;
                                  if (nindx != NULL)
                                          *nindx = indx;
                                  KASSERT((oid->oid_kind & CTLFLAG_DYING) == 0,
                                      ("%s found DYING node %p", __func__, oid));
                                  return (0);
                          }
                          lsp = SYSCTL_CHILDREN(oid);
                  } else if (indx == namelen) {
                          if ((oid->oid_kind & CTLFLAG_DORMANT) != 0)
                                  return (ENOENT);
                          *noid = oid;
                          if (nindx != NULL)
                                  *nindx = indx;
                          KASSERT((oid->oid_kind & CTLFLAG_DYING) == 0,
                              ("%s found DYING node %p", __func__, oid));
                          return (0);
                  } else {
                          return (ENOTDIR);
                  }
          }
          return (ENOENT);
  }
  
  /*
   * Traverse our tree, and find the right node, execute whatever it points
   * to, and return the resulting error code.
   */
  
  static int
  sysctl_root(SYSCTL_HANDLER_ARGS)
  {
          struct sysctl_oid *oid;
          struct rm_priotracker tracker;
          int error, indx, lvl;
  
          SYSCTL_RLOCK(&tracker);
  
          error = sysctl_find_oid(arg1, arg2, &oid, &indx, req);
          if (error)
                  goto out;
  
          if ((oid->oid_kind & CTLTYPE) == CTLTYPE_NODE) {
                  /*
                   * You can't call a sysctl when it's a node, but has
                   * no handler.  Inform the user that it's a node.
                   * The indx may or may not be the same as namelen.
                   */
                  if (oid->oid_handler == NULL) {
                          error = EISDIR;
                          goto out;
                  }
          }
  
          /* Is this sysctl writable? */
          if (req->newptr && !(oid->oid_kind & CTLFLAG_WR)) {
                  error = EPERM;
                  goto out;
          }
  
          KASSERT(req->td != NULL, ("sysctl_root(): req->td == NULL"));
  
  #ifdef CAPABILITY_MODE
          /*
           * If the process is in capability mode, then don't permit reading or
           * writing unless specifically granted for the node.
           */
          if (IN_CAPABILITY_MODE(req->td)) {
                  if ((req->oldptr && !(oid->oid_kind & CTLFLAG_CAPRD)) ||
                      (req->newptr && !(oid->oid_kind & CTLFLAG_CAPWR))) {
                          error = EPERM;
                          goto out;
                  }
          }
  #endif
  
          /* Is this sysctl sensitive to securelevels? */
          if (req->newptr && (oid->oid_kind & CTLFLAG_SECURE)) {
                  lvl = (oid->oid_kind & CTLMASK_SECURE) >> CTLSHIFT_SECURE;
                  error = securelevel_gt(req->td->td_ucred, lvl);
                  if (error)
                          goto out;
          }
  
          /* Is this sysctl writable by only privileged users? */
          if (req->newptr && !(oid->oid_kind & CTLFLAG_ANYBODY)) {
                  int priv;
  
                  if (oid->oid_kind & CTLFLAG_PRISON)
                          priv = PRIV_SYSCTL_WRITEJAIL;
  #ifdef VIMAGE
                  else if ((oid->oid_kind & CTLFLAG_VNET) &&
                       prison_owns_vnet(req->td->td_ucred))
                          priv = PRIV_SYSCTL_WRITEJAIL;
  #endif
                  else
                          priv = PRIV_SYSCTL_WRITE;
                  error = priv_check(req->td, priv);
                  if (error)
                          goto out;
          }
  
          if (!oid->oid_handler) {
                  error = EINVAL;
                  goto out;
          }
  
          if ((oid->oid_kind & CTLTYPE) == CTLTYPE_NODE) {
                  arg1 = (int *)arg1 + indx;
                  arg2 -= indx;
          } else {
                  arg1 = oid->oid_arg1;
                  arg2 = oid->oid_arg2;
          }
  #ifdef MAC
          error = mac_system_check_sysctl(req->td->td_ucred, oid, arg1, arg2,
              req);
          if (error != 0)
                  goto out;
  #endif
  #ifdef VIMAGE
          if ((oid->oid_kind & CTLFLAG_VNET) && arg1 != NULL)
                  arg1 = (void *)(curvnet->vnet_data_base + (uintptr_t)arg1);
  #endif
          error = sysctl_root_handler_locked(oid, arg1, arg2, req, &tracker);
  
  out:
          SYSCTL_RUNLOCK(&tracker);
          return (error);
  }
  
  #ifndef _SYS_SYSPROTO_H_
  struct sysctl_args {
          int     *name;
          u_int   namelen;
          void    *old;
          size_t  *oldlenp;
          void    *new;
          size_t  newlen;
  };
  #endif
  int
  sys___sysctl(struct thread *td, struct sysctl_args *uap)
  {
          int error, i, name[CTL_MAXNAME];
          size_t j;
  
          if (uap->namelen > CTL_MAXNAME || uap->namelen < 2)
                  return (EINVAL);
  
          error = copyin(uap->name, &name, uap->namelen * sizeof(int));
          if (error)
                  return (error);
  
          error = userland_sysctl(td, name, uap->namelen,
                  uap->old, uap->oldlenp, 0,
                  uap->new, uap->newlen, &j, 0);
          if (error && error != ENOMEM)
                  return (error);
          if (uap->oldlenp) {
                  i = copyout(&j, uap->oldlenp, sizeof(j));
                  if (i)
                          return (i);
          }
          return (error);
  }
  
  int
  kern___sysctlbyname(struct thread *td, const char *oname, size_t namelen,
      void *old, size_t *oldlenp, void *new, size_t newlen, size_t *retval,
      int flags, bool inkernel)
  {
          int oid[CTL_MAXNAME];
          char namebuf[16];
          char *name;
          size_t oidlen;
          int error;
  
          if (namelen > MAXPATHLEN || namelen == 0)
                  return (EINVAL);
          name = namebuf;
          if (namelen > sizeof(namebuf))
                  name = malloc(namelen, M_SYSCTL, M_WAITOK);
          error = copyin(oname, name, namelen);
          if (error != 0)
                  goto out;
  
          oid[0] = CTL_SYSCTL;
          oid[1] = CTL_SYSCTL_NAME2OID;
          oidlen = sizeof(oid);
          error = kernel_sysctl(td, oid, 2, oid, &oidlen, (void *)name, namelen,
              retval, flags);
          if (error != 0)
                  goto out;
          error = userland_sysctl(td, oid, *retval / sizeof(int), old, oldlenp,
              inkernel, new, newlen, retval, flags);
  
  out:
          if (namelen > sizeof(namebuf))
                  free(name, M_SYSCTL);
          return (error);
  }
  
  #ifndef _SYS_SYSPROTO_H_
  struct __sysctlbyname_args {
          const char      *name;
          size_t  namelen;
          void    *old;
          size_t  *oldlenp;
          void    *new;
          size_t  newlen;
  };
  #endif
  int
  sys___sysctlbyname(struct thread *td, struct __sysctlbyname_args *uap)
  {
          size_t rv;
          int error;
  
          error = kern___sysctlbyname(td, uap->name, uap->namelen, uap->old,
              uap->oldlenp, uap->new, uap->newlen, &rv, 0, 0);
          if (error != 0)
                  return (error);
          if (uap->oldlenp != NULL)
                  error = copyout(&rv, uap->oldlenp, sizeof(rv));
  
          return (error);
  }
  
  /*
   * This is used from various compatibility syscalls too.  That's why name
   * must be in kernel space.
   */
  int
  userland_sysctl(struct thread *td, int *name, u_int namelen, void *old,
      size_t *oldlenp, int inkernel, const void *new, size_t newlen,
      size_t *retval, int flags)
  {
          int error = 0, memlocked;
          struct sysctl_req req;
  
          bzero(&req, sizeof req);
  
          req.td = td;
          req.flags = flags;
  
          if (oldlenp) {
                  if (inkernel) {
                          req.oldlen = *oldlenp;
                  } else {
                          error = copyin(oldlenp, &req.oldlen, sizeof(*oldlenp));
                          if (error)
                                  return (error);
                  }
          }
          req.validlen = req.oldlen;
          req.oldptr = old;
  
          if (new != NULL) {
                  req.newlen = newlen;
                  req.newptr = new;
          }
  
          req.oldfunc = sysctl_old_user;
          req.newfunc = sysctl_new_user;
          req.lock = REQ_UNWIRED;
  
  #ifdef KTRACE
          if (KTRPOINT(curthread, KTR_SYSCTL))
                  ktrsysctl(name, namelen);
  #endif
          memlocked = 0;
          if (req.oldptr && req.oldlen > 4 * PAGE_SIZE) {
                  memlocked = 1;
                  sx_xlock(&sysctlmemlock);
          }
          CURVNET_SET(TD_TO_VNET(td));
  
          for (;;) {
                  req.oldidx = 0;
                  req.newidx = 0;
                  error = sysctl_root(0, name, namelen, &req);
                  if (error != EAGAIN)
                          break;
                  kern_yield(PRI_USER);
          }
  
          CURVNET_RESTORE();
  
          if (req.lock == REQ_WIRED && req.validlen > 0)
                  vsunlock(req.oldptr, req.validlen);
          if (memlocked)
                  sx_xunlock(&sysctlmemlock);
  
          if (error && error != ENOMEM)
                  return (error);
  
          if (retval) {
                  if (req.oldptr && req.oldidx > req.validlen)
                          *retval = req.validlen;
                  else
                          *retval = req.oldidx;
          }
          return (error);
  }
  
  /*
   * Drain into a sysctl struct.  The user buffer should be wired if a page
   * fault would cause issue.
   */
  static int
  sbuf_sysctl_drain(void *arg, const char *data, int len)
  {
          struct sysctl_req *req = arg;
          int error;
  
          error = SYSCTL_OUT(req, data, len);
          KASSERT(error >= 0, ("Got unexpected negative value %d", error));
          return (error == 0 ? len : -error);
  }
  
  struct sbuf *
  sbuf_new_for_sysctl(struct sbuf *s, char *buf, int length,
      struct sysctl_req *req)
  {
  
          /* Supply a default buffer size if none given. */
          if (buf == NULL && length == 0)
                  length = 64;
          s = sbuf_new(s, buf, length, SBUF_FIXEDLEN | SBUF_INCLUDENUL);
          sbuf_set_drain(s, sbuf_sysctl_drain, req);
          return (s);
  }
  
  #ifdef DDB
  
  /* The current OID the debugger is working with */
  static struct sysctl_oid *g_ddb_oid;
  
  /* The current flags specified by the user */
  static int g_ddb_sysctl_flags;
  
  /* Check to see if the last sysctl printed */
  static int g_ddb_sysctl_printed;
  
  static const int ctl_sign[CTLTYPE+1] = {
          [CTLTYPE_INT] = 1,
          [CTLTYPE_LONG] = 1,
          [CTLTYPE_S8] = 1,
          [CTLTYPE_S16] = 1,
          [CTLTYPE_S32] = 1,
          [CTLTYPE_S64] = 1,
  };
  
  static const int ctl_size[CTLTYPE+1] = {
          [CTLTYPE_INT] = sizeof(int),
          [CTLTYPE_UINT] = sizeof(u_int),
          [CTLTYPE_LONG] = sizeof(long),
          [CTLTYPE_ULONG] = sizeof(u_long),
          [CTLTYPE_S8] = sizeof(int8_t),
          [CTLTYPE_S16] = sizeof(int16_t),
          [CTLTYPE_S32] = sizeof(int32_t),
          [CTLTYPE_S64] = sizeof(int64_t),
          [CTLTYPE_U8] = sizeof(uint8_t),
          [CTLTYPE_U16] = sizeof(uint16_t),
          [CTLTYPE_U32] = sizeof(uint32_t),
          [CTLTYPE_U64] = sizeof(uint64_t),
  };
  
  #define DB_SYSCTL_NAME_ONLY     0x001   /* Compare with -N */
  #define DB_SYSCTL_VALUE_ONLY    0x002   /* Compare with -n */
  #define DB_SYSCTL_OPAQUE        0x004   /* Compare with -o */
  #define DB_SYSCTL_HEX           0x008   /* Compare with -x */
  
  #define DB_SYSCTL_SAFE_ONLY     0x100   /* Only simple types */
  
  static const char db_sysctl_modifs[] = {
          'N', 'n', 'o', 'x',
  };
  
  static const int db_sysctl_modif_values[] = {
          DB_SYSCTL_NAME_ONLY, DB_SYSCTL_VALUE_ONLY,
          DB_SYSCTL_OPAQUE, DB_SYSCTL_HEX,
  };
  
  /* Handlers considered safe to print while recursing */
  static int (* const db_safe_handlers[])(SYSCTL_HANDLER_ARGS) = {
          sysctl_handle_bool,
          sysctl_handle_8,
          sysctl_handle_16,
          sysctl_handle_32,
          sysctl_handle_64,
          sysctl_handle_int,
          sysctl_handle_long,
          sysctl_handle_string,
          sysctl_handle_opaque,
  };
  
  /*
   * Use in place of sysctl_old_kernel to print sysctl values.
   *
   * Compare to the output handling in show_var from sbin/sysctl/sysctl.c
   */
  static int
  sysctl_old_ddb(struct sysctl_req *req, const void *ptr, size_t len)
  {
          const u_char *val, *p;
          const char *sep1;
          size_t intlen, slen;
          uintmax_t umv;
          intmax_t mv;
          int sign, ctltype, hexlen, xflag, error;
  
          /* Suppress false-positive GCC uninitialized variable warnings */
          mv = 0;
          umv = 0;
  
          slen = len;
          val = p = ptr;
  
          if (ptr == NULL) {
                  error = 0;
                  goto out;
          }
  
          /* We are going to print */
          g_ddb_sysctl_printed = 1;
  
          xflag = g_ddb_sysctl_flags & DB_SYSCTL_HEX;
  
          ctltype = (g_ddb_oid->oid_kind & CTLTYPE);
          sign = ctl_sign[ctltype];
          intlen = ctl_size[ctltype];
  
          switch (ctltype) {
          case CTLTYPE_NODE:
          case CTLTYPE_STRING:
                  db_printf("%.*s", (int) len, (const char *) p);
                  error = 0;
                  goto out;
  
          case CTLTYPE_INT:
          case CTLTYPE_UINT:
          case CTLTYPE_LONG:
          case CTLTYPE_ULONG:
          case CTLTYPE_S8:
          case CTLTYPE_S16:
          case CTLTYPE_S32:
          case CTLTYPE_S64:
          case CTLTYPE_U8:
          case CTLTYPE_U16:
          case CTLTYPE_U32:
          case CTLTYPE_U64:
                  hexlen = 2 + (intlen * CHAR_BIT + 3) / 4;
                  sep1 = "";
                  while (len >= intlen) {
                          switch (ctltype) {
                          case CTLTYPE_INT:
                          case CTLTYPE_UINT:
                                  umv = *(const u_int *)p;
                                  mv = *(const int *)p;
                                  break;
                          case CTLTYPE_LONG:
                          case CTLTYPE_ULONG:
                                  umv = *(const u_long *)p;
                                  mv = *(const long *)p;
                                  break;
                          case CTLTYPE_S8:
                          case CTLTYPE_U8:
                                  umv = *(const uint8_t *)p;
                                  mv = *(const int8_t *)p;
                                  break;
                          case CTLTYPE_S16:
                          case CTLTYPE_U16:
                                  umv = *(const uint16_t *)p;
                                  mv = *(const int16_t *)p;
                                  break;
                          case CTLTYPE_S32:
                          case CTLTYPE_U32:
                                  umv = *(const uint32_t *)p;
                                  mv = *(const int32_t *)p;
                                  break;
                          case CTLTYPE_S64:
                          case CTLTYPE_U64:
                                  umv = *(const uint64_t *)p;
                                  mv = *(const int64_t *)p;
                                  break;
                          }
  
                          db_printf("%s", sep1);
                          if (xflag)
                                  db_printf("%#0*jx", hexlen, umv);
                          else if (!sign)
                                  db_printf("%ju", umv);
                          else if (g_ddb_oid->oid_fmt[1] == 'K') {
                                  /* Kelvins are currently unsupported. */
                                  error = EOPNOTSUPP;
                                  goto out;
                          } else
                                  db_printf("%jd", mv);
  
                          sep1 = " ";
                          len -= intlen;
                          p += intlen;
                  }
                  error = 0;
                  goto out;
  
          case CTLTYPE_OPAQUE:
                  /* TODO: Support struct functions. */
  
                  /* FALLTHROUGH */
          default:
                  db_printf("Format:%s Length:%zu Dump:0x",
                      g_ddb_oid->oid_fmt, len);
                  while (len-- && (xflag || p < val + 16))
                          db_printf("%02x", *p++);
                  if (!xflag && len > 16)
                          db_printf("...");
                  error = 0;
                  goto out;
          }
  
  out:
          req->oldidx += slen;
          return (error);
  }
  
  /*
   * Avoid setting new sysctl values from the debugger
   */
  static int
  sysctl_new_ddb(struct sysctl_req *req, void *p, size_t l)
  {
  
          if (!req->newptr)
                  return (0);
  
          /* Changing sysctls from the debugger is currently unsupported */
          return (EPERM);
  }
  
  /*
   * Run a sysctl handler with the DDB oldfunc and newfunc attached.
   * Instead of copying any output to a buffer we'll dump it right to
   * the console.
   */
  static int
  db_sysctl(struct sysctl_oid *oidp, int *name, u_int namelen,
      void *old, size_t *oldlenp, size_t *retval, int flags)
  {
          struct sysctl_req req;
          int error;
  
          /* Setup the request */
          bzero(&req, sizeof req);
          req.td = kdb_thread;
          req.oldfunc = sysctl_old_ddb;
          req.newfunc = sysctl_new_ddb;
          req.lock = REQ_UNWIRED;
          if (oldlenp) {
                  req.oldlen = *oldlenp;
          }
          req.validlen = req.oldlen;
          if (old) {
                  req.oldptr = old;
          }
  
          /* Setup our globals for sysctl_old_ddb */
          g_ddb_oid = oidp;
          g_ddb_sysctl_flags = flags;
          g_ddb_sysctl_printed = 0;
  
          error = sysctl_root(0, name, namelen, &req);
  
          /* Reset globals */
          g_ddb_oid = NULL;
          g_ddb_sysctl_flags = 0;
  
          if (retval) {
                  if (req.oldptr && req.oldidx > req.validlen)
                          *retval = req.validlen;
                  else
                          *retval = req.oldidx;
          }
          return (error);
  }
  
  /*
   * Show a sysctl's name
   */
  static void
  db_show_oid_name(int *oid, size_t nlen)
  {
          struct sysctl_oid *oidp;
          int qoid[CTL_MAXNAME+2];
          int error;
  
          qoid[0] = 0;
          memcpy(qoid + 2, oid, nlen * sizeof(int));
          qoid[1] = 1;
  
          error = sysctl_find_oid(qoid, nlen + 2, &oidp, NULL, NULL);
          if (error)
                  db_error("sysctl name oid");
  
          error = db_sysctl(oidp, qoid, nlen + 2, NULL, NULL, NULL, 0);
          if (error)
                  db_error("sysctl name");
  }
  
  /*
   * Check to see if an OID is safe to print from ddb.
   */
  static bool
  db_oid_safe(const struct sysctl_oid *oidp)
  {
          for (unsigned int i = 0; i < nitems(db_safe_handlers); ++i) {
                  if (oidp->oid_handler == db_safe_handlers[i])
                          return (true);
          }
  
          return (false);
  }
  
  /*
   * Show a sysctl at a specific OID
   * Compare to the input handling in show_var from sbin/sysctl/sysctl.c
   */
  static int
  db_show_oid(struct sysctl_oid *oidp, int *oid, size_t nlen, int flags)
  {
          int error, xflag, oflag, Nflag, nflag;
          size_t len;
  
          xflag = flags & DB_SYSCTL_HEX;
          oflag = flags & DB_SYSCTL_OPAQUE;
          nflag = flags & DB_SYSCTL_VALUE_ONLY;
          Nflag = flags & DB_SYSCTL_NAME_ONLY;
  
          if ((oidp->oid_kind & CTLTYPE) == CTLTYPE_OPAQUE &&
              (!xflag && !oflag))
                  return (0);
  
          if (Nflag) {
                  db_show_oid_name(oid, nlen);
                  error = 0;
                  goto out;
          }
  
          if (!nflag) {
                  db_show_oid_name(oid, nlen);
                  db_printf(": ");
          }
  
          if ((flags & DB_SYSCTL_SAFE_ONLY) && !db_oid_safe(oidp)) {
                  db_printf("Skipping, unsafe to print while recursing.");
                  error = 0;
                  goto out;
          }
  
          /* Try once, and ask about the size */
          len = 0;
          error = db_sysctl(oidp, oid, nlen,
              NULL, NULL, &len, flags);
          if (error)
                  goto out;
  
          if (!g_ddb_sysctl_printed)
                  /* Lie about the size */
                  error = db_sysctl(oidp, oid, nlen,
                      (void *) 1, &len, NULL, flags);
  
  out:
          db_printf("\n");
          return (error);
  }
  
  /*
   * Show all sysctls under a specific OID
   * Compare to sysctl_all from sbin/sysctl/sysctl.c
   */
  static int
  db_show_sysctl_all(int *oid, size_t len, int flags)
  {
          struct sysctl_oid *oidp;
          int name1[CTL_MAXNAME + 2], name2[CTL_MAXNAME + 2];
          size_t l1, l2;
  
          name1[0] = CTL_SYSCTL;
          name1[1] = CTL_SYSCTL_NEXT;
          l1 = 2;
          if (len) {
                  memcpy(name1 + 2, oid, len * sizeof(int));
                  l1 += len;
          } else {
                  name1[2] = CTL_KERN;
                  l1++;
          }
          for (;;) {
                  int i, error;
  
                  l2 = sizeof(name2);
                  error = kernel_sysctl(kdb_thread, name1, l1,
                      name2, &l2, NULL, 0, &l2, 0);
                  if (error != 0) {
                          if (error == ENOENT)
                                  return (0);
                          else
                                  db_error("sysctl(next)");
                  }
  
                  l2 /= sizeof(int);
  
                  if (l2 < (unsigned int)len)
                          return (0);
  
                  for (i = 0; i < len; i++)
                          if (name2[i] != oid[i])
                                  return (0);
  
                  /* Find the OID in question */
                  error = sysctl_find_oid(name2, l2, &oidp, NULL, NULL);
                  if (error)
                          return (error);
  
                  i = db_show_oid(oidp, name2, l2, flags | DB_SYSCTL_SAFE_ONLY);
  
                  if (db_pager_quit)
                          return (0);
  
                  memcpy(name1+2, name2, l2 * sizeof(int));
                  l1 = 2 + l2;
          }
  }
  
  /*
   * Show a sysctl by its user facing string
   */
  static int
  db_sysctlbyname(char *name, int flags)
  {
          struct sysctl_oid *oidp;
          int oid[CTL_MAXNAME];
          int error, nlen;
  
          error = name2oid(name, oid, &nlen, &oidp);
          if (error) {
                  return (error);
          }
  
          if ((oidp->oid_kind & CTLTYPE) == CTLTYPE_NODE) {
                  db_show_sysctl_all(oid, nlen, flags);
          } else {
                  error = db_show_oid(oidp, oid, nlen, flags);
          }
  
          return (error);
  }
  
  static void
  db_sysctl_cmd_usage(void)
  {
          db_printf(
              " sysctl [/Nnox] <sysctl>                                       \n"
              "                                                               \n"
              " <sysctl> The name of the sysctl to show.                      \n"
              "                                                               \n"
              " Show a sysctl by hooking into SYSCTL_IN and SYSCTL_OUT.       \n"
              " This will work for most sysctls, but should not be used       \n"
              " with sysctls that are known to malloc.                        \n"
              "                                                               \n"
              " While recursing any \"unsafe\" sysctls will be skipped.       \n"
              " Call sysctl directly on the sysctl to try printing the        \n"
              " skipped sysctl. This is unsafe and may make the ddb           \n"
              " session unusable.                                             \n"
              "                                                               \n"
              " Arguments:                                                    \n"
              "   /N      Display only the name of the sysctl.                \n"
              "   /n      Display only the value of the sysctl.               \n"
              "   /o      Display opaque values.                              \n"
              "   /x      Display the sysctl in hex.                          \n"
              "                                                               \n"
              "For example:                                                   \n"
              "sysctl vm.v_free_min                                           \n"
              "vn.v_free_min: 12669                                           \n"
              );
  }
  
  /*
   * Show a specific sysctl similar to sysctl (8).
   */
  DB_COMMAND_FLAGS(sysctl, db_sysctl_cmd, CS_OWN)
  {
          char name[TOK_STRING_SIZE];
          int error, i, t, flags;
  
          /* Parse the modifiers */
          t = db_read_token();
          if (t == tSLASH || t == tMINUS) {
                  t = db_read_token();
                  if (t != tIDENT) {
                          db_printf("Bad modifier\n");
                          error = EINVAL;
                          goto out;
                  }
                  db_strcpy(modif, db_tok_string);
          }
          else {
                  db_unread_token(t);
                  modif[0] = '\0';
          }
  
          flags = 0;
          for (i = 0; i < nitems(db_sysctl_modifs); i++) {
                  if (strchr(modif, db_sysctl_modifs[i])) {
                          flags |= db_sysctl_modif_values[i];
                  }
          }
  
          /* Parse the sysctl names */
          t = db_read_token();
          if (t != tIDENT) {
                  db_printf("Need sysctl name\n");
                  error = EINVAL;
                  goto out;
          }
  
          /* Copy the name into a temporary buffer */
          db_strcpy(name, db_tok_string);
  
          /* Ensure there is no trailing cruft */
          t = db_read_token();
          if (t != tEOL) {
                  db_printf("Unexpected sysctl argument\n");
                  error = EINVAL;
                  goto out;
          }
  
          error = db_sysctlbyname(name, flags);
          if (error == ENOENT) {
                  db_printf("unknown oid: '%s'\n", db_tok_string);
                  goto out;
          } else if (error) {
                  db_printf("%s: error: %d\n", db_tok_string, error);
                  goto out;
          }
  
  out:
          /* Ensure we eat all of our text */
          db_flush_lex();
  
          if (error == EINVAL) {
                  db_sysctl_cmd_usage();
          }
  }
  
  #endif /* DDB */

Cache object: de31e234494ab6528a61f7d2655964d8