MFC r258366:

[FreeBSD/stable/10.git] / sys / vm / vm_map.c

/*-
 * Copyright (c) 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * The Mach Operating System project at Carnegie-Mellon University.
 *
 * 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.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      from: @(#)vm_map.c      8.3 (Berkeley) 1/12/94
 *
 *
 * Copyright (c) 1987, 1990 Carnegie-Mellon University.
 * All rights reserved.
 *
 * Authors: Avadis Tevanian, Jr., Michael Wayne Young
 *
 * Permission to use, copy, modify and distribute this software and
 * its documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 *
 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 *
 * Carnegie Mellon requests users of this software to return to
 *
 *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
 *  School of Computer Science
 *  Carnegie Mellon University
 *  Pittsburgh PA 15213-3890
 *
 * any improvements or extensions that they make and grant Carnegie the
 * rights to redistribute these changes.
 */

/*
 *      Virtual memory mapping module.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/vmmeter.h>
#include <sys/mman.h>
#include <sys/vnode.h>
#include <sys/racct.h>
#include <sys/resourcevar.h>
#include <sys/rwlock.h>
#include <sys/file.h>
#include <sys/sysctl.h>
#include <sys/sysent.h>
#include <sys/shm.h>

#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_page.h>
#include <vm/vm_object.h>
#include <vm/vm_pager.h>
#include <vm/vm_kern.h>
#include <vm/vm_extern.h>
#include <vm/vnode_pager.h>
#include <vm/swap_pager.h>
#include <vm/uma.h>

/*
 *      Virtual memory maps provide for the mapping, protection,
 *      and sharing of virtual memory objects.  In addition,
 *      this module provides for an efficient virtual copy of
 *      memory from one map to another.
 *
 *      Synchronization is required prior to most operations.
 *
 *      Maps consist of an ordered doubly-linked list of simple
 *      entries; a self-adjusting binary search tree of these
 *      entries is used to speed up lookups.
 *
 *      Since portions of maps are specified by start/end addresses,
 *      which may not align with existing map entries, all
 *      routines merely "clip" entries to these start/end values.
 *      [That is, an entry is split into two, bordering at a
 *      start or end value.]  Note that these clippings may not
 *      always be necessary (as the two resulting entries are then
 *      not changed); however, the clipping is done for convenience.
 *
 *      As mentioned above, virtual copy operations are performed
 *      by copying VM object references from one map to
 *      another, and then marking both regions as copy-on-write.
 */

static struct mtx map_sleep_mtx;
static uma_zone_t mapentzone;
static uma_zone_t kmapentzone;
static uma_zone_t mapzone;
static uma_zone_t vmspace_zone;
static int vmspace_zinit(void *mem, int size, int flags);
static int vm_map_zinit(void *mem, int ize, int flags);
static void _vm_map_init(vm_map_t map, pmap_t pmap, vm_offset_t min,
    vm_offset_t max);
static void vm_map_entry_deallocate(vm_map_entry_t entry, boolean_t system_map);
static void vm_map_entry_dispose(vm_map_t map, vm_map_entry_t entry);
#ifdef INVARIANTS
static void vm_map_zdtor(void *mem, int size, void *arg);
static void vmspace_zdtor(void *mem, int size, void *arg);
#endif

#define ENTRY_CHARGED(e) ((e)->cred != NULL || \
    ((e)->object.vm_object != NULL && (e)->object.vm_object->cred != NULL && \
     !((e)->eflags & MAP_ENTRY_NEEDS_COPY)))

/* 
 * PROC_VMSPACE_{UN,}LOCK() can be a noop as long as vmspaces are type
 * stable.
 */
#define PROC_VMSPACE_LOCK(p) do { } while (0)
#define PROC_VMSPACE_UNLOCK(p) do { } while (0)

/*
 *      VM_MAP_RANGE_CHECK:     [ internal use only ]
 *
 *      Asserts that the starting and ending region
 *      addresses fall within the valid range of the map.
 */
#define VM_MAP_RANGE_CHECK(map, start, end)             \
                {                                       \
                if (start < vm_map_min(map))            \
                        start = vm_map_min(map);        \
                if (end > vm_map_max(map))              \
                        end = vm_map_max(map);          \
                if (start > end)                        \
                        start = end;                    \
                }

/*
 *      vm_map_startup:
 *
 *      Initialize the vm_map module.  Must be called before
 *      any other vm_map routines.
 *
 *      Map and entry structures are allocated from the general
 *      purpose memory pool with some exceptions:
 *
 *      - The kernel map and kmem submap are allocated statically.
 *      - Kernel map entries are allocated out of a static pool.
 *
 *      These restrictions are necessary since malloc() uses the
 *      maps and requires map entries.
 */

void
vm_map_startup(void)
{
        mtx_init(&map_sleep_mtx, "vm map sleep mutex", NULL, MTX_DEF);
        mapzone = uma_zcreate("MAP", sizeof(struct vm_map), NULL,
#ifdef INVARIANTS
            vm_map_zdtor,
#else
            NULL,
#endif
            vm_map_zinit, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
        uma_prealloc(mapzone, MAX_KMAP);
        kmapentzone = uma_zcreate("KMAP ENTRY", sizeof(struct vm_map_entry),
            NULL, NULL, NULL, NULL, UMA_ALIGN_PTR,
            UMA_ZONE_MTXCLASS | UMA_ZONE_VM);
        mapentzone = uma_zcreate("MAP ENTRY", sizeof(struct vm_map_entry),
            NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
        vmspace_zone = uma_zcreate("VMSPACE", sizeof(struct vmspace), NULL,
#ifdef INVARIANTS
            vmspace_zdtor,
#else
            NULL,
#endif
            vmspace_zinit, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
}

static int
vmspace_zinit(void *mem, int size, int flags)
{
        struct vmspace *vm;

        vm = (struct vmspace *)mem;

        vm->vm_map.pmap = NULL;
        (void)vm_map_zinit(&vm->vm_map, sizeof(vm->vm_map), flags);
        PMAP_LOCK_INIT(vmspace_pmap(vm));
        return (0);
}

static int
vm_map_zinit(void *mem, int size, int flags)
{
        vm_map_t map;

        map = (vm_map_t)mem;
        memset(map, 0, sizeof(*map));
        mtx_init(&map->system_mtx, "vm map (system)", NULL, MTX_DEF | MTX_DUPOK);
        sx_init(&map->lock, "vm map (user)");
        return (0);
}

#ifdef INVARIANTS
static void
vmspace_zdtor(void *mem, int size, void *arg)
{
        struct vmspace *vm;

        vm = (struct vmspace *)mem;

        vm_map_zdtor(&vm->vm_map, sizeof(vm->vm_map), arg);
}
static void
vm_map_zdtor(void *mem, int size, void *arg)
{
        vm_map_t map;

        map = (vm_map_t)mem;
        KASSERT(map->nentries == 0,
            ("map %p nentries == %d on free.",
            map, map->nentries));
        KASSERT(map->size == 0,
            ("map %p size == %lu on free.",
            map, (unsigned long)map->size));
}
#endif  /* INVARIANTS */

/*
 * Allocate a vmspace structure, including a vm_map and pmap,
 * and initialize those structures.  The refcnt is set to 1.
 *
 * If 'pinit' is NULL then the embedded pmap is initialized via pmap_pinit().
 */
struct vmspace *
vmspace_alloc(vm_offset_t min, vm_offset_t max, pmap_pinit_t pinit)
{
        struct vmspace *vm;

        vm = uma_zalloc(vmspace_zone, M_WAITOK);

        KASSERT(vm->vm_map.pmap == NULL, ("vm_map.pmap must be NULL"));

        if (pinit == NULL)
                pinit = &pmap_pinit;

        if (!pinit(vmspace_pmap(vm))) {
                uma_zfree(vmspace_zone, vm);
                return (NULL);
        }
        CTR1(KTR_VM, "vmspace_alloc: %p", vm);
        _vm_map_init(&vm->vm_map, vmspace_pmap(vm), min, max);
        vm->vm_refcnt = 1;
        vm->vm_shm = NULL;
        vm->vm_swrss = 0;
        vm->vm_tsize = 0;
        vm->vm_dsize = 0;
        vm->vm_ssize = 0;
        vm->vm_taddr = 0;
        vm->vm_daddr = 0;
        vm->vm_maxsaddr = 0;
        return (vm);
}

static void
vmspace_container_reset(struct proc *p)
{

#ifdef RACCT
        PROC_LOCK(p);
        racct_set(p, RACCT_DATA, 0);
        racct_set(p, RACCT_STACK, 0);
        racct_set(p, RACCT_RSS, 0);
        racct_set(p, RACCT_MEMLOCK, 0);
        racct_set(p, RACCT_VMEM, 0);
        PROC_UNLOCK(p);
#endif
}

static inline void
vmspace_dofree(struct vmspace *vm)
{

        CTR1(KTR_VM, "vmspace_free: %p", vm);

        /*
         * Make sure any SysV shm is freed, it might not have been in
         * exit1().
         */
        shmexit(vm);

        /*
         * Lock the map, to wait out all other references to it.
         * Delete all of the mappings and pages they hold, then call
         * the pmap module to reclaim anything left.
         */
        (void)vm_map_remove(&vm->vm_map, vm->vm_map.min_offset,
            vm->vm_map.max_offset);

        pmap_release(vmspace_pmap(vm));
        vm->vm_map.pmap = NULL;
        uma_zfree(vmspace_zone, vm);
}

void
vmspace_free(struct vmspace *vm)
{

        if (vm->vm_refcnt == 0)
                panic("vmspace_free: attempt to free already freed vmspace");

        if (atomic_fetchadd_int(&vm->vm_refcnt, -1) == 1)
                vmspace_dofree(vm);
}

void
vmspace_exitfree(struct proc *p)
{
        struct vmspace *vm;

        PROC_VMSPACE_LOCK(p);
        vm = p->p_vmspace;
        p->p_vmspace = NULL;
        PROC_VMSPACE_UNLOCK(p);
        KASSERT(vm == &vmspace0, ("vmspace_exitfree: wrong vmspace"));
        vmspace_free(vm);
}

void
vmspace_exit(struct thread *td)
{
        int refcnt;
        struct vmspace *vm;
        struct proc *p;

        /*
         * Release user portion of address space.
         * This releases references to vnodes,
         * which could cause I/O if the file has been unlinked.
         * Need to do this early enough that we can still sleep.
         *
         * The last exiting process to reach this point releases as
         * much of the environment as it can. vmspace_dofree() is the
         * slower fallback in case another process had a temporary
         * reference to the vmspace.
         */

        p = td->td_proc;
        vm = p->p_vmspace;
        atomic_add_int(&vmspace0.vm_refcnt, 1);
        do {
                refcnt = vm->vm_refcnt;
                if (refcnt > 1 && p->p_vmspace != &vmspace0) {
                        /* Switch now since other proc might free vmspace */
                        PROC_VMSPACE_LOCK(p);
                        p->p_vmspace = &vmspace0;
                        PROC_VMSPACE_UNLOCK(p);
                        pmap_activate(td);
                }
        } while (!atomic_cmpset_int(&vm->vm_refcnt, refcnt, refcnt - 1));
        if (refcnt == 1) {
                if (p->p_vmspace != vm) {
                        /* vmspace not yet freed, switch back */
                        PROC_VMSPACE_LOCK(p);
                        p->p_vmspace = vm;
                        PROC_VMSPACE_UNLOCK(p);
                        pmap_activate(td);
                }
                pmap_remove_pages(vmspace_pmap(vm));
                /* Switch now since this proc will free vmspace */
                PROC_VMSPACE_LOCK(p);
                p->p_vmspace = &vmspace0;
                PROC_VMSPACE_UNLOCK(p);
                pmap_activate(td);
                vmspace_dofree(vm);
        }
        vmspace_container_reset(p);
}

/* Acquire reference to vmspace owned by another process. */

struct vmspace *
vmspace_acquire_ref(struct proc *p)
{
        struct vmspace *vm;
        int refcnt;

        PROC_VMSPACE_LOCK(p);
        vm = p->p_vmspace;
        if (vm == NULL) {
                PROC_VMSPACE_UNLOCK(p);
                return (NULL);
        }
        do {
                refcnt = vm->vm_refcnt;
                if (refcnt <= 0) {      /* Avoid 0->1 transition */
                        PROC_VMSPACE_UNLOCK(p);
                        return (NULL);
                }
        } while (!atomic_cmpset_int(&vm->vm_refcnt, refcnt, refcnt + 1));
        if (vm != p->p_vmspace) {
                PROC_VMSPACE_UNLOCK(p);
                vmspace_free(vm);
                return (NULL);
        }
        PROC_VMSPACE_UNLOCK(p);
        return (vm);
}

void
_vm_map_lock(vm_map_t map, const char *file, int line)
{

        if (map->system_map)
                mtx_lock_flags_(&map->system_mtx, 0, file, line);
        else
                sx_xlock_(&map->lock, file, line);
        map->timestamp++;
}

static void
vm_map_process_deferred(void)
{
        struct thread *td;
        vm_map_entry_t entry, next;
        vm_object_t object;

        td = curthread;
        entry = td->td_map_def_user;
        td->td_map_def_user = NULL;
        while (entry != NULL) {
                next = entry->next;
                if ((entry->eflags & MAP_ENTRY_VN_WRITECNT) != 0) {
                        /*
                         * Decrement the object's writemappings and
                         * possibly the vnode's v_writecount.
                         */
                        KASSERT((entry->eflags & MAP_ENTRY_IS_SUB_MAP) == 0,
                            ("Submap with writecount"));
                        object = entry->object.vm_object;
                        KASSERT(object != NULL, ("No object for writecount"));
                        vnode_pager_release_writecount(object, entry->start,
                            entry->end);
                }
                vm_map_entry_deallocate(entry, FALSE);
                entry = next;
        }
}

void
_vm_map_unlock(vm_map_t map, const char *file, int line)
{

        if (map->system_map)
                mtx_unlock_flags_(&map->system_mtx, 0, file, line);
        else {
                sx_xunlock_(&map->lock, file, line);
                vm_map_process_deferred();
        }
}

void
_vm_map_lock_read(vm_map_t map, const char *file, int line)
{

        if (map->system_map)
                mtx_lock_flags_(&map->system_mtx, 0, file, line);
        else
                sx_slock_(&map->lock, file, line);
}

void
_vm_map_unlock_read(vm_map_t map, const char *file, int line)
{

        if (map->system_map)
                mtx_unlock_flags_(&map->system_mtx, 0, file, line);
        else {
                sx_sunlock_(&map->lock, file, line);
                vm_map_process_deferred();
        }
}

int
_vm_map_trylock(vm_map_t map, const char *file, int line)
{
        int error;

        error = map->system_map ?
            !mtx_trylock_flags_(&map->system_mtx, 0, file, line) :
            !sx_try_xlock_(&map->lock, file, line);
        if (error == 0)
                map->timestamp++;
        return (error == 0);
}

int
_vm_map_trylock_read(vm_map_t map, const char *file, int line)
{
        int error;

        error = map->system_map ?
            !mtx_trylock_flags_(&map->system_mtx, 0, file, line) :
            !sx_try_slock_(&map->lock, file, line);
        return (error == 0);
}

/*
 *      _vm_map_lock_upgrade:   [ internal use only ]
 *
 *      Tries to upgrade a read (shared) lock on the specified map to a write
 *      (exclusive) lock.  Returns the value "0" if the upgrade succeeds and a
 *      non-zero value if the upgrade fails.  If the upgrade fails, the map is
 *      returned without a read or write lock held.
 *
 *      Requires that the map be read locked.
 */
int
_vm_map_lock_upgrade(vm_map_t map, const char *file, int line)
{
        unsigned int last_timestamp;

        if (map->system_map) {
                mtx_assert_(&map->system_mtx, MA_OWNED, file, line);
        } else {
                if (!sx_try_upgrade_(&map->lock, file, line)) {
                        last_timestamp = map->timestamp;
                        sx_sunlock_(&map->lock, file, line);
                        vm_map_process_deferred();
                        /*
                         * If the map's timestamp does not change while the
                         * map is unlocked, then the upgrade succeeds.
                         */
                        sx_xlock_(&map->lock, file, line);
                        if (last_timestamp != map->timestamp) {
                                sx_xunlock_(&map->lock, file, line);
                                return (1);
                        }
                }
        }
        map->timestamp++;
        return (0);
}

void
_vm_map_lock_downgrade(vm_map_t map, const char *file, int line)
{

        if (map->system_map) {
                mtx_assert_(&map->system_mtx, MA_OWNED, file, line);
        } else
                sx_downgrade_(&map->lock, file, line);
}

/*
 *      vm_map_locked:
 *
 *      Returns a non-zero value if the caller holds a write (exclusive) lock
 *      on the specified map and the value "0" otherwise.
 */
int
vm_map_locked(vm_map_t map)
{

        if (map->system_map)
                return (mtx_owned(&map->system_mtx));
        else
                return (sx_xlocked(&map->lock));
}

#ifdef INVARIANTS
static void
_vm_map_assert_locked(vm_map_t map, const char *file, int line)
{

        if (map->system_map)
                mtx_assert_(&map->system_mtx, MA_OWNED, file, line);
        else
                sx_assert_(&map->lock, SA_XLOCKED, file, line);
}

#define VM_MAP_ASSERT_LOCKED(map) \
    _vm_map_assert_locked(map, LOCK_FILE, LOCK_LINE)
#else
#define VM_MAP_ASSERT_LOCKED(map)
#endif

/*
 *      _vm_map_unlock_and_wait:
 *
 *      Atomically releases the lock on the specified map and puts the calling
 *      thread to sleep.  The calling thread will remain asleep until either
 *      vm_map_wakeup() is performed on the map or the specified timeout is
 *      exceeded.
 *
 *      WARNING!  This function does not perform deferred deallocations of
 *      objects and map entries.  Therefore, the calling thread is expected to
 *      reacquire the map lock after reawakening and later perform an ordinary
 *      unlock operation, such as vm_map_unlock(), before completing its
 *      operation on the map.
 */
int
_vm_map_unlock_and_wait(vm_map_t map, int timo, const char *file, int line)
{

        mtx_lock(&map_sleep_mtx);
        if (map->system_map)
                mtx_unlock_flags_(&map->system_mtx, 0, file, line);
        else
                sx_xunlock_(&map->lock, file, line);
        return (msleep(&map->root, &map_sleep_mtx, PDROP | PVM, "vmmaps",
            timo));
}

/*
 *      vm_map_wakeup:
 *
 *      Awaken any threads that have slept on the map using
 *      vm_map_unlock_and_wait().
 */
void
vm_map_wakeup(vm_map_t map)
{

        /*
         * Acquire and release map_sleep_mtx to prevent a wakeup()
         * from being performed (and lost) between the map unlock
         * and the msleep() in _vm_map_unlock_and_wait().
         */
        mtx_lock(&map_sleep_mtx);
        mtx_unlock(&map_sleep_mtx);
        wakeup(&map->root);
}

void
vm_map_busy(vm_map_t map)
{

        VM_MAP_ASSERT_LOCKED(map);
        map->busy++;
}

void
vm_map_unbusy(vm_map_t map)
{

        VM_MAP_ASSERT_LOCKED(map);
        KASSERT(map->busy, ("vm_map_unbusy: not busy"));
        if (--map->busy == 0 && (map->flags & MAP_BUSY_WAKEUP)) {
                vm_map_modflags(map, 0, MAP_BUSY_WAKEUP);
                wakeup(&map->busy);
        }
}

void 
vm_map_wait_busy(vm_map_t map)
{

        VM_MAP_ASSERT_LOCKED(map);
        while (map->busy) {
                vm_map_modflags(map, MAP_BUSY_WAKEUP, 0);
                if (map->system_map)
                        msleep(&map->busy, &map->system_mtx, 0, "mbusy", 0);
                else
                        sx_sleep(&map->busy, &map->lock, 0, "mbusy", 0);
        }
        map->timestamp++;
}

long
vmspace_resident_count(struct vmspace *vmspace)
{
        return pmap_resident_count(vmspace_pmap(vmspace));
}

/*
 *      vm_map_create:
 *
 *      Creates and returns a new empty VM map with
 *      the given physical map structure, and having
 *      the given lower and upper address bounds.
 */
vm_map_t
vm_map_create(pmap_t pmap, vm_offset_t min, vm_offset_t max)
{
        vm_map_t result;

        result = uma_zalloc(mapzone, M_WAITOK);
        CTR1(KTR_VM, "vm_map_create: %p", result);
        _vm_map_init(result, pmap, min, max);
        return (result);
}

/*
 * Initialize an existing vm_map structure
 * such as that in the vmspace structure.
 */
static void
_vm_map_init(vm_map_t map, pmap_t pmap, vm_offset_t min, vm_offset_t max)
{

        map->header.next = map->header.prev = &map->header;
        map->needs_wakeup = FALSE;
        map->system_map = 0;
        map->pmap = pmap;
        map->min_offset = min;
        map->max_offset = max;
        map->flags = 0;
        map->root = NULL;
        map->timestamp = 0;
        map->busy = 0;
}

void
vm_map_init(vm_map_t map, pmap_t pmap, vm_offset_t min, vm_offset_t max)
{

        _vm_map_init(map, pmap, min, max);
        mtx_init(&map->system_mtx, "system map", NULL, MTX_DEF | MTX_DUPOK);
        sx_init(&map->lock, "user map");
}

/*
 *      vm_map_entry_dispose:   [ internal use only ]
 *
 *      Inverse of vm_map_entry_create.
 */
static void
vm_map_entry_dispose(vm_map_t map, vm_map_entry_t entry)
{
        uma_zfree(map->system_map ? kmapentzone : mapentzone, entry);
}

/*
 *      vm_map_entry_create:    [ internal use only ]
 *
 *      Allocates a VM map entry for insertion.
 *      No entry fields are filled in.
 */
static vm_map_entry_t
vm_map_entry_create(vm_map_t map)
{
        vm_map_entry_t new_entry;

        if (map->system_map)
                new_entry = uma_zalloc(kmapentzone, M_NOWAIT);
        else
                new_entry = uma_zalloc(mapentzone, M_WAITOK);
        if (new_entry == NULL)
                panic("vm_map_entry_create: kernel resources exhausted");
        return (new_entry);
}

/*
 *      vm_map_entry_set_behavior:
 *
 *      Set the expected access behavior, either normal, random, or
 *      sequential.
 */
static inline void
vm_map_entry_set_behavior(vm_map_entry_t entry, u_char behavior)
{
        entry->eflags = (entry->eflags & ~MAP_ENTRY_BEHAV_MASK) |
            (behavior & MAP_ENTRY_BEHAV_MASK);
}

/*
 *      vm_map_entry_set_max_free:
 *
 *      Set the max_free field in a vm_map_entry.
 */
static inline void
vm_map_entry_set_max_free(vm_map_entry_t entry)
{

        entry->max_free = entry->adj_free;
        if (entry->left != NULL && entry->left->max_free > entry->max_free)
                entry->max_free = entry->left->max_free;
        if (entry->right != NULL && entry->right->max_free > entry->max_free)
                entry->max_free = entry->right->max_free;
}

/*
 *      vm_map_entry_splay:
 *
 *      The Sleator and Tarjan top-down splay algorithm with the
 *      following variation.  Max_free must be computed bottom-up, so
 *      on the downward pass, maintain the left and right spines in
 *      reverse order.  Then, make a second pass up each side to fix
 *      the pointers and compute max_free.  The time bound is O(log n)
 *      amortized.
 *
 *      The new root is the vm_map_entry containing "addr", or else an
 *      adjacent entry (lower or higher) if addr is not in the tree.
 *
 *      The map must be locked, and leaves it so.
 *
 *      Returns: the new root.
 */
static vm_map_entry_t
vm_map_entry_splay(vm_offset_t addr, vm_map_entry_t root)
{
        vm_map_entry_t llist, rlist;
        vm_map_entry_t ltree, rtree;
        vm_map_entry_t y;

        /* Special case of empty tree. */
        if (root == NULL)
                return (root);

        /*
         * Pass One: Splay down the tree until we find addr or a NULL
         * pointer where addr would go.  llist and rlist are the two
         * sides in reverse order (bottom-up), with llist linked by
         * the right pointer and rlist linked by the left pointer in
         * the vm_map_entry.  Wait until Pass Two to set max_free on
         * the two spines.
         */
        llist = NULL;
        rlist = NULL;
        for (;;) {
                /* root is never NULL in here. */
                if (addr < root->start) {
                        y = root->left;
                        if (y == NULL)
                                break;
                        if (addr < y->start && y->left != NULL) {
                                /* Rotate right and put y on rlist. */
                                root->left = y->right;
                                y->right = root;
                                vm_map_entry_set_max_free(root);
                                root = y->left;
                                y->left = rlist;
                                rlist = y;
                        } else {
                                /* Put root on rlist. */
                                root->left = rlist;
                                rlist = root;
                                root = y;
                        }
                } else if (addr >= root->end) {
                        y = root->right;
                        if (y == NULL)
                                break;
                        if (addr >= y->end && y->right != NULL) {
                                /* Rotate left and put y on llist. */
                                root->right = y->left;
                                y->left = root;
                                vm_map_entry_set_max_free(root);
                                root = y->right;
                                y->right = llist;
                                llist = y;
                        } else {
                                /* Put root on llist. */
                                root->right = llist;
                                llist = root;
                                root = y;
                        }
                } else
                        break;
        }

        /*
         * Pass Two: Walk back up the two spines, flip the pointers
         * and set max_free.  The subtrees of the root go at the
         * bottom of llist and rlist.
         */
        ltree = root->left;
        while (llist != NULL) {
                y = llist->right;
                llist->right = ltree;
                vm_map_entry_set_max_free(llist);
                ltree = llist;
                llist = y;
        }
        rtree = root->right;
        while (rlist != NULL) {
                y = rlist->left;
                rlist->left = rtree;
                vm_map_entry_set_max_free(rlist);
                rtree = rlist;
                rlist = y;
        }

        /*
         * Final assembly: add ltree and rtree as subtrees of root.
         */
        root->left = ltree;
        root->right = rtree;
        vm_map_entry_set_max_free(root);

        return (root);
}

/*
 *      vm_map_entry_{un,}link:
 *
 *      Insert/remove entries from maps.
 */
static void
vm_map_entry_link(vm_map_t map,
                  vm_map_entry_t after_where,
                  vm_map_entry_t entry)
{

        CTR4(KTR_VM,
            "vm_map_entry_link: map %p, nentries %d, entry %p, after %p", map,
            map->nentries, entry, after_where);
        VM_MAP_ASSERT_LOCKED(map);
        map->nentries++;
        entry->prev = after_where;
        entry->next = after_where->next;
        entry->next->prev = entry;
        after_where->next = entry;

        if (after_where != &map->header) {
                if (after_where != map->root)
                        vm_map_entry_splay(after_where->start, map->root);
                entry->right = after_where->right;
                entry->left = after_where;
                after_where->right = NULL;
                after_where->adj_free = entry->start - after_where->end;
                vm_map_entry_set_max_free(after_where);
        } else {
                entry->right = map->root;
                entry->left = NULL;
        }
        entry->adj_free = (entry->next == &map->header ? map->max_offset :
            entry->next->start) - entry->end;
        vm_map_entry_set_max_free(entry);
        map->root = entry;
}

static void
vm_map_entry_unlink(vm_map_t map,
                    vm_map_entry_t entry)
{
        vm_map_entry_t next, prev, root;

        VM_MAP_ASSERT_LOCKED(map);
        if (entry != map->root)
                vm_map_entry_splay(entry->start, map->root);
        if (entry->left == NULL)
                root = entry->right;
        else {
                root = vm_map_entry_splay(entry->start, entry->left);
                root->right = entry->right;
                root->adj_free = (entry->next == &map->header ? map->max_offset :
                    entry->next->start) - root->end;
                vm_map_entry_set_max_free(root);
        }
        map->root = root;

        prev = entry->prev;
        next = entry->next;
        next->prev = prev;
        prev->next = next;
        map->nentries--;
        CTR3(KTR_VM, "vm_map_entry_unlink: map %p, nentries %d, entry %p", map,
            map->nentries, entry);
}

/*
 *      vm_map_entry_resize_free:
 *
 *      Recompute the amount of free space following a vm_map_entry
 *      and propagate that value up the tree.  Call this function after
 *      resizing a map entry in-place, that is, without a call to
 *      vm_map_entry_link() or _unlink().
 *
 *      The map must be locked, and leaves it so.
 */
static void
vm_map_entry_resize_free(vm_map_t map, vm_map_entry_t entry)
{

        /*
         * Using splay trees without parent pointers, propagating
         * max_free up the tree is done by moving the entry to the
         * root and making the change there.
         */
        if (entry != map->root)
                map->root = vm_map_entry_splay(entry->start, map->root);

        entry->adj_free = (entry->next == &map->header ? map->max_offset :
            entry->next->start) - entry->end;
        vm_map_entry_set_max_free(entry);
}

/*
 *      vm_map_lookup_entry:    [ internal use only ]
 *
 *      Finds the map entry containing (or
 *      immediately preceding) the specified address
 *      in the given map; the entry is returned
 *      in the "entry" parameter.  The boolean
 *      result indicates whether the address is
 *      actually contained in the map.
 */
boolean_t
vm_map_lookup_entry(
        vm_map_t map,
        vm_offset_t address,
        vm_map_entry_t *entry)  /* OUT */
{
        vm_map_entry_t cur;
        boolean_t locked;

        /*
         * If the map is empty, then the map entry immediately preceding
         * "address" is the map's header.
         */
        cur = map->root;
        if (cur == NULL)
                *entry = &map->header;
        else if (address >= cur->start && cur->end > address) {
                *entry = cur;
                return (TRUE);
        } else if ((locked = vm_map_locked(map)) ||
            sx_try_upgrade(&map->lock)) {
                /*
                 * Splay requires a write lock on the map.  However, it only
                 * restructures the binary search tree; it does not otherwise
                 * change the map.  Thus, the map's timestamp need not change
                 * on a temporary upgrade.
                 */
                map->root = cur = vm_map_entry_splay(address, cur);
                if (!locked)
                        sx_downgrade(&map->lock);

                /*
                 * If "address" is contained within a map entry, the new root
                 * is that map entry.  Otherwise, the new root is a map entry
                 * immediately before or after "address".
                 */
                if (address >= cur->start) {
                        *entry = cur;
                        if (cur->end > address)
                                return (TRUE);
                } else
                        *entry = cur->prev;
        } else
                /*
                 * Since the map is only locked for read access, perform a
                 * standard binary search tree lookup for "address".
                 */
                for (;;) {
                        if (address < cur->start) {
                                if (cur->left == NULL) {
                                        *entry = cur->prev;
                                        break;
                                }
                                cur = cur->left;
                        } else if (cur->end > address) {
                                *entry = cur;
                                return (TRUE);
                        } else {
                                if (cur->right == NULL) {
                                        *entry = cur;
                                        break;
                                }
                                cur = cur->right;
                        }
                }
        return (FALSE);
}

/*
 *      vm_map_insert:
 *
 *      Inserts the given whole VM object into the target
 *      map at the specified address range.  The object's
 *      size should match that of the address range.
 *
 *      Requires that the map be locked, and leaves it so.
 *
 *      If object is non-NULL, ref count must be bumped by caller
 *      prior to making call to account for the new entry.
 */
int
vm_map_insert(vm_map_t map, vm_object_t object, vm_ooffset_t offset,
              vm_offset_t start, vm_offset_t end, vm_prot_t prot, vm_prot_t max,
              int cow)
{
        vm_map_entry_t new_entry;
        vm_map_entry_t prev_entry;
        vm_map_entry_t temp_entry;
        vm_eflags_t protoeflags;
        struct ucred *cred;
        vm_inherit_t inheritance;
        boolean_t charge_prev_obj;

        VM_MAP_ASSERT_LOCKED(map);

        /*
         * Check that the start and end points are not bogus.
         */
        if ((start < map->min_offset) || (end > map->max_offset) ||
            (start >= end))
                return (KERN_INVALID_ADDRESS);

        /*
         * Find the entry prior to the proposed starting address; if it's part
         * of an existing entry, this range is bogus.
         */
        if (vm_map_lookup_entry(map, start, &temp_entry))
                return (KERN_NO_SPACE);

        prev_entry = temp_entry;

        /*
         * Assert that the next entry doesn't overlap the end point.
         */
        if ((prev_entry->next != &map->header) &&
            (prev_entry->next->start < end))
                return (KERN_NO_SPACE);

        protoeflags = 0;
        charge_prev_obj = FALSE;

        if (cow & MAP_COPY_ON_WRITE)
                protoeflags |= MAP_ENTRY_COW|MAP_ENTRY_NEEDS_COPY;

        if (cow & MAP_NOFAULT) {
                protoeflags |= MAP_ENTRY_NOFAULT;

                KASSERT(object == NULL,
                        ("vm_map_insert: paradoxical MAP_NOFAULT request"));
        }
        if (cow & MAP_DISABLE_SYNCER)
                protoeflags |= MAP_ENTRY_NOSYNC;
        if (cow & MAP_DISABLE_COREDUMP)
                protoeflags |= MAP_ENTRY_NOCOREDUMP;
        if (cow & MAP_VN_WRITECOUNT)
                protoeflags |= MAP_ENTRY_VN_WRITECNT;
        if (cow & MAP_INHERIT_SHARE)
                inheritance = VM_INHERIT_SHARE;
        else
                inheritance = VM_INHERIT_DEFAULT;

        cred = NULL;
        KASSERT((object != kmem_object && object != kernel_object) ||
            ((object == kmem_object || object == kernel_object) &&
                !(protoeflags & MAP_ENTRY_NEEDS_COPY)),
            ("kmem or kernel object and cow"));
        if (cow & (MAP_ACC_NO_CHARGE | MAP_NOFAULT))
                goto charged;
        if ((cow & MAP_ACC_CHARGED) || ((prot & VM_PROT_WRITE) &&
            ((protoeflags & MAP_ENTRY_NEEDS_COPY) || object == NULL))) {
                if (!(cow & MAP_ACC_CHARGED) && !swap_reserve(end - start))
                        return (KERN_RESOURCE_SHORTAGE);
                KASSERT(object == NULL || (protoeflags & MAP_ENTRY_NEEDS_COPY) ||
                    object->cred == NULL,
                    ("OVERCOMMIT: vm_map_insert o %p", object));
                cred = curthread->td_ucred;
                crhold(cred);
                if (object == NULL && !(protoeflags & MAP_ENTRY_NEEDS_COPY))
                        charge_prev_obj = TRUE;
        }

charged:
        /* Expand the kernel pmap, if necessary. */
        if (map == kernel_map && end > kernel_vm_end)
                pmap_growkernel(end);
        if (object != NULL) {
                /*
                 * OBJ_ONEMAPPING must be cleared unless this mapping
                 * is trivially proven to be the only mapping for any
                 * of the object's pages.  (Object granularity
                 * reference counting is insufficient to recognize
                 * aliases with precision.)
                 */
                VM_OBJECT_WLOCK(object);
                if (object->ref_count > 1 || object->shadow_count != 0)
                        vm_object_clear_flag(object, OBJ_ONEMAPPING);
                VM_OBJECT_WUNLOCK(object);
        }
        else if ((prev_entry != &map->header) &&
                 (prev_entry->eflags == protoeflags) &&
                 (prev_entry->end == start) &&
                 (prev_entry->wired_count == 0) &&
                 (prev_entry->cred == cred ||
                  (prev_entry->object.vm_object != NULL &&
                   (prev_entry->object.vm_object->cred == cred))) &&
                   vm_object_coalesce(prev_entry->object.vm_object,
                       prev_entry->offset,
                       (vm_size_t)(prev_entry->end - prev_entry->start),
                       (vm_size_t)(end - prev_entry->end), charge_prev_obj)) {
                /*
                 * We were able to extend the object.  Determine if we
                 * can extend the previous map entry to include the
                 * new range as well.
                 */
                if ((prev_entry->inheritance == inheritance) &&
                    (prev_entry->protection == prot) &&
                    (prev_entry->max_protection == max)) {
                        map->size += (end - prev_entry->end);
                        prev_entry->end = end;
                        vm_map_entry_resize_free(map, prev_entry);
                        vm_map_simplify_entry(map, prev_entry);
                        if (cred != NULL)
                                crfree(cred);
                        return (KERN_SUCCESS);
                }

                /*
                 * If we can extend the object but cannot extend the
                 * map entry, we have to create a new map entry.  We
                 * must bump the ref count on the extended object to
                 * account for it.  object may be NULL.
                 */
                object = prev_entry->object.vm_object;
                offset = prev_entry->offset +
                        (prev_entry->end - prev_entry->start);
                vm_object_reference(object);
                if (cred != NULL && object != NULL && object->cred != NULL &&
                    !(prev_entry->eflags & MAP_ENTRY_NEEDS_COPY)) {
                        /* Object already accounts for this uid. */
                        crfree(cred);
                        cred = NULL;
                }
        }

        /*
         * NOTE: if conditionals fail, object can be NULL here.  This occurs
         * in things like the buffer map where we manage kva but do not manage
         * backing objects.
         */

        /*
         * Create a new entry
         */
        new_entry = vm_map_entry_create(map);
        new_entry->start = start;
        new_entry->end = end;
        new_entry->cred = NULL;

        new_entry->eflags = protoeflags;
        new_entry->object.vm_object = object;
        new_entry->offset = offset;
        new_entry->avail_ssize = 0;

        new_entry->inheritance = inheritance;
        new_entry->protection = prot;
        new_entry->max_protection = max;
        new_entry->wired_count = 0;
        new_entry->read_ahead = VM_FAULT_READ_AHEAD_INIT;
        new_entry->next_read = OFF_TO_IDX(offset);

        KASSERT(cred == NULL || !ENTRY_CHARGED(new_entry),
            ("OVERCOMMIT: vm_map_insert leaks vm_map %p", new_entry));
        new_entry->cred = cred;

        /*
         * Insert the new entry into the list
         */
        vm_map_entry_link(map, prev_entry, new_entry);
        map->size += new_entry->end - new_entry->start;

        /*
         * It may be possible to merge the new entry with the next and/or
         * previous entries.  However, due to MAP_STACK_* being a hack, a
         * panic can result from merging such entries.
         */
        if ((cow & (MAP_STACK_GROWS_DOWN | MAP_STACK_GROWS_UP)) == 0)
                vm_map_simplify_entry(map, new_entry);

        if (cow & (MAP_PREFAULT|MAP_PREFAULT_PARTIAL)) {
                vm_map_pmap_enter(map, start, prot,
                                    object, OFF_TO_IDX(offset), end - start,
                                    cow & MAP_PREFAULT_PARTIAL);
        }

        return (KERN_SUCCESS);
}

/*
 *      vm_map_findspace:
 *
 *      Find the first fit (lowest VM address) for "length" free bytes
 *      beginning at address >= start in the given map.
 *
 *      In a vm_map_entry, "adj_free" is the amount of free space
 *      adjacent (higher address) to this entry, and "max_free" is the
 *      maximum amount of contiguous free space in its subtree.  This
 *      allows finding a free region in one path down the tree, so
 *      O(log n) amortized with splay trees.
 *
 *      The map must be locked, and leaves it so.
 *
 *      Returns: 0 on success, and starting address in *addr,
 *               1 if insufficient space.
 */
int
vm_map_findspace(vm_map_t map, vm_offset_t start, vm_size_t length,
    vm_offset_t *addr)  /* OUT */
{
        vm_map_entry_t entry;
        vm_offset_t st;

        /*
         * Request must fit within min/max VM address and must avoid
         * address wrap.
         */
        if (start < map->min_offset)
                start = map->min_offset;
        if (start + length > map->max_offset || start + length < start)
                return (1);

        /* Empty tree means wide open address space. */
        if (map->root == NULL) {
                *addr = start;
                return (0);
        }

        /*
         * After splay, if start comes before root node, then there
         * must be a gap from start to the root.
         */
        map->root = vm_map_entry_splay(start, map->root);
        if (start + length <= map->root->start) {
                *addr = start;
                return (0);
        }

        /*
         * Root is the last node that might begin its gap before
         * start, and this is the last comparison where address
         * wrap might be a problem.
         */
        st = (start > map->root->end) ? start : map->root->end;
        if (length <= map->root->end + map->root->adj_free - st) {
                *addr = st;
                return (0);
        }

        /* With max_free, can immediately tell if no solution. */
        entry = map->root->right;
        if (entry == NULL || length > entry->max_free)
                return (1);

        /*
         * Search the right subtree in the order: left subtree, root,
         * right subtree (first fit).  The previous splay implies that
         * all regions in the right subtree have addresses > start.
         */
        while (entry != NULL) {
                if (entry->left != NULL && entry->left->max_free >= length)
                        entry = entry->left;
                else if (entry->adj_free >= length) {
                        *addr = entry->end;
                        return (0);
                } else
                        entry = entry->right;
        }

        /* Can't get here, so panic if we do. */
        panic("vm_map_findspace: max_free corrupt");
}

int
vm_map_fixed(vm_map_t map, vm_object_t object, vm_ooffset_t offset,
    vm_offset_t start, vm_size_t length, vm_prot_t prot,
    vm_prot_t max, int cow)
{
        vm_offset_t end;
        int result;

        end = start + length;
        vm_map_lock(map);
        VM_MAP_RANGE_CHECK(map, start, end);
        (void) vm_map_delete(map, start, end);
        result = vm_map_insert(map, object, offset, start, end, prot,
            max, cow);
        vm_map_unlock(map);
        return (result);
}

/*
 *      vm_map_find finds an unallocated region in the target address
 *      map with the given length.  The search is defined to be
 *      first-fit from the specified address; the region found is
 *      returned in the same parameter.
 *
 *      If object is non-NULL, ref count must be bumped by caller
 *      prior to making call to account for the new entry.
 */
int
vm_map_find(vm_map_t map, vm_object_t object, vm_ooffset_t offset,
            vm_offset_t *addr,  /* IN/OUT */
            vm_size_t length, vm_offset_t max_addr, int find_space,
            vm_prot_t prot, vm_prot_t max, int cow)
{
        vm_offset_t alignment, initial_addr, start;
        int result;

        if (find_space == VMFS_OPTIMAL_SPACE && (object == NULL ||
            (object->flags & OBJ_COLORED) == 0))
                find_space = VMFS_ANY_SPACE;
        if (find_space >> 8 != 0) {
                KASSERT((find_space & 0xff) == 0, ("bad VMFS flags"));
                alignment = (vm_offset_t)1 << (find_space >> 8);
        } else
                alignment = 0;
        initial_addr = *addr;
again:
        start = initial_addr;
        vm_map_lock(map);
        do {
                if (find_space != VMFS_NO_SPACE) {
                        if (vm_map_findspace(map, start, length, addr) ||
                            (max_addr != 0 && *addr + length > max_addr)) {
                                vm_map_unlock(map);
                                if (find_space == VMFS_OPTIMAL_SPACE) {
                                        find_space = VMFS_ANY_SPACE;
                                        goto again;
                                }
                                return (KERN_NO_SPACE);
                        }
                        switch (find_space) {
                        case VMFS_SUPER_SPACE:
                        case VMFS_OPTIMAL_SPACE:
                                pmap_align_superpage(object, offset, addr,
                                    length);
                                break;
                        case VMFS_ANY_SPACE:
                                break;
                        default:
                                if ((*addr & (alignment - 1)) != 0) {
                                        *addr &= ~(alignment - 1);
                                        *addr += alignment;
                                }
                                break;
                        }

                        start = *addr;
                }
                result = vm_map_insert(map, object, offset, start, start +
                    length, prot, max, cow);
        } while (result == KERN_NO_SPACE && find_space != VMFS_NO_SPACE &&
            find_space != VMFS_ANY_SPACE);
        vm_map_unlock(map);
        return (result);
}

/*
 *      vm_map_simplify_entry:
 *
 *      Simplify the given map entry by merging with either neighbor.  This
 *      routine also has the ability to merge with both neighbors.
 *
 *      The map must be locked.
 *
 *      This routine guarentees that the passed entry remains valid (though
 *      possibly extended).  When merging, this routine may delete one or
 *      both neighbors.
 */
void
vm_map_simplify_entry(vm_map_t map, vm_map_entry_t entry)
{
        vm_map_entry_t next, prev;
        vm_size_t prevsize, esize;

        if (entry->eflags & (MAP_ENTRY_IN_TRANSITION | MAP_ENTRY_IS_SUB_MAP))
                return;

        prev = entry->prev;
        if (prev != &map->header) {
                prevsize = prev->end - prev->start;
                if ( (prev->end == entry->start) &&
                     (prev->object.vm_object == entry->object.vm_object) &&
                     (!prev->object.vm_object ||
                        (prev->offset + prevsize == entry->offset)) &&
                     (prev->eflags == entry->eflags) &&
                     (prev->protection == entry->protection) &&
                     (prev->max_protection == entry->max_protection) &&
                     (prev->inheritance == entry->inheritance) &&
                     (prev->wired_count == entry->wired_count) &&
                     (prev->cred == entry->cred)) {
                        vm_map_entry_unlink(map, prev);
                        entry->start = prev->start;
                        entry->offset = prev->offset;
                        if (entry->prev != &map->header)
                                vm_map_entry_resize_free(map, entry->prev);

                        /*
                         * If the backing object is a vnode object,
                         * vm_object_deallocate() calls vrele().
                         * However, vrele() does not lock the vnode
                         * because the vnode has additional
                         * references.  Thus, the map lock can be kept
                         * without causing a lock-order reversal with
                         * the vnode lock.
                         *
                         * Since we count the number of virtual page
                         * mappings in object->un_pager.vnp.writemappings,
                         * the writemappings value should not be adjusted
                         * when the entry is disposed of.
                         */
                        if (prev->object.vm_object)
                                vm_object_deallocate(prev->object.vm_object);
                        if (prev->cred != NULL)
                                crfree(prev->cred);
                        vm_map_entry_dispose(map, prev);
                }
        }

        next = entry->next;
        if (next != &map->header) {
                esize = entry->end - entry->start;
                if ((entry->end == next->start) &&
                    (next->object.vm_object == entry->object.vm_object) &&
                     (!entry->object.vm_object ||
                        (entry->offset + esize == next->offset)) &&
                    (next->eflags == entry->eflags) &&
                    (next->protection == entry->protection) &&
                    (next->max_protection == entry->max_protection) &&
                    (next->inheritance == entry->inheritance) &&
                    (next->wired_count == entry->wired_count) &&
                    (next->cred == entry->cred)) {
                        vm_map_entry_unlink(map, next);
                        entry->end = next->end;
                        vm_map_entry_resize_free(map, entry);

                        /*
                         * See comment above.
                         */
                        if (next->object.vm_object)
                                vm_object_deallocate(next->object.vm_object);
                        if (next->cred != NULL)
                                crfree(next->cred);
                        vm_map_entry_dispose(map, next);
                }
        }
}
/*
 *      vm_map_clip_start:      [ internal use only ]
 *
 *      Asserts that the given entry begins at or after
 *      the specified address; if necessary,
 *      it splits the entry into two.
 */
#define vm_map_clip_start(map, entry, startaddr) \
{ \
        if (startaddr > entry->start) \
                _vm_map_clip_start(map, entry, startaddr); \
}

/*
 *      This routine is called only when it is known that
 *      the entry must be split.
 */
static void
_vm_map_clip_start(vm_map_t map, vm_map_entry_t entry, vm_offset_t start)
{
        vm_map_entry_t new_entry;

        VM_MAP_ASSERT_LOCKED(map);

        /*
         * Split off the front portion -- note that we must insert the new
         * entry BEFORE this one, so that this entry has the specified
         * starting address.
         */
        vm_map_simplify_entry(map, entry);

        /*
         * If there is no object backing this entry, we might as well create
         * one now.  If we defer it, an object can get created after the map
         * is clipped, and individual objects will be created for the split-up
         * map.  This is a bit of a hack, but is also about the best place to
         * put this improvement.
         */
        if (entry->object.vm_object == NULL && !map->system_map) {
                vm_object_t object;
                object = vm_object_allocate(OBJT_DEFAULT,
                                atop(entry->end - entry->start));
                entry->object.vm_object = object;
                entry->offset = 0;
                if (entry->cred != NULL) {
                        object->cred = entry->cred;
                        object->charge = entry->end - entry->start;
                        entry->cred = NULL;
                }
        } else if (entry->object.vm_object != NULL &&
                   ((entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) &&
                   entry->cred != NULL) {
                VM_OBJECT_WLOCK(entry->object.vm_object);
                KASSERT(entry->object.vm_object->cred == NULL,
                    ("OVERCOMMIT: vm_entry_clip_start: both cred e %p", entry));
                entry->object.vm_object->cred = entry->cred;
                entry->object.vm_object->charge = entry->end - entry->start;
                VM_OBJECT_WUNLOCK(entry->object.vm_object);
                entry->cred = NULL;
        }

        new_entry = vm_map_entry_create(map);
        *new_entry = *entry;

        new_entry->end = start;
        entry->offset += (start - entry->start);
        entry->start = start;
        if (new_entry->cred != NULL)
                crhold(entry->cred);

        vm_map_entry_link(map, entry->prev, new_entry);

        if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
                vm_object_reference(new_entry->object.vm_object);
                /*
                 * The object->un_pager.vnp.writemappings for the
                 * object of MAP_ENTRY_VN_WRITECNT type entry shall be
                 * kept as is here.  The virtual pages are
                 * re-distributed among the clipped entries, so the sum is
                 * left the same.
                 */
        }
}

/*
 *      vm_map_clip_end:        [ internal use only ]
 *
 *      Asserts that the given entry ends at or before
 *      the specified address; if necessary,
 *      it splits the entry into two.
 */
#define vm_map_clip_end(map, entry, endaddr) \
{ \
        if ((endaddr) < (entry->end)) \
                _vm_map_clip_end((map), (entry), (endaddr)); \
}

/*
 *      This routine is called only when it is known that
 *      the entry must be split.
 */
static void
_vm_map_clip_end(vm_map_t map, vm_map_entry_t entry, vm_offset_t end)
{
        vm_map_entry_t new_entry;

        VM_MAP_ASSERT_LOCKED(map);

        /*
         * If there is no object backing this entry, we might as well create
         * one now.  If we defer it, an object can get created after the map
         * is clipped, and individual objects will be created for the split-up
         * map.  This is a bit of a hack, but is also about the best place to
         * put this improvement.
         */
        if (entry->object.vm_object == NULL && !map->system_map) {
                vm_object_t object;
                object = vm_object_allocate(OBJT_DEFAULT,
                                atop(entry->end - entry->start));
                entry->object.vm_object = object;
                entry->offset = 0;
                if (entry->cred != NULL) {
                        object->cred = entry->cred;
                        object->charge = entry->end - entry->start;
                        entry->cred = NULL;
                }
        } else if (entry->object.vm_object != NULL &&
                   ((entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) &&
                   entry->cred != NULL) {
                VM_OBJECT_WLOCK(entry->object.vm_object);
                KASSERT(entry->object.vm_object->cred == NULL,
                    ("OVERCOMMIT: vm_entry_clip_end: both cred e %p", entry));
                entry->object.vm_object->cred = entry->cred;
                entry->object.vm_object->charge = entry->end - entry->start;
                VM_OBJECT_WUNLOCK(entry->object.vm_object);
                entry->cred = NULL;
        }

        /*
         * Create a new entry and insert it AFTER the specified entry
         */
        new_entry = vm_map_entry_create(map);
        *new_entry = *entry;

        new_entry->start = entry->end = end;
        new_entry->offset += (end - entry->start);
        if (new_entry->cred != NULL)
                crhold(entry->cred);

        vm_map_entry_link(map, entry, new_entry);

        if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
                vm_object_reference(new_entry->object.vm_object);
        }
}

/*
 *      vm_map_submap:          [ kernel use only ]
 *
 *      Mark the given range as handled by a subordinate map.
 *
 *      This range must have been created with vm_map_find,
 *      and no other operations may have been performed on this
 *      range prior to calling vm_map_submap.
 *
 *      Only a limited number of operations can be performed
 *      within this rage after calling vm_map_submap:
 *              vm_fault
 *      [Don't try vm_map_copy!]
 *
 *      To remove a submapping, one must first remove the
 *      range from the superior map, and then destroy the
 *      submap (if desired).  [Better yet, don't try it.]
 */
int
vm_map_submap(
        vm_map_t map,
        vm_offset_t start,
        vm_offset_t end,
        vm_map_t submap)
{
        vm_map_entry_t entry;
        int result = KERN_INVALID_ARGUMENT;

        vm_map_lock(map);

        VM_MAP_RANGE_CHECK(map, start, end);

        if (vm_map_lookup_entry(map, start, &entry)) {
                vm_map_clip_start(map, entry, start);
        } else
                entry = entry->next;

        vm_map_clip_end(map, entry, end);

        if ((entry->start == start) && (entry->end == end) &&
            ((entry->eflags & MAP_ENTRY_COW) == 0) &&
            (entry->object.vm_object == NULL)) {
                entry->object.sub_map = submap;
                entry->eflags |= MAP_ENTRY_IS_SUB_MAP;
                result = KERN_SUCCESS;
        }
        vm_map_unlock(map);

        return (result);
}

/*
 * The maximum number of pages to map
 */
#define MAX_INIT_PT     96

/*
 *      vm_map_pmap_enter:
 *
 *      Preload read-only mappings for the specified object's resident pages
 *      into the target map.  If "flags" is MAP_PREFAULT_PARTIAL, then only
 *      the resident pages within the address range [addr, addr + ulmin(size,
 *      ptoa(MAX_INIT_PT))) are mapped.  Otherwise, all resident pages within
 *      the specified address range are mapped.  This eliminates many soft
 *      faults on process startup and immediately after an mmap(2).  Because
 *      these are speculative mappings, cached pages are not reactivated and
 *      mapped.
 */
void
vm_map_pmap_enter(vm_map_t map, vm_offset_t addr, vm_prot_t prot,
    vm_object_t object, vm_pindex_t pindex, vm_size_t size, int flags)
{
        vm_offset_t start;
        vm_page_t p, p_start;
        vm_pindex_t psize, tmpidx;

        if ((prot & (VM_PROT_READ | VM_PROT_EXECUTE)) == 0 || object == NULL)
                return;
        VM_OBJECT_RLOCK(object);
        if (object->type == OBJT_DEVICE || object->type == OBJT_SG) {
                VM_OBJECT_RUNLOCK(object);
                VM_OBJECT_WLOCK(object);
                if (object->type == OBJT_DEVICE || object->type == OBJT_SG) {
                        pmap_object_init_pt(map->pmap, addr, object, pindex,
                            size);
                        VM_OBJECT_WUNLOCK(object);
                        return;
                }
                VM_OBJECT_LOCK_DOWNGRADE(object);
        }

        psize = atop(size);
        if (psize > MAX_INIT_PT && (flags & MAP_PREFAULT_PARTIAL) != 0)
                psize = MAX_INIT_PT;
        if (psize + pindex > object->size) {
                if (object->size < pindex) {
                        VM_OBJECT_RUNLOCK(object);
                        return;
                }
                psize = object->size - pindex;
        }

        start = 0;
        p_start = NULL;

        p = vm_page_find_least(object, pindex);
        /*
         * Assert: the variable p is either (1) the page with the
         * least pindex greater than or equal to the parameter pindex
         * or (2) NULL.
         */
        for (;
             p != NULL && (tmpidx = p->pindex - pindex) < psize;
             p = TAILQ_NEXT(p, listq)) {
                /*
                 * don't allow an madvise to blow away our really
                 * free pages allocating pv entries.
                 */
                if ((flags & MAP_PREFAULT_MADVISE) &&
                    cnt.v_free_count < cnt.v_free_reserved) {
                        psize = tmpidx;
                        break;
                }
                if (p->valid == VM_PAGE_BITS_ALL) {
                        if (p_start == NULL) {
                                start = addr + ptoa(tmpidx);
                                p_start = p;
                        }
                } else if (p_start != NULL) {
                        pmap_enter_object(map->pmap, start, addr +
                            ptoa(tmpidx), p_start, prot);
                        p_start = NULL;
                }
        }
        if (p_start != NULL)
                pmap_enter_object(map->pmap, start, addr + ptoa(psize),
                    p_start, prot);
        VM_OBJECT_RUNLOCK(object);
}

/*
 *      vm_map_protect:
 *
 *      Sets the protection of the specified address
 *      region in the target map.  If "set_max" is
 *      specified, the maximum protection is to be set;
 *      otherwise, only the current protection is affected.
 */
int
vm_map_protect(vm_map_t map, vm_offset_t start, vm_offset_t end,
               vm_prot_t new_prot, boolean_t set_max)
{
        vm_map_entry_t current, entry;
        vm_object_t obj;
        struct ucred *cred;
        vm_prot_t old_prot;

        vm_map_lock(map);

        VM_MAP_RANGE_CHECK(map, start, end);

        if (vm_map_lookup_entry(map, start, &entry)) {
                vm_map_clip_start(map, entry, start);
        } else {
                entry = entry->next;
        }

        /*
         * Make a first pass to check for protection violations.
         */
        current = entry;
        while ((current != &map->header) && (current->start < end)) {
                if (current->eflags & MAP_ENTRY_IS_SUB_MAP) {
                        vm_map_unlock(map);
                        return (KERN_INVALID_ARGUMENT);
                }
                if ((new_prot & current->max_protection) != new_prot) {
                        vm_map_unlock(map);
                        return (KERN_PROTECTION_FAILURE);
                }
                current = current->next;
        }


        /*
         * Do an accounting pass for private read-only mappings that
         * now will do cow due to allowed write (e.g. debugger sets
         * breakpoint on text segment)
         */
        for (current = entry; (current != &map->header) &&
             (current->start < end); current = current->next) {

                vm_map_clip_end(map, current, end);

                if (set_max ||
                    ((new_prot & ~(current->protection)) & VM_PROT_WRITE) == 0 ||
                    ENTRY_CHARGED(current)) {
                        continue;
                }

                cred = curthread->td_ucred;
                obj = current->object.vm_object;

                if (obj == NULL || (current->eflags & MAP_ENTRY_NEEDS_COPY)) {
                        if (!swap_reserve(current->end - current->start)) {
                                vm_map_unlock(map);
                                return (KERN_RESOURCE_SHORTAGE);
                        }
                        crhold(cred);
                        current->cred = cred;
                        continue;
                }

                VM_OBJECT_WLOCK(obj);
                if (obj->type != OBJT_DEFAULT && obj->type != OBJT_SWAP) {
                        VM_OBJECT_WUNLOCK(obj);
                        continue;
                }

                /*
                 * Charge for the whole object allocation now, since
                 * we cannot distinguish between non-charged and
                 * charged clipped mapping of the same object later.
                 */
                KASSERT(obj->charge == 0,
                    ("vm_map_protect: object %p overcharged\n", obj));
                if (!swap_reserve(ptoa(obj->size))) {
                        VM_OBJECT_WUNLOCK(obj);
                        vm_map_unlock(map);
                        return (KERN_RESOURCE_SHORTAGE);
                }

                crhold(cred);
                obj->cred = cred;
                obj->charge = ptoa(obj->size);
                VM_OBJECT_WUNLOCK(obj);
        }

        /*
         * Go back and fix up protections. [Note that clipping is not
         * necessary the second time.]
         */
        current = entry;
        while ((current != &map->header) && (current->start < end)) {
                old_prot = current->protection;

                if (set_max)
                        current->protection =
                            (current->max_protection = new_prot) &
                            old_prot;
                else
                        current->protection = new_prot;

                if ((current->eflags & (MAP_ENTRY_COW | MAP_ENTRY_USER_WIRED))
                     == (MAP_ENTRY_COW | MAP_ENTRY_USER_WIRED) &&
                    (current->protection & VM_PROT_WRITE) != 0 &&
                    (old_prot & VM_PROT_WRITE) == 0) {
                        vm_fault_copy_entry(map, map, current, current, NULL);
                }

                /*
                 * When restricting access, update the physical map.  Worry
                 * about copy-on-write here.
                 */
                if ((old_prot & ~current->protection) != 0) {
#define MASK(entry)     (((entry)->eflags & MAP_ENTRY_COW) ? ~VM_PROT_WRITE : \
                                                        VM_PROT_ALL)
                        pmap_protect(map->pmap, current->start,
                            current->end,
                            current->protection & MASK(current));
#undef  MASK
                }
                vm_map_simplify_entry(map, current);
                current = current->next;
        }
        vm_map_unlock(map);
        return (KERN_SUCCESS);
}

/*
 *      vm_map_madvise:
 *
 *      This routine traverses a processes map handling the madvise
 *      system call.  Advisories are classified as either those effecting
 *      the vm_map_entry structure, or those effecting the underlying
 *      objects.
 */
int
vm_map_madvise(
        vm_map_t map,
        vm_offset_t start,
        vm_offset_t end,
        int behav)
{
        vm_map_entry_t current, entry;
        int modify_map = 0;

        /*
         * Some madvise calls directly modify the vm_map_entry, in which case
         * we need to use an exclusive lock on the map and we need to perform
         * various clipping operations.  Otherwise we only need a read-lock
         * on the map.
         */
        switch(behav) {
        case MADV_NORMAL:
        case MADV_SEQUENTIAL:
        case MADV_RANDOM:
        case MADV_NOSYNC:
        case MADV_AUTOSYNC:
        case MADV_NOCORE:
        case MADV_CORE:
                modify_map = 1;
                vm_map_lock(map);
                break;
        case MADV_WILLNEED:
        case MADV_DONTNEED:
        case MADV_FREE:
                vm_map_lock_read(map);
                break;
        default:
                return (KERN_INVALID_ARGUMENT);
        }

        /*
         * Locate starting entry and clip if necessary.
         */
        VM_MAP_RANGE_CHECK(map, start, end);

        if (vm_map_lookup_entry(map, start, &entry)) {
                if (modify_map)
                        vm_map_clip_start(map, entry, start);
        } else {
                entry = entry->next;
        }

        if (modify_map) {
                /*
                 * madvise behaviors that are implemented in the vm_map_entry.
                 *
                 * We clip the vm_map_entry so that behavioral changes are
                 * limited to the specified address range.
                 */
                for (current = entry;
                     (current != &map->header) && (current->start < end);
                     current = current->next
                ) {
                        if (current->eflags & MAP_ENTRY_IS_SUB_MAP)
                                continue;

                        vm_map_clip_end(map, current, end);

                        switch (behav) {
                        case MADV_NORMAL:
                                vm_map_entry_set_behavior(current, MAP_ENTRY_BEHAV_NORMAL);
                                break;
                        case MADV_SEQUENTIAL:
                                vm_map_entry_set_behavior(current, MAP_ENTRY_BEHAV_SEQUENTIAL);
                                break;
                        case MADV_RANDOM:
                                vm_map_entry_set_behavior(current, MAP_ENTRY_BEHAV_RANDOM);
                                break;
                        case MADV_NOSYNC:
                                current->eflags |= MAP_ENTRY_NOSYNC;
                                break;
                        case MADV_AUTOSYNC:
                                current->eflags &= ~MAP_ENTRY_NOSYNC;
                                break;
                        case MADV_NOCORE:
                                current->eflags |= MAP_ENTRY_NOCOREDUMP;
                                break;
                        case MADV_CORE:
                                current->eflags &= ~MAP_ENTRY_NOCOREDUMP;
                                break;
                        default:
                                break;
                        }
                        vm_map_simplify_entry(map, current);
                }
                vm_map_unlock(map);
        } else {
                vm_pindex_t pstart, pend;

                /*
                 * madvise behaviors that are implemented in the underlying
                 * vm_object.
                 *
                 * Since we don't clip the vm_map_entry, we have to clip
                 * the vm_object pindex and count.
                 */
                for (current = entry;
                     (current != &map->header) && (current->start < end);
                     current = current->next
                ) {
                        vm_offset_t useEnd, useStart;

                        if (current->eflags & MAP_ENTRY_IS_SUB_MAP)
                                continue;

                        pstart = OFF_TO_IDX(current->offset);
                        pend = pstart + atop(current->end - current->start);
                        useStart = current->start;
                        useEnd = current->end;

                        if (current->start < start) {
                                pstart += atop(start - current->start);
                                useStart = start;
                        }
                        if (current->end > end) {
                                pend -= atop(current->end - end);
                                useEnd = end;
                        }

                        if (pstart >= pend)
                                continue;

                        /*
                         * Perform the pmap_advise() before clearing
                         * PGA_REFERENCED in vm_page_advise().  Otherwise, a
                         * concurrent pmap operation, such as pmap_remove(),
                         * could clear a reference in the pmap and set
                         * PGA_REFERENCED on the page before the pmap_advise()
                         * had completed.  Consequently, the page would appear
                         * referenced based upon an old reference that
                         * occurred before this pmap_advise() ran.
                         */
                        if (behav == MADV_DONTNEED || behav == MADV_FREE)
                                pmap_advise(map->pmap, useStart, useEnd,
                                    behav);

                        vm_object_madvise(current->object.vm_object, pstart,
                            pend, behav);
                        if (behav == MADV_WILLNEED) {
                                vm_map_pmap_enter(map,
                                    useStart,
                                    current->protection,
                                    current->object.vm_object,
                                    pstart,
                                    ptoa(pend - pstart),
                                    MAP_PREFAULT_MADVISE
                                );
                        }
                }
                vm_map_unlock_read(map);
        }
        return (0);
}


/*
 *      vm_map_inherit:
 *
 *      Sets the inheritance of the specified address
 *      range in the target map.  Inheritance
 *      affects how the map will be shared with
 *      child maps at the time of vmspace_fork.
 */
int
vm_map_inherit(vm_map_t map, vm_offset_t start, vm_offset_t end,
               vm_inherit_t new_inheritance)
{
        vm_map_entry_t entry;
        vm_map_entry_t temp_entry;

        switch (new_inheritance) {
        case VM_INHERIT_NONE:
        case VM_INHERIT_COPY:
        case VM_INHERIT_SHARE:
                break;
        default:
                return (KERN_INVALID_ARGUMENT);
        }
        vm_map_lock(map);
        VM_MAP_RANGE_CHECK(map, start, end);
        if (vm_map_lookup_entry(map, start, &temp_entry)) {
                entry = temp_entry;
                vm_map_clip_start(map, entry, start);
        } else
                entry = temp_entry->next;
        while ((entry != &map->header) && (entry->start < end)) {
                vm_map_clip_end(map, entry, end);
                entry->inheritance = new_inheritance;
                vm_map_simplify_entry(map, entry);
                entry = entry->next;
        }
        vm_map_unlock(map);
        return (KERN_SUCCESS);
}

/*
 *      vm_map_unwire:
 *
 *      Implements both kernel and user unwiring.
 */
int
vm_map_unwire(vm_map_t map, vm_offset_t start, vm_offset_t end,
    int flags)
{
        vm_map_entry_t entry, first_entry, tmp_entry;
        vm_offset_t saved_start;
        unsigned int last_timestamp;
        int rv;
        boolean_t need_wakeup, result, user_unwire;

        user_unwire = (flags & VM_MAP_WIRE_USER) ? TRUE : FALSE;
        vm_map_lock(map);
        VM_MAP_RANGE_CHECK(map, start, end);
        if (!vm_map_lookup_entry(map, start, &first_entry)) {
                if (flags & VM_MAP_WIRE_HOLESOK)
                        first_entry = first_entry->next;
                else {
                        vm_map_unlock(map);
                        return (KERN_INVALID_ADDRESS);
                }
        }
        last_timestamp = map->timestamp;
        entry = first_entry;
        while (entry != &map->header && entry->start < end) {
                if (entry->eflags & MAP_ENTRY_IN_TRANSITION) {
                        /*
                         * We have not yet clipped the entry.
                         */
                        saved_start = (start >= entry->start) ? start :
                            entry->start;
                        entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
                        if (vm_map_unlock_and_wait(map, 0)) {
                                /*
                                 * Allow interruption of user unwiring?
                                 */
                        }
                        vm_map_lock(map);
                        if (last_timestamp+1 != map->timestamp) {
                                /*
                                 * Look again for the entry because the map was
                                 * modified while it was unlocked.
                                 * Specifically, the entry may have been
                                 * clipped, merged, or deleted.
                                 */
                                if (!vm_map_lookup_entry(map, saved_start,
                                    &tmp_entry)) {
                                        if (flags & VM_MAP_WIRE_HOLESOK)
                                                tmp_entry = tmp_entry->next;
                                        else {
                                                if (saved_start == start) {
                                                        /*
                                                         * First_entry has been deleted.
                                                         */
                                                        vm_map_unlock(map);
                                                        return (KERN_INVALID_ADDRESS);
                                                }
                                                end = saved_start;
                                                rv = KERN_INVALID_ADDRESS;
                                                goto done;
                                        }
                                }
                                if (entry == first_entry)
                                        first_entry = tmp_entry;
                                else
                                        first_entry = NULL;
                                entry = tmp_entry;
                        }
                        last_timestamp = map->timestamp;
                        continue;
                }
                vm_map_clip_start(map, entry, start);
                vm_map_clip_end(map, entry, end);
                /*
                 * Mark the entry in case the map lock is released.  (See
                 * above.)
                 */
                KASSERT((entry->eflags & MAP_ENTRY_IN_TRANSITION) == 0 &&
                    entry->wiring_thread == NULL,
                    ("owned map entry %p", entry));
                entry->eflags |= MAP_ENTRY_IN_TRANSITION;
                entry->wiring_thread = curthread;
                /*
                 * Check the map for holes in the specified region.
                 * If VM_MAP_WIRE_HOLESOK was specified, skip this check.
                 */
                if (((flags & VM_MAP_WIRE_HOLESOK) == 0) &&
                    (entry->end < end && (entry->next == &map->header ||
                    entry->next->start > entry->end))) {
                        end = entry->end;
                        rv = KERN_INVALID_ADDRESS;
                        goto done;
                }
                /*
                 * If system unwiring, require that the entry is system wired.
                 */
                if (!user_unwire &&
                    vm_map_entry_system_wired_count(entry) == 0) {
                        end = entry->end;
                        rv = KERN_INVALID_ARGUMENT;
                        goto done;
                }
                entry = entry->next;
        }
        rv = KERN_SUCCESS;
done:
        need_wakeup = FALSE;
        if (first_entry == NULL) {
                result = vm_map_lookup_entry(map, start, &first_entry);
                if (!result && (flags & VM_MAP_WIRE_HOLESOK))
                        first_entry = first_entry->next;
                else
                        KASSERT(result, ("vm_map_unwire: lookup failed"));
        }
        for (entry = first_entry; entry != &map->header && entry->start < end;
            entry = entry->next) {
                /*
                 * If VM_MAP_WIRE_HOLESOK was specified, an empty
                 * space in the unwired region could have been mapped
                 * while the map lock was dropped for draining
                 * MAP_ENTRY_IN_TRANSITION.  Moreover, another thread
                 * could be simultaneously wiring this new mapping
                 * entry.  Detect these cases and skip any entries
                 * marked as in transition by us.
                 */
                if ((entry->eflags & MAP_ENTRY_IN_TRANSITION) == 0 ||
                    entry->wiring_thread != curthread) {
                        KASSERT((flags & VM_MAP_WIRE_HOLESOK) != 0,
                            ("vm_map_unwire: !HOLESOK and new/changed entry"));
                        continue;
                }

                if (rv == KERN_SUCCESS && (!user_unwire ||
                    (entry->eflags & MAP_ENTRY_USER_WIRED))) {
                        if (user_unwire)
                                entry->eflags &= ~MAP_ENTRY_USER_WIRED;
                        entry->wired_count--;
                        if (entry->wired_count == 0) {
                                /*
                                 * Retain the map lock.
                                 */
                                vm_fault_unwire(map, entry->start, entry->end,
                                    entry->object.vm_object != NULL &&
                                    (entry->object.vm_object->flags &
                                    OBJ_FICTITIOUS) != 0);
                        }
                }
                KASSERT((entry->eflags & MAP_ENTRY_IN_TRANSITION) != 0,
                    ("vm_map_unwire: in-transition flag missing %p", entry));
                KASSERT(entry->wiring_thread == curthread,
                    ("vm_map_unwire: alien wire %p", entry));
                entry->eflags &= ~MAP_ENTRY_IN_TRANSITION;
                entry->wiring_thread = NULL;
                if (entry->eflags & MAP_ENTRY_NEEDS_WAKEUP) {
                        entry->eflags &= ~MAP_ENTRY_NEEDS_WAKEUP;
                        need_wakeup = TRUE;
                }
                vm_map_simplify_entry(map, entry);
        }
        vm_map_unlock(map);
        if (need_wakeup)
                vm_map_wakeup(map);
        return (rv);
}

/*
 *      vm_map_wire:
 *
 *      Implements both kernel and user wiring.
 */
int
vm_map_wire(vm_map_t map, vm_offset_t start, vm_offset_t end,
    int flags)
{
        vm_map_entry_t entry, first_entry, tmp_entry;
        vm_offset_t saved_end, saved_start;
        unsigned int last_timestamp;
        int rv;
        boolean_t fictitious, need_wakeup, result, user_wire;
        vm_prot_t prot;

        prot = 0;
        if (flags & VM_MAP_WIRE_WRITE)
                prot |= VM_PROT_WRITE;
        user_wire = (flags & VM_MAP_WIRE_USER) ? TRUE : FALSE;
        vm_map_lock(map);
        VM_MAP_RANGE_CHECK(map, start, end);
        if (!vm_map_lookup_entry(map, start, &first_entry)) {
                if (flags & VM_MAP_WIRE_HOLESOK)
                        first_entry = first_entry->next;
                else {
                        vm_map_unlock(map);
                        return (KERN_INVALID_ADDRESS);
                }
        }
        last_timestamp = map->timestamp;
        entry = first_entry;
        while (entry != &map->header && entry->start < end) {
                if (entry->eflags & MAP_ENTRY_IN_TRANSITION) {
                        /*
                         * We have not yet clipped the entry.
                         */
                        saved_start = (start >= entry->start) ? start :
                            entry->start;
                        entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
                        if (vm_map_unlock_and_wait(map, 0)) {
                                /*
                                 * Allow interruption of user wiring?
                                 */
                        }
                        vm_map_lock(map);
                        if (last_timestamp + 1 != map->timestamp) {
                                /*
                                 * Look again for the entry because the map was
                                 * modified while it was unlocked.
                                 * Specifically, the entry may have been
                                 * clipped, merged, or deleted.
                                 */
                                if (!vm_map_lookup_entry(map, saved_start,
                                    &tmp_entry)) {
                                        if (flags & VM_MAP_WIRE_HOLESOK)
                                                tmp_entry = tmp_entry->next;
                                        else {
                                                if (saved_start == start) {
                                                        /*
                                                         * first_entry has been deleted.
                                                         */
                                                        vm_map_unlock(map);
                                                        return (KERN_INVALID_ADDRESS);
                                                }
                                                end = saved_start;
                                                rv = KERN_INVALID_ADDRESS;
                                                goto done;
                                        }
                                }
                                if (entry == first_entry)
                                        first_entry = tmp_entry;
                                else
                                        first_entry = NULL;
                                entry = tmp_entry;
                        }
                        last_timestamp = map->timestamp;
                        continue;
                }
                vm_map_clip_start(map, entry, start);
                vm_map_clip_end(map, entry, end);
                /*
                 * Mark the entry in case the map lock is released.  (See
                 * above.)
                 */
                KASSERT((entry->eflags & MAP_ENTRY_IN_TRANSITION) == 0 &&
                    entry->wiring_thread == NULL,
                    ("owned map entry %p", entry));
                entry->eflags |= MAP_ENTRY_IN_TRANSITION;
                entry->wiring_thread = curthread;
                if ((entry->protection & (VM_PROT_READ | VM_PROT_EXECUTE)) == 0
                    || (entry->protection & prot) != prot) {
                        entry->eflags |= MAP_ENTRY_WIRE_SKIPPED;
                        if ((flags & VM_MAP_WIRE_HOLESOK) == 0) {
                                end = entry->end;
                                rv = KERN_INVALID_ADDRESS;
                                goto done;
                        }
                        goto next_entry;
                }
                if (entry->wired_count == 0) {
                        entry->wired_count++;
                        saved_start = entry->start;
                        saved_end = entry->end;
                        fictitious = entry->object.vm_object != NULL &&
                            (entry->object.vm_object->flags &
                            OBJ_FICTITIOUS) != 0;
                        /*
                         * Release the map lock, relying on the in-transition
                         * mark.  Mark the map busy for fork.
                         */
                        vm_map_busy(map);
                        vm_map_unlock(map);
                        rv = vm_fault_wire(map, saved_start, saved_end,
                            fictitious);
                        vm_map_lock(map);
                        vm_map_unbusy(map);
                        if (last_timestamp + 1 != map->timestamp) {
                                /*
                                 * Look again for the entry because the map was
                                 * modified while it was unlocked.  The entry
                                 * may have been clipped, but NOT merged or
                                 * deleted.
                                 */
                                result = vm_map_lookup_entry(map, saved_start,
                                    &tmp_entry);
                                KASSERT(result, ("vm_map_wire: lookup failed"));
                                if (entry == first_entry)
                                        first_entry = tmp_entry;
                                else
                                        first_entry = NULL;
                                entry = tmp_entry;
                                while (entry->end < saved_end) {
                                        if (rv != KERN_SUCCESS) {
                                                KASSERT(entry->wired_count == 1,
                                                    ("vm_map_wire: bad count"));
                                                entry->wired_count = -1;
                                        }
                                        entry = entry->next;
                                }
                        }
                        last_timestamp = map->timestamp;
                        if (rv != KERN_SUCCESS) {
                                KASSERT(entry->wired_count == 1,
                                    ("vm_map_wire: bad count"));
                                /*
                                 * Assign an out-of-range value to represent
                                 * the failure to wire this entry.
                                 */
                                entry->wired_count = -1;
                                end = entry->end;
                                goto done;
                        }
                } else if (!user_wire ||
                           (entry->eflags & MAP_ENTRY_USER_WIRED) == 0) {
                        entry->wired_count++;
                }
                /*
                 * Check the map for holes in the specified region.
                 * If VM_MAP_WIRE_HOLESOK was specified, skip this check.
                 */
        next_entry:
                if (((flags & VM_MAP_WIRE_HOLESOK) == 0) &&
                    (entry->end < end && (entry->next == &map->header ||
                    entry->next->start > entry->end))) {
                        end = entry->end;
                        rv = KERN_INVALID_ADDRESS;
                        goto done;
                }
                entry = entry->next;
        }
        rv = KERN_SUCCESS;
done:
        need_wakeup = FALSE;
        if (first_entry == NULL) {
                result = vm_map_lookup_entry(map, start, &first_entry);
                if (!result && (flags & VM_MAP_WIRE_HOLESOK))
                        first_entry = first_entry->next;
                else
                        KASSERT(result, ("vm_map_wire: lookup failed"));
        }
        for (entry = first_entry; entry != &map->header && entry->start < end;
            entry = entry->next) {
                if ((entry->eflags & MAP_ENTRY_WIRE_SKIPPED) != 0)
                        goto next_entry_done;

                /*
                 * If VM_MAP_WIRE_HOLESOK was specified, an empty
                 * space in the unwired region could have been mapped
                 * while the map lock was dropped for faulting in the
                 * pages or draining MAP_ENTRY_IN_TRANSITION.
                 * Moreover, another thread could be simultaneously
                 * wiring this new mapping entry.  Detect these cases
                 * and skip any entries marked as in transition by us.
                 */
                if ((entry->eflags & MAP_ENTRY_IN_TRANSITION) == 0 ||
                    entry->wiring_thread != curthread) {
                        KASSERT((flags & VM_MAP_WIRE_HOLESOK) != 0,
                            ("vm_map_wire: !HOLESOK and new/changed entry"));
                        continue;
                }

                if (rv == KERN_SUCCESS) {
                        if (user_wire)
                                entry->eflags |= MAP_ENTRY_USER_WIRED;
                } else if (entry->wired_count == -1) {
                        /*
                         * Wiring failed on this entry.  Thus, unwiring is
                         * unnecessary.
                         */
                        entry->wired_count = 0;
                } else {
                        if (!user_wire ||
                            (entry->eflags & MAP_ENTRY_USER_WIRED) == 0)
                                entry->wired_count--;
                        if (entry->wired_count == 0) {
                                /*
                                 * Retain the map lock.
                                 */
                                vm_fault_unwire(map, entry->start, entry->end,
                                    entry->object.vm_object != NULL &&
                                    (entry->object.vm_object->flags &
                                    OBJ_FICTITIOUS) != 0);
                        }
                }
        next_entry_done:
                KASSERT((entry->eflags & MAP_ENTRY_IN_TRANSITION) != 0,
                    ("vm_map_wire: in-transition flag missing %p", entry));
                KASSERT(entry->wiring_thread == curthread,
                    ("vm_map_wire: alien wire %p", entry));
                entry->eflags &= ~(MAP_ENTRY_IN_TRANSITION |
                    MAP_ENTRY_WIRE_SKIPPED);
                entry->wiring_thread = NULL;
                if (entry->eflags & MAP_ENTRY_NEEDS_WAKEUP) {
                        entry->eflags &= ~MAP_ENTRY_NEEDS_WAKEUP;
                        need_wakeup = TRUE;
                }
                vm_map_simplify_entry(map, entry);
        }
        vm_map_unlock(map);
        if (need_wakeup)
                vm_map_wakeup(map);
        return (rv);
}

/*
 * vm_map_sync
 *
 * Push any dirty cached pages in the address range to their pager.
 * If syncio is TRUE, dirty pages are written synchronously.
 * If invalidate is TRUE, any cached pages are freed as well.
 *
 * If the size of the region from start to end is zero, we are
 * supposed to flush all modified pages within the region containing
 * start.  Unfortunately, a region can be split or coalesced with
 * neighboring regions, making it difficult to determine what the
 * original region was.  Therefore, we approximate this requirement by
 * flushing the current region containing start.
 *
 * Returns an error if any part of the specified range is not mapped.
 */
int
vm_map_sync(
        vm_map_t map,
        vm_offset_t start,
        vm_offset_t end,
        boolean_t syncio,
        boolean_t invalidate)
{
        vm_map_entry_t current;
        vm_map_entry_t entry;
        vm_size_t size;
        vm_object_t object;
        vm_ooffset_t offset;
        unsigned int last_timestamp;
        boolean_t failed;

        vm_map_lock_read(map);
        VM_MAP_RANGE_CHECK(map, start, end);
        if (!vm_map_lookup_entry(map, start, &entry)) {
                vm_map_unlock_read(map);
                return (KERN_INVALID_ADDRESS);
        } else if (start == end) {
                start = entry->start;
                end = entry->end;
        }
        /*
         * Make a first pass to check for user-wired memory and holes.
         */
        for (current = entry; current != &map->header && current->start < end;
            current = current->next) {
                if (invalidate && (current->eflags & MAP_ENTRY_USER_WIRED)) {
                        vm_map_unlock_read(map);
                        return (KERN_INVALID_ARGUMENT);
                }
                if (end > current->end &&
                    (current->next == &map->header ||
                        current->end != current->next->start)) {
                        vm_map_unlock_read(map);
                        return (KERN_INVALID_ADDRESS);
                }
        }

        if (invalidate)
                pmap_remove(map->pmap, start, end);
        failed = FALSE;

        /*
         * Make a second pass, cleaning/uncaching pages from the indicated
         * objects as we go.
         */
        for (current = entry; current != &map->header && current->start < end;) {
                offset = current->offset + (start - current->start);
                size = (end <= current->end ? end : current->end) - start;
                if (current->eflags & MAP_ENTRY_IS_SUB_MAP) {
                        vm_map_t smap;
                        vm_map_entry_t tentry;
                        vm_size_t tsize;

                        smap = current->object.sub_map;
                        vm_map_lock_read(smap);
                        (void) vm_map_lookup_entry(smap, offset, &tentry);
                        tsize = tentry->end - offset;
                        if (tsize < size)
                                size = tsize;
                        object = tentry->object.vm_object;
                        offset = tentry->offset + (offset - tentry->start);
                        vm_map_unlock_read(smap);
                } else {
                        object = current->object.vm_object;
                }
                vm_object_reference(object);
                last_timestamp = map->timestamp;
                vm_map_unlock_read(map);
                if (!vm_object_sync(object, offset, size, syncio, invalidate))
                        failed = TRUE;
                start += size;
                vm_object_deallocate(object);
                vm_map_lock_read(map);
                if (last_timestamp == map->timestamp ||
                    !vm_map_lookup_entry(map, start, &current))
                        current = current->next;
        }

        vm_map_unlock_read(map);
        return (failed ? KERN_FAILURE : KERN_SUCCESS);
}

/*
 *      vm_map_entry_unwire:    [ internal use only ]
 *
 *      Make the region specified by this entry pageable.
 *
 *      The map in question should be locked.
 *      [This is the reason for this routine's existence.]
 */
static void
vm_map_entry_unwire(vm_map_t map, vm_map_entry_t entry)
{
        vm_fault_unwire(map, entry->start, entry->end,
            entry->object.vm_object != NULL &&
            (entry->object.vm_object->flags & OBJ_FICTITIOUS) != 0);
        entry->wired_count = 0;
}

static void
vm_map_entry_deallocate(vm_map_entry_t entry, boolean_t system_map)
{

        if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) == 0)
                vm_object_deallocate(entry->object.vm_object);
        uma_zfree(system_map ? kmapentzone : mapentzone, entry);
}

/*
 *      vm_map_entry_delete:    [ internal use only ]
 *
 *      Deallocate the given entry from the target map.
 */
static void
vm_map_entry_delete(vm_map_t map, vm_map_entry_t entry)
{
        vm_object_t object;
        vm_pindex_t offidxstart, offidxend, count, size1;
        vm_ooffset_t size;

        vm_map_entry_unlink(map, entry);
        object = entry->object.vm_object;
        size = entry->end - entry->start;
        map->size -= size;

        if (entry->cred != NULL) {
                swap_release_by_cred(size, entry->cred);
                crfree(entry->cred);
        }

        if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) == 0 &&
            (object != NULL)) {
                KASSERT(entry->cred == NULL || object->cred == NULL ||
                    (entry->eflags & MAP_ENTRY_NEEDS_COPY),
                    ("OVERCOMMIT vm_map_entry_delete: both cred %p", entry));
                count = OFF_TO_IDX(size);
                offidxstart = OFF_TO_IDX(entry->offset);
                offidxend = offidxstart + count;
                VM_OBJECT_WLOCK(object);
                if (object->ref_count != 1 &&
                    ((object->flags & (OBJ_NOSPLIT|OBJ_ONEMAPPING)) == OBJ_ONEMAPPING ||
                    object == kernel_object || object == kmem_object)) {
                        vm_object_collapse(object);

                        /*
                         * The option OBJPR_NOTMAPPED can be passed here
                         * because vm_map_delete() already performed
                         * pmap_remove() on the only mapping to this range
                         * of pages. 
                         */
                        vm_object_page_remove(object, offidxstart, offidxend,
                            OBJPR_NOTMAPPED);
                        if (object->type == OBJT_SWAP)
                                swap_pager_freespace(object, offidxstart, count);
                        if (offidxend >= object->size &&
                            offidxstart < object->size) {
                                size1 = object->size;
                                object->size = offidxstart;
                                if (object->cred != NULL) {
                                        size1 -= object->size;
                                        KASSERT(object->charge >= ptoa(size1),
                                            ("vm_map_entry_delete: object->charge < 0"));
                                        swap_release_by_cred(ptoa(size1), object->cred);
                                        object->charge -= ptoa(size1);
                                }
                        }
                }
                VM_OBJECT_WUNLOCK(object);
        } else
                entry->object.vm_object = NULL;
        if (map->system_map)
                vm_map_entry_deallocate(entry, TRUE);
        else {
                entry->next = curthread->td_map_def_user;
                curthread->td_map_def_user = entry;
        }
}

/*
 *      vm_map_delete:  [ internal use only ]
 *
 *      Deallocates the given address range from the target
 *      map.
 */
int
vm_map_delete(vm_map_t map, vm_offset_t start, vm_offset_t end)
{
        vm_map_entry_t entry;
        vm_map_entry_t first_entry;

        VM_MAP_ASSERT_LOCKED(map);

        /*
         * Find the start of the region, and clip it
         */
        if (!vm_map_lookup_entry(map, start, &first_entry))
                entry = first_entry->next;
        else {
                entry = first_entry;
                vm_map_clip_start(map, entry, start);
        }

        /*
         * Step through all entries in this region
         */
        while ((entry != &map->header) && (entry->start < end)) {
                vm_map_entry_t next;

                /*
                 * Wait for wiring or unwiring of an entry to complete.
                 * Also wait for any system wirings to disappear on
                 * user maps.
                 */
                if ((entry->eflags & MAP_ENTRY_IN_TRANSITION) != 0 ||
                    (vm_map_pmap(map) != kernel_pmap &&
                    vm_map_entry_system_wired_count(entry) != 0)) {
                        unsigned int last_timestamp;
                        vm_offset_t saved_start;
                        vm_map_entry_t tmp_entry;

                        saved_start = entry->start;
                        entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
                        last_timestamp = map->timestamp;
                        (void) vm_map_unlock_and_wait(map, 0);
                        vm_map_lock(map);
                        if (last_timestamp + 1 != map->timestamp) {
                                /*
                                 * Look again for the entry because the map was
                                 * modified while it was unlocked.
                                 * Specifically, the entry may have been
                                 * clipped, merged, or deleted.
                                 */
                                if (!vm_map_lookup_entry(map, saved_start,
                                                         &tmp_entry))
                                        entry = tmp_entry->next;
                                else {
                                        entry = tmp_entry;
                                        vm_map_clip_start(map, entry,
                                                          saved_start);
                                }
                        }
                        continue;
                }
                vm_map_clip_end(map, entry, end);

                next = entry->next;

                /*
                 * Unwire before removing addresses from the pmap; otherwise,
                 * unwiring will put the entries back in the pmap.
                 */
                if (entry->wired_count != 0) {
                        vm_map_entry_unwire(map, entry);
                }

                pmap_remove(map->pmap, entry->start, entry->end);

                /*
                 * Delete the entry only after removing all pmap
                 * entries pointing to its pages.  (Otherwise, its
                 * page frames may be reallocated, and any modify bits
                 * will be set in the wrong object!)
                 */
                vm_map_entry_delete(map, entry);
                entry = next;
        }
        return (KERN_SUCCESS);
}

/*
 *      vm_map_remove:
 *
 *      Remove the given address range from the target map.
 *      This is the exported form of vm_map_delete.
 */
int
vm_map_remove(vm_map_t map, vm_offset_t start, vm_offset_t end)
{
        int result;

        vm_map_lock(map);
        VM_MAP_RANGE_CHECK(map, start, end);
        result = vm_map_delete(map, start, end);
        vm_map_unlock(map);
        return (result);
}

/*
 *      vm_map_check_protection:
 *
 *      Assert that the target map allows the specified privilege on the
 *      entire address region given.  The entire region must be allocated.
 *
 *      WARNING!  This code does not and should not check whether the
 *      contents of the region is accessible.  For example a smaller file
 *      might be mapped into a larger address space.
 *
 *      NOTE!  This code is also called by munmap().
 *
 *      The map must be locked.  A read lock is sufficient.
 */
boolean_t
vm_map_check_protection(vm_map_t map, vm_offset_t start, vm_offset_t end,
                        vm_prot_t protection)
{
        vm_map_entry_t entry;
        vm_map_entry_t tmp_entry;

        if (!vm_map_lookup_entry(map, start, &tmp_entry))
                return (FALSE);
        entry = tmp_entry;

        while (start < end) {
                if (entry == &map->header)
                        return (FALSE);
                /*
                 * No holes allowed!
                 */
                if (start < entry->start)
                        return (FALSE);
                /*
                 * Check protection associated with entry.
                 */
                if ((entry->protection & protection) != protection)
                        return (FALSE);
                /* go to next entry */
                start = entry->end;
                entry = entry->next;
        }
        return (TRUE);
}

/*
 *      vm_map_copy_entry:
 *
 *      Copies the contents of the source entry to the destination
 *      entry.  The entries *must* be aligned properly.
 */
static void
vm_map_copy_entry(
        vm_map_t src_map,
        vm_map_t dst_map,
        vm_map_entry_t src_entry,
        vm_map_entry_t dst_entry,
        vm_ooffset_t *fork_charge)
{
        vm_object_t src_object;
        vm_map_entry_t fake_entry;
        vm_offset_t size;
        struct ucred *cred;
        int charged;

        VM_MAP_ASSERT_LOCKED(dst_map);

        if ((dst_entry->eflags|src_entry->eflags) & MAP_ENTRY_IS_SUB_MAP)
                return;

        if (src_entry->wired_count == 0) {

                /*
                 * If the source entry is marked needs_copy, it is already
                 * write-protected.
                 */
                if ((src_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) {
                        pmap_protect(src_map->pmap,
                            src_entry->start,
                            src_entry->end,
                            src_entry->protection & ~VM_PROT_WRITE);
                }

                /*
                 * Make a copy of the object.
                 */
                size = src_entry->end - src_entry->start;
                if ((src_object = src_entry->object.vm_object) != NULL) {
                        VM_OBJECT_WLOCK(src_object);
                        charged = ENTRY_CHARGED(src_entry);
                        if ((src_object->handle == NULL) &&
                                (src_object->type == OBJT_DEFAULT ||
                                 src_object->type == OBJT_SWAP)) {
                                vm_object_collapse(src_object);
                                if ((src_object->flags & (OBJ_NOSPLIT|OBJ_ONEMAPPING)) == OBJ_ONEMAPPING) {
                                        vm_object_split(src_entry);
                                        src_object = src_entry->object.vm_object;
                                }
                        }
                        vm_object_reference_locked(src_object);
                        vm_object_clear_flag(src_object, OBJ_ONEMAPPING);
                        if (src_entry->cred != NULL &&
                            !(src_entry->eflags & MAP_ENTRY_NEEDS_COPY)) {
                                KASSERT(src_object->cred == NULL,
                                    ("OVERCOMMIT: vm_map_copy_entry: cred %p",
                                     src_object));
                                src_object->cred = src_entry->cred;
                                src_object->charge = size;
                        }
                        VM_OBJECT_WUNLOCK(src_object);
                        dst_entry->object.vm_object = src_object;
                        if (charged) {
                                cred = curthread->td_ucred;
                                crhold(cred);
                                dst_entry->cred = cred;
                                *fork_charge += size;
                                if (!(src_entry->eflags &
                                      MAP_ENTRY_NEEDS_COPY)) {
                                        crhold(cred);
                                        src_entry->cred = cred;
                                        *fork_charge += size;
                                }
                        }
                        src_entry->eflags |= (MAP_ENTRY_COW|MAP_ENTRY_NEEDS_COPY);
                        dst_entry->eflags |= (MAP_ENTRY_COW|MAP_ENTRY_NEEDS_COPY);
                        dst_entry->offset = src_entry->offset;
                        if (src_entry->eflags & MAP_ENTRY_VN_WRITECNT) {
                                /*
                                 * MAP_ENTRY_VN_WRITECNT cannot
                                 * indicate write reference from
                                 * src_entry, since the entry is
                                 * marked as needs copy.  Allocate a
                                 * fake entry that is used to
                                 * decrement object->un_pager.vnp.writecount
                                 * at the appropriate time.  Attach
                                 * fake_entry to the deferred list.
                                 */
                                fake_entry = vm_map_entry_create(dst_map);
                                fake_entry->eflags = MAP_ENTRY_VN_WRITECNT;
                                src_entry->eflags &= ~MAP_ENTRY_VN_WRITECNT;
                                vm_object_reference(src_object);
                                fake_entry->object.vm_object = src_object;
                                fake_entry->start = src_entry->start;
                                fake_entry->end = src_entry->end;
                                fake_entry->next = curthread->td_map_def_user;
                                curthread->td_map_def_user = fake_entry;
                        }
                } else {
                        dst_entry->object.vm_object = NULL;
                        dst_entry->offset = 0;
                        if (src_entry->cred != NULL) {
                                dst_entry->cred = curthread->td_ucred;
                                crhold(dst_entry->cred);
                                *fork_charge += size;
                        }
                }

                pmap_copy(dst_map->pmap, src_map->pmap, dst_entry->start,
                    dst_entry->end - dst_entry->start, src_entry->start);
        } else {
                /*
                 * Of course, wired down pages can't be set copy-on-write.
                 * Cause wired pages to be copied into the new map by
                 * simulating faults (the new pages are pageable)
                 */
                vm_fault_copy_entry(dst_map, src_map, dst_entry, src_entry,
                    fork_charge);
        }
}

/*
 * vmspace_map_entry_forked:
 * Update the newly-forked vmspace each time a map entry is inherited
 * or copied.  The values for vm_dsize and vm_tsize are approximate
 * (and mostly-obsolete ideas in the face of mmap(2) et al.)
 */
static void
vmspace_map_entry_forked(const struct vmspace *vm1, struct vmspace *vm2,
    vm_map_entry_t entry)
{
        vm_size_t entrysize;
        vm_offset_t newend;

        entrysize = entry->end - entry->start;
        vm2->vm_map.size += entrysize;
        if (entry->eflags & (MAP_ENTRY_GROWS_DOWN | MAP_ENTRY_GROWS_UP)) {
                vm2->vm_ssize += btoc(entrysize);
        } else if (entry->start >= (vm_offset_t)vm1->vm_daddr &&
            entry->start < (vm_offset_t)vm1->vm_daddr + ctob(vm1->vm_dsize)) {
                newend = MIN(entry->end,
                    (vm_offset_t)vm1->vm_daddr + ctob(vm1->vm_dsize));
                vm2->vm_dsize += btoc(newend - entry->start);
        } else if (entry->start >= (vm_offset_t)vm1->vm_taddr &&
            entry->start < (vm_offset_t)vm1->vm_taddr + ctob(vm1->vm_tsize)) {
                newend = MIN(entry->end,
                    (vm_offset_t)vm1->vm_taddr + ctob(vm1->vm_tsize));
                vm2->vm_tsize += btoc(newend - entry->start);
        }
}

/*
 * vmspace_fork:
 * Create a new process vmspace structure and vm_map
 * based on those of an existing process.  The new map
 * is based on the old map, according to the inheritance
 * values on the regions in that map.
 *
 * XXX It might be worth coalescing the entries added to the new vmspace.
 *
 * The source map must not be locked.
 */
struct vmspace *
vmspace_fork(struct vmspace *vm1, vm_ooffset_t *fork_charge)
{
        struct vmspace *vm2;
        vm_map_t new_map, old_map;
        vm_map_entry_t new_entry, old_entry;
        vm_object_t object;
        int locked;

        old_map = &vm1->vm_map;
        /* Copy immutable fields of vm1 to vm2. */
        vm2 = vmspace_alloc(old_map->min_offset, old_map->max_offset, NULL);
        if (vm2 == NULL)
                return (NULL);
        vm2->vm_taddr = vm1->vm_taddr;
        vm2->vm_daddr = vm1->vm_daddr;
        vm2->vm_maxsaddr = vm1->vm_maxsaddr;
        vm_map_lock(old_map);
        if (old_map->busy)
                vm_map_wait_busy(old_map);
        new_map = &vm2->vm_map;
        locked = vm_map_trylock(new_map); /* trylock to silence WITNESS */
        KASSERT(locked, ("vmspace_fork: lock failed"));

        old_entry = old_map->header.next;

        while (old_entry != &old_map->header) {
                if (old_entry->eflags & MAP_ENTRY_IS_SUB_MAP)
                        panic("vm_map_fork: encountered a submap");

                switch (old_entry->inheritance) {
                case VM_INHERIT_NONE:
                        break;

                case VM_INHERIT_SHARE:
                        /*
                         * Clone the entry, creating the shared object if necessary.
                         */
                        object = old_entry->object.vm_object;
                        if (object == NULL) {
                                object = vm_object_allocate(OBJT_DEFAULT,
                                        atop(old_entry->end - old_entry->start));
                                old_entry->object.vm_object = object;
                                old_entry->offset = 0;
                                if (old_entry->cred != NULL) {
                                        object->cred = old_entry->cred;
                                        object->charge = old_entry->end -
                                            old_entry->start;
                                        old_entry->cred = NULL;
                                }
                        }

                        /*
                         * Add the reference before calling vm_object_shadow
                         * to insure that a shadow object is created.
                         */
                        vm_object_reference(object);
                        if (old_entry->eflags & MAP_ENTRY_NEEDS_COPY) {
                                vm_object_shadow(&old_entry->object.vm_object,
                                    &old_entry->offset,
                                    old_entry->end - old_entry->start);
                                old_entry->eflags &= ~MAP_ENTRY_NEEDS_COPY;
                                /* Transfer the second reference too. */
                                vm_object_reference(
                                    old_entry->object.vm_object);

                                /*
                                 * As in vm_map_simplify_entry(), the
                                 * vnode lock will not be acquired in
                                 * this call to vm_object_deallocate().
                                 */
                                vm_object_deallocate(object);
                                object = old_entry->object.vm_object;
                        }
                        VM_OBJECT_WLOCK(object);
                        vm_object_clear_flag(object, OBJ_ONEMAPPING);
                        if (old_entry->cred != NULL) {
                                KASSERT(object->cred == NULL, ("vmspace_fork both cred"));
                                object->cred = old_entry->cred;
                                object->charge = old_entry->end - old_entry->start;
                                old_entry->cred = NULL;
                        }

                        /*
                         * Assert the correct state of the vnode
                         * v_writecount while the object is locked, to
                         * not relock it later for the assertion
                         * correctness.
                         */
                        if (old_entry->eflags & MAP_ENTRY_VN_WRITECNT &&
                            object->type == OBJT_VNODE) {
                                KASSERT(((struct vnode *)object->handle)->
                                    v_writecount > 0,
                                    ("vmspace_fork: v_writecount %p", object));
                                KASSERT(object->un_pager.vnp.writemappings > 0,
                                    ("vmspace_fork: vnp.writecount %p",
                                    object));
                        }
                        VM_OBJECT_WUNLOCK(object);

                        /*
                         * Clone the entry, referencing the shared object.
                         */
                        new_entry = vm_map_entry_create(new_map);
                        *new_entry = *old_entry;
                        new_entry->eflags &= ~(MAP_ENTRY_USER_WIRED |
                            MAP_ENTRY_IN_TRANSITION);
                        new_entry->wiring_thread = NULL;
                        new_entry->wired_count = 0;
                        if (new_entry->eflags & MAP_ENTRY_VN_WRITECNT) {
                                vnode_pager_update_writecount(object,
                                    new_entry->start, new_entry->end);
                        }

                        /*
                         * Insert the entry into the new map -- we know we're
                         * inserting at the end of the new map.
                         */
                        vm_map_entry_link(new_map, new_map->header.prev,
                            new_entry);
                        vmspace_map_entry_forked(vm1, vm2, new_entry);

                        /*
                         * Update the physical map
                         */
                        pmap_copy(new_map->pmap, old_map->pmap,
                            new_entry->start,
                            (old_entry->end - old_entry->start),
                            old_entry->start);
                        break;

                case VM_INHERIT_COPY:
                        /*
                         * Clone the entry and link into the map.
                         */
                        new_entry = vm_map_entry_create(new_map);
                        *new_entry = *old_entry;
                        /*
                         * Copied entry is COW over the old object.
                         */
                        new_entry->eflags &= ~(MAP_ENTRY_USER_WIRED |
                            MAP_ENTRY_IN_TRANSITION | MAP_ENTRY_VN_WRITECNT);
                        new_entry->wiring_thread = NULL;
                        new_entry->wired_count = 0;
                        new_entry->object.vm_object = NULL;
                        new_entry->cred = NULL;
                        vm_map_entry_link(new_map, new_map->header.prev,
                            new_entry);
                        vmspace_map_entry_forked(vm1, vm2, new_entry);
                        vm_map_copy_entry(old_map, new_map, old_entry,
                            new_entry, fork_charge);
                        break;
                }
                old_entry = old_entry->next;
        }
        /*
         * Use inlined vm_map_unlock() to postpone handling the deferred
         * map entries, which cannot be done until both old_map and
         * new_map locks are released.
         */
        sx_xunlock(&old_map->lock);
        sx_xunlock(&new_map->lock);
        vm_map_process_deferred();

        return (vm2);
}

int
vm_map_stack(vm_map_t map, vm_offset_t addrbos, vm_size_t max_ssize,
    vm_prot_t prot, vm_prot_t max, int cow)
{
        vm_map_entry_t new_entry, prev_entry;
        vm_offset_t bot, top;
        vm_size_t growsize, init_ssize;
        int orient, rv;
        rlim_t lmemlim, vmemlim;

        /*
         * The stack orientation is piggybacked with the cow argument.
         * Extract it into orient and mask the cow argument so that we
         * don't pass it around further.
         * NOTE: We explicitly allow bi-directional stacks.
         */
        orient = cow & (MAP_STACK_GROWS_DOWN|MAP_STACK_GROWS_UP);
        cow &= ~orient;
        KASSERT(orient != 0, ("No stack grow direction"));

        if (addrbos < vm_map_min(map) ||
            addrbos > vm_map_max(map) ||
            addrbos + max_ssize < addrbos)
                return (KERN_NO_SPACE);

        growsize = sgrowsiz;
        init_ssize = (max_ssize < growsize) ? max_ssize : growsize;

        PROC_LOCK(curproc);
        lmemlim = lim_cur(curproc, RLIMIT_MEMLOCK);
        vmemlim = lim_cur(curproc, RLIMIT_VMEM);
        PROC_UNLOCK(curproc);

        vm_map_lock(map);

        /* If addr is already mapped, no go */
        if (vm_map_lookup_entry(map, addrbos, &prev_entry)) {
                vm_map_unlock(map);
                return (KERN_NO_SPACE);
        }

        if (!old_mlock && map->flags & MAP_WIREFUTURE) {
                if (ptoa(pmap_wired_count(map->pmap)) + init_ssize > lmemlim) {
                        vm_map_unlock(map);
                        return (KERN_NO_SPACE);
                }
        }

        /* If we would blow our VMEM resource limit, no go */
        if (map->size + init_ssize > vmemlim) {
                vm_map_unlock(map);
                return (KERN_NO_SPACE);
        }

        /*
         * If we can't accomodate max_ssize in the current mapping, no go.
         * However, we need to be aware that subsequent user mappings might
         * map into the space we have reserved for stack, and currently this
         * space is not protected.
         *
         * Hopefully we will at least detect this condition when we try to
         * grow the stack.
         */
        if ((prev_entry->next != &map->header) &&
            (prev_entry->next->start < addrbos + max_ssize)) {
                vm_map_unlock(map);
                return (KERN_NO_SPACE);
        }

        /*
         * We initially map a stack of only init_ssize.  We will grow as
         * needed later.  Depending on the orientation of the stack (i.e.
         * the grow direction) we either map at the top of the range, the
         * bottom of the range or in the middle.
         *
         * Note: we would normally expect prot and max to be VM_PROT_ALL,
         * and cow to be 0.  Possibly we should eliminate these as input
         * parameters, and just pass these values here in the insert call.
         */
        if (orient == MAP_STACK_GROWS_DOWN)
                bot = addrbos + max_ssize - init_ssize;
        else if (orient == MAP_STACK_GROWS_UP)
                bot = addrbos;
        else
                bot = round_page(addrbos + max_ssize/2 - init_ssize/2);
        top = bot + init_ssize;
        rv = vm_map_insert(map, NULL, 0, bot, top, prot, max, cow);

        /* Now set the avail_ssize amount. */
        if (rv == KERN_SUCCESS) {
                if (prev_entry != &map->header)
                        vm_map_clip_end(map, prev_entry, bot);
                new_entry = prev_entry->next;
                if (new_entry->end != top || new_entry->start != bot)
                        panic("Bad entry start/end for new stack entry");

                new_entry->avail_ssize = max_ssize - init_ssize;
                if (orient & MAP_STACK_GROWS_DOWN)
                        new_entry->eflags |= MAP_ENTRY_GROWS_DOWN;
                if (orient & MAP_STACK_GROWS_UP)
                        new_entry->eflags |= MAP_ENTRY_GROWS_UP;
        }

        vm_map_unlock(map);
        return (rv);
}

static int stack_guard_page = 0;
TUNABLE_INT("security.bsd.stack_guard_page", &stack_guard_page);
SYSCTL_INT(_security_bsd, OID_AUTO, stack_guard_page, CTLFLAG_RW,
    &stack_guard_page, 0,
    "Insert stack guard page ahead of the growable segments.");

/* Attempts to grow a vm stack entry.  Returns KERN_SUCCESS if the
 * desired address is already mapped, or if we successfully grow
 * the stack.  Also returns KERN_SUCCESS if addr is outside the
 * stack range (this is strange, but preserves compatibility with
 * the grow function in vm_machdep.c).
 */
int
vm_map_growstack(struct proc *p, vm_offset_t addr)
{
        vm_map_entry_t next_entry, prev_entry;
        vm_map_entry_t new_entry, stack_entry;
        struct vmspace *vm = p->p_vmspace;
        vm_map_t map = &vm->vm_map;
        vm_offset_t end;
        vm_size_t growsize;
        size_t grow_amount, max_grow;
        rlim_t lmemlim, stacklim, vmemlim;
        int is_procstack, rv;
        struct ucred *cred;
#ifdef notyet
        uint64_t limit;
#endif
#ifdef RACCT
        int error;
#endif

Retry:
        PROC_LOCK(p);
        lmemlim = lim_cur(p, RLIMIT_MEMLOCK);
        stacklim = lim_cur(p, RLIMIT_STACK);
        vmemlim = lim_cur(p, RLIMIT_VMEM);
        PROC_UNLOCK(p);

        vm_map_lock_read(map);

        /* If addr is already in the entry range, no need to grow.*/
        if (vm_map_lookup_entry(map, addr, &prev_entry)) {
                vm_map_unlock_read(map);
                return (KERN_SUCCESS);
        }

        next_entry = prev_entry->next;
        if (!(prev_entry->eflags & MAP_ENTRY_GROWS_UP)) {
                /*
                 * This entry does not grow upwards. Since the address lies
                 * beyond this entry, the next entry (if one exists) has to
                 * be a downward growable entry. The entry list header is
                 * never a growable entry, so it suffices to check the flags.
                 */
                if (!(next_entry->eflags & MAP_ENTRY_GROWS_DOWN)) {
                        vm_map_unlock_read(map);
                        return (KERN_SUCCESS);
                }
                stack_entry = next_entry;
        } else {
                /*
                 * This entry grows upward. If the next entry does not at
                 * least grow downwards, this is the entry we need to grow.
                 * otherwise we have two possible choices and we have to
                 * select one.
                 */
                if (next_entry->eflags & MAP_ENTRY_GROWS_DOWN) {
                        /*
                         * We have two choices; grow the entry closest to
                         * the address to minimize the amount of growth.
                         */
                        if (addr - prev_entry->end <= next_entry->start - addr)
                                stack_entry = prev_entry;
                        else
                                stack_entry = next_entry;
                } else
                        stack_entry = prev_entry;
        }

        if (stack_entry == next_entry) {
                KASSERT(stack_entry->eflags & MAP_ENTRY_GROWS_DOWN, ("foo"));
                KASSERT(addr < stack_entry->start, ("foo"));
                end = (prev_entry != &map->header) ? prev_entry->end :
                    stack_entry->start - stack_entry->avail_ssize;
                grow_amount = roundup(stack_entry->start - addr, PAGE_SIZE);
                max_grow = stack_entry->start - end;
        } else {
                KASSERT(stack_entry->eflags & MAP_ENTRY_GROWS_UP, ("foo"));
                KASSERT(addr >= stack_entry->end, ("foo"));
                end = (next_entry != &map->header) ? next_entry->start :
                    stack_entry->end + stack_entry->avail_ssize;
                grow_amount = roundup(addr + 1 - stack_entry->end, PAGE_SIZE);
                max_grow = end - stack_entry->end;
        }

        if (grow_amount > stack_entry->avail_ssize) {
                vm_map_unlock_read(map);
                return (KERN_NO_SPACE);
        }

        /*
         * If there is no longer enough space between the entries nogo, and
         * adjust the available space.  Note: this  should only happen if the
         * user has mapped into the stack area after the stack was created,
         * and is probably an error.
         *
         * This also effectively destroys any guard page the user might have
         * intended by limiting the stack size.
         */
        if (grow_amount + (stack_guard_page ? PAGE_SIZE : 0) > max_grow) {
                if (vm_map_lock_upgrade(map))
                        goto Retry;

                stack_entry->avail_ssize = max_grow;

                vm_map_unlock(map);
                return (KERN_NO_SPACE);
        }

        is_procstack = (addr >= (vm_offset_t)vm->vm_maxsaddr) ? 1 : 0;

        /*
         * If this is the main process stack, see if we're over the stack
         * limit.
         */
        if (is_procstack && (ctob(vm->vm_ssize) + grow_amount > stacklim)) {
                vm_map_unlock_read(map);
                return (KERN_NO_SPACE);
        }
#ifdef RACCT
        PROC_LOCK(p);
        if (is_procstack &&
            racct_set(p, RACCT_STACK, ctob(vm->vm_ssize) + grow_amount)) {
                PROC_UNLOCK(p);
                vm_map_unlock_read(map);
                return (KERN_NO_SPACE);
        }
        PROC_UNLOCK(p);
#endif

        /* Round up the grow amount modulo sgrowsiz */
        growsize = sgrowsiz;
        grow_amount = roundup(grow_amount, growsize);
        if (grow_amount > stack_entry->avail_ssize)
                grow_amount = stack_entry->avail_ssize;
        if (is_procstack && (ctob(vm->vm_ssize) + grow_amount > stacklim)) {
                grow_amount = trunc_page((vm_size_t)stacklim) -
                    ctob(vm->vm_ssize);
        }
#ifdef notyet
        PROC_LOCK(p);
        limit = racct_get_available(p, RACCT_STACK);
        PROC_UNLOCK(p);
        if (is_procstack && (ctob(vm->vm_ssize) + grow_amount > limit))
                grow_amount = limit - ctob(vm->vm_ssize);
#endif
        if (!old_mlock && map->flags & MAP_WIREFUTURE) {
                if (ptoa(pmap_wired_count(map->pmap)) + grow_amount > lmemlim) {
                        vm_map_unlock_read(map);
                        rv = KERN_NO_SPACE;
                        goto out;
                }
#ifdef RACCT
                PROC_LOCK(p);
                if (racct_set(p, RACCT_MEMLOCK,
                    ptoa(pmap_wired_count(map->pmap)) + grow_amount)) {
                        PROC_UNLOCK(p);
                        vm_map_unlock_read(map);
                        rv = KERN_NO_SPACE;
                        goto out;
                }
                PROC_UNLOCK(p);
#endif
        }
        /* If we would blow our VMEM resource limit, no go */
        if (map->size + grow_amount > vmemlim) {
                vm_map_unlock_read(map);
                rv = KERN_NO_SPACE;
                goto out;
        }
#ifdef RACCT
        PROC_LOCK(p);
        if (racct_set(p, RACCT_VMEM, map->size + grow_amount)) {
                PROC_UNLOCK(p);
                vm_map_unlock_read(map);
                rv = KERN_NO_SPACE;
                goto out;
        }
        PROC_UNLOCK(p);
#endif

        if (vm_map_lock_upgrade(map))
                goto Retry;

        if (stack_entry == next_entry) {
                /*
                 * Growing downward.
                 */
                /* Get the preliminary new entry start value */
                addr = stack_entry->start - grow_amount;

                /*
                 * If this puts us into the previous entry, cut back our
                 * growth to the available space. Also, see the note above.
                 */
                if (addr < end) {
                        stack_entry->avail_ssize = max_grow;
                        addr = end;
                        if (stack_guard_page)
                                addr += PAGE_SIZE;
                }

                rv = vm_map_insert(map, NULL, 0, addr, stack_entry->start,
                    next_entry->protection, next_entry->max_protection, 0);

                /* Adjust the available stack space by the amount we grew. */
                if (rv == KERN_SUCCESS) {
                        if (prev_entry != &map->header)
                                vm_map_clip_end(map, prev_entry, addr);
                        new_entry = prev_entry->next;
                        KASSERT(new_entry == stack_entry->prev, ("foo"));
                        KASSERT(new_entry->end == stack_entry->start, ("foo"));
                        KASSERT(new_entry->start == addr, ("foo"));
                        grow_amount = new_entry->end - new_entry->start;
                        new_entry->avail_ssize = stack_entry->avail_ssize -
                            grow_amount;
                        stack_entry->eflags &= ~MAP_ENTRY_GROWS_DOWN;
                        new_entry->eflags |= MAP_ENTRY_GROWS_DOWN;
                }
        } else {
                /*
                 * Growing upward.
                 */
                addr = stack_entry->end + grow_amount;

                /*
                 * If this puts us into the next entry, cut back our growth
                 * to the available space. Also, see the note above.
                 */
                if (addr > end) {
                        stack_entry->avail_ssize = end - stack_entry->end;
                        addr = end;
                        if (stack_guard_page)
                                addr -= PAGE_SIZE;
                }

                grow_amount = addr - stack_entry->end;
                cred = stack_entry->cred;
                if (cred == NULL && stack_entry->object.vm_object != NULL)
                        cred = stack_entry->object.vm_object->cred;
                if (cred != NULL && !swap_reserve_by_cred(grow_amount, cred))
                        rv = KERN_NO_SPACE;
                /* Grow the underlying object if applicable. */
                else if (stack_entry->object.vm_object == NULL ||
                         vm_object_coalesce(stack_entry->object.vm_object,
                         stack_entry->offset,
                         (vm_size_t)(stack_entry->end - stack_entry->start),
                         (vm_size_t)grow_amount, cred != NULL)) {
                        map->size += (addr - stack_entry->end);
                        /* Update the current entry. */
                        stack_entry->end = addr;
                        stack_entry->avail_ssize -= grow_amount;
                        vm_map_entry_resize_free(map, stack_entry);
                        rv = KERN_SUCCESS;

                        if (next_entry != &map->header)
                                vm_map_clip_start(map, next_entry, addr);
                } else
                        rv = KERN_FAILURE;
        }

        if (rv == KERN_SUCCESS && is_procstack)
                vm->vm_ssize += btoc(grow_amount);

        vm_map_unlock(map);

        /*
         * Heed the MAP_WIREFUTURE flag if it was set for this process.
         */
        if (rv == KERN_SUCCESS && (map->flags & MAP_WIREFUTURE)) {
                vm_map_wire(map,
                    (stack_entry == next_entry) ? addr : addr - grow_amount,
                    (stack_entry == next_entry) ? stack_entry->start : addr,
                    (p->p_flag & P_SYSTEM)
                    ? VM_MAP_WIRE_SYSTEM|VM_MAP_WIRE_NOHOLES
                    : VM_MAP_WIRE_USER|VM_MAP_WIRE_NOHOLES);
        }

out:
#ifdef RACCT
        if (rv != KERN_SUCCESS) {
                PROC_LOCK(p);
                error = racct_set(p, RACCT_VMEM, map->size);
                KASSERT(error == 0, ("decreasing RACCT_VMEM failed"));
                if (!old_mlock) {
                        error = racct_set(p, RACCT_MEMLOCK,
                            ptoa(pmap_wired_count(map->pmap)));
                        KASSERT(error == 0, ("decreasing RACCT_MEMLOCK failed"));
                }
                error = racct_set(p, RACCT_STACK, ctob(vm->vm_ssize));
                KASSERT(error == 0, ("decreasing RACCT_STACK failed"));
                PROC_UNLOCK(p);
        }
#endif

        return (rv);
}

/*
 * Unshare the specified VM space for exec.  If other processes are
 * mapped to it, then create a new one.  The new vmspace is null.
 */
int
vmspace_exec(struct proc *p, vm_offset_t minuser, vm_offset_t maxuser)
{
        struct vmspace *oldvmspace = p->p_vmspace;
        struct vmspace *newvmspace;

        newvmspace = vmspace_alloc(minuser, maxuser, NULL);
        if (newvmspace == NULL)
                return (ENOMEM);
        newvmspace->vm_swrss = oldvmspace->vm_swrss;
        /*
         * This code is written like this for prototype purposes.  The
         * goal is to avoid running down the vmspace here, but let the
         * other process's that are still using the vmspace to finally
         * run it down.  Even though there is little or no chance of blocking
         * here, it is a good idea to keep this form for future mods.
         */
        PROC_VMSPACE_LOCK(p);
        p->p_vmspace = newvmspace;
        PROC_VMSPACE_UNLOCK(p);
        if (p == curthread->td_proc)
                pmap_activate(curthread);
        vmspace_free(oldvmspace);
        return (0);
}

/*
 * Unshare the specified VM space for forcing COW.  This
 * is called by rfork, for the (RFMEM|RFPROC) == 0 case.
 */
int
vmspace_unshare(struct proc *p)
{
        struct vmspace *oldvmspace = p->p_vmspace;
        struct vmspace *newvmspace;
        vm_ooffset_t fork_charge;

        if (oldvmspace->vm_refcnt == 1)
                return (0);
        fork_charge = 0;
        newvmspace = vmspace_fork(oldvmspace, &fork_charge);
        if (newvmspace == NULL)
                return (ENOMEM);
        if (!swap_reserve_by_cred(fork_charge, p->p_ucred)) {
                vmspace_free(newvmspace);
                return (ENOMEM);
        }
        PROC_VMSPACE_LOCK(p);
        p->p_vmspace = newvmspace;
        PROC_VMSPACE_UNLOCK(p);
        if (p == curthread->td_proc)
                pmap_activate(curthread);
        vmspace_free(oldvmspace);
        return (0);
}

/*
 *      vm_map_lookup:
 *
 *      Finds the VM object, offset, and
 *      protection for a given virtual address in the
 *      specified map, assuming a page fault of the
 *      type specified.
 *
 *      Leaves the map in question locked for read; return
 *      values are guaranteed until a vm_map_lookup_done
 *      call is performed.  Note that the map argument
 *      is in/out; the returned map must be used in
 *      the call to vm_map_lookup_done.
 *
 *      A handle (out_entry) is returned for use in
 *      vm_map_lookup_done, to make that fast.
 *
 *      If a lookup is requested with "write protection"
 *      specified, the map may be changed to perform virtual
 *      copying operations, although the data referenced will
 *      remain the same.
 */
int
vm_map_lookup(vm_map_t *var_map,                /* IN/OUT */
              vm_offset_t vaddr,
              vm_prot_t fault_typea,
              vm_map_entry_t *out_entry,        /* OUT */
              vm_object_t *object,              /* OUT */
              vm_pindex_t *pindex,              /* OUT */
              vm_prot_t *out_prot,              /* OUT */
              boolean_t *wired)                 /* OUT */
{
        vm_map_entry_t entry;
        vm_map_t map = *var_map;
        vm_prot_t prot;
        vm_prot_t fault_type = fault_typea;
        vm_object_t eobject;
        vm_size_t size;
        struct ucred *cred;

RetryLookup:;

        vm_map_lock_read(map);

        /*
         * Lookup the faulting address.
         */
        if (!vm_map_lookup_entry(map, vaddr, out_entry)) {
                vm_map_unlock_read(map);
                return (KERN_INVALID_ADDRESS);
        }

        entry = *out_entry;

        /*
         * Handle submaps.
         */
        if (entry->eflags & MAP_ENTRY_IS_SUB_MAP) {
                vm_map_t old_map = map;

                *var_map = map = entry->object.sub_map;
                vm_map_unlock_read(old_map);
                goto RetryLookup;
        }

        /*
         * Check whether this task is allowed to have this page.
         */
        prot = entry->protection;
        fault_type &= (VM_PROT_READ|VM_PROT_WRITE|VM_PROT_EXECUTE);
        if ((fault_type & prot) != fault_type || prot == VM_PROT_NONE) {
                vm_map_unlock_read(map);
                return (KERN_PROTECTION_FAILURE);
        }
        if ((entry->eflags & MAP_ENTRY_USER_WIRED) &&
            (entry->eflags & MAP_ENTRY_COW) &&
            (fault_type & VM_PROT_WRITE)) {
                vm_map_unlock_read(map);
                return (KERN_PROTECTION_FAILURE);
        }
        if ((fault_typea & VM_PROT_COPY) != 0 &&
            (entry->max_protection & VM_PROT_WRITE) == 0 &&
            (entry->eflags & MAP_ENTRY_COW) == 0) {
                vm_map_unlock_read(map);
                return (KERN_PROTECTION_FAILURE);
        }

        /*
         * If this page is not pageable, we have to get it for all possible
         * accesses.
         */
        *wired = (entry->wired_count != 0);
        if (*wired)
                fault_type = entry->protection;
        size = entry->end - entry->start;
        /*
         * If the entry was copy-on-write, we either ...
         */
        if (entry->eflags & MAP_ENTRY_NEEDS_COPY) {
                /*
                 * If we want to write the page, we may as well handle that
                 * now since we've got the map locked.
                 *
                 * If we don't need to write the page, we just demote the
                 * permissions allowed.
                 */
                if ((fault_type & VM_PROT_WRITE) != 0 ||
                    (fault_typea & VM_PROT_COPY) != 0) {
                        /*
                         * Make a new object, and place it in the object
                         * chain.  Note that no new references have appeared
                         * -- one just moved from the map to the new
                         * object.
                         */
                        if (vm_map_lock_upgrade(map))
                                goto RetryLookup;

                        if (entry->cred == NULL) {
                                /*
                                 * The debugger owner is charged for
                                 * the memory.
                                 */
                                cred = curthread->td_ucred;
                                crhold(cred);
                                if (!swap_reserve_by_cred(size, cred)) {
                                        crfree(cred);
                                        vm_map_unlock(map);
                                        return (KERN_RESOURCE_SHORTAGE);
                                }
                                entry->cred = cred;
                        }
                        vm_object_shadow(&entry->object.vm_object,
                            &entry->offset, size);
                        entry->eflags &= ~MAP_ENTRY_NEEDS_COPY;
                        eobject = entry->object.vm_object;
                        if (eobject->cred != NULL) {
                                /*
                                 * The object was not shadowed.
                                 */
                                swap_release_by_cred(size, entry->cred);
                                crfree(entry->cred);
                                entry->cred = NULL;
                        } else if (entry->cred != NULL) {
                                VM_OBJECT_WLOCK(eobject);
                                eobject->cred = entry->cred;
                                eobject->charge = size;
                                VM_OBJECT_WUNLOCK(eobject);
                                entry->cred = NULL;
                        }

                        vm_map_lock_downgrade(map);
                } else {
                        /*
                         * We're attempting to read a copy-on-write page --
                         * don't allow writes.
                         */
                        prot &= ~VM_PROT_WRITE;
                }
        }

        /*
         * Create an object if necessary.
         */
        if (entry->object.vm_object == NULL &&
            !map->system_map) {
                if (vm_map_lock_upgrade(map))
                        goto RetryLookup;
                entry->object.vm_object = vm_object_allocate(OBJT_DEFAULT,
                    atop(size));
                entry->offset = 0;
                if (entry->cred != NULL) {
                        VM_OBJECT_WLOCK(entry->object.vm_object);
                        entry->object.vm_object->cred = entry->cred;
                        entry->object.vm_object->charge = size;
                        VM_OBJECT_WUNLOCK(entry->object.vm_object);
                        entry->cred = NULL;
                }
                vm_map_lock_downgrade(map);
        }

        /*
         * Return the object/offset from this entry.  If the entry was
         * copy-on-write or empty, it has been fixed up.
         */
        *pindex = OFF_TO_IDX((vaddr - entry->start) + entry->offset);
        *object = entry->object.vm_object;

        *out_prot = prot;
        return (KERN_SUCCESS);
}

/*
 *      vm_map_lookup_locked:
 *
 *      Lookup the faulting address.  A version of vm_map_lookup that returns 
 *      KERN_FAILURE instead of blocking on map lock or memory allocation.
 */
int
vm_map_lookup_locked(vm_map_t *var_map,         /* IN/OUT */
                     vm_offset_t vaddr,
                     vm_prot_t fault_typea,
                     vm_map_entry_t *out_entry, /* OUT */
                     vm_object_t *object,       /* OUT */
                     vm_pindex_t *pindex,       /* OUT */
                     vm_prot_t *out_prot,       /* OUT */
                     boolean_t *wired)          /* OUT */
{
        vm_map_entry_t entry;
        vm_map_t map = *var_map;
        vm_prot_t prot;
        vm_prot_t fault_type = fault_typea;

        /*
         * Lookup the faulting address.
         */
        if (!vm_map_lookup_entry(map, vaddr, out_entry))
                return (KERN_INVALID_ADDRESS);

        entry = *out_entry;

        /*
         * Fail if the entry refers to a submap.
         */
        if (entry->eflags & MAP_ENTRY_IS_SUB_MAP)
                return (KERN_FAILURE);

        /*
         * Check whether this task is allowed to have this page.
         */
        prot = entry->protection;
        fault_type &= VM_PROT_READ | VM_PROT_WRITE | VM_PROT_EXECUTE;
        if ((fault_type & prot) != fault_type)
                return (KERN_PROTECTION_FAILURE);
        if ((entry->eflags & MAP_ENTRY_USER_WIRED) &&
            (entry->eflags & MAP_ENTRY_COW) &&
            (fault_type & VM_PROT_WRITE))
                return (KERN_PROTECTION_FAILURE);

        /*
         * If this page is not pageable, we have to get it for all possible
         * accesses.
         */
        *wired = (entry->wired_count != 0);
        if (*wired)
                fault_type = entry->protection;

        if (entry->eflags & MAP_ENTRY_NEEDS_COPY) {
                /*
                 * Fail if the entry was copy-on-write for a write fault.
                 */
                if (fault_type & VM_PROT_WRITE)
                        return (KERN_FAILURE);
                /*
                 * We're attempting to read a copy-on-write page --
                 * don't allow writes.
                 */
                prot &= ~VM_PROT_WRITE;
        }

        /*
         * Fail if an object should be created.
         */
        if (entry->object.vm_object == NULL && !map->system_map)
                return (KERN_FAILURE);

        /*
         * Return the object/offset from this entry.  If the entry was
         * copy-on-write or empty, it has been fixed up.
         */
        *pindex = OFF_TO_IDX((vaddr - entry->start) + entry->offset);
        *object = entry->object.vm_object;

        *out_prot = prot;
        return (KERN_SUCCESS);
}

/*
 *      vm_map_lookup_done:
 *
 *      Releases locks acquired by a vm_map_lookup
 *      (according to the handle returned by that lookup).
 */
void
vm_map_lookup_done(vm_map_t map, vm_map_entry_t entry)
{
        /*
         * Unlock the main-level map
         */
        vm_map_unlock_read(map);
}

#include "opt_ddb.h"
#ifdef DDB
#include <sys/kernel.h>

#include <ddb/ddb.h>

static void
vm_map_print(vm_map_t map)
{
        vm_map_entry_t entry;

        db_iprintf("Task map %p: pmap=%p, nentries=%d, version=%u\n",
            (void *)map,
            (void *)map->pmap, map->nentries, map->timestamp);

        db_indent += 2;
        for (entry = map->header.next; entry != &map->header;
            entry = entry->next) {
                db_iprintf("map entry %p: start=%p, end=%p\n",
                    (void *)entry, (void *)entry->start, (void *)entry->end);
                {
                        static char *inheritance_name[4] =
                        {"share", "copy", "none", "donate_copy"};

                        db_iprintf(" prot=%x/%x/%s",
                            entry->protection,
                            entry->max_protection,
                            inheritance_name[(int)(unsigned char)entry->inheritance]);
                        if (entry->wired_count != 0)
                                db_printf(", wired");
                }
                if (entry->eflags & MAP_ENTRY_IS_SUB_MAP) {
                        db_printf(", share=%p, offset=0x%jx\n",
                            (void *)entry->object.sub_map,
                            (uintmax_t)entry->offset);
                        if ((entry->prev == &map->header) ||
                            (entry->prev->object.sub_map !=
                                entry->object.sub_map)) {
                                db_indent += 2;
                                vm_map_print((vm_map_t)entry->object.sub_map);
                                db_indent -= 2;
                        }
                } else {
                        if (entry->cred != NULL)
                                db_printf(", ruid %d", entry->cred->cr_ruid);
                        db_printf(", object=%p, offset=0x%jx",
                            (void *)entry->object.vm_object,
                            (uintmax_t)entry->offset);
                        if (entry->object.vm_object && entry->object.vm_object->cred)
                                db_printf(", obj ruid %d charge %jx",
                                    entry->object.vm_object->cred->cr_ruid,
                                    (uintmax_t)entry->object.vm_object->charge);
                        if (entry->eflags & MAP_ENTRY_COW)
                                db_printf(", copy (%s)",
                                    (entry->eflags & MAP_ENTRY_NEEDS_COPY) ? "needed" : "done");
                        db_printf("\n");

                        if ((entry->prev == &map->header) ||
                            (entry->prev->object.vm_object !=
                                entry->object.vm_object)) {
                                db_indent += 2;
                                vm_object_print((db_expr_t)(intptr_t)
                                                entry->object.vm_object,
                                                1, 0, (char *)0);
                                db_indent -= 2;
                        }
                }
        }
        db_indent -= 2;
}

DB_SHOW_COMMAND(map, map)
{

        if (!have_addr) {
                db_printf("usage: show map <addr>\n");
                return;
        }
        vm_map_print((vm_map_t)addr);
}

DB_SHOW_COMMAND(procvm, procvm)
{
        struct proc *p;

        if (have_addr) {
                p = (struct proc *) addr;
        } else {
                p = curproc;
        }

        db_printf("p = %p, vmspace = %p, map = %p, pmap = %p\n",
            (void *)p, (void *)p->p_vmspace, (void *)&p->p_vmspace->vm_map,
            (void *)vmspace_pmap(p->p_vmspace));

        vm_map_print((vm_map_t)&p->p_vmspace->vm_map);
}

#endif /* DDB */