uma: Avoid depleting keg reserves when filling a bucket

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

/*-
 * SPDX-License-Identifier: (BSD-3-Clause AND MIT-CMU)
 *
 * 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.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      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/elf.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_pageout.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 vmspace_zone;
static int vmspace_zinit(void *mem, int size, 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);
static void vm_map_entry_unwire(vm_map_t map, vm_map_entry_t entry);
static int vm_map_growstack(vm_map_t map, vm_offset_t addr,
    vm_map_entry_t gap_entry);
static 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);
#ifdef INVARIANTS
static void vmspace_zdtor(void *mem, int size, void *arg);
#endif
static int vm_map_stack_locked(vm_map_t map, vm_offset_t addrbos,
    vm_size_t max_ssize, vm_size_t growsize, vm_prot_t prot, vm_prot_t max,
    int cow);
static void vm_map_wire_entry_failure(vm_map_t map, vm_map_entry_t entry,
    vm_offset_t failed_addr);

#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);
        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_map_t map;

        vm = (struct vmspace *)mem;
        map = &vm->vm_map;

        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)");
        PMAP_LOCK_INIT(vmspace_pmap(vm));
        return (0);
}

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

        vm = (struct vmspace *)mem;
        KASSERT(vm->vm_map.nentries == 0,
            ("vmspace %p nentries == %d on free", vm, vm->vm_map.nentries));
        KASSERT(vm->vm_map.size == 0,
            ("vmspace %p size == %ju on free", vm, (uintmax_t)vm->vm_map.size));
}
#endif  /* INVARIANTS */

/*
 * Allocate a vmspace structure, including a vm_map and pmap,
 * and initialize those structures.  The refcnt is set to 1.
 */
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(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);
}

#ifdef RACCT
static void
vmspace_container_reset(struct proc *p)
{

        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_map_min(&vm->vm_map),
            vm_map_max(&vm->vm_map));

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

void
vmspace_free(struct vmspace *vm)
{

        WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
            "vmspace_free() called");

        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);
        refcnt = vm->vm_refcnt;
        do {
                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_fcmpset_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);
        }
#ifdef RACCT
        if (racct_enable)
                vmspace_container_reset(p);
#endif
}

/* 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);
        }
        refcnt = vm->vm_refcnt;
        do {
                if (refcnt <= 0) {      /* Avoid 0->1 transition */
                        PROC_VMSPACE_UNLOCK(p);
                        return (NULL);
                }
        } while (!atomic_fcmpset_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);
}

/*
 * Switch between vmspaces in an AIO kernel process.
 *
 * The new vmspace is either the vmspace of a user process obtained
 * from an active AIO request or the initial vmspace of the AIO kernel
 * process (when it is idling).  Because user processes will block to
 * drain any active AIO requests before proceeding in exit() or
 * execve(), the reference count for vmspaces from AIO requests can
 * never be 0.  Similarly, AIO kernel processes hold an extra
 * reference on their initial vmspace for the life of the process.  As
 * a result, the 'newvm' vmspace always has a non-zero reference
 * count.  This permits an additional reference on 'newvm' to be
 * acquired via a simple atomic increment rather than the loop in
 * vmspace_acquire_ref() above.
 */
void
vmspace_switch_aio(struct vmspace *newvm)
{
        struct vmspace *oldvm;

        /* XXX: Need some way to assert that this is an aio daemon. */

        KASSERT(newvm->vm_refcnt > 0,
            ("vmspace_switch_aio: newvm unreferenced"));

        oldvm = curproc->p_vmspace;
        if (oldvm == newvm)
                return;

        /*
         * Point to the new address space and refer to it.
         */
        curproc->p_vmspace = newvm;
        atomic_add_int(&newvm->vm_refcnt, 1);

        /* Activate the new mapping. */
        pmap_activate(curthread);

        vmspace_free(oldvm);
}

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++;
}

void
vm_map_entry_set_vnode_text(vm_map_entry_t entry, bool add)
{
        vm_object_t object;
        struct vnode *vp;
        bool vp_held;

        if ((entry->eflags & MAP_ENTRY_VN_EXEC) == 0)
                return;
        KASSERT((entry->eflags & MAP_ENTRY_IS_SUB_MAP) == 0,
            ("Submap with execs"));
        object = entry->object.vm_object;
        KASSERT(object != NULL, ("No object for text, entry %p", entry));
        if ((object->flags & OBJ_ANON) != 0)
                object = object->handle;
        else
                KASSERT(object->backing_object == NULL,
                    ("non-anon object %p shadows", object));
        KASSERT(object != NULL, ("No content object for text, entry %p obj %p",
            entry, entry->object.vm_object));

        /*
         * Mostly, we do not lock the backing object.  It is
         * referenced by the entry we are processing, so it cannot go
         * away.
         */
        vp = NULL;
        vp_held = false;
        if (object->type == OBJT_DEAD) {
                /*
                 * For OBJT_DEAD objects, v_writecount was handled in
                 * vnode_pager_dealloc().
                 */
        } else if (object->type == OBJT_VNODE) {
                vp = object->handle;
        } else if (object->type == OBJT_SWAP) {
                KASSERT((object->flags & OBJ_TMPFS_NODE) != 0,
                    ("vm_map_entry_set_vnode_text: swap and !TMPFS "
                    "entry %p, object %p, add %d", entry, object, add));
                /*
                 * Tmpfs VREG node, which was reclaimed, has
                 * OBJ_TMPFS_NODE flag set, but not OBJ_TMPFS.  In
                 * this case there is no v_writecount to adjust.
                 */
                VM_OBJECT_RLOCK(object);
                if ((object->flags & OBJ_TMPFS) != 0) {
                        vp = object->un_pager.swp.swp_tmpfs;
                        if (vp != NULL) {
                                vhold(vp);
                                vp_held = true;
                        }
                }
                VM_OBJECT_RUNLOCK(object);
        } else {
                KASSERT(0,
                    ("vm_map_entry_set_vnode_text: wrong object type, "
                    "entry %p, object %p, add %d", entry, object, add));
        }
        if (vp != NULL) {
                if (add) {
                        VOP_SET_TEXT_CHECKED(vp);
                } else {
                        vn_lock(vp, LK_SHARED | LK_RETRY);
                        VOP_UNSET_TEXT_CHECKED(vp);
                        VOP_UNLOCK(vp);
                }
                if (vp_held)
                        vdrop(vp);
        }
}

/*
 * Use a different name for this vm_map_entry field when it's use
 * is not consistent with its use as part of an ordered search tree.
 */
#define defer_next right

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->defer_next;
                MPASS((entry->eflags & (MAP_ENTRY_WRITECNT |
                    MAP_ENTRY_VN_EXEC)) != (MAP_ENTRY_WRITECNT |
                    MAP_ENTRY_VN_EXEC));
                if ((entry->eflags & MAP_ENTRY_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"));
                        vm_pager_release_writecount(object, entry->start,
                            entry->end);
                }
                vm_map_entry_set_vnode_text(entry, false);
                vm_map_entry_deallocate(entry, FALSE);
                entry = next;
        }
}

#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)

enum { VMMAP_CHECK_NONE, VMMAP_CHECK_UNLOCK, VMMAP_CHECK_ALL };
#ifdef DIAGNOSTIC
static int enable_vmmap_check = VMMAP_CHECK_UNLOCK;
#else
static int enable_vmmap_check = VMMAP_CHECK_NONE;
#endif
SYSCTL_INT(_debug, OID_AUTO, vmmap_check, CTLFLAG_RWTUN,
    &enable_vmmap_check, 0, "Enable vm map consistency checking");

static void _vm_map_assert_consistent(vm_map_t map, int check);

#define VM_MAP_ASSERT_CONSISTENT(map) \
    _vm_map_assert_consistent(map, VMMAP_CHECK_ALL)
#ifdef DIAGNOSTIC
#define VM_MAP_UNLOCK_CONSISTENT(map) do {                              \
        if (map->nupdates > map->nentries) {                            \
                _vm_map_assert_consistent(map, VMMAP_CHECK_UNLOCK);     \
                map->nupdates = 0;                                      \
        }                                                               \
} while (0)
#else
#define VM_MAP_UNLOCK_CONSISTENT(map)
#endif
#else
#define VM_MAP_ASSERT_LOCKED(map)
#define VM_MAP_ASSERT_CONSISTENT(map)
#define VM_MAP_UNLOCK_CONSISTENT(map)
#endif /* INVARIANTS */

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

        VM_MAP_UNLOCK_CONSISTENT(map);
        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 {
                VM_MAP_UNLOCK_CONSISTENT(map);
                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));
}

/*
 *      _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)
{

        VM_MAP_UNLOCK_CONSISTENT(map);
        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));
}

/*
 * 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.eflags = MAP_ENTRY_HEADER;
        map->needs_wakeup = FALSE;
        map->system_map = 0;
        map->pmap = pmap;
        map->header.end = min;
        map->header.start = max;
        map->flags = 0;
        map->header.left = map->header.right = &map->header;
        map->root = NULL;
        map->timestamp = 0;
        map->busy = 0;
        map->anon_loc = 0;
#ifdef DIAGNOSTIC
        map->nupdates = 0;
#endif
}

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, "vm map (system)", NULL,
            MTX_DEF | MTX_DUPOK);
        sx_init(&map->lock, "vm map (user)");
}

/*
 *      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_max_free_{left,right}:
 *
 *      Compute the size of the largest free gap between two entries,
 *      one the root of a tree and the other the ancestor of that root
 *      that is the least or greatest ancestor found on the search path.
 */
static inline vm_size_t
vm_map_entry_max_free_left(vm_map_entry_t root, vm_map_entry_t left_ancestor)
{

        return (root->left != left_ancestor ?
            root->left->max_free : root->start - left_ancestor->end);
}

static inline vm_size_t
vm_map_entry_max_free_right(vm_map_entry_t root, vm_map_entry_t right_ancestor)
{

        return (root->right != right_ancestor ?
            root->right->max_free : right_ancestor->start - root->end);
}

/*
 *      vm_map_entry_{pred,succ}:
 *
 *      Find the {predecessor, successor} of the entry by taking one step
 *      in the appropriate direction and backtracking as much as necessary.
 *      vm_map_entry_succ is defined in vm_map.h.
 */
static inline vm_map_entry_t
vm_map_entry_pred(vm_map_entry_t entry)
{
        vm_map_entry_t prior;

        prior = entry->left;
        if (prior->right->start < entry->start) {
                do
                        prior = prior->right;
                while (prior->right != entry);
        }
        return (prior);
}

static inline vm_size_t
vm_size_max(vm_size_t a, vm_size_t b)
{

        return (a > b ? a : b);
}

#define SPLAY_LEFT_STEP(root, y, llist, rlist, test) do {               \
        vm_map_entry_t z;                                               \
        vm_size_t max_free;                                             \
                                                                        \
        /*                                                              \
         * Infer root->right->max_free == root->max_free when           \
         * y->max_free < root->max_free || root->max_free == 0.         \
         * Otherwise, look right to find it.                            \
         */                                                             \
        y = root->left;                                                 \
        max_free = root->max_free;                                      \
        KASSERT(max_free == vm_size_max(                                \
            vm_map_entry_max_free_left(root, llist),                    \
            vm_map_entry_max_free_right(root, rlist)),                  \
            ("%s: max_free invariant fails", __func__));                \
        if (max_free - 1 < vm_map_entry_max_free_left(root, llist))     \
                max_free = vm_map_entry_max_free_right(root, rlist);    \
        if (y != llist && (test)) {                                     \
                /* Rotate right and make y root. */                     \
                z = y->right;                                           \
                if (z != root) {                                        \
                        root->left = z;                                 \
                        y->right = root;                                \
                        if (max_free < y->max_free)                     \
                            root->max_free = max_free =                 \
                            vm_size_max(max_free, z->max_free);         \
                } else if (max_free < y->max_free)                      \
                        root->max_free = max_free =                     \
                            vm_size_max(max_free, root->start - y->end);\
                root = y;                                               \
                y = root->left;                                         \
        }                                                               \
        /* Copy right->max_free.  Put root on rlist. */                 \
        root->max_free = max_free;                                      \
        KASSERT(max_free == vm_map_entry_max_free_right(root, rlist),   \
            ("%s: max_free not copied from right", __func__));          \
        root->left = rlist;                                             \
        rlist = root;                                                   \
        root = y != llist ? y : NULL;                                   \
} while (0)

#define SPLAY_RIGHT_STEP(root, y, llist, rlist, test) do {              \
        vm_map_entry_t z;                                               \
        vm_size_t max_free;                                             \
                                                                        \
        /*                                                              \
         * Infer root->left->max_free == root->max_free when            \
         * y->max_free < root->max_free || root->max_free == 0.         \
         * Otherwise, look left to find it.                             \
         */                                                             \
        y = root->right;                                                \
        max_free = root->max_free;                                      \
        KASSERT(max_free == vm_size_max(                                \
            vm_map_entry_max_free_left(root, llist),                    \
            vm_map_entry_max_free_right(root, rlist)),                  \
            ("%s: max_free invariant fails", __func__));                \
        if (max_free - 1 < vm_map_entry_max_free_right(root, rlist))    \
                max_free = vm_map_entry_max_free_left(root, llist);     \
        if (y != rlist && (test)) {                                     \
                /* Rotate left and make y root. */                      \
                z = y->left;                                            \
                if (z != root) {                                        \
                        root->right = z;                                \
                        y->left = root;                                 \
                        if (max_free < y->max_free)                     \
                            root->max_free = max_free =                 \
                            vm_size_max(max_free, z->max_free);         \
                } else if (max_free < y->max_free)                      \
                        root->max_free = max_free =                     \
                            vm_size_max(max_free, y->start - root->end);\
                root = y;                                               \
                y = root->right;                                        \
        }                                                               \
        /* Copy left->max_free.  Put root on llist. */                  \
        root->max_free = max_free;                                      \
        KASSERT(max_free == vm_map_entry_max_free_left(root, llist),    \
            ("%s: max_free not copied from left", __func__));           \
        root->right = llist;                                            \
        llist = root;                                                   \
        root = y != rlist ? y : NULL;                                   \
} while (0)

/*
 * Walk down the tree until we find addr or a gap where addr would go, breaking
 * off left and right subtrees of nodes less than, or greater than addr.  Treat
 * subtrees with root->max_free < length as empty trees.  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, and both
 * lists terminated by &map->header.  This function, and the subsequent call to
 * vm_map_splay_merge_{left,right,pred,succ}, rely on the start and end address
 * values in &map->header.
 */
static __always_inline vm_map_entry_t
vm_map_splay_split(vm_map_t map, vm_offset_t addr, vm_size_t length,
    vm_map_entry_t *llist, vm_map_entry_t *rlist)
{
        vm_map_entry_t left, right, root, y;

        left = right = &map->header;
        root = map->root;
        while (root != NULL && root->max_free >= length) {
                KASSERT(left->end <= root->start &&
                    root->end <= right->start,
                    ("%s: root not within tree bounds", __func__));
                if (addr < root->start) {
                        SPLAY_LEFT_STEP(root, y, left, right,
                            y->max_free >= length && addr < y->start);
                } else if (addr >= root->end) {
                        SPLAY_RIGHT_STEP(root, y, left, right,
                            y->max_free >= length && addr >= y->end);
                } else
                        break;
        }
        *llist = left;
        *rlist = right;
        return (root);
}

static __always_inline void
vm_map_splay_findnext(vm_map_entry_t root, vm_map_entry_t *rlist)
{
        vm_map_entry_t hi, right, y;

        right = *rlist;
        hi = root->right == right ? NULL : root->right;
        if (hi == NULL)
                return;
        do
                SPLAY_LEFT_STEP(hi, y, root, right, true);
        while (hi != NULL);
        *rlist = right;
}

static __always_inline void
vm_map_splay_findprev(vm_map_entry_t root, vm_map_entry_t *llist)
{
        vm_map_entry_t left, lo, y;

        left = *llist;
        lo = root->left == left ? NULL : root->left;
        if (lo == NULL)
                return;
        do
                SPLAY_RIGHT_STEP(lo, y, left, root, true);
        while (lo != NULL);
        *llist = left;
}

static inline void
vm_map_entry_swap(vm_map_entry_t *a, vm_map_entry_t *b)
{
        vm_map_entry_t tmp;

        tmp = *b;
        *b = *a;
        *a = tmp;
}

/*
 * 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.
 */
static vm_size_t
vm_map_splay_merge_left_walk(vm_map_entry_t header, vm_map_entry_t root,
    vm_map_entry_t tail, vm_size_t max_free, vm_map_entry_t llist)
{
        do {
                /*
                 * The max_free values of the children of llist are in
                 * llist->max_free and max_free.  Update with the
                 * max value.
                 */
                llist->max_free = max_free =
                    vm_size_max(llist->max_free, max_free);
                vm_map_entry_swap(&llist->right, &tail);
                vm_map_entry_swap(&tail, &llist);
        } while (llist != header);
        root->left = tail;
        return (max_free);
}

/*
 * When llist is known to be the predecessor of root.
 */
static inline vm_size_t
vm_map_splay_merge_pred(vm_map_entry_t header, vm_map_entry_t root,
    vm_map_entry_t llist)
{
        vm_size_t max_free;

        max_free = root->start - llist->end;
        if (llist != header) {
                max_free = vm_map_splay_merge_left_walk(header, root,
                    root, max_free, llist);
        } else {
                root->left = header;
                header->right = root;
        }
        return (max_free);
}

/*
 * When llist may or may not be the predecessor of root.
 */
static inline vm_size_t
vm_map_splay_merge_left(vm_map_entry_t header, vm_map_entry_t root,
    vm_map_entry_t llist)
{
        vm_size_t max_free;

        max_free = vm_map_entry_max_free_left(root, llist);
        if (llist != header) {
                max_free = vm_map_splay_merge_left_walk(header, root,
                    root->left == llist ? root : root->left,
                    max_free, llist);
        }
        return (max_free);
}

static vm_size_t
vm_map_splay_merge_right_walk(vm_map_entry_t header, vm_map_entry_t root,
    vm_map_entry_t tail, vm_size_t max_free, vm_map_entry_t rlist)
{
        do {
                /*
                 * The max_free values of the children of rlist are in
                 * rlist->max_free and max_free.  Update with the
                 * max value.
                 */
                rlist->max_free = max_free =
                    vm_size_max(rlist->max_free, max_free);
                vm_map_entry_swap(&rlist->left, &tail);
                vm_map_entry_swap(&tail, &rlist);
        } while (rlist != header);
        root->right = tail;
        return (max_free);
}

/*
 * When rlist is known to be the succecessor of root.
 */
static inline vm_size_t
vm_map_splay_merge_succ(vm_map_entry_t header, vm_map_entry_t root,
    vm_map_entry_t rlist)
{
        vm_size_t max_free;

        max_free = rlist->start - root->end;
        if (rlist != header) {
                max_free = vm_map_splay_merge_right_walk(header, root,
                    root, max_free, rlist);
        } else {
                root->right = header;
                header->left = root;
        }
        return (max_free);
}

/*
 * When rlist may or may not be the succecessor of root.
 */
static inline vm_size_t
vm_map_splay_merge_right(vm_map_entry_t header, vm_map_entry_t root,
    vm_map_entry_t rlist)
{
        vm_size_t max_free;

        max_free = vm_map_entry_max_free_right(root, rlist);
        if (rlist != header) {
                max_free = vm_map_splay_merge_right_walk(header, root,
                    root->right == rlist ? root : root->right,
                    max_free, rlist);
        }
        return (max_free);
}

/*
 *      vm_map_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 tree is threaded, which means that there are no null pointers.
 *      When a node has no left child, its left pointer points to its
 *      predecessor, which the last ancestor on the search path from the root
 *      where the search branched right.  Likewise, when a node has no right
 *      child, its right pointer points to its successor.  The map header node
 *      is the predecessor of the first map entry, and the successor of the
 *      last.
 *
 *      The new root is the vm_map_entry containing "addr", or else an
 *      adjacent entry (lower if possible) 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_splay(vm_map_t map, vm_offset_t addr)
{
        vm_map_entry_t header, llist, rlist, root;
        vm_size_t max_free_left, max_free_right;

        header = &map->header;
        root = vm_map_splay_split(map, addr, 0, &llist, &rlist);
        if (root != NULL) {
                max_free_left = vm_map_splay_merge_left(header, root, llist);
                max_free_right = vm_map_splay_merge_right(header, root, rlist);
        } else if (llist != header) {
                /*
                 * Recover the greatest node in the left
                 * subtree and make it the root.
                 */
                root = llist;
                llist = root->right;
                max_free_left = vm_map_splay_merge_left(header, root, llist);
                max_free_right = vm_map_splay_merge_succ(header, root, rlist);
        } else if (rlist != header) {
                /*
                 * Recover the least node in the right
                 * subtree and make it the root.
                 */
                root = rlist;
                rlist = root->left;
                max_free_left = vm_map_splay_merge_pred(header, root, llist);
                max_free_right = vm_map_splay_merge_right(header, root, rlist);
        } else {
                /* There is no root. */
                return (NULL);
        }
        root->max_free = vm_size_max(max_free_left, max_free_right);
        map->root = root;
        VM_MAP_ASSERT_CONSISTENT(map);
        return (root);
}

/*
 *      vm_map_entry_{un,}link:
 *
 *      Insert/remove entries from maps.  On linking, if new entry clips
 *      existing entry, trim existing entry to avoid overlap, and manage
 *      offsets.  On unlinking, merge disappearing entry with neighbor, if
 *      called for, and manage offsets.  Callers should not modify fields in
 *      entries already mapped.
 */
static void
vm_map_entry_link(vm_map_t map, vm_map_entry_t entry)
{
        vm_map_entry_t header, llist, rlist, root;
        vm_size_t max_free_left, max_free_right;

        CTR3(KTR_VM,
            "vm_map_entry_link: map %p, nentries %d, entry %p", map,
            map->nentries, entry);
        VM_MAP_ASSERT_LOCKED(map);
        map->nentries++;
        header = &map->header;
        root = vm_map_splay_split(map, entry->start, 0, &llist, &rlist);
        if (root == NULL) {
                /*
                 * The new entry does not overlap any existing entry in the
                 * map, so it becomes the new root of the map tree.
                 */
                max_free_left = vm_map_splay_merge_pred(header, entry, llist);
                max_free_right = vm_map_splay_merge_succ(header, entry, rlist);
        } else if (entry->start == root->start) {
                /*
                 * The new entry is a clone of root, with only the end field
                 * changed.  The root entry will be shrunk to abut the new
                 * entry, and will be the right child of the new root entry in
                 * the modified map.
                 */
                KASSERT(entry->end < root->end,
                    ("%s: clip_start not within entry", __func__));
                vm_map_splay_findprev(root, &llist);
                root->offset += entry->end - root->start;
                root->start = entry->end;
                max_free_left = vm_map_splay_merge_pred(header, entry, llist);
                max_free_right = root->max_free = vm_size_max(
                    vm_map_splay_merge_pred(entry, root, entry),
                    vm_map_splay_merge_right(header, root, rlist));
        } else {
                /*
                 * The new entry is a clone of root, with only the start field
                 * changed.  The root entry will be shrunk to abut the new
                 * entry, and will be the left child of the new root entry in
                 * the modified map.
                 */
                KASSERT(entry->end == root->end,
                    ("%s: clip_start not within entry", __func__));
                vm_map_splay_findnext(root, &rlist);
                entry->offset += entry->start - root->start;
                root->end = entry->start;
                max_free_left = root->max_free = vm_size_max(
                    vm_map_splay_merge_left(header, root, llist),
                    vm_map_splay_merge_succ(entry, root, entry));
                max_free_right = vm_map_splay_merge_succ(header, entry, rlist);
        }
        entry->max_free = vm_size_max(max_free_left, max_free_right);
        map->root = entry;
        VM_MAP_ASSERT_CONSISTENT(map);
}

enum unlink_merge_type {
        UNLINK_MERGE_NONE,
        UNLINK_MERGE_NEXT
};

static void
vm_map_entry_unlink(vm_map_t map, vm_map_entry_t entry,
    enum unlink_merge_type op)
{
        vm_map_entry_t header, llist, rlist, root;
        vm_size_t max_free_left, max_free_right;

        VM_MAP_ASSERT_LOCKED(map);
        header = &map->header;
        root = vm_map_splay_split(map, entry->start, 0, &llist, &rlist);
        KASSERT(root != NULL,
            ("vm_map_entry_unlink: unlink object not mapped"));

        vm_map_splay_findprev(root, &llist);
        vm_map_splay_findnext(root, &rlist);
        if (op == UNLINK_MERGE_NEXT) {
                rlist->start = root->start;
                rlist->offset = root->offset;
        }
        if (llist != header) {
                root = llist;
                llist = root->right;
                max_free_left = vm_map_splay_merge_left(header, root, llist);
                max_free_right = vm_map_splay_merge_succ(header, root, rlist);
        } else if (rlist != header) {
                root = rlist;
                rlist = root->left;
                max_free_left = vm_map_splay_merge_pred(header, root, llist);
                max_free_right = vm_map_splay_merge_right(header, root, rlist);
        } else {
                header->left = header->right = header;
                root = NULL;
        }
        if (root != NULL)
                root->max_free = vm_size_max(max_free_left, max_free_right);
        map->root = root;
        VM_MAP_ASSERT_CONSISTENT(map);
        map->nentries--;
        CTR3(KTR_VM, "vm_map_entry_unlink: map %p, nentries %d, entry %p", map,
            map->nentries, entry);
}

/*
 *      vm_map_entry_resize:
 *
 *      Resize a vm_map_entry, recompute the amount of free space that
 *      follows it and propagate that value up the tree.
 *
 *      The map must be locked, and leaves it so.
 */
static void
vm_map_entry_resize(vm_map_t map, vm_map_entry_t entry, vm_size_t grow_amount)
{
        vm_map_entry_t header, llist, rlist, root;

        VM_MAP_ASSERT_LOCKED(map);
        header = &map->header;
        root = vm_map_splay_split(map, entry->start, 0, &llist, &rlist);
        KASSERT(root != NULL, ("%s: resize object not mapped", __func__));
        vm_map_splay_findnext(root, &rlist);
        entry->end += grow_amount;
        root->max_free = vm_size_max(
            vm_map_splay_merge_left(header, root, llist),
            vm_map_splay_merge_succ(header, root, rlist));
        map->root = root;
        VM_MAP_ASSERT_CONSISTENT(map);
        CTR4(KTR_VM, "%s: map %p, nentries %d, entry %p",
            __func__, map, map->nentries, 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, header, lbound, ubound;
        boolean_t locked;

        /*
         * If the map is empty, then the map entry immediately preceding
         * "address" is the map's header.
         */
        header = &map->header;
        cur = map->root;
        if (cur == NULL) {
                *entry = header;
                return (FALSE);
        }
        if (address >= cur->start && cur->end > address) {
                *entry = cur;
                return (TRUE);
        }
        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.
                 */
                cur = vm_map_splay(map, address);
                if (!locked) {
                        VM_MAP_UNLOCK_CONSISTENT(map);
                        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 = header;
                        return (FALSE);
                }
                *entry = cur;
                return (address < cur->end);
        }
        /*
         * Since the map is only locked for read access, perform a
         * standard binary search tree lookup for "address".
         */
        lbound = ubound = header;
        for (;;) {
                if (address < cur->start) {
                        ubound = cur;
                        cur = cur->left;
                        if (cur == lbound)
                                break;
                } else if (cur->end <= address) {
                        lbound = cur;
                        cur = cur->right;
                        if (cur == ubound)
                                break;
                } else {
                        *entry = cur;
                        return (TRUE);
                }
        }
        *entry = lbound;
        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, next_entry, prev_entry;
        struct ucred *cred;
        vm_eflags_t protoeflags;
        vm_inherit_t inheritance;
        u_long bdry;
        u_int bidx;

        VM_MAP_ASSERT_LOCKED(map);
        KASSERT(object != kernel_object ||
            (cow & MAP_COPY_ON_WRITE) == 0,
            ("vm_map_insert: kernel object and COW"));
        KASSERT(object == NULL || (cow & MAP_NOFAULT) == 0 ||
            (cow & MAP_SPLIT_BOUNDARY_MASK) != 0,
            ("vm_map_insert: paradoxical MAP_NOFAULT request, obj %p cow %#x",
            object, cow));
        KASSERT((prot & ~max) == 0,
            ("prot %#x is not subset of max_prot %#x", prot, max));

        /*
         * Check that the start and end points are not bogus.
         */
        if (start == end || !vm_map_range_valid(map, 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, &prev_entry))
                return (KERN_NO_SPACE);

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

        if ((cow & MAP_CREATE_GUARD) != 0 && (object != NULL ||
            max != VM_PROT_NONE))
                return (KERN_INVALID_ARGUMENT);

        protoeflags = 0;
        if (cow & MAP_COPY_ON_WRITE)
                protoeflags |= MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY;
        if (cow & MAP_NOFAULT)
                protoeflags |= MAP_ENTRY_NOFAULT;
        if (cow & MAP_DISABLE_SYNCER)
                protoeflags |= MAP_ENTRY_NOSYNC;
        if (cow & MAP_DISABLE_COREDUMP)
                protoeflags |= MAP_ENTRY_NOCOREDUMP;
        if (cow & MAP_STACK_GROWS_DOWN)
                protoeflags |= MAP_ENTRY_GROWS_DOWN;
        if (cow & MAP_STACK_GROWS_UP)
                protoeflags |= MAP_ENTRY_GROWS_UP;
        if (cow & MAP_WRITECOUNT)
                protoeflags |= MAP_ENTRY_WRITECNT;
        if (cow & MAP_VN_EXEC)
                protoeflags |= MAP_ENTRY_VN_EXEC;
        if ((cow & MAP_CREATE_GUARD) != 0)
                protoeflags |= MAP_ENTRY_GUARD;
        if ((cow & MAP_CREATE_STACK_GAP_DN) != 0)
                protoeflags |= MAP_ENTRY_STACK_GAP_DN;
        if ((cow & MAP_CREATE_STACK_GAP_UP) != 0)
                protoeflags |= MAP_ENTRY_STACK_GAP_UP;
        if (cow & MAP_INHERIT_SHARE)
                inheritance = VM_INHERIT_SHARE;
        else
                inheritance = VM_INHERIT_DEFAULT;
        if ((cow & MAP_SPLIT_BOUNDARY_MASK) != 0) {
                /* This magically ignores index 0, for usual page size. */
                bidx = (cow & MAP_SPLIT_BOUNDARY_MASK) >>
                    MAP_SPLIT_BOUNDARY_SHIFT;
                if (bidx >= MAXPAGESIZES)
                        return (KERN_INVALID_ARGUMENT);
                bdry = pagesizes[bidx] - 1;
                if ((start & bdry) != 0 || (end & bdry) != 0)
                        return (KERN_INVALID_ARGUMENT);
                protoeflags |= bidx << MAP_ENTRY_SPLIT_BOUNDARY_SHIFT;
        }

        cred = NULL;
        if ((cow & (MAP_ACC_NO_CHARGE | MAP_NOFAULT | MAP_CREATE_GUARD)) != 0)
                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) != 0 ||
                    object->cred == NULL,
                    ("overcommit: vm_map_insert o %p", object));
                cred = curthread->td_ucred;
        }

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.)
                 */
                if ((object->flags & OBJ_ANON) != 0) {
                        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->eflags & ~MAP_ENTRY_USER_WIRED) ==
            protoeflags &&
            (cow & (MAP_STACK_GROWS_DOWN | MAP_STACK_GROWS_UP |
            MAP_VN_EXEC)) == 0 &&
            prev_entry->end == start && (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), cred != NULL &&
            (protoeflags & MAP_ENTRY_NEEDS_COPY) == 0)) {
                /*
                 * 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 &&
                    prev_entry->wired_count == 0) {
                        KASSERT((prev_entry->eflags & MAP_ENTRY_USER_WIRED) ==
                            0, ("prev_entry %p has incoherent wiring",
                            prev_entry));
                        if ((prev_entry->eflags & MAP_ENTRY_GUARD) == 0)
                                map->size += end - prev_entry->end;
                        vm_map_entry_resize(map, prev_entry,
                            end - prev_entry->end);
                        vm_map_try_merge_entries(map, prev_entry, next_entry);
                        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. */
                        cred = NULL;
                }
        }
        if (cred != NULL)
                crhold(cred);

        /*
         * 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->inheritance = inheritance;
        new_entry->protection = prot;
        new_entry->max_protection = max;
        new_entry->wired_count = 0;
        new_entry->wiring_thread = NULL;
        new_entry->read_ahead = VM_FAULT_READ_AHEAD_INIT;
        new_entry->next_read = start;

        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, new_entry);
        if ((new_entry->eflags & MAP_ENTRY_GUARD) == 0)
                map->size += new_entry->end - new_entry->start;

        /*
         * Try to coalesce the new entry with both the previous and next
         * entries in the list.  Previously, we only attempted to coalesce
         * with the previous entry when object is NULL.  Here, we handle the
         * other cases, which are less common.
         */
        vm_map_try_merge_entries(map, prev_entry, new_entry);
        vm_map_try_merge_entries(map, new_entry, next_entry);

        if ((cow & (MAP_PREFAULT | MAP_PREFAULT_PARTIAL)) != 0) {
                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, "max_free" is the maximum amount of
 *      contiguous free space between an entry in its subtree and a
 *      neighbor of that entry.  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: starting address if sufficient space,
 *               vm_map_max(map)-length+1 if insufficient space.
 */
vm_offset_t
vm_map_findspace(vm_map_t map, vm_offset_t start, vm_size_t length)
{
        vm_map_entry_t header, llist, rlist, root, y;
        vm_size_t left_length, max_free_left, max_free_right;
        vm_offset_t gap_end;

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

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

        /*
         * After splay_split, if start is within an entry, push it to the start
         * of the following gap.  If rlist is at the end of the gap containing
         * start, save the end of that gap in gap_end to see if the gap is big
         * enough; otherwise set gap_end to start skip gap-checking and move
         * directly to a search of the right subtree.
         */
        header = &map->header;
        root = vm_map_splay_split(map, start, length, &llist, &rlist);
        gap_end = rlist->start;
        if (root != NULL) {
                start = root->end;
                if (root->right != rlist)
                        gap_end = start;
                max_free_left = vm_map_splay_merge_left(header, root, llist);
                max_free_right = vm_map_splay_merge_right(header, root, rlist);
        } else if (rlist != header) {
                root = rlist;
                rlist = root->left;
                max_free_left = vm_map_splay_merge_pred(header, root, llist);
                max_free_right = vm_map_splay_merge_right(header, root, rlist);
        } else {
                root = llist;
                llist = root->right;
                max_free_left = vm_map_splay_merge_left(header, root, llist);
                max_free_right = vm_map_splay_merge_succ(header, root, rlist);
        }
        root->max_free = vm_size_max(max_free_left, max_free_right);
        map->root = root;
        VM_MAP_ASSERT_CONSISTENT(map);
        if (length <= gap_end - start)
                return (start);

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

        /*
         * Splay for the least large-enough gap in the right subtree.
         */
        llist = rlist = header;
        for (left_length = 0;;
            left_length = vm_map_entry_max_free_left(root, llist)) {
                if (length <= left_length)
                        SPLAY_LEFT_STEP(root, y, llist, rlist,
                            length <= vm_map_entry_max_free_left(y, llist));
                else
                        SPLAY_RIGHT_STEP(root, y, llist, rlist,
                            length > vm_map_entry_max_free_left(y, root));
                if (root == NULL)
                        break;
        }
        root = llist;
        llist = root->right;
        max_free_left = vm_map_splay_merge_left(header, root, llist);
        if (rlist == header) {
                root->max_free = vm_size_max(max_free_left,
                    vm_map_splay_merge_succ(header, root, rlist));
        } else {
                y = rlist;
                rlist = y->left;
                y->max_free = vm_size_max(
                    vm_map_splay_merge_pred(root, y, root),
                    vm_map_splay_merge_right(header, y, rlist));
                root->max_free = vm_size_max(max_free_left, y->max_free);
        }
        map->root = root;
        VM_MAP_ASSERT_CONSISTENT(map);
        return (root->end);
}

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;
        KASSERT((cow & (MAP_STACK_GROWS_DOWN | MAP_STACK_GROWS_UP)) == 0 ||
            object == NULL,
            ("vm_map_fixed: non-NULL backing object for stack"));
        vm_map_lock(map);
        VM_MAP_RANGE_CHECK(map, start, end);
        if ((cow & MAP_CHECK_EXCL) == 0) {
                result = vm_map_delete(map, start, end);
                if (result != KERN_SUCCESS)
                        goto out;
        }
        if ((cow & (MAP_STACK_GROWS_DOWN | MAP_STACK_GROWS_UP)) != 0) {
                result = vm_map_stack_locked(map, start, length, sgrowsiz,
                    prot, max, cow);
        } else {
                result = vm_map_insert(map, object, offset, start, end,
                    prot, max, cow);
        }
out:
        vm_map_unlock(map);
        return (result);
}

static const int aslr_pages_rnd_64[2] = {0x1000, 0x10};
static const int aslr_pages_rnd_32[2] = {0x100, 0x4};

static int cluster_anon = 1;
SYSCTL_INT(_vm, OID_AUTO, cluster_anon, CTLFLAG_RW,
    &cluster_anon, 0,
    "Cluster anonymous mappings: 0 = no, 1 = yes if no hint, 2 = always");

static bool
clustering_anon_allowed(vm_offset_t addr)
{

        switch (cluster_anon) {
        case 0:
                return (false);
        case 1:
                return (addr == 0);
        case 2:
        default:
                return (true);
        }
}

static long aslr_restarts;
SYSCTL_LONG(_vm, OID_AUTO, aslr_restarts, CTLFLAG_RD,
    &aslr_restarts, 0,
    "Number of aslr failures");

/*
 * Searches for the specified amount of free space in the given map with the
 * specified alignment.  Performs an address-ordered, first-fit search from
 * the given address "*addr", with an optional upper bound "max_addr".  If the
 * parameter "alignment" is zero, then the alignment is computed from the
 * given (object, offset) pair so as to enable the greatest possible use of
 * superpage mappings.  Returns KERN_SUCCESS and the address of the free space
 * in "*addr" if successful.  Otherwise, returns KERN_NO_SPACE.
 *
 * The map must be locked.  Initially, there must be at least "length" bytes
 * of free space at the given address.
 */
static int
vm_map_alignspace(vm_map_t map, vm_object_t object, vm_ooffset_t offset,
    vm_offset_t *addr, vm_size_t length, vm_offset_t max_addr,
    vm_offset_t alignment)
{
        vm_offset_t aligned_addr, free_addr;

        VM_MAP_ASSERT_LOCKED(map);
        free_addr = *addr;
        KASSERT(free_addr == vm_map_findspace(map, free_addr, length),
            ("caller failed to provide space %#jx at address %p",
             (uintmax_t)length, (void *)free_addr));
        for (;;) {
                /*
                 * At the start of every iteration, the free space at address
                 * "*addr" is at least "length" bytes.
                 */
                if (alignment == 0)
                        pmap_align_superpage(object, offset, addr, length);
                else if ((*addr & (alignment - 1)) != 0) {
                        *addr &= ~(alignment - 1);
                        *addr += alignment;
                }
                aligned_addr = *addr;
                if (aligned_addr == free_addr) {
                        /*
                         * Alignment did not change "*addr", so "*addr" must
                         * still provide sufficient free space.
                         */
                        return (KERN_SUCCESS);
                }

                /*
                 * Test for address wrap on "*addr".  A wrapped "*addr" could
                 * be a valid address, in which case vm_map_findspace() cannot
                 * be relied upon to fail.
                 */
                if (aligned_addr < free_addr)
                        return (KERN_NO_SPACE);
                *addr = vm_map_findspace(map, aligned_addr, length);
                if (*addr + length > vm_map_max(map) ||
                    (max_addr != 0 && *addr + length > max_addr))
                        return (KERN_NO_SPACE);
                free_addr = *addr;
                if (free_addr == aligned_addr) {
                        /*
                         * If a successful call to vm_map_findspace() did not
                         * change "*addr", then "*addr" must still be aligned
                         * and provide sufficient free space.
                         */
                        return (KERN_SUCCESS);
                }
        }
}

int
vm_map_find_aligned(vm_map_t map, vm_offset_t *addr, vm_size_t length,
    vm_offset_t max_addr, vm_offset_t alignment)
{
        /* XXXKIB ASLR eh ? */
        *addr = vm_map_findspace(map, *addr, length);
        if (*addr + length > vm_map_max(map) ||
            (max_addr != 0 && *addr + length > max_addr))
                return (KERN_NO_SPACE);
        return (vm_map_alignspace(map, NULL, 0, addr, length, max_addr,
            alignment));
}

/*
 *      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, curr_min_addr, min_addr;
        int gap, pidx, rv, try;
        bool cluster, en_aslr, update_anon;

        KASSERT((cow & (MAP_STACK_GROWS_DOWN | MAP_STACK_GROWS_UP)) == 0 ||
            object == NULL,
            ("vm_map_find: non-NULL backing object for stack"));
        MPASS((cow & MAP_REMAP) == 0 || (find_space == VMFS_NO_SPACE &&
            (cow & (MAP_STACK_GROWS_DOWN | MAP_STACK_GROWS_UP)) == 0));
        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;
        en_aslr = (map->flags & MAP_ASLR) != 0;
        update_anon = cluster = clustering_anon_allowed(*addr) &&
            (map->flags & MAP_IS_SUB_MAP) == 0 && max_addr == 0 &&
            find_space != VMFS_NO_SPACE && object == NULL &&
            (cow & (MAP_INHERIT_SHARE | MAP_STACK_GROWS_UP |
            MAP_STACK_GROWS_DOWN)) == 0 && prot != PROT_NONE;
        curr_min_addr = min_addr = *addr;
        if (en_aslr && min_addr == 0 && !cluster &&
            find_space != VMFS_NO_SPACE &&
            (map->flags & MAP_ASLR_IGNSTART) != 0)
                curr_min_addr = min_addr = vm_map_min(map);
        try = 0;
        vm_map_lock(map);
        if (cluster) {
                curr_min_addr = map->anon_loc;
                if (curr_min_addr == 0)
                        cluster = false;
        }
        if (find_space != VMFS_NO_SPACE) {
                KASSERT(find_space == VMFS_ANY_SPACE ||
                    find_space == VMFS_OPTIMAL_SPACE ||
                    find_space == VMFS_SUPER_SPACE ||
                    alignment != 0, ("unexpected VMFS flag"));
again:
                /*
                 * When creating an anonymous mapping, try clustering
                 * with an existing anonymous mapping first.
                 *
                 * We make up to two attempts to find address space
                 * for a given find_space value. The first attempt may
                 * apply randomization or may cluster with an existing
                 * anonymous mapping. If this first attempt fails,
                 * perform a first-fit search of the available address
                 * space.
                 *
                 * If all tries failed, and find_space is
                 * VMFS_OPTIMAL_SPACE, fallback to VMFS_ANY_SPACE.
                 * Again enable clustering and randomization.
                 */
                try++;
                MPASS(try <= 2);

                if (try == 2) {
                        /*
                         * Second try: we failed either to find a
                         * suitable region for randomizing the
                         * allocation, or to cluster with an existing
                         * mapping.  Retry with free run.
                         */
                        curr_min_addr = (map->flags & MAP_ASLR_IGNSTART) != 0 ?
                            vm_map_min(map) : min_addr;
                        atomic_add_long(&aslr_restarts, 1);
                }

                if (try == 1 && en_aslr && !cluster) {
                        /*
                         * Find space for allocation, including
                         * gap needed for later randomization.
                         */
                        pidx = MAXPAGESIZES > 1 && pagesizes[1] != 0 &&
                            (find_space == VMFS_SUPER_SPACE || find_space ==
                            VMFS_OPTIMAL_SPACE) ? 1 : 0;
                        gap = vm_map_max(map) > MAP_32BIT_MAX_ADDR &&
                            (max_addr == 0 || max_addr > MAP_32BIT_MAX_ADDR) ?
                            aslr_pages_rnd_64[pidx] : aslr_pages_rnd_32[pidx];
                        *addr = vm_map_findspace(map, curr_min_addr,
                            length + gap * pagesizes[pidx]);
                        if (*addr + length + gap * pagesizes[pidx] >
                            vm_map_max(map))
                                goto again;
                        /* And randomize the start address. */
                        *addr += (arc4random() % gap) * pagesizes[pidx];
                        if (max_addr != 0 && *addr + length > max_addr)
                                goto again;
                } else {
                        *addr = vm_map_findspace(map, curr_min_addr, length);
                        if (*addr + length > vm_map_max(map) ||
                            (max_addr != 0 && *addr + length > max_addr)) {
                                if (cluster) {
                                        cluster = false;
                                        MPASS(try == 1);
                                        goto again;
                                }
                                rv = KERN_NO_SPACE;
                                goto done;
                        }
                }

                if (find_space != VMFS_ANY_SPACE &&
                    (rv = vm_map_alignspace(map, object, offset, addr, length,
                    max_addr, alignment)) != KERN_SUCCESS) {
                        if (find_space == VMFS_OPTIMAL_SPACE) {
                                find_space = VMFS_ANY_SPACE;
                                curr_min_addr = min_addr;
                                cluster = update_anon;
                                try = 0;
                                goto again;
                        }
                        goto done;
                }
        } else if ((cow & MAP_REMAP) != 0) {
                if (!vm_map_range_valid(map, *addr, *addr + length)) {
                        rv = KERN_INVALID_ADDRESS;
                        goto done;
                }
                rv = vm_map_delete(map, *addr, *addr + length);
                if (rv != KERN_SUCCESS)
                        goto done;
        }
        if ((cow & (MAP_STACK_GROWS_DOWN | MAP_STACK_GROWS_UP)) != 0) {
                rv = vm_map_stack_locked(map, *addr, length, sgrowsiz, prot,
                    max, cow);
        } else {
                rv = vm_map_insert(map, object, offset, *addr, *addr + length,
                    prot, max, cow);
        }
        if (rv == KERN_SUCCESS && update_anon)
                map->anon_loc = *addr + length;
done:
        vm_map_unlock(map);
        return (rv);
}

/*
 *      vm_map_find_min() is a variant of vm_map_find() that takes an
 *      additional parameter (min_addr) and treats the given address
 *      (*addr) differently.  Specifically, it treats *addr as a hint
 *      and not as the minimum address where the mapping is created.
 *
 *      This function works in two phases.  First, it tries to
 *      allocate above the hint.  If that fails and the hint is
 *      greater than min_addr, it performs a second pass, replacing
 *      the hint with min_addr as the minimum address for the
 *      allocation.
 */
int
vm_map_find_min(vm_map_t map, vm_object_t object, vm_ooffset_t offset,
    vm_offset_t *addr, vm_size_t length, vm_offset_t min_addr,
    vm_offset_t max_addr, int find_space, vm_prot_t prot, vm_prot_t max,
    int cow)
{
        vm_offset_t hint;
        int rv;

        hint = *addr;
        for (;;) {
                rv = vm_map_find(map, object, offset, addr, length, max_addr,
                    find_space, prot, max, cow);
                if (rv == KERN_SUCCESS || min_addr >= hint)
                        return (rv);
                *addr = hint = min_addr;
        }
}

/*
 * A map entry with any of the following flags set must not be merged with
 * another entry.
 */
#define MAP_ENTRY_NOMERGE_MASK  (MAP_ENTRY_GROWS_DOWN | MAP_ENTRY_GROWS_UP | \
            MAP_ENTRY_IN_TRANSITION | MAP_ENTRY_IS_SUB_MAP | MAP_ENTRY_VN_EXEC)

static bool
vm_map_mergeable_neighbors(vm_map_entry_t prev, vm_map_entry_t entry)
{

        KASSERT((prev->eflags & MAP_ENTRY_NOMERGE_MASK) == 0 ||
            (entry->eflags & MAP_ENTRY_NOMERGE_MASK) == 0,
            ("vm_map_mergeable_neighbors: neither %p nor %p are mergeable",
            prev, entry));
        return (prev->end == entry->start &&
            prev->object.vm_object == entry->object.vm_object &&
            (prev->object.vm_object == NULL ||
            prev->offset + (prev->end - prev->start) == 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);
}

static void
vm_map_merged_neighbor_dispose(vm_map_t map, vm_map_entry_t entry)
{

        /*
         * 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 (entry->object.vm_object != NULL)
                vm_object_deallocate(entry->object.vm_object);
        if (entry->cred != NULL)
                crfree(entry->cred);
        vm_map_entry_dispose(map, entry);
}

/*
 *      vm_map_try_merge_entries:
 *
 *      Compare the given map entry to its predecessor, and merge its precessor
 *      into it if possible.  The entry remains valid, and may be extended.
 *      The predecessor may be deleted.
 *
 *      The map must be locked.
 */
void
vm_map_try_merge_entries(vm_map_t map, vm_map_entry_t prev_entry,
    vm_map_entry_t entry)
{

        VM_MAP_ASSERT_LOCKED(map);
        if ((entry->eflags & MAP_ENTRY_NOMERGE_MASK) == 0 &&
            vm_map_mergeable_neighbors(prev_entry, entry)) {
                vm_map_entry_unlink(map, prev_entry, UNLINK_MERGE_NEXT);
                vm_map_merged_neighbor_dispose(map, prev_entry);
        }
}

/*
 *      vm_map_entry_back:
 *
 *      Allocate an object to back a map entry.
 */
static inline void
vm_map_entry_back(vm_map_entry_t entry)
{
        vm_object_t object;

        KASSERT(entry->object.vm_object == NULL,
            ("map entry %p has backing object", entry));
        KASSERT((entry->eflags & MAP_ENTRY_IS_SUB_MAP) == 0,
            ("map entry %p is a submap", entry));
        object = vm_object_allocate_anon(atop(entry->end - entry->start), NULL,
            entry->cred, entry->end - entry->start);
        entry->object.vm_object = object;
        entry->offset = 0;
        entry->cred = NULL;
}

/*
 *      vm_map_entry_charge_object
 *
 *      If there is no object backing this entry, create one.  Otherwise, if
 *      the entry has cred, give it to the backing object.
 */
static inline void
vm_map_entry_charge_object(vm_map_t map, vm_map_entry_t entry)
{

        VM_MAP_ASSERT_LOCKED(map);
        KASSERT((entry->eflags & MAP_ENTRY_IS_SUB_MAP) == 0,
            ("map entry %p is a submap", entry));
        if (entry->object.vm_object == NULL && !map->system_map &&
            (entry->eflags & MAP_ENTRY_GUARD) == 0)
                vm_map_entry_back(entry);
        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: %s: both cred e %p", __func__, 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;
        }
}

/*
 *      vm_map_entry_clone
 *
 *      Create a duplicate map entry for clipping.
 */
static vm_map_entry_t
vm_map_entry_clone(vm_map_t map, vm_map_entry_t entry)
{
        vm_map_entry_t new_entry;

        VM_MAP_ASSERT_LOCKED(map);

        /*
         * Create a backing object now, if none exists, so that more individual
         * objects won't be created after the map entry is split.
         */
        vm_map_entry_charge_object(map, entry);

        /* Clone the entry. */
        new_entry = vm_map_entry_create(map);
        *new_entry = *entry;
        if (new_entry->cred != NULL)
                crhold(entry->cred);
        if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
                vm_object_reference(new_entry->object.vm_object);
                vm_map_entry_set_vnode_text(new_entry, true);
                /*
                 * The object->un_pager.vnp.writemappings for the object of
                 * MAP_ENTRY_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.
                 */
        }
        return (new_entry);
}

/*
 *      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.
 */
static int
vm_map_clip_start(vm_map_t map, vm_map_entry_t entry, vm_offset_t startaddr)
{
        vm_map_entry_t new_entry;
        int bdry_idx;

        if (!map->system_map)
                WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
                    "%s: map %p entry %p start 0x%jx", __func__, map, entry,
                    (uintmax_t)startaddr);

        if (startaddr <= entry->start)
                return (KERN_SUCCESS);

        VM_MAP_ASSERT_LOCKED(map);
        KASSERT(entry->end > startaddr && entry->start < startaddr,
            ("%s: invalid clip of entry %p", __func__, entry));

        bdry_idx = (entry->eflags & MAP_ENTRY_SPLIT_BOUNDARY_MASK) >>
            MAP_ENTRY_SPLIT_BOUNDARY_SHIFT;
        if (bdry_idx != 0) {
                if ((startaddr & (pagesizes[bdry_idx] - 1)) != 0)
                        return (KERN_INVALID_ARGUMENT);
        }

        new_entry = vm_map_entry_clone(map, entry);

        /*
         * Split off the front portion.  Insert the new entry BEFORE this one,
         * so that this entry has the specified starting address.
         */
        new_entry->end = startaddr;
        vm_map_entry_link(map, new_entry);
        return (KERN_SUCCESS);
}

/*
 *      vm_map_lookup_clip_start:
 *
 *      Find the entry at or just after 'start', and clip it if 'start' is in
 *      the interior of the entry.  Return entry after 'start', and in
 *      prev_entry set the entry before 'start'.
 */
static int
vm_map_lookup_clip_start(vm_map_t map, vm_offset_t start,
    vm_map_entry_t *res_entry, vm_map_entry_t *prev_entry)
{
        vm_map_entry_t entry;
        int rv;

        if (!map->system_map)
                WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
                    "%s: map %p start 0x%jx prev %p", __func__, map,
                    (uintmax_t)start, prev_entry);

        if (vm_map_lookup_entry(map, start, prev_entry)) {
                entry = *prev_entry;
                rv = vm_map_clip_start(map, entry, start);
                if (rv != KERN_SUCCESS)
                        return (rv);
                *prev_entry = vm_map_entry_pred(entry);
        } else
                entry = vm_map_entry_succ(*prev_entry);
        *res_entry = entry;
        return (KERN_SUCCESS);
}

/*
 *      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.
 */
static int
vm_map_clip_end(vm_map_t map, vm_map_entry_t entry, vm_offset_t endaddr)
{
        vm_map_entry_t new_entry;
        int bdry_idx;

        if (!map->system_map)
                WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
                    "%s: map %p entry %p end 0x%jx", __func__, map, entry,
                    (uintmax_t)endaddr);

        if (endaddr >= entry->end)
                return (KERN_SUCCESS);

        VM_MAP_ASSERT_LOCKED(map);
        KASSERT(entry->start < endaddr && entry->end > endaddr,
            ("%s: invalid clip of entry %p", __func__, entry));

        bdry_idx = (entry->eflags & MAP_ENTRY_SPLIT_BOUNDARY_MASK) >>
            MAP_ENTRY_SPLIT_BOUNDARY_SHIFT;
        if (bdry_idx != 0) {
                if ((endaddr & (pagesizes[bdry_idx] - 1)) != 0)
                        return (KERN_INVALID_ARGUMENT);
        }

        new_entry = vm_map_entry_clone(map, entry);

        /*
         * Split off the back portion.  Insert the new entry AFTER this one,
         * so that this entry has the specified ending address.
         */
        new_entry->start = endaddr;
        vm_map_entry_link(map, new_entry);

        return (KERN_SUCCESS);
}

/*
 *      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;

        result = KERN_INVALID_ARGUMENT;

        vm_map_lock(submap);
        submap->flags |= MAP_IS_SUB_MAP;
        vm_map_unlock(submap);

        vm_map_lock(map);
        VM_MAP_RANGE_CHECK(map, start, end);
        if (vm_map_lookup_entry(map, start, &entry) && entry->end >= end &&
            (entry->eflags & MAP_ENTRY_COW) == 0 &&
            entry->object.vm_object == NULL) {
                result = vm_map_clip_start(map, entry, start);
                if (result != KERN_SUCCESS)
                        goto unlock;
                result = vm_map_clip_end(map, entry, end);
                if (result != KERN_SUCCESS)
                        goto unlock;
                entry->object.sub_map = submap;
                entry->eflags |= MAP_ENTRY_IS_SUB_MAP;
                result = KERN_SUCCESS;
        }
unlock:
        vm_map_unlock(map);

        if (result != KERN_SUCCESS) {
                vm_map_lock(submap);
                submap->flags &= ~MAP_IS_SUB_MAP;
                vm_map_unlock(submap);
        }
        return (result);
}

/*
 * The maximum number of pages to map if MAP_PREFAULT_PARTIAL is specified
 */
#define MAX_INIT_PT     96

/*
 *      vm_map_pmap_enter:
 *
 *      Preload the specified map's pmap with mappings to the specified
 *      object's memory-resident pages.  No further physical pages are
 *      allocated, and no further virtual pages are retrieved from secondary
 *      storage.  If the specified flags include MAP_PREFAULT_PARTIAL, then a
 *      limited number of page mappings are created at the low-end of the
 *      specified address range.  (For this purpose, a superpage mapping
 *      counts as one page mapping.)  Otherwise, all resident pages within
 *      the specified address range are mapped.
 */
static 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 mask, psize, threshold, tmpidx;

        if ((prot & (VM_PROT_READ | VM_PROT_EXECUTE)) == 0 || object == NULL)
                return;
        if (object->type == OBJT_DEVICE || object->type == OBJT_SG) {
                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);
        } else
                VM_OBJECT_RLOCK(object);

        psize = atop(size);
        if (psize + pindex > object->size) {
                if (pindex >= object->size) {
                        VM_OBJECT_RUNLOCK(object);
                        return;
                }
                psize = object->size - pindex;
        }

        start = 0;
        p_start = NULL;
        threshold = MAX_INIT_PT;

        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) != 0 &&
                    vm_page_count_severe()) ||
                    ((flags & MAP_PREFAULT_PARTIAL) != 0 &&
                    tmpidx >= threshold)) {
                        psize = tmpidx;
                        break;
                }
                if (vm_page_all_valid(p)) {
                        if (p_start == NULL) {
                                start = addr + ptoa(tmpidx);
                                p_start = p;
                        }
                        /* Jump ahead if a superpage mapping is possible. */
                        if (p->psind > 0 && ((addr + ptoa(tmpidx)) &
                            (pagesizes[p->psind] - 1)) == 0) {
                                mask = atop(pagesizes[p->psind]) - 1;
                                if (tmpidx + mask < psize &&
                                    vm_page_ps_test(p, PS_ALL_VALID, NULL)) {
                                        p += mask;
                                        threshold += mask;
                                }
                        }
                } 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 entry, first_entry, in_tran, prev_entry;
        vm_object_t obj;
        struct ucred *cred;
        vm_prot_t old_prot;
        int rv;

        if (start == end)
                return (KERN_SUCCESS);

again:
        in_tran = NULL;
        vm_map_lock(map);

        /*
         * Ensure that we are not concurrently wiring pages.  vm_map_wire() may
         * need to fault pages into the map and will drop the map lock while
         * doing so, and the VM object may end up in an inconsistent state if we
         * update the protection on the map entry in between faults.
         */
        vm_map_wait_busy(map);

        VM_MAP_RANGE_CHECK(map, start, end);

        if (!vm_map_lookup_entry(map, start, &first_entry))
                first_entry = vm_map_entry_succ(first_entry);

        /*
         * Make a first pass to check for protection violations.
         */
        for (entry = first_entry; entry->start < end;
            entry = vm_map_entry_succ(entry)) {
                if ((entry->eflags & MAP_ENTRY_GUARD) != 0)
                        continue;
                if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0) {
                        vm_map_unlock(map);
                        return (KERN_INVALID_ARGUMENT);
                }
                if ((new_prot & entry->max_protection) != new_prot) {
                        vm_map_unlock(map);
                        return (KERN_PROTECTION_FAILURE);
                }
                if ((entry->eflags & MAP_ENTRY_IN_TRANSITION) != 0)
                        in_tran = entry;
        }

        /*
         * Postpone the operation until all in-transition map entries have
         * stabilized.  An in-transition entry might already have its pages
         * wired and wired_count incremented, but not yet have its
         * MAP_ENTRY_USER_WIRED flag set.  In which case, we would fail to call
         * vm_fault_copy_entry() in the final loop below.
         */
        if (in_tran != NULL) {
                in_tran->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
                vm_map_unlock_and_wait(map, 0);
                goto again;
        }

        /*
         * Before changing the protections, try to reserve swap space for any
         * private (i.e., copy-on-write) mappings that are transitioning from
         * read-only to read/write access.  If a reservation fails, break out
         * of this loop early and let the next loop simplify the entries, since
         * some may now be mergeable.
         */
        rv = vm_map_clip_start(map, first_entry, start);
        if (rv != KERN_SUCCESS) {
                vm_map_unlock(map);
                return (rv);
        }
        for (entry = first_entry; entry->start < end;
            entry = vm_map_entry_succ(entry)) {
                rv = vm_map_clip_end(map, entry, end);
                if (rv != KERN_SUCCESS) {
                        vm_map_unlock(map);
                        return (rv);
                }

                if (set_max ||
                    ((new_prot & ~entry->protection) & VM_PROT_WRITE) == 0 ||
                    ENTRY_CHARGED(entry) ||
                    (entry->eflags & MAP_ENTRY_GUARD) != 0) {
                        continue;
                }

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

                if (obj == NULL ||
                    (entry->eflags & MAP_ENTRY_NEEDS_COPY) != 0) {
                        if (!swap_reserve(entry->end - entry->start)) {
                                rv = KERN_RESOURCE_SHORTAGE;
                                end = entry->end;
                                break;
                        }
                        crhold(cred);
                        entry->cred = cred;
                        continue;
                }

                if (obj->type != OBJT_DEFAULT && obj->type != OBJT_SWAP)
                        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 (entry %p)",
                    obj, entry));
                if (!swap_reserve(ptoa(obj->size))) {
                        VM_OBJECT_WUNLOCK(obj);
                        rv = KERN_RESOURCE_SHORTAGE;
                        end = entry->end;
                        break;
                }

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

        /*
         * If enough swap space was available, go back and fix up protections.
         * Otherwise, just simplify entries, since some may have been modified.
         * [Note that clipping is not necessary the second time.]
         */
        for (prev_entry = vm_map_entry_pred(first_entry), entry = first_entry;
            entry->start < end;
            vm_map_try_merge_entries(map, prev_entry, entry),
            prev_entry = entry, entry = vm_map_entry_succ(entry)) {
                if (rv != KERN_SUCCESS ||
                    (entry->eflags & MAP_ENTRY_GUARD) != 0)
                        continue;

                old_prot = entry->protection;

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

                /*
                 * For user wired map entries, the normal lazy evaluation of
                 * write access upgrades through soft page faults is
                 * undesirable.  Instead, immediately copy any pages that are
                 * copy-on-write and enable write access in the physical map.
                 */
                if ((entry->eflags & MAP_ENTRY_USER_WIRED) != 0 &&
                    (entry->protection & VM_PROT_WRITE) != 0 &&
                    (old_prot & VM_PROT_WRITE) == 0)
                        vm_fault_copy_entry(map, map, entry, entry, NULL);

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

/*
 *      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 entry, prev_entry;
        int rv;
        bool modify_map;

        /*
         * 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:
                if (start == end)
                        return (0);
                modify_map = true;
                vm_map_lock(map);
                break;
        case MADV_WILLNEED:
        case MADV_DONTNEED:
        case MADV_FREE:
                if (start == end)
                        return (0);
                modify_map = false;
                vm_map_lock_read(map);
                break;
        default:
                return (EINVAL);
        }

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

        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.
                 */
                rv = vm_map_lookup_clip_start(map, start, &entry, &prev_entry);
                if (rv != KERN_SUCCESS) {
                        vm_map_unlock(map);
                        return (vm_mmap_to_errno(rv));
                }

                for (; entry->start < end; prev_entry = entry,
                    entry = vm_map_entry_succ(entry)) {
                        if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0)
                                continue;

                        rv = vm_map_clip_end(map, entry, end);
                        if (rv != KERN_SUCCESS) {
                                vm_map_unlock(map);
                                return (vm_mmap_to_errno(rv));
                        }

                        switch (behav) {
                        case MADV_NORMAL:
                                vm_map_entry_set_behavior(entry,
                                    MAP_ENTRY_BEHAV_NORMAL);
                                break;
                        case MADV_SEQUENTIAL:
                                vm_map_entry_set_behavior(entry,
                                    MAP_ENTRY_BEHAV_SEQUENTIAL);
                                break;
                        case MADV_RANDOM:
                                vm_map_entry_set_behavior(entry,
                                    MAP_ENTRY_BEHAV_RANDOM);
                                break;
                        case MADV_NOSYNC:
                                entry->eflags |= MAP_ENTRY_NOSYNC;
                                break;
                        case MADV_AUTOSYNC:
                                entry->eflags &= ~MAP_ENTRY_NOSYNC;
                                break;
                        case MADV_NOCORE:
                                entry->eflags |= MAP_ENTRY_NOCOREDUMP;
                                break;
                        case MADV_CORE:
                                entry->eflags &= ~MAP_ENTRY_NOCOREDUMP;
                                break;
                        default:
                                break;
                        }
                        vm_map_try_merge_entries(map, prev_entry, entry);
                }
                vm_map_try_merge_entries(map, prev_entry, entry);
                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.
                 */
                if (!vm_map_lookup_entry(map, start, &entry))
                        entry = vm_map_entry_succ(entry);
                for (; entry->start < end;
                    entry = vm_map_entry_succ(entry)) {
                        vm_offset_t useEnd, useStart;

                        if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0)
                                continue;

                        /*
                         * MADV_FREE would otherwise rewind time to
                         * the creation of the shadow object.  Because
                         * we hold the VM map read-locked, neither the
                         * entry's object nor the presence of a
                         * backing object can change.
                         */
                        if (behav == MADV_FREE &&
                            entry->object.vm_object != NULL &&
                            entry->object.vm_object->backing_object != NULL)
                                continue;

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

                        if (entry->start < start) {
                                pstart += atop(start - entry->start);
                                useStart = start;
                        }
                        if (entry->end > end) {
                                pend -= atop(entry->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(entry->object.vm_object, pstart,
                            pend, behav);

                        /*
                         * Pre-populate paging structures in the
                         * WILLNEED case.  For wired entries, the
                         * paging structures are already populated.
                         */
                        if (behav == MADV_WILLNEED &&
                            entry->wired_count == 0) {
                                vm_map_pmap_enter(map,
                                    useStart,
                                    entry->protection,
                                    entry->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, lentry, prev_entry, start_entry;
        int rv;

        switch (new_inheritance) {
        case VM_INHERIT_NONE:
        case VM_INHERIT_COPY:
        case VM_INHERIT_SHARE:
        case VM_INHERIT_ZERO:
                break;
        default:
                return (KERN_INVALID_ARGUMENT);
        }
        if (start == end)
                return (KERN_SUCCESS);
        vm_map_lock(map);
        VM_MAP_RANGE_CHECK(map, start, end);
        rv = vm_map_lookup_clip_start(map, start, &start_entry, &prev_entry);
        if (rv != KERN_SUCCESS)
                goto unlock;
        if (vm_map_lookup_entry(map, end - 1, &lentry)) {
                rv = vm_map_clip_end(map, lentry, end);
                if (rv != KERN_SUCCESS)
                        goto unlock;
        }
        if (new_inheritance == VM_INHERIT_COPY) {
                for (entry = start_entry; entry->start < end;
                    prev_entry = entry, entry = vm_map_entry_succ(entry)) {
                        if ((entry->eflags & MAP_ENTRY_SPLIT_BOUNDARY_MASK)
                            != 0) {
                                rv = KERN_INVALID_ARGUMENT;
                                goto unlock;
                        }
                }
        }
        for (entry = start_entry; entry->start < end; prev_entry = entry,
            entry = vm_map_entry_succ(entry)) {
                KASSERT(entry->end <= end, ("non-clipped entry %p end %jx %jx",
                    entry, (uintmax_t)entry->end, (uintmax_t)end));
                if ((entry->eflags & MAP_ENTRY_GUARD) == 0 ||
                    new_inheritance != VM_INHERIT_ZERO)
                        entry->inheritance = new_inheritance;
                vm_map_try_merge_entries(map, prev_entry, entry);
        }
        vm_map_try_merge_entries(map, prev_entry, entry);
unlock:
        vm_map_unlock(map);
        return (rv);
}

/*
 *      vm_map_entry_in_transition:
 *
 *      Release the map lock, and sleep until the entry is no longer in
 *      transition.  Awake and acquire the map lock.  If the map changed while
 *      another held the lock, lookup a possibly-changed entry at or after the
 *      'start' position of the old entry.
 */
static vm_map_entry_t
vm_map_entry_in_transition(vm_map_t map, vm_offset_t in_start,
    vm_offset_t *io_end, bool holes_ok, vm_map_entry_t in_entry)
{
        vm_map_entry_t entry;
        vm_offset_t start;
        u_int last_timestamp;

        VM_MAP_ASSERT_LOCKED(map);
        KASSERT((in_entry->eflags & MAP_ENTRY_IN_TRANSITION) != 0,
            ("not in-tranition map entry %p", in_entry));
        /*
         * We have not yet clipped the entry.
         */
        start = MAX(in_start, in_entry->start);
        in_entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
        last_timestamp = map->timestamp;
        if (vm_map_unlock_and_wait(map, 0)) {
                /*
                 * Allow interruption of user wiring/unwiring?
                 */
        }
        vm_map_lock(map);
        if (last_timestamp + 1 == map->timestamp)
                return (in_entry);

        /*
         * 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, start, &entry)) {
                if (!holes_ok) {
                        *io_end = start;
                        return (NULL);
                }
                entry = vm_map_entry_succ(entry);
        }
        return (entry);
}

/*
 *      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, next_entry, prev_entry;
        int rv;
        bool holes_ok, need_wakeup, user_unwire;

        if (start == end)
                return (KERN_SUCCESS);
        holes_ok = (flags & VM_MAP_WIRE_HOLESOK) != 0;
        user_unwire = (flags & VM_MAP_WIRE_USER) != 0;
        vm_map_lock(map);
        VM_MAP_RANGE_CHECK(map, start, end);
        if (!vm_map_lookup_entry(map, start, &first_entry)) {
                if (holes_ok)
                        first_entry = vm_map_entry_succ(first_entry);
                else {
                        vm_map_unlock(map);
                        return (KERN_INVALID_ADDRESS);
                }
        }
        rv = KERN_SUCCESS;
        for (entry = first_entry; entry->start < end; entry = next_entry) {
                if (entry->eflags & MAP_ENTRY_IN_TRANSITION) {
                        /*
                         * We have not yet clipped the entry.
                         */
                        next_entry = vm_map_entry_in_transition(map, start,
                            &end, holes_ok, entry);
                        if (next_entry == NULL) {
                                if (entry == first_entry) {
                                        vm_map_unlock(map);
                                        return (KERN_INVALID_ADDRESS);
                                }
                                rv = KERN_INVALID_ADDRESS;
                                break;
                        }
                        first_entry = (entry == first_entry) ?
                            next_entry : NULL;
                        continue;
                }
                rv = vm_map_clip_start(map, entry, start);
                if (rv != KERN_SUCCESS)
                        break;
                rv = vm_map_clip_end(map, entry, end);
                if (rv != KERN_SUCCESS)
                        break;

                /*
                 * 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;
                next_entry = vm_map_entry_succ(entry);
                /*
                 * Check the map for holes in the specified region.
                 * If holes_ok, skip this check.
                 */
                if (!holes_ok &&
                    entry->end < end && next_entry->start > entry->end) {
                        end = entry->end;
                        rv = KERN_INVALID_ADDRESS;
                        break;
                }
                /*
                 * 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;
                        break;
                }
        }
        need_wakeup = false;
        if (first_entry == NULL &&
            !vm_map_lookup_entry(map, start, &first_entry)) {
                KASSERT(holes_ok, ("vm_map_unwire: lookup failed"));
                prev_entry = first_entry;
                entry = vm_map_entry_succ(first_entry);
        } else {
                prev_entry = vm_map_entry_pred(first_entry);
                entry = first_entry;
        }
        for (; entry->start < end;
            prev_entry = entry, entry = vm_map_entry_succ(entry)) {
                /*
                 * If holes_ok 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(holes_ok,
                            ("vm_map_unwire: !HOLESOK and new/changed entry"));
                        continue;
                }

                if (rv == KERN_SUCCESS && (!user_unwire ||
                    (entry->eflags & MAP_ENTRY_USER_WIRED))) {
                        if (entry->wired_count == 1)
                                vm_map_entry_unwire(map, entry);
                        else
                                entry->wired_count--;
                        if (user_unwire)
                                entry->eflags &= ~MAP_ENTRY_USER_WIRED;
                }
                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_try_merge_entries(map, prev_entry, entry);
        }
        vm_map_try_merge_entries(map, prev_entry, entry);
        vm_map_unlock(map);
        if (need_wakeup)
                vm_map_wakeup(map);
        return (rv);
}

static void
vm_map_wire_user_count_sub(u_long npages)
{

        atomic_subtract_long(&vm_user_wire_count, npages);
}

static bool
vm_map_wire_user_count_add(u_long npages)
{
        u_long wired;

        wired = vm_user_wire_count;
        do {
                if (npages + wired > vm_page_max_user_wired)
                        return (false);
        } while (!atomic_fcmpset_long(&vm_user_wire_count, &wired,
            npages + wired));

        return (true);
}

/*
 *      vm_map_wire_entry_failure:
 *
 *      Handle a wiring failure on the given entry.
 *
 *      The map should be locked.
 */
static void
vm_map_wire_entry_failure(vm_map_t map, vm_map_entry_t entry,
    vm_offset_t failed_addr)
{

        VM_MAP_ASSERT_LOCKED(map);
        KASSERT((entry->eflags & MAP_ENTRY_IN_TRANSITION) != 0 &&
            entry->wired_count == 1,
            ("vm_map_wire_entry_failure: entry %p isn't being wired", entry));
        KASSERT(failed_addr < entry->end,
            ("vm_map_wire_entry_failure: entry %p was fully wired", entry));

        /*
         * If any pages at the start of this entry were successfully wired,
         * then unwire them.
         */
        if (failed_addr > entry->start) {
                pmap_unwire(map->pmap, entry->start, failed_addr);
                vm_object_unwire(entry->object.vm_object, entry->offset,
                    failed_addr - entry->start, PQ_ACTIVE);
        }

        /*
         * Assign an out-of-range value to represent the failure to wire this
         * entry.
         */
        entry->wired_count = -1;
}

int
vm_map_wire(vm_map_t map, vm_offset_t start, vm_offset_t end, int flags)
{
        int rv;

        vm_map_lock(map);
        rv = vm_map_wire_locked(map, start, end, flags);
        vm_map_unlock(map);
        return (rv);
}

/*
 *      vm_map_wire_locked:
 *
 *      Implements both kernel and user wiring.  Returns with the map locked,
 *      the map lock may be dropped.
 */
int
vm_map_wire_locked(vm_map_t map, vm_offset_t start, vm_offset_t end, int flags)
{
        vm_map_entry_t entry, first_entry, next_entry, prev_entry;
        vm_offset_t faddr, saved_end, saved_start;
        u_long incr, npages;
        u_int bidx, last_timestamp;
        int rv;
        bool holes_ok, need_wakeup, user_wire;
        vm_prot_t prot;

        VM_MAP_ASSERT_LOCKED(map);

        if (start == end)
                return (KERN_SUCCESS);
        prot = 0;
        if (flags & VM_MAP_WIRE_WRITE)
                prot |= VM_PROT_WRITE;
        holes_ok = (flags & VM_MAP_WIRE_HOLESOK) != 0;
        user_wire = (flags & VM_MAP_WIRE_USER) != 0;
        VM_MAP_RANGE_CHECK(map, start, end);
        if (!vm_map_lookup_entry(map, start, &first_entry)) {
                if (holes_ok)
                        first_entry = vm_map_entry_succ(first_entry);
                else
                        return (KERN_INVALID_ADDRESS);
        }
        for (entry = first_entry; entry->start < end; entry = next_entry) {
                if (entry->eflags & MAP_ENTRY_IN_TRANSITION) {
                        /*
                         * We have not yet clipped the entry.
                         */
                        next_entry = vm_map_entry_in_transition(map, start,
                            &end, holes_ok, entry);
                        if (next_entry == NULL) {
                                if (entry == first_entry)
                                        return (KERN_INVALID_ADDRESS);
                                rv = KERN_INVALID_ADDRESS;
                                goto done;
                        }
                        first_entry = (entry == first_entry) ?
                            next_entry : NULL;
                        continue;
                }
                rv = vm_map_clip_start(map, entry, start);
                if (rv != KERN_SUCCESS)
                        goto done;
                rv = vm_map_clip_end(map, entry, end);
                if (rv != KERN_SUCCESS)
                        goto done;

                /*
                 * 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 (!holes_ok) {
                                end = entry->end;
                                rv = KERN_INVALID_ADDRESS;
                                goto done;
                        }
                } else if (entry->wired_count == 0) {
                        entry->wired_count++;

                        npages = atop(entry->end - entry->start);
                        if (user_wire && !vm_map_wire_user_count_add(npages)) {
                                vm_map_wire_entry_failure(map, entry,
                                    entry->start);
                                end = entry->end;
                                rv = KERN_RESOURCE_SHORTAGE;
                                goto done;
                        }

                        /*
                         * Release the map lock, relying on the in-transition
                         * mark.  Mark the map busy for fork.
                         */
                        saved_start = entry->start;
                        saved_end = entry->end;
                        last_timestamp = map->timestamp;
                        bidx = (entry->eflags & MAP_ENTRY_SPLIT_BOUNDARY_MASK)
                            >> MAP_ENTRY_SPLIT_BOUNDARY_SHIFT;
                        incr =  pagesizes[bidx];
                        vm_map_busy(map);
                        vm_map_unlock(map);

                        for (faddr = saved_start; faddr < saved_end;
                            faddr += incr) {
                                /*
                                 * Simulate a fault to get the page and enter
                                 * it into the physical map.
                                 */
                                rv = vm_fault(map, faddr, VM_PROT_NONE,
                                    VM_FAULT_WIRE, NULL);
                                if (rv != KERN_SUCCESS)
                                        break;
                        }
                        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.
                                 */
                                if (!vm_map_lookup_entry(map, saved_start,
                                    &next_entry))
                                        KASSERT(false,
                                            ("vm_map_wire: lookup failed"));
                                first_entry = (entry == first_entry) ?
                                    next_entry : NULL;
                                for (entry = next_entry; entry->end < saved_end;
                                    entry = vm_map_entry_succ(entry)) {
                                        /*
                                         * In case of failure, handle entries
                                         * that were not fully wired here;
                                         * fully wired entries are handled
                                         * later.
                                         */
                                        if (rv != KERN_SUCCESS &&
                                            faddr < entry->end)
                                                vm_map_wire_entry_failure(map,
                                                    entry, faddr);
                                }
                        }
                        if (rv != KERN_SUCCESS) {
                                vm_map_wire_entry_failure(map, entry, faddr);
                                if (user_wire)
                                        vm_map_wire_user_count_sub(npages);
                                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 holes_ok was specified, skip this check.
                 */
                next_entry = vm_map_entry_succ(entry);
                if (!holes_ok &&
                    entry->end < end && next_entry->start > entry->end) {
                        end = entry->end;
                        rv = KERN_INVALID_ADDRESS;
                        goto done;
                }
        }
        rv = KERN_SUCCESS;
done:
        need_wakeup = false;
        if (first_entry == NULL &&
            !vm_map_lookup_entry(map, start, &first_entry)) {
                KASSERT(holes_ok, ("vm_map_wire: lookup failed"));
                prev_entry = first_entry;
                entry = vm_map_entry_succ(first_entry);
        } else {
                prev_entry = vm_map_entry_pred(first_entry);
                entry = first_entry;
        }
        for (; entry->start < end;
            prev_entry = entry, entry = vm_map_entry_succ(entry)) {
                /*
                 * If holes_ok 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 not by us.
                 *
                 * Another way to get an entry not marked with
                 * MAP_ENTRY_IN_TRANSITION is after failed clipping,
                 * which set rv to KERN_INVALID_ARGUMENT.
                 */
                if ((entry->eflags & MAP_ENTRY_IN_TRANSITION) == 0 ||
                    entry->wiring_thread != curthread) {
                        KASSERT(holes_ok || rv == KERN_INVALID_ARGUMENT,
                            ("vm_map_wire: !HOLESOK and new/changed entry"));
                        continue;
                }

                if ((entry->eflags & MAP_ENTRY_WIRE_SKIPPED) != 0) {
                        /* do nothing */
                } else 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) {
                        /*
                         * Undo the wiring.  Wiring succeeded on this entry
                         * but failed on a later entry.  
                         */
                        if (entry->wired_count == 1) {
                                vm_map_entry_unwire(map, entry);
                                if (user_wire)
                                        vm_map_wire_user_count_sub(
                                            atop(entry->end - entry->start));
                        } else
                                entry->wired_count--;
                }
                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_try_merge_entries(map, prev_entry, entry);
        }
        vm_map_try_merge_entries(map, prev_entry, entry);
        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 entry, first_entry, next_entry;
        vm_size_t size;
        vm_object_t object;
        vm_ooffset_t offset;
        unsigned int last_timestamp;
        int bdry_idx;
        boolean_t failed;

        vm_map_lock_read(map);
        VM_MAP_RANGE_CHECK(map, start, end);
        if (!vm_map_lookup_entry(map, start, &first_entry)) {
                vm_map_unlock_read(map);
                return (KERN_INVALID_ADDRESS);
        } else if (start == end) {
                start = first_entry->start;
                end = first_entry->end;
        }

        /*
         * Make a first pass to check for user-wired memory, holes,
         * and partial invalidation of largepage mappings.
         */
        for (entry = first_entry; entry->start < end; entry = next_entry) {
                if (invalidate) {
                        if ((entry->eflags & MAP_ENTRY_USER_WIRED) != 0) {
                                vm_map_unlock_read(map);
                                return (KERN_INVALID_ARGUMENT);
                        }
                        bdry_idx = (entry->eflags &
                            MAP_ENTRY_SPLIT_BOUNDARY_MASK) >>
                            MAP_ENTRY_SPLIT_BOUNDARY_SHIFT;
                        if (bdry_idx != 0 &&
                            ((start & (pagesizes[bdry_idx] - 1)) != 0 ||
                            (end & (pagesizes[bdry_idx] - 1)) != 0)) {
                                vm_map_unlock_read(map);
                                return (KERN_INVALID_ARGUMENT);
                        }
                }
                next_entry = vm_map_entry_succ(entry);
                if (end > entry->end &&
                    entry->end != next_entry->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 (entry = first_entry; entry->start < end;) {
                offset = entry->offset + (start - entry->start);
                size = (end <= entry->end ? end : entry->end) - start;
                if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0) {
                        vm_map_t smap;
                        vm_map_entry_t tentry;
                        vm_size_t tsize;

                        smap = entry->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 = entry->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, &entry))
                        entry = vm_map_entry_succ(entry);
        }

        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_size_t size;

        VM_MAP_ASSERT_LOCKED(map);
        KASSERT(entry->wired_count > 0,
            ("vm_map_entry_unwire: entry %p isn't wired", entry));

        size = entry->end - entry->start;
        if ((entry->eflags & MAP_ENTRY_USER_WIRED) != 0)
                vm_map_wire_user_count_sub(atop(size));
        pmap_unwire(map->pmap, entry->start, entry->end);
        vm_object_unwire(entry->object.vm_object, entry->offset, size,
            PQ_ACTIVE);
        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, size1;
        vm_size_t size;

        vm_map_entry_unlink(map, entry, UNLINK_MERGE_NONE);
        object = entry->object.vm_object;

        if ((entry->eflags & MAP_ENTRY_GUARD) != 0) {
                MPASS(entry->cred == NULL);
                MPASS((entry->eflags & MAP_ENTRY_IS_SUB_MAP) == 0);
                MPASS(object == NULL);
                vm_map_entry_deallocate(entry, map->system_map);
                return;
        }

        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) {
                entry->object.vm_object = NULL;
        } else if ((object->flags & OBJ_ANON) != 0 ||
            object == kernel_object) {
                KASSERT(entry->cred == NULL || object->cred == NULL ||
                    (entry->eflags & MAP_ENTRY_NEEDS_COPY),
                    ("OVERCOMMIT vm_map_entry_delete: both cred %p", entry));
                offidxstart = OFF_TO_IDX(entry->offset);
                offidxend = offidxstart + atop(size);
                VM_OBJECT_WLOCK(object);
                if (object->ref_count != 1 &&
                    ((object->flags & OBJ_ONEMAPPING) != 0 ||
                    object == kernel_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 (offidxend >= object->size &&
                            offidxstart < object->size) {
                                size1 = object->size;
                                object->size = offidxstart;
                                if (object->cred != NULL) {
                                        size1 -= object->size;
                                        KASSERT(object->charge >= ptoa(size1),
                                            ("object %p charge < 0", object));
                                        swap_release_by_cred(ptoa(size1),
                                            object->cred);
                                        object->charge -= ptoa(size1);
                                }
                        }
                }
                VM_OBJECT_WUNLOCK(object);
        }
        if (map->system_map)
                vm_map_entry_deallocate(entry, TRUE);
        else {
                entry->defer_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, next_entry, scratch_entry;
        int rv;

        VM_MAP_ASSERT_LOCKED(map);

        if (start == end)
                return (KERN_SUCCESS);

        /*
         * Find the start of the region, and clip it.
         * Step through all entries in this region.
         */
        rv = vm_map_lookup_clip_start(map, start, &entry, &scratch_entry);
        if (rv != KERN_SUCCESS)
                return (rv);
        for (; entry->start < end; entry = next_entry) {
                /*
                 * 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;

                        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.
                                 */
                                rv = vm_map_lookup_clip_start(map, saved_start,
                                    &next_entry, &scratch_entry);
                                if (rv != KERN_SUCCESS)
                                        break;
                        } else
                                next_entry = entry;
                        continue;
                }

                /* XXXKIB or delete to the upper superpage boundary ? */
                rv = vm_map_clip_end(map, entry, end);
                if (rv != KERN_SUCCESS)
                        break;
                next_entry = vm_map_entry_succ(entry);

                /*
                 * 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);

                /*
                 * Remove mappings for the pages, but only if the
                 * mappings could exist.  For instance, it does not
                 * make sense to call pmap_remove() for guard entries.
                 */
                if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0 ||
                    entry->object.vm_object != NULL)
                        pmap_remove(map->pmap, entry->start, entry->end);

                if (entry->end == map->anon_loc)
                        map->anon_loc = entry->start;

                /*
                 * 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);
        }
        return (rv);
}

/*
 *      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) {
                /*
                 * 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 = vm_map_entry_succ(entry);
        }
        return (TRUE);
}

/*
 *
 *      vm_map_copy_swap_object:
 *
 *      Copies a swap-backed object from an existing map entry to a
 *      new one.  Carries forward the swap charge.  May change the
 *      src object on return.
 */
static void
vm_map_copy_swap_object(vm_map_entry_t src_entry, vm_map_entry_t dst_entry,
    vm_offset_t size, vm_ooffset_t *fork_charge)
{
        vm_object_t src_object;
        struct ucred *cred;
        int charged;

        src_object = src_entry->object.vm_object;
        charged = ENTRY_CHARGED(src_entry);
        if ((src_object->flags & OBJ_ANON) != 0) {
                VM_OBJECT_WLOCK(src_object);
                vm_object_collapse(src_object);
                if ((src_object->flags & OBJ_ONEMAPPING) != 0) {
                        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);
                VM_OBJECT_WUNLOCK(src_object);
        } else
                vm_object_reference(src_object);
        if (src_entry->cred != NULL &&
            !(src_entry->eflags & MAP_ENTRY_NEEDS_COPY)) {
                KASSERT(src_object->cred == NULL,
                    ("OVERCOMMIT: vm_map_copy_anon_entry: cred %p",
                     src_object));
                src_object->cred = src_entry->cred;
                src_object->charge = size;
        }
        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;
                }
        }
}

/*
 *      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;

        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 ||
            (src_entry->protection & VM_PROT_WRITE) == 0) {
                /*
                 * If the source entry is marked needs_copy, it is already
                 * write-protected.
                 */
                if ((src_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0 &&
                    (src_entry->protection & VM_PROT_WRITE) != 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) {
                        if (src_object->type == OBJT_DEFAULT ||
                            src_object->type == OBJT_SWAP) {
                                vm_map_copy_swap_object(src_entry, dst_entry,
                                    size, fork_charge);
                                /* May have split/collapsed, reload obj. */
                                src_object = src_entry->object.vm_object;
                        } else {
                                vm_object_reference(src_object);
                                dst_entry->object.vm_object = src_object;
                        }
                        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_WRITECNT) {
                                /*
                                 * MAP_ENTRY_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 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_WRITECNT;
                                src_entry->eflags &= ~MAP_ENTRY_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->defer_next =
                                    curthread->td_map_def_user;
                                curthread->td_map_def_user = fake_entry;
                        }

                        pmap_copy(dst_map->pmap, src_map->pmap,
                            dst_entry->start, dst_entry->end - dst_entry->start,
                            src_entry->start);
                } 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;
                        }
                }
        } else {
                /*
                 * We don't want to make writeable wired pages copy-on-write.
                 * Immediately copy these pages into the new map by simulating
                 * page 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;

        if ((entry->eflags & MAP_ENTRY_GUARD) != 0)
                return;
        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 error, locked;
        vm_inherit_t inh;

        old_map = &vm1->vm_map;
        /* Copy immutable fields of vm1 to vm2. */
        vm2 = vmspace_alloc(vm_map_min(old_map), vm_map_max(old_map),
            pmap_pinit);
        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"));

        error = pmap_vmspace_copy(new_map->pmap, old_map->pmap);
        if (error != 0) {
                sx_xunlock(&old_map->lock);
                sx_xunlock(&new_map->lock);
                vm_map_process_deferred();
                vmspace_free(vm2);
                return (NULL);
        }

        new_map->anon_loc = old_map->anon_loc;
        new_map->flags |= old_map->flags & (MAP_ASLR | MAP_ASLR_IGNSTART);

        VM_MAP_ENTRY_FOREACH(old_entry, old_map) {
                if ((old_entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0)
                        panic("vm_map_fork: encountered a submap");

                inh = old_entry->inheritance;
                if ((old_entry->eflags & MAP_ENTRY_GUARD) != 0 &&
                    inh != VM_INHERIT_NONE)
                        inh = VM_INHERIT_COPY;

                switch (inh) {
                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) {
                                vm_map_entry_back(old_entry);
                                object = old_entry->object.vm_object;
                        }

                        /*
                         * 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->cred,
                                    /* Transfer the second reference too. */
                                    true);
                                old_entry->eflags &= ~MAP_ENTRY_NEEDS_COPY;
                                old_entry->cred = NULL;

                                /*
                                 * As in vm_map_merged_neighbor_dispose(),
                                 * the vnode lock will not be acquired in
                                 * this call to vm_object_deallocate().
                                 */
                                vm_object_deallocate(object);
                                object = old_entry->object.vm_object;
                        } else {
                                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_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_WRITECNT) {
                                vm_pager_update_writecount(object,
                                    new_entry->start, new_entry->end);
                        }
                        vm_map_entry_set_vnode_text(new_entry, true);

                        /*
                         * 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_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_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_entry);
                        vmspace_map_entry_forked(vm1, vm2, new_entry);
                        vm_map_copy_entry(old_map, new_map, old_entry,
                            new_entry, fork_charge);
                        vm_map_entry_set_vnode_text(new_entry, true);
                        break;

                case VM_INHERIT_ZERO:
                        /*
                         * Create a new anonymous mapping entry modelled from
                         * the old one.
                         */
                        new_entry = vm_map_entry_create(new_map);
                        memset(new_entry, 0, sizeof(*new_entry));

                        new_entry->start = old_entry->start;
                        new_entry->end = old_entry->end;
                        new_entry->eflags = old_entry->eflags &
                            ~(MAP_ENTRY_USER_WIRED | MAP_ENTRY_IN_TRANSITION |
                            MAP_ENTRY_WRITECNT | MAP_ENTRY_VN_EXEC |
                            MAP_ENTRY_SPLIT_BOUNDARY_MASK);
                        new_entry->protection = old_entry->protection;
                        new_entry->max_protection = old_entry->max_protection;
                        new_entry->inheritance = VM_INHERIT_ZERO;

                        vm_map_entry_link(new_map, new_entry);
                        vmspace_map_entry_forked(vm1, vm2, new_entry);

                        new_entry->cred = curthread->td_ucred;
                        crhold(new_entry->cred);
                        *fork_charge += (new_entry->end - new_entry->start);

                        break;
                }
        }
        /*
         * 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);
}

/*
 * Create a process's stack for exec_new_vmspace().  This function is never
 * asked to wire the newly created stack.
 */
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_size_t growsize, init_ssize;
        rlim_t vmemlim;
        int rv;

        MPASS((map->flags & MAP_WIREFUTURE) == 0);
        growsize = sgrowsiz;
        init_ssize = (max_ssize < growsize) ? max_ssize : growsize;
        vm_map_lock(map);
        vmemlim = lim_cur(curthread, RLIMIT_VMEM);
        /* If we would blow our VMEM resource limit, no go */
        if (map->size + init_ssize > vmemlim) {
                rv = KERN_NO_SPACE;
                goto out;
        }
        rv = vm_map_stack_locked(map, addrbos, max_ssize, growsize, prot,
            max, cow);
out:
        vm_map_unlock(map);
        return (rv);
}

static int stack_guard_page = 1;
SYSCTL_INT(_security_bsd, OID_AUTO, stack_guard_page, CTLFLAG_RWTUN,
    &stack_guard_page, 0,
    "Specifies the number of guard pages for a stack that grows");

static int
vm_map_stack_locked(vm_map_t map, vm_offset_t addrbos, vm_size_t max_ssize,
    vm_size_t growsize, vm_prot_t prot, vm_prot_t max, int cow)
{
        vm_map_entry_t new_entry, prev_entry;
        vm_offset_t bot, gap_bot, gap_top, top;
        vm_size_t init_ssize, sgp;
        int orient, rv;

        /*
         * 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.
         */
        orient = cow & (MAP_STACK_GROWS_DOWN | MAP_STACK_GROWS_UP);
        KASSERT(orient != 0, ("No stack grow direction"));
        KASSERT(orient != (MAP_STACK_GROWS_DOWN | MAP_STACK_GROWS_UP),
            ("bi-dir stack"));

        if (max_ssize == 0 ||
            !vm_map_range_valid(map, addrbos, addrbos + max_ssize))
                return (KERN_INVALID_ADDRESS);
        sgp = ((curproc->p_flag2 & P2_STKGAP_DISABLE) != 0 ||
            (curproc->p_fctl0 & NT_FREEBSD_FCTL_STKGAP_DISABLE) != 0) ? 0 :
            (vm_size_t)stack_guard_page * PAGE_SIZE;
        if (sgp >= max_ssize)
                return (KERN_INVALID_ARGUMENT);

        init_ssize = growsize;
        if (max_ssize < init_ssize + sgp)
                init_ssize = max_ssize - sgp;

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

        /*
         * If we can't accommodate max_ssize in the current mapping, no go.
         */
        if (vm_map_entry_succ(prev_entry)->start < addrbos + max_ssize)
                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;
                top = bot + init_ssize;
                gap_bot = addrbos;
                gap_top = bot;
        } else /* if (orient == MAP_STACK_GROWS_UP) */ {
                bot = addrbos;
                top = bot + init_ssize;
                gap_bot = top;
                gap_top = addrbos + max_ssize;
        }
        rv = vm_map_insert(map, NULL, 0, bot, top, prot, max, cow);
        if (rv != KERN_SUCCESS)
                return (rv);
        new_entry = vm_map_entry_succ(prev_entry);
        KASSERT(new_entry->end == top || new_entry->start == bot,
            ("Bad entry start/end for new stack entry"));
        KASSERT((orient & MAP_STACK_GROWS_DOWN) == 0 ||
            (new_entry->eflags & MAP_ENTRY_GROWS_DOWN) != 0,
            ("new entry lacks MAP_ENTRY_GROWS_DOWN"));
        KASSERT((orient & MAP_STACK_GROWS_UP) == 0 ||
            (new_entry->eflags & MAP_ENTRY_GROWS_UP) != 0,
            ("new entry lacks MAP_ENTRY_GROWS_UP"));
        if (gap_bot == gap_top)
                return (KERN_SUCCESS);
        rv = vm_map_insert(map, NULL, 0, gap_bot, gap_top, VM_PROT_NONE,
            VM_PROT_NONE, MAP_CREATE_GUARD | (orient == MAP_STACK_GROWS_DOWN ?
            MAP_CREATE_STACK_GAP_DN : MAP_CREATE_STACK_GAP_UP));
        if (rv == KERN_SUCCESS) {
                /*
                 * Gap can never successfully handle a fault, so
                 * read-ahead logic is never used for it.  Re-use
                 * next_read of the gap entry to store
                 * stack_guard_page for vm_map_growstack().
                 */
                if (orient == MAP_STACK_GROWS_DOWN)
                        vm_map_entry_pred(new_entry)->next_read = sgp;
                else
                        vm_map_entry_succ(new_entry)->next_read = sgp;
        } else {
                (void)vm_map_delete(map, bot, top);
        }
        return (rv);
}

/*
 * Attempts to grow a vm stack entry.  Returns KERN_SUCCESS if we
 * successfully grow the stack.
 */
static int
vm_map_growstack(vm_map_t map, vm_offset_t addr, vm_map_entry_t gap_entry)
{
        vm_map_entry_t stack_entry;
        struct proc *p;
        struct vmspace *vm;
        struct ucred *cred;
        vm_offset_t gap_end, gap_start, grow_start;
        vm_size_t grow_amount, guard, max_grow;
        rlim_t lmemlim, stacklim, vmemlim;
        int rv, rv1;
        bool gap_deleted, grow_down, is_procstack;
#ifdef notyet
        uint64_t limit;
#endif
#ifdef RACCT
        int error;
#endif

        p = curproc;
        vm = p->p_vmspace;

        /*
         * Disallow stack growth when the access is performed by a
         * debugger or AIO daemon.  The reason is that the wrong
         * resource limits are applied.
         */
        if (p != initproc && (map != &p->p_vmspace->vm_map ||
            p->p_textvp == NULL))
                return (KERN_FAILURE);

        MPASS(!map->system_map);

        lmemlim = lim_cur(curthread, RLIMIT_MEMLOCK);
        stacklim = lim_cur(curthread, RLIMIT_STACK);
        vmemlim = lim_cur(curthread, RLIMIT_VMEM);
retry:
        /* If addr is not in a hole for a stack grow area, no need to grow. */
        if (gap_entry == NULL && !vm_map_lookup_entry(map, addr, &gap_entry))
                return (KERN_FAILURE);
        if ((gap_entry->eflags & MAP_ENTRY_GUARD) == 0)
                return (KERN_SUCCESS);
        if ((gap_entry->eflags & MAP_ENTRY_STACK_GAP_DN) != 0) {
                stack_entry = vm_map_entry_succ(gap_entry);
                if ((stack_entry->eflags & MAP_ENTRY_GROWS_DOWN) == 0 ||
                    stack_entry->start != gap_entry->end)
                        return (KERN_FAILURE);
                grow_amount = round_page(stack_entry->start - addr);
                grow_down = true;
        } else if ((gap_entry->eflags & MAP_ENTRY_STACK_GAP_UP) != 0) {
                stack_entry = vm_map_entry_pred(gap_entry);
                if ((stack_entry->eflags & MAP_ENTRY_GROWS_UP) == 0 ||
                    stack_entry->end != gap_entry->start)
                        return (KERN_FAILURE);
                grow_amount = round_page(addr + 1 - stack_entry->end);
                grow_down = false;
        } else {
                return (KERN_FAILURE);
        }
        guard = ((curproc->p_flag2 & P2_STKGAP_DISABLE) != 0 ||
            (curproc->p_fctl0 & NT_FREEBSD_FCTL_STKGAP_DISABLE) != 0) ? 0 :
            gap_entry->next_read;
        max_grow = gap_entry->end - gap_entry->start;
        if (guard > max_grow)
                return (KERN_NO_SPACE);
        max_grow -= guard;
        if (grow_amount > max_grow)
                return (KERN_NO_SPACE);

        /*
         * If this is the main process stack, see if we're over the stack
         * limit.
         */
        is_procstack = addr >= (vm_offset_t)vm->vm_maxsaddr &&
            addr < (vm_offset_t)p->p_sysent->sv_usrstack;
        if (is_procstack && (ctob(vm->vm_ssize) + grow_amount > stacklim))
                return (KERN_NO_SPACE);

#ifdef RACCT
        if (racct_enable) {
                PROC_LOCK(p);
                if (is_procstack && racct_set(p, RACCT_STACK,
                    ctob(vm->vm_ssize) + grow_amount)) {
                        PROC_UNLOCK(p);
                        return (KERN_NO_SPACE);
                }
                PROC_UNLOCK(p);
        }
#endif

        grow_amount = roundup(grow_amount, sgrowsiz);
        if (grow_amount > max_grow)
                grow_amount = max_grow;
        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) != 0) {
                if (ptoa(pmap_wired_count(map->pmap)) + grow_amount > lmemlim) {
                        rv = KERN_NO_SPACE;
                        goto out;
                }
#ifdef RACCT
                if (racct_enable) {
                        PROC_LOCK(p);
                        if (racct_set(p, RACCT_MEMLOCK,
                            ptoa(pmap_wired_count(map->pmap)) + grow_amount)) {
                                PROC_UNLOCK(p);
                                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) {
                rv = KERN_NO_SPACE;
                goto out;
        }
#ifdef RACCT
        if (racct_enable) {
                PROC_LOCK(p);
                if (racct_set(p, RACCT_VMEM, map->size + grow_amount)) {
                        PROC_UNLOCK(p);
                        rv = KERN_NO_SPACE;
                        goto out;
                }
                PROC_UNLOCK(p);
        }
#endif

        if (vm_map_lock_upgrade(map)) {
                gap_entry = NULL;
                vm_map_lock_read(map);
                goto retry;
        }

        if (grow_down) {
                grow_start = gap_entry->end - grow_amount;
                if (gap_entry->start + grow_amount == gap_entry->end) {
                        gap_start = gap_entry->start;
                        gap_end = gap_entry->end;
                        vm_map_entry_delete(map, gap_entry);
                        gap_deleted = true;
                } else {
                        MPASS(gap_entry->start < gap_entry->end - grow_amount);
                        vm_map_entry_resize(map, gap_entry, -grow_amount);
                        gap_deleted = false;
                }
                rv = vm_map_insert(map, NULL, 0, grow_start,
                    grow_start + grow_amount,
                    stack_entry->protection, stack_entry->max_protection,
                    MAP_STACK_GROWS_DOWN);
                if (rv != KERN_SUCCESS) {
                        if (gap_deleted) {
                                rv1 = vm_map_insert(map, NULL, 0, gap_start,
                                    gap_end, VM_PROT_NONE, VM_PROT_NONE,
                                    MAP_CREATE_GUARD | MAP_CREATE_STACK_GAP_DN);
                                MPASS(rv1 == KERN_SUCCESS);
                        } else
                                vm_map_entry_resize(map, gap_entry,
                                    grow_amount);
                }
        } else {
                grow_start = 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),
                    grow_amount, cred != NULL)) {
                        if (gap_entry->start + grow_amount == gap_entry->end) {
                                vm_map_entry_delete(map, gap_entry);
                                vm_map_entry_resize(map, stack_entry,
                                    grow_amount);
                        } else {
                                gap_entry->start += grow_amount;
                                stack_entry->end += grow_amount;
                        }
                        map->size += grow_amount;
                        rv = KERN_SUCCESS;
                } else
                        rv = KERN_FAILURE;
        }
        if (rv == KERN_SUCCESS && is_procstack)
                vm->vm_ssize += btoc(grow_amount);

        /*
         * Heed the MAP_WIREFUTURE flag if it was set for this process.
         */
        if (rv == KERN_SUCCESS && (map->flags & MAP_WIREFUTURE) != 0) {
                rv = vm_map_wire_locked(map, grow_start,
                    grow_start + grow_amount,
                    VM_MAP_WIRE_USER | VM_MAP_WIRE_NOHOLES);
        }
        vm_map_lock_downgrade(map);

out:
#ifdef RACCT
        if (racct_enable && 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;

        KASSERT((curthread->td_pflags & TDP_EXECVMSPC) == 0,
            ("vmspace_exec recursed"));
        newvmspace = vmspace_alloc(minuser, maxuser, pmap_pinit);
        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);
        curthread->td_pflags |= TDP_EXECVMSPC;
        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;
        vm_object_t eobject;
        vm_size_t size;
        struct ucred *cred;

RetryLookup:

        vm_map_lock_read(map);

RetryLookupLocked:
        /*
         * 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;
        if ((fault_typea & VM_PROT_FAULT_LOOKUP) != 0) {
                fault_typea &= ~VM_PROT_FAULT_LOOKUP;
                if (prot == VM_PROT_NONE && map != kernel_map &&
                    (entry->eflags & MAP_ENTRY_GUARD) != 0 &&
                    (entry->eflags & (MAP_ENTRY_STACK_GAP_DN |
                    MAP_ENTRY_STACK_GAP_UP)) != 0 &&
                    vm_map_growstack(map, vaddr, entry) == KERN_SUCCESS)
                        goto RetryLookupLocked;
        }
        fault_type = fault_typea & VM_PROT_ALL;
        if ((fault_type & prot) != fault_type || prot == VM_PROT_NONE) {
                vm_map_unlock_read(map);
                return (KERN_PROTECTION_FAILURE);
        }
        KASSERT((prot & VM_PROT_WRITE) == 0 || (entry->eflags &
            (MAP_ENTRY_USER_WIRED | MAP_ENTRY_NEEDS_COPY)) !=
            (MAP_ENTRY_USER_WIRED | MAP_ENTRY_NEEDS_COPY),
            ("entry %p flags %x", entry, entry->eflags));
        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;
                        }
                        eobject = entry->object.vm_object;
                        vm_object_shadow(&entry->object.vm_object,
                            &entry->offset, size, entry->cred, false);
                        if (eobject == entry->object.vm_object) {
                                /*
                                 * The object was not shadowed.
                                 */
                                swap_release_by_cred(size, entry->cred);
                                crfree(entry->cred);
                        }
                        entry->cred = NULL;
                        entry->eflags &= ~MAP_ENTRY_NEEDS_COPY;

                        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_anon(atop(size),
                    NULL, entry->cred, entry->cred != NULL ? size : 0);
                entry->offset = 0;
                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 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);
}

vm_offset_t
vm_map_max_KBI(const struct vm_map *map)
{

        return (vm_map_max(map));
}

vm_offset_t
vm_map_min_KBI(const struct vm_map *map)
{

        return (vm_map_min(map));
}

pmap_t
vm_map_pmap_KBI(vm_map_t map)
{

        return (map->pmap);
}

bool
vm_map_range_valid_KBI(vm_map_t map, vm_offset_t start, vm_offset_t end)
{

        return (vm_map_range_valid(map, start, end));
}

#ifdef INVARIANTS
static void
_vm_map_assert_consistent(vm_map_t map, int check)
{
        vm_map_entry_t entry, prev;
        vm_map_entry_t cur, header, lbound, ubound;
        vm_size_t max_left, max_right;

#ifdef DIAGNOSTIC
        ++map->nupdates;
#endif
        if (enable_vmmap_check != check)
                return;

        header = prev = &map->header;
        VM_MAP_ENTRY_FOREACH(entry, map) {
                KASSERT(prev->end <= entry->start,
                    ("map %p prev->end = %jx, start = %jx", map,
                    (uintmax_t)prev->end, (uintmax_t)entry->start));
                KASSERT(entry->start < entry->end,
                    ("map %p start = %jx, end = %jx", map,
                    (uintmax_t)entry->start, (uintmax_t)entry->end));
                KASSERT(entry->left == header ||
                    entry->left->start < entry->start,
                    ("map %p left->start = %jx, start = %jx", map,
                    (uintmax_t)entry->left->start, (uintmax_t)entry->start));
                KASSERT(entry->right == header ||
                    entry->start < entry->right->start,
                    ("map %p start = %jx, right->start = %jx", map,
                    (uintmax_t)entry->start, (uintmax_t)entry->right->start));
                cur = map->root;
                lbound = ubound = header;
                for (;;) {
                        if (entry->start < cur->start) {
                                ubound = cur;
                                cur = cur->left;
                                KASSERT(cur != lbound,
                                    ("map %p cannot find %jx",
                                    map, (uintmax_t)entry->start));
                        } else if (cur->end <= entry->start) {
                                lbound = cur;
                                cur = cur->right;
                                KASSERT(cur != ubound,
                                    ("map %p cannot find %jx",
                                    map, (uintmax_t)entry->start));
                        } else {
                                KASSERT(cur == entry,
                                    ("map %p cannot find %jx",
                                    map, (uintmax_t)entry->start));
                                break;
                        }
                }
                max_left = vm_map_entry_max_free_left(entry, lbound);
                max_right = vm_map_entry_max_free_right(entry, ubound);
                KASSERT(entry->max_free == vm_size_max(max_left, max_right),
                    ("map %p max = %jx, max_left = %jx, max_right = %jx", map,
                    (uintmax_t)entry->max_free,
                    (uintmax_t)max_left, (uintmax_t)max_right));
                prev = entry;
        }
        KASSERT(prev->end <= entry->start,
            ("map %p prev->end = %jx, start = %jx", map,
            (uintmax_t)prev->end, (uintmax_t)entry->start));
}
#endif

#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, prev;

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

        db_indent += 2;
        prev = &map->header;
        VM_MAP_ENTRY_FOREACH(entry, map) {
                db_iprintf("map entry %p: start=%p, end=%p, eflags=%#x, \n",
                    (void *)entry, (void *)entry->start, (void *)entry->end,
                    entry->eflags);
                {
                        static const char * const 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 (prev == &map->header ||
                            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 (prev == &map->header ||
                            prev->object.vm_object !=
                                entry->object.vm_object) {
                                db_indent += 2;
                                vm_object_print((db_expr_t)(intptr_t)
                                                entry->object.vm_object,
                                                0, 0, (char *)0);
                                db_indent -= 2;
                        }
                }
                prev = entry;
        }
        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 = db_lookup_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 */