kernel - Fix a major (pageable) memory leak

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

/*
 * (MPSAFE)
 *
 * 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.
 *
 * $FreeBSD: src/sys/vm/vm_map.c,v 1.187.2.19 2003/05/27 00:47:02 alc Exp $
 */

/*
 *      Virtual memory mapping module.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/serialize.h>
#include <sys/lock.h>
#include <sys/vmmeter.h>
#include <sys/mman.h>
#include <sys/vnode.h>
#include <sys/resourcevar.h>
#include <sys/shm.h>
#include <sys/tree.h>
#include <sys/malloc.h>
#include <sys/objcache.h>

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

#include <sys/thread2.h>
#include <sys/random.h>
#include <sys/sysctl.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 hint and a RB tree is used to speed-up lookups.
 *
 * Callers looking to modify maps specify start/end addresses which cause
 * the related map entry to be clipped if necessary, and then later
 * recombined if the pieces remained compatible.
 *
 * 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 __boolean_t vmspace_ctor(void *obj, void *privdata, int ocflags);
static void vmspace_dtor(void *obj, void *privdata);
static void vmspace_terminate(struct vmspace *vm, int final);

MALLOC_DEFINE(M_VMSPACE, "vmspace", "vmspace objcache backingstore");
static struct objcache *vmspace_cache;

/*
 * per-cpu page table cross mappings are initialized in early boot
 * and might require a considerable number of vm_map_entry structures.
 */
#define MAPENTRYBSP_CACHE       (MAXCPU+1)
#define MAPENTRYAP_CACHE        8

static struct vm_zone mapentzone_store, mapzone_store;
static vm_zone_t mapentzone, mapzone;
static struct vm_object mapentobj, mapobj;

static struct vm_map_entry map_entry_init[MAX_MAPENT];
static struct vm_map_entry cpu_map_entry_init_bsp[MAPENTRYBSP_CACHE];
static struct vm_map_entry cpu_map_entry_init_ap[MAXCPU][MAPENTRYAP_CACHE];
static struct vm_map map_init[MAX_KMAP];

static int randomize_mmap;
SYSCTL_INT(_vm, OID_AUTO, randomize_mmap, CTLFLAG_RW, &randomize_mmap, 0,
    "Randomize mmap offsets");
static int vm_map_relock_enable = 1;
SYSCTL_INT(_vm, OID_AUTO, map_relock_enable, CTLFLAG_RW,
           &vm_map_relock_enable, 0, "Randomize mmap offsets");

static void vm_map_entry_shadow(vm_map_entry_t entry, int addref);
static vm_map_entry_t vm_map_entry_create(vm_map_t map, int *);
static void vm_map_entry_dispose (vm_map_t map, vm_map_entry_t entry, int *);
static void _vm_map_clip_end (vm_map_t, vm_map_entry_t, vm_offset_t, int *);
static void _vm_map_clip_start (vm_map_t, vm_map_entry_t, vm_offset_t, int *);
static void vm_map_entry_delete (vm_map_t, vm_map_entry_t, int *);
static void vm_map_entry_unwire (vm_map_t, vm_map_entry_t);
static void vm_map_copy_entry (vm_map_t, vm_map_t, vm_map_entry_t,
                vm_map_entry_t);
static void vm_map_unclip_range (vm_map_t map, vm_map_entry_t start_entry, vm_offset_t start, vm_offset_t end, int *count, int flags);

/*
 * 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 is allocated statically.
 *      - Initial kernel map entries are allocated out of a static pool.
 *      - We must set ZONE_SPECIAL here or the early boot code can get
 *        stuck if there are >63 cores.
 *
 *      These restrictions are necessary since malloc() uses the
 *      maps and requires map entries.
 *
 * Called from the low level boot code only.
 */
void
vm_map_startup(void)
{
        mapzone = &mapzone_store;
        zbootinit(mapzone, "MAP", sizeof (struct vm_map),
                map_init, MAX_KMAP);
        mapentzone = &mapentzone_store;
        zbootinit(mapentzone, "MAP ENTRY", sizeof (struct vm_map_entry),
                  map_entry_init, MAX_MAPENT);
        mapentzone_store.zflags |= ZONE_SPECIAL;
}

/*
 * Called prior to any vmspace allocations.
 *
 * Called from the low level boot code only.
 */
void
vm_init2(void) 
{
        vmspace_cache = objcache_create_mbacked(M_VMSPACE,
                                                sizeof(struct vmspace),
                                                0, ncpus * 4,
                                                vmspace_ctor, vmspace_dtor,
                                                NULL);
        zinitna(mapentzone, &mapentobj, NULL, 0, 0, 
                ZONE_USE_RESERVE | ZONE_SPECIAL, 1);
        zinitna(mapzone, &mapobj, NULL, 0, 0, 0, 1);
        pmap_init2();
        vm_object_init2();
}

/*
 * objcache support.  We leave the pmap root cached as long as possible
 * for performance reasons.
 */
static
__boolean_t
vmspace_ctor(void *obj, void *privdata, int ocflags)
{
        struct vmspace *vm = obj;

        bzero(vm, sizeof(*vm));
        vm->vm_refcnt = (u_int)-1;

        return 1;
}

static
void
vmspace_dtor(void *obj, void *privdata)
{
        struct vmspace *vm = obj;

        KKASSERT(vm->vm_refcnt == (u_int)-1);
        pmap_puninit(vmspace_pmap(vm));
}

/*
 * Red black tree functions
 *
 * The caller must hold the related map lock.
 */
static int rb_vm_map_compare(vm_map_entry_t a, vm_map_entry_t b);
RB_GENERATE(vm_map_rb_tree, vm_map_entry, rb_entry, rb_vm_map_compare);

/* a->start is address, and the only field has to be initialized */
static int
rb_vm_map_compare(vm_map_entry_t a, vm_map_entry_t b)
{
        if (a->start < b->start)
                return(-1);
        else if (a->start > b->start)
                return(1);
        return(0);
}

/*
 * Initialize vmspace ref/hold counts vmspace0.  There is a holdcnt for
 * every refcnt.
 */
void
vmspace_initrefs(struct vmspace *vm)
{
        vm->vm_refcnt = 1;
        vm->vm_holdcnt = 1;
}

/*
 * Allocate a vmspace structure, including a vm_map and pmap.
 * Initialize numerous fields.  While the initial allocation is zerod,
 * subsequence reuse from the objcache leaves elements of the structure
 * intact (particularly the pmap), so portions must be zerod.
 *
 * Returns a referenced vmspace.
 *
 * No requirements.
 */
struct vmspace *
vmspace_alloc(vm_offset_t min, vm_offset_t max)
{
        struct vmspace *vm;

        vm = objcache_get(vmspace_cache, M_WAITOK);

        bzero(&vm->vm_startcopy,
              (char *)&vm->vm_endcopy - (char *)&vm->vm_startcopy);
        vm_map_init(&vm->vm_map, min, max, NULL);       /* initializes token */

        /*
         * NOTE: hold to acquires token for safety.
         *
         * On return vmspace is referenced (refs=1, hold=1).  That is,
         * each refcnt also has a holdcnt.  There can be additional holds
         * (holdcnt) above and beyond the refcnt.  Finalization is handled in
         * two stages, one on refs 1->0, and the the second on hold 1->0.
         */
        KKASSERT(vm->vm_holdcnt == 0);
        KKASSERT(vm->vm_refcnt == (u_int)-1);
        vmspace_initrefs(vm);
        vmspace_hold(vm);
        pmap_pinit(vmspace_pmap(vm));           /* (some fields reused) */
        vm->vm_map.pmap = vmspace_pmap(vm);     /* XXX */
        vm->vm_shm = NULL;
        vm->vm_flags = 0;
        cpu_vmspace_alloc(vm);
        vmspace_drop(vm);

        return (vm);
}

/*
 * NOTE: Can return -1 if the vmspace is exiting.
 */
int
vmspace_getrefs(struct vmspace *vm)
{
        return ((int)vm->vm_refcnt);
}

/*
 * A vmspace object must already have a non-zero hold to be able to gain
 * further holds on it.
 */
static void
vmspace_hold_notoken(struct vmspace *vm)
{
        KKASSERT(vm->vm_holdcnt != 0);
        refcount_acquire(&vm->vm_holdcnt);
}

static void
vmspace_drop_notoken(struct vmspace *vm)
{
        if (refcount_release(&vm->vm_holdcnt)) {
                if (vm->vm_refcnt == (u_int)-1) {
                        vmspace_terminate(vm, 1);
                }
        }
}

void
vmspace_hold(struct vmspace *vm)
{
        vmspace_hold_notoken(vm);
        lwkt_gettoken(&vm->vm_map.token);
}

void
vmspace_drop(struct vmspace *vm)
{
        lwkt_reltoken(&vm->vm_map.token);
        vmspace_drop_notoken(vm);
}

/*
 * A vmspace object must not be in a terminated state to be able to obtain
 * additional refs on it.
 *
 * Ref'ing a vmspace object also increments its hold count.
 */
void
vmspace_ref(struct vmspace *vm)
{
        KKASSERT((int)vm->vm_refcnt >= 0);
        vmspace_hold_notoken(vm);
        refcount_acquire(&vm->vm_refcnt);
}

/*
 * Release a ref on the vmspace.  On the 1->0 transition we do stage-1
 * termination of the vmspace.  Then, on the final drop of the hold we
 * will do stage-2 final termination.
 */
void
vmspace_rel(struct vmspace *vm)
{
        if (refcount_release(&vm->vm_refcnt)) {
                vm->vm_refcnt = (u_int)-1;      /* no other refs possible */
                vmspace_terminate(vm, 0);
        }
        vmspace_drop_notoken(vm);
}

/*
 * This is called during exit indicating that the vmspace is no
 * longer in used by an exiting process, but the process has not yet
 * been reaped.
 *
 * We release the refcnt but not the associated holdcnt.
 *
 * No requirements.
 */
void
vmspace_relexit(struct vmspace *vm)
{
        if (refcount_release(&vm->vm_refcnt)) {
                vm->vm_refcnt = (u_int)-1;      /* no other refs possible */
                vmspace_terminate(vm, 0);
        }
}

/*
 * Called during reap to disconnect the remainder of the vmspace from
 * the process.  On the hold drop the vmspace termination is finalized.
 *
 * No requirements.
 */
void
vmspace_exitfree(struct proc *p)
{
        struct vmspace *vm;

        vm = p->p_vmspace;
        p->p_vmspace = NULL;
        vmspace_drop_notoken(vm);
}

/*
 * Called in two cases:
 *
 * (1) When the last refcnt is dropped and the vmspace becomes inactive,
 *     called with final == 0.  refcnt will be (u_int)-1 at this point,
 *     and holdcnt will still be non-zero.
 *
 * (2) When holdcnt becomes 0, called with final == 1.  There should no
 *     longer be anyone with access to the vmspace.
 *
 * VMSPACE_EXIT1 flags the primary deactivation
 * VMSPACE_EXIT2 flags the last reap
 */
static void
vmspace_terminate(struct vmspace *vm, int final)
{
        int count;

        lwkt_gettoken(&vm->vm_map.token);
        if (final == 0) {
                KKASSERT((vm->vm_flags & VMSPACE_EXIT1) == 0);

                /*
                 * Get rid of most of the resources.  Leave the kernel pmap
                 * intact.
                 */
                vm->vm_flags |= VMSPACE_EXIT1;
                shmexit(vm);
                pmap_remove_pages(vmspace_pmap(vm), VM_MIN_USER_ADDRESS,
                                  VM_MAX_USER_ADDRESS);
                vm_map_remove(&vm->vm_map, VM_MIN_USER_ADDRESS,
                              VM_MAX_USER_ADDRESS);
                lwkt_reltoken(&vm->vm_map.token);
        } else {
                KKASSERT((vm->vm_flags & VMSPACE_EXIT1) != 0);
                KKASSERT((vm->vm_flags & VMSPACE_EXIT2) == 0);

                /*
                 * Get rid of remaining basic resources.
                 */
                vm->vm_flags |= VMSPACE_EXIT2;
                cpu_vmspace_free(vm);
                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.
                 */
                count = vm_map_entry_reserve(MAP_RESERVE_COUNT);
                vm_map_lock(&vm->vm_map);
                vm_map_delete(&vm->vm_map, vm->vm_map.min_offset,
                              vm->vm_map.max_offset, &count);
                vm_map_unlock(&vm->vm_map);
                vm_map_entry_release(count);

                lwkt_gettoken(&vmspace_pmap(vm)->pm_token);
                pmap_release(vmspace_pmap(vm));
                lwkt_reltoken(&vmspace_pmap(vm)->pm_token);
                lwkt_reltoken(&vm->vm_map.token);
                objcache_put(vmspace_cache, vm);
        }
}

/*
 * Swap useage is determined by taking the proportional swap used by
 * VM objects backing the VM map.  To make up for fractional losses,
 * if the VM object has any swap use at all the associated map entries
 * count for at least 1 swap page.
 *
 * No requirements.
 */
int
vmspace_swap_count(struct vmspace *vm)
{
        vm_map_t map = &vm->vm_map;
        vm_map_entry_t cur;
        vm_object_t object;
        int count = 0;
        int n;

        vmspace_hold(vm);
        for (cur = map->header.next; cur != &map->header; cur = cur->next) {
                switch(cur->maptype) {
                case VM_MAPTYPE_NORMAL:
                case VM_MAPTYPE_VPAGETABLE:
                        if ((object = cur->object.vm_object) == NULL)
                                break;
                        if (object->swblock_count) {
                                n = (cur->end - cur->start) / PAGE_SIZE;
                                count += object->swblock_count *
                                    SWAP_META_PAGES * n / object->size + 1;
                        }
                        break;
                default:
                        break;
                }
        }
        vmspace_drop(vm);

        return(count);
}

/*
 * Calculate the approximate number of anonymous pages in use by
 * this vmspace.  To make up for fractional losses, we count each
 * VM object as having at least 1 anonymous page.
 *
 * No requirements.
 */
int
vmspace_anonymous_count(struct vmspace *vm)
{
        vm_map_t map = &vm->vm_map;
        vm_map_entry_t cur;
        vm_object_t object;
        int count = 0;

        vmspace_hold(vm);
        for (cur = map->header.next; cur != &map->header; cur = cur->next) {
                switch(cur->maptype) {
                case VM_MAPTYPE_NORMAL:
                case VM_MAPTYPE_VPAGETABLE:
                        if ((object = cur->object.vm_object) == NULL)
                                break;
                        if (object->type != OBJT_DEFAULT &&
                            object->type != OBJT_SWAP) {
                                break;
                        }
                        count += object->resident_page_count;
                        break;
                default:
                        break;
                }
        }
        vmspace_drop(vm);

        return(count);
}

/*
 * Creates and returns a new empty VM map with the given physical map
 * structure, and having the given lower and upper address bounds.
 *
 * No requirements.
 */
vm_map_t
vm_map_create(vm_map_t result, pmap_t pmap, vm_offset_t min, vm_offset_t max)
{
        if (result == NULL)
                result = zalloc(mapzone);
        vm_map_init(result, min, max, pmap);
        return (result);
}

/*
 * Initialize an existing vm_map structure such as that in the vmspace
 * structure.  The pmap is initialized elsewhere.
 *
 * No requirements.
 */
void
vm_map_init(struct vm_map *map, vm_offset_t min, vm_offset_t max, pmap_t pmap)
{
        map->header.next = map->header.prev = &map->header;
        RB_INIT(&map->rb_root);
        map->nentries = 0;
        map->size = 0;
        map->system_map = 0;
        map->min_offset = min;
        map->max_offset = max;
        map->pmap = pmap;
        map->first_free = &map->header;
        map->hint = &map->header;
        map->timestamp = 0;
        map->flags = 0;
        lwkt_token_init(&map->token, "vm_map");
        lockinit(&map->lock, "vm_maplk", (hz + 9) / 10, 0);
}

/*
 * Shadow the vm_map_entry's object.  This typically needs to be done when
 * a write fault is taken on an entry which had previously been cloned by
 * fork().  The shared object (which might be NULL) must become private so
 * we add a shadow layer above it.
 *
 * Object allocation for anonymous mappings is defered as long as possible.
 * When creating a shadow, however, the underlying object must be instantiated
 * so it can be shared.
 *
 * If the map segment is governed by a virtual page table then it is
 * possible to address offsets beyond the mapped area.  Just allocate
 * a maximally sized object for this case.
 *
 * The vm_map must be exclusively locked.
 * No other requirements.
 */
static
void
vm_map_entry_shadow(vm_map_entry_t entry, int addref)
{
        if (entry->maptype == VM_MAPTYPE_VPAGETABLE) {
                vm_object_shadow(&entry->object.vm_object, &entry->offset,
                                 0x7FFFFFFF, addref);   /* XXX */
        } else {
                vm_object_shadow(&entry->object.vm_object, &entry->offset,
                                 atop(entry->end - entry->start), addref);
        }
        entry->eflags &= ~MAP_ENTRY_NEEDS_COPY;
}

/*
 * Allocate an object for a vm_map_entry.
 *
 * Object allocation for anonymous mappings is defered as long as possible.
 * This function is called when we can defer no longer, generally when a map
 * entry might be split or forked or takes a page fault.
 *
 * If the map segment is governed by a virtual page table then it is
 * possible to address offsets beyond the mapped area.  Just allocate
 * a maximally sized object for this case.
 *
 * The vm_map must be exclusively locked.
 * No other requirements.
 */
void 
vm_map_entry_allocate_object(vm_map_entry_t entry)
{
        vm_object_t obj;

        if (entry->maptype == VM_MAPTYPE_VPAGETABLE) {
                obj = vm_object_allocate(OBJT_DEFAULT, 0x7FFFFFFF); /* XXX */
        } else {
                obj = vm_object_allocate(OBJT_DEFAULT,
                                         atop(entry->end - entry->start));
        }
        entry->object.vm_object = obj;
        entry->offset = 0;
}

/*
 * Set an initial negative count so the first attempt to reserve
 * space preloads a bunch of vm_map_entry's for this cpu.  Also
 * pre-allocate 2 vm_map_entries which will be needed by zalloc() to
 * map a new page for vm_map_entry structures.  SMP systems are
 * particularly sensitive.
 *
 * This routine is called in early boot so we cannot just call
 * vm_map_entry_reserve().
 *
 * Called from the low level boot code only (for each cpu)
 *
 * WARNING! Take care not to have too-big a static/BSS structure here
 *          as MAXCPU can be 256+, otherwise the loader's 64MB heap
 *          can get blown out by the kernel plus the initrd image.
 */
void
vm_map_entry_reserve_cpu_init(globaldata_t gd)
{
        vm_map_entry_t entry;
        int count;
        int i;

        gd->gd_vme_avail -= MAP_RESERVE_COUNT * 2;
        if (gd->gd_cpuid == 0) {
                entry = &cpu_map_entry_init_bsp[0];
                count = MAPENTRYBSP_CACHE;
        } else {
                entry = &cpu_map_entry_init_ap[gd->gd_cpuid][0];
                count = MAPENTRYAP_CACHE;
        }
        for (i = 0; i < count; ++i, ++entry) {
                entry->next = gd->gd_vme_base;
                gd->gd_vme_base = entry;
        }
}

/*
 * Reserves vm_map_entry structures so code later on can manipulate
 * map_entry structures within a locked map without blocking trying
 * to allocate a new vm_map_entry.
 *
 * No requirements.
 */
int
vm_map_entry_reserve(int count)
{
        struct globaldata *gd = mycpu;
        vm_map_entry_t entry;

        /*
         * Make sure we have enough structures in gd_vme_base to handle
         * the reservation request.
         *
         * The critical section protects access to the per-cpu gd.
         */
        crit_enter();
        while (gd->gd_vme_avail < count) {
                entry = zalloc(mapentzone);
                entry->next = gd->gd_vme_base;
                gd->gd_vme_base = entry;
                ++gd->gd_vme_avail;
        }
        gd->gd_vme_avail -= count;
        crit_exit();

        return(count);
}

/*
 * Releases previously reserved vm_map_entry structures that were not
 * used.  If we have too much junk in our per-cpu cache clean some of
 * it out.
 *
 * No requirements.
 */
void
vm_map_entry_release(int count)
{
        struct globaldata *gd = mycpu;
        vm_map_entry_t entry;

        crit_enter();
        gd->gd_vme_avail += count;
        while (gd->gd_vme_avail > MAP_RESERVE_SLOP) {
                entry = gd->gd_vme_base;
                KKASSERT(entry != NULL);
                gd->gd_vme_base = entry->next;
                --gd->gd_vme_avail;
                crit_exit();
                zfree(mapentzone, entry);
                crit_enter();
        }
        crit_exit();
}

/*
 * Reserve map entry structures for use in kernel_map itself.  These
 * entries have *ALREADY* been reserved on a per-cpu basis when the map
 * was inited.  This function is used by zalloc() to avoid a recursion
 * when zalloc() itself needs to allocate additional kernel memory.
 *
 * This function works like the normal reserve but does not load the
 * vm_map_entry cache (because that would result in an infinite
 * recursion).  Note that gd_vme_avail may go negative.  This is expected.
 *
 * Any caller of this function must be sure to renormalize after
 * potentially eating entries to ensure that the reserve supply
 * remains intact.
 *
 * No requirements.
 */
int
vm_map_entry_kreserve(int count)
{
        struct globaldata *gd = mycpu;

        crit_enter();
        gd->gd_vme_avail -= count;
        crit_exit();
        KASSERT(gd->gd_vme_base != NULL,
                ("no reserved entries left, gd_vme_avail = %d",
                gd->gd_vme_avail));
        return(count);
}

/*
 * Release previously reserved map entries for kernel_map.  We do not
 * attempt to clean up like the normal release function as this would
 * cause an unnecessary (but probably not fatal) deep procedure call.
 *
 * No requirements.
 */
void
vm_map_entry_krelease(int count)
{
        struct globaldata *gd = mycpu;

        crit_enter();
        gd->gd_vme_avail += count;
        crit_exit();
}

/*
 * Allocates a VM map entry for insertion.  No entry fields are filled in.
 *
 * The entries should have previously been reserved.  The reservation count
 * is tracked in (*countp).
 *
 * No requirements.
 */
static vm_map_entry_t
vm_map_entry_create(vm_map_t map, int *countp)
{
        struct globaldata *gd = mycpu;
        vm_map_entry_t entry;

        KKASSERT(*countp > 0);
        --*countp;
        crit_enter();
        entry = gd->gd_vme_base;
        KASSERT(entry != NULL, ("gd_vme_base NULL! count %d", *countp));
        gd->gd_vme_base = entry->next;
        crit_exit();

        return(entry);
}

/*
 * Dispose of a vm_map_entry that is no longer being referenced.
 *
 * No requirements.
 */
static void
vm_map_entry_dispose(vm_map_t map, vm_map_entry_t entry, int *countp)
{
        struct globaldata *gd = mycpu;

        KKASSERT(map->hint != entry);
        KKASSERT(map->first_free != entry);

        ++*countp;
        crit_enter();
        entry->next = gd->gd_vme_base;
        gd->gd_vme_base = entry;
        crit_exit();
}


/*
 * Insert/remove entries from maps.
 *
 * The related map must be exclusively locked.
 * The caller must hold map->token
 * No other requirements.
 */
static __inline void
vm_map_entry_link(vm_map_t map,
                  vm_map_entry_t after_where,
                  vm_map_entry_t entry)
{
        ASSERT_VM_MAP_LOCKED(map);

        map->nentries++;
        entry->prev = after_where;
        entry->next = after_where->next;
        entry->next->prev = entry;
        after_where->next = entry;
        if (vm_map_rb_tree_RB_INSERT(&map->rb_root, entry))
                panic("vm_map_entry_link: dup addr map %p ent %p", map, entry);
}

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

        ASSERT_VM_MAP_LOCKED(map);

        if (entry->eflags & MAP_ENTRY_IN_TRANSITION) {
                panic("vm_map_entry_unlink: attempt to mess with "
                      "locked entry! %p", entry);
        }
        prev = entry->prev;
        next = entry->next;
        next->prev = prev;
        prev->next = next;
        vm_map_rb_tree_RB_REMOVE(&map->rb_root, entry);
        map->nentries--;
}

/*
 * Finds the map entry containing (or immediately preceding) the specified
 * address in the given map.  The entry is returned in (*entry).
 *
 * The boolean result indicates whether the address is actually contained
 * in the map.
 *
 * The related map must be locked.
 * No other requirements.
 */
boolean_t
vm_map_lookup_entry(vm_map_t map, vm_offset_t address, vm_map_entry_t *entry)
{
        vm_map_entry_t tmp;
        vm_map_entry_t last;

        ASSERT_VM_MAP_LOCKED(map);
#if 0
        /*
         * XXX TEMPORARILY DISABLED.  For some reason our attempt to revive
         * the hint code with the red-black lookup meets with system crashes
         * and lockups.  We do not yet know why.
         *
         * It is possible that the problem is related to the setting
         * of the hint during map_entry deletion, in the code specified
         * at the GGG comment later on in this file.
         *
         * YYY More likely it's because this function can be called with
         * a shared lock on the map, resulting in map->hint updates possibly
         * racing.  Fixed now but untested.
         */
        /*
         * Quickly check the cached hint, there's a good chance of a match.
         */
        tmp = map->hint;
        cpu_ccfence();
        if (tmp != &map->header) {
                if (address >= tmp->start && address < tmp->end) {
                        *entry = tmp;
                        return(TRUE);
                }
        }
#endif

        /*
         * Locate the record from the top of the tree.  'last' tracks the
         * closest prior record and is returned if no match is found, which
         * in binary tree terms means tracking the most recent right-branch
         * taken.  If there is no prior record, &map->header is returned.
         */
        last = &map->header;
        tmp = RB_ROOT(&map->rb_root);

        while (tmp) {
                if (address >= tmp->start) {
                        if (address < tmp->end) {
                                *entry = tmp;
                                map->hint = tmp;
                                return(TRUE);
                        }
                        last = tmp;
                        tmp = RB_RIGHT(tmp, rb_entry);
                } else {
                        tmp = RB_LEFT(tmp, rb_entry);
                }
        }
        *entry = last;
        return (FALSE);
}

/*
 * 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.
 *
 * The map must be exclusively locked.
 * The object must be held.
 * The caller must have reserved sufficient vm_map_entry structures.
 *
 * 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, int *countp, void *map_object, void *map_aux,
              vm_ooffset_t offset, vm_offset_t start, vm_offset_t end,
              vm_maptype_t maptype,
              vm_prot_t prot, vm_prot_t max, int cow)
{
        vm_map_entry_t new_entry;
        vm_map_entry_t prev_entry;
        vm_map_entry_t temp_entry;
        vm_eflags_t protoeflags;
        int must_drop = 0;
        vm_object_t object;

        if (maptype == VM_MAPTYPE_UKSMAP)
                object = NULL;
        else
                object = map_object;

        ASSERT_VM_MAP_LOCKED(map);
        if (object)
                ASSERT_LWKT_TOKEN_HELD(vm_object_token(object));

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

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

        prev_entry = temp_entry;

        /*
         * Assert that the next entry doesn't overlap the end point.
         */

        if ((prev_entry->next != &map->header) &&
            (prev_entry->next->start < end))
                return (KERN_NO_SPACE);

        protoeflags = 0;

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

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

                KASSERT(object == NULL,
                        ("vm_map_insert: paradoxical MAP_NOFAULT request"));
        }
        if (cow & MAP_DISABLE_SYNCER)
                protoeflags |= MAP_ENTRY_NOSYNC;
        if (cow & MAP_DISABLE_COREDUMP)
                protoeflags |= MAP_ENTRY_NOCOREDUMP;
        if (cow & MAP_IS_STACK)
                protoeflags |= MAP_ENTRY_STACK;
        if (cow & MAP_IS_KSTACK)
                protoeflags |= MAP_ENTRY_KSTACK;

        lwkt_gettoken(&map->token);

        if (object) {
                /*
                 * When object is non-NULL, it could be shared with another
                 * process.  We have to set or clear OBJ_ONEMAPPING 
                 * appropriately.
                 *
                 * NOTE: This flag is only applicable to DEFAULT and SWAP
                 *       objects and will already be clear in other types
                 *       of objects, so a shared object lock is ok for
                 *       VNODE objects.
                 */
                if ((object->ref_count > 1) || (object->shadow_count != 0)) {
                        vm_object_clear_flag(object, OBJ_ONEMAPPING);
                }
        }
        else if ((prev_entry != &map->header) &&
                 (prev_entry->eflags == protoeflags) &&
                 (prev_entry->end == start) &&
                 (prev_entry->wired_count == 0) &&
                 prev_entry->maptype == maptype &&
                 maptype == VM_MAPTYPE_NORMAL &&
                 ((prev_entry->object.vm_object == NULL) ||
                  vm_object_coalesce(prev_entry->object.vm_object,
                                     OFF_TO_IDX(prev_entry->offset),
                                     (vm_size_t)(prev_entry->end - prev_entry->start),
                                     (vm_size_t)(end - prev_entry->end)))) {
                /*
                 * 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 == VM_INHERIT_DEFAULT) &&
                    (prev_entry->protection == prot) &&
                    (prev_entry->max_protection == max)) {
                        map->size += (end - prev_entry->end);
                        prev_entry->end = end;
                        vm_map_simplify_entry(map, prev_entry, countp);
                        lwkt_reltoken(&map->token);
                        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.
                 *
                 * XXX if object is NULL should we set offset to 0 here ?
                 */
                object = prev_entry->object.vm_object;
                offset = prev_entry->offset +
                        (prev_entry->end - prev_entry->start);
                if (object) {
                        vm_object_hold(object);
                        vm_object_chain_wait(object, 0);
                        vm_object_reference_locked(object);
                        must_drop = 1;
                        map_object = object;
                }
        }

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

        /*
         * Create a new entry
         */

        new_entry = vm_map_entry_create(map, countp);
        new_entry->start = start;
        new_entry->end = end;

        new_entry->maptype = maptype;
        new_entry->eflags = protoeflags;
        new_entry->object.map_object = map_object;
        new_entry->aux.master_pde = 0;          /* in case size is different */
        new_entry->aux.map_aux = map_aux;
        new_entry->offset = offset;

        new_entry->inheritance = VM_INHERIT_DEFAULT;
        new_entry->protection = prot;
        new_entry->max_protection = max;
        new_entry->wired_count = 0;

        /*
         * Insert the new entry into the list
         */

        vm_map_entry_link(map, prev_entry, new_entry);
        map->size += new_entry->end - new_entry->start;

        /*
         * Update the free space hint.  Entries cannot overlap.
         * An exact comparison is needed to avoid matching
         * against the map->header.
         */
        if ((map->first_free == prev_entry) &&
            (prev_entry->end == new_entry->start)) {
                map->first_free = new_entry;
        }

#if 0
        /*
         * Temporarily removed to avoid MAP_STACK panic, due to
         * MAP_STACK being a huge hack.  Will be added back in
         * when MAP_STACK (and the user stack mapping) is fixed.
         */
        /*
         * It may be possible to simplify the entry
         */
        vm_map_simplify_entry(map, new_entry, countp);
#endif

        /*
         * Try to pre-populate the page table.  Mappings governed by virtual
         * page tables cannot be prepopulated without a lot of work, so
         * don't try.
         */
        if ((cow & (MAP_PREFAULT|MAP_PREFAULT_PARTIAL)) &&
            maptype != VM_MAPTYPE_VPAGETABLE &&
            maptype != VM_MAPTYPE_UKSMAP) {
                int dorelock = 0;
                if (vm_map_relock_enable && (cow & MAP_PREFAULT_RELOCK)) {
                        dorelock = 1;
                        vm_object_lock_swap();
                        vm_object_drop(object);
                }
                pmap_object_init_pt(map->pmap, start, prot,
                                    object, OFF_TO_IDX(offset), end - start,
                                    cow & MAP_PREFAULT_PARTIAL);
                if (dorelock) {
                        vm_object_hold(object);
                        vm_object_lock_swap();
                }
        }
        if (must_drop)
                vm_object_drop(object);

        lwkt_reltoken(&map->token);
        return (KERN_SUCCESS);
}

/*
 * Find sufficient space for `length' bytes in the given map, starting at
 * `start'.  Returns 0 on success, 1 on no space.
 *
 * This function will returned an arbitrarily aligned pointer.  If no
 * particular alignment is required you should pass align as 1.  Note that
 * the map may return PAGE_SIZE aligned pointers if all the lengths used in
 * the map are a multiple of PAGE_SIZE, even if you pass a smaller align
 * argument.
 *
 * 'align' should be a power of 2 but is not required to be.
 *
 * The map must be exclusively locked.
 * No other requirements.
 */
int
vm_map_findspace(vm_map_t map, vm_offset_t start, vm_size_t length,
                 vm_size_t align, int flags, vm_offset_t *addr)
{
        vm_map_entry_t entry, next;
        vm_offset_t end;
        vm_offset_t align_mask;

        if (start < map->min_offset)
                start = map->min_offset;
        if (start > map->max_offset)
                return (1);

        /*
         * If the alignment is not a power of 2 we will have to use
         * a mod/division, set align_mask to a special value.
         */
        if ((align | (align - 1)) + 1 != (align << 1))
                align_mask = (vm_offset_t)-1;
        else
                align_mask = align - 1;

        /*
         * Look for the first possible address; if there's already something
         * at this address, we have to start after it.
         */
        if (start == map->min_offset) {
                if ((entry = map->first_free) != &map->header)
                        start = entry->end;
        } else {
                vm_map_entry_t tmp;

                if (vm_map_lookup_entry(map, start, &tmp))
                        start = tmp->end;
                entry = tmp;
        }

        /*
         * Look through the rest of the map, trying to fit a new region in the
         * gap between existing regions, or after the very last region.
         */
        for (;; start = (entry = next)->end) {
                /*
                 * Adjust the proposed start by the requested alignment,
                 * be sure that we didn't wrap the address.
                 */
                if (align_mask == (vm_offset_t)-1)
                        end = ((start + align - 1) / align) * align;
                else
                        end = (start + align_mask) & ~align_mask;
                if (end < start)
                        return (1);
                start = end;
                /*
                 * Find the end of the proposed new region.  Be sure we didn't
                 * go beyond the end of the map, or wrap around the address.
                 * Then check to see if this is the last entry or if the 
                 * proposed end fits in the gap between this and the next
                 * entry.
                 */
                end = start + length;
                if (end > map->max_offset || end < start)
                        return (1);
                next = entry->next;

                /*
                 * If the next entry's start address is beyond the desired
                 * end address we may have found a good entry.
                 *
                 * If the next entry is a stack mapping we do not map into
                 * the stack's reserved space.
                 *
                 * XXX continue to allow mapping into the stack's reserved
                 * space if doing a MAP_STACK mapping inside a MAP_STACK
                 * mapping, for backwards compatibility.  But the caller
                 * really should use MAP_STACK | MAP_TRYFIXED if they
                 * want to do that.
                 */
                if (next == &map->header)
                        break;
                if (next->start >= end) {
                        if ((next->eflags & MAP_ENTRY_STACK) == 0)
                                break;
                        if (flags & MAP_STACK)
                                break;
                        if (next->start - next->aux.avail_ssize >= end)
                                break;
                }
        }
        map->hint = entry;

        /*
         * Grow the kernel_map if necessary.  pmap_growkernel() will panic
         * if it fails.  The kernel_map is locked and nothing can steal
         * our address space if pmap_growkernel() blocks.
         *
         * NOTE: This may be unconditionally called for kldload areas on
         *       x86_64 because these do not bump kernel_vm_end (which would
         *       fill 128G worth of page tables!).  Therefore we must not
         *       retry.
         */
        if (map == &kernel_map) {
                vm_offset_t kstop;

                kstop = round_page(start + length);
                if (kstop > kernel_vm_end)
                        pmap_growkernel(start, kstop);
        }
        *addr = start;
        return (0);
}

/*
 * vm_map_find finds an unallocated region in the target address map with
 * the given length and allocates it.  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.
 *
 * No requirements.  This function will lock the map temporarily.
 */
int
vm_map_find(vm_map_t map, void *map_object, void *map_aux,
            vm_ooffset_t offset, vm_offset_t *addr,
            vm_size_t length, vm_size_t align,
            boolean_t fitit,
            vm_maptype_t maptype,
            vm_prot_t prot, vm_prot_t max,
            int cow)
{
        vm_offset_t start;
        vm_object_t object;
        int result;
        int count;

        if (maptype == VM_MAPTYPE_UKSMAP)
                object = NULL;
        else
                object = map_object;

        start = *addr;

        count = vm_map_entry_reserve(MAP_RESERVE_COUNT);
        vm_map_lock(map);
        if (object)
                vm_object_hold_shared(object);
        if (fitit) {
                if (vm_map_findspace(map, start, length, align, 0, addr)) {
                        if (object)
                                vm_object_drop(object);
                        vm_map_unlock(map);
                        vm_map_entry_release(count);
                        return (KERN_NO_SPACE);
                }
                start = *addr;
        }
        result = vm_map_insert(map, &count, map_object, map_aux,
                               offset, start, start + length,
                               maptype, prot, max, cow);
        if (object)
                vm_object_drop(object);
        vm_map_unlock(map);
        vm_map_entry_release(count);

        return (result);
}

/*
 * Simplify the given map entry by merging with either neighbor.  This
 * routine also has the ability to merge with both neighbors.
 *
 * This routine guarentees that the passed entry remains valid (though
 * possibly extended).  When merging, this routine may delete one or
 * both neighbors.  No action is taken on entries which have their
 * in-transition flag set.
 *
 * The map must be exclusively locked.
 */
void
vm_map_simplify_entry(vm_map_t map, vm_map_entry_t entry, int *countp)
{
        vm_map_entry_t next, prev;
        vm_size_t prevsize, esize;

        if (entry->eflags & MAP_ENTRY_IN_TRANSITION) {
                ++mycpu->gd_cnt.v_intrans_coll;
                return;
        }

        if (entry->maptype == VM_MAPTYPE_SUBMAP)
                return;
        if (entry->maptype == VM_MAPTYPE_UKSMAP)
                return;

        prev = entry->prev;
        if (prev != &map->header) {
                prevsize = prev->end - prev->start;
                if ( (prev->end == entry->start) &&
                     (prev->maptype == entry->maptype) &&
                     (prev->object.vm_object == entry->object.vm_object) &&
                     (!prev->object.vm_object ||
                        (prev->offset + prevsize == entry->offset)) &&
                     (prev->eflags == entry->eflags) &&
                     (prev->protection == entry->protection) &&
                     (prev->max_protection == entry->max_protection) &&
                     (prev->inheritance == entry->inheritance) &&
                     (prev->wired_count == entry->wired_count)) {
                        if (map->first_free == prev)
                                map->first_free = entry;
                        if (map->hint == prev)
                                map->hint = entry;
                        vm_map_entry_unlink(map, prev);
                        entry->start = prev->start;
                        entry->offset = prev->offset;
                        if (prev->object.vm_object)
                                vm_object_deallocate(prev->object.vm_object);
                        vm_map_entry_dispose(map, prev, countp);
                }
        }

        next = entry->next;
        if (next != &map->header) {
                esize = entry->end - entry->start;
                if ((entry->end == next->start) &&
                    (next->maptype == entry->maptype) &&
                    (next->object.vm_object == entry->object.vm_object) &&
                     (!entry->object.vm_object ||
                        (entry->offset + esize == next->offset)) &&
                    (next->eflags == entry->eflags) &&
                    (next->protection == entry->protection) &&
                    (next->max_protection == entry->max_protection) &&
                    (next->inheritance == entry->inheritance) &&
                    (next->wired_count == entry->wired_count)) {
                        if (map->first_free == next)
                                map->first_free = entry;
                        if (map->hint == next)
                                map->hint = entry;
                        vm_map_entry_unlink(map, next);
                        entry->end = next->end;
                        if (next->object.vm_object)
                                vm_object_deallocate(next->object.vm_object);
                        vm_map_entry_dispose(map, next, countp);
                }
        }
}

/*
 * Asserts that the given entry begins at or after the specified address.
 * If necessary, it splits the entry into two.
 */
#define vm_map_clip_start(map, entry, startaddr, countp)                \
{                                                                       \
        if (startaddr > entry->start)                                   \
                _vm_map_clip_start(map, entry, startaddr, countp);      \
}

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

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

        vm_map_simplify_entry(map, entry, countp);

        /*
         * If there is no object backing this entry, we might as well create
         * one now.  If we defer it, an object can get created after the map
         * is clipped, and individual objects will be created for the split-up
         * map.  This is a bit of a hack, but is also about the best place to
         * put this improvement.
         */
        if (entry->object.vm_object == NULL && !map->system_map) {
                vm_map_entry_allocate_object(entry);
        }

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

        new_entry->end = start;
        entry->offset += (start - entry->start);
        entry->start = start;

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

        switch(entry->maptype) {
        case VM_MAPTYPE_NORMAL:
        case VM_MAPTYPE_VPAGETABLE:
                if (new_entry->object.vm_object) {
                        vm_object_hold(new_entry->object.vm_object);
                        vm_object_chain_wait(new_entry->object.vm_object, 0);
                        vm_object_reference_locked(new_entry->object.vm_object);
                        vm_object_drop(new_entry->object.vm_object);
                }
                break;
        default:
                break;
        }
}

/*
 * Asserts that the given entry ends at or before the specified address.
 * If necessary, it splits the entry into two.
 *
 * The map must be exclusively locked.
 */
#define vm_map_clip_end(map, entry, endaddr, countp)            \
{                                                               \
        if (endaddr < entry->end)                               \
                _vm_map_clip_end(map, entry, endaddr, countp);  \
}

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

        /*
         * If there is no object backing this entry, we might as well create
         * one now.  If we defer it, an object can get created after the map
         * is clipped, and individual objects will be created for the split-up
         * map.  This is a bit of a hack, but is also about the best place to
         * put this improvement.
         */

        if (entry->object.vm_object == NULL && !map->system_map) {
                vm_map_entry_allocate_object(entry);
        }

        /*
         * Create a new entry and insert it AFTER the specified entry
         */

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

        new_entry->start = entry->end = end;
        new_entry->offset += (end - entry->start);

        vm_map_entry_link(map, entry, new_entry);

        switch(entry->maptype) {
        case VM_MAPTYPE_NORMAL:
        case VM_MAPTYPE_VPAGETABLE:
                if (new_entry->object.vm_object) {
                        vm_object_hold(new_entry->object.vm_object);
                        vm_object_chain_wait(new_entry->object.vm_object, 0);
                        vm_object_reference_locked(new_entry->object.vm_object);
                        vm_object_drop(new_entry->object.vm_object);
                }
                break;
        default:
                break;
        }
}

/*
 * Asserts that the starting and ending region addresses fall within the
 * valid range for 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;                    \
}

/*
 * Used to block when an in-transition collison occurs.  The map
 * is unlocked for the sleep and relocked before the return.
 */
void
vm_map_transition_wait(vm_map_t map)
{
        tsleep_interlock(map, 0);
        vm_map_unlock(map);
        tsleep(map, PINTERLOCKED, "vment", 0);
        vm_map_lock(map);
}

/*
 * When we do blocking operations with the map lock held it is
 * possible that a clip might have occured on our in-transit entry,
 * requiring an adjustment to the entry in our loop.  These macros
 * help the pageable and clip_range code deal with the case.  The
 * conditional costs virtually nothing if no clipping has occured.
 */

#define CLIP_CHECK_BACK(entry, save_start)              \
    do {                                                \
            while (entry->start != save_start) {        \
                    entry = entry->prev;                \
                    KASSERT(entry != &map->header, ("bad entry clip")); \
            }                                           \
    } while(0)

#define CLIP_CHECK_FWD(entry, save_end)                 \
    do {                                                \
            while (entry->end != save_end) {            \
                    entry = entry->next;                \
                    KASSERT(entry != &map->header, ("bad entry clip")); \
            }                                           \
    } while(0)


/*
 * Clip the specified range and return the base entry.  The
 * range may cover several entries starting at the returned base
 * and the first and last entry in the covering sequence will be
 * properly clipped to the requested start and end address.
 *
 * If no holes are allowed you should pass the MAP_CLIP_NO_HOLES
 * flag.
 *
 * The MAP_ENTRY_IN_TRANSITION flag will be set for the entries
 * covered by the requested range.
 *
 * The map must be exclusively locked on entry and will remain locked
 * on return. If no range exists or the range contains holes and you
 * specified that no holes were allowed, NULL will be returned.  This
 * routine may temporarily unlock the map in order avoid a deadlock when
 * sleeping.
 */
static
vm_map_entry_t
vm_map_clip_range(vm_map_t map, vm_offset_t start, vm_offset_t end, 
                  int *countp, int flags)
{
        vm_map_entry_t start_entry;
        vm_map_entry_t entry;

        /*
         * Locate the entry and effect initial clipping.  The in-transition
         * case does not occur very often so do not try to optimize it.
         */
again:
        if (vm_map_lookup_entry(map, start, &start_entry) == FALSE)
                return (NULL);
        entry = start_entry;
        if (entry->eflags & MAP_ENTRY_IN_TRANSITION) {
                entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
                ++mycpu->gd_cnt.v_intrans_coll;
                ++mycpu->gd_cnt.v_intrans_wait;
                vm_map_transition_wait(map);
                /*
                 * entry and/or start_entry may have been clipped while
                 * we slept, or may have gone away entirely.  We have
                 * to restart from the lookup.
                 */
                goto again;
        }

        /*
         * Since we hold an exclusive map lock we do not have to restart
         * after clipping, even though clipping may block in zalloc.
         */
        vm_map_clip_start(map, entry, start, countp);
        vm_map_clip_end(map, entry, end, countp);
        entry->eflags |= MAP_ENTRY_IN_TRANSITION;

        /*
         * Scan entries covered by the range.  When working on the next
         * entry a restart need only re-loop on the current entry which
         * we have already locked, since 'next' may have changed.  Also,
         * even though entry is safe, it may have been clipped so we
         * have to iterate forwards through the clip after sleeping.
         */
        while (entry->next != &map->header && entry->next->start < end) {
                vm_map_entry_t next = entry->next;

                if (flags & MAP_CLIP_NO_HOLES) {
                        if (next->start > entry->end) {
                                vm_map_unclip_range(map, start_entry,
                                        start, entry->end, countp, flags);
                                return(NULL);
                        }
                }

                if (next->eflags & MAP_ENTRY_IN_TRANSITION) {
                        vm_offset_t save_end = entry->end;
                        next->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
                        ++mycpu->gd_cnt.v_intrans_coll;
                        ++mycpu->gd_cnt.v_intrans_wait;
                        vm_map_transition_wait(map);

                        /*
                         * clips might have occured while we blocked.
                         */
                        CLIP_CHECK_FWD(entry, save_end);
                        CLIP_CHECK_BACK(start_entry, start);
                        continue;
                }
                /*
                 * No restart necessary even though clip_end may block, we
                 * are holding the map lock.
                 */
                vm_map_clip_end(map, next, end, countp);
                next->eflags |= MAP_ENTRY_IN_TRANSITION;
                entry = next;
        }
        if (flags & MAP_CLIP_NO_HOLES) {
                if (entry->end != end) {
                        vm_map_unclip_range(map, start_entry,
                                start, entry->end, countp, flags);
                        return(NULL);
                }
        }
        return(start_entry);
}

/*
 * Undo the effect of vm_map_clip_range().  You should pass the same
 * flags and the same range that you passed to vm_map_clip_range().
 * This code will clear the in-transition flag on the entries and
 * wake up anyone waiting.  This code will also simplify the sequence
 * and attempt to merge it with entries before and after the sequence.
 *
 * The map must be locked on entry and will remain locked on return.
 *
 * Note that you should also pass the start_entry returned by
 * vm_map_clip_range().  However, if you block between the two calls
 * with the map unlocked please be aware that the start_entry may
 * have been clipped and you may need to scan it backwards to find
 * the entry corresponding with the original start address.  You are
 * responsible for this, vm_map_unclip_range() expects the correct
 * start_entry to be passed to it and will KASSERT otherwise.
 */
static
void
vm_map_unclip_range(vm_map_t map, vm_map_entry_t start_entry,
                    vm_offset_t start, vm_offset_t end,
                    int *countp, int flags)
{
        vm_map_entry_t entry;

        entry = start_entry;

        KASSERT(entry->start == start, ("unclip_range: illegal base entry"));
        while (entry != &map->header && entry->start < end) {
                KASSERT(entry->eflags & MAP_ENTRY_IN_TRANSITION,
                        ("in-transition flag not set during unclip on: %p",
                        entry));
                KASSERT(entry->end <= end,
                        ("unclip_range: tail wasn't clipped"));
                entry->eflags &= ~MAP_ENTRY_IN_TRANSITION;
                if (entry->eflags & MAP_ENTRY_NEEDS_WAKEUP) {
                        entry->eflags &= ~MAP_ENTRY_NEEDS_WAKEUP;
                        wakeup(map);
                }
                entry = entry->next;
        }

        /*
         * Simplification does not block so there is no restart case.
         */
        entry = start_entry;
        while (entry != &map->header && entry->start < end) {
                vm_map_simplify_entry(map, entry, countp);
                entry = entry->next;
        }
}

/*
 * 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().
 *
 * Submappings cannot be removed.
 *
 * No requirements.
 */
int
vm_map_submap(vm_map_t map, vm_offset_t start, vm_offset_t end, vm_map_t submap)
{
        vm_map_entry_t entry;
        int result = KERN_INVALID_ARGUMENT;
        int count;

        count = vm_map_entry_reserve(MAP_RESERVE_COUNT);
        vm_map_lock(map);

        VM_MAP_RANGE_CHECK(map, start, end);

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

        vm_map_clip_end(map, entry, end, &count);

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

        return (result);
}

/*
 * 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.
 *
 * The protection is not applicable to submaps, but is applicable to normal
 * maps and maps governed by virtual page tables.  For example, when operating
 * on a virtual page table our protection basically controls how COW occurs
 * on the backing object, whereas the virtual page table abstraction itself
 * is an abstraction for userland.
 *
 * No requirements.
 */
int
vm_map_protect(vm_map_t map, vm_offset_t start, vm_offset_t end,
               vm_prot_t new_prot, boolean_t set_max)
{
        vm_map_entry_t current;
        vm_map_entry_t entry;
        int count;

        count = vm_map_entry_reserve(MAP_RESERVE_COUNT);
        vm_map_lock(map);

        VM_MAP_RANGE_CHECK(map, start, end);

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

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

        /*
         * Go back and fix up protections. [Note that clipping is not
         * necessary the second time.]
         */
        current = entry;

        while ((current != &map->header) && (current->start < end)) {
                vm_prot_t old_prot;

                vm_map_clip_end(map, current, end, &count);

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

                /*
                 * Update physical map if necessary. Worry about copy-on-write
                 * here -- CHECK THIS XXX
                 */

                if (current->protection != old_prot) {
#define MASK(entry)     (((entry)->eflags & MAP_ENTRY_COW) ? ~VM_PROT_WRITE : \
                                                        VM_PROT_ALL)

                        pmap_protect(map->pmap, current->start,
                            current->end,
                            current->protection & MASK(current));
#undef  MASK
                }

                vm_map_simplify_entry(map, current, &count);

                current = current->next;
        }

        vm_map_unlock(map);
        vm_map_entry_release(count);
        return (KERN_SUCCESS);
}

/*
 * 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.
 *
 * The <value> argument is used for extended madvise calls.
 *
 * No requirements.
 */
int
vm_map_madvise(vm_map_t map, vm_offset_t start, vm_offset_t end,
               int behav, off_t value)
{
        vm_map_entry_t current, entry;
        int modify_map = 0;
        int error = 0;
        int count;

        /*
         * 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.
         */

        count = vm_map_entry_reserve(MAP_RESERVE_COUNT);

        switch(behav) {
        case MADV_NORMAL:
        case MADV_SEQUENTIAL:
        case MADV_RANDOM:
        case MADV_NOSYNC:
        case MADV_AUTOSYNC:
        case MADV_NOCORE:
        case MADV_CORE:
        case MADV_SETMAP:
        case MADV_INVAL:
                modify_map = 1;
                vm_map_lock(map);
                break;
        case MADV_WILLNEED:
        case MADV_DONTNEED:
        case MADV_FREE:
                vm_map_lock_read(map);
                break;
        default:
                vm_map_entry_release(count);
                return (EINVAL);
        }

        /*
         * Locate starting entry and clip if necessary.
         */

        VM_MAP_RANGE_CHECK(map, start, end);

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

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

                        vm_map_clip_end(map, current, end, &count);

                        switch (behav) {
                        case MADV_NORMAL:
                                vm_map_entry_set_behavior(current, MAP_ENTRY_BEHAV_NORMAL);
                                break;
                        case MADV_SEQUENTIAL:
                                vm_map_entry_set_behavior(current, MAP_ENTRY_BEHAV_SEQUENTIAL);
                                break;
                        case MADV_RANDOM:
                                vm_map_entry_set_behavior(current, MAP_ENTRY_BEHAV_RANDOM);
                                break;
                        case MADV_NOSYNC:
                                current->eflags |= MAP_ENTRY_NOSYNC;
                                break;
                        case MADV_AUTOSYNC:
                                current->eflags &= ~MAP_ENTRY_NOSYNC;
                                break;
                        case MADV_NOCORE:
                                current->eflags |= MAP_ENTRY_NOCOREDUMP;
                                break;
                        case MADV_CORE:
                                current->eflags &= ~MAP_ENTRY_NOCOREDUMP;
                                break;
                        case MADV_INVAL:
                                /*
                                 * Invalidate the related pmap entries, used
                                 * to flush portions of the real kernel's
                                 * pmap when the caller has removed or
                                 * modified existing mappings in a virtual
                                 * page table.
                                 */
                                pmap_remove(map->pmap,
                                            current->start, current->end);
                                break;
                        case MADV_SETMAP:
                                /*
                                 * Set the page directory page for a map
                                 * governed by a virtual page table.  Mark
                                 * the entry as being governed by a virtual
                                 * page table if it is not.
                                 *
                                 * XXX the page directory page is stored
                                 * in the avail_ssize field if the map_entry.
                                 *
                                 * XXX the map simplification code does not
                                 * compare this field so weird things may
                                 * happen if you do not apply this function
                                 * to the entire mapping governed by the
                                 * virtual page table.
                                 */
                                if (current->maptype != VM_MAPTYPE_VPAGETABLE) {
                                        error = EINVAL;
                                        break;
                                }
                                current->aux.master_pde = value;
                                pmap_remove(map->pmap,
                                            current->start, current->end);
                                break;
                        default:
                                error = EINVAL;
                                break;
                        }
                        vm_map_simplify_entry(map, current, &count);
                }
                vm_map_unlock(map);
        } else {
                vm_pindex_t pindex;
                int count;

                /*
                 * 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.
                 *
                 * NOTE!  We currently do not support these functions on
                 * virtual page tables.
                 */
                for (current = entry;
                     (current != &map->header) && (current->start < end);
                     current = current->next
                ) {
                        vm_offset_t useStart;

                        if (current->maptype != VM_MAPTYPE_NORMAL)
                                continue;

                        pindex = OFF_TO_IDX(current->offset);
                        count = atop(current->end - current->start);
                        useStart = current->start;

                        if (current->start < start) {
                                pindex += atop(start - current->start);
                                count -= atop(start - current->start);
                                useStart = start;
                        }
                        if (current->end > end)
                                count -= atop(current->end - end);

                        if (count <= 0)
                                continue;

                        vm_object_madvise(current->object.vm_object,
                                          pindex, count, behav);

                        /*
                         * Try to populate the page table.  Mappings governed
                         * by virtual page tables cannot be pre-populated
                         * without a lot of work so don't try.
                         */
                        if (behav == MADV_WILLNEED &&
                            current->maptype != VM_MAPTYPE_VPAGETABLE) {
                                pmap_object_init_pt(
                                    map->pmap, 
                                    useStart,
                                    current->protection,
                                    current->object.vm_object,
                                    pindex, 
                                    (count << PAGE_SHIFT),
                                    MAP_PREFAULT_MADVISE
                                );
                        }
                }
                vm_map_unlock_read(map);
        }
        vm_map_entry_release(count);
        return(error);
}       


/*
 * 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 vm_map_fork.
 */
int
vm_map_inherit(vm_map_t map, vm_offset_t start, vm_offset_t end,
               vm_inherit_t new_inheritance)
{
        vm_map_entry_t entry;
        vm_map_entry_t temp_entry;
        int count;

        switch (new_inheritance) {
        case VM_INHERIT_NONE:
        case VM_INHERIT_COPY:
        case VM_INHERIT_SHARE:
                break;
        default:
                return (KERN_INVALID_ARGUMENT);
        }

        count = vm_map_entry_reserve(MAP_RESERVE_COUNT);
        vm_map_lock(map);

        VM_MAP_RANGE_CHECK(map, start, end);

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

        while ((entry != &map->header) && (entry->start < end)) {
                vm_map_clip_end(map, entry, end, &count);

                entry->inheritance = new_inheritance;

                vm_map_simplify_entry(map, entry, &count);

                entry = entry->next;
        }
        vm_map_unlock(map);
        vm_map_entry_release(count);
        return (KERN_SUCCESS);
}

/*
 * Implement the semantics of mlock
 */
int
vm_map_unwire(vm_map_t map, vm_offset_t start, vm_offset_t real_end,
              boolean_t new_pageable)
{
        vm_map_entry_t entry;
        vm_map_entry_t start_entry;
        vm_offset_t end;
        int rv = KERN_SUCCESS;
        int count;

        count = vm_map_entry_reserve(MAP_RESERVE_COUNT);
        vm_map_lock(map);
        VM_MAP_RANGE_CHECK(map, start, real_end);
        end = real_end;

        start_entry = vm_map_clip_range(map, start, end, &count,
                                        MAP_CLIP_NO_HOLES);
        if (start_entry == NULL) {
                vm_map_unlock(map);
                vm_map_entry_release(count);
                return (KERN_INVALID_ADDRESS);
        }

        if (new_pageable == 0) {
                entry = start_entry;
                while ((entry != &map->header) && (entry->start < end)) {
                        vm_offset_t save_start;
                        vm_offset_t save_end;

                        /*
                         * Already user wired or hard wired (trivial cases)
                         */
                        if (entry->eflags & MAP_ENTRY_USER_WIRED) {
                                entry = entry->next;
                                continue;
                        }
                        if (entry->wired_count != 0) {
                                entry->wired_count++;
                                entry->eflags |= MAP_ENTRY_USER_WIRED;
                                entry = entry->next;
                                continue;
                        }

                        /*
                         * A new wiring requires instantiation of appropriate
                         * management structures and the faulting in of the
                         * page.
                         */
                        if (entry->maptype == VM_MAPTYPE_NORMAL ||
                            entry->maptype == VM_MAPTYPE_VPAGETABLE) {
                                int copyflag = entry->eflags &
                                               MAP_ENTRY_NEEDS_COPY;
                                if (copyflag && ((entry->protection &
                                                  VM_PROT_WRITE) != 0)) {
                                        vm_map_entry_shadow(entry, 0);
                                } else if (entry->object.vm_object == NULL &&
                                           !map->system_map) {
                                        vm_map_entry_allocate_object(entry);
                                }
                        }
                        entry->wired_count++;
                        entry->eflags |= MAP_ENTRY_USER_WIRED;

                        /*
                         * Now fault in the area.  Note that vm_fault_wire()
                         * may release the map lock temporarily, it will be
                         * relocked on return.  The in-transition
                         * flag protects the entries. 
                         */
                        save_start = entry->start;
                        save_end = entry->end;
                        rv = vm_fault_wire(map, entry, TRUE, 0);
                        if (rv) {
                                CLIP_CHECK_BACK(entry, save_start);
                                for (;;) {
                                        KASSERT(entry->wired_count == 1, ("bad wired_count on entry"));
                                        entry->eflags &= ~MAP_ENTRY_USER_WIRED;
                                        entry->wired_count = 0;
                                        if (entry->end == save_end)
                                                break;
                                        entry = entry->next;
                                        KASSERT(entry != &map->header, ("bad entry clip during backout"));
                                }
                                end = save_start;       /* unwire the rest */
                                break;
                        }
                        /*
                         * note that even though the entry might have been
                         * clipped, the USER_WIRED flag we set prevents
                         * duplication so we do not have to do a 
                         * clip check.
                         */
                        entry = entry->next;
                }

                /*
                 * If we failed fall through to the unwiring section to
                 * unwire what we had wired so far.  'end' has already
                 * been adjusted.
                 */
                if (rv)
                        new_pageable = 1;

                /*
                 * start_entry might have been clipped if we unlocked the
                 * map and blocked.  No matter how clipped it has gotten
                 * there should be a fragment that is on our start boundary.
                 */
                CLIP_CHECK_BACK(start_entry, start);
        }

        /*
         * Deal with the unwiring case.
         */
        if (new_pageable) {
                /*
                 * This is the unwiring case.  We must first ensure that the
                 * range to be unwired is really wired down.  We know there
                 * are no holes.
                 */
                entry = start_entry;
                while ((entry != &map->header) && (entry->start < end)) {
                        if ((entry->eflags & MAP_ENTRY_USER_WIRED) == 0) {
                                rv = KERN_INVALID_ARGUMENT;
                                goto done;
                        }
                        KASSERT(entry->wired_count != 0, ("wired count was 0 with USER_WIRED set! %p", entry));
                        entry = entry->next;
                }

                /*
                 * Now decrement the wiring count for each region. If a region
                 * becomes completely unwired, unwire its physical pages and
                 * mappings.
                 */
                /*
                 * The map entries are processed in a loop, checking to
                 * make sure the entry is wired and asserting it has a wired
                 * count. However, another loop was inserted more-or-less in
                 * the middle of the unwiring path. This loop picks up the
                 * "entry" loop variable from the first loop without first
                 * setting it to start_entry. Naturally, the secound loop
                 * is never entered and the pages backing the entries are
                 * never unwired. This can lead to a leak of wired pages.
                 */
                entry = start_entry;
                while ((entry != &map->header) && (entry->start < end)) {
                        KASSERT(entry->eflags & MAP_ENTRY_USER_WIRED,
                                ("expected USER_WIRED on entry %p", entry));
                        entry->eflags &= ~MAP_ENTRY_USER_WIRED;
                        entry->wired_count--;
                        if (entry->wired_count == 0)
                                vm_fault_unwire(map, entry);
                        entry = entry->next;
                }
        }
done:
        vm_map_unclip_range(map, start_entry, start, real_end, &count,
                MAP_CLIP_NO_HOLES);
        map->timestamp++;
        vm_map_unlock(map);
        vm_map_entry_release(count);
        return (rv);
}

/*
 * Sets the pageability of the specified address range in the target map.
 * Regions specified as not pageable require locked-down physical
 * memory and physical page maps.
 *
 * The map must not be locked, but a reference must remain to the map
 * throughout the call.
 *
 * This function may be called via the zalloc path and must properly
 * reserve map entries for kernel_map.
 *
 * No requirements.
 */
int
vm_map_wire(vm_map_t map, vm_offset_t start, vm_offset_t real_end, int kmflags)
{
        vm_map_entry_t entry;
        vm_map_entry_t start_entry;
        vm_offset_t end;
        int rv = KERN_SUCCESS;
        int count;

        if (kmflags & KM_KRESERVE)
                count = vm_map_entry_kreserve(MAP_RESERVE_COUNT);
        else
                count = vm_map_entry_reserve(MAP_RESERVE_COUNT);
        vm_map_lock(map);
        VM_MAP_RANGE_CHECK(map, start, real_end);
        end = real_end;

        start_entry = vm_map_clip_range(map, start, end, &count,
                                        MAP_CLIP_NO_HOLES);
        if (start_entry == NULL) {
                vm_map_unlock(map);
                rv = KERN_INVALID_ADDRESS;
                goto failure;
        }
        if ((kmflags & KM_PAGEABLE) == 0) {
                /*
                 * Wiring.  
                 *
                 * 1.  Holding the write lock, we create any shadow or zero-fill
                 * objects that need to be created. Then we clip each map
                 * entry to the region to be wired and increment its wiring
                 * count.  We create objects before clipping the map entries
                 * to avoid object proliferation.
                 *
                 * 2.  We downgrade to a read lock, and call vm_fault_wire to
                 * fault in the pages for any newly wired area (wired_count is
                 * 1).
                 *
                 * Downgrading to a read lock for vm_fault_wire avoids a 
                 * possible deadlock with another process that may have faulted
                 * on one of the pages to be wired (it would mark the page busy,
                 * blocking us, then in turn block on the map lock that we
                 * hold).  Because of problems in the recursive lock package,
                 * we cannot upgrade to a write lock in vm_map_lookup.  Thus,
                 * any actions that require the write lock must be done
                 * beforehand.  Because we keep the read lock on the map, the
                 * copy-on-write status of the entries we modify here cannot
                 * change.
                 */
                entry = start_entry;
                while ((entry != &map->header) && (entry->start < end)) {
                        /*
                         * Trivial case if the entry is already wired
                         */
                        if (entry->wired_count) {
                                entry->wired_count++;
                                entry = entry->next;
                                continue;
                        }

                        /*
                         * The entry is being newly wired, we have to setup
                         * appropriate management structures.  A shadow 
                         * object is required for a copy-on-write region,
                         * or a normal object for a zero-fill region.  We
                         * do not have to do this for entries that point to sub
                         * maps because we won't hold the lock on the sub map.
                         */
                        if (entry->maptype == VM_MAPTYPE_NORMAL ||
                            entry->maptype == VM_MAPTYPE_VPAGETABLE) {
                                int copyflag = entry->eflags &
                                               MAP_ENTRY_NEEDS_COPY;
                                if (copyflag && ((entry->protection &
                                                  VM_PROT_WRITE) != 0)) {
                                        vm_map_entry_shadow(entry, 0);
                                } else if (entry->object.vm_object == NULL &&
                                           !map->system_map) {
                                        vm_map_entry_allocate_object(entry);
                                }
                        }

                        entry->wired_count++;
                        entry = entry->next;
                }

                /*
                 * Pass 2.
                 */

                /*
                 * HACK HACK HACK HACK
                 *
                 * vm_fault_wire() temporarily unlocks the map to avoid
                 * deadlocks.  The in-transition flag from vm_map_clip_range
                 * call should protect us from changes while the map is
                 * unlocked.  T
                 *
                 * NOTE: Previously this comment stated that clipping might
                 *       still occur while the entry is unlocked, but from
                 *       what I can tell it actually cannot.
                 *
                 *       It is unclear whether the CLIP_CHECK_*() calls
                 *       are still needed but we keep them in anyway.
                 *
                 * HACK HACK HACK HACK
                 */

                entry = start_entry;
                while (entry != &map->header && entry->start < end) {
                        /*
                         * If vm_fault_wire fails for any page we need to undo
                         * what has been done.  We decrement the wiring count
                         * for those pages which have not yet been wired (now)
                         * and unwire those that have (later).
                         */
                        vm_offset_t save_start = entry->start;
                        vm_offset_t save_end = entry->end;

                        if (entry->wired_count == 1)
                                rv = vm_fault_wire(map, entry, FALSE, kmflags);
                        if (rv) {
                                CLIP_CHECK_BACK(entry, save_start);
                                for (;;) {
                                        KASSERT(entry->wired_count == 1, ("wired_count changed unexpectedly"));
                                        entry->wired_count = 0;
                                        if (entry->end == save_end)
                                                break;
                                        entry = entry->next;
                                        KASSERT(entry != &map->header, ("bad entry clip during backout"));
                                }
                                end = save_start;
                                break;
                        }
                        CLIP_CHECK_FWD(entry, save_end);
                        entry = entry->next;
                }

                /*
                 * If a failure occured undo everything by falling through
                 * to the unwiring code.  'end' has already been adjusted
                 * appropriately.
                 */
                if (rv)
                        kmflags |= KM_PAGEABLE;

                /*
                 * start_entry is still IN_TRANSITION but may have been 
                 * clipped since vm_fault_wire() unlocks and relocks the
                 * map.  No matter how clipped it has gotten there should
                 * be a fragment that is on our start boundary.
                 */
                CLIP_CHECK_BACK(start_entry, start);
        }

        if (kmflags & KM_PAGEABLE) {
                /*
                 * This is the unwiring case.  We must first ensure that the
                 * range to be unwired is really wired down.  We know there
                 * are no holes.
                 */
                entry = start_entry;
                while ((entry != &map->header) && (entry->start < end)) {
                        if (entry->wired_count == 0) {
                                rv = KERN_INVALID_ARGUMENT;
                                goto done;
                        }
                        entry = entry->next;
                }

                /*
                 * Now decrement the wiring count for each region. If a region
                 * becomes completely unwired, unwire its physical pages and
                 * mappings.
                 */
                entry = start_entry;
                while ((entry != &map->header) && (entry->start < end)) {
                        entry->wired_count--;
                        if (entry->wired_count == 0)
                                vm_fault_unwire(map, entry);
                        entry = entry->next;
                }
        }
done:
        vm_map_unclip_range(map, start_entry, start, real_end,
                            &count, MAP_CLIP_NO_HOLES);
        map->timestamp++;
        vm_map_unlock(map);
failure:
        if (kmflags & KM_KRESERVE)
                vm_map_entry_krelease(count);
        else
                vm_map_entry_release(count);
        return (rv);
}

/*
 * Mark a newly allocated address range as wired but do not fault in
 * the pages.  The caller is expected to load the pages into the object.
 *
 * The map must be locked on entry and will remain locked on return.
 * No other requirements.
 */
void
vm_map_set_wired_quick(vm_map_t map, vm_offset_t addr, vm_size_t size,
                       int *countp)
{
        vm_map_entry_t scan;
        vm_map_entry_t entry;

        entry = vm_map_clip_range(map, addr, addr + size,
                                  countp, MAP_CLIP_NO_HOLES);
        for (scan = entry;
             scan != &map->header && scan->start < addr + size;
             scan = scan->next) {
            KKASSERT(scan->wired_count == 0);
            scan->wired_count = 1;
        }
        vm_map_unclip_range(map, entry, addr, addr + size,
                            countp, MAP_CLIP_NO_HOLES);
}

/*
 * 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.
 *
 * This routine is called by sys_msync()
 *
 * Returns an error if any part of the specified range is not mapped.
 *
 * No requirements.
 */
int
vm_map_clean(vm_map_t map, vm_offset_t start, vm_offset_t end,
             boolean_t syncio, boolean_t invalidate)
{
        vm_map_entry_t current;
        vm_map_entry_t entry;
        vm_size_t size;
        vm_object_t object;
        vm_object_t tobj;
        vm_ooffset_t offset;

        vm_map_lock_read(map);
        VM_MAP_RANGE_CHECK(map, start, end);
        if (!vm_map_lookup_entry(map, start, &entry)) {
                vm_map_unlock_read(map);
                return (KERN_INVALID_ADDRESS);
        }
        lwkt_gettoken(&map->token);

        /*
         * Make a first pass to check for holes.
         */
        for (current = entry; current->start < end; current = current->next) {
                if (current->maptype == VM_MAPTYPE_SUBMAP) {
                        lwkt_reltoken(&map->token);
                        vm_map_unlock_read(map);
                        return (KERN_INVALID_ARGUMENT);
                }
                if (end > current->end &&
                    (current->next == &map->header ||
                        current->end != current->next->start)) {
                        lwkt_reltoken(&map->token);
                        vm_map_unlock_read(map);
                        return (KERN_INVALID_ADDRESS);
                }
        }

        if (invalidate)
                pmap_remove(vm_map_pmap(map), start, end);

        /*
         * Make a second pass, cleaning/uncaching pages from the indicated
         * objects as we go.
         */
        for (current = entry; current->start < end; current = current->next) {
                offset = current->offset + (start - current->start);
                size = (end <= current->end ? end : current->end) - start;

                switch(current->maptype) {
                case VM_MAPTYPE_SUBMAP:
                {
                        vm_map_t smap;
                        vm_map_entry_t tentry;
                        vm_size_t tsize;

                        smap = current->object.sub_map;
                        vm_map_lock_read(smap);
                        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);
                        break;
                }
                case VM_MAPTYPE_NORMAL:
                case VM_MAPTYPE_VPAGETABLE:
                        object = current->object.vm_object;
                        break;
                default:
                        object = NULL;
                        break;
                }

                if (object)
                        vm_object_hold(object);

                /*
                 * Note that there is absolutely no sense in writing out
                 * anonymous objects, so we track down the vnode object
                 * to write out.
                 * We invalidate (remove) all pages from the address space
                 * anyway, for semantic correctness.
                 *
                 * note: certain anonymous maps, such as MAP_NOSYNC maps,
                 * may start out with a NULL object.
                 */
                while (object && (tobj = object->backing_object) != NULL) {
                        vm_object_hold(tobj);
                        if (tobj == object->backing_object) {
                                vm_object_lock_swap();
                                offset += object->backing_object_offset;
                                vm_object_drop(object);
                                object = tobj;
                                if (object->size < OFF_TO_IDX(offset + size))
                                        size = IDX_TO_OFF(object->size) -
                                               offset;
                                break;
                        }
                        vm_object_drop(tobj);
                }
                if (object && (object->type == OBJT_VNODE) && 
                    (current->protection & VM_PROT_WRITE) &&
                    (object->flags & OBJ_NOMSYNC) == 0) {
                        /*
                         * Flush pages if writing is allowed, invalidate them
                         * if invalidation requested.  Pages undergoing I/O
                         * will be ignored by vm_object_page_remove().
                         *
                         * We cannot lock the vnode and then wait for paging
                         * to complete without deadlocking against vm_fault.
                         * Instead we simply call vm_object_page_remove() and
                         * allow it to block internally on a page-by-page 
                         * basis when it encounters pages undergoing async 
                         * I/O.
                         */
                        int flags;

                        /* no chain wait needed for vnode objects */
                        vm_object_reference_locked(object);
                        vn_lock(object->handle, LK_EXCLUSIVE | LK_RETRY);
                        flags = (syncio || invalidate) ? OBJPC_SYNC : 0;
                        flags |= invalidate ? OBJPC_INVAL : 0;

                        /*
                         * When operating on a virtual page table just
                         * flush the whole object.  XXX we probably ought
                         * to 
                         */
                        switch(current->maptype) {
                        case VM_MAPTYPE_NORMAL:
                                vm_object_page_clean(object,
                                    OFF_TO_IDX(offset),
                                    OFF_TO_IDX(offset + size + PAGE_MASK),
                                    flags);
                                break;
                        case VM_MAPTYPE_VPAGETABLE:
                                vm_object_page_clean(object, 0, 0, flags);
                                break;
                        }
                        vn_unlock(((struct vnode *)object->handle));
                        vm_object_deallocate_locked(object);
                }
                if (object && invalidate &&
                   ((object->type == OBJT_VNODE) ||
                    (object->type == OBJT_DEVICE) ||
                    (object->type == OBJT_MGTDEVICE))) {
                        int clean_only = 
                                ((object->type == OBJT_DEVICE) ||
                                (object->type == OBJT_MGTDEVICE)) ? FALSE : TRUE;
                        /* no chain wait needed for vnode/device objects */
                        vm_object_reference_locked(object);
                        switch(current->maptype) {
                        case VM_MAPTYPE_NORMAL:
                                vm_object_page_remove(object,
                                    OFF_TO_IDX(offset),
                                    OFF_TO_IDX(offset + size + PAGE_MASK),
                                    clean_only);
                                break;
                        case VM_MAPTYPE_VPAGETABLE:
                                vm_object_page_remove(object, 0, 0, clean_only);
                                break;
                        }
                        vm_object_deallocate_locked(object);
                }
                start += size;
                if (object)
                        vm_object_drop(object);
        }

        lwkt_reltoken(&map->token);
        vm_map_unlock_read(map);

        return (KERN_SUCCESS);
}

/*
 * Make the region specified by this entry pageable.
 *
 * The vm_map must be exclusively locked.
 */
static void 
vm_map_entry_unwire(vm_map_t map, vm_map_entry_t entry)
{
        entry->eflags &= ~MAP_ENTRY_USER_WIRED;
        entry->wired_count = 0;
        vm_fault_unwire(map, entry);
}

/*
 * Deallocate the given entry from the target map.
 *
 * The vm_map must be exclusively locked.
 */
static void
vm_map_entry_delete(vm_map_t map, vm_map_entry_t entry, int *countp)
{
        vm_map_entry_unlink(map, entry);
        map->size -= entry->end - entry->start;

        switch(entry->maptype) {
        case VM_MAPTYPE_NORMAL:
        case VM_MAPTYPE_VPAGETABLE:
        case VM_MAPTYPE_SUBMAP:
                vm_object_deallocate(entry->object.vm_object);
                break;
        case VM_MAPTYPE_UKSMAP:
                /* XXX TODO */
                break;
        default:
                break;
        }

        vm_map_entry_dispose(map, entry, countp);
}

/*
 * Deallocates the given address range from the target map.
 *
 * The vm_map must be exclusively locked.
 */
int
vm_map_delete(vm_map_t map, vm_offset_t start, vm_offset_t end, int *countp)
{
        vm_object_t object;
        vm_map_entry_t entry;
        vm_map_entry_t first_entry;

        ASSERT_VM_MAP_LOCKED(map);
        lwkt_gettoken(&map->token);
again:
        /*
         * Find the start of the region, and clip it.  Set entry to point
         * at the first record containing the requested address or, if no
         * such record exists, the next record with a greater address.  The
         * loop will run from this point until a record beyond the termination
         * address is encountered.
         *
         * map->hint must be adjusted to not point to anything we delete,
         * so set it to the entry prior to the one being deleted.
         *
         * GGG see other GGG comment.
         */
        if (vm_map_lookup_entry(map, start, &first_entry)) {
                entry = first_entry;
                vm_map_clip_start(map, entry, start, countp);
                map->hint = entry->prev;        /* possible problem XXX */
        } else {
                map->hint = first_entry;        /* possible problem XXX */
                entry = first_entry->next;
        }

        /*
         * If a hole opens up prior to the current first_free then
         * adjust first_free.  As with map->hint, map->first_free
         * cannot be left set to anything we might delete.
         */
        if (entry == &map->header) {
                map->first_free = &map->header;
        } else if (map->first_free->start >= start) {
                map->first_free = entry->prev;
        }

        /*
         * Step through all entries in this region
         */
        while ((entry != &map->header) && (entry->start < end)) {
                vm_map_entry_t next;
                vm_offset_t s, e;
                vm_pindex_t offidxstart, offidxend, count;

                /*
                 * If we hit an in-transition entry we have to sleep and
                 * retry.  It's easier (and not really slower) to just retry
                 * since this case occurs so rarely and the hint is already
                 * pointing at the right place.  We have to reset the
                 * start offset so as not to accidently delete an entry
                 * another process just created in vacated space.
                 */
                if (entry->eflags & MAP_ENTRY_IN_TRANSITION) {
                        entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
                        start = entry->start;
                        ++mycpu->gd_cnt.v_intrans_coll;
                        ++mycpu->gd_cnt.v_intrans_wait;
                        vm_map_transition_wait(map);
                        goto again;
                }
                vm_map_clip_end(map, entry, end, countp);

                s = entry->start;
                e = entry->end;
                next = entry->next;

                offidxstart = OFF_TO_IDX(entry->offset);
                count = OFF_TO_IDX(e - s);

                switch(entry->maptype) {
                case VM_MAPTYPE_NORMAL:
                case VM_MAPTYPE_VPAGETABLE:
                case VM_MAPTYPE_SUBMAP:
                        object = entry->object.vm_object;
                        break;
                default:
                        object = NULL;
                        break;
                }

                /*
                 * 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);

                offidxend = offidxstart + count;

                if (object == &kernel_object) {
                        vm_object_hold(object);
                        vm_object_page_remove(object, offidxstart,
                                              offidxend, FALSE);
                        vm_object_drop(object);
                } else if (object && object->type != OBJT_DEFAULT &&
                           object->type != OBJT_SWAP) {
                        /*
                         * vnode object routines cannot be chain-locked,
                         * but since we aren't removing pages from the
                         * object here we can use a shared hold.
                         */
                        vm_object_hold_shared(object);
                        pmap_remove(map->pmap, s, e);
                        vm_object_drop(object);
                } else if (object) {
                        vm_object_hold(object);
                        vm_object_chain_acquire(object, 0);
                        pmap_remove(map->pmap, s, e);

                        if (object != NULL &&
                            object->ref_count != 1 &&
                            (object->flags & (OBJ_NOSPLIT|OBJ_ONEMAPPING)) ==
                             OBJ_ONEMAPPING &&
                            (object->type == OBJT_DEFAULT ||
                             object->type == OBJT_SWAP)) {
                                vm_object_collapse(object, NULL);
                                vm_object_page_remove(object, offidxstart,
                                                      offidxend, FALSE);
                                if (object->type == OBJT_SWAP) {
                                        swap_pager_freespace(object,
                                                             offidxstart,
                                                             count);
                                }
                                if (offidxend >= object->size &&
                                    offidxstart < object->size) {
                                        object->size = offidxstart;
                                }
                        }
                        vm_object_chain_release(object);
                        vm_object_drop(object);
                } else if (entry->maptype == VM_MAPTYPE_UKSMAP) {
                        pmap_remove(map->pmap, s, e);
                }

                /*
                 * Delete the entry (which may delete the object) 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, countp);
                entry = next;
        }
        lwkt_reltoken(&map->token);
        return (KERN_SUCCESS);
}

/*
 * Remove the given address range from the target map.
 * This is the exported form of vm_map_delete.
 *
 * No requirements.
 */
int
vm_map_remove(vm_map_t map, vm_offset_t start, vm_offset_t end)
{
        int result;
        int count;

        count = vm_map_entry_reserve(MAP_RESERVE_COUNT);
        vm_map_lock(map);
        VM_MAP_RANGE_CHECK(map, start, end);
        result = vm_map_delete(map, start, end, &count);
        vm_map_unlock(map);
        vm_map_entry_release(count);

        return (result);
}

/*
 * Assert that the target map allows the specified privilege on the
 * entire address region given.  The entire region must be allocated.
 *
 * The caller must specify whether the vm_map is already locked or not.
 */
boolean_t
vm_map_check_protection(vm_map_t map, vm_offset_t start, vm_offset_t end,
                        vm_prot_t protection, boolean_t have_lock)
{
        vm_map_entry_t entry;
        vm_map_entry_t tmp_entry;
        boolean_t result;

        if (have_lock == FALSE)
                vm_map_lock_read(map);

        if (!vm_map_lookup_entry(map, start, &tmp_entry)) {
                if (have_lock == FALSE)
                        vm_map_unlock_read(map);
                return (FALSE);
        }
        entry = tmp_entry;

        result = TRUE;
        while (start < end) {
                if (entry == &map->header) {
                        result = FALSE;
                        break;
                }
                /*
                 * No holes allowed!
                 */

                if (start < entry->start) {
                        result = FALSE;
                        break;
                }
                /*
                 * Check protection associated with entry.
                 */

                if ((entry->protection & protection) != protection) {
                        result = FALSE;
                        break;
                }
                /* go to next entry */

                start = entry->end;
                entry = entry->next;
        }
        if (have_lock == FALSE)
                vm_map_unlock_read(map);
        return (result);
}

/*
 * If appropriate this function shadows the original object with a new object
 * and moves the VM pages from the original object to the new object.
 * The original object will also be collapsed, if possible.
 *
 * We can only do this for normal memory objects with a single mapping, and
 * it only makes sense to do it if there are 2 or more refs on the original
 * object.  i.e. typically a memory object that has been extended into
 * multiple vm_map_entry's with non-overlapping ranges.
 *
 * This makes it easier to remove unused pages and keeps object inheritance
 * from being a negative impact on memory usage.
 *
 * On return the (possibly new) entry->object.vm_object will have an
 * additional ref on it for the caller to dispose of (usually by cloning
 * the vm_map_entry).  The additional ref had to be done in this routine
 * to avoid racing a collapse.  The object's ONEMAPPING flag will also be
 * cleared.
 *
 * The vm_map must be locked and its token held.
 */
static void
vm_map_split(vm_map_entry_t entry)
{
        /* OPTIMIZED */
        vm_object_t oobject, nobject, bobject;
        vm_offset_t s, e;
        vm_page_t m;
        vm_pindex_t offidxstart, offidxend, idx;
        vm_size_t size;
        vm_ooffset_t offset;
        int useshadowlist;

        /*
         * Optimize away object locks for vnode objects.  Important exit/exec
         * critical path.
         *
         * OBJ_ONEMAPPING doesn't apply to vnode objects but clear the flag
         * anyway.
         */
        oobject = entry->object.vm_object;
        if (oobject->type != OBJT_DEFAULT && oobject->type != OBJT_SWAP) {
                vm_object_reference_quick(oobject);
                vm_object_clear_flag(oobject, OBJ_ONEMAPPING);
                return;
        }

        /*
         * Setup.  Chain lock the original object throughout the entire
         * routine to prevent new page faults from occuring.
         *
         * XXX can madvise WILLNEED interfere with us too?
         */
        vm_object_hold(oobject);
        vm_object_chain_acquire(oobject, 0);

        /*
         * Original object cannot be split?  Might have also changed state.
         */
        if (oobject->handle == NULL || (oobject->type != OBJT_DEFAULT &&
                                        oobject->type != OBJT_SWAP)) {
                vm_object_chain_release(oobject);
                vm_object_reference_locked(oobject);
                vm_object_clear_flag(oobject, OBJ_ONEMAPPING);
                vm_object_drop(oobject);
                return;
        }

        /*
         * Collapse original object with its backing store as an
         * optimization to reduce chain lengths when possible.
         *
         * If ref_count <= 1 there aren't other non-overlapping vm_map_entry's
         * for oobject, so there's no point collapsing it.
         *
         * Then re-check whether the object can be split.
         */
        vm_object_collapse(oobject, NULL);

        if (oobject->ref_count <= 1 ||
            (oobject->type != OBJT_DEFAULT && oobject->type != OBJT_SWAP) ||
            (oobject->flags & (OBJ_NOSPLIT|OBJ_ONEMAPPING)) != OBJ_ONEMAPPING) {
                vm_object_chain_release(oobject);
                vm_object_reference_locked(oobject);
                vm_object_clear_flag(oobject, OBJ_ONEMAPPING);
                vm_object_drop(oobject);
                return;
        }

        /*
         * Acquire the chain lock on the backing object.
         *
         * Give bobject an additional ref count for when it will be shadowed
         * by nobject.
         */
        useshadowlist = 0;
        if ((bobject = oobject->backing_object) != NULL) {
                if (bobject->type != OBJT_VNODE) {
                        useshadowlist = 1;
                        vm_object_hold(bobject);
                        vm_object_chain_wait(bobject, 0);
                        vm_object_reference_locked(bobject);
                        vm_object_chain_acquire(bobject, 0);
                        KKASSERT(bobject->backing_object == bobject);
                        KKASSERT((bobject->flags & OBJ_DEAD) == 0);
                } else {
                        vm_object_reference_quick(bobject);
                }
        }

        /*
         * Calculate the object page range and allocate the new object.
         */
        offset = entry->offset;
        s = entry->start;
        e = entry->end;

        offidxstart = OFF_TO_IDX(offset);
        offidxend = offidxstart + OFF_TO_IDX(e - s);
        size = offidxend - offidxstart;

        switch(oobject->type) {
        case OBJT_DEFAULT:
                nobject = default_pager_alloc(NULL, IDX_TO_OFF(size),
                                              VM_PROT_ALL, 0);
                break;
        case OBJT_SWAP:
                nobject = swap_pager_alloc(NULL, IDX_TO_OFF(size),
                                           VM_PROT_ALL, 0);
                break;
        default:
                /* not reached */
                nobject = NULL;
                KKASSERT(0);
        }

        if (nobject == NULL) {
                if (bobject) {
                        if (useshadowlist) {
                                vm_object_chain_release(bobject);
                                vm_object_deallocate(bobject);
                                vm_object_drop(bobject);
                        } else {
                                vm_object_deallocate(bobject);
                        }
                }
                vm_object_chain_release(oobject);
                vm_object_reference_locked(oobject);
                vm_object_clear_flag(oobject, OBJ_ONEMAPPING);
                vm_object_drop(oobject);
                return;
        }

        /*
         * The new object will replace entry->object.vm_object so it needs
         * a second reference (the caller expects an additional ref).
         */
        vm_object_hold(nobject);
        vm_object_reference_locked(nobject);
        vm_object_chain_acquire(nobject, 0);

        /*
         * nobject shadows bobject (oobject already shadows bobject).
         */
        if (bobject) {
                nobject->backing_object_offset =
                    oobject->backing_object_offset + IDX_TO_OFF(offidxstart);
                nobject->backing_object = bobject;
                if (useshadowlist) {
                        bobject->shadow_count++;
                        bobject->generation++;
                        LIST_INSERT_HEAD(&bobject->shadow_head,
                                         nobject, shadow_list);
                        vm_object_clear_flag(bobject, OBJ_ONEMAPPING); /*XXX*/
                        vm_object_chain_release(bobject);
                        vm_object_drop(bobject);
                        vm_object_set_flag(nobject, OBJ_ONSHADOW);
                }
        }

        /*
         * Move the VM pages from oobject to nobject
         */
        for (idx = 0; idx < size; idx++) {
                vm_page_t m;

                m = vm_page_lookup_busy_wait(oobject, offidxstart + idx,
                                             TRUE, "vmpg");
                if (m == NULL)
                        continue;

                /*
                 * We must wait for pending I/O to complete before we can
                 * rename the page.
                 *
                 * We do not have to VM_PROT_NONE the page as mappings should
                 * not be changed by this operation.
                 *
                 * NOTE: The act of renaming a page updates chaingen for both
                 *       objects.
                 */
                vm_page_rename(m, nobject, idx);
                /* page automatically made dirty by rename and cache handled */
                /* page remains busy */
        }

        if (oobject->type == OBJT_SWAP) {
                vm_object_pip_add(oobject, 1);
                /*
                 * copy oobject pages into nobject and destroy unneeded
                 * pages in shadow object.
                 */
                swap_pager_copy(oobject, nobject, offidxstart, 0);
                vm_object_pip_wakeup(oobject);
        }

        /*
         * Wakeup the pages we played with.  No spl protection is needed
         * for a simple wakeup.
         */
        for (idx = 0; idx < size; idx++) {
                m = vm_page_lookup(nobject, idx);
                if (m) {
                        KKASSERT(m->flags & PG_BUSY);
                        vm_page_wakeup(m);
                }
        }
        entry->object.vm_object = nobject;
        entry->offset = 0LL;

        /*
         * Cleanup
         *
         * NOTE: There is no need to remove OBJ_ONEMAPPING from oobject, the
         *       related pages were moved and are no longer applicable to the
         *       original object.
         *
         * NOTE: Deallocate oobject (due to its entry->object.vm_object being
         *       replaced by nobject).
         */
        vm_object_chain_release(nobject);
        vm_object_drop(nobject);
        if (bobject && useshadowlist) {
                vm_object_chain_release(bobject);
                vm_object_drop(bobject);
        }
        vm_object_chain_release(oobject);
        /*vm_object_clear_flag(oobject, OBJ_ONEMAPPING);*/
        vm_object_deallocate_locked(oobject);
        vm_object_drop(oobject);
}

/*
 * Copies the contents of the source entry to the destination
 * entry.  The entries *must* be aligned properly.
 *
 * The vm_maps must be exclusively locked.
 * The vm_map's token must be held.
 *
 * Because the maps are locked no faults can be in progress during the
 * operation.
 */
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_object_t src_object;

        if (dst_entry->maptype == VM_MAPTYPE_SUBMAP ||
            dst_entry->maptype == VM_MAPTYPE_UKSMAP)
                return;
        if (src_entry->maptype == VM_MAPTYPE_SUBMAP ||
            src_entry->maptype == VM_MAPTYPE_UKSMAP)
                return;

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

                /*
                 * Make a copy of the object.
                 *
                 * The object must be locked prior to checking the object type
                 * and for the call to vm_object_collapse() and vm_map_split().
                 * We cannot use *_hold() here because the split code will
                 * probably try to destroy the object.  The lock is a pool
                 * token and doesn't care.
                 *
                 * We must bump src_map->timestamp when setting
                 * MAP_ENTRY_NEEDS_COPY to force any concurrent fault
                 * to retry, otherwise the concurrent fault might improperly
                 * install a RW pte when its supposed to be a RO(COW) pte.
                 * This race can occur because a vnode-backed fault may have
                 * to temporarily release the map lock.
                 */
                if (src_entry->object.vm_object != NULL) {
                        vm_map_split(src_entry);
                        src_object = src_entry->object.vm_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;
                        ++src_map->timestamp;
                } else {
                        dst_entry->object.vm_object = NULL;
                        dst_entry->offset = 0;
                }

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

/*
 * 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.
 *
 * The source map must not be locked.
 * No requirements.
 */
static void vmspace_fork_normal_entry(vm_map_t old_map, vm_map_t new_map,
                          vm_map_entry_t old_entry, int *countp);
static void vmspace_fork_uksmap_entry(vm_map_t old_map, vm_map_t new_map,
                          vm_map_entry_t old_entry, int *countp);

struct vmspace *
vmspace_fork(struct vmspace *vm1)
{
        struct vmspace *vm2;
        vm_map_t old_map = &vm1->vm_map;
        vm_map_t new_map;
        vm_map_entry_t old_entry;
        int count;

        lwkt_gettoken(&vm1->vm_map.token);
        vm_map_lock(old_map);

        vm2 = vmspace_alloc(old_map->min_offset, old_map->max_offset);
        lwkt_gettoken(&vm2->vm_map.token);
        bcopy(&vm1->vm_startcopy, &vm2->vm_startcopy,
            (caddr_t)&vm1->vm_endcopy - (caddr_t)&vm1->vm_startcopy);
        new_map = &vm2->vm_map; /* XXX */
        new_map->timestamp = 1;

        vm_map_lock(new_map);

        count = 0;
        old_entry = old_map->header.next;
        while (old_entry != &old_map->header) {
                ++count;
                old_entry = old_entry->next;
        }

        count = vm_map_entry_reserve(count + MAP_RESERVE_COUNT);

        old_entry = old_map->header.next;
        while (old_entry != &old_map->header) {
                switch(old_entry->maptype) {
                case VM_MAPTYPE_SUBMAP:
                        panic("vm_map_fork: encountered a submap");
                        break;
                case VM_MAPTYPE_UKSMAP:
                        vmspace_fork_uksmap_entry(old_map, new_map,
                                                  old_entry, &count);
                        break;
                case VM_MAPTYPE_NORMAL:
                case VM_MAPTYPE_VPAGETABLE:
                        vmspace_fork_normal_entry(old_map, new_map,
                                                  old_entry, &count);
                        break;
                }
                old_entry = old_entry->next;
        }

        new_map->size = old_map->size;
        vm_map_unlock(old_map);
        vm_map_unlock(new_map);
        vm_map_entry_release(count);

        lwkt_reltoken(&vm2->vm_map.token);
        lwkt_reltoken(&vm1->vm_map.token);

        return (vm2);
}

static
void
vmspace_fork_normal_entry(vm_map_t old_map, vm_map_t new_map,
                          vm_map_entry_t old_entry, int *countp)
{
        vm_map_entry_t new_entry;
        vm_object_t object;

        switch (old_entry->inheritance) {
        case VM_INHERIT_NONE:
                break;
        case VM_INHERIT_SHARE:
                /*
                 * Clone the entry, creating the shared object if
                 * necessary.
                 */
                if (old_entry->object.vm_object == NULL)
                        vm_map_entry_allocate_object(old_entry);

                if (old_entry->eflags & MAP_ENTRY_NEEDS_COPY) {
                        /*
                         * Shadow a map_entry which needs a copy,
                         * replacing its object with a new object
                         * that points to the old one.  Ask the
                         * shadow code to automatically add an
                         * additional ref.  We can't do it afterwords
                         * because we might race a collapse.  The call
                         * to vm_map_entry_shadow() will also clear
                         * OBJ_ONEMAPPING.
                         */
                        vm_map_entry_shadow(old_entry, 1);
                } else if (old_entry->object.vm_object) {
                        /*
                         * We will make a shared copy of the object,
                         * and must clear OBJ_ONEMAPPING.
                         *
                         * Optimize vnode objects.  OBJ_ONEMAPPING
                         * is non-applicable but clear it anyway,
                         * and its terminal so we don'th ave to deal
                         * with chains.  Reduces SMP conflicts.
                         *
                         * XXX assert that object.vm_object != NULL
                         *     since we allocate it above.
                         */
                        object = old_entry->object.vm_object;
                        if (object->type == OBJT_VNODE) {
                                vm_object_reference_quick(object);
                                vm_object_clear_flag(object,
                                                     OBJ_ONEMAPPING);
                        } else {
                                vm_object_hold(object);
                                vm_object_chain_wait(object, 0);
                                vm_object_reference_locked(object);
                                vm_object_clear_flag(object,
                                                     OBJ_ONEMAPPING);
                                vm_object_drop(object);
                        }
                }

                /*
                 * Clone the entry.  We've already bumped the ref on
                 * any vm_object.
                 */
                new_entry = vm_map_entry_create(new_map, countp);
                *new_entry = *old_entry;
                new_entry->eflags &= ~MAP_ENTRY_USER_WIRED;
                new_entry->wired_count = 0;

                /*
                 * Insert the entry into the new map -- we know we're
                 * inserting at the end of the new map.
                 */

                vm_map_entry_link(new_map, new_map->header.prev,
                                  new_entry);

                /*
                 * 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, countp);
                *new_entry = *old_entry;
                new_entry->eflags &= ~MAP_ENTRY_USER_WIRED;
                new_entry->wired_count = 0;
                new_entry->object.vm_object = NULL;
                vm_map_entry_link(new_map, new_map->header.prev,
                                  new_entry);
                vm_map_copy_entry(old_map, new_map, old_entry,
                                  new_entry);
                break;
        }
}

/*
 * When forking user-kernel shared maps, the map might change in the
 * child so do not try to copy the underlying pmap entries.
 */
static
void
vmspace_fork_uksmap_entry(vm_map_t old_map, vm_map_t new_map,
                          vm_map_entry_t old_entry, int *countp)
{
        vm_map_entry_t new_entry;

        new_entry = vm_map_entry_create(new_map, countp);
        *new_entry = *old_entry;
        new_entry->eflags &= ~MAP_ENTRY_USER_WIRED;
        new_entry->wired_count = 0;
        vm_map_entry_link(new_map, new_map->header.prev,
                          new_entry);
}

/*
 * Create an auto-grow stack entry
 *
 * No requirements.
 */
int
vm_map_stack (vm_map_t map, vm_offset_t addrbos, vm_size_t max_ssize,
              int flags, vm_prot_t prot, vm_prot_t max, int cow)
{
        vm_map_entry_t  prev_entry;
        vm_map_entry_t  new_stack_entry;
        vm_size_t       init_ssize;
        int             rv;
        int             count;
        vm_offset_t     tmpaddr;

        cow |= MAP_IS_STACK;

        if (max_ssize < sgrowsiz)
                init_ssize = max_ssize;
        else
                init_ssize = sgrowsiz;

        count = vm_map_entry_reserve(MAP_RESERVE_COUNT);
        vm_map_lock(map);

        /*
         * Find space for the mapping
         */
        if ((flags & (MAP_FIXED | MAP_TRYFIXED)) == 0) {
                if (vm_map_findspace(map, addrbos, max_ssize, 1,
                                     flags, &tmpaddr)) {
                        vm_map_unlock(map);
                        vm_map_entry_release(count);
                        return (KERN_NO_SPACE);
                }
                addrbos = tmpaddr;
        }

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

#if 0
        /* XXX already handled by kern_mmap() */
        /* If we would blow our VMEM resource limit, no go */
        if (map->size + init_ssize >
            curproc->p_rlimit[RLIMIT_VMEM].rlim_cur) {
                vm_map_unlock(map);
                vm_map_entry_release(count);
                return (KERN_NO_SPACE);
        }
#endif

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

        /*
         * We initially map a stack of only init_ssize.  We will
         * grow as needed later.  Since this is to be a grow 
         * down stack, we map at the top of the range.
         *
         * 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.
         */
        rv = vm_map_insert(map, &count, NULL, NULL,
                           0, addrbos + max_ssize - init_ssize,
                           addrbos + max_ssize,
                           VM_MAPTYPE_NORMAL,
                           prot, max, cow);

        /* Now set the avail_ssize amount */
        if (rv == KERN_SUCCESS) {
                if (prev_entry != &map->header)
                        vm_map_clip_end(map, prev_entry, addrbos + max_ssize - init_ssize, &count);
                new_stack_entry = prev_entry->next;
                if (new_stack_entry->end   != addrbos + max_ssize ||
                    new_stack_entry->start != addrbos + max_ssize - init_ssize)
                        panic ("Bad entry start/end for new stack entry");
                else 
                        new_stack_entry->aux.avail_ssize = max_ssize - init_ssize;
        }

        vm_map_unlock(map);
        vm_map_entry_release(count);
        return (rv);
}

/*
 * Attempts to grow a vm stack entry.  Returns KERN_SUCCESS if the
 * desired address is already mapped, or if we successfully grow
 * the stack.  Also returns KERN_SUCCESS if addr is outside the
 * stack range (this is strange, but preserves compatibility with
 * the grow function in vm_machdep.c).
 *
 * No requirements.
 */
int
vm_map_growstack (struct proc *p, vm_offset_t addr)
{
        vm_map_entry_t prev_entry;
        vm_map_entry_t stack_entry;
        vm_map_entry_t new_stack_entry;
        struct vmspace *vm = p->p_vmspace;
        vm_map_t map = &vm->vm_map;
        vm_offset_t    end;
        int grow_amount;
        int rv = KERN_SUCCESS;
        int is_procstack;
        int use_read_lock = 1;
        int count;

        count = vm_map_entry_reserve(MAP_RESERVE_COUNT);
Retry:
        if (use_read_lock)
                vm_map_lock_read(map);
        else
                vm_map_lock(map);

        /* If addr is already in the entry range, no need to grow.*/
        if (vm_map_lookup_entry(map, addr, &prev_entry))
                goto done;

        if ((stack_entry = prev_entry->next) == &map->header)
                goto done;
        if (prev_entry == &map->header) 
                end = stack_entry->start - stack_entry->aux.avail_ssize;
        else
                end = prev_entry->end;

        /*
         * This next test mimics the old grow function in vm_machdep.c.
         * It really doesn't quite make sense, but we do it anyway
         * for compatibility.
         *
         * If not growable stack, return success.  This signals the
         * caller to proceed as he would normally with normal vm.
         */
        if (stack_entry->aux.avail_ssize < 1 ||
            addr >= stack_entry->start ||
            addr <  stack_entry->start - stack_entry->aux.avail_ssize) {
                goto done;
        } 
        
        /* Find the minimum grow amount */
        grow_amount = roundup (stack_entry->start - addr, PAGE_SIZE);
        if (grow_amount > stack_entry->aux.avail_ssize) {
                rv = KERN_NO_SPACE;
                goto done;
        }

        /*
         * If there is no longer enough space between the entries
         * nogo, and adjust the available space.  Note: this 
         * should only happen if the user has mapped into the
         * stack area after the stack was created, and is
         * probably an error.
         *
         * This also effectively destroys any guard page the user
         * might have intended by limiting the stack size.
         */
        if (grow_amount > stack_entry->start - end) {
                if (use_read_lock && vm_map_lock_upgrade(map)) {
                        /* lost lock */
                        use_read_lock = 0;
                        goto Retry;
                }
                use_read_lock = 0;
                stack_entry->aux.avail_ssize = stack_entry->start - end;
                rv = KERN_NO_SPACE;
                goto done;
        }

        is_procstack = addr >= (vm_offset_t)vm->vm_maxsaddr;

        /* If this is the main process stack, see if we're over the 
         * stack limit.
         */
        if (is_procstack && (ctob(vm->vm_ssize) + grow_amount >
                             p->p_rlimit[RLIMIT_STACK].rlim_cur)) {
                rv = KERN_NO_SPACE;
                goto done;
        }

        /* Round up the grow amount modulo SGROWSIZ */
        grow_amount = roundup (grow_amount, sgrowsiz);
        if (grow_amount > stack_entry->aux.avail_ssize) {
                grow_amount = stack_entry->aux.avail_ssize;
        }
        if (is_procstack && (ctob(vm->vm_ssize) + grow_amount >
                             p->p_rlimit[RLIMIT_STACK].rlim_cur)) {
                grow_amount = p->p_rlimit[RLIMIT_STACK].rlim_cur -
                              ctob(vm->vm_ssize);
        }

        /* If we would blow our VMEM resource limit, no go */
        if (map->size + grow_amount > p->p_rlimit[RLIMIT_VMEM].rlim_cur) {
                rv = KERN_NO_SPACE;
                goto done;
        }

        if (use_read_lock && vm_map_lock_upgrade(map)) {
                /* lost lock */
                use_read_lock = 0;
                goto Retry;
        }
        use_read_lock = 0;

        /* Get the preliminary new entry start value */
        addr = stack_entry->start - grow_amount;

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

        rv = vm_map_insert(map, &count, NULL, NULL,
                           0, addr, stack_entry->start,
                           VM_MAPTYPE_NORMAL,
                           VM_PROT_ALL, VM_PROT_ALL, 0);

        /* Adjust the available stack space by the amount we grew. */
        if (rv == KERN_SUCCESS) {
                if (prev_entry != &map->header)
                        vm_map_clip_end(map, prev_entry, addr, &count);
                new_stack_entry = prev_entry->next;
                if (new_stack_entry->end   != stack_entry->start  ||
                    new_stack_entry->start != addr)
                        panic ("Bad stack grow start/end in new stack entry");
                else {
                        new_stack_entry->aux.avail_ssize =
                                stack_entry->aux.avail_ssize -
                                (new_stack_entry->end - new_stack_entry->start);
                        if (is_procstack)
                                vm->vm_ssize += btoc(new_stack_entry->end -
                                                     new_stack_entry->start);
                }

                if (map->flags & MAP_WIREFUTURE)
                        vm_map_unwire(map, new_stack_entry->start,
                                      new_stack_entry->end, FALSE);
        }

done:
        if (use_read_lock)
                vm_map_unlock_read(map);
        else
                vm_map_unlock(map);
        vm_map_entry_release(count);
        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.
 *
 * No requirements.
 */
void
vmspace_exec(struct proc *p, struct vmspace *vmcopy) 
{
        struct vmspace *oldvmspace = p->p_vmspace;
        struct vmspace *newvmspace;
        vm_map_t map = &p->p_vmspace->vm_map;

        /*
         * If we are execing a resident vmspace we fork it, otherwise
         * we create a new vmspace.  Note that exitingcnt is not
         * copied to the new vmspace.
         */
        lwkt_gettoken(&oldvmspace->vm_map.token);
        if (vmcopy)  {
                newvmspace = vmspace_fork(vmcopy);
                lwkt_gettoken(&newvmspace->vm_map.token);
        } else {
                newvmspace = vmspace_alloc(map->min_offset, map->max_offset);
                lwkt_gettoken(&newvmspace->vm_map.token);
                bcopy(&oldvmspace->vm_startcopy, &newvmspace->vm_startcopy,
                      (caddr_t)&oldvmspace->vm_endcopy -
                       (caddr_t)&oldvmspace->vm_startcopy);
        }

        /*
         * Finish initializing the vmspace before assigning it
         * to the process.  The vmspace will become the current vmspace
         * if p == curproc.
         */
        pmap_pinit2(vmspace_pmap(newvmspace));
        pmap_replacevm(p, newvmspace, 0);
        lwkt_reltoken(&newvmspace->vm_map.token);
        lwkt_reltoken(&oldvmspace->vm_map.token);
        vmspace_rel(oldvmspace);
}

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

        lwkt_gettoken(&oldvmspace->vm_map.token);
        if (vmspace_getrefs(oldvmspace) == 1) {
                lwkt_reltoken(&oldvmspace->vm_map.token);
                return;
        }
        newvmspace = vmspace_fork(oldvmspace);
        lwkt_gettoken(&newvmspace->vm_map.token);
        pmap_pinit2(vmspace_pmap(newvmspace));
        pmap_replacevm(p, newvmspace, 0);
        lwkt_reltoken(&newvmspace->vm_map.token);
        lwkt_reltoken(&oldvmspace->vm_map.token);
        vmspace_rel(oldvmspace);
}

/*
 * vm_map_hint: return the beginning of the best area suitable for
 * creating a new mapping with "prot" protection.
 *
 * No requirements.
 */
vm_offset_t
vm_map_hint(struct proc *p, vm_offset_t addr, vm_prot_t prot)
{
        struct vmspace *vms = p->p_vmspace;

        if (!randomize_mmap || addr != 0) {
                /*
                 * Set a reasonable start point for the hint if it was
                 * not specified or if it falls within the heap space.
                 * Hinted mmap()s do not allocate out of the heap space.
                 */
                if (addr == 0 ||
                    (addr >= round_page((vm_offset_t)vms->vm_taddr) &&
                     addr < round_page((vm_offset_t)vms->vm_daddr + maxdsiz))) {
                        addr = round_page((vm_offset_t)vms->vm_daddr + maxdsiz);
                }

                return addr;
        }

#ifdef notyet
#ifdef __i386__
        /*
         * If executable skip first two pages, otherwise start
         * after data + heap region.
         */
        if ((prot & VM_PROT_EXECUTE) &&
            ((vm_offset_t)vms->vm_daddr >= I386_MAX_EXE_ADDR)) {
                addr = (PAGE_SIZE * 2) +
                    (karc4random() & (I386_MAX_EXE_ADDR / 2 - 1));
                return (round_page(addr));
        }
#endif /* __i386__ */
#endif /* notyet */

        addr = (vm_offset_t)vms->vm_daddr + MAXDSIZ;
        addr += karc4random() & (MIN((256 * 1024 * 1024), MAXDSIZ) - 1);

        return (round_page(addr));
}

/*
 * 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.
 *
 * No requirements.
 */
int
vm_map_lookup(vm_map_t *var_map,                /* IN/OUT */
              vm_offset_t vaddr,
              vm_prot_t fault_typea,
              vm_map_entry_t *out_entry,        /* OUT */
              vm_object_t *object,              /* OUT */
              vm_pindex_t *pindex,              /* OUT */
              vm_prot_t *out_prot,              /* OUT */
              boolean_t *wired)                 /* OUT */
{
        vm_map_entry_t entry;
        vm_map_t map = *var_map;
        vm_prot_t prot;
        vm_prot_t fault_type = fault_typea;
        int use_read_lock = 1;
        int rv = KERN_SUCCESS;

RetryLookup:
        if (use_read_lock)
                vm_map_lock_read(map);
        else
                vm_map_lock(map);

        /*
         * If the map has an interesting hint, try it before calling full
         * blown lookup routine.
         */
        entry = map->hint;
        cpu_ccfence();
        *out_entry = entry;
        *object = NULL;

        if ((entry == &map->header) ||
            (vaddr < entry->start) || (vaddr >= entry->end)) {
                vm_map_entry_t tmp_entry;

                /*
                 * Entry was either not a valid hint, or the vaddr was not
                 * contained in the entry, so do a full lookup.
                 */
                if (!vm_map_lookup_entry(map, vaddr, &tmp_entry)) {
                        rv = KERN_INVALID_ADDRESS;
                        goto done;
                }

                entry = tmp_entry;
                *out_entry = entry;
        }
        
        /*
         * Handle submaps.
         */
        if (entry->maptype == VM_MAPTYPE_SUBMAP) {
                vm_map_t old_map = map;

                *var_map = map = entry->object.sub_map;
                if (use_read_lock)
                        vm_map_unlock_read(old_map);
                else
                        vm_map_unlock(old_map);
                use_read_lock = 1;
                goto RetryLookup;
        }

        /*
         * Check whether this task is allowed to have this page.
         * Note the special case for MAP_ENTRY_COW
         * pages with an override.  This is to implement a forced
         * COW for debuggers.
         */

        if (fault_type & VM_PROT_OVERRIDE_WRITE)
                prot = entry->max_protection;
        else
                prot = entry->protection;

        fault_type &= (VM_PROT_READ|VM_PROT_WRITE|VM_PROT_EXECUTE);
        if ((fault_type & prot) != fault_type) {
                rv = KERN_PROTECTION_FAILURE;
                goto done;
        }

        if ((entry->eflags & MAP_ENTRY_USER_WIRED) &&
            (entry->eflags & MAP_ENTRY_COW) &&
            (fault_type & VM_PROT_WRITE) &&
            (fault_typea & VM_PROT_OVERRIDE_WRITE) == 0) {
                rv = KERN_PROTECTION_FAILURE;
                goto done;
        }

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

        /*
         * Virtual page tables may need to update the accessed (A) bit
         * in a page table entry.  Upgrade the fault to a write fault for
         * that case if the map will support it.  If the map does not support
         * it the page table entry simply will not be updated.
         */
        if (entry->maptype == VM_MAPTYPE_VPAGETABLE) {
                if (prot & VM_PROT_WRITE)
                        fault_type |= VM_PROT_WRITE;
        }

        if (curthread->td_lwp && curthread->td_lwp->lwp_vmspace &&
            pmap_emulate_ad_bits(&curthread->td_lwp->lwp_vmspace->vm_pmap)) {
                if ((prot & VM_PROT_WRITE) == 0)
                        fault_type |= VM_PROT_WRITE;
        }

        /*
         * Only NORMAL and VPAGETABLE maps are object-based.  UKSMAPs are not.
         */
        if (entry->maptype != VM_MAPTYPE_NORMAL &&
            entry->maptype != VM_MAPTYPE_VPAGETABLE) {
                *object = NULL;
                goto skip;
        }

        /*
         * 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) {
                        /*
                         * 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 (use_read_lock && vm_map_lock_upgrade(map)) {
                                /* lost lock */
                                use_read_lock = 0;
                                goto RetryLookup;
                        }
                        use_read_lock = 0;

                        vm_map_entry_shadow(entry, 0);
                } 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 (use_read_lock && vm_map_lock_upgrade(map))  {
                        /* lost lock */
                        use_read_lock = 0;
                        goto RetryLookup;
                }
                use_read_lock = 0;
                vm_map_entry_allocate_object(entry);
        }

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

skip:
        *pindex = OFF_TO_IDX((vaddr - entry->start) + entry->offset);

        /*
         * Return whether this is the only map sharing this data.  On
         * success we return with a read lock held on the map.  On failure
         * we return with the map unlocked.
         */
        *out_prot = prot;
done:
        if (rv == KERN_SUCCESS) {
                if (use_read_lock == 0)
                        vm_map_lock_downgrade(map);
        } else if (use_read_lock) {
                vm_map_unlock_read(map);
        } else {
                vm_map_unlock(map);
        }
        return (rv);
}

/*
 * Releases locks acquired by a vm_map_lookup()
 * (according to the handle returned by that lookup).
 *
 * No other requirements.
 */
void
vm_map_lookup_done(vm_map_t map, vm_map_entry_t entry, int count)
{
        /*
         * Unlock the main-level map
         */
        vm_map_unlock_read(map);
        if (count)
                vm_map_entry_release(count);
}

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

#include <ddb/ddb.h>

/*
 * Debugging only
 */
DB_SHOW_COMMAND(map, vm_map_print)
{
        static int nlines;
        /* XXX convert args. */
        vm_map_t map = (vm_map_t)addr;
        boolean_t full = have_addr;

        vm_map_entry_t entry;

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

        if (!full && db_indent)
                return;

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

                        db_iprintf(" prot=%x/%x/%s",
                            entry->protection,
                            entry->max_protection,
                            inheritance_name[(int)(unsigned char)entry->inheritance]);
                        if (entry->wired_count != 0)
                                db_printf(", wired");
                }
                switch(entry->maptype) {
                case VM_MAPTYPE_SUBMAP:
                        /* XXX no %qd in kernel.  Truncate entry->offset. */
                        db_printf(", share=%p, offset=0x%lx\n",
                            (void *)entry->object.sub_map,
                            (long)entry->offset);
                        nlines++;
                        if ((entry->prev == &map->header) ||
                            (entry->prev->object.sub_map !=
                                entry->object.sub_map)) {
                                db_indent += 2;
                                vm_map_print((db_expr_t)(intptr_t)
                                             entry->object.sub_map,
                                             full, 0, NULL);
                                db_indent -= 2;
                        }
                        break;
                case VM_MAPTYPE_NORMAL:
                case VM_MAPTYPE_VPAGETABLE:
                        /* XXX no %qd in kernel.  Truncate entry->offset. */
                        db_printf(", object=%p, offset=0x%lx",
                            (void *)entry->object.vm_object,
                            (long)entry->offset);
                        if (entry->eflags & MAP_ENTRY_COW)
                                db_printf(", copy (%s)",
                                    (entry->eflags & MAP_ENTRY_NEEDS_COPY) ? "needed" : "done");
                        db_printf("\n");
                        nlines++;

                        if ((entry->prev == &map->header) ||
                            (entry->prev->object.vm_object !=
                                entry->object.vm_object)) {
                                db_indent += 2;
                                vm_object_print((db_expr_t)(intptr_t)
                                                entry->object.vm_object,
                                                full, 0, NULL);
                                nlines += 4;
                                db_indent -= 2;
                        }
                        break;
                case VM_MAPTYPE_UKSMAP:
                        db_printf(", uksmap=%p, offset=0x%lx",
                            (void *)entry->object.uksmap,
                            (long)entry->offset);
                        if (entry->eflags & MAP_ENTRY_COW)
                                db_printf(", copy (%s)",
                                    (entry->eflags & MAP_ENTRY_NEEDS_COPY) ? "needed" : "done");
                        db_printf("\n");
                        nlines++;
                        break;
                default:
                        break;
                }
        }
        db_indent -= 2;
        if (db_indent == 0)
                nlines = 0;
}

/*
 * Debugging only
 */
DB_SHOW_COMMAND(procvm, procvm)
{
        struct proc *p;

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

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

        vm_map_print((db_expr_t)(intptr_t)&p->p_vmspace->vm_map, 1, 0, NULL);
}

#endif /* DDB */