HAMMER 60I/Many: Mirroring

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

/*
 * Copyright (c) 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * The Mach Operating System project at Carnegie-Mellon University.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      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 $
 * $DragonFly: src/sys/vm/vm_map.c,v 1.56 2007/04/29 18:25:41 dillon Exp $
 */

/*
 *      Virtual memory mapping module.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/proc.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 <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/sysref2.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 single hint is used to speed up lookups.
 *
 *      Since portions of maps are specified by start/end addresses,
 *      which may not align with existing map entries, all
 *      routines merely "clip" entries to these start/end values.
 *      [That is, an entry is split into two, bordering at a
 *      start or end value.]  Note that these clippings may not
 *      always be necessary (as the two resulting entries are then
 *      not changed); however, the clipping is done for convenience.
 *
 *      As mentioned above, virtual copy operations are performed
 *      by copying VM object references from one map to
 *      another, and then marking both regions as copy-on-write.
 */

static void vmspace_terminate(struct vmspace *vm);
static void vmspace_dtor(void *obj, void *private);

MALLOC_DEFINE(M_VMSPACE, "vmspace", "vmspace objcache backingstore");

struct sysref_class vmspace_sysref_class = {
        .name =         "vmspace",
        .mtype =        M_VMSPACE,
        .proto =        SYSREF_PROTO_VMSPACE,
        .offset =       offsetof(struct vmspace, vm_sysref),
        .objsize =      sizeof(struct vmspace),
        .mag_capacity = 32,
        .flags = SRC_MANAGEDINIT,
        .dtor = vmspace_dtor,
        .ops = {
                .terminate = (sysref_terminate_func_t)vmspace_terminate
        }
};

#define VMEPERCPU       2

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[MAXCPU][VMEPERCPU];
static struct vm_map map_init[MAX_KMAP];

static void vm_map_entry_shadow(vm_map_entry_t entry);
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_split (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);

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

/*
 *      vm_init2 - called prior to any vmspace allocations
 */
void
vm_init2(void) 
{
        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();
}


/*
 * Red black tree functions
 */
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);
}

/*
 * 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.
 *
 * The structure is not considered activated until we call sysref_activate().
 */
struct vmspace *
vmspace_alloc(vm_offset_t min, vm_offset_t max)
{
        struct vmspace *vm;

        vm = sysref_alloc(&vmspace_sysref_class);
        bzero(&vm->vm_startcopy,
              (char *)&vm->vm_endcopy - (char *)&vm->vm_startcopy);
        vm_map_init(&vm->vm_map, min, max, NULL);
        pmap_pinit(vmspace_pmap(vm));           /* (some fields reused) */
        vm->vm_map.pmap = vmspace_pmap(vm);             /* XXX */
        vm->vm_shm = NULL;
        vm->vm_exitingcnt = 0;
        cpu_vmspace_alloc(vm);
        sysref_activate(&vm->vm_sysref);
        return (vm);
}

/*
 * dtor function - Some elements of the pmap are retained in the
 * free-cached vmspaces to improve performance.  We have to clean them up
 * here before returning the vmspace to the memory pool.
 */
static void
vmspace_dtor(void *obj, void *private)
{
        struct vmspace *vm = obj;

        pmap_puninit(vmspace_pmap(vm));
}

/*
 * Called in two cases: 
 *
 * (1) When the last sysref is dropped, but exitingcnt might still be
 *     non-zero.
 *
 * (2) When there are no sysrefs (i.e. refcnt is negative) left and the
 *     exitingcnt becomes zero
 *
 * sysref will not scrap the object until we call sysref_put() once more
 * after the last ref has been dropped.
 */
static void
vmspace_terminate(struct vmspace *vm)
{
        int count;

        /*
         * If exitingcnt is non-zero we can't get rid of the entire vmspace
         * yet, but we can scrap user memory.
         */
        if (vm->vm_exitingcnt) {
                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);

                return;
        }
        cpu_vmspace_free(vm);

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

        KKASSERT(vm->vm_upcalls == NULL);

        /*
         * 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);

        pmap_release(vmspace_pmap(vm));
        sysref_put(&vm->vm_sysref);
}

/*
 * This is called in the wait*() handling code.  The vmspace can be terminated
 * after the last wait is finished using it.
 */
void
vmspace_exitfree(struct proc *p)
{
        struct vmspace *vm;

        vm = p->p_vmspace;
        p->p_vmspace = NULL;

        if (--vm->vm_exitingcnt == 0 && sysref_isinactive(&vm->vm_sysref))
                vmspace_terminate(vm);
}

/*
 * vmspace_swap_count() - count the approximate swap useage in pages for a
 *                        vmspace.
 *
 *      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.
 */
int
vmspace_swap_count(struct vmspace *vmspace)
{
        vm_map_t map = &vmspace->vm_map;
        vm_map_entry_t cur;
        vm_object_t object;
        int count = 0;
        int n;

        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_SWAP)
                                break;
                        n = (cur->end - cur->start) / PAGE_SIZE;
                        if (object->un_pager.swp.swp_bcount) {
                                count += object->un_pager.swp.swp_bcount *
                                    SWAP_META_PAGES * n / object->size + 1;
                        }
                        break;
                default:
                        break;
                }
        }
        return(count);
}


/*
 *      vm_map_create:
 *
 *      Creates and returns a new empty VM map with
 *      the given physical map structure, and having
 *      the given lower and upper address bounds.
 */
vm_map_t
vm_map_create(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 set elsewhere.
 */
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->infork = 0;
        map->min_offset = min;
        map->max_offset = max;
        map->pmap = pmap;
        map->first_free = &map->header;
        map->hint = &map->header;
        map->timestamp = 0;
        lockinit(&map->lock, "thrd_sleep", 0, 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.
 */
static
void
vm_map_entry_shadow(vm_map_entry_t entry)
{
        if (entry->maptype == VM_MAPTYPE_VPAGETABLE) {
                vm_object_shadow(&entry->object.vm_object, &entry->offset,
                                 0x7FFFFFFF);   /* XXX */
        } else {
                vm_object_shadow(&entry->object.vm_object, &entry->offset,
                                 atop(entry->end - entry->start));
        }
        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.
 */
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;
}

/*
 *      vm_map_entry_reserve_cpu_init:
 *
 *      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().
 *
 *      May be called for a gd other then mycpu, but may only be called
 *      during early boot.
 */
void
vm_map_entry_reserve_cpu_init(globaldata_t gd)
{
        vm_map_entry_t entry;
        int i;

        gd->gd_vme_avail -= MAP_RESERVE_COUNT * 2;
        entry = &cpu_map_entry_init[gd->gd_cpuid][0];
        for (i = 0; i < VMEPERCPU; ++i, ++entry) {
                entry->next = gd->gd_vme_base;
                gd->gd_vme_base = entry;
        }
}

/*
 *      vm_map_entry_reserve:
 *
 *      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.
 */
int
vm_map_entry_reserve(int count)
{
        struct globaldata *gd = mycpu;
        vm_map_entry_t entry;

        crit_enter();

        /*
         * Make sure we have enough structures in gd_vme_base to handle
         * the reservation request.
         */
        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);
}

/*
 *      vm_map_entry_release:
 *
 *      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.
 */
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();
}

/*
 *      vm_map_entry_kreserve:
 *
 *      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.
 */
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\n", gd->gd_vme_avail));
        return(count);
}

/*
 *      vm_map_entry_krelease:
 *
 *      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.
 */
void
vm_map_entry_krelease(int count)
{
        struct globaldata *gd = mycpu;

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

/*
 *      vm_map_entry_create:    [ internal use only ]
 *
 *      Allocates a VM map entry for insertion.  No entry fields are filled 
 *      in.
 *
 *      This routine may be called from an interrupt thread but not a FAST
 *      interrupt.  This routine may recurse the map lock.
 */
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);
}

/*
 *      vm_map_entry_dispose:   [ internal use only ]
 *
 *      Dispose of a vm_map_entry that is no longer being referenced.  This
 *      function may be called from an interrupt.
 */
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();
}


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

        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--;
}

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

#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.
         */
        /*
         * Quickly check the cached hint, there's a good chance of a match.
         */
        if (map->hint != &map->header) {
                tmp = map->hint;
                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);
}

/*
 *      vm_map_insert:
 *
 *      Inserts the given whole VM object into the target
 *      map at the specified address range.  The object's
 *      size should match that of the address range.
 *
 *      Requires that the map be locked, and leaves it so.  Requires that
 *      sufficient vm_map_entry structures have been reserved and tracks
 *      the use via countp.
 *
 *      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,
              vm_object_t object, 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;

        /*
         * 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 (object) {
                /*
                 * When object is non-NULL, it could be shared with another
                 * process.  We have to set or clear OBJ_ONEMAPPING 
                 * appropriately.
                 */
                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 &&
                 ((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);
                        return (KERN_SUCCESS);
                }

                /*
                 * If we can extend the object but cannot extend the
                 * map entry, we have to create a new map entry.  We
                 * must bump the ref count on the extended object to
                 * account for it.  object may be NULL.
                 */
                object = prev_entry->object.vm_object;
                offset = prev_entry->offset +
                        (prev_entry->end - prev_entry->start);
                vm_object_reference(object);
        }

        /*
         * 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.vm_object = object;
        new_entry->offset = offset;
        new_entry->aux.master_pde = 0;

        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
         */
        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) {
                pmap_object_init_pt(map->pmap, start, prot,
                                    object, OFF_TO_IDX(offset), end - start,
                                    cow & MAP_PREFAULT_PARTIAL);
        }

        return (KERN_SUCCESS);
}

/*
 * Find sufficient space for `length' bytes in the given map, starting at
 * `start'.  The map must be locked.  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.
 */
int
vm_map_findspace(
        vm_map_t map,
        vm_offset_t start,
        vm_size_t length,
        vm_offset_t align,
        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;

retry:
        /*
         * 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 (next == &map->header || next->start >= end)
                        break;
        }
        map->hint = entry;
        if (map == &kernel_map) {
                vm_offset_t ksize;
                if ((ksize = round_page(start + length)) > kernel_vm_end) {
                        pmap_growkernel(ksize);
                        goto retry;
                }
        }
        *addr = start;
        return (0);
}

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

        start = *addr;

        count = vm_map_entry_reserve(MAP_RESERVE_COUNT);
        vm_map_lock(map);
        if (find_space) {
                if (vm_map_findspace(map, start, length, 1, addr)) {
                        vm_map_unlock(map);
                        vm_map_entry_release(count);
                        return (KERN_NO_SPACE);
                }
                start = *addr;
        }
        result = vm_map_insert(map, &count, object, offset,
                               start, start + length,
                               maptype,
                               prot, max,
                               cow);
        vm_map_unlock(map);
        vm_map_entry_release(count);

        return (result);
}

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

        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);
                }
        }
}
/*
 *      vm_map_clip_start:      [ internal use only ]
 *
 *      Asserts that the given entry begins at or after
 *      the specified address; if necessary,
 *      it splits the entry into two.
 */
#define vm_map_clip_start(map, entry, startaddr, 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.
 */
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:
                vm_object_reference(new_entry->object.vm_object);
                break;
        default:
                break;
        }
}

/*
 *      vm_map_clip_end:        [ internal use only ]
 *
 *      Asserts that the given entry ends at or before
 *      the specified address; if necessary,
 *      it splits the entry into two.
 */

#define vm_map_clip_end(map, entry, endaddr, 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.
 */
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:
                vm_object_reference(new_entry->object.vm_object);
                break;
        default:
                break;
        }
}

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

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

/*
 * CLIP_CHECK_BACK
 * CLIP_CHECK_FWD
 *
 *      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)


/*
 *      vm_map_clip_range:      [ kernel use only ]
 *
 *      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);
}

/*
 *      vm_map_unclip_range:    [ kernel use only ]
 *
 *      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;
        }
}

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

/*
 * vm_map_protect:
 *
 * Sets the protection of the specified address region in the target map. 
 * If "set_max" is specified, the maximum protection is to be set;
 * otherwise, only the current protection is affected.
 *
 * 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.
 */
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);
}

/*
 *      vm_map_madvise:
 *
 *      This routine traverses a processes map handling the madvise
 *      system call.  Advisories are classified as either those effecting
 *      the vm_map_entry structure, or those effecting the underlying 
 *      objects.
 *
 *      The <value> argument is used for extended madvise calls.
 */
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);
}       


/*
 *      vm_map_inherit:
 *
 *      Sets the inheritance of the specified address
 *      range in the target map.  Inheritance
 *      affects how the map will be shared with
 *      child maps at the time of 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_SUBMAP) {
                                int copyflag = entry->eflags & MAP_ENTRY_NEEDS_COPY;
                                if (copyflag && ((entry->protection & VM_PROT_WRITE) != 0)) {
                                        vm_map_entry_shadow(entry);
                                } 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);
                        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);
}

/*
 *      vm_map_wire:
 *
 *      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.
 */
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_SUBMAP) {
                                int copyflag = entry->eflags & MAP_ENTRY_NEEDS_COPY;
                                if (copyflag &&
                                    ((entry->protection & VM_PROT_WRITE) != 0)) {
                                        vm_map_entry_shadow(entry);
                                } 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
                 *
                 * Unlock the map to avoid deadlocks.  The in-transit flag
                 * protects us from most changes but note that
                 * clipping may still occur.  To prevent clipping from
                 * occuring after the unlock, except for when we are
                 * blocking in vm_fault_wire, we must run in a critical
                 * section, otherwise our accesses to entry->start and 
                 * entry->end could be corrupted.  We have to enter the
                 * critical section prior to unlocking so start_entry does
                 * not change out from under us at the very beginning of the
                 * loop.
                 *
                 * HACK HACK HACK HACK
                 */

                crit_enter();

                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);
                        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;
                }
                crit_exit();

                /*
                 * 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);
}

/*
 * vm_map_set_wired_quick()
 *
 *      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.
 */
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(entry->wired_count == 0);
            entry->wired_count = 1;                                              
        }
        vm_map_unclip_range(map, entry, addr, addr + size, countp, MAP_CLIP_NO_HOLES);
}

/*
 * vm_map_clean
 *
 * 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.
 *
 * Returns an error if any part of the specified range is not mapped.
 */
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_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);
        }
        /*
         * Make a first pass to check for holes.
         */
        for (current = entry; current->start < end; current = current->next) {
                if (current->maptype == VM_MAPTYPE_SUBMAP) {
                        vm_map_unlock_read(map);
                        return (KERN_INVALID_ARGUMENT);
                }
                if (end > current->end &&
                    (current->next == &map->header ||
                        current->end != current->next->start)) {
                        vm_map_unlock_read(map);
                        return (KERN_INVALID_ADDRESS);
                }
        }

        if (invalidate)
                pmap_remove(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;
                if (current->maptype == 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);
                } else {
                        object = current->object.vm_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 && object->backing_object) {
                        offset += object->backing_object_offset;
                        object = object->backing_object;
                        if (object->size < OFF_TO_IDX( offset + size))
                                size = IDX_TO_OFF(object->size) - offset;
                }
                if (object && (object->type == OBJT_VNODE) && 
                    (current->protection & VM_PROT_WRITE)) {
                        /*
                         * 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;

                        vm_object_reference(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(object);
                }
                if (object && invalidate &&
                   ((object->type == OBJT_VNODE) ||
                    (object->type == OBJT_DEVICE))) {
                        int clean_only = 
                                (object->type == OBJT_DEVICE) ? FALSE : TRUE;
                        vm_object_reference(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(object);
                }
                start += size;
        }

        vm_map_unlock_read(map);
        return (KERN_SUCCESS);
}

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

/*
 *      vm_map_entry_delete:    [ internal use only ]
 *
 *      Deallocate the given entry from the target map.
 */
static void
vm_map_entry_delete(vm_map_t map, vm_map_entry_t entry, 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:
                vm_object_deallocate(entry->object.vm_object);
                break;
        default:
                break;
        }

        vm_map_entry_dispose(map, entry, countp);
}

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

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);
                object = entry->object.vm_object;

                /*
                 * 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_page_remove(object, offidxstart, offidxend, FALSE);
                } else {
                        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);
                                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;
                                }
                        }
                }

                /*
                 * 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;
        }
        return (KERN_SUCCESS);
}

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

/*
 *      vm_map_check_protection:
 *
 *      Assert that the target map allows the specified
 *      privilege on the entire address region given.
 *      The entire region must be allocated.
 */
boolean_t
vm_map_check_protection(vm_map_t map, vm_offset_t start, vm_offset_t end,
                        vm_prot_t protection)
{
        vm_map_entry_t entry;
        vm_map_entry_t tmp_entry;

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

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

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

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

                start = entry->end;
                entry = entry->next;
        }
        return (TRUE);
}

/*
 * Split the pages in a map entry into a new object.  This affords
 * easier removal of unused pages, and keeps object inheritance from
 * being a negative impact on memory usage.
 */
static void
vm_map_split(vm_map_entry_t entry)
{
        vm_page_t m;
        vm_object_t orig_object, new_object, source;
        vm_offset_t s, e;
        vm_pindex_t offidxstart, offidxend, idx;
        vm_size_t size;
        vm_ooffset_t offset;

        orig_object = entry->object.vm_object;
        if (orig_object->type != OBJT_DEFAULT && orig_object->type != OBJT_SWAP)
                return;
        if (orig_object->ref_count <= 1)
                return;

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

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

        new_object = vm_pager_allocate(orig_object->type, NULL,
                                       IDX_TO_OFF(size), VM_PROT_ALL, 0);
        if (new_object == NULL)
                return;

        source = orig_object->backing_object;
        if (source != NULL) {
                vm_object_reference(source);    /* Referenced by new_object */
                LIST_INSERT_HEAD(&source->shadow_head,
                                  new_object, shadow_list);
                vm_object_clear_flag(source, OBJ_ONEMAPPING);
                new_object->backing_object_offset = 
                        orig_object->backing_object_offset + IDX_TO_OFF(offidxstart);
                new_object->backing_object = source;
                source->shadow_count++;
                source->generation++;
        }

        for (idx = 0; idx < size; idx++) {
                vm_page_t m;

                /*
                 * A critical section is required to avoid a race between
                 * the lookup and an interrupt/unbusy/free and our busy
                 * check.
                 */
                crit_enter();
        retry:
                m = vm_page_lookup(orig_object, offidxstart + idx);
                if (m == NULL) {
                        crit_exit();
                        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.
                 */
                if (vm_page_sleep_busy(m, TRUE, "spltwt"))
                        goto retry;
                vm_page_busy(m);
                vm_page_rename(m, new_object, idx);
                /* page automatically made dirty by rename and cache handled */
                vm_page_busy(m);
                crit_exit();
        }

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

        /*
         * 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(new_object, idx);
                if (m)
                        vm_page_wakeup(m);
        }

        entry->object.vm_object = new_object;
        entry->offset = 0LL;
        vm_object_deallocate(orig_object);
}

/*
 *      vm_map_copy_entry:
 *
 *      Copies the contents of the source entry to the destination
 *      entry.  The entries *must* be aligned properly.
 */
static void
vm_map_copy_entry(vm_map_t src_map, vm_map_t dst_map,
        vm_map_entry_t src_entry, vm_map_entry_t dst_entry)
{
        vm_object_t src_object;

        if (dst_entry->maptype == VM_MAPTYPE_SUBMAP)
                return;
        if (src_entry->maptype == VM_MAPTYPE_SUBMAP)
                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.
                 */
                if ((src_object = src_entry->object.vm_object) != NULL) {
                        if ((src_object->handle == NULL) &&
                                (src_object->type == OBJT_DEFAULT ||
                                 src_object->type == OBJT_SWAP)) {
                                vm_object_collapse(src_object);
                                if ((src_object->flags & (OBJ_NOSPLIT|OBJ_ONEMAPPING)) == OBJ_ONEMAPPING) {
                                        vm_map_split(src_entry);
                                        src_object = src_entry->object.vm_object;
                                }
                        }

                        vm_object_reference(src_object);
                        vm_object_clear_flag(src_object, OBJ_ONEMAPPING);
                        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;
                } 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.
 */
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;
        vm_map_entry_t new_entry;
        vm_object_t object;
        int count;

        vm_map_lock(old_map);
        old_map->infork = 1;

        /*
         * XXX Note: upcalls are not copied.
         */
        vm2 = vmspace_alloc(old_map->min_offset, old_map->max_offset);
        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;

        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) {
                if (old_entry->maptype == VM_MAPTYPE_SUBMAP)
                        panic("vm_map_fork: encountered a submap");

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

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

                        /*
                         * Add the reference before calling vm_map_entry_shadow
                         * to insure that a shadow object is created.
                         */
                        vm_object_reference(object);
                        if (old_entry->eflags & MAP_ENTRY_NEEDS_COPY) {
                                vm_map_entry_shadow(old_entry);
                                /* Transfer the second reference too. */
                                vm_object_reference(
                                    old_entry->object.vm_object);
                                vm_object_deallocate(object);
                                object = old_entry->object.vm_object;
                        }
                        vm_object_clear_flag(object, OBJ_ONEMAPPING);

                        /*
                         * Clone the entry, referencing the shared object.
                         */
                        new_entry = vm_map_entry_create(new_map, &count);
                        *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, &count);
                        *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;
                }
                old_entry = old_entry->next;
        }

        new_map->size = old_map->size;
        old_map->infork = 0;
        vm_map_unlock(old_map);
        vm_map_entry_release(count);

        return (vm2);
}

int
vm_map_stack (vm_map_t map, vm_offset_t addrbos, vm_size_t max_ssize,
              vm_prot_t prot, vm_prot_t max, int cow)
{
        vm_map_entry_t prev_entry;
        vm_map_entry_t new_stack_entry;
        vm_size_t      init_ssize;
        int            rv;
        int             count;

        if (VM_MIN_USER_ADDRESS > 0 && addrbos < VM_MIN_USER_ADDRESS)
                return (KERN_NO_SPACE);

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

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

        /* 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 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);
        }

        /* 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, 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).
 */
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)) {
                        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)) {
                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, 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);
                }
        }

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.
 */
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 and upcalls
         * are not copied to the new vmspace.
         */
        if (vmcopy)  {
            newvmspace = vmspace_fork(vmcopy);
        } else {
            newvmspace = vmspace_alloc(map->min_offset, map->max_offset);
            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);
        sysref_put(&oldvmspace->vm_sysref);
}

/*
 * Unshare the specified VM space for forcing COW.  This
 * is called by rfork, for the (RFMEM|RFPROC) == 0 case.
 *
 * The exitingcnt test is not strictly necessary but has been
 * included for code sanity (to make the code a bit more deterministic).
 */

void
vmspace_unshare(struct proc *p) 
{
        struct vmspace *oldvmspace = p->p_vmspace;
        struct vmspace *newvmspace;

        if (oldvmspace->vm_sysref.refcnt == 1 && oldvmspace->vm_exitingcnt == 0)
                return;
        newvmspace = vmspace_fork(oldvmspace);
        pmap_pinit2(vmspace_pmap(newvmspace));
        pmap_replacevm(p, newvmspace, 0);
        sysref_put(&oldvmspace->vm_sysref);
}

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

        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 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)) {
                                use_read_lock = 0;
                                goto RetryLookup;
                        }
                        use_read_lock = 0;

                        vm_map_entry_shadow(entry);
                } 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))  {
                        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.
         */

        *pindex = OFF_TO_IDX((vaddr - entry->start) + entry->offset);
        *object = entry->object.vm_object;

        /*
         * 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);
}

/*
 *      vm_map_lookup_done:
 *
 *      Releases locks acquired by a vm_map_lookup
 *      (according to the handle returned by that lookup).
 */

void
vm_map_lookup_done(vm_map_t map, vm_map_entry_t entry, 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>

/*
 *      vm_map_print:   [ debug ]
 */
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");
                }
                if (entry->maptype == 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, (char *)0);
                                db_indent -= 2;
                        }
                } else {
                        /* 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, (char *)0);
                                nlines += 4;
                                db_indent -= 2;
                        }
                }
        }
        db_indent -= 2;
        if (db_indent == 0)
                nlines = 0;
}


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 */