FreeBSD/Linux Kernel Cross Reference
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: releng/5.1/sys/vm/vm_map.c 114317 2003-04-30 19:18:09Z alc $
     */
    
    /*
     *      Virtual memory mapping module.
     */
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/ktr.h>
    #include <sys/lock.h>
    #include <sys/mutex.h>
    #include <sys/proc.h>
    #include <sys/vmmeter.h>
    #include <sys/mman.h>
    #include <sys/vnode.h>
    #include <sys/resourcevar.h>
    #include <sys/sysent.h>
    #include <sys/shm.h>
    
    #include <vm/vm.h>
    #include <vm/vm_param.h>
    #include <vm/pmap.h>
    #include <vm/vm_map.h>
    #include <vm/vm_page.h>
    #include <vm/vm_object.h>
    #include <vm/vm_pager.h>
    #include <vm/vm_kern.h>
    #include <vm/vm_extern.h>
    #include <vm/swap_pager.h>
    #include <vm/uma.h>
    
    /*
     *      Virtual memory maps provide for the mapping, protection,
     *      and sharing of virtual memory objects.  In addition,
     *      this module provides for an efficient virtual copy of
    *      memory from one map to another.
    *
    *      Synchronization is required prior to most operations.
    *
    *      Maps consist of an ordered doubly-linked list of simple
    *      entries; a 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.
    */
   
   /*
    *      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.
    */
   
   static struct mtx map_sleep_mtx;
   static uma_zone_t mapentzone;
   static uma_zone_t kmapentzone;
   static uma_zone_t mapzone;
   static uma_zone_t vmspace_zone;
   static struct vm_object kmapentobj;
   static void vmspace_zinit(void *mem, int size);
   static void vmspace_zfini(void *mem, int size);
   static void vm_map_zinit(void *mem, int size);
   static void vm_map_zfini(void *mem, int size);
   static void _vm_map_init(vm_map_t map, vm_offset_t min, vm_offset_t max);
   
   #ifdef INVARIANTS
   static void vm_map_zdtor(void *mem, int size, void *arg);
   static void vmspace_zdtor(void *mem, int size, void *arg);
   #endif
   
   void
   vm_map_startup(void)
   {
           mtx_init(&map_sleep_mtx, "vm map sleep mutex", NULL, MTX_DEF);
           mapzone = uma_zcreate("MAP", sizeof(struct vm_map), NULL,
   #ifdef INVARIANTS
               vm_map_zdtor,
   #else
               NULL,
   #endif
               vm_map_zinit, vm_map_zfini, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
           uma_prealloc(mapzone, MAX_KMAP);
           kmapentzone = uma_zcreate("KMAP ENTRY", sizeof(struct vm_map_entry), 
               NULL, NULL, NULL, NULL, UMA_ALIGN_PTR,
               UMA_ZONE_MTXCLASS | UMA_ZONE_VM);
           uma_prealloc(kmapentzone, MAX_KMAPENT);
           mapentzone = uma_zcreate("MAP ENTRY", sizeof(struct vm_map_entry), 
               NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
           uma_prealloc(mapentzone, MAX_MAPENT);
   }
   
   static void
   vmspace_zfini(void *mem, int size)
   {
           struct vmspace *vm;
   
           vm = (struct vmspace *)mem;
   
           vm_map_zfini(&vm->vm_map, sizeof(vm->vm_map));
   }
   
   static void
   vmspace_zinit(void *mem, int size)
   {
           struct vmspace *vm;
   
           vm = (struct vmspace *)mem;
   
           vm_map_zinit(&vm->vm_map, sizeof(vm->vm_map));
   }
   
   static void
   vm_map_zfini(void *mem, int size)
   {
           vm_map_t map;
   
           map = (vm_map_t)mem;
           mtx_destroy(&map->system_mtx);
           lockdestroy(&map->lock);
   }
   
   static void
   vm_map_zinit(void *mem, int size)
   {
           vm_map_t map;
   
           map = (vm_map_t)mem;
           map->nentries = 0;
           map->size = 0;
           map->infork = 0;
           mtx_init(&map->system_mtx, "system map", NULL, MTX_DEF | MTX_DUPOK);
           lockinit(&map->lock, PVM, "thrd_sleep", 0, LK_NOPAUSE);
   }
   
   #ifdef INVARIANTS
   static void
   vmspace_zdtor(void *mem, int size, void *arg)
   {
           struct vmspace *vm;
   
           vm = (struct vmspace *)mem;
   
           vm_map_zdtor(&vm->vm_map, sizeof(vm->vm_map), arg);
   }
   static void
   vm_map_zdtor(void *mem, int size, void *arg)
   {
           vm_map_t map;
   
           map = (vm_map_t)mem;
           KASSERT(map->nentries == 0,
               ("map %p nentries == %d on free.", 
               map, map->nentries));
           KASSERT(map->size == 0,
               ("map %p size == %lu on free.",
               map, (unsigned long)map->size));
           KASSERT(map->infork == 0,
               ("map %p infork == %d on free.",
               map, map->infork));
   }
   #endif  /* INVARIANTS */
   
   /*
    * Allocate a vmspace structure, including a vm_map and pmap,
    * and initialize those structures.  The refcnt is set to 1.
    * The remaining fields must be initialized by the caller.
    */
   struct vmspace *
   vmspace_alloc(min, max)
           vm_offset_t min, max;
   {
           struct vmspace *vm;
   
           GIANT_REQUIRED;
           vm = uma_zalloc(vmspace_zone, M_WAITOK);
           CTR1(KTR_VM, "vmspace_alloc: %p", vm);
           _vm_map_init(&vm->vm_map, min, max);
           pmap_pinit(vmspace_pmap(vm));
           vm->vm_map.pmap = vmspace_pmap(vm);             /* XXX */
           vm->vm_refcnt = 1;
           vm->vm_shm = NULL;
           vm->vm_exitingcnt = 0;
           return (vm);
   }
   
   void
   vm_init2(void) 
   {
           uma_zone_set_obj(kmapentzone, &kmapentobj, lmin(cnt.v_page_count,
               (VM_MAX_KERNEL_ADDRESS - KERNBASE) / PAGE_SIZE) / 8);
           vmspace_zone = uma_zcreate("VMSPACE", sizeof(struct vmspace), NULL,
   #ifdef INVARIANTS
               vmspace_zdtor,
   #else
               NULL,
   #endif
               vmspace_zinit, vmspace_zfini, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
           pmap_init2();
   }
   
   static __inline void
   vmspace_dofree(struct vmspace *vm)
   {
           CTR1(KTR_VM, "vmspace_free: %p", vm);
   
           /*
            * Make sure any SysV shm is freed, it might not have been in
            * exit1().
            */
           shmexit(vm);
   
           /*
            * Lock the map, to wait out all other references to it.
            * Delete all of the mappings and pages they hold, then call
            * the pmap module to reclaim anything left.
            */
           vm_map_lock(&vm->vm_map);
           (void) vm_map_delete(&vm->vm_map, vm->vm_map.min_offset,
               vm->vm_map.max_offset);
           vm_map_unlock(&vm->vm_map);
   
           pmap_release(vmspace_pmap(vm));
           uma_zfree(vmspace_zone, vm);
   }
   
   void
   vmspace_free(struct vmspace *vm)
   {
           GIANT_REQUIRED;
   
           if (vm->vm_refcnt == 0)
                   panic("vmspace_free: attempt to free already freed vmspace");
   
           if (--vm->vm_refcnt == 0 && vm->vm_exitingcnt == 0)
                   vmspace_dofree(vm);
   }
   
   void
   vmspace_exitfree(struct proc *p)
   {
           struct vmspace *vm;
   
           GIANT_REQUIRED;
           vm = p->p_vmspace;
           p->p_vmspace = NULL;
   
           /*
            * cleanup by parent process wait()ing on exiting child.  vm_refcnt
            * may not be 0 (e.g. fork() and child exits without exec()ing).
            * exitingcnt may increment above 0 and drop back down to zero
            * several times while vm_refcnt is held non-zero.  vm_refcnt
            * may also increment above 0 and drop back down to zero several 
            * times while vm_exitingcnt is held non-zero.
            * 
            * The last wait on the exiting child's vmspace will clean up 
            * the remainder of the vmspace.
            */
           if (--vm->vm_exitingcnt == 0 && vm->vm_refcnt == 0)
                   vmspace_dofree(vm);
   }
   
   /*
    * vmspace_swap_count() - count the approximate swap useage in pages for a
    *                        vmspace.
    *
    *      The map must be locked.
    *
    *      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;
           int count = 0;
   
           for (cur = map->header.next; cur != &map->header; cur = cur->next) {
                   vm_object_t object;
   
                   if ((cur->eflags & MAP_ENTRY_IS_SUB_MAP) == 0 &&
                       (object = cur->object.vm_object) != NULL) {
                           VM_OBJECT_LOCK(object);
                           if (object->type == OBJT_SWAP &&
                               object->un_pager.swp.swp_bcount != 0) {
                                   int n = (cur->end - cur->start) / PAGE_SIZE;
   
                                   count += object->un_pager.swp.swp_bcount *
                                       SWAP_META_PAGES * n / object->size + 1;
                           }
                           VM_OBJECT_UNLOCK(object);
                   }
           }
           return (count);
   }
   
   void
   _vm_map_lock(vm_map_t map, const char *file, int line)
   {
           int error;
   
           if (map->system_map)
                   _mtx_lock_flags(&map->system_mtx, 0, file, line);
           else {
                   error = lockmgr(&map->lock, LK_EXCLUSIVE, NULL, curthread);
                   KASSERT(error == 0, ("%s: failed to get lock", __func__));
           }
           map->timestamp++;
   }
   
   void
   _vm_map_unlock(vm_map_t map, const char *file, int line)
   {
   
           if (map->system_map)
                   _mtx_unlock_flags(&map->system_mtx, 0, file, line);
           else
                   lockmgr(&map->lock, LK_RELEASE, NULL, curthread);
   }
   
   void
   _vm_map_lock_read(vm_map_t map, const char *file, int line)
   {
           int error;
   
           if (map->system_map)
                   _mtx_lock_flags(&map->system_mtx, 0, file, line);
           else {
                   error = lockmgr(&map->lock, LK_EXCLUSIVE, NULL, curthread);
                   KASSERT(error == 0, ("%s: failed to get lock", __func__));
           }
   }
   
   void
   _vm_map_unlock_read(vm_map_t map, const char *file, int line)
   {
   
           if (map->system_map)
                   _mtx_unlock_flags(&map->system_mtx, 0, file, line);
           else
                   lockmgr(&map->lock, LK_RELEASE, NULL, curthread);
   }
   
   int
   _vm_map_trylock(vm_map_t map, const char *file, int line)
   {
           int error;
   
           error = map->system_map ?
               !_mtx_trylock(&map->system_mtx, 0, file, line) :
               lockmgr(&map->lock, LK_EXCLUSIVE | LK_NOWAIT, NULL, curthread);
           if (error == 0)
                   map->timestamp++;
           return (error == 0);
   }
   
   int
   _vm_map_trylock_read(vm_map_t map, const char *file, int line)
   {
           int error;
   
           error = map->system_map ?
               !_mtx_trylock(&map->system_mtx, 0, file, line) :
               lockmgr(&map->lock, LK_EXCLUSIVE | LK_NOWAIT, NULL, curthread);
           return (error == 0);
   }
   
   int
   _vm_map_lock_upgrade(vm_map_t map, const char *file, int line)
   {
   
           if (map->system_map) {
   #ifdef INVARIANTS
                   _mtx_assert(&map->system_mtx, MA_OWNED, file, line);
   #endif
           } else
                   KASSERT(lockstatus(&map->lock, curthread) == LK_EXCLUSIVE,
                       ("%s: lock not held", __func__));
           map->timestamp++;
           return (0);
   }
   
   void
   _vm_map_lock_downgrade(vm_map_t map, const char *file, int line)
   {
   
           if (map->system_map) {
   #ifdef INVARIANTS
                   _mtx_assert(&map->system_mtx, MA_OWNED, file, line);
   #endif
           } else
                   KASSERT(lockstatus(&map->lock, curthread) == LK_EXCLUSIVE,
                       ("%s: lock not held", __func__));
   }
   
   /*
    *      vm_map_unlock_and_wait:
    */
   int
   vm_map_unlock_and_wait(vm_map_t map, boolean_t user_wait)
   {
   
           mtx_lock(&map_sleep_mtx);
           vm_map_unlock(map);
           return (msleep(&map->root, &map_sleep_mtx, PDROP | PVM, "vmmaps", 0));
   }
   
   /*
    *      vm_map_wakeup:
    */
   void
   vm_map_wakeup(vm_map_t map)
   {
   
           /*
            * Acquire and release map_sleep_mtx to prevent a wakeup()
            * from being performed (and lost) between the vm_map_unlock()
            * and the msleep() in vm_map_unlock_and_wait().
            */
           mtx_lock(&map_sleep_mtx);
           mtx_unlock(&map_sleep_mtx);
           wakeup(&map->root);
   }
   
   long
   vmspace_resident_count(struct vmspace *vmspace)
   {
           return pmap_resident_count(vmspace_pmap(vmspace));
   }
   
   /*
    *      vm_map_create:
    *
    *      Creates and returns a new empty VM map with
    *      the given physical map structure, and having
    *      the given lower and upper address bounds.
    */
   vm_map_t
   vm_map_create(pmap_t pmap, vm_offset_t min, vm_offset_t max)
   {
           vm_map_t result;
   
           result = uma_zalloc(mapzone, M_WAITOK);
           CTR1(KTR_VM, "vm_map_create: %p", result);
           _vm_map_init(result, min, max);
           result->pmap = pmap;
           return (result);
   }
   
   /*
    * Initialize an existing vm_map structure
    * such as that in the vmspace structure.
    * The pmap is set elsewhere.
    */
   static void
   _vm_map_init(vm_map_t map, vm_offset_t min, vm_offset_t max)
   {
   
           map->header.next = map->header.prev = &map->header;
           map->needs_wakeup = FALSE;
           map->system_map = 0;
           map->min_offset = min;
           map->max_offset = max;
           map->first_free = &map->header;
           map->root = NULL;
           map->timestamp = 0;
   }
   
   void
   vm_map_init(vm_map_t map, vm_offset_t min, vm_offset_t max)
   {
           _vm_map_init(map, min, max);
           mtx_init(&map->system_mtx, "system map", NULL, MTX_DEF | MTX_DUPOK);
           lockinit(&map->lock, PVM, "thrd_sleep", 0, LK_NOPAUSE);
   }
   
   /*
    *      vm_map_entry_dispose:   [ internal use only ]
    *
    *      Inverse of vm_map_entry_create.
    */
   static void
   vm_map_entry_dispose(vm_map_t map, vm_map_entry_t entry)
   {
           uma_zfree(map->system_map ? kmapentzone : mapentzone, entry);
   }
   
   /*
    *      vm_map_entry_create:    [ internal use only ]
    *
    *      Allocates a VM map entry for insertion.
    *      No entry fields are filled in.
    */
   static vm_map_entry_t
   vm_map_entry_create(vm_map_t map)
   {
           vm_map_entry_t new_entry;
   
           if (map->system_map)
                   new_entry = uma_zalloc(kmapentzone, M_NOWAIT);
           else
                   new_entry = uma_zalloc(mapentzone, M_WAITOK);
           if (new_entry == NULL)
                   panic("vm_map_entry_create: kernel resources exhausted");
           return (new_entry);
   }
   
   /*
    *      vm_map_entry_set_behavior:
    *
    *      Set the expected access behavior, either normal, random, or
    *      sequential.
    */
   static __inline void
   vm_map_entry_set_behavior(vm_map_entry_t entry, u_char behavior)
   {
           entry->eflags = (entry->eflags & ~MAP_ENTRY_BEHAV_MASK) |
               (behavior & MAP_ENTRY_BEHAV_MASK);
   }
   
   /*
    *      vm_map_entry_splay:
    *
    *      Implements Sleator and Tarjan's top-down splay algorithm.  Returns
    *      the vm_map_entry containing the given address.  If, however, that
    *      address is not found in the vm_map, returns a vm_map_entry that is
    *      adjacent to the address, coming before or after it.
    */
   static vm_map_entry_t
   vm_map_entry_splay(vm_offset_t address, vm_map_entry_t root)
   {
           struct vm_map_entry dummy;
           vm_map_entry_t lefttreemax, righttreemin, y;
   
           if (root == NULL)
                   return (root);
           lefttreemax = righttreemin = &dummy;
           for (;; root = y) {
                   if (address < root->start) {
                           if ((y = root->left) == NULL)
                                   break;
                           if (address < y->start) {
                                   /* Rotate right. */
                                   root->left = y->right;
                                   y->right = root;
                                   root = y;
                                   if ((y = root->left) == NULL)
                                           break;
                           }
                           /* Link into the new root's right tree. */
                           righttreemin->left = root;
                           righttreemin = root;
                   } else if (address >= root->end) {
                           if ((y = root->right) == NULL)
                                   break;
                           if (address >= y->end) {
                                   /* Rotate left. */
                                   root->right = y->left;
                                   y->left = root;
                                   root = y;
                                   if ((y = root->right) == NULL)
                                           break;
                           }
                           /* Link into the new root's left tree. */
                           lefttreemax->right = root;
                           lefttreemax = root;
                   } else
                           break;
           }
           /* Assemble the new root. */
           lefttreemax->right = root->left;
           righttreemin->left = root->right;
           root->left = dummy.right;
           root->right = dummy.left;
           return (root);
   }
   
   /*
    *      vm_map_entry_{un,}link:
    *
    *      Insert/remove entries from maps.
    */
   static void
   vm_map_entry_link(vm_map_t map,
                     vm_map_entry_t after_where,
                     vm_map_entry_t entry)
   {
   
           CTR4(KTR_VM,
               "vm_map_entry_link: map %p, nentries %d, entry %p, after %p", map,
               map->nentries, entry, after_where);
           map->nentries++;
           entry->prev = after_where;
           entry->next = after_where->next;
           entry->next->prev = entry;
           after_where->next = entry;
   
           if (after_where != &map->header) {
                   if (after_where != map->root)
                           vm_map_entry_splay(after_where->start, map->root);
                   entry->right = after_where->right;
                   entry->left = after_where;
                   after_where->right = NULL;
           } else {
                   entry->right = map->root;
                   entry->left = NULL;
           }
           map->root = entry;
   }
   
   static void
   vm_map_entry_unlink(vm_map_t map,
                       vm_map_entry_t entry)
   {
           vm_map_entry_t next, prev, root;
   
           if (entry != map->root)
                   vm_map_entry_splay(entry->start, map->root);
           if (entry->left == NULL)
                   root = entry->right;
           else {
                   root = vm_map_entry_splay(entry->start, entry->left);
                   root->right = entry->right;
           }
           map->root = root;
   
           prev = entry->prev;
           next = entry->next;
           next->prev = prev;
           prev->next = next;
           map->nentries--;
           CTR3(KTR_VM, "vm_map_entry_unlink: map %p, nentries %d, entry %p", map,
               map->nentries, entry);
   }
   
   /*
    *      vm_map_lookup_entry:    [ internal use only ]
    *
    *      Finds the map entry containing (or
    *      immediately preceding) the specified address
    *      in the given map; the entry is returned
    *      in the "entry" parameter.  The boolean
    *      result indicates whether the address is
    *      actually contained in the map.
    */
   boolean_t
   vm_map_lookup_entry(
           vm_map_t map,
           vm_offset_t address,
           vm_map_entry_t *entry)  /* OUT */
   {
           vm_map_entry_t cur;
   
           cur = vm_map_entry_splay(address, map->root);
           if (cur == NULL)
                   *entry = &map->header;
           else {
                   map->root = cur;
   
                   if (address >= cur->start) {
                           *entry = cur;
                           if (cur->end > address)
                                   return (TRUE);
                   } else
                           *entry = cur->prev;
           }
           return (FALSE);
   }
   
   /*
    *      vm_map_insert:
    *
    *      Inserts the given whole VM object into the target
    *      map at the specified address range.  The object's
    *      size should match that of the address range.
    *
    *      Requires that the map be locked, and leaves it so.
    *
    *      If object is non-NULL, ref count must be bumped by caller
    *      prior to making call to account for the new entry.
    */
   int
   vm_map_insert(vm_map_t map, vm_object_t object, vm_ooffset_t offset,
                 vm_offset_t start, vm_offset_t end, vm_prot_t prot, vm_prot_t max,
                 int cow)
   {
           vm_map_entry_t new_entry;
           vm_map_entry_t prev_entry;
           vm_map_entry_t temp_entry;
           vm_eflags_t protoeflags;
   
           /*
            * 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 != NULL) {
                   /*
                    * OBJ_ONEMAPPING must be cleared unless this mapping
                    * is trivially proven to be the only mapping for any
                    * of the object's pages.  (Object granularity
                    * reference counting is insufficient to recognize
                    * aliases with precision.) 
                    */
                   if (object != kmem_object)
                           mtx_lock(&Giant);
                   VM_OBJECT_LOCK(object);
                   if (object->ref_count > 1 || object->shadow_count != 0)
                           vm_object_clear_flag(object, OBJ_ONEMAPPING);
                   VM_OBJECT_UNLOCK(object);
                   if (object != kmem_object)
                           mtx_unlock(&Giant);
           }
           else if ((prev_entry != &map->header) &&
                    (prev_entry->eflags == protoeflags) &&
                    (prev_entry->end == start) &&
                    (prev_entry->wired_count == 0) &&
                    ((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);
                           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);
           new_entry->start = start;
           new_entry->end = end;
   
           new_entry->eflags = protoeflags;
           new_entry->object.vm_object = object;
           new_entry->offset = offset;
           new_entry->avail_ssize = 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);
   #endif
   
           if (cow & (MAP_PREFAULT|MAP_PREFAULT_PARTIAL)) {
                   mtx_lock(&Giant);
                   pmap_object_init_pt(map->pmap, start,
                                       object, OFF_TO_IDX(offset), end - start,
                                       cow & MAP_PREFAULT_PARTIAL);
                   mtx_unlock(&Giant);
           }
   
           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.
    */
   int
   vm_map_findspace(
           vm_map_t map,
           vm_offset_t start,
           vm_size_t length,
           vm_offset_t *addr)
   {
           vm_map_entry_t entry, next;
           vm_offset_t end;
   
           if (start < map->min_offset)
                   start = map->min_offset;
           if (start > map->max_offset)
                   return (1);
   
           /*
            * Look for the first possible address; if there's already something
            * at this address, we have to start after it.
            */
           if (start == map->min_offset) {
                   if ((entry = map->first_free) != &map->header)
                           start = entry->end;
           } else {
                   vm_map_entry_t tmp;
   
                   if (vm_map_lookup_entry(map, start, &tmp))
                           start = tmp->end;
                   entry = tmp;
           }
   
           /*
            * Look through the rest of the map, trying to fit a new region in the
            * gap between existing regions, or after the very last region.
            */
           for (;; start = (entry = next)->end) {
                   /*
                    * 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;
                    * if so, we lose.  Otherwise, if this is the last entry, or
                    * if the proposed new region fits before the next entry, we
                    * win.
                    */
                   end = start + length;
                   if (end > map->max_offset || end < start)
                           return (1);
                   next = entry->next;
                   if (next == &map->header || next->start >= end)
                           break;
           }
           *addr = start;
           if (map == kernel_map) {
                   vm_offset_t ksize;
                   if ((ksize = round_page(start + length)) > kernel_vm_end) {
                           pmap_growkernel(ksize);
                   }
           }
           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,  /* IN/OUT */
              vm_size_t length, boolean_t find_space, vm_prot_t prot,
              vm_prot_t max, int cow)
  {
          vm_offset_t start;
          int result, s = 0;
  
          start = *addr;
  
          if (map == kmem_map)
                  s = splvm();
  
          vm_map_lock(map);
          if (find_space) {
                  if (vm_map_findspace(map, start, length, addr)) {
                          vm_map_unlock(map);
                          if (map == kmem_map)
                                  splx(s);
                          return (KERN_NO_SPACE);
                  }
                  start = *addr;
          }
          result = vm_map_insert(map, object, offset,
                  start, start + length, prot, max, cow);
          vm_map_unlock(map);
  
          if (map == kmem_map)
                  splx(s);
  
          return (result);
  }
  
  /*
   *      vm_map_simplify_entry:
   *
   *      Simplify the given map entry by merging with either neighbor.  This
   *      routine also has the ability to merge with both neighbors.
   *
   *      The map must be locked.
   *
   *      This routine guarentees that the passed entry remains valid (though
   *      possibly extended).  When merging, this routine may delete one or
   *      both neighbors.
   */
  void
  vm_map_simplify_entry(vm_map_t map, vm_map_entry_t entry)
  {
          vm_map_entry_t next, prev;
          vm_size_t prevsize, esize;
  
          if (entry->eflags & (MAP_ENTRY_IN_TRANSITION | MAP_ENTRY_IS_SUB_MAP))
                  return;
  
          prev = entry->prev;
          if (prev != &map->header) {
                  prevsize = prev->end - prev->start;
                  if ( (prev->end == entry->start) &&
                       (prev->object.vm_object == entry->object.vm_object) &&
                       (!prev->object.vm_object ||
                          (prev->offset + prevsize == entry->offset)) &&
                       (prev->eflags == entry->eflags) &&
                       (prev->protection == entry->protection) &&
                       (prev->max_protection == entry->max_protection) &&
                       (prev->inheritance == entry->inheritance) &&
                       (prev->wired_count == entry->wired_count)) {
                          if (map->first_free == prev)
                                  map->first_free = 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);
                  }
          }
  
          next = entry->next;
          if (next != &map->header) {
                  esize = entry->end - entry->start;
                  if ((entry->end == next->start) &&
                      (next->object.vm_object == entry->object.vm_object) &&
                       (!entry->object.vm_object ||
                          (entry->offset + esize == next->offset)) &&
                      (next->eflags == entry->eflags) &&
                      (next->protection == entry->protection) &&
                      (next->max_protection == entry->max_protection) &&
                      (next->inheritance == entry->inheritance) &&
                      (next->wired_count == entry->wired_count)) {
                          if (map->first_free == next)
                                  map->first_free = 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);
                  }
          }
  }
  /*
   *      vm_map_clip_start:      [ internal use only ]
   *
   *      Asserts that the given entry begins at or after
   *      the specified address; if necessary,
   *      it splits the entry into two.
   */
  #define vm_map_clip_start(map, entry, startaddr) \
  { \
          if (startaddr > entry->start) \
                  _vm_map_clip_start(map, entry, startaddr); \
  }
  
  /*
   *      This routine is called only when it is known that
   *      the entry must be split.
   */
  static void
  _vm_map_clip_start(vm_map_t map, vm_map_entry_t entry, vm_offset_t start)
  {
          vm_map_entry_t new_entry;
  
          /*
           * Split off the front portion -- note that we must insert the new
           * entry BEFORE this one, so that this entry has the specified
           * starting address.
           */
          vm_map_simplify_entry(map, entry);
  
          /*
           * If there is no object backing this entry, we might as well create
           * one now.  If we defer it, an object can get created after the map
           * is clipped, and individual objects will be created for the split-up
           * map.  This is a bit of a hack, but is also about the best place to
           * put this improvement.
           */
          if (entry->object.vm_object == NULL && !map->system_map) {
                  vm_object_t object;
                  object = vm_object_allocate(OBJT_DEFAULT,
                                  atop(entry->end - entry->start));
                  entry->object.vm_object = object;
                  entry->offset = 0;
          }
  
          new_entry = vm_map_entry_create(map);
          *new_entry = *entry;
  
          new_entry->end = start;
          entry->offset += (start - entry->start);
          entry->start = start;
  
          vm_map_entry_link(map, entry->prev, new_entry);
  
          if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
                  vm_object_reference(new_entry->object.vm_object);
          }
  }
  
  /*
   *      vm_map_clip_end:        [ internal use only ]
   *
   *      Asserts that the given entry ends at or before
   *      the specified address; if necessary,
   *      it splits the entry into two.
   */
  #define vm_map_clip_end(map, entry, endaddr) \
  { \
          if ((endaddr) < (entry->end)) \
                  _vm_map_clip_end((map), (entry), (endaddr)); \
  }
  
  /*
   *      This routine is called only when it is known that
   *      the entry must be split.
   */
  static void
  _vm_map_clip_end(vm_map_t map, vm_map_entry_t entry, vm_offset_t end)
  {
          vm_map_entry_t new_entry;
  
          /*
           * If there is no object backing this entry, we might as well create
           * one now.  If we defer it, an object can get created after the map
           * is clipped, and individual objects will be created for the split-up
           * map.  This is a bit of a hack, but is also about the best place to
           * put this improvement.
           */
          if (entry->object.vm_object == NULL && !map->system_map) {
                  vm_object_t object;
                  object = vm_object_allocate(OBJT_DEFAULT,
                                  atop(entry->end - entry->start));
                  entry->object.vm_object = object;
                  entry->offset = 0;
          }
  
          /*
           * Create a new entry and insert it AFTER the specified entry
           */
          new_entry = vm_map_entry_create(map);
          *new_entry = *entry;
  
          new_entry->start = entry->end = end;
          new_entry->offset += (end - entry->start);
  
          vm_map_entry_link(map, entry, new_entry);
  
          if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
                  vm_object_reference(new_entry->object.vm_object);
          }
  }
  
  /*
   *      VM_MAP_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_submap:          [ kernel use only ]
   *
   *      Mark the given range as handled by a subordinate map.
   *
   *      This range must have been created with vm_map_find,
   *      and no other operations may have been performed on this
   *      range prior to calling vm_map_submap.
   *
   *      Only a limited number of operations can be performed
   *      within this rage after calling vm_map_submap:
   *              vm_fault
   *      [Don't try vm_map_copy!]
   *
   *      To remove a submapping, one must first remove the
   *      range from the superior map, and then destroy the
   *      submap (if desired).  [Better yet, don't try it.]
   */
  int
  vm_map_submap(
          vm_map_t map,
          vm_offset_t start,
          vm_offset_t end,
          vm_map_t submap)
  {
          vm_map_entry_t entry;
          int result = KERN_INVALID_ARGUMENT;
  
          vm_map_lock(map);
  
          VM_MAP_RANGE_CHECK(map, start, end);
  
          if (vm_map_lookup_entry(map, start, &entry)) {
                  vm_map_clip_start(map, entry, start);
          } else
                  entry = entry->next;
  
          vm_map_clip_end(map, entry, end);
  
          if ((entry->start == start) && (entry->end == end) &&
              ((entry->eflags & MAP_ENTRY_COW) == 0) &&
              (entry->object.vm_object == NULL)) {
                  entry->object.sub_map = submap;
                  entry->eflags |= MAP_ENTRY_IS_SUB_MAP;
                  result = KERN_SUCCESS;
          }
          vm_map_unlock(map);
  
          return (result);
  }
  
  /*
   *      vm_map_protect:
   *
   *      Sets the protection of the specified address
   *      region in the target map.  If "set_max" is
   *      specified, the maximum protection is to be set;
   *      otherwise, only the current protection is affected.
   */
  int
  vm_map_protect(vm_map_t map, vm_offset_t start, vm_offset_t end,
                 vm_prot_t new_prot, boolean_t set_max)
  {
          vm_map_entry_t current;
          vm_map_entry_t entry;
  
          vm_map_lock(map);
  
          VM_MAP_RANGE_CHECK(map, start, end);
  
          if (vm_map_lookup_entry(map, start, &entry)) {
                  vm_map_clip_start(map, entry, start);
          } else {
                  entry = entry->next;
          }
  
          /*
           * Make a first pass to check for protection violations.
           */
          current = entry;
          while ((current != &map->header) && (current->start < end)) {
                  if (current->eflags & MAP_ENTRY_IS_SUB_MAP) {
                          vm_map_unlock(map);
                          return (KERN_INVALID_ARGUMENT);
                  }
                  if ((new_prot & current->max_protection) != new_prot) {
                          vm_map_unlock(map);
                          return (KERN_PROTECTION_FAILURE);
                  }
                  current = current->next;
          }
  
          /*
           * 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);
  
                  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) {
                          mtx_lock(&Giant);
                          vm_page_lock_queues();
  #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_page_unlock_queues();
                          mtx_unlock(&Giant);
                  }
                  vm_map_simplify_entry(map, current);
                  current = current->next;
          }
          vm_map_unlock(map);
          return (KERN_SUCCESS);
  }
  
  /*
   *      vm_map_madvise:
   *
   *      This routine traverses a processes map handling the madvise
   *      system call.  Advisories are classified as either those effecting
   *      the vm_map_entry structure, or those effecting the underlying 
   *      objects.
   */
  int
  vm_map_madvise(
          vm_map_t map,
          vm_offset_t start, 
          vm_offset_t end,
          int behav)
  {
          vm_map_entry_t current, entry;
          int modify_map = 0;
  
          /*
           * Some madvise calls directly modify the vm_map_entry, in which case
           * we need to use an exclusive lock on the map and we need to perform 
           * various clipping operations.  Otherwise we only need a read-lock
           * on the map.
           */
          switch(behav) {
          case MADV_NORMAL:
          case MADV_SEQUENTIAL:
          case MADV_RANDOM:
          case MADV_NOSYNC:
          case MADV_AUTOSYNC:
          case MADV_NOCORE:
          case MADV_CORE:
                  modify_map = 1;
                  vm_map_lock(map);
                  break;
          case MADV_WILLNEED:
          case MADV_DONTNEED:
          case MADV_FREE:
                  vm_map_lock_read(map);
                  break;
          default:
                  return (KERN_INVALID_ARGUMENT);
          }
  
          /*
           * Locate starting entry and clip if necessary.
           */
          VM_MAP_RANGE_CHECK(map, start, end);
  
          if (vm_map_lookup_entry(map, start, &entry)) {
                  if (modify_map)
                          vm_map_clip_start(map, entry, start);
          } else {
                  entry = entry->next;
          }
  
          if (modify_map) {
                  /*
                   * madvise behaviors that are implemented in the vm_map_entry.
                   *
                   * We clip the vm_map_entry so that behavioral changes are
                   * limited to the specified address range.
                   */
                  for (current = entry;
                       (current != &map->header) && (current->start < end);
                       current = current->next
                  ) {
                          if (current->eflags & MAP_ENTRY_IS_SUB_MAP)
                                  continue;
  
                          vm_map_clip_end(map, current, end);
  
                          switch (behav) {
                          case MADV_NORMAL:
                                  vm_map_entry_set_behavior(current, MAP_ENTRY_BEHAV_NORMAL);
                                  break;
                          case MADV_SEQUENTIAL:
                                  vm_map_entry_set_behavior(current, MAP_ENTRY_BEHAV_SEQUENTIAL);
                                  break;
                          case MADV_RANDOM:
                                  vm_map_entry_set_behavior(current, MAP_ENTRY_BEHAV_RANDOM);
                                  break;
                          case MADV_NOSYNC:
                                  current->eflags |= MAP_ENTRY_NOSYNC;
                                  break;
                          case MADV_AUTOSYNC:
                                  current->eflags &= ~MAP_ENTRY_NOSYNC;
                                  break;
                          case MADV_NOCORE:
                                  current->eflags |= MAP_ENTRY_NOCOREDUMP;
                                  break;
                          case MADV_CORE:
                                  current->eflags &= ~MAP_ENTRY_NOCOREDUMP;
                                  break;
                          default:
                                  break;
                          }
                          vm_map_simplify_entry(map, current);
                  }
                  vm_map_unlock(map);
          } else {
                  vm_pindex_t 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.
                   */
                  for (current = entry;
                       (current != &map->header) && (current->start < end);
                       current = current->next
                  ) {
                          vm_offset_t useStart;
  
                          if (current->eflags & MAP_ENTRY_IS_SUB_MAP)
                                  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);
                          if (behav == MADV_WILLNEED) {
                                  mtx_lock(&Giant);
                                  pmap_object_init_pt(
                                      map->pmap, 
                                      useStart,
                                      current->object.vm_object,
                                      pindex, 
                                      (count << PAGE_SHIFT),
                                      MAP_PREFAULT_MADVISE
                                  );
                                  mtx_unlock(&Giant);
                          }
                  }
                  vm_map_unlock_read(map);
          }
          return (0);
  }       
  
  
  /*
   *      vm_map_inherit:
   *
   *      Sets the inheritance of the specified address
   *      range in the target map.  Inheritance
   *      affects how the map will be shared with
   *      child maps at the time of 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;
  
          switch (new_inheritance) {
          case VM_INHERIT_NONE:
          case VM_INHERIT_COPY:
          case VM_INHERIT_SHARE:
                  break;
          default:
                  return (KERN_INVALID_ARGUMENT);
          }
          vm_map_lock(map);
          VM_MAP_RANGE_CHECK(map, start, end);
          if (vm_map_lookup_entry(map, start, &temp_entry)) {
                  entry = temp_entry;
                  vm_map_clip_start(map, entry, start);
          } else
                  entry = temp_entry->next;
          while ((entry != &map->header) && (entry->start < end)) {
                  vm_map_clip_end(map, entry, end);
                  entry->inheritance = new_inheritance;
                  vm_map_simplify_entry(map, entry);
                  entry = entry->next;
          }
          vm_map_unlock(map);
          return (KERN_SUCCESS);
  }
  
  /*
   *      vm_map_unwire:
   *
   *      Implements both kernel and user unwiring.
   */
  int
  vm_map_unwire(vm_map_t map, vm_offset_t start, vm_offset_t end,
          boolean_t user_unwire)
  {
          vm_map_entry_t entry, first_entry, tmp_entry;
          vm_offset_t saved_start;
          unsigned int last_timestamp;
          int rv;
          boolean_t need_wakeup, result;
  
          vm_map_lock(map);
          VM_MAP_RANGE_CHECK(map, start, end);
          if (!vm_map_lookup_entry(map, start, &first_entry)) {
                  vm_map_unlock(map);
                  return (KERN_INVALID_ADDRESS);
          }
          last_timestamp = map->timestamp;
          entry = first_entry;
          while (entry != &map->header && entry->start < end) {
                  if (entry->eflags & MAP_ENTRY_IN_TRANSITION) {
                          /*
                           * We have not yet clipped the entry.
                           */
                          saved_start = (start >= entry->start) ? start :
                              entry->start;
                          entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
                          if (vm_map_unlock_and_wait(map, user_unwire)) {
                                  /*
                                   * Allow interruption of user unwiring?
                                   */
                          }
                          vm_map_lock(map);
                          if (last_timestamp+1 != map->timestamp) {
                                  /*
                                   * Look again for the entry because the map was
                                   * modified while it was unlocked.
                                   * Specifically, the entry may have been
                                   * clipped, merged, or deleted.
                                   */
                                  if (!vm_map_lookup_entry(map, saved_start,
                                      &tmp_entry)) {
                                          if (saved_start == start) {
                                                  /*
                                                   * First_entry has been deleted.
                                                   */
                                                  vm_map_unlock(map);
                                                  return (KERN_INVALID_ADDRESS);
                                          }
                                          end = saved_start;
                                          rv = KERN_INVALID_ADDRESS;
                                          goto done;
                                  }
                                  if (entry == first_entry)
                                          first_entry = tmp_entry;
                                  else
                                          first_entry = NULL;
                                  entry = tmp_entry;
                          }
                          last_timestamp = map->timestamp;
                          continue;
                  }
                  vm_map_clip_start(map, entry, start);
                  vm_map_clip_end(map, entry, end);
                  /*
                   * Mark the entry in case the map lock is released.  (See
                   * above.)
                   */
                  entry->eflags |= MAP_ENTRY_IN_TRANSITION;
                  /*
                   * Check the map for holes in the specified region.
                   */
                  if (entry->end < end && (entry->next == &map->header ||
                      entry->next->start > entry->end)) {
                          end = entry->end;
                          rv = KERN_INVALID_ADDRESS;
                          goto done;
                  }
                  /*
                   * Require that the entry is wired.
                   */
                  if (entry->wired_count == 0 || (user_unwire &&
                      (entry->eflags & MAP_ENTRY_USER_WIRED) == 0)) {
                          end = entry->end;
                          rv = KERN_INVALID_ARGUMENT;
                          goto done;
                  }
                  entry = entry->next;
          }
          rv = KERN_SUCCESS;
  done:
          need_wakeup = FALSE;
          if (first_entry == NULL) {
                  result = vm_map_lookup_entry(map, start, &first_entry);
                  KASSERT(result, ("vm_map_unwire: lookup failed"));
          }
          entry = first_entry;
          while (entry != &map->header && entry->start < end) {
                  if (rv == KERN_SUCCESS) {
                          if (user_unwire)
                                  entry->eflags &= ~MAP_ENTRY_USER_WIRED;
                          entry->wired_count--;
                          if (entry->wired_count == 0) {
                                  /*
                                   * Retain the map lock.
                                   */
                                  vm_fault_unwire(map, entry->start, entry->end);
                          }
                  }
                  KASSERT(entry->eflags & MAP_ENTRY_IN_TRANSITION,
                          ("vm_map_unwire: in-transition flag missing"));
                  entry->eflags &= ~MAP_ENTRY_IN_TRANSITION;
                  if (entry->eflags & MAP_ENTRY_NEEDS_WAKEUP) {
                          entry->eflags &= ~MAP_ENTRY_NEEDS_WAKEUP;
                          need_wakeup = TRUE;
                  }
                  vm_map_simplify_entry(map, entry);
                  entry = entry->next;
          }
          vm_map_unlock(map);
          if (need_wakeup)
                  vm_map_wakeup(map);
          return (rv);
  }
  
  /*
   *      vm_map_wire:
   *
   *      Implements both kernel and user wiring.
   */
  int
  vm_map_wire(vm_map_t map, vm_offset_t start, vm_offset_t end,
          boolean_t user_wire)
  {
          vm_map_entry_t entry, first_entry, tmp_entry;
          vm_offset_t saved_end, saved_start;
          unsigned int last_timestamp;
          int rv;
          boolean_t need_wakeup, result;
  
          vm_map_lock(map);
          VM_MAP_RANGE_CHECK(map, start, end);
          if (!vm_map_lookup_entry(map, start, &first_entry)) {
                  vm_map_unlock(map);
                  return (KERN_INVALID_ADDRESS);
          }
          last_timestamp = map->timestamp;
          entry = first_entry;
          while (entry != &map->header && entry->start < end) {
                  if (entry->eflags & MAP_ENTRY_IN_TRANSITION) {
                          /*
                           * We have not yet clipped the entry.
                           */
                          saved_start = (start >= entry->start) ? start :
                              entry->start;
                          entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
                          if (vm_map_unlock_and_wait(map, user_wire)) {
                                  /*
                                   * Allow interruption of user wiring?
                                   */
                          }
                          vm_map_lock(map);
                          if (last_timestamp + 1 != map->timestamp) {
                                  /*
                                   * Look again for the entry because the map was
                                   * modified while it was unlocked.
                                   * Specifically, the entry may have been
                                   * clipped, merged, or deleted.
                                   */
                                  if (!vm_map_lookup_entry(map, saved_start,
                                      &tmp_entry)) {
                                          if (saved_start == start) {
                                                  /*
                                                   * first_entry has been deleted.
                                                   */
                                                  vm_map_unlock(map);
                                                  return (KERN_INVALID_ADDRESS);
                                          }
                                          end = saved_start;
                                          rv = KERN_INVALID_ADDRESS;
                                          goto done;
                                  }
                                  if (entry == first_entry)
                                          first_entry = tmp_entry;
                                  else
                                          first_entry = NULL;
                                  entry = tmp_entry;
                          }
                          last_timestamp = map->timestamp;
                          continue;
                  }
                  vm_map_clip_start(map, entry, start);
                  vm_map_clip_end(map, entry, end);
                  /*
                   * Mark the entry in case the map lock is released.  (See
                   * above.)
                   */
                  entry->eflags |= MAP_ENTRY_IN_TRANSITION;
                  /*
                   *
                   */
                  if (entry->wired_count == 0) {
                          entry->wired_count++;
                          saved_start = entry->start;
                          saved_end = entry->end;
                          /*
                           * Release the map lock, relying on the in-transition
                           * mark.
                           */
                          vm_map_unlock(map);
                          rv = vm_fault_wire(map, saved_start, saved_end,
                              user_wire);
                          vm_map_lock(map);
                          if (last_timestamp + 1 != map->timestamp) {
                                  /*
                                   * Look again for the entry because the map was
                                   * modified while it was unlocked.  The entry
                                   * may have been clipped, but NOT merged or
                                   * deleted.
                                   */
                                  result = vm_map_lookup_entry(map, saved_start,
                                      &tmp_entry);
                                  KASSERT(result, ("vm_map_wire: lookup failed"));
                                  if (entry == first_entry)
                                          first_entry = tmp_entry;
                                  else
                                          first_entry = NULL;
                                  entry = tmp_entry;
                                  while (entry->end < saved_end) {
                                          if (rv != KERN_SUCCESS) {
                                                  KASSERT(entry->wired_count == 1,
                                                      ("vm_map_wire: bad count"));
                                                  entry->wired_count = -1;
                                          }
                                          entry = entry->next;
                                  }
                          }
                          last_timestamp = map->timestamp;
                          if (rv != KERN_SUCCESS) {
                                  KASSERT(entry->wired_count == 1,
                                      ("vm_map_wire: bad count"));
                                  /*
                                   * Assign an out-of-range value to represent
                                   * the failure to wire this entry.
                                   */
                                  entry->wired_count = -1;
                                  end = entry->end;
                                  goto done;
                          }
                  } else if (!user_wire ||
                             (entry->eflags & MAP_ENTRY_USER_WIRED) == 0) {
                          entry->wired_count++;
                  }
                  /*
                   * Check the map for holes in the specified region.
                   */
                  if (entry->end < end && (entry->next == &map->header ||
                      entry->next->start > entry->end)) {
                          end = entry->end;
                          rv = KERN_INVALID_ADDRESS;
                          goto done;
                  }
                  entry = entry->next;
          }
          rv = KERN_SUCCESS;
  done:
          need_wakeup = FALSE;
          if (first_entry == NULL) {
                  result = vm_map_lookup_entry(map, start, &first_entry);
                  KASSERT(result, ("vm_map_wire: lookup failed"));
          }
          entry = first_entry;
          while (entry != &map->header && entry->start < end) {
                  if (rv == KERN_SUCCESS) {
                          if (user_wire)
                                  entry->eflags |= MAP_ENTRY_USER_WIRED;
                  } else if (entry->wired_count == -1) {
                          /*
                           * Wiring failed on this entry.  Thus, unwiring is
                           * unnecessary.
                           */
                          entry->wired_count = 0;
                  } else {
                          if (!user_wire ||
                              (entry->eflags & MAP_ENTRY_USER_WIRED) == 0)
                                  entry->wired_count--;
                          if (entry->wired_count == 0) {
                                  /*
                                   * Retain the map lock.
                                   */
                                  vm_fault_unwire(map, entry->start, entry->end);
                          }
                  }
                  KASSERT(entry->eflags & MAP_ENTRY_IN_TRANSITION,
                          ("vm_map_wire: in-transition flag missing"));
                  entry->eflags &= ~MAP_ENTRY_IN_TRANSITION;
                  if (entry->eflags & MAP_ENTRY_NEEDS_WAKEUP) {
                          entry->eflags &= ~MAP_ENTRY_NEEDS_WAKEUP;
                          need_wakeup = TRUE;
                  }
                  vm_map_simplify_entry(map, entry);
                  entry = entry->next;
          }
          vm_map_unlock(map);
          if (need_wakeup)
                  vm_map_wakeup(map);
          return (rv);
  }
  
  /*
   * 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;
  
          GIANT_REQUIRED;
  
          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->eflags & MAP_ENTRY_IS_SUB_MAP) {
                          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) {
                  vm_page_lock_queues();
                  pmap_remove(map->pmap, start, end);
                  vm_page_unlock_queues();
          }
          /*
           * 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->eflags & MAP_ENTRY_IS_SUB_MAP) {
                          vm_map_t smap;
                          vm_map_entry_t tentry;
                          vm_size_t tsize;
  
                          smap = current->object.sub_map;
                          vm_map_lock_read(smap);
                          (void) vm_map_lookup_entry(smap, offset, &tentry);
                          tsize = tentry->end - offset;
                          if (tsize < size)
                                  size = tsize;
                          object = tentry->object.vm_object;
                          offset = tentry->offset + (offset - tentry->start);
                          vm_map_unlock_read(smap);
                  } else {
                          object = current->object.vm_object;
                  }
                  /*
                   * 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) {
                          object = object->backing_object;
                          offset += object->backing_object_offset;
                          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, curthread);
                          flags = (syncio || invalidate) ? OBJPC_SYNC : 0;
                          flags |= invalidate ? OBJPC_INVAL : 0;
                          VM_OBJECT_LOCK(object);
                          vm_object_page_clean(object,
                              OFF_TO_IDX(offset),
                              OFF_TO_IDX(offset + size + PAGE_MASK),
                              flags);
                          VM_OBJECT_UNLOCK(object);
                          VOP_UNLOCK(object->handle, 0, curthread);
                          vm_object_deallocate(object);
                  }
                  if (object && invalidate &&
                      ((object->type == OBJT_VNODE) ||
                       (object->type == OBJT_DEVICE))) {
                          VM_OBJECT_LOCK(object);
                          vm_object_page_remove(object,
                              OFF_TO_IDX(offset),
                              OFF_TO_IDX(offset + size + PAGE_MASK),
                              FALSE);
                          VM_OBJECT_UNLOCK(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)
  {
          vm_fault_unwire(map, entry->start, entry->end);
          entry->wired_count = 0;
  }
  
  /*
   *      vm_map_entry_delete:    [ internal use only ]
   *
   *      Deallocate the given entry from the target map.
   */
  static void
  vm_map_entry_delete(vm_map_t map, vm_map_entry_t entry)
  {
          vm_map_entry_unlink(map, entry);
          map->size -= entry->end - entry->start;
  
          if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
                  vm_object_deallocate(entry->object.vm_object);
          }
  
          vm_map_entry_dispose(map, entry);
  }
  
  /*
   *      vm_map_delete:  [ internal use only ]
   *
   *      Deallocates the given address range from the target
   *      map.
   */
  int
  vm_map_delete(vm_map_t map, vm_offset_t start, vm_offset_t end)
  {
          vm_object_t object;
          vm_map_entry_t entry;
          vm_map_entry_t first_entry;
  
          /*
           * Find the start of the region, and clip it
           */
          if (!vm_map_lookup_entry(map, start, &first_entry))
                  entry = first_entry->next;
          else {
                  entry = first_entry;
                  vm_map_clip_start(map, entry, start);
          }
  
          /*
           * Save the free space hint
           */
          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;
  
                  /*
                   * Wait for wiring or unwiring of an entry to complete.
                   */
                  if ((entry->eflags & MAP_ENTRY_IN_TRANSITION) != 0) {
                          unsigned int last_timestamp;
                          vm_offset_t saved_start;
                          vm_map_entry_t tmp_entry;
  
                          saved_start = entry->start;
                          entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
                          last_timestamp = map->timestamp;
                          (void) vm_map_unlock_and_wait(map, FALSE);
                          vm_map_lock(map);
                          if (last_timestamp + 1 != map->timestamp) {
                                  /*
                                   * Look again for the entry because the map was
                                   * modified while it was unlocked.
                                   * Specifically, the entry may have been
                                   * clipped, merged, or deleted.
                                   */
                                  if (!vm_map_lookup_entry(map, saved_start,
                                                           &tmp_entry))
                                          entry = tmp_entry->next;
                                  else {
                                          entry = tmp_entry;
                                          vm_map_clip_start(map, entry,
                                                            saved_start);
                                  }
                          }
                          continue;
                  }
                  vm_map_clip_end(map, entry, end);
  
                  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 || object == kmem_object) {
                          if (object == kernel_object)
                                  GIANT_REQUIRED;
                          VM_OBJECT_LOCK(object);
                          vm_object_page_remove(object, offidxstart, offidxend, FALSE);
                          VM_OBJECT_UNLOCK(object);
                  } else {
                          mtx_lock(&Giant);
                          vm_page_lock_queues();
                          pmap_remove(map->pmap, s, e);
                          vm_page_unlock_queues();
                          if (object != NULL) {
                                  VM_OBJECT_LOCK(object);
                                  if (object->ref_count != 1 &&
                                      (object->flags & (OBJ_NOSPLIT|OBJ_ONEMAPPING)) == OBJ_ONEMAPPING &&
                                      (object->type == OBJT_DEFAULT || object->type == OBJT_SWAP)) {
                                          VM_OBJECT_UNLOCK(object);
                                          vm_object_collapse(object);
                                          VM_OBJECT_LOCK(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;
                                  }
                                  VM_OBJECT_UNLOCK(object);
                          }
                          mtx_unlock(&Giant);
                  }
  
                  /*
                   * 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);
                  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, s = 0;
  
          if (map == kmem_map)
                  s = splvm();
  
          vm_map_lock(map);
          VM_MAP_RANGE_CHECK(map, start, end);
          result = vm_map_delete(map, start, end);
          vm_map_unlock(map);
  
          if (map == kmem_map)
                  splx(s);
  
          return (result);
  }
  
  /*
   *      vm_map_check_protection:
   *
   *      Assert that the target map allows the specified privilege on the
   *      entire address region given.  The entire region must be allocated.
   *
   *      WARNING!  This code does not and should not check whether the
   *      contents of the region is accessible.  For example a smaller file
   *      might be mapped into a larger address space.
   *
   *      NOTE!  This code is also called by munmap().
   */
  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;
  
          vm_map_lock_read(map);
          if (!vm_map_lookup_entry(map, start, &tmp_entry)) {
                  vm_map_unlock_read(map);
                  return (FALSE);
          }
          entry = tmp_entry;
  
          while (start < end) {
                  if (entry == &map->header) {
                          vm_map_unlock_read(map);
                          return (FALSE);
                  }
                  /*
                   * No holes allowed!
                   */
                  if (start < entry->start) {
                          vm_map_unlock_read(map);
                          return (FALSE);
                  }
                  /*
                   * Check protection associated with entry.
                   */
                  if ((entry->protection & protection) != protection) {
                          vm_map_unlock_read(map);
                          return (FALSE);
                  }
                  /* go to next entry */
                  start = entry->end;
                  entry = entry->next;
          }
          vm_map_unlock_read(map);
          return (TRUE);
  }
  
  /*
   *      vm_map_copy_entry:
   *
   *      Copies the contents of the source entry to the destination
   *      entry.  The entries *must* be aligned properly.
   */
  static void
  vm_map_copy_entry(
          vm_map_t src_map,
          vm_map_t dst_map,
          vm_map_entry_t src_entry, 
          vm_map_entry_t dst_entry)
  {
          vm_object_t src_object;
  
          if ((dst_entry->eflags|src_entry->eflags) & MAP_ENTRY_IS_SUB_MAP)
                  return;
  
          if (src_entry->wired_count == 0) {
  
                  /*
                   * If the source entry is marked needs_copy, it is already
                   * write-protected.
                   */
                  if ((src_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) {
                          vm_page_lock_queues();
                          pmap_protect(src_map->pmap,
                              src_entry->start,
                              src_entry->end,
                              src_entry->protection & ~VM_PROT_WRITE);
                          vm_page_unlock_queues();
                  }
  
                  /*
                   * 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_object_split(src_entry);
                                          src_object = src_entry->object.vm_object;
                                  }
                          }
  
                          vm_object_reference(src_object);
                          VM_OBJECT_LOCK(src_object);
                          vm_object_clear_flag(src_object, OBJ_ONEMAPPING);
                          VM_OBJECT_UNLOCK(src_object);
                          dst_entry->object.vm_object = src_object;
                          src_entry->eflags |= (MAP_ENTRY_COW|MAP_ENTRY_NEEDS_COPY);
                          dst_entry->eflags |= (MAP_ENTRY_COW|MAP_ENTRY_NEEDS_COPY);
                          dst_entry->offset = src_entry->offset;
                  } 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;
  
          GIANT_REQUIRED;
  
          vm_map_lock(old_map);
          old_map->infork = 1;
  
          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;
  
          old_entry = old_map->header.next;
  
          while (old_entry != &old_map->header) {
                  if (old_entry->eflags & MAP_ENTRY_IS_SUB_MAP)
                          panic("vm_map_fork: encountered a submap");
  
                  switch (old_entry->inheritance) {
                  case VM_INHERIT_NONE:
                          break;
  
                  case VM_INHERIT_SHARE:
                          /*
                           * Clone the entry, creating the shared object if necessary.
                           */
                          object = old_entry->object.vm_object;
                          if (object == NULL) {
                                  object = vm_object_allocate(OBJT_DEFAULT,
                                          atop(old_entry->end - old_entry->start));
                                  old_entry->object.vm_object = object;
                                  old_entry->offset = (vm_offset_t) 0;
                          }
  
                          /*
                           * Add the reference before calling vm_object_shadow
                           * to insure that a shadow object is created.
                           */
                          vm_object_reference(object);
                          if (old_entry->eflags & MAP_ENTRY_NEEDS_COPY) {
                                  vm_object_shadow(&old_entry->object.vm_object,
                                          &old_entry->offset,
                                          atop(old_entry->end - old_entry->start));
                                  old_entry->eflags &= ~MAP_ENTRY_NEEDS_COPY;
                                  /* Transfer the second reference too. */
                                  vm_object_reference(
                                      old_entry->object.vm_object);
                                  vm_object_deallocate(object);
                                  object = old_entry->object.vm_object;
                          }
                          VM_OBJECT_LOCK(object);
                          vm_object_clear_flag(object, OBJ_ONEMAPPING);
                          VM_OBJECT_UNLOCK(object);
  
                          /*
                           * Clone the entry, referencing the shared object.
                           */
                          new_entry = vm_map_entry_create(new_map);
                          *new_entry = *old_entry;
                          new_entry->eflags &= ~MAP_ENTRY_USER_WIRED;
                          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);
                          *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);
  
          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;
  
          if (addrbos < vm_map_min(map))
                  return (KERN_NO_SPACE);
  
          if (max_ssize < sgrowsiz)
                  init_ssize = max_ssize;
          else
                  init_ssize = sgrowsiz;
  
          vm_map_lock(map);
  
          /* If addr is already mapped, no go */
          if (vm_map_lookup_entry(map, addrbos, &prev_entry)) {
                  vm_map_unlock(map);
                  return (KERN_NO_SPACE);
          }
  
          /* If we would blow our VMEM resource limit, no go */
          if (map->size + init_ssize >
              curthread->td_proc->p_rlimit[RLIMIT_VMEM].rlim_cur) {
                  vm_map_unlock(map);
                  return (KERN_NO_SPACE);
          }
  
          /* If we can't accomodate max_ssize in the current mapping,
           * no go.  However, we need to be aware that subsequent user
           * mappings might map into the space we have reserved for
           * stack, and currently this space is not protected.  
           * 
           * Hopefully we will at least detect this condition 
           * when we try to grow the stack.
           */
          if ((prev_entry->next != &map->header) &&
              (prev_entry->next->start < addrbos + max_ssize)) {
                  vm_map_unlock(map);
                  return (KERN_NO_SPACE);
          }
  
          /* We initially map a stack of only init_ssize.  We will
           * grow as needed later.  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, NULL, 0, addrbos + max_ssize - init_ssize,
                             addrbos + max_ssize, 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);
                  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->avail_ssize = max_ssize - init_ssize;
          }
  
          vm_map_unlock(map);
          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;
          int      is_procstack;
  
          GIANT_REQUIRED;
          
  Retry:
          vm_map_lock_read(map);
  
          /* If addr is already in the entry range, no need to grow.*/
          if (vm_map_lookup_entry(map, addr, &prev_entry)) {
                  vm_map_unlock_read(map);
                  return (KERN_SUCCESS);
          }
  
          if ((stack_entry = prev_entry->next) == &map->header) {
                  vm_map_unlock_read(map);
                  return (KERN_SUCCESS);
          } 
          if (prev_entry == &map->header) 
                  end = stack_entry->start - stack_entry->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->avail_ssize < 1 ||
              addr >= stack_entry->start ||
              addr <  stack_entry->start - stack_entry->avail_ssize) {
                  vm_map_unlock_read(map);
                  return (KERN_SUCCESS);
          } 
          
          /* Find the minimum grow amount */
          grow_amount = roundup (stack_entry->start - addr, PAGE_SIZE);
          if (grow_amount > stack_entry->avail_ssize) {
                  vm_map_unlock_read(map);
                  return (KERN_NO_SPACE);
          }
  
          /* If there is no longer enough space between the entries
           * nogo, and adjust the available space.  Note: this 
           * should only happen if the user has mapped into the
           * stack area after the stack was created, and is
           * probably an error.
           *
           * This also effectively destroys any guard page the user
           * might have intended by limiting the stack size.
           */
          if (grow_amount > stack_entry->start - end) {
                  if (vm_map_lock_upgrade(map))
                          goto Retry;
  
                  stack_entry->avail_ssize = stack_entry->start - end;
  
                  vm_map_unlock(map);
                  return (KERN_NO_SPACE);
          }
  
          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)) {
                  vm_map_unlock_read(map);
                  return (KERN_NO_SPACE);
          }
  
          /* Round up the grow amount modulo SGROWSIZ */
          grow_amount = roundup (grow_amount, sgrowsiz);
          if (grow_amount > stack_entry->avail_ssize) {
                  grow_amount = stack_entry->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 >
              curthread->td_proc->p_rlimit[RLIMIT_VMEM].rlim_cur) {
                  vm_map_unlock_read(map);
                  return (KERN_NO_SPACE);
          }
  
          if (vm_map_lock_upgrade(map))
                  goto Retry;
  
          /* Get the preliminary new entry start value */
          addr = stack_entry->start - grow_amount;
  
          /* If this puts us into the previous entry, cut back our growth
           * to the available space.  Also, see the note above.
           */
          if (addr < end) {
                  stack_entry->avail_ssize = stack_entry->start - end;
                  addr = end;
          }
  
          rv = vm_map_insert(map, NULL, 0, addr, stack_entry->start,
              p->p_sysent->sv_stackprot, 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);
                  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->avail_ssize = stack_entry->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);
                  }
          }
  
          vm_map_unlock(map);
          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, vm_offset_t minuser, vm_offset_t maxuser)
  {
          struct vmspace *oldvmspace = p->p_vmspace;
          struct vmspace *newvmspace;
  
          GIANT_REQUIRED;
          newvmspace = vmspace_alloc(minuser, maxuser);
          bcopy(&oldvmspace->vm_startcopy, &newvmspace->vm_startcopy,
              (caddr_t) (newvmspace + 1) - (caddr_t) &newvmspace->vm_startcopy);
          /*
           * This code is written like this for prototype purposes.  The
           * goal is to avoid running down the vmspace here, but let the
           * other process's that are still using the vmspace to finally
           * run it down.  Even though there is little or no chance of blocking
           * here, it is a good idea to keep this form for future mods.
           */
          p->p_vmspace = newvmspace;
          pmap_pinit2(vmspace_pmap(newvmspace));
          vmspace_free(oldvmspace);
          if (p == curthread->td_proc)            /* XXXKSE ? */
                  pmap_activate(curthread);
  }
  
  /*
   * Unshare the specified VM space for forcing COW.  This
   * is called by rfork, for the (RFMEM|RFPROC) == 0 case.
   */
  void
  vmspace_unshare(struct proc *p)
  {
          struct vmspace *oldvmspace = p->p_vmspace;
          struct vmspace *newvmspace;
  
          GIANT_REQUIRED;
          if (oldvmspace->vm_refcnt == 1)
                  return;
          newvmspace = vmspace_fork(oldvmspace);
          p->p_vmspace = newvmspace;
          pmap_pinit2(vmspace_pmap(newvmspace));
          vmspace_free(oldvmspace);
          if (p == curthread->td_proc)            /* XXXKSE ? */
                  pmap_activate(curthread);
  }
  
  /*
   *      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;
  
  RetryLookup:;
          /*
           * Lookup the faulting address.
           */
  
          vm_map_lock_read(map);
  #define RETURN(why) \
                  { \
                  vm_map_unlock_read(map); \
                  return (why); \
                  }
  
          /*
           * If the map has an interesting hint, try it before calling full
           * blown lookup routine.
           */
          entry = map->root;
          *out_entry = entry;
          if (entry == NULL ||
              (vaddr < entry->start) || (vaddr >= entry->end)) {
                  /*
                   * 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, out_entry))
                          RETURN(KERN_INVALID_ADDRESS);
  
                  entry = *out_entry;
          }
          
          /*
           * Handle submaps.
           */
          if (entry->eflags & MAP_ENTRY_IS_SUB_MAP) {
                  vm_map_t old_map = map;
  
                  *var_map = map = entry->object.sub_map;
                  vm_map_unlock_read(old_map);
                  goto RetryLookup;
          }
  
          /*
           * Check whether this task is allowed to have this page.
           * 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) {
                          RETURN(KERN_PROTECTION_FAILURE);
          }
          if ((entry->eflags & MAP_ENTRY_USER_WIRED) &&
              (entry->eflags & MAP_ENTRY_COW) &&
              (fault_type & VM_PROT_WRITE) &&
              (fault_typea & VM_PROT_OVERRIDE_WRITE) == 0) {
                  RETURN(KERN_PROTECTION_FAILURE);
          }
  
          /*
           * If this page is not pageable, we have to get it for all possible
           * accesses.
           */
          *wired = (entry->wired_count != 0);
          if (*wired)
                  prot = fault_type = entry->protection;
  
          /*
           * 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 (vm_map_lock_upgrade(map))
                                  goto RetryLookup;
  
                          vm_object_shadow(
                              &entry->object.vm_object,
                              &entry->offset,
                              atop(entry->end - entry->start));
                          entry->eflags &= ~MAP_ENTRY_NEEDS_COPY;
  
                          vm_map_lock_downgrade(map);
                  } else {
                          /*
                           * We're attempting to read a copy-on-write page --
                           * don't allow writes.
                           */
                          prot &= ~VM_PROT_WRITE;
                  }
          }
  
          /*
           * Create an object if necessary.
           */
          if (entry->object.vm_object == NULL &&
              !map->system_map) {
                  if (vm_map_lock_upgrade(map)) 
                          goto RetryLookup;
                  entry->object.vm_object = vm_object_allocate(OBJT_DEFAULT,
                      atop(entry->end - entry->start));
                  entry->offset = 0;
                  vm_map_lock_downgrade(map);
          }
  
          /*
           * Return the object/offset from this entry.  If the entry was
           * copy-on-write or empty, it has been fixed up.
           */
          *pindex = OFF_TO_IDX((vaddr - entry->start) + entry->offset);
          *object = entry->object.vm_object;
  
          /*
           * Return whether this is the only map sharing this data.
           */
          *out_prot = prot;
          return (KERN_SUCCESS);
  
  #undef  RETURN
  }
  
  /*
   *      vm_map_lookup_done:
   *
   *      Releases locks acquired by a vm_map_lookup
   *      (according to the handle returned by that lookup).
   */
  void
  vm_map_lookup_done(vm_map_t map, vm_map_entry_t entry)
  {
          /*
           * Unlock the main-level map
           */
          vm_map_unlock_read(map);
  }
  
  #include "opt_ddb.h"
  #ifdef DDB
  #include <sys/kernel.h>
  
  #include <ddb/ddb.h>
  
  /*
   *      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->eflags & MAP_ENTRY_IS_SUB_MAP) {
                          db_printf(", share=%p, offset=0x%jx\n",
                              (void *)entry->object.sub_map,
                              (uintmax_t)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 {
                          db_printf(", object=%p, offset=0x%jx",
                              (void *)entry->object.vm_object,
                              (uintmax_t)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 */