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: src/sys/vm/vm_map.c,v 1.57.2.8 1999/09/05 08:24:28 peter Exp $
     */
    
    /*
     *      Virtual memory mapping module.
     */
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/malloc.h>
    #include <sys/proc.h>
    #include <sys/queue.h>
    #include <sys/vmmeter.h>
    #include <sys/mman.h>
    
    #include <vm/vm.h>
    #include <vm/vm_param.h>
    #include <vm/vm_prot.h>
    #include <vm/vm_inherit.h>
    #include <vm/lock.h>
    #include <vm/pmap.h>
    #include <vm/vm_map.h>
    #include <vm/vm_page.h>
    #include <vm/vm_object.h>
    #include <vm/vm_kern.h>
    #include <vm/vm_pager.h>
    #include <vm/vm_extern.h>
    #include <vm/default_pager.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.
    *
    *      In order to properly represent the sharing of virtual
    *      memory regions among maps, the map structure is bi-level.
    *      Top-level ("address") maps refer to regions of sharable
    *      virtual memory.  These regions are implemented as
    *      ("sharing") maps, which then refer to the actual virtual
    *      memory objects.  When two address maps "share" memory,
    *      their top-level maps both have references to the same
    *      sharing map.  When memory is virtual-copied from one
    *      address map to another, the references in the sharing
    *      maps are actually copied -- no copying occurs at the
    *      virtual memory object level.
    *
    *      Since portions of maps are specified by start/end addreses,
    *      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.
    *      No attempt is currently made to "glue back together" two
    *      abutting entries.
    *
    *      As mentioned above, virtual copy operations are performed
    *      by copying VM object references from one sharing map to
    *      another, and then marking both regions as copy-on-write.
    *      It is important to note that only one writeable reference
    *      to a VM object region exists in any map -- this means that
    *      shadow object creation can be delayed until a write operation
    *      occurs.
    */
   
   /*
    *      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.
    */
   
   vm_offset_t kentry_data;
   vm_size_t kentry_data_size;
   static vm_map_entry_t kentry_free;
   static vm_map_t kmap_free;
   extern char kstack[];
   extern int inmprotect;
   
   static int kentry_count;
   static vm_offset_t mapvm_start, mapvm, mapvmmax;
   static int mapvmpgcnt;
   
   static struct vm_map_entry *mappool;
   static int mappoolcnt;
   #define KENTRY_LOW_WATER 128
   
   static void _vm_map_clip_end __P((vm_map_t, vm_map_entry_t, vm_offset_t));
   static void _vm_map_clip_start __P((vm_map_t, vm_map_entry_t, vm_offset_t));
   static vm_map_entry_t vm_map_entry_create __P((vm_map_t));
   static void vm_map_entry_delete __P((vm_map_t, vm_map_entry_t));
   static void vm_map_entry_dispose __P((vm_map_t, vm_map_entry_t));
   static void vm_map_entry_unwire __P((vm_map_t, vm_map_entry_t));
   static void vm_map_copy_entry __P((vm_map_t, vm_map_t, vm_map_entry_t,
                   vm_map_entry_t));
   
   void
   vm_map_startup()
   {
           register int i;
           register vm_map_entry_t mep;
           vm_map_t mp;
   
           /*
            * Static map structures for allocation before initialization of
            * kernel map or kmem map.  vm_map_create knows how to deal with them.
            */
           kmap_free = mp = (vm_map_t) kentry_data;
           i = MAX_KMAP;
           while (--i > 0) {
                   mp->header.next = (vm_map_entry_t) (mp + 1);
                   mp++;
           }
           mp++->header.next = NULL;
   
           /*
            * Form a free list of statically allocated kernel map entries with
            * the rest.
            */
           kentry_free = mep = (vm_map_entry_t) mp;
           kentry_count = i = (kentry_data_size - MAX_KMAP * sizeof *mp) / sizeof *mep;
           while (--i > 0) {
                   mep->next = mep + 1;
                   mep++;
           }
           mep->next = NULL;
   }
   
   /*
    * 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, pageable)
           vm_offset_t min, max;
           int pageable;
   {
           register struct vmspace *vm;
   
           if (mapvmpgcnt == 0 && mapvm == 0) {
                   mapvmpgcnt = (cnt.v_page_count * sizeof(struct vm_map_entry) + PAGE_SIZE - 1) / PAGE_SIZE;
                   mapvm_start = mapvm = kmem_alloc_pageable(kernel_map,
                           mapvmpgcnt * PAGE_SIZE);
                   mapvmmax = mapvm_start + mapvmpgcnt * PAGE_SIZE;
                   if (!mapvm)
                           mapvmpgcnt = 0;
           }
           MALLOC(vm, struct vmspace *, sizeof(struct vmspace), M_VMMAP, M_WAITOK);
           bzero(vm, (caddr_t) &vm->vm_startcopy - (caddr_t) vm);
           vm_map_init(&vm->vm_map, min, max, pageable);
           pmap_pinit(&vm->vm_pmap);
           vm->vm_map.pmap = &vm->vm_pmap;         /* XXX */
           vm->vm_refcnt = 1;
           return (vm);
   }
   
   void
   vmspace_free(vm)
           register struct vmspace *vm;
   {
   
           if (vm->vm_refcnt == 0)
                   panic("vmspace_free: attempt to free already freed vmspace");
   
           if (--vm->vm_refcnt == 0) {
   
                   /*
                    * 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);
   
                   while( vm->vm_map.ref_count != 1)
                           tsleep(&vm->vm_map.ref_count, PVM, "vmsfre", 0);
                   --vm->vm_map.ref_count;
                   vm_object_pmap_remove(vm->vm_upages_obj,
                           0, vm->vm_upages_obj->size);
                   vm_object_deallocate(vm->vm_upages_obj);
                   pmap_release(&vm->vm_pmap);
                   FREE(vm, M_VMMAP);
           } else {
                   wakeup(&vm->vm_map.ref_count);
           }
   }
   
   /*
    *      vm_map_create:
    *
    *      Creates and returns a new empty VM map with
    *      the given physical map structure, and having
    *      the given lower and upper address bounds.
    */
   vm_map_t
   vm_map_create(pmap, min, max, pageable)
           pmap_t pmap;
           vm_offset_t min, max;
           boolean_t pageable;
   {
           register vm_map_t result;
   
           if (kmem_map == NULL) {
                   result = kmap_free;
                   if (result == NULL)
                           panic("vm_map_create: out of maps");
                   kmap_free = (vm_map_t) result->header.next;
           } else
                   MALLOC(result, vm_map_t, sizeof(struct vm_map),
                       M_VMMAP, M_WAITOK);
   
           vm_map_init(result, min, max, pageable);
           result->pmap = pmap;
           return (result);
   }
   
   /*
    * Initialize an existing vm_map structure
    * such as that in the vmspace structure.
    * The pmap is set elsewhere.
    */
   void
   vm_map_init(map, min, max, pageable)
           register struct vm_map *map;
           vm_offset_t min, max;
           boolean_t pageable;
   {
           map->header.next = map->header.prev = &map->header;
           map->nentries = 0;
           map->size = 0;
           map->ref_count = 1;
           map->is_main_map = TRUE;
           map->min_offset = min;
           map->max_offset = max;
           map->entries_pageable = pageable;
           map->first_free = &map->header;
           map->hint = &map->header;
           map->timestamp = 0;
           lock_init(&map->lock, TRUE);
   }
   
   /*
    *      vm_map_entry_dispose:   [ internal use only ]
    *
    *      Inverse of vm_map_entry_create.
    */
   static void
   vm_map_entry_dispose(map, entry)
           vm_map_t map;
           vm_map_entry_t entry;
   {
           int s;
   
           if (map == kernel_map || map == kmem_map ||
                   map == mb_map || map == pager_map) {
                   s = splvm();
                   entry->next = kentry_free;
                   kentry_free = entry;
                   ++kentry_count;
                   splx(s);
           } else {
                   entry->next = mappool;
                   mappool = entry;
                   ++mappoolcnt;
           }
   }
   
   /*
    *      vm_map_entry_create:    [ internal use only ]
    *
    *      Allocates a VM map entry for insertion.
    *      No entry fields are filled in.  This routine is
    */
   static vm_map_entry_t
   vm_map_entry_create(map)
           vm_map_t map;
   {
           vm_map_entry_t entry;
           int i;
           int s;
   
           /*
            * This is a *very* nasty (and sort of incomplete) hack!!!!
            */
           if (kentry_count < KENTRY_LOW_WATER) {
                   s = splvm();
                   if (mapvmpgcnt && mapvm) {
                           vm_page_t m;
   
                           m = vm_page_alloc(kernel_object,
                                   OFF_TO_IDX(mapvm - VM_MIN_KERNEL_ADDRESS),
                                       (map == kmem_map || map == mb_map) ? VM_ALLOC_INTERRUPT : VM_ALLOC_NORMAL);
   
                           if (m) {
                                   int newentries;
   
                                   newentries = (PAGE_SIZE / sizeof(struct vm_map_entry));
                                   vm_page_wire(m);
                                   PAGE_WAKEUP(m);
                                   m->valid = VM_PAGE_BITS_ALL;
                                   pmap_kenter(mapvm, VM_PAGE_TO_PHYS(m));
                                   m->flags |= PG_WRITEABLE;
   
                                   entry = (vm_map_entry_t) mapvm;
                                   mapvm += PAGE_SIZE;
                                   --mapvmpgcnt;
   
                                   for (i = 0; i < newentries; i++) {
                                           vm_map_entry_dispose(kernel_map, entry);
                                           entry++;
                                   }
                           }
                   }
                   splx(s);
           }
   
           if (map == kernel_map || map == kmem_map ||
                   map == mb_map || map == pager_map) {
                   s = splvm();
                   entry = kentry_free;
                   if (entry) {
                           kentry_free = entry->next;
                           --kentry_count;
                   } else {
                           panic("vm_map_entry_create: out of map entries for kernel");
                   }
                   splx(s);
           } else {
                   entry = mappool;
                   if (entry) {
                           mappool = entry->next;
                           --mappoolcnt;
                   } else {
                           MALLOC(entry, vm_map_entry_t, sizeof(struct vm_map_entry),
                               M_VMMAPENT, M_WAITOK);
                   }
           }
   
           return (entry);
   }
   
   /*
    *      vm_map_entry_{un,}link:
    *
    *      Insert/remove entries from maps.
    */
   #define vm_map_entry_link(map, after_where, entry) \
                   { \
                   (map)->nentries++; \
                   (entry)->prev = (after_where); \
                   (entry)->next = (after_where)->next; \
                   (entry)->prev->next = (entry); \
                   (entry)->next->prev = (entry); \
                   }
   #define vm_map_entry_unlink(map, entry) \
                   { \
                   (map)->nentries--; \
                   (entry)->next->prev = (entry)->prev; \
                   (entry)->prev->next = (entry)->next; \
                   }
   
   /*
    *      vm_map_reference:
    *
    *      Creates another valid reference to the given map.
    *
    */
   void
   vm_map_reference(map)
           register vm_map_t map;
   {
           if (map == NULL)
                   return;
   
           map->ref_count++;
   }
   
   /*
    *      vm_map_deallocate:
    *
    *      Removes a reference from the specified map,
    *      destroying it if no references remain.
    *      The map should not be locked.
    */
   void
   vm_map_deallocate(map)
           register vm_map_t map;
   {
           register int c;
   
           if (map == NULL)
                   return;
   
           c = map->ref_count;
   
           if (c == 0)
                   panic("vm_map_deallocate: deallocating already freed map");
   
           if (c != 1) {
                   --map->ref_count;
                   wakeup(&map->ref_count);
                   return;
           }
           /*
            * Lock the map, to wait out all other references to it.
            */
   
           vm_map_lock(map);
           (void) vm_map_delete(map, map->min_offset, map->max_offset);
           --map->ref_count;
           if( map->ref_count != 0) {
                   vm_map_unlock(map);
                   return;
           }
   
           pmap_destroy(map->pmap);
           FREE(map, M_VMMAP);
   }
   
   /*
    *      SAVE_HINT:
    *
    *      Saves the specified entry as the hint for
    *      future lookups.
    */
   #define SAVE_HINT(map,value) \
                   (map)->hint = (value);
   
   /*
    *      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(map, address, entry)
           register vm_map_t map;
           register vm_offset_t address;
           vm_map_entry_t *entry;  /* OUT */
   {
           register vm_map_entry_t cur;
           register vm_map_entry_t last;
   
           /*
            * Start looking either from the head of the list, or from the hint.
            */
   
           cur = map->hint;
   
           if (cur == &map->header)
                   cur = cur->next;
   
           if (address >= cur->start) {
                   /*
                    * Go from hint to end of list.
                    *
                    * But first, make a quick check to see if we are already looking
                    * at the entry we want (which is usually the case). Note also
                    * that we don't need to save the hint here... it is the same
                    * hint (unless we are at the header, in which case the hint
                    * didn't buy us anything anyway).
                    */
                   last = &map->header;
                   if ((cur != last) && (cur->end > address)) {
                           *entry = cur;
                           return (TRUE);
                   }
           } else {
                   /*
                    * Go from start to hint, *inclusively*
                    */
                   last = cur->next;
                   cur = map->header.next;
           }
   
           /*
            * Search linearly
            */
   
           while (cur != last) {
                   if (cur->end > address) {
                           if (address >= cur->start) {
                                   /*
                                    * Save this lookup for future hints, and
                                    * return
                                    */
   
                                   *entry = cur;
                                   SAVE_HINT(map, cur);
                                   return (TRUE);
                           }
                           break;
                   }
                   cur = cur->next;
           }
           *entry = cur->prev;
           SAVE_HINT(map, *entry);
           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.
    */
   int
   vm_map_insert(map, object, offset, start, end, prot, max, cow)
           vm_map_t map;
           vm_object_t object;
           vm_ooffset_t offset;
           vm_offset_t start;
           vm_offset_t end;
           vm_prot_t prot, max;
           int cow;
   {
           register vm_map_entry_t new_entry;
           register vm_map_entry_t prev_entry;
           vm_map_entry_t temp_entry;
           vm_object_t prev_object;
           u_char protoeflags;
   
           if ((object != NULL) && (cow & MAP_NOFAULT)) {
                   panic("vm_map_insert: paradoxical MAP_NOFAULT request");
           }
   
           /*
            * 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_NEEDED)
                   protoeflags |= MAP_ENTRY_NEEDS_COPY;
   
           if (cow & MAP_COPY_ON_WRITE)
                   protoeflags |= MAP_ENTRY_COW;
   
           if (cow & MAP_NOFAULT)
                   protoeflags |= MAP_ENTRY_NOFAULT;
   
           /*
            * See if we can avoid creating a new entry by extending one of our
            * neighbors.  Or at least extend the object.
            */
   
           if ((object == NULL) &&
               (prev_entry != &map->header) &&
               (( prev_entry->eflags & (MAP_ENTRY_IS_A_MAP | MAP_ENTRY_IS_SUB_MAP)) == 0) &&
               (prev_entry->end == start) &&
               (prev_entry->wired_count == 0)) {
                   
   
                   if ((protoeflags == prev_entry->eflags) &&
                       ((cow & MAP_NOFAULT) ||
                        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)))) {
   
                           /*
                            * Coalesced the two objects.  Can we extend the
                            * previous map entry to include the new range?
                            */
                           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;
                                   if ((cow & MAP_NOFAULT) == 0) {
                                           prev_object = prev_entry->object.vm_object;
                                           default_pager_convert_to_swapq(prev_object);
                                   }
                                   return (KERN_SUCCESS);
                           }
                           else {
                                   object = prev_entry->object.vm_object;
                                   offset = prev_entry->offset + (prev_entry->end -
                                                                  prev_entry->start);
   
                                   vm_object_reference(object);
                           }
                   }
           }
   
           /*
            * 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;
   
           if (map->is_main_map) {
                   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;
   
           default_pager_convert_to_swapq(object);
           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(map, start, length, addr)
           register vm_map_t map;
           register vm_offset_t start;
           vm_size_t length;
           vm_offset_t *addr;
   {
           register vm_map_entry_t entry, next;
           register 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;
           }
           SAVE_HINT(map, entry);
           *addr = start;
           if (map == kernel_map && round_page(start + length) > kernel_vm_end)
                   pmap_growkernel(round_page(start + length));
           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.
    *
    */
   int
   vm_map_find(map, object, offset, addr, length, find_space, prot, max, cow)
           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, max;
           int cow;
   {
           register vm_offset_t start;
           int result, s = 0;
   
           start = *addr;
   
           if (map == kmem_map || map == mb_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 || map == mb_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 || map == mb_map)
                   splx(s);
   
           return (result);
   }
   
   /*
    *      vm_map_simplify_entry:
    *
    *      Simplify the given map entry by merging with either neighbor.
    */
   void
   vm_map_simplify_entry(map, 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_IS_SUB_MAP|MAP_ENTRY_IS_A_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->object.vm_object->behavior == entry->object.vm_object->behavior)) &&
                        (!prev->object.vm_object ||
                           (prev->offset + prevsize == entry->offset)) &&
                        (prev->eflags == entry->eflags) &&
                        (prev->protection == entry->protection) &&
                        (prev->max_protection == entry->max_protection) &&
                        (prev->inheritance == entry->inheritance) &&
                        (prev->wired_count == entry->wired_count)) {
                           if (map->first_free == prev)
                                   map->first_free = entry;
                           if (map->hint == prev)
                                   map->hint = entry;
                           vm_map_entry_unlink(map, prev);
                           entry->start = prev->start;
                           entry->offset = prev->offset;
                           if (prev->object.vm_object)
                                   vm_object_deallocate(prev->object.vm_object);
                           vm_map_entry_dispose(map, prev);
                   }
           }
   
           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) &&
                       (!next->object.vm_object || (next->object.vm_object->behavior == entry->object.vm_object->behavior)) &&
                        (!entry->object.vm_object ||
                           (entry->offset + esize == next->offset)) &&
                       (next->eflags == entry->eflags) &&
                       (next->protection == entry->protection) &&
                       (next->max_protection == entry->max_protection) &&
                       (next->inheritance == entry->inheritance) &&
                       (next->wired_count == entry->wired_count)) {
                           if (map->first_free == next)
                                   map->first_free = entry;
                           if (map->hint == next)
                                   map->hint = entry;
                           vm_map_entry_unlink(map, next);
                           entry->end = next->end;
                           if (next->object.vm_object)
                                   vm_object_deallocate(next->object.vm_object);
                           vm_map_entry_dispose(map, next);
                   }
           }
   }
   /*
    *      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(map, entry, start)
           register vm_map_t map;
           register vm_map_entry_t entry;
           register vm_offset_t start;
   {
           register 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) {
                           vm_object_t object;
   
                           object = vm_object_allocate(OBJT_DEFAULT,
                                           OFF_TO_IDX(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_A_MAP|MAP_ENTRY_IS_SUB_MAP))
                   vm_map_reference(new_entry->object.share_map);
           else
                   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(map, entry, end)
           register vm_map_t map;
           register vm_map_entry_t entry;
           register vm_offset_t end;
   {
           register 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) {
                          vm_object_t object;
  
                          object = vm_object_allocate(OBJT_DEFAULT,
                                          OFF_TO_IDX(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_A_MAP|MAP_ENTRY_IS_SUB_MAP))
                  vm_map_reference(new_entry->object.share_map);
          else
                  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(map, start, end, submap)
          register vm_map_t map;
          register vm_offset_t start;
          register vm_offset_t end;
          vm_map_t submap;
  {
          vm_map_entry_t entry;
          register 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_IS_A_MAP|MAP_ENTRY_COW)) == 0) &&
              (entry->object.vm_object == NULL)) {
                  entry->eflags |= MAP_ENTRY_IS_SUB_MAP;
                  vm_map_reference(entry->object.sub_map = submap);
                  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(map, start, end, new_prot, set_max)
          register vm_map_t map;
          register vm_offset_t start;
          register vm_offset_t end;
          register vm_prot_t new_prot;
          register boolean_t set_max;
  {
          register 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) {
  #define MASK(entry)     (((entry)->eflags & MAP_ENTRY_COW) ? ~VM_PROT_WRITE : \
                                                          VM_PROT_ALL)
  #define max(a,b)        ((a) > (b) ? (a) : (b))
  
                          if (current->eflags & MAP_ENTRY_IS_A_MAP) {
                                  vm_map_entry_t share_entry;
                                  vm_offset_t share_end;
  
                                  vm_map_lock(current->object.share_map);
                                  (void) vm_map_lookup_entry(
                                      current->object.share_map,
                                      current->offset,
                                      &share_entry);
                                  share_end = current->offset +
                                      (current->end - current->start);
                                  while ((share_entry !=
                                          &current->object.share_map->header) &&
                                      (share_entry->start < share_end)) {
  
                                          pmap_protect(map->pmap,
                                              (max(share_entry->start,
                                                      current->offset) -
                                                  current->offset +
                                                  current->start),
                                              min(share_entry->end,
                                                  share_end) -
                                              current->offset +
                                              current->start,
                                              current->protection &
                                              MASK(share_entry));
  
                                          share_entry = share_entry->next;
                                  }
                                  vm_map_unlock(current->object.share_map);
                          } else
                                  pmap_protect(map->pmap, current->start,
                                      current->end,
                                      current->protection & MASK(entry));
  #undef  max
  #undef  MASK
                  }
  
                  vm_map_simplify_entry(map, current);
  
                  current = current->next;
          }
  
          vm_map_unlock(map);
          return (KERN_SUCCESS);
  }
  
  /*
   *      vm_map_madvise:
   *
   *      This routine traverses a processes map handling the madvise
   *      system call.
   */
  void
  vm_map_madvise(map, pmap, start, end, advise)
          vm_map_t map;
          pmap_t pmap;
          vm_offset_t start, end;
          int advise;
  {
          register 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;
  
          for(current = entry;
                  (current != &map->header) && (current->start < end);
                  current = current->next) {
                  vm_size_t size = current->end - current->start;
  
                  if (current->eflags & (MAP_ENTRY_IS_A_MAP|MAP_ENTRY_IS_SUB_MAP)) {
                          continue;
                  }
  
                  /*
                   * Create an object if needed
                   */
                  if (current->object.vm_object == NULL) {
                          vm_object_t object;
                          object = vm_object_allocate(OBJT_DEFAULT, OFF_TO_IDX(size));
                          current->object.vm_object = object;
                          current->offset = 0;
                  }
  
                  vm_map_clip_end(map, current, end);
                  switch (advise) {
          case MADV_NORMAL:
                          current->object.vm_object->behavior = OBJ_NORMAL;
                          break;
          case MADV_SEQUENTIAL:
                          current->object.vm_object->behavior = OBJ_SEQUENTIAL;
                          break;
          case MADV_RANDOM:
                          current->object.vm_object->behavior = OBJ_RANDOM;
                          break;
          /*
           * Right now, we could handle DONTNEED and WILLNEED with common code.
           * They are mostly the same, except for the potential async reads (NYI).
           */
          case MADV_FREE:
          case MADV_DONTNEED:
                          {
                                  vm_pindex_t pindex;
                                  int count;
                                  size = current->end - current->start;
                                  pindex = OFF_TO_IDX(entry->offset);
                                  count = OFF_TO_IDX(size);
                                  /*
                                   * MADV_DONTNEED removes the page from all
                                   * pmaps, so pmap_remove is not necessary.
                                   */
                                  vm_object_madvise(current->object.vm_object,
                                          pindex, count, advise);
                          }
                          break;
  
          case MADV_WILLNEED:
                          {
                                  vm_pindex_t pindex;
                                  int count;
                                  size = current->end - current->start;
                                  pindex = OFF_TO_IDX(current->offset);
                                  count = OFF_TO_IDX(size);
                                  vm_object_madvise(current->object.vm_object,
                                          pindex, count, advise);
                                  pmap_object_init_pt(pmap, current->start,
                                          current->object.vm_object, pindex,
                                          (count << PAGE_SHIFT), 0);
                          }
                          break;
  
          default:
                          break;
                  }
          }
  
          vm_map_simplify_entry(map, entry);
          vm_map_unlock(map);
          return;
  }       
  
  
  /*
   *      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(map, start, end, new_inheritance)
          register vm_map_t map;
          register vm_offset_t start;
          register vm_offset_t end;
          register vm_inherit_t new_inheritance;
  {
          register 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;
  
                  entry = entry->next;
          }
  
          vm_map_simplify_entry(map, temp_entry);
          vm_map_unlock(map);
          return (KERN_SUCCESS);
  }
  
  /*
   * Implement the semantics of mlock
   */
  int
  vm_map_user_pageable(map, start, end, new_pageable)
          register vm_map_t map;
          register vm_offset_t start;
          register vm_offset_t end;
          register boolean_t new_pageable;
  {
          register vm_map_entry_t entry;
          vm_map_entry_t start_entry;
          register vm_offset_t failed = 0;
          int rv;
  
          vm_map_lock(map);
          VM_MAP_RANGE_CHECK(map, start, end);
  
          if (vm_map_lookup_entry(map, start, &start_entry) == FALSE) {
                  vm_map_unlock(map);
                  return (KERN_INVALID_ADDRESS);
          }
  
          if (new_pageable) {
  
                  entry = start_entry;
                  vm_map_clip_start(map, entry, start);
  
                  /*
                   * Now decrement the wiring count for each region. If a region
                   * becomes completely unwired, unwire its physical pages and
                   * mappings.
                   */
                  lock_set_recursive(&map->lock);
  
                  entry = start_entry;
                  while ((entry != &map->header) && (entry->start < end)) {
                          if (entry->eflags & MAP_ENTRY_USER_WIRED) {
                                  vm_map_clip_end(map, entry, end);
                                  entry->eflags &= ~MAP_ENTRY_USER_WIRED;
                                  entry->wired_count--;
                                  if (entry->wired_count == 0)
                                          vm_fault_unwire(map, entry->start, entry->end);
                          }
                          entry = entry->next;
                  }
                  vm_map_simplify_entry(map, start_entry);
                  lock_clear_recursive(&map->lock);
          } else {
  
                  /*
                   * Because of the possiblity of blocking, etc.  We restart
                   * through the process's map entries from beginning so that
                   * we don't end up depending on a map entry that could have
                   * changed.
                   */
          rescan:
  
                  entry = start_entry;
  
                  while ((entry != &map->header) && (entry->start < end)) {
  
                          if (entry->eflags & MAP_ENTRY_USER_WIRED) {
                                  entry = entry->next;
                                  continue;
                          }
                          
                          if (entry->wired_count != 0) {
                                  entry->wired_count++;
                                  entry->eflags |= MAP_ENTRY_USER_WIRED;
                                  entry = entry->next;
                                  continue;
                          }
  
                          /* Here on entry being newly wired */
  
                          if ((entry->eflags & (MAP_ENTRY_IS_A_MAP|MAP_ENTRY_IS_SUB_MAP)) == 0) {
                                  int copyflag = entry->eflags & MAP_ENTRY_NEEDS_COPY;
                                  if (copyflag && ((entry->protection & VM_PROT_WRITE) != 0)) {
  
                                          vm_object_shadow(&entry->object.vm_object,
                                              &entry->offset,
                                              OFF_TO_IDX(entry->end
                                                  - entry->start));
                                          entry->eflags &= ~MAP_ENTRY_NEEDS_COPY;
  
                                  } else if (entry->object.vm_object == NULL) {
  
                                          entry->object.vm_object =
                                              vm_object_allocate(OBJT_DEFAULT,
                                                  OFF_TO_IDX(entry->end - entry->start));
                                          entry->offset = (vm_offset_t) 0;
  
                                  }
                                  default_pager_convert_to_swapq(entry->object.vm_object);
                          }
  
                          vm_map_clip_start(map, entry, start);
                          vm_map_clip_end(map, entry, end);
  
                          entry->wired_count++;
                          entry->eflags |= MAP_ENTRY_USER_WIRED;
  
                          /* First we need to allow map modifications */
                          lock_set_recursive(&map->lock);
                          lock_write_to_read(&map->lock);
  
                          rv = vm_fault_user_wire(map, entry->start, entry->end);
                          if (rv) {
  
                                  entry->wired_count--;
                                  entry->eflags &= ~MAP_ENTRY_USER_WIRED;
  
                                  lock_clear_recursive(&map->lock);
                                  vm_map_unlock(map);
                                  
                                  (void) vm_map_user_pageable(map, start, entry->start, TRUE);
                                  return rv;
                          }
  
                          lock_clear_recursive(&map->lock);
                          lock_read_to_write(&map->lock);
  
                          goto rescan;
                  }
          }
          vm_map_unlock(map);
          return KERN_SUCCESS;
  }
  
  /*
   *      vm_map_pageable:
   *
   *      Sets the pageability of the specified address
   *      range in the target map.  Regions specified
   *      as not pageable require locked-down physical
   *      memory and physical page maps.
   *
   *      The map must not be locked, but a reference
   *      must remain to the map throughout the call.
   */
  int
  vm_map_pageable(map, start, end, new_pageable)
          register vm_map_t map;
          register vm_offset_t start;
          register vm_offset_t end;
          register boolean_t new_pageable;
  {
          register vm_map_entry_t entry;
          vm_map_entry_t start_entry;
          register vm_offset_t failed = 0;
          int rv;
  
          vm_map_lock(map);
  
          VM_MAP_RANGE_CHECK(map, start, end);
  
          /*
           * Only one pageability change may take place at one time, since
           * vm_fault assumes it will be called only once for each
           * wiring/unwiring.  Therefore, we have to make sure we're actually
           * changing the pageability for the entire region.  We do so before
           * making any changes.
           */
  
          if (vm_map_lookup_entry(map, start, &start_entry) == FALSE) {
                  vm_map_unlock(map);
                  return (KERN_INVALID_ADDRESS);
          }
          entry = start_entry;
  
          /*
           * Actions are rather different for wiring and unwiring, so we have
           * two separate cases.
           */
  
          if (new_pageable) {
  
                  vm_map_clip_start(map, entry, start);
  
                  /*
                   * Unwiring.  First ensure that the range to be unwired is
                   * really wired down and that there are no holes.
                   */
                  while ((entry != &map->header) && (entry->start < end)) {
  
                          if (entry->wired_count == 0 ||
                              (entry->end < end &&
                                  (entry->next == &map->header ||
                                      entry->next->start > entry->end))) {
                                  vm_map_unlock(map);
                                  return (KERN_INVALID_ARGUMENT);
                          }
                          entry = entry->next;
                  }
  
                  /*
                   * Now decrement the wiring count for each region. If a region
                   * becomes completely unwired, unwire its physical pages and
                   * mappings.
                   */
                  lock_set_recursive(&map->lock);
  
                  entry = start_entry;
                  while ((entry != &map->header) && (entry->start < end)) {
                          vm_map_clip_end(map, entry, end);
  
                          entry->wired_count--;
                          if (entry->wired_count == 0)
                                  vm_fault_unwire(map, entry->start, entry->end);
  
                          entry = entry->next;
                  }
                  vm_map_simplify_entry(map, start_entry);
                  lock_clear_recursive(&map->lock);
          } else {
                  /*
                   * Wiring.  We must do this in two passes:
                   *
                   * 1.  Holding the write lock, we create any shadow or zero-fill
                   * objects that need to be created. Then we clip each map
                   * entry to the region to be wired and increment its wiring
                   * count.  We create objects before clipping the map entries
                   * to avoid object proliferation.
                   *
                   * 2.  We downgrade to a read lock, and call vm_fault_wire to
                   * fault in the pages for any newly wired area (wired_count is
                   * 1).
                   *
                   * Downgrading to a read lock for vm_fault_wire avoids a possible
                   * deadlock with another process that may have faulted on one
                   * of the pages to be wired (it would mark the page busy,
                   * blocking us, then in turn block on the map lock that we
                   * hold).  Because of problems in the recursive lock package,
                   * we cannot upgrade to a write lock in vm_map_lookup.  Thus,
                   * any actions that require the write lock must be done
                   * beforehand.  Because we keep the read lock on the map, the
                   * copy-on-write status of the entries we modify here cannot
                   * change.
                   */
  
                  /*
                   * Pass 1.
                   */
                  while ((entry != &map->header) && (entry->start < end)) {
                          if (entry->wired_count == 0) {
  
                                  /*
                                   * Perform actions of vm_map_lookup that need
                                   * the write lock on the map: create a shadow
                                   * object for a copy-on-write region, or an
                                   * object for a zero-fill region.
                                   *
                                   * We don't have to do this for entries that
                                   * point to sharing maps, because we won't
                                   * hold the lock on the sharing map.
                                   */
                                  if ((entry->eflags & (MAP_ENTRY_IS_A_MAP|MAP_ENTRY_IS_SUB_MAP)) == 0) {
                                          int copyflag = entry->eflags & MAP_ENTRY_NEEDS_COPY;
                                          if (copyflag &&
                                              ((entry->protection & VM_PROT_WRITE) != 0)) {
  
                                                  vm_object_shadow(&entry->object.vm_object,
                                                      &entry->offset,
                                                      OFF_TO_IDX(entry->end
                                                          - entry->start));
                                                  entry->eflags &= ~MAP_ENTRY_NEEDS_COPY;
                                          } else if (entry->object.vm_object == NULL) {
                                                  entry->object.vm_object =
                                                      vm_object_allocate(OBJT_DEFAULT,
                                                          OFF_TO_IDX(entry->end - entry->start));
                                                  entry->offset = (vm_offset_t) 0;
                                          }
                                          default_pager_convert_to_swapq(entry->object.vm_object);
                                  }
                          }
                          vm_map_clip_start(map, entry, start);
                          vm_map_clip_end(map, entry, end);
                          entry->wired_count++;
  
                          /*
                           * Check for holes
                           */
                          if (entry->end < end &&
                              (entry->next == &map->header ||
                                  entry->next->start > entry->end)) {
                                  /*
                                   * Found one.  Object creation actions do not
                                   * need to be undone, but the wired counts
                                   * need to be restored.
                                   */
                                  while (entry != &map->header && entry->end > start) {
                                          entry->wired_count--;
                                          entry = entry->prev;
                                  }
                                  vm_map_unlock(map);
                                  return (KERN_INVALID_ARGUMENT);
                          }
                          entry = entry->next;
                  }
  
                  /*
                   * Pass 2.
                   */
  
                  /*
                   * HACK HACK HACK HACK
                   *
                   * If we are wiring in the kernel map or a submap of it,
                   * unlock the map to avoid deadlocks.  We trust that the
                   * kernel is well-behaved, and therefore will not do
                   * anything destructive to this region of the map while
                   * we have it unlocked.  We cannot trust user processes
                   * to do the same.
                   *
                   * HACK HACK HACK HACK
                   */
                  if (vm_map_pmap(map) == kernel_pmap) {
                          vm_map_unlock(map);     /* trust me ... */
                  } else {
                          lock_set_recursive(&map->lock);
                          lock_write_to_read(&map->lock);
                  }
  
                  rv = 0;
                  entry = start_entry;
                  while (entry != &map->header && entry->start < end) {
                          /*
                           * If vm_fault_wire fails for any page we need to undo
                           * what has been done.  We decrement the wiring count
                           * for those pages which have not yet been wired (now)
                           * and unwire those that have (later).
                           *
                           * XXX this violates the locking protocol on the map,
                           * needs to be fixed.
                           */
                          if (rv)
                                  entry->wired_count--;
                          else if (entry->wired_count == 1) {
                                  rv = vm_fault_wire(map, entry->start, entry->end);
                                  if (rv) {
                                          failed = entry->start;
                                          entry->wired_count--;
                                  }
                          }
                          entry = entry->next;
                  }
  
                  if (vm_map_pmap(map) == kernel_pmap) {
                          vm_map_lock(map);
                  } else {
                          lock_clear_recursive(&map->lock);
                  }
                  if (rv) {
                          vm_map_unlock(map);
                          (void) vm_map_pageable(map, start, failed, TRUE);
                          return (rv);
                  }
                  vm_map_simplify_entry(map, start_entry);
          }
  
          vm_map_unlock(map);
  
          return (KERN_SUCCESS);
  }
  
  /*
   * 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(map, start, end, syncio, invalidate)
          vm_map_t map;
          vm_offset_t start;
          vm_offset_t end;
          boolean_t syncio;
          boolean_t invalidate;
  {
          register vm_map_entry_t current;
          vm_map_entry_t entry;
          vm_size_t size;
          vm_object_t object;
          vm_ooffset_t offset;
  
          vm_map_lock_read(map);
          VM_MAP_RANGE_CHECK(map, start, end);
          if (!vm_map_lookup_entry(map, start, &entry)) {
                  vm_map_unlock_read(map);
                  return (KERN_INVALID_ADDRESS);
          }
          /*
           * Make a first pass to check for holes.
           */
          for (current = entry; current->start < end; current = current->next) {
                  if (current->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);
                  }
          }
  
          /*
           * 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_A_MAP|MAP_ENTRY_IS_SUB_MAP)) {
                          register vm_map_t smap;
                          vm_map_entry_t tentry;
                          vm_size_t tsize;
  
                          smap = current->object.share_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.
                   */
                  while (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 (invalidate)
                          pmap_remove(vm_map_pmap(map), current->start,
                                  current->start + size);
                  if (object && (object->type == OBJT_VNODE)) {
                          /*
                           * Flush pages if writing is allowed. XXX should we continue
                           * on an error?
                           *
                           * XXX Doing async I/O and then removing all the pages from
                           *     the object before it completes is probably a very bad
                           *     idea.
                           */
                          if (current->protection & VM_PROT_WRITE) {
                                  vm_object_page_clean(object,
                                          OFF_TO_IDX(offset),
                                          OFF_TO_IDX(offset + size),
                                          (syncio||invalidate)?1:0, TRUE);
                                  if (invalidate)
                                          vm_object_page_remove(object,
                                                  OFF_TO_IDX(offset),
                                                  OFF_TO_IDX(offset + size),
                                                  FALSE);
                          }
                  }
                  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(map, entry)
          vm_map_t map;
          register 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(map, entry)
          register vm_map_t map;
          register vm_map_entry_t entry;
  {
          vm_map_entry_unlink(map, entry);
          map->size -= entry->end - entry->start;
  
          if (entry->eflags & (MAP_ENTRY_IS_A_MAP|MAP_ENTRY_IS_SUB_MAP)) {
                  vm_map_deallocate(entry->object.share_map);
          } else {
                  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.
   *
   *      When called with a sharing map, removes pages from
   *      that region from all physical maps.
   */
  int
  vm_map_delete(map, start, end)
          register vm_map_t map;
          vm_offset_t start;
          register vm_offset_t end;
  {
          register 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);
  
                  /*
                   * Fix the lookup hint now, rather than each time though the
                   * loop.
                   */
  
                  SAVE_HINT(map, entry->prev);
          }
  
          /*
           * 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_object_t object;
                  vm_ooffset_t offset;
  
                  vm_map_clip_end(map, entry, end);
  
                  next = entry->next;
                  s = entry->start;
                  e = entry->end;
                  offset = entry->offset;
  
                  /*
                   * Unwire before removing addresses from the pmap; otherwise,
                   * unwiring will put the entries back in the pmap.
                   */
  
                  object = entry->object.vm_object;
                  if (entry->wired_count != 0)
                          vm_map_entry_unwire(map, entry);
  
                  /*
                   * If this is a sharing map, we must remove *all* references
                   * to this data, since we can't find all of the physical maps
                   * which are sharing it.
                   */
  
                  if (object == kernel_object || object == kmem_object) {
                          vm_object_page_remove(object, OFF_TO_IDX(offset),
                              OFF_TO_IDX(offset + (e - s)), FALSE);
                  } else if (!map->is_main_map) {
                          vm_object_pmap_remove(object,
                              OFF_TO_IDX(offset),
                              OFF_TO_IDX(offset + (e - s)));
                  } else {
                          pmap_remove(map->pmap, s, e);
                  }
  
                  /*
                   * Delete the entry (which may delete the object) only after
                   * removing all pmap entries pointing to its pages.
                   * (Otherwise, its page frames may be reallocated, and any
                   * modify bits will be set in the wrong object!)
                   */
  
                  vm_map_entry_delete(map, entry);
                  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(map, start, end)
          register vm_map_t map;
          register vm_offset_t start;
          register vm_offset_t end;
  {
          register int result, s = 0;
  
          if (map == kmem_map || map == mb_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 || map == mb_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.
   */
  boolean_t
  vm_map_check_protection(map, start, end, protection)
          register vm_map_t map;
          register vm_offset_t start;
          register vm_offset_t end;
          register vm_prot_t protection;
  {
          register vm_map_entry_t entry;
          vm_map_entry_t tmp_entry;
  
          if (!vm_map_lookup_entry(map, start, &tmp_entry)) {
                  return (FALSE);
          }
          entry = tmp_entry;
  
          while (start < end) {
                  if (entry == &map->header) {
                          return (FALSE);
                  }
                  /*
                   * No holes allowed!
                   */
  
                  if (start < entry->start) {
                          return (FALSE);
                  }
                  /*
                   * Check protection associated with entry.
                   */
  
                  if ((entry->protection & protection) != protection) {
                          return (FALSE);
                  }
                  /* go to next entry */
  
                  start = entry->end;
                  entry = entry->next;
          }
          return (TRUE);
  }
  
  /*
   *      vm_map_copy_entry:
   *
   *      Copies the contents of the source entry to the destination
   *      entry.  The entries *must* be aligned properly.
   */
  static void
  vm_map_copy_entry(src_map, dst_map, src_entry, dst_entry)
          vm_map_t src_map, dst_map;
          register vm_map_entry_t src_entry, dst_entry;
  {
          if ((dst_entry->eflags|src_entry->eflags) &
                  (MAP_ENTRY_IS_A_MAP|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) {
  
                          boolean_t su;
  
                          /*
                           * If the source entry has only one mapping, we can
                           * just protect the virtual address range.
                           */
                          if (!(su = src_map->is_main_map)) {
                                  su = (src_map->ref_count == 1);
                          }
                          if (su) {
                                  pmap_protect(src_map->pmap,
                                      src_entry->start,
                                      src_entry->end,
                                      src_entry->protection & ~VM_PROT_WRITE);
                          } else {
                                  vm_object_pmap_copy(src_entry->object.vm_object,
                                      OFF_TO_IDX(src_entry->offset),
                                      OFF_TO_IDX(src_entry->offset + (src_entry->end
                                          - src_entry->start)));
                          }
                  }
  
                  /*
                   * Make a copy of the object.
                   */
                  if (src_entry->object.vm_object) {
                          if ((src_entry->object.vm_object->handle == NULL) &&
                                  (src_entry->object.vm_object->type == OBJT_DEFAULT ||
                                   src_entry->object.vm_object->type == OBJT_SWAP))
                                  vm_object_collapse(src_entry->object.vm_object);
                          ++src_entry->object.vm_object->ref_count;
                          src_entry->eflags |= (MAP_ENTRY_COW|MAP_ENTRY_NEEDS_COPY);
                          dst_entry->eflags |= (MAP_ENTRY_COW|MAP_ENTRY_NEEDS_COPY);
                          dst_entry->object.vm_object =
                                  src_entry->object.vm_object;
                          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(vm1)
          register struct vmspace *vm1;
  {
          register 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;
          pmap_t new_pmap;
          vm_object_t object;
  
          vm_map_lock(old_map);
  
          vm2 = vmspace_alloc(old_map->min_offset, old_map->max_offset,
              old_map->entries_pageable);
          bcopy(&vm1->vm_startcopy, &vm2->vm_startcopy,
              (caddr_t) (vm1 + 1) - (caddr_t) &vm1->vm_startcopy);
          new_pmap = &vm2->vm_pmap;       /* XXX */
          new_map = &vm2->vm_map; /* XXX */
  
          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,
                                                              OFF_TO_IDX(old_entry->end -
                                                                         old_entry->start));
                                  old_entry->object.vm_object = object;
                                  old_entry->offset = (vm_offset_t) 0;
                          } else if (old_entry->eflags & MAP_ENTRY_NEEDS_COPY) {
                                  vm_object_shadow(&old_entry->object.vm_object,
                                                   &old_entry->offset,
                                                   OFF_TO_IDX(old_entry->end -
                                                          old_entry->start));
  
                                  old_entry->eflags &= ~MAP_ENTRY_NEEDS_COPY;
                                  object = old_entry->object.vm_object;
                          }
  
                          /*
                           * Clone the entry, referencing the sharing map.
                           */
                          new_entry = vm_map_entry_create(new_map);
                          *new_entry = *old_entry;
                          new_entry->wired_count = 0;
                          ++object->ref_count;
  
                          /*
                           * 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->wired_count = 0;
                          new_entry->object.vm_object = NULL;
                          new_entry->eflags &= ~MAP_ENTRY_IS_A_MAP;
                          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;
          vm_map_unlock(old_map);
  
          return (vm2);
  }
  
  /*
   *      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(var_map, vaddr, fault_type, out_entry,
      object, pindex, out_prot, wired, single_use)
          vm_map_t *var_map;      /* IN/OUT */
          register vm_offset_t vaddr;
          register vm_prot_t fault_type;
  
          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 */
          boolean_t *single_use;  /* OUT */
  {
          vm_map_t share_map;
          vm_offset_t share_offset;
          register vm_map_entry_t entry;
          register vm_map_t map = *var_map;
          register vm_prot_t prot;
          register boolean_t su;
  
  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->hint;
  
          *out_entry = entry;
  
          if ((entry == &map->header) ||
              (vaddr < entry->start) || (vaddr >= entry->end)) {
                  vm_map_entry_t tmp_entry;
  
                  /*
                   * Entry was either not a valid hint, or the vaddr was not
                   * contained in the entry, so do a full lookup.
                   */
                  if (!vm_map_lookup_entry(map, vaddr, &tmp_entry))
                          RETURN(KERN_INVALID_ADDRESS);
  
                  entry = tmp_entry;
                  *out_entry = 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.
           */
  
          prot = entry->protection;
          if ((fault_type & VM_PROT_OVERRIDE_WRITE) == 0 ||
                  (entry->eflags & MAP_ENTRY_COW) == 0 ||
                  (entry->wired_count != 0)) {
                  if ((fault_type & (prot)) !=
                      (fault_type & ~VM_PROT_OVERRIDE_WRITE))
                          RETURN(KERN_PROTECTION_FAILURE);
          }
  
          /*
           * If this page is not pageable, we have to get it for all possible
           * accesses.
           */
  
          *wired = (entry->wired_count != 0);
          if (*wired)
                  prot = fault_type = entry->protection;
  
          /*
           * If we don't already have a VM object, track it down.
           */
  
          su = (entry->eflags & MAP_ENTRY_IS_A_MAP) == 0;
          if (su) {
                  share_map = map;
                  share_offset = vaddr;
          } else {
                  vm_map_entry_t share_entry;
  
                  /*
                   * Compute the sharing map, and offset into it.
                   */
  
                  share_map = entry->object.share_map;
                  share_offset = (vaddr - entry->start) + entry->offset;
  
                  /*
                   * Look for the backing store object and offset
                   */
  
                  vm_map_lock_read(share_map);
  
                  if (!vm_map_lookup_entry(share_map, share_offset,
                          &share_entry)) {
                          vm_map_unlock_read(share_map);
                          RETURN(KERN_INVALID_ADDRESS);
                  }
                  entry = share_entry;
          }
  
          /*
           * 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 sharing 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 share map to the new
                           * object.
                           */
  
                          if (lock_read_to_write(&share_map->lock)) {
                                  if (share_map != map)
                                          vm_map_unlock_read(map);
                                  goto RetryLookup;
                          }
                          vm_object_shadow(
                              &entry->object.vm_object,
                              &entry->offset,
                              OFF_TO_IDX(entry->end - entry->start));
  
                          entry->eflags &= ~MAP_ENTRY_NEEDS_COPY;
  
                          lock_write_to_read(&share_map->lock);
                  } 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) {
  
                  if (lock_read_to_write(&share_map->lock)) {
                          if (share_map != map)
                                  vm_map_unlock_read(map);
                          goto RetryLookup;
                  }
                  entry->object.vm_object = vm_object_allocate(OBJT_DEFAULT,
                      OFF_TO_IDX(entry->end - entry->start));
                  entry->offset = 0;
                  lock_write_to_read(&share_map->lock);
          }
  
          if (entry->object.vm_object != NULL)
                  default_pager_convert_to_swapq(entry->object.vm_object);
          /*
           * 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((share_offset - entry->start) + entry->offset);
          *object = entry->object.vm_object;
  
          /*
           * Return whether this is the only map sharing this data.
           */
  
          if (!su) {
                  su = (share_map->ref_count == 1);
          }
          *out_prot = prot;
          *single_use = su;
  
          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(map, entry)
          register vm_map_t map;
          vm_map_entry_t entry;
  {
          /*
           * If this entry references a map, unlock it first.
           */
  
          if (entry->eflags & MAP_ENTRY_IS_A_MAP)
                  vm_map_unlock_read(entry->object.share_map);
  
          /*
           * 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)
  {
          /* XXX convert args. */
          register vm_map_t map = (vm_map_t)addr;
          boolean_t full = have_addr;
  
          register vm_map_entry_t entry;
  
          db_iprintf("%s map 0x%x: pmap=0x%x,ref=%d,nentries=%d,version=%d\n",
              (map->is_main_map ? "Task" : "Share"),
              (int) map, (int) (map->pmap), map->ref_count, map->nentries,
              map->timestamp);
  
          if (!full && db_indent)
                  return;
  
          db_indent += 2;
          for (entry = map->header.next; entry != &map->header;
              entry = entry->next) {
                  db_iprintf("map entry 0x%x: start=0x%x, end=0x%x, ",
                      (int) entry, (int) entry->start, (int) entry->end);
                  if (map->is_main_map) {
                          static char *inheritance_name[4] =
                          {"share", "copy", "none", "donate_copy"};
  
                          db_printf("prot=%x/%x/%s, ",
                              entry->protection,
                              entry->max_protection,
                              inheritance_name[entry->inheritance]);
                          if (entry->wired_count != 0)
                                  db_printf("wired, ");
                  }
                  if (entry->eflags & (MAP_ENTRY_IS_A_MAP|MAP_ENTRY_IS_SUB_MAP)) {
                          db_printf("share=0x%x, offset=0x%x\n",
                              (int) entry->object.share_map,
                              (int) entry->offset);
                          if ((entry->prev == &map->header) ||
                              ((entry->prev->eflags & MAP_ENTRY_IS_A_MAP) == 0) ||
                              (entry->prev->object.share_map !=
                                  entry->object.share_map)) {
                                  db_indent += 2;
                                  vm_map_print((int)entry->object.share_map,
                                               full, 0, (char *)0);
                                  db_indent -= 2;
                          }
                  } else {
                          db_printf("object=0x%x, offset=0x%x",
                              (int) entry->object.vm_object,
                              (int) entry->offset);
                          if (entry->eflags & MAP_ENTRY_COW)
                                  db_printf(", copy (%s)",
                                      (entry->eflags & MAP_ENTRY_NEEDS_COPY) ? "needed" : "done");
                          db_printf("\n");
  
                          if ((entry->prev == &map->header) ||
                              (entry->prev->eflags & MAP_ENTRY_IS_A_MAP) ||
                              (entry->prev->object.vm_object !=
                                  entry->object.vm_object)) {
                                  db_indent += 2;
                                  vm_object_print((int)entry->object.vm_object,
                                                  full, 0, (char *)0);
                                  db_indent -= 2;
                          }
                  }
          }
          db_indent -= 2;
  }
  #endif /* DDB */

Cache object: 83530d4b5632f2739ee940fbf26ab23d