FreeBSD/Linux Kernel Cross Reference
sys/vm/vm_map.c

     /*-
      * SPDX-License-Identifier: (BSD-3-Clause AND MIT-CMU)
      *
      * Copyright (c) 1991, 1993
      *      The Regents of the University of California.  All rights reserved.
      *
      * This code is derived from software contributed to Berkeley by
      * The Mach Operating System project at Carnegie-Mellon University.
      *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      from: @(#)vm_map.c      8.3 (Berkeley) 1/12/94
     *
     *
     * Copyright (c) 1987, 1990 Carnegie-Mellon University.
     * All rights reserved.
     *
     * Authors: Avadis Tevanian, Jr., Michael Wayne Young
     *
     * Permission to use, copy, modify and distribute this software and
     * its documentation is hereby granted, provided that both the copyright
     * notice and this permission notice appear in all copies of the
     * software, derivative works or modified versions, and any portions
     * thereof, and that both notices appear in supporting documentation.
     *
     * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
     * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
     * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
     *
     * Carnegie Mellon requests users of this software to return to
     *
     *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
     *  School of Computer Science
     *  Carnegie Mellon University
     *  Pittsburgh PA 15213-3890
     *
     * any improvements or extensions that they make and grant Carnegie the
     * rights to redistribute these changes.
     */
    
    /*
     *      Virtual memory mapping module.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/elf.h>
    #include <sys/kernel.h>
    #include <sys/ktr.h>
    #include <sys/lock.h>
    #include <sys/mutex.h>
    #include <sys/proc.h>
    #include <sys/vmmeter.h>
    #include <sys/mman.h>
    #include <sys/vnode.h>
    #include <sys/racct.h>
    #include <sys/resourcevar.h>
    #include <sys/rwlock.h>
    #include <sys/file.h>
    #include <sys/sysctl.h>
    #include <sys/sysent.h>
    #include <sys/shm.h>
    
    #include <vm/vm.h>
    #include <vm/vm_param.h>
    #include <vm/pmap.h>
    #include <vm/vm_map.h>
    #include <vm/vm_page.h>
    #include <vm/vm_pageout.h>
    #include <vm/vm_object.h>
    #include <vm/vm_pager.h>
    #include <vm/vm_kern.h>
    #include <vm/vm_extern.h>
    #include <vm/vnode_pager.h>
   #include <vm/swap_pager.h>
   #include <vm/uma.h>
   
   /*
    *      Virtual memory maps provide for the mapping, protection,
    *      and sharing of virtual memory objects.  In addition,
    *      this module provides for an efficient virtual copy of
    *      memory from one map to another.
    *
    *      Synchronization is required prior to most operations.
    *
    *      Maps consist of an ordered doubly-linked list of simple
    *      entries; a self-adjusting binary search tree of these
    *      entries is used to speed up lookups.
    *
    *      Since portions of maps are specified by start/end addresses,
    *      which may not align with existing map entries, all
    *      routines merely "clip" entries to these start/end values.
    *      [That is, an entry is split into two, bordering at a
    *      start or end value.]  Note that these clippings may not
    *      always be necessary (as the two resulting entries are then
    *      not changed); however, the clipping is done for convenience.
    *
    *      As mentioned above, virtual copy operations are performed
    *      by copying VM object references from one map to
    *      another, and then marking both regions as copy-on-write.
    */
   
   static struct mtx map_sleep_mtx;
   static uma_zone_t mapentzone;
   static uma_zone_t kmapentzone;
   static uma_zone_t vmspace_zone;
   static int vmspace_zinit(void *mem, int size, int flags);
   static void _vm_map_init(vm_map_t map, pmap_t pmap, vm_offset_t min,
       vm_offset_t max);
   static void vm_map_entry_deallocate(vm_map_entry_t entry, boolean_t system_map);
   static void vm_map_entry_dispose(vm_map_t map, vm_map_entry_t entry);
   static void vm_map_entry_unwire(vm_map_t map, vm_map_entry_t entry);
   static int vm_map_growstack(vm_map_t map, vm_offset_t addr,
       vm_map_entry_t gap_entry);
   static void vm_map_pmap_enter(vm_map_t map, vm_offset_t addr, vm_prot_t prot,
       vm_object_t object, vm_pindex_t pindex, vm_size_t size, int flags);
   #ifdef INVARIANTS
   static void vmspace_zdtor(void *mem, int size, void *arg);
   #endif
   static int vm_map_stack_locked(vm_map_t map, vm_offset_t addrbos,
       vm_size_t max_ssize, vm_size_t growsize, vm_prot_t prot, vm_prot_t max,
       int cow);
   static void vm_map_wire_entry_failure(vm_map_t map, vm_map_entry_t entry,
       vm_offset_t failed_addr);
   
   #define ENTRY_CHARGED(e) ((e)->cred != NULL || \
       ((e)->object.vm_object != NULL && (e)->object.vm_object->cred != NULL && \
        !((e)->eflags & MAP_ENTRY_NEEDS_COPY)))
   
   /* 
    * PROC_VMSPACE_{UN,}LOCK() can be a noop as long as vmspaces are type
    * stable.
    */
   #define PROC_VMSPACE_LOCK(p) do { } while (0)
   #define PROC_VMSPACE_UNLOCK(p) do { } while (0)
   
   /*
    *      VM_MAP_RANGE_CHECK:     [ internal use only ]
    *
    *      Asserts that the starting and ending region
    *      addresses fall within the valid range of the map.
    */
   #define VM_MAP_RANGE_CHECK(map, start, end)             \
                   {                                       \
                   if (start < vm_map_min(map))            \
                           start = vm_map_min(map);        \
                   if (end > vm_map_max(map))              \
                           end = vm_map_max(map);          \
                   if (start > end)                        \
                           start = end;                    \
                   }
   
   #ifndef UMA_MD_SMALL_ALLOC
   
   /*
    * Allocate a new slab for kernel map entries.  The kernel map may be locked or
    * unlocked, depending on whether the request is coming from the kernel map or a
    * submap.  This function allocates a virtual address range directly from the
    * kernel map instead of the kmem_* layer to avoid recursion on the kernel map
    * lock and also to avoid triggering allocator recursion in the vmem boundary
    * tag allocator.
    */
   static void *
   kmapent_alloc(uma_zone_t zone, vm_size_t bytes, int domain, uint8_t *pflag,
       int wait)
   {
           vm_offset_t addr;
           int error, locked;
   
           *pflag = UMA_SLAB_PRIV;
   
           if (!(locked = vm_map_locked(kernel_map)))
                   vm_map_lock(kernel_map);
           addr = vm_map_findspace(kernel_map, vm_map_min(kernel_map), bytes);
           if (addr + bytes < addr || addr + bytes > vm_map_max(kernel_map))
                   panic("%s: kernel map is exhausted", __func__);
           error = vm_map_insert(kernel_map, NULL, 0, addr, addr + bytes,
               VM_PROT_RW, VM_PROT_RW, MAP_NOFAULT);
           if (error != KERN_SUCCESS)
                   panic("%s: vm_map_insert() failed: %d", __func__, error);
           if (!locked)
                   vm_map_unlock(kernel_map);
           error = kmem_back_domain(domain, kernel_object, addr, bytes, M_NOWAIT |
               M_USE_RESERVE | (wait & M_ZERO));
           if (error == KERN_SUCCESS) {
                   return ((void *)addr);
           } else {
                   if (!locked)
                           vm_map_lock(kernel_map);
                   vm_map_delete(kernel_map, addr, bytes);
                   if (!locked)
                           vm_map_unlock(kernel_map);
                   return (NULL);
           }
   }
   
   static void
   kmapent_free(void *item, vm_size_t size, uint8_t pflag)
   {
           vm_offset_t addr;
           int error __diagused;
   
           if ((pflag & UMA_SLAB_PRIV) == 0)
                   /* XXX leaked */
                   return;
   
           addr = (vm_offset_t)item;
           kmem_unback(kernel_object, addr, size);
           error = vm_map_remove(kernel_map, addr, addr + size);
           KASSERT(error == KERN_SUCCESS,
               ("%s: vm_map_remove failed: %d", __func__, error));
   }
   
   /*
    * The worst-case upper bound on the number of kernel map entries that may be
    * created before the zone must be replenished in _vm_map_unlock().
    */
   #define KMAPENT_RESERVE         1
   
   #endif /* !UMD_MD_SMALL_ALLOC */
   
   /*
    *      vm_map_startup:
    *
    *      Initialize the vm_map module.  Must be called before any other vm_map
    *      routines.
    *
    *      User map and entry structures are allocated from the general purpose
    *      memory pool.  Kernel maps are statically defined.  Kernel map entries
    *      require special handling to avoid recursion; see the comments above
    *      kmapent_alloc() and in vm_map_entry_create().
    */
   void
   vm_map_startup(void)
   {
           mtx_init(&map_sleep_mtx, "vm map sleep mutex", NULL, MTX_DEF);
   
           /*
            * Disable the use of per-CPU buckets: map entry allocation is
            * serialized by the kernel map lock.
            */
           kmapentzone = uma_zcreate("KMAP ENTRY", sizeof(struct vm_map_entry),
               NULL, NULL, NULL, NULL, UMA_ALIGN_PTR,
               UMA_ZONE_VM | UMA_ZONE_NOBUCKET);
   #ifndef UMA_MD_SMALL_ALLOC
           /* Reserve an extra map entry for use when replenishing the reserve. */
           uma_zone_reserve(kmapentzone, KMAPENT_RESERVE + 1);
           uma_prealloc(kmapentzone, KMAPENT_RESERVE + 1);
           uma_zone_set_allocf(kmapentzone, kmapent_alloc);
           uma_zone_set_freef(kmapentzone, kmapent_free);
   #endif
   
           mapentzone = uma_zcreate("MAP ENTRY", sizeof(struct vm_map_entry),
               NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
           vmspace_zone = uma_zcreate("VMSPACE", sizeof(struct vmspace), NULL,
   #ifdef INVARIANTS
               vmspace_zdtor,
   #else
               NULL,
   #endif
               vmspace_zinit, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
   }
   
   static int
   vmspace_zinit(void *mem, int size, int flags)
   {
           struct vmspace *vm;
           vm_map_t map;
   
           vm = (struct vmspace *)mem;
           map = &vm->vm_map;
   
           memset(map, 0, sizeof(*map));
           mtx_init(&map->system_mtx, "vm map (system)", NULL,
               MTX_DEF | MTX_DUPOK);
           sx_init(&map->lock, "vm map (user)");
           PMAP_LOCK_INIT(vmspace_pmap(vm));
           return (0);
   }
   
   #ifdef INVARIANTS
   static void
   vmspace_zdtor(void *mem, int size, void *arg)
   {
           struct vmspace *vm;
   
           vm = (struct vmspace *)mem;
           KASSERT(vm->vm_map.nentries == 0,
               ("vmspace %p nentries == %d on free", vm, vm->vm_map.nentries));
           KASSERT(vm->vm_map.size == 0,
               ("vmspace %p size == %ju on free", vm, (uintmax_t)vm->vm_map.size));
   }
   #endif  /* INVARIANTS */
   
   /*
    * Allocate a vmspace structure, including a vm_map and pmap,
    * and initialize those structures.  The refcnt is set to 1.
    */
   struct vmspace *
   vmspace_alloc(vm_offset_t min, vm_offset_t max, pmap_pinit_t pinit)
   {
           struct vmspace *vm;
   
           vm = uma_zalloc(vmspace_zone, M_WAITOK);
           KASSERT(vm->vm_map.pmap == NULL, ("vm_map.pmap must be NULL"));
           if (!pinit(vmspace_pmap(vm))) {
                   uma_zfree(vmspace_zone, vm);
                   return (NULL);
           }
           CTR1(KTR_VM, "vmspace_alloc: %p", vm);
           _vm_map_init(&vm->vm_map, vmspace_pmap(vm), min, max);
           refcount_init(&vm->vm_refcnt, 1);
           vm->vm_shm = NULL;
           vm->vm_swrss = 0;
           vm->vm_tsize = 0;
           vm->vm_dsize = 0;
           vm->vm_ssize = 0;
           vm->vm_taddr = 0;
           vm->vm_daddr = 0;
           vm->vm_maxsaddr = 0;
           return (vm);
   }
   
   #ifdef RACCT
   static void
   vmspace_container_reset(struct proc *p)
   {
   
           PROC_LOCK(p);
           racct_set(p, RACCT_DATA, 0);
           racct_set(p, RACCT_STACK, 0);
           racct_set(p, RACCT_RSS, 0);
           racct_set(p, RACCT_MEMLOCK, 0);
           racct_set(p, RACCT_VMEM, 0);
           PROC_UNLOCK(p);
   }
   #endif
   
   static inline void
   vmspace_dofree(struct vmspace *vm)
   {
   
           CTR1(KTR_VM, "vmspace_free: %p", vm);
   
           /*
            * Make sure any SysV shm is freed, it might not have been in
            * exit1().
            */
           shmexit(vm);
   
           /*
            * Lock the map, to wait out all other references to it.
            * Delete all of the mappings and pages they hold, then call
            * the pmap module to reclaim anything left.
            */
           (void)vm_map_remove(&vm->vm_map, vm_map_min(&vm->vm_map),
               vm_map_max(&vm->vm_map));
   
           pmap_release(vmspace_pmap(vm));
           vm->vm_map.pmap = NULL;
           uma_zfree(vmspace_zone, vm);
   }
   
   void
   vmspace_free(struct vmspace *vm)
   {
   
           WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
               "vmspace_free() called");
   
           if (refcount_release(&vm->vm_refcnt))
                   vmspace_dofree(vm);
   }
   
   void
   vmspace_exitfree(struct proc *p)
   {
           struct vmspace *vm;
   
           PROC_VMSPACE_LOCK(p);
           vm = p->p_vmspace;
           p->p_vmspace = NULL;
           PROC_VMSPACE_UNLOCK(p);
           KASSERT(vm == &vmspace0, ("vmspace_exitfree: wrong vmspace"));
           vmspace_free(vm);
   }
   
   void
   vmspace_exit(struct thread *td)
   {
           struct vmspace *vm;
           struct proc *p;
           bool released;
   
           p = td->td_proc;
           vm = p->p_vmspace;
   
           /*
            * Prepare to release the vmspace reference.  The thread that releases
            * the last reference is responsible for tearing down the vmspace.
            * However, threads not releasing the final reference must switch to the
            * kernel's vmspace0 before the decrement so that the subsequent pmap
            * deactivation does not modify a freed vmspace.
            */
           refcount_acquire(&vmspace0.vm_refcnt);
           if (!(released = refcount_release_if_last(&vm->vm_refcnt))) {
                   if (p->p_vmspace != &vmspace0) {
                           PROC_VMSPACE_LOCK(p);
                           p->p_vmspace = &vmspace0;
                           PROC_VMSPACE_UNLOCK(p);
                           pmap_activate(td);
                   }
                   released = refcount_release(&vm->vm_refcnt);
           }
           if (released) {
                   /*
                    * pmap_remove_pages() expects the pmap to be active, so switch
                    * back first if necessary.
                    */
                   if (p->p_vmspace != vm) {
                           PROC_VMSPACE_LOCK(p);
                           p->p_vmspace = vm;
                           PROC_VMSPACE_UNLOCK(p);
                           pmap_activate(td);
                   }
                   pmap_remove_pages(vmspace_pmap(vm));
                   PROC_VMSPACE_LOCK(p);
                   p->p_vmspace = &vmspace0;
                   PROC_VMSPACE_UNLOCK(p);
                   pmap_activate(td);
                   vmspace_dofree(vm);
           }
   #ifdef RACCT
           if (racct_enable)
                   vmspace_container_reset(p);
   #endif
   }
   
   /* Acquire reference to vmspace owned by another process. */
   
   struct vmspace *
   vmspace_acquire_ref(struct proc *p)
   {
           struct vmspace *vm;
   
           PROC_VMSPACE_LOCK(p);
           vm = p->p_vmspace;
           if (vm == NULL || !refcount_acquire_if_not_zero(&vm->vm_refcnt)) {
                   PROC_VMSPACE_UNLOCK(p);
                   return (NULL);
           }
           if (vm != p->p_vmspace) {
                   PROC_VMSPACE_UNLOCK(p);
                   vmspace_free(vm);
                   return (NULL);
           }
           PROC_VMSPACE_UNLOCK(p);
           return (vm);
   }
   
   /*
    * Switch between vmspaces in an AIO kernel process.
    *
    * The new vmspace is either the vmspace of a user process obtained
    * from an active AIO request or the initial vmspace of the AIO kernel
    * process (when it is idling).  Because user processes will block to
    * drain any active AIO requests before proceeding in exit() or
    * execve(), the reference count for vmspaces from AIO requests can
    * never be 0.  Similarly, AIO kernel processes hold an extra
    * reference on their initial vmspace for the life of the process.  As
    * a result, the 'newvm' vmspace always has a non-zero reference
    * count.  This permits an additional reference on 'newvm' to be
    * acquired via a simple atomic increment rather than the loop in
    * vmspace_acquire_ref() above.
    */
   void
   vmspace_switch_aio(struct vmspace *newvm)
   {
           struct vmspace *oldvm;
   
           /* XXX: Need some way to assert that this is an aio daemon. */
   
           KASSERT(refcount_load(&newvm->vm_refcnt) > 0,
               ("vmspace_switch_aio: newvm unreferenced"));
   
           oldvm = curproc->p_vmspace;
           if (oldvm == newvm)
                   return;
   
           /*
            * Point to the new address space and refer to it.
            */
           curproc->p_vmspace = newvm;
           refcount_acquire(&newvm->vm_refcnt);
   
           /* Activate the new mapping. */
           pmap_activate(curthread);
   
           vmspace_free(oldvm);
   }
   
   void
   _vm_map_lock(vm_map_t map, const char *file, int line)
   {
   
           if (map->system_map)
                   mtx_lock_flags_(&map->system_mtx, 0, file, line);
           else
                   sx_xlock_(&map->lock, file, line);
           map->timestamp++;
   }
   
   void
   vm_map_entry_set_vnode_text(vm_map_entry_t entry, bool add)
   {
           vm_object_t object;
           struct vnode *vp;
           bool vp_held;
   
           if ((entry->eflags & MAP_ENTRY_VN_EXEC) == 0)
                   return;
           KASSERT((entry->eflags & MAP_ENTRY_IS_SUB_MAP) == 0,
               ("Submap with execs"));
           object = entry->object.vm_object;
           KASSERT(object != NULL, ("No object for text, entry %p", entry));
           if ((object->flags & OBJ_ANON) != 0)
                   object = object->handle;
           else
                   KASSERT(object->backing_object == NULL,
                       ("non-anon object %p shadows", object));
           KASSERT(object != NULL, ("No content object for text, entry %p obj %p",
               entry, entry->object.vm_object));
   
           /*
            * Mostly, we do not lock the backing object.  It is
            * referenced by the entry we are processing, so it cannot go
            * away.
            */
           vm_pager_getvp(object, &vp, &vp_held);
           if (vp != NULL) {
                   if (add) {
                           VOP_SET_TEXT_CHECKED(vp);
                   } else {
                           vn_lock(vp, LK_SHARED | LK_RETRY);
                           VOP_UNSET_TEXT_CHECKED(vp);
                           VOP_UNLOCK(vp);
                   }
                   if (vp_held)
                           vdrop(vp);
           }
   }
   
   /*
    * Use a different name for this vm_map_entry field when it's use
    * is not consistent with its use as part of an ordered search tree.
    */
   #define defer_next right
   
   static void
   vm_map_process_deferred(void)
   {
           struct thread *td;
           vm_map_entry_t entry, next;
           vm_object_t object;
   
           td = curthread;
           entry = td->td_map_def_user;
           td->td_map_def_user = NULL;
           while (entry != NULL) {
                   next = entry->defer_next;
                   MPASS((entry->eflags & (MAP_ENTRY_WRITECNT |
                       MAP_ENTRY_VN_EXEC)) != (MAP_ENTRY_WRITECNT |
                       MAP_ENTRY_VN_EXEC));
                   if ((entry->eflags & MAP_ENTRY_WRITECNT) != 0) {
                           /*
                            * Decrement the object's writemappings and
                            * possibly the vnode's v_writecount.
                            */
                           KASSERT((entry->eflags & MAP_ENTRY_IS_SUB_MAP) == 0,
                               ("Submap with writecount"));
                           object = entry->object.vm_object;
                           KASSERT(object != NULL, ("No object for writecount"));
                           vm_pager_release_writecount(object, entry->start,
                               entry->end);
                   }
                   vm_map_entry_set_vnode_text(entry, false);
                   vm_map_entry_deallocate(entry, FALSE);
                   entry = next;
           }
   }
   
   #ifdef INVARIANTS
   static void
   _vm_map_assert_locked(vm_map_t map, const char *file, int line)
   {
   
           if (map->system_map)
                   mtx_assert_(&map->system_mtx, MA_OWNED, file, line);
           else
                   sx_assert_(&map->lock, SA_XLOCKED, file, line);
   }
   
   #define VM_MAP_ASSERT_LOCKED(map) \
       _vm_map_assert_locked(map, LOCK_FILE, LOCK_LINE)
   
   enum { VMMAP_CHECK_NONE, VMMAP_CHECK_UNLOCK, VMMAP_CHECK_ALL };
   #ifdef DIAGNOSTIC
   static int enable_vmmap_check = VMMAP_CHECK_UNLOCK;
   #else
   static int enable_vmmap_check = VMMAP_CHECK_NONE;
   #endif
   SYSCTL_INT(_debug, OID_AUTO, vmmap_check, CTLFLAG_RWTUN,
       &enable_vmmap_check, 0, "Enable vm map consistency checking");
   
   static void _vm_map_assert_consistent(vm_map_t map, int check);
   
   #define VM_MAP_ASSERT_CONSISTENT(map) \
       _vm_map_assert_consistent(map, VMMAP_CHECK_ALL)
   #ifdef DIAGNOSTIC
   #define VM_MAP_UNLOCK_CONSISTENT(map) do {                              \
           if (map->nupdates > map->nentries) {                            \
                   _vm_map_assert_consistent(map, VMMAP_CHECK_UNLOCK);     \
                   map->nupdates = 0;                                      \
           }                                                               \
   } while (0)
   #else
   #define VM_MAP_UNLOCK_CONSISTENT(map)
   #endif
   #else
   #define VM_MAP_ASSERT_LOCKED(map)
   #define VM_MAP_ASSERT_CONSISTENT(map)
   #define VM_MAP_UNLOCK_CONSISTENT(map)
   #endif /* INVARIANTS */
   
   void
   _vm_map_unlock(vm_map_t map, const char *file, int line)
   {
   
           VM_MAP_UNLOCK_CONSISTENT(map);
           if (map->system_map) {
   #ifndef UMA_MD_SMALL_ALLOC
                   if (map == kernel_map && (map->flags & MAP_REPLENISH) != 0) {
                           uma_prealloc(kmapentzone, 1);
                           map->flags &= ~MAP_REPLENISH;
                   }
   #endif
                   mtx_unlock_flags_(&map->system_mtx, 0, file, line);
           } else {
                   sx_xunlock_(&map->lock, file, line);
                   vm_map_process_deferred();
           }
   }
   
   void
   _vm_map_lock_read(vm_map_t map, const char *file, int line)
   {
   
           if (map->system_map)
                   mtx_lock_flags_(&map->system_mtx, 0, file, line);
           else
                   sx_slock_(&map->lock, file, line);
   }
   
   void
   _vm_map_unlock_read(vm_map_t map, const char *file, int line)
   {
   
           if (map->system_map) {
                   KASSERT((map->flags & MAP_REPLENISH) == 0,
                       ("%s: MAP_REPLENISH leaked", __func__));
                   mtx_unlock_flags_(&map->system_mtx, 0, file, line);
           } else {
                   sx_sunlock_(&map->lock, file, line);
                   vm_map_process_deferred();
           }
   }
   
   int
   _vm_map_trylock(vm_map_t map, const char *file, int line)
   {
           int error;
   
           error = map->system_map ?
               !mtx_trylock_flags_(&map->system_mtx, 0, file, line) :
               !sx_try_xlock_(&map->lock, file, line);
           if (error == 0)
                   map->timestamp++;
           return (error == 0);
   }
   
   int
   _vm_map_trylock_read(vm_map_t map, const char *file, int line)
   {
           int error;
   
           error = map->system_map ?
               !mtx_trylock_flags_(&map->system_mtx, 0, file, line) :
               !sx_try_slock_(&map->lock, file, line);
           return (error == 0);
   }
   
   /*
    *      _vm_map_lock_upgrade:   [ internal use only ]
    *
    *      Tries to upgrade a read (shared) lock on the specified map to a write
    *      (exclusive) lock.  Returns the value "" if the upgrade succeeds and a
    *      non-zero value if the upgrade fails.  If the upgrade fails, the map is
    *      returned without a read or write lock held.
    *
    *      Requires that the map be read locked.
    */
   int
   _vm_map_lock_upgrade(vm_map_t map, const char *file, int line)
   {
           unsigned int last_timestamp;
   
           if (map->system_map) {
                   mtx_assert_(&map->system_mtx, MA_OWNED, file, line);
           } else {
                   if (!sx_try_upgrade_(&map->lock, file, line)) {
                           last_timestamp = map->timestamp;
                           sx_sunlock_(&map->lock, file, line);
                           vm_map_process_deferred();
                           /*
                            * If the map's timestamp does not change while the
                            * map is unlocked, then the upgrade succeeds.
                            */
                           sx_xlock_(&map->lock, file, line);
                           if (last_timestamp != map->timestamp) {
                                   sx_xunlock_(&map->lock, file, line);
                                   return (1);
                           }
                   }
           }
           map->timestamp++;
           return (0);
   }
   
   void
   _vm_map_lock_downgrade(vm_map_t map, const char *file, int line)
   {
   
           if (map->system_map) {
                   KASSERT((map->flags & MAP_REPLENISH) == 0,
                       ("%s: MAP_REPLENISH leaked", __func__));
                   mtx_assert_(&map->system_mtx, MA_OWNED, file, line);
           } else {
                   VM_MAP_UNLOCK_CONSISTENT(map);
                   sx_downgrade_(&map->lock, file, line);
           }
   }
   
   /*
    *      vm_map_locked:
    *
    *      Returns a non-zero value if the caller holds a write (exclusive) lock
    *      on the specified map and the value "" otherwise.
    */
   int
   vm_map_locked(vm_map_t map)
   {
   
           if (map->system_map)
                   return (mtx_owned(&map->system_mtx));
           else
                   return (sx_xlocked(&map->lock));
   }
   
   /*
    *      _vm_map_unlock_and_wait:
    *
    *      Atomically releases the lock on the specified map and puts the calling
    *      thread to sleep.  The calling thread will remain asleep until either
    *      vm_map_wakeup() is performed on the map or the specified timeout is
    *      exceeded.
    *
    *      WARNING!  This function does not perform deferred deallocations of
    *      objects and map entries.  Therefore, the calling thread is expected to
    *      reacquire the map lock after reawakening and later perform an ordinary
    *      unlock operation, such as vm_map_unlock(), before completing its
    *      operation on the map.
    */
   int
   _vm_map_unlock_and_wait(vm_map_t map, int timo, const char *file, int line)
   {
   
           VM_MAP_UNLOCK_CONSISTENT(map);
           mtx_lock(&map_sleep_mtx);
           if (map->system_map) {
                   KASSERT((map->flags & MAP_REPLENISH) == 0,
                       ("%s: MAP_REPLENISH leaked", __func__));
                   mtx_unlock_flags_(&map->system_mtx, 0, file, line);
           } else {
                   sx_xunlock_(&map->lock, file, line);
           }
           return (msleep(&map->root, &map_sleep_mtx, PDROP | PVM, "vmmaps",
               timo));
   }
   
   /*
    *      vm_map_wakeup:
    *
    *      Awaken any threads that have slept on the map using
    *      vm_map_unlock_and_wait().
    */
   void
   vm_map_wakeup(vm_map_t map)
   {
   
           /*
            * Acquire and release map_sleep_mtx to prevent a wakeup()
            * from being performed (and lost) between the map unlock
            * and the msleep() in _vm_map_unlock_and_wait().
            */
           mtx_lock(&map_sleep_mtx);
           mtx_unlock(&map_sleep_mtx);
           wakeup(&map->root);
   }
   
   void
   vm_map_busy(vm_map_t map)
   {
   
           VM_MAP_ASSERT_LOCKED(map);
           map->busy++;
   }
   
   void
   vm_map_unbusy(vm_map_t map)
   {
   
           VM_MAP_ASSERT_LOCKED(map);
           KASSERT(map->busy, ("vm_map_unbusy: not busy"));
           if (--map->busy == 0 && (map->flags & MAP_BUSY_WAKEUP)) {
                   vm_map_modflags(map, 0, MAP_BUSY_WAKEUP);
                   wakeup(&map->busy);
           }
   }
   
   void 
   vm_map_wait_busy(vm_map_t map)
   {
   
           VM_MAP_ASSERT_LOCKED(map);
           while (map->busy) {
                   vm_map_modflags(map, MAP_BUSY_WAKEUP, 0);
                   if (map->system_map)
                           msleep(&map->busy, &map->system_mtx, 0, "mbusy", 0);
                   else
                           sx_sleep(&map->busy, &map->lock, 0, "mbusy", 0);
           }
           map->timestamp++;
   }
   
   long
   vmspace_resident_count(struct vmspace *vmspace)
   {
           return pmap_resident_count(vmspace_pmap(vmspace));
   }
   
   /*
    * Initialize an existing vm_map structure
    * such as that in the vmspace structure.
    */
   static void
   _vm_map_init(vm_map_t map, pmap_t pmap, vm_offset_t min, vm_offset_t max)
   {
   
           map->header.eflags = MAP_ENTRY_HEADER;
           map->needs_wakeup = FALSE;
           map->system_map = 0;
           map->pmap = pmap;
           map->header.end = min;
           map->header.start = max;
           map->flags = 0;
           map->header.left = map->header.right = &map->header;
           map->root = NULL;
           map->timestamp = 0;
           map->busy = 0;
           map->anon_loc = 0;
   #ifdef DIAGNOSTIC
           map->nupdates = 0;
   #endif
   }
   
   void
   vm_map_init(vm_map_t map, pmap_t pmap, vm_offset_t min, vm_offset_t max)
   {
   
           _vm_map_init(map, pmap, min, max);
           mtx_init(&map->system_mtx, "vm map (system)", NULL,
               MTX_DEF | MTX_DUPOK);
           sx_init(&map->lock, "vm map (user)");
   }
   
   /*
    *      vm_map_entry_dispose:   [ internal use only ]
    *
    *      Inverse of vm_map_entry_create.
    */
   static void
   vm_map_entry_dispose(vm_map_t map, vm_map_entry_t entry)
   {
           uma_zfree(map->system_map ? kmapentzone : mapentzone, entry);
   }
   
   /*
    *      vm_map_entry_create:    [ internal use only ]
    *
    *      Allocates a VM map entry for insertion.
    *      No entry fields are filled in.
    */
   static vm_map_entry_t
   vm_map_entry_create(vm_map_t map)
   {
           vm_map_entry_t new_entry;
   
   #ifndef UMA_MD_SMALL_ALLOC
           if (map == kernel_map) {
                   VM_MAP_ASSERT_LOCKED(map);
   
                   /*
                    * A new slab of kernel map entries cannot be allocated at this
                    * point because the kernel map has not yet been updated to
                    * reflect the caller's request.  Therefore, we allocate a new
                    * map entry, dipping into the reserve if necessary, and set a
                    * flag indicating that the reserve must be replenished before
                    * the map is unlocked.
                    */
                   new_entry = uma_zalloc(kmapentzone, M_NOWAIT | M_NOVM);
                   if (new_entry == NULL) {
                           new_entry = uma_zalloc(kmapentzone,
                               M_NOWAIT | M_NOVM | M_USE_RESERVE);
                           kernel_map->flags |= MAP_REPLENISH;
                   }
           } else
   #endif
           if (map->system_map) {
                   new_entry = uma_zalloc(kmapentzone, M_NOWAIT);
           } else {
                   new_entry = uma_zalloc(mapentzone, M_WAITOK);
           }
           KASSERT(new_entry != NULL,
               ("vm_map_entry_create: kernel resources exhausted"));
           return (new_entry);
   }
   
   /*
    *      vm_map_entry_set_behavior:
    *
    *      Set the expected access behavior, either normal, random, or
    *      sequential.
    */
   static inline void
   vm_map_entry_set_behavior(vm_map_entry_t entry, u_char behavior)
   {
           entry->eflags = (entry->eflags & ~MAP_ENTRY_BEHAV_MASK) |
               (behavior & MAP_ENTRY_BEHAV_MASK);
   }
   
   /*
    *      vm_map_entry_max_free_{left,right}:
    *
    *      Compute the size of the largest free gap between two entries,
    *      one the root of a tree and the other the ancestor of that root
    *      that is the least or greatest ancestor found on the search path.
    */
   static inline vm_size_t
   vm_map_entry_max_free_left(vm_map_entry_t root, vm_map_entry_t left_ancestor)
   {
   
           return (root->left != left_ancestor ?
               root->left->max_free : root->start - left_ancestor->end);
   }
  
  static inline vm_size_t
  vm_map_entry_max_free_right(vm_map_entry_t root, vm_map_entry_t right_ancestor)
  {
  
          return (root->right != right_ancestor ?
              root->right->max_free : right_ancestor->start - root->end);
  }
  
  /*
   *      vm_map_entry_{pred,succ}:
   *
   *      Find the {predecessor, successor} of the entry by taking one step
   *      in the appropriate direction and backtracking as much as necessary.
   *      vm_map_entry_succ is defined in vm_map.h.
   */
  static inline vm_map_entry_t
  vm_map_entry_pred(vm_map_entry_t entry)
  {
          vm_map_entry_t prior;
  
          prior = entry->left;
          if (prior->right->start < entry->start) {
                  do
                          prior = prior->right;
                  while (prior->right != entry);
          }
          return (prior);
  }
  
  static inline vm_size_t
  vm_size_max(vm_size_t a, vm_size_t b)
  {
  
          return (a > b ? a : b);
  }
  
  #define SPLAY_LEFT_STEP(root, y, llist, rlist, test) do {               \
          vm_map_entry_t z;                                               \
          vm_size_t max_free;                                             \
                                                                          \
          /*                                                              \
           * Infer root->right->max_free == root->max_free when           \
           * y->max_free < root->max_free || root->max_free == 0.         \
           * Otherwise, look right to find it.                            \
           */                                                             \
          y = root->left;                                                 \
          max_free = root->max_free;                                      \
          KASSERT(max_free == vm_size_max(                                \
              vm_map_entry_max_free_left(root, llist),                    \
              vm_map_entry_max_free_right(root, rlist)),                  \
              ("%s: max_free invariant fails", __func__));                \
          if (max_free - 1 < vm_map_entry_max_free_left(root, llist))     \
                  max_free = vm_map_entry_max_free_right(root, rlist);    \
          if (y != llist && (test)) {                                     \
                  /* Rotate right and make y root. */                     \
                  z = y->right;                                           \
                  if (z != root) {                                        \
                          root->left = z;                                 \
                          y->right = root;                                \
                          if (max_free < y->max_free)                     \
                              root->max_free = max_free =                 \
                              vm_size_max(max_free, z->max_free);         \
                  } else if (max_free < y->max_free)                      \
                          root->max_free = max_free =                     \
                              vm_size_max(max_free, root->start - y->end);\
                  root = y;                                               \
                  y = root->left;                                         \
          }                                                               \
          /* Copy right->max_free.  Put root on rlist. */                 \
          root->max_free = max_free;                                      \
          KASSERT(max_free == vm_map_entry_max_free_right(root, rlist),   \
              ("%s: max_free not copied from right", __func__));          \
          root->left = rlist;                                             \
          rlist = root;                                                   \
          root = y != llist ? y : NULL;                                   \
  } while (0)
  
  #define SPLAY_RIGHT_STEP(root, y, llist, rlist, test) do {              \
          vm_map_entry_t z;                                               \
          vm_size_t max_free;                                             \
                                                                          \
          /*                                                              \
           * Infer root->left->max_free == root->max_free when            \
           * y->max_free < root->max_free || root->max_free == 0.         \
           * Otherwise, look left to find it.                             \
           */                                                             \
          y = root->right;                                                \
          max_free = root->max_free;                                      \
          KASSERT(max_free == vm_size_max(                                \
              vm_map_entry_max_free_left(root, llist),                    \
              vm_map_entry_max_free_right(root, rlist)),                  \
              ("%s: max_free invariant fails", __func__));                \
          if (max_free - 1 < vm_map_entry_max_free_right(root, rlist))    \
                  max_free = vm_map_entry_max_free_left(root, llist);     \
          if (y != rlist && (test)) {                                     \
                  /* Rotate left and make y root. */                      \
                  z = y->left;                                            \
                  if (z != root) {                                        \
                          root->right = z;                                \
                          y->left = root;                                 \
                          if (max_free < y->max_free)                     \
                              root->max_free = max_free =                 \
                              vm_size_max(max_free, z->max_free);         \
                  } else if (max_free < y->max_free)                      \
                          root->max_free = max_free =                     \
                              vm_size_max(max_free, y->start - root->end);\
                  root = y;                                               \
                  y = root->right;                                        \
          }                                                               \
          /* Copy left->max_free.  Put root on llist. */                  \
          root->max_free = max_free;                                      \
          KASSERT(max_free == vm_map_entry_max_free_left(root, llist),    \
              ("%s: max_free not copied from left", __func__));           \
          root->right = llist;                                            \
          llist = root;                                                   \
          root = y != rlist ? y : NULL;                                   \
  } while (0)
  
  /*
   * Walk down the tree until we find addr or a gap where addr would go, breaking
   * off left and right subtrees of nodes less than, or greater than addr.  Treat
   * subtrees with root->max_free < length as empty trees.  llist and rlist are
   * the two sides in reverse order (bottom-up), with llist linked by the right
   * pointer and rlist linked by the left pointer in the vm_map_entry, and both
   * lists terminated by &map->header.  This function, and the subsequent call to
   * vm_map_splay_merge_{left,right,pred,succ}, rely on the start and end address
   * values in &map->header.
   */
  static __always_inline vm_map_entry_t
  vm_map_splay_split(vm_map_t map, vm_offset_t addr, vm_size_t length,
      vm_map_entry_t *llist, vm_map_entry_t *rlist)
  {
          vm_map_entry_t left, right, root, y;
  
          left = right = &map->header;
          root = map->root;
          while (root != NULL && root->max_free >= length) {
                  KASSERT(left->end <= root->start &&
                      root->end <= right->start,
                      ("%s: root not within tree bounds", __func__));
                  if (addr < root->start) {
                          SPLAY_LEFT_STEP(root, y, left, right,
                              y->max_free >= length && addr < y->start);
                  } else if (addr >= root->end) {
                          SPLAY_RIGHT_STEP(root, y, left, right,
                              y->max_free >= length && addr >= y->end);
                  } else
                          break;
          }
          *llist = left;
          *rlist = right;
          return (root);
  }
  
  static __always_inline void
  vm_map_splay_findnext(vm_map_entry_t root, vm_map_entry_t *rlist)
  {
          vm_map_entry_t hi, right, y;
  
          right = *rlist;
          hi = root->right == right ? NULL : root->right;
          if (hi == NULL)
                  return;
          do
                  SPLAY_LEFT_STEP(hi, y, root, right, true);
          while (hi != NULL);
          *rlist = right;
  }
  
  static __always_inline void
  vm_map_splay_findprev(vm_map_entry_t root, vm_map_entry_t *llist)
  {
          vm_map_entry_t left, lo, y;
  
          left = *llist;
          lo = root->left == left ? NULL : root->left;
          if (lo == NULL)
                  return;
          do
                  SPLAY_RIGHT_STEP(lo, y, left, root, true);
          while (lo != NULL);
          *llist = left;
  }
  
  static inline void
  vm_map_entry_swap(vm_map_entry_t *a, vm_map_entry_t *b)
  {
          vm_map_entry_t tmp;
  
          tmp = *b;
          *b = *a;
          *a = tmp;
  }
  
  /*
   * Walk back up the two spines, flip the pointers and set max_free.  The
   * subtrees of the root go at the bottom of llist and rlist.
   */
  static vm_size_t
  vm_map_splay_merge_left_walk(vm_map_entry_t header, vm_map_entry_t root,
      vm_map_entry_t tail, vm_size_t max_free, vm_map_entry_t llist)
  {
          do {
                  /*
                   * The max_free values of the children of llist are in
                   * llist->max_free and max_free.  Update with the
                   * max value.
                   */
                  llist->max_free = max_free =
                      vm_size_max(llist->max_free, max_free);
                  vm_map_entry_swap(&llist->right, &tail);
                  vm_map_entry_swap(&tail, &llist);
          } while (llist != header);
          root->left = tail;
          return (max_free);
  }
  
  /*
   * When llist is known to be the predecessor of root.
   */
  static inline vm_size_t
  vm_map_splay_merge_pred(vm_map_entry_t header, vm_map_entry_t root,
      vm_map_entry_t llist)
  {
          vm_size_t max_free;
  
          max_free = root->start - llist->end;
          if (llist != header) {
                  max_free = vm_map_splay_merge_left_walk(header, root,
                      root, max_free, llist);
          } else {
                  root->left = header;
                  header->right = root;
          }
          return (max_free);
  }
  
  /*
   * When llist may or may not be the predecessor of root.
   */
  static inline vm_size_t
  vm_map_splay_merge_left(vm_map_entry_t header, vm_map_entry_t root,
      vm_map_entry_t llist)
  {
          vm_size_t max_free;
  
          max_free = vm_map_entry_max_free_left(root, llist);
          if (llist != header) {
                  max_free = vm_map_splay_merge_left_walk(header, root,
                      root->left == llist ? root : root->left,
                      max_free, llist);
          }
          return (max_free);
  }
  
  static vm_size_t
  vm_map_splay_merge_right_walk(vm_map_entry_t header, vm_map_entry_t root,
      vm_map_entry_t tail, vm_size_t max_free, vm_map_entry_t rlist)
  {
          do {
                  /*
                   * The max_free values of the children of rlist are in
                   * rlist->max_free and max_free.  Update with the
                   * max value.
                   */
                  rlist->max_free = max_free =
                      vm_size_max(rlist->max_free, max_free);
                  vm_map_entry_swap(&rlist->left, &tail);
                  vm_map_entry_swap(&tail, &rlist);
          } while (rlist != header);
          root->right = tail;
          return (max_free);
  }
  
  /*
   * When rlist is known to be the succecessor of root.
   */
  static inline vm_size_t
  vm_map_splay_merge_succ(vm_map_entry_t header, vm_map_entry_t root,
      vm_map_entry_t rlist)
  {
          vm_size_t max_free;
  
          max_free = rlist->start - root->end;
          if (rlist != header) {
                  max_free = vm_map_splay_merge_right_walk(header, root,
                      root, max_free, rlist);
          } else {
                  root->right = header;
                  header->left = root;
          }
          return (max_free);
  }
  
  /*
   * When rlist may or may not be the succecessor of root.
   */
  static inline vm_size_t
  vm_map_splay_merge_right(vm_map_entry_t header, vm_map_entry_t root,
      vm_map_entry_t rlist)
  {
          vm_size_t max_free;
  
          max_free = vm_map_entry_max_free_right(root, rlist);
          if (rlist != header) {
                  max_free = vm_map_splay_merge_right_walk(header, root,
                      root->right == rlist ? root : root->right,
                      max_free, rlist);
          }
          return (max_free);
  }
  
  /*
   *      vm_map_splay:
   *
   *      The Sleator and Tarjan top-down splay algorithm with the
   *      following variation.  Max_free must be computed bottom-up, so
   *      on the downward pass, maintain the left and right spines in
   *      reverse order.  Then, make a second pass up each side to fix
   *      the pointers and compute max_free.  The time bound is O(log n)
   *      amortized.
   *
   *      The tree is threaded, which means that there are no null pointers.
   *      When a node has no left child, its left pointer points to its
   *      predecessor, which the last ancestor on the search path from the root
   *      where the search branched right.  Likewise, when a node has no right
   *      child, its right pointer points to its successor.  The map header node
   *      is the predecessor of the first map entry, and the successor of the
   *      last.
   *
   *      The new root is the vm_map_entry containing "addr", or else an
   *      adjacent entry (lower if possible) if addr is not in the tree.
   *
   *      The map must be locked, and leaves it so.
   *
   *      Returns: the new root.
   */
  static vm_map_entry_t
  vm_map_splay(vm_map_t map, vm_offset_t addr)
  {
          vm_map_entry_t header, llist, rlist, root;
          vm_size_t max_free_left, max_free_right;
  
          header = &map->header;
          root = vm_map_splay_split(map, addr, 0, &llist, &rlist);
          if (root != NULL) {
                  max_free_left = vm_map_splay_merge_left(header, root, llist);
                  max_free_right = vm_map_splay_merge_right(header, root, rlist);
          } else if (llist != header) {
                  /*
                   * Recover the greatest node in the left
                   * subtree and make it the root.
                   */
                  root = llist;
                  llist = root->right;
                  max_free_left = vm_map_splay_merge_left(header, root, llist);
                  max_free_right = vm_map_splay_merge_succ(header, root, rlist);
          } else if (rlist != header) {
                  /*
                   * Recover the least node in the right
                   * subtree and make it the root.
                   */
                  root = rlist;
                  rlist = root->left;
                  max_free_left = vm_map_splay_merge_pred(header, root, llist);
                  max_free_right = vm_map_splay_merge_right(header, root, rlist);
          } else {
                  /* There is no root. */
                  return (NULL);
          }
          root->max_free = vm_size_max(max_free_left, max_free_right);
          map->root = root;
          VM_MAP_ASSERT_CONSISTENT(map);
          return (root);
  }
  
  /*
   *      vm_map_entry_{un,}link:
   *
   *      Insert/remove entries from maps.  On linking, if new entry clips
   *      existing entry, trim existing entry to avoid overlap, and manage
   *      offsets.  On unlinking, merge disappearing entry with neighbor, if
   *      called for, and manage offsets.  Callers should not modify fields in
   *      entries already mapped.
   */
  static void
  vm_map_entry_link(vm_map_t map, vm_map_entry_t entry)
  {
          vm_map_entry_t header, llist, rlist, root;
          vm_size_t max_free_left, max_free_right;
  
          CTR3(KTR_VM,
              "vm_map_entry_link: map %p, nentries %d, entry %p", map,
              map->nentries, entry);
          VM_MAP_ASSERT_LOCKED(map);
          map->nentries++;
          header = &map->header;
          root = vm_map_splay_split(map, entry->start, 0, &llist, &rlist);
          if (root == NULL) {
                  /*
                   * The new entry does not overlap any existing entry in the
                   * map, so it becomes the new root of the map tree.
                   */
                  max_free_left = vm_map_splay_merge_pred(header, entry, llist);
                  max_free_right = vm_map_splay_merge_succ(header, entry, rlist);
          } else if (entry->start == root->start) {
                  /*
                   * The new entry is a clone of root, with only the end field
                   * changed.  The root entry will be shrunk to abut the new
                   * entry, and will be the right child of the new root entry in
                   * the modified map.
                   */
                  KASSERT(entry->end < root->end,
                      ("%s: clip_start not within entry", __func__));
                  vm_map_splay_findprev(root, &llist);
                  root->offset += entry->end - root->start;
                  root->start = entry->end;
                  max_free_left = vm_map_splay_merge_pred(header, entry, llist);
                  max_free_right = root->max_free = vm_size_max(
                      vm_map_splay_merge_pred(entry, root, entry),
                      vm_map_splay_merge_right(header, root, rlist));
          } else {
                  /*
                   * The new entry is a clone of root, with only the start field
                   * changed.  The root entry will be shrunk to abut the new
                   * entry, and will be the left child of the new root entry in
                   * the modified map.
                   */
                  KASSERT(entry->end == root->end,
                      ("%s: clip_start not within entry", __func__));
                  vm_map_splay_findnext(root, &rlist);
                  entry->offset += entry->start - root->start;
                  root->end = entry->start;
                  max_free_left = root->max_free = vm_size_max(
                      vm_map_splay_merge_left(header, root, llist),
                      vm_map_splay_merge_succ(entry, root, entry));
                  max_free_right = vm_map_splay_merge_succ(header, entry, rlist);
          }
          entry->max_free = vm_size_max(max_free_left, max_free_right);
          map->root = entry;
          VM_MAP_ASSERT_CONSISTENT(map);
  }
  
  enum unlink_merge_type {
          UNLINK_MERGE_NONE,
          UNLINK_MERGE_NEXT
  };
  
  static void
  vm_map_entry_unlink(vm_map_t map, vm_map_entry_t entry,
      enum unlink_merge_type op)
  {
          vm_map_entry_t header, llist, rlist, root;
          vm_size_t max_free_left, max_free_right;
  
          VM_MAP_ASSERT_LOCKED(map);
          header = &map->header;
          root = vm_map_splay_split(map, entry->start, 0, &llist, &rlist);
          KASSERT(root != NULL,
              ("vm_map_entry_unlink: unlink object not mapped"));
  
          vm_map_splay_findprev(root, &llist);
          vm_map_splay_findnext(root, &rlist);
          if (op == UNLINK_MERGE_NEXT) {
                  rlist->start = root->start;
                  rlist->offset = root->offset;
          }
          if (llist != header) {
                  root = llist;
                  llist = root->right;
                  max_free_left = vm_map_splay_merge_left(header, root, llist);
                  max_free_right = vm_map_splay_merge_succ(header, root, rlist);
          } else if (rlist != header) {
                  root = rlist;
                  rlist = root->left;
                  max_free_left = vm_map_splay_merge_pred(header, root, llist);
                  max_free_right = vm_map_splay_merge_right(header, root, rlist);
          } else {
                  header->left = header->right = header;
                  root = NULL;
          }
          if (root != NULL)
                  root->max_free = vm_size_max(max_free_left, max_free_right);
          map->root = root;
          VM_MAP_ASSERT_CONSISTENT(map);
          map->nentries--;
          CTR3(KTR_VM, "vm_map_entry_unlink: map %p, nentries %d, entry %p", map,
              map->nentries, entry);
  }
  
  /*
   *      vm_map_entry_resize:
   *
   *      Resize a vm_map_entry, recompute the amount of free space that
   *      follows it and propagate that value up the tree.
   *
   *      The map must be locked, and leaves it so.
   */
  static void
  vm_map_entry_resize(vm_map_t map, vm_map_entry_t entry, vm_size_t grow_amount)
  {
          vm_map_entry_t header, llist, rlist, root;
  
          VM_MAP_ASSERT_LOCKED(map);
          header = &map->header;
          root = vm_map_splay_split(map, entry->start, 0, &llist, &rlist);
          KASSERT(root != NULL, ("%s: resize object not mapped", __func__));
          vm_map_splay_findnext(root, &rlist);
          entry->end += grow_amount;
          root->max_free = vm_size_max(
              vm_map_splay_merge_left(header, root, llist),
              vm_map_splay_merge_succ(header, root, rlist));
          map->root = root;
          VM_MAP_ASSERT_CONSISTENT(map);
          CTR4(KTR_VM, "%s: map %p, nentries %d, entry %p",
              __func__, map, map->nentries, entry);
  }
  
  /*
   *      vm_map_lookup_entry:    [ internal use only ]
   *
   *      Finds the map entry containing (or
   *      immediately preceding) the specified address
   *      in the given map; the entry is returned
   *      in the "entry" parameter.  The boolean
   *      result indicates whether the address is
   *      actually contained in the map.
   */
  boolean_t
  vm_map_lookup_entry(
          vm_map_t map,
          vm_offset_t address,
          vm_map_entry_t *entry)  /* OUT */
  {
          vm_map_entry_t cur, header, lbound, ubound;
          boolean_t locked;
  
          /*
           * If the map is empty, then the map entry immediately preceding
           * "address" is the map's header.
           */
          header = &map->header;
          cur = map->root;
          if (cur == NULL) {
                  *entry = header;
                  return (FALSE);
          }
          if (address >= cur->start && cur->end > address) {
                  *entry = cur;
                  return (TRUE);
          }
          if ((locked = vm_map_locked(map)) ||
              sx_try_upgrade(&map->lock)) {
                  /*
                   * Splay requires a write lock on the map.  However, it only
                   * restructures the binary search tree; it does not otherwise
                   * change the map.  Thus, the map's timestamp need not change
                   * on a temporary upgrade.
                   */
                  cur = vm_map_splay(map, address);
                  if (!locked) {
                          VM_MAP_UNLOCK_CONSISTENT(map);
                          sx_downgrade(&map->lock);
                  }
  
                  /*
                   * If "address" is contained within a map entry, the new root
                   * is that map entry.  Otherwise, the new root is a map entry
                   * immediately before or after "address".
                   */
                  if (address < cur->start) {
                          *entry = header;
                          return (FALSE);
                  }
                  *entry = cur;
                  return (address < cur->end);
          }
          /*
           * Since the map is only locked for read access, perform a
           * standard binary search tree lookup for "address".
           */
          lbound = ubound = header;
          for (;;) {
                  if (address < cur->start) {
                          ubound = cur;
                          cur = cur->left;
                          if (cur == lbound)
                                  break;
                  } else if (cur->end <= address) {
                          lbound = cur;
                          cur = cur->right;
                          if (cur == ubound)
                                  break;
                  } else {
                          *entry = cur;
                          return (TRUE);
                  }
          }
          *entry = lbound;
          return (FALSE);
  }
  
  /*
   *      vm_map_insert:
   *
   *      Inserts the given whole VM object into the target
   *      map at the specified address range.  The object's
   *      size should match that of the address range.
   *
   *      Requires that the map be locked, and leaves it so.
   *
   *      If object is non-NULL, ref count must be bumped by caller
   *      prior to making call to account for the new entry.
   */
  int
  vm_map_insert(vm_map_t map, vm_object_t object, vm_ooffset_t offset,
      vm_offset_t start, vm_offset_t end, vm_prot_t prot, vm_prot_t max, int cow)
  {
          vm_map_entry_t new_entry, next_entry, prev_entry;
          struct ucred *cred;
          vm_eflags_t protoeflags;
          vm_inherit_t inheritance;
          u_long bdry;
          u_int bidx;
  
          VM_MAP_ASSERT_LOCKED(map);
          KASSERT(object != kernel_object ||
              (cow & MAP_COPY_ON_WRITE) == 0,
              ("vm_map_insert: kernel object and COW"));
          KASSERT(object == NULL || (cow & MAP_NOFAULT) == 0 ||
              (cow & MAP_SPLIT_BOUNDARY_MASK) != 0,
              ("vm_map_insert: paradoxical MAP_NOFAULT request, obj %p cow %#x",
              object, cow));
          KASSERT((prot & ~max) == 0,
              ("prot %#x is not subset of max_prot %#x", prot, max));
  
          /*
           * Check that the start and end points are not bogus.
           */
          if (start == end || !vm_map_range_valid(map, start, end))
                  return (KERN_INVALID_ADDRESS);
  
          if ((map->flags & MAP_WXORX) != 0 && (prot & (VM_PROT_WRITE |
              VM_PROT_EXECUTE)) == (VM_PROT_WRITE | VM_PROT_EXECUTE))
                  return (KERN_PROTECTION_FAILURE);
  
          /*
           * Find the entry prior to the proposed starting address; if it's part
           * of an existing entry, this range is bogus.
           */
          if (vm_map_lookup_entry(map, start, &prev_entry))
                  return (KERN_NO_SPACE);
  
          /*
           * Assert that the next entry doesn't overlap the end point.
           */
          next_entry = vm_map_entry_succ(prev_entry);
          if (next_entry->start < end)
                  return (KERN_NO_SPACE);
  
          if ((cow & MAP_CREATE_GUARD) != 0 && (object != NULL ||
              max != VM_PROT_NONE))
                  return (KERN_INVALID_ARGUMENT);
  
          protoeflags = 0;
          if (cow & MAP_COPY_ON_WRITE)
                  protoeflags |= MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY;
          if (cow & MAP_NOFAULT)
                  protoeflags |= MAP_ENTRY_NOFAULT;
          if (cow & MAP_DISABLE_SYNCER)
                  protoeflags |= MAP_ENTRY_NOSYNC;
          if (cow & MAP_DISABLE_COREDUMP)
                  protoeflags |= MAP_ENTRY_NOCOREDUMP;
          if (cow & MAP_STACK_GROWS_DOWN)
                  protoeflags |= MAP_ENTRY_GROWS_DOWN;
          if (cow & MAP_STACK_GROWS_UP)
                  protoeflags |= MAP_ENTRY_GROWS_UP;
          if (cow & MAP_WRITECOUNT)
                  protoeflags |= MAP_ENTRY_WRITECNT;
          if (cow & MAP_VN_EXEC)
                  protoeflags |= MAP_ENTRY_VN_EXEC;
          if ((cow & MAP_CREATE_GUARD) != 0)
                  protoeflags |= MAP_ENTRY_GUARD;
          if ((cow & MAP_CREATE_STACK_GAP_DN) != 0)
                  protoeflags |= MAP_ENTRY_STACK_GAP_DN;
          if ((cow & MAP_CREATE_STACK_GAP_UP) != 0)
                  protoeflags |= MAP_ENTRY_STACK_GAP_UP;
          if (cow & MAP_INHERIT_SHARE)
                  inheritance = VM_INHERIT_SHARE;
          else
                  inheritance = VM_INHERIT_DEFAULT;
          if ((cow & MAP_SPLIT_BOUNDARY_MASK) != 0) {
                  /* This magically ignores index 0, for usual page size. */
                  bidx = (cow & MAP_SPLIT_BOUNDARY_MASK) >>
                      MAP_SPLIT_BOUNDARY_SHIFT;
                  if (bidx >= MAXPAGESIZES)
                          return (KERN_INVALID_ARGUMENT);
                  bdry = pagesizes[bidx] - 1;
                  if ((start & bdry) != 0 || (end & bdry) != 0)
                          return (KERN_INVALID_ARGUMENT);
                  protoeflags |= bidx << MAP_ENTRY_SPLIT_BOUNDARY_SHIFT;
          }
  
          cred = NULL;
          if ((cow & (MAP_ACC_NO_CHARGE | MAP_NOFAULT | MAP_CREATE_GUARD)) != 0)
                  goto charged;
          if ((cow & MAP_ACC_CHARGED) || ((prot & VM_PROT_WRITE) &&
              ((protoeflags & MAP_ENTRY_NEEDS_COPY) || object == NULL))) {
                  if (!(cow & MAP_ACC_CHARGED) && !swap_reserve(end - start))
                          return (KERN_RESOURCE_SHORTAGE);
                  KASSERT(object == NULL ||
                      (protoeflags & MAP_ENTRY_NEEDS_COPY) != 0 ||
                      object->cred == NULL,
                      ("overcommit: vm_map_insert o %p", object));
                  cred = curthread->td_ucred;
          }
  
  charged:
          /* Expand the kernel pmap, if necessary. */
          if (map == kernel_map && end > kernel_vm_end)
                  pmap_growkernel(end);
          if (object != NULL) {
                  /*
                   * OBJ_ONEMAPPING must be cleared unless this mapping
                   * is trivially proven to be the only mapping for any
                   * of the object's pages.  (Object granularity
                   * reference counting is insufficient to recognize
                   * aliases with precision.)
                   */
                  if ((object->flags & OBJ_ANON) != 0) {
                          VM_OBJECT_WLOCK(object);
                          if (object->ref_count > 1 || object->shadow_count != 0)
                                  vm_object_clear_flag(object, OBJ_ONEMAPPING);
                          VM_OBJECT_WUNLOCK(object);
                  }
          } else if ((prev_entry->eflags & ~MAP_ENTRY_USER_WIRED) ==
              protoeflags &&
              (cow & (MAP_STACK_GROWS_DOWN | MAP_STACK_GROWS_UP |
              MAP_VN_EXEC)) == 0 &&
              prev_entry->end == start && (prev_entry->cred == cred ||
              (prev_entry->object.vm_object != NULL &&
              prev_entry->object.vm_object->cred == cred)) &&
              vm_object_coalesce(prev_entry->object.vm_object,
              prev_entry->offset,
              (vm_size_t)(prev_entry->end - prev_entry->start),
              (vm_size_t)(end - prev_entry->end), cred != NULL &&
              (protoeflags & MAP_ENTRY_NEEDS_COPY) == 0)) {
                  /*
                   * We were able to extend the object.  Determine if we
                   * can extend the previous map entry to include the
                   * new range as well.
                   */
                  if (prev_entry->inheritance == inheritance &&
                      prev_entry->protection == prot &&
                      prev_entry->max_protection == max &&
                      prev_entry->wired_count == 0) {
                          KASSERT((prev_entry->eflags & MAP_ENTRY_USER_WIRED) ==
                              0, ("prev_entry %p has incoherent wiring",
                              prev_entry));
                          if ((prev_entry->eflags & MAP_ENTRY_GUARD) == 0)
                                  map->size += end - prev_entry->end;
                          vm_map_entry_resize(map, prev_entry,
                              end - prev_entry->end);
                          vm_map_try_merge_entries(map, prev_entry, next_entry);
                          return (KERN_SUCCESS);
                  }
  
                  /*
                   * If we can extend the object but cannot extend the
                   * map entry, we have to create a new map entry.  We
                   * must bump the ref count on the extended object to
                   * account for it.  object may be NULL.
                   */
                  object = prev_entry->object.vm_object;
                  offset = prev_entry->offset +
                      (prev_entry->end - prev_entry->start);
                  vm_object_reference(object);
                  if (cred != NULL && object != NULL && object->cred != NULL &&
                      !(prev_entry->eflags & MAP_ENTRY_NEEDS_COPY)) {
                          /* Object already accounts for this uid. */
                          cred = NULL;
                  }
          }
          if (cred != NULL)
                  crhold(cred);
  
          /*
           * Create a new entry
           */
          new_entry = vm_map_entry_create(map);
          new_entry->start = start;
          new_entry->end = end;
          new_entry->cred = NULL;
  
          new_entry->eflags = protoeflags;
          new_entry->object.vm_object = object;
          new_entry->offset = offset;
  
          new_entry->inheritance = inheritance;
          new_entry->protection = prot;
          new_entry->max_protection = max;
          new_entry->wired_count = 0;
          new_entry->wiring_thread = NULL;
          new_entry->read_ahead = VM_FAULT_READ_AHEAD_INIT;
          new_entry->next_read = start;
  
          KASSERT(cred == NULL || !ENTRY_CHARGED(new_entry),
              ("overcommit: vm_map_insert leaks vm_map %p", new_entry));
          new_entry->cred = cred;
  
          /*
           * Insert the new entry into the list
           */
          vm_map_entry_link(map, new_entry);
          if ((new_entry->eflags & MAP_ENTRY_GUARD) == 0)
                  map->size += new_entry->end - new_entry->start;
  
          /*
           * Try to coalesce the new entry with both the previous and next
           * entries in the list.  Previously, we only attempted to coalesce
           * with the previous entry when object is NULL.  Here, we handle the
           * other cases, which are less common.
           */
          vm_map_try_merge_entries(map, prev_entry, new_entry);
          vm_map_try_merge_entries(map, new_entry, next_entry);
  
          if ((cow & (MAP_PREFAULT | MAP_PREFAULT_PARTIAL)) != 0) {
                  vm_map_pmap_enter(map, start, prot, object, OFF_TO_IDX(offset),
                      end - start, cow & MAP_PREFAULT_PARTIAL);
          }
  
          return (KERN_SUCCESS);
  }
  
  /*
   *      vm_map_findspace:
   *
   *      Find the first fit (lowest VM address) for "length" free bytes
   *      beginning at address >= start in the given map.
   *
   *      In a vm_map_entry, "max_free" is the maximum amount of
   *      contiguous free space between an entry in its subtree and a
   *      neighbor of that entry.  This allows finding a free region in
   *      one path down the tree, so O(log n) amortized with splay
   *      trees.
   *
   *      The map must be locked, and leaves it so.
   *
   *      Returns: starting address if sufficient space,
   *               vm_map_max(map)-length+1 if insufficient space.
   */
  vm_offset_t
  vm_map_findspace(vm_map_t map, vm_offset_t start, vm_size_t length)
  {
          vm_map_entry_t header, llist, rlist, root, y;
          vm_size_t left_length, max_free_left, max_free_right;
          vm_offset_t gap_end;
  
          VM_MAP_ASSERT_LOCKED(map);
  
          /*
           * Request must fit within min/max VM address and must avoid
           * address wrap.
           */
          start = MAX(start, vm_map_min(map));
          if (start >= vm_map_max(map) || length > vm_map_max(map) - start)
                  return (vm_map_max(map) - length + 1);
  
          /* Empty tree means wide open address space. */
          if (map->root == NULL)
                  return (start);
  
          /*
           * After splay_split, if start is within an entry, push it to the start
           * of the following gap.  If rlist is at the end of the gap containing
           * start, save the end of that gap in gap_end to see if the gap is big
           * enough; otherwise set gap_end to start skip gap-checking and move
           * directly to a search of the right subtree.
           */
          header = &map->header;
          root = vm_map_splay_split(map, start, length, &llist, &rlist);
          gap_end = rlist->start;
          if (root != NULL) {
                  start = root->end;
                  if (root->right != rlist)
                          gap_end = start;
                  max_free_left = vm_map_splay_merge_left(header, root, llist);
                  max_free_right = vm_map_splay_merge_right(header, root, rlist);
          } else if (rlist != header) {
                  root = rlist;
                  rlist = root->left;
                  max_free_left = vm_map_splay_merge_pred(header, root, llist);
                  max_free_right = vm_map_splay_merge_right(header, root, rlist);
          } else {
                  root = llist;
                  llist = root->right;
                  max_free_left = vm_map_splay_merge_left(header, root, llist);
                  max_free_right = vm_map_splay_merge_succ(header, root, rlist);
          }
          root->max_free = vm_size_max(max_free_left, max_free_right);
          map->root = root;
          VM_MAP_ASSERT_CONSISTENT(map);
          if (length <= gap_end - start)
                  return (start);
  
          /* With max_free, can immediately tell if no solution. */
          if (root->right == header || length > root->right->max_free)
                  return (vm_map_max(map) - length + 1);
  
          /*
           * Splay for the least large-enough gap in the right subtree.
           */
          llist = rlist = header;
          for (left_length = 0;;
              left_length = vm_map_entry_max_free_left(root, llist)) {
                  if (length <= left_length)
                          SPLAY_LEFT_STEP(root, y, llist, rlist,
                              length <= vm_map_entry_max_free_left(y, llist));
                  else
                          SPLAY_RIGHT_STEP(root, y, llist, rlist,
                              length > vm_map_entry_max_free_left(y, root));
                  if (root == NULL)
                          break;
          }
          root = llist;
          llist = root->right;
          max_free_left = vm_map_splay_merge_left(header, root, llist);
          if (rlist == header) {
                  root->max_free = vm_size_max(max_free_left,
                      vm_map_splay_merge_succ(header, root, rlist));
          } else {
                  y = rlist;
                  rlist = y->left;
                  y->max_free = vm_size_max(
                      vm_map_splay_merge_pred(root, y, root),
                      vm_map_splay_merge_right(header, y, rlist));
                  root->max_free = vm_size_max(max_free_left, y->max_free);
          }
          map->root = root;
          VM_MAP_ASSERT_CONSISTENT(map);
          return (root->end);
  }
  
  int
  vm_map_fixed(vm_map_t map, vm_object_t object, vm_ooffset_t offset,
      vm_offset_t start, vm_size_t length, vm_prot_t prot,
      vm_prot_t max, int cow)
  {
          vm_offset_t end;
          int result;
  
          end = start + length;
          KASSERT((cow & (MAP_STACK_GROWS_DOWN | MAP_STACK_GROWS_UP)) == 0 ||
              object == NULL,
              ("vm_map_fixed: non-NULL backing object for stack"));
          vm_map_lock(map);
          VM_MAP_RANGE_CHECK(map, start, end);
          if ((cow & MAP_CHECK_EXCL) == 0) {
                  result = vm_map_delete(map, start, end);
                  if (result != KERN_SUCCESS)
                          goto out;
          }
          if ((cow & (MAP_STACK_GROWS_DOWN | MAP_STACK_GROWS_UP)) != 0) {
                  result = vm_map_stack_locked(map, start, length, sgrowsiz,
                      prot, max, cow);
          } else {
                  result = vm_map_insert(map, object, offset, start, end,
                      prot, max, cow);
          }
  out:
          vm_map_unlock(map);
          return (result);
  }
  
  static const int aslr_pages_rnd_64[2] = {0x1000, 0x10};
  static const int aslr_pages_rnd_32[2] = {0x100, 0x4};
  
  static int cluster_anon = 1;
  SYSCTL_INT(_vm, OID_AUTO, cluster_anon, CTLFLAG_RW,
      &cluster_anon, 0,
      "Cluster anonymous mappings: 0 = no, 1 = yes if no hint, 2 = always");
  
  static bool
  clustering_anon_allowed(vm_offset_t addr)
  {
  
          switch (cluster_anon) {
          case 0:
                  return (false);
          case 1:
                  return (addr == 0);
          case 2:
          default:
                  return (true);
          }
  }
  
  static long aslr_restarts;
  SYSCTL_LONG(_vm, OID_AUTO, aslr_restarts, CTLFLAG_RD,
      &aslr_restarts, 0,
      "Number of aslr failures");
  
  /*
   * Searches for the specified amount of free space in the given map with the
   * specified alignment.  Performs an address-ordered, first-fit search from
   * the given address "*addr", with an optional upper bound "max_addr".  If the
   * parameter "alignment" is zero, then the alignment is computed from the
   * given (object, offset) pair so as to enable the greatest possible use of
   * superpage mappings.  Returns KERN_SUCCESS and the address of the free space
   * in "*addr" if successful.  Otherwise, returns KERN_NO_SPACE.
   *
   * The map must be locked.  Initially, there must be at least "length" bytes
   * of free space at the given address.
   */
  static int
  vm_map_alignspace(vm_map_t map, vm_object_t object, vm_ooffset_t offset,
      vm_offset_t *addr, vm_size_t length, vm_offset_t max_addr,
      vm_offset_t alignment)
  {
          vm_offset_t aligned_addr, free_addr;
  
          VM_MAP_ASSERT_LOCKED(map);
          free_addr = *addr;
          KASSERT(free_addr == vm_map_findspace(map, free_addr, length),
              ("caller failed to provide space %#jx at address %p",
               (uintmax_t)length, (void *)free_addr));
          for (;;) {
                  /*
                   * At the start of every iteration, the free space at address
                   * "*addr" is at least "length" bytes.
                   */
                  if (alignment == 0)
                          pmap_align_superpage(object, offset, addr, length);
                  else
                          *addr = roundup2(*addr, alignment);
                  aligned_addr = *addr;
                  if (aligned_addr == free_addr) {
                          /*
                           * Alignment did not change "*addr", so "*addr" must
                           * still provide sufficient free space.
                           */
                          return (KERN_SUCCESS);
                  }
  
                  /*
                   * Test for address wrap on "*addr".  A wrapped "*addr" could
                   * be a valid address, in which case vm_map_findspace() cannot
                   * be relied upon to fail.
                   */
                  if (aligned_addr < free_addr)
                          return (KERN_NO_SPACE);
                  *addr = vm_map_findspace(map, aligned_addr, length);
                  if (*addr + length > vm_map_max(map) ||
                      (max_addr != 0 && *addr + length > max_addr))
                          return (KERN_NO_SPACE);
                  free_addr = *addr;
                  if (free_addr == aligned_addr) {
                          /*
                           * If a successful call to vm_map_findspace() did not
                           * change "*addr", then "*addr" must still be aligned
                           * and provide sufficient free space.
                           */
                          return (KERN_SUCCESS);
                  }
          }
  }
  
  int
  vm_map_find_aligned(vm_map_t map, vm_offset_t *addr, vm_size_t length,
      vm_offset_t max_addr, vm_offset_t alignment)
  {
          /* XXXKIB ASLR eh ? */
          *addr = vm_map_findspace(map, *addr, length);
          if (*addr + length > vm_map_max(map) ||
              (max_addr != 0 && *addr + length > max_addr))
                  return (KERN_NO_SPACE);
          return (vm_map_alignspace(map, NULL, 0, addr, length, max_addr,
              alignment));
  }
  
  /*
   *      vm_map_find finds an unallocated region in the target address
   *      map with the given length.  The search is defined to be
   *      first-fit from the specified address; the region found is
   *      returned in the same parameter.
   *
   *      If object is non-NULL, ref count must be bumped by caller
   *      prior to making call to account for the new entry.
   */
  int
  vm_map_find(vm_map_t map, vm_object_t object, vm_ooffset_t offset,
              vm_offset_t *addr,  /* IN/OUT */
              vm_size_t length, vm_offset_t max_addr, int find_space,
              vm_prot_t prot, vm_prot_t max, int cow)
  {
          vm_offset_t alignment, curr_min_addr, min_addr;
          int gap, pidx, rv, try;
          bool cluster, en_aslr, update_anon;
  
          KASSERT((cow & (MAP_STACK_GROWS_DOWN | MAP_STACK_GROWS_UP)) == 0 ||
              object == NULL,
              ("vm_map_find: non-NULL backing object for stack"));
          MPASS((cow & MAP_REMAP) == 0 || (find_space == VMFS_NO_SPACE &&
              (cow & (MAP_STACK_GROWS_DOWN | MAP_STACK_GROWS_UP)) == 0));
          if (find_space == VMFS_OPTIMAL_SPACE && (object == NULL ||
              (object->flags & OBJ_COLORED) == 0))
                  find_space = VMFS_ANY_SPACE;
          if (find_space >> 8 != 0) {
                  KASSERT((find_space & 0xff) == 0, ("bad VMFS flags"));
                  alignment = (vm_offset_t)1 << (find_space >> 8);
          } else
                  alignment = 0;
          en_aslr = (map->flags & MAP_ASLR) != 0;
          update_anon = cluster = clustering_anon_allowed(*addr) &&
              (map->flags & MAP_IS_SUB_MAP) == 0 && max_addr == 0 &&
              find_space != VMFS_NO_SPACE && object == NULL &&
              (cow & (MAP_INHERIT_SHARE | MAP_STACK_GROWS_UP |
              MAP_STACK_GROWS_DOWN)) == 0 && prot != PROT_NONE;
          curr_min_addr = min_addr = *addr;
          if (en_aslr && min_addr == 0 && !cluster &&
              find_space != VMFS_NO_SPACE &&
              (map->flags & MAP_ASLR_IGNSTART) != 0)
                  curr_min_addr = min_addr = vm_map_min(map);
          try = 0;
          vm_map_lock(map);
          if (cluster) {
                  curr_min_addr = map->anon_loc;
                  if (curr_min_addr == 0)
                          cluster = false;
          }
          if (find_space != VMFS_NO_SPACE) {
                  KASSERT(find_space == VMFS_ANY_SPACE ||
                      find_space == VMFS_OPTIMAL_SPACE ||
                      find_space == VMFS_SUPER_SPACE ||
                      alignment != 0, ("unexpected VMFS flag"));
  again:
                  /*
                   * When creating an anonymous mapping, try clustering
                   * with an existing anonymous mapping first.
                   *
                   * We make up to two attempts to find address space
                   * for a given find_space value. The first attempt may
                   * apply randomization or may cluster with an existing
                   * anonymous mapping. If this first attempt fails,
                   * perform a first-fit search of the available address
                   * space.
                   *
                   * If all tries failed, and find_space is
                   * VMFS_OPTIMAL_SPACE, fallback to VMFS_ANY_SPACE.
                   * Again enable clustering and randomization.
                   */
                  try++;
                  MPASS(try <= 2);
  
                  if (try == 2) {
                          /*
                           * Second try: we failed either to find a
                           * suitable region for randomizing the
                           * allocation, or to cluster with an existing
                           * mapping.  Retry with free run.
                           */
                          curr_min_addr = (map->flags & MAP_ASLR_IGNSTART) != 0 ?
                              vm_map_min(map) : min_addr;
                          atomic_add_long(&aslr_restarts, 1);
                  }
  
                  if (try == 1 && en_aslr && !cluster) {
                          /*
                           * Find space for allocation, including
                           * gap needed for later randomization.
                           */
                          pidx = MAXPAGESIZES > 1 && pagesizes[1] != 0 &&
                              (find_space == VMFS_SUPER_SPACE || find_space ==
                              VMFS_OPTIMAL_SPACE) ? 1 : 0;
                          gap = vm_map_max(map) > MAP_32BIT_MAX_ADDR &&
                              (max_addr == 0 || max_addr > MAP_32BIT_MAX_ADDR) ?
                              aslr_pages_rnd_64[pidx] : aslr_pages_rnd_32[pidx];
                          *addr = vm_map_findspace(map, curr_min_addr,
                              length + gap * pagesizes[pidx]);
                          if (*addr + length + gap * pagesizes[pidx] >
                              vm_map_max(map))
                                  goto again;
                          /* And randomize the start address. */
                          *addr += (arc4random() % gap) * pagesizes[pidx];
                          if (max_addr != 0 && *addr + length > max_addr)
                                  goto again;
                  } else {
                          *addr = vm_map_findspace(map, curr_min_addr, length);
                          if (*addr + length > vm_map_max(map) ||
                              (max_addr != 0 && *addr + length > max_addr)) {
                                  if (cluster) {
                                          cluster = false;
                                          MPASS(try == 1);
                                          goto again;
                                  }
                                  rv = KERN_NO_SPACE;
                                  goto done;
                          }
                  }
  
                  if (find_space != VMFS_ANY_SPACE &&
                      (rv = vm_map_alignspace(map, object, offset, addr, length,
                      max_addr, alignment)) != KERN_SUCCESS) {
                          if (find_space == VMFS_OPTIMAL_SPACE) {
                                  find_space = VMFS_ANY_SPACE;
                                  curr_min_addr = min_addr;
                                  cluster = update_anon;
                                  try = 0;
                                  goto again;
                          }
                          goto done;
                  }
          } else if ((cow & MAP_REMAP) != 0) {
                  if (!vm_map_range_valid(map, *addr, *addr + length)) {
                          rv = KERN_INVALID_ADDRESS;
                          goto done;
                  }
                  rv = vm_map_delete(map, *addr, *addr + length);
                  if (rv != KERN_SUCCESS)
                          goto done;
          }
          if ((cow & (MAP_STACK_GROWS_DOWN | MAP_STACK_GROWS_UP)) != 0) {
                  rv = vm_map_stack_locked(map, *addr, length, sgrowsiz, prot,
                      max, cow);
          } else {
                  rv = vm_map_insert(map, object, offset, *addr, *addr + length,
                      prot, max, cow);
          }
          if (rv == KERN_SUCCESS && update_anon)
                  map->anon_loc = *addr + length;
  done:
          vm_map_unlock(map);
          return (rv);
  }
  
  /*
   *      vm_map_find_min() is a variant of vm_map_find() that takes an
   *      additional parameter (min_addr) and treats the given address
   *      (*addr) differently.  Specifically, it treats *addr as a hint
   *      and not as the minimum address where the mapping is created.
   *
   *      This function works in two phases.  First, it tries to
   *      allocate above the hint.  If that fails and the hint is
   *      greater than min_addr, it performs a second pass, replacing
   *      the hint with min_addr as the minimum address for the
   *      allocation.
   */
  int
  vm_map_find_min(vm_map_t map, vm_object_t object, vm_ooffset_t offset,
      vm_offset_t *addr, vm_size_t length, vm_offset_t min_addr,
      vm_offset_t max_addr, int find_space, vm_prot_t prot, vm_prot_t max,
      int cow)
  {
          vm_offset_t hint;
          int rv;
  
          hint = *addr;
          for (;;) {
                  rv = vm_map_find(map, object, offset, addr, length, max_addr,
                      find_space, prot, max, cow);
                  if (rv == KERN_SUCCESS || min_addr >= hint)
                          return (rv);
                  *addr = hint = min_addr;
          }
  }
  
  /*
   * A map entry with any of the following flags set must not be merged with
   * another entry.
   */
  #define MAP_ENTRY_NOMERGE_MASK  (MAP_ENTRY_GROWS_DOWN | MAP_ENTRY_GROWS_UP | \
              MAP_ENTRY_IN_TRANSITION | MAP_ENTRY_IS_SUB_MAP | MAP_ENTRY_VN_EXEC)
  
  static bool
  vm_map_mergeable_neighbors(vm_map_entry_t prev, vm_map_entry_t entry)
  {
  
          KASSERT((prev->eflags & MAP_ENTRY_NOMERGE_MASK) == 0 ||
              (entry->eflags & MAP_ENTRY_NOMERGE_MASK) == 0,
              ("vm_map_mergeable_neighbors: neither %p nor %p are mergeable",
              prev, entry));
          return (prev->end == entry->start &&
              prev->object.vm_object == entry->object.vm_object &&
              (prev->object.vm_object == NULL ||
              prev->offset + (prev->end - prev->start) == entry->offset) &&
              prev->eflags == entry->eflags &&
              prev->protection == entry->protection &&
              prev->max_protection == entry->max_protection &&
              prev->inheritance == entry->inheritance &&
              prev->wired_count == entry->wired_count &&
              prev->cred == entry->cred);
  }
  
  static void
  vm_map_merged_neighbor_dispose(vm_map_t map, vm_map_entry_t entry)
  {
  
          /*
           * If the backing object is a vnode object, vm_object_deallocate()
           * calls vrele().  However, vrele() does not lock the vnode because
           * the vnode has additional references.  Thus, the map lock can be
           * kept without causing a lock-order reversal with the vnode lock.
           *
           * Since we count the number of virtual page mappings in
           * object->un_pager.vnp.writemappings, the writemappings value
           * should not be adjusted when the entry is disposed of.
           */
          if (entry->object.vm_object != NULL)
                  vm_object_deallocate(entry->object.vm_object);
          if (entry->cred != NULL)
                  crfree(entry->cred);
          vm_map_entry_dispose(map, entry);
  }
  
  /*
   *      vm_map_try_merge_entries:
   *
   *      Compare the given map entry to its predecessor, and merge its precessor
   *      into it if possible.  The entry remains valid, and may be extended.
   *      The predecessor may be deleted.
   *
   *      The map must be locked.
   */
  void
  vm_map_try_merge_entries(vm_map_t map, vm_map_entry_t prev_entry,
      vm_map_entry_t entry)
  {
  
          VM_MAP_ASSERT_LOCKED(map);
          if ((entry->eflags & MAP_ENTRY_NOMERGE_MASK) == 0 &&
              vm_map_mergeable_neighbors(prev_entry, entry)) {
                  vm_map_entry_unlink(map, prev_entry, UNLINK_MERGE_NEXT);
                  vm_map_merged_neighbor_dispose(map, prev_entry);
          }
  }
  
  /*
   *      vm_map_entry_back:
   *
   *      Allocate an object to back a map entry.
   */
  static inline void
  vm_map_entry_back(vm_map_entry_t entry)
  {
          vm_object_t object;
  
          KASSERT(entry->object.vm_object == NULL,
              ("map entry %p has backing object", entry));
          KASSERT((entry->eflags & MAP_ENTRY_IS_SUB_MAP) == 0,
              ("map entry %p is a submap", entry));
          object = vm_object_allocate_anon(atop(entry->end - entry->start), NULL,
              entry->cred, entry->end - entry->start);
          entry->object.vm_object = object;
          entry->offset = 0;
          entry->cred = NULL;
  }
  
  /*
   *      vm_map_entry_charge_object
   *
   *      If there is no object backing this entry, create one.  Otherwise, if
   *      the entry has cred, give it to the backing object.
   */
  static inline void
  vm_map_entry_charge_object(vm_map_t map, vm_map_entry_t entry)
  {
  
          VM_MAP_ASSERT_LOCKED(map);
          KASSERT((entry->eflags & MAP_ENTRY_IS_SUB_MAP) == 0,
              ("map entry %p is a submap", entry));
          if (entry->object.vm_object == NULL && !map->system_map &&
              (entry->eflags & MAP_ENTRY_GUARD) == 0)
                  vm_map_entry_back(entry);
          else if (entry->object.vm_object != NULL &&
              ((entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) &&
              entry->cred != NULL) {
                  VM_OBJECT_WLOCK(entry->object.vm_object);
                  KASSERT(entry->object.vm_object->cred == NULL,
                      ("OVERCOMMIT: %s: both cred e %p", __func__, entry));
                  entry->object.vm_object->cred = entry->cred;
                  entry->object.vm_object->charge = entry->end - entry->start;
                  VM_OBJECT_WUNLOCK(entry->object.vm_object);
                  entry->cred = NULL;
          }
  }
  
  /*
   *      vm_map_entry_clone
   *
   *      Create a duplicate map entry for clipping.
   */
  static vm_map_entry_t
  vm_map_entry_clone(vm_map_t map, vm_map_entry_t entry)
  {
          vm_map_entry_t new_entry;
  
          VM_MAP_ASSERT_LOCKED(map);
  
          /*
           * Create a backing object now, if none exists, so that more individual
           * objects won't be created after the map entry is split.
           */
          vm_map_entry_charge_object(map, entry);
  
          /* Clone the entry. */
          new_entry = vm_map_entry_create(map);
          *new_entry = *entry;
          if (new_entry->cred != NULL)
                  crhold(entry->cred);
          if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
                  vm_object_reference(new_entry->object.vm_object);
                  vm_map_entry_set_vnode_text(new_entry, true);
                  /*
                   * The object->un_pager.vnp.writemappings for the object of
                   * MAP_ENTRY_WRITECNT type entry shall be kept as is here.  The
                   * virtual pages are re-distributed among the clipped entries,
                   * so the sum is left the same.
                   */
          }
          return (new_entry);
  }
  
  /*
   *      vm_map_clip_start:      [ internal use only ]
   *
   *      Asserts that the given entry begins at or after
   *      the specified address; if necessary,
   *      it splits the entry into two.
   */
  static int
  vm_map_clip_start(vm_map_t map, vm_map_entry_t entry, vm_offset_t startaddr)
  {
          vm_map_entry_t new_entry;
          int bdry_idx;
  
          if (!map->system_map)
                  WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
                      "%s: map %p entry %p start 0x%jx", __func__, map, entry,
                      (uintmax_t)startaddr);
  
          if (startaddr <= entry->start)
                  return (KERN_SUCCESS);
  
          VM_MAP_ASSERT_LOCKED(map);
          KASSERT(entry->end > startaddr && entry->start < startaddr,
              ("%s: invalid clip of entry %p", __func__, entry));
  
          bdry_idx = (entry->eflags & MAP_ENTRY_SPLIT_BOUNDARY_MASK) >>
              MAP_ENTRY_SPLIT_BOUNDARY_SHIFT;
          if (bdry_idx != 0) {
                  if ((startaddr & (pagesizes[bdry_idx] - 1)) != 0)
                          return (KERN_INVALID_ARGUMENT);
          }
  
          new_entry = vm_map_entry_clone(map, entry);
  
          /*
           * Split off the front portion.  Insert the new entry BEFORE this one,
           * so that this entry has the specified starting address.
           */
          new_entry->end = startaddr;
          vm_map_entry_link(map, new_entry);
          return (KERN_SUCCESS);
  }
  
  /*
   *      vm_map_lookup_clip_start:
   *
   *      Find the entry at or just after 'start', and clip it if 'start' is in
   *      the interior of the entry.  Return entry after 'start', and in
   *      prev_entry set the entry before 'start'.
   */
  static int
  vm_map_lookup_clip_start(vm_map_t map, vm_offset_t start,
      vm_map_entry_t *res_entry, vm_map_entry_t *prev_entry)
  {
          vm_map_entry_t entry;
          int rv;
  
          if (!map->system_map)
                  WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
                      "%s: map %p start 0x%jx prev %p", __func__, map,
                      (uintmax_t)start, prev_entry);
  
          if (vm_map_lookup_entry(map, start, prev_entry)) {
                  entry = *prev_entry;
                  rv = vm_map_clip_start(map, entry, start);
                  if (rv != KERN_SUCCESS)
                          return (rv);
                  *prev_entry = vm_map_entry_pred(entry);
          } else
                  entry = vm_map_entry_succ(*prev_entry);
          *res_entry = entry;
          return (KERN_SUCCESS);
  }
  
  /*
   *      vm_map_clip_end:        [ internal use only ]
   *
   *      Asserts that the given entry ends at or before
   *      the specified address; if necessary,
   *      it splits the entry into two.
   */
  static int
  vm_map_clip_end(vm_map_t map, vm_map_entry_t entry, vm_offset_t endaddr)
  {
          vm_map_entry_t new_entry;
          int bdry_idx;
  
          if (!map->system_map)
                  WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
                      "%s: map %p entry %p end 0x%jx", __func__, map, entry,
                      (uintmax_t)endaddr);
  
          if (endaddr >= entry->end)
                  return (KERN_SUCCESS);
  
          VM_MAP_ASSERT_LOCKED(map);
          KASSERT(entry->start < endaddr && entry->end > endaddr,
              ("%s: invalid clip of entry %p", __func__, entry));
  
          bdry_idx = (entry->eflags & MAP_ENTRY_SPLIT_BOUNDARY_MASK) >>
              MAP_ENTRY_SPLIT_BOUNDARY_SHIFT;
          if (bdry_idx != 0) {
                  if ((endaddr & (pagesizes[bdry_idx] - 1)) != 0)
                          return (KERN_INVALID_ARGUMENT);
          }
  
          new_entry = vm_map_entry_clone(map, entry);
  
          /*
           * Split off the back portion.  Insert the new entry AFTER this one,
           * so that this entry has the specified ending address.
           */
          new_entry->start = endaddr;
          vm_map_entry_link(map, new_entry);
  
          return (KERN_SUCCESS);
  }
  
  /*
   *      vm_map_submap:          [ kernel use only ]
   *
   *      Mark the given range as handled by a subordinate map.
   *
   *      This range must have been created with vm_map_find,
   *      and no other operations may have been performed on this
   *      range prior to calling vm_map_submap.
   *
   *      Only a limited number of operations can be performed
   *      within this rage after calling vm_map_submap:
   *              vm_fault
   *      [Don't try vm_map_copy!]
   *
   *      To remove a submapping, one must first remove the
   *      range from the superior map, and then destroy the
   *      submap (if desired).  [Better yet, don't try it.]
   */
  int
  vm_map_submap(
          vm_map_t map,
          vm_offset_t start,
          vm_offset_t end,
          vm_map_t submap)
  {
          vm_map_entry_t entry;
          int result;
  
          result = KERN_INVALID_ARGUMENT;
  
          vm_map_lock(submap);
          submap->flags |= MAP_IS_SUB_MAP;
          vm_map_unlock(submap);
  
          vm_map_lock(map);
          VM_MAP_RANGE_CHECK(map, start, end);
          if (vm_map_lookup_entry(map, start, &entry) && entry->end >= end &&
              (entry->eflags & MAP_ENTRY_COW) == 0 &&
              entry->object.vm_object == NULL) {
                  result = vm_map_clip_start(map, entry, start);
                  if (result != KERN_SUCCESS)
                          goto unlock;
                  result = vm_map_clip_end(map, entry, end);
                  if (result != KERN_SUCCESS)
                          goto unlock;
                  entry->object.sub_map = submap;
                  entry->eflags |= MAP_ENTRY_IS_SUB_MAP;
                  result = KERN_SUCCESS;
          }
  unlock:
          vm_map_unlock(map);
  
          if (result != KERN_SUCCESS) {
                  vm_map_lock(submap);
                  submap->flags &= ~MAP_IS_SUB_MAP;
                  vm_map_unlock(submap);
          }
          return (result);
  }
  
  /*
   * The maximum number of pages to map if MAP_PREFAULT_PARTIAL is specified
   */
  #define MAX_INIT_PT     96
  
  /*
   *      vm_map_pmap_enter:
   *
   *      Preload the specified map's pmap with mappings to the specified
   *      object's memory-resident pages.  No further physical pages are
   *      allocated, and no further virtual pages are retrieved from secondary
   *      storage.  If the specified flags include MAP_PREFAULT_PARTIAL, then a
   *      limited number of page mappings are created at the low-end of the
   *      specified address range.  (For this purpose, a superpage mapping
   *      counts as one page mapping.)  Otherwise, all resident pages within
   *      the specified address range are mapped.
   */
  static void
  vm_map_pmap_enter(vm_map_t map, vm_offset_t addr, vm_prot_t prot,
      vm_object_t object, vm_pindex_t pindex, vm_size_t size, int flags)
  {
          vm_offset_t start;
          vm_page_t p, p_start;
          vm_pindex_t mask, psize, threshold, tmpidx;
  
          if ((prot & (VM_PROT_READ | VM_PROT_EXECUTE)) == 0 || object == NULL)
                  return;
          if (object->type == OBJT_DEVICE || object->type == OBJT_SG) {
                  VM_OBJECT_WLOCK(object);
                  if (object->type == OBJT_DEVICE || object->type == OBJT_SG) {
                          pmap_object_init_pt(map->pmap, addr, object, pindex,
                              size);
                          VM_OBJECT_WUNLOCK(object);
                          return;
                  }
                  VM_OBJECT_LOCK_DOWNGRADE(object);
          } else
                  VM_OBJECT_RLOCK(object);
  
          psize = atop(size);
          if (psize + pindex > object->size) {
                  if (pindex >= object->size) {
                          VM_OBJECT_RUNLOCK(object);
                          return;
                  }
                  psize = object->size - pindex;
          }
  
          start = 0;
          p_start = NULL;
          threshold = MAX_INIT_PT;
  
          p = vm_page_find_least(object, pindex);
          /*
           * Assert: the variable p is either (1) the page with the
           * least pindex greater than or equal to the parameter pindex
           * or (2) NULL.
           */
          for (;
               p != NULL && (tmpidx = p->pindex - pindex) < psize;
               p = TAILQ_NEXT(p, listq)) {
                  /*
                   * don't allow an madvise to blow away our really
                   * free pages allocating pv entries.
                   */
                  if (((flags & MAP_PREFAULT_MADVISE) != 0 &&
                      vm_page_count_severe()) ||
                      ((flags & MAP_PREFAULT_PARTIAL) != 0 &&
                      tmpidx >= threshold)) {
                          psize = tmpidx;
                          break;
                  }
                  if (vm_page_all_valid(p)) {
                          if (p_start == NULL) {
                                  start = addr + ptoa(tmpidx);
                                  p_start = p;
                          }
                          /* Jump ahead if a superpage mapping is possible. */
                          if (p->psind > 0 && ((addr + ptoa(tmpidx)) &
                              (pagesizes[p->psind] - 1)) == 0) {
                                  mask = atop(pagesizes[p->psind]) - 1;
                                  if (tmpidx + mask < psize &&
                                      vm_page_ps_test(p, PS_ALL_VALID, NULL)) {
                                          p += mask;
                                          threshold += mask;
                                  }
                          }
                  } else if (p_start != NULL) {
                          pmap_enter_object(map->pmap, start, addr +
                              ptoa(tmpidx), p_start, prot);
                          p_start = NULL;
                  }
          }
          if (p_start != NULL)
                  pmap_enter_object(map->pmap, start, addr + ptoa(psize),
                      p_start, prot);
          VM_OBJECT_RUNLOCK(object);
  }
  
  /*
   *      vm_map_protect:
   *
   *      Sets the protection and/or the maximum protection of the
   *      specified address region in the target map.
   */
  int
  vm_map_protect(vm_map_t map, vm_offset_t start, vm_offset_t end,
      vm_prot_t new_prot, vm_prot_t new_maxprot, int flags)
  {
          vm_map_entry_t entry, first_entry, in_tran, prev_entry;
          vm_object_t obj;
          struct ucred *cred;
          vm_prot_t old_prot;
          int rv;
  
          if (start == end)
                  return (KERN_SUCCESS);
  
          if ((flags & (VM_MAP_PROTECT_SET_PROT | VM_MAP_PROTECT_SET_MAXPROT)) ==
              (VM_MAP_PROTECT_SET_PROT | VM_MAP_PROTECT_SET_MAXPROT) &&
              (new_prot & new_maxprot) != new_prot)
                  return (KERN_OUT_OF_BOUNDS);
  
  again:
          in_tran = NULL;
          vm_map_lock(map);
  
          if ((map->flags & MAP_WXORX) != 0 &&
              (flags & VM_MAP_PROTECT_SET_PROT) != 0 &&
              (new_prot & (VM_PROT_WRITE | VM_PROT_EXECUTE)) == (VM_PROT_WRITE |
              VM_PROT_EXECUTE)) {
                  vm_map_unlock(map);
                  return (KERN_PROTECTION_FAILURE);
          }
  
          /*
           * Ensure that we are not concurrently wiring pages.  vm_map_wire() may
           * need to fault pages into the map and will drop the map lock while
           * doing so, and the VM object may end up in an inconsistent state if we
           * update the protection on the map entry in between faults.
           */
          vm_map_wait_busy(map);
  
          VM_MAP_RANGE_CHECK(map, start, end);
  
          if (!vm_map_lookup_entry(map, start, &first_entry))
                  first_entry = vm_map_entry_succ(first_entry);
  
          /*
           * Make a first pass to check for protection violations.
           */
          for (entry = first_entry; entry->start < end;
              entry = vm_map_entry_succ(entry)) {
                  if ((entry->eflags & MAP_ENTRY_GUARD) != 0)
                          continue;
                  if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0) {
                          vm_map_unlock(map);
                          return (KERN_INVALID_ARGUMENT);
                  }
                  if ((flags & VM_MAP_PROTECT_SET_PROT) == 0)
                          new_prot = entry->protection;
                  if ((flags & VM_MAP_PROTECT_SET_MAXPROT) == 0)
                          new_maxprot = entry->max_protection;
                  if ((new_prot & entry->max_protection) != new_prot ||
                      (new_maxprot & entry->max_protection) != new_maxprot) {
                          vm_map_unlock(map);
                          return (KERN_PROTECTION_FAILURE);
                  }
                  if ((entry->eflags & MAP_ENTRY_IN_TRANSITION) != 0)
                          in_tran = entry;
          }
  
          /*
           * Postpone the operation until all in-transition map entries have
           * stabilized.  An in-transition entry might already have its pages
           * wired and wired_count incremented, but not yet have its
           * MAP_ENTRY_USER_WIRED flag set.  In which case, we would fail to call
           * vm_fault_copy_entry() in the final loop below.
           */
          if (in_tran != NULL) {
                  in_tran->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
                  vm_map_unlock_and_wait(map, 0);
                  goto again;
          }
  
          /*
           * Before changing the protections, try to reserve swap space for any
           * private (i.e., copy-on-write) mappings that are transitioning from
           * read-only to read/write access.  If a reservation fails, break out
           * of this loop early and let the next loop simplify the entries, since
           * some may now be mergeable.
           */
          rv = vm_map_clip_start(map, first_entry, start);
          if (rv != KERN_SUCCESS) {
                  vm_map_unlock(map);
                  return (rv);
          }
          for (entry = first_entry; entry->start < end;
              entry = vm_map_entry_succ(entry)) {
                  rv = vm_map_clip_end(map, entry, end);
                  if (rv != KERN_SUCCESS) {
                          vm_map_unlock(map);
                          return (rv);
                  }
  
                  if ((flags & VM_MAP_PROTECT_SET_PROT) == 0 ||
                      ((new_prot & ~entry->protection) & VM_PROT_WRITE) == 0 ||
                      ENTRY_CHARGED(entry) ||
                      (entry->eflags & MAP_ENTRY_GUARD) != 0)
                          continue;
  
                  cred = curthread->td_ucred;
                  obj = entry->object.vm_object;
  
                  if (obj == NULL ||
                      (entry->eflags & MAP_ENTRY_NEEDS_COPY) != 0) {
                          if (!swap_reserve(entry->end - entry->start)) {
                                  rv = KERN_RESOURCE_SHORTAGE;
                                  end = entry->end;
                                  break;
                          }
                          crhold(cred);
                          entry->cred = cred;
                          continue;
                  }
  
                  VM_OBJECT_WLOCK(obj);
                  if ((obj->flags & OBJ_SWAP) == 0) {
                          VM_OBJECT_WUNLOCK(obj);
                          continue;
                  }
  
                  /*
                   * Charge for the whole object allocation now, since
                   * we cannot distinguish between non-charged and
                   * charged clipped mapping of the same object later.
                   */
                  KASSERT(obj->charge == 0,
                      ("vm_map_protect: object %p overcharged (entry %p)",
                      obj, entry));
                  if (!swap_reserve(ptoa(obj->size))) {
                          VM_OBJECT_WUNLOCK(obj);
                          rv = KERN_RESOURCE_SHORTAGE;
                          end = entry->end;
                          break;
                  }
  
                  crhold(cred);
                  obj->cred = cred;
                  obj->charge = ptoa(obj->size);
                  VM_OBJECT_WUNLOCK(obj);
          }
  
          /*
           * If enough swap space was available, go back and fix up protections.
           * Otherwise, just simplify entries, since some may have been modified.
           * [Note that clipping is not necessary the second time.]
           */
          for (prev_entry = vm_map_entry_pred(first_entry), entry = first_entry;
              entry->start < end;
              vm_map_try_merge_entries(map, prev_entry, entry),
              prev_entry = entry, entry = vm_map_entry_succ(entry)) {
                  if (rv != KERN_SUCCESS ||
                      (entry->eflags & MAP_ENTRY_GUARD) != 0)
                          continue;
  
                  old_prot = entry->protection;
  
                  if ((flags & VM_MAP_PROTECT_SET_MAXPROT) != 0) {
                          entry->max_protection = new_maxprot;
                          entry->protection = new_maxprot & old_prot;
                  }
                  if ((flags & VM_MAP_PROTECT_SET_PROT) != 0)
                          entry->protection = new_prot;
  
                  /*
                   * For user wired map entries, the normal lazy evaluation of
                   * write access upgrades through soft page faults is
                   * undesirable.  Instead, immediately copy any pages that are
                   * copy-on-write and enable write access in the physical map.
                   */
                  if ((entry->eflags & MAP_ENTRY_USER_WIRED) != 0 &&
                      (entry->protection & VM_PROT_WRITE) != 0 &&
                      (old_prot & VM_PROT_WRITE) == 0)
                          vm_fault_copy_entry(map, map, entry, entry, NULL);
  
                  /*
                   * When restricting access, update the physical map.  Worry
                   * about copy-on-write here.
                   */
                  if ((old_prot & ~entry->protection) != 0) {
  #define MASK(entry)     (((entry)->eflags & MAP_ENTRY_COW) ? ~VM_PROT_WRITE : \
                                                          VM_PROT_ALL)
                          pmap_protect(map->pmap, entry->start,
                              entry->end,
                              entry->protection & MASK(entry));
  #undef  MASK
                  }
          }
          vm_map_try_merge_entries(map, prev_entry, entry);
          vm_map_unlock(map);
          return (rv);
  }
  
  /*
   *      vm_map_madvise:
   *
   *      This routine traverses a processes map handling the madvise
   *      system call.  Advisories are classified as either those effecting
   *      the vm_map_entry structure, or those effecting the underlying
   *      objects.
   */
  int
  vm_map_madvise(
          vm_map_t map,
          vm_offset_t start,
          vm_offset_t end,
          int behav)
  {
          vm_map_entry_t entry, prev_entry;
          int rv;
          bool modify_map;
  
          /*
           * Some madvise calls directly modify the vm_map_entry, in which case
           * we need to use an exclusive lock on the map and we need to perform
           * various clipping operations.  Otherwise we only need a read-lock
           * on the map.
           */
          switch(behav) {
          case MADV_NORMAL:
          case MADV_SEQUENTIAL:
          case MADV_RANDOM:
          case MADV_NOSYNC:
          case MADV_AUTOSYNC:
          case MADV_NOCORE:
          case MADV_CORE:
                  if (start == end)
                          return (0);
                  modify_map = true;
                  vm_map_lock(map);
                  break;
          case MADV_WILLNEED:
          case MADV_DONTNEED:
          case MADV_FREE:
                  if (start == end)
                          return (0);
                  modify_map = false;
                  vm_map_lock_read(map);
                  break;
          default:
                  return (EINVAL);
          }
  
          /*
           * Locate starting entry and clip if necessary.
           */
          VM_MAP_RANGE_CHECK(map, start, end);
  
          if (modify_map) {
                  /*
                   * madvise behaviors that are implemented in the vm_map_entry.
                   *
                   * We clip the vm_map_entry so that behavioral changes are
                   * limited to the specified address range.
                   */
                  rv = vm_map_lookup_clip_start(map, start, &entry, &prev_entry);
                  if (rv != KERN_SUCCESS) {
                          vm_map_unlock(map);
                          return (vm_mmap_to_errno(rv));
                  }
  
                  for (; entry->start < end; prev_entry = entry,
                      entry = vm_map_entry_succ(entry)) {
                          if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0)
                                  continue;
  
                          rv = vm_map_clip_end(map, entry, end);
                          if (rv != KERN_SUCCESS) {
                                  vm_map_unlock(map);
                                  return (vm_mmap_to_errno(rv));
                          }
  
                          switch (behav) {
                          case MADV_NORMAL:
                                  vm_map_entry_set_behavior(entry,
                                      MAP_ENTRY_BEHAV_NORMAL);
                                  break;
                          case MADV_SEQUENTIAL:
                                  vm_map_entry_set_behavior(entry,
                                      MAP_ENTRY_BEHAV_SEQUENTIAL);
                                  break;
                          case MADV_RANDOM:
                                  vm_map_entry_set_behavior(entry,
                                      MAP_ENTRY_BEHAV_RANDOM);
                                  break;
                          case MADV_NOSYNC:
                                  entry->eflags |= MAP_ENTRY_NOSYNC;
                                  break;
                          case MADV_AUTOSYNC:
                                  entry->eflags &= ~MAP_ENTRY_NOSYNC;
                                  break;
                          case MADV_NOCORE:
                                  entry->eflags |= MAP_ENTRY_NOCOREDUMP;
                                  break;
                          case MADV_CORE:
                                  entry->eflags &= ~MAP_ENTRY_NOCOREDUMP;
                                  break;
                          default:
                                  break;
                          }
                          vm_map_try_merge_entries(map, prev_entry, entry);
                  }
                  vm_map_try_merge_entries(map, prev_entry, entry);
                  vm_map_unlock(map);
          } else {
                  vm_pindex_t pstart, pend;
  
                  /*
                   * madvise behaviors that are implemented in the underlying
                   * vm_object.
                   *
                   * Since we don't clip the vm_map_entry, we have to clip
                   * the vm_object pindex and count.
                   */
                  if (!vm_map_lookup_entry(map, start, &entry))
                          entry = vm_map_entry_succ(entry);
                  for (; entry->start < end;
                      entry = vm_map_entry_succ(entry)) {
                          vm_offset_t useEnd, useStart;
  
                          if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0)
                                  continue;
  
                          /*
                           * MADV_FREE would otherwise rewind time to
                           * the creation of the shadow object.  Because
                           * we hold the VM map read-locked, neither the
                           * entry's object nor the presence of a
                           * backing object can change.
                           */
                          if (behav == MADV_FREE &&
                              entry->object.vm_object != NULL &&
                              entry->object.vm_object->backing_object != NULL)
                                  continue;
  
                          pstart = OFF_TO_IDX(entry->offset);
                          pend = pstart + atop(entry->end - entry->start);
                          useStart = entry->start;
                          useEnd = entry->end;
  
                          if (entry->start < start) {
                                  pstart += atop(start - entry->start);
                                  useStart = start;
                          }
                          if (entry->end > end) {
                                  pend -= atop(entry->end - end);
                                  useEnd = end;
                          }
  
                          if (pstart >= pend)
                                  continue;
  
                          /*
                           * Perform the pmap_advise() before clearing
                           * PGA_REFERENCED in vm_page_advise().  Otherwise, a
                           * concurrent pmap operation, such as pmap_remove(),
                           * could clear a reference in the pmap and set
                           * PGA_REFERENCED on the page before the pmap_advise()
                           * had completed.  Consequently, the page would appear
                           * referenced based upon an old reference that
                           * occurred before this pmap_advise() ran.
                           */
                          if (behav == MADV_DONTNEED || behav == MADV_FREE)
                                  pmap_advise(map->pmap, useStart, useEnd,
                                      behav);
  
                          vm_object_madvise(entry->object.vm_object, pstart,
                              pend, behav);
  
                          /*
                           * Pre-populate paging structures in the
                           * WILLNEED case.  For wired entries, the
                           * paging structures are already populated.
                           */
                          if (behav == MADV_WILLNEED &&
                              entry->wired_count == 0) {
                                  vm_map_pmap_enter(map,
                                      useStart,
                                      entry->protection,
                                      entry->object.vm_object,
                                      pstart,
                                      ptoa(pend - pstart),
                                      MAP_PREFAULT_MADVISE
                                  );
                          }
                  }
                  vm_map_unlock_read(map);
          }
          return (0);
  }
  
  /*
   *      vm_map_inherit:
   *
   *      Sets the inheritance of the specified address
   *      range in the target map.  Inheritance
   *      affects how the map will be shared with
   *      child maps at the time of vmspace_fork.
   */
  int
  vm_map_inherit(vm_map_t map, vm_offset_t start, vm_offset_t end,
                 vm_inherit_t new_inheritance)
  {
          vm_map_entry_t entry, lentry, prev_entry, start_entry;
          int rv;
  
          switch (new_inheritance) {
          case VM_INHERIT_NONE:
          case VM_INHERIT_COPY:
          case VM_INHERIT_SHARE:
          case VM_INHERIT_ZERO:
                  break;
          default:
                  return (KERN_INVALID_ARGUMENT);
          }
          if (start == end)
                  return (KERN_SUCCESS);
          vm_map_lock(map);
          VM_MAP_RANGE_CHECK(map, start, end);
          rv = vm_map_lookup_clip_start(map, start, &start_entry, &prev_entry);
          if (rv != KERN_SUCCESS)
                  goto unlock;
          if (vm_map_lookup_entry(map, end - 1, &lentry)) {
                  rv = vm_map_clip_end(map, lentry, end);
                  if (rv != KERN_SUCCESS)
                          goto unlock;
          }
          if (new_inheritance == VM_INHERIT_COPY) {
                  for (entry = start_entry; entry->start < end;
                      prev_entry = entry, entry = vm_map_entry_succ(entry)) {
                          if ((entry->eflags & MAP_ENTRY_SPLIT_BOUNDARY_MASK)
                              != 0) {
                                  rv = KERN_INVALID_ARGUMENT;
                                  goto unlock;
                          }
                  }
          }
          for (entry = start_entry; entry->start < end; prev_entry = entry,
              entry = vm_map_entry_succ(entry)) {
                  KASSERT(entry->end <= end, ("non-clipped entry %p end %jx %jx",
                      entry, (uintmax_t)entry->end, (uintmax_t)end));
                  if ((entry->eflags & MAP_ENTRY_GUARD) == 0 ||
                      new_inheritance != VM_INHERIT_ZERO)
                          entry->inheritance = new_inheritance;
                  vm_map_try_merge_entries(map, prev_entry, entry);
          }
          vm_map_try_merge_entries(map, prev_entry, entry);
  unlock:
          vm_map_unlock(map);
          return (rv);
  }
  
  /*
   *      vm_map_entry_in_transition:
   *
   *      Release the map lock, and sleep until the entry is no longer in
   *      transition.  Awake and acquire the map lock.  If the map changed while
   *      another held the lock, lookup a possibly-changed entry at or after the
   *      'start' position of the old entry.
   */
  static vm_map_entry_t
  vm_map_entry_in_transition(vm_map_t map, vm_offset_t in_start,
      vm_offset_t *io_end, bool holes_ok, vm_map_entry_t in_entry)
  {
          vm_map_entry_t entry;
          vm_offset_t start;
          u_int last_timestamp;
  
          VM_MAP_ASSERT_LOCKED(map);
          KASSERT((in_entry->eflags & MAP_ENTRY_IN_TRANSITION) != 0,
              ("not in-tranition map entry %p", in_entry));
          /*
           * We have not yet clipped the entry.
           */
          start = MAX(in_start, in_entry->start);
          in_entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
          last_timestamp = map->timestamp;
          if (vm_map_unlock_and_wait(map, 0)) {
                  /*
                   * Allow interruption of user wiring/unwiring?
                   */
          }
          vm_map_lock(map);
          if (last_timestamp + 1 == map->timestamp)
                  return (in_entry);
  
          /*
           * Look again for the entry because the map was modified while it was
           * unlocked.  Specifically, the entry may have been clipped, merged, or
           * deleted.
           */
          if (!vm_map_lookup_entry(map, start, &entry)) {
                  if (!holes_ok) {
                          *io_end = start;
                          return (NULL);
                  }
                  entry = vm_map_entry_succ(entry);
          }
          return (entry);
  }
  
  /*
   *      vm_map_unwire:
   *
   *      Implements both kernel and user unwiring.
   */
  int
  vm_map_unwire(vm_map_t map, vm_offset_t start, vm_offset_t end,
      int flags)
  {
          vm_map_entry_t entry, first_entry, next_entry, prev_entry;
          int rv;
          bool holes_ok, need_wakeup, user_unwire;
  
          if (start == end)
                  return (KERN_SUCCESS);
          holes_ok = (flags & VM_MAP_WIRE_HOLESOK) != 0;
          user_unwire = (flags & VM_MAP_WIRE_USER) != 0;
          vm_map_lock(map);
          VM_MAP_RANGE_CHECK(map, start, end);
          if (!vm_map_lookup_entry(map, start, &first_entry)) {
                  if (holes_ok)
                          first_entry = vm_map_entry_succ(first_entry);
                  else {
                          vm_map_unlock(map);
                          return (KERN_INVALID_ADDRESS);
                  }
          }
          rv = KERN_SUCCESS;
          for (entry = first_entry; entry->start < end; entry = next_entry) {
                  if (entry->eflags & MAP_ENTRY_IN_TRANSITION) {
                          /*
                           * We have not yet clipped the entry.
                           */
                          next_entry = vm_map_entry_in_transition(map, start,
                              &end, holes_ok, entry);
                          if (next_entry == NULL) {
                                  if (entry == first_entry) {
                                          vm_map_unlock(map);
                                          return (KERN_INVALID_ADDRESS);
                                  }
                                  rv = KERN_INVALID_ADDRESS;
                                  break;
                          }
                          first_entry = (entry == first_entry) ?
                              next_entry : NULL;
                          continue;
                  }
                  rv = vm_map_clip_start(map, entry, start);
                  if (rv != KERN_SUCCESS)
                          break;
                  rv = vm_map_clip_end(map, entry, end);
                  if (rv != KERN_SUCCESS)
                          break;
  
                  /*
                   * Mark the entry in case the map lock is released.  (See
                   * above.)
                   */
                  KASSERT((entry->eflags & MAP_ENTRY_IN_TRANSITION) == 0 &&
                      entry->wiring_thread == NULL,
                      ("owned map entry %p", entry));
                  entry->eflags |= MAP_ENTRY_IN_TRANSITION;
                  entry->wiring_thread = curthread;
                  next_entry = vm_map_entry_succ(entry);
                  /*
                   * Check the map for holes in the specified region.
                   * If holes_ok, skip this check.
                   */
                  if (!holes_ok &&
                      entry->end < end && next_entry->start > entry->end) {
                          end = entry->end;
                          rv = KERN_INVALID_ADDRESS;
                          break;
                  }
                  /*
                   * If system unwiring, require that the entry is system wired.
                   */
                  if (!user_unwire &&
                      vm_map_entry_system_wired_count(entry) == 0) {
                          end = entry->end;
                          rv = KERN_INVALID_ARGUMENT;
                          break;
                  }
          }
          need_wakeup = false;
          if (first_entry == NULL &&
              !vm_map_lookup_entry(map, start, &first_entry)) {
                  KASSERT(holes_ok, ("vm_map_unwire: lookup failed"));
                  prev_entry = first_entry;
                  entry = vm_map_entry_succ(first_entry);
          } else {
                  prev_entry = vm_map_entry_pred(first_entry);
                  entry = first_entry;
          }
          for (; entry->start < end;
              prev_entry = entry, entry = vm_map_entry_succ(entry)) {
                  /*
                   * If holes_ok was specified, an empty
                   * space in the unwired region could have been mapped
                   * while the map lock was dropped for draining
                   * MAP_ENTRY_IN_TRANSITION.  Moreover, another thread
                   * could be simultaneously wiring this new mapping
                   * entry.  Detect these cases and skip any entries
                   * marked as in transition by us.
                   */
                  if ((entry->eflags & MAP_ENTRY_IN_TRANSITION) == 0 ||
                      entry->wiring_thread != curthread) {
                          KASSERT(holes_ok,
                              ("vm_map_unwire: !HOLESOK and new/changed entry"));
                          continue;
                  }
  
                  if (rv == KERN_SUCCESS && (!user_unwire ||
                      (entry->eflags & MAP_ENTRY_USER_WIRED))) {
                          if (entry->wired_count == 1)
                                  vm_map_entry_unwire(map, entry);
                          else
                                  entry->wired_count--;
                          if (user_unwire)
                                  entry->eflags &= ~MAP_ENTRY_USER_WIRED;
                  }
                  KASSERT((entry->eflags & MAP_ENTRY_IN_TRANSITION) != 0,
                      ("vm_map_unwire: in-transition flag missing %p", entry));
                  KASSERT(entry->wiring_thread == curthread,
                      ("vm_map_unwire: alien wire %p", entry));
                  entry->eflags &= ~MAP_ENTRY_IN_TRANSITION;
                  entry->wiring_thread = NULL;
                  if (entry->eflags & MAP_ENTRY_NEEDS_WAKEUP) {
                          entry->eflags &= ~MAP_ENTRY_NEEDS_WAKEUP;
                          need_wakeup = true;
                  }
                  vm_map_try_merge_entries(map, prev_entry, entry);
          }
          vm_map_try_merge_entries(map, prev_entry, entry);
          vm_map_unlock(map);
          if (need_wakeup)
                  vm_map_wakeup(map);
          return (rv);
  }
  
  static void
  vm_map_wire_user_count_sub(u_long npages)
  {
  
          atomic_subtract_long(&vm_user_wire_count, npages);
  }
  
  static bool
  vm_map_wire_user_count_add(u_long npages)
  {
          u_long wired;
  
          wired = vm_user_wire_count;
          do {
                  if (npages + wired > vm_page_max_user_wired)
                          return (false);
          } while (!atomic_fcmpset_long(&vm_user_wire_count, &wired,
              npages + wired));
  
          return (true);
  }
  
  /*
   *      vm_map_wire_entry_failure:
   *
   *      Handle a wiring failure on the given entry.
   *
   *      The map should be locked.
   */
  static void
  vm_map_wire_entry_failure(vm_map_t map, vm_map_entry_t entry,
      vm_offset_t failed_addr)
  {
  
          VM_MAP_ASSERT_LOCKED(map);
          KASSERT((entry->eflags & MAP_ENTRY_IN_TRANSITION) != 0 &&
              entry->wired_count == 1,
              ("vm_map_wire_entry_failure: entry %p isn't being wired", entry));
          KASSERT(failed_addr < entry->end,
              ("vm_map_wire_entry_failure: entry %p was fully wired", entry));
  
          /*
           * If any pages at the start of this entry were successfully wired,
           * then unwire them.
           */
          if (failed_addr > entry->start) {
                  pmap_unwire(map->pmap, entry->start, failed_addr);
                  vm_object_unwire(entry->object.vm_object, entry->offset,
                      failed_addr - entry->start, PQ_ACTIVE);
          }
  
          /*
           * Assign an out-of-range value to represent the failure to wire this
           * entry.
           */
          entry->wired_count = -1;
  }
  
  int
  vm_map_wire(vm_map_t map, vm_offset_t start, vm_offset_t end, int flags)
  {
          int rv;
  
          vm_map_lock(map);
          rv = vm_map_wire_locked(map, start, end, flags);
          vm_map_unlock(map);
          return (rv);
  }
  
  /*
   *      vm_map_wire_locked:
   *
   *      Implements both kernel and user wiring.  Returns with the map locked,
   *      the map lock may be dropped.
   */
  int
  vm_map_wire_locked(vm_map_t map, vm_offset_t start, vm_offset_t end, int flags)
  {
          vm_map_entry_t entry, first_entry, next_entry, prev_entry;
          vm_offset_t faddr, saved_end, saved_start;
          u_long incr, npages;
          u_int bidx, last_timestamp;
          int rv;
          bool holes_ok, need_wakeup, user_wire;
          vm_prot_t prot;
  
          VM_MAP_ASSERT_LOCKED(map);
  
          if (start == end)
                  return (KERN_SUCCESS);
          prot = 0;
          if (flags & VM_MAP_WIRE_WRITE)
                  prot |= VM_PROT_WRITE;
          holes_ok = (flags & VM_MAP_WIRE_HOLESOK) != 0;
          user_wire = (flags & VM_MAP_WIRE_USER) != 0;
          VM_MAP_RANGE_CHECK(map, start, end);
          if (!vm_map_lookup_entry(map, start, &first_entry)) {
                  if (holes_ok)
                          first_entry = vm_map_entry_succ(first_entry);
                  else
                          return (KERN_INVALID_ADDRESS);
          }
          for (entry = first_entry; entry->start < end; entry = next_entry) {
                  if (entry->eflags & MAP_ENTRY_IN_TRANSITION) {
                          /*
                           * We have not yet clipped the entry.
                           */
                          next_entry = vm_map_entry_in_transition(map, start,
                              &end, holes_ok, entry);
                          if (next_entry == NULL) {
                                  if (entry == first_entry)
                                          return (KERN_INVALID_ADDRESS);
                                  rv = KERN_INVALID_ADDRESS;
                                  goto done;
                          }
                          first_entry = (entry == first_entry) ?
                              next_entry : NULL;
                          continue;
                  }
                  rv = vm_map_clip_start(map, entry, start);
                  if (rv != KERN_SUCCESS)
                          goto done;
                  rv = vm_map_clip_end(map, entry, end);
                  if (rv != KERN_SUCCESS)
                          goto done;
  
                  /*
                   * Mark the entry in case the map lock is released.  (See
                   * above.)
                   */
                  KASSERT((entry->eflags & MAP_ENTRY_IN_TRANSITION) == 0 &&
                      entry->wiring_thread == NULL,
                      ("owned map entry %p", entry));
                  entry->eflags |= MAP_ENTRY_IN_TRANSITION;
                  entry->wiring_thread = curthread;
                  if ((entry->protection & (VM_PROT_READ | VM_PROT_EXECUTE)) == 0
                      || (entry->protection & prot) != prot) {
                          entry->eflags |= MAP_ENTRY_WIRE_SKIPPED;
                          if (!holes_ok) {
                                  end = entry->end;
                                  rv = KERN_INVALID_ADDRESS;
                                  goto done;
                          }
                  } else if (entry->wired_count == 0) {
                          entry->wired_count++;
  
                          npages = atop(entry->end - entry->start);
                          if (user_wire && !vm_map_wire_user_count_add(npages)) {
                                  vm_map_wire_entry_failure(map, entry,
                                      entry->start);
                                  end = entry->end;
                                  rv = KERN_RESOURCE_SHORTAGE;
                                  goto done;
                          }
  
                          /*
                           * Release the map lock, relying on the in-transition
                           * mark.  Mark the map busy for fork.
                           */
                          saved_start = entry->start;
                          saved_end = entry->end;
                          last_timestamp = map->timestamp;
                          bidx = (entry->eflags & MAP_ENTRY_SPLIT_BOUNDARY_MASK)
                              >> MAP_ENTRY_SPLIT_BOUNDARY_SHIFT;
                          incr =  pagesizes[bidx];
                          vm_map_busy(map);
                          vm_map_unlock(map);
  
                          for (faddr = saved_start; faddr < saved_end;
                              faddr += incr) {
                                  /*
                                   * Simulate a fault to get the page and enter
                                   * it into the physical map.
                                   */
                                  rv = vm_fault(map, faddr, VM_PROT_NONE,
                                      VM_FAULT_WIRE, NULL);
                                  if (rv != KERN_SUCCESS)
                                          break;
                          }
                          vm_map_lock(map);
                          vm_map_unbusy(map);
                          if (last_timestamp + 1 != map->timestamp) {
                                  /*
                                   * Look again for the entry because the map was
                                   * modified while it was unlocked.  The entry
                                   * may have been clipped, but NOT merged or
                                   * deleted.
                                   */
                                  if (!vm_map_lookup_entry(map, saved_start,
                                      &next_entry))
                                          KASSERT(false,
                                              ("vm_map_wire: lookup failed"));
                                  first_entry = (entry == first_entry) ?
                                      next_entry : NULL;
                                  for (entry = next_entry; entry->end < saved_end;
                                      entry = vm_map_entry_succ(entry)) {
                                          /*
                                           * In case of failure, handle entries
                                           * that were not fully wired here;
                                           * fully wired entries are handled
                                           * later.
                                           */
                                          if (rv != KERN_SUCCESS &&
                                              faddr < entry->end)
                                                  vm_map_wire_entry_failure(map,
                                                      entry, faddr);
                                  }
                          }
                          if (rv != KERN_SUCCESS) {
                                  vm_map_wire_entry_failure(map, entry, faddr);
                                  if (user_wire)
                                          vm_map_wire_user_count_sub(npages);
                                  end = entry->end;
                                  goto done;
                          }
                  } else if (!user_wire ||
                             (entry->eflags & MAP_ENTRY_USER_WIRED) == 0) {
                          entry->wired_count++;
                  }
                  /*
                   * Check the map for holes in the specified region.
                   * If holes_ok was specified, skip this check.
                   */
                  next_entry = vm_map_entry_succ(entry);
                  if (!holes_ok &&
                      entry->end < end && next_entry->start > entry->end) {
                          end = entry->end;
                          rv = KERN_INVALID_ADDRESS;
                          goto done;
                  }
          }
          rv = KERN_SUCCESS;
  done:
          need_wakeup = false;
          if (first_entry == NULL &&
              !vm_map_lookup_entry(map, start, &first_entry)) {
                  KASSERT(holes_ok, ("vm_map_wire: lookup failed"));
                  prev_entry = first_entry;
                  entry = vm_map_entry_succ(first_entry);
          } else {
                  prev_entry = vm_map_entry_pred(first_entry);
                  entry = first_entry;
          }
          for (; entry->start < end;
              prev_entry = entry, entry = vm_map_entry_succ(entry)) {
                  /*
                   * If holes_ok was specified, an empty
                   * space in the unwired region could have been mapped
                   * while the map lock was dropped for faulting in the
                   * pages or draining MAP_ENTRY_IN_TRANSITION.
                   * Moreover, another thread could be simultaneously
                   * wiring this new mapping entry.  Detect these cases
                   * and skip any entries marked as in transition not by us.
                   *
                   * Another way to get an entry not marked with
                   * MAP_ENTRY_IN_TRANSITION is after failed clipping,
                   * which set rv to KERN_INVALID_ARGUMENT.
                   */
                  if ((entry->eflags & MAP_ENTRY_IN_TRANSITION) == 0 ||
                      entry->wiring_thread != curthread) {
                          KASSERT(holes_ok || rv == KERN_INVALID_ARGUMENT,
                              ("vm_map_wire: !HOLESOK and new/changed entry"));
                          continue;
                  }
  
                  if ((entry->eflags & MAP_ENTRY_WIRE_SKIPPED) != 0) {
                          /* do nothing */
                  } else if (rv == KERN_SUCCESS) {
                          if (user_wire)
                                  entry->eflags |= MAP_ENTRY_USER_WIRED;
                  } else if (entry->wired_count == -1) {
                          /*
                           * Wiring failed on this entry.  Thus, unwiring is
                           * unnecessary.
                           */
                          entry->wired_count = 0;
                  } else if (!user_wire ||
                      (entry->eflags & MAP_ENTRY_USER_WIRED) == 0) {
                          /*
                           * Undo the wiring.  Wiring succeeded on this entry
                           * but failed on a later entry.  
                           */
                          if (entry->wired_count == 1) {
                                  vm_map_entry_unwire(map, entry);
                                  if (user_wire)
                                          vm_map_wire_user_count_sub(
                                              atop(entry->end - entry->start));
                          } else
                                  entry->wired_count--;
                  }
                  KASSERT((entry->eflags & MAP_ENTRY_IN_TRANSITION) != 0,
                      ("vm_map_wire: in-transition flag missing %p", entry));
                  KASSERT(entry->wiring_thread == curthread,
                      ("vm_map_wire: alien wire %p", entry));
                  entry->eflags &= ~(MAP_ENTRY_IN_TRANSITION |
                      MAP_ENTRY_WIRE_SKIPPED);
                  entry->wiring_thread = NULL;
                  if (entry->eflags & MAP_ENTRY_NEEDS_WAKEUP) {
                          entry->eflags &= ~MAP_ENTRY_NEEDS_WAKEUP;
                          need_wakeup = true;
                  }
                  vm_map_try_merge_entries(map, prev_entry, entry);
          }
          vm_map_try_merge_entries(map, prev_entry, entry);
          if (need_wakeup)
                  vm_map_wakeup(map);
          return (rv);
  }
  
  /*
   * vm_map_sync
   *
   * Push any dirty cached pages in the address range to their pager.
   * If syncio is TRUE, dirty pages are written synchronously.
   * If invalidate is TRUE, any cached pages are freed as well.
   *
   * If the size of the region from start to end is zero, we are
   * supposed to flush all modified pages within the region containing
   * start.  Unfortunately, a region can be split or coalesced with
   * neighboring regions, making it difficult to determine what the
   * original region was.  Therefore, we approximate this requirement by
   * flushing the current region containing start.
   *
   * Returns an error if any part of the specified range is not mapped.
   */
  int
  vm_map_sync(
          vm_map_t map,
          vm_offset_t start,
          vm_offset_t end,
          boolean_t syncio,
          boolean_t invalidate)
  {
          vm_map_entry_t entry, first_entry, next_entry;
          vm_size_t size;
          vm_object_t object;
          vm_ooffset_t offset;
          unsigned int last_timestamp;
          int bdry_idx;
          boolean_t failed;
  
          vm_map_lock_read(map);
          VM_MAP_RANGE_CHECK(map, start, end);
          if (!vm_map_lookup_entry(map, start, &first_entry)) {
                  vm_map_unlock_read(map);
                  return (KERN_INVALID_ADDRESS);
          } else if (start == end) {
                  start = first_entry->start;
                  end = first_entry->end;
          }
  
          /*
           * Make a first pass to check for user-wired memory, holes,
           * and partial invalidation of largepage mappings.
           */
          for (entry = first_entry; entry->start < end; entry = next_entry) {
                  if (invalidate) {
                          if ((entry->eflags & MAP_ENTRY_USER_WIRED) != 0) {
                                  vm_map_unlock_read(map);
                                  return (KERN_INVALID_ARGUMENT);
                          }
                          bdry_idx = (entry->eflags &
                              MAP_ENTRY_SPLIT_BOUNDARY_MASK) >>
                              MAP_ENTRY_SPLIT_BOUNDARY_SHIFT;
                          if (bdry_idx != 0 &&
                              ((start & (pagesizes[bdry_idx] - 1)) != 0 ||
                              (end & (pagesizes[bdry_idx] - 1)) != 0)) {
                                  vm_map_unlock_read(map);
                                  return (KERN_INVALID_ARGUMENT);
                          }
                  }
                  next_entry = vm_map_entry_succ(entry);
                  if (end > entry->end &&
                      entry->end != next_entry->start) {
                          vm_map_unlock_read(map);
                          return (KERN_INVALID_ADDRESS);
                  }
          }
  
          if (invalidate)
                  pmap_remove(map->pmap, start, end);
          failed = FALSE;
  
          /*
           * Make a second pass, cleaning/uncaching pages from the indicated
           * objects as we go.
           */
          for (entry = first_entry; entry->start < end;) {
                  offset = entry->offset + (start - entry->start);
                  size = (end <= entry->end ? end : entry->end) - start;
                  if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0) {
                          vm_map_t smap;
                          vm_map_entry_t tentry;
                          vm_size_t tsize;
  
                          smap = entry->object.sub_map;
                          vm_map_lock_read(smap);
                          (void) vm_map_lookup_entry(smap, offset, &tentry);
                          tsize = tentry->end - offset;
                          if (tsize < size)
                                  size = tsize;
                          object = tentry->object.vm_object;
                          offset = tentry->offset + (offset - tentry->start);
                          vm_map_unlock_read(smap);
                  } else {
                          object = entry->object.vm_object;
                  }
                  vm_object_reference(object);
                  last_timestamp = map->timestamp;
                  vm_map_unlock_read(map);
                  if (!vm_object_sync(object, offset, size, syncio, invalidate))
                          failed = TRUE;
                  start += size;
                  vm_object_deallocate(object);
                  vm_map_lock_read(map);
                  if (last_timestamp == map->timestamp ||
                      !vm_map_lookup_entry(map, start, &entry))
                          entry = vm_map_entry_succ(entry);
          }
  
          vm_map_unlock_read(map);
          return (failed ? KERN_FAILURE : KERN_SUCCESS);
  }
  
  /*
   *      vm_map_entry_unwire:    [ internal use only ]
   *
   *      Make the region specified by this entry pageable.
   *
   *      The map in question should be locked.
   *      [This is the reason for this routine's existence.]
   */
  static void
  vm_map_entry_unwire(vm_map_t map, vm_map_entry_t entry)
  {
          vm_size_t size;
  
          VM_MAP_ASSERT_LOCKED(map);
          KASSERT(entry->wired_count > 0,
              ("vm_map_entry_unwire: entry %p isn't wired", entry));
  
          size = entry->end - entry->start;
          if ((entry->eflags & MAP_ENTRY_USER_WIRED) != 0)
                  vm_map_wire_user_count_sub(atop(size));
          pmap_unwire(map->pmap, entry->start, entry->end);
          vm_object_unwire(entry->object.vm_object, entry->offset, size,
              PQ_ACTIVE);
          entry->wired_count = 0;
  }
  
  static void
  vm_map_entry_deallocate(vm_map_entry_t entry, boolean_t system_map)
  {
  
          if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) == 0)
                  vm_object_deallocate(entry->object.vm_object);
          uma_zfree(system_map ? kmapentzone : mapentzone, entry);
  }
  
  /*
   *      vm_map_entry_delete:    [ internal use only ]
   *
   *      Deallocate the given entry from the target map.
   */
  static void
  vm_map_entry_delete(vm_map_t map, vm_map_entry_t entry)
  {
          vm_object_t object;
          vm_pindex_t offidxstart, offidxend, size1;
          vm_size_t size;
  
          vm_map_entry_unlink(map, entry, UNLINK_MERGE_NONE);
          object = entry->object.vm_object;
  
          if ((entry->eflags & MAP_ENTRY_GUARD) != 0) {
                  MPASS(entry->cred == NULL);
                  MPASS((entry->eflags & MAP_ENTRY_IS_SUB_MAP) == 0);
                  MPASS(object == NULL);
                  vm_map_entry_deallocate(entry, map->system_map);
                  return;
          }
  
          size = entry->end - entry->start;
          map->size -= size;
  
          if (entry->cred != NULL) {
                  swap_release_by_cred(size, entry->cred);
                  crfree(entry->cred);
          }
  
          if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0 || object == NULL) {
                  entry->object.vm_object = NULL;
          } else if ((object->flags & OBJ_ANON) != 0 ||
              object == kernel_object) {
                  KASSERT(entry->cred == NULL || object->cred == NULL ||
                      (entry->eflags & MAP_ENTRY_NEEDS_COPY),
                      ("OVERCOMMIT vm_map_entry_delete: both cred %p", entry));
                  offidxstart = OFF_TO_IDX(entry->offset);
                  offidxend = offidxstart + atop(size);
                  VM_OBJECT_WLOCK(object);
                  if (object->ref_count != 1 &&
                      ((object->flags & OBJ_ONEMAPPING) != 0 ||
                      object == kernel_object)) {
                          vm_object_collapse(object);
  
                          /*
                           * The option OBJPR_NOTMAPPED can be passed here
                           * because vm_map_delete() already performed
                           * pmap_remove() on the only mapping to this range
                           * of pages. 
                           */
                          vm_object_page_remove(object, offidxstart, offidxend,
                              OBJPR_NOTMAPPED);
                          if (offidxend >= object->size &&
                              offidxstart < object->size) {
                                  size1 = object->size;
                                  object->size = offidxstart;
                                  if (object->cred != NULL) {
                                          size1 -= object->size;
                                          KASSERT(object->charge >= ptoa(size1),
                                              ("object %p charge < 0", object));
                                          swap_release_by_cred(ptoa(size1),
                                              object->cred);
                                          object->charge -= ptoa(size1);
                                  }
                          }
                  }
                  VM_OBJECT_WUNLOCK(object);
          }
          if (map->system_map)
                  vm_map_entry_deallocate(entry, TRUE);
          else {
                  entry->defer_next = curthread->td_map_def_user;
                  curthread->td_map_def_user = entry;
          }
  }
  
  /*
   *      vm_map_delete:  [ internal use only ]
   *
   *      Deallocates the given address range from the target
   *      map.
   */
  int
  vm_map_delete(vm_map_t map, vm_offset_t start, vm_offset_t end)
  {
          vm_map_entry_t entry, next_entry, scratch_entry;
          int rv;
  
          VM_MAP_ASSERT_LOCKED(map);
  
          if (start == end)
                  return (KERN_SUCCESS);
  
          /*
           * Find the start of the region, and clip it.
           * Step through all entries in this region.
           */
          rv = vm_map_lookup_clip_start(map, start, &entry, &scratch_entry);
          if (rv != KERN_SUCCESS)
                  return (rv);
          for (; entry->start < end; entry = next_entry) {
                  /*
                   * Wait for wiring or unwiring of an entry to complete.
                   * Also wait for any system wirings to disappear on
                   * user maps.
                   */
                  if ((entry->eflags & MAP_ENTRY_IN_TRANSITION) != 0 ||
                      (vm_map_pmap(map) != kernel_pmap &&
                      vm_map_entry_system_wired_count(entry) != 0)) {
                          unsigned int last_timestamp;
                          vm_offset_t saved_start;
  
                          saved_start = entry->start;
                          entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
                          last_timestamp = map->timestamp;
                          (void) vm_map_unlock_and_wait(map, 0);
                          vm_map_lock(map);
                          if (last_timestamp + 1 != map->timestamp) {
                                  /*
                                   * Look again for the entry because the map was
                                   * modified while it was unlocked.
                                   * Specifically, the entry may have been
                                   * clipped, merged, or deleted.
                                   */
                                  rv = vm_map_lookup_clip_start(map, saved_start,
                                      &next_entry, &scratch_entry);
                                  if (rv != KERN_SUCCESS)
                                          break;
                          } else
                                  next_entry = entry;
                          continue;
                  }
  
                  /* XXXKIB or delete to the upper superpage boundary ? */
                  rv = vm_map_clip_end(map, entry, end);
                  if (rv != KERN_SUCCESS)
                          break;
                  next_entry = vm_map_entry_succ(entry);
  
                  /*
                   * Unwire before removing addresses from the pmap; otherwise,
                   * unwiring will put the entries back in the pmap.
                   */
                  if (entry->wired_count != 0)
                          vm_map_entry_unwire(map, entry);
  
                  /*
                   * Remove mappings for the pages, but only if the
                   * mappings could exist.  For instance, it does not
                   * make sense to call pmap_remove() for guard entries.
                   */
                  if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0 ||
                      entry->object.vm_object != NULL)
                          pmap_remove(map->pmap, entry->start, entry->end);
  
                  if (entry->end == map->anon_loc)
                          map->anon_loc = entry->start;
  
                  /*
                   * Delete the entry only after removing all pmap
                   * entries pointing to its pages.  (Otherwise, its
                   * page frames may be reallocated, and any modify bits
                   * will be set in the wrong object!)
                   */
                  vm_map_entry_delete(map, entry);
          }
          return (rv);
  }
  
  /*
   *      vm_map_remove:
   *
   *      Remove the given address range from the target map.
   *      This is the exported form of vm_map_delete.
   */
  int
  vm_map_remove(vm_map_t map, vm_offset_t start, vm_offset_t end)
  {
          int result;
  
          vm_map_lock(map);
          VM_MAP_RANGE_CHECK(map, start, end);
          result = vm_map_delete(map, start, end);
          vm_map_unlock(map);
          return (result);
  }
  
  /*
   *      vm_map_check_protection:
   *
   *      Assert that the target map allows the specified privilege on the
   *      entire address region given.  The entire region must be allocated.
   *
   *      WARNING!  This code does not and should not check whether the
   *      contents of the region is accessible.  For example a smaller file
   *      might be mapped into a larger address space.
   *
   *      NOTE!  This code is also called by munmap().
   *
   *      The map must be locked.  A read lock is sufficient.
   */
  boolean_t
  vm_map_check_protection(vm_map_t map, vm_offset_t start, vm_offset_t end,
                          vm_prot_t protection)
  {
          vm_map_entry_t entry;
          vm_map_entry_t tmp_entry;
  
          if (!vm_map_lookup_entry(map, start, &tmp_entry))
                  return (FALSE);
          entry = tmp_entry;
  
          while (start < end) {
                  /*
                   * No holes allowed!
                   */
                  if (start < entry->start)
                          return (FALSE);
                  /*
                   * Check protection associated with entry.
                   */
                  if ((entry->protection & protection) != protection)
                          return (FALSE);
                  /* go to next entry */
                  start = entry->end;
                  entry = vm_map_entry_succ(entry);
          }
          return (TRUE);
  }
  
  /*
   *
   *      vm_map_copy_swap_object:
   *
   *      Copies a swap-backed object from an existing map entry to a
   *      new one.  Carries forward the swap charge.  May change the
   *      src object on return.
   */
  static void
  vm_map_copy_swap_object(vm_map_entry_t src_entry, vm_map_entry_t dst_entry,
      vm_offset_t size, vm_ooffset_t *fork_charge)
  {
          vm_object_t src_object;
          struct ucred *cred;
          int charged;
  
          src_object = src_entry->object.vm_object;
          charged = ENTRY_CHARGED(src_entry);
          if ((src_object->flags & OBJ_ANON) != 0) {
                  VM_OBJECT_WLOCK(src_object);
                  vm_object_collapse(src_object);
                  if ((src_object->flags & OBJ_ONEMAPPING) != 0) {
                          vm_object_split(src_entry);
                          src_object = src_entry->object.vm_object;
                  }
                  vm_object_reference_locked(src_object);
                  vm_object_clear_flag(src_object, OBJ_ONEMAPPING);
                  VM_OBJECT_WUNLOCK(src_object);
          } else
                  vm_object_reference(src_object);
          if (src_entry->cred != NULL &&
              !(src_entry->eflags & MAP_ENTRY_NEEDS_COPY)) {
                  KASSERT(src_object->cred == NULL,
                      ("OVERCOMMIT: vm_map_copy_anon_entry: cred %p",
                       src_object));
                  src_object->cred = src_entry->cred;
                  src_object->charge = size;
          }
          dst_entry->object.vm_object = src_object;
          if (charged) {
                  cred = curthread->td_ucred;
                  crhold(cred);
                  dst_entry->cred = cred;
                  *fork_charge += size;
                  if (!(src_entry->eflags & MAP_ENTRY_NEEDS_COPY)) {
                          crhold(cred);
                          src_entry->cred = cred;
                          *fork_charge += size;
                  }
          }
  }
  
  /*
   *      vm_map_copy_entry:
   *
   *      Copies the contents of the source entry to the destination
   *      entry.  The entries *must* be aligned properly.
   */
  static void
  vm_map_copy_entry(
          vm_map_t src_map,
          vm_map_t dst_map,
          vm_map_entry_t src_entry,
          vm_map_entry_t dst_entry,
          vm_ooffset_t *fork_charge)
  {
          vm_object_t src_object;
          vm_map_entry_t fake_entry;
          vm_offset_t size;
  
          VM_MAP_ASSERT_LOCKED(dst_map);
  
          if ((dst_entry->eflags|src_entry->eflags) & MAP_ENTRY_IS_SUB_MAP)
                  return;
  
          if (src_entry->wired_count == 0 ||
              (src_entry->protection & VM_PROT_WRITE) == 0) {
                  /*
                   * If the source entry is marked needs_copy, it is already
                   * write-protected.
                   */
                  if ((src_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0 &&
                      (src_entry->protection & VM_PROT_WRITE) != 0) {
                          pmap_protect(src_map->pmap,
                              src_entry->start,
                              src_entry->end,
                              src_entry->protection & ~VM_PROT_WRITE);
                  }
  
                  /*
                   * Make a copy of the object.
                   */
                  size = src_entry->end - src_entry->start;
                  if ((src_object = src_entry->object.vm_object) != NULL) {
                          if ((src_object->flags & OBJ_SWAP) != 0) {
                                  vm_map_copy_swap_object(src_entry, dst_entry,
                                      size, fork_charge);
                                  /* May have split/collapsed, reload obj. */
                                  src_object = src_entry->object.vm_object;
                          } else {
                                  vm_object_reference(src_object);
                                  dst_entry->object.vm_object = src_object;
                          }
                          src_entry->eflags |= MAP_ENTRY_COW |
                              MAP_ENTRY_NEEDS_COPY;
                          dst_entry->eflags |= MAP_ENTRY_COW |
                              MAP_ENTRY_NEEDS_COPY;
                          dst_entry->offset = src_entry->offset;
                          if (src_entry->eflags & MAP_ENTRY_WRITECNT) {
                                  /*
                                   * MAP_ENTRY_WRITECNT cannot
                                   * indicate write reference from
                                   * src_entry, since the entry is
                                   * marked as needs copy.  Allocate a
                                   * fake entry that is used to
                                   * decrement object->un_pager writecount
                                   * at the appropriate time.  Attach
                                   * fake_entry to the deferred list.
                                   */
                                  fake_entry = vm_map_entry_create(dst_map);
                                  fake_entry->eflags = MAP_ENTRY_WRITECNT;
                                  src_entry->eflags &= ~MAP_ENTRY_WRITECNT;
                                  vm_object_reference(src_object);
                                  fake_entry->object.vm_object = src_object;
                                  fake_entry->start = src_entry->start;
                                  fake_entry->end = src_entry->end;
                                  fake_entry->defer_next =
                                      curthread->td_map_def_user;
                                  curthread->td_map_def_user = fake_entry;
                          }
  
                          pmap_copy(dst_map->pmap, src_map->pmap,
                              dst_entry->start, dst_entry->end - dst_entry->start,
                              src_entry->start);
                  } else {
                          dst_entry->object.vm_object = NULL;
                          dst_entry->offset = 0;
                          if (src_entry->cred != NULL) {
                                  dst_entry->cred = curthread->td_ucred;
                                  crhold(dst_entry->cred);
                                  *fork_charge += size;
                          }
                  }
          } else {
                  /*
                   * We don't want to make writeable wired pages copy-on-write.
                   * Immediately copy these pages into the new map by simulating
                   * page faults.  The new pages are pageable.
                   */
                  vm_fault_copy_entry(dst_map, src_map, dst_entry, src_entry,
                      fork_charge);
          }
  }
  
  /*
   * vmspace_map_entry_forked:
   * Update the newly-forked vmspace each time a map entry is inherited
   * or copied.  The values for vm_dsize and vm_tsize are approximate
   * (and mostly-obsolete ideas in the face of mmap(2) et al.)
   */
  static void
  vmspace_map_entry_forked(const struct vmspace *vm1, struct vmspace *vm2,
      vm_map_entry_t entry)
  {
          vm_size_t entrysize;
          vm_offset_t newend;
  
          if ((entry->eflags & MAP_ENTRY_GUARD) != 0)
                  return;
          entrysize = entry->end - entry->start;
          vm2->vm_map.size += entrysize;
          if (entry->eflags & (MAP_ENTRY_GROWS_DOWN | MAP_ENTRY_GROWS_UP)) {
                  vm2->vm_ssize += btoc(entrysize);
          } else if (entry->start >= (vm_offset_t)vm1->vm_daddr &&
              entry->start < (vm_offset_t)vm1->vm_daddr + ctob(vm1->vm_dsize)) {
                  newend = MIN(entry->end,
                      (vm_offset_t)vm1->vm_daddr + ctob(vm1->vm_dsize));
                  vm2->vm_dsize += btoc(newend - entry->start);
          } else if (entry->start >= (vm_offset_t)vm1->vm_taddr &&
              entry->start < (vm_offset_t)vm1->vm_taddr + ctob(vm1->vm_tsize)) {
                  newend = MIN(entry->end,
                      (vm_offset_t)vm1->vm_taddr + ctob(vm1->vm_tsize));
                  vm2->vm_tsize += btoc(newend - entry->start);
          }
  }
  
  /*
   * vmspace_fork:
   * Create a new process vmspace structure and vm_map
   * based on those of an existing process.  The new map
   * is based on the old map, according to the inheritance
   * values on the regions in that map.
   *
   * XXX It might be worth coalescing the entries added to the new vmspace.
   *
   * The source map must not be locked.
   */
  struct vmspace *
  vmspace_fork(struct vmspace *vm1, vm_ooffset_t *fork_charge)
  {
          struct vmspace *vm2;
          vm_map_t new_map, old_map;
          vm_map_entry_t new_entry, old_entry;
          vm_object_t object;
          int error, locked __diagused;
          vm_inherit_t inh;
  
          old_map = &vm1->vm_map;
          /* Copy immutable fields of vm1 to vm2. */
          vm2 = vmspace_alloc(vm_map_min(old_map), vm_map_max(old_map),
              pmap_pinit);
          if (vm2 == NULL)
                  return (NULL);
  
          vm2->vm_taddr = vm1->vm_taddr;
          vm2->vm_daddr = vm1->vm_daddr;
          vm2->vm_maxsaddr = vm1->vm_maxsaddr;
          vm2->vm_stacktop = vm1->vm_stacktop;
          vm2->vm_shp_base = vm1->vm_shp_base;
          vm_map_lock(old_map);
          if (old_map->busy)
                  vm_map_wait_busy(old_map);
          new_map = &vm2->vm_map;
          locked = vm_map_trylock(new_map); /* trylock to silence WITNESS */
          KASSERT(locked, ("vmspace_fork: lock failed"));
  
          error = pmap_vmspace_copy(new_map->pmap, old_map->pmap);
          if (error != 0) {
                  sx_xunlock(&old_map->lock);
                  sx_xunlock(&new_map->lock);
                  vm_map_process_deferred();
                  vmspace_free(vm2);
                  return (NULL);
          }
  
          new_map->anon_loc = old_map->anon_loc;
          new_map->flags |= old_map->flags & (MAP_ASLR | MAP_ASLR_IGNSTART |
              MAP_ASLR_STACK | MAP_WXORX);
  
          VM_MAP_ENTRY_FOREACH(old_entry, old_map) {
                  if ((old_entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0)
                          panic("vm_map_fork: encountered a submap");
  
                  inh = old_entry->inheritance;
                  if ((old_entry->eflags & MAP_ENTRY_GUARD) != 0 &&
                      inh != VM_INHERIT_NONE)
                          inh = VM_INHERIT_COPY;
  
                  switch (inh) {
                  case VM_INHERIT_NONE:
                          break;
  
                  case VM_INHERIT_SHARE:
                          /*
                           * Clone the entry, creating the shared object if
                           * necessary.
                           */
                          object = old_entry->object.vm_object;
                          if (object == NULL) {
                                  vm_map_entry_back(old_entry);
                                  object = old_entry->object.vm_object;
                          }
  
                          /*
                           * Add the reference before calling vm_object_shadow
                           * to insure that a shadow object is created.
                           */
                          vm_object_reference(object);
                          if (old_entry->eflags & MAP_ENTRY_NEEDS_COPY) {
                                  vm_object_shadow(&old_entry->object.vm_object,
                                      &old_entry->offset,
                                      old_entry->end - old_entry->start,
                                      old_entry->cred,
                                      /* Transfer the second reference too. */
                                      true);
                                  old_entry->eflags &= ~MAP_ENTRY_NEEDS_COPY;
                                  old_entry->cred = NULL;
  
                                  /*
                                   * As in vm_map_merged_neighbor_dispose(),
                                   * the vnode lock will not be acquired in
                                   * this call to vm_object_deallocate().
                                   */
                                  vm_object_deallocate(object);
                                  object = old_entry->object.vm_object;
                          } else {
                                  VM_OBJECT_WLOCK(object);
                                  vm_object_clear_flag(object, OBJ_ONEMAPPING);
                                  if (old_entry->cred != NULL) {
                                          KASSERT(object->cred == NULL,
                                              ("vmspace_fork both cred"));
                                          object->cred = old_entry->cred;
                                          object->charge = old_entry->end -
                                              old_entry->start;
                                          old_entry->cred = NULL;
                                  }
  
                                  /*
                                   * Assert the correct state of the vnode
                                   * v_writecount while the object is locked, to
                                   * not relock it later for the assertion
                                   * correctness.
                                   */
                                  if (old_entry->eflags & MAP_ENTRY_WRITECNT &&
                                      object->type == OBJT_VNODE) {
                                          KASSERT(((struct vnode *)object->
                                              handle)->v_writecount > 0,
                                              ("vmspace_fork: v_writecount %p",
                                              object));
                                          KASSERT(object->un_pager.vnp.
                                              writemappings > 0,
                                              ("vmspace_fork: vnp.writecount %p",
                                              object));
                                  }
                                  VM_OBJECT_WUNLOCK(object);
                          }
  
                          /*
                           * Clone the entry, referencing the shared object.
                           */
                          new_entry = vm_map_entry_create(new_map);
                          *new_entry = *old_entry;
                          new_entry->eflags &= ~(MAP_ENTRY_USER_WIRED |
                              MAP_ENTRY_IN_TRANSITION);
                          new_entry->wiring_thread = NULL;
                          new_entry->wired_count = 0;
                          if (new_entry->eflags & MAP_ENTRY_WRITECNT) {
                                  vm_pager_update_writecount(object,
                                      new_entry->start, new_entry->end);
                          }
                          vm_map_entry_set_vnode_text(new_entry, true);
  
                          /*
                           * Insert the entry into the new map -- we know we're
                           * inserting at the end of the new map.
                           */
                          vm_map_entry_link(new_map, new_entry);
                          vmspace_map_entry_forked(vm1, vm2, new_entry);
  
                          /*
                           * Update the physical map
                           */
                          pmap_copy(new_map->pmap, old_map->pmap,
                              new_entry->start,
                              (old_entry->end - old_entry->start),
                              old_entry->start);
                          break;
  
                  case VM_INHERIT_COPY:
                          /*
                           * Clone the entry and link into the map.
                           */
                          new_entry = vm_map_entry_create(new_map);
                          *new_entry = *old_entry;
                          /*
                           * Copied entry is COW over the old object.
                           */
                          new_entry->eflags &= ~(MAP_ENTRY_USER_WIRED |
                              MAP_ENTRY_IN_TRANSITION | MAP_ENTRY_WRITECNT);
                          new_entry->wiring_thread = NULL;
                          new_entry->wired_count = 0;
                          new_entry->object.vm_object = NULL;
                          new_entry->cred = NULL;
                          vm_map_entry_link(new_map, new_entry);
                          vmspace_map_entry_forked(vm1, vm2, new_entry);
                          vm_map_copy_entry(old_map, new_map, old_entry,
                              new_entry, fork_charge);
                          vm_map_entry_set_vnode_text(new_entry, true);
                          break;
  
                  case VM_INHERIT_ZERO:
                          /*
                           * Create a new anonymous mapping entry modelled from
                           * the old one.
                           */
                          new_entry = vm_map_entry_create(new_map);
                          memset(new_entry, 0, sizeof(*new_entry));
  
                          new_entry->start = old_entry->start;
                          new_entry->end = old_entry->end;
                          new_entry->eflags = old_entry->eflags &
                              ~(MAP_ENTRY_USER_WIRED | MAP_ENTRY_IN_TRANSITION |
                              MAP_ENTRY_WRITECNT | MAP_ENTRY_VN_EXEC |
                              MAP_ENTRY_SPLIT_BOUNDARY_MASK);
                          new_entry->protection = old_entry->protection;
                          new_entry->max_protection = old_entry->max_protection;
                          new_entry->inheritance = VM_INHERIT_ZERO;
  
                          vm_map_entry_link(new_map, new_entry);
                          vmspace_map_entry_forked(vm1, vm2, new_entry);
  
                          new_entry->cred = curthread->td_ucred;
                          crhold(new_entry->cred);
                          *fork_charge += (new_entry->end - new_entry->start);
  
                          break;
                  }
          }
          /*
           * Use inlined vm_map_unlock() to postpone handling the deferred
           * map entries, which cannot be done until both old_map and
           * new_map locks are released.
           */
          sx_xunlock(&old_map->lock);
          sx_xunlock(&new_map->lock);
          vm_map_process_deferred();
  
          return (vm2);
  }
  
  /*
   * Create a process's stack for exec_new_vmspace().  This function is never
   * asked to wire the newly created stack.
   */
  int
  vm_map_stack(vm_map_t map, vm_offset_t addrbos, vm_size_t max_ssize,
      vm_prot_t prot, vm_prot_t max, int cow)
  {
          vm_size_t growsize, init_ssize;
          rlim_t vmemlim;
          int rv;
  
          MPASS((map->flags & MAP_WIREFUTURE) == 0);
          growsize = sgrowsiz;
          init_ssize = (max_ssize < growsize) ? max_ssize : growsize;
          vm_map_lock(map);
          vmemlim = lim_cur(curthread, RLIMIT_VMEM);
          /* If we would blow our VMEM resource limit, no go */
          if (map->size + init_ssize > vmemlim) {
                  rv = KERN_NO_SPACE;
                  goto out;
          }
          rv = vm_map_stack_locked(map, addrbos, max_ssize, growsize, prot,
              max, cow);
  out:
          vm_map_unlock(map);
          return (rv);
  }
  
  static int stack_guard_page = 1;
  SYSCTL_INT(_security_bsd, OID_AUTO, stack_guard_page, CTLFLAG_RWTUN,
      &stack_guard_page, 0,
      "Specifies the number of guard pages for a stack that grows");
  
  static int
  vm_map_stack_locked(vm_map_t map, vm_offset_t addrbos, vm_size_t max_ssize,
      vm_size_t growsize, vm_prot_t prot, vm_prot_t max, int cow)
  {
          vm_map_entry_t new_entry, prev_entry;
          vm_offset_t bot, gap_bot, gap_top, top;
          vm_size_t init_ssize, sgp;
          int orient, rv;
  
          /*
           * The stack orientation is piggybacked with the cow argument.
           * Extract it into orient and mask the cow argument so that we
           * don't pass it around further.
           */
          orient = cow & (MAP_STACK_GROWS_DOWN | MAP_STACK_GROWS_UP);
          KASSERT(orient != 0, ("No stack grow direction"));
          KASSERT(orient != (MAP_STACK_GROWS_DOWN | MAP_STACK_GROWS_UP),
              ("bi-dir stack"));
  
          if (max_ssize == 0 ||
              !vm_map_range_valid(map, addrbos, addrbos + max_ssize))
                  return (KERN_INVALID_ADDRESS);
          sgp = ((curproc->p_flag2 & P2_STKGAP_DISABLE) != 0 ||
              (curproc->p_fctl0 & NT_FREEBSD_FCTL_STKGAP_DISABLE) != 0) ? 0 :
              (vm_size_t)stack_guard_page * PAGE_SIZE;
          if (sgp >= max_ssize)
                  return (KERN_INVALID_ARGUMENT);
  
          init_ssize = growsize;
          if (max_ssize < init_ssize + sgp)
                  init_ssize = max_ssize - sgp;
  
          /* If addr is already mapped, no go */
          if (vm_map_lookup_entry(map, addrbos, &prev_entry))
                  return (KERN_NO_SPACE);
  
          /*
           * If we can't accommodate max_ssize in the current mapping, no go.
           */
          if (vm_map_entry_succ(prev_entry)->start < addrbos + max_ssize)
                  return (KERN_NO_SPACE);
  
          /*
           * We initially map a stack of only init_ssize.  We will grow as
           * needed later.  Depending on the orientation of the stack (i.e.
           * the grow direction) we either map at the top of the range, the
           * bottom of the range or in the middle.
           *
           * Note: we would normally expect prot and max to be VM_PROT_ALL,
           * and cow to be 0.  Possibly we should eliminate these as input
           * parameters, and just pass these values here in the insert call.
           */
          if (orient == MAP_STACK_GROWS_DOWN) {
                  bot = addrbos + max_ssize - init_ssize;
                  top = bot + init_ssize;
                  gap_bot = addrbos;
                  gap_top = bot;
          } else /* if (orient == MAP_STACK_GROWS_UP) */ {
                  bot = addrbos;
                  top = bot + init_ssize;
                  gap_bot = top;
                  gap_top = addrbos + max_ssize;
          }
          rv = vm_map_insert(map, NULL, 0, bot, top, prot, max, cow);
          if (rv != KERN_SUCCESS)
                  return (rv);
          new_entry = vm_map_entry_succ(prev_entry);
          KASSERT(new_entry->end == top || new_entry->start == bot,
              ("Bad entry start/end for new stack entry"));
          KASSERT((orient & MAP_STACK_GROWS_DOWN) == 0 ||
              (new_entry->eflags & MAP_ENTRY_GROWS_DOWN) != 0,
              ("new entry lacks MAP_ENTRY_GROWS_DOWN"));
          KASSERT((orient & MAP_STACK_GROWS_UP) == 0 ||
              (new_entry->eflags & MAP_ENTRY_GROWS_UP) != 0,
              ("new entry lacks MAP_ENTRY_GROWS_UP"));
          if (gap_bot == gap_top)
                  return (KERN_SUCCESS);
          rv = vm_map_insert(map, NULL, 0, gap_bot, gap_top, VM_PROT_NONE,
              VM_PROT_NONE, MAP_CREATE_GUARD | (orient == MAP_STACK_GROWS_DOWN ?
              MAP_CREATE_STACK_GAP_DN : MAP_CREATE_STACK_GAP_UP));
          if (rv == KERN_SUCCESS) {
                  /*
                   * Gap can never successfully handle a fault, so
                   * read-ahead logic is never used for it.  Re-use
                   * next_read of the gap entry to store
                   * stack_guard_page for vm_map_growstack().
                   */
                  if (orient == MAP_STACK_GROWS_DOWN)
                          vm_map_entry_pred(new_entry)->next_read = sgp;
                  else
                          vm_map_entry_succ(new_entry)->next_read = sgp;
          } else {
                  (void)vm_map_delete(map, bot, top);
          }
          return (rv);
  }
  
  /*
   * Attempts to grow a vm stack entry.  Returns KERN_SUCCESS if we
   * successfully grow the stack.
   */
  static int
  vm_map_growstack(vm_map_t map, vm_offset_t addr, vm_map_entry_t gap_entry)
  {
          vm_map_entry_t stack_entry;
          struct proc *p;
          struct vmspace *vm;
          struct ucred *cred;
          vm_offset_t gap_end, gap_start, grow_start;
          vm_size_t grow_amount, guard, max_grow;
          rlim_t lmemlim, stacklim, vmemlim;
          int rv, rv1 __diagused;
          bool gap_deleted, grow_down, is_procstack;
  #ifdef notyet
          uint64_t limit;
  #endif
  #ifdef RACCT
          int error __diagused;
  #endif
  
          p = curproc;
          vm = p->p_vmspace;
  
          /*
           * Disallow stack growth when the access is performed by a
           * debugger or AIO daemon.  The reason is that the wrong
           * resource limits are applied.
           */
          if (p != initproc && (map != &p->p_vmspace->vm_map ||
              p->p_textvp == NULL))
                  return (KERN_FAILURE);
  
          MPASS(!map->system_map);
  
          lmemlim = lim_cur(curthread, RLIMIT_MEMLOCK);
          stacklim = lim_cur(curthread, RLIMIT_STACK);
          vmemlim = lim_cur(curthread, RLIMIT_VMEM);
  retry:
          /* If addr is not in a hole for a stack grow area, no need to grow. */
          if (gap_entry == NULL && !vm_map_lookup_entry(map, addr, &gap_entry))
                  return (KERN_FAILURE);
          if ((gap_entry->eflags & MAP_ENTRY_GUARD) == 0)
                  return (KERN_SUCCESS);
          if ((gap_entry->eflags & MAP_ENTRY_STACK_GAP_DN) != 0) {
                  stack_entry = vm_map_entry_succ(gap_entry);
                  if ((stack_entry->eflags & MAP_ENTRY_GROWS_DOWN) == 0 ||
                      stack_entry->start != gap_entry->end)
                          return (KERN_FAILURE);
                  grow_amount = round_page(stack_entry->start - addr);
                  grow_down = true;
          } else if ((gap_entry->eflags & MAP_ENTRY_STACK_GAP_UP) != 0) {
                  stack_entry = vm_map_entry_pred(gap_entry);
                  if ((stack_entry->eflags & MAP_ENTRY_GROWS_UP) == 0 ||
                      stack_entry->end != gap_entry->start)
                          return (KERN_FAILURE);
                  grow_amount = round_page(addr + 1 - stack_entry->end);
                  grow_down = false;
          } else {
                  return (KERN_FAILURE);
          }
          guard = ((curproc->p_flag2 & P2_STKGAP_DISABLE) != 0 ||
              (curproc->p_fctl0 & NT_FREEBSD_FCTL_STKGAP_DISABLE) != 0) ? 0 :
              gap_entry->next_read;
          max_grow = gap_entry->end - gap_entry->start;
          if (guard > max_grow)
                  return (KERN_NO_SPACE);
          max_grow -= guard;
          if (grow_amount > max_grow)
                  return (KERN_NO_SPACE);
  
          /*
           * If this is the main process stack, see if we're over the stack
           * limit.
           */
          is_procstack = addr >= (vm_offset_t)vm->vm_maxsaddr &&
              addr < (vm_offset_t)vm->vm_stacktop;
          if (is_procstack && (ctob(vm->vm_ssize) + grow_amount > stacklim))
                  return (KERN_NO_SPACE);
  
  #ifdef RACCT
          if (racct_enable) {
                  PROC_LOCK(p);
                  if (is_procstack && racct_set(p, RACCT_STACK,
                      ctob(vm->vm_ssize) + grow_amount)) {
                          PROC_UNLOCK(p);
                          return (KERN_NO_SPACE);
                  }
                  PROC_UNLOCK(p);
          }
  #endif
  
          grow_amount = roundup(grow_amount, sgrowsiz);
          if (grow_amount > max_grow)
                  grow_amount = max_grow;
          if (is_procstack && (ctob(vm->vm_ssize) + grow_amount > stacklim)) {
                  grow_amount = trunc_page((vm_size_t)stacklim) -
                      ctob(vm->vm_ssize);
          }
  
  #ifdef notyet
          PROC_LOCK(p);
          limit = racct_get_available(p, RACCT_STACK);
          PROC_UNLOCK(p);
          if (is_procstack && (ctob(vm->vm_ssize) + grow_amount > limit))
                  grow_amount = limit - ctob(vm->vm_ssize);
  #endif
  
          if (!old_mlock && (map->flags & MAP_WIREFUTURE) != 0) {
                  if (ptoa(pmap_wired_count(map->pmap)) + grow_amount > lmemlim) {
                          rv = KERN_NO_SPACE;
                          goto out;
                  }
  #ifdef RACCT
                  if (racct_enable) {
                          PROC_LOCK(p);
                          if (racct_set(p, RACCT_MEMLOCK,
                              ptoa(pmap_wired_count(map->pmap)) + grow_amount)) {
                                  PROC_UNLOCK(p);
                                  rv = KERN_NO_SPACE;
                                  goto out;
                          }
                          PROC_UNLOCK(p);
                  }
  #endif
          }
  
          /* If we would blow our VMEM resource limit, no go */
          if (map->size + grow_amount > vmemlim) {
                  rv = KERN_NO_SPACE;
                  goto out;
          }
  #ifdef RACCT
          if (racct_enable) {
                  PROC_LOCK(p);
                  if (racct_set(p, RACCT_VMEM, map->size + grow_amount)) {
                          PROC_UNLOCK(p);
                          rv = KERN_NO_SPACE;
                          goto out;
                  }
                  PROC_UNLOCK(p);
          }
  #endif
  
          if (vm_map_lock_upgrade(map)) {
                  gap_entry = NULL;
                  vm_map_lock_read(map);
                  goto retry;
          }
  
          if (grow_down) {
                  grow_start = gap_entry->end - grow_amount;
                  if (gap_entry->start + grow_amount == gap_entry->end) {
                          gap_start = gap_entry->start;
                          gap_end = gap_entry->end;
                          vm_map_entry_delete(map, gap_entry);
                          gap_deleted = true;
                  } else {
                          MPASS(gap_entry->start < gap_entry->end - grow_amount);
                          vm_map_entry_resize(map, gap_entry, -grow_amount);
                          gap_deleted = false;
                  }
                  rv = vm_map_insert(map, NULL, 0, grow_start,
                      grow_start + grow_amount,
                      stack_entry->protection, stack_entry->max_protection,
                      MAP_STACK_GROWS_DOWN);
                  if (rv != KERN_SUCCESS) {
                          if (gap_deleted) {
                                  rv1 = vm_map_insert(map, NULL, 0, gap_start,
                                      gap_end, VM_PROT_NONE, VM_PROT_NONE,
                                      MAP_CREATE_GUARD | MAP_CREATE_STACK_GAP_DN);
                                  MPASS(rv1 == KERN_SUCCESS);
                          } else
                                  vm_map_entry_resize(map, gap_entry,
                                      grow_amount);
                  }
          } else {
                  grow_start = stack_entry->end;
                  cred = stack_entry->cred;
                  if (cred == NULL && stack_entry->object.vm_object != NULL)
                          cred = stack_entry->object.vm_object->cred;
                  if (cred != NULL && !swap_reserve_by_cred(grow_amount, cred))
                          rv = KERN_NO_SPACE;
                  /* Grow the underlying object if applicable. */
                  else if (stack_entry->object.vm_object == NULL ||
                      vm_object_coalesce(stack_entry->object.vm_object,
                      stack_entry->offset,
                      (vm_size_t)(stack_entry->end - stack_entry->start),
                      grow_amount, cred != NULL)) {
                          if (gap_entry->start + grow_amount == gap_entry->end) {
                                  vm_map_entry_delete(map, gap_entry);
                                  vm_map_entry_resize(map, stack_entry,
                                      grow_amount);
                          } else {
                                  gap_entry->start += grow_amount;
                                  stack_entry->end += grow_amount;
                          }
                          map->size += grow_amount;
                          rv = KERN_SUCCESS;
                  } else
                          rv = KERN_FAILURE;
          }
          if (rv == KERN_SUCCESS && is_procstack)
                  vm->vm_ssize += btoc(grow_amount);
  
          /*
           * Heed the MAP_WIREFUTURE flag if it was set for this process.
           */
          if (rv == KERN_SUCCESS && (map->flags & MAP_WIREFUTURE) != 0) {
                  rv = vm_map_wire_locked(map, grow_start,
                      grow_start + grow_amount,
                      VM_MAP_WIRE_USER | VM_MAP_WIRE_NOHOLES);
          }
          vm_map_lock_downgrade(map);
  
  out:
  #ifdef RACCT
          if (racct_enable && rv != KERN_SUCCESS) {
                  PROC_LOCK(p);
                  error = racct_set(p, RACCT_VMEM, map->size);
                  KASSERT(error == 0, ("decreasing RACCT_VMEM failed"));
                  if (!old_mlock) {
                          error = racct_set(p, RACCT_MEMLOCK,
                              ptoa(pmap_wired_count(map->pmap)));
                          KASSERT(error == 0, ("decreasing RACCT_MEMLOCK failed"));
                  }
                  error = racct_set(p, RACCT_STACK, ctob(vm->vm_ssize));
                  KASSERT(error == 0, ("decreasing RACCT_STACK failed"));
                  PROC_UNLOCK(p);
          }
  #endif
  
          return (rv);
  }
  
  /*
   * Unshare the specified VM space for exec.  If other processes are
   * mapped to it, then create a new one.  The new vmspace is null.
   */
  int
  vmspace_exec(struct proc *p, vm_offset_t minuser, vm_offset_t maxuser)
  {
          struct vmspace *oldvmspace = p->p_vmspace;
          struct vmspace *newvmspace;
  
          KASSERT((curthread->td_pflags & TDP_EXECVMSPC) == 0,
              ("vmspace_exec recursed"));
          newvmspace = vmspace_alloc(minuser, maxuser, pmap_pinit);
          if (newvmspace == NULL)
                  return (ENOMEM);
          newvmspace->vm_swrss = oldvmspace->vm_swrss;
          /*
           * This code is written like this for prototype purposes.  The
           * goal is to avoid running down the vmspace here, but let the
           * other process's that are still using the vmspace to finally
           * run it down.  Even though there is little or no chance of blocking
           * here, it is a good idea to keep this form for future mods.
           */
          PROC_VMSPACE_LOCK(p);
          p->p_vmspace = newvmspace;
          PROC_VMSPACE_UNLOCK(p);
          if (p == curthread->td_proc)
                  pmap_activate(curthread);
          curthread->td_pflags |= TDP_EXECVMSPC;
          return (0);
  }
  
  /*
   * Unshare the specified VM space for forcing COW.  This
   * is called by rfork, for the (RFMEM|RFPROC) == 0 case.
   */
  int
  vmspace_unshare(struct proc *p)
  {
          struct vmspace *oldvmspace = p->p_vmspace;
          struct vmspace *newvmspace;
          vm_ooffset_t fork_charge;
  
          /*
           * The caller is responsible for ensuring that the reference count
           * cannot concurrently transition 1 -> 2.
           */
          if (refcount_load(&oldvmspace->vm_refcnt) == 1)
                  return (0);
          fork_charge = 0;
          newvmspace = vmspace_fork(oldvmspace, &fork_charge);
          if (newvmspace == NULL)
                  return (ENOMEM);
          if (!swap_reserve_by_cred(fork_charge, p->p_ucred)) {
                  vmspace_free(newvmspace);
                  return (ENOMEM);
          }
          PROC_VMSPACE_LOCK(p);
          p->p_vmspace = newvmspace;
          PROC_VMSPACE_UNLOCK(p);
          if (p == curthread->td_proc)
                  pmap_activate(curthread);
          vmspace_free(oldvmspace);
          return (0);
  }
  
  /*
   *      vm_map_lookup:
   *
   *      Finds the VM object, offset, and
   *      protection for a given virtual address in the
   *      specified map, assuming a page fault of the
   *      type specified.
   *
   *      Leaves the map in question locked for read; return
   *      values are guaranteed until a vm_map_lookup_done
   *      call is performed.  Note that the map argument
   *      is in/out; the returned map must be used in
   *      the call to vm_map_lookup_done.
   *
   *      A handle (out_entry) is returned for use in
   *      vm_map_lookup_done, to make that fast.
   *
   *      If a lookup is requested with "write protection"
   *      specified, the map may be changed to perform virtual
   *      copying operations, although the data referenced will
   *      remain the same.
   */
  int
  vm_map_lookup(vm_map_t *var_map,                /* IN/OUT */
                vm_offset_t vaddr,
                vm_prot_t fault_typea,
                vm_map_entry_t *out_entry,        /* OUT */
                vm_object_t *object,              /* OUT */
                vm_pindex_t *pindex,              /* OUT */
                vm_prot_t *out_prot,              /* OUT */
                boolean_t *wired)                 /* OUT */
  {
          vm_map_entry_t entry;
          vm_map_t map = *var_map;
          vm_prot_t prot;
          vm_prot_t fault_type;
          vm_object_t eobject;
          vm_size_t size;
          struct ucred *cred;
  
  RetryLookup:
  
          vm_map_lock_read(map);
  
  RetryLookupLocked:
          /*
           * Lookup the faulting address.
           */
          if (!vm_map_lookup_entry(map, vaddr, out_entry)) {
                  vm_map_unlock_read(map);
                  return (KERN_INVALID_ADDRESS);
          }
  
          entry = *out_entry;
  
          /*
           * Handle submaps.
           */
          if (entry->eflags & MAP_ENTRY_IS_SUB_MAP) {
                  vm_map_t old_map = map;
  
                  *var_map = map = entry->object.sub_map;
                  vm_map_unlock_read(old_map);
                  goto RetryLookup;
          }
  
          /*
           * Check whether this task is allowed to have this page.
           */
          prot = entry->protection;
          if ((fault_typea & VM_PROT_FAULT_LOOKUP) != 0) {
                  fault_typea &= ~VM_PROT_FAULT_LOOKUP;
                  if (prot == VM_PROT_NONE && map != kernel_map &&
                      (entry->eflags & MAP_ENTRY_GUARD) != 0 &&
                      (entry->eflags & (MAP_ENTRY_STACK_GAP_DN |
                      MAP_ENTRY_STACK_GAP_UP)) != 0 &&
                      vm_map_growstack(map, vaddr, entry) == KERN_SUCCESS)
                          goto RetryLookupLocked;
          }
          fault_type = fault_typea & VM_PROT_ALL;
          if ((fault_type & prot) != fault_type || prot == VM_PROT_NONE) {
                  vm_map_unlock_read(map);
                  return (KERN_PROTECTION_FAILURE);
          }
          KASSERT((prot & VM_PROT_WRITE) == 0 || (entry->eflags &
              (MAP_ENTRY_USER_WIRED | MAP_ENTRY_NEEDS_COPY)) !=
              (MAP_ENTRY_USER_WIRED | MAP_ENTRY_NEEDS_COPY),
              ("entry %p flags %x", entry, entry->eflags));
          if ((fault_typea & VM_PROT_COPY) != 0 &&
              (entry->max_protection & VM_PROT_WRITE) == 0 &&
              (entry->eflags & MAP_ENTRY_COW) == 0) {
                  vm_map_unlock_read(map);
                  return (KERN_PROTECTION_FAILURE);
          }
  
          /*
           * If this page is not pageable, we have to get it for all possible
           * accesses.
           */
          *wired = (entry->wired_count != 0);
          if (*wired)
                  fault_type = entry->protection;
          size = entry->end - entry->start;
  
          /*
           * If the entry was copy-on-write, we either ...
           */
          if (entry->eflags & MAP_ENTRY_NEEDS_COPY) {
                  /*
                   * If we want to write the page, we may as well handle that
                   * now since we've got the map locked.
                   *
                   * If we don't need to write the page, we just demote the
                   * permissions allowed.
                   */
                  if ((fault_type & VM_PROT_WRITE) != 0 ||
                      (fault_typea & VM_PROT_COPY) != 0) {
                          /*
                           * Make a new object, and place it in the object
                           * chain.  Note that no new references have appeared
                           * -- one just moved from the map to the new
                           * object.
                           */
                          if (vm_map_lock_upgrade(map))
                                  goto RetryLookup;
  
                          if (entry->cred == NULL) {
                                  /*
                                   * The debugger owner is charged for
                                   * the memory.
                                   */
                                  cred = curthread->td_ucred;
                                  crhold(cred);
                                  if (!swap_reserve_by_cred(size, cred)) {
                                          crfree(cred);
                                          vm_map_unlock(map);
                                          return (KERN_RESOURCE_SHORTAGE);
                                  }
                                  entry->cred = cred;
                          }
                          eobject = entry->object.vm_object;
                          vm_object_shadow(&entry->object.vm_object,
                              &entry->offset, size, entry->cred, false);
                          if (eobject == entry->object.vm_object) {
                                  /*
                                   * The object was not shadowed.
                                   */
                                  swap_release_by_cred(size, entry->cred);
                                  crfree(entry->cred);
                          }
                          entry->cred = NULL;
                          entry->eflags &= ~MAP_ENTRY_NEEDS_COPY;
  
                          vm_map_lock_downgrade(map);
                  } else {
                          /*
                           * We're attempting to read a copy-on-write page --
                           * don't allow writes.
                           */
                          prot &= ~VM_PROT_WRITE;
                  }
          }
  
          /*
           * Create an object if necessary.
           */
          if (entry->object.vm_object == NULL && !map->system_map) {
                  if (vm_map_lock_upgrade(map))
                          goto RetryLookup;
                  entry->object.vm_object = vm_object_allocate_anon(atop(size),
                      NULL, entry->cred, size);
                  entry->offset = 0;
                  entry->cred = NULL;
                  vm_map_lock_downgrade(map);
          }
  
          /*
           * Return the object/offset from this entry.  If the entry was
           * copy-on-write or empty, it has been fixed up.
           */
          *pindex = OFF_TO_IDX((vaddr - entry->start) + entry->offset);
          *object = entry->object.vm_object;
  
          *out_prot = prot;
          return (KERN_SUCCESS);
  }
  
  /*
   *      vm_map_lookup_locked:
   *
   *      Lookup the faulting address.  A version of vm_map_lookup that returns 
   *      KERN_FAILURE instead of blocking on map lock or memory allocation.
   */
  int
  vm_map_lookup_locked(vm_map_t *var_map,         /* IN/OUT */
                       vm_offset_t vaddr,
                       vm_prot_t fault_typea,
                       vm_map_entry_t *out_entry, /* OUT */
                       vm_object_t *object,       /* OUT */
                       vm_pindex_t *pindex,       /* OUT */
                       vm_prot_t *out_prot,       /* OUT */
                       boolean_t *wired)          /* OUT */
  {
          vm_map_entry_t entry;
          vm_map_t map = *var_map;
          vm_prot_t prot;
          vm_prot_t fault_type = fault_typea;
  
          /*
           * Lookup the faulting address.
           */
          if (!vm_map_lookup_entry(map, vaddr, out_entry))
                  return (KERN_INVALID_ADDRESS);
  
          entry = *out_entry;
  
          /*
           * Fail if the entry refers to a submap.
           */
          if (entry->eflags & MAP_ENTRY_IS_SUB_MAP)
                  return (KERN_FAILURE);
  
          /*
           * Check whether this task is allowed to have this page.
           */
          prot = entry->protection;
          fault_type &= VM_PROT_READ | VM_PROT_WRITE | VM_PROT_EXECUTE;
          if ((fault_type & prot) != fault_type)
                  return (KERN_PROTECTION_FAILURE);
  
          /*
           * If this page is not pageable, we have to get it for all possible
           * accesses.
           */
          *wired = (entry->wired_count != 0);
          if (*wired)
                  fault_type = entry->protection;
  
          if (entry->eflags & MAP_ENTRY_NEEDS_COPY) {
                  /*
                   * Fail if the entry was copy-on-write for a write fault.
                   */
                  if (fault_type & VM_PROT_WRITE)
                          return (KERN_FAILURE);
                  /*
                   * We're attempting to read a copy-on-write page --
                   * don't allow writes.
                   */
                  prot &= ~VM_PROT_WRITE;
          }
  
          /*
           * Fail if an object should be created.
           */
          if (entry->object.vm_object == NULL && !map->system_map)
                  return (KERN_FAILURE);
  
          /*
           * Return the object/offset from this entry.  If the entry was
           * copy-on-write or empty, it has been fixed up.
           */
          *pindex = OFF_TO_IDX((vaddr - entry->start) + entry->offset);
          *object = entry->object.vm_object;
  
          *out_prot = prot;
          return (KERN_SUCCESS);
  }
  
  /*
   *      vm_map_lookup_done:
   *
   *      Releases locks acquired by a vm_map_lookup
   *      (according to the handle returned by that lookup).
   */
  void
  vm_map_lookup_done(vm_map_t map, vm_map_entry_t entry)
  {
          /*
           * Unlock the main-level map
           */
          vm_map_unlock_read(map);
  }
  
  vm_offset_t
  vm_map_max_KBI(const struct vm_map *map)
  {
  
          return (vm_map_max(map));
  }
  
  vm_offset_t
  vm_map_min_KBI(const struct vm_map *map)
  {
  
          return (vm_map_min(map));
  }
  
  pmap_t
  vm_map_pmap_KBI(vm_map_t map)
  {
  
          return (map->pmap);
  }
  
  bool
  vm_map_range_valid_KBI(vm_map_t map, vm_offset_t start, vm_offset_t end)
  {
  
          return (vm_map_range_valid(map, start, end));
  }
  
  #ifdef INVARIANTS
  static void
  _vm_map_assert_consistent(vm_map_t map, int check)
  {
          vm_map_entry_t entry, prev;
          vm_map_entry_t cur, header, lbound, ubound;
          vm_size_t max_left, max_right;
  
  #ifdef DIAGNOSTIC
          ++map->nupdates;
  #endif
          if (enable_vmmap_check != check)
                  return;
  
          header = prev = &map->header;
          VM_MAP_ENTRY_FOREACH(entry, map) {
                  KASSERT(prev->end <= entry->start,
                      ("map %p prev->end = %jx, start = %jx", map,
                      (uintmax_t)prev->end, (uintmax_t)entry->start));
                  KASSERT(entry->start < entry->end,
                      ("map %p start = %jx, end = %jx", map,
                      (uintmax_t)entry->start, (uintmax_t)entry->end));
                  KASSERT(entry->left == header ||
                      entry->left->start < entry->start,
                      ("map %p left->start = %jx, start = %jx", map,
                      (uintmax_t)entry->left->start, (uintmax_t)entry->start));
                  KASSERT(entry->right == header ||
                      entry->start < entry->right->start,
                      ("map %p start = %jx, right->start = %jx", map,
                      (uintmax_t)entry->start, (uintmax_t)entry->right->start));
                  cur = map->root;
                  lbound = ubound = header;
                  for (;;) {
                          if (entry->start < cur->start) {
                                  ubound = cur;
                                  cur = cur->left;
                                  KASSERT(cur != lbound,
                                      ("map %p cannot find %jx",
                                      map, (uintmax_t)entry->start));
                          } else if (cur->end <= entry->start) {
                                  lbound = cur;
                                  cur = cur->right;
                                  KASSERT(cur != ubound,
                                      ("map %p cannot find %jx",
                                      map, (uintmax_t)entry->start));
                          } else {
                                  KASSERT(cur == entry,
                                      ("map %p cannot find %jx",
                                      map, (uintmax_t)entry->start));
                                  break;
                          }
                  }
                  max_left = vm_map_entry_max_free_left(entry, lbound);
                  max_right = vm_map_entry_max_free_right(entry, ubound);
                  KASSERT(entry->max_free == vm_size_max(max_left, max_right),
                      ("map %p max = %jx, max_left = %jx, max_right = %jx", map,
                      (uintmax_t)entry->max_free,
                      (uintmax_t)max_left, (uintmax_t)max_right));
                  prev = entry;
          }
          KASSERT(prev->end <= entry->start,
              ("map %p prev->end = %jx, start = %jx", map,
              (uintmax_t)prev->end, (uintmax_t)entry->start));
  }
  #endif
  
  #include "opt_ddb.h"
  #ifdef DDB
  #include <sys/kernel.h>
  
  #include <ddb/ddb.h>
  
  static void
  vm_map_print(vm_map_t map)
  {
          vm_map_entry_t entry, prev;
  
          db_iprintf("Task map %p: pmap=%p, nentries=%d, version=%u\n",
              (void *)map,
              (void *)map->pmap, map->nentries, map->timestamp);
  
          db_indent += 2;
          prev = &map->header;
          VM_MAP_ENTRY_FOREACH(entry, map) {
                  db_iprintf("map entry %p: start=%p, end=%p, eflags=%#x, \n",
                      (void *)entry, (void *)entry->start, (void *)entry->end,
                      entry->eflags);
                  {
                          static const char * const inheritance_name[4] =
                          {"share", "copy", "none", "donate_copy"};
  
                          db_iprintf(" prot=%x/%x/%s",
                              entry->protection,
                              entry->max_protection,
                              inheritance_name[(int)(unsigned char)
                              entry->inheritance]);
                          if (entry->wired_count != 0)
                                  db_printf(", wired");
                  }
                  if (entry->eflags & MAP_ENTRY_IS_SUB_MAP) {
                          db_printf(", share=%p, offset=0x%jx\n",
                              (void *)entry->object.sub_map,
                              (uintmax_t)entry->offset);
                          if (prev == &map->header ||
                              prev->object.sub_map !=
                                  entry->object.sub_map) {
                                  db_indent += 2;
                                  vm_map_print((vm_map_t)entry->object.sub_map);
                                  db_indent -= 2;
                          }
                  } else {
                          if (entry->cred != NULL)
                                  db_printf(", ruid %d", entry->cred->cr_ruid);
                          db_printf(", object=%p, offset=0x%jx",
                              (void *)entry->object.vm_object,
                              (uintmax_t)entry->offset);
                          if (entry->object.vm_object && entry->object.vm_object->cred)
                                  db_printf(", obj ruid %d charge %jx",
                                      entry->object.vm_object->cred->cr_ruid,
                                      (uintmax_t)entry->object.vm_object->charge);
                          if (entry->eflags & MAP_ENTRY_COW)
                                  db_printf(", copy (%s)",
                                      (entry->eflags & MAP_ENTRY_NEEDS_COPY) ? "needed" : "done");
                          db_printf("\n");
  
                          if (prev == &map->header ||
                              prev->object.vm_object !=
                                  entry->object.vm_object) {
                                  db_indent += 2;
                                  vm_object_print((db_expr_t)(intptr_t)
                                                  entry->object.vm_object,
                                                  0, 0, (char *)0);
                                  db_indent -= 2;
                          }
                  }
                  prev = entry;
          }
          db_indent -= 2;
  }
  
  DB_SHOW_COMMAND(map, map)
  {
  
          if (!have_addr) {
                  db_printf("usage: show map <addr>\n");
                  return;
          }
          vm_map_print((vm_map_t)addr);
  }
  
  DB_SHOW_COMMAND(procvm, procvm)
  {
          struct proc *p;
  
          if (have_addr) {
                  p = db_lookup_proc(addr);
          } else {
                  p = curproc;
          }
  
          db_printf("p = %p, vmspace = %p, map = %p, pmap = %p\n",
              (void *)p, (void *)p->p_vmspace, (void *)&p->p_vmspace->vm_map,
              (void *)vmspace_pmap(p->p_vmspace));
  
          vm_map_print((vm_map_t)&p->p_vmspace->vm_map);
  }
  
  #endif /* DDB */