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NetBSD/sys/vm/vm_mmap.c

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/*
* Copyright (c) 1988 University of Utah.
* Copyright (c) 1991 The Regents of the University of California.
* All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* the Systems Programming Group of the University of Utah Computer
* Science Department.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* from: Utah Hdr: vm_mmap.c 1.3 90/01/21
* from: @(#)vm_mmap.c 7.5 (Berkeley) 6/28/91
* $Id: vm_mmap.c,v 1.13 1993/11/12 05:57:43 cgd Exp $
*/
/*
* Mapped file (mmap) interface to VM
*/
#include "param.h"
#include "systm.h"
#include "filedesc.h"
#include "proc.h"
#include "vnode.h"
#include "miscfs/specfs/specdev.h" /* XXX */
#include "file.h"
#include "mman.h"
#include "conf.h"
#include "vm.h"
#include "vm_pager.h"
#include "vm_prot.h"
#include "vm_statistics.h"
#ifdef DEBUG
int mmapdebug = 0;
#define MDB_FOLLOW 0x01
#define MDB_SYNC 0x02
#define MDB_MAPIT 0x04
#endif
/* ARGSUSED */
getpagesize(p, uap, retval)
struct proc *p;
void *uap;
int *retval;
{
*retval = NBPG * CLSIZE;
return (0);
}
struct sbrk_args {
int incr;
};
/* ARGSUSED */
sbrk(p, uap, retval)
struct proc *p;
struct sbrk_args *uap;
int *retval;
{
/* Not yet implemented */
return (EOPNOTSUPP);
}
struct sstk_args {
int incr;
};
/* ARGSUSED */
sstk(p, uap, retval)
struct proc *p;
struct sstk_args *uap;
int *retval;
{
/* Not yet implemented */
return (EOPNOTSUPP);
}
struct smmap_args {
caddr_t addr;
int len;
int prot;
int flags;
int fd;
off_t pos;
};
smmap(p, uap, retval)
struct proc *p;
register struct smmap_args *uap;
int *retval;
{
register struct filedesc *fdp = p->p_fd;
register struct file *fp;
struct vnode *vp;
vm_offset_t addr;
vm_size_t size;
vm_prot_t prot;
vm_prot_t maxprot;
caddr_t handle;
int mtype, error;
int flags = uap->flags;
#ifdef DEBUG
if (mmapdebug & MDB_FOLLOW)
printf("mmap(%d): addr %x len %x pro %x flg %x fd %d pos %x\n",
p->p_pid, uap->addr, uap->len, uap->prot,
flags, uap->fd, uap->pos);
#endif
/*
* Make sure one of the sharing types is specified
*/
mtype = flags & MAP_TYPE;
switch (mtype) {
case MAP_FILE:
case MAP_ANON:
break;
default:
return(EINVAL);
}
/*
* Address (if FIXED) must be page aligned.
* Size is implicitly rounded to a page boundary.
*/
addr = (vm_offset_t) uap->addr;
if ((flags & MAP_FIXED) && (addr & page_mask) || uap->len < 0)
return(EINVAL);
size = (vm_size_t) round_page(uap->len);
if ((flags & MAP_FIXED) && (addr + size > VM_MAXUSER_ADDRESS))
return EINVAL;
/*
* XXX if no hint provided for a non-fixed mapping place it after
* the end of the largest possible heap.
*
* There should really be a pmap call to determine a reasonable
* location.
*/
if (addr == 0 && (flags & MAP_FIXED) == 0)
addr = round_page(p->p_vmspace->vm_daddr + MAXDSIZ);
/*
* Mapping file or named anonymous, get fp for validation
*/
if (mtype == MAP_FILE || uap->fd != -1) {
if (((unsigned)uap->fd) >= fdp->fd_nfiles ||
(fp = fdp->fd_ofiles[uap->fd]) == NULL)
return(EBADF);
}
/*
* If we are mapping a file we need to check various
* file/vnode related things.
*/
if (mtype == MAP_FILE) {
/*
* Obtain vnode and make sure it is of appropriate type
*/
if (fp->f_type != DTYPE_VNODE)
return(EINVAL);
vp = (struct vnode *)fp->f_data;
if (vp->v_type != VREG && vp->v_type != VCHR)
return(EINVAL);
/*
* Ensure that file protection and desired protection
* are compatible. Note that we only worry about writability
* if mapping is shared. XXX (cgd) -- coalese access checks
* and permissions setting.
*/
if ((uap->prot & PROT_READ) && (fp->f_flag & FREAD) == 0 ||
((flags & MAP_SHARED) &&
(uap->prot & PROT_WRITE) && (fp->f_flag & FWRITE) == 0))
return(EACCES);
handle = (caddr_t)vp;
/*
* Map maximum protections to MACH style
*/
maxprot = VM_PROT_EXECUTE; /* ??? */
if (fp->f_flag & FREAD)
maxprot |= VM_PROT_READ;
if(uap->flags & MAP_SHARED) {
if (fp->f_flag & FWRITE)
maxprot |= VM_PROT_WRITE;
} else
maxprot |= VM_PROT_WRITE;
} else if (uap->fd != -1) {
maxprot = VM_PROT_ALL;
handle = (caddr_t)fp;
} else {
maxprot = VM_PROT_ALL;
handle = NULL;
}
/*
* Map current protections to MACH style
*/
prot = VM_PROT_NONE;
if (uap->prot & PROT_READ)
prot |= VM_PROT_READ;
if (uap->prot & PROT_WRITE)
prot |= VM_PROT_WRITE;
if (uap->prot & PROT_EXEC)
prot |= VM_PROT_EXECUTE;
error = vm_mmap(&p->p_vmspace->vm_map, &addr, size, prot, maxprot,
flags, handle, (vm_offset_t)uap->pos);
if (error == 0)
*retval = (int) addr;
return(error);
}
struct msync_args {
caddr_t addr;
int len;
};
msync(p, uap, retval)
struct proc *p;
struct msync_args *uap;
int *retval;
{
vm_offset_t addr, objoff, oaddr;
vm_size_t size, osize;
vm_prot_t prot, mprot;
vm_inherit_t inherit;
vm_object_t object;
boolean_t shared;
int rv;
#ifdef DEBUG
if (mmapdebug & (MDB_FOLLOW|MDB_SYNC))
printf("msync(%d): addr %x len %x\n",
p->p_pid, uap->addr, uap->len);
#endif
if (((int)uap->addr & page_mask) || uap->len < 0)
return(EINVAL);
addr = oaddr = (vm_offset_t)uap->addr;
osize = (vm_size_t)uap->len;
/*
* Region must be entirely contained in a single entry
*/
if (!vm_map_is_allocated(&p->p_vmspace->vm_map, addr, addr+osize,
TRUE))
return(EINVAL);
/*
* Determine the object associated with that entry
* (object is returned locked on KERN_SUCCESS)
*/
rv = vm_region(&p->p_vmspace->vm_map, &addr, &size, &prot, &mprot,
&inherit, &shared, &object, &objoff);
if (rv != KERN_SUCCESS)
return(EINVAL);
#ifdef DEBUG
if (mmapdebug & MDB_SYNC)
printf("msync: region: object %x addr %x size %d objoff %d\n",
object, addr, size, objoff);
#endif
/*
* Do not msync non-vnoded backed objects.
*/
if (object->internal || object->pager == NULL ||
object->pager->pg_type != PG_VNODE) {
vm_object_unlock(object);
return(EINVAL);
}
objoff += oaddr - addr;
if (osize == 0)
osize = size;
#ifdef DEBUG
if (mmapdebug & MDB_SYNC)
printf("msync: cleaning/flushing object range [%x-%x)\n",
objoff, objoff+osize);
#endif
if (prot & VM_PROT_WRITE)
vm_object_page_clean(object, objoff, objoff+osize);
/*
* (XXX)
* Bummer, gotta flush all cached pages to ensure
* consistency with the file system cache.
*/
vm_object_page_remove(object, objoff, objoff+osize);
vm_object_unlock(object);
return(0);
}
struct munmap_args {
caddr_t addr;
int len;
};
munmap(p, uap, retval)
register struct proc *p;
register struct munmap_args *uap;
int *retval;
{
vm_offset_t addr;
vm_size_t size;
#ifdef DEBUG
if (mmapdebug & MDB_FOLLOW)
printf("munmap(%d): addr %x len %x\n",
p->p_pid, uap->addr, uap->len);
#endif
addr = (vm_offset_t) uap->addr;
if ((addr & page_mask) || uap->len < 0)
return(EINVAL);
size = (vm_size_t) round_page(uap->len);
if (size == 0)
return(0);
if (addr + size >= VM_MAXUSER_ADDRESS)
return EINVAL;
if (!vm_map_is_allocated(&p->p_vmspace->vm_map, addr, addr+size,
FALSE))
return(EINVAL);
/* returns nothing but KERN_SUCCESS anyway */
(void) vm_map_remove(&p->p_vmspace->vm_map, addr, addr+size);
return(0);
}
munmapfd(p, fd)
register struct proc *p;
{
#ifdef DEBUG
if (mmapdebug & MDB_FOLLOW)
printf("munmapfd(%d): fd %d\n", p->p_pid, fd);
#endif
/*
* XXX -- should vm_deallocate any regions mapped to this file
*/
p->p_fd->fd_ofileflags[fd] &= ~UF_MAPPED;
}
struct mprotect_args {
caddr_t addr;
int len;
int prot;
};
mprotect(p, uap, retval)
struct proc *p;
struct mprotect_args *uap;
int *retval;
{
vm_offset_t addr;
vm_size_t size;
register vm_prot_t prot;
#ifdef DEBUG
if (mmapdebug & MDB_FOLLOW)
printf("mprotect(%d): addr %x len %x prot %d\n",
p->p_pid, uap->addr, uap->len, uap->prot);
#endif
addr = (vm_offset_t) uap->addr;
if ((addr & page_mask) || uap->len < 0)
return(EINVAL);
size = (vm_size_t) uap->len;
/*
* Map protections
*/
prot = VM_PROT_NONE;
if (uap->prot & PROT_READ)
prot |= VM_PROT_READ;
if (uap->prot & PROT_WRITE)
prot |= VM_PROT_WRITE;
if (uap->prot & PROT_EXEC)
prot |= VM_PROT_EXECUTE;
switch (vm_map_protect(&p->p_vmspace->vm_map, addr, addr+size, prot,
FALSE)) {
case KERN_SUCCESS:
return (0);
case KERN_PROTECTION_FAILURE:
return (EACCES);
}
return (EINVAL);
}
struct madvise_args {
caddr_t addr;
int len;
int behav;
};
/* ARGSUSED */
madvise(p, uap, retval)
struct proc *p;
struct madvise_args *uap;
int *retval;
{
/* Not yet implemented */
return (EOPNOTSUPP);
}
struct mincore_args {
caddr_t addr;
int len;
char *vec;
};
/* ARGSUSED */
mincore(p, uap, retval)
struct proc *p;
struct mincore_args *uap;
int *retval;
{
/* Not yet implemented */
return (EOPNOTSUPP);
}
/*
* Internal version of mmap.
* Currently used by mmap, exec, and sys5 shared memory.
* Handle is:
* MAP_FILE: a vnode pointer
* MAP_ANON: NULL or a file pointer
*/
vm_mmap(map, addr, size, prot, maxprot, flags, handle, foff)
register vm_map_t map;
register vm_offset_t *addr;
register vm_size_t size;
vm_prot_t prot;
vm_prot_t maxprot;
register int flags;
caddr_t handle; /* XXX should be vp */
vm_offset_t foff;
{
register vm_pager_t pager;
boolean_t fitit;
vm_object_t object;
struct vnode *vp;
int type;
int rv = KERN_SUCCESS;
if (size == 0)
return (0);
if ((flags & MAP_FIXED) == 0) {
fitit = TRUE;
*addr = round_page(*addr);
} else {
fitit = FALSE;
(void) vm_deallocate(map, *addr, size);
}
/*
* Lookup/allocate pager. All except an unnamed anonymous lookup
* gain a reference to ensure continued existance of the object.
* (XXX the exception is to appease the pageout daemon)
*/
if ((flags & MAP_TYPE) == MAP_ANON)
type = PG_DFLT;
else {
vp = (struct vnode *)handle;
if (vp->v_type == VCHR) {
type = PG_DEVICE;
handle = (caddr_t)vp->v_rdev;
} else
type = PG_VNODE;
}
pager = vm_pager_allocate(type, handle, size, prot, foff);
if (pager == NULL)
return (type == PG_DEVICE ? EINVAL : ENOMEM);
/*
* Find object and release extra reference gained by lookup
*/
object = vm_object_lookup(pager);
vm_object_deallocate(object);
/*
* Anonymous memory.
*/
if ((flags & MAP_TYPE) == MAP_ANON) {
rv = vm_allocate_with_pager(map, addr, size, fitit,
pager, (vm_offset_t)foff, TRUE);
if (rv != KERN_SUCCESS) {
if (handle == NULL)
vm_pager_deallocate(pager);
else
vm_object_deallocate(object);
goto out;
}
/*
* The object of unnamed anonymous regions was just created
* find it for pager_cache.
*/
if (handle == NULL)
object = vm_object_lookup(pager);
/*
* Don't cache anonymous objects.
* Loses the reference gained by vm_pager_allocate.
*/
(void) pager_cache(object, FALSE);
#ifdef DEBUG
if (mmapdebug & MDB_MAPIT)
printf("vm_mmap(%d): ANON *addr %x size %x pager %x\n",
curproc->p_pid, *addr, size, pager);
#endif
}
/*
* Must be type MAP_FILE.
* Distinguish between character special and regular files.
*/
else if (vp->v_type == VCHR) {
rv = vm_allocate_with_pager(map, addr, size, fitit,
pager, (vm_offset_t)foff, FALSE);
/*
* Uncache the object and lose the reference gained
* by vm_pager_allocate(). If the call to
* vm_allocate_with_pager() was sucessful, then we
* gained an additional reference ensuring the object
* will continue to exist. If the call failed then
* the deallocate call below will terminate the
* object which is fine.
*/
(void) pager_cache(object, FALSE);
if (rv != KERN_SUCCESS)
goto out;
}
/*
* A regular file
*/
else {
#ifdef DEBUG
if (object == NULL)
printf("vm_mmap: no object: vp %x, pager %x\n",
vp, pager);
#endif
/*
* Map it directly.
* Allows modifications to go out to the vnode.
*/
if (flags & MAP_SHARED) {
rv = vm_allocate_with_pager(map, addr, size,
fitit, pager,
(vm_offset_t)foff, FALSE);
if (rv != KERN_SUCCESS) {
vm_object_deallocate(object);
goto out;
}
/*
* Don't cache the object. This is the easiest way
* of ensuring that data gets back to the filesystem
* because vnode_pager_deallocate() will fsync the
* vnode. pager_cache() will lose the extra ref.
*/
if (prot & VM_PROT_WRITE)
pager_cache(object, FALSE);
else
vm_object_deallocate(object);
}
/*
* Copy-on-write of file. Two flavors.
* MAP_COPY is true COW, you essentially get a snapshot of
* the region at the time of mapping. MAP_PRIVATE means only
* that your changes are not reflected back to the object.
* Changes made by others will be seen.
*/
else {
vm_map_t tmap;
vm_offset_t off;
/* locate and allocate the target address space */
rv = vm_map_find(map, NULL, (vm_offset_t)0,
addr, size, fitit);
if (rv != KERN_SUCCESS) {
vm_object_deallocate(object);
goto out;
}
tmap = vm_map_create(pmap_create(size), VM_MIN_ADDRESS,
VM_MIN_ADDRESS+size, TRUE);
off = VM_MIN_ADDRESS;
rv = vm_allocate_with_pager(tmap, &off, size,
TRUE, pager,
(vm_offset_t)foff, FALSE);
if (rv != KERN_SUCCESS) {
vm_object_deallocate(object);
vm_map_deallocate(tmap);
goto out;
}
/*
* (XXX)
* MAP_PRIVATE implies that we see changes made by
* others. To ensure that we need to guarentee that
* no copy object is created (otherwise original
* pages would be pushed to the copy object and we
* would never see changes made by others). We
* totally sleeze it right now by marking the object
* internal temporarily.
*/
if ((flags & MAP_COPY) == 0)
object->internal = TRUE;
rv = vm_map_copy(map, tmap, *addr, size, off,
FALSE, FALSE);
object->internal = FALSE;
/*
* (XXX)
* My oh my, this only gets worse...
* Force creation of a shadow object so that
* vm_map_fork will do the right thing.
*/
if ((flags & MAP_COPY) == 0) {
vm_map_t tmap;
vm_map_entry_t tentry;
vm_object_t tobject;
vm_offset_t toffset;
vm_prot_t tprot;
boolean_t twired, tsu;
tmap = map;
vm_map_lookup(&tmap, *addr, VM_PROT_WRITE,
&tentry, &tobject, &toffset,
&tprot, &twired, &tsu);
vm_map_lookup_done(tmap, tentry);
}
/*
* (XXX)
* Map copy code cannot detect sharing unless a
* sharing map is involved. So we cheat and write
* protect everything ourselves.
*/
vm_object_pmap_copy(object, (vm_offset_t)foff,
(vm_offset_t)foff+size);
vm_object_deallocate(object);
vm_map_deallocate(tmap);
if (rv != KERN_SUCCESS)
goto out;
}
#ifdef DEBUG
if (mmapdebug & MDB_MAPIT)
printf("vm_mmap(%d): FILE *addr %x size %x pager %x\n",
curproc->p_pid, *addr, size, pager);
#endif
}
/*
* Correct protection (default is VM_PROT_ALL).
* Note that we set the maximum protection. This may not be
* entirely correct. The maximum protection is be based on
* the object permissions where it makes sense (e.g. a vnode).
*/
rv = vm_map_protect(map, *addr, *addr+size, prot, FALSE);
if (rv != KERN_SUCCESS) {
(void) vm_deallocate(map, *addr, size);
goto out;
}
/*
* We only need to set max_protection in case it's
* unequal to its default, which is VM_PROT_DEFAULT.
*/
if(maxprot != VM_PROT_DEFAULT) {
rv = vm_map_protect(map, *addr, *addr+size, maxprot, TRUE);
if (rv != KERN_SUCCESS) {
(void) vm_deallocate(map, *addr, size);
goto out;
}
}
/*
* Shared memory is also shared with children.
*/
if (flags & MAP_SHARED) {
rv = vm_inherit(map, *addr, size, VM_INHERIT_SHARE);
if (rv != KERN_SUCCESS) {
(void) vm_deallocate(map, *addr, size);
goto out;
}
}
out:
#ifdef DEBUG
if (mmapdebug & MDB_MAPIT)
printf("vm_mmap: rv %d\n", rv);
#endif
switch (rv) {
case KERN_SUCCESS:
return (0);
case KERN_INVALID_ADDRESS:
case KERN_NO_SPACE:
return (ENOMEM);
case KERN_PROTECTION_FAILURE:
return (EACCES);
default:
return (EINVAL);
}
}
/*
* Internal bastardized version of MACHs vm_region system call.
* Given address and size it returns map attributes as well
* as the (locked) object mapped at that location.
*/
vm_region(map, addr, size, prot, max_prot, inheritance, shared, object, objoff)
vm_map_t map;
vm_offset_t *addr; /* IN/OUT */
vm_size_t *size; /* OUT */
vm_prot_t *prot; /* OUT */
vm_prot_t *max_prot; /* OUT */
vm_inherit_t *inheritance; /* OUT */
boolean_t *shared; /* OUT */
vm_object_t *object; /* OUT */
vm_offset_t *objoff; /* OUT */
{
vm_map_entry_t tmp_entry;
register
vm_map_entry_t entry;
register
vm_offset_t tmp_offset;
vm_offset_t start;
if (map == NULL)
return(KERN_INVALID_ARGUMENT);
start = *addr;
vm_map_lock_read(map);
if (!vm_map_lookup_entry(map, start, &tmp_entry)) {
if ((entry = tmp_entry->next) == &map->header) {
vm_map_unlock_read(map);
return(KERN_NO_SPACE);
}
start = entry->start;
*addr = start;
} else
entry = tmp_entry;
*prot = entry->protection;
*max_prot = entry->max_protection;
*inheritance = entry->inheritance;
tmp_offset = entry->offset + (start - entry->start);
*size = (entry->end - start);
if (entry->is_a_map) {
register vm_map_t share_map;
vm_size_t share_size;
share_map = entry->object.share_map;
vm_map_lock_read(share_map);
(void) vm_map_lookup_entry(share_map, tmp_offset, &tmp_entry);
if ((share_size = (tmp_entry->end - tmp_offset)) < *size)
*size = share_size;
vm_object_lock(tmp_entry->object);
*object = tmp_entry->object.vm_object;
*objoff = tmp_entry->offset + (tmp_offset - tmp_entry->start);
*shared = (share_map->ref_count != 1);
vm_map_unlock_read(share_map);
} else {
vm_object_lock(entry->object);
*object = entry->object.vm_object;
*objoff = tmp_offset;
*shared = FALSE;
}
vm_map_unlock_read(map);
return(KERN_SUCCESS);
}
/*
* Yet another bastard routine.
*/
vm_allocate_with_pager(map, addr, size, fitit, pager, poffset, internal)
register vm_map_t map;
register vm_offset_t *addr;
register vm_size_t size;
boolean_t fitit;
vm_pager_t pager;
vm_offset_t poffset;
boolean_t internal;
{
register vm_object_t object;
register int result;
if (map == NULL)
return(KERN_INVALID_ARGUMENT);
*addr = trunc_page(*addr);
size = round_page(size);
/*
* Lookup the pager/paging-space in the object cache.
* If it's not there, then create a new object and cache
* it.
*/
object = vm_object_lookup(pager);
vm_stat.lookups++;
if (object == NULL) {
object = vm_object_allocate(size);
vm_object_enter(object, pager);
} else
vm_stat.hits++;
object->internal = internal;
result = vm_map_find(map, object, poffset, addr, size, fitit);
if (result != KERN_SUCCESS)
vm_object_deallocate(object);
else if (pager != NULL)
vm_object_setpager(object, pager, (vm_offset_t) 0, TRUE);
return(result);
}
/*
* XXX: this routine belongs in vm_map.c.
*
* Returns TRUE if the range [start - end) is allocated in either
* a single entry (single_entry == TRUE) or multiple contiguous
* entries (single_entry == FALSE).
*
* start and end should be page aligned.
*/
boolean_t
vm_map_is_allocated(map, start, end, single_entry)
vm_map_t map;
vm_offset_t start, end;
boolean_t single_entry;
{
vm_map_entry_t mapent;
register vm_offset_t nend;
vm_map_lock_read(map);
/*
* Start address not in any entry
*/
if (!vm_map_lookup_entry(map, start, &mapent)) {
vm_map_unlock_read(map);
return (FALSE);
}
/*
* Find the maximum stretch of contiguously allocated space
*/
nend = mapent->end;
if (!single_entry) {
mapent = mapent->next;
while (mapent != &map->header && mapent->start == nend) {
nend = mapent->end;
mapent = mapent->next;
}
}
vm_map_unlock_read(map);
return (end <= nend);
}
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