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NetBSD/sys/vm/vm_fault.c

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/*
* Copyright (c) 1991 Regents of the University of California.
* All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* The Mach Operating System project at Carnegie-Mellon University.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)vm_fault.c 7.6 (Berkeley) 5/7/91
*
*
* 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.
*/
static char rcsid[] = "$Header: /cvsroot/src/sys/vm/Attic/vm_fault.c,v 1.2 1993/04/09 15:54:56 cgd Exp $";
/*
* Page fault handling module.
*/
#include "param.h"
#include "vm.h"
#include "vm_page.h"
#include "vm_pageout.h"
/*
* vm_fault:
*
* Handle a page fault occuring at the given address,
* requiring the given permissions, in the map specified.
* If successful, the page is inserted into the
* associated physical map.
*
* NOTE: the given address should be truncated to the
* proper page address.
*
* KERN_SUCCESS is returned if the page fault is handled; otherwise,
* a standard error specifying why the fault is fatal is returned.
*
*
* The map in question must be referenced, and remains so.
* Caller may hold no locks.
*/
vm_fault(map, vaddr, fault_type, change_wiring)
vm_map_t map;
vm_offset_t vaddr;
vm_prot_t fault_type;
boolean_t change_wiring;
{
vm_object_t first_object;
vm_offset_t first_offset;
vm_map_entry_t entry;
register vm_object_t object;
register vm_offset_t offset;
register vm_page_t m;
vm_page_t first_m;
vm_prot_t prot;
int result;
boolean_t wired;
boolean_t su;
boolean_t lookup_still_valid;
boolean_t page_exists;
vm_page_t old_m;
vm_object_t next_object;
vm_stat.faults++; /* needs lock XXX */
/*
* Recovery actions
*/
#define FREE_PAGE(m) { \
PAGE_WAKEUP(m); \
vm_page_lock_queues(); \
vm_page_free(m); \
vm_page_unlock_queues(); \
}
#define RELEASE_PAGE(m) { \
PAGE_WAKEUP(m); \
vm_page_lock_queues(); \
vm_page_activate(m); \
vm_page_unlock_queues(); \
}
#define UNLOCK_MAP { \
if (lookup_still_valid) { \
vm_map_lookup_done(map, entry); \
lookup_still_valid = FALSE; \
} \
}
#define UNLOCK_THINGS { \
object->paging_in_progress--; \
vm_object_unlock(object); \
if (object != first_object) { \
vm_object_lock(first_object); \
FREE_PAGE(first_m); \
first_object->paging_in_progress--; \
vm_object_unlock(first_object); \
} \
UNLOCK_MAP; \
}
#define UNLOCK_AND_DEALLOCATE { \
UNLOCK_THINGS; \
vm_object_deallocate(first_object); \
}
RetryFault: ;
/*
* Find the backing store object and offset into
* it to begin the search.
*/
if ((result = vm_map_lookup(&map, vaddr, fault_type, &entry,
&first_object, &first_offset,
&prot, &wired, &su)) != KERN_SUCCESS) {
return(result);
}
lookup_still_valid = TRUE;
if (wired)
fault_type = prot;
first_m = NULL;
/*
* Make a reference to this object to
* prevent its disposal while we are messing with
* it. Once we have the reference, the map is free
* to be diddled. Since objects reference their
* shadows (and copies), they will stay around as well.
*/
vm_object_lock(first_object);
first_object->ref_count++;
first_object->paging_in_progress++;
/*
* INVARIANTS (through entire routine):
*
* 1) At all times, we must either have the object
* lock or a busy page in some object to prevent
* some other thread from trying to bring in
* the same page.
*
* Note that we cannot hold any locks during the
* pager access or when waiting for memory, so
* we use a busy page then.
*
* Note also that we aren't as concerned about
* more than one thead attempting to pager_data_unlock
* the same page at once, so we don't hold the page
* as busy then, but do record the highest unlock
* value so far. [Unlock requests may also be delivered
* out of order.]
*
* 2) Once we have a busy page, we must remove it from
* the pageout queues, so that the pageout daemon
* will not grab it away.
*
* 3) To prevent another thread from racing us down the
* shadow chain and entering a new page in the top
* object before we do, we must keep a busy page in
* the top object while following the shadow chain.
*
* 4) We must increment paging_in_progress on any object
* for which we have a busy page, to prevent
* vm_object_collapse from removing the busy page
* without our noticing.
*/
/*
* Search for the page at object/offset.
*/
object = first_object;
offset = first_offset;
/*
* See whether this page is resident
*/
while (TRUE) {
m = vm_page_lookup(object, offset);
if (m != NULL) {
/*
* If the page is being brought in,
* wait for it and then retry.
*/
if (m->busy) {
#ifdef DOTHREADS
int wait_result;
PAGE_ASSERT_WAIT(m, !change_wiring);
UNLOCK_THINGS;
thread_wakeup(&vm_pages_needed); /* XXX! -- what does this do? */
thread_block();
wait_result = current_thread()->wait_result;
vm_object_deallocate(first_object);
if (wait_result != THREAD_AWAKENED)
return(KERN_SUCCESS);
goto RetryFault;
#else
PAGE_ASSERT_WAIT(m, !change_wiring);
UNLOCK_THINGS;
thread_wakeup(&vm_pages_needed); /* XXX! */
thread_block();
vm_object_deallocate(first_object);
goto RetryFault;
#endif
}
if (m->absent)
panic("vm_fault: absent");
/*
* If the desired access to this page has
* been locked out, request that it be unlocked.
*/
if (fault_type & m->page_lock) {
#ifdef DOTHREADS
int wait_result;
if ((fault_type & m->unlock_request) != fault_type)
panic("vm_fault: pager_data_unlock");
PAGE_ASSERT_WAIT(m, !change_wiring);
UNLOCK_THINGS;
thread_wakeup(&vm_pages_needed); /* XXX! -- what does this do? */
thread_block();
wait_result = current_thread()->wait_result;
vm_object_deallocate(first_object);
if (wait_result != THREAD_AWAKENED)
return(KERN_SUCCESS);
goto RetryFault;
#else
if ((fault_type & m->unlock_request) != fault_type)
panic("vm_fault: pager_data_unlock");
PAGE_ASSERT_WAIT(m, !change_wiring);
UNLOCK_THINGS;
thread_wakeup(&vm_pages_needed); /* XXX */
thread_block();
vm_object_deallocate(first_object);
goto RetryFault;
#endif
}
/*
* Remove the page from the pageout daemon's
* reach while we play with it.
*/
vm_page_lock_queues();
if (m->inactive) {
queue_remove(&vm_page_queue_inactive, m,
vm_page_t, pageq);
m->inactive = FALSE;
vm_page_inactive_count--;
vm_stat.reactivations++;
}
if (m->active) {
queue_remove(&vm_page_queue_active, m,
vm_page_t, pageq);
m->active = FALSE;
vm_page_active_count--;
}
vm_page_unlock_queues();
/*
* Mark page busy for other threads.
*/
m->busy = TRUE;
m->absent = FALSE;
break;
}
if (((object->pager != NULL) &&
(!change_wiring || wired))
|| (object == first_object)) {
/*
* Allocate a new page for this object/offset
* pair.
*/
m = vm_page_alloc(object, offset);
if (m == NULL) {
UNLOCK_AND_DEALLOCATE;
VM_WAIT;
goto RetryFault;
}
}
if ((object->pager != NULL) &&
(!change_wiring || wired)) {
int rv;
/*
* Now that we have a busy page, we can
* release the object lock.
*/
vm_object_unlock(object);
/*
* Call the pager to retrieve the data, if any,
* after releasing the lock on the map.
*/
UNLOCK_MAP;
rv = vm_pager_get(object->pager, m, TRUE);
if (rv == VM_PAGER_OK) {
/*
* Found the page.
* Leave it busy while we play with it.
*/
vm_object_lock(object);
/*
* Relookup in case pager changed page.
* Pager is responsible for disposition
* of old page if moved.
*/
m = vm_page_lookup(object, offset);
vm_stat.pageins++;
m->fake = FALSE;
pmap_clear_modify(VM_PAGE_TO_PHYS(m));
break;
}
/*
* Remove the bogus page (which does not
* exist at this object/offset); before
* doing so, we must get back our object
* lock to preserve our invariant.
*
* Also wake up any other thread that may want
* to bring in this page.
*
* If this is the top-level object, we must
* leave the busy page to prevent another
* thread from rushing past us, and inserting
* the page in that object at the same time
* that we are.
*/
vm_object_lock(object);
/*
* Data outside the range of the pager; an error
*/
if (rv == VM_PAGER_BAD) {
FREE_PAGE(m);
UNLOCK_AND_DEALLOCATE;
return(KERN_PROTECTION_FAILURE); /* XXX */
}
if (object != first_object) {
FREE_PAGE(m);
/*
* XXX - we cannot just fall out at this
* point, m has been freed and is invalid!
*/
}
}
/*
* We get here if the object has no pager (or unwiring)
* or the pager doesn't have the page.
*/
if (object == first_object)
first_m = m;
/*
* Move on to the next object. Lock the next
* object before unlocking the current one.
*/
offset += object->shadow_offset;
next_object = object->shadow;
if (next_object == NULL) {
/*
* If there's no object left, fill the page
* in the top object with zeros.
*/
if (object != first_object) {
object->paging_in_progress--;
vm_object_unlock(object);
object = first_object;
offset = first_offset;
m = first_m;
vm_object_lock(object);
}
first_m = NULL;
vm_page_zero_fill(m);
vm_stat.zero_fill_count++;
m->fake = FALSE;
m->absent = FALSE;
break;
}
else {
vm_object_lock(next_object);
if (object != first_object)
object->paging_in_progress--;
vm_object_unlock(object);
object = next_object;
object->paging_in_progress++;
}
}
if (m->absent || m->active || m->inactive || !m->busy)
panic("vm_fault: absent or active or inactive or not busy after main loop");
/*
* PAGE HAS BEEN FOUND.
* [Loop invariant still holds -- the object lock
* is held.]
*/
old_m = m; /* save page that would be copied */
/*
* If the page is being written, but isn't
* already owned by the top-level object,
* we have to copy it into a new page owned
* by the top-level object.
*/
if (object != first_object) {
/*
* We only really need to copy if we
* want to write it.
*/
if (fault_type & VM_PROT_WRITE) {
/*
* If we try to collapse first_object at this
* point, we may deadlock when we try to get
* the lock on an intermediate object (since we
* have the bottom object locked). We can't
* unlock the bottom object, because the page
* we found may move (by collapse) if we do.
*
* Instead, we first copy the page. Then, when
* we have no more use for the bottom object,
* we unlock it and try to collapse.
*
* Note that we copy the page even if we didn't
* need to... that's the breaks.
*/
/*
* We already have an empty page in
* first_object - use it.
*/
vm_page_copy(m, first_m);
first_m->fake = FALSE;
first_m->absent = FALSE;
/*
* If another map is truly sharing this
* page with us, we have to flush all
* uses of the original page, since we
* can't distinguish those which want the
* original from those which need the
* new copy.
*
* XXX If we know that only one map has
* access to this page, then we could
* avoid the pmap_page_protect() call.
*/
vm_page_lock_queues();
vm_page_activate(m);
pmap_page_protect(VM_PAGE_TO_PHYS(m), VM_PROT_NONE);
vm_page_unlock_queues();
/*
* We no longer need the old page or object.
*/
PAGE_WAKEUP(m);
object->paging_in_progress--;
vm_object_unlock(object);
/*
* Only use the new page below...
*/
vm_stat.cow_faults++;
m = first_m;
object = first_object;
offset = first_offset;
/*
* Now that we've gotten the copy out of the
* way, let's try to collapse the top object.
*/
vm_object_lock(object);
/*
* But we have to play ugly games with
* paging_in_progress to do that...
*/
object->paging_in_progress--;
vm_object_collapse(object);
object->paging_in_progress++;
}
else {
prot &= (~VM_PROT_WRITE);
m->copy_on_write = TRUE;
}
}
if (m->active || m->inactive)
panic("vm_fault: active or inactive before copy object handling");
/*
* If the page is being written, but hasn't been
* copied to the copy-object, we have to copy it there.
*/
RetryCopy:
if (first_object->copy != NULL) {
vm_object_t copy_object = first_object->copy;
vm_offset_t copy_offset;
vm_page_t copy_m;
/*
* We only need to copy if we want to write it.
*/
if ((fault_type & VM_PROT_WRITE) == 0) {
prot &= ~VM_PROT_WRITE;
m->copy_on_write = TRUE;
}
else {
/*
* Try to get the lock on the copy_object.
*/
if (!vm_object_lock_try(copy_object)) {
vm_object_unlock(object);
/* should spin a bit here... */
vm_object_lock(object);
goto RetryCopy;
}
/*
* Make another reference to the copy-object,
* to keep it from disappearing during the
* copy.
*/
copy_object->ref_count++;
/*
* Does the page exist in the copy?
*/
copy_offset = first_offset
- copy_object->shadow_offset;
copy_m = vm_page_lookup(copy_object, copy_offset);
if (page_exists = (copy_m != NULL)) {
if (copy_m->busy) {
#ifdef DOTHREADS
int wait_result;
/*
* If the page is being brought
* in, wait for it and then retry.
*/
PAGE_ASSERT_WAIT(copy_m, !change_wiring);
RELEASE_PAGE(m);
copy_object->ref_count--;
vm_object_unlock(copy_object);
UNLOCK_THINGS;
thread_wakeup(&vm_pages_needed); /* XXX! -- what does this do? */
thread_block();
wait_result = current_thread()->wait_result;
vm_object_deallocate(first_object);
if (wait_result != THREAD_AWAKENED)
return(KERN_SUCCESS);
goto RetryFault;
#else
/*
* If the page is being brought
* in, wait for it and then retry.
*/
PAGE_ASSERT_WAIT(copy_m, !change_wiring);
RELEASE_PAGE(m);
copy_object->ref_count--;
vm_object_unlock(copy_object);
UNLOCK_THINGS;
thread_wakeup(&vm_pages_needed); /* XXX */
thread_block();
vm_object_deallocate(first_object);
goto RetryFault;
#endif
}
}
/*
* If the page is not in memory (in the object)
* and the object has a pager, we have to check
* if the pager has the data in secondary
* storage.
*/
if (!page_exists) {
/*
* If we don't allocate a (blank) page
* here... another thread could try
* to page it in, allocate a page, and
* then block on the busy page in its
* shadow (first_object). Then we'd
* trip over the busy page after we
* found that the copy_object's pager
* doesn't have the page...
*/
copy_m = vm_page_alloc(copy_object,
copy_offset);
if (copy_m == NULL) {
/*
* Wait for a page, then retry.
*/
RELEASE_PAGE(m);
copy_object->ref_count--;
vm_object_unlock(copy_object);
UNLOCK_AND_DEALLOCATE;
VM_WAIT;
goto RetryFault;
}
if (copy_object->pager != NULL) {
vm_object_unlock(object);
vm_object_unlock(copy_object);
UNLOCK_MAP;
page_exists = vm_pager_has_page(
copy_object->pager,
(copy_offset + copy_object->paging_offset));
vm_object_lock(copy_object);
/*
* Since the map is unlocked, someone
* else could have copied this object
* and put a different copy_object
* between the two. Or, the last
* reference to the copy-object (other
* than the one we have) may have
* disappeared - if that has happened,
* we don't need to make the copy.
*/
if (copy_object->shadow != object ||
copy_object->ref_count == 1) {
/*
* Gaah... start over!
*/
FREE_PAGE(copy_m);
vm_object_unlock(copy_object);
vm_object_deallocate(copy_object);
/* may block */
vm_object_lock(object);
goto RetryCopy;
}
vm_object_lock(object);
if (page_exists) {
/*
* We didn't need the page
*/
FREE_PAGE(copy_m);
}
}
}
if (!page_exists) {
/*
* Must copy page into copy-object.
*/
vm_page_copy(m, copy_m);
copy_m->fake = FALSE;
copy_m->absent = FALSE;
/*
* Things to remember:
* 1. The copied page must be marked 'dirty'
* so it will be paged out to the copy
* object.
* 2. If the old page was in use by any users
* of the copy-object, it must be removed
* from all pmaps. (We can't know which
* pmaps use it.)
*/
vm_page_lock_queues();
pmap_page_protect(VM_PAGE_TO_PHYS(old_m),
VM_PROT_NONE);
copy_m->clean = FALSE;
vm_page_activate(copy_m); /* XXX */
vm_page_unlock_queues();
PAGE_WAKEUP(copy_m);
}
/*
* The reference count on copy_object must be
* at least 2: one for our extra reference,
* and at least one from the outside world
* (we checked that when we last locked
* copy_object).
*/
copy_object->ref_count--;
vm_object_unlock(copy_object);
m->copy_on_write = FALSE;
}
}
if (m->active || m->inactive)
panic("vm_fault: active or inactive before retrying lookup");
/*
* We must verify that the maps have not changed
* since our last lookup.
*/
if (!lookup_still_valid) {
vm_object_t retry_object;
vm_offset_t retry_offset;
vm_prot_t retry_prot;
/*
* Since map entries may be pageable, make sure we can
* take a page fault on them.
*/
vm_object_unlock(object);
/*
* To avoid trying to write_lock the map while another
* thread has it read_locked (in vm_map_pageable), we
* do not try for write permission. If the page is
* still writable, we will get write permission. If it
* is not, or has been marked needs_copy, we enter the
* mapping without write permission, and will merely
* take another fault.
*/
result = vm_map_lookup(&map, vaddr,
fault_type & ~VM_PROT_WRITE, &entry,
&retry_object, &retry_offset, &retry_prot,
&wired, &su);
vm_object_lock(object);
/*
* If we don't need the page any longer, put it on the
* active list (the easiest thing to do here). If no
* one needs it, pageout will grab it eventually.
*/
if (result != KERN_SUCCESS) {
RELEASE_PAGE(m);
UNLOCK_AND_DEALLOCATE;
return(result);
}
lookup_still_valid = TRUE;
if ((retry_object != first_object) ||
(retry_offset != first_offset)) {
RELEASE_PAGE(m);
UNLOCK_AND_DEALLOCATE;
goto RetryFault;
}
/*
* Check whether the protection has changed or the object
* has been copied while we left the map unlocked.
* Changing from read to write permission is OK - we leave
* the page write-protected, and catch the write fault.
* Changing from write to read permission means that we
* can't mark the page write-enabled after all.
*/
prot &= retry_prot;
if (m->copy_on_write)
prot &= ~VM_PROT_WRITE;
}
/*
* (the various bits we're fiddling with here are locked by
* the object's lock)
*/
/* XXX This distorts the meaning of the copy_on_write bit */
if (prot & VM_PROT_WRITE)
m->copy_on_write = FALSE;
/*
* It's critically important that a wired-down page be faulted
* only once in each map for which it is wired.
*/
if (m->active || m->inactive)
panic("vm_fault: active or inactive before pmap_enter");
vm_object_unlock(object);
/*
* Put this page into the physical map.
* We had to do the unlock above because pmap_enter
* may cause other faults. We don't put the
* page back on the active queue until later so
* that the page-out daemon won't find us (yet).
*/
pmap_enter(map->pmap, vaddr, VM_PAGE_TO_PHYS(m),
prot & ~(m->page_lock), wired);
/*
* If the page is not wired down, then put it where the
* pageout daemon can find it.
*/
vm_object_lock(object);
vm_page_lock_queues();
if (change_wiring) {
if (wired)
vm_page_wire(m);
else
vm_page_unwire(m);
}
else
vm_page_activate(m);
vm_page_unlock_queues();
/*
* Unlock everything, and return
*/
PAGE_WAKEUP(m);
UNLOCK_AND_DEALLOCATE;
return(KERN_SUCCESS);
}
/*
* vm_fault_wire:
*
* Wire down a range of virtual addresses in a map.
*/
void vm_fault_wire(map, start, end)
vm_map_t map;
vm_offset_t start, end;
{
register vm_offset_t va;
register pmap_t pmap;
pmap = vm_map_pmap(map);
/*
* Inform the physical mapping system that the
* range of addresses may not fault, so that
* page tables and such can be locked down as well.
*/
pmap_pageable(pmap, start, end, FALSE);
/*
* We simulate a fault to get the page and enter it
* in the physical map.
*/
for (va = start; va < end; va += PAGE_SIZE) {
(void) vm_fault(map, va, VM_PROT_NONE, TRUE);
}
}
/*
* vm_fault_unwire:
*
* Unwire a range of virtual addresses in a map.
*/
void vm_fault_unwire(map, start, end)
vm_map_t map;
vm_offset_t start, end;
{
register vm_offset_t va, pa;
register pmap_t pmap;
pmap = vm_map_pmap(map);
/*
* Since the pages are wired down, we must be able to
* get their mappings from the physical map system.
*/
vm_page_lock_queues();
for (va = start; va < end; va += PAGE_SIZE) {
pa = pmap_extract(pmap, va);
if (pa == (vm_offset_t) 0) {
panic("unwire: page not in pmap");
}
pmap_change_wiring(pmap, va, FALSE);
vm_page_unwire(PHYS_TO_VM_PAGE(pa));
}
vm_page_unlock_queues();
/*
* Inform the physical mapping system that the range
* of addresses may fault, so that page tables and
* such may be unwired themselves.
*/
pmap_pageable(pmap, start, end, TRUE);
}
/*
* Routine:
* vm_fault_copy_entry
* Function:
* Copy all of the pages from a wired-down map entry to another.
*
* In/out conditions:
* The source and destination maps must be locked for write.
* The source map entry must be wired down (or be a sharing map
* entry corresponding to a main map entry that is wired down).
*/
void vm_fault_copy_entry(dst_map, src_map, dst_entry, src_entry)
vm_map_t dst_map;
vm_map_t src_map;
vm_map_entry_t dst_entry;
vm_map_entry_t src_entry;
{
vm_object_t dst_object;
vm_object_t src_object;
vm_offset_t dst_offset;
vm_offset_t src_offset;
vm_prot_t prot;
vm_offset_t vaddr;
vm_page_t dst_m;
vm_page_t src_m;
#ifdef lint
src_map++;
#endif lint
src_object = src_entry->object.vm_object;
src_offset = src_entry->offset;
/*
* Create the top-level object for the destination entry.
* (Doesn't actually shadow anything - we copy the pages
* directly.)
*/
dst_object = vm_object_allocate(
(vm_size_t) (dst_entry->end - dst_entry->start));
dst_entry->object.vm_object = dst_object;
dst_entry->offset = 0;
prot = dst_entry->max_protection;
/*
* Loop through all of the pages in the entry's range, copying
* each one from the source object (it should be there) to the
* destination object.
*/
for (vaddr = dst_entry->start, dst_offset = 0;
vaddr < dst_entry->end;
vaddr += PAGE_SIZE, dst_offset += PAGE_SIZE) {
/*
* Allocate a page in the destination object
*/
vm_object_lock(dst_object);
do {
dst_m = vm_page_alloc(dst_object, dst_offset);
if (dst_m == NULL) {
vm_object_unlock(dst_object);
VM_WAIT;
vm_object_lock(dst_object);
}
} while (dst_m == NULL);
/*
* Find the page in the source object, and copy it in.
* (Because the source is wired down, the page will be
* in memory.)
*/
vm_object_lock(src_object);
src_m = vm_page_lookup(src_object, dst_offset + src_offset);
if (src_m == NULL)
panic("vm_fault_copy_wired: page missing");
vm_page_copy(src_m, dst_m);
/*
* Enter it in the pmap...
*/
vm_object_unlock(src_object);
vm_object_unlock(dst_object);
pmap_enter(dst_map->pmap, vaddr, VM_PAGE_TO_PHYS(dst_m),
prot, FALSE);
/*
* Mark it no longer busy, and put it on the active list.
*/
vm_object_lock(dst_object);
vm_page_lock_queues();
vm_page_activate(dst_m);
vm_page_unlock_queues();
PAGE_WAKEUP(dst_m);
vm_object_unlock(dst_object);
}
}
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