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Fixed a bad bug in vm_copy_on_write_area(): the area's cache offset was not taken 

into account when remapping the pages read-only; it could have overwritten valid
page mappings this way. This was also the reason for the Terminal to crash - it
does now work as it should, although some keys don't work (like tab completion)).
vm_copy_area() no longer always sets B_KERNEL_WRITE_AREA if no kernel protection
was specified, but mirrors the userland protection (for example, the x86 MMU is
not able to have a page writable in kernel but not in userland). This caused
some areas to be read/write when read-only would have been enough.
vm_copy_area() now panics when vm_copy_on_write_area() fails - that's of course
no real solution, but it's bettern than letting it silently fail.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@13768 a95241bf-73f2-0310-859d-f6bbb57e9c96
This commit is contained in:
Axel Dörfler 2005-07-19 18:00:31 +00:00
parent c05350e781
commit 230a037ed4
1 changed files with 23 additions and 8 deletions
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31
src/system/kernel/vm/vm.cpp
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@ -767,7 +767,8 @@ vm_create_anonymous_area(aspace_id aid, const char *name, void **address,
size = PAGE_ALIGN(size);
if (wiring == B_CONTIGUOUS) {
// we try to allocate the page run here upfront as this may easily fail for obvious reasons
// we try to allocate the page run here upfront as this may easily
// fail for obvious reasons
page = vm_page_allocate_page_run(PAGE_STATE_CLEAR, size / B_PAGE_SIZE);
if (page == NULL) {
vm_put_aspace(aspace);
@ -1292,6 +1293,9 @@ _vm_put_area(vm_area *area, bool aspaceLocked)
vm_address_space *aspace;
bool removeit = false;
//TRACE(("_vm_put_area(area = %p, aspaceLocked = %s)\n",
// area, aspaceLocked ? "yes" : "no"));
// we should never get here, but if we do, we can handle it
if (area->id == RESERVED_AREA_ID)
return false;
@ -1389,6 +1393,8 @@ vm_copy_on_write_area(vm_area *area)
upperCacheRef->cache = upperCache;
// we need to manually alter the ref_count
// ToDo: investigate a bit deeper if this is really correct
// (doesn't look like it, but it works)
lowerCacheRef->ref_count = upperCacheRef->ref_count;
upperCacheRef->ref_count = 1;
@ -1400,10 +1406,11 @@ vm_copy_on_write_area(vm_area *area)
map = &area->aspace->translation_map;
map->ops->lock(map);
map->ops->unmap(map, area->base, area->base + area->size - 1);
map->ops->unmap(map, area->base, area->base - 1 + area->size);
for (page = lowerCache->page_list; page; page = page->cache_next) {
map->ops->map(map, area->base + page->offset, page->ppn * B_PAGE_SIZE, protection);
map->ops->map(map, area->base + (page->offset - area->cache_offset),
page->ppn * B_PAGE_SIZE, protection);
}
map->ops->unlock(map);
@ -1429,9 +1436,14 @@ vm_copy_area(aspace_id addressSpaceID, const char *name, void **_address, uint32
vm_cache_ref *cacheRef;
vm_area *target, *source;
status_t status;
bool writableCopy = (protection & (B_KERNEL_WRITE_AREA | B_WRITE_AREA)) != 0;
if ((protection & B_KERNEL_PROTECTION) == 0)
protection |= B_KERNEL_READ_AREA | B_KERNEL_WRITE_AREA;
if ((protection & B_KERNEL_PROTECTION) == 0) {
// set the same protection for the kernel as for userland
protection |= B_KERNEL_READ_AREA;
if (writableCopy)
protection |= B_KERNEL_WRITE_AREA;
}
if ((source = vm_get_area(sourceID)) == NULL)
return B_BAD_VALUE;
@ -1448,7 +1460,7 @@ vm_copy_area(aspace_id addressSpaceID, const char *name, void **_address, uint32
status = map_backing_store(addressSpace, cacheRef->cache->store, _address,
source->cache_offset, source->size, addressSpec, source->wiring, protection,
protection & (B_KERNEL_WRITE_AREA | B_WRITE_AREA) ? REGION_PRIVATE_MAP : REGION_NO_PRIVATE_MAP,
writableCopy ? REGION_PRIVATE_MAP : REGION_NO_PRIVATE_MAP,
&target, name);
if (status < B_OK)
@ -1456,8 +1468,11 @@ vm_copy_area(aspace_id addressSpaceID, const char *name, void **_address, uint32
// If the source area is writable, we need to move it one layer up as well
if ((source->protection & (B_KERNEL_WRITE_AREA | B_WRITE_AREA)) != 0)
vm_copy_on_write_area(source);
if ((source->protection & (B_KERNEL_WRITE_AREA | B_WRITE_AREA)) != 0) {
// ToDo: do something more useful if this fails!
if (vm_copy_on_write_area(source) < B_OK)
panic("vm_copy_on_write_area() failed!\n");
}
// we want to return the ID of the newly created area
status = target->id;