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Check that the page which is freed as zeroed, indeed has all-zero content.

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This catches some rare mysterious failures at the source.  The check
is only performed on architectures which implement direct map, and
only enabled with option DIAGNOSTIC, similar to other costly
consistency checks.

Reviewed by:	alc, markj
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
This commit is contained in:
Konstantin Belousov 2017-10-21 17:28:12 +00:00
parent 09fdf1f84c
commit 422fe502b3
1 changed files with 10 additions and 0 deletions
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10
sys/vm/vm_page.c
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@ -2780,6 +2780,16 @@ bool
vm_page_free_prep(vm_page_t m, bool pagequeue_locked)
{
#if defined(DIAGNOSTIC) && defined(PHYS_TO_DMAP)
if ((m->flags & PG_ZERO) != 0) {
uint64_t *p;
int i;
p = (uint64_t *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(m));
for (i = 0; i < PAGE_SIZE / sizeof(uint64_t); i++, p++)
KASSERT(*p == 0, ("vm_page_free_prep %p PG_ZERO %d %jx",
m, i, (uintmax_t)*p));
}
#endif
if ((m->oflags & VPO_UNMANAGED) == 0) {
vm_page_lock_assert(m, MA_OWNED);
KASSERT(!pmap_page_is_mapped(m),