Author: kib
Date: Sat Oct 21 17:28:12 2017
New Revision: 324824
URL: https://svnweb.freebsd.org/changeset/base/324824
Log:
Check that the page which is freed as zeroed, indeed has all-zero content.
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
Modified:
head/sys/vm/vm_page.c
Modified: head/sys/vm/vm_page.c
==============================================================================
--- head/sys/vm/vm_page.c Sat Oct 21 16:55:52 2017 (r324823)
+++ head/sys/vm/vm_page.c Sat Oct 21 17:28:12 2017 (r324824)
@@ -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),
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