Author: nwhitehorn
Date: Sun Dec 1 17:28:28 2013
New Revision: 258800
URL: http://svnweb.freebsd.org/changeset/base/258800
Log:
The kernel stack guard pages are only below the stack pointer, not above.
Prevent erroneous detection of stack overflows on legitimate faults on the
page after this thread's stack.
MFC after: 3 days
Modified:
head/sys/powerpc/aim/trap_subr32.S
head/sys/powerpc/aim/trap_subr64.S
Modified: head/sys/powerpc/aim/trap_subr32.S
==============================================================================
--- head/sys/powerpc/aim/trap_subr32.S Sun Dec 1 17:00:57 2013
(r258799)
+++ head/sys/powerpc/aim/trap_subr32.S Sun Dec 1 17:28:28 2013
(r258800)
@@ -664,11 +664,12 @@ disitrap:
stw %r31,(PC_TEMPSAVE+CPUSAVE_AIM_DSISR)(%r1)
#ifdef KDB
- /* Try and detect a kernel stack overflow */
+ /* Try to detect a kernel stack overflow */
mfsrr1 %r31
mtcr %r31
bt 17,realtrap /* branch is user mode */
mfsprg1 %r31 /* get old SP */
+ clrrwi %r31,%r31,11 /* Round SP down to nearest page */
sub. %r30,%r31,%r30 /* SP - DAR */
bge 1f
neg %r30,%r30 /* modulo value */
Modified: head/sys/powerpc/aim/trap_subr64.S
==============================================================================
--- head/sys/powerpc/aim/trap_subr64.S Sun Dec 1 17:00:57 2013
(r258799)
+++ head/sys/powerpc/aim/trap_subr64.S Sun Dec 1 17:28:28 2013
(r258800)
@@ -569,11 +569,12 @@ disitrap:
std %r31,(PC_TEMPSAVE+CPUSAVE_AIM_DSISR)(%r1)
#ifdef KDB
- /* Try and detect a kernel stack overflow */
+ /* Try to detect a kernel stack overflow */
mfsrr1 %r31
mtcr %r31
bt 17,realtrap /* branch is user mode */
mfsprg1 %r31 /* get old SP */
+ clrrdi %r31,%r31,11 /* Round SP down to nearest page */
sub. %r30,%r31,%r30 /* SP - DAR */
bge 1f
neg %r30,%r30 /* modulo value */
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