[compiler-rt] r243470 - Add commentary explaining PPC access to return address
Bill Schmidt
wschmidt at linux.vnet.ibm.com
Tue Jul 28 13:05:06 PDT 2015
Author: wschmidt
Date: Tue Jul 28 15:05:06 2015
New Revision: 243470
URL: http://llvm.org/viewvc/llvm-project?rev=243470&view=rev
Log:
Add commentary explaining PPC access to return address
Modified:
compiler-rt/trunk/lib/sanitizer_common/sanitizer_stacktrace.cc
Modified: compiler-rt/trunk/lib/sanitizer_common/sanitizer_stacktrace.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/sanitizer_common/sanitizer_stacktrace.cc?rev=243470&r1=243469&r2=243470&view=diff
==============================================================================
--- compiler-rt/trunk/lib/sanitizer_common/sanitizer_stacktrace.cc (original)
+++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_stacktrace.cc Tue Jul 28 15:05:06 2015
@@ -84,6 +84,9 @@ void BufferedStackTrace::FastUnwindStack
IsAligned((uptr)frame, sizeof(*frame)) &&
size < max_depth) {
#ifdef __powerpc__
+ // PowerPC ABIs specify that the return address is saved at offset
+ // 16 of the *caller's* stack frame. Thus we must dereference the
+ // back chain to find the caller frame before extracting it.
uhwptr *caller_frame = (uhwptr*)frame[0];
if (!IsValidFrame((uptr)caller_frame, stack_top, bottom) ||
!IsAligned((uptr)caller_frame, sizeof(uhwptr)))
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