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Adding a comment to explain r273886 ("Stop unwinding the stack when a close-to-zero PC is found"). NFC. 

llvm-svn: 274010
This commit is contained in:
Kuba Brecka 2016-06-28 12:53:20 +00:00
parent 248cfb9752
commit cdf257f4d8
2 changed files with 6 additions and 0 deletions
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3
compiler-rt/lib/sanitizer_common/sanitizer_stacktrace.cc
View File

@ -93,6 +93,9 @@ void BufferedStackTrace::FastUnwindStack(uptr pc, uptr bp, uptr stack_top,
#else
uhwptr pc1 = frame[1];
#endif
// Let's assume that any pointer in the 0th page (i.e. <0x1000 on i386 and
// x86_64) is invalid and stop unwinding here. If we're adding support for
// a platform where this isn't true, we need to reconsider this check.
if (pc1 < kPageSize)
break;
if (pc1 != pc) {

3
compiler-rt/lib/sanitizer_common/sanitizer_unwind_linux_libcdep.cc
View File

@ -109,6 +109,9 @@ _Unwind_Reason_Code Unwind_Trace(struct _Unwind_Context *ctx, void *param) {
CHECK_LT(arg->stack->size, arg->max_depth);
uptr pc = Unwind_GetIP(ctx);
const uptr kPageSize = GetPageSizeCached();
// Let's assume that any pointer in the 0th page (i.e. <0x1000 on i386 and
// x86_64) is invalid and stop unwinding here. If we're adding support for
// a platform where this isn't true, we need to reconsider this check.
if (pc < kPageSize) return UNWIND_STOP;
arg->stack->trace_buffer[arg->stack->size++] = pc;
if (arg->stack->size == arg->max_depth) return UNWIND_STOP;