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[asan] Fix comparison in BufferedStackTrace::LocatePcInTrace 

Summary:
Debug builds can have larger distance between stack trace and PC on that stack.
If we assume that PC is always correct we can snap it to the nearest trace.

Reviewers: eugenis

Subscribers: llvm-commits, kubabrecka

Differential Revision: https://reviews.llvm.org/D28342

llvm-svn: 291173
This commit is contained in:
Vitaly Buka 2017-01-05 21:04:47 +00:00
parent 83963995c6
commit 006aaaf59c
1 changed files with 6 additions and 11 deletions
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17
compiler-rt/lib/sanitizer_common/sanitizer_stacktrace.cc
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@ -106,10 +106,6 @@ void BufferedStackTrace::FastUnwindStack(uptr pc, uptr bp, uptr stack_top,
}
}
static bool MatchPc(uptr cur_pc, uptr trace_pc, uptr threshold) {
return cur_pc - trace_pc <= threshold || trace_pc - cur_pc <= threshold;
}
void BufferedStackTrace::PopStackFrames(uptr count) {
CHECK_LT(count, size);
size -= count;
@ -118,15 +114,14 @@ void BufferedStackTrace::PopStackFrames(uptr count) {
}
}
static uptr Distance(uptr a, uptr b) { return a < b ? b - a : a - b; }
uptr BufferedStackTrace::LocatePcInTrace(uptr pc) {
// Use threshold to find PC in stack trace, as PC we want to unwind from may
// slightly differ from return address in the actual unwinded stack trace.
const int kPcThreshold = 350;
for (uptr i = 0; i < size; ++i) {
if (MatchPc(pc, trace[i], kPcThreshold))
return i;
uptr best = 0;
for (uptr i = 1; i < size; ++i) {
if (Distance(trace[i], pc) < Distance(trace[best], pc)) best = i;
}
return 0;
return best;
}
} // namespace __sanitizer