Revert "[libFuzzer] always install signal handler with SA_ONSTACK" #153114
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…vm#147422)" This reverts commit aee4f2b.
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@llvm/pr-subscribers-compiler-rt-sanitizer Author: Keith Randall (randall77) ChangesReverts llvm/llvm-project#147422 Seems to be causing problems with tracebacks. Probably the trackback code doesn't know how to switch back to the regular stack after it gets to the top of the signal stack. Full diff: https://github.com/llvm/llvm-project/pull/153114.diff 1 Files Affected:
diff --git a/compiler-rt/lib/fuzzer/FuzzerUtilPosix.cpp b/compiler-rt/lib/fuzzer/FuzzerUtilPosix.cpp
index b1bb1387876e0..ae22ecf108420 100644
--- a/compiler-rt/lib/fuzzer/FuzzerUtilPosix.cpp
+++ b/compiler-rt/lib/fuzzer/FuzzerUtilPosix.cpp
@@ -78,14 +78,10 @@ static void SetSigaction(int signum,
}
struct sigaction new_sigact = {};
- // SA_ONSTACK is required for certain runtimes that use small stacks, for
- // instance the Go runtime.
- // See https://github.com/golang/go/issues/49075
- // Address sanitizer also wants SA_ONSTACK, and the fuzzer and sanitizer
- // often run together.
- // SA_ONSTACK is a no-op unless someone also calls sigaltstack. That is left
- // up to code that needs it.
- new_sigact.sa_flags = SA_SIGINFO | SA_ONSTACK;
+ // Address sanitizer needs SA_ONSTACK (causing the signal handler to run on a
+ // dedicated stack) in order to be able to detect stack overflows; keep the
+ // flag if it's set.
+ new_sigact.sa_flags = SA_SIGINFO | (sigact.sa_flags & SA_ONSTACK);
new_sigact.sa_sigaction = callback;
if (sigaction(signum, &new_sigact, nullptr)) {
Printf("libFuzzer: sigaction failed with %d\n", errno);
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vitalybuka
approved these changes
Aug 12, 2025
wrotki
approved these changes
Aug 12, 2025
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I asked for this revert, will merge on behalf of @randall77
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Reverts #147422
Seems to be causing problems with tracebacks. Probably the trackback code doesn't know how to switch back to the regular stack after it gets to the top of the signal stack.