1 files changed, 34 insertions, 15 deletions
diff --git a/compiler-rt/lib/gwp_asan/optional/backtrace_sanitizer_common.cpp b/compiler-rt/lib/gwp_asan/optional/backtrace_sanitizer_common.cpp
index 3ac4b52bfc27..e6cce86e3b7b 100644
--- a/compiler-rt/lib/gwp_asan/optional/backtrace_sanitizer_common.cpp
+++ b/compiler-rt/lib/gwp_asan/optional/backtrace_sanitizer_common.cpp
@@ -22,30 +22,47 @@ void __sanitizer::BufferedStackTrace::UnwindImpl(uptr pc, uptr bp,
                                                  void *context,
                                                  bool request_fast,
                                                  u32 max_depth) {
-  if (!StackTrace::WillUseFastUnwind(request_fast)) {
-    return Unwind(max_depth, pc, bp, context, 0, 0, request_fast);
-  }
-  Unwind(max_depth, pc, 0, context, 0, 0, false);
+  if (!StackTrace::WillUseFastUnwind(request_fast))
+    return Unwind(max_depth, pc, 0, context, 0, 0, false);
+
+  uptr top = 0;
+  uptr bottom = 0;
+  GetThreadStackTopAndBottom(/*at_initialization*/ false, &top, &bottom);
+
+  return Unwind(max_depth, pc, bp, context, top, bottom, request_fast);
 }
 
 namespace {
-size_t Backtrace(uintptr_t *TraceBuffer, size_t Size) {
+size_t BacktraceCommon(uintptr_t *TraceBuffer, size_t Size, void *Context) {
+  // Use the slow sanitizer unwinder in the segv handler. Fast frame pointer
+  // unwinders can end up dropping frames because the kernel sigreturn() frame's
+  // return address is the return address at time of fault. This has the result
+  // of never actually capturing the PC where the signal was raised.
+  bool UseFastUnwind = (Context == nullptr);
+
   __sanitizer::BufferedStackTrace Trace;
   Trace.Reset();
   if (Size > __sanitizer::kStackTraceMax)
     Size = __sanitizer::kStackTraceMax;
 
   Trace.Unwind((__sanitizer::uptr)__builtin_return_address(0),
-               (__sanitizer::uptr)__builtin_frame_address(0),
-               /* ucontext */ nullptr,
-               /* fast unwind */ true, Size - 1);
+               (__sanitizer::uptr)__builtin_frame_address(0), Context,
+               UseFastUnwind, Size - 1);
 
   memcpy(TraceBuffer, Trace.trace, Trace.size * sizeof(uintptr_t));
   return Trace.size;
 }
 
+size_t Backtrace(uintptr_t *TraceBuffer, size_t Size) {
+  return BacktraceCommon(TraceBuffer, Size, nullptr);
+}
+
+size_t SegvBacktrace(uintptr_t *TraceBuffer, size_t Size, void *Context) {
+  return BacktraceCommon(TraceBuffer, Size, Context);
+}
+
 static void PrintBacktrace(uintptr_t *Trace, size_t TraceLength,
-                           gwp_asan::crash_handler::Printf_t Printf) {
+                           gwp_asan::Printf_t Printf) {
   __sanitizer::StackTrace StackTrace;
   StackTrace.trace = reinterpret_cast<__sanitizer::uptr *>(Trace);
   StackTrace.size = TraceLength;
@@ -60,21 +77,23 @@ static void PrintBacktrace(uintptr_t *Trace, size_t TraceLength,
 } // anonymous namespace
 
 namespace gwp_asan {
-namespace options {
+namespace backtrace {
+
 // This function is thread-compatible. It must be synchronised in respect to any
 // other calls to getBacktraceFunction(), calls to getPrintBacktraceFunction(),
 // and calls to either of the functions that they return. Furthermore, this may
 // require synchronisation with any calls to sanitizer_common that use flags.
 // Generally, this function will be called during the initialisation of the
 // allocator, which is done in a thread-compatible manner.
-Backtrace_t getBacktraceFunction() {
+options::Backtrace_t getBacktraceFunction() {
   // The unwinder requires the default flags to be set.
   __sanitizer::SetCommonFlagsDefaults();
   __sanitizer::InitializeCommonFlags();
   return Backtrace;
 }
-crash_handler::PrintBacktrace_t getPrintBacktraceFunction() {
-  return PrintBacktrace;
-}
-} // namespace options
+
+PrintBacktrace_t getPrintBacktraceFunction() { return PrintBacktrace; }
+SegvBacktrace_t getSegvBacktraceFunction() { return SegvBacktrace; }
+
+} // namespace backtrace
 } // namespace gwp_asan