[compiler-rt] fa27255 - [sanitizer] Fall back to fast unwinder

[Fangrui Song via llvm-commits]

Author: Fangrui Song
Date: 2021-05-14T12:27:33-07:00
New Revision: fa27255d16c322e2d09b5fe05d2b569634f0fb6f

URL: https://github.com/llvm/llvm-project/commit/fa27255d16c322e2d09b5fe05d2b569634f0fb6f
DIFF: https://github.com/llvm/llvm-project/commit/fa27255d16c322e2d09b5fe05d2b569634f0fb6f.diff

LOG: [sanitizer] Fall back to fast unwinder

`-fno-exceptions -fno-asynchronous-unwind-tables` compiled programs don't
produce .eh_frame on Linux and other ELF platforms, so the slow unwinder cannot
print stack traces. Just fall back to the fast unwinder: this allows
-fno-asynchronous-unwind-tables without requiring the sanitizer option
`fast_unwind_on_fatal=1`

Reviewed By: #sanitizers, vitalybuka

Differential Revision: https://reviews.llvm.org/D102046

Added: 
    compiler-rt/test/sanitizer_common/TestCases/Linux/symbolize_stack_fp.cpp

Modified: 
    compiler-rt/lib/sanitizer_common/sanitizer_stacktrace_libcdep.cpp

Removed: 
    


################################################################################
diff  --git a/compiler-rt/lib/sanitizer_common/sanitizer_stacktrace_libcdep.cpp b/compiler-rt/lib/sanitizer_common/sanitizer_stacktrace_libcdep.cpp
index 738633209f08..a9222e001555 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_stacktrace_libcdep.cpp
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_stacktrace_libcdep.cpp
@@ -82,12 +82,15 @@ void BufferedStackTrace::Unwind(u32 max_depth, uptr pc, uptr bp, void *context,
       UnwindSlow(pc, context, max_depth);
     else
       UnwindSlow(pc, max_depth);
+    // If there are too few frames, the program may be built with
+    // -fno-asynchronous-unwind-tables. Fall back to fast unwinder below.
+    if (size > 2)
+      return;
 #else
     UNREACHABLE("slow unwind requested but not available");
 #endif
-  } else {
-    UnwindFast(pc, bp, stack_top, stack_bottom, max_depth);
   }
+  UnwindFast(pc, bp, stack_top, stack_bottom, max_depth);
 }
 
 static int GetModuleAndOffsetForPc(uptr pc, char *module_name,

diff  --git a/compiler-rt/test/sanitizer_common/TestCases/Linux/symbolize_stack_fp.cpp b/compiler-rt/test/sanitizer_common/TestCases/Linux/symbolize_stack_fp.cpp
new file mode 100644
index 000000000000..204adb52902e
--- /dev/null
+++ b/compiler-rt/test/sanitizer_common/TestCases/Linux/symbolize_stack_fp.cpp
@@ -0,0 +1,35 @@
+/// When the main program doesn't use .eh_frame, the slow unwinder does not work.
+/// Test that we can fall back to the fast unwinder.
+// RUN: %clangxx -O0 -g1 -fno-exceptions -fno-unwind-tables -fno-asynchronous-unwind-tables -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer %s -o %t
+// RUN: llvm-readelf -S %t | FileCheck %s --check-prefix=SEC
+// RUN: %run %t 2>&1 | FileCheck %s
+
+/// No .eh_frame && -g => .debug_frame
+// SEC: .debug_frame
+
+#include <sanitizer/common_interface_defs.h>
+#include <vector>
+
+template <int N>
+struct A {
+  template <class T>
+  void RecursiveTemplateFunction(const T &t);
+};
+
+template <int N>
+template <class T>
+__attribute__((noinline)) void A<N>::RecursiveTemplateFunction(const T &) {
+  std::vector<T> t;
+  return A<N - 1>().RecursiveTemplateFunction(t);
+}
+
+template <>
+template <class T>
+__attribute__((noinline)) void A<0>::RecursiveTemplateFunction(const T &) {
+  __sanitizer_print_stack_trace();
+}
+
+int main() {
+  // CHECK: {{vector<.*vector<.*vector<.*vector<.*vector<}}
+  A<10>().RecursiveTemplateFunction(0);
+}