[compiler-rt] Fix/workaround for OS X truncated stacktraces taken by external tools

[kubamracek]

Summary

This patch is a proposed solution for https://code.google.com/p/address-sanitizer/issues/detail?id=375:

When the stacktraces are captured and printed by ASan itself, they are fine, but when the program has already printed the report (or is just printing it), capturing a stacktrace via other means is broken. "Other means" include OS X CrashReporter, debuggers or calling backtrace() within the program. For example calling backtrace() from a sanitizer_set_death_callback function prints a very truncated stacktrace:

0   crashlog-stacktraces.c.tmp          0x000000010fb1c397 death_function + 471
1   libclang_rt.asan_osx_dynamic.dylib  0x000000010fb72c1f _ZN11__sanitizer3DieEv + 15

The same can happen even within lldb (I'm seeing this for 32-bit x86):

(lldb) bt
* thread #1: tid = 0x9ec2d, 0x0000209a crashlog-stacktraces.c.tmp`death_function + 42 at crashlog-stacktraces.c:10, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1
  * frame #0: 0x0000209a crashlog-stacktraces.c.tmp`death_function + 42 at crashlog-stacktraces.c:10
    frame #1: 0x0005eaf6 libclang_rt.asan_osx_dynamic.dylib`__sanitizer::Die() + 22
    frame #2: 0x00058136 libclang_rt.asan_osx_dynamic.dylib`__asan::ScopedInErrorReport::~ScopedInErrorReport() + 102
    frame #3: 0x00057fcf libclang_rt.asan_osx_dynamic.dylib`__asan::ScopedInErrorReport::~ScopedInErrorReport() + 15
    frame #4: 0x00057acc libclang_rt.asan_osx_dynamic.dylib`__asan_report_error + 4204
(lldb)

This patch forces __asan_report_error to always have a stack frame by using the ENABLE_FRAME_POINTER macro, which we are already using elsewhere (asan_mac.cc).

[kubamracek]

Adding the testcase into the patch.

[kubamracek]

Landed in r226878.

lib/asan/asan_mac.cc

   void (^asan_block)(void);  \
   int parent_tid = GetCurrentTidOrInvalid(); \
   asan_block = ^(void) { \
     GET_STACK_TRACE_THREAD; \
     asan_register_worker_thread(parent_tid, &stack); \
     work(); \
   }
 
-// Forces the compiler to generate a frame pointer in the function.
-#define ENABLE_FRAME_POINTER                                       \
-  do {                                                             \
-    volatile uptr enable_fp;                                       \
-    enable_fp = GET_CURRENT_FRAME();                               \
-  } while (0)
-
 INTERCEPTOR(void, dispatch_async,
             dispatch_queue_t dq, void(^work)(void)) {
   ENABLE_FRAME_POINTER;
   GET_ASAN_BLOCK(work);
   REAL(dispatch_async)(dq, asan_block);
 }
 
 INTERCEPTOR(void, dispatch_group_async,

lib/asan/asan_report.cc

 
 }  // namespace __asan
 
 // --------------------------- Interface --------------------- {{{1
 using namespace __asan;  // NOLINT
 
 void __asan_report_error(uptr pc, uptr bp, uptr sp, uptr addr, int is_write,
                          uptr access_size) {
+  ENABLE_FRAME_POINTER;
+  
   // Determine the error type.
   const char *bug_descr = "unknown-crash";
   if (AddrIsInMem(addr)) {
     u8 *shadow_addr = (u8*)MemToShadow(addr);
     // If we are accessing 16 bytes, look at the second shadow byte.
     if (*shadow_addr == 0 && access_size > SHADOW_GRANULARITY)
       shadow_addr++;
     // If we are in the partial right redzone, look at the next shadow byte.

lib/sanitizer_common/sanitizer_internal_defs.h

 #define HANDLE_EINTR(res, f)                                       \
   {                                                                \
     int rverrno;                                                   \
     do {                                                           \
       res = (f);                                                   \
     } while (internal_iserror(res, &rverrno) && rverrno == EINTR); \
   }
 
+// Forces the compiler to generate a frame pointer in the function.
+#define ENABLE_FRAME_POINTER                                       \
+  do {                                                             \
+    volatile uptr enable_fp;                                       \
+    enable_fp = GET_CURRENT_FRAME();                               \
+  } while (0)
+
 #endif  // SANITIZER_DEFS_H

test/asan/TestCases/Darwin/crashlog-stacktraces.c

+// RUN: %clang_asan -O0 %s -o %t
+// RUN: not %run %t 2>&1 | FileCheck %s
+
+#include <execinfo.h>
+#include <sanitizer/common_interface_defs.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+void death_function() {
+  fprintf(stderr, "DEATH CALLBACK\n");
+
+  void* callstack[128];
+  int i, frames = backtrace(callstack, 128);
+  char** strs = backtrace_symbols(callstack, frames);
+  for (i = 0; i < frames; ++i) {
+    fprintf(stderr, "%s\n", strs[i]);
+  }
+  free(strs);
+
+  fprintf(stderr, "END OF BACKTRACE\n");
+}
+
+int fault_function() {
+  char *x = (char*)malloc(10 * sizeof(char));
+  free(x);
+  return x[5];  // BOOM
+}
+
+int main() {
+  __sanitizer_set_death_callback(death_function);
+  fault_function();
+  return 0;
+}
+
+// CHECK: {{.*ERROR: AddressSanitizer: heap-use-after-free on address}}
+// CHECK: {{READ of size 1 at 0x.* thread T0}}
+// CHECK: {{    #0 0x.* in fault_function}}
+
+// CHECK: DEATH CALLBACK
+// CHECK: death_function
+// CHECK: fault_function
+// CHECK: main
+// CHECK: END OF BACKTRACE