[compiler-rt] r273886 - [sanitizer] Stop unwinding the stack when a close-to-zero PC is found

[Kuba Brecka via llvm-commits]

Author: kuba.brecka
Date: Mon Jun 27 10:32:18 2016
New Revision: 273886

URL: http://llvm.org/viewvc/llvm-project?rev=273886&view=rev
Log:
[sanitizer] Stop unwinding the stack when a close-to-zero PC is found

On OS X, we often get stack trace in a report that ends with a 0x0 frame.  To get rid of it, let's trim the stack trace when we find a close-to-zero value, which is obviously not a valid PC.

Differential Revision: http://reviews.llvm.org/D14656


Modified:
    compiler-rt/trunk/lib/sanitizer_common/sanitizer_common.cc
    compiler-rt/trunk/lib/sanitizer_common/sanitizer_common.h
    compiler-rt/trunk/lib/sanitizer_common/sanitizer_stacktrace.cc
    compiler-rt/trunk/lib/sanitizer_common/sanitizer_unwind_linux_libcdep.cc
    compiler-rt/trunk/lib/sanitizer_common/tests/sanitizer_stacktrace_test.cc

Modified: compiler-rt/trunk/lib/sanitizer_common/sanitizer_common.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/sanitizer_common/sanitizer_common.cc?rev=273886&r1=273885&r2=273886&view=diff
==============================================================================
--- compiler-rt/trunk/lib/sanitizer_common/sanitizer_common.cc (original)
+++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_common.cc Mon Jun 27 10:32:18 2016
@@ -25,13 +25,7 @@ namespace __sanitizer {
 const char *SanitizerToolName = "SanitizerTool";
 
 atomic_uint32_t current_verbosity;
-
-uptr GetPageSizeCached() {
-  static uptr PageSize;
-  if (!PageSize)
-    PageSize = GetPageSize();
-  return PageSize;
-}
+uptr PageSizeCached;
 
 StaticSpinMutex report_file_mu;
 ReportFile report_file = {&report_file_mu, kStderrFd, "", "", 0};

Modified: compiler-rt/trunk/lib/sanitizer_common/sanitizer_common.h
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/sanitizer_common/sanitizer_common.h?rev=273886&r1=273885&r2=273886&view=diff
==============================================================================
--- compiler-rt/trunk/lib/sanitizer_common/sanitizer_common.h (original)
+++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_common.h Mon Jun 27 10:32:18 2016
@@ -63,7 +63,12 @@ INLINE int Verbosity() {
 }
 
 uptr GetPageSize();
-uptr GetPageSizeCached();
+extern uptr PageSizeCached;
+INLINE uptr GetPageSizeCached() {
+  if (!PageSizeCached)
+    PageSizeCached = GetPageSize();
+  return PageSizeCached;
+}
 uptr GetMmapGranularity();
 uptr GetMaxVirtualAddress();
 // Threads

Modified: compiler-rt/trunk/lib/sanitizer_common/sanitizer_stacktrace.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/sanitizer_common/sanitizer_stacktrace.cc?rev=273886&r1=273885&r2=273886&view=diff
==============================================================================
--- compiler-rt/trunk/lib/sanitizer_common/sanitizer_stacktrace.cc (original)
+++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_stacktrace.cc Mon Jun 27 10:32:18 2016
@@ -66,6 +66,7 @@ static inline uhwptr *GetCanonicFrame(up
 
 void BufferedStackTrace::FastUnwindStack(uptr pc, uptr bp, uptr stack_top,
                                          uptr stack_bottom, u32 max_depth) {
+  const uptr kPageSize = GetPageSizeCached();
   CHECK_GE(max_depth, 2);
   trace_buffer[0] = pc;
   size = 1;
@@ -92,6 +93,8 @@ void BufferedStackTrace::FastUnwindStack
 #else
     uhwptr pc1 = frame[1];
 #endif
+    if (pc1 < kPageSize)
+      break;
     if (pc1 != pc) {
       trace_buffer[size++] = (uptr) pc1;
     }

Modified: compiler-rt/trunk/lib/sanitizer_common/sanitizer_unwind_linux_libcdep.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/sanitizer_common/sanitizer_unwind_linux_libcdep.cc?rev=273886&r1=273885&r2=273886&view=diff
==============================================================================
--- compiler-rt/trunk/lib/sanitizer_common/sanitizer_unwind_linux_libcdep.cc (original)
+++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_unwind_linux_libcdep.cc Mon Jun 27 10:32:18 2016
@@ -108,6 +108,8 @@ _Unwind_Reason_Code Unwind_Trace(struct
   UnwindTraceArg *arg = (UnwindTraceArg*)param;
   CHECK_LT(arg->stack->size, arg->max_depth);
   uptr pc = Unwind_GetIP(ctx);
+  const uptr kPageSize = GetPageSizeCached();
+  if (pc < kPageSize) return UNWIND_STOP;
   arg->stack->trace_buffer[arg->stack->size++] = pc;
   if (arg->stack->size == arg->max_depth) return UNWIND_STOP;
   return UNWIND_CONTINUE;

Modified: compiler-rt/trunk/lib/sanitizer_common/tests/sanitizer_stacktrace_test.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/sanitizer_common/tests/sanitizer_stacktrace_test.cc?rev=273886&r1=273885&r2=273886&view=diff
==============================================================================
--- compiler-rt/trunk/lib/sanitizer_common/tests/sanitizer_stacktrace_test.cc (original)
+++ compiler-rt/trunk/lib/sanitizer_common/tests/sanitizer_stacktrace_test.cc Mon Jun 27 10:32:18 2016
@@ -136,6 +136,19 @@ TEST_F(FastUnwindTest, FPBelowPrevFP) {
   EXPECT_EQ(PC(1), trace.trace[1]);
 }
 
+TEST_F(FastUnwindTest, CloseToZeroFrame) {
+  // Make one pc a NULL pointer.
+  fake_stack[5] = 0x0;
+  if (!TryFastUnwind(kStackTraceMax))
+    return;
+  // The stack should be truncated at the NULL pointer (and not include it).
+  EXPECT_EQ(3U, trace.size);
+  EXPECT_EQ(start_pc, trace.trace[0]);
+  for (uptr i = 1; i < 3U; i++) {
+    EXPECT_EQ(PC(i*2 - 1), trace.trace[i]);
+  }
+}
+
 TEST(SlowUnwindTest, ShortStackTrace) {
   if (StackTrace::WillUseFastUnwind(false))
     return;