commit ac2f3dd5cbea96a2a101791b6808b9437382e184
author Christopher Ferris <cferris@google.com> Wed Mar 22 19:05:50 2017 -0700
committer Christopher Ferris <cferris@google.com> Thu Mar 23 09:45:10 2017 -0700
tree 9c4fdb51a506261e21373106590df93516dc0826
parent 4d099d1576105faa53b58097b4f816231f676431

Verify at least 2 frames out of signal handler.

Modify the test slightly to make sure that the unwinder properly unwinds
through at least 2 frames outside of the signal handler. This guarantees
that if the first frame outside of the handler happens to be garbage,
this test will fail.

Bug: 34468756

Test: Ran the unit tests on fugu, angler (both 32 bit and 64 bit).
Change-Id: I6b76ac9fc1df9ed6fd5bbcc6f5fa4bf458354dff

tests/stack_unwinding_test.cpp

diff --git a/tests/stack_unwinding_test.cpp b/tests/stack_unwinding_test.cpp
index afd9e7f..bb58ae4 100644
--- a/tests/stack_unwinding_test.cpp
+++ b/tests/stack_unwinding_test.cpp
@@ -90,15 +90,20 @@
 }
 
 static void verify_unwind_data(const UnwindData& unwind_data) {
-  EXPECT_GT(unwind_data.handler_frame_count, unwind_data.expected_frame_count);
+  // In order to avoid a false positive, the caller must have at least 2 frames
+  // outside of the signal handler. This avoids a case where the only frame
+  // right after the signal handler winds up being garbage.
+  EXPECT_GT(unwind_data.handler_frame_count, unwind_data.expected_frame_count + 1);
+
   EXPECT_EQ(unwind_data.handler_frame_count + 1, unwind_data.handler_one_deeper_frame_count);
 }
 
-TEST(stack_unwinding, unwind_through_signal_frame) {
+static void noinline UnwindTest() {
   g_unwind_data = {};
-  ScopedSignalHandler ssh(SIGUSR1, UnwindSignalHandler);
 
   _Unwind_Backtrace(FrameCounter, &g_unwind_data.expected_frame_count);
+  ASSERT_LE(2, g_unwind_data.expected_frame_count)
+      << "The current call must contain at least 2 frames for the test to be valid.";
 
   ASSERT_EQ(0, kill(getpid(), SIGUSR1));
   while (!g_unwind_data.signal_handler_complete) {}
@@ -106,14 +111,15 @@
   verify_unwind_data(g_unwind_data);
 }
 
+TEST(stack_unwinding, unwind_through_signal_frame) {
+  ScopedSignalHandler ssh(SIGUSR1, UnwindSignalHandler);
+
+  UnwindTest();
+}
+
 // On LP32, the SA_SIGINFO flag gets you __restore_rt instead of __restore.
 TEST(stack_unwinding, unwind_through_signal_frame_SA_SIGINFO) {
-  g_unwind_data = {};
   ScopedSignalHandler ssh(SIGUSR1, UnwindSignalHandler, SA_SIGINFO);
 
-  _Unwind_Backtrace(FrameCounter, &g_unwind_data.expected_frame_count);
-  ASSERT_EQ(0, kill(getpid(), SIGUSR1));
-  while (!g_unwind_data.signal_handler_complete) {}
-
-  verify_unwind_data(g_unwind_data);
+  UnwindTest();
 }