CFI: Add diagnostic information to likely CFI violation stack traces.

If CFI enforcement is enabled and we receive a SIGILL, it is most likely
that a CFI check failed. Add a reference to the CFI documentation to the
stack trace to make it easier to identify and investigate CFI violations.

Also add an end marker to stack traces to make it easier for automated
tools to extract stack traces.

BUG=464797
R=thakis@chromium.org

Review URL: https://codereview.chromium.org/1267423002

Cr-Commit-Position: refs/heads/master@{#342246}

1 files changed, 13 insertions, 0 deletions

diff --git a/base/debug/stack_trace_posix.cc b/base/debug/stack_trace_posix.cc
index 9593962..dbbec36 100644
--- a/base/debug/stack_trace_posix.cc
+++ b/base/debug/stack_trace_posix.cc
@@ -281,6 +281,16 @@ void StackDumpSignalHandler(int signal, siginfo_t* info, void* void_context) {
   }
   PrintToStderr("\n");
 
+#if defined(CFI_ENFORCEMENT)
+  if (signal == SIGILL && info->si_code == ILL_ILLOPN) {
+    PrintToStderr(
+        "CFI: Most likely a control flow integrity violation; for more "
+        "information see:\n");
+    PrintToStderr(
+        "https://www.chromium.org/developers/testing/control-flow-integrity\n");
+  }
+#endif
+
   debug::StackTrace().Print();
 
 #if defined(OS_LINUX)
@@ -395,6 +405,9 @@ void StackDumpSignalHandler(int signal, siginfo_t* info, void* void_context) {
   write(STDERR_FILENO, buf, std::min(len, sizeof(buf) - 1));
 #endif  // ARCH_CPU_32_BITS
 #endif  // defined(OS_MACOSX)
+
+  PrintToStderr("[end of stack trace]\n");
+
   _exit(1);
 }