Fix stack walking to notice if the frame is obviously not valid.

base/debug/stack_trace.cc

Index: base/debug/stack_trace.cc
diff --git a/base/debug/stack_trace.cc b/base/debug/stack_trace.cc
index 94ff7d0755ab50a650ebcee9dfbe05ab287972b2..6c3940456e9f79969fd16ddf4a93af4cdd4307ea 100644
--- a/base/debug/stack_trace.cc
+++ b/base/debug/stack_trace.cc
@@ -111,12 +111,13 @@ bool IsStackFrameValid(uintptr_t fp, uintptr_t prev_fp, uintptr_t stack_end) {
   // Check alignment.
   if (fp & (sizeof(uintptr_t) - 1)) return false;
 
+  // A PC that is too small means we've gone off the end of the stack.
+  if (GetStackFramePC(fp) < 32768)

[Mark Mentovai, 2017/02/15 21:05:57]

You could go even bigger. On x86_64, you’ll generally have a tremendous
pagezero. macOS’ default __PAGEZERO is 1 << 32, for example. But I guess that
most things that wind up looking like they’re running from code down here are
going to be at smallish addresses, so the existing 32k is fine.

[erikchen, 2017/02/15 21:52:45]

Also, this is run on all plaforms.

[Wez, 2017/02/15 22:38:22]

Maybe use a kConstant here, so we can define it to a suitable value on a
per-platform basis easily in future?

[erikchen, 2017/02/15 22:52:24]

Done.

+    return false;
+
   if (stack_end) {
     // Both fp[0] and fp[1] must be within the stack.
     if (fp > stack_end - 2 * sizeof(uintptr_t)) return false;
-
-    // Additional check to filter out false positives.
-    if (GetStackFramePC(fp) < 32768) return false;
   }
 
   return true;