Link stack frames of JNI stubs to JNI callbacks.

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 f3ffef360f0680a8a36cdabc4fa43c5ee1fc390c..8b95a2c17cff1a0249b5faa1818ac91114efc9e9 100644
--- a/base/debug/stack_trace.cc
+++ b/base/debug/stack_trace.cc
@@ -176,6 +176,17 @@ uintptr_t ScanStackForNextFrame(uintptr_t fp, uintptr_t stack_end) {
   return 0;
 }
 
+// Links stack frame |fp| to |parent_fp|, so that during stack unwinding

[Primiano Tucci (use gerrit), 2016/10/13 20:03:21]

I think you commented this already in the .h. Usually that is fine.

[Dmitry Skiba, 2016/10/17 22:09:11]

That was for ScopedStackFrameLinker thing, and I remember you asked earlier what
fp and parent_fp arguments are, so I decided to put comment here too.

+// TraceStackFramePointers() visits |parent_fp| after visiting |fp|.
+// Both frame pointers must come from __builtin_frame_address().
+// Returns previous stack frame |fp| was linked to.
+void* LinkStackFrames(void* fpp, void* parent_fp) {
+  uintptr_t fp = reinterpret_cast<uintptr_t>(fpp) - kStackFrameAdjustment;
+  void* prev_parent_fp = reinterpret_cast<void**>(fp)[0];
+  reinterpret_cast<void**>(fp)[0] = parent_fp;
+  return prev_parent_fp;
+}
+
 #endif  // HAVE_TRACE_STACK_FRAME_POINTERS
 
 }  // namespace
@@ -245,6 +256,13 @@ size_t TraceStackFramePointers(const void** out_trace,
   return depth;
 }
 
+ScopedStackFrameLinker::ScopedStackFrameLinker(void* fp, void* parent_fp)
+  : fp_(fp), original_parent_fp_(LinkStackFrames(fp, parent_fp)) {}
+
+ScopedStackFrameLinker::~ScopedStackFrameLinker() {
+  LinkStackFrames(fp_, original_parent_fp_);

[Primiano Tucci (use gerrit), 2016/10/13 20:03:21]

could you add a CHECK here that verifies that the content of the fp saved on the
stack still matches what you did set in the ctor, before resetting?
If something goes unexpectedly wrong at least we'd fail very fast showing where
the problem is.
I'd make this a CHECK and not a DCHECK beause almost nobody uses debug on
android builds.

[Dmitry Skiba, 2016/10/17 22:09:11]

Done.

+}
+
 #endif  // HAVE_TRACE_STACK_FRAME_POINTERS
 
 }  // namespace debug