Link stack frames of JNI stubs to JNI callbacks.

base/android/jni_android.h

Index: base/android/jni_android.h
diff --git a/base/android/jni_android.h b/base/android/jni_android.h
index 909e3daf7a303d0d3ed52275fb96e8a63725dd31..3030f112094d6e554261736999e833969259b30f 100644
--- a/base/android/jni_android.h
+++ b/base/android/jni_android.h
@@ -14,6 +14,41 @@
 #include "base/atomicops.h"
 #include "base/base_export.h"
 #include "base/compiler_specific.h"
+#include "base/debug/stack_trace.h"
+#include "base/macros.h"
+
+#if HAVE_TRACE_STACK_FRAME_POINTERS
+
+// When profiling is enabled (enable_profiling=true) this macro is added to
+// all generated JNI stubs so that it becomes the last thing that runs before
+// control goes into Java.
+//
+// This macro saves stack frame pointer of the current function. Saved value
+// used later by JNI_PROFILING_ENTERED_NATIVE.
+#define JNI_PROFILING_LEAVING_NATIVE \

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

I'd just call these JNI_SAVE_FRAME_POINTER and JNI_LINK_SAVED_FRAME_POINTER to
remove this naming-layer-hopping you force readers to go to.
Concretely, right now when I look at the JNI generator and I see LEAVING_NATIVE
I have to remember that this is  the place where you save and the other is where
you restore.
In few words: don't generalize concepts unless you really need to. Direct names
are way easier to follow.

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

Done.

+  base::android::JNIStackFrameSaver jni_frame_saver( \
+      __builtin_frame_address(0))
+
+// When profiling is enabled (enable_profiling=true) this macro is added to
+// all generated JNI callbacks so that it becomes the first thing that runs
+// after control returns from Java.
+//
+// This macro links stack frame of the current function to the stack frame
+// saved by JNI_PROFILING_LEAVING_NATIVE, allowing frame-based unwinding
+// (used by the heap profiler) to produce complete traces.
+#define JNI_PROFILING_ENTERED_NATIVE \
+  base::debug::ScopedStackFrameLinker jni_frame_linker( \
+      __builtin_frame_address(0), \
+      base::android::JNIStackFrameSaver::SavedFrame())
+
+
+#else
+
+// Frame-based stack unwinding is not supported, do nothing.
+#define JNI_PROFILING_LEAVING_NATIVE
+#define JNI_PROFILING_ENTERED_NATIVE
+
+#endif  // HAVE_TRACE_STACK_FRAME_POINTERS
 
 namespace base {
 namespace android {
@@ -122,6 +157,22 @@ BASE_EXPORT void CheckException(JNIEnv* env);
 BASE_EXPORT std::string GetJavaExceptionInfo(JNIEnv* env,
                                              jthrowable java_throwable);
 
+#if HAVE_TRACE_STACK_FRAME_POINTERS
+
+// Saves caller's PC and stack frame in a thread-local variable.
+// Implemented only when profiling is enabled (enable_profiling=true).
+class BASE_EXPORT JNIStackFrameSaver {
+ public:
+  JNIStackFrameSaver(void* current_fp);
+  ~JNIStackFrameSaver();
+  static void* SavedFrame();

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

s/SavedFrame/GetLastFrameSavedForCurrentThread()/

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

This feels unnecessarily long. I think we should either rename the class to
something like ScopedJNIPerThreadStackFrameSaver and leave SavedFrame() as is,
or just leave all those details to the class comment, as they are now.

+ private:

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

micro-nit: add \n after private:

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

Done.

+  void* previous_fp_;
+  DISALLOW_COPY_AND_ASSIGN(JNIStackFrameSaver);

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

micro-nit: add extra \n before DISALLOW

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

Done.

+};
+
+#endif  // HAVE_TRACE_STACK_FRAME_POINTERS
+
 }  // namespace android
 }  // namespace base