Link stack frames of JNI stubs to JNI callbacks.

base/debug/stack_trace.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_DEBUG_STACK_TRACE_H_
 #define BASE_DEBUG_STACK_TRACE_H_
 
 #include <stddef.h>
 
 #include <iosfwd>
 #include <string>
 
 #include "base/base_export.h"
+#include "base/macros.h"
 #include "build/build_config.h"
 
 #if defined(OS_POSIX)
 #include <unistd.h>
 #endif
 
 #if defined(OS_WIN)
 struct _EXCEPTION_POINTERS;
 struct _CONTEXT;
 #endif
@@ skipping 82 matching lines @@
 // reliable than StackTrace. It should work for debug and profiling builds,
 // but not for release builds (although there are some exceptions).
 //
 // Writes at most |max_depth| frames (instruction pointers) into |out_trace|
 // after skipping |skip_initial| frames. Note that the function itself is not
 // added to the trace so |skip_initial| should be 0 in most cases.
 // Returns number of frames written.
 BASE_EXPORT size_t TraceStackFramePointers(const void** out_trace,
                                            size_t max_depth,
                                            size_t skip_initial);
+
+// Links stack frame |fp| to |parent_fp|, so that during stack unwinding
+// TraceStackFramePointers() visits |parent_fp| after visiting |fp|.
+// Both frame pointers must come from __builtin_frame_address().

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

+0 (i.e. __builtin_frame_address(0))

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

Not necessarily, if __builtin_frame_address(7) works on your platform, you can
as well use it.

+// Destructor restores original linkage of |fp| to avoid corrupting caller's
+// frame register on return.
+//
+// This class can be used to repair broken stack frame chain in cases
+// when execution flow goes into code built without frame pointers:
+//
+// void DoWork() {
+//   CallJava();
+// }
+// static __thread void*  g_saved_fp;
+// void CallJava() {
+//   g_saved_fp = __builtin_frame_address(0);
+//   JNI->Call(...); // indirectly calls JavaCallback()
+// }
+// void JavaCallback() {
+//   ScopedStackFrameLinker linker(__builtin_frame_address(0), g_saved_fp);
+//   ...
+//   TraceStackFramePointers(...);
+// }
+//
+// This produces the following trace:
+//
+// #0 JavaCallback()
+// #1 <address of the code inside JVM that called JavaCallback>
+// #2 DoWork()
+// ...rest of the trace...
+//
+// JVM doesn't use frame pointers, so when JavaCallback() is called back by

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

Honestly I think that these lines of comment (148-154) belong to jni_android

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

The fact that JNI is used in explanation how ScopedStackFrameLinker works is
just a coincidence, I'll reword it to use 'Some Library' instead.

+// JVM, stack frame register contains bogus value that becomes JavaCallback's
+// parent frame address. Without LinkStackFrames() unwinding would've stopped
+// at that bogus frame address yielding just two first frames (#0 and #1).
+// LinkStackFrames() overwrites JavaCallback's parent frame address with
+// CallJava's frame, so unwinder produces full trace without even noticing
+// that stack frame chain was broken.
+class BASE_EXPORT ScopedStackFrameLinker {
+ public:
+  ScopedStackFrameLinker(void* fp, void* parent_fp);
+  ~ScopedStackFrameLinker();
+ private:

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

nit \n here and below (before disallow)

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

Done.

+  void* fp_;
+  void* original_parent_fp_;
+  DISALLOW_COPY_AND_ASSIGN(ScopedStackFrameLinker);
+};
+
 #endif  // HAVE_TRACE_STACK_FRAME_POINTERS
 
 namespace internal {
 
 #if defined(OS_POSIX) && !defined(OS_ANDROID)
 // POSIX doesn't define any async-signal safe function for converting
 // an integer to ASCII. We'll have to define our own version.
 // itoa_r() converts a (signed) integer to ASCII. It returns "buf", if the
 // conversion was successful or NULL otherwise. It never writes more than "sz"
 // bytes. Output will be truncated as needed, and a NUL character is always
 // appended.
 BASE_EXPORT char *itoa_r(intptr_t i,
                          char *buf,
                          size_t sz,
                          int base,
                          size_t padding);
 #endif  // defined(OS_POSIX) && !defined(OS_ANDROID)
 
 }  // namespace internal
 
 }  // namespace debug
 }  // namespace base
 
 #endif  // BASE_DEBUG_STACK_TRACE_H_