Index: base/debug/stack_trace.h |
diff --git a/base/debug/stack_trace.h b/base/debug/stack_trace.h |
index 23e7b5164b63472409a92e992c5c1095dfa48d26..13287247a2807997bbce1f66e08bef5440bd1dbf 100644 |
--- a/base/debug/stack_trace.h |
+++ b/base/debug/stack_trace.h |
@@ -11,6 +11,7 @@ |
#include <string> |
#include "base/base_export.h" |
+#include "base/macros.h" |
#include "build/build_config.h" |
#if defined(OS_POSIX) |
@@ -113,6 +114,54 @@ class BASE_EXPORT StackTrace { |
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) wor
|
+// 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-
Dmitry Skiba
2016/10/17 22:09:11
The fact that JNI is used in explanation how Scope
|
+// 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 { |