Get a backtrace in Chrome for Android.

base/debug/stack_trace_android.cc

Index: base/debug/stack_trace_android.cc
diff --git a/base/debug/stack_trace_android.cc b/base/debug/stack_trace_android.cc
index d71d246da63b68d5c74e910b55590e5ff1217fcb..050a2d8c501904b17e3bee5cf13993fafd639026 100644
--- a/base/debug/stack_trace_android.cc
+++ b/base/debug/stack_trace_android.cc
@@ -7,6 +7,7 @@
 #include <signal.h>
 #include <sys/types.h>
 #include <unistd.h>
+#include <unwind.h>  // TODO(dmikurube): Remove.  See http://crbug.com/236855.
 
 #include "base/logging.h"
 
@@ -15,6 +16,59 @@
 #define SIGSTKFLT SIGSEGV
 #endif
 
+// TODO(dmikurube): Remove when Bionic's get_backtrace() gets popular.
+// See http://crbug.com/236855.
+namespace {
+
+/* depends how the system includes define this */
+#ifdef HAVE_UNWIND_CONTEXT_STRUCT
+typedef struct _Unwind_Context __unwind_context;
+#else
+typedef _Unwind_Context __unwind_context;
+#endif
+
+struct stack_crawl_state_t {
+  uintptr_t* frames;
+  size_t frame_count;
+  size_t max_depth;
+  bool have_skipped_self;
+
+  stack_crawl_state_t(uintptr_t* frames, size_t max_depth)
+      : frames(frames),
+        frame_count(0),
+        max_depth(max_depth),
+        have_skipped_self(false) {
+  }
+};
+
+static _Unwind_Reason_Code tracer(__unwind_context* context, void* arg) {
+  stack_crawl_state_t* state = static_cast<stack_crawl_state_t*>(arg);
+
+#if defined(__clang__)
+  // Vanilla Clang's unwind.h doesn't have _Unwind_GetIP for ARM.
+  // See http://crbug.com/236855, too.
+  uintptr_t ip = 0;
+  _Unwind_VRS_Get(context, _UVRSC_CORE, 15, _UVRSD_UINT32, &ip);
+  ip &= ~(uintptr_t)0x1;  // remove thumb mode bit
+#else
+  uintptr_t ip = _Unwind_GetIP(context);
+#endif
+
+  // The first stack frame is this function itself.  Skip it.
+  if (ip != 0 && !state->have_skipped_self) {
+    state->have_skipped_self = true;
+    return _URC_NO_REASON;
+  }
+
+  state->frames[state->frame_count++] = ip;
+  if (state->frame_count >= state->max_depth)
+    return _URC_END_OF_STACK;
+  else
+    return _URC_NO_REASON;
+}
+
+}  // namespace
+
 namespace base {
 namespace debug {
 
@@ -31,6 +85,12 @@ bool EnableInProcessStackDumping() {
 }
 
 StackTrace::StackTrace() {
+  // TODO(dmikurube): Replace it with Bionic's get_backtrace().
+  // See http://crbug.com/236855.
+  stack_crawl_state_t state(reinterpret_cast<uintptr_t*>(trace_), kMaxTraces);
+  _Unwind_Backtrace(tracer, &state);
+  count_ = state.frame_count;
+  // TODO(dmikurube): Symbolize in Chrome.
 }
 
 // Sends fake SIGSTKFLT signals to let the Android linker and debuggerd dump