commit 0ca49b09add6f8d0fc3254984cb3f87d192b910b
author Yabin Cui <yabinc@google.com> Sun Dec 10 17:55:12 2017 -0800
committer Yabin Cui <yabinc@google.com> Sun Dec 10 18:00:35 2017 -0800
tree a9817a12857178e5de2ede7c5be1b709c4b9956a
parent d65c6ba9552816382fd760024574a1a6d353f2a4

libBacktraceOffline: try both .debug_frame and .ARM.exidx on arm.

Currently, libBacktraceOffline doesn't try .ARM.exidx if a function
appears in .debug_frame. This make it can't unwind through functions
appear in both .debug_frame and .ARM.exidx, but having dwarf instructions
not accepted by libunwind.
This patch fixes this by trying first .debug_frame then .ARM.exidx on arm.

Bug: http://b/69383534
Test: run libbacktrace_test on arm.

Change-Id: Ib95dd56d5cc123a20948e880b51b28ddc04b4a6e

libbacktrace/BacktraceOffline.cpp

diff --git a/libbacktrace/BacktraceOffline.cpp b/libbacktrace/BacktraceOffline.cpp
index 3041492..641f712 100644
--- a/libbacktrace/BacktraceOffline.cpp
+++ b/libbacktrace/BacktraceOffline.cpp
@@ -222,6 +222,7 @@
     } else {
       num_ignore_frames--;
     }
+    is_debug_frame_used_ = false;
     ret = unw_step(&cursor);
   } while (ret > 0 && num_frames < MAX_BACKTRACE_FRAMES);
 
@@ -318,7 +319,8 @@
       }
     }
   }
-  if (debug_frame->has_debug_frame || debug_frame->has_gnu_debugdata) {
+  if (!is_debug_frame_used_ && (debug_frame->has_debug_frame || debug_frame->has_gnu_debugdata)) {
+    is_debug_frame_used_ = true;
     unw_dyn_info_t di;
     unw_word_t segbase = map.start - debug_frame->min_vaddr;
     // TODO: http://b/32916571