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

@@ -222,6 +222,7 @@ bool BacktraceOffline::Unwind(size_t num_ignore_frames, ucontext_t* context) {
     } 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 @@ bool BacktraceOffline::FindProcInfo(unw_addr_space_t addr_space, uint64_t ip,
       }
     }
   }
-  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

libbacktrace/BacktraceOffline.h

@@ -48,7 +48,8 @@ class BacktraceOffline : public Backtrace {
                    bool cache_file)
       : Backtrace(pid, tid, map),
         cache_file_(cache_file),
-        context_(nullptr) {
+        context_(nullptr),
+        is_debug_frame_used_(false) {
     stack_space_.start = stack.start;
     stack_space_.end = stack.end;
     stack_space_.data = stack.data;
@@ -78,6 +79,14 @@ class BacktraceOffline : public Backtrace {
   Space arm_extab_space_;
   Space arm_exidx_space_;
   Space stack_space_;
+
+  // is_debug_frame_used_ is to make sure we can try both .debug_frame and .ARM.exidx in
+  // FindProcInfo() on ARM. One example is EsxContext::Clear() in
+  // vendor/lib/egl/libGLESv2_adreno.so. EsxContext::Clear() appears in both .debug_frame and
+  // .ARM.exidx. However, libunwind fails to execute debug_frame instruction
+  // "DW_CFA_offset_extended: r265 at cfa-48". So we need to try .ARM.exidx to unwind that
+  // function.
+  bool is_debug_frame_used_;
 };
 
 #endif  // _LIBBACKTRACE_BACKTRACE_OFFLINE_H

libbacktrace/backtrace_offline_test.cpp

@@ -357,68 +357,24 @@ TEST(libbacktrace, offline_arm_exidx) {
   BacktraceOfflineTest("arm", "libbacktrace_test_arm_exidx.so");
 }
 
-// This test tests the situation that ranges of functions covered by .eh_frame and .ARM.exidx
-// overlap with each other, which appears in /system/lib/libart.so.
-TEST(libbacktrace, offline_unwind_mix_eh_frame_and_arm_exidx) {
-  // TODO: For now, only run on the given arch.
-  if (std::string(ABI_STRING) != "arm") {
+static void LibUnwindingTest(const std::string& arch, const std::string& testdata_name,
+                             const std::string& testlib_name) {
+  if (std::string(ABI_STRING) != arch) {
     GTEST_LOG_(INFO) << "Skipping test since offline for arm on " << ABI_STRING
                      << " isn't supported.";
     return;
   }
-  const std::string testlib_path(GetTestPath("libart.so"));
+  const std::string testlib_path(GetTestPath(testlib_name));
   struct stat st;
   ASSERT_EQ(0, stat(testlib_path.c_str(), &st)) << "can't find testlib " << testlib_path;
 
-  const std::string offline_testdata_path(GetTestPath("offline_testdata_for_libart"));
+  const std::string offline_testdata_path(GetTestPath(testdata_name));
   OfflineTestData testdata;
   ASSERT_TRUE(ReadOfflineTestData(offline_testdata_path, &testdata));
 
-  // Fix path of /system/lib/libart.so.
+  // Fix path of the testlib.
   for (auto& map : testdata.maps) {
-    if (map.name.find("libart.so") != std::string::npos) {
-      map.name = testlib_path;
-    }
-  }
-
-  // Do offline backtrace.
-  std::unique_ptr<BacktraceMap> map(BacktraceMap::Create(testdata.pid, testdata.maps));
-  ASSERT_TRUE(map != nullptr);
-
-  std::unique_ptr<Backtrace> backtrace(
-      Backtrace::CreateOffline(testdata.pid, testdata.tid, map.get(), testdata.stack_info));
-  ASSERT_TRUE(backtrace != nullptr);
-
-  ucontext_t ucontext = GetUContextFromUnwContext(testdata.unw_context);
-  ASSERT_TRUE(backtrace->Unwind(0, &ucontext));
-
-  // The last frame is outside of libart.so
-  ASSERT_EQ(testdata.symbols.size() + 1, backtrace->NumFrames());
-  for (size_t i = 0; i + 1 < backtrace->NumFrames(); ++i) {
-    uintptr_t vaddr_in_file =
-        backtrace->GetFrame(i)->pc - testdata.maps[0].start + testdata.maps[0].load_bias;
-    std::string name = FunctionNameForAddress(vaddr_in_file, testdata.symbols);
-    ASSERT_EQ(name, testdata.symbols[i].name);
-  }
-}
-
-TEST(libbacktrace, offline_debug_frame_with_load_bias) {
-  if (std::string(ABI_STRING) != "arm") {
-    GTEST_LOG_(INFO) << "Skipping test since offline for arm on " << ABI_STRING
-                     << " isn't supported.";
-    return;
-  }
-  const std::string testlib_path(GetTestPath("libandroid_runtime.so"));
-  struct stat st;
-  ASSERT_EQ(0, stat(testlib_path.c_str(), &st)) << "can't find testlib " << testlib_path;
-
-  const std::string offline_testdata_path(GetTestPath("offline_testdata_for_libandroid_runtime"));
-  OfflineTestData testdata;
-  ASSERT_TRUE(ReadOfflineTestData(offline_testdata_path, &testdata));
-
-  // Fix path of /system/lib/libandroid_runtime.so.
-  for (auto& map : testdata.maps) {
-    if (map.name.find("libandroid_runtime.so") != std::string::npos) {
+    if (map.name.find(testlib_name) != std::string::npos) {
       map.name = testlib_path;
     }
   }
@@ -442,3 +398,17 @@ TEST(libbacktrace, offline_debug_frame_with_load_bias) {
     ASSERT_EQ(name, testdata.symbols[i].name);
   }
 }
+
+// This test tests the situation that ranges of functions covered by .eh_frame and .ARM.exidx
+// overlap with each other, which appears in /system/lib/libart.so.
+TEST(libbacktrace, offline_unwind_mix_eh_frame_and_arm_exidx) {
+  LibUnwindingTest("arm", "offline_testdata_for_libart", "libart.so");
+}
+
+TEST(libbacktrace, offline_debug_frame_with_load_bias) {
+  LibUnwindingTest("arm", "offline_testdata_for_libandroid_runtime", "libandroid_runtime.so");
+}
+
+TEST(libbacktrace, offline_try_armexidx_after_debug_frame) {
+  LibUnwindingTest("arm", "offline_testdata_for_libGLESv2_adreno", "libGLESv2_adreno.so");
+}

libbacktrace/testdata/arm/offline_testdata_for_libGLESv2_adreno

@@ -0,0 +1,6 @@
+pid: 7288 tid: 31656
+regs: pc: cc416235 sp: cc17f000
+map: start: cc361000 end: cc758000 offset: 0 load_bias: 9000 flags: 5 name: /vendor/lib/egl/libGLESv2_adreno.so
+stack: start: cc17f254 end: cc17f258 size: 4 b36141cc
+function: start: be1f0 end: be304 name: EsxContext::Clear(unsigned int, unsigned int, unsigned int, EsxClearValues*)
+function: start: be058 end: be1f0 name: EsxContext::ClearBuffersForDebug()