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Commit af16967e authored by Christopher Ferris's avatar Christopher Ferris
Browse files

Method to avoid skipping frames for local unwinds. 

In cases where there might be a crash in the unwind library itself,
we need a method to avoid skipping these frames or we won't be able
to see the actual crash.

Added unit test for this behavior.

Bug: 74121887

Test: Ran unit tests on host and target.
Change-Id: I45825020c174016af39dd8ffdc67acb72a24ad4d
(cherry picked from commit 458f4e72)
parent 677bed57

libbacktrace/UnwindStack.cpp

+3 −0
Original line number Diff line number Diff line
@@ -163,6 +163,9 @@ bool UnwindStackCurrent::UnwindFromContext(size_t num_ignore_frames, void* ucont 
  }



  std::vector<std::string> skip_names{"libunwindstack.so", "libbacktrace.so"};

  if (!skip_frames_) {

    skip_names.clear();

  }

  return Backtrace::Unwind(regs.get(), GetMap(), &frames_, num_ignore_frames, &skip_names, &error_);

}

libbacktrace/backtrace_test.cpp

+39 −3
Original line number Diff line number Diff line
@@ -69,6 +69,9 @@ 
// Number of simultaneous threads running in our forked process.

#define NUM_PTRACE_THREADS 5



// The list of shared libaries that make up the backtrace library.

static std::vector<std::string> kBacktraceLibs{"libunwindstack.so", "libbacktrace.so"};



struct thread_t {

  pid_t tid;

  int32_t state;
@@ -256,15 +259,48 @@ TEST(libbacktrace, local_no_unwind_frames) { 
  VERIFY_NO_ERROR(backtrace->GetError().error_code);



  ASSERT_TRUE(backtrace->NumFrames() != 0);

  // None of the frames should be in the backtrace libraries.

  for (const auto& frame : *backtrace ) {

    if (BacktraceMap::IsValid(frame.map)) {

      const std::string name = basename(frame.map.name.c_str());

      ASSERT_TRUE(name != "libunwind.so" && name != "libbacktrace.so")

        << DumpFrames(backtrace.get());

      for (const auto& lib : kBacktraceLibs) {

        ASSERT_TRUE(name != lib) << DumpFrames(backtrace.get());

      }

    }

  }

}



TEST(libbacktrace, local_unwind_frames) {

  // Verify that a local unwind with the skip frames disabled does include

  // frames within the backtrace libraries.

  std::unique_ptr<Backtrace> backtrace(Backtrace::Create(getpid(), getpid()));

  ASSERT_TRUE(backtrace.get() != nullptr);

  backtrace->SetSkipFrames(false);

  ASSERT_TRUE(backtrace->Unwind(0));

  VERIFY_NO_ERROR(backtrace->GetError().error_code);



  ASSERT_TRUE(backtrace->NumFrames() != 0);

  size_t first_frame_non_backtrace_lib = 0;

  for (const auto& frame : *backtrace) {

    if (BacktraceMap::IsValid(frame.map)) {

      const std::string name = basename(frame.map.name.c_str());

      bool found = false;

      for (const auto& lib : kBacktraceLibs) {

        if (name == lib) {

          found = true;

          break;

        }

      }

      if (!found) {

        first_frame_non_backtrace_lib = frame.num;

        break;

      }

    }

  }



  ASSERT_NE(0U, first_frame_non_backtrace_lib) << "No frames found in backtrace libraries:\n"

                                               << DumpFrames(backtrace.get());

}



TEST(libbacktrace, local_trace) {

  ASSERT_NE(test_level_one(1, 2, 3, 4, VerifyLevelBacktrace, nullptr), 0);

libbacktrace/include/backtrace/Backtrace.h

+6 −0
Original line number Diff line number Diff line
@@ -204,6 +204,9 @@ class Backtrace { 


  std::string GetErrorString(BacktraceUnwindError error);



  // Set whether to skip frames in libbacktrace/libunwindstack when doing a local unwind.

  void SetSkipFrames(bool skip_frames) { skip_frames_ = skip_frames; }



 protected:

  Backtrace(pid_t pid, pid_t tid, BacktraceMap* map);
@@ -223,6 +226,9 @@ class Backtrace { 


  std::vector<backtrace_frame_data_t> frames_;



  // Skip frames in libbacktrace/libunwindstack when doing a local unwind.

  bool skip_frames_ = true;



  BacktraceUnwindError error_;

};