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Commit f8808281 authored by Yabin Cui's avatar Yabin Cui
Browse files

libbacktrace: export offline unwinding failures. 

This is to help debugging different offline unwiding failures.

Bug: http://b/69383534
Test: run backtrace_test.
Change-Id: I5ed4837027a9f17d032925e97e9f5927161444b3
parent 80bfeeef

libbacktrace/Backtrace.cpp

+28 −17
Original line number Diff line number Diff line
@@ -142,7 +142,7 @@ Backtrace* Backtrace::Create(pid_t pid, pid_t tid, BacktraceMap* map) { 
}



std::string Backtrace::GetErrorString(BacktraceUnwindError error) {

  switch (error) {

  switch (error.error_code) {

    case BACKTRACE_UNWIND_NO_ERROR:

      return "No error";

    case BACKTRACE_UNWIND_ERROR_SETUP_FAILED:
@@ -159,5 +159,16 @@ std::string Backtrace::GetErrorString(BacktraceUnwindError error) { 
      return "Attempt to use an unsupported feature";

    case BACKTRACE_UNWIND_ERROR_NO_CONTEXT:

      return "Attempt to do an offline unwind without a context";

    case BACKTRACE_UNWIND_ERROR_EXCEED_MAX_FRAMES_LIMIT:

      return "Exceed MAX_BACKTRACE_FRAMES limit";

    case BACKTRACE_UNWIND_ERROR_ACCESS_MEM_FAILED:

      return android::base::StringPrintf("Failed to read memory at addr 0x%" PRIx64,

                                         error.error_info.addr);

    case BACKTRACE_UNWIND_ERROR_ACCESS_REG_FAILED:

      return android::base::StringPrintf("Failed to read register %" PRIu64, error.error_info.regno);

    case BACKTRACE_UNWIND_ERROR_FIND_PROC_INFO_FAILED:

      return "Failed to find a function in debug sections";

    case BACKTRACE_UNWIND_ERROR_EXECUTE_DWARF_INSTRUCTION_FAILED:

      return "Failed to execute dwarf instructions in debug sections";

  }

}

libbacktrace/BacktraceCurrent.cpp

+7 −7
Original line number Diff line number Diff line
@@ -67,11 +67,11 @@ size_t BacktraceCurrent::Read(uintptr_t addr, uint8_t* buffer, size_t bytes) { 
bool BacktraceCurrent::Unwind(size_t num_ignore_frames, ucontext_t* ucontext) {

  if (GetMap() == nullptr) {

    // Without a map object, we can't do anything.

    error_ = BACKTRACE_UNWIND_ERROR_MAP_MISSING;

    error_.error_code = BACKTRACE_UNWIND_ERROR_MAP_MISSING;

    return false;

  }



  error_ = BACKTRACE_UNWIND_NO_ERROR;

  error_.error_code = BACKTRACE_UNWIND_NO_ERROR;

  if (ucontext) {

    return UnwindFromContext(num_ignore_frames, ucontext);

  }
@@ -163,7 +163,7 @@ bool BacktraceCurrent::UnwindThread(size_t num_ignore_frames) { 
    BACK_ASYNC_SAFE_LOGE("sigaction failed: %s", strerror(errno));

    ThreadEntry::Remove(entry);

    pthread_mutex_unlock(&g_sigaction_mutex);

    error_ = BACKTRACE_UNWIND_ERROR_INTERNAL;

    error_.error_code = BACKTRACE_UNWIND_ERROR_INTERNAL;

    return false;

  }
@@ -171,9 +171,9 @@ bool BacktraceCurrent::UnwindThread(size_t num_ignore_frames) { 
    // Do not emit an error message, this might be expected. Set the

    // error and let the caller decide.

    if (errno == ESRCH) {

      error_ = BACKTRACE_UNWIND_ERROR_THREAD_DOESNT_EXIST;

      error_.error_code = BACKTRACE_UNWIND_ERROR_THREAD_DOESNT_EXIST;

    } else {

      error_ = BACKTRACE_UNWIND_ERROR_INTERNAL;

      error_.error_code = BACKTRACE_UNWIND_ERROR_INTERNAL;

    }



    sigaction(THREAD_SIGNAL, &oldact, nullptr);
@@ -218,9 +218,9 @@ bool BacktraceCurrent::UnwindThread(size_t num_ignore_frames) { 
  } else {

    // Check to see if the thread has disappeared.

    if (tgkill(Pid(), Tid(), 0) == -1 && errno == ESRCH) {

      error_ = BACKTRACE_UNWIND_ERROR_THREAD_DOESNT_EXIST;

      error_.error_code = BACKTRACE_UNWIND_ERROR_THREAD_DOESNT_EXIST;

    } else {

      error_ = BACKTRACE_UNWIND_ERROR_THREAD_TIMEOUT;

      error_.error_code = BACKTRACE_UNWIND_ERROR_THREAD_TIMEOUT;

      BACK_ASYNC_SAFE_LOGE("Timed out waiting for signal handler to get ucontext data.");

    }

  }

libbacktrace/BacktraceOffline.cpp

+30 −6
Original line number Diff line number Diff line
@@ -174,11 +174,11 @@ static unw_accessors_t accessors = { 
bool BacktraceOffline::Unwind(size_t num_ignore_frames, ucontext_t* context) {

  if (context == nullptr) {

    BACK_LOGW("The context is needed for offline backtracing.");

    error_ = BACKTRACE_UNWIND_ERROR_NO_CONTEXT;

    error_.error_code = BACKTRACE_UNWIND_ERROR_NO_CONTEXT;

    return false;

  }

  context_ = context;

  error_ = BACKTRACE_UNWIND_NO_ERROR;

  error_.error_code = BACKTRACE_UNWIND_NO_ERROR;



  unw_addr_space_t addr_space = unw_create_addr_space(&accessors, 0);

  unw_cursor_t cursor;
@@ -186,11 +186,11 @@ bool BacktraceOffline::Unwind(size_t num_ignore_frames, ucontext_t* context) { 
  if (ret != 0) {

    BACK_LOGW("unw_init_remote failed %d", ret);

    unw_destroy_addr_space(addr_space);

    error_ = BACKTRACE_UNWIND_ERROR_SETUP_FAILED;

    error_.error_code = BACKTRACE_UNWIND_ERROR_SETUP_FAILED;

    return false;

  }

  size_t num_frames = 0;

  do {

  while (true) {

    unw_word_t pc;

    ret = unw_get_reg(&cursor, UNW_REG_IP, &pc);

    if (ret < 0) {
@@ -224,7 +224,17 @@ bool BacktraceOffline::Unwind(size_t num_ignore_frames, ucontext_t* context) { 
    }

    is_debug_frame_used_ = false;

    ret = unw_step(&cursor);

  } while (ret > 0 && num_frames < MAX_BACKTRACE_FRAMES);

    if (ret <= 0) {

      if (error_.error_code == BACKTRACE_UNWIND_NO_ERROR) {

        error_.error_code = BACKTRACE_UNWIND_ERROR_EXECUTE_DWARF_INSTRUCTION_FAILED;

      }

      break;

    }

    if (num_frames == MAX_BACKTRACE_FRAMES) {

      error_.error_code = BACKTRACE_UNWIND_ERROR_EXCEED_MAX_FRAMES_LIMIT;

      break;

    }

  }



  unw_destroy_addr_space(addr_space);

  context_ = nullptr;
@@ -259,21 +269,30 @@ size_t BacktraceOffline::Read(uintptr_t addr, uint8_t* buffer, size_t bytes) { 
    return read_size;

  }

  read_size = stack_space_.Read(addr, buffer, bytes);

  if (read_size != 0) {

    return read_size;

  }

  error_.error_code = BACKTRACE_UNWIND_ERROR_ACCESS_MEM_FAILED;

  error_.error_info.addr = addr;

  return 0;

}



bool BacktraceOffline::FindProcInfo(unw_addr_space_t addr_space, uint64_t ip,

                                    unw_proc_info_t* proc_info, int need_unwind_info) {

  backtrace_map_t map;

  FillInMap(ip, &map);

  if (!BacktraceMap::IsValid(map)) {

    error_.error_code = BACKTRACE_UNWIND_ERROR_FIND_PROC_INFO_FAILED;

    return false;

  }

  const std::string& filename = map.name;

  DebugFrameInfo* debug_frame = GetDebugFrameInFile(filename);

  if (debug_frame == nullptr) {

    error_.error_code = BACKTRACE_UNWIND_ERROR_FIND_PROC_INFO_FAILED;

    return false;

  }

  // Each FindProcInfo() is a new attempt to unwind, so reset the reason.

  error_.error_code = BACKTRACE_UNWIND_NO_ERROR;



  eh_frame_hdr_space_.Clear();

  eh_frame_space_.Clear();
@@ -367,6 +386,7 @@ bool BacktraceOffline::FindProcInfo(unw_addr_space_t addr_space, uint64_t ip, 
      }

    }

  }

  error_.error_code = BACKTRACE_UNWIND_ERROR_FIND_PROC_INFO_FAILED;

  return false;

}
@@ -548,6 +568,10 @@ bool BacktraceOffline::ReadReg(size_t reg, uint64_t* value) { 
  UNUSED(value);

  result = false;

#endif

  if (!result) {

    error_.error_code = BACKTRACE_UNWIND_ERROR_ACCESS_REG_FAILED;

    error_.error_info.regno = reg;

  }

  return result;

}

libbacktrace/BacktraceOffline.h

+1 −3
Original line number Diff line number Diff line
@@ -32,9 +32,7 @@ struct Space { 
  uint64_t end;

  const uint8_t* data;



  Space() {

    Clear();

  }

  Space() { Clear(); }



  void Clear();

  size_t Read(uint64_t addr, uint8_t* buffer, size_t size);

libbacktrace/UnwindCurrent.cpp

+2 −2
Original line number Diff line number Diff line
@@ -81,7 +81,7 @@ bool UnwindCurrent::UnwindFromContext(size_t num_ignore_frames, ucontext_t* ucon 
    int ret = unw_getcontext(&context_);

    if (ret < 0) {

      BACK_LOGW("unw_getcontext failed %d", ret);

      error_ = BACKTRACE_UNWIND_ERROR_SETUP_FAILED;

      error_.error_code = BACKTRACE_UNWIND_ERROR_SETUP_FAILED;

      return false;

    }

  } else {
@@ -93,7 +93,7 @@ bool UnwindCurrent::UnwindFromContext(size_t num_ignore_frames, ucontext_t* ucon 
  int ret = unw_init_local(cursor.get(), &context_);

  if (ret < 0) {

    BACK_LOGW("unw_init_local failed %d", ret);

    error_ = BACKTRACE_UNWIND_ERROR_SETUP_FAILED;

    error_.error_code = BACKTRACE_UNWIND_ERROR_SETUP_FAILED;

    return false;

  }

  initialized_ = true;