libbacktrace/Backtrace.cpp

/*
 * Copyright (C) 2013 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <inttypes.h>
#include <stdint.h>
#include <stdlib.h>
#include <sys/types.h>
#include <ucontext.h>

#include <string>

#include <android-base/stringprintf.h>
#include <android-base/threads.h>

#include <backtrace/Backtrace.h>
#include <backtrace/BacktraceMap.h>

#include "BacktraceLog.h"
#include "UnwindStack.h"

using android::base::StringPrintf;

extern "C" char* __cxa_demangle(const char*, char*, size_t*, int*);

//-------------------------------------------------------------------------
// Backtrace functions.
//-------------------------------------------------------------------------
Backtrace::Backtrace(pid_t pid, pid_t tid, BacktraceMap* map)
    : pid_(pid), tid_(tid), map_(map), map_shared_(true) {
  if (map_ == nullptr) {
    map_ = BacktraceMap::Create(pid);
    map_shared_ = false;
  }
}

Backtrace::~Backtrace() {
  if (map_ && !map_shared_) {
    delete map_;
    map_ = nullptr;
  }
}

std::string Backtrace::GetFunctionName(uint64_t pc, uint64_t* offset, const backtrace_map_t* map) {
  backtrace_map_t map_value;
  if (map == nullptr) {
    FillInMap(pc, &map_value);
    map = &map_value;
  }
  // If no map is found, or this map is backed by a device, then return nothing.
  if (map->start == 0 || (map->flags & PROT_DEVICE_MAP)) {
    return "";
  }
  std::string name(GetFunctionNameRaw(pc, offset));
  char* demangled_name = __cxa_demangle(name.c_str(), nullptr, nullptr, nullptr);
  if (demangled_name != nullptr) {
    name = demangled_name;
    free(demangled_name);
    return name;
  }
  return name;
}

bool Backtrace::VerifyReadWordArgs(uint64_t ptr, word_t* out_value) {
  if (ptr & (sizeof(word_t)-1)) {
    BACK_LOGW("invalid pointer %p", reinterpret_cast<void*>(ptr));
    *out_value = static_cast<word_t>(-1);
    return false;
  }
  return true;
}

std::string Backtrace::FormatFrameData(size_t frame_num) {
  if (frame_num >= frames_.size()) {
    return "";
  }
  return FormatFrameData(&frames_[frame_num]);
}

std::string Backtrace::FormatFrameData(const backtrace_frame_data_t* frame) {
  std::string map_name;
  if (BacktraceMap::IsValid(frame->map)) {
    map_name = frame->map.Name();
    if (!frame->map.name.empty()) {
      if (map_name[0] == '[' && map_name[map_name.size() - 1] == ']') {
        map_name.resize(map_name.size() - 1);
        map_name += StringPrintf(":%" PRIPTR "]", frame->map.start);
      }
    }
  } else {
    map_name = "<unknown>";
  }

  std::string line(StringPrintf("#%02zu pc %" PRIPTR "  ", frame->num, frame->rel_pc));
  line += map_name;
  // Special handling for non-zero offset maps, we need to print that
  // information.
  if (frame->map.offset != 0) {
    line += " (offset " + StringPrintf("0x%" PRIx64, frame->map.offset) + ")";
  }
  if (!frame->func_name.empty()) {
    line += " (" + frame->func_name;
    if (frame->func_offset) {
      line += StringPrintf("+%" PRIu64, frame->func_offset);
    }
    line += ')';
  }

  return line;
}

void Backtrace::FillInMap(uint64_t pc, backtrace_map_t* map) {
  if (map_ != nullptr) {
    map_->FillIn(pc, map);
  }
}

Backtrace* Backtrace::Create(pid_t pid, pid_t tid, BacktraceMap* map) {
  if (pid == BACKTRACE_CURRENT_PROCESS) {
    pid = getpid();
    if (tid == BACKTRACE_CURRENT_THREAD) {
      tid = android::base::GetThreadId();
    }
  } else if (tid == BACKTRACE_CURRENT_THREAD) {
    tid = pid;
  }

  if (pid == getpid()) {
    return new UnwindStackCurrent(pid, tid, map);
  } else {
    return new UnwindStackPtrace(pid, tid, map);
  }
}

std::string Backtrace::GetErrorString(BacktraceUnwindError error) {
  switch (error.error_code) {
    case BACKTRACE_UNWIND_NO_ERROR:
      return "No error";
    case BACKTRACE_UNWIND_ERROR_SETUP_FAILED:
      return "Setup failed";
    case BACKTRACE_UNWIND_ERROR_MAP_MISSING:
      return "No map found";
    case BACKTRACE_UNWIND_ERROR_INTERNAL:
      return "Internal libbacktrace error, please submit a bugreport";
    case BACKTRACE_UNWIND_ERROR_THREAD_DOESNT_EXIST:
      return "Thread doesn't exist";
    case BACKTRACE_UNWIND_ERROR_THREAD_TIMEOUT:
      return "Thread has not responded to signal in time";
    case BACKTRACE_UNWIND_ERROR_UNSUPPORTED_OPERATION:
      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";
    case BACKTRACE_UNWIND_ERROR_UNWIND_INFO:
      return "Failed to unwind due to invalid unwind information";
    case BACKTRACE_UNWIND_ERROR_REPEATED_FRAME:
      return "Failed to unwind due to same sp/pc repeating";
    case BACKTRACE_UNWIND_ERROR_INVALID_ELF:
      return "Failed to unwind due to invalid elf";
  }
}