include/backtrace/Backtrace.h

/*
 * 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.
 */

#ifndef _BACKTRACE_BACKTRACE_H
#define _BACKTRACE_BACKTRACE_H

#include <inttypes.h>
#include <stdint.h>

#include <string>
#include <vector>

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

#if __LP64__
#define PRIPTR "016" PRIxPTR
typedef uint64_t word_t;
#else
#define PRIPTR "08" PRIxPTR
typedef uint32_t word_t;
#endif

enum BacktraceUnwindError : uint32_t {
  BACKTRACE_UNWIND_NO_ERROR,
  // Something failed while trying to perform the setup to begin the unwind.
  BACKTRACE_UNWIND_ERROR_SETUP_FAILED,
  // There is no map information to use with the unwind.
  BACKTRACE_UNWIND_ERROR_MAP_MISSING,
  // An error occurred that indicates a programming error.
  BACKTRACE_UNWIND_ERROR_INTERNAL,
  // The thread to unwind has disappeared before the unwind can begin.
  BACKTRACE_UNWIND_ERROR_THREAD_DOESNT_EXIST,
  // The thread to unwind has not responded to a signal in a timely manner.
  BACKTRACE_UNWIND_ERROR_THREAD_TIMEOUT,
  // Attempt to do an unsupported operation.
  BACKTRACE_UNWIND_ERROR_UNSUPPORTED_OPERATION,
  // Attempt to do an offline unwind without a context.
  BACKTRACE_UNWIND_ERROR_NO_CONTEXT,
};

struct backtrace_frame_data_t {
  size_t num;             // The current fame number.
  uintptr_t pc;           // The absolute pc.
  uintptr_t sp;           // The top of the stack.
  size_t stack_size;      // The size of the stack, zero indicate an unknown stack size.
  backtrace_map_t map;    // The map associated with the given pc.
  std::string func_name;  // The function name associated with this pc, NULL if not found.
  uintptr_t func_offset;  // pc relative to the start of the function, only valid if func_name is not NULL.
};

#if defined(__APPLE__)
struct __darwin_ucontext;
typedef __darwin_ucontext ucontext_t;
#else
struct ucontext;
typedef ucontext ucontext_t;
#endif

struct backtrace_stackinfo_t {
  uint64_t start;
  uint64_t end;
  const uint8_t* data;
};

class Backtrace {
public:
  // Create the correct Backtrace object based on what is to be unwound.
  // If pid < 0 or equals the current pid, then the Backtrace object
  // corresponds to the current process.
  // If pid < 0 or equals the current pid and tid >= 0, then the Backtrace
  // object corresponds to a thread in the current process.
  // If pid >= 0 and tid < 0, then the Backtrace object corresponds to a
  // different process.
  // Tracing a thread in a different process is not supported.
  // If map is NULL, then create the map and manage it internally.
  // If map is not NULL, the map is still owned by the caller.
  static Backtrace* Create(pid_t pid, pid_t tid, BacktraceMap* map = NULL);

  // Create an offline Backtrace object that can be used to do an unwind without a process
  // that is still running. If cache_file is set to true, then elf information will be cached
  // for this call. The cached information survives until the calling process ends. This means
  // that subsequent calls to create offline Backtrace objects will continue to use the same
  // cache. It also assumes that the elf files used for each offline unwind are the same.
  static Backtrace* CreateOffline(pid_t pid, pid_t tid, BacktraceMap* map,
                                  const backtrace_stackinfo_t& stack, bool cache_file = false);

  virtual ~Backtrace();

  // Get the current stack trace and store in the backtrace_ structure.
  virtual bool Unwind(size_t num_ignore_frames, ucontext_t* context = NULL) = 0;

  // Get the function name and offset into the function given the pc.
  // If the string is empty, then no valid function name was found.
  virtual std::string GetFunctionName(uintptr_t pc, uintptr_t* offset);

  // Fill in the map data associated with the given pc.
  virtual void FillInMap(uintptr_t pc, backtrace_map_t* map);

  // Read the data at a specific address.
  virtual bool ReadWord(uintptr_t ptr, word_t* out_value) = 0;

  // Read arbitrary data from a specific address. If a read request would
  // span from one map to another, this call only reads up until the end
  // of the current map.
  // Returns the total number of bytes actually read.
  virtual size_t Read(uintptr_t addr, uint8_t* buffer, size_t bytes) = 0;

  // Create a string representing the formatted line of backtrace information
  // for a single frame.
  virtual std::string FormatFrameData(size_t frame_num);
  virtual std::string FormatFrameData(const backtrace_frame_data_t* frame);

  pid_t Pid() const { return pid_; }
  pid_t Tid() const { return tid_; }
  size_t NumFrames() const { return frames_.size(); }

  const backtrace_frame_data_t* GetFrame(size_t frame_num) {
    if (frame_num >= frames_.size()) {
      return NULL;
    }
    return &frames_[frame_num];
  }

  typedef std::vector<backtrace_frame_data_t>::iterator iterator;
  iterator begin() { return frames_.begin(); }
  iterator end() { return frames_.end(); }

  typedef std::vector<backtrace_frame_data_t>::const_iterator const_iterator;
  const_iterator begin() const { return frames_.begin(); }
  const_iterator end() const { return frames_.end(); }

  BacktraceMap* GetMap() { return map_; }

  BacktraceUnwindError GetError() { return error_; }

  std::string GetErrorString(BacktraceUnwindError error);

protected:
  Backtrace(pid_t pid, pid_t tid, BacktraceMap* map);

  // The name returned is not demangled, GetFunctionName() takes care of
  // demangling the name.
  virtual std::string GetFunctionNameRaw(uintptr_t pc, uintptr_t* offset) = 0;

  virtual bool VerifyReadWordArgs(uintptr_t ptr, word_t* out_value);

  bool BuildMap();

  pid_t pid_;
  pid_t tid_;

  BacktraceMap* map_;
  bool map_shared_;

  std::vector<backtrace_frame_data_t> frames_;

  BacktraceUnwindError error_;
};

#endif // _BACKTRACE_BACKTRACE_H