/*
 * Copyright (C) 2021 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 _LIBUNWINDSTACK_UTILS_OFFLINE_UNWIND_UTILS_H
#define _LIBUNWINDSTACK_UTILS_OFFLINE_UNWIND_UTILS_H

#include <filesystem>
#include <memory>
#include <string>

#include <unwindstack/Unwinder.h>

#include "MemoryOffline.h"

// These utils facilitate performing offline unwinds. Offline unwinds are similar to local
// unwinds, however, instead of pausing the process to gather the current execution state
// (stack, registers, Elf / maps), a snapshot of the process is taken. This snapshot data
// is used at a later time (when the process is no longer running) to unwind the process
// at the point the snapshot was taken.
//
// Offline unwinds simulate one of the most common use cases of the Unwinder. These types of
// unwinds are performed by two of the largest clients of libunwindstack: Perfetto and Simpleperf.
//
// Offline unwind snapshots were obtained using the following approach:
// 1. (Optional) Flash a virtual or physical device with the internal Android build rather than
//    an AOSP build to have additional and more complex apps to unwind.
// 2. Determine the pid of the app/process you want to unwind. View all of the running
//    processes with `adb shell ps -A`  or `adb shell ps -A | grep name.of.process` if you know
//    the (package) name of the process.
// 3. (Optional) If you want to ensure that an application is compiled or that the compiled code is
//    erased (e.g. want interpreter / JIT frames in the unwind), run `adb shell cmd package compile`
//    based on the options provided here
//    (https://source.android.com/devices/tech/dalvik/jit-compiler).
// 4. Ensure the process is running and in a "desired state" when you execute
//    `adb shell /bin/unwind_for_offline [options] pid`. For example:
//   a. If you are unwinding the bluetooth process and want the unwind to contain the bluetooth
//      ELF (libbluetooth.so), try to pair with a device over bluetooth. Make sure you use the
//      `-t` and `-e` flags.
//   b. You will likely see more variation in the thread snapshots (especially if you are trying
//      to capture JIT/interpreter frames) if you ensure the app is not-idle when you run
//      `unwind_for_offline`. E.g. immediately run unwind_for_offline after searching for a
//      landmark in Google Maps.
// 5. Grab the desired snapshot directories with `adb pull ...`
// 6. (Optional) Reduce the size of copied ELFs:
//   a. Use tools/share_common_elfs.sh to eliminate copies of the same ELF files that are already
//      used by other 'libunwindstack/offline_files/' subdirectories.
//   b. Strip ELFs of all sections that are not needed for unwinding and/or symbolization.
//   c. Compress/Zip the entire snapshot directory.
// 7. Use the path to the snapshot directory(ies) for the `offline_files_dirs` parameter to
//    `OfflineUnwindUtils::Init`.
//
// See b/192012600 for additional information regarding Offline Unwind Benchmarks.
namespace unwindstack {
std::string GetOfflineFilesDirectory();

std::string DumpFrames(const Unwinder& unwinder);

bool AddMemory(std::string file_name, MemoryOfflineParts* parts, std::string& error_msg);

class OfflineUnwindUtils {
 public:
  Regs* GetRegs() { return regs_.get(); }

  Maps* GetMaps() { return maps_.get(); }

  std::shared_ptr<Memory> GetProcessMemory() { return process_memory_; }

  std::string GetOfflineDirectory() { return offline_dir_; }

  bool Init(const std::string& offline_files_dir, ArchEnum arch, std::string& error_msg,
            bool add_stack = true, bool set_maps = true);

  bool ResetMaps(std::string& error_msg);

  bool SetProcessMemory(std::string& error_msg);

  bool SetJitProcessMemory(std::string& error_msg);

  void ReturnToCurrentWorkingDirectory() { std::filesystem::current_path(cwd_); }

 private:
  bool SetRegs(ArchEnum arch, std::string& error_msg);

  template <typename AddressType>
  bool ReadRegs(RegsImpl<AddressType>* regs,
                const std::unordered_map<std::string, uint32_t>& name_to_reg,
                std::string& error_msg);

  static std::unordered_map<std::string, uint32_t> arm_regs_;
  static std::unordered_map<std::string, uint32_t> arm64_regs_;
  static std::unordered_map<std::string, uint32_t> x86_regs_;
  static std::unordered_map<std::string, uint32_t> x86_64_regs_;

  std::string cwd_;
  std::string offline_dir_;
  std::string map_buffer_;
  std::unique_ptr<Regs> regs_;
  std::unique_ptr<Maps> maps_;
  std::shared_ptr<Memory> process_memory_;
};

}  // namespace unwindstack

#endif  // _LIBUNWINDSTACK_UTILS_OFFLINE_UNWIND_UTILS_H