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/*
* 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
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