引言
在使用 Chrome 浏览器的过程中，偶尔会遇到浏览器崩溃的情况。为了找出崩溃的原因并修复问题，我们需要对崩溃后的 .dmp 文件进行详细分析。本文将详细介绍如何从用户的系统中获取崩溃日志文件，使用 minidump_stackwalk 查看浏览器版本信息，下载对应的 symbols 文件，并使用 LLDB 进行详细分析。
第一步：获取崩溃日志文件
1.1 收集 .dmp 文件
当 Chrome 浏览器崩溃时，系统通常会生成一个 .dmp 文件，该文件包含了崩溃时的堆栈信息。用户可以在 Chrome 的崩溃报告目录中找到这些文件。路径通常为：
- Windows: C:\Users<Username>\AppData\Local\Google\Chrome\User Data\Crash Reports
- macOS: ~/Library/Application Support/Google/Chrome/Crash Reports
- Linux: ~/.config/google-chrome/Crash Reports
第二步：使用 minidump_stackwalk 查看浏览器版本信息
2.1 安装 minidump_stackwalk
确保你的系统上安装了 minidump_stackwalk。你可以通过以下命令安装：
# macOS 和 Linux
brew install breakpad
或者从源码编译安装：
git clone https://chromium.googlesource.com/breakpad/breakpad
cd breakpad
./configure
make
sudo make install
2.2 使用 minidump_stackwalk 查看信息
使用 minidump_stackwalk 工具查看 .dmp 文件中的浏览器版本信息：
minidump_stackwalk your_crash.dmp /path/to/symbols
该命令会输出崩溃的详细信息，包括浏览器版本、模块列表等。根据输出的版本信息，
第三步：下载 symbols 文件
3.1 访问 Chrome 官方网站
根据 minidump_stackwalk 输出的版本信息，访问 Chrome 官方下载页面 下载对应的 symbols 文件。通常，symbols 文件可以在 Chrome 的开发者资源页面找到。
github 上有一个辅助下载脚本(download_symbols.py)，有些处理过时了，略作修改如下所示：
#!/usr/bin/env python3
# Copyright 2021 The Chromium Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
"""Downloads symbols for official, Google Chrome builds.Usage:./download_symbols.py -v 91.0.4449.6 -a x86_64 -c stable -o /dest/pathThis can also be used as a Python module.
"""import argparse
import csv
import os.path
import platform
import subprocess
import sys
import urllib.request as request# 这个地址已经失效了，channel 需要手动指定（比如 【stable】，可以在 https://chromiumdash.appspot.com/releases?platform=Mac 中查看）
_OMAHAPROXY_HISTORY = 'https://omahaproxy.appspot.com/history?os=mac&format=json'_DSYM_URL_TEMPLATE = 'https://dl.google.com/chrome/mac/{channel}/dsym/googlechrome-{version}-{arch}-dsym.tar.bz2'def download_chrome_symbols(version, channel, arch, dest_dir):"""Downloads and extracts the official Google Chrome dSYM files to asubdirectory of `dest_dir`.Args:version: The version to download symbols for.channel: The release channel to download symbols for. If None, attemptsto guess the channel.arch: The CPU architecture to download symbols for.dest_dir: The location to download symbols to. The dSYMs will beextracted to a subdirectory of this directory.Returns:The path to the directory containing the dSYMs, which will be asubdirectory of `dest_dir`."""if channel is None:channel = _identify_channel(version, arch)if channel:print('Using release channel {} for {}'.format(channel, version),file=sys.stderr)else:print('Could not identify channel for Chrome version {}'.format(version),file=sys.stderr)return Noneextracted_dir = _download_and_extract(version, channel, arch, dest_dir)if not extracted_dir:print('Could not find dSYMs for Chrome {} {}'.format(version, arch),file=sys.stderr)return extracted_dirdef get_symbol_directory(version, channel, arch, dest_dir):"""Returns the parent directory for dSYMs given the specified parameters."""_, dest = _get_url_and_dest(version, channel, arch, dest_dir)return destdef _identify_channel(version, arch):"""Attempts to guess the release channel given a Chrome version and CPUarchitecture."""# First try querying OmahaProxy for the release.with request.urlopen(_OMAHAPROXY_HISTORY) as release_history:history = csv.DictReader(release_history.read().decode('utf8').split('\n'))for row in history:if row['version'] == version:return row['channel']# Fall back to sending HEAD HTTP requests to each of the possible symbol# locations.print('Unable to identify release channel for {}, now brute-force searching'.format(version),file=sys.stderr)for channel in ('stable', 'beta', 'dev', 'canary'):url, _ = _get_url_and_dest(version, channel, arch, '')req = request.Request(url, method='HEAD')try:resp = request.urlopen(req)if resp.code == 200:return channelexcept:continuereturn Nonedef _get_url_and_dest(version, channel, arch, dest_dir):"""Returns a the symbol archive URL and local destination directory giventhe format parameters."""args = {'channel': channel, 'arch': arch, 'version': version}url = _DSYM_URL_TEMPLATE.format(**args)dest_dir = os.path.join(dest_dir,'googlechrome-{version}-{arch}-dsym'.format(**args))return url, dest_dirdef _download_and_extract(version, channel, arch, dest_dir):"""Performs the download and extraction of the symbol files. Returns thepath to the extracted symbol files on success, None on error."""url, dest_dir = _get_url_and_dest(version, channel, arch, dest_dir)if not os.path.isdir(dest_dir):os.mkdir(dest_dir)print('download from {}'.format(url), file=sys.stderr)print(url, file=sys.stderr)try:with request.urlopen(url) as symbol_request:print('Downloading and extracting symbols to {}'.format(dest_dir),file=sys.stderr)print('This will take a minute...', file=sys.stderr)if _extract_symbols_to(symbol_request, dest_dir):return dest_direxcept:print('load failed!!!', file=sys.stderr)passreturn Nonedef _extract_symbols_to(symbol_request, dest_dir):"""Performs a streaming extract of the symbol files.Args:symbol_request: The HTTPResponse object for the symbol URL.dest_dir: The destination directory into which the files will beextracted.Returns: True on successful download and extraction, False on error."""proc = subprocess.Popen(['tar', 'xjf', '-'],cwd=dest_dir,stdin=subprocess.PIPE,stdout=sys.stderr,stderr=sys.stderr)while True:data = symbol_request.read(4096)if not data:proc.stdin.close()breakproc.stdin.write(data)proc.wait()return proc.returncode == 0def main():parser = argparse.ArgumentParser()parser.add_argument('--version','-v',required=True,help='Version to download.')parser.add_argument('--channel','-c',help='Chrome release channel for the version. The channel will be ' \'guessed if not specified.')parser.add_argument('--arch','-a',help='CPU architecture to download, defaults to that of the current OS.')parser.add_argument('--out','-o',required=True,help='Directory to download the symbols to.')args = parser.parse_args()arch = args.archif not arch:arch = platform.machine()if not os.path.isdir(args.out):print('--out destination is not a directory.', file=sys.stderr)return Falsereturn download_chrome_symbols(args.version, args.channel, arch, args.out)if __name__ == '__main__':main()
3.2 放置 symbols 文件
将下载的 symbols 文件放置在你指定的目录，例如 /path/to/symbols。
第四步：使用 LLDB 进行详细分析
4.1 安装 LLDB
确保你的系统上安装了 LLDB。大多数现代 macOS 和 Linux 发行版都自带了 LLDB，Windows 用户可以通过 Visual Studio 安装。
4.2 使用 LLDB 分析 .dmp 文件
打开终端，使用以下命令加载 .dmp 文件并进行分析：
lldb
(lldb) settings set target.exec-search-paths /symbol/file/path
(lldb) target create --core "/dmp/file/path"
(lldb) thread backtrace all
确保将 /path/to/executables 替换为你的 symbols 文件路径。
4.3 查看堆栈跟踪
使用以下命令查看崩溃时的堆栈跟踪：
(lldb) bt
这将显示详细的堆栈跟踪信息，帮助你定位崩溃的具体位置。之前定位过一个问题如下图所示：
可以看出发生了 OOM，内存占用过大导致崩溃。
4.4 进一步调试
根据堆栈跟踪信息，你可以进一步调试，例如：
- 检查变量值
- 打印内存内容
- 断点调试
(lldb) frame variable
(lldb) memory read --size 16 --format x --count 10 <address>
结论
这一过程有助于深入理解崩溃的原因，并采取相应的修复措施。希望本文能帮助你有效地分析 Chrome 浏览器的崩溃问题。如果你有任何疑问，欢迎一起探讨。
