GDB Mozilla symbol server

symbols.py

# Any copyright is dedicated to the Public Domain.
# http://creativecommons.org/publicdomain/zero/1.0/
#
# A GDB Python script to fetch debug symbols from the Mozilla symbol server.
#
# To use, run `source /path/to/symbols.py` in GDB 7.9 or newer, or
# put that in your ~/.gdbinit.

from __future__ import print_function

import gzip
import io
import itertools
import os
import shutil
import sys
try:
    from urllib.request import urlopen
    from urllib.parse import urljoin, quote
except ImportError:
    from urllib2 import urlopen
    from urllib import quote
    from urlparse import urljoin

SYMBOL_SERVER_URL = 'https://s3-us-west-2.amazonaws.com/org.mozilla.crash-stats.symbols-public/v1/'

debug_dir = os.path.join(os.environ['HOME'], '.cache', 'gdb')
cache_dir = os.path.join(debug_dir, '.build-id')

def munge_build_id(build_id):
    '''
    Breakpad stuffs the build id into a GUID struct so the bytes are
    flipped from the standard presentation.
    '''
    b = list(map(''.join, list(zip(*[iter(build_id.upper())]*2))))
    return ''.join(itertools.chain(reversed(b[:4]), reversed(b[4:6]),
                                   reversed(b[6:8]), b[8:16])) + '0'

def try_fetch_symbols(filename, build_id, destination):
    debug_file = os.path.join(destination, build_id[:2], build_id[2:] + '.debug')
    if os.path.exists(debug_file):
        return debug_file
    try:
        d = os.path.dirname(debug_file)
        if not os.path.isdir(d):
            os.makedirs(d)
    except OSError:
        pass
    path = os.path.join(filename, munge_build_id(build_id), filename + '.dbg.gz')
    url = urljoin(SYMBOL_SERVER_URL, quote(path))
    try:
        u = urlopen(url)
        if u.getcode() != 200:
            return None
        print('Fetching symbols from {0}'.format(url))
        with open(debug_file, 'wb') as f, gzip.GzipFile(fileobj=io.BytesIO(u.read()), mode='r') as z:
            shutil.copyfileobj(z, f)
            return debug_file
    except:
        return None


def is_moz_binary(filename):
    '''
    Try to determine if a file lives in a Firefox install dir, to save
    HTTP requests for things that aren't going to work.
    '''
    # The linux-gate VDSO doesn't have a real filename.
    if not os.path.isfile(filename):
        return False
    while True:
        filename = os.path.dirname(filename)
        if filename == '/':
            return False
        if os.path.isfile(os.path.join(filename, 'application.ini')):
            return True


def fetch_symbols_for(objfile):
    build_id = objfile.build_id if hasattr(objfile, 'build_id') else None
    if getattr(objfile, 'owner', None) is not None or any(o.owner == objfile for o in gdb.objfiles()):
        # This is either a separate debug file or this file already
        # has symbols in a separate debug file.
        return
    if build_id and is_moz_binary(objfile.filename):
        debug_file = try_fetch_symbols(os.path.basename(objfile.filename), build_id, cache_dir)
        if debug_file:
            objfile.add_separate_debug_file(debug_file)


def new_objfile(event):
    fetch_symbols_for(event.new_objfile)


def fetch_symbols():
    '''
    Try to fetch symbols for all loaded modules.
    '''
    for objfile in gdb.objfiles():
        fetch_symbols_for(objfile)

# Create our debug cache dir.
try:
    if not os.path.isdir(cache_dir):
        os.makedirs(cache_dir)
except OSError:
    pass

# Set it as a debug-file-directory.
try:
    dirs = gdb.parameter('debug-file-directory').split(':')
except gdb.error:
    dirs = []
if debug_dir not in dirs:
    dirs.append(debug_dir)
    gdb.execute('set debug-file-directory %s' % ':'.join(dirs))

gdb.events.new_objfile.connect(new_objfile)

I got an infinite loop in def is_moz_binary(filename): with an objfile.filename that is system-supplied DSO at 0x7fff4939b000. Stripping dirnames from that lead to an empty string.

I changed it like this:

-        if filename == '/':
+        if filename == '/' or not filename:

Thanks! That hang on startup had been driving me nuts but I never got around to investigating it!

symbols.mozilla.org is switching to GCP soon. One of the consequences of that is that it'll no longer be saving uploaded symbols to that S3 bucket.

I suggest switching to https://symbols.mozilla.org/ as the SYMBOL_SERVER_URL. I'm pretty sure that'll work fine.