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# 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.
import gzip
import io
import itertools
import os
import shutil
try:
from urllib.error import HTTPError, URLError
from urllib.parse import quote, urljoin
from urllib.request import urlopen
except ImportError:
from urllib import quote
from urllib2 import urlopen
from urlparse import urljoin
SYMBOL_SERVER_URL = "https://symbols.mozilla.org/"
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(f"Fetching symbols from {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 (URLError, HTTPError):
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 == "/" or not 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 {}".format(":".join(dirs)))
gdb.events.new_objfile.connect(new_objfile)
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