# 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)