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#!/usr/bin/env python
#
# Copyright (C) 2018 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.
"""
A tool to extract kernel information from a kernel image.
"""
import argparse
import subprocess
import sys
import re
CONFIG_PREFIX = b'IKCFG_ST'
GZIP_HEADER = b'\037\213\010'
COMPRESSION_ALGO = (
(["gzip", "-d"], GZIP_HEADER),
(["xz", "-d"], b'\3757zXZ\000'),
(["bzip2", "-d"], b'BZh'),
(["lz4", "-d", "-l"], b'\002\041\114\030'),
# These are not supported in the build system yet.
# (["unlzma"], b'\135\0\0\0'),
# (["lzop", "-d"], b'\211\114\132'),
)
# "Linux version " UTS_RELEASE " (" LINUX_COMPILE_BY "@"
# LINUX_COMPILE_HOST ") (" LINUX_COMPILER ") " UTS_VERSION "\n";
LINUX_BANNER_PREFIX = b'Linux version '
LINUX_BANNER_REGEX = LINUX_BANNER_PREFIX.decode() + \
r'(?P<release>(?P<version>[0-9]+[.][0-9]+[.][0-9]+).*) \(.*@.*\) \((?P<compiler>.*)\) .*\n'
def get_from_release(input_bytes, start_idx, key):
null_idx = input_bytes.find(b'\x00', start_idx)
if null_idx < 0:
return None
try:
linux_banner = input_bytes[start_idx:null_idx].decode()
except UnicodeDecodeError:
return None
mo = re.match(LINUX_BANNER_REGEX, linux_banner)
if mo:
return mo.group(key)
return None
def dump_from_release(input_bytes, key):
"""
Helper of dump_version and dump_release
"""
idx = 0
while True:
idx = input_bytes.find(LINUX_BANNER_PREFIX, idx)
if idx < 0:
return None
value = get_from_release(input_bytes, idx, key)
if value:
return value.encode()
idx += len(LINUX_BANNER_PREFIX)
def dump_version(input_bytes):
"""
Dump kernel version, w.x.y, from input_bytes. Search for the string
"Linux version " and do pattern matching after it. See LINUX_BANNER_REGEX.
"""
return dump_from_release(input_bytes, "version")
def dump_compiler(input_bytes):
"""
Dump kernel version, w.x.y, from input_bytes. Search for the string
"Linux version " and do pattern matching after it. See LINUX_BANNER_REGEX.
"""
return dump_from_release(input_bytes, "compiler")
def dump_release(input_bytes):
"""
Dump kernel release, w.x.y-..., from input_bytes. Search for the string
"Linux version " and do pattern matching after it. See LINUX_BANNER_REGEX.
"""
return dump_from_release(input_bytes, "release")
def dump_configs(input_bytes):
"""
Dump kernel configuration from input_bytes. This can be done when
CONFIG_IKCONFIG is enabled, which is a requirement on Treble devices.
The kernel configuration is archived in GZip format right after the magic
string 'IKCFG_ST' in the built kernel.
"""
# Search for magic string + GZip header
idx = input_bytes.find(CONFIG_PREFIX + GZIP_HEADER)
if idx < 0:
return None
# Seek to the start of the archive
idx += len(CONFIG_PREFIX)
sp = subprocess.Popen(["gzip", "-d", "-c"], stdin=subprocess.PIPE,
stdout=subprocess.PIPE, stderr=subprocess.PIPE)
o, _ = sp.communicate(input=input_bytes[idx:])
if sp.returncode == 1: # error
return None
# success or trailing garbage warning
assert sp.returncode in (0, 2), sp.returncode
return o
def try_decompress_bytes(cmd, input_bytes):
sp = subprocess.Popen(cmd, stdin=subprocess.PIPE, stdout=subprocess.PIPE,
stderr=subprocess.PIPE)
o, _ = sp.communicate(input=input_bytes)
# ignore errors
return o
def try_decompress(cmd, search_bytes, input_bytes):
idx = 0
while True:
idx = input_bytes.find(search_bytes, idx)
if idx < 0:
return
yield try_decompress_bytes(cmd, input_bytes[idx:])
idx += 1
def decompress_dump(func, input_bytes):
"""
Run func(input_bytes) first; and if that fails (returns value evaluates to
False), then try different decompression algorithm before running func.
"""
o = func(input_bytes)
if o:
return o
for cmd, search_bytes in COMPRESSION_ALGO:
for decompressed in try_decompress(cmd, search_bytes, input_bytes):
if decompressed:
o = decompress_dump(func, decompressed)
if o:
return o
# Force decompress the whole file even if header doesn't match
decompressed = try_decompress_bytes(cmd, input_bytes)
if decompressed:
o = decompress_dump(func, decompressed)
if o:
return o
def dump_to_file(f, dump_fn, input_bytes, desc):
"""
Call decompress_dump(dump_fn, input_bytes) and write to f. If it fails, return
False; otherwise return True.
"""
if f is not None:
o = decompress_dump(dump_fn, input_bytes)
if o:
f.write(o)
else:
sys.stderr.write(
"Cannot extract kernel {}".format(desc))
return False
return True
def to_bytes_io(b):
"""
Make b, which is either sys.stdout or sys.stdin, receive bytes as arguments.
"""
return b.buffer if sys.version_info.major == 3 else b
def main():
parser = argparse.ArgumentParser(
formatter_class=argparse.RawTextHelpFormatter,
description=__doc__ +
"\nThese algorithms are tried when decompressing the image:\n " +
" ".join(tup[0][0] for tup in COMPRESSION_ALGO))
parser.add_argument('--input',
help='Input kernel image. If not specified, use stdin',
metavar='FILE',
type=argparse.FileType('rb'),
default=to_bytes_io(sys.stdin))
parser.add_argument('--output-configs',
help='If specified, write configs. Use stdout if no file '
'is specified.',
metavar='FILE',
nargs='?',
type=argparse.FileType('wb'),
const=to_bytes_io(sys.stdout))
parser.add_argument('--output-version',
help='If specified, write version. Use stdout if no file '
'is specified.',
metavar='FILE',
nargs='?',
type=argparse.FileType('wb'),
const=to_bytes_io(sys.stdout))
parser.add_argument('--output-release',
help='If specified, write kernel release. Use stdout if '
'no file is specified.',
metavar='FILE',
nargs='?',
type=argparse.FileType('wb'),
const=to_bytes_io(sys.stdout))
parser.add_argument('--output-compiler',
help='If specified, write the compiler information. Use stdout if no file '
'is specified.',
metavar='FILE',
nargs='?',
type=argparse.FileType('wb'),
const=to_bytes_io(sys.stdout))
parser.add_argument('--tools',
help='Decompression tools to use. If not specified, PATH '
'is searched.',
metavar='ALGORITHM:EXECUTABLE',
nargs='*')
args = parser.parse_args()
tools = {pair[0]: pair[1]
for pair in (token.split(':') for token in args.tools or [])}
for cmd, _ in COMPRESSION_ALGO:
if cmd[0] in tools:
cmd[0] = tools[cmd[0]]
input_bytes = args.input.read()
ret = 0
if not dump_to_file(args.output_configs, dump_configs, input_bytes,
"configs in {}".format(args.input.name)):
ret = 1
if not dump_to_file(args.output_version, dump_version, input_bytes,
"version in {}".format(args.input.name)):
ret = 1
if not dump_to_file(args.output_release, dump_release, input_bytes,
"kernel release in {}".format(args.input.name)):
ret = 1
if not dump_to_file(args.output_compiler, dump_compiler, input_bytes,
"kernel compiler in {}".format(args.input.name)):
ret = 1
return ret
if __name__ == '__main__':
sys.exit(main())
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