1#!/usr/bin/env python 2# 3# Copyright (C) 2018 The Android Open Source Project 4# 5# Licensed under the Apache License, Version 2.0 (the "License"); 6# you may not use this file except in compliance with the License. 7# You may obtain a copy of the License at 8# 9# http://www.apache.org/licenses/LICENSE-2.0 10# 11# Unless required by applicable law or agreed to in writing, software 12# distributed under the License is distributed on an "AS IS" BASIS, 13# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14# See the License for the specific language governing permissions and 15# limitations under the License. 16 17""" 18A tool to extract kernel information from a kernel image. 19""" 20 21import argparse 22import subprocess 23import sys 24import re 25 26CONFIG_PREFIX = b'IKCFG_ST' 27GZIP_HEADER = b'\037\213\010' 28COMPRESSION_ALGO = ( 29 (["gzip", "-d"], GZIP_HEADER), 30 (["xz", "-d"], b'\3757zXZ\000'), 31 (["bzip2", "-d"], b'BZh'), 32 (["lz4", "-d", "-l"], b'\002\041\114\030'), 33 34 # These are not supported in the build system yet. 35 # (["unlzma"], b'\135\0\0\0'), 36 # (["lzop", "-d"], b'\211\114\132'), 37) 38 39# "Linux version " UTS_RELEASE " (" LINUX_COMPILE_BY "@" 40# LINUX_COMPILE_HOST ") (" LINUX_COMPILER ") " UTS_VERSION "\n"; 41LINUX_BANNER_PREFIX = b'Linux version ' 42LINUX_BANNER_REGEX = LINUX_BANNER_PREFIX + \ 43 r'([0-9]+[.][0-9]+[.][0-9]+).* \(.*@.*\) \(.*\) .*\n' 44 45 46def get_version(input_bytes, start_idx): 47 null_idx = input_bytes.find('\x00', start_idx) 48 if null_idx < 0: 49 return None 50 try: 51 linux_banner = input_bytes[start_idx:null_idx].decode() 52 except UnicodeDecodeError: 53 return None 54 mo = re.match(LINUX_BANNER_REGEX, linux_banner) 55 if mo: 56 return mo.group(1) 57 return None 58 59 60def dump_version(input_bytes): 61 idx = 0 62 while True: 63 idx = input_bytes.find(LINUX_BANNER_PREFIX, idx) 64 if idx < 0: 65 return None 66 67 version = get_version(input_bytes, idx) 68 if version: 69 return version 70 71 idx += len(LINUX_BANNER_PREFIX) 72 73 74def dump_configs(input_bytes): 75 """ 76 Dump kernel configuration from input_bytes. This can be done when 77 CONFIG_IKCONFIG is enabled, which is a requirement on Treble devices. 78 79 The kernel configuration is archived in GZip format right after the magic 80 string 'IKCFG_ST' in the built kernel. 81 """ 82 83 # Search for magic string + GZip header 84 idx = input_bytes.find(CONFIG_PREFIX + GZIP_HEADER) 85 if idx < 0: 86 return None 87 88 # Seek to the start of the archive 89 idx += len(CONFIG_PREFIX) 90 91 sp = subprocess.Popen(["gzip", "-d", "-c"], stdin=subprocess.PIPE, 92 stdout=subprocess.PIPE, stderr=subprocess.PIPE) 93 o, _ = sp.communicate(input=input_bytes[idx:]) 94 if sp.returncode == 1: # error 95 return None 96 97 # success or trailing garbage warning 98 assert sp.returncode in (0, 2), sp.returncode 99 100 return o 101 102 103def try_decompress_bytes(cmd, input_bytes): 104 sp = subprocess.Popen(cmd, stdin=subprocess.PIPE, stdout=subprocess.PIPE, 105 stderr=subprocess.PIPE) 106 o, _ = sp.communicate(input=input_bytes) 107 # ignore errors 108 return o 109 110 111def try_decompress(cmd, search_bytes, input_bytes): 112 idx = 0 113 while True: 114 idx = input_bytes.find(search_bytes, idx) 115 if idx < 0: 116 raise StopIteration() 117 118 yield try_decompress_bytes(cmd, input_bytes[idx:]) 119 idx += 1 120 121 122def decompress_dump(func, input_bytes): 123 """ 124 Run func(input_bytes) first; and if that fails (returns value evaluates to 125 False), then try different decompression algorithm before running func. 126 """ 127 o = func(input_bytes) 128 if o: 129 return o 130 for cmd, search_bytes in COMPRESSION_ALGO: 131 for decompressed in try_decompress(cmd, search_bytes, input_bytes): 132 if decompressed: 133 o = decompress_dump(func, decompressed) 134 if o: 135 return o 136 # Force decompress the whole file even if header doesn't match 137 decompressed = try_decompress_bytes(cmd, input_bytes) 138 if decompressed: 139 o = decompress_dump(func, decompressed) 140 if o: 141 return o 142 143def main(): 144 parser = argparse.ArgumentParser( 145 formatter_class=argparse.RawTextHelpFormatter, 146 description=__doc__ + 147 "\nThese algorithms are tried when decompressing the image:\n " + 148 " ".join(tup[0][0] for tup in COMPRESSION_ALGO)) 149 parser.add_argument('--input', 150 help='Input kernel image. If not specified, use stdin', 151 metavar='FILE', 152 type=argparse.FileType('rb'), 153 default=sys.stdin) 154 parser.add_argument('--output-configs', 155 help='If specified, write configs. Use stdout if no file ' 156 'is specified.', 157 metavar='FILE', 158 nargs='?', 159 type=argparse.FileType('wb'), 160 const=sys.stdout) 161 parser.add_argument('--output-version', 162 help='If specified, write version. Use stdout if no file ' 163 'is specified.', 164 metavar='FILE', 165 nargs='?', 166 type=argparse.FileType('wb'), 167 const=sys.stdout) 168 parser.add_argument('--tools', 169 help='Decompression tools to use. If not specified, PATH ' 170 'is searched.', 171 metavar='ALGORITHM:EXECUTABLE', 172 nargs='*') 173 args = parser.parse_args() 174 175 tools = {pair[0]: pair[1] 176 for pair in (token.split(':') for token in args.tools or [])} 177 for cmd, _ in COMPRESSION_ALGO: 178 if cmd[0] in tools: 179 cmd[0] = tools[cmd[0]] 180 181 input_bytes = args.input.read() 182 183 ret = 0 184 if args.output_configs is not None: 185 o = decompress_dump(dump_configs, input_bytes) 186 if o: 187 args.output_configs.write(o) 188 else: 189 sys.stderr.write( 190 "Cannot extract kernel configs in {}".format(args.input.name)) 191 ret = 1 192 if args.output_version is not None: 193 o = decompress_dump(dump_version, input_bytes) 194 if o: 195 args.output_version.write(o) 196 else: 197 sys.stderr.write( 198 "Cannot extract kernel versions in {}".format(args.input.name)) 199 ret = 1 200 201 return ret 202 203 204if __name__ == '__main__': 205 exit(main()) 206