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#!/usr/bin/env python
# Copyright 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.
"""unpacks the bootimage.
Extracts the kernel, ramdisk, second bootloader, dtb and recovery dtbo images.
"""
from __future__ import print_function
from argparse import ArgumentParser, FileType
from struct import unpack
import os
def create_out_dir(dir_path):
"""creates a directory 'dir_path' if it does not exist"""
if not os.path.exists(dir_path):
os.makedirs(dir_path)
def extract_image(offset, size, bootimage, extracted_image_name):
"""extracts an image from the bootimage"""
bootimage.seek(offset)
with open(extracted_image_name, 'wb') as file_out:
file_out.write(bootimage.read(size))
def get_number_of_pages(image_size, page_size):
"""calculates the number of pages required for the image"""
return (image_size + page_size - 1) / page_size
def unpack_bootimage(args):
"""extracts kernel, ramdisk, second bootloader and recovery dtbo"""
boot_magic = unpack('8s', args.boot_img.read(8))
print('boot_magic: %s' % boot_magic)
kernel_ramdisk_second_info = unpack('10I', args.boot_img.read(10 * 4))
print('kernel_size: %s' % kernel_ramdisk_second_info[0])
print('kernel load address: %#x' % kernel_ramdisk_second_info[1])
print('ramdisk size: %s' % kernel_ramdisk_second_info[2])
print('ramdisk load address: %#x' % kernel_ramdisk_second_info[3])
print('second bootloader size: %s' % kernel_ramdisk_second_info[4])
print('second bootloader load address: %#x' % kernel_ramdisk_second_info[5])
print('kernel tags load address: %#x' % kernel_ramdisk_second_info[6])
print('page size: %s' % kernel_ramdisk_second_info[7])
print('boot image header version: %s' % kernel_ramdisk_second_info[8])
print('os version and patch level: %s' % kernel_ramdisk_second_info[9])
product_name = unpack('16s', args.boot_img.read(16))
print('product name: %s' % product_name)
cmdline = unpack('512s', args.boot_img.read(512))
print('command line args: %s' % cmdline)
args.boot_img.read(32) # ignore SHA
extra_cmdline = unpack('1024s', args.boot_img.read(1024))
print('additional command line args: %s' % extra_cmdline)
kernel_size = kernel_ramdisk_second_info[0]
ramdisk_size = kernel_ramdisk_second_info[2]
second_size = kernel_ramdisk_second_info[4]
page_size = kernel_ramdisk_second_info[7]
version = kernel_ramdisk_second_info[8]
if version > 0:
recovery_dtbo_size = unpack('I', args.boot_img.read(1 * 4))[0]
print('recovery dtbo size: %s' % recovery_dtbo_size)
recovery_dtbo_offset = unpack('Q', args.boot_img.read(8))[0]
print('recovery dtbo offset: %#x' % recovery_dtbo_offset)
boot_header_size = unpack('I', args.boot_img.read(4))[0]
print('boot header size: %s' % boot_header_size)
else:
recovery_dtbo_size = 0
if version > 1:
dtb_size = unpack('I', args.boot_img.read(4))[0]
print('dtb size: %s' % dtb_size)
dtb_load_address = unpack('Q', args.boot_img.read(8))[0]
print('dtb address: %#x' % dtb_load_address)
else:
dtb_size = 0
# The first page contains the boot header
num_header_pages = 1
num_kernel_pages = get_number_of_pages(kernel_size, page_size)
kernel_offset = page_size * num_header_pages # header occupies a page
image_info_list = [(kernel_offset, kernel_size, 'kernel')]
num_ramdisk_pages = get_number_of_pages(ramdisk_size, page_size)
ramdisk_offset = page_size * (num_header_pages + num_kernel_pages
) # header + kernel
image_info_list.append((ramdisk_offset, ramdisk_size, 'ramdisk'))
if second_size > 0:
second_offset = page_size * (
num_header_pages + num_kernel_pages + num_ramdisk_pages
) # header + kernel + ramdisk
image_info_list.append((second_offset, second_size, 'second'))
if recovery_dtbo_size > 0:
image_info_list.append((recovery_dtbo_offset, recovery_dtbo_size,
'recovery_dtbo'))
if dtb_size > 0:
num_second_pages = get_number_of_pages(second_size, page_size)
num_recovery_dtbo_pages = get_number_of_pages(recovery_dtbo_size, page_size)
dtb_offset = page_size * (
num_header_pages + num_kernel_pages + num_ramdisk_pages + num_second_pages +
num_recovery_dtbo_pages
)
image_info_list.append((dtb_offset, dtb_size, 'dtb'))
for image_info in image_info_list:
extract_image(image_info[0], image_info[1], args.boot_img,
os.path.join(args.out, image_info[2]))
def parse_cmdline():
"""parse command line arguments"""
parser = ArgumentParser(
description='Unpacks boot.img/recovery.img, extracts the kernel,'
'ramdisk, second bootloader, recovery dtbo and dtb')
parser.add_argument(
'--boot_img',
help='path to boot image',
type=FileType('rb'),
required=True)
parser.add_argument('--out', help='path to out binaries', default='out')
return parser.parse_args()
def main():
"""parse arguments and unpack boot image"""
args = parse_cmdline()
create_out_dir(args.out)
unpack_bootimage(args)
if __name__ == '__main__':
main()
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