#!/usr/bin/env python3 """ # SPDX-License-Identifier: GPL-2.0-or-later # # sercomm-kernel-header.py: Creates Sercomm kernel header # # Copyright © 2022 Mikhail Zhilkin """ import argparse import binascii import os import struct KERNEL_HEADER_SIZE = 0x100 PADDING = 0xff ROOTFS_FAKE_HEADER = "UBI#" def auto_int(x): return int(x, 0) def create_kernel_header(args): out_file = open(args.header_file, "wb") header = get_kernel_header(args) out_file.write(header) out_file.close() def get_kernel_header(args): header = bytearray([PADDING] * KERNEL_HEADER_SIZE) struct.pack_into('<L', header, 0xc, 0xffffff02) struct.pack_into('<L', header, 0x1c, 0x0) struct.pack_into('<L', header, 0x34, 0x0) struct.pack_into('<L', header, 0x10, args.kernel_offset) struct.pack_into('<L', header, 0x28, args.rootfs_offset) if (args.rootfs_file): if (args.rootfs_checking_size): rootfs_size = args.rootfs_checking_size else: rootfs_size = os.path.getsize(args.rootfs_file) buf = open(args.rootfs_file,'rb').read(rootfs_size) crc = binascii.crc32(buf) & 0xffffffff else: rootfs_size = len(ROOTFS_FAKE_HEADER) crc = binascii.crc32(str.encode(ROOTFS_FAKE_HEADER)) & \ 0xffffffff struct.pack_into('<L', header, 0x2c, rootfs_size) struct.pack_into('<L', header, 0x30, crc) rootfs_end_offset = args.rootfs_offset + rootfs_size struct.pack_into('<L', header, 0x4, rootfs_end_offset) kernel_size = os.path.getsize(args.kernel_file) struct.pack_into('<L', header, 0x14, kernel_size) buf = open(args.kernel_file,'rb').read() crc = binascii.crc32(buf) & 0xffffffff struct.pack_into('<L', header, 0x18, crc) crc = binascii.crc32(header) & 0xffffffff struct.pack_into('<L', header, 0x8, crc) struct.pack_into('<L', header, 0x0, 0x726553) return header def main(): global args parser = argparse.ArgumentParser(description='This script generates \ a kernel header for the Sercomm mt7621 devices') parser.add_argument('--kernel-image', dest='kernel_file', action='store', type=str, help='Path to a Kernel binary image') parser.add_argument('--kernel-offset', dest='kernel_offset', action='store', type=auto_int, help='Kernel offset') parser.add_argument('--rootfs-offset', dest='rootfs_offset', action='store', type=auto_int, help='RootFS offset') parser.add_argument('--output-header', dest='header_file', action='store', type=str, help='Output kernel header file') parser.add_argument('--rootfs-image', dest='rootfs_file', action='store', type=str, help='Path to RootFS binary image (optional)') parser.add_argument('--rootfs-checking-size', dest='rootfs_checking_size', action='store', type=auto_int, help='Bytes count for CRC calculation (optional)') args = parser.parse_args() if ((not args.kernel_file) or (not args.kernel_offset) or (not args.rootfs_offset) or (not args.header_file)): parser.print_help() exit() create_kernel_header(args) main()