scripts/sercomm-kernel-header.py

   1 #!/usr/bin/env python3
   2 """
   3 # SPDX-License-Identifier: GPL-2.0-or-later
   4 #
   5 # sercomm-kernel-header.py: Creates Sercomm kernel header
   6 #
   7 # Copyright © 2022 Mikhail Zhilkin
   8 """
   9
  10 import argparse
  11 import binascii
  12 import os
  13 import struct
  14
  15 KERNEL_HEADER_SIZE = 0x100
  16 PADDING = 0xff
  17 ROOTFS_FAKE_HEADER = "UBI#"
  18
  19 def auto_int(x):
  20         return int(x, 0)
  21
  22 def create_kernel_header(args):
  23         out_file = open(args.header_file, "wb")
  24         header = get_kernel_header(args)
  25         out_file.write(header)
  26         out_file.close()
  27
  28 def get_kernel_header(args):
  29         header = bytearray([PADDING] * KERNEL_HEADER_SIZE)
  30
  31         struct.pack_into('<L', header, 0xc, 0xffffff02)
  32         struct.pack_into('<L', header, 0x1c, 0x0)
  33         struct.pack_into('<L', header, 0x34, 0x0)
  34         struct.pack_into('<L', header, 0x10, args.kernel_offset)
  35         struct.pack_into('<L', header, 0x28, args.rootfs_offset)
  36
  37         if (args.rootfs_file):
  38                 if (args.rootfs_checking_size):
  39                         rootfs_size = args.rootfs_checking_size
  40                 else:
  41                         rootfs_size = os.path.getsize(args.rootfs_file)
  42                 buf = open(args.rootfs_file,'rb').read(rootfs_size)
  43                 crc = binascii.crc32(buf) & 0xffffffff
  44         else:
  45                 rootfs_size = len(ROOTFS_FAKE_HEADER)
  46                 crc = binascii.crc32(str.encode(ROOTFS_FAKE_HEADER)) & \
  47                       0xffffffff
  48         struct.pack_into('<L', header, 0x2c, rootfs_size)
  49         struct.pack_into('<L', header, 0x30, crc)
  50
  51         kernel_size = os.path.getsize(args.kernel_file)
  52         struct.pack_into('<L', header, 0x14, kernel_size)
  53
  54         kernel_end_offset = args.kernel_offset + kernel_size
  55         struct.pack_into('<L', header, 0x4, kernel_end_offset)
  56
  57         buf = open(args.kernel_file,'rb').read()
  58         crc = binascii.crc32(buf) & 0xffffffff
  59         struct.pack_into('<L', header, 0x18, crc)
  60
  61         crc = binascii.crc32(header) & 0xffffffff
  62         struct.pack_into('<L', header, 0x8, crc)
  63
  64         struct.pack_into('<L', header, 0x0, 0x726553)
  65
  66         return header
  67
  68 def main():
  69         global args
  70
  71         parser = argparse.ArgumentParser(description='This script generates \
  72                 a kernel header for the Sercomm mt7621 devices')
  73
  74         parser.add_argument('--kernel-image',
  75                 dest='kernel_file',
  76                 action='store',
  77                 type=str,
  78                 help='Path to a Kernel binary image')
  79
  80         parser.add_argument('--kernel-offset',
  81                 dest='kernel_offset',
  82                 action='store',
  83                 type=auto_int,
  84                 help='Kernel offset')
  85
  86         parser.add_argument('--rootfs-offset',
  87                 dest='rootfs_offset',
  88                 action='store',
  89                 type=auto_int,
  90                 help='RootFS offset')
  91
  92         parser.add_argument('--output-header',
  93                 dest='header_file',
  94                 action='store',
  95                 type=str,
  96                 help='Output kernel header file')
  97
  98         parser.add_argument('--rootfs-image',
  99                 dest='rootfs_file',
 100                 action='store',
 101                 type=str,
 102                 help='Path to RootFS binary image (optional)')
 103
 104         parser.add_argument('--rootfs-checking-size',
 105                 dest='rootfs_checking_size',
 106                 action='store',
 107                 type=auto_int,
 108                 help='Bytes count for CRC calculation (optional)')
 109
 110         args = parser.parse_args()
 111
 112         if ((not args.kernel_file) or
 113             (not args.kernel_offset) or
 114             (not args.rootfs_offset) or
 115             (not args.header_file)):
 116                 parser.print_help()
 117                 exit()
 118
 119         create_kernel_header(args)
 120
 121 main()