utils/lock_u_boot_console

#!/usr/bin/env python
# Copyright 2018 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
"""Lock/unlock the u-boot console."""

import argparse
import binascii
import logging
import mmap
import os
import struct


SD_PATH = '/dev/mmcblk0'
BOOTDELAY = 'bootdelay'
ENV_OFFSET = 0x200
LOCK = '0'
UNLOCK = '5'


def main():
  """The Main program."""
  parser = argparse.ArgumentParser(
      description='Lock/unlock the u-boot console',
      formatter_class=argparse.ArgumentDefaultsHelpFormatter)
  parser.add_argument('-l', '--lock', dest='lock', action='store_true',
                      help='lock the u-boot console')
  parser.add_argument('-u', '--unlock', dest='unlock', action='store_true',
                      help='unlock the u-boot console')
  parser.add_argument('-v', '--verbose', action='count', dest='verbose',
                      help='increase message verbosity')

  options = parser.parse_args()
  verbosity_map = {0: logging.INFO, 1: logging.DEBUG}
  verbosity = verbosity_map.get(options.verbose or 0, logging.NOTSET)
  log_format = '%(asctime)s %(levelname)s '
  if options.verbose > 0:
    log_format += '(%(filename)s:%(lineno)d) '
  log_format += '%(message)s'

  log_config = {'level': verbosity,
                'format': log_format}
  logging.basicConfig(**log_config)

  if options.lock and options.unlock:
    logging.error('Lock and unlock at the same time?')
    exit(1)

  # Mmap the SD card image, for the first 5K area.
  # The u-boot environment variables are stored at 0x200, size: 4K.
  fd = os.open(SD_PATH, os.O_RDWR)
  mm = mmap.mmap(fd, 5 * 1024, access=mmap.ACCESS_WRITE)

  # Find bootdelay, i.e. how long to wait to skip u-boot console.
  pattern = BOOTDELAY + '='
  index = mm.find(pattern, ENV_OFFSET)
  logging.debug('index found: %d', index)
  if index == -1:
    logging.error('Pattern %s not found', pattern)
    exit(2)
  index += len(pattern)

  is_changed = False
  value = mm[index]
  if value not in (LOCK, UNLOCK):
    logging.error('The boot_delay value not expected: %r', value)
    exit(3)

  # Original bootdelay value is 5, meaning unlocked. Change it to 0 for
  # locking the console.
  logging.debug('original value: %d', int(value))
  if options.unlock:
    if value != UNLOCK:
      mm[index] = UNLOCK
      logging.info('Unlocked the u-boot console')
      is_changed = True
    else:
      logging.info('Already in unlocked state; nothing to do')
  elif options.lock:
    if value != LOCK:
      mm[index] = LOCK
      logging.info('Locked the u-boot console')
      is_changed = True
    else:
      logging.info('Already in locked state; nothing to do')
  else:
    logging.info('Current lock state: %s',
                 'locked' if value == LOCK else 'unlocked')

  if is_changed:
    value = mm[index]
    logging.debug('new value: %d', int(value))
    # Update the crc32 of the data, starting from the 0x204 to the end
    # (0x200+4K), and keep it in 0x200.
    crc = binascii.crc32(mm[ENV_OFFSET+4:ENV_OFFSET+4096])
    mm[ENV_OFFSET:ENV_OFFSET+4] = struct.pack('<i', crc)


if __name__ == '__main__':
  main()