blob: 3898da00d33d6637d8f36560ede4c8745b3b9fcb [file] [log] [blame]
# Copyright (c) 2010 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.
from optparse import OptionParser
import binascii
import struct
import sys
# This script allows listing, reading and writing environment variables for
# u-boot, that usually live in an area of a block device (NVRAM, e.g. NAND or
# NOR flash).
# The u-boot environment variable area is a crc (4 bytes) followed by all
# environment variables as "key=value" strings (\0-terminated) with \0\0
# (empty string) to indicate the end.
class SizeError(Exception):
def ReadEnviron(file, size=0, offset=0):
"""Reads the u-boot environment variables from a file into a dict."""
f = open(file, "rb")
if size:
data =
data =
(crc,) = struct.unpack("I", data[0:4])
real_data = data[4:]
real_crc = binascii.crc32(real_data) & 0xffffffff
environ = {}
for s in real_data.split('\0'):
if not s:
key, value = s.split('=', 1)
environ[key] = value
return (environ, len(data), crc == real_crc)
def WriteEnviron(file, environ, size, offset=0):
"""Writes the u-boot environment variables from a dict into a file."""
strings = ['%s=%s' % (k, environ[k]) for k in environ]
data = '\0'.join(strings + [''])
# pad with \0
if len(data) <= size-4:
data = data + '\0'*(size-len(data)-4)
raise SizeError
crc = binascii.crc32(data) & 0xffffffff
f = open(file, "r+b")
f.write(struct.pack("I", crc)[0:4])
def main(argv):
parser = OptionParser()
parser.add_option('-f', '--file', type='string', dest='filename')
parser.add_option('-o', '--offset', type='int', dest='offset', default=0)
parser.add_option('-s', '--size', type='int', dest='size', default=0)
parser.add_option('--out', type='string', dest='out_filename')
parser.add_option('--out-offset', type='string', dest='out_offset')
parser.add_option('--out-size', type='string', dest='out_size')
parser.add_option('--list', action='store_true', dest='list')
parser.add_option('--force', action='store_true', dest='force')
parser.add_option('--get', type='string', action='append', dest='get',
parser.add_option('--set', type='string', action='append', dest='set',
(options, args) = parser.parse_args()
(environ, size, crc) = ReadEnviron(options.filename, options.size,
if not crc:
sys.stderr.write('Bad CRC\n')
if not options.force:
if options.list:
for key in environ:
print "%s=%s" % (key, environ[key])
for key in options.get:
print environ[key]
except KeyError:
print ''
do_write = False
for key_value in options.set:
key, value = key_value.split('=', 1)
environ[key] = value
do_write = True
if do_write:
out_filename = options.out_filename
out_offset = options.out_offset
out_size = options.out_size
if not out_filename:
out_filename = options.filename
out_offset = options.offset
out_size = size
WriteEnviron(out_filename, environ, out_size, out_offset)
if __name__ == '__main__':