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Nikos Skalkotos authored
Fixed many `E127 continuation line over-indented for visual indent' errors
f99fe99d
gpt.py 11.42 KiB
# Copyright 2012 GRNET S.A. All rights reserved.
#
# Redistribution and use in source and binary forms, with or
# without modification, are permitted provided that the following
# conditions are met:
#
# 1. Redistributions of source code must retain the above
# copyright notice, this list of conditions and the following
# disclaimer.
#
# 2. Redistributions in binary form must reproduce the above
# copyright notice, this list of conditions and the following
# disclaimer in the documentation and/or other materials
# provided with the distribution.
#
# THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS
# OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GRNET S.A OR
# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.
#
# The views and conclusions contained in the software and
# documentation are those of the authors and should not be
# interpreted as representing official policies, either expressed
# or implied, of GRNET S.A.
import struct
import sys
import uuid
import binascii
BLOCKSIZE = 512
class MBR(object):
"""Represents a Master Boot Record."""
class Partition(object):
format = "<B3sB3sLL"
def __init__(self, raw_part):
(
self.status,
self.start,
self.type,
self.end,
self.first_sector,
self.sector_count
) = struct.unpack(self.format, raw_part)
def pack(self):
return struct.pack(self.format,
self.status,
self.start,
self.type,
self.end,
self.first_sector,
self.sector_count)
@staticmethod
def size():
"""Returns the size of an MBR partition entry"""
return struct.calcsize(MBR.Partition.format)
def __str__(self):
start = self.unpack_chs(self.start)
end = self.unpack_chs(self.end)
return "%d %s %d %s %d %d" % (self.status, start, self.type, end,
self.first_sector, self.sector_count)
def unpack_chs(self, chs):
"""Unpacks a CHS address string to a tuple."""
assert len(chs) == 3
head = struct.unpack('<B', chs[0])[0]
sector = struct.unpack('<B', chs[1])[0] & 0x3f
cylinder = (struct.unpack('<B', chs[1])[0] & 0xC0) << 2 | \
struct.unpack('<B', chs[2])[0]
return (cylinder, head, sector)
def pack_chs(self, cylinder, head, sector):
"""Packs a CHS tuple to an address string."""
assert 1 <= sector <= 63
assert 0 <= cylinder <= 1023
assert 0 <= head <= 255
byte0 = head
byte1 = (cylinder >> 2) & 0xC0 | sector
byte2 = cylinder & 0xff
return struct.pack('<BBB', byte0, byte1, byte2)
format = "<444s2x16s16s16s16s2s"
"""
Offset Length Contents
0 440(max. 446) code area
440 2(optional) disk signature
444 2 Usually nulls
446 16 Partition 0
462 16 Partition 1
478 16 Partition 2
494 16 Partition 3
510 2 MBR signature
"""
def __init__(self, block):
raw_part = {}
(self.code_area,
raw_part[0],
raw_part[1],
raw_part[2],
raw_part[3],
self.signature) = struct.unpack(self.format, block)
self.part = {}
for i in range(4):
self.part[i] = self.Partition(raw_part[i])
@staticmethod
def size():
"""Returns the size of a Master Boot Record."""
return struct.calcsize(MBR.format)
def pack(self):
"""Packs an MBR to a binary string."""
return struct.pack(self.format,
self.code_area,
self.part[0].pack(),
self.part[1].pack(),
self.part[2].pack(),
self.part[3].pack(),
self.signature)
def __str__(self):
ret = ""
for i in range(4):
ret += "Partition %d: %s\n" % (i, self.part[i])
ret += "Signature: %s %s\n" % (hex(ord(self.signature[0])),
hex(ord(self.signature[1])))
return ret
class GPTPartitionTable(object):
"""Represents a GUID Partition Table."""
class GPTHeader(object):
"""Represents a GPT Header of a GUID Partition Table."""
format = "<8s4sII4xQQQQ16sQIII"
"""
Offset Length Contents
0 8 bytes Signature
8 4 bytes Revision
12 4 bytes Header size in little endian
16 4 bytes CRC32 of header
20 4 bytes Reserved; must be zero
24 8 bytes Current LBA
32 8 bytes Backup LBA
40 8 bytes First usable LBA for partitions
48 8 bytes Last usable LBA
56 16 bytes Disk GUID
72 8 bytes Partition entries starting LBA
80 4 bytes Number of partition entries
84 4 bytes Size of a partition entry
88 4 bytes CRC32 of partition array
92 * Reserved; must be zeroes
LBA size Total
"""
def __init__(self, block):
(self.signature,
self.revision,
self.hdr_size,
self.header_crc32,
self.current_lba,
self.backup_lba,
self.first_usable_lba,
self.last_usable_lba,
self.uuid,
self.part_entry_start,
self.part_count,
self.part_entry_size,
self.part_crc32) = struct.unpack(self.format, block)
def pack(self):
"""Packs a GPT Header to a binary string."""
return struct.pack(self.format,
self.signature,
self.revision,
self.hdr_size,
self.header_crc32,
self.current_lba,
self.backup_lba,
self.first_usable_lba,
self.last_usable_lba,
self.uuid,
self.part_entry_start,
self.part_count,
self.part_entry_size,
self.part_crc32)
@staticmethod
def size():
"""Returns the size of a GPT Header."""
return struct.calcsize(GPTPartitionTable.GPTHeader.format)
def __str__(self):
return "Signature: %s\n" % self.signature + \
"Revision: %r\n" % self.revision + \
"Header Size: %d\n" % self.hdr_size + \
"CRC32: %d\n" % self.header_crc32 + \
"Current LBA: %d\n" % self.current_lba + \
"Backup LBA: %d\n" % self.backup_lba + \
"First Usable LBA: %d\n" % self.first_usable_lba + \
"Last Usable LBA: %d\n" % self.last_usable_lba + \
"Disk GUID: %s\n" % uuid.UUID(bytes=self.uuid) + \
"Partition entries starting LBA: %d\n" % \
self.part_entry_start + \
"Number of Partition entries: %d\n" % self.part_count + \
"Size of a partition entry: %d\n" % self.part_entry_size + \
"CRC32 of partition array: %s\n" % self.part_crc32
def __init__(self, disk):
self.disk = disk
with open(disk, "rb") as d:
# MBR (Logical block address 0)
lba0 = d.read(BLOCKSIZE)
self.mbr = MBR(lba0)
# Primary GPT Header (LBA 1)
raw_header = d.read(self.GPTHeader.size())
self.primary = self.GPTHeader(raw_header)
# Partition entries (LBA 2...34)
d.seek(self.primary.part_entry_start * BLOCKSIZE)
entries_size = self.primary.part_count * \
self.primary.part_entry_size
self.part_entries = d.read(entries_size)
# Secondary GPT Header (LBA -1)
d.seek(self.primary.backup_lba * BLOCKSIZE)
raw_header = d.read(self.GPTHeader.size())
self.secondary = self.GPTHeader(raw_header)
def size(self):
"""Returns the payload size of GPT partitioned device."""
return (self.primary.backup_lba + 1) * BLOCKSIZE
def shrink(self, size, old_size):
"""Move the secondary GPT Header entries to the address specified by
size parameter.
"""
# Most partition manipulation programs leave 2048 sector after the last
# partition
aligned = size + 2048 * BLOCKSIZE
# new_size is at least: size + Partition Entries + Secondary GPT Header
new_size = aligned if aligned <= old_size else \
size + len(self.part_entries) + BLOCKSIZE
assert new_size <= old_size, "The secodary GPT fits in the device"
if new_size == self.size():
return new_size
lba_count = new_size // BLOCKSIZE
# Correct MBR
#TODO: Check if the partition tables is hybrid
self.mbr.part[0].sector_count = (new_size // BLOCKSIZE) - 1
# Fix Primary header
self.primary.header_crc32 = 0
self.primary.backup_lba = lba_count - 1 # LBA-1
self.primary.last_usable_lba = lba_count - 34 # LBA-34
self.primary.header_crc32 = \
binascii.crc32(self.primary.pack()) & 0xffffffff
# Fix Secondary header
self.secondary.header_crc32 = 0
self.secondary.current_lba = self.primary.backup_lba
self.secondary.last_usable_lba = lba_count - 34 # LBA-34
self.secondary.part_entry_start = lba_count - 33 # LBA-33
self.secondary.header_crc32 = \
binascii.crc32(self.secondary.pack()) & 0xffffffff
# Copy the new partition table back to the device
with open(self.disk, "wb") as d:
d.write(self.mbr.pack())
d.write(self.primary.pack())
d.write('\x00' * (BLOCKSIZE - self.primary.size()))
d.seek(self.secondary.part_entry_start * BLOCKSIZE)
d.write(self.part_entries)
d.seek(self.primary.backup_lba * BLOCKSIZE)
d.write(self.secondary.pack())
d.write('\x00' * (BLOCKSIZE - self.secondary.size()))
return new_size
if __name__ == '__main__':
ptable = GPTPartitionTable(sys.argv[1])
print "MBR:\n%s" % ptable.mbr
print "Primary partition table:\n%s" % ptable.primary
print "Secondary partition table:\n%s" % ptable.secondary
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