root / image_creator / gpt.py @ bf3a282c
History | View | Annotate | Download (11.8 kB)
| 1 |
# Copyright 2012 GRNET S.A. All rights reserved.
|
|---|---|
| 2 |
#
|
| 3 |
# Redistribution and use in source and binary forms, with or
|
| 4 |
# without modification, are permitted provided that the following
|
| 5 |
# conditions are met:
|
| 6 |
#
|
| 7 |
# 1. Redistributions of source code must retain the above
|
| 8 |
# copyright notice, this list of conditions and the following
|
| 9 |
# disclaimer.
|
| 10 |
#
|
| 11 |
# 2. Redistributions in binary form must reproduce the above
|
| 12 |
# copyright notice, this list of conditions and the following
|
| 13 |
# disclaimer in the documentation and/or other materials
|
| 14 |
# provided with the distribution.
|
| 15 |
#
|
| 16 |
# THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS
|
| 17 |
# OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
|
| 18 |
# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
|
| 19 |
# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GRNET S.A OR
|
| 20 |
# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
|
| 21 |
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
|
| 22 |
# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
|
| 23 |
# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
|
| 24 |
# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
| 25 |
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
|
| 26 |
# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
| 27 |
# POSSIBILITY OF SUCH DAMAGE.
|
| 28 |
#
|
| 29 |
# The views and conclusions contained in the software and
|
| 30 |
# documentation are those of the authors and should not be
|
| 31 |
# interpreted as representing official policies, either expressed
|
| 32 |
# or implied, of GRNET S.A.
|
| 33 |
|
| 34 |
import struct |
| 35 |
import sys |
| 36 |
import uuid |
| 37 |
import binascii |
| 38 |
|
| 39 |
BLOCKSIZE = 512
|
| 40 |
|
| 41 |
|
| 42 |
class MBR(object): |
| 43 |
"""Represents a Master Boot Record."""
|
| 44 |
class Partition(object): |
| 45 |
"""Represents a partition entry in MBR"""
|
| 46 |
format = "<B3sB3sLL"
|
| 47 |
|
| 48 |
def __init__(self, raw_part): |
| 49 |
"""Create a Partition instance"""
|
| 50 |
( |
| 51 |
self.status,
|
| 52 |
self.start,
|
| 53 |
self.type,
|
| 54 |
self.end,
|
| 55 |
self.first_sector,
|
| 56 |
self.sector_count
|
| 57 |
) = struct.unpack(self.format, raw_part)
|
| 58 |
|
| 59 |
def pack(self): |
| 60 |
"""Pack the partition values into a binary string"""
|
| 61 |
return struct.pack(self.format, |
| 62 |
self.status,
|
| 63 |
self.start,
|
| 64 |
self.type,
|
| 65 |
self.end,
|
| 66 |
self.first_sector,
|
| 67 |
self.sector_count)
|
| 68 |
|
| 69 |
@staticmethod
|
| 70 |
def size(): |
| 71 |
"""Returns the size of an MBR partition entry"""
|
| 72 |
return struct.calcsize(MBR.Partition.format)
|
| 73 |
|
| 74 |
def __str__(self): |
| 75 |
start = self.unpack_chs(self.start) |
| 76 |
end = self.unpack_chs(self.end) |
| 77 |
return "%d %s %d %s %d %d" % (self.status, start, self.type, end, |
| 78 |
self.first_sector, self.sector_count) |
| 79 |
|
| 80 |
def unpack_chs(self, chs): |
| 81 |
"""Unpacks a CHS address string to a tuple."""
|
| 82 |
|
| 83 |
assert len(chs) == 3 |
| 84 |
|
| 85 |
head = struct.unpack('<B', chs[0])[0] |
| 86 |
sector = struct.unpack('<B', chs[1])[0] & 0x3f |
| 87 |
cylinder = (struct.unpack('<B', chs[1])[0] & 0xC0) << 2 | \ |
| 88 |
struct.unpack('<B', chs[2])[0] |
| 89 |
|
| 90 |
return (cylinder, head, sector)
|
| 91 |
|
| 92 |
def pack_chs(self, cylinder, head, sector): |
| 93 |
"""Packs a CHS tuple to an address string."""
|
| 94 |
|
| 95 |
assert 1 <= sector <= 63 |
| 96 |
assert 0 <= cylinder <= 1023 |
| 97 |
assert 0 <= head <= 255 |
| 98 |
|
| 99 |
byte0 = head |
| 100 |
byte1 = (cylinder >> 2) & 0xC0 | sector |
| 101 |
byte2 = cylinder & 0xff
|
| 102 |
|
| 103 |
return struct.pack('<BBB', byte0, byte1, byte2) |
| 104 |
|
| 105 |
format = "<444s2x16s16s16s16s2s"
|
| 106 |
"""
|
| 107 |
Offset Length Contents
|
| 108 |
0 440(max. 446) code area
|
| 109 |
440 2(optional) disk signature
|
| 110 |
444 2 Usually nulls
|
| 111 |
446 16 Partition 0
|
| 112 |
462 16 Partition 1
|
| 113 |
478 16 Partition 2
|
| 114 |
494 16 Partition 3
|
| 115 |
510 2 MBR signature
|
| 116 |
"""
|
| 117 |
def __init__(self, block): |
| 118 |
"""Create an MBR instance"""
|
| 119 |
raw_part = {}
|
| 120 |
(self.code_area,
|
| 121 |
raw_part[0],
|
| 122 |
raw_part[1],
|
| 123 |
raw_part[2],
|
| 124 |
raw_part[3],
|
| 125 |
self.signature) = struct.unpack(self.format, block) |
| 126 |
|
| 127 |
self.part = {}
|
| 128 |
for i in range(4): |
| 129 |
self.part[i] = self.Partition(raw_part[i]) |
| 130 |
|
| 131 |
@staticmethod
|
| 132 |
def size(): |
| 133 |
"""Return the size of a Master Boot Record."""
|
| 134 |
return struct.calcsize(MBR.format)
|
| 135 |
|
| 136 |
def pack(self): |
| 137 |
"""Pack an MBR to a binary string."""
|
| 138 |
return struct.pack(self.format, |
| 139 |
self.code_area,
|
| 140 |
self.part[0].pack(), |
| 141 |
self.part[1].pack(), |
| 142 |
self.part[2].pack(), |
| 143 |
self.part[3].pack(), |
| 144 |
self.signature)
|
| 145 |
|
| 146 |
def __str__(self): |
| 147 |
ret = ""
|
| 148 |
for i in range(4): |
| 149 |
ret += "Partition %d: %s\n" % (i, self.part[i]) |
| 150 |
ret += "Signature: %s %s\n" % (hex(ord(self.signature[0])), |
| 151 |
hex(ord(self.signature[1]))) |
| 152 |
return ret
|
| 153 |
|
| 154 |
|
| 155 |
class GPTPartitionTable(object): |
| 156 |
"""Represents a GUID Partition Table."""
|
| 157 |
class GPTHeader(object): |
| 158 |
"""Represents a GPT Header of a GUID Partition Table."""
|
| 159 |
format = "<8s4sII4xQQQQ16sQIII"
|
| 160 |
"""
|
| 161 |
Offset Length Contents
|
| 162 |
0 8 bytes Signature
|
| 163 |
8 4 bytes Revision
|
| 164 |
12 4 bytes Header size in little endian
|
| 165 |
16 4 bytes CRC32 of header
|
| 166 |
20 4 bytes Reserved; must be zero
|
| 167 |
24 8 bytes Current LBA
|
| 168 |
32 8 bytes Backup LBA
|
| 169 |
40 8 bytes First usable LBA for partitions
|
| 170 |
48 8 bytes Last usable LBA
|
| 171 |
56 16 bytes Disk GUID
|
| 172 |
72 8 bytes Partition entries starting LBA
|
| 173 |
80 4 bytes Number of partition entries
|
| 174 |
84 4 bytes Size of a partition entry
|
| 175 |
88 4 bytes CRC32 of partition array
|
| 176 |
92 * Reserved; must be zeroes
|
| 177 |
LBA size Total
|
| 178 |
"""
|
| 179 |
|
| 180 |
def __init__(self, block): |
| 181 |
"""Create a GPTHeader instance"""
|
| 182 |
(self.signature,
|
| 183 |
self.revision,
|
| 184 |
self.hdr_size,
|
| 185 |
self.header_crc32,
|
| 186 |
self.current_lba,
|
| 187 |
self.backup_lba,
|
| 188 |
self.first_usable_lba,
|
| 189 |
self.last_usable_lba,
|
| 190 |
self.uuid,
|
| 191 |
self.part_entry_start,
|
| 192 |
self.part_count,
|
| 193 |
self.part_entry_size,
|
| 194 |
self.part_crc32) = struct.unpack(self.format, block) |
| 195 |
|
| 196 |
def pack(self): |
| 197 |
"""Packs a GPT Header to a binary string."""
|
| 198 |
return struct.pack(self.format, |
| 199 |
self.signature,
|
| 200 |
self.revision,
|
| 201 |
self.hdr_size,
|
| 202 |
self.header_crc32,
|
| 203 |
self.current_lba,
|
| 204 |
self.backup_lba,
|
| 205 |
self.first_usable_lba,
|
| 206 |
self.last_usable_lba,
|
| 207 |
self.uuid,
|
| 208 |
self.part_entry_start,
|
| 209 |
self.part_count,
|
| 210 |
self.part_entry_size,
|
| 211 |
self.part_crc32)
|
| 212 |
|
| 213 |
@staticmethod
|
| 214 |
def size(): |
| 215 |
"""Return the size of a GPT Header."""
|
| 216 |
return struct.calcsize(GPTPartitionTable.GPTHeader.format)
|
| 217 |
|
| 218 |
def __str__(self): |
| 219 |
"""Print a GPTHeader"""
|
| 220 |
return "Signature: %s\n" % self.signature + \ |
| 221 |
"Revision: %r\n" % self.revision + \ |
| 222 |
"Header Size: %d\n" % self.hdr_size + \ |
| 223 |
"CRC32: %d\n" % self.header_crc32 + \ |
| 224 |
"Current LBA: %d\n" % self.current_lba + \ |
| 225 |
"Backup LBA: %d\n" % self.backup_lba + \ |
| 226 |
"First Usable LBA: %d\n" % self.first_usable_lba + \ |
| 227 |
"Last Usable LBA: %d\n" % self.last_usable_lba + \ |
| 228 |
"Disk GUID: %s\n" % uuid.UUID(bytes=self.uuid) + \ |
| 229 |
"Partition entries starting LBA: %d\n" % \
|
| 230 |
self.part_entry_start + \
|
| 231 |
"Number of Partition entries: %d\n" % self.part_count + \ |
| 232 |
"Size of a partition entry: %d\n" % self.part_entry_size + \ |
| 233 |
"CRC32 of partition array: %s\n" % self.part_crc32 |
| 234 |
|
| 235 |
def __init__(self, disk): |
| 236 |
"""Create a GPTPartitionTable instance"""
|
| 237 |
self.disk = disk
|
| 238 |
with open(disk, "rb") as d: |
| 239 |
# MBR (Logical block address 0)
|
| 240 |
lba0 = d.read(BLOCKSIZE) |
| 241 |
self.mbr = MBR(lba0)
|
| 242 |
|
| 243 |
# Primary GPT Header (LBA 1)
|
| 244 |
raw_header = d.read(self.GPTHeader.size())
|
| 245 |
self.primary = self.GPTHeader(raw_header) |
| 246 |
|
| 247 |
# Partition entries (LBA 2...34)
|
| 248 |
d.seek(self.primary.part_entry_start * BLOCKSIZE)
|
| 249 |
entries_size = self.primary.part_count * \
|
| 250 |
self.primary.part_entry_size
|
| 251 |
self.part_entries = d.read(entries_size)
|
| 252 |
|
| 253 |
# Secondary GPT Header (LBA -1)
|
| 254 |
d.seek(self.primary.backup_lba * BLOCKSIZE)
|
| 255 |
raw_header = d.read(self.GPTHeader.size())
|
| 256 |
self.secondary = self.GPTHeader(raw_header) |
| 257 |
|
| 258 |
def size(self): |
| 259 |
"""Return the payload size of GPT partitioned device."""
|
| 260 |
return (self.primary.backup_lba + 1) * BLOCKSIZE |
| 261 |
|
| 262 |
def shrink(self, size, old_size): |
| 263 |
"""Move the secondary GPT Header entries to the address specified by
|
| 264 |
size parameter.
|
| 265 |
"""
|
| 266 |
|
| 267 |
# Most partition manipulation programs leave 2048 sector after the last
|
| 268 |
# partition
|
| 269 |
aligned = size + 2048 * BLOCKSIZE
|
| 270 |
|
| 271 |
# new_size is at least: size + Partition Entries + Secondary GPT Header
|
| 272 |
new_size = aligned if aligned <= old_size else \ |
| 273 |
size + len(self.part_entries) + BLOCKSIZE |
| 274 |
|
| 275 |
assert new_size <= old_size, "The secodary GPT fits in the device" |
| 276 |
|
| 277 |
if new_size == self.size(): |
| 278 |
return new_size
|
| 279 |
|
| 280 |
lba_count = new_size // BLOCKSIZE |
| 281 |
|
| 282 |
# Correct MBR
|
| 283 |
#TODO: Check if the partition tables is hybrid
|
| 284 |
self.mbr.part[0].sector_count = (new_size // BLOCKSIZE) - 1 |
| 285 |
|
| 286 |
# Fix Primary header
|
| 287 |
self.primary.header_crc32 = 0 |
| 288 |
self.primary.backup_lba = lba_count - 1 # LBA-1 |
| 289 |
self.primary.last_usable_lba = lba_count - 34 # LBA-34 |
| 290 |
self.primary.header_crc32 = \
|
| 291 |
binascii.crc32(self.primary.pack()) & 0xffffffff |
| 292 |
|
| 293 |
# Fix Secondary header
|
| 294 |
self.secondary.header_crc32 = 0 |
| 295 |
self.secondary.current_lba = self.primary.backup_lba |
| 296 |
self.secondary.last_usable_lba = lba_count - 34 # LBA-34 |
| 297 |
self.secondary.part_entry_start = lba_count - 33 # LBA-33 |
| 298 |
self.secondary.header_crc32 = \
|
| 299 |
binascii.crc32(self.secondary.pack()) & 0xffffffff |
| 300 |
|
| 301 |
# Copy the new partition table back to the device
|
| 302 |
with open(self.disk, "wb") as d: |
| 303 |
d.write(self.mbr.pack())
|
| 304 |
d.write(self.primary.pack())
|
| 305 |
d.write('\x00' * (BLOCKSIZE - self.primary.size())) |
| 306 |
d.write(self.part_entries)
|
| 307 |
d.seek(self.secondary.part_entry_start * BLOCKSIZE)
|
| 308 |
d.write(self.part_entries)
|
| 309 |
d.seek(self.primary.backup_lba * BLOCKSIZE)
|
| 310 |
d.write(self.secondary.pack())
|
| 311 |
d.write('\x00' * (BLOCKSIZE - self.secondary.size())) |
| 312 |
|
| 313 |
return new_size
|
| 314 |
|
| 315 |
if __name__ == '__main__': |
| 316 |
ptable = GPTPartitionTable(sys.argv[1])
|
| 317 |
|
| 318 |
print "MBR:\n%s" % ptable.mbr |
| 319 |
print "Primary partition table:\n%s" % ptable.primary |
| 320 |
print "Secondary partition table:\n%s" % ptable.secondary |
| 321 |
|
| 322 |
# vim: set sta sts=4 shiftwidth=4 sw=4 et ai :
|