--- /dev/null
+# 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):
+ 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
+ )
+
+ def show(self):
+ start = self.unpack_chs(self.start)
+ end = self.unpack_chs(self.end)
+ print "%d %s %d %s %d %d" % (self.status, start, self.type, end,
+ self.first_sector, self.sector_count)
+
+ def unpack_chs(self, chs):
+
+ 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):
+
+ 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])
+
+ def pack(self):
+ 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 show(self):
+ for i in range(4):
+ print "Part %d: " % i,
+ self.part[i].show()
+
+
+class GPTPartitionTable(object):
+ class GPTHeader(object):
+ 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.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):
+ return struct.pack(self.format,
+ self.signature, \
+ self.revision, \
+ self.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
+ )
+
+ def show(self):
+ print "Signature: %s" % self.signature
+ print "Revision: %r" % self.revision
+ print "Header Size: %d" % self.size
+ print "CRC32: %d" % self.header_crc32
+ print "Current LBA: %d" % self.current_lba
+ print "Backup LBA: %d" % self.backup_lba
+ print "First Usable LBA: %d" % self.first_usable_lba
+ print "Last Usable LBA: %d" % self.last_usable_lba
+ print "Disk GUID: %s" % uuid.UUID(bytes=self.uuid)
+ print "Partition entries starting LBA: %d" % self.part_entry_start
+ print "Number of Partition entries: %d" % self.part_count
+ print "Size of a partition entry: %d" % self.part_entry_size
+ print "CRC32 of partition array: %s" % 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)
+ lba1 = d.read(BLOCKSIZE)
+ self.primary = self.GPTHeader(lba1[:92])
+ # 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)
+ lba_1 = d.read(BLOCKSIZE)
+ self.secondary = self.GPTHeader(lba_1[:92])
+
+ def size(self):
+ return (self.primary.backup_lba + 1) * BLOCKSIZE
+
+ def shrink(self, size):
+
+ if size == self.size():
+ return size
+
+ assert size < self.size()
+
+ # new_size = size + Partition Entries + Secondary GPT Header
+ new_size = size + len(self.part_entries) + BLOCKSIZE
+ new_size = ((new_size + 4095) // 4096) * 4096 # align to 4K
+ lba_count = new_size // BLOCKSIZE
+
+ # Correct MBR
+ #TODO: Check for hybrid partition tables
+ self.mbr.part[0].sector_count = (new_size // BLOCKSIZE) - 1
+
+ # Correct 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
+
+ # Correct Secondary header entries
+ 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(struct.pack("%ss" % BLOCKSIZE, '\x00' * BLOCKSIZE))
+ d.seek(BLOCKSIZE)
+ d.write(self.primary.pack())
+ d.seek(self.secondary.part_entry_start * BLOCKSIZE)
+ d.write(self.part_entries)
+ d.seek(self.primary.backup_lba * BLOCKSIZE)
+ d.write(struct.pack("%ss" % BLOCKSIZE, '\x00' * BLOCKSIZE))
+ d.seek(self.primary.backup_lba * BLOCKSIZE)
+ d.write(self.secondary.pack())
+
+ return new_size
+
+if __name__ == '__main__':
+ ptable = GPTPartitionTable(sys.argv[1])
+
+ print "MBR:"
+ ptable.mbr.show()
+ print
+ print "Primary partition table:"
+ ptable.primary.show()
+ print
+ print "Secondary partition table:"
+ ptable.secondary.show()
+
+# vim: set sta sts=4 shiftwidth=4 sw=4 et ai :
projects / snf-image-creator / blobdiff