root / snf-image-helper / disklabel.py @ 501e19ec
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#!/usr/bin/env python
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#
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# -*- coding: utf-8 -*-
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#
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# Copyright (C) 2013 GRNET S.A.
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful, but
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# WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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# 02110-1301, USA.
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"""This module provides the code for handling BSD disklabels"""
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import struct |
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import sys |
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import os |
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import cStringIO |
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import optparse |
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from collections import namedtuple |
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from collections import OrderedDict |
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BLOCKSIZE = 512
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LABELSECTOR = 1
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LABELOFFSET = 0
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BBSIZE = 8192 # size of boot area with label |
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SBSIZE = 8192 # max size of fs superblock |
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DISKMAGIC = 0x82564557
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class MBR(object): |
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"""Represents a Master Boot Record."""
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class Partition(object): |
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"""Represents a partition entry in MBR"""
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format = "<B3sB3sLL"
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def __init__(self, raw_part): |
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"""Create a Partition instance"""
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(self.status,
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self.start,
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self.type,
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self.end,
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self.first_sector,
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self.sector_count
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) = struct.unpack(self.format, raw_part)
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def pack(self): |
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"""Pack the partition values into a binary string"""
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return struct.pack(self.format, |
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self.status,
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self.start,
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self.type,
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self.end,
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self.first_sector,
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self.sector_count)
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@staticmethod
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def size(): |
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"""Returns the size of an MBR partition entry"""
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return struct.calcsize(MBR.Partition.format)
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def __str__(self): |
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start = self.unpack_chs(self.start) |
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end = self.unpack_chs(self.end) |
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return "%d %s %d %s %d %d" % (self.status, start, self.type, end, |
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self.first_sector, self.sector_count) |
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@staticmethod
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def unpack_chs(chs): |
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"""Unpacks a CHS address string to a tuple."""
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assert len(chs) == 3 |
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head = struct.unpack('<B', chs[0])[0] |
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sector = struct.unpack('<B', chs[1])[0] & 0x3f |
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cylinder = (struct.unpack('<B', chs[1])[0] & 0xC0) << 2 | \ |
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struct.unpack('<B', chs[2])[0] |
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return (cylinder, head, sector)
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@staticmethod
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def pack_chs(cylinder, head, sector): |
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"""Packs a CHS tuple to an address string."""
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assert 1 <= sector <= 63 |
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assert 0 <= head <= 255 |
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assert 0 <= cylinder |
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# If the cylinders overflow then put the value (1023, 254, 63) to
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# the tuple. At least this is what OpenBSD does.
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if cylinder > 1023: |
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cylinder = 1023
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head = 254
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sector = 63
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byte0 = head |
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byte1 = (cylinder >> 2) & 0xC0 | sector |
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byte2 = cylinder & 0xff
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return struct.pack('<BBB', byte0, byte1, byte2) |
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format = "<444s2x16s16s16s16s2s"
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"""
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Offset Length Contents
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0 440(max. 446) code area
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440 2(optional) disk signature
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444 2 Usually nulls
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446 16 Partition 0
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462 16 Partition 1
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478 16 Partition 2
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494 16 Partition 3
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510 2 MBR signature
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"""
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def __init__(self, block): |
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"""Create an MBR instance"""
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raw_part = {}
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(self.code_area,
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raw_part[0],
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raw_part[1],
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raw_part[2],
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raw_part[3],
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self.signature) = struct.unpack(self.format, block) |
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self.part = {}
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for i in range(4): |
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self.part[i] = self.Partition(raw_part[i]) |
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@staticmethod
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def size(): |
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"""Return the size of a Master Boot Record."""
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return struct.calcsize(MBR.format)
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def pack(self): |
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"""Pack an MBR to a binary string."""
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return struct.pack(self.format, |
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self.code_area,
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self.part[0].pack(), |
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self.part[1].pack(), |
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self.part[2].pack(), |
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self.part[3].pack(), |
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self.signature)
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def __str__(self): |
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ret = ""
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for i in range(4): |
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ret += "Partition %d: %s\n" % (i, self.part[i]) |
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ret += "Signature: %s %s\n" % (hex(ord(self.signature[0])), |
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hex(ord(self.signature[1]))) |
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title = "Master Boot Record"
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return "%s\n%s\n%s\n" % (title, len(title) * "=", ret) |
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class Disk(object): |
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"""Represents an BSD Disk"""
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def __init__(self, device): |
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"""Create a Disk instance"""
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self.device = device
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self.part_num = None |
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self.disklabel = None |
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with open(device, "rb") as d: |
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sector0 = d.read(BLOCKSIZE) |
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self.mbr = MBR(sector0)
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for i in range(4): |
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ptype = self.mbr.part[i].type
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if ptype in (0xa5, 0xa6, 0xa9): |
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d.seek(BLOCKSIZE * self.mbr.part[i].first_sector)
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self.part_num = i
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if ptype == 0xa5: # FreeBSD |
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self.disklabel = BSD_Disklabel(d)
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elif ptype == 0xa6: # OpenBSD |
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self.disklabel = OpenBSD_Disklabel(d)
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else: # NetBSD |
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self.disklabel = BSD_Disklabel(d)
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break
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assert self.disklabel is not None, "No *BSD partition found" |
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def write(self): |
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"""Write the changes back to the media"""
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with open(self.device, 'rw+b') as d: |
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d.write(self.mbr.pack())
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d.seek(self.mbr.part[self.part_num].first_sector * BLOCKSIZE) |
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self.disklabel.write_to(d)
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def __str__(self): |
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return str(self.mbr) + str(self.disklabel) |
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def enlarge(self, new_size): |
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"""Enlarge the disk and return the last usable sector"""
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# Fix the disklabel
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end = self.disklabel.enlarge(new_size)
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# Fix the MBR
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start = self.mbr.part[self.part_num].first_sector |
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self.mbr.part[self.part_num].sector_count = end - start + 1 |
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ntracks = self.disklabel.field['ntracks'] |
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nsectors = self.disklabel.field['nsectors'] |
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cylinder = end // (ntracks * nsectors) |
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header = (end // nsectors) % ntracks |
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sector = (end % nsectors) + 1
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chs = MBR.Partition.pack_chs(cylinder, header, sector) |
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self.mbr.part[self.part_num].end = chs |
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def enlarge_last_partition(self): |
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"""Enlarge the last partition to cover up all the free space"""
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self.disklabel.enlarge_last_partition()
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def get_last_partition_id(self): |
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"""Get the ID of the last partition"""
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return self.disklabel.get_last_partition_id() |
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def get_duid(self): |
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return self.disklabel.field['uid'] |
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class DisklabelBase(object): |
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"""Disklabel base class"""
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def __init__(self, device): |
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"""Create a Disklabel instance"""
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raise NotImplementedError |
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def pack(self, checksum=None): |
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"""Return a binary copy of the Disklabel block"""
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out = OrderedDict() |
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for k, v in self.field.items(): |
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out[k] = v |
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if checksum is not None: |
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out['checksum'] = checksum
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return struct.pack(self.format, * out.values() + [self.ptable.pack()]) |
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def compute_checksum(self): |
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"""Compute the checksum of the disklabel"""
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raw = cStringIO.StringIO(self.pack(0)) |
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checksum = 0
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try:
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uint16 = raw.read(2)
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while uint16 != "": |
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checksum ^= struct.unpack('<H', uint16)[0] |
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uint16 = raw.read(2)
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finally:
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raw.close() |
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return checksum
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def enlarge(self, new_size): |
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"""Enlarge the disk and return the last usable sector"""
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raise NotImplementedError |
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def write_to(self, device): |
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"""Write the disklabel to a device"""
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# The disklabel starts at sector 1
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device.seek(BLOCKSIZE, os.SEEK_CUR) |
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device.write(self.pack())
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def enlarge_last_partition(self): |
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"""Enlarge the last partition to consume all the usable space"""
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raise NotImplementedError |
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def get_last_partition_id(self): |
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"""Get the ID of the last partition"""
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raise NotImplementedError |
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def __str__(self): |
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"""Print the Disklabel"""
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raise NotImplementedError |
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class PartitionTableBase(object): |
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"""Base Class for disklabel partition tables"""
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@property
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def format(self): |
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"""Partition table format string"""
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raise NotImplementedError |
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Partition = namedtuple('Partition', '') |
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def __init__(self, ptable, pnumber): |
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"""Create a Partition Table instance"""
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self.part = []
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size = struct.calcsize(self.format)
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raw = cStringIO.StringIO(ptable) |
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try:
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for i in range(pnumber): |
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p = self.Partition(
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*struct.unpack(self.format, raw.read(size)))
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self.part.append(p)
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finally:
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raw.close() |
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def __str__(self): |
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"""Print the Partition table"""
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val = ""
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for i in range(len(self.part)): |
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val += "%c: %s\n" % (chr(ord('a') + i), str(self.part[i])) |
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return val
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def pack(self): |
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"""Packs the partition table into a binary string."""
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ret = ""
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for i in range(len(self.part)): |
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ret += struct.pack(self.format, *self.part[i]) |
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return ret + ((364 - len(self.part) * 16) * '\x00') |
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class BSD_Disklabel(DisklabelBase): |
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"""Represents an BSD Disklabel"""
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class PartitionTable(PartitionTableBase): |
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"""Represents a BSD Partition Table"""
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format = "<IIIBBH"
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"""
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Partition Entry:
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Offset Length Contents
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0 4 Number of sectors in partition
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4 4 Starting sector
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8 4 Filesystem basic fragment size
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12 1 Filesystem type
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13 1 Filesystem fragments per block
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14 2 Filesystem cylinders per group
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"""
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Partition = namedtuple( |
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'Partition', 'size, offset, fsize, fstype, frag, cpg') |
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format = "<IHH16s16sIIIIIIHHIHHHHIII20s20sIHHII364s"
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"""
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Offset Length Contents
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0 4 Magic
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4 2 Drive Type
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6 2 Subtype
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8 16 Type Name
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24 16 Pack Identifier
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32 4 Bytes per sector
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36 4 Data sectors per track
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40 4 Tracks per cylinder
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44 4 Data cylinders per unit
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48 4 Data sectors per cylinder
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52 4 Data sectors per unit
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56 2 Spare sectors per track
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58 2 Spare sectors per cylinder
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60 4 Alternative cylinders per unit
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64 2 Rotation Speed
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66 2 Hardware sector interleave
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68 2 Sector 0 skew, per track
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70 2 Sector 0 skew, per cylinder
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72 4 Head switch time
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76 4 Track-to-track seek
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80 4 Generic Flags
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84 5*4 Drive-type specific information
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104 5*4 Reserved for future use
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124 4 Magic Number
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128 2 Xor of data including partitions
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130 2 Number of partitions following
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132 4 size of boot area at sn0, bytes
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136 4 Max size of fs superblock, bytes
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140 16*16 Partition Table
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"""
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class OpenBSD_Disklabel(DisklabelBase): |
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"""Represents an OpenBSD Disklabel"""
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class PartitionTable(PartitionTableBase): |
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"""Reprepsents an OpenBSD Partition Table"""
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format = "<IIHHBBH"
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"""
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Partition Entry:
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Offset Length Contents
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0 4 Number of sectors in the partition
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4 4 Starting sector
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8 2 Starting sector (high part)
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10 2 Number of sectors (high part)
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12 1 Filesystem type
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13 1 Filesystem Fragment per block
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14 2 FS cylinders per group
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"""
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|
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Partition = namedtuple( |
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'Partition', 'size, offset, offseth, sizeh, fstype, frag, cpg') |
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|
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def setpsize(self, i, size): |
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"""Set size for partition i"""
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tmp = self.part[i]
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self.part[i] = self.Partition( |
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size & 0xffffffff, tmp.offset, tmp.offseth, size >> 32, |
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tmp.fstype, tmp.frag, tmp.cpg) |
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|
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def getpsize(self, i): |
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"""Get size for partition i"""
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return (self.part[i].sizeh << 32) + self.part[i].size |
| 421 |
|
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def setpoffset(self, i, offset): |
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"""Set offset for partition i"""
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tmp = self.part[i]
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self.part[i] = self.Partition( |
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tmp.size, offset & 0xffffffff, offset >> 32, tmp.sizeh, |
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tmp.frag, tmp.cpg) |
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|
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def getpoffset(self, i): |
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"""Get offset for partition i"""
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return (self.part[i].offseth << 32) + self.part[i].offset |
| 432 |
|
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format = "<IHH16s16sIIIIII8sIHHIII20sHH16sIHHII364s"
|
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|
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def __init__(self, device): |
| 436 |
"""Create a DiskLabel instance"""
|
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|
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device.seek(BLOCKSIZE, os.SEEK_CUR) |
| 439 |
# The offset of the disklabel from the beginning of the partition is
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# one sector
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sector1 = device.read(BLOCKSIZE) |
| 442 |
|
| 443 |
d_ = OrderedDict() # Off Len Content
|
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(d_["magic"], # 0 4 Magic |
| 445 |
d_["dtype"], # 4 2 Drive Type |
| 446 |
d_["subtype"], # 6 2 Subtype |
| 447 |
d_["typename"], # 8 16 Type Name |
| 448 |
d_["packname"], # 24 16 Pack Identifier |
| 449 |
d_["secsize"], # 32 4 Bytes per sector |
| 450 |
d_["nsectors"], # 36 4 Data sectors per track |
| 451 |
d_["ntracks"], # 40 4 Tracks per cylinder |
| 452 |
d_["ncylinders"], # 44 4 Data cylinders per unit |
| 453 |
d_["secpercyl"], # 48 4 Data sectors per cylinder |
| 454 |
d_["secperunit"], # 52 4 Data sectors per unit |
| 455 |
d_["uid"], # 56 8 Unique label identifier |
| 456 |
d_["acylinders"], # 64 4 Alt cylinders per unit |
| 457 |
d_["bstarth"], # 68 2 Start of useable region (high part) |
| 458 |
d_["bendh"], # 70 2 Size of usable region (high part) |
| 459 |
d_["bstart"], # 72 4 Start of useable region |
| 460 |
d_["bend"], # 76 4 End of usable region |
| 461 |
d_["flags"], # 80 4 Generic Flags |
| 462 |
d_["drivedata"], # 84 5*4 Drive-type specific information |
| 463 |
d_["secperunith"], # 104 2 Number of data sectors (high part) |
| 464 |
d_["version"], # 106 2 Version |
| 465 |
d_["spare"], # 108 4*4 Reserved for future use |
| 466 |
d_["magic2"], # 124 4 Magic number |
| 467 |
d_["checksum"], # 128 2 Xor of data including partitions |
| 468 |
d_["npartitions"], # 130 2 Number of partitions in following |
| 469 |
d_["bbsize"], # 132 4 size of boot area at sn0, bytes |
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d_["sbsize"], # 136 4 Max size of fs superblock, bytes |
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ptable_raw # 140 16*16 Partition Table
|
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) = struct.unpack(self.format, sector1)
|
| 473 |
|
| 474 |
assert d_['magic'] == d_['magic2'] == DISKMAGIC, "Disklabel not valid" |
| 475 |
self.ptable = self.PartitionTable(ptable_raw, d_['npartitions']) |
| 476 |
self.field = d_
|
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|
| 478 |
def setdsize(self, dsize): |
| 479 |
"""Set disk size"""
|
| 480 |
self.field['secperunith'] = dsize >> 32 |
| 481 |
self.field['secperunit'] = dsize & 0xffffffff |
| 482 |
|
| 483 |
def getdsize(self): |
| 484 |
"""Get disk size"""
|
| 485 |
return (self.field['secperunith'] << 32) + self.field['secperunit'] |
| 486 |
|
| 487 |
dsize = property(getdsize, setdsize, None, "disk size") |
| 488 |
|
| 489 |
def setbstart(self, bstart): |
| 490 |
"""Set start of useable region"""
|
| 491 |
self.field['bstarth'] = bstart >> 32 |
| 492 |
self.field['bstart'] = bstart & 0xffffffff |
| 493 |
|
| 494 |
def getbstart(self): |
| 495 |
"""Get start of usable region"""
|
| 496 |
return (self.field['bstarth'] << 32) + self.field['bstart'] |
| 497 |
|
| 498 |
bstart = property(getbstart, setbstart, None, "usable region start") |
| 499 |
|
| 500 |
def setbend(self, bend): |
| 501 |
"""Set size of useable region"""
|
| 502 |
self.field['bendh'] = bend >> 32 |
| 503 |
self.field['bend'] = bend & 0xffffffff |
| 504 |
|
| 505 |
def getbend(self): |
| 506 |
"""Get size of usable region"""
|
| 507 |
return (self.field['bendh'] << 32) + self.field['bend'] |
| 508 |
|
| 509 |
bend = property(getbend, setbend, None, "usable region size") |
| 510 |
|
| 511 |
def enlarge(self, new_size): |
| 512 |
"""Enlarge the disk and return the last usable sector"""
|
| 513 |
|
| 514 |
assert new_size >= self.dsize, \ |
| 515 |
"New size cannot be smaller that %s" % self.dsize |
| 516 |
|
| 517 |
# Fix the disklabel
|
| 518 |
self.dsize = new_size
|
| 519 |
self.field['ncylinders'] = self.dsize // (self.field['nsectors'] * |
| 520 |
self.field['ntracks']) |
| 521 |
self.bend = (self.field['ncylinders'] * self.field['nsectors'] * |
| 522 |
self.field['ntracks']) |
| 523 |
|
| 524 |
# Partition 'c' descriptes the entire disk
|
| 525 |
self.ptable.setpsize(2, new_size) |
| 526 |
|
| 527 |
# Update the checksum
|
| 528 |
self.checksum = self.compute_checksum() |
| 529 |
|
| 530 |
# bend is the size and not the end of the usable region. I named it
|
| 531 |
# like this because this is how it is named in OpenBSD. To get the last
|
| 532 |
# usable sector you need to reduce this value by one.
|
| 533 |
return self.bend - 1 |
| 534 |
|
| 535 |
def get_last_partition_id(self): |
| 536 |
"""Returns the id of the last partition"""
|
| 537 |
part = 0
|
| 538 |
end = 0
|
| 539 |
# Don't check partition 'c' which is the whole disk
|
| 540 |
for i in filter(lambda x: x != 2, range(len(self.ptable.part))): |
| 541 |
curr_end = self.ptable.getpsize(i) + self.ptable.getpoffset(i) |
| 542 |
if end < curr_end:
|
| 543 |
end = curr_end |
| 544 |
part = i |
| 545 |
|
| 546 |
assert end > 0, "No partition found" |
| 547 |
|
| 548 |
return part
|
| 549 |
|
| 550 |
def enlarge_last_partition(self): |
| 551 |
"""Enlarge the last partition to cover up all the free space"""
|
| 552 |
|
| 553 |
part_num = self.get_last_partition_id()
|
| 554 |
|
| 555 |
end = self.ptable.getpsize(part_num) + self.ptable.getpoffset(part_num) |
| 556 |
|
| 557 |
assert end > 0, "No partition found" |
| 558 |
|
| 559 |
if self.ptable.part[part_num].fstype == 1: # Swap partition. |
| 560 |
#TODO: Maybe create a warning?
|
| 561 |
return
|
| 562 |
|
| 563 |
if end > (self.bend - 1024): |
| 564 |
return
|
| 565 |
|
| 566 |
self.ptable.setpsize(
|
| 567 |
part_num, self.bend - self.ptable.getpoffset(part_num) - 1024) |
| 568 |
|
| 569 |
self.field['checksum'] = self.compute_checksum() |
| 570 |
|
| 571 |
def __str__(self): |
| 572 |
"""Print the Disklabel"""
|
| 573 |
|
| 574 |
title = "Disklabel"
|
| 575 |
typename = self.field['typename'].strip('\x00').strip() |
| 576 |
packname = self.field['packname'].strip('\x00').strip() |
| 577 |
duid = "".join(x.encode('hex') for x in self.field['uid']) |
| 578 |
return \
|
| 579 |
"%s\n%s\n" % (title, len(title) * "=") + \ |
| 580 |
"Magic Number: 0x%(magic)x\n" \
|
| 581 |
"Drive type: %(dtype)d\n" \
|
| 582 |
"Subtype: %(subtype)d\n" % self.field + \ |
| 583 |
"Typename: %s\n" % typename + \
|
| 584 |
"Pack Identifier: %s\n" % packname + \
|
| 585 |
"# of bytes per sector: %(secsize)d\n" \
|
| 586 |
"# of data sectors per track: %(nsectors)d\n" \
|
| 587 |
"# of tracks per cylinder: %(ntracks)d\n" \
|
| 588 |
"# of data cylinders per unit: %(ncylinders)d\n" \
|
| 589 |
"# of data sectors per cylinder: %(secpercyl)d\n" \
|
| 590 |
"# of data sectors per unit: %(secperunit)d\n" % self.field + \ |
| 591 |
"DUID: %s\n" % duid + \
|
| 592 |
"Alt. cylinders per unit: %(acylinders)d\n" \
|
| 593 |
"Start of useable region (high part): %(bstarth)d\n" \
|
| 594 |
"Size of useable region (high part): %(bendh)d\n" \
|
| 595 |
"Start of useable region: %(bstart)d\n" \
|
| 596 |
"End of usable region: %(bend)d\n" \
|
| 597 |
"Generic Flags: %(flags)r\n" \
|
| 598 |
"Drive data: %(drivedata)r\n" \
|
| 599 |
"Number of data sectors (high part): %(secperunith)d\n" \
|
| 600 |
"Version: %(version)d\n" \
|
| 601 |
"Reserved for future use: %(spare)r\n" \
|
| 602 |
"The magic number again: 0x%(magic2)x\n" \
|
| 603 |
"Checksum: %(checksum)d\n" \
|
| 604 |
"Number of partitions: %(npartitions)d\n" \
|
| 605 |
"Size of boot aread at sn0: %(bbsize)d\n" \
|
| 606 |
"Max size of fs superblock: %(sbsize)d\n" % self.field + \ |
| 607 |
"%s" % self.ptable |
| 608 |
|
| 609 |
|
| 610 |
if __name__ == '__main__': |
| 611 |
|
| 612 |
usage = "Usage: %prog [options] <input_media>"
|
| 613 |
parser = optparse.OptionParser(usage=usage) |
| 614 |
|
| 615 |
parser.add_option("-l", "--list", action="store_true", dest="list", |
| 616 |
default=False,
|
| 617 |
help="list the disklabel on the specified media")
|
| 618 |
parser.add_option("--get-last-partition", action="store_true", |
| 619 |
dest="last_part", default=False, |
| 620 |
help="print the label of the last partition")
|
| 621 |
parser.add_option("--get-duid", action="store_true", dest="duid", |
| 622 |
default=False,
|
| 623 |
help="print the disklabel unique identifier")
|
| 624 |
parser.add_option("-d", "--enlarge-disk", type="int", dest="disk_size", |
| 625 |
default=None, metavar="SIZE", |
| 626 |
help="Enlarge the disk to this SIZE (in sectors)")
|
| 627 |
parser.add_option( |
| 628 |
"-p", "--enlarge-partition", action="store_true", |
| 629 |
dest="enlarge_partition", default=False, |
| 630 |
help="Enlarge the last partition to cover up the free space")
|
| 631 |
|
| 632 |
options, args = parser.parse_args(sys.argv[1:])
|
| 633 |
|
| 634 |
if len(args) != 1: |
| 635 |
parser.error("Wrong number of arguments")
|
| 636 |
|
| 637 |
disk = Disk(args[0])
|
| 638 |
|
| 639 |
if options.list:
|
| 640 |
print disk
|
| 641 |
sys.exit(0)
|
| 642 |
|
| 643 |
if options.duid:
|
| 644 |
print "%s" % "".join(x.encode('hex') for x in disk.get_duid()) |
| 645 |
sys.exit(0)
|
| 646 |
|
| 647 |
if options.last_part:
|
| 648 |
print "%c" % chr(ord('a') + disk.get_last_partition_id()) |
| 649 |
|
| 650 |
if options.disk_size is not None: |
| 651 |
disk.enlarge(options.disk_size) |
| 652 |
|
| 653 |
if options.enlarge_partition:
|
| 654 |
disk.enlarge_last_partition() |
| 655 |
|
| 656 |
disk.write() |
| 657 |
|
| 658 |
sys.exit(0)
|
| 659 |
|
| 660 |
# vim: set sta sts=4 shiftwidth=4 sw=4 et ai :
|