Attachment 3426 Details for Bug 22221

Python-Skript zum Dumpen einer Qcow2-Imagedatei

qcow2.py (text/plain), 9.52 KB, created by Philipp Hahn on 2011-08-04 16:32 CEST

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Creator: Philipp Hahn

Created: 2011-08-04 16:32 CEST

Size: 9.52 KB

patch

obsolete

>#!/usr/bin/python
>#
># Dump Qcow2 file structure
>#
># qemu-img create -f qcow2 -o preallocation=off      /tmp/test.qcow2 1G
># qemu-img create -f qcow2 -o preallocation=metadata /tmp/test.qcow2 1G
># qemu-img snapshot -c Test1234                      /tmp/test.qcow2
># qemu-io -c 'write 0 512' -c flush -c quit          /tmp/test.qcow2
>import sys
>import os
>import math
>from struct import Struct as _Struct
>import time
>
>class Struct(_Struct):
>	def __init__(self, fmt):
>		f = ''
>		for l in fmt.splitlines():
>			try:
>				i = l.index('#')
>				if i >= 0:
>					l = l[:i]
>			except ValueError:
>				pass
>			l = l.strip()
>			if l:
>				f = f + l
>		_Struct.__init__(self, f)
>
>QCowHeader = Struct('''> #big-endian
>		4s	#uint32_t magic;
>		I	#uint32_t version;
>		Q	#uint64_t backing_file_offset;
>		I	#uint32_t backing_file_size;
>		I	#uint32_t cluster_bits;
>		Q	#uint64_t size; /* in bytes */
>		I	#uint32_t crypt_method;
>		I	#uint32_t l1_size;
>		Q	#uint64_t l1_table_offset;
>		Q	#uint64_t refcount_table_offset;
>		I	#uint32_t refcount_table_clusters;
>		I	#uint32_t nb_snapshots;
>		Q	#uint64_t snapshots_offset;
>		''')
>
>QCowSnapshotHeader = Struct('''> #big-endian
>		Q	#uint64_t l1_table_offset;
>		I	#uint32_t l1_size;
>		H	#uint16_t id_str_size;
>		H	#uint16_t name_size;
>		I	#uint32_t date_sec;
>		I	#uint32_t date_nsec;
>		Q	#uint64_t vm_clock_nsec;
>		I	#uint32_t vm_state_size;
>		I	#uint32_t extra_data_size; /* for extension */
>			#/* extra data follows */
>			#/* id_str follows */
>			#/* name follows  */
>		''')
>
>LD512 = int(math.log(512) / math.log(2))
>LD2M = int(math.log(2<<20) / math.log(2))
>def human(size):
>	'''Print size as human readable string.
>	>>> human(0)
>	'0 B'
>	>>> human(1)
>	'1 B'
>	>>> human(1023)
>	'1023 B'
>	>>> human(1024)
>	'1 KiB'
>	'''
>	if size < 1024: return '%s B' % size
>	size >>= 10
>	if size < 1024: return '%s KiB' % size
>	size >>= 10
>	if size < 1024: return '%s MiB' % size
>	size >>= 10
>	if size < 1024: return '%s GiB' % size
>	size >>= 10
>	if size < 1024: return '%s TiB' % size
>	size >>= 10
>	return '%s PiB' % size
>
>def round_up(value, size):
>	'''Round value ot to next size.
>	>>> round_up(0, 2)
>	0
>	>>> round_up(1, 2)
>	2
>	'''
>	bitmask = size - 1
>	assert not (size & bitmask), "size is not a power of 2"
>	value += bitmask
>	value &= ~bitmask
>	return value
>
>def aligned(value, size):
>	'''Test if value is aligned to size.
>	>>> aligned(1, 2)
>	False
>	>>> aligned(4, 2)
>	True
>	'''
>	bitmask = size - 1
>	value &= bitmask
>	return value == 0
>
>def dump_QCowHeader(f):
>	d = f.read(QCowHeader.size)
>	magic, version, backing_file_offset, backing_file_size, cluster_bits, size, crypt_method, l1_size, l1_table_offset, refcount_table_offset, refcount_table_clusters, nb_snapshots, snapshots_offset = QCowHeader.unpack_from(d)
>	print 'magic=%r:	%s' % (magic, magic == 'QFI\xfb')
>	print 'version=%d:	%s' % (version, version == 2)
>	print 'backing_file_offset=0x%016x:	%s' % (backing_file_offset, 0 <= backing_file_offset < fsize)
>	print 'backing_file_size=0x%08x:	%s' % (backing_file_size, 0 <= backing_file_offset + backing_file_size < fsize)
>	print 'cluster_bits=%d:	%s' % (cluster_bits, LD512 <= cluster_bits <= LD2M)
>	global cluster_size
>	cluster_size = 1 << cluster_bits
>	global l2_bits
>	l2_bits = cluster_bits - 3
>	assert 0 < l2_bits
>	global l2_size
>	l2_size = 1 << l2_bits
>	print 'size=%s: %s' % (human(size), True)
>	print 'crypt_method=0x%08x: %s' % (crypt_method, 0 <= crypt_method <= 1)
>	global l1_size_min
>	l1_size_min = size / cluster_size / l2_size
>	print 'l1_size=%d: %s' % (l1_size, l1_size_min <= l1_size)
>	print 'l1_table_offset=0x%016x:	%s' % (l1_table_offset, 0 <= l1_table_offset < fsize and aligned(l1_table_offset, cluster_size))
>	print 'refcount_table_offset=0x%016x:	%s' % (refcount_table_offset, 0 <= refcount_table_offset < fsize and aligned(refcount_table_offset, cluster_size))
>	print 'refcount_table_clusters=%d:	%s' % (refcount_table_clusters, 0 <= refcount_table_offset + refcount_table_clusters * cluster_size < fsize)
>	print 'nb_snapshots=%d:	%s' % (nb_snapshots, 0 <= nb_snapshots)
>	print 'snapshots_offset=0x%016x:	%s' % (snapshots_offset, 0 <= snapshots_offset < fsize and aligned(snapshots_offset, cluster_size))
>
>	if backing_file_offset and backing_file_size > 0:
>		f.seek(backing_file_offset, os.SEEK_SET)
>		backing_file = f.read(backing_file_size)
>		print 'backing_file=%r: %s' % (backing_file, True)
>	
>	f.seek(refcount_table_offset)
>	d = f.read(cluster_size * refcount_table_clusters)
>	refcount_table_len = cluster_size * refcount_table_clusters / 8
>	RCT = Struct('''>	#big-endian
>			%dQ''' % refcount_table_len)
>	RCTE = Struct('''>	#big-endian
>			%dH''' % (cluster_size / 2))
>	refcount_table = RCT.unpack_from(d)
>	for i in range(refcount_table_len):
>		offset = refcount_table[i]
>		if not offset: continue
>		print 'refcount_table[%d]=0x%016x: %s' % (i, offset, 0 <= offset < fsize and aligned(offset, cluster_size))
>		f.seek(offset)
>		d = f.read(cluster_size)
>		refcount_table_entry = RCTE.unpack_from(d)
>		for j in range(cluster_size / 2):
>			refcount = refcount_table_entry[j]
>			if not refcount: continue
>			cluster = i * (cluster_size / 2) + j
>			print ' [%d][%d]=[%d]=%d:	%s' % (i, j, cluster, refcount, 0 <= refcount <= nb_snapshots + 1 and 0 <= cluster * cluster_size < fsize)
>
>	f.seek(l1_table_offset)
>	dump_L1(f, l1_size)
>
>	if nb_snapshots > 0:
>		f.seek(snapshots_offset, os.SEEK_SET)
>		for snapshot in range(nb_snapshots):
>			print ' Snapshot #%d' % (snapshot,)
>			dump_QCowSnapshotHeader(f)
>
>def dump_L1(f, l1_size, prefix=''):
>	L1 = Struct('''>	#big-endian
>			%dQ	#offset''' % l1_size)
>	d = f.read(round_up(L1.size, cluster_size))
>	l1_table = L1.unpack_from(d)
>	for i in range(l1_size):
>		copied = (l1_table[i] & 1L << 63) != 0
>		compressed = (l1_table[i] & 1L << 62) != 0
>		offset = l1_table[i] & ~(3L << 62)
>		print '%sL1[%d]=0x%016x: %s' % (prefix, i, l1_table[i], 0 <= offset < fsize)
>		if offset > 0:
>			f.seek(offset)
>			dump_L2(f, prefix)
>
>def dump_L2(f, prefix=''):
>	L2 = Struct('''>	#big-endian
>			%dQ	#offset''' % l2_size)
>	d = f.read(L2.size)
>	l2_table = L2.unpack_from(d)
>	for i in range(l2_size):
>		copied = (l2_table[i] & 1L << 63) != 0
>		compressed = (l2_table[i] & 1L << 62) != 0
>		offset = l2_table[i] & ~(3L << 62)
>		if not offset: continue
>		print '%s L2[%d]=0x%016x: %s' % (prefix, i, l2_table[i], 0 <= offset < fsize)
>
>def dump_QCowSnapshotHeader(f):
>	d = f.read(QCowSnapshotHeader.size)
>	l1_table_offset, l1_size, id_str_size, name_size, date_sec, date_nsec, vm_clock_nsec, vm_state_size, extra_data_size = QCowSnapshotHeader.unpack_from(d)
>	print '  l1_table_offset=0x%016x:	%s' % (l1_table_offset, 0 <= l1_table_offset < fsize and aligned(l1_table_offset, cluster_size))
>	print '  l1_size=%d: %s' % (l1_size, l1_size_min <= l1_size)
>	print '  id_str_size=%d: %s' % (id_str_size, 0 <= id_str_size)
>	print '  name_size=%d: %s' % (name_size, 0 <= name_size)
>	print '  date_sec=%s: %s' % (time.strftime('%Y-%m-%d %H:%M:%S', time.localtime(date_sec)), 0 <= date_sec)
>	print '  date_nsec=%d: %s' % (date_nsec, 0 <= date_nsec < 1000000000)
>	print '  vm_clock_nsec=%d: %s' % (vm_clock_nsec, 0 <= vm_clock_nsec)
>	print '  vm_state_size=0x%08x: %s' % (vm_state_size, 0 <= vm_state_size)
>	print '  extra_data_size=0x%08x: %s' % (extra_data_size, 0 <= extra_data_size)
>	if extra_data_size > 0:
>		extra_data = f.read(extra_data_size)
>		print '  extra_data=%d: %s' % (len(extra_data), len(extra_data) == extra_data_size)
>	if id_str_size > 0:
>		id_str = f.read(id_str_size)
>		print '  id_str=%r: %s' % (id_str, len(id_str) == id_str_size)
>	if name_size > 0:
>		name = f.read(name_size)
>		print '  name=%r: %s' % (name, len(name) == name_size)
>	if vm_state_size > 0:
>		vm_state = f.read(vm_state_size)
>		print '  vm_state=%d: %s' % (len(vm_state), len(vm_state) == vm_state_size)
>	ssize = QCowSnapshotHeader.size + extra_data_size + id_str_size + name_size + vm_state_size
>	if ssize & 7:
>		pad = f.read(8 - ssize & 7)
>
>	pos = f.tell()
>	f.seek(l1_table_offset)
>	dump_L1(f, l1_size, '  ')
>	f.seek(pos)
>
>def read(f, pos, count=1):
>	f.seek(0)
>	d = f.read(QCowHeader.size)
>	magic, version, backing_file_offset, backing_file_size, cluster_bits, size, crypt_method, l1_size, l1_table_offset, refcount_table_offset, refcount_table_clusters, nb_snapshots, snapshots_offset = QCowHeader.unpack_from(d)
>	if crypt_method:
>		raise NotImplemented('Qcow2 encryption')
>
>	cluster_size = 1 << cluster_bits
>	l2_bits = cluster_bits - 3
>	l2_size = 1 << l2_bits
>
>	if pos >= size:
>		raise EOFError()
>	cluster_index = pos & (cluster_size - 1L)
>	pos >>= cluster_bits
>	l2_index = pos & (l2_size - 1L)
>	l1_index = pos >> l2_bits
>
>	f.seek(l1_table_offset)
>	L1 = Struct('''>	#big-endian
>			%dQ	#offset''' % l1_size)
>	d = f.read(round_up(L1.size, cluster_size))
>	l1_table = L1.unpack_from(d)
>	l2_table_offset = l1_table[l1_index]
>	if not l2_table_offset:
>		return None # '\0' * min(cluster_size * l2_size, size - pos)
>	if l2_table_offset & (1L << 62):
>		raise NotImplemented('Qcow2 compression')
>	l2_table_offset &= ~(3L << 62)
>
>	f.seek(l2_table_offset)
>	L2 = Struct('''>	#big-endian
>			%dQ	#offset''' % l2_size)
>	d = f.read(L2.size)
>	l2_table = L2.unpack_from(d)
>	cluster_offset = l2_table[l2_index]
>	if not cluster_offset:
>		return None # '\0' * min(cluster_size, size - pos)
>	if cluster_offset & (1L << 62):
>		raise NotImplemented('Qcow2 compression')
>	cluster_offset &= ~(3L << 62)
>
>	f.seek(cluster_offset)
>	d = f.read(cluster_size)
>	return d[cluster_index]
>
>if __name__ == '__main__':
>	import doctest
>	doctest.testmod()
>
>	try:
>		NAME = sys.argv[1]
>	except IndexError:
>		NAME = '/tmp/test.qcow2'
>	f = open(NAME, 'r')
>	fsize = os.fstat(f.fileno()).st_size
>	try:
>		dump_QCowHeader(f)
>		#print read(f, 0)
>		#print read(f, 511)
>		#print read(f, 512)
>		#print read(f, (1 << 30 - 1))
>		#print read(f, 1 << 30)
>	finally:
>		f.close()

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Attachments on bug 22221: 3179 | 3425 | 3426