From 6e19b3c4e0b40b08ccb550a0c0a65798f3a17ac8 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Wed, 15 Feb 2012 16:36:03 +0100 Subject: [PATCH] qemu-iotests: qcow2.py This adds a tool that is meant to inspect and edit qcow2 files in a low-level way, that wouldn't be possible with qemu-img/io, for example by adding yet unknown extensions or flags. This way we can test whether qemu deals properly with future backwards compatible extensions. For now, let's start with the image header and header extensions. Signed-off-by: Kevin Wolf --- tests/qemu-iotests/qcow2.py | 207 ++++++++++++++++++++++++++++++++++++ 1 file changed, 207 insertions(+) create mode 100755 tests/qemu-iotests/qcow2.py diff --git a/tests/qemu-iotests/qcow2.py b/tests/qemu-iotests/qcow2.py new file mode 100755 index 0000000000..bfb47e88fc --- /dev/null +++ b/tests/qemu-iotests/qcow2.py @@ -0,0 +1,207 @@ +#!/usr/bin/env python + +import sys +import struct +import string + +class QcowHeaderExtension: + + def __init__(self, magic, length, data): + self.magic = magic + self.length = length + self.data = data + + @classmethod + def create(cls, magic, data): + return QcowHeaderExtension(magic, len(data), data) + +class QcowHeader: + + uint32_t = 'I' + uint64_t = 'Q' + + fields = [ + # Version 2 header fields + [ uint32_t, '%#x', 'magic' ], + [ uint32_t, '%d', 'version' ], + [ uint64_t, '%#x', 'backing_file_offset' ], + [ uint32_t, '%#x', 'backing_file_size' ], + [ uint32_t, '%d', 'cluster_bits' ], + [ uint64_t, '%d', 'size' ], + [ uint32_t, '%d', 'crypt_method' ], + [ uint32_t, '%d', 'l1_size' ], + [ uint64_t, '%#x', 'l1_table_offset' ], + [ uint64_t, '%#x', 'refcount_table_offset' ], + [ uint32_t, '%d', 'refcount_table_clusters' ], + [ uint32_t, '%d', 'nb_snapshots' ], + [ uint64_t, '%#x', 'snapshot_offset' ], + ]; + + fmt = '>' + ''.join(field[0] for field in fields) + + def __init__(self, fd): + + buf_size = struct.calcsize(QcowHeader.fmt) + + fd.seek(0) + buf = fd.read(buf_size) + + header = struct.unpack(QcowHeader.fmt, buf) + self.__dict__ = dict((field[2], header[i]) + for i, field in enumerate(QcowHeader.fields)) + + self.cluster_size = 1 << self.cluster_bits + + fd.seek(self.get_header_length()) + self.load_extensions(fd) + + if self.backing_file_offset: + fd.seek(self.backing_file_offset) + self.backing_file = fd.read(self.backing_file_size) + else: + self.backing_file = None + + def get_header_length(self): + if self.version == 2: + return 72 + else: + raise Exception("version != 2 not supported") + + def load_extensions(self, fd): + self.extensions = [] + + if self.backing_file_offset != 0: + end = min(self.cluster_size, self.backing_file_offset) + else: + end = self.cluster_size + + while fd.tell() < end: + (magic, length) = struct.unpack('>II', fd.read(8)) + if magic == 0: + break + else: + padded = (length + 7) & ~7 + data = fd.read(padded) + self.extensions.append(QcowHeaderExtension(magic, length, data)) + + def update_extensions(self, fd): + + fd.seek(self.get_header_length()) + extensions = self.extensions + extensions.append(QcowHeaderExtension(0, 0, "")) + for ex in extensions: + buf = struct.pack('>II', ex.magic, ex.length) + fd.write(buf) + fd.write(ex.data) + + if self.backing_file != None: + self.backing_file_offset = fd.tell() + fd.write(self.backing_file) + + if fd.tell() > self.cluster_size: + raise Exception("I think I just broke the image...") + + + def update(self, fd): + header_bytes = self.get_header_length() + + self.update_extensions(fd) + + fd.seek(0) + header = tuple(self.__dict__[f] for t, p, f in QcowHeader.fields) + buf = struct.pack(QcowHeader.fmt, *header) + buf = buf[0:header_bytes-1] + fd.write(buf) + + def dump(self): + for f in QcowHeader.fields: + print "%-25s" % f[2], f[1] % self.__dict__[f[2]] + print "" + + def dump_extensions(self): + for ex in self.extensions: + + data = ex.data[:ex.length] + if all(c in string.printable for c in data): + data = "'%s'" % data + else: + data = "" + + print "Header extension:" + print "%-25s %#x" % ("magic", ex.magic) + print "%-25s %d" % ("length", ex.length) + print "%-25s %s" % ("data", data) + print "" + + +def cmd_dump_header(fd): + h = QcowHeader(fd) + h.dump() + h.dump_extensions() + +def cmd_add_header_ext(fd, magic, data): + try: + magic = int(magic, 0) + except: + print "'%s' is not a valid magic number" % magic + sys.exit(1) + + h = QcowHeader(fd) + h.extensions.append(QcowHeaderExtension.create(magic, data)) + h.update(fd) + +def cmd_del_header_ext(fd, magic): + try: + magic = int(magic, 0) + except: + print "'%s' is not a valid magic number" % magic + sys.exit(1) + + h = QcowHeader(fd) + found = False + + for ex in h.extensions: + if ex.magic == magic: + found = True + h.extensions.remove(ex) + + if not found: + print "No such header extension" + return + + h.update(fd) + +cmds = [ + [ 'dump-header', cmd_dump_header, 0, 'Dump image header and header extensions' ], + [ 'add-header-ext', cmd_add_header_ext, 2, 'Add a header extension' ], + [ 'del-header-ext', cmd_del_header_ext, 1, 'Delete a header extension' ], +] + +def main(filename, cmd, args): + fd = open(filename, "r+b") + try: + for name, handler, num_args, desc in cmds: + if name != cmd: + continue + elif len(args) != num_args: + usage() + return + else: + handler(fd, *args) + return + print "Unknown command '%s'" % cmd + finally: + fd.close() + +def usage(): + print "Usage: %s [, ...]" % sys.argv[0] + print "" + print "Supported commands:" + for name, handler, num_args, desc in cmds: + print " %-20s - %s" % (name, desc) + +if len(sys.argv) < 3: + usage() + sys.exit(1) + +main(sys.argv[1], sys.argv[2], sys.argv[3:])