diff options
Diffstat (limited to 'tests/qemu-iotests/qcow2_format.py')
| -rw-r--r-- | tests/qemu-iotests/qcow2_format.py | 286 |
1 files changed, 286 insertions, 0 deletions
diff --git a/tests/qemu-iotests/qcow2_format.py b/tests/qemu-iotests/qcow2_format.py new file mode 100644 index 0000000000..0f65fd161d --- /dev/null +++ b/tests/qemu-iotests/qcow2_format.py @@ -0,0 +1,286 @@ +# Library for manipulations with qcow2 image +# +# Copyright (c) 2020 Virtuozzo International GmbH. +# +# This program is free software; you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation; either version 2 of the License, or +# (at your option) any later version. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see <http://www.gnu.org/licenses/>. +# + +import struct +import string + + +class Qcow2Field: + + def __init__(self, value): + self.value = value + + def __str__(self): + return str(self.value) + + +class Flags64(Qcow2Field): + + def __str__(self): + bits = [] + for bit in range(64): + if self.value & (1 << bit): + bits.append(bit) + return str(bits) + + +class Enum(Qcow2Field): + + def __str__(self): + return f'{self.value:#x} ({self.mapping.get(self.value, "<unknown>")})' + + +class Qcow2StructMeta(type): + + # Mapping from c types to python struct format + ctypes = { + 'u8': 'B', + 'u16': 'H', + 'u32': 'I', + 'u64': 'Q' + } + + def __init__(self, name, bases, attrs): + if 'fields' in attrs: + self.fmt = '>' + ''.join(self.ctypes[f[0]] for f in self.fields) + + +class Qcow2Struct(metaclass=Qcow2StructMeta): + + """Qcow2Struct: base class for qcow2 data structures + + Successors should define fields class variable, which is: list of tuples, + each of three elements: + - c-type (one of 'u8', 'u16', 'u32', 'u64') + - format (format_spec to use with .format() when dump or 'mask' to dump + bitmasks) + - field name + """ + + def __init__(self, fd=None, offset=None, data=None): + """ + Two variants: + 1. Specify data. fd and offset must be None. + 2. Specify fd and offset, data must be None. offset may be omitted + in this case, than current position of fd is used. + """ + if data is None: + assert fd is not None + buf_size = struct.calcsize(self.fmt) + if offset is not None: + fd.seek(offset) + data = fd.read(buf_size) + else: + assert fd is None and offset is None + + values = struct.unpack(self.fmt, data) + self.__dict__ = dict((field[2], values[i]) + for i, field in enumerate(self.fields)) + + def dump(self): + for f in self.fields: + value = self.__dict__[f[2]] + if isinstance(f[1], str): + value_str = f[1].format(value) + else: + value_str = str(f[1](value)) + + print('{:<25} {}'.format(f[2], value_str)) + + +class Qcow2BitmapExt(Qcow2Struct): + + fields = ( + ('u32', '{}', 'nb_bitmaps'), + ('u32', '{}', 'reserved32'), + ('u64', '{:#x}', 'bitmap_directory_size'), + ('u64', '{:#x}', 'bitmap_directory_offset') + ) + + +QCOW2_EXT_MAGIC_BITMAPS = 0x23852875 + + +class QcowHeaderExtension(Qcow2Struct): + + class Magic(Enum): + mapping = { + 0xe2792aca: 'Backing format', + 0x6803f857: 'Feature table', + 0x0537be77: 'Crypto header', + QCOW2_EXT_MAGIC_BITMAPS: 'Bitmaps', + 0x44415441: 'Data file' + } + + fields = ( + ('u32', Magic, 'magic'), + ('u32', '{}', 'length') + # length bytes of data follows + # then padding to next multiply of 8 + ) + + def __init__(self, magic=None, length=None, data=None, fd=None): + """ + Support both loading from fd and creation from user data. + For fd-based creation current position in a file will be used to read + the data. + + This should be somehow refactored and functionality should be moved to + superclass (to allow creation of any qcow2 struct), but then, fields + of variable length (data here) should be supported in base class + somehow. Note also, that we probably want to parse different + extensions. Should they be subclasses of this class, or how to do it + better? Should it be something like QAPI union with discriminator field + (magic here). So, it's a TODO. We'll see how to properly refactor this + when we have more qcow2 structures. + """ + if fd is None: + assert all(v is not None for v in (magic, length, data)) + self.magic = magic + self.length = length + if length % 8 != 0: + padding = 8 - (length % 8) + data += b'\0' * padding + self.data = data + else: + assert all(v is None for v in (magic, length, data)) + super().__init__(fd=fd) + padded = (self.length + 7) & ~7 + self.data = fd.read(padded) + assert self.data is not None + + if self.magic == QCOW2_EXT_MAGIC_BITMAPS: + self.obj = Qcow2BitmapExt(data=self.data) + else: + self.obj = None + + def dump(self): + super().dump() + + if self.obj is None: + data = self.data[:self.length] + if all(c in string.printable.encode('ascii') for c in data): + data = f"'{ data.decode('ascii') }'" + else: + data = '<binary>' + print(f'{"data":<25} {data}') + else: + self.obj.dump() + + @classmethod + def create(cls, magic, data): + return QcowHeaderExtension(magic, len(data), data) + + +class QcowHeader(Qcow2Struct): + + fields = ( + # Version 2 header fields + ('u32', '{:#x}', 'magic'), + ('u32', '{}', 'version'), + ('u64', '{:#x}', 'backing_file_offset'), + ('u32', '{:#x}', 'backing_file_size'), + ('u32', '{}', 'cluster_bits'), + ('u64', '{}', 'size'), + ('u32', '{}', 'crypt_method'), + ('u32', '{}', 'l1_size'), + ('u64', '{:#x}', 'l1_table_offset'), + ('u64', '{:#x}', 'refcount_table_offset'), + ('u32', '{}', 'refcount_table_clusters'), + ('u32', '{}', 'nb_snapshots'), + ('u64', '{:#x}', 'snapshot_offset'), + + # Version 3 header fields + ('u64', Flags64, 'incompatible_features'), + ('u64', Flags64, 'compatible_features'), + ('u64', Flags64, 'autoclear_features'), + ('u32', '{}', 'refcount_order'), + ('u32', '{}', 'header_length'), + ) + + def __init__(self, fd): + super().__init__(fd=fd, offset=0) + + self.set_defaults() + self.cluster_size = 1 << self.cluster_bits + + fd.seek(self.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 set_defaults(self): + if self.version == 2: + self.incompatible_features = 0 + self.compatible_features = 0 + self.autoclear_features = 0 + self.refcount_order = 4 + self.header_length = 72 + + 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: + ext = QcowHeaderExtension(fd=fd) + if ext.magic == 0: + break + else: + self.extensions.append(ext) + + def update_extensions(self, fd): + + fd.seek(self.header_length) + extensions = self.extensions + extensions.append(QcowHeaderExtension(0, 0, b'')) + for ex in extensions: + buf = struct.pack('>II', ex.magic, ex.length) + fd.write(buf) + fd.write(ex.data) + + if self.backing_file is not 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.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_extensions(self): + for ex in self.extensions: + print('Header extension:') + ex.dump() + print() |