Read and dump entries from the bitmap directory of QCOW2 image with the script qcow2.py.
Header extension: magic 0x23852875 (Bitmaps) ... Bitmap name bitmap-1 flag auto table size 8 (bytes) bitmap_table_offset 0x90000 bitmap_table_size 1 flags 0 type 1 granularity_bits 16 name_size 8 extra_data_size 0 Suggested-by: Kevin Wolf <kw...@redhat.com> Signed-off-by: Andrey Shinkevich <andrey.shinkev...@virtuozzo.com> Reviewed-by: Eric Blake <ebl...@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com> --- tests/qemu-iotests/qcow2_format.py | 75 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 75 insertions(+) diff --git a/tests/qemu-iotests/qcow2_format.py b/tests/qemu-iotests/qcow2_format.py index d4f0000..a7868a7 100644 --- a/tests/qemu-iotests/qcow2_format.py +++ b/tests/qemu-iotests/qcow2_format.py @@ -103,6 +103,10 @@ class Qcow2Struct(metaclass=Qcow2StructMeta): print('{:<25} {}'.format(f[2], value_str)) +# seek relative to the current position in the file +FROM_CURRENT = 1 + + class Qcow2BitmapExt(Qcow2Struct): fields = ( @@ -112,6 +116,73 @@ class Qcow2BitmapExt(Qcow2Struct): ('u64', '{:#x}', 'bitmap_directory_offset') ) + def read_bitmap_directory(self, fd): + self.bitmaps = [] + fd.seek(self.bitmap_directory_offset) + buf_size = struct.calcsize(Qcow2BitmapDirEntry.fmt) + + for n in range(self.nb_bitmaps): + buf = fd.read(buf_size) + dir_entry = Qcow2BitmapDirEntry(data=buf) + fd.seek(dir_entry.extra_data_size, FROM_CURRENT) + bitmap_name = fd.read(dir_entry.name_size) + dir_entry.name = bitmap_name.decode('ascii') + self.bitmaps.append(dir_entry) + entry_raw_size = dir_entry.bitmap_dir_entry_raw_size() + shift = ((entry_raw_size + 7) & ~7) - entry_raw_size + fd.seek(shift, FROM_CURRENT) + + def load(self, fd): + self.read_bitmap_directory(fd) + + def dump(self): + super().dump() + for bm in self.bitmaps: + bm.dump_bitmap_dir_entry() + + +BME_FLAG_IN_USE = 1 << 0 +BME_FLAG_AUTO = 1 << 1 + + +class Qcow2BitmapDirEntry(Qcow2Struct): + + name = '' + + fields = ( + ('u64', '{:#x}', 'bitmap_table_offset'), + ('u32', '{}', 'bitmap_table_size'), + ('u32', '{}', 'flags'), + ('u8', '{}', 'type'), + ('u8', '{}', 'granularity_bits'), + ('u16', '{}', 'name_size'), + ('u32', '{}', 'extra_data_size') + ) + + def __init__(self, data): + super().__init__(data=data) + + self.bitmap_table_bytes = self.bitmap_table_size \ + * struct.calcsize('Q') + + self.bitmap_flags = [] + if (self.flags & BME_FLAG_IN_USE): + self.bitmap_flags.append("in-use") + if (self.flags & BME_FLAG_AUTO): + self.bitmap_flags.append("auto") + + def bitmap_dir_entry_raw_size(self): + return struct.calcsize(self.fmt) + self.name_size + \ + self.extra_data_size + + def dump_bitmap_dir_entry(self): + print() + print(f'{"Bitmap name":<25} {self.name}') + for fl in self.bitmap_flags: + print(f'{"flag":<25} {fl}') + print(f'{"table size ":<25} {self.bitmap_table_bytes} {"(bytes)"}') + super().dump() + QCOW2_EXT_MAGIC_BITMAPS = 0x23852875 @@ -253,6 +324,10 @@ class QcowHeader(Qcow2Struct): else: self.extensions.append(ext) + for ext in self.extensions: + if ext.obj is not None: + ext.obj.load(fd) + def update_extensions(self, fd): fd.seek(self.header_length) -- 1.8.3.1