diff options
| -rw-r--r-- | block/dmg.c | 49 |
1 files changed, 45 insertions, 4 deletions
diff --git a/block/dmg.c b/block/dmg.c index e455886d2b..918345954b 100644 --- a/block/dmg.c +++ b/block/dmg.c @@ -131,6 +131,48 @@ static void update_max_chunk_size(BDRVDMGState *s, uint32_t chunk, } } +static int64_t dmg_find_koly_offset(BlockDriverState *file_bs, Error **errp) +{ + int64_t length; + int64_t offset = 0; + uint8_t buffer[515]; + int i, ret; + + /* bdrv_getlength returns a multiple of block size (512), rounded up. Since + * dmg images can have odd sizes, try to look for the "koly" magic which + * marks the begin of the UDIF trailer (512 bytes). This magic can be found + * in the last 511 bytes of the second-last sector or the first 4 bytes of + * the last sector (search space: 515 bytes) */ + length = bdrv_getlength(file_bs); + if (length < 0) { + error_setg_errno(errp, -length, + "Failed to get file size while reading UDIF trailer"); + return length; + } else if (length < 512) { + error_set(errp, ERROR_CLASS_GENERIC_ERROR, + "dmg file must be at least 512 bytes long"); + return -EINVAL; + } + if (length > 511 + 512) { + offset = length - 511 - 512; + } + length = length < 515 ? length : 515; + ret = bdrv_pread(file_bs, offset, buffer, length); + if (ret < 0) { + error_setg_errno(errp, -ret, "Failed while reading UDIF trailer"); + return ret; + } + for (i = 0; i < length - 3; i++) { + if (buffer[i] == 'k' && buffer[i+1] == 'o' && + buffer[i+2] == 'l' && buffer[i+3] == 'y') { + return offset + i; + } + } + error_set(errp, ERROR_CLASS_GENERIC_ERROR, + "Could not locate UDIF trailer in dmg file"); + return -EINVAL; +} + static int dmg_open(BlockDriverState *bs, QDict *options, int flags, Error **errp) { @@ -145,15 +187,14 @@ static int dmg_open(BlockDriverState *bs, QDict *options, int flags, s->n_chunks = 0; s->offsets = s->lengths = s->sectors = s->sectorcounts = NULL; - /* read offset of info blocks */ - offset = bdrv_getlength(bs->file); + /* locate the UDIF trailer */ + offset = dmg_find_koly_offset(bs->file, errp); if (offset < 0) { ret = offset; goto fail; } - offset -= 0x1d8; - ret = read_uint64(bs, offset, &info_begin); + ret = read_uint64(bs, offset + 0x28, &info_begin); if (ret < 0) { goto fail; } else if (info_begin == 0) { |