block/vhdx.h

   1 /*
   2  * Block driver for Hyper-V VHDX Images
   3  *
   4  * Copyright (c) 2013 Red Hat, Inc.,
   5  *
   6  * Authors:
   7  *  Jeff Cody <jcody@redhat.com>
   8  *
   9  *  This is based on the "VHDX Format Specification v0.95", published 4/12/2012
  10  *  by Microsoft:
  11  *      https://www.microsoft.com/en-us/download/details.aspx?id=29681
  12  *
  13  * This work is licensed under the terms of the GNU LGPL, version 2 or later.
  14  * See the COPYING.LIB file in the top-level directory.
  15  *
  16  */
  17
  18 #ifndef BLOCK_VHDX_H
  19 #define BLOCK_VHDX_H
  20
  21 /* Structures and fields present in the VHDX file */
  22
  23 /* The header section has the following blocks,
  24  * each block is 64KB:
  25  *
  26  * _____________________________________________________________________________
  27  * | File Id. |   Header 1    | Header 2   | Region Table |  Reserved (768KB)  |
  28  * |----------|---------------|------------|--------------|--------------------|
  29  * |          |               |            |              |                    |
  30  * 0.........64KB...........128KB........192KB..........256KB................1MB
  31  */
  32
  33 #define VHDX_HEADER_BLOCK_SIZE      (64*1024)
  34
  35 #define VHDX_FILE_ID_OFFSET         0
  36 #define VHDX_HEADER1_OFFSET         (VHDX_HEADER_BLOCK_SIZE*1)
  37 #define VHDX_HEADER2_OFFSET         (VHDX_HEADER_BLOCK_SIZE*2)
  38 #define VHDX_REGION_TABLE_OFFSET    (VHDX_HEADER_BLOCK_SIZE*3)
  39
  40
  41 /*
  42  * A note on the use of MS-GUID fields.  For more details on the GUID,
  43  * please see: https://en.wikipedia.org/wiki/Globally_unique_identifier.
  44  *
  45  * The VHDX specification only states that these are MS GUIDs, and which
  46  * bytes are data1-data4. It makes no mention of what algorithm should be used
  47  * to generate the GUID, nor what standard.  However, looking at the specified
  48  * known GUID fields, it appears the GUIDs are:
  49  *  Standard/DCE GUID type  (noted by 10b in the MSB of byte 0 of .data4)
  50  *  Random algorithm        (noted by 0x4XXX for .data3)
  51  */
  52
  53 /* ---- HEADER SECTION STRUCTURES ---- */
  54
  55 /* These structures are ones that are defined in the VHDX specification
  56  * document */
  57
  58 typedef struct VHDXFileIdentifier {
  59     uint64_t    signature;              /* "vhdxfile" in ASCII */
  60     uint16_t    creator[256];           /* optional; utf-16 string to identify
  61                                            the vhdx file creator.  Diagnotistic
  62                                            only */
  63 } VHDXFileIdentifier;
  64
  65
  66 /* the guid is a 16 byte unique ID - the definition for this used by
  67  * Microsoft is not just 16 bytes though - it is a structure that is defined,
  68  * so we need to follow it here so that endianness does not trip us up */
  69
  70 typedef struct MSGUID {
  71     uint32_t  data1;
  72     uint16_t  data2;
  73     uint16_t  data3;
  74     uint8_t   data4[8];
  75 } MSGUID;
  76
  77 #define guid_eq(a, b) \
  78     (memcmp(&(a), &(b), sizeof(MSGUID)) == 0)
  79
  80 #define VHDX_HEADER_SIZE (4*1024)   /* although the vhdx_header struct in disk
  81                                        is only 582 bytes, for purposes of crc
  82                                        the header is the first 4KB of the 64KB
  83                                        block */
  84
  85 /* The full header is 4KB, although the actual header data is much smaller.
  86  * But for the checksum calculation, it is over the entire 4KB structure,
  87  * not just the defined portion of it */
  88 typedef struct QEMU_PACKED VHDXHeader {
  89     uint32_t    signature;              /* "head" in ASCII */
  90     uint32_t    checksum;               /* CRC-32C hash of the whole header */
  91     uint64_t    sequence_number;        /* Seq number of this header.  Each
  92                                            VHDX file has 2 of these headers,
  93                                            and only the header with the highest
  94                                            sequence number is valid */
  95     MSGUID      file_write_guid;       /* 128 bit unique identifier. Must be
  96                                            updated to new, unique value before
  97                                            the first modification is made to
  98                                            file */
  99     MSGUID      data_write_guid;        /* 128 bit unique identifier. Must be
 100                                            updated to new, unique value before
 101                                            the first modification is made to
 102                                            visible data.   Visbile data is
 103                                            defined as:
 104                                                     - system & user metadata
 105                                                     - raw block data
 106                                                     - disk size
 107                                                     - any change that will
 108                                                       cause the virtual disk
 109                                                       sector read to differ
 110
 111                                            This does not need to change if
 112                                            blocks are re-arranged */
 113     MSGUID      log_guid;               /* 128 bit unique identifier. If zero,
 114                                            there is no valid log. If non-zero,
 115                                            log entries with this guid are
 116                                            valid. */
 117     uint16_t    log_version;            /* version of the log format. Mustn't be
 118                                            zero, unless log_guid is also zero */
 119     uint16_t    version;                /* version of th evhdx file.  Currently,
 120                                            only supported version is "1" */
 121     uint32_t    log_length;             /* length of the log.  Must be multiple
 122                                            of 1MB */
 123     uint64_t    log_offset;             /* byte offset in the file of the log.
 124                                            Must also be a multiple of 1MB */
 125 } VHDXHeader;
 126
 127 /* Header for the region table block */
 128 typedef struct QEMU_PACKED VHDXRegionTableHeader {
 129     uint32_t    signature;              /* "regi" in ASCII */
 130     uint32_t    checksum;               /* CRC-32C hash of the 64KB table */
 131     uint32_t    entry_count;            /* number of valid entries */
 132     uint32_t    reserved;
 133 } VHDXRegionTableHeader;
 134
 135 /* Individual region table entry.  There may be a maximum of 2047 of these
 136  *
 137  *  There are two known region table properties.  Both are required.
 138  *  BAT (block allocation table):  2DC27766F62342009D64115E9BFD4A08
 139  *  Metadata:                      8B7CA20647904B9AB8FE575F050F886E
 140  */
 141 #define VHDX_REGION_ENTRY_REQUIRED  0x01    /* if set, parser must understand
 142                                                this entry in order to open
 143                                                file */
 144 typedef struct QEMU_PACKED VHDXRegionTableEntry {
 145     MSGUID      guid;                   /* 128-bit unique identifier */
 146     uint64_t    file_offset;            /* offset of the object in the file.
 147                                            Must be multiple of 1MB */
 148     uint32_t    length;                 /* length, in bytes, of the object */
 149     uint32_t    data_bits;
 150 } VHDXRegionTableEntry;
 151
 152
 153 /* ---- LOG ENTRY STRUCTURES ---- */
 154 #define VHDX_LOG_HDR_SIZE 64
 155 typedef struct QEMU_PACKED VHDXLogEntryHeader {
 156     uint32_t    signature;              /* "loge" in ASCII */
 157     uint32_t    checksum;               /* CRC-32C hash of the 64KB table */
 158     uint32_t    entry_length;           /* length in bytes, multiple of 1MB */
 159     uint32_t    tail;                   /* byte offset of first log entry of a
 160                                            seq, where this entry is the last
 161                                            entry */
 162     uint64_t    sequence_number;        /* incremented with each log entry.
 163                                            May not be zero. */
 164     uint32_t    descriptor_count;       /* number of descriptors in this log
 165                                            entry, must be >= 0 */
 166     uint32_t    reserved;
 167     MSGUID      log_guid;               /* value of the log_guid from
 168                                            vhdx_header.  If not found in
 169                                            vhdx_header, it is invalid */
 170     uint64_t    flushed_file_offset;    /* see spec for full details - this
 171                                            should be vhdx file size in bytes */
 172     uint64_t    last_file_offset;       /* size in bytes that all allocated
 173                                            file structures fit into */
 174 } VHDXLogEntryHeader;
 175
 176 #define VHDX_LOG_DESC_SIZE 32
 177
 178 typedef struct QEMU_PACKED VHDXLogDescriptor {
 179     uint32_t    signature;              /* "zero" or "desc" in ASCII */
 180     union  {
 181         uint32_t    reserved;           /* zero desc */
 182         uint32_t    trailing_bytes;     /* data desc: bytes 4092-4096 of the
 183                                            data sector */
 184     };
 185     union {
 186         uint64_t    zero_length;        /* zero desc: length of the section to
 187                                            zero */
 188         uint64_t    leading_bytes;      /* data desc: bytes 0-7 of the data
 189                                            sector */
 190     };
 191     uint64_t    file_offset;            /* file offset to write zeros - multiple
 192                                            of 4kB */
 193     uint64_t    sequence_number;        /* must match same field in
 194                                            vhdx_log_entry_header */
 195 } VHDXLogDescriptor;
 196
 197 typedef struct QEMU_PACKED VHDXLogDataSector {
 198     uint32_t    data_signature;         /* "data" in ASCII */
 199     uint32_t    sequence_high;          /* 4 MSB of 8 byte sequence_number */
 200     uint8_t     data[4084];             /* raw data, bytes 8-4091 (inclusive).
 201                                            see the data descriptor field for the
 202                                            other mising bytes */
 203     uint32_t    sequence_low;           /* 4 LSB of 8 byte sequence_number */
 204 } VHDXLogDataSector;
 205
 206
 207
 208 /* block states - different state values depending on whether it is a
 209  * payload block, or a sector block. */
 210
 211 #define PAYLOAD_BLOCK_NOT_PRESENT       0
 212 #define PAYLOAD_BLOCK_UNDEFINED         1
 213 #define PAYLOAD_BLOCK_ZERO              2
 214 #define PAYLOAD_BLOCK_UNMAPPED          5
 215 #define PAYLOAD_BLOCK_FULL_PRESENT      6
 216 #define PAYLOAD_BLOCK_PARTIALLY_PRESENT 7
 217
 218 #define SB_BLOCK_NOT_PRESENT    0
 219 #define SB_BLOCK_PRESENT        6
 220
 221 /* per the spec */
 222 #define VHDX_MAX_SECTORS_PER_BLOCK  (1<<23)
 223
 224 /* upper 44 bits are the file offset in 1MB units lower 3 bits are the state
 225    other bits are reserved */
 226 #define VHDX_BAT_STATE_BIT_MASK 0x07
 227 #define VHDX_BAT_FILE_OFF_BITS (64-44)
 228 typedef uint64_t VHDXBatEntry;
 229
 230 /* ---- METADATA REGION STRUCTURES ---- */
 231
 232 #define VHDX_METADATA_ENTRY_SIZE 32
 233 #define VHDX_METADATA_MAX_ENTRIES 2047  /* not including the header */
 234 #define VHDX_METADATA_TABLE_MAX_SIZE \
 235     (VHDX_METADATA_ENTRY_SIZE * (VHDX_METADATA_MAX_ENTRIES+1))
 236 typedef struct QEMU_PACKED VHDXMetadataTableHeader {
 237     uint64_t    signature;              /* "metadata" in ASCII */
 238     uint16_t    reserved;
 239     uint16_t    entry_count;            /* number table entries. <= 2047 */
 240     uint32_t    reserved2[5];
 241 } VHDXMetadataTableHeader;
 242
 243 #define VHDX_META_FLAGS_IS_USER         0x01    /* max 1024 entries */
 244 #define VHDX_META_FLAGS_IS_VIRTUAL_DISK 0x02    /* virtual disk metadata if set,
 245                                                    otherwise file metdata */
 246 #define VHDX_META_FLAGS_IS_REQUIRED     0x04    /* parse must understand this
 247                                                    entry to open the file */
 248 typedef struct QEMU_PACKED VHDXMetadataTableEntry {
 249     MSGUID      item_id;                /* 128-bit identifier for metadata */
 250     uint32_t    offset;                 /* byte offset of the metadata.  At
 251                                            least 64kB.  Relative to start of
 252                                            metadata region */
 253                                         /* note: if length = 0, so is offset */
 254     uint32_t    length;                 /* length of metadata. <= 1MB. */
 255     uint32_t    data_bits;      /* least-significant 3 bits are flags, the
 256                                    rest are reserved (see above) */
 257     uint32_t    reserved2;
 258 } VHDXMetadataTableEntry;
 259
 260 #define VHDX_PARAMS_LEAVE_BLOCKS_ALLOCED 0x01   /* Do not change any blocks to
 261                                                    be BLOCK_NOT_PRESENT.
 262                                                    If set indicates a fixed
 263                                                    size VHDX file */
 264 #define VHDX_PARAMS_HAS_PARENT           0x02    /* has parent / backing file */
 265 typedef struct QEMU_PACKED VHDXFileParameters {
 266     uint32_t    block_size;             /* size of each payload block, always
 267                                            power of 2, <= 256MB and >= 1MB. */
 268     uint32_t data_bits;     /* least-significant 2 bits are flags, the rest
 269                                are reserved (see above) */
 270 } VHDXFileParameters;
 271
 272 typedef struct QEMU_PACKED VHDXVirtualDiskSize {
 273     uint64_t    virtual_disk_size;      /* Size of the virtual disk, in bytes.
 274                                            Must be multiple of the sector size,
 275                                            max of 64TB */
 276 } VHDXVirtualDiskSize;
 277
 278 typedef struct QEMU_PACKED VHDXPage83Data {
 279     MSGUID      page_83_data[16];       /* unique id for scsi devices that
 280                                            support page 0x83 */
 281 } VHDXPage83Data;
 282
 283 typedef struct QEMU_PACKED VHDXVirtualDiskLogicalSectorSize {
 284     uint32_t    logical_sector_size;    /* virtual disk sector size (in bytes).
 285                                            Can only be 512 or 4096 bytes */
 286 } VHDXVirtualDiskLogicalSectorSize;
 287
 288 typedef struct QEMU_PACKED VHDXVirtualDiskPhysicalSectorSize {
 289     uint32_t    physical_sector_size;   /* physical sector size (in bytes).
 290                                            Can only be 512 or 4096 bytes */
 291 } VHDXVirtualDiskPhysicalSectorSize;
 292
 293 typedef struct QEMU_PACKED VHDXParentLocatorHeader {
 294     MSGUID      locator_type[16];       /* type of the parent virtual disk. */
 295     uint16_t    reserved;
 296     uint16_t    key_value_count;        /* number of key/value pairs for this
 297                                            locator */
 298 } VHDXParentLocatorHeader;
 299
 300 /* key and value strings are UNICODE strings, UTF-16 LE encoding, no NULs */
 301 typedef struct QEMU_PACKED VHDXParentLocatorEntry {
 302     uint32_t    key_offset;             /* offset in metadata for key, > 0 */
 303     uint32_t    value_offset;           /* offset in metadata for value, >0 */
 304     uint16_t    key_length;             /* length of entry key, > 0 */
 305     uint16_t    value_length;           /* length of entry value, > 0 */
 306 } VHDXParentLocatorEntry;
 307
 308
 309 /* ----- END VHDX SPECIFICATION STRUCTURES ---- */
 310
 311
 312 uint32_t vhdx_checksum_calc(uint32_t crc, uint8_t *buf, size_t size,
 313                             int crc_offset);
 314
 315 bool vhdx_checksum_is_valid(uint8_t *buf, size_t size, int crc_offset);
 316
 317
 318 static void leguid_to_cpus(MSGUID *guid)
 319 {
 320     le32_to_cpus(&guid->data1);
 321     le16_to_cpus(&guid->data2);
 322     le16_to_cpus(&guid->data3);
 323 }
 324
 325 #endif