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 326