/* * Block driver for Hyper-V VHDX Images * * Copyright (c) 2013 Red Hat, Inc., * * Authors: * Jeff Cody * * This is based on the "VHDX Format Specification v0.95", published 4/12/2012 * by Microsoft: * https://www.microsoft.com/en-us/download/details.aspx?id=29681 * * This work is licensed under the terms of the GNU LGPL, version 2 or later. * See the COPYING.LIB file in the top-level directory. * */ #ifndef BLOCK_VHDX_H #define BLOCK_VHDX_H /* Structures and fields present in the VHDX file */ /* The header section has the following blocks, * each block is 64KB: * * _____________________________________________________________________________ * | File Id. | Header 1 | Header 2 | Region Table | Reserved (768KB) | * |----------|---------------|------------|--------------|--------------------| * | | | | | | * 0.........64KB...........128KB........192KB..........256KB................1MB */ #define VHDX_HEADER_BLOCK_SIZE (64*1024) #define VHDX_FILE_ID_OFFSET 0 #define VHDX_HEADER1_OFFSET (VHDX_HEADER_BLOCK_SIZE*1) #define VHDX_HEADER2_OFFSET (VHDX_HEADER_BLOCK_SIZE*2) #define VHDX_REGION_TABLE_OFFSET (VHDX_HEADER_BLOCK_SIZE*3) /* * A note on the use of MS-GUID fields. For more details on the GUID, * please see: https://en.wikipedia.org/wiki/Globally_unique_identifier. * * The VHDX specification only states that these are MS GUIDs, and which * bytes are data1-data4. It makes no mention of what algorithm should be used * to generate the GUID, nor what standard. However, looking at the specified * known GUID fields, it appears the GUIDs are: * Standard/DCE GUID type (noted by 10b in the MSB of byte 0 of .data4) * Random algorithm (noted by 0x4XXX for .data3) */ /* ---- HEADER SECTION STRUCTURES ---- */ /* These structures are ones that are defined in the VHDX specification * document */ typedef struct VHDXFileIdentifier { uint64_t signature; /* "vhdxfile" in ASCII */ uint16_t creator[256]; /* optional; utf-16 string to identify the vhdx file creator. Diagnotistic only */ } VHDXFileIdentifier; /* the guid is a 16 byte unique ID - the definition for this used by * Microsoft is not just 16 bytes though - it is a structure that is defined, * so we need to follow it here so that endianness does not trip us up */ typedef struct MSGUID { uint32_t data1; uint16_t data2; uint16_t data3; uint8_t data4[8]; } MSGUID; #define guid_eq(a, b) \ (memcmp(&(a), &(b), sizeof(MSGUID)) == 0) #define VHDX_HEADER_SIZE (4*1024) /* although the vhdx_header struct in disk is only 582 bytes, for purposes of crc the header is the first 4KB of the 64KB block */ /* The full header is 4KB, although the actual header data is much smaller. * But for the checksum calculation, it is over the entire 4KB structure, * not just the defined portion of it */ typedef struct QEMU_PACKED VHDXHeader { uint32_t signature; /* "head" in ASCII */ uint32_t checksum; /* CRC-32C hash of the whole header */ uint64_t sequence_number; /* Seq number of this header. Each VHDX file has 2 of these headers, and only the header with the highest sequence number is valid */ MSGUID file_write_guid; /* 128 bit unique identifier. Must be updated to new, unique value before the first modification is made to file */ MSGUID data_write_guid; /* 128 bit unique identifier. Must be updated to new, unique value before the first modification is made to visible data. Visbile data is defined as: - system & user metadata - raw block data - disk size - any change that will cause the virtual disk sector read to differ This does not need to change if blocks are re-arranged */ MSGUID log_guid; /* 128 bit unique identifier. If zero, there is no valid log. If non-zero, log entries with this guid are valid. */ uint16_t log_version; /* version of the log format. Mustn't be zero, unless log_guid is also zero */ uint16_t version; /* version of th evhdx file. Currently, only supported version is "1" */ uint32_t log_length; /* length of the log. Must be multiple of 1MB */ uint64_t log_offset; /* byte offset in the file of the log. Must also be a multiple of 1MB */ } VHDXHeader; /* Header for the region table block */ typedef struct QEMU_PACKED VHDXRegionTableHeader { uint32_t signature; /* "regi" in ASCII */ uint32_t checksum; /* CRC-32C hash of the 64KB table */ uint32_t entry_count; /* number of valid entries */ uint32_t reserved; } VHDXRegionTableHeader; /* Individual region table entry. There may be a maximum of 2047 of these * * There are two known region table properties. Both are required. * BAT (block allocation table): 2DC27766F62342009D64115E9BFD4A08 * Metadata: 8B7CA20647904B9AB8FE575F050F886E */ #define VHDX_REGION_ENTRY_REQUIRED 0x01 /* if set, parser must understand this entry in order to open file */ typedef struct QEMU_PACKED VHDXRegionTableEntry { MSGUID guid; /* 128-bit unique identifier */ uint64_t file_offset; /* offset of the object in the file. Must be multiple of 1MB */ uint32_t length; /* length, in bytes, of the object */ uint32_t data_bits; } VHDXRegionTableEntry; /* ---- LOG ENTRY STRUCTURES ---- */ #define VHDX_LOG_HDR_SIZE 64 typedef struct QEMU_PACKED VHDXLogEntryHeader { uint32_t signature; /* "loge" in ASCII */ uint32_t checksum; /* CRC-32C hash of the 64KB table */ uint32_t entry_length; /* length in bytes, multiple of 1MB */ uint32_t tail; /* byte offset of first log entry of a seq, where this entry is the last entry */ uint64_t sequence_number; /* incremented with each log entry. May not be zero. */ uint32_t descriptor_count; /* number of descriptors in this log entry, must be >= 0 */ uint32_t reserved; MSGUID log_guid; /* value of the log_guid from vhdx_header. If not found in vhdx_header, it is invalid */ uint64_t flushed_file_offset; /* see spec for full details - this should be vhdx file size in bytes */ uint64_t last_file_offset; /* size in bytes that all allocated file structures fit into */ } VHDXLogEntryHeader; #define VHDX_LOG_DESC_SIZE 32 typedef struct QEMU_PACKED VHDXLogDescriptor { uint32_t signature; /* "zero" or "desc" in ASCII */ union { uint32_t reserved; /* zero desc */ uint32_t trailing_bytes; /* data desc: bytes 4092-4096 of the data sector */ }; union { uint64_t zero_length; /* zero desc: length of the section to zero */ uint64_t leading_bytes; /* data desc: bytes 0-7 of the data sector */ }; uint64_t file_offset; /* file offset to write zeros - multiple of 4kB */ uint64_t sequence_number; /* must match same field in vhdx_log_entry_header */ } VHDXLogDescriptor; typedef struct QEMU_PACKED VHDXLogDataSector { uint32_t data_signature; /* "data" in ASCII */ uint32_t sequence_high; /* 4 MSB of 8 byte sequence_number */ uint8_t data[4084]; /* raw data, bytes 8-4091 (inclusive). see the data descriptor field for the other mising bytes */ uint32_t sequence_low; /* 4 LSB of 8 byte sequence_number */ } VHDXLogDataSector; /* block states - different state values depending on whether it is a * payload block, or a sector block. */ #define PAYLOAD_BLOCK_NOT_PRESENT 0 #define PAYLOAD_BLOCK_UNDEFINED 1 #define PAYLOAD_BLOCK_ZERO 2 #define PAYLOAD_BLOCK_UNMAPPED 5 #define PAYLOAD_BLOCK_FULL_PRESENT 6 #define PAYLOAD_BLOCK_PARTIALLY_PRESENT 7 #define SB_BLOCK_NOT_PRESENT 0 #define SB_BLOCK_PRESENT 6 /* per the spec */ #define VHDX_MAX_SECTORS_PER_BLOCK (1<<23) /* upper 44 bits are the file offset in 1MB units lower 3 bits are the state other bits are reserved */ #define VHDX_BAT_STATE_BIT_MASK 0x07 #define VHDX_BAT_FILE_OFF_BITS (64-44) typedef uint64_t VHDXBatEntry; /* ---- METADATA REGION STRUCTURES ---- */ #define VHDX_METADATA_ENTRY_SIZE 32 #define VHDX_METADATA_MAX_ENTRIES 2047 /* not including the header */ #define VHDX_METADATA_TABLE_MAX_SIZE \ (VHDX_METADATA_ENTRY_SIZE * (VHDX_METADATA_MAX_ENTRIES+1)) typedef struct QEMU_PACKED VHDXMetadataTableHeader { uint64_t signature; /* "metadata" in ASCII */ uint16_t reserved; uint16_t entry_count; /* number table entries. <= 2047 */ uint32_t reserved2[5]; } VHDXMetadataTableHeader; #define VHDX_META_FLAGS_IS_USER 0x01 /* max 1024 entries */ #define VHDX_META_FLAGS_IS_VIRTUAL_DISK 0x02 /* virtual disk metadata if set, otherwise file metdata */ #define VHDX_META_FLAGS_IS_REQUIRED 0x04 /* parse must understand this entry to open the file */ typedef struct QEMU_PACKED VHDXMetadataTableEntry { MSGUID item_id; /* 128-bit identifier for metadata */ uint32_t offset; /* byte offset of the metadata. At least 64kB. Relative to start of metadata region */ /* note: if length = 0, so is offset */ uint32_t length; /* length of metadata. <= 1MB. */ uint32_t data_bits; /* least-significant 3 bits are flags, the rest are reserved (see above) */ uint32_t reserved2; } VHDXMetadataTableEntry; #define VHDX_PARAMS_LEAVE_BLOCKS_ALLOCED 0x01 /* Do not change any blocks to be BLOCK_NOT_PRESENT. If set indicates a fixed size VHDX file */ #define VHDX_PARAMS_HAS_PARENT 0x02 /* has parent / backing file */ typedef struct QEMU_PACKED VHDXFileParameters { uint32_t block_size; /* size of each payload block, always power of 2, <= 256MB and >= 1MB. */ uint32_t data_bits; /* least-significant 2 bits are flags, the rest are reserved (see above) */ } VHDXFileParameters; typedef struct QEMU_PACKED VHDXVirtualDiskSize { uint64_t virtual_disk_size; /* Size of the virtual disk, in bytes. Must be multiple of the sector size, max of 64TB */ } VHDXVirtualDiskSize; typedef struct QEMU_PACKED VHDXPage83Data { MSGUID page_83_data[16]; /* unique id for scsi devices that support page 0x83 */ } VHDXPage83Data; typedef struct QEMU_PACKED VHDXVirtualDiskLogicalSectorSize { uint32_t logical_sector_size; /* virtual disk sector size (in bytes). Can only be 512 or 4096 bytes */ } VHDXVirtualDiskLogicalSectorSize; typedef struct QEMU_PACKED VHDXVirtualDiskPhysicalSectorSize { uint32_t physical_sector_size; /* physical sector size (in bytes). Can only be 512 or 4096 bytes */ } VHDXVirtualDiskPhysicalSectorSize; typedef struct QEMU_PACKED VHDXParentLocatorHeader { MSGUID locator_type[16]; /* type of the parent virtual disk. */ uint16_t reserved; uint16_t key_value_count; /* number of key/value pairs for this locator */ } VHDXParentLocatorHeader; /* key and value strings are UNICODE strings, UTF-16 LE encoding, no NULs */ typedef struct QEMU_PACKED VHDXParentLocatorEntry { uint32_t key_offset; /* offset in metadata for key, > 0 */ uint32_t value_offset; /* offset in metadata for value, >0 */ uint16_t key_length; /* length of entry key, > 0 */ uint16_t value_length; /* length of entry value, > 0 */ } VHDXParentLocatorEntry; /* ----- END VHDX SPECIFICATION STRUCTURES ---- */ uint32_t vhdx_checksum_calc(uint32_t crc, uint8_t *buf, size_t size, int crc_offset); bool vhdx_checksum_is_valid(uint8_t *buf, size_t size, int crc_offset); static void leguid_to_cpus(MSGUID *guid) { le32_to_cpus(&guid->data1); le16_to_cpus(&guid->data2); le16_to_cpus(&guid->data3); } #endif