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block: vhdx header for the QEMU support of VHDX images
This is based on Microsoft's VHDX specification: "VHDX Format Specification v0.95", published 4/12/2012 https://www.microsoft.com/en-us/download/details.aspx?id=29681 These structures define the various header, metadata, and other block structures defined in the VHDX specification. Signed-off-by: Jeff Cody <jcody@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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/* | ||
* Block driver for Hyper-V VHDX Images | ||
* | ||
* Copyright (c) 2013 Red Hat, Inc., | ||
* | ||
* Authors: | ||
* Jeff Cody <jcody@redhat.com> | ||
* | ||
* 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. | ||
* | ||
*/ | ||
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#ifndef BLOCK_VHDX_H | ||
#define BLOCK_VHDX_H | ||
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/* Structures and fields present in the VHDX file */ | ||
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/* 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 | ||
*/ | ||
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#define VHDX_HEADER_BLOCK_SIZE (64*1024) | ||
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#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) | ||
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/* | ||
* 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) | ||
*/ | ||
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/* ---- HEADER SECTION STRUCTURES ---- */ | ||
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/* These structures are ones that are defined in the VHDX specification | ||
* document */ | ||
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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; | ||
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/* 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 */ | ||
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typedef struct MSGUID { | ||
uint32_t data1; | ||
uint16_t data2; | ||
uint16_t data3; | ||
uint8_t data4[8]; | ||
} MSGUID; | ||
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#define guid_eq(a, b) \ | ||
(memcmp(&(a), &(b), sizeof(MSGUID)) == 0) | ||
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#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 */ | ||
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/* 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; | ||
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/* 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; | ||
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/* 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; | ||
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/* ---- 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 | ||
sould be vhdx file size in bytes */ | ||
uint64_t last_file_offset; /* size in bytes that all allocated | ||
file structures fit into */ | ||
} VHDXLogEntryHeader; | ||
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#define VHDX_LOG_DESC_SIZE 32 | ||
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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; | ||
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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; | ||
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/* block states - different state values depending on whether it is a | ||
* payload block, or a sector block. */ | ||
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#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 | ||
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#define SB_BLOCK_NOT_PRESENT 0 | ||
#define SB_BLOCK_PRESENT 6 | ||
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/* per the spec */ | ||
#define VHDX_MAX_SECTORS_PER_BLOCK (1<<23) | ||
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/* 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; | ||
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/* ---- METADATA REGION STRUCTURES ---- */ | ||
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#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; | ||
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#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; | ||
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#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; | ||
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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; | ||
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typedef struct QEMU_PACKED VHDXPage83Data { | ||
MSGUID page_83_data[16]; /* unique id for scsi devices that | ||
support page 0x83 */ | ||
} VHDXPage83Data; | ||
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typedef struct QEMU_PACKED VHDXVirtualDiskLogicalSectorSize { | ||
uint32_t logical_sector_size; /* virtual disk sector size (in bytes). | ||
Can only be 512 or 4096 bytes */ | ||
} VHDXVirtualDiskLogicalSectorSize; | ||
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typedef struct QEMU_PACKED VHDXVirtualDiskPhysicalSectorSize { | ||
uint32_t physical_sector_size; /* physical sector size (in bytes). | ||
Can only be 512 or 4096 bytes */ | ||
} VHDXVirtualDiskPhysicalSectorSize; | ||
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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; | ||
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/* 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; | ||
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/* ----- END VHDX SPECIFICATION STRUCTURES ---- */ | ||
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#endif |