82 lines
2.3 KiB
C
82 lines
2.3 KiB
C
#ifndef _XFS_CKSUM_H
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#define _XFS_CKSUM_H 1
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#define XFS_CRC_SEED (~(__uint32_t)0)
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/*
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* Calculate the intermediate checksum for a buffer that has the CRC field
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* inside it. The offset of the 32bit crc fields is passed as the
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* cksum_offset parameter. We do not modify the buffer during verification,
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* hence we have to split the CRC calculation across the cksum_offset.
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*/
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static inline __uint32_t
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xfs_start_cksum_safe(char *buffer, size_t length, unsigned long cksum_offset)
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{
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__uint32_t zero = 0;
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__uint32_t crc;
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/* Calculate CRC up to the checksum. */
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crc = crc32c(XFS_CRC_SEED, buffer, cksum_offset);
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/* Skip checksum field */
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crc = crc32c(crc, &zero, sizeof(__u32));
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/* Calculate the rest of the CRC. */
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return crc32c(crc, &buffer[cksum_offset + sizeof(__be32)],
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length - (cksum_offset + sizeof(__be32)));
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}
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/*
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* Fast CRC method where the buffer is modified. Callers must have exclusive
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* access to the buffer while the calculation takes place.
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*/
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static inline __uint32_t
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xfs_start_cksum_update(char *buffer, size_t length, unsigned long cksum_offset)
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{
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/* zero the CRC field */
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*(__le32 *)(buffer + cksum_offset) = 0;
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/* single pass CRC calculation for the entire buffer */
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return crc32c(XFS_CRC_SEED, buffer, length);
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}
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/*
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* Convert the intermediate checksum to the final ondisk format.
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*
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* The CRC32c calculation uses LE format even on BE machines, but returns the
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* result in host endian format. Hence we need to byte swap it back to LE format
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* so that it is consistent on disk.
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*/
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static inline __le32
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xfs_end_cksum(__uint32_t crc)
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{
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return ~cpu_to_le32(crc);
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}
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/*
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* Helper to generate the checksum for a buffer.
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*
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* This modifies the buffer temporarily - callers must have exclusive
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* access to the buffer while the calculation takes place.
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*/
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static inline void
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xfs_update_cksum(char *buffer, size_t length, unsigned long cksum_offset)
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{
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__uint32_t crc = xfs_start_cksum_update(buffer, length, cksum_offset);
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*(__le32 *)(buffer + cksum_offset) = xfs_end_cksum(crc);
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}
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/*
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* Helper to verify the checksum for a buffer.
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*/
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static inline int
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xfs_verify_cksum(char *buffer, size_t length, unsigned long cksum_offset)
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{
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__uint32_t crc = xfs_start_cksum_safe(buffer, length, cksum_offset);
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return *(__le32 *)(buffer + cksum_offset) == xfs_end_cksum(crc);
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}
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#endif /* _XFS_CKSUM_H */
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