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1/* SPDX-License-Identifier: GPL-2.0 */2#ifndef _XFS_CKSUM_H3#define _XFS_CKSUM_H 14 5#define XFS_CRC_SEED (~(uint32_t)0)6 7/*8 * Calculate the intermediate checksum for a buffer that has the CRC field9 * inside it. The offset of the 32bit crc fields is passed as the10 * cksum_offset parameter. We do not modify the buffer during verification,11 * hence we have to split the CRC calculation across the cksum_offset.12 */13static inline uint32_t14xfs_start_cksum_safe(char *buffer, size_t length, unsigned long cksum_offset)15{16 uint32_t zero = 0;17 uint32_t crc;18 19 /* Calculate CRC up to the checksum. */20 crc = crc32c(XFS_CRC_SEED, buffer, cksum_offset);21 22 /* Skip checksum field */23 crc = crc32c(crc, &zero, sizeof(__u32));24 25 /* Calculate the rest of the CRC. */26 return crc32c(crc, &buffer[cksum_offset + sizeof(__be32)],27 length - (cksum_offset + sizeof(__be32)));28}29 30/*31 * Fast CRC method where the buffer is modified. Callers must have exclusive32 * access to the buffer while the calculation takes place.33 */34static inline uint32_t35xfs_start_cksum_update(char *buffer, size_t length, unsigned long cksum_offset)36{37 /* zero the CRC field */38 *(__le32 *)(buffer + cksum_offset) = 0;39 40 /* single pass CRC calculation for the entire buffer */41 return crc32c(XFS_CRC_SEED, buffer, length);42}43 44/*45 * Convert the intermediate checksum to the final ondisk format.46 *47 * The CRC32c calculation uses LE format even on BE machines, but returns the48 * result in host endian format. Hence we need to byte swap it back to LE format49 * so that it is consistent on disk.50 */51static inline __le3252xfs_end_cksum(uint32_t crc)53{54 return ~cpu_to_le32(crc);55}56 57/*58 * Helper to generate the checksum for a buffer.59 *60 * This modifies the buffer temporarily - callers must have exclusive61 * access to the buffer while the calculation takes place.62 */63static inline void64xfs_update_cksum(char *buffer, size_t length, unsigned long cksum_offset)65{66 uint32_t crc = xfs_start_cksum_update(buffer, length, cksum_offset);67 68 *(__le32 *)(buffer + cksum_offset) = xfs_end_cksum(crc);69}70 71/*72 * Helper to verify the checksum for a buffer.73 */74static inline int75xfs_verify_cksum(char *buffer, size_t length, unsigned long cksum_offset)76{77 uint32_t crc = xfs_start_cksum_safe(buffer, length, cksum_offset);78 79 return *(__le32 *)(buffer + cksum_offset) == xfs_end_cksum(crc);80}81 82#endif /* _XFS_CKSUM_H */83