1 #ifndef _XFS_CKSUM_H 2 #define _XFS_CKSUM_H 1 3 4 #define XFS_CRC_SEED (~(__uint32_t)0) 5 6 /* 7 * Calculate the intermediate checksum for a buffer that has the CRC field 8 * inside it. The offset of the 32bit crc fields is passed as the 9 * cksum_offset parameter. We do not modify the buffer during verification, 10 * hence we have to split the CRC calculation across the cksum_offset. 11 */ 12 static inline __uint32_t 13 xfs_start_cksum_safe(char *buffer, size_t length, unsigned long cksum_offset) 14 { 15 __uint32_t zero = 0; 16 __uint32_t crc; 17 18 /* Calculate CRC up to the checksum. */ 19 crc = crc32c(XFS_CRC_SEED, buffer, cksum_offset); 20 21 /* Skip checksum field */ 22 crc = crc32c(crc, &zero, sizeof(__u32)); 23 24 /* Calculate the rest of the CRC. */ 25 return crc32c(crc, &buffer[cksum_offset + sizeof(__be32)], 26 length - (cksum_offset + sizeof(__be32))); 27 } 28 29 /* 30 * Fast CRC method where the buffer is modified. Callers must have exclusive 31 * access to the buffer while the calculation takes place. 32 */ 33 static inline __uint32_t 34 xfs_start_cksum_update(char *buffer, size_t length, unsigned long cksum_offset) 35 { 36 /* zero the CRC field */ 37 *(__le32 *)(buffer + cksum_offset) = 0; 38 39 /* single pass CRC calculation for the entire buffer */ 40 return crc32c(XFS_CRC_SEED, buffer, length); 41 } 42 43 /* 44 * Convert the intermediate checksum to the final ondisk format. 45 * 46 * The CRC32c calculation uses LE format even on BE machines, but returns the 47 * result in host endian format. Hence we need to byte swap it back to LE format 48 * so that it is consistent on disk. 49 */ 50 static inline __le32 51 xfs_end_cksum(__uint32_t crc) 52 { 53 return ~cpu_to_le32(crc); 54 } 55 56 /* 57 * Helper to generate the checksum for a buffer. 58 * 59 * This modifies the buffer temporarily - callers must have exclusive 60 * access to the buffer while the calculation takes place. 61 */ 62 static inline void 63 xfs_update_cksum(char *buffer, size_t length, unsigned long cksum_offset) 64 { 65 __uint32_t crc = xfs_start_cksum_update(buffer, length, cksum_offset); 66 67 *(__le32 *)(buffer + cksum_offset) = xfs_end_cksum(crc); 68 } 69 70 /* 71 * Helper to verify the checksum for a buffer. 72 */ 73 static inline int 74 xfs_verify_cksum(char *buffer, size_t length, unsigned long cksum_offset) 75 { 76 __uint32_t crc = xfs_start_cksum_safe(buffer, length, cksum_offset); 77 78 return *(__le32 *)(buffer + cksum_offset) == xfs_end_cksum(crc); 79 } 80 81 #endif /* _XFS_CKSUM_H */ 82