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.
10 */
11 static inline __uint32_t
xfs_start_cksum(char * buffer,size_t length,unsigned long cksum_offset)12 xfs_start_cksum(char *buffer, size_t length, unsigned long cksum_offset)
13 {
14 __uint32_t zero = 0;
15 __uint32_t crc;
16
17 /* Calculate CRC up to the checksum. */
18 crc = crc32c(XFS_CRC_SEED, buffer, cksum_offset);
19
20 /* Skip checksum field */
21 crc = crc32c(crc, &zero, sizeof(__u32));
22
23 /* Calculate the rest of the CRC. */
24 return crc32c(crc, &buffer[cksum_offset + sizeof(__be32)],
25 length - (cksum_offset + sizeof(__be32)));
26 }
27
28 /*
29 * Convert the intermediate checksum to the final ondisk format.
30 *
31 * The CRC32c calculation uses LE format even on BE machines, but returns the
32 * result in host endian format. Hence we need to byte swap it back to LE format
33 * so that it is consistent on disk.
34 */
35 static inline __le32
xfs_end_cksum(__uint32_t crc)36 xfs_end_cksum(__uint32_t crc)
37 {
38 return ~cpu_to_le32(crc);
39 }
40
41 /*
42 * Helper to generate the checksum for a buffer.
43 */
44 static inline void
xfs_update_cksum(char * buffer,size_t length,unsigned long cksum_offset)45 xfs_update_cksum(char *buffer, size_t length, unsigned long cksum_offset)
46 {
47 __uint32_t crc = xfs_start_cksum(buffer, length, cksum_offset);
48
49 *(__le32 *)(buffer + cksum_offset) = xfs_end_cksum(crc);
50 }
51
52 /*
53 * Helper to verify the checksum for a buffer.
54 */
55 static inline int
xfs_verify_cksum(char * buffer,size_t length,unsigned long cksum_offset)56 xfs_verify_cksum(char *buffer, size_t length, unsigned long cksum_offset)
57 {
58 __uint32_t crc = xfs_start_cksum(buffer, length, cksum_offset);
59
60 return *(__le32 *)(buffer + cksum_offset) == xfs_end_cksum(crc);
61 }
62
63 #endif /* _XFS_CKSUM_H */
64