1*4882a593Smuzhiyun /* SPDX-License-Identifier: GPL-2.0 */
2*4882a593Smuzhiyun #ifndef _XFS_CKSUM_H
3*4882a593Smuzhiyun #define _XFS_CKSUM_H 1
4*4882a593Smuzhiyun
5*4882a593Smuzhiyun #define XFS_CRC_SEED (~(uint32_t)0)
6*4882a593Smuzhiyun
7*4882a593Smuzhiyun /*
8*4882a593Smuzhiyun * Calculate the intermediate checksum for a buffer that has the CRC field
9*4882a593Smuzhiyun * inside it. The offset of the 32bit crc fields is passed as the
10*4882a593Smuzhiyun * cksum_offset parameter. We do not modify the buffer during verification,
11*4882a593Smuzhiyun * hence we have to split the CRC calculation across the cksum_offset.
12*4882a593Smuzhiyun */
13*4882a593Smuzhiyun static inline uint32_t
xfs_start_cksum_safe(char * buffer,size_t length,unsigned long cksum_offset)14*4882a593Smuzhiyun xfs_start_cksum_safe(char *buffer, size_t length, unsigned long cksum_offset)
15*4882a593Smuzhiyun {
16*4882a593Smuzhiyun uint32_t zero = 0;
17*4882a593Smuzhiyun uint32_t crc;
18*4882a593Smuzhiyun
19*4882a593Smuzhiyun /* Calculate CRC up to the checksum. */
20*4882a593Smuzhiyun crc = crc32c(XFS_CRC_SEED, buffer, cksum_offset);
21*4882a593Smuzhiyun
22*4882a593Smuzhiyun /* Skip checksum field */
23*4882a593Smuzhiyun crc = crc32c(crc, &zero, sizeof(__u32));
24*4882a593Smuzhiyun
25*4882a593Smuzhiyun /* Calculate the rest of the CRC. */
26*4882a593Smuzhiyun return crc32c(crc, &buffer[cksum_offset + sizeof(__be32)],
27*4882a593Smuzhiyun length - (cksum_offset + sizeof(__be32)));
28*4882a593Smuzhiyun }
29*4882a593Smuzhiyun
30*4882a593Smuzhiyun /*
31*4882a593Smuzhiyun * Fast CRC method where the buffer is modified. Callers must have exclusive
32*4882a593Smuzhiyun * access to the buffer while the calculation takes place.
33*4882a593Smuzhiyun */
34*4882a593Smuzhiyun static inline uint32_t
xfs_start_cksum_update(char * buffer,size_t length,unsigned long cksum_offset)35*4882a593Smuzhiyun xfs_start_cksum_update(char *buffer, size_t length, unsigned long cksum_offset)
36*4882a593Smuzhiyun {
37*4882a593Smuzhiyun /* zero the CRC field */
38*4882a593Smuzhiyun *(__le32 *)(buffer + cksum_offset) = 0;
39*4882a593Smuzhiyun
40*4882a593Smuzhiyun /* single pass CRC calculation for the entire buffer */
41*4882a593Smuzhiyun return crc32c(XFS_CRC_SEED, buffer, length);
42*4882a593Smuzhiyun }
43*4882a593Smuzhiyun
44*4882a593Smuzhiyun /*
45*4882a593Smuzhiyun * Convert the intermediate checksum to the final ondisk format.
46*4882a593Smuzhiyun *
47*4882a593Smuzhiyun * The CRC32c calculation uses LE format even on BE machines, but returns the
48*4882a593Smuzhiyun * result in host endian format. Hence we need to byte swap it back to LE format
49*4882a593Smuzhiyun * so that it is consistent on disk.
50*4882a593Smuzhiyun */
51*4882a593Smuzhiyun static inline __le32
xfs_end_cksum(uint32_t crc)52*4882a593Smuzhiyun xfs_end_cksum(uint32_t crc)
53*4882a593Smuzhiyun {
54*4882a593Smuzhiyun return ~cpu_to_le32(crc);
55*4882a593Smuzhiyun }
56*4882a593Smuzhiyun
57*4882a593Smuzhiyun /*
58*4882a593Smuzhiyun * Helper to generate the checksum for a buffer.
59*4882a593Smuzhiyun *
60*4882a593Smuzhiyun * This modifies the buffer temporarily - callers must have exclusive
61*4882a593Smuzhiyun * access to the buffer while the calculation takes place.
62*4882a593Smuzhiyun */
63*4882a593Smuzhiyun static inline void
xfs_update_cksum(char * buffer,size_t length,unsigned long cksum_offset)64*4882a593Smuzhiyun xfs_update_cksum(char *buffer, size_t length, unsigned long cksum_offset)
65*4882a593Smuzhiyun {
66*4882a593Smuzhiyun uint32_t crc = xfs_start_cksum_update(buffer, length, cksum_offset);
67*4882a593Smuzhiyun
68*4882a593Smuzhiyun *(__le32 *)(buffer + cksum_offset) = xfs_end_cksum(crc);
69*4882a593Smuzhiyun }
70*4882a593Smuzhiyun
71*4882a593Smuzhiyun /*
72*4882a593Smuzhiyun * Helper to verify the checksum for a buffer.
73*4882a593Smuzhiyun */
74*4882a593Smuzhiyun static inline int
xfs_verify_cksum(char * buffer,size_t length,unsigned long cksum_offset)75*4882a593Smuzhiyun xfs_verify_cksum(char *buffer, size_t length, unsigned long cksum_offset)
76*4882a593Smuzhiyun {
77*4882a593Smuzhiyun uint32_t crc = xfs_start_cksum_safe(buffer, length, cksum_offset);
78*4882a593Smuzhiyun
79*4882a593Smuzhiyun return *(__le32 *)(buffer + cksum_offset) == xfs_end_cksum(crc);
80*4882a593Smuzhiyun }
81*4882a593Smuzhiyun
82*4882a593Smuzhiyun #endif /* _XFS_CKSUM_H */
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