1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Normal 64-bit CRC calculation.
4 *
5 * This is a basic crc64 implementation following ECMA-182 specification,
6 * which can be found from,
7 * http://www.ecma-international.org/publications/standards/Ecma-182.htm
8 *
9 * Dr. Ross N. Williams has a great document to introduce the idea of CRC
10 * algorithm, here the CRC64 code is also inspired by the table-driven
11 * algorithm and detail example from this paper. This paper can be found
12 * from,
13 * http://www.ross.net/crc/download/crc_v3.txt
14 *
15 * crc64table[256] is the lookup table of a table-driven 64-bit CRC
16 * calculation, which is generated by gen_crc64table.c in kernel build
17 * time. The polynomial of crc64 arithmetic is from ECMA-182 specification
18 * as well, which is defined as,
19 *
20 * x^64 + x^62 + x^57 + x^55 + x^54 + x^53 + x^52 + x^47 + x^46 + x^45 +
21 * x^40 + x^39 + x^38 + x^37 + x^35 + x^33 + x^32 + x^31 + x^29 + x^27 +
22 * x^24 + x^23 + x^22 + x^21 + x^19 + x^17 + x^13 + x^12 + x^10 + x^9 +
23 * x^7 + x^4 + x + 1
24 *
25 * Copyright 2018 SUSE Linux.
26 * Author: Coly Li <colyli@suse.de>
27 */
28
29 #include <linux/module.h>
30 #include <linux/types.h>
31 #include "crc64table.h"
32
33 MODULE_DESCRIPTION("CRC64 calculations");
34 MODULE_LICENSE("GPL v2");
35
36 /**
37 * crc64_be - Calculate bitwise big-endian ECMA-182 CRC64
38 * @crc: seed value for computation. 0 or (u64)~0 for a new CRC calculation,
39 or the previous crc64 value if computing incrementally.
40 * @p: pointer to buffer over which CRC64 is run
41 * @len: length of buffer @p
42 */
43 u64 __pure crc64_be(u64 crc, const void *p, size_t len)
44 {
45 size_t i, t;
46
47 const unsigned char *_p = p;
48
49 for (i = 0; i < len; i++) {
50 t = ((crc >> 56) ^ (*_p++)) & 0xFF;
51 crc = crc64table[t] ^ (crc << 8);
52 }
53
54 return crc;
55 }
56 EXPORT_SYMBOL_GPL(crc64_be);