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 * https://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 * crc64rocksoft[256] table is from the Rocksoft specification polynomial
26 * defined as,
27 *
28 * x^64 + x^63 + x^61 + x^59 + x^58 + x^56 + x^55 + x^52 + x^49 + x^48 + x^47 +
29 * x^46 + x^44 + x^41 + x^37 + x^36 + x^34 + x^32 + x^31 + x^28 + x^26 + x^23 +
30 * x^22 + x^19 + x^16 + x^13 + x^12 + x^10 + x^9 + x^6 + x^4 + x^3 + 1
31 *
32 * Copyright 2018 SUSE Linux.
33 * Author: Coly Li <colyli@suse.de>
34 */
35
36 #include <linux/module.h>
37 #include <linux/types.h>
38 #include <linux/crc64.h>
39 #include "crc64table.h"
40
41 MODULE_DESCRIPTION("CRC64 calculations");
42 MODULE_LICENSE("GPL v2");
43
44 /**
45 * crc64_be - Calculate bitwise big-endian ECMA-182 CRC64
46 * @crc: seed value for computation. 0 or (u64)~0 for a new CRC calculation,
47 * or the previous crc64 value if computing incrementally.
48 * @p: pointer to buffer over which CRC64 is run
49 * @len: length of buffer @p
50 */
51 u64 __pure crc64_be(u64 crc, const void *p, size_t len)
52 {
53 size_t i, t;
54
55 const unsigned char *_p = p;
56
57 for (i = 0; i < len; i++) {
58 t = ((crc >> 56) ^ (*_p++)) & 0xFF;
59 crc = crc64table[t] ^ (crc << 8);
60 }
61
62 return crc;
63 }
64 EXPORT_SYMBOL_GPL(crc64_be);
65
66 /**
67 * crc64_rocksoft_generic - Calculate bitwise Rocksoft CRC64
68 * @crc: seed value for computation. 0 for a new CRC calculation, or the
69 * previous crc64 value if computing incrementally.
70 * @p: pointer to buffer over which CRC64 is run
71 * @len: length of buffer @p
72 */
73 u64 __pure crc64_rocksoft_generic(u64 crc, const void *p, size_t len)
74 {
75 const unsigned char *_p = p;
76 size_t i;
77
78 crc = ~crc;
79
80 for (i = 0; i < len; i++)
81 crc = (crc >> 8) ^ crc64rocksofttable[(crc & 0xff) ^ *_p++];
82
83 return ~crc;
84 }
85 EXPORT_SYMBOL_GPL(crc64_rocksoft_generic);
86
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