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 | |