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 * 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 <linux/crc64.h> 32 #include "crc64table.h" 33 34 MODULE_DESCRIPTION("CRC64 calculations"); 35 MODULE_LICENSE("GPL v2"); 36 37 /** 38 * crc64_be - Calculate bitwise big-endian ECMA-182 CRC64 39 * @crc: seed value for computation. 0 or (u64)~0 for a new CRC calculation, 40 or the previous crc64 value if computing incrementally. 41 * @p: pointer to buffer over which CRC64 is run 42 * @len: length of buffer @p 43 */ 44 u64 __pure crc64_be(u64 crc, const void *p, size_t len) 45 { 46 size_t i, t; 47 48 const unsigned char *_p = p; 49 50 for (i = 0; i < len; i++) { 51 t = ((crc >> 56) ^ (*_p++)) & 0xFF; 52 crc = crc64table[t] ^ (crc << 8); 53 } 54 55 return crc; 56 } 57 EXPORT_SYMBOL_GPL(crc64_be); 58