cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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crc64.c (2687B)

      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
     41MODULE_DESCRIPTION("CRC64 calculations");
     42MODULE_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 */
     51u64 __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}
     64EXPORT_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 */
     73u64 __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}
     85EXPORT_SYMBOL_GPL(crc64_rocksoft_generic);