cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
Log | Files | Refs | README | LICENSE | sfeed.txt

crc8.c (2478B)

      1/*
      2 * Copyright (c) 2011 Broadcom Corporation
      3 *
      4 * Permission to use, copy, modify, and/or distribute this software for any
      5 * purpose with or without fee is hereby granted, provided that the above
      6 * copyright notice and this permission notice appear in all copies.
      7 *
      8 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
      9 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
     10 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
     11 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
     12 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
     13 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
     14 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
     15 */
     16
     17#define pr_fmt(fmt)		KBUILD_MODNAME ": " fmt
     18
     19#include <linux/module.h>
     20#include <linux/crc8.h>
     21#include <linux/printk.h>
     22
     23/**
     24 * crc8_populate_msb - fill crc table for given polynomial in reverse bit order.
     25 *
     26 * @table:	table to be filled.
     27 * @polynomial:	polynomial for which table is to be filled.
     28 */
     29void crc8_populate_msb(u8 table[CRC8_TABLE_SIZE], u8 polynomial)
     30{
     31	int i, j;
     32	const u8 msbit = 0x80;
     33	u8 t = msbit;
     34
     35	table[0] = 0;
     36
     37	for (i = 1; i < CRC8_TABLE_SIZE; i *= 2) {
     38		t = (t << 1) ^ (t & msbit ? polynomial : 0);
     39		for (j = 0; j < i; j++)
     40			table[i+j] = table[j] ^ t;
     41	}
     42}
     43EXPORT_SYMBOL(crc8_populate_msb);
     44
     45/**
     46 * crc8_populate_lsb - fill crc table for given polynomial in regular bit order.
     47 *
     48 * @table:	table to be filled.
     49 * @polynomial:	polynomial for which table is to be filled.
     50 */
     51void crc8_populate_lsb(u8 table[CRC8_TABLE_SIZE], u8 polynomial)
     52{
     53	int i, j;
     54	u8 t = 1;
     55
     56	table[0] = 0;
     57
     58	for (i = (CRC8_TABLE_SIZE >> 1); i; i >>= 1) {
     59		t = (t >> 1) ^ (t & 1 ? polynomial : 0);
     60		for (j = 0; j < CRC8_TABLE_SIZE; j += 2*i)
     61			table[i+j] = table[j] ^ t;
     62	}
     63}
     64EXPORT_SYMBOL(crc8_populate_lsb);
     65
     66/**
     67 * crc8 - calculate a crc8 over the given input data.
     68 *
     69 * @table: crc table used for calculation.
     70 * @pdata: pointer to data buffer.
     71 * @nbytes: number of bytes in data buffer.
     72 * @crc: previous returned crc8 value.
     73 */
     74u8 crc8(const u8 table[CRC8_TABLE_SIZE], const u8 *pdata, size_t nbytes, u8 crc)
     75{
     76	/* loop over the buffer data */
     77	while (nbytes-- > 0)
     78		crc = table[(crc ^ *pdata++) & 0xff];
     79
     80	return crc;
     81}
     82EXPORT_SYMBOL(crc8);
     83
     84MODULE_DESCRIPTION("CRC8 (by Williams, Ross N.) function");
     85MODULE_AUTHOR("Broadcom Corporation");
     86MODULE_LICENSE("Dual BSD/GPL");