gen_crc64table.c

 1// SPDX-License-Identifier: GPL-2.0
 2/*
 3 * This host program runs at kernel build time and generates the lookup tables
 4 * used by the generic CRC64 code.
 5 *
 6 * Copyright 2018 SUSE Linux.
 7 *   Author: Coly Li <colyli@suse.de>
 8 */
 9#include <inttypes.h>
10#include <stdio.h>
11
12#define CRC64_ECMA182_POLY 0x42F0E1EBA9EA3693ULL
13#define CRC64_NVME_POLY 0x9A6C9329AC4BC9B5ULL
14
15static uint64_t crc64_table[256] = {0};
16static uint64_t crc64_nvme_table[256] = {0};
17
18static void generate_reflected_crc64_table(uint64_t table[256], uint64_t poly)
19{
20	uint64_t i, j, c, crc;
21
22	for (i = 0; i < 256; i++) {
23		crc = 0ULL;
24		c = i;
25
26		for (j = 0; j < 8; j++) {
27			if ((crc ^ (c >> j)) & 1)
28				crc = (crc >> 1) ^ poly;
29			else
30				crc >>= 1;
31		}
32		table[i] = crc;
33	}
34}
35
36static void generate_crc64_table(uint64_t table[256], uint64_t poly)
37{
38	uint64_t i, j, c, crc;
39
40	for (i = 0; i < 256; i++) {
41		crc = 0;
42		c = i << 56;
43
44		for (j = 0; j < 8; j++) {
45			if ((crc ^ c) & 0x8000000000000000ULL)
46				crc = (crc << 1) ^ poly;
47			else
48				crc <<= 1;
49			c <<= 1;
50		}
51
52		table[i] = crc;
53	}
54}
55
56static void output_table(uint64_t table[256])
57{
58	int i;
59
60	for (i = 0; i < 256; i++) {
61		printf("\t0x%016" PRIx64 "ULL", table[i]);
62		if (i & 0x1)
63			printf(",\n");
64		else
65			printf(", ");
66	}
67	printf("};\n");
68}
69
70static void print_crc64_tables(void)
71{
72	printf("/* this file is generated - do not edit */\n\n");
73	printf("#include <linux/types.h>\n");
74	printf("#include <linux/cache.h>\n\n");
75	printf("static const u64 ____cacheline_aligned crc64table[256] = {\n");
76	output_table(crc64_table);
77
78	printf("\nstatic const u64 ____cacheline_aligned crc64nvmetable[256] = {\n");
79	output_table(crc64_nvme_table);
80}
81
82int main(int argc, char *argv[])
83{
84	generate_crc64_table(crc64_table, CRC64_ECMA182_POLY);
85	generate_reflected_crc64_table(crc64_nvme_table, CRC64_NVME_POLY);
86	print_crc64_tables();
87	return 0;
88}