1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Generate lookup table for the table-driven CRC64 calculation.
4 *
5 * gen_crc64table is executed in kernel build time and generates
6 * lib/crc64table.h. This header is included by lib/crc64.c for
7 * the table-driven CRC64 calculation.
8 *
9 * See lib/crc64.c for more information about which specification
10 * and polynomial arithmetic that gen_crc64table.c follows to
11 * generate the lookup table.
12 *
13 * Copyright 2018 SUSE Linux.
14 *   Author: Coly Li <colyli@suse.de>
15 */
16#include <inttypes.h>
17#include <stdio.h>
18
19#define CRC64_ECMA182_POLY 0x42F0E1EBA9EA3693ULL
20#define CRC64_ROCKSOFT_POLY 0x9A6C9329AC4BC9B5ULL
21
22static uint64_t crc64_table[256] = {0};
23static uint64_t crc64_rocksoft_table[256] = {0};
24
25static void generate_reflected_crc64_table(uint64_t table[256], uint64_t poly)
26{
27	uint64_t i, j, c, crc;
28
29	for (i = 0; i < 256; i++) {
30		crc = 0ULL;
31		c = i;
32
33		for (j = 0; j < 8; j++) {
34			if ((crc ^ (c >> j)) & 1)
35				crc = (crc >> 1) ^ poly;
36			else
37				crc >>= 1;
38		}
39		table[i] = crc;
40	}
41}
42
43static void generate_crc64_table(uint64_t table[256], uint64_t poly)
44{
45	uint64_t i, j, c, crc;
46
47	for (i = 0; i < 256; i++) {
48		crc = 0;
49		c = i << 56;
50
51		for (j = 0; j < 8; j++) {
52			if ((crc ^ c) & 0x8000000000000000ULL)
53				crc = (crc << 1) ^ poly;
54			else
55				crc <<= 1;
56			c <<= 1;
57		}
58
59		table[i] = crc;
60	}
61}
62
63static void output_table(uint64_t table[256])
64{
65	int i;
66
67	for (i = 0; i < 256; i++) {
68		printf("\t0x%016" PRIx64 "ULL", table[i]);
69		if (i & 0x1)
70			printf(",\n");
71		else
72			printf(", ");
73	}
74	printf("};\n");
75}
76
77static void print_crc64_tables(void)
78{
79	printf("/* this file is generated - do not edit */\n\n");
80	printf("#include <linux/types.h>\n");
81	printf("#include <linux/cache.h>\n\n");
82	printf("static const u64 ____cacheline_aligned crc64table[256] = {\n");
83	output_table(crc64_table);
84
85	printf("\nstatic const u64 ____cacheline_aligned crc64rocksofttable[256] = {\n");
86	output_table(crc64_rocksoft_table);
87}
88
89int main(int argc, char *argv[])
90{
91	generate_crc64_table(crc64_table, CRC64_ECMA182_POLY);
92	generate_reflected_crc64_table(crc64_rocksoft_table, CRC64_ROCKSOFT_POLY);
93	print_crc64_tables();
94	return 0;
95}
96