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 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
21static uint64_t crc64_table[256] = {0};
22
23static void generate_crc64_table(void)
24{
25	uint64_t i, j, c, crc;
26
27	for (i = 0; i < 256; i++) {
28		crc = 0;
29		c = i << 56;
30
31		for (j = 0; j < 8; j++) {
32			if ((crc ^ c) & 0x8000000000000000ULL)
33				crc = (crc << 1) ^ CRC64_ECMA182_POLY;
34			else
35				crc <<= 1;
36			c <<= 1;
37		}
38
39		crc64_table[i] = crc;
40	}
41}
42
43static void print_crc64_table(void)
44{
45	int i;
46
47	printf("/* this file is generated - do not edit */\n\n");
48	printf("#include <linux/types.h>\n");
49	printf("#include <linux/cache.h>\n\n");
50	printf("static const u64 ____cacheline_aligned crc64table[256] = {\n");
51	for (i = 0; i < 256; i++) {
52		printf("\t0x%016" PRIx64 "ULL", crc64_table[i]);
53		if (i & 0x1)
54			printf(",\n");
55		else
56			printf(", ");
57	}
58	printf("};\n");
59}
60
61int main(int argc, char *argv[])
62{
63	generate_crc64_table();
64	print_crc64_table();
65	return 0;
66}