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 
21 static uint64_t crc64_table[256] = {0};
22 
generate_crc64_table(void)23 static 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 
print_crc64_table(void)43 static 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 
main(int argc,char * argv[])61 int main(int argc, char *argv[])
62 {
63 	generate_crc64_table();
64 	print_crc64_table();
65 	return 0;
66 }
67