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 #include <linux/swab.h>
20 
21 #define CRC64_ECMA182_POLY 0x42F0E1EBA9EA3693ULL
22 
23 static uint64_t crc64_table[256] = {0};
24 
generate_crc64_table(void)25 static void generate_crc64_table(void)
26 {
27 	uint64_t i, j, c, crc;
28 
29 	for (i = 0; i < 256; i++) {
30 		crc = 0;
31 		c = i << 56;
32 
33 		for (j = 0; j < 8; j++) {
34 			if ((crc ^ c) & 0x8000000000000000ULL)
35 				crc = (crc << 1) ^ CRC64_ECMA182_POLY;
36 			else
37 				crc <<= 1;
38 			c <<= 1;
39 		}
40 
41 		crc64_table[i] = crc;
42 	}
43 }
44 
print_crc64_table(void)45 static void print_crc64_table(void)
46 {
47 	int i;
48 
49 	printf("/* this file is generated - do not edit */\n\n");
50 	printf("#include <linux/types.h>\n");
51 	printf("#include <linux/cache.h>\n\n");
52 	printf("static const u64 ____cacheline_aligned crc64table[256] = {\n");
53 	for (i = 0; i < 256; i++) {
54 		printf("\t0x%016" PRIx64 "ULL", crc64_table[i]);
55 		if (i & 0x1)
56 			printf(",\n");
57 		else
58 			printf(", ");
59 	}
60 	printf("};\n");
61 }
62 
main(int argc,char * argv[])63 int main(int argc, char *argv[])
64 {
65 	generate_crc64_table();
66 	print_crc64_table();
67 	return 0;
68 }
69