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
22 static uint64_t crc64_table[256] = {0};
23 static uint64_t crc64_rocksoft_table[256] = {0};
24
25 static 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
43 static 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
63 static 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
77 static 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
89 int 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
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