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 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 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 61 int main(int argc, char *argv[]) 62 { 63 generate_crc64_table(); 64 print_crc64_table(); 65 return 0; 66 } 67