lib/gen_crc64table.c

   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
  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
  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
  63 int main(int argc, char *argv[])
  64 {
  65         generate_crc64_table();
  66         print_crc64_table();
  67         return 0;
  68 }