drivers/md/mktables.c

   1 #ident "$Id: mktables.c,v 1.2 2002/12/12 22:41:27 hpa Exp $"
   2 /* ----------------------------------------------------------------------- *
   3  *
   4  *   Copyright 2002 H. Peter Anvin - All Rights Reserved
   5  *
   6  *   This program is free software; you can redistribute it and/or modify
   7  *   it under the terms of the GNU General Public License as published by
   8  *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
   9  *   Bostom MA 02111-1307, USA; either version 2 of the License, or
  10  *   (at your option) any later version; incorporated herein by reference.
  11  *
  12  * ----------------------------------------------------------------------- */
  13
  14 /*
  15  * mktables.c
  16  *
  17  * Make RAID-6 tables.  This is a host user space program to be run at
  18  * compile time.
  19  */
  20
  21 #include <stdio.h>
  22 #include <string.h>
  23 #include <inttypes.h>
  24 #include <stdlib.h>
  25 #include <time.h>
  26
  27 static uint8_t gfmul(uint8_t a, uint8_t b)
  28 {
  29         uint8_t v = 0;
  30
  31         while (b) {
  32                 if (b & 1)
  33                         v ^= a;
  34                 a = (a << 1) ^ (a & 0x80 ? 0x1d : 0);
  35                 b >>= 1;
  36         }
  37
  38         return v;
  39 }
  40
  41 static uint8_t gfpow(uint8_t a, int b)
  42 {
  43         uint8_t v = 1;
  44
  45         b %= 255;
  46         if (b < 0)
  47                 b += 255;
  48
  49         while (b) {
  50                 if (b & 1)
  51                         v = gfmul(v, a);
  52                 a = gfmul(a, a);
  53                 b >>= 1;
  54         }
  55
  56         return v;
  57 }
  58
  59 int main(int argc, char *argv[])
  60 {
  61         int i, j, k;
  62         uint8_t v;
  63         uint8_t exptbl[256], invtbl[256];
  64
  65         printf("#include \"raid6.h\"\n");
  66
  67         /* Compute multiplication table */
  68         printf("\nconst u8  __attribute__((aligned(256)))\n"
  69                 "raid6_gfmul[256][256] =\n"
  70                 "{\n");
  71         for (i = 0; i < 256; i++) {
  72                 printf("\t{\n");
  73                 for (j = 0; j < 256; j += 8) {
  74                         printf("\t\t");
  75                         for (k = 0; k < 8; k++)
  76                                 printf("0x%02x, ", gfmul(i, j+k));
  77                         printf("\n");
  78                 }
  79                 printf("\t},\n");
  80         }
  81         printf("};\n");
  82
  83         /* Compute power-of-2 table (exponent) */
  84         v = 1;
  85         printf("\nconst u8 __attribute__((aligned(256)))\n"
  86                 "raid6_gfexp[256] =\n"
  87                 "{\n");
  88         for (i = 0; i < 256; i += 8) {
  89                 printf("\t");
  90                 for (j = 0; j < 8; j++) {
  91                         exptbl[i+j] = v;
  92                         printf("0x%02x, ", v);
  93                         v = gfmul(v, 2);
  94                         if (v == 1)
  95                                 v = 0;  /* For entry 255, not a real entry */
  96                 }
  97                 printf("\n");
  98         }
  99         printf("};\n");
 100
 101         /* Compute inverse table x^-1 == x^254 */
 102         printf("\nconst u8 __attribute__((aligned(256)))\n"
 103                 "raid6_gfinv[256] =\n"
 104                 "{\n");
 105         for (i = 0; i < 256; i += 8) {
 106                 printf("\t");
 107                 for (j = 0; j < 8; j++) {
 108                         v = gfpow(i+j, 254);
 109                         invtbl[i+j] = v;
 110                         printf("0x%02x, ", v);
 111                 }
 112                 printf("\n");
 113         }
 114         printf("};\n");
 115
 116         /* Compute inv(2^x + 1) (exponent-xor-inverse) table */
 117         printf("\nconst u8 __attribute__((aligned(256)))\n"
 118                 "raid6_gfexi[256] =\n"
 119                 "{\n");
 120         for (i = 0; i < 256; i += 8) {
 121                 printf("\t");
 122                 for (j = 0; j < 8; j++)
 123                         printf("0x%02x, ", invtbl[exptbl[i+j]^1]);
 124                 printf("\n");
 125         }
 126         printf("};\n\n");
 127
 128         return 0;
 129 }