drivers/md/mktables.c

   1 /* -*- linux-c -*- ------------------------------------------------------- *
   2  *
   3  *   Copyright 2002-2007 H. Peter Anvin - All Rights Reserved
   4  *
   5  *   This file is part of the Linux kernel, and is made available under
   6  *   the terms of the GNU General Public License version 2 or (at your
   7  *   option) any later version; incorporated herein by reference.
   8  *
   9  * ----------------------------------------------------------------------- */
  10
  11 /*
  12  * mktables.c
  13  *
  14  * Make RAID-6 tables.  This is a host user space program to be run at
  15  * compile time.
  16  */
  17
  18 #include <stdio.h>
  19 #include <string.h>
  20 #include <inttypes.h>
  21 #include <stdlib.h>
  22 #include <time.h>
  23
  24 static uint8_t gfmul(uint8_t a, uint8_t b)
  25 {
  26         uint8_t v = 0;
  27
  28         while (b) {
  29                 if (b & 1)
  30                         v ^= a;
  31                 a = (a << 1) ^ (a & 0x80 ? 0x1d : 0);
  32                 b >>= 1;
  33         }
  34
  35         return v;
  36 }
  37
  38 static uint8_t gfpow(uint8_t a, int b)
  39 {
  40         uint8_t v = 1;
  41
  42         b %= 255;
  43         if (b < 0)
  44                 b += 255;
  45
  46         while (b) {
  47                 if (b & 1)
  48                         v = gfmul(v, a);
  49                 a = gfmul(a, a);
  50                 b >>= 1;
  51         }
  52
  53         return v;
  54 }
  55
  56 int main(int argc, char *argv[])
  57 {
  58         int i, j, k;
  59         uint8_t v;
  60         uint8_t exptbl[256], invtbl[256];
  61
  62         printf("#include \"raid6.h\"\n");
  63
  64         /* Compute multiplication table */
  65         printf("\nconst u8  __attribute__((aligned(256)))\n"
  66                 "raid6_gfmul[256][256] =\n"
  67                 "{\n");
  68         for (i = 0; i < 256; i++) {
  69                 printf("\t{\n");
  70                 for (j = 0; j < 256; j += 8) {
  71                         printf("\t\t");
  72                         for (k = 0; k < 8; k++)
  73                                 printf("0x%02x,%c", gfmul(i, j + k),
  74                                        (k == 7) ? '\n' : ' ');
  75                 }
  76                 printf("\t},\n");
  77         }
  78         printf("};\n");
  79
  80         /* Compute power-of-2 table (exponent) */
  81         v = 1;
  82         printf("\nconst u8 __attribute__((aligned(256)))\n"
  83                "raid6_gfexp[256] =\n" "{\n");
  84         for (i = 0; i < 256; i += 8) {
  85                 printf("\t");
  86                 for (j = 0; j < 8; j++) {
  87                         exptbl[i + j] = v;
  88                         printf("0x%02x,%c", v, (j == 7) ? '\n' : ' ');
  89                         v = gfmul(v, 2);
  90                         if (v == 1)
  91                                 v = 0;  /* For entry 255, not a real entry */
  92                 }
  93         }
  94         printf("};\n");
  95
  96         /* Compute inverse table x^-1 == x^254 */
  97         printf("\nconst u8 __attribute__((aligned(256)))\n"
  98                "raid6_gfinv[256] =\n" "{\n");
  99         for (i = 0; i < 256; i += 8) {
 100                 printf("\t");
 101                 for (j = 0; j < 8; j++) {
 102                         invtbl[i + j] = v = gfpow(i + j, 254);
 103                         printf("0x%02x,%c", v, (j == 7) ? '\n' : ' ');
 104                 }
 105         }
 106         printf("};\n");
 107
 108         /* Compute inv(2^x + 1) (exponent-xor-inverse) table */
 109         printf("\nconst u8 __attribute__((aligned(256)))\n"
 110                "raid6_gfexi[256] =\n" "{\n");
 111         for (i = 0; i < 256; i += 8) {
 112                 printf("\t");
 113                 for (j = 0; j < 8; j++)
 114                         printf("0x%02x,%c", invtbl[exptbl[i + j] ^ 1],
 115                                (j == 7) ? '\n' : ' ');
 116         }
 117         printf("};\n");
 118
 119         return 0;
 120 }