mktables.c

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/* -*- linux-c -*- ------------------------------------------------------- *
 *
 *   Copyright 2002-2007 H. Peter Anvin - All Rights Reserved
 *
 *   This file is part of the Linux kernel, and is made available under
 *   the terms of the GNU General Public License version 2 or (at your
 *   option) any later version; incorporated herein by reference.
 *
 * ----------------------------------------------------------------------- */

/*
 * mktables.c
 *
 * Make RAID-6 tables.  This is a host user space program to be run at
 * compile time.
 */

#include <stdio.h>
#include <string.h>
#include <inttypes.h>
#include <stdlib.h>
#include <time.h>

static uint8_t gfmul(uint8_t a, uint8_t b)
{
    uint8_t v = 0;

    while (b) {
        if (b & 1)
            v ^= a;
        a = (a << 1) ^ (a & 0x80 ? 0x1d : 0);
        b >>= 1;
    }

    return v;
}

static uint8_t gfpow(uint8_t a, int b)
{
    uint8_t v = 1;

    b %= 255;
    if (b < 0)
        b += 255;

    while (b) {
        if (b & 1)
            v = gfmul(v, a);
        a = gfmul(a, a);
        b >>= 1;
    }

    return v;
}

int main(int argc, char *argv[])
{
    int i, j, k;
    uint8_t v;
    uint8_t exptbl[256], invtbl[256];

    printf("#include <linux/raid/pq.h>\n");
    printf("#include <linux/export.h>\n");

    /* Compute multiplication table */
    printf("\nconst u8  __attribute__((aligned(256)))\n"
        "raid6_gfmul[256][256] =\n"
        "{\n");
    for (i = 0; i < 256; i++) {
        printf("\t{\n");
        for (j = 0; j < 256; j += 8) {
            printf("\t\t");
            for (k = 0; k < 8; k++)
                printf("0x%02x,%c", gfmul(i, j + k),
                       (k == 7) ? '\n' : ' ');
        }
        printf("\t},\n");
    }
    printf("};\n");
    printf("#ifdef __KERNEL__\n");
    printf("EXPORT_SYMBOL(raid6_gfmul);\n");
    printf("#endif\n");

    /* Compute vector multiplication table */
    printf("\nconst u8  __attribute__((aligned(256)))\n"
        "raid6_vgfmul[256][32] =\n"
        "{\n");
    for (i = 0; i < 256; i++) {
        printf("\t{\n");
        for (j = 0; j < 16; j += 8) {
            printf("\t\t");
            for (k = 0; k < 8; k++)
                printf("0x%02x,%c", gfmul(i, j + k),
                       (k == 7) ? '\n' : ' ');
        }
        for (j = 0; j < 16; j += 8) {
            printf("\t\t");
            for (k = 0; k < 8; k++)
                printf("0x%02x,%c", gfmul(i, (j + k) << 4),
                       (k == 7) ? '\n' : ' ');
        }
        printf("\t},\n");
    }
    printf("};\n");
    printf("#ifdef __KERNEL__\n");
    printf("EXPORT_SYMBOL(raid6_vgfmul);\n");
    printf("#endif\n");

    /* Compute power-of-2 table (exponent) */
    v = 1;
    printf("\nconst u8 __attribute__((aligned(256)))\n"
           "raid6_gfexp[256] =\n" "{\n");
    for (i = 0; i < 256; i += 8) {
        printf("\t");
        for (j = 0; j < 8; j++) {
            exptbl[i + j] = v;
            printf("0x%02x,%c", v, (j == 7) ? '\n' : ' ');
            v = gfmul(v, 2);
            if (v == 1)
                v = 0;  /* For entry 255, not a real entry */
        }
    }
    printf("};\n");
    printf("#ifdef __KERNEL__\n");
    printf("EXPORT_SYMBOL(raid6_gfexp);\n");
    printf("#endif\n");

    /* Compute inverse table x^-1 == x^254 */
    printf("\nconst u8 __attribute__((aligned(256)))\n"
           "raid6_gfinv[256] =\n" "{\n");
    for (i = 0; i < 256; i += 8) {
        printf("\t");
        for (j = 0; j < 8; j++) {
            invtbl[i + j] = v = gfpow(i + j, 254);
            printf("0x%02x,%c", v, (j == 7) ? '\n' : ' ');
        }
    }
    printf("};\n");
    printf("#ifdef __KERNEL__\n");
    printf("EXPORT_SYMBOL(raid6_gfinv);\n");
    printf("#endif\n");

    /* Compute inv(2^x + 1) (exponent-xor-inverse) table */
    printf("\nconst u8 __attribute__((aligned(256)))\n"
           "raid6_gfexi[256] =\n" "{\n");
    for (i = 0; i < 256; i += 8) {
        printf("\t");
        for (j = 0; j < 8; j++)
            printf("0x%02x,%c", invtbl[exptbl[i + j] ^ 1],
                   (j == 7) ? '\n' : ' ');
    }
    printf("};\n");
    printf("#ifdef __KERNEL__\n");
    printf("EXPORT_SYMBOL(raid6_gfexi);\n");
    printf("#endif\n");

    return 0;
}