// SPDX-License-Identifier: GPL-2.0-or-later
/* -*- linux-c -*- ------------------------------------------------------- *
 *
 *   Copyright 2002-2007 H. Peter Anvin - All Rights Reserved
 *
 * ----------------------------------------------------------------------- */

/*
 * 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("#ifdef __KERNEL__\n");
        printf("#include <linux/export.h>\n");
        printf("#endif\n");
        printf("#include <linux/raid/pq.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 log-of-2 table */
        printf("\nconst u8 __attribute__((aligned(256)))\n"
               "raid6_gflog[256] =\n" "{\n");
        for (i = 0; i < 256; i += 8) {
                printf("\t");
                for (j = 0; j < 8; j++) {
                        v = 255;
                        for (k = 0; k < 256; k++)
                                if (exptbl[k] == (i + j)) {
                                        v = k;
                                        break;
                                }
                        printf("0x%02x,%c", v, (j == 7) ? '\n' : ' ');
                }
        }
        printf("};\n");
        printf("#ifdef __KERNEL__\n");
        printf("EXPORT_SYMBOL(raid6_gflog);\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;
}