// SPDX-License-Identifier: GPL-2.0
/*
 * Tests for Generic Reed Solomon encoder / decoder library
 *
 * Written by Ferdinand Blomqvist
 * Based on previous work by Phil Karn, KA9Q
 */
#include <linux/rslib.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/random.h>
#include <linux/slab.h>

enum verbosity {
        V_SILENT,
        V_PROGRESS,
        V_CSUMMARY
};

enum method {
        CORR_BUFFER,
        CALLER_SYNDROME,
        IN_PLACE
};

#define __param(type, name, init, msg)          \
        static type name = init;                \
        module_param(name, type, 0444);         \
        MODULE_PARM_DESC(name, msg)

__param(int, v, V_PROGRESS, "Verbosity level");
__param(int, ewsc, 1, "Erasures without symbol corruption");
__param(int, bc, 1, "Test for correct behaviour beyond error correction capacity");

struct etab {
        int     symsize;
        int     genpoly;
        int     fcs;
        int     prim;
        int     nroots;
        int     ntrials;
};

/* List of codes to test */
static struct etab Tab[] = {
        {2,     0x7,    1,      1,      1,      100000  },
        {3,     0xb,    1,      1,      2,      100000  },
        {3,     0xb,    1,      1,      3,      100000  },
        {3,     0xb,    2,      1,      4,      100000  },
        {4,     0x13,   1,      1,      4,      10000   },
        {5,     0x25,   1,      1,      6,      1000    },
        {6,     0x43,   3,      1,      8,      1000    },
        {7,     0x89,   1,      1,      14,     500     },
        {8,     0x11d,  1,      1,      30,     100     },
        {8,     0x187,  112,    11,     32,     100     },
        {9,     0x211,  1,      1,      33,     80      },
        {0, 0, 0, 0, 0, 0},
};


struct estat {
        int     dwrong;
        int     irv;
        int     wepos;
        int     nwords;
};

struct bcstat {
        int     rfail;
        int     rsuccess;
        int     noncw;
        int     nwords;
};

struct wspace {
        uint16_t        *c;             /* sent codeword */
        uint16_t        *r;             /* received word */
        uint16_t        *s;             /* syndrome */
        uint16_t        *corr;          /* correction buffer */
        int             *errlocs;
        int             *derrlocs;
};

struct pad {
        int     mult;
        int     shift;
};

static struct pad pad_coef[] = {
        { 0, 0 },
        { 1, 2 },
        { 1, 1 },
        { 3, 2 },
        { 1, 0 },
};

static void free_ws(struct wspace *ws)
{
        if (!ws)
                return;

        kfree(ws->errlocs);
        kfree(ws->c);
        kfree(ws);
}

static struct wspace *alloc_ws(struct rs_codec *rs)
{
        int nroots = rs->nroots;
        struct wspace *ws;
        int nn = rs->nn;

        ws = kzalloc(sizeof(*ws), GFP_KERNEL);
        if (!ws)
                return NULL;

        ws->c = kmalloc_array(2 * (nn + nroots),
                                sizeof(uint16_t), GFP_KERNEL);
        if (!ws->c)
                goto err;

        ws->r = ws->c + nn;
        ws->s = ws->r + nn;
        ws->corr = ws->s + nroots;

        ws->errlocs = kmalloc_array(nn + nroots, sizeof(int), GFP_KERNEL);
        if (!ws->errlocs)
                goto err;

        ws->derrlocs = ws->errlocs + nn;
        return ws;

err:
        free_ws(ws);
        return NULL;
}


/*
 * Generates a random codeword and stores it in c. Generates random errors and
 * erasures, and stores the random word with errors in r. Erasure positions are
 * stored in derrlocs, while errlocs has one of three values in every position:
 *
 * 0 if there is no error in this position;
 * 1 if there is a symbol error in this position;
 * 2 if there is an erasure without symbol corruption.
 *
 * Returns the number of corrupted symbols.
 */
static int get_rcw_we(struct rs_control *rs, struct wspace *ws,
                        int len, int errs, int eras)
{
        int nroots = rs->codec->nroots;
        int *derrlocs = ws->derrlocs;
        int *errlocs = ws->errlocs;
        int dlen = len - nroots;
        int nn = rs->codec->nn;
        uint16_t *c = ws->c;
        uint16_t *r = ws->r;
        int errval;
        int errloc;
        int i;

        /* Load c with random data and encode */
        for (i = 0; i < dlen; i++)
                c[i] = prandom_u32() & nn;

        memset(c + dlen, 0, nroots * sizeof(*c));
        encode_rs16(rs, c, dlen, c + dlen, 0);

        /* Make copyand add errors and erasures */
        memcpy(r, c, len * sizeof(*r));
        memset(errlocs, 0, len * sizeof(*errlocs));
        memset(derrlocs, 0, nroots * sizeof(*derrlocs));

        /* Generating random errors */
        for (i = 0; i < errs; i++) {
                do {
                        /* Error value must be nonzero */
                        errval = prandom_u32() & nn;
                } while (errval == 0);

                do {
                        /* Must not choose the same location twice */
                        errloc = prandom_u32() % len;
                } while (errlocs[errloc] != 0);

                errlocs[errloc] = 1;
                r[errloc] ^= errval;
        }

        /* Generating random erasures */
        for (i = 0; i < eras; i++) {
                do {
                        /* Must not choose the same location twice */
                        errloc = prandom_u32() % len;
                } while (errlocs[errloc] != 0);

                derrlocs[i] = errloc;

                if (ewsc && (prandom_u32() & 1)) {
                        /* Erasure with the symbol intact */
                        errlocs[errloc] = 2;
                } else {
                        /* Erasure with corrupted symbol */
                        do {
                                /* Error value must be nonzero */
                                errval = prandom_u32() & nn;
                        } while (errval == 0);

                        errlocs[errloc] = 1;
                        r[errloc] ^= errval;
                        errs++;
                }
        }

        return errs;
}

static void fix_err(uint16_t *data, int nerrs, uint16_t *corr, int *errlocs)
{
        int i;

        for (i = 0; i < nerrs; i++)
                data[errlocs[i]] ^= corr[i];
}

static void compute_syndrome(struct rs_control *rsc, uint16_t *data,
                                int len, uint16_t *syn)
{
        struct rs_codec *rs = rsc->codec;
        uint16_t *alpha_to = rs->alpha_to;
        uint16_t *index_of = rs->index_of;
        int nroots = rs->nroots;
        int prim = rs->prim;
        int fcr = rs->fcr;
        int i, j;

        /* Calculating syndrome */
        for (i = 0; i < nroots; i++) {
                syn[i] = data[0];
                for (j = 1; j < len; j++) {
                        if (syn[i] == 0) {
                                syn[i] = data[j];
                        } else {
                                syn[i] = data[j] ^
                                        alpha_to[rs_modnn(rs, index_of[syn[i]]
                                                + (fcr + i) * prim)];
                        }
                }
        }

        /* Convert to index form */
        for (i = 0; i < nroots; i++)
                syn[i] = rs->index_of[syn[i]];
}

/* Test up to error correction capacity */
static void test_uc(struct rs_control *rs, int len, int errs,
                int eras, int trials, struct estat *stat,
                struct wspace *ws, int method)
{
        int dlen = len - rs->codec->nroots;
        int *derrlocs = ws->derrlocs;
        int *errlocs = ws->errlocs;
        uint16_t *corr = ws->corr;
        uint16_t *c = ws->c;
        uint16_t *r = ws->r;
        uint16_t *s = ws->s;
        int derrs, nerrs;
        int i, j;

        for (j = 0; j < trials; j++) {
                nerrs = get_rcw_we(rs, ws, len, errs, eras);

                switch (method) {
                case CORR_BUFFER:
                        derrs = decode_rs16(rs, r, r + dlen, dlen,
                                        NULL, eras, derrlocs, 0, corr);
                        fix_err(r, derrs, corr, derrlocs);
                        break;
                case CALLER_SYNDROME:
                        compute_syndrome(rs, r, len, s);
                        derrs = decode_rs16(rs, NULL, NULL, dlen,
                                        s, eras, derrlocs, 0, corr);
                        fix_err(r, derrs, corr, derrlocs);
                        break;
                case IN_PLACE:
                        derrs = decode_rs16(rs, r, r + dlen, dlen,
                                        NULL, eras, derrlocs, 0, NULL);
                        break;
                default:
                        continue;
                }

                if (derrs != nerrs)
                        stat->irv++;

                if (method != IN_PLACE) {
                        for (i = 0; i < derrs; i++) {
                                if (errlocs[derrlocs[i]] != 1)
                                        stat->wepos++;
                        }
                }

                if (memcmp(r, c, len * sizeof(*r)))
                        stat->dwrong++;
        }
        stat->nwords += trials;
}

static int ex_rs_helper(struct rs_control *rs, struct wspace *ws,
                        int len, int trials, int method)
{
        static const char * const desc[] = {
                "Testing correction buffer interface...",
                "Testing with caller provided syndrome...",
                "Testing in-place interface..."
        };

        struct estat stat = {0, 0, 0, 0};
        int nroots = rs->codec->nroots;
        int errs, eras, retval;

        if (v >= V_PROGRESS)
                pr_info("  %s\n", desc[method]);

        for (errs = 0; errs <= nroots / 2; errs++)
                for (eras = 0; eras <= nroots - 2 * errs; eras++)
                        test_uc(rs, len, errs, eras, trials, &stat, ws, method);

        if (v >= V_CSUMMARY) {
                pr_info("    Decodes wrong:        %d / %d\n",
                                stat.dwrong, stat.nwords);
                pr_info("    Wrong return value:   %d / %d\n",
                                stat.irv, stat.nwords);
                if (method != IN_PLACE)
                        pr_info("    Wrong error position: %d\n", stat.wepos);
        }

        retval = stat.dwrong + stat.wepos + stat.irv;
        if (retval && v >= V_PROGRESS)
                pr_warn("    FAIL: %d decoding failures!\n", retval);

        return retval;
}

static int exercise_rs(struct rs_control *rs, struct wspace *ws,
                       int len, int trials)
{

        int retval = 0;
        int i;

        if (v >= V_PROGRESS)
                pr_info("Testing up to error correction capacity...\n");

        for (i = 0; i <= IN_PLACE; i++)
                retval |= ex_rs_helper(rs, ws, len, trials, i);

        return retval;
}

/* Tests for correct behaviour beyond error correction capacity */
static void test_bc(struct rs_control *rs, int len, int errs,
                int eras, int trials, struct bcstat *stat,
                struct wspace *ws)
{
        int nroots = rs->codec->nroots;
        int dlen = len - nroots;
        int *derrlocs = ws->derrlocs;
        uint16_t *corr = ws->corr;
        uint16_t *r = ws->r;
        int derrs, j;

        for (j = 0; j < trials; j++) {
                get_rcw_we(rs, ws, len, errs, eras);
                derrs = decode_rs16(rs, r, r + dlen, dlen,
                                NULL, eras, derrlocs, 0, corr);
                fix_err(r, derrs, corr, derrlocs);

                if (derrs >= 0) {
                        stat->rsuccess++;

                        /*
                         * We check that the returned word is actually a
                         * codeword. The obvious way to do this would be to
                         * compute the syndrome, but we don't want to replicate
                         * that code here. However, all the codes are in
                         * systematic form, and therefore we can encode the
                         * returned word, and see whether the parity changes or
                         * not.
                         */
                        memset(corr, 0, nroots * sizeof(*corr));
                        encode_rs16(rs, r, dlen, corr, 0);

                        if (memcmp(r + dlen, corr, nroots * sizeof(*corr)))
                                stat->noncw++;
                } else {
                        stat->rfail++;
                }
        }
        stat->nwords += trials;
}

static int exercise_rs_bc(struct rs_control *rs, struct wspace *ws,
                          int len, int trials)
{
        struct bcstat stat = {0, 0, 0, 0};
        int nroots = rs->codec->nroots;
        int errs, eras, cutoff;

        if (v >= V_PROGRESS)
                pr_info("Testing beyond error correction capacity...\n");

        for (errs = 1; errs <= nroots; errs++) {
                eras = nroots - 2 * errs + 1;
                if (eras < 0)
                        eras = 0;

                cutoff = nroots <= len - errs ? nroots : len - errs;
                for (; eras <= cutoff; eras++)
                        test_bc(rs, len, errs, eras, trials, &stat, ws);
        }

        if (v >= V_CSUMMARY) {
                pr_info("  decoder gives up:        %d / %d\n",
                                stat.rfail, stat.nwords);
                pr_info("  decoder returns success: %d / %d\n",
                                stat.rsuccess, stat.nwords);
                pr_info("    not a codeword:        %d / %d\n",
                                stat.noncw, stat.rsuccess);
        }

        if (stat.noncw && v >= V_PROGRESS)
                pr_warn("    FAIL: %d silent failures!\n", stat.noncw);

        return stat.noncw;
}

static int run_exercise(struct etab *e)
{
        int nn = (1 << e->symsize) - 1;
        int kk = nn - e->nroots;
        struct rs_control *rsc;
        int retval = -ENOMEM;
        int max_pad = kk - 1;
        int prev_pad = -1;
        struct wspace *ws;
        int i;

        rsc = init_rs(e->symsize, e->genpoly, e->fcs, e->prim, e->nroots);
        if (!rsc)
                return retval;

        ws = alloc_ws(rsc->codec);
        if (!ws)
                goto err;

        retval = 0;
        for (i = 0; i < ARRAY_SIZE(pad_coef); i++) {
                int pad = (pad_coef[i].mult * max_pad) >> pad_coef[i].shift;
                int len = nn - pad;

                if (pad == prev_pad)
                        continue;

                prev_pad = pad;
                if (v >= V_PROGRESS) {
                        pr_info("Testing (%d,%d)_%d code...\n",
                                        len, kk - pad, nn + 1);
                }

                retval |= exercise_rs(rsc, ws, len, e->ntrials);
                if (bc)
                        retval |= exercise_rs_bc(rsc, ws, len, e->ntrials);
        }

        free_ws(ws);

err:
        free_rs(rsc);
        return retval;
}

static int __init test_rslib_init(void)
{
        int i, fail = 0;

        for (i = 0; Tab[i].symsize != 0 ; i++) {
                int retval;

                retval = run_exercise(Tab + i);
                if (retval < 0)
                        return -ENOMEM;

                fail |= retval;
        }

        if (fail)
                pr_warn("rslib: test failed\n");
        else
                pr_info("rslib: test ok\n");

        return -EAGAIN; /* Fail will directly unload the module */
}

static void __exit test_rslib_exit(void)
{
}

module_init(test_rslib_init)
module_exit(test_rslib_exit)

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Ferdinand Blomqvist");
MODULE_DESCRIPTION("Reed-Solomon library test");