// 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] = get_random_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 = get_random_u32() & nn;
} while (errval == 0);
do {
/* Must not choose the same location twice */
errloc = get_random_u32_below(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 = get_random_u32_below(len);
} while (errlocs[errloc] != 0);
derrlocs[i] = errloc;
if (ewsc && get_random_u32_below(2)) {
/* Erasure with the symbol intact */
errlocs[errloc] = 2;
} else {
/* Erasure with corrupted symbol */
do {
/* Error value must be nonzero */
errval = get_random_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");
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