diff options
| -rw-r--r-- | lib/Kconfig.debug | 12 | ||||
| -rw-r--r-- | lib/reed_solomon/Makefile | 2 | ||||
| -rw-r--r-- | lib/reed_solomon/decode_rs.c | 115 | ||||
| -rw-r--r-- | lib/reed_solomon/reed_solomon.c | 12 | ||||
| -rw-r--r-- | lib/reed_solomon/test_rslib.c | 518 |
5 files changed, 624 insertions, 35 deletions
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index cbdfae379896..b0d71d9293dc 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1754,6 +1754,18 @@ config RBTREE_TEST A benchmark measuring the performance of the rbtree library. Also includes rbtree invariant checks. +config REED_SOLOMON_TEST + tristate "Reed-Solomon library test" + depends on DEBUG_KERNEL || m + select REED_SOLOMON + select REED_SOLOMON_ENC16 + select REED_SOLOMON_DEC16 + help + This option enables the self-test function of rslib at boot, + or at module load time. + + If unsure, say N. + config INTERVAL_TREE_TEST tristate "Interval tree test" depends on DEBUG_KERNEL diff --git a/lib/reed_solomon/Makefile b/lib/reed_solomon/Makefile index ba9d7a3329eb..5d4fa68f26cb 100644 --- a/lib/reed_solomon/Makefile +++ b/lib/reed_solomon/Makefile @@ -4,4 +4,4 @@ # obj-$(CONFIG_REED_SOLOMON) += reed_solomon.o - +obj-$(CONFIG_REED_SOLOMON_TEST) += test_rslib.o diff --git a/lib/reed_solomon/decode_rs.c b/lib/reed_solomon/decode_rs.c index 1db74eb098d0..805de84ae83d 100644 --- a/lib/reed_solomon/decode_rs.c +++ b/lib/reed_solomon/decode_rs.c @@ -22,6 +22,7 @@ uint16_t *index_of = rs->index_of; uint16_t u, q, tmp, num1, num2, den, discr_r, syn_error; int count = 0; + int num_corrected; uint16_t msk = (uint16_t) rs->nn; /* @@ -39,11 +40,21 @@ /* Check length parameter for validity */ pad = nn - nroots - len; - BUG_ON(pad < 0 || pad >= nn); + BUG_ON(pad < 0 || pad >= nn - nroots); /* Does the caller provide the syndrome ? */ - if (s != NULL) - goto decode; + if (s != NULL) { + for (i = 0; i < nroots; i++) { + /* The syndrome is in index form, + * so nn represents zero + */ + if (s[i] != nn) + goto decode; + } + + /* syndrome is zero, no errors to correct */ + return 0; + } /* form the syndromes; i.e., evaluate data(x) at roots of * g(x) */ @@ -88,8 +99,7 @@ /* if syndrome is zero, data[] is a codeword and there are no * errors to correct. So return data[] unmodified */ - count = 0; - goto finish; + return 0; } decode: @@ -99,9 +109,9 @@ if (no_eras > 0) { /* Init lambda to be the erasure locator polynomial */ lambda[1] = alpha_to[rs_modnn(rs, - prim * (nn - 1 - eras_pos[0]))]; + prim * (nn - 1 - (eras_pos[0] + pad)))]; for (i = 1; i < no_eras; i++) { - u = rs_modnn(rs, prim * (nn - 1 - eras_pos[i])); + u = rs_modnn(rs, prim * (nn - 1 - (eras_pos[i] + pad))); for (j = i + 1; j > 0; j--) { tmp = index_of[lambda[j - 1]]; if (tmp != nn) { @@ -175,6 +185,15 @@ if (lambda[i] != nn) deg_lambda = i; } + + if (deg_lambda == 0) { + /* + * deg(lambda) is zero even though the syndrome is non-zero + * => uncorrectable error detected + */ + return -EBADMSG; + } + /* Find roots of error+erasure locator polynomial by Chien search */ memcpy(®[1], &lambda[1], nroots * sizeof(reg[0])); count = 0; /* Number of roots of lambda(x) */ @@ -188,6 +207,12 @@ } if (q != 0) continue; /* Not a root */ + + if (k < pad) { + /* Impossible error location. Uncorrectable error. */ + return -EBADMSG; + } + /* store root (index-form) and error location number */ root[count] = i; loc[count] = k; @@ -202,8 +227,7 @@ * deg(lambda) unequal to number of roots => uncorrectable * error detected */ - count = -EBADMSG; - goto finish; + return -EBADMSG; } /* * Compute err+eras evaluator poly omega(x) = s(x)*lambda(x) (modulo @@ -223,7 +247,9 @@ /* * Compute error values in poly-form. num1 = omega(inv(X(l))), num2 = * inv(X(l))**(fcr-1) and den = lambda_pr(inv(X(l))) all in poly-form + * Note: we reuse the buffer for b to store the correction pattern */ + num_corrected = 0; for (j = count - 1; j >= 0; j--) { num1 = 0; for (i = deg_omega; i >= 0; i--) { @@ -231,6 +257,13 @@ num1 ^= alpha_to[rs_modnn(rs, omega[i] + i * root[j])]; } + + if (num1 == 0) { + /* Nothing to correct at this position */ + b[j] = 0; + continue; + } + num2 = alpha_to[rs_modnn(rs, root[j] * (fcr - 1) + nn)]; den = 0; @@ -242,30 +275,52 @@ i * root[j])]; } } - /* Apply error to data */ - if (num1 != 0 && loc[j] >= pad) { - uint16_t cor = alpha_to[rs_modnn(rs,index_of[num1] + - index_of[num2] + - nn - index_of[den])]; - /* Store the error correction pattern, if a - * correction buffer is available */ - if (corr) { - corr[j] = cor; - } else { - /* If a data buffer is given and the - * error is inside the message, - * correct it */ - if (data && (loc[j] < (nn - nroots))) - data[loc[j] - pad] ^= cor; - } + + b[j] = alpha_to[rs_modnn(rs, index_of[num1] + + index_of[num2] + + nn - index_of[den])]; + num_corrected++; + } + + /* + * We compute the syndrome of the 'error' and check that it matches + * the syndrome of the received word + */ + for (i = 0; i < nroots; i++) { + tmp = 0; + for (j = 0; j < count; j++) { + if (b[j] == 0) + continue; + + k = (fcr + i) * prim * (nn-loc[j]-1); + tmp ^= alpha_to[rs_modnn(rs, index_of[b[j]] + k)]; } + + if (tmp != alpha_to[s[i]]) + return -EBADMSG; } -finish: - if (eras_pos != NULL) { - for (i = 0; i < count; i++) - eras_pos[i] = loc[i] - pad; + /* + * Store the error correction pattern, if a + * correction buffer is available + */ + if (corr && eras_pos) { + j = 0; + for (i = 0; i < count; i++) { + if (b[i]) { + corr[j] = b[i]; + eras_pos[j++] = loc[i] - pad; + } + } + } else if (data && par) { + /* Apply error to data and parity */ + for (i = 0; i < count; i++) { + if (loc[i] < (nn - nroots)) + data[loc[i] - pad] ^= b[i]; + else + par[loc[i] - pad - len] ^= b[i]; + } } - return count; + return num_corrected; } diff --git a/lib/reed_solomon/reed_solomon.c b/lib/reed_solomon/reed_solomon.c index e5fdc8b9e856..bbc01bad3053 100644 --- a/lib/reed_solomon/reed_solomon.c +++ b/lib/reed_solomon/reed_solomon.c @@ -340,7 +340,8 @@ EXPORT_SYMBOL_GPL(encode_rs8); * @data: data field of a given type * @par: received parity data field * @len: data length - * @s: syndrome data field (if NULL, syndrome is calculated) + * @s: syndrome data field, must be in index form + * (if NULL, syndrome is calculated) * @no_eras: number of erasures * @eras_pos: position of erasures, can be NULL * @invmsk: invert data mask (will be xored on data, not on parity!) @@ -354,7 +355,8 @@ EXPORT_SYMBOL_GPL(encode_rs8); * decoding, so the caller has to ensure that decoder invocations are * serialized. * - * Returns the number of corrected bits or -EBADMSG for uncorrectable errors. + * Returns the number of corrected symbols or -EBADMSG for uncorrectable + * errors. The count includes errors in the parity. */ int decode_rs8(struct rs_control *rsc, uint8_t *data, uint16_t *par, int len, uint16_t *s, int no_eras, int *eras_pos, uint16_t invmsk, @@ -391,7 +393,8 @@ EXPORT_SYMBOL_GPL(encode_rs16); * @data: data field of a given type * @par: received parity data field * @len: data length - * @s: syndrome data field (if NULL, syndrome is calculated) + * @s: syndrome data field, must be in index form + * (if NULL, syndrome is calculated) * @no_eras: number of erasures * @eras_pos: position of erasures, can be NULL * @invmsk: invert data mask (will be xored on data, not on parity!) @@ -403,7 +406,8 @@ EXPORT_SYMBOL_GPL(encode_rs16); * decoding, so the caller has to ensure that decoder invocations are * serialized. * - * Returns the number of corrected bits or -EBADMSG for uncorrectable errors. + * Returns the number of corrected symbols or -EBADMSG for uncorrectable + * errors. The count includes errors in the parity. */ int decode_rs16(struct rs_control *rsc, uint16_t *data, uint16_t *par, int len, uint16_t *s, int no_eras, int *eras_pos, uint16_t invmsk, diff --git a/lib/reed_solomon/test_rslib.c b/lib/reed_solomon/test_rslib.c new file mode 100644 index 000000000000..4eb29f365ece --- /dev/null +++ b/lib/reed_solomon/test_rslib.c @@ -0,0 +1,518 @@ +// 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 obious 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"); |