^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 2) * Generic binary BCH encoding/decoding library
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 3) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 4) * This program is free software; you can redistribute it and/or modify it
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 5) * under the terms of the GNU General Public License version 2 as published by
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 6) * the Free Software Foundation.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 7) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 8) * This program is distributed in the hope that it will be useful, but WITHOUT
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 9) * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10) * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11) * more details.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13) * You should have received a copy of the GNU General Public License along with
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14) * this program; if not, write to the Free Software Foundation, Inc., 51
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15) * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17) * Copyright © 2011 Parrot S.A.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19) * Author: Ivan Djelic <ivan.djelic@parrot.com>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21) * Description:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23) * This library provides runtime configurable encoding/decoding of binary
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24) * Bose-Chaudhuri-Hocquenghem (BCH) codes.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26) * Call bch_init to get a pointer to a newly allocated bch_control structure for
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27) * the given m (Galois field order), t (error correction capability) and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28) * (optional) primitive polynomial parameters.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30) * Call bch_encode to compute and store ecc parity bytes to a given buffer.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31) * Call bch_decode to detect and locate errors in received data.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33) * On systems supporting hw BCH features, intermediate results may be provided
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34) * to bch_decode in order to skip certain steps. See bch_decode() documentation
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 35) * for details.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 36) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 37) * Option CONFIG_BCH_CONST_PARAMS can be used to force fixed values of
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 38) * parameters m and t; thus allowing extra compiler optimizations and providing
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 39) * better (up to 2x) encoding performance. Using this option makes sense when
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 40) * (m,t) are fixed and known in advance, e.g. when using BCH error correction
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 41) * on a particular NAND flash device.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 42) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 43) * Algorithmic details:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 44) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 45) * Encoding is performed by processing 32 input bits in parallel, using 4
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 46) * remainder lookup tables.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 47) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 48) * The final stage of decoding involves the following internal steps:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 49) * a. Syndrome computation
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 50) * b. Error locator polynomial computation using Berlekamp-Massey algorithm
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 51) * c. Error locator root finding (by far the most expensive step)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 52) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 53) * In this implementation, step c is not performed using the usual Chien search.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 54) * Instead, an alternative approach described in [1] is used. It consists in
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 55) * factoring the error locator polynomial using the Berlekamp Trace algorithm
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 56) * (BTA) down to a certain degree (4), after which ad hoc low-degree polynomial
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 57) * solving techniques [2] are used. The resulting algorithm, called BTZ, yields
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 58) * much better performance than Chien search for usual (m,t) values (typically
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 59) * m >= 13, t < 32, see [1]).
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 60) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 61) * [1] B. Biswas, V. Herbert. Efficient root finding of polynomials over fields
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 62) * of characteristic 2, in: Western European Workshop on Research in Cryptology
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 63) * - WEWoRC 2009, Graz, Austria, LNCS, Springer, July 2009, to appear.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 64) * [2] [Zin96] V.A. Zinoviev. On the solution of equations of degree 10 over
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 65) * finite fields GF(2^q). In Rapport de recherche INRIA no 2829, 1996.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 66) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 67)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 68) #include <linux/kernel.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 69) #include <linux/errno.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 70) #include <linux/init.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 71) #include <linux/module.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 72) #include <linux/slab.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 73) #include <linux/bitops.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 74) #include <asm/byteorder.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 75) #include <linux/bch.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 76)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 77) #if defined(CONFIG_BCH_CONST_PARAMS)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 78) #define GF_M(_p) (CONFIG_BCH_CONST_M)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 79) #define GF_T(_p) (CONFIG_BCH_CONST_T)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 80) #define GF_N(_p) ((1 << (CONFIG_BCH_CONST_M))-1)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 81) #define BCH_MAX_M (CONFIG_BCH_CONST_M)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 82) #define BCH_MAX_T (CONFIG_BCH_CONST_T)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 83) #else
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 84) #define GF_M(_p) ((_p)->m)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 85) #define GF_T(_p) ((_p)->t)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 86) #define GF_N(_p) ((_p)->n)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 87) #define BCH_MAX_M 15 /* 2KB */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 88) #define BCH_MAX_T 64 /* 64 bit correction */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 89) #endif
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 90)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 91) #define BCH_ECC_WORDS(_p) DIV_ROUND_UP(GF_M(_p)*GF_T(_p), 32)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 92) #define BCH_ECC_BYTES(_p) DIV_ROUND_UP(GF_M(_p)*GF_T(_p), 8)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 93)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 94) #define BCH_ECC_MAX_WORDS DIV_ROUND_UP(BCH_MAX_M * BCH_MAX_T, 32)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 95)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 96) #ifndef dbg
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 97) #define dbg(_fmt, args...) do {} while (0)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 98) #endif
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 99)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 100) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 101) * represent a polynomial over GF(2^m)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 102) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 103) struct gf_poly {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 104) unsigned int deg; /* polynomial degree */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 105) unsigned int c[]; /* polynomial terms */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 106) };
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 107)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 108) /* given its degree, compute a polynomial size in bytes */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 109) #define GF_POLY_SZ(_d) (sizeof(struct gf_poly)+((_d)+1)*sizeof(unsigned int))
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 110)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 111) /* polynomial of degree 1 */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 112) struct gf_poly_deg1 {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 113) struct gf_poly poly;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 114) unsigned int c[2];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 115) };
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 116)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 117) static u8 swap_bits_table[] = {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 118) 0x00, 0x80, 0x40, 0xc0, 0x20, 0xa0, 0x60, 0xe0,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 119) 0x10, 0x90, 0x50, 0xd0, 0x30, 0xb0, 0x70, 0xf0,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 120) 0x08, 0x88, 0x48, 0xc8, 0x28, 0xa8, 0x68, 0xe8,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 121) 0x18, 0x98, 0x58, 0xd8, 0x38, 0xb8, 0x78, 0xf8,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 122) 0x04, 0x84, 0x44, 0xc4, 0x24, 0xa4, 0x64, 0xe4,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 123) 0x14, 0x94, 0x54, 0xd4, 0x34, 0xb4, 0x74, 0xf4,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 124) 0x0c, 0x8c, 0x4c, 0xcc, 0x2c, 0xac, 0x6c, 0xec,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 125) 0x1c, 0x9c, 0x5c, 0xdc, 0x3c, 0xbc, 0x7c, 0xfc,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 126) 0x02, 0x82, 0x42, 0xc2, 0x22, 0xa2, 0x62, 0xe2,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 127) 0x12, 0x92, 0x52, 0xd2, 0x32, 0xb2, 0x72, 0xf2,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 128) 0x0a, 0x8a, 0x4a, 0xca, 0x2a, 0xaa, 0x6a, 0xea,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 129) 0x1a, 0x9a, 0x5a, 0xda, 0x3a, 0xba, 0x7a, 0xfa,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 130) 0x06, 0x86, 0x46, 0xc6, 0x26, 0xa6, 0x66, 0xe6,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 131) 0x16, 0x96, 0x56, 0xd6, 0x36, 0xb6, 0x76, 0xf6,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 132) 0x0e, 0x8e, 0x4e, 0xce, 0x2e, 0xae, 0x6e, 0xee,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 133) 0x1e, 0x9e, 0x5e, 0xde, 0x3e, 0xbe, 0x7e, 0xfe,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 134) 0x01, 0x81, 0x41, 0xc1, 0x21, 0xa1, 0x61, 0xe1,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 135) 0x11, 0x91, 0x51, 0xd1, 0x31, 0xb1, 0x71, 0xf1,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 136) 0x09, 0x89, 0x49, 0xc9, 0x29, 0xa9, 0x69, 0xe9,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 137) 0x19, 0x99, 0x59, 0xd9, 0x39, 0xb9, 0x79, 0xf9,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 138) 0x05, 0x85, 0x45, 0xc5, 0x25, 0xa5, 0x65, 0xe5,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 139) 0x15, 0x95, 0x55, 0xd5, 0x35, 0xb5, 0x75, 0xf5,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 140) 0x0d, 0x8d, 0x4d, 0xcd, 0x2d, 0xad, 0x6d, 0xed,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 141) 0x1d, 0x9d, 0x5d, 0xdd, 0x3d, 0xbd, 0x7d, 0xfd,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 142) 0x03, 0x83, 0x43, 0xc3, 0x23, 0xa3, 0x63, 0xe3,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 143) 0x13, 0x93, 0x53, 0xd3, 0x33, 0xb3, 0x73, 0xf3,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 144) 0x0b, 0x8b, 0x4b, 0xcb, 0x2b, 0xab, 0x6b, 0xeb,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 145) 0x1b, 0x9b, 0x5b, 0xdb, 0x3b, 0xbb, 0x7b, 0xfb,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 146) 0x07, 0x87, 0x47, 0xc7, 0x27, 0xa7, 0x67, 0xe7,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 147) 0x17, 0x97, 0x57, 0xd7, 0x37, 0xb7, 0x77, 0xf7,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 148) 0x0f, 0x8f, 0x4f, 0xcf, 0x2f, 0xaf, 0x6f, 0xef,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 149) 0x1f, 0x9f, 0x5f, 0xdf, 0x3f, 0xbf, 0x7f, 0xff,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 150) };
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 151)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 152) static u8 swap_bits(struct bch_control *bch, u8 in)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 153) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 154) if (!bch->swap_bits)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 155) return in;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 156)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 157) return swap_bits_table[in];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 158) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 159)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 160) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 161) * same as bch_encode(), but process input data one byte at a time
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 162) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 163) static void bch_encode_unaligned(struct bch_control *bch,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 164) const unsigned char *data, unsigned int len,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 165) uint32_t *ecc)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 166) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 167) int i;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 168) const uint32_t *p;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 169) const int l = BCH_ECC_WORDS(bch)-1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 170)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 171) while (len--) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 172) u8 tmp = swap_bits(bch, *data++);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 173)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 174) p = bch->mod8_tab + (l+1)*(((ecc[0] >> 24)^(tmp)) & 0xff);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 175)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 176) for (i = 0; i < l; i++)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 177) ecc[i] = ((ecc[i] << 8)|(ecc[i+1] >> 24))^(*p++);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 178)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 179) ecc[l] = (ecc[l] << 8)^(*p);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 180) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 181) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 182)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 183) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 184) * convert ecc bytes to aligned, zero-padded 32-bit ecc words
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 185) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 186) static void load_ecc8(struct bch_control *bch, uint32_t *dst,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 187) const uint8_t *src)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 188) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 189) uint8_t pad[4] = {0, 0, 0, 0};
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 190) unsigned int i, nwords = BCH_ECC_WORDS(bch)-1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 191)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 192) for (i = 0; i < nwords; i++, src += 4)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 193) dst[i] = ((u32)swap_bits(bch, src[0]) << 24) |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 194) ((u32)swap_bits(bch, src[1]) << 16) |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 195) ((u32)swap_bits(bch, src[2]) << 8) |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 196) swap_bits(bch, src[3]);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 197)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 198) memcpy(pad, src, BCH_ECC_BYTES(bch)-4*nwords);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 199) dst[nwords] = ((u32)swap_bits(bch, pad[0]) << 24) |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 200) ((u32)swap_bits(bch, pad[1]) << 16) |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 201) ((u32)swap_bits(bch, pad[2]) << 8) |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 202) swap_bits(bch, pad[3]);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 203) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 204)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 205) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 206) * convert 32-bit ecc words to ecc bytes
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 207) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 208) static void store_ecc8(struct bch_control *bch, uint8_t *dst,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 209) const uint32_t *src)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 210) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 211) uint8_t pad[4];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 212) unsigned int i, nwords = BCH_ECC_WORDS(bch)-1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 213)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 214) for (i = 0; i < nwords; i++) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 215) *dst++ = swap_bits(bch, src[i] >> 24);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 216) *dst++ = swap_bits(bch, src[i] >> 16);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 217) *dst++ = swap_bits(bch, src[i] >> 8);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 218) *dst++ = swap_bits(bch, src[i]);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 219) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 220) pad[0] = swap_bits(bch, src[nwords] >> 24);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 221) pad[1] = swap_bits(bch, src[nwords] >> 16);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 222) pad[2] = swap_bits(bch, src[nwords] >> 8);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 223) pad[3] = swap_bits(bch, src[nwords]);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 224) memcpy(dst, pad, BCH_ECC_BYTES(bch)-4*nwords);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 225) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 226)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 227) /**
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 228) * bch_encode - calculate BCH ecc parity of data
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 229) * @bch: BCH control structure
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 230) * @data: data to encode
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 231) * @len: data length in bytes
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 232) * @ecc: ecc parity data, must be initialized by caller
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 233) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 234) * The @ecc parity array is used both as input and output parameter, in order to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 235) * allow incremental computations. It should be of the size indicated by member
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 236) * @ecc_bytes of @bch, and should be initialized to 0 before the first call.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 237) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 238) * The exact number of computed ecc parity bits is given by member @ecc_bits of
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 239) * @bch; it may be less than m*t for large values of t.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 240) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 241) void bch_encode(struct bch_control *bch, const uint8_t *data,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 242) unsigned int len, uint8_t *ecc)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 243) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 244) const unsigned int l = BCH_ECC_WORDS(bch)-1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 245) unsigned int i, mlen;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 246) unsigned long m;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 247) uint32_t w, r[BCH_ECC_MAX_WORDS];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 248) const size_t r_bytes = BCH_ECC_WORDS(bch) * sizeof(*r);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 249) const uint32_t * const tab0 = bch->mod8_tab;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 250) const uint32_t * const tab1 = tab0 + 256*(l+1);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 251) const uint32_t * const tab2 = tab1 + 256*(l+1);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 252) const uint32_t * const tab3 = tab2 + 256*(l+1);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 253) const uint32_t *pdata, *p0, *p1, *p2, *p3;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 254)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 255) if (WARN_ON(r_bytes > sizeof(r)))
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 256) return;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 257)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 258) if (ecc) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 259) /* load ecc parity bytes into internal 32-bit buffer */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 260) load_ecc8(bch, bch->ecc_buf, ecc);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 261) } else {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 262) memset(bch->ecc_buf, 0, r_bytes);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 263) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 264)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 265) /* process first unaligned data bytes */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 266) m = ((unsigned long)data) & 3;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 267) if (m) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 268) mlen = (len < (4-m)) ? len : 4-m;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 269) bch_encode_unaligned(bch, data, mlen, bch->ecc_buf);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 270) data += mlen;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 271) len -= mlen;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 272) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 273)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 274) /* process 32-bit aligned data words */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 275) pdata = (uint32_t *)data;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 276) mlen = len/4;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 277) data += 4*mlen;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 278) len -= 4*mlen;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 279) memcpy(r, bch->ecc_buf, r_bytes);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 280)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 281) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 282) * split each 32-bit word into 4 polynomials of weight 8 as follows:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 283) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 284) * 31 ...24 23 ...16 15 ... 8 7 ... 0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 285) * xxxxxxxx yyyyyyyy zzzzzzzz tttttttt
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 286) * tttttttt mod g = r0 (precomputed)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 287) * zzzzzzzz 00000000 mod g = r1 (precomputed)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 288) * yyyyyyyy 00000000 00000000 mod g = r2 (precomputed)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 289) * xxxxxxxx 00000000 00000000 00000000 mod g = r3 (precomputed)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 290) * xxxxxxxx yyyyyyyy zzzzzzzz tttttttt mod g = r0^r1^r2^r3
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 291) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 292) while (mlen--) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 293) /* input data is read in big-endian format */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 294) w = cpu_to_be32(*pdata++);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 295) if (bch->swap_bits)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 296) w = (u32)swap_bits(bch, w) |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 297) ((u32)swap_bits(bch, w >> 8) << 8) |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 298) ((u32)swap_bits(bch, w >> 16) << 16) |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 299) ((u32)swap_bits(bch, w >> 24) << 24);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 300) w ^= r[0];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 301) p0 = tab0 + (l+1)*((w >> 0) & 0xff);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 302) p1 = tab1 + (l+1)*((w >> 8) & 0xff);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 303) p2 = tab2 + (l+1)*((w >> 16) & 0xff);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 304) p3 = tab3 + (l+1)*((w >> 24) & 0xff);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 305)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 306) for (i = 0; i < l; i++)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 307) r[i] = r[i+1]^p0[i]^p1[i]^p2[i]^p3[i];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 308)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 309) r[l] = p0[l]^p1[l]^p2[l]^p3[l];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 310) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 311) memcpy(bch->ecc_buf, r, r_bytes);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 312)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 313) /* process last unaligned bytes */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 314) if (len)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 315) bch_encode_unaligned(bch, data, len, bch->ecc_buf);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 316)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 317) /* store ecc parity bytes into original parity buffer */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 318) if (ecc)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 319) store_ecc8(bch, ecc, bch->ecc_buf);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 320) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 321) EXPORT_SYMBOL_GPL(bch_encode);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 322)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 323) static inline int modulo(struct bch_control *bch, unsigned int v)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 324) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 325) const unsigned int n = GF_N(bch);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 326) while (v >= n) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 327) v -= n;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 328) v = (v & n) + (v >> GF_M(bch));
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 329) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 330) return v;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 331) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 332)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 333) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 334) * shorter and faster modulo function, only works when v < 2N.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 335) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 336) static inline int mod_s(struct bch_control *bch, unsigned int v)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 337) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 338) const unsigned int n = GF_N(bch);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 339) return (v < n) ? v : v-n;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 340) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 341)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 342) static inline int deg(unsigned int poly)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 343) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 344) /* polynomial degree is the most-significant bit index */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 345) return fls(poly)-1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 346) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 347)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 348) static inline int parity(unsigned int x)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 349) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 350) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 351) * public domain code snippet, lifted from
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 352) * http://www-graphics.stanford.edu/~seander/bithacks.html
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 353) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 354) x ^= x >> 1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 355) x ^= x >> 2;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 356) x = (x & 0x11111111U) * 0x11111111U;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 357) return (x >> 28) & 1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 358) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 359)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 360) /* Galois field basic operations: multiply, divide, inverse, etc. */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 361)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 362) static inline unsigned int gf_mul(struct bch_control *bch, unsigned int a,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 363) unsigned int b)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 364) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 365) return (a && b) ? bch->a_pow_tab[mod_s(bch, bch->a_log_tab[a]+
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 366) bch->a_log_tab[b])] : 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 367) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 368)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 369) static inline unsigned int gf_sqr(struct bch_control *bch, unsigned int a)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 370) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 371) return a ? bch->a_pow_tab[mod_s(bch, 2*bch->a_log_tab[a])] : 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 372) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 373)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 374) static inline unsigned int gf_div(struct bch_control *bch, unsigned int a,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 375) unsigned int b)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 376) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 377) return a ? bch->a_pow_tab[mod_s(bch, bch->a_log_tab[a]+
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 378) GF_N(bch)-bch->a_log_tab[b])] : 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 379) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 380)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 381) static inline unsigned int gf_inv(struct bch_control *bch, unsigned int a)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 382) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 383) return bch->a_pow_tab[GF_N(bch)-bch->a_log_tab[a]];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 384) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 385)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 386) static inline unsigned int a_pow(struct bch_control *bch, int i)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 387) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 388) return bch->a_pow_tab[modulo(bch, i)];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 389) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 390)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 391) static inline int a_log(struct bch_control *bch, unsigned int x)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 392) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 393) return bch->a_log_tab[x];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 394) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 395)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 396) static inline int a_ilog(struct bch_control *bch, unsigned int x)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 397) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 398) return mod_s(bch, GF_N(bch)-bch->a_log_tab[x]);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 399) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 400)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 401) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 402) * compute 2t syndromes of ecc polynomial, i.e. ecc(a^j) for j=1..2t
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 403) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 404) static void compute_syndromes(struct bch_control *bch, uint32_t *ecc,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 405) unsigned int *syn)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 406) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 407) int i, j, s;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 408) unsigned int m;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 409) uint32_t poly;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 410) const int t = GF_T(bch);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 411)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 412) s = bch->ecc_bits;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 413)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 414) /* make sure extra bits in last ecc word are cleared */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 415) m = ((unsigned int)s) & 31;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 416) if (m)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 417) ecc[s/32] &= ~((1u << (32-m))-1);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 418) memset(syn, 0, 2*t*sizeof(*syn));
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 419)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 420) /* compute v(a^j) for j=1 .. 2t-1 */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 421) do {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 422) poly = *ecc++;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 423) s -= 32;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 424) while (poly) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 425) i = deg(poly);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 426) for (j = 0; j < 2*t; j += 2)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 427) syn[j] ^= a_pow(bch, (j+1)*(i+s));
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 428)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 429) poly ^= (1 << i);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 430) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 431) } while (s > 0);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 432)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 433) /* v(a^(2j)) = v(a^j)^2 */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 434) for (j = 0; j < t; j++)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 435) syn[2*j+1] = gf_sqr(bch, syn[j]);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 436) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 437)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 438) static void gf_poly_copy(struct gf_poly *dst, struct gf_poly *src)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 439) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 440) memcpy(dst, src, GF_POLY_SZ(src->deg));
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 441) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 442)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 443) static int compute_error_locator_polynomial(struct bch_control *bch,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 444) const unsigned int *syn)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 445) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 446) const unsigned int t = GF_T(bch);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 447) const unsigned int n = GF_N(bch);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 448) unsigned int i, j, tmp, l, pd = 1, d = syn[0];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 449) struct gf_poly *elp = bch->elp;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 450) struct gf_poly *pelp = bch->poly_2t[0];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 451) struct gf_poly *elp_copy = bch->poly_2t[1];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 452) int k, pp = -1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 453)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 454) memset(pelp, 0, GF_POLY_SZ(2*t));
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 455) memset(elp, 0, GF_POLY_SZ(2*t));
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 456)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 457) pelp->deg = 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 458) pelp->c[0] = 1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 459) elp->deg = 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 460) elp->c[0] = 1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 461)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 462) /* use simplified binary Berlekamp-Massey algorithm */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 463) for (i = 0; (i < t) && (elp->deg <= t); i++) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 464) if (d) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 465) k = 2*i-pp;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 466) gf_poly_copy(elp_copy, elp);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 467) /* e[i+1](X) = e[i](X)+di*dp^-1*X^2(i-p)*e[p](X) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 468) tmp = a_log(bch, d)+n-a_log(bch, pd);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 469) for (j = 0; j <= pelp->deg; j++) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 470) if (pelp->c[j]) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 471) l = a_log(bch, pelp->c[j]);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 472) elp->c[j+k] ^= a_pow(bch, tmp+l);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 473) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 474) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 475) /* compute l[i+1] = max(l[i]->c[l[p]+2*(i-p]) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 476) tmp = pelp->deg+k;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 477) if (tmp > elp->deg) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 478) elp->deg = tmp;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 479) gf_poly_copy(pelp, elp_copy);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 480) pd = d;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 481) pp = 2*i;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 482) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 483) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 484) /* di+1 = S(2i+3)+elp[i+1].1*S(2i+2)+...+elp[i+1].lS(2i+3-l) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 485) if (i < t-1) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 486) d = syn[2*i+2];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 487) for (j = 1; j <= elp->deg; j++)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 488) d ^= gf_mul(bch, elp->c[j], syn[2*i+2-j]);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 489) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 490) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 491) dbg("elp=%s\n", gf_poly_str(elp));
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 492) return (elp->deg > t) ? -1 : (int)elp->deg;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 493) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 494)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 495) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 496) * solve a m x m linear system in GF(2) with an expected number of solutions,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 497) * and return the number of found solutions
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 498) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 499) static int solve_linear_system(struct bch_control *bch, unsigned int *rows,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 500) unsigned int *sol, int nsol)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 501) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 502) const int m = GF_M(bch);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 503) unsigned int tmp, mask;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 504) int rem, c, r, p, k, param[BCH_MAX_M];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 505)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 506) k = 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 507) mask = 1 << m;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 508)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 509) /* Gaussian elimination */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 510) for (c = 0; c < m; c++) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 511) rem = 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 512) p = c-k;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 513) /* find suitable row for elimination */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 514) for (r = p; r < m; r++) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 515) if (rows[r] & mask) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 516) if (r != p) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 517) tmp = rows[r];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 518) rows[r] = rows[p];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 519) rows[p] = tmp;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 520) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 521) rem = r+1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 522) break;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 523) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 524) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 525) if (rem) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 526) /* perform elimination on remaining rows */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 527) tmp = rows[p];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 528) for (r = rem; r < m; r++) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 529) if (rows[r] & mask)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 530) rows[r] ^= tmp;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 531) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 532) } else {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 533) /* elimination not needed, store defective row index */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 534) param[k++] = c;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 535) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 536) mask >>= 1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 537) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 538) /* rewrite system, inserting fake parameter rows */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 539) if (k > 0) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 540) p = k;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 541) for (r = m-1; r >= 0; r--) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 542) if ((r > m-1-k) && rows[r])
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 543) /* system has no solution */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 544) return 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 545)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 546) rows[r] = (p && (r == param[p-1])) ?
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 547) p--, 1u << (m-r) : rows[r-p];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 548) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 549) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 550)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 551) if (nsol != (1 << k))
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 552) /* unexpected number of solutions */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 553) return 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 554)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 555) for (p = 0; p < nsol; p++) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 556) /* set parameters for p-th solution */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 557) for (c = 0; c < k; c++)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 558) rows[param[c]] = (rows[param[c]] & ~1)|((p >> c) & 1);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 559)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 560) /* compute unique solution */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 561) tmp = 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 562) for (r = m-1; r >= 0; r--) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 563) mask = rows[r] & (tmp|1);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 564) tmp |= parity(mask) << (m-r);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 565) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 566) sol[p] = tmp >> 1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 567) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 568) return nsol;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 569) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 570)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 571) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 572) * this function builds and solves a linear system for finding roots of a degree
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 573) * 4 affine monic polynomial X^4+aX^2+bX+c over GF(2^m).
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 574) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 575) static int find_affine4_roots(struct bch_control *bch, unsigned int a,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 576) unsigned int b, unsigned int c,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 577) unsigned int *roots)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 578) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 579) int i, j, k;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 580) const int m = GF_M(bch);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 581) unsigned int mask = 0xff, t, rows[16] = {0,};
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 582)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 583) j = a_log(bch, b);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 584) k = a_log(bch, a);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 585) rows[0] = c;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 586)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 587) /* buid linear system to solve X^4+aX^2+bX+c = 0 */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 588) for (i = 0; i < m; i++) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 589) rows[i+1] = bch->a_pow_tab[4*i]^
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 590) (a ? bch->a_pow_tab[mod_s(bch, k)] : 0)^
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 591) (b ? bch->a_pow_tab[mod_s(bch, j)] : 0);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 592) j++;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 593) k += 2;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 594) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 595) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 596) * transpose 16x16 matrix before passing it to linear solver
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 597) * warning: this code assumes m < 16
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 598) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 599) for (j = 8; j != 0; j >>= 1, mask ^= (mask << j)) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 600) for (k = 0; k < 16; k = (k+j+1) & ~j) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 601) t = ((rows[k] >> j)^rows[k+j]) & mask;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 602) rows[k] ^= (t << j);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 603) rows[k+j] ^= t;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 604) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 605) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 606) return solve_linear_system(bch, rows, roots, 4);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 607) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 608)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 609) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 610) * compute root r of a degree 1 polynomial over GF(2^m) (returned as log(1/r))
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 611) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 612) static int find_poly_deg1_roots(struct bch_control *bch, struct gf_poly *poly,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 613) unsigned int *roots)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 614) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 615) int n = 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 616)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 617) if (poly->c[0])
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 618) /* poly[X] = bX+c with c!=0, root=c/b */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 619) roots[n++] = mod_s(bch, GF_N(bch)-bch->a_log_tab[poly->c[0]]+
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 620) bch->a_log_tab[poly->c[1]]);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 621) return n;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 622) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 623)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 624) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 625) * compute roots of a degree 2 polynomial over GF(2^m)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 626) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 627) static int find_poly_deg2_roots(struct bch_control *bch, struct gf_poly *poly,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 628) unsigned int *roots)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 629) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 630) int n = 0, i, l0, l1, l2;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 631) unsigned int u, v, r;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 632)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 633) if (poly->c[0] && poly->c[1]) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 634)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 635) l0 = bch->a_log_tab[poly->c[0]];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 636) l1 = bch->a_log_tab[poly->c[1]];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 637) l2 = bch->a_log_tab[poly->c[2]];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 638)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 639) /* using z=a/bX, transform aX^2+bX+c into z^2+z+u (u=ac/b^2) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 640) u = a_pow(bch, l0+l2+2*(GF_N(bch)-l1));
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 641) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 642) * let u = sum(li.a^i) i=0..m-1; then compute r = sum(li.xi):
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 643) * r^2+r = sum(li.(xi^2+xi)) = sum(li.(a^i+Tr(a^i).a^k)) =
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 644) * u + sum(li.Tr(a^i).a^k) = u+a^k.Tr(sum(li.a^i)) = u+a^k.Tr(u)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 645) * i.e. r and r+1 are roots iff Tr(u)=0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 646) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 647) r = 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 648) v = u;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 649) while (v) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 650) i = deg(v);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 651) r ^= bch->xi_tab[i];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 652) v ^= (1 << i);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 653) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 654) /* verify root */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 655) if ((gf_sqr(bch, r)^r) == u) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 656) /* reverse z=a/bX transformation and compute log(1/r) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 657) roots[n++] = modulo(bch, 2*GF_N(bch)-l1-
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 658) bch->a_log_tab[r]+l2);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 659) roots[n++] = modulo(bch, 2*GF_N(bch)-l1-
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 660) bch->a_log_tab[r^1]+l2);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 661) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 662) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 663) return n;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 664) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 665)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 666) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 667) * compute roots of a degree 3 polynomial over GF(2^m)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 668) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 669) static int find_poly_deg3_roots(struct bch_control *bch, struct gf_poly *poly,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 670) unsigned int *roots)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 671) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 672) int i, n = 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 673) unsigned int a, b, c, a2, b2, c2, e3, tmp[4];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 674)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 675) if (poly->c[0]) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 676) /* transform polynomial into monic X^3 + a2X^2 + b2X + c2 */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 677) e3 = poly->c[3];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 678) c2 = gf_div(bch, poly->c[0], e3);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 679) b2 = gf_div(bch, poly->c[1], e3);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 680) a2 = gf_div(bch, poly->c[2], e3);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 681)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 682) /* (X+a2)(X^3+a2X^2+b2X+c2) = X^4+aX^2+bX+c (affine) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 683) c = gf_mul(bch, a2, c2); /* c = a2c2 */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 684) b = gf_mul(bch, a2, b2)^c2; /* b = a2b2 + c2 */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 685) a = gf_sqr(bch, a2)^b2; /* a = a2^2 + b2 */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 686)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 687) /* find the 4 roots of this affine polynomial */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 688) if (find_affine4_roots(bch, a, b, c, tmp) == 4) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 689) /* remove a2 from final list of roots */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 690) for (i = 0; i < 4; i++) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 691) if (tmp[i] != a2)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 692) roots[n++] = a_ilog(bch, tmp[i]);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 693) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 694) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 695) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 696) return n;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 697) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 698)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 699) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 700) * compute roots of a degree 4 polynomial over GF(2^m)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 701) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 702) static int find_poly_deg4_roots(struct bch_control *bch, struct gf_poly *poly,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 703) unsigned int *roots)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 704) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 705) int i, l, n = 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 706) unsigned int a, b, c, d, e = 0, f, a2, b2, c2, e4;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 707)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 708) if (poly->c[0] == 0)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 709) return 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 710)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 711) /* transform polynomial into monic X^4 + aX^3 + bX^2 + cX + d */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 712) e4 = poly->c[4];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 713) d = gf_div(bch, poly->c[0], e4);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 714) c = gf_div(bch, poly->c[1], e4);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 715) b = gf_div(bch, poly->c[2], e4);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 716) a = gf_div(bch, poly->c[3], e4);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 717)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 718) /* use Y=1/X transformation to get an affine polynomial */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 719) if (a) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 720) /* first, eliminate cX by using z=X+e with ae^2+c=0 */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 721) if (c) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 722) /* compute e such that e^2 = c/a */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 723) f = gf_div(bch, c, a);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 724) l = a_log(bch, f);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 725) l += (l & 1) ? GF_N(bch) : 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 726) e = a_pow(bch, l/2);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 727) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 728) * use transformation z=X+e:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 729) * z^4+e^4 + a(z^3+ez^2+e^2z+e^3) + b(z^2+e^2) +cz+ce+d
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 730) * z^4 + az^3 + (ae+b)z^2 + (ae^2+c)z+e^4+be^2+ae^3+ce+d
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 731) * z^4 + az^3 + (ae+b)z^2 + e^4+be^2+d
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 732) * z^4 + az^3 + b'z^2 + d'
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 733) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 734) d = a_pow(bch, 2*l)^gf_mul(bch, b, f)^d;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 735) b = gf_mul(bch, a, e)^b;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 736) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 737) /* now, use Y=1/X to get Y^4 + b/dY^2 + a/dY + 1/d */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 738) if (d == 0)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 739) /* assume all roots have multiplicity 1 */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 740) return 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 741)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 742) c2 = gf_inv(bch, d);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 743) b2 = gf_div(bch, a, d);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 744) a2 = gf_div(bch, b, d);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 745) } else {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 746) /* polynomial is already affine */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 747) c2 = d;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 748) b2 = c;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 749) a2 = b;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 750) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 751) /* find the 4 roots of this affine polynomial */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 752) if (find_affine4_roots(bch, a2, b2, c2, roots) == 4) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 753) for (i = 0; i < 4; i++) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 754) /* post-process roots (reverse transformations) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 755) f = a ? gf_inv(bch, roots[i]) : roots[i];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 756) roots[i] = a_ilog(bch, f^e);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 757) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 758) n = 4;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 759) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 760) return n;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 761) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 762)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 763) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 764) * build monic, log-based representation of a polynomial
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 765) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 766) static void gf_poly_logrep(struct bch_control *bch,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 767) const struct gf_poly *a, int *rep)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 768) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 769) int i, d = a->deg, l = GF_N(bch)-a_log(bch, a->c[a->deg]);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 770)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 771) /* represent 0 values with -1; warning, rep[d] is not set to 1 */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 772) for (i = 0; i < d; i++)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 773) rep[i] = a->c[i] ? mod_s(bch, a_log(bch, a->c[i])+l) : -1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 774) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 775)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 776) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 777) * compute polynomial Euclidean division remainder in GF(2^m)[X]
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 778) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 779) static void gf_poly_mod(struct bch_control *bch, struct gf_poly *a,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 780) const struct gf_poly *b, int *rep)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 781) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 782) int la, p, m;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 783) unsigned int i, j, *c = a->c;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 784) const unsigned int d = b->deg;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 785)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 786) if (a->deg < d)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 787) return;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 788)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 789) /* reuse or compute log representation of denominator */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 790) if (!rep) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 791) rep = bch->cache;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 792) gf_poly_logrep(bch, b, rep);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 793) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 794)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 795) for (j = a->deg; j >= d; j--) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 796) if (c[j]) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 797) la = a_log(bch, c[j]);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 798) p = j-d;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 799) for (i = 0; i < d; i++, p++) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 800) m = rep[i];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 801) if (m >= 0)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 802) c[p] ^= bch->a_pow_tab[mod_s(bch,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 803) m+la)];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 804) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 805) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 806) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 807) a->deg = d-1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 808) while (!c[a->deg] && a->deg)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 809) a->deg--;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 810) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 811)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 812) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 813) * compute polynomial Euclidean division quotient in GF(2^m)[X]
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 814) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 815) static void gf_poly_div(struct bch_control *bch, struct gf_poly *a,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 816) const struct gf_poly *b, struct gf_poly *q)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 817) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 818) if (a->deg >= b->deg) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 819) q->deg = a->deg-b->deg;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 820) /* compute a mod b (modifies a) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 821) gf_poly_mod(bch, a, b, NULL);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 822) /* quotient is stored in upper part of polynomial a */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 823) memcpy(q->c, &a->c[b->deg], (1+q->deg)*sizeof(unsigned int));
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 824) } else {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 825) q->deg = 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 826) q->c[0] = 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 827) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 828) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 829)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 830) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 831) * compute polynomial GCD (Greatest Common Divisor) in GF(2^m)[X]
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 832) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 833) static struct gf_poly *gf_poly_gcd(struct bch_control *bch, struct gf_poly *a,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 834) struct gf_poly *b)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 835) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 836) struct gf_poly *tmp;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 837)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 838) dbg("gcd(%s,%s)=", gf_poly_str(a), gf_poly_str(b));
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 839)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 840) if (a->deg < b->deg) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 841) tmp = b;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 842) b = a;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 843) a = tmp;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 844) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 845)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 846) while (b->deg > 0) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 847) gf_poly_mod(bch, a, b, NULL);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 848) tmp = b;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 849) b = a;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 850) a = tmp;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 851) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 852)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 853) dbg("%s\n", gf_poly_str(a));
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 854)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 855) return a;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 856) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 857)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 858) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 859) * Given a polynomial f and an integer k, compute Tr(a^kX) mod f
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 860) * This is used in Berlekamp Trace algorithm for splitting polynomials
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 861) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 862) static void compute_trace_bk_mod(struct bch_control *bch, int k,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 863) const struct gf_poly *f, struct gf_poly *z,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 864) struct gf_poly *out)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 865) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 866) const int m = GF_M(bch);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 867) int i, j;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 868)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 869) /* z contains z^2j mod f */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 870) z->deg = 1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 871) z->c[0] = 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 872) z->c[1] = bch->a_pow_tab[k];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 873)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 874) out->deg = 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 875) memset(out, 0, GF_POLY_SZ(f->deg));
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 876)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 877) /* compute f log representation only once */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 878) gf_poly_logrep(bch, f, bch->cache);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 879)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 880) for (i = 0; i < m; i++) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 881) /* add a^(k*2^i)(z^(2^i) mod f) and compute (z^(2^i) mod f)^2 */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 882) for (j = z->deg; j >= 0; j--) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 883) out->c[j] ^= z->c[j];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 884) z->c[2*j] = gf_sqr(bch, z->c[j]);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 885) z->c[2*j+1] = 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 886) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 887) if (z->deg > out->deg)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 888) out->deg = z->deg;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 889)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 890) if (i < m-1) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 891) z->deg *= 2;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 892) /* z^(2(i+1)) mod f = (z^(2^i) mod f)^2 mod f */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 893) gf_poly_mod(bch, z, f, bch->cache);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 894) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 895) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 896) while (!out->c[out->deg] && out->deg)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 897) out->deg--;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 898)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 899) dbg("Tr(a^%d.X) mod f = %s\n", k, gf_poly_str(out));
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 900) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 901)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 902) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 903) * factor a polynomial using Berlekamp Trace algorithm (BTA)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 904) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 905) static void factor_polynomial(struct bch_control *bch, int k, struct gf_poly *f,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 906) struct gf_poly **g, struct gf_poly **h)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 907) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 908) struct gf_poly *f2 = bch->poly_2t[0];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 909) struct gf_poly *q = bch->poly_2t[1];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 910) struct gf_poly *tk = bch->poly_2t[2];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 911) struct gf_poly *z = bch->poly_2t[3];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 912) struct gf_poly *gcd;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 913)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 914) dbg("factoring %s...\n", gf_poly_str(f));
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 915)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 916) *g = f;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 917) *h = NULL;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 918)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 919) /* tk = Tr(a^k.X) mod f */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 920) compute_trace_bk_mod(bch, k, f, z, tk);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 921)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 922) if (tk->deg > 0) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 923) /* compute g = gcd(f, tk) (destructive operation) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 924) gf_poly_copy(f2, f);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 925) gcd = gf_poly_gcd(bch, f2, tk);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 926) if (gcd->deg < f->deg) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 927) /* compute h=f/gcd(f,tk); this will modify f and q */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 928) gf_poly_div(bch, f, gcd, q);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 929) /* store g and h in-place (clobbering f) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 930) *h = &((struct gf_poly_deg1 *)f)[gcd->deg].poly;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 931) gf_poly_copy(*g, gcd);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 932) gf_poly_copy(*h, q);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 933) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 934) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 935) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 936)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 937) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 938) * find roots of a polynomial, using BTZ algorithm; see the beginning of this
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 939) * file for details
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 940) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 941) static int find_poly_roots(struct bch_control *bch, unsigned int k,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 942) struct gf_poly *poly, unsigned int *roots)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 943) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 944) int cnt;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 945) struct gf_poly *f1, *f2;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 946)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 947) switch (poly->deg) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 948) /* handle low degree polynomials with ad hoc techniques */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 949) case 1:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 950) cnt = find_poly_deg1_roots(bch, poly, roots);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 951) break;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 952) case 2:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 953) cnt = find_poly_deg2_roots(bch, poly, roots);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 954) break;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 955) case 3:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 956) cnt = find_poly_deg3_roots(bch, poly, roots);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 957) break;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 958) case 4:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 959) cnt = find_poly_deg4_roots(bch, poly, roots);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 960) break;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 961) default:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 962) /* factor polynomial using Berlekamp Trace Algorithm (BTA) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 963) cnt = 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 964) if (poly->deg && (k <= GF_M(bch))) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 965) factor_polynomial(bch, k, poly, &f1, &f2);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 966) if (f1)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 967) cnt += find_poly_roots(bch, k+1, f1, roots);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 968) if (f2)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 969) cnt += find_poly_roots(bch, k+1, f2, roots+cnt);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 970) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 971) break;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 972) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 973) return cnt;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 974) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 975)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 976) #if defined(USE_CHIEN_SEARCH)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 977) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 978) * exhaustive root search (Chien) implementation - not used, included only for
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 979) * reference/comparison tests
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 980) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 981) static int chien_search(struct bch_control *bch, unsigned int len,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 982) struct gf_poly *p, unsigned int *roots)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 983) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 984) int m;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 985) unsigned int i, j, syn, syn0, count = 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 986) const unsigned int k = 8*len+bch->ecc_bits;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 987)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 988) /* use a log-based representation of polynomial */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 989) gf_poly_logrep(bch, p, bch->cache);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 990) bch->cache[p->deg] = 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 991) syn0 = gf_div(bch, p->c[0], p->c[p->deg]);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 992)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 993) for (i = GF_N(bch)-k+1; i <= GF_N(bch); i++) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 994) /* compute elp(a^i) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 995) for (j = 1, syn = syn0; j <= p->deg; j++) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 996) m = bch->cache[j];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 997) if (m >= 0)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 998) syn ^= a_pow(bch, m+j*i);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 999) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1000) if (syn == 0) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1001) roots[count++] = GF_N(bch)-i;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1002) if (count == p->deg)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1003) break;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1004) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1005) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1006) return (count == p->deg) ? count : 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1007) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1008) #define find_poly_roots(_p, _k, _elp, _loc) chien_search(_p, len, _elp, _loc)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1009) #endif /* USE_CHIEN_SEARCH */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1010)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1011) /**
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1012) * bch_decode - decode received codeword and find bit error locations
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1013) * @bch: BCH control structure
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1014) * @data: received data, ignored if @calc_ecc is provided
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1015) * @len: data length in bytes, must always be provided
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1016) * @recv_ecc: received ecc, if NULL then assume it was XORed in @calc_ecc
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1017) * @calc_ecc: calculated ecc, if NULL then calc_ecc is computed from @data
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1018) * @syn: hw computed syndrome data (if NULL, syndrome is calculated)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1019) * @errloc: output array of error locations
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1020) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1021) * Returns:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1022) * The number of errors found, or -EBADMSG if decoding failed, or -EINVAL if
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1023) * invalid parameters were provided
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1024) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1025) * Depending on the available hw BCH support and the need to compute @calc_ecc
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1026) * separately (using bch_encode()), this function should be called with one of
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1027) * the following parameter configurations -
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1028) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1029) * by providing @data and @recv_ecc only:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1030) * bch_decode(@bch, @data, @len, @recv_ecc, NULL, NULL, @errloc)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1031) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1032) * by providing @recv_ecc and @calc_ecc:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1033) * bch_decode(@bch, NULL, @len, @recv_ecc, @calc_ecc, NULL, @errloc)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1034) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1035) * by providing ecc = recv_ecc XOR calc_ecc:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1036) * bch_decode(@bch, NULL, @len, NULL, ecc, NULL, @errloc)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1037) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1038) * by providing syndrome results @syn:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1039) * bch_decode(@bch, NULL, @len, NULL, NULL, @syn, @errloc)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1040) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1041) * Once bch_decode() has successfully returned with a positive value, error
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1042) * locations returned in array @errloc should be interpreted as follows -
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1043) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1044) * if (errloc[n] >= 8*len), then n-th error is located in ecc (no need for
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1045) * data correction)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1046) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1047) * if (errloc[n] < 8*len), then n-th error is located in data and can be
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1048) * corrected with statement data[errloc[n]/8] ^= 1 << (errloc[n] % 8);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1049) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1050) * Note that this function does not perform any data correction by itself, it
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1051) * merely indicates error locations.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1052) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1053) int bch_decode(struct bch_control *bch, const uint8_t *data, unsigned int len,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1054) const uint8_t *recv_ecc, const uint8_t *calc_ecc,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1055) const unsigned int *syn, unsigned int *errloc)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1056) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1057) const unsigned int ecc_words = BCH_ECC_WORDS(bch);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1058) unsigned int nbits;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1059) int i, err, nroots;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1060) uint32_t sum;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1061)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1062) /* sanity check: make sure data length can be handled */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1063) if (8*len > (bch->n-bch->ecc_bits))
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1064) return -EINVAL;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1065)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1066) /* if caller does not provide syndromes, compute them */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1067) if (!syn) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1068) if (!calc_ecc) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1069) /* compute received data ecc into an internal buffer */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1070) if (!data || !recv_ecc)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1071) return -EINVAL;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1072) bch_encode(bch, data, len, NULL);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1073) } else {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1074) /* load provided calculated ecc */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1075) load_ecc8(bch, bch->ecc_buf, calc_ecc);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1076) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1077) /* load received ecc or assume it was XORed in calc_ecc */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1078) if (recv_ecc) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1079) load_ecc8(bch, bch->ecc_buf2, recv_ecc);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1080) /* XOR received and calculated ecc */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1081) for (i = 0, sum = 0; i < (int)ecc_words; i++) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1082) bch->ecc_buf[i] ^= bch->ecc_buf2[i];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1083) sum |= bch->ecc_buf[i];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1084) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1085) if (!sum)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1086) /* no error found */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1087) return 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1088) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1089) compute_syndromes(bch, bch->ecc_buf, bch->syn);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1090) syn = bch->syn;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1091) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1092)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1093) err = compute_error_locator_polynomial(bch, syn);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1094) if (err > 0) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1095) nroots = find_poly_roots(bch, 1, bch->elp, errloc);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1096) if (err != nroots)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1097) err = -1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1098) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1099) if (err > 0) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1100) /* post-process raw error locations for easier correction */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1101) nbits = (len*8)+bch->ecc_bits;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1102) for (i = 0; i < err; i++) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1103) if (errloc[i] >= nbits) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1104) err = -1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1105) break;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1106) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1107) errloc[i] = nbits-1-errloc[i];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1108) if (!bch->swap_bits)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1109) errloc[i] = (errloc[i] & ~7) |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1110) (7-(errloc[i] & 7));
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1111) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1112) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1113) return (err >= 0) ? err : -EBADMSG;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1114) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1115) EXPORT_SYMBOL_GPL(bch_decode);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1116)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1117) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1118) * generate Galois field lookup tables
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1119) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1120) static int build_gf_tables(struct bch_control *bch, unsigned int poly)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1121) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1122) unsigned int i, x = 1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1123) const unsigned int k = 1 << deg(poly);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1124)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1125) /* primitive polynomial must be of degree m */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1126) if (k != (1u << GF_M(bch)))
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1127) return -1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1128)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1129) for (i = 0; i < GF_N(bch); i++) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1130) bch->a_pow_tab[i] = x;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1131) bch->a_log_tab[x] = i;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1132) if (i && (x == 1))
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1133) /* polynomial is not primitive (a^i=1 with 0<i<2^m-1) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1134) return -1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1135) x <<= 1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1136) if (x & k)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1137) x ^= poly;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1138) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1139) bch->a_pow_tab[GF_N(bch)] = 1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1140) bch->a_log_tab[0] = 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1141)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1142) return 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1143) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1144)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1145) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1146) * compute generator polynomial remainder tables for fast encoding
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1147) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1148) static void build_mod8_tables(struct bch_control *bch, const uint32_t *g)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1149) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1150) int i, j, b, d;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1151) uint32_t data, hi, lo, *tab;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1152) const int l = BCH_ECC_WORDS(bch);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1153) const int plen = DIV_ROUND_UP(bch->ecc_bits+1, 32);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1154) const int ecclen = DIV_ROUND_UP(bch->ecc_bits, 32);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1155)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1156) memset(bch->mod8_tab, 0, 4*256*l*sizeof(*bch->mod8_tab));
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1157)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1158) for (i = 0; i < 256; i++) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1159) /* p(X)=i is a small polynomial of weight <= 8 */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1160) for (b = 0; b < 4; b++) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1161) /* we want to compute (p(X).X^(8*b+deg(g))) mod g(X) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1162) tab = bch->mod8_tab + (b*256+i)*l;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1163) data = i << (8*b);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1164) while (data) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1165) d = deg(data);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1166) /* subtract X^d.g(X) from p(X).X^(8*b+deg(g)) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1167) data ^= g[0] >> (31-d);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1168) for (j = 0; j < ecclen; j++) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1169) hi = (d < 31) ? g[j] << (d+1) : 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1170) lo = (j+1 < plen) ?
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1171) g[j+1] >> (31-d) : 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1172) tab[j] ^= hi|lo;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1173) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1174) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1175) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1176) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1177) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1178)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1179) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1180) * build a base for factoring degree 2 polynomials
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1181) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1182) static int build_deg2_base(struct bch_control *bch)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1183) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1184) const int m = GF_M(bch);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1185) int i, j, r;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1186) unsigned int sum, x, y, remaining, ak = 0, xi[BCH_MAX_M];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1187)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1188) /* find k s.t. Tr(a^k) = 1 and 0 <= k < m */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1189) for (i = 0; i < m; i++) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1190) for (j = 0, sum = 0; j < m; j++)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1191) sum ^= a_pow(bch, i*(1 << j));
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1192)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1193) if (sum) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1194) ak = bch->a_pow_tab[i];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1195) break;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1196) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1197) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1198) /* find xi, i=0..m-1 such that xi^2+xi = a^i+Tr(a^i).a^k */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1199) remaining = m;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1200) memset(xi, 0, sizeof(xi));
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1201)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1202) for (x = 0; (x <= GF_N(bch)) && remaining; x++) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1203) y = gf_sqr(bch, x)^x;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1204) for (i = 0; i < 2; i++) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1205) r = a_log(bch, y);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1206) if (y && (r < m) && !xi[r]) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1207) bch->xi_tab[r] = x;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1208) xi[r] = 1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1209) remaining--;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1210) dbg("x%d = %x\n", r, x);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1211) break;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1212) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1213) y ^= ak;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1214) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1215) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1216) /* should not happen but check anyway */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1217) return remaining ? -1 : 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1218) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1219)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1220) static void *bch_alloc(size_t size, int *err)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1221) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1222) void *ptr;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1223)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1224) ptr = kmalloc(size, GFP_KERNEL);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1225) if (ptr == NULL)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1226) *err = 1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1227) return ptr;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1228) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1229)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1230) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1231) * compute generator polynomial for given (m,t) parameters.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1232) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1233) static uint32_t *compute_generator_polynomial(struct bch_control *bch)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1234) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1235) const unsigned int m = GF_M(bch);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1236) const unsigned int t = GF_T(bch);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1237) int n, err = 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1238) unsigned int i, j, nbits, r, word, *roots;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1239) struct gf_poly *g;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1240) uint32_t *genpoly;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1241)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1242) g = bch_alloc(GF_POLY_SZ(m*t), &err);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1243) roots = bch_alloc((bch->n+1)*sizeof(*roots), &err);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1244) genpoly = bch_alloc(DIV_ROUND_UP(m*t+1, 32)*sizeof(*genpoly), &err);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1245)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1246) if (err) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1247) kfree(genpoly);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1248) genpoly = NULL;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1249) goto finish;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1250) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1251)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1252) /* enumerate all roots of g(X) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1253) memset(roots , 0, (bch->n+1)*sizeof(*roots));
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1254) for (i = 0; i < t; i++) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1255) for (j = 0, r = 2*i+1; j < m; j++) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1256) roots[r] = 1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1257) r = mod_s(bch, 2*r);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1258) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1259) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1260) /* build generator polynomial g(X) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1261) g->deg = 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1262) g->c[0] = 1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1263) for (i = 0; i < GF_N(bch); i++) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1264) if (roots[i]) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1265) /* multiply g(X) by (X+root) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1266) r = bch->a_pow_tab[i];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1267) g->c[g->deg+1] = 1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1268) for (j = g->deg; j > 0; j--)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1269) g->c[j] = gf_mul(bch, g->c[j], r)^g->c[j-1];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1270)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1271) g->c[0] = gf_mul(bch, g->c[0], r);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1272) g->deg++;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1273) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1274) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1275) /* store left-justified binary representation of g(X) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1276) n = g->deg+1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1277) i = 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1278)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1279) while (n > 0) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1280) nbits = (n > 32) ? 32 : n;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1281) for (j = 0, word = 0; j < nbits; j++) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1282) if (g->c[n-1-j])
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1283) word |= 1u << (31-j);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1284) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1285) genpoly[i++] = word;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1286) n -= nbits;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1287) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1288) bch->ecc_bits = g->deg;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1289)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1290) finish:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1291) kfree(g);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1292) kfree(roots);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1293)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1294) return genpoly;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1295) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1296)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1297) /**
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1298) * bch_init - initialize a BCH encoder/decoder
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1299) * @m: Galois field order, should be in the range 5-15
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1300) * @t: maximum error correction capability, in bits
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1301) * @prim_poly: user-provided primitive polynomial (or 0 to use default)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1302) * @swap_bits: swap bits within data and syndrome bytes
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1303) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1304) * Returns:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1305) * a newly allocated BCH control structure if successful, NULL otherwise
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1306) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1307) * This initialization can take some time, as lookup tables are built for fast
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1308) * encoding/decoding; make sure not to call this function from a time critical
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1309) * path. Usually, bch_init() should be called on module/driver init and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1310) * bch_free() should be called to release memory on exit.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1311) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1312) * You may provide your own primitive polynomial of degree @m in argument
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1313) * @prim_poly, or let bch_init() use its default polynomial.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1314) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1315) * Once bch_init() has successfully returned a pointer to a newly allocated
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1316) * BCH control structure, ecc length in bytes is given by member @ecc_bytes of
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1317) * the structure.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1318) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1319) struct bch_control *bch_init(int m, int t, unsigned int prim_poly,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1320) bool swap_bits)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1321) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1322) int err = 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1323) unsigned int i, words;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1324) uint32_t *genpoly;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1325) struct bch_control *bch = NULL;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1326)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1327) const int min_m = 5;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1328)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1329) /* default primitive polynomials */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1330) static const unsigned int prim_poly_tab[] = {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1331) 0x25, 0x43, 0x83, 0x11d, 0x211, 0x409, 0x805, 0x1053, 0x201b,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1332) 0x402b, 0x8003,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1333) };
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1334)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1335) #if defined(CONFIG_BCH_CONST_PARAMS)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1336) if ((m != (CONFIG_BCH_CONST_M)) || (t != (CONFIG_BCH_CONST_T))) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1337) printk(KERN_ERR "bch encoder/decoder was configured to support "
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1338) "parameters m=%d, t=%d only!\n",
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1339) CONFIG_BCH_CONST_M, CONFIG_BCH_CONST_T);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1340) goto fail;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1341) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1342) #endif
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1343) if ((m < min_m) || (m > BCH_MAX_M))
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1344) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1345) * values of m greater than 15 are not currently supported;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1346) * supporting m > 15 would require changing table base type
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1347) * (uint16_t) and a small patch in matrix transposition
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1348) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1349) goto fail;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1350)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1351) if (t > BCH_MAX_T)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1352) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1353) * we can support larger than 64 bits if necessary, at the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1354) * cost of higher stack usage.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1355) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1356) goto fail;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1357)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1358) /* sanity checks */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1359) if ((t < 1) || (m*t >= ((1 << m)-1)))
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1360) /* invalid t value */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1361) goto fail;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1362)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1363) /* select a primitive polynomial for generating GF(2^m) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1364) if (prim_poly == 0)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1365) prim_poly = prim_poly_tab[m-min_m];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1366)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1367) bch = kzalloc(sizeof(*bch), GFP_KERNEL);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1368) if (bch == NULL)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1369) goto fail;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1370)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1371) bch->m = m;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1372) bch->t = t;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1373) bch->n = (1 << m)-1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1374) words = DIV_ROUND_UP(m*t, 32);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1375) bch->ecc_bytes = DIV_ROUND_UP(m*t, 8);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1376) bch->a_pow_tab = bch_alloc((1+bch->n)*sizeof(*bch->a_pow_tab), &err);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1377) bch->a_log_tab = bch_alloc((1+bch->n)*sizeof(*bch->a_log_tab), &err);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1378) bch->mod8_tab = bch_alloc(words*1024*sizeof(*bch->mod8_tab), &err);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1379) bch->ecc_buf = bch_alloc(words*sizeof(*bch->ecc_buf), &err);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1380) bch->ecc_buf2 = bch_alloc(words*sizeof(*bch->ecc_buf2), &err);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1381) bch->xi_tab = bch_alloc(m*sizeof(*bch->xi_tab), &err);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1382) bch->syn = bch_alloc(2*t*sizeof(*bch->syn), &err);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1383) bch->cache = bch_alloc(2*t*sizeof(*bch->cache), &err);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1384) bch->elp = bch_alloc((t+1)*sizeof(struct gf_poly_deg1), &err);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1385) bch->swap_bits = swap_bits;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1386)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1387) for (i = 0; i < ARRAY_SIZE(bch->poly_2t); i++)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1388) bch->poly_2t[i] = bch_alloc(GF_POLY_SZ(2*t), &err);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1389)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1390) if (err)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1391) goto fail;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1392)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1393) err = build_gf_tables(bch, prim_poly);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1394) if (err)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1395) goto fail;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1396)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1397) /* use generator polynomial for computing encoding tables */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1398) genpoly = compute_generator_polynomial(bch);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1399) if (genpoly == NULL)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1400) goto fail;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1401)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1402) build_mod8_tables(bch, genpoly);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1403) kfree(genpoly);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1404)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1405) err = build_deg2_base(bch);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1406) if (err)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1407) goto fail;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1408)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1409) return bch;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1410)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1411) fail:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1412) bch_free(bch);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1413) return NULL;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1414) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1415) EXPORT_SYMBOL_GPL(bch_init);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1416)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1417) /**
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1418) * bch_free - free the BCH control structure
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1419) * @bch: BCH control structure to release
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1420) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1421) void bch_free(struct bch_control *bch)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1422) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1423) unsigned int i;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1424)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1425) if (bch) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1426) kfree(bch->a_pow_tab);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1427) kfree(bch->a_log_tab);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1428) kfree(bch->mod8_tab);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1429) kfree(bch->ecc_buf);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1430) kfree(bch->ecc_buf2);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1431) kfree(bch->xi_tab);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1432) kfree(bch->syn);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1433) kfree(bch->cache);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1434) kfree(bch->elp);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1435)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1436) for (i = 0; i < ARRAY_SIZE(bch->poly_2t); i++)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1437) kfree(bch->poly_2t[i]);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1438)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1439) kfree(bch);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1440) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1441) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1442) EXPORT_SYMBOL_GPL(bch_free);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1443)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1444) MODULE_LICENSE("GPL");
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1445) MODULE_AUTHOR("Ivan Djelic <ivan.djelic@parrot.com>");
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1446) MODULE_DESCRIPTION("Binary BCH encoder/decoder");
Orange Pi5 kernel
Deprecated Linux kernel 5.10.110 for OrangePi 5/5B/5+ boards
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