LXR linux/lib/ts

   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 * lib/ts_fsm.c    A naive finite state machine text search approach
   4 *
   5 * Authors:     Thomas Graf <tgraf@suug.ch>
   6 *
   7 * ==========================================================================
   8 *
   9 *   A finite state machine consists of n states (struct ts_fsm_token)
  10 *   representing the pattern as a finite automaton. The data is read
  11 *   sequentially on an octet basis. Every state token specifies the number
  12 *   of recurrences and the type of value accepted which can be either a
  13 *   specific character or ctype based set of characters. The available
  14 *   type of recurrences include 1, (0|1), [0 n], and [1 n].
  15 *
  16 *   The algorithm differs between strict/non-strict mode specifying
  17 *   whether the pattern has to start at the first octet. Strict mode
  18 *   is enabled by default and can be disabled by inserting
  19 *   TS_FSM_HEAD_IGNORE as the first token in the chain.
  20 *
  21 *   The runtime performance of the algorithm should be around O(n),
  22 *   however while in strict mode the average runtime can be better.
  23 */
  24
  25#include <linux/module.h>
  26#include <linux/types.h>
  27#include <linux/string.h>
  28#include <linux/ctype.h>
  29#include <linux/textsearch.h>
  30#include <linux/textsearch_fsm.h>
  31
  32struct ts_fsm
  33{
  34        unsigned int            ntokens;
  35        struct ts_fsm_token     tokens[];
  36};
  37
  38/* other values derived from ctype.h */
  39#define _A              0x100 /* ascii */
  40#define _W              0x200 /* wildcard */
  41
  42/* Map to _ctype flags and some magic numbers */
  43static const u16 token_map[TS_FSM_TYPE_MAX+1] = {
  44        [TS_FSM_SPECIFIC] = 0,
  45        [TS_FSM_WILDCARD] = _W,
  46        [TS_FSM_CNTRL]    = _C,
  47        [TS_FSM_LOWER]    = _L,
  48        [TS_FSM_UPPER]    = _U,
  49        [TS_FSM_PUNCT]    = _P,
  50        [TS_FSM_SPACE]    = _S,
  51        [TS_FSM_DIGIT]    = _D,
  52        [TS_FSM_XDIGIT]   = _D | _X,
  53        [TS_FSM_ALPHA]    = _U | _L,
  54        [TS_FSM_ALNUM]    = _U | _L | _D,
  55        [TS_FSM_PRINT]    = _P | _U | _L | _D | _SP,
  56        [TS_FSM_GRAPH]    = _P | _U | _L | _D,
  57        [TS_FSM_ASCII]    = _A,
  58};
  59
  60static const u16 token_lookup_tbl[256] = {
  61_W|_A|_C,      _W|_A|_C,     _W|_A|_C,     _W|_A|_C,            /*   0-  3 */
  62_W|_A|_C,      _W|_A|_C,     _W|_A|_C,     _W|_A|_C,            /*   4-  7 */
  63_W|_A|_C,      _W|_A|_C|_S,  _W|_A|_C|_S,  _W|_A|_C|_S,         /*   8- 11 */
  64_W|_A|_C|_S,   _W|_A|_C|_S,  _W|_A|_C,     _W|_A|_C,            /*  12- 15 */
  65_W|_A|_C,      _W|_A|_C,     _W|_A|_C,     _W|_A|_C,            /*  16- 19 */
  66_W|_A|_C,      _W|_A|_C,     _W|_A|_C,     _W|_A|_C,            /*  20- 23 */
  67_W|_A|_C,      _W|_A|_C,     _W|_A|_C,     _W|_A|_C,            /*  24- 27 */
  68_W|_A|_C,      _W|_A|_C,     _W|_A|_C,     _W|_A|_C,            /*  28- 31 */
  69_W|_A|_S|_SP,  _W|_A|_P,     _W|_A|_P,     _W|_A|_P,            /*  32- 35 */
  70_W|_A|_P,      _W|_A|_P,     _W|_A|_P,     _W|_A|_P,            /*  36- 39 */
  71_W|_A|_P,      _W|_A|_P,     _W|_A|_P,     _W|_A|_P,            /*  40- 43 */
  72_W|_A|_P,      _W|_A|_P,     _W|_A|_P,     _W|_A|_P,            /*  44- 47 */
  73_W|_A|_D,      _W|_A|_D,     _W|_A|_D,     _W|_A|_D,            /*  48- 51 */
  74_W|_A|_D,      _W|_A|_D,     _W|_A|_D,     _W|_A|_D,            /*  52- 55 */
  75_W|_A|_D,      _W|_A|_D,     _W|_A|_P,     _W|_A|_P,            /*  56- 59 */
  76_W|_A|_P,      _W|_A|_P,     _W|_A|_P,     _W|_A|_P,            /*  60- 63 */
  77_W|_A|_P,      _W|_A|_U|_X,  _W|_A|_U|_X,  _W|_A|_U|_X,         /*  64- 67 */
  78_W|_A|_U|_X,   _W|_A|_U|_X,  _W|_A|_U|_X,  _W|_A|_U,            /*  68- 71 */
  79_W|_A|_U,      _W|_A|_U,     _W|_A|_U,     _W|_A|_U,            /*  72- 75 */
  80_W|_A|_U,      _W|_A|_U,     _W|_A|_U,     _W|_A|_U,            /*  76- 79 */
  81_W|_A|_U,      _W|_A|_U,     _W|_A|_U,     _W|_A|_U,            /*  80- 83 */
  82_W|_A|_U,      _W|_A|_U,     _W|_A|_U,     _W|_A|_U,            /*  84- 87 */
  83_W|_A|_U,      _W|_A|_U,     _W|_A|_U,     _W|_A|_P,            /*  88- 91 */
  84_W|_A|_P,      _W|_A|_P,     _W|_A|_P,     _W|_A|_P,            /*  92- 95 */
  85_W|_A|_P,      _W|_A|_L|_X,  _W|_A|_L|_X,  _W|_A|_L|_X,         /*  96- 99 */
  86_W|_A|_L|_X,   _W|_A|_L|_X,  _W|_A|_L|_X,  _W|_A|_L,            /* 100-103 */
  87_W|_A|_L,      _W|_A|_L,     _W|_A|_L,     _W|_A|_L,            /* 104-107 */
  88_W|_A|_L,      _W|_A|_L,     _W|_A|_L,     _W|_A|_L,            /* 108-111 */
  89_W|_A|_L,      _W|_A|_L,     _W|_A|_L,     _W|_A|_L,            /* 112-115 */
  90_W|_A|_L,      _W|_A|_L,     _W|_A|_L,     _W|_A|_L,            /* 116-119 */
  91_W|_A|_L,      _W|_A|_L,     _W|_A|_L,     _W|_A|_P,            /* 120-123 */
  92_W|_A|_P,      _W|_A|_P,     _W|_A|_P,     _W|_A|_C,            /* 124-127 */
  93_W,            _W,           _W,           _W,                  /* 128-131 */
  94_W,            _W,           _W,           _W,                  /* 132-135 */
  95_W,            _W,           _W,           _W,                  /* 136-139 */
  96_W,            _W,           _W,           _W,                  /* 140-143 */
  97_W,            _W,           _W,           _W,                  /* 144-147 */
  98_W,            _W,           _W,           _W,                  /* 148-151 */
  99_W,            _W,           _W,           _W,                  /* 152-155 */
 100_W,            _W,           _W,           _W,                  /* 156-159 */
 101_W|_S|_SP,     _W|_P,        _W|_P,        _W|_P,               /* 160-163 */
 102_W|_P,         _W|_P,        _W|_P,        _W|_P,               /* 164-167 */
 103_W|_P,         _W|_P,        _W|_P,        _W|_P,               /* 168-171 */
 104_W|_P,         _W|_P,        _W|_P,        _W|_P,               /* 172-175 */
 105_W|_P,         _W|_P,        _W|_P,        _W|_P,               /* 176-179 */
 106_W|_P,         _W|_P,        _W|_P,        _W|_P,               /* 180-183 */
 107_W|_P,         _W|_P,        _W|_P,        _W|_P,               /* 184-187 */
 108_W|_P,         _W|_P,        _W|_P,        _W|_P,               /* 188-191 */
 109_W|_U,         _W|_U,        _W|_U,        _W|_U,               /* 192-195 */
 110_W|_U,         _W|_U,        _W|_U,        _W|_U,               /* 196-199 */
 111_W|_U,         _W|_U,        _W|_U,        _W|_U,               /* 200-203 */
 112_W|_U,         _W|_U,        _W|_U,        _W|_U,               /* 204-207 */
 113_W|_U,         _W|_U,        _W|_U,        _W|_U,               /* 208-211 */
 114_W|_U,         _W|_U,        _W|_U,        _W|_P,               /* 212-215 */
 115_W|_U,         _W|_U,        _W|_U,        _W|_U,               /* 216-219 */
 116_W|_U,         _W|_U,        _W|_U,        _W|_L,               /* 220-223 */
 117_W|_L,         _W|_L,        _W|_L,        _W|_L,               /* 224-227 */
 118_W|_L,         _W|_L,        _W|_L,        _W|_L,               /* 228-231 */
 119_W|_L,         _W|_L,        _W|_L,        _W|_L,               /* 232-235 */
 120_W|_L,         _W|_L,        _W|_L,        _W|_L,               /* 236-239 */
 121_W|_L,         _W|_L,        _W|_L,        _W|_L,               /* 240-243 */
 122_W|_L,         _W|_L,        _W|_L,        _W|_P,               /* 244-247 */
 123_W|_L,         _W|_L,        _W|_L,        _W|_L,               /* 248-251 */
 124_W|_L,         _W|_L,        _W|_L,        _W|_L};              /* 252-255 */
 125
 126static inline int match_token(struct ts_fsm_token *t, u8 d)
 127{
 128        if (t->type)
 129                return (token_lookup_tbl[d] & t->type) != 0;
 130        else
 131                return t->value == d;
 132}
 133
 134static unsigned int fsm_find(struct ts_config *conf, struct ts_state *state)
 135{
 136        struct ts_fsm *fsm = ts_config_priv(conf);
 137        struct ts_fsm_token *cur = NULL, *next;
 138        unsigned int match_start, block_idx = 0, tok_idx;
 139        unsigned block_len = 0, strict, consumed = state->offset;
 140        const u8 *data;
 141
 142#define GET_NEXT_BLOCK()                \
 143({      consumed += block_idx;          \
 144        block_idx = 0;                  \
 145        block_len = conf->get_next_block(consumed, &data, conf, state); })
 146
 147#define TOKEN_MISMATCH()                \
 148        do {                            \
 149                if (strict)             \
 150                        goto no_match;  \
 151                block_idx++;            \
 152                goto startover;         \
 153        } while(0)
 154
 155#define end_of_data() unlikely(block_idx >= block_len && !GET_NEXT_BLOCK())
 156
 157        if (end_of_data())
 158                goto no_match;
 159
 160        strict = fsm->tokens[0].recur != TS_FSM_HEAD_IGNORE;
 161
 162startover:
 163        match_start = consumed + block_idx;
 164
 165        for (tok_idx = 0; tok_idx < fsm->ntokens; tok_idx++) {
 166                cur = &fsm->tokens[tok_idx];
 167
 168                if (likely(tok_idx < (fsm->ntokens - 1)))
 169                        next = &fsm->tokens[tok_idx + 1];
 170                else
 171                        next = NULL;
 172
 173                switch (cur->recur) {
 174                case TS_FSM_SINGLE:
 175                        if (end_of_data())
 176                                goto no_match;
 177
 178                        if (!match_token(cur, data[block_idx]))
 179                                TOKEN_MISMATCH();
 180                        break;
 181
 182                case TS_FSM_PERHAPS:
 183                        if (end_of_data() ||
 184                            !match_token(cur, data[block_idx]))
 185                                continue;
 186                        break;
 187
 188                case TS_FSM_MULTI:
 189                        if (end_of_data())
 190                                goto no_match;
 191
 192                        if (!match_token(cur, data[block_idx]))
 193                                TOKEN_MISMATCH();
 194
 195                        block_idx++;
 196                        fallthrough;
 197
 198                case TS_FSM_ANY:
 199                        if (next == NULL)
 200                                goto found_match;
 201
 202                        if (end_of_data())
 203                                continue;
 204
 205                        while (!match_token(next, data[block_idx])) {
 206                                if (!match_token(cur, data[block_idx]))
 207                                        TOKEN_MISMATCH();
 208                                block_idx++;
 209                                if (end_of_data())
 210                                        goto no_match;
 211                        }
 212                        continue;
 213
 214                /*
 215                 * Optimization: Prefer small local loop over jumping
 216                 * back and forth until garbage at head is munched.
 217                 */
 218                case TS_FSM_HEAD_IGNORE:
 219                        if (end_of_data())
 220                                continue;
 221
 222                        while (!match_token(next, data[block_idx])) {
 223                                /*
 224                                 * Special case, don't start over upon
 225                                 * a mismatch, give the user the
 226                                 * chance to specify the type of data
 227                                 * allowed to be ignored.
 228                                 */
 229                                if (!match_token(cur, data[block_idx]))
 230                                        goto no_match;
 231
 232                                block_idx++;
 233                                if (end_of_data())
 234                                        goto no_match;
 235                        }
 236
 237                        match_start = consumed + block_idx;
 238                        continue;
 239                }
 240
 241                block_idx++;
 242        }
 243
 244        if (end_of_data())
 245                goto found_match;
 246
 247no_match:
 248        return UINT_MAX;
 249
 250found_match:
 251        state->offset = consumed + block_idx;
 252        return match_start;
 253}
 254
 255static struct ts_config *fsm_init(const void *pattern, unsigned int len,
 256                                    gfp_t gfp_mask, int flags)
 257{
 258        int i, err = -EINVAL;
 259        struct ts_config *conf;
 260        struct ts_fsm *fsm;
 261        struct ts_fsm_token *tokens = (struct ts_fsm_token *) pattern;
 262        unsigned int ntokens = len / sizeof(*tokens);
 263        size_t priv_size = sizeof(*fsm) + len;
 264
 265        if (len  % sizeof(struct ts_fsm_token) || ntokens < 1)
 266                goto errout;
 267
 268        if (flags & TS_IGNORECASE)
 269                goto errout;
 270
 271        for (i = 0; i < ntokens; i++) {
 272                struct ts_fsm_token *t = &tokens[i];
 273
 274                if (t->type > TS_FSM_TYPE_MAX || t->recur > TS_FSM_RECUR_MAX)
 275                        goto errout;
 276
 277                if (t->recur == TS_FSM_HEAD_IGNORE &&
 278                    (i != 0 || i == (ntokens - 1)))
 279                        goto errout;
 280        }
 281
 282        conf = alloc_ts_config(priv_size, gfp_mask);
 283        if (IS_ERR(conf))
 284                return conf;
 285
 286        conf->flags = flags;
 287        fsm = ts_config_priv(conf);
 288        fsm->ntokens = ntokens;
 289        memcpy(fsm->tokens, pattern, len);
 290
 291        for (i = 0; i < fsm->ntokens; i++) {
 292                struct ts_fsm_token *t = &fsm->tokens[i];
 293                t->type = token_map[t->type];
 294        }
 295
 296        return conf;
 297
 298errout:
 299        return ERR_PTR(err);
 300}
 301
 302static void *fsm_get_pattern(struct ts_config *conf)
 303{
 304        struct ts_fsm *fsm = ts_config_priv(conf);
 305        return fsm->tokens;
 306}
 307
 308static unsigned int fsm_get_pattern_len(struct ts_config *conf)
 309{
 310        struct ts_fsm *fsm = ts_config_priv(conf);
 311        return fsm->ntokens * sizeof(struct ts_fsm_token);
 312}
 313
 314static struct ts_ops fsm_ops = {
 315        .name             = "fsm",
 316        .find             = fsm_find,
 317        .init             = fsm_init,
 318        .get_pattern      = fsm_get_pattern,
 319        .get_pattern_len  = fsm_get_pattern_len,
 320        .owner            = THIS_MODULE,
 321        .list             = LIST_HEAD_INIT(fsm_ops.list)
 322};
 323
 324static int __init init_fsm(void)
 325{
 326        return textsearch_register(&fsm_ops);
 327}
 328
 329static void __exit exit_fsm(void)
 330{
 331        textsearch_unregister(&fsm_ops);
 332}
 333
 334MODULE_LICENSE("GPL");
 335
 336module_init(init_fsm);
 337module_exit(exit_fsm);
 338