linux/lib/ts_fsm.c
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   1/*
   2 * lib/ts_fsm.c    A naive finite state machine text search approach
   3 *
   4 *              This program is free software; you can redistribute it and/or
   5 *              modify it under the terms of the GNU General Public License
   6 *              as published by the Free Software Foundation; either version
   7 *              2 of the License, or (at your option) any later version.
   8 *
   9 * Authors:     Thomas Graf <tgraf@suug.ch>
  10 *
  11 * ==========================================================================
  12 *
  13 *   A finite state machine consists of n states (struct ts_fsm_token)
  14 *   representing the pattern as a finite automation. The data is read
  15 *   sequentially on an octet basis. Every state token specifies the number
  16 *   of recurrences and the type of value accepted which can be either a
  17 *   specific character or ctype based set of characters. The available
  18 *   type of recurrences include 1, (0|1), [0 n], and [1 n].
  19 *
  20 *   The algorithm differs between strict/non-strict mode specifying
  21 *   whether the pattern has to start at the first octet. Strict mode
  22 *   is enabled by default and can be disabled by inserting
  23 *   TS_FSM_HEAD_IGNORE as the first token in the chain.
  24 *
  25 *   The runtime performance of the algorithm should be around O(n),
  26 *   however while in strict mode the average runtime can be better.
  27 */
  28
  29#include <linux/module.h>
  30#include <linux/types.h>
  31#include <linux/string.h>
  32#include <linux/ctype.h>
  33#include <linux/textsearch.h>
  34#include <linux/textsearch_fsm.h>
  35
  36struct ts_fsm
  37{
  38        unsigned int            ntokens;
  39        struct ts_fsm_token     tokens[0];
  40};
  41
  42/* other values derived from ctype.h */
  43#define _A              0x100 /* ascii */
  44#define _W              0x200 /* wildcard */
  45
  46/* Map to _ctype flags and some magic numbers */
  47static const u16 token_map[TS_FSM_TYPE_MAX+1] = {
  48        [TS_FSM_SPECIFIC] = 0,
  49        [TS_FSM_WILDCARD] = _W,
  50        [TS_FSM_CNTRL]    = _C,
  51        [TS_FSM_LOWER]    = _L,
  52        [TS_FSM_UPPER]    = _U,
  53        [TS_FSM_PUNCT]    = _P,
  54        [TS_FSM_SPACE]    = _S,
  55        [TS_FSM_DIGIT]    = _D,
  56        [TS_FSM_XDIGIT]   = _D | _X,
  57        [TS_FSM_ALPHA]    = _U | _L,
  58        [TS_FSM_ALNUM]    = _U | _L | _D,
  59        [TS_FSM_PRINT]    = _P | _U | _L | _D | _SP,
  60        [TS_FSM_GRAPH]    = _P | _U | _L | _D,
  61        [TS_FSM_ASCII]    = _A,
  62};
  63
  64static const u16 token_lookup_tbl[256] = {
  65_W|_A|_C,      _W|_A|_C,     _W|_A|_C,     _W|_A|_C,            /*   0-  3 */
  66_W|_A|_C,      _W|_A|_C,     _W|_A|_C,     _W|_A|_C,            /*   4-  7 */
  67_W|_A|_C,      _W|_A|_C|_S,  _W|_A|_C|_S,  _W|_A|_C|_S,         /*   8- 11 */
  68_W|_A|_C|_S,   _W|_A|_C|_S,  _W|_A|_C,     _W|_A|_C,            /*  12- 15 */
  69_W|_A|_C,      _W|_A|_C,     _W|_A|_C,     _W|_A|_C,            /*  16- 19 */
  70_W|_A|_C,      _W|_A|_C,     _W|_A|_C,     _W|_A|_C,            /*  20- 23 */
  71_W|_A|_C,      _W|_A|_C,     _W|_A|_C,     _W|_A|_C,            /*  24- 27 */
  72_W|_A|_C,      _W|_A|_C,     _W|_A|_C,     _W|_A|_C,            /*  28- 31 */
  73_W|_A|_S|_SP,  _W|_A|_P,     _W|_A|_P,     _W|_A|_P,            /*  32- 35 */
  74_W|_A|_P,      _W|_A|_P,     _W|_A|_P,     _W|_A|_P,            /*  36- 39 */
  75_W|_A|_P,      _W|_A|_P,     _W|_A|_P,     _W|_A|_P,            /*  40- 43 */
  76_W|_A|_P,      _W|_A|_P,     _W|_A|_P,     _W|_A|_P,            /*  44- 47 */
  77_W|_A|_D,      _W|_A|_D,     _W|_A|_D,     _W|_A|_D,            /*  48- 51 */
  78_W|_A|_D,      _W|_A|_D,     _W|_A|_D,     _W|_A|_D,            /*  52- 55 */
  79_W|_A|_D,      _W|_A|_D,     _W|_A|_P,     _W|_A|_P,            /*  56- 59 */
  80_W|_A|_P,      _W|_A|_P,     _W|_A|_P,     _W|_A|_P,            /*  60- 63 */
  81_W|_A|_P,      _W|_A|_U|_X,  _W|_A|_U|_X,  _W|_A|_U|_X,         /*  64- 67 */
  82_W|_A|_U|_X,   _W|_A|_U|_X,  _W|_A|_U|_X,  _W|_A|_U,            /*  68- 71 */
  83_W|_A|_U,      _W|_A|_U,     _W|_A|_U,     _W|_A|_U,            /*  72- 75 */
  84_W|_A|_U,      _W|_A|_U,     _W|_A|_U,     _W|_A|_U,            /*  76- 79 */
  85_W|_A|_U,      _W|_A|_U,     _W|_A|_U,     _W|_A|_U,            /*  80- 83 */
  86_W|_A|_U,      _W|_A|_U,     _W|_A|_U,     _W|_A|_U,            /*  84- 87 */
  87_W|_A|_U,      _W|_A|_U,     _W|_A|_U,     _W|_A|_P,            /*  88- 91 */
  88_W|_A|_P,      _W|_A|_P,     _W|_A|_P,     _W|_A|_P,            /*  92- 95 */
  89_W|_A|_P,      _W|_A|_L|_X,  _W|_A|_L|_X,  _W|_A|_L|_X,         /*  96- 99 */
  90_W|_A|_L|_X,   _W|_A|_L|_X,  _W|_A|_L|_X,  _W|_A|_L,            /* 100-103 */
  91_W|_A|_L,      _W|_A|_L,     _W|_A|_L,     _W|_A|_L,            /* 104-107 */
  92_W|_A|_L,      _W|_A|_L,     _W|_A|_L,     _W|_A|_L,            /* 108-111 */
  93_W|_A|_L,      _W|_A|_L,     _W|_A|_L,     _W|_A|_L,            /* 112-115 */
  94_W|_A|_L,      _W|_A|_L,     _W|_A|_L,     _W|_A|_L,            /* 116-119 */
  95_W|_A|_L,      _W|_A|_L,     _W|_A|_L,     _W|_A|_P,            /* 120-123 */
  96_W|_A|_P,      _W|_A|_P,     _W|_A|_P,     _W|_A|_C,            /* 124-127 */
  97_W,            _W,           _W,           _W,                  /* 128-131 */
  98_W,            _W,           _W,           _W,                  /* 132-135 */
  99_W,            _W,           _W,           _W,                  /* 136-139 */
 100_W,            _W,           _W,           _W,                  /* 140-143 */
 101_W,            _W,           _W,           _W,                  /* 144-147 */
 102_W,            _W,           _W,           _W,                  /* 148-151 */
 103_W,            _W,           _W,           _W,                  /* 152-155 */
 104_W,            _W,           _W,           _W,                  /* 156-159 */
 105_W|_S|_SP,     _W|_P,        _W|_P,        _W|_P,               /* 160-163 */
 106_W|_P,         _W|_P,        _W|_P,        _W|_P,               /* 164-167 */
 107_W|_P,         _W|_P,        _W|_P,        _W|_P,               /* 168-171 */
 108_W|_P,         _W|_P,        _W|_P,        _W|_P,               /* 172-175 */
 109_W|_P,         _W|_P,        _W|_P,        _W|_P,               /* 176-179 */
 110_W|_P,         _W|_P,        _W|_P,        _W|_P,               /* 180-183 */
 111_W|_P,         _W|_P,        _W|_P,        _W|_P,               /* 184-187 */
 112_W|_P,         _W|_P,        _W|_P,        _W|_P,               /* 188-191 */
 113_W|_U,         _W|_U,        _W|_U,        _W|_U,               /* 192-195 */
 114_W|_U,         _W|_U,        _W|_U,        _W|_U,               /* 196-199 */
 115_W|_U,         _W|_U,        _W|_U,        _W|_U,               /* 200-203 */
 116_W|_U,         _W|_U,        _W|_U,        _W|_U,               /* 204-207 */
 117_W|_U,         _W|_U,        _W|_U,        _W|_U,               /* 208-211 */
 118_W|_U,         _W|_U,        _W|_U,        _W|_P,               /* 212-215 */
 119_W|_U,         _W|_U,        _W|_U,        _W|_U,               /* 216-219 */
 120_W|_U,         _W|_U,        _W|_U,        _W|_L,               /* 220-223 */
 121_W|_L,         _W|_L,        _W|_L,        _W|_L,               /* 224-227 */
 122_W|_L,         _W|_L,        _W|_L,        _W|_L,               /* 228-231 */
 123_W|_L,         _W|_L,        _W|_L,        _W|_L,               /* 232-235 */
 124_W|_L,         _W|_L,        _W|_L,        _W|_L,               /* 236-239 */
 125_W|_L,         _W|_L,        _W|_L,        _W|_L,               /* 240-243 */
 126_W|_L,         _W|_L,        _W|_L,        _W|_P,               /* 244-247 */
 127_W|_L,         _W|_L,        _W|_L,        _W|_L,               /* 248-251 */
 128_W|_L,         _W|_L,        _W|_L,        _W|_L};              /* 252-255 */
 129
 130static inline int match_token(struct ts_fsm_token *t, u8 d)
 131{
 132        if (t->type)
 133                return (token_lookup_tbl[d] & t->type) != 0;
 134        else
 135                return t->value == d;
 136}
 137
 138static unsigned int fsm_find(struct ts_config *conf, struct ts_state *state)
 139{
 140        struct ts_fsm *fsm = ts_config_priv(conf);
 141        struct ts_fsm_token *cur = NULL, *next;
 142        unsigned int match_start, block_idx = 0, tok_idx;
 143        unsigned block_len = 0, strict, consumed = state->offset;
 144        const u8 *data;
 145
 146#define GET_NEXT_BLOCK()                \
 147({      consumed += block_idx;          \
 148        block_idx = 0;                  \
 149        block_len = conf->get_next_block(consumed, &data, conf, state); })
 150
 151#define TOKEN_MISMATCH()                \
 152        do {                            \
 153                if (strict)             \
 154                        goto no_match;  \
 155                block_idx++;            \
 156                goto startover;         \
 157        } while(0)
 158
 159#define end_of_data() unlikely(block_idx >= block_len && !GET_NEXT_BLOCK())
 160
 161        if (end_of_data())
 162                goto no_match;
 163
 164        strict = fsm->tokens[0].recur != TS_FSM_HEAD_IGNORE;
 165
 166startover:
 167        match_start = consumed + block_idx;
 168
 169        for (tok_idx = 0; tok_idx < fsm->ntokens; tok_idx++) {
 170                cur = &fsm->tokens[tok_idx];
 171
 172                if (likely(tok_idx < (fsm->ntokens - 1)))
 173                        next = &fsm->tokens[tok_idx + 1];
 174                else
 175                        next = NULL;
 176
 177                switch (cur->recur) {
 178                case TS_FSM_SINGLE:
 179                        if (end_of_data())
 180                                goto no_match;
 181
 182                        if (!match_token(cur, data[block_idx]))
 183                                TOKEN_MISMATCH();
 184                        break;
 185
 186                case TS_FSM_PERHAPS:
 187                        if (end_of_data() ||
 188                            !match_token(cur, data[block_idx]))
 189                                continue;
 190                        break;
 191
 192                case TS_FSM_MULTI:
 193                        if (end_of_data())
 194                                goto no_match;
 195
 196                        if (!match_token(cur, data[block_idx]))
 197                                TOKEN_MISMATCH();
 198
 199                        block_idx++;
 200                        /* fall through */
 201
 202                case TS_FSM_ANY:
 203                        if (next == NULL)
 204                                goto found_match;
 205
 206                        if (end_of_data())
 207                                continue;
 208
 209                        while (!match_token(next, data[block_idx])) {
 210                                if (!match_token(cur, data[block_idx]))
 211                                        TOKEN_MISMATCH();
 212                                block_idx++;
 213                                if (end_of_data())
 214                                        goto no_match;
 215                        }
 216                        continue;
 217
 218                /*
 219                 * Optimization: Prefer small local loop over jumping
 220                 * back and forth until garbage at head is munched.
 221                 */
 222                case TS_FSM_HEAD_IGNORE:
 223                        if (end_of_data())
 224                                continue;
 225
 226                        while (!match_token(next, data[block_idx])) {
 227                                /*
 228                                 * Special case, don't start over upon
 229                                 * a mismatch, give the user the
 230                                 * chance to specify the type of data
 231                                 * allowed to be ignored.
 232                                 */
 233                                if (!match_token(cur, data[block_idx]))
 234                                        goto no_match;
 235
 236                                block_idx++;
 237                                if (end_of_data())
 238                                        goto no_match;
 239                        }
 240
 241                        match_start = consumed + block_idx;
 242                        continue;
 243                }
 244
 245                block_idx++;
 246        }
 247
 248        if (end_of_data())
 249                goto found_match;
 250
 251no_match:
 252        return UINT_MAX;
 253
 254found_match:
 255        state->offset = consumed + block_idx;
 256        return match_start;
 257}
 258
 259static struct ts_config *fsm_init(const void *pattern, unsigned int len,
 260                                    gfp_t gfp_mask, int flags)
 261{
 262        int i, err = -EINVAL;
 263        struct ts_config *conf;
 264        struct ts_fsm *fsm;
 265        struct ts_fsm_token *tokens = (struct ts_fsm_token *) pattern;
 266        unsigned int ntokens = len / sizeof(*tokens);
 267        size_t priv_size = sizeof(*fsm) + len;
 268
 269        if (len  % sizeof(struct ts_fsm_token) || ntokens < 1)
 270                goto errout;
 271
 272        if (flags & TS_IGNORECASE)
 273                goto errout;
 274
 275        for (i = 0; i < ntokens; i++) {
 276                struct ts_fsm_token *t = &tokens[i];
 277
 278                if (t->type > TS_FSM_TYPE_MAX || t->recur > TS_FSM_RECUR_MAX)
 279                        goto errout;
 280
 281                if (t->recur == TS_FSM_HEAD_IGNORE &&
 282                    (i != 0 || i == (ntokens - 1)))
 283                        goto errout;
 284        }
 285
 286        conf = alloc_ts_config(priv_size, gfp_mask);
 287        if (IS_ERR(conf))
 288                return conf;
 289
 290        conf->flags = flags;
 291        fsm = ts_config_priv(conf);
 292        fsm->ntokens = ntokens;
 293        memcpy(fsm->tokens, pattern, len);
 294
 295        for (i = 0; i < fsm->ntokens; i++) {
 296                struct ts_fsm_token *t = &fsm->tokens[i];
 297                t->type = token_map[t->type];
 298        }
 299
 300        return conf;
 301
 302errout:
 303        return ERR_PTR(err);
 304}
 305
 306static void *fsm_get_pattern(struct ts_config *conf)
 307{
 308        struct ts_fsm *fsm = ts_config_priv(conf);
 309        return fsm->tokens;
 310}
 311
 312static unsigned int fsm_get_pattern_len(struct ts_config *conf)
 313{
 314        struct ts_fsm *fsm = ts_config_priv(conf);
 315        return fsm->ntokens * sizeof(struct ts_fsm_token);
 316}
 317
 318static struct ts_ops fsm_ops = {
 319        .name             = "fsm",
 320        .find             = fsm_find,
 321        .init             = fsm_init,
 322        .get_pattern      = fsm_get_pattern,
 323        .get_pattern_len  = fsm_get_pattern_len,
 324        .owner            = THIS_MODULE,
 325        .list             = LIST_HEAD_INIT(fsm_ops.list)
 326};
 327
 328static int __init init_fsm(void)
 329{
 330        return textsearch_register(&fsm_ops);
 331}
 332
 333static void __exit exit_fsm(void)
 334{
 335        textsearch_unregister(&fsm_ops);
 336}
 337
 338MODULE_LICENSE("GPL");
 339
 340module_init(init_fsm);
 341module_exit(exit_fsm);
 342
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