lib/ts_fsm.c

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This source file includes following definitions.
match_token
fsm_find
fsm_init
fsm_get_pattern
fsm_get_pattern_len
init_fsm
exit_fsm
   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 
  32 struct ts_fsm
  33 {
  34         unsigned int            ntokens;
  35         struct ts_fsm_token     tokens[0];
  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 */
  43 static 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 
  60 static 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 
 126 static 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 
 134 static 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 
 162 startover:
 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                         /* fall through */
 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 
 247 no_match:
 248         return UINT_MAX;
 249 
 250 found_match:
 251         state->offset = consumed + block_idx;
 252         return match_start;
 253 }
 254 
 255 static 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 
 298 errout:
 299         return ERR_PTR(err);
 300 }
 301 
 302 static void *fsm_get_pattern(struct ts_config *conf)
 303 {
 304         struct ts_fsm *fsm = ts_config_priv(conf);
 305         return fsm->tokens;
 306 }
 307 
 308 static 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 
 314 static 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 
 324 static int __init init_fsm(void)
 325 {
 326         return textsearch_register(&fsm_ops);
 327 }
 328 
 329 static void __exit exit_fsm(void)
 330 {
 331         textsearch_unregister(&fsm_ops);
 332 }
 333 
 334 MODULE_LICENSE("GPL");
 335 
 336 module_init(init_fsm);
 337 module_exit(exit_fsm);
/* [<][>][^][v][top][bottom][index][help] */
root/lib/ts_fsm.c

DEFINITIONS
