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Linux/lib/ts_fsm.c

  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 
 36 struct 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 */
 47 static 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 
 64 static 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 
130 static 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 
138 static 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 
166 startover:
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 
251 no_match:
252         return UINT_MAX;
253 
254 found_match:
255         state->offset = consumed + block_idx;
256         return match_start;
257 }
258 
259 static 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 
302 errout:
303         return ERR_PTR(err);
304 }
305 
306 static void *fsm_get_pattern(struct ts_config *conf)
307 {
308         struct ts_fsm *fsm = ts_config_priv(conf);
309         return fsm->tokens;
310 }
311 
312 static 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 
318 static 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 
328 static int __init init_fsm(void)
329 {
330         return textsearch_register(&fsm_ops);
331 }
332 
333 static void __exit exit_fsm(void)
334 {
335         textsearch_unregister(&fsm_ops);
336 }
337 
338 MODULE_LICENSE("GPL");
339 
340 module_init(init_fsm);
341 module_exit(exit_fsm);
342 

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