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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 <[email protected]>
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);
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