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[];
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 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
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_DESCRIPTION("naive finite state machine text search");
335 MODULE_LICENSE("GPL");
336
337 module_init(init_fsm);
338 module_exit(exit_fsm);
339
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