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