xref: /openbmc/linux/lib/ts_fsm.c (revision 7fd53f41)
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_LICENSE("GPL");
335 
336 module_init(init_fsm);
337 module_exit(exit_fsm);
338