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