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 37 struct 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 */ 48 static 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 65 static 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 */ 130 131 static 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 } 138 139 static 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; 166 167 startover: 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; 251 252 no_match: 253 return UINT_MAX; 254 255 found_match: 256 state->offset = consumed + block_idx; 257 return match_start; 258 } 259 260 static 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; 298 299 errout: 300 return ERR_PTR(err); 301 } 302 303 static void *fsm_get_pattern(struct ts_config *conf) 304 { 305 struct ts_fsm *fsm = ts_config_priv(conf); 306 return fsm->tokens; 307 } 308 309 static 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 } 314 315 static 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 }; 324 325 static int __init init_fsm(void) 326 { 327 return textsearch_register(&fsm_ops); 328 } 329 330 static void __exit exit_fsm(void) 331 { 332 textsearch_unregister(&fsm_ops); 333 } 334 335 MODULE_LICENSE("GPL"); 336 337 module_init(init_fsm); 338 module_exit(exit_fsm); 339