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