// SPDX-License-Identifier: GPL-2.0-or-later /* * lib/ts_fsm.c A naive finite state machine text search approach * * Authors: Thomas Graf <tgraf@suug.ch> * * ========================================================================== * * A finite state machine consists of n states (struct ts_fsm_token) * representing the pattern as a finite automaton. The data is read * sequentially on an octet basis. Every state token specifies the number * of recurrences and the type of value accepted which can be either a * specific character or ctype based set of characters. The available * type of recurrences include 1, (0|1), [0 n], and [1 n]. * * The algorithm differs between strict/non-strict mode specifying * whether the pattern has to start at the first octet. Strict mode * is enabled by default and can be disabled by inserting * TS_FSM_HEAD_IGNORE as the first token in the chain. * * The runtime performance of the algorithm should be around O(n), * however while in strict mode the average runtime can be better. */ #include <linux/module.h> #include <linux/types.h> #include <linux/string.h> #include <linux/ctype.h> #include <linux/textsearch.h> #include <linux/textsearch_fsm.h> struct ts_fsm { unsigned int ntokens; struct ts_fsm_token tokens[]; }; /* other values derived from ctype.h */ #define _A 0x100 /* ascii */ #define _W 0x200 /* wildcard */ /* Map to _ctype flags and some magic numbers */ static const u16 token_map[TS_FSM_TYPE_MAX+1] = { [TS_FSM_SPECIFIC] = 0, [TS_FSM_WILDCARD] = _W, [TS_FSM_CNTRL] = _C, [TS_FSM_LOWER] = _L, [TS_FSM_UPPER] = _U, [TS_FSM_PUNCT] = _P, [TS_FSM_SPACE] = _S, [TS_FSM_DIGIT] = _D, [TS_FSM_XDIGIT] = _D | _X, [TS_FSM_ALPHA] = _U | _L, [TS_FSM_ALNUM] = _U | _L | _D, [TS_FSM_PRINT] = _P | _U | _L | _D | _SP, [TS_FSM_GRAPH] = _P | _U | _L | _D, [TS_FSM_ASCII] = _A, }; static const u16 token_lookup_tbl[256] = { _W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 0- 3 */ _W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 4- 7 */ _W|_A|_C, _W|_A|_C|_S, _W|_A|_C|_S, _W|_A|_C|_S, /* 8- 11 */ _W|_A|_C|_S, _W|_A|_C|_S, _W|_A|_C, _W|_A|_C, /* 12- 15 */ _W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 16- 19 */ _W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 20- 23 */ _W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 24- 27 */ _W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 28- 31 */ _W|_A|_S|_SP, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 32- 35 */ _W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 36- 39 */ _W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 40- 43 */ _W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 44- 47 */ _W|_A|_D, _W|_A|_D, _W|_A|_D, _W|_A|_D, /* 48- 51 */ _W|_A|_D, _W|_A|_D, _W|_A|_D, _W|_A|_D, /* 52- 55 */ _W|_A|_D, _W|_A|_D, _W|_A|_P, _W|_A|_P, /* 56- 59 */ _W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 60- 63 */ _W|_A|_P, _W|_A|_U|_X, _W|_A|_U|_X, _W|_A|_U|_X, /* 64- 67 */ _W|_A|_U|_X, _W|_A|_U|_X, _W|_A|_U|_X, _W|_A|_U, /* 68- 71 */ _W|_A|_U, _W|_A|_U, _W|_A|_U, _W|_A|_U, /* 72- 75 */ _W|_A|_U, _W|_A|_U, _W|_A|_U, _W|_A|_U, /* 76- 79 */ _W|_A|_U, _W|_A|_U, _W|_A|_U, _W|_A|_U, /* 80- 83 */ _W|_A|_U, _W|_A|_U, _W|_A|_U, _W|_A|_U, /* 84- 87 */ _W|_A|_U, _W|_A|_U, _W|_A|_U, _W|_A|_P, /* 88- 91 */ _W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 92- 95 */ _W|_A|_P, _W|_A|_L|_X, _W|_A|_L|_X, _W|_A|_L|_X, /* 96- 99 */ _W|_A|_L|_X, _W|_A|_L|_X, _W|_A|_L|_X, _W|_A|_L, /* 100-103 */ _W|_A|_L, _W|_A|_L, _W|_A|_L, _W|_A|_L, /* 104-107 */ _W|_A|_L, _W|_A|_L, _W|_A|_L, _W|_A|_L, /* 108-111 */ _W|_A|_L, _W|_A|_L, _W|_A|_L, _W|_A|_L, /* 112-115 */ _W|_A|_L, _W|_A|_L, _W|_A|_L, _W|_A|_L, /* 116-119 */ _W|_A|_L, _W|_A|_L, _W|_A|_L, _W|_A|_P, /* 120-123 */ _W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_C, /* 124-127 */ _W, _W, _W, _W, /* 128-131 */ _W, _W, _W, _W, /* 132-135 */ _W, _W, _W, _W, /* 136-139 */ _W, _W, _W, _W, /* 140-143 */ _W, _W, _W, _W, /* 144-147 */ _W, _W, _W, _W, /* 148-151 */ _W, _W, _W, _W, /* 152-155 */ _W, _W, _W, _W, /* 156-159 */ _W|_S|_SP, _W|_P, _W|_P, _W|_P, /* 160-163 */ _W|_P, _W|_P, _W|_P, _W|_P, /* 164-167 */ _W|_P, _W|_P, _W|_P, _W|_P, /* 168-171 */ _W|_P, _W|_P, _W|_P, _W|_P, /* 172-175 */ _W|_P, _W|_P, _W|_P, _W|_P, /* 176-179 */ _W|_P, _W|_P, _W|_P, _W|_P, /* 180-183 */ _W|_P, _W|_P, _W|_P, _W|_P, /* 184-187 */ _W|_P, _W|_P, _W|_P, _W|_P, /* 188-191 */ _W|_U, _W|_U, _W|_U, _W|_U, /* 192-195 */ _W|_U, _W|_U, _W|_U, _W|_U, /* 196-199 */ _W|_U, _W|_U, _W|_U, _W|_U, /* 200-203 */ _W|_U, _W|_U, _W|_U, _W|_U, /* 204-207 */ _W|_U, _W|_U, _W|_U, _W|_U, /* 208-211 */ _W|_U, _W|_U, _W|_U, _W|_P, /* 212-215 */ _W|_U, _W|_U, _W|_U, _W|_U, /* 216-219 */ _W|_U, _W|_U, _W|_U, _W|_L, /* 220-223 */ _W|_L, _W|_L, _W|_L, _W|_L, /* 224-227 */ _W|_L, _W|_L, _W|_L, _W|_L, /* 228-231 */ _W|_L, _W|_L, _W|_L, _W|_L, /* 232-235 */ _W|_L, _W|_L, _W|_L, _W|_L, /* 236-239 */ _W|_L, _W|_L, _W|_L, _W|_L, /* 240-243 */ _W|_L, _W|_L, _W|_L, _W|_P, /* 244-247 */ _W|_L, _W|_L, _W|_L, _W|_L, /* 248-251 */ _W|_L, _W|_L, _W|_L, _W|_L}; /* 252-255 */ static inline int match_token(struct ts_fsm_token *t, u8 d) { if (t->type) return (token_lookup_tbl[d] & t->type) != 0; else return t->value == d; } static unsigned int fsm_find(struct ts_config *conf, struct ts_state *state) { struct ts_fsm *fsm = ts_config_priv(conf); struct ts_fsm_token *cur = NULL, *next; unsigned int match_start, block_idx = 0, tok_idx; unsigned block_len = 0, strict, consumed = state->offset; const u8 *data; #define GET_NEXT_BLOCK() \ ({ consumed += block_idx; \ block_idx = 0; \ block_len = conf->get_next_block(consumed, &data, conf, state); }) #define TOKEN_MISMATCH() \ do { \ if (strict) \ goto no_match; \ block_idx++; \ goto startover; \ } while(0) #define end_of_data() unlikely(block_idx >= block_len && !GET_NEXT_BLOCK()) if (end_of_data()) goto no_match; strict = fsm->tokens[0].recur != TS_FSM_HEAD_IGNORE; startover: match_start = consumed + block_idx; for (tok_idx = 0; tok_idx < fsm->ntokens; tok_idx++) { cur = &fsm->tokens[tok_idx]; if (likely(tok_idx < (fsm->ntokens - 1))) next = &fsm->tokens[tok_idx + 1]; else next = NULL; switch (cur->recur) { case TS_FSM_SINGLE: if (end_of_data()) goto no_match; if (!match_token(cur, data[block_idx])) TOKEN_MISMATCH(); break; case TS_FSM_PERHAPS: if (end_of_data() || !match_token(cur, data[block_idx])) continue; break; case TS_FSM_MULTI: if (end_of_data()) goto no_match; if (!match_token(cur, data[block_idx])) TOKEN_MISMATCH(); block_idx++; fallthrough; case TS_FSM_ANY: if (next == NULL) goto found_match; if (end_of_data()) continue; while (!match_token(next, data[block_idx])) { if (!match_token(cur, data[block_idx])) TOKEN_MISMATCH(); block_idx++; if (end_of_data()) goto no_match; } continue; /* * Optimization: Prefer small local loop over jumping * back and forth until garbage at head is munched. */ case TS_FSM_HEAD_IGNORE: if (end_of_data()) continue; while (!match_token(next, data[block_idx])) { /* * Special case, don't start over upon * a mismatch, give the user the * chance to specify the type of data * allowed to be ignored. */ if (!match_token(cur, data[block_idx])) goto no_match; block_idx++; if (end_of_data()) goto no_match; } match_start = consumed + block_idx; continue; } block_idx++; } if (end_of_data()) goto found_match; no_match: return UINT_MAX; found_match: state->offset = consumed + block_idx; return match_start; } static struct ts_config *fsm_init(const void *pattern, unsigned int len, gfp_t gfp_mask, int flags) { int i, err = -EINVAL; struct ts_config *conf; struct ts_fsm *fsm; struct ts_fsm_token *tokens = (struct ts_fsm_token *) pattern; unsigned int ntokens = len / sizeof(*tokens); size_t priv_size = sizeof(*fsm) + len; if (len % sizeof(struct ts_fsm_token) || ntokens < 1) goto errout; if (flags & TS_IGNORECASE) goto errout; for (i = 0; i < ntokens; i++) { struct ts_fsm_token *t = &tokens[i]; if (t->type > TS_FSM_TYPE_MAX || t->recur > TS_FSM_RECUR_MAX) goto errout; if (t->recur == TS_FSM_HEAD_IGNORE && (i != 0 || i == (ntokens - 1))) goto errout; } conf = alloc_ts_config(priv_size, gfp_mask); if (IS_ERR(conf)) return conf; conf->flags = flags; fsm = ts_config_priv(conf); fsm->ntokens = ntokens; memcpy(fsm->tokens, pattern, len); for (i = 0; i < fsm->ntokens; i++) { struct ts_fsm_token *t = &fsm->tokens[i]; t->type = token_map[t->type]; } return conf; errout: return ERR_PTR(err); } static void *fsm_get_pattern(struct ts_config *conf) { struct ts_fsm *fsm = ts_config_priv(conf); return fsm->tokens; } static unsigned int fsm_get_pattern_len(struct ts_config *conf) { struct ts_fsm *fsm = ts_config_priv(conf); return fsm->ntokens * sizeof(struct ts_fsm_token); } static struct ts_ops fsm_ops = { .name = "fsm", .find = fsm_find, .init = fsm_init, .get_pattern = fsm_get_pattern, .get_pattern_len = fsm_get_pattern_len, .owner = THIS_MODULE, .list = LIST_HEAD_INIT(fsm_ops.list) }; static int __init init_fsm(void) { return textsearch_register(&fsm_ops); } static void __exit exit_fsm(void) { textsearch_unregister(&fsm_ops); } MODULE_LICENSE("GPL"); module_init(init_fsm); module_exit(exit_fsm);