diff options
Diffstat (limited to 'lib/ts_fsm.c')
| -rw-r--r-- | lib/ts_fsm.c | 337 |
1 files changed, 337 insertions, 0 deletions
diff --git a/lib/ts_fsm.c b/lib/ts_fsm.c new file mode 100644 index 000000000..ab749ec10 --- /dev/null +++ b/lib/ts_fsm.c @@ -0,0 +1,337 @@ +// 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++; + /* fall through */ + + 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); |