| // 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_DESCRIPTION("naive finite state machine text search"); |
| MODULE_LICENSE("GPL"); |
| |
| module_init(init_fsm); |
| module_exit(exit_fsm); |
