Root/lib/ts_fsm.c

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 an 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 specifying
21 * whether the pattern has to start at the first octet. 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/module.h>
30#include <linux/types.h>
31#include <linux/string.h>
32#include <linux/ctype.h>
33#include <linux/textsearch.h>
34#include <linux/textsearch_fsm.h>
35
36struct ts_fsm
37{
38    unsigned int ntokens;
39    struct ts_fsm_token tokens[0];
40};
41
42/* other values derived from ctype.h */
43#define _A 0x100 /* ascii */
44#define _W 0x200 /* wildcard */
45
46/* Map to _ctype flags and some magic numbers */
47static const u16 token_map[TS_FSM_TYPE_MAX+1] = {
48    [TS_FSM_SPECIFIC] = 0,
49    [TS_FSM_WILDCARD] = _W,
50    [TS_FSM_CNTRL] = _C,
51    [TS_FSM_LOWER] = _L,
52    [TS_FSM_UPPER] = _U,
53    [TS_FSM_PUNCT] = _P,
54    [TS_FSM_SPACE] = _S,
55    [TS_FSM_DIGIT] = _D,
56    [TS_FSM_XDIGIT] = _D | _X,
57    [TS_FSM_ALPHA] = _U | _L,
58    [TS_FSM_ALNUM] = _U | _L | _D,
59    [TS_FSM_PRINT] = _P | _U | _L | _D | _SP,
60    [TS_FSM_GRAPH] = _P | _U | _L | _D,
61    [TS_FSM_ASCII] = _A,
62};
63
64static const u16 token_lookup_tbl[256] = {
65_W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 0- 3 */
66_W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 4- 7 */
67_W|_A|_C, _W|_A|_C|_S, _W|_A|_C|_S, _W|_A|_C|_S, /* 8- 11 */
68_W|_A|_C|_S, _W|_A|_C|_S, _W|_A|_C, _W|_A|_C, /* 12- 15 */
69_W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 16- 19 */
70_W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 20- 23 */
71_W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 24- 27 */
72_W|_A|_C, _W|_A|_C, _W|_A|_C, _W|_A|_C, /* 28- 31 */
73_W|_A|_S|_SP, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 32- 35 */
74_W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 36- 39 */
75_W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 40- 43 */
76_W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 44- 47 */
77_W|_A|_D, _W|_A|_D, _W|_A|_D, _W|_A|_D, /* 48- 51 */
78_W|_A|_D, _W|_A|_D, _W|_A|_D, _W|_A|_D, /* 52- 55 */
79_W|_A|_D, _W|_A|_D, _W|_A|_P, _W|_A|_P, /* 56- 59 */
80_W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 60- 63 */
81_W|_A|_P, _W|_A|_U|_X, _W|_A|_U|_X, _W|_A|_U|_X, /* 64- 67 */
82_W|_A|_U|_X, _W|_A|_U|_X, _W|_A|_U|_X, _W|_A|_U, /* 68- 71 */
83_W|_A|_U, _W|_A|_U, _W|_A|_U, _W|_A|_U, /* 72- 75 */
84_W|_A|_U, _W|_A|_U, _W|_A|_U, _W|_A|_U, /* 76- 79 */
85_W|_A|_U, _W|_A|_U, _W|_A|_U, _W|_A|_U, /* 80- 83 */
86_W|_A|_U, _W|_A|_U, _W|_A|_U, _W|_A|_U, /* 84- 87 */
87_W|_A|_U, _W|_A|_U, _W|_A|_U, _W|_A|_P, /* 88- 91 */
88_W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_P, /* 92- 95 */
89_W|_A|_P, _W|_A|_L|_X, _W|_A|_L|_X, _W|_A|_L|_X, /* 96- 99 */
90_W|_A|_L|_X, _W|_A|_L|_X, _W|_A|_L|_X, _W|_A|_L, /* 100-103 */
91_W|_A|_L, _W|_A|_L, _W|_A|_L, _W|_A|_L, /* 104-107 */
92_W|_A|_L, _W|_A|_L, _W|_A|_L, _W|_A|_L, /* 108-111 */
93_W|_A|_L, _W|_A|_L, _W|_A|_L, _W|_A|_L, /* 112-115 */
94_W|_A|_L, _W|_A|_L, _W|_A|_L, _W|_A|_L, /* 116-119 */
95_W|_A|_L, _W|_A|_L, _W|_A|_L, _W|_A|_P, /* 120-123 */
96_W|_A|_P, _W|_A|_P, _W|_A|_P, _W|_A|_C, /* 124-127 */
97_W, _W, _W, _W, /* 128-131 */
98_W, _W, _W, _W, /* 132-135 */
99_W, _W, _W, _W, /* 136-139 */
100_W, _W, _W, _W, /* 140-143 */
101_W, _W, _W, _W, /* 144-147 */
102_W, _W, _W, _W, /* 148-151 */
103_W, _W, _W, _W, /* 152-155 */
104_W, _W, _W, _W, /* 156-159 */
105_W|_S|_SP, _W|_P, _W|_P, _W|_P, /* 160-163 */
106_W|_P, _W|_P, _W|_P, _W|_P, /* 164-167 */
107_W|_P, _W|_P, _W|_P, _W|_P, /* 168-171 */
108_W|_P, _W|_P, _W|_P, _W|_P, /* 172-175 */
109_W|_P, _W|_P, _W|_P, _W|_P, /* 176-179 */
110_W|_P, _W|_P, _W|_P, _W|_P, /* 180-183 */
111_W|_P, _W|_P, _W|_P, _W|_P, /* 184-187 */
112_W|_P, _W|_P, _W|_P, _W|_P, /* 188-191 */
113_W|_U, _W|_U, _W|_U, _W|_U, /* 192-195 */
114_W|_U, _W|_U, _W|_U, _W|_U, /* 196-199 */
115_W|_U, _W|_U, _W|_U, _W|_U, /* 200-203 */
116_W|_U, _W|_U, _W|_U, _W|_U, /* 204-207 */
117_W|_U, _W|_U, _W|_U, _W|_U, /* 208-211 */
118_W|_U, _W|_U, _W|_U, _W|_P, /* 212-215 */
119_W|_U, _W|_U, _W|_U, _W|_U, /* 216-219 */
120_W|_U, _W|_U, _W|_U, _W|_L, /* 220-223 */
121_W|_L, _W|_L, _W|_L, _W|_L, /* 224-227 */
122_W|_L, _W|_L, _W|_L, _W|_L, /* 228-231 */
123_W|_L, _W|_L, _W|_L, _W|_L, /* 232-235 */
124_W|_L, _W|_L, _W|_L, _W|_L, /* 236-239 */
125_W|_L, _W|_L, _W|_L, _W|_L, /* 240-243 */
126_W|_L, _W|_L, _W|_L, _W|_P, /* 244-247 */
127_W|_L, _W|_L, _W|_L, _W|_L, /* 248-251 */
128_W|_L, _W|_L, _W|_L, _W|_L}; /* 252-255 */
129
130static inline int match_token(struct ts_fsm_token *t, u8 d)
131{
132    if (t->type)
133        return (token_lookup_tbl[d] & t->type) != 0;
134    else
135        return t->value == d;
136}
137
138static unsigned int fsm_find(struct ts_config *conf, struct ts_state *state)
139{
140    struct ts_fsm *fsm = ts_config_priv(conf);
141    struct ts_fsm_token *cur = NULL, *next;
142    unsigned int match_start, block_idx = 0, tok_idx;
143    unsigned block_len = 0, strict, consumed = state->offset;
144    const u8 *data;
145
146#define GET_NEXT_BLOCK() \
147({ consumed += block_idx; \
148    block_idx = 0; \
149    block_len = conf->get_next_block(consumed, &data, conf, state); })
150
151#define TOKEN_MISMATCH() \
152    do { \
153        if (strict) \
154            goto no_match; \
155        block_idx++; \
156        goto startover; \
157    } while(0)
158
159#define end_of_data() unlikely(block_idx >= block_len && !GET_NEXT_BLOCK())
160
161    if (end_of_data())
162        goto no_match;
163
164    strict = fsm->tokens[0].recur != TS_FSM_HEAD_IGNORE;
165
166startover:
167    match_start = consumed + block_idx;
168
169    for (tok_idx = 0; tok_idx < fsm->ntokens; tok_idx++) {
170        cur = &fsm->tokens[tok_idx];
171
172        if (likely(tok_idx < (fsm->ntokens - 1)))
173            next = &fsm->tokens[tok_idx + 1];
174        else
175            next = NULL;
176
177        switch (cur->recur) {
178        case TS_FSM_SINGLE:
179            if (end_of_data())
180                goto no_match;
181
182            if (!match_token(cur, data[block_idx]))
183                TOKEN_MISMATCH();
184            break;
185
186        case TS_FSM_PERHAPS:
187            if (end_of_data() ||
188                !match_token(cur, data[block_idx]))
189                continue;
190            break;
191
192        case TS_FSM_MULTI:
193            if (end_of_data())
194                goto no_match;
195
196            if (!match_token(cur, data[block_idx]))
197                TOKEN_MISMATCH();
198
199            block_idx++;
200            /* fall through */
201
202        case TS_FSM_ANY:
203            if (next == NULL)
204                goto found_match;
205
206            if (end_of_data())
207                continue;
208
209            while (!match_token(next, data[block_idx])) {
210                if (!match_token(cur, data[block_idx]))
211                    TOKEN_MISMATCH();
212                block_idx++;
213                if (end_of_data())
214                    goto no_match;
215            }
216            continue;
217
218        /*
219         * Optimization: Prefer small local loop over jumping
220         * back and forth until garbage at head is munched.
221         */
222        case TS_FSM_HEAD_IGNORE:
223            if (end_of_data())
224                continue;
225
226            while (!match_token(next, data[block_idx])) {
227                /*
228                 * Special case, don't start over upon
229                 * a mismatch, give the user the
230                 * chance to specify the type of data
231                 * allowed to be ignored.
232                 */
233                if (!match_token(cur, data[block_idx]))
234                    goto no_match;
235
236                block_idx++;
237                if (end_of_data())
238                    goto no_match;
239            }
240
241            match_start = consumed + block_idx;
242            continue;
243        }
244
245        block_idx++;
246    }
247
248    if (end_of_data())
249        goto found_match;
250
251no_match:
252    return UINT_MAX;
253
254found_match:
255    state->offset = consumed + block_idx;
256    return match_start;
257}
258
259static struct ts_config *fsm_init(const void *pattern, unsigned int len,
260                    gfp_t gfp_mask, int flags)
261{
262    int i, err = -EINVAL;
263    struct ts_config *conf;
264    struct ts_fsm *fsm;
265    struct ts_fsm_token *tokens = (struct ts_fsm_token *) pattern;
266    unsigned int ntokens = len / sizeof(*tokens);
267    size_t priv_size = sizeof(*fsm) + len;
268
269    if (len % sizeof(struct ts_fsm_token) || ntokens < 1)
270        goto errout;
271
272    if (flags & TS_IGNORECASE)
273        goto errout;
274
275    for (i = 0; i < ntokens; i++) {
276        struct ts_fsm_token *t = &tokens[i];
277
278        if (t->type > TS_FSM_TYPE_MAX || t->recur > TS_FSM_RECUR_MAX)
279            goto errout;
280
281        if (t->recur == TS_FSM_HEAD_IGNORE &&
282            (i != 0 || i == (ntokens - 1)))
283            goto errout;
284    }
285
286    conf = alloc_ts_config(priv_size, gfp_mask);
287    if (IS_ERR(conf))
288        return conf;
289
290    conf->flags = flags;
291    fsm = ts_config_priv(conf);
292    fsm->ntokens = ntokens;
293    memcpy(fsm->tokens, pattern, len);
294
295    for (i = 0; i < fsm->ntokens; i++) {
296        struct ts_fsm_token *t = &fsm->tokens[i];
297        t->type = token_map[t->type];
298    }
299
300    return conf;
301
302errout:
303    return ERR_PTR(err);
304}
305
306static void *fsm_get_pattern(struct ts_config *conf)
307{
308    struct ts_fsm *fsm = ts_config_priv(conf);
309    return fsm->tokens;
310}
311
312static unsigned int fsm_get_pattern_len(struct ts_config *conf)
313{
314    struct ts_fsm *fsm = ts_config_priv(conf);
315    return fsm->ntokens * sizeof(struct ts_fsm_token);
316}
317
318static struct ts_ops fsm_ops = {
319    .name = "fsm",
320    .find = fsm_find,
321    .init = fsm_init,
322    .get_pattern = fsm_get_pattern,
323    .get_pattern_len = fsm_get_pattern_len,
324    .owner = THIS_MODULE,
325    .list = LIST_HEAD_INIT(fsm_ops.list)
326};
327
328static int __init init_fsm(void)
329{
330    return textsearch_register(&fsm_ops);
331}
332
333static void __exit exit_fsm(void)
334{
335    textsearch_unregister(&fsm_ops);
336}
337
338MODULE_LICENSE("GPL");
339
340module_init(init_fsm);
341module_exit(exit_fsm);
342

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