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v3.5.6
  1/*
  2 * lib/ts_bm.c		Boyer-Moore text search implementation
  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:	Pablo Neira Ayuso <pablo@eurodev.net>
 10 *
 11 * ==========================================================================
 12 * 
 13 *   Implements Boyer-Moore string matching algorithm:
 14 *
 15 *   [1] A Fast String Searching Algorithm, R.S. Boyer and Moore.
 16 *       Communications of the Association for Computing Machinery, 
 17 *       20(10), 1977, pp. 762-772.
 18 *       http://www.cs.utexas.edu/users/moore/publications/fstrpos.pdf
 19 *
 20 *   [2] Handbook of Exact String Matching Algorithms, Thierry Lecroq, 2004
 21 *       http://www-igm.univ-mlv.fr/~lecroq/string/string.pdf
 22 *
 23 *   Note: Since Boyer-Moore (BM) performs searches for matchings from right 
 24 *   to left, it's still possible that a matching could be spread over 
 25 *   multiple blocks, in that case this algorithm won't find any coincidence.
 26 *   
 27 *   If you're willing to ensure that such thing won't ever happen, use the
 28 *   Knuth-Pratt-Morris (KMP) implementation instead. In conclusion, choose 
 29 *   the proper string search algorithm depending on your setting. 
 30 *
 31 *   Say you're using the textsearch infrastructure for filtering, NIDS or 
 32 *   any similar security focused purpose, then go KMP. Otherwise, if you 
 33 *   really care about performance, say you're classifying packets to apply
 34 *   Quality of Service (QoS) policies, and you don't mind about possible
 35 *   matchings spread over multiple fragments, then go BM.
 36 */
 37
 38#include <linux/kernel.h>
 39#include <linux/module.h>
 40#include <linux/types.h>
 41#include <linux/string.h>
 42#include <linux/ctype.h>
 43#include <linux/textsearch.h>
 44
 45/* Alphabet size, use ASCII */
 46#define ASIZE 256
 47
 48#if 0
 49#define DEBUGP printk
 50#else
 51#define DEBUGP(args, format...)
 52#endif
 53
 54struct ts_bm
 55{
 56	u8 *		pattern;
 57	unsigned int	patlen;
 58	unsigned int 	bad_shift[ASIZE];
 59	unsigned int	good_shift[0];
 60};
 61
 62static unsigned int bm_find(struct ts_config *conf, struct ts_state *state)
 63{
 64	struct ts_bm *bm = ts_config_priv(conf);
 65	unsigned int i, text_len, consumed = state->offset;
 66	const u8 *text;
 67	int shift = bm->patlen - 1, bs;
 68	const u8 icase = conf->flags & TS_IGNORECASE;
 69
 70	for (;;) {
 71		text_len = conf->get_next_block(consumed, &text, conf, state);
 72
 73		if (unlikely(text_len == 0))
 74			break;
 75
 76		while (shift < text_len) {
 77			DEBUGP("Searching in position %d (%c)\n", 
 78				shift, text[shift]);
 79			for (i = 0; i < bm->patlen; i++) 
 80				if ((icase ? toupper(text[shift-i])
 81				    : text[shift-i])
 82					!= bm->pattern[bm->patlen-1-i])
 83				     goto next;
 84
 85			/* London calling... */
 86			DEBUGP("found!\n");
 87			return consumed += (shift-(bm->patlen-1));
 88
 89next:			bs = bm->bad_shift[text[shift-i]];
 90
 91			/* Now jumping to... */
 92			shift = max_t(int, shift-i+bs, shift+bm->good_shift[i]);
 93		}
 94		consumed += text_len;
 95	}
 96
 97	return UINT_MAX;
 98}
 99
100static int subpattern(u8 *pattern, int i, int j, int g)
101{
102	int x = i+g-1, y = j+g-1, ret = 0;
103
104	while(pattern[x--] == pattern[y--]) {
105		if (y < 0) {
106			ret = 1;
107			break;
108		}
109		if (--g == 0) {
110			ret = pattern[i-1] != pattern[j-1];
111			break;
112		}
113	}
114
115	return ret;
116}
117
118static void compute_prefix_tbl(struct ts_bm *bm, int flags)
119{
120	int i, j, g;
121
122	for (i = 0; i < ASIZE; i++)
123		bm->bad_shift[i] = bm->patlen;
124	for (i = 0; i < bm->patlen - 1; i++) {
125		bm->bad_shift[bm->pattern[i]] = bm->patlen - 1 - i;
126		if (flags & TS_IGNORECASE)
127			bm->bad_shift[tolower(bm->pattern[i])]
128			    = bm->patlen - 1 - i;
129	}
130
131	/* Compute the good shift array, used to match reocurrences 
132	 * of a subpattern */
133	bm->good_shift[0] = 1;
134	for (i = 1; i < bm->patlen; i++)
135		bm->good_shift[i] = bm->patlen;
136        for (i = bm->patlen-1, g = 1; i > 0; g++, i--) {
137		for (j = i-1; j >= 1-g ; j--)
138			if (subpattern(bm->pattern, i, j, g)) {
139				bm->good_shift[g] = bm->patlen-j-g;
140				break;
141			}
142	}
143}
144
145static struct ts_config *bm_init(const void *pattern, unsigned int len,
146				 gfp_t gfp_mask, int flags)
147{
148	struct ts_config *conf;
149	struct ts_bm *bm;
150	int i;
151	unsigned int prefix_tbl_len = len * sizeof(unsigned int);
152	size_t priv_size = sizeof(*bm) + len + prefix_tbl_len;
153
154	conf = alloc_ts_config(priv_size, gfp_mask);
155	if (IS_ERR(conf))
156		return conf;
157
158	conf->flags = flags;
159	bm = ts_config_priv(conf);
160	bm->patlen = len;
161	bm->pattern = (u8 *) bm->good_shift + prefix_tbl_len;
162	if (flags & TS_IGNORECASE)
163		for (i = 0; i < len; i++)
164			bm->pattern[i] = toupper(((u8 *)pattern)[i]);
165	else
166		memcpy(bm->pattern, pattern, len);
167	compute_prefix_tbl(bm, flags);
168
169	return conf;
170}
171
172static void *bm_get_pattern(struct ts_config *conf)
173{
174	struct ts_bm *bm = ts_config_priv(conf);
175	return bm->pattern;
176}
177
178static unsigned int bm_get_pattern_len(struct ts_config *conf)
179{
180	struct ts_bm *bm = ts_config_priv(conf);
181	return bm->patlen;
182}
183
184static struct ts_ops bm_ops = {
185	.name		  = "bm",
186	.find		  = bm_find,
187	.init		  = bm_init,
188	.get_pattern	  = bm_get_pattern,
189	.get_pattern_len  = bm_get_pattern_len,
190	.owner		  = THIS_MODULE,
191	.list		  = LIST_HEAD_INIT(bm_ops.list)
192};
193
194static int __init init_bm(void)
195{
196	return textsearch_register(&bm_ops);
197}
198
199static void __exit exit_bm(void)
200{
201	textsearch_unregister(&bm_ops);
202}
203
204MODULE_LICENSE("GPL");
205
206module_init(init_bm);
207module_exit(exit_bm);
v3.15
  1/*
  2 * lib/ts_bm.c		Boyer-Moore text search implementation
  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:	Pablo Neira Ayuso <pablo@eurodev.net>
 10 *
 11 * ==========================================================================
 12 * 
 13 *   Implements Boyer-Moore string matching algorithm:
 14 *
 15 *   [1] A Fast String Searching Algorithm, R.S. Boyer and Moore.
 16 *       Communications of the Association for Computing Machinery, 
 17 *       20(10), 1977, pp. 762-772.
 18 *       http://www.cs.utexas.edu/users/moore/publications/fstrpos.pdf
 19 *
 20 *   [2] Handbook of Exact String Matching Algorithms, Thierry Lecroq, 2004
 21 *       http://www-igm.univ-mlv.fr/~lecroq/string/string.pdf
 22 *
 23 *   Note: Since Boyer-Moore (BM) performs searches for matchings from right 
 24 *   to left, it's still possible that a matching could be spread over 
 25 *   multiple blocks, in that case this algorithm won't find any coincidence.
 26 *   
 27 *   If you're willing to ensure that such thing won't ever happen, use the
 28 *   Knuth-Pratt-Morris (KMP) implementation instead. In conclusion, choose 
 29 *   the proper string search algorithm depending on your setting. 
 30 *
 31 *   Say you're using the textsearch infrastructure for filtering, NIDS or 
 32 *   any similar security focused purpose, then go KMP. Otherwise, if you 
 33 *   really care about performance, say you're classifying packets to apply
 34 *   Quality of Service (QoS) policies, and you don't mind about possible
 35 *   matchings spread over multiple fragments, then go BM.
 36 */
 37
 38#include <linux/kernel.h>
 39#include <linux/module.h>
 40#include <linux/types.h>
 41#include <linux/string.h>
 42#include <linux/ctype.h>
 43#include <linux/textsearch.h>
 44
 45/* Alphabet size, use ASCII */
 46#define ASIZE 256
 47
 48#if 0
 49#define DEBUGP printk
 50#else
 51#define DEBUGP(args, format...)
 52#endif
 53
 54struct ts_bm
 55{
 56	u8 *		pattern;
 57	unsigned int	patlen;
 58	unsigned int 	bad_shift[ASIZE];
 59	unsigned int	good_shift[0];
 60};
 61
 62static unsigned int bm_find(struct ts_config *conf, struct ts_state *state)
 63{
 64	struct ts_bm *bm = ts_config_priv(conf);
 65	unsigned int i, text_len, consumed = state->offset;
 66	const u8 *text;
 67	int shift = bm->patlen - 1, bs;
 68	const u8 icase = conf->flags & TS_IGNORECASE;
 69
 70	for (;;) {
 71		text_len = conf->get_next_block(consumed, &text, conf, state);
 72
 73		if (unlikely(text_len == 0))
 74			break;
 75
 76		while (shift < text_len) {
 77			DEBUGP("Searching in position %d (%c)\n", 
 78				shift, text[shift]);
 79			for (i = 0; i < bm->patlen; i++) 
 80				if ((icase ? toupper(text[shift-i])
 81				    : text[shift-i])
 82					!= bm->pattern[bm->patlen-1-i])
 83				     goto next;
 84
 85			/* London calling... */
 86			DEBUGP("found!\n");
 87			return consumed += (shift-(bm->patlen-1));
 88
 89next:			bs = bm->bad_shift[text[shift-i]];
 90
 91			/* Now jumping to... */
 92			shift = max_t(int, shift-i+bs, shift+bm->good_shift[i]);
 93		}
 94		consumed += text_len;
 95	}
 96
 97	return UINT_MAX;
 98}
 99
100static int subpattern(u8 *pattern, int i, int j, int g)
101{
102	int x = i+g-1, y = j+g-1, ret = 0;
103
104	while(pattern[x--] == pattern[y--]) {
105		if (y < 0) {
106			ret = 1;
107			break;
108		}
109		if (--g == 0) {
110			ret = pattern[i-1] != pattern[j-1];
111			break;
112		}
113	}
114
115	return ret;
116}
117
118static void compute_prefix_tbl(struct ts_bm *bm, int flags)
119{
120	int i, j, g;
121
122	for (i = 0; i < ASIZE; i++)
123		bm->bad_shift[i] = bm->patlen;
124	for (i = 0; i < bm->patlen - 1; i++) {
125		bm->bad_shift[bm->pattern[i]] = bm->patlen - 1 - i;
126		if (flags & TS_IGNORECASE)
127			bm->bad_shift[tolower(bm->pattern[i])]
128			    = bm->patlen - 1 - i;
129	}
130
131	/* Compute the good shift array, used to match reocurrences 
132	 * of a subpattern */
133	bm->good_shift[0] = 1;
134	for (i = 1; i < bm->patlen; i++)
135		bm->good_shift[i] = bm->patlen;
136        for (i = bm->patlen-1, g = 1; i > 0; g++, i--) {
137		for (j = i-1; j >= 1-g ; j--)
138			if (subpattern(bm->pattern, i, j, g)) {
139				bm->good_shift[g] = bm->patlen-j-g;
140				break;
141			}
142	}
143}
144
145static struct ts_config *bm_init(const void *pattern, unsigned int len,
146				 gfp_t gfp_mask, int flags)
147{
148	struct ts_config *conf;
149	struct ts_bm *bm;
150	int i;
151	unsigned int prefix_tbl_len = len * sizeof(unsigned int);
152	size_t priv_size = sizeof(*bm) + len + prefix_tbl_len;
153
154	conf = alloc_ts_config(priv_size, gfp_mask);
155	if (IS_ERR(conf))
156		return conf;
157
158	conf->flags = flags;
159	bm = ts_config_priv(conf);
160	bm->patlen = len;
161	bm->pattern = (u8 *) bm->good_shift + prefix_tbl_len;
162	if (flags & TS_IGNORECASE)
163		for (i = 0; i < len; i++)
164			bm->pattern[i] = toupper(((u8 *)pattern)[i]);
165	else
166		memcpy(bm->pattern, pattern, len);
167	compute_prefix_tbl(bm, flags);
168
169	return conf;
170}
171
172static void *bm_get_pattern(struct ts_config *conf)
173{
174	struct ts_bm *bm = ts_config_priv(conf);
175	return bm->pattern;
176}
177
178static unsigned int bm_get_pattern_len(struct ts_config *conf)
179{
180	struct ts_bm *bm = ts_config_priv(conf);
181	return bm->patlen;
182}
183
184static struct ts_ops bm_ops = {
185	.name		  = "bm",
186	.find		  = bm_find,
187	.init		  = bm_init,
188	.get_pattern	  = bm_get_pattern,
189	.get_pattern_len  = bm_get_pattern_len,
190	.owner		  = THIS_MODULE,
191	.list		  = LIST_HEAD_INIT(bm_ops.list)
192};
193
194static int __init init_bm(void)
195{
196	return textsearch_register(&bm_ops);
197}
198
199static void __exit exit_bm(void)
200{
201	textsearch_unregister(&bm_ops);
202}
203
204MODULE_LICENSE("GPL");
205
206module_init(init_bm);
207module_exit(exit_bm);