blob: a3e500ad51d7d23b207b11f94a6b8922a3d2b37f [file] [log] [blame]
Thomas Graf2de4ff72005-06-23 20:49:30 -07001/*
2 * lib/textsearch.c Generic text search interface
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>
Pablo Neira Ayusoe03ba842007-12-01 00:03:52 +110010 * Pablo Neira Ayuso <pablo@netfilter.org>
Thomas Graf2de4ff72005-06-23 20:49:30 -070011 *
12 * ==========================================================================
13 *
14 * INTRODUCTION
15 *
16 * The textsearch infrastructure provides text searching facitilies for
17 * both linear and non-linear data. Individual search algorithms are
18 * implemented in modules and chosen by the user.
19 *
20 * ARCHITECTURE
21 *
22 * User
23 * +----------------+
24 * | finish()|<--------------(6)-----------------+
25 * |get_next_block()|<--------------(5)---------------+ |
26 * | | Algorithm | |
27 * | | +------------------------------+
28 * | | | init() find() destroy() |
29 * | | +------------------------------+
30 * | | Core API ^ ^ ^
31 * | | +---------------+ (2) (4) (8)
32 * | (1)|----->| prepare() |---+ | |
33 * | (3)|----->| find()/next() |-----------+ |
34 * | (7)|----->| destroy() |----------------------+
35 * +----------------+ +---------------+
36 *
37 * (1) User configures a search by calling _prepare() specifying the
38 * search parameters such as the pattern and algorithm name.
39 * (2) Core requests the algorithm to allocate and initialize a search
40 * configuration according to the specified parameters.
41 * (3) User starts the search(es) by calling _find() or _next() to
42 * fetch subsequent occurrences. A state variable is provided
Robert P. J. Dayd08df602007-02-17 19:07:33 +010043 * to the algorithm to store persistent variables.
Thomas Graf2de4ff72005-06-23 20:49:30 -070044 * (4) Core eventually resets the search offset and forwards the find()
45 * request to the algorithm.
46 * (5) Algorithm calls get_next_block() provided by the user continously
47 * to fetch the data to be searched in block by block.
48 * (6) Algorithm invokes finish() after the last call to get_next_block
49 * to clean up any leftovers from get_next_block. (Optional)
50 * (7) User destroys the configuration by calling _destroy().
51 * (8) Core notifies the algorithm to destroy algorithm specific
52 * allocations. (Optional)
53 *
54 * USAGE
55 *
56 * Before a search can be performed, a configuration must be created
57 * by calling textsearch_prepare() specyfing the searching algorithm and
58 * the pattern to look for. The returned configuration may then be used
59 * for an arbitary amount of times and even in parallel as long as a
60 * separate struct ts_state variable is provided to every instance.
61 *
62 * The actual search is performed by either calling textsearch_find_-
63 * continuous() for linear data or by providing an own get_next_block()
64 * implementation and calling textsearch_find(). Both functions return
65 * the position of the first occurrence of the patern or UINT_MAX if
66 * no match was found. Subsequent occurences can be found by calling
67 * textsearch_next() regardless of the linearity of the data.
68 *
69 * Once you're done using a configuration it must be given back via
70 * textsearch_destroy.
71 *
72 * EXAMPLE
73 *
74 * int pos;
75 * struct ts_config *conf;
76 * struct ts_state state;
77 * const char *pattern = "chicken";
78 * const char *example = "We dance the funky chicken";
79 *
80 * conf = textsearch_prepare("kmp", pattern, strlen(pattern),
81 * GFP_KERNEL, TS_AUTOLOAD);
82 * if (IS_ERR(conf)) {
83 * err = PTR_ERR(conf);
84 * goto errout;
85 * }
86 *
87 * pos = textsearch_find_continuous(conf, &state, example, strlen(example));
88 * if (pos != UINT_MAX)
89 * panic("Oh my god, dancing chickens at %d\n", pos);
90 *
91 * textsearch_destroy(conf);
92 *
93 * ==========================================================================
94 */
95
Thomas Graf2de4ff72005-06-23 20:49:30 -070096#include <linux/module.h>
97#include <linux/types.h>
98#include <linux/string.h>
99#include <linux/init.h>
Franck Bui-Huu82524742008-05-12 21:21:05 +0200100#include <linux/rculist.h>
Thomas Graf2de4ff72005-06-23 20:49:30 -0700101#include <linux/rcupdate.h>
102#include <linux/err.h>
103#include <linux/textsearch.h>
104
105static LIST_HEAD(ts_ops);
106static DEFINE_SPINLOCK(ts_mod_lock);
107
108static inline struct ts_ops *lookup_ts_algo(const char *name)
109{
110 struct ts_ops *o;
111
112 rcu_read_lock();
113 list_for_each_entry_rcu(o, &ts_ops, list) {
114 if (!strcmp(name, o->name)) {
115 if (!try_module_get(o->owner))
116 o = NULL;
117 rcu_read_unlock();
118 return o;
119 }
120 }
121 rcu_read_unlock();
122
123 return NULL;
124}
125
126/**
127 * textsearch_register - register a textsearch module
128 * @ops: operations lookup table
129 *
130 * This function must be called by textsearch modules to announce
131 * their presence. The specified &@ops must have %name set to a
132 * unique identifier and the callbacks find(), init(), get_pattern(),
133 * and get_pattern_len() must be implemented.
134 *
135 * Returns 0 or -EEXISTS if another module has already registered
136 * with same name.
137 */
138int textsearch_register(struct ts_ops *ops)
139{
140 int err = -EEXIST;
141 struct ts_ops *o;
142
143 if (ops->name == NULL || ops->find == NULL || ops->init == NULL ||
144 ops->get_pattern == NULL || ops->get_pattern_len == NULL)
145 return -EINVAL;
146
147 spin_lock(&ts_mod_lock);
148 list_for_each_entry(o, &ts_ops, list) {
149 if (!strcmp(ops->name, o->name))
150 goto errout;
151 }
152
153 list_add_tail_rcu(&ops->list, &ts_ops);
154 err = 0;
155errout:
156 spin_unlock(&ts_mod_lock);
157 return err;
158}
159
160/**
161 * textsearch_unregister - unregister a textsearch module
162 * @ops: operations lookup table
163 *
164 * This function must be called by textsearch modules to announce
165 * their disappearance for examples when the module gets unloaded.
166 * The &ops parameter must be the same as the one during the
167 * registration.
168 *
169 * Returns 0 on success or -ENOENT if no matching textsearch
170 * registration was found.
171 */
172int textsearch_unregister(struct ts_ops *ops)
173{
174 int err = 0;
175 struct ts_ops *o;
176
177 spin_lock(&ts_mod_lock);
178 list_for_each_entry(o, &ts_ops, list) {
179 if (o == ops) {
180 list_del_rcu(&o->list);
181 goto out;
182 }
183 }
184
185 err = -ENOENT;
186out:
187 spin_unlock(&ts_mod_lock);
188 return err;
189}
190
191struct ts_linear_state
192{
193 unsigned int len;
194 const void *data;
195};
196
197static unsigned int get_linear_data(unsigned int consumed, const u8 **dst,
198 struct ts_config *conf,
199 struct ts_state *state)
200{
201 struct ts_linear_state *st = (struct ts_linear_state *) state->cb;
202
203 if (likely(consumed < st->len)) {
204 *dst = st->data + consumed;
205 return st->len - consumed;
206 }
207
208 return 0;
209}
210
211/**
212 * textsearch_find_continuous - search a pattern in continuous/linear data
213 * @conf: search configuration
214 * @state: search state
215 * @data: data to search in
216 * @len: length of data
217 *
218 * A simplified version of textsearch_find() for continuous/linear data.
219 * Call textsearch_next() to retrieve subsequent matches.
220 *
221 * Returns the position of first occurrence of the pattern or
Robert P. J. Day72fd4a32007-02-10 01:45:59 -0800222 * %UINT_MAX if no occurrence was found.
Thomas Graf2de4ff72005-06-23 20:49:30 -0700223 */
224unsigned int textsearch_find_continuous(struct ts_config *conf,
225 struct ts_state *state,
226 const void *data, unsigned int len)
227{
228 struct ts_linear_state *st = (struct ts_linear_state *) state->cb;
229
230 conf->get_next_block = get_linear_data;
231 st->data = data;
232 st->len = len;
233
234 return textsearch_find(conf, state);
235}
236
237/**
238 * textsearch_prepare - Prepare a search
239 * @algo: name of search algorithm
240 * @pattern: pattern data
241 * @len: length of pattern
242 * @gfp_mask: allocation mask
243 * @flags: search flags
244 *
245 * Looks up the search algorithm module and creates a new textsearch
246 * configuration for the specified pattern. Upon completion all
247 * necessary refcnts are held and the configuration must be put back
248 * using textsearch_put() after usage.
249 *
250 * Note: The format of the pattern may not be compatible between
251 * the various search algorithms.
252 *
253 * Returns a new textsearch configuration according to the specified
Pablo Neira Ayusoe03ba842007-12-01 00:03:52 +1100254 * parameters or a ERR_PTR(). If a zero length pattern is passed, this
255 * function returns EINVAL.
Thomas Graf2de4ff72005-06-23 20:49:30 -0700256 */
257struct ts_config *textsearch_prepare(const char *algo, const void *pattern,
Al Virofd4f2df2005-10-21 03:18:50 -0400258 unsigned int len, gfp_t gfp_mask, int flags)
Thomas Graf2de4ff72005-06-23 20:49:30 -0700259{
260 int err = -ENOENT;
261 struct ts_config *conf;
262 struct ts_ops *ops;
263
Pablo Neira Ayusoe03ba842007-12-01 00:03:52 +1100264 if (len == 0)
265 return ERR_PTR(-EINVAL);
266
Thomas Graf2de4ff72005-06-23 20:49:30 -0700267 ops = lookup_ts_algo(algo);
268#ifdef CONFIG_KMOD
269 /*
270 * Why not always autoload you may ask. Some users are
271 * in a situation where requesting a module may deadlock,
272 * especially when the module is located on a NFS mount.
273 */
274 if (ops == NULL && flags & TS_AUTOLOAD) {
275 request_module("ts_%s", algo);
276 ops = lookup_ts_algo(algo);
277 }
278#endif
279
280 if (ops == NULL)
281 goto errout;
282
283 conf = ops->init(pattern, len, gfp_mask);
284 if (IS_ERR(conf)) {
285 err = PTR_ERR(conf);
286 goto errout;
287 }
288
289 conf->ops = ops;
290 return conf;
291
292errout:
293 if (ops)
294 module_put(ops->owner);
295
296 return ERR_PTR(err);
297}
298
299/**
300 * textsearch_destroy - destroy a search configuration
301 * @conf: search configuration
302 *
303 * Releases all references of the configuration and frees
304 * up the memory.
305 */
306void textsearch_destroy(struct ts_config *conf)
307{
308 if (conf->ops) {
309 if (conf->ops->destroy)
310 conf->ops->destroy(conf);
311 module_put(conf->ops->owner);
312 }
313
314 kfree(conf);
315}
316
317EXPORT_SYMBOL(textsearch_register);
318EXPORT_SYMBOL(textsearch_unregister);
319EXPORT_SYMBOL(textsearch_prepare);
320EXPORT_SYMBOL(textsearch_find_continuous);
321EXPORT_SYMBOL(textsearch_destroy);