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1// SPDX-License-Identifier: GPL-2.0-or-later2/*3 * lib/textsearch.c Generic text search interface4 *5 * Authors: Thomas Graf <tgraf@suug.ch>6 * Pablo Neira Ayuso <pablo@netfilter.org>7 *8 * ==========================================================================9 */10 11/**12 * DOC: ts_intro13 * INTRODUCTION14 *15 * The textsearch infrastructure provides text searching facilities for16 * both linear and non-linear data. Individual search algorithms are17 * implemented in modules and chosen by the user.18 *19 * ARCHITECTURE20 *21 * .. code-block:: none22 *23 * User24 * +----------------+25 * | finish()|<--------------(6)-----------------+26 * |get_next_block()|<--------------(5)---------------+ |27 * | | Algorithm | |28 * | | +------------------------------+29 * | | | init() find() destroy() |30 * | | +------------------------------+31 * | | Core API ^ ^ ^32 * | | +---------------+ (2) (4) (8)33 * | (1)|----->| prepare() |---+ | |34 * | (3)|----->| find()/next() |-----------+ |35 * | (7)|----->| destroy() |----------------------+36 * +----------------+ +---------------+37 *38 * (1) User configures a search by calling textsearch_prepare() specifying39 * the search parameters such as the pattern and algorithm name.40 * (2) Core requests the algorithm to allocate and initialize a search41 * configuration according to the specified parameters.42 * (3) User starts the search(es) by calling textsearch_find() or43 * textsearch_next() to fetch subsequent occurrences. A state variable44 * is provided to the algorithm to store persistent variables.45 * (4) Core eventually resets the search offset and forwards the find()46 * request to the algorithm.47 * (5) Algorithm calls get_next_block() provided by the user continuously48 * to fetch the data to be searched in block by block.49 * (6) Algorithm invokes finish() after the last call to get_next_block50 * to clean up any leftovers from get_next_block. (Optional)51 * (7) User destroys the configuration by calling textsearch_destroy().52 * (8) Core notifies the algorithm to destroy algorithm specific53 * allocations. (Optional)54 *55 * USAGE56 *57 * Before a search can be performed, a configuration must be created58 * by calling textsearch_prepare() specifying the searching algorithm,59 * the pattern to look for and flags. As a flag, you can set TS_IGNORECASE60 * to perform case insensitive matching. But it might slow down61 * performance of algorithm, so you should use it at own your risk.62 * The returned configuration may then be used for an arbitrary63 * amount of times and even in parallel as long as a separate struct64 * ts_state variable is provided to every instance.65 *66 * The actual search is performed by either calling67 * textsearch_find_continuous() for linear data or by providing68 * an own get_next_block() implementation and69 * calling textsearch_find(). Both functions return70 * the position of the first occurrence of the pattern or UINT_MAX if71 * no match was found. Subsequent occurrences can be found by calling72 * textsearch_next() regardless of the linearity of the data.73 *74 * Once you're done using a configuration it must be given back via75 * textsearch_destroy.76 *77 * EXAMPLE::78 *79 * int pos;80 * struct ts_config *conf;81 * struct ts_state state;82 * const char *pattern = "chicken";83 * const char *example = "We dance the funky chicken";84 *85 * conf = textsearch_prepare("kmp", pattern, strlen(pattern),86 * GFP_KERNEL, TS_AUTOLOAD);87 * if (IS_ERR(conf)) {88 * err = PTR_ERR(conf);89 * goto errout;90 * }91 *92 * pos = textsearch_find_continuous(conf, &state, example, strlen(example));93 * if (pos != UINT_MAX)94 * panic("Oh my god, dancing chickens at %d\n", pos);95 *96 * textsearch_destroy(conf);97 */98/* ========================================================================== */99 100#include <linux/module.h>101#include <linux/types.h>102#include <linux/string.h>103#include <linux/init.h>104#include <linux/rculist.h>105#include <linux/rcupdate.h>106#include <linux/err.h>107#include <linux/textsearch.h>108#include <linux/slab.h>109 110static LIST_HEAD(ts_ops);111static DEFINE_SPINLOCK(ts_mod_lock);112 113static inline struct ts_ops *lookup_ts_algo(const char *name)114{115 struct ts_ops *o;116 117 rcu_read_lock();118 list_for_each_entry_rcu(o, &ts_ops, list) {119 if (!strcmp(name, o->name)) {120 if (!try_module_get(o->owner))121 o = NULL;122 rcu_read_unlock();123 return o;124 }125 }126 rcu_read_unlock();127 128 return NULL;129}130 131/**132 * textsearch_register - register a textsearch module133 * @ops: operations lookup table134 *135 * This function must be called by textsearch modules to announce136 * their presence. The specified &@ops must have %name set to a137 * unique identifier and the callbacks find(), init(), get_pattern(),138 * and get_pattern_len() must be implemented.139 *140 * Returns 0 or -EEXISTS if another module has already registered141 * with same name.142 */143int textsearch_register(struct ts_ops *ops)144{145 int err = -EEXIST;146 struct ts_ops *o;147 148 if (ops->name == NULL || ops->find == NULL || ops->init == NULL ||149 ops->get_pattern == NULL || ops->get_pattern_len == NULL)150 return -EINVAL;151 152 spin_lock(&ts_mod_lock);153 list_for_each_entry(o, &ts_ops, list) {154 if (!strcmp(ops->name, o->name))155 goto errout;156 }157 158 list_add_tail_rcu(&ops->list, &ts_ops);159 err = 0;160errout:161 spin_unlock(&ts_mod_lock);162 return err;163}164EXPORT_SYMBOL(textsearch_register);165 166/**167 * textsearch_unregister - unregister a textsearch module168 * @ops: operations lookup table169 *170 * This function must be called by textsearch modules to announce171 * their disappearance for examples when the module gets unloaded.172 * The &ops parameter must be the same as the one during the173 * registration.174 *175 * Returns 0 on success or -ENOENT if no matching textsearch176 * registration was found.177 */178int textsearch_unregister(struct ts_ops *ops)179{180 int err = 0;181 struct ts_ops *o;182 183 spin_lock(&ts_mod_lock);184 list_for_each_entry(o, &ts_ops, list) {185 if (o == ops) {186 list_del_rcu(&o->list);187 goto out;188 }189 }190 191 err = -ENOENT;192out:193 spin_unlock(&ts_mod_lock);194 return err;195}196EXPORT_SYMBOL(textsearch_unregister);197 198struct ts_linear_state199{200 unsigned int len;201 const void *data;202};203 204static unsigned int get_linear_data(unsigned int consumed, const u8 **dst,205 struct ts_config *conf,206 struct ts_state *state)207{208 struct ts_linear_state *st = (struct ts_linear_state *) state->cb;209 210 if (likely(consumed < st->len)) {211 *dst = st->data + consumed;212 return st->len - consumed;213 }214 215 return 0;216}217 218/**219 * textsearch_find_continuous - search a pattern in continuous/linear data220 * @conf: search configuration221 * @state: search state222 * @data: data to search in223 * @len: length of data224 *225 * A simplified version of textsearch_find() for continuous/linear data.226 * Call textsearch_next() to retrieve subsequent matches.227 *228 * Returns the position of first occurrence of the pattern or229 * %UINT_MAX if no occurrence was found.230 */231unsigned int textsearch_find_continuous(struct ts_config *conf,232 struct ts_state *state,233 const void *data, unsigned int len)234{235 struct ts_linear_state *st = (struct ts_linear_state *) state->cb;236 237 conf->get_next_block = get_linear_data;238 st->data = data;239 st->len = len;240 241 return textsearch_find(conf, state);242}243EXPORT_SYMBOL(textsearch_find_continuous);244 245/**246 * textsearch_prepare - Prepare a search247 * @algo: name of search algorithm248 * @pattern: pattern data249 * @len: length of pattern250 * @gfp_mask: allocation mask251 * @flags: search flags252 *253 * Looks up the search algorithm module and creates a new textsearch254 * configuration for the specified pattern.255 *256 * Note: The format of the pattern may not be compatible between257 * the various search algorithms.258 *259 * Returns a new textsearch configuration according to the specified260 * parameters or a ERR_PTR(). If a zero length pattern is passed, this261 * function returns EINVAL.262 */263struct ts_config *textsearch_prepare(const char *algo, const void *pattern,264 unsigned int len, gfp_t gfp_mask, int flags)265{266 int err = -ENOENT;267 struct ts_config *conf;268 struct ts_ops *ops;269 270 if (len == 0)271 return ERR_PTR(-EINVAL);272 273 ops = lookup_ts_algo(algo);274#ifdef CONFIG_MODULES275 /*276 * Why not always autoload you may ask. Some users are277 * in a situation where requesting a module may deadlock,278 * especially when the module is located on a NFS mount.279 */280 if (ops == NULL && flags & TS_AUTOLOAD) {281 request_module("ts_%s", algo);282 ops = lookup_ts_algo(algo);283 }284#endif285 286 if (ops == NULL)287 goto errout;288 289 conf = ops->init(pattern, len, gfp_mask, flags);290 if (IS_ERR(conf)) {291 err = PTR_ERR(conf);292 goto errout;293 }294 295 conf->ops = ops;296 return conf;297 298errout:299 if (ops)300 module_put(ops->owner);301 302 return ERR_PTR(err);303}304EXPORT_SYMBOL(textsearch_prepare);305 306/**307 * textsearch_destroy - destroy a search configuration308 * @conf: search configuration309 *310 * Releases all references of the configuration and frees311 * up the memory.312 */313void textsearch_destroy(struct ts_config *conf)314{315 if (conf->ops) {316 if (conf->ops->destroy)317 conf->ops->destroy(conf);318 module_put(conf->ops->owner);319 }320 321 kfree(conf);322}323EXPORT_SYMBOL(textsearch_destroy);324