/* * lib/textsearch.c Generic text search interface * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. * * Authors: Thomas Graf * Pablo Neira Ayuso * * ========================================================================== * * INTRODUCTION * * The textsearch infrastructure provides text searching facitilies for * both linear and non-linear data. Individual search algorithms are * implemented in modules and chosen by the user. * * ARCHITECTURE * * User * +----------------+ * | finish()| * |get_next_block()| * | | Algorithm | | * | | +------------------------------+ * | | | init() find() destroy() | * | | +------------------------------+ * | | Core API ^ ^ ^ * | | +---------------+ (2) (4) (8) * | (1)|----->| prepare() |---+ | | * | (3)|----->| find()/next() |-----------+ | * | (7)|----->| destroy() |----------------------+ * +----------------+ +---------------+ * * (1) User configures a search by calling _prepare() specifying the * search parameters such as the pattern and algorithm name. * (2) Core requests the algorithm to allocate and initialize a search * configuration according to the specified parameters. * (3) User starts the search(es) by calling _find() or _next() to * fetch subsequent occurrences. A state variable is provided * to the algorithm to store persistent variables. * (4) Core eventually resets the search offset and forwards the find() * request to the algorithm. * (5) Algorithm calls get_next_block() provided by the user continously * to fetch the data to be searched in block by block. * (6) Algorithm invokes finish() after the last call to get_next_block * to clean up any leftovers from get_next_block. (Optional) * (7) User destroys the configuration by calling _destroy(). * (8) Core notifies the algorithm to destroy algorithm specific * allocations. (Optional) * * USAGE * * Before a search can be performed, a configuration must be created * by calling textsearch_prepare() specifying the searching algorithm, * the pattern to look for and flags. As a flag, you can set TS_IGNORECASE * to perform case insensitive matching. But it might slow down * performance of algorithm, so you should use it at own your risk. * The returned configuration may then be used for an arbitary * amount of times and even in parallel as long as a separate struct * ts_state variable is provided to every instance. * * The actual search is performed by either calling textsearch_find_- * continuous() for linear data or by providing an own get_next_block() * implementation and calling textsearch_find(). Both functions return * the position of the first occurrence of the patern or UINT_MAX if * no match was found. Subsequent occurences can be found by calling * textsearch_next() regardless of the linearity of the data. * * Once you're done using a configuration it must be given back via * textsearch_destroy. * * EXAMPLE * * int pos; * struct ts_config *conf; * struct ts_state state; * const char *pattern = "chicken"; * const char *example = "We dance the funky chicken"; * * conf = textsearch_prepare("kmp", pattern, strlen(pattern), * GFP_KERNEL, TS_AUTOLOAD); * if (IS_ERR(conf)) { * err = PTR_ERR(conf); * goto errout; * } * * pos = textsearch_find_continuous(conf, &state, example, strlen(example)); * if (pos != UINT_MAX) * panic("Oh my god, dancing chickens at %d\n", pos); * * textsearch_destroy(conf); * ========================================================================== */ #include #include #include #include #include #include #include #include static LIST_HEAD(ts_ops); static DEFINE_SPINLOCK(ts_mod_lock); static inline struct ts_ops *lookup_ts_algo(const char *name) { struct ts_ops *o; rcu_read_lock(); list_for_each_entry_rcu(o, &ts_ops, list) { if (!strcmp(name, o->name)) { if (!try_module_get(o->owner)) o = NULL; rcu_read_unlock(); return o; } } rcu_read_unlock(); return NULL; } /** * textsearch_register - register a textsearch module * @ops: operations lookup table * * This function must be called by textsearch modules to announce * their presence. The specified &@ops must have %name set to a * unique identifier and the callbacks find(), init(), get_pattern(), * and get_pattern_len() must be implemented. * * Returns 0 or -EEXISTS if another module has already registered * with same name. */ int textsearch_register(struct ts_ops *ops) { int err = -EEXIST; struct ts_ops *o; if (ops->name == NULL || ops->find == NULL || ops->init == NULL || ops->get_pattern == NULL || ops->get_pattern_len == NULL) return -EINVAL; spin_lock(&ts_mod_lock); list_for_each_entry(o, &ts_ops, list) { if (!strcmp(ops->name, o->name)) goto errout; } list_add_tail_rcu(&ops->list, &ts_ops); err = 0; errout: spin_unlock(&ts_mod_lock); return err; } /** * textsearch_unregister - unregister a textsearch module * @ops: operations lookup table * * This function must be called by textsearch modules to announce * their disappearance for examples when the module gets unloaded. * The &ops parameter must be the same as the one during the * registration. * * Returns 0 on success or -ENOENT if no matching textsearch * registration was found. */ int textsearch_unregister(struct ts_ops *ops) { int err = 0; struct ts_ops *o; spin_lock(&ts_mod_lock); list_for_each_entry(o, &ts_ops, list) { if (o == ops) { list_del_rcu(&o->list); goto out; } } err = -ENOENT; out: spin_unlock(&ts_mod_lock); return err; } struct ts_linear_state { unsigned int len; const void *data; }; static unsigned int get_linear_data(unsigned int consumed, const u8 **dst, struct ts_config *conf, struct ts_state *state) { struct ts_linear_state *st = (struct ts_linear_state *) state->cb; if (likely(consumed < st->len)) { *dst = st->data + consumed; return st->len - consumed; } return 0; } /** * textsearch_find_continuous - search a pattern in continuous/linear data * @conf: search configuration * @state: search state * @data: data to search in * @len: length of data * * A simplified version of textsearch_find() for continuous/linear data. * Call textsearch_next() to retrieve subsequent matches. * * Returns the position of first occurrence of the pattern or * %UINT_MAX if no occurrence was found. */ unsigned int textsearch_find_continuous(struct ts_config *conf, struct ts_state *state, const void *data, unsigned int len) { struct ts_linear_state *st = (struct ts_linear_state *) state->cb; conf->get_next_block = get_linear_data; st->data = data; st->len = len; return textsearch_find(conf, state); } /** * textsearch_prepare - Prepare a search * @algo: name of search algorithm * @pattern: pattern data * @len: length of pattern * @gfp_mask: allocation mask * @flags: search flags * * Looks up the search algorithm module and creates a new textsearch * configuration for the specified pattern. Upon completion all * necessary refcnts are held and the configuration must be put back * using textsearch_put() after usage. * * Note: The format of the pattern may not be compatible between * the various search algorithms. * * Returns a new textsearch configuration according to the specified * parameters or a ERR_PTR(). If a zero length pattern is passed, this * function returns EINVAL. */ struct ts_config *textsearch_prepare(const char *algo, const void *pattern, unsigned int len, gfp_t gfp_mask, int flags) { int err = -ENOENT; struct ts_config *conf; struct ts_ops *ops; if (len == 0) return ERR_PTR(-EINVAL); ops = lookup_ts_algo(algo); #ifdef CONFIG_MODULES /* * Why not always autoload you may ask. Some users are * in a situation where requesting a module may deadlock, * especially when the module is located on a NFS mount. */ if (ops == NULL && flags & TS_AUTOLOAD) { request_module("ts_%s", algo); ops = lookup_ts_algo(algo); } #endif if (ops == NULL) goto errout; conf = ops->init(pattern, len, gfp_mask, flags); if (IS_ERR(conf)) { err = PTR_ERR(conf); goto errout; } conf->ops = ops; return conf; errout: if (ops) module_put(ops->owner); return ERR_PTR(err); } /** * textsearch_destroy - destroy a search configuration * @conf: search configuration * * Releases all references of the configuration and frees * up the memory. */ void textsearch_destroy(struct ts_config *conf) { if (conf->ops) { if (conf->ops->destroy) conf->ops->destroy(conf); module_put(conf->ops->owner); } kfree(conf); } EXPORT_SYMBOL(textsearch_register); EXPORT_SYMBOL(textsearch_unregister); EXPORT_SYMBOL(textsearch_prepare); EXPORT_SYMBOL(textsearch_find_continuous); EXPORT_SYMBOL(textsearch_destroy);
