// SPDX-License-Identifier: GPL-2.0-or-later /* * lib/textsearch.c Generic text search interface * * Authors: Thomas Graf <[email protected]> * Pablo Neira Ayuso <[email protected]> * * ========================================================================== */ /** * DOC: ts_intro * INTRODUCTION * * The textsearch infrastructure provides text searching facilities for * both linear and non-linear data. Individual search algorithms are * implemented in modules and chosen by the user. * * ARCHITECTURE * * .. code-block:: none * * User * +----------------+ * | finish()|<--------------(6)-----------------+ * |get_next_block()|<--------------(5)---------------+ | * | | Algorithm | | * | | +------------------------------+ * | | | init() find() destroy() | * | | +------------------------------+ * | | Core API ^ ^ ^ * | | +---------------+ (2) (4) (8) * | (1)|----->| prepare() |---+ | | * | (3)|----->| find()/next() |-----------+ | * | (7)|----->| destroy() |----------------------+ * +----------------+ +---------------+ * * (1) User configures a search by calling textsearch_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 textsearch_find() or * textsearch_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 continuously * 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 textsearch_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 arbitrary * 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 pattern or UINT_MAX if * no match was found. Subsequent occurrences 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 <linux/module.h> #include <linux/types.h> #include <linux/string.h> #include <linux/init.h> #include <linux/rculist.h> #include <linux/rcupdate.h> #include <linux/err.h> #include <linux/textsearch.h> #include <linux/slab.h> static LIST_HEAD(ts_ops); static DEFINE_SPINLOCK(ts_mod_lock); static inline struct ts_ops *lookup_ts_algo(const char *name) { … } /** * 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) { … } EXPORT_SYMBOL(…); /** * 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) { … } EXPORT_SYMBOL(…); struct ts_linear_state { … }; static unsigned int get_linear_data(unsigned int consumed, const u8 **dst, struct ts_config *conf, struct ts_state *state) { … } /** * 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) { … } EXPORT_SYMBOL(…); /** * 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. * * 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) { … } EXPORT_SYMBOL(…); /** * 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) { … } EXPORT_SYMBOL(…);
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