kernel/jump_label.c - linux - Git at Google

 /*
  * jump label support
  *
  * Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
  * Copyright (C) 2011 Peter Zijlstra
  *
  */
 #include <linux/memory.h>
 #include <linux/uaccess.h>
 #include <linux/module.h>
 #include <linux/list.h>
 #include <linux/slab.h>
 #include <linux/sort.h>
 #include <linux/err.h>
 #include <linux/static_key.h>
 #include <linux/jump_label_ratelimit.h>
 #include <linux/bug.h>

 #ifdef HAVE_JUMP_LABEL

 /* mutex to protect coming/going of the the jump_label table */
 static DEFINE_MUTEX(jump_label_mutex);

 void jump_label_lock(void)
 {
 	mutex_lock(&jump_label_mutex);
 }

 void jump_label_unlock(void)
 {
 	mutex_unlock(&jump_label_mutex);
 }

 static int jump_label_cmp(const void *a, const void *b)
 {
 	const struct jump_entry *jea = a;
 	const struct jump_entry *jeb = b;

 	if (jea->key < jeb->key)
 		return -1;

 	if (jea->key > jeb->key)
 		return 1;

 	return 0;
 }

 static void
 jump_label_sort_entries(struct jump_entry *start, struct jump_entry *stop)
 {
 	unsigned long size;

 	size = (((unsigned long)stop - (unsigned long)start)
 					/ sizeof(struct jump_entry));
 	sort(start, size, sizeof(struct jump_entry), jump_label_cmp, NULL);
 }

 static void jump_label_update(struct static_key *key);

 /*
  * There are similar definitions for the !HAVE_JUMP_LABEL case in jump_label.h.
  * The use of 'atomic_read()' requires atomic.h and its problematic for some
  * kernel headers such as kernel.h and others. Since static_key_count() is not
  * used in the branch statements as it is for the !HAVE_JUMP_LABEL case its ok
  * to have it be a function here. Similarly, for 'static_key_enable()' and
  * 'static_key_disable()', which require bug.h. This should allow jump_label.h
  * to be included from most/all places for HAVE_JUMP_LABEL.
  */
 int static_key_count(struct static_key *key)
 {
 	/*
 	 * -1 means the first static_key_slow_inc() is in progress.
 	 *  static_key_enabled() must return true, so return 1 here.
 	 */
 	int n = atomic_read(&key->enabled);

 	return n >= 0 ? n : 1;
 }
 EXPORT_SYMBOL_GPL(static_key_count);

 void static_key_enable(struct static_key *key)
 {
 	int count = static_key_count(key);

 	WARN_ON_ONCE(count < 0 || count > 1);

 	if (!count)
 		static_key_slow_inc(key);
 }
 EXPORT_SYMBOL_GPL(static_key_enable);

 void static_key_disable(struct static_key *key)
 {
 	int count = static_key_count(key);

 	WARN_ON_ONCE(count < 0 || count > 1);

 	if (count)
 		static_key_slow_dec(key);
 }
 EXPORT_SYMBOL_GPL(static_key_disable);

 void static_key_slow_inc(struct static_key *key)
 {
 	int v, v1;

 	STATIC_KEY_CHECK_USE();

 	/*
 	 * Careful if we get concurrent static_key_slow_inc() calls;
 	 * later calls must wait for the first one to _finish_ the
 	 * jump_label_update() process.  At the same time, however,
 	 * the jump_label_update() call below wants to see
 	 * static_key_enabled(&key) for jumps to be updated properly.
 	 *
 	 * So give a special meaning to negative key->enabled: it sends
 	 * static_key_slow_inc() down the slow path, and it is non-zero
 	 * so it counts as "enabled" in jump_label_update().  Note that
 	 * atomic_inc_unless_negative() checks >= 0, so roll our own.
 	 */
 	for (v = atomic_read(&key->enabled); v > 0; v = v1) {
 		v1 = atomic_cmpxchg(&key->enabled, v, v + 1);
 		if (likely(v1 == v))
 			return;
 	}

 	jump_label_lock();
 	if (atomic_read(&key->enabled) == 0) {
 		atomic_set(&key->enabled, -1);
 		jump_label_update(key);
 		atomic_set(&key->enabled, 1);
 	} else {
 		atomic_inc(&key->enabled);
 	}
 	jump_label_unlock();
 }
 EXPORT_SYMBOL_GPL(static_key_slow_inc);

 static void __static_key_slow_dec(struct static_key *key,
 		unsigned long rate_limit, struct delayed_work *work)
 {
 	/*
 	 * The negative count check is valid even when a negative
 	 * key->enabled is in use by static_key_slow_inc(); a
 	 * __static_key_slow_dec() before the first static_key_slow_inc()
 	 * returns is unbalanced, because all other static_key_slow_inc()
 	 * instances block while the update is in progress.
 	 */
 	if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex)) {
 		WARN(atomic_read(&key->enabled) < 0,
 		     "jump label: negative count!\n");
 		return;
 	}

 	if (rate_limit) {
 		atomic_inc(&key->enabled);
 		schedule_delayed_work(work, rate_limit);
 	} else {
 		jump_label_update(key);
 	}
 	jump_label_unlock();
 }

 static void jump_label_update_timeout(struct work_struct *work)
 {
 	struct static_key_deferred *key =
 		container_of(work, struct static_key_deferred, work.work);
 	__static_key_slow_dec(&key->key, 0, NULL);
 }

 void static_key_slow_dec(struct static_key *key)
 {
 	STATIC_KEY_CHECK_USE();
 	__static_key_slow_dec(key, 0, NULL);
 }
 EXPORT_SYMBOL_GPL(static_key_slow_dec);

 void static_key_slow_dec_deferred(struct static_key_deferred *key)
 {
 	STATIC_KEY_CHECK_USE();
 	__static_key_slow_dec(&key->key, key->timeout, &key->work);
 }
 EXPORT_SYMBOL_GPL(static_key_slow_dec_deferred);

 void jump_label_rate_limit(struct static_key_deferred *key,
 		unsigned long rl)
 {
 	STATIC_KEY_CHECK_USE();
 	key->timeout = rl;
 	INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
 }
 EXPORT_SYMBOL_GPL(jump_label_rate_limit);

 static int addr_conflict(struct jump_entry *entry, void *start, void *end)
 {
 	if (entry->code <= (unsigned long)end &&
 		entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
 		return 1;

 	return 0;
 }

 static int __jump_label_text_reserved(struct jump_entry *iter_start,
 		struct jump_entry *iter_stop, void *start, void *end)
 {
 	struct jump_entry *iter;

 	iter = iter_start;
 	while (iter < iter_stop) {
 		if (addr_conflict(iter, start, end))
 			return 1;
 		iter++;
 	}

 	return 0;
 }

 /*
  * Update code which is definitely not currently executing.
  * Architectures which need heavyweight synchronization to modify
  * running code can override this to make the non-live update case
  * cheaper.
  */
 void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry,
 					    enum jump_label_type type)
 {
 	arch_jump_label_transform(entry, type);
 }

 static inline struct jump_entry *static_key_entries(struct static_key *key)
 {
 	return (struct jump_entry *)((unsigned long)key->entries & ~JUMP_TYPE_MASK);
 }

 static inline bool static_key_type(struct static_key *key)
 {
 	return (unsigned long)key->entries & JUMP_TYPE_MASK;
 }

 static inline struct static_key *jump_entry_key(struct jump_entry *entry)
 {
 	return (struct static_key *)((unsigned long)entry->key & ~1UL);
 }

 static bool jump_entry_branch(struct jump_entry *entry)
 {
 	return (unsigned long)entry->key & 1UL;
 }

 static enum jump_label_type jump_label_type(struct jump_entry *entry)
 {
 	struct static_key *key = jump_entry_key(entry);
 	bool enabled = static_key_enabled(key);
 	bool branch = jump_entry_branch(entry);

 	/* See the comment in linux/jump_label.h */
 	return enabled ^ branch;
 }

 static void __jump_label_update(struct static_key *key,
 				struct jump_entry *entry,
 				struct jump_entry *stop)
 {
 	for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
 		/*
 		 * entry->code set to 0 invalidates module init text sections
 		 * kernel_text_address() verifies we are not in core kernel
 		 * init code, see jump_label_invalidate_module_init().
 		 */
 		if (entry->code && kernel_text_address(entry->code))
 			arch_jump_label_transform(entry, jump_label_type(entry));
 	}
 }

 void __init jump_label_init(void)
 {
 	struct jump_entry *iter_start = __start___jump_table;
 	struct jump_entry *iter_stop = __stop___jump_table;
 	struct static_key *key = NULL;
 	struct jump_entry *iter;

 	/*
 	 * Since we are initializing the static_key.enabled field with
 	 * with the 'raw' int values (to avoid pulling in atomic.h) in
 	 * jump_label.h, let's make sure that is safe. There are only two
 	 * cases to check since we initialize to 0 or 1.
 	 */
 	BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
 	BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);

 	if (static_key_initialized)
 		return;

 	jump_label_lock();
 	jump_label_sort_entries(iter_start, iter_stop);

 	for (iter = iter_start; iter < iter_stop; iter++) {
 		struct static_key *iterk;

 		/* rewrite NOPs */
 		if (jump_label_type(iter) == JUMP_LABEL_NOP)
 			arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);

 		iterk = jump_entry_key(iter);
 		if (iterk == key)
 			continue;

 		key = iterk;
 		/*
 		 * Set key->entries to iter, but preserve JUMP_LABEL_TRUE_BRANCH.
 		 */
 		*((unsigned long *)&key->entries) += (unsigned long)iter;
 #ifdef CONFIG_MODULES
 		key->next = NULL;
 #endif
 	}
 	static_key_initialized = true;
 	jump_label_unlock();
 }

 #ifdef CONFIG_MODULES

 static enum jump_label_type jump_label_init_type(struct jump_entry *entry)
 {
 	struct static_key *key = jump_entry_key(entry);
 	bool type = static_key_type(key);
 	bool branch = jump_entry_branch(entry);

 	/* See the comment in linux/jump_label.h */
 	return type ^ branch;
 }

 struct static_key_mod {
 	struct static_key_mod *next;
 	struct jump_entry *entries;
 	struct module *mod;
 };

 static int __jump_label_mod_text_reserved(void *start, void *end)
 {
 	struct module *mod;

 	preempt_disable();
 	mod = __module_text_address((unsigned long)start);
 	WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
 	preempt_enable();

 	if (!mod)
 		return 0;


 	return __jump_label_text_reserved(mod->jump_entries,
 				mod->jump_entries + mod->num_jump_entries,
 				start, end);
 }

 static void __jump_label_mod_update(struct static_key *key)
 {
 	struct static_key_mod *mod;

 	for (mod = key->next; mod; mod = mod->next) {
 		struct module *m = mod->mod;

 		__jump_label_update(key, mod->entries,
 				    m->jump_entries + m->num_jump_entries);
 	}
 }

 /***
  * apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
  * @mod: module to patch
  *
  * Allow for run-time selection of the optimal nops. Before the module
  * loads patch these with arch_get_jump_label_nop(), which is specified by
  * the arch specific jump label code.
  */
 void jump_label_apply_nops(struct module *mod)
 {
 	struct jump_entry *iter_start = mod->jump_entries;
 	struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 	struct jump_entry *iter;

 	/* if the module doesn't have jump label entries, just return */
 	if (iter_start == iter_stop)
 		return;

 	for (iter = iter_start; iter < iter_stop; iter++) {
 		/* Only write NOPs for arch_branch_static(). */
 		if (jump_label_init_type(iter) == JUMP_LABEL_NOP)
 			arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
 	}
 }

 static int jump_label_add_module(struct module *mod)
 {
 	struct jump_entry *iter_start = mod->jump_entries;
 	struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 	struct jump_entry *iter;
 	struct static_key *key = NULL;
 	struct static_key_mod *jlm;

 	/* if the module doesn't have jump label entries, just return */
 	if (iter_start == iter_stop)
 		return 0;

 	jump_label_sort_entries(iter_start, iter_stop);

 	for (iter = iter_start; iter < iter_stop; iter++) {
 		struct static_key *iterk;

 		iterk = jump_entry_key(iter);
 		if (iterk == key)
 			continue;

 		key = iterk;
 		if (within_module(iter->key, mod)) {
 			/*
 			 * Set key->entries to iter, but preserve JUMP_LABEL_TRUE_BRANCH.
 			 */
 			*((unsigned long *)&key->entries) += (unsigned long)iter;
 			key->next = NULL;
 			continue;
 		}
 		jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
 		if (!jlm)
 			return -ENOMEM;
 		jlm->mod = mod;
 		jlm->entries = iter;
 		jlm->next = key->next;
 		key->next = jlm;

 		/* Only update if we've changed from our initial state */
 		if (jump_label_type(iter) != jump_label_init_type(iter))
 			__jump_label_update(key, iter, iter_stop);
 	}

 	return 0;
 }

 static void jump_label_del_module(struct module *mod)
 {
 	struct jump_entry *iter_start = mod->jump_entries;
 	struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 	struct jump_entry *iter;
 	struct static_key *key = NULL;
 	struct static_key_mod *jlm, **prev;

 	for (iter = iter_start; iter < iter_stop; iter++) {
 		if (jump_entry_key(iter) == key)
 			continue;

 		key = jump_entry_key(iter);

 		if (within_module(iter->key, mod))
 			continue;

 		prev = &key->next;
 		jlm = key->next;

 		while (jlm && jlm->mod != mod) {
 			prev = &jlm->next;
 			jlm = jlm->next;
 		}

 		if (jlm) {
 			*prev = jlm->next;
 			kfree(jlm);
 		}
 	}
 }

 static void jump_label_invalidate_module_init(struct module *mod)
 {
 	struct jump_entry *iter_start = mod->jump_entries;
 	struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
 	struct jump_entry *iter;

 	for (iter = iter_start; iter < iter_stop; iter++) {
 		if (within_module_init(iter->code, mod))
 			iter->code = 0;
 	}
 }

 static int
 jump_label_module_notify(struct notifier_block *self, unsigned long val,
 			 void *data)
 {
 	struct module *mod = data;
 	int ret = 0;

 	switch (val) {
 	case MODULE_STATE_COMING:
 		jump_label_lock();
 		ret = jump_label_add_module(mod);
 		if (ret)
 			jump_label_del_module(mod);
 		jump_label_unlock();
 		break;
 	case MODULE_STATE_GOING:
 		jump_label_lock();
 		jump_label_del_module(mod);
 		jump_label_unlock();
 		break;
 	case MODULE_STATE_LIVE:
 		jump_label_lock();
 		jump_label_invalidate_module_init(mod);
 		jump_label_unlock();
 		break;
 	}

 	return notifier_from_errno(ret);
 }

 static struct notifier_block jump_label_module_nb = {
 	.notifier_call = jump_label_module_notify,
 	.priority = 1, /* higher than tracepoints */
 };

 static __init int jump_label_init_module(void)
 {
 	return register_module_notifier(&jump_label_module_nb);
 }
 early_initcall(jump_label_init_module);

 #endif /* CONFIG_MODULES */

 /***
  * jump_label_text_reserved - check if addr range is reserved
  * @start: start text addr
  * @end: end text addr
  *
  * checks if the text addr located between @start and @end
  * overlaps with any of the jump label patch addresses. Code
  * that wants to modify kernel text should first verify that
  * it does not overlap with any of the jump label addresses.
  * Caller must hold jump_label_mutex.
  *
  * returns 1 if there is an overlap, 0 otherwise
  */
 int jump_label_text_reserved(void *start, void *end)
 {
 	int ret = __jump_label_text_reserved(__start___jump_table,
 			__stop___jump_table, start, end);

 	if (ret)
 		return ret;

 #ifdef CONFIG_MODULES
 	ret = __jump_label_mod_text_reserved(start, end);
 #endif
 	return ret;
 }

 static void jump_label_update(struct static_key *key)
 {
 	struct jump_entry *stop = __stop___jump_table;
 	struct jump_entry *entry = static_key_entries(key);
 #ifdef CONFIG_MODULES
 	struct module *mod;

 	__jump_label_mod_update(key);

 	preempt_disable();
 	mod = __module_address((unsigned long)key);
 	if (mod)
 		stop = mod->jump_entries + mod->num_jump_entries;
 	preempt_enable();
 #endif
 	/* if there are no users, entry can be NULL */
 	if (entry)
 		__jump_label_update(key, entry, stop);
 }

 #ifdef CONFIG_STATIC_KEYS_SELFTEST
 static DEFINE_STATIC_KEY_TRUE(sk_true);
 static DEFINE_STATIC_KEY_FALSE(sk_false);

 static __init int jump_label_test(void)
 {
 	int i;

 	for (i = 0; i < 2; i++) {
 		WARN_ON(static_key_enabled(&sk_true.key) != true);
 		WARN_ON(static_key_enabled(&sk_false.key) != false);

 		WARN_ON(!static_branch_likely(&sk_true));
 		WARN_ON(!static_branch_unlikely(&sk_true));
 		WARN_ON(static_branch_likely(&sk_false));
 		WARN_ON(static_branch_unlikely(&sk_false));

 		static_branch_disable(&sk_true);
 		static_branch_enable(&sk_false);

 		WARN_ON(static_key_enabled(&sk_true.key) == true);
 		WARN_ON(static_key_enabled(&sk_false.key) == false);

 		WARN_ON(static_branch_likely(&sk_true));
 		WARN_ON(static_branch_unlikely(&sk_true));
 		WARN_ON(!static_branch_likely(&sk_false));
 		WARN_ON(!static_branch_unlikely(&sk_false));

 		static_branch_enable(&sk_true);
 		static_branch_disable(&sk_false);
 	}

 	return 0;
 }
 late_initcall(jump_label_test);
 #endif /* STATIC_KEYS_SELFTEST */

 #endif /* HAVE_JUMP_LABEL */
	/*
	* jump label support
	*
	* Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
	* Copyright (C) 2011 Peter Zijlstra
	*
	*/
	#include <linux/memory.h>
	#include <linux/uaccess.h>
	#include <linux/module.h>
	#include <linux/list.h>
	#include <linux/slab.h>
	#include <linux/sort.h>
	#include <linux/err.h>
	#include <linux/static_key.h>
	#include <linux/jump_label_ratelimit.h>
	#include <linux/bug.h>

	#ifdef HAVE_JUMP_LABEL

	/* mutex to protect coming/going of the the jump_label table */
	static DEFINE_MUTEX(jump_label_mutex);

	void jump_label_lock(void)
	{
	mutex_lock(&jump_label_mutex);
	}

	void jump_label_unlock(void)
	{
	mutex_unlock(&jump_label_mutex);
	}

	static int jump_label_cmp(const void a, const void b)
	{
	const struct jump_entry *jea = a;
	const struct jump_entry *jeb = b;

	if (jea->key < jeb->key)
	return -1;

	if (jea->key > jeb->key)
	return 1;

	return 0;
	}

	static void
	jump_label_sort_entries(struct jump_entry start, struct jump_entry stop)
	{
	unsigned long size;

	size = (((unsigned long)stop - (unsigned long)start)
	/ sizeof(struct jump_entry));
	sort(start, size, sizeof(struct jump_entry), jump_label_cmp, NULL);
	}

	static void jump_label_update(struct static_key *key);

	/*
	* There are similar definitions for the !HAVE_JUMP_LABEL case in jump_label.h.
	* The use of 'atomic_read()' requires atomic.h and its problematic for some
	* kernel headers such as kernel.h and others. Since static_key_count() is not
	* used in the branch statements as it is for the !HAVE_JUMP_LABEL case its ok
	* to have it be a function here. Similarly, for 'static_key_enable()' and
	* 'static_key_disable()', which require bug.h. This should allow jump_label.h
	* to be included from most/all places for HAVE_JUMP_LABEL.
	*/
	int static_key_count(struct static_key *key)
	{
	/*
	* -1 means the first static_key_slow_inc() is in progress.
	* static_key_enabled() must return true, so return 1 here.
	*/
	int n = atomic_read(&key->enabled);

	return n >= 0 ? n : 1;
	}
	EXPORT_SYMBOL_GPL(static_key_count);

	void static_key_enable(struct static_key *key)
	{
	int count = static_key_count(key);

	WARN_ON_ONCE(count < 0 \|\| count > 1);

	if (!count)
	static_key_slow_inc(key);
	}
	EXPORT_SYMBOL_GPL(static_key_enable);

	void static_key_disable(struct static_key *key)
	{
	int count = static_key_count(key);

	WARN_ON_ONCE(count < 0 \|\| count > 1);

	if (count)
	static_key_slow_dec(key);
	}
	EXPORT_SYMBOL_GPL(static_key_disable);

	void static_key_slow_inc(struct static_key *key)
	{
	int v, v1;

	STATIC_KEY_CHECK_USE();

	/*
	* Careful if we get concurrent static_key_slow_inc() calls;
	* later calls must wait for the first one to _finish_ the
	* jump_label_update() process. At the same time, however,
	* the jump_label_update() call below wants to see
	* static_key_enabled(&key) for jumps to be updated properly.
	*
	* So give a special meaning to negative key->enabled: it sends
	* static_key_slow_inc() down the slow path, and it is non-zero
	* so it counts as "enabled" in jump_label_update(). Note that
	* atomic_inc_unless_negative() checks >= 0, so roll our own.
	*/
	for (v = atomic_read(&key->enabled); v > 0; v = v1) {
	v1 = atomic_cmpxchg(&key->enabled, v, v + 1);
	if (likely(v1 == v))
	return;
	}

	jump_label_lock();
	if (atomic_read(&key->enabled) == 0) {
	atomic_set(&key->enabled, -1);
	jump_label_update(key);
	atomic_set(&key->enabled, 1);
	} else {
	atomic_inc(&key->enabled);
	}
	jump_label_unlock();
	}
	EXPORT_SYMBOL_GPL(static_key_slow_inc);

	static void __static_key_slow_dec(struct static_key *key,
	unsigned long rate_limit, struct delayed_work *work)
	{
	/*
	* The negative count check is valid even when a negative
	* key->enabled is in use by static_key_slow_inc(); a
	* __static_key_slow_dec() before the first static_key_slow_inc()
	* returns is unbalanced, because all other static_key_slow_inc()
	* instances block while the update is in progress.
	*/
	if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex)) {
	WARN(atomic_read(&key->enabled) < 0,
	"jump label: negative count!\n");
	return;
	}

	if (rate_limit) {
	atomic_inc(&key->enabled);
	schedule_delayed_work(work, rate_limit);
	} else {
	jump_label_update(key);
	}
	jump_label_unlock();
	}

	static void jump_label_update_timeout(struct work_struct *work)
	{
	struct static_key_deferred *key =
	container_of(work, struct static_key_deferred, work.work);
	__static_key_slow_dec(&key->key, 0, NULL);
	}

	void static_key_slow_dec(struct static_key *key)
	{
	STATIC_KEY_CHECK_USE();
	__static_key_slow_dec(key, 0, NULL);
	}
	EXPORT_SYMBOL_GPL(static_key_slow_dec);

	void static_key_slow_dec_deferred(struct static_key_deferred *key)
	{
	STATIC_KEY_CHECK_USE();
	__static_key_slow_dec(&key->key, key->timeout, &key->work);
	}
	EXPORT_SYMBOL_GPL(static_key_slow_dec_deferred);

	void jump_label_rate_limit(struct static_key_deferred *key,
	unsigned long rl)
	{
	STATIC_KEY_CHECK_USE();
	key->timeout = rl;
	INIT_DELAYED_WORK(&key->work, jump_label_update_timeout);
	}
	EXPORT_SYMBOL_GPL(jump_label_rate_limit);

	static int addr_conflict(struct jump_entry entry, void start, void *end)
	{
	if (entry->code <= (unsigned long)end &&
	entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
	return 1;

	return 0;
	}

	static int __jump_label_text_reserved(struct jump_entry *iter_start,
	struct jump_entry iter_stop, void start, void *end)
	{
	struct jump_entry *iter;

	iter = iter_start;
	while (iter < iter_stop) {
	if (addr_conflict(iter, start, end))
	return 1;
	iter++;
	}

	return 0;
	}

	/*
	* Update code which is definitely not currently executing.
	* Architectures which need heavyweight synchronization to modify
	* running code can override this to make the non-live update case
	* cheaper.
	*/
	void __weak __init_or_module arch_jump_label_transform_static(struct jump_entry *entry,
	enum jump_label_type type)
	{
	arch_jump_label_transform(entry, type);
	}

	static inline struct jump_entry static_key_entries(struct static_key key)
	{
	return (struct jump_entry *)((unsigned long)key->entries & ~JUMP_TYPE_MASK);
	}

	static inline bool static_key_type(struct static_key *key)
	{
	return (unsigned long)key->entries & JUMP_TYPE_MASK;
	}

	static inline struct static_key jump_entry_key(struct jump_entry entry)
	{
	return (struct static_key *)((unsigned long)entry->key & ~1UL);
	}

	static bool jump_entry_branch(struct jump_entry *entry)
	{
	return (unsigned long)entry->key & 1UL;
	}

	static enum jump_label_type jump_label_type(struct jump_entry *entry)
	{
	struct static_key *key = jump_entry_key(entry);
	bool enabled = static_key_enabled(key);
	bool branch = jump_entry_branch(entry);

	/* See the comment in linux/jump_label.h */
	return enabled ^ branch;
	}

	static void __jump_label_update(struct static_key *key,
	struct jump_entry *entry,
	struct jump_entry *stop)
	{
	for (; (entry < stop) && (jump_entry_key(entry) == key); entry++) {
	/*
	* entry->code set to 0 invalidates module init text sections
	* kernel_text_address() verifies we are not in core kernel
	* init code, see jump_label_invalidate_module_init().
	*/
	if (entry->code && kernel_text_address(entry->code))
	arch_jump_label_transform(entry, jump_label_type(entry));
	}
	}

	void __init jump_label_init(void)
	{
	struct jump_entry *iter_start = __start___jump_table;
	struct jump_entry *iter_stop = __stop___jump_table;
	struct static_key *key = NULL;
	struct jump_entry *iter;

	/*
	* Since we are initializing the static_key.enabled field with
	* with the 'raw' int values (to avoid pulling in atomic.h) in
	* jump_label.h, let's make sure that is safe. There are only two
	* cases to check since we initialize to 0 or 1.
	*/
	BUILD_BUG_ON((int)ATOMIC_INIT(0) != 0);
	BUILD_BUG_ON((int)ATOMIC_INIT(1) != 1);

	if (static_key_initialized)
	return;

	jump_label_lock();
	jump_label_sort_entries(iter_start, iter_stop);

	for (iter = iter_start; iter < iter_stop; iter++) {
	struct static_key *iterk;

	/* rewrite NOPs */
	if (jump_label_type(iter) == JUMP_LABEL_NOP)
	arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);

	iterk = jump_entry_key(iter);
	if (iterk == key)
	continue;

	key = iterk;
	/*
	* Set key->entries to iter, but preserve JUMP_LABEL_TRUE_BRANCH.
	*/
	((unsigned long )&key->entries) += (unsigned long)iter;
	#ifdef CONFIG_MODULES
	key->next = NULL;
	#endif
	}
	static_key_initialized = true;
	jump_label_unlock();
	}

	#ifdef CONFIG_MODULES

	static enum jump_label_type jump_label_init_type(struct jump_entry *entry)
	{
	struct static_key *key = jump_entry_key(entry);
	bool type = static_key_type(key);
	bool branch = jump_entry_branch(entry);

	/* See the comment in linux/jump_label.h */
	return type ^ branch;
	}

	struct static_key_mod {
	struct static_key_mod *next;
	struct jump_entry *entries;
	struct module *mod;
	};

	static int __jump_label_mod_text_reserved(void start, void end)
	{
	struct module *mod;

	preempt_disable();
	mod = __module_text_address((unsigned long)start);
	WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
	preempt_enable();

	if (!mod)
	return 0;


	return __jump_label_text_reserved(mod->jump_entries,
	mod->jump_entries + mod->num_jump_entries,
	start, end);
	}

	static void __jump_label_mod_update(struct static_key *key)
	{
	struct static_key_mod *mod;

	for (mod = key->next; mod; mod = mod->next) {
	struct module *m = mod->mod;

	__jump_label_update(key, mod->entries,
	m->jump_entries + m->num_jump_entries);
	}
	}

	/***
	* apply_jump_label_nops - patch module jump labels with arch_get_jump_label_nop()
	* @mod: module to patch
	*
	* Allow for run-time selection of the optimal nops. Before the module
	* loads patch these with arch_get_jump_label_nop(), which is specified by
	* the arch specific jump label code.
	*/
	void jump_label_apply_nops(struct module *mod)
	{
	struct jump_entry *iter_start = mod->jump_entries;
	struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
	struct jump_entry *iter;

	/* if the module doesn't have jump label entries, just return */
	if (iter_start == iter_stop)
	return;

	for (iter = iter_start; iter < iter_stop; iter++) {
	/* Only write NOPs for arch_branch_static(). */
	if (jump_label_init_type(iter) == JUMP_LABEL_NOP)
	arch_jump_label_transform_static(iter, JUMP_LABEL_NOP);
	}
	}

	static int jump_label_add_module(struct module *mod)
	{
	struct jump_entry *iter_start = mod->jump_entries;
	struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
	struct jump_entry *iter;
	struct static_key *key = NULL;
	struct static_key_mod *jlm;

	/* if the module doesn't have jump label entries, just return */
	if (iter_start == iter_stop)
	return 0;

	jump_label_sort_entries(iter_start, iter_stop);

	for (iter = iter_start; iter < iter_stop; iter++) {
	struct static_key *iterk;

	iterk = jump_entry_key(iter);
	if (iterk == key)
	continue;

	key = iterk;
	if (within_module(iter->key, mod)) {
	/*
	* Set key->entries to iter, but preserve JUMP_LABEL_TRUE_BRANCH.
	*/
	((unsigned long )&key->entries) += (unsigned long)iter;
	key->next = NULL;
	continue;
	}
	jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);
	if (!jlm)
	return -ENOMEM;
	jlm->mod = mod;
	jlm->entries = iter;
	jlm->next = key->next;
	key->next = jlm;

	/* Only update if we've changed from our initial state */
	if (jump_label_type(iter) != jump_label_init_type(iter))
	__jump_label_update(key, iter, iter_stop);
	}

	return 0;
	}

	static void jump_label_del_module(struct module *mod)
	{
	struct jump_entry *iter_start = mod->jump_entries;
	struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
	struct jump_entry *iter;
	struct static_key *key = NULL;
	struct static_key_mod jlm, *prev;

	for (iter = iter_start; iter < iter_stop; iter++) {
	if (jump_entry_key(iter) == key)
	continue;

	key = jump_entry_key(iter);

	if (within_module(iter->key, mod))
	continue;

	prev = &key->next;
	jlm = key->next;

	while (jlm && jlm->mod != mod) {
	prev = &jlm->next;
	jlm = jlm->next;
	}

	if (jlm) {
	*prev = jlm->next;
	kfree(jlm);
	}
	}
	}

	static void jump_label_invalidate_module_init(struct module *mod)
	{
	struct jump_entry *iter_start = mod->jump_entries;
	struct jump_entry *iter_stop = iter_start + mod->num_jump_entries;
	struct jump_entry *iter;

	for (iter = iter_start; iter < iter_stop; iter++) {
	if (within_module_init(iter->code, mod))
	iter->code = 0;
	}
	}

	static int
	jump_label_module_notify(struct notifier_block *self, unsigned long val,
	void *data)
	{
	struct module *mod = data;
	int ret = 0;

	switch (val) {
	case MODULE_STATE_COMING:
	jump_label_lock();
	ret = jump_label_add_module(mod);
	if (ret)
	jump_label_del_module(mod);
	jump_label_unlock();
	break;
	case MODULE_STATE_GOING:
	jump_label_lock();
	jump_label_del_module(mod);
	jump_label_unlock();
	break;
	case MODULE_STATE_LIVE:
	jump_label_lock();
	jump_label_invalidate_module_init(mod);
	jump_label_unlock();
	break;
	}

	return notifier_from_errno(ret);
	}

	static struct notifier_block jump_label_module_nb = {
	.notifier_call = jump_label_module_notify,
	.priority = 1, /* higher than tracepoints */
	};

	static __init int jump_label_init_module(void)
	{
	return register_module_notifier(&jump_label_module_nb);
	}
	early_initcall(jump_label_init_module);

	#endif /* CONFIG_MODULES */

	/***
	* jump_label_text_reserved - check if addr range is reserved
	* @start: start text addr
	* @end: end text addr
	*
	* checks if the text addr located between @start and @end
	* overlaps with any of the jump label patch addresses. Code
	* that wants to modify kernel text should first verify that
	* it does not overlap with any of the jump label addresses.
	* Caller must hold jump_label_mutex.
	*
	* returns 1 if there is an overlap, 0 otherwise
	*/
	int jump_label_text_reserved(void start, void end)
	{
	int ret = __jump_label_text_reserved(__start___jump_table,
	__stop___jump_table, start, end);

	if (ret)
	return ret;

	#ifdef CONFIG_MODULES
	ret = __jump_label_mod_text_reserved(start, end);
	#endif
	return ret;
	}

	static void jump_label_update(struct static_key *key)
	{
	struct jump_entry *stop = __stop___jump_table;
	struct jump_entry *entry = static_key_entries(key);
	#ifdef CONFIG_MODULES
	struct module *mod;

	__jump_label_mod_update(key);

	preempt_disable();
	mod = __module_address((unsigned long)key);
	if (mod)
	stop = mod->jump_entries + mod->num_jump_entries;
	preempt_enable();
	#endif
	/* if there are no users, entry can be NULL */
	if (entry)
	__jump_label_update(key, entry, stop);
	}

	#ifdef CONFIG_STATIC_KEYS_SELFTEST
	static DEFINE_STATIC_KEY_TRUE(sk_true);
	static DEFINE_STATIC_KEY_FALSE(sk_false);

	static __init int jump_label_test(void)
	{
	int i;

	for (i = 0; i < 2; i++) {
	WARN_ON(static_key_enabled(&sk_true.key) != true);
	WARN_ON(static_key_enabled(&sk_false.key) != false);

	WARN_ON(!static_branch_likely(&sk_true));
	WARN_ON(!static_branch_unlikely(&sk_true));
	WARN_ON(static_branch_likely(&sk_false));
	WARN_ON(static_branch_unlikely(&sk_false));

	static_branch_disable(&sk_true);
	static_branch_enable(&sk_false);

	WARN_ON(static_key_enabled(&sk_true.key) == true);
	WARN_ON(static_key_enabled(&sk_false.key) == false);

	WARN_ON(static_branch_likely(&sk_true));
	WARN_ON(static_branch_unlikely(&sk_true));
	WARN_ON(!static_branch_likely(&sk_false));
	WARN_ON(!static_branch_unlikely(&sk_false));

	static_branch_enable(&sk_true);
	static_branch_disable(&sk_false);
	}

	return 0;
	}
	late_initcall(jump_label_test);
	#endif /* STATIC_KEYS_SELFTEST */

	#endif /* HAVE_JUMP_LABEL */