kernel/jump_label.c - linux - Git at Google

 /*
  * jump label support
  *
  * Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
  * Copyright (C) 2011 Peter Zijlstra <pzijlstr@redhat.com>
  *
  */
 #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/jump_label.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);
 }

 bool jump_label_enabled(struct jump_label_key *key)
 {
 	return !!atomic_read(&key->enabled);
 }

 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 jump_label_key *key, int enable);

 void jump_label_inc(struct jump_label_key *key)
 {
 	if (atomic_inc_not_zero(&key->enabled))
 		return;

 	jump_label_lock();
 	if (atomic_add_return(1, &key->enabled) == 1)
 		jump_label_update(key, JUMP_LABEL_ENABLE);
 	jump_label_unlock();
 }

 void jump_label_dec(struct jump_label_key *key)
 {
 	if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex))
 		return;

 	jump_label_update(key, JUMP_LABEL_DISABLE);
 	jump_label_unlock();
 }

 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;
 }

 static void __jump_label_update(struct jump_label_key *key,
 				struct jump_entry *entry,
 				struct jump_entry *stop, int enable)
 {
 	for (; (entry < stop) &&
 	      (entry->key == (jump_label_t)(unsigned long)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, enable);
 	}
 }

 /*
  * Not all archs need this.
  */
 void __weak arch_jump_label_text_poke_early(jump_label_t addr)
 {
 }

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

 	jump_label_lock();
 	jump_label_sort_entries(iter_start, iter_stop);

 	for (iter = iter_start; iter < iter_stop; iter++) {
 		arch_jump_label_text_poke_early(iter->code);
 		if (iter->key == (jump_label_t)(unsigned long)key)
 			continue;

 		key = (struct jump_label_key *)(unsigned long)iter->key;
 		atomic_set(&key->enabled, 0);
 		key->entries = iter;
 #ifdef CONFIG_MODULES
 		key->next = NULL;
 #endif
 	}
 	jump_label_unlock();

 	return 0;
 }
 early_initcall(jump_label_init);

 #ifdef CONFIG_MODULES

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

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

 	mod = __module_text_address((unsigned long)start);
 	if (!mod)
 		return 0;

 	WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);

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

 static void __jump_label_mod_update(struct jump_label_key *key, int enable)
 {
 	struct jump_label_mod *mod = key->next;

 	while (mod) {
 		struct module *m = mod->mod;

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

 /***
  * 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++)
 		arch_jump_label_text_poke_early(iter->code);
 }

 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 jump_label_key *key = NULL;
 	struct jump_label_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++) {
 		if (iter->key == (jump_label_t)(unsigned long)key)
 			continue;

 		key = (struct jump_label_key *)(unsigned long)iter->key;

 		if (__module_address(iter->key) == mod) {
 			atomic_set(&key->enabled, 0);
 			key->entries = iter;
 			key->next = NULL;
 			continue;
 		}

 		jlm = kzalloc(sizeof(struct jump_label_mod), GFP_KERNEL);
 		if (!jlm)
 			return -ENOMEM;

 		jlm->mod = mod;
 		jlm->entries = iter;
 		jlm->next = key->next;
 		key->next = jlm;

 		if (jump_label_enabled(key))
 			__jump_label_update(key, iter, iter_stop,
 					    JUMP_LABEL_ENABLE);
 	}

 	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 jump_label_key *key = NULL;
 	struct jump_label_mod *jlm, **prev;

 	for (iter = iter_start; iter < iter_stop; iter++) {
 		if (iter->key == (jump_label_t)(unsigned long)key)
 			continue;

 		key = (struct jump_label_key *)(unsigned long)iter->key;

 		if (__module_address(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);
 }

 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 jump_label_key *key, int enable)
 {
 	struct jump_entry *entry = key->entries, *stop = __stop___jump_table;

 #ifdef CONFIG_MODULES
 	struct module *mod = __module_address((jump_label_t)key);

 	__jump_label_mod_update(key, enable);

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

 #endif
	/*
	* jump label support
	*
	* Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
	* Copyright (C) 2011 Peter Zijlstra <pzijlstr@redhat.com>
	*
	*/
	#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/jump_label.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);
	}

	bool jump_label_enabled(struct jump_label_key *key)
	{
	return !!atomic_read(&key->enabled);
	}

	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 jump_label_key *key, int enable);

	void jump_label_inc(struct jump_label_key *key)
	{
	if (atomic_inc_not_zero(&key->enabled))
	return;

	jump_label_lock();
	if (atomic_add_return(1, &key->enabled) == 1)
	jump_label_update(key, JUMP_LABEL_ENABLE);
	jump_label_unlock();
	}

	void jump_label_dec(struct jump_label_key *key)
	{
	if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex))
	return;

	jump_label_update(key, JUMP_LABEL_DISABLE);
	jump_label_unlock();
	}

	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;
	}

	static void __jump_label_update(struct jump_label_key *key,
	struct jump_entry *entry,
	struct jump_entry *stop, int enable)
	{
	for (; (entry < stop) &&
	(entry->key == (jump_label_t)(unsigned long)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, enable);
	}
	}

	/*
	* Not all archs need this.
	*/
	void __weak arch_jump_label_text_poke_early(jump_label_t addr)
	{
	}

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

	jump_label_lock();
	jump_label_sort_entries(iter_start, iter_stop);

	for (iter = iter_start; iter < iter_stop; iter++) {
	arch_jump_label_text_poke_early(iter->code);
	if (iter->key == (jump_label_t)(unsigned long)key)
	continue;

	key = (struct jump_label_key *)(unsigned long)iter->key;
	atomic_set(&key->enabled, 0);
	key->entries = iter;
	#ifdef CONFIG_MODULES
	key->next = NULL;
	#endif
	}
	jump_label_unlock();

	return 0;
	}
	early_initcall(jump_label_init);

	#ifdef CONFIG_MODULES

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

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

	mod = __module_text_address((unsigned long)start);
	if (!mod)
	return 0;

	WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);

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

	static void __jump_label_mod_update(struct jump_label_key *key, int enable)
	{
	struct jump_label_mod *mod = key->next;

	while (mod) {
	struct module *m = mod->mod;

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

	/***
	* 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++)
	arch_jump_label_text_poke_early(iter->code);
	}

	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 jump_label_key *key = NULL;
	struct jump_label_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++) {
	if (iter->key == (jump_label_t)(unsigned long)key)
	continue;

	key = (struct jump_label_key *)(unsigned long)iter->key;

	if (__module_address(iter->key) == mod) {
	atomic_set(&key->enabled, 0);
	key->entries = iter;
	key->next = NULL;
	continue;
	}

	jlm = kzalloc(sizeof(struct jump_label_mod), GFP_KERNEL);
	if (!jlm)
	return -ENOMEM;

	jlm->mod = mod;
	jlm->entries = iter;
	jlm->next = key->next;
	key->next = jlm;

	if (jump_label_enabled(key))
	__jump_label_update(key, iter, iter_stop,
	JUMP_LABEL_ENABLE);
	}

	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 jump_label_key *key = NULL;
	struct jump_label_mod jlm, *prev;

	for (iter = iter_start; iter < iter_stop; iter++) {
	if (iter->key == (jump_label_t)(unsigned long)key)
	continue;

	key = (struct jump_label_key *)(unsigned long)iter->key;

	if (__module_address(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);
	}

	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 jump_label_key *key, int enable)
	{
	struct jump_entry entry = key->entries, stop = __stop___jump_table;

	#ifdef CONFIG_MODULES
	struct module *mod = __module_address((jump_label_t)key);

	__jump_label_mod_update(key, enable);

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

	#endif