/*
   * 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>

  #include <linux/cpu.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);

  static void static_key_slow_inc_cpuslocked(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);

  		/*
  		 * Ensure that if the above cmpxchg loop observes our positive
  		 * value, it must also observe all the text changes.
  		 */
  		atomic_set_release(&key->enabled, 1);

  	} else {
  		atomic_inc(&key->enabled);
  	}

  	jump_label_unlock();

  }
  
  void static_key_slow_inc(struct static_key *key)
  {
  	cpus_read_lock();
  	static_key_slow_inc_cpuslocked(key);

  	cpus_read_unlock();

  }

  EXPORT_SYMBOL_GPL(static_key_slow_inc);

  void static_key_enable_cpuslocked(struct static_key *key)

  {
  	STATIC_KEY_CHECK_USE();

  	if (atomic_read(&key->enabled) > 0) {
  		WARN_ON_ONCE(atomic_read(&key->enabled) != 1);
  		return;
  	}

  	jump_label_lock();
  	if (atomic_read(&key->enabled) == 0) {
  		atomic_set(&key->enabled, -1);
  		jump_label_update(key);

  		/*
  		 * See static_key_slow_inc().
  		 */
  		atomic_set_release(&key->enabled, 1);

  	}
  	jump_label_unlock();

  }
  EXPORT_SYMBOL_GPL(static_key_enable_cpuslocked);
  
  void static_key_enable(struct static_key *key)
  {
  	cpus_read_lock();
  	static_key_enable_cpuslocked(key);

  	cpus_read_unlock();
  }
  EXPORT_SYMBOL_GPL(static_key_enable);

  void static_key_disable_cpuslocked(struct static_key *key)

  {
  	STATIC_KEY_CHECK_USE();

  	if (atomic_read(&key->enabled) != 1) {
  		WARN_ON_ONCE(atomic_read(&key->enabled) != 0);
  		return;
  	}

  	jump_label_lock();
  	if (atomic_cmpxchg(&key->enabled, 1, 0))
  		jump_label_update(key);
  	jump_label_unlock();

  }
  EXPORT_SYMBOL_GPL(static_key_disable_cpuslocked);
  
  void static_key_disable(struct static_key *key)
  {
  	cpus_read_lock();
  	static_key_disable_cpuslocked(key);

  	cpus_read_unlock();
  }
  EXPORT_SYMBOL_GPL(static_key_disable);

  static void static_key_slow_dec_cpuslocked(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!
  ");

  		return;

  	}

  	if (rate_limit) {
  		atomic_inc(&key->enabled);
  		schedule_delayed_work(work, rate_limit);

  	} else {

  		jump_label_update(key);

  	}

  	jump_label_unlock();

  }
  
  static void __static_key_slow_dec(struct static_key *key,
  				  unsigned long rate_limit,
  				  struct delayed_work *work)
  {
  	cpus_read_lock();
  	static_key_slow_dec_cpuslocked(key, rate_limit, work);

  	cpus_read_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 static_key_deferred_flush(struct static_key_deferred *key)
  {
  	STATIC_KEY_CHECK_USE();
  	flush_delayed_work(&key->work);
  }
  EXPORT_SYMBOL_GPL(static_key_deferred_flush);

  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)

  {

  	WARN_ON_ONCE(key->type & JUMP_TYPE_LINKED);
  	return (struct jump_entry *)(key->type & ~JUMP_TYPE_MASK);

  }

  static inline bool static_key_type(struct static_key *key)

  {

  	return key->type & JUMP_TYPE_TRUE;
  }
  
  static inline bool static_key_linked(struct static_key *key)
  {
  	return key->type & JUMP_TYPE_LINKED;
  }
  
  static inline void static_key_clear_linked(struct static_key *key)
  {
  	key->type &= ~JUMP_TYPE_LINKED;
  }
  
  static inline void static_key_set_linked(struct static_key *key)
  {
  	key->type |= JUMP_TYPE_LINKED;

  }

  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;

  }

  /***
   * A 'struct static_key' uses a union such that it either points directly
   * to a table of 'struct jump_entry' or to a linked list of modules which in
   * turn point to 'struct jump_entry' tables.
   *
   * The two lower bits of the pointer are used to keep track of which pointer
   * type is in use and to store the initial branch direction, we use an access
   * function which preserves these bits.
   */
  static void static_key_set_entries(struct static_key *key,
  				   struct jump_entry *entries)
  {
  	unsigned long type;
  
  	WARN_ON_ONCE((unsigned long)entries & JUMP_TYPE_MASK);
  	type = key->type & JUMP_TYPE_MASK;
  	key->entries = entries;
  	key->type |= type;
  }

  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;

  	cpus_read_lock();

  	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;

  		static_key_set_entries(key, iter);

  	}

  	static_key_initialized = true;

  	jump_label_unlock();

  	cpus_read_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 inline struct static_key_mod *static_key_mod(struct static_key *key)
  {
  	WARN_ON_ONCE(!(key->type & JUMP_TYPE_LINKED));
  	return (struct static_key_mod *)(key->type & ~JUMP_TYPE_MASK);
  }
  
  /***
   * key->type and key->next are the same via union.
   * This sets key->next and preserves the type bits.
   *
   * See additional comments above static_key_set_entries().
   */
  static void static_key_set_mod(struct static_key *key,
  			       struct static_key_mod *mod)
  {
  	unsigned long type;
  
  	WARN_ON_ONCE((unsigned long)mod & JUMP_TYPE_MASK);
  	type = key->type & JUMP_TYPE_MASK;
  	key->next = mod;
  	key->type |= type;
  }

  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 = static_key_mod(key); mod; mod = mod->next) {
  		struct jump_entry *stop;
  		struct module *m;
  
  		/*
  		 * NULL if the static_key is defined in a module
  		 * that does not use it
  		 */
  		if (!mod->entries)
  			continue;

  		m = mod->mod;
  		if (!m)
  			stop = __stop___jump_table;
  		else
  			stop = m->jump_entries + m->num_jump_entries;
  		__jump_label_update(key, mod->entries, stop);

  	}
  }
  
  /***
   * 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, *jlm2;

  
  	/* 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)) {

  			static_key_set_entries(key, iter);

  			continue;

  		}

  		jlm = kzalloc(sizeof(struct static_key_mod), GFP_KERNEL);

  		if (!jlm)
  			return -ENOMEM;

  		if (!static_key_linked(key)) {
  			jlm2 = kzalloc(sizeof(struct static_key_mod),
  				       GFP_KERNEL);
  			if (!jlm2) {
  				kfree(jlm);
  				return -ENOMEM;
  			}
  			preempt_disable();
  			jlm2->mod = __module_address((unsigned long)key);
  			preempt_enable();
  			jlm2->entries = static_key_entries(key);
  			jlm2->next = NULL;
  			static_key_set_mod(key, jlm2);
  			static_key_set_linked(key);
  		}

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

  		jlm->next = static_key_mod(key);
  		static_key_set_mod(key, jlm);
  		static_key_set_linked(key);

  		/* 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;

  		/* No memory during module load */
  		if (WARN_ON(!static_key_linked(key)))
  			continue;

  		prev = &key->next;

  		jlm = static_key_mod(key);

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

  		/* No memory during module load */
  		if (WARN_ON(!jlm))
  			continue;
  
  		if (prev == &key->next)
  			static_key_set_mod(key, jlm->next);
  		else

  			*prev = jlm->next;

  
  		kfree(jlm);
  
  		jlm = static_key_mod(key);
  		/* if only one etry is left, fold it back into the static_key */
  		if (jlm->next == NULL) {
  			static_key_set_entries(key, jlm->entries);
  			static_key_clear_linked(key);

  			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;

  	cpus_read_lock();
  	jump_label_lock();

  	switch (val) {
  	case MODULE_STATE_COMING:

  		ret = jump_label_add_module(mod);

  		if (ret) {
  			WARN(1, "Failed to allocatote memory: jump_label may not work properly.
  ");

  			jump_label_del_module(mod);

  		}

  		break;
  	case MODULE_STATE_GOING:

  		jump_label_del_module(mod);

  		break;

  	case MODULE_STATE_LIVE:

  		jump_label_invalidate_module_init(mod);

  		break;

  	}

  	jump_label_unlock();
  	cpus_read_unlock();

  	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;

  #ifdef CONFIG_MODULES

  	struct module *mod;

  	if (static_key_linked(key)) {
  		__jump_label_mod_update(key);
  		return;
  	}

  	preempt_disable();
  	mod = __module_address((unsigned long)key);

  	if (mod)
  		stop = mod->jump_entries + mod->num_jump_entries;

  	preempt_enable();

  #endif

  	entry = static_key_entries(key);

  	/* 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;
  }

  early_initcall(jump_label_test);

  #endif /* STATIC_KEYS_SELFTEST */
  
  #endif /* HAVE_JUMP_LABEL */