/*
   * 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/static_key.h>

  #include <linux/jump_label_ratelimit.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, int enable);

  void static_key_slow_inc(struct static_key *key)

  {

  	STATIC_KEY_CHECK_USE();

  	if (atomic_inc_not_zero(&key->enabled))
  		return;

  	jump_label_lock();

  	if (atomic_read(&key->enabled) == 0) {
  		if (!jump_label_get_branch_default(key))
  			jump_label_update(key, JUMP_LABEL_ENABLE);
  		else
  			jump_label_update(key, JUMP_LABEL_DISABLE);
  	}

  	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)

  {

  	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 {
  		if (!jump_label_get_branch_default(key))
  			jump_label_update(key, JUMP_LABEL_DISABLE);
  		else
  			jump_label_update(key, JUMP_LABEL_ENABLE);
  	}

  	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 void __jump_label_update(struct static_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);
  	}

  }

  static enum jump_label_type jump_label_type(struct static_key *key)
  {
  	bool true_branch = jump_label_get_branch_default(key);
  	bool state = static_key_enabled(key);
  
  	if ((!true_branch && state) || (true_branch && !state))
  		return JUMP_LABEL_ENABLE;
  
  	return JUMP_LABEL_DISABLE;
  }

  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;

  	jump_label_lock();

  	jump_label_sort_entries(iter_start, iter_stop);
  
  	for (iter = iter_start; iter < iter_stop; iter++) {

  		struct static_key *iterk;

  		iterk = (struct static_key *)(unsigned long)iter->key;
  		arch_jump_label_transform_static(iter, jump_label_type(iterk));

  		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

  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;
  
  	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 static_key *key, int enable)

  {

  	struct static_key_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_transform_static(iter, JUMP_LABEL_DISABLE);

  	}

  }

  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 = (struct static_key *)(unsigned long)iter->key;
  		if (iterk == key)
  			continue;

  		key = iterk;

  		if (__module_address(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;

  		if (jump_label_type(key) == JUMP_LABEL_ENABLE)

  			__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 static_key *key = NULL;
  	struct static_key_mod *jlm, **prev;

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

  		key = (struct static_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 static_key *key, int enable)

  {

  	struct jump_entry *stop = __stop___jump_table;
  	struct jump_entry *entry = jump_label_get_entries(key);

  
  #ifdef CONFIG_MODULES

  	struct module *mod = __module_address((unsigned long)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