kernel/bpf/hashtab.c - linux - Git at Google

 /* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of version 2 of the GNU General Public
  * License as published by the Free Software Foundation.
  *
  * This program is distributed in the hope that it will be useful, but
  * WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  * General Public License for more details.
  */
 #include <linux/bpf.h>
 #include <linux/jhash.h>
 #include <linux/filter.h>
 #include <linux/vmalloc.h>

 struct bpf_htab {
 	struct bpf_map map;
 	struct hlist_head *buckets;
 	raw_spinlock_t lock;
 	u32 count;	/* number of elements in this hashtable */
 	u32 n_buckets;	/* number of hash buckets */
 	u32 elem_size;	/* size of each element in bytes */
 };

 /* each htab element is struct htab_elem + key + value */
 struct htab_elem {
 	struct hlist_node hash_node;
 	struct rcu_head rcu;
 	u32 hash;
 	char key[0] __aligned(8);
 };

 /* Called from syscall */
 static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
 {
 	struct bpf_htab *htab;
 	int err, i;

 	htab = kzalloc(sizeof(*htab), GFP_USER);
 	if (!htab)
 		return ERR_PTR(-ENOMEM);

 	/* mandatory map attributes */
 	htab->map.key_size = attr->key_size;
 	htab->map.value_size = attr->value_size;
 	htab->map.max_entries = attr->max_entries;

 	/* check sanity of attributes.
 	 * value_size == 0 may be allowed in the future to use map as a set
 	 */
 	err = -EINVAL;
 	if (htab->map.max_entries == 0 || htab->map.key_size == 0 ||
 	    htab->map.value_size == 0)
 		goto free_htab;

 	/* hash table size must be power of 2 */
 	htab->n_buckets = roundup_pow_of_two(htab->map.max_entries);

 	err = -E2BIG;
 	if (htab->map.key_size > MAX_BPF_STACK)
 		/* eBPF programs initialize keys on stack, so they cannot be
 		 * larger than max stack size
 		 */
 		goto free_htab;

 	err = -ENOMEM;
 	/* prevent zero size kmalloc and check for u32 overflow */
 	if (htab->n_buckets == 0 ||
 	    htab->n_buckets > U32_MAX / sizeof(struct hlist_head))
 		goto free_htab;

 	htab->buckets = kmalloc_array(htab->n_buckets, sizeof(struct hlist_head),
 				      GFP_USER | __GFP_NOWARN);

 	if (!htab->buckets) {
 		htab->buckets = vmalloc(htab->n_buckets * sizeof(struct hlist_head));
 		if (!htab->buckets)
 			goto free_htab;
 	}

 	for (i = 0; i < htab->n_buckets; i++)
 		INIT_HLIST_HEAD(&htab->buckets[i]);

 	raw_spin_lock_init(&htab->lock);
 	htab->count = 0;

 	htab->elem_size = sizeof(struct htab_elem) +
 			  round_up(htab->map.key_size, 8) +
 			  htab->map.value_size;

 	htab->map.pages = round_up(htab->n_buckets * sizeof(struct hlist_head) +
 				   htab->elem_size * htab->map.max_entries,
 				   PAGE_SIZE) >> PAGE_SHIFT;
 	return &htab->map;

 free_htab:
 	kfree(htab);
 	return ERR_PTR(err);
 }

 static inline u32 htab_map_hash(const void *key, u32 key_len)
 {
 	return jhash(key, key_len, 0);
 }

 static inline struct hlist_head *select_bucket(struct bpf_htab *htab, u32 hash)
 {
 	return &htab->buckets[hash & (htab->n_buckets - 1)];
 }

 static struct htab_elem *lookup_elem_raw(struct hlist_head *head, u32 hash,
 					 void *key, u32 key_size)
 {
 	struct htab_elem *l;

 	hlist_for_each_entry_rcu(l, head, hash_node)
 		if (l->hash == hash && !memcmp(&l->key, key, key_size))
 			return l;

 	return NULL;
 }

 /* Called from syscall or from eBPF program */
 static void *htab_map_lookup_elem(struct bpf_map *map, void *key)
 {
 	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
 	struct hlist_head *head;
 	struct htab_elem *l;
 	u32 hash, key_size;

 	/* Must be called with rcu_read_lock. */
 	WARN_ON_ONCE(!rcu_read_lock_held());

 	key_size = map->key_size;

 	hash = htab_map_hash(key, key_size);

 	head = select_bucket(htab, hash);

 	l = lookup_elem_raw(head, hash, key, key_size);

 	if (l)
 		return l->key + round_up(map->key_size, 8);

 	return NULL;
 }

 /* Called from syscall */
 static int htab_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
 {
 	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
 	struct hlist_head *head;
 	struct htab_elem *l, *next_l;
 	u32 hash, key_size;
 	int i;

 	WARN_ON_ONCE(!rcu_read_lock_held());

 	key_size = map->key_size;

 	hash = htab_map_hash(key, key_size);

 	head = select_bucket(htab, hash);

 	/* lookup the key */
 	l = lookup_elem_raw(head, hash, key, key_size);

 	if (!l) {
 		i = 0;
 		goto find_first_elem;
 	}

 	/* key was found, get next key in the same bucket */
 	next_l = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu(&l->hash_node)),
 				  struct htab_elem, hash_node);

 	if (next_l) {
 		/* if next elem in this hash list is non-zero, just return it */
 		memcpy(next_key, next_l->key, key_size);
 		return 0;
 	}

 	/* no more elements in this hash list, go to the next bucket */
 	i = hash & (htab->n_buckets - 1);
 	i++;

 find_first_elem:
 	/* iterate over buckets */
 	for (; i < htab->n_buckets; i++) {
 		head = select_bucket(htab, i);

 		/* pick first element in the bucket */
 		next_l = hlist_entry_safe(rcu_dereference_raw(hlist_first_rcu(head)),
 					  struct htab_elem, hash_node);
 		if (next_l) {
 			/* if it's not empty, just return it */
 			memcpy(next_key, next_l->key, key_size);
 			return 0;
 		}
 	}

 	/* itereated over all buckets and all elements */
 	return -ENOENT;
 }

 /* Called from syscall or from eBPF program */
 static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
 				u64 map_flags)
 {
 	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
 	struct htab_elem *l_new, *l_old;
 	struct hlist_head *head;
 	unsigned long flags;
 	u32 key_size;
 	int ret;

 	if (map_flags > BPF_EXIST)
 		/* unknown flags */
 		return -EINVAL;

 	WARN_ON_ONCE(!rcu_read_lock_held());

 	/* allocate new element outside of lock */
 	l_new = kmalloc(htab->elem_size, GFP_ATOMIC);
 	if (!l_new)
 		return -ENOMEM;

 	key_size = map->key_size;

 	memcpy(l_new->key, key, key_size);
 	memcpy(l_new->key + round_up(key_size, 8), value, map->value_size);

 	l_new->hash = htab_map_hash(l_new->key, key_size);

 	/* bpf_map_update_elem() can be called in_irq() */
 	raw_spin_lock_irqsave(&htab->lock, flags);

 	head = select_bucket(htab, l_new->hash);

 	l_old = lookup_elem_raw(head, l_new->hash, key, key_size);

 	if (!l_old && unlikely(htab->count >= map->max_entries)) {
 		/* if elem with this 'key' doesn't exist and we've reached
 		 * max_entries limit, fail insertion of new elem
 		 */
 		ret = -E2BIG;
 		goto err;
 	}

 	if (l_old && map_flags == BPF_NOEXIST) {
 		/* elem already exists */
 		ret = -EEXIST;
 		goto err;
 	}

 	if (!l_old && map_flags == BPF_EXIST) {
 		/* elem doesn't exist, cannot update it */
 		ret = -ENOENT;
 		goto err;
 	}

 	/* add new element to the head of the list, so that concurrent
 	 * search will find it before old elem
 	 */
 	hlist_add_head_rcu(&l_new->hash_node, head);
 	if (l_old) {
 		hlist_del_rcu(&l_old->hash_node);
 		kfree_rcu(l_old, rcu);
 	} else {
 		htab->count++;
 	}
 	raw_spin_unlock_irqrestore(&htab->lock, flags);

 	return 0;
 err:
 	raw_spin_unlock_irqrestore(&htab->lock, flags);
 	kfree(l_new);
 	return ret;
 }

 /* Called from syscall or from eBPF program */
 static int htab_map_delete_elem(struct bpf_map *map, void *key)
 {
 	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
 	struct hlist_head *head;
 	struct htab_elem *l;
 	unsigned long flags;
 	u32 hash, key_size;
 	int ret = -ENOENT;

 	WARN_ON_ONCE(!rcu_read_lock_held());

 	key_size = map->key_size;

 	hash = htab_map_hash(key, key_size);

 	raw_spin_lock_irqsave(&htab->lock, flags);

 	head = select_bucket(htab, hash);

 	l = lookup_elem_raw(head, hash, key, key_size);

 	if (l) {
 		hlist_del_rcu(&l->hash_node);
 		htab->count--;
 		kfree_rcu(l, rcu);
 		ret = 0;
 	}

 	raw_spin_unlock_irqrestore(&htab->lock, flags);
 	return ret;
 }

 static void delete_all_elements(struct bpf_htab *htab)
 {
 	int i;

 	for (i = 0; i < htab->n_buckets; i++) {
 		struct hlist_head *head = select_bucket(htab, i);
 		struct hlist_node *n;
 		struct htab_elem *l;

 		hlist_for_each_entry_safe(l, n, head, hash_node) {
 			hlist_del_rcu(&l->hash_node);
 			htab->count--;
 			kfree(l);
 		}
 	}
 }

 /* Called when map->refcnt goes to zero, either from workqueue or from syscall */
 static void htab_map_free(struct bpf_map *map)
 {
 	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);

 	/* at this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
 	 * so the programs (can be more than one that used this map) were
 	 * disconnected from events. Wait for outstanding critical sections in
 	 * these programs to complete
 	 */
 	synchronize_rcu();

 	/* some of kfree_rcu() callbacks for elements of this map may not have
 	 * executed. It's ok. Proceed to free residual elements and map itself
 	 */
 	delete_all_elements(htab);
 	kvfree(htab->buckets);
 	kfree(htab);
 }

 static const struct bpf_map_ops htab_ops = {
 	.map_alloc = htab_map_alloc,
 	.map_free = htab_map_free,
 	.map_get_next_key = htab_map_get_next_key,
 	.map_lookup_elem = htab_map_lookup_elem,
 	.map_update_elem = htab_map_update_elem,
 	.map_delete_elem = htab_map_delete_elem,
 };

 static struct bpf_map_type_list htab_type __read_mostly = {
 	.ops = &htab_ops,
 	.type = BPF_MAP_TYPE_HASH,
 };

 static int __init register_htab_map(void)
 {
 	bpf_register_map_type(&htab_type);
 	return 0;
 }
 late_initcall(register_htab_map);
	/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of version 2 of the GNU General Public
	* License as published by the Free Software Foundation.
	*
	* This program is distributed in the hope that it will be useful, but
	* WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	* General Public License for more details.
	*/
	#include <linux/bpf.h>
	#include <linux/jhash.h>
	#include <linux/filter.h>
	#include <linux/vmalloc.h>

	struct bpf_htab {
	struct bpf_map map;
	struct hlist_head *buckets;
	raw_spinlock_t lock;
	u32 count; /* number of elements in this hashtable */
	u32 n_buckets; /* number of hash buckets */
	u32 elem_size; /* size of each element in bytes */
	};

	/* each htab element is struct htab_elem + key + value */
	struct htab_elem {
	struct hlist_node hash_node;
	struct rcu_head rcu;
	u32 hash;
	char key[0] __aligned(8);
	};

	/* Called from syscall */
	static struct bpf_map htab_map_alloc(union bpf_attr attr)
	{
	struct bpf_htab *htab;
	int err, i;

	htab = kzalloc(sizeof(*htab), GFP_USER);
	if (!htab)
	return ERR_PTR(-ENOMEM);

	/* mandatory map attributes */
	htab->map.key_size = attr->key_size;
	htab->map.value_size = attr->value_size;
	htab->map.max_entries = attr->max_entries;

	/* check sanity of attributes.
	* value_size == 0 may be allowed in the future to use map as a set
	*/
	err = -EINVAL;
	if (htab->map.max_entries == 0 \|\| htab->map.key_size == 0 \|\|
	htab->map.value_size == 0)
	goto free_htab;

	/* hash table size must be power of 2 */
	htab->n_buckets = roundup_pow_of_two(htab->map.max_entries);

	err = -E2BIG;
	if (htab->map.key_size > MAX_BPF_STACK)
	/* eBPF programs initialize keys on stack, so they cannot be
	* larger than max stack size
	*/
	goto free_htab;

	err = -ENOMEM;
	/* prevent zero size kmalloc and check for u32 overflow */
	if (htab->n_buckets == 0 \|\|
	htab->n_buckets > U32_MAX / sizeof(struct hlist_head))
	goto free_htab;

	htab->buckets = kmalloc_array(htab->n_buckets, sizeof(struct hlist_head),
	GFP_USER \| __GFP_NOWARN);

	if (!htab->buckets) {
	htab->buckets = vmalloc(htab->n_buckets * sizeof(struct hlist_head));
	if (!htab->buckets)
	goto free_htab;
	}

	for (i = 0; i < htab->n_buckets; i++)
	INIT_HLIST_HEAD(&htab->buckets[i]);

	raw_spin_lock_init(&htab->lock);
	htab->count = 0;

	htab->elem_size = sizeof(struct htab_elem) +
	round_up(htab->map.key_size, 8) +
	htab->map.value_size;

	htab->map.pages = round_up(htab->n_buckets * sizeof(struct hlist_head) +
	htab->elem_size * htab->map.max_entries,
	PAGE_SIZE) >> PAGE_SHIFT;
	return &htab->map;

	free_htab:
	kfree(htab);
	return ERR_PTR(err);
	}

	static inline u32 htab_map_hash(const void *key, u32 key_len)
	{
	return jhash(key, key_len, 0);
	}

	static inline struct hlist_head select_bucket(struct bpf_htab htab, u32 hash)
	{
	return &htab->buckets[hash & (htab->n_buckets - 1)];
	}

	static struct htab_elem lookup_elem_raw(struct hlist_head head, u32 hash,
	void *key, u32 key_size)
	{
	struct htab_elem *l;

	hlist_for_each_entry_rcu(l, head, hash_node)
	if (l->hash == hash && !memcmp(&l->key, key, key_size))
	return l;

	return NULL;
	}

	/* Called from syscall or from eBPF program */
	static void htab_map_lookup_elem(struct bpf_map map, void *key)
	{
	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
	struct hlist_head *head;
	struct htab_elem *l;
	u32 hash, key_size;

	/* Must be called with rcu_read_lock. */
	WARN_ON_ONCE(!rcu_read_lock_held());

	key_size = map->key_size;

	hash = htab_map_hash(key, key_size);

	head = select_bucket(htab, hash);

	l = lookup_elem_raw(head, hash, key, key_size);

	if (l)
	return l->key + round_up(map->key_size, 8);

	return NULL;
	}

	/* Called from syscall */
	static int htab_map_get_next_key(struct bpf_map map, void key, void *next_key)
	{
	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
	struct hlist_head *head;
	struct htab_elem l, next_l;
	u32 hash, key_size;
	int i;

	WARN_ON_ONCE(!rcu_read_lock_held());

	key_size = map->key_size;

	hash = htab_map_hash(key, key_size);

	head = select_bucket(htab, hash);

	/* lookup the key */
	l = lookup_elem_raw(head, hash, key, key_size);

	if (!l) {
	i = 0;
	goto find_first_elem;
	}

	/* key was found, get next key in the same bucket */
	next_l = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu(&l->hash_node)),
	struct htab_elem, hash_node);

	if (next_l) {
	/* if next elem in this hash list is non-zero, just return it */
	memcpy(next_key, next_l->key, key_size);
	return 0;
	}

	/* no more elements in this hash list, go to the next bucket */
	i = hash & (htab->n_buckets - 1);
	i++;

	find_first_elem:
	/* iterate over buckets */
	for (; i < htab->n_buckets; i++) {
	head = select_bucket(htab, i);

	/* pick first element in the bucket */
	next_l = hlist_entry_safe(rcu_dereference_raw(hlist_first_rcu(head)),
	struct htab_elem, hash_node);
	if (next_l) {
	/* if it's not empty, just return it */
	memcpy(next_key, next_l->key, key_size);
	return 0;
	}
	}

	/* itereated over all buckets and all elements */
	return -ENOENT;
	}

	/* Called from syscall or from eBPF program */
	static int htab_map_update_elem(struct bpf_map map, void key, void *value,
	u64 map_flags)
	{
	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
	struct htab_elem l_new, l_old;
	struct hlist_head *head;
	unsigned long flags;
	u32 key_size;
	int ret;

	if (map_flags > BPF_EXIST)
	/* unknown flags */
	return -EINVAL;

	WARN_ON_ONCE(!rcu_read_lock_held());

	/* allocate new element outside of lock */
	l_new = kmalloc(htab->elem_size, GFP_ATOMIC);
	if (!l_new)
	return -ENOMEM;

	key_size = map->key_size;

	memcpy(l_new->key, key, key_size);
	memcpy(l_new->key + round_up(key_size, 8), value, map->value_size);

	l_new->hash = htab_map_hash(l_new->key, key_size);

	/* bpf_map_update_elem() can be called in_irq() */
	raw_spin_lock_irqsave(&htab->lock, flags);

	head = select_bucket(htab, l_new->hash);

	l_old = lookup_elem_raw(head, l_new->hash, key, key_size);

	if (!l_old && unlikely(htab->count >= map->max_entries)) {
	/* if elem with this 'key' doesn't exist and we've reached
	* max_entries limit, fail insertion of new elem
	*/
	ret = -E2BIG;
	goto err;
	}

	if (l_old && map_flags == BPF_NOEXIST) {
	/* elem already exists */
	ret = -EEXIST;
	goto err;
	}

	if (!l_old && map_flags == BPF_EXIST) {
	/* elem doesn't exist, cannot update it */
	ret = -ENOENT;
	goto err;
	}

	/* add new element to the head of the list, so that concurrent
	* search will find it before old elem
	*/
	hlist_add_head_rcu(&l_new->hash_node, head);
	if (l_old) {
	hlist_del_rcu(&l_old->hash_node);
	kfree_rcu(l_old, rcu);
	} else {
	htab->count++;
	}
	raw_spin_unlock_irqrestore(&htab->lock, flags);

	return 0;
	err:
	raw_spin_unlock_irqrestore(&htab->lock, flags);
	kfree(l_new);
	return ret;
	}

	/* Called from syscall or from eBPF program */
	static int htab_map_delete_elem(struct bpf_map map, void key)
	{
	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
	struct hlist_head *head;
	struct htab_elem *l;
	unsigned long flags;
	u32 hash, key_size;
	int ret = -ENOENT;

	WARN_ON_ONCE(!rcu_read_lock_held());

	key_size = map->key_size;

	hash = htab_map_hash(key, key_size);

	raw_spin_lock_irqsave(&htab->lock, flags);

	head = select_bucket(htab, hash);

	l = lookup_elem_raw(head, hash, key, key_size);

	if (l) {
	hlist_del_rcu(&l->hash_node);
	htab->count--;
	kfree_rcu(l, rcu);
	ret = 0;
	}

	raw_spin_unlock_irqrestore(&htab->lock, flags);
	return ret;
	}

	static void delete_all_elements(struct bpf_htab *htab)
	{
	int i;

	for (i = 0; i < htab->n_buckets; i++) {
	struct hlist_head *head = select_bucket(htab, i);
	struct hlist_node *n;
	struct htab_elem *l;

	hlist_for_each_entry_safe(l, n, head, hash_node) {
	hlist_del_rcu(&l->hash_node);
	htab->count--;
	kfree(l);
	}
	}
	}

	/* Called when map->refcnt goes to zero, either from workqueue or from syscall */
	static void htab_map_free(struct bpf_map *map)
	{
	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);

	/* at this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
	* so the programs (can be more than one that used this map) were
	* disconnected from events. Wait for outstanding critical sections in
	* these programs to complete
	*/
	synchronize_rcu();

	/* some of kfree_rcu() callbacks for elements of this map may not have
	* executed. It's ok. Proceed to free residual elements and map itself
	*/
	delete_all_elements(htab);
	kvfree(htab->buckets);
	kfree(htab);
	}

	static const struct bpf_map_ops htab_ops = {
	.map_alloc = htab_map_alloc,
	.map_free = htab_map_free,
	.map_get_next_key = htab_map_get_next_key,
	.map_lookup_elem = htab_map_lookup_elem,
	.map_update_elem = htab_map_update_elem,
	.map_delete_elem = htab_map_delete_elem,
	};

	static struct bpf_map_type_list htab_type __read_mostly = {
	.ops = &htab_ops,
	.type = BPF_MAP_TYPE_HASH,
	};

	static int __init register_htab_map(void)
	{
	bpf_register_map_type(&htab_type);
	return 0;
	}
	late_initcall(register_htab_map);