mirror of
https://github.com/torvalds/linux
synced 2024-09-06 09:51:23 +00:00
bpf: add hashtable type of eBPF maps
add new map type BPF_MAP_TYPE_HASH and its implementation - maps are created/destroyed by userspace. Both userspace and eBPF programs can lookup/update/delete elements from the map - eBPF programs can be called in_irq(), so use spin_lock_irqsave() mechanism for concurrent updates - key/value are opaque range of bytes (aligned to 8 bytes) - user space provides 3 configuration attributes via BPF syscall: key_size, value_size, max_entries - map takes care of allocating/freeing key/value pairs - map_update_elem() must fail to insert new element when max_entries limit is reached to make sure that eBPF programs cannot exhaust memory - map_update_elem() replaces elements in an atomic way - optimized for speed of lookup() which can be called multiple times from eBPF program which itself is triggered by high volume of events . in the future JIT compiler may recognize lookup() call and optimize it further, since key_size is constant for life of eBPF program Signed-off-by: Alexei Starovoitov <ast@plumgrid.com> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
parent
3274f52073
commit
0f8e4bd8a1
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@ -111,6 +111,7 @@ enum bpf_cmd {
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enum bpf_map_type {
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BPF_MAP_TYPE_UNSPEC,
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BPF_MAP_TYPE_HASH,
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};
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enum bpf_prog_type {
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@ -1,5 +1,5 @@
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obj-y := core.o
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obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o
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obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o hashtab.o
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ifdef CONFIG_TEST_BPF
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obj-$(CONFIG_BPF_SYSCALL) += test_stub.o
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endif
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362
kernel/bpf/hashtab.c
Normal file
362
kernel/bpf/hashtab.c
Normal file
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@ -0,0 +1,362 @@
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/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of version 2 of the GNU General Public
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* License as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*/
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#include <linux/bpf.h>
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#include <linux/jhash.h>
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#include <linux/filter.h>
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#include <linux/vmalloc.h>
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struct bpf_htab {
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struct bpf_map map;
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struct hlist_head *buckets;
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spinlock_t lock;
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u32 count; /* number of elements in this hashtable */
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u32 n_buckets; /* number of hash buckets */
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u32 elem_size; /* size of each element in bytes */
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};
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/* each htab element is struct htab_elem + key + value */
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struct htab_elem {
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struct hlist_node hash_node;
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struct rcu_head rcu;
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u32 hash;
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char key[0] __aligned(8);
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};
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/* Called from syscall */
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static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
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{
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struct bpf_htab *htab;
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int err, i;
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htab = kzalloc(sizeof(*htab), GFP_USER);
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if (!htab)
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return ERR_PTR(-ENOMEM);
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/* mandatory map attributes */
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htab->map.key_size = attr->key_size;
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htab->map.value_size = attr->value_size;
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htab->map.max_entries = attr->max_entries;
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/* check sanity of attributes.
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* value_size == 0 may be allowed in the future to use map as a set
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*/
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err = -EINVAL;
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if (htab->map.max_entries == 0 || htab->map.key_size == 0 ||
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htab->map.value_size == 0)
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goto free_htab;
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/* hash table size must be power of 2 */
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htab->n_buckets = roundup_pow_of_two(htab->map.max_entries);
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err = -E2BIG;
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if (htab->map.key_size > MAX_BPF_STACK)
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/* eBPF programs initialize keys on stack, so they cannot be
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* larger than max stack size
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*/
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goto free_htab;
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err = -ENOMEM;
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htab->buckets = kmalloc_array(htab->n_buckets, sizeof(struct hlist_head),
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GFP_USER | __GFP_NOWARN);
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if (!htab->buckets) {
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htab->buckets = vmalloc(htab->n_buckets * sizeof(struct hlist_head));
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if (!htab->buckets)
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goto free_htab;
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}
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for (i = 0; i < htab->n_buckets; i++)
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INIT_HLIST_HEAD(&htab->buckets[i]);
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spin_lock_init(&htab->lock);
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htab->count = 0;
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htab->elem_size = sizeof(struct htab_elem) +
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round_up(htab->map.key_size, 8) +
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htab->map.value_size;
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return &htab->map;
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free_htab:
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kfree(htab);
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return ERR_PTR(err);
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}
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static inline u32 htab_map_hash(const void *key, u32 key_len)
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{
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return jhash(key, key_len, 0);
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}
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static inline struct hlist_head *select_bucket(struct bpf_htab *htab, u32 hash)
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{
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return &htab->buckets[hash & (htab->n_buckets - 1)];
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}
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static struct htab_elem *lookup_elem_raw(struct hlist_head *head, u32 hash,
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void *key, u32 key_size)
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{
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struct htab_elem *l;
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hlist_for_each_entry_rcu(l, head, hash_node)
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if (l->hash == hash && !memcmp(&l->key, key, key_size))
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return l;
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return NULL;
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}
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/* Called from syscall or from eBPF program */
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static void *htab_map_lookup_elem(struct bpf_map *map, void *key)
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{
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struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
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struct hlist_head *head;
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struct htab_elem *l;
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u32 hash, key_size;
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/* Must be called with rcu_read_lock. */
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WARN_ON_ONCE(!rcu_read_lock_held());
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key_size = map->key_size;
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hash = htab_map_hash(key, key_size);
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head = select_bucket(htab, hash);
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l = lookup_elem_raw(head, hash, key, key_size);
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if (l)
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return l->key + round_up(map->key_size, 8);
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return NULL;
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}
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/* Called from syscall */
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static int htab_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
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{
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struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
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struct hlist_head *head;
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struct htab_elem *l, *next_l;
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u32 hash, key_size;
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int i;
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WARN_ON_ONCE(!rcu_read_lock_held());
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key_size = map->key_size;
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hash = htab_map_hash(key, key_size);
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head = select_bucket(htab, hash);
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/* lookup the key */
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l = lookup_elem_raw(head, hash, key, key_size);
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if (!l) {
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i = 0;
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goto find_first_elem;
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}
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/* key was found, get next key in the same bucket */
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next_l = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu(&l->hash_node)),
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struct htab_elem, hash_node);
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if (next_l) {
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/* if next elem in this hash list is non-zero, just return it */
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memcpy(next_key, next_l->key, key_size);
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return 0;
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}
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/* no more elements in this hash list, go to the next bucket */
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i = hash & (htab->n_buckets - 1);
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i++;
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find_first_elem:
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/* iterate over buckets */
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for (; i < htab->n_buckets; i++) {
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head = select_bucket(htab, i);
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/* pick first element in the bucket */
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next_l = hlist_entry_safe(rcu_dereference_raw(hlist_first_rcu(head)),
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struct htab_elem, hash_node);
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if (next_l) {
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/* if it's not empty, just return it */
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memcpy(next_key, next_l->key, key_size);
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return 0;
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}
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}
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/* itereated over all buckets and all elements */
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return -ENOENT;
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}
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/* Called from syscall or from eBPF program */
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static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
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u64 map_flags)
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{
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struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
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struct htab_elem *l_new, *l_old;
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struct hlist_head *head;
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unsigned long flags;
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u32 key_size;
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int ret;
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if (map_flags > BPF_EXIST)
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/* unknown flags */
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return -EINVAL;
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WARN_ON_ONCE(!rcu_read_lock_held());
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/* allocate new element outside of lock */
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l_new = kmalloc(htab->elem_size, GFP_ATOMIC);
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if (!l_new)
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return -ENOMEM;
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key_size = map->key_size;
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memcpy(l_new->key, key, key_size);
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memcpy(l_new->key + round_up(key_size, 8), value, map->value_size);
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l_new->hash = htab_map_hash(l_new->key, key_size);
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/* bpf_map_update_elem() can be called in_irq() */
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spin_lock_irqsave(&htab->lock, flags);
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head = select_bucket(htab, l_new->hash);
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l_old = lookup_elem_raw(head, l_new->hash, key, key_size);
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if (!l_old && unlikely(htab->count >= map->max_entries)) {
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/* if elem with this 'key' doesn't exist and we've reached
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* max_entries limit, fail insertion of new elem
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*/
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ret = -E2BIG;
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goto err;
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}
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if (l_old && map_flags == BPF_NOEXIST) {
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/* elem already exists */
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ret = -EEXIST;
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goto err;
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}
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if (!l_old && map_flags == BPF_EXIST) {
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/* elem doesn't exist, cannot update it */
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ret = -ENOENT;
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goto err;
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}
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/* add new element to the head of the list, so that concurrent
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* search will find it before old elem
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*/
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hlist_add_head_rcu(&l_new->hash_node, head);
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if (l_old) {
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hlist_del_rcu(&l_old->hash_node);
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kfree_rcu(l_old, rcu);
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} else {
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htab->count++;
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}
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spin_unlock_irqrestore(&htab->lock, flags);
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return 0;
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err:
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spin_unlock_irqrestore(&htab->lock, flags);
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kfree(l_new);
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return ret;
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}
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/* Called from syscall or from eBPF program */
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static int htab_map_delete_elem(struct bpf_map *map, void *key)
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{
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struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
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struct hlist_head *head;
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struct htab_elem *l;
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unsigned long flags;
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u32 hash, key_size;
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int ret = -ENOENT;
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WARN_ON_ONCE(!rcu_read_lock_held());
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key_size = map->key_size;
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hash = htab_map_hash(key, key_size);
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spin_lock_irqsave(&htab->lock, flags);
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head = select_bucket(htab, hash);
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l = lookup_elem_raw(head, hash, key, key_size);
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if (l) {
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hlist_del_rcu(&l->hash_node);
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htab->count--;
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kfree_rcu(l, rcu);
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ret = 0;
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}
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spin_unlock_irqrestore(&htab->lock, flags);
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return ret;
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}
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static void delete_all_elements(struct bpf_htab *htab)
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{
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int i;
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for (i = 0; i < htab->n_buckets; i++) {
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struct hlist_head *head = select_bucket(htab, i);
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struct hlist_node *n;
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struct htab_elem *l;
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hlist_for_each_entry_safe(l, n, head, hash_node) {
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hlist_del_rcu(&l->hash_node);
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htab->count--;
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kfree(l);
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}
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}
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}
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/* Called when map->refcnt goes to zero, either from workqueue or from syscall */
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static void htab_map_free(struct bpf_map *map)
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{
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struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
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/* at this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
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* so the programs (can be more than one that used this map) were
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* disconnected from events. Wait for outstanding critical sections in
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* these programs to complete
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*/
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synchronize_rcu();
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/* some of kfree_rcu() callbacks for elements of this map may not have
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* executed. It's ok. Proceed to free residual elements and map itself
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*/
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delete_all_elements(htab);
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kvfree(htab->buckets);
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kfree(htab);
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}
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static struct bpf_map_ops htab_ops = {
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.map_alloc = htab_map_alloc,
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.map_free = htab_map_free,
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.map_get_next_key = htab_map_get_next_key,
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.map_lookup_elem = htab_map_lookup_elem,
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.map_update_elem = htab_map_update_elem,
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.map_delete_elem = htab_map_delete_elem,
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};
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static struct bpf_map_type_list tl = {
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.ops = &htab_ops,
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.type = BPF_MAP_TYPE_HASH,
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};
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static int __init register_htab_map(void)
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{
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bpf_register_map_type(&tl);
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return 0;
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}
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late_initcall(register_htab_map);
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