linux/kernel/bpf/hashtab.c
Alexei Starovoitov 4fe8435909 bpf: convert htab map to hlist_nulls
when all map elements are pre-allocated one cpu can delete and reuse htab_elem
while another cpu is still walking the hlist. In such case the lookup may
miss the element. Convert hlist to hlist_nulls to avoid such scenario.
When bucket lock is taken there is no need to take such precautions,
so only convert map_lookup and map_get_next to nulls.
The race window is extremely small and only reproducible with explicit
udelay() inside lookup_nulls_elem_raw()

Similar to hlist add hlist_nulls_for_each_entry_safe() and
hlist_nulls_entry_safe() helpers.

Fixes: 6c90598174 ("bpf: pre-allocate hash map elements")
Reported-by: Jonathan Perry <jonperry@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-03-09 13:27:17 -08:00

1196 lines
30 KiB
C

/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
* Copyright (c) 2016 Facebook
*
* 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/rculist_nulls.h>
#include "percpu_freelist.h"
#include "bpf_lru_list.h"
struct bucket {
struct hlist_nulls_head head;
raw_spinlock_t lock;
};
struct bpf_htab {
struct bpf_map map;
struct bucket *buckets;
void *elems;
union {
struct pcpu_freelist freelist;
struct bpf_lru lru;
};
void __percpu *extra_elems;
atomic_t count; /* number of elements in this hashtable */
u32 n_buckets; /* number of hash buckets */
u32 elem_size; /* size of each element in bytes */
};
enum extra_elem_state {
HTAB_NOT_AN_EXTRA_ELEM = 0,
HTAB_EXTRA_ELEM_FREE,
HTAB_EXTRA_ELEM_USED
};
/* each htab element is struct htab_elem + key + value */
struct htab_elem {
union {
struct hlist_nulls_node hash_node;
struct {
void *padding;
union {
struct bpf_htab *htab;
struct pcpu_freelist_node fnode;
};
};
};
union {
struct rcu_head rcu;
enum extra_elem_state state;
struct bpf_lru_node lru_node;
};
u32 hash;
char key[0] __aligned(8);
};
static bool htab_lru_map_delete_node(void *arg, struct bpf_lru_node *node);
static bool htab_is_lru(const struct bpf_htab *htab)
{
return htab->map.map_type == BPF_MAP_TYPE_LRU_HASH ||
htab->map.map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH;
}
static bool htab_is_percpu(const struct bpf_htab *htab)
{
return htab->map.map_type == BPF_MAP_TYPE_PERCPU_HASH ||
htab->map.map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH;
}
static inline void htab_elem_set_ptr(struct htab_elem *l, u32 key_size,
void __percpu *pptr)
{
*(void __percpu **)(l->key + key_size) = pptr;
}
static inline void __percpu *htab_elem_get_ptr(struct htab_elem *l, u32 key_size)
{
return *(void __percpu **)(l->key + key_size);
}
static struct htab_elem *get_htab_elem(struct bpf_htab *htab, int i)
{
return (struct htab_elem *) (htab->elems + i * htab->elem_size);
}
static void htab_free_elems(struct bpf_htab *htab)
{
int i;
if (!htab_is_percpu(htab))
goto free_elems;
for (i = 0; i < htab->map.max_entries; i++) {
void __percpu *pptr;
pptr = htab_elem_get_ptr(get_htab_elem(htab, i),
htab->map.key_size);
free_percpu(pptr);
}
free_elems:
bpf_map_area_free(htab->elems);
}
static struct htab_elem *prealloc_lru_pop(struct bpf_htab *htab, void *key,
u32 hash)
{
struct bpf_lru_node *node = bpf_lru_pop_free(&htab->lru, hash);
struct htab_elem *l;
if (node) {
l = container_of(node, struct htab_elem, lru_node);
memcpy(l->key, key, htab->map.key_size);
return l;
}
return NULL;
}
static int prealloc_init(struct bpf_htab *htab)
{
int err = -ENOMEM, i;
htab->elems = bpf_map_area_alloc(htab->elem_size *
htab->map.max_entries);
if (!htab->elems)
return -ENOMEM;
if (!htab_is_percpu(htab))
goto skip_percpu_elems;
for (i = 0; i < htab->map.max_entries; i++) {
u32 size = round_up(htab->map.value_size, 8);
void __percpu *pptr;
pptr = __alloc_percpu_gfp(size, 8, GFP_USER | __GFP_NOWARN);
if (!pptr)
goto free_elems;
htab_elem_set_ptr(get_htab_elem(htab, i), htab->map.key_size,
pptr);
}
skip_percpu_elems:
if (htab_is_lru(htab))
err = bpf_lru_init(&htab->lru,
htab->map.map_flags & BPF_F_NO_COMMON_LRU,
offsetof(struct htab_elem, hash) -
offsetof(struct htab_elem, lru_node),
htab_lru_map_delete_node,
htab);
else
err = pcpu_freelist_init(&htab->freelist);
if (err)
goto free_elems;
if (htab_is_lru(htab))
bpf_lru_populate(&htab->lru, htab->elems,
offsetof(struct htab_elem, lru_node),
htab->elem_size, htab->map.max_entries);
else
pcpu_freelist_populate(&htab->freelist,
htab->elems + offsetof(struct htab_elem, fnode),
htab->elem_size, htab->map.max_entries);
return 0;
free_elems:
htab_free_elems(htab);
return err;
}
static void prealloc_destroy(struct bpf_htab *htab)
{
htab_free_elems(htab);
if (htab_is_lru(htab))
bpf_lru_destroy(&htab->lru);
else
pcpu_freelist_destroy(&htab->freelist);
}
static int alloc_extra_elems(struct bpf_htab *htab)
{
void __percpu *pptr;
int cpu;
pptr = __alloc_percpu_gfp(htab->elem_size, 8, GFP_USER | __GFP_NOWARN);
if (!pptr)
return -ENOMEM;
for_each_possible_cpu(cpu) {
((struct htab_elem *)per_cpu_ptr(pptr, cpu))->state =
HTAB_EXTRA_ELEM_FREE;
}
htab->extra_elems = pptr;
return 0;
}
/* Called from syscall */
static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
{
bool percpu = (attr->map_type == BPF_MAP_TYPE_PERCPU_HASH ||
attr->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH);
bool lru = (attr->map_type == BPF_MAP_TYPE_LRU_HASH ||
attr->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH);
/* percpu_lru means each cpu has its own LRU list.
* it is different from BPF_MAP_TYPE_PERCPU_HASH where
* the map's value itself is percpu. percpu_lru has
* nothing to do with the map's value.
*/
bool percpu_lru = (attr->map_flags & BPF_F_NO_COMMON_LRU);
bool prealloc = !(attr->map_flags & BPF_F_NO_PREALLOC);
struct bpf_htab *htab;
int err, i;
u64 cost;
BUILD_BUG_ON(offsetof(struct htab_elem, htab) !=
offsetof(struct htab_elem, hash_node.pprev));
BUILD_BUG_ON(offsetof(struct htab_elem, fnode.next) !=
offsetof(struct htab_elem, hash_node.pprev));
if (lru && !capable(CAP_SYS_ADMIN))
/* LRU implementation is much complicated than other
* maps. Hence, limit to CAP_SYS_ADMIN for now.
*/
return ERR_PTR(-EPERM);
if (attr->map_flags & ~(BPF_F_NO_PREALLOC | BPF_F_NO_COMMON_LRU))
/* reserved bits should not be used */
return ERR_PTR(-EINVAL);
if (!lru && percpu_lru)
return ERR_PTR(-EINVAL);
if (lru && !prealloc)
return ERR_PTR(-ENOTSUPP);
htab = kzalloc(sizeof(*htab), GFP_USER);
if (!htab)
return ERR_PTR(-ENOMEM);
/* mandatory map attributes */
htab->map.map_type = attr->map_type;
htab->map.key_size = attr->key_size;
htab->map.value_size = attr->value_size;
htab->map.max_entries = attr->max_entries;
htab->map.map_flags = attr->map_flags;
/* 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;
if (percpu_lru) {
/* ensure each CPU's lru list has >=1 elements.
* since we are at it, make each lru list has the same
* number of elements.
*/
htab->map.max_entries = roundup(attr->max_entries,
num_possible_cpus());
if (htab->map.max_entries < attr->max_entries)
htab->map.max_entries = rounddown(attr->max_entries,
num_possible_cpus());
}
/* 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;
if (htab->map.value_size >= KMALLOC_MAX_SIZE -
MAX_BPF_STACK - sizeof(struct htab_elem))
/* if value_size is bigger, the user space won't be able to
* access the elements via bpf syscall. This check also makes
* sure that the elem_size doesn't overflow and it's
* kmalloc-able later in htab_map_update_elem()
*/
goto free_htab;
if (percpu && round_up(htab->map.value_size, 8) > PCPU_MIN_UNIT_SIZE)
/* make sure the size for pcpu_alloc() is reasonable */
goto free_htab;
htab->elem_size = sizeof(struct htab_elem) +
round_up(htab->map.key_size, 8);
if (percpu)
htab->elem_size += sizeof(void *);
else
htab->elem_size += round_up(htab->map.value_size, 8);
/* prevent zero size kmalloc and check for u32 overflow */
if (htab->n_buckets == 0 ||
htab->n_buckets > U32_MAX / sizeof(struct bucket))
goto free_htab;
cost = (u64) htab->n_buckets * sizeof(struct bucket) +
(u64) htab->elem_size * htab->map.max_entries;
if (percpu)
cost += (u64) round_up(htab->map.value_size, 8) *
num_possible_cpus() * htab->map.max_entries;
else
cost += (u64) htab->elem_size * num_possible_cpus();
if (cost >= U32_MAX - PAGE_SIZE)
/* make sure page count doesn't overflow */
goto free_htab;
htab->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
/* if map size is larger than memlock limit, reject it early */
err = bpf_map_precharge_memlock(htab->map.pages);
if (err)
goto free_htab;
err = -ENOMEM;
htab->buckets = bpf_map_area_alloc(htab->n_buckets *
sizeof(struct bucket));
if (!htab->buckets)
goto free_htab;
for (i = 0; i < htab->n_buckets; i++) {
INIT_HLIST_NULLS_HEAD(&htab->buckets[i].head, i);
raw_spin_lock_init(&htab->buckets[i].lock);
}
if (!percpu && !lru) {
/* lru itself can remove the least used element, so
* there is no need for an extra elem during map_update.
*/
err = alloc_extra_elems(htab);
if (err)
goto free_buckets;
}
if (prealloc) {
err = prealloc_init(htab);
if (err)
goto free_extra_elems;
}
return &htab->map;
free_extra_elems:
free_percpu(htab->extra_elems);
free_buckets:
bpf_map_area_free(htab->buckets);
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 bucket *__select_bucket(struct bpf_htab *htab, u32 hash)
{
return &htab->buckets[hash & (htab->n_buckets - 1)];
}
static inline struct hlist_nulls_head *select_bucket(struct bpf_htab *htab, u32 hash)
{
return &__select_bucket(htab, hash)->head;
}
/* this lookup function can only be called with bucket lock taken */
static struct htab_elem *lookup_elem_raw(struct hlist_nulls_head *head, u32 hash,
void *key, u32 key_size)
{
struct hlist_nulls_node *n;
struct htab_elem *l;
hlist_nulls_for_each_entry_rcu(l, n, head, hash_node)
if (l->hash == hash && !memcmp(&l->key, key, key_size))
return l;
return NULL;
}
/* can be called without bucket lock. it will repeat the loop in
* the unlikely event when elements moved from one bucket into another
* while link list is being walked
*/
static struct htab_elem *lookup_nulls_elem_raw(struct hlist_nulls_head *head,
u32 hash, void *key,
u32 key_size, u32 n_buckets)
{
struct hlist_nulls_node *n;
struct htab_elem *l;
again:
hlist_nulls_for_each_entry_rcu(l, n, head, hash_node)
if (l->hash == hash && !memcmp(&l->key, key, key_size))
return l;
if (unlikely(get_nulls_value(n) != (hash & (n_buckets - 1))))
goto again;
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_nulls_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_nulls_elem_raw(head, hash, key, key_size, htab->n_buckets);
return l;
}
static void *htab_map_lookup_elem(struct bpf_map *map, void *key)
{
struct htab_elem *l = __htab_map_lookup_elem(map, key);
if (l)
return l->key + round_up(map->key_size, 8);
return NULL;
}
static void *htab_lru_map_lookup_elem(struct bpf_map *map, void *key)
{
struct htab_elem *l = __htab_map_lookup_elem(map, key);
if (l) {
bpf_lru_node_set_ref(&l->lru_node);
return l->key + round_up(map->key_size, 8);
}
return NULL;
}
/* It is called from the bpf_lru_list when the LRU needs to delete
* older elements from the htab.
*/
static bool htab_lru_map_delete_node(void *arg, struct bpf_lru_node *node)
{
struct bpf_htab *htab = (struct bpf_htab *)arg;
struct htab_elem *l = NULL, *tgt_l;
struct hlist_nulls_head *head;
struct hlist_nulls_node *n;
unsigned long flags;
struct bucket *b;
tgt_l = container_of(node, struct htab_elem, lru_node);
b = __select_bucket(htab, tgt_l->hash);
head = &b->head;
raw_spin_lock_irqsave(&b->lock, flags);
hlist_nulls_for_each_entry_rcu(l, n, head, hash_node)
if (l == tgt_l) {
hlist_nulls_del_rcu(&l->hash_node);
break;
}
raw_spin_unlock_irqrestore(&b->lock, flags);
return l == tgt_l;
}
/* 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_nulls_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_nulls_elem_raw(head, hash, key, key_size, htab->n_buckets);
if (!l) {
i = 0;
goto find_first_elem;
}
/* key was found, get next key in the same bucket */
next_l = hlist_nulls_entry_safe(rcu_dereference_raw(hlist_nulls_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_nulls_entry_safe(rcu_dereference_raw(hlist_nulls_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;
}
}
/* iterated over all buckets and all elements */
return -ENOENT;
}
static void htab_elem_free(struct bpf_htab *htab, struct htab_elem *l)
{
if (htab->map.map_type == BPF_MAP_TYPE_PERCPU_HASH)
free_percpu(htab_elem_get_ptr(l, htab->map.key_size));
kfree(l);
}
static void htab_elem_free_rcu(struct rcu_head *head)
{
struct htab_elem *l = container_of(head, struct htab_elem, rcu);
struct bpf_htab *htab = l->htab;
/* must increment bpf_prog_active to avoid kprobe+bpf triggering while
* we're calling kfree, otherwise deadlock is possible if kprobes
* are placed somewhere inside of slub
*/
preempt_disable();
__this_cpu_inc(bpf_prog_active);
htab_elem_free(htab, l);
__this_cpu_dec(bpf_prog_active);
preempt_enable();
}
static void free_htab_elem(struct bpf_htab *htab, struct htab_elem *l)
{
if (l->state == HTAB_EXTRA_ELEM_USED) {
l->state = HTAB_EXTRA_ELEM_FREE;
return;
}
if (!(htab->map.map_flags & BPF_F_NO_PREALLOC)) {
pcpu_freelist_push(&htab->freelist, &l->fnode);
} else {
atomic_dec(&htab->count);
l->htab = htab;
call_rcu(&l->rcu, htab_elem_free_rcu);
}
}
static void pcpu_copy_value(struct bpf_htab *htab, void __percpu *pptr,
void *value, bool onallcpus)
{
if (!onallcpus) {
/* copy true value_size bytes */
memcpy(this_cpu_ptr(pptr), value, htab->map.value_size);
} else {
u32 size = round_up(htab->map.value_size, 8);
int off = 0, cpu;
for_each_possible_cpu(cpu) {
bpf_long_memcpy(per_cpu_ptr(pptr, cpu),
value + off, size);
off += size;
}
}
}
static struct htab_elem *alloc_htab_elem(struct bpf_htab *htab, void *key,
void *value, u32 key_size, u32 hash,
bool percpu, bool onallcpus,
bool old_elem_exists)
{
u32 size = htab->map.value_size;
bool prealloc = !(htab->map.map_flags & BPF_F_NO_PREALLOC);
struct htab_elem *l_new;
void __percpu *pptr;
int err = 0;
if (prealloc) {
struct pcpu_freelist_node *l;
l = pcpu_freelist_pop(&htab->freelist);
if (!l)
err = -E2BIG;
else
l_new = container_of(l, struct htab_elem, fnode);
} else {
if (atomic_inc_return(&htab->count) > htab->map.max_entries) {
atomic_dec(&htab->count);
err = -E2BIG;
} else {
l_new = kmalloc(htab->elem_size,
GFP_ATOMIC | __GFP_NOWARN);
if (!l_new)
return ERR_PTR(-ENOMEM);
}
}
if (err) {
if (!old_elem_exists)
return ERR_PTR(err);
/* if we're updating the existing element and the hash table
* is full, use per-cpu extra elems
*/
l_new = this_cpu_ptr(htab->extra_elems);
if (l_new->state != HTAB_EXTRA_ELEM_FREE)
return ERR_PTR(-E2BIG);
l_new->state = HTAB_EXTRA_ELEM_USED;
} else {
l_new->state = HTAB_NOT_AN_EXTRA_ELEM;
}
memcpy(l_new->key, key, key_size);
if (percpu) {
/* round up value_size to 8 bytes */
size = round_up(size, 8);
if (prealloc) {
pptr = htab_elem_get_ptr(l_new, key_size);
} else {
/* alloc_percpu zero-fills */
pptr = __alloc_percpu_gfp(size, 8,
GFP_ATOMIC | __GFP_NOWARN);
if (!pptr) {
kfree(l_new);
return ERR_PTR(-ENOMEM);
}
}
pcpu_copy_value(htab, pptr, value, onallcpus);
if (!prealloc)
htab_elem_set_ptr(l_new, key_size, pptr);
} else {
memcpy(l_new->key + round_up(key_size, 8), value, size);
}
l_new->hash = hash;
return l_new;
}
static int check_flags(struct bpf_htab *htab, struct htab_elem *l_old,
u64 map_flags)
{
if (l_old && map_flags == BPF_NOEXIST)
/* elem already exists */
return -EEXIST;
if (!l_old && map_flags == BPF_EXIST)
/* elem doesn't exist, cannot update it */
return -ENOENT;
return 0;
}
/* 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 = NULL, *l_old;
struct hlist_nulls_head *head;
unsigned long flags;
struct bucket *b;
u32 key_size, hash;
int ret;
if (unlikely(map_flags > BPF_EXIST))
/* unknown flags */
return -EINVAL;
WARN_ON_ONCE(!rcu_read_lock_held());
key_size = map->key_size;
hash = htab_map_hash(key, key_size);
b = __select_bucket(htab, hash);
head = &b->head;
/* bpf_map_update_elem() can be called in_irq() */
raw_spin_lock_irqsave(&b->lock, flags);
l_old = lookup_elem_raw(head, hash, key, key_size);
ret = check_flags(htab, l_old, map_flags);
if (ret)
goto err;
l_new = alloc_htab_elem(htab, key, value, key_size, hash, false, false,
!!l_old);
if (IS_ERR(l_new)) {
/* all pre-allocated elements are in use or memory exhausted */
ret = PTR_ERR(l_new);
goto err;
}
/* add new element to the head of the list, so that
* concurrent search will find it before old elem
*/
hlist_nulls_add_head_rcu(&l_new->hash_node, head);
if (l_old) {
hlist_nulls_del_rcu(&l_old->hash_node);
free_htab_elem(htab, l_old);
}
ret = 0;
err:
raw_spin_unlock_irqrestore(&b->lock, flags);
return ret;
}
static int htab_lru_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 = NULL;
struct hlist_nulls_head *head;
unsigned long flags;
struct bucket *b;
u32 key_size, hash;
int ret;
if (unlikely(map_flags > BPF_EXIST))
/* unknown flags */
return -EINVAL;
WARN_ON_ONCE(!rcu_read_lock_held());
key_size = map->key_size;
hash = htab_map_hash(key, key_size);
b = __select_bucket(htab, hash);
head = &b->head;
/* For LRU, we need to alloc before taking bucket's
* spinlock because getting free nodes from LRU may need
* to remove older elements from htab and this removal
* operation will need a bucket lock.
*/
l_new = prealloc_lru_pop(htab, key, hash);
if (!l_new)
return -ENOMEM;
memcpy(l_new->key + round_up(map->key_size, 8), value, map->value_size);
/* bpf_map_update_elem() can be called in_irq() */
raw_spin_lock_irqsave(&b->lock, flags);
l_old = lookup_elem_raw(head, hash, key, key_size);
ret = check_flags(htab, l_old, map_flags);
if (ret)
goto err;
/* add new element to the head of the list, so that
* concurrent search will find it before old elem
*/
hlist_nulls_add_head_rcu(&l_new->hash_node, head);
if (l_old) {
bpf_lru_node_set_ref(&l_new->lru_node);
hlist_nulls_del_rcu(&l_old->hash_node);
}
ret = 0;
err:
raw_spin_unlock_irqrestore(&b->lock, flags);
if (ret)
bpf_lru_push_free(&htab->lru, &l_new->lru_node);
else if (l_old)
bpf_lru_push_free(&htab->lru, &l_old->lru_node);
return ret;
}
static int __htab_percpu_map_update_elem(struct bpf_map *map, void *key,
void *value, u64 map_flags,
bool onallcpus)
{
struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
struct htab_elem *l_new = NULL, *l_old;
struct hlist_nulls_head *head;
unsigned long flags;
struct bucket *b;
u32 key_size, hash;
int ret;
if (unlikely(map_flags > BPF_EXIST))
/* unknown flags */
return -EINVAL;
WARN_ON_ONCE(!rcu_read_lock_held());
key_size = map->key_size;
hash = htab_map_hash(key, key_size);
b = __select_bucket(htab, hash);
head = &b->head;
/* bpf_map_update_elem() can be called in_irq() */
raw_spin_lock_irqsave(&b->lock, flags);
l_old = lookup_elem_raw(head, hash, key, key_size);
ret = check_flags(htab, l_old, map_flags);
if (ret)
goto err;
if (l_old) {
/* per-cpu hash map can update value in-place */
pcpu_copy_value(htab, htab_elem_get_ptr(l_old, key_size),
value, onallcpus);
} else {
l_new = alloc_htab_elem(htab, key, value, key_size,
hash, true, onallcpus, false);
if (IS_ERR(l_new)) {
ret = PTR_ERR(l_new);
goto err;
}
hlist_nulls_add_head_rcu(&l_new->hash_node, head);
}
ret = 0;
err:
raw_spin_unlock_irqrestore(&b->lock, flags);
return ret;
}
static int __htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key,
void *value, u64 map_flags,
bool onallcpus)
{
struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
struct htab_elem *l_new = NULL, *l_old;
struct hlist_nulls_head *head;
unsigned long flags;
struct bucket *b;
u32 key_size, hash;
int ret;
if (unlikely(map_flags > BPF_EXIST))
/* unknown flags */
return -EINVAL;
WARN_ON_ONCE(!rcu_read_lock_held());
key_size = map->key_size;
hash = htab_map_hash(key, key_size);
b = __select_bucket(htab, hash);
head = &b->head;
/* For LRU, we need to alloc before taking bucket's
* spinlock because LRU's elem alloc may need
* to remove older elem from htab and this removal
* operation will need a bucket lock.
*/
if (map_flags != BPF_EXIST) {
l_new = prealloc_lru_pop(htab, key, hash);
if (!l_new)
return -ENOMEM;
}
/* bpf_map_update_elem() can be called in_irq() */
raw_spin_lock_irqsave(&b->lock, flags);
l_old = lookup_elem_raw(head, hash, key, key_size);
ret = check_flags(htab, l_old, map_flags);
if (ret)
goto err;
if (l_old) {
bpf_lru_node_set_ref(&l_old->lru_node);
/* per-cpu hash map can update value in-place */
pcpu_copy_value(htab, htab_elem_get_ptr(l_old, key_size),
value, onallcpus);
} else {
pcpu_copy_value(htab, htab_elem_get_ptr(l_new, key_size),
value, onallcpus);
hlist_nulls_add_head_rcu(&l_new->hash_node, head);
l_new = NULL;
}
ret = 0;
err:
raw_spin_unlock_irqrestore(&b->lock, flags);
if (l_new)
bpf_lru_push_free(&htab->lru, &l_new->lru_node);
return ret;
}
static int htab_percpu_map_update_elem(struct bpf_map *map, void *key,
void *value, u64 map_flags)
{
return __htab_percpu_map_update_elem(map, key, value, map_flags, false);
}
static int htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key,
void *value, u64 map_flags)
{
return __htab_lru_percpu_map_update_elem(map, key, value, map_flags,
false);
}
/* 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_nulls_head *head;
struct bucket *b;
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);
b = __select_bucket(htab, hash);
head = &b->head;
raw_spin_lock_irqsave(&b->lock, flags);
l = lookup_elem_raw(head, hash, key, key_size);
if (l) {
hlist_nulls_del_rcu(&l->hash_node);
free_htab_elem(htab, l);
ret = 0;
}
raw_spin_unlock_irqrestore(&b->lock, flags);
return ret;
}
static int htab_lru_map_delete_elem(struct bpf_map *map, void *key)
{
struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
struct hlist_nulls_head *head;
struct bucket *b;
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);
b = __select_bucket(htab, hash);
head = &b->head;
raw_spin_lock_irqsave(&b->lock, flags);
l = lookup_elem_raw(head, hash, key, key_size);
if (l) {
hlist_nulls_del_rcu(&l->hash_node);
ret = 0;
}
raw_spin_unlock_irqrestore(&b->lock, flags);
if (l)
bpf_lru_push_free(&htab->lru, &l->lru_node);
return ret;
}
static void delete_all_elements(struct bpf_htab *htab)
{
int i;
for (i = 0; i < htab->n_buckets; i++) {
struct hlist_nulls_head *head = select_bucket(htab, i);
struct hlist_nulls_node *n;
struct htab_elem *l;
hlist_nulls_for_each_entry_safe(l, n, head, hash_node) {
hlist_nulls_del_rcu(&l->hash_node);
if (l->state != HTAB_EXTRA_ELEM_USED)
htab_elem_free(htab, 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 free_htab_elem() callbacks for elements of this map may
* not have executed. Wait for them.
*/
rcu_barrier();
if (htab->map.map_flags & BPF_F_NO_PREALLOC)
delete_all_elements(htab);
else
prealloc_destroy(htab);
free_percpu(htab->extra_elems);
bpf_map_area_free(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 __ro_after_init = {
.ops = &htab_ops,
.type = BPF_MAP_TYPE_HASH,
};
static const struct bpf_map_ops htab_lru_ops = {
.map_alloc = htab_map_alloc,
.map_free = htab_map_free,
.map_get_next_key = htab_map_get_next_key,
.map_lookup_elem = htab_lru_map_lookup_elem,
.map_update_elem = htab_lru_map_update_elem,
.map_delete_elem = htab_lru_map_delete_elem,
};
static struct bpf_map_type_list htab_lru_type __ro_after_init = {
.ops = &htab_lru_ops,
.type = BPF_MAP_TYPE_LRU_HASH,
};
/* Called from eBPF program */
static void *htab_percpu_map_lookup_elem(struct bpf_map *map, void *key)
{
struct htab_elem *l = __htab_map_lookup_elem(map, key);
if (l)
return this_cpu_ptr(htab_elem_get_ptr(l, map->key_size));
else
return NULL;
}
static void *htab_lru_percpu_map_lookup_elem(struct bpf_map *map, void *key)
{
struct htab_elem *l = __htab_map_lookup_elem(map, key);
if (l) {
bpf_lru_node_set_ref(&l->lru_node);
return this_cpu_ptr(htab_elem_get_ptr(l, map->key_size));
}
return NULL;
}
int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value)
{
struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
struct htab_elem *l;
void __percpu *pptr;
int ret = -ENOENT;
int cpu, off = 0;
u32 size;
/* per_cpu areas are zero-filled and bpf programs can only
* access 'value_size' of them, so copying rounded areas
* will not leak any kernel data
*/
size = round_up(map->value_size, 8);
rcu_read_lock();
l = __htab_map_lookup_elem(map, key);
if (!l)
goto out;
if (htab_is_lru(htab))
bpf_lru_node_set_ref(&l->lru_node);
pptr = htab_elem_get_ptr(l, map->key_size);
for_each_possible_cpu(cpu) {
bpf_long_memcpy(value + off,
per_cpu_ptr(pptr, cpu), size);
off += size;
}
ret = 0;
out:
rcu_read_unlock();
return ret;
}
int bpf_percpu_hash_update(struct bpf_map *map, void *key, void *value,
u64 map_flags)
{
struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
int ret;
rcu_read_lock();
if (htab_is_lru(htab))
ret = __htab_lru_percpu_map_update_elem(map, key, value,
map_flags, true);
else
ret = __htab_percpu_map_update_elem(map, key, value, map_flags,
true);
rcu_read_unlock();
return ret;
}
static const struct bpf_map_ops htab_percpu_ops = {
.map_alloc = htab_map_alloc,
.map_free = htab_map_free,
.map_get_next_key = htab_map_get_next_key,
.map_lookup_elem = htab_percpu_map_lookup_elem,
.map_update_elem = htab_percpu_map_update_elem,
.map_delete_elem = htab_map_delete_elem,
};
static struct bpf_map_type_list htab_percpu_type __ro_after_init = {
.ops = &htab_percpu_ops,
.type = BPF_MAP_TYPE_PERCPU_HASH,
};
static const struct bpf_map_ops htab_lru_percpu_ops = {
.map_alloc = htab_map_alloc,
.map_free = htab_map_free,
.map_get_next_key = htab_map_get_next_key,
.map_lookup_elem = htab_lru_percpu_map_lookup_elem,
.map_update_elem = htab_lru_percpu_map_update_elem,
.map_delete_elem = htab_lru_map_delete_elem,
};
static struct bpf_map_type_list htab_lru_percpu_type __ro_after_init = {
.ops = &htab_lru_percpu_ops,
.type = BPF_MAP_TYPE_LRU_PERCPU_HASH,
};
static int __init register_htab_map(void)
{
bpf_register_map_type(&htab_type);
bpf_register_map_type(&htab_percpu_type);
bpf_register_map_type(&htab_lru_type);
bpf_register_map_type(&htab_lru_percpu_type);
return 0;
}
late_initcall(register_htab_map);