bpf: Split bpf_local_storage to bpf_sk_storage
A purely mechanical change:
bpf_sk_storage.c = bpf_sk_storage.c + bpf_local_storage.c
bpf_sk_storage.h = bpf_sk_storage.h + bpf_local_storage.h
Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20200825182919.1118197-5-kpsingh@chromium.org
diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c
new file mode 100644
index 0000000..ffa7d11
--- /dev/null
+++ b/kernel/bpf/bpf_local_storage.c
@@ -0,0 +1,600 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2019 Facebook */
+#include <linux/rculist.h>
+#include <linux/list.h>
+#include <linux/hash.h>
+#include <linux/types.h>
+#include <linux/spinlock.h>
+#include <linux/bpf.h>
+#include <linux/btf_ids.h>
+#include <linux/bpf_local_storage.h>
+#include <net/sock.h>
+#include <uapi/linux/sock_diag.h>
+#include <uapi/linux/btf.h>
+
+#define BPF_LOCAL_STORAGE_CREATE_FLAG_MASK (BPF_F_NO_PREALLOC | BPF_F_CLONE)
+
+static struct bpf_local_storage_map_bucket *
+select_bucket(struct bpf_local_storage_map *smap,
+ struct bpf_local_storage_elem *selem)
+{
+ return &smap->buckets[hash_ptr(selem, smap->bucket_log)];
+}
+
+static int mem_charge(struct bpf_local_storage_map *smap, void *owner, u32 size)
+{
+ struct bpf_map *map = &smap->map;
+
+ if (!map->ops->map_local_storage_charge)
+ return 0;
+
+ return map->ops->map_local_storage_charge(smap, owner, size);
+}
+
+static void mem_uncharge(struct bpf_local_storage_map *smap, void *owner,
+ u32 size)
+{
+ struct bpf_map *map = &smap->map;
+
+ if (map->ops->map_local_storage_uncharge)
+ map->ops->map_local_storage_uncharge(smap, owner, size);
+}
+
+static struct bpf_local_storage __rcu **
+owner_storage(struct bpf_local_storage_map *smap, void *owner)
+{
+ struct bpf_map *map = &smap->map;
+
+ return map->ops->map_owner_storage_ptr(owner);
+}
+
+static bool selem_linked_to_storage(const struct bpf_local_storage_elem *selem)
+{
+ return !hlist_unhashed(&selem->snode);
+}
+
+static bool selem_linked_to_map(const struct bpf_local_storage_elem *selem)
+{
+ return !hlist_unhashed(&selem->map_node);
+}
+
+struct bpf_local_storage_elem *
+bpf_selem_alloc(struct bpf_local_storage_map *smap, void *owner,
+ void *value, bool charge_mem)
+{
+ struct bpf_local_storage_elem *selem;
+
+ if (charge_mem && mem_charge(smap, owner, smap->elem_size))
+ return NULL;
+
+ selem = kzalloc(smap->elem_size, GFP_ATOMIC | __GFP_NOWARN);
+ if (selem) {
+ if (value)
+ memcpy(SDATA(selem)->data, value, smap->map.value_size);
+ return selem;
+ }
+
+ if (charge_mem)
+ mem_uncharge(smap, owner, smap->elem_size);
+
+ return NULL;
+}
+
+/* local_storage->lock must be held and selem->local_storage == local_storage.
+ * The caller must ensure selem->smap is still valid to be
+ * dereferenced for its smap->elem_size and smap->cache_idx.
+ */
+bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_storage,
+ struct bpf_local_storage_elem *selem,
+ bool uncharge_mem)
+{
+ struct bpf_local_storage_map *smap;
+ bool free_local_storage;
+ void *owner;
+
+ smap = rcu_dereference(SDATA(selem)->smap);
+ owner = local_storage->owner;
+
+ /* All uncharging on the owner must be done first.
+ * The owner may be freed once the last selem is unlinked
+ * from local_storage.
+ */
+ if (uncharge_mem)
+ mem_uncharge(smap, owner, smap->elem_size);
+
+ free_local_storage = hlist_is_singular_node(&selem->snode,
+ &local_storage->list);
+ if (free_local_storage) {
+ mem_uncharge(smap, owner, sizeof(struct bpf_local_storage));
+ local_storage->owner = NULL;
+
+ /* After this RCU_INIT, owner may be freed and cannot be used */
+ RCU_INIT_POINTER(*owner_storage(smap, owner), NULL);
+
+ /* local_storage is not freed now. local_storage->lock is
+ * still held and raw_spin_unlock_bh(&local_storage->lock)
+ * will be done by the caller.
+ *
+ * Although the unlock will be done under
+ * rcu_read_lock(), it is more intutivie to
+ * read if kfree_rcu(local_storage, rcu) is done
+ * after the raw_spin_unlock_bh(&local_storage->lock).
+ *
+ * Hence, a "bool free_local_storage" is returned
+ * to the caller which then calls the kfree_rcu()
+ * after unlock.
+ */
+ }
+ hlist_del_init_rcu(&selem->snode);
+ if (rcu_access_pointer(local_storage->cache[smap->cache_idx]) ==
+ SDATA(selem))
+ RCU_INIT_POINTER(local_storage->cache[smap->cache_idx], NULL);
+
+ kfree_rcu(selem, rcu);
+
+ return free_local_storage;
+}
+
+static void __bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem)
+{
+ struct bpf_local_storage *local_storage;
+ bool free_local_storage = false;
+
+ if (unlikely(!selem_linked_to_storage(selem)))
+ /* selem has already been unlinked from sk */
+ return;
+
+ local_storage = rcu_dereference(selem->local_storage);
+ raw_spin_lock_bh(&local_storage->lock);
+ if (likely(selem_linked_to_storage(selem)))
+ free_local_storage = bpf_selem_unlink_storage_nolock(
+ local_storage, selem, true);
+ raw_spin_unlock_bh(&local_storage->lock);
+
+ if (free_local_storage)
+ kfree_rcu(local_storage, rcu);
+}
+
+void bpf_selem_link_storage_nolock(struct bpf_local_storage *local_storage,
+ struct bpf_local_storage_elem *selem)
+{
+ RCU_INIT_POINTER(selem->local_storage, local_storage);
+ hlist_add_head(&selem->snode, &local_storage->list);
+}
+
+void bpf_selem_unlink_map(struct bpf_local_storage_elem *selem)
+{
+ struct bpf_local_storage_map *smap;
+ struct bpf_local_storage_map_bucket *b;
+
+ if (unlikely(!selem_linked_to_map(selem)))
+ /* selem has already be unlinked from smap */
+ return;
+
+ smap = rcu_dereference(SDATA(selem)->smap);
+ b = select_bucket(smap, selem);
+ raw_spin_lock_bh(&b->lock);
+ if (likely(selem_linked_to_map(selem)))
+ hlist_del_init_rcu(&selem->map_node);
+ raw_spin_unlock_bh(&b->lock);
+}
+
+void bpf_selem_link_map(struct bpf_local_storage_map *smap,
+ struct bpf_local_storage_elem *selem)
+{
+ struct bpf_local_storage_map_bucket *b = select_bucket(smap, selem);
+
+ raw_spin_lock_bh(&b->lock);
+ RCU_INIT_POINTER(SDATA(selem)->smap, smap);
+ hlist_add_head_rcu(&selem->map_node, &b->list);
+ raw_spin_unlock_bh(&b->lock);
+}
+
+void bpf_selem_unlink(struct bpf_local_storage_elem *selem)
+{
+ /* Always unlink from map before unlinking from local_storage
+ * because selem will be freed after successfully unlinked from
+ * the local_storage.
+ */
+ bpf_selem_unlink_map(selem);
+ __bpf_selem_unlink_storage(selem);
+}
+
+struct bpf_local_storage_data *
+bpf_local_storage_lookup(struct bpf_local_storage *local_storage,
+ struct bpf_local_storage_map *smap,
+ bool cacheit_lockit)
+{
+ struct bpf_local_storage_data *sdata;
+ struct bpf_local_storage_elem *selem;
+
+ /* Fast path (cache hit) */
+ sdata = rcu_dereference(local_storage->cache[smap->cache_idx]);
+ if (sdata && rcu_access_pointer(sdata->smap) == smap)
+ return sdata;
+
+ /* Slow path (cache miss) */
+ hlist_for_each_entry_rcu(selem, &local_storage->list, snode)
+ if (rcu_access_pointer(SDATA(selem)->smap) == smap)
+ break;
+
+ if (!selem)
+ return NULL;
+
+ sdata = SDATA(selem);
+ if (cacheit_lockit) {
+ /* spinlock is needed to avoid racing with the
+ * parallel delete. Otherwise, publishing an already
+ * deleted sdata to the cache will become a use-after-free
+ * problem in the next bpf_local_storage_lookup().
+ */
+ raw_spin_lock_bh(&local_storage->lock);
+ if (selem_linked_to_storage(selem))
+ rcu_assign_pointer(local_storage->cache[smap->cache_idx],
+ sdata);
+ raw_spin_unlock_bh(&local_storage->lock);
+ }
+
+ return sdata;
+}
+
+static int check_flags(const struct bpf_local_storage_data *old_sdata,
+ u64 map_flags)
+{
+ if (old_sdata && (map_flags & ~BPF_F_LOCK) == BPF_NOEXIST)
+ /* elem already exists */
+ return -EEXIST;
+
+ if (!old_sdata && (map_flags & ~BPF_F_LOCK) == BPF_EXIST)
+ /* elem doesn't exist, cannot update it */
+ return -ENOENT;
+
+ return 0;
+}
+
+int bpf_local_storage_alloc(void *owner,
+ struct bpf_local_storage_map *smap,
+ struct bpf_local_storage_elem *first_selem)
+{
+ struct bpf_local_storage *prev_storage, *storage;
+ struct bpf_local_storage **owner_storage_ptr;
+ int err;
+
+ err = mem_charge(smap, owner, sizeof(*storage));
+ if (err)
+ return err;
+
+ storage = kzalloc(sizeof(*storage), GFP_ATOMIC | __GFP_NOWARN);
+ if (!storage) {
+ err = -ENOMEM;
+ goto uncharge;
+ }
+
+ INIT_HLIST_HEAD(&storage->list);
+ raw_spin_lock_init(&storage->lock);
+ storage->owner = owner;
+
+ bpf_selem_link_storage_nolock(storage, first_selem);
+ bpf_selem_link_map(smap, first_selem);
+
+ owner_storage_ptr =
+ (struct bpf_local_storage **)owner_storage(smap, owner);
+ /* Publish storage to the owner.
+ * Instead of using any lock of the kernel object (i.e. owner),
+ * cmpxchg will work with any kernel object regardless what
+ * the running context is, bh, irq...etc.
+ *
+ * From now on, the owner->storage pointer (e.g. sk->sk_bpf_storage)
+ * is protected by the storage->lock. Hence, when freeing
+ * the owner->storage, the storage->lock must be held before
+ * setting owner->storage ptr to NULL.
+ */
+ prev_storage = cmpxchg(owner_storage_ptr, NULL, storage);
+ if (unlikely(prev_storage)) {
+ bpf_selem_unlink_map(first_selem);
+ err = -EAGAIN;
+ goto uncharge;
+
+ /* Note that even first_selem was linked to smap's
+ * bucket->list, first_selem can be freed immediately
+ * (instead of kfree_rcu) because
+ * bpf_local_storage_map_free() does a
+ * synchronize_rcu() before walking the bucket->list.
+ * Hence, no one is accessing selem from the
+ * bucket->list under rcu_read_lock().
+ */
+ }
+
+ return 0;
+
+uncharge:
+ kfree(storage);
+ mem_uncharge(smap, owner, sizeof(*storage));
+ return err;
+}
+
+/* sk cannot be going away because it is linking new elem
+ * to sk->sk_bpf_storage. (i.e. sk->sk_refcnt cannot be 0).
+ * Otherwise, it will become a leak (and other memory issues
+ * during map destruction).
+ */
+struct bpf_local_storage_data *
+bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap,
+ void *value, u64 map_flags)
+{
+ struct bpf_local_storage_data *old_sdata = NULL;
+ struct bpf_local_storage_elem *selem;
+ struct bpf_local_storage *local_storage;
+ int err;
+
+ /* BPF_EXIST and BPF_NOEXIST cannot be both set */
+ if (unlikely((map_flags & ~BPF_F_LOCK) > BPF_EXIST) ||
+ /* BPF_F_LOCK can only be used in a value with spin_lock */
+ unlikely((map_flags & BPF_F_LOCK) &&
+ !map_value_has_spin_lock(&smap->map)))
+ return ERR_PTR(-EINVAL);
+
+ local_storage = rcu_dereference(*owner_storage(smap, owner));
+ if (!local_storage || hlist_empty(&local_storage->list)) {
+ /* Very first elem for the owner */
+ err = check_flags(NULL, map_flags);
+ if (err)
+ return ERR_PTR(err);
+
+ selem = bpf_selem_alloc(smap, owner, value, true);
+ if (!selem)
+ return ERR_PTR(-ENOMEM);
+
+ err = bpf_local_storage_alloc(owner, smap, selem);
+ if (err) {
+ kfree(selem);
+ mem_uncharge(smap, owner, smap->elem_size);
+ return ERR_PTR(err);
+ }
+
+ return SDATA(selem);
+ }
+
+ if ((map_flags & BPF_F_LOCK) && !(map_flags & BPF_NOEXIST)) {
+ /* Hoping to find an old_sdata to do inline update
+ * such that it can avoid taking the local_storage->lock
+ * and changing the lists.
+ */
+ old_sdata =
+ bpf_local_storage_lookup(local_storage, smap, false);
+ err = check_flags(old_sdata, map_flags);
+ if (err)
+ return ERR_PTR(err);
+ if (old_sdata && selem_linked_to_storage(SELEM(old_sdata))) {
+ copy_map_value_locked(&smap->map, old_sdata->data,
+ value, false);
+ return old_sdata;
+ }
+ }
+
+ raw_spin_lock_bh(&local_storage->lock);
+
+ /* Recheck local_storage->list under local_storage->lock */
+ if (unlikely(hlist_empty(&local_storage->list))) {
+ /* A parallel del is happening and local_storage is going
+ * away. It has just been checked before, so very
+ * unlikely. Return instead of retry to keep things
+ * simple.
+ */
+ err = -EAGAIN;
+ goto unlock_err;
+ }
+
+ old_sdata = bpf_local_storage_lookup(local_storage, smap, false);
+ err = check_flags(old_sdata, map_flags);
+ if (err)
+ goto unlock_err;
+
+ if (old_sdata && (map_flags & BPF_F_LOCK)) {
+ copy_map_value_locked(&smap->map, old_sdata->data, value,
+ false);
+ selem = SELEM(old_sdata);
+ goto unlock;
+ }
+
+ /* local_storage->lock is held. Hence, we are sure
+ * we can unlink and uncharge the old_sdata successfully
+ * later. Hence, instead of charging the new selem now
+ * and then uncharge the old selem later (which may cause
+ * a potential but unnecessary charge failure), avoid taking
+ * a charge at all here (the "!old_sdata" check) and the
+ * old_sdata will not be uncharged later during
+ * bpf_selem_unlink_storage_nolock().
+ */
+ selem = bpf_selem_alloc(smap, owner, value, !old_sdata);
+ if (!selem) {
+ err = -ENOMEM;
+ goto unlock_err;
+ }
+
+ /* First, link the new selem to the map */
+ bpf_selem_link_map(smap, selem);
+
+ /* Second, link (and publish) the new selem to local_storage */
+ bpf_selem_link_storage_nolock(local_storage, selem);
+
+ /* Third, remove old selem, SELEM(old_sdata) */
+ if (old_sdata) {
+ bpf_selem_unlink_map(SELEM(old_sdata));
+ bpf_selem_unlink_storage_nolock(local_storage, SELEM(old_sdata),
+ false);
+ }
+
+unlock:
+ raw_spin_unlock_bh(&local_storage->lock);
+ return SDATA(selem);
+
+unlock_err:
+ raw_spin_unlock_bh(&local_storage->lock);
+ return ERR_PTR(err);
+}
+
+u16 bpf_local_storage_cache_idx_get(struct bpf_local_storage_cache *cache)
+{
+ u64 min_usage = U64_MAX;
+ u16 i, res = 0;
+
+ spin_lock(&cache->idx_lock);
+
+ for (i = 0; i < BPF_LOCAL_STORAGE_CACHE_SIZE; i++) {
+ if (cache->idx_usage_counts[i] < min_usage) {
+ min_usage = cache->idx_usage_counts[i];
+ res = i;
+
+ /* Found a free cache_idx */
+ if (!min_usage)
+ break;
+ }
+ }
+ cache->idx_usage_counts[res]++;
+
+ spin_unlock(&cache->idx_lock);
+
+ return res;
+}
+
+void bpf_local_storage_cache_idx_free(struct bpf_local_storage_cache *cache,
+ u16 idx)
+{
+ spin_lock(&cache->idx_lock);
+ cache->idx_usage_counts[idx]--;
+ spin_unlock(&cache->idx_lock);
+}
+
+void bpf_local_storage_map_free(struct bpf_local_storage_map *smap)
+{
+ struct bpf_local_storage_elem *selem;
+ struct bpf_local_storage_map_bucket *b;
+ unsigned int i;
+
+ /* Note that this map might be concurrently cloned from
+ * bpf_sk_storage_clone. Wait for any existing bpf_sk_storage_clone
+ * RCU read section to finish before proceeding. New RCU
+ * read sections should be prevented via bpf_map_inc_not_zero.
+ */
+ synchronize_rcu();
+
+ /* bpf prog and the userspace can no longer access this map
+ * now. No new selem (of this map) can be added
+ * to the owner->storage or to the map bucket's list.
+ *
+ * The elem of this map can be cleaned up here
+ * or when the storage is freed e.g.
+ * by bpf_sk_storage_free() during __sk_destruct().
+ */
+ for (i = 0; i < (1U << smap->bucket_log); i++) {
+ b = &smap->buckets[i];
+
+ rcu_read_lock();
+ /* No one is adding to b->list now */
+ while ((selem = hlist_entry_safe(
+ rcu_dereference_raw(hlist_first_rcu(&b->list)),
+ struct bpf_local_storage_elem, map_node))) {
+ bpf_selem_unlink(selem);
+ cond_resched_rcu();
+ }
+ rcu_read_unlock();
+ }
+
+ /* While freeing the storage we may still need to access the map.
+ *
+ * e.g. when bpf_sk_storage_free() has unlinked selem from the map
+ * which then made the above while((selem = ...)) loop
+ * exit immediately.
+ *
+ * However, while freeing the storage one still needs to access the
+ * smap->elem_size to do the uncharging in
+ * bpf_selem_unlink_storage_nolock().
+ *
+ * Hence, wait another rcu grace period for the storage to be freed.
+ */
+ synchronize_rcu();
+
+ kvfree(smap->buckets);
+ kfree(smap);
+}
+
+int bpf_local_storage_map_alloc_check(union bpf_attr *attr)
+{
+ if (attr->map_flags & ~BPF_LOCAL_STORAGE_CREATE_FLAG_MASK ||
+ !(attr->map_flags & BPF_F_NO_PREALLOC) ||
+ attr->max_entries ||
+ attr->key_size != sizeof(int) || !attr->value_size ||
+ /* Enforce BTF for userspace sk dumping */
+ !attr->btf_key_type_id || !attr->btf_value_type_id)
+ return -EINVAL;
+
+ if (!bpf_capable())
+ return -EPERM;
+
+ if (attr->value_size > BPF_LOCAL_STORAGE_MAX_VALUE_SIZE)
+ return -E2BIG;
+
+ return 0;
+}
+
+struct bpf_local_storage_map *bpf_local_storage_map_alloc(union bpf_attr *attr)
+{
+ struct bpf_local_storage_map *smap;
+ unsigned int i;
+ u32 nbuckets;
+ u64 cost;
+ int ret;
+
+ smap = kzalloc(sizeof(*smap), GFP_USER | __GFP_NOWARN);
+ if (!smap)
+ return ERR_PTR(-ENOMEM);
+ bpf_map_init_from_attr(&smap->map, attr);
+
+ nbuckets = roundup_pow_of_two(num_possible_cpus());
+ /* Use at least 2 buckets, select_bucket() is undefined behavior with 1 bucket */
+ nbuckets = max_t(u32, 2, nbuckets);
+ smap->bucket_log = ilog2(nbuckets);
+ cost = sizeof(*smap->buckets) * nbuckets + sizeof(*smap);
+
+ ret = bpf_map_charge_init(&smap->map.memory, cost);
+ if (ret < 0) {
+ kfree(smap);
+ return ERR_PTR(ret);
+ }
+
+ smap->buckets = kvcalloc(sizeof(*smap->buckets), nbuckets,
+ GFP_USER | __GFP_NOWARN);
+ if (!smap->buckets) {
+ bpf_map_charge_finish(&smap->map.memory);
+ kfree(smap);
+ return ERR_PTR(-ENOMEM);
+ }
+
+ for (i = 0; i < nbuckets; i++) {
+ INIT_HLIST_HEAD(&smap->buckets[i].list);
+ raw_spin_lock_init(&smap->buckets[i].lock);
+ }
+
+ smap->elem_size =
+ sizeof(struct bpf_local_storage_elem) + attr->value_size;
+
+ return smap;
+}
+
+int bpf_local_storage_map_check_btf(const struct bpf_map *map,
+ const struct btf *btf,
+ const struct btf_type *key_type,
+ const struct btf_type *value_type)
+{
+ u32 int_data;
+
+ if (BTF_INFO_KIND(key_type->info) != BTF_KIND_INT)
+ return -EINVAL;
+
+ int_data = *(u32 *)(key_type + 1);
+ if (BTF_INT_BITS(int_data) != 32 || BTF_INT_OFFSET(int_data))
+ return -EINVAL;
+
+ return 0;
+}
