bpf: introduce cgroup storage maps

This commit introduces BPF_MAP_TYPE_CGROUP_STORAGE maps:
a special type of maps which are implementing the cgroup storage.

>From the userspace point of view it's almost a generic
hash map with the (cgroup inode id, attachment type) pair
used as a key.

The only difference is that some operations are restricted:
  1) a user can't create new entries,
  2) a user can't remove existing entries.

The lookup from userspace is o(log(n)).

Signed-off-by: Roman Gushchin <guro@fb.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 376 insertions, 0 deletions

diff --git a/kernel/bpf/local_storage.c b/kernel/bpf/local_storage.c
new file mode 100644
index 000000000000..f23d3fdeba23
--- /dev/null
+++ b/kernel/bpf/local_storage.c
@@ -0,0 +1,376 @@
+//SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf-cgroup.h>
+#include <linux/bpf.h>
+#include <linux/bug.h>
+#include <linux/filter.h>
+#include <linux/mm.h>
+#include <linux/rbtree.h>
+#include <linux/slab.h>
+
+#ifdef CONFIG_CGROUP_BPF
+
+#define LOCAL_STORAGE_CREATE_FLAG_MASK					\
+	(BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY)
+
+struct bpf_cgroup_storage_map {
+	struct bpf_map map;
+
+	spinlock_t lock;
+	struct bpf_prog *prog;
+	struct rb_root root;
+	struct list_head list;
+};
+
+static struct bpf_cgroup_storage_map *map_to_storage(struct bpf_map *map)
+{
+	return container_of(map, struct bpf_cgroup_storage_map, map);
+}
+
+static int bpf_cgroup_storage_key_cmp(
+	const struct bpf_cgroup_storage_key *key1,
+	const struct bpf_cgroup_storage_key *key2)
+{
+	if (key1->cgroup_inode_id < key2->cgroup_inode_id)
+		return -1;
+	else if (key1->cgroup_inode_id > key2->cgroup_inode_id)
+		return 1;
+	else if (key1->attach_type < key2->attach_type)
+		return -1;
+	else if (key1->attach_type > key2->attach_type)
+		return 1;
+	return 0;
+}
+
+static struct bpf_cgroup_storage *cgroup_storage_lookup(
+	struct bpf_cgroup_storage_map *map, struct bpf_cgroup_storage_key *key,
+	bool locked)
+{
+	struct rb_root *root = &map->root;
+	struct rb_node *node;
+
+	if (!locked)
+		spin_lock_bh(&map->lock);
+
+	node = root->rb_node;
+	while (node) {
+		struct bpf_cgroup_storage *storage;
+
+		storage = container_of(node, struct bpf_cgroup_storage, node);
+
+		switch (bpf_cgroup_storage_key_cmp(key, &storage->key)) {
+		case -1:
+			node = node->rb_left;
+			break;
+		case 1:
+			node = node->rb_right;
+			break;
+		default:
+			if (!locked)
+				spin_unlock_bh(&map->lock);
+			return storage;
+		}
+	}
+
+	if (!locked)
+		spin_unlock_bh(&map->lock);
+
+	return NULL;
+}
+
+static int cgroup_storage_insert(struct bpf_cgroup_storage_map *map,
+				 struct bpf_cgroup_storage *storage)
+{
+	struct rb_root *root = &map->root;
+	struct rb_node **new = &(root->rb_node), *parent = NULL;
+
+	while (*new) {
+		struct bpf_cgroup_storage *this;
+
+		this = container_of(*new, struct bpf_cgroup_storage, node);
+
+		parent = *new;
+		switch (bpf_cgroup_storage_key_cmp(&storage->key, &this->key)) {
+		case -1:
+			new = &((*new)->rb_left);
+			break;
+		case 1:
+			new = &((*new)->rb_right);
+			break;
+		default:
+			return -EEXIST;
+		}
+	}
+
+	rb_link_node(&storage->node, parent, new);
+	rb_insert_color(&storage->node, root);
+
+	return 0;
+}
+
+static void *cgroup_storage_lookup_elem(struct bpf_map *_map, void *_key)
+{
+	struct bpf_cgroup_storage_map *map = map_to_storage(_map);
+	struct bpf_cgroup_storage_key *key = _key;
+	struct bpf_cgroup_storage *storage;
+
+	storage = cgroup_storage_lookup(map, key, false);
+	if (!storage)
+		return NULL;
+
+	return &READ_ONCE(storage->buf)->data[0];
+}
+
+static int cgroup_storage_update_elem(struct bpf_map *map, void *_key,
+				      void *value, u64 flags)
+{
+	struct bpf_cgroup_storage_key *key = _key;
+	struct bpf_cgroup_storage *storage;
+	struct bpf_storage_buffer *new;
+
+	if (flags & BPF_NOEXIST)
+		return -EINVAL;
+
+	storage = cgroup_storage_lookup((struct bpf_cgroup_storage_map *)map,
+					key, false);
+	if (!storage)
+		return -ENOENT;
+
+	new = kmalloc_node(sizeof(struct bpf_storage_buffer) +
+			   map->value_size, __GFP_ZERO | GFP_USER,
+			   map->numa_node);
+	if (!new)
+		return -ENOMEM;
+
+	memcpy(&new->data[0], value, map->value_size);
+
+	new = xchg(&storage->buf, new);
+	kfree_rcu(new, rcu);
+
+	return 0;
+}
+
+static int cgroup_storage_get_next_key(struct bpf_map *_map, void *_key,
+				       void *_next_key)
+{
+	struct bpf_cgroup_storage_map *map = map_to_storage(_map);
+	struct bpf_cgroup_storage_key *key = _key;
+	struct bpf_cgroup_storage_key *next = _next_key;
+	struct bpf_cgroup_storage *storage;
+
+	spin_lock_bh(&map->lock);
+
+	if (list_empty(&map->list))
+		goto enoent;
+
+	if (key) {
+		storage = cgroup_storage_lookup(map, key, true);
+		if (!storage)
+			goto enoent;
+
+		storage = list_next_entry(storage, list);
+		if (!storage)
+			goto enoent;
+	} else {
+		storage = list_first_entry(&map->list,
+					 struct bpf_cgroup_storage, list);
+	}
+
+	spin_unlock_bh(&map->lock);
+	next->attach_type = storage->key.attach_type;
+	next->cgroup_inode_id = storage->key.cgroup_inode_id;
+	return 0;
+
+enoent:
+	spin_unlock_bh(&map->lock);
+	return -ENOENT;
+}
+
+static struct bpf_map *cgroup_storage_map_alloc(union bpf_attr *attr)
+{
+	int numa_node = bpf_map_attr_numa_node(attr);
+	struct bpf_cgroup_storage_map *map;
+
+	if (attr->key_size != sizeof(struct bpf_cgroup_storage_key))
+		return ERR_PTR(-EINVAL);
+
+	if (attr->value_size > PAGE_SIZE)
+		return ERR_PTR(-E2BIG);
+
+	if (attr->map_flags & ~LOCAL_STORAGE_CREATE_FLAG_MASK)
+		/* reserved bits should not be used */
+		return ERR_PTR(-EINVAL);
+
+	if (attr->max_entries)
+		/* max_entries is not used and enforced to be 0 */
+		return ERR_PTR(-EINVAL);
+
+	map = kmalloc_node(sizeof(struct bpf_cgroup_storage_map),
+			   __GFP_ZERO | GFP_USER, numa_node);
+	if (!map)
+		return ERR_PTR(-ENOMEM);
+
+	map->map.pages = round_up(sizeof(struct bpf_cgroup_storage_map),
+				  PAGE_SIZE) >> PAGE_SHIFT;
+
+	/* copy mandatory map attributes */
+	bpf_map_init_from_attr(&map->map, attr);
+
+	spin_lock_init(&map->lock);
+	map->root = RB_ROOT;
+	INIT_LIST_HEAD(&map->list);
+
+	return &map->map;
+}
+
+static void cgroup_storage_map_free(struct bpf_map *_map)
+{
+	struct bpf_cgroup_storage_map *map = map_to_storage(_map);
+
+	WARN_ON(!RB_EMPTY_ROOT(&map->root));
+	WARN_ON(!list_empty(&map->list));
+
+	kfree(map);
+}
+
+static int cgroup_storage_delete_elem(struct bpf_map *map, void *key)
+{
+	return -EINVAL;
+}
+
+const struct bpf_map_ops cgroup_storage_map_ops = {
+	.map_alloc = cgroup_storage_map_alloc,
+	.map_free = cgroup_storage_map_free,
+	.map_get_next_key = cgroup_storage_get_next_key,
+	.map_lookup_elem = cgroup_storage_lookup_elem,
+	.map_update_elem = cgroup_storage_update_elem,
+	.map_delete_elem = cgroup_storage_delete_elem,
+};
+
+int bpf_cgroup_storage_assign(struct bpf_prog *prog, struct bpf_map *_map)
+{
+	struct bpf_cgroup_storage_map *map = map_to_storage(_map);
+	int ret = -EBUSY;
+
+	spin_lock_bh(&map->lock);
+
+	if (map->prog && map->prog != prog)
+		goto unlock;
+	if (prog->aux->cgroup_storage && prog->aux->cgroup_storage != _map)
+		goto unlock;
+
+	map->prog = prog;
+	prog->aux->cgroup_storage = _map;
+	ret = 0;
+unlock:
+	spin_unlock_bh(&map->lock);
+
+	return ret;
+}
+
+void bpf_cgroup_storage_release(struct bpf_prog *prog, struct bpf_map *_map)
+{
+	struct bpf_cgroup_storage_map *map = map_to_storage(_map);
+
+	spin_lock_bh(&map->lock);
+	if (map->prog == prog) {
+		WARN_ON(prog->aux->cgroup_storage != _map);
+		map->prog = NULL;
+		prog->aux->cgroup_storage = NULL;
+	}
+	spin_unlock_bh(&map->lock);
+}
+
+struct bpf_cgroup_storage *bpf_cgroup_storage_alloc(struct bpf_prog *prog)
+{
+	struct bpf_cgroup_storage *storage;
+	struct bpf_map *map;
+	u32 pages;
+
+	map = prog->aux->cgroup_storage;
+	if (!map)
+		return NULL;
+
+	pages = round_up(sizeof(struct bpf_cgroup_storage) +
+			 sizeof(struct bpf_storage_buffer) +
+			 map->value_size, PAGE_SIZE) >> PAGE_SHIFT;
+	if (bpf_map_charge_memlock(map, pages))
+		return ERR_PTR(-EPERM);
+
+	storage = kmalloc_node(sizeof(struct bpf_cgroup_storage),
+			       __GFP_ZERO | GFP_USER, map->numa_node);
+	if (!storage) {
+		bpf_map_uncharge_memlock(map, pages);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	storage->buf = kmalloc_node(sizeof(struct bpf_storage_buffer) +
+				    map->value_size, __GFP_ZERO | GFP_USER,
+				    map->numa_node);
+	if (!storage->buf) {
+		bpf_map_uncharge_memlock(map, pages);
+		kfree(storage);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	storage->map = (struct bpf_cgroup_storage_map *)map;
+
+	return storage;
+}
+
+void bpf_cgroup_storage_free(struct bpf_cgroup_storage *storage)
+{
+	u32 pages;
+	struct bpf_map *map;
+
+	if (!storage)
+		return;
+
+	map = &storage->map->map;
+	pages = round_up(sizeof(struct bpf_cgroup_storage) +
+			 sizeof(struct bpf_storage_buffer) +
+			 map->value_size, PAGE_SIZE) >> PAGE_SHIFT;
+	bpf_map_uncharge_memlock(map, pages);
+
+	kfree_rcu(storage->buf, rcu);
+	kfree_rcu(storage, rcu);
+}
+
+void bpf_cgroup_storage_link(struct bpf_cgroup_storage *storage,
+			     struct cgroup *cgroup,
+			     enum bpf_attach_type type)
+{
+	struct bpf_cgroup_storage_map *map;
+
+	if (!storage)
+		return;
+
+	storage->key.attach_type = type;
+	storage->key.cgroup_inode_id = cgroup->kn->id.id;
+
+	map = storage->map;
+
+	spin_lock_bh(&map->lock);
+	WARN_ON(cgroup_storage_insert(map, storage));
+	list_add(&storage->list, &map->list);
+	spin_unlock_bh(&map->lock);
+}
+
+void bpf_cgroup_storage_unlink(struct bpf_cgroup_storage *storage)
+{
+	struct bpf_cgroup_storage_map *map;
+	struct rb_root *root;
+
+	if (!storage)
+		return;
+
+	map = storage->map;
+
+	spin_lock_bh(&map->lock);
+	root = &map->root;
+	rb_erase(&storage->node, root);
+
+	list_del(&storage->list);
+	spin_unlock_bh(&map->lock);
+}
+
+#endif