xref: /openbmc/linux/kernel/bpf/local_storage.c (revision d7ba4cc9)

// SPDX-License-Identifier: GPL-2.0
#include <linux/bpf-cgroup.h>
#include <linux/bpf.h>
#include <linux/bpf_local_storage.h>
#include <linux/btf.h>
#include <linux/bug.h>
#include <linux/filter.h>
#include <linux/mm.h>
#include <linux/rbtree.h>
#include <linux/slab.h>
#include <uapi/linux/btf.h>
#include <linux/btf_ids.h>

#ifdef CONFIG_CGROUP_BPF

#include "../cgroup/cgroup-internal.h"

#define LOCAL_STORAGE_CREATE_FLAG_MASK					\
	(BPF_F_NUMA_NODE | BPF_F_ACCESS_MASK)

struct bpf_cgroup_storage_map {
	struct bpf_map map;

	spinlock_t lock;
	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 bool attach_type_isolated(const struct bpf_map *map)
{
	return map->key_size == sizeof(struct bpf_cgroup_storage_key);
}

static int bpf_cgroup_storage_key_cmp(const struct bpf_cgroup_storage_map *map,
				      const void *_key1, const void *_key2)
{
	if (attach_type_isolated(&map->map)) {
		const struct bpf_cgroup_storage_key *key1 = _key1;
		const struct bpf_cgroup_storage_key *key2 = _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;
	} else {
		const __u64 *cgroup_inode_id1 = _key1;
		const __u64 *cgroup_inode_id2 = _key2;

		if (*cgroup_inode_id1 < *cgroup_inode_id2)
			return -1;
		else if (*cgroup_inode_id1 > *cgroup_inode_id2)
			return 1;
	}
	return 0;
}

struct bpf_cgroup_storage *
cgroup_storage_lookup(struct bpf_cgroup_storage_map *map,
		      void *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(map, 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(map, &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 *storage;

	storage = cgroup_storage_lookup(map, key, false);
	if (!storage)
		return NULL;

	return &READ_ONCE(storage->buf)->data[0];
}

static long cgroup_storage_update_elem(struct bpf_map *map, void *key,
				       void *value, u64 flags)
{
	struct bpf_cgroup_storage *storage;
	struct bpf_storage_buffer *new;

	if (unlikely(flags & ~(BPF_F_LOCK | BPF_EXIST)))
		return -EINVAL;

	if (unlikely((flags & BPF_F_LOCK) &&
		     !btf_record_has_field(map->record, BPF_SPIN_LOCK)))
		return -EINVAL;

	storage = cgroup_storage_lookup((struct bpf_cgroup_storage_map *)map,
					key, false);
	if (!storage)
		return -ENOENT;

	if (flags & BPF_F_LOCK) {
		copy_map_value_locked(map, storage->buf->data, value, false);
		return 0;
	}

	new = bpf_map_kmalloc_node(map, struct_size(new, data, map->value_size),
				   __GFP_ZERO | GFP_NOWAIT | __GFP_NOWARN,
				   map->numa_node);
	if (!new)
		return -ENOMEM;

	memcpy(&new->data[0], value, map->value_size);
	check_and_init_map_value(map, new->data);

	new = xchg(&storage->buf, new);
	kfree_rcu(new, rcu);

	return 0;
}

int bpf_percpu_cgroup_storage_copy(struct bpf_map *_map, void *key,
				   void *value)
{
	struct bpf_cgroup_storage_map *map = map_to_storage(_map);
	struct bpf_cgroup_storage *storage;
	int cpu, off = 0;
	u32 size;

	rcu_read_lock();
	storage = cgroup_storage_lookup(map, key, false);
	if (!storage) {
		rcu_read_unlock();
		return -ENOENT;
	}

	/* 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);
	for_each_possible_cpu(cpu) {
		bpf_long_memcpy(value + off,
				per_cpu_ptr(storage->percpu_buf, cpu), size);
		off += size;
	}
	rcu_read_unlock();
	return 0;
}

int bpf_percpu_cgroup_storage_update(struct bpf_map *_map, void *key,
				     void *value, u64 map_flags)
{
	struct bpf_cgroup_storage_map *map = map_to_storage(_map);
	struct bpf_cgroup_storage *storage;
	int cpu, off = 0;
	u32 size;

	if (map_flags != BPF_ANY && map_flags != BPF_EXIST)
		return -EINVAL;

	rcu_read_lock();
	storage = cgroup_storage_lookup(map, key, false);
	if (!storage) {
		rcu_read_unlock();
		return -ENOENT;
	}

	/* the user space will provide round_up(value_size, 8) bytes that
	 * will be copied into per-cpu area. bpf programs can only access
	 * value_size of it. During lookup the same extra bytes will be
	 * returned or zeros which were zero-filled by percpu_alloc,
	 * so no kernel data leaks possible
	 */
	size = round_up(_map->value_size, 8);
	for_each_possible_cpu(cpu) {
		bpf_long_memcpy(per_cpu_ptr(storage->percpu_buf, cpu),
				value + off, size);
		off += size;
	}
	rcu_read_unlock();
	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 *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_map);
		if (!storage)
			goto enoent;
	} else {
		storage = list_first_entry(&map->list,
					 struct bpf_cgroup_storage, list_map);
	}

	spin_unlock_bh(&map->lock);

	if (attach_type_isolated(&map->map)) {
		struct bpf_cgroup_storage_key *next = _next_key;
		*next = storage->key;
	} else {
		__u64 *next = _next_key;
		*next = 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)
{
	__u32 max_value_size = BPF_LOCAL_STORAGE_MAX_VALUE_SIZE;
	int numa_node = bpf_map_attr_numa_node(attr);
	struct bpf_cgroup_storage_map *map;

	/* percpu is bound by PCPU_MIN_UNIT_SIZE, non-percu
	 * is the same as other local storages.
	 */
	if (attr->map_type == BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE)
		max_value_size = min_t(__u32, max_value_size,
				       PCPU_MIN_UNIT_SIZE);

	if (attr->key_size != sizeof(struct bpf_cgroup_storage_key) &&
	    attr->key_size != sizeof(__u64))
		return ERR_PTR(-EINVAL);

	if (attr->value_size == 0)
		return ERR_PTR(-EINVAL);

	if (attr->value_size > max_value_size)
		return ERR_PTR(-E2BIG);

	if (attr->map_flags & ~LOCAL_STORAGE_CREATE_FLAG_MASK ||
	    !bpf_map_flags_access_ok(attr->map_flags))
		return ERR_PTR(-EINVAL);

	if (attr->max_entries)
		/* max_entries is not used and enforced to be 0 */
		return ERR_PTR(-EINVAL);

	map = bpf_map_area_alloc(sizeof(struct bpf_cgroup_storage_map), numa_node);
	if (!map)
		return ERR_PTR(-ENOMEM);

	/* 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);
	struct list_head *storages = &map->list;
	struct bpf_cgroup_storage *storage, *stmp;

	cgroup_lock();

	list_for_each_entry_safe(storage, stmp, storages, list_map) {
		bpf_cgroup_storage_unlink(storage);
		bpf_cgroup_storage_free(storage);
	}

	cgroup_unlock();

	WARN_ON(!RB_EMPTY_ROOT(&map->root));
	WARN_ON(!list_empty(&map->list));

	bpf_map_area_free(map);
}

static long cgroup_storage_delete_elem(struct bpf_map *map, void *key)
{
	return -EINVAL;
}

static int cgroup_storage_check_btf(const struct bpf_map *map,
				    const struct btf *btf,
				    const struct btf_type *key_type,
				    const struct btf_type *value_type)
{
	if (attach_type_isolated(map)) {
		struct btf_member *m;
		u32 offset, size;

		/* Key is expected to be of struct bpf_cgroup_storage_key type,
		 * which is:
		 * struct bpf_cgroup_storage_key {
		 *	__u64	cgroup_inode_id;
		 *	__u32	attach_type;
		 * };
		 */

		/*
		 * Key_type must be a structure with two fields.
		 */
		if (BTF_INFO_KIND(key_type->info) != BTF_KIND_STRUCT ||
		    BTF_INFO_VLEN(key_type->info) != 2)
			return -EINVAL;

		/*
		 * The first field must be a 64 bit integer at 0 offset.
		 */
		m = (struct btf_member *)(key_type + 1);
		size = sizeof_field(struct bpf_cgroup_storage_key, cgroup_inode_id);
		if (!btf_member_is_reg_int(btf, key_type, m, 0, size))
			return -EINVAL;

		/*
		 * The second field must be a 32 bit integer at 64 bit offset.
		 */
		m++;
		offset = offsetof(struct bpf_cgroup_storage_key, attach_type);
		size = sizeof_field(struct bpf_cgroup_storage_key, attach_type);
		if (!btf_member_is_reg_int(btf, key_type, m, offset, size))
			return -EINVAL;
	} else {
		u32 int_data;

		/*
		 * Key is expected to be u64, which stores the cgroup_inode_id
		 */

		if (BTF_INFO_KIND(key_type->info) != BTF_KIND_INT)
			return -EINVAL;

		int_data = *(u32 *)(key_type + 1);
		if (BTF_INT_BITS(int_data) != 64 || BTF_INT_OFFSET(int_data))
			return -EINVAL;
	}

	return 0;
}

static void cgroup_storage_seq_show_elem(struct bpf_map *map, void *key,
					 struct seq_file *m)
{
	enum bpf_cgroup_storage_type stype;
	struct bpf_cgroup_storage *storage;
	int cpu;

	rcu_read_lock();
	storage = cgroup_storage_lookup(map_to_storage(map), key, false);
	if (!storage) {
		rcu_read_unlock();
		return;
	}

	btf_type_seq_show(map->btf, map->btf_key_type_id, key, m);
	stype = cgroup_storage_type(map);
	if (stype == BPF_CGROUP_STORAGE_SHARED) {
		seq_puts(m, ": ");
		btf_type_seq_show(map->btf, map->btf_value_type_id,
				  &READ_ONCE(storage->buf)->data[0], m);
		seq_puts(m, "\n");
	} else {
		seq_puts(m, ": {\n");
		for_each_possible_cpu(cpu) {
			seq_printf(m, "\tcpu%d: ", cpu);
			btf_type_seq_show(map->btf, map->btf_value_type_id,
					  per_cpu_ptr(storage->percpu_buf, cpu),
					  m);
			seq_puts(m, "\n");
		}
		seq_puts(m, "}\n");
	}
	rcu_read_unlock();
}

static u64 cgroup_storage_map_usage(const struct bpf_map *map)
{
	/* Currently the dynamically allocated elements are not counted. */
	return sizeof(struct bpf_cgroup_storage_map);
}

BTF_ID_LIST_SINGLE(cgroup_storage_map_btf_ids, struct,
		   bpf_cgroup_storage_map)
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,
	.map_check_btf = cgroup_storage_check_btf,
	.map_seq_show_elem = cgroup_storage_seq_show_elem,
	.map_mem_usage = cgroup_storage_map_usage,
	.map_btf_id = &cgroup_storage_map_btf_ids[0],
};

int bpf_cgroup_storage_assign(struct bpf_prog_aux *aux, struct bpf_map *_map)
{
	enum bpf_cgroup_storage_type stype = cgroup_storage_type(_map);

	if (aux->cgroup_storage[stype] &&
	    aux->cgroup_storage[stype] != _map)
		return -EBUSY;

	aux->cgroup_storage[stype] = _map;
	return 0;
}

static size_t bpf_cgroup_storage_calculate_size(struct bpf_map *map, u32 *pages)
{
	size_t size;

	if (cgroup_storage_type(map) == BPF_CGROUP_STORAGE_SHARED) {
		size = sizeof(struct bpf_storage_buffer) + map->value_size;
		*pages = round_up(sizeof(struct bpf_cgroup_storage) + size,
				  PAGE_SIZE) >> PAGE_SHIFT;
	} else {
		size = map->value_size;
		*pages = round_up(round_up(size, 8) * num_possible_cpus(),
				  PAGE_SIZE) >> PAGE_SHIFT;
	}

	return size;
}

struct bpf_cgroup_storage *bpf_cgroup_storage_alloc(struct bpf_prog *prog,
					enum bpf_cgroup_storage_type stype)
{
	const gfp_t gfp = __GFP_ZERO | GFP_USER;
	struct bpf_cgroup_storage *storage;
	struct bpf_map *map;
	size_t size;
	u32 pages;

	map = prog->aux->cgroup_storage[stype];
	if (!map)
		return NULL;

	size = bpf_cgroup_storage_calculate_size(map, &pages);

	storage = bpf_map_kmalloc_node(map, sizeof(struct bpf_cgroup_storage),
				       gfp, map->numa_node);
	if (!storage)
		goto enomem;

	if (stype == BPF_CGROUP_STORAGE_SHARED) {
		storage->buf = bpf_map_kmalloc_node(map, size, gfp,
						    map->numa_node);
		if (!storage->buf)
			goto enomem;
		check_and_init_map_value(map, storage->buf->data);
	} else {
		storage->percpu_buf = bpf_map_alloc_percpu(map, size, 8, gfp);
		if (!storage->percpu_buf)
			goto enomem;
	}

	storage->map = (struct bpf_cgroup_storage_map *)map;

	return storage;

enomem:
	kfree(storage);
	return ERR_PTR(-ENOMEM);
}

static void free_shared_cgroup_storage_rcu(struct rcu_head *rcu)
{
	struct bpf_cgroup_storage *storage =
		container_of(rcu, struct bpf_cgroup_storage, rcu);

	kfree(storage->buf);
	kfree(storage);
}

static void free_percpu_cgroup_storage_rcu(struct rcu_head *rcu)
{
	struct bpf_cgroup_storage *storage =
		container_of(rcu, struct bpf_cgroup_storage, rcu);

	free_percpu(storage->percpu_buf);
	kfree(storage);
}

void bpf_cgroup_storage_free(struct bpf_cgroup_storage *storage)
{
	enum bpf_cgroup_storage_type stype;
	struct bpf_map *map;

	if (!storage)
		return;

	map = &storage->map->map;
	stype = cgroup_storage_type(map);
	if (stype == BPF_CGROUP_STORAGE_SHARED)
		call_rcu(&storage->rcu, free_shared_cgroup_storage_rcu);
	else
		call_rcu(&storage->rcu, free_percpu_cgroup_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_id(cgroup);

	map = storage->map;

	spin_lock_bh(&map->lock);
	WARN_ON(cgroup_storage_insert(map, storage));
	list_add(&storage->list_map, &map->list);
	list_add(&storage->list_cg, &cgroup->bpf.storages);
	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_map);
	list_del(&storage->list_cg);
	spin_unlock_bh(&map->lock);
}

#endif