Commit db20fd2b authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by David S. Miller
Browse files

bpf: add lookup/update/delete/iterate methods to BPF maps 



'maps' is a generic storage of different types for sharing data between kernel
and userspace.

The maps are accessed from user space via BPF syscall, which has commands:

- create a map with given type and attributes
  fd = bpf(BPF_MAP_CREATE, union bpf_attr *attr, u32 size)
  returns fd or negative error

- lookup key in a given map referenced by fd
  err = bpf(BPF_MAP_LOOKUP_ELEM, union bpf_attr *attr, u32 size)
  using attr->map_fd, attr->key, attr->value
  returns zero and stores found elem into value or negative error

- create or update key/value pair in a given map
  err = bpf(BPF_MAP_UPDATE_ELEM, union bpf_attr *attr, u32 size)
  using attr->map_fd, attr->key, attr->value
  returns zero or negative error

- find and delete element by key in a given map
  err = bpf(BPF_MAP_DELETE_ELEM, union bpf_attr *attr, u32 size)
  using attr->map_fd, attr->key

- iterate map elements (based on input key return next_key)
  err = bpf(BPF_MAP_GET_NEXT_KEY, union bpf_attr *attr, u32 size)
  using attr->map_fd, attr->key, attr->next_key

- close(fd) deletes the map

Signed-off-by: default avatarAlexei Starovoitov <ast@plumgrid.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 749730ce

include/linux/bpf.h

+8 −0
Original line number Diff line number Diff line
@@ -9,6 +9,7 @@ 


#include <uapi/linux/bpf.h>

#include <linux/workqueue.h>

#include <linux/file.h>



struct bpf_map;
@@ -17,6 +18,12 @@ struct bpf_map_ops { 
	/* funcs callable from userspace (via syscall) */

	struct bpf_map *(*map_alloc)(union bpf_attr *attr);

	void (*map_free)(struct bpf_map *);

	int (*map_get_next_key)(struct bpf_map *map, void *key, void *next_key);



	/* funcs callable from userspace and from eBPF programs */

	void *(*map_lookup_elem)(struct bpf_map *map, void *key);

	int (*map_update_elem)(struct bpf_map *map, void *key, void *value);

	int (*map_delete_elem)(struct bpf_map *map, void *key);

};



struct bpf_map {
@@ -37,5 +44,6 @@ struct bpf_map_type_list { 


void bpf_register_map_type(struct bpf_map_type_list *tl);

void bpf_map_put(struct bpf_map *map);

struct bpf_map *bpf_map_get(struct fd f);



#endif /* _LINUX_BPF_H */

include/uapi/linux/bpf.h

+38 −0
Original line number Diff line number Diff line
@@ -70,6 +70,35 @@ enum bpf_cmd { 
	 * map is deleted when fd is closed

	 */

	BPF_MAP_CREATE,



	/* lookup key in a given map

	 * err = bpf(BPF_MAP_LOOKUP_ELEM, union bpf_attr *attr, u32 size)

	 * Using attr->map_fd, attr->key, attr->value

	 * returns zero and stores found elem into value

	 * or negative error

	 */

	BPF_MAP_LOOKUP_ELEM,



	/* create or update key/value pair in a given map

	 * err = bpf(BPF_MAP_UPDATE_ELEM, union bpf_attr *attr, u32 size)

	 * Using attr->map_fd, attr->key, attr->value

	 * returns zero or negative error

	 */

	BPF_MAP_UPDATE_ELEM,



	/* find and delete elem by key in a given map

	 * err = bpf(BPF_MAP_DELETE_ELEM, union bpf_attr *attr, u32 size)

	 * Using attr->map_fd, attr->key

	 * returns zero or negative error

	 */

	BPF_MAP_DELETE_ELEM,



	/* lookup key in a given map and return next key

	 * err = bpf(BPF_MAP_GET_NEXT_KEY, union bpf_attr *attr, u32 size)

	 * Using attr->map_fd, attr->key, attr->next_key

	 * returns zero and stores next key or negative error

	 */

	BPF_MAP_GET_NEXT_KEY,

};



enum bpf_map_type {
@@ -83,6 +112,15 @@ union bpf_attr { 
		__u32	value_size;	/* size of value in bytes */

		__u32	max_entries;	/* max number of entries in a map */

	};



	struct { /* anonymous struct used by BPF_MAP_*_ELEM commands */

		__u32		map_fd;

		__aligned_u64	key;

		union {

			__aligned_u64 value;

			__aligned_u64 next_key;

		};

	};

} __attribute__((aligned(8)));



#endif /* _UAPI__LINUX_BPF_H__ */

kernel/bpf/syscall.c

+235 −0
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ 
#include <linux/syscalls.h>

#include <linux/slab.h>

#include <linux/anon_inodes.h>

#include <linux/file.h>



static LIST_HEAD(bpf_map_types);
@@ -111,6 +112,228 @@ free_map: 
	return err;

}



/* if error is returned, fd is released.

 * On success caller should complete fd access with matching fdput()

 */

struct bpf_map *bpf_map_get(struct fd f)

{

	struct bpf_map *map;



	if (!f.file)

		return ERR_PTR(-EBADF);



	if (f.file->f_op != &bpf_map_fops) {

		fdput(f);

		return ERR_PTR(-EINVAL);

	}



	map = f.file->private_data;



	return map;

}



/* helper to convert user pointers passed inside __aligned_u64 fields */

static void __user *u64_to_ptr(__u64 val)

{

	return (void __user *) (unsigned long) val;

}



/* last field in 'union bpf_attr' used by this command */

#define BPF_MAP_LOOKUP_ELEM_LAST_FIELD value



static int map_lookup_elem(union bpf_attr *attr)

{

	void __user *ukey = u64_to_ptr(attr->key);

	void __user *uvalue = u64_to_ptr(attr->value);

	int ufd = attr->map_fd;

	struct fd f = fdget(ufd);

	struct bpf_map *map;

	void *key, *value;

	int err;



	if (CHECK_ATTR(BPF_MAP_LOOKUP_ELEM))

		return -EINVAL;



	map = bpf_map_get(f);

	if (IS_ERR(map))

		return PTR_ERR(map);



	err = -ENOMEM;

	key = kmalloc(map->key_size, GFP_USER);

	if (!key)

		goto err_put;



	err = -EFAULT;

	if (copy_from_user(key, ukey, map->key_size) != 0)

		goto free_key;



	err = -ESRCH;

	rcu_read_lock();

	value = map->ops->map_lookup_elem(map, key);

	if (!value)

		goto err_unlock;



	err = -EFAULT;

	if (copy_to_user(uvalue, value, map->value_size) != 0)

		goto err_unlock;



	err = 0;



err_unlock:

	rcu_read_unlock();

free_key:

	kfree(key);

err_put:

	fdput(f);

	return err;

}



#define BPF_MAP_UPDATE_ELEM_LAST_FIELD value



static int map_update_elem(union bpf_attr *attr)

{

	void __user *ukey = u64_to_ptr(attr->key);

	void __user *uvalue = u64_to_ptr(attr->value);

	int ufd = attr->map_fd;

	struct fd f = fdget(ufd);

	struct bpf_map *map;

	void *key, *value;

	int err;



	if (CHECK_ATTR(BPF_MAP_UPDATE_ELEM))

		return -EINVAL;



	map = bpf_map_get(f);

	if (IS_ERR(map))

		return PTR_ERR(map);



	err = -ENOMEM;

	key = kmalloc(map->key_size, GFP_USER);

	if (!key)

		goto err_put;



	err = -EFAULT;

	if (copy_from_user(key, ukey, map->key_size) != 0)

		goto free_key;



	err = -ENOMEM;

	value = kmalloc(map->value_size, GFP_USER);

	if (!value)

		goto free_key;



	err = -EFAULT;

	if (copy_from_user(value, uvalue, map->value_size) != 0)

		goto free_value;



	/* eBPF program that use maps are running under rcu_read_lock(),

	 * therefore all map accessors rely on this fact, so do the same here

	 */

	rcu_read_lock();

	err = map->ops->map_update_elem(map, key, value);

	rcu_read_unlock();



free_value:

	kfree(value);

free_key:

	kfree(key);

err_put:

	fdput(f);

	return err;

}



#define BPF_MAP_DELETE_ELEM_LAST_FIELD key



static int map_delete_elem(union bpf_attr *attr)

{

	void __user *ukey = u64_to_ptr(attr->key);

	int ufd = attr->map_fd;

	struct fd f = fdget(ufd);

	struct bpf_map *map;

	void *key;

	int err;



	if (CHECK_ATTR(BPF_MAP_DELETE_ELEM))

		return -EINVAL;



	map = bpf_map_get(f);

	if (IS_ERR(map))

		return PTR_ERR(map);



	err = -ENOMEM;

	key = kmalloc(map->key_size, GFP_USER);

	if (!key)

		goto err_put;



	err = -EFAULT;

	if (copy_from_user(key, ukey, map->key_size) != 0)

		goto free_key;



	rcu_read_lock();

	err = map->ops->map_delete_elem(map, key);

	rcu_read_unlock();



free_key:

	kfree(key);

err_put:

	fdput(f);

	return err;

}



/* last field in 'union bpf_attr' used by this command */

#define BPF_MAP_GET_NEXT_KEY_LAST_FIELD next_key



static int map_get_next_key(union bpf_attr *attr)

{

	void __user *ukey = u64_to_ptr(attr->key);

	void __user *unext_key = u64_to_ptr(attr->next_key);

	int ufd = attr->map_fd;

	struct fd f = fdget(ufd);

	struct bpf_map *map;

	void *key, *next_key;

	int err;



	if (CHECK_ATTR(BPF_MAP_GET_NEXT_KEY))

		return -EINVAL;



	map = bpf_map_get(f);

	if (IS_ERR(map))

		return PTR_ERR(map);



	err = -ENOMEM;

	key = kmalloc(map->key_size, GFP_USER);

	if (!key)

		goto err_put;



	err = -EFAULT;

	if (copy_from_user(key, ukey, map->key_size) != 0)

		goto free_key;



	err = -ENOMEM;

	next_key = kmalloc(map->key_size, GFP_USER);

	if (!next_key)

		goto free_key;



	rcu_read_lock();

	err = map->ops->map_get_next_key(map, key, next_key);

	rcu_read_unlock();

	if (err)

		goto free_next_key;



	err = -EFAULT;

	if (copy_to_user(unext_key, next_key, map->key_size) != 0)

		goto free_next_key;



	err = 0;



free_next_key:

	kfree(next_key);

free_key:

	kfree(key);

err_put:

	fdput(f);

	return err;

}



SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, size)

{

	union bpf_attr attr = {};
@@ -160,6 +383,18 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz 
	case BPF_MAP_CREATE:

		err = map_create(&attr);

		break;

	case BPF_MAP_LOOKUP_ELEM:

		err = map_lookup_elem(&attr);

		break;

	case BPF_MAP_UPDATE_ELEM:

		err = map_update_elem(&attr);

		break;

	case BPF_MAP_DELETE_ELEM:

		err = map_delete_elem(&attr);

		break;

	case BPF_MAP_GET_NEXT_KEY:

		err = map_get_next_key(&attr);

		break;

	default:

		err = -EINVAL;

		break;

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