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: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Alexei Starovoitov 2014-09-26 00:16:59 -07:00 committed by David S. Miller
parent 749730ce42
commit db20fd2b01
3 changed files with 281 additions and 0 deletions

View File

@ -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 */

View File

@ -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__ */

View File

@ -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;