Commit 14dc6f04 authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by David S. Miller
Browse files

bpf: Add syscall lookup support for fd array and htab 



This patch allows userspace to do BPF_MAP_LOOKUP_ELEM on
BPF_MAP_TYPE_PROG_ARRAY,
BPF_MAP_TYPE_ARRAY_OF_MAPS and
BPF_MAP_TYPE_HASH_OF_MAPS.

The lookup returns a prog-id or map-id to the userspace.
The userspace can then use the BPF_PROG_GET_FD_BY_ID
or BPF_MAP_GET_FD_BY_ID to get a fd.

Signed-off-by: default avatarMartin KaFai Lau <kafai@fb.com>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 77b0d361

include/linux/bpf.h

+3 −0
Original line number Diff line number Diff line
@@ -36,6 +36,7 @@ struct bpf_map_ops { 
				int fd);

	void (*map_fd_put_ptr)(void *ptr);

	u32 (*map_gen_lookup)(struct bpf_map *map, struct bpf_insn *insn_buf);

	u32 (*map_fd_sys_lookup_elem)(void *ptr);

};



struct bpf_map {
@@ -288,9 +289,11 @@ int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value); 


int bpf_fd_array_map_update_elem(struct bpf_map *map, struct file *map_file,

				 void *key, void *value, u64 map_flags);

int bpf_fd_array_map_lookup_elem(struct bpf_map *map, void *key, u32 *value);

void bpf_fd_array_map_clear(struct bpf_map *map);

int bpf_fd_htab_map_update_elem(struct bpf_map *map, struct file *map_file,

				void *key, void *value, u64 map_flags);

int bpf_fd_htab_map_lookup_elem(struct bpf_map *map, void *key, u32 *value);



/* memcpy that is used with 8-byte aligned pointers, power-of-8 size and

 * forced to use 'long' read/writes to try to atomically copy long counters.

kernel/bpf/arraymap.c

+27 −0
Original line number Diff line number Diff line
@@ -334,6 +334,26 @@ static void *fd_array_map_lookup_elem(struct bpf_map *map, void *key) 
	return NULL;

}



/* only called from syscall */

int bpf_fd_array_map_lookup_elem(struct bpf_map *map, void *key, u32 *value)

{

	void **elem, *ptr;

	int ret =  0;



	if (!map->ops->map_fd_sys_lookup_elem)

		return -ENOTSUPP;



	rcu_read_lock();

	elem = array_map_lookup_elem(map, key);

	if (elem && (ptr = READ_ONCE(*elem)))

		*value = map->ops->map_fd_sys_lookup_elem(ptr);

	else

		ret = -ENOENT;

	rcu_read_unlock();



	return ret;

}



/* only called from syscall */

int bpf_fd_array_map_update_elem(struct bpf_map *map, struct file *map_file,

				 void *key, void *value, u64 map_flags)
@@ -400,6 +420,11 @@ static void prog_fd_array_put_ptr(void *ptr) 
	bpf_prog_put(ptr);

}



static u32 prog_fd_array_sys_lookup_elem(void *ptr)

{

	return ((struct bpf_prog *)ptr)->aux->id;

}



/* decrement refcnt of all bpf_progs that are stored in this map */

void bpf_fd_array_map_clear(struct bpf_map *map)

{
@@ -418,6 +443,7 @@ const struct bpf_map_ops prog_array_map_ops = { 
	.map_delete_elem = fd_array_map_delete_elem,

	.map_fd_get_ptr = prog_fd_array_get_ptr,

	.map_fd_put_ptr = prog_fd_array_put_ptr,

	.map_fd_sys_lookup_elem = prog_fd_array_sys_lookup_elem,

};



static struct bpf_event_entry *bpf_event_entry_gen(struct file *perf_file,
@@ -585,4 +611,5 @@ const struct bpf_map_ops array_of_maps_map_ops = { 
	.map_delete_elem = fd_array_map_delete_elem,

	.map_fd_get_ptr = bpf_map_fd_get_ptr,

	.map_fd_put_ptr = bpf_map_fd_put_ptr,

	.map_fd_sys_lookup_elem = bpf_map_fd_sys_lookup_elem,

};

kernel/bpf/hashtab.c

+21 −0
Original line number Diff line number Diff line
@@ -1243,6 +1243,26 @@ static void fd_htab_map_free(struct bpf_map *map) 
	htab_map_free(map);

}



/* only called from syscall */

int bpf_fd_htab_map_lookup_elem(struct bpf_map *map, void *key, u32 *value)

{

	void **ptr;

	int ret = 0;



	if (!map->ops->map_fd_sys_lookup_elem)

		return -ENOTSUPP;



	rcu_read_lock();

	ptr = htab_map_lookup_elem(map, key);

	if (ptr)

		*value = map->ops->map_fd_sys_lookup_elem(READ_ONCE(*ptr));

	else

		ret = -ENOENT;

	rcu_read_unlock();



	return ret;

}



/* only called from syscall */

int bpf_fd_htab_map_update_elem(struct bpf_map *map, struct file *map_file,

				void *key, void *value, u64 map_flags)
@@ -1305,4 +1325,5 @@ const struct bpf_map_ops htab_of_maps_map_ops = { 
	.map_delete_elem = htab_map_delete_elem,

	.map_fd_get_ptr = bpf_map_fd_get_ptr,

	.map_fd_put_ptr = bpf_map_fd_put_ptr,

	.map_fd_sys_lookup_elem = bpf_map_fd_sys_lookup_elem,

};

kernel/bpf/map_in_map.c

+5 −0
Original line number Diff line number Diff line
@@ -95,3 +95,8 @@ void bpf_map_fd_put_ptr(void *ptr) 
	 */

	bpf_map_put(ptr);

}



u32 bpf_map_fd_sys_lookup_elem(void *ptr)

{

	return ((struct bpf_map *)ptr)->id;

}

kernel/bpf/map_in_map.h

+1 −0
Original line number Diff line number Diff line
@@ -19,5 +19,6 @@ bool bpf_map_meta_equal(const struct bpf_map *meta0, 
void *bpf_map_fd_get_ptr(struct bpf_map *map, struct file *map_file,

			 int ufd);

void bpf_map_fd_put_ptr(void *ptr);

u32 bpf_map_fd_sys_lookup_elem(void *ptr);



#endif

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