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Commit c6110222 authored by Daniel Borkmann's avatar Daniel Borkmann Committed by Alexei Starovoitov
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bpf: add map_lookup_elem_sys_only for lookups from syscall side 



Add a callback map_lookup_elem_sys_only() that map implementations
could use over map_lookup_elem() from system call side in case the
map implementation needs to handle the latter differently than from
the BPF data path. If map_lookup_elem_sys_only() is set, this will
be preferred pick for map lookups out of user space. This hook is
used in a follow-up fix for LRU map, but once development window
opens, we can convert other map types from map_lookup_elem() (here,
the one called upon BPF_MAP_LOOKUP_ELEM cmd is meant) over to use
the callback to simplify and clean up the latter.

Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 2474c628

include/linux/bpf.h

+1 −0
Original line number Diff line number Diff line
@@ -36,6 +36,7 @@ struct bpf_map_ops { 
	void (*map_free)(struct bpf_map *map);

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

	void (*map_release_uref)(struct bpf_map *map);

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



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

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

kernel/bpf/syscall.c

+4 −1
Original line number Diff line number Diff line
@@ -808,6 +808,9 @@ static int map_lookup_elem(union bpf_attr *attr) 
		err = map->ops->map_peek_elem(map, value);

	} else {

		rcu_read_lock();

		if (map->ops->map_lookup_elem_sys_only)

			ptr = map->ops->map_lookup_elem_sys_only(map, key);

		else

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

		if (IS_ERR(ptr)) {

			err = PTR_ERR(ptr);