Commit c6110222 authored May 14, 2019 by Daniel Borkmann Committed by Alexei Starovoitov May 14, 2019

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: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei 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);

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