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Date: Thu, 23 May 2019 21:06:52 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Daniel Borkmann <daniel@...earbox.net>, Martin KaFai Lau <kafai@...com>, Alexei Starovoitov <ast@...nel.org> Subject: [PATCH 4.19 113/114] bpf: add map_lookup_elem_sys_only for lookups from syscall side From: Daniel Borkmann <daniel@...earbox.net> commit c6110222c6f49ea68169f353565eb865488a8619 upstream. 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@...earbox.net> Acked-by: Martin KaFai Lau <kafai@...com> Signed-off-by: Alexei Starovoitov <ast@...nel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- include/linux/bpf.h | 1 + kernel/bpf/syscall.c | 5 ++++- 2 files changed, 5 insertions(+), 1 deletion(-) --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -34,6 +34,7 @@ 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); --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -721,7 +721,10 @@ static int map_lookup_elem(union bpf_att err = bpf_fd_reuseport_array_lookup_elem(map, key, value); } else { rcu_read_lock(); - ptr = map->ops->map_lookup_elem(map, key); + 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 (ptr) memcpy(value, ptr, value_size); rcu_read_unlock();
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