From: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxx>
Acked-by: Martin KaFai Lau <kafai@xxxxxx>
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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();
