[PATCH net-next 4/7] bpf: fix BPF_MAP_LOOKUP_ELEM command return code

Alexei Starovoitov
2014-11-04T02:55:13Z

fix errno of BPF_MAP_LOOKUP_ELEM command as bpf manpage
described it in commit b4fc1a460f30("Merge branch 'bpf-next'"):
-----
BPF_MAP_LOOKUP_ELEM
int bpf_lookup_elem(int fd, void *key, void *value)
{
union bpf_attr attr = {
.map_fd = fd,
.key = ptr_to_u64(key),
.value = ptr_to_u64(value),
};

return bpf(BPF_MAP_LOOKUP_ELEM, &attr, sizeof(attr));
}
bpf() syscall looks up an element with given key in a map fd.
If element is found it returns zero and stores element's value
into value. If element is not found it returns -1 and sets
errno to ENOENT.

and further down in manpage:

ENOENT For BPF_MAP_LOOKUP_ELEM or BPF_MAP_DELETE_ELEM, indicates that
element with given key was not found.
-----

In general all BPF commands return ENOENT when map element is not found
(including BPF_MAP_GET_NEXT_KEY and BPF_MAP_UPDATE_ELEM with
flags == BPF_MAP_UPDATE_ONLY)

Subsequent patch adds a testsuite to check return values for all of
these combinations.

Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
---

I don't think this patch is needed for 'net', since 'net' has syscall shell
only. Actual map types and their implementations are being introduced by
this set of patches.

kernel/bpf/syscall.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index c0d03bf317a2..088ac0b1b106 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -169,7 +169,7 @@ static int map_lookup_elem(union bpf_attr *attr)
if (copy_from_user(key, ukey, map->key_size) != 0)
goto free_key;

- err = -ESRCH;
+ err = -ENOENT;
rcu_read_lock();
value = map->ops->map_lookup_elem(map, key);
if (!value)
--
1.7.9.5