[RFC bpf-next 2/4] bpf: return EOPNOTSUPP when map lookup isn't supported

[Prashant Bhole <bhole_prashant_q7@lab.ntt.co.jp>]

Return ERR_PTR(-EOPNOTSUPP) from map_lookup_elem() methods of below
map types:
- BPF_MAP_TYPE_PROG_ARRAY
- BPF_MAP_TYPE_STACK_TRACE
- BPF_MAP_TYPE_XSKMAP
- BPF_MAP_TYPE_SOCKMAP/BPF_MAP_TYPE_SOCKHASH

Signed-off-by: Prashant Bhole <bhole_prashant_q7@lab.ntt.co.jp>
---
 kernel/bpf/arraymap.c | 2 +-
 kernel/bpf/sockmap.c  | 2 +-
 kernel/bpf/stackmap.c | 2 +-
 kernel/bpf/xskmap.c   | 2 +-
 4 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index dded84cbe814..24583da9ffd1 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -449,7 +449,7 @@ static void fd_array_map_free(struct bpf_map *map)
 
 static void *fd_array_map_lookup_elem(struct bpf_map *map, void *key)
 {
-	return NULL;
+	return ERR_PTR(-EOPNOTSUPP);
 }
 
 /* only called from syscall */
diff --git a/kernel/bpf/sockmap.c b/kernel/bpf/sockmap.c
index 488ef9663c01..e50922a802f7 100644
--- a/kernel/bpf/sockmap.c
+++ b/kernel/bpf/sockmap.c
@@ -2076,7 +2076,7 @@ int sockmap_get_from_fd(const union bpf_attr *attr, int type,
 
 static void *sock_map_lookup(struct bpf_map *map, void *key)
 {
-	return NULL;
+	return ERR_PTR(-EOPNOTSUPP);
 }
 
 static int sock_map_update_elem(struct bpf_map *map,
diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index 8061a439ef18..b2ade10f7ec3 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -505,7 +505,7 @@ const struct bpf_func_proto bpf_get_stack_proto = {
 /* Called from eBPF program */
 static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
 {
-	return NULL;
+	return ERR_PTR(-EOPNOTSUPP);
 }
 
 /* Called from syscall */
diff --git a/kernel/bpf/xskmap.c b/kernel/bpf/xskmap.c
index 9f8463afda9c..ef0b7b6ef8a5 100644
--- a/kernel/bpf/xskmap.c
+++ b/kernel/bpf/xskmap.c
@@ -154,7 +154,7 @@ void __xsk_map_flush(struct bpf_map *map)
 
 static void *xsk_map_lookup_elem(struct bpf_map *map, void *key)
 {
-	return NULL;
+	return ERR_PTR(-EOPNOTSUPP);
 }
 
 static int xsk_map_update_elem(struct bpf_map *map, void *key, void *value,
-- 
2.17.1