selftests/bpf: Add new bpf_iter context structs to fix build on old kernels

Add bpf_iter__bpf_map_elem and bpf_iter__bpf_sk_storage_map to bpf_iter.h.

Fixes: 3b1c420b ("selftests/bpf: Add a test for bpf sk_storage_map iterator")
Fixes: 2a7c2fff ("selftests/bpf: Add test for bpf hash map iterators")
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200727233345.1686358-1-andriin@fb.com

tools/testing/selftests/bpf/progs/bpf_iter.h

@@ -11,6 +11,8 @@
 #define tcp6_sock tcp6_sock___not_used
 #define bpf_iter__udp bpf_iter__udp___not_used
 #define udp6_sock udp6_sock___not_used
+#define bpf_iter__bpf_map_elem bpf_iter__bpf_map_elem___not_used
+#define bpf_iter__bpf_sk_storage_map bpf_iter__bpf_sk_storage_map___not_used
 #include "vmlinux.h"
 #undef bpf_iter_meta
 #undef bpf_iter__bpf_map
@@ -22,6 +24,8 @@
 #undef tcp6_sock
 #undef bpf_iter__udp
 #undef udp6_sock
+#undef bpf_iter__bpf_map_elem
+#undef bpf_iter__bpf_sk_storage_map
 
 struct bpf_iter_meta {
 	struct seq_file *seq;
@@ -78,3 +82,17 @@ struct udp6_sock {
 	struct udp_sock	udp;
 	struct ipv6_pinfo inet6;
 } __attribute__((preserve_access_index));
+
+struct bpf_iter__bpf_map_elem {
+	struct bpf_iter_meta *meta;
+	struct bpf_map *map;
+	void *key;
+	void *value;
+};
+
+struct bpf_iter__bpf_sk_storage_map {
+	struct bpf_iter_meta *meta;
+	struct bpf_map *map;
+	struct sock *sk;
+	void *value;
+};