selftests/bpf: Test cgroup_iter.

Add a selftest for cgroup_iter. The selftest creates a mini cgroup tree
of the following structure:

    ROOT (working cgroup)
     |
   PARENT
  /      \
CHILD1  CHILD2

and tests the following scenarios:

 - invalid cgroup fd.
 - pre-order walk over descendants from PARENT.
 - post-order walk over descendants from PARENT.
 - walk of ancestors from PARENT.
 - process only a single object (i.e. PARENT).
 - early termination.

Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Hao Luo <haoluo@google.com>
Link: https://lore.kernel.org/r/20220824233117.1312810-3-haoluo@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/bpf_iter.h b/tools/testing/selftests/bpf/progs/bpf_iter.h
index e9846606690d..c41ee80533ca 100644
--- a/tools/testing/selftests/bpf/progs/bpf_iter.h
+++ b/tools/testing/selftests/bpf/progs/bpf_iter.h
@@ -17,6 +17,7 @@
 #define bpf_iter__bpf_sk_storage_map bpf_iter__bpf_sk_storage_map___not_used
 #define bpf_iter__sockmap bpf_iter__sockmap___not_used
 #define bpf_iter__bpf_link bpf_iter__bpf_link___not_used
+#define bpf_iter__cgroup bpf_iter__cgroup___not_used
 #define btf_ptr btf_ptr___not_used
 #define BTF_F_COMPACT BTF_F_COMPACT___not_used
 #define BTF_F_NONAME BTF_F_NONAME___not_used
@@ -40,6 +41,7 @@
 #undef bpf_iter__bpf_sk_storage_map
 #undef bpf_iter__sockmap
 #undef bpf_iter__bpf_link
+#undef bpf_iter__cgroup
 #undef btf_ptr
 #undef BTF_F_COMPACT
 #undef BTF_F_NONAME
@@ -141,6 +143,11 @@ struct bpf_iter__bpf_link {
 	struct bpf_link *link;
 };
 
+struct bpf_iter__cgroup {
+	struct bpf_iter_meta *meta;
+	struct cgroup *cgroup;
+} __attribute__((preserve_access_index));
+
 struct btf_ptr {
 	void *ptr;
 	__u32 type_id;