[PATCH bpf-next 2/2] selftests/bpf: validate nulled-out struct_ops program is handled properly

[Andrii Nakryiko <andrii@xxxxxxxxxx>]

Add a selftests validating that it's possible to have some struct_ops
callback set declaratively, then disable it (by setting to NULL)
programmatically. Libbpf should detect that such program should be
loaded, even if host kernel doesn't have type information for it.

Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
 .../bpf/prog_tests/test_struct_ops_module.c    | 18 ++++++++++++++++--
 .../selftests/bpf/progs/struct_ops_module.c    |  7 +++++++
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/test_struct_ops_module.c b/tools/testing/selftests/bpf/prog_tests/test_struct_ops_module.c
index 7cf2b9ddd3e1..bd39586abd5a 100644
--- a/tools/testing/selftests/bpf/prog_tests/test_struct_ops_module.c
+++ b/tools/testing/selftests/bpf/prog_tests/test_struct_ops_module.c
@@ -66,6 +66,7 @@ static void test_struct_ops_load(void)
 	 * auto-loading, or it will fail to load.
 	 */
 	bpf_program__set_autoload(skel->progs.test_2, false);
+	bpf_map__set_autocreate(skel->maps.testmod_zeroed, false);
 
 	err = struct_ops_module__load(skel);
 	if (!ASSERT_OK(err, "struct_ops_module_load"))
@@ -103,6 +104,10 @@ static void test_struct_ops_not_zeroed(void)
 	if (!ASSERT_OK_PTR(skel, "struct_ops_module_open"))
 		return;
 
+	skel->struct_ops.testmod_zeroed->zeroed = 0;
+	/* zeroed_op prog should be not loaded automatically now */
+	skel->struct_ops.testmod_zeroed->zeroed_op = NULL;
+
 	err = struct_ops_module__load(skel);
 	ASSERT_OK(err, "struct_ops_module_load");
 
@@ -118,6 +123,7 @@ static void test_struct_ops_not_zeroed(void)
 	 * value of "zeroed" is non-zero.
 	 */
 	skel->struct_ops.testmod_zeroed->zeroed = 0xdeadbeef;
+	skel->struct_ops.testmod_zeroed->zeroed_op = NULL;
 	err = struct_ops_module__load(skel);
 	ASSERT_ERR(err, "struct_ops_module_load_not_zeroed");
 
@@ -148,15 +154,23 @@ static void test_struct_ops_incompatible(void)
 {
 	struct struct_ops_module *skel;
 	struct bpf_link *link;
+	int err;
 
-	skel = struct_ops_module__open_and_load();
-	if (!ASSERT_OK_PTR(skel, "open_and_load"))
+	skel = struct_ops_module__open();
+	if (!ASSERT_OK_PTR(skel, "struct_ops_module_open"))
 		return;
 
+	bpf_map__set_autocreate(skel->maps.testmod_zeroed, false);
+
+	err = struct_ops_module__load(skel);
+	if (!ASSERT_OK(err, "skel_load"))
+		goto cleanup;
+
 	link = bpf_map__attach_struct_ops(skel->maps.testmod_incompatible);
 	if (ASSERT_OK_PTR(link, "attach_struct_ops"))
 		bpf_link__destroy(link);
 
+cleanup:
 	struct_ops_module__destroy(skel);
 }
 
diff --git a/tools/testing/selftests/bpf/progs/struct_ops_module.c b/tools/testing/selftests/bpf/progs/struct_ops_module.c
index 63b065dae002..40109be2b3ae 100644
--- a/tools/testing/selftests/bpf/progs/struct_ops_module.c
+++ b/tools/testing/selftests/bpf/progs/struct_ops_module.c
@@ -63,10 +63,17 @@ struct bpf_testmod_ops___zeroed {
 	int zeroed;
 };
 
+SEC("?struct_ops/test_3")
+int BPF_PROG(zeroed_op)
+{
+	return 1;
+}
+
 SEC(".struct_ops.link")
 struct bpf_testmod_ops___zeroed testmod_zeroed = {
 	.test_1 = (void *)test_1,
 	.test_2 = (void *)test_2_v2,
+	.zeroed_op = (void *)zeroed_op,
 };
 
 struct bpf_testmod_ops___incompatible {
-- 
2.43.0