selftests/bpf: Verify struct_ops autoload/autocreate sync

Check that autocreate flags of struct_ops map cause autoload of
struct_ops corresponding programs:
- when struct_ops program is referenced only from a map for which
  autocreate is set to false, that program should not be loaded;
- when struct_ops program with autoload == false is set to be used
  from a map with autocreate == true using shadow var,
  that program should be loaded;
- when struct_ops program is not referenced from any map object load
  should fail.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240306104529.6453-10-eddyz87@gmail.com

tools/testing/selftests/bpf/prog_tests/bad_struct_ops.c

@@ -2,6 +2,7 @@
 
 #include <test_progs.h>
 #include "bad_struct_ops.skel.h"
+#include "bad_struct_ops2.skel.h"
 
 static void invalid_prog_reuse(void)
 {
@@ -28,8 +29,39 @@ cleanup:
 	bad_struct_ops__destroy(skel);
 }
 
+static void unused_program(void)
+{
+	struct bad_struct_ops2 *skel;
+	char *log = NULL;
+	int err;
+
+	skel = bad_struct_ops2__open();
+	if (!ASSERT_OK_PTR(skel, "bad_struct_ops2__open"))
+		return;
+
+	/* struct_ops programs not referenced from any maps are open
+	 * with autoload set to true.
+	 */
+	ASSERT_TRUE(bpf_program__autoload(skel->progs.foo), "foo autoload == true");
+
+	if (start_libbpf_log_capture())
+		goto cleanup;
+
+	err = bad_struct_ops2__load(skel);
+	ASSERT_ERR(err, "bad_struct_ops2__load should fail");
+	log = stop_libbpf_log_capture();
+	ASSERT_HAS_SUBSTR(log, "prog 'foo': failed to load",
+			  "message about 'foo' failing to load");
+
+cleanup:
+	free(log);
+	bad_struct_ops2__destroy(skel);
+}
+
 void test_bad_struct_ops(void)
 {
 	if (test__start_subtest("invalid_prog_reuse"))
 		invalid_prog_reuse();
+	if (test__start_subtest("unused_program"))
+		unused_program();
 }

tools/testing/selftests/bpf/prog_tests/struct_ops_autocreate.c

@@ -2,6 +2,7 @@
 
 #include <test_progs.h>
 #include "struct_ops_autocreate.skel.h"
+#include "struct_ops_autocreate2.skel.h"
 
 static void cant_load_full_object(void)
 {
@@ -43,18 +44,20 @@ static void can_load_partial_object(void)
 	if (!ASSERT_OK_PTR(skel, "struct_ops_autocreate__open_opts"))
 		return;
 
-	err = bpf_program__set_autoload(skel->progs.test_2, false);
-	if (!ASSERT_OK(err, "bpf_program__set_autoload"))
-		goto cleanup;
-
 	err = bpf_map__set_autocreate(skel->maps.testmod_2, false);
 	if (!ASSERT_OK(err, "bpf_map__set_autocreate"))
 		goto cleanup;
 
+	ASSERT_TRUE(bpf_program__autoload(skel->progs.test_1), "test_1 default autoload");
+	ASSERT_TRUE(bpf_program__autoload(skel->progs.test_2), "test_2 default autoload");
+
 	err = struct_ops_autocreate__load(skel);
 	if (ASSERT_OK(err, "struct_ops_autocreate__load"))
 		goto cleanup;
 
+	ASSERT_TRUE(bpf_program__autoload(skel->progs.test_1), "test_1 actual autoload");
+	ASSERT_FALSE(bpf_program__autoload(skel->progs.test_2), "test_2 actual autoload");
+
 	link = bpf_map__attach_struct_ops(skel->maps.testmod_1);
 	if (!ASSERT_OK_PTR(link, "bpf_map__attach_struct_ops"))
 		goto cleanup;
@@ -67,10 +70,50 @@ cleanup:
 	struct_ops_autocreate__destroy(skel);
 }
 
+/* Swap test_mod1->test_1 program from 'bar' to 'foo' using shadow vars.
+ * test_mod1 load should enable autoload for 'foo'.
+ */
+static void autoload_and_shadow_vars(void)
+{
+	struct struct_ops_autocreate2 *skel = NULL;
+	struct bpf_link *link = NULL;
+	int err;
+
+	skel = struct_ops_autocreate2__open();
+	if (!ASSERT_OK_PTR(skel, "struct_ops_autocreate__open_opts"))
+		return;
+
+	ASSERT_FALSE(bpf_program__autoload(skel->progs.foo), "foo default autoload");
+	ASSERT_FALSE(bpf_program__autoload(skel->progs.bar), "bar default autoload");
+
+	/* loading map testmod_1 would switch foo's autoload to true */
+	skel->struct_ops.testmod_1->test_1 = skel->progs.foo;
+
+	err = struct_ops_autocreate2__load(skel);
+	if (ASSERT_OK(err, "struct_ops_autocreate__load"))
+		goto cleanup;
+
+	ASSERT_TRUE(bpf_program__autoload(skel->progs.foo), "foo actual autoload");
+	ASSERT_FALSE(bpf_program__autoload(skel->progs.bar), "bar actual autoload");
+
+	link = bpf_map__attach_struct_ops(skel->maps.testmod_1);
+	if (!ASSERT_OK_PTR(link, "bpf_map__attach_struct_ops"))
+		goto cleanup;
+
+	/* test_1() would be called from bpf_dummy_reg2() in bpf_testmod.c */
+	err = ASSERT_EQ(skel->bss->test_1_result, 42, "test_1_result");
+
+cleanup:
+	bpf_link__destroy(link);
+	struct_ops_autocreate2__destroy(skel);
+}
+
 void test_struct_ops_autocreate(void)
 {
 	if (test__start_subtest("cant_load_full_object"))
 		cant_load_full_object();
 	if (test__start_subtest("can_load_partial_object"))
 		can_load_partial_object();
+	if (test__start_subtest("autoload_and_shadow_vars"))
+		autoload_and_shadow_vars();
 }

tools/testing/selftests/bpf/progs/bad_struct_ops2.c

@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+char _license[] SEC("license") = "GPL";
+
+/* This is an unused struct_ops program, it lacks corresponding
+ * struct_ops map, which provides attachment information.
+ * W/o additional configuration attempt to load such
+ * BPF object file would fail.
+ */
+SEC("struct_ops/foo")
+void foo(void) {}

tools/testing/selftests/bpf/progs/struct_ops_autocreate2.c

@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+int test_1_result = 0;
+
+SEC("?struct_ops/test_1")
+int BPF_PROG(foo)
+{
+	test_1_result = 42;
+	return 0;
+}
+
+SEC("?struct_ops/test_1")
+int BPF_PROG(bar)
+{
+	test_1_result = 24;
+	return 0;
+}
+
+struct bpf_testmod_ops {
+	int (*test_1)(void);
+};
+
+SEC(".struct_ops.link")
+struct bpf_testmod_ops testmod_1 = {
+	.test_1 = (void *)bar
+};