selftests/bpf: Tests libbpf autoattach APIs

Adds test for libbpf APIs that toggle bpf program auto-attaching.
Signed-off-by: Hao Luo <haoluo@google.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220816234012.910255-2-haoluo@google.com

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

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022 Google */
+
+#include <test_progs.h>
+#include "test_autoattach.skel.h"
+
+void test_autoattach(void)
+{
+	struct test_autoattach *skel;
+
+	skel = test_autoattach__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_open_and_load"))
+		goto cleanup;
+
+	/* disable auto-attach for prog2 */
+	bpf_program__set_autoattach(skel->progs.prog2, false);
+	ASSERT_TRUE(bpf_program__autoattach(skel->progs.prog1), "autoattach_prog1");
+	ASSERT_FALSE(bpf_program__autoattach(skel->progs.prog2), "autoattach_prog2");
+	if (!ASSERT_OK(test_autoattach__attach(skel), "skel_attach"))
+		goto cleanup;
+
+	usleep(1);
+
+	ASSERT_TRUE(skel->bss->prog1_called, "attached_prog1");
+	ASSERT_FALSE(skel->bss->prog2_called, "attached_prog2");
+
+cleanup:
+	test_autoattach__destroy(skel);
+}
+

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

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022 Google */
+
+#include "vmlinux.h"
+#include <bpf/bpf_tracing.h>
+
+bool prog1_called = false;
+bool prog2_called = false;
+
+SEC("raw_tp/sys_enter")
+int prog1(const void *ctx)
+{
+	prog1_called = true;
+	return 0;
+}
+
+SEC("raw_tp/sys_exit")
+int prog2(const void *ctx)
+{
+	prog2_called = true;
+	return 0;
+}
+