selftests/bpf: Add selftest for attaching fexit to __noreturn functions

The reuslt:

  $ tools/testing/selftests/bpf/test_progs --name=fexit_noreturns
  #99      fexit_noreturns:OK
  Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: Yafang Shao <[email protected]>

Author: laoar

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

@@ -0,0 +1,13 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <test_progs.h>
+#include "fexit_noreturns.skel.h"
+
+void test_fexit_noreturns(void)
+{
+	struct fexit_noreturns *fexit_skel;
+
+	fexit_skel = fexit_noreturns__open_and_load();
+	ASSERT_NULL(fexit_skel, "fexit_load");
+	ASSERT_EQ(errno, EINVAL, "can't load fexit_noreturns");
+}

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

@@ -0,0 +1,13 @@
+// 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";
+
+SEC("fexit/do_exit")
+int BPF_PROG(noreturns)
+{
+	return 0;
+}