selftests/bpf: Split test_attach_probe into multi subtests

In order to adapt to the older kernel, now we split the "attach_probe"
testing into multi subtests:

  manual // manual attach tests for kprobe/uprobe
  auto // auto-attach tests for kprobe and uprobe
  kprobe-sleepable // kprobe sleepable test
  uprobe-lib // uprobe tests for library function by name
  uprobe-sleepable // uprobe sleepable test
  uprobe-ref_ctr // uprobe ref_ctr test

As sleepable kprobe needs to set BPF_F_SLEEPABLE flag before loading,
we need to move it to a stand alone skel file, in case of it is not
supported by kernel and make the whole loading fail.

Therefore, we can only enable part of the subtests for older kernel.
Signed-off-by: Menglong Dong <imagedong@tencent.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Biao Jiang <benbjiang@tencent.com>
Link: https://lore.kernel.org/bpf/20230306064833.7932-3-imagedong@tencent.com

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

+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2017 Facebook
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_core_read.h>
+#include "bpf_misc.h"
+
+int kprobe_res = 0;
+
+/**
+ * This program will be manually made sleepable on the userspace side
+ * and should thus be unattachable.
+ */
+SEC("kprobe/" SYS_PREFIX "sys_nanosleep")
+int handle_kprobe_sleepable(struct pt_regs *ctx)
+{
+	kprobe_res = 1;
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";

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

@@ -37,17 +37,6 @@ int BPF_KSYSCALL(handle_kprobe_auto, struct __kernel_timespec *req, struct __ker
 	return 0;
 }
 
-/**
- * This program will be manually made sleepable on the userspace side
- * and should thus be unattachable.
- */
-SEC("kprobe/" SYS_PREFIX "sys_nanosleep")
-int handle_kprobe_sleepable(struct pt_regs *ctx)
-{
-	kprobe_res = 2;
-	return 0;
-}
-
 SEC("kretprobe")
 int handle_kretprobe(struct pt_regs *ctx)
 {
@@ -76,6 +65,18 @@ int handle_uretprobe(struct pt_regs *ctx)
 	return 0;
 }
 
+SEC("uprobe")
+int handle_uprobe_ref_ctr(struct pt_regs *ctx)
+{
+	return 0;
+}
+
+SEC("uretprobe")
+int handle_uretprobe_ref_ctr(struct pt_regs *ctx)
+{
+	return 0;
+}
+
 SEC("uprobe")
 int handle_uprobe_byname(struct pt_regs *ctx)
 {