tracing: switch to kernel_clone()

The old _do_fork() helper is removed in favor of the new kernel_clone() helper.
The latter adheres to naming conventions for kernel internal syscall helpers.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Cc: Alexandre Chartre <alexandre.chartre@oracle.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Xiao Yang <yangx.jy@cn.fujitsu.com>
Cc: Tom Zanussi <zanussi@kernel.org>
Cc: linux-doc@vger.kernel.org
Cc: linux-kselftest@vger.kernel.org
Link: https://lore.kernel.org/r/20200819104655.436656-11-christian.brauner@ubuntu.com

samples/kprobes/kretprobe_example.c

@@ -8,7 +8,7 @@
  *
  * usage: insmod kretprobe_example.ko func=<func_name>
  *
- * If no func_name is specified, _do_fork is instrumented
+ * If no func_name is specified, kernel_clone is instrumented
  *
  * For more information on theory of operation of kretprobes, see
  * Documentation/staging/kprobes.rst
@@ -26,7 +26,7 @@
 #include <linux/limits.h>
 #include <linux/sched.h>
 
-static char func_name[NAME_MAX] = "_do_fork";
+static char func_name[NAME_MAX] = "kernel_clone";
 module_param_string(func, func_name, NAME_MAX, S_IRUGO);
 MODULE_PARM_DESC(func, "Function to kretprobe; this module will report the"
 			" function's execution time");