selftests/ftrace: Fix ftrace test cases to check unsupported

Since dynamic function tracer can be disabled, set_ftrace_filter
can be disappeared. Test cases which depends on it, must check
whether the set_ftrace_filter exists or not before testing
and if not, return as unsupported.

Also, if the function tracer itself is disabled, we can not
set "function" to current_tracer. Test cases must check it
before testing, and return as unsupported.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

tools/testing/selftests/ftrace/test.d/ftrace/func-filter-stacktrace.tc

@@ -3,6 +3,8 @@
 # description: ftrace - stacktrace filter command
 # flags: instance
 
+[ ! -f set_ftrace_filter ] && exit_unsupported
+
 echo _do_fork:stacktrace >> set_ftrace_filter
 
 grep -q "_do_fork:stacktrace:unlimited" set_ftrace_filter

tools/testing/selftests/ftrace/test.d/ftrace/func_cpumask.tc

@@ -15,6 +15,11 @@ if [ $NP -eq 1 ] ;then
   exit_unresolved
 fi
 
+if ! grep -q "function" available_tracers ; then
+  echo "Function trace is not enabled"
+  exit_unsupported
+fi
+
 ORIG_CPUMASK=`cat tracing_cpumask`
 
 do_reset() {