diff --git a/kernel/trace/trace_printk.c b/kernel/trace/trace_printk.c
index f96f038..ad1d616 100644
--- a/kernel/trace/trace_printk.c
+++ b/kernel/trace/trace_printk.c
@@ -36,6 +36,10 @@ struct trace_bprintk_fmt {
 static inline struct trace_bprintk_fmt *lookup_format(const char *fmt)
 {
 	struct trace_bprintk_fmt *pos;
+
+	if (!fmt)
+		return ERR_PTR(-EINVAL);
+
 	list_for_each_entry(pos, &trace_bprintk_fmt_list, list) {
 		if (!strcmp(pos->fmt, fmt))
 			return pos;
@@ -57,7 +61,8 @@ void hold_module_trace_bprintk_format(const char **start, const char **end)
 	for (iter = start; iter < end; iter++) {
 		struct trace_bprintk_fmt *tb_fmt = lookup_format(*iter);
 		if (tb_fmt) {
-			*iter = tb_fmt->fmt;
+			if (!IS_ERR(tb_fmt))
+				*iter = tb_fmt->fmt;
 			continue;
 		}
 
diff --git a/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist-mod.tc b/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist-mod.tc
index c2b61c4..0bf5085 100644
--- a/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist-mod.tc
+++ b/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist-mod.tc
@@ -23,15 +23,14 @@ if [ ! -f events/sched/sched_process_fork/trigger ]; then
     exit_unsupported
 fi
 
-reset_tracer
-do_reset
-
-FEATURE=`grep hist events/sched/sched_process_fork/trigger`
-if [ -z "$FEATURE" ]; then
+if [ ! -f events/sched/sched_process_fork/hist ]; then
     echo "hist trigger is not supported"
     exit_unsupported
 fi
 
+reset_tracer
+do_reset
+
 echo "Test histogram with execname modifier"
 
 echo 'hist:keys=common_pid.execname' > events/sched/sched_process_fork/trigger
diff --git a/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist.tc b/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist.tc
index b2902d4..a00184c 100644
--- a/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist.tc
+++ b/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist.tc
@@ -23,15 +23,14 @@ if [ ! -f events/sched/sched_process_fork/trigger ]; then
     exit_unsupported
 fi
 
-reset_tracer
-do_reset
-
-FEATURE=`grep hist events/sched/sched_process_fork/trigger`
-if [ -z "$FEATURE" ]; then
+if [ ! -f events/sched/sched_process_fork/hist ]; then
     echo "hist trigger is not supported"
     exit_unsupported
 fi
 
+reset_tracer
+do_reset
+
 echo "Test histogram basic tigger"
 
 echo 'hist:keys=parent_pid:vals=child_pid' > events/sched/sched_process_fork/trigger
diff --git a/tools/testing/selftests/ftrace/test.d/trigger/trigger-multihist.tc b/tools/testing/selftests/ftrace/test.d/trigger/trigger-multihist.tc
index 03c4a46..3478b00 100644
--- a/tools/testing/selftests/ftrace/test.d/trigger/trigger-multihist.tc
+++ b/tools/testing/selftests/ftrace/test.d/trigger/trigger-multihist.tc
@@ -23,15 +23,14 @@ if [ ! -f events/sched/sched_process_fork/trigger ]; then
     exit_unsupported
 fi
 
-reset_tracer
-do_reset
-
-FEATURE=`grep hist events/sched/sched_process_fork/trigger`
-if [ -z "$FEATURE" ]; then
+if [ ! -f events/sched/sched_process_fork/hist ]; then
     echo "hist trigger is not supported"
     exit_unsupported
 fi
 
+reset_tracer
+do_reset
+
 reset_trigger
 
 echo "Test histogram multiple tiggers"