selftests/ftrace: Add kprobe event with $comm argument testcase

Add kprobe-event with $comm argument testcase to
ftracetest. This not only checks syntax but
also checks log file.
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Shuah Khan (Samsung OSG) <shuah@kernel.org>

tools/testing/selftests/ftrace/test.d/kprobe/kprobe_args_comm.tc

+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# description: Kprobe event with comm arguments
+
+[ -f kprobe_events ] || exit_unsupported # this is configurable
+
+grep -A1 "fetcharg:" README | grep -q "\$comm" || exit_unsupported # this is too old
+
+echo 'p:testprobe _do_fork comm=$comm ' > kprobe_events
+grep testprobe kprobe_events | grep -q 'comm=$comm'
+test -d events/kprobes/testprobe
+
+echo 1 > events/kprobes/testprobe/enable
+( echo "forked")
+grep testprobe trace | grep -q 'comm=".*"'
+
+exit 0