selftests/ftrace: Add test case to test adding and removing of event probe

Add a test case that adds an event probe, makes sure that it works, and
then removes it.

Link: https://lore.kernel.org/linux-kselftest/20210819152825.526931866@goodmis.org/
Link: https://lkml.kernel.org/r/20210820204742.274591200@goodmis.org

Cc: "Tzvetomir Stoyanov" <tz.stoyanov@gmail.com>
Cc: Tom Zanussi <zanussi@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: linux-kselftest@vger.kernel.org
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

tools/testing/selftests/ftrace/test.d/dynevent/add_remove_eprobe.tc

+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# description: Generic dynamic event - add/remove eprobe events
+# requires: dynamic_events events/syscalls/sys_enter_openat "e[:[<group>/]<event>] <attached-group>.<attached-event> [<args>]":README
+
+echo 0 > events/enable
+
+clear_dynamic_events
+
+SYSTEM="syscalls"
+EVENT="sys_enter_openat"
+FIELD="filename"
+EPROBE="eprobe_open"
+
+echo "e:$EPROBE $SYSTEM/$EVENT file=+0(\$filename):ustring" >> dynamic_events
+
+grep -q "$EPROBE" dynamic_events
+test -d events/eprobes/$EPROBE
+
+echo 1 > events/eprobes/$EPROBE/enable
+ls
+echo 0 > events/eprobes/$EPROBE/enable
+
+content=`grep '^ *ls-' trace | grep 'file='`
+nocontent=`grep '^ *ls-' trace | grep 'file=' | grep -v -e '"/' -e '"."'` || true
+
+if [ -z "$content" ]; then
+	exit_fail
+fi
+
+if [ ! -z "$nocontent" ]; then
+	exit_fail
+fi
+
+echo "-:$EPROBE" >> dynamic_events
+
+! grep -q "$EPROBE" dynamic_events
+! test -d events/eprobes/$EPROBE
+
+clear_trace