selftests/ftrace: Select an existing function in kprobe_eventname test

Running the ftrace selftests on the latest kernel caused the
kprobe_eventname test to fail. It was due to the test that searches for
a function with at "dot" in the name and adding a probe to that.
Unfortunately, for this test, it picked:

 optimize_nops.isra.2.cold.4

Which happens to be marked as "__init", which means it no longer exists
in the kernel! (kallsyms keeps those function names around for tracing
purposes)

As only functions that still exist are in the
available_filter_functions file, as they are removed when the functions
are freed at boot or module exit, have the test search for a function
with ".isra." in the name as well as being in the
available_filter_functions (if the file exists).

Link: http://lkml.kernel.org/r/20190322150923.1b58eca5@gandalf.local.home
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_eventname.tc b/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_eventname.tc
index 3fb70e01b1fe18b5c67c2176460522b6fcd4d2dc..3ff236719b6e87891d42ef4f27fb585d21ad9ca3 100644 (file)
--- a/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_eventname.tc
+++ b/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_eventname.tc
@@ -24,7 +24,21 @@ test -d events/kprobes2/event2 || exit_failure
 
 :;: "Add an event on dot function without name" ;:
 
-FUNC=`grep -m 10 " [tT] .*\.isra\..*$" /proc/kallsyms | tail -n 1 | cut -f 3 -d " "`
+find_dot_func() {
+       if [ ! -f available_filter_functions ]; then
+               grep -m 10 " [tT] .*\.isra\..*$" /proc/kallsyms | tail -n 1 | cut -f 3 -d " "
+               return;
+       fi
+
+       grep " [tT] .*\.isra\..*" /proc/kallsyms | cut -f 3 -d " " | while read f; do
+               if grep -s $f available_filter_functions; then
+                       echo $f
+                       break
+               fi
+       done
+}
+
+FUNC=`find_dot_func | tail -n 1`
 [ "x" != "x$FUNC" ] || exit_unresolved
 echo "p $FUNC" > kprobe_events
 EVENT=`grep $FUNC kprobe_events | cut -f 1 -d " " | cut -f 2 -d:`