linux-kernel - [PATCH] selftests/ftrace: Select an existing function in kprobe

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Date:   Fri, 22 Mar 2019 15:09:23 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        Shuah Khan <shuahkhan@...il.com>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH] selftests/ftrace: Select an existing function in
 kprobe_eventname test

From: Steven Rostedt (VMware) <rostedt@...dmis.org>

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).

Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.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 3fb70e01b1fe..3ff236719b6e 100644
--- 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:`