selftests: Extract single-test shell logic from lib.mk

In order to improve the reusability of the kselftest test running logic,
this extracts the single-test logic from lib.mk into kselftest/runner.sh
which lib.mk can call directly. No changes in output.

As part of the change, this moves the "summary" Makefile logic around
to set a new "logfile" output. This will be used again in the future
"emit_tests" target as well.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

tools/testing/selftests/kselftest/runner.sh

@@ -0,0 +1,32 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+#
+# Runs a set of tests in a given subdirectory.
+export skip_rc=4
+export logfile=/dev/stdout
+
+run_one()
+{
+	TEST="$1"
+	NUM="$2"
+
+	BASENAME_TEST=$(basename $TEST)
+
+	TEST_HDR_MSG="selftests: "`basename $PWD`:" $BASENAME_TEST"
+	echo "$TEST_HDR_MSG"
+	echo "========================================"
+	if [ ! -x "$TEST" ]; then
+		echo "$TEST_HDR_MSG: Warning: file $TEST is not executable, correct this."
+		echo "not ok 1..$test_num $TEST_HDR_MSG [FAIL]"
+	else
+		cd `dirname $TEST` > /dev/null
+		(./$BASENAME_TEST >> "$logfile" 2>&1 &&
+		echo "ok 1..$test_num $TEST_HDR_MSG [PASS]") ||
+		(if [ $? -eq $skip_rc ]; then	\
+			echo "not ok 1..$test_num $TEST_HDR_MSG [SKIP]"
+		else
+			echo "not ok 1..$test_num $TEST_HDR_MSG [FAIL]"
+		fi)
+		cd - >/dev/null
+	fi
+}