selftests/kselftest/runner/run_one(): allow running non-executable files

When running a test program, 'run_one()' checks if the program has the
execution permission and fails if it doesn't.  However, it's easy to
mistakenly lose the permissions, as some common tools like 'diff' don't
support the permission change well[1].  Compared to that, making mistakes
in the test program's path would only rare, as those are explicitly listed
in 'TEST_PROGS'.  Therefore, it might make more sense to resolve the
situation on our own and run the program.

For this reason, this commit makes the test program runner function still
print the warning message but to try parsing the interpreter of the
program and to explicitly run it with the interpreter, in this case.

[1] https://lore.kernel.org/mm-commits/[email protected]/

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: SeongJae Park <[email protected]>
Suggested-by: Greg Kroah-Hartman <[email protected]>
Cc: Shuah Khan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

tools/testing/selftests/kselftest/runner.sh

@@ -33,9 +33,9 @@ tap_timeout()
 {
 	# Make sure tests will time out if utility is available.
 	if [ -x /usr/bin/timeout ] ; then
-		/usr/bin/timeout --foreground "$kselftest_timeout" "$1"
+		/usr/bin/timeout --foreground "$kselftest_timeout" $1
 	else
-		"$1"
+		$1
 	fi
 }
 
@@ -65,17 +65,25 @@ run_one()
 
 	TEST_HDR_MSG="selftests: $DIR: $BASENAME_TEST"
 	echo "# $TEST_HDR_MSG"
-	if [ ! -x "$TEST" ]; then
-		echo -n "# Warning: file $TEST is "
-		if [ ! -e "$TEST" ]; then
-			echo "missing!"
-		else
-			echo "not executable, correct this."
-		fi
+	if [ ! -e "$TEST" ]; then
+		echo "# Warning: file $TEST is missing!"
 		echo "not ok $test_num $TEST_HDR_MSG"
 	else
+		cmd="./$BASENAME_TEST"
+		if [ ! -x "$TEST" ]; then
+			echo "# Warning: file $TEST is not executable"
+
+			if [ $(head -n 1 "$TEST" | cut -c -2) = "#!" ]
+			then
+				interpreter=$(head -n 1 "$TEST" | cut -c 3-)
+				cmd="$interpreter ./$BASENAME_TEST"
+			else
+				echo "not ok $test_num $TEST_HDR_MSG"
+				return
+			fi
+		fi
 		cd `dirname $TEST` > /dev/null
-		((((( tap_timeout ./$BASENAME_TEST 2>&1; echo $? >&3) |
+		((((( tap_timeout "$cmd" 2>&1; echo $? >&3) |
 			tap_prefix >&4) 3>&1) |
 			(read xs; exit $xs)) 4>>"$logfile" &&
 		echo "ok $test_num $TEST_HDR_MSG") ||