I custom make all my serial cables using RJ45 to DB9 adapters. I wire the adapters to use Ethernet pins 4,5,7. I mark an adapter as straight or as X-over depending on how I wired pins 2 and 3. On straight I wire DB9.2 to Cat5.4 and DB9.3 to Cat5.5. on X-over I wire DB9.2 to Cat5.5 and DB9.3 to Cat5.4.

If manufacturers did things correctly the a Female,Female able would
always be X-Over, and a Male,Female would always be straight. There should not be a Male,Male, but if there is one it should be straight.