Pointers and (library) code were shared all over the place, not just in the message passing system. Still, on a modern CPU you could certainly do an implementat

Pointers and (library) code were shared all over the place, not just in the message passing system. Still, on a modern CPU you could certainly do an implementation that either copies small messages, or just passes an entire page for a longer message. You'd need some kind of special AllocMsg function that takes the size of the message you want to send, let the OS decide if it should be sent by remapping a page or by copying.