You sound like you’re living in the weeds, friend.

What’s MPK? And by UID I assume you’re not talking about the system level user ID but some kind of processor-level process ID?

Not a kernel expert but this is how it reads to me.

Instead of connecting via a socket through the kernel, this would allow processes to execute functions of other processes already in memory.

This would normally be prevented by processor memory protections, but a new processor feature has functionality to allow this now.