Let's make this the URL? I think the resolution makes for a more interesting discussion, and it does still talk about the provisional design in brief.

The plan described there is to use a signal (SIGSYS) to jump back into the process. This involves multiple kernel/userpace switches as most likely you need some Linux syscalls to emulate the MS Windows one.

I like the idea of using eBPF to run an emulation layer. That has potential to be more efficient and doesn't require the running process to cooperate so closely with the syscall emulation. Then this would probably lead to extensions to eBPF and its tooling which should be useful for other things!