Comment by TheCondor

Every operating system I’ve worked on has had a tiny few lines of relatively isolated code for this sort of thing. Even some crappy RTOSes, it seems it is natural to want to abstract it. You need to forge a number into a physical address pointer, not just a pointer. Look at some Linux drivers, they will have some offsets defined but they don’t just create a void* and assign it to a memory location, they use macros and helper functions to fix things up. They can even check if the address is in reserved io spaces and do things like that. There are also helpers to write the bytes to those addresses. It’s a tiny amount of code that is usually already abstracted.

I don’t know. Seems like a lot of kernels do extra things so driver writers can write fairly normal looking C and produce fairly safe drivers without just arbitrarily assigning pointers addresses from numbers. And even if you use C as your comparison, those helpers will often be written with some assembly language (read C isn’t completely good enough for the task all by itself) I don’t know of it existing but a kernel in go with ref counting GC and a handful of cgo primitives seems very possible and maybe even delightful to work on.