Comment by londons_explore

I would hope that all memory outside the known ranges is denied by default... Apple should know all the memory mapped hardware in the SoC, so why would they allow IO to something that doesn't exist?

It's just a few lines of code to parse the memory map and deny all undefined regions. As well as being good for security, it also helps find out-of-bounds write bugs, and ensures you can't accidentally ship an out of date memory map.