[dathinab]

Also very important with 64 bit there is a lot more room to play with. Also there is address layout randomization which at last on 64bit every program _should_ be compiled with.

Also on 64 bit isn't the last memory page like the first unmappable (I think at last on linux it is).

Lastly isn't there a region of unmapable virtual address space on 64 bit in the middle of the virtual address space due to the chips which are doing mmap not handling full 64bit of virtual address space?? I sadly can't find any info about this but I remember having read about it before? Maybe I mixed something up.

[masklinn]

> Lastly isn't there a region of unmapable virtual address space on 64 bit in the middle of the virtual address space due to the chips which are doing mmap not handling full 64bit of virtual address space?

Yes. ARM64 currently has a 48b address space split in two ranges (0 to 00007FFFFFFFFFFF and FFFF800000000000 to FFFFFFFFFFFFFFFF), ARMv8 requires 48b and allows 52 but apparently the sizes of the userspace and kernel regions are configurable (though limited by the chip aka you could reduce the size of the kernel space down from 48b but can't increase it).