Hello All, I'm reading x86_64 source code and trying to understand where are fixmaps space in the virtual memory space. If I understand correctly (but i'm really not sure about it), fixmap space is after vsyscall space. As Documentation/x86/x86_64/mm.txt says vsyscall virtual space is: ffffffffff600000 - ffffffffffdfffff (=8 MB) vsyscalls Also I see that FIXADDR_START and FIXADDR_TOP and are: FIXADDR_START - 0xffffffffff779000L FIXADDR_TOP - 0xffffffffff7ff000L on my machine. With these addressess FIXADDR_START/FIXADDR_TOP overlap vsyscalls area. Is it correct case that fixmaps are in vsyscal virtual memory space or I'm wrong somewhere? Thank you.