HelenOS sources

root/kernel/arch/amd64/include/arch/

[..]
arch.h asm.h bios/ boot/ context.h
context_struct.h cpu.h cpuid.h cycle.h ddi/
drivers/ faddr.h fpu_context.h interrupt.h istate.h
istate_struct.h kseg.h kseg_struct.h mm/ pm.h
proc/ smp/ stack.h syscall.h types.h
vreg.h
[..]
HelenOS homepage, sources at GitHub