HelenOS sources

root/kernel/generic/include/

[..]
align.h arch.h assert.h atomic.h barrier.h
bitops.h byteorder.h cap/ cc.h config.h
console/ context.h cpu.h cpu/ ddi/
debug.h debug/ errno.h fpu_context.h halt.h
interrupt.h ipc/ lib/ log.h macros.h
main/ member.h memw.h mm/ panic.h
preemption.h print.h printf/ proc/ security/
smp/ stacktrace.h stdio.h symtab.h synch/
syscall/ sysinfo/ time/ trace.h typedefs.h
udebug/ userspace.h verify.h
[..]
HelenOS homepage, sources at GitHub