HelenOS sources

write_rflags      282 kernel/arch/amd64/include/arch/asm.h 	write_rflags((uint64_t) ipl);
write_rflags      115 kernel/arch/amd64/src/amd64.c 	write_rflags(read_rflags() & ~(RFLAGS_IOPL | RFLAGS_NT));
HelenOS homepage, sources at GitHub