EF> What does NetBSD/amd64 use the fs register for? JS> TLS base register. Amongst the dozens of expansions of "TLS", I suppose it's Thread Local Storage here? I suppose then neither 0 nor 0x17 are valid values, then? I don't have much of a clue of 80x86; why does %fs:0 work for 0 and fault for 0x17?