SEL_LDT
#define ISLDT(s) ((s)&SEL_LDT) /* is it local or global */
#define LSEL(s,r) (((s)<<3) | SEL_LDT | r) /* a local selector */
gcore_usd_to_ssd(udp, pldt++, SEL_LDT(i));
int sel = SEL_LDT(7);
ssd.sel = SEL_LDT(i);
usd_to_ssd(udp, ssd++, SEL_LDT(i));