pcb_gsd
memcpy(&pcb->pcb_gsd, &gdtstore[GUDATA_SEL], sizeof(pcb->pcb_gsd));
(union descriptor *)&pcb->pcb_gsd);
memcpy(&pcb->pcb_gsd, &gdtstore[GUDATA_SEL], sizeof(pcb->pcb_gsd));
memcpy(&gsd, &pcb->pcb_gsd, sizeof(gsd));
struct segment_descriptor pcb_gsd; /* %gs descriptor */
memcpy(&pcb->pcb_gsd, &usd.sd,
sd = (void *)&curpcb->pcb_gsd;