VALID_USER_FSEL32
!(VALID_USER_FSEL32(scp->sc_fs) && pcb->pcb_fs != 0))
!(VALID_USER_FSEL32(gr[_REG32_FS]) && pcb->pcb_fs != 0))
!(VALID_USER_FSEL32(regs->r_fs) && pcb->pcb_fs != 0))
!(VALID_USER_FSEL32(scp->sc_fs) && pcb->pcb_fs != 0))