PS_IOPL
iopl = (PS_IOPL & 0x1000); /* ring 1 */
rp->r_ps = PSL_USER | (rp->r_ps & PS_IOPL);
rp->r_ps = PSL_USER | (rp->r_ps & PS_IOPL);
greg_t oldpl = rp->r_ps & PS_IOPL;
greg_t newpl = arg2 & PS_IOPL;