/* XXXKSE  All the code below only works in 1:1   needs changing */
        ext = (struct pcb_ext *)kmem_alloc(kernel_map, ctob(IOPAGES+1));
        if (ext == 0)
                return (ENOMEM);
        bzero(ext, sizeof(struct pcb_ext));
        /* -16 is so we can convert a trapframe into vm86trapframe inplace */
        ext->ext_tss.tss_esp0 = td->td_kstack + ctob(KSTACK_PAGES) -
            sizeof(struct pcb) - 16;
        ext->ext_tss.tss_ss0 = GSEL(GDATA_SEL, SEL_KPL);
        /*
         * The last byte of the i/o map must be followed by an 0xff byte.
         * We arbitrarily allocate 16 bytes here, to keep the starting
         * address on a doubleword boundary.
         */
        offset = PAGE_SIZE - 16;
        ext->ext_tss.tss_ioopt =
            (offset - ((unsigned)&ext->ext_tss - (unsigned)ext)) << 16;
        ext->ext_iomap = (caddr_t)ext + offset;
        ext->ext_vm86.vm86_intmap = (caddr_t)ext + offset - 32;

        addr = (u_long *)ext->ext_vm86.vm86_intmap;
        for (i = 0; i < (ctob(IOPAGES) + 32 + 16) / sizeof(u_long); i++)
                *addr++ = ~0;

        ssd.ssd_base = (unsigned)&ext->ext_tss;
        ssd.ssd_limit -= ((unsigned)&ext->ext_tss - (unsigned)ext);
        ssdtosd(&ssd, &ext->ext_tssd);

        KASSERT(td->td_proc == curthread->td_proc, ("giving TSS to !curproc"));
        KASSERT(td->td_pcb->pcb_ext == 0, ("already have a TSS!"));
        mtx_lock_spin(&sched_lock);
        td->td_pcb->pcb_ext = ext;

        /* switch to the new TSS after syscall completes */
        td->td_flags |= TDF_NEEDRESCHED;
        mtx_unlock_spin(&sched_lock);

        return 0;
}

static int
i386_set_ioperm(td, args)
        struct thread *td;
        char *args;
{
        int i, error;