void switch_if_needed(uint32_t ticks) {
task_t *current = current_task();
current->rem_quantum--;
current->ticks++;
if (!current->rem_quantum) {
restart_quantum(current);
switch_tasks();
}
}
int emu_iret(unsigned char *lina)
{
trace("iret\n");
if (! opa.pe) {
Bit32u tmp;
int width = opa.opb;
if (REG(esp) > 0x10000 - 3*width) {
set_guest_exc(12, 0);
goto exc;
}
if (get_memory(LWORD(ss), LWORD(esp), ®(eip), width))
goto exc;
if (width == 2)
REG(eip) &= 0xffff;
LWORD(esp) += width;
if (get_memory(LWORD(ss), LWORD(esp), &tmp, 2)) /* always only use 16 bits */
goto exc;
REG(cs) = tmp;
LWORD(esp) += width;
if (get_memory(LWORD(ss), LWORD(esp), &tmp, width))
goto exc;
LWORD(eflags) = tmp;
LWORD(esp) += width;
if (width == 4) {
/* 32 bit -- VM, IOPL, VIP, and VIF are unmodified */
REG(eflags) = ((tmp & ~(VM_MASK | IOPL_MASK | VIP_MASK | VIF_MASK)) |
(REG(eflags) & (VM_MASK | IOPL_MASK | VIP_MASK | VIF_MASK)));
} else {
/* 16 bit -- IOPL is unmodified */
REG(eflags) = ((tmp & ~(0xffff000 | IOPL_MASK)) |
(REG(eflags) & (0xffff000 | IOPL_MASK)));
}
trace("%d byte iret; eip=%x cs=%x, eflags=%x; new lina=%x\n", opa.opb,
REG(eip), REG(cs), REG(eflags), (u_int)lina);
} else {
/* PROTECTED-MODE */
if (REG(eflags) & NT_MASK) {
/* TASK-RETURN */
Bit16u old_sel = vmstate.tr_sel;
struct seg_descr *old_tss;
struct Ts *ts = (struct Ts*)vmstate.tr_base;
struct seg_descr tss;
Bit16u selector = ts->ts_link;
int err;
if (get_tss_descriptor(selector, &tss, 1) ||
switch_tasks(selector, &tss))
goto exc;
ts->ts_t = 0; /* We probably got here because this was set, to let us emulate it. */
/* mark the descriptor of the abandoned task as "not busy" */
ASSERT((old_sel & ~7) == 0);
ASSERT((old_sel & ~7) >= vmstate.g_gdt_limit);
err = set_get_any(&vmstate.g_gdt_base, (u_int*)&old_tss);
ASSERT(!err);
old_tss += (old_sel >> 3);
old_tss->type &= ~2;
} else {
