Make shadow IDT a complete IDT with 256 entries.
This simplifies the code a little, in preparation for allowing
alternate system call vectors in guests (Plan 9 uses 0x40).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/drivers/lguest/interrupts_and_traps.c b/drivers/lguest/interrupts_and_traps.c
index 3973123..0dfb090 100644
--- a/drivers/lguest/interrupts_and_traps.c
+++ b/drivers/lguest/interrupts_and_traps.c
@@ -218,10 +218,9 @@
* system calls down from 1750ns to 270ns. Plus, if lguest didn't do it, all
* the other hypervisors would tease it.
*
- * This routine determines if a trap can be delivered directly. */
-static int direct_trap(const struct lguest *lg,
- const struct desc_struct *trap,
- unsigned int num)
+ * This routine indicates if a particular trap number could be delivered
+ * directly. */
+static int direct_trap(unsigned int num)
{
/* Hardware interrupts don't go to the Guest at all (except system
* call). */
@@ -232,14 +231,7 @@
* fault address), general protection faults (in/out emulation) and
* device not available (TS handling), and of course, the hypercall
* trap. */
- if (num == 14 || num == 13 || num == 7 || num == LGUEST_TRAP_ENTRY)
- return 0;
-
- /* Only trap gates (type 15) can go direct to the Guest. Interrupt
- * gates (type 14) disable interrupts as they are entered, which we
- * never let the Guest do. Not present entries (type 0x0) also can't
- * go direct, of course 8) */
- return idt_type(trap->a, trap->b) == 0xF;
+ return num != 14 && num != 13 && num != 7 && num != LGUEST_TRAP_ENTRY;
}
/*:*/
@@ -348,15 +340,11 @@
* to copy this again. */
lg->changed |= CHANGED_IDT;
- /* The IDT which we keep in "struct lguest" only contains 32 entries
- * for the traps and LGUEST_IRQS (32) entries for interrupts. We
- * ignore attempts to set handlers for higher interrupt numbers, except
- * for the system call "interrupt" at 128: we have a special IDT entry
- * for that. */
- if (num < ARRAY_SIZE(lg->idt))
+ /* Check that the Guest doesn't try to step outside the bounds. */
+ if (num >= ARRAY_SIZE(lg->idt))
+ kill_guest(lg, "Setting idt entry %u", num);
+ else
set_trap(lg, &lg->idt[num], num, lo, hi);
- else if (num == SYSCALL_VECTOR)
- set_trap(lg, &lg->syscall_idt, num, lo, hi);
}
/* The default entry for each interrupt points into the Switcher routines which
@@ -399,20 +387,21 @@
/* We can simply copy the direct traps, otherwise we use the default
* ones in the Switcher: they will return to the Host. */
- for (i = 0; i < FIRST_EXTERNAL_VECTOR; i++) {
- if (direct_trap(lg, &lg->idt[i], i))
+ for (i = 0; i < ARRAY_SIZE(lg->idt); i++) {
+ /* If no Guest can ever override this trap, leave it alone. */
+ if (!direct_trap(i))
+ continue;
+
+ /* Only trap gates (type 15) can go direct to the Guest.
+ * Interrupt gates (type 14) disable interrupts as they are
+ * entered, which we never let the Guest do. Not present
+ * entries (type 0x0) also can't go direct, of course. */
+ if (idt_type(lg->idt[i].a, lg->idt[i].b) == 0xF)
idt[i] = lg->idt[i];
else
+ /* Reset it to the default. */
default_idt_entry(&idt[i], i, def[i]);
}
-
- /* Don't forget the system call trap! The IDT entries for other
- * interupts never change, so no need to copy them. */
- i = SYSCALL_VECTOR;
- if (direct_trap(lg, &lg->syscall_idt, i))
- idt[i] = lg->syscall_idt;
- else
- default_idt_entry(&idt[i], i, def[i]);
}
void guest_set_clockevent(struct lguest *lg, unsigned long delta)