diff options
Diffstat (limited to 'drivers/lguest/interrupts_and_traps.c')
| -rw-r--r-- | drivers/lguest/interrupts_and_traps.c | 49 |
1 files changed, 19 insertions, 30 deletions
diff --git a/drivers/lguest/interrupts_and_traps.c b/drivers/lguest/interrupts_and_traps.c index 39731232d82..0dfb0903aa6 100644 --- a/drivers/lguest/interrupts_and_traps.c +++ b/drivers/lguest/interrupts_and_traps.c @@ -218,10 +218,9 @@ int deliver_trap(struct lguest *lg, unsigned int num) * 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 @@ static int direct_trap(const struct lguest *lg, * 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 @@ void load_guest_idt_entry(struct lguest *lg, unsigned int num, u32 lo, u32 hi) * 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 @@ void copy_traps(const struct lguest *lg, struct desc_struct *idt, /* 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) |