diff options
Diffstat (limited to 'drivers/lguest/interrupts_and_traps.c')
| -rw-r--r-- | drivers/lguest/interrupts_and_traps.c | 125 |
1 files changed, 83 insertions, 42 deletions
diff --git a/drivers/lguest/interrupts_and_traps.c b/drivers/lguest/interrupts_and_traps.c index 39731232d82..82966982cb3 100644 --- a/drivers/lguest/interrupts_and_traps.c +++ b/drivers/lguest/interrupts_and_traps.c @@ -12,8 +12,14 @@ * them first, so we also have a way of "reflecting" them into the Guest as if * they had been delivered to it directly. :*/ #include <linux/uaccess.h> +#include <linux/interrupt.h> +#include <linux/module.h> #include "lg.h" +/* Allow Guests to use a non-128 (ie. non-Linux) syscall trap. */ +static unsigned int syscall_vector = SYSCALL_VECTOR; +module_param(syscall_vector, uint, 0444); + /* The address of the interrupt handler is split into two bits: */ static unsigned long idt_address(u32 lo, u32 hi) { @@ -39,7 +45,7 @@ static void push_guest_stack(struct lguest *lg, unsigned long *gstack, u32 val) { /* Stack grows upwards: move stack then write value. */ *gstack -= 4; - lgwrite_u32(lg, *gstack, val); + lgwrite(lg, *gstack, u32, val); } /*H:210 The set_guest_interrupt() routine actually delivers the interrupt or @@ -56,8 +62,9 @@ static void push_guest_stack(struct lguest *lg, unsigned long *gstack, u32 val) * it). */ static void set_guest_interrupt(struct lguest *lg, u32 lo, u32 hi, int has_err) { - unsigned long gstack; + unsigned long gstack, origstack; u32 eflags, ss, irq_enable; + unsigned long virtstack; /* There are two cases for interrupts: one where the Guest is already * in the kernel, and a more complex one where the Guest is in @@ -65,8 +72,10 @@ static void set_guest_interrupt(struct lguest *lg, u32 lo, u32 hi, int has_err) if ((lg->regs->ss&0x3) != GUEST_PL) { /* The Guest told us their kernel stack with the SET_STACK * hypercall: both the virtual address and the segment */ - gstack = guest_pa(lg, lg->esp1); + virtstack = lg->esp1; ss = lg->ss1; + + origstack = gstack = guest_pa(lg, virtstack); /* We push the old stack segment and pointer onto the new * stack: when the Guest does an "iret" back from the interrupt * handler the CPU will notice they're dropping privilege @@ -75,8 +84,10 @@ static void set_guest_interrupt(struct lguest *lg, u32 lo, u32 hi, int has_err) push_guest_stack(lg, &gstack, lg->regs->esp); } else { /* We're staying on the same Guest (kernel) stack. */ - gstack = guest_pa(lg, lg->regs->esp); + virtstack = lg->regs->esp; ss = lg->regs->ss; + + origstack = gstack = guest_pa(lg, virtstack); } /* Remember that we never let the Guest actually disable interrupts, so @@ -102,7 +113,7 @@ static void set_guest_interrupt(struct lguest *lg, u32 lo, u32 hi, int has_err) /* Now we've pushed all the old state, we change the stack, the code * segment and the address to execute. */ lg->regs->ss = ss; - lg->regs->esp = gstack + lg->page_offset; + lg->regs->esp = virtstack + (gstack - origstack); lg->regs->cs = (__KERNEL_CS|GUEST_PL); lg->regs->eip = idt_address(lo, hi); @@ -165,7 +176,7 @@ void maybe_do_interrupt(struct lguest *lg) /* Look at the IDT entry the Guest gave us for this interrupt. The * first 32 (FIRST_EXTERNAL_VECTOR) entries are for traps, so we skip * over them. */ - idt = &lg->idt[FIRST_EXTERNAL_VECTOR+irq]; + idt = &lg->arch.idt[FIRST_EXTERNAL_VECTOR+irq]; /* If they don't have a handler (yet?), we just ignore it */ if (idt_present(idt->a, idt->b)) { /* OK, mark it no longer pending and deliver it. */ @@ -183,6 +194,47 @@ void maybe_do_interrupt(struct lguest *lg) * timer interrupt. */ write_timestamp(lg); } +/*:*/ + +/* Linux uses trap 128 for system calls. Plan9 uses 64, and Ron Minnich sent + * me a patch, so we support that too. It'd be a big step for lguest if half + * the Plan 9 user base were to start using it. + * + * Actually now I think of it, it's possible that Ron *is* half the Plan 9 + * userbase. Oh well. */ +static bool could_be_syscall(unsigned int num) +{ + /* Normal Linux SYSCALL_VECTOR or reserved vector? */ + return num == SYSCALL_VECTOR || num == syscall_vector; +} + +/* The syscall vector it wants must be unused by Host. */ +bool check_syscall_vector(struct lguest *lg) +{ + u32 vector; + + if (get_user(vector, &lg->lguest_data->syscall_vec)) + return false; + + return could_be_syscall(vector); +} + +int init_interrupts(void) +{ + /* If they want some strange system call vector, reserve it now */ + if (syscall_vector != SYSCALL_VECTOR + && test_and_set_bit(syscall_vector, used_vectors)) { + printk("lg: couldn't reserve syscall %u\n", syscall_vector); + return -EBUSY; + } + return 0; +} + +void free_interrupts(void) +{ + if (syscall_vector != SYSCALL_VECTOR) + clear_bit(syscall_vector, used_vectors); +} /*H:220 Now we've got the routines to deliver interrupts, delivering traps * like page fault is easy. The only trick is that Intel decided that some @@ -197,14 +249,14 @@ int deliver_trap(struct lguest *lg, unsigned int num) { /* Trap numbers are always 8 bit, but we set an impossible trap number * for traps inside the Switcher, so check that here. */ - if (num >= ARRAY_SIZE(lg->idt)) + if (num >= ARRAY_SIZE(lg->arch.idt)) return 0; /* Early on the Guest hasn't set the IDT entries (or maybe it put a * bogus one in): if we fail here, the Guest will be killed. */ - if (!idt_present(lg->idt[num].a, lg->idt[num].b)) + if (!idt_present(lg->arch.idt[num].a, lg->arch.idt[num].b)) return 0; - set_guest_interrupt(lg, lg->idt[num].a, lg->idt[num].b, has_err(num)); + set_guest_interrupt(lg, lg->arch.idt[num].a, lg->arch.idt[num].b, has_err(num)); return 1; } @@ -218,28 +270,20 @@ 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). */ - if (num >= FIRST_EXTERNAL_VECTOR && num != SYSCALL_VECTOR) + if (num >= FIRST_EXTERNAL_VECTOR && !could_be_syscall(num)) return 0; /* The Host needs to see page faults (for shadow paging and to save the * 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 +392,11 @@ 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)) - set_trap(lg, &lg->idt[num], num, lo, hi); - else if (num == SYSCALL_VECTOR) - set_trap(lg, &lg->syscall_idt, num, lo, hi); + /* Check that the Guest doesn't try to step outside the bounds. */ + if (num >= ARRAY_SIZE(lg->arch.idt)) + kill_guest(lg, "Setting idt entry %u", num); + else + set_trap(lg, &lg->arch.idt[num], num, lo, hi); } /* The default entry for each interrupt points into the Switcher routines which @@ -399,20 +439,21 @@ 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)) - idt[i] = lg->idt[i]; + for (i = 0; i < ARRAY_SIZE(lg->arch.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->arch.idt[i].a, lg->arch.idt[i].b) == 0xF) + idt[i] = lg->arch.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) |