X-Git-Url: http://pilppa.org/gitweb/gitweb.cgi?a=blobdiff_plain;f=drivers%2Flguest%2Finterrupts_and_traps.c;h=0414ddf875871729c00742c00cb6bf45a558eac8;hb=a6bd8e13034dd7d60b6f14217096efa192d0adc1;hp=49aa55577d0dec0e2543c2a8801b91ebc98b1359;hpb=edd5f25f7475013b44f7942bb3b25022792a9c9d;p=linux-2.6-omap-h63xx.git diff --git a/drivers/lguest/interrupts_and_traps.c b/drivers/lguest/interrupts_and_traps.c index 49aa55577d0..0414ddf8758 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 +#include +#include #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) { @@ -35,11 +41,11 @@ static int idt_present(u32 lo, u32 hi) /* We need a helper to "push" a value onto the Guest's stack, since that's a * big part of what delivering an interrupt does. */ -static void push_guest_stack(struct lguest *lg, unsigned long *gstack, u32 val) +static void push_guest_stack(struct lg_cpu *cpu, unsigned long *gstack, u32 val) { /* Stack grows upwards: move stack then write value. */ *gstack -= 4; - lgwrite_u32(lg, *gstack, val); + lgwrite(cpu, *gstack, u32, val); } /*H:210 The set_guest_interrupt() routine actually delivers the interrupt or @@ -54,87 +60,91 @@ static void push_guest_stack(struct lguest *lg, unsigned long *gstack, u32 val) * We set up the stack just like the CPU does for a real interrupt, so it's * identical for the Guest (and the standard "iret" instruction will undo * it). */ -static void set_guest_interrupt(struct lguest *lg, u32 lo, u32 hi, int has_err) +static void set_guest_interrupt(struct lg_cpu *cpu, 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 * userspace. We check the privilege level to find out. */ - if ((lg->regs->ss&0x3) != GUEST_PL) { + if ((cpu->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); - ss = lg->ss1; + virtstack = cpu->esp1; + ss = cpu->ss1; + + origstack = gstack = guest_pa(cpu, 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 * levels and expect these here. */ - push_guest_stack(lg, &gstack, lg->regs->ss); - push_guest_stack(lg, &gstack, lg->regs->esp); + push_guest_stack(cpu, &gstack, cpu->regs->ss); + push_guest_stack(cpu, &gstack, cpu->regs->esp); } else { /* We're staying on the same Guest (kernel) stack. */ - gstack = guest_pa(lg, lg->regs->esp); - ss = lg->regs->ss; + virtstack = cpu->regs->esp; + ss = cpu->regs->ss; + + origstack = gstack = guest_pa(cpu, virtstack); } /* Remember that we never let the Guest actually disable interrupts, so * the "Interrupt Flag" bit is always set. We copy that bit from the - * Guest's "irq_enabled" field into the eflags word: the Guest copies - * it back in "lguest_iret". */ - eflags = lg->regs->eflags; - if (get_user(irq_enable, &lg->lguest_data->irq_enabled) == 0 + * Guest's "irq_enabled" field into the eflags word: we saw the Guest + * copy it back in "lguest_iret". */ + eflags = cpu->regs->eflags; + if (get_user(irq_enable, &cpu->lg->lguest_data->irq_enabled) == 0 && !(irq_enable & X86_EFLAGS_IF)) eflags &= ~X86_EFLAGS_IF; /* An interrupt is expected to push three things on the stack: the old * "eflags" word, the old code segment, and the old instruction * pointer. */ - push_guest_stack(lg, &gstack, eflags); - push_guest_stack(lg, &gstack, lg->regs->cs); - push_guest_stack(lg, &gstack, lg->regs->eip); + push_guest_stack(cpu, &gstack, eflags); + push_guest_stack(cpu, &gstack, cpu->regs->cs); + push_guest_stack(cpu, &gstack, cpu->regs->eip); /* For the six traps which supply an error code, we push that, too. */ if (has_err) - push_guest_stack(lg, &gstack, lg->regs->errcode); + push_guest_stack(cpu, &gstack, cpu->regs->errcode); /* 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->cs = (__KERNEL_CS|GUEST_PL); - lg->regs->eip = idt_address(lo, hi); + cpu->regs->ss = ss; + cpu->regs->esp = virtstack + (gstack - origstack); + cpu->regs->cs = (__KERNEL_CS|GUEST_PL); + cpu->regs->eip = idt_address(lo, hi); /* There are two kinds of interrupt handlers: 0xE is an "interrupt * gate" which expects interrupts to be disabled on entry. */ if (idt_type(lo, hi) == 0xE) - if (put_user(0, &lg->lguest_data->irq_enabled)) - kill_guest(lg, "Disabling interrupts"); + if (put_user(0, &cpu->lg->lguest_data->irq_enabled)) + kill_guest(cpu, "Disabling interrupts"); } -/*H:200 +/*H:205 * Virtual Interrupts. * * maybe_do_interrupt() gets called before every entry to the Guest, to see if * we should divert the Guest to running an interrupt handler. */ -void maybe_do_interrupt(struct lguest *lg) +void maybe_do_interrupt(struct lg_cpu *cpu) { unsigned int irq; DECLARE_BITMAP(blk, LGUEST_IRQS); struct desc_struct *idt; /* If the Guest hasn't even initialized yet, we can do nothing. */ - if (!lg->lguest_data) + if (!cpu->lg->lguest_data) return; /* Take our "irqs_pending" array and remove any interrupts the Guest * wants blocked: the result ends up in "blk". */ - if (copy_from_user(&blk, lg->lguest_data->blocked_interrupts, + if (copy_from_user(&blk, cpu->lg->lguest_data->blocked_interrupts, sizeof(blk))) return; - - bitmap_andnot(blk, lg->irqs_pending, blk, LGUEST_IRQS); + bitmap_andnot(blk, cpu->irqs_pending, blk, LGUEST_IRQS); /* Find the first interrupt. */ irq = find_first_bit(blk, LGUEST_IRQS); @@ -144,19 +154,20 @@ void maybe_do_interrupt(struct lguest *lg) /* They may be in the middle of an iret, where they asked us never to * deliver interrupts. */ - if (lg->regs->eip >= lg->noirq_start && lg->regs->eip < lg->noirq_end) + if (cpu->regs->eip >= cpu->lg->noirq_start && + (cpu->regs->eip < cpu->lg->noirq_end)) return; /* If they're halted, interrupts restart them. */ - if (lg->halted) { + if (cpu->halted) { /* Re-enable interrupts. */ - if (put_user(X86_EFLAGS_IF, &lg->lguest_data->irq_enabled)) - kill_guest(lg, "Re-enabling interrupts"); - lg->halted = 0; + if (put_user(X86_EFLAGS_IF, &cpu->lg->lguest_data->irq_enabled)) + kill_guest(cpu, "Re-enabling interrupts"); + cpu->halted = 0; } else { /* Otherwise we check if they have interrupts disabled. */ u32 irq_enabled; - if (get_user(irq_enabled, &lg->lguest_data->irq_enabled)) + if (get_user(irq_enabled, &cpu->lg->lguest_data->irq_enabled)) irq_enabled = 0; if (!irq_enabled) return; @@ -165,15 +176,15 @@ 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 = &cpu->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. */ - clear_bit(irq, lg->irqs_pending); + clear_bit(irq, cpu->irqs_pending); /* set_guest_interrupt() takes the interrupt descriptor and a * flag to say whether this interrupt pushes an error code onto * the stack as well: virtual interrupts never do. */ - set_guest_interrupt(lg, idt->a, idt->b, 0); + set_guest_interrupt(cpu, idt->a, idt->b, 0); } /* Every time we deliver an interrupt, we update the timestamp in the @@ -181,65 +192,100 @@ void maybe_do_interrupt(struct lguest *lg) * did this more often, but it can actually be quite slow: doing it * here is a compromise which means at least it gets updated every * timer interrupt. */ - write_timestamp(lg); + write_timestamp(cpu); +} +/*:*/ + +/* 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 - * traps should have error codes: */ +/*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 traps + * should have error codes: */ static int has_err(unsigned int trap) { return (trap == 8 || (trap >= 10 && trap <= 14) || trap == 17); } /* deliver_trap() returns true if it could deliver the trap. */ -int deliver_trap(struct lguest *lg, unsigned int num) +int deliver_trap(struct lg_cpu *cpu, 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(cpu->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(cpu->arch.idt[num].a, cpu->arch.idt[num].b)) return 0; - set_guest_interrupt(lg, lg->idt[num].a, lg->idt[num].b, has_err(num)); + set_guest_interrupt(cpu, cpu->arch.idt[num].a, + cpu->arch.idt[num].b, has_err(num)); return 1; } /*H:250 Here's the hard part: returning to the Host every time a trap happens * and then calling deliver_trap() and re-entering the Guest is slow. - * Particularly because Guest userspace system calls are traps (trap 128). + * Particularly because Guest userspace system calls are traps (usually trap + * 128). * * So we'd like to set up the IDT to tell the CPU to deliver traps directly * into the Guest. This is possible, but the complexities cause the size of * this file to double! However, 150 lines of code is worth writing for taking * system calls down from 1750ns to 270ns. Plus, if lguest didn't do it, all - * the other hypervisors would tease it. + * the other hypervisors would beat it up at lunchtime. * - * 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; } /*:*/ @@ -263,15 +309,18 @@ static int direct_trap(const struct lguest *lg, * the Guest. * * Which is deeply unfair, because (literally!) it wasn't the Guests' fault. */ -void pin_stack_pages(struct lguest *lg) +void pin_stack_pages(struct lg_cpu *cpu) { unsigned int i; /* Depending on the CONFIG_4KSTACKS option, the Guest can have one or * two pages of stack space. */ - for (i = 0; i < lg->stack_pages; i++) - /* The stack grows *upwards*, hence the subtraction */ - pin_page(lg, lg->esp1 - i * PAGE_SIZE); + for (i = 0; i < cpu->lg->stack_pages; i++) + /* The stack grows *upwards*, so the address we're given is the + * start of the page after the kernel stack. Subtract one to + * get back onto the first stack page, and keep subtracting to + * get to the rest of the stack pages. */ + pin_page(cpu, cpu->esp1 - 1 - i * PAGE_SIZE); } /* Direct traps also mean that we need to know whenever the Guest wants to use @@ -282,29 +331,29 @@ void pin_stack_pages(struct lguest *lg) * * In Linux each process has its own kernel stack, so this happens a lot: we * change stacks on each context switch. */ -void guest_set_stack(struct lguest *lg, u32 seg, u32 esp, unsigned int pages) +void guest_set_stack(struct lg_cpu *cpu, u32 seg, u32 esp, unsigned int pages) { - /* You are not allowd have a stack segment with privilege level 0: bad + /* You are not allowed have a stack segment with privilege level 0: bad * Guest! */ if ((seg & 0x3) != GUEST_PL) - kill_guest(lg, "bad stack segment %i", seg); + kill_guest(cpu, "bad stack segment %i", seg); /* We only expect one or two stack pages. */ if (pages > 2) - kill_guest(lg, "bad stack pages %u", pages); + kill_guest(cpu, "bad stack pages %u", pages); /* Save where the stack is, and how many pages */ - lg->ss1 = seg; - lg->esp1 = esp; - lg->stack_pages = pages; + cpu->ss1 = seg; + cpu->esp1 = esp; + cpu->lg->stack_pages = pages; /* Make sure the new stack pages are mapped */ - pin_stack_pages(lg); + pin_stack_pages(cpu); } /* All this reference to mapping stacks leads us neatly into the other complex * part of the Host: page table handling. */ /*H:235 This is the routine which actually checks the Guest's IDT entry and - * transfers it into our entry in "struct lguest": */ -static void set_trap(struct lguest *lg, struct desc_struct *trap, + * transfers it into the entry in "struct lguest": */ +static void set_trap(struct lg_cpu *cpu, struct desc_struct *trap, unsigned int num, u32 lo, u32 hi) { u8 type = idt_type(lo, hi); @@ -317,7 +366,7 @@ static void set_trap(struct lguest *lg, struct desc_struct *trap, /* We only support interrupt and trap gates. */ if (type != 0xE && type != 0xF) - kill_guest(lg, "bad IDT type %i", type); + kill_guest(cpu, "bad IDT type %i", type); /* We only copy the handler address, present bit, privilege level and * type. The privilege level controls where the trap can be triggered @@ -334,7 +383,7 @@ static void set_trap(struct lguest *lg, struct desc_struct *trap, * * We saw the Guest setting Interrupt Descriptor Table (IDT) entries with the * LHCALL_LOAD_IDT_ENTRY hypercall before: that comes here. */ -void load_guest_idt_entry(struct lguest *lg, unsigned int num, u32 lo, u32 hi) +void load_guest_idt_entry(struct lg_cpu *cpu, unsigned int num, u32 lo, u32 hi) { /* Guest never handles: NMI, doublefault, spurious interrupt or * hypercall. We ignore when it tries to set them. */ @@ -343,17 +392,13 @@ void load_guest_idt_entry(struct lguest *lg, unsigned int num, u32 lo, u32 hi) /* Mark the IDT as changed: next time the Guest runs we'll know we have * 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); + cpu->changed |= CHANGED_IDT; + + /* Check that the Guest doesn't try to step outside the bounds. */ + if (num >= ARRAY_SIZE(cpu->arch.idt)) + kill_guest(cpu, "Setting idt entry %u", num); + else + set_trap(cpu, &cpu->arch.idt[num], num, lo, hi); } /* The default entry for each interrupt points into the Switcher routines which @@ -389,55 +434,75 @@ void setup_default_idt_entries(struct lguest_ro_state *state, /*H:240 We don't use the IDT entries in the "struct lguest" directly, instead * we copy them into the IDT which we've set up for Guests on this CPU, just * before we run the Guest. This routine does that copy. */ -void copy_traps(const struct lguest *lg, struct desc_struct *idt, +void copy_traps(const struct lg_cpu *cpu, struct desc_struct *idt, const unsigned long *def) { unsigned int i; /* 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(cpu->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(cpu->arch.idt[i].a, cpu->arch.idt[i].b) == 0xF) + idt[i] = cpu->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) +/*H:200 + * The Guest Clock. + * + * There are two sources of virtual interrupts. We saw one in lguest_user.c: + * the Launcher sending interrupts for virtual devices. The other is the Guest + * timer interrupt. + * + * The Guest uses the LHCALL_SET_CLOCKEVENT hypercall to tell us how long to + * the next timer interrupt (in nanoseconds). We use the high-resolution timer + * infrastructure to set a callback at that time. + * + * 0 means "turn off the clock". */ +void guest_set_clockevent(struct lg_cpu *cpu, unsigned long delta) { ktime_t expires; if (unlikely(delta == 0)) { /* Clock event device is shutting down. */ - hrtimer_cancel(&lg->hrt); + hrtimer_cancel(&cpu->hrt); return; } + /* We use wallclock time here, so the Guest might not be running for + * all the time between now and the timer interrupt it asked for. This + * is almost always the right thing to do. */ expires = ktime_add_ns(ktime_get_real(), delta); - hrtimer_start(&lg->hrt, expires, HRTIMER_MODE_ABS); + hrtimer_start(&cpu->hrt, expires, HRTIMER_MODE_ABS); } +/* This is the function called when the Guest's timer expires. */ static enum hrtimer_restart clockdev_fn(struct hrtimer *timer) { - struct lguest *lg = container_of(timer, struct lguest, hrt); + struct lg_cpu *cpu = container_of(timer, struct lg_cpu, hrt); - set_bit(0, lg->irqs_pending); - if (lg->halted) - wake_up_process(lg->tsk); + /* Remember the first interrupt is the timer interrupt. */ + set_bit(0, cpu->irqs_pending); + /* If the Guest is actually stopped, we need to wake it up. */ + if (cpu->halted) + wake_up_process(cpu->tsk); return HRTIMER_NORESTART; } -void init_clockdev(struct lguest *lg) +/* This sets up the timer for this Guest. */ +void init_clockdev(struct lg_cpu *cpu) { - hrtimer_init(&lg->hrt, CLOCK_REALTIME, HRTIMER_MODE_ABS); - lg->hrt.function = clockdev_fn; + hrtimer_init(&cpu->hrt, CLOCK_REALTIME, HRTIMER_MODE_ABS); + cpu->hrt.function = clockdev_fn; }