diff options
Diffstat (limited to 'drivers/lguest')
| -rw-r--r-- | drivers/lguest/Kconfig | 2 | ||||
| -rw-r--r-- | drivers/lguest/core.c | 30 | ||||
| -rw-r--r-- | drivers/lguest/hypercalls.c | 14 | ||||
| -rw-r--r-- | drivers/lguest/interrupts_and_traps.c | 57 | ||||
| -rw-r--r-- | drivers/lguest/lg.h | 28 | ||||
| -rw-r--r-- | drivers/lguest/lguest_user.c | 127 | ||||
| -rw-r--r-- | drivers/lguest/page_tables.c | 396 | ||||
| -rw-r--r-- | drivers/lguest/segments.c | 2 |
8 files changed, 531 insertions, 125 deletions
diff --git a/drivers/lguest/Kconfig b/drivers/lguest/Kconfig index a3d3cbab359..0aaa0597a62 100644 --- a/drivers/lguest/Kconfig +++ b/drivers/lguest/Kconfig @@ -1,6 +1,6 @@ config LGUEST tristate "Linux hypervisor example code" - depends on X86_32 && EXPERIMENTAL && !X86_PAE && FUTEX + depends on X86_32 && EXPERIMENTAL && EVENTFD select HVC_DRIVER ---help--- This is a very simple module which allows you to run diff --git a/drivers/lguest/core.c b/drivers/lguest/core.c index 4845fb3cf74..a6974e9b8eb 100644 --- a/drivers/lguest/core.c +++ b/drivers/lguest/core.c @@ -95,7 +95,7 @@ static __init int map_switcher(void) * array of struct pages. It increments that pointer, but we don't * care. */ pagep = switcher_page; - err = map_vm_area(switcher_vma, PAGE_KERNEL, &pagep); + err = map_vm_area(switcher_vma, PAGE_KERNEL_EXEC, &pagep); if (err) { printk("lguest: map_vm_area failed: %i\n", err); goto free_vma; @@ -188,6 +188,9 @@ int run_guest(struct lg_cpu *cpu, unsigned long __user *user) { /* We stop running once the Guest is dead. */ while (!cpu->lg->dead) { + unsigned int irq; + bool more; + /* First we run any hypercalls the Guest wants done. */ if (cpu->hcall) do_hypercalls(cpu); @@ -195,23 +198,23 @@ int run_guest(struct lg_cpu *cpu, unsigned long __user *user) /* It's possible the Guest did a NOTIFY hypercall to the * Launcher, in which case we return from the read() now. */ if (cpu->pending_notify) { - if (put_user(cpu->pending_notify, user)) - return -EFAULT; - return sizeof(cpu->pending_notify); + if (!send_notify_to_eventfd(cpu)) { + if (put_user(cpu->pending_notify, user)) + return -EFAULT; + return sizeof(cpu->pending_notify); + } } /* Check for signals */ if (signal_pending(current)) return -ERESTARTSYS; - /* If Waker set break_out, return to Launcher. */ - if (cpu->break_out) - return -EAGAIN; - /* Check if there are any interrupts which can be delivered now: * if so, this sets up the hander to be executed when we next * run the Guest. */ - maybe_do_interrupt(cpu); + irq = interrupt_pending(cpu, &more); + if (irq < LGUEST_IRQS) + try_deliver_interrupt(cpu, irq, more); /* All long-lived kernel loops need to check with this horrible * thing called the freezer. If the Host is trying to suspend, @@ -224,10 +227,15 @@ int run_guest(struct lg_cpu *cpu, unsigned long __user *user) break; /* If the Guest asked to be stopped, we sleep. The Guest's - * clock timer or LHREQ_BREAK from the Waker will wake us. */ + * clock timer will wake us. */ if (cpu->halted) { set_current_state(TASK_INTERRUPTIBLE); - schedule(); + /* Just before we sleep, make sure no interrupt snuck in + * which we should be doing. */ + if (interrupt_pending(cpu, &more) < LGUEST_IRQS) + set_current_state(TASK_RUNNING); + else + schedule(); continue; } diff --git a/drivers/lguest/hypercalls.c b/drivers/lguest/hypercalls.c index 54d66f05fef..c29ffa19cb7 100644 --- a/drivers/lguest/hypercalls.c +++ b/drivers/lguest/hypercalls.c @@ -37,6 +37,10 @@ static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args) /* This call does nothing, except by breaking out of the Guest * it makes us process all the asynchronous hypercalls. */ break; + case LHCALL_SEND_INTERRUPTS: + /* This call does nothing too, but by breaking out of the Guest + * it makes us process any pending interrupts. */ + break; case LHCALL_LGUEST_INIT: /* You can't get here unless you're already initialized. Don't * do that. */ @@ -73,11 +77,21 @@ static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args) guest_set_stack(cpu, args->arg1, args->arg2, args->arg3); break; case LHCALL_SET_PTE: +#ifdef CONFIG_X86_PAE + guest_set_pte(cpu, args->arg1, args->arg2, + __pte(args->arg3 | (u64)args->arg4 << 32)); +#else guest_set_pte(cpu, args->arg1, args->arg2, __pte(args->arg3)); +#endif + break; + case LHCALL_SET_PGD: + guest_set_pgd(cpu->lg, args->arg1, args->arg2); break; +#ifdef CONFIG_X86_PAE case LHCALL_SET_PMD: guest_set_pmd(cpu->lg, args->arg1, args->arg2); break; +#endif case LHCALL_SET_CLOCKEVENT: guest_set_clockevent(cpu, args->arg1); break; diff --git a/drivers/lguest/interrupts_and_traps.c b/drivers/lguest/interrupts_and_traps.c index 6e99adbe194..0e9067b0d50 100644 --- a/drivers/lguest/interrupts_and_traps.c +++ b/drivers/lguest/interrupts_and_traps.c @@ -128,30 +128,39 @@ static void set_guest_interrupt(struct lg_cpu *cpu, u32 lo, u32 hi, /*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 lg_cpu *cpu) + * interrupt_pending() returns the first pending interrupt which isn't blocked + * by the Guest. It is called before every entry to the Guest, and just before + * we go to sleep when the Guest has halted itself. */ +unsigned int interrupt_pending(struct lg_cpu *cpu, bool *more) { 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 (!cpu->lg->lguest_data) - return; + return LGUEST_IRQS; /* Take our "irqs_pending" array and remove any interrupts the Guest * wants blocked: the result ends up in "blk". */ if (copy_from_user(&blk, cpu->lg->lguest_data->blocked_interrupts, sizeof(blk))) - return; + return LGUEST_IRQS; bitmap_andnot(blk, cpu->irqs_pending, blk, LGUEST_IRQS); /* Find the first interrupt. */ irq = find_first_bit(blk, LGUEST_IRQS); - /* None? Nothing to do */ - if (irq >= LGUEST_IRQS) - return; + *more = find_next_bit(blk, LGUEST_IRQS, irq+1); + + return irq; +} + +/* This actually diverts the Guest to running an interrupt handler, once an + * interrupt has been identified by interrupt_pending(). */ +void try_deliver_interrupt(struct lg_cpu *cpu, unsigned int irq, bool more) +{ + struct desc_struct *idt; + + BUG_ON(irq >= LGUEST_IRQS); /* They may be in the middle of an iret, where they asked us never to * deliver interrupts. */ @@ -170,8 +179,12 @@ void maybe_do_interrupt(struct lg_cpu *cpu) u32 irq_enabled; if (get_user(irq_enabled, &cpu->lg->lguest_data->irq_enabled)) irq_enabled = 0; - if (!irq_enabled) + if (!irq_enabled) { + /* Make sure they know an IRQ is pending. */ + put_user(X86_EFLAGS_IF, + &cpu->lg->lguest_data->irq_pending); return; + } } /* Look at the IDT entry the Guest gave us for this interrupt. The @@ -194,6 +207,25 @@ void maybe_do_interrupt(struct lg_cpu *cpu) * here is a compromise which means at least it gets updated every * timer interrupt. */ write_timestamp(cpu); + + /* If there are no other interrupts we want to deliver, clear + * the pending flag. */ + if (!more) + put_user(0, &cpu->lg->lguest_data->irq_pending); +} + +/* And this is the routine when we want to set an interrupt for the Guest. */ +void set_interrupt(struct lg_cpu *cpu, unsigned int irq) +{ + /* Next time the Guest runs, the core code will see if it can deliver + * this interrupt. */ + set_bit(irq, cpu->irqs_pending); + + /* Make sure it sees it; it might be asleep (eg. halted), or + * running the Guest right now, in which case kick_process() + * will knock it out. */ + if (!wake_up_process(cpu->tsk)) + kick_process(cpu->tsk); } /*:*/ @@ -510,10 +542,7 @@ static enum hrtimer_restart clockdev_fn(struct hrtimer *timer) struct lg_cpu *cpu = container_of(timer, struct lg_cpu, hrt); /* 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); + set_interrupt(cpu, 0); return HRTIMER_NORESTART; } diff --git a/drivers/lguest/lg.h b/drivers/lguest/lg.h index af92a176697..d4e8979735c 100644 --- a/drivers/lguest/lg.h +++ b/drivers/lguest/lg.h @@ -49,7 +49,7 @@ struct lg_cpu { u32 cr2; int ts; u32 esp1; - u8 ss1; + u16 ss1; /* Bitmap of what has changed: see CHANGED_* above. */ int changed; @@ -71,9 +71,7 @@ struct lg_cpu { /* Virtual clock device */ struct hrtimer hrt; - /* Do we need to stop what we're doing and return to userspace? */ - int break_out; - wait_queue_head_t break_wq; + /* Did the Guest tell us to halt? */ int halted; /* Pending virtual interrupts */ @@ -82,6 +80,16 @@ struct lg_cpu { struct lg_cpu_arch arch; }; +struct lg_eventfd { + unsigned long addr; + struct file *event; +}; + +struct lg_eventfd_map { + unsigned int num; + struct lg_eventfd map[]; +}; + /* The private info the thread maintains about the guest. */ struct lguest { @@ -102,6 +110,8 @@ struct lguest unsigned int stack_pages; u32 tsc_khz; + struct lg_eventfd_map *eventfds; + /* Dead? */ const char *dead; }; @@ -137,9 +147,13 @@ int run_guest(struct lg_cpu *cpu, unsigned long __user *user); * in the kernel. */ #define pgd_flags(x) (pgd_val(x) & ~PAGE_MASK) #define pgd_pfn(x) (pgd_val(x) >> PAGE_SHIFT) +#define pmd_flags(x) (pmd_val(x) & ~PAGE_MASK) +#define pmd_pfn(x) (pmd_val(x) >> PAGE_SHIFT) /* interrupts_and_traps.c: */ -void maybe_do_interrupt(struct lg_cpu *cpu); +unsigned int interrupt_pending(struct lg_cpu *cpu, bool *more); +void try_deliver_interrupt(struct lg_cpu *cpu, unsigned int irq, bool more); +void set_interrupt(struct lg_cpu *cpu, unsigned int irq); bool deliver_trap(struct lg_cpu *cpu, unsigned int num); void load_guest_idt_entry(struct lg_cpu *cpu, unsigned int i, u32 low, u32 hi); @@ -150,6 +164,7 @@ void setup_default_idt_entries(struct lguest_ro_state *state, void copy_traps(const struct lg_cpu *cpu, struct desc_struct *idt, const unsigned long *def); void guest_set_clockevent(struct lg_cpu *cpu, unsigned long delta); +bool send_notify_to_eventfd(struct lg_cpu *cpu); void init_clockdev(struct lg_cpu *cpu); bool check_syscall_vector(struct lguest *lg); int init_interrupts(void); @@ -168,7 +183,10 @@ void copy_gdt_tls(const struct lg_cpu *cpu, struct desc_struct *gdt); int init_guest_pagetable(struct lguest *lg); void free_guest_pagetable(struct lguest *lg); void guest_new_pagetable(struct lg_cpu *cpu, unsigned long pgtable); +void guest_set_pgd(struct lguest *lg, unsigned long gpgdir, u32 i); +#ifdef CONFIG_X86_PAE void guest_set_pmd(struct lguest *lg, unsigned long gpgdir, u32 i); +#endif void guest_pagetable_clear_all(struct lg_cpu *cpu); void guest_pagetable_flush_user(struct lg_cpu *cpu); void guest_set_pte(struct lg_cpu *cpu, unsigned long gpgdir, diff --git a/drivers/lguest/lguest_user.c b/drivers/lguest/lguest_user.c index b8ee103eed5..32e29712105 100644 --- a/drivers/lguest/lguest_user.c +++ b/drivers/lguest/lguest_user.c @@ -7,32 +7,83 @@ #include <linux/miscdevice.h> #include <linux/fs.h> #include <linux/sched.h> +#include <linux/eventfd.h> +#include <linux/file.h> #include "lg.h" -/*L:055 When something happens, the Waker process needs a way to stop the - * kernel running the Guest and return to the Launcher. So the Waker writes - * LHREQ_BREAK and the value "1" to /dev/lguest to do this. Once the Launcher - * has done whatever needs attention, it writes LHREQ_BREAK and "0" to release - * the Waker. */ -static int break_guest_out(struct lg_cpu *cpu, const unsigned long __user*input) +bool send_notify_to_eventfd(struct lg_cpu *cpu) { - unsigned long on; + unsigned int i; + struct lg_eventfd_map *map; + + /* lg->eventfds is RCU-protected */ + rcu_read_lock(); + map = rcu_dereference(cpu->lg->eventfds); + for (i = 0; i < map->num; i++) { + if (map->map[i].addr == cpu->pending_notify) { + eventfd_signal(map->map[i].event, 1); + cpu->pending_notify = 0; + break; + } + } + rcu_read_unlock(); + return cpu->pending_notify == 0; +} - /* Fetch whether they're turning break on or off. */ - if (get_user(on, input) != 0) - return -EFAULT; +static int add_eventfd(struct lguest *lg, unsigned long addr, int fd) +{ + struct lg_eventfd_map *new, *old = lg->eventfds; - if (on) { - cpu->break_out = 1; - /* Pop it out of the Guest (may be running on different CPU) */ - wake_up_process(cpu->tsk); - /* Wait for them to reset it */ - return wait_event_interruptible(cpu->break_wq, !cpu->break_out); - } else { - cpu->break_out = 0; - wake_up(&cpu->break_wq); - return 0; + if (!addr) + return -EINVAL; + + /* Replace the old array with the new one, carefully: others can + * be accessing it at the same time */ + new = kmalloc(sizeof(*new) + sizeof(new->map[0]) * (old->num + 1), + GFP_KERNEL); + if (!new) + return -ENOMEM; + + /* First make identical copy. */ + memcpy(new->map, old->map, sizeof(old->map[0]) * old->num); + new->num = old->num; + + /* Now append new entry. */ + new->map[new->num].addr = addr; + new->map[new->num].event = eventfd_fget(fd); + if (IS_ERR(new->map[new->num].event)) { + kfree(new); + return PTR_ERR(new->map[new->num].event); } + new->num++; + + /* Now put new one in place. */ + rcu_assign_pointer(lg->eventfds, new); + + /* We're not in a big hurry. Wait until noone's looking at old + * version, then delete it. */ + synchronize_rcu(); + kfree(old); + + return 0; +} + +static int attach_eventfd(struct lguest *lg, const unsigned long __user *input) +{ + unsigned long addr, fd; + int err; + + if (get_user(addr, input) != 0) + return -EFAULT; + input++; + if (get_user(fd, input) != 0) + return -EFAULT; + + mutex_lock(&lguest_lock); + err = add_eventfd(lg, addr, fd); + mutex_unlock(&lguest_lock); + + return 0; } /*L:050 Sending an interrupt is done by writing LHREQ_IRQ and an interrupt @@ -45,9 +96,8 @@ static int user_send_irq(struct lg_cpu *cpu, const unsigned long __user *input) return -EFAULT; if (irq >= LGUEST_IRQS) return -EINVAL; - /* Next time the Guest runs, the core code will see if it can deliver - * this interrupt. */ - set_bit(irq, cpu->irqs_pending); + + set_interrupt(cpu, irq); return 0; } @@ -126,9 +176,6 @@ static int lg_cpu_start(struct lg_cpu *cpu, unsigned id, unsigned long start_ip) * address. */ lguest_arch_setup_regs(cpu, start_ip); - /* Initialize the queue for the Waker to wait on */ - init_waitqueue_head(&cpu->break_wq); - /* We keep a pointer to the Launcher task (ie. current task) for when * other Guests want to wake this one (eg. console input). */ cpu->tsk = current; @@ -185,6 +232,13 @@ static int initialize(struct file *file, const unsigned long __user *input) goto unlock; } + lg->eventfds = kmalloc(sizeof(*lg->eventfds), GFP_KERNEL); + if (!lg->eventfds) { + err = -ENOMEM; + goto free_lg; + } + lg->eventfds->num = 0; + /* Populate the easy fields of our "struct lguest" */ lg->mem_base = (void __user *)args[0]; lg->pfn_limit = args[1]; @@ -192,7 +246,7 @@ static int initialize(struct file *file, const unsigned long __user *input) /* This is the first cpu (cpu 0) and it will start booting at args[2] */ err = lg_cpu_start(&lg->cpus[0], 0, args[2]); if (err) - goto release_guest; + goto free_eventfds; /* Initialize the Guest's shadow page tables, using the toplevel * address the Launcher gave us. This allocates memory, so can fail. */ @@ -211,7 +265,9 @@ static int initialize(struct file *file, const unsigned long __user *input) free_regs: /* FIXME: This should be in free_vcpu */ free_page(lg->cpus[0].regs_page); -release_guest: +free_eventfds: + kfree(lg->eventfds); +free_lg: kfree(lg); unlock: mutex_unlock(&lguest_lock); @@ -252,11 +308,6 @@ static ssize_t write(struct file *file, const char __user *in, /* Once the Guest is dead, you can only read() why it died. */ if (lg->dead) return -ENOENT; - - /* If you're not the task which owns the Guest, all you can do - * is break the Launcher out of running the Guest. */ - if (current != cpu->tsk && req != LHREQ_BREAK) - return -EPERM; } switch (req) { @@ -264,8 +315,8 @@ static ssize_t write(struct file *file, const char __user *in, return initialize(file, input); case LHREQ_IRQ: return user_send_irq(cpu, input); - case LHREQ_BREAK: - return break_guest_out(cpu, input); + case LHREQ_EVENTFD: + return attach_eventfd(lg, input); default: return -EINVAL; } @@ -303,6 +354,12 @@ static int close(struct inode *inode, struct file *file) * the Launcher's memory management structure. */ mmput(lg->cpus[i].mm); } + + /* Release any eventfds they registered. */ + for (i = 0; i < lg->eventfds->num; i++) + fput(lg->eventfds->map[i].event); + kfree(lg->eventfds); + /* If lg->dead doesn't contain an error code it will be NULL or a * kmalloc()ed string, either of which is ok to hand to kfree(). */ if (!IS_ERR(lg->dead)) diff --git a/drivers/lguest/page_tables.c b/drivers/lguest/page_tables.c index a059cf9980f..a6fe1abda24 100644 --- a/drivers/lguest/page_tables.c +++ b/drivers/lguest/page_tables.c @@ -53,6 +53,17 @@ * page. */ #define SWITCHER_PGD_INDEX (PTRS_PER_PGD - 1) +/* For PAE we need the PMD index as well. We use the last 2MB, so we + * will need the last pmd entry of the last pmd page. */ +#ifdef CONFIG_X86_PAE +#define SWITCHER_PMD_INDEX (PTRS_PER_PMD - 1) +#define RESERVE_MEM 2U +#define CHECK_GPGD_MASK _PAGE_PRESENT +#else +#define RESERVE_MEM 4U +#define CHECK_GPGD_MASK _PAGE_TABLE +#endif + /* We actually need a separate PTE page for each CPU. Remember that after the * Switcher code itself comes two pages for each CPU, and we don't want this * CPU's guest to see the pages of any other CPU. */ @@ -73,24 +84,59 @@ static pgd_t *spgd_addr(struct lg_cpu *cpu, u32 i, unsigned long vaddr) { unsigned int index = pgd_index(vaddr); +#ifndef CONFIG_X86_PAE /* We kill any Guest trying to touch the Switcher addresses. */ if (index >= SWITCHER_PGD_INDEX) { kill_guest(cpu, "attempt to access switcher pages"); index = 0; } +#endif /* Return a pointer index'th pgd entry for the i'th page table. */ return &cpu->lg->pgdirs[i].pgdir[index]; } +#ifdef CONFIG_X86_PAE +/* This routine then takes the PGD entry given above, which contains the + * address of the PMD page. It then returns a pointer to the PMD entry for the + * given address. */ +static pmd_t *spmd_addr(struct lg_cpu *cpu, pgd_t spgd, unsigned long vaddr) +{ + unsigned int index = pmd_index(vaddr); + pmd_t *page; + + /* We kill any Guest trying to touch the Switcher addresses. */ + if (pgd_index(vaddr) == SWITCHER_PGD_INDEX && + index >= SWITCHER_PMD_INDEX) { + kill_guest(cpu, "attempt to access switcher pages"); + index = 0; + } + + /* You should never call this if the PGD entry wasn't valid */ + BUG_ON(!(pgd_flags(spgd) & _PAGE_PRESENT)); + page = __va(pgd_pfn(spgd) << PAGE_SHIFT); + + return &page[index]; +} +#endif + /* This routine then takes the page directory entry returned above, which * contains the address of the page table entry (PTE) page. It then returns a * pointer to the PTE entry for the given address. */ -static pte_t *spte_addr(pgd_t spgd, unsigned long vaddr) +static pte_t *spte_addr(struct lg_cpu *cpu, pgd_t spgd, unsigned long vaddr) { +#ifdef CONFIG_X86_PAE + pmd_t *pmd = spmd_addr(cpu, spgd, vaddr); + pte_t *page = __va(pmd_pfn(*pmd) << PAGE_SHIFT); + + /* You should never call this if the PMD entry wasn't valid */ + BUG_ON(!(pmd_flags(*pmd) & _PAGE_PRESENT)); +#else pte_t *page = __va(pgd_pfn(spgd) << PAGE_SHIFT); /* You should never call this if the PGD entry wasn't valid */ BUG_ON(!(pgd_flags(spgd) & _PAGE_PRESENT)); - return &page[(vaddr >> PAGE_SHIFT) % PTRS_PER_PTE]; +#endif + + return &page[pte_index(vaddr)]; } /* These two functions just like the above two, except they access the Guest @@ -101,12 +147,32 @@ static unsigned long gpgd_addr(struct lg_cpu *cpu, unsigned long vaddr) return cpu->lg->pgdirs[cpu->cpu_pgd].gpgdir + index * sizeof(pgd_t); } -static unsigned long gpte_addr(pgd_t gpgd, unsigned long vaddr) +#ifdef CONFIG_X86_PAE +static unsigned long gpmd_addr(pgd_t gpgd, unsigned long vaddr) +{ + unsigned long gpage = pgd_pfn(gpgd) << PAGE_SHIFT; + BUG_ON(!(pgd_flags(gpgd) & _PAGE_PRESENT)); + return gpage + pmd_index(vaddr) * sizeof(pmd_t); +} + +static unsigned long gpte_addr(struct lg_cpu *cpu, + pmd_t gpmd, unsigned long vaddr) +{ + unsigned long gpage = pmd_pfn(gpmd) << PAGE_SHIFT; + + BUG_ON(!(pmd_flags(gpmd) & _PAGE_PRESENT)); + return gpage + pte_index(vaddr) * sizeof(pte_t); +} +#else +static unsigned long gpte_addr(struct lg_cpu *cpu, + pgd_t gpgd, unsigned long vaddr) { unsigned long gpage = pgd_pfn(gpgd) << PAGE_SHIFT; + BUG_ON(!(pgd_flags(gpgd) & _PAGE_PRESENT)); - return gpage + ((vaddr>>PAGE_SHIFT) % PTRS_PER_PTE) * sizeof(pte_t); + return gpage + pte_index(vaddr) * sizeof(pte_t); } +#endif /*:*/ /*M:014 get_pfn is slow: we could probably try to grab batches of pages here as @@ -171,7 +237,7 @@ static void release_pte(pte_t pte) /* Remember that get_user_pages_fast() took a reference to the page, in * get_pfn()? We have to put it back now. */ if (pte_flags(pte) & _PAGE_PRESENT) - put_page(pfn_to_page(pte_pfn(pte))); + put_page(pte_page(pte)); } /*:*/ @@ -184,11 +250,20 @@ static void check_gpte(struct lg_cpu *cpu, pte_t gpte) static void check_gpgd(struct lg_cpu *cpu, pgd_t gpgd) { - if ((pgd_flags(gpgd) & ~_PAGE_TABLE) || + if ((pgd_flags(gpgd) & ~CHECK_GPGD_MASK) || (pgd_pfn(gpgd) >= cpu->lg->pfn_limit)) kill_guest(cpu, "bad page directory entry"); } +#ifdef CONFIG_X86_PAE +static void check_gpmd(struct lg_cpu *cpu, pmd_t gpmd) +{ + if ((pmd_flags(gpmd) & ~_PAGE_TABLE) || + (pmd_pfn(gpmd) >= cpu->lg->pfn_limit)) + kill_guest(cpu, "bad page middle directory entry"); +} +#endif + /*H:330 * (i) Looking up a page table entry when the Guest faults. * @@ -207,6 +282,11 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode) pte_t gpte; pte_t *spte; +#ifdef CONFIG_X86_PAE + pmd_t *spmd; + pmd_t gpmd; +#endif + /* First step: get the top-level Guest page table entry. */ gpgd = lgread(cpu, gpgd_addr(cpu, vaddr), pgd_t); /* Toplevel not present? We can't map it in. */ @@ -228,12 +308,45 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode) check_gpgd(cpu, gpgd); /* And we copy the flags to the shadow PGD entry. The page * number in the shadow PGD is the page we just allocated. */ - *spgd = __pgd(__pa(ptepage) | pgd_flags(gpgd)); + set_pgd(spgd, __pgd(__pa(ptepage) | pgd_flags(gpgd))); } +#ifdef CONFIG_X86_PAE + gpmd = lgread(cpu, gpmd_addr(gpgd, vaddr), pmd_t); + /* middle level not present? We can't map it in. */ + if (!(pmd_flags(gpmd) & _PAGE_PRESENT)) + return false; + + /* Now look at the matching shadow entry. */ + spmd = spmd_addr(cpu, *spgd, vaddr); + + if (!(pmd_flags(*spmd) & _PAGE_PRESENT)) { + /* No shadow entry: allocate a new shadow PTE page. */ + unsigned long ptepage = get_zeroed_page(GFP_KERNEL); + + /* This is not really the Guest's fault, but killing it is + * simple for this corner case. */ + if (!ptepage) { + kill_guest(cpu, "out of memory allocating pte page"); + return false; + } + + /* We check that the Guest pmd is OK. */ + check_gpmd(cpu, gpmd); + + /* And we copy the flags to the shadow PMD entry. The page + * number in the shadow PMD is the page we just allocated. */ + native_set_pmd(spmd, __pmd(__pa(ptepage) | pmd_flags(gpmd))); + } + + /* OK, now we look at the lower level in the Guest page table: keep its + * address, because we might update it later. */ + gpte_ptr = gpte_addr(cpu, gpmd, vaddr); +#else /* OK, now we look at the lower level in the Guest page table: keep its * address, because we might update it later. */ - gpte_ptr = gpte_addr(gpgd, vaddr); + gpte_ptr = gpte_addr(cpu, gpgd, vaddr); +#endif gpte = lgread(cpu, gpte_ptr, pte_t); /* If this page isn't in the Guest page tables, we can't page it in. */ @@ -259,7 +372,7 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode) gpte = pte_mkdirty(gpte); /* Get the pointer to the shadow PTE entry we're going to set. */ - spte = spte_addr(*spgd, vaddr); + spte = spte_addr(cpu, *spgd, vaddr); /* If there was a valid shadow PTE entry here before, we release it. * This can happen with a write to a previously read-only entry. */ release_pte(*spte); @@ -273,7 +386,7 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode) * table entry, even if the Guest says it's writable. That way * we will come back here when a write does actually occur, so * we can update the Guest's _PAGE_DIRTY flag. */ - *spte = gpte_to_spte(cpu, pte_wrprotect(gpte), 0); + native_set_pte(spte, gpte_to_spte(cpu, pte_wrprotect(gpte), 0)); /* Finally, we write the Guest PTE entry back: we've set the * _PAGE_ACCESSED and maybe the _PAGE_DIRTY flags. */ @@ -301,14 +414,23 @@ static bool page_writable(struct lg_cpu *cpu, unsigned long vaddr) pgd_t *spgd; unsigned long flags; +#ifdef CONFIG_X86_PAE + pmd_t *spmd; +#endif /* Look at the current top level entry: is it present? */ spgd = spgd_addr(cpu, cpu->cpu_pgd, vaddr); if (!(pgd_flags(*spgd) & _PAGE_PRESENT)) return false; +#ifdef CONFIG_X86_PAE + spmd = spmd_addr(cpu, *spgd, vaddr); + if (!(pmd_flags(*spmd) & _PAGE_PRESENT)) + return false; +#endif + /* Check the flags on the pte entry itself: it must be present and * writable. */ - flags = pte_flags(*(spte_addr(*spgd, vaddr))); + flags = pte_flags(*(spte_addr(cpu, *spgd, vaddr))); return (flags & (_PAGE_PRESENT|_PAGE_RW)) == (_PAGE_PRESENT|_PAGE_RW); } @@ -322,8 +444,43 @@ void pin_page(struct lg_cpu *cpu, unsigned long vaddr) kill_guest(cpu, "bad stack page %#lx", vaddr); } +#ifdef CONFIG_X86_PAE +static void release_pmd(pmd_t *spmd) +{ + /* If the entry's not present, there's nothing to release. */ + if (pmd_flags(*spmd) & _PAGE_PRESENT) { + unsigned int i; + pte_t *ptepage = __va(pmd_pfn(*spmd) << PAGE_SHIFT); + /* For each entry in the page, we might need to release it. */ + for (i = 0; i < PTRS_PER_PTE; i++) + release_pte(ptepage[i]); + /* Now we can free the page of PTEs */ + free_page((long)ptepage); + /* And zero out the PMD entry so we never release it twice. */ + native_set_pmd(spmd, __pmd(0)); + } +} + +static void release_pgd(pgd_t *spgd) +{ + /* If the entry's not present, there's nothing to release. */ + if (pgd_flags(*spgd) & _PAGE_PRESENT) { + unsigned int i; + pmd_t *pmdpage = __va(pgd_pfn(*spgd) << PAGE_SHIFT); + + for (i = 0; i < PTRS_PER_PMD; i++) + release_pmd(&pmdpage[i]); + + /* Now we can free the page of PMDs */ + free_page((long)pmdpage); + /* And zero out the PGD entry so we never release it twice. */ + set_pgd(spgd, __pgd(0)); + } +} + +#else /* !CONFIG_X86_PAE */ /*H:450 If we chase down the release_pgd() code, it looks like this: */ -static void release_pgd(struct lguest *lg, pgd_t *spgd) +static void release_pgd(pgd_t *spgd) { /* If the entry's not present, there's nothing to release. */ if (pgd_flags(*spgd) & _PAGE_PRESENT) { @@ -341,7 +498,7 @@ static void release_pgd(struct lguest *lg, pgd_t *spgd) *spgd = __pgd(0); } } - +#endif /*H:445 We saw flush_user_mappings() twice: once from the flush_user_mappings() * hypercall and once in new_pgdir() when we re-used a top-level pgdir page. * It simply releases every PTE page from 0 up to the Guest's kernel address. */ @@ -350,7 +507,7 @@ static void flush_user_mappings(struct lguest *lg, int idx) unsigned int i; /* Release every pgd entry up to the kernel's address. */ for (i = 0; i < pgd_index(lg->kernel_address); i++) - release_pgd(lg, lg->pgdirs[idx].pgdir + i); + release_pgd(lg->pgdirs[idx].pgdir + i); } /*H:440 (v) Flushing (throwing away) page tables, @@ -369,7 +526,9 @@ unsigned long guest_pa(struct lg_cpu *cpu, unsigned long vaddr) { pgd_t gpgd; pte_t gpte; - +#ifdef CONFIG_X86_PAE + pmd_t gpmd; +#endif /* First step: get the top-level Guest page table entry. */ gpgd = lgread(cpu, gpgd_addr(cpu, vaddr), pgd_t); /* Toplevel not present? We can't map it in. */ @@ -378,7 +537,14 @@ unsigned long guest_pa(struct lg_cpu *cpu, unsigned long vaddr) return -1UL; } - gpte = lgread(cpu, gpte_addr(gpgd, vaddr), pte_t); +#ifdef CONFIG_X86_PAE + gpmd = lgread(cpu, gpmd_addr(gpgd, vaddr), pmd_t); + if (!(pmd_flags(gpmd) & _PAGE_PRESENT)) + kill_guest(cpu, "Bad address %#lx", vaddr); + gpte = lgread(cpu, gpte_addr(cpu, gpmd, vaddr), pte_t); +#else + gpte = lgread(cpu, gpte_addr(cpu, gpgd, vaddr), pte_t); +#endif if (!(pte_flags(gpte) & _PAGE_PRESENT)) kill_guest(cpu, "Bad address %#lx", vaddr); @@ -405,6 +571,9 @@ static unsigned int new_pgdir(struct lg_cpu *cpu, int *blank_pgdir) { unsigned int next; +#ifdef CONFIG_X86_PAE + pmd_t *pmd_table; +#endif /* We pick one entry at random to throw out. Choosing the Least * Recently Used might be better, but this is easy. */ @@ -416,10 +585,27 @@ static unsigned int new_pgdir(struct lg_cpu *cpu, /* If the allocation fails, just keep using the one we have */ if (!cpu->lg->pgdirs[next].pgdir) next = cpu->cpu_pgd; - else - /* This is a blank page, so there are no kernel - * mappings: caller must map the stack! */ + else { +#ifdef CONFIG_X86_PAE + /* In PAE mode, allocate a pmd page and populate the + * last pgd entry. */ + pmd_table = (pmd_t *)get_zeroed_page(GFP_KERNEL); + if (!pmd_table) { + free_page((long)cpu->lg->pgdirs[next].pgdir); + set_pgd(cpu->lg->pgdirs[next].pgdir, __pgd(0)); + next = cpu->cpu_pgd; + } else { + set_pgd(cpu->lg->pgdirs[next].pgdir + + SWITCHER_PGD_INDEX, + __pgd(__pa(pmd_table) | _PAGE_PRESENT)); + /* This is a blank page, so there are no kernel + * mappings: caller must map the stack! */ + *blank_pgdir = 1; + } +#else *blank_pgdir = 1; +#endif + } } /* Record which Guest toplevel this shadows. */ cpu->lg->pgdirs[next].gpgdir = gpgdir; @@ -431,7 +617,7 @@ static unsigned int new_pgdir(struct lg_cpu *cpu, /*H:430 (iv) Switching page tables * - * Now we've seen all the page table setting and manipulation, let's see what + * Now we've seen all the page table setting and manipulation, let's see * what happens when the Guest changes page tables (ie. changes the top-level * pgdir). This occurs on almost every context switch. */ void guest_new_pagetable(struct lg_cpu *cpu, unsigned long pgtable) @@ -460,10 +646,25 @@ static void release_all_pagetables(struct lguest *lg) /* Every shadow pagetable this Guest has */ for (i = 0; i < ARRAY_SIZE(lg->pgdirs); i++) - if (lg->pgdirs[i].pgdir) + if (lg->pgdirs[i].pgdir) { +#ifdef CONFIG_X86_PAE + pgd_t *spgd; + pmd_t *pmdpage; + unsigned int k; + + /* Get the last pmd page. */ + spgd = lg->pgdirs[i].pgdir + SWITCHER_PGD_INDEX; + pmdpage = __va(pgd_pfn(*spgd) << PAGE_SHIFT); + + /* And release the pmd entries of that pmd page, + * except for the switcher pmd. */ + for (k = 0; k < SWITCHER_PMD_INDEX; k++) + release_pmd(&pmdpage[k]); +#endif /* Every PGD entry except the Switcher at the top */ for (j = 0; j < SWITCHER_PGD_INDEX; j++) - release_pgd(lg, lg->pgdirs[i].pgdir + j); + release_pgd(lg->pgdirs[i].pgdir + j); + } } /* We also throw away everything when a Guest tells us it's changed a kernel @@ -504,24 +705,37 @@ static void do_set_pte(struct lg_cpu *cpu, int idx, { /* Look up the matching shadow page directory entry. */ pgd_t *spgd = spgd_addr(cpu, idx, vaddr); +#ifdef CONFIG_X86_PAE + pmd_t *spmd; +#endif /* If the top level isn't present, there's no entry to update. */ if (pgd_flags(*spgd) & _PAGE_PRESENT) { - /* Otherwise, we start by releasing the existing entry. */ - pte_t *spte = spte_addr(*spgd, vaddr); - release_pte(*spte); - - /* If they're setting this entry as dirty or accessed, we might - * as well put that entry they've given us in now. This shaves - * 10% off a copy-on-write micro-benchmark. */ - if (pte_flags(gpte) & (_PAGE_DIRTY | _PAGE_ACCESSED)) { - check_gpte(cpu, gpte); - *spte = gpte_to_spte(cpu, gpte, - pte_flags(gpte) & _PAGE_DIRTY); - } else - /* Otherwise kill it and we can demand_page() it in - * later. */ - *spte = __pte(0); +#ifdef CONFIG_X86_PAE + spmd = spmd_addr(cpu, *spgd, vaddr); + if (pmd_flags(*spmd) & _PAGE_PRESENT) { +#endif + /* Otherwise, we start by releasing + * the existing entry. */ + pte_t *spte = spte_addr(cpu, *spgd, vaddr); + release_pte(*spte); + + /* If they're setting this entry as dirty or accessed, + * we might as well put that entry they've given us + * in now. This shaves 10% off a + * copy-on-write micro-benchmark. */ + if (pte_flags(gpte) & (_PAGE_DIRTY | _PAGE_ACCESSED)) { + check_gpte(cpu, gpte); + native_set_pte(spte, + gpte_to_spte(cpu, gpte, + pte_flags(gpte) & _PAGE_DIRTY)); + } else + /* Otherwise kill it and we can demand_page() + * it in later. */ + native_set_pte(spte, __pte(0)); +#ifdef CONFIG_X86_PAE + } +#endif } } @@ -568,12 +782,10 @@ void guest_set_pte(struct lg_cpu *cpu, * * So with that in mind here's our code to to update a (top-level) PGD entry: */ -void guest_set_pmd(struct lguest *lg, unsigned long gpgdir, u32 idx) +void guest_set_pgd(struct lguest *lg, unsigned long gpgdir, u32 idx) { int pgdir; - /* The kernel seems to try to initialize this early on: we ignore its - * attempts to map over the Switcher. */ if (idx >= SWITCHER_PGD_INDEX) return; @@ -581,8 +793,14 @@ void guest_set_pmd(struct lguest *lg, unsigned long gpgdir, u32 idx) pgdir = find_pgdir(lg, gpgdir); if (pgdir < ARRAY_SIZE(lg->pgdirs)) /* ... throw it away. */ - release_pgd(lg, lg->pgdirs[pgdir].pgdir + idx); + release_pgd(lg->pgdirs[pgdir].pgdir + idx); } +#ifdef CONFIG_X86_PAE +void guest_set_pmd(struct lguest *lg, unsigned long pmdp, u32 idx) +{ + guest_pagetable_clear_all(&lg->cpus[0]); +} +#endif /* Once we know how much memory we have we can construct simple identity * (which set virtual == physical) and linear mappings @@ -596,8 +814,16 @@ static unsigned long setup_pagetables(struct lguest *lg, { pgd_t __user *pgdir; pte_t __user *linear; - unsigned int mapped_pages, i, linear_pages, phys_linear; unsigned long mem_base = (unsigned long)lg->mem_base; + unsigned int mapped_pages, i, linear_pages; +#ifdef CONFIG_X86_PAE + pmd_t __user *pmds; + unsigned int j; + pgd_t pgd; + pmd_t pmd; +#else + unsigned int phys_linear; +#endif /* We have mapped_pages frames to map, so we need * linear_pages page tables to map them. */ @@ -610,6 +836,9 @@ static unsigned long setup_pagetables(struct lguest *lg, /* Now we use the next linear_pages pages as pte pages */ linear = (void *)pgdir - linear_pages * PAGE_SIZE; +#ifdef CONFIG_X86_PAE + pmds = (void *)linear - PAGE_SIZE; +#endif /* Linear mapping is easy: put every page's address into the * mapping in order. */ for (i = 0; i < mapped_pages; i++) { @@ -621,6 +850,22 @@ static unsigned long setup_pagetables(struct lguest *lg, /* The top level points to the linear page table pages above. * We setup the identity and linear mappings here. */ +#ifdef CONFIG_X86_PAE + for (i = j = 0; i < mapped_pages && j < PTRS_PER_PMD; + i += PTRS_PER_PTE, j++) { + native_set_pmd(&pmd, __pmd(((unsigned long)(linear + i) + - mem_base) | _PAGE_PRESENT | _PAGE_RW | _PAGE_USER)); + + if (copy_to_user(&pmds[j], &pmd, sizeof(pmd)) != 0) + return -EFAULT; + } + + set_pgd(&pgd, __pgd(((u32)pmds - mem_base) | _PAGE_PRESENT)); + if (copy_to_user(&pgdir[0], &pgd, sizeof(pgd)) != 0) + return -EFAULT; + if (copy_to_user(&pgdir[3], &pgd, sizeof(pgd)) != 0) + return -EFAULT; +#else phys_linear = (unsigned long)linear - mem_base; for (i = 0; i < mapped_pages; i += PTRS_PER_PTE) { pgd_t pgd; @@ -633,6 +878,7 @@ static unsigned long setup_pagetables(struct lguest *lg, &pgd, sizeof(pgd))) return -EFAULT; } +#endif /* We return the top level (guest-physical) address: remember where * this is. */ @@ -648,7 +894,10 @@ int init_guest_pagetable(struct lguest *lg) u64 mem; u32 initrd_size; struct boot_params __user *boot = (struct boot_params *)lg->mem_base; - +#ifdef CONFIG_X86_PAE + pgd_t *pgd; + pmd_t *pmd_table; +#endif /* Get the Guest memory size and the ramdisk size from the boot header * located at lg->mem_base (Guest address 0). */ if (copy_from_user(&mem, &boot->e820_map[0].size, sizeof(mem)) @@ -663,6 +912,15 @@ int init_guest_pagetable(struct lguest *lg) lg->pgdirs[0].pgdir = (pgd_t *)get_zeroed_page(GFP_KERNEL); if (!lg->pgdirs[0].pgdir) return -ENOMEM; +#ifdef CONFIG_X86_PAE + pgd = lg->pgdirs[0].pgdir; + pmd_table = (pmd_t *) get_zeroed_page(GFP_KERNEL); + if (!pmd_table) + return -ENOMEM; + + set_pgd(pgd + SWITCHER_PGD_INDEX, + __pgd(__pa(pmd_table) | _PAGE_PRESENT)); +#endif lg->cpus[0].cpu_pgd = 0; return 0; } @@ -672,17 +930,24 @@ void page_table_guest_data_init(struct lg_cpu *cpu) { /* We get the kernel address: above this is all kernel memory. */ if (get_user(cpu->lg->kernel_address, - &cpu->lg->lguest_data->kernel_address) - /* We tell the Guest that it can't use the top 4MB of virtual - * addresses used by the Switcher. */ - || put_user(4U*1024*1024, &cpu->lg->lguest_data->reserve_mem) - || put_user(cpu->lg->pgdirs[0].gpgdir, &cpu->lg->lguest_data->pgdir)) + &cpu->lg->lguest_data->kernel_address) + /* We tell the Guest that it can't use the top 2 or 4 MB + * of virtual addresses used by the Switcher. */ + || put_user(RESERVE_MEM * 1024 * 1024, + &cpu->lg->lguest_data->reserve_mem) + || put_user(cpu->lg->pgdirs[0].gpgdir, + &cpu->lg->lguest_data->pgdir)) kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data); /* In flush_user_mappings() we loop from 0 to * "pgd_index(lg->kernel_address)". This assumes it won't hit the * Switcher mappings, so check that now. */ +#ifdef CONFIG_X86_PAE + if (pgd_index(cpu->lg->kernel_address) == SWITCHER_PGD_INDEX && + pmd_index(cpu->lg->kernel_address) == SWITCHER_PMD_INDEX) +#else if (pgd_index(cpu->lg->kernel_address) >= SWITCHER_PGD_INDEX) +#endif kill_guest(cpu, "bad kernel address %#lx", cpu->lg->kernel_address); } @@ -708,16 +973,30 @@ void free_guest_pagetable(struct lguest *lg) void map_switcher_in_guest(struct lg_cpu *cpu, struct lguest_pages *pages) { pte_t *switcher_pte_page = __get_cpu_var(switcher_pte_pages); - pgd_t switcher_pgd; pte_t regs_pte; unsigned long pfn; +#ifdef CONFIG_X86_PAE + pmd_t switcher_pmd; + pmd_t *pmd_table; + + native_set_pmd(&switcher_pmd, pfn_pmd(__pa(switcher_pte_page) >> + PAGE_SHIFT, PAGE_KERNEL_EXEC)); + + pmd_table = __va(pgd_pfn(cpu->lg-> + pgdirs[cpu->cpu_pgd].pgdir[SWITCHER_PGD_INDEX]) + << PAGE_SHIFT); + native_set_pmd(&pmd_table[SWITCHER_PMD_INDEX], switcher_pmd); +#else + pgd_t switcher_pgd; + /* Make the last PGD entry for this Guest point to the Switcher's PTE * page for this CPU (with appropriate flags). */ - switcher_pgd = __pgd(__pa(switcher_pte_page) | __PAGE_KERNEL); + switcher_pgd = __pgd(__pa(switcher_pte_page) | __PAGE_KERNEL_EXEC); cpu->lg->pgdirs[cpu->cpu_pgd].pgdir[SWITCHER_PGD_INDEX] = switcher_pgd; +#endif /* We also change the Switcher PTE page. When we're running the Guest, * we want the Guest's "regs" page to appear where the first Switcher * page for this CPU is. This is an optimization: when the Switcher @@ -726,8 +1005,9 @@ void map_switcher_in_guest(struct lg_cpu *cpu, struct lguest_pages *pages) * page is already mapped there, we don't have to copy them out * again. */ pfn = __pa(cpu->regs_page) >> PAGE_SHIFT; - regs_pte = pfn_pte(pfn, __pgprot(__PAGE_KERNEL)); - switcher_pte_page[(unsigned long)pages/PAGE_SIZE%PTRS_PER_PTE] = regs_pte; + native_set_pte(®s_pte, pfn_pte(pfn, PAGE_KERNEL)); + native_set_pte(&switcher_pte_page[pte_index((unsigned long)pages)], + regs_pte); } /*:*/ @@ -752,21 +1032,21 @@ static __init void populate_switcher_pte_page(unsigned int cpu, /* The first entries are easy: they map the Switcher code. */ for (i = 0; i < pages; i++) { - pte[i] = mk_pte(switcher_page[i], - __pgprot(_PAGE_PRESENT|_PAGE_ACCESSED)); + native_set_pte(&pte[i], mk_pte(switcher_page[i], + __pgprot(_PAGE_PRESENT|_PAGE_ACCESSED))); } /* The only other thing we map is this CPU's pair of pages. */ i = pages + cpu*2; /* First page (Guest registers) is writable from the Guest */ - pte[i] = pfn_pte(page_to_pfn(switcher_page[i]), - __pgprot(_PAGE_PRESENT|_PAGE_ACCESSED|_PAGE_RW)); + native_set_pte(&pte[i], pfn_pte(page_to_pfn(switcher_page[i]), + __pgprot(_PAGE_PRESENT|_PAGE_ACCESSED|_PAGE_RW))); /* The second page contains the "struct lguest_ro_state", and is * read-only. */ - pte[i+1] = pfn_pte(page_to_pfn(switcher_page[i+1]), - __pgprot(_PAGE_PRESENT|_PAGE_ACCESSED)); + native_set_pte(&pte[i+1], pfn_pte(page_to_pfn(switcher_page[i+1]), + __pgprot(_PAGE_PRESENT|_PAGE_ACCESSED))); } /* We've made it through the page table code. Perhaps our tired brains are diff --git a/drivers/lguest/segments.c b/drivers/lguest/segments.c index 7ede64ffeef..482ed5a1875 100644 --- a/drivers/lguest/segments.c +++ b/drivers/lguest/segments.c @@ -150,7 +150,7 @@ void load_guest_gdt_entry(struct lg_cpu *cpu, u32 num, u32 lo, u32 hi) { /* We assume the Guest has the same number of GDT entries as the * Host, otherwise we'd have to dynamically allocate the Guest GDT. */ - if (num > ARRAY_SIZE(cpu->arch.gdt)) + if (num >= ARRAY_SIZE(cpu->arch.gdt)) kill_guest(cpu, "too many gdt entries %i", num); /* Set it up, then fix it. */ |