diff options
Diffstat (limited to 'drivers/lguest/interrupts_and_traps.c')
| -rw-r--r-- | drivers/lguest/interrupts_and_traps.c | 629 |
1 files changed, 420 insertions, 209 deletions
diff --git a/drivers/lguest/interrupts_and_traps.c b/drivers/lguest/interrupts_and_traps.c index 39731232d82..70dfcdc29f1 100644 --- a/drivers/lguest/interrupts_and_traps.c +++ b/drivers/lguest/interrupts_and_traps.c @@ -1,4 +1,5 @@ -/*P:800 Interrupts (traps) are complicated enough to earn their own file. +/*P:800 + * Interrupts (traps) are complicated enough to earn their own file. * There are three classes of interrupts: * * 1) Real hardware interrupts which occur while we're running the Guest, @@ -10,39 +11,52 @@ * just like real hardware would deliver them. Traps from the Guest can be set * up to go directly back into the Guest, but sometimes the Host wants to see * them first, so we also have a way of "reflecting" them into the Guest as if - * they had been delivered to it directly. :*/ + * they had been delivered to it directly. +:*/ #include <linux/uaccess.h> +#include <linux/interrupt.h> +#include <linux/module.h> +#include <linux/sched.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) { return (lo & 0x0000FFFF) | (hi & 0xFFFF0000); } -/* The "type" of the interrupt handler is a 4 bit field: we only support a - * couple of types. */ +/* + * The "type" of the interrupt handler is a 4 bit field: we only support a + * couple of types. + */ static int idt_type(u32 lo, u32 hi) { return (hi >> 8) & 0xF; } /* An IDT entry can't be used unless the "present" bit is set. */ -static int idt_present(u32 lo, u32 hi) +static bool idt_present(u32 lo, u32 hi) { return (hi & 0x8000); } -/* 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) +/* + * 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 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 +/*H:210 + * The set_guest_interrupt() routine actually delivers the interrupt or * trap. The mechanics of delivering traps and interrupts to the Guest are the * same, except some traps have an "error code" which gets pushed onto the * stack as well: the caller tells us if this is one. @@ -53,261 +67,412 @@ 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) + * it). + */ +static void set_guest_interrupt(struct lg_cpu *cpu, u32 lo, u32 hi, + bool 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 + /* + * 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) { - /* 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; - /* We push the old stack segment and pointer onto the new + * userspace. We check the privilege level to find out. + */ + 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. + */ + 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); + * levels and expect these here. + */ + 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 + /* + * 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 + /* + * 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); + * pointer. + */ + 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); - - /* 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); - - /* There are two kinds of interrupt handlers: 0xE is an "interrupt - * gate" which expects interrupts to be disabled on entry. */ + 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. + */ + cpu->regs->ss = ss; + cpu->regs->esp = virtstack + (gstack - origstack); + cpu->regs->cs = (__KERNEL_CS|GUEST_PL); + cpu->regs->eip = idt_address(lo, hi); + + /* + * Trapping always clears these flags: + * TF: Trap flag + * VM: Virtual 8086 mode + * RF: Resume + * NT: Nested task. + */ + cpu->regs->eflags &= + ~(X86_EFLAGS_TF|X86_EFLAGS_VM|X86_EFLAGS_RF|X86_EFLAGS_NT); + + /* + * 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) + * 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 (!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 (!cpu->lg->lguest_data) + 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; - - bitmap_andnot(blk, lg->irqs_pending, blk, LGUEST_IRQS); + 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. */ - if (lg->regs->eip >= lg->noirq_start && lg->regs->eip < lg->noirq_end) + /* + * They may be in the middle of an iret, where they asked us never to + * deliver interrupts. + */ + 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) + 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 + /* + * 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]; + * over them. + */ + 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); - /* set_guest_interrupt() takes the interrupt descriptor and a + 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); + * the stack as well: virtual interrupts never do. + */ + set_guest_interrupt(cpu, idt->a, idt->b, false); } - /* Every time we deliver an interrupt, we update the timestamp in the + /* + * Every time we deliver an interrupt, we update the timestamp in the * Guest's lguest_data struct. It would be better for the Guest if we * 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); + * 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); } +/*:*/ -/*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) +/* + * 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) { + if (test_bit(syscall_vector, used_vectors) || + vector_used_by_percpu_irq(syscall_vector)) { + printk(KERN_ERR "lg: couldn't reserve syscall %u\n", + syscall_vector); + return -EBUSY; + } + set_bit(syscall_vector, used_vectors); + } + + 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: + */ +static bool 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) +bool 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)) - 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)) - return 0; - set_guest_interrupt(lg, lg->idt[num].a, lg->idt[num].b, has_err(num)); - return 1; + /* + * 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(cpu->arch.idt)) + return false; + + /* + * 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(cpu->arch.idt[num].a, cpu->arch.idt[num].b)) + return false; + set_guest_interrupt(cpu, cpu->arch.idt[num].a, + cpu->arch.idt[num].b, has_err(num)); + return true; } -/*H:250 Here's the hard part: returning to the Host every time a trap happens +/*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 bool 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) - return 0; - - /* The Host needs to see page faults (for shadow paging and to save the + /* + * Hardware interrupts don't go to the Guest at all (except system + * call). + */ + if (num >= FIRST_EXTERNAL_VECTOR && !could_be_syscall(num)) + return false; + + /* + * 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; + * device not available (TS handling) and of course, the hypercall trap. + */ + return num != 14 && num != 13 && num != 7 && num != LGUEST_TRAP_ENTRY; } /*:*/ -/*M:005 The Guest has the ability to turn its interrupt gates into trap gates, +/*M:005 + * The Guest has the ability to turn its interrupt gates into trap gates, * if it is careful. The Host will let trap gates can go directly to the * Guest, but the Guest needs the interrupts atomically disabled for an * interrupt gate. It can do this by pointing the trap gate at instructions - * within noirq_start and noirq_end, where it can safely disable interrupts. */ + * within noirq_start and noirq_end, where it can safely disable interrupts. + */ -/*M:006 The Guests do not use the sysenter (fast system call) instruction, +/*M:006 + * The Guests do not use the sysenter (fast system call) instruction, * because it's hardcoded to enter privilege level 0 and so can't go direct. * It's about twice as fast as the older "int 0x80" system call, so it might * still be worthwhile to handle it in the Switcher and lcall down to the * Guest. The sysenter semantics are hairy tho: search for that keyword in - * entry.S :*/ + * entry.S +:*/ -/*H:260 When we make traps go directly into the Guest, we need to make sure +/*H:260 + * When we make traps go directly into the Guest, we need to make sure * the kernel stack is valid (ie. mapped in the page tables). Otherwise, the * CPU trying to deliver the trap will fault while trying to push the interrupt * words on the stack: this is called a double fault, and it forces us to kill * the Guest. * - * Which is deeply unfair, because (literally!) it wasn't the Guests' fault. */ -void pin_stack_pages(struct lguest *lg) + * Which is deeply unfair, because (literally!) it wasn't the Guests' fault. + */ +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*, so the address we're given is the + /* + * Depending on the CONFIG_4KSTACKS option, the Guest can have one or + * two pages of stack space. + */ + 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(lg, lg->esp1 - 1 - i * PAGE_SIZE); + * 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 - * a different kernel stack, so we can change the IDT entries to use that - * stack. The IDT entries expect a virtual address, so unlike most addresses +/* + * Direct traps also mean that we need to know whenever the Guest wants to use + * a different kernel stack, so we can change the guest TSS to use that + * stack. The TSS entries expect a virtual address, so unlike most addresses * the Guest gives us, the "esp" (stack pointer) value here is virtual, not * physical. * * 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) + * change stacks on each context switch. + */ +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 - * Guest! */ + /* + * You're not allowed 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. */ +/* + * 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, +/*H:235 + * This is the routine which actually checks the Guest's IDT entry and + * 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); @@ -320,59 +485,74 @@ 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 + /* + * We only copy the handler address, present bit, privilege level and * type. The privilege level controls where the trap can be triggered * manually with an "int" instruction. This is usually GUEST_PL, - * except for system calls which userspace can use. */ + * except for system calls which userspace can use. + */ trap->a = ((__KERNEL_CS|GUEST_PL)<<16) | (lo&0x0000FFFF); trap->b = (hi&0xFFFFEF00); } -/*H:230 While we're here, dealing with delivering traps and interrupts to the +/*H:230 + * While we're here, dealing with delivering traps and interrupts to the * Guest, we might as well complete the picture: how the Guest tells us where * it wants them to go. This would be simple, except making traps fast * requires some tricks. * * 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) + * LHCALL_LOAD_IDT_ENTRY hypercall before: that comes here. + */ +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. */ + /* + * Guest never handles: NMI, doublefault, spurious interrupt or + * hypercall. We ignore when it tries to set them. + */ if (num == 2 || num == 8 || num == 15 || num == LGUEST_TRAP_ENTRY) return; - /* 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); + /* + * Mark the IDT as changed: next time the Guest runs we'll know we have + * to copy this again. + */ + 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 +/* + * The default entry for each interrupt points into the Switcher routines which * simply return to the Host. The run_guest() loop will then call - * deliver_trap() to bounce it back into the Guest. */ + * deliver_trap() to bounce it back into the Guest. + */ static void default_idt_entry(struct desc_struct *idt, int trap, - const unsigned long handler) + const unsigned long handler, + const struct desc_struct *base) { /* A present interrupt gate. */ u32 flags = 0x8e00; - /* Set the privilege level on the entry for the hypercall: this allows - * the Guest to use the "int" instruction to trigger it. */ + /* + * Set the privilege level on the entry for the hypercall: this allows + * the Guest to use the "int" instruction to trigger it. + */ if (trap == LGUEST_TRAP_ENTRY) flags |= (GUEST_PL << 13); + else if (base) + /* + * Copy privilege level from what Guest asked for. This allows + * debug (int 3) traps from Guest userspace, for example. + */ + flags |= (base->b & 0x6000); /* Now pack it into the IDT entry in its weird format. */ idt->a = (LGUEST_CS<<16) | (handler&0x0000FFFF); @@ -386,61 +566,92 @@ void setup_default_idt_entries(struct lguest_ro_state *state, unsigned int i; for (i = 0; i < ARRAY_SIZE(state->guest_idt); i++) - default_idt_entry(&state->guest_idt[i], i, def[i]); + default_idt_entry(&state->guest_idt[i], i, def[i], NULL); } -/*H:240 We don't use the IDT entries in the "struct lguest" directly, instead +/*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, + * before we run the Guest. This routine does that copy. + */ +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]; + /* + * 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 < ARRAY_SIZE(cpu->arch.idt); i++) { + const struct desc_struct *gidt = &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 it can't go direct, we still need to copy the priv. level: + * they might want to give userspace access to a software + * interrupt. + */ + if (idt_type(gidt->a, gidt->b) == 0xF) + idt[i] = *gidt; else - default_idt_entry(&idt[i], i, def[i]); + default_idt_entry(&idt[i], i, def[i], gidt); } - - /* 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_interrupt(cpu, 0); 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; } |