![Rusty Russell](/assets/img/avatar_default.png)
The netfilter code had very good documentation: the Netfilter Hacking HOWTO. Noone ever read it. So this time I'm trying something different, using a bit of Knuthiness. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
282 lines
7.4 KiB
C
282 lines
7.4 KiB
C
/*P:800 Interrupts (traps) are complicated enough to earn their own file.
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* There are three classes of interrupts:
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*
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* 1) Real hardware interrupts which occur while we're running the Guest,
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* 2) Interrupts for virtual devices attached to the Guest, and
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* 3) Traps and faults from the Guest.
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*
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* Real hardware interrupts must be delivered to the Host, not the Guest.
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* Virtual interrupts must be delivered to the Guest, but we make them look
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* just like real hardware would deliver them. Traps from the Guest can be set
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* up to go directly back into the Guest, but sometimes the Host wants to see
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* them first, so we also have a way of "reflecting" them into the Guest as if
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* they had been delivered to it directly. :*/
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#include <linux/uaccess.h>
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#include "lg.h"
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static unsigned long idt_address(u32 lo, u32 hi)
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{
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return (lo & 0x0000FFFF) | (hi & 0xFFFF0000);
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}
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static int idt_type(u32 lo, u32 hi)
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{
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return (hi >> 8) & 0xF;
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}
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static int idt_present(u32 lo, u32 hi)
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{
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return (hi & 0x8000);
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}
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static void push_guest_stack(struct lguest *lg, unsigned long *gstack, u32 val)
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{
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*gstack -= 4;
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lgwrite_u32(lg, *gstack, val);
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}
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static void set_guest_interrupt(struct lguest *lg, u32 lo, u32 hi, int has_err)
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{
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unsigned long gstack;
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u32 eflags, ss, irq_enable;
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/* If they want a ring change, we use new stack and push old ss/esp */
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if ((lg->regs->ss&0x3) != GUEST_PL) {
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gstack = guest_pa(lg, lg->esp1);
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ss = lg->ss1;
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push_guest_stack(lg, &gstack, lg->regs->ss);
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push_guest_stack(lg, &gstack, lg->regs->esp);
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} else {
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gstack = guest_pa(lg, lg->regs->esp);
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ss = lg->regs->ss;
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}
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/* We use IF bit in eflags to indicate whether irqs were enabled
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(it's always 1, since irqs are enabled when guest is running). */
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eflags = lg->regs->eflags;
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if (get_user(irq_enable, &lg->lguest_data->irq_enabled) == 0
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&& !(irq_enable & X86_EFLAGS_IF))
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eflags &= ~X86_EFLAGS_IF;
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push_guest_stack(lg, &gstack, eflags);
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push_guest_stack(lg, &gstack, lg->regs->cs);
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push_guest_stack(lg, &gstack, lg->regs->eip);
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if (has_err)
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push_guest_stack(lg, &gstack, lg->regs->errcode);
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/* Change the real stack so switcher returns to trap handler */
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lg->regs->ss = ss;
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lg->regs->esp = gstack + lg->page_offset;
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lg->regs->cs = (__KERNEL_CS|GUEST_PL);
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lg->regs->eip = idt_address(lo, hi);
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/* Disable interrupts for an interrupt gate. */
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if (idt_type(lo, hi) == 0xE)
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if (put_user(0, &lg->lguest_data->irq_enabled))
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kill_guest(lg, "Disabling interrupts");
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}
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void maybe_do_interrupt(struct lguest *lg)
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{
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unsigned int irq;
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DECLARE_BITMAP(blk, LGUEST_IRQS);
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struct desc_struct *idt;
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if (!lg->lguest_data)
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return;
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/* Mask out any interrupts they have blocked. */
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if (copy_from_user(&blk, lg->lguest_data->blocked_interrupts,
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sizeof(blk)))
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return;
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bitmap_andnot(blk, lg->irqs_pending, blk, LGUEST_IRQS);
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irq = find_first_bit(blk, LGUEST_IRQS);
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if (irq >= LGUEST_IRQS)
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return;
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if (lg->regs->eip >= lg->noirq_start && lg->regs->eip < lg->noirq_end)
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return;
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/* If they're halted, we re-enable interrupts. */
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if (lg->halted) {
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/* Re-enable interrupts. */
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if (put_user(X86_EFLAGS_IF, &lg->lguest_data->irq_enabled))
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kill_guest(lg, "Re-enabling interrupts");
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lg->halted = 0;
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} else {
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/* Maybe they have interrupts disabled? */
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u32 irq_enabled;
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if (get_user(irq_enabled, &lg->lguest_data->irq_enabled))
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irq_enabled = 0;
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if (!irq_enabled)
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return;
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}
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idt = &lg->idt[FIRST_EXTERNAL_VECTOR+irq];
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if (idt_present(idt->a, idt->b)) {
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clear_bit(irq, lg->irqs_pending);
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set_guest_interrupt(lg, idt->a, idt->b, 0);
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}
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}
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static int has_err(unsigned int trap)
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{
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return (trap == 8 || (trap >= 10 && trap <= 14) || trap == 17);
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}
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int deliver_trap(struct lguest *lg, unsigned int num)
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{
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u32 lo = lg->idt[num].a, hi = lg->idt[num].b;
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if (!idt_present(lo, hi))
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return 0;
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set_guest_interrupt(lg, lo, hi, has_err(num));
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return 1;
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}
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static int direct_trap(const struct lguest *lg,
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const struct desc_struct *trap,
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unsigned int num)
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{
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/* Hardware interrupts don't go to guest (except syscall). */
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if (num >= FIRST_EXTERNAL_VECTOR && num != SYSCALL_VECTOR)
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return 0;
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/* We intercept page fault (demand shadow paging & cr2 saving)
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protection fault (in/out emulation) and device not
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available (TS handling), and hypercall */
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if (num == 14 || num == 13 || num == 7 || num == LGUEST_TRAP_ENTRY)
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return 0;
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/* Interrupt gates (0xE) or not present (0x0) can't go direct. */
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return idt_type(trap->a, trap->b) == 0xF;
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}
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void pin_stack_pages(struct lguest *lg)
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{
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unsigned int i;
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for (i = 0; i < lg->stack_pages; i++)
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pin_page(lg, lg->esp1 - i * PAGE_SIZE);
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}
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void guest_set_stack(struct lguest *lg, u32 seg, u32 esp, unsigned int pages)
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{
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/* You cannot have a stack segment with priv level 0. */
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if ((seg & 0x3) != GUEST_PL)
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kill_guest(lg, "bad stack segment %i", seg);
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if (pages > 2)
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kill_guest(lg, "bad stack pages %u", pages);
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lg->ss1 = seg;
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lg->esp1 = esp;
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lg->stack_pages = pages;
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pin_stack_pages(lg);
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}
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/* Set up trap in IDT. */
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static void set_trap(struct lguest *lg, struct desc_struct *trap,
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unsigned int num, u32 lo, u32 hi)
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{
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u8 type = idt_type(lo, hi);
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if (!idt_present(lo, hi)) {
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trap->a = trap->b = 0;
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return;
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}
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if (type != 0xE && type != 0xF)
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kill_guest(lg, "bad IDT type %i", type);
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trap->a = ((__KERNEL_CS|GUEST_PL)<<16) | (lo&0x0000FFFF);
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trap->b = (hi&0xFFFFEF00);
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}
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void load_guest_idt_entry(struct lguest *lg, unsigned int num, u32 lo, u32 hi)
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{
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/* Guest never handles: NMI, doublefault, hypercall, spurious irq. */
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if (num == 2 || num == 8 || num == 15 || num == LGUEST_TRAP_ENTRY)
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return;
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lg->changed |= CHANGED_IDT;
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if (num < ARRAY_SIZE(lg->idt))
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set_trap(lg, &lg->idt[num], num, lo, hi);
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else if (num == SYSCALL_VECTOR)
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set_trap(lg, &lg->syscall_idt, num, lo, hi);
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}
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static void default_idt_entry(struct desc_struct *idt,
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int trap,
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const unsigned long handler)
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{
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u32 flags = 0x8e00;
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/* They can't "int" into any of them except hypercall. */
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if (trap == LGUEST_TRAP_ENTRY)
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flags |= (GUEST_PL << 13);
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idt->a = (LGUEST_CS<<16) | (handler&0x0000FFFF);
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idt->b = (handler&0xFFFF0000) | flags;
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}
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void setup_default_idt_entries(struct lguest_ro_state *state,
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const unsigned long *def)
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{
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unsigned int i;
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for (i = 0; i < ARRAY_SIZE(state->guest_idt); i++)
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default_idt_entry(&state->guest_idt[i], i, def[i]);
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}
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void copy_traps(const struct lguest *lg, struct desc_struct *idt,
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const unsigned long *def)
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{
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unsigned int i;
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/* All hardware interrupts are same whatever the guest: only the
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* traps might be different. */
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for (i = 0; i < FIRST_EXTERNAL_VECTOR; i++) {
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if (direct_trap(lg, &lg->idt[i], i))
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idt[i] = lg->idt[i];
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else
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default_idt_entry(&idt[i], i, def[i]);
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}
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i = SYSCALL_VECTOR;
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if (direct_trap(lg, &lg->syscall_idt, i))
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idt[i] = lg->syscall_idt;
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else
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default_idt_entry(&idt[i], i, def[i]);
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}
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void guest_set_clockevent(struct lguest *lg, unsigned long delta)
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{
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ktime_t expires;
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if (unlikely(delta == 0)) {
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/* Clock event device is shutting down. */
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hrtimer_cancel(&lg->hrt);
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return;
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}
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expires = ktime_add_ns(ktime_get_real(), delta);
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hrtimer_start(&lg->hrt, expires, HRTIMER_MODE_ABS);
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}
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static enum hrtimer_restart clockdev_fn(struct hrtimer *timer)
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{
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struct lguest *lg = container_of(timer, struct lguest, hrt);
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set_bit(0, lg->irqs_pending);
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if (lg->halted)
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wake_up_process(lg->tsk);
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return HRTIMER_NORESTART;
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}
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void init_clockdev(struct lguest *lg)
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{
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hrtimer_init(&lg->hrt, CLOCK_REALTIME, HRTIMER_MODE_ABS);
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lg->hrt.function = clockdev_fn;
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}
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