lguest: the host code

This is the code for the "lg.ko" module, which allows lguest guests to
be launched.

[akpm@linux-foundation.org: update for futex-new-private-futexes]
[akpm@linux-foundation.org: build fix]
[jmorris@namei.org: lguest: use hrtimers]
[akpm@linux-foundation.org: x86_64 build fix]
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Andi Kleen <ak@suse.de>
Cc: Eric Dumazet <dada1@cosmosbay.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 268 insertions, 0 deletions

diff --git a/drivers/lguest/interrupts_and_traps.c b/drivers/lguest/interrupts_and_traps.c
new file mode 100644
index 0000000..d9de5bb
--- /dev/null
+++ b/drivers/lguest/interrupts_and_traps.c
@@ -0,0 +1,268 @@
+#include <linux/uaccess.h>
+#include "lg.h"
+
+static unsigned long idt_address(u32 lo, u32 hi)
+{
+	return (lo & 0x0000FFFF) | (hi & 0xFFFF0000);
+}
+
+static int idt_type(u32 lo, u32 hi)
+{
+	return (hi >> 8) & 0xF;
+}
+
+static int idt_present(u32 lo, u32 hi)
+{
+	return (hi & 0x8000);
+}
+
+static void push_guest_stack(struct lguest *lg, unsigned long *gstack, u32 val)
+{
+	*gstack -= 4;
+	lgwrite_u32(lg, *gstack, val);
+}
+
+static void set_guest_interrupt(struct lguest *lg, u32 lo, u32 hi, int has_err)
+{
+	unsigned long gstack;
+	u32 eflags, ss, irq_enable;
+
+	/* If they want a ring change, we use new stack and push old ss/esp */
+	if ((lg->regs->ss&0x3) != GUEST_PL) {
+		gstack = guest_pa(lg, lg->esp1);
+		ss = lg->ss1;
+		push_guest_stack(lg, &gstack, lg->regs->ss);
+		push_guest_stack(lg, &gstack, lg->regs->esp);
+	} else {
+		gstack = guest_pa(lg, lg->regs->esp);
+		ss = lg->regs->ss;
+	}
+
+	/* We use IF bit in eflags to indicate whether irqs were disabled
+	   (it's always 0, since irqs are enabled when guest is running). */
+	eflags = lg->regs->eflags;
+	if (get_user(irq_enable, &lg->lguest_data->irq_enabled))
+		irq_enable = 0;
+	eflags |= (irq_enable & X86_EFLAGS_IF);
+
+	push_guest_stack(lg, &gstack, eflags);
+	push_guest_stack(lg, &gstack, lg->regs->cs);
+	push_guest_stack(lg, &gstack, lg->regs->eip);
+
+	if (has_err)
+		push_guest_stack(lg, &gstack, lg->regs->errcode);
+
+	/* Change the real stack so switcher returns to trap handler */
+	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);
+
+	/* Disable interrupts for an interrupt gate. */
+	if (idt_type(lo, hi) == 0xE)
+		if (put_user(0, &lg->lguest_data->irq_enabled))
+			kill_guest(lg, "Disabling interrupts");
+}
+
+void maybe_do_interrupt(struct lguest *lg)
+{
+	unsigned int irq;
+	DECLARE_BITMAP(blk, LGUEST_IRQS);
+	struct desc_struct *idt;
+
+	if (!lg->lguest_data)
+		return;
+
+	/* Mask out any interrupts they have blocked. */
+	if (copy_from_user(&blk, lg->lguest_data->blocked_interrupts,
+			   sizeof(blk)))
+		return;
+
+	bitmap_andnot(blk, lg->irqs_pending, blk, LGUEST_IRQS);
+
+	irq = find_first_bit(blk, LGUEST_IRQS);
+	if (irq >= LGUEST_IRQS)
+		return;
+
+	if (lg->regs->eip >= lg->noirq_start && lg->regs->eip < lg->noirq_end)
+		return;
+
+	/* If they're halted, we re-enable interrupts. */
+	if (lg->halted) {
+		/* Re-enable interrupts. */
+		if (put_user(X86_EFLAGS_IF, &lg->lguest_data->irq_enabled))
+			kill_guest(lg, "Re-enabling interrupts");
+		lg->halted = 0;
+	} else {
+		/* Maybe they have interrupts disabled? */
+		u32 irq_enabled;
+		if (get_user(irq_enabled, &lg->lguest_data->irq_enabled))
+			irq_enabled = 0;
+		if (!irq_enabled)
+			return;
+	}
+
+	idt = &lg->idt[FIRST_EXTERNAL_VECTOR+irq];
+	if (idt_present(idt->a, idt->b)) {
+		clear_bit(irq, lg->irqs_pending);
+		set_guest_interrupt(lg, idt->a, idt->b, 0);
+	}
+}
+
+static int has_err(unsigned int trap)
+{
+	return (trap == 8 || (trap >= 10 && trap <= 14) || trap == 17);
+}
+
+int deliver_trap(struct lguest *lg, unsigned int num)
+{
+	u32 lo = lg->idt[num].a, hi = lg->idt[num].b;
+
+	if (!idt_present(lo, hi))
+		return 0;
+	set_guest_interrupt(lg, lo, hi, has_err(num));
+	return 1;
+}
+
+static int direct_trap(const struct lguest *lg,
+		       const struct desc_struct *trap,
+		       unsigned int num)
+{
+	/* Hardware interrupts don't go to guest (except syscall). */
+	if (num >= FIRST_EXTERNAL_VECTOR && num != SYSCALL_VECTOR)
+		return 0;
+
+	/* We intercept page fault (demand shadow paging & cr2 saving)
+	   protection fault (in/out emulation) and device not
+	   available (TS handling), and hypercall */
+	if (num == 14 || num == 13 || num == 7 || num == LGUEST_TRAP_ENTRY)
+		return 0;
+
+	/* Interrupt gates (0xE) or not present (0x0) can't go direct. */
+	return idt_type(trap->a, trap->b) == 0xF;
+}
+
+void pin_stack_pages(struct lguest *lg)
+{
+	unsigned int i;
+
+	for (i = 0; i < lg->stack_pages; i++)
+		pin_page(lg, lg->esp1 - i * PAGE_SIZE);
+}
+
+void guest_set_stack(struct lguest *lg, u32 seg, u32 esp, unsigned int pages)
+{
+	/* You cannot have a stack segment with priv level 0. */
+	if ((seg & 0x3) != GUEST_PL)
+		kill_guest(lg, "bad stack segment %i", seg);
+	if (pages > 2)
+		kill_guest(lg, "bad stack pages %u", pages);
+	lg->ss1 = seg;
+	lg->esp1 = esp;
+	lg->stack_pages = pages;
+	pin_stack_pages(lg);
+}
+
+/* Set up trap in IDT. */
+static void set_trap(struct lguest *lg, struct desc_struct *trap,
+		     unsigned int num, u32 lo, u32 hi)
+{
+	u8 type = idt_type(lo, hi);
+
+	if (!idt_present(lo, hi)) {
+		trap->a = trap->b = 0;
+		return;
+	}
+
+	if (type != 0xE && type != 0xF)
+		kill_guest(lg, "bad IDT type %i", type);
+
+	trap->a = ((__KERNEL_CS|GUEST_PL)<<16) | (lo&0x0000FFFF);
+	trap->b = (hi&0xFFFFEF00);
+}
+
+void load_guest_idt_entry(struct lguest *lg, unsigned int num, u32 lo, u32 hi)
+{
+	/* Guest never handles: NMI, doublefault, hypercall, spurious irq. */
+	if (num == 2 || num == 8 || num == 15 || num == LGUEST_TRAP_ENTRY)
+		return;
+
+	lg->changed |= CHANGED_IDT;
+	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);
+}
+
+static void default_idt_entry(struct desc_struct *idt,
+			      int trap,
+			      const unsigned long handler)
+{
+	u32 flags = 0x8e00;
+
+	/* They can't "int" into any of them except hypercall. */
+	if (trap == LGUEST_TRAP_ENTRY)
+		flags |= (GUEST_PL << 13);
+
+	idt->a = (LGUEST_CS<<16) | (handler&0x0000FFFF);
+	idt->b = (handler&0xFFFF0000) | flags;
+}
+
+void setup_default_idt_entries(struct lguest_ro_state *state,
+			       const unsigned long *def)
+{
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(state->guest_idt); i++)
+		default_idt_entry(&state->guest_idt[i], i, def[i]);
+}
+
+void copy_traps(const struct lguest *lg, struct desc_struct *idt,
+		const unsigned long *def)
+{
+	unsigned int i;
+
+	/* All hardware interrupts are same whatever the guest: only the
+	 * traps might be different. */
+	for (i = 0; i < FIRST_EXTERNAL_VECTOR; i++) {
+		if (direct_trap(lg, &lg->idt[i], i))
+			idt[i] = lg->idt[i];
+		else
+			default_idt_entry(&idt[i], i, def[i]);
+	}
+	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)
+{
+	ktime_t expires;
+
+	if (unlikely(delta == 0)) {
+		/* Clock event device is shutting down. */
+		hrtimer_cancel(&lg->hrt);
+		return;
+	}
+
+	expires = ktime_add_ns(ktime_get_real(), delta);
+	hrtimer_start(&lg->hrt, expires, HRTIMER_MODE_ABS);
+}
+
+static enum hrtimer_restart clockdev_fn(struct hrtimer *timer)
+{
+	struct lguest *lg = container_of(timer, struct lguest, hrt);
+
+	set_bit(0, lg->irqs_pending);
+	if (lg->halted)
+		wake_up_process(lg->tsk);
+	return HRTIMER_NORESTART;
+}
+
+void init_clockdev(struct lguest *lg)
+{
+	hrtimer_init(&lg->hrt, CLOCK_REALTIME, HRTIMER_MODE_ABS);
+	lg->hrt.function = clockdev_fn;
+}