Initial import

1 files changed, 841 insertions, 0 deletions

diff --git a/arch/x86/kernel/vm86_32.c b/arch/x86/kernel/vm86_32.c
new file mode 100644
index 000000000..fc9db6ef2
--- /dev/null
+++ b/arch/x86/kernel/vm86_32.c
@@ -0,0 +1,841 @@
+/*
+ *  Copyright (C) 1994  Linus Torvalds
+ *
+ *  29 dec 2001 - Fixed oopses caused by unchecked access to the vm86
+ *                stack - Manfred Spraul <manfred@colorfullife.com>
+ *
+ *  22 mar 2002 - Manfred detected the stackfaults, but didn't handle
+ *                them correctly. Now the emulation will be in a
+ *                consistent state after stackfaults - Kasper Dupont
+ *                <kasperd@daimi.au.dk>
+ *
+ *  22 mar 2002 - Added missing clear_IF in set_vflags_* Kasper Dupont
+ *                <kasperd@daimi.au.dk>
+ *
+ *  ?? ??? 2002 - Fixed premature returns from handle_vm86_fault
+ *                caused by Kasper Dupont's changes - Stas Sergeev
+ *
+ *   4 apr 2002 - Fixed CHECK_IF_IN_TRAP broken by Stas' changes.
+ *                Kasper Dupont <kasperd@daimi.au.dk>
+ *
+ *   9 apr 2002 - Changed syntax of macros in handle_vm86_fault.
+ *                Kasper Dupont <kasperd@daimi.au.dk>
+ *
+ *   9 apr 2002 - Changed stack access macros to jump to a label
+ *                instead of returning to userspace. This simplifies
+ *                do_int, and is needed by handle_vm6_fault. Kasper
+ *                Dupont <kasperd@daimi.au.dk>
+ *
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/capability.h>
+#include <linux/errno.h>
+#include <linux/interrupt.h>
+#include <linux/syscalls.h>
+#include <linux/sched.h>
+#include <linux/kernel.h>
+#include <linux/signal.h>
+#include <linux/string.h>
+#include <linux/mm.h>
+#include <linux/smp.h>
+#include <linux/highmem.h>
+#include <linux/ptrace.h>
+#include <linux/audit.h>
+#include <linux/stddef.h>
+
+#include <asm/uaccess.h>
+#include <asm/io.h>
+#include <asm/tlbflush.h>
+#include <asm/irq.h>
+
+/*
+ * Known problems:
+ *
+ * Interrupt handling is not guaranteed:
+ * - a real x86 will disable all interrupts for one instruction
+ *   after a "mov ss,xx" to make stack handling atomic even without
+ *   the 'lss' instruction. We can't guarantee this in v86 mode,
+ *   as the next instruction might result in a page fault or similar.
+ * - a real x86 will have interrupts disabled for one instruction
+ *   past the 'sti' that enables them. We don't bother with all the
+ *   details yet.
+ *
+ * Let's hope these problems do not actually matter for anything.
+ */
+
+
+#define KVM86	((struct kernel_vm86_struct *)regs)
+#define VMPI	KVM86->vm86plus
+
+
+/*
+ * 8- and 16-bit register defines..
+ */
+#define AL(regs)	(((unsigned char *)&((regs)->pt.ax))[0])
+#define AH(regs)	(((unsigned char *)&((regs)->pt.ax))[1])
+#define IP(regs)	(*(unsigned short *)&((regs)->pt.ip))
+#define SP(regs)	(*(unsigned short *)&((regs)->pt.sp))
+
+/*
+ * virtual flags (16 and 32-bit versions)
+ */
+#define VFLAGS	(*(unsigned short *)&(current->thread.v86flags))
+#define VEFLAGS	(current->thread.v86flags)
+
+#define set_flags(X, new, mask) \
+((X) = ((X) & ~(mask)) | ((new) & (mask)))
+
+#define SAFE_MASK	(0xDD5)
+#define RETURN_MASK	(0xDFF)
+
+/* convert kernel_vm86_regs to vm86_regs */
+static int copy_vm86_regs_to_user(struct vm86_regs __user *user,
+				  const struct kernel_vm86_regs *regs)
+{
+	int ret = 0;
+
+	/*
+	 * kernel_vm86_regs is missing gs, so copy everything up to
+	 * (but not including) orig_eax, and then rest including orig_eax.
+	 */
+	ret += copy_to_user(user, regs, offsetof(struct kernel_vm86_regs, pt.orig_ax));
+	ret += copy_to_user(&user->orig_eax, &regs->pt.orig_ax,
+			    sizeof(struct kernel_vm86_regs) -
+			    offsetof(struct kernel_vm86_regs, pt.orig_ax));
+
+	return ret;
+}
+
+/* convert vm86_regs to kernel_vm86_regs */
+static int copy_vm86_regs_from_user(struct kernel_vm86_regs *regs,
+				    const struct vm86_regs __user *user,
+				    unsigned extra)
+{
+	int ret = 0;
+
+	/* copy ax-fs inclusive */
+	ret += copy_from_user(regs, user, offsetof(struct kernel_vm86_regs, pt.orig_ax));
+	/* copy orig_ax-__gsh+extra */
+	ret += copy_from_user(&regs->pt.orig_ax, &user->orig_eax,
+			      sizeof(struct kernel_vm86_regs) -
+			      offsetof(struct kernel_vm86_regs, pt.orig_ax) +
+			      extra);
+	return ret;
+}
+
+struct pt_regs *save_v86_state(struct kernel_vm86_regs *regs)
+{
+	struct tss_struct *tss;
+	struct pt_regs *ret;
+	unsigned long tmp;
+
+	/*
+	 * This gets called from entry.S with interrupts disabled, but
+	 * from process context. Enable interrupts here, before trying
+	 * to access user space.
+	 */
+	local_irq_enable();
+
+	if (!current->thread.vm86_info) {
+		pr_alert("no vm86_info: BAD\n");
+		do_exit(SIGSEGV);
+	}
+	set_flags(regs->pt.flags, VEFLAGS, X86_EFLAGS_VIF | current->thread.v86mask);
+	tmp = copy_vm86_regs_to_user(&current->thread.vm86_info->regs, regs);
+	tmp += put_user(current->thread.screen_bitmap, &current->thread.vm86_info->screen_bitmap);
+	if (tmp) {
+		pr_alert("could not access userspace vm86_info\n");
+		do_exit(SIGSEGV);
+	}
+
+	tss = &per_cpu(cpu_tss, get_cpu());
+	current->thread.sp0 = current->thread.saved_sp0;
+	current->thread.sysenter_cs = __KERNEL_CS;
+	load_sp0(tss, &current->thread);
+	current->thread.saved_sp0 = 0;
+	put_cpu();
+
+	ret = KVM86->regs32;
+
+	ret->fs = current->thread.saved_fs;
+	set_user_gs(ret, current->thread.saved_gs);
+
+	return ret;
+}
+
+static void mark_screen_rdonly(struct mm_struct *mm)
+{
+	pgd_t *pgd;
+	pud_t *pud;
+	pmd_t *pmd;
+	pte_t *pte;
+	spinlock_t *ptl;
+	int i;
+
+	down_write(&mm->mmap_sem);
+	pgd = pgd_offset(mm, 0xA0000);
+	if (pgd_none_or_clear_bad(pgd))
+		goto out;
+	pud = pud_offset(pgd, 0xA0000);
+	if (pud_none_or_clear_bad(pud))
+		goto out;
+	pmd = pmd_offset(pud, 0xA0000);
+	split_huge_page_pmd_mm(mm, 0xA0000, pmd);
+	if (pmd_none_or_clear_bad(pmd))
+		goto out;
+	pte = pte_offset_map_lock(mm, pmd, 0xA0000, &ptl);
+	for (i = 0; i < 32; i++) {
+		if (pte_present(*pte))
+			set_pte(pte, pte_wrprotect(*pte));
+		pte++;
+	}
+	pte_unmap_unlock(pte, ptl);
+out:
+	up_write(&mm->mmap_sem);
+	flush_tlb();
+}
+
+
+
+static int do_vm86_irq_handling(int subfunction, int irqnumber);
+static void do_sys_vm86(struct kernel_vm86_struct *info, struct task_struct *tsk);
+
+SYSCALL_DEFINE1(vm86old, struct vm86_struct __user *, v86)
+{
+	struct kernel_vm86_struct info; /* declare this _on top_,
+					 * this avoids wasting of stack space.
+					 * This remains on the stack until we
+					 * return to 32 bit user space.
+					 */
+	struct task_struct *tsk = current;
+	int tmp;
+
+	if (tsk->thread.saved_sp0)
+		return -EPERM;
+	tmp = copy_vm86_regs_from_user(&info.regs, &v86->regs,
+				       offsetof(struct kernel_vm86_struct, vm86plus) -
+				       sizeof(info.regs));
+	if (tmp)
+		return -EFAULT;
+	memset(&info.vm86plus, 0, (int)&info.regs32 - (int)&info.vm86plus);
+	info.regs32 = current_pt_regs();
+	tsk->thread.vm86_info = v86;
+	do_sys_vm86(&info, tsk);
+	return 0;	/* we never return here */
+}
+
+
+SYSCALL_DEFINE2(vm86, unsigned long, cmd, unsigned long, arg)
+{
+	struct kernel_vm86_struct info; /* declare this _on top_,
+					 * this avoids wasting of stack space.
+					 * This remains on the stack until we
+					 * return to 32 bit user space.
+					 */
+	struct task_struct *tsk;
+	int tmp;
+	struct vm86plus_struct __user *v86;
+
+	tsk = current;
+	switch (cmd) {
+	case VM86_REQUEST_IRQ:
+	case VM86_FREE_IRQ:
+	case VM86_GET_IRQ_BITS:
+	case VM86_GET_AND_RESET_IRQ:
+		return do_vm86_irq_handling(cmd, (int)arg);
+	case VM86_PLUS_INSTALL_CHECK:
+		/*
+		 * NOTE: on old vm86 stuff this will return the error
+		 *  from access_ok(), because the subfunction is
+		 *  interpreted as (invalid) address to vm86_struct.
+		 *  So the installation check works.
+		 */
+		return 0;
+	}
+
+	/* we come here only for functions VM86_ENTER, VM86_ENTER_NO_BYPASS */
+	if (tsk->thread.saved_sp0)
+		return -EPERM;
+	v86 = (struct vm86plus_struct __user *)arg;
+	tmp = copy_vm86_regs_from_user(&info.regs, &v86->regs,
+				       offsetof(struct kernel_vm86_struct, regs32) -
+				       sizeof(info.regs));
+	if (tmp)
+		return -EFAULT;
+	info.regs32 = current_pt_regs();
+	info.vm86plus.is_vm86pus = 1;
+	tsk->thread.vm86_info = (struct vm86_struct __user *)v86;
+	do_sys_vm86(&info, tsk);
+	return 0;	/* we never return here */
+}
+
+
+static void do_sys_vm86(struct kernel_vm86_struct *info, struct task_struct *tsk)
+{
+	struct tss_struct *tss;
+/*
+ * make sure the vm86() system call doesn't try to do anything silly
+ */
+	info->regs.pt.ds = 0;
+	info->regs.pt.es = 0;
+	info->regs.pt.fs = 0;
+#ifndef CONFIG_X86_32_LAZY_GS
+	info->regs.pt.gs = 0;
+#endif
+
+/*
+ * The flags register is also special: we cannot trust that the user
+ * has set it up safely, so this makes sure interrupt etc flags are
+ * inherited from protected mode.
+ */
+	VEFLAGS = info->regs.pt.flags;
+	info->regs.pt.flags &= SAFE_MASK;
+	info->regs.pt.flags |= info->regs32->flags & ~SAFE_MASK;
+	info->regs.pt.flags |= X86_VM_MASK;
+
+	switch (info->cpu_type) {
+	case CPU_286:
+		tsk->thread.v86mask = 0;
+		break;
+	case CPU_386:
+		tsk->thread.v86mask = X86_EFLAGS_NT | X86_EFLAGS_IOPL;
+		break;
+	case CPU_486:
+		tsk->thread.v86mask = X86_EFLAGS_AC | X86_EFLAGS_NT | X86_EFLAGS_IOPL;
+		break;
+	default:
+		tsk->thread.v86mask = X86_EFLAGS_ID | X86_EFLAGS_AC | X86_EFLAGS_NT | X86_EFLAGS_IOPL;
+		break;
+	}
+
+/*
+ * Save old state, set default return value (%ax) to 0 (VM86_SIGNAL)
+ */
+	info->regs32->ax = VM86_SIGNAL;
+	tsk->thread.saved_sp0 = tsk->thread.sp0;
+	tsk->thread.saved_fs = info->regs32->fs;
+	tsk->thread.saved_gs = get_user_gs(info->regs32);
+
+	tss = &per_cpu(cpu_tss, get_cpu());
+	tsk->thread.sp0 = (unsigned long) &info->VM86_TSS_ESP0;
+	if (cpu_has_sep)
+		tsk->thread.sysenter_cs = 0;
+	load_sp0(tss, &tsk->thread);
+	put_cpu();
+
+	tsk->thread.screen_bitmap = info->screen_bitmap;
+	if (info->flags & VM86_SCREEN_BITMAP)
+		mark_screen_rdonly(tsk->mm);
+
+	/*call __audit_syscall_exit since we do not exit via the normal paths */
+#ifdef CONFIG_AUDITSYSCALL
+	if (unlikely(current->audit_context))
+		__audit_syscall_exit(1, 0);
+#endif
+
+	__asm__ __volatile__(
+		"movl %0,%%esp\n\t"
+		"movl %1,%%ebp\n\t"
+#ifdef CONFIG_X86_32_LAZY_GS
+		"mov  %2, %%gs\n\t"
+#endif
+		"jmp resume_userspace"
+		: /* no outputs */
+		:"r" (&info->regs), "r" (task_thread_info(tsk)), "r" (0));
+	/* we never return here */
+}
+
+static inline void return_to_32bit(struct kernel_vm86_regs *regs16, int retval)
+{
+	struct pt_regs *regs32;
+
+	regs32 = save_v86_state(regs16);
+	regs32->ax = retval;
+	__asm__ __volatile__("movl %0,%%esp\n\t"
+		"movl %1,%%ebp\n\t"
+		"jmp resume_userspace"
+		: : "r" (regs32), "r" (current_thread_info()));
+}
+
+static inline void set_IF(struct kernel_vm86_regs *regs)
+{
+	VEFLAGS |= X86_EFLAGS_VIF;
+	if (VEFLAGS & X86_EFLAGS_VIP)
+		return_to_32bit(regs, VM86_STI);
+}
+
+static inline void clear_IF(struct kernel_vm86_regs *regs)
+{
+	VEFLAGS &= ~X86_EFLAGS_VIF;
+}
+
+static inline void clear_TF(struct kernel_vm86_regs *regs)
+{
+	regs->pt.flags &= ~X86_EFLAGS_TF;
+}
+
+static inline void clear_AC(struct kernel_vm86_regs *regs)
+{
+	regs->pt.flags &= ~X86_EFLAGS_AC;
+}
+
+/*
+ * It is correct to call set_IF(regs) from the set_vflags_*
+ * functions. However someone forgot to call clear_IF(regs)
+ * in the opposite case.
+ * After the command sequence CLI PUSHF STI POPF you should
+ * end up with interrupts disabled, but you ended up with
+ * interrupts enabled.
+ *  ( I was testing my own changes, but the only bug I
+ *    could find was in a function I had not changed. )
+ * [KD]
+ */
+
+static inline void set_vflags_long(unsigned long flags, struct kernel_vm86_regs *regs)
+{
+	set_flags(VEFLAGS, flags, current->thread.v86mask);
+	set_flags(regs->pt.flags, flags, SAFE_MASK);
+	if (flags & X86_EFLAGS_IF)
+		set_IF(regs);
+	else
+		clear_IF(regs);
+}
+
+static inline void set_vflags_short(unsigned short flags, struct kernel_vm86_regs *regs)
+{
+	set_flags(VFLAGS, flags, current->thread.v86mask);
+	set_flags(regs->pt.flags, flags, SAFE_MASK);
+	if (flags & X86_EFLAGS_IF)
+		set_IF(regs);
+	else
+		clear_IF(regs);
+}
+
+static inline unsigned long get_vflags(struct kernel_vm86_regs *regs)
+{
+	unsigned long flags = regs->pt.flags & RETURN_MASK;
+
+	if (VEFLAGS & X86_EFLAGS_VIF)
+		flags |= X86_EFLAGS_IF;
+	flags |= X86_EFLAGS_IOPL;
+	return flags | (VEFLAGS & current->thread.v86mask);
+}
+
+static inline int is_revectored(int nr, struct revectored_struct *bitmap)
+{
+	__asm__ __volatile__("btl %2,%1\n\tsbbl %0,%0"
+		:"=r" (nr)
+		:"m" (*bitmap), "r" (nr));
+	return nr;
+}
+
+#define val_byte(val, n) (((__u8 *)&val)[n])
+
+#define pushb(base, ptr, val, err_label) \
+	do { \
+		__u8 __val = val; \
+		ptr--; \
+		if (put_user(__val, base + ptr) < 0) \
+			goto err_label; \
+	} while (0)
+
+#define pushw(base, ptr, val, err_label) \
+	do { \
+		__u16 __val = val; \
+		ptr--; \
+		if (put_user(val_byte(__val, 1), base + ptr) < 0) \
+			goto err_label; \
+		ptr--; \
+		if (put_user(val_byte(__val, 0), base + ptr) < 0) \
+			goto err_label; \
+	} while (0)
+
+#define pushl(base, ptr, val, err_label) \
+	do { \
+		__u32 __val = val; \
+		ptr--; \
+		if (put_user(val_byte(__val, 3), base + ptr) < 0) \
+			goto err_label; \
+		ptr--; \
+		if (put_user(val_byte(__val, 2), base + ptr) < 0) \
+			goto err_label; \
+		ptr--; \
+		if (put_user(val_byte(__val, 1), base + ptr) < 0) \
+			goto err_label; \
+		ptr--; \
+		if (put_user(val_byte(__val, 0), base + ptr) < 0) \
+			goto err_label; \
+	} while (0)
+
+#define popb(base, ptr, err_label) \
+	({ \
+		__u8 __res; \
+		if (get_user(__res, base + ptr) < 0) \
+			goto err_label; \
+		ptr++; \
+		__res; \
+	})
+
+#define popw(base, ptr, err_label) \
+	({ \
+		__u16 __res; \
+		if (get_user(val_byte(__res, 0), base + ptr) < 0) \
+			goto err_label; \
+		ptr++; \
+		if (get_user(val_byte(__res, 1), base + ptr) < 0) \
+			goto err_label; \
+		ptr++; \
+		__res; \
+	})
+
+#define popl(base, ptr, err_label) \
+	({ \
+		__u32 __res; \
+		if (get_user(val_byte(__res, 0), base + ptr) < 0) \
+			goto err_label; \
+		ptr++; \
+		if (get_user(val_byte(__res, 1), base + ptr) < 0) \
+			goto err_label; \
+		ptr++; \
+		if (get_user(val_byte(__res, 2), base + ptr) < 0) \
+			goto err_label; \
+		ptr++; \
+		if (get_user(val_byte(__res, 3), base + ptr) < 0) \
+			goto err_label; \
+		ptr++; \
+		__res; \
+	})
+
+/* There are so many possible reasons for this function to return
+ * VM86_INTx, so adding another doesn't bother me. We can expect
+ * userspace programs to be able to handle it. (Getting a problem
+ * in userspace is always better than an Oops anyway.) [KD]
+ */
+static void do_int(struct kernel_vm86_regs *regs, int i,
+    unsigned char __user *ssp, unsigned short sp)
+{
+	unsigned long __user *intr_ptr;
+	unsigned long segoffs;
+
+	if (regs->pt.cs == BIOSSEG)
+		goto cannot_handle;
+	if (is_revectored(i, &KVM86->int_revectored))
+		goto cannot_handle;
+	if (i == 0x21 && is_revectored(AH(regs), &KVM86->int21_revectored))
+		goto cannot_handle;
+	intr_ptr = (unsigned long __user *) (i << 2);
+	if (get_user(segoffs, intr_ptr))
+		goto cannot_handle;
+	if ((segoffs >> 16) == BIOSSEG)
+		goto cannot_handle;
+	pushw(ssp, sp, get_vflags(regs), cannot_handle);
+	pushw(ssp, sp, regs->pt.cs, cannot_handle);
+	pushw(ssp, sp, IP(regs), cannot_handle);
+	regs->pt.cs = segoffs >> 16;
+	SP(regs) -= 6;
+	IP(regs) = segoffs & 0xffff;
+	clear_TF(regs);
+	clear_IF(regs);
+	clear_AC(regs);
+	return;
+
+cannot_handle:
+	return_to_32bit(regs, VM86_INTx + (i << 8));
+}
+
+int handle_vm86_trap(struct kernel_vm86_regs *regs, long error_code, int trapno)
+{
+	if (VMPI.is_vm86pus) {
+		if ((trapno == 3) || (trapno == 1)) {
+			KVM86->regs32->ax = VM86_TRAP + (trapno << 8);
+			/* setting this flag forces the code in entry_32.S to
+			   the path where we call save_v86_state() and change
+			   the stack pointer to KVM86->regs32 */
+			set_thread_flag(TIF_NOTIFY_RESUME);
+			return 0;
+		}
+		do_int(regs, trapno, (unsigned char __user *) (regs->pt.ss << 4), SP(regs));
+		return 0;
+	}
+	if (trapno != 1)
+		return 1; /* we let this handle by the calling routine */
+	current->thread.trap_nr = trapno;
+	current->thread.error_code = error_code;
+	force_sig(SIGTRAP, current);
+	return 0;
+}
+
+void handle_vm86_fault(struct kernel_vm86_regs *regs, long error_code)
+{
+	unsigned char opcode;
+	unsigned char __user *csp;
+	unsigned char __user *ssp;
+	unsigned short ip, sp, orig_flags;
+	int data32, pref_done;
+
+#define CHECK_IF_IN_TRAP \
+	if (VMPI.vm86dbg_active && VMPI.vm86dbg_TFpendig) \
+		newflags |= X86_EFLAGS_TF
+#define VM86_FAULT_RETURN do { \
+	if (VMPI.force_return_for_pic  && (VEFLAGS & (X86_EFLAGS_IF | X86_EFLAGS_VIF))) \
+		return_to_32bit(regs, VM86_PICRETURN); \
+	if (orig_flags & X86_EFLAGS_TF) \
+		handle_vm86_trap(regs, 0, 1); \
+	return; } while (0)
+
+	orig_flags = *(unsigned short *)&regs->pt.flags;
+
+	csp = (unsigned char __user *) (regs->pt.cs << 4);
+	ssp = (unsigned char __user *) (regs->pt.ss << 4);
+	sp = SP(regs);
+	ip = IP(regs);
+
+	data32 = 0;
+	pref_done = 0;
+	do {
+		switch (opcode = popb(csp, ip, simulate_sigsegv)) {
+		case 0x66:      /* 32-bit data */     data32 = 1; break;
+		case 0x67:      /* 32-bit address */  break;
+		case 0x2e:      /* CS */              break;
+		case 0x3e:      /* DS */              break;
+		case 0x26:      /* ES */              break;
+		case 0x36:      /* SS */              break;
+		case 0x65:      /* GS */              break;
+		case 0x64:      /* FS */              break;
+		case 0xf2:      /* repnz */       break;
+		case 0xf3:      /* rep */             break;
+		default: pref_done = 1;
+		}
+	} while (!pref_done);
+
+	switch (opcode) {
+
+	/* pushf */
+	case 0x9c:
+		if (data32) {
+			pushl(ssp, sp, get_vflags(regs), simulate_sigsegv);
+			SP(regs) -= 4;
+		} else {
+			pushw(ssp, sp, get_vflags(regs), simulate_sigsegv);
+			SP(regs) -= 2;
+		}
+		IP(regs) = ip;
+		VM86_FAULT_RETURN;
+
+	/* popf */
+	case 0x9d:
+		{
+		unsigned long newflags;
+		if (data32) {
+			newflags = popl(ssp, sp, simulate_sigsegv);
+			SP(regs) += 4;
+		} else {
+			newflags = popw(ssp, sp, simulate_sigsegv);
+			SP(regs) += 2;
+		}
+		IP(regs) = ip;
+		CHECK_IF_IN_TRAP;
+		if (data32)
+			set_vflags_long(newflags, regs);
+		else
+			set_vflags_short(newflags, regs);
+
+		VM86_FAULT_RETURN;
+		}
+
+	/* int xx */
+	case 0xcd: {
+		int intno = popb(csp, ip, simulate_sigsegv);
+		IP(regs) = ip;
+		if (VMPI.vm86dbg_active) {
+			if ((1 << (intno & 7)) & VMPI.vm86dbg_intxxtab[intno >> 3])
+				return_to_32bit(regs, VM86_INTx + (intno << 8));
+		}
+		do_int(regs, intno, ssp, sp);
+		return;
+	}
+
+	/* iret */
+	case 0xcf:
+		{
+		unsigned long newip;
+		unsigned long newcs;
+		unsigned long newflags;
+		if (data32) {
+			newip = popl(ssp, sp, simulate_sigsegv);
+			newcs = popl(ssp, sp, simulate_sigsegv);
+			newflags = popl(ssp, sp, simulate_sigsegv);
+			SP(regs) += 12;
+		} else {
+			newip = popw(ssp, sp, simulate_sigsegv);
+			newcs = popw(ssp, sp, simulate_sigsegv);
+			newflags = popw(ssp, sp, simulate_sigsegv);
+			SP(regs) += 6;
+		}
+		IP(regs) = newip;
+		regs->pt.cs = newcs;
+		CHECK_IF_IN_TRAP;
+		if (data32) {
+			set_vflags_long(newflags, regs);
+		} else {
+			set_vflags_short(newflags, regs);
+		}
+		VM86_FAULT_RETURN;
+		}
+
+	/* cli */
+	case 0xfa:
+		IP(regs) = ip;
+		clear_IF(regs);
+		VM86_FAULT_RETURN;
+
+	/* sti */
+	/*
+	 * Damn. This is incorrect: the 'sti' instruction should actually
+	 * enable interrupts after the /next/ instruction. Not good.
+	 *
+	 * Probably needs some horsing around with the TF flag. Aiee..
+	 */
+	case 0xfb:
+		IP(regs) = ip;
+		set_IF(regs);
+		VM86_FAULT_RETURN;
+
+	default:
+		return_to_32bit(regs, VM86_UNKNOWN);
+	}
+
+	return;
+
+simulate_sigsegv:
+	/* FIXME: After a long discussion with Stas we finally
+	 *        agreed, that this is wrong. Here we should
+	 *        really send a SIGSEGV to the user program.
+	 *        But how do we create the correct context? We
+	 *        are inside a general protection fault handler
+	 *        and has just returned from a page fault handler.
+	 *        The correct context for the signal handler
+	 *        should be a mixture of the two, but how do we
+	 *        get the information? [KD]
+	 */
+	return_to_32bit(regs, VM86_UNKNOWN);
+}
+
+/* ---------------- vm86 special IRQ passing stuff ----------------- */
+
+#define VM86_IRQNAME		"vm86irq"
+
+static struct vm86_irqs {
+	struct task_struct *tsk;
+	int sig;
+} vm86_irqs[16];
+
+static DEFINE_SPINLOCK(irqbits_lock);
+static int irqbits;
+
+#define ALLOWED_SIGS (1 /* 0 = don't send a signal */ \
+	| (1 << SIGUSR1) | (1 << SIGUSR2) | (1 << SIGIO)  | (1 << SIGURG) \
+	| (1 << SIGUNUSED))
+
+static irqreturn_t irq_handler(int intno, void *dev_id)
+{
+	int irq_bit;
+	unsigned long flags;
+
+	spin_lock_irqsave(&irqbits_lock, flags);
+	irq_bit = 1 << intno;
+	if ((irqbits & irq_bit) || !vm86_irqs[intno].tsk)
+		goto out;
+	irqbits |= irq_bit;
+	if (vm86_irqs[intno].sig)
+		send_sig(vm86_irqs[intno].sig, vm86_irqs[intno].tsk, 1);
+	/*
+	 * IRQ will be re-enabled when user asks for the irq (whether
+	 * polling or as a result of the signal)
+	 */
+	disable_irq_nosync(intno);
+	spin_unlock_irqrestore(&irqbits_lock, flags);
+	return IRQ_HANDLED;
+
+out:
+	spin_unlock_irqrestore(&irqbits_lock, flags);
+	return IRQ_NONE;
+}
+
+static inline void free_vm86_irq(int irqnumber)
+{
+	unsigned long flags;
+
+	free_irq(irqnumber, NULL);
+	vm86_irqs[irqnumber].tsk = NULL;
+
+	spin_lock_irqsave(&irqbits_lock, flags);
+	irqbits &= ~(1 << irqnumber);
+	spin_unlock_irqrestore(&irqbits_lock, flags);
+}
+
+void release_vm86_irqs(struct task_struct *task)
+{
+	int i;
+	for (i = FIRST_VM86_IRQ ; i <= LAST_VM86_IRQ; i++)
+	    if (vm86_irqs[i].tsk == task)
+		free_vm86_irq(i);
+}
+
+static inline int get_and_reset_irq(int irqnumber)
+{
+	int bit;
+	unsigned long flags;
+	int ret = 0;
+
+	if (invalid_vm86_irq(irqnumber)) return 0;
+	if (vm86_irqs[irqnumber].tsk != current) return 0;
+	spin_lock_irqsave(&irqbits_lock, flags);
+	bit = irqbits & (1 << irqnumber);
+	irqbits &= ~bit;
+	if (bit) {
+		enable_irq(irqnumber);
+		ret = 1;
+	}
+
+	spin_unlock_irqrestore(&irqbits_lock, flags);
+	return ret;
+}
+
+
+static int do_vm86_irq_handling(int subfunction, int irqnumber)
+{
+	int ret;
+	switch (subfunction) {
+		case VM86_GET_AND_RESET_IRQ: {
+			return get_and_reset_irq(irqnumber);
+		}
+		case VM86_GET_IRQ_BITS: {
+			return irqbits;
+		}
+		case VM86_REQUEST_IRQ: {
+			int sig = irqnumber >> 8;
+			int irq = irqnumber & 255;
+			if (!capable(CAP_SYS_ADMIN)) return -EPERM;
+			if (!((1 << sig) & ALLOWED_SIGS)) return -EPERM;
+			if (invalid_vm86_irq(irq)) return -EPERM;
+			if (vm86_irqs[irq].tsk) return -EPERM;
+			ret = request_irq(irq, &irq_handler, 0, VM86_IRQNAME, NULL);
+			if (ret) return ret;
+			vm86_irqs[irq].sig = sig;
+			vm86_irqs[irq].tsk = current;
+			return irq;
+		}
+		case  VM86_FREE_IRQ: {
+			if (invalid_vm86_irq(irqnumber)) return -EPERM;
+			if (!vm86_irqs[irqnumber].tsk) return 0;
+			if (vm86_irqs[irqnumber].tsk != current) return -EPERM;
+			free_vm86_irq(irqnumber);
+			return 0;
+		}
+	}
+	return -EINVAL;
+}
+