i386: move kernel

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 843 insertions, 0 deletions

diff --git a/arch/x86/kernel/vm86_32.c b/arch/x86/kernel/vm86_32.c
new file mode 100644
index 000000000000..f2dcd1d27c0a
--- /dev/null
+++ b/arch/x86/kernel/vm86_32.c
@@ -0,0 +1,843 @@
+/*
+ *  linux/kernel/vm86.c
+ *
+ *  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>
+ *
+ */
+
+#include <linux/capability.h>
+#include <linux/errno.h>
+#include <linux/interrupt.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.eax))[0])
+#define AH(regs)        (((unsigned char *)&((regs)->pt.eax))[1])
+#define IP(regs)        (*(unsigned short *)&((regs)->pt.eip))
+#define SP(regs)        (*(unsigned short *)&((regs)->pt.esp))
+
+/*
+ * 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 xgs, 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_eax));
+        ret += copy_to_user(&user->orig_eax, &regs->pt.orig_eax,
+                            sizeof(struct kernel_vm86_regs) -
+                            offsetof(struct kernel_vm86_regs, pt.orig_eax));
+
+        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 eax-xfs inclusive */
+        ret += copy_from_user(regs, user, offsetof(struct kernel_vm86_regs, pt.orig_eax));
+        /* copy orig_eax-__gsh+extra */
+        ret += copy_from_user(&regs->pt.orig_eax, &user->orig_eax,
+                              sizeof(struct kernel_vm86_regs) -
+                              offsetof(struct kernel_vm86_regs, pt.orig_eax) +
+                              extra);
+        return ret;
+}
+
+struct pt_regs * FASTCALL(save_v86_state(struct kernel_vm86_regs * regs));
+struct pt_regs * fastcall 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) {
+                printk("no vm86_info: BAD\n");
+                do_exit(SIGSEGV);
+        }
+        set_flags(regs->pt.eflags, VEFLAGS, VIF_MASK | 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) {
+                printk("vm86: could not access userspace vm86_info\n");
+                do_exit(SIGSEGV);
+        }
+
+        tss = &per_cpu(init_tss, get_cpu());
+        current->thread.esp0 = current->thread.saved_esp0;
+        current->thread.sysenter_cs = __KERNEL_CS;
+        load_esp0(tss, &current->thread);
+        current->thread.saved_esp0 = 0;
+        put_cpu();
+
+        ret = KVM86->regs32;
+
+        ret->xfs = current->thread.saved_fs;
+        loadsegment(gs, 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;
+
+        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);
+        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:
+        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);
+
+asmlinkage int sys_vm86old(struct pt_regs regs)
+{
+        struct vm86_struct __user *v86 = (struct vm86_struct __user *)regs.ebx;
+        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, ret = -EPERM;
+
+        tsk = current;
+        if (tsk->thread.saved_esp0)
+                goto out;
+        tmp = copy_vm86_regs_from_user(&info.regs, &v86->regs,
+                                       offsetof(struct kernel_vm86_struct, vm86plus) -
+                                       sizeof(info.regs));
+        ret = -EFAULT;
+        if (tmp)
+                goto out;
+        memset(&info.vm86plus, 0, (int)&info.regs32 - (int)&info.vm86plus);
+        info.regs32 = &regs;
+        tsk->thread.vm86_info = v86;
+        do_sys_vm86(&info, tsk);
+        ret = 0;        /* we never return here */
+out:
+        return ret;
+}
+
+
+asmlinkage int sys_vm86(struct pt_regs regs)
+{
+        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, ret;
+        struct vm86plus_struct __user *v86;
+
+        tsk = current;
+        switch (regs.ebx) {
+                case VM86_REQUEST_IRQ:
+                case VM86_FREE_IRQ:
+                case VM86_GET_IRQ_BITS:
+                case VM86_GET_AND_RESET_IRQ:
+                        ret = do_vm86_irq_handling(regs.ebx, (int)regs.ecx);
+                        goto out;
+                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.
+                         */
+                        ret = 0;
+                        goto out;
+        }
+
+        /* we come here only for functions VM86_ENTER, VM86_ENTER_NO_BYPASS */
+        ret = -EPERM;
+        if (tsk->thread.saved_esp0)
+                goto out;
+        v86 = (struct vm86plus_struct __user *)regs.ecx;
+        tmp = copy_vm86_regs_from_user(&info.regs, &v86->regs,
+                                       offsetof(struct kernel_vm86_struct, regs32) -
+                                       sizeof(info.regs));
+        ret = -EFAULT;
+        if (tmp)
+                goto out;
+        info.regs32 = &regs;
+        info.vm86plus.is_vm86pus = 1;
+        tsk->thread.vm86_info = (struct vm86_struct __user *)v86;
+        do_sys_vm86(&info, tsk);
+        ret = 0;        /* we never return here */
+out:
+        return ret;
+}
+
+
+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.xds = 0;
+        info->regs.pt.xes = 0;
+        info->regs.pt.xfs = 0;
+
+/* we are clearing gs later just before "jmp resume_userspace",
+ * because it is not saved/restored.
+ */
+
+/*
+ * The eflags 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.eflags;
+        info->regs.pt.eflags &= SAFE_MASK;
+        info->regs.pt.eflags |= info->regs32->eflags & ~SAFE_MASK;
+        info->regs.pt.eflags |= VM_MASK;
+
+        switch (info->cpu_type) {
+                case CPU_286:
+                        tsk->thread.v86mask = 0;
+                        break;
+                case CPU_386:
+                        tsk->thread.v86mask = NT_MASK | IOPL_MASK;
+                        break;
+                case CPU_486:
+                        tsk->thread.v86mask = AC_MASK | NT_MASK | IOPL_MASK;
+                        break;
+                default:
+                        tsk->thread.v86mask = ID_MASK | AC_MASK | NT_MASK | IOPL_MASK;
+                        break;
+        }
+
+/*
+ * Save old state, set default return value (%eax) to 0
+ */
+        info->regs32->eax = 0;
+        tsk->thread.saved_esp0 = tsk->thread.esp0;
+        tsk->thread.saved_fs = info->regs32->xfs;
+        savesegment(gs, tsk->thread.saved_gs);
+
+        tss = &per_cpu(init_tss, get_cpu());
+        tsk->thread.esp0 = (unsigned long) &info->VM86_TSS_ESP0;
+        if (cpu_has_sep)
+                tsk->thread.sysenter_cs = 0;
+        load_esp0(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 */
+        if (unlikely(current->audit_context))
+                audit_syscall_exit(AUDITSC_RESULT(0), 0);
+
+        __asm__ __volatile__(
+                "movl %0,%%esp\n\t"
+                "movl %1,%%ebp\n\t"
+                "mov  %2, %%gs\n\t"
+                "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->eax = 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 |= VIF_MASK;
+        if (VEFLAGS & VIP_MASK)
+                return_to_32bit(regs, VM86_STI);
+}
+
+static inline void clear_IF(struct kernel_vm86_regs * regs)
+{
+        VEFLAGS &= ~VIF_MASK;
+}
+
+static inline void clear_TF(struct kernel_vm86_regs * regs)
+{
+        regs->pt.eflags &= ~TF_MASK;
+}
+
+static inline void clear_AC(struct kernel_vm86_regs * regs)
+{
+        regs->pt.eflags &= ~AC_MASK;
+}
+
+/* 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 interrups 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 eflags, struct kernel_vm86_regs * regs)
+{
+        set_flags(VEFLAGS, eflags, current->thread.v86mask);
+        set_flags(regs->pt.eflags, eflags, SAFE_MASK);
+        if (eflags & IF_MASK)
+                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.eflags, flags, SAFE_MASK);
+        if (flags & IF_MASK)
+                set_IF(regs);
+        else
+                clear_IF(regs);
+}
+
+static inline unsigned long get_vflags(struct kernel_vm86_regs * regs)
+{
+        unsigned long flags = regs->pt.eflags & RETURN_MASK;
+
+        if (VEFLAGS & VIF_MASK)
+                flags |= IF_MASK;
+        flags |= IOPL_MASK;
+        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.xcs == 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.xcs, cannot_handle);
+        pushw(ssp, sp, IP(regs), cannot_handle);
+        regs->pt.xcs = 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) )
+                        return_to_32bit(regs, VM86_TRAP + (trapno << 8));
+                do_int(regs, trapno, (unsigned char __user *) (regs->pt.xss << 4), SP(regs));
+                return 0;
+        }
+        if (trapno !=1)
+                return 1; /* we let this handle by the calling routine */
+        if (current->ptrace & PT_PTRACED) {
+                unsigned long flags;
+                spin_lock_irqsave(&current->sighand->siglock, flags);
+                sigdelset(&current->blocked, SIGTRAP);
+                recalc_sigpending();
+                spin_unlock_irqrestore(&current->sighand->siglock, flags);
+        }
+        send_sig(SIGTRAP, current, 1);
+        current->thread.trap_no = trapno;
+        current->thread.error_code = error_code;
+        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 |= TF_MASK
+#define VM86_FAULT_RETURN do { \
+        if (VMPI.force_return_for_pic  && (VEFLAGS & (IF_MASK | VIF_MASK))) \
+                return_to_32bit(regs, VM86_PICRETURN); \
+        if (orig_flags & TF_MASK) \
+                handle_vm86_trap(regs, 0, 1); \
+        return; } while (0)
+
+        orig_flags = *(unsigned short *)&regs->pt.eflags;
+
+        csp = (unsigned char __user *) (regs->pt.xcs << 4);
+        ssp = (unsigned char __user *) (regs->pt.xss << 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.xcs = 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;
+}
+