Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 832 insertions, 0 deletions

diff --git a/arch/x86/kernel/vm86_32.c b/arch/x86/kernel/vm86_32.c
new file mode 100644
index 0000000000..e9e803a4d4
--- /dev/null
+++ b/arch/x86/kernel/vm86_32.c
@@ -0,0 +1,832 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  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/sched/task_stack.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 <linux/slab.h>
+#include <linux/security.h>
+
+#include <linux/uaccess.h>
+#include <asm/io.h>
+#include <asm/tlbflush.h>
+#include <asm/irq.h>
+#include <asm/traps.h>
+#include <asm/vm86.h>
+#include <asm/switch_to.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.
+ */
+
+
+/*
+ * 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.vm86->veflags))
+#define VEFLAGS	(current->thread.vm86->veflags)
+
+#define set_flags(X, new, mask) \
+((X) = ((X) & ~(mask)) | ((new) & (mask)))
+
+#define SAFE_MASK	(0xDD5)
+#define RETURN_MASK	(0xDFF)
+
+void save_v86_state(struct kernel_vm86_regs *regs, int retval)
+{
+	struct task_struct *tsk = current;
+	struct vm86plus_struct __user *user;
+	struct vm86 *vm86 = current->thread.vm86;
+
+	/*
+	 * 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();
+
+	BUG_ON(!vm86);
+
+	set_flags(regs->pt.flags, VEFLAGS, X86_EFLAGS_VIF | vm86->veflags_mask);
+	user = vm86->user_vm86;
+
+	if (!user_access_begin(user, vm86->vm86plus.is_vm86pus ?
+		       sizeof(struct vm86plus_struct) :
+		       sizeof(struct vm86_struct)))
+		goto Efault;
+
+	unsafe_put_user(regs->pt.bx, &user->regs.ebx, Efault_end);
+	unsafe_put_user(regs->pt.cx, &user->regs.ecx, Efault_end);
+	unsafe_put_user(regs->pt.dx, &user->regs.edx, Efault_end);
+	unsafe_put_user(regs->pt.si, &user->regs.esi, Efault_end);
+	unsafe_put_user(regs->pt.di, &user->regs.edi, Efault_end);
+	unsafe_put_user(regs->pt.bp, &user->regs.ebp, Efault_end);
+	unsafe_put_user(regs->pt.ax, &user->regs.eax, Efault_end);
+	unsafe_put_user(regs->pt.ip, &user->regs.eip, Efault_end);
+	unsafe_put_user(regs->pt.cs, &user->regs.cs, Efault_end);
+	unsafe_put_user(regs->pt.flags, &user->regs.eflags, Efault_end);
+	unsafe_put_user(regs->pt.sp, &user->regs.esp, Efault_end);
+	unsafe_put_user(regs->pt.ss, &user->regs.ss, Efault_end);
+	unsafe_put_user(regs->es, &user->regs.es, Efault_end);
+	unsafe_put_user(regs->ds, &user->regs.ds, Efault_end);
+	unsafe_put_user(regs->fs, &user->regs.fs, Efault_end);
+	unsafe_put_user(regs->gs, &user->regs.gs, Efault_end);
+
+	/*
+	 * Don't write screen_bitmap in case some user had a value there
+	 * and expected it to remain unchanged.
+	 */
+
+	user_access_end();
+
+exit_vm86:
+	preempt_disable();
+	tsk->thread.sp0 = vm86->saved_sp0;
+	tsk->thread.sysenter_cs = __KERNEL_CS;
+	update_task_stack(tsk);
+	refresh_sysenter_cs(&tsk->thread);
+	vm86->saved_sp0 = 0;
+	preempt_enable();
+
+	memcpy(&regs->pt, &vm86->regs32, sizeof(struct pt_regs));
+
+	loadsegment(gs, vm86->regs32.gs);
+
+	regs->pt.ax = retval;
+	return;
+
+Efault_end:
+	user_access_end();
+Efault:
+	pr_alert("could not access userspace vm86 info\n");
+	force_exit_sig(SIGSEGV);
+	goto exit_vm86;
+}
+
+static int do_vm86_irq_handling(int subfunction, int irqnumber);
+static long do_sys_vm86(struct vm86plus_struct __user *user_vm86, bool plus);
+
+SYSCALL_DEFINE1(vm86old, struct vm86_struct __user *, user_vm86)
+{
+	return do_sys_vm86((struct vm86plus_struct __user *) user_vm86, false);
+}
+
+
+SYSCALL_DEFINE2(vm86, unsigned long, cmd, unsigned long, arg)
+{
+	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 */
+	return do_sys_vm86((struct vm86plus_struct __user *) arg, true);
+}
+
+
+static long do_sys_vm86(struct vm86plus_struct __user *user_vm86, bool plus)
+{
+	struct task_struct *tsk = current;
+	struct vm86 *vm86 = tsk->thread.vm86;
+	struct kernel_vm86_regs vm86regs;
+	struct pt_regs *regs = current_pt_regs();
+	unsigned long err = 0;
+	struct vm86_struct v;
+
+	err = security_mmap_addr(0);
+	if (err) {
+		/*
+		 * vm86 cannot virtualize the address space, so vm86 users
+		 * need to manage the low 1MB themselves using mmap.  Given
+		 * that BIOS places important data in the first page, vm86
+		 * is essentially useless if mmap_min_addr != 0.  DOSEMU,
+		 * for example, won't even bother trying to use vm86 if it
+		 * can't map a page at virtual address 0.
+		 *
+		 * To reduce the available kernel attack surface, simply
+		 * disallow vm86(old) for users who cannot mmap at va 0.
+		 *
+		 * The implementation of security_mmap_addr will allow
+		 * suitably privileged users to map va 0 even if
+		 * vm.mmap_min_addr is set above 0, and we want this
+		 * behavior for vm86 as well, as it ensures that legacy
+		 * tools like vbetool will not fail just because of
+		 * vm.mmap_min_addr.
+		 */
+		pr_info_once("Denied a call to vm86(old) from %s[%d] (uid: %d).  Set the vm.mmap_min_addr sysctl to 0 and/or adjust LSM mmap_min_addr policy to enable vm86 if you are using a vm86-based DOS emulator.\n",
+			     current->comm, task_pid_nr(current),
+			     from_kuid_munged(&init_user_ns, current_uid()));
+		return -EPERM;
+	}
+
+	if (!vm86) {
+		if (!(vm86 = kzalloc(sizeof(*vm86), GFP_KERNEL)))
+			return -ENOMEM;
+		tsk->thread.vm86 = vm86;
+	}
+	if (vm86->saved_sp0)
+		return -EPERM;
+
+	if (copy_from_user(&v, user_vm86,
+			offsetof(struct vm86_struct, int_revectored)))
+		return -EFAULT;
+
+
+	/* VM86_SCREEN_BITMAP had numerous bugs and appears to have no users. */
+	if (v.flags & VM86_SCREEN_BITMAP) {
+		char comm[TASK_COMM_LEN];
+
+		pr_info_once("vm86: '%s' uses VM86_SCREEN_BITMAP, which is no longer supported\n", get_task_comm(comm, current));
+		return -EINVAL;
+	}
+
+	memset(&vm86regs, 0, sizeof(vm86regs));
+
+	vm86regs.pt.bx = v.regs.ebx;
+	vm86regs.pt.cx = v.regs.ecx;
+	vm86regs.pt.dx = v.regs.edx;
+	vm86regs.pt.si = v.regs.esi;
+	vm86regs.pt.di = v.regs.edi;
+	vm86regs.pt.bp = v.regs.ebp;
+	vm86regs.pt.ax = v.regs.eax;
+	vm86regs.pt.ip = v.regs.eip;
+	vm86regs.pt.cs = v.regs.cs;
+	vm86regs.pt.flags = v.regs.eflags;
+	vm86regs.pt.sp = v.regs.esp;
+	vm86regs.pt.ss = v.regs.ss;
+	vm86regs.es = v.regs.es;
+	vm86regs.ds = v.regs.ds;
+	vm86regs.fs = v.regs.fs;
+	vm86regs.gs = v.regs.gs;
+
+	vm86->flags = v.flags;
+	vm86->cpu_type = v.cpu_type;
+
+	if (copy_from_user(&vm86->int_revectored,
+			   &user_vm86->int_revectored,
+			   sizeof(struct revectored_struct)))
+		return -EFAULT;
+	if (copy_from_user(&vm86->int21_revectored,
+			   &user_vm86->int21_revectored,
+			   sizeof(struct revectored_struct)))
+		return -EFAULT;
+	if (plus) {
+		if (copy_from_user(&vm86->vm86plus, &user_vm86->vm86plus,
+				   sizeof(struct vm86plus_info_struct)))
+			return -EFAULT;
+		vm86->vm86plus.is_vm86pus = 1;
+	} else
+		memset(&vm86->vm86plus, 0,
+		       sizeof(struct vm86plus_info_struct));
+
+	memcpy(&vm86->regs32, regs, sizeof(struct pt_regs));
+	vm86->user_vm86 = user_vm86;
+
+/*
+ * 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 = vm86regs.pt.flags;
+	vm86regs.pt.flags &= SAFE_MASK;
+	vm86regs.pt.flags |= regs->flags & ~SAFE_MASK;
+	vm86regs.pt.flags |= X86_VM_MASK;
+
+	vm86regs.pt.orig_ax = regs->orig_ax;
+
+	switch (vm86->cpu_type) {
+	case CPU_286:
+		vm86->veflags_mask = 0;
+		break;
+	case CPU_386:
+		vm86->veflags_mask = X86_EFLAGS_NT | X86_EFLAGS_IOPL;
+		break;
+	case CPU_486:
+		vm86->veflags_mask = X86_EFLAGS_AC | X86_EFLAGS_NT | X86_EFLAGS_IOPL;
+		break;
+	default:
+		vm86->veflags_mask = X86_EFLAGS_ID | X86_EFLAGS_AC | X86_EFLAGS_NT | X86_EFLAGS_IOPL;
+		break;
+	}
+
+/*
+ * Save old state
+ */
+	vm86->saved_sp0 = tsk->thread.sp0;
+	savesegment(gs, vm86->regs32.gs);
+
+	/* make room for real-mode segments */
+	preempt_disable();
+	tsk->thread.sp0 += 16;
+
+	if (boot_cpu_has(X86_FEATURE_SEP)) {
+		tsk->thread.sysenter_cs = 0;
+		refresh_sysenter_cs(&tsk->thread);
+	}
+
+	update_task_stack(tsk);
+	preempt_enable();
+
+	memcpy((struct kernel_vm86_regs *)regs, &vm86regs, sizeof(vm86regs));
+	return regs->ax;
+}
+
+static inline void set_IF(struct kernel_vm86_regs *regs)
+{
+	VEFLAGS |= X86_EFLAGS_VIF;
+}
+
+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.vm86->veflags_mask);
+	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.vm86->veflags_mask);
+	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.vm86->veflags_mask);
+}
+
+static inline int is_revectored(int nr, struct revectored_struct *bitmap)
+{
+	return test_bit(nr, bitmap->__map);
+}
+
+#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;
+	struct vm86 *vm86 = current->thread.vm86;
+
+	if (regs->pt.cs == BIOSSEG)
+		goto cannot_handle;
+	if (is_revectored(i, &vm86->int_revectored))
+		goto cannot_handle;
+	if (i == 0x21 && is_revectored(AH(regs), &vm86->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:
+	save_v86_state(regs, VM86_INTx + (i << 8));
+}
+
+int handle_vm86_trap(struct kernel_vm86_regs *regs, long error_code, int trapno)
+{
+	struct vm86 *vm86 = current->thread.vm86;
+
+	if (vm86->vm86plus.is_vm86pus) {
+		if ((trapno == 3) || (trapno == 1)) {
+			save_v86_state(regs, VM86_TRAP + (trapno << 8));
+			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);
+	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;
+	struct vm86plus_info_struct *vmpi = &current->thread.vm86->vm86plus;
+
+#define CHECK_IF_IN_TRAP \
+	if (vmpi->vm86dbg_active && vmpi->vm86dbg_TFpendig) \
+		newflags |= X86_EFLAGS_TF
+
+	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;
+		goto 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);
+
+		goto check_vip;
+		}
+
+	/* 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]) {
+				save_v86_state(regs, VM86_INTx + (intno << 8));
+				return;
+			}
+		}
+		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);
+		}
+		goto check_vip;
+		}
+
+	/* cli */
+	case 0xfa:
+		IP(regs) = ip;
+		clear_IF(regs);
+		goto 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);
+		goto check_vip;
+
+	default:
+		save_v86_state(regs, VM86_UNKNOWN);
+	}
+
+	return;
+
+check_vip:
+	if ((VEFLAGS & (X86_EFLAGS_VIP | X86_EFLAGS_VIF)) ==
+	    (X86_EFLAGS_VIP | X86_EFLAGS_VIF)) {
+		save_v86_state(regs, VM86_STI);
+		return;
+	}
+
+vm86_fault_return:
+	if (vmpi->force_return_for_pic  && (VEFLAGS & (X86_EFLAGS_IF | X86_EFLAGS_VIF))) {
+		save_v86_state(regs, VM86_PICRETURN);
+		return;
+	}
+	if (orig_flags & X86_EFLAGS_TF)
+		handle_vm86_trap(regs, 0, X86_TRAP_DB);
+	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]
+	 */
+	save_v86_state(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;
+}
+