.\" Copyright 1993 Rickard E. Faith (faith@cs.unc.edu)

.\" Copyright 1997 Andries E. Brouwer (aeb@cwi.nl)

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.TH VM86 2 2009-02-20 "Linux" "Linux Programmer's Manual"

.SH NAME

vm86old, vm86 \- enter virtual 8086 mode

.SH SYNOPSIS

.B #include <sys/vm86.h>

.PP

.BI "int vm86old(struct vm86_struct *" info );

.PP

.BI "int vm86(unsigned long " fn ", struct vm86plus_struct *" v86 );

.SH DESCRIPTION

The system call

.BR vm86 ()

was introduced in Linux 0.97p2.

In Linux 2.1.15 and 2.0.28, it was renamed to

.BR vm86old (),

and a new

.BR vm86 ()

was introduced.

The definition of

.IR "struct vm86_struct"

was changed

in 1.1.8 and 1.1.9.

.PP

These calls cause the process to enter VM86 mode (virtual-8086 in Intel

literature), and are used by

.BR dosemu .

.PP

VM86 mode is an emulation of real mode within a protected mode task.

.SH RETURN VALUE

On success, zero is returned.

On error, \-1 is returned, and

.I errno

is set appropriately.

.SH ERRORS

.TP

.B EFAULT

This return value is specific to i386 and indicates a problem with getting

user-space data.

.TP

.B ENOSYS

This return value indicates the call is not implemented on the present

architecture.

.TP

.B EPERM

Saved kernel stack exists.

(This is a kernel sanity check; the saved

stack should exist only within vm86 mode itself.)

.SH CONFORMING TO

This call is specific to Linux on 32-bit Intel processors,

and should not be used in programs intended to be portable.

.SH COLOPHON

This page is part of release 4.15 of the Linux

.I man-pages

project.

A description of the project,

information about reporting bugs,

and the latest version of this page,

can be found at

\%https://www.kernel.org/doc/man\-pages/.