man2/vm86.2

   1 .\" Copyright 1993 Rickard E. Faith (faith@cs.unc.edu)
   2 .\" Copyright 1997 Andries E. Brouwer (aeb@cwi.nl)
   3 .\"
   4 .\" SPDX-License-Identifier: Linux-man-pages-copyleft
   5 .\"
   6 .TH VM86 2 2021-03-22 "Linux" "Linux Programmer's Manual"
   7 .SH NAME
   8 vm86old, vm86 \- enter virtual 8086 mode
   9 .SH LIBRARY
  10 Standard C library
  11 .RI ( libc ", " \-lc )
  12 .SH SYNOPSIS
  13 .nf
  14 .B #include <sys/vm86.h>
  15 .PP
  16 .BI "int vm86old(struct vm86_struct *" info );
  17 .BI "int vm86(unsigned long " fn ", struct vm86plus_struct *" v86 );
  18 .fi
  19 .SH DESCRIPTION
  20 The system call
  21 .BR vm86 ()
  22 was introduced in Linux 0.97p2.
  23 In Linux 2.1.15 and 2.0.28, it was renamed to
  24 .BR vm86old (),
  25 and a new
  26 .BR vm86 ()
  27 was introduced.
  28 The definition of
  29 .IR "struct vm86_struct"
  30 was changed
  31 in 1.1.8 and 1.1.9.
  32 .PP
  33 These calls cause the process to enter VM86 mode (virtual-8086 in Intel
  34 literature), and are used by
  35 .BR dosemu .
  36 .PP
  37 VM86 mode is an emulation of real mode within a protected mode task.
  38 .SH RETURN VALUE
  39 On success, zero is returned.
  40 On error, \-1 is returned, and
  41 .I errno
  42 is set to indicate the error.
  43 .SH ERRORS
  44 .TP
  45 .B EFAULT
  46 This return value is specific to i386 and indicates a problem with getting
  47 user-space data.
  48 .TP
  49 .B ENOSYS
  50 This return value indicates the call is not implemented on the present
  51 architecture.
  52 .TP
  53 .B EPERM
  54 Saved kernel stack exists.
  55 (This is a kernel sanity check; the saved
  56 stack should exist only within vm86 mode itself.)
  57 .SH CONFORMING TO
  58 This call is specific to Linux on 32-bit Intel processors,
  59 and should not be used in programs intended to be portable.