.\" $OpenBSD: i386_vm86.2,v 1.12 2008/06/26 05:42:04 ray Exp $ .\" $NetBSD: i386_vm86.2,v 1.1 1996/02/21 00:21:52 jtk Exp $ .\" .\" Copyright (c) 1996 The NetBSD Foundation, Inc. .\" All rights reserved. .\" .\" This code is derived from software contributed to The NetBSD Foundation .\" by John Kohl. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS .\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED .\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR .\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE .\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR .\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF .\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS .\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN .\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE .\" POSSIBILITY OF SUCH DAMAGE. .\" .\" from: @(#)fork.2 6.5 (Berkeley) 3/10/91 .\" .Dd $Mdocdate: June 26 2008 $ .Dt I386_VM86 2 i386 .Os .Sh NAME .Nm i386_vm86 .Nd set virtual 8086 processor registers and mode .Sh SYNOPSIS .Fd #include .Fd #include .Fd #include .Fd #include .Fd #include .Ft int .Fn i386_vm86 "struct vm86_struct *vmcp" .Sh DESCRIPTION .Fn i386_vm86 will set the process into virtual 8086 mode using the registers and selectors specified by the context pointed to by .Ar vmcp . The processor registers are set from .Ar vmcp->substr.regs , and the emulated processor type from .Ar vmcp->substr.ss_cpu_type . .Pp The kernel keeps a pointer to the context, and uses the tables stored at .Ar vmcp->int_byuser and .Ar vmcp->int21_byuser for fast virtual interrupt handling. If the .Ar n Ns Li th bit is clear in the first of these arrays, then the kernel may directly emulate the real-mode x86 INT .Ar n instruction handling. If the .Ar n Ns Li th bit is set, then the process is delivered a signal when an INT instruction is executed. .Pp Since MS-DOS puts many DOS functions onto interrupt 21, it is handled specially: the .Ar k Ns Li th bit in the .Ar vmcp->int21_byuser array is checked when INT .Ar 21 is requested and the .Ar ah register is .Ar k . .Pp .Sy Note: Code using the .Fn i386_vm86 function must be compiled using .Cm -li386 . .Sh RETURN VALUES This routine does not normally return: 32-bit mode will be restored by the delivery of a signal to the process. In case of an error in setting the VM86 mode, a value of \-1 is returned and the global variable .Va errno is set to indicate the error. .Sh ERRORS .Fn i386_vm86 will fail if: .Bl -tag -width [EINVAL] .It Bq Er EFAULT The state at .Ar vmcp was not readable to the user process. .El .Sh REFERENCES .Rs .%A Intel .%T i386 Microprocessor Programmer's Reference Manual .Re