107 lines
3.7 KiB
Groff
107 lines
3.7 KiB
Groff
.\" $NetBSD: i386_vm86.2,v 1.6 1999/07/02 15:14:07 simonb Exp $
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.\"
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.\" Copyright (c) 1996 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by John Kohl.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the NetBSD
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.\" Foundation, Inc. and its contributors.
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.\" 4. Neither the name of The NetBSD Foundation nor the names of its
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.\" contributors may be used to endorse or promote products derived
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.\" from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" from: @(#)fork.2 6.5 (Berkeley) 3/10/91
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.\"
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.Dd February 20, 1996
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.Dt I386_VM86 2
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.Os
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.Sh NAME
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.Nm i386_vm86
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.Nd set virtual 8086 processor registers and mode
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.Sh LIBRARY
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.Lb libi386
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.Sh SYNOPSIS
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.Fd #include <sys/types.h>
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.Fd #include <signal.h>
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.Fd #include <machine/segments.h>
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.Fd #include <machine/sysarch.h>
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.Fd #include <machine/vm86.h>
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.Ft int
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.Fn i386_vm86 "struct vm86_struct *vmcp"
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.Sh DESCRIPTION
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.Fn i386_vm86
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will set the process into virtual 8086 mode using the registers and
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selectors specified by the context pointed to by
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.Ar vmcp .
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The processor registers are set from
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.Ar vmcp->substr.regs ,
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and the emulated processor type from
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.Ar vmcp->substr.ss_cpu_type .
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.Pp
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The kernel keeps a pointer to the context, and uses the tables stored at
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.Ar vmcp->int_byuser
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and
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.Ar vmcp->int21_byuser
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for fast virtual interrupt handling. If the
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.Ar n th
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bit is clear in the first of
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these arrays, then the kernel may directly emulate the real-mode x86 INT
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.Ar n
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instruction handling. If the
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.Ar n
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th bit is set, then the process is
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delivered a signal when an INT instruction is executed.
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.Pp
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Since MS-DOS puts many DOS functions onto interrupt 21, it is handled
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specially: the
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.Ar k
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th bit in the
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.Ar vmcp->int21_byuser
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array is checked when INT
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.Ar 21
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is requested and the
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.Ar ah
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register is
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.Ar k .
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.Sh RETURN VALUES
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This routine does not normally return: 32-bit mode will be restored by
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the delivery of a signal to the process. In case of an error in setting
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the VM86 mode, a value of -1 is returned and the global variable
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.Va errno
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is set to indicate the error.
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.Sh ERRORS
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.Fn i386_vm86
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will fail if:
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.Bl -tag -width [EINVAL]
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.It Bq Er EFAULT
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The state at
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.Ar vmcp
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was not readable to the user process.
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.El
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.Sh REFERENCES
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i386 Microprocessor Programmer's Reference Manual, Intel
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