mirror of https://github.com/mkerrisk/man-pages
100 lines
3.2 KiB
Groff
100 lines
3.2 KiB
Groff
.\" Hey Emacs! This file is -*- nroff -*- source.
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.\"
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.\" Copyright 1993 Rickard E. Faith (faith@cs.unc.edu)
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.\" Portions extracted from linux/kernel/ioport.c (no copyright notice).
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\"
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.\" Modified Tue Aug 1 16:47 1995 by Jochen Karrer
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.\" <cip307@cip.physik.uni-wuerzburg.de>
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.\" Modified Tue Oct 22 08:11:14 EDT 1996 by Eric S. Raymond <esr@thyrsus.com>
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.\" Modified Fri Nov 27 14:50:36 CET 1998 by Andries Brouwer <aeb@cwi.nl>
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.\" Modified, 27 May 2004, Michael Kerrisk <mtk-manpages@gmx.net>
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.\" Added notes on capability requirements
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.\"
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.TH IOPL 2 2004-05-27 "Linux 2.6.6" "Linux Programmer's Manual"
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.SH NAME
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iopl \- change I/O privilege level
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.SH SYNOPSIS
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.B #include <sys/io.h>
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.sp
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.BI "int iopl(int " level );
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.SH DESCRIPTION
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.BR iopl ()
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changes the I/O privilege level of the current process, as specified in
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.IR level .
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This call is necessary to allow 8514-compatible X servers to run under
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Linux.
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Since these X servers require access to all 65536 I/O ports, the
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.BR ioperm ()
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call is not sufficient.
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In addition to granting unrestricted I/O port access, running at a higher
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I/O privilege level also allows the process to disable interrupts.
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This will probably crash the system, and is not recommended.
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Permissions are inherited by
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.BR fork ()
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and
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.BR exec ().
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The I/O privilege level for a normal process is 0.
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This call is mostly for the i386 architecture.
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On many other architectures it does not exist or will always
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return an error.
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.SH "RETURN VALUE"
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On success, zero is returned.
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On error, \-1 is returned, and
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.I errno
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is set appropriately.
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.SH ERRORS
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.TP
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.B EINVAL
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.I level
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is greater than 3.
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.TP
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.B ENOSYS
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This call is unimplemented.
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.TP
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.B EPERM
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The calling process has insufficient privilege to call
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.BR iopl ();
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the
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.B CAP_SYS_RAWIO
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capability is required.
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.SH "CONFORMING TO"
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\fBiopl\fP() is Linux specific and should not be used in processes
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intended to be portable.
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.SH NOTES
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Libc5 treats it as a system call and has a prototype in
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.IR <unistd.h> .
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Glibc1 does not have a prototype.
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Glibc2 has a prototype both in
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.I <sys/io.h>
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and in
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.IR <sys/perm.h> .
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Avoid the latter, it is available on i386 only.
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.SH "SEE ALSO"
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.BR ioperm (2),
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.BR capabilities (7)
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