.\" Hey Emacs! This file is -*- nroff -*- source.
.\"
.\" Copyright (c) 1993 Michael Haardt
.\" (michael@moria.de)
.\" Fri Apr  2 11:32:09 MET DST 1993
.\"
.\" This is free documentation; you can redistribute it and/or
.\" modify it under the terms of the GNU General Public License as
.\" published by the Free Software Foundation; either version 2 of
.\" the License, or (at your option) any later version.
.\"
.\" The GNU General Public License's references to "object code"
.\" and "executables" are to be interpreted as the output of any
.\" document formatting or typesetting system, including
.\" intermediate and printed output.
.\"
.\" This manual is distributed in the hope that it will be useful,
.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
.\" GNU General Public License for more details.
.\"
.\" You should have received a copy of the GNU General Public
.\" License along with this manual; if not, write to the Free
.\" Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111,
.\" USA.
.\"
.\" Modified Sat Jul 24 15:12:05 1993 by Rik Faith <faith@cs.unc.edu>
.\" Modified Tue Aug  1 16:27    1995 by Jochen Karrer
.\"                              <cip307@cip.physik.uni-wuerzburg.de>
.\" Modified Tue Oct 22 08:11:14 EDT 1996 by Eric S. Raymond <esr@thyrsus.com>
.\" Modified Mon Feb 15 17:28:41 CET 1999 by Andries E. Brouwer <aeb@cwi.nl>
.\" Modified, 27 May 2004, Michael Kerrisk <mtk.manpages@gmail.com>
.\"     Added notes on capability requirements
.\"
.TH IOPERM 2 2007-06-15 "Linux" "Linux Programmer's Manual"
.SH NAME
ioperm \- set port input/output permissions
.SH SYNOPSIS
.B #include <unistd.h>
/* for libc5 */
.br
.B #include <sys/io.h>
/* for glibc */
.sp
.BI "int ioperm(unsigned long " from ", unsigned long " num ", int " turn_on );
.SH DESCRIPTION
.BR ioperm ()
sets the port access permission bits for the calling process for
\fInum\fP bytes starting from port address \fIfrom\fP to the value
\fIturn_on\fP.
If \fIturn_on\fP is nonzero, the calling process must be privileged
.RB ( CAP_SYS_RAWIO ).

.\" FIXME is the following ("Only the first 0x3ff I/O ports can be
.\" specified in this manner") still true?  Looking at changes in
.\" include/asm-i386/processor.h between 2.4 and 2.6 suggests
.\" that the limit is different in 2.6.
Only the first 0x3ff I/O ports can be specified in this manner.
For more ports, the
.BR iopl (2)
system call must be used.

Permissions are not inherited by the child created by
.BR fork (2).
Permissions are preserved across
.BR execve (2);
this is useful for giving port access permissions to unprivileged
programs.

This call is mostly for the i386 architecture.
On many other architectures it does not exist or will always
return an error.
.SH "RETURN VALUE"
On success, zero is returned.
On error, \-1 is returned, and
.I errno
is set appropriately.
.SH ERRORS
.TP
.B EINVAL
Invalid values for
.I from
or
.IR num .
.TP
.B EIO
(on PowerPC) This call is not supported.
.TP
.B ENOMEM
.\" Could not allocate I/O bitmap.
Out of memory.
.TP
.B EPERM
The calling process has insufficient privilege.
.SH "CONFORMING TO"
.BR ioperm ()
is Linux-specific and should not be used in programs
intended to be portable.
.SH NOTES
Libc5 treats it as a system call and has a prototype in
.IR <unistd.h> .
Glibc1 does not have a prototype.
Glibc2 has a prototype both in
.I <sys/io.h>
and in
.IR <sys/perm.h> .
Avoid the latter, it is available on i386 only.
.SH "SEE ALSO"
.BR iopl (2),
.BR capabilities (7)
.SH COLOPHON
This page is part of release 3.44 of the Linux
.I man-pages
project.
A description of the project,
and information about reporting bugs,
can be found at
http://www.kernel.org/doc/man-pages/.