mirror of https://github.com/mkerrisk/man-pages
124 lines
3.5 KiB
Groff
124 lines
3.5 KiB
Groff
.\" Copyright (c) 1993 Michael Haardt
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.\" (michael@moria.de)
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.\" Fri Apr 2 11:32:09 MET DST 1993
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.\"
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.\" %%%LICENSE_START(GPLv2+_DOC_FULL)
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.\" This is free documentation; you can redistribute it and/or
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.\" modify it under the terms of the GNU General Public License as
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.\" published by the Free Software Foundation; either version 2 of
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.\" the License, or (at your option) any later version.
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.\"
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.\" The GNU General Public License's references to "object code"
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.\" and "executables" are to be interpreted as the output of any
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.\" document formatting or typesetting system, including
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.\" intermediate and printed output.
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.\"
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.\" This manual is distributed in the hope that it will be useful,
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.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
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.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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.\" GNU General Public License for more details.
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.\"
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.\" You should have received a copy of the GNU General Public
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.\" License along with this manual; if not, see
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.\" <http://www.gnu.org/licenses/>.
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.\" %%%LICENSE_END
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.\"
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.\" Modified Sat Jul 24 15:12:05 1993 by Rik Faith <faith@cs.unc.edu>
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.\" Modified Tue Aug 1 16:27 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 Mon Feb 15 17:28:41 CET 1999 by Andries E. Brouwer <aeb@cwi.nl>
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.\" Modified, 27 May 2004, Michael Kerrisk <mtk.manpages@gmail.com>
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.\" Added notes on capability requirements
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.\"
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.TH IOPERM 2 2021-03-22 "Linux" "Linux Programmer's Manual"
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.SH NAME
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ioperm \- set port input/output permissions
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.SH SYNOPSIS
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.nf
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.BR "#include <sys/io.h>" " /* for glibc */"
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.PP
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.BI "int ioperm(unsigned long " from ", unsigned long " num ", int " turn_on );
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.fi
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.SH DESCRIPTION
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.BR ioperm ()
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sets the port access permission bits for the calling thread for
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.I num
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bits starting from port address
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.IR from .
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If
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.I turn_on
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is nonzero, then permission for the specified bits is enabled;
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otherwise it is disabled.
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If
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.I turn_on
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is nonzero, the calling thread must be privileged
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.RB ( CAP_SYS_RAWIO ).
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.PP
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Before Linux 2.6.8,
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only the first 0x3ff I/O ports could be specified in this manner.
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For more ports, the
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.BR iopl (2)
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system call had to be used (with a
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.I level
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argument of 3).
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Since Linux 2.6.8, 65,536 I/O ports can be specified.
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.PP
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Permissions are inherited by the child created by
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.BR fork (2)
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(but see NOTES).
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Permissions are preserved across
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.BR execve (2);
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this is useful for giving port access permissions to unprivileged
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programs.
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.PP
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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 to indicate the error.
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.SH ERRORS
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.TP
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.B EINVAL
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Invalid values for
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.I from
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or
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.IR num .
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.TP
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.B EIO
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(on PowerPC) This call is not supported.
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.TP
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.B ENOMEM
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.\" Could not allocate I/O bitmap.
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Out of memory.
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.TP
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.B EPERM
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The calling thread has insufficient privilege.
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.SH CONFORMING TO
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.BR ioperm ()
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is Linux-specific and should not be used in programs
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intended to be portable.
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.SH NOTES
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The
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.I /proc/ioports
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file shows the I/O ports that are currently allocated on the system.
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.PP
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Before Linux 2.4,
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permissions were not inherited by a child created by
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.BR fork (2).
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.PP
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Glibc has an
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.BR ioperm ()
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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 iopl (2),
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.BR outb (2),
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.BR capabilities (7)
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