-.\" Hey Emacs! This file is -*- nroff -*- source.
-.\"
.\" Copyright 1993 Rickard E. Faith (faith@cs.unc.edu)
.\" Portions extracted from linux/kernel/ioport.c (no copyright notice).
.\"
+.\" %%%LICENSE_START(VERBATIM)
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
.\" permission notice identical to this one.
-.\"
+.\"
.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date. The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
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+.\"
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+.\" %%%LICENSE_END
.\"
-.\" Modified Tue Aug 1 16:47 1995 by Jochen Karrer
+.\" Modified Tue Aug 1 16:47 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 Fri Nov 27 14:50:36 CET 1998 by Andries Brouwer <aeb@cwi.nl>
-.\" Modified, 27 May 2004, Michael Kerrisk <mtk16@ext.canterbury.ac.nz>
+.\" Modified, 27 May 2004, Michael Kerrisk <mtk.manpages@gmail.com>
.\" Added notes on capability requirements
.\"
-.TH IOPL 2 2004-05-27 "Linux 2.6.6" "Linux Programmer's Manual"
+.TH IOPL 2 2016-03-15 "Linux" "Linux Programmer's Manual"
.SH NAME
iopl \- change I/O privilege level
.SH SYNOPSIS
.sp
.BI "int iopl(int " level );
.SH DESCRIPTION
-.B iopl
-changes the I/O privilege level of the current process, as specified in
+.BR iopl ()
+changes the I/O privilege level of the calling process,
+as specified by the two least significant bits in
.IR level .
This call is necessary to allow 8514-compatible X servers to run under
-Linux. Since these X servers require access to all 65536 I/O ports, the
-.B ioperm
+Linux.
+Since these X servers require access to all 65536 I/O ports, the
+.BR ioperm (2)
call is not sufficient.
In addition to granting unrestricted I/O port access, running at a higher
-I/O privilege level also allows the process to disable interrupts. This
-will probably crash the system, and is not recommended.
+I/O privilege level also allows the process to disable interrupts.
+This will probably crash the system, and is not recommended.
-Permissions are inherited by fork and exec.
+Permissions are not inherited by the child process created by
+.BR fork (2)
+and are not preserved across
+.BR execve (2)
+(but see NOTES).
The I/O privilege level for a normal process is 0.
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
+.SH RETURN VALUE
+On success, zero is returned.
+On error, \-1 is returned, and
.I errno
is set appropriately.
.SH ERRORS
This call is unimplemented.
.TP
.B EPERM
-The calling process has insufficient privilege to call
-.BR iopl ;
+The calling process has insufficient privilege to call
+.BR iopl ();
the
.B CAP_SYS_RAWIO
-capability is required.
-.SH "CONFORMING TO"
-\fBiopl\fP is Linux specific and should not be used in processes
+capability is required to raise the I/O privilege level
+above its current value.
+.SH CONFORMING TO
+.BR iopl ()
+is Linux-specific and should not be used in programs that are
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
+.\" 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"
+
+Prior to Linux 3.7,
+on some architectures (such as i386), permissions
+.I were
+inherited by the child produced by
+.BR fork (2)
+and were preserved across
+.BR execve (2).
+This behavior was inadvertently changed in Linux 3.7,
+and won't be reinstated.
+.SH SEE ALSO
.BR ioperm (2),
+.BR outb (2),
.BR capabilities (7)
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