iopl — change I/O privilege level
#include <sys/io.h>
int
iopl( |
int level); |
iopl() changes the I/O
privilege level of the calling thread, as specified by the
two least significant bits in level.
The I/O privilege level for a normal thread is 0. Permissions are inherited from parents to children.
This call is deprecated, is significantly slower than ioperm(2), and is only provided for older X servers which require access to all 65536 I/O ports. It is mostly for the i386 architecture. On many other architectures it does not exist or will always return an error.
On success, zero is returned. On error, −1 is
returned, and errno is set to
indicate the error.
level is
greater than 3.
This call is unimplemented.
The calling thread has insufficient privilege to
call iopl(); the
CAP_SYS_RAWIO capability
is required to raise the I/O privilege level above its
current value.
iopl() is Linux-specific and
should not be used in programs that are intended to be
portable.
Glibc2 has a prototype both in <sys/io.h>
and in <sys/perm.h>
Avoid the latter, it is available on i386 only.
Prior to Linux 5.5 iopl()
allowed the thread to disable interrupts while running at a
higher I/O privilege level. This will probably crash the
system, and is not recommended.
Prior to Linux 3.7, on some architectures (such as i386),
permissions were
inherited by the child produced by fork(2) and were preserved
across execve(2). This behavior
was inadvertently changed in Linux 3.7, and won't be
reinstated.
This page is part of release 5.11 of the Linux man-pages project. A
description of the project, information about reporting bugs,
and the latest version of this page, can be found at
https://www.kernel.org/doc/man−pages/.
|
Copyright 1993 Rickard E. Faith (faithcs.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. Permission is granted to copy and distribute modified versions of this 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 Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date.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 the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. %%%LICENSE_END Modified Tue Aug 1 16:47 1995 by Jochen Karrer <cip307cip.physik.uni-wuerzburg.de> Modified Tue Oct 22 08:11:14 EDT 1996 by Eric S. Raymond <esrthyrsus.com> Modified Fri Nov 27 14:50:36 CET 1998 by Andries Brouwer <aebcwi.nl> Modified, 27 May 2004, Michael Kerrisk <mtk.manpagesgmail.com> Added notes on capability requirements |