ioperm(2) — Linux manual pages

Linux manual pages	Section 2

Name

ioperm — set port input/output permissions

Synopsis

#include <unistd.h>
/* for libc5 */

#include <sys/io.h>
/* for glibc */

`int ioperm(`	unsigned long `from`,
	unsigned long `num`,
	int `turn_on)`;

DESCRIPTION

ioperm() sets the port access permission bits for the calling process for num bytes starting from port address from to the value turn_on. If turn_on is nonzero, the calling process must be privileged (CAP_SYS_RAWIO).

Only the first 0x3ff I/O ports can be specified in this manner. For more ports, the iopl(2) system call must be used.

Permissions are not inherited by the child created by fork(2). Permissions are preserved across 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.

RETURN VALUE

On success, zero is returned. On error, −1 is returned, and errno is set appropriately.

ERRORS

EINVAL: Invalid values for from or num.
EIO: (on PowerPC) This call is not supported.
ENOMEM: Out of memory.
EPERM: The calling process has insufficient privilege.

CONFORMING TO

ioperm() is Linux-specific and should not be used in programs intended to be portable.

NOTES

Libc5 treats it as a system call and has a prototype in <unistd.h> Glibc1 does not have a prototype. Glibc2 has a prototype both in <sys/io.h> and in <sys/perm.h> Avoid the latter, it is available on i386 only.

COLOPHON

This page is part of release 3.24 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.

Copyright (c) 1993 Michael Haardt
(michaelmoria.de)
Fri Apr  2 11:32:09 MET DST 1993

This is free documentation; you can redistribute it and/or
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published by the Free Software Foundation; either version 2 of
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Modified Sat Jul 24 15:12:05 1993 by Rik Faith <faithcs.unc.edu>
Modified Tue Aug  1 16:27    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 Mon Feb 15 17:28:41 CET 1999 by Andries E. Brouwer <aebcwi.nl>
Modified, 27 May 2004, Michael Kerrisk <mtk.manpagesgmail.com>
    Added notes on capability requirements