Manpage of IOPERM

IOPERM

Section: Linux Programmer's Manual (2)
Updated: 2016-03-15
Index
 

NAME

ioperm - set port input/output permissions  

SYNOPSIS

#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 thread for numbits starting from port address from. If turn_onis nonzero, then permission for the specified bits is enabled; otherwise it is disabled. If turn_onis nonzero, the calling thread must be privileged (CAP_SYS_RAWIO).

Before Linux 2.6.8, only the first 0x3ff I/O ports could be specified in this manner. For more ports, the iopl(2) system call had to be used (with a levelargument of 3). Since Linux 2.6.8, 65,536 I/O ports can be specified.

Permissions are inherited by the child created by fork(2) (but see NOTES). 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 errnois set appropriately.  

ERRORS

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

CONFORMING TO

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

NOTES

The /proc/ioportsfile shows the I/O ports that are currently allocated on the system.

Before Linux 2.4, permissions were not inherited by a child created by fork(2).

Glibc has an ioperm() prototype both in <sys/io.h>and in <sys/perm.h>. Avoid the latter, it is available on i386 only.  

SEE ALSO

iopl(2), outb(2), capabilities(7)


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
CONFORMING TO
NOTES
SEE ALSO

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