IOPERM(2)                           Linux Programmer's Manual                           IOPERM(2)



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 num bits starting
       from port address from.  If turn_on is nonzero, then permission for the specified bits  is
       enabled;  otherwise  it  is  disabled.   If turn_on is 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 level argument of 3).  Since
       Linux 2.6.8, 65,536 I/O ports can be specified.

       Permissions are not inherited by the child created by fork(2);  following  a  fork(2)  the
       child  must  turn  on  those  permissions that it needs.  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 thread has insufficient privilege.

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

NOTES
       The /proc/ioports file shows the I/O ports that are currently allocated on the system.

       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)

COLOPHON
       This page is part of release 3.74 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 http://www.kernel.org/doc/man-pages/.



Linux                                       2014-08-19                                  IOPERM(2)