ioperm – set port input/output permissions

NAME

       ioperm - set port input/output permissions

SYNOPSIS

       #include  /* for libc5 */
       #include  /* 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.

       Libc5 treats it as a system call and has a prototype in .
       Glibc1 does not have a prototype.  Glibc2 has a prototype both in
        and in .  Avoid the latter, it is available on
       i386 only.

SEE ALSO

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

COLOPHON

       This page is part of release 3.55 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/.

Linux                            2013-03-12                        IOPERM(2)