IOPERM(2) Linux Programmers Manual IOPERM(2)
ioperm - set port input/output permissions
#include /* for libc5 */
#include /* for glibc */
int ioperm(unsigned long from, unsigned long num, int turn_on);
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 non-zero, the calling process must be privileged
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). Permis
sions are preserved across execve(2); this is useful for giving port
access permissions to non-privileged programs.
This call is mostly for the i386 architecture. On many other architec
tures it does not exist or will always return an error.
On success, zero is returned. On error, -1 is returned, and errno is
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.
ioperm() is Linux-specific and should not be used in programs intended
to be portable.
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
This page is part of release 3.05 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 2007-06-15 IOPERM(2)