Ioperm sets the port access permission bits for the process for
num bytes starting from port address from to the value
turn_on. The use of ioperm requires root privileges.
Only the first 0x3ff I/O ports can be specified in this manner. For more ports,
the iopl function must be used. Permissions are not inherited on fork,
but on exec they are. This is useful for giving port access permissions to
This call is mostly for the i386 architecture. On many other architectures it
does not exist or will always return an error.
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.