iopl

IOPL(2)			  Linux Programmer’s Manual		      IOPL(2)



NAME
       iopl - change I/O privilege level

SYNOPSIS
       #include <sys/io.h>

       int iopl(int level);

DESCRIPTION
       iopl changes the I/O privilege level of the current process, as speci-
       fied in level.

       This call is necessary to allow 8514-compatible X servers to run under
       Linux.	Since  these X servers require access to all 65536 I/O ports,
       the ioperm call is not sufficient.

       In addition to granting unrestricted I/O port  access,  running	at  a
       higher  I/O  privilege level also allows the process to disable inter-
       rupts.  This will probably crash the system, and is not recommended.

       Permissions are inherited by fork and exec.

       The I/O privilege level for a normal process is 0.

       This call is mostly for the i386 architecture.  On many	other  archi-
       tectures 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 level is greater than 3.

       EPERM  The current user is not the super-user.

       ENOSYS This call is unimplemented.

CONFORMING TO
       iopl is Linux specific and should not be used in processes intended to
       be portable.

NOTES
       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.

SEE ALSO
       ioperm(2)



Linux 0.99.11			  1993-07-24			      IOPL(2)