IOPL (2)
change I/O privilege level
SYNOPSIS
#include <unistd.h>
/* for libc5 */
#include <sys/io.h>
/* for glibc */
int iopl(int level );
DESCRIPTION
iopl
changes the I/O privilege level of the current process, as specified 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 interrupts. 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.
RETURN VALUE
On success, zero is returned. On error, -1 is returned, and
errno
is set appropriately.
ERRORS
EINVAL
EPERM
The current user is not the super-user.
NOTES FROM THE KERNEL SOURCE
iopl
has to be used when you want to access the I/O ports beyond the 0x3ff
range: to get the full 65536 ports bitmapped you'd need 8kB of
bitmaps/process, which is a bit excessive.
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
|
|
