IOPL(2) Linux Programmer's Manual IOPL(2)
NAME
iopl - change I/O privilege level
SYNOPSIS
#include<sys/io.h>
intiopl(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.
RETURNVALUE
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.
CONFORMINGTO
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.
SEEALSO
ioperm(2)
Linux 0.99.11 1993-07-24 IOPL(2)
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