iopl - change I/O privilege level
int iopl(int level);
iopl changes the I/O privilege level of the current process, as specified
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.
On success, zero is returned. On error, -1 is returned, and errno is
EINVAL level is greater than 3.
EPERM The current user is not the super-user.
NOTES FROM THE KERNEL SOURCE [Toc] [Back]
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.
iopl is Linux specific and should not be used in processes intended to
Under libc5, the prototype for iopl() was given in <unistd.h>.
Linux 0.99.11 1993-07-24 IOPL(2)
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