| NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | NOTES | SEE ALSO | COLOPHON | The Linux Programming Interface |
IOPL(2) Linux Programmer's Manual IOPL(2)
iopl - change I/O privilege level
#include <sys/io.h>
int iopl(int level);
iopl() changes the I/O privilege level of the calling 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(2)
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(2) and execve(2).
The I/O privilege level for a normal process is 0.
This call is mostly for the i386 architecture. On many other architectures it
does not exist or will always return an error.
On success, zero is returned. On error, -1 is returned, and errno is set
appropriately.
EINVAL level is greater than 3.
ENOSYS This call is unimplemented.
EPERM The calling process has insufficient privilege to call iopl(); the
CAP_SYS_RAWIO capability is required.
iopl() is Linux-specific and should not be used in processes intended to be
portable.
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.
ioperm(2), capabilities(7)
This page is part of release 3.32 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can be found
at http://www.kernel.org/doc/man-pages/.
Linux 2004-05-27 IOPL(2)
HTML rendering created 2010-12-03 by Michael Kerrisk, author of The Linux Programming Interface