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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | NOTES | SEE ALSO | COLOPHON |
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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 thread, as
specified by the two least significant bits in level.
The I/O privilege level for a normal thread is 0. Permissions
are inherited from parents to children.
This call is deprecated, is significantly slower than ioperm(2),
and is only provided for older X servers which require access to
all 65536 I/O ports. It 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 to indicate the error.
EINVAL level is greater than 3.
ENOSYS This call is unimplemented.
EPERM The calling thread has insufficient privilege to call
iopl(); the CAP_SYS_RAWIO capability is required to raise
the I/O privilege level above its current value.
iopl() is Linux-specific and should not be used in programs that
are intended to be portable.
Glibc2 has a prototype both in <sys/io.h> and in <sys/perm.h>.
Avoid the latter, it is available on i386 only.
Prior to Linux 5.5 iopl() allowed the thread to disable
interrupts while running at a higher I/O privilege level. This
will probably crash the system, and is not recommended.
Prior to Linux 3.7, on some architectures (such as i386),
permissions were inherited by the child produced by fork(2) and
were preserved across execve(2). This behavior was inadvertently
changed in Linux 3.7, and won't be reinstated.
ioperm(2), outb(2), capabilities(7)
This page is part of release 5.13 of the Linux man-pages project.
A description of the project, information about reporting bugs,
and the latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
Linux 2021-03-22 IOPL(2)
Pages that refer to this page: ioperm(2), outb(2), syscalls(2), unimplemented(2), systemd.exec(5), capabilities(7)
Copyright and license for this manual page
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