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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | NOTES | SEE ALSO | COLOPHON |
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 appropriately.
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 5.08 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 2020-08-13 IOPL(2)
Pages that refer to this page: afs_syscall(2) , break(2) , fattach(2) , fdetach(2) , getmsg(2) , getpmsg(2) , gtty(2) , inb(2) , inb_p(2) , inl(2) , inl_p(2) , insb(2) , insl(2) , insw(2) , inw(2) , inw_p(2) , ioperm(2) , isastream(2) , lock(2) , madvise1(2) , mpx(2) , outb(2) , outb_p(2) , outl(2) , outl_p(2) , outsb(2) , outsl(2) , outsw(2) , outw(2) , outw_p(2) , phys(2) , prof(2) , putmsg(2) , putpmsg(2) , security(2) , stty(2) , syscalls(2) , tuxcall(2) , unimplemented(2) , vserver(2) , systemd.exec(5) , capabilities(7)
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