diff options
Diffstat (limited to 'man2/iopl.2')
| -rw-r--r-- | man2/iopl.2 | 92 |
1 files changed, 92 insertions, 0 deletions
diff --git a/man2/iopl.2 b/man2/iopl.2 new file mode 100644 index 0000000..239d206 --- /dev/null +++ b/man2/iopl.2 @@ -0,0 +1,92 @@ +.\" Copyright 1993 Rickard E. Faith (faith@cs.unc.edu) +.\" Portions extracted from linux/kernel/ioport.c (no copyright notice). +.\" +.\" SPDX-License-Identifier: Linux-man-pages-copyleft +.\" +.\" Modified Tue Aug 1 16:47 1995 by Jochen Karrer +.\" <cip307@cip.physik.uni-wuerzburg.de> +.\" Modified Tue Oct 22 08:11:14 EDT 1996 by Eric S. Raymond <esr@thyrsus.com> +.\" Modified Fri Nov 27 14:50:36 CET 1998 by Andries Brouwer <aeb@cwi.nl> +.\" Modified, 27 May 2004, Michael Kerrisk <mtk.manpages@gmail.com> +.\" Added notes on capability requirements +.\" +.TH iopl 2 2023-03-30 "Linux man-pages 6.05.01" +.SH NAME +iopl \- change I/O privilege level +.SH LIBRARY +Standard C library +.RI ( libc ", " \-lc ) +.SH SYNOPSIS +.nf +.B #include <sys/io.h> +.PP +.BI "[[deprecated]] int iopl(int " level ); +.fi +.SH DESCRIPTION +.BR iopl () +changes the I/O privilege level of the calling thread, +as specified by the two least significant bits in +.IR level . +.PP +The I/O privilege level for a normal thread is 0. +Permissions are inherited from parents to children. +.PP +This call is deprecated, is significantly slower than +.BR 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. +.SH RETURN VALUE +On success, zero is returned. +On error, \-1 is returned, and +.I errno +is set to indicate the error. +.SH ERRORS +.TP +.B EINVAL +.I level +is greater than 3. +.TP +.B ENOSYS +This call is unimplemented. +.TP +.B EPERM +The calling thread has insufficient privilege to call +.BR iopl (); +the +.B CAP_SYS_RAWIO +capability is required to raise the I/O privilege level +above its current value. +.SH VERSIONS +.\" Libc5 treats it as a system call and has a prototype in +.\" .IR <unistd.h> . +.\" glibc1 does not have a prototype. +glibc2 has a prototype both in +.I <sys/io.h> +and in +.IR <sys/perm.h> . +Avoid the latter, it is available on i386 only. +.SH STANDARDS +Linux. +.SH HISTORY +Prior to Linux 5.5 +.BR 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. +.PP +Prior to Linux 3.7, +on some architectures (such as i386), permissions +.I were +inherited by the child produced by +.BR fork (2) +and were preserved across +.BR execve (2). +This behavior was inadvertently changed in Linux 3.7, +and won't be reinstated. +.SH SEE ALSO +.BR ioperm (2), +.BR outb (2), +.BR capabilities (7) |