172 lines
4.0 KiB
HTML
172 lines
4.0 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of IOPL</TITLE>
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</HEAD><BODY>
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<H1>IOPL</H1>
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Section: Linux Programmer's Manual (2)<BR>Updated: 2017-09-15<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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iopl - change I/O privilege level
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<B>#include <<A HREF="file:///usr/include/sys/io.h">sys/io.h</A>></B>
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<P>
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<B>int iopl(int </B><I>level</I><B>);</B>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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<B>iopl</B>()
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changes the I/O privilege level of the calling process,
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as specified by the two least significant bits in
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<I>level</I>.
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<P>
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This call is necessary to allow 8514-compatible X servers to run under
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Linux.
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Since these X servers require access to all 65536 I/O ports, the
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<B><A HREF="/cgi-bin/man/man2html?2+ioperm">ioperm</A></B>(2)
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call is not sufficient.
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<P>
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In addition to granting unrestricted I/O port access, running at a higher
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I/O privilege level also allows the process to disable interrupts.
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This will probably crash the system, and is not recommended.
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<P>
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Permissions are not inherited by the child process created by
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<B><A HREF="/cgi-bin/man/man2html?2+fork">fork</A></B>(2)
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and are not preserved across
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<B><A HREF="/cgi-bin/man/man2html?2+execve">execve</A></B>(2)
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(but see NOTES).
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<P>
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The I/O privilege level for a normal process is 0.
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<P>
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This call is mostly for the i386 architecture.
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On many other architectures it does not exist or will always
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return an error.
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<A NAME="lbAE"> </A>
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<H2>RETURN VALUE</H2>
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On success, zero is returned.
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On error, -1 is returned, and
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<I>errno</I>
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is set appropriately.
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<A NAME="lbAF"> </A>
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<H2>ERRORS</H2>
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<DL COMPACT>
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<DT id="1"><B>EINVAL</B>
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<DD>
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<I>level</I>
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is greater than 3.
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<DT id="2"><B>ENOSYS</B>
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<DD>
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This call is unimplemented.
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<DT id="3"><B>EPERM</B>
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<DD>
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The calling process has insufficient privilege to call
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<B>iopl</B>();
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the
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<B>CAP_SYS_RAWIO</B>
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capability is required to raise the I/O privilege level
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above its current value.
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</DL>
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<A NAME="lbAG"> </A>
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<H2>CONFORMING TO</H2>
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<B>iopl</B>()
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is Linux-specific and should not be used in programs that are
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intended to be portable.
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<A NAME="lbAH"> </A>
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<H2>NOTES</H2>
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Glibc2 has a prototype both in
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<I><<A HREF="file:///usr/include/sys/io.h">sys/io.h</A>></I>
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and in
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<I><<A HREF="file:///usr/include/sys/perm.h">sys/perm.h</A>></I>.
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Avoid the latter, it is available on i386 only.
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<P>
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Prior to Linux 3.7,
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on some architectures (such as i386), permissions
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<I>were</I>
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inherited by the child produced by
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<B><A HREF="/cgi-bin/man/man2html?2+fork">fork</A></B>(2)
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and were preserved across
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<B><A HREF="/cgi-bin/man/man2html?2+execve">execve</A></B>(2).
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This behavior was inadvertently changed in Linux 3.7,
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and won't be reinstated.
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<A NAME="lbAI"> </A>
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?2+ioperm">ioperm</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+outb">outb</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?7+capabilities">capabilities</A></B>(7)
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<A NAME="lbAJ"> </A>
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<H2>COLOPHON</H2>
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This page is part of release 5.05 of the Linux
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<I>man-pages</I>
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project.
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A description of the project,
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information about reporting bugs,
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and the latest version of this page,
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can be found at
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<A HREF="https://www.kernel.org/doc/man-pages/.">https://www.kernel.org/doc/man-pages/.</A>
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="4"><A HREF="#lbAB">NAME</A><DD>
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<DT id="5"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="6"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="7"><A HREF="#lbAE">RETURN VALUE</A><DD>
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<DT id="8"><A HREF="#lbAF">ERRORS</A><DD>
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<DT id="9"><A HREF="#lbAG">CONFORMING TO</A><DD>
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<DT id="10"><A HREF="#lbAH">NOTES</A><DD>
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<DT id="11"><A HREF="#lbAI">SEE ALSO</A><DD>
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<DT id="12"><A HREF="#lbAJ">COLOPHON</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:05:33 GMT, March 31, 2021
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</BODY>
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</HTML>
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