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Linux系统调用

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<TITLE>Syscall specifications of Linux - iopl</TITLE>
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<H2><A NAME="SEC92" HREF="syscalls_toc.html#SEC92" tppabs="http://personal.xfol.com/%7erezaie/syscall/syscalls_toc.html#SEC92">iopl</A></H2>
<P>
<H3>SYNOPSIS</H3>
<P>
<CODE>int iopl(int <VAR>level</VAR>);</CODE>
<P>
<H3>PARAMETERS</H3>
<P>
<VAR>level</VAR>: [in] the new io level of the process, in the range [0,3].
<P>
<H3>DESCRIPTION</H3>
<P>
Changes the io privilege level of the current task. The task must have
superuser privileges to use the call. The task can get total io
privileges this way.
<P>
<H3>RETURN VALUE</H3>
<P>
On success zero is returned. On error -1 is returned and <CODE>errno</CODE> is
set to one of the following values:
<P>
<UL>
<LI><CODE>EINVAL</CODE>: <VAR>level</VAR> has an invalid value.
<LI><CODE>EPERM</CODE>: the calling process is not superuser.
</UL>
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