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Date: Fri, 9 Nov 2001 22:30:53 +0100
From: Pavel Machek <pavel@ucw.cz>
To: Riley Williams <rhw@MemAlpha.cx>
Cc: kernel list <linux-kernel@vger.kernel.org>
Subject: Re: PROBLEM: Linux updates RTC secretly when clock synchronizes
Message-ID: <20011109223053.A964@atrey.karlin.mff.cuni.cz>
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Hi!

> >> According to your comments, you prefer (2).
> >>
> >> I most definitely prefer (1).
> 
> > Hmm, and if some malicious software insmods kernel module to work
> > around your printk()?
> 
> ...it gets "Port busy" when it tries to access the RTC ports that the
> RTC driver built into the kernel already has opened exclusively. At
> least, that's my understanding of the situation at present.

It does not work that way. Userland does iopl(0), and then it just
bangs any port it wants to.

> > We are talking root only here.
> 
> Are we?
> 
> Unless I've misunderstood the arguments so far, the aim is to take the
> RTC driver out of the kernel altogether and replace it with a usermode
> driver to do the same thing. As I see it, that opens up far too many

No. Aim is to leave /dev/rtc in kernel, but make kernel never write to
RTC at its own will.
								Pavel
-- 
Casualities in World Trade Center: 6453 dead inside the building,
cryptography in U.S.A. and free speech in Czech Republic.
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