From: ebiederm@xmission.com (Eric W. Biederman)
To: Linus Torvalds <torvalds@transmeta.com>
Cc: Jamie Lokier <jamie@shareable.org>, Jos Hulzink <josh@stack.nl>,
Andi Kleen <ak@muc.de>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] Use correct x86 reboot vector
Date: 11 May 2003 11:54:20 -0600 [thread overview]
Message-ID: <m1k7cx74j7.fsf@frodo.biederman.org> (raw)
In-Reply-To: <Pine.LNX.4.44.0305102043320.28287-100000@home.transmeta.com>
Linus Torvalds <torvalds@transmeta.com> writes:
> On Sat, 10 May 2003, Jamie Lokier wrote:
> > Jos Hulzink wrote:
> > > For the sake of bad behaving BIOSes however, I'd vote for the f000:fff0
> > > vector, unless someone can hand me a paper that says it is wrong.
> >
> > I agree, for the simple reason that it is what the chip does on a
> > hardware reset signal.
>
> Hmm.. Doesnt' a _real_ hardware reset actually use a magic segment that
> isn't even really true real mode? I have this memory that the reset value
> for a i386 has CS=0xf000, but the shadow base register actually contains
> 0xffff0000. In other words, the CPU actually starts up in "unreal" mode,
> and will fetch the first instruction from physical address 0xfffffff0.
>
> At least that was true on an original 386. It's something that could
> easily have changed since.
Correct. And no one has changed it since. I use that all of the time.
> In other words, you're all wrong. Nyaah, nyaah.
However 0xf000:fff0 is as close as you can get, and since that is usually
RAM it can do something different on a reset vs a reboot if it wants
to.
Using 0xf000 is just polite as it allows relative jumps.
Eric
next prev parent reply other threads:[~2003-05-11 17:44 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-05-10 2:56 [PATCH] Use correct x86 reboot vector Andi Kleen
2003-05-10 3:35 ` CaT
2003-05-10 3:58 ` H. Peter Anvin
2003-05-10 14:49 ` Alan Cox
2003-05-10 16:17 ` Jamie Lokier
2003-05-10 18:47 ` Jos Hulzink
2003-05-11 18:01 ` Eric W. Biederman
2003-05-11 17:24 ` Alan Cox
2003-05-11 19:04 ` Eric W. Biederman
2003-05-12 5:48 ` [PATCH] always shutdown on the bootstrap processor Eric W. Biederman
2003-05-10 16:15 ` [PATCH] Use correct x86 reboot vector Jamie Lokier
2003-05-10 17:09 ` Randy.Dunlap
2003-05-10 19:41 ` Jos Hulzink
2003-05-10 18:10 ` Jamie Lokier
2003-05-10 20:55 ` Jos Hulzink
2003-05-11 3:50 ` Linus Torvalds
2003-05-11 9:37 ` Jos Hulzink
2003-05-11 14:01 ` Jamie Lokier
2003-05-11 17:38 ` Davide Libenzi
2003-05-11 17:56 ` Eric W. Biederman
2003-05-11 18:23 ` Davide Libenzi
2003-05-11 19:12 ` Eric W. Biederman
2003-05-12 15:36 ` Maciej W. Rozycki
2003-05-13 6:35 ` H. Peter Anvin
2003-05-11 18:38 ` Linus Torvalds
2003-05-11 19:00 ` Matt Mackall
2003-05-11 19:16 ` Eric W. Biederman
2003-05-12 1:07 ` H. Peter Anvin
2003-05-11 19:10 ` Eric W. Biederman
2003-05-11 18:43 ` Christer Weinigel
2003-05-11 20:22 ` wingel
2003-05-11 20:26 ` Davide Libenzi
2003-05-11 17:54 ` Eric W. Biederman [this message]
2003-05-13 12:49 Chuck Ebbert
2003-05-13 18:45 ` H. Peter Anvin
2003-05-13 19:04 ` Richard B. Johnson
2003-05-13 19:27 ` H. Peter Anvin
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