linux-kernel - Re: [PATCH] fix i486 boot failure due to stale %ds

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <alpine.LFD.0.999.0711041615380.15101@woody.linux-foundation.org>
Date:	Sun, 4 Nov 2007 16:23:11 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	"H. Peter Anvin" <hpa@...or.com>
cc:	Jeremy Fitzhardinge <jeremy@...p.org>,
	Mikael Pettersson <mikpe@...uu.se>,
	linux-kernel@...r.kernel.org, mingo@...hat.com, tglx@...utronix.de
Subject: Re: [PATCH] fix i486 boot failure due to stale %ds

On Sun, 4 Nov 2007, Linus Torvalds wrote:
> 
> So I'd suggest having both jumps back-to-back, but realistically, the 
> first regular short jump is actually the one that is more important. 
> That's the one that really matters on i386/i486 class machines, and later 
> CPU's will generally do the right thing even with _neither_ jump there.

That's obviously badly phrased.

The far jump is obviously required on all CPU's in order for us to 
actually finally get to 32-bit protected mode and reload CS, but what I 
*meant* was that we certainly also know that "unreal mode" works and is 
used by various strange DOS extenders, and that not doing the far jump 
isn't really required for having a "working setup" - it's just going to be 
a rather limited mode.

So the short jump is required for the code to *work*. The long jump is 
required only to get us the 32-bit mode we *want* and out of the odd 
"half-way" state. Two different issues.

		Linus
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/