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Date: Mon, 12 Aug 2002 12:49:33 +0200 (CEST)
From: Ingo Molnar <mingo@elte.hu>
Reply-To: Ingo Molnar <mingo@elte.hu>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>,
       Linus Torvalds <torvalds@transmeta.com>, <linux-kernel@vger.kernel.org>,
       <julliard@winehq.com>, <ldb@ldb.ods.org>
Subject: Re: [patch] tls-2.5.31-C3
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On 12 Aug 2002, Alan Cox wrote:

> > No. The problem is that there are some BIOS's that contain code that (even
> > though they are called in protected mode) load 0x40 into ds and expect to
> > be able to reference stuff ...  Causes really interesting OOPSs :-(
> 
> Which does mean you can steal the old TLS value and put it back across
> the calls just by changing the TLS data for that process. For that
> matter on Windows emulation I thought Windows also needed 0x40 to be the
> same offset as the BIOS does so can't we leave it hardwired ?

i have no problem with hardwiring it (and excluding it from the TLS
allocation/setting syscalls) - in fact i almost did it that way. The
question is, is the required descriptor format 100% the same for all APM
variants, Wine and Windows and DOS emulators? It would suck if we had a
bad descriptor and also removed the ability of Wine to trap 0x40 access.

but, couldnt APM use its own private GDT for real-mode calls, with 0x40
filled in properly? That would pretty much decouple things.

	Ingo

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