Re: [PATCH 4/21] i386 Broken bios common

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Linus Torvalds wrote:

On Mon, 7 Nov 2005, Zachary Amsden wrote:

Both the APM BIOS and PnP BIOS code use a segment hack to simulate real
mode selector 0x40 (which points to the BIOS data area at 0x00400 in
real mode).  Several broken BIOSen use selector 0x40 as if they were
running in real mode, which we make work by faking up selector 0x40 in
the GDT to point to physical memory starting at 0x400.  We limit the
access to the remainder of this physical page using a byte granular
limit.  Rather than have this tricky code in multiple places, it makes
sense to define it in one place, and the GDT makes a very convenient
place for it.  Use GDT entry 4 as the BAD_BIOS_CACHE segment.

I'd much rather use entry 8 instead, which should just automatically mean that selector 0x40 _always_ points to virtual address 0x400. No switching etc..

Isn't this what Wine already has to work around, or something?

Ingo, can we move the TLS selectors upwards, or does user space perhaps know about the current TLS layout? Wine in particular may well know ;(


I thought the point was that Wine needs to point GDT entry 8 into userspace.

	-hpa
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