Re: [PATCH] x86-boot: don't request VBE2 information

From: H. Peter Anvin
Date: Thu Mar 06 2008 - 10:16:50 EST


Peter Korsgaard wrote:
The new x86 setup code (4fd06960f120) broke booting on an old P3/500MHz
with an onboard Voodoo3 of mine. After debugging it, it turned out
to be caused by the fact that the vesa probing now asks for VBE2 data.

Disassembing the video BIOS shows that it overflows the vesa_general_info
structure when VBE2 data is requested because the source addresses for the
information strings which get strcpy'ed to the buffer lie outside the 32K
BIOS code (and hence contain long sequences of 0xff's).


I'm slightly concerned about this, because we *do* use VBE2 data - just not the stuff that this particular BIOS seems to key on (and break.)

On the other hand, until we get an example on something that breaks with the change, we might as well try it, since we have an example on something that breaks with it. We should monitor carefully, though.

-hpa
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