[syslinux] Conditional kernel selection based on CPUID/DMI info

Jeffrey Hutzelman jhutz at cmu.edu
Tue Jan 29 17:37:01 PST 2008

--On Tuesday, January 29, 2008 02:54:53 PM -0800 "H. Peter Anvin" 
<hpa at zytor.com> wrote:

> Jeffrey Hutzelman wrote:
>> So far, I've avoided any com32 modules.  Previous comboot modules I've
>> done  have been farily trivial and com32 seemed more effort than it was
>> worth.  That's clearly not the case here, and doing it in C would be
>> quite a bit  more maintainable, but it wouldn't have met my need -- the
>> original purpose  of the bioschk module was to detect a buggy BIOS that
>> made user interaction  from a com32 module impossible.  What actually
>> happened was that I deployed  new menus using menu.c32 instead of PXE's
>> built-in menu capability, and our  staff started complaining that they
>> could no longer select anything from  the menu!
>> The bug is not in SYSLINUX, BTW.  I'm pretty sure it's been discussed
>> here  before, and Dell has acknowledged it.  Unfortunately, that was
>> over a year  ago, and the platform in question is officially EOL, so
>> there's not much  hope of a fix from them.  Their own BIOS updater run
>> under MEMDISK has the  same problem; I had to put together a version
>> that would boot and do the  update without asking for confirmation.
> I recently fixed an interaction between Dell BIOSes and SYSLINUX (it was
> a syslinux bug which only bit when COM32 modules where invoked.)  The
> only other Dell bug that I know about off the top of my head only bit
> with isolinux.
> I looked for the discussion you described, couldn't find it offhand.  I
> found a problem with OptiPlex GX620, said to be fixed in BIOS version
> A12 (the bug was present only in version A11, supposedly), is this the
> one?

Yes, that's the one.  Note that while the issue was introduced in A11 and 
Dell said the issue _would be_ fixed in A12, no such version was ever 
released.  We're a little behind, but not much -- the problem occurs with 
3.53, and as I mentioned, also with the memdisk in that version.  At some 
point I'll try something newer, but that requires forward-porting a patch I 
have yet to send you, and I haven't found the time to look at it.

-- Jeff

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