Re: [i386 BOOT CODE] kernel bootable again

[H. Peter Anvin]

Frank Sorenson wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Pascal Bellard wrote:
>
> > Hello,
> >
> > Please find attached a patch to build i386/x86_64 kernel directly
> > bootable. It may be usefull for rescue floppies and installation
> > floppies.
>
>
> Pascal,
>
> In commit f8eeaaf4180334a8e5c3582fe62a5f8176a8c124, build.c has already
> changed, and I don't believe it's very compatible with this change.
>
> See
> http://www.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=f8eeaaf4180334a8e5c3582fe62a5f8176a8c124
>
> Also, we'll need to see comments from H. Peter Anvin on this patch.
> CC'ing him.

Geometry detection by looking for error returns is fundamentally broken. 
 Way too many non-traditional floppies (USB, IDE...) do not handle this 
at all, they will return successfully, with the data being the data from 
a sector from another track, and thus you end up with aliasing and a 
corrupt boot.  You can do it with fingerprinting, but that's complex and 
error-prone.

In short, this made sense in 1991, but it hasn't made sense for a very 
long time now.  Resurrecting bootsect.S is *NOT* a good idea.

	-hpa
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