[syslinux] [BUG] boot failure since syslinux-3.00

[H. Peter Anvin]

Sebastian Herbszt wrote:
> H. Peter Anvin wrote:
>> I have no idea.  The BIOS you pointed me to unambiguously claims EDD is 
>> supported, it clearly also has code to use EDD, and yet it fails when 
>> one attempts to use it.
> 
> I have traced the bios a bit and got to where it does the read from port 0x1f0:
> 000fa6fa: (                    ): cli                       ; fa
> 000fa6fb: (                    ): rep insw word ptr es:[di], dx ; f36d
> 000fa6fd: (                    ): sti                       ; fb
> 
> It does hit this twice. First time via int13h, ah=02h from the bios to read to 0x7c00
> and the second time from extlinux via int13h, ah=42h to read to 0x7e00. The first hit
> does obviously succeed since extlinux is loaded and memory at 0x7c00 gets populated
> but the correct data. When it hits 0xfa6fa the second time the memory at 0x7e00 doesn't
> seem to get populated with any data (it stays filled with zeros). Didn't figure out why (yet).
> 

Bochs spews out some pretty conclusive data on the debug console: the 
BIOS seems to do internal LBA to CHS conversion, and does so incorrectly.

	-hpa