[ipxe-devel] FATAL: int13_eltorito: call with AX=4d00. Please report

Michael Brown mbrown at fensystems.co.uk
Wed Jan 2 23:01:34 GMT 2013


On Wednesday 02 Jan 2013 22:18:12 Michael Brown wrote:
> When int13_load_mbr() fails (since drive 0xa0 does not have a valid MBR
> present), we try int13_load_eltorito().  This issues INT 13,4d00 to read
> the El Torito boot catalog, relying upon the BIOS to return with an error
> if the drive isn't actually a CD-ROM.
> 
> I have no idea why VirtualBox would treat INT 13,4d00 on a non-CDROM drive
> as being worthy of a fatal error.

The attached patch adds a call to INT 13,4b01 to check that the drive is a CD-
ROM before attempting to boot from it.  I have verified that this is sufficient 
to prevent the "FATAL: int13_eltorito: call with AX=4d00" error.

It doesn't seem to be possible to use "sanboot --drive XX" to boot from the 
CD-ROM drive within VirtualBox; all drive numbers from 0x80 to 0xff return an 
error from INT 13,4b01.  It's possible that the VirtualBox BIOS doesn't bother 
setting up an INT 13 drive for the CD-ROM unless the BIOS is attempting a CD-
ROM boot.

Given that it seems to be impossible to use "sanboot --drive XX" in this way 
under VirtualBox, I'm not sure whether or not it's worth applying the patch.  
Thoughts?

Michael
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