Can't get a rom image below 512k?

steven james pyro at
Thu Nov 14 09:52:00 CET 2002

On Thu, 14 Nov 2002, Andrew Kohlsmith wrote:

> > If all else fails, it should be possable to generate an image by just
> > concatenating the etherboot .elf binary, some padding, and the two
> > linuxbios.strip binaries together.
> The _two_ linuxbios.strip binaries?  I only see the one in my build tree.  I 
> was going to try and use mkflashimg but I think I need a DoC bit or two I 
> haven't figured out yet.  :-)


One will be the fallback image, the other is the primary. If you're not
building for fallback, then you'll just have the primary, but will need to
adjust things so that it's base is at ffffxxxx rather than fffexxxx, or
build a 'fallback' image but with ZKERNEL_START moved down to the bottom
of your FLASH instead of ffff0000. In a fallback image, ZKERNEL_START
normally points so that the fallback image can find the primary. In a
primary image, it points to the bottom of flash (typically) and is used to
find your primary payload.


> > recent objdump (that supports i8086 arch) with -D (disassemble all) can
> > help to see where the pieces should go. Just remember that the top of the
> > rom will appear at f0000 at boot time in real mode. Once it gets through
> > __protected_start, you'll be up at the top of memory in i386 arch
> > (ffffxxxx or in primary linuxbios at fffexxxx). One of these days, I'll
> > need to write this up :-)
> :-)  I am an old x86 hacker (real and protected modes), but I haven't actively 
> used my old knowledge for several years.  It's embarassing how much I've 
> lost.  I will do what I can along the way to try and document it as I 
> (re)learn it (especially the boot process that LinuxBIOS takes).
> Regards,
> Andrew
> _______________________________________________
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> Linuxbios at

-------------------------steven james, director of research, linux labs
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