[syslinux] deepdive .0 extension

H. Peter Anvin hpa at zytor.com
Tue Aug 12 08:36:42 PDT 2008


Thomas Ekstrand wrote:
> Hi!
> 
> I know the .0 extension is off limits for linux kernels but what happens when the kernel file extension is .0 ?
> 
> I'm trying to troubleshoot our system because everytime someone tries to boot a kernel image with a .0 extension it overwrites a large part of the clients BIOS flash. I've tried it on a different system with other hardware and it only hangs (like it should I presume) yet it is not an individual error I've had several of these system in for fixing.
> 
> so what is the PXE code doing in the systems BIOS?
> 

It overwrites random memory, which can of course have disastrous 
effects. However, a Linux kernel is way too big to fit in the low memory 
area; as a result, it will spill into the I/O area which contains the 
screen and the system BIOS RAM shadow.  It is *supposed* to be treated 
as a ROM at this point, but apparently on your system it triggers a 
flash command.

At one point there was a size test, but I believe it was dropped due to 
restructuring.  It looks like it really needs to come back.

	-hpa




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