[flashrom] success hacking DELL Dimension 4100

Bertho Grandpied y31415926536 at yahoo.fr
Tue Mar 12 17:59:26 CET 2013

Some time ago, "Andrew Goodbody" noted :
>> I'm pretty sure that the detection of FWH devices requires
>> writing to the address space used and you cannot do that as
>> you cannot set the BIOS WE bit in the chipset. So unless you
>> can get around the SMI protection of that bit then there is
>> no way to detect the chip in use. Even if you did detect it,
>> you still could not program it.

And I responded : 
> I'll check whether the BIOS also has locked access to SMRAM
> - usually it wasn't done at the time. If the SMRAM is
> accessible from outside SMM, it would be straightforward to
> bypass the protection (just replace an RSM instruction as
> the SMI "handler" ;-)

Which was done successfully a mompent ago... BIOS was not locking the SMM settings on this Intel board fortunately, so replacing a plain RSM instruction at the SMI origin (A000:8000) took just a couple minutes' hacking, then for sure Flashrom was able to detect the FWH, to dump and also to update the flash image successfully :=) 

This complete circumvention of the (idiotic) BIOS 'protection' has achieved my original purpose - be able to modify the BIOS ad libitum. I did not have to search for the specific GPIO or similar method which the official BIOS patchers use. 



More information about the flashrom mailing list