[flashrom] Fwd: BIOS Write Enable bit problem.

Rich Futyma rich.futyma at sanmina.com
Mon Feb 11 16:30:06 CET 2013


Thank you for your reply. I guess this is where the security and the open
stand against each other :).

On Mon, Feb 11, 2013 at 2:31 AM, Andrew Goodbody <ajg4tadpole at gmail.com>wrote:

> On 10/02/13 00:45, Rich Futyma wrote:
>> Would happen to know which linux driver handles this interrupt?
> SMM code is loaded into SMRAM during BIOS POST. Then the access to SMRAM
> is locked so that SMRAM is only visible when an SMI is active. The CPU
> cannot access SMRAM when no SMI is active. The CPU immediately starts to
> execute code from SMRAM once it receives the SMI.
> There is no Linux code involved, this is all initialised before any OS
> code is loaded.
>  Also, do you know where is this "correct handshake" described? It seems
>> that once bit 1 is set it can only be cleared by the reset.
> No. This handshake is not public knowledge AFAIK. It would not be much of
> a protection mechanism if everyone, including the virus writers, knew how
> to bypass it. I would expect the handshake to involve cryptography as well.
> Andrew

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