RE: [OpenBIOS] l440gx+ nvram writing ...

[Wallace I. Kroeker]

Hello Ron,

Here is my take after reading the documentation (the documentation seems to
be identical for the 440bx).

Intel (or some other BIOS maker) write a BIOS.  This BIOS has the SMI
handler in it.  The SMI handler has a signature that it expects from the
Flash software (written by the said BIOS maker).  The signature is something
that they won't want to divulge to keep people from inadvertently
(maliciously) flashing BIOS.

So how can you get around this?  The following steps seem logical:
    1.  Write your own BIOS that has an SMI handler with your own
signature.
    2.  Use the Flash update utility for your Board to flash your BIOS
into place
    3.  Write your own Flash update utility which supplies your
signature to your BIOS

Or the following sequence of steps:
    1.  Write your own BIOS that has an SMI handler with your own
signature.
    2.  Use LoadBios to put your BIOS in place (NOTE: you will be
redefining the SMI handler at this point to be your own)
    3.  Proceed to write your BIOS to FLASH

Now that sounds simple enough but I suspect the tricky part is the SMI
handler.

I really don't think the signature is that magical but rather a
hand-shaking/security feature.

Wallace
> -----Original Message-----
> From:	Ronald G. Minnich [SMTP:[e-mail]]
> Sent:	Monday, February 07, 2000 4:32 PM
> To:	[e-mail]
> Subject:	Re: [OpenBIOS] l440gx+ nvram writing ...
>
> On Mon, 7 Feb 2000, Edwin Rhodes wrote:
> > Well if thats the case, lets hope to god that freedos will do the trick!
>
> :)
>
> not that simple. You'll still have to solve the problem for freedos of
> unlocking the key.
>
> Go to intel and get doc # 245141-001 of 3/1999. Check page 19, para 2.3.2
> We need to see how that is handled. I've got requests in to Intel and
> VALinux now. We'll see how it goes.
>
> ron
>
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l440gx+ nvram writing ...

[Ronald G. Minnich]

On Tue, 8 Feb 2000, Wallace I. Kroeker wrote:
> Intel (or some other BIOS maker) write a BIOS.  This BIOS has the SMI
> handler in it.  The SMI handler has a signature that it expects from the
> Flash software (written by the said BIOS maker).  The signature is something
> that they won't want to divulge to keep people from inadvertently
> (maliciously) flashing BIOS.

The interesting question: what does the SMI handler do when it gets the
sig? How does it get the sig: you put it in eax? you put it somewhere in
memory? you put it ... well, you get my drift.

How is writing to the NVRAM enabled by SMI handler? it sets a bit
somewhere? where?
> Write your own BIOS that has an SMI handler with your own
>
> signature.

you still need to answer the "hardware enable" question to do this. We
need to know what the SMI handler is doing to enable bios writes.
> Use the Flash update utility for your Board to flash your BIOS
>
> into place

I would do this, but the flash utilities don't appear to know how to flash
the low 1/2 MB of the flash ram!
> Write your own BIOS that has an SMI handler with your own
>
> signature.

Again, we're stuck on unlocking the write enable for NVRAM.
> Use LoadBios to put your BIOS in place (NOTE: you will be
>
> redefining the SMI handler at this point to be your own)

I don't think the SMI handler is tricky. But I'm pretty sure the trick is
in what you do when you want to enable writing that nvram. There's where
I'm stuck.

ron

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