Re: [PATCH v0] Support to disable reed-solomon codes

[Richard Laager <rlaager@wiktel.com>]

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I'm not at all familiar with this part of GRUB, so take this with a big
grain of salt.

On Sat, 2013-11-02 at 20:05 -0700, Jonathan McCune wrote:
> I think it should be possible to generate all the necessary signatures
> at *build time* instead of *install time*

If I understand your email correctly, you're saying that at build time,
grub builds core.img. Then at install time, it calculates:
  "core.img.rs" = Reed-Solomon(core.img)
Then it writes the "core.img.rs" data to disk. At boot time, GRUB reads
the "core.img.rs" data from disk, corrects errors, to reproduce
core.img, which is executed.

If you want to verify at boot time, you just do it after the error
correction step. But it sounds like you want to verify the bits on disk
from the host environment. Rather than "backing out" the Reed-Solomon
coding, why not do it the other way around? Verify core.img, then
re-encode the known good copy (for which code already exists as part of
the installation procedure) and then just compare that to what is
actually on disk?

-- 
Richard

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