vboot: ec_sync: Switch to new CBFS API

This patch changes the vboot EC sync code to use the new CBFS API. As a
consequence, we have to map the whole EC image file at once (because the
new API doesn't support partial mapping). This should be fine on the
only platform that uses this code (Google_Volteer/_Dedede family)
because they are x86 devices that support direct mapping from flash, but
the code was originally written to more carefully map the file in
smaller steps to be theoretically able to support Arm devices.

EC sync in romstage for devices without memory-mapped flash would be
hard to combine with CBFS verification because there's not enough SRAM
to ever hold the whole file in memory at once, but we can't validate the
file hash until we have loaded the whole file and for performance (or
TOCTOU-safety, if applicable) reasons we wouldn't want to load anything
more than once. The "good" solution for this would be to introduce a
CBFS streaming API can slowly feed chunks of the file into a callback
but in the end still return a "hash valid/invalid" result to the caller.
If use cases like this become pressing in the future, we may have to
implement such an API.

However, for now this code is the only part of coreboot with constraints
like that, it was only ever used on platforms that do support
memory-mapped flash, and due to the new EC-EFS2 model used on more
recent Chrome OS devices we don't currently anticipate this to ever be
needed again. Therefore this patch goes the easier way of just papering
over the problem and punting the work of implementing a more generic
solution until we actually have a real need for it.

Signed-off-by: Julius Werner <jwerner@chromium.org>
Change-Id: I7e263272aef3463f3b2924887d96de9b2607f5e5
Reviewed-on: https://review.coreboot.org/c/coreboot/+/52280
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

0 files changed, 0 insertions, 0 deletions