futility: gbb: Avoid unnecessary search of FMAP

For commands such as `futility gbb --set --flags=0x140`, futility first
reads the GBB section from the flash, modifies the section, and then
writes back the section to the flash. The write, however, requires
another search of the FMAP section, in order to locate the GBB section
in the flash.

This unnecessary search can be avoided by reading the FMAP section
together with the GBB section. The FMAP data will be stored in the image
buffer, so that the FMAP layout can be retrieved directly from the
buffer for subsequent writes.

This will also prevent the misleading warnings from showing up:

 Failed to read fmap from buffer.
 WARNING: flashrom_write_image: could not read fmap from image, r=1,
 falling back to read from rom

BUG=b:260531154
TEST=emerge-corsola vboot_reference
TEST=make runtests
TEST=No warnings and errors were shown with
     `futility gbb --set --flash --flags=0x140`
BRANCH=none

Change-Id: I50029ae5d9c5ecb347f47e980e7c3b772ecc0f18
Signed-off-by: Yu-Ping Wu <yupingso@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/4251504
Reviewed-by: Hung-Te Lin <hungte@chromium.org>

0 files changed, 0 insertions, 0 deletions