vboot2: Add more precise recovery reasons to firmware verification

vboot1 kept track of an internal "LoadFirmware() check" value for both
firmware slots and encoded the value for the slot that managed to go
further in the verification flow into a special range of recovery
reasons. vboot2 instead uses the generic "invalid RW" reason for all
firmware verification failures and communicates further information
through the subcode.

While the subcode may be good enough for developers, it's difficult to
communicate failure reasons to "normal" users (like non-firmware
developers) on the TAB screen. Currently we just display a couple of
numbers that people won't know how to interpret and "RW firmware failed
signature check" for any verification error (including rollback, which
might be the most commonly encountered in practice).

Since our recovery reason space is big enough (and we don't reuse old
numbers anyway), we might as well reuse the more precise numbers (and
strings) from vboot1 to communicate the failure reason, even if we don't
implement its "which slot came further" algorithm. This patch translates
the most common/useful VBSD_LF_CHECK numbers into plain VB2_RECOVERY
reasons and uses them where appropriate.

TEST=make runtests VBOOT2=1
test_that my_jerry firmware_CorruptBothFwSigAB
firmware_CorruptBothFwBodyAB firmware_RollbackFirmware
(Confirmed that matched recovery reasons are the more precise ones in
the 0x10-0x1F range.)

Change-Id: I51ecf1b820d1faa40405cb84377380d6f3f6ca1d
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/248392
Reviewed-by: Bill Richardson <wfrichar@chromium.org>
4 files changed