vb20: add vb2api_check_hash_get_digest() for retrieving hash result

For x86 systems, which resume through the boot reset vector, to
implement vboot verification of the memory init code one needs
check that the slot chosen on the resume path is the same as
the original boot path. That check is done by storing the
resulting hash of the slot. However, vb2api doesn't export
the resulting hash from vb2api_check_hash(). Thus, provide
a variant which saves the resulting digest in the supplied
buffer.

BUG=chrome-os-partner:46049
BRANCH=glados
TEST=Suspended and resumed on chell. Also, tested with an EC build
     which returns a bad hash to ensure that is properly caught.

Change-Id: Ic20be2024afedabc2d8bc767f1b794376348523c
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/323460
Reviewed-by: Randall Spangler <rspangler@chromium.org>
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/firmware/2lib/include/2return_codes.h b/firmware/2lib/include/2return_codes.h
index 4201b693..1d1ed531 100644
--- a/firmware/2lib/include/2return_codes.h
+++ b/firmware/2lib/include/2return_codes.h
@@ -523,6 +523,9 @@ enum vb2_return_code {
 	/* Phase one passing through secdata's request to reboot */
 	VB2_ERROR_API_PHASE1_SECDATA_REBOOT,
 
+	/* Digest buffer passed into vb2api_check_hash incorrect. */
+	VB2_ERROR_API_CHECK_DIGEST_SIZE,
+
         /**********************************************************************
 	 * Errors which may be generated by implementations of vb2ex functions.
 	 * Implementation may also return its own specific errors, which should