chip/g: Run unrestricted image even if Board ID can't be read

Previously, an error reading Board ID would prevent any image from
running, even a wildcard (unrestricted) image with mask=flags=0 which
would match any Board ID.

Now, if Board ID can't be read, match the image against
type=type_inv=flags=0.  This will match only an unrestricted image.

(This is better than checking directly for an unrestricted image,
because that check is more susceptible to clock-jitter-induced errors.)

BUG=b:67651806
BRANCH=cr50
TEST=Hack read_board_id() to return error.  See that an unrestricted
     image will now boot.

Change-Id: I1071e146b4541e8efd50c8409b8f76012a107731
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/713574
Reviewed-by: Mary Ruthven <mruthven@chromium.org>

1 files changed, 11 insertions, 2 deletions

diff --git a/chip/g/board_id.c b/chip/g/board_id.c
index ac47d973be..569540eb62 100644
--- a/chip/g/board_id.c
+++ b/chip/g/board_id.c
@@ -103,8 +103,17 @@ uint32_t board_id_mismatch(const struct SignedHeader *sh)
 		sh = get_current_image_header();
 
 	/* Get Board ID from INFO1. */
-	if (read_board_id(&id) != EC_SUCCESS)
-		return 1;
+	if (read_board_id(&id) != EC_SUCCESS) {
+		/*
+		 * On failure, set id fields to 0.  This will only match an
+		 * unrestricted image header (board_id_mask=board_id_flags=0),
+		 * which would run on any Board ID.
+		 *
+		 * Don't return error, because that would prevent all images
+		 * from running.
+		 */
+		id.type = id.type_inv = id.flags = 0;
+	}
 
 	return check_board_id_vs_header(&id, sh);
 }