chromeos: vboot2: Add TPM PCR extension support

ChromeOS/vboot devices expect the TPM PCRs 0 and 1 to be extended with
digests that attest the chosen boot mode (developer/recovery) and the
HWID in a secure way. This patch uses the newly added vboot2 support
functions to fetch these digests and store them in the TPM.

CQ-DEPEND=CL:244542
BRANCH=veyron
BUG=chromium:451609
TEST=Booted Jerry. Confirmed that PCR0 contains the same value as on my
vboot1 Blaze and Falco (and PCR1 contains some non-zero hash).

Original-Change-Id: I7037b8198c09fccee5440c4c85f0821166784cec
Original-Signed-off-by: Julius Werner <jwerner@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/245119
Original-Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Original-Reviewed-by: Daisuke Nojiri <dnojiri@chromium.org>

(cherry picked from commit 8b44e13098cb7493091f2ce6c4ab423f2cbf0177)
Signed-off-by: Aaron Durbin <adurbin@chromium.org>

Change-Id: I549de8c07353683633fbf73e4ee62ba0ed72ff89
Reviewed-on: http://review.coreboot.org/9706
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

src/include/antirollback.h

@@ -12,6 +12,7 @@
 #include "tpm_lite/tss_constants.h"
 
 struct vb2_context;
+enum vb2_pcr_digest;
 
 /* TPM NVRAM location indices. */
 #define FIRMWARE_NV_INDEX               0x1007
@@ -50,6 +51,12 @@ uint32_t antirollback_lock_space_firmware(void);
  * only.
  */
 
+/**
+ * Ask vboot for a digest and extend a TPM PCR with it.
+ */
+uint32_t tpm_extend_pcr(struct vb2_context *ctx, int pcr,
+			enum vb2_pcr_digest which_digest);
+
 /**
  * Issue a TPM_Clear and reenable/reactivate the TPM.
  */