vboot2: add verstage

Verstage will host vboot2 for firmware verification.
It's a stage in the sense that it has its own set of toolchains, compiler flags,
and includes. This allows us to easily add object files as needed. But
it's directly linked to bootblock. This allows us to avoid code
duplication for stage loading and jumping (e.g. cbfs driver) for the boards
where bootblock has to run in a different architecture (e.g. Tegra124).
To avoid name space conflict, verstage symbols are prefixed with verstage_.

TEST=Built with VBOOT2_VERIFY_FIRMWARE on/off. Booted Nyan Blaze.
BUG=None
BRANCH=none
Signed-off-by: Daisuke Nojiri <dnojiri@chromium.org>
Change-Id: Iad57741157ec70426c676e46c5855e6797ac1dac
Reviewed-on: https://chromium-review.googlesource.com/204376
Reviewed-by: Randall Spangler <rspangler@chromium.org>

src/vendorcode/google/chromeos/Kconfig

@@ -82,6 +82,14 @@ config VBOOT_VERIFY_FIRMWARE
 	  Enabling VBOOT_VERIFY_FIRMWARE will use vboot to verify the ramstage
 	  and boot loader.
 
+config VBOOT2_VERIFY_FIRMWARE
+  bool "Firmware Verification with vboot2"
+  default n
+  depends on CHROMEOS
+  help
+	  Enabling VBOOT2_VERIFY_FIRMWARE will use vboot2 to verify the romstage
+	  and boot loader.
+
 config EC_SOFTWARE_SYNC
 	bool "Enable EC software sync"
 	default n

src/vendorcode/google/chromeos/Makefile.inc

@@ -104,3 +104,12 @@ $(VB_LIB):
 		fwlib
 
 endif
+
+ifeq ($(CONFIG_VBOOT2_VERIFY_FIRMWARE),y)
+VERSTAGE_LIB = $(obj)/vendorcode/google/chromeos/verstage.a
+$(VERSTAGE_LIB): $$(verstage-objs)
+	@printf "    AR         $(subst $(obj)/,,$(@))\n"
+	$(AR_verstage) rc $@.tmp $(verstage-objs)
+	@printf "    OBJCOPY    $(subst $(obj)/,,$(@))\n"
+	$(OBJCOPY_verstage) --prefix-symbols=verstage_ $@.tmp $@
+endif