chromeos: vboot_loader: Add support for SW_WP_ENABLED flag

Set VB_INIT_FLAG_SW_WP_ENABLED according to the status returned by an
optional platform / mainboard function vboot_get_sw_write_protect().

BUG=chrome-os-partner:26777
TEST=Manual on Rambi with all patches in sequence:
`crossystem sw_wpsw_boot` prints 0
`flashrom --wp-enable` and reboot
`crossystem sw_wpsw_boot` prints 1
BRANCH=Rambi

Original-Change-Id: Ifb852d75cc106d10120cfee0a396b0662282051a
Original-Signed-off-by: Shawn Nematbakhsh <shawnn@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/190096
Original-Reviewed-by: Aaron Durbin <adurbin@chromium.org>
(cherry picked from commit c4668fc8a9ab31d9cf876b3d9ad3405756d4d683)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>

Change-Id: Idace325439958f6b490d2e6705d55e95305c4b2a
Reviewed-on: http://review.coreboot.org/7750
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Tested-by: build bot (Jenkins)

src/vendorcode/google/chromeos/chromeos.h

@@ -35,6 +35,9 @@ void save_vbnv(const uint8_t *vbnv_copy);
 void init_chromeos(int bootmode);
 
 struct romstage_handoff;
+
+/* TODO(shawnn): Remove these CONFIGs and define default weak functions
+ * that can be overridden in the platform / MB code. */
 #if CONFIG_VBOOT_VERIFY_FIRMWARE
 /*
  * This is a dual purpose routine. If dest is non-NULL the region at
@@ -57,6 +60,7 @@ static inline int vboot_get_handoff_info(void **addr, uint32_t *size)
 }
 static inline int vboot_skip_display_init(void) { return 0; }
 #endif
+int vboot_get_sw_write_protect(void);
 
 #include "gnvs.h"
 struct device;

src/vendorcode/google/chromeos/vboot_handoff.c

@@ -93,6 +93,12 @@ void *vboot_get_region(uintptr_t offset_addr, size_t size, void *dest)
        }
 }
 
+int __attribute((weak)) vboot_get_sw_write_protect(void)
+{
+	// Can be implemented by a platform / mainboard
+	return 0;
+}
+
 static void *vboot_get_payload(size_t *len)
 {
 	struct vboot_handoff *vboot_handoff;

src/vendorcode/google/chromeos/vboot_loader.c

@@ -249,6 +249,8 @@ static void vboot_invoke_wrapper(struct vboot_handoff *vboot_handoff)
 		*iflags |= VB_INIT_FLAG_REC_BUTTON_PRESSED;
 	if (get_write_protect_state())
 		*iflags |= VB_INIT_FLAG_WP_ENABLED;
+	if (vboot_get_sw_write_protect())
+		*iflags |= VB_INIT_FLAG_SW_WP_ENABLED;
 	if (CONFIG_VIRTUAL_DEV_SWITCH)
 		*iflags |= VB_INIT_FLAG_VIRTUAL_DEV_SWITCH;
 	if (CONFIG_EC_SOFTWARE_SYNC) {