Protect the kernel version space from redefinition.

vboot_firmware/include/rollback_index.h

Index: vboot_firmware/include/rollback_index.h
diff --git a/vboot_firmware/include/rollback_index.h b/vboot_firmware/include/rollback_index.h
index 9be97b9737f04a5152dee8aa3ca249471b1ce698..c5c650e6bb5e9e46d743409497a64feb1c26ec75 100644
--- a/vboot_firmware/include/rollback_index.h
+++ b/vboot_firmware/include/rollback_index.h
@@ -25,7 +25,13 @@ extern uint16_t g_kernel_version;
 #define KERNEL_VERSIONS_NV_INDEX        0x1002
 #define TPM_IS_INITIALIZED_NV_INDEX     0x1003
 #define KERNEL_VERSIONS_BACKUP_NV_INDEX 0x1004
-#define KERNEL_BACKUP_IS_VALID_NV_INDEX 0x1005
+#define KERNEL_MUST_USE_BACKUP_NV_INDEX 0x1005
+
+/* Unique ID to detect kernel space redefinition */
+#define KERNEL_SPACE_UID "GRWL"        /* unique ID with secret meaning */
+#define KERNEL_SPACE_UID_SIZE (sizeof(KERNEL_SPACE_UID) - 1)
+#define KERNEL_SPACE_INIT_DATA ((uint8_t*) "\0\0\0\0" KERNEL_SPACE_UID)
+#define KERNEL_SPACE_SIZE (sizeof(uint32_t) + KERNEL_SPACE_UID_SIZE)
 
 /* All functions return 0 if successful, non-zero if error */
 uint32_t SetupTPM(void);