Add a --vblock option to firmware_utility to only output the verification block.

src/platform/vboot_reference/vfirmware/firmware_image.c

 /* Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  *
  * Functions for generating and manipulating a verified boot firmware image.
  */
 
 #include "firmware_image.h"
 
 #include <sys/types.h>
@@ skipping 240 matching lines @@
   Free(header_blob);
 
   if (st.overrun || st.remaining_len != 0) { /* Underrun or Overrun. */
     Free(firmware_blob);
     return NULL;
   }
   return firmware_blob;
 }
 
 int WriteFirmwareImage(const char* input_file,
-                       const FirmwareImage* image) {
+                       const FirmwareImage* image,
+                       int is_only_vblock) {
   int fd;
+  int success = 1;
   uint8_t* firmware_blob;
   uint64_t blob_len;
 
   if (!image)
     return 0;
   if (-1 == (fd = creat(input_file, S_IRWXU))) {
     debug("Couldn't open file for writing.\n");
     return 0;
   }
 
   firmware_blob = GetFirmwareBlob(image, &blob_len);
   if (!firmware_blob) {
     debug("Couldn't create firmware blob from FirmwareImage.\n");
     return 0;
   }
-  if (blob_len != write(fd, firmware_blob, blob_len)) {
-    debug("Couldn't write Firmware Image to file: %s\n", input_file);
-    Free(firmware_blob);
-    close(fd);
-    return 0;
+  if (!is_only_vblock) {
+    if (blob_len != write(fd, firmware_blob, blob_len)) {
+      debug("Couldn't write Firmware Image to file: %s\n", input_file);
+      success = 0;
+    }
+  } else {
+    /* Exclude the firmware_data. */
+    int vblock_len = blob_len - image->firmware_len;
+    if (vblock_len != write(fd, firmware_blob, vblock_len)) {
+      debug("Couldn't write Firmware Image verifcation block to file: %s\n",
+            input_file);
+      success = 0;
+    }
   }
   Free(firmware_blob);
   close(fd);
-  return 1;
+  return success;
 }
 
 void PrintFirmwareImage(const FirmwareImage* image) {
   if (!image)
     return;
 
   /* Print header. */
   debug("Header Length = %d\n"
          "Firmware Signature Algorithm = %s\n"
          "Firmware Key Version = %d\n\n",
@@ skipping 165 matching lines @@
     Free(firmware_buf);
     return 0;
   }
   image->firmware_signature = (uint8_t*) Malloc(signature_len);
   Memcpy(image->firmware_signature, firmware_signature, signature_len);
   Free(firmware_signature);
   Free(firmware_buf);
   Free(preamble_blob);
   return 1;
 }