Ignore the AlternateLBA field in the GPT headers.

src/platform/vboot_reference/vboot_firmware/lib/cgptlib/cgptlib_internal.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.
  */
 
 #include "cgptlib.h"
 #include "cgptlib_internal.h"
 #include "crc32.h"
 #include "gpt.h"
 #include "utility.h"
@@ skipping 58 matching lines @@
   if ((h->number_of_entries < MIN_NUMBER_OF_ENTRIES) ||
       (h->number_of_entries > MAX_NUMBER_OF_ENTRIES) ||
       (h->number_of_entries * h->size_of_entry != TOTAL_ENTRIES_SIZE))
     return 1;
 
   /* Check locations for the header and its entries.  The primary
    * immediately follows the PMBR, and is followed by its entries.
    * The secondary is at the end of the drive, preceded by its
    * entries. */
   if (is_secondary) {
-    if ((h->my_lba != drive_sectors - 1) || (h->alternate_lba != 1))
+    if (h->my_lba != drive_sectors - 1)
       return 1;
     if (h->entries_lba != h->my_lba - GPT_ENTRIES_SECTORS)
       return 1;
   } else {
-    if ((h->my_lba != 1) || (h->alternate_lba != drive_sectors - 1))
+    if (h->my_lba != 1)
       return 1;
     if (h->entries_lba != h->my_lba + 1)
       return 1;
   }
 
   /* FirstUsableLBA must be after the end of the primary GPT table
    * array.  LastUsableLBA must be before the start of the secondary
    * GPT table array.  FirstUsableLBA <= LastUsableLBA. */
   if (h->first_usable_lba < 2 + GPT_ENTRIES_SECTORS)
     return 1;
@@ skipping 244 matching lines @@
   e->attributes |= ((uint64_t)priority << CGPT_ATTRIBUTE_PRIORITY_OFFSET) &
       CGPT_ATTRIBUTE_PRIORITY_MASK;
 }
 
 
 void SetEntryTries(GptEntry* e, int tries) {
   e->attributes &= ~CGPT_ATTRIBUTE_TRIES_MASK;
   e->attributes |= ((uint64_t)tries << CGPT_ATTRIBUTE_TRIES_OFFSET) &
       CGPT_ATTRIBUTE_TRIES_MASK;
 }