Describe PMBR in terms of syslinux GPT extension.

show.c

 /*-
  * Copyright (c) 2002 Marcel Moolenaar
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 165 matching lines @@
 
                         /* Show the uuid of each partition. */
                         {
                                 char *s;
                                 uuid_to_string(&ent->ent_uuid, &s, NULL);
                                 printf(" (ID: %s)", s);
                                 free(s);
                         }
                         break;
                 case MAP_TYPE_PMBR:
-                        printf("PMBR");
+                        mbr = m->map_data;
+                        if (le16toh(mbr->magic_number) == MBR_MAGIC)
+                        {
+                                char *s;
+                                uuid_to_string(&mbr->boot_guid, &s, NULL);
+                                printf("PMBR (Boot GUID: %s)", s);
+                                free(s);
+                        }
+                        else
+                        {
+                            printf("PMBR (no magic)");
+                        }
                         break;
                 }
                 putchar('\n');
                 m = m->map_next;
         }
 }
 
 int
 cmd_show(int argc, char *argv[])
 {
@@ skipping 22 matching lines @@
                         continue;
                 }
 
                 show(fd);
 
                 gpt_close(fd);
         }
 
         return (0);
 }