Describe PMBR in terms of syslinux GPT extension.

gpt.h

 /*-
  * 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 39 matching lines @@
         uint8_t         part_typ;               /* partition type */
         uint8_t         part_ehd;               /* end head */
         uint8_t         part_esect;             /* end sector */
         uint8_t         part_ecyl;              /* end cylinder */
         uint16_t        part_start_lo;          /* absolute starting ... */
         uint16_t        part_start_hi;          /* ... sector number */
         uint16_t        part_size_lo;           /* partition size ... */
         uint16_t        part_size_hi;           /* ... in sectors */
 };
 
 struct mbr {

[tedbo, 2010/03/12 22:32:48]

The original struct represented a generic MBR with up to 446 byes of code data.
The new struct is specific to the syslinux GPT new protocol (as was the code to
make it bootable in boot.c). Maybe add a comment here that explains that this is
specific to the Syslinux GTP MBR boot protocol?

-        uint16_t        mbr_code[223];
+        uint8_t         mbr_code[424];
+        uuid_t          boot_guid;
+        uint32_t        disk_id;
+        uint16_t        magic_number;
+#define MBR_MAGIC       0x9A1D
         struct mbr_part mbr_part[4];
         uint16_t        mbr_sig;
 #define MBR_SIG         0xAA55
 };
 
 extern char *device_name;
 extern off_t mediasz;
 extern u_int parts;
 extern u_int secsz;
 extern int readonly, verbose;
@@ skipping 12 matching lines @@
 int     cmd_boot(int, char *[]);
 int     cmd_create(int, char *[]);
 int     cmd_destroy(int, char *[]);
 int     cmd_label(int, char *[]);
 int     cmd_migrate(int, char *[]);
 int     cmd_recover(int, char *[]);
 int     cmd_remove(int, char *[]);
 int     cmd_show(int, char *[]);
 
 #endif /* _GPT_H_ */