GPT (GUID) partition table: format specification

KS implementation details

License: CC0-1.0

This page hosts a formal specification of GPT (GUID) partition table using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.

Block diagram

Format specification in Kaitai Struct YAML

meta:
  id: gpt_partition_table
  title: GPT (GUID) partition table
  endian: le
  license: CC0-1.0
doc-ref: Specification taken from https://en.wikipedia.org/wiki/GUID_Partition_Table
instances:
  sector_size:
    value: 0x200
    # Default is 0x200 for 512 byte sectors, set to 0x1000 to parse 4096 byte sectors.
  primary:
    io: _root._io
    pos: _root.sector_size
    type: partition_header
  backup:
    io: _root._io
    pos: _io.size - _root.sector_size
    type: partition_header
types:
  partition_entry:
    seq:
      - id: type_guid
        size: 0x10
      - id: guid
        size: 0x10
      - id: first_lba
        type: u8
      - id: last_lba
        type: u8
      - id: attributes
        type: u8
      - id: name
        type: str
        encoding: UTF-16LE
        size: 0x48
  partition_header:
    seq:
      - id: signature
        contents: [0x45, 0x46, 0x49, 0x20, 0x50, 0x41, 0x52, 0x54]
      - id: revision
        type: u4
      - id: header_size
        type: u4
      - id: crc32_header
        type: u4
      - id: reserved
        type: u4
      - id: current_lba
        type: u8
      - id: backup_lba
        type: u8
      - id: first_usable_lba
        type: u8
      - id: last_usable_lba
        type: u8
      - id: disk_guid
        size: 0x10
      - id: entries_start
        type: u8
      - id: entries_count
        type: u4
      - id: entries_size
        type: u4
      - id: crc32_array
        type: u4
      # The document states "Reserved; must be zeroes for the rest of the block".
      # It would be pointless to process a data structure that must be zeroed.
    instances:
      entries:
        io: _root._io
        pos: entries_start * _root.sector_size
        size: entries_size
        type: partition_entry
        repeat: expr
        repeat-expr: entries_count