Block diagram
.trx file format is widely used for distribution of firmware updates for Broadcom devices. The most well-known are ASUS routers.
Fundamentally, it includes a footer which acts as a safeguard against installing a firmware package on a wrong hardware model or version, and a header which list numerous partitions packaged inside a single .trx file.
trx files not necessarily contain all these headers.
This page hosts a formal specification of Broadcom devices .trx firmware packaging using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.
meta:
id: broadcom_trx
title: Broadcom devices .trx firmware packaging
file-extension: trx
license: GPL-2.0-or-later
ks-version: 0.9
bit-endian: le
encoding: utf-8
endian: le
-license: |
Copyright (C) 2004 Manuel Novoa III <mjn3@codepoet.org>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
USA
doc: |
.trx file format is widely used for distribution of firmware
updates for Broadcom devices. The most well-known are ASUS routers.
Fundamentally, it includes a footer which acts as a safeguard
against installing a firmware package on a wrong hardware model or
version, and a header which list numerous partitions packaged inside
a single .trx file.
trx files not necessarily contain all these headers.
doc-ref:
- https://github.com/openwrt/firmware-utils/blob/a2c80c5/src/trx.c
- https://web.archive.org/web/20190127154419/https://openwrt.org/docs/techref/header
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/mtd/partitions/brcm,trx.txt
instances:
header:
pos: 0
type: header
tail:
pos: _io.size - sizeof<tail>
type: tail
types:
revision:
seq:
- id: major
type: u1
- id: minor
type: u1
version:
seq:
- id: major
type: u1
- id: minor
type: u1
- id: patch
type: u1
- id: tweak
type: u1
tail:
doc: "A safeguard against installation of firmware to an incompatible device"
seq:
- id: version
type: version
doc: "1.9.2.7 by default"
- id: product_id
type: strz
size: 12
- id: comp_hw
type: hw_comp_info
repeat: expr
repeat-expr: 4
doc: "0.02 - 2.99"
- id: reserved
size: 32
types:
hw_comp_info:
seq:
- id: min
type: revision
- id: max
type: revision
header:
seq:
- id: magic
contents: "HDR0"
- id: len
type: u4
doc: Length of file including header
- id: crc32
type: u4
doc: "CRC from `version` (??? todo: see the original and disambiguate) to end of file"
- id: version
type: u2
- id: flags
type: flags
- id: partitions
type: partition(_index)
doc: "Offsets of partitions from start of header"
repeat: until
repeat-until: _index >= 4 or not _.is_present
types:
partition:
params:
- id: idx
type: u1
seq:
- id: ofs_body
type: u4
instances:
is_present:
value: ofs_body != 0
is_last:
value: "(idx == _parent.partitions.size - 1) or (not _parent.partitions[idx + 1].is_present)"
if: is_present
len_body:
value: "is_last ? (_root._io.size - ofs_body) : _parent.partitions[idx + 1].ofs_body"
if: is_present
body:
io: _root._io
pos: ofs_body
size: len_body
if: is_present
flags:
seq:
- id: flags
type: b1
repeat: expr
repeat-expr: 16