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Firmware Modification Kit

Most of the time you don't really need to re-build DD-WRT to make your desired changes. Now, this process has been made easy with the Firmware Modification Kit.

Firmware Modification Kit Documentation and Download

Description

This kit gives the user the ability to make changes to a firmware image without recompiling the firmware sources. It works by extracting the firmware into its component parts, then extracting the squashfs-lzma based file system (other file systems can be supported with tweaks). The user can then make modifications to the extracted file system, then rebuild the firmware image.

Why is this useful?

A list of some of the many reasons this might be desired are: add initialization scripts install new packages (remember, packages pre-installed are compressed much better) extend web UI remove un-needed packages mix-and-match packages from various DD-WRT variants WARNING: Due to abuse by those re-branding DD-WRT and selling it, or pre-flashed routers with it on eBay, builds dated later than 08/04/2006 have some protections against re-branding the web UI.

Where to get the kit

The latest documentation and download link can always be found here: http://www.bitsum.com/firmware_mod_tools.htm

Requirements

I've worked hard to make sure the requirements are low enough for anyone to use this kit. However, to reduce distribution costs and better represent the multi-platform capabilities of this kit, the binary tools in the kit do automatically build themselves the first time you run one of the scripts. Any machine set up to build anything C or C++ on the machine will probably be ready. The few requirements are all basic items that everyone has easy access to:

  1. A compatible platform. The following are specifically supported (or specifically unsupported):
    1. LINUX
    2. OS X  
    3. CYGWIN **alpha stage testing (!! built firmwares may not boot !!)**
  2. GNU C (gcc)
  3. GNU C++ (g++)
  4. Standard C runtime library development
  5. Standard C++ runtime library development
  6. GNU make
  7. TAR and GZIP (optional, used by ipkg_install.sh)

For OS X, installing the Mac OS X Developer Tools will supply the needed GNU C and C++ compilers and make utility.

Compatibility

Any cybertan style firmware image format should that uses squashfs-lzma as a root file system work fine. Firmwares that use regular squashfs or other file systems (i.e. cramfs) will work if the steps that extract the file system and rebuild the file system are tweaked. As is, it is compatible with the following:

Firmware Notes
DD-WRT
OpenWrt probably not at the moment - should require older mksquashfs if using White Russian
FreeWrt untested
Sveasoft Alchemy/Talismen untested
HyperWrt untested

I may extend default support to cramfs, regular squashfs, and older squashfs and squashfs-lzma versions if there is sufficient demand. Note that for firmwares that do have an easy to use build system and/or an image builder utility, i.e. OpenWrt, this kit is of less use.

Instructions

I've written two scripts that simply the process considerably. Basically, it's a one-step process to extract the firmware, and a one-step process to rebuild the firmware.

Extracting the firmware (extract_firmware.sh)

Simply run extract_firmware.sh with the following parameters. You must run this tool from inside the directory it exists in.

$ ./extract_firmware.sh firmware.bin working_directory/
firmware.bin 
the firmware image you want to extract, i.e. DD-WRT.v23_MICRO_GENERIC.BIN.
working_directory 
the working directory you want to use. This is where the intermediate files and the extracted file system will be stored. Note that files in the working directory may be deleted!

It doesn't matter which firmware image you supply, i.e. for a WRT54G or an ASUS WL-500G. These images are usually all the same and differ only in the header format. The rebuilding process will create images for the various models.

An extraction log is created as extract.log.

Modifying the firmware (manual and/or ipkg_install.sh)

Modifying the firmware is simple. The file system is stored in the working directory you supplied to extract_firmware.sh. Here are the subfolders of this directory:

   rootfs/ 
       This is where the file system is. Make modifications here.
   image_parts/ 
       This is where intermediate files are stored. If you need to replace the kernel (not at all recommended), you can do so by replacing vmlinuz here.

One merely changes, adds, or removes files in rootfs/ to make changes to the firmware's file system. After you're done making changes, rebuild the firmware. Installing packages (.IPK) Packages are pre-built collections of files pertaining to a set of software. OpenWrt and DD-WRT both use packages, and most are cross-compatible. These packages are stored in a tar/gzip archive of a pre-defined structure that includes some control files. You can extract and copy the files manually, or use the ipkg_install.sh script included with this kit. For a list of some of the available packages (not all may work), see http://ftp.selfnet.de/pub/openwrt/backports/rc5/ . Example use:

$ ./ipkg_install.sh some_package-1.2.5.ipk working_directory/
some_package-1.2.5.ipkg 
would be the filename of the package.
working_directory 
is the same working directory you supplied to the extract_firmware.sh script.


Re-building the firmware (build_firmware.sh)

Rebuilding the firmware is as easy as extracting it. Use the build_firmware.sh script to automate the process. You must run this tool from inside the directory it exists in. Example use:

$ ./build_firmware.sh output_directory/ working_directory/
output_directory 
the path to which the created firmware images should be stored. If images already exist here, they will be over-written. Firmware images for various models will be emitted (these images are all the same but have different header patterns so they are accepted by the target models).
working_directory 
the working directory supplied to extract_firmware.sh.

A building log is created as build.log.

Building DD-WRT from Source

Building DD-WRT from source is not that difficult, but don't expect the build system to be as well maintained as OpenWrt. Brainslayer has not the time to do everything. Until the day comes that DD-WRT will build without any extra steps, I've written some scripts that will set up a build environment for DD-WRT. Newer builds of DD-WRT may break compatibility with these scripts. If this happens and I don't update them, please take the time to update them if you are sure your changes are appropriate.

Requirements

To build DD-WRT, you need a Linux machine. It should work on any reasonably modern machine with basic development tools installed.

Pre-requisites (todo: someone please finish this list -- most/all of the openwrt pre-requisites are required):

  • Automake v1.9.4
  • GNU Make v?
  • GCC/G++ v4
  • ncurses v?
  • binutils v?
  • tar
  • gzip

Organization

WiP DD-WRT's source is organized like so:

src/            source
  router/       packages 
  linux/        kernel
opt/            make/control

Source Retrivial

The first step is to retrieve the desired DD-WRT version. You can do this by either downloading from the DD-WRT downloads section, or by checking out using Subversion.

Subversion

First you'll need to get subversion, available at http://subversion.tigris.org/ For some Linux distributions, you should be able to get subversion using the package manager tool.

After installing, you can get the latest source from DD-WRT by running the following command:

svn co svn://svn.dd-wrt.com/DD-WRT .

That will download the source into the current directory, you could change the directory by changing the "." at the end to the directory you would like the source in. Leaving out the "." will download everything to a "DD-WRT" sub-directory.

Download Section

Another way to get the source is to download it from the Downloads Section. Afterwards you need to extract it which is done simply by using a command like:

tar -jxvf nameoffile.tar.bz

Instructions

You'll need the 3.4.6 and 4.1.0 mipsl uclibc toolchains. The mips-uclibc 3.4.6 toolchain is used for building the kernel and the 4.1.0 mipsel-uclibc toolchain is used for building the user-mode packages. Unpack the toolchains wherever you desire, the scripts below will set up symlinks appropriately.

After running these scripts below, to build DD-WRT you simply need to:

 1. Add the 4.1.0 toolchains bin folder to your path environment variable. i.e. PATH=$PATH:/home/db90h/toolchains/4.1.0-uclibc
 2. In DD-WRT/opt run ./install.sh. Running ./install_* to build a particular variant requires you rebuild shared code first.

These two scripts should be saved to ready_ddwrt.sh and ready_ddwrt_root.sh. You can download them [here]. These work as of DD-WRT v23 SP2 beta 08/03/06.

#!/bin/sh
#
# title: ready_ddwrt.sh
# version: 1.1
# author: Jeremy Collake <jeremy@bitsum.com> aka db90h
#
# This silly script will prepare a build environment
# for DD-WRT. You must also run ready_ddwrt_root.sh.
#
# The toolchains path isn't actually used in this script.
#
MINPARAMS=1
if [ $# -lt "$MINPARAMS" ]
	then
	echo usage:
	echo    ready_ddwrt.sh [ddwrt_base_path]
	echo
	echo i.e.:
	echo    ready_ddwrt.sh /home/db90h/DD-WRT /home/db90h/4.1.0-ucliblc
	echo
	exit 1
fi  

ME=`whoami`
DDROOT=$1

echo I am $ME
echo DD-WRT is at $DDROOT

echo ................................................................
echo creating some symlinks
echo ................................................................
rm $DDROOT/src/linux/brcm/linux.v23/include/asm
ln -s $DDROOT/src/linux/brcm/linux.v23/include/asm-mips $DDROOT/src/linux/brcm/linux.v23/include/asm
echo done

echo ................................................................
echo adjusting some attributes
echo ................................................................
chmod +x $DDROOT/src/router/iptables/extensions/.dccp-test 
chmod +x $DDROOT/src/router/iptables/extensions/.layer7-test
echo done

echo ................................................................
echo re-building some tools
echo ................................................................
cd $DDROOT
# make bb_mkdep
cd src/router/busybox/scripts 
rm bb_mkdep
make bb_mkdep 
# make jsformat
cd ../../../.. 
cd src/router/tools 
rm jsformat
make jsformat 
cd ../../..
cd src/squashfs-tools/
rm mksquashfs-lzma
make 
cp mksquashfs-lzma ../linux/brcm/linux.v23/scripts/squashfs
cd ../..
echo done

This second script needs to be run as root ...

#!/bin/sh
#
# title: ready_ddwrt_root.sh
# version: 1.1
# author: Jeremy Collake <jeremy@bitsum.com> aka db90h
#
# This silly script will prepare a build environment
# for DD-WRT. You must also run ready_ddwrt.sh.
#
MINPARAMS=2
if [ $# -lt "$MINPARAMS" ]
	then
	echo 
	echo This script needs root access.
	echo
	echo usage:
	echo    ready_ddwrt_root.sh [ddwrt_base_path] [3.4.6_toolchain_base_path]
	echo
	echo i.e.:
	echo    ready_ddwrt_root.sh /home/db90h/DD-WRT /home/db90h/3.4.6-ucliblc-0.9.28
	echo
	exit 1
fi  

ME=`whoami`
DDROOT=$1
TCHAIN=$2

echo I am $ME
echo DD-WRT is at $DDROOT
echo mipsl-uclibc-x toolchain is at $TCHAIN

echo ................................................................
echo creating some symlinks
echo ................................................................
# duh, this will already be here
mkdir -p /opt
rm /opt/3.3.6
ln -s $TCHAIN /opt/3.3.6
rm /GruppenLW
ln -s $DDROOT/image /GruppenLW

echo All done!

--Jcollake 21:05, 5 Aug 2006 (CEST)

Changing DD-WRT

Work in progress DD-WRT is easily reconfigured. In the /src/router folder you'll find .config* files for each type of distribution. Use 'make menuconfig' to edit the appropriate configuration files. The /src/router/busybox folder contains .config* files for its configuration. Just edit them in a similar way.

Change micro configuration: WARNING: Before and after doing this you need to copy and restore the "Internal Options" section of the .config files. These options don't seem to be in #the Config template.

cd DD-WRT/src/router
cp .config .config_micro
make menuconfig
cp .config_micro .config

Change micro Busybox configuration:

cd DD-WRT/src/router/busybox
cp .config .config_micro
make menuconfig
cp .config_micro .config

Change micro kernel configuration:

cd DD-WRT/src/router/busybox
cp .config .config_micro
make menuconfig
cp .config_micro .config

--Jcollake 20:11, 6 Aug 2006 (CEST)