=========
Buildroot
=========

.. include:: header.rst

.. TODO: tarball (with sources)

.. contents:: Contents

Building the Root File System
=============================

#. Download and untar buildroot::

    wget http://buildroot.uclibc.org/downloads/buildroot-2009.02.tar.bz2
    tar xjvf buildroot-2009.02.tar.bz2
    cd buildroot-2009.02/

#. Configure buildroot.  Refer to the Section below, `Configuring the
   Root Filesystem`_, for specfic configuration
   options::

    make menuconfig

   Alternatively, if you have an old configuration file that you wish
   to reuse, do this::

    cp buildroot-crosstool-ng-simple-config .config
    make oldconfig

#. Tell buildroot to build all the packages you selected, and create a
   root filesystem image::

    unset  CC CXX CPP CFLAGS INCLUDES CXXFLAGS LD_LIBRARY_PATH LIBRARY_PATH CPATH
    export CC CXX CPP CFLAGS INCLUDES CXXFLAGS LD_LIBRARY_PATH LIBRARY_PATH CPATH
    make

   When buildroot is done building, it will have produced the following
   image of the root filesystem::

    binaries/uclibc/rootfs.powerpc.tar.gz

   If you do not see this file, then that most likely means one of
   two things:

   - You did not enable "tar the root filesystem" with "gzip" compression
     (described in Section `Configuring the Root Filesystem`_).
   - The build failed

#. The root filesystem image needs a small patch to enable logins on the
   uartlite port.  To apply this patch, we need to extract image, apply
   the patch, then regenerate the tar archive::

    mkdir rootfs-tmp
    fakeroot

    tar xzvf binaries/uclibc/rootfs.powerpc.tar.gz -C rootfs-tmp

    cd rootfs-tmp
    patch etc/inittab << EOF
    Index: etc/inittab
    ===================================================================
    --- etc.orig/inittab
    +++ etc/inittab
    @@ -29,6 +29,7 @@

     # Put a getty on the serial port
     #ttyS0::respawn:/sbin/getty -L ttyS0 115200 vt100
    +ttyUL0::respawn:/sbin/getty -L ttyUL0 115200 vt100

     # Logging junk
     null::sysinit:/bin/touch /var/log/messages
    EOF
    tar czvf ../rootfs.powerpc.patched.tar.gz .
    genext2fs -d . -b 4096 ../initrd.patched.ext2

    exit # leave the fakeroot shell
    cat initrd.patched.ext2 | gzip > initrd.patched.ext2.gz

   Now, there is a root filesystem image: initrd.patched.ext2.gz.
   This is the one that you should use as an initrd for the Linux kernel
   (you'll eventually rename it to ramdisk.image.gz)::

    cp initrd.patched.ext2.gz <linux>/arch/powerpc/boot/ramdisk.image.gz

   It is fairly easy to generate an initramfs, but you have to take
   care to create a "/init" file (because initramfs does not recognize
   "/sbin/init").  You can probably achieve this by creating a symlink
   from "/init" to "/bin/busybox".

.. TODO:

.. - Add /dev/ttyUL0 (nice!!  Buildroot already creates these!!  And they
  are even already added to /etc/securetty)::

..     mknod dev/ttyUL0 c 204 187

.. - inittab ttyUL0 patch::



Configuring the Root Filesystem
===============================

.. figure:: im-edited/buildroot-menuconfig-01.png

- Target Architecture: powerpc
- Target Architecture Variant: 405
- Target options
- Build options

  - Download dir: ${HOME}/sources

- Toolchain 

  - Toolchain type: External binary toolchain
  - Enable large file support: Yes
  - Enable RPC: Yes
  - Use software floating point by default: Yes
  - Thread library implementation: linuxthreads (stable/old)
  - Build/install c++ compiler and libstdc++?: Yes
  - External toolchain path: /home/xilinx/crosstool-ng-1.3.2/powerpc-405-linux-uclibc
  - External toolchain prefix: powerpc-405-linux-uclibc

- Target filesystem options 

  - tar the root filesystem: Yes

    - Compression method: gzip

Error Messages and Patches
==========================

"cannot find /lib/libc.so.0"
----------------------------

If you select certain packages in buildroot, you may come across this
message: "cannot find /lib/libc.so.0".  This happened to me when I
selected the packages from MTD utils.

To workaround this problem, I manually edited my uClibc toolchain
installation (based on crosstool-ng) as follows:

  Edit ``/home/xilinx/crosstool-ng-1.3.2/powerpc-405-linux-uclibc/powerpc-405-linux-uclibc/sys-root/usr/lib/libc.so``
  by replacing absolute paths with relative paths (see `Help with Patch
  Files <patch-file-help.html>`_ for more information)::

    Index: lib/libc.so
    ===================================================================
    --- lib.orig/libc.so
    +++ lib/libc.so
    @@ -2,4 +2,4 @@
      * Use the shared library, but some functions are only in
      * the static library, so try that secondarily. */
     OUTPUT_FORMAT ( elf32-powerpc )
    -GROUP ( /lib/libc.so.0 /usr/lib/uclibc_nonshared.a AS_NEEDED ( /lib/ld-uClibc.so.0 ) )
    +GROUP ( ../lib/libc.so.0 ../usr/lib/uclibc_nonshared.a AS_NEEDED ( ../lib/ld-uClibc.so.0 ) )




Downloads
=========

- `buildroot-crosstool-ng-simple-config <distfiles/buildroot-crosstool-ng-simple-config>`_