Building the GNU Classpath for ARM

My preferred method now for building packages on the TS-7xxx series of single board computers (SBC's) is to use the gentoo stage3 filesystem as an NFS root, which comes with a C/C++ compiler and most of the necessary utilities. It is much slower, but this way I don't have to work around any strange cross-compiling issues or annoying pkgconfig native-executable requirements which tend to pollute configure scripts for most higher level applications.

The target I'm building for is an ARM 920T processor from cirrus - the EP93xx series of processors - which have only recently acquired a decent level of support in the Linux kernel. Also, as of gcc-4.1.1 the Thumb instruction set is supported as well, although I don't really use it. The ARM EABI is quite useful for those that require floating point functionality, but most of what my company does requires integer math for the most part. For that reason, the stage3 filesystem I use for my NFS root is the arm-softfloat-linux-uclibc stage3 filesystem located here:

http://adelie.polymtl.ca/experimental/arm/embedded/stages/stage3-arm-uclibc-softfloat-20050811.tar.bz2

However, please feel free to select any Gentoo mirror from this site:

http://www.gentoo.org/main/en/mirrors.xml

I've posted several sets of instructions for those that would also like to use the 2.6 kernel I've compiled for the TS-7xxx boards as well. If you're interested, please see the mailing list archives:

http://tech.groups.yahoo.com/group/ts-7000/message/6574

You can also download the kernel directly from here:

http://vaiprime.visibleassets.com/~cfriedt/zImage-2.6

and the config, here:

http://vaiprime.visibleassets.com/~cfriedt/linux-2.6.20.6.config

I recently changed my kernel configuration to include swap functionality, specifically because compiling the gnu classpath for the arm used over 3 times as much memory than was available on the board.

The tricky part though, is that Linux doesn't play very well with swap files on an NFS filesystem. But after doing a bit of googling, I found that there is 1 commonly used work-around.

# dd if=/dev/zero of=/mnt/swapfile bs=1024 count=$((1024*256))
# losetup /dev/loop0 /mnt/swapfile
# mkswap /dev/loop0
# swapon /dev/loop0

In the above section, I've created a 256MB swap file for the linux kernel, and it is accessed by the kernel through a loop device, which offers some apparently greater level of control than simply using swapon /mnt/swapfile.

I'm still compiling the gnu classpath, and I'm not sure exactly how far along the process is, but here are some of the memory usage figures:

=========================
MemTotal: 62192 kB
MemFree: 2728 kB
SwapCached: 12172 kB
SwapTotal: 262136 kB
SwapFree: 127772 kB
=========================

I'll continue to update this blog post as the compilation proceeds, but it's already been going for 2 hours steadily...