A “Hello World” class to test the JVM will be:

class HelloWorldJamVM {
	public static void main(String[] args) {
		System.out.println("hello world");
	}
}

saved as HelloWorldJamVM.java. However, executing a “Hello World” requires longer steps than writing that class.

In order for the JamVM 1.5.4 to run on Ubuntu, we need (1) build-essential (certainly so) and (2) GCJ with dependency of (3) zlib1g-dev. It’s all available in the Karmic ARM repo. Another thing that we need is GNU Classpath 0.98.

Following the instruction, as root we can then configure, make, make install, make install-strip sources under jamvm-1.5.4 directory. Continue them with the classpath-0.98 sources by configuring as follow

./configure --disable-gtk-peer --disable-gconf-peer --disable-plugin --disable-Werror

and then make install as usual. The whole compiling will run slow for sure as QEMU emulates ARM far from nearing native processor performance in my case.

We can compile the above “Hello World” using GCJ with the command javac, which is actually linked to /usr/bin/gcj-wrapper-4.4.

javac HelloWorldJamVM.java

A HelloWorldJamVM.class bytecode file will appear and we can run this with JamVM

PATH=$PATH:/usr/local/jamvm/bin 
export PATH
jamvm HelloWorldJamVM

QEMU with Ubuntu ARM Cortex A8 running JamVM embedded JVM

Ready-to-use image for from the old Ubuntu 9.10 Karmic is avalaible as suggested in RootStock Wiki .

To run Ubuntu 10,04 Lucid you can create similar .img filled by RootStock generated root file system as described in this post generating lucid-arm.img. Boot image is obtained from Lucid port page, of which I saved with the name vmlinuz-lucid-current-ports which is actually linux kernel 2.6.32-21. Running QEMU is then:

qemu-system-arm -M versatilepb -cpu cortex-a8 \
  -kernel vmlinuz-lucid-current-ports \
  -hda lucid-arm.img -m 256 -append "root=/dev/sda mem=256M devtmpfs.mount=0 rw"

However, adding -redir tcp:3232::22 isn’t directly working (although telnet is showing both directions are functional). This redirection is working with the Karmic image which gives instant ssh on my host laptop as in:

ssh localhost -oPort=3232 -l ubuntu

Note: successful QEMU machine image probably won’t boot successfully with the real board. I can’t use kernel 2.6.38-10 for Lucid rootfs on QEMU, but successfully boot that on DevKit8500D board.

QEMU console of Ubuntu 10.04 VM