porting openJDK to MINIX

[Bob Vandette]

On Dec 14, 2012, at 9:31 AM, Andrew Haley wrote:

> On 12/14/2012 01:19 PM, John Smith wrote:
> 
>> I need to port openJDK to MINIX (and also write some bytecode
>> interpreter if not the whole JVM, it only needs to run .class files
>> compiler is not needed). Given that I'm CS student on second year, I
>> would be very thankful if somebody can point me in right direction,
>> suggest some literature or give me some insight for solving this
>> problem. Also, if its possible for somebody to roughly estimate how
>> much time is needed for this project, it would help me to get a
>> better picture.
> 
> I think there is a porting guide, but I've never seen it.
> 
> With regard to the CPU:
> 
> If you're prepared to use the Zero port, which is written in C++, it's
> just a matter of recompilation.  Zero on the current HotSpot is
> broken, but you can use an earlier version.

In my experience, it's not quite just a recompilation.  You need to link against
the libffi (Foreign Function Interface), assuming your platform is support by libffi.   
This provides frame handling similar to the frame manager in the non-Zero implementation.

Bob Vandette

> 
> If you're prepared to use the C++ interpreter with some assembler
> help, that's a bigger job.  You'll need to write an assembler (HotSpot
> use its own) and code to link Java and native code.
> 
> If you want to write the whole bytecode interpreter in assembler
> that's a much bigger job: I'd estimate 6 months to one year -- if you
> know what you're doing.
> 
> With regard to the OS:
> 
> I don't know how long it would take to port the OS layer.  There are
> already ports to Solaris and Linux, so you have a good starting point.
> It's the really low-level interfaces that will give you trouble,
> though.
> 
> Andrew.