porting openJDK to MINIX

[Roman Kennke]

Am Freitag, den 14.12.2012, 14:31 +0000 schrieb Andrew Haley:
> 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.

Or use the one in OpenJDK8. That one's not broken.

> 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.

As far as I know, Minix is x86-only, so it should be possible to use
what's in Hotspot already. Even  the template interpreter and JIT might
just work.

> 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.

Yeah. I don't know anything about Minix, except that it's Unix-y. There
are those many little peculiarities in the interpretation of Unix/Posix
though, as well as little unnerving build-toolchain differences. Then
there's the graphics stack, if that's X11, it's probably fine.
Otherwise.. you gotta write that too.

Regards, Roman