Re: bpf jit

[Zoltán Herczeg <hzmester%freemail.hu@localhost>]

Hi NetBSD devs,

> > Lack of documentation, as you already pointed out, contributes to this as
> > well.  There are various other questions unanswered, e.g. would we diverge
> > SLJIT code in favour of better integration into NetBSD?  Would the changes
> > be committed to upstream or we would maintain SLJIT ourselves or perhaps
> > would even take over the maintenance?
> >
> The author of sljit is in the discussion. Perhaps he can answer these
> questions?

The primary design points of sljit:
1) be lightweight - lighter than a library. In PCRE-JIT the compiler is simply 
included with a #include, so it is not possible to use the JIT compiler through 
PCRE, and the unnecessary functions (i.e. floating point arithmetic) are also 
removed by the linker.
2) easy to learn - looks like a simplified assembler.
3) cover the general features of widely used CPUs, instead of creating another 
RISC instruction translator. That is a major difference compared to other 
lightweight JITs (libjit, GNU lightning). 

We can add new features as long as they don't hurt other use cases, i.e. NetBSD 
kernel specific defines, if they are properly guarded by ifdefs. We can also 
add autotools based build system, .so versioning, etc. Just we should never 
forget that all of these features are optional. Of course we need someone who 
is willing to maintain these features.

Anyway, thanks to the PCRE library, sljit is now widely tested. I got feedback 
from IBM AIX users on PowerPC, Longsoon based MIPS sytems, etc, and we were 
able to make sljit work with a few minor changes.

Regards,
Zoltan