lib32 support for ARM64

[Warner Losh]

On Thu, Feb 16, 2017 at 10:42 AM,  <fuz at fuz.su> wrote:
> Hello!
>
> I have recently started to use FreeBSD on my Raspberry Pi 3, when I
> noticed that there is no lib32 support, i.e. you cannot run 32 bit ARM
> binaries. As I am currently a student with a lot of time to kill during
> the summer, I am thinking about implementing this. I would like to know:
>
>  * what needs to be ported/adapted to get lib32 support working?
>  * has there been any existing work in this direction?
>  * is there interest in implementing this feature?
>  * if yes, would this feature be suitable for a gsoc project?
>
> I have no experience in working on the FreeBSD kernel except for a
> one-line patch I wrote to get an LPT port card running. I have (for a
> student) very good knowledge of programming in C. I know how to read and
> write assembly code. I have a reasonable idea of how the FreeBSD kernel
> is structured.

There's two issues here: (1) building lib32 stuff. It isn't hard, but
lots of grunt work given the differences between the tool chains for
armv6 and arm64. (2) Running the 32-bit binaries (which we don't
support).

Past experience suggests it's on the order of a few days to a couple
of weeks worth of work. But arm wasn't setup for 32/64 bit sharing so
it is likely going to be on the longer end of that, if not a bit
longer. Especially for a more junior person, so it would be a little
small on the GSoC scale, but no worse than some other GSoCs that have
been completed successfully.

Warner