Re: ppc64le and 32-bit LE userland compatibility

[Segher Boessenkool <segher@kernel.crashing.org>]

On Sun, May 31, 2020 at 12:57:12AM +0000, Will Springer wrote:
> On Saturday, May 30, 2020 12:22:12 PM PDT Segher Boessenkool wrote:
> > The original sysv PowerPC supplement
> > http://refspecs.linux-foundation.org/elf/elfspec_ppc.pdf
> > supports LE as well, and most powerpcle ports use that.  But, the
> > big-endian Linux ABI differs in quite a few places, and it of course
> > makes a lot better sense if powerpcle-linux follows that.
> 
> Right, I should have clarified I was talking about Linux ABIs 
> specifically.

That was the link you deleted.

> > What patches did you need?  I regularly build >30 cross compilers (on
> > both BE and LE hosts; I haven't used 32-bit hosts for a long time, but
> > in the past those worked fine as well).  I also cross-built
> > powerpcle-linux-gcc quite a few times (from powerpc64le, from powerpc64,
> > from various x86).
> 
> There was just an assumption that LE == powerpc64le in libgo, spotted by 
> q66 (daniel@ on the CC). I just pushed the patch to [1].

Please send GCC patches to gcc-patches@ ?

> > Almost no project that used 32-bit PowerPC in LE mode has sent patches
> > to the upstreams.
> 
> Right, but I have heard concerns from at least one person familiar with 
> the ppc kernel about breaking existing users of this arch-endianness 
> combo, if any. It seems likely that none of those use upstream, though ^^;

So we don't care, because we *cannot* care.

> > A huge factor in having good GCC support for powerpcle-linux (or
> > anything else) is someone needs to regularly test it, and share test
> > results with us (via gcc-testresults@).  Hint hint hint :-)
> > 
> > That way we know it is in good shape, know when we are regressing it,
> > know there is interest in it.
> 
> Once I have more of a bootstrapped userland than a barely-functional 
> cross chroot, I'll get back to you on that :)

Cool!  Looking forward to it.

Thanks,


Segher