Re: [PATCH v7 5/6] powerpc/64: Make COMPAT user-selectable disabled on littleendian by default.

[Michael Ellerman]

Segher Boessenkool <segher@xxxxxxxxxxxxxxxxxxx> writes:
> On Mon, Sep 02, 2019 at 12:03:12PM +1000, Michael Ellerman wrote:
>> Michal Suchanek <msuchanek@xxxxxxx> writes:
>> > On bigendian ppc64 it is common to have 32bit legacy binaries but much
>> > less so on littleendian.
>> 
>> I think the toolchain people will tell you that there is no 32-bit
>> little endian ABI defined at all, if anything works it's by accident.
                ^
                v2

> There of course is a lot of powerpcle-* support.  The ABI used for it
> on linux is the SYSV ABI, just like on BE 32-bit.

I was talking about ELFv2, which is 64-bit only. But that was based on
me thinking we had a hard assumption in the kernel that ppc64le kernels
always expect ELFv2 userland. Looking at the code though I was wrong
about that, it looks like we will run little endian ELFv1 binaries,
though I don't think anyone is testing it.

> There also is specific powerpcle-linux support in GCC, and in binutils,
> too.  Also, config.guess/config.sub supports it.  Half a year ago this
> all built fine (no, I don't test it often either).
>
> I don't think glibc supports it though, so I wonder if anyone builds an
> actual system with it?  Maybe busybox or the like?
>
>> So I think we should not make this selectable, unless someone puts their
>> hand up to say they want it and are willing to test it and keep it
>> working.
>
> What about actual 32-bit LE systems?  Does anyone still use those?

Not that I've ever heard of.

cheers