Re: [PATCH] powerpc/64: BE option to use ELFv2 ABI for big endian kernels

[Nicholas Piggin <npiggin@gmail.com>]

Segher Boessenkool's on March 4, 2020 9:09 am:
> Hi!
> 
> On Tue, Mar 03, 2020 at 11:45:27AM +1000, Nicholas Piggin wrote:
>> Provide an option to use ELFv2 ABI for big endian builds. This works on
>> GCC and clang (since 2014). it is is not officially supported by the GNU
>> toolchain, but it can give some useful advantages of the ELFv2 ABI for
>> BE (e.g., less stack usage). Some distros build BE ELFv2 userspace.
> 
> It is not officially supported in the sense that a) as a host config,
> it does not exist *at all* (this isn't relevant for the kernel, it does
> not use a libc or other libraries, of course); and b) as a target config,
> it is not supported in the sense that no one tests it, so we cannot say
> anything about what quality code it generates, if it works at all, etc.

Yep.

> But we *do* allow "-mbig -mabi=elfv2", it's just a chicken-and-egg
> problem to have this properly tested.  If someone would regularly test
> it (incl. sending the test results to gcc-testresults@), I don't see why
> it would not become a supported platform.
> 
>> +override flavour := linux-ppc64v2
> 
> That isn't a good name, heh.  This isn't "v2" of anything...  Spell out
> the name "ELFv2"?  Or as "elfv2"?  It is just a name after all, it is
> version 1 in all three version fields in the ELF headers!

Yeah okay. This part is only for some weird little perl asm generator
script, but probably better to be careful. linux-ppc64-elfv2 ?

> 
> 
> Anyway, looks like it will work, let's see where this goes :-)
> 
> Reviewed-by: Segher Boessenkool <segher@kernel.crashing.org>
> 
> 
> Segher
>