PowerPC64 future proof kernel toc, revised for lld

[Michael Ellerman]

Alan Modra <amodra at gmail.com> writes:
> On Wed, Mar 10, 2021 at 01:44:57PM +0100, Christophe Leroy wrote:
>> 
>> Le 10/03/2021 à 13:25, Alan Modra a écrit :
>> > On Wed, Mar 10, 2021 at 08:33:37PM +1100, Alexey Kardashevskiy wrote:
>> > > One more question - the older version had a construct "DEFINED (.TOC.) ?
>> > > .TOC. : ..." in case .TOC. is not defined (too old ld? too old gcc?) but the
>> > > newer patch seems assuming it is always defined, when was it added? I have
>> > > the same check in SLOF, for example, do I still need it?
>> > 
>> > .TOC. symbol support was first added 2012-11-06, so you need
>> > binutils-2.24 or later to use .TOC. as a symbol.
>> > 
>> 
>> As of today, minimum requirement to build kernel is binutils 2.23, see https://urldefense.proofpoint.com/v2/url?u=https-3A__www.kernel.org_doc_html_latest_process_changes.html-23current-2Dminimal-2Drequirements&d=DwIDAw&c=jf_iaSHvJObTbx-siA1ZOg&r=uzpscot8Q8p-51o1Gp1vnzKV94bfny2qmUdVe821lv0&m=SYi605mn0I1hf1QoHuvHXtS_Z-R6JJHbzS34cEtV2Tk&s=47ckf3yxVcP6RwRb8D9viYOQSWpf6rXrnWj4YM4OTJ0&e= 
>
> Yes, and arch/powerpc/Makefile complains about 2.24.  So for powerpc
> that means you need to go to at least 2.25.  

Not quite. It only complains for little endian builds, and only if you
have stock 2.24, it will allow a 2.24.<something>.

I do most of my builds with 2.34, so I have no issue with newer
binutils. But we try not to increase the minimum version too rapidly to
accommodate folks using older and/or "Enterprise" distros that are stuck
on old toolchains.

I think we are within our rights to increase the minimum requirement for
powerpc builds, if it brings advantages we can identify.

The way to do that would be to add a new check in our arch Makefile that
rejects the older versions.

cheers