[PATCH 1/5] kbuild: allow architectures to use thin archives instead of ld -r

[Nicholas Piggin]

On Sat, 6 Aug 2016 22:10:45 +0200
Sam Ravnborg <sam at ravnborg.org> wrote:

> Hi Nicholas.
> 
> On Fri, Aug 05, 2016 at 10:11:59PM +1000, Nicholas Piggin wrote:
> > From: Stephen Rothwell <sfr at canb.auug.org.au>
> > 
> > ld -r is an incremental link used to create built-in.o files in build
> > subdirectories. It produces relocatable object files containing all
> > its input files, and these are are then pulled together and relocated
> > in the final link. Aside from the bloat, this constrains the final
> > link relocations, which has bitten large powerpc builds with
> > unresolvable relocations in the final link.
> > 
> > Alan Modra has recommended the kernel use thin archives for linking.
> > This is an alternative and means that the linker has more information
> > available to it when it links the kernel.
> > 
> > This patch enables a config option architectures can select,  
> If we want to do this, then I suggest to make the logic reverse.
> Architectures that for some reasons cannot use this should
> have the possibility to avoid it. But let it be enabled by default.

I was thinking the build matrix (architectures x build options x toolchains)
is a bit too large to switch it for everybody. I've far from even tested it
for a fraction of powerpc builds. I would prefer arch maintainers to switch
it themselves, but I do hope we can move everybody and just remove the old
method within a few releases.

But I'm happy to go with whatever arch and kbuild maintainers prefer, so I
appreciate any discussion on it.

Thanks,
Nick