Subject: Re: [PATCH] [POWERPC] Fix bootwrapper builds with newer gcc versions

From: Benjamin Herrenschmidt <[email-masked]>
Date: Sat, 03 May 2008 17:50:17 +1000

On Fri, 2008-05-02 at 16:38 -0700, David Miller wrote:
> Oh, I forgot about how far function calls are done on powerpc.
> Yes, that will suck.
> 
> Is there some way to map all of the modules in the low 32-bits and
> thus aovid the trampolines?  The powerpc call instruction can cover
> 4GB like on sparc right?
> 
> Actually, I remember there is some linkage register that has
> to be setup on powerpc with the code model you guys use, is
> that the problem?

The TOC yes, so we end up doing cross-TOC calls, which we would want to
avoid to get to base runtime stuff such as the save/restore bits.

Especially useless since those runtime don't need a TOC at all :-)

Best would be if we could get those runtime bits linked in the module
itself, but I don't know enough about our toolchain to know if that's
easy (I suppose everything is always possible :-)

I can ask my local expert next week.

Ben.