Re: 32-bit PowerPC sdata linker problem

[Alan Modra <amodra@gmail.com>]

On Fri, Jun 06, 2014 at 11:01:10AM +0200, Sebastian Huber wrote:
> I performed a git bisect and found this:
> 
> 93d1b056cb396d6468781fe0e40dd769891bed32 is the first bad commit
> commit 93d1b056cb396d6468781fe0e40dd769891bed32
> Author: Alan Modra <amodra@gmail.com>
> Date:   Tue May 20 11:42:42 2014 +0930
> 
>     Rewrite ppc32 backend .sdata and .sdata2 handling

Hmm, I'm surprised that your git bisect found this patch.  Was
_SDA_BASE_ set differently before this?

>                 0x00000000000dfc00                _SDA_BASE_
>                 0x00000000000d7f78                ppc_exc_lock_std

>      4b8:       28 05 00 00     cmplwi  r5,0
>                         4ba: R_PPC_SDAREL16     ppc_exc_lock_std

ppc_exc_lock_std@sdarel will be calculating 0xd7f78 - 0xdfc00
which is 0xf...fff8378, and that falls foul of

commit 86c9573369616e7437481b6e5533aef3a435cdcf
Author: Alan Modra <amodra@gmail.com>
Date:   Sat Mar 8 13:05:06 2014 +1030

    Better overflow checking for powerpc32 relocations

cmplwi has an *unsigned* 16-bit field, and we now check the overflow
properly.

I wonder how many more of these we'll hit, and whether the uproar will
be enough that I'll be forced to relax the checks?

-- 
Alan Modra
Australia Development Lab, IBM