On Wed, 2017-12-06 at 19:12:28 UTC, Desnes Augusto Nunes do Rosario wrote:

powerpc64 gcc can generate code that offsets an address, to access part of
an object in memory. If the address is a -mcmodel=medium toc pointer
relative address then code like the following is possible.

 addis r9,r2,var@toc@ha
 ld r3,var@toc@l(r9)
 ld r4,(var+8)@toc@l(r9)

This works fine so long as var is naturally aligned, *and* r2 is
sufficiently aligned. If not, there is a possibility that the offset added
to access var+8 wraps over a n*64k+32k boundary. Modules don't have any
guarantee that r2 is sufficiently aligned. Moreover, code generated by
older compilers generates a .toc section with 2**0 alignment, which can
result in relocation failures at module load time even without the wrap
problem.

Thus, this patch links modules with an aligned .toc section (Makefile and
module.lds changes), and forces alignment for out of tree modules or those
without a .toc section (module_64.c changes).

Signed-off-by: Alan Modra <redacted>
[ desnesn: updated patch to apply to powerpc-next kernel v4.15 ]
Signed-off-by: Desnes A. Nunes do Rosario <redacted>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/5c45b5280196a92c4437f5648209c5

cheers