[PATCH] arm: add an option for erratum 657417

[Arnd Bergmann]

On Friday 26 August 2016, Nicholas Piggin wrote:
> > I still see a problem with big-endian builds failing with
> > thinarc/gc-sections, I'll investigate that some other day,
> > or you could have a look at that if you want to make sure
> > it's an ARM specific problem, not something with your
> > patches in general.
> > 
> > The patch that I sent for enabling the two on ARM blocks
> > out CONFIG_CPU_BIG_ENDIAN, so just revert that hunk to see
> > the problem. It's possible that it only breaks when doing
> > a big-endian build after a little-endian build without
> > a "make clean" inbetween.
> 
> I'm able to build big endian ARM allyesconfig with thin
> archives and gc-sections, worked fine.
> 
> There have been a few bugs in powerpc when failing to notice
> the change when endian of builds was swapped, so maybe you
> got bitten by something similar.

I tracked this down as well now, and it's also a problem on my
local machine, your patches are fine. In order to debug
the other problem, I was building with
"make LD=/home/arnd/..../ld" to try out different
versions of the linker, and that caused the "LD += -EB"
line from arch/arm/Makefile to be ignored.

We should probably override LDFLAGS rather than LD
(and AFLAGS instead of AS) for big-endian builds, but
that is unrelated to your work.

	Arnd