ARM: pxa/corgi: armv5te kernel 4.12 fails to decompress compiled with gcc7

[Russell King - ARM Linux]

On Wed, Oct 18, 2017 at 12:39:13PM +0200, Petr Cvek wrote:
> 
> 
> Dne 17.10.2017 v 10:18 Andrea Adami napsal(a):
> >On Tue, Oct 17, 2017 at 10:10 AM, Petr Cvek <petrcvekcz at gmail.com> wrote:
> >>If it is a problem with gcc (as Russell said before), there is no way you
> >>can fix it in the kernel. Only compiling it with an older gcc version can
> >>help.
> >>
> 
> BTW you could add "alignment=2" (same as /proc/cpu/alignment) in your kernel
> parameters and kernel should check it even before you boot userspace.
> 
> But it will be *extra* slow as there will be many exceptions in the kernel
> and an emulation of the unaligned instructions. It is not a real permanent
> fix.

That's wrong.

Alignment exceptions are always fixed up in the kernel.  The parameter
(and what you set by writing /proc/cpu/alignment) sets the behaviour of
_userspace_ alignment exceptions.

> It should be possible to use up to march=armv5t as I elaborated it in the
> other mail.

If you're building for PXA, it's an ARMv5 architecture.  The kernel will
use -march=armv5te for all ARMv5 architectures.  Moreover, because one
of the PXA2* symbols should also be selected, CPU_XSCALE will also be
enabled, which means we will pass -mtune=xscale to the compiler.

The exception is if CPU_FEROCEON is enabled, in which case we will pass
-mtune=marvell-f to the kernel if supported by the compiler.

-- 
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