DWord alignment on ARMv7

Russell King - ARM Linux linux at arm.linux.org.uk
Fri Mar 4 03:02:10 PST 2016

On Fri, Mar 04, 2016 at 11:48:10AM +0100, Ard Biesheuvel wrote:
> I don't think it is the job of the filesystem driver to reason about
> whether get_unaligned_le64() does the right thing under any particular
> configuration. If ARM's implementation of get_unaligned_le64() issues
> load instructions that result in a trap, it is misbehaving and should
> be fixed.

It's not ARMs implementation, we don't have our own implementation, but
we seem to (today) use asm-generic stuff, which is sub-optimal.

Looking at the state of that, I guess we need to implement our own
asm/unaligned.h - and as the asm-generic stuff assumes that all
access sizes fall into the same categories, I'm guessing we'll need
to implement _all_ accessors ourselves.

That really sounds very sub-optimal, but I don't see any other solution
which wouldn't make the asm-generic stuff even more painful to follow
through multiple include files than it already is today.

RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/
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