[U-Boot] [PATCH] disk:efi: avoid unaligned access on efi partition

Albert ARIBAUD
2013-10-15T17:07:49Z

Hi M?ns,

On Tue, 15 Oct 2013 17:29:24 +0100, M?ns Rullg?rd <mans@mansr.com>
wrote:

> Albert ARIBAUD <albert.u.boot@aribaud.net> writes:
>
> > Hi M?ns,
> >
> > On Tue, 15 Oct 2013 16:23:44 +0100, M?ns Rullg?rd <mans@mansr.com>
> > wrote:
> >
> >> On the compiler side, gcc traditionally did not issue unaligned
> >> load/store instructions on ARM.
> >
> > Please be specific: gcc did not emit *native* unaligned accesses.
>
> Please explain what you mean by "native unaligned access".

By this I mean an unaligned access performed with a single transfer,
initiated by a single processor instruction, as opposed to an
unaligned access performed with a series of smaller, aligned,
transfers (and possibly additional operations) initiated by a sequence
of processor instructions (emulated, if you will).

Prior to 4.7, gcc did emit unaligned accesses if instructed to at the
source code level; they were however emulated. From 4.7 onward, it was
possible to choose whether unaligned transfers should be performed
native or emulated, the default being native for ARMv6+, and emulated
for the rest.

Amicalement,
--
Albert.