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

Albert ARIBAUD
2013-10-14T13:48:11Z

Hi M?ns,

On Mon, 14 Oct 2013 14:05:13 +0100, M?ns Rullg?rd <mans@mansr.com>
wrote:

> Albert ARIBAUD <albert.u.boot@aribaud.net> writes:
>
> >> > Please do not advise using native unaligned accesses on code that is
> >> > not strictly used by ARMv6+ architectures: the present code, for
> >> > instance, might be run on pre-ARMv6 or non-ARM platforms, and thus,
> >> > should never assume ability to perform unaligned accesses natively.
> >>
> >> I'm advising no such thing. I said two things:
> >>
> >> 1. Declaring a struct with the 'packed' attribute makes gcc
> >> automatically generate correct code for all targets. _IF_ the
> >> selected target supports unaligned ldr/str, these might get used.
> >>
> >> 2. If your target is ARMv6 or later _AND_ you enable strict alignment
> >> checking in the system control register, you _MUST_ build with the
> >> -mno-unaligned-access flag.
> >
> > Then I apologize; I had read "Note that on ARMv6 and later ldr/str
> > support unaligned addresses unless this is explicitly disabled in
> > the system control register" as a suggestion to use that capability.
>
> If building for ARMv6 or later, I do suggest allowing unaligned
> accesses. The moment you add -march=armv6 (or equivalent), you allow
> for a number of things not supported by older versions, so why not
> unaligned memory accesses?

doc/README.arm-unaligned-accesses probably has the answer to your
question, especially from line 21 onward. If not, I'll be happy to
provide further clarification.

Amicalement,
--
Albert.