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SubjectRe: [PATCH] ARM: Do not allow unaligned accesses when CONFIG_ALIGNMENT_TRAP
On Fri, May 27, 2011 at 09:38:08AM +0100, Catalin Marinas wrote:
> OK, I tried this now:
>
> -fconserve-stack: we get unaligned accesses on the stack because the
> newer versions of gcc turned unaligned accesses on by default.
>
> -fconserve-stack -mno-unaligned-access: the stack variables are aligned.
> We probably get the benefit of -fconserve-stack as well.
>
> So as per the initial post in this thread, we could have
> -mno-unaligned-access on ARM always on (when CONFIG_ALIGNMENT_TRAP). As
> Nicolas suggested, we could compile some files with -munaligned-access
> (and maybe -fno-conserve-stack).
>
> I raised this with the gcc guys so they are looking into it. But it
> really doesn't look like a gcc bug as long as -mno-unaligned-access is
> taken into account.

Ok, we need to check one last thing, and that's what the behaviour is
with -mno-unaligned-access and packed structures (such as the ethernet
header). If it makes no difference, then I suggest we always build
with -mno-unaligned-access.


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