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Message-Id: <20101015020310.5a4eddbd.akpm@linux-foundation.org>
Date: Fri, 15 Oct 2010 02:03:10 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Andi Kleen <andi@...stfloor.org>
Cc: Eric Paris <eparis@...hat.com>, linux-kernel@...r.kernel.org,
jengelh@...ozas.de, davem@...emloft.net
Subject: Re: [PATCH] types.h: define __aligned_u64 and expose to userspace
On Fri, 15 Oct 2010 10:43:11 +0200 Andi Kleen <andi@...stfloor.org> wrote:
> On Fri, Oct 15, 2010 at 12:24:55AM -0400, Eric Paris wrote:
> > We currently have a kernel internal type called aligned_u64 which aligns
> > __u64's on 8 bytes boundaries even on systems which would normally align
> > them on 4 byte boundaries. This patch creates a new type __aligned_u64
> > which does the same thing but which is exposed to userspace rather than
> > being kernel internal.
> >
> > Based-on-patch-by: Andreas Gruenbacher <agruen@...e.de>
> > Signed-off-by: Eric Paris <eparis@...hat.com>
>
> Acked-by: Andi Kleen <ak@...ux.intel.com>
>
> but only if you:
>
> > +/* this is a special 64bit data type that is 8-byte aligned */
>
> Expand this comment a bit that that using this type as a
> replacement for u64 is recommended
> for any user visible 64bit value in a structure and that it
> avoids problem with the compat layer on x86-64.
>
Well yes, I was actually about to write that comment. But it should
describe the compat problems fully?
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