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Date: Tue, 27 Aug 2013 16:40:55 +0100
From: Andrew Turner <andrew@fubar.geek.nz>
To: Warner Losh <imp@bsdimp.com>
Subject: Re: ARM network trouble after recent mbuf changes
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Cc: freebsd-arm <freebsd-arm@FreeBSD.org>, Andre Oppermann <andre@freebsd.org>
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On Tue, 27 Aug 2013 07:26:03 -0600
Warner Losh <imp@bsdimp.com> wrote:

> 
> On Aug 27, 2013, at 3:28 AM, Andrew Turner wrote:
> 
> > On Tue, 27 Aug 2013 08:53:13 +0200
> > Andre Oppermann <andre@freebsd.org> wrote:
> >> Please try the patch below to confirm.  If it fixes your problem
> >> for now I'm going to commit as an immediate fix while searching
> >> for a better long term stable solution.
> >> 
> > 
> > I tried this with a CTASSERT to check if struct m_hdr is the correct
> > length. In this test the size is incorrect. It appears __ILP32__ is
> > not defined on ARM.
> > 
> > I have tested a fix suggested by Hans Petter Selasky where we mark
> > m_hdr with __aligned(8). With this change I can netboot a
> > PandaBoard.
> 
> Isn't that a bug with our arm compiler then?

No, on ARM EABI the definition of the size of a struct is to be the
smallest multiple of its alignment. As we are increasing the alignment
to 8-byte and the struct without this alignment is not a multiple of
8-bytes adding this alignment will pad to struct to use the unused 4
bytes between this and the next struct.

Andrew
> 
> Warner
> 
>