From owner-freebsd-alpha  Sun Aug 13 17:58:12 2000
Delivered-To: freebsd-alpha@freebsd.org
Received: from mailserv.waikato.ac.nz (mailserv.waikato.ac.nz [130.217.66.61])
	by hub.freebsd.org (Postfix) with ESMTP id AD2A337B830
	for <alpha@FreeBSD.ORG>; Sun, 13 Aug 2000 17:58:07 -0700 (PDT)
	(envelope-from mjl12@waikato.ac.nz)
Received: from stu_ex2.waikato.ac.nz (stu-ex2.waikato.ac.nz [130.217.70.20])
	by mailserv.waikato.ac.nz (8.9.3/8.9.0) with ESMTP id NAA25260;
	Mon, 14 Aug 2000 13:02:12 +1200
Received: by stu-ex2.waikato.ac.nz with Internet Mail Service (5.5.2650.21)
	id <23A4W4NR>; Mon, 14 Aug 2000 12:53:28 +1200
Message-ID: <45E87454FFC2D211AD9800508B65009420F8E4@stu-ex1.waikato.ac.nz>
From: "MATTHEW JOHN,LUCKIE" <mjl12@waikato.ac.nz>
To: alpha@FreeBSD.ORG
Cc: jdp@polstra.com
Subject: RE: kernel modules/unaligned access fault
Date: Mon, 14 Aug 2000 12:57:54 +1200
MIME-Version: 1.0
X-Mailer: Internet Mail Service (5.5.2650.21)
Content-Type: text/plain;
	charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
Sender: owner-freebsd-alpha@FreeBSD.ORG
Precedence: bulk
X-Loop: FreeBSD.org

thanks for this
everything seems to go ok now with the bcopy

would you mind explaining to me the rules of programming for the alpha =
in
terms of unaligned accesses.
the original version of the code went
getnanotime(&pr->ts);
and then i byte ordered the members of the struct at a later date - all
inside the mbuf->m_data
but i got the uac fault at the call to the getnanotime.

I would just be interested to know a bit more so i can optimise my code =
a
bit more rather than copy data where i perhaps might not need to.

thanks again

Matthew

> -----Original Message-----
> From:	John Polstra [SMTP:jdp@polstra.com]
> Sent:	Monday, August 14, 2000 5:44 AM
> To:	alpha@freebsd.org
> Cc:	mjl12@waikato.ac.nz
> Subject:	Re: kernel modules/unaligned access fault
>=20
> In article =
<45E87454FFC2D211AD9800508B650094BA4E3E@stu-ex1.waikato.ac.nz>,
> MATTHEW JOHN,LUCKIE <mjl12@waikato.ac.nz> wrote:
> >=20
> > I am running into problems with the timestamping, whereby i am =
getting
> an
> > unaligned access fault panic.
> > I am making a call to getnanotime, with the results getting copied =
into
> a
> > bit of data in the mbuf that is offset 48 bytes in the packet
> [...]
> > m->m_data +=3D 4; /* 44 bytes offset */
> > pr =3D mtod(m, struct pathrecord *pr);
> > pr->ip =3D 0;
> > getnanotime(&ts);
> > ts.ts_sec =3D htonl(ts.ts_sec);
> > ts.ts_nsec =3D htonl(ts.ts_nsec);
> > pr->ts =3D ts; /* crashes in this line, 44 bytes offset from m_data =
*/
>=20
> Instead of assigning it directly like that, use bcopy() to copy it
> into place.
>=20
>     bcopy(&ts, &pr->ts, sizeof ts);
>=20
> John
> --=20
>   John Polstra
> jdp@polstra.com
>   John D. Polstra & Co., Inc.                        Seattle, =
Washington
> USA
>   "Disappointment is a good sign of basic intelligence."  -- =
Ch=F6gyam
> Trungpa


To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-alpha" in the body of the message