From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:39231)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <drjones@redhat.com>) id 1ZtNR6-0005U3-HC
	for qemu-devel@nongnu.org; Mon, 02 Nov 2015 17:18:45 -0500
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <drjones@redhat.com>) id 1ZtNR2-0007eE-ID
	for qemu-devel@nongnu.org; Mon, 02 Nov 2015 17:18:44 -0500
Received: from mx1.redhat.com ([209.132.183.28]:42580)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <drjones@redhat.com>) id 1ZtNR2-0007dr-DJ
	for qemu-devel@nongnu.org; Mon, 02 Nov 2015 17:18:40 -0500
Date: Mon, 2 Nov 2015 16:18:33 -0600
From: Andrew Jones <drjones@redhat.com>
Message-ID: <20151102221833.GC5279@hawk.localdomain>
References: <1446212690-7656-2-git-send-email-eduardo.otubo@profitbricks.com>
	<1446486994-29913-1-git-send-email-drjones@redhat.com>
	<CAFEAcA8Hqq1ZBQnJ-EBx9GHSoibMs-DecBX_r4MOUEhMQmhZnQ@mail.gmail.com>
	<20151102190435.GB5279@hawk.localdomain>
	<CAFEAcA92_j+=htFaqBTcMud4BuDEW1cUy-w_AaUUF4yGCUAqVQ@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAFEAcA92_j+=htFaqBTcMud4BuDEW1cUy-w_AaUUF4yGCUAqVQ@mail.gmail.com>
Subject: Re: [Qemu-devel] [PATCH v2] seccomp: add cacheflush to whitelist
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: QEMU Developers <qemu-devel@nongnu.org>, Eduardo Otubo <eduardo.otubo@profitbricks.com>

On Mon, Nov 02, 2015 at 08:37:15PM +0000, Peter Maydell wrote:
> On 2 November 2015 at 19:04, Andrew Jones <drjones@redhat.com> wrote:
> > On Mon, Nov 02, 2015 at 06:09:41PM +0000, Peter Maydell wrote:
> >> On 2 November 2015 at 17:56, Andrew Jones <drjones@redhat.com> wrote:
> >> > cacheflush is an arm-specific syscall that qemu built for arm
> >> > uses. Add it to the whitelist, but only if we're linking with
> >> > a recent enough libseccomp.
> >> >
> >> > Signed-off-by: Andrew Jones <drjones@redhat.com>
> >> > ---
> >> > v2: only add cacheflush if libseccomp supports it
> >> >
> >> >  qemu-seccomp.c | 9 ++++++++-
> >> >  1 file changed, 8 insertions(+), 1 deletion(-)
> >> >
> >> > diff --git a/qemu-seccomp.c b/qemu-seccomp.c
> >> > index 80d034a8d5190..e76097e958779 100644
> >> > --- a/qemu-seccomp.c
> >> > +++ b/qemu-seccomp.c
> >> > @@ -16,6 +16,10 @@
> >> >  #include <seccomp.h>
> >> >  #include "sysemu/seccomp.h"
> >> >
> >> > +#if SCMP_VER_MAJOR >= 2 && SCMP_VER_MINOR >= 2 && SCMP_VER_MICRO >= 3
> >> > +#define HAVE_CACHEFLUSH
> >> > +#endif
> >>
> >> This will claim that a hypothetical future version 3.0.0 does not
> >> have cacheflush...
> >
> > Indeed. Sigh... In that case, how about just
> >
> > #if defined(TARGET_ARM) || defined(TARGET_AARCH64)
> >     { SCMP_SYS(cacheflush), 240 },
> > #endif
> 
> You want to be checking based on the host architecture,
> not the target architecture. Also, not doing the check based
> on seccomp version means there's no hint in the code that the
> ifdefs become obsolete if we raise our cross-architecture
> minimum seccomp version requirement in the future, so really
> a version check is better I think.

Right. OK, I'll stop flinging junk and pull a better version
check together.

Thanks,
drew

> 
> thanks
> -- PMM
>