From mboxrd@z Thu Jan  1 00:00:00 1970
From: Thomas Hellstrom <thellstrom@vmware.com>
Subject: Re: [PATCH 2/5] drm: Break out ioctl permission check to a separate
	function
Date: Thu, 13 Mar 2014 13:11:12 +0100
Message-ID: <5321A060.8090406@vmware.com>
References: <1394708244-6565-1-git-send-email-thellstrom@vmware.com>
	<1394708244-6565-3-git-send-email-thellstrom@vmware.com>
	<CANq1E4ShMH3gend4=xkPaKUpChW8zWPC+DgVc-U+4OAm3zZrxw@mail.gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <dri-devel-bounces@lists.freedesktop.org>
Received: from smtp-outbound-1.vmware.com (smtp-outbound-1.vmware.com
	[208.91.2.12])
	by gabe.freedesktop.org (Postfix) with ESMTP id 8D66CFAEA4
	for <dri-devel@lists.freedesktop.org>;
	Thu, 13 Mar 2014 05:11:17 -0700 (PDT)
In-Reply-To: <CANq1E4ShMH3gend4=xkPaKUpChW8zWPC+DgVc-U+4OAm3zZrxw@mail.gmail.com>
List-Unsubscribe: <http://lists.freedesktop.org/mailman/options/dri-devel>,
	<mailto:dri-devel-request@lists.freedesktop.org?subject=unsubscribe>
List-Archive: <http://lists.freedesktop.org/archives/dri-devel>
List-Post: <mailto:dri-devel@lists.freedesktop.org>
List-Help: <mailto:dri-devel-request@lists.freedesktop.org?subject=help>
List-Subscribe: <http://lists.freedesktop.org/mailman/listinfo/dri-devel>,
	<mailto:dri-devel-request@lists.freedesktop.org?subject=subscribe>
Sender: dri-devel-bounces@lists.freedesktop.org
Errors-To: dri-devel-bounces@lists.freedesktop.org
To: David Herrmann <dh.herrmann@gmail.com>
Cc: Dave Airlie <airlied@redhat.com>, Thomas Hellstrom <thellstrom@vmware.com>, linux-graphics-maintainer@vmware.com, "dri-devel@lists.freedesktop.org" <dri-devel@lists.freedesktop.org>
List-Id: dri-devel@lists.freedesktop.org

Hi.

Thanks for reviewing. I'll incorporate your suggestions, except this
one, and resend.


On 03/13/2014 12:19 PM, David Herrmann wrote:
> Hi
>
> On Thu, Mar 13, 2014 at 11:57 AM, Thomas Hellstrom
> <thellstrom@vmware.com> wrote:
...

-               if (cmd & IOC_IN) {
-                       if (copy_from_user(kdata, (void __user *)arg,
-                                          usize) != 0) {
-                               retcode = -EFAULT;
+       retcode = drm_ioctl_permit(ioctl->flags, file_priv);
+       if (unlikely(retcode))

> That "unlikely" seems redundant given that all error paths in
> drm_ioctl_permit() already are "unlikely".

Yes, we know that's true, but I don't think compilers in general can
combine branch prediction hints in that way,
or even have the information necessary to do it.
I mean even if each individual test resulting in an error is unlikely,
how could the compiler know that
all tests combined would result in an error being unlikely?

/Thomas