Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932228AbdCUKQ6 (ORCPT ); Tue, 21 Mar 2017 06:16:58 -0400 Received: from mail.fireflyinternet.com ([109.228.58.192]:50616 "EHLO fireflyinternet.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754338AbdCUKQ4 (ORCPT ); Tue, 21 Mar 2017 06:16:56 -0400 X-Default-Received-SPF: pass (skip=forwardok (res=PASS)) x-ip-name=78.156.65.138; Date: Tue, 21 Mar 2017 10:16:52 +0000 From: Chris Wilson To: Arnd Bergmann Cc: Daniel Vetter , Jani Nikula , David Airlie , Joonas Lahtinen , Tvrtko Ursulin , Matthew Auld , intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/3] drm/i915: allocate mock file pointer dynamically Message-ID: <20170321101652.GC11338@nuc-i3427.alporthouse.com> Mail-Followup-To: Chris Wilson , Arnd Bergmann , Daniel Vetter , Jani Nikula , David Airlie , Joonas Lahtinen , Tvrtko Ursulin , Matthew Auld , intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org References: <20170320094335.1266306-1-arnd@arndb.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170320094335.1266306-1-arnd@arndb.de> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2105 Lines: 48 On Mon, Mar 20, 2017 at 10:40:27AM +0100, Arnd Bergmann wrote: > A struct file is a bit too large to put on the kernel stack in general > and triggers a warning for low settings of CONFIG_FRAME_WARN: > > drivers/gpu/drm/i915/selftests/mock_drm.c: In function 'mock_file': > drivers/gpu/drm/i915/selftests/mock_drm.c:46:1: error: the frame size of 1328 bytes is larger than 1280 bytes [-Werror=frame-larger-than=] > drivers/gpu/drm/i915/selftests/mock_drm.c: In function 'mock_file_free': > drivers/gpu/drm/i915/selftests/mock_drm.c:54:1: error: the frame size of 1312 bytes is larger than 1280 bytes [-Werror=frame-larger-than=] > > It's also slightly dangerous to leave a reference to a stack object > in the drm_file structure after leaving the stack frame. > This changes the code to just allocate the object dynamically > and release it when we are done with it. > > Fixes: 66d9cb5d805a ("drm/i915: Mock the GEM device for self-testing") > Signed-off-by: Arnd Bergmann > --- > drivers/gpu/drm/i915/selftests/mock_drm.c | 12 +++++++----- > 1 file changed, 7 insertions(+), 5 deletions(-) > > diff --git a/drivers/gpu/drm/i915/selftests/mock_drm.c b/drivers/gpu/drm/i915/selftests/mock_drm.c > index 113dec05c7dc..18514065c93d 100644 > --- a/drivers/gpu/drm/i915/selftests/mock_drm.c > +++ b/drivers/gpu/drm/i915/selftests/mock_drm.c > @@ -32,15 +32,15 @@ static inline struct inode fake_inode(struct drm_i915_private *i915) > struct drm_file *mock_file(struct drm_i915_private *i915) > { > struct inode inode = fake_inode(i915); > - struct file filp = {}; > + struct file *filp = kzalloc(sizeof(struct file), GFP_KERNEL); > struct drm_file *file; > int err; > > - err = drm_open(&inode, &filp); > + err = drm_open(&inode, filp); > if (unlikely(err)) > return ERR_PTR(err); > > - file = filp.private_data; > + file = filp->private_data; What I don't like about this approach is that we leak the unwanted inode/file. We only want the drm_file here and any access to above that inside i915.ko is fubar. -Chris -- Chris Wilson, Intel Open Source Technology Centre