From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jani Nikula Subject: Re: [PATCH linux-next] i915: intel_set_mode: Reduce stack allocation from 500 bytes to 2 pointers Date: Fri, 07 Dec 2012 13:47:46 +0200 Message-ID: <87zk1qm6cd.fsf@intel.com> References: <1354815755-83271-1-git-send-email-tim.gardner@canonical.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: In-Reply-To: <1354815755-83271-1-git-send-email-tim.gardner@canonical.com> Sender: linux-kernel-owner@vger.kernel.org To: linux-kernel@vger.kernel.org Cc: Daniel Vetter , Tim Gardner , dri-devel@lists.freedesktop.org List-Id: dri-devel@lists.freedesktop.org On Thu, 06 Dec 2012, Tim Gardner wrote: > smatch warning: > > drivers/gpu/drm/i915/intel_display.c:7019 intel_set_mode() warn: function puts > 500 bytes on stack > > Refactor so that saved_mode and saved_hwmode are dynamically allocated as opposed > to being automatic variables. 500 bytes seems like it could run the potential for blowing > the kernel stack, especially if struct drm_display_mode ever grows significantly. Hi Tim, seems reasonable, but please find a few comments inline. BR, Jani. > > Cc: Daniel Vetter > Cc: David Airlie > Cc: dri-devel@lists.freedesktop.org > Signed-off-by: Tim Gardner > --- > drivers/gpu/drm/i915/intel_display.c | 18 +++++++++++++----- > 1 file changed, 13 insertions(+), 5 deletions(-) > > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c > index de51489..f8754d6 100644 > --- a/drivers/gpu/drm/i915/intel_display.c > +++ b/drivers/gpu/drm/i915/intel_display.c > @@ -7739,11 +7739,18 @@ bool intel_set_mode(struct drm_crtc *crtc, > { > struct drm_device *dev = crtc->dev; > drm_i915_private_t *dev_priv = dev->dev_private; > - struct drm_display_mode *adjusted_mode, saved_mode, saved_hwmode; > + struct drm_display_mode *adjusted_mode, *saved_mode, *saved_hwmode; > struct intel_crtc *intel_crtc; > unsigned disable_pipes, prepare_pipes, modeset_pipes; > bool ret = true; > > + saved_mode = kmalloc(2*sizeof(*saved_mode), GFP_KERNEL); Style nitpick, missing spaces around the first *. > + if (!saved_mode) { > + pr_err("i915: Could not allocate saved display mode.\n"); Please use DRM_ERROR(). > + return false; > + } > + saved_hwmode = saved_mode + 1; > + > intel_modeset_affected_pipes(crtc, &modeset_pipes, > &prepare_pipes, &disable_pipes); > > @@ -7753,8 +7760,8 @@ bool intel_set_mode(struct drm_crtc *crtc, > for_each_intel_crtc_masked(dev, disable_pipes, intel_crtc) > intel_crtc_disable(&intel_crtc->base); > > - saved_hwmode = crtc->hwmode; > - saved_mode = crtc->mode; > + *saved_hwmode = crtc->hwmode; > + *saved_mode = crtc->mode; > > /* Hack: Because we don't (yet) support global modeset on multiple > * crtcs, we don't keep track of the new mode for more than one crtc. You are missing a kfree in the adjusted_mode error path after this hunk. > @@ -7817,12 +7824,13 @@ bool intel_set_mode(struct drm_crtc *crtc, > done: > drm_mode_destroy(dev, adjusted_mode); > if (!ret && crtc->enabled) { > - crtc->hwmode = saved_hwmode; > - crtc->mode = saved_mode; > + crtc->hwmode = *saved_hwmode; > + crtc->mode = *saved_mode; > } else { > intel_modeset_check_state(dev); > } > > + kfree(saved_mode); > return ret; > } > > -- > 1.7.9.5 > > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > http://lists.freedesktop.org/mailman/listinfo/dri-devel From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933088Ab2LGLq4 (ORCPT ); Fri, 7 Dec 2012 06:46:56 -0500 Received: from mga02.intel.com ([134.134.136.20]:7323 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932675Ab2LGLqz (ORCPT ); Fri, 7 Dec 2012 06:46:55 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.84,236,1355126400"; d="scan'208";a="230290877" From: Jani Nikula To: Tim Gardner , linux-kernel@vger.kernel.org Cc: Daniel Vetter , Tim Gardner , dri-devel@lists.freedesktop.org Subject: Re: [PATCH linux-next] i915: intel_set_mode: Reduce stack allocation from 500 bytes to 2 pointers In-Reply-To: <1354815755-83271-1-git-send-email-tim.gardner@canonical.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo References: <1354815755-83271-1-git-send-email-tim.gardner@canonical.com> User-Agent: Notmuch/0.14+142~gf454854 (http://notmuchmail.org) Emacs/23.3.1 (x86_64-pc-linux-gnu) Date: Fri, 07 Dec 2012 13:47:46 +0200 Message-ID: <87zk1qm6cd.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 06 Dec 2012, Tim Gardner wrote: > smatch warning: > > drivers/gpu/drm/i915/intel_display.c:7019 intel_set_mode() warn: function puts > 500 bytes on stack > > Refactor so that saved_mode and saved_hwmode are dynamically allocated as opposed > to being automatic variables. 500 bytes seems like it could run the potential for blowing > the kernel stack, especially if struct drm_display_mode ever grows significantly. Hi Tim, seems reasonable, but please find a few comments inline. BR, Jani. > > Cc: Daniel Vetter > Cc: David Airlie > Cc: dri-devel@lists.freedesktop.org > Signed-off-by: Tim Gardner > --- > drivers/gpu/drm/i915/intel_display.c | 18 +++++++++++++----- > 1 file changed, 13 insertions(+), 5 deletions(-) > > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c > index de51489..f8754d6 100644 > --- a/drivers/gpu/drm/i915/intel_display.c > +++ b/drivers/gpu/drm/i915/intel_display.c > @@ -7739,11 +7739,18 @@ bool intel_set_mode(struct drm_crtc *crtc, > { > struct drm_device *dev = crtc->dev; > drm_i915_private_t *dev_priv = dev->dev_private; > - struct drm_display_mode *adjusted_mode, saved_mode, saved_hwmode; > + struct drm_display_mode *adjusted_mode, *saved_mode, *saved_hwmode; > struct intel_crtc *intel_crtc; > unsigned disable_pipes, prepare_pipes, modeset_pipes; > bool ret = true; > > + saved_mode = kmalloc(2*sizeof(*saved_mode), GFP_KERNEL); Style nitpick, missing spaces around the first *. > + if (!saved_mode) { > + pr_err("i915: Could not allocate saved display mode.\n"); Please use DRM_ERROR(). > + return false; > + } > + saved_hwmode = saved_mode + 1; > + > intel_modeset_affected_pipes(crtc, &modeset_pipes, > &prepare_pipes, &disable_pipes); > > @@ -7753,8 +7760,8 @@ bool intel_set_mode(struct drm_crtc *crtc, > for_each_intel_crtc_masked(dev, disable_pipes, intel_crtc) > intel_crtc_disable(&intel_crtc->base); > > - saved_hwmode = crtc->hwmode; > - saved_mode = crtc->mode; > + *saved_hwmode = crtc->hwmode; > + *saved_mode = crtc->mode; > > /* Hack: Because we don't (yet) support global modeset on multiple > * crtcs, we don't keep track of the new mode for more than one crtc. You are missing a kfree in the adjusted_mode error path after this hunk. > @@ -7817,12 +7824,13 @@ bool intel_set_mode(struct drm_crtc *crtc, > done: > drm_mode_destroy(dev, adjusted_mode); > if (!ret && crtc->enabled) { > - crtc->hwmode = saved_hwmode; > - crtc->mode = saved_mode; > + crtc->hwmode = *saved_hwmode; > + crtc->mode = *saved_mode; > } else { > intel_modeset_check_state(dev); > } > > + kfree(saved_mode); > return ret; > } > > -- > 1.7.9.5 > > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > http://lists.freedesktop.org/mailman/listinfo/dri-devel