From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 58895C3F2D7 for ; Tue, 3 Mar 2020 18:02:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3927C2072D for ; Tue, 3 Mar 2020 18:02:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388142AbgCCSCH (ORCPT ); Tue, 3 Mar 2020 13:02:07 -0500 Received: from mga07.intel.com ([134.134.136.100]:25490 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388130AbgCCSCE (ORCPT ); Tue, 3 Mar 2020 13:02:04 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 03 Mar 2020 10:02:04 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,511,1574150400"; d="scan'208";a="233714477" Received: from stinkbox.fi.intel.com (HELO stinkbox) ([10.237.72.174]) by orsmga008.jf.intel.com with SMTP; 03 Mar 2020 10:02:00 -0800 Received: by stinkbox (sSMTP sendmail emulation); Tue, 03 Mar 2020 20:01:59 +0200 Date: Tue, 3 Mar 2020 20:01:59 +0200 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Kees Cook Cc: Maarten Lankhorst , Maxime Ripard , David Airlie , Daniel Vetter , dri-devel@lists.freedesktop.org, Alexander Potapenko , linux-kernel@vger.kernel.org Subject: Re: [PATCH] drm/edid: Distribute switch variables for initialization Message-ID: <20200303180159.GA13686@intel.com> References: <20200220062229.68762-1-keescook@chromium.org> <202003022038.07A611E@keescook> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <202003022038.07A611E@keescook> X-Patchwork-Hint: comment User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 02, 2020 at 08:39:37PM -0800, Kees Cook wrote: > On Wed, Feb 19, 2020 at 10:22:29PM -0800, Kees Cook wrote: > > Variables declared in a switch statement before any case statements > > cannot be automatically initialized with compiler instrumentation (as > > they are not part of any execution flow). With GCC's proposed automatic > > stack variable initialization feature, this triggers a warning (and they > > don't get initialized). Clang's automatic stack variable initialization > > (via CONFIG_INIT_STACK_ALL=y) doesn't throw a warning, but it also > > doesn't initialize such variables[1]. Note that these warnings (or silent > > skipping) happen before the dead-store elimination optimization phase, > > so even when the automatic initializations are later elided in favor of > > direct initializations, the warnings remain. > > > > To avoid these problems, move such variables into the "case" where > > they're used or lift them up into the main function body. > > > > drivers/gpu/drm/drm_edid.c: In function ‘drm_edid_to_eld’: > > drivers/gpu/drm/drm_edid.c:4395:9: warning: statement will never be executed [-Wswitch-unreachable] > > 4395 | int sad_count; > > | ^~~~~~~~~ > > > > [1] https://bugs.llvm.org/show_bug.cgi?id=44916 > > > > Signed-off-by: Kees Cook > > Ping. Can someone pick this up, please? > > Thanks! > > -Kees > > > --- > > drivers/gpu/drm/drm_edid.c | 5 +++-- > > 1 file changed, 3 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c > > index 805fb004c8eb..2941b65b427f 100644 > > --- a/drivers/gpu/drm/drm_edid.c > > +++ b/drivers/gpu/drm/drm_edid.c > > @@ -4392,9 +4392,9 @@ static void drm_edid_to_eld(struct drm_connector *connector, struct edid *edid) > > dbl = cea_db_payload_len(db); > > > > switch (cea_db_tag(db)) { > > - int sad_count; > > + case AUDIO_BLOCK: { I've never been a fan of {} inside switch statements. I'd just move this one level up. > > > > - case AUDIO_BLOCK: > > + int sad_count; > > /* Audio Data Block, contains SADs */ > > sad_count = min(dbl / 3, 15 - total_sad_count); > > if (sad_count >= 1) > > @@ -4402,6 +4402,7 @@ static void drm_edid_to_eld(struct drm_connector *connector, struct edid *edid) > > &db[1], sad_count * 3); > > total_sad_count += sad_count; > > break; > > + } > > case SPEAKER_BLOCK: > > /* Speaker Allocation Data Block */ > > if (dbl >= 1) > > > > -- > Kees Cook > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel -- Ville Syrjälä Intel