From patchwork Thu May 20 09:22:48 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 444354 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=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT 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 3C8D0C43460 for ; Thu, 20 May 2021 10:15:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 220FA613F1 for ; Thu, 20 May 2021 10:15:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235259AbhETKQ0 (ORCPT ); Thu, 20 May 2021 06:16:26 -0400 Received: from mail.kernel.org ([198.145.29.99]:47630 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235879AbhETKMr (ORCPT ); Thu, 20 May 2021 06:12:47 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 85D4061975; Thu, 20 May 2021 09:43:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1621503834; bh=XsdDTwSFfJXZwE1+awnEP3rzY8IZwkKLjJ4kL8qGcpw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ycYT2raTu4ZR9NeEiAjuKE46lWvlO8a593ecqy9wUKfdOzahOukB6/mx4kNNNssmD 3TQIhda1nOpuD7BmNYzL89FdKIp99lGuIipzvt9S82xd64V8IsZe1Zuv0yCAR48ho2 UklaKeAogshhaM3WhO5t7giuCmhJpuLqgFnMveHo= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Randy Dunlap , Josh Poimboeuf , Linus Walleij , Sasha Levin Subject: [PATCH 4.19 399/425] pinctrl: ingenic: Improve unreachable code generation Date: Thu, 20 May 2021 11:22:48 +0200 Message-Id: <20210520092144.509729406@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210520092131.308959589@linuxfoundation.org> References: <20210520092131.308959589@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Josh Poimboeuf [ Upstream commit d6d43a92172085a2681e06a0d06aac53c7bcdd12 ] In the second loop of ingenic_pinconf_set(), it annotates the switch default case as unreachable(). The annotation is technically correct, because that same case would have resulted in an early function return in the previous loop. However, the compiled code is suboptimal. GCC seems to work extra hard to ensure that the unreachable code path triggers undefined behavior. The function would fall through to start executing whatever function happens to be next in the compilation unit. This is problematic because: a) it adds unnecessary 'ensure undefined behavior' logic, and corresponding i-cache footprint; and b) it's less robust -- if a bug were to be introduced, falling through to the next function would be catastrophic. Yet another issue is that, while objtool normally understands unreachable() annotations, there's one special case where it doesn't: when the annotation occurs immediately after a 'ret' instruction. That happens to be the case here because unreachable() is immediately before the return. Remove the unreachable() annotation and replace it with a comment. This simplifies the code generation and changes the unreachable error path to just silently return instead of corrupting execution. This fixes the following objtool warning: drivers/pinctrl/pinctrl-ingenic.o: warning: objtool: ingenic_pinconf_set() falls through to next function ingenic_pinconf_group_set() Reported-by: Randy Dunlap Signed-off-by: Josh Poimboeuf Link: https://lore.kernel.org/r/bc20fdbcb826512cf76b7dfd0972740875931b19.1582212881.git.jpoimboe@redhat.com Signed-off-by: Linus Walleij Signed-off-by: Sasha Levin --- drivers/pinctrl/pinctrl-ingenic.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/pinctrl/pinctrl-ingenic.c b/drivers/pinctrl/pinctrl-ingenic.c index a5accffbc8c9..babf6d011264 100644 --- a/drivers/pinctrl/pinctrl-ingenic.c +++ b/drivers/pinctrl/pinctrl-ingenic.c @@ -642,7 +642,8 @@ static int ingenic_pinconf_set(struct pinctrl_dev *pctldev, unsigned int pin, break; default: - unreachable(); + /* unreachable */ + break; } }