From patchwork Mon May 18 17:36:44 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 225831 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=-11.8 required=3.0 tests=DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING, SIGNED_OFF_BY, 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 98C1FC433E1 for ; Mon, 18 May 2020 17:48:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7B2BE20657 for ; Mon, 18 May 2020 17:48:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589824108; bh=a0NLWS3QJt7MKaKO9P9HaX7eVr/E/TNU487wIQOzNww=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=ENtVGuUi2o5nMUC5iMrx2lE2SMZ23BvZqVdKJWlin9+EnzTSTAGAuaLs17iX72VZi +oBskK/Icj3Yzyjjq057+iMIGDRf6/vpb10r1sSYem8tAJGXrdQv/cOBTbSr8z5rup EsMQvbsezoVMGRo1O3drD6tmQm6gOkeRSeVtdm2g= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730373AbgERRs0 (ORCPT ); Mon, 18 May 2020 13:48:26 -0400 Received: from mail.kernel.org ([198.145.29.99]:49276 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730364AbgERRsZ (ORCPT ); Mon, 18 May 2020 13:48:25 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9A4CD20657; Mon, 18 May 2020 17:48:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589824105; bh=a0NLWS3QJt7MKaKO9P9HaX7eVr/E/TNU487wIQOzNww=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=IlsPLjSz5wzr8l1JkmWbuQGSFw3aNkJ1XMDdVy21mcCglRAZ1gu0N2XKPJkN73ECl tBXPQ0vpgkm0iFsqW+5BhbGpYl3bJGH+bwES/FIvemhoxbeoyCPttRkLflivWXzAyz +b3WX94Y6h6k/Xhv+XhyLjETQvw1hGg7ehpBcQao= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Masahiro Yamada , Nathan Chancellor , Nick Desaulniers Subject: [PATCH 4.14 072/114] kbuild: compute false-positive -Wmaybe-uninitialized cases in Kconfig Date: Mon, 18 May 2020 19:36:44 +0200 Message-Id: <20200518173515.964584767@linuxfoundation.org> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200518173503.033975649@linuxfoundation.org> References: <20200518173503.033975649@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Masahiro Yamada commit b303c6df80c9f8f13785aa83a0471fca7e38b24d upstream. Since -Wmaybe-uninitialized was introduced by GCC 4.7, we have patched various false positives: - commit e74fc973b6e5 ("Turn off -Wmaybe-uninitialized when building with -Os") turned off this option for -Os. - commit 815eb71e7149 ("Kbuild: disable 'maybe-uninitialized' warning for CONFIG_PROFILE_ALL_BRANCHES") turned off this option for CONFIG_PROFILE_ALL_BRANCHES - commit a76bcf557ef4 ("Kbuild: enable -Wmaybe-uninitialized warning for "make W=1"") turned off this option for GCC < 4.9 Arnd provided more explanation in https://lkml.org/lkml/2017/3/14/903 I think this looks better by shifting the logic from Makefile to Kconfig. Link: https://github.com/ClangBuiltLinux/linux/issues/350 Signed-off-by: Masahiro Yamada Reviewed-by: Nathan Chancellor Tested-by: Nick Desaulniers Signed-off-by: Greg Kroah-Hartman --- Makefile | 11 ++++------- init/Kconfig | 17 +++++++++++++++++ kernel/trace/Kconfig | 1 + 3 files changed, 22 insertions(+), 7 deletions(-) --- a/Makefile +++ b/Makefile @@ -656,17 +656,14 @@ KBUILD_CFLAGS += $(call cc-disable-warni KBUILD_CFLAGS += $(call cc-disable-warning, attribute-alias) ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE -KBUILD_CFLAGS += -Os $(call cc-disable-warning,maybe-uninitialized,) -else -ifdef CONFIG_PROFILE_ALL_BRANCHES -KBUILD_CFLAGS += -O2 $(call cc-disable-warning,maybe-uninitialized,) +KBUILD_CFLAGS += -Os else KBUILD_CFLAGS += -O2 endif -endif -KBUILD_CFLAGS += $(call cc-ifversion, -lt, 0409, \ - $(call cc-disable-warning,maybe-uninitialized,)) +ifdef CONFIG_CC_DISABLE_WARN_MAYBE_UNINITIALIZED +KBUILD_CFLAGS += -Wno-maybe-uninitialized +endif # Tell gcc to never replace conditional load with a non-conditional one KBUILD_CFLAGS += $(call cc-option,--param=allow-store-data-races=0) --- a/init/Kconfig +++ b/init/Kconfig @@ -16,6 +16,22 @@ config DEFCONFIG_LIST default "$ARCH_DEFCONFIG" default "arch/$ARCH/defconfig" +config CC_HAS_WARN_MAYBE_UNINITIALIZED + def_bool $(cc-option,-Wmaybe-uninitialized) + help + GCC >= 4.7 supports this option. + +config CC_DISABLE_WARN_MAYBE_UNINITIALIZED + bool + depends on CC_HAS_WARN_MAYBE_UNINITIALIZED + default CC_IS_GCC && GCC_VERSION < 40900 # unreliable for GCC < 4.9 + help + GCC's -Wmaybe-uninitialized is not reliable by definition. + Lots of false positive warnings are produced in some cases. + + If this option is enabled, -Wno-maybe-uninitialzed is passed + to the compiler to suppress maybe-uninitialized warnings. + config CONSTRUCTORS bool depends on !UML @@ -1044,6 +1060,7 @@ config CC_OPTIMIZE_FOR_PERFORMANCE config CC_OPTIMIZE_FOR_SIZE bool "Optimize for size" + imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives help Enabling this option will pass "-Os" instead of "-O2" to your compiler resulting in a smaller kernel. --- a/kernel/trace/Kconfig +++ b/kernel/trace/Kconfig @@ -345,6 +345,7 @@ config PROFILE_ANNOTATED_BRANCHES config PROFILE_ALL_BRANCHES bool "Profile all if conditionals" if !FORTIFY_SOURCE select TRACE_BRANCH_PROFILING + imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives help This tracer profiles all branch conditions. Every if () taken in the kernel is recorded whether it hit or miss.