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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,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 DB5B6C2BA19 for ; Wed, 15 Apr 2020 16:53:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B294B208FE for ; Wed, 15 Apr 2020 16:53:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586969585; bh=Fl4LMr8tfhnu5I5/m4JsWq9kVGAsJCZEwYG3/7yjBSc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=EYK9Tq9D8HLDgRWn8241oWB0CRWdNGU+KCc/y1PbtcXkJfcg+2U1wkMdmOZtPz+zz pch73HVOZrhcZDtVFYmDDuDluy7mJVXTEuWBb5nMzKsDA2dmpJhw5ltFBodV+XRsdS A2aKAIlrYp6+Fjfr4Rqwd6wm2H6Q7i81Hx1HYkEw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404386AbgDOQxE (ORCPT ); Wed, 15 Apr 2020 12:53:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:54698 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2410484AbgDOQwv (ORCPT ); Wed, 15 Apr 2020 12:52:51 -0400 Received: from localhost.localdomain (unknown [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id DABAC208FE; Wed, 15 Apr 2020 16:52:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586969571; bh=Fl4LMr8tfhnu5I5/m4JsWq9kVGAsJCZEwYG3/7yjBSc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=oTxe5nW1LeD77zlUfP+9luRCQxFWUlOaAVLtZGWWqYFy/PWSNFw1GAjaVghaa6iWP Kd6pnTiHfK3q6clheUTPN1AqMfxMCEi1LgwKYMigxiUla/83wxyVC8uogCffafC24o 0J2f4RyJnvmSX3Vn/1MLbw71j95IpyvYe6zk6nLE= From: Will Deacon To: linux-kernel@vger.kernel.org Cc: linux-arch@vger.kernel.org, kernel-team@android.com, Will Deacon , Michael Ellerman , Peter Zijlstra , Linus Torvalds , Segher Boessenkool , Christian Borntraeger , Luc Van Oostenryck , Arnd Bergmann , Peter Oberparleiter , Masahiro Yamada , Nick Desaulniers Subject: [PATCH v3 01/12] compiler/gcc: Emit build-time warning for GCC prior to version 4.8 Date: Wed, 15 Apr 2020 17:52:07 +0100 Message-Id: <20200415165218.20251-2-will@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200415165218.20251-1-will@kernel.org> References: <20200415165218.20251-1-will@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Prior to version 4.8, GCC may miscompile READ_ONCE() by erroneously discarding the 'volatile' qualifier: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145 We've been working around this using some nasty hacks which make READ_ONCE() both horribly complicated and also prevent us from enforcing that it is only used on scalar types. Since GCC 4.8 is pretty old for kernel builds now, emit a warning if we detect it during the build. Suggested-by: Linus Torvalds Cc: Peter Zijlstra Cc: Michael Ellerman Cc: Arnd Bergmann Cc: Christian Borntraeger Cc: Masahiro Yamada Signed-off-by: Will Deacon --- init/Kconfig | 4 ++-- scripts/Kconfig.include | 9 +++++++++ 2 files changed, 11 insertions(+), 2 deletions(-) diff --git a/init/Kconfig b/init/Kconfig index 9e22ee8fbd75..816b8b4a5e9e 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -9,11 +9,11 @@ config DEFCONFIG_LIST default "arch/$(SRCARCH)/configs/$(KBUILD_DEFCONFIG)" config CC_IS_GCC - def_bool $(success,$(CC) --version | head -n 1 | grep -q gcc) + def_bool $(cc-is-gcc) config GCC_VERSION int - default $(shell,$(srctree)/scripts/gcc-version.sh $(CC)) if CC_IS_GCC + default $(gcc-version) if CC_IS_GCC default 0 config LD_VERSION diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include index c264da2b9b30..5261e9d6b50b 100644 --- a/scripts/Kconfig.include +++ b/scripts/Kconfig.include @@ -54,3 +54,12 @@ $(error-if,$(success, $(LD) -v | grep -q gold), gold linker '$(LD)' not supporte cc-option-bit = $(if-success,$(CC) -Werror $(1) -E -x c /dev/null -o /dev/null,$(1)) m32-flag := $(cc-option-bit,-m32) m64-flag := $(cc-option-bit,-m64) + +# gcc version including patch level +gcc-version := $(shell,$(srctree)/scripts/gcc-version.sh $(CC)) + +# Return y if the compiler is GCC, n otherwise +cc-is-gcc := $(success,$(CC) --version | head -n 1 | grep -q gcc) + +# Warn if the compiler is GCC prior to 4.8 +$(warning-if,$(if-success,[ $(gcc-version) -lt 40800 ],$(cc-is-gcc),n),"Your compiler is old and may miscompile the kernel due to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145 - please upgrade it.") -- 2.26.0.110.g2183baf09c-goog