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 A3F7FC2D0DB for ; Thu, 23 Jan 2020 15:33:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 79A03214AF for ; Thu, 23 Jan 2020 15:33:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579793636; bh=CbL1aJ0UwkU97AqOSFgTSE6EmAKzy4J8APOtpuCZjCc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=l1TqD0kzuqFq0GyiWnPzpyyaHNi+HX5I24Qh+yuWAy26FvtEd2VgAsZ55QYC+gGtC 7JzHI6oG7a7/IgmdepDryUdIpIM/j2I4IPguChhRPxVSSgdxnHTMOYldUiLy9/V7YT 4VoZVJ/H6+91orD1xTF/6RE97SMrXDgUVTFsiDyA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729045AbgAWPdz (ORCPT ); Thu, 23 Jan 2020 10:33:55 -0500 Received: from mail.kernel.org ([198.145.29.99]:51508 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726232AbgAWPdy (ORCPT ); Thu, 23 Jan 2020 10:33:54 -0500 Received: from localhost.localdomain (236.31.169.217.in-addr.arpa [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 96C4A21D7D; Thu, 23 Jan 2020 15:33:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579793633; bh=CbL1aJ0UwkU97AqOSFgTSE6EmAKzy4J8APOtpuCZjCc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fXFFB+X+SSjeiz5f5JzyONAFNVXBbiLfiQj/kLw4ZaMP2Rbqd1JAGsO/T96Jh1LNC VbeHGTcVzNSriENLnYP6A/XByytHTbn++yflEp/QPPU+MfsbRtu8YJnEP+jJJvsKDm SoyXZDUDjiNO4aP4XOUmr6SCEw+NZj7jHrj2sCSU= 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 v2 01/10] compiler/gcc: Emit build-time warning for GCC prior to version 4.8 Date: Thu, 23 Jan 2020 15:33:32 +0000 Message-Id: <20200123153341.19947-2-will@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200123153341.19947-1-will@kernel.org> References: <20200123153341.19947-1-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 | 6 ++++++ 2 files changed, 8 insertions(+), 2 deletions(-) diff --git a/init/Kconfig b/init/Kconfig index a34064a031a5..bdc2f1b1667b 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -10,11 +10,11 @@ config DEFCONFIG_LIST default "arch/$(ARCH)/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 CC_IS_CLANG diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include index d4adfbe42690..4e645a798b56 100644 --- a/scripts/Kconfig.include +++ b/scripts/Kconfig.include @@ -40,3 +40,9 @@ $(error-if,$(success, $(LD) -v | grep -q gold), gold linker '$(LD)' not supporte # 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.") -- 2.25.0.341.g760bfbb309-goog