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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 7D15DC4321A for ; Fri, 28 Jun 2019 20:37:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4C901208CB for ; Fri, 28 Jun 2019 20:37:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1561754270; bh=9EXpoFnBbMdrxcl40ZXbwS9ICKS0sIKQS1CjVCKVsGc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=dLrQn8lk9eh3yTLw4403W+jgoabHM9GIMaDA2NE/8hx+uIFULdlOqpi4NirP/h9dK UGjgX/p7pcTUDMKDCnGC07iOXqBSHrj7ZQWISy8iuMafXxOzP1/GhdfZrfRbT0eU7l 0BqcIQo+7+Xx0N6pg85NGWncWwAyK2X99vSMXIwU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727148AbfF1Uht (ORCPT ); Fri, 28 Jun 2019 16:37:49 -0400 Received: from mail.kernel.org ([198.145.29.99]:58228 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727147AbfF1Uht (ORCPT ); Fri, 28 Jun 2019 16:37:49 -0400 Received: from localhost (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (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 C158F2086D; Fri, 28 Jun 2019 20:37:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1561754269; bh=9EXpoFnBbMdrxcl40ZXbwS9ICKS0sIKQS1CjVCKVsGc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=XlbQ33nnYGsUm0saOo8jLWnWWADTqkE32DPzbH1LTgBOtTgyFe+oZEw30pJYHeqQS 2u5jtRZ7wDeFvGkBKBwVfIh5INWkqkwYu7aSFdglzwpVvNhDT4MSd8kfBBiKN4rXDS Zr6POXQDahna6siYeguGvdEPDzLmVjqPPlYLQExA= Date: Fri, 28 Jun 2019 16:37:47 -0400 From: Sasha Levin To: Nick Desaulniers Cc: Tony Battersby , Greg Kroah-Hartman , stable , Miguel Ojeda , Nathan Chancellor , Josh Poimboeuf , Andy Lutomirski Subject: Re: Regression: cannot compile kernel 4.14 with old gcc Message-ID: <20190628203747.GH11506@sasha-vm> References: <54a67814-1c9a-14c9-3a7d-947b08369514@cybernetics.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Fri, Jun 28, 2019 at 09:42:21AM -0700, Nick Desaulniers wrote: >On Fri, Jun 28, 2019 at 8:53 AM Tony Battersby wrote: >> >> Old versions of gcc cannot compile 4.14 since 4.14.113: >> >> ./include/asm-generic/fixmap.h:37: error: implicit declaration of function ‘__builtin_unreachable’ >> >> The stable commit that caused the problem is 82017e26e515 ("compiler.h: >> update definition of unreachable()") (upstream commit fe0640eb30b7). >> Reverting the commit fixes the problem. >> >> Kernel 4.17 dropped support for older versions of gcc in upstream commit >> cafa0010cd51 ("Raise the minimum required gcc version to 4.6"). This >> was not backported to 4.14 since that would go against the stable kernel >> rules. >> >> Upstream commit 815f0ddb346c ("include/linux/compiler*.h: make >> compiler-*.h mutually exclusive") was a fix for cafa0010cd51. This was >> not backported to 4.14. >> >> Upstream commit fe0640eb30b7 ("compiler.h: update definition of >> unreachable()") was a fix for 815f0ddb346c. This is the commit that was >> backported to 4.14. But it only fixed a problem introduced in the other >> commits, and without those commits, it ends up introducing a problem >> instead of fixing one. So I recommend reverting that patch in 4.14, >> which will enable old gcc to compile 4.14 again. If I understand >> correctly, I believe that clang will still be able to compile 4.14 with >> the patch reverted, although I haven't tried to compile with clang. >> >> The problematic commit is not present in 4.9.x, 4.4.x, 3.18.x, or 3.16.x. > >$ make CC=clang -j71 arch/x86/mm/fault.o >produces no objtool warning with upstream commit fe0640eb30b7 reverted. > >x86 defconfig w/ Clang also have no issue with that reverted on 4.14.y. > >Revert away. > >Greg, Sasha, >Do you need a patch file for that, or can you please push a >$ cd linux-stable >$ git checkout 4.14.y >$ git revert 82017e26e51596ee577171a33f357377ec6513b5 You got it. >-- >Thanks, >~Nick Desaulniers