From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: ARC-Seal: i=1; a=rsa-sha256; t=1518383996; cv=none; d=google.com; s=arc-20160816; b=wMySduu0EDM17d655K/ir3CJ1pKamuvMvtYGQyrjGvmnHEYy9mUFlvmA59lRlm9xHg Md5LIgmfbBzheE9HaXp1qPeqOKsQprUvHq6LDUuyWtsi7WkTAExmQewd945Ly97pgzFy /KY/S04A2qDsKGP/thUlnt2toWYTKHv70zd5fNeu9f5AalsSwFzY3KdCQFs8Fz4WHwcx zcsCpwI5jWHsGxhVX8/axg/t/iNuCg8uApwZkbzYZiI2ElWvrO4oZnkp7I/S01AWpax1 WWlRoK2Y1hzVDQ764N4YTvpcKtG2ED/CP76sAylzapa9lnxF+yrgTqFQMWuWHe/Eiuiy IrIg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=cc:to:subject:message-id:date:from:references:in-reply-to:sender :mime-version:dkim-signature:dkim-signature :arc-authentication-results; bh=E4upVd9LOZb4cnqKo7RdEVCrn20gYwmowIX6bhjZVm0=; b=v9kGLaU+D2IfQ82FzeryuBlFQP5kqkBPmHldfS4FLsEQHJ3XaguYXCYtD3HbAuO42E vByhP7pnGHmK84Uz9u8LeqxueeT5qQA8KmJ+UtO6mDlB2aO9MCNOZCT1Ggv7Co41T/ld AKy/U/bmBOGm1StJ8Sdc3t+atcOqwCVPjOMVd5A6ObzzV+Ru6SnwV0CtUzgFD9E2IN2j getUDIi3xAF8tG8YtAj+Str3yqzGaxJk8lwv68WKxpKsXJGTXC3iZoVp6otqFndfVMan Z5tpUb/V9pg5H6dZHhYJkkNP3lc17YcdrKi3j7XEnOkt+i85/NYqRLn4leZqOSrdWeld w9ZQ== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=pxKxL7yM; dkim=pass header.i=@chromium.org header.s=google header.b=WNHICy79; spf=pass (google.com: domain of keescook@google.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=keescook@google.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=chromium.org Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=pxKxL7yM; dkim=pass header.i=@chromium.org header.s=google header.b=WNHICy79; spf=pass (google.com: domain of keescook@google.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=keescook@google.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=chromium.org X-Google-Smtp-Source: AH8x2262oaLb7zT/BTqmG+FX/FDfWTPqkKuRcrTfHpUaIaCoeE7o7r+LYyugh1HG5G3XmnOI4WDxhLJv2c4Fe5THuI0= MIME-Version: 1.0 Sender: keescook@google.com In-Reply-To: References: <20180210054843.z3g7wvcmlccvww3h@huvuddator> <20180210074924.3nhxsza5zdbaahxx@huvuddator> <20180210080556.mycqsjhxbaguwhay@huvuddator> <20180210085519.737ckf4bcl57h4g2@huvuddator> <20180211103432.pf2ot6nd7nbhdhsy@huvuddator> From: Kees Cook Date: Sun, 11 Feb 2018 13:19:54 -0800 X-Google-Sender-Auth: -s67sCmW7Lbvwwe0SMG07mVIKLA Message-ID: Subject: Re: [RFC PATCH 4/7] kconfig: support new special property shell= To: Arnd Bergmann Cc: Linus Torvalds , Ulf Magnusson , Masahiro Yamada , Linux Kbuild mailing list , Greg Kroah-Hartman , Andrew Morton , Nicolas Pitre , "Luis R . Rodriguez" , Randy Dunlap , Sam Ravnborg , Michal Marek , Martin Schwidefsky , Pavel Machek , linux-s390 , Jiri Kosina , Linux Kernel Mailing List , Tejun Heo , Ingo Molnar , "Van De Ven, Arjan" , Geert Uytterhoeven Content-Type: text/plain; charset="UTF-8" X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1591850368607646970?= X-GMAIL-MSGID: =?utf-8?q?1592141017433490725?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Sun, Feb 11, 2018 at 1:10 PM, Arnd Bergmann wrote: > On Sun, Feb 11, 2018 at 9:06 PM, Linus Torvalds > wrote: >> On Sun, Feb 11, 2018 at 11:53 AM, Linus Torvalds >> wrote: >>> >>> Well, it's still not a very *big* bump. With modern distros being at >>> 7.3, and people testing pre-releases of gcc-8, something like gcc-4.5 >>> is still pretty darn ancient. >> >> ... it's worth noting that our _documentation_ may claim that gcc-3.2 >> is the minimum supported version, but Arnd pointed out that a few >> months ago that apparently nothing older than 4.1 has actually worked >> for a longish while, and gcc-4.3 was needed on several architectures. >> >> So the _real_ jump in required gcc version would be from 4.1 (4.3 in >> many cases) to 4.5, not from our documented "3.2 minimum". >> >> Arnd claimed that some architectures needed even newer-than-4.3, but I >> assume that's limited to things like RISC-V that simply don't have old >> gcc support at all. > > Right. Also architecture specific features may need something more recent, > and in some cases like the 'initializer for anonymous union needs extra > curly braces', a trivial change would make it work, but a lot of architectures > have obviously never been built with toolchains old enough to actually > run into those cases. > > Geert is the only person I know that actively uses gcc-4.1, and he actually > sent some patches that seem to get additional architectures to build on > that version, when they were previously on gcc-4.3+. > > gcc-4.3 in turn is used by default on SLES11, which is still in support, > and I've even worked with someone who used that compiler to build > new kernels, since that was what happened to be installed on his > shared build server. In this case, having gcc-4.3 actively refused to > force him to use a new compiler would have saved us some > debugging trouble. > > In my tests last year, I identified gcc-4.6 as a nice minimum level, IIRC > gcc-4.5 was unable to build some of the newer ARM targets. For reference, the original discussion started here: https://lkml.org/lkml/2016/12/16/174 I thread-necromancied it here: https://lkml.org/lkml/2017/4/16/276 Modern analysis of compilers vs versions here: https://lkml.org/lkml/2017/4/24/481 and seeming conclusion was here: https://lkml.org/lkml/2017/4/25/66 Quoted: >> - To keep it simple, we update the README.rst to say that a minimum >> gcc-4.3 is required, while recommending gcc-4.9 for all architectures >> - Support for gcc-4.0 and earlier gets removed from linux/compiler.h, >> and instead we add a summary of what I found, explaining that >> gcc-4.1 has active users on a few architectures. >> - We make the Makefile show a warning once during compilation for >> gcc earlier than 4.3. But yes, if Linus wants 4.5 over 4.3, I would agree with Arnd: let's take it to 4.6 instead. -Kees -- Kees Cook Pixel Security