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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 1485CC433B4 for ; Tue, 4 May 2021 05:31:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D4671611EE for ; Tue, 4 May 2021 05:31:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229806AbhEDFbv (ORCPT ); Tue, 4 May 2021 01:31:51 -0400 Received: from mail.thorsis.com ([92.198.35.195]:57485 "EHLO mail.thorsis.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229719AbhEDFbt (ORCPT ); Tue, 4 May 2021 01:31:49 -0400 Received: from localhost (localhost [127.0.0.1]) by mail.thorsis.com (Postfix) with ESMTP id A8A461AB6; Tue, 4 May 2021 07:30:52 +0200 (CEST) X-Virus-Scanned: Debian amavisd-new at mail.thorsis.com Received: from mail.thorsis.com ([127.0.0.1]) by localhost (mail.thorsis.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id hSn2JZxRetDo; Tue, 4 May 2021 07:30:52 +0200 (CEST) Received: by mail.thorsis.com (Postfix, from userid 109) id 2843E3581; Tue, 4 May 2021 07:30:52 +0200 (CEST) Date: Tue, 4 May 2021 07:30:30 +0200 From: Alexander Dahl To: Arnd Bergmann Cc: Matthew Wilcox , Linus Torvalds , Segher Boessenkool , Joe Perches , Miguel Ojeda , Masahiro Yamada , Albert Ou , Linux Kbuild mailing list , Greg Kroah-Hartman , Jonathan Corbet , Linux Doc Mailing List , linux-kernel , Palmer Dabbelt , Paul Walmsley , Catalin Marinas , Miguel Ojeda , Paul Mackerras , linux-riscv , linuxppc-dev , Will Deacon , Linux ARM Subject: Re: [PATCH] Raise the minimum GCC version to 5.2 Message-ID: Mail-Followup-To: Arnd Bergmann , Matthew Wilcox , Linus Torvalds , Segher Boessenkool , Joe Perches , Miguel Ojeda , Masahiro Yamada , Albert Ou , Linux Kbuild mailing list , Greg Kroah-Hartman , Jonathan Corbet , Linux Doc Mailing List , linux-kernel , Palmer Dabbelt , Paul Walmsley , Catalin Marinas , Miguel Ojeda , Paul Mackerras , linux-riscv , linuxppc-dev , Will Deacon , Linux ARM References: <20210501151538.145449-1-masahiroy@kernel.org> <3943bc020f6227c8801907317fc113aa13ad4bad.camel@perches.com> <20210502183030.GF10366@gate.crashing.org> <81a926a3bdb70debe3ae2b13655ea8d249fb9991.camel@perches.com> <20210502203253.GH10366@gate.crashing.org> <20210502223007.GZ1847222@casper.infradead.org> Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Arnd, Am Mon, May 03, 2021 at 11:25:21AM +0200 schrieb Arnd Bergmann: > On Mon, May 3, 2021 at 9:35 AM Alexander Dahl wrote: > > > > Desktops and servers are all nice, however I just want to make you > > aware, there are embedded users forced to stick to older cross > > toolchains for different reasons as well, e.g. in industrial > > environment. :-) > > > > This is no show stopper for us, I just wanted to let you be aware. > > Can you be more specific about what scenarios you are thinking of, > what the motivations are for using an old compiler with a new kernel > on embedded systems, and what you think a realistic maximum > time would be between compiler updates? One reason might be certification. For certain industrial applications like support for complex field bus protocols, you need to get your devices tested by an external partner running extensive test suites. This is time consuming and expensive. Changing the toolchain of your system then, would be a massive change which would require recertification, while you could argue just updating a single component like the kernel and building everything again, does not require the whole testing process again. Thin ice, I know. > One scenario that I've seen previously is where user space and > kernel are built together as a source based distribution (OE, buildroot, > openwrt, ...), and the compiler is picked to match the original sources > of the user space because that is best tested, but the same compiler > then gets used to build the kernel as well because that is the default > in the build environment. One problem we actually ran into in BSPs like that (we build with ptxdist, however build system doesn't matter here, it could as well have been buildroot etc.) was things* failing to build with newer compilers, things we could not or did not want to fix, so staying with an older toolchain was the obvious choice. *Things as in bootloaders for an armv5 platform. > There are two problems I see with this logic: > > - Running the latest kernel to avoid security problems is of course > a good idea, but if one runs that with ten year old user space that > is never updated, the system is likely to end up just as insecure. > Not all bugs are in the kernel. Agreed. > - The same logic that applies to ancient user space staying with > an ancient compiler (it's better tested in this combination) also > applies to the kernel: running the latest kernel on an old compiler > is something that few people test, and tends to run into more bugs > than using the compiler that other developers used to test that > kernel. What we actually did: building recent userspace and kernel with older toolchains, because bootloader. I know, there are several possibilities to solve this kind of lock: - built bootloader with different compiler - update bootloader - … As said before, this is no problem for me now, I can work around it, but to give an idea what could keep people on older toolchains. Greets Alex 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=-4.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 446D7C433ED for ; Tue, 4 May 2021 05:31:37 +0000 (UTC) Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id B868E611EE for ; Tue, 4 May 2021 05:31:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B868E611EE Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=thorsis.com Authentication-Results: mail.kernel.org; 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Tue, 04 May 2021 05:30:56 +0000 Received: from localhost (localhost [127.0.0.1]) by mail.thorsis.com (Postfix) with ESMTP id 044C41B3D; Tue, 4 May 2021 07:30:50 +0200 (CEST) X-Virus-Scanned: Debian amavisd-new at mail.thorsis.com Received: from mail.thorsis.com ([127.0.0.1]) by localhost (mail.thorsis.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id xew6O0H1a2uJ; Tue, 4 May 2021 07:30:49 +0200 (CEST) Received: by mail.thorsis.com (Postfix, from userid 109) id 766AC10B4; Tue, 4 May 2021 07:30:48 +0200 (CEST) Date: Tue, 4 May 2021 07:30:30 +0200 From: Alexander Dahl To: Arnd Bergmann Cc: Matthew Wilcox , Linus Torvalds , Segher Boessenkool , Joe Perches , Miguel Ojeda , Masahiro Yamada , Albert Ou , Linux Kbuild mailing list , Greg Kroah-Hartman , Jonathan Corbet , Linux Doc Mailing List , linux-kernel , Palmer Dabbelt , Paul Walmsley , Catalin Marinas , Miguel Ojeda , Paul Mackerras , linux-riscv , linuxppc-dev , Will Deacon , Linux ARM Subject: Re: [PATCH] Raise the minimum GCC version to 5.2 Message-ID: Mail-Followup-To: Arnd Bergmann , Matthew Wilcox , Linus Torvalds , Segher Boessenkool , Joe Perches , Miguel Ojeda , Masahiro Yamada , Albert Ou , Linux Kbuild mailing list , Greg Kroah-Hartman , Jonathan Corbet , Linux Doc Mailing List , linux-kernel , Palmer Dabbelt , Paul Walmsley , Catalin Marinas , Miguel Ojeda , Paul Mackerras , linux-riscv , linuxppc-dev , Will Deacon , Linux ARM References: <20210501151538.145449-1-masahiroy@kernel.org> <3943bc020f6227c8801907317fc113aa13ad4bad.camel@perches.com> <20210502183030.GF10366@gate.crashing.org> <81a926a3bdb70debe3ae2b13655ea8d249fb9991.camel@perches.com> <20210502203253.GH10366@gate.crashing.org> <20210502223007.GZ1847222@casper.infradead.org> Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210503_223054_646790_FBCAD44C X-CRM114-Status: GOOD ( 34.28 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org SGVsbG8gQXJuZCwKCkFtIE1vbiwgTWF5IDAzLCAyMDIxIGF0IDExOjI1OjIxQU0gKzAyMDAgc2No cmllYiBBcm5kIEJlcmdtYW5uOgo+IE9uIE1vbiwgTWF5IDMsIDIwMjEgYXQgOTozNSBBTSBBbGV4 YW5kZXIgRGFobCA8YWRhQHRob3JzaXMuY29tPiB3cm90ZToKPiA+Cj4gPiBEZXNrdG9wcyBhbmQg c2VydmVycyBhcmUgYWxsIG5pY2UsIGhvd2V2ZXIgSSBqdXN0IHdhbnQgdG8gbWFrZSB5b3UKPiA+ IGF3YXJlLCB0aGVyZSBhcmUgZW1iZWRkZWQgdXNlcnMgZm9yY2VkIHRvIHN0aWNrIHRvIG9sZGVy IGNyb3NzCj4gPiB0b29sY2hhaW5zIGZvciBkaWZmZXJlbnQgcmVhc29ucyBhcyB3ZWxsLCBlLmcu IGluIGluZHVzdHJpYWwKPiA+IGVudmlyb25tZW50LiA6LSkKPiA+Cj4gPiBUaGlzIGlzIG5vIHNo b3cgc3RvcHBlciBmb3IgdXMsIEkganVzdCB3YW50ZWQgdG8gbGV0IHlvdSBiZSBhd2FyZS4KPiAK PiBDYW4geW91IGJlIG1vcmUgc3BlY2lmaWMgYWJvdXQgd2hhdCBzY2VuYXJpb3MgeW91IGFyZSB0 aGlua2luZyBvZiwKPiB3aGF0IHRoZSBtb3RpdmF0aW9ucyBhcmUgZm9yIHVzaW5nIGFuIG9sZCBj b21waWxlciB3aXRoIGEgbmV3IGtlcm5lbAo+IG9uIGVtYmVkZGVkIHN5c3RlbXMsIGFuZCB3aGF0 IHlvdSB0aGluayBhIHJlYWxpc3RpYyBtYXhpbXVtCj4gdGltZSB3b3VsZCBiZSBiZXR3ZWVuIGNv bXBpbGVyIHVwZGF0ZXM/CgpPbmUgcmVhc29uIG1pZ2h0IGJlIGNlcnRpZmljYXRpb24uIEZvciBj ZXJ0YWluIGluZHVzdHJpYWwgYXBwbGljYXRpb25zCmxpa2Ugc3VwcG9ydCBmb3IgY29tcGxleCBm aWVsZCBidXMgcHJvdG9jb2xzLCB5b3UgbmVlZCB0byBnZXQgeW91cgpkZXZpY2VzIHRlc3RlZCBi eSBhbiBleHRlcm5hbCBwYXJ0bmVyIHJ1bm5pbmcgZXh0ZW5zaXZlIHRlc3Qgc3VpdGVzLgpUaGlz IGlzIHRpbWUgY29uc3VtaW5nIGFuZCBleHBlbnNpdmUuIAoKQ2hhbmdpbmcgdGhlIHRvb2xjaGFp biBvZiB5b3VyIHN5c3RlbSB0aGVuLCB3b3VsZCBiZSBhIG1hc3NpdmUgY2hhbmdlCndoaWNoIHdv dWxkIHJlcXVpcmUgcmVjZXJ0aWZpY2F0aW9uLCB3aGlsZSB5b3UgY291bGQgYXJndWUganVzdAp1 cGRhdGluZyBhIHNpbmdsZSBjb21wb25lbnQgbGlrZSB0aGUga2VybmVsIGFuZCBidWlsZGluZyBl dmVyeXRoaW5nCmFnYWluLCBkb2VzIG5vdCByZXF1aXJlIHRoZSB3aG9sZSB0ZXN0aW5nIHByb2Nl c3MgYWdhaW4uIAoKVGhpbiBpY2UsIEkga25vdy4KCj4gT25lIHNjZW5hcmlvIHRoYXQgSSd2ZSBz ZWVuIHByZXZpb3VzbHkgaXMgd2hlcmUgdXNlciBzcGFjZSBhbmQKPiBrZXJuZWwgYXJlIGJ1aWx0 IHRvZ2V0aGVyIGFzIGEgc291cmNlIGJhc2VkIGRpc3RyaWJ1dGlvbiAoT0UsIGJ1aWxkcm9vdCwK PiBvcGVud3J0LCAuLi4pLCBhbmQgdGhlIGNvbXBpbGVyIGlzIHBpY2tlZCB0byBtYXRjaCB0aGUg b3JpZ2luYWwgc291cmNlcwo+IG9mIHRoZSB1c2VyIHNwYWNlIGJlY2F1c2UgdGhhdCBpcyBiZXN0 IHRlc3RlZCwgYnV0IHRoZSBzYW1lIGNvbXBpbGVyCj4gdGhlbiBnZXRzIHVzZWQgdG8gYnVpbGQg dGhlIGtlcm5lbCBhcyB3ZWxsIGJlY2F1c2UgdGhhdCBpcyB0aGUgZGVmYXVsdAo+IGluIHRoZSBi dWlsZCBlbnZpcm9ubWVudC4KCk9uZSBwcm9ibGVtIHdlIGFjdHVhbGx5IHJhbiBpbnRvIGluIEJT UHMgbGlrZSB0aGF0ICh3ZSBidWlsZCB3aXRoCnB0eGRpc3QsIGhvd2V2ZXIgYnVpbGQgc3lzdGVt IGRvZXNuJ3QgbWF0dGVyIGhlcmUsIGl0IGNvdWxkIGFzIHdlbGwKaGF2ZSBiZWVuIGJ1aWxkcm9v dCBldGMuKSB3YXMgdGhpbmdzKiBmYWlsaW5nIHRvIGJ1aWxkIHdpdGggbmV3ZXIKY29tcGlsZXJz LCB0aGluZ3Mgd2UgY291bGQgbm90IG9yIGRpZCBub3Qgd2FudCB0byBmaXgsIHNvIHN0YXlpbmcg d2l0aAphbiBvbGRlciB0b29sY2hhaW4gd2FzIHRoZSBvYnZpb3VzIGNob2ljZS4gCgoqVGhpbmdz IGFzIGluIGJvb3Rsb2FkZXJzIGZvciBhbiBhcm12NSBwbGF0Zm9ybS4KCj4gVGhlcmUgYXJlIHR3 byBwcm9ibGVtcyBJIHNlZSB3aXRoIHRoaXMgbG9naWM6Cj4gCj4gLSBSdW5uaW5nIHRoZSBsYXRl c3Qga2VybmVsIHRvIGF2b2lkIHNlY3VyaXR5IHByb2JsZW1zIGlzIG9mIGNvdXJzZQo+ICAgYSBn b29kIGlkZWEsIGJ1dCBpZiBvbmUgcnVucyB0aGF0IHdpdGggdGVuIHllYXIgb2xkIHVzZXIgc3Bh Y2UgdGhhdAo+ICAgaXMgbmV2ZXIgdXBkYXRlZCwgdGhlIHN5c3RlbSBpcyBsaWtlbHkgdG8gZW5k IHVwIGp1c3QgYXMgaW5zZWN1cmUuCj4gICBOb3QgYWxsIGJ1Z3MgYXJlIGluIHRoZSBrZXJuZWwu CgpBZ3JlZWQuCgo+IC0gVGhlIHNhbWUgbG9naWMgdGhhdCBhcHBsaWVzIHRvIGFuY2llbnQgdXNl ciBzcGFjZSBzdGF5aW5nIHdpdGgKPiAgIGFuIGFuY2llbnQgY29tcGlsZXIgKGl0J3MgYmV0dGVy IHRlc3RlZCBpbiB0aGlzIGNvbWJpbmF0aW9uKSBhbHNvCj4gICBhcHBsaWVzIHRvIHRoZSBrZXJu ZWw6IHJ1bm5pbmcgdGhlIGxhdGVzdCBrZXJuZWwgb24gYW4gb2xkIGNvbXBpbGVyCj4gICBpcyBz b21ldGhpbmcgdGhhdCBmZXcgcGVvcGxlIHRlc3QsIGFuZCB0ZW5kcyB0byBydW4gaW50byBtb3Jl IGJ1Z3MKPiAgIHRoYW4gdXNpbmcgdGhlIGNvbXBpbGVyIHRoYXQgb3RoZXIgZGV2ZWxvcGVycyB1 c2VkIHRvIHRlc3QgdGhhdAo+ICAga2VybmVsLgoKV2hhdCB3ZSBhY3R1YWxseSBkaWQ6IGJ1aWxk aW5nIHJlY2VudCB1c2Vyc3BhY2UgYW5kIGtlcm5lbCB3aXRoIG9sZGVyCnRvb2xjaGFpbnMsIGJl Y2F1c2UgYm9vdGxvYWRlci4gSSBrbm93LCB0aGVyZSBhcmUgc2V2ZXJhbApwb3NzaWJpbGl0aWVz IHRvIHNvbHZlIHRoaXMga2luZCBvZiBsb2NrOgoKLSBidWlsdCBib290bG9hZGVyIHdpdGggZGlm ZmVyZW50IGNvbXBpbGVyCi0gdXBkYXRlIGJvb3Rsb2FkZXIKLSDigKYKCkFzIHNhaWQgYmVmb3Jl LCB0aGlzIGlzIG5vIHByb2JsZW0gZm9yIG1lIG5vdywgSSBjYW4gd29yayBhcm91bmQgaXQsCmJ1 dCB0byBnaXZlIGFuIGlkZWEgd2hhdCBjb3VsZCBrZWVwIHBlb3BsZSBvbiBvbGRlciB0b29sY2hh aW5zLgoKR3JlZXRzCkFsZXgKCgpfX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f X19fX19fX19fXwpsaW51eC1yaXNjdiBtYWlsaW5nIGxpc3QKbGludXgtcmlzY3ZAbGlzdHMuaW5m cmFkZWFkLm9yZwpodHRwOi8vbGlzdHMuaW5mcmFkZWFkLm9yZy9tYWlsbWFuL2xpc3RpbmZvL2xp bnV4LXJpc2N2Cg== 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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 64A24C433B4 for ; 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Tue, 4 May 2021 15:30:54 +1000 (AEST) Received: from localhost (localhost [127.0.0.1]) by mail.thorsis.com (Postfix) with ESMTP id 31A1210B4 for ; Tue, 4 May 2021 07:30:50 +0200 (CEST) X-Virus-Scanned: Debian amavisd-new at mail.thorsis.com Received: from mail.thorsis.com ([127.0.0.1]) by localhost (mail.thorsis.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id LrZ_vSUSsYeu for ; Tue, 4 May 2021 07:30:50 +0200 (CEST) Received: by mail.thorsis.com (Postfix, from userid 109) id AC59C3581; Tue, 4 May 2021 07:30:49 +0200 (CEST) Date: Tue, 4 May 2021 07:30:30 +0200 From: Alexander Dahl To: Arnd Bergmann Subject: Re: [PATCH] Raise the minimum GCC version to 5.2 Message-ID: Mail-Followup-To: Arnd Bergmann , Matthew Wilcox , Linus Torvalds , Segher Boessenkool , Joe Perches , Miguel Ojeda , Masahiro Yamada , Albert Ou , Linux Kbuild mailing list , Greg Kroah-Hartman , Jonathan Corbet , Linux Doc Mailing List , linux-kernel , Palmer Dabbelt , Paul Walmsley , Catalin Marinas , Miguel Ojeda , Paul Mackerras , linux-riscv , linuxppc-dev , Will Deacon , Linux ARM References: <20210501151538.145449-1-masahiroy@kernel.org> <3943bc020f6227c8801907317fc113aa13ad4bad.camel@perches.com> <20210502183030.GF10366@gate.crashing.org> <81a926a3bdb70debe3ae2b13655ea8d249fb9991.camel@perches.com> <20210502203253.GH10366@gate.crashing.org> <20210502223007.GZ1847222@casper.infradead.org> Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Albert Ou , Catalin Marinas , Linux Kbuild mailing list , Greg Kroah-Hartman , Masahiro Yamada , Jonathan Corbet , Linux Doc Mailing List , linux-kernel , Matthew Wilcox , Miguel Ojeda , Will Deacon , Palmer Dabbelt , Paul Walmsley , Joe Perches , Paul Mackerras , linux-riscv , Miguel Ojeda , Linus Torvalds , Linux ARM , linuxppc-dev Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Hello Arnd, Am Mon, May 03, 2021 at 11:25:21AM +0200 schrieb Arnd Bergmann: > On Mon, May 3, 2021 at 9:35 AM Alexander Dahl wrote: > > > > Desktops and servers are all nice, however I just want to make you > > aware, there are embedded users forced to stick to older cross > > toolchains for different reasons as well, e.g. in industrial > > environment. :-) > > > > This is no show stopper for us, I just wanted to let you be aware. > > Can you be more specific about what scenarios you are thinking of, > what the motivations are for using an old compiler with a new kernel > on embedded systems, and what you think a realistic maximum > time would be between compiler updates? One reason might be certification. For certain industrial applications like support for complex field bus protocols, you need to get your devices tested by an external partner running extensive test suites. This is time consuming and expensive. Changing the toolchain of your system then, would be a massive change which would require recertification, while you could argue just updating a single component like the kernel and building everything again, does not require the whole testing process again. Thin ice, I know. > One scenario that I've seen previously is where user space and > kernel are built together as a source based distribution (OE, buildroot, > openwrt, ...), and the compiler is picked to match the original sources > of the user space because that is best tested, but the same compiler > then gets used to build the kernel as well because that is the default > in the build environment. One problem we actually ran into in BSPs like that (we build with ptxdist, however build system doesn't matter here, it could as well have been buildroot etc.) was things* failing to build with newer compilers, things we could not or did not want to fix, so staying with an older toolchain was the obvious choice. *Things as in bootloaders for an armv5 platform. > There are two problems I see with this logic: > > - Running the latest kernel to avoid security problems is of course > a good idea, but if one runs that with ten year old user space that > is never updated, the system is likely to end up just as insecure. > Not all bugs are in the kernel. Agreed. > - The same logic that applies to ancient user space staying with > an ancient compiler (it's better tested in this combination) also > applies to the kernel: running the latest kernel on an old compiler > is something that few people test, and tends to run into more bugs > than using the compiler that other developers used to test that > kernel. What we actually did: building recent userspace and kernel with older toolchains, because bootloader. I know, there are several possibilities to solve this kind of lock: - built bootloader with different compiler - update bootloader - … As said before, this is no problem for me now, I can work around it, but to give an idea what could keep people on older toolchains. Greets Alex 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=-4.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 48118C433B4 for ; Tue, 4 May 2021 05:32:46 +0000 (UTC) Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id BF26161042 for ; Tue, 4 May 2021 05:32:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BF26161042 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=thorsis.com Authentication-Results: mail.kernel.org; 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Tue, 04 May 2021 05:30:56 +0000 Received: from localhost (localhost [127.0.0.1]) by mail.thorsis.com (Postfix) with ESMTP id 044C41B3D; Tue, 4 May 2021 07:30:50 +0200 (CEST) X-Virus-Scanned: Debian amavisd-new at mail.thorsis.com Received: from mail.thorsis.com ([127.0.0.1]) by localhost (mail.thorsis.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id xew6O0H1a2uJ; Tue, 4 May 2021 07:30:49 +0200 (CEST) Received: by mail.thorsis.com (Postfix, from userid 109) id 766AC10B4; Tue, 4 May 2021 07:30:48 +0200 (CEST) Date: Tue, 4 May 2021 07:30:30 +0200 From: Alexander Dahl To: Arnd Bergmann Cc: Matthew Wilcox , Linus Torvalds , Segher Boessenkool , Joe Perches , Miguel Ojeda , Masahiro Yamada , Albert Ou , Linux Kbuild mailing list , Greg Kroah-Hartman , Jonathan Corbet , Linux Doc Mailing List , linux-kernel , Palmer Dabbelt , Paul Walmsley , Catalin Marinas , Miguel Ojeda , Paul Mackerras , linux-riscv , linuxppc-dev , Will Deacon , Linux ARM Subject: Re: [PATCH] Raise the minimum GCC version to 5.2 Message-ID: Mail-Followup-To: Arnd Bergmann , Matthew Wilcox , Linus Torvalds , Segher Boessenkool , Joe Perches , Miguel Ojeda , Masahiro Yamada , Albert Ou , Linux Kbuild mailing list , Greg Kroah-Hartman , Jonathan Corbet , Linux Doc Mailing List , linux-kernel , Palmer Dabbelt , Paul Walmsley , Catalin Marinas , Miguel Ojeda , Paul Mackerras , linux-riscv , linuxppc-dev , Will Deacon , Linux ARM References: <20210501151538.145449-1-masahiroy@kernel.org> <3943bc020f6227c8801907317fc113aa13ad4bad.camel@perches.com> <20210502183030.GF10366@gate.crashing.org> <81a926a3bdb70debe3ae2b13655ea8d249fb9991.camel@perches.com> <20210502203253.GH10366@gate.crashing.org> <20210502223007.GZ1847222@casper.infradead.org> Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210503_223054_646790_FBCAD44C X-CRM114-Status: GOOD ( 34.28 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org SGVsbG8gQXJuZCwKCkFtIE1vbiwgTWF5IDAzLCAyMDIxIGF0IDExOjI1OjIxQU0gKzAyMDAgc2No cmllYiBBcm5kIEJlcmdtYW5uOgo+IE9uIE1vbiwgTWF5IDMsIDIwMjEgYXQgOTozNSBBTSBBbGV4 YW5kZXIgRGFobCA8YWRhQHRob3JzaXMuY29tPiB3cm90ZToKPiA+Cj4gPiBEZXNrdG9wcyBhbmQg c2VydmVycyBhcmUgYWxsIG5pY2UsIGhvd2V2ZXIgSSBqdXN0IHdhbnQgdG8gbWFrZSB5b3UKPiA+ IGF3YXJlLCB0aGVyZSBhcmUgZW1iZWRkZWQgdXNlcnMgZm9yY2VkIHRvIHN0aWNrIHRvIG9sZGVy IGNyb3NzCj4gPiB0b29sY2hhaW5zIGZvciBkaWZmZXJlbnQgcmVhc29ucyBhcyB3ZWxsLCBlLmcu IGluIGluZHVzdHJpYWwKPiA+IGVudmlyb25tZW50LiA6LSkKPiA+Cj4gPiBUaGlzIGlzIG5vIHNo b3cgc3RvcHBlciBmb3IgdXMsIEkganVzdCB3YW50ZWQgdG8gbGV0IHlvdSBiZSBhd2FyZS4KPiAK PiBDYW4geW91IGJlIG1vcmUgc3BlY2lmaWMgYWJvdXQgd2hhdCBzY2VuYXJpb3MgeW91IGFyZSB0 aGlua2luZyBvZiwKPiB3aGF0IHRoZSBtb3RpdmF0aW9ucyBhcmUgZm9yIHVzaW5nIGFuIG9sZCBj b21waWxlciB3aXRoIGEgbmV3IGtlcm5lbAo+IG9uIGVtYmVkZGVkIHN5c3RlbXMsIGFuZCB3aGF0 IHlvdSB0aGluayBhIHJlYWxpc3RpYyBtYXhpbXVtCj4gdGltZSB3b3VsZCBiZSBiZXR3ZWVuIGNv bXBpbGVyIHVwZGF0ZXM/CgpPbmUgcmVhc29uIG1pZ2h0IGJlIGNlcnRpZmljYXRpb24uIEZvciBj ZXJ0YWluIGluZHVzdHJpYWwgYXBwbGljYXRpb25zCmxpa2Ugc3VwcG9ydCBmb3IgY29tcGxleCBm aWVsZCBidXMgcHJvdG9jb2xzLCB5b3UgbmVlZCB0byBnZXQgeW91cgpkZXZpY2VzIHRlc3RlZCBi eSBhbiBleHRlcm5hbCBwYXJ0bmVyIHJ1bm5pbmcgZXh0ZW5zaXZlIHRlc3Qgc3VpdGVzLgpUaGlz IGlzIHRpbWUgY29uc3VtaW5nIGFuZCBleHBlbnNpdmUuIAoKQ2hhbmdpbmcgdGhlIHRvb2xjaGFp biBvZiB5b3VyIHN5c3RlbSB0aGVuLCB3b3VsZCBiZSBhIG1hc3NpdmUgY2hhbmdlCndoaWNoIHdv dWxkIHJlcXVpcmUgcmVjZXJ0aWZpY2F0aW9uLCB3aGlsZSB5b3UgY291bGQgYXJndWUganVzdAp1 cGRhdGluZyBhIHNpbmdsZSBjb21wb25lbnQgbGlrZSB0aGUga2VybmVsIGFuZCBidWlsZGluZyBl dmVyeXRoaW5nCmFnYWluLCBkb2VzIG5vdCByZXF1aXJlIHRoZSB3aG9sZSB0ZXN0aW5nIHByb2Nl c3MgYWdhaW4uIAoKVGhpbiBpY2UsIEkga25vdy4KCj4gT25lIHNjZW5hcmlvIHRoYXQgSSd2ZSBz ZWVuIHByZXZpb3VzbHkgaXMgd2hlcmUgdXNlciBzcGFjZSBhbmQKPiBrZXJuZWwgYXJlIGJ1aWx0 IHRvZ2V0aGVyIGFzIGEgc291cmNlIGJhc2VkIGRpc3RyaWJ1dGlvbiAoT0UsIGJ1aWxkcm9vdCwK PiBvcGVud3J0LCAuLi4pLCBhbmQgdGhlIGNvbXBpbGVyIGlzIHBpY2tlZCB0byBtYXRjaCB0aGUg b3JpZ2luYWwgc291cmNlcwo+IG9mIHRoZSB1c2VyIHNwYWNlIGJlY2F1c2UgdGhhdCBpcyBiZXN0 IHRlc3RlZCwgYnV0IHRoZSBzYW1lIGNvbXBpbGVyCj4gdGhlbiBnZXRzIHVzZWQgdG8gYnVpbGQg dGhlIGtlcm5lbCBhcyB3ZWxsIGJlY2F1c2UgdGhhdCBpcyB0aGUgZGVmYXVsdAo+IGluIHRoZSBi dWlsZCBlbnZpcm9ubWVudC4KCk9uZSBwcm9ibGVtIHdlIGFjdHVhbGx5IHJhbiBpbnRvIGluIEJT UHMgbGlrZSB0aGF0ICh3ZSBidWlsZCB3aXRoCnB0eGRpc3QsIGhvd2V2ZXIgYnVpbGQgc3lzdGVt IGRvZXNuJ3QgbWF0dGVyIGhlcmUsIGl0IGNvdWxkIGFzIHdlbGwKaGF2ZSBiZWVuIGJ1aWxkcm9v dCBldGMuKSB3YXMgdGhpbmdzKiBmYWlsaW5nIHRvIGJ1aWxkIHdpdGggbmV3ZXIKY29tcGlsZXJz LCB0aGluZ3Mgd2UgY291bGQgbm90IG9yIGRpZCBub3Qgd2FudCB0byBmaXgsIHNvIHN0YXlpbmcg d2l0aAphbiBvbGRlciB0b29sY2hhaW4gd2FzIHRoZSBvYnZpb3VzIGNob2ljZS4gCgoqVGhpbmdz IGFzIGluIGJvb3Rsb2FkZXJzIGZvciBhbiBhcm12NSBwbGF0Zm9ybS4KCj4gVGhlcmUgYXJlIHR3 byBwcm9ibGVtcyBJIHNlZSB3aXRoIHRoaXMgbG9naWM6Cj4gCj4gLSBSdW5uaW5nIHRoZSBsYXRl c3Qga2VybmVsIHRvIGF2b2lkIHNlY3VyaXR5IHByb2JsZW1zIGlzIG9mIGNvdXJzZQo+ICAgYSBn b29kIGlkZWEsIGJ1dCBpZiBvbmUgcnVucyB0aGF0IHdpdGggdGVuIHllYXIgb2xkIHVzZXIgc3Bh Y2UgdGhhdAo+ICAgaXMgbmV2ZXIgdXBkYXRlZCwgdGhlIHN5c3RlbSBpcyBsaWtlbHkgdG8gZW5k IHVwIGp1c3QgYXMgaW5zZWN1cmUuCj4gICBOb3QgYWxsIGJ1Z3MgYXJlIGluIHRoZSBrZXJuZWwu CgpBZ3JlZWQuCgo+IC0gVGhlIHNhbWUgbG9naWMgdGhhdCBhcHBsaWVzIHRvIGFuY2llbnQgdXNl ciBzcGFjZSBzdGF5aW5nIHdpdGgKPiAgIGFuIGFuY2llbnQgY29tcGlsZXIgKGl0J3MgYmV0dGVy IHRlc3RlZCBpbiB0aGlzIGNvbWJpbmF0aW9uKSBhbHNvCj4gICBhcHBsaWVzIHRvIHRoZSBrZXJu ZWw6IHJ1bm5pbmcgdGhlIGxhdGVzdCBrZXJuZWwgb24gYW4gb2xkIGNvbXBpbGVyCj4gICBpcyBz b21ldGhpbmcgdGhhdCBmZXcgcGVvcGxlIHRlc3QsIGFuZCB0ZW5kcyB0byBydW4gaW50byBtb3Jl IGJ1Z3MKPiAgIHRoYW4gdXNpbmcgdGhlIGNvbXBpbGVyIHRoYXQgb3RoZXIgZGV2ZWxvcGVycyB1 c2VkIHRvIHRlc3QgdGhhdAo+ICAga2VybmVsLgoKV2hhdCB3ZSBhY3R1YWxseSBkaWQ6IGJ1aWxk aW5nIHJlY2VudCB1c2Vyc3BhY2UgYW5kIGtlcm5lbCB3aXRoIG9sZGVyCnRvb2xjaGFpbnMsIGJl Y2F1c2UgYm9vdGxvYWRlci4gSSBrbm93LCB0aGVyZSBhcmUgc2V2ZXJhbApwb3NzaWJpbGl0aWVz IHRvIHNvbHZlIHRoaXMga2luZCBvZiBsb2NrOgoKLSBidWlsdCBib290bG9hZGVyIHdpdGggZGlm ZmVyZW50IGNvbXBpbGVyCi0gdXBkYXRlIGJvb3Rsb2FkZXIKLSDigKYKCkFzIHNhaWQgYmVmb3Jl LCB0aGlzIGlzIG5vIHByb2JsZW0gZm9yIG1lIG5vdywgSSBjYW4gd29yayBhcm91bmQgaXQsCmJ1 dCB0byBnaXZlIGFuIGlkZWEgd2hhdCBjb3VsZCBrZWVwIHBlb3BsZSBvbiBvbGRlciB0b29sY2hh aW5zLgoKR3JlZXRzCkFsZXgKCgpfX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f X19fX19fX19fXwpsaW51eC1hcm0ta2VybmVsIG1haWxpbmcgbGlzdApsaW51eC1hcm0ta2VybmVs QGxpc3RzLmluZnJhZGVhZC5vcmcKaHR0cDovL2xpc3RzLmluZnJhZGVhZC5vcmcvbWFpbG1hbi9s aXN0aW5mby9saW51eC1hcm0ta2VybmVsCg==