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=-0.8 required=3.0 tests=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 9B37DC2BB55 for ; Thu, 16 Apr 2020 20:20:56 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (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 72FBC2076D for ; Thu, 16 Apr 2020 20:20:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 72FBC2076D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=deneb.enyo.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 4939b9211VzDsNW for ; Fri, 17 Apr 2020 06:20:53 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=deneb.enyo.de (client-ip=37.24.231.21; helo=albireo.enyo.de; envelope-from=fw@deneb.enyo.de; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=deneb.enyo.de Received: from albireo.enyo.de (albireo.enyo.de [37.24.231.21]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4939XP4qvGzDrPB for ; Fri, 17 Apr 2020 06:18:28 +1000 (AEST) Received: from [172.17.203.2] (helo=deneb.enyo.de) by albireo.enyo.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) id 1jPAxm-0006kd-Sh; Thu, 16 Apr 2020 20:18:18 +0000 Received: from fw by deneb.enyo.de with local (Exim 4.92) (envelope-from ) id 1jPAxm-0005WN-Nn; Thu, 16 Apr 2020 22:18:18 +0200 From: Florian Weimer To: Nicholas Piggin via Libc-alpha Subject: Re: [musl] Powerpc Linux 'scv' system call ABI proposal take 2 References: <1586931450.ub4c8cq8dj.astroid@bobo.none> <20200415225539.GL11469@brightrain.aerifal.cx> <1586994952.nnxigedbu2.astroid@bobo.none> <20200416004843.GO11469@brightrain.aerifal.cx> <1587002854.f0slo0111r.astroid@bobo.none> <20200416023542.GP11469@brightrain.aerifal.cx> <1587004907.ioxh0bxsln.astroid@bobo.none> Date: Thu, 16 Apr 2020 22:18:18 +0200 In-Reply-To: <1587004907.ioxh0bxsln.astroid@bobo.none> (Nicholas Piggin via Libc-alpha's message of "Thu, 16 Apr 2020 12:53:31 +1000") Message-ID: <87wo6fchh1.fsf@mid.deneb.enyo.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable 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: libc-dev@lists.llvm.org, Rich Felker , linuxppc-dev@lists.ozlabs.org, Nicholas Piggin , musl@lists.openwall.com Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" * Nicholas Piggin via Libc-alpha: > We may or may not be getting a new ABI that will use instructions not=20 > supported by old processors. > > https://sourceware.org/legacy-ml/binutils/2019-05/msg00331.html > > Current ABI continues to work of course and be the default for some=20 > time, but building for new one would give some opportunity to drop > such support for old procs, at least for glibc. If I recall correctly, during last year's GNU Tools Cauldron, I think it was pretty clear that this was only to be used for intra-DSO ABIs, not cross-DSO optimization. Relocatable object files have an ABI, too, of course, so that's why there's a ABI documentation needed. For cross-DSO optimization, the link editor would look at the DSO being linked in, check if it uses the -mfuture ABI, and apply some shortcuts. But at that point, if the DSO is swapped back to a version built without -mfuture, it no longer works with those newly linked binaries against the -mfuture version. Such a thing is a clear ABI bump, and based what I remember from Cauldron, that is not the plan here. (I don't have any insider knowledge=E2=80=94I just don't want people to read this think: gosh, yet another POWER ABI bump. But the PCREL stuff *is* exciting!)