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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 0F1F5C43441 for ; Mon, 26 Nov 2018 08:28:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D44A620855 for ; Mon, 26 Nov 2018 08:28:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D44A620855 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726547AbeKZTWL (ORCPT ); Mon, 26 Nov 2018 14:22:11 -0500 Received: from mx1.redhat.com ([209.132.183.28]:42808 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726199AbeKZTWK (ORCPT ); Mon, 26 Nov 2018 14:22:10 -0500 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 211A32D80B; Mon, 26 Nov 2018 08:28:48 +0000 (UTC) Received: from oldenburg.str.redhat.com (ovpn-117-10.ams2.redhat.com [10.36.117.10]) by smtp.corp.redhat.com (Postfix) with ESMTPS id AEB931054FAE; Mon, 26 Nov 2018 08:28:42 +0000 (UTC) From: Florian Weimer To: Mathieu Desnoyers Cc: Rich Felker , carlos , Joseph Myers , Szabolcs Nagy , libc-alpha , Thomas Gleixner , Ben Maurer , Peter Zijlstra , "Paul E. McKenney" , Boqun Feng , Will Deacon , Dave Watson , Paul Turner , linux-kernel , linux-api Subject: Re: [RFC PATCH v4 1/5] glibc: Perform rseq(2) registration at nptl init and thread creation References: <20181121183936.8176-1-mathieu.desnoyers@efficios.com> <20181122171010.GH23599@brightrain.aerifal.cx> <871s7cvt1l.fsf@oldenburg.str.redhat.com> <20181123142843.GJ23599@brightrain.aerifal.cx> <1150466925.11664.1542992720871.JavaMail.zimbra@efficios.com> <20181123173019.GK23599@brightrain.aerifal.cx> <865273158.11687.1542995541389.JavaMail.zimbra@efficios.com> <20181123183558.GM23599@brightrain.aerifal.cx> <1758017676.12041.1543007347347.JavaMail.zimbra@efficios.com> Date: Mon, 26 Nov 2018 09:28:34 +0100 In-Reply-To: <1758017676.12041.1543007347347.JavaMail.zimbra@efficios.com> (Mathieu Desnoyers's message of "Fri, 23 Nov 2018 16:09:07 -0500 (EST)") Message-ID: <87bm6cqm31.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Mon, 26 Nov 2018 08:28:48 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Mathieu Desnoyers: > Using a "weak" symbol in early adopter libraries is important, so they > can be loaded together into the same process without causing loader > errors due to many definitions of the same strong symbol. This is not how ELF dynamic linking works. If the symbol name is the same, one definition interposes the others. You need to ensure that the symbol has the same size everywhere, though. There are some tricky interactions with symbol versions, too. (The interposing libraries must not use symbol versioning.) Thanks, Florian