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 61BCEC43387 for ; Mon, 14 Jan 2019 18:55:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3299C2064C for ; Mon, 14 Jan 2019 18:55:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726856AbfANSzl (ORCPT ); Mon, 14 Jan 2019 13:55:41 -0500 Received: from mx1.redhat.com ([209.132.183.28]:47492 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726745AbfANSzl (ORCPT ); Mon, 14 Jan 2019 13:55:41 -0500 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B1CF8C0CB586; Mon, 14 Jan 2019 18:55:40 +0000 (UTC) Received: from oldenburg2.str.redhat.com (ovpn-116-20.ams2.redhat.com [10.36.116.20]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E5CCB4C48E; Mon, 14 Jan 2019 18:55:09 +0000 (UTC) From: Florian Weimer To: Mathieu Desnoyers Cc: carlos , Joseph Myers , Szabolcs Nagy , libc-alpha , Thomas Gleixner , Ben Maurer , Peter Zijlstra , "Paul E. McKenney" , Boqun Feng , Will Deacon , Dave Watson , Paul Turner , Rich Felker , linux-kernel , linux-api Subject: Re: [RFC PATCH glibc 1/4] glibc: Perform rseq(2) registration at nptl init and thread creation (v4) References: <20181204192141.4684-1-mathieu.desnoyers@efficios.com> <87h8fkz6qx.fsf@oldenburg2.str.redhat.com> <1681283664.1380.1547152315426.JavaMail.zimbra@efficios.com> Date: Mon, 14 Jan 2019 19:55:07 +0100 In-Reply-To: <1681283664.1380.1547152315426.JavaMail.zimbra@efficios.com> (Mathieu Desnoyers's message of "Thu, 10 Jan 2019 15:31:55 -0500 (EST)") Message-ID: <87fttv9iic.fsf@oldenburg2.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Mon, 14 Jan 2019 18:55:41 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Mathieu Desnoyers: > Therefore, both symbols will end up in > sysdeps/unix/sysv/linux/Versions. I'm not sure what you mean by that. The physical location in the directory tree has little effect on which shared object the symbol is placed in; that will need other changes. >> By the way, you could avoid the need for unregistration if you allocated >> the rseq areas persistently, index by TID. They are quite small, so >> with the typical PID range, maybe the wasted memory due to changing TIDs >> would be acceptable? > > Would we be able to access those __rseq_abi as normal TLS IE model > variables ? The overhead of indexing an array matters for a > fast-path. No, that wouldn't be possible in this case. You would need another indirection. Thanks, Florian