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_PASS,URIBL_BLOCKED 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 B4DCFECE566 for ; Thu, 20 Sep 2018 20:20:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 14F9820867 for ; Thu, 20 Sep 2018 20:20:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 14F9820867 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=codesourcery.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 S2388149AbeIUCFy (ORCPT ); Thu, 20 Sep 2018 22:05:54 -0400 Received: from relay1.mentorg.com ([192.94.38.131]:41276 "EHLO relay1.mentorg.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727252AbeIUCFx (ORCPT ); Thu, 20 Sep 2018 22:05:53 -0400 Received: from nat-ies.mentorg.com ([192.94.31.2] helo=svr-ies-mbx-01.mgc.mentorg.com) by relay1.mentorg.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-SHA384:256) id 1g35RA-0005Ly-MQ from joseph_myers@mentor.com ; Thu, 20 Sep 2018 13:20:32 -0700 Received: from digraph.polyomino.org.uk (137.202.0.90) by svr-ies-mbx-01.mgc.mentorg.com (139.181.222.1) with Microsoft SMTP Server (TLS) id 15.0.1320.4; Thu, 20 Sep 2018 21:20:29 +0100 Received: from jsm28 (helo=localhost) by digraph.polyomino.org.uk with local-esmtp (Exim 4.90_1) (envelope-from ) id 1g35R6-0005Zu-MR; Thu, 20 Sep 2018 20:20:28 +0000 Date: Thu, 20 Sep 2018 20:20:28 +0000 From: Joseph Myers X-X-Sender: jsm28@digraph.polyomino.org.uk To: Mathieu Desnoyers CC: carlos , Florian Weimer , Thomas Gleixner , Ben Maurer , Peter Zijlstra , "Paul E. McKenney" , Boqun Feng , Will Deacon , Dave Watson , Paul Turner , libc-alpha , linux-kernel , linux-api Subject: Re: [RFC PATCH] glibc: Perform rseq(2) registration at nptl init and thread creation In-Reply-To: <1619649568.9014.1537474457166.JavaMail.zimbra@efficios.com> Message-ID: References: <20180919144438.1066-1-mathieu.desnoyers@efficios.com> <67473000.8399.1537375994645.JavaMail.zimbra@efficios.com> <1619649568.9014.1537474457166.JavaMail.zimbra@efficios.com> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" X-Originating-IP: [137.202.0.90] X-ClientProxiedBy: svr-ies-mbx-01.mgc.mentorg.com (139.181.222.1) To svr-ies-mbx-01.mgc.mentorg.com (139.181.222.1) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 20 Sep 2018, Mathieu Desnoyers wrote: > Are you saying glibc has an explicit check for the kernel version visible > from /proc before using specific features ? If so, how can this work with > the variety of feature backports we find in the distribution kernels out > there ? See sysdeps/unix/sysv/linux/dl-sysdep.c and sysdeps/unix/sysv/linux/dl-osinfo.h. As I said, Carlos has proposed removing that check. > For too-old headers at compile time, one possibility is that we don't event > expose the __rseq_abi TLS symbol. OTOH, if we need to keep exposing it anyway > for ABI consistency purposes, then we'd leave its cpu_id field at the initial > value (-1). But that would require that we copy linux/rseq.h into the glibc > source tree. The ABI needs to be independent of the kernel headers used. I don't think you need to copy linux/rseq.h; all you should need is to e.g. define an array of suitable size and alignment with the relevant member initialized and a suitable explanatory comment. -- Joseph S. Myers joseph@codesourcery.com