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=-4.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 7311AC433E0 for ; Wed, 15 Jul 2020 13:42:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4196D2064B for ; Wed, 15 Jul 2020 13:42:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="JjKDYqty" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731945AbgGONmX (ORCPT ); Wed, 15 Jul 2020 09:42:23 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:35336 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1731932AbgGONmW (ORCPT ); Wed, 15 Jul 2020 09:42:22 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1594820541; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=GmdifN6+jrtO/pnaOcy0zvVaVx7ysyob4B6XZ2mQELI=; b=JjKDYqtyq6WElWpmYAOlZjmz2xa2I4QwUDXwnyVx8bf4tX+0fsYHkefserGPZnk+ilSL84 ntRd+7Yp8UI++50yuj//VfW/mMGEmr6BkwUkZre+b2fk/JkD9H0eS/ZfBLLygdiKjddshS JmPVYVzrE2v/yc9J/69cb7Y0bnIC4qs= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-170-wLQPDBG3NQ221ncxurkX1g-1; Wed, 15 Jul 2020 09:42:20 -0400 X-MC-Unique: wLQPDBG3NQ221ncxurkX1g-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 4EFBE100AA22; Wed, 15 Jul 2020 13:42:18 +0000 (UTC) Received: from oldenburg2.str.redhat.com (ovpn-112-228.ams2.redhat.com [10.36.112.228]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 42F27710D6; Wed, 15 Jul 2020 13:42:13 +0000 (UTC) From: Florian Weimer To: Mathieu Desnoyers Cc: carlos , Peter Zijlstra , linux-kernel , Thomas Gleixner , paulmck , Boqun Feng , "H. Peter Anvin" , Paul Turner , linux-api , Christian Brauner Subject: Re: [RFC PATCH 2/4] rseq: Allow extending struct rseq References: <20200714030348.6214-1-mathieu.desnoyers@efficios.com> <87mu42bepq.fsf@oldenburg2.str.redhat.com> <131549905.11442.1594731035989.JavaMail.zimbra@efficios.com> <87a7028d5u.fsf@oldenburg2.str.redhat.com> <2452161.11491.1594732791558.JavaMail.zimbra@efficios.com> <71f08b3a-56f5-0e0f-53b0-cc680f7e8181@redhat.com> <2053637148.14136.1594818777608.JavaMail.zimbra@efficios.com> <87y2nk29rp.fsf@oldenburg2.str.redhat.com> <882700738.14181.1594819884049.JavaMail.zimbra@efficios.com> Date: Wed, 15 Jul 2020 15:42:11 +0200 In-Reply-To: <882700738.14181.1594819884049.JavaMail.zimbra@efficios.com> (Mathieu Desnoyers's message of "Wed, 15 Jul 2020 09:31:24 -0400 (EDT)") Message-ID: <87mu4028uk.fsf@oldenburg2.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Sender: linux-api-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org * Mathieu Desnoyers: > So indeed it could be done today without upgrading the toolchains by > writing custom assembler for each architecture to get the thread's > struct rseq. AFAIU the ABI to access the thread pointer is fixed for > each architecture, right ? Yes, determining the thread pointer and access initial-exec TLS variables is baked into the ABI. > How would this allow early-rseq-adopter libraries to interact with > glibc ? Under all extension proposals I've seen so far, early adopters are essentially incompatible with glibc rseq registration. I don't think you can have it both ways. Thanks, Florian