From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-1.mimecast.com (us-smtp-2.mimecast.com [205.139.110.61]) by sourceware.org (Postfix) with ESMTP id D50F73851C12 for ; Tue, 14 Jul 2020 13:55:04 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org D50F73851C12 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-84-5H-mF4pgMyuXolGV8ghBMg-1; Tue, 14 Jul 2020 09:55:02 -0400 X-MC-Unique: 5H-mF4pgMyuXolGV8ghBMg-1 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 mimecast-mx01.redhat.com (Postfix) with ESMTPS id BB8B58014D7; Tue, 14 Jul 2020 13:55:01 +0000 (UTC) Received: from oldenburg2.str.redhat.com (ovpn-112-246.ams2.redhat.com [10.36.112.246]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 773E25C1B2; Tue, 14 Jul 2020 13:55:00 +0000 (UTC) From: Florian Weimer To: Christian Brauner Cc: Mathieu Desnoyers , libc-alpha , Joseph Myers Subject: Re: [RFC PATCH glibc] Linux: Use fixed rseq_len value for rseq registration References: <20200713193434.30440-1-mathieu.desnoyers@efficios.com> <87zh82bhsl.fsf@oldenburg2.str.redhat.com> <2077401180.11408.1594729873506.JavaMail.zimbra@efficios.com> <87zh826x9s.fsf@oldenburg2.str.redhat.com> <20200714133352.ykv6qg6brzqlrc26@wittgenstein> Date: Tue, 14 Jul 2020 15:54:58 +0200 In-Reply-To: <20200714133352.ykv6qg6brzqlrc26@wittgenstein> (Christian Brauner's message of "Tue, 14 Jul 2020 15:33:52 +0200") Message-ID: <87v9iq6w25.fsf@oldenburg2.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Spam-Status: No, score=-7.4 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 14 Jul 2020 13:55:05 -0000 * Christian Brauner: >> It works reliably as long as glibc only ever uses the minimum rseq size. >> And since glibc monopolizes the rseq registration, applications cannot >> register a larger area. So there is no way to make use of any future >> kernel extensions. > > But when you bump ABI in glibc you can switch to a new rseq size, no? We are expected to support interposers with their own definition __rseq_abi, which could be smaller. Thanks, Florian