From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-1.mimecast.com (us-smtp-delivery-1.mimecast.com [207.211.31.120]) by sourceware.org (Postfix) with ESMTP id B3B703938C12 for ; Wed, 24 Jun 2020 08:59:36 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org B3B703938C12 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-405-8xmlgd5PPr2Lx1-T465EXA-1; Wed, 24 Jun 2020 04:59:34 -0400 X-MC-Unique: 8xmlgd5PPr2Lx1-T465EXA-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 B4E11800597; Wed, 24 Jun 2020 08:59:33 +0000 (UTC) Received: from oldenburg2.str.redhat.com (ovpn-113-18.ams2.redhat.com [10.36.113.18]) by smtp.corp.redhat.com (Postfix) with ESMTPS id DFFFF5C290; Wed, 24 Jun 2020 08:59:32 +0000 (UTC) From: Florian Weimer To: Nikos Dragazis Cc: gcc-help@gcc.gnu.org Subject: Re: Force global-dynamic TLS model References: <889e96a3-f7d0-4703-c3d7-66a4d5913d72@arrikto.com> Date: Wed, 24 Jun 2020 10:59:31 +0200 In-Reply-To: <889e96a3-f7d0-4703-c3d7-66a4d5913d72@arrikto.com> (Nikos Dragazis's message of "Tue, 23 Jun 2020 23:37:24 +0300") Message-ID: <87bll8et58.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=-8.0 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_H3, RCVD_IN_MSPIKE_WL, 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: gcc-help@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-help mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 24 Jun 2020 08:59:37 -0000 * Nikos Dragazis: > For example, let's say we have an ELF executable that defines and > accesses a TLS variable. From gcc's man page, I read that, in this case, > gcc will use the initial-exec TLS model by default. My question is if we > can change that and, say, use the global-dynamic model. To this end, I > have tried the `-ftls-model=global-dynamic` option and the `tls_model` > gcc variable attribute. None of these worked. Try -ftls-model=global-dynamic -fpic. This will prevent GCC from performing relaxation. For many targets, the link editor still performs relaxation. To turn this off, you will have to link the executable with -shared, I think, with some hackery to produce an executable that can actually be run. Thanks, Florian