From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-1.mimecast.com (us-smtp-delivery-1.mimecast.com [205.139.110.120]) by sourceware.org (Postfix) with ESMTP id 79C64385BF83 for ; Tue, 7 Apr 2020 09:11:20 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 79C64385BF83 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-362-OGHuHQ6jO2K32Omas-ENHw-1; Tue, 07 Apr 2020 05:11:16 -0400 X-MC-Unique: OGHuHQ6jO2K32Omas-ENHw-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 76E178017F3; Tue, 7 Apr 2020 09:11:15 +0000 (UTC) Received: from oldenburg2.str.redhat.com (ovpn-114-61.ams2.redhat.com [10.36.114.61]) by smtp.corp.redhat.com (Postfix) with ESMTPS id AFB851001DF2; Tue, 7 Apr 2020 09:11:14 +0000 (UTC) From: Florian Weimer To: William Tambe via Libc-help Subject: Re: Can TLS be implemented switching from MAP_SHARED to MAP_PRIVATE a page reserved for TLS variables ?? References: Date: Tue, 07 Apr 2020 11:11:12 +0200 In-Reply-To: (William Tambe via Libc-help's message of "Mon, 6 Apr 2020 19:57:34 -0400") Message-ID: <87pncj8xu7.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 2.84 on 10.5.11.22 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Content-Transfer-Encoding: quoted-printable X-Spam-Status: No, score=-12.6 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_DNSWL_NONE, 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-help@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-help mailing list List-Unsubscribe: , List-Archive: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 07 Apr 2020 09:11:22 -0000 * William Tambe via Libc-help: > Can TLS be implemented switching from MAP_SHARED to MAP_PRIVATE a page > reserved for TLS variables ? Backing storage for some TLS variables will still be allocated using malloc, so this has only limited effect in any case. > Switching such a page from MAP_SHARED to MAP_PRIVATE would effectively > make it local to that thread. NPTL depends on the TCB be accessible across different threads, so this is not possible. C makes cross-thread access implementation-defined, but I expect that quite a few programs expect it to work, so you may have to support is an extension. Thanks, Florian