From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) by sourceware.org (Postfix) with ESMTP id AE3193877036 for ; Mon, 30 Nov 2020 10:29:00 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org AE3193877036 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-167-fh-MT_1EMsyIYTfAX9NmQw-1; Mon, 30 Nov 2020 05:28:58 -0500 X-MC-Unique: fh-MT_1EMsyIYTfAX9NmQw-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 2B74757240; Mon, 30 Nov 2020 10:28:57 +0000 (UTC) Received: from oldenburg2.str.redhat.com (ovpn-112-44.ams2.redhat.com [10.36.112.44]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 515CB5C1D1; Mon, 30 Nov 2020 10:28:56 +0000 (UTC) From: Florian Weimer To: Topi Miettinen Cc: Topi Miettinen via Libc-alpha , Szabolcs Nagy Subject: Re: [RFC PATCH 0/3] Improved ALSR References: <20201004130938.64575-1-toiwoton@gmail.com> <20201123164112.GH20578@arm.com> <015eb923-b4dc-57dc-b9bf-cdeb38fa2c15@gmail.com> <87tutf4uib.fsf@oldenburg2.str.redhat.com> <87pn432e0q.fsf@oldenburg2.str.redhat.com> Date: Mon, 30 Nov 2020 11:28:54 +0100 In-Reply-To: (Topi Miettinen's message of "Tue, 24 Nov 2020 13:59:20 +0200") Message-ID: <877dq3f89l.fsf@oldenburg2.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (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=-6.8 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: 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: Mon, 30 Nov 2020 10:29:02 -0000 * Topi Miettinen: > FYI, the effect of full ASLR of mmap() by kernel also seems small: > > # echo 3 >/proc/sys/kernel/randomize_va_space > # time ./malloc-vs-sbrk > > real 0m19.489s > user 0m1.263s > sys 0m18.211s > # time ./malloc-vs-sbrk 1 > > real 0m19.532s > user 0m1.148s > sys 0m18.366s The value 3 doesn't do anything in a mainline kernel. I think you will see rather catastrophic effects if you have a workload that triggers TLB misses. I expect that the cost of walking page tables increases dramatically with full ASLR. Thanks, Florian -- Red Hat GmbH, https://de.redhat.com/ , Registered seat: Grasbrunn, Commercial register: Amtsgericht Muenchen, HRB 153243, Managing Directors: Charles Cachera, Brian Klemm, Laurie Krebs, Michael O'Neill