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 9318C383F84A for ; Fri, 12 Mar 2021 13:35:34 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 9318C383F84A 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-601-B6F6LC5JMZC2XUd2r87TLQ-1; Fri, 12 Mar 2021 08:35:32 -0500 X-MC-Unique: B6F6LC5JMZC2XUd2r87TLQ-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 7F1F6107ACCA; Fri, 12 Mar 2021 13:35:31 +0000 (UTC) Received: from oldenburg.str.redhat.com (ovpn-112-77.ams2.redhat.com [10.36.112.77]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C94CA60877; Fri, 12 Mar 2021 13:35:30 +0000 (UTC) From: Florian Weimer To: Adhemerval Zanella Cc: Adhemerval Zanella via Libc-alpha Subject: Re: [PATCH v4 1/5] support: Add support_stack_alloc References: <20210310152633.3916978-1-adhemerval.zanella@linaro.org> <875z1zrnuq.fsf@oldenburg.str.redhat.com> <36d689c0-33d3-6606-115c-ece42826de10@linaro.org> Date: Fri, 12 Mar 2021 14:35:43 +0100 In-Reply-To: <36d689c0-33d3-6606-115c-ece42826de10@linaro.org> (Adhemerval Zanella's message of "Fri, 12 Mar 2021 10:24:26 -0300") Message-ID: <87v99w4hqo.fsf@oldenburg.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 10.5.11.13 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Spam-Status: No, score=-6.5 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_DNSWL_LOW, 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: Fri, 12 Mar 2021 13:35:35 -0000 * Adhemerval Zanella: > On 10/03/2021 13:10, Florian Weimer wrote: >> * Adhemerval Zanella via Libc-alpha: >> >>> + /* Use MAP_NORESERVE so that RAM will not be wasted on the guard >>> + bands; touch all the pages of the actual stack before returning, >>> + so we know they are allocated. */ >>> + void *alloc_base = xmmap (0, >>> + alloc_size, >>> + PROT_READ|PROT_WRITE, >>> + MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE|MAP_STACK, >>> + -1); >>> + xmprotect (alloc_base, guardsize, PROT_NONE); >>> + xmprotect (alloc_base + guardsize + stacksize, guardsize, PROT_NONE); >> >> The usual pattern is to map with PROT_NONE and then use >> PROT_READ|PROT_WRITE with mprotect. >> >> Rest looks okay, thanks. >> >> Florian >> > > Ok, I will fix it and push upstream. Just to be clear, it avoids the need for MAP_NORESERVE. Thanks, Florian