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 [170.10.129.124]) by sourceware.org (Postfix) with ESMTPS id 42EF73858401 for ; Tue, 21 Dec 2021 14:28:08 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 42EF73858401 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-113-ub_cSuvTNyOFrTccvrCk6g-1; Tue, 21 Dec 2021 09:28:04 -0500 X-MC-Unique: ub_cSuvTNyOFrTccvrCk6g-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 59DEE86A060; Tue, 21 Dec 2021 14:28:02 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.39.192.104]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 213C35BD1D; Tue, 21 Dec 2021 14:27:59 +0000 (UTC) From: Florian Weimer To: Adhemerval Zanella Cc: libc-alpha@sourceware.org, John Mellor-Crummey , Ben Woodard Subject: Re: [PATCH v6 20/20] elf: Add SVE support for aarch64 rtld-audit References: <20211115183734.531155-1-adhemerval.zanella@linaro.org> <20211115183734.531155-21-adhemerval.zanella@linaro.org> Date: Tue, 21 Dec 2021 15:27:58 +0100 In-Reply-To: <20211115183734.531155-21-adhemerval.zanella@linaro.org> (Adhemerval Zanella's message of "Mon, 15 Nov 2021 15:37:34 -0300") Message-ID: <87r1a69gnl.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Spam-Status: No, score=-6.3 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_NONE, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) 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, 21 Dec 2021 14:28:09 -0000 * Adhemerval Zanella: > To implement lazy binding is enabled when profiling or auditing used, > even when STO_AARCH64_VARIANT_PCS is set. Also, to not incur in > performance penalties on architecture without SVE, the PLT entrypoint > is set to a newer one, _dl_runtime_profile_sve, which is used iff > 'hwcap' has HWCAP_SVE bit set. > > This should be a fair assumption since SVE has a defined set of > registers for argument passing and return values. A new ABI with either > different argument passing or different registers would require a > different PLT entry, but I assume this would require another symbol flag > anyway (or at least a different ELF mark to indicate so). Someone familiar with SVE needs to review this. The restriction to the currently-specified vector calling convention seems to be a bit arbitrary to me. To me, STO_AARCH64_VARIANT_PCS strongly suggests that the toolchain makes every conceivable attempt to support arbitrary calling conventions, but that's probably just me. Thanks, Florian