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 AA1CC3875499 for ; Wed, 15 Jul 2020 14:56:37 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org AA1CC3875499 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-263-yq7lO66YOr-Oujfu1p46Jw-1; Wed, 15 Jul 2020 10:56:32 -0400 X-MC-Unique: yq7lO66YOr-Oujfu1p46Jw-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 9EF408B427B; Wed, 15 Jul 2020 14:56:04 +0000 (UTC) Received: from oldenburg2.str.redhat.com (ovpn-112-228.ams2.redhat.com [10.36.112.228]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 43E3B19C4F; Wed, 15 Jul 2020 14:56:02 +0000 (UTC) From: Florian Weimer To: Mark Wielaard Cc: libc-alpha@sourceware.org, gcc@gcc.gnu.org, llvm-dev@lists.llvm.org, x86-64-abi@googlegroups.com, "Mallappa\, Premachandra" , "H.J. Lu" , Michael Matz , Tom Stellard , Jeff Law Subject: Re: New x86-64 micro-architecture levels References: <87365zz3a6.fsf@oldenburg2.str.redhat.com> Date: Wed, 15 Jul 2020 16:56:00 +0200 In-Reply-To: (Mark Wielaard's message of "Wed, 15 Jul 2020 16:38:52 +0200") Message-ID: <87o8ogzv27.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 10.5.11.23 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Spam-Status: No, score=-7.3 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_H2, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=unavailable 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: Wed, 15 Jul 2020 14:56:38 -0000 * Mark Wielaard: > One thing that wasn't clear to me from this proposal is how the glibc > dynamic loader checks for the CPU feature flags. This is important for > valgrind since it can communicate those through different means. cpuid > interception, auxv AT_HWCAP/AT_HWCAP2 interception (but not AT_PLATFORM > at the moment) and of course we can generate SIGILL for unsupported > instructions. We currently don't intercept /proc/cpuinfo (but could). glibc uses CPUID in combination with XGETBV. There is also a masking feature which I have not reviewed, but given that it only takes features away, I don't think it matters to valgrind. Thanks, Florian