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 A02853857C46 for ; Fri, 18 Sep 2020 08:06:13 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org A02853857C46 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-39-96tOv3PcOZ-MdNddux9qfw-1; Fri, 18 Sep 2020 04:06:09 -0400 X-MC-Unique: 96tOv3PcOZ-MdNddux9qfw-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 40B5C912C0B; Fri, 18 Sep 2020 08:06:08 +0000 (UTC) Received: from oldenburg2.str.redhat.com (ovpn-113-177.ams2.redhat.com [10.36.113.177]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 84FA460C13; Fri, 18 Sep 2020 08:06:07 +0000 (UTC) From: Florian Weimer To: "H.J. Lu via Libc-alpha" Subject: Re: [PATCH 1/3] x86: Initialize CPU info via IFUNC relocation [BZ 26203] References: <20200912134441.2407884-1-hjl.tools@gmail.com> <20200912134441.2407884-2-hjl.tools@gmail.com> Date: Fri, 18 Sep 2020 10:06:05 +0200 In-Reply-To: <20200912134441.2407884-2-hjl.tools@gmail.com> (H. J. Lu via Libc-alpha's message of "Sat, 12 Sep 2020 06:44:39 -0700") Message-ID: <874knva4r6.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 10.5.11.12 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Spam-Status: No, score=-8.0 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_H5, 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, 18 Sep 2020 08:06:15 -0000 * H. J. Lu via Libc-alpha: > X86 CPU features in ld.so are initialized by init_cpu_features, which is > invoked by DL_PLATFORM_INIT from _dl_sysdep_start. But when ld.so is > loaded by static executable, DL_PLATFORM_INIT is never called. I don't think that's accurate. It's called from elf/dl-support.c in the static case. But I agree that it's too late in this case. > Also x86 cache info in libc.o and libc.a is initialized by a > constructor which may be called too late. Instead, we should > initialize x86 CPU features and cache info by initializing dummy > function pointers via IFUNC relocation. Why would ld put this special IRELATIVE relocation first? I'm sorry, but this looks very brittle. I think there's an existing mechanism for this corner case, ARCH_SETUP_IREL. Could you use that? 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