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 [170.10.133.124]) by sourceware.org (Postfix) with ESMTPS id D1A083857803 for ; Thu, 28 Oct 2021 06:55:46 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org D1A083857803 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-154-1s3z4o1cMICUZKH4tnqOIw-1; Thu, 28 Oct 2021 02:55:42 -0400 X-MC-Unique: 1s3z4o1cMICUZKH4tnqOIw-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 4A526100CCC0; Thu, 28 Oct 2021 06:55:41 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.39.194.250]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 42BC35C3E0; Thu, 28 Oct 2021 06:55:40 +0000 (UTC) From: Florian Weimer To: "H.J. Lu" Cc: "H.J. Lu via Libc-alpha" , Binutils Subject: Re: RFC: Add GNU_PROPERTY_1_GLIBC_2_NEEDED References: <87zgqvq03g.fsf@oldenburg.str.redhat.com> Date: Thu, 28 Oct 2021 08:55:38 +0200 In-Reply-To: (H. J. Lu's message of "Tue, 26 Oct 2021 08:51:29 -0700") Message-ID: <87v91hljth.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 10.5.11.16 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_H2, 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: Thu, 28 Oct 2021 06:55:48 -0000 * H. J. Lu: >> This proposal may conflict in spirit with the glibc proposal to support >> preloadable symbol version (so you can add _dl_find_eh_frame@GLIBC_2.35 >> to a glibc 2.28 installation, for example). So far, symbol versions > > Why will adding a glibc version dependency change the preload > behavior? Previously, we thought we could relax the version coverage check to enable adding completely new symbol versions by preloading an implementation. With BIND_NOW, this is completely safe because missing symbols are still detected. But this turns unreliable once glibc versions are tied to ELF implementation features. Preloading an implementation of _dl_find_eh_frame@GLIBC_2.35 (for example) will not add dynamic linker features first implemented in glibc 2.35. >> The problem that linkers and loaders ignore unknown types should be >> tackled in a different way, e.g. by flagging critical types in some way. >> See: >> >> Critical program headers and dynamic tags >> >> > > This won't help the existing ld.so binaries which this proposal > is addressing. We need to increase the ABI version once, to signal the requirement for critical tags checking. Thanks, Florian