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 E06503857033 for ; Tue, 4 May 2021 12:04:36 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org E06503857033 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-487-ShOvjC8wMQmVJyqnEkZBIg-1; Tue, 04 May 2021 08:04:31 -0400 X-MC-Unique: ShOvjC8wMQmVJyqnEkZBIg-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 AC4E9DF8A9; Tue, 4 May 2021 12:04:30 +0000 (UTC) Received: from oldenburg.str.redhat.com (ovpn-112-137.ams2.redhat.com [10.36.112.137]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 949DC60C0F; Tue, 4 May 2021 12:04:29 +0000 (UTC) From: Florian Weimer To: "H.J. Lu" Cc: GNU C Library , Andreas Schwab Subject: Re: [RFC] elf: Implement filtering of symbols historically defined in libpthread References: <87h7jqguew.fsf@oldenburg.str.redhat.com> Date: Tue, 04 May 2021 14:04:43 +0200 In-Reply-To: (H. J. Lu's message of "Tue, 4 May 2021 04:47:38 -0700") Message-ID: <87k0oeln6s.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 10.5.11.12 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Spam-Status: No, score=-6.0 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_H4, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_PASS, TXREP, URIBL_BLACK 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: Tue, 04 May 2021 12:04:38 -0000 * H. J. Lu: > Since we want to detect the binaries which were linked against glibc > older than 2.34, we should use the glibc version to check the old > binaries. The patch attempts to detect old main programs by looking for the GLIBC_2.34 symbol version. Since we added __libc_start_main@GLIBC_2.34 (which is called from our version of _start), all standard main programs linked with glibc 2.34 or later will have this symbol version. > Of course, we should make a complete list of functions which are > really implemented in libpthread.so and will be moved to libc.so in > glibc 2.34. I'm not sure if it is necessary to do this for *all* symbols. Formally, a symbol added after glibc 2.0 is not suitable for detecting the potential multi-threaded nature of a process because the application could be built for an earlier glibc version, where the symbol is not available, but pthread_create can still create new threads. The use of pthread_mutexattr_gettype@@GLIBC_2.1 as the detection symbol does not follow the rule, of course. With the explicit table approach (as in the patch), we can add additional lookup symbols later, so I think we can start out with the GLIBC_2.0 and GLIBC_2.1 symbols plus thrd_exit (the latter is also used by gnulib for some reason). Thanks, Florian