From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS17314 8.43.84.0/22 X-Spam-Status: No, score=-3.7 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED,RDNS_DYNAMIC,SPF_HELO_PASS,SPF_PASS shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from sourceware.org (ip-8-43-85-97.sourceware.org [8.43.85.97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by dcvr.yhbt.net (Postfix) with ESMTPS id 242471F5AE for ; Tue, 4 May 2021 12:43:18 +0000 (UTC) Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 79552398B88D; Tue, 4 May 2021 12:43:09 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 79552398B88D DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1620132189; bh=WzvGJzm1CosgaVuXYarjCO9rpsgwbjeCLXUouLT7PFE=; h=To:Subject:References:Date:In-Reply-To:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:Cc: From; b=ua/x5DtG6Scg4b32LcVrsohJfU3VcGJW4ujIfbLbSLZEDsZH+8I9kZWYg4AlgGtN5 YJ9AzV6pLLT3VNiCTn6nYqjEwBK8IE9ALpRdWB4IyIxSG/X2dxj8MHZ8w2hmvQWOiG WZxdn3dgGC/Hvmred5h4lNUa8fhZGFEeD9r1lk2g= Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by sourceware.org (Postfix) with ESMTP id D3201398B88D for ; Tue, 4 May 2021 12:43:06 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org D3201398B88D 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-486-5vu5l-cSP7yT_4i3tFLHlA-1; Tue, 04 May 2021 08:43:05 -0400 X-MC-Unique: 5vu5l-cSP7yT_4i3tFLHlA-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 38F21107ACE3; Tue, 4 May 2021 12:43:04 +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 2F0F85D72F; Tue, 4 May 2021 12:43:03 +0000 (UTC) To: "H.J. Lu" Subject: Re: [RFC] elf: Implement filtering of symbols historically defined in libpthread References: <87h7jqguew.fsf@oldenburg.str.redhat.com> <87k0oeln6s.fsf@oldenburg.str.redhat.com> <87wnsek7ku.fsf@oldenburg.str.redhat.com> <87sg32k79x.fsf@oldenburg.str.redhat.com> Date: Tue, 04 May 2021 14:43:17 +0200 In-Reply-To: (H. J. Lu's message of "Tue, 4 May 2021 05:36:57 -0700") Message-ID: <87lf8uk6u2.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 10.5.11.15 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain 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: , From: Florian Weimer via Libc-alpha Reply-To: Florian Weimer Cc: Andreas Schwab , GNU C Library Errors-To: libc-alpha-bounces@sourceware.org Sender: "Libc-alpha" * H. J. Lu: > On Tue, May 4, 2021 at 5:33 AM Florian Weimer wrote: >> >> * H. J. Lu: >> >> > On Tue, May 4, 2021 at 5:27 AM Florian Weimer wrote: >> >> >> >> * H. J. Lu: >> >> >> >> >> 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. >> >> >> >> > Can we invent a symbol or version to detect the older binaries? >> >> > If not, can GNU property, ABI note, .... help here? >> >> >> >> I think we have all we need due to __libc_start_main@@GLIBC_2.34. It >> >> was an unrelated change, but it helps here as well. >> > >> > So your patch isn't required? Can you add some tests to verify it? >> >> No, the patch uses the absence of GLIBC_2.34 for detecting old binaries. >> >> We cannot use symbol versions in other ways because one key >> characteristic of weak references and underlinking is the lack of >> version information on the symbol itself. > > Can we add support for binary testcases like this, even if it can only > run on a single target? It shouldn't be too hard. Yes, we can verify the binding status of weak symbols with a smaller assembler program that was linked against a stub libc.so.6 library that only contains the soname and no symbols. As the code is architecture-agnostic, testing on e.g. x86-64 should be sufficient. We cannot easily verify the behavior of real-world binaries because re-linking them with current binutils probably changes behavior. Thanks, Florian