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: AS3215 2.6.0.0/16 X-Spam-Status: No, score=-4.2 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED,SPF_HELO_PASS,SPF_PASS shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from sourceware.org (server2.sourceware.org [IPv6:2620:52:3:1:0:246e:9693:128c]) (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 3672D1F8C6 for ; Tue, 27 Jul 2021 18:15:33 +0000 (UTC) Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 29562383A824 for ; Tue, 27 Jul 2021 18:15:32 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 29562383A824 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1627409732; bh=Fdw37alCujHkZDy6HLrCRU53qSg5F7QgWoz8xzIpTeQ=; h=References:In-Reply-To:Date:Subject:To:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:Cc: From; b=gbBclhp5MTvrrkGjgm9OZ+Ygfkx/NEUXIf6RqnalwT/AFUokFJNB0jpj7anPLVP+R oYxjJRnuMpN13vCTOGl1im33vqpuPVIDUIQoCBVBhT7vX42J8EPPqmdEcvsShYCdu7 U7L0BSb12iSfMuFJv4UHc3zrZ0zDP+DfYTvvZRHQ= Received: from mail-pj1-x1030.google.com (mail-pj1-x1030.google.com [IPv6:2607:f8b0:4864:20::1030]) by sourceware.org (Postfix) with ESMTPS id F2FA83857C7E for ; Tue, 27 Jul 2021 18:15:10 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org F2FA83857C7E Received: by mail-pj1-x1030.google.com with SMTP id j18-20020a17090aeb12b029017737e6c349so392203pjz.0 for ; Tue, 27 Jul 2021 11:15:10 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=Fdw37alCujHkZDy6HLrCRU53qSg5F7QgWoz8xzIpTeQ=; b=lenuMinDziVvzmpBCrYKmrW1kp+dz2PmH9+gh4PDCLlDkDzbtyTiwIS4DHnzDspFyj j+rgkluFl465qpxeWIK7hldELzsDsNLaLuw0/J+MWJ6CJMOqKEO9T9faFF40gUp+PA45 ReIsS4jyAkyHkAaug0/XyZcncidcqr3n1jO4hR7/0agmuyPjayM2rAewKZ7dUdqAXcLE 5xU04rHQ6B06AR8+FDGuEjGmZgBS584TtL2/aychgYcxB5ZxaZ8tEf41+Sk0mbRU1pg4 dgim4mK+RvzQchD+yObobUk8Cv0afgeEm+i3EGjFc7tjbISak98CFXpedpIOrYL06Ubi pWOQ== X-Gm-Message-State: AOAM530vcQOKLIKT6nx7B/EaL/6YG+4qh0fcmTT5sTcPg5M5bdeT11t0 Qf3wdk+69qs8R8oJnwUkVU9if7lzPwozKu3CWsQ= X-Google-Smtp-Source: ABdhPJxBZKn5UCl5WsSMTQ/16hDEMBZ4Sm5wJkVIVabi720t4UqQcpe7oAL2PrkLbRVOl9Ff5ZOOzks36wCx8aIp7go= X-Received: by 2002:a17:902:684a:b029:12b:8d3e:68dc with SMTP id f10-20020a170902684ab029012b8d3e68dcmr20046103pln.79.1627409710067; Tue, 27 Jul 2021 11:15:10 -0700 (PDT) MIME-Version: 1.0 References: <20200626193228.1953-4-danielwa@cisco.com> <87ftah5yh8.fsf@oldenburg2.str.redhat.com> <210c992f-b034-3ef7-440c-f67ab1b3acdb@redhat.com> <87366h5xmi.fsf@oldenburg2.str.redhat.com> <7e2fb426-cf03-a8e7-6524-a5f81fcf5b9e@redhat.com> <87ftagyhra.fsf@mid.deneb.enyo.de> <8a15bd93-e4cc-a3bc-f902-5b3e701ec4e3@redhat.com> <87y2o61chx.fsf@oldenburg2.str.redhat.com> <20210727173958.GB1633923@zorba> In-Reply-To: <20210727173958.GB1633923@zorba> Date: Tue, 27 Jul 2021 11:14:33 -0700 Message-ID: Subject: Re: [RFC PATCH 3/3] add r_debug multiple namespaces support To: Daniel Walker Content-Type: text/plain; charset="UTF-8" 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: "H.J. Lu via Libc-alpha" Reply-To: "H.J. Lu" Cc: Florian Weimer , Carlos O'Donell via Libc-alpha , Pedro Alves , Conan C Huang , "Metzger, Markus T" , Florian Weimer , Jeremy Stenglein , xe-linux-external@cisco.com Errors-To: libc-alpha-bounces+e=80x24.org@sourceware.org Sender: "Libc-alpha" On Tue, Jul 27, 2021 at 10:40 AM Daniel Walker wrote: > > On Fri, Jul 23, 2021 at 04:38:33PM -0700, H.J. Lu wrote: > > On Mon, Jun 29, 2020 at 2:49 AM Florian Weimer via Libc-alpha > > wrote: > > > > > > * Carlos O'Donell via Libc-alpha: > > > > > > >>> I'm not sure it would work to version _r_debug, since the debugger > > > >>> is using DT_DEBUG and we only get to put one value in that > > > >>> .dynamic entry. > > > >> > > > >> The symbol version is needed to avoid problems due to copy relocations > > > >> if the symbol is referenced directly from the main program. Without > > > >> that, the object could be truncated. It's not a debugger > > > >> compatibility feature. > > > > > > > > Correct, but this violates *how* you're supposed to use _r_debug. > > > > > > If it is possible to link against it, we need to add the new symbol > > > version, in my opinion. > > > > > > > In the dynamic case it is different. The symbol should be looked up > > > > via DT_DEBUG only which always points to the library-local address > > > > of the data object (and the most recent version). In effect this > > > > bypasses the COPY relocation? > > > > > > How is this supposed to work if the dynamic linker does contain > > > DT_DEBUG? > > > > > > I only observe DT_DEBUG in PIE binaries, but since the dynamic loader is > > > mapped at a random address even for ET_EXEC main programs, there must be > > > some other mechanism to locate it. > > > > > > Thanks, > > > Florian > > > > > > > I opened: > > > > https://gitlab.com/x86-psABIs/Linux-ABI/-/issues/2 > > > > with a proposal to extend struct r_debug for libraries loaded with > > dlmopen, I'd like to resolve it for the next releases of glibc, binutils > > and GDB. > > > I have an updated set of changes which add a new dynamic entry > DT_DEBUG_DLMOPEN, which was recommended by Carlos. We're still testing the > implementation. I'm open to support different implementations. Let's work on it after glibc 2.34 is branched. > I found while working on this project that the clang linker adds 3 proprietary new > dynamic entries. So there is demand to make adding to the table easier. > > Daniel -- H.J.