From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pj1-x1031.google.com (mail-pj1-x1031.google.com [IPv6:2607:f8b0:4864:20::1031]) by sourceware.org (Postfix) with ESMTPS id 083BA3858404; Thu, 28 Oct 2021 13:38:25 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 083BA3858404 Received: by mail-pj1-x1031.google.com with SMTP id k2-20020a17090ac50200b001a218b956aaso4744873pjt.2; Thu, 28 Oct 2021 06:38:24 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=mYGK4Py6G2g4NUrN/t1jzuiFIK4JbFcPN2iIp1DG0lY=; b=JRPrsnHYviBsUy4b+jtQyuEiXuwJxeFIim6LxMZ0jXhLUoIcOLvPhmEv+peqs/z0E/ 1c7Foc4glRnABJEMigaLg5NGJ+YE3b8EMvu89Swdaj9TAeWS2gjLHqgOtf+xptmqb69e bPbndgqIoyIg14ObLgxrdGO7kO3D9dDz4sYcJfayGHpH/imhF8fUCGfAK6Sm/4ZmoWiR gHVV1RO1XhpsFiK9306xomIlmJeJ+ImgSfcasI0UcwuRZ2y43gq/EVzJ8zBYJS59+5Lb KhtJEc99yMndLsA6KypklosKT4WiGicvqXyIxyk7n1w0fczxYKxuEknLe/bVOKHM9r4R Se1g== X-Gm-Message-State: AOAM531vSu/qPli5hs5+8HRtls5yrIH0/fMyFmUKTMs2rCy2694LlwAJ smA4+PASHyESyEFFoVUUdcTjCwngYtOzZEq6JCyxHznYBHg= X-Google-Smtp-Source: ABdhPJwoWWeEEbNhPNfgA8/Cnrwuoh7VmjgriOGPJkYoz8vrRR8kokXR6U9w5pT9Y9/hPpK3UUYWdz7jK7Yg2xl0lV0= X-Received: by 2002:a17:90b:1b4d:: with SMTP id nv13mr13180657pjb.28.1635428304134; Thu, 28 Oct 2021 06:38:24 -0700 (PDT) MIME-Version: 1.0 References: <87zgqvq03g.fsf@oldenburg.str.redhat.com> <87v91hljth.fsf@oldenburg.str.redhat.com> In-Reply-To: <87v91hljth.fsf@oldenburg.str.redhat.com> From: "H.J. Lu" Date: Thu, 28 Oct 2021 06:37:48 -0700 Message-ID: Subject: Re: RFC: Add GNU_PROPERTY_1_GLIBC_2_NEEDED To: Florian Weimer Cc: "H.J. Lu via Libc-alpha" , Binutils Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-3023.8 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, FREEMAIL_FROM, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, 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 13:38:27 -0000 On Wed, Oct 27, 2021 at 11:55 PM Florian Weimer wrote: > > * 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. I am not sure if I am following your concerns. We have an ELF feature, like DT_RELR, which is tied to a glibc version. The binary with DT_RELR will crash with the older glibcs. And you DON'T want such a binary with a dependency on the required glibc version. Can you tell me why? > >> 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. > Which ABI version? .note.ABI-tag or EI_ABIVERSION? A binary linked against glibc 2.40 without DT_RELR can run with glibc 2.34. But a binary linked against glibc 2.30 with DT_RELR won't run with glibc 2.34 at all. Increasing the ABI version doesn't solve the DT_RELR issue. -- H.J.