From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-out.m-online.net (mail-out.m-online.net [212.18.0.9]) by sourceware.org (Postfix) with ESMTPS id 27A1E3858D28 for ; Mon, 25 Apr 2022 15:14:15 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 27A1E3858D28 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=linux-m68k.org Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=nefkom.net Received: from frontend01.mail.m-online.net (unknown [192.168.8.182]) by mail-out.m-online.net (Postfix) with ESMTP id 4Kn7pF58MPz1qy4Y; Mon, 25 Apr 2022 17:14:13 +0200 (CEST) Received: from localhost (dynscan1.mnet-online.de [192.168.6.70]) by mail.m-online.net (Postfix) with ESMTP id 4Kn7pF4tlnz1qqkC; Mon, 25 Apr 2022 17:14:13 +0200 (CEST) X-Virus-Scanned: amavisd-new at mnet-online.de Received: from mail.mnet-online.de ([192.168.8.182]) by localhost (dynscan1.mail.m-online.net [192.168.6.70]) (amavisd-new, port 10024) with ESMTP id GQoed3IES_Oc; Mon, 25 Apr 2022 17:14:12 +0200 (CEST) X-Auth-Info: VIqrjyf1T+csaHdHfqY4KbrCiHq25yDkT+EuUDJg4Ch+pyR8KD54DVjs1EZLNNIV Received: from igel.home (ppp-46-244-179-29.dynamic.mnet-online.de [46.244.179.29]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.mnet-online.de (Postfix) with ESMTPSA; Mon, 25 Apr 2022 17:14:12 +0200 (CEST) Received: by igel.home (Postfix, from userid 1000) id 65E1A2C39D2; Mon, 25 Apr 2022 17:14:12 +0200 (CEST) From: Andreas Schwab To: Fangrui Song Cc: libc-alpha@sourceware.org, Adhemerval Zanella Subject: Re: [PATCH] elf: Move post-relocation code of _dl_start into _dl_start_final References: <20220424014529.347497-1-maskray@google.com> X-Yow: Tex SEX! The HOME of WHEELS! The dripping of COFFEE!! Take me to Minnesota but don't EMBARRASS me!! Date: Mon, 25 Apr 2022 17:14:12 +0200 In-Reply-To: <20220424014529.347497-1-maskray@google.com> (Fangrui Song's message of "Sat, 23 Apr 2022 18:45:29 -0700") Message-ID: <87a6c95h6j.fsf@igel.home> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Spam-Status: No, score=-2.8 required=5.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS, KAM_DMARC_STATUS, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL, 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: Mon, 25 Apr 2022 15:14:19 -0000 On Apr 23 2022, Fangrui Song wrote: > On non-PI_STATIC_AND_HIDDEN architectures, getting the address of > _rtld_local_ro (for GLRO (dl_final_object)) goes through a GOT entry. > The GOT load may be reordered before self relocation, leading to an > unrelocated/incorrect _rtld_local_ro address. > > 84e02af1ebc9988126eebe60bf19226cea835623 tickled GCC powerpc32 to > reorder the GOT load before relative relocations, leading to ld.so > crash. This is similar to the m68k issue fixed by > a8e9b5b8079d18116ca69c9797e77804ecf2ee7e. > > Move code after self relocation into _dl_start_final to avoid the > reordering. This fixes powerpc32 and may help other architectures when > ELF_DYNAMIC_RELOCATE is simplified in the future. Ok. -- Andreas Schwab, schwab@linux-m68k.org GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510 2552 DF73 E780 A9DA AEC1 "And now for something completely different."