From patchwork Fri Jun 26 19:32:27 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Daniel Walker X-Patchwork-Id: 39807 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 07818388C030; Fri, 26 Jun 2020 19:32:40 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 07818388C030 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1593199960; bh=SphwH9CSYF5d5+SHoc56ayZE+Kwk/+1sRe6H9R5RX04=; h=To:Subject:Date:List-Id:List-Unsubscribe:List-Archive:List-Post: List-Help:List-Subscribe:From:Reply-To:Cc:From; b=ZrsZQkRFzxZJB9M5vMk8vP7YiinSDVDkvL14/M90as8PmnpetfVrB4ysA5wimaWvW AkjNxkpcZ3oVyrUB9WidDB0dbEPHuKOdTSmwnCaJDgHAdMs3TS7+S/OUzQ4ODfbTSx PHxm0IFa4Eb/4kROuqp+FY9cX4yWS8iCxBcVI7jE= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from rcdn-iport-2.cisco.com (rcdn-iport-2.cisco.com [173.37.86.73]) by sourceware.org (Postfix) with ESMTPS id DE6973870854 for ; Fri, 26 Jun 2020 19:32:35 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org DE6973870854 X-IronPort-AV: E=Sophos;i="5.75,282,1589241600"; d="scan'208";a="793215497" Received: from alln-core-8.cisco.com ([173.36.13.141]) by rcdn-iport-2.cisco.com with ESMTP/TLS/DHE-RSA-SEED-SHA; 26 Jun 2020 19:32:35 +0000 Received: from zorba.cisco.com ([10.24.15.228]) by alln-core-8.cisco.com (8.15.2/8.15.2) with ESMTP id 05QJWSW5030756; Fri, 26 Jun 2020 19:32:30 GMT To: libc-alpha@sourceware.org Subject: [RFC PATCH 2/3] glibc: dlopen RTLD_NOLOAD optimization Date: Fri, 26 Jun 2020 12:32:27 -0700 Message-Id: <20200626193228.1953-3-danielwa@cisco.com> X-Mailer: git-send-email 2.17.1 X-Auto-Response-Suppress: DR, OOF, AutoReply X-Outbound-SMTP-Client: 10.24.15.228, [10.24.15.228] X-Outbound-Node: alln-core-8.cisco.com X-Spam-Status: No, score=-17.4 required=5.0 tests=BAYES_00, DKIMWL_WL_MED, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL, SPF_HELO_PASS, SPF_PASS, TXREP, USER_IN_DEF_DKIM_WL 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-Patchwork-Original-From: Daniel Walker via Libc-alpha From: Daniel Walker Reply-To: Daniel Walker Cc: Conan C Huang , Jeremy Stenglein , xe-linux-external@cisco.com Errors-To: libc-alpha-bounces@sourceware.org Sender: "Libc-alpha" From: Conan C Huang This is a fix for GLIBC Bugzilla #25615: dlopen RTLD_NOLOAD optimization When dlopen with RTLD_NOLOAD flag, loader should simply return the link_map or NULL and promote flags like RTLD_GLOBAL and RTLD_NODELETE. Loader shouldn't need to process any dependencies. In dl_open_worker, loader should avoid calling _dl_map_object_deps. _dl_map_object_deps is very time consuming on low-end platforms with lots of library dependencies. Loader retrains the same functionality during flag promotions: RTLD_GLOBAL RTLD_NODELETE https://sourceware.org/bugzilla/show_bug.cgi?id=25615 --- elf/dl-open.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/elf/dl-open.c b/elf/dl-open.c index 9b3606c491..cfef39ec53 100644 --- a/elf/dl-open.c +++ b/elf/dl-open.c @@ -542,7 +542,9 @@ dl_open_worker (void *a) ++new->l_direct_opencount; /* It was already open. */ - if (__glibc_unlikely (new->l_searchlist.r_list != NULL)) + if (__glibc_unlikely (new->l_searchlist.r_list != NULL) || + (__glibc_unlikely (mode & RTLD_NOLOAD) && + __glibc_unlikely (!(mode & RTLD_GLOBAL)))) { /* Let the user know about the opencount. */ if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_FILES))