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: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-4.0 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_EF,HEADER_FROM_DIFFERENT_DOMAINS, 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 (server1.sourceware.org [209.132.180.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dcvr.yhbt.net (Postfix) with ESMTPS id 70AC41F463 for ; Wed, 27 Nov 2019 18:58:18 +0000 (UTC) DomainKey-Signature: a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:date:from:to:subject:in-reply-to:references :reply-to:mime-version:content-transfer-encoding:content-type :message-id; q=dns; s=default; b=OlZQ6MSXpExHFmK14+wMMSJJhVDK0bO 3lESjlqzxZoUBdAtzW79qYV9Ho5uaj/QTPdwSP0tNkA/upzD6oEFA7KC5XRZkLLS 5iRn17RidjgZsPMFj9TyjHaMLwNA0NNVC95wam/mFDv3XRO729H1Jt93tEe0eAwA UZ7KNCjIJmfo= DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:date:from:to:subject:in-reply-to:references :reply-to:mime-version:content-transfer-encoding:content-type :message-id; s=default; bh=Mwowd7Ysna+jv3uehcz5/bLbjsY=; b=gPaVF QAdJmqzUsJn8oGfd88HW4rjgrqMhbMJcSgat7XTQ0mMwp1ZtZgt1x0K4lP2q5hEA glN3PS/JrtFfFOxHTgz1us49VF87Kx1mb7NKo3zrOsx3b7Px/UmfUl6Y77DYHUYD 4iQU4+Haxabe73WQkoPmqRU95W6xFhZ+s1AczI= Received: (qmail 74597 invoked by alias); 27 Nov 2019 18:58:16 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Received: (qmail 74589 invoked by uid 89); 27 Nov 2019 18:58:15 -0000 Authentication-Results: sourceware.org; auth=none X-HELO: mx1.osci.io X-Gerrit-PatchSet: 2 Date: Wed, 27 Nov 2019 13:58:10 -0500 From: "Florian Weimer (Code Review)" To: Florian Weimer , Szabolcs Nagy , Carlos O'Donell , libc-alpha@sourceware.org Auto-Submitted: auto-generated X-Gerrit-MessageType: newpatchset Subject: [review v2] dlsym: Do not determine caller link map if not needed X-Gerrit-Change-Id: Ide5d9e2cc7ac25a0ffae8fb4c26def0c898efa29 X-Gerrit-Change-Number: 528 X-Gerrit-ChangeURL: X-Gerrit-Commit: 7245de950d45afa4cbf1a9eb3a7f62a94ce943ec In-Reply-To: References: Reply-To: fweimer@redhat.com, fweimer@redhat.com, szabolcs.nagy@arm.com, libc-alpha@sourceware.org, carlos@redhat.com MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Disposition: inline User-Agent: Gerrit/3.0.3-79-g83ff7f88f1 Content-Type: text/plain; charset=UTF-8 Message-Id: <20191127185810.4CD3820AF6@gnutoolchain-gerrit.osci.io> Change URL: https://gnutoolchain-gerrit.osci.io/r/c/glibc/+/528 ...................................................................... dlsym: Do not determine caller link map if not needed Obtaining the link map is potentially very slow because it requires iterating over all loaded objects in the current implementation. If the caller supplied an explicit handle (i.e., not one of the RTLD_* constants), the dlsym implementation does not need the identity of the caller (except in the special case of auditing), so this change avoids computing it in that case. Even in the minimal case (dlsym called from a main program linked with -dl), this shows a small speedup, perhaps around five percent. The performance improvement can be arbitrarily large in principle (if _dl_find_dso_for_object has to iterate over many link maps). Change-Id: Ide5d9e2cc7ac25a0ffae8fb4c26def0c898efa29 --- M elf/dl-sym.c 1 file changed, 21 insertions(+), 4 deletions(-) diff --git a/elf/dl-sym.c b/elf/dl-sym.c index 8209342..7282e09 100644 --- a/elf/dl-sym.c +++ b/elf/dl-sym.c @@ -80,6 +80,18 @@ args->flags, NULL); } +/* Return the link map containing the caller address. */ +static inline struct link_map * +find_caller_link_map (ElfW(Addr) caller) +{ + struct link_map *l = _dl_find_dso_for_object (caller); + if (l != NULL) + return l; + else + /* If the address is not recognized the call comes from the main + program (we hope). */ + return GL(dl_ns)[LM_ID_BASE]._ns_loaded; +} static void * do_sym (void *handle, const char *name, void *who, @@ -89,13 +101,13 @@ lookup_t result; ElfW(Addr) caller = (ElfW(Addr)) who; - struct link_map *l = _dl_find_dso_for_object (caller); - /* If the address is not recognized the call comes from the main - program (we hope). */ - struct link_map *match = l ? l : GL(dl_ns)[LM_ID_BASE]._ns_loaded; + /* Link map of the caller if needed. */ + struct link_map *match = NULL; if (handle == RTLD_DEFAULT) { + match = find_caller_link_map (caller); + /* Search the global scope. We have the simple case where we look up in the scope of an object which was part of the initial binary. And then the more complex part @@ -128,6 +140,8 @@ } else if (handle == RTLD_NEXT) { + match = find_caller_link_map (caller); + if (__glibc_unlikely (match == GL(dl_ns)[LM_ID_BASE]._ns_loaded)) { if (match == NULL @@ -187,6 +201,9 @@ unsigned int ndx = (ref - (ElfW(Sym) *) D_PTR (result, l_info[DT_SYMTAB])); + if (match == NULL) + match = find_caller_link_map (caller); + if ((match->l_audit_any_plt | result->l_audit_any_plt) != 0) { unsigned int altvalue = 0; -- Gerrit-Project: glibc Gerrit-Branch: master Gerrit-Change-Id: Ide5d9e2cc7ac25a0ffae8fb4c26def0c898efa29 Gerrit-Change-Number: 528 Gerrit-PatchSet: 2 Gerrit-Owner: Florian Weimer Gerrit-Reviewer: Carlos O'Donell Gerrit-Reviewer: Szabolcs Nagy Gerrit-MessageType: newpatchset