From patchwork Wed Nov 27 18:58:10 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Adhemerval Zanella (Code Review)" X-Patchwork-Id: 1201749 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=sourceware.org (client-ip=209.132.180.131; helo=sourceware.org; envelope-from=libc-alpha-return-107438-incoming=patchwork.ozlabs.org@sourceware.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=gnutoolchain-gerrit.osci.io Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; secure) header.d=sourceware.org header.i=@sourceware.org header.b="mS4nK/xa"; dkim-atps=neutral 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 ozlabs.org (Postfix) with ESMTPS id 47NVR21m0gz9sTF for ; Thu, 28 Nov 2019 05:58:22 +1100 (AEDT) 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=ogzuIGRpFcJStvVaND3X/VvK8lLARf9 AP+yXEnuww1WfIQXpFCYeQaJka/+HBqwBMpKfe9LiwVAemfpmYrvwWjpuuh7GYBW OE4cP5iwH0iQfA9YolCKRe1p22yrKda/6NsYI9RypIZHY2+xJBJXFuJ8zno6GEic lkQJMjwAiiD8= 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=mS4nK /xaEaBuUl3wwwvoPQaLpR9TOb/os1XyrIGgClhIpBNHcYys53t/MmpuQtCjb2++H NyMTY2P4xIXZ0DlgBDrGkLahD8+zUkjsBRMUW1mhnQR9AhMPUVDmjodv1tOSgLpr OIm+fIu6HGurqg74uVpDlLQ9cWH9oXLTQgTJcU= 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 Delivered-To: mailing list libc-alpha@sourceware.org Received: (qmail 74589 invoked by uid 89); 27 Nov 2019 18:58:15 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-21.5 required=5.0 tests=AWL, BAYES_00, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3 autolearn=ham version=3.3.1 spammy=1286 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-Disposition: inline User-Agent: Gerrit/3.0.3-79-g83ff7f88f1 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;