From patchwork Fri Nov 8 14:50:13 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: 1191944 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-106813-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="tCFfoc+6"; 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 478jqk6xmfz9sNH for ; Sat, 9 Nov 2019 01:50:26 +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:cc:message-id:subject:references :reply-to:mime-version:content-transfer-encoding:content-type; q=dns; s=default; b=e/PuvK9uAd/8Pb6rUREUu845VYuoBJr29t+lISPlnYc QLJhA6K/8AJ+0r1+EwxoCsxrP8/Ocyfz7WOhnknbfA2QCeP2ktxojc/xvY10WyfC tZBjAfrL37A53IYM72liP1XpWSkjIxoouKXWXUVNj2ndu2Zd4QZZxJ52iV0lQvX8 = 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:cc:message-id:subject:references :reply-to:mime-version:content-transfer-encoding:content-type; s=default; bh=vCKZpQ7yCcax35FzmCVNPcftDK8=; b=tCFfoc+6F1omai3P3 nj5Ze68bvLtqwJur2ExFtDpZAc6HELSNlcU77TyTt2CJsT3MXCuTZ0U+pqa9W7Rf HaSibFrelEvPiDj7JTpf5qoz0mfajKEhfiMQrtni0ZwuhAn41ysfjUM7Qs5Gzrsn G+c1V9uueLRDXFH1Iu9JdFdD8c= Received: (qmail 12579 invoked by alias); 8 Nov 2019 14:50:20 -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 12493 invoked by uid 89); 8 Nov 2019 14:50:20 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-26.9 required=5.0 tests=BAYES_00, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3 autolearn=ham version=3.3.1 spammy=auditing X-HELO: mx1.osci.io X-Gerrit-PatchSet: 1 Date: Fri, 8 Nov 2019 09:50:13 -0500 From: "Florian Weimer (Code Review)" To: libc-alpha@sourceware.org Cc: Florian Weimer Message-ID: Auto-Submitted: auto-generated X-Gerrit-MessageType: newchange Subject: [review] 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: f4adfc9645132874eb4b57e0c76f627db102dddd References: Reply-To: fweimer@redhat.com, fweimer@redhat.com, libc-alpha@sourceware.org MIME-Version: 1.0 Content-Disposition: inline User-Agent: Gerrit/3.0.3-75-g9005159e5d 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 cause 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 Reviewed-by: Carlos O'Donell Reviewed-by: Carlos O'Donell --- 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;