From patchwork Tue Apr 26 21:04:03 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: d wk X-Patchwork-Id: 615298 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org 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 3qvbF33SCkz9t4B for ; Wed, 27 Apr 2016 07:04:23 +1000 (AEST) Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; secure) header.d=sourceware.org header.i=@sourceware.org header.b=fz3duGVC; dkim-atps=neutral DomainKey-Signature: a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:mime-version:in-reply-to:references:date :message-id:subject:from:to:content-type; q=dns; s=default; b=xS O+DtFJWzM/YCk666eIRBqKTG8Le/OJIiMDloZBwtuIUQE2OAL38dX8vEYaGpn71d sPb1inLNmW7VF43Thu3d0AX2U07ZvN48rtlR8nHrwfpyOQDVVMEIRhQtjWRUx0ea 49pcfDSJZZN1TjTIf1GJW13HzWqVntGZHkSzsO7F8= 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:mime-version:in-reply-to:references:date :message-id:subject:from:to:content-type; s=default; bh=2H4ZvwLC UUtz9eDims7aMarUhIQ=; b=fz3duGVC3FkYxxkl2NHaxCY9+YCgvHcPJLC7WiVd 5+wD3NupdMNnTY3nvV3vOgOeHaqtR0IcckqnVoe7ZwYbigArtoOlSCKSEEU/nx+g FRCYZ4Gt8AhQ/C34hr9EopzQpFxu7d/i3PPxl3EMx2Vl13QCSSWH4QniiMJGiESn iAg= Received: (qmail 27100 invoked by alias); 26 Apr 2016 21:04:16 -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 27088 invoked by uid 89); 26 Apr 2016 21:04:16 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.6 required=5.0 tests=BAYES_00, FREEMAIL_FROM, RCVD_IN_DNSWL_LOW, SPF_PASS autolearn=ham version=3.3.2 spammy= X-HELO: mail-ig0-f193.google.com X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:date :message-id:subject:from:to; bh=vu2uxuR3p+ojWHS6UBo+As7xHMLTAatLHmC6YqTadMU=; b=mQsZW/ZS9O9dzSgtvhIE9liYkI87F3tvHMcJvtXBg8iQfz8oFokAJgMPdOO9/T18Hg Ll1VaX2/wwTfVhbfpmeFbXTICDVMtp3HV5OKbYiuYHqgpgVxobmkiMSVfb2TBqYq+ZOV 3VJVmFox4aptUVeggN2CT1JX7bZ6JCCA9lMcu2ntDhK76/qDNpJTTr/x542gXbyGbiNX GwMgMyvHjnpeB01oD5d5ll3v213w2id8QeJSSoWQBxX8HC1HZAAmzyPDDzk4IGMEuhaz LusMNDdD9PtZuPYeTwWojOcaO5RNkC4mjO4SWDZh3q4poT3edC2OsFGm5Uw21wv8Kap/ LzwQ== X-Gm-Message-State: AOPr4FWuUZ4z2Da+Hy44hVND5n9sHlkqM40KQiZLys9lFK37xKeYic4eKFOVqcIDlcwPAKvbzM5D0Qf1YKjbIQ== MIME-Version: 1.0 X-Received: by 10.50.142.97 with SMTP id rv1mr6161930igb.74.1461704644020; Tue, 26 Apr 2016 14:04:04 -0700 (PDT) In-Reply-To: References: Date: Tue, 26 Apr 2016 17:04:03 -0400 Message-ID: Subject: Re: [PATCH] Support -z initfirst for multiple shared libraries From: d wk To: libc-alpha@sourceware.org Apologies, I renamed `node' to `new_node' at the last moment and broke the patch. It should be easy to figure out, but here's a fixed version. ----[ cut here ]---- Support -z initfirst for multiple shared libraries (run in load order). This is particularly useful when combined with LD_PRELOAD, as it is then possible to run constructors before any code in other libraries runs. --- elf/dl-init.c | 9 ++++++++- elf/dl-load.c | 19 ++++++++++++++++++- elf/dl-support.c | 4 ++-- sysdeps/generic/ldsodefs.h | 7 +++++-- 4 files changed, 33 insertions(+), 6 deletions(-) diff --git a/elf/dl-init.c b/elf/dl-init.c index 818c3aa..da59d1f 100644 --- a/elf/dl-init.c +++ b/elf/dl-init.c @@ -84,7 +84,14 @@ _dl_init (struct link_map *main_map, int argc, char **argv, char **env) if (__glibc_unlikely (GL(dl_initfirst) != NULL)) { - call_init (GL(dl_initfirst), argc, argv, env); + struct initfirst_list *initfirst; + for(initfirst = GL(dl_initfirst); initfirst; initfirst = initfirst->next) + { + call_init (initfirst->which, argc, argv, env); + } + + /* We do not try to free this list, as the memory will not be reclaimed + by the allocator unless there were no intervening malloc()'s. */ GL(dl_initfirst) = NULL; } diff --git a/elf/dl-load.c b/elf/dl-load.c index c0d6249..5288b8f 100644 --- a/elf/dl-load.c +++ b/elf/dl-load.c @@ -1388,7 +1388,24 @@ cannot enable executable stack as shared object requires"); /* Remember whether this object must be initialized first. */ if (l->l_flags_1 & DF_1_INITFIRST) - GL(dl_initfirst) = l; + { + struct initfirst_list *new_node = malloc(sizeof(*new_node)); + struct initfirst_list *it = GL(dl_initfirst); + new_node->which = l; + new_node->next = NULL; + + /* We append to the end of the linked list. Whichever library was loaded + first has higher initfirst priority. This means that LD_PRELOAD + initfirst overrides initfirst in libraries linked normally. */ + if (!it) + GL(dl_initfirst) = new_node; + else + { + while (it->next) + it = it->next; + it->next = new_node; + } + } /* Finally the file information. */ l->l_file_id = id; diff --git a/elf/dl-support.c b/elf/dl-support.c index c30194c..d8b8acc 100644 --- a/elf/dl-support.c +++ b/elf/dl-support.c @@ -147,8 +147,8 @@ struct r_search_path_elem *_dl_all_dirs; /* All directories after startup. */ struct r_search_path_elem *_dl_init_all_dirs; -/* The object to be initialized first. */ -struct link_map *_dl_initfirst; +/* The list of objects to be initialized first. */ +struct initfirst_list *_dl_initfirst; /* Descriptor to write debug messages to. */ int _dl_debug_fd = STDERR_FILENO; diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h index ddec0be..198c089 100644 --- a/sysdeps/generic/ldsodefs.h +++ b/sysdeps/generic/ldsodefs.h @@ -326,8 +326,11 @@ struct rtld_global /* Incremented whenever something may have been added to dl_loaded. */ EXTERN unsigned long long _dl_load_adds; - /* The object to be initialized first. */ - EXTERN struct link_map *_dl_initfirst; + /* The list of objects to be initialized first. */ + EXTERN struct initfirst_list { + struct link_map *which; + struct initfirst_list *next; + } *_dl_initfirst; #if HP_SMALL_TIMING_AVAIL /* Start time on CPU clock. */