From patchwork Tue Feb 9 17:18:22 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vivek Dasmohapatra X-Patchwork-Id: 41985 X-Patchwork-Delegate: azanella@linux.vnet.ibm.com 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 4661B398B84F; Tue, 9 Feb 2021 17:18:51 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 4661B398B84F DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1612891131; bh=LHustSIPYTuPuaKBjWjIVS96n+gzmalsSFiz2G6mzgI=; h=To:Subject:Date:In-Reply-To:References:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To: From; b=KcCPZw8Z53HLSOe6n/vGPEjHYzn17VkO/kd16lf8APaI41cVMoiH3JO9TIRYgoS73 pYWtlrjv1rOGK/+C2SK9N4qMjYc1ygiIjTSqPTnOThiIXHH91rcqFDCJ9IdJWzREc5 FPC7J44z9evwi5oTarJlWCjFqnHH3wnRPyyynlE0= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from bhuna.collabora.co.uk (bhuna.collabora.co.uk [IPv6:2a00:1098:0:82:1000:25:2eeb:e3e3]) by sourceware.org (Postfix) with ESMTPS id CC0103955415 for ; Tue, 9 Feb 2021 17:18:46 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org CC0103955415 Received: from noise.lan (unknown [IPv6:2001:4d48:ad5c:ef00:8e70:5aff:fe59:c29c]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: vivek) by bhuna.collabora.co.uk (Postfix) with ESMTPSA id E6F8C1F451D7 for ; Tue, 9 Feb 2021 17:18:45 +0000 (GMT) To: libc-alpha@sourceware.org Subject: [RFC][PATCH v8 03/20] elf/dl-object.c: Implement a helper function to proxy link_map entries Date: Tue, 9 Feb 2021 17:18:22 +0000 Message-Id: <20210209171839.7911-4-vivek@collabora.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210209171839.7911-1-vivek@collabora.com> References: <20210209171839.7911-1-vivek@collabora.com> MIME-Version: 1.0 X-Spam-Status: No, score=-13.7 required=5.0 tests=BAYES_00, GIT_PATCH_0, KAM_DMARC_STATUS, SPF_HELO_PASS, SPF_PASS, TXREP 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: =?utf-8?q?Vivek_Das=C2=A0Mohapatra_via_Libc-alpha?= From: Vivek Dasmohapatra Reply-To: =?utf-8?q?Vivek_Das=C2=A0Mohapatra?= Errors-To: libc-alpha-bounces@sourceware.org Sender: "Libc-alpha" Provides the minimal functionality needed to take an existing link_map entry and create a proxy for it in the specified namespace. --- elf/dl-object.c | 84 ++++++++++++++++++++++++++++++++++++++ sysdeps/generic/ldsodefs.h | 5 +++ 2 files changed, 89 insertions(+) diff --git a/elf/dl-object.c b/elf/dl-object.c index 1875599eb2..1a9d35c96b 100644 --- a/elf/dl-object.c +++ b/elf/dl-object.c @@ -21,6 +21,7 @@ #include #include #include +#include #include @@ -50,6 +51,89 @@ _dl_add_to_namespace_list (struct link_map *new, Lmid_t nsid) __rtld_lock_unlock_recursive (GL(dl_load_write_lock)); } +/* Proxy an existing link map entry into a new link map: + This is based on _dl_new_object, skipping the steps we know we won't need + because this is mostly just a shell for the l_real pointer holding the real + link map entry (normally l == l->l_real, but not for ld.so in non-main + link maps or RTLD_SHARED proxies). + It also flags the proxy by setting l_proxy, and sets the the no-delete + flag in the original if it is an lt_loaded. */ +struct link_map * +_dl_new_proxy (struct link_map *old, int mode, Lmid_t nsid) +{ + const char *name; + struct link_map *new; + struct libname_list *newname; +#ifdef SHARED + unsigned int na = GLRO(dl_naudit); + + if ((mode & __RTLD_OPENEXEC) != 0) + na = DL_NNS; + + size_t audit_space = na * sizeof (struct auditstate); +#else +# define audit_space 0 +#endif + + name = old->l_name; + + /* Find the original link map entry if `old' is itself a proxy. */ + while (old && old->l_proxy) + old = old->l_real; + + if (old == NULL) + _dl_signal_error (EINVAL, name, NULL, N_("cannot proxy NULL link_map")); + + /* Object already exists in the target namespace. This should get handled + by dl_open_worker but just in case we get this far, handle it: */ + if (__glibc_unlikely (old->l_ns == nsid)) + { + /* Not actually possible, given the sanity checks above. */ + if (old->l_proxy) + return old; + + _dl_signal_error (EEXIST, name, NULL, + N_("existing object cannot be demoted to a proxy")); + } + + /* Now duplicate as little of _dl_new_object as possible to get a + working proxied object in the target link map. */ + new = (struct link_map *) calloc (sizeof (*new) + audit_space + + sizeof (struct link_map *) + + sizeof (*newname) + PATH_MAX, 1); + + if (new == NULL) + _dl_signal_error (ENOMEM, name, NULL, + N_("cannot create shared object descriptor")); + + /* Specific to the proxy. */ + new->l_real = old; + new->l_proxy = 1; + new->l_ns = nsid; + + /* Copied from the origin. */ + new->l_libname = old->l_libname; + new->l_name = old->l_name; + /* Proxies are considered lt_loaded if the real entry type is lt_library. */ + new->l_type = (old->l_type == lt_library) ? lt_loaded : old->l_type; + + if (__glibc_unlikely (mode & RTLD_NODELETE)) + new->l_flags_1 |= DF_1_NODELETE; + + /* Specific to the origin. Ideally we'd do some accounting here but + for now it's easier to pin the original so the proxy remains valid. */ + if (old->l_type == lt_loaded) + old->l_flags_1 |= DF_1_NODELETE; + + /* Fix up the searchlist so that relocations work. */ + _dl_map_object_deps (new, NULL, 0, 0, + mode & (__RTLD_DLOPEN | RTLD_DEEPBIND | __RTLD_AUDIT)); + + /* And finally put the proxy in the target namespace. */ + _dl_add_to_namespace_list (new, nsid); + + return new; +} /* Allocate a `struct link_map' for a new object being loaded, and enter it into the _dl_loaded list. */ diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h index 9720a4e446..f58b4ac49f 100644 --- a/sysdeps/generic/ldsodefs.h +++ b/sysdeps/generic/ldsodefs.h @@ -974,6 +974,11 @@ extern lookup_t _dl_lookup_symbol_x (const char *undef, struct link_map *skip_map) attribute_hidden; +/* Proxy an existing link map entry into a new link map */ +extern struct link_map *_dl_new_proxy (struct link_map *old, + int mode, + Lmid_t nsid) + attribute_hidden; /* Restricted version of _dl_lookup_symbol_x. Searches MAP (and only MAP) for the symbol UNDEF_NAME, with GNU hash NEW_HASH (computed