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Tue, 20 May 2025 09:25:47 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.2.16.247]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 1C8D330001AB for ; Tue, 20 May 2025 09:25:45 +0000 (UTC) From: Florian Weimer To: libc-alpha@sourceware.org Subject: [PATCH v6 21/23] elf: Extract rtld_setup_phdr function from dl_main In-Reply-To: Message-ID: References: X-From-Line: fdc5890a2766eeff077120338f6a5e515613b02b Mon Sep 17 00:00:00 2001 Date: Tue, 20 May 2025 11:25:42 +0200 User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: w5pSdGYigNRWWUuUIhkkUdi9bQdoADSlin64qXL2b04_1747733147 X-Mimecast-Originator: redhat.com X-Spam-Status: No, score=-11.1 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H5, RCVD_IN_MSPIKE_WL, RCVD_IN_VALIDITY_RPBL_BLOCKED, RCVD_IN_VALIDITY_SAFE_BLOCKED, SPF_HELO_NONE, SPF_NONE, TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: libc-alpha-bounces~patchwork=sourceware.org@sourceware.org Remove historic binutils reference from comment and update how this data is used by applications. --- elf/rtld.c | 59 +++++++++++++++++++++++++++++------------------------- 1 file changed, 32 insertions(+), 27 deletions(-) diff --git a/elf/rtld.c b/elf/rtld.c index 3af8ee63c3..7301c80a13 100644 --- a/elf/rtld.c +++ b/elf/rtld.c @@ -1238,6 +1238,37 @@ rtld_setup_main_map (struct link_map *main_map) return has_interp; } +/* Set up the program header information for the dynamic linker + itself. It can be accessed via _r_debug and dl_iterate_phdr + callbacks. */ +static void +rtld_setup_phdr (void) +{ + /* Starting from binutils-2.23, the linker will define the magic + symbol __ehdr_start to point to our own ELF header if it is + visible in a segment that also includes the phdrs. */ + + const ElfW(Ehdr) *rtld_ehdr = &__ehdr_start; + assert (rtld_ehdr->e_ehsize == sizeof *rtld_ehdr); + assert (rtld_ehdr->e_phentsize == sizeof (ElfW(Phdr))); + + const ElfW(Phdr) *rtld_phdr = (const void *) rtld_ehdr + rtld_ehdr->e_phoff; + + _dl_rtld_map.l_phdr = rtld_phdr; + _dl_rtld_map.l_phnum = rtld_ehdr->e_phnum; + + + /* PT_GNU_RELRO is usually the last phdr. */ + size_t cnt = rtld_ehdr->e_phnum; + while (cnt-- > 0) + if (rtld_phdr[cnt].p_type == PT_GNU_RELRO) + { + _dl_rtld_map.l_relro_addr = rtld_phdr[cnt].p_vaddr; + _dl_rtld_map.l_relro_size = rtld_phdr[cnt].p_memsz; + break; + } +} + /* Adjusts the contents of the stack and related globals for the user entry point. The ld.so processed skip_args arguments and bumped _dl_argv and _dl_argc accordingly. Those arguments are removed from @@ -1704,33 +1735,7 @@ dl_main (const ElfW(Phdr) *phdr, ++GL(dl_ns)[LM_ID_BASE]._ns_nloaded; ++GL(dl_load_adds); - /* Starting from binutils-2.23, the linker will define the magic symbol - __ehdr_start to point to our own ELF header if it is visible in a - segment that also includes the phdrs. If that's not available, we use - the old method that assumes the beginning of the file is part of the - lowest-addressed PT_LOAD segment. */ - - /* Set up the program header information for the dynamic linker - itself. It is needed in the dl_iterate_phdr callbacks. */ - const ElfW(Ehdr) *rtld_ehdr = &__ehdr_start; - assert (rtld_ehdr->e_ehsize == sizeof *rtld_ehdr); - assert (rtld_ehdr->e_phentsize == sizeof (ElfW(Phdr))); - - const ElfW(Phdr) *rtld_phdr = (const void *) rtld_ehdr + rtld_ehdr->e_phoff; - - _dl_rtld_map.l_phdr = rtld_phdr; - _dl_rtld_map.l_phnum = rtld_ehdr->e_phnum; - - - /* PT_GNU_RELRO is usually the last phdr. */ - size_t cnt = rtld_ehdr->e_phnum; - while (cnt-- > 0) - if (rtld_phdr[cnt].p_type == PT_GNU_RELRO) - { - _dl_rtld_map.l_relro_addr = rtld_phdr[cnt].p_vaddr; - _dl_rtld_map.l_relro_size = rtld_phdr[cnt].p_memsz; - break; - } + rtld_setup_phdr (); /* Add the dynamic linker to the TLS list if it also uses TLS. */ if (_dl_rtld_map.l_tls_blocksize != 0)