From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by sourceware.org (Postfix) with ESMTPS id 409A93858D37 for ; Tue, 23 Aug 2022 19:13:27 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 409A93858D37 Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-627-qZpa3NXjN9ykz-_9zlDC8w-1; Tue, 23 Aug 2022 15:13:25 -0400 X-MC-Unique: qZpa3NXjN9ykz-_9zlDC8w-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 329361C13943 for ; Tue, 23 Aug 2022 19:13:25 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.39.192.143]) by smtp.corp.redhat.com (Postfix) with ESMTPS id AC6AF492C3B for ; Tue, 23 Aug 2022 19:13:24 +0000 (UTC) From: Florian Weimer To: Florian Weimer via Libc-alpha Subject: Re: [PATCH v2] Detect ld.so and libc.so version inconsistency during startup References: <87h722276j.fsf@oldenburg.str.redhat.com> Date: Tue, 23 Aug 2022 21:13:22 +0200 In-Reply-To: <87h722276j.fsf@oldenburg.str.redhat.com> (Florian Weimer via Libc-alpha's message of "Tue, 23 Aug 2022 19:36:36 +0200") Message-ID: <878rne22p9.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.85 on 10.11.54.10 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Spam-Status: No, score=-4.8 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_DNSWL_LOW, SPF_HELO_NONE, SPF_NONE, TXREP, T_SCC_BODY_TEXT_LINE, URIBL_BLACK autolearn=no 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: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 23 Aug 2022 19:13:30 -0000 * Florian Weimer via Libc-alpha: > The files NEWS, include/link.h, and sysdeps/generic/ldsodefs.h > contribute to the version fingerprint used for detection. The > fingerprint can be further refined using the --with-extra-version-id > configure argument. > > _dl_call_libc_early_init is replaced with _dl_lookup_libc_early_init. > The new function is used store a pointer to libc.so's > __libc_early_init function in the libc_map_early_init member of the > ld.so namespace structure. This function pointer can then be called > directly, so the separate invocation function is no longer needed. > > The versioned symbol lookup needs the symbol versioning data > structures, so the initialization of libc_map and libc_map_early_init > is now done from _dl_check_map_versions, after this information > becomes available. (_dl_map_object_from_fd does not set this up > in time, so the initialization code had to be moved from there.) > This means that the separate initialization code can be removed from > dl_main because _dl_check_map_versions covers all maps, including > the initial executable loaded by the kernel. The lookup still happens > before relocation and the invocation of IFUNC resolvers, so IFUNC > resolvers are protected from ABI mismatch. > > The __libc_early_init function pointer is not protected because > so little code runs between the pointer write and the invocation > (only dynamic linker code and IFUNC resolvers). > > --- > v2: Really quite different. I moved the __libc_early_init lookup before > relocation processing, which had a bunch of knock-on effects. > Re-tested on i386-linux-gnu and x86_64-linux-gnu. > build-many-glibcs.py is still running. build-many-glibcs.py passed. I also manually verified with GDB that libc_map is still initialized when running the install libc.so.6 directly (not with an explicit loader invocation): (gdb) print _rtld_global._dl_ns[0].libc_map $1 = (struct link_map *) 0x7ffff7ffe380 (gdb) print _rtld_global._dl_ns[0].libc_map_early_init $2 = (void (*)(_Bool)) 0x5555556909f0 <__libc_early_init_jBsH275t> So that special initialization code I removed from the !rtld_is_main case really isn't needed anymore. Thanks, Florian