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(localhost [IPv6:::1]) by gnu-cfl-2.localdomain (Postfix) with ESMTP id B25BFC035E; Wed, 18 Aug 2021 13:00:24 -0700 (PDT) From: "H.J. Lu" To: libc-alpha@sourceware.org Cc: gdb@sourceware.org, Daniel Walker Subject: [PATCH v4 0/2] Extend struct r_debug to support multiple namespaces Date: Wed, 18 Aug 2021 13:00:22 -0700 Message-Id: <20210818200024.3240116-1-hjl.tools@gmail.com> X-Mailer: git-send-email 2.31.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-3027.2 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, FREEMAIL_FROM, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: gdb@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 18 Aug 2021 20:00:37 -0000 Changes in the v4 patch: 1. Improve the empty namespace removal from the namespace linked list. 2. Check r_version == 0 for the unused namespace. Changes in the v3 patch: 1. Remove the empty namespace from the namespace linked list. 2. Properly add the new namespace to the linked list. Changes in the v2 patch: 1. Bump r_version to 2. 2. Don't add DT_DEBUGSZ. 3. Add struct r_debug_extended to extend struct r_debug. 4. Don't update the r_state field in the copy of _r_debug in executable since it is not consumed by the program. --- Glibc does not provide an interface for debugger to access libraries loaded in multiple namespaces via dlmopen. The current rtld-debugger interface is described in the file: elf/rtld-debugger-interface.txt under the "Standard debugger interface" heading. This interface only provides access to the first link-map (LM_ID_BASE). 1. Bump r_version to 2. This triggers the GDB bug: https://sourceware.org/bugzilla/show_bug.cgi?id=28236 2. Add struct r_debug_extended to extend struct r_debug into a linked-list, where each element correlates to an unique namespace. 3. Remove the empty namespace from the namespace linked list and clear its r_version field. 4. Add the new namespace, whose r_version field is 0, to the namespace linked list. 5. Initialize the r_debug_extended structure only if its r_version field is 0 and update its r_map field if it is NULL. 6. Add a hidden symbol, _r_debug_extended, for struct r_debug_extended. 7. Provide the compatibility symbol, _r_debug, with size of struct r_debug, as an alise of _r_debug_extended, for programs which reference _r_debug. Glibc does not provide an interface for debugger to access libraries loaded in multiple namespaces via dlmopen. The current rtld-debugger interface is described in the file: elf/rtld-debugger-interface.txt under the "Standard debugger interface" heading. This interface only provides access to the first link-map (LM_ID_BASE). 1. Bump r_version to 2. This triggers the GDB bug: https://sourceware.org/bugzilla/show_bug.cgi?id=28236 2. Add struct r_debug_extended to extend struct r_debug into a linked-list, where each element correlates to an unique namespace. 3. Remove the empty namespace from the namespace linked list and clear its r_version field. 4. Add the new namespace, whose r_version field is 0, to the namespace linked list. 5. Initialize the r_debug_extended structure only if its r_version field is 0 and update its r_map field if it is NULL. 6. Add a hidden symbol, _r_debug_extended, for struct r_debug_extended. 7. Provide the compatibility symbol, _r_debug, with size of struct r_debug, as an alise of _r_debug_extended, for programs which reference _r_debug. H.J. Lu (2): Add declare_object_symbol_alias for assembly codes [BZ #28128] Extend struct r_debug to support multiple namespaces NEWS | 9 ++++- csu/Makefile | 3 ++ csu/rtld-sizes.sym | 4 ++ elf/Makefile | 22 ++++++++++- elf/dl-close.c | 23 ++++++++++- elf/dl-debug-symbols-gen.c | 24 ++++++++++++ elf/dl-debug-symbols.S | 31 +++++++++++++++ elf/dl-debug.c | 44 ++++++++++++--------- elf/dl-load.c | 2 +- elf/dl-open.c | 2 +- elf/dl-reloc-static-pie.c | 4 +- elf/link.h | 69 +++++++++++++++++++++++++-------- elf/rtld-debugger-interface.txt | 14 +++++++ elf/rtld.c | 6 +-- elf/tst-dlmopen4.c | 68 ++++++++++++++++++++++++++++++++ include/libc-symbols.h | 12 +++--- include/link.h | 4 ++ sysdeps/generic/ldsodefs.h | 5 ++- 18 files changed, 291 insertions(+), 55 deletions(-) create mode 100644 csu/rtld-sizes.sym create mode 100644 elf/dl-debug-symbols-gen.c create mode 100644 elf/dl-debug-symbols.S create mode 100644 elf/tst-dlmopen4.c -- 2.31.1