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(localhost [IPv6:::1]) by gnu-tgl-3.localdomain (Postfix) with ESMTP id 3843BC021F; Tue, 1 Mar 2022 08:16:31 -0800 (PST) From: "H.J. Lu" To: libc-alpha@sourceware.org Cc: Fangrui Song , Joseph Myers Subject: [PATCH v4 0/5] Support DT_RELR relative relocation format Date: Tue, 1 Mar 2022 08:16:26 -0800 Message-Id: <20220301161631.185162-1-hjl.tools@gmail.com> X-Mailer: git-send-email 2.35.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-3022.4 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, T_SCC_BODY_TEXT_LINE, URIBL_BLACK autolearn=no autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) 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, 01 Mar 2022 16:16:39 -0000 The empty version map is used for GLIBC_ABI_DT_RELR. But lld doesn't support empty version map. Should we require linker with empty version map support for glibc build? H.J. --- Changes in v4: 1. Always enable GLIBC_ABI_DT_RELR check. 2. Use $(OBJDUMP) instead of $(NM) for GLIBC_ABI_DT_RELR check. Changes in v3: 1. Don't define SUPPORT_DT_RELR. 2. Enable DT_RELR in glibc shared libraries and position independent executables (PIE) automatically if linker supports -z pack-relative-relocs. Changes in v2: 1. Enable DT_RELR for all targets. 2. Issue an error if there is a DT_RELR entry without GLIBC_ABI_DT_RELR dependency nor GLIBC_PRIVATE definition. --- PIE and shared objects usually have many relative relocations. In 2017/2018, SHT_RELR/DT_RELR was proposed on https://groups.google.com/g/generic-abi/c/bX460iggiKg/m/GxjM0L-PBAAJ ("Proposal for a new section type SHT_RELR") and is a pre-standard. RELR usually takes 3% or smaller space than R_*_RELATIVE relocations. The virtual memory size of a mostly statically linked PIE is typically 5~10% smaller. Binutils 2.38 supports DT_RELR on x86 with the -z report-relative-reloc option. When DT_RELR is enabled, ld adds a GLIBC_ABI_DT_RELR symbol version dependency on libc.so to outputs. Issue an error if there is a DT_RELR entry without GLIBC_ABI_DT_RELR dependency nor GLIBC_PRIVATE definition. DT_RELR is enabled in glibc shared libraries and position independent executables (PIE) automatically if linker supports -z pack-relative-relocs. The DT_RELR usage in glibc can be disabled with --disable-default-dt-relr. Tested with binutils 2.38 on i686, x86-64 and x32. Fangrui Song (1): elf: Support DT_RELR relative relocation format [BZ #27924] H.J. Lu (4): elf: Properly handle zero DT_RELA/DT_REL values Add GLIBC_ABI_DT_RELR for DT_RELR support Add --disable-default-dt-relr NEWS: Mention DT_RELR support INSTALL | 6 ++++ Makeconfig | 19 ++++++++++++ Makerules | 2 ++ NEWS | 2 +- configure | 60 +++++++++++++++++++++++++++++++++++++ configure.ac | 23 +++++++++++++++ elf/Makefile | 34 +++++++++++++++++++-- elf/Versions | 5 ++++ elf/dl-version.c | 33 +++++++++++++++++++-- elf/dynamic-link.h | 40 ++++++++++++++++++++++++- elf/elf.h | 13 ++++++-- elf/get-dynamic-info.h | 19 ++++++++++-- elf/libc-abi-version.exp | 1 + elf/tst-relr-pie.c | 1 + elf/tst-relr.c | 64 ++++++++++++++++++++++++++++++++++++++++ include/link.h | 6 ++++ manual/install.texi | 5 ++++ scripts/abilist.awk | 2 ++ scripts/versions.awk | 7 ++++- 19 files changed, 329 insertions(+), 13 deletions(-) create mode 100644 elf/libc-abi-version.exp create mode 100644 elf/tst-relr-pie.c create mode 100644 elf/tst-relr.c -- 2.35.1