| Message ID | 20220310200329.1935466-1-hjl.tools@gmail.com |
|---|---|
| Headers | show |
| Series | Support DT_RELR relative relocation format | expand |
On 2022-03-10, H.J. Lu wrote: >Changes in v6: > >1. Move ELF_DYNAMIC_DO_RELR before ELF_DYNAMIC_DO_REL. > >Changes in v5: > >1. Update NEWS entry with the linker option, -z pack-relative-relocs. >2. Remove elf/libc-abi-version.exp and use $(READELF) to check >GLIBC_ABI_DT_RELR. > >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 | 3 +- > configure | 60 +++++++++++++++++++++++++++++++++++++++ > configure.ac | 23 +++++++++++++++ > elf/Makefile | 30 ++++++++++++++++++-- > elf/Versions | 5 ++++ > elf/dl-version.c | 33 ++++++++++++++++++++-- > elf/dynamic-link.h | 40 +++++++++++++++++++++++++- > elf/elf.h | 13 +++++++-- > elf/get-dynamic-info.h | 19 +++++++++++-- > 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 ++++- > 18 files changed, 325 insertions(+), 13 deletions(-) > create mode 100644 elf/tst-relr-pie.c > create mode 100644 elf/tst-relr.c > >-- >2.35.1 > Thanks. Every change looks good to me now. Other folks can check my extensive comments on previous iterations on the patch series https://sourceware.org/pipermail/libc-alpha/2022-March/ Reviewed-by: Fangrui Song <maskray@google.com>
Changes in v6: 1. Move ELF_DYNAMIC_DO_RELR before ELF_DYNAMIC_DO_REL. Changes in v5: 1. Update NEWS entry with the linker option, -z pack-relative-relocs. 2. Remove elf/libc-abi-version.exp and use $(READELF) to check GLIBC_ABI_DT_RELR. 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 | 3 +- configure | 60 +++++++++++++++++++++++++++++++++++++++ configure.ac | 23 +++++++++++++++ elf/Makefile | 30 ++++++++++++++++++-- elf/Versions | 5 ++++ elf/dl-version.c | 33 ++++++++++++++++++++-- elf/dynamic-link.h | 40 +++++++++++++++++++++++++- elf/elf.h | 13 +++++++-- elf/get-dynamic-info.h | 19 +++++++++++-- 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 ++++- 18 files changed, 325 insertions(+), 13 deletions(-) create mode 100644 elf/tst-relr-pie.c create mode 100644 elf/tst-relr.c