[PATCH 0/10] ld: Implement DT_RELR for x86
H.J. Lu
hjl.tools@gmail.com
Fri Jan 7 19:06:21 GMT 2022
Hi Nick,
I'd like to enable DT_RELR for x86 in binutils 2.38.
H.J.
---
DT_RELR encodes consecutive R_*_RELATIVE relocations in GOT (the global
offset table) and data sections in a compact format:
https://groups.google.com/g/generic-abi/c/bX460iggiKg
On some targets, R_*_RELATIVE relocations are counted and the GOT offsets
are allocated when setting the dynamic section sizes after seeing all
relocations. R_*_RELATIVE relocations are generated while relocating
sections after section layout has been finalized.
To prepare for DT_RELR implementation on these targets, extract
_bfd_elf_link_iterate_on_relocs from _bfd_elf_link_check_relocs so
that a backend can scan relocations in elf_backend_always_size_sections
For x86 targets, the old check_relocs is renamed to scan_relocs and a
new check_relocs is added to chek input sections and create dynamic
relocation sections so that they will be mapped to output sections.
scan_relocs is now called from elf_backend_always_size_sections.
On some targets, the DT_RELR section size can be computed only after all
symbols addresses can be determined:
1. Update ldelf_map_segments to pass need_layout to
_bfd_elf_map_sections_to_segments which will size DT_RELR section and
set need_layout to true if the DT_RELR section size is changed.
2. Set the preliminary DT_RELR section size before mapping sections to
segments and set the final DT_RELR section size after regular symbol
processing is done.
On x86, DT_RELR is implemented with linker relaxation:
1. During linker relaxation, we scan input relocations with the same
logic in relocate_section to determine if a relative relocation should
be generated and save the relative relocation candidate information for
sizing the DT_RELR section later after all symbols addresses can be
determined. For these relative relocations which can't be placed in
the DT_RELR section, they will be placed in the rela.dyn/rel.dyn
section.
2. When DT_RELR is enabled, _bfd_elf_map_sections_to_segments calls a
backend function to size the DT_RELR section which will compute the
DT_RELR section size and tell ldelf_map_segments to layout sections
again when the DT_RELR section size has been increased.
3. After regular symbol processing is finished, bfd_elf_final_link calls
a backend function to finish the DT_RELR section.
When DT_RELR is enabled, to avoid random run-time crash with older glibc
binaries without DT_RELR support, add a GLIBC_ABI_DT_RELR symbol version,
which is provided by glibc with DT_RELR support, dependency on the shared
C library if it provides a GLIBC_2.XX symbol version.
It can build DT_RELR enabled glibc successfully on x86-64, x32 and
i686.
H.J. Lu (10):
ld: Extract _bfd_elf_link_iterate_on_relocs
elf: Add .relr.dyn to special_sections_r
elf: Extract _bfd_elf_process_reverse_copy
elf: Pass need_layout to _bfd_elf_map_sections_to_segments
ld: Initial DT_RELR support
elf: Add size_relative_relocs and finish_relative_relocs
elf: Support DT_RELR in linker tests
x86: Add DT_RELR support
ld: Add simple DT_RELR tests
ld: Add glibc dependency for DT_RELR
bfd/elf-bfd.h | 19 +-
bfd/elf.c | 22 +-
bfd/elf32-i386.c | 112 +-
bfd/elf64-x86-64.c | 118 +-
bfd/elflink.c | 191 ++-
bfd/elfxx-target.h | 8 +
bfd/elfxx-x86.c | 1022 +++++++++++++++++
bfd/elfxx-x86.h | 197 +++-
binutils/testsuite/lib/binutils-common.exp | 1 +
include/bfdlink.h | 4 +
ld/NEWS | 3 +
ld/emulparams/dt-relr.sh | 21 +
ld/emulparams/elf32_x86_64.sh | 1 +
ld/emulparams/elf_i386.sh | 1 +
ld/emulparams/elf_x86_64.sh | 1 +
ld/emultempl/elf.em | 5 +-
ld/ld.texi | 16 +-
ld/ldelf.c | 13 +
ld/ldelfgen.c | 3 +-
ld/lexsup.c | 1 +
ld/scripttempl/elf.sc | 4 +
ld/testsuite/config/default.exp | 16 +
ld/testsuite/ld-elf/dt-relr-1.s | 13 +
ld/testsuite/ld-elf/dt-relr-1a.d | 10 +
ld/testsuite/ld-elf/dt-relr-1b.d | 9 +
ld/testsuite/ld-elf/dt-relr-1c.d | 9 +
ld/testsuite/ld-elf/dt-relr-2.s | 20 +
ld/testsuite/ld-elf/dt-relr-2a.d | 10 +
ld/testsuite/ld-elf/dt-relr-2b.d | 17 +
ld/testsuite/ld-elf/dt-relr-2c.d | 17 +
ld/testsuite/ld-elf/dt-relr-2d.d | 9 +
ld/testsuite/ld-elf/dt-relr-2e.d | 9 +
ld/testsuite/ld-elf/dt-relr-2f.d | 8 +
ld/testsuite/ld-elf/dt-relr-2g.d | 9 +
ld/testsuite/ld-elf/dt-relr-2h.d | 9 +
ld/testsuite/ld-elf/dt-relr-glibc-1.c | 11 +
ld/testsuite/ld-elf/dt-relr-glibc-1a.rd | 4 +
ld/testsuite/ld-elf/dt-relr-glibc-1b.rd | 7 +
ld/testsuite/ld-elf/dt-relr.exp | 44 +
ld/testsuite/ld-elf/shared.exp | 3 +-
ld/testsuite/ld-i386/export-class.exp | 2 +-
ld/testsuite/ld-i386/i386.exp | 20 +-
ld/testsuite/ld-i386/ibt-plt-2a.d | 2 +-
ld/testsuite/ld-i386/ibt-plt-3a.d | 2 +-
ld/testsuite/ld-i386/ibt-plt-3c.d | 2 +-
ld/testsuite/ld-i386/pr27491-1a.d | 4 +-
ld/testsuite/ld-i386/report-reloc-1.d | 2 +-
ld/testsuite/ld-ifunc/ifunc-2-i386-now.d | 2 +-
.../ld-ifunc/ifunc-2-local-i386-now.d | 2 +-
.../ld-ifunc/ifunc-2-local-x86-64-now.d | 2 +-
ld/testsuite/ld-ifunc/ifunc-2-x86-64-now.d | 2 +-
ld/testsuite/ld-ifunc/pr17154-x86-64-now.d | 2 +-
ld/testsuite/ld-ifunc/pr17154-x86-64.d | 2 +-
ld/testsuite/ld-x86-64/bnd-branch-1-now.d | 2 +-
ld/testsuite/ld-x86-64/bnd-ifunc-1-now.d | 2 +-
ld/testsuite/ld-x86-64/bnd-ifunc-2-now.d | 2 +-
ld/testsuite/ld-x86-64/bnd-ifunc-2.d | 2 +-
ld/testsuite/ld-x86-64/bnd-plt-1-now.d | 2 +-
ld/testsuite/ld-x86-64/bnd-plt-1.d | 2 +-
ld/testsuite/ld-x86-64/export-class.exp | 3 +-
ld/testsuite/ld-x86-64/ibt-plt-2a-x32.d | 2 +-
ld/testsuite/ld-x86-64/ibt-plt-2a.d | 2 +-
ld/testsuite/ld-x86-64/ibt-plt-3a-x32.d | 2 +-
ld/testsuite/ld-x86-64/ibt-plt-3a.d | 2 +-
ld/testsuite/ld-x86-64/ilp32-4.d | 2 +-
ld/testsuite/ld-x86-64/load1c.d | 2 +-
ld/testsuite/ld-x86-64/load1d.d | 2 +-
ld/testsuite/ld-x86-64/pr13082-2b.d | 2 +-
ld/testsuite/ld-x86-64/pr14207.d | 2 +-
ld/testsuite/ld-x86-64/pr18176.d | 2 +-
ld/testsuite/ld-x86-64/pr19162.d | 2 +-
ld/testsuite/ld-x86-64/pr19636-2d.d | 2 +-
ld/testsuite/ld-x86-64/pr19636-2l.d | 2 +-
ld/testsuite/ld-x86-64/pr20253-1d.d | 2 +-
ld/testsuite/ld-x86-64/pr20253-1f.d | 2 +-
ld/testsuite/ld-x86-64/pr20253-1j.d | 2 +-
ld/testsuite/ld-x86-64/pr20253-1l.d | 2 +-
ld/testsuite/ld-x86-64/pr27491-1a.d | 4 +-
ld/testsuite/ld-x86-64/report-reloc-1-x32.d | 2 +-
ld/testsuite/ld-x86-64/report-reloc-1.d | 2 +-
ld/testsuite/ld-x86-64/x86-64.exp | 65 +-
81 files changed, 1931 insertions(+), 234 deletions(-)
create mode 100644 ld/emulparams/dt-relr.sh
create mode 100644 ld/testsuite/ld-elf/dt-relr-1.s
create mode 100644 ld/testsuite/ld-elf/dt-relr-1a.d
create mode 100644 ld/testsuite/ld-elf/dt-relr-1b.d
create mode 100644 ld/testsuite/ld-elf/dt-relr-1c.d
create mode 100644 ld/testsuite/ld-elf/dt-relr-2.s
create mode 100644 ld/testsuite/ld-elf/dt-relr-2a.d
create mode 100644 ld/testsuite/ld-elf/dt-relr-2b.d
create mode 100644 ld/testsuite/ld-elf/dt-relr-2c.d
create mode 100644 ld/testsuite/ld-elf/dt-relr-2d.d
create mode 100644 ld/testsuite/ld-elf/dt-relr-2e.d
create mode 100644 ld/testsuite/ld-elf/dt-relr-2f.d
create mode 100644 ld/testsuite/ld-elf/dt-relr-2g.d
create mode 100644 ld/testsuite/ld-elf/dt-relr-2h.d
create mode 100644 ld/testsuite/ld-elf/dt-relr-glibc-1.c
create mode 100644 ld/testsuite/ld-elf/dt-relr-glibc-1a.rd
create mode 100644 ld/testsuite/ld-elf/dt-relr-glibc-1b.rd
create mode 100644 ld/testsuite/ld-elf/dt-relr.exp
--
2.33.1
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