Add a -z pack-relative-relocs option to enable DT_RELR and create a
relr.dyn section for DT_RELR. DT_RELR is implemented with the linker
relaxation infrastructure, but it doesn't require the --relax option
enabled. -z pack-relative-relocs implies -z combreloc. -z nocombreloc
implies -z nopack-relative-relocs.
-z pack-relative-relocs is chosen over the similar option in lld,
--pack-dyn-relocs=relr, to implement a glibc binary lockout mechanism
with a special glibc version symbol, to avoid random crashes of DT_RELR
binaries with the existing glibc binaries.
bfd/
* elf-bfd.h (elf_link_hash_table): Add srelrdyn.
* elflink.c (_bfd_elf_link_create_dynamic_sections): Create a
.relr.dyn section for DT_RELR.
include/
* bfdlink.h (bfd_link_info): Add enable_dt_relr.
ld/
* News: Mention -z pack-relative-relocs and
-z nopack-relative-relocs.
* ld.texi: Document -z pack-relative-relocs and
-z nopack-relative-relocs.
* ldelf.c (ldelf_after_parse): Disable DT_RELR if not building
PIE nor shared library. Add 3 spare dynamic tags for DT_RELR,
DT_RELRSZ and DT_RELRENT.
* ldlang.c (lang_relax_sections): Also enable relaxation if
DT_RELR is enabled.
* emulparams/elf32_x86_64.sh: Source dt-relr.sh.
* emulparams/elf_i386.sh: Likewise.
* emulparams/elf_x86_64.sh: Likewise.
* emulparams/dt-relr.sh: New file.
* scripttempl/elf.sc: Support .relr.dyn.
