When handling absolute relocations for global symbols bind within the
shared object, AArch64 will generate one dynamic RELATIVE relocation,
but won't apply the value for this absolution relocations at static
linking stage. This is different from AArch64 gold linker and x86-64.
This is not a bug as AArch64 is RELA, there is only guarantee that
relocation addend is placed in the relocation entry. But some
system softwares originally writen for x86-64 might assume AArch64
bfd linker gets the same behavior as x86-64, then they could take
advantage of this buy skipping those RELATIVE dynamic relocations
if the load address is the same as the static linking address.
This patch makes AArch64 BFD linker applies absolution relocations at
static linking stage for scenario described above. Meanwhile old AArch64
android loader has a bug (PR19163) which relies on current linker behavior
as a workaround, so the same option --no-apply-dynamic-relocs added.
Some early revisions of the Cortex-A53 have an erratum (843419). The
details of the erratum are quite complex and involve dynamic
conditions. For the purposes of the workaround we have simplified the
static conditions to an ADRP in the last two instructions of a 4KByte
page, followed within four instructions by a load/store dependent on
the ADRP.
This patch adds support to conservatively scan for and workaround
Cortex A53 erratum 843419. There are two different workaround
strategies used. The first is to rewrite ADRP instructions which form
part of an erratum sequence with an ADR instruction. In situations
where the ADR provides insufficient offset the dependent load or store
instruction from the sequence is moved to a stub section and branches
are inserted from the original sequence to the relocated instruction
and back again.
Stub section sizes are rounded up to a multiple of 4096 in order to
ensure that the act of inserting work around stubs does not create
more errata sequences.
Workaround stubs are always inserted into the stub section associated
with the input section containing the erratum sequence. This ensures
that the fully relocated form of the veneered load store instruction
is available at the point in time when the stub section is written.
2014-10-22 Tejas Belagod <tejas.belagod@arm.com>
bfd/
* bfd-in.h (bfd_elf64_aarch64_set_options): Add a parameter.
* bfd-in2.h (bfd_elf64_aarch64_set_options): Likewise.
* elfnn-aarch64.c (aarch64_erratum_835769_stub): New.
(elf_aarch64_stub_type): Add new type
aarch64_stub_erratum_835769_veneer.
(elf_aarch64_stub_hash_entry): New fields for erratum 835769.
(aarch64_erratum_835769_fix): New data struct to record erratum
835769.
(elf_aarch64_link_hash_table: Global flags for 835769.
(aarch64_build_one_stub): Add case for 835769.
(aarch64_size_one_stub): Likewise.
(aarch64_mem_op_p, aarch64_mlxl_p,
aarch64_erratum_sequence,erratum_835769_scan):
New. Decode and scan functions for erratum 835769.
(elf_aarch64_create_or_find_stub_sec): New.
(elfNN_aarch64_size_stubs): Look for erratum 835769 and record
them.
(bfd_elfNN_aarch64_set_options: Set global flag for 835769.
(erratum_835769_branch_to_stub_data,
make_branch_to_erratum_835769_stub):New. Connect up all the
erratum stubs to occurances by branches.
(elfNN_aarch64_write_section): New hook.
(aarch64_map_one_stub): Output erratum stub symbol.
(elfNN_aarch64_size_dynamic_sections): Init mapping symbol
information for erratum 835769.
(elf_backend_write_section): Define.
ld/
* emultempl/aarch64elf.em: Add command-line option for erratum
835769.
ld/testsuite/
* ld-aarch64/aarch64-elf.exp (aarch64elftests): Drive erratum
835769 tests.
* ld-aarch64/erratum835769.d: New.
* ld-aarch64/erratum835769.s: New.
Tie output section statements to their associated output section via
output section userdata. This allows us to avoid hash lookups which
are slower and fail when multiple output sections have the same name.
* ldlang.h (lang_output_section_get): Define.
* ldlang.c (lang_output_section_get): Likewise.
(init_os): Set the output_section userdata to the output
section statement.
* emultempl/hppaelf.em: Use lang_output_section_get instead of
lang_output_section_find where applicable.
* emultempl/aarch64elf.em: Likewise.
* emultempl/aix.em: Likewise.
* emultempl/armelf.em: Likewise.
* emultempl/m68hc1xelf.em: Likewise.
* emultempl/metagelf.em: Likewise.
* emultempl/mipself.em: Likewise.
* emultempl/ppc64elf.em: Likewise.
* emultempl/spuelf.em: Likewise.
