This is in preparation for the next patch adding Spectre variant 2
mitigation for PowerPC and PowerPC64. Besides tidying code involved
in stub output (to reduce the number of places where bctr is output),
the patch adds some user visible features:
1) PowerPC64 ELFv2 global entry stubs now are aligned under the
control of --plt-align, with a default alignment of 32 bytes.
2) PowerPC64 __glink_PLTresolve is no longer padded out with nops.
3) PowerPC32 PLT stubs are aligned under the control of --plt-align,
with the default alignment being 16 bytes as before.
4) The PowerPC32 branch/nop table emitted before __glink_PLTresolve
is now smaller in many cases. It was sized incorrectly when the
__tls_get_addr_opt stub was used, and unnecessarily included space
for local ifuncs.
bfd/
* elf32-ppc.c (GLINK_ENTRY_SIZE): Add parameters, handle
__tls_get_addr_opt, and alignment sizing.
(TLS_GET_ADDR_GLINK_SIZE): Delete.
(is_nonpic_glink_stub): Don't use GLINK_ENTRY_SIZE.
(ppc_elf_get_synthetic_symtab): Recognize stubs spaced at 4, 6,
or 8 insns.
(ppc_elf_link_hash_table_create): Init new ppc_elf_params field.
(allocate_dynrelocs): Use new GLINK_ENTRY_SIZE.
(ppc_elf_size_dynamic_sections): Likewise. Size branch table
by PLT reloc count.
(write_glink_stub): Handle __tls_get_addr_opt stub.
Pad out to size given by GLINK_ENTRY_SIZE.
(ppc_elf_relocate_section): Adjust write_glink_stub call.
(ppc_elf_finish_dynamic_symbol): Likewise.
(ppc_elf_finish_dynamic_sections): Write PLTresolve without using
insn array since so many need rewriting.
* elf32-ppc.h (struct ppc_elf_params): Add plt_stub_align.
* elf64-ppc.c (GLINK_PLTRESOLVE_SIZE): Rename from
GLINK_CALL_STUB_SIZE. Add htab param and evaluate to size without
nops. Adjust all uses.
(ppc64_elf_get_synthetic_symtab): Don't use GLINK_CALL_STUB_SIZE
in glink_vma calculation.
(struct ppc_link_hash_table): Add global_entry section pointer.
(create_linkage_sections): Create separate section for global
entry stubs.
(PPC_LO, PPC_HI, PPC_HA): Move earlier.
(size_global_entry_stubs): Handle sizing for aligned stubs.
(ppc64_elf_size_dynamic_sections): Handle global_entry alloc,
and don't stash end of glink branch table in rawsize.
(ppc_build_one_stub): Rewrite stub size calculations.
(build_global_entry_stubs): Use new section.
(ppc64_elf_build_stubs): Don't pad __glink_PLTresolve with nops.
Build lazy link stubs out to end of section. Build global entry
stubs in new section.
gold/
* options.h (plt_align): Support for PowerPC32 too.
* powerpc.cc (Stub_table::stub_align): Heed --plt-align for 32-bit.
(Stub_table::plt_call_size, branch_stub_size): Tidy.
(Stub_table::plt_call_align): Implement using stub_align.
(Output_data_glink::global_entry_align): New function.
(Output_data_glink::global_entry_off): New function.
(Output_data_glink::global_entry_address): Use global_entry_off.
(Output_data_glink::pltresolve_size): New function, replacing
pltresolve_size_ constant. Update all uses.
(Output_data_glink::add_global_entry): Align offset.
(Output_data_glink::set_final_data_size): Use global_entry_align.
(Stub_table::do_write): Don't pad __glink_PLTrelsolve with nops.
Tidy stub output. Use global_entry_off.
ld/
* emultempl/ppc32elf.em (params): Init new field.
(enum ppc32_opt): New enum to define OPTION_* values. Add
OPTION_PLT_ALIGN and OPTION_NO_PLT_ALIGN.
(PARSE_AND_LIST_LONGOPTS): Handle new options.
(PARSE_AND_LIST_ARGS_CASES): Likewise.
(PARSE_AND_LIST_OPTIONS): Likewise. Break up help output.
* emultempl/ppc64elf.em (ppc_add_stub_section): Init alignment
correctly for negative --plt-stub-align.
* testsuite/ld-powerpc/elfv2exe.d,
* testsuite/ld-powerpc/elfv2so.d,
* testsuite/ld-powerpc/relbrlt.d,
* testsuite/ld-powerpc/relbrlt.s,
* testsuite/ld-powerpc/tlsexe.d,
* testsuite/ld-powerpc/tlsexe.r,
* testsuite/ld-powerpc/tlsexe32.d,
* testsuite/ld-powerpc/tlsexe32.g,
* testsuite/ld-powerpc/tlsexe32.r,
* testsuite/ld-powerpc/tlsexetoc.d,
* testsuite/ld-powerpc/tlsexetoc.r,
* testsuite/ld-powerpc/tlsopt5_32.d,
* testsuite/ld-powerpc/tlsso.d,
* testsuite/ld-powerpc/tlstocso.d: Update for changed stub order.
This change is to support the new ELFv2 ABI, which uses the value in
r12 on function entry to calculate the got/toc pointer.
bfd/
* elf64-ppc.c (build_plt_stub): Switch stubs to use r11 as base
reg and r12 as destination.
(ppc_build_one_stub): Likewise.
(ppc64_elf_build_stubs): Likewise for glink.
ld/testsuite/
* ld-powerpc/tls.s: Add proper .opd entry for _start.
* ld-powerpc/tlstoc.s: Likewise.
* ld-powerpc/relbrlt.d: Update for changed stubs.
* ld-powerpc/tls.d: Update for changed stubs and _start .opd entry.
* ld-powerpc/tls.g: Likewise.
* ld-powerpc/tlsexe.d: Likewise.
* ld-powerpc/tlsexe.g: Likewise.
* ld-powerpc/tlsexe.r: Likewise.
* ld-powerpc/tlsexetoc.d: Likewise.
* ld-powerpc/tlsexetoc.g: Likewise.
* ld-powerpc/tlsexetoc.r: Likewise.
* ld-powerpc/tlsso.d: Likewise.
* ld-powerpc/tlsso.g: Likewise.
* ld-powerpc/tlsso.r: Likewise.
* ld-powerpc/tlstoc.d: Likewise.
* ld-powerpc/tlstoc.g: Likewise.
* ld-powerpc/tlstocso.d: Likewise.
* ld-powerpc/tlstocso.g: Likewise.
* ld-powerpc/tlstocso.r: Likewise.
* elf64-ppc.c (follow_link, elf_follow_link, ppc_follow_link): New
functions. Use throughout.
(ppc64_elf_copy_indirect_symbol): Set direct symbol "oh" field
from indirect symbol.
(lookup_fdh): Rename from get_fdh. Follow indirect sym links.
(add_symbol_adjust): Simplify.
(defined_code_entry, defined_func_desc): New functions.
(ppc64_elf_gc_keep): Follow indirect sym links. Use defined_code_entry.
(ppc64_elf_gc_mark_dynamic_ref): Use defined_func_desc and
defined_code_entry to follow indirect sym links.
(ppc64_elf_gc_mark_hook, func_desc_adjust): Likewise.
(ppc_type_of_stub): Follow indirect sym links.
(toc_adjusting_stub_needed): Likewise.
(ppc_build_one_stub): Likewise. Make undefined dot-symbols weak
rather than defining them at stub.
(ppc64_elf_relocate_section): Rewrite call test to avoid multiple
assignments in test.
ld/testsuite/
* ld-powerpc/tlsso.d: Update.
* ld-powerpc/tlsso.r: Update.
* ld-powerpc/tlstocso.d: Update.
* ld-powerpc/tlstocso.r: Update.
