To support IBT in Intel Control-flow Enforcement Technology (CET)
instructions:
https://software.intel.com/sites/default/files/managed/4d/2a/control-flow-enforcement-technology-preview.pdf
#define GNU_PROPERTY_X86_FEATURE_1_AND 0xc0000002
#define GNU_PROPERTY_X86_FEATURE_1_IBT (1U << 0)
are added to GNU program properties to indicate that all executable
sections are compatible with IBT when ENDBR instruction starts each
valid target where an indirect branch instruction can land.
GNU_PROPERTY_X86_FEATURE_1_IBT is set on output only if it is set on
all relocatable inputs.
The followings changes are made to the Procedure Linkage Table (PLT):
1. For 64-bit x86-64, PLT is changed to
PLT0: push GOT[1]
bnd jmp *GOT[2]
nop
...
PLTn: endbr64
push namen_reloc_index
bnd jmp PLT0
together with the second PLT section:
PLTn: endbr64
bnd jmp *GOT[namen_index]
nop
BND prefix is also added so that IBT-enabled PLT is compatible with MPX.
2. For 32-bit x86-64 (x32) and i386, PLT is changed to
PLT0: push GOT[1]
jmp *GOT[2]
nop
...
PLTn: endbr64 # endbr32 for i386.
push namen_reloc_index
jmp PLT0
together with the second PLT section:
PLTn: endbr64 # endbr32 for i386.
jmp *GOT[namen_index]
nop
BND prefix isn't used since MPX isn't supported on x32 and BND registers
aren't used in parameter passing on i386.
GOT is an array of addresses. Initially, GOT[namen_index] is filled
with the address of the ENDBR instruction of the corresponding entry
in the first PLT section. The function, namen, is called via the
ENDBR instruction in the second PLT entry. GOT[namen_index] is updated
to the actual address of the function, namen, at run-time.
2 linker command line options are added:
1. -z ibtplt: Generate IBT-enabled PLT.
2. -z ibt: Generate GNU_PROPERTY_X86_FEATURE_1_IBT in GNU program
properties as well as IBT-enabled PLT.
bfd/
* elf32-i386.c (elf_i386_lazy_ibt_plt0_entry): New.
(elf_i386_lazy_ibt_plt_entry): Likewise.
(elf_i386_pic_lazy_ibt_plt0_entry): Likewise.
(elf_i386_non_lazy_ibt_plt_entry): Likewise.
(elf_i386_pic_non_lazy_ibt_plt_entry): Likewise.
(elf_i386_eh_frame_lazy_ibt_plt): Likewise.
(elf_i386_lazy_plt_layout): Likewise.
(elf_i386_non_lazy_plt_layout): Likewise.
(elf_i386_link_hash_entry): Add plt_second.
(elf_i386_link_hash_table): Add plt_second and
plt_second_eh_frame.
(elf_i386_allocate_dynrelocs): Use the second PLT if needed.
(elf_i386_size_dynamic_sections): Use .plt.got unwind info for
the second PLT. Check the second PLT.
(elf_i386_relocate_section): Use the second PLT to resolve
PLT reference if needed.
(elf_i386_finish_dynamic_symbol): Fill and use the second PLT if
needed.
(elf_i386_finish_dynamic_sections): Set sh_entsize on the
second PLT. Generate unwind info for the second PLT.
(elf_i386_plt_type): Add plt_second.
(elf_i386_get_synthetic_symtab): Support the second PLT.
(elf_i386_parse_gnu_properties): Support
GNU_PROPERTY_X86_FEATURE_1_AND.
(elf_i386_merge_gnu_properties): Support
GNU_PROPERTY_X86_FEATURE_1_AND. If info->ibt is set, turn
on GNU_PROPERTY_X86_FEATURE_1_IBT
(elf_i386_link_setup_gnu_properties): If info->ibt is set,
turn on GNU_PROPERTY_X86_FEATURE_1_IBT. Use IBT-enabled PLT
for info->ibtplt, info->ibt or GNU_PROPERTY_X86_FEATURE_1_IBT
is set on all relocatable inputs.
* elf64-x86-64.c (elf_x86_64_lazy_ibt_plt_entry): New.
(elf_x32_lazy_ibt_plt_entry): Likewise.
(elf_x86_64_non_lazy_ibt_plt_entry): Likewise.
(elf_x32_non_lazy_ibt_plt_entry): Likewise.
(elf_x86_64_eh_frame_lazy_ibt_plt): Likewise.
(elf_x32_eh_frame_lazy_ibt_plt): Likewise.
(elf_x86_64_lazy_ibt_plt): Likewise.
(elf_x32_lazy_ibt_plt): Likewise.
(elf_x86_64_non_lazy_ibt_plt): Likewise.
(elf_x32_non_lazy_ibt_plt): Likewise.
(elf_x86_64_get_synthetic_symtab): Support the second PLT.
(elf_x86_64_parse_gnu_properties): Support
GNU_PROPERTY_X86_FEATURE_1_AND.
(elf_x86_64_merge_gnu_properties): Support
GNU_PROPERTY_X86_FEATURE_1_AND. If info->ibt is set, turn
on GNU_PROPERTY_X86_FEATURE_1_IBT
(elf_x86_64_link_setup_gnu_properties): If info->ibt is set,
turn on GNU_PROPERTY_X86_FEATURE_1_IBT. Use IBT-enabled PLT
for info->ibtplt, info->ibt or GNU_PROPERTY_X86_FEATURE_1_IBT
is set on all relocatable inputs.
binutils/
* readelf.c (decode_x86_feature): New.
(print_gnu_property_note): Call decode_x86_feature on
GNU_PROPERTY_X86_FEATURE_1_AND.
* testsuite/binutils-all/i386/empty.d: New file.
* testsuite/binutils-all/i386/empty.s: Likewise.
* testsuite/binutils-all/i386/ibt.d: Likewise.
* testsuite/binutils-all/i386/ibt.s: Likewise.
* testsuite/binutils-all/x86-64/empty-x32.d: Likewise.
* testsuite/binutils-all/x86-64/empty.d: Likewise.
* testsuite/binutils-all/x86-64/empty.s: Likewise.
* testsuite/binutils-all/x86-64/ibt-x32.d: Likewise.
* testsuite/binutils-all/x86-64/ibt.d: Likewise.
* testsuite/binutils-all/x86-64/ibt.s: Likewise.
include/
* bfdlink.h (bfd_link_info): Add ibtplt and ibt.
* elf/common.h (GNU_PROPERTY_X86_FEATURE_1_AND): New.
(GNU_PROPERTY_X86_FEATURE_1_IBT): Likewise.
ld/
* Makefile.am (ELF_X86_DEPS): Add $(srcdir)/emulparams/cet.sh.
* Makefile.in: Regenerated.
* NEWS: Mention GNU_PROPERTY_X86_FEATURE_1_IBT, -z ibtplt
and -z ibt.
* emulparams/cet.sh: New file.
* testsuite/ld-i386/ibt-plt-1.d: Likewise.
* testsuite/ld-i386/ibt-plt-1.s: Likewise.
* testsuite/ld-i386/ibt-plt-2.s: Likewise.
* testsuite/ld-i386/ibt-plt-2a.d: Likewise.
* testsuite/ld-i386/ibt-plt-2b.d: Likewise.
* testsuite/ld-i386/ibt-plt-2c.d: Likewise.
* testsuite/ld-i386/ibt-plt-2d.d: Likewise.
* testsuite/ld-i386/ibt-plt-3.s: Likewise.
* testsuite/ld-i386/ibt-plt-3a.d: Likewise.
* testsuite/ld-i386/ibt-plt-3b.d: Likewise.
* testsuite/ld-i386/ibt-plt-3c.d: Likewise.
* testsuite/ld-i386/ibt-plt-3d.d: Likewise.
* testsuite/ld-i386/plt-main-ibt.dd: Likewise.
* testsuite/ld-i386/plt-pie-ibt.dd: Likewise.
* testsuite/ld-i386/property-x86-empty.s: Likewise.
* testsuite/ld-i386/property-x86-ibt.s: Likewise.
* testsuite/ld-i386/property-x86-ibt1a.d: Likewise.
* testsuite/ld-i386/property-x86-ibt1b.d: Likewise.
* testsuite/ld-i386/property-x86-ibt2.d: Likewise.
* testsuite/ld-i386/property-x86-ibt3a.d: Likewise.
* testsuite/ld-i386/property-x86-ibt3b.d: Likewise.
* testsuite/ld-i386/property-x86-ibt4.d: Likewise.
* testsuite/ld-i386/property-x86-ibt5.d: Likewise.
* testsuite/ld-x86-64/ibt-plt-1-x32.d: Likewise.
* testsuite/ld-x86-64/ibt-plt-1.d: Likewise.
* testsuite/ld-x86-64/ibt-plt-1.s: Likewise.
* testsuite/ld-x86-64/ibt-plt-2.s: Likewise.
* testsuite/ld-x86-64/ibt-plt-2a-x32.d: Likewise.
* testsuite/ld-x86-64/ibt-plt-2a.d: Likewise.
* testsuite/ld-x86-64/ibt-plt-2b-x32.d: Likewise.
* testsuite/ld-x86-64/ibt-plt-2b.d: Likewise.
* testsuite/ld-x86-64/ibt-plt-2c-x32.d: Likewise.
* testsuite/ld-x86-64/ibt-plt-2c.d: Likewise.
* testsuite/ld-x86-64/ibt-plt-2d-x32.d: Likewise.
* testsuite/ld-x86-64/ibt-plt-2d.d: Likewise.
* testsuite/ld-x86-64/ibt-plt-3.s: Likewise.
* testsuite/ld-x86-64/ibt-plt-3a-x32.d: Likewise.
* testsuite/ld-x86-64/ibt-plt-3a.d: Likewise.
* testsuite/ld-x86-64/ibt-plt-3b-x32.d: Likewise.
* testsuite/ld-x86-64/ibt-plt-3b.d: Likewise.
* testsuite/ld-x86-64/ibt-plt-3c-x32.d: Likewise.
* testsuite/ld-x86-64/ibt-plt-3c.d: Likewise.
* testsuite/ld-x86-64/ibt-plt-3d-x32.d: Likewise.
* testsuite/ld-x86-64/ibt-plt-3d.d: Likewise.
* testsuite/ld-x86-64/plt-main-ibt-now.rd: Likewise.
* testsuite/ld-x86-64/plt-main-ibt-x32.dd: Likewise.
* testsuite/ld-x86-64/plt-main-ibt.dd: Likewise.
* testsuite/ld-x86-64/property-x86-empty.s: Likewise.
* testsuite/ld-x86-64/property-x86-ibt.s: Likewise.
* testsuite/ld-x86-64/property-x86-ibt1a-x32.d: Likewise.
* testsuite/ld-x86-64/property-x86-ibt1a.d: Likewise.
* testsuite/ld-x86-64/property-x86-ibt1b-x32.d: Likewise.
* testsuite/ld-x86-64/property-x86-ibt1b.d: Likewise.
* testsuite/ld-x86-64/property-x86-ibt2-x32.d: Likewise.
* testsuite/ld-x86-64/property-x86-ibt2.d: Likewise.
* testsuite/ld-x86-64/property-x86-ibt3a-x32.d: Likewise.
* testsuite/ld-x86-64/property-x86-ibt3a.d: Likewise.
* testsuite/ld-x86-64/property-x86-ibt3b-x32.d: Likewise.
* testsuite/ld-x86-64/property-x86-ibt3b.d: Likewise.
* testsuite/ld-x86-64/property-x86-ibt4-x32.d: Likewise.
* testsuite/ld-x86-64/property-x86-ibt4.d: Likewise.
* testsuite/ld-x86-64/property-x86-ibt5-x32.d: Likewise.
* testsuite/ld-x86-64/property-x86-ibt5.d: Likewise.
* emulparams/elf32_x86_64.sh: Source emulparams/cet.sh.
(TINY_READONLY_SECTION): Add .plt.sec.
* emulparams/elf_i386.sh: Likewise.
* emulparams/elf_x86_64.sh: Source emulparams/cet.sh.
* ld.texinfo: Document -z ibtplt and -z ibt.
* testsuite/ld-i386/i386.exp: Run IBT and IBT PLT tests.
* testsuite/ld-x86-64/x86-64.exp: Likewise.
* testsuite/ld-x86-64/pr21481b.S (check): Updated for x32.
Since the BFD section count may not be cleared for shared objects during
linking, we should check the DYNAMIC bit for input shared objects.
bfd/
PR ld/21626
* elf-properties.c (_bfd_elf_link_setup_gnu_properties): Check
the DYNAMIC bit instead of bfd_count_sections.
ld/
PR ld/21626
* testsuite/ld-i386/i386.exp: Run ld/21626 tests.
* testsuite/ld-x86-64/x86-64.exp: Likewise.
For some pc-relative relocations we want to allow them under PIC mode while
a normal global symbol defined in the same dynamic object can still bind
externally through copy relocation. So, we should not allow pc-relative
relocation against such symbol.
SYMBOL_REFERENCES_LOCAL should be used and is more accurate than the original
individual checks.
bfd/
* elfnn-aarch64.c (elfNN_aarch64_final_link_relocate): Use
SYMBOL_REFERENCES_LOCAL.
ld/
* testsuite/ld-aarch64/aarch64-elf.exp: Update test name
* testsuite/ld-aarch64/pcrel.s: Add new testcases.
* testsuite/ld-aarch64/pcrel_pic_undefined.d: Update the expected
warnings.
* testsuite/ld-aarch64/pcrel_pic_defined_local.d: Rename ...
* testsuite/ld-aarch64/pcrel_pic_defined.d: ... to this.
Update expected warnings.
As discussed at the PR, this patch tries to avoid COPY relocation generation
and propagate the original relocation into runtime if it was relocating on
writable section. The ELIMINATE_COPY_RELOCS has been set to true and it's
underlying infrastructure has been improved so that the COPY reloc elimination
at least working on absoluate relocations (ABS64) on AArch64.
BFD linker copy relocation elimination framwork requires the backend to always
allocate dynrelocs for all those relocation types that are possible to introduce
copy relocations. This is for adjust_dynamic_symbol hook to be able to get all
symbol reference information. Should one symbol is referenced by more than one
relocations, if there is any of them needs copy relocation then linker should
generate it.
bfd/
PR ld/21532
* elfnn-aarch64.c (ELIMINATE_COPY_RELOCS): Set to 1.
(elfNN_aarch64_final_link_relocate): Also propagate relocations to
runtime for if there needs copy relocation elimination.
(need_copy_relocation_p): New function. Return true for symbol with
pc-relative references and if it's against read-only sections.
(elfNN_aarch64_adjust_dynamic_symbol): Use need_copy_relocation_p.
(elfNN_aarch64_check_relocs): Allocate dynrelocs for relocation types
that are related with accessing external objects.
(elfNN_aarch64_gc_sweep_hook): Sync the relocation types with the change
in elfNN_aarch64_check_relocs.
ld/
* testsuite/ld-aarch64/copy-reloc-exe-2.s: New test source file.
* testsuite/ld-aarch64/copy-reloc-2.d: New test.
* testsuite/ld-aarch64/copy-reloc-exe-eliminate.s: New test source file.
* testsuite/ld-aarch64/copy-reloc-eliminate.d: New test.
* testsuite/ld-aarch64/copy-reloc-so.s: Define new global objects.
* testsuite/ld-aarch64/aarch64-elf.exp: Run new tests.
ld-gc/pr20022.d requires support for dynamic relocations in .text
section.
PR ld/20022
* testsuite/ld-gc/pr20022.d: Skip on targets without dynamic
relocations in .text section.
Symbol lookup in linker will always fail on targets with leading char
in symbol name since __start_SECNAME and __stop_SECNAME in C may be
___start_SECNAME and ___stop_SECNAME in assembly. Also tests with
--gc-sections always fails on targets without --gc-sections support.
* testsuite/ld-elf/pr21562a.d: Skip on targets with leading char
in in symbol name or without --gc-sections.
* testsuite/ld-elf/pr21562b.d: Likewise.
* testsuite/ld-elf/pr21562c.d: Likewise.
* testsuite/ld-elf/pr21562d.d: Likewise.
* testsuite/ld-elf/pr21562i.d: Likewise.
* testsuite/ld-elf/pr21562j.d: Likewise.
* testsuite/ld-elf/pr21562k.d: Likewise.
* testsuite/ld-elf/pr21562l.d: Likewise.
* testsuite/ld-elf/pr21562m.d: Likewise.
* testsuite/ld-elf/pr21562n.d: Likewise.
* testsuite/ld-elf/pr21562e.d: Skip on targets with leading char
in symbol name.
* testsuite/ld-elf/pr21562f.d: Likewise.
* testsuite/ld-elf/pr21562g.d: Likewise.
* testsuite/ld-elf/pr21562h.d: Likewise.
Symbol lookup in linker will always fail on targets with leading char
in symbol name since __start_SECNAME and __stop_SECNAME in C may be
___start_SECNAME and ___stop_SECNAME in assembly.
* testsuite/ld-elf/sizeofa.d: Skip on targets with leading char
in symbol name.
* testsuite/ld-elf/sizeofb.d: Likewise.
* testsuite/ld-elf/startofa.d: Likewise.
* testsuite/ld-elf/startofb.d: Likewise.
__start_SECNAME and __stop_SECNAME shouldn't be defined for "ld -r".
* ldlang.c (lang_set_startof): Skip if config.build_constructors
is FALSE.
* testsuite/ld-elf/sizeofc.d: New file.
* testsuite/ld-elf/startofc.d: Likewise.
Currently, linker will define __start_SECNAME and __stop_SECNAME symbols
only for orphaned sections.
However, during garbage collection, ELF linker marks all sections with
references to __start_SECNAME and __stop_SECNAME symbols as used even
when section SECNAME isn't an orphaned section and linker won't define
__start_SECNAME nor __stop_SECNAME. And ELF linker stores the first
input section whose name matches __start_SECNAME or __stop_SECNAME in
u.undef.section for garbage collection. If these symbols are provided
in linker script, u.undef.section is set to the section where they will
defined by linker script, which leads to the incorrect output.
This patch changes linker to always define referenced __start_SECNAME and
__stop_SECNAME if the input section name is the same as the output section
name, which is always true for orphaned sections, and SECNAME is a C
identifier. Also __start_SECNAME and __stop_SECNAME symbols are marked
as hidden by ELF linker so that __start_SECNAME and __stop_SECNAME symbols
for section SECNAME in different modules are unique. For garbage
collection, ELF linker stores the first matched input section in the
unused vtable field.
bfd/
PR ld/20022
PR ld/21557
PR ld/21562
PR ld/21571
* elf-bfd.h (elf_link_hash_entry): Add start_stop. Change the
vtable field to a union.
(_bfd_elf_is_start_stop): Removed.
* elf32-i386.c (elf_i386_convert_load_reloc): Also check for
__start_SECNAME and __stop_SECNAME symbols.
* elf64-x86-64.c (elf_x86_64_convert_load_reloc): Likewise.
* elflink.c (_bfd_elf_is_start_stop): Removed.
(_bfd_elf_gc_mark_rsec): Check start_stop instead of calling
_bfd_elf_is_start_stop.
(elf_gc_propagate_vtable_entries_used): Skip __start_SECNAME and
__stop_SECNAME symbols. Updated.
(elf_gc_smash_unused_vtentry_relocs): Likewise.
(bfd_elf_gc_record_vtinherit): Likewise.
(bfd_elf_gc_record_vtentry): Likewise.
ld/
PR ld/20022
PR ld/21557
PR ld/21562
PR ld/21571
* ld.texinfo: Update __start_SECNAME/__stop_SECNAME symbols.
* ldlang.c (lang_insert_orphan): Move handling of __start_SECNAME
and __stop_SECNAME symbols to ...
(lang_set_startof): Here. Also define __start_SECNAME and
__stop_SECNAME for -Ur.
* emultempl/elf32.em (gld${EMULATION_NAME}_after_open): Mark
referenced __start_SECNAME and __stop_SECNAME symbols as hidden
and set start_stop for garbage collection.
* testsuite/ld-elf/pr21562a.d: New file.
* testsuite/ld-elf/pr21562a.s: Likewise.
* testsuite/ld-elf/pr21562a.t: Likewise.
* testsuite/ld-elf/pr21562b.d: Likewise.
* testsuite/ld-elf/pr21562b.s: Likewise.
* testsuite/ld-elf/pr21562b.t: Likewise.
* testsuite/ld-elf/pr21562c.d: Likewise.
* testsuite/ld-elf/pr21562c.t: Likewise.
* testsuite/ld-elf/pr21562d.d: Likewise.
* testsuite/ld-elf/pr21562d.t: Likewise.
* testsuite/ld-elf/pr21562e.d: Likewise.
* testsuite/ld-elf/pr21562f.d: Likewise.
* testsuite/ld-elf/pr21562g.d: Likewise.
* testsuite/ld-elf/pr21562h.d: Likewise.
* testsuite/ld-elf/pr21562i.d: Likewise.
* testsuite/ld-elf/pr21562j.d: Likewise.
* testsuite/ld-elf/pr21562k.d: Likewise.
* testsuite/ld-elf/pr21562l.d: Likewise.
* testsuite/ld-elf/pr21562m.d: Likewise.
* testsuite/ld-elf/pr21562n.d: Likewise.
* testsuite/ld-gc/pr20022.d: Likewise.
* testsuite/ld-gc/pr20022a.s: Likewise.
* testsuite/ld-gc/pr20022b.s: Likewise.
* testsuite/ld-gc/gc.exp: Run PR ld/20022 tests.
* testsuite/ld-gc/pr19161.d: Also accept local __start_SECNAME
symbol.
* testsuite/ld-gc/start.d: Likewise.
* testsuite/ld-x86-64/lea1a.d: Updated.
* testsuite/ld-x86-64/lea1b.d: Updated.
* testsuite/ld-x86-64/lea1d.d: Updated.
* testsuite/ld-x86-64/lea1e.d: Likewise.
Test -Ur with __start_SECNAME, __stop_SECNAME, .startof.SECNAME and
.sizeof.SECNAME. __start_SECNAME and __stop_SECNAME should be defined
to the start and the end of section SECNAME. .startof.SECNAME and
.sizeof.SECNAME should be undefined.
* testsuite/ld-elf/sizeof.d: New file.
* testsuite/ld-elf/sizeof.s: Likewise.
* testsuite/ld-elf/startof.d: Likewise.
* testsuite/ld-elf/startof.s: Likewise.
arm-none-eabi-ld supports shared libraries. However, the toolchain may be
configured to generate statically linked executable by default.
It is required to have --no-dynamic-linker option before adding dynamic symbol
to static executable.
For dynamically linked executable, the behavior won't change.
ld/ChangeLog
2017-06-13 Renlin Li <renlin.li@arm.com>
* testsuite/ld-elf/shared.exp (build_tests): Add --no-dynamic-linker
option to rdynamic-1 and dynamic-1 tests.
This reverts commit bc327528fd.
This patch can only be committed after PC-relative relocation types
support on copy relocation elimination is also completed.
In the case of static relocation, the GOT entries are fixed at link time
and are set by the linker.
In order to compute the right TLS offset it is necessary to add TCB_SIZE
to the offset, just in case the dynamic linker is not expected to be
executed (static linked case).
This problem does appear in dynamic linked applications, as the dynamic
linker is adding this TCB_SIZE by operating the TCB block structure.
Problem revealed in GLIBC with static linking.
bfd/ChangeLog:
Cupertino Miranda <cmiranda@synopsys.com>
arc-got.h (relocate_fix_got_relocs_for_got_info): Added TCB_SIZE to
patched section contents for TLS IE reloc.
elf32-arc.c: Remove TCB_SIZE preprocessor macro.
Rebase to 0006
Dump local IFUNC functions in the map file when generating IRELATIVE
relocations if -Map is used.
bfd/
* elf32-i386.c (elf_i386_check_relocs): Set local IFUNC symbol
name. Use local IFUNC symbol name string to report unsupported
non-PIC call to IFUNC function.
(elf_i386_relocate_section): Dump local IFUNC name with minfo
when generating R_386_IRELATIVE relocation.
(elf_i386_finish_dynamic_symbol): Likewise.
* elf_x86_64_check_relocs (elf_x86_64_check_relocs): Set local
IFUNC symbol name.
(elf_x86_64_relocate_section): Dump local IFUNC name with minfo
when generating R_X86_64_IRELATIVE relocation.
(elf_x86_64_finish_dynamic_symbol): Likewise.
ld/
* testsuite/ld-ifunc/ifunc-1-local-x86.d: Pass
"-Map tmpdir/ifunc-1-local-x86.map" to ld and check
ifunc-1-local-x86.map.
* testsuite/ld-ifunc/ifunc-1-x86.d: Pass
"-Map tmpdir/ifunc-1-x86.map" to ld and check ifunc-1-x86.map.
* testsuite/ld-ifunc/ifunc-1-local-x86.map: New file.
* testsuite/ld-ifunc/ifunc-1-x86.map: Likewise.
As discussed at the PR, this patch tries to avoid COPY relocation generation
and propagate the original relocation into runtime if it was relocating on
writable section. The ELIMINATE_COPY_RELOCS has been set to true and it's
underlying infrastructure has been improved so that the COPY reloc elimination
at least working on absoluate relocations (ABS64) after this patch.
bfd/
PR ld/21532
* elfnn-aarch64.c (ELIMINATE_COPY_RELOCS): Set to 1.
(elfNN_aarch64_final_link_relocate): Also propagate relocations to
runtime for copy relocation elimination cases.
(alias_readonly_dynrelocs): New function.
(elfNN_aarch64_adjust_dynamic_symbol): Keep the dynamic relocs instead
of generating copy relocation if it is not against read-only sections.
(elfNN_aarch64_check_relocs): Likewise.
ld/
* testsuite/ld-aarch64/copy-reloc-eliminate.d: New test.
* testsuite/ld-aarch64/copy-reloc-exe-eliminate.s: New test source file.
* testsuite/ld-aarch64/aarch64-elf.exp: Run new testcase.
Various targets fail this testcase due to ld not supporting binary output.
* testsuite/ld-unique/pr21529.d: xfail aarch64, arm, hppa, ia64,
nds32, and score. Match any output.
This commit adds a new linker feature: the ability to resolve section
groups as part of a relocatable link.
Currently section groups are automatically resolved when performing a
final link, and are carried through when performing a relocatable link.
By carried through this means that one copy of each section group (from
all the copies that might be found in all the input files) is placed
into the output file. Sections that are part of a section group will
not match input section specifiers within a linker script and are
forcibly kept as separate sections.
There is a slight resemblance between section groups and common
section. Like section groups, common sections are carried through when
performing a relocatable link, and resolved (allocated actual space)
only at final link time.
However, with common sections there is an ability to force the linker to
allocate space for the common sections when performing a relocatable
link, there's currently no such ability for section groups.
This commit adds such a mechanism. This new facility can be accessed in
two ways, first there's a command line switch --force-group-allocation,
second, there's a new linker script command FORCE_GROUP_ALLOCATION. If
one of these is used when performing a relocatable link then the linker
will resolve the section groups as though it were performing a final
link, the section group will be deleted, and the members of the group
will be placed like normal input sections. If there are multiple copies
of the group (from multiple input files) then only one copy of the group
members will be placed, the duplicate copies will be discarded.
Unlike common sections that have the --no-define-common command line
flag, and INHIBIT_COMMON_ALLOCATION linker script command there is no
way to prevent group resolution during a final link, this is because the
ELF gABI specifically prohibits the presence of SHT_GROUP sections in a
fully linked executable. However, the code as written should make
adding such a feature trivial, setting the new resolve_section_groups
flag to false during a final link should work as you'd expect.
bfd/ChangeLog:
* elf.c (_bfd_elf_make_section_from_shdr): Don't initially mark
SEC_GROUP sections as SEC_EXCLUDE.
(bfd_elf_set_group_contents): Replace use of abort with an assert.
(assign_section_numbers): Use resolve_section_groups flag instead
of relocatable link type.
(_bfd_elf_init_private_section_data): Use resolve_section_groups
flag instead of checking the final_link flag for part of the
checks in here. Fix white space as a result.
* elflink.c (elf_link_input_bfd): Use resolve_section_groups flag
instead of relocatable link type.
(bfd_elf_final_link): Likewise.
include/ChangeLog:
* bfdlink.h (struct bfd_link_info): Add new resolve_section_groups
flag.
ld/ChangeLog:
* ld.h (struct args_type): Add force_group_allocation field.
* ldgram.y: Add support for FORCE_GROUP_ALLOCATION.
* ldlex.h: Likewise.
* ldlex.l: Likewise.
* lexsup.c: Likewise.
* ldlang.c (unique_section_p): Check resolve_section_groups flag
not the relaxable link flag.
(lang_add_section): Discard section groups when we're resolving
groups. Clear the SEC_LINK_ONCE flag if we're resolving section
groups.
* ldmain.c (main): Initialise resolve_section_groups flag in
link_info based on command line flags.
* testsuite/ld-elf/group11.d: New file.
* testsuite/ld-elf/group12.d: New file.
* testsuite/ld-elf/group12.ld: New file.
* NEWS: Mention new features.
* ld.texinfo (Options): Document --force-group-allocation.
(Miscellaneous Commands): Document FORCE_GROUP_ALLOCATION.
Since it is incorrect to convert
bnd call *foo@GOTPCREL(%rip)
to
bnd nop
call foo
this patch removes the "-z prefix-nop" option from x86 linker.
* emulparams/call_nop.sh: Remove -z prefix-nop.
* ld.texinfo: Likewise.
* testsuite/ld-i386/call3c.d: Check for linker error.
* testsuite/ld-x86-64/call1c.d: Likewise.
ELFv2 functions with localentry:0 are those with a single entry point,
ie. global entry == local entry, and that have no requirement on r2 or
r12, and guarantee r2 is unchanged on return. Such an external
function can be called via the PLT without saving r2 or restoring it
on return, avoiding a common load-hit-store for small functions. The
optimization is attractive. The TOC pointer load-hit-store is a major
reason why calls to small functions that need no register saves, or
with shrink-wrap, no register saves on a fast path, are slow on
powerpc64le.
To be safe, this optimization needs ld.so support to check that the
run-time matches link-time function implementation. If a function
in a shared library with st_other localentry non-zero is called
without saving and restoring r2, r2 will be trashed on return, leading
to segfaults. For that reason the optimization does not happen for
weak functions since a weak definition is a fairly solid hint that the
function will likely be overridden. I'm also not enabling the
optimization by default unless glibc-2.26 is detected, which should
have the ld.so checks implemented.
bfd/
* elf64-ppc.c (struct ppc_link_hash_table): Add has_plt_localentry0.
(ppc64_elf_merge_symbol_attribute): Merge localentry bits from
dynamic objects.
(is_elfv2_localentry0): New function.
(ppc64_elf_tls_setup): Default params->plt_localentry0.
(plt_stub_size): Adjust size for tls_get_addr_opt stub.
(build_tls_get_addr_stub): Use a simpler stub when r2 is not saved.
(ppc64_elf_size_stubs): Leave stub_type as ppc_stub_plt_call for
optimized localentry:0 stubs.
(ppc64_elf_build_stubs): Save r2 in ELFv2 __glink_PLTresolve.
(ppc64_elf_relocate_section): Leave nop unchanged for optimized
localentry:0 stubs.
(ppc64_elf_finish_dynamic_sections): Set PPC64_OPT_LOCALENTRY in
DT_PPC64_OPT.
* elf64-ppc.h (struct ppc64_elf_params): Add plt_localentry0.
include/
* elf/ppc64.h (PPC64_OPT_LOCALENTRY): Define.
ld/
* emultempl/ppc64elf.em (params): Init plt_localentry0 field.
(enum ppc64_opt): New, replacing OPTION_* defines. Add
OPTION_PLT_LOCALENTRY, and OPTION_NO_PLT_LOCALENTRY.
(PARSE_AND_LIST_*): Support --plt-localentry and --no-plt-localentry.
* testsuite/ld-powerpc/elfv2so.d: Update.
* testsuite/ld-powerpc/powerpc.exp (TLS opt 5): Use --no-plt-localentry.
* testsuite/ld-powerpc/tlsopt5.d: Update.
Verify that debug section is removed by garbage collection when there
is a .note.gnu.property section.
* testsuite/ld-i386/i386.exp: Run property-x86-4a and
property-x86-4b.
* testsuite/ld-x86-64/x86-64.exp: Likewise.
* testsuite/ld-i386/property-x86-4a.d: New file.
* testsuite/ld-i386/property-x86-4a.s: Likewise.
* testsuite/ld-i386/property-x86-4b.d: Likewise.
* testsuite/ld-i386/property-x86-4b.s: Likewise.
* testsuite/ld-x86-64/property-x86-4a.d: Likewise.
* testsuite/ld-x86-64/property-x86-4a.s: Likewise.
* testsuite/ld-x86-64/property-x86-4b.d: Likewise.
* testsuite/ld-x86-64/property-x86-4b.s: Likewise.
PR ld/21251
* ldfile.c (ldfile_add_library_path): If the path starts with
$SYSROOT then use the sysroot as the real prefix.
* ldlang.c (lang_add_input_file): Treat $SYSROOT in the same
way as =.
* ldlex.l: Add $SYSROOT as allow prefix for a filename.
* ld.texinfo (-L): Document that $SYSROOT acts like = when
prefixing a library search path.
(INPUT): Likewise.
* testsuite/ld-scripts/sysroot-prefix.exp: Add $SYSROOT prefix
tests.
-gdwarf-sections doesn't work on targets that lack support to emit
address size relative relocs. The testcase as it was avoided
-gdwarf-sections doing anything by providing a non-empty .debug_line.
It's better to not use -gdwarf-sections. Also, the testcase failed
to match the output for 16-bit address targets like avr.
PR ld/20882
* testsuite/ld-gc/pr20882.d: Don't pass -gdwarf-sections to gas.
Allow for 16-bit address targets and match expected data fully.
* testsuite/ld-gc/pr20882a.s: Delete .debug_line section.
* testsuite/ld-gc/pr20882b.s: Likewise.
* testsuite/ld-gc/pr20882c.s: Likewise.
If a debug section is referenced by a kept debug section, it should
also be kept.
Some targets, like mips, keep input files when there are some special
sections, like .gnu.attributes, even if input file is unused otherwise.
In this case, all debug sections are kept. The new test will fail on
such targets. We can either fix those targets or XFAIL the test.
bfd/
PR ld/20882
* elflink.c (elf_gc_mark_debug_section): New function.
(_bfd_elf_gc_mark_extra_sections): Mark any debug sections
referenced by kept debug sections.
ld/
PR ld/20882
* testsuite/ld-gc/gc.exp: Run pr20882.
* testsuite/ld-gc/pr20882.d: New file.
* testsuite/ld-gc/pr20882a.s: Likewise.
* testsuite/ld-gc/pr20882b.s: Likewise.
* testsuite/ld-gc/pr20882c.s: Likewise.
If there are more than GNU property note in an input, we should merge
X86_ISA_1_USED and X86_ISA_1_NEEDED properties.
bfd/
* elf32-i386.c (elf_i386_parse_gnu_properties): Merge
GNU_PROPERTY_X86_ISA_1_USED and GNU_PROPERTY_X86_ISA_1_NEEDED
properties.
* elf64-x86-64.c (elf_x86_64_parse_gnu_properties): Likewise.
ld/
* testsuite/ld-i386/i386.exp: Run property-x86-3.
* testsuite/ld-x86-64/x86-64.exp: Likewise.
* testsuite/ld-i386/property-x86-3.d: New file.
* testsuite/ld-i386/property-x86-3.s: Likewise.
* testsuite/ld-x86-64/property-x86-3.d: Likewise.
* testsuite/ld-x86-64/property-x86-3.s: Likewise.
Rename .plt.bnd to .plt.sec to indicate that this is used as the second
PLT section. There is no change in run-time behavior. We also scan the
.plt.sec section to synthesize PLT symbols.
bfd/
* elf64-x86-64.c (elf_x86_64_link_hash_entry): Rename plt_bnd
to plt_second.
(elf_x86_64_link_hash_table): Rename plt_bnd/plt_bnd_eh_frame
to plt_second/plt_second_eh_frame.
(elf_x86_64_link_hash_newfunc): Updated.
(elf_x86_64_allocate_dynrelocs): Likewise.
(elf_x86_64_size_dynamic_sections): Likewise.
(elf_x86_64_relocate_section): Likewise.
(elf_x86_64_finish_dynamic_symbol): Likewise.
(elf_x86_64_finish_dynamic_sections): Likewise.
(elf_x86_64_plt_type): Rename plt_bnd to plt_second.
(elf_x86_64_get_synthetic_symtab): Updated. Also scan the
.plt.sec section.
(elf_backend_setup_gnu_properties): Updated. Create the
.plt.sec section instead of the .plt.sec section.
ld/
* emulparams/elf_x86_64.sh (TINY_READONLY_SECTION): Replace
.plt.bnd with .plt.sec.
* testsuite/ld-x86-64/bnd-ifunc-1-now.d: Likewise.
* testsuite/ld-x86-64/bnd-ifunc-2-now.d: Likewise.
* testsuite/ld-x86-64/bnd-ifunc-2.d: Likewise.
* testsuite/ld-x86-64/bnd-plt-1-now.d: Likewise.
* testsuite/ld-x86-64/bnd-plt-1.d: Likewise.
* testsuite/ld-x86-64/mpx3.dd: Likewise.
* testsuite/ld-x86-64/mpx3n.dd: Likewise.
* testsuite/ld-x86-64/mpx4.dd: Likewise.
* testsuite/ld-x86-64/mpx4n.dd: Likewise.
* testsuite/ld-x86-64/plt-main-bnd-now.rd: Likewise.
* testsuite/ld-x86-64/pr21038b-now.d: Likewise.
* testsuite/ld-x86-64/pr21038b.d: Likewise.
* testsuite/ld-x86-64/pr21038c-now.d: Likewise.
* testsuite/ld-x86-64/pr21038c.d: Likewise.
This patch partially reverses:
commit 25070364b0
Author: H.J. Lu <hjl.tools@gmail.com>
Date: Sat May 16 07:00:21 2015 -0700
Don't generate PLT relocations for now binding
to support LD_AUDIT and LD_PROFILE with -z now. If there is an existing
GOT relocation, it is still used to avoid PLT relocation against the same
function symbol.
bfd/
* elf32-i386.c (elf_i386_allocate_dynrelocs): Partially revert
commit 25070364b0.
* elf64-x86-64.c (elf_x86_64_allocate_dynrelocs): Likewse.
ld/
* testsuite/ld-i386/plt-pic2.dd: Updated.
* testsuite/ld-i386/plt2.dd: Likewise.
* testsuite/ld-i386/plt2.rd: Likewise.
* testsuite/ld-i386/pr17689now.rd: Likewise.
* testsuite/ld-ifunc/ifunc-16-i386-now.d: Likewise.
* testsuite/ld-ifunc/ifunc-16-x86-64-now.d: Likewise.
* testsuite/ld-ifunc/pr17154-i386-now.d: Likewise.
* testsuite/ld-ifunc/pr17154-x86-64-now.d: Likewise.
* testsuite/ld-x86-64/bnd-branch-1-now.d: Likewise.
* testsuite/ld-x86-64/bnd-ifunc-2-now.d: Likewise.
* testsuite/ld-x86-64/bnd-plt-1-now.d: Likewise.
* testsuite/ld-x86-64/plt2.dd: Likewise.
* testsuite/ld-x86-64/plt2.rd: Likewise.
* testsuite/ld-x86-64/pr17689now.rd: Likewise.
* testsuite/ld-x86-64/pr21038b-now.d: Likewise.
* testsuite/ld-x86-64/pr21038c-now.d: Likewise.
When -z bndplt is used, we must use the .plt.bnd entry for IFUNC function
address.
bfd/
PR ld/21481
* elf64-x86-64.c (elf_x86_64_finish_dynamic_symbol): Use .plt.bnd
for IFUNC function address.
ld/
PR ld/21481
* testsuite/ld-x86-64/pr21481a.c: New file.
* testsuite/ld-x86-64/pr21481b.S: Likewise.
* testsuite/ld-x86-64/x86-64.exp: Run PR ld/21481 tests.
On x86-64, the procedure linkage table (PLT) is used to
1. Call external function.
2. Call internal IFUNC function. The best implementation is selected
for the target processor at run-time.
3. Act as the canonical function address.
4. Support LD_AUDIT to audit external function calls.
5. Support LD_PROFILE to profile external function calls.
PLT looks like:
PLT0: push GOT[1]
jmp *GOT[2]
nop
PLT1: jmp *GOT[name1_index]
push name1_reloc_index
jmp PLT0
GOT is an array of addresses. Initially the GOT entry of name1 is
filled with the address of the "push name1_reloc_index" instruction.
The function, name1, is called via "jmp *GOT[name1]" in the PLT entry.
Even when lazy binding is disabled by "-z now", the PLT0 entry may
still be used with LD_AUDIT or LD_PROFILE if PLT entry is used for
canonical function address.
When linker is invoked with "-z bndplt", a different PLT layout in .plt
is used:
PLT0: push GOT[1]
bnd jmp *GOT[2]
nop
PLT1: push name1_reloc_index
bnd jmp PLT0
nop
together with a second PLT section, .pl.bnd:
PLT1: bnd jmp *GOT[name1_index]
nop
where the GOT entry of name1 is filled with the address of the push
instruction of the corresponding entry in .plt.
1. With lazy binding, when the external function, name1, is called the
first time, dynamic linker is called via PLT0 to update GOT[name1_index]
with the actual address of name1 and transfers control to name1
afterwards.
2. PLT is also used to call a local IFUNC function, name1, run-time
loader updates GOT[name1_index] when loading the module.
This patch
1. Remove PLT layout configurations from x86-64 backend_data.
2. Add generic, lay and non-lazy PLT layout configurations to x86-64
link_hash_table. Generic PLT layout includes the PLT entry templates,
information how to update the first instruction in PLT and PLT eh_frame
informaton, which are initialized in x86-64 setup_gnu_properties, based
on "-z bndplt" and target selection. PLT section alignment is also set
to PLT entry size for non-NaCl target.
3. Remove elf_x86_64_create_dynamic_sections. create_dynamic_sections
isn't always called, but GOT relocations need GOT relocations. Instead,
create all x86-64 specific dynamic sections with alignment to their entry
size in x86-64 setup_gnu_properties, which initializes elf.dynobj, so
that x86-64 check_relocs can be simplified.
4. Rewrite elf_x86_64_get_synthetic_symtab to check PLT sections against
all dynamic relocations to support both lazy and non-lazy PLTs.
There is no change in PLT. The only externally visible change is the
improvement of synthetic PLT symbols for .plt.got.
bfd/
* elf64-x86-64.c (PLT_ENTRY_SIZE): Renamed to ...
(LAZY_PLT_ENTRY_SIZE): This.
(NON_LAZY_PLT_ENTRY_SIZE): New.
(elf_x86_64_plt0_entry): Renamed to ...
(elf_x86_64_lazy_plt0_entry): This.
(elf_x86_64_plt_entry): Renamed to ...
(elf_x86_64_lazy_plt_entry): This.
(elf_x86_64_bnd_plt0_entry): Renamed to ...
(elf_x86_64_lazy_bnd_plt0_entry): This.
(elf_x86_64_legacy_plt_entry): Removed.
(elf_x86_64_bnd_plt_entry): Renamed to ...
(elf_x86_64_lazy_bnd_plt_entry): This.
(elf_x86_64_legacy_plt2_entry): Renamed to ...
(elf_x86_64_non_lazy_plt_entry): This.
(elf_x86_64_bnd_plt2_entry): Renamed to ...
(elf_x86_64_non_lazy_bnd_plt_entry): This.
(elf_x86_64_eh_frame_plt): Renamed to ...
(elf_x86_64_eh_frame_lazy_plt): This.
(elf_x86_64_eh_frame_bnd_plt): Renamed to ...
(elf_x86_64_eh_frame_lazy_bnd_plt): This.
(elf_x86_64_eh_frame_plt_got): Renamed to ...
(elf_x86_64_eh_frame_non_lazy_plt): This.
(elf_x86_64_lazy_plt_layout): New.
(elf_x86_64_non_lazy_plt_layout): Likewise.
(elf_x86_64_plt_layout): Likewise.
(elf_x86_64_backend_data): Remove PLT layout information. Add
os for target system.
(GET_PLT_ENTRY_SIZE): Removed.
(elf_x86_64_lazy_plt): New.
(elf_x86_64_non_lazy_plt): Likewise.
(elf_x86_64_lazy_bnd_plt): Likewise.
(elf_x86_64_non_lazy_bnd_plt): Likewise.
(elf_x86-64_arch_bed): Updated.
(elf_x86_64_link_hash_table): Add plt, lazy_plt and non_lazy_plt.
(elf_x86_64_create_dynamic_sections): Removed.
(elf_x86_64_check_relocs): Don't check elf.dynobj. Don't call
_bfd_elf_create_ifunc_sections nor _bfd_elf_create_got_section.
(elf_x86-64_adjust_dynamic_symbol): Updated.
(elf_x86_64_allocate_dynrelocs): Updated. Pass 0 as PLT header
size to _bfd_elf_allocate_ifunc_dyn_relocs and don't allocate
size for PLT0 if there is no PLT0. Get plt_entry_size from
non_lazy_plt for non-lazy PLT entries.
(elf_x86_64_size_dynamic_sections): Updated. Get plt_entry_size
from non_lazy_plt for non-lazy PLT entries.
(elf_x86-64_relocate_section): Updated. Properly get PLT index
if there is no PLT0.
(elf_x86_64_finish_dynamic_symbol): Updated. Fill the first slot
in the PLT entry with generic PLT layout. Fill the non-lazy PLT
entries with non-lazy PLT layout. Don't fill the second and third
slots in the PLT entry if there is no PLT0.
(elf_x86_64_finish_dynamic_sections): Updated. Don't fill PLT0
if there is no PLT0. Set sh_entsize on the .plt.got section.
(compare_relocs): New.
(elf_x86_64_plt_type): Likewise.
(elf_x86_64_plt): Likewise.
(elf_x86_64_nacl_plt): New. Forward declaration.
(elf_x86_64_get_plt_sym_val): Removed.
(elf_x86_64_get_synthetic_symtab): Rewrite to check PLT sections
against all dynamic relocations.
(elf_x86_64_link_setup_gnu_properties): New function.
(elf_backend_create_dynamic_sections): Updated.
(elf_backend_setup_gnu_properties): New.
(elf_x86_64_nacl_plt): New.
(elf_x86_64_nacl_arch_bed): Updated.
ld/
* testsuite/ld-ifunc/ifunc-16-x86-64-now.d: New file.
* testsuite/ld-ifunc/ifunc-2-local-x86-64-now.d: Likewise.
* testsuite/ld-ifunc/ifunc-2-x86-64-now.d: Likewise.
* testsuite/ld-ifunc/pr17154-x86-64-now.d: Likewise.
* testsuite/ld-x86-64/bnd-branch-1-now.d: Likewise.
* testsuite/ld-x86-64/bnd-ifunc-1-now.d: Likewise.
* testsuite/ld-x86-64/bnd-ifunc-2-now.d: Likewise.
* testsuite/ld-x86-64/bnd-plt-1-now.d: Likewise.
* testsuite/ld-x86-64/mpx3n.dd: Likewise.
* testsuite/ld-x86-64/mpx4n.dd: Likewise.
* testsuite/ld-x86-64/plt-main-bnd-now.rd: Likewise.
* testsuite/ld-x86-64/plt2.dd: Likewise.
* testsuite/ld-x86-64/plt2.rd: Likewise.
* testsuite/ld-x86-64/plt2.s: Likewise.
* testsuite/ld-x86-64/pr20830a-now.d: Likewise.
* testsuite/ld-x86-64/pr20830b-now.d: Likewise.
* testsuite/ld-x86-64/pr21038a-now.d: Likewise.
* testsuite/ld-x86-64/pr21038b-now.d: Likewise.
* testsuite/ld-x86-64/pr21038c-now.d: Likewise.
* testsuite/ld-x86-64/load1b-nacl.d: Updated.
* testsuite/ld-x86-64/load1b.d: Likewise.
* testsuite/ld-x86-64/plt-main-bnd.dd: Likewise.
* testsuite/ld-x86-64/pr20253-1h.d: Likewise.
* testsuite/ld-x86-64/pr20830a.d: Update the .plt.got section
with func@plt.
* testsuite/ld-x86-64/pr20830b.d: Likewise.
* testsuite/ld-x86-64/pr21038a.d: Likewise.
* testsuite/ld-x86-64/pr21038c.d: Likewise.
* testsuite/ld-x86-64/mpx.exp: Add some -z now tests.
* testsuite/ld-x86-64/x86-64.exp: Likewise.
On i386, the procedure linkage table (PLT) is used to
1. Call external function.
2. Call internal IFUNC function. The best implementation is selected
for the target processor at run-time.
3. Act as the canonical function address.
4. Support LD_AUDIT to audit external function calls.
5. Support LD_PROFILE to profile external function calls.
PLT looks like:
PLT0: push GOT[1]
jmp *GOT[2]
nop
PLT1: jmp *GOT[name1_index]
push name1_reloc_index
jmp PLT0
GOT is an array of addresses. Initially the GOT entry of name1 is
filled with the address of the "push name1_reloc_index" instruction.
The function, name1, is called via "jmp *GOT[name1]" in the PLT entry.
Even when lazy binding is disabled by "-z now", the PLT0 entry may
still be used with LD_AUDIT or LD_PROFILE if PLT entry is used for
canonical function address.
1. With lazy binding, when the external function, name1, is called the
first time, dynamic linker is called via PLT0 to update GOT[name1_index]
with the actual address of name1 and transfers control to name1
afterwards.
2. PLT is also used to call a local IFUNC function, name1, run-time
loader updates GOT[name1_index] when loading the module.
This patch
1. Remove PLT layout configurations from i386 backend_data.
2. Add generic, lay and non-lazy PLT layout configurations to i386
link_hash_table. Generic PLT layout includes the PLT entry templates,
information how to update the first instruction in PLT and PLT eh_frame
informaton, which are initialized in i386 setup_gnu_properties, based
on PIC and target selection. PLT section alignment is also set to PLT
entry size for non-NaCl/VxWorks target.
3. Remove elf_i386_create_dynamic_sections. create_dynamic_sections
isn't always called, but GOT relocations need GOT relocations. Instead,
create all i386 specific dynamic sections in i386 setup_gnu_properties,
which initializes elf.dynobj, so that i386 check_relocs can be simplified.
4. Rewrite elf_i386_get_synthetic_symtab to check PLT sections against
all dynamic relocations to support both lazy and non-lazy PLTs.
bfd/
* elf32-i386.c (PLT_ENTRY_SIZE): Renamed to ...
(LAZY_PLT_ENTRY_SIZE): This.
(NON_LAZY_PLT_ENTRY_SIZE): New.
(elf_i386_plt0_entry): Renamed to ...
(elf_i386_lazy_plt0_entry): This.
(elf_i386_plt_entry): Renamed to ...
(elf_i386_lazy_plt_entry): This.
(elf_i386_pic_plt0_entry): Renamed to ...
(elf_i386_pic_lazy_plt0_entry): This.
(elf_i386_pic_plt_entry): Renamed to ...
(elf_i386_pic_lazy_plt_entry): This.
(elf_i386_got_plt_entry): Renamed to ...
(elf_i386_non_lazy_plt_entry): This.
(elf_i386_pic_got_plt_entry): Renamed to ...
(elf_i386_pic_non_lazy_plt_entry): This.
(elf_i386_eh_frame_plt): Renamed to ...
(elf_i386_eh_frame_lazy_plt): This.
(elf_i386_eh_frame_plt_got): Renamed to ...
(elf_i386_eh_frame_non_lazy_plt): This.
(elf_i386_plt_layout): Renamed to ...
(elf_i386_lazy_plt_layout): This. Remove eh_frame_plt_got and
eh_frame_plt_got_size.
(elf_i386_non_lazy_plt_layout): New.
(elf_i386_plt_layout): Likewise.
(elf_i386_non_lazy_plt): Likewise.
(GET_PLT_ENTRY_SIZE): Removed.
(elf_i386_plt): Renamed to ...
(elf_i386_lazy_plt): This.
(elf_i386_backend_data): Remove plt. Rename is_vxworks to os.
(elf_i386_arch_bed): Updated.
(elf_i386_link_hash_table): Add plt, lazy_plt and non_lazy_plt.
(elf_i386_create_dynamic_sections): Removed.
(elf_i386_check_relocs): Don't check elf.dynobj. Don't call
_bfd_elf_create_ifunc_sections nor _bfd_elf_create_got_section.
(elf_i386_adjust_dynamic_symbol): Updated.
(elf_i386_allocate_dynrelocs): Updated. Pass 0 as PLT header
size to _bfd_elf_allocate_ifunc_dyn_relocs and don't allocate
size for PLT0 if there is no PLT0.
(elf_i386_size_dynamic_sections): Updated. Check whether GOT
output section is discarded only if GOT isn't empty.
(elf_i386_relocate_section): Updated. Properly get PLT index
if there is no PLT0.
(elf_i386_finish_dynamic_symbol): Updated. Don't fill the
second and third slots in the PLT entry if there is no PLT0.
(elf_i386_finish_dynamic_sections): Updated. Don't fill PLT0
if there is no PLT0. Set sh_entsize on the .plt.got section.
(elf_i386_nacl_plt): Forward declaration.
(elf_i386_get_plt_sym_val): Removed.
(elf_i386_get_synthetic_symtab): Rewrite to check PLT sections
against all dynamic relocations.
(elf_i386_link_setup_gnu_properties): New function.
(elf_backend_create_dynamic_sections): Updated.
(elf_backend_setup_gnu_properties): New.
(elf_i386_nacl_plt): Updated.
(elf_i386_nacl_arch_bed): Likewise.
(elf_i386_vxworks_arch_bed): Likewise.
ld/
* testsuite/ld-i386/i386.exp: Add some -z now tests.
* testsuite/ld-i386/plt-pic2.dd: New file.
* testsuite/ld-i386/plt2.dd: Likewise.
* testsuite/ld-i386/plt2.rd: Likewise.
* testsuite/ld-i386/plt2.s: Likewise.
* testsuite/ld-ifunc/ifunc-16-i386-now.d: Likewise.
* testsuite/ld-ifunc/ifunc-2-i386-now.d: Likewise.
* testsuite/ld-ifunc/ifunc-2-local-i386-now.d: Likewise.
* testsuite/ld-ifunc/pr17154-i386-now.d: Likewise.
* testsuite/ld-i386/pr20830.d: Update the .plt.got section
with func@plt.
For ELF targets --out-implib currently generates an executable file
(e_type is ET_EXEC) despite the file being expected to be linked against
some other object file to make an executable later. It seems therefore
more sensible to make the import library a relocatable object file
(e_type set to ET_REL).
Incidentally, as dicted by requirement 8 of
"ARM v8-M Security Extensions: Requirements on Development Tools"
(document ARM-ECM-0359818) version 1.0, import libraries generated when
using --cmse-implib *must* be relocatable object file so this commit
also adds an assert there in case the type of ELF import library is
changed again in the future.
2017-05-08 Thomas Preud'homme <thomas.preudhomme@arm.com>
bfd/
* elflink.c (elf_output_implib): Remove executable flag from import
library bfd.
* elf32-arm.c (elf32_arm_filter_implib_symbols): Assert that the import
library is a relocatable object file.
ld/
* testsuite/ld-arm/arm-elf.exp
(Secure gateway import library generation): Check e_type field
of import library and executable produced.
* testsuite/ld-arm/cmse-implib.type: Expectations for e_type field.
Fix a host of problems related to adjustment of
symbol values and sizes when relaxing for avr.
1. Adjust symbol size first before adjusting symbol
value. Otherwise, a symbol whose value just got adjusted to the
relaxed address also ends up getting resized. See pr21404-1.s.
2. Reduce symbol sizes only if their span is below an
alignment boundary. Otherwise, the size gets decremented once when the
actual instruction is relaxed and padding bytes are added, and again
when the padding bytes are deleted (if padding ends up being unnecessary).
pr21404-2.s addresses that, and this bug is really the root cause of PR21404.
3. Adjust all symbol values before an alignment boundary.
Previous code did not adjust symbol values if they fell in the
would-be padded area, resulting in incorrect symbol values in some
cases (see pr21404-3.s).
4. Increase symbol sizes if alignment directives require so.
As pr21404-4.s shows
.global nonzero_sym
L1:
jmp L1
nonzero_sym:
nop
nop
.p2align 2
.size nonzero_sym, .-nonzero_sym
The two nops satisfy the 4 byte alignment at assembly time and
therefore the size of nonzero_sym is 4. Relaxation shortens
the 4 byte jmp to a 2 byte rjmp, and to satisfy 4 byte alignment
the code places 2 extra padding bytes after the nops, increasing
nonzero_sym's size by 2. This wasn't handled before.
If the assembly code does not have any align directives, then the
boundary is the section size, and symbol values and sizes == boundary
should also get adjusted. To handle that case, add a did_pad variable
and use that to determine whether it should use < boundary or <= boundary.
Also get rid of reloc_toaddr, which is now redundant. toaddr is now not
adjusted to handle the above case - the newly added
did_pad variable does the job.
pr21404-{5,6,7,8} are the same testcases written for local symbols, as
the code handles them slightly differently.
