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binutils-gdb/ld/ChangeLog
H.J. Lu 0ff2b86e7c Create the second PLT for BND relocations 
Intel MPX introduces 4 bound registers, which will be used for parameter
passing in x86-64.  Bound registers are cleared by branch instructions.
Branch instructions with BND prefix will keep bound register contents.
This leads to 2 requirements to 64-bit MPX run-time:

1. Dynamic linker (ld.so) should save and restore bound registers during
symbol lookup.
2. Change the current 16-byte PLT0:

  ff 35 08 00 00 00	pushq  GOT+8(%rip)
  ff 25 00 10 00	jmpq  *GOT+16(%rip)
  0f 1f 40 00		nopl   0x0(%rax)

and 16-byte PLT1:

  ff 25 00 00 00 00    	jmpq   *name@GOTPCREL(%rip)
  68 00 00 00 00       	pushq  $index
  e9 00 00 00 00       	jmpq   PLT0

which clear bound registers, to preserve bound registers.

We use 2 new relocations:

to mark branch instructions with BND prefix.

When linker sees any R_X86_64_PC32_BND or R_X86_64_PLT32_BND relocations,
it switches to a different PLT0:

  ff 35 08 00 00 00	pushq  GOT+8(%rip)
  f2 ff 25 00 10 00	bnd jmpq *GOT+16(%rip)
  0f 1f 00		nopl   (%rax)

to preserve bound registers for symbol lookup and it also creates an
external PLT section, .pl.bnd.  Linker will create a BND PLT1 entry
in .plt:

  68 00 00 00 00       	pushq  $index
  f2 e9 00 00 00 00     bnd jmpq PLT0
  0f 1f 44 00 00        nopl 0(%rax,%rax,1)

and a 8-byte BND PLT entry in .plt.bnd:

  f2 ff 25 00 00 00 00  bnd jmpq *name@GOTPCREL(%rip)
  90			nop

Otherwise, linker will create a legacy PLT1 entry in .plt:

  68 00 00 00 00       	pushq  $index
  e9 00 00 00 00        jmpq PLT0
  66 0f 1f 44 00 00     nopw 0(%rax,%rax,1)

and a 8-byte legacy PLT in .plt.bnd:

  ff 25 00 00 00 00     jmpq  *name@GOTPCREL(%rip)
  66 90                 xchg  %ax,%ax

The initial value of the GOT entry for "name" will be set to the the
"pushq" instruction in the corresponding entry in .plt.  Linker will
resolve reference of symbol "name" to the entry in the second PLT,
.plt.bnd.

Prelink stores the offset of pushq of PLT1 (plt_base + 0x10) in GOT[1]
and GOT[1] is stored in GOT[3].  We can undo prelink in GOT by computing
the corresponding the pushq offset with

GOT[1] + (GOT offset - &GOT[3]) * 2

Since for each entry in .plt except for PLT0 we create a 8-byte entry in
.plt.bnd, there is extra 8-byte per PLT symbol.

We also investigated the 16-byte entry for .plt.bnd.  We compared the
8-byte entry vs the the 16-byte entry for .plt.bnd on Sandy Bridge.
There are no performance differences in SPEC CPU 2000/2006 as well as
micro benchmarks.

Pros:
	No change to undo prelink in dynamic linker.
	Only 8-byte memory overhead for each PLT symbol.
Cons:
	Extra .plt.bnd section is needed.
	Extra 8 byte for legacy branches to PLT.
	GDB is unware of the new layout of .plt and .plt.bnd.

bfd/

	* elf64-x86-64.c (elf_x86_64_bnd_plt0_entry): New.
	(elf_x86_64_legacy_plt_entry): Likewise.
	(elf_x86_64_bnd_plt_entry): Likewise.
	(elf_x86_64_legacy_plt2_entry): Likewise.
	(elf_x86_64_bnd_plt2_entry): Likewise.
	(elf_x86_64_bnd_arch_bed): Likewise.
	(elf_x86_64_link_hash_entry): Add has_bnd_reloc and plt_bnd.
	(elf_x86_64_link_hash_table): Add plt_bnd.
	(elf_x86_64_link_hash_newfunc): Initialize has_bnd_reloc and
	plt_bnd.
	(elf_x86_64_copy_indirect_symbol): Also copy has_bnd_reloc.
	(elf_x86_64_check_relocs): Create the second PLT for Intel MPX
	in 64-bit mode.
	(elf_x86_64_allocate_dynrelocs): Handle the second PLT for IFUNC
	symbols.  Resolve call to the second PLT if it is created.
	(elf_x86_64_size_dynamic_sections): Keep the second PLT section.
	(elf_x86_64_relocate_section): Resolve PLT references to the
	second PLT if it is created.
	(elf_x86_64_finish_dynamic_symbol): Use BND PLT0 and fill the
	second PLT entry for BND relocation.
	(elf_x86_64_finish_dynamic_sections): Use MPX backend data if
	the second PLT is created.
	(elf_x86_64_get_synthetic_symtab): New.
	(bfd_elf64_get_synthetic_symtab): Likewise.  Undefine for NaCl.

ld/

	* emulparams/elf_x86_64.sh (TINY_READONLY_SECTION): New.

ld/testsuite/

	* ld-x86-64/mpx.exp: Run bnd-ifunc-1 and bnd-plt-1.
	* ld-x86-64/bnd-ifunc-1.d: New file.
	* ld-x86-64/bnd-ifunc-1.s: Likewise.
	* ld-x86-64/bnd-plt-1.d: Likewise.
2014-02-19 11:48:23 -08:00

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2014-02-19 Igor Zamyatin <igor.zamyatin@intel.com>
H.J. Lu <hongjiu.lu@intel.com>
* emulparams/elf_x86_64.sh (TINY_READONLY_SECTION): New.
2014-02-19 Alan Modra <amodra@gmail.com>
* emultempl/ppc64elf.em (params): Init new field.
(ppc_create_output_section_statements): Set params.save_restore_funcs
default.
(PARSE_AND_LIST_*): Add support for --save-restore-funcs and
--no-save-restore-funcs.
2014-02-17 Alan Modra <amodra@gmail.com>
* emultemps/ppc64elf.em (params): New static struct replacing
various other static vars. Adjust code throughout file.
2014-02-17 Alan Modra <amodra@gmail.com>
* emultempl/ppc32elf.em (ppc_after_open_output): Really enable
ppc476 workaround for ld -r.
2014-02-12 Alan Modra <amodra@gmail.com>
* emultempl/ppc32elf.em (pagesize): New static var.
(ppc_after_open_output): Set params.pagesize_p2 from pagesize.
(PARSE_AND_LIST_ARGS_CASES): Adjust to use pagesize.
2014-02-11 Andrew Pinski <apinski@cavium.com>
* emulparams/aarch64linux32.sh (LIBPATH_SUFFIX): Change to ilp32.
(ELF_INTERPRETER_NAME): Define.
* emulparams/aarch64linux32b.sh (ELF_INTERPRETER_NAME): Define.
2014-02-10 Alan Modra <amodra@gmail.com>
* po/ld.pot: Regenerate.
2014-02-03 Alan Modra <amodra@gmail.com>
* emultempl/ppc32elf.em (no_tls_get_addr_opt, emit_stub_syms)
plt_style): Delete. Adjust all refs to instead use..
(params): ..this. New variable.
(ppc_after_open_output): New function. Tweak params and pass to
ppc_elf_link_params.
(ppc_after_open): Adjust ppc_elf_select_plt_layout call.
(ppc_before_allocation): Adjust ppc_elf_tls_setup call. Enable
relaxation for ppc476 workaround.
(PARSE_AND_LIST_*): Add --{no-,}ppc476-workaround support.
(LDEMUL_CREATE_OUTPUT_SECTION_STATEMENTS): Define.
2014-02-02 Sebastian Huber <sebastian.huber@embedded-brains.de>
* ld/ld.texinfo: Change ALIGN_WITH_INPUT documentation.
* ld/ldlang.c (lang_size_sections_1): Add dotdelta
variable which reflects the VMA change due to alignment
requirements. Use dotdelta do change the LMA if
ALIGN_WITH_INPUT is requested.
2014-02-01 Hans-Peter Nilsson <hp@bitrange.com>
* emultempl/mmix-elfnmmo.em (mmix_after_allocation): Fix typo in
call to bfd_set_section_vma exposed by recent bfd_set_section_vma
change.
2014-01-30 Sandra Loosemore <sandra@codesourcery.com>
* Makefile.am (enios2elf.c, enios2linux.c): Update dependencies.
* Makefile.in: Regenerated.
* emulparams/nios2elf.sh (EXTRA_EM_FILE): Set.
* emulparams/nios2linux.sh (EXTRA_EM_FILE): Set.
* emultempl/nios2elf.em: New file.
* gen-doc.texi (NIOSII): Set.
* ld.texinfo (NIOSII): Set.
2014-01-28 Nick Clifton <nickc@redhat.com>
* Makefile.am: Remove obsolete MSP430 emulations.
* configure.tgt: Likewise.
* emulparams/msp430all.sh: Likewise.
* Makefile.in: Regenerate.
2014-01-24 H.J. Lu <hongjiu.lu@intel.com>
PR ld/16498
* emultempl/elf32.em (gld${EMULATION_NAME}_place_orphan): Improve
orphaned TLS section handling.
2014-01-24 Alan Modra <amodra@gmail.com>
* ldlang.c (lang_output_section_find_by_flags): Be careful to
test look->bfd_section->flags if available rather than
look->flags. Separate SEC_THREAD_LOCAL handling from
SEC_READONLY loop, and rewrite.
2014-01-22 Alan Modra <amodra@gmail.com>
* ldlang.c (asneeded_list_head, asneeded_list_tail): New vars.
(lang_init): Initialise them.
(lang_print_asneeded): New function.
(lang_process): Call lang_print_asneeded.
* ldlang.h (struct asneeded_minfo): New.
(asneeded_list_tail): Declare.
* ldmain.c (add_archive_element): Improve archive map heading.
* ldmisc.c (minfo): Stash --as-needed info.
2014-01-22 Alan Modra <amodra@gmail.com>
* ld.h (struct map_symbol_def): Move to..
* ldlang.h: ..here.
* ldlang.c (print_assignment): Don't set expld.assign_name to dot.
2014-01-22 Alan Modra <amodra@gmail.com>
* ld.texinfo (Output Section Discarding): Mention assigning to dot
as a way of keeping otherwise empty sections.
* ldexp.c (is_dot, is_value, is_sym_value, is_dot_ne_0,
is_dot_plus_0, is_align_conditional): New predicates.
(exp_fold_tree_1): Set SEC_KEEP when assigning to dot inside an
output section, except for some special cases.
* scripttempl/elfmicroblaze.sc: Use canonical form to align at
end of .heap and .stack.
2014-01-20 Marcus Shawcroft <marcus.shawcroft@arm.com>
* emulparams/aarch64linuxb.sh (ELF_INTERPRETER_NAME): Define.
2014-01-20 Marcus Shawcroft <marcus.shawcroft@arm.com>
* emulparams/aarch64linux.sh (ELF_INTERPRETER_NAME): Define.
2014-01-20 Alan Modra <amodra@gmail.com>
* ldlang.h (struct lang_definedness_hash_entry): Add by_object and
by_script. Make iteration a single bit field.
(lang_track_definedness, lang_symbol_definition_iteration): Delete.
(lang_symbol_defined): Declare.
* ldlang.c (lang_statement_iteration): Expand comment a little.
(lang_init <lang_definedness_table>): Make it bigger.
(lang_track_definedness, lang_symbol_definition): Delete.
(lang_definedness_newfunc): Update.
(lang_symbol_defined): New function.
(lang_update_definedness): Create entries here. Do track whether
script definition of symbol is valid, even when also defined in
an object file.
* ldexp.c (fold_name <DEFINED>): Update.
(fold_name <NAME>): Allow self-assignment for absolute symbols
defined in a linker script.
2014-01-20 Guy Martin <gmsoft@tuxicoman.be>
Alan Modra <amodra@gmail.com>
* 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.
2014-01-17 Alan Modra <amodra@gmail.com>
* genscripts.sh (COMPILE_IN): Don't set if already set.
* emulparams/nds32elf.sh: Don't clear EMULATION_LIBPATH, set
COMPILE_IN=no.
* emulparams/nds32elf16m.sh: Likewise.
* emulparams/nds32elf_linux.sh: Likewise.
* emultempl/aix.em: Test COMPILE_IN value is "yes".
* emultempl/armcoff.em: Likewise.
* emultempl/elf32.em: Likewise.
* emultempl/generic.em: Likewise.
* emultempl/gld960.em: Likewise.
* emultempl/gld960c.em: Likewise.
* emultempl/linux.em: Likewise.
* emultempl/lnk960.em: Likewise.
* emultempl/m68kcoff.em: Likewise.
* emultempl/sunos.em: Likewise.
* emultempl/ticoff.em: Likewise.
2014-01-16 H.J. Lu <hongjiu.lu@intel.com>
PR ld/16456
* genscripts.sh: Don't search directory with LIBPATH_SUFFIX_SKIP
suffix.
* emulparams/elf32_x86_64.sh (LIBPATH_SUFFIX_SKIP): Set to 64
for elf32_x86_64 emulation.
* emulparams/elf_i386.sh (LIBPATH_SUFFIX_SKIP): Set to 64
for elf_i386 emulation.
2014-01-16 Alan Modra <amodra@gmail.com>
* ld.h (fat_section_userdata_type, get_userdata): Move to..
* ldlang.h (input_section_userdata_type, get_userdata): ..here.
* ldlang.c (init_map_userdata): Delete. Fold into..
(sort_def_symbol): ..here. Don't attach input section userdata
to output sections or global bfd sections.
(lang_map): Don't pre-allocate input section userdata.
(init_os): Don't allocate userdata for output sections.
(print_all_symbols): Update.
2014-01-15 H.J. Lu <hongjiu.lu@intel.com>
* emultempl/elf32.em (gld${EMULATION_NAME}_before_allocation):
Silence uninitialized warning on ehdr_start_save with older
GCC.
2014-01-15 Alan Modra <amodra@gmail.com>
* emultempl/elf32.em (gld${EMULATION_NAME}_before_allocation): Define
__ehdr_start before size_dynamic_sections and restore afterwards.
2014-01-10 Alan Modra <amodra@gmail.com>
PR ld/14207
PR ld/16322
PR binutils/16323
* ldlang.c (lang_size_sections): Remove unneeded RELRO base
adjust. Tidy comments.
* ld.texinfo (DATA_SEGMENT_RELRO_END): Correct description.
2014-01-10 Hans-Peter Nilsson <hp@axis.com>
* emulparams/crislinux.sh (COMMONPAGESIZE): Define.
2014-01-08 H.J. Lu <hongjiu.lu@intel.com>
PR ld/14207
PR ld/16322
PR binutils/16323
* ldlang.c (lang_size_sections): Properly align RELRO base.
2014-01-08 H.J. Lu <hongjiu.lu@intel.com>
* ldver.c (ldversion): Update copyright year to 2014.
For older changes see ChangeLog-2013
Copyright (C) 2014 Free Software Foundation, Inc.
Copying and distribution of this file, with or without modification,
are permitted in any medium without royalty provided the copyright
notice and this notice are preserved.
Local Variables:
mode: change-log
left-margin: 8
fill-column: 74
version-control: never
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