binutils-gdb modified for the FreeChainXenon project
Find a file
H.J. Lu 38b123494b x86-64: Improve PLT generation and synthetic PLT symbols
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.
2017-05-08 12:24:29 -07:00
bfd x86-64: Improve PLT generation and synthetic PLT symbols 2017-05-08 12:24:29 -07:00
binutils Cast relcount to unsigned long when comparing with sec->reloc_count 2017-05-02 12:16:26 -07:00
config picflag.m4 high bit set in comment 2017-01-05 00:02:57 +10:30
cpu Update the openrisc previous program counter (ppc) when running code in the cgen based simulator. 2017-03-20 15:33:51 +00:00
elfcpp Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
etc update-copyright.py for binutils 2017-01-05 00:03:07 +10:30
gas MIPS16/GAS: Relax 32-bit non-PIC PC-relative synthetic instructions 2017-05-03 20:47:40 +01:00
gdb Remove some uses of MAX_REGISTER_SIZE from mips-tdep.c 2017-05-08 09:40:07 +01:00
gold [GOLD] testsuite/plugin_section_order.c fix 2017-04-27 11:54:29 +09:30
gprof Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
include Handle symbol defined in IR and referenced in DSO 2017-04-20 07:48:35 -07:00
intl Regen intl/configure 2015-08-31 12:53:36 +09:30
ld x86-64: Improve PLT generation and synthetic PLT symbols 2017-05-08 12:24:29 -07:00
libdecnumber Remove leading/trailing white spaces in ChangeLog 2015-07-24 04:16:47 -07:00
libiberty cplus_demangle_fill_component: Handle DEMANGLE_COMPONENT_RVALUE_REFERENCE 2017-03-27 14:18:41 +01:00
opcodes RISC-V: Fix disassemble for c.li, c.andi and c.addiw 2017-05-04 03:20:30 -07:00
readline Improve MinGW support in Readline 2016-09-17 11:50:37 +03:00
sim Fix ldn/stn multiple instructions. Fix testcases with unaligned data. 2017-04-22 16:36:01 -07:00
texinfo
zlib Sync ZLIB with FSF GCC sources, bringing in version 1.2.11. 2017-02-20 12:52:22 +00:00
.cvsignore
.gitattributes Add a .gitattributes file for use with git-merge-changelog 2014-07-25 18:07:23 -04:00
.gitignore Add archives and make stamps to the .gitignore file. 2016-09-27 15:10:42 +01:00
ChangeLog * config.sub: Sync with master version in config project. 2017-04-13 02:34:19 -07:00
compile Update from upstream Automake 2014-11-16 13:43:48 +01:00
config-ml.in Sync toplevel files with GCC 2015-07-27 07:49:05 -07:00
config.guess Sync top level config files with master versions in the FSF config project. 2017-03-22 14:01:03 +00:00
config.rpath
config.sub * config.sub: Sync with master version in config project. 2017-04-13 02:34:19 -07:00
configure Sync top-level make and configure files with FSF GCC mainline versions. 2017-01-23 11:55:48 +00:00
configure.ac Sync top-level make and configure files with FSF GCC mainline versions. 2017-01-23 11:55:48 +00:00
COPYING
COPYING.LIB
COPYING.LIBGLOSS
COPYING.NEWLIB
COPYING3
COPYING3.LIB
depcomp Update from upstream Automake 2014-11-16 13:43:48 +01:00
djunpack.bat
install-sh Update from upstream Automake 2014-11-16 13:43:48 +01:00
libtool.m4 Sync top-level btool.m4 with GCC 2016-01-12 08:44:52 -08:00
ltgcc.m4
ltmain.sh
ltoptions.m4
ltsugar.m4
ltversion.m4
lt~obsolete.m4
MAINTAINERS Update description of ownership of files in include/ 2014-11-04 16:14:14 -08:00
Makefile.def Sync top-level make and configure files with FSF GCC mainline versions. 2017-01-23 11:55:48 +00:00
Makefile.in Sync top-level make and configure files with FSF GCC mainline versions. 2017-01-23 11:55:48 +00:00
Makefile.tpl Sync top-level make and configure files with FSF GCC mainline versions. 2017-01-23 11:55:48 +00:00
makefile.vms
missing Update from upstream Automake 2014-11-16 13:43:48 +01:00
mkdep
mkinstalldirs Update from upstream Automake 2014-11-16 13:43:48 +01:00
move-if-change Update `move-if-change' from gnulib 2014-11-16 17:04:02 +01:00
README
README-maintainer-mode
setup.com
src-release.sh fix gdb version parsing in src-release.sh 2016-01-17 10:01:55 +04:00
symlink-tree
ylwrap Update from upstream Automake 2014-11-16 13:43:48 +01:00

		   README for GNU development tools

This directory contains various GNU compilers, assemblers, linkers, 
debuggers, etc., plus their support routines, definitions, and documentation.

If you are receiving this as part of a GDB release, see the file gdb/README.
If with a binutils release, see binutils/README;  if with a libg++ release,
see libg++/README, etc.  That'll give you info about this
package -- supported targets, how to use it, how to report bugs, etc.

It is now possible to automatically configure and build a variety of
tools with one command.  To build all of the tools contained herein,
run the ``configure'' script here, e.g.:

	./configure 
	make

To install them (by default in /usr/local/bin, /usr/local/lib, etc),
then do:
	make install

(If the configure script can't determine your type of computer, give it
the name as an argument, for instance ``./configure sun4''.  You can
use the script ``config.sub'' to test whether a name is recognized; if
it is, config.sub translates it to a triplet specifying CPU, vendor,
and OS.)

If you have more than one compiler on your system, it is often best to
explicitly set CC in the environment before running configure, and to
also set CC when running make.  For example (assuming sh/bash/ksh):

	CC=gcc ./configure
	make

A similar example using csh:

	setenv CC gcc
	./configure
	make

Much of the code and documentation enclosed is copyright by
the Free Software Foundation, Inc.  See the file COPYING or
COPYING.LIB in the various directories, for a description of the
GNU General Public License terms under which you can copy the files.

REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info
on where and how to report problems.