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H.J. Lu dd7e64d45b Optimize out i386/x86-64 JUMP_SLOT relocation
When there are both PLT and GOT references to the same function symbol,
linker will create a GOTPLT slot for PLT entry and a GOT slot for GOT
reference.  A run-time JUMP_SLOT relocation is created to update the
GOTPLT slot and a run-time GLOB_DAT relocation is created to update the
GOT slot.  Both JUMP_SLOT and GLOB_DAT relocations will apply the same
symbol value to GOTPLT and GOT slots, respectively, at run-time.

This optimization combines GOTPLT and GOT slots into a single GOT slot
and removes the run-time JUMP_SLOT relocation.  It replaces the regular
PLT entry:

	indirect jump	[GOTPLT slot]
	push		relocation index
	jump		PLT0

with an GOT PLT entry with an indirect jump via the GOT slot:

	indirect jump	[GOT slot]
	nop

and resolves PLT reference to the GOT PLT entry.

We must avoid this optimization if pointer equality is needed since
we don't clear symbol value in this case and the dynamic linker won't
update the GOT slot.  Otherwise, the resulting binary will get into an
infinite loop at run-time.

bfd/

	* elf32-i386.c (elf_i386_got_plt_entry): New.
	(elf_i386_pic_got_plt_entry): Likewise.
	(elf_i386_link_hash_entry): Add plt_got.
	(elf_i386_link_hash_table): Likewise.
	(elf_i386_link_hash_newfunc): Initialize plt_got.offset to -1.
	(elf_i386_get_local_sym_hash): Likewise.
	(elf_i386_check_relocs): Create the GOT PLT if there are both
	PLT and GOT references when the regular PLT is used.
	(elf_i386_allocate_dynrelocs): Use the GOT PLT if there are
	both PLT and GOT references unless pointer equality is needed.
	(elf_i386_relocate_section): Also check the GOT PLT when
	resolving R_386_PLT32.
	(elf_i386_finish_dynamic_symbol): Use the GOT PLT if it is
	available.

	* elf64-x86-64.c (elf_x86_64_link_hash_entry): Add plt_got.
	(elf_x86_64_link_hash_table): Likewise.
	(elf_x86_64_link_hash_newfunc): Initialize plt_got.offset to -1.
	(elf_x86_64_get_local_sym_hash): Likewise.
	(elf_x86_64_check_relocs): Create the GOT PLT if there are both
	PLT and GOT references when the regular PLT is used.
	(elf_x86_64_allocate_dynrelocs): Use the GOT PLT if there are
	both PLT and GOT references unless pointer equality is needed.
	(elf_x86_64_relocate_section): Also check the GOT PLT when
	resolving R_X86_64_PLT32.
	(elf_x86_64_finish_dynamic_symbol): Use the GOT PLT if it is
	available.

ld/

	* emulparams/elf_i386.sh (TINY_READONLY_SECTION): New.
	* emulparams/elf_x86_64.sh (TINY_READONLY_SECTION): Add .plt.got.

ld/testsuite/

	* ld-i386/i386.exp: Add run-time relocation tests for plt-main.
	* ld-i386/plt-main.rd: New file.
	* ld-x86-64/plt-main-bnd.dd: Likewise.
	* ld-x86-64/plt-main.rd: Likewise.
	* ld-x86-64/x86-64.exp: Add run-time relocation tests for
	plt-main.
2014-11-25 05:05:39 -08:00
bfd Optimize out i386/x86-64 JUMP_SLOT relocation 2014-11-25 05:05:39 -08:00
binutils Update libtool.m4 from GCC trunk 2014-11-24 09:14:09 -08:00
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ChangeLog Update libtool.m4 from GCC trunk 2014-11-24 09:14:09 -08:00
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		   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.