binutils-gdb/ld
H.J. Lu bae420ef26 Optimize x86 GOT32X/GOTPCRELX relocations
R_386_GOT32X, R_X86_64_GOTPCRELX and R_X86_64_REX_GOTPCRELX relocations
retrieve the symbol address via its GOT slot.  If the symbol address is
known at the link-time, we can use it directly by changing instruction
encoding.  Indirect branch can only be converted to PC relative direct
branch.  MOV can be changed to LEA or encoded differently with signed
address.  The subset of binary operations can be encoded only with
signed address.

If undefined weak symbol is resolved to zero link-time, we can use it
as address.  Zero addresss can't used with PC relative direct branch
when PIC is true since the current PC is unknown.  In 64-bit, 32-bit
relocation for PC relatiave direct branch to zero may also overflow.

If this optimization causes relocation overflow, --no-relax can be used
to work around it.

bfd/

	PR ld/19609
	* elf32-i386.c (elf_i386_convert_load): Convert to R_386_32 for
	load with locally bound symbols if PIC is false or there is no
	base register.  Optimize branch to 0 if PIC is false.
	(elf_i386_relocate_section): Don't generate dynamic relocations
	against undefined weak symbols if PIC is false.
	* elf64-x86-64.c (elf_x86_64_convert_load): Disable optimization
	if we can't estimate relocation overflow with --no-relax.
	Convert to R_X86_64_32S/R_X86_64_32 for load with locally bound
	symbols if PIC is false.  Optimize branch to 0 if PIC is false.
	(elf_x86_64_relocate_section): Don't generate dynamic relocations
	against undefined weak symbols if PIC is false.

ld/

	PR ld/19609
	* testsuite/ld-i386/got1.dd: Updated.
	* testsuite/ld-i386/lea1c.d: Likewise.
	* testsuite/ld-i386/load1-nacl.d: Likewise.
	* testsuite/ld-i386/load1.d: Likewise.
	* testsuite/ld-i386/load4b.d: Likewise.
	* testsuite/ld-i386/load5b.d: Likewise.
	* testsuite/ld-i386/mov1b.d: Likewise.
	* testsuite/ld-x86-64/mov1b.d: Likewise.
	* testsuite/ld-x86-64/mov1d.d: Likewise.
	* testsuite/ld-ifunc/ifunc-21-i386.d: Likewise.
	* testsuite/ld-ifunc/ifunc-21-x86-64.d: Likewise.
	* testsuite/ld-ifunc/ifunc-22-i386.d: Likewise.
	* testsuite/ld-ifunc/ifunc-22-x86-64.d: Likewise.
	* testsuite/ld-x86-64/gotpcrel1.dd: Likewise.
	* testsuite/ld-x86-64/lea1a.d: Likewise.
	* testsuite/ld-x86-64/lea1b.d: Likewise.
	* testsuite/ld-x86-64/lea1c.d: Likewise.
	* testsuite/ld-x86-64/lea1d.d: Likewise.
	* testsuite/ld-x86-64/lea1e.d: Likewise.
	* testsuite/ld-x86-64/lea1f.d: Likewise.
	* testsuite/ld-x86-64/mov1b.d: Likewise.
	* testsuite/ld-x86-64/mov1d.d: Likewise.
	* testsuite/ld-x86-64/pr13082-3b.d: Likewise.
	* testsuite/ld-x86-64/pr13082-4b.d: Likewise.
	* testsuite/ld-x86-64/lea1.s: Add tests for 32-bit registers.
	* testsuite/ld-i386/pr19609-1.s: New file.
	* testsuite/ld-i386/pr19609-1a.d: Likewise.
	* testsuite/ld-i386/pr19609-1b.d: Likewise.
	* testsuite/ld-i386/pr19609-1c.d: Likewise.
	* testsuite/ld-i386/pr19609-1d.d: Likewise.
	* testsuite/ld-i386/pr19609-1e.d: Likewise.
	* testsuite/ld-i386/pr19609-1f.d: Likewise.
	* testsuite/ld-i386/pr19609-1g.d: Likewise.
	* testsuite/ld-i386/pr19609-1h.d: Likewise.
	* testsuite/ld-i386/pr19609-1i.d: Likewise.
	* testsuite/ld-i386/pr19609-2.s: Likewise.
	* testsuite/ld-i386/pr19609-2a.d: Likewise.
	* testsuite/ld-i386/pr19609-2b.d: Likewise.
	* testsuite/ld-i386/pr19609-2c.d: Likewise.
	* testsuite/ld-i386/undefweak.s: Likewise.
	* testsuite/ld-i386/undefweaka.d: Likewise.
	* testsuite/ld-i386/undefweakb.d: Likewise.
	* testsuite/ld-x86-64/pr13082-3c.d: Likewise.
	* testsuite/ld-x86-64/pr13082-3d.d: Likewise.
	* testsuite/ld-x86-64/pr19609-1.s: Likewise.
	* testsuite/ld-x86-64/pr19609-1a.d: Likewise.
	* testsuite/ld-x86-64/pr19609-1b.d: Likewise.
	* testsuite/ld-x86-64/pr19609-1c.d: Likewise.
	* testsuite/ld-x86-64/pr19609-1d.d: Likewise.
	* testsuite/ld-x86-64/pr19609-1e.d: Likewise.
	* testsuite/ld-x86-64/pr19609-1f.d: Likewise.
	* testsuite/ld-x86-64/pr19609-1g.d: Likewise.
	* testsuite/ld-x86-64/pr19609-1h.d: Likewise.
	* testsuite/ld-x86-64/pr19609-1i.d: Likewise.
	* testsuite/ld-x86-64/pr19609-1j.d: Likewise.
	* testsuite/ld-x86-64/pr19609-1k.d: Likewise.
	* testsuite/ld-x86-64/pr19609-1l.d: Likewise.
	* testsuite/ld-x86-64/pr19609-1m.d: Likewise.
	* testsuite/ld-x86-64/pr19609-2.s: Likewise.
	* testsuite/ld-x86-64/pr19609-2a.d: Likewise.
	* testsuite/ld-x86-64/pr19609-2b.d: Likewise.
	* testsuite/ld-x86-64/pr19609-2c.d: Likewise.
	* testsuite/ld-x86-64/pr19609-2d.d: Likewise.
	* testsuite/ld-x86-64/pr19609-3.s: Likewise.
	* testsuite/ld-x86-64/pr19609-3a.d: Likewise.
	* testsuite/ld-x86-64/pr19609-3b.d: Likewise.
	* testsuite/ld-x86-64/pr19609-4.s: Likewise.
	* testsuite/ld-x86-64/pr19609-4a.d: Likewise.
	* testsuite/ld-x86-64/pr19609-4b.d: Likewise.
	* testsuite/ld-x86-64/pr19609-4c.d: Likewise.
	* testsuite/ld-x86-64/pr19609-4d.d: Likewise.
	* testsuite/ld-x86-64/pr19609-4e.d: Likewise.
	* testsuite/ld-x86-64/pr19609-5.s: Likewise.
	* testsuite/ld-x86-64/pr19609-5a.d: Likewise.
	* testsuite/ld-x86-64/pr19609-5b.d: Likewise.
	* testsuite/ld-x86-64/pr19609-5c.d: Likewise.
	* testsuite/ld-x86-64/pr19609-5d.d: Likewise.
	* testsuite/ld-x86-64/pr19609-5e.d: Likewise.
	* testsuite/ld-x86-64/pr19609-6.s: Likewise.
	* testsuite/ld-x86-64/pr19609-6a.d: Likewise.
	* testsuite/ld-x86-64/pr19609-6b.d: Likewise.
	* testsuite/ld-x86-64/pr19609-6c.d: Likewise.
	* testsuite/ld-x86-64/pr19609-6d.d: Likewise.
	* testsuite/ld-x86-64/pr19609-7.s: Likewise.
	* testsuite/ld-x86-64/pr19609-7a.d: Likewise.
	* testsuite/ld-x86-64/pr19609-7b.d: Likewise.
	* testsuite/ld-x86-64/pr19609-7c.d: Likewise.
	* testsuite/ld-x86-64/pr19609-7d.d: Likewise.
	* testsuite/ld-i386/i386.exp: Run undefweak tests and tests for
	PR ld/19609.
	* testsuite/ld-x86-64/x86-64.exp: Run pr13082-3c, pr13082-3d
	and tests for PR ld/19609.
2016-02-26 09:39:24 -08:00
..
emulparams [x86] Resolve non-PIC undefweak symbols in executable 2016-02-26 04:55:57 -08:00
emultempl Properly implement STT_COMMON 2016-02-26 05:01:34 -08:00
po Copyright update for binutils 2016-01-01 23:00:01 +10:30
scripttempl Prevent .noinit section from incorrect placement for AVR. 2016-01-25 22:33:25 +03:00
testsuite Optimize x86 GOT32X/GOTPCRELX relocations 2016-02-26 09:39:24 -08:00
.gitignore
aclocal.m4
ChangeLog Optimize x86 GOT32X/GOTPCRELX relocations 2016-02-26 09:39:24 -08:00
ChangeLog-0001
ChangeLog-0203
ChangeLog-2004
ChangeLog-2005
ChangeLog-2006
ChangeLog-2007
ChangeLog-2008
ChangeLog-2009 Remove trailing spaces in ld 2015-08-12 04:46:43 -07:00
ChangeLog-2010
ChangeLog-2011
ChangeLog-2012
ChangeLog-2013
ChangeLog-2014
ChangeLog-2015 binutils ChangeLog rotation 2016-01-01 22:59:17 +10:30
ChangeLog-9197 Remove trailing spaces in ld 2015-08-12 04:46:43 -07:00
ChangeLog-9899
config.in Reset x86 Linux targets to not compressing debug sections by default. Enable compression of debug sections by default in the linker, if so configured. 2015-10-21 13:15:39 +01:00
configure Replace == with = in ld/configure.ac 2016-01-29 07:49:18 -08:00
configure.ac Replace == with = in ld/configure.ac 2016-01-29 07:49:18 -08:00
configure.host Copyright update for binutils 2016-01-01 23:00:01 +10:30
configure.tgt Copyright update for binutils 2016-01-01 23:00:01 +10:30
deffile.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
deffilep.y Copyright update for binutils 2016-01-01 23:00:01 +10:30
dep-in.sed
elf-hints-local.h
fdl.texi
gen-doc.texi Copyright update for binutils 2016-01-01 23:00:01 +10:30
genscrba.sh
genscripts.sh Copyright update for binutils 2016-01-01 23:00:01 +10:30
h8-doc.texi Copyright update for binutils 2016-01-01 23:00:01 +10:30
ld.h Remove unused field from ld_config_type structure. 2016-02-25 10:33:29 +00:00
ld.texinfo Properly implement STT_COMMON 2016-02-26 05:01:34 -08:00
ldbuildid.c Copyright update for binutils 2016-01-01 23:00:01 +10:30
ldbuildid.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
ldcref.c Copyright update for binutils 2016-01-01 23:00:01 +10:30
ldctor.c Copyright update for binutils 2016-01-01 23:00:01 +10:30
ldctor.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
ldemul.c Copyright update for binutils 2016-01-01 23:00:01 +10:30
ldemul.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
ldexp.c Copyright update for binutils 2016-01-01 23:00:01 +10:30
ldexp.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
ldfile.c Copyright update for binutils 2016-01-01 23:00:01 +10:30
ldfile.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
ldgram.y Copyright update for binutils 2016-01-01 23:00:01 +10:30
ldint.texinfo Copyright update for binutils 2016-01-01 23:00:01 +10:30
ldlang.c Copyright update for binutils 2016-01-01 23:00:01 +10:30
ldlang.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
ldlex-wrapper.c Copyright update for binutils 2016-01-01 23:00:01 +10:30
ldlex.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
ldlex.l Copyright update for binutils 2016-01-01 23:00:01 +10:30
ldmain.c [x86] Resolve non-PIC undefweak symbols in executable 2016-02-26 04:55:57 -08:00
ldmain.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
ldmisc.c Copyright update for binutils 2016-01-01 23:00:01 +10:30
ldmisc.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
ldver.c Copyright update for binutils 2016-01-01 23:00:01 +10:30
ldver.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
ldwrite.c Copyright update for binutils 2016-01-01 23:00:01 +10:30
ldwrite.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
lexsup.c Properly implement STT_COMMON 2016-02-26 05:01:34 -08:00
MAINTAINERS Copyright update for binutils 2016-01-01 23:00:01 +10:30
Makefile.am [x86] Resolve non-PIC undefweak symbols in executable 2016-02-26 04:55:57 -08:00
Makefile.in [x86] Resolve non-PIC undefweak symbols in executable 2016-02-26 04:55:57 -08:00
mri.c Copyright update for binutils 2016-01-01 23:00:01 +10:30
mri.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
NEWS Properly implement STT_COMMON 2016-02-26 05:01:34 -08:00
pe-dll.c Copyright update for binutils 2016-01-01 23:00:01 +10:30
pe-dll.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
pep-dll.c Copyright update for binutils 2016-01-01 23:00:01 +10:30
pep-dll.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
plugin.c Copyright update for binutils 2016-01-01 23:00:01 +10:30
plugin.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
README Copyright update for binutils 2016-01-01 23:00:01 +10:30
stamp-h.in
sysdep.h Copyright update for binutils 2016-01-01 23:00:01 +10:30
testplug2.c Copyright update for binutils 2016-01-01 23:00:01 +10:30
testplug3.c Copyright update for binutils 2016-01-01 23:00:01 +10:30
testplug.c Copyright update for binutils 2016-01-01 23:00:01 +10:30
TODO

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		README for LD

This is the GNU linker.  It is distributed with other "binary
utilities" which should be in ../binutils.  See ../binutils/README for
more general notes, including where to send bug reports.

There are many features of the linker:

* The linker uses a Binary File Descriptor library (../bfd)
  that it uses to read and write object files.  This helps
  insulate the linker itself from the format of object files.

* The linker supports a number of different object file
  formats.  It can even handle multiple formats at once:
  Read two input formats and write a third.

* The linker can be configured for cross-linking.

* The linker supports a control language.

* There is a user manual (ld.texinfo), as well as the
  beginnings of an internals manual (ldint.texinfo).

Installation
============

See ../binutils/README.

If you want to make a cross-linker, you may want to specify
a different search path of -lfoo libraries than the default.
You can do this by setting the LIB_PATH variable in ./Makefile
or using the --with-lib-path configure switch.

To build just the linker, make the target all-ld from the top level
directory (one directory above this one).

Porting to a new target
=======================

See the ldint.texinfo manual.

Reporting bugs etc
===========================

See ../binutils/README.

Known problems
==============

The Solaris linker normally exports all dynamic symbols from an
executable.  The GNU linker does not do this by default.  This is
because the GNU linker tries to present the same interface for all
similar targets (in this case, all native ELF targets).  This does not
matter for normal programs, but it can make a difference for programs
which try to dlopen an executable, such as PERL or Tcl.  You can make
the GNU linker export all dynamic symbols with the -E or
--export-dynamic command line option.

HP/UX 9.01 has a shell bug that causes the linker scripts to be
generated incorrectly.  The symptom of this appears to be "fatal error
- scanner input buffer overflow" error messages.  There are various
workarounds to this:
  * Build and install bash, and build with "make SHELL=bash".
  * Update to a version of HP/UX with a working shell (e.g., 9.05).
  * Replace "(. ${srcdir}/scripttempl/${SCRIPT_NAME}.sc)" in
    genscripts.sh with "sh ${srcdir}..." (no parens) and make sure the
    emulparams script used exports any shell variables it sets.

Copyright (C) 2012-2016 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.