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81ff47b3a5
binutils-gdb/ld
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Maciej W. Rozycki 81ff47b3a5 PR ld/20828: Fix linker script symbols wrongly forced local with section GC 
Fix a generic ELF linker regression introduced with a chain of changes
made to unused input section garbage collection:

- commit 1a766c6843 ("Also hide symbols without PLT nor GOT
  references."),
  <https://sourceware.org/ml/binutils/2011-09/msg00076.html>,

- commit 1d5316ab67 ("PR ld/13177: garbage collector retains zombie
  references to external libraries"),
  <https://sourceware.org/ml/binutils/2011-10/msg00161.html>,

- commit 6673f753c0 ("Fix PR 12772, garbage collection of dynamic
  syms"), <https://sourceware.org/ml/binutils/2011-12/msg00077.html>,

causing the garbage collection of unused symbols present in a DSO
involved in a link to make identically named symbols ordinarily defined
(i.e. not hidden or PROVIDEd) by a linker script local, even though the
latter symbols are supposed to be global as if no DSO defined them as
well.

This is because linker script assignments are processed very late as
`lang_process' proceeds, down in the call to `ldemul_before_allocation',
which is made after the call to `lang_gc_sections' to do input section
garbage collecting.  Consequently if unused, then any such DSO-defined
symbol has already been garbage-collected and internally marked local.
It would ordinarily be removed from dynamic symbol table output, however
a linker script assignment correctly replaces its original definition
with the new one and enters it into the dynamic symbol table produced as
it is supposed to be exported.  The original local marking is however
retained making the symbol local in the dynamic symbol table and
therefore not available externally.  This also causes a sorting problem
with the MIPS target, which does not expect non-section local dynamic
symbols to be output and produces an invalid binary.

Fix the problem then, by removing the `forced_local' marking for the
offending case and add suitable test cases.  First to verify that unused
symbols ordinarily defined with linker script assignments remain
exported in the context of input section garbage collection whether or
not a DSO defining identically named symbols is present in the link.
Second that a linker version script still correctly retains or removes
such symbols as requested.

	bfd/
	PR ld/20828
	* elflink.c (bfd_elf_record_link_assignment): Clear any
	`forced_local' marking for DSO symbols that are not being
	provided.

	ld/
	PR ld/20828
	* testsuite/ld-elf/pr20828-1.sd: New test.
	* testsuite/ld-elf/pr20828-2a.sd: New test.
	* testsuite/ld-elf/pr20828-2b.sd: New test.
	* testsuite/ld-elf/pr20828.ld: New test linker script.
	* testsuite/ld-elf/pr20828.ver: New test version script.
	* testsuite/ld-elf/pr20828.s: New test source.
	* testsuite/ld-elf/shared.exp: Run the new test.
2017-01-18 18:30:34 +00:00
..
emulparams X32: Place .plt.got section after .plt section 2017-01-10 13:57:39 -08:00
emultempl Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
po Updated Swedish translations for GAS and LD subdirectories. 2017-01-16 10:59:23 +00:00
scripttempl Support -z relro on hppa 2017-01-02 22:42:45 +10:30
testsuite PR ld/20828: Fix linker script symbols wrongly forced local with section GC 2017-01-18 18:30:34 +00:00
.gitignore
aclocal.m4
ChangeLog PR ld/20828: Fix linker script symbols wrongly forced local with section GC 2017-01-18 18:30:34 +00:00
ChangeLog-0001
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ChangeLog-2013
ChangeLog-2014
ChangeLog-2015
ChangeLog-2016 ChangeLog rotation 2017-01-02 13:55:05 +10:30
ChangeLog-9197
ChangeLog-9899
config.in
configure Run more ld tests when not native 2017-01-02 23:48:08 +10:30
configure.ac Run more ld tests when not native 2017-01-02 23:48:08 +10:30
configure.host Run more ld tests when not native 2017-01-02 23:48:08 +10:30
configure.tgt Add support for x86/64 redox target. 2017-01-11 15:05:53 +00:00
deffile.h Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
deffilep.y Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
dep-in.sed
elf-hints-local.h
fdl.texi
gen-doc.texi Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
genscrba.sh
genscripts.sh Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
h8-doc.texi Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
ld.h Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
ld.texinfo Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
ldbuildid.c Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
ldbuildid.h Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
ldcref.c Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
ldctor.c Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
ldctor.h Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
ldemul.c Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
ldemul.h Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
ldexp.c Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
ldexp.h Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
ldfile.c Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
ldfile.h Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
ldgram.y Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
ldint.texinfo Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
ldlang.c Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
ldlang.h Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
ldlex-wrapper.c Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
ldlex.h Use noyywrap option in lex files. 2017-01-04 16:05:22 +00:00
ldlex.l Use noyywrap option in lex files. 2017-01-04 16:05:22 +00:00
ldmain.c Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
ldmain.h Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
ldmisc.c Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
ldmisc.h Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
ldver.c Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
ldver.h Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
ldwrite.c Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
ldwrite.h Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
lexsup.c Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
MAINTAINERS Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
Makefile.am [ARC] Add new linker emulation for nps 2017-01-10 10:55:13 +00:00
Makefile.in [ARC] Add new linker emulation for nps 2017-01-10 10:55:13 +00:00
mri.c Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
mri.h Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
NEWS Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
pe-dll.c Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
pe-dll.h Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
pep-dll.c Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
pep-dll.h Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
plugin.c Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
plugin.h Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
README Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
stamp-h.in
sysdep.h Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
testplug2.c Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
testplug3.c Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
testplug4.c Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
testplug.c Update year range in copyright notice of all files. 2017-01-02 14:08:56 +10:30
TODO

README

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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) 2012-2017 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.