gold/
PR gold/22915
* x86_64.cc (Output_data_plt_x86_64_ibt): New class.
(Target_x86_64::do_make_data_plt): (All instantiations) Check for
IBT feature bit and create IBT PLTs.
The original patch did not give the target enough hooks to discover that
an input object file does not have a particular property. For the
GNU_PROPERTY_X86_FEATURE_1_AND property, for example, where a missing
property should be assumed to be all zeroes, and ANDed with other
object modules, this is essential. We now store the target-specific
properties locally in the Target structure as native uint32_t fields,
then AND the per-object feature bits with the program's feature bits
when we're finished processing each input object file. The target-specific
properties are then added back to the output note section during
finalization.
gold/
PR gold/22914
* layout.cc (read_sized_value): Fix spelling of section name.
(Layout::layout_gnu_property): Call Sized_target::record_gnu_property
for target-specific properties;
don't store them with target-independent properties yet.
(Layout::merge_gnu_properties): New method.
(Layout::add_gnu_property): New method.
(Layout::create_gnu_properties_note): Call target to finalize
target-specific properties. Fix spelling of output section name.
* layout.h (Layout::merge_gnu_properties): New method.
(Layout::add_gnu_property): New method.
* object.cc (Sized_relobj_file::do_layout): Call
Layout::merge_gnu_properties.
* target.h (Target::merge_gnu_property): Remove.
(Target::finalize_gnu_properties): New method.
(Target::do_merge_gnu_property): Move to Sized_target and rename.
(Target::do_finalize_gnu_properties): New virtual method.
(Sized_target::record_gnu_property): Moved and renamed from
Target::do_merge_gnu_property.
(Sized_target::merge_gnu_properties): New virtual method.
* x86_64.cc (Target_x86_64::isa_1_used_, isa_1_needed_)
(feature_1_, object_feature_1_, seen_first_object_): New data members.
(Target_x86_64::do_merge_gnu_property): Rename to ...
(Target_x86_64::record_gnu_property): ... this. Save target-specific
properties in Target class object.
(Target_x86_64::merge_gnu_properties): New method.
(add_property): New static inline function.
(Target_x86_64::do_finalize_gnu_properties): New method.
* testsuite/Makefile.am (gnu_property_test): Remove C source file;
link directly without compiler driver.
* testsuite/Makefile.in: Regenerate.
* testsuite/gnu_property_a.S: Add _start.
Replacing push_back() with emplace_back() eliminates the calls to the
copy constructor, but I still had to provide explicit copy constructors
because of the call to vector::reserve(), which tries to instantiate them
even though they'll never actually be called when reserve() is called
on an empty vector.
gold/
* incremental.cc (Sized_incremental_binary::setup_readers): Use
emplace_back for GCC 5 and later.
* incremental.h (Incremental_binary::Input_reader): Provide copy
constructor.
(Sized_incremental_binary::Sized_input_reader): Likewise.
elfcpp/
PR gold/22914
* elfcpp.h (NT_GNU_PROPERTY_TYPE_0): New note type.
(GNU_PROPERTY_*): New Gnu property types.
* x86_64.h (GNU_PROPERTY_X86_FEATURE_1_IBT)
(GNU_PROPERTY_X86_FEATURE_1_SHSTK): New x86 feature bits.
gold/
PR gold/22914
* layout.cc (Layout::Layout): Initialize gnu_properties_.
(read_sized_value, write_sized_value): New functions.
(Layout::layout_gnu_property): New method.
(Layout::create_notes): Call create_gnu_properties_note.
(Layout::create_gnu_properties_note): New method.
* layout.h (Layout::layout_gnu_property): New method.
(Layout::create_gnu_properties_note): New method.
(Layout::Gnu_property, Layout::Gnu_properties): New types.
(Layout::gnu_properties_): New data member.
* object.cc (Sized_relobj_file::layout_gnu_property_section): New
method.
(Sized_relobj_file::do_layout): Handle .note.gnu.property sections.
* object.h (Sized_relobj_file::layout_gnu_property_section): New
method.
* target.h (Target::merge_gnu_property): New method.
(Target::do_merge_gnu_property): New virtual method.
* x86_64.cc (Target_x86_64::do_merge_gnu_property): New method.
* testsuite/Makefile.am (gnu_property_test): New test case.
* testsuite/Makefile.in: Regenerate.
* testsuite/gnu_property_a.S: New source file.
* testsuite/gnu_property_b.S: New source file.
* testsuite/gnu_property_c.S: New source file.
* testsuite/gnu_property_main.c: New source file.
* testsuite/gnu_property_test.sh: New test script.
When we have a weak reference to a symbol defined in an
as-needed library, and that library ends up not-needed, gold
simply clears the version information in the symbol table, even
if the symbol could have been resolved by a needed library later
in the link order. This results in a loss of version information,
which can cause the program to bind to the wrong version at run
time.
This patch lets a dynamic definition override an earlier one if
the earlier one is from a not-needed library, so that we can
retain the version information from the binding to the needed
library. In order to do that, the tracking of needed/not-needed
had to be moved up to symbol resolution time, instead of during
Symbol_table::set_dynsym_indexes().
In cases where we still end up discarding version information,
I've added a warning.
For the original problem report and discussion, see:
https://stackoverflow.com/questions/50751421/undefined-behavior-in-shared-lib-using-libpthread-but-not-having-it-in-elf-as-d
gold/
* resolve.cc (Symbol_table::resolve): Rename tobinding to
orig_tobinding. Call set_is_needed() for objects that resolve
non-weak references.
(Symbol_table::should_override): Allow a dynamic definition to
override an earlier one in a not-needed library.
* symtab.cc (Symbol_table::set_dynsym_indexes): Remove separate
processing for as-needed symbols. Add warning when discarding
version informatin.
* testsuite/Makefile.am (weak_as_needed): New test case.
* testsuite/Makefile.in: Regenerate.
* testsuite/weak_as_needed.sh: New test script.
* testsuite/weak_as_needed_a.c: New source file.
* testsuite/weak_as_needed_b.c: New source file.
* testsuite/weak_as_needed_b.script: New version script.
* testsuite/weak_as_needed_c.c: New source file.
* testsuite/weak_as_needed_c.script: New version script.
gold/
PR gold/23268
* dynobj.cc (Versions::Versions): Change init for needs_base_version_.
(Versions::record_version): Add verdefs for both shared objects and
executables.
(Versions::add_def): Likewise for base version.
(Versions::add_need): Don't add base version for executables.
(Versions::version_index): Look up version for both shared objects and
executables.
* testsuite/Makefile.am (ver_test_14): New test case.
* testsuite/Makefile.in: Regenerate.
* testsuite/ver_test_14.script: New version script.
* testsuite/ver_test_14.sh: New test script.
The autotools library macro (AX_PTHREAD) is now used to detect if
pthreads is present and multi-threaded linking in gold is automatically
enabled if it is found. This enables multi-threaded gold on platforms
where pthreads is enabled via other methods than just -lpthread
(e.g., MinGW).
2018-06-19 Joshua Watt <jpewhacker@gmail.com>
Cary Coutant <ccoutant@gmail.com>
gold/
* configure.ac: Replace manual thread configuration with AX_PTHREAD.
Add --enable-threads=auto.
* Makefile.am (THREADFLAGS, THREADLIBS): New defines.
(AM_CFLAGS, AM_CXXFLAGS): Add $(THREADFLAGS.
(THREADSLIB): Remove; change all references to THREADLIBS.
* Makefile.in: Regenerate.
* aclocal.m4: Regenerate.
* config.in: Regenerate.
* configure: Regenerate.
* testsuite/Makefile.am (THREADSLIB): Replace with...
(THREADFLAGS, THREADLIBS): ... these.
(LDADD): Remove; add as individual defines for...
(object_unittest, binary_unittest, leb128_unittest)
(overflow_unittest): ... these tests.
(tls_test, tls_pic_test, tls_pie_test, tls_pie_pic_test)
(tls_shared_test, tls_shared_ie_test, tls_shared_gd_to_ie_test)
(tls_shared_gnu2_gd_to_ie_test, tls_shared_gnu2_test_LDFLAGS)
(tls_shared_nonpic_test_LDFLAGS): Add $(THREADFLAGS) and ($THREADLIBS).
* testsuite/Makefile.in: Regenerate.
When trying to run the update-gnulib.sh script in gdb, I get this:
Error: Wrong automake version (Unescaped left brace in regex is deprecated, passed through in regex; marked by <-- HERE in m/\${ <-- HERE ([^ =:+{}]+)}/ at /opt/automake/1.11.1/bin/automake line 4113.), we need 1.11.1.
Aborting.
Apparently, it's an issue with a regex in automake that triggers a
warning starting with Perl 5.22. It has been fixed in automake 1.15.1.
So I think it's a good excuse to bump the versions of autoconf and
automake used in the gnulib import. And to avoid requiring multiple
builds of autoconf/automake, it was suggested that we bump the required
version of those tools for all binutils-gdb.
For autoconf, the 2.69 version is universally available, so it's an easy
choice. For automake, different distros and distro versions have
different automake versions. But 1.15.1 seems to be the most readily
available as a package. In any case, it's easy to build it from source.
I removed the version checks from AUTOMAKE_OPTIONS and AC_PREREQ,
because I don't think they are useful in our case. They only specify a
lower bound for the acceptable version of automake/autoconf. That's
useful if you let the user choose the version of the tool they want to
use, but want to set a minimum version (because you use a feature that
was introduced in that version). In our case, we force people to use a
specific version anyway. For the autoconf version, we have the check in
config/override.m4 that enforces the version we want. It will be one
less thing to update next time we change autotools version.
I hit a few categories of problems that required some changes. They are
described below along with the chosen solutions.
Problem 1:
configure.ac:17: warning: AM_INIT_AUTOMAKE: two- and three-arguments forms are deprecated. For more info, see:
configure.ac:17: http://www.gnu.org/software/automake/manual/automake.html#Modernize-AM_005fINIT_005fAUTOMAKE-invocation
Solution 1:
Adjust the code based on the example at that URL.
Problem 2 (in zlib/):
Makefile.am: error: required file './INSTALL' not found
Makefile.am: 'automake --add-missing' can install 'INSTALL'
Makefile.am: error: required file './NEWS' not found
Makefile.am: error: required file './AUTHORS' not found
Makefile.am: error: required file './COPYING' not found
Makefile.am: 'automake --add-missing' can install 'COPYING'
Solution 2:
Add the foreign option to AUTOMAKE_OPTIONS.
Problem 3:
doc/Makefile.am:20: error: support for Cygnus-style trees has been removed
Solution 3:
Remove the cygnus options.
Problem 4:
Makefile.am:656: warning: 'INCLUDES' is the old name for 'AM_CPPFLAGS' (or '*_CPPFLAGS')
Solution 4:
Rename "INCLUDES = " to "AM_CPPFLAGS += " (because AM_CPPFLAGS is
already defined earlier).
Problem 5:
doc/Makefile.am:71: warning: suffix '.texinfo' for Texinfo files is discouraged; use '.texi' instead
doc/Makefile.am: warning: Oops!
doc/Makefile.am: It appears this file (or files included by it) are triggering
doc/Makefile.am: an undocumented, soon-to-be-removed automake hack.
doc/Makefile.am: Future automake versions will no longer place in the builddir
doc/Makefile.am: (rather than in the srcdir) the generated '.info' files that
doc/Makefile.am: appear to be cleaned, by e.g. being listed in CLEANFILES or
doc/Makefile.am: DISTCLEANFILES.
doc/Makefile.am: If you want your '.info' files to be placed in the builddir
doc/Makefile.am: rather than in the srcdir, you have to use the shiny new
doc/Makefile.am: 'info-in-builddir' automake option.
Solution 5:
Rename .texinfo files to .texi.
Problem 6:
doc/Makefile.am: warning: Oops!
doc/Makefile.am: It appears this file (or files included by it) are triggering
doc/Makefile.am: an undocumented, soon-to-be-removed automake hack.
doc/Makefile.am: Future automake versions will no longer place in the builddir
doc/Makefile.am: (rather than in the srcdir) the generated '.info' files that
doc/Makefile.am: appear to be cleaned, by e.g. being listed in CLEANFILES or
doc/Makefile.am: DISTCLEANFILES.
doc/Makefile.am: If you want your '.info' files to be placed in the builddir
doc/Makefile.am: rather than in the srcdir, you have to use the shiny new
doc/Makefile.am: 'info-in-builddir' automake option.
Solution 6:
Remove the hack at the bottom of doc/Makefile.am and use
the info-in-builddir automake option.
Problem 7:
doc/Makefile.am:35: error: required file '../texinfo.tex' not found
doc/Makefile.am:35: 'automake --add-missing' can install 'texinfo.tex'
Solution 7:
Use the no-texinfo.tex automake option. We also have one in
texinfo/texinfo.tex, not sure if we should point to that, or move it
(or a newer version of it added with automake --add-missing) to
top-level.
Problem 8:
Makefile.am:131: warning: source file 'config/tc-aarch64.c' is in a subdirectory,
Makefile.am:131: but option 'subdir-objects' is disabled
automake: warning: possible forward-incompatibility.
automake: At least a source file is in a subdirectory, but the 'subdir-objects'
automake: automake option hasn't been enabled. For now, the corresponding output
automake: object file(s) will be placed in the top-level directory. However,
automake: this behaviour will change in future Automake versions: they will
automake: unconditionally cause object files to be placed in the same subdirectory
automake: of the corresponding sources.
automake: You are advised to start using 'subdir-objects' option throughout your
automake: project, to avoid future incompatibilities.
Solution 8:
Use subdir-objects, that means adjusting references to some .o that will now
be in config/.
Problem 9:
configure.ac:375: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call detected in body
../../lib/autoconf/lang.m4:193: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2601: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2617: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:639: AS_IF is expanded from...
../../lib/autoconf/general.m4:2042: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2063: AC_CACHE_CHECK is expanded from...
configure.ac:375: the top level
Solution 9:
Use AC_LANG_SOURCE, or use proper quoting.
Problem 10 (in intl/):
configure.ac:7: warning: AC_COMPILE_IFELSE was called before AC_USE_SYSTEM_EXTENSIONS
/usr/share/aclocal/threadlib.m4:36: gl_THREADLIB_EARLY_BODY is expanded from...
/usr/share/aclocal/threadlib.m4:29: gl_THREADLIB_EARLY is expanded from...
/usr/share/aclocal/threadlib.m4:318: gl_THREADLIB is expanded from...
/usr/share/aclocal/lock.m4:9: gl_LOCK is expanded from...
/usr/share/aclocal/intl.m4:211: gt_INTL_SUBDIR_CORE is expanded from...
/usr/share/aclocal/intl.m4:25: AM_INTL_SUBDIR is expanded from...
/usr/share/aclocal/gettext.m4:57: AM_GNU_GETTEXT is expanded from...
configure.ac:7: the top level
Solution 10:
Add AC_USE_SYSTEM_EXTENSIONS in configure.ac.
ChangeLog:
* libtool.m4: Use AC_LANG_SOURCE.
* configure.ac: Remove AC_PREREQ, use AC_LANG_SOURCE.
* README-maintainer-mode: Update version requirements.
* ar-lib: New file.
* test-driver: New file.
* configure: Re-generate.
bfd/ChangeLog:
* Makefile.am (AUTOMAKE_OPTIONS): Remove 1.11.
(INCLUDES): Rename to ...
(AM_CPPFLAGS): ... this.
* configure.ac: Remove AC_PREREQ.
* doc/Makefile.am (AUTOMAKE_OPTIONS): Remove 1.9, cygnus, add
info-in-builddir no-texinfo.tex.
(info_TEXINFOS): Rename bfd.texinfo to bfd.texi.
* doc/bfd.texinfo: Rename to ...
* doc/bfd.texi: ... this.
* Makefile.in: Re-generate.
* aclocal.m4: Re-generate.
* config.in: Re-generate.
* configure: Re-generate.
* doc/Makefile.in: Re-generate.
binutils/ChangeLog:
* configure.ac: Remove AC_PREREQ.
* doc/Makefile.am (AUTOMAKE_OPTIONS): Remove cygnus, add
info-in-builddir no-texinfo.tex.
* Makefile.in: Re-generate.
* aclocal.m4: Re-generate.
* config.in: Re-generate.
* configure: Re-generate.
* doc/Makefile.in: Re-generate.
config/ChangeLog:
* override.m4 (_GCC_AUTOCONF_VERSION): Bump from 2.64 to 2.69.
etc/ChangeLog:
* configure.in: Remove AC_PREREQ.
* configure: Re-generate.
gas/ChangeLog:
* Makefile.am (AUTOMAKE_OPTIONS): Remove 1.11, add subdir-objects.
(TARG_CPU_O, OBJ_FORMAT_O, ATOF_TARG_O): Add config/ prefix.
* configure.ac (TARG_CPU_O, OBJ_FORMAT_O, ATOF_TARG_O, emfiles,
extra_objects): Add config/ prefix.
* doc/as.texinfo: Rename to...
* doc/as.texi: ... this.
* doc/Makefile.am: Rename as.texinfo to as.texi throughout.
Remove DISTCLEANFILES hack.
(AUTOMAKE_OPTIONS): Remove 1.8, cygnus, add no-texinfo.tex and
info-in-builddir.
* Makefile.in: Re-generate.
* aclocal.m4: Re-generate.
* config.in: Re-generate.
* configure: Re-generate.
* doc/Makefile.in: Re-generate.
gdb/ChangeLog:
* common/common-defs.h (PACKAGE_NAME, PACKAGE_VERSION,
PACKAGE_STRING, PACKAGE_TARNAME): Undefine.
* configure.ac: Remove AC_PREREQ, add missing quoting.
* gnulib/configure.ac: Modernize usage of
AC_INIT/AM_INIT_AUTOMAKE. Remove AC_PREREQ.
* gnulib/update-gnulib.sh (AUTOCONF_VERSION): Bump to 2.69.
(AUTOMAKE_VERSION): Bump to 1.15.1.
* configure: Re-generate.
* config.in: Re-generate.
* aclocal.m4: Re-generate.
* gnulib/aclocal.m4: Re-generate.
* gnulib/config.in: Re-generate.
* gnulib/configure: Re-generate.
* gnulib/import/Makefile.in: Re-generate.
gdb/gdbserver/ChangeLog:
* configure.ac: Remove AC_PREREQ, add missing quoting.
* configure: Re-generate.
* config.in: Re-generate.
* aclocal.m4: Re-generate.
gdb/testsuite/ChangeLog:
* configure.ac: Remove AC_PREREQ.
* configure: Re-generate.
gold/ChangeLog:
* configure.ac: Remove AC_PREREQ, add missing quoting and usage
of AC_LANG_SOURCE.
* Makefile.in: Re-generate.
* aclocal.m4: Re-generate.
* configure: Re-generate.
* testsuite/Makefile.in: Re-generate.
gprof/ChangeLog:
* configure.ac: Remove AC_PREREQ.
* Makefile.am: Remove DISTCLEANFILES hack.
(AUTOMAKE_OPTIONS): Remove 1.11, add info-in-builddir.
* Makefile.in: Re-generate.
* aclocal.m4: Re-generate.
* configure: Re-generate.
* gconfig.in: Re-generate.
intl/ChangeLog:
* configure.ac: Add AC_USE_SYSTEM_EXTENSIONS, remove AC_PREREQ.
* configure: Re-generate.
* config.h.in: Re-generate.
* aclocal.m4: Re-generate.
ld/ChangeLog:
* configure.ac: Remove AC_PREREQ.
* Makefile.am: Remove DISTCLEANFILES hack, rename ld.texinfo to
ld.texi, ldint.texinfo to ldint.texi throughout.
(AUTOMAKE_OPTIONS): Add info-in-builddir.
* README: Rename ld.texinfo to ld.texi, ldint.texinfo to
ldint.texi throughout.
* gen-doc.texi: Likewise.
* h8-doc.texi: Likewise.
* ld.texinfo: Rename to ...
* ld.texi: ... this.
* ldint.texinfo: Rename to ...
* ldint.texi: ... this.
* Makefile.in: Re-generate.
* aclocal.m4: Re-generate.
* config.in: Re-generate.
* configure: Re-generate.
libdecnumber/ChangeLog:
* configure.ac: Remove AC_PREREQ.
* configure: Re-generate.
* aclocal.m4.
libiberty/ChangeLog:
* configure.ac: Remove AC_PREREQ.
* configure: Re-generate.
* config.in: Re-generate.
opcodes/ChangeLog:
* Makefile.am (AUTOMAKE_OPTIONS): Remove 1.11.
* configure.ac: Remove AC_PREREQ.
* Makefile.in: Re-generate.
* aclocal.m4: Re-generate.
* configure: Re-generate.
readline/ChangeLog.gdb:
* configure: Re-generate.
* examples/rlfe/configure: Re-generate.
sim/ChangeLog:
* All configure.ac: Remove AC_PREREQ.
* All configure: Re-generate.
zlib/ChangeLog.bin-gdb:
* configure.ac: Modernize AC_INIT call, remove AC_PREREQ.
* Makefile.am (AUTOMAKE_OPTIONS): Remove 1.8, cygnus, add
foreign.
* Makefile.in: Re-generate.
* aclocal.m4: Re-generate.
* configure: Re-generate.
Gold resolves GOT-relative relocs relative to the GOT base +
0x8000 when the GOT is larger than 0x8000. However, previously
the _GLOBAL_OFFSET_TABLE_ symbol was set to GOT base + 0x8000
when the .got.plt was larger than 0x8000. This patch makes both
checks use the size of the .got section so that they agree when
to add 0x8000.
During --icf processing, gold was incorrectly processing the relocation
addend for references to items in a merge section. PC-relative references
and other forms of reference with a biased base address require a
non-section local symbol, where the addend is purely the bias.
gold/
PR gold/20642
PR gold/22820
* gc.h (gc_process_relocs): Flag STT_SECTION symbols in symvec.
* icf.cc (get_section_contents): For merge sections, ignore the
addend for relocations against non-section symbols.
gold/
PR gold/16504
* dynobj.cc (Versions::symbol_section_contents): Don't set
VERSYM_HIDDEN flag for undefined symbols.
* symtab.cc (Symbol_table::add_from_object): Don't override default
version definition with a different default version.
* symtab.h (Symbol::from_dyn): New method.
* testsuite/plugin_test.c (struct sym_info): Add ver field.
(claim_file_hook): Pass symbol version to plugin API.
(parse_readelf_line): Parse symbol version.
* testsuite/Makefile.am (ver_test_pr16504): New test case.
* testsuite/Makefile.in: Regenerate.
* testsuite/ver_test_pr16504.sh: New test script.
* testsuite/ver_test_pr16504_a.c: New source file.
* testsuite/ver_test_pr16504_a.script: New version script.
* testsuite/ver_test_pr16504_b.c: New source file.
* testsuite/ver_test_pr16504_b.script: New version script.
When checking a R_ARM_TARGET[12] relocation, we need a valid target
pointer, but the garbage collection code was passing a NULL instead.
The previous fix for this bug fixed the call to
scan.global_reloc_may_be_function_pointer, but missed the similar
call to scan.local_reloc_may_be_function_pointer.
gold/
PR gold/23046
* gc.h (gc_process_relocs): Pass target to
scan.local_reloc_may_be_function_pointer.
When checking a R_ARM_TARGET[12] relocation, we need a valid target
pointer, but the garbage collection code was passing a NULL instead.
gold/
PR gold/23046
* gc.h (gc_process_relocs): Pass target to
scan.global_reloc_may_be_function_pointer.
The gold change is to pick up HJ's PR22318 AC_PLUGINS update. The
ld change is to correct a file I generated from a modified tree.
gold/
* configure: Regenerate.
ld/
* po/BLD-POTFILES.in: Regenerate.
In addition to the existing relocs we need two more to mark all
instructions in the call sequence, PLTCALL on the call itself (plus
the toc restore insn for ppc64), and PLTSEQ on others. All
relocations in a particular sequence have the same symbol.
Example ppc64 ELFv2 assembly:
.reloc .,R_PPC64_PLTSEQ,puts
std 2,24(1)
addis 12,2,puts@plt@ha # .reloc .,R_PPC64_PLT16_HA,puts
ld 12,puts@plt@l(12) # .reloc .,R_PPC64_PLT16_LO_DS,puts
.reloc .,R_PPC64_PLTSEQ,puts
mtctr 12
.reloc .,R_PPC64_PLTCALL,puts
bctrl
ld 2,24(1)
Example ppc32 -fPIC assembly:
addis 12,30,puts+32768@plt@ha # .reloc .,R_PPC_PLT16_HA,puts+0x8000
lwz 12,12,puts+32768@plt@l # .reloc .,R_PPC_PLT16_LO,puts+0x8000
.reloc .,R_PPC_PLTSEQ,puts+32768
mtctr 12
.reloc .,R_PPC_PLTCALL,puts+32768
bctrl
Marking sequences like this allows the linker to convert them to nops
and a direct call if the target symbol turns out to be local.
When the call is __tls_get_addr, each relocation shown above is paired
with an R_PPC*_TLSLD or R_PPC*_TLSGD reloc to additionally mark the
sequence for possible TLS optimization. The TLSLD or TLSGD relocs are
emitted first.
include/
* elf/ppc.h (R_PPC_PLTSEQ, R_PPC_PLTCALL): Define.
* elf/ppc64.h (R_PPC64_PLTSEQ, R_PPC64_PLTCALL): Define.
bfd/
* elf32-ppc.c (ppc_elf_howto_raw): Add PLTSEQ and PLTCALL howtos.
(is_plt_seq_reloc): New function.
(ppc_elf_check_relocs): Handle PLTSEQ and PLTCALL relocs.
(ppc_elf_tls_optimize): Handle inline plt call sequence.
(ppc_elf_relax_section): Handle PLTCALL reloc.
(ppc_elf_relocate_section): Nop out inline plt call sequence when
resolving locally.
* elf64-ppc.c (ppc64_elf_howto_raw): Add R_PPC64_PLTSEQ and
R_PPC64_PLTCALL entries. Comment R_PPC64_TOCSAVE.
(has_tls_get_addr_call): Correct comment.
(is_branch_reloc): Add PLTCALL.
(is_plt_seq_reloc): New function.
(ppc64_elf_check_relocs): Handle PLT16_LO_DS reloc. Set
has_tls_reloc for R_PPC64_TLSGD and R_PPC64_TLSLD. Create plt
entry for R_PPC64_PLTCALL.
(ppc64_elf_tls_optimize): Handle inline plt call sequence.
(ppc_type_of_stub): Handle PLTCALL reloc.
(toc_adjusting_stub_needed): Likewise.
(ppc64_elf_relocate_section): Set "can_plt_call" for PLTCALL
reloc insn. Nop out inline plt call sequence when resolving
locally. Handle __tls_get_addr inline plt call optimization.
elfcpp/
* powerpc.h (R_POWERPC_PLTSEQ, R_POWERPC_PLTCALL): Define.
gold/
* powerpc.cc (Target_powerpc::Track_tls::maybe_skip_tls_get_addr_call):
Handle inline plt sequence relocs.
(Stub_table::Plt_stub_key::Plt_stub_key): Likewise.
(Target_powerpc::Scan::reloc_needs_plt_for_ifunc): Likewise.
(Target_powerpc::Relocate::relocate): Likewise.
Necessary if gcc is to use PLT16 relocs to implement -mlongcall, and
there isn't a good technical reason why local symbols should be
excluded from PLT16 support. Non-ifunc local symbol PLT entries go in
a separate section to other PLT entries. In a fixed position
executable they won't need to be relocated, and in a PIE or shared
library I chose to not implement lazy relocation.
bfd/
* elf64-ppc.c (LOCAL_PLT_ENTRY_SIZE): Define.
(struct ppc_stub_hash_entry): Add symtype field.
(PLT_KEEP): Define.
(struct ppc_link_hash_table): Add pltlocal and relpltlocal.
(create_linkage_sections): Create pltlocal and relpltlocal.
(ppc64_elf_check_relocs): Allow PLT relocs on local symbols.
Set PLT_KEEP.
(ppc64_elf_adjust_dynamic_symbol): Keep PLT entries for inline calls.
(allocate_dynrelocs): Allocate pltlocal and relpltlocal.
(ppc64_elf_size_dynamic_sections): Size pltlocal and relpltlocal.
Keep PLT entries for inline calls against locals.
(ppc_build_one_stub): Use pltlocal as appropriate.
(ppc_size_one_stub): Likewise.
(ppc64_elf_size_stubs): Set symtype.
(build_global_entry_stubs_and_plt): Init pltlocal and write
relpltlocal for globals.
(write_plt_relocs_for_local_syms): Likewise for local syms.
(ppc64_elf_relocate_section): Support PLT for local syms.
* elf32-ppc.c (PLT_KEEP): Define.
(struct ppc_elf_link_hash_table): Add pltlocal and relpltlocal.
(ppc_elf_create_glink): Create pltlocal and relpltlocal.
(ppc_elf_check_relocs): Allow PLT relocs on local symbols.
Set PLT_KEEP. Adjust update_local_sym_info call.
(ppc_elf_adjust_dynamic_symbol): Keep PLT entries for inline calls.
(allocate_dynrelocs): Allocate pltlocal and relpltlocal.
(ppc_elf_size_dynamic_sections): Size pltlocal and relpltlocal.
(ppc_elf_relocate_section): Support PLT16 relocs for local syms.
(write_global_sym_plt): Init pltlocal and write relpltlocal.
(ppc_finish_symbols): Likewise for locals.
ld/
* emulparams/elf32ppc.sh (OTHER_RELRO_SECTIONS_2): Add .branch_lt.
(OTHER_GOT_RELOC_SECTIONS): Add .rela.branch_lt.
* testsuite/ld-powerpc/elfv2so.d: Update for symbol/stub reordering.
* testsuite/ld-powerpc/relbrlt.d: Likewise.
* testsuite/ld-powerpc/relbrlt.s: Likewise.
* testsuite/ld-powerpc/tlsso.r: Likewise.
* testsuite/ld-powerpc/tlstocso.r: Likewise.
gold/
* powerpc.cc (Target_powerpc::lplt_): New variable.
(Target_powerpc::lplt_section): Associated accessor.
(Target_powerpc::plt_off): Handle local non-ifunc symbols.
(Target_powerpc::make_lplt_section): New function.
(Target_powerpc::make_local_plt_entry): New function.
(Powerpc_relobj::do_relocate_sections): Write out lplt.
(Output_data_plt_powerpc::first_plt_entry_offset): Zero for lplt.
(Output_data_plt_powerpc::add_local_entry): New function.
(Output_data_plt_powerpc::do_write): Ignore lplt.
(Target_powerpc::make_iplt_section): Make lplt first.
(Target_powerpc::make_brlt_section): Make .branch_lt relro.
(Target_powerpc::Scan::local): Handle PLT16 relocs.
The PowerPC64 ELFv2 ABI and the PowerPC SysV ABI support a number of
relocations that can be used to create and access a PLT entry.
However, the relocs are not well defined. The PLT16 family of relocs
talk about "the section offset or address of the procedure linkage
table entry". It's plain that we do need a relative address when PIC
as otherwise we'd have dynamic text relocations, but "section offset"
doesn't specify which section. The most obvious one, ".plt", isn't
that useful because there is no readily available way of addressing
the start of the ".plt" section. Much more useful would be "the
GOT/TOC-pointer relative offset of the procedure linkage table entry",
and I suppose you could argue that is a "section offset" of sorts.
For PowerPC64 it is better to use the same TOC-pointer relative
addressing even when non-PIC, since ".plt" may be located outside the
range of a 32-bit address. However, for ppc32 we do want an absolute
address when non-PIC as a GOT pointer may not be set up. Also, for
ppc32 PIC we have a similar situation to R_PPC_PLTREL24 in that the
GOT pointer is set to a location in the .got2 section and we need to
specify the .got2 offset in the PLT16 reloc addend.
This patch supports PLT16 relocations using these semantics. This is
not an ABI change for ppc32 since the relocations were not previously
supported by GNU ld, but is for ppc64 where some of the PLT16 relocs
were supported. I'm not particularly concerned since the old ppc64
PLT16 reloc semantics made them almost completely useless.
bfd/
* elf32-ppc.c (ppc_elf_check_relocs): Handle PLT16 relocs.
(ppc_elf_relocate_section): Likewise.
* elf64-ppc.c (ppc64_elf_check_relocs): Handle PLT16_LO_DS.
(ppc64_elf_relocate_section): Likewise. Correct PLT16
resolution to plt entry relative to toc pointer.
gold/
* powerpc.cc (Target_powerpc::plt_off): New functions.
(is_plt16_reloc): New function.
(Stub_table::plt_off): Use Target_powerpc::plt_off.
(Stub_table::plt_call_size): Use plt_off.
(Stub_table::do_write): Likewise.
(Target_powerpc::Scan::get_reference_flags): Return RELATIVE_REF
for PLT16 relocations.
(Target_powerpc::Scan::reloc_needs_plt_for_ifunc): Return true
for PLT16 relocations.
(Target_powerpc::Scan::global): Make a PLT entry for PLT16 relocations.
(Target_powerpc::Relocate::relocate): Support PLT16 relocations.
(Powerpc_scan_relocatable_reloc::global_strategy): Return RELOC_SPECIAL
for ppc32 plt16 relocs.
Relocations referring to discarded sections are now treated as errors
instead of warnings.
Also with this patch, we will now print the section group signature and the
object file with the prevailing definition of that group along with the
name of the symbol that the relocation is referring to. This additional
information should be much more useful to anyone trying to track down
the source of such errors.
To do so, we now map each discarded section to the Kept_section info in
the Layout class, and defer the logic that maps a discarded section to
its counterpart in the kept group. This gives us the information we need
to identify the signature symbol given the discarded section, and the
name of the object file that provided the prevailing (i.e., first)
definition of that group.
gold/
* object.cc (Sized_relobj_file::include_section_group): Store
reference to Kept_section info for discarded comdat sections
regardless of size. Move size checking to map_to_kept_section.
(Sized_relobj_file::include_linkonce_section): Likewise.
(Sized_relobj_file::map_to_kept_section): Add section name parameter.
Insert size checking logic from above functions.
(Sized_relobj_file::find_kept_section_object): New method.
(Sized_relobj_file::get_symbol_name): New method.
* object.h (Sized_relobj_file::map_to_kept_section): Add section_name
parameter. Adjust all callers.
(Sized_relobj_file::find_kept_section_object): New method.
(Sized_relobj_file::get_symbol_name): New method.
(Sized_relobj_file::Kept_comdat_section): Replace object and shndx
fields with sh_size, kept_section, symndx, and is_comdat fields.
(Sized_relobj_file::set_kept_comdat_section): Replace kept_object
and kept_shndx parameters with is_comdat, symndx, sh_size, and
kept_section.
(Sized_relobj_file::get_kept_comdat_section): Likewise.
* target-reloc.h (enum Comdat_behavior): Change CB_WARNING to CB_ERROR.
Adjust all references.
(issue_undefined_symbol_error): New function template.
(relocate_section): Pass section name to map_to_kept_section.
Move discarded section code to new function above.
* aarch64.cc (Target_aarch64::scan_reloc_section_for_stubs): Move
declaration for gsym out one level. Call issue_discarded_error.
* arm.cc (Target_arm::scan_reloc_section_for_stubs): Likewise.
* powerpc.cc (Relocate_comdat_behavior): Change CB_WARNING to CB_ERROR.
The record_got_page_entry function records and updates the maximum
number of GOT page entries which may be required by an object. In the
case where an existing GOT page entry was expanded, only the entry
belonging to output GOT would have its page count updated. This leaves
the entry belonging to the object GOT with the num_pages count of 1 it
was originally initialized with. Later on when GOTs are being merged in a
multi-got link, this causes the value of entry->num_pages in
add_got_page_entries to always be 1 and underestimates the number of pages
required for the new entry. This in turn leads to an assertion failure in
get_got_page_offset where we run out of pages.
Fix by obtaining the object's GOT entry unconditionally and not just
the first time it gets created. Now that entry2 is always valid, remove
the useless NULL checks.
gold/
PR gold/22770
* mips.cc (Mips_got_info::record_got_page_entry): Fetch existing
page entries for the object's GOT.
During a -r (or --emit-relocs) link, if two sections had the same name but
different section types, gold would put relocations for both sections into
the same relocation section even though the data sections remained separate.
For .eh_frame sections, when one section is PROGBITS and another is
X86_64_UNWIND, we really should be using the UNWIND section type and
combining the sections anyway. For other sections, we should be
creating one relocation section for each output data section.
gold/
PR gold/23016
* incremental.cc (can_incremental_update): Check for unwind section
type.
* layout.h (Layout::layout): Add sh_type parameter.
* layout.cc (Layout::layout): Likewise.
(Layout::layout_reloc): Create new output reloc section if data
section does not already have one.
(Layout::layout_eh_frame): Check for unwind section type.
(Layout::make_eh_frame_section): Use unwind section type for .eh_frame
and .eh_frame_hdr.
* object.h (Sized_relobj_file::Shdr_write): New typedef.
(Sized_relobj_file::layout_section): Add sh_type parameter.
(Sized_relobj_file::Deferred_layout::Deferred_layout): Add sh_type
parameter.
* object.cc (Sized_relobj_file::check_eh_frame_flags): Check for
unwind section type.
(Sized_relobj_file::layout_section): Add sh_type parameter; pass it
to Layout::layout.
(Sized_relobj_file::do_layout): Make local copy of sh_type.
Force .eh_frame sections to unwind section type.
Pass sh_type to layout_section.
(Sized_relobj_file<size, big_endian>::do_layout_deferred_sections):
Pass sh_type to layout_section.
* output.cc (Output_section::Output_section): Initialize reloc_section_.
* output.h (Output_section::reloc_section): New method.
(Output_section::set_reloc_section): New method.
(Output_section::reloc_section_): New data member.
* target.h (Target::unwind_section_type): New method.
(Target::Target_info::unwind_section_type): New data member.
* aarch64.cc (aarch64_info): Add unwind_section_type.
* arm.cc (arm_info, arm_nacl_info): Likewise.
* i386.cc (i386_info, i386_nacl_info, iamcu_info): Likewise.
* mips.cc (mips_info, mips_nacl_info): Likewise.
* powerpc.cc (powerpc_info): Likewise.
* s390.cc (s390_info): Likewise.
* sparc.cc (sparc_info): Likewise.
* tilegx.cc (tilegx_info): Likewise.
* x86_64.cc (x86_64_info, x86_64_nacl_info): Likewise.
* testsuite/Makefile.am (pr23016_1, pr23016_2): New test cases.
* testsuite/Makefile.in: Regenerate.
* testsuite/testfile.cc: Add unwind_section_type.
* testsuite/pr23016_1.sh: New test script.
* testsuite/pr23016_1a.s: New source file.
* testsuite/pr23016_1b.s: New source file.
* testsuite/pr23016_2.sh: New test script.
* testsuite/pr23016_2a.s: New source file.
* testsuite/pr23016_2b.s: New source file.
In PR 22868, two IR files provide conflicting visibility for a symbol.
When a def with PROTECTED visibility is seen after a def with DEFAULT
visibility, gold does not override the visibility. Later, if the
replacement object define the symbol with DEFAULT visibility, the symbol
remains DEFAULT. This was caused by a recent change to allow multiply-defined
absolute symbols, combined with the fact that the plugin framework was using
SHN_ABS as the section index for placeholder symbols. The solution is to
use a real (but arbitrary) section index.
gold/
PR gold/22868
* plugin.cc (Sized_pluginobj::do_add_symbols): Use a real section
index instead of SHN_ABS for defined symbols.
* testsuite/Makefile.am (plugin_pr22868): New test case.
* testsuite/Makefile.in: Regenerate
* testsuite/plugin_pr22868.sh: New test script.
* testsuite/plugin_pr22868_a.c: New source file.
* testsuite/plugin_pr22868_b.c: New source file.
This option does not merge certain text sections with prefixes
.text.hot, .text.unlikely, .text.startup and .text.exit.
* layout.cc (Layout::default_section_order): Check for text section
prefixes.
(Layout::text_section_name_mapping): New static member.
(Layout::text_section_name_mapping_count): New static member.
(Layout::match_section_name): New static function.
(Layout::output_section_name): Check for text section prefixes.
* layout.h (Output_section_order::ORDER_TEXT_HOT): New enum value.
(Output_section_order::ORDER_TEXT_STARTUP): New enum value.
(Output_section_order::ORDER_TEXT_EXIT): New enum value.
(Output_section_order::ORDER_TEXT_UNLIKELY): New enum value.
(Layout::text_section_name_mapping): New static member.
(Layout::text_section_name_mapping_count): New static member.
(Layout::match_section_name): New static function.
* options.h (keep_text_section_prefix): New -z option.
* testsuite/Makefile.am (keep_text_section_prefix): New test.
* testsuite/Makefile.in: Regenerate.
* testsuite/keep_text_section_prefix.cc: New test source.
* testsuite/keep_text_section_prefix.sh: New test script.
2018-02-07 Sriraman Tallam <tmsriram@google.com>
* expression.cc (Symbol_expression::set_expr_sym_in_real_elf):
New method.
(Unary_expression::set_expr_sym_in_real_elf): New method.
(Binary_expression::set_expr_sym_in_real_elf): New method.
(Trinary_expression::set_expr_sym_in_real_elf): New method.
* plugin.cc (get_symbol_resolution_info): Fix symbol resolution if
defined or used in defsyms.
* plugin.h (Plugin_manager::is_defsym_def): New method.
(Plugin_manager::Plugin_manager): Initialize defsym_defines_set_.
(Plugin_manager::defsym_defines_set_): New member.
(Plugin_manager::Defsym_defines_set): New typedef.
* script.cc (Script_options::set_defsym_uses_in_real_elf): New method.
(Script_options::find_defsym_defs): New method.
* script.h (Expression::set_expr_sym_in_real_elf): New method.
(Symbol_assignment::is_defsym): New method.
(Symbol_assignment::value): New method.
(Script_options::find_defsym_defs): New method.
(Script_options::set_defsym_uses_in_real_elf): New method.
* testsuite/Makefile.am (plugin_test_defsym): New test.
* testsuite/Makefile.in: Regenerate.
* testsuite/plugin_test.c: Check for new symbol resolution.
* testsuite/plugin_test_defsym.sh: New script.
* testsuite/plugin_test_defsym.c: New test source.
This reverts most of commit 1be5d8d3bb.
Left in place are addition of --no-plt-align to some ppc32 ld tests
and the ld.texinfo --no-plt-thread-safe fix.
Reads the maximum_operations_per_instruction field, added in DWARF-4 to the
line number program header.
gold/
* PR gold/22776
* dwarf_reader.cc (Sized_dwarf_line_info::read_header_prolog): Add
support for DWARF-4 line number tables.
* dwarf_reader.h (Sized_dwarf_line_info::max_ops_per_insn): New field.
Asking for ppc32 plt call stubs to be aligned at 32 byte boundaries
didn't quite work. For ld.bfd they were spaced 32 bytes apart, but
only started on a 16 byte boundary. ld.gold also didn't get it right.
Finding that bug made me check over the ppc64 plt stub alignment,
where I found that negative values for alignment (meaning align to
minimize boundary crossing) were not accepted. Since no one has
complained about that, I guess I could have removed the feature from
ld.bfd documentation, but I've opted instead to correct the code.
I've also added an optional alignment paramenter for ppc32
--plt-align, for some consistency with gold and ppc64 ld.bfd.
bfd/
* elf32-ppc.c (ppc_elf_create_glink): Correct alignment of .glink.
* elf64-ppc.c (ppc64_elf_size_stubs): Handle negative plt_stub_align.
(ppc64_elf_build_stubs): Likewise.
gold/
* powerpc.cc (param_plt_align): New function supplying default
--plt-align values. Use it..
(Stub_table::plt_call_align): ..here, and..
(Output_data_glink::global_entry_align): ..here.
(Stub_table::stub_align): Correct 32-bit minimum alignment.
ld/
* emultempl/ppc32elf.em: Support optional --plt-align arg.
* emultempl/ppc64elf.em: Support negative --plt-align arg.
This is in preparation for the next patch adding Spectre variant 2
mitigation for PowerPC and PowerPC64. Besides tidying code involved
in stub output (to reduce the number of places where bctr is output),
the patch adds some user visible features:
1) PowerPC64 ELFv2 global entry stubs now are aligned under the
control of --plt-align, with a default alignment of 32 bytes.
2) PowerPC64 __glink_PLTresolve is no longer padded out with nops.
3) PowerPC32 PLT stubs are aligned under the control of --plt-align,
with the default alignment being 16 bytes as before.
4) The PowerPC32 branch/nop table emitted before __glink_PLTresolve
is now smaller in many cases. It was sized incorrectly when the
__tls_get_addr_opt stub was used, and unnecessarily included space
for local ifuncs.
bfd/
* elf32-ppc.c (GLINK_ENTRY_SIZE): Add parameters, handle
__tls_get_addr_opt, and alignment sizing.
(TLS_GET_ADDR_GLINK_SIZE): Delete.
(is_nonpic_glink_stub): Don't use GLINK_ENTRY_SIZE.
(ppc_elf_get_synthetic_symtab): Recognize stubs spaced at 4, 6,
or 8 insns.
(ppc_elf_link_hash_table_create): Init new ppc_elf_params field.
(allocate_dynrelocs): Use new GLINK_ENTRY_SIZE.
(ppc_elf_size_dynamic_sections): Likewise. Size branch table
by PLT reloc count.
(write_glink_stub): Handle __tls_get_addr_opt stub.
Pad out to size given by GLINK_ENTRY_SIZE.
(ppc_elf_relocate_section): Adjust write_glink_stub call.
(ppc_elf_finish_dynamic_symbol): Likewise.
(ppc_elf_finish_dynamic_sections): Write PLTresolve without using
insn array since so many need rewriting.
* elf32-ppc.h (struct ppc_elf_params): Add plt_stub_align.
* elf64-ppc.c (GLINK_PLTRESOLVE_SIZE): Rename from
GLINK_CALL_STUB_SIZE. Add htab param and evaluate to size without
nops. Adjust all uses.
(ppc64_elf_get_synthetic_symtab): Don't use GLINK_CALL_STUB_SIZE
in glink_vma calculation.
(struct ppc_link_hash_table): Add global_entry section pointer.
(create_linkage_sections): Create separate section for global
entry stubs.
(PPC_LO, PPC_HI, PPC_HA): Move earlier.
(size_global_entry_stubs): Handle sizing for aligned stubs.
(ppc64_elf_size_dynamic_sections): Handle global_entry alloc,
and don't stash end of glink branch table in rawsize.
(ppc_build_one_stub): Rewrite stub size calculations.
(build_global_entry_stubs): Use new section.
(ppc64_elf_build_stubs): Don't pad __glink_PLTresolve with nops.
Build lazy link stubs out to end of section. Build global entry
stubs in new section.
gold/
* options.h (plt_align): Support for PowerPC32 too.
* powerpc.cc (Stub_table::stub_align): Heed --plt-align for 32-bit.
(Stub_table::plt_call_size, branch_stub_size): Tidy.
(Stub_table::plt_call_align): Implement using stub_align.
(Output_data_glink::global_entry_align): New function.
(Output_data_glink::global_entry_off): New function.
(Output_data_glink::global_entry_address): Use global_entry_off.
(Output_data_glink::pltresolve_size): New function, replacing
pltresolve_size_ constant. Update all uses.
(Output_data_glink::add_global_entry): Align offset.
(Output_data_glink::set_final_data_size): Use global_entry_align.
(Stub_table::do_write): Don't pad __glink_PLTrelsolve with nops.
Tidy stub output. Use global_entry_off.
ld/
* emultempl/ppc32elf.em (params): Init new field.
(enum ppc32_opt): New enum to define OPTION_* values. Add
OPTION_PLT_ALIGN and OPTION_NO_PLT_ALIGN.
(PARSE_AND_LIST_LONGOPTS): Handle new options.
(PARSE_AND_LIST_ARGS_CASES): Likewise.
(PARSE_AND_LIST_OPTIONS): Likewise. Break up help output.
* emultempl/ppc64elf.em (ppc_add_stub_section): Init alignment
correctly for negative --plt-stub-align.
* testsuite/ld-powerpc/elfv2exe.d,
* testsuite/ld-powerpc/elfv2so.d,
* testsuite/ld-powerpc/relbrlt.d,
* testsuite/ld-powerpc/relbrlt.s,
* testsuite/ld-powerpc/tlsexe.d,
* testsuite/ld-powerpc/tlsexe.r,
* testsuite/ld-powerpc/tlsexe32.d,
* testsuite/ld-powerpc/tlsexe32.g,
* testsuite/ld-powerpc/tlsexe32.r,
* testsuite/ld-powerpc/tlsexetoc.d,
* testsuite/ld-powerpc/tlsexetoc.r,
* testsuite/ld-powerpc/tlsopt5_32.d,
* testsuite/ld-powerpc/tlsso.d,
* testsuite/ld-powerpc/tlstocso.d: Update for changed stub order.
PR 22042 complained that garbage text was being printed in the help
for the -fuse-ld option; this was caused by passing an empty string
to the gettext() function, which sometimes returns garbage when passed
an empty string. The quick fix was to replace "" with NULL as the helparg,
but that changed the parsing of the option, as gold uses the helparg to
determine whether an option takes an argument. This patch adds a
non-empty helparg string to fix both problems.
gold/
PR gold/22694
* options.h (-fuse-ld): Add correct helparg.
