New gold linker option -z,text-unlikely-segment.
2017-10-04 Sriraman Tallam <tmsriram@google.com> * options.h (-z,text_unlikely_segment): New option. * layout.cc (Layout::layout): Create new output section for .text.unlikely sections with the new option. (Layout::segment_precedes): Check for the new option when segment flags match. * testsuite/text_unlikely_segment.cc: New test source. * testsuite/text_unlikely_segment.sh: New test script. * testsuite/Makefile.am (text_unlikely_segment): New test. * testsuite/Makefile.in: Regenerate.
This commit is contained in:
Sriraman Tallam
parent
f3012016f0
commit
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7 changed files with 178 additions and 25 deletions
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@ -1,3 +1,15 @@
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2017-10-04 Sriraman Tallam <tmsriram@google.com>
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* options.h (-z,text_unlikely_segment): New option.
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* layout.cc (Layout::layout): Create new output section
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for .text.unlikely sections with the new option.
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(Layout::segment_precedes): Check for the new option
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when segment flags match.
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* testsuite/text_unlikely_segment.cc: New test source.
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* testsuite/text_unlikely_segment.sh: New test script.
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* testsuite/Makefile.am (text_unlikely_segment): New test.
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* testsuite/Makefile.in: Regenerate.
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2017-10-19 Umesh Kalappa <ukalappa@cisco.com>
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* arm.cc (Stub::do_fixed_endian_write):Far call stubs support for arm
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@ -1178,38 +1178,62 @@ Layout::layout(Sized_relobj_file<size, big_endian>* object, unsigned int shndx,
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}
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else
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{
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// Plugins can choose to place one or more subsets of sections in
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// unique segments and this is done by mapping these section subsets
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// to unique output sections. Check if this section needs to be
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// remapped to a unique output section.
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Section_segment_map::iterator it
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= this->section_segment_map_.find(Const_section_id(object, shndx));
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if (it == this->section_segment_map_.end())
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{
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os = this->choose_output_section(object, name, sh_type,
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shdr.get_sh_flags(), true,
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ORDER_INVALID, false, false,
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true);
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}
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else
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{
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// We know the name of the output section, directly call
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// get_output_section here by-passing choose_output_section.
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// All ".text.unlikely.*" sections can be moved to a unique
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// segment with --text-unlikely-segment option.
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bool text_unlikely_segment
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= (parameters->options().text_unlikely_segment()
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&& is_prefix_of(".text.unlikely",
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object->section_name(shndx).c_str()));
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if (text_unlikely_segment)
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{
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elfcpp::Elf_Xword flags
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= this->get_output_section_flags(shdr.get_sh_flags());
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const char* os_name = it->second->name;
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Stringpool::Key name_key;
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os_name = this->namepool_.add(os_name, true, &name_key);
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const char* os_name = this->namepool_.add(".text.unlikely", true,
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&name_key);
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os = this->get_output_section(os_name, name_key, sh_type, flags,
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ORDER_INVALID, false);
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if (!os->is_unique_segment())
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// Map this output section to a unique segment. This is done to
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// separate "text" that is not likely to be executed from "text"
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// that is likely executed.
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os->set_is_unique_segment();
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}
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else
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{
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// Plugins can choose to place one or more subsets of sections in
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// unique segments and this is done by mapping these section subsets
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// to unique output sections. Check if this section needs to be
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// remapped to a unique output section.
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Section_segment_map::iterator it
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= this->section_segment_map_.find(Const_section_id(object, shndx));
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if (it == this->section_segment_map_.end())
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{
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os->set_is_unique_segment();
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os->set_extra_segment_flags(it->second->flags);
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os->set_segment_alignment(it->second->align);
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os = this->choose_output_section(object, name, sh_type,
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shdr.get_sh_flags(), true,
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ORDER_INVALID, false, false,
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true);
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}
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}
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else
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{
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// We know the name of the output section, directly call
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// get_output_section here by-passing choose_output_section.
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elfcpp::Elf_Xword flags
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= this->get_output_section_flags(shdr.get_sh_flags());
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const char* os_name = it->second->name;
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Stringpool::Key name_key;
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os_name = this->namepool_.add(os_name, true, &name_key);
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os = this->get_output_section(os_name, name_key, sh_type, flags,
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ORDER_INVALID, false);
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if (!os->is_unique_segment())
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{
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os->set_is_unique_segment();
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os->set_extra_segment_flags(it->second->flags);
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os->set_segment_alignment(it->second->align);
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}
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}
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}
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if (os == NULL)
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return NULL;
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}
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@ -3449,7 +3473,8 @@ Layout::segment_precedes(const Output_segment* seg1,
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// here if plugins want unique segments for subsets of sections.
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gold_assert(this->script_options_->saw_phdrs_clause()
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|| parameters->options().any_section_start()
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|| this->is_unique_segment_for_sections_specified());
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|| this->is_unique_segment_for_sections_specified()
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|| parameters->options().text_unlikely_segment());
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return false;
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}
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@ -1492,6 +1492,11 @@ class General_options
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DEFINE_bool_alias(textoff, text, options::DASH_Z, '\0',
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N_("Permit relocations in read-only segments"),
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NULL, true);
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DEFINE_bool(text_unlikely_segment, options::DASH_Z, '\0', false,
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N_("Move .text.unlikely sections to a separate segment."),
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N_("Do not move .text.unlikely sections to a separate "
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"segment."));
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public:
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typedef options::Dir_list Dir_list;
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@ -340,6 +340,16 @@ section_sorting_name: section_sorting_name.o gcctestdir/ld
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section_sorting_name.stdout: section_sorting_name
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$(TEST_NM) -n --synthetic section_sorting_name > section_sorting_name.stdout
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check_SCRIPTS += text_unlikely_segment.sh
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check_DATA += text_unlikely_segment_readelf.stdout
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MOSTLYCLEANFILES += text_unlikely_segment
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text_unlikely_segment.o: text_unlikely_segment.cc
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$(CXXCOMPILE) -O0 -c -ffunction-sections -g -o $@ $<
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text_unlikely_segment: text_unlikely_segment.o gcctestdir/ld
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$(CXXLINK) -Bgcctestdir/ -Wl,-z,text-unlikely-segment text_unlikely_segment.o
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text_unlikely_segment_readelf.stdout: text_unlikely_segment
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$(TEST_READELF) -Wl $< >$@
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check_PROGRAMS += icf_virtual_function_folding_test
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MOSTLYCLEANFILES += icf_virtual_function_folding_test icf_virtual_function_folding_test.map
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icf_virtual_function_folding_test.o: icf_virtual_function_folding_test.cc
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@ -87,6 +87,7 @@ check_PROGRAMS = $(am__EXEEXT_1) $(am__EXEEXT_2) $(am__EXEEXT_3) \
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@GCC_TRUE@@NATIVE_LINKER_TRUE@ final_layout.sh \
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@GCC_TRUE@@NATIVE_LINKER_TRUE@ text_section_grouping.sh \
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@GCC_TRUE@@NATIVE_LINKER_TRUE@ section_sorting_name.sh \
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@GCC_TRUE@@NATIVE_LINKER_TRUE@ text_unlikely_segment.sh \
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@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_preemptible_functions_test.sh \
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@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_string_merge_test.sh \
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@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_sht_rel_addend_test.sh \
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@ -114,6 +115,7 @@ check_PROGRAMS = $(am__EXEEXT_1) $(am__EXEEXT_2) $(am__EXEEXT_3) \
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@GCC_TRUE@@NATIVE_LINKER_TRUE@ text_section_grouping.stdout \
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@GCC_TRUE@@NATIVE_LINKER_TRUE@ text_section_no_grouping.stdout \
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@GCC_TRUE@@NATIVE_LINKER_TRUE@ section_sorting_name.stdout \
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@GCC_TRUE@@NATIVE_LINKER_TRUE@ text_unlikely_segment_readelf.stdout \
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@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_preemptible_functions_test.stdout \
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@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_string_merge_test.stdout \
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@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_sht_rel_addend_test.stdout \
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@ -139,6 +141,7 @@ check_PROGRAMS = $(am__EXEEXT_1) $(am__EXEEXT_2) $(am__EXEEXT_3) \
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@GCC_TRUE@@NATIVE_LINKER_TRUE@ text_section_grouping \
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@GCC_TRUE@@NATIVE_LINKER_TRUE@ text_section_no_grouping \
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@GCC_TRUE@@NATIVE_LINKER_TRUE@ section_sorting_name \
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@GCC_TRUE@@NATIVE_LINKER_TRUE@ text_unlikely_segment \
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@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_virtual_function_folding_test \
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@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_virtual_function_folding_test.map \
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@GCC_TRUE@@NATIVE_LINKER_TRUE@ icf_preemptible_functions_test \
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@ -5148,6 +5151,8 @@ text_section_grouping.sh.log: text_section_grouping.sh
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@p='text_section_grouping.sh'; $(am__check_pre) $(LOG_COMPILE) "$$tst" $(am__check_post)
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section_sorting_name.sh.log: section_sorting_name.sh
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@p='section_sorting_name.sh'; $(am__check_pre) $(LOG_COMPILE) "$$tst" $(am__check_post)
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text_unlikely_segment.sh.log: text_unlikely_segment.sh
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@p='text_unlikely_segment.sh'; $(am__check_pre) $(LOG_COMPILE) "$$tst" $(am__check_post)
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icf_preemptible_functions_test.sh.log: icf_preemptible_functions_test.sh
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@p='icf_preemptible_functions_test.sh'; $(am__check_pre) $(LOG_COMPILE) "$$tst" $(am__check_post)
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icf_string_merge_test.sh.log: icf_string_merge_test.sh
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@ -6015,6 +6020,12 @@ uninstall-am:
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@GCC_TRUE@@NATIVE_LINKER_TRUE@ $(CXXLINK) -Bgcctestdir/ -Wl,--sort-section=name section_sorting_name.o
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@GCC_TRUE@@NATIVE_LINKER_TRUE@section_sorting_name.stdout: section_sorting_name
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@GCC_TRUE@@NATIVE_LINKER_TRUE@ $(TEST_NM) -n --synthetic section_sorting_name > section_sorting_name.stdout
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@GCC_TRUE@@NATIVE_LINKER_TRUE@text_unlikely_segment.o: text_unlikely_segment.cc
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@GCC_TRUE@@NATIVE_LINKER_TRUE@ $(CXXCOMPILE) -O0 -c -ffunction-sections -g -o $@ $<
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@GCC_TRUE@@NATIVE_LINKER_TRUE@text_unlikely_segment: text_unlikely_segment.o gcctestdir/ld
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@GCC_TRUE@@NATIVE_LINKER_TRUE@ $(CXXLINK) -Bgcctestdir/ -Wl,-z,text-unlikely-segment text_unlikely_segment.o
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@GCC_TRUE@@NATIVE_LINKER_TRUE@text_unlikely_segment_readelf.stdout: text_unlikely_segment
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@GCC_TRUE@@NATIVE_LINKER_TRUE@ $(TEST_READELF) -Wl $< >$@
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@GCC_TRUE@@NATIVE_LINKER_TRUE@icf_virtual_function_folding_test.o: icf_virtual_function_folding_test.cc
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@GCC_TRUE@@NATIVE_LINKER_TRUE@ $(CXXCOMPILE) -O0 -c -ffunction-sections -fPIE -g -o $@ $<
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@GCC_TRUE@@NATIVE_LINKER_TRUE@icf_virtual_function_folding_test: icf_virtual_function_folding_test.o gcctestdir/ld
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30
gold/testsuite/text_unlikely_segment.cc
Normal file
30
gold/testsuite/text_unlikely_segment.cc
Normal file
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@ -0,0 +1,30 @@
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/* text_unlikey_segment.cc -- a test case for gold
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Copyright (C) 2017 onwards Free Software Foundation, Inc.
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Written by Sriraman Tallam <tmsriram@google.com>
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This file is part of gold.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
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MA 02110-1301, USA. */
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__attribute__((section(".text.unlikely")))
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int foo(void) {
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return 0;
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}
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int main(void) {
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return 0;
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}
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60
gold/testsuite/text_unlikely_segment.sh
Executable file
60
gold/testsuite/text_unlikely_segment.sh
Executable file
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@ -0,0 +1,60 @@
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#!/bin/sh
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# plugin_final_layout.sh -- test
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# Copyright (C) 2011-2017 Free Software Foundation, Inc.
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# Written by Sriraman Tallam <tmsriram@google.com>.
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# This file is part of gold.
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 3 of the License, or
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# (at your option) any later version.
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
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# MA 02110-1301, USA.
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# The goal of this program is to verify if -z,text-unlikely-segment works as
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# intended. File text_unlikely_segment.cc is part of this test.
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set -e
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# With readelf -l, an ELF Section to Segment mapping is printed as :
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##############################################
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# Section to Segment mapping:
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# Segment Sections...
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# ...
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# 0x .text.unlikely
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# ...
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##############################################
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# Check if .text.unlikely is the only section in the segment.
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check_unique_segment()
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{
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awk "
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BEGIN { saw_section = 0; saw_unique = 0; }
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/$2/ { saw_section = 1; }
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/[ ]*0[0-9][ ]*$2[ ]*\$/ { saw_unique = 1; }
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END {
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if (!saw_section)
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{
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printf \"Section $2 not seen in output\\n\";
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exit 1;
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}
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else if (!saw_unique)
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{
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printf \"Unique segment not seen for: $2\\n\";
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exit 1;
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}
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}" $1
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}
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check_unique_segment text_unlikely_segment_readelf.stdout ".text.unlikely"
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