compiler/elf_writer_quick.cc - platform/art - Gitiles

 /*
  * Copyright (C) 2012 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #include "elf_writer_quick.h"

 #include <unordered_map>
 #include <unordered_set>

 #include "base/logging.h"
 #include "base/unix_file/fd_file.h"
 #include "compiled_method.h"
 #include "dex_file-inl.h"
 #include "driver/compiler_driver.h"
 #include "driver/compiler_options.h"
 #include "elf_builder.h"
 #include "elf_file.h"
 #include "elf_utils.h"
 #include "elf_writer_debug.h"
 #include "globals.h"
 #include "leb128.h"
 #include "oat.h"
 #include "oat_writer.h"
 #include "utils.h"

 namespace art {

 // .eh_frame and .debug_frame are almost identical.
 // Except for some minor formatting differences, the main difference
 // is that .eh_frame is allocated within the running program because
 // it is used by C++ exception handling (which we do not use so we
 // can choose either).  C++ compilers generally tend to use .eh_frame
 // because if they need it sometimes, they might as well always use it.
 constexpr dwarf::CFIFormat kCFIFormat = dwarf::DW_EH_FRAME_FORMAT;

 template <typename ElfTypes>
 bool ElfWriterQuick<ElfTypes>::Create(File* elf_file,
                                       OatWriter* oat_writer,
                                       const std::vector<const DexFile*>& dex_files,
                                       const std::string& android_root,
                                       bool is_host,
                                       const CompilerDriver& driver) {
   ElfWriterQuick elf_writer(driver, elf_file);
   return elf_writer.Write(oat_writer, dex_files, android_root, is_host);
 }

 template <typename ElfTypes>
 static void WriteDebugSymbols(ElfBuilder<ElfTypes>* builder, OatWriter* oat_writer);

 // Encode patch locations in .oat_patches format.
 template <typename ElfTypes>
 void ElfWriterQuick<ElfTypes>::EncodeOatPatches(
     const OatWriter::PatchLocationsMap& sections,
     std::vector<uint8_t>* buffer) {
   for (const auto& section : sections) {
     const std::string& name = section.first;
     std::vector<uintptr_t>* locations = section.second.get();
     DCHECK(!name.empty());
     std::sort(locations->begin(), locations->end());
     // Reserve buffer space - guess 2 bytes per ULEB128.
     buffer->reserve(buffer->size() + name.size() + locations->size() * 2);
     // Write null-terminated section name.
     const uint8_t* name_data = reinterpret_cast<const uint8_t*>(name.c_str());
     buffer->insert(buffer->end(), name_data, name_data + name.size() + 1);
     // Write placeholder for data length.
     size_t length_pos = buffer->size();
     EncodeUnsignedLeb128(buffer, UINT32_MAX);
     // Write LEB128 encoded list of advances (deltas between consequtive addresses).
     size_t data_pos = buffer->size();
     uintptr_t address = 0;  // relative to start of section.
     for (uintptr_t location : *locations) {
       DCHECK_LT(location - address, UINT32_MAX) << "Large gap between patch locations";
       EncodeUnsignedLeb128(buffer, location - address);
       address = location;
     }
     // Update length.
     UpdateUnsignedLeb128(buffer->data() + length_pos, buffer->size() - data_pos);
   }
   buffer->push_back(0);  // End of sections.
 }

 class RodataWriter FINAL : public CodeOutput {
  public:
   explicit RodataWriter(OatWriter* oat_writer) : oat_writer_(oat_writer) {}

   bool Write(OutputStream* out) OVERRIDE {
     return oat_writer_->WriteRodata(out);
   }

  private:
   OatWriter* oat_writer_;
 };

 class TextWriter FINAL : public CodeOutput {
  public:
   explicit TextWriter(OatWriter* oat_writer) : oat_writer_(oat_writer) {}

   bool Write(OutputStream* out) OVERRIDE {
     return oat_writer_->WriteCode(out);
   }

  private:
   OatWriter* oat_writer_;
 };

 enum PatchResult {
   kAbsoluteAddress,  // Absolute memory location.
   kPointerRelativeAddress,  // Offset relative to the location of the pointer.
   kSectionRelativeAddress,  // Offset relative to start of containing section.
 };

 // Patch memory addresses within a buffer.
 // It assumes that the unpatched addresses are offsets relative to base_address.
 // (which generally means method's low_pc relative to the start of .text)
 template <typename Elf_Addr, typename Address, PatchResult kPatchResult>
 static void Patch(const std::vector<uintptr_t>& patch_locations,
                   Elf_Addr buffer_address, Elf_Addr base_address,
                   std::vector<uint8_t>* buffer) {
   for (uintptr_t location : patch_locations) {
     typedef __attribute__((__aligned__(1))) Address UnalignedAddress;
     auto* to_patch = reinterpret_cast<UnalignedAddress*>(buffer->data() + location);
     switch (kPatchResult) {
       case kAbsoluteAddress:
         *to_patch = (base_address + *to_patch);
         break;
       case kPointerRelativeAddress:
         *to_patch = (base_address + *to_patch) - (buffer_address + location);
         break;
       case kSectionRelativeAddress:
         *to_patch = (base_address + *to_patch) - buffer_address;
         break;
     }
   }
 }

 template <typename ElfTypes>
 bool ElfWriterQuick<ElfTypes>::Write(
     OatWriter* oat_writer,
     const std::vector<const DexFile*>& dex_files_unused ATTRIBUTE_UNUSED,
     const std::string& android_root_unused ATTRIBUTE_UNUSED,
     bool is_host_unused ATTRIBUTE_UNUSED) {
   using Elf_Addr = typename ElfTypes::Addr;
   const InstructionSet isa = compiler_driver_->GetInstructionSet();

   // Setup the builder with the main OAT sections (.rodata .text .bss).
   const size_t rodata_size = oat_writer->GetOatHeader().GetExecutableOffset();
   const size_t text_size = oat_writer->GetSize() - rodata_size;
   const size_t bss_size = oat_writer->GetBssSize();
   RodataWriter rodata_writer(oat_writer);
   TextWriter text_writer(oat_writer);
   std::unique_ptr<ElfBuilder<ElfTypes>> builder(new ElfBuilder<ElfTypes>(
       isa, rodata_size, &rodata_writer, text_size, &text_writer, bss_size));

   // Add debug sections.
   // They are stack allocated here (in the same scope as the builder),
   // but they are registred with the builder only if they are used.
   using RawSection = typename ElfBuilder<ElfTypes>::RawSection;
   const auto* text = builder->GetText();
   const bool is64bit = Is64BitInstructionSet(isa);
   const int pointer_size = GetInstructionSetPointerSize(isa);
   RawSection eh_frame(".eh_frame", SHT_PROGBITS, SHF_ALLOC, nullptr, 0, kPageSize, 0,
                       is64bit ? Patch<Elf_Addr, uint64_t, kPointerRelativeAddress> :
                                 Patch<Elf_Addr, uint32_t, kPointerRelativeAddress>,
                       text);
   RawSection eh_frame_hdr(".eh_frame_hdr", SHT_PROGBITS, SHF_ALLOC, nullptr, 0, 4, 0,
                           Patch<Elf_Addr, uint32_t, kSectionRelativeAddress>, text);
   RawSection debug_frame(".debug_frame", SHT_PROGBITS, 0, nullptr, 0, pointer_size, 0,
                          is64bit ? Patch<Elf_Addr, uint64_t, kAbsoluteAddress> :
                                    Patch<Elf_Addr, uint32_t, kAbsoluteAddress>,
                          text);
   RawSection debug_info(".debug_info", SHT_PROGBITS, 0, nullptr, 0, 1, 0,
                         Patch<Elf_Addr, uint32_t, kAbsoluteAddress>, text);
   RawSection debug_abbrev(".debug_abbrev", SHT_PROGBITS, 0, nullptr, 0, 1, 0);
   RawSection debug_str(".debug_str", SHT_PROGBITS, 0, nullptr, 0, 1, 0);
   RawSection debug_line(".debug_line", SHT_PROGBITS, 0, nullptr, 0, 1, 0,
                         Patch<Elf_Addr, uint32_t, kAbsoluteAddress>, text);
   if (!oat_writer->GetMethodDebugInfo().empty()) {
     if (compiler_driver_->GetCompilerOptions().GetIncludeCFI()) {
       if (kCFIFormat == dwarf::DW_EH_FRAME_FORMAT) {
         dwarf::WriteCFISection(
             compiler_driver_, oat_writer,
             dwarf::DW_EH_PE_pcrel, kCFIFormat,
             eh_frame.GetBuffer(), eh_frame.GetPatchLocations(),
             eh_frame_hdr.GetBuffer(), eh_frame_hdr.GetPatchLocations());
         builder->RegisterSection(&eh_frame);
         builder->RegisterSection(&eh_frame_hdr);
       } else {
         DCHECK(kCFIFormat == dwarf::DW_DEBUG_FRAME_FORMAT);
         dwarf::WriteCFISection(
             compiler_driver_, oat_writer,
             dwarf::DW_EH_PE_absptr, kCFIFormat,
             debug_frame.GetBuffer(), debug_frame.GetPatchLocations(),
             nullptr, nullptr);
         builder->RegisterSection(&debug_frame);
         *oat_writer->GetAbsolutePatchLocationsFor(".debug_frame") =
             *debug_frame.GetPatchLocations();
       }
     }
     if (compiler_driver_->GetCompilerOptions().GetIncludeDebugSymbols()) {
       // Add methods to .symtab.
       WriteDebugSymbols(builder.get(), oat_writer);
       // Generate DWARF .debug_* sections.
       dwarf::WriteDebugSections(
           compiler_driver_, oat_writer,
           debug_info.GetBuffer(), debug_info.GetPatchLocations(),
           debug_abbrev.GetBuffer(),
           debug_str.GetBuffer(),
           debug_line.GetBuffer(), debug_line.GetPatchLocations());
       builder->RegisterSection(&debug_info);
       builder->RegisterSection(&debug_abbrev);
       builder->RegisterSection(&debug_str);
       builder->RegisterSection(&debug_line);
       *oat_writer->GetAbsolutePatchLocationsFor(".debug_info") =
           *debug_info.GetPatchLocations();
       *oat_writer->GetAbsolutePatchLocationsFor(".debug_line") =
           *debug_line.GetPatchLocations();
     }
   }

   // Add relocation section.
   RawSection oat_patches(".oat_patches", SHT_OAT_PATCH, 0, nullptr, 0, 1, 0);
   if (compiler_driver_->GetCompilerOptions().GetIncludePatchInformation() ||
       // ElfWriter::Fixup will be called regardless and it needs to be able
       // to patch debug sections so we have to include patches for them.
       compiler_driver_->GetCompilerOptions().GetIncludeDebugSymbols()) {
     EncodeOatPatches(oat_writer->GetAbsolutePatchLocations(), oat_patches.GetBuffer());
     builder->RegisterSection(&oat_patches);
   }

   return builder->Write(elf_file_);
 }

 template <typename ElfTypes>
 static void WriteDebugSymbols(ElfBuilder<ElfTypes>* builder, OatWriter* oat_writer) {
   const std::vector<OatWriter::DebugInfo>& method_info = oat_writer->GetMethodDebugInfo();

   // Find all addresses (low_pc) which contain deduped methods.
   // The first instance of method is not marked deduped_, but the rest is.
   std::unordered_set<uint32_t> deduped_addresses;
   for (auto it = method_info.begin(); it != method_info.end(); ++it) {
     if (it->deduped_) {
       deduped_addresses.insert(it->low_pc_);
     }
   }

   auto* symtab = builder->GetSymtab();
   for (auto it = method_info.begin(); it != method_info.end(); ++it) {
     if (it->deduped_) {
       continue;  // Add symbol only for the first instance.
     }
     std::string name = PrettyMethod(it->dex_method_index_, *it->dex_file_, true);
     if (deduped_addresses.find(it->low_pc_) != deduped_addresses.end()) {
       name += " [DEDUPED]";
     }

     uint32_t low_pc = it->low_pc_;
     // Add in code delta, e.g., thumb bit 0 for Thumb2 code.
     low_pc += it->compiled_method_->CodeDelta();
     symtab->AddSymbol(name, builder->GetText(), low_pc,
                       true, it->high_pc_ - it->low_pc_, STB_GLOBAL, STT_FUNC);

     // Conforming to aaelf, add $t mapping symbol to indicate start of a sequence of thumb2
     // instructions, so that disassembler tools can correctly disassemble.
     if (it->compiled_method_->GetInstructionSet() == kThumb2) {
       symtab->AddSymbol("$t", builder->GetText(), it->low_pc_ & ~1, true,
                         0, STB_LOCAL, STT_NOTYPE);
     }
   }
 }

 // Explicit instantiations
 template class ElfWriterQuick<ElfTypes32>;
 template class ElfWriterQuick<ElfTypes64>;

 }  // namespace art
	/*
	* Copyright (C) 2012 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#include "elf_writer_quick.h"

	#include <unordered_map>
	#include <unordered_set>

	#include "base/logging.h"
	#include "base/unix_file/fd_file.h"
	#include "compiled_method.h"
	#include "dex_file-inl.h"
	#include "driver/compiler_driver.h"
	#include "driver/compiler_options.h"
	#include "elf_builder.h"
	#include "elf_file.h"
	#include "elf_utils.h"
	#include "elf_writer_debug.h"
	#include "globals.h"
	#include "leb128.h"
	#include "oat.h"
	#include "oat_writer.h"
	#include "utils.h"

	namespace art {

	// .eh_frame and .debug_frame are almost identical.
	// Except for some minor formatting differences, the main difference
	// is that .eh_frame is allocated within the running program because
	// it is used by C++ exception handling (which we do not use so we
	// can choose either). C++ compilers generally tend to use .eh_frame
	// because if they need it sometimes, they might as well always use it.
	constexpr dwarf::CFIFormat kCFIFormat = dwarf::DW_EH_FRAME_FORMAT;

	template <typename ElfTypes>
	bool ElfWriterQuick<ElfTypes>::Create(File* elf_file,
	OatWriter* oat_writer,
	const std::vector<const DexFile*>& dex_files,
	const std::string& android_root,
	bool is_host,
	const CompilerDriver& driver) {
	ElfWriterQuick elf_writer(driver, elf_file);
	return elf_writer.Write(oat_writer, dex_files, android_root, is_host);
	}

	template <typename ElfTypes>
	static void WriteDebugSymbols(ElfBuilder<ElfTypes>* builder, OatWriter* oat_writer);

	// Encode patch locations in .oat_patches format.
	template <typename ElfTypes>
	void ElfWriterQuick<ElfTypes>::EncodeOatPatches(
	const OatWriter::PatchLocationsMap& sections,
	std::vector<uint8_t>* buffer) {
	for (const auto& section : sections) {
	const std::string& name = section.first;
	std::vector<uintptr_t>* locations = section.second.get();
	DCHECK(!name.empty());
	std::sort(locations->begin(), locations->end());
	// Reserve buffer space - guess 2 bytes per ULEB128.
	buffer->reserve(buffer->size() + name.size() + locations->size() * 2);
	// Write null-terminated section name.
	const uint8_t* name_data = reinterpret_cast<const uint8_t*>(name.c_str());
	buffer->insert(buffer->end(), name_data, name_data + name.size() + 1);
	// Write placeholder for data length.
	size_t length_pos = buffer->size();
	EncodeUnsignedLeb128(buffer, UINT32_MAX);
	// Write LEB128 encoded list of advances (deltas between consequtive addresses).
	size_t data_pos = buffer->size();
	uintptr_t address = 0; // relative to start of section.
	for (uintptr_t location : *locations) {
	DCHECK_LT(location - address, UINT32_MAX) << "Large gap between patch locations";
	EncodeUnsignedLeb128(buffer, location - address);
	address = location;
	}
	// Update length.
	UpdateUnsignedLeb128(buffer->data() + length_pos, buffer->size() - data_pos);
	}
	buffer->push_back(0); // End of sections.
	}

	class RodataWriter FINAL : public CodeOutput {
	public:
	explicit RodataWriter(OatWriter* oat_writer) : oat_writer_(oat_writer) {}

	bool Write(OutputStream* out) OVERRIDE {
	return oat_writer_->WriteRodata(out);
	}

	private:
	OatWriter* oat_writer_;
	};

	class TextWriter FINAL : public CodeOutput {
	public:
	explicit TextWriter(OatWriter* oat_writer) : oat_writer_(oat_writer) {}

	bool Write(OutputStream* out) OVERRIDE {
	return oat_writer_->WriteCode(out);
	}

	private:
	OatWriter* oat_writer_;
	};

	enum PatchResult {
	kAbsoluteAddress, // Absolute memory location.
	kPointerRelativeAddress, // Offset relative to the location of the pointer.
	kSectionRelativeAddress, // Offset relative to start of containing section.
	};

	// Patch memory addresses within a buffer.
	// It assumes that the unpatched addresses are offsets relative to base_address.
	// (which generally means method's low_pc relative to the start of .text)
	template <typename Elf_Addr, typename Address, PatchResult kPatchResult>
	static void Patch(const std::vector<uintptr_t>& patch_locations,
	Elf_Addr buffer_address, Elf_Addr base_address,
	std::vector<uint8_t>* buffer) {
	for (uintptr_t location : patch_locations) {
	typedef __attribute__((__aligned__(1))) Address UnalignedAddress;
	auto* to_patch = reinterpret_cast<UnalignedAddress*>(buffer->data() + location);
	switch (kPatchResult) {
	case kAbsoluteAddress:
	to_patch = (base_address + to_patch);
	break;
	case kPointerRelativeAddress:
	to_patch = (base_address + to_patch) - (buffer_address + location);
	break;
	case kSectionRelativeAddress:
	to_patch = (base_address + to_patch) - buffer_address;
	break;
	}
	}
	}

	template <typename ElfTypes>
	bool ElfWriterQuick<ElfTypes>::Write(
	OatWriter* oat_writer,
	const std::vector<const DexFile*>& dex_files_unused ATTRIBUTE_UNUSED,
	const std::string& android_root_unused ATTRIBUTE_UNUSED,
	bool is_host_unused ATTRIBUTE_UNUSED) {
	using Elf_Addr = typename ElfTypes::Addr;
	const InstructionSet isa = compiler_driver_->GetInstructionSet();

	// Setup the builder with the main OAT sections (.rodata .text .bss).
	const size_t rodata_size = oat_writer->GetOatHeader().GetExecutableOffset();
	const size_t text_size = oat_writer->GetSize() - rodata_size;
	const size_t bss_size = oat_writer->GetBssSize();
	RodataWriter rodata_writer(oat_writer);
	TextWriter text_writer(oat_writer);
	std::unique_ptr<ElfBuilder<ElfTypes>> builder(new ElfBuilder<ElfTypes>(
	isa, rodata_size, &rodata_writer, text_size, &text_writer, bss_size));

	// Add debug sections.
	// They are stack allocated here (in the same scope as the builder),
	// but they are registred with the builder only if they are used.
	using RawSection = typename ElfBuilder<ElfTypes>::RawSection;
	const auto* text = builder->GetText();
	const bool is64bit = Is64BitInstructionSet(isa);
	const int pointer_size = GetInstructionSetPointerSize(isa);
	RawSection eh_frame(".eh_frame", SHT_PROGBITS, SHF_ALLOC, nullptr, 0, kPageSize, 0,
	is64bit ? Patch<Elf_Addr, uint64_t, kPointerRelativeAddress> :
	Patch<Elf_Addr, uint32_t, kPointerRelativeAddress>,
	text);
	RawSection eh_frame_hdr(".eh_frame_hdr", SHT_PROGBITS, SHF_ALLOC, nullptr, 0, 4, 0,
	Patch<Elf_Addr, uint32_t, kSectionRelativeAddress>, text);
	RawSection debug_frame(".debug_frame", SHT_PROGBITS, 0, nullptr, 0, pointer_size, 0,
	is64bit ? Patch<Elf_Addr, uint64_t, kAbsoluteAddress> :
	Patch<Elf_Addr, uint32_t, kAbsoluteAddress>,
	text);
	RawSection debug_info(".debug_info", SHT_PROGBITS, 0, nullptr, 0, 1, 0,
	Patch<Elf_Addr, uint32_t, kAbsoluteAddress>, text);
	RawSection debug_abbrev(".debug_abbrev", SHT_PROGBITS, 0, nullptr, 0, 1, 0);
	RawSection debug_str(".debug_str", SHT_PROGBITS, 0, nullptr, 0, 1, 0);
	RawSection debug_line(".debug_line", SHT_PROGBITS, 0, nullptr, 0, 1, 0,
	Patch<Elf_Addr, uint32_t, kAbsoluteAddress>, text);
	if (!oat_writer->GetMethodDebugInfo().empty()) {
	if (compiler_driver_->GetCompilerOptions().GetIncludeCFI()) {
	if (kCFIFormat == dwarf::DW_EH_FRAME_FORMAT) {
	dwarf::WriteCFISection(
	compiler_driver_, oat_writer,
	dwarf::DW_EH_PE_pcrel, kCFIFormat,
	eh_frame.GetBuffer(), eh_frame.GetPatchLocations(),
	eh_frame_hdr.GetBuffer(), eh_frame_hdr.GetPatchLocations());
	builder->RegisterSection(&eh_frame);
	builder->RegisterSection(&eh_frame_hdr);
	} else {
	DCHECK(kCFIFormat == dwarf::DW_DEBUG_FRAME_FORMAT);
	dwarf::WriteCFISection(
	compiler_driver_, oat_writer,
	dwarf::DW_EH_PE_absptr, kCFIFormat,
	debug_frame.GetBuffer(), debug_frame.GetPatchLocations(),
	nullptr, nullptr);
	builder->RegisterSection(&debug_frame);
	*oat_writer->GetAbsolutePatchLocationsFor(".debug_frame") =
	*debug_frame.GetPatchLocations();
	}
	}
	if (compiler_driver_->GetCompilerOptions().GetIncludeDebugSymbols()) {
	// Add methods to .symtab.
	WriteDebugSymbols(builder.get(), oat_writer);
	// Generate DWARF .debug_* sections.
	dwarf::WriteDebugSections(
	compiler_driver_, oat_writer,
	debug_info.GetBuffer(), debug_info.GetPatchLocations(),
	debug_abbrev.GetBuffer(),
	debug_str.GetBuffer(),
	debug_line.GetBuffer(), debug_line.GetPatchLocations());
	builder->RegisterSection(&debug_info);
	builder->RegisterSection(&debug_abbrev);
	builder->RegisterSection(&debug_str);
	builder->RegisterSection(&debug_line);
	*oat_writer->GetAbsolutePatchLocationsFor(".debug_info") =
	*debug_info.GetPatchLocations();
	*oat_writer->GetAbsolutePatchLocationsFor(".debug_line") =
	*debug_line.GetPatchLocations();
	}
	}

	// Add relocation section.
	RawSection oat_patches(".oat_patches", SHT_OAT_PATCH, 0, nullptr, 0, 1, 0);
	if (compiler_driver_->GetCompilerOptions().GetIncludePatchInformation() \|\|
	// ElfWriter::Fixup will be called regardless and it needs to be able
	// to patch debug sections so we have to include patches for them.
	compiler_driver_->GetCompilerOptions().GetIncludeDebugSymbols()) {
	EncodeOatPatches(oat_writer->GetAbsolutePatchLocations(), oat_patches.GetBuffer());
	builder->RegisterSection(&oat_patches);
	}

	return builder->Write(elf_file_);
	}

	template <typename ElfTypes>
	static void WriteDebugSymbols(ElfBuilder<ElfTypes>* builder, OatWriter* oat_writer) {
	const std::vector<OatWriter::DebugInfo>& method_info = oat_writer->GetMethodDebugInfo();

	// Find all addresses (low_pc) which contain deduped methods.
	// The first instance of method is not marked deduped_, but the rest is.
	std::unordered_set<uint32_t> deduped_addresses;
	for (auto it = method_info.begin(); it != method_info.end(); ++it) {
	if (it->deduped_) {
	deduped_addresses.insert(it->low_pc_);
	}
	}

	auto* symtab = builder->GetSymtab();
	for (auto it = method_info.begin(); it != method_info.end(); ++it) {
	if (it->deduped_) {
	continue; // Add symbol only for the first instance.
	}
	std::string name = PrettyMethod(it->dex_method_index_, *it->dex_file_, true);
	if (deduped_addresses.find(it->low_pc_) != deduped_addresses.end()) {
	name += " [DEDUPED]";
	}

	uint32_t low_pc = it->low_pc_;
	// Add in code delta, e.g., thumb bit 0 for Thumb2 code.
	low_pc += it->compiled_method_->CodeDelta();
	symtab->AddSymbol(name, builder->GetText(), low_pc,
	true, it->high_pc_ - it->low_pc_, STB_GLOBAL, STT_FUNC);

	// Conforming to aaelf, add $t mapping symbol to indicate start of a sequence of thumb2
	// instructions, so that disassembler tools can correctly disassemble.
	if (it->compiled_method_->GetInstructionSet() == kThumb2) {
	symtab->AddSymbol("$t", builder->GetText(), it->low_pc_ & ~1, true,
	0, STB_LOCAL, STT_NOTYPE);
	}
	}
	}

	// Explicit instantiations
	template class ElfWriterQuick<ElfTypes32>;
	template class ElfWriterQuick<ElfTypes64>;

	} // namespace art