compiler/elf_writer_quick.cc - platform/art - Git at Google

 /*
  * 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/casts.h"
 #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.
 // Let's use .debug_frame because it is easier to strip or compress.
 constexpr dwarf::CFIFormat kCFIFormat = dwarf::DW_DEBUG_FRAME_FORMAT;

 // The ARM specification defines three special mapping symbols
 // $a, $t and $d which mark ARM, Thumb and data ranges respectively.
 // These symbols can be used by tools, for example, to pretty
 // print instructions correctly.  Objdump will use them if they
 // exist, but it will still work well without them.
 // However, these extra symbols take space, so let's just generate
 // one symbol which marks the whole .text section as code.
 constexpr bool kGenerateSingleArmMappingSymbol = true;

 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);

 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) {
   const InstructionSet isa = compiler_driver_->GetInstructionSet();
   std::unique_ptr<BufferedOutputStream> output_stream(
       new BufferedOutputStream(new FileOutputStream(elf_file_)));
   std::unique_ptr<ElfBuilder<ElfTypes>> builder(
       new ElfBuilder<ElfTypes>(isa, output_stream.get()));

   builder->Start();

   auto* rodata = builder->GetRoData();
   auto* text = builder->GetText();
   auto* bss = builder->GetBss();

   rodata->Start();
   if (!oat_writer->WriteRodata(rodata)) {
     return false;
   }
   rodata->End();

   text->Start();
   if (!oat_writer->WriteCode(text)) {
     return false;
   }
   text->End();

   if (oat_writer->GetBssSize() != 0) {
     bss->Start();
     bss->SetSize(oat_writer->GetBssSize());
     bss->End();
   }

   builder->WriteDynamicSection(elf_file_->GetPath());

   if (compiler_driver_->GetCompilerOptions().GetGenerateDebugInfo()) {
     const auto& method_infos = oat_writer->GetMethodDebugInfo();
     if (!method_infos.empty()) {
       // Add methods to .symtab.
       WriteDebugSymbols(builder.get(), oat_writer);
       // Generate CFI (stack unwinding information).
       dwarf::WriteCFISection(builder.get(), method_infos, kCFIFormat);
       // Write DWARF .debug_* sections.
       dwarf::WriteDebugSections(builder.get(), method_infos);
     }
   }

   // Add relocation section for .text.
   if (compiler_driver_->GetCompilerOptions().GetIncludePatchInformation()) {
     // Note that ElfWriter::Fixup will be called regardless and therefore
     // we need to include oat_patches for debug sections unconditionally.
     builder->WritePatches(".text.oat_patches", &oat_writer->GetAbsolutePatchLocations());
   }

   builder->End();

   return builder->Good() && output_stream->Flush();
 }

 template <typename ElfTypes>
 static void WriteDebugSymbols(ElfBuilder<ElfTypes>* builder, OatWriter* oat_writer) {
   const std::vector<OatWriter::DebugInfo>& method_info = oat_writer->GetMethodDebugInfo();
   bool generated_mapping_symbol = false;
   auto* strtab = builder->GetStrTab();
   auto* symtab = builder->GetSymTab();

   if (method_info.empty()) {
     return;
   }

   // 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_);
     }
   }

   strtab->Start();
   strtab->Write("");  // strtab should start with empty string.
   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->Add(strtab->Write(name), builder->GetText(), low_pc,
                 true, it->high_pc_ - it->low_pc_, STB_GLOBAL, STT_FUNC);

     // Conforming to aaelf, add $t mapping symbol to indicate start of a sequence of thumb2
     // instructions, so that disassembler tools can correctly disassemble.
     // Note that even if we generate just a single mapping symbol, ARM's Streamline
     // requires it to match function symbol.  Just address 0 does not work.
     if (it->compiled_method_->GetInstructionSet() == kThumb2) {
       if (!generated_mapping_symbol || !kGenerateSingleArmMappingSymbol) {
         symtab->Add(strtab->Write("$t"), builder->GetText(), it->low_pc_ & ~1,
                     true, 0, STB_LOCAL, STT_NOTYPE);
         generated_mapping_symbol = true;
       }
     }
   }
   strtab->End();

   // Symbols are buffered and written after names (because they are smaller).
   // We could also do two passes in this function to avoid the buffering.
   symtab->Start();
   symtab->Write();
   symtab->End();
 }

 // 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/casts.h"
	#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.
	// Let's use .debug_frame because it is easier to strip or compress.
	constexpr dwarf::CFIFormat kCFIFormat = dwarf::DW_DEBUG_FRAME_FORMAT;

	// The ARM specification defines three special mapping symbols
	// $a, $t and $d which mark ARM, Thumb and data ranges respectively.
	// These symbols can be used by tools, for example, to pretty
	// print instructions correctly. Objdump will use them if they
	// exist, but it will still work well without them.
	// However, these extra symbols take space, so let's just generate
	// one symbol which marks the whole .text section as code.
	constexpr bool kGenerateSingleArmMappingSymbol = true;

	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);

	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) {
	const InstructionSet isa = compiler_driver_->GetInstructionSet();
	std::unique_ptr<BufferedOutputStream> output_stream(
	new BufferedOutputStream(new FileOutputStream(elf_file_)));
	std::unique_ptr<ElfBuilder<ElfTypes>> builder(
	new ElfBuilder<ElfTypes>(isa, output_stream.get()));

	builder->Start();

	auto* rodata = builder->GetRoData();
	auto* text = builder->GetText();
	auto* bss = builder->GetBss();

	rodata->Start();
	if (!oat_writer->WriteRodata(rodata)) {
	return false;
	}
	rodata->End();

	text->Start();
	if (!oat_writer->WriteCode(text)) {
	return false;
	}
	text->End();

	if (oat_writer->GetBssSize() != 0) {
	bss->Start();
	bss->SetSize(oat_writer->GetBssSize());
	bss->End();
	}

	builder->WriteDynamicSection(elf_file_->GetPath());

	if (compiler_driver_->GetCompilerOptions().GetGenerateDebugInfo()) {
	const auto& method_infos = oat_writer->GetMethodDebugInfo();
	if (!method_infos.empty()) {
	// Add methods to .symtab.
	WriteDebugSymbols(builder.get(), oat_writer);
	// Generate CFI (stack unwinding information).
	dwarf::WriteCFISection(builder.get(), method_infos, kCFIFormat);
	// Write DWARF .debug_* sections.
	dwarf::WriteDebugSections(builder.get(), method_infos);
	}
	}

	// Add relocation section for .text.
	if (compiler_driver_->GetCompilerOptions().GetIncludePatchInformation()) {
	// Note that ElfWriter::Fixup will be called regardless and therefore
	// we need to include oat_patches for debug sections unconditionally.
	builder->WritePatches(".text.oat_patches", &oat_writer->GetAbsolutePatchLocations());
	}

	builder->End();

	return builder->Good() && output_stream->Flush();
	}

	template <typename ElfTypes>
	static void WriteDebugSymbols(ElfBuilder<ElfTypes>* builder, OatWriter* oat_writer) {
	const std::vector<OatWriter::DebugInfo>& method_info = oat_writer->GetMethodDebugInfo();
	bool generated_mapping_symbol = false;
	auto* strtab = builder->GetStrTab();
	auto* symtab = builder->GetSymTab();

	if (method_info.empty()) {
	return;
	}

	// 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_);
	}
	}

	strtab->Start();
	strtab->Write(""); // strtab should start with empty string.
	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->Add(strtab->Write(name), builder->GetText(), low_pc,
	true, it->high_pc_ - it->low_pc_, STB_GLOBAL, STT_FUNC);

	// Conforming to aaelf, add $t mapping symbol to indicate start of a sequence of thumb2
	// instructions, so that disassembler tools can correctly disassemble.
	// Note that even if we generate just a single mapping symbol, ARM's Streamline
	// requires it to match function symbol. Just address 0 does not work.
	if (it->compiled_method_->GetInstructionSet() == kThumb2) {
	if (!generated_mapping_symbol \|\| !kGenerateSingleArmMappingSymbol) {
	symtab->Add(strtab->Write("$t"), builder->GetText(), it->low_pc_ & ~1,
	true, 0, STB_LOCAL, STT_NOTYPE);
	generated_mapping_symbol = true;
	}
	}
	}
	strtab->End();

	// Symbols are buffered and written after names (because they are smaller).
	// We could also do two passes in this function to avoid the buffering.
	symtab->Start();
	symtab->Write();
	symtab->End();
	}

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

	} // namespace art