llvm/tools/yaml2obj/yaml2coff.cpp - toolchain/llvm-project - Gitiles

 //===- yaml2coff - Convert YAML to a COFF object file ---------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
 /// \brief The COFF component of yaml2obj.
 ///
 //===----------------------------------------------------------------------===//

 #include "yaml2obj.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/Object/COFF.h"
 #include "llvm/ObjectYAML/COFFYAML.h"
 #include "llvm/Support/Endian.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/SourceMgr.h"
 #include "llvm/Support/raw_ostream.h"
 #include <vector>

 using namespace llvm;

 /// This parses a yaml stream that represents a COFF object file.
 /// See docs/yaml2obj for the yaml scheema.
 struct COFFParser {
   COFFParser(COFFYAML::Object &Obj)
       : Obj(Obj), SectionTableStart(0), SectionTableSize(0) {
     // A COFF string table always starts with a 4 byte size field. Offsets into
     // it include this size, so allocate it now.
     StringTable.append(4, char(0));
   }

   bool useBigObj() const {
     return static_cast<int32_t>(Obj.Sections.size()) >
            COFF::MaxNumberOfSections16;
   }

   bool isPE() const { return Obj.OptionalHeader.hasValue(); }
   bool is64Bit() const {
     return Obj.Header.Machine == COFF::IMAGE_FILE_MACHINE_AMD64;
   }

   uint32_t getFileAlignment() const {
     return Obj.OptionalHeader->Header.FileAlignment;
   }

   unsigned getHeaderSize() const {
     return useBigObj() ? COFF::Header32Size : COFF::Header16Size;
   }

   unsigned getSymbolSize() const {
     return useBigObj() ? COFF::Symbol32Size : COFF::Symbol16Size;
   }

   bool parseSections() {
     for (std::vector<COFFYAML::Section>::iterator i = Obj.Sections.begin(),
            e = Obj.Sections.end(); i != e; ++i) {
       COFFYAML::Section &Sec = *i;

       // If the name is less than 8 bytes, store it in place, otherwise
       // store it in the string table.
       StringRef Name = Sec.Name;

       if (Name.size() <= COFF::NameSize) {
         std::copy(Name.begin(), Name.end(), Sec.Header.Name);
       } else {
         // Add string to the string table and format the index for output.
         unsigned Index = getStringIndex(Name);
         std::string str = utostr(Index);
         if (str.size() > 7) {
           errs() << "String table got too large";
           return false;
         }
         Sec.Header.Name[0] = '/';
         std::copy(str.begin(), str.end(), Sec.Header.Name + 1);
       }

       Sec.Header.Characteristics |= (Log2_32(Sec.Alignment) + 1) << 20;
     }
     return true;
   }

   bool parseSymbols() {
     for (std::vector<COFFYAML::Symbol>::iterator i = Obj.Symbols.begin(),
            e = Obj.Symbols.end(); i != e; ++i) {
       COFFYAML::Symbol &Sym = *i;

       // If the name is less than 8 bytes, store it in place, otherwise
       // store it in the string table.
       StringRef Name = Sym.Name;
       if (Name.size() <= COFF::NameSize) {
         std::copy(Name.begin(), Name.end(), Sym.Header.Name);
       } else {
         // Add string to the string table and format the index for output.
         unsigned Index = getStringIndex(Name);
         *reinterpret_cast<support::aligned_ulittle32_t*>(
             Sym.Header.Name + 4) = Index;
       }

       Sym.Header.Type = Sym.SimpleType;
       Sym.Header.Type |= Sym.ComplexType << COFF::SCT_COMPLEX_TYPE_SHIFT;
     }
     return true;
   }

   bool parse() {
     if (!parseSections())
       return false;
     if (!parseSymbols())
       return false;
     return true;
   }

   unsigned getStringIndex(StringRef Str) {
     StringMap<unsigned>::iterator i = StringTableMap.find(Str);
     if (i == StringTableMap.end()) {
       unsigned Index = StringTable.size();
       StringTable.append(Str.begin(), Str.end());
       StringTable.push_back(0);
       StringTableMap[Str] = Index;
       return Index;
     }
     return i->second;
   }

   COFFYAML::Object &Obj;

   StringMap<unsigned> StringTableMap;
   std::string StringTable;
   uint32_t SectionTableStart;
   uint32_t SectionTableSize;
 };

 // Take a CP and assign addresses and sizes to everything. Returns false if the
 // layout is not valid to do.
 static bool layoutOptionalHeader(COFFParser &CP) {
   if (!CP.isPE())
     return true;
   unsigned PEHeaderSize = CP.is64Bit() ? sizeof(object::pe32plus_header)
                                        : sizeof(object::pe32_header);
   CP.Obj.Header.SizeOfOptionalHeader =
       PEHeaderSize +
       sizeof(object::data_directory) * (COFF::NUM_DATA_DIRECTORIES + 1);
   return true;
 }

 namespace {
 enum { DOSStubSize = 128 };
 }

 // Take a CP and assign addresses and sizes to everything. Returns false if the
 // layout is not valid to do.
 static bool layoutCOFF(COFFParser &CP) {
   // The section table starts immediately after the header, including the
   // optional header.
   CP.SectionTableStart =
       CP.getHeaderSize() + CP.Obj.Header.SizeOfOptionalHeader;
   if (CP.isPE())
     CP.SectionTableStart += DOSStubSize + sizeof(COFF::PEMagic);
   CP.SectionTableSize = COFF::SectionSize * CP.Obj.Sections.size();

   uint32_t CurrentSectionDataOffset =
       CP.SectionTableStart + CP.SectionTableSize;

   // Assign each section data address consecutively.
   for (COFFYAML::Section &S : CP.Obj.Sections) {
     if (S.SectionData.binary_size() > 0) {
       CurrentSectionDataOffset = alignTo(CurrentSectionDataOffset,
                                          CP.isPE() ? CP.getFileAlignment() : 4);
       S.Header.SizeOfRawData = S.SectionData.binary_size();
       if (CP.isPE())
         S.Header.SizeOfRawData =
             alignTo(S.Header.SizeOfRawData, CP.getFileAlignment());
       S.Header.PointerToRawData = CurrentSectionDataOffset;
       CurrentSectionDataOffset += S.Header.SizeOfRawData;
       if (!S.Relocations.empty()) {
         S.Header.PointerToRelocations = CurrentSectionDataOffset;
         S.Header.NumberOfRelocations = S.Relocations.size();
         CurrentSectionDataOffset +=
             S.Header.NumberOfRelocations * COFF::RelocationSize;
       }
     } else {
       S.Header.SizeOfRawData = 0;
       S.Header.PointerToRawData = 0;
     }
   }

   uint32_t SymbolTableStart = CurrentSectionDataOffset;

   // Calculate number of symbols.
   uint32_t NumberOfSymbols = 0;
   for (std::vector<COFFYAML::Symbol>::iterator i = CP.Obj.Symbols.begin(),
                                                e = CP.Obj.Symbols.end();
                                                i != e; ++i) {
     uint32_t NumberOfAuxSymbols = 0;
     if (i->FunctionDefinition)
       NumberOfAuxSymbols += 1;
     if (i->bfAndefSymbol)
       NumberOfAuxSymbols += 1;
     if (i->WeakExternal)
       NumberOfAuxSymbols += 1;
     if (!i->File.empty())
       NumberOfAuxSymbols +=
           (i->File.size() + CP.getSymbolSize() - 1) / CP.getSymbolSize();
     if (i->SectionDefinition)
       NumberOfAuxSymbols += 1;
     if (i->CLRToken)
       NumberOfAuxSymbols += 1;
     i->Header.NumberOfAuxSymbols = NumberOfAuxSymbols;
     NumberOfSymbols += 1 + NumberOfAuxSymbols;
   }

   // Store all the allocated start addresses in the header.
   CP.Obj.Header.NumberOfSections = CP.Obj.Sections.size();
   CP.Obj.Header.NumberOfSymbols = NumberOfSymbols;
   if (NumberOfSymbols > 0 || CP.StringTable.size() > 4)
     CP.Obj.Header.PointerToSymbolTable = SymbolTableStart;
   else
     CP.Obj.Header.PointerToSymbolTable = 0;

   *reinterpret_cast<support::ulittle32_t *>(&CP.StringTable[0])
     = CP.StringTable.size();

   return true;
 }

 template <typename value_type>
 struct binary_le_impl {
   value_type Value;
   binary_le_impl(value_type V) : Value(V) {}
 };

 template <typename value_type>
 raw_ostream &operator <<( raw_ostream &OS
                         , const binary_le_impl<value_type> &BLE) {
   char Buffer[sizeof(BLE.Value)];
   support::endian::write<value_type, support::little, support::unaligned>(
     Buffer, BLE.Value);
   OS.write(Buffer, sizeof(BLE.Value));
   return OS;
 }

 template <typename value_type>
 binary_le_impl<value_type> binary_le(value_type V) {
   return binary_le_impl<value_type>(V);
 }

 template <size_t NumBytes> struct zeros_impl {};

 template <size_t NumBytes>
 raw_ostream &operator<<(raw_ostream &OS, const zeros_impl<NumBytes> &) {
   char Buffer[NumBytes];
   memset(Buffer, 0, sizeof(Buffer));
   OS.write(Buffer, sizeof(Buffer));
   return OS;
 }

 template <typename T>
 zeros_impl<sizeof(T)> zeros(const T &) {
   return zeros_impl<sizeof(T)>();
 }

 struct num_zeros_impl {
   size_t N;
   num_zeros_impl(size_t N) : N(N) {}
 };

 raw_ostream &operator<<(raw_ostream &OS, const num_zeros_impl &NZI) {
   for (size_t I = 0; I != NZI.N; ++I)
     OS.write(0);
   return OS;
 }

 static num_zeros_impl num_zeros(size_t N) {
   num_zeros_impl NZI(N);
   return NZI;
 }

 template <typename T>
 static uint32_t initializeOptionalHeader(COFFParser &CP, uint16_t Magic, T Header) {
   memset(Header, 0, sizeof(*Header));
   Header->Magic = Magic;
   Header->SectionAlignment = CP.Obj.OptionalHeader->Header.SectionAlignment;
   Header->FileAlignment = CP.Obj.OptionalHeader->Header.FileAlignment;
   uint32_t SizeOfCode = 0, SizeOfInitializedData = 0,
            SizeOfUninitializedData = 0;
   uint32_t SizeOfHeaders = alignTo(CP.SectionTableStart + CP.SectionTableSize,
                                    Header->FileAlignment);
   uint32_t SizeOfImage = alignTo(SizeOfHeaders, Header->SectionAlignment);
   uint32_t BaseOfData = 0;
   for (const COFFYAML::Section &S : CP.Obj.Sections) {
     if (S.Header.Characteristics & COFF::IMAGE_SCN_CNT_CODE)
       SizeOfCode += S.Header.SizeOfRawData;
     if (S.Header.Characteristics & COFF::IMAGE_SCN_CNT_INITIALIZED_DATA)
       SizeOfInitializedData += S.Header.SizeOfRawData;
     if (S.Header.Characteristics & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA)
       SizeOfUninitializedData += S.Header.SizeOfRawData;
     if (S.Name.equals(".text"))
       Header->BaseOfCode = S.Header.VirtualAddress; // RVA
     else if (S.Name.equals(".data"))
       BaseOfData = S.Header.VirtualAddress; // RVA
     if (S.Header.VirtualAddress)
       SizeOfImage += alignTo(S.Header.VirtualSize, Header->SectionAlignment);
   }
   Header->SizeOfCode = SizeOfCode;
   Header->SizeOfInitializedData = SizeOfInitializedData;
   Header->SizeOfUninitializedData = SizeOfUninitializedData;
   Header->AddressOfEntryPoint =
       CP.Obj.OptionalHeader->Header.AddressOfEntryPoint; // RVA
   Header->ImageBase = CP.Obj.OptionalHeader->Header.ImageBase;
   Header->MajorOperatingSystemVersion =
       CP.Obj.OptionalHeader->Header.MajorOperatingSystemVersion;
   Header->MinorOperatingSystemVersion =
       CP.Obj.OptionalHeader->Header.MinorOperatingSystemVersion;
   Header->MajorImageVersion =
       CP.Obj.OptionalHeader->Header.MajorImageVersion;
   Header->MinorImageVersion =
       CP.Obj.OptionalHeader->Header.MinorImageVersion;
   Header->MajorSubsystemVersion =
       CP.Obj.OptionalHeader->Header.MajorSubsystemVersion;
   Header->MinorSubsystemVersion =
       CP.Obj.OptionalHeader->Header.MinorSubsystemVersion;
   Header->SizeOfImage = SizeOfImage;
   Header->SizeOfHeaders = SizeOfHeaders;
   Header->Subsystem = CP.Obj.OptionalHeader->Header.Subsystem;
   Header->DLLCharacteristics = CP.Obj.OptionalHeader->Header.DLLCharacteristics;
   Header->SizeOfStackReserve = CP.Obj.OptionalHeader->Header.SizeOfStackReserve;
   Header->SizeOfStackCommit = CP.Obj.OptionalHeader->Header.SizeOfStackCommit;
   Header->SizeOfHeapReserve = CP.Obj.OptionalHeader->Header.SizeOfHeapReserve;
   Header->SizeOfHeapCommit = CP.Obj.OptionalHeader->Header.SizeOfHeapCommit;
   Header->NumberOfRvaAndSize = COFF::NUM_DATA_DIRECTORIES + 1;
   return BaseOfData;
 }

 static bool writeCOFF(COFFParser &CP, raw_ostream &OS) {
   if (CP.isPE()) {
     // PE files start with a DOS stub.
     object::dos_header DH;
     memset(&DH, 0, sizeof(DH));

     // DOS EXEs start with "MZ" magic.
     DH.Magic[0] = 'M';
     DH.Magic[1] = 'Z';
     // Initializing the AddressOfRelocationTable is strictly optional but
     // mollifies certain tools which expect it to have a value greater than
     // 0x40.
     DH.AddressOfRelocationTable = sizeof(DH);
     // This is the address of the PE signature.
     DH.AddressOfNewExeHeader = DOSStubSize;

     // Write out our DOS stub.
     OS.write(reinterpret_cast<char *>(&DH), sizeof(DH));
     // Write padding until we reach the position of where our PE signature
     // should live.
     OS << num_zeros(DOSStubSize - sizeof(DH));
     // Write out the PE signature.
     OS.write(COFF::PEMagic, sizeof(COFF::PEMagic));
   }
   if (CP.useBigObj()) {
     OS << binary_le(static_cast<uint16_t>(COFF::IMAGE_FILE_MACHINE_UNKNOWN))
        << binary_le(static_cast<uint16_t>(0xffff))
        << binary_le(static_cast<uint16_t>(COFF::BigObjHeader::MinBigObjectVersion))
        << binary_le(CP.Obj.Header.Machine)
        << binary_le(CP.Obj.Header.TimeDateStamp);
     OS.write(COFF::BigObjMagic, sizeof(COFF::BigObjMagic));
     OS << zeros(uint32_t(0))
        << zeros(uint32_t(0))
        << zeros(uint32_t(0))
        << zeros(uint32_t(0))
        << binary_le(CP.Obj.Header.NumberOfSections)
        << binary_le(CP.Obj.Header.PointerToSymbolTable)
        << binary_le(CP.Obj.Header.NumberOfSymbols);
   } else {
     OS << binary_le(CP.Obj.Header.Machine)
        << binary_le(static_cast<int16_t>(CP.Obj.Header.NumberOfSections))
        << binary_le(CP.Obj.Header.TimeDateStamp)
        << binary_le(CP.Obj.Header.PointerToSymbolTable)
        << binary_le(CP.Obj.Header.NumberOfSymbols)
        << binary_le(CP.Obj.Header.SizeOfOptionalHeader)
        << binary_le(CP.Obj.Header.Characteristics);
   }
   if (CP.isPE()) {
     if (CP.is64Bit()) {
       object::pe32plus_header PEH;
       initializeOptionalHeader(CP, COFF::PE32Header::PE32_PLUS, &PEH);
       OS.write(reinterpret_cast<char *>(&PEH), sizeof(PEH));
     } else {
       object::pe32_header PEH;
       uint32_t BaseOfData = initializeOptionalHeader(CP, COFF::PE32Header::PE32, &PEH);
       PEH.BaseOfData = BaseOfData;
       OS.write(reinterpret_cast<char *>(&PEH), sizeof(PEH));
     }
     for (const Optional<COFF::DataDirectory> &DD :
          CP.Obj.OptionalHeader->DataDirectories) {
       if (!DD.hasValue()) {
         OS << zeros(uint32_t(0));
         OS << zeros(uint32_t(0));
       } else {
         OS << binary_le(DD->RelativeVirtualAddress);
         OS << binary_le(DD->Size);
       }
     }
     OS << zeros(uint32_t(0));
     OS << zeros(uint32_t(0));
   }

   assert(OS.tell() == CP.SectionTableStart);
   // Output section table.
   for (std::vector<COFFYAML::Section>::iterator i = CP.Obj.Sections.begin(),
                                                 e = CP.Obj.Sections.end();
                                                 i != e; ++i) {
     OS.write(i->Header.Name, COFF::NameSize);
     OS << binary_le(i->Header.VirtualSize)
        << binary_le(i->Header.VirtualAddress)
        << binary_le(i->Header.SizeOfRawData)
        << binary_le(i->Header.PointerToRawData)
        << binary_le(i->Header.PointerToRelocations)
        << binary_le(i->Header.PointerToLineNumbers)
        << binary_le(i->Header.NumberOfRelocations)
        << binary_le(i->Header.NumberOfLineNumbers)
        << binary_le(i->Header.Characteristics);
   }
   assert(OS.tell() == CP.SectionTableStart + CP.SectionTableSize);

   unsigned CurSymbol = 0;
   StringMap<unsigned> SymbolTableIndexMap;
   for (std::vector<COFFYAML::Symbol>::iterator I = CP.Obj.Symbols.begin(),
                                                E = CP.Obj.Symbols.end();
        I != E; ++I) {
     SymbolTableIndexMap[I->Name] = CurSymbol;
     CurSymbol += 1 + I->Header.NumberOfAuxSymbols;
   }

   // Output section data.
   for (const COFFYAML::Section &S : CP.Obj.Sections) {
     if (!S.Header.SizeOfRawData)
       continue;
     assert(S.Header.PointerToRawData >= OS.tell());
     OS << num_zeros(S.Header.PointerToRawData - OS.tell());
     S.SectionData.writeAsBinary(OS);
     assert(S.Header.SizeOfRawData >= S.SectionData.binary_size());
     OS << num_zeros(S.Header.SizeOfRawData - S.SectionData.binary_size());
     for (const COFFYAML::Relocation &R : S.Relocations) {
       uint32_t SymbolTableIndex = SymbolTableIndexMap[R.SymbolName];
       OS << binary_le(R.VirtualAddress)
          << binary_le(SymbolTableIndex)
          << binary_le(R.Type);
     }
   }

   // Output symbol table.

   for (std::vector<COFFYAML::Symbol>::const_iterator i = CP.Obj.Symbols.begin(),
                                                      e = CP.Obj.Symbols.end();
                                                      i != e; ++i) {
     OS.write(i->Header.Name, COFF::NameSize);
     OS << binary_le(i->Header.Value);
     if (CP.useBigObj())
        OS << binary_le(i->Header.SectionNumber);
     else
        OS << binary_le(static_cast<int16_t>(i->Header.SectionNumber));
     OS << binary_le(i->Header.Type)
        << binary_le(i->Header.StorageClass)
        << binary_le(i->Header.NumberOfAuxSymbols);

     if (i->FunctionDefinition)
       OS << binary_le(i->FunctionDefinition->TagIndex)
          << binary_le(i->FunctionDefinition->TotalSize)
          << binary_le(i->FunctionDefinition->PointerToLinenumber)
          << binary_le(i->FunctionDefinition->PointerToNextFunction)
          << zeros(i->FunctionDefinition->unused)
          << num_zeros(CP.getSymbolSize() - COFF::Symbol16Size);
     if (i->bfAndefSymbol)
       OS << zeros(i->bfAndefSymbol->unused1)
          << binary_le(i->bfAndefSymbol->Linenumber)
          << zeros(i->bfAndefSymbol->unused2)
          << binary_le(i->bfAndefSymbol->PointerToNextFunction)
          << zeros(i->bfAndefSymbol->unused3)
          << num_zeros(CP.getSymbolSize() - COFF::Symbol16Size);
     if (i->WeakExternal)
       OS << binary_le(i->WeakExternal->TagIndex)
          << binary_le(i->WeakExternal->Characteristics)
          << zeros(i->WeakExternal->unused)
          << num_zeros(CP.getSymbolSize() - COFF::Symbol16Size);
     if (!i->File.empty()) {
       unsigned SymbolSize = CP.getSymbolSize();
       uint32_t NumberOfAuxRecords =
           (i->File.size() + SymbolSize - 1) / SymbolSize;
       uint32_t NumberOfAuxBytes = NumberOfAuxRecords * SymbolSize;
       uint32_t NumZeros = NumberOfAuxBytes - i->File.size();
       OS.write(i->File.data(), i->File.size());
       OS << num_zeros(NumZeros);
     }
     if (i->SectionDefinition)
       OS << binary_le(i->SectionDefinition->Length)
          << binary_le(i->SectionDefinition->NumberOfRelocations)
          << binary_le(i->SectionDefinition->NumberOfLinenumbers)
          << binary_le(i->SectionDefinition->CheckSum)
          << binary_le(static_cast<int16_t>(i->SectionDefinition->Number))
          << binary_le(i->SectionDefinition->Selection)
          << zeros(i->SectionDefinition->unused)
          << binary_le(static_cast<int16_t>(i->SectionDefinition->Number >> 16))
          << num_zeros(CP.getSymbolSize() - COFF::Symbol16Size);
     if (i->CLRToken)
       OS << binary_le(i->CLRToken->AuxType)
          << zeros(i->CLRToken->unused1)
          << binary_le(i->CLRToken->SymbolTableIndex)
          << zeros(i->CLRToken->unused2)
          << num_zeros(CP.getSymbolSize() - COFF::Symbol16Size);
   }

   // Output string table.
   if (CP.Obj.Header.PointerToSymbolTable)
     OS.write(&CP.StringTable[0], CP.StringTable.size());
   return true;
 }

 int yaml2coff(yaml::Input &YIn, raw_ostream &Out) {
   COFFYAML::Object Doc;
   YIn >> Doc;
   if (YIn.error()) {
     errs() << "yaml2obj: Failed to parse YAML file!\n";
     return 1;
   }

   COFFParser CP(Doc);
   if (!CP.parse()) {
     errs() << "yaml2obj: Failed to parse YAML file!\n";
     return 1;
   }

   if (!layoutOptionalHeader(CP)) {
     errs() << "yaml2obj: Failed to layout optional header for COFF file!\n";
     return 1;
   }
   if (!layoutCOFF(CP)) {
     errs() << "yaml2obj: Failed to layout COFF file!\n";
     return 1;
   }
   if (!writeCOFF(CP, Out)) {
     errs() << "yaml2obj: Failed to write COFF file!\n";
     return 1;
   }
   return 0;
 }
	//===- yaml2coff - Convert YAML to a COFF object file ---------------------===//
	//
	// The LLVM Compiler Infrastructure
	//
	// This file is distributed under the University of Illinois Open Source
	// License. See LICENSE.TXT for details.
	//
	//===----------------------------------------------------------------------===//
	///
	/// \file
	/// \brief The COFF component of yaml2obj.
	///
	//===----------------------------------------------------------------------===//

	#include "yaml2obj.h"
	#include "llvm/ADT/STLExtras.h"
	#include "llvm/ADT/SmallString.h"
	#include "llvm/ADT/StringExtras.h"
	#include "llvm/ADT/StringMap.h"
	#include "llvm/ADT/StringSwitch.h"
	#include "llvm/Object/COFF.h"
	#include "llvm/ObjectYAML/COFFYAML.h"
	#include "llvm/Support/Endian.h"
	#include "llvm/Support/MemoryBuffer.h"
	#include "llvm/Support/SourceMgr.h"
	#include "llvm/Support/raw_ostream.h"
	#include <vector>

	using namespace llvm;

	/// This parses a yaml stream that represents a COFF object file.
	/// See docs/yaml2obj for the yaml scheema.
	struct COFFParser {
	COFFParser(COFFYAML::Object &Obj)
	: Obj(Obj), SectionTableStart(0), SectionTableSize(0) {
	// A COFF string table always starts with a 4 byte size field. Offsets into
	// it include this size, so allocate it now.
	StringTable.append(4, char(0));
	}

	bool useBigObj() const {
	return static_cast<int32_t>(Obj.Sections.size()) >
	COFF::MaxNumberOfSections16;
	}

	bool isPE() const { return Obj.OptionalHeader.hasValue(); }
	bool is64Bit() const {
	return Obj.Header.Machine == COFF::IMAGE_FILE_MACHINE_AMD64;
	}

	uint32_t getFileAlignment() const {
	return Obj.OptionalHeader->Header.FileAlignment;
	}

	unsigned getHeaderSize() const {
	return useBigObj() ? COFF::Header32Size : COFF::Header16Size;
	}

	unsigned getSymbolSize() const {
	return useBigObj() ? COFF::Symbol32Size : COFF::Symbol16Size;
	}

	bool parseSections() {
	for (std::vector<COFFYAML::Section>::iterator i = Obj.Sections.begin(),
	e = Obj.Sections.end(); i != e; ++i) {
	COFFYAML::Section &Sec = *i;

	// If the name is less than 8 bytes, store it in place, otherwise
	// store it in the string table.
	StringRef Name = Sec.Name;

	if (Name.size() <= COFF::NameSize) {
	std::copy(Name.begin(), Name.end(), Sec.Header.Name);
	} else {
	// Add string to the string table and format the index for output.
	unsigned Index = getStringIndex(Name);
	std::string str = utostr(Index);
	if (str.size() > 7) {
	errs() << "String table got too large";
	return false;
	}
	Sec.Header.Name[0] = '/';
	std::copy(str.begin(), str.end(), Sec.Header.Name + 1);
	}

	Sec.Header.Characteristics \|= (Log2_32(Sec.Alignment) + 1) << 20;
	}
	return true;
	}

	bool parseSymbols() {
	for (std::vector<COFFYAML::Symbol>::iterator i = Obj.Symbols.begin(),
	e = Obj.Symbols.end(); i != e; ++i) {
	COFFYAML::Symbol &Sym = *i;

	// If the name is less than 8 bytes, store it in place, otherwise
	// store it in the string table.
	StringRef Name = Sym.Name;
	if (Name.size() <= COFF::NameSize) {
	std::copy(Name.begin(), Name.end(), Sym.Header.Name);
	} else {
	// Add string to the string table and format the index for output.
	unsigned Index = getStringIndex(Name);
	reinterpret_cast<support::aligned_ulittle32_t>(
	Sym.Header.Name + 4) = Index;
	}

	Sym.Header.Type = Sym.SimpleType;
	Sym.Header.Type \|= Sym.ComplexType << COFF::SCT_COMPLEX_TYPE_SHIFT;
	}
	return true;
	}

	bool parse() {
	if (!parseSections())
	return false;
	if (!parseSymbols())
	return false;
	return true;
	}

	unsigned getStringIndex(StringRef Str) {
	StringMap<unsigned>::iterator i = StringTableMap.find(Str);
	if (i == StringTableMap.end()) {
	unsigned Index = StringTable.size();
	StringTable.append(Str.begin(), Str.end());
	StringTable.push_back(0);
	StringTableMap[Str] = Index;
	return Index;
	}
	return i->second;
	}

	COFFYAML::Object &Obj;

	StringMap<unsigned> StringTableMap;
	std::string StringTable;
	uint32_t SectionTableStart;
	uint32_t SectionTableSize;
	};

	// Take a CP and assign addresses and sizes to everything. Returns false if the
	// layout is not valid to do.
	static bool layoutOptionalHeader(COFFParser &CP) {
	if (!CP.isPE())
	return true;
	unsigned PEHeaderSize = CP.is64Bit() ? sizeof(object::pe32plus_header)
	: sizeof(object::pe32_header);
	CP.Obj.Header.SizeOfOptionalHeader =
	PEHeaderSize +
	sizeof(object::data_directory) * (COFF::NUM_DATA_DIRECTORIES + 1);
	return true;
	}

	namespace {
	enum { DOSStubSize = 128 };
	}

	// Take a CP and assign addresses and sizes to everything. Returns false if the
	// layout is not valid to do.
	static bool layoutCOFF(COFFParser &CP) {
	// The section table starts immediately after the header, including the
	// optional header.
	CP.SectionTableStart =
	CP.getHeaderSize() + CP.Obj.Header.SizeOfOptionalHeader;
	if (CP.isPE())
	CP.SectionTableStart += DOSStubSize + sizeof(COFF::PEMagic);
	CP.SectionTableSize = COFF::SectionSize * CP.Obj.Sections.size();

	uint32_t CurrentSectionDataOffset =
	CP.SectionTableStart + CP.SectionTableSize;

	// Assign each section data address consecutively.
	for (COFFYAML::Section &S : CP.Obj.Sections) {
	if (S.SectionData.binary_size() > 0) {
	CurrentSectionDataOffset = alignTo(CurrentSectionDataOffset,
	CP.isPE() ? CP.getFileAlignment() : 4);
	S.Header.SizeOfRawData = S.SectionData.binary_size();
	if (CP.isPE())
	S.Header.SizeOfRawData =
	alignTo(S.Header.SizeOfRawData, CP.getFileAlignment());
	S.Header.PointerToRawData = CurrentSectionDataOffset;
	CurrentSectionDataOffset += S.Header.SizeOfRawData;
	if (!S.Relocations.empty()) {
	S.Header.PointerToRelocations = CurrentSectionDataOffset;
	S.Header.NumberOfRelocations = S.Relocations.size();
	CurrentSectionDataOffset +=
	S.Header.NumberOfRelocations * COFF::RelocationSize;
	}
	} else {
	S.Header.SizeOfRawData = 0;
	S.Header.PointerToRawData = 0;
	}
	}

	uint32_t SymbolTableStart = CurrentSectionDataOffset;

	// Calculate number of symbols.
	uint32_t NumberOfSymbols = 0;
	for (std::vector<COFFYAML::Symbol>::iterator i = CP.Obj.Symbols.begin(),
	e = CP.Obj.Symbols.end();
	i != e; ++i) {
	uint32_t NumberOfAuxSymbols = 0;
	if (i->FunctionDefinition)
	NumberOfAuxSymbols += 1;
	if (i->bfAndefSymbol)
	NumberOfAuxSymbols += 1;
	if (i->WeakExternal)
	NumberOfAuxSymbols += 1;
	if (!i->File.empty())
	NumberOfAuxSymbols +=
	(i->File.size() + CP.getSymbolSize() - 1) / CP.getSymbolSize();
	if (i->SectionDefinition)
	NumberOfAuxSymbols += 1;
	if (i->CLRToken)
	NumberOfAuxSymbols += 1;
	i->Header.NumberOfAuxSymbols = NumberOfAuxSymbols;
	NumberOfSymbols += 1 + NumberOfAuxSymbols;
	}

	// Store all the allocated start addresses in the header.
	CP.Obj.Header.NumberOfSections = CP.Obj.Sections.size();
	CP.Obj.Header.NumberOfSymbols = NumberOfSymbols;
	if (NumberOfSymbols > 0 \|\| CP.StringTable.size() > 4)
	CP.Obj.Header.PointerToSymbolTable = SymbolTableStart;
	else
	CP.Obj.Header.PointerToSymbolTable = 0;

	reinterpret_cast<support::ulittle32_t >(&CP.StringTable[0])
	= CP.StringTable.size();

	return true;
	}

	template <typename value_type>
	struct binary_le_impl {
	value_type Value;
	binary_le_impl(value_type V) : Value(V) {}
	};

	template <typename value_type>
	raw_ostream &operator <<( raw_ostream &OS
	, const binary_le_impl<value_type> &BLE) {
	char Buffer[sizeof(BLE.Value)];
	support::endian::write<value_type, support::little, support::unaligned>(
	Buffer, BLE.Value);
	OS.write(Buffer, sizeof(BLE.Value));
	return OS;
	}

	template <typename value_type>
	binary_le_impl<value_type> binary_le(value_type V) {
	return binary_le_impl<value_type>(V);
	}

	template <size_t NumBytes> struct zeros_impl {};

	template <size_t NumBytes>
	raw_ostream &operator<<(raw_ostream &OS, const zeros_impl<NumBytes> &) {
	char Buffer[NumBytes];
	memset(Buffer, 0, sizeof(Buffer));
	OS.write(Buffer, sizeof(Buffer));
	return OS;
	}

	template <typename T>
	zeros_impl<sizeof(T)> zeros(const T &) {
	return zeros_impl<sizeof(T)>();
	}

	struct num_zeros_impl {
	size_t N;
	num_zeros_impl(size_t N) : N(N) {}
	};

	raw_ostream &operator<<(raw_ostream &OS, const num_zeros_impl &NZI) {
	for (size_t I = 0; I != NZI.N; ++I)
	OS.write(0);
	return OS;
	}

	static num_zeros_impl num_zeros(size_t N) {
	num_zeros_impl NZI(N);
	return NZI;
	}

	template <typename T>
	static uint32_t initializeOptionalHeader(COFFParser &CP, uint16_t Magic, T Header) {
	memset(Header, 0, sizeof(*Header));
	Header->Magic = Magic;
	Header->SectionAlignment = CP.Obj.OptionalHeader->Header.SectionAlignment;
	Header->FileAlignment = CP.Obj.OptionalHeader->Header.FileAlignment;
	uint32_t SizeOfCode = 0, SizeOfInitializedData = 0,
	SizeOfUninitializedData = 0;
	uint32_t SizeOfHeaders = alignTo(CP.SectionTableStart + CP.SectionTableSize,
	Header->FileAlignment);
	uint32_t SizeOfImage = alignTo(SizeOfHeaders, Header->SectionAlignment);
	uint32_t BaseOfData = 0;
	for (const COFFYAML::Section &S : CP.Obj.Sections) {
	if (S.Header.Characteristics & COFF::IMAGE_SCN_CNT_CODE)
	SizeOfCode += S.Header.SizeOfRawData;
	if (S.Header.Characteristics & COFF::IMAGE_SCN_CNT_INITIALIZED_DATA)
	SizeOfInitializedData += S.Header.SizeOfRawData;
	if (S.Header.Characteristics & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA)
	SizeOfUninitializedData += S.Header.SizeOfRawData;
	if (S.Name.equals(".text"))
	Header->BaseOfCode = S.Header.VirtualAddress; // RVA
	else if (S.Name.equals(".data"))
	BaseOfData = S.Header.VirtualAddress; // RVA
	if (S.Header.VirtualAddress)
	SizeOfImage += alignTo(S.Header.VirtualSize, Header->SectionAlignment);
	}
	Header->SizeOfCode = SizeOfCode;
	Header->SizeOfInitializedData = SizeOfInitializedData;
	Header->SizeOfUninitializedData = SizeOfUninitializedData;
	Header->AddressOfEntryPoint =
	CP.Obj.OptionalHeader->Header.AddressOfEntryPoint; // RVA
	Header->ImageBase = CP.Obj.OptionalHeader->Header.ImageBase;
	Header->MajorOperatingSystemVersion =
	CP.Obj.OptionalHeader->Header.MajorOperatingSystemVersion;
	Header->MinorOperatingSystemVersion =
	CP.Obj.OptionalHeader->Header.MinorOperatingSystemVersion;
	Header->MajorImageVersion =
	CP.Obj.OptionalHeader->Header.MajorImageVersion;
	Header->MinorImageVersion =
	CP.Obj.OptionalHeader->Header.MinorImageVersion;
	Header->MajorSubsystemVersion =
	CP.Obj.OptionalHeader->Header.MajorSubsystemVersion;
	Header->MinorSubsystemVersion =
	CP.Obj.OptionalHeader->Header.MinorSubsystemVersion;
	Header->SizeOfImage = SizeOfImage;
	Header->SizeOfHeaders = SizeOfHeaders;
	Header->Subsystem = CP.Obj.OptionalHeader->Header.Subsystem;
	Header->DLLCharacteristics = CP.Obj.OptionalHeader->Header.DLLCharacteristics;
	Header->SizeOfStackReserve = CP.Obj.OptionalHeader->Header.SizeOfStackReserve;
	Header->SizeOfStackCommit = CP.Obj.OptionalHeader->Header.SizeOfStackCommit;
	Header->SizeOfHeapReserve = CP.Obj.OptionalHeader->Header.SizeOfHeapReserve;
	Header->SizeOfHeapCommit = CP.Obj.OptionalHeader->Header.SizeOfHeapCommit;
	Header->NumberOfRvaAndSize = COFF::NUM_DATA_DIRECTORIES + 1;
	return BaseOfData;
	}

	static bool writeCOFF(COFFParser &CP, raw_ostream &OS) {
	if (CP.isPE()) {
	// PE files start with a DOS stub.
	object::dos_header DH;
	memset(&DH, 0, sizeof(DH));

	// DOS EXEs start with "MZ" magic.
	DH.Magic[0] = 'M';
	DH.Magic[1] = 'Z';
	// Initializing the AddressOfRelocationTable is strictly optional but
	// mollifies certain tools which expect it to have a value greater than
	// 0x40.
	DH.AddressOfRelocationTable = sizeof(DH);
	// This is the address of the PE signature.
	DH.AddressOfNewExeHeader = DOSStubSize;

	// Write out our DOS stub.
	OS.write(reinterpret_cast<char *>(&DH), sizeof(DH));
	// Write padding until we reach the position of where our PE signature
	// should live.
	OS << num_zeros(DOSStubSize - sizeof(DH));
	// Write out the PE signature.
	OS.write(COFF::PEMagic, sizeof(COFF::PEMagic));
	}
	if (CP.useBigObj()) {
	OS << binary_le(static_cast<uint16_t>(COFF::IMAGE_FILE_MACHINE_UNKNOWN))
	<< binary_le(static_cast<uint16_t>(0xffff))
	<< binary_le(static_cast<uint16_t>(COFF::BigObjHeader::MinBigObjectVersion))
	<< binary_le(CP.Obj.Header.Machine)
	<< binary_le(CP.Obj.Header.TimeDateStamp);
	OS.write(COFF::BigObjMagic, sizeof(COFF::BigObjMagic));
	OS << zeros(uint32_t(0))
	<< zeros(uint32_t(0))
	<< zeros(uint32_t(0))
	<< zeros(uint32_t(0))
	<< binary_le(CP.Obj.Header.NumberOfSections)
	<< binary_le(CP.Obj.Header.PointerToSymbolTable)
	<< binary_le(CP.Obj.Header.NumberOfSymbols);
	} else {
	OS << binary_le(CP.Obj.Header.Machine)
	<< binary_le(static_cast<int16_t>(CP.Obj.Header.NumberOfSections))
	<< binary_le(CP.Obj.Header.TimeDateStamp)
	<< binary_le(CP.Obj.Header.PointerToSymbolTable)
	<< binary_le(CP.Obj.Header.NumberOfSymbols)
	<< binary_le(CP.Obj.Header.SizeOfOptionalHeader)
	<< binary_le(CP.Obj.Header.Characteristics);
	}
	if (CP.isPE()) {
	if (CP.is64Bit()) {
	object::pe32plus_header PEH;
	initializeOptionalHeader(CP, COFF::PE32Header::PE32_PLUS, &PEH);
	OS.write(reinterpret_cast<char *>(&PEH), sizeof(PEH));
	} else {
	object::pe32_header PEH;
	uint32_t BaseOfData = initializeOptionalHeader(CP, COFF::PE32Header::PE32, &PEH);
	PEH.BaseOfData = BaseOfData;
	OS.write(reinterpret_cast<char *>(&PEH), sizeof(PEH));
	}
	for (const Optional<COFF::DataDirectory> &DD :
	CP.Obj.OptionalHeader->DataDirectories) {
	if (!DD.hasValue()) {
	OS << zeros(uint32_t(0));
	OS << zeros(uint32_t(0));
	} else {
	OS << binary_le(DD->RelativeVirtualAddress);
	OS << binary_le(DD->Size);
	}
	}
	OS << zeros(uint32_t(0));
	OS << zeros(uint32_t(0));
	}

	assert(OS.tell() == CP.SectionTableStart);
	// Output section table.
	for (std::vector<COFFYAML::Section>::iterator i = CP.Obj.Sections.begin(),
	e = CP.Obj.Sections.end();
	i != e; ++i) {
	OS.write(i->Header.Name, COFF::NameSize);
	OS << binary_le(i->Header.VirtualSize)
	<< binary_le(i->Header.VirtualAddress)
	<< binary_le(i->Header.SizeOfRawData)
	<< binary_le(i->Header.PointerToRawData)
	<< binary_le(i->Header.PointerToRelocations)
	<< binary_le(i->Header.PointerToLineNumbers)
	<< binary_le(i->Header.NumberOfRelocations)
	<< binary_le(i->Header.NumberOfLineNumbers)
	<< binary_le(i->Header.Characteristics);
	}
	assert(OS.tell() == CP.SectionTableStart + CP.SectionTableSize);

	unsigned CurSymbol = 0;
	StringMap<unsigned> SymbolTableIndexMap;
	for (std::vector<COFFYAML::Symbol>::iterator I = CP.Obj.Symbols.begin(),
	E = CP.Obj.Symbols.end();
	I != E; ++I) {
	SymbolTableIndexMap[I->Name] = CurSymbol;
	CurSymbol += 1 + I->Header.NumberOfAuxSymbols;
	}

	// Output section data.
	for (const COFFYAML::Section &S : CP.Obj.Sections) {
	if (!S.Header.SizeOfRawData)
	continue;
	assert(S.Header.PointerToRawData >= OS.tell());
	OS << num_zeros(S.Header.PointerToRawData - OS.tell());
	S.SectionData.writeAsBinary(OS);
	assert(S.Header.SizeOfRawData >= S.SectionData.binary_size());
	OS << num_zeros(S.Header.SizeOfRawData - S.SectionData.binary_size());
	for (const COFFYAML::Relocation &R : S.Relocations) {
	uint32_t SymbolTableIndex = SymbolTableIndexMap[R.SymbolName];
	OS << binary_le(R.VirtualAddress)
	<< binary_le(SymbolTableIndex)
	<< binary_le(R.Type);
	}
	}

	// Output symbol table.

	for (std::vector<COFFYAML::Symbol>::const_iterator i = CP.Obj.Symbols.begin(),
	e = CP.Obj.Symbols.end();
	i != e; ++i) {
	OS.write(i->Header.Name, COFF::NameSize);
	OS << binary_le(i->Header.Value);
	if (CP.useBigObj())
	OS << binary_le(i->Header.SectionNumber);
	else
	OS << binary_le(static_cast<int16_t>(i->Header.SectionNumber));
	OS << binary_le(i->Header.Type)
	<< binary_le(i->Header.StorageClass)
	<< binary_le(i->Header.NumberOfAuxSymbols);

	if (i->FunctionDefinition)
	OS << binary_le(i->FunctionDefinition->TagIndex)
	<< binary_le(i->FunctionDefinition->TotalSize)
	<< binary_le(i->FunctionDefinition->PointerToLinenumber)
	<< binary_le(i->FunctionDefinition->PointerToNextFunction)
	<< zeros(i->FunctionDefinition->unused)
	<< num_zeros(CP.getSymbolSize() - COFF::Symbol16Size);
	if (i->bfAndefSymbol)
	OS << zeros(i->bfAndefSymbol->unused1)
	<< binary_le(i->bfAndefSymbol->Linenumber)
	<< zeros(i->bfAndefSymbol->unused2)
	<< binary_le(i->bfAndefSymbol->PointerToNextFunction)
	<< zeros(i->bfAndefSymbol->unused3)
	<< num_zeros(CP.getSymbolSize() - COFF::Symbol16Size);
	if (i->WeakExternal)
	OS << binary_le(i->WeakExternal->TagIndex)
	<< binary_le(i->WeakExternal->Characteristics)
	<< zeros(i->WeakExternal->unused)
	<< num_zeros(CP.getSymbolSize() - COFF::Symbol16Size);
	if (!i->File.empty()) {
	unsigned SymbolSize = CP.getSymbolSize();
	uint32_t NumberOfAuxRecords =
	(i->File.size() + SymbolSize - 1) / SymbolSize;
	uint32_t NumberOfAuxBytes = NumberOfAuxRecords * SymbolSize;
	uint32_t NumZeros = NumberOfAuxBytes - i->File.size();
	OS.write(i->File.data(), i->File.size());
	OS << num_zeros(NumZeros);
	}
	if (i->SectionDefinition)
	OS << binary_le(i->SectionDefinition->Length)
	<< binary_le(i->SectionDefinition->NumberOfRelocations)
	<< binary_le(i->SectionDefinition->NumberOfLinenumbers)
	<< binary_le(i->SectionDefinition->CheckSum)
	<< binary_le(static_cast<int16_t>(i->SectionDefinition->Number))
	<< binary_le(i->SectionDefinition->Selection)
	<< zeros(i->SectionDefinition->unused)
	<< binary_le(static_cast<int16_t>(i->SectionDefinition->Number >> 16))
	<< num_zeros(CP.getSymbolSize() - COFF::Symbol16Size);
	if (i->CLRToken)
	OS << binary_le(i->CLRToken->AuxType)
	<< zeros(i->CLRToken->unused1)
	<< binary_le(i->CLRToken->SymbolTableIndex)
	<< zeros(i->CLRToken->unused2)
	<< num_zeros(CP.getSymbolSize() - COFF::Symbol16Size);
	}

	// Output string table.
	if (CP.Obj.Header.PointerToSymbolTable)
	OS.write(&CP.StringTable[0], CP.StringTable.size());
	return true;
	}

	int yaml2coff(yaml::Input &YIn, raw_ostream &Out) {
	COFFYAML::Object Doc;
	YIn >> Doc;
	if (YIn.error()) {
	errs() << "yaml2obj: Failed to parse YAML file!\n";
	return 1;
	}

	COFFParser CP(Doc);
	if (!CP.parse()) {
	errs() << "yaml2obj: Failed to parse YAML file!\n";
	return 1;
	}

	if (!layoutOptionalHeader(CP)) {
	errs() << "yaml2obj: Failed to layout optional header for COFF file!\n";
	return 1;
	}
	if (!layoutCOFF(CP)) {
	errs() << "yaml2obj: Failed to layout COFF file!\n";
	return 1;
	}
	if (!writeCOFF(CP, Out)) {
	errs() << "yaml2obj: Failed to write COFF file!\n";
	return 1;
	}
	return 0;
	}