lib/CodeGen/ELFWriter.cpp

   1 //===-- ELFWriter.cpp - Target-independent ELF Writer code ----------------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file implements the target-independent ELF writer.  This file writes out
  11 // the ELF file in the following order:
  12 //
  13 //  #1. ELF Header
  14 //  #2. '.text' section
  15 //  #3. '.data' section
  16 //  #4. '.bss' section  (conceptual position in file)
  17 //  ...
  18 //  #X. '.shstrtab' section
  19 //  #Y. Section Table
  20 //
  21 // The entries in the section table are laid out as:
  22 //  #0. Null entry [required]
  23 //  #1. ".text" entry - the program code
  24 //  #2. ".data" entry - global variables with initializers.     [ if needed ]
  25 //  #3. ".bss" entry  - global variables without initializers.  [ if needed ]
  26 //  ...
  27 //  #N. ".shstrtab" entry - String table for the section names.
  28 //
  29 //===----------------------------------------------------------------------===//
  30
  31 #define DEBUG_TYPE "elfwriter"
  32 #include "ELF.h"
  33 #include "ELFWriter.h"
  34 #include "ELFCodeEmitter.h"
  35 #include "llvm/Constants.h"
  36 #include "llvm/Module.h"
  37 #include "llvm/PassManager.h"
  38 #include "llvm/DerivedTypes.h"
  39 #include "llvm/CodeGen/BinaryObject.h"
  40 #include "llvm/CodeGen/FileWriters.h"
  41 #include "llvm/CodeGen/MachineCodeEmitter.h"
  42 #include "llvm/CodeGen/ObjectCodeEmitter.h"
  43 #include "llvm/CodeGen/MachineCodeEmitter.h"
  44 #include "llvm/CodeGen/MachineConstantPool.h"
  45 #include "llvm/MC/MCContext.h"
  46 #include "llvm/MC/MCSectionELF.h"
  47 #include "llvm/Target/TargetAsmInfo.h"
  48 #include "llvm/Target/TargetData.h"
  49 #include "llvm/Target/TargetELFWriterInfo.h"
  50 #include "llvm/Target/TargetLowering.h"
  51 #include "llvm/Target/TargetLoweringObjectFile.h"
  52 #include "llvm/Target/TargetMachine.h"
  53 #include "llvm/Support/Mangler.h"
  54 #include "llvm/Support/Streams.h"
  55 #include "llvm/Support/raw_ostream.h"
  56 #include "llvm/Support/Debug.h"
  57 #include "llvm/Support/ErrorHandling.h"
  58
  59 using namespace llvm;
  60
  61 char ELFWriter::ID = 0;
  62
  63 /// AddELFWriter - Add the ELF writer to the function pass manager
  64 ObjectCodeEmitter *llvm::AddELFWriter(PassManagerBase &PM,
  65                                       raw_ostream &O,
  66                                       TargetMachine &TM) {
  67   ELFWriter *EW = new ELFWriter(O, TM);
  68   PM.add(EW);
  69   return EW->getObjectCodeEmitter();
  70 }
  71
  72 //===----------------------------------------------------------------------===//
  73 //                          ELFWriter Implementation
  74 //===----------------------------------------------------------------------===//
  75
  76 ELFWriter::ELFWriter(raw_ostream &o, TargetMachine &tm)
  77   : MachineFunctionPass(&ID), O(o), TM(tm),
  78     OutContext(*new MCContext()),
  79     TLOF(TM.getTargetLowering()->getObjFileLowering()),
  80     is64Bit(TM.getTargetData()->getPointerSizeInBits() == 64),
  81     isLittleEndian(TM.getTargetData()->isLittleEndian()),
  82     ElfHdr(isLittleEndian, is64Bit) {
  83
  84   TAI = TM.getTargetAsmInfo();
  85   TEW = TM.getELFWriterInfo();
  86
  87   // Create the object code emitter object for this target.
  88   ElfCE = new ELFCodeEmitter(*this);
  89
  90   // Inital number of sections
  91   NumSections = 0;
  92 }
  93
  94 ELFWriter::~ELFWriter() {
  95   delete ElfCE;
  96   delete &OutContext;
  97 }
  98
  99 // doInitialization - Emit the file header and all of the global variables for
 100 // the module to the ELF file.
 101 bool ELFWriter::doInitialization(Module &M) {
 102   // Initialize TargetLoweringObjectFile.
 103   const_cast<TargetLoweringObjectFile&>(TLOF).Initialize(OutContext, TM);
 104
 105   Mang = new Mangler(M);
 106
 107   // ELF Header
 108   // ----------
 109   // Fields e_shnum e_shstrndx are only known after all section have
 110   // been emitted. They locations in the ouput buffer are recorded so
 111   // to be patched up later.
 112   //
 113   // Note
 114   // ----
 115   // emitWord method behaves differently for ELF32 and ELF64, writing
 116   // 4 bytes in the former and 8 in the last for *_off and *_addr elf types
 117
 118   ElfHdr.emitByte(0x7f); // e_ident[EI_MAG0]
 119   ElfHdr.emitByte('E');  // e_ident[EI_MAG1]
 120   ElfHdr.emitByte('L');  // e_ident[EI_MAG2]
 121   ElfHdr.emitByte('F');  // e_ident[EI_MAG3]
 122
 123   ElfHdr.emitByte(TEW->getEIClass()); // e_ident[EI_CLASS]
 124   ElfHdr.emitByte(TEW->getEIData());  // e_ident[EI_DATA]
 125   ElfHdr.emitByte(EV_CURRENT);        // e_ident[EI_VERSION]
 126   ElfHdr.emitAlignment(16);           // e_ident[EI_NIDENT-EI_PAD]
 127
 128   ElfHdr.emitWord16(ET_REL);             // e_type
 129   ElfHdr.emitWord16(TEW->getEMachine()); // e_machine = target
 130   ElfHdr.emitWord32(EV_CURRENT);         // e_version
 131   ElfHdr.emitWord(0);                    // e_entry, no entry point in .o file
 132   ElfHdr.emitWord(0);                    // e_phoff, no program header for .o
 133   ELFHdr_e_shoff_Offset = ElfHdr.size();
 134   ElfHdr.emitWord(0);                    // e_shoff = sec hdr table off in bytes
 135   ElfHdr.emitWord32(TEW->getEFlags());   // e_flags = whatever the target wants
 136   ElfHdr.emitWord16(TEW->getHdrSize());  // e_ehsize = ELF header size
 137   ElfHdr.emitWord16(0);                  // e_phentsize = prog header entry size
 138   ElfHdr.emitWord16(0);                  // e_phnum = # prog header entries = 0
 139
 140   // e_shentsize = Section header entry size
 141   ElfHdr.emitWord16(TEW->getSHdrSize());
 142
 143   // e_shnum     = # of section header ents
 144   ELFHdr_e_shnum_Offset = ElfHdr.size();
 145   ElfHdr.emitWord16(0); // Placeholder
 146
 147   // e_shstrndx  = Section # of '.shstrtab'
 148   ELFHdr_e_shstrndx_Offset = ElfHdr.size();
 149   ElfHdr.emitWord16(0); // Placeholder
 150
 151   // Add the null section, which is required to be first in the file.
 152   getNullSection();
 153
 154   // The first entry in the symtab is the null symbol and the second
 155   // is a local symbol containing the module/file name
 156   SymbolList.push_back(new ELFSym());
 157   SymbolList.push_back(ELFSym::getFileSym());
 158
 159   return false;
 160 }
 161
 162 // AddPendingGlobalSymbol - Add a global to be processed and to
 163 // the global symbol lookup, use a zero index because the table
 164 // index will be determined later.
 165 void ELFWriter::AddPendingGlobalSymbol(const GlobalValue *GV,
 166                                        bool AddToLookup /* = false */) {
 167   PendingGlobals.insert(GV);
 168   if (AddToLookup)
 169     GblSymLookup[GV] = 0;
 170 }
 171
 172 // AddPendingExternalSymbol - Add the external to be processed
 173 // and to the external symbol lookup, use a zero index because
 174 // the symbol table index will be determined later.
 175 void ELFWriter::AddPendingExternalSymbol(const char *External) {
 176   PendingExternals.insert(External);
 177   ExtSymLookup[External] = 0;
 178 }
 179
 180 ELFSection &ELFWriter::getDataSection() {
 181   const MCSectionELF *Data = (const MCSectionELF *)TLOF.getDataSection();
 182   return getSection(Data->getSectionName(), Data->getType(),
 183                     Data->getFlags(), 4);
 184 }
 185
 186 ELFSection &ELFWriter::getBSSSection() {
 187   const MCSectionELF *BSS = (const MCSectionELF *)TLOF.getBSSSection();
 188   return getSection(BSS->getSectionName(), BSS->getType(), BSS->getFlags(), 4);
 189 }
 190
 191 // getCtorSection - Get the static constructor section
 192 ELFSection &ELFWriter::getCtorSection() {
 193   const MCSectionELF *Ctor = (const MCSectionELF *)TLOF.getStaticCtorSection();
 194   return getSection(Ctor->getSectionName(), Ctor->getType(), Ctor->getFlags());
 195 }
 196
 197 // getDtorSection - Get the static destructor section
 198 ELFSection &ELFWriter::getDtorSection() {
 199   const MCSectionELF *Dtor = (const MCSectionELF *)TLOF.getStaticDtorSection();
 200   return getSection(Dtor->getSectionName(), Dtor->getType(), Dtor->getFlags());
 201 }
 202
 203 // getTextSection - Get the text section for the specified function
 204 ELFSection &ELFWriter::getTextSection(Function *F) {
 205   const MCSectionELF *Text =
 206     (const MCSectionELF *)TLOF.SectionForGlobal(F, Mang, TM);
 207   return getSection(Text->getSectionName(), Text->getType(), Text->getFlags());
 208 }
 209
 210 // getJumpTableSection - Get a read only section for constants when
 211 // emitting jump tables. TODO: add PIC support
 212 ELFSection &ELFWriter::getJumpTableSection() {
 213   const MCSectionELF *JT =
 214     (const MCSectionELF *)TLOF.getSectionForConstant(SectionKind::getReadOnly());
 215   return getSection(JT->getSectionName(), JT->getType(), JT->getFlags(),
 216                     TM.getTargetData()->getPointerABIAlignment());
 217 }
 218
 219 // getConstantPoolSection - Get a constant pool section based on the machine
 220 // constant pool entry type and relocation info.
 221 ELFSection &ELFWriter::getConstantPoolSection(MachineConstantPoolEntry &CPE) {
 222   SectionKind Kind;
 223   switch (CPE.getRelocationInfo()) {
 224   default: llvm_unreachable("Unknown section kind");
 225   case 2: Kind = SectionKind::getReadOnlyWithRel(); break;
 226   case 1:
 227     Kind = SectionKind::getReadOnlyWithRelLocal();
 228     break;
 229   case 0:
 230     switch (TM.getTargetData()->getTypeAllocSize(CPE.getType())) {
 231     case 4:  Kind = SectionKind::getMergeableConst4(); break;
 232     case 8:  Kind = SectionKind::getMergeableConst8(); break;
 233     case 16: Kind = SectionKind::getMergeableConst16(); break;
 234     default: Kind = SectionKind::getMergeableConst(); break;
 235     }
 236   }
 237
 238   const MCSectionELF *CPSect =
 239     (const MCSectionELF *)TLOF.getSectionForConstant(Kind);
 240   return getSection(CPSect->getSectionName(), CPSect->getType(),
 241                     CPSect->getFlags(), CPE.getAlignment());
 242 }
 243
 244 // getRelocSection - Return the relocation section of section 'S'. 'RelA'
 245 // is true if the relocation section contains entries with addends.
 246 ELFSection &ELFWriter::getRelocSection(ELFSection &S) {
 247   unsigned SectionType = TEW->hasRelocationAddend() ?
 248                 ELFSection::SHT_RELA : ELFSection::SHT_REL;
 249
 250   std::string SectionName(".rel");
 251   if (TEW->hasRelocationAddend())
 252     SectionName.append("a");
 253   SectionName.append(S.getName());
 254
 255   return getSection(SectionName, SectionType, 0, TEW->getPrefELFAlignment());
 256 }
 257
 258 // getGlobalELFVisibility - Returns the ELF specific visibility type
 259 unsigned ELFWriter::getGlobalELFVisibility(const GlobalValue *GV) {
 260   switch (GV->getVisibility()) {
 261   default:
 262     llvm_unreachable("unknown visibility type");
 263   case GlobalValue::DefaultVisibility:
 264     return ELFSym::STV_DEFAULT;
 265   case GlobalValue::HiddenVisibility:
 266     return ELFSym::STV_HIDDEN;
 267   case GlobalValue::ProtectedVisibility:
 268     return ELFSym::STV_PROTECTED;
 269   }
 270   return 0;
 271 }
 272
 273 // getGlobalELFBinding - Returns the ELF specific binding type
 274 unsigned ELFWriter::getGlobalELFBinding(const GlobalValue *GV) {
 275   if (GV->hasInternalLinkage())
 276     return ELFSym::STB_LOCAL;
 277
 278   if (GV->isWeakForLinker() && !GV->hasCommonLinkage())
 279     return ELFSym::STB_WEAK;
 280
 281   return ELFSym::STB_GLOBAL;
 282 }
 283
 284 // getGlobalELFType - Returns the ELF specific type for a global
 285 unsigned ELFWriter::getGlobalELFType(const GlobalValue *GV) {
 286   if (GV->isDeclaration())
 287     return ELFSym::STT_NOTYPE;
 288
 289   if (isa<Function>(GV))
 290     return ELFSym::STT_FUNC;
 291
 292   return ELFSym::STT_OBJECT;
 293 }
 294
 295 // IsELFUndefSym - True if the global value must be marked as a symbol
 296 // which points to a SHN_UNDEF section. This means that the symbol has
 297 // no definition on the module.
 298 static bool IsELFUndefSym(const GlobalValue *GV) {
 299   return GV->isDeclaration() || (isa<Function>(GV));
 300 }
 301
 302 // AddToSymbolList - Update the symbol lookup and If the symbol is
 303 // private add it to PrivateSyms list, otherwise to SymbolList.
 304 void ELFWriter::AddToSymbolList(ELFSym *GblSym) {
 305   assert(GblSym->isGlobalValue() && "Symbol must be a global value");
 306
 307   const GlobalValue *GV = GblSym->getGlobalValue();
 308   if (GV->hasPrivateLinkage()) {
 309     // For a private symbols, keep track of the index inside
 310     // the private list since it will never go to the symbol
 311     // table and won't be patched up later.
 312     PrivateSyms.push_back(GblSym);
 313     GblSymLookup[GV] = PrivateSyms.size()-1;
 314   } else {
 315     // Non private symbol are left with zero indices until
 316     // they are patched up during the symbol table emition
 317     // (where the indicies are created).
 318     SymbolList.push_back(GblSym);
 319     GblSymLookup[GV] = 0;
 320   }
 321 }
 322
 323 // EmitGlobal - Choose the right section for global and emit it
 324 void ELFWriter::EmitGlobal(const GlobalValue *GV) {
 325
 326   // Check if the referenced symbol is already emitted
 327   if (GblSymLookup.find(GV) != GblSymLookup.end())
 328     return;
 329
 330   // Handle ELF Bind, Visibility and Type for the current symbol
 331   unsigned SymBind = getGlobalELFBinding(GV);
 332   unsigned SymType = getGlobalELFType(GV);
 333   bool IsUndefSym = IsELFUndefSym(GV);
 334
 335   ELFSym *GblSym = IsUndefSym ? ELFSym::getUndefGV(GV, SymBind)
 336     : ELFSym::getGV(GV, SymBind, SymType, getGlobalELFVisibility(GV));
 337
 338   if (!IsUndefSym) {
 339     assert(isa<GlobalVariable>(GV) && "GV not a global variable!");
 340     const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV);
 341
 342     // Handle special llvm globals
 343     if (EmitSpecialLLVMGlobal(GVar))
 344       return;
 345
 346     // Get the ELF section where this global belongs from TLOF
 347     const MCSectionELF *S =
 348       (const MCSectionELF *)TLOF.SectionForGlobal(GV, Mang, TM);
 349     ELFSection &ES =
 350       getSection(S->getSectionName(), S->getType(), S->getFlags());
 351     SectionKind Kind = S->getKind();
 352
 353     // The symbol align should update the section alignment if needed
 354     const TargetData *TD = TM.getTargetData();
 355     unsigned Align = TD->getPreferredAlignment(GVar);
 356     unsigned Size = TD->getTypeAllocSize(GVar->getInitializer()->getType());
 357     GblSym->Size = Size;
 358
 359     if (S->IsCommon()) { // Symbol must go to a common section
 360       GblSym->SectionIdx = ELFSection::SHN_COMMON;
 361
 362       // A new linkonce section is created for each global in the
 363       // common section, the default alignment is 1 and the symbol
 364       // value contains its alignment.
 365       ES.Align = 1;
 366       GblSym->Value = Align;
 367
 368     } else if (Kind.isBSS() || Kind.isThreadBSS()) { // Symbol goes to BSS.
 369       GblSym->SectionIdx = ES.SectionIdx;
 370
 371       // Update the size with alignment and the next object can
 372       // start in the right offset in the section
 373       if (Align) ES.Size = (ES.Size + Align-1) & ~(Align-1);
 374       ES.Align = std::max(ES.Align, Align);
 375
 376       // GblSym->Value should contain the virtual offset inside the section.
 377       // Virtual because the BSS space is not allocated on ELF objects
 378       GblSym->Value = ES.Size;
 379       ES.Size += Size;
 380
 381     } else { // The symbol must go to some kind of data section
 382       GblSym->SectionIdx = ES.SectionIdx;
 383
 384       // GblSym->Value should contain the symbol offset inside the section,
 385       // and all symbols should start on their required alignment boundary
 386       ES.Align = std::max(ES.Align, Align);
 387       ES.emitAlignment(Align);
 388       GblSym->Value = ES.size();
 389
 390       // Emit the global to the data section 'ES'
 391       EmitGlobalConstant(GVar->getInitializer(), ES);
 392     }
 393   }
 394
 395   AddToSymbolList(GblSym);
 396 }
 397
 398 void ELFWriter::EmitGlobalConstantStruct(const ConstantStruct *CVS,
 399                                          ELFSection &GblS) {
 400
 401   // Print the fields in successive locations. Pad to align if needed!
 402   const TargetData *TD = TM.getTargetData();
 403   unsigned Size = TD->getTypeAllocSize(CVS->getType());
 404   const StructLayout *cvsLayout = TD->getStructLayout(CVS->getType());
 405   uint64_t sizeSoFar = 0;
 406   for (unsigned i = 0, e = CVS->getNumOperands(); i != e; ++i) {
 407     const Constant* field = CVS->getOperand(i);
 408
 409     // Check if padding is needed and insert one or more 0s.
 410     uint64_t fieldSize = TD->getTypeAllocSize(field->getType());
 411     uint64_t padSize = ((i == e-1 ? Size : cvsLayout->getElementOffset(i+1))
 412                         - cvsLayout->getElementOffset(i)) - fieldSize;
 413     sizeSoFar += fieldSize + padSize;
 414
 415     // Now print the actual field value.
 416     EmitGlobalConstant(field, GblS);
 417
 418     // Insert padding - this may include padding to increase the size of the
 419     // current field up to the ABI size (if the struct is not packed) as well
 420     // as padding to ensure that the next field starts at the right offset.
 421     GblS.emitZeros(padSize);
 422   }
 423   assert(sizeSoFar == cvsLayout->getSizeInBytes() &&
 424          "Layout of constant struct may be incorrect!");
 425 }
 426
 427 void ELFWriter::EmitGlobalConstant(const Constant *CV, ELFSection &GblS) {
 428   const TargetData *TD = TM.getTargetData();
 429   unsigned Size = TD->getTypeAllocSize(CV->getType());
 430
 431   if (const ConstantArray *CVA = dyn_cast<ConstantArray>(CV)) {
 432     for (unsigned i = 0, e = CVA->getNumOperands(); i != e; ++i)
 433       EmitGlobalConstant(CVA->getOperand(i), GblS);
 434     return;
 435   } else if (isa<ConstantAggregateZero>(CV)) {
 436     GblS.emitZeros(Size);
 437     return;
 438   } else if (const ConstantStruct *CVS = dyn_cast<ConstantStruct>(CV)) {
 439     EmitGlobalConstantStruct(CVS, GblS);
 440     return;
 441   } else if (const ConstantFP *CFP = dyn_cast<ConstantFP>(CV)) {
 442     APInt Val = CFP->getValueAPF().bitcastToAPInt();
 443     if (CFP->getType() == Type::getDoubleTy(CV->getContext()))
 444       GblS.emitWord64(Val.getZExtValue());
 445     else if (CFP->getType() == Type::getFloatTy(CV->getContext()))
 446       GblS.emitWord32(Val.getZExtValue());
 447     else if (CFP->getType() == Type::getX86_FP80Ty(CV->getContext())) {
 448       unsigned PadSize =
 449              TD->getTypeAllocSize(Type::getX86_FP80Ty(CV->getContext()))-
 450              TD->getTypeStoreSize(Type::getX86_FP80Ty(CV->getContext()));
 451       GblS.emitWordFP80(Val.getRawData(), PadSize);
 452     } else if (CFP->getType() == Type::getPPC_FP128Ty(CV->getContext()))
 453       llvm_unreachable("PPC_FP128Ty global emission not implemented");
 454     return;
 455   } else if (const ConstantInt *CI = dyn_cast<ConstantInt>(CV)) {
 456     if (Size == 1)
 457       GblS.emitByte(CI->getZExtValue());
 458     else if (Size == 2)
 459       GblS.emitWord16(CI->getZExtValue());
 460     else if (Size == 4)
 461       GblS.emitWord32(CI->getZExtValue());
 462     else
 463       EmitGlobalConstantLargeInt(CI, GblS);
 464     return;
 465   } else if (const ConstantVector *CP = dyn_cast<ConstantVector>(CV)) {
 466     const VectorType *PTy = CP->getType();
 467     for (unsigned I = 0, E = PTy->getNumElements(); I < E; ++I)
 468       EmitGlobalConstant(CP->getOperand(I), GblS);
 469     return;
 470   } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV)) {
 471     // Resolve a constant expression which returns a (Constant, Offset)
 472     // pair. If 'Res.first' is a GlobalValue, emit a relocation with
 473     // the offset 'Res.second', otherwise emit a global constant like
 474     // it is always done for not contant expression types.
 475     CstExprResTy Res = ResolveConstantExpr(CE);
 476     const Constant *Op = Res.first;
 477
 478     if (isa<GlobalValue>(Op))
 479       EmitGlobalDataRelocation(cast<const GlobalValue>(Op),
 480                                TD->getTypeAllocSize(Op->getType()),
 481                                GblS, Res.second);
 482     else
 483       EmitGlobalConstant(Op, GblS);
 484
 485     return;
 486   } else if (CV->getType()->getTypeID() == Type::PointerTyID) {
 487     // Fill the data entry with zeros or emit a relocation entry
 488     if (isa<ConstantPointerNull>(CV))
 489       GblS.emitZeros(Size);
 490     else
 491       EmitGlobalDataRelocation(cast<const GlobalValue>(CV),
 492                                Size, GblS);
 493     return;
 494   } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CV)) {
 495     // This is a constant address for a global variable or function and
 496     // therefore must be referenced using a relocation entry.
 497     EmitGlobalDataRelocation(GV, Size, GblS);
 498     return;
 499   }
 500
 501   std::string msg;
 502   raw_string_ostream ErrorMsg(msg);
 503   ErrorMsg << "Constant unimp for type: " << *CV->getType();
 504   llvm_report_error(ErrorMsg.str());
 505 }
 506
 507 // ResolveConstantExpr - Resolve the constant expression until it stop
 508 // yielding other constant expressions.
 509 CstExprResTy ELFWriter::ResolveConstantExpr(const Constant *CV) {
 510   const TargetData *TD = TM.getTargetData();
 511
 512   // There ins't constant expression inside others anymore
 513   if (!isa<ConstantExpr>(CV))
 514     return std::make_pair(CV, 0);
 515
 516   const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV);
 517   switch (CE->getOpcode()) {
 518   case Instruction::BitCast:
 519     return ResolveConstantExpr(CE->getOperand(0));
 520
 521   case Instruction::GetElementPtr: {
 522     const Constant *ptrVal = CE->getOperand(0);
 523     SmallVector<Value*, 8> idxVec(CE->op_begin()+1, CE->op_end());
 524     int64_t Offset = TD->getIndexedOffset(ptrVal->getType(), &idxVec[0],
 525                                           idxVec.size());
 526     return std::make_pair(ptrVal, Offset);
 527   }
 528   case Instruction::IntToPtr: {
 529     Constant *Op = CE->getOperand(0);
 530     Op = ConstantExpr::getIntegerCast(Op, TD->getIntPtrType(CV->getContext()),
 531                                       false/*ZExt*/);
 532     return ResolveConstantExpr(Op);
 533   }
 534   case Instruction::PtrToInt: {
 535     Constant *Op = CE->getOperand(0);
 536     const Type *Ty = CE->getType();
 537
 538     // We can emit the pointer value into this slot if the slot is an
 539     // integer slot greater or equal to the size of the pointer.
 540     if (TD->getTypeAllocSize(Ty) == TD->getTypeAllocSize(Op->getType()))
 541       return ResolveConstantExpr(Op);
 542
 543     llvm_unreachable("Integer size less then pointer size");
 544   }
 545   case Instruction::Add:
 546   case Instruction::Sub: {
 547     // Only handle cases where there's a constant expression with GlobalValue
 548     // as first operand and ConstantInt as second, which are the cases we can
 549     // solve direclty using a relocation entry. GlobalValue=Op0, CstInt=Op1
 550     // 1)  Instruction::Add  => (global) + CstInt
 551     // 2)  Instruction::Sub  => (global) + -CstInt
 552     const Constant *Op0 = CE->getOperand(0);
 553     const Constant *Op1 = CE->getOperand(1);
 554     assert(isa<ConstantInt>(Op1) && "Op1 must be a ConstantInt");
 555
 556     CstExprResTy Res = ResolveConstantExpr(Op0);
 557     assert(isa<GlobalValue>(Res.first) && "Op0 must be a GlobalValue");
 558
 559     const APInt &RHS = cast<ConstantInt>(Op1)->getValue();
 560     switch (CE->getOpcode()) {
 561     case Instruction::Add:
 562       return std::make_pair(Res.first, RHS.getSExtValue());
 563     case Instruction::Sub:
 564       return std::make_pair(Res.first, (-RHS).getSExtValue());
 565     }
 566   }
 567   }
 568
 569   std::string msg(CE->getOpcodeName());
 570   raw_string_ostream ErrorMsg(msg);
 571   ErrorMsg << ": Unsupported ConstantExpr type";
 572   llvm_report_error(ErrorMsg.str());
 573
 574   return std::make_pair(CV, 0); // silence warning
 575 }
 576
 577 void ELFWriter::EmitGlobalDataRelocation(const GlobalValue *GV, unsigned Size,
 578                                          ELFSection &GblS, int64_t Offset) {
 579   // Create the relocation entry for the global value
 580   MachineRelocation MR =
 581     MachineRelocation::getGV(GblS.getCurrentPCOffset(),
 582                              TEW->getAbsoluteLabelMachineRelTy(),
 583                              const_cast<GlobalValue*>(GV),
 584                              Offset);
 585
 586   // Fill the data entry with zeros
 587   GblS.emitZeros(Size);
 588
 589   // Add the relocation entry for the current data section
 590   GblS.addRelocation(MR);
 591 }
 592
 593 void ELFWriter::EmitGlobalConstantLargeInt(const ConstantInt *CI,
 594                                            ELFSection &S) {
 595   const TargetData *TD = TM.getTargetData();
 596   unsigned BitWidth = CI->getBitWidth();
 597   assert(isPowerOf2_32(BitWidth) &&
 598          "Non-power-of-2-sized integers not handled!");
 599
 600   const uint64_t *RawData = CI->getValue().getRawData();
 601   uint64_t Val = 0;
 602   for (unsigned i = 0, e = BitWidth / 64; i != e; ++i) {
 603     Val = (TD->isBigEndian()) ? RawData[e - i - 1] : RawData[i];
 604     S.emitWord64(Val);
 605   }
 606 }
 607
 608 /// EmitSpecialLLVMGlobal - Check to see if the specified global is a
 609 /// special global used by LLVM.  If so, emit it and return true, otherwise
 610 /// do nothing and return false.
 611 bool ELFWriter::EmitSpecialLLVMGlobal(const GlobalVariable *GV) {
 612   if (GV->getName() == "llvm.used")
 613     llvm_unreachable("not implemented yet");
 614
 615   // Ignore debug and non-emitted data.  This handles llvm.compiler.used.
 616   if (GV->getSection() == "llvm.metadata" ||
 617       GV->hasAvailableExternallyLinkage())
 618     return true;
 619
 620   if (!GV->hasAppendingLinkage()) return false;
 621
 622   assert(GV->hasInitializer() && "Not a special LLVM global!");
 623
 624   const TargetData *TD = TM.getTargetData();
 625   unsigned Align = TD->getPointerPrefAlignment();
 626   if (GV->getName() == "llvm.global_ctors") {
 627     ELFSection &Ctor = getCtorSection();
 628     Ctor.emitAlignment(Align);
 629     EmitXXStructorList(GV->getInitializer(), Ctor);
 630     return true;
 631   }
 632
 633   if (GV->getName() == "llvm.global_dtors") {
 634     ELFSection &Dtor = getDtorSection();
 635     Dtor.emitAlignment(Align);
 636     EmitXXStructorList(GV->getInitializer(), Dtor);
 637     return true;
 638   }
 639
 640   return false;
 641 }
 642
 643 /// EmitXXStructorList - Emit the ctor or dtor list.  This just emits out the
 644 /// function pointers, ignoring the init priority.
 645 void ELFWriter::EmitXXStructorList(Constant *List, ELFSection &Xtor) {
 646   // Should be an array of '{ int, void ()* }' structs.  The first value is the
 647   // init priority, which we ignore.
 648   if (!isa<ConstantArray>(List)) return;
 649   ConstantArray *InitList = cast<ConstantArray>(List);
 650   for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i)
 651     if (ConstantStruct *CS = dyn_cast<ConstantStruct>(InitList->getOperand(i))){
 652       if (CS->getNumOperands() != 2) return;  // Not array of 2-element structs.
 653
 654       if (CS->getOperand(1)->isNullValue())
 655         return;  // Found a null terminator, exit printing.
 656       // Emit the function pointer.
 657       EmitGlobalConstant(CS->getOperand(1), Xtor);
 658     }
 659 }
 660
 661 bool ELFWriter::runOnMachineFunction(MachineFunction &MF) {
 662   // Nothing to do here, this is all done through the ElfCE object above.
 663   return false;
 664 }
 665
 666 /// doFinalization - Now that the module has been completely processed, emit
 667 /// the ELF file to 'O'.
 668 bool ELFWriter::doFinalization(Module &M) {
 669   // Emit .data section placeholder
 670   getDataSection();
 671
 672   // Emit .bss section placeholder
 673   getBSSSection();
 674
 675   // Build and emit data, bss and "common" sections.
 676   for (Module::global_iterator I = M.global_begin(), E = M.global_end();
 677        I != E; ++I)
 678     EmitGlobal(I);
 679
 680   // Emit all pending globals
 681   for (PendingGblsIter I = PendingGlobals.begin(), E = PendingGlobals.end();
 682        I != E; ++I)
 683     EmitGlobal(*I);
 684
 685   // Emit all pending externals
 686   for (PendingExtsIter I = PendingExternals.begin(), E = PendingExternals.end();
 687        I != E; ++I)
 688     SymbolList.push_back(ELFSym::getExtSym(*I));
 689
 690   // Emit non-executable stack note
 691   if (TAI->getNonexecutableStackDirective())
 692     getNonExecStackSection();
 693
 694   // Emit a symbol for each section created until now, skip null section
 695   for (unsigned i = 1, e = SectionList.size(); i < e; ++i) {
 696     ELFSection &ES = *SectionList[i];
 697     ELFSym *SectionSym = ELFSym::getSectionSym();
 698     SectionSym->SectionIdx = ES.SectionIdx;
 699     SymbolList.push_back(SectionSym);
 700     ES.Sym = SymbolList.back();
 701   }
 702
 703   // Emit string table
 704   EmitStringTable(M.getModuleIdentifier());
 705
 706   // Emit the symbol table now, if non-empty.
 707   EmitSymbolTable();
 708
 709   // Emit the relocation sections.
 710   EmitRelocations();
 711
 712   // Emit the sections string table.
 713   EmitSectionTableStringTable();
 714
 715   // Dump the sections and section table to the .o file.
 716   OutputSectionsAndSectionTable();
 717
 718   // We are done with the abstract symbols.
 719   SymbolList.clear();
 720   SectionList.clear();
 721   NumSections = 0;
 722
 723   // Release the name mangler object.
 724   delete Mang; Mang = 0;
 725   return false;
 726 }
 727
 728 // RelocateField - Patch relocatable field with 'Offset' in 'BO'
 729 // using a 'Value' of known 'Size'
 730 void ELFWriter::RelocateField(BinaryObject &BO, uint32_t Offset,
 731                               int64_t Value, unsigned Size) {
 732   if (Size == 32)
 733     BO.fixWord32(Value, Offset);
 734   else if (Size == 64)
 735     BO.fixWord64(Value, Offset);
 736   else
 737     llvm_unreachable("don't know howto patch relocatable field");
 738 }
 739
 740 /// EmitRelocations - Emit relocations
 741 void ELFWriter::EmitRelocations() {
 742
 743   // True if the target uses the relocation entry to hold the addend,
 744   // otherwise the addend is written directly to the relocatable field.
 745   bool HasRelA = TEW->hasRelocationAddend();
 746
 747   // Create Relocation sections for each section which needs it.
 748   for (unsigned i=0, e=SectionList.size(); i != e; ++i) {
 749     ELFSection &S = *SectionList[i];
 750
 751     // This section does not have relocations
 752     if (!S.hasRelocations()) continue;
 753     ELFSection &RelSec = getRelocSection(S);
 754
 755     // 'Link' - Section hdr idx of the associated symbol table
 756     // 'Info' - Section hdr idx of the section to which the relocation applies
 757     ELFSection &SymTab = getSymbolTableSection();
 758     RelSec.Link = SymTab.SectionIdx;
 759     RelSec.Info = S.SectionIdx;
 760     RelSec.EntSize = TEW->getRelocationEntrySize();
 761
 762     // Get the relocations from Section
 763     std::vector<MachineRelocation> Relos = S.getRelocations();
 764     for (std::vector<MachineRelocation>::iterator MRI = Relos.begin(),
 765          MRE = Relos.end(); MRI != MRE; ++MRI) {
 766       MachineRelocation &MR = *MRI;
 767
 768       // Relocatable field offset from the section start
 769       unsigned RelOffset = MR.getMachineCodeOffset();
 770
 771       // Symbol index in the symbol table
 772       unsigned SymIdx = 0;
 773
 774       // Target specific relocation field type and size
 775       unsigned RelType = TEW->getRelocationType(MR.getRelocationType());
 776       unsigned RelTySize = TEW->getRelocationTySize(RelType);
 777       int64_t Addend = 0;
 778
 779       // There are several machine relocations types, and each one of
 780       // them needs a different approach to retrieve the symbol table index.
 781       if (MR.isGlobalValue()) {
 782         const GlobalValue *G = MR.getGlobalValue();
 783         int64_t GlobalOffset = MR.getConstantVal();
 784         SymIdx = GblSymLookup[G];
 785         if (G->hasPrivateLinkage()) {
 786           // If the target uses a section offset in the relocation:
 787           // SymIdx + Addend = section sym for global + section offset
 788           unsigned SectionIdx = PrivateSyms[SymIdx]->SectionIdx;
 789           Addend = PrivateSyms[SymIdx]->Value + GlobalOffset;
 790           SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
 791         } else {
 792           Addend = TEW->getDefaultAddendForRelTy(RelType, GlobalOffset);
 793         }
 794       } else if (MR.isExternalSymbol()) {
 795         const char *ExtSym = MR.getExternalSymbol();
 796         SymIdx = ExtSymLookup[ExtSym];
 797         Addend = TEW->getDefaultAddendForRelTy(RelType);
 798       } else {
 799         // Get the symbol index for the section symbol
 800         unsigned SectionIdx = MR.getConstantVal();
 801         SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
 802
 803         // The symbol offset inside the section
 804         int64_t SymOffset = (int64_t)MR.getResultPointer();
 805
 806         // For pc relative relocations where symbols are defined in the same
 807         // section they are referenced, ignore the relocation entry and patch
 808         // the relocatable field with the symbol offset directly.
 809         if (S.SectionIdx == SectionIdx && TEW->isPCRelativeRel(RelType)) {
 810           int64_t Value = TEW->computeRelocation(SymOffset, RelOffset, RelType);
 811           RelocateField(S, RelOffset, Value, RelTySize);
 812           continue;
 813         }
 814
 815         Addend = TEW->getDefaultAddendForRelTy(RelType, SymOffset);
 816       }
 817
 818       // The target without addend on the relocation symbol must be
 819       // patched in the relocation place itself to contain the addend
 820       // otherwise write zeros to make sure there is no garbage there
 821       RelocateField(S, RelOffset, HasRelA ? 0 : Addend, RelTySize);
 822
 823       // Get the relocation entry and emit to the relocation section
 824       ELFRelocation Rel(RelOffset, SymIdx, RelType, HasRelA, Addend);
 825       EmitRelocation(RelSec, Rel, HasRelA);
 826     }
 827   }
 828 }
 829
 830 /// EmitRelocation - Write relocation 'Rel' to the relocation section 'Rel'
 831 void ELFWriter::EmitRelocation(BinaryObject &RelSec, ELFRelocation &Rel,
 832                                bool HasRelA) {
 833   RelSec.emitWord(Rel.getOffset());
 834   RelSec.emitWord(Rel.getInfo(is64Bit));
 835   if (HasRelA)
 836     RelSec.emitWord(Rel.getAddend());
 837 }
 838
 839 /// EmitSymbol - Write symbol 'Sym' to the symbol table 'SymbolTable'
 840 void ELFWriter::EmitSymbol(BinaryObject &SymbolTable, ELFSym &Sym) {
 841   if (is64Bit) {
 842     SymbolTable.emitWord32(Sym.NameIdx);
 843     SymbolTable.emitByte(Sym.Info);
 844     SymbolTable.emitByte(Sym.Other);
 845     SymbolTable.emitWord16(Sym.SectionIdx);
 846     SymbolTable.emitWord64(Sym.Value);
 847     SymbolTable.emitWord64(Sym.Size);
 848   } else {
 849     SymbolTable.emitWord32(Sym.NameIdx);
 850     SymbolTable.emitWord32(Sym.Value);
 851     SymbolTable.emitWord32(Sym.Size);
 852     SymbolTable.emitByte(Sym.Info);
 853     SymbolTable.emitByte(Sym.Other);
 854     SymbolTable.emitWord16(Sym.SectionIdx);
 855   }
 856 }
 857
 858 /// EmitSectionHeader - Write section 'Section' header in 'SHdrTab'
 859 /// Section Header Table
 860 void ELFWriter::EmitSectionHeader(BinaryObject &SHdrTab,
 861                                   const ELFSection &SHdr) {
 862   SHdrTab.emitWord32(SHdr.NameIdx);
 863   SHdrTab.emitWord32(SHdr.Type);
 864   if (is64Bit) {
 865     SHdrTab.emitWord64(SHdr.Flags);
 866     SHdrTab.emitWord(SHdr.Addr);
 867     SHdrTab.emitWord(SHdr.Offset);
 868     SHdrTab.emitWord64(SHdr.Size);
 869     SHdrTab.emitWord32(SHdr.Link);
 870     SHdrTab.emitWord32(SHdr.Info);
 871     SHdrTab.emitWord64(SHdr.Align);
 872     SHdrTab.emitWord64(SHdr.EntSize);
 873   } else {
 874     SHdrTab.emitWord32(SHdr.Flags);
 875     SHdrTab.emitWord(SHdr.Addr);
 876     SHdrTab.emitWord(SHdr.Offset);
 877     SHdrTab.emitWord32(SHdr.Size);
 878     SHdrTab.emitWord32(SHdr.Link);
 879     SHdrTab.emitWord32(SHdr.Info);
 880     SHdrTab.emitWord32(SHdr.Align);
 881     SHdrTab.emitWord32(SHdr.EntSize);
 882   }
 883 }
 884
 885 /// EmitStringTable - If the current symbol table is non-empty, emit the string
 886 /// table for it
 887 void ELFWriter::EmitStringTable(const std::string &ModuleName) {
 888   if (!SymbolList.size()) return;  // Empty symbol table.
 889   ELFSection &StrTab = getStringTableSection();
 890
 891   // Set the zero'th symbol to a null byte, as required.
 892   StrTab.emitByte(0);
 893
 894   // Walk on the symbol list and write symbol names into the string table.
 895   unsigned Index = 1;
 896   for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
 897     ELFSym &Sym = *(*I);
 898
 899     std::string Name;
 900     if (Sym.isGlobalValue())
 901       Name.append(Mang->getMangledName(Sym.getGlobalValue()));
 902     else if (Sym.isExternalSym())
 903       Name.append(Sym.getExternalSymbol());
 904     else if (Sym.isFileType())
 905       Name.append(ModuleName);
 906
 907     if (Name.empty()) {
 908       Sym.NameIdx = 0;
 909     } else {
 910       Sym.NameIdx = Index;
 911       StrTab.emitString(Name);
 912
 913       // Keep track of the number of bytes emitted to this section.
 914       Index += Name.size()+1;
 915     }
 916   }
 917   assert(Index == StrTab.size());
 918   StrTab.Size = Index;
 919 }
 920
 921 // SortSymbols - On the symbol table local symbols must come before
 922 // all other symbols with non-local bindings. The return value is
 923 // the position of the first non local symbol.
 924 unsigned ELFWriter::SortSymbols() {
 925   unsigned FirstNonLocalSymbol;
 926   std::vector<ELFSym*> LocalSyms, OtherSyms;
 927
 928   for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
 929     if ((*I)->isLocalBind())
 930       LocalSyms.push_back(*I);
 931     else
 932       OtherSyms.push_back(*I);
 933   }
 934   SymbolList.clear();
 935   FirstNonLocalSymbol = LocalSyms.size();
 936
 937   for (unsigned i = 0; i < FirstNonLocalSymbol; ++i)
 938     SymbolList.push_back(LocalSyms[i]);
 939
 940   for (ELFSymIter I=OtherSyms.begin(), E=OtherSyms.end(); I != E; ++I)
 941     SymbolList.push_back(*I);
 942
 943   LocalSyms.clear();
 944   OtherSyms.clear();
 945
 946   return FirstNonLocalSymbol;
 947 }
 948
 949 /// EmitSymbolTable - Emit the symbol table itself.
 950 void ELFWriter::EmitSymbolTable() {
 951   if (!SymbolList.size()) return;  // Empty symbol table.
 952
 953   // Now that we have emitted the string table and know the offset into the
 954   // string table of each symbol, emit the symbol table itself.
 955   ELFSection &SymTab = getSymbolTableSection();
 956   SymTab.Align = TEW->getPrefELFAlignment();
 957
 958   // Section Index of .strtab.
 959   SymTab.Link = getStringTableSection().SectionIdx;
 960
 961   // Size of each symtab entry.
 962   SymTab.EntSize = TEW->getSymTabEntrySize();
 963
 964   // Reorder the symbol table with local symbols first!
 965   unsigned FirstNonLocalSymbol = SortSymbols();
 966
 967   // Emit all the symbols to the symbol table.
 968   for (unsigned i = 0, e = SymbolList.size(); i < e; ++i) {
 969     ELFSym &Sym = *SymbolList[i];
 970
 971     // Emit symbol to the symbol table
 972     EmitSymbol(SymTab, Sym);
 973
 974     // Record the symbol table index for each symbol
 975     if (Sym.isGlobalValue())
 976       GblSymLookup[Sym.getGlobalValue()] = i;
 977     else if (Sym.isExternalSym())
 978       ExtSymLookup[Sym.getExternalSymbol()] = i;
 979
 980     // Keep track on the symbol index into the symbol table
 981     Sym.SymTabIdx = i;
 982   }
 983
 984   // One greater than the symbol table index of the last local symbol
 985   SymTab.Info = FirstNonLocalSymbol;
 986   SymTab.Size = SymTab.size();
 987 }
 988
 989 /// EmitSectionTableStringTable - This method adds and emits a section for the
 990 /// ELF Section Table string table: the string table that holds all of the
 991 /// section names.
 992 void ELFWriter::EmitSectionTableStringTable() {
 993   // First step: add the section for the string table to the list of sections:
 994   ELFSection &SHStrTab = getSectionHeaderStringTableSection();
 995
 996   // Now that we know which section number is the .shstrtab section, update the
 997   // e_shstrndx entry in the ELF header.
 998   ElfHdr.fixWord16(SHStrTab.SectionIdx, ELFHdr_e_shstrndx_Offset);
 999
1000   // Set the NameIdx of each section in the string table and emit the bytes for
1001   // the string table.
1002   unsigned Index = 0;
1003
1004   for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
1005     ELFSection &S = *(*I);
1006     // Set the index into the table.  Note if we have lots of entries with
1007     // common suffixes, we could memoize them here if we cared.
1008     S.NameIdx = Index;
1009     SHStrTab.emitString(S.getName());
1010
1011     // Keep track of the number of bytes emitted to this section.
1012     Index += S.getName().size()+1;
1013   }
1014
1015   // Set the size of .shstrtab now that we know what it is.
1016   assert(Index == SHStrTab.size());
1017   SHStrTab.Size = Index;
1018 }
1019
1020 /// OutputSectionsAndSectionTable - Now that we have constructed the file header
1021 /// and all of the sections, emit these to the ostream destination and emit the
1022 /// SectionTable.
1023 void ELFWriter::OutputSectionsAndSectionTable() {
1024   // Pass #1: Compute the file offset for each section.
1025   size_t FileOff = ElfHdr.size();   // File header first.
1026
1027   // Adjust alignment of all section if needed, skip the null section.
1028   for (unsigned i=1, e=SectionList.size(); i < e; ++i) {
1029     ELFSection &ES = *SectionList[i];
1030     if (!ES.size()) {
1031       ES.Offset = FileOff;
1032       continue;
1033     }
1034
1035     // Update Section size
1036     if (!ES.Size)
1037       ES.Size = ES.size();
1038
1039     // Align FileOff to whatever the alignment restrictions of the section are.
1040     if (ES.Align)
1041       FileOff = (FileOff+ES.Align-1) & ~(ES.Align-1);
1042
1043     ES.Offset = FileOff;
1044     FileOff += ES.Size;
1045   }
1046
1047   // Align Section Header.
1048   unsigned TableAlign = TEW->getPrefELFAlignment();
1049   FileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
1050
1051   // Now that we know where all of the sections will be emitted, set the e_shnum
1052   // entry in the ELF header.
1053   ElfHdr.fixWord16(NumSections, ELFHdr_e_shnum_Offset);
1054
1055   // Now that we know the offset in the file of the section table, update the
1056   // e_shoff address in the ELF header.
1057   ElfHdr.fixWord(FileOff, ELFHdr_e_shoff_Offset);
1058
1059   // Now that we know all of the data in the file header, emit it and all of the
1060   // sections!
1061   O.write((char *)&ElfHdr.getData()[0], ElfHdr.size());
1062   FileOff = ElfHdr.size();
1063
1064   // Section Header Table blob
1065   BinaryObject SHdrTable(isLittleEndian, is64Bit);
1066
1067   // Emit all of sections to the file and build the section header table.
1068   for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
1069     ELFSection &S = *(*I);
1070     DOUT << "SectionIdx: " << S.SectionIdx << ", Name: " << S.getName()
1071          << ", Size: " << S.Size << ", Offset: " << S.Offset
1072          << ", SectionData Size: " << S.size() << "\n";
1073
1074     // Align FileOff to whatever the alignment restrictions of the section are.
1075     if (S.size()) {
1076       if (S.Align)  {
1077         for (size_t NewFileOff = (FileOff+S.Align-1) & ~(S.Align-1);
1078              FileOff != NewFileOff; ++FileOff)
1079           O << (char)0xAB;
1080       }
1081       O.write((char *)&S.getData()[0], S.Size);
1082       FileOff += S.Size;
1083     }
1084
1085     EmitSectionHeader(SHdrTable, S);
1086   }
1087
1088   // Align output for the section table.
1089   for (size_t NewFileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
1090        FileOff != NewFileOff; ++FileOff)
1091     O << (char)0xAB;
1092
1093   // Emit the section table itself.
1094   O.write((char *)&SHdrTable.getData()[0], SHdrTable.size());
1095 }