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/MC/MCAsmInfo.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/Debug.h"
  54 #include "llvm/Support/ErrorHandling.h"
  55 #include "llvm/Support/Mangler.h"
  56 #include "llvm/Support/raw_ostream.h"
  57
  58 using namespace llvm;
  59
  60 char ELFWriter::ID = 0;
  61
  62 /// AddELFWriter - Add the ELF writer to the function pass manager
  63 ObjectCodeEmitter *llvm::AddELFWriter(PassManagerBase &PM,
  64                                       raw_ostream &O,
  65                                       TargetMachine &TM) {
  66   ELFWriter *EW = new ELFWriter(O, TM);
  67   PM.add(EW);
  68   return EW->getObjectCodeEmitter();
  69 }
  70
  71 //===----------------------------------------------------------------------===//
  72 //                          ELFWriter Implementation
  73 //===----------------------------------------------------------------------===//
  74
  75 ELFWriter::ELFWriter(raw_ostream &o, TargetMachine &tm)
  76   : MachineFunctionPass(&ID), O(o), TM(tm),
  77     OutContext(*new MCContext()),
  78     TLOF(TM.getTargetLowering()->getObjFileLowering()),
  79     is64Bit(TM.getTargetData()->getPointerSizeInBits() == 64),
  80     isLittleEndian(TM.getTargetData()->isLittleEndian()),
  81     ElfHdr(isLittleEndian, is64Bit) {
  82
  83   MAI = TM.getMCAsmInfo();
  84   TEW = TM.getELFWriterInfo();
  85
  86   // Create the object code emitter object for this target.
  87   ElfCE = new ELFCodeEmitter(*this);
  88
  89   // Inital number of sections
  90   NumSections = 0;
  91 }
  92
  93 ELFWriter::~ELFWriter() {
  94   delete ElfCE;
  95   delete &OutContext;
  96
  97   while(!SymbolList.empty()) {
  98     delete SymbolList.back();
  99     SymbolList.pop_back();
 100   }
 101
 102   while(!PrivateSyms.empty()) {
 103     delete PrivateSyms.back();
 104     PrivateSyms.pop_back();
 105   }
 106
 107   while(!SectionList.empty()) {
 108     delete SectionList.back();
 109     SectionList.pop_back();
 110   }
 111
 112   // Release the name mangler object.
 113   delete Mang; Mang = 0;
 114 }
 115
 116 // doInitialization - Emit the file header and all of the global variables for
 117 // the module to the ELF file.
 118 bool ELFWriter::doInitialization(Module &M) {
 119   // Initialize TargetLoweringObjectFile.
 120   const_cast<TargetLoweringObjectFile&>(TLOF).Initialize(OutContext, TM);
 121
 122   Mang = new Mangler(M);
 123
 124   // ELF Header
 125   // ----------
 126   // Fields e_shnum e_shstrndx are only known after all section have
 127   // been emitted. They locations in the ouput buffer are recorded so
 128   // to be patched up later.
 129   //
 130   // Note
 131   // ----
 132   // emitWord method behaves differently for ELF32 and ELF64, writing
 133   // 4 bytes in the former and 8 in the last for *_off and *_addr elf types
 134
 135   ElfHdr.emitByte(0x7f); // e_ident[EI_MAG0]
 136   ElfHdr.emitByte('E');  // e_ident[EI_MAG1]
 137   ElfHdr.emitByte('L');  // e_ident[EI_MAG2]
 138   ElfHdr.emitByte('F');  // e_ident[EI_MAG3]
 139
 140   ElfHdr.emitByte(TEW->getEIClass()); // e_ident[EI_CLASS]
 141   ElfHdr.emitByte(TEW->getEIData());  // e_ident[EI_DATA]
 142   ElfHdr.emitByte(EV_CURRENT);        // e_ident[EI_VERSION]
 143   ElfHdr.emitAlignment(16);           // e_ident[EI_NIDENT-EI_PAD]
 144
 145   ElfHdr.emitWord16(ET_REL);             // e_type
 146   ElfHdr.emitWord16(TEW->getEMachine()); // e_machine = target
 147   ElfHdr.emitWord32(EV_CURRENT);         // e_version
 148   ElfHdr.emitWord(0);                    // e_entry, no entry point in .o file
 149   ElfHdr.emitWord(0);                    // e_phoff, no program header for .o
 150   ELFHdr_e_shoff_Offset = ElfHdr.size();
 151   ElfHdr.emitWord(0);                    // e_shoff = sec hdr table off in bytes
 152   ElfHdr.emitWord32(TEW->getEFlags());   // e_flags = whatever the target wants
 153   ElfHdr.emitWord16(TEW->getHdrSize());  // e_ehsize = ELF header size
 154   ElfHdr.emitWord16(0);                  // e_phentsize = prog header entry size
 155   ElfHdr.emitWord16(0);                  // e_phnum = # prog header entries = 0
 156
 157   // e_shentsize = Section header entry size
 158   ElfHdr.emitWord16(TEW->getSHdrSize());
 159
 160   // e_shnum     = # of section header ents
 161   ELFHdr_e_shnum_Offset = ElfHdr.size();
 162   ElfHdr.emitWord16(0); // Placeholder
 163
 164   // e_shstrndx  = Section # of '.shstrtab'
 165   ELFHdr_e_shstrndx_Offset = ElfHdr.size();
 166   ElfHdr.emitWord16(0); // Placeholder
 167
 168   // Add the null section, which is required to be first in the file.
 169   getNullSection();
 170
 171   // The first entry in the symtab is the null symbol and the second
 172   // is a local symbol containing the module/file name
 173   SymbolList.push_back(new ELFSym());
 174   SymbolList.push_back(ELFSym::getFileSym());
 175
 176   return false;
 177 }
 178
 179 // AddPendingGlobalSymbol - Add a global to be processed and to
 180 // the global symbol lookup, use a zero index because the table
 181 // index will be determined later.
 182 void ELFWriter::AddPendingGlobalSymbol(const GlobalValue *GV,
 183                                        bool AddToLookup /* = false */) {
 184   PendingGlobals.insert(GV);
 185   if (AddToLookup)
 186     GblSymLookup[GV] = 0;
 187 }
 188
 189 // AddPendingExternalSymbol - Add the external to be processed
 190 // and to the external symbol lookup, use a zero index because
 191 // the symbol table index will be determined later.
 192 void ELFWriter::AddPendingExternalSymbol(const char *External) {
 193   PendingExternals.insert(External);
 194   ExtSymLookup[External] = 0;
 195 }
 196
 197 ELFSection &ELFWriter::getDataSection() {
 198   const MCSectionELF *Data = (const MCSectionELF *)TLOF.getDataSection();
 199   return getSection(Data->getSectionName(), Data->getType(),
 200                     Data->getFlags(), 4);
 201 }
 202
 203 ELFSection &ELFWriter::getBSSSection() {
 204   const MCSectionELF *BSS = (const MCSectionELF *)TLOF.getBSSSection();
 205   return getSection(BSS->getSectionName(), BSS->getType(), BSS->getFlags(), 4);
 206 }
 207
 208 // getCtorSection - Get the static constructor section
 209 ELFSection &ELFWriter::getCtorSection() {
 210   const MCSectionELF *Ctor = (const MCSectionELF *)TLOF.getStaticCtorSection();
 211   return getSection(Ctor->getSectionName(), Ctor->getType(), Ctor->getFlags());
 212 }
 213
 214 // getDtorSection - Get the static destructor section
 215 ELFSection &ELFWriter::getDtorSection() {
 216   const MCSectionELF *Dtor = (const MCSectionELF *)TLOF.getStaticDtorSection();
 217   return getSection(Dtor->getSectionName(), Dtor->getType(), Dtor->getFlags());
 218 }
 219
 220 // getTextSection - Get the text section for the specified function
 221 ELFSection &ELFWriter::getTextSection(Function *F) {
 222   const MCSectionELF *Text =
 223     (const MCSectionELF *)TLOF.SectionForGlobal(F, Mang, TM);
 224   return getSection(Text->getSectionName(), Text->getType(), Text->getFlags());
 225 }
 226
 227 // getJumpTableSection - Get a read only section for constants when
 228 // emitting jump tables. TODO: add PIC support
 229 ELFSection &ELFWriter::getJumpTableSection() {
 230   const MCSectionELF *JT =
 231     (const MCSectionELF *)TLOF.getSectionForConstant(SectionKind::getReadOnly());
 232   return getSection(JT->getSectionName(), JT->getType(), JT->getFlags(),
 233                     TM.getTargetData()->getPointerABIAlignment());
 234 }
 235
 236 // getConstantPoolSection - Get a constant pool section based on the machine
 237 // constant pool entry type and relocation info.
 238 ELFSection &ELFWriter::getConstantPoolSection(MachineConstantPoolEntry &CPE) {
 239   SectionKind Kind;
 240   switch (CPE.getRelocationInfo()) {
 241   default: llvm_unreachable("Unknown section kind");
 242   case 2: Kind = SectionKind::getReadOnlyWithRel(); break;
 243   case 1:
 244     Kind = SectionKind::getReadOnlyWithRelLocal();
 245     break;
 246   case 0:
 247     switch (TM.getTargetData()->getTypeAllocSize(CPE.getType())) {
 248     case 4:  Kind = SectionKind::getMergeableConst4(); break;
 249     case 8:  Kind = SectionKind::getMergeableConst8(); break;
 250     case 16: Kind = SectionKind::getMergeableConst16(); break;
 251     default: Kind = SectionKind::getMergeableConst(); break;
 252     }
 253   }
 254
 255   const MCSectionELF *CPSect =
 256     (const MCSectionELF *)TLOF.getSectionForConstant(Kind);
 257   return getSection(CPSect->getSectionName(), CPSect->getType(),
 258                     CPSect->getFlags(), CPE.getAlignment());
 259 }
 260
 261 // getRelocSection - Return the relocation section of section 'S'. 'RelA'
 262 // is true if the relocation section contains entries with addends.
 263 ELFSection &ELFWriter::getRelocSection(ELFSection &S) {
 264   unsigned SectionType = TEW->hasRelocationAddend() ?
 265                 ELFSection::SHT_RELA : ELFSection::SHT_REL;
 266
 267   std::string SectionName(".rel");
 268   if (TEW->hasRelocationAddend())
 269     SectionName.append("a");
 270   SectionName.append(S.getName());
 271
 272   return getSection(SectionName, SectionType, 0, TEW->getPrefELFAlignment());
 273 }
 274
 275 // getGlobalELFVisibility - Returns the ELF specific visibility type
 276 unsigned ELFWriter::getGlobalELFVisibility(const GlobalValue *GV) {
 277   switch (GV->getVisibility()) {
 278   default:
 279     llvm_unreachable("unknown visibility type");
 280   case GlobalValue::DefaultVisibility:
 281     return ELFSym::STV_DEFAULT;
 282   case GlobalValue::HiddenVisibility:
 283     return ELFSym::STV_HIDDEN;
 284   case GlobalValue::ProtectedVisibility:
 285     return ELFSym::STV_PROTECTED;
 286   }
 287   return 0;
 288 }
 289
 290 // getGlobalELFBinding - Returns the ELF specific binding type
 291 unsigned ELFWriter::getGlobalELFBinding(const GlobalValue *GV) {
 292   if (GV->hasInternalLinkage())
 293     return ELFSym::STB_LOCAL;
 294
 295   if (GV->isWeakForLinker() && !GV->hasCommonLinkage())
 296     return ELFSym::STB_WEAK;
 297
 298   return ELFSym::STB_GLOBAL;
 299 }
 300
 301 // getGlobalELFType - Returns the ELF specific type for a global
 302 unsigned ELFWriter::getGlobalELFType(const GlobalValue *GV) {
 303   if (GV->isDeclaration())
 304     return ELFSym::STT_NOTYPE;
 305
 306   if (isa<Function>(GV))
 307     return ELFSym::STT_FUNC;
 308
 309   return ELFSym::STT_OBJECT;
 310 }
 311
 312 // IsELFUndefSym - True if the global value must be marked as a symbol
 313 // which points to a SHN_UNDEF section. This means that the symbol has
 314 // no definition on the module.
 315 static bool IsELFUndefSym(const GlobalValue *GV) {
 316   return GV->isDeclaration() || (isa<Function>(GV));
 317 }
 318
 319 // AddToSymbolList - Update the symbol lookup and If the symbol is
 320 // private add it to PrivateSyms list, otherwise to SymbolList.
 321 void ELFWriter::AddToSymbolList(ELFSym *GblSym) {
 322   assert(GblSym->isGlobalValue() && "Symbol must be a global value");
 323
 324   const GlobalValue *GV = GblSym->getGlobalValue();
 325   if (GV->hasPrivateLinkage()) {
 326     // For a private symbols, keep track of the index inside
 327     // the private list since it will never go to the symbol
 328     // table and won't be patched up later.
 329     PrivateSyms.push_back(GblSym);
 330     GblSymLookup[GV] = PrivateSyms.size()-1;
 331   } else {
 332     // Non private symbol are left with zero indices until
 333     // they are patched up during the symbol table emition
 334     // (where the indicies are created).
 335     SymbolList.push_back(GblSym);
 336     GblSymLookup[GV] = 0;
 337   }
 338 }
 339
 340 // EmitGlobal - Choose the right section for global and emit it
 341 void ELFWriter::EmitGlobal(const GlobalValue *GV) {
 342
 343   // Check if the referenced symbol is already emitted
 344   if (GblSymLookup.find(GV) != GblSymLookup.end())
 345     return;
 346
 347   // Handle ELF Bind, Visibility and Type for the current symbol
 348   unsigned SymBind = getGlobalELFBinding(GV);
 349   unsigned SymType = getGlobalELFType(GV);
 350   bool IsUndefSym = IsELFUndefSym(GV);
 351
 352   ELFSym *GblSym = IsUndefSym ? ELFSym::getUndefGV(GV, SymBind)
 353     : ELFSym::getGV(GV, SymBind, SymType, getGlobalELFVisibility(GV));
 354
 355   if (!IsUndefSym) {
 356     assert(isa<GlobalVariable>(GV) && "GV not a global variable!");
 357     const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV);
 358
 359     // Handle special llvm globals
 360     if (EmitSpecialLLVMGlobal(GVar))
 361       return;
 362
 363     // Get the ELF section where this global belongs from TLOF
 364     const MCSectionELF *S =
 365       (const MCSectionELF *)TLOF.SectionForGlobal(GV, Mang, TM);
 366     ELFSection &ES =
 367       getSection(S->getSectionName(), S->getType(), S->getFlags());
 368     SectionKind Kind = S->getKind();
 369
 370     // The symbol align should update the section alignment if needed
 371     const TargetData *TD = TM.getTargetData();
 372     unsigned Align = TD->getPreferredAlignment(GVar);
 373     unsigned Size = TD->getTypeAllocSize(GVar->getInitializer()->getType());
 374     GblSym->Size = Size;
 375
 376     if (S->HasCommonSymbols()) { // Symbol must go to a common section
 377       GblSym->SectionIdx = ELFSection::SHN_COMMON;
 378
 379       // A new linkonce section is created for each global in the
 380       // common section, the default alignment is 1 and the symbol
 381       // value contains its alignment.
 382       ES.Align = 1;
 383       GblSym->Value = Align;
 384
 385     } else if (Kind.isBSS() || Kind.isThreadBSS()) { // Symbol goes to BSS.
 386       GblSym->SectionIdx = ES.SectionIdx;
 387
 388       // Update the size with alignment and the next object can
 389       // start in the right offset in the section
 390       if (Align) ES.Size = (ES.Size + Align-1) & ~(Align-1);
 391       ES.Align = std::max(ES.Align, Align);
 392
 393       // GblSym->Value should contain the virtual offset inside the section.
 394       // Virtual because the BSS space is not allocated on ELF objects
 395       GblSym->Value = ES.Size;
 396       ES.Size += Size;
 397
 398     } else { // The symbol must go to some kind of data section
 399       GblSym->SectionIdx = ES.SectionIdx;
 400
 401       // GblSym->Value should contain the symbol offset inside the section,
 402       // and all symbols should start on their required alignment boundary
 403       ES.Align = std::max(ES.Align, Align);
 404       ES.emitAlignment(Align);
 405       GblSym->Value = ES.size();
 406
 407       // Emit the global to the data section 'ES'
 408       EmitGlobalConstant(GVar->getInitializer(), ES);
 409     }
 410   }
 411
 412   AddToSymbolList(GblSym);
 413 }
 414
 415 void ELFWriter::EmitGlobalConstantStruct(const ConstantStruct *CVS,
 416                                          ELFSection &GblS) {
 417
 418   // Print the fields in successive locations. Pad to align if needed!
 419   const TargetData *TD = TM.getTargetData();
 420   unsigned Size = TD->getTypeAllocSize(CVS->getType());
 421   const StructLayout *cvsLayout = TD->getStructLayout(CVS->getType());
 422   uint64_t sizeSoFar = 0;
 423   for (unsigned i = 0, e = CVS->getNumOperands(); i != e; ++i) {
 424     const Constant* field = CVS->getOperand(i);
 425
 426     // Check if padding is needed and insert one or more 0s.
 427     uint64_t fieldSize = TD->getTypeAllocSize(field->getType());
 428     uint64_t padSize = ((i == e-1 ? Size : cvsLayout->getElementOffset(i+1))
 429                         - cvsLayout->getElementOffset(i)) - fieldSize;
 430     sizeSoFar += fieldSize + padSize;
 431
 432     // Now print the actual field value.
 433     EmitGlobalConstant(field, GblS);
 434
 435     // Insert padding - this may include padding to increase the size of the
 436     // current field up to the ABI size (if the struct is not packed) as well
 437     // as padding to ensure that the next field starts at the right offset.
 438     GblS.emitZeros(padSize);
 439   }
 440   assert(sizeSoFar == cvsLayout->getSizeInBytes() &&
 441          "Layout of constant struct may be incorrect!");
 442 }
 443
 444 void ELFWriter::EmitGlobalConstant(const Constant *CV, ELFSection &GblS) {
 445   const TargetData *TD = TM.getTargetData();
 446   unsigned Size = TD->getTypeAllocSize(CV->getType());
 447
 448   if (const ConstantArray *CVA = dyn_cast<ConstantArray>(CV)) {
 449     for (unsigned i = 0, e = CVA->getNumOperands(); i != e; ++i)
 450       EmitGlobalConstant(CVA->getOperand(i), GblS);
 451     return;
 452   } else if (isa<ConstantAggregateZero>(CV)) {
 453     GblS.emitZeros(Size);
 454     return;
 455   } else if (const ConstantStruct *CVS = dyn_cast<ConstantStruct>(CV)) {
 456     EmitGlobalConstantStruct(CVS, GblS);
 457     return;
 458   } else if (const ConstantFP *CFP = dyn_cast<ConstantFP>(CV)) {
 459     APInt Val = CFP->getValueAPF().bitcastToAPInt();
 460     if (CFP->getType() == Type::getDoubleTy(CV->getContext()))
 461       GblS.emitWord64(Val.getZExtValue());
 462     else if (CFP->getType() == Type::getFloatTy(CV->getContext()))
 463       GblS.emitWord32(Val.getZExtValue());
 464     else if (CFP->getType() == Type::getX86_FP80Ty(CV->getContext())) {
 465       unsigned PadSize =
 466              TD->getTypeAllocSize(Type::getX86_FP80Ty(CV->getContext()))-
 467              TD->getTypeStoreSize(Type::getX86_FP80Ty(CV->getContext()));
 468       GblS.emitWordFP80(Val.getRawData(), PadSize);
 469     } else if (CFP->getType() == Type::getPPC_FP128Ty(CV->getContext()))
 470       llvm_unreachable("PPC_FP128Ty global emission not implemented");
 471     return;
 472   } else if (const ConstantInt *CI = dyn_cast<ConstantInt>(CV)) {
 473     if (Size == 1)
 474       GblS.emitByte(CI->getZExtValue());
 475     else if (Size == 2)
 476       GblS.emitWord16(CI->getZExtValue());
 477     else if (Size == 4)
 478       GblS.emitWord32(CI->getZExtValue());
 479     else
 480       EmitGlobalConstantLargeInt(CI, GblS);
 481     return;
 482   } else if (const ConstantVector *CP = dyn_cast<ConstantVector>(CV)) {
 483     const VectorType *PTy = CP->getType();
 484     for (unsigned I = 0, E = PTy->getNumElements(); I < E; ++I)
 485       EmitGlobalConstant(CP->getOperand(I), GblS);
 486     return;
 487   } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV)) {
 488     // Resolve a constant expression which returns a (Constant, Offset)
 489     // pair. If 'Res.first' is a GlobalValue, emit a relocation with
 490     // the offset 'Res.second', otherwise emit a global constant like
 491     // it is always done for not contant expression types.
 492     CstExprResTy Res = ResolveConstantExpr(CE);
 493     const Constant *Op = Res.first;
 494
 495     if (isa<GlobalValue>(Op))
 496       EmitGlobalDataRelocation(cast<const GlobalValue>(Op),
 497                                TD->getTypeAllocSize(Op->getType()),
 498                                GblS, Res.second);
 499     else
 500       EmitGlobalConstant(Op, GblS);
 501
 502     return;
 503   } else if (CV->getType()->getTypeID() == Type::PointerTyID) {
 504     // Fill the data entry with zeros or emit a relocation entry
 505     if (isa<ConstantPointerNull>(CV))
 506       GblS.emitZeros(Size);
 507     else
 508       EmitGlobalDataRelocation(cast<const GlobalValue>(CV),
 509                                Size, GblS);
 510     return;
 511   } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CV)) {
 512     // This is a constant address for a global variable or function and
 513     // therefore must be referenced using a relocation entry.
 514     EmitGlobalDataRelocation(GV, Size, GblS);
 515     return;
 516   }
 517
 518   std::string msg;
 519   raw_string_ostream ErrorMsg(msg);
 520   ErrorMsg << "Constant unimp for type: " << *CV->getType();
 521   llvm_report_error(ErrorMsg.str());
 522 }
 523
 524 // ResolveConstantExpr - Resolve the constant expression until it stop
 525 // yielding other constant expressions.
 526 CstExprResTy ELFWriter::ResolveConstantExpr(const Constant *CV) {
 527   const TargetData *TD = TM.getTargetData();
 528
 529   // There ins't constant expression inside others anymore
 530   if (!isa<ConstantExpr>(CV))
 531     return std::make_pair(CV, 0);
 532
 533   const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV);
 534   switch (CE->getOpcode()) {
 535   case Instruction::BitCast:
 536     return ResolveConstantExpr(CE->getOperand(0));
 537
 538   case Instruction::GetElementPtr: {
 539     const Constant *ptrVal = CE->getOperand(0);
 540     SmallVector<Value*, 8> idxVec(CE->op_begin()+1, CE->op_end());
 541     int64_t Offset = TD->getIndexedOffset(ptrVal->getType(), &idxVec[0],
 542                                           idxVec.size());
 543     return std::make_pair(ptrVal, Offset);
 544   }
 545   case Instruction::IntToPtr: {
 546     Constant *Op = CE->getOperand(0);
 547     Op = ConstantExpr::getIntegerCast(Op, TD->getIntPtrType(CV->getContext()),
 548                                       false/*ZExt*/);
 549     return ResolveConstantExpr(Op);
 550   }
 551   case Instruction::PtrToInt: {
 552     Constant *Op = CE->getOperand(0);
 553     const Type *Ty = CE->getType();
 554
 555     // We can emit the pointer value into this slot if the slot is an
 556     // integer slot greater or equal to the size of the pointer.
 557     if (TD->getTypeAllocSize(Ty) == TD->getTypeAllocSize(Op->getType()))
 558       return ResolveConstantExpr(Op);
 559
 560     llvm_unreachable("Integer size less then pointer size");
 561   }
 562   case Instruction::Add:
 563   case Instruction::Sub: {
 564     // Only handle cases where there's a constant expression with GlobalValue
 565     // as first operand and ConstantInt as second, which are the cases we can
 566     // solve direclty using a relocation entry. GlobalValue=Op0, CstInt=Op1
 567     // 1)  Instruction::Add  => (global) + CstInt
 568     // 2)  Instruction::Sub  => (global) + -CstInt
 569     const Constant *Op0 = CE->getOperand(0);
 570     const Constant *Op1 = CE->getOperand(1);
 571     assert(isa<ConstantInt>(Op1) && "Op1 must be a ConstantInt");
 572
 573     CstExprResTy Res = ResolveConstantExpr(Op0);
 574     assert(isa<GlobalValue>(Res.first) && "Op0 must be a GlobalValue");
 575
 576     const APInt &RHS = cast<ConstantInt>(Op1)->getValue();
 577     switch (CE->getOpcode()) {
 578     case Instruction::Add:
 579       return std::make_pair(Res.first, RHS.getSExtValue());
 580     case Instruction::Sub:
 581       return std::make_pair(Res.first, (-RHS).getSExtValue());
 582     }
 583   }
 584   }
 585
 586   std::string msg(CE->getOpcodeName());
 587   raw_string_ostream ErrorMsg(msg);
 588   ErrorMsg << ": Unsupported ConstantExpr type";
 589   llvm_report_error(ErrorMsg.str());
 590
 591   return std::make_pair(CV, 0); // silence warning
 592 }
 593
 594 void ELFWriter::EmitGlobalDataRelocation(const GlobalValue *GV, unsigned Size,
 595                                          ELFSection &GblS, int64_t Offset) {
 596   // Create the relocation entry for the global value
 597   MachineRelocation MR =
 598     MachineRelocation::getGV(GblS.getCurrentPCOffset(),
 599                              TEW->getAbsoluteLabelMachineRelTy(),
 600                              const_cast<GlobalValue*>(GV),
 601                              Offset);
 602
 603   // Fill the data entry with zeros
 604   GblS.emitZeros(Size);
 605
 606   // Add the relocation entry for the current data section
 607   GblS.addRelocation(MR);
 608 }
 609
 610 void ELFWriter::EmitGlobalConstantLargeInt(const ConstantInt *CI,
 611                                            ELFSection &S) {
 612   const TargetData *TD = TM.getTargetData();
 613   unsigned BitWidth = CI->getBitWidth();
 614   assert(isPowerOf2_32(BitWidth) &&
 615          "Non-power-of-2-sized integers not handled!");
 616
 617   const uint64_t *RawData = CI->getValue().getRawData();
 618   uint64_t Val = 0;
 619   for (unsigned i = 0, e = BitWidth / 64; i != e; ++i) {
 620     Val = (TD->isBigEndian()) ? RawData[e - i - 1] : RawData[i];
 621     S.emitWord64(Val);
 622   }
 623 }
 624
 625 /// EmitSpecialLLVMGlobal - Check to see if the specified global is a
 626 /// special global used by LLVM.  If so, emit it and return true, otherwise
 627 /// do nothing and return false.
 628 bool ELFWriter::EmitSpecialLLVMGlobal(const GlobalVariable *GV) {
 629   if (GV->getName() == "llvm.used")
 630     llvm_unreachable("not implemented yet");
 631
 632   // Ignore debug and non-emitted data.  This handles llvm.compiler.used.
 633   if (GV->getSection() == "llvm.metadata" ||
 634       GV->hasAvailableExternallyLinkage())
 635     return true;
 636
 637   if (!GV->hasAppendingLinkage()) return false;
 638
 639   assert(GV->hasInitializer() && "Not a special LLVM global!");
 640
 641   const TargetData *TD = TM.getTargetData();
 642   unsigned Align = TD->getPointerPrefAlignment();
 643   if (GV->getName() == "llvm.global_ctors") {
 644     ELFSection &Ctor = getCtorSection();
 645     Ctor.emitAlignment(Align);
 646     EmitXXStructorList(GV->getInitializer(), Ctor);
 647     return true;
 648   }
 649
 650   if (GV->getName() == "llvm.global_dtors") {
 651     ELFSection &Dtor = getDtorSection();
 652     Dtor.emitAlignment(Align);
 653     EmitXXStructorList(GV->getInitializer(), Dtor);
 654     return true;
 655   }
 656
 657   return false;
 658 }
 659
 660 /// EmitXXStructorList - Emit the ctor or dtor list.  This just emits out the
 661 /// function pointers, ignoring the init priority.
 662 void ELFWriter::EmitXXStructorList(Constant *List, ELFSection &Xtor) {
 663   // Should be an array of '{ int, void ()* }' structs.  The first value is the
 664   // init priority, which we ignore.
 665   if (!isa<ConstantArray>(List)) return;
 666   ConstantArray *InitList = cast<ConstantArray>(List);
 667   for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i)
 668     if (ConstantStruct *CS = dyn_cast<ConstantStruct>(InitList->getOperand(i))){
 669       if (CS->getNumOperands() != 2) return;  // Not array of 2-element structs.
 670
 671       if (CS->getOperand(1)->isNullValue())
 672         return;  // Found a null terminator, exit printing.
 673       // Emit the function pointer.
 674       EmitGlobalConstant(CS->getOperand(1), Xtor);
 675     }
 676 }
 677
 678 bool ELFWriter::runOnMachineFunction(MachineFunction &MF) {
 679   // Nothing to do here, this is all done through the ElfCE object above.
 680   return false;
 681 }
 682
 683 /// doFinalization - Now that the module has been completely processed, emit
 684 /// the ELF file to 'O'.
 685 bool ELFWriter::doFinalization(Module &M) {
 686   // Emit .data section placeholder
 687   getDataSection();
 688
 689   // Emit .bss section placeholder
 690   getBSSSection();
 691
 692   // Build and emit data, bss and "common" sections.
 693   for (Module::global_iterator I = M.global_begin(), E = M.global_end();
 694        I != E; ++I)
 695     EmitGlobal(I);
 696
 697   // Emit all pending globals
 698   for (PendingGblsIter I = PendingGlobals.begin(), E = PendingGlobals.end();
 699        I != E; ++I)
 700     EmitGlobal(*I);
 701
 702   // Emit all pending externals
 703   for (PendingExtsIter I = PendingExternals.begin(), E = PendingExternals.end();
 704        I != E; ++I)
 705     SymbolList.push_back(ELFSym::getExtSym(*I));
 706
 707   // Emit non-executable stack note
 708   if (MAI->getNonexecutableStackDirective())
 709     getNonExecStackSection();
 710
 711   // Emit a symbol for each section created until now, skip null section
 712   for (unsigned i = 1, e = SectionList.size(); i < e; ++i) {
 713     ELFSection &ES = *SectionList[i];
 714     ELFSym *SectionSym = ELFSym::getSectionSym();
 715     SectionSym->SectionIdx = ES.SectionIdx;
 716     SymbolList.push_back(SectionSym);
 717     ES.Sym = SymbolList.back();
 718   }
 719
 720   // Emit string table
 721   EmitStringTable(M.getModuleIdentifier());
 722
 723   // Emit the symbol table now, if non-empty.
 724   EmitSymbolTable();
 725
 726   // Emit the relocation sections.
 727   EmitRelocations();
 728
 729   // Emit the sections string table.
 730   EmitSectionTableStringTable();
 731
 732   // Dump the sections and section table to the .o file.
 733   OutputSectionsAndSectionTable();
 734
 735   return false;
 736 }
 737
 738 // RelocateField - Patch relocatable field with 'Offset' in 'BO'
 739 // using a 'Value' of known 'Size'
 740 void ELFWriter::RelocateField(BinaryObject &BO, uint32_t Offset,
 741                               int64_t Value, unsigned Size) {
 742   if (Size == 32)
 743     BO.fixWord32(Value, Offset);
 744   else if (Size == 64)
 745     BO.fixWord64(Value, Offset);
 746   else
 747     llvm_unreachable("don't know howto patch relocatable field");
 748 }
 749
 750 /// EmitRelocations - Emit relocations
 751 void ELFWriter::EmitRelocations() {
 752
 753   // True if the target uses the relocation entry to hold the addend,
 754   // otherwise the addend is written directly to the relocatable field.
 755   bool HasRelA = TEW->hasRelocationAddend();
 756
 757   // Create Relocation sections for each section which needs it.
 758   for (unsigned i=0, e=SectionList.size(); i != e; ++i) {
 759     ELFSection &S = *SectionList[i];
 760
 761     // This section does not have relocations
 762     if (!S.hasRelocations()) continue;
 763     ELFSection &RelSec = getRelocSection(S);
 764
 765     // 'Link' - Section hdr idx of the associated symbol table
 766     // 'Info' - Section hdr idx of the section to which the relocation applies
 767     ELFSection &SymTab = getSymbolTableSection();
 768     RelSec.Link = SymTab.SectionIdx;
 769     RelSec.Info = S.SectionIdx;
 770     RelSec.EntSize = TEW->getRelocationEntrySize();
 771
 772     // Get the relocations from Section
 773     std::vector<MachineRelocation> Relos = S.getRelocations();
 774     for (std::vector<MachineRelocation>::iterator MRI = Relos.begin(),
 775          MRE = Relos.end(); MRI != MRE; ++MRI) {
 776       MachineRelocation &MR = *MRI;
 777
 778       // Relocatable field offset from the section start
 779       unsigned RelOffset = MR.getMachineCodeOffset();
 780
 781       // Symbol index in the symbol table
 782       unsigned SymIdx = 0;
 783
 784       // Target specific relocation field type and size
 785       unsigned RelType = TEW->getRelocationType(MR.getRelocationType());
 786       unsigned RelTySize = TEW->getRelocationTySize(RelType);
 787       int64_t Addend = 0;
 788
 789       // There are several machine relocations types, and each one of
 790       // them needs a different approach to retrieve the symbol table index.
 791       if (MR.isGlobalValue()) {
 792         const GlobalValue *G = MR.getGlobalValue();
 793         int64_t GlobalOffset = MR.getConstantVal();
 794         SymIdx = GblSymLookup[G];
 795         if (G->hasPrivateLinkage()) {
 796           // If the target uses a section offset in the relocation:
 797           // SymIdx + Addend = section sym for global + section offset
 798           unsigned SectionIdx = PrivateSyms[SymIdx]->SectionIdx;
 799           Addend = PrivateSyms[SymIdx]->Value + GlobalOffset;
 800           SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
 801         } else {
 802           Addend = TEW->getDefaultAddendForRelTy(RelType, GlobalOffset);
 803         }
 804       } else if (MR.isExternalSymbol()) {
 805         const char *ExtSym = MR.getExternalSymbol();
 806         SymIdx = ExtSymLookup[ExtSym];
 807         Addend = TEW->getDefaultAddendForRelTy(RelType);
 808       } else {
 809         // Get the symbol index for the section symbol
 810         unsigned SectionIdx = MR.getConstantVal();
 811         SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
 812
 813         // The symbol offset inside the section
 814         int64_t SymOffset = (int64_t)MR.getResultPointer();
 815
 816         // For pc relative relocations where symbols are defined in the same
 817         // section they are referenced, ignore the relocation entry and patch
 818         // the relocatable field with the symbol offset directly.
 819         if (S.SectionIdx == SectionIdx && TEW->isPCRelativeRel(RelType)) {
 820           int64_t Value = TEW->computeRelocation(SymOffset, RelOffset, RelType);
 821           RelocateField(S, RelOffset, Value, RelTySize);
 822           continue;
 823         }
 824
 825         Addend = TEW->getDefaultAddendForRelTy(RelType, SymOffset);
 826       }
 827
 828       // The target without addend on the relocation symbol must be
 829       // patched in the relocation place itself to contain the addend
 830       // otherwise write zeros to make sure there is no garbage there
 831       RelocateField(S, RelOffset, HasRelA ? 0 : Addend, RelTySize);
 832
 833       // Get the relocation entry and emit to the relocation section
 834       ELFRelocation Rel(RelOffset, SymIdx, RelType, HasRelA, Addend);
 835       EmitRelocation(RelSec, Rel, HasRelA);
 836     }
 837   }
 838 }
 839
 840 /// EmitRelocation - Write relocation 'Rel' to the relocation section 'Rel'
 841 void ELFWriter::EmitRelocation(BinaryObject &RelSec, ELFRelocation &Rel,
 842                                bool HasRelA) {
 843   RelSec.emitWord(Rel.getOffset());
 844   RelSec.emitWord(Rel.getInfo(is64Bit));
 845   if (HasRelA)
 846     RelSec.emitWord(Rel.getAddend());
 847 }
 848
 849 /// EmitSymbol - Write symbol 'Sym' to the symbol table 'SymbolTable'
 850 void ELFWriter::EmitSymbol(BinaryObject &SymbolTable, ELFSym &Sym) {
 851   if (is64Bit) {
 852     SymbolTable.emitWord32(Sym.NameIdx);
 853     SymbolTable.emitByte(Sym.Info);
 854     SymbolTable.emitByte(Sym.Other);
 855     SymbolTable.emitWord16(Sym.SectionIdx);
 856     SymbolTable.emitWord64(Sym.Value);
 857     SymbolTable.emitWord64(Sym.Size);
 858   } else {
 859     SymbolTable.emitWord32(Sym.NameIdx);
 860     SymbolTable.emitWord32(Sym.Value);
 861     SymbolTable.emitWord32(Sym.Size);
 862     SymbolTable.emitByte(Sym.Info);
 863     SymbolTable.emitByte(Sym.Other);
 864     SymbolTable.emitWord16(Sym.SectionIdx);
 865   }
 866 }
 867
 868 /// EmitSectionHeader - Write section 'Section' header in 'SHdrTab'
 869 /// Section Header Table
 870 void ELFWriter::EmitSectionHeader(BinaryObject &SHdrTab,
 871                                   const ELFSection &SHdr) {
 872   SHdrTab.emitWord32(SHdr.NameIdx);
 873   SHdrTab.emitWord32(SHdr.Type);
 874   if (is64Bit) {
 875     SHdrTab.emitWord64(SHdr.Flags);
 876     SHdrTab.emitWord(SHdr.Addr);
 877     SHdrTab.emitWord(SHdr.Offset);
 878     SHdrTab.emitWord64(SHdr.Size);
 879     SHdrTab.emitWord32(SHdr.Link);
 880     SHdrTab.emitWord32(SHdr.Info);
 881     SHdrTab.emitWord64(SHdr.Align);
 882     SHdrTab.emitWord64(SHdr.EntSize);
 883   } else {
 884     SHdrTab.emitWord32(SHdr.Flags);
 885     SHdrTab.emitWord(SHdr.Addr);
 886     SHdrTab.emitWord(SHdr.Offset);
 887     SHdrTab.emitWord32(SHdr.Size);
 888     SHdrTab.emitWord32(SHdr.Link);
 889     SHdrTab.emitWord32(SHdr.Info);
 890     SHdrTab.emitWord32(SHdr.Align);
 891     SHdrTab.emitWord32(SHdr.EntSize);
 892   }
 893 }
 894
 895 /// EmitStringTable - If the current symbol table is non-empty, emit the string
 896 /// table for it
 897 void ELFWriter::EmitStringTable(const std::string &ModuleName) {
 898   if (!SymbolList.size()) return;  // Empty symbol table.
 899   ELFSection &StrTab = getStringTableSection();
 900
 901   // Set the zero'th symbol to a null byte, as required.
 902   StrTab.emitByte(0);
 903
 904   // Walk on the symbol list and write symbol names into the string table.
 905   unsigned Index = 1;
 906   for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
 907     ELFSym &Sym = *(*I);
 908
 909     std::string Name;
 910     if (Sym.isGlobalValue())
 911       Name.append(Mang->getMangledName(Sym.getGlobalValue()));
 912     else if (Sym.isExternalSym())
 913       Name.append(Sym.getExternalSymbol());
 914     else if (Sym.isFileType())
 915       Name.append(ModuleName);
 916
 917     if (Name.empty()) {
 918       Sym.NameIdx = 0;
 919     } else {
 920       Sym.NameIdx = Index;
 921       StrTab.emitString(Name);
 922
 923       // Keep track of the number of bytes emitted to this section.
 924       Index += Name.size()+1;
 925     }
 926   }
 927   assert(Index == StrTab.size());
 928   StrTab.Size = Index;
 929 }
 930
 931 // SortSymbols - On the symbol table local symbols must come before
 932 // all other symbols with non-local bindings. The return value is
 933 // the position of the first non local symbol.
 934 unsigned ELFWriter::SortSymbols() {
 935   unsigned FirstNonLocalSymbol;
 936   std::vector<ELFSym*> LocalSyms, OtherSyms;
 937
 938   for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
 939     if ((*I)->isLocalBind())
 940       LocalSyms.push_back(*I);
 941     else
 942       OtherSyms.push_back(*I);
 943   }
 944   SymbolList.clear();
 945   FirstNonLocalSymbol = LocalSyms.size();
 946
 947   for (unsigned i = 0; i < FirstNonLocalSymbol; ++i)
 948     SymbolList.push_back(LocalSyms[i]);
 949
 950   for (ELFSymIter I=OtherSyms.begin(), E=OtherSyms.end(); I != E; ++I)
 951     SymbolList.push_back(*I);
 952
 953   LocalSyms.clear();
 954   OtherSyms.clear();
 955
 956   return FirstNonLocalSymbol;
 957 }
 958
 959 /// EmitSymbolTable - Emit the symbol table itself.
 960 void ELFWriter::EmitSymbolTable() {
 961   if (!SymbolList.size()) return;  // Empty symbol table.
 962
 963   // Now that we have emitted the string table and know the offset into the
 964   // string table of each symbol, emit the symbol table itself.
 965   ELFSection &SymTab = getSymbolTableSection();
 966   SymTab.Align = TEW->getPrefELFAlignment();
 967
 968   // Section Index of .strtab.
 969   SymTab.Link = getStringTableSection().SectionIdx;
 970
 971   // Size of each symtab entry.
 972   SymTab.EntSize = TEW->getSymTabEntrySize();
 973
 974   // Reorder the symbol table with local symbols first!
 975   unsigned FirstNonLocalSymbol = SortSymbols();
 976
 977   // Emit all the symbols to the symbol table.
 978   for (unsigned i = 0, e = SymbolList.size(); i < e; ++i) {
 979     ELFSym &Sym = *SymbolList[i];
 980
 981     // Emit symbol to the symbol table
 982     EmitSymbol(SymTab, Sym);
 983
 984     // Record the symbol table index for each symbol
 985     if (Sym.isGlobalValue())
 986       GblSymLookup[Sym.getGlobalValue()] = i;
 987     else if (Sym.isExternalSym())
 988       ExtSymLookup[Sym.getExternalSymbol()] = i;
 989
 990     // Keep track on the symbol index into the symbol table
 991     Sym.SymTabIdx = i;
 992   }
 993
 994   // One greater than the symbol table index of the last local symbol
 995   SymTab.Info = FirstNonLocalSymbol;
 996   SymTab.Size = SymTab.size();
 997 }
 998
 999 /// EmitSectionTableStringTable - This method adds and emits a section for the
1000 /// ELF Section Table string table: the string table that holds all of the
1001 /// section names.
1002 void ELFWriter::EmitSectionTableStringTable() {
1003   // First step: add the section for the string table to the list of sections:
1004   ELFSection &SHStrTab = getSectionHeaderStringTableSection();
1005
1006   // Now that we know which section number is the .shstrtab section, update the
1007   // e_shstrndx entry in the ELF header.
1008   ElfHdr.fixWord16(SHStrTab.SectionIdx, ELFHdr_e_shstrndx_Offset);
1009
1010   // Set the NameIdx of each section in the string table and emit the bytes for
1011   // the string table.
1012   unsigned Index = 0;
1013
1014   for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
1015     ELFSection &S = *(*I);
1016     // Set the index into the table.  Note if we have lots of entries with
1017     // common suffixes, we could memoize them here if we cared.
1018     S.NameIdx = Index;
1019     SHStrTab.emitString(S.getName());
1020
1021     // Keep track of the number of bytes emitted to this section.
1022     Index += S.getName().size()+1;
1023   }
1024
1025   // Set the size of .shstrtab now that we know what it is.
1026   assert(Index == SHStrTab.size());
1027   SHStrTab.Size = Index;
1028 }
1029
1030 /// OutputSectionsAndSectionTable - Now that we have constructed the file header
1031 /// and all of the sections, emit these to the ostream destination and emit the
1032 /// SectionTable.
1033 void ELFWriter::OutputSectionsAndSectionTable() {
1034   // Pass #1: Compute the file offset for each section.
1035   size_t FileOff = ElfHdr.size();   // File header first.
1036
1037   // Adjust alignment of all section if needed, skip the null section.
1038   for (unsigned i=1, e=SectionList.size(); i < e; ++i) {
1039     ELFSection &ES = *SectionList[i];
1040     if (!ES.size()) {
1041       ES.Offset = FileOff;
1042       continue;
1043     }
1044
1045     // Update Section size
1046     if (!ES.Size)
1047       ES.Size = ES.size();
1048
1049     // Align FileOff to whatever the alignment restrictions of the section are.
1050     if (ES.Align)
1051       FileOff = (FileOff+ES.Align-1) & ~(ES.Align-1);
1052
1053     ES.Offset = FileOff;
1054     FileOff += ES.Size;
1055   }
1056
1057   // Align Section Header.
1058   unsigned TableAlign = TEW->getPrefELFAlignment();
1059   FileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
1060
1061   // Now that we know where all of the sections will be emitted, set the e_shnum
1062   // entry in the ELF header.
1063   ElfHdr.fixWord16(NumSections, ELFHdr_e_shnum_Offset);
1064
1065   // Now that we know the offset in the file of the section table, update the
1066   // e_shoff address in the ELF header.
1067   ElfHdr.fixWord(FileOff, ELFHdr_e_shoff_Offset);
1068
1069   // Now that we know all of the data in the file header, emit it and all of the
1070   // sections!
1071   O.write((char *)&ElfHdr.getData()[0], ElfHdr.size());
1072   FileOff = ElfHdr.size();
1073
1074   // Section Header Table blob
1075   BinaryObject SHdrTable(isLittleEndian, is64Bit);
1076
1077   // Emit all of sections to the file and build the section header table.
1078   for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
1079     ELFSection &S = *(*I);
1080     DEBUG(errs() << "SectionIdx: " << S.SectionIdx << ", Name: " << S.getName()
1081                  << ", Size: " << S.Size << ", Offset: " << S.Offset
1082                  << ", SectionData Size: " << S.size() << "\n");
1083
1084     // Align FileOff to whatever the alignment restrictions of the section are.
1085     if (S.size()) {
1086       if (S.Align)  {
1087         for (size_t NewFileOff = (FileOff+S.Align-1) & ~(S.Align-1);
1088              FileOff != NewFileOff; ++FileOff)
1089           O << (char)0xAB;
1090       }
1091       O.write((char *)&S.getData()[0], S.Size);
1092       FileOff += S.Size;
1093     }
1094
1095     EmitSectionHeader(SHdrTable, S);
1096   }
1097
1098   // Align output for the section table.
1099   for (size_t NewFileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
1100        FileOff != NewFileOff; ++FileOff)
1101     O << (char)0xAB;
1102
1103   // Emit the section table itself.
1104   O.write((char *)&SHdrTable.getData()[0], SHdrTable.size());
1105 }