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/MachineCodeEmitter.h"
  41 #include "llvm/CodeGen/ObjectCodeEmitter.h"
  42 #include "llvm/CodeGen/MachineCodeEmitter.h"
  43 #include "llvm/CodeGen/MachineConstantPool.h"
  44 #include "llvm/MC/MCContext.h"
  45 #include "llvm/MC/MCSectionELF.h"
  46 #include "llvm/MC/MCAsmInfo.h"
  47 #include "llvm/Target/Mangler.h"
  48 #include "llvm/Target/TargetAsmInfo.h"
  49 #include "llvm/Target/TargetData.h"
  50 #include "llvm/Target/TargetELFWriterInfo.h"
  51 #include "llvm/Target/TargetLowering.h"
  52 #include "llvm/Target/TargetLoweringObjectFile.h"
  53 #include "llvm/Target/TargetMachine.h"
  54 #include "llvm/Support/Debug.h"
  55 #include "llvm/Support/ErrorHandling.h"
  56 #include "llvm/Support/raw_ostream.h"
  57 #include "llvm/ADT/SmallString.h"
  58 using namespace llvm;
  59
  60 char ELFWriter::ID = 0;
  61
  62 //===----------------------------------------------------------------------===//
  63 //                          ELFWriter Implementation
  64 //===----------------------------------------------------------------------===//
  65
  66 ELFWriter::ELFWriter(raw_ostream &o, TargetMachine &tm)
  67   : MachineFunctionPass(ID), O(o), TM(tm),
  68     OutContext(*new MCContext(*TM.getMCAsmInfo(), new TargetAsmInfo(tm))),
  69     TLOF(TM.getTargetLowering()->getObjFileLowering()),
  70     is64Bit(TM.getTargetData()->getPointerSizeInBits() == 64),
  71     isLittleEndian(TM.getTargetData()->isLittleEndian()),
  72     ElfHdr(isLittleEndian, is64Bit) {
  73
  74   MAI = TM.getMCAsmInfo();
  75   TEW = TM.getELFWriterInfo();
  76
  77   // Create the object code emitter object for this target.
  78   ElfCE = new ELFCodeEmitter(*this);
  79
  80   // Initial number of sections
  81   NumSections = 0;
  82 }
  83
  84 ELFWriter::~ELFWriter() {
  85   delete ElfCE;
  86   delete &OutContext;
  87
  88   while(!SymbolList.empty()) {
  89     delete SymbolList.back();
  90     SymbolList.pop_back();
  91   }
  92
  93   while(!PrivateSyms.empty()) {
  94     delete PrivateSyms.back();
  95     PrivateSyms.pop_back();
  96   }
  97
  98   while(!SectionList.empty()) {
  99     delete SectionList.back();
 100     SectionList.pop_back();
 101   }
 102
 103   // Release the name mangler object.
 104   delete Mang; Mang = 0;
 105 }
 106
 107 // doInitialization - Emit the file header and all of the global variables for
 108 // the module to the ELF file.
 109 bool ELFWriter::doInitialization(Module &M) {
 110   // Initialize TargetLoweringObjectFile.
 111   const_cast<TargetLoweringObjectFile&>(TLOF).Initialize(OutContext, TM);
 112
 113   Mang = new Mangler(OutContext, *TM.getTargetData());
 114
 115   // ELF Header
 116   // ----------
 117   // Fields e_shnum e_shstrndx are only known after all section have
 118   // been emitted. They locations in the ouput buffer are recorded so
 119   // to be patched up later.
 120   //
 121   // Note
 122   // ----
 123   // emitWord method behaves differently for ELF32 and ELF64, writing
 124   // 4 bytes in the former and 8 in the last for *_off and *_addr elf types
 125
 126   ElfHdr.emitByte(0x7f); // e_ident[EI_MAG0]
 127   ElfHdr.emitByte('E');  // e_ident[EI_MAG1]
 128   ElfHdr.emitByte('L');  // e_ident[EI_MAG2]
 129   ElfHdr.emitByte('F');  // e_ident[EI_MAG3]
 130
 131   ElfHdr.emitByte(TEW->getEIClass()); // e_ident[EI_CLASS]
 132   ElfHdr.emitByte(TEW->getEIData());  // e_ident[EI_DATA]
 133   ElfHdr.emitByte(ELF::EV_CURRENT);   // e_ident[EI_VERSION]
 134   ElfHdr.emitAlignment(16);           // e_ident[EI_NIDENT-EI_PAD]
 135
 136   ElfHdr.emitWord16(ELF::ET_REL);        // e_type
 137   ElfHdr.emitWord16(TEW->getEMachine()); // e_machine = target
 138   ElfHdr.emitWord32(ELF::EV_CURRENT);    // e_version
 139   ElfHdr.emitWord(0);                    // e_entry, no entry point in .o file
 140   ElfHdr.emitWord(0);                    // e_phoff, no program header for .o
 141   ELFHdr_e_shoff_Offset = ElfHdr.size();
 142   ElfHdr.emitWord(0);                    // e_shoff = sec hdr table off in bytes
 143   ElfHdr.emitWord32(TEW->getEFlags());   // e_flags = whatever the target wants
 144   ElfHdr.emitWord16(TEW->getHdrSize());  // e_ehsize = ELF header size
 145   ElfHdr.emitWord16(0);                  // e_phentsize = prog header entry size
 146   ElfHdr.emitWord16(0);                  // e_phnum = # prog header entries = 0
 147
 148   // e_shentsize = Section header entry size
 149   ElfHdr.emitWord16(TEW->getSHdrSize());
 150
 151   // e_shnum     = # of section header ents
 152   ELFHdr_e_shnum_Offset = ElfHdr.size();
 153   ElfHdr.emitWord16(0); // Placeholder
 154
 155   // e_shstrndx  = Section # of '.shstrtab'
 156   ELFHdr_e_shstrndx_Offset = ElfHdr.size();
 157   ElfHdr.emitWord16(0); // Placeholder
 158
 159   // Add the null section, which is required to be first in the file.
 160   getNullSection();
 161
 162   // The first entry in the symtab is the null symbol and the second
 163   // is a local symbol containing the module/file name
 164   SymbolList.push_back(new ELFSym());
 165   SymbolList.push_back(ELFSym::getFileSym());
 166
 167   return false;
 168 }
 169
 170 // AddPendingGlobalSymbol - Add a global to be processed and to
 171 // the global symbol lookup, use a zero index because the table
 172 // index will be determined later.
 173 void ELFWriter::AddPendingGlobalSymbol(const GlobalValue *GV,
 174                                        bool AddToLookup /* = false */) {
 175   PendingGlobals.insert(GV);
 176   if (AddToLookup)
 177     GblSymLookup[GV] = 0;
 178 }
 179
 180 // AddPendingExternalSymbol - Add the external to be processed
 181 // and to the external symbol lookup, use a zero index because
 182 // the symbol table index will be determined later.
 183 void ELFWriter::AddPendingExternalSymbol(const char *External) {
 184   PendingExternals.insert(External);
 185   ExtSymLookup[External] = 0;
 186 }
 187
 188 ELFSection &ELFWriter::getDataSection() {
 189   const MCSectionELF *Data = (const MCSectionELF *)TLOF.getDataSection();
 190   return getSection(Data->getSectionName(), Data->getType(),
 191                     Data->getFlags(), 4);
 192 }
 193
 194 ELFSection &ELFWriter::getBSSSection() {
 195   const MCSectionELF *BSS = (const MCSectionELF *)TLOF.getBSSSection();
 196   return getSection(BSS->getSectionName(), BSS->getType(), BSS->getFlags(), 4);
 197 }
 198
 199 // getCtorSection - Get the static constructor section
 200 ELFSection &ELFWriter::getCtorSection() {
 201   const MCSectionELF *Ctor = (const MCSectionELF *)TLOF.getStaticCtorSection();
 202   return getSection(Ctor->getSectionName(), Ctor->getType(), Ctor->getFlags());
 203 }
 204
 205 // getDtorSection - Get the static destructor section
 206 ELFSection &ELFWriter::getDtorSection() {
 207   const MCSectionELF *Dtor = (const MCSectionELF *)TLOF.getStaticDtorSection();
 208   return getSection(Dtor->getSectionName(), Dtor->getType(), Dtor->getFlags());
 209 }
 210
 211 // getTextSection - Get the text section for the specified function
 212 ELFSection &ELFWriter::getTextSection(const Function *F) {
 213   const MCSectionELF *Text =
 214     (const MCSectionELF *)TLOF.SectionForGlobal(F, Mang, TM);
 215   return getSection(Text->getSectionName(), Text->getType(), Text->getFlags());
 216 }
 217
 218 // getJumpTableSection - Get a read only section for constants when
 219 // emitting jump tables. TODO: add PIC support
 220 ELFSection &ELFWriter::getJumpTableSection() {
 221   const MCSectionELF *JT =
 222     (const MCSectionELF *)TLOF.getSectionForConstant(SectionKind::getReadOnly());
 223   return getSection(JT->getSectionName(), JT->getType(), JT->getFlags(),
 224                     TM.getTargetData()->getPointerABIAlignment());
 225 }
 226
 227 // getConstantPoolSection - Get a constant pool section based on the machine
 228 // constant pool entry type and relocation info.
 229 ELFSection &ELFWriter::getConstantPoolSection(MachineConstantPoolEntry &CPE) {
 230   SectionKind Kind;
 231   switch (CPE.getRelocationInfo()) {
 232   default: llvm_unreachable("Unknown section kind");
 233   case 2: Kind = SectionKind::getReadOnlyWithRel(); break;
 234   case 1:
 235     Kind = SectionKind::getReadOnlyWithRelLocal();
 236     break;
 237   case 0:
 238     switch (TM.getTargetData()->getTypeAllocSize(CPE.getType())) {
 239     case 4:  Kind = SectionKind::getMergeableConst4(); break;
 240     case 8:  Kind = SectionKind::getMergeableConst8(); break;
 241     case 16: Kind = SectionKind::getMergeableConst16(); break;
 242     default: Kind = SectionKind::getMergeableConst(); break;
 243     }
 244   }
 245
 246   const MCSectionELF *CPSect =
 247     (const MCSectionELF *)TLOF.getSectionForConstant(Kind);
 248   return getSection(CPSect->getSectionName(), CPSect->getType(),
 249                     CPSect->getFlags(), CPE.getAlignment());
 250 }
 251
 252 // getRelocSection - Return the relocation section of section 'S'. 'RelA'
 253 // is true if the relocation section contains entries with addends.
 254 ELFSection &ELFWriter::getRelocSection(ELFSection &S) {
 255   unsigned SectionType = TEW->hasRelocationAddend() ?
 256                 ELF::SHT_RELA : ELF::SHT_REL;
 257
 258   std::string SectionName(".rel");
 259   if (TEW->hasRelocationAddend())
 260     SectionName.append("a");
 261   SectionName.append(S.getName());
 262
 263   return getSection(SectionName, SectionType, 0, TEW->getPrefELFAlignment());
 264 }
 265
 266 // getGlobalELFVisibility - Returns the ELF specific visibility type
 267 unsigned ELFWriter::getGlobalELFVisibility(const GlobalValue *GV) {
 268   switch (GV->getVisibility()) {
 269   default:
 270     llvm_unreachable("unknown visibility type");
 271   case GlobalValue::DefaultVisibility:
 272     return ELF::STV_DEFAULT;
 273   case GlobalValue::HiddenVisibility:
 274     return ELF::STV_HIDDEN;
 275   case GlobalValue::ProtectedVisibility:
 276     return ELF::STV_PROTECTED;
 277   }
 278   return 0;
 279 }
 280
 281 // getGlobalELFBinding - Returns the ELF specific binding type
 282 unsigned ELFWriter::getGlobalELFBinding(const GlobalValue *GV) {
 283   if (GV->hasInternalLinkage())
 284     return ELF::STB_LOCAL;
 285
 286   if (GV->isWeakForLinker() && !GV->hasCommonLinkage())
 287     return ELF::STB_WEAK;
 288
 289   return ELF::STB_GLOBAL;
 290 }
 291
 292 // getGlobalELFType - Returns the ELF specific type for a global
 293 unsigned ELFWriter::getGlobalELFType(const GlobalValue *GV) {
 294   if (GV->isDeclaration())
 295     return ELF::STT_NOTYPE;
 296
 297   if (isa<Function>(GV))
 298     return ELF::STT_FUNC;
 299
 300   return ELF::STT_OBJECT;
 301 }
 302
 303 // IsELFUndefSym - True if the global value must be marked as a symbol
 304 // which points to a SHN_UNDEF section. This means that the symbol has
 305 // no definition on the module.
 306 static bool IsELFUndefSym(const GlobalValue *GV) {
 307   return GV->isDeclaration() || (isa<Function>(GV));
 308 }
 309
 310 // AddToSymbolList - Update the symbol lookup and If the symbol is
 311 // private add it to PrivateSyms list, otherwise to SymbolList.
 312 void ELFWriter::AddToSymbolList(ELFSym *GblSym) {
 313   assert(GblSym->isGlobalValue() && "Symbol must be a global value");
 314
 315   const GlobalValue *GV = GblSym->getGlobalValue();
 316   if (GV->hasPrivateLinkage()) {
 317     // For a private symbols, keep track of the index inside
 318     // the private list since it will never go to the symbol
 319     // table and won't be patched up later.
 320     PrivateSyms.push_back(GblSym);
 321     GblSymLookup[GV] = PrivateSyms.size()-1;
 322   } else {
 323     // Non private symbol are left with zero indices until
 324     // they are patched up during the symbol table emition
 325     // (where the indicies are created).
 326     SymbolList.push_back(GblSym);
 327     GblSymLookup[GV] = 0;
 328   }
 329 }
 330
 331 /// HasCommonSymbols - True if this section holds common symbols, this is
 332 /// indicated on the ELF object file by a symbol with SHN_COMMON section
 333 /// header index.
 334 static bool HasCommonSymbols(const MCSectionELF &S) {
 335   // FIXME: this is wrong, a common symbol can be in .data for example.
 336   if (StringRef(S.getSectionName()).startswith(".gnu.linkonce."))
 337     return true;
 338
 339   return false;
 340 }
 341
 342
 343 // EmitGlobal - Choose the right section for global and emit it
 344 void ELFWriter::EmitGlobal(const GlobalValue *GV) {
 345
 346   // Check if the referenced symbol is already emitted
 347   if (GblSymLookup.find(GV) != GblSymLookup.end())
 348     return;
 349
 350   // Handle ELF Bind, Visibility and Type for the current symbol
 351   unsigned SymBind = getGlobalELFBinding(GV);
 352   unsigned SymType = getGlobalELFType(GV);
 353   bool IsUndefSym = IsELFUndefSym(GV);
 354
 355   ELFSym *GblSym = IsUndefSym ? ELFSym::getUndefGV(GV, SymBind)
 356     : ELFSym::getGV(GV, SymBind, SymType, getGlobalELFVisibility(GV));
 357
 358   if (!IsUndefSym) {
 359     assert(isa<GlobalVariable>(GV) && "GV not a global variable!");
 360     const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV);
 361
 362     // Handle special llvm globals
 363     if (EmitSpecialLLVMGlobal(GVar))
 364       return;
 365
 366     // Get the ELF section where this global belongs from TLOF
 367     const MCSectionELF *S =
 368       (const MCSectionELF *)TLOF.SectionForGlobal(GV, Mang, TM);
 369     ELFSection &ES =
 370       getSection(S->getSectionName(), S->getType(), S->getFlags());
 371     SectionKind Kind = S->getKind();
 372
 373     // The symbol align should update the section alignment if needed
 374     const TargetData *TD = TM.getTargetData();
 375     unsigned Align = TD->getPreferredAlignment(GVar);
 376     unsigned Size = TD->getTypeAllocSize(GVar->getInitializer()->getType());
 377     GblSym->Size = Size;
 378
 379     if (HasCommonSymbols(*S)) { // Symbol must go to a common section
 380       GblSym->SectionIdx = ELF::SHN_COMMON;
 381
 382       // A new linkonce section is created for each global in the
 383       // common section, the default alignment is 1 and the symbol
 384       // value contains its alignment.
 385       ES.Align = 1;
 386       GblSym->Value = Align;
 387
 388     } else if (Kind.isBSS() || Kind.isThreadBSS()) { // Symbol goes to BSS.
 389       GblSym->SectionIdx = ES.SectionIdx;
 390
 391       // Update the size with alignment and the next object can
 392       // start in the right offset in the section
 393       if (Align) ES.Size = (ES.Size + Align-1) & ~(Align-1);
 394       ES.Align = std::max(ES.Align, Align);
 395
 396       // GblSym->Value should contain the virtual offset inside the section.
 397       // Virtual because the BSS space is not allocated on ELF objects
 398       GblSym->Value = ES.Size;
 399       ES.Size += Size;
 400
 401     } else { // The symbol must go to some kind of data section
 402       GblSym->SectionIdx = ES.SectionIdx;
 403
 404       // GblSym->Value should contain the symbol offset inside the section,
 405       // and all symbols should start on their required alignment boundary
 406       ES.Align = std::max(ES.Align, Align);
 407       ES.emitAlignment(Align);
 408       GblSym->Value = ES.size();
 409
 410       // Emit the global to the data section 'ES'
 411       EmitGlobalConstant(GVar->getInitializer(), ES);
 412     }
 413   }
 414
 415   AddToSymbolList(GblSym);
 416 }
 417
 418 void ELFWriter::EmitGlobalConstantStruct(const ConstantStruct *CVS,
 419                                          ELFSection &GblS) {
 420
 421   // Print the fields in successive locations. Pad to align if needed!
 422   const TargetData *TD = TM.getTargetData();
 423   unsigned Size = TD->getTypeAllocSize(CVS->getType());
 424   const StructLayout *cvsLayout = TD->getStructLayout(CVS->getType());
 425   uint64_t sizeSoFar = 0;
 426   for (unsigned i = 0, e = CVS->getNumOperands(); i != e; ++i) {
 427     const Constant* field = CVS->getOperand(i);
 428
 429     // Check if padding is needed and insert one or more 0s.
 430     uint64_t fieldSize = TD->getTypeAllocSize(field->getType());
 431     uint64_t padSize = ((i == e-1 ? Size : cvsLayout->getElementOffset(i+1))
 432                         - cvsLayout->getElementOffset(i)) - fieldSize;
 433     sizeSoFar += fieldSize + padSize;
 434
 435     // Now print the actual field value.
 436     EmitGlobalConstant(field, GblS);
 437
 438     // Insert padding - this may include padding to increase the size of the
 439     // current field up to the ABI size (if the struct is not packed) as well
 440     // as padding to ensure that the next field starts at the right offset.
 441     GblS.emitZeros(padSize);
 442   }
 443   assert(sizeSoFar == cvsLayout->getSizeInBytes() &&
 444          "Layout of constant struct may be incorrect!");
 445 }
 446
 447 void ELFWriter::EmitGlobalConstant(const Constant *CV, ELFSection &GblS) {
 448   const TargetData *TD = TM.getTargetData();
 449   unsigned Size = TD->getTypeAllocSize(CV->getType());
 450
 451   if (const ConstantArray *CVA = dyn_cast<ConstantArray>(CV)) {
 452     for (unsigned i = 0, e = CVA->getNumOperands(); i != e; ++i)
 453       EmitGlobalConstant(CVA->getOperand(i), GblS);
 454     return;
 455   } else if (isa<ConstantAggregateZero>(CV)) {
 456     GblS.emitZeros(Size);
 457     return;
 458   } else if (const ConstantStruct *CVS = dyn_cast<ConstantStruct>(CV)) {
 459     EmitGlobalConstantStruct(CVS, GblS);
 460     return;
 461   } else if (const ConstantFP *CFP = dyn_cast<ConstantFP>(CV)) {
 462     APInt Val = CFP->getValueAPF().bitcastToAPInt();
 463     if (CFP->getType()->isDoubleTy())
 464       GblS.emitWord64(Val.getZExtValue());
 465     else if (CFP->getType()->isFloatTy())
 466       GblS.emitWord32(Val.getZExtValue());
 467     else if (CFP->getType()->isX86_FP80Ty()) {
 468       unsigned PadSize = TD->getTypeAllocSize(CFP->getType())-
 469                          TD->getTypeStoreSize(CFP->getType());
 470       GblS.emitWordFP80(Val.getRawData(), PadSize);
 471     } else if (CFP->getType()->isPPC_FP128Ty())
 472       llvm_unreachable("PPC_FP128Ty global emission not implemented");
 473     return;
 474   } else if (const ConstantInt *CI = dyn_cast<ConstantInt>(CV)) {
 475     if (Size == 1)
 476       GblS.emitByte(CI->getZExtValue());
 477     else if (Size == 2)
 478       GblS.emitWord16(CI->getZExtValue());
 479     else if (Size == 4)
 480       GblS.emitWord32(CI->getZExtValue());
 481     else
 482       EmitGlobalConstantLargeInt(CI, GblS);
 483     return;
 484   } else if (const ConstantVector *CP = dyn_cast<ConstantVector>(CV)) {
 485     const VectorType *PTy = CP->getType();
 486     for (unsigned I = 0, E = PTy->getNumElements(); I < E; ++I)
 487       EmitGlobalConstant(CP->getOperand(I), GblS);
 488     return;
 489   } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV)) {
 490     // Resolve a constant expression which returns a (Constant, Offset)
 491     // pair. If 'Res.first' is a GlobalValue, emit a relocation with
 492     // the offset 'Res.second', otherwise emit a global constant like
 493     // it is always done for not contant expression types.
 494     CstExprResTy Res = ResolveConstantExpr(CE);
 495     const Constant *Op = Res.first;
 496
 497     if (isa<GlobalValue>(Op))
 498       EmitGlobalDataRelocation(cast<const GlobalValue>(Op),
 499                                TD->getTypeAllocSize(Op->getType()),
 500                                GblS, Res.second);
 501     else
 502       EmitGlobalConstant(Op, GblS);
 503
 504     return;
 505   } else if (CV->getType()->getTypeID() == Type::PointerTyID) {
 506     // Fill the data entry with zeros or emit a relocation entry
 507     if (isa<ConstantPointerNull>(CV))
 508       GblS.emitZeros(Size);
 509     else
 510       EmitGlobalDataRelocation(cast<const GlobalValue>(CV),
 511                                Size, GblS);
 512     return;
 513   } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CV)) {
 514     // This is a constant address for a global variable or function and
 515     // therefore must be referenced using a relocation entry.
 516     EmitGlobalDataRelocation(GV, Size, GblS);
 517     return;
 518   }
 519
 520   std::string msg;
 521   raw_string_ostream ErrorMsg(msg);
 522   ErrorMsg << "Constant unimp for type: " << *CV->getType();
 523   report_fatal_error(ErrorMsg.str());
 524 }
 525
 526 // ResolveConstantExpr - Resolve the constant expression until it stop
 527 // yielding other constant expressions.
 528 CstExprResTy ELFWriter::ResolveConstantExpr(const Constant *CV) {
 529   const TargetData *TD = TM.getTargetData();
 530
 531   // There ins't constant expression inside others anymore
 532   if (!isa<ConstantExpr>(CV))
 533     return std::make_pair(CV, 0);
 534
 535   const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV);
 536   switch (CE->getOpcode()) {
 537   case Instruction::BitCast:
 538     return ResolveConstantExpr(CE->getOperand(0));
 539
 540   case Instruction::GetElementPtr: {
 541     const Constant *ptrVal = CE->getOperand(0);
 542     SmallVector<Value*, 8> idxVec(CE->op_begin()+1, CE->op_end());
 543     int64_t Offset = TD->getIndexedOffset(ptrVal->getType(), &idxVec[0],
 544                                           idxVec.size());
 545     return std::make_pair(ptrVal, Offset);
 546   }
 547   case Instruction::IntToPtr: {
 548     Constant *Op = CE->getOperand(0);
 549     Op = ConstantExpr::getIntegerCast(Op, TD->getIntPtrType(CV->getContext()),
 550                                       false/*ZExt*/);
 551     return ResolveConstantExpr(Op);
 552   }
 553   case Instruction::PtrToInt: {
 554     Constant *Op = CE->getOperand(0);
 555     const Type *Ty = CE->getType();
 556
 557     // We can emit the pointer value into this slot if the slot is an
 558     // integer slot greater or equal to the size of the pointer.
 559     if (TD->getTypeAllocSize(Ty) == TD->getTypeAllocSize(Op->getType()))
 560       return ResolveConstantExpr(Op);
 561
 562     llvm_unreachable("Integer size less then pointer size");
 563   }
 564   case Instruction::Add:
 565   case Instruction::Sub: {
 566     // Only handle cases where there's a constant expression with GlobalValue
 567     // as first operand and ConstantInt as second, which are the cases we can
 568     // solve direclty using a relocation entry. GlobalValue=Op0, CstInt=Op1
 569     // 1)  Instruction::Add  => (global) + CstInt
 570     // 2)  Instruction::Sub  => (global) + -CstInt
 571     const Constant *Op0 = CE->getOperand(0);
 572     const Constant *Op1 = CE->getOperand(1);
 573     assert(isa<ConstantInt>(Op1) && "Op1 must be a ConstantInt");
 574
 575     CstExprResTy Res = ResolveConstantExpr(Op0);
 576     assert(isa<GlobalValue>(Res.first) && "Op0 must be a GlobalValue");
 577
 578     const APInt &RHS = cast<ConstantInt>(Op1)->getValue();
 579     switch (CE->getOpcode()) {
 580     case Instruction::Add:
 581       return std::make_pair(Res.first, RHS.getSExtValue());
 582     case Instruction::Sub:
 583       return std::make_pair(Res.first, (-RHS).getSExtValue());
 584     }
 585   }
 586   }
 587
 588   report_fatal_error(CE->getOpcodeName() +
 589                      StringRef(": Unsupported ConstantExpr type"));
 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(const Constant *List, ELFSection &Xtor) {
 663   // Should be an array of '{ i32, void ()* }' structs.  The first value is the
 664   // init priority, which we ignore.
 665   if (List->isNullValue()) return;
 666   const ConstantArray *InitList = cast<ConstantArray>(List);
 667   for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i) {
 668     if (InitList->getOperand(i)->isNullValue())
 669       continue;
 670     ConstantStruct *CS = cast<ConstantStruct>(InitList->getOperand(i));
 671
 672     if (CS->getOperand(1)->isNullValue())
 673       continue;
 674
 675     // Emit the function pointer.
 676     EmitGlobalConstant(CS->getOperand(1), Xtor);
 677   }
 678 }
 679
 680 bool ELFWriter::runOnMachineFunction(MachineFunction &MF) {
 681   // Nothing to do here, this is all done through the ElfCE object above.
 682   return false;
 683 }
 684
 685 /// doFinalization - Now that the module has been completely processed, emit
 686 /// the ELF file to 'O'.
 687 bool ELFWriter::doFinalization(Module &M) {
 688   // Emit .data section placeholder
 689   getDataSection();
 690
 691   // Emit .bss section placeholder
 692   getBSSSection();
 693
 694   // Build and emit data, bss and "common" sections.
 695   for (Module::global_iterator I = M.global_begin(), E = M.global_end();
 696        I != E; ++I)
 697     EmitGlobal(I);
 698
 699   // Emit all pending globals
 700   for (PendingGblsIter I = PendingGlobals.begin(), E = PendingGlobals.end();
 701        I != E; ++I)
 702     EmitGlobal(*I);
 703
 704   // Emit all pending externals
 705   for (PendingExtsIter I = PendingExternals.begin(), E = PendingExternals.end();
 706        I != E; ++I)
 707     SymbolList.push_back(ELFSym::getExtSym(*I));
 708
 709   // Emit a symbol for each section created until now, skip null section
 710   for (unsigned i = 1, e = SectionList.size(); i < e; ++i) {
 711     ELFSection &ES = *SectionList[i];
 712     ELFSym *SectionSym = ELFSym::getSectionSym();
 713     SectionSym->SectionIdx = ES.SectionIdx;
 714     SymbolList.push_back(SectionSym);
 715     ES.Sym = SymbolList.back();
 716   }
 717
 718   // Emit string table
 719   EmitStringTable(M.getModuleIdentifier());
 720
 721   // Emit the symbol table now, if non-empty.
 722   EmitSymbolTable();
 723
 724   // Emit the relocation sections.
 725   EmitRelocations();
 726
 727   // Emit the sections string table.
 728   EmitSectionTableStringTable();
 729
 730   // Dump the sections and section table to the .o file.
 731   OutputSectionsAndSectionTable();
 732
 733   return false;
 734 }
 735
 736 // RelocateField - Patch relocatable field with 'Offset' in 'BO'
 737 // using a 'Value' of known 'Size'
 738 void ELFWriter::RelocateField(BinaryObject &BO, uint32_t Offset,
 739                               int64_t Value, unsigned Size) {
 740   if (Size == 32)
 741     BO.fixWord32(Value, Offset);
 742   else if (Size == 64)
 743     BO.fixWord64(Value, Offset);
 744   else
 745     llvm_unreachable("don't know howto patch relocatable field");
 746 }
 747
 748 /// EmitRelocations - Emit relocations
 749 void ELFWriter::EmitRelocations() {
 750
 751   // True if the target uses the relocation entry to hold the addend,
 752   // otherwise the addend is written directly to the relocatable field.
 753   bool HasRelA = TEW->hasRelocationAddend();
 754
 755   // Create Relocation sections for each section which needs it.
 756   for (unsigned i=0, e=SectionList.size(); i != e; ++i) {
 757     ELFSection &S = *SectionList[i];
 758
 759     // This section does not have relocations
 760     if (!S.hasRelocations()) continue;
 761     ELFSection &RelSec = getRelocSection(S);
 762
 763     // 'Link' - Section hdr idx of the associated symbol table
 764     // 'Info' - Section hdr idx of the section to which the relocation applies
 765     ELFSection &SymTab = getSymbolTableSection();
 766     RelSec.Link = SymTab.SectionIdx;
 767     RelSec.Info = S.SectionIdx;
 768     RelSec.EntSize = TEW->getRelocationEntrySize();
 769
 770     // Get the relocations from Section
 771     std::vector<MachineRelocation> Relos = S.getRelocations();
 772     for (std::vector<MachineRelocation>::iterator MRI = Relos.begin(),
 773          MRE = Relos.end(); MRI != MRE; ++MRI) {
 774       MachineRelocation &MR = *MRI;
 775
 776       // Relocatable field offset from the section start
 777       unsigned RelOffset = MR.getMachineCodeOffset();
 778
 779       // Symbol index in the symbol table
 780       unsigned SymIdx = 0;
 781
 782       // Target specific relocation field type and size
 783       unsigned RelType = TEW->getRelocationType(MR.getRelocationType());
 784       unsigned RelTySize = TEW->getRelocationTySize(RelType);
 785       int64_t Addend = 0;
 786
 787       // There are several machine relocations types, and each one of
 788       // them needs a different approach to retrieve the symbol table index.
 789       if (MR.isGlobalValue()) {
 790         const GlobalValue *G = MR.getGlobalValue();
 791         int64_t GlobalOffset = MR.getConstantVal();
 792         SymIdx = GblSymLookup[G];
 793         if (G->hasPrivateLinkage()) {
 794           // If the target uses a section offset in the relocation:
 795           // SymIdx + Addend = section sym for global + section offset
 796           unsigned SectionIdx = PrivateSyms[SymIdx]->SectionIdx;
 797           Addend = PrivateSyms[SymIdx]->Value + GlobalOffset;
 798           SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
 799         } else {
 800           Addend = TEW->getDefaultAddendForRelTy(RelType, GlobalOffset);
 801         }
 802       } else if (MR.isExternalSymbol()) {
 803         const char *ExtSym = MR.getExternalSymbol();
 804         SymIdx = ExtSymLookup[ExtSym];
 805         Addend = TEW->getDefaultAddendForRelTy(RelType);
 806       } else {
 807         // Get the symbol index for the section symbol
 808         unsigned SectionIdx = MR.getConstantVal();
 809         SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
 810
 811         // The symbol offset inside the section
 812         int64_t SymOffset = (int64_t)MR.getResultPointer();
 813
 814         // For pc relative relocations where symbols are defined in the same
 815         // section they are referenced, ignore the relocation entry and patch
 816         // the relocatable field with the symbol offset directly.
 817         if (S.SectionIdx == SectionIdx && TEW->isPCRelativeRel(RelType)) {
 818           int64_t Value = TEW->computeRelocation(SymOffset, RelOffset, RelType);
 819           RelocateField(S, RelOffset, Value, RelTySize);
 820           continue;
 821         }
 822
 823         Addend = TEW->getDefaultAddendForRelTy(RelType, SymOffset);
 824       }
 825
 826       // The target without addend on the relocation symbol must be
 827       // patched in the relocation place itself to contain the addend
 828       // otherwise write zeros to make sure there is no garbage there
 829       RelocateField(S, RelOffset, HasRelA ? 0 : Addend, RelTySize);
 830
 831       // Get the relocation entry and emit to the relocation section
 832       ELFRelocation Rel(RelOffset, SymIdx, RelType, HasRelA, Addend);
 833       EmitRelocation(RelSec, Rel, HasRelA);
 834     }
 835   }
 836 }
 837
 838 /// EmitRelocation - Write relocation 'Rel' to the relocation section 'Rel'
 839 void ELFWriter::EmitRelocation(BinaryObject &RelSec, ELFRelocation &Rel,
 840                                bool HasRelA) {
 841   RelSec.emitWord(Rel.getOffset());
 842   RelSec.emitWord(Rel.getInfo(is64Bit));
 843   if (HasRelA)
 844     RelSec.emitWord(Rel.getAddend());
 845 }
 846
 847 /// EmitSymbol - Write symbol 'Sym' to the symbol table 'SymbolTable'
 848 void ELFWriter::EmitSymbol(BinaryObject &SymbolTable, ELFSym &Sym) {
 849   if (is64Bit) {
 850     SymbolTable.emitWord32(Sym.NameIdx);
 851     SymbolTable.emitByte(Sym.Info);
 852     SymbolTable.emitByte(Sym.Other);
 853     SymbolTable.emitWord16(Sym.SectionIdx);
 854     SymbolTable.emitWord64(Sym.Value);
 855     SymbolTable.emitWord64(Sym.Size);
 856   } else {
 857     SymbolTable.emitWord32(Sym.NameIdx);
 858     SymbolTable.emitWord32(Sym.Value);
 859     SymbolTable.emitWord32(Sym.Size);
 860     SymbolTable.emitByte(Sym.Info);
 861     SymbolTable.emitByte(Sym.Other);
 862     SymbolTable.emitWord16(Sym.SectionIdx);
 863   }
 864 }
 865
 866 /// EmitSectionHeader - Write section 'Section' header in 'SHdrTab'
 867 /// Section Header Table
 868 void ELFWriter::EmitSectionHeader(BinaryObject &SHdrTab,
 869                                   const ELFSection &SHdr) {
 870   SHdrTab.emitWord32(SHdr.NameIdx);
 871   SHdrTab.emitWord32(SHdr.Type);
 872   if (is64Bit) {
 873     SHdrTab.emitWord64(SHdr.Flags);
 874     SHdrTab.emitWord(SHdr.Addr);
 875     SHdrTab.emitWord(SHdr.Offset);
 876     SHdrTab.emitWord64(SHdr.Size);
 877     SHdrTab.emitWord32(SHdr.Link);
 878     SHdrTab.emitWord32(SHdr.Info);
 879     SHdrTab.emitWord64(SHdr.Align);
 880     SHdrTab.emitWord64(SHdr.EntSize);
 881   } else {
 882     SHdrTab.emitWord32(SHdr.Flags);
 883     SHdrTab.emitWord(SHdr.Addr);
 884     SHdrTab.emitWord(SHdr.Offset);
 885     SHdrTab.emitWord32(SHdr.Size);
 886     SHdrTab.emitWord32(SHdr.Link);
 887     SHdrTab.emitWord32(SHdr.Info);
 888     SHdrTab.emitWord32(SHdr.Align);
 889     SHdrTab.emitWord32(SHdr.EntSize);
 890   }
 891 }
 892
 893 /// EmitStringTable - If the current symbol table is non-empty, emit the string
 894 /// table for it
 895 void ELFWriter::EmitStringTable(const std::string &ModuleName) {
 896   if (!SymbolList.size()) return;  // Empty symbol table.
 897   ELFSection &StrTab = getStringTableSection();
 898
 899   // Set the zero'th symbol to a null byte, as required.
 900   StrTab.emitByte(0);
 901
 902   // Walk on the symbol list and write symbol names into the string table.
 903   unsigned Index = 1;
 904   for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
 905     ELFSym &Sym = *(*I);
 906
 907     std::string Name;
 908     if (Sym.isGlobalValue()) {
 909       SmallString<40> NameStr;
 910       Mang->getNameWithPrefix(NameStr, Sym.getGlobalValue(), false);
 911       Name.append(NameStr.begin(), NameStr.end());
 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(dbgs() << "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 }