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   // Inital 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 // EmitGlobal - Choose the right section for global and emit it
 332 void ELFWriter::EmitGlobal(const GlobalValue *GV) {
 333
 334   // Check if the referenced symbol is already emitted
 335   if (GblSymLookup.find(GV) != GblSymLookup.end())
 336     return;
 337
 338   // Handle ELF Bind, Visibility and Type for the current symbol
 339   unsigned SymBind = getGlobalELFBinding(GV);
 340   unsigned SymType = getGlobalELFType(GV);
 341   bool IsUndefSym = IsELFUndefSym(GV);
 342
 343   ELFSym *GblSym = IsUndefSym ? ELFSym::getUndefGV(GV, SymBind)
 344     : ELFSym::getGV(GV, SymBind, SymType, getGlobalELFVisibility(GV));
 345
 346   if (!IsUndefSym) {
 347     assert(isa<GlobalVariable>(GV) && "GV not a global variable!");
 348     const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV);
 349
 350     // Handle special llvm globals
 351     if (EmitSpecialLLVMGlobal(GVar))
 352       return;
 353
 354     // Get the ELF section where this global belongs from TLOF
 355     const MCSectionELF *S =
 356       (const MCSectionELF *)TLOF.SectionForGlobal(GV, Mang, TM);
 357     ELFSection &ES =
 358       getSection(S->getSectionName(), S->getType(), S->getFlags());
 359     SectionKind Kind = S->getKind();
 360
 361     // The symbol align should update the section alignment if needed
 362     const TargetData *TD = TM.getTargetData();
 363     unsigned Align = TD->getPreferredAlignment(GVar);
 364     unsigned Size = TD->getTypeAllocSize(GVar->getInitializer()->getType());
 365     GblSym->Size = Size;
 366
 367     if (S->HasCommonSymbols()) { // Symbol must go to a common section
 368       GblSym->SectionIdx = ELF::SHN_COMMON;
 369
 370       // A new linkonce section is created for each global in the
 371       // common section, the default alignment is 1 and the symbol
 372       // value contains its alignment.
 373       ES.Align = 1;
 374       GblSym->Value = Align;
 375
 376     } else if (Kind.isBSS() || Kind.isThreadBSS()) { // Symbol goes to BSS.
 377       GblSym->SectionIdx = ES.SectionIdx;
 378
 379       // Update the size with alignment and the next object can
 380       // start in the right offset in the section
 381       if (Align) ES.Size = (ES.Size + Align-1) & ~(Align-1);
 382       ES.Align = std::max(ES.Align, Align);
 383
 384       // GblSym->Value should contain the virtual offset inside the section.
 385       // Virtual because the BSS space is not allocated on ELF objects
 386       GblSym->Value = ES.Size;
 387       ES.Size += Size;
 388
 389     } else { // The symbol must go to some kind of data section
 390       GblSym->SectionIdx = ES.SectionIdx;
 391
 392       // GblSym->Value should contain the symbol offset inside the section,
 393       // and all symbols should start on their required alignment boundary
 394       ES.Align = std::max(ES.Align, Align);
 395       ES.emitAlignment(Align);
 396       GblSym->Value = ES.size();
 397
 398       // Emit the global to the data section 'ES'
 399       EmitGlobalConstant(GVar->getInitializer(), ES);
 400     }
 401   }
 402
 403   AddToSymbolList(GblSym);
 404 }
 405
 406 void ELFWriter::EmitGlobalConstantStruct(const ConstantStruct *CVS,
 407                                          ELFSection &GblS) {
 408
 409   // Print the fields in successive locations. Pad to align if needed!
 410   const TargetData *TD = TM.getTargetData();
 411   unsigned Size = TD->getTypeAllocSize(CVS->getType());
 412   const StructLayout *cvsLayout = TD->getStructLayout(CVS->getType());
 413   uint64_t sizeSoFar = 0;
 414   for (unsigned i = 0, e = CVS->getNumOperands(); i != e; ++i) {
 415     const Constant* field = CVS->getOperand(i);
 416
 417     // Check if padding is needed and insert one or more 0s.
 418     uint64_t fieldSize = TD->getTypeAllocSize(field->getType());
 419     uint64_t padSize = ((i == e-1 ? Size : cvsLayout->getElementOffset(i+1))
 420                         - cvsLayout->getElementOffset(i)) - fieldSize;
 421     sizeSoFar += fieldSize + padSize;
 422
 423     // Now print the actual field value.
 424     EmitGlobalConstant(field, GblS);
 425
 426     // Insert padding - this may include padding to increase the size of the
 427     // current field up to the ABI size (if the struct is not packed) as well
 428     // as padding to ensure that the next field starts at the right offset.
 429     GblS.emitZeros(padSize);
 430   }
 431   assert(sizeSoFar == cvsLayout->getSizeInBytes() &&
 432          "Layout of constant struct may be incorrect!");
 433 }
 434
 435 void ELFWriter::EmitGlobalConstant(const Constant *CV, ELFSection &GblS) {
 436   const TargetData *TD = TM.getTargetData();
 437   unsigned Size = TD->getTypeAllocSize(CV->getType());
 438
 439   if (const ConstantArray *CVA = dyn_cast<ConstantArray>(CV)) {
 440     for (unsigned i = 0, e = CVA->getNumOperands(); i != e; ++i)
 441       EmitGlobalConstant(CVA->getOperand(i), GblS);
 442     return;
 443   } else if (isa<ConstantAggregateZero>(CV)) {
 444     GblS.emitZeros(Size);
 445     return;
 446   } else if (const ConstantStruct *CVS = dyn_cast<ConstantStruct>(CV)) {
 447     EmitGlobalConstantStruct(CVS, GblS);
 448     return;
 449   } else if (const ConstantFP *CFP = dyn_cast<ConstantFP>(CV)) {
 450     APInt Val = CFP->getValueAPF().bitcastToAPInt();
 451     if (CFP->getType()->isDoubleTy())
 452       GblS.emitWord64(Val.getZExtValue());
 453     else if (CFP->getType()->isFloatTy())
 454       GblS.emitWord32(Val.getZExtValue());
 455     else if (CFP->getType()->isX86_FP80Ty()) {
 456       unsigned PadSize = TD->getTypeAllocSize(CFP->getType())-
 457                          TD->getTypeStoreSize(CFP->getType());
 458       GblS.emitWordFP80(Val.getRawData(), PadSize);
 459     } else if (CFP->getType()->isPPC_FP128Ty())
 460       llvm_unreachable("PPC_FP128Ty global emission not implemented");
 461     return;
 462   } else if (const ConstantInt *CI = dyn_cast<ConstantInt>(CV)) {
 463     if (Size == 1)
 464       GblS.emitByte(CI->getZExtValue());
 465     else if (Size == 2)
 466       GblS.emitWord16(CI->getZExtValue());
 467     else if (Size == 4)
 468       GblS.emitWord32(CI->getZExtValue());
 469     else
 470       EmitGlobalConstantLargeInt(CI, GblS);
 471     return;
 472   } else if (const ConstantVector *CP = dyn_cast<ConstantVector>(CV)) {
 473     const VectorType *PTy = CP->getType();
 474     for (unsigned I = 0, E = PTy->getNumElements(); I < E; ++I)
 475       EmitGlobalConstant(CP->getOperand(I), GblS);
 476     return;
 477   } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV)) {
 478     // Resolve a constant expression which returns a (Constant, Offset)
 479     // pair. If 'Res.first' is a GlobalValue, emit a relocation with
 480     // the offset 'Res.second', otherwise emit a global constant like
 481     // it is always done for not contant expression types.
 482     CstExprResTy Res = ResolveConstantExpr(CE);
 483     const Constant *Op = Res.first;
 484
 485     if (isa<GlobalValue>(Op))
 486       EmitGlobalDataRelocation(cast<const GlobalValue>(Op),
 487                                TD->getTypeAllocSize(Op->getType()),
 488                                GblS, Res.second);
 489     else
 490       EmitGlobalConstant(Op, GblS);
 491
 492     return;
 493   } else if (CV->getType()->getTypeID() == Type::PointerTyID) {
 494     // Fill the data entry with zeros or emit a relocation entry
 495     if (isa<ConstantPointerNull>(CV))
 496       GblS.emitZeros(Size);
 497     else
 498       EmitGlobalDataRelocation(cast<const GlobalValue>(CV),
 499                                Size, GblS);
 500     return;
 501   } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CV)) {
 502     // This is a constant address for a global variable or function and
 503     // therefore must be referenced using a relocation entry.
 504     EmitGlobalDataRelocation(GV, Size, GblS);
 505     return;
 506   }
 507
 508   std::string msg;
 509   raw_string_ostream ErrorMsg(msg);
 510   ErrorMsg << "Constant unimp for type: " << *CV->getType();
 511   report_fatal_error(ErrorMsg.str());
 512 }
 513
 514 // ResolveConstantExpr - Resolve the constant expression until it stop
 515 // yielding other constant expressions.
 516 CstExprResTy ELFWriter::ResolveConstantExpr(const Constant *CV) {
 517   const TargetData *TD = TM.getTargetData();
 518
 519   // There ins't constant expression inside others anymore
 520   if (!isa<ConstantExpr>(CV))
 521     return std::make_pair(CV, 0);
 522
 523   const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV);
 524   switch (CE->getOpcode()) {
 525   case Instruction::BitCast:
 526     return ResolveConstantExpr(CE->getOperand(0));
 527
 528   case Instruction::GetElementPtr: {
 529     const Constant *ptrVal = CE->getOperand(0);
 530     SmallVector<Value*, 8> idxVec(CE->op_begin()+1, CE->op_end());
 531     int64_t Offset = TD->getIndexedOffset(ptrVal->getType(), &idxVec[0],
 532                                           idxVec.size());
 533     return std::make_pair(ptrVal, Offset);
 534   }
 535   case Instruction::IntToPtr: {
 536     Constant *Op = CE->getOperand(0);
 537     Op = ConstantExpr::getIntegerCast(Op, TD->getIntPtrType(CV->getContext()),
 538                                       false/*ZExt*/);
 539     return ResolveConstantExpr(Op);
 540   }
 541   case Instruction::PtrToInt: {
 542     Constant *Op = CE->getOperand(0);
 543     const Type *Ty = CE->getType();
 544
 545     // We can emit the pointer value into this slot if the slot is an
 546     // integer slot greater or equal to the size of the pointer.
 547     if (TD->getTypeAllocSize(Ty) == TD->getTypeAllocSize(Op->getType()))
 548       return ResolveConstantExpr(Op);
 549
 550     llvm_unreachable("Integer size less then pointer size");
 551   }
 552   case Instruction::Add:
 553   case Instruction::Sub: {
 554     // Only handle cases where there's a constant expression with GlobalValue
 555     // as first operand and ConstantInt as second, which are the cases we can
 556     // solve direclty using a relocation entry. GlobalValue=Op0, CstInt=Op1
 557     // 1)  Instruction::Add  => (global) + CstInt
 558     // 2)  Instruction::Sub  => (global) + -CstInt
 559     const Constant *Op0 = CE->getOperand(0);
 560     const Constant *Op1 = CE->getOperand(1);
 561     assert(isa<ConstantInt>(Op1) && "Op1 must be a ConstantInt");
 562
 563     CstExprResTy Res = ResolveConstantExpr(Op0);
 564     assert(isa<GlobalValue>(Res.first) && "Op0 must be a GlobalValue");
 565
 566     const APInt &RHS = cast<ConstantInt>(Op1)->getValue();
 567     switch (CE->getOpcode()) {
 568     case Instruction::Add:
 569       return std::make_pair(Res.first, RHS.getSExtValue());
 570     case Instruction::Sub:
 571       return std::make_pair(Res.first, (-RHS).getSExtValue());
 572     }
 573   }
 574   }
 575
 576   report_fatal_error(CE->getOpcodeName() +
 577                      StringRef(": Unsupported ConstantExpr type"));
 578
 579   return std::make_pair(CV, 0); // silence warning
 580 }
 581
 582 void ELFWriter::EmitGlobalDataRelocation(const GlobalValue *GV, unsigned Size,
 583                                          ELFSection &GblS, int64_t Offset) {
 584   // Create the relocation entry for the global value
 585   MachineRelocation MR =
 586     MachineRelocation::getGV(GblS.getCurrentPCOffset(),
 587                              TEW->getAbsoluteLabelMachineRelTy(),
 588                              const_cast<GlobalValue*>(GV),
 589                              Offset);
 590
 591   // Fill the data entry with zeros
 592   GblS.emitZeros(Size);
 593
 594   // Add the relocation entry for the current data section
 595   GblS.addRelocation(MR);
 596 }
 597
 598 void ELFWriter::EmitGlobalConstantLargeInt(const ConstantInt *CI,
 599                                            ELFSection &S) {
 600   const TargetData *TD = TM.getTargetData();
 601   unsigned BitWidth = CI->getBitWidth();
 602   assert(isPowerOf2_32(BitWidth) &&
 603          "Non-power-of-2-sized integers not handled!");
 604
 605   const uint64_t *RawData = CI->getValue().getRawData();
 606   uint64_t Val = 0;
 607   for (unsigned i = 0, e = BitWidth / 64; i != e; ++i) {
 608     Val = (TD->isBigEndian()) ? RawData[e - i - 1] : RawData[i];
 609     S.emitWord64(Val);
 610   }
 611 }
 612
 613 /// EmitSpecialLLVMGlobal - Check to see if the specified global is a
 614 /// special global used by LLVM.  If so, emit it and return true, otherwise
 615 /// do nothing and return false.
 616 bool ELFWriter::EmitSpecialLLVMGlobal(const GlobalVariable *GV) {
 617   if (GV->getName() == "llvm.used")
 618     llvm_unreachable("not implemented yet");
 619
 620   // Ignore debug and non-emitted data.  This handles llvm.compiler.used.
 621   if (GV->getSection() == "llvm.metadata" ||
 622       GV->hasAvailableExternallyLinkage())
 623     return true;
 624
 625   if (!GV->hasAppendingLinkage()) return false;
 626
 627   assert(GV->hasInitializer() && "Not a special LLVM global!");
 628
 629   const TargetData *TD = TM.getTargetData();
 630   unsigned Align = TD->getPointerPrefAlignment();
 631   if (GV->getName() == "llvm.global_ctors") {
 632     ELFSection &Ctor = getCtorSection();
 633     Ctor.emitAlignment(Align);
 634     EmitXXStructorList(GV->getInitializer(), Ctor);
 635     return true;
 636   }
 637
 638   if (GV->getName() == "llvm.global_dtors") {
 639     ELFSection &Dtor = getDtorSection();
 640     Dtor.emitAlignment(Align);
 641     EmitXXStructorList(GV->getInitializer(), Dtor);
 642     return true;
 643   }
 644
 645   return false;
 646 }
 647
 648 /// EmitXXStructorList - Emit the ctor or dtor list.  This just emits out the
 649 /// function pointers, ignoring the init priority.
 650 void ELFWriter::EmitXXStructorList(Constant *List, ELFSection &Xtor) {
 651   // Should be an array of '{ int, void ()* }' structs.  The first value is the
 652   // init priority, which we ignore.
 653   if (!isa<ConstantArray>(List)) return;
 654   ConstantArray *InitList = cast<ConstantArray>(List);
 655   for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i)
 656     if (ConstantStruct *CS = dyn_cast<ConstantStruct>(InitList->getOperand(i))){
 657       if (CS->getNumOperands() != 2) return;  // Not array of 2-element structs.
 658
 659       if (CS->getOperand(1)->isNullValue())
 660         return;  // Found a null terminator, exit printing.
 661       // Emit the function pointer.
 662       EmitGlobalConstant(CS->getOperand(1), Xtor);
 663     }
 664 }
 665
 666 bool ELFWriter::runOnMachineFunction(MachineFunction &MF) {
 667   // Nothing to do here, this is all done through the ElfCE object above.
 668   return false;
 669 }
 670
 671 /// doFinalization - Now that the module has been completely processed, emit
 672 /// the ELF file to 'O'.
 673 bool ELFWriter::doFinalization(Module &M) {
 674   // Emit .data section placeholder
 675   getDataSection();
 676
 677   // Emit .bss section placeholder
 678   getBSSSection();
 679
 680   // Build and emit data, bss and "common" sections.
 681   for (Module::global_iterator I = M.global_begin(), E = M.global_end();
 682        I != E; ++I)
 683     EmitGlobal(I);
 684
 685   // Emit all pending globals
 686   for (PendingGblsIter I = PendingGlobals.begin(), E = PendingGlobals.end();
 687        I != E; ++I)
 688     EmitGlobal(*I);
 689
 690   // Emit all pending externals
 691   for (PendingExtsIter I = PendingExternals.begin(), E = PendingExternals.end();
 692        I != E; ++I)
 693     SymbolList.push_back(ELFSym::getExtSym(*I));
 694
 695   // Emit a symbol for each section created until now, skip null section
 696   for (unsigned i = 1, e = SectionList.size(); i < e; ++i) {
 697     ELFSection &ES = *SectionList[i];
 698     ELFSym *SectionSym = ELFSym::getSectionSym();
 699     SectionSym->SectionIdx = ES.SectionIdx;
 700     SymbolList.push_back(SectionSym);
 701     ES.Sym = SymbolList.back();
 702   }
 703
 704   // Emit string table
 705   EmitStringTable(M.getModuleIdentifier());
 706
 707   // Emit the symbol table now, if non-empty.
 708   EmitSymbolTable();
 709
 710   // Emit the relocation sections.
 711   EmitRelocations();
 712
 713   // Emit the sections string table.
 714   EmitSectionTableStringTable();
 715
 716   // Dump the sections and section table to the .o file.
 717   OutputSectionsAndSectionTable();
 718
 719   return false;
 720 }
 721
 722 // RelocateField - Patch relocatable field with 'Offset' in 'BO'
 723 // using a 'Value' of known 'Size'
 724 void ELFWriter::RelocateField(BinaryObject &BO, uint32_t Offset,
 725                               int64_t Value, unsigned Size) {
 726   if (Size == 32)
 727     BO.fixWord32(Value, Offset);
 728   else if (Size == 64)
 729     BO.fixWord64(Value, Offset);
 730   else
 731     llvm_unreachable("don't know howto patch relocatable field");
 732 }
 733
 734 /// EmitRelocations - Emit relocations
 735 void ELFWriter::EmitRelocations() {
 736
 737   // True if the target uses the relocation entry to hold the addend,
 738   // otherwise the addend is written directly to the relocatable field.
 739   bool HasRelA = TEW->hasRelocationAddend();
 740
 741   // Create Relocation sections for each section which needs it.
 742   for (unsigned i=0, e=SectionList.size(); i != e; ++i) {
 743     ELFSection &S = *SectionList[i];
 744
 745     // This section does not have relocations
 746     if (!S.hasRelocations()) continue;
 747     ELFSection &RelSec = getRelocSection(S);
 748
 749     // 'Link' - Section hdr idx of the associated symbol table
 750     // 'Info' - Section hdr idx of the section to which the relocation applies
 751     ELFSection &SymTab = getSymbolTableSection();
 752     RelSec.Link = SymTab.SectionIdx;
 753     RelSec.Info = S.SectionIdx;
 754     RelSec.EntSize = TEW->getRelocationEntrySize();
 755
 756     // Get the relocations from Section
 757     std::vector<MachineRelocation> Relos = S.getRelocations();
 758     for (std::vector<MachineRelocation>::iterator MRI = Relos.begin(),
 759          MRE = Relos.end(); MRI != MRE; ++MRI) {
 760       MachineRelocation &MR = *MRI;
 761
 762       // Relocatable field offset from the section start
 763       unsigned RelOffset = MR.getMachineCodeOffset();
 764
 765       // Symbol index in the symbol table
 766       unsigned SymIdx = 0;
 767
 768       // Target specific relocation field type and size
 769       unsigned RelType = TEW->getRelocationType(MR.getRelocationType());
 770       unsigned RelTySize = TEW->getRelocationTySize(RelType);
 771       int64_t Addend = 0;
 772
 773       // There are several machine relocations types, and each one of
 774       // them needs a different approach to retrieve the symbol table index.
 775       if (MR.isGlobalValue()) {
 776         const GlobalValue *G = MR.getGlobalValue();
 777         int64_t GlobalOffset = MR.getConstantVal();
 778         SymIdx = GblSymLookup[G];
 779         if (G->hasPrivateLinkage()) {
 780           // If the target uses a section offset in the relocation:
 781           // SymIdx + Addend = section sym for global + section offset
 782           unsigned SectionIdx = PrivateSyms[SymIdx]->SectionIdx;
 783           Addend = PrivateSyms[SymIdx]->Value + GlobalOffset;
 784           SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
 785         } else {
 786           Addend = TEW->getDefaultAddendForRelTy(RelType, GlobalOffset);
 787         }
 788       } else if (MR.isExternalSymbol()) {
 789         const char *ExtSym = MR.getExternalSymbol();
 790         SymIdx = ExtSymLookup[ExtSym];
 791         Addend = TEW->getDefaultAddendForRelTy(RelType);
 792       } else {
 793         // Get the symbol index for the section symbol
 794         unsigned SectionIdx = MR.getConstantVal();
 795         SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
 796
 797         // The symbol offset inside the section
 798         int64_t SymOffset = (int64_t)MR.getResultPointer();
 799
 800         // For pc relative relocations where symbols are defined in the same
 801         // section they are referenced, ignore the relocation entry and patch
 802         // the relocatable field with the symbol offset directly.
 803         if (S.SectionIdx == SectionIdx && TEW->isPCRelativeRel(RelType)) {
 804           int64_t Value = TEW->computeRelocation(SymOffset, RelOffset, RelType);
 805           RelocateField(S, RelOffset, Value, RelTySize);
 806           continue;
 807         }
 808
 809         Addend = TEW->getDefaultAddendForRelTy(RelType, SymOffset);
 810       }
 811
 812       // The target without addend on the relocation symbol must be
 813       // patched in the relocation place itself to contain the addend
 814       // otherwise write zeros to make sure there is no garbage there
 815       RelocateField(S, RelOffset, HasRelA ? 0 : Addend, RelTySize);
 816
 817       // Get the relocation entry and emit to the relocation section
 818       ELFRelocation Rel(RelOffset, SymIdx, RelType, HasRelA, Addend);
 819       EmitRelocation(RelSec, Rel, HasRelA);
 820     }
 821   }
 822 }
 823
 824 /// EmitRelocation - Write relocation 'Rel' to the relocation section 'Rel'
 825 void ELFWriter::EmitRelocation(BinaryObject &RelSec, ELFRelocation &Rel,
 826                                bool HasRelA) {
 827   RelSec.emitWord(Rel.getOffset());
 828   RelSec.emitWord(Rel.getInfo(is64Bit));
 829   if (HasRelA)
 830     RelSec.emitWord(Rel.getAddend());
 831 }
 832
 833 /// EmitSymbol - Write symbol 'Sym' to the symbol table 'SymbolTable'
 834 void ELFWriter::EmitSymbol(BinaryObject &SymbolTable, ELFSym &Sym) {
 835   if (is64Bit) {
 836     SymbolTable.emitWord32(Sym.NameIdx);
 837     SymbolTable.emitByte(Sym.Info);
 838     SymbolTable.emitByte(Sym.Other);
 839     SymbolTable.emitWord16(Sym.SectionIdx);
 840     SymbolTable.emitWord64(Sym.Value);
 841     SymbolTable.emitWord64(Sym.Size);
 842   } else {
 843     SymbolTable.emitWord32(Sym.NameIdx);
 844     SymbolTable.emitWord32(Sym.Value);
 845     SymbolTable.emitWord32(Sym.Size);
 846     SymbolTable.emitByte(Sym.Info);
 847     SymbolTable.emitByte(Sym.Other);
 848     SymbolTable.emitWord16(Sym.SectionIdx);
 849   }
 850 }
 851
 852 /// EmitSectionHeader - Write section 'Section' header in 'SHdrTab'
 853 /// Section Header Table
 854 void ELFWriter::EmitSectionHeader(BinaryObject &SHdrTab,
 855                                   const ELFSection &SHdr) {
 856   SHdrTab.emitWord32(SHdr.NameIdx);
 857   SHdrTab.emitWord32(SHdr.Type);
 858   if (is64Bit) {
 859     SHdrTab.emitWord64(SHdr.Flags);
 860     SHdrTab.emitWord(SHdr.Addr);
 861     SHdrTab.emitWord(SHdr.Offset);
 862     SHdrTab.emitWord64(SHdr.Size);
 863     SHdrTab.emitWord32(SHdr.Link);
 864     SHdrTab.emitWord32(SHdr.Info);
 865     SHdrTab.emitWord64(SHdr.Align);
 866     SHdrTab.emitWord64(SHdr.EntSize);
 867   } else {
 868     SHdrTab.emitWord32(SHdr.Flags);
 869     SHdrTab.emitWord(SHdr.Addr);
 870     SHdrTab.emitWord(SHdr.Offset);
 871     SHdrTab.emitWord32(SHdr.Size);
 872     SHdrTab.emitWord32(SHdr.Link);
 873     SHdrTab.emitWord32(SHdr.Info);
 874     SHdrTab.emitWord32(SHdr.Align);
 875     SHdrTab.emitWord32(SHdr.EntSize);
 876   }
 877 }
 878
 879 /// EmitStringTable - If the current symbol table is non-empty, emit the string
 880 /// table for it
 881 void ELFWriter::EmitStringTable(const std::string &ModuleName) {
 882   if (!SymbolList.size()) return;  // Empty symbol table.
 883   ELFSection &StrTab = getStringTableSection();
 884
 885   // Set the zero'th symbol to a null byte, as required.
 886   StrTab.emitByte(0);
 887
 888   // Walk on the symbol list and write symbol names into the string table.
 889   unsigned Index = 1;
 890   for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
 891     ELFSym &Sym = *(*I);
 892
 893     std::string Name;
 894     if (Sym.isGlobalValue()) {
 895       SmallString<40> NameStr;
 896       Mang->getNameWithPrefix(NameStr, Sym.getGlobalValue(), false);
 897       Name.append(NameStr.begin(), NameStr.end());
 898     } else if (Sym.isExternalSym())
 899       Name.append(Sym.getExternalSymbol());
 900     else if (Sym.isFileType())
 901       Name.append(ModuleName);
 902
 903     if (Name.empty()) {
 904       Sym.NameIdx = 0;
 905     } else {
 906       Sym.NameIdx = Index;
 907       StrTab.emitString(Name);
 908
 909       // Keep track of the number of bytes emitted to this section.
 910       Index += Name.size()+1;
 911     }
 912   }
 913   assert(Index == StrTab.size());
 914   StrTab.Size = Index;
 915 }
 916
 917 // SortSymbols - On the symbol table local symbols must come before
 918 // all other symbols with non-local bindings. The return value is
 919 // the position of the first non local symbol.
 920 unsigned ELFWriter::SortSymbols() {
 921   unsigned FirstNonLocalSymbol;
 922   std::vector<ELFSym*> LocalSyms, OtherSyms;
 923
 924   for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
 925     if ((*I)->isLocalBind())
 926       LocalSyms.push_back(*I);
 927     else
 928       OtherSyms.push_back(*I);
 929   }
 930   SymbolList.clear();
 931   FirstNonLocalSymbol = LocalSyms.size();
 932
 933   for (unsigned i = 0; i < FirstNonLocalSymbol; ++i)
 934     SymbolList.push_back(LocalSyms[i]);
 935
 936   for (ELFSymIter I=OtherSyms.begin(), E=OtherSyms.end(); I != E; ++I)
 937     SymbolList.push_back(*I);
 938
 939   LocalSyms.clear();
 940   OtherSyms.clear();
 941
 942   return FirstNonLocalSymbol;
 943 }
 944
 945 /// EmitSymbolTable - Emit the symbol table itself.
 946 void ELFWriter::EmitSymbolTable() {
 947   if (!SymbolList.size()) return;  // Empty symbol table.
 948
 949   // Now that we have emitted the string table and know the offset into the
 950   // string table of each symbol, emit the symbol table itself.
 951   ELFSection &SymTab = getSymbolTableSection();
 952   SymTab.Align = TEW->getPrefELFAlignment();
 953
 954   // Section Index of .strtab.
 955   SymTab.Link = getStringTableSection().SectionIdx;
 956
 957   // Size of each symtab entry.
 958   SymTab.EntSize = TEW->getSymTabEntrySize();
 959
 960   // Reorder the symbol table with local symbols first!
 961   unsigned FirstNonLocalSymbol = SortSymbols();
 962
 963   // Emit all the symbols to the symbol table.
 964   for (unsigned i = 0, e = SymbolList.size(); i < e; ++i) {
 965     ELFSym &Sym = *SymbolList[i];
 966
 967     // Emit symbol to the symbol table
 968     EmitSymbol(SymTab, Sym);
 969
 970     // Record the symbol table index for each symbol
 971     if (Sym.isGlobalValue())
 972       GblSymLookup[Sym.getGlobalValue()] = i;
 973     else if (Sym.isExternalSym())
 974       ExtSymLookup[Sym.getExternalSymbol()] = i;
 975
 976     // Keep track on the symbol index into the symbol table
 977     Sym.SymTabIdx = i;
 978   }
 979
 980   // One greater than the symbol table index of the last local symbol
 981   SymTab.Info = FirstNonLocalSymbol;
 982   SymTab.Size = SymTab.size();
 983 }
 984
 985 /// EmitSectionTableStringTable - This method adds and emits a section for the
 986 /// ELF Section Table string table: the string table that holds all of the
 987 /// section names.
 988 void ELFWriter::EmitSectionTableStringTable() {
 989   // First step: add the section for the string table to the list of sections:
 990   ELFSection &SHStrTab = getSectionHeaderStringTableSection();
 991
 992   // Now that we know which section number is the .shstrtab section, update the
 993   // e_shstrndx entry in the ELF header.
 994   ElfHdr.fixWord16(SHStrTab.SectionIdx, ELFHdr_e_shstrndx_Offset);
 995
 996   // Set the NameIdx of each section in the string table and emit the bytes for
 997   // the string table.
 998   unsigned Index = 0;
 999
1000   for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
1001     ELFSection &S = *(*I);
1002     // Set the index into the table.  Note if we have lots of entries with
1003     // common suffixes, we could memoize them here if we cared.
1004     S.NameIdx = Index;
1005     SHStrTab.emitString(S.getName());
1006
1007     // Keep track of the number of bytes emitted to this section.
1008     Index += S.getName().size()+1;
1009   }
1010
1011   // Set the size of .shstrtab now that we know what it is.
1012   assert(Index == SHStrTab.size());
1013   SHStrTab.Size = Index;
1014 }
1015
1016 /// OutputSectionsAndSectionTable - Now that we have constructed the file header
1017 /// and all of the sections, emit these to the ostream destination and emit the
1018 /// SectionTable.
1019 void ELFWriter::OutputSectionsAndSectionTable() {
1020   // Pass #1: Compute the file offset for each section.
1021   size_t FileOff = ElfHdr.size();   // File header first.
1022
1023   // Adjust alignment of all section if needed, skip the null section.
1024   for (unsigned i=1, e=SectionList.size(); i < e; ++i) {
1025     ELFSection &ES = *SectionList[i];
1026     if (!ES.size()) {
1027       ES.Offset = FileOff;
1028       continue;
1029     }
1030
1031     // Update Section size
1032     if (!ES.Size)
1033       ES.Size = ES.size();
1034
1035     // Align FileOff to whatever the alignment restrictions of the section are.
1036     if (ES.Align)
1037       FileOff = (FileOff+ES.Align-1) & ~(ES.Align-1);
1038
1039     ES.Offset = FileOff;
1040     FileOff += ES.Size;
1041   }
1042
1043   // Align Section Header.
1044   unsigned TableAlign = TEW->getPrefELFAlignment();
1045   FileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
1046
1047   // Now that we know where all of the sections will be emitted, set the e_shnum
1048   // entry in the ELF header.
1049   ElfHdr.fixWord16(NumSections, ELFHdr_e_shnum_Offset);
1050
1051   // Now that we know the offset in the file of the section table, update the
1052   // e_shoff address in the ELF header.
1053   ElfHdr.fixWord(FileOff, ELFHdr_e_shoff_Offset);
1054
1055   // Now that we know all of the data in the file header, emit it and all of the
1056   // sections!
1057   O.write((char *)&ElfHdr.getData()[0], ElfHdr.size());
1058   FileOff = ElfHdr.size();
1059
1060   // Section Header Table blob
1061   BinaryObject SHdrTable(isLittleEndian, is64Bit);
1062
1063   // Emit all of sections to the file and build the section header table.
1064   for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
1065     ELFSection &S = *(*I);
1066     DEBUG(dbgs() << "SectionIdx: " << S.SectionIdx << ", Name: " << S.getName()
1067                  << ", Size: " << S.Size << ", Offset: " << S.Offset
1068                  << ", SectionData Size: " << S.size() << "\n");
1069
1070     // Align FileOff to whatever the alignment restrictions of the section are.
1071     if (S.size()) {
1072       if (S.Align)  {
1073         for (size_t NewFileOff = (FileOff+S.Align-1) & ~(S.Align-1);
1074              FileOff != NewFileOff; ++FileOff)
1075           O << (char)0xAB;
1076       }
1077       O.write((char *)&S.getData()[0], S.Size);
1078       FileOff += S.Size;
1079     }
1080
1081     EmitSectionHeader(SHdrTable, S);
1082   }
1083
1084   // Align output for the section table.
1085   for (size_t NewFileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
1086        FileOff != NewFileOff; ++FileOff)
1087     O << (char)0xAB;
1088
1089   // Emit the section table itself.
1090   O.write((char *)&SHdrTable.getData()[0], SHdrTable.size());
1091 }