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/MCSection.h"
  47 #include "llvm/Target/TargetAsmInfo.h"
  48 #include "llvm/Target/TargetData.h"
  49 #include "llvm/Target/TargetELFWriterInfo.h"
  50 #include "llvm/Target/TargetLowering.h"
  51 #include "llvm/Target/TargetLoweringObjectFile.h"
  52 #include "llvm/Target/TargetMachine.h"
  53 #include "llvm/Support/Mangler.h"
  54 #include "llvm/Support/Streams.h"
  55 #include "llvm/Support/raw_ostream.h"
  56 #include "llvm/Support/Debug.h"
  57 #include "llvm/Support/ErrorHandling.h"
  58
  59 using namespace llvm;
  60
  61 char ELFWriter::ID = 0;
  62
  63 /// AddELFWriter - Add the ELF writer to the function pass manager
  64 ObjectCodeEmitter *llvm::AddELFWriter(PassManagerBase &PM,
  65                                       raw_ostream &O,
  66                                       TargetMachine &TM) {
  67   ELFWriter *EW = new ELFWriter(O, TM);
  68   PM.add(EW);
  69   return EW->getObjectCodeEmitter();
  70 }
  71
  72 //===----------------------------------------------------------------------===//
  73 //                          ELFWriter Implementation
  74 //===----------------------------------------------------------------------===//
  75
  76 ELFWriter::ELFWriter(raw_ostream &o, TargetMachine &tm)
  77   : MachineFunctionPass(&ID), O(o), TM(tm),
  78     OutContext(*new MCContext()),
  79     TLOF(TM.getTargetLowering()->getObjFileLowering()),
  80     is64Bit(TM.getTargetData()->getPointerSizeInBits() == 64),
  81     isLittleEndian(TM.getTargetData()->isLittleEndian()),
  82     ElfHdr(isLittleEndian, is64Bit) {
  83
  84   TAI = TM.getTargetAsmInfo();
  85   TEW = TM.getELFWriterInfo();
  86
  87   // Create the object code emitter object for this target.
  88   ElfCE = new ELFCodeEmitter(*this);
  89
  90   // Inital number of sections
  91   NumSections = 0;
  92 }
  93
  94 ELFWriter::~ELFWriter() {
  95   delete ElfCE;
  96   delete &OutContext;
  97 }
  98
  99 // doInitialization - Emit the file header and all of the global variables for
 100 // the module to the ELF file.
 101 bool ELFWriter::doInitialization(Module &M) {
 102   // Initialize TargetLoweringObjectFile.
 103   const_cast<TargetLoweringObjectFile&>(TLOF).Initialize(OutContext, TM);
 104
 105   Mang = new Mangler(M);
 106
 107   // ELF Header
 108   // ----------
 109   // Fields e_shnum e_shstrndx are only known after all section have
 110   // been emitted. They locations in the ouput buffer are recorded so
 111   // to be patched up later.
 112   //
 113   // Note
 114   // ----
 115   // emitWord method behaves differently for ELF32 and ELF64, writing
 116   // 4 bytes in the former and 8 in the last for *_off and *_addr elf types
 117
 118   ElfHdr.emitByte(0x7f); // e_ident[EI_MAG0]
 119   ElfHdr.emitByte('E');  // e_ident[EI_MAG1]
 120   ElfHdr.emitByte('L');  // e_ident[EI_MAG2]
 121   ElfHdr.emitByte('F');  // e_ident[EI_MAG3]
 122
 123   ElfHdr.emitByte(TEW->getEIClass()); // e_ident[EI_CLASS]
 124   ElfHdr.emitByte(TEW->getEIData());  // e_ident[EI_DATA]
 125   ElfHdr.emitByte(EV_CURRENT);        // e_ident[EI_VERSION]
 126   ElfHdr.emitAlignment(16);           // e_ident[EI_NIDENT-EI_PAD]
 127
 128   ElfHdr.emitWord16(ET_REL);             // e_type
 129   ElfHdr.emitWord16(TEW->getEMachine()); // e_machine = target
 130   ElfHdr.emitWord32(EV_CURRENT);         // e_version
 131   ElfHdr.emitWord(0);                    // e_entry, no entry point in .o file
 132   ElfHdr.emitWord(0);                    // e_phoff, no program header for .o
 133   ELFHdr_e_shoff_Offset = ElfHdr.size();
 134   ElfHdr.emitWord(0);                    // e_shoff = sec hdr table off in bytes
 135   ElfHdr.emitWord32(TEW->getEFlags());   // e_flags = whatever the target wants
 136   ElfHdr.emitWord16(TEW->getHdrSize());  // e_ehsize = ELF header size
 137   ElfHdr.emitWord16(0);                  // e_phentsize = prog header entry size
 138   ElfHdr.emitWord16(0);                  // e_phnum = # prog header entries = 0
 139
 140   // e_shentsize = Section header entry size
 141   ElfHdr.emitWord16(TEW->getSHdrSize());
 142
 143   // e_shnum     = # of section header ents
 144   ELFHdr_e_shnum_Offset = ElfHdr.size();
 145   ElfHdr.emitWord16(0); // Placeholder
 146
 147   // e_shstrndx  = Section # of '.shstrtab'
 148   ELFHdr_e_shstrndx_Offset = ElfHdr.size();
 149   ElfHdr.emitWord16(0); // Placeholder
 150
 151   // Add the null section, which is required to be first in the file.
 152   getNullSection();
 153
 154   // The first entry in the symtab is the null symbol and the second
 155   // is a local symbol containing the module/file name
 156   SymbolList.push_back(new ELFSym());
 157   SymbolList.push_back(ELFSym::getFileSym());
 158
 159   return false;
 160 }
 161
 162 // addGlobalSymbol - Add a global to be processed and to the global symbol
 163 // lookup, use a zero index because the table index will be determined later.
 164 void ELFWriter::addGlobalSymbol(const GlobalValue *GV,
 165                                 bool AddToLookup /* = false */) {
 166   PendingGlobals.insert(GV);
 167   if (AddToLookup)
 168     GblSymLookup[GV] = 0;
 169 }
 170
 171 // addExternalSymbol - Add the external to be processed and to the
 172 // external symbol lookup, use a zero index because the symbol
 173 // table index will be determined later
 174 void ELFWriter::addExternalSymbol(const char *External) {
 175   PendingExternals.insert(External);
 176   ExtSymLookup[External] = 0;
 177 }
 178
 179 // getCtorSection - Get the static constructor section
 180 ELFSection &ELFWriter::getCtorSection() {
 181   const MCSection *Ctor = TLOF.getStaticCtorSection();
 182   return getSection(Ctor->getName(), ELFSection::SHT_PROGBITS,
 183                     getElfSectionFlags(Ctor->getKind()));
 184 }
 185
 186 // getDtorSection - Get the static destructor section
 187 ELFSection &ELFWriter::getDtorSection() {
 188   const MCSection *Dtor = TLOF.getStaticDtorSection();
 189   return getSection(Dtor->getName(), ELFSection::SHT_PROGBITS,
 190                     getElfSectionFlags(Dtor->getKind()));
 191 }
 192
 193 // getTextSection - Get the text section for the specified function
 194 ELFSection &ELFWriter::getTextSection(Function *F) {
 195   const MCSection *Text = TLOF.SectionForGlobal(F, Mang, TM);
 196   return getSection(Text->getName(), ELFSection::SHT_PROGBITS,
 197                     getElfSectionFlags(Text->getKind()));
 198 }
 199
 200 // getJumpTableSection - Get a read only section for constants when
 201 // emitting jump tables. TODO: add PIC support
 202 ELFSection &ELFWriter::getJumpTableSection() {
 203   const MCSection *JT = TLOF.getSectionForConstant(SectionKind::getReadOnly());
 204   return getSection(JT->getName(),
 205                     ELFSection::SHT_PROGBITS,
 206                     getElfSectionFlags(JT->getKind()),
 207                     TM.getTargetData()->getPointerABIAlignment());
 208 }
 209
 210 // getConstantPoolSection - Get a constant pool section based on the machine
 211 // constant pool entry type and relocation info.
 212 ELFSection &ELFWriter::getConstantPoolSection(MachineConstantPoolEntry &CPE) {
 213   SectionKind Kind;
 214   switch (CPE.getRelocationInfo()) {
 215   default: llvm_unreachable("Unknown section kind");
 216   case 2: Kind = SectionKind::getReadOnlyWithRel(); break;
 217   case 1:
 218     Kind = SectionKind::getReadOnlyWithRelLocal();
 219     break;
 220   case 0:
 221     switch (TM.getTargetData()->getTypeAllocSize(CPE.getType())) {
 222     case 4:  Kind = SectionKind::getMergeableConst4(); break;
 223     case 8:  Kind = SectionKind::getMergeableConst8(); break;
 224     case 16: Kind = SectionKind::getMergeableConst16(); break;
 225     default: Kind = SectionKind::getMergeableConst(); break;
 226     }
 227   }
 228
 229   return getSection(TLOF.getSectionForConstant(Kind)->getName(),
 230                     ELFSection::SHT_PROGBITS,
 231                     getElfSectionFlags(Kind),
 232                     CPE.getAlignment());
 233 }
 234
 235 // getRelocSection - Return the relocation section of section 'S'. 'RelA'
 236 // is true if the relocation section contains entries with addends.
 237 ELFSection &ELFWriter::getRelocSection(ELFSection &S) {
 238   unsigned SectionHeaderTy = TEW->hasRelocationAddend() ?
 239                               ELFSection::SHT_RELA : ELFSection::SHT_REL;
 240   std::string RelSName(".rel");
 241   if (TEW->hasRelocationAddend())
 242     RelSName.append("a");
 243   RelSName.append(S.getName());
 244
 245   return getSection(RelSName, SectionHeaderTy, 0, TEW->getPrefELFAlignment());
 246 }
 247
 248 // getGlobalELFVisibility - Returns the ELF specific visibility type
 249 unsigned ELFWriter::getGlobalELFVisibility(const GlobalValue *GV) {
 250   switch (GV->getVisibility()) {
 251   default:
 252     llvm_unreachable("unknown visibility type");
 253   case GlobalValue::DefaultVisibility:
 254     return ELFSym::STV_DEFAULT;
 255   case GlobalValue::HiddenVisibility:
 256     return ELFSym::STV_HIDDEN;
 257   case GlobalValue::ProtectedVisibility:
 258     return ELFSym::STV_PROTECTED;
 259   }
 260   return 0;
 261 }
 262
 263 // getGlobalELFBinding - Returns the ELF specific binding type
 264 unsigned ELFWriter::getGlobalELFBinding(const GlobalValue *GV) {
 265   if (GV->hasInternalLinkage())
 266     return ELFSym::STB_LOCAL;
 267
 268   if (GV->isWeakForLinker() && !GV->hasCommonLinkage())
 269     return ELFSym::STB_WEAK;
 270
 271   return ELFSym::STB_GLOBAL;
 272 }
 273
 274 // getGlobalELFType - Returns the ELF specific type for a global
 275 unsigned ELFWriter::getGlobalELFType(const GlobalValue *GV) {
 276   if (GV->isDeclaration())
 277     return ELFSym::STT_NOTYPE;
 278
 279   if (isa<Function>(GV))
 280     return ELFSym::STT_FUNC;
 281
 282   return ELFSym::STT_OBJECT;
 283 }
 284
 285 // getElfSectionFlags - Get the ELF Section Header flags based
 286 // on the flags defined in SectionKind.h.
 287 unsigned ELFWriter::getElfSectionFlags(SectionKind Kind, bool IsAlloc) {
 288   unsigned ElfSectionFlags = 0;
 289
 290   if (IsAlloc)
 291     ElfSectionFlags |= ELFSection::SHF_ALLOC;
 292   if (Kind.isText())
 293     ElfSectionFlags |= ELFSection::SHF_EXECINSTR;
 294   if (Kind.isWriteable())
 295     ElfSectionFlags |= ELFSection::SHF_WRITE;
 296   if (Kind.isMergeableConst() || Kind.isMergeableCString())
 297     ElfSectionFlags |= ELFSection::SHF_MERGE;
 298   if (Kind.isThreadLocal())
 299     ElfSectionFlags |= ELFSection::SHF_TLS;
 300   if (Kind.isMergeableCString())
 301     ElfSectionFlags |= ELFSection::SHF_STRINGS;
 302
 303   return ElfSectionFlags;
 304 }
 305
 306 // isUndefOrNull - The constant is either a null initialized value or an
 307 // undefined one.
 308 static bool isUndefOrNull(const Constant *CV) {
 309   return (CV->isNullValue() || isa<UndefValue>(CV));
 310 }
 311
 312 // isELFUndefSym - the symbol has no section and must be placed in
 313 // the symbol table with a reference to the null section.
 314 static bool isELFUndefSym(const GlobalValue *GV) {
 315   // Functions which make up until this point references are an undef symbol
 316   return GV->isDeclaration() || (isa<Function>(GV));
 317 }
 318
 319 // isELFBssSym - for an undef or null value, the symbol must go to a bss
 320 // section if it's not weak for linker, otherwise it's a common sym.
 321 static bool isELFBssSym(const GlobalVariable *GV, SectionKind Kind) {
 322   const Constant *CV = GV->getInitializer();
 323
 324   return (!Kind.isMergeableCString() &&
 325           isUndefOrNull(CV) &&
 326           !GV->isWeakForLinker());
 327 }
 328
 329 // isELFCommonSym - for an undef or null value, the symbol must go to a
 330 // common section if it's weak for linker, otherwise bss.
 331 static bool isELFCommonSym(const GlobalVariable *GV) {
 332   return (isUndefOrNull(GV->getInitializer()) && GV->isWeakForLinker());
 333 }
 334
 335 // EmitGlobal - Choose the right section for global and emit it
 336 void ELFWriter::EmitGlobal(const GlobalValue *GV) {
 337
 338   // Check if the referenced symbol is already emitted
 339   if (GblSymLookup.find(GV) != GblSymLookup.end())
 340     return;
 341
 342   // Handle ELF Bind, Visibility and Type for the current symbol
 343   unsigned SymBind = getGlobalELFBinding(GV);
 344   unsigned SymType = getGlobalELFType(GV);
 345
 346   // All undef symbols have the same binding, type and visibily and
 347   // are classified regardless of their type.
 348   ELFSym *GblSym = isELFUndefSym(GV) ? ELFSym::getUndefGV(GV, SymBind)
 349     : ELFSym::getGV(GV, SymBind, SymType, getGlobalELFVisibility(GV));
 350
 351   if (!isELFUndefSym(GV)) {
 352     assert(isa<GlobalVariable>(GV) && "GV not a global variable!");
 353     const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV);
 354
 355     // Handle special llvm globals
 356     if (EmitSpecialLLVMGlobal(GVar))
 357       return;
 358
 359     // Get the ELF section where this global belongs from TLOF
 360     const MCSection *S = TLOF.SectionForGlobal(GV, Mang, TM);
 361     SectionKind Kind = ((MCSectionELF*)S)->getKind();
 362     unsigned SectionFlags = getElfSectionFlags(Kind);
 363
 364     // The symbol align should update the section alignment if needed
 365     const TargetData *TD = TM.getTargetData();
 366     unsigned Align = TD->getPreferredAlignment(GVar);
 367     unsigned Size = TD->getTypeAllocSize(GVar->getInitializer()->getType());
 368     GblSym->Size = Size;
 369
 370     if (isELFCommonSym(GVar)) {
 371       GblSym->SectionIdx = ELFSection::SHN_COMMON;
 372       getSection(S->getName(), ELFSection::SHT_NOBITS, SectionFlags, 1);
 373
 374       // A new linkonce section is created for each global in the
 375       // common section, the default alignment is 1 and the symbol
 376       // value contains its alignment.
 377       GblSym->Value = Align;
 378
 379     } else if (isELFBssSym(GVar, Kind)) {
 380       ELFSection &ES =
 381         getSection(S->getName(), ELFSection::SHT_NOBITS, SectionFlags);
 382       GblSym->SectionIdx = ES.SectionIdx;
 383
 384       // Update the size with alignment and the next object can
 385       // start in the right offset in the section
 386       if (Align) ES.Size = (ES.Size + Align-1) & ~(Align-1);
 387       ES.Align = std::max(ES.Align, Align);
 388
 389       // GblSym->Value should contain the virtual offset inside the section.
 390       // Virtual because the BSS space is not allocated on ELF objects
 391       GblSym->Value = ES.Size;
 392       ES.Size += Size;
 393
 394     } else { // The symbol must go to some kind of data section
 395       ELFSection &ES =
 396         getSection(S->getName(), ELFSection::SHT_PROGBITS, SectionFlags);
 397       GblSym->SectionIdx = ES.SectionIdx;
 398
 399       // GblSym->Value should contain the symbol offset inside the section,
 400       // and all symbols should start on their required alignment boundary
 401       ES.Align = std::max(ES.Align, Align);
 402       ES.emitAlignment(Align);
 403       GblSym->Value = ES.size();
 404
 405       // Emit the global to the data section 'ES'
 406       EmitGlobalConstant(GVar->getInitializer(), ES);
 407     }
 408   }
 409
 410   if (GV->hasPrivateLinkage()) {
 411     // For a private symbols, keep track of the index inside the
 412     // private list since it will never go to the symbol table and
 413     // won't be patched up later.
 414     PrivateSyms.push_back(GblSym);
 415     GblSymLookup[GV] = PrivateSyms.size()-1;
 416   } else {
 417     // Non private symbol are left with zero indices until they are patched
 418     // up during the symbol table emition (where the indicies are created).
 419     SymbolList.push_back(GblSym);
 420     GblSymLookup[GV] = 0;
 421   }
 422 }
 423
 424 void ELFWriter::EmitGlobalConstantStruct(const ConstantStruct *CVS,
 425                                          ELFSection &GblS) {
 426
 427   // Print the fields in successive locations. Pad to align if needed!
 428   const TargetData *TD = TM.getTargetData();
 429   unsigned Size = TD->getTypeAllocSize(CVS->getType());
 430   const StructLayout *cvsLayout = TD->getStructLayout(CVS->getType());
 431   uint64_t sizeSoFar = 0;
 432   for (unsigned i = 0, e = CVS->getNumOperands(); i != e; ++i) {
 433     const Constant* field = CVS->getOperand(i);
 434
 435     // Check if padding is needed and insert one or more 0s.
 436     uint64_t fieldSize = TD->getTypeAllocSize(field->getType());
 437     uint64_t padSize = ((i == e-1 ? Size : cvsLayout->getElementOffset(i+1))
 438                         - cvsLayout->getElementOffset(i)) - fieldSize;
 439     sizeSoFar += fieldSize + padSize;
 440
 441     // Now print the actual field value.
 442     EmitGlobalConstant(field, GblS);
 443
 444     // Insert padding - this may include padding to increase the size of the
 445     // current field up to the ABI size (if the struct is not packed) as well
 446     // as padding to ensure that the next field starts at the right offset.
 447     GblS.emitZeros(padSize);
 448   }
 449   assert(sizeSoFar == cvsLayout->getSizeInBytes() &&
 450          "Layout of constant struct may be incorrect!");
 451 }
 452
 453 void ELFWriter::EmitGlobalConstant(const Constant *CV, ELFSection &GblS) {
 454   const TargetData *TD = TM.getTargetData();
 455   unsigned Size = TD->getTypeAllocSize(CV->getType());
 456
 457   if (const ConstantArray *CVA = dyn_cast<ConstantArray>(CV)) {
 458     for (unsigned i = 0, e = CVA->getNumOperands(); i != e; ++i)
 459       EmitGlobalConstant(CVA->getOperand(i), GblS);
 460     return;
 461   } else if (isa<ConstantAggregateZero>(CV)) {
 462     GblS.emitZeros(Size);
 463     return;
 464   } else if (const ConstantStruct *CVS = dyn_cast<ConstantStruct>(CV)) {
 465     EmitGlobalConstantStruct(CVS, GblS);
 466     return;
 467   } else if (const ConstantFP *CFP = dyn_cast<ConstantFP>(CV)) {
 468     APInt Val = CFP->getValueAPF().bitcastToAPInt();
 469     if (CFP->getType() == Type::DoubleTy)
 470       GblS.emitWord64(Val.getZExtValue());
 471     else if (CFP->getType() == Type::FloatTy)
 472       GblS.emitWord32(Val.getZExtValue());
 473     else if (CFP->getType() == Type::X86_FP80Ty) {
 474       unsigned PadSize = TD->getTypeAllocSize(Type::X86_FP80Ty)-
 475                          TD->getTypeStoreSize(Type::X86_FP80Ty);
 476       GblS.emitWordFP80(Val.getRawData(), PadSize);
 477     } else if (CFP->getType() == Type::PPC_FP128Ty)
 478       llvm_unreachable("PPC_FP128Ty global emission not implemented");
 479     return;
 480   } else if (const ConstantInt *CI = dyn_cast<ConstantInt>(CV)) {
 481     if (Size == 1)
 482       GblS.emitByte(CI->getZExtValue());
 483     else if (Size == 2)
 484       GblS.emitWord16(CI->getZExtValue());
 485     else if (Size == 4)
 486       GblS.emitWord32(CI->getZExtValue());
 487     else
 488       EmitGlobalConstantLargeInt(CI, GblS);
 489     return;
 490   } else if (const ConstantVector *CP = dyn_cast<ConstantVector>(CV)) {
 491     const VectorType *PTy = CP->getType();
 492     for (unsigned I = 0, E = PTy->getNumElements(); I < E; ++I)
 493       EmitGlobalConstant(CP->getOperand(I), GblS);
 494     return;
 495   } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV)) {
 496     switch (CE->getOpcode()) {
 497     case Instruction::BitCast: {
 498       EmitGlobalConstant(CE->getOperand(0), GblS);
 499       return;
 500     }
 501     case Instruction::GetElementPtr: {
 502       const Constant *ptrVal = CE->getOperand(0);
 503       SmallVector<Value*, 8> idxVec(CE->op_begin()+1, CE->op_end());
 504       int64_t Offset = TD->getIndexedOffset(ptrVal->getType(), &idxVec[0],
 505                                             idxVec.size());
 506       EmitGlobalDataRelocation(cast<const GlobalValue>(ptrVal),
 507                                TD->getTypeAllocSize(ptrVal->getType()),
 508                                GblS, Offset);
 509       return;
 510     }
 511     case Instruction::IntToPtr: {
 512       Constant *Op = CE->getOperand(0);
 513       Op = ConstantExpr::getIntegerCast(Op, TD->getIntPtrType(), false/*ZExt*/);
 514       EmitGlobalConstant(Op, GblS);
 515       return;
 516     }
 517     }
 518     std::string msg(CE->getOpcodeName());
 519     raw_string_ostream ErrorMsg(msg);
 520     ErrorMsg << ": Unsupported ConstantExpr type";
 521     llvm_report_error(ErrorMsg.str());
 522   } else if (CV->getType()->getTypeID() == Type::PointerTyID) {
 523     // Fill the data entry with zeros or emit a relocation entry
 524     if (isa<ConstantPointerNull>(CV))
 525       GblS.emitZeros(Size);
 526     else
 527       EmitGlobalDataRelocation(cast<const GlobalValue>(CV),
 528                                Size, GblS);
 529     return;
 530   } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CV)) {
 531     // This is a constant address for a global variable or function and
 532     // therefore must be referenced using a relocation entry.
 533     EmitGlobalDataRelocation(GV, Size, GblS);
 534     return;
 535   }
 536
 537   std::string msg;
 538   raw_string_ostream ErrorMsg(msg);
 539   ErrorMsg << "Constant unimp for type: " << *CV->getType();
 540   llvm_report_error(ErrorMsg.str());
 541 }
 542
 543 void ELFWriter::EmitGlobalDataRelocation(const GlobalValue *GV, unsigned Size,
 544                                          ELFSection &GblS, uint64_t Offset) {
 545   // Create the relocation entry for the global value
 546   MachineRelocation MR =
 547     MachineRelocation::getGV(GblS.getCurrentPCOffset(),
 548                              TEW->getAbsoluteLabelMachineRelTy(),
 549                              const_cast<GlobalValue*>(GV),
 550                              Offset);
 551
 552   // Fill the data entry with zeros
 553   GblS.emitZeros(Size);
 554
 555   // Add the relocation entry for the current data section
 556   GblS.addRelocation(MR);
 557 }
 558
 559 void ELFWriter::EmitGlobalConstantLargeInt(const ConstantInt *CI,
 560                                            ELFSection &S) {
 561   const TargetData *TD = TM.getTargetData();
 562   unsigned BitWidth = CI->getBitWidth();
 563   assert(isPowerOf2_32(BitWidth) &&
 564          "Non-power-of-2-sized integers not handled!");
 565
 566   const uint64_t *RawData = CI->getValue().getRawData();
 567   uint64_t Val = 0;
 568   for (unsigned i = 0, e = BitWidth / 64; i != e; ++i) {
 569     Val = (TD->isBigEndian()) ? RawData[e - i - 1] : RawData[i];
 570     S.emitWord64(Val);
 571   }
 572 }
 573
 574 /// EmitSpecialLLVMGlobal - Check to see if the specified global is a
 575 /// special global used by LLVM.  If so, emit it and return true, otherwise
 576 /// do nothing and return false.
 577 bool ELFWriter::EmitSpecialLLVMGlobal(const GlobalVariable *GV) {
 578   if (GV->getName() == "llvm.used")
 579     llvm_unreachable("not implemented yet");
 580
 581   // Ignore debug and non-emitted data.  This handles llvm.compiler.used.
 582   if (GV->getSection() == "llvm.metadata" ||
 583       GV->hasAvailableExternallyLinkage())
 584     return true;
 585
 586   if (!GV->hasAppendingLinkage()) return false;
 587
 588   assert(GV->hasInitializer() && "Not a special LLVM global!");
 589
 590   const TargetData *TD = TM.getTargetData();
 591   unsigned Align = TD->getPointerPrefAlignment();
 592   if (GV->getName() == "llvm.global_ctors") {
 593     ELFSection &Ctor = getCtorSection();
 594     Ctor.emitAlignment(Align);
 595     EmitXXStructorList(GV->getInitializer(), Ctor);
 596     return true;
 597   }
 598
 599   if (GV->getName() == "llvm.global_dtors") {
 600     ELFSection &Dtor = getDtorSection();
 601     Dtor.emitAlignment(Align);
 602     EmitXXStructorList(GV->getInitializer(), Dtor);
 603     return true;
 604   }
 605
 606   return false;
 607 }
 608
 609 /// EmitXXStructorList - Emit the ctor or dtor list.  This just emits out the
 610 /// function pointers, ignoring the init priority.
 611 void ELFWriter::EmitXXStructorList(Constant *List, ELFSection &Xtor) {
 612   // Should be an array of '{ int, void ()* }' structs.  The first value is the
 613   // init priority, which we ignore.
 614   if (!isa<ConstantArray>(List)) return;
 615   ConstantArray *InitList = cast<ConstantArray>(List);
 616   for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i)
 617     if (ConstantStruct *CS = dyn_cast<ConstantStruct>(InitList->getOperand(i))){
 618       if (CS->getNumOperands() != 2) return;  // Not array of 2-element structs.
 619
 620       if (CS->getOperand(1)->isNullValue())
 621         return;  // Found a null terminator, exit printing.
 622       // Emit the function pointer.
 623       EmitGlobalConstant(CS->getOperand(1), Xtor);
 624     }
 625 }
 626
 627 bool ELFWriter::runOnMachineFunction(MachineFunction &MF) {
 628   // Nothing to do here, this is all done through the ElfCE object above.
 629   return false;
 630 }
 631
 632 /// doFinalization - Now that the module has been completely processed, emit
 633 /// the ELF file to 'O'.
 634 bool ELFWriter::doFinalization(Module &M) {
 635   // Emit .data section placeholder
 636   getDataSection();
 637
 638   // Emit .bss section placeholder
 639   getBSSSection();
 640
 641   // Build and emit data, bss and "common" sections.
 642   for (Module::global_iterator I = M.global_begin(), E = M.global_end();
 643        I != E; ++I)
 644     EmitGlobal(I);
 645
 646   // Emit all pending globals
 647   for (PendingGblsIter I = PendingGlobals.begin(), E = PendingGlobals.end();
 648        I != E; ++I)
 649     EmitGlobal(*I);
 650
 651   // Emit all pending externals
 652   for (PendingExtsIter I = PendingExternals.begin(), E = PendingExternals.end();
 653        I != E; ++I)
 654     SymbolList.push_back(ELFSym::getExtSym(*I));
 655
 656   // Emit non-executable stack note
 657   if (TAI->getNonexecutableStackDirective())
 658     getNonExecStackSection();
 659
 660   // Emit a symbol for each section created until now, skip null section
 661   for (unsigned i = 1, e = SectionList.size(); i < e; ++i) {
 662     ELFSection &ES = *SectionList[i];
 663     ELFSym *SectionSym = ELFSym::getSectionSym();
 664     SectionSym->SectionIdx = ES.SectionIdx;
 665     SymbolList.push_back(SectionSym);
 666     ES.Sym = SymbolList.back();
 667   }
 668
 669   // Emit string table
 670   EmitStringTable(M.getModuleIdentifier());
 671
 672   // Emit the symbol table now, if non-empty.
 673   EmitSymbolTable();
 674
 675   // Emit the relocation sections.
 676   EmitRelocations();
 677
 678   // Emit the sections string table.
 679   EmitSectionTableStringTable();
 680
 681   // Dump the sections and section table to the .o file.
 682   OutputSectionsAndSectionTable();
 683
 684   // We are done with the abstract symbols.
 685   SymbolList.clear();
 686   SectionList.clear();
 687   NumSections = 0;
 688
 689   // Release the name mangler object.
 690   delete Mang; Mang = 0;
 691   return false;
 692 }
 693
 694 // RelocateField - Patch relocatable field with 'Offset' in 'BO'
 695 // using a 'Value' of known 'Size'
 696 void ELFWriter::RelocateField(BinaryObject &BO, uint32_t Offset,
 697                               int64_t Value, unsigned Size) {
 698   if (Size == 32)
 699     BO.fixWord32(Value, Offset);
 700   else if (Size == 64)
 701     BO.fixWord64(Value, Offset);
 702   else
 703     llvm_unreachable("don't know howto patch relocatable field");
 704 }
 705
 706 /// EmitRelocations - Emit relocations
 707 void ELFWriter::EmitRelocations() {
 708
 709   // True if the target uses the relocation entry to hold the addend,
 710   // otherwise the addend is written directly to the relocatable field.
 711   bool HasRelA = TEW->hasRelocationAddend();
 712
 713   // Create Relocation sections for each section which needs it.
 714   for (unsigned i=0, e=SectionList.size(); i != e; ++i) {
 715     ELFSection &S = *SectionList[i];
 716
 717     // This section does not have relocations
 718     if (!S.hasRelocations()) continue;
 719     ELFSection &RelSec = getRelocSection(S);
 720
 721     // 'Link' - Section hdr idx of the associated symbol table
 722     // 'Info' - Section hdr idx of the section to which the relocation applies
 723     ELFSection &SymTab = getSymbolTableSection();
 724     RelSec.Link = SymTab.SectionIdx;
 725     RelSec.Info = S.SectionIdx;
 726     RelSec.EntSize = TEW->getRelocationEntrySize();
 727
 728     // Get the relocations from Section
 729     std::vector<MachineRelocation> Relos = S.getRelocations();
 730     for (std::vector<MachineRelocation>::iterator MRI = Relos.begin(),
 731          MRE = Relos.end(); MRI != MRE; ++MRI) {
 732       MachineRelocation &MR = *MRI;
 733
 734       // Relocatable field offset from the section start
 735       unsigned RelOffset = MR.getMachineCodeOffset();
 736
 737       // Symbol index in the symbol table
 738       unsigned SymIdx = 0;
 739
 740       // Target specific relocation field type and size
 741       unsigned RelType = TEW->getRelocationType(MR.getRelocationType());
 742       unsigned RelTySize = TEW->getRelocationTySize(RelType);
 743       int64_t Addend = 0;
 744
 745       // There are several machine relocations types, and each one of
 746       // them needs a different approach to retrieve the symbol table index.
 747       if (MR.isGlobalValue()) {
 748         const GlobalValue *G = MR.getGlobalValue();
 749         int64_t GlobalOffset = MR.getConstantVal();
 750         SymIdx = GblSymLookup[G];
 751         if (G->hasPrivateLinkage()) {
 752           // If the target uses a section offset in the relocation:
 753           // SymIdx + Addend = section sym for global + section offset
 754           unsigned SectionIdx = PrivateSyms[SymIdx]->SectionIdx;
 755           Addend = PrivateSyms[SymIdx]->Value + GlobalOffset;
 756           SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
 757         } else {
 758           Addend = TEW->getDefaultAddendForRelTy(RelType, GlobalOffset);
 759         }
 760       } else if (MR.isExternalSymbol()) {
 761         const char *ExtSym = MR.getExternalSymbol();
 762         SymIdx = ExtSymLookup[ExtSym];
 763         Addend = TEW->getDefaultAddendForRelTy(RelType);
 764       } else {
 765         // Get the symbol index for the section symbol
 766         unsigned SectionIdx = MR.getConstantVal();
 767         SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
 768
 769         // The symbol offset inside the section
 770         int64_t SymOffset = (int64_t)MR.getResultPointer();
 771
 772         // For pc relative relocations where symbols are defined in the same
 773         // section they are referenced, ignore the relocation entry and patch
 774         // the relocatable field with the symbol offset directly.
 775         if (S.SectionIdx == SectionIdx && TEW->isPCRelativeRel(RelType)) {
 776           int64_t Value = TEW->computeRelocation(SymOffset, RelOffset, RelType);
 777           RelocateField(S, RelOffset, Value, RelTySize);
 778           continue;
 779         }
 780
 781         Addend = TEW->getDefaultAddendForRelTy(RelType, SymOffset);
 782       }
 783
 784       // The target without addend on the relocation symbol must be
 785       // patched in the relocation place itself to contain the addend
 786       // otherwise write zeros to make sure there is no garbage there
 787       RelocateField(S, RelOffset, HasRelA ? 0 : Addend, RelTySize);
 788
 789       // Get the relocation entry and emit to the relocation section
 790       ELFRelocation Rel(RelOffset, SymIdx, RelType, HasRelA, Addend);
 791       EmitRelocation(RelSec, Rel, HasRelA);
 792     }
 793   }
 794 }
 795
 796 /// EmitRelocation - Write relocation 'Rel' to the relocation section 'Rel'
 797 void ELFWriter::EmitRelocation(BinaryObject &RelSec, ELFRelocation &Rel,
 798                                bool HasRelA) {
 799   RelSec.emitWord(Rel.getOffset());
 800   RelSec.emitWord(Rel.getInfo(is64Bit));
 801   if (HasRelA)
 802     RelSec.emitWord(Rel.getAddend());
 803 }
 804
 805 /// EmitSymbol - Write symbol 'Sym' to the symbol table 'SymbolTable'
 806 void ELFWriter::EmitSymbol(BinaryObject &SymbolTable, ELFSym &Sym) {
 807   if (is64Bit) {
 808     SymbolTable.emitWord32(Sym.NameIdx);
 809     SymbolTable.emitByte(Sym.Info);
 810     SymbolTable.emitByte(Sym.Other);
 811     SymbolTable.emitWord16(Sym.SectionIdx);
 812     SymbolTable.emitWord64(Sym.Value);
 813     SymbolTable.emitWord64(Sym.Size);
 814   } else {
 815     SymbolTable.emitWord32(Sym.NameIdx);
 816     SymbolTable.emitWord32(Sym.Value);
 817     SymbolTable.emitWord32(Sym.Size);
 818     SymbolTable.emitByte(Sym.Info);
 819     SymbolTable.emitByte(Sym.Other);
 820     SymbolTable.emitWord16(Sym.SectionIdx);
 821   }
 822 }
 823
 824 /// EmitSectionHeader - Write section 'Section' header in 'SHdrTab'
 825 /// Section Header Table
 826 void ELFWriter::EmitSectionHeader(BinaryObject &SHdrTab,
 827                                   const ELFSection &SHdr) {
 828   SHdrTab.emitWord32(SHdr.NameIdx);
 829   SHdrTab.emitWord32(SHdr.Type);
 830   if (is64Bit) {
 831     SHdrTab.emitWord64(SHdr.Flags);
 832     SHdrTab.emitWord(SHdr.Addr);
 833     SHdrTab.emitWord(SHdr.Offset);
 834     SHdrTab.emitWord64(SHdr.Size);
 835     SHdrTab.emitWord32(SHdr.Link);
 836     SHdrTab.emitWord32(SHdr.Info);
 837     SHdrTab.emitWord64(SHdr.Align);
 838     SHdrTab.emitWord64(SHdr.EntSize);
 839   } else {
 840     SHdrTab.emitWord32(SHdr.Flags);
 841     SHdrTab.emitWord(SHdr.Addr);
 842     SHdrTab.emitWord(SHdr.Offset);
 843     SHdrTab.emitWord32(SHdr.Size);
 844     SHdrTab.emitWord32(SHdr.Link);
 845     SHdrTab.emitWord32(SHdr.Info);
 846     SHdrTab.emitWord32(SHdr.Align);
 847     SHdrTab.emitWord32(SHdr.EntSize);
 848   }
 849 }
 850
 851 /// EmitStringTable - If the current symbol table is non-empty, emit the string
 852 /// table for it
 853 void ELFWriter::EmitStringTable(const std::string &ModuleName) {
 854   if (!SymbolList.size()) return;  // Empty symbol table.
 855   ELFSection &StrTab = getStringTableSection();
 856
 857   // Set the zero'th symbol to a null byte, as required.
 858   StrTab.emitByte(0);
 859
 860   // Walk on the symbol list and write symbol names into the string table.
 861   unsigned Index = 1;
 862   for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
 863     ELFSym &Sym = *(*I);
 864
 865     std::string Name;
 866     if (Sym.isGlobalValue())
 867       // Use the name mangler to uniquify the LLVM symbol.
 868       Name.append(Mang->getMangledName(Sym.getGlobalValue()));
 869     else if (Sym.isExternalSym())
 870       Name.append(Sym.getExternalSymbol());
 871     else if (Sym.isFileType())
 872       Name.append(ModuleName);
 873
 874     if (Name.empty()) {
 875       Sym.NameIdx = 0;
 876     } else {
 877       Sym.NameIdx = Index;
 878       StrTab.emitString(Name);
 879
 880       // Keep track of the number of bytes emitted to this section.
 881       Index += Name.size()+1;
 882     }
 883   }
 884   assert(Index == StrTab.size());
 885   StrTab.Size = Index;
 886 }
 887
 888 // SortSymbols - On the symbol table local symbols must come before
 889 // all other symbols with non-local bindings. The return value is
 890 // the position of the first non local symbol.
 891 unsigned ELFWriter::SortSymbols() {
 892   unsigned FirstNonLocalSymbol;
 893   std::vector<ELFSym*> LocalSyms, OtherSyms;
 894
 895   for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
 896     if ((*I)->isLocalBind())
 897       LocalSyms.push_back(*I);
 898     else
 899       OtherSyms.push_back(*I);
 900   }
 901   SymbolList.clear();
 902   FirstNonLocalSymbol = LocalSyms.size();
 903
 904   for (unsigned i = 0; i < FirstNonLocalSymbol; ++i)
 905     SymbolList.push_back(LocalSyms[i]);
 906
 907   for (ELFSymIter I=OtherSyms.begin(), E=OtherSyms.end(); I != E; ++I)
 908     SymbolList.push_back(*I);
 909
 910   LocalSyms.clear();
 911   OtherSyms.clear();
 912
 913   return FirstNonLocalSymbol;
 914 }
 915
 916 /// EmitSymbolTable - Emit the symbol table itself.
 917 void ELFWriter::EmitSymbolTable() {
 918   if (!SymbolList.size()) return;  // Empty symbol table.
 919
 920   // Now that we have emitted the string table and know the offset into the
 921   // string table of each symbol, emit the symbol table itself.
 922   ELFSection &SymTab = getSymbolTableSection();
 923   SymTab.Align = TEW->getPrefELFAlignment();
 924
 925   // Section Index of .strtab.
 926   SymTab.Link = getStringTableSection().SectionIdx;
 927
 928   // Size of each symtab entry.
 929   SymTab.EntSize = TEW->getSymTabEntrySize();
 930
 931   // Reorder the symbol table with local symbols first!
 932   unsigned FirstNonLocalSymbol = SortSymbols();
 933
 934   // Emit all the symbols to the symbol table.
 935   for (unsigned i = 0, e = SymbolList.size(); i < e; ++i) {
 936     ELFSym &Sym = *SymbolList[i];
 937
 938     // Emit symbol to the symbol table
 939     EmitSymbol(SymTab, Sym);
 940
 941     // Record the symbol table index for each symbol
 942     if (Sym.isGlobalValue())
 943       GblSymLookup[Sym.getGlobalValue()] = i;
 944     else if (Sym.isExternalSym())
 945       ExtSymLookup[Sym.getExternalSymbol()] = i;
 946
 947     // Keep track on the symbol index into the symbol table
 948     Sym.SymTabIdx = i;
 949   }
 950
 951   // One greater than the symbol table index of the last local symbol
 952   SymTab.Info = FirstNonLocalSymbol;
 953   SymTab.Size = SymTab.size();
 954 }
 955
 956 /// EmitSectionTableStringTable - This method adds and emits a section for the
 957 /// ELF Section Table string table: the string table that holds all of the
 958 /// section names.
 959 void ELFWriter::EmitSectionTableStringTable() {
 960   // First step: add the section for the string table to the list of sections:
 961   ELFSection &SHStrTab = getSectionHeaderStringTableSection();
 962
 963   // Now that we know which section number is the .shstrtab section, update the
 964   // e_shstrndx entry in the ELF header.
 965   ElfHdr.fixWord16(SHStrTab.SectionIdx, ELFHdr_e_shstrndx_Offset);
 966
 967   // Set the NameIdx of each section in the string table and emit the bytes for
 968   // the string table.
 969   unsigned Index = 0;
 970
 971   for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
 972     ELFSection &S = *(*I);
 973     // Set the index into the table.  Note if we have lots of entries with
 974     // common suffixes, we could memoize them here if we cared.
 975     S.NameIdx = Index;
 976     SHStrTab.emitString(S.getName());
 977
 978     // Keep track of the number of bytes emitted to this section.
 979     Index += S.getName().size()+1;
 980   }
 981
 982   // Set the size of .shstrtab now that we know what it is.
 983   assert(Index == SHStrTab.size());
 984   SHStrTab.Size = Index;
 985 }
 986
 987 /// OutputSectionsAndSectionTable - Now that we have constructed the file header
 988 /// and all of the sections, emit these to the ostream destination and emit the
 989 /// SectionTable.
 990 void ELFWriter::OutputSectionsAndSectionTable() {
 991   // Pass #1: Compute the file offset for each section.
 992   size_t FileOff = ElfHdr.size();   // File header first.
 993
 994   // Adjust alignment of all section if needed, skip the null section.
 995   for (unsigned i=1, e=SectionList.size(); i < e; ++i) {
 996     ELFSection &ES = *SectionList[i];
 997     if (!ES.size()) {
 998       ES.Offset = FileOff;
 999       continue;
1000     }
1001
1002     // Update Section size
1003     if (!ES.Size)
1004       ES.Size = ES.size();
1005
1006     // Align FileOff to whatever the alignment restrictions of the section are.
1007     if (ES.Align)
1008       FileOff = (FileOff+ES.Align-1) & ~(ES.Align-1);
1009
1010     ES.Offset = FileOff;
1011     FileOff += ES.Size;
1012   }
1013
1014   // Align Section Header.
1015   unsigned TableAlign = TEW->getPrefELFAlignment();
1016   FileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
1017
1018   // Now that we know where all of the sections will be emitted, set the e_shnum
1019   // entry in the ELF header.
1020   ElfHdr.fixWord16(NumSections, ELFHdr_e_shnum_Offset);
1021
1022   // Now that we know the offset in the file of the section table, update the
1023   // e_shoff address in the ELF header.
1024   ElfHdr.fixWord(FileOff, ELFHdr_e_shoff_Offset);
1025
1026   // Now that we know all of the data in the file header, emit it and all of the
1027   // sections!
1028   O.write((char *)&ElfHdr.getData()[0], ElfHdr.size());
1029   FileOff = ElfHdr.size();
1030
1031   // Section Header Table blob
1032   BinaryObject SHdrTable(isLittleEndian, is64Bit);
1033
1034   // Emit all of sections to the file and build the section header table.
1035   for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
1036     ELFSection &S = *(*I);
1037     DOUT << "SectionIdx: " << S.SectionIdx << ", Name: " << S.getName()
1038          << ", Size: " << S.Size << ", Offset: " << S.Offset
1039          << ", SectionData Size: " << S.size() << "\n";
1040
1041     // Align FileOff to whatever the alignment restrictions of the section are.
1042     if (S.size()) {
1043       if (S.Align)  {
1044         for (size_t NewFileOff = (FileOff+S.Align-1) & ~(S.Align-1);
1045              FileOff != NewFileOff; ++FileOff)
1046           O << (char)0xAB;
1047       }
1048       O.write((char *)&S.getData()[0], S.Size);
1049       FileOff += S.Size;
1050     }
1051
1052     EmitSectionHeader(SHdrTable, S);
1053   }
1054
1055   // Align output for the section table.
1056   for (size_t NewFileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
1057        FileOff != NewFileOff; ++FileOff)
1058     O << (char)0xAB;
1059
1060   // Emit the section table itself.
1061   O.write((char *)&SHdrTable.getData()[0], SHdrTable.size());
1062 }