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())
 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())
 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 // isELFUndefSym - the symbol has no section and must be placed in
 307 // the symbol table with a reference to the null section.
 308 static bool isELFUndefSym(const GlobalValue *GV) {
 309   // Functions which make up until this point references are an undef symbol
 310   return GV->isDeclaration() || (isa<Function>(GV));
 311 }
 312
 313 // isELFBssSym - for an undef or null value, the symbol must go to a bss
 314 // section if it's not weak for linker, otherwise it's a common sym.
 315 static bool isELFBssSym(const GlobalVariable *GV) {
 316   const Constant *CV = GV->getInitializer();
 317   return ((CV->isNullValue() || isa<UndefValue>(CV)) && !GV->isWeakForLinker());
 318 }
 319
 320 // isELFCommonSym - for an undef or null value, the symbol must go to a
 321 // common section if it's weak for linker, otherwise bss.
 322 static bool isELFCommonSym(const GlobalVariable *GV) {
 323   const Constant *CV = GV->getInitializer();
 324   return ((CV->isNullValue() || isa<UndefValue>(CV)) && GV->isWeakForLinker());
 325 }
 326
 327 // isELFDataSym - if the symbol is an initialized but no null constant
 328 // it must go to some kind of data section
 329 static bool isELFDataSym(const Constant *CV) {
 330   return (!(CV->isNullValue() || isa<UndefValue>(CV)));
 331 }
 332
 333 // EmitGlobal - Choose the right section for global and emit it
 334 void ELFWriter::EmitGlobal(const GlobalValue *GV) {
 335
 336   // Check if the referenced symbol is already emitted
 337   if (GblSymLookup.find(GV) != GblSymLookup.end())
 338     return;
 339
 340   // Handle ELF Bind, Visibility and Type for the current symbol
 341   unsigned SymBind = getGlobalELFBinding(GV);
 342   unsigned SymType = getGlobalELFType(GV);
 343
 344   // All undef symbols have the same binding, type and visibily and
 345   // are classified regardless of their type.
 346   ELFSym *GblSym = isELFUndefSym(GV) ? ELFSym::getUndefGV(GV)
 347     : ELFSym::getGV(GV, SymBind, SymType, getGlobalELFVisibility(GV));
 348
 349   if (!isELFUndefSym(GV)) {
 350     assert(isa<GlobalVariable>(GV) && "GV not a global variable!");
 351     const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV);
 352
 353     // Handle special llvm globals
 354     if (EmitSpecialLLVMGlobal(GVar))
 355       return;
 356
 357     // Get the ELF section where this global belongs from TLOF
 358     const MCSection *S = TLOF.SectionForGlobal(GV, Mang, TM);
 359     unsigned SectionFlags = getElfSectionFlags(((MCSectionELF*)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 (isELFCommonSym(GVar)) {
 368       GblSym->SectionIdx = ELFSection::SHN_COMMON;
 369       getSection(S->getName(), ELFSection::SHT_NOBITS, SectionFlags, 1);
 370
 371       // A new linkonce section is created for each global in the
 372       // common section, the default alignment is 1 and the symbol
 373       // value contains its alignment.
 374       GblSym->Value = Align;
 375
 376     } else if (isELFBssSym(GVar)) {
 377       ELFSection &ES =
 378         getSection(S->getName(), ELFSection::SHT_NOBITS, SectionFlags);
 379       GblSym->SectionIdx = ES.SectionIdx;
 380
 381       // Update the size with alignment and the next object can
 382       // start in the right offset in the section
 383       if (Align) ES.Size = (ES.Size + Align-1) & ~(Align-1);
 384       ES.Align = std::max(ES.Align, Align);
 385
 386       // GblSym->Value should contain the virtual offset inside the section.
 387       // Virtual because the BSS space is not allocated on ELF objects
 388       GblSym->Value = ES.Size;
 389       ES.Size += Size;
 390
 391     } else if (isELFDataSym(GV)) {
 392       ELFSection &ES =
 393         getSection(S->getName(), ELFSection::SHT_PROGBITS, SectionFlags);
 394       GblSym->SectionIdx = ES.SectionIdx;
 395
 396       // GblSym->Value should contain the symbol offset inside the section,
 397       // and all symbols should start on their required alignment boundary
 398       ES.Align = std::max(ES.Align, Align);
 399       GblSym->Value = (ES.size() + (Align-1)) & (-Align);
 400       ES.emitAlignment(ES.Align);
 401
 402       // Emit the global to the data section 'ES'
 403       EmitGlobalConstant(GVar->getInitializer(), ES);
 404     }
 405   }
 406
 407   if (GV->hasPrivateLinkage()) {
 408     // For a private symbols, keep track of the index inside the
 409     // private list since it will never go to the symbol table and
 410     // won't be patched up later.
 411     PrivateSyms.push_back(GblSym);
 412     GblSymLookup[GV] = PrivateSyms.size()-1;
 413   } else {
 414     // Non private symbol are left with zero indices until they are patched
 415     // up during the symbol table emition (where the indicies are created).
 416     SymbolList.push_back(GblSym);
 417     GblSymLookup[GV] = 0;
 418   }
 419 }
 420
 421 void ELFWriter::EmitGlobalConstantStruct(const ConstantStruct *CVS,
 422                                          ELFSection &GblS) {
 423
 424   // Print the fields in successive locations. Pad to align if needed!
 425   const TargetData *TD = TM.getTargetData();
 426   unsigned Size = TD->getTypeAllocSize(CVS->getType());
 427   const StructLayout *cvsLayout = TD->getStructLayout(CVS->getType());
 428   uint64_t sizeSoFar = 0;
 429   for (unsigned i = 0, e = CVS->getNumOperands(); i != e; ++i) {
 430     const Constant* field = CVS->getOperand(i);
 431
 432     // Check if padding is needed and insert one or more 0s.
 433     uint64_t fieldSize = TD->getTypeAllocSize(field->getType());
 434     uint64_t padSize = ((i == e-1 ? Size : cvsLayout->getElementOffset(i+1))
 435                         - cvsLayout->getElementOffset(i)) - fieldSize;
 436     sizeSoFar += fieldSize + padSize;
 437
 438     // Now print the actual field value.
 439     EmitGlobalConstant(field, GblS);
 440
 441     // Insert padding - this may include padding to increase the size of the
 442     // current field up to the ABI size (if the struct is not packed) as well
 443     // as padding to ensure that the next field starts at the right offset.
 444     for (unsigned p=0; p < padSize; p++)
 445       GblS.emitByte(0);
 446   }
 447   assert(sizeSoFar == cvsLayout->getSizeInBytes() &&
 448          "Layout of constant struct may be incorrect!");
 449 }
 450
 451 void ELFWriter::EmitGlobalConstant(const Constant *CV, ELFSection &GblS) {
 452   const TargetData *TD = TM.getTargetData();
 453   unsigned Size = TD->getTypeAllocSize(CV->getType());
 454
 455   if (const ConstantArray *CVA = dyn_cast<ConstantArray>(CV)) {
 456     if (CVA->isString()) {
 457       std::string GblStr = CVA->getAsString();
 458       GblStr.resize(GblStr.size()-1);
 459       GblS.emitString(GblStr);
 460     } else { // Not a string.  Print the values in successive locations
 461       for (unsigned i = 0, e = CVA->getNumOperands(); i != e; ++i)
 462         EmitGlobalConstant(CVA->getOperand(i), GblS);
 463     }
 464     return;
 465   } else if (const ConstantStruct *CVS = dyn_cast<ConstantStruct>(CV)) {
 466     EmitGlobalConstantStruct(CVS, GblS);
 467     return;
 468   } else if (const ConstantFP *CFP = dyn_cast<ConstantFP>(CV)) {
 469     uint64_t Val = CFP->getValueAPF().bitcastToAPInt().getZExtValue();
 470     if (CFP->getType() == Type::DoubleTy)
 471       GblS.emitWord64(Val);
 472     else if (CFP->getType() == Type::FloatTy)
 473       GblS.emitWord32(Val);
 474     else if (CFP->getType() == Type::X86_FP80Ty) {
 475       llvm_unreachable("X86_FP80Ty global emission not implemented");
 476     } else if (CFP->getType() == Type::PPC_FP128Ty)
 477       llvm_unreachable("PPC_FP128Ty global emission not implemented");
 478     return;
 479   } else if (const ConstantInt *CI = dyn_cast<ConstantInt>(CV)) {
 480     if (Size == 4)
 481       GblS.emitWord32(CI->getZExtValue());
 482     else if (Size == 8)
 483       GblS.emitWord64(CI->getZExtValue());
 484     else
 485       llvm_unreachable("LargeInt global emission not implemented");
 486     return;
 487   } else if (const ConstantVector *CP = dyn_cast<ConstantVector>(CV)) {
 488     const VectorType *PTy = CP->getType();
 489     for (unsigned I = 0, E = PTy->getNumElements(); I < E; ++I)
 490       EmitGlobalConstant(CP->getOperand(I), GblS);
 491     return;
 492   } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV)) {
 493     if (CE->getOpcode() == Instruction::BitCast) {
 494       EmitGlobalConstant(CE->getOperand(0), GblS);
 495       return;
 496     }
 497     std::string msg(CE->getOpcodeName());
 498     raw_string_ostream ErrorMsg(msg);
 499     ErrorMsg << ": Unsupported ConstantExpr type";
 500     llvm_report_error(ErrorMsg.str());
 501   } else if (CV->getType()->getTypeID() == Type::PointerTyID) {
 502     // Fill the data entry with zeros or emit a relocation entry
 503     if (isa<ConstantPointerNull>(CV)) {
 504       for (unsigned i=0; i < Size; ++i)
 505         GblS.emitByte(0);
 506     } else {
 507       emitGlobalDataRelocation(cast<const GlobalValue>(CV),
 508                                TD->getPointerSize(), GblS);
 509     }
 510     return;
 511   } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CV)) {
 512     // This is a constant address for a global variable or function and
 513     // therefore must be referenced using a relocation entry.
 514     emitGlobalDataRelocation(GV, Size, GblS);
 515     return;
 516   }
 517
 518   std::string msg;
 519   raw_string_ostream ErrorMsg(msg);
 520   ErrorMsg << "Constant unimp for type: " << *CV->getType();
 521   llvm_report_error(ErrorMsg.str());
 522 }
 523
 524 void ELFWriter::emitGlobalDataRelocation(const GlobalValue *GV, unsigned Size,
 525                                          ELFSection &GblS) {
 526   // Create the relocation entry for the global value
 527   MachineRelocation MR =
 528     MachineRelocation::getGV(GblS.getCurrentPCOffset(),
 529                              TEW->getAbsoluteLabelMachineRelTy(),
 530                              const_cast<GlobalValue*>(GV));
 531
 532   // Fill the data entry with zeros
 533   for (unsigned i=0; i < Size; ++i)
 534     GblS.emitByte(0);
 535
 536   // Add the relocation entry for the current data section
 537   GblS.addRelocation(MR);
 538 }
 539
 540 /// EmitSpecialLLVMGlobal - Check to see if the specified global is a
 541 /// special global used by LLVM.  If so, emit it and return true, otherwise
 542 /// do nothing and return false.
 543 bool ELFWriter::EmitSpecialLLVMGlobal(const GlobalVariable *GV) {
 544   if (GV->getName() == "llvm.used")
 545     llvm_unreachable("not implemented yet");
 546
 547   // Ignore debug and non-emitted data.  This handles llvm.compiler.used.
 548   if (GV->getSection() == "llvm.metadata" ||
 549       GV->hasAvailableExternallyLinkage())
 550     return true;
 551
 552   if (!GV->hasAppendingLinkage()) return false;
 553
 554   assert(GV->hasInitializer() && "Not a special LLVM global!");
 555
 556   const TargetData *TD = TM.getTargetData();
 557   unsigned Align = TD->getPointerPrefAlignment();
 558   if (GV->getName() == "llvm.global_ctors") {
 559     ELFSection &Ctor = getCtorSection();
 560     Ctor.emitAlignment(Align);
 561     EmitXXStructorList(GV->getInitializer(), Ctor);
 562     return true;
 563   }
 564
 565   if (GV->getName() == "llvm.global_dtors") {
 566     ELFSection &Dtor = getDtorSection();
 567     Dtor.emitAlignment(Align);
 568     EmitXXStructorList(GV->getInitializer(), Dtor);
 569     return true;
 570   }
 571
 572   return false;
 573 }
 574
 575 /// EmitXXStructorList - Emit the ctor or dtor list.  This just emits out the
 576 /// function pointers, ignoring the init priority.
 577 void ELFWriter::EmitXXStructorList(Constant *List, ELFSection &Xtor) {
 578   // Should be an array of '{ int, void ()* }' structs.  The first value is the
 579   // init priority, which we ignore.
 580   if (!isa<ConstantArray>(List)) return;
 581   ConstantArray *InitList = cast<ConstantArray>(List);
 582   for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i)
 583     if (ConstantStruct *CS = dyn_cast<ConstantStruct>(InitList->getOperand(i))){
 584       if (CS->getNumOperands() != 2) return;  // Not array of 2-element structs.
 585
 586       if (CS->getOperand(1)->isNullValue())
 587         return;  // Found a null terminator, exit printing.
 588       // Emit the function pointer.
 589       EmitGlobalConstant(CS->getOperand(1), Xtor);
 590     }
 591 }
 592
 593 bool ELFWriter::runOnMachineFunction(MachineFunction &MF) {
 594   // Nothing to do here, this is all done through the ElfCE object above.
 595   return false;
 596 }
 597
 598 /// doFinalization - Now that the module has been completely processed, emit
 599 /// the ELF file to 'O'.
 600 bool ELFWriter::doFinalization(Module &M) {
 601   // Emit .data section placeholder
 602   getDataSection();
 603
 604   // Emit .bss section placeholder
 605   getBSSSection();
 606
 607   // Build and emit data, bss and "common" sections.
 608   for (Module::global_iterator I = M.global_begin(), E = M.global_end();
 609        I != E; ++I)
 610     EmitGlobal(I);
 611
 612   // Emit all pending globals
 613   for (PendingGblsIter I = PendingGlobals.begin(), E = PendingGlobals.end();
 614        I != E; ++I)
 615     EmitGlobal(*I);
 616
 617   // Emit all pending externals
 618   for (PendingExtsIter I = PendingExternals.begin(), E = PendingExternals.end();
 619        I != E; ++I)
 620     SymbolList.push_back(ELFSym::getExtSym(*I));
 621
 622   // Emit non-executable stack note
 623   if (TAI->getNonexecutableStackDirective())
 624     getNonExecStackSection();
 625
 626   // Emit a symbol for each section created until now, skip null section
 627   for (unsigned i = 1, e = SectionList.size(); i < e; ++i) {
 628     ELFSection &ES = *SectionList[i];
 629     ELFSym *SectionSym = ELFSym::getSectionSym();
 630     SectionSym->SectionIdx = ES.SectionIdx;
 631     SymbolList.push_back(SectionSym);
 632     ES.Sym = SymbolList.back();
 633   }
 634
 635   // Emit string table
 636   EmitStringTable(M.getModuleIdentifier());
 637
 638   // Emit the symbol table now, if non-empty.
 639   EmitSymbolTable();
 640
 641   // Emit the relocation sections.
 642   EmitRelocations();
 643
 644   // Emit the sections string table.
 645   EmitSectionTableStringTable();
 646
 647   // Dump the sections and section table to the .o file.
 648   OutputSectionsAndSectionTable();
 649
 650   // We are done with the abstract symbols.
 651   SymbolList.clear();
 652   SectionList.clear();
 653   NumSections = 0;
 654
 655   // Release the name mangler object.
 656   delete Mang; Mang = 0;
 657   return false;
 658 }
 659
 660 // RelocateField - Patch relocatable field with 'Offset' in 'BO'
 661 // using a 'Value' of known 'Size'
 662 void ELFWriter::RelocateField(BinaryObject &BO, uint32_t Offset,
 663                               int64_t Value, unsigned Size) {
 664   if (Size == 32)
 665     BO.fixWord32(Value, Offset);
 666   else if (Size == 64)
 667     BO.fixWord64(Value, Offset);
 668   else
 669     llvm_unreachable("don't know howto patch relocatable field");
 670 }
 671
 672 /// EmitRelocations - Emit relocations
 673 void ELFWriter::EmitRelocations() {
 674
 675   // True if the target uses the relocation entry to hold the addend,
 676   // otherwise the addend is written directly to the relocatable field.
 677   bool HasRelA = TEW->hasRelocationAddend();
 678
 679   // Create Relocation sections for each section which needs it.
 680   for (unsigned i=0, e=SectionList.size(); i != e; ++i) {
 681     ELFSection &S = *SectionList[i];
 682
 683     // This section does not have relocations
 684     if (!S.hasRelocations()) continue;
 685     ELFSection &RelSec = getRelocSection(S);
 686
 687     // 'Link' - Section hdr idx of the associated symbol table
 688     // 'Info' - Section hdr idx of the section to which the relocation applies
 689     ELFSection &SymTab = getSymbolTableSection();
 690     RelSec.Link = SymTab.SectionIdx;
 691     RelSec.Info = S.SectionIdx;
 692     RelSec.EntSize = TEW->getRelocationEntrySize();
 693
 694     // Get the relocations from Section
 695     std::vector<MachineRelocation> Relos = S.getRelocations();
 696     for (std::vector<MachineRelocation>::iterator MRI = Relos.begin(),
 697          MRE = Relos.end(); MRI != MRE; ++MRI) {
 698       MachineRelocation &MR = *MRI;
 699
 700       // Relocatable field offset from the section start
 701       unsigned RelOffset = MR.getMachineCodeOffset();
 702
 703       // Symbol index in the symbol table
 704       unsigned SymIdx = 0;
 705
 706       // Target specific relocation field type and size
 707       unsigned RelType = TEW->getRelocationType(MR.getRelocationType());
 708       unsigned RelTySize = TEW->getRelocationTySize(RelType);
 709       int64_t Addend = 0;
 710
 711       // There are several machine relocations types, and each one of
 712       // them needs a different approach to retrieve the symbol table index.
 713       if (MR.isGlobalValue()) {
 714         const GlobalValue *G = MR.getGlobalValue();
 715         SymIdx = GblSymLookup[G];
 716         if (G->hasPrivateLinkage()) {
 717           // If the target uses a section offset in the relocation:
 718           // SymIdx + Addend = section sym for global + section offset
 719           unsigned SectionIdx = PrivateSyms[SymIdx]->SectionIdx;
 720           Addend = PrivateSyms[SymIdx]->Value;
 721           SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
 722         } else {
 723           int64_t GlobalOffset = MR.getConstantVal();
 724           Addend = TEW->getDefaultAddendForRelTy(RelType, GlobalOffset);
 725         }
 726       } else if (MR.isExternalSymbol()) {
 727         const char *ExtSym = MR.getExternalSymbol();
 728         SymIdx = ExtSymLookup[ExtSym];
 729         Addend = TEW->getDefaultAddendForRelTy(RelType);
 730       } else {
 731         // Get the symbol index for the section symbol
 732         unsigned SectionIdx = MR.getConstantVal();
 733         SymIdx = SectionList[SectionIdx]->getSymbolTableIndex();
 734
 735         // The symbol offset inside the section
 736         int64_t SymOffset = (int64_t)MR.getResultPointer();
 737
 738         // For pc relative relocations where symbols are defined in the same
 739         // section they are referenced, ignore the relocation entry and patch
 740         // the relocatable field with the symbol offset directly.
 741         if (S.SectionIdx == SectionIdx && TEW->isPCRelativeRel(RelType)) {
 742           int64_t Value = TEW->computeRelocation(SymOffset, RelOffset, RelType);
 743           RelocateField(S, RelOffset, Value, RelTySize);
 744           continue;
 745         }
 746
 747         Addend = TEW->getDefaultAddendForRelTy(RelType, SymOffset);
 748       }
 749
 750       // The target without addend on the relocation symbol must be
 751       // patched in the relocation place itself to contain the addend
 752       // otherwise write zeros to make sure there is no garbage there
 753       RelocateField(S, RelOffset, HasRelA ? 0 : Addend, RelTySize);
 754
 755       // Get the relocation entry and emit to the relocation section
 756       ELFRelocation Rel(RelOffset, SymIdx, RelType, HasRelA, Addend);
 757       EmitRelocation(RelSec, Rel, HasRelA);
 758     }
 759   }
 760 }
 761
 762 /// EmitRelocation - Write relocation 'Rel' to the relocation section 'Rel'
 763 void ELFWriter::EmitRelocation(BinaryObject &RelSec, ELFRelocation &Rel,
 764                                bool HasRelA) {
 765   RelSec.emitWord(Rel.getOffset());
 766   RelSec.emitWord(Rel.getInfo(is64Bit));
 767   if (HasRelA)
 768     RelSec.emitWord(Rel.getAddend());
 769 }
 770
 771 /// EmitSymbol - Write symbol 'Sym' to the symbol table 'SymbolTable'
 772 void ELFWriter::EmitSymbol(BinaryObject &SymbolTable, ELFSym &Sym) {
 773   if (is64Bit) {
 774     SymbolTable.emitWord32(Sym.NameIdx);
 775     SymbolTable.emitByte(Sym.Info);
 776     SymbolTable.emitByte(Sym.Other);
 777     SymbolTable.emitWord16(Sym.SectionIdx);
 778     SymbolTable.emitWord64(Sym.Value);
 779     SymbolTable.emitWord64(Sym.Size);
 780   } else {
 781     SymbolTable.emitWord32(Sym.NameIdx);
 782     SymbolTable.emitWord32(Sym.Value);
 783     SymbolTable.emitWord32(Sym.Size);
 784     SymbolTable.emitByte(Sym.Info);
 785     SymbolTable.emitByte(Sym.Other);
 786     SymbolTable.emitWord16(Sym.SectionIdx);
 787   }
 788 }
 789
 790 /// EmitSectionHeader - Write section 'Section' header in 'SHdrTab'
 791 /// Section Header Table
 792 void ELFWriter::EmitSectionHeader(BinaryObject &SHdrTab,
 793                                   const ELFSection &SHdr) {
 794   SHdrTab.emitWord32(SHdr.NameIdx);
 795   SHdrTab.emitWord32(SHdr.Type);
 796   if (is64Bit) {
 797     SHdrTab.emitWord64(SHdr.Flags);
 798     SHdrTab.emitWord(SHdr.Addr);
 799     SHdrTab.emitWord(SHdr.Offset);
 800     SHdrTab.emitWord64(SHdr.Size);
 801     SHdrTab.emitWord32(SHdr.Link);
 802     SHdrTab.emitWord32(SHdr.Info);
 803     SHdrTab.emitWord64(SHdr.Align);
 804     SHdrTab.emitWord64(SHdr.EntSize);
 805   } else {
 806     SHdrTab.emitWord32(SHdr.Flags);
 807     SHdrTab.emitWord(SHdr.Addr);
 808     SHdrTab.emitWord(SHdr.Offset);
 809     SHdrTab.emitWord32(SHdr.Size);
 810     SHdrTab.emitWord32(SHdr.Link);
 811     SHdrTab.emitWord32(SHdr.Info);
 812     SHdrTab.emitWord32(SHdr.Align);
 813     SHdrTab.emitWord32(SHdr.EntSize);
 814   }
 815 }
 816
 817 /// EmitStringTable - If the current symbol table is non-empty, emit the string
 818 /// table for it
 819 void ELFWriter::EmitStringTable(const std::string &ModuleName) {
 820   if (!SymbolList.size()) return;  // Empty symbol table.
 821   ELFSection &StrTab = getStringTableSection();
 822
 823   // Set the zero'th symbol to a null byte, as required.
 824   StrTab.emitByte(0);
 825
 826   // Walk on the symbol list and write symbol names into the string table.
 827   unsigned Index = 1;
 828   for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
 829     ELFSym &Sym = *(*I);
 830
 831     std::string Name;
 832     if (Sym.isGlobalValue())
 833       // Use the name mangler to uniquify the LLVM symbol.
 834       Name.append(Mang->getMangledName(Sym.getGlobalValue()));
 835     else if (Sym.isExternalSym())
 836       Name.append(Sym.getExternalSymbol());
 837     else if (Sym.isFileType())
 838       Name.append(ModuleName);
 839
 840     if (Name.empty()) {
 841       Sym.NameIdx = 0;
 842     } else {
 843       Sym.NameIdx = Index;
 844       StrTab.emitString(Name);
 845
 846       // Keep track of the number of bytes emitted to this section.
 847       Index += Name.size()+1;
 848     }
 849   }
 850   assert(Index == StrTab.size());
 851   StrTab.Size = Index;
 852 }
 853
 854 // SortSymbols - On the symbol table local symbols must come before
 855 // all other symbols with non-local bindings. The return value is
 856 // the position of the first non local symbol.
 857 unsigned ELFWriter::SortSymbols() {
 858   unsigned FirstNonLocalSymbol;
 859   std::vector<ELFSym*> LocalSyms, OtherSyms;
 860
 861   for (ELFSymIter I=SymbolList.begin(), E=SymbolList.end(); I != E; ++I) {
 862     if ((*I)->isLocalBind())
 863       LocalSyms.push_back(*I);
 864     else
 865       OtherSyms.push_back(*I);
 866   }
 867   SymbolList.clear();
 868   FirstNonLocalSymbol = LocalSyms.size();
 869
 870   for (unsigned i = 0; i < FirstNonLocalSymbol; ++i)
 871     SymbolList.push_back(LocalSyms[i]);
 872
 873   for (ELFSymIter I=OtherSyms.begin(), E=OtherSyms.end(); I != E; ++I)
 874     SymbolList.push_back(*I);
 875
 876   LocalSyms.clear();
 877   OtherSyms.clear();
 878
 879   return FirstNonLocalSymbol;
 880 }
 881
 882 /// EmitSymbolTable - Emit the symbol table itself.
 883 void ELFWriter::EmitSymbolTable() {
 884   if (!SymbolList.size()) return;  // Empty symbol table.
 885
 886   // Now that we have emitted the string table and know the offset into the
 887   // string table of each symbol, emit the symbol table itself.
 888   ELFSection &SymTab = getSymbolTableSection();
 889   SymTab.Align = TEW->getPrefELFAlignment();
 890
 891   // Section Index of .strtab.
 892   SymTab.Link = getStringTableSection().SectionIdx;
 893
 894   // Size of each symtab entry.
 895   SymTab.EntSize = TEW->getSymTabEntrySize();
 896
 897   // Reorder the symbol table with local symbols first!
 898   unsigned FirstNonLocalSymbol = SortSymbols();
 899
 900   // Emit all the symbols to the symbol table.
 901   for (unsigned i = 0, e = SymbolList.size(); i < e; ++i) {
 902     ELFSym &Sym = *SymbolList[i];
 903
 904     // Emit symbol to the symbol table
 905     EmitSymbol(SymTab, Sym);
 906
 907     // Record the symbol table index for each symbol
 908     if (Sym.isGlobalValue())
 909       GblSymLookup[Sym.getGlobalValue()] = i;
 910     else if (Sym.isExternalSym())
 911       ExtSymLookup[Sym.getExternalSymbol()] = i;
 912
 913     // Keep track on the symbol index into the symbol table
 914     Sym.SymTabIdx = i;
 915   }
 916
 917   // One greater than the symbol table index of the last local symbol
 918   SymTab.Info = FirstNonLocalSymbol;
 919   SymTab.Size = SymTab.size();
 920 }
 921
 922 /// EmitSectionTableStringTable - This method adds and emits a section for the
 923 /// ELF Section Table string table: the string table that holds all of the
 924 /// section names.
 925 void ELFWriter::EmitSectionTableStringTable() {
 926   // First step: add the section for the string table to the list of sections:
 927   ELFSection &SHStrTab = getSectionHeaderStringTableSection();
 928
 929   // Now that we know which section number is the .shstrtab section, update the
 930   // e_shstrndx entry in the ELF header.
 931   ElfHdr.fixWord16(SHStrTab.SectionIdx, ELFHdr_e_shstrndx_Offset);
 932
 933   // Set the NameIdx of each section in the string table and emit the bytes for
 934   // the string table.
 935   unsigned Index = 0;
 936
 937   for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
 938     ELFSection &S = *(*I);
 939     // Set the index into the table.  Note if we have lots of entries with
 940     // common suffixes, we could memoize them here if we cared.
 941     S.NameIdx = Index;
 942     SHStrTab.emitString(S.getName());
 943
 944     // Keep track of the number of bytes emitted to this section.
 945     Index += S.getName().size()+1;
 946   }
 947
 948   // Set the size of .shstrtab now that we know what it is.
 949   assert(Index == SHStrTab.size());
 950   SHStrTab.Size = Index;
 951 }
 952
 953 /// OutputSectionsAndSectionTable - Now that we have constructed the file header
 954 /// and all of the sections, emit these to the ostream destination and emit the
 955 /// SectionTable.
 956 void ELFWriter::OutputSectionsAndSectionTable() {
 957   // Pass #1: Compute the file offset for each section.
 958   size_t FileOff = ElfHdr.size();   // File header first.
 959
 960   // Adjust alignment of all section if needed, skip the null section.
 961   for (unsigned i=1, e=SectionList.size(); i < e; ++i) {
 962     ELFSection &ES = *SectionList[i];
 963     if (!ES.size()) {
 964       ES.Offset = FileOff;
 965       continue;
 966     }
 967
 968     // Update Section size
 969     if (!ES.Size)
 970       ES.Size = ES.size();
 971
 972     // Align FileOff to whatever the alignment restrictions of the section are.
 973     if (ES.Align)
 974       FileOff = (FileOff+ES.Align-1) & ~(ES.Align-1);
 975
 976     ES.Offset = FileOff;
 977     FileOff += ES.Size;
 978   }
 979
 980   // Align Section Header.
 981   unsigned TableAlign = TEW->getPrefELFAlignment();
 982   FileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
 983
 984   // Now that we know where all of the sections will be emitted, set the e_shnum
 985   // entry in the ELF header.
 986   ElfHdr.fixWord16(NumSections, ELFHdr_e_shnum_Offset);
 987
 988   // Now that we know the offset in the file of the section table, update the
 989   // e_shoff address in the ELF header.
 990   ElfHdr.fixWord(FileOff, ELFHdr_e_shoff_Offset);
 991
 992   // Now that we know all of the data in the file header, emit it and all of the
 993   // sections!
 994   O.write((char *)&ElfHdr.getData()[0], ElfHdr.size());
 995   FileOff = ElfHdr.size();
 996
 997   // Section Header Table blob
 998   BinaryObject SHdrTable(isLittleEndian, is64Bit);
 999
1000   // Emit all of sections to the file and build the section header table.
1001   for (ELFSectionIter I=SectionList.begin(), E=SectionList.end(); I != E; ++I) {
1002     ELFSection &S = *(*I);
1003     DOUT << "SectionIdx: " << S.SectionIdx << ", Name: " << S.getName()
1004          << ", Size: " << S.Size << ", Offset: " << S.Offset
1005          << ", SectionData Size: " << S.size() << "\n";
1006
1007     // Align FileOff to whatever the alignment restrictions of the section are.
1008     if (S.size()) {
1009       if (S.Align)  {
1010         for (size_t NewFileOff = (FileOff+S.Align-1) & ~(S.Align-1);
1011              FileOff != NewFileOff; ++FileOff)
1012           O << (char)0xAB;
1013       }
1014       O.write((char *)&S.getData()[0], S.Size);
1015       FileOff += S.Size;
1016     }
1017
1018     EmitSectionHeader(SHdrTable, S);
1019   }
1020
1021   // Align output for the section table.
1022   for (size_t NewFileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
1023        FileOff != NewFileOff; ++FileOff)
1024     O << (char)0xAB;
1025
1026   // Emit the section table itself.
1027   O.write((char *)&SHdrTable.getData()[0], SHdrTable.size());
1028 }