lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp

   1 //===-- RuntimeDyldELF.cpp - Run-time dynamic linker for MC-JIT -*- C++ -*-===//
   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 // Implementation of ELF support for the MC-JIT runtime dynamic linker.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #define DEBUG_TYPE "dyld"
  15 #include "RuntimeDyldELF.h"
  16 #include "JITRegistrar.h"
  17 #include "ObjectImageCommon.h"
  18 #include "llvm/ADT/OwningPtr.h"
  19 #include "llvm/ADT/StringRef.h"
  20 #include "llvm/ADT/STLExtras.h"
  21 #include "llvm/ADT/IntervalMap.h"
  22 #include "llvm/Object/ObjectFile.h"
  23 #include "llvm/ExecutionEngine/ObjectImage.h"
  24 #include "llvm/ExecutionEngine/ObjectBuffer.h"
  25 #include "llvm/Support/ELF.h"
  26 #include "llvm/ADT/Triple.h"
  27 #include "llvm/Object/ELF.h"
  28 using namespace llvm;
  29 using namespace llvm::object;
  30
  31 namespace {
  32
  33 static inline
  34 error_code check(error_code Err) {
  35   if (Err) {
  36     report_fatal_error(Err.message());
  37   }
  38   return Err;
  39 }
  40
  41 template<support::endianness target_endianness, bool is64Bits>
  42 class DyldELFObject : public ELFObjectFile<target_endianness, is64Bits> {
  43   LLVM_ELF_IMPORT_TYPES(target_endianness, is64Bits)
  44
  45   typedef Elf_Shdr_Impl<target_endianness, is64Bits> Elf_Shdr;
  46   typedef Elf_Sym_Impl<target_endianness, is64Bits> Elf_Sym;
  47   typedef Elf_Rel_Impl<target_endianness, is64Bits, false> Elf_Rel;
  48   typedef Elf_Rel_Impl<target_endianness, is64Bits, true> Elf_Rela;
  49
  50   typedef Elf_Ehdr_Impl<target_endianness, is64Bits> Elf_Ehdr;
  51
  52   typedef typename ELFDataTypeTypedefHelper<
  53           target_endianness, is64Bits>::value_type addr_type;
  54
  55 public:
  56   DyldELFObject(MemoryBuffer *Wrapper, error_code &ec);
  57
  58   void updateSectionAddress(const SectionRef &Sec, uint64_t Addr);
  59   void updateSymbolAddress(const SymbolRef &Sym, uint64_t Addr);
  60
  61   // Methods for type inquiry through isa, cast and dyn_cast
  62   static inline bool classof(const Binary *v) {
  63     return (isa<ELFObjectFile<target_endianness, is64Bits> >(v)
  64             && classof(cast<ELFObjectFile<target_endianness, is64Bits> >(v)));
  65   }
  66   static inline bool classof(
  67       const ELFObjectFile<target_endianness, is64Bits> *v) {
  68     return v->isDyldType();
  69   }
  70 };
  71
  72 template<support::endianness target_endianness, bool is64Bits>
  73 class ELFObjectImage : public ObjectImageCommon {
  74   protected:
  75     DyldELFObject<target_endianness, is64Bits> *DyldObj;
  76     bool Registered;
  77
  78   public:
  79     ELFObjectImage(ObjectBuffer *Input,
  80                    DyldELFObject<target_endianness, is64Bits> *Obj)
  81     : ObjectImageCommon(Input, Obj),
  82       DyldObj(Obj),
  83       Registered(false) {}
  84
  85     virtual ~ELFObjectImage() {
  86       if (Registered)
  87         deregisterWithDebugger();
  88     }
  89
  90     // Subclasses can override these methods to update the image with loaded
  91     // addresses for sections and common symbols
  92     virtual void updateSectionAddress(const SectionRef &Sec, uint64_t Addr)
  93     {
  94       DyldObj->updateSectionAddress(Sec, Addr);
  95     }
  96
  97     virtual void updateSymbolAddress(const SymbolRef &Sym, uint64_t Addr)
  98     {
  99       DyldObj->updateSymbolAddress(Sym, Addr);
 100     }
 101
 102     virtual void registerWithDebugger()
 103     {
 104       JITRegistrar::getGDBRegistrar().registerObject(*Buffer);
 105       Registered = true;
 106     }
 107     virtual void deregisterWithDebugger()
 108     {
 109       JITRegistrar::getGDBRegistrar().deregisterObject(*Buffer);
 110     }
 111 };
 112
 113 // The MemoryBuffer passed into this constructor is just a wrapper around the
 114 // actual memory.  Ultimately, the Binary parent class will take ownership of
 115 // this MemoryBuffer object but not the underlying memory.
 116 template<support::endianness target_endianness, bool is64Bits>
 117 DyldELFObject<target_endianness, is64Bits>::DyldELFObject(MemoryBuffer *Wrapper,
 118                                                           error_code &ec)
 119   : ELFObjectFile<target_endianness, is64Bits>(Wrapper, ec) {
 120   this->isDyldELFObject = true;
 121 }
 122
 123 template<support::endianness target_endianness, bool is64Bits>
 124 void DyldELFObject<target_endianness, is64Bits>::updateSectionAddress(
 125                                                        const SectionRef &Sec,
 126                                                        uint64_t Addr) {
 127   DataRefImpl ShdrRef = Sec.getRawDataRefImpl();
 128   Elf_Shdr *shdr = const_cast<Elf_Shdr*>(
 129                           reinterpret_cast<const Elf_Shdr *>(ShdrRef.p));
 130
 131   // This assumes the address passed in matches the target address bitness
 132   // The template-based type cast handles everything else.
 133   shdr->sh_addr = static_cast<addr_type>(Addr);
 134 }
 135
 136 template<support::endianness target_endianness, bool is64Bits>
 137 void DyldELFObject<target_endianness, is64Bits>::updateSymbolAddress(
 138                                                        const SymbolRef &SymRef,
 139                                                        uint64_t Addr) {
 140
 141   Elf_Sym *sym = const_cast<Elf_Sym*>(
 142                                  ELFObjectFile<target_endianness, is64Bits>::
 143                                    getSymbol(SymRef.getRawDataRefImpl()));
 144
 145   // This assumes the address passed in matches the target address bitness
 146   // The template-based type cast handles everything else.
 147   sym->st_value = static_cast<addr_type>(Addr);
 148 }
 149
 150 } // namespace
 151
 152
 153 namespace llvm {
 154
 155 ObjectImage *RuntimeDyldELF::createObjectImage(ObjectBuffer *Buffer) {
 156   if (Buffer->getBufferSize() < ELF::EI_NIDENT)
 157     llvm_unreachable("Unexpected ELF object size");
 158   std::pair<unsigned char, unsigned char> Ident = std::make_pair(
 159                          (uint8_t)Buffer->getBufferStart()[ELF::EI_CLASS],
 160                          (uint8_t)Buffer->getBufferStart()[ELF::EI_DATA]);
 161   error_code ec;
 162
 163   if (Ident.first == ELF::ELFCLASS32 && Ident.second == ELF::ELFDATA2LSB) {
 164     DyldELFObject<support::little, false> *Obj =
 165            new DyldELFObject<support::little, false>(Buffer->getMemBuffer(), ec);
 166     return new ELFObjectImage<support::little, false>(Buffer, Obj);
 167   }
 168   else if (Ident.first == ELF::ELFCLASS32 && Ident.second == ELF::ELFDATA2MSB) {
 169     DyldELFObject<support::big, false> *Obj =
 170            new DyldELFObject<support::big, false>(Buffer->getMemBuffer(), ec);
 171     return new ELFObjectImage<support::big, false>(Buffer, Obj);
 172   }
 173   else if (Ident.first == ELF::ELFCLASS64 && Ident.second == ELF::ELFDATA2MSB) {
 174     DyldELFObject<support::big, true> *Obj =
 175            new DyldELFObject<support::big, true>(Buffer->getMemBuffer(), ec);
 176     return new ELFObjectImage<support::big, true>(Buffer, Obj);
 177   }
 178   else if (Ident.first == ELF::ELFCLASS64 && Ident.second == ELF::ELFDATA2LSB) {
 179     DyldELFObject<support::little, true> *Obj =
 180            new DyldELFObject<support::little, true>(Buffer->getMemBuffer(), ec);
 181     return new ELFObjectImage<support::little, true>(Buffer, Obj);
 182   }
 183   else
 184     llvm_unreachable("Unexpected ELF format");
 185 }
 186
 187 RuntimeDyldELF::~RuntimeDyldELF() {
 188 }
 189
 190 void RuntimeDyldELF::resolveX86_64Relocation(uint8_t *LocalAddress,
 191                                              uint64_t FinalAddress,
 192                                              uint64_t Value,
 193                                              uint32_t Type,
 194                                              int64_t Addend) {
 195   switch (Type) {
 196   default:
 197     llvm_unreachable("Relocation type not implemented yet!");
 198   break;
 199   case ELF::R_X86_64_64: {
 200     uint64_t *Target = (uint64_t*)(LocalAddress);
 201     *Target = Value + Addend;
 202     break;
 203   }
 204   case ELF::R_X86_64_32:
 205   case ELF::R_X86_64_32S: {
 206     Value += Addend;
 207     assert((Type == ELF::R_X86_64_32 && (Value <= UINT32_MAX)) ||
 208            (Type == ELF::R_X86_64_32S &&
 209              ((int64_t)Value <= INT32_MAX && (int64_t)Value >= INT32_MIN)));
 210     uint32_t TruncatedAddr = (Value & 0xFFFFFFFF);
 211     uint32_t *Target = reinterpret_cast<uint32_t*>(LocalAddress);
 212     *Target = TruncatedAddr;
 213     break;
 214   }
 215   case ELF::R_X86_64_PC32: {
 216     uint32_t *Placeholder = reinterpret_cast<uint32_t*>(LocalAddress);
 217     int64_t RealOffset = *Placeholder + Value + Addend - FinalAddress;
 218     assert(RealOffset <= INT32_MAX && RealOffset >= INT32_MIN);
 219     int32_t TruncOffset = (RealOffset & 0xFFFFFFFF);
 220     *Placeholder = TruncOffset;
 221     break;
 222   }
 223   }
 224 }
 225
 226 void RuntimeDyldELF::resolveX86Relocation(uint8_t *LocalAddress,
 227                                           uint32_t FinalAddress,
 228                                           uint32_t Value,
 229                                           uint32_t Type,
 230                                           int32_t Addend) {
 231   switch (Type) {
 232   case ELF::R_386_32: {
 233     uint32_t *Target = (uint32_t*)(LocalAddress);
 234     uint32_t Placeholder = *Target;
 235     *Target = Placeholder + Value + Addend;
 236     break;
 237   }
 238   case ELF::R_386_PC32: {
 239     uint32_t *Placeholder = reinterpret_cast<uint32_t*>(LocalAddress);
 240     uint32_t RealOffset = *Placeholder + Value + Addend - FinalAddress;
 241     *Placeholder = RealOffset;
 242     break;
 243     }
 244     default:
 245       // There are other relocation types, but it appears these are the
 246       // only ones currently used by the LLVM ELF object writer
 247       llvm_unreachable("Relocation type not implemented yet!");
 248       break;
 249   }
 250 }
 251
 252 void RuntimeDyldELF::resolveARMRelocation(uint8_t *LocalAddress,
 253                                           uint32_t FinalAddress,
 254                                           uint32_t Value,
 255                                           uint32_t Type,
 256                                           int32_t Addend) {
 257   // TODO: Add Thumb relocations.
 258   uint32_t* TargetPtr = (uint32_t*)LocalAddress;
 259   Value += Addend;
 260
 261   DEBUG(dbgs() << "resolveARMRelocation, LocalAddress: " << LocalAddress
 262                << " FinalAddress: " << format("%p",FinalAddress)
 263                << " Value: " << format("%x",Value)
 264                << " Type: " << format("%x",Type)
 265                << " Addend: " << format("%x",Addend)
 266                << "\n");
 267
 268   switch(Type) {
 269   default:
 270     llvm_unreachable("Not implemented relocation type!");
 271
 272   // Write a 32bit value to relocation address, taking into account the
 273   // implicit addend encoded in the target.
 274   case ELF::R_ARM_ABS32 :
 275     *TargetPtr += Value;
 276     break;
 277
 278   // Write first 16 bit of 32 bit value to the mov instruction.
 279   // Last 4 bit should be shifted.
 280   case ELF::R_ARM_MOVW_ABS_NC :
 281     // We are not expecting any other addend in the relocation address.
 282     // Using 0x000F0FFF because MOVW has its 16 bit immediate split into 2
 283     // non-contiguous fields.
 284     assert((*TargetPtr & 0x000F0FFF) == 0);
 285     Value = Value & 0xFFFF;
 286     *TargetPtr |= Value & 0xFFF;
 287     *TargetPtr |= ((Value >> 12) & 0xF) << 16;
 288     break;
 289
 290   // Write last 16 bit of 32 bit value to the mov instruction.
 291   // Last 4 bit should be shifted.
 292   case ELF::R_ARM_MOVT_ABS :
 293     // We are not expecting any other addend in the relocation address.
 294     // Use 0x000F0FFF for the same reason as R_ARM_MOVW_ABS_NC.
 295     assert((*TargetPtr & 0x000F0FFF) == 0);
 296     Value = (Value >> 16) & 0xFFFF;
 297     *TargetPtr |= Value & 0xFFF;
 298     *TargetPtr |= ((Value >> 12) & 0xF) << 16;
 299     break;
 300
 301   // Write 24 bit relative value to the branch instruction.
 302   case ELF::R_ARM_PC24 :    // Fall through.
 303   case ELF::R_ARM_CALL :    // Fall through.
 304   case ELF::R_ARM_JUMP24 :
 305     int32_t RelValue = static_cast<int32_t>(Value - FinalAddress - 8);
 306     RelValue = (RelValue & 0x03FFFFFC) >> 2;
 307     *TargetPtr &= 0xFF000000;
 308     *TargetPtr |= RelValue;
 309     break;
 310   }
 311 }
 312
 313 void RuntimeDyldELF::resolveMIPSRelocation(uint8_t *LocalAddress,
 314                                            uint32_t FinalAddress,
 315                                            uint32_t Value,
 316                                            uint32_t Type,
 317                                            int32_t Addend) {
 318   uint32_t* TargetPtr = (uint32_t*)LocalAddress;
 319   Value += Addend;
 320
 321   DEBUG(dbgs() << "resolveMipselocation, LocalAddress: " << LocalAddress
 322                << " FinalAddress: " << format("%p",FinalAddress)
 323                << " Value: " << format("%x",Value)
 324                << " Type: " << format("%x",Type)
 325                << " Addend: " << format("%x",Addend)
 326                << "\n");
 327
 328   switch(Type) {
 329   default:
 330     llvm_unreachable("Not implemented relocation type!");
 331     break;
 332   case ELF::R_MIPS_32:
 333     *TargetPtr = Value + (*TargetPtr);
 334     break;
 335   case ELF::R_MIPS_26:
 336     *TargetPtr = ((*TargetPtr) & 0xfc000000) | (( Value & 0x0fffffff) >> 2);
 337     break;
 338   case ELF::R_MIPS_HI16:
 339     // Get the higher 16-bits. Also add 1 if bit 15 is 1.
 340     Value += ((*TargetPtr) & 0x0000ffff) << 16;
 341     *TargetPtr = ((*TargetPtr) & 0xffff0000) |
 342                  (((Value + 0x8000) >> 16) & 0xffff);
 343     break;
 344    case ELF::R_MIPS_LO16:
 345     Value += ((*TargetPtr) & 0x0000ffff);
 346     *TargetPtr = ((*TargetPtr) & 0xffff0000) | (Value & 0xffff);
 347     break;
 348    }
 349 }
 350
 351 // Return the .TOC. section address to R_PPC64_TOC relocations.
 352 uint64_t RuntimeDyldELF::findPPC64TOC() const {
 353   // The TOC consists of sections .got, .toc, .tocbss, .plt in that
 354   // order. The TOC starts where the first of these sections starts.
 355   SectionList::const_iterator it = Sections.begin();
 356   SectionList::const_iterator ite = Sections.end();
 357   for (; it != ite; ++it) {
 358     if (it->Name == ".got" ||
 359         it->Name == ".toc" ||
 360         it->Name == ".tocbss" ||
 361         it->Name == ".plt")
 362       break;
 363   }
 364   if (it == ite) {
 365     // This may happen for
 366     // * references to TOC base base (sym@toc, .odp relocation) without
 367     // a .toc directive.
 368     // In this case just use the first section (which is usually
 369     // the .odp) since the code won't reference the .toc base
 370     // directly.
 371     it = Sections.begin();
 372   }
 373   assert (it != ite);
 374   // Per the ppc64-elf-linux ABI, The TOC base is TOC value plus 0x8000
 375   // thus permitting a full 64 Kbytes segment.
 376   return it->LoadAddress + 0x8000;
 377 }
 378
 379 // Returns the sections and offset associated with the ODP entry referenced
 380 // by Symbol.
 381 void RuntimeDyldELF::findOPDEntrySection(ObjectImage &Obj,
 382                                          ObjSectionToIDMap &LocalSections,
 383                                          RelocationValueRef &Rel) {
 384   // Get the ELF symbol value (st_value) to compare with Relocation offset in
 385   // .opd entries
 386
 387   error_code err;
 388   for (section_iterator si = Obj.begin_sections(),
 389      se = Obj.end_sections(); si != se; si.increment(err)) {
 390     StringRef SectionName;
 391     check(si->getName(SectionName));
 392     if (SectionName != ".opd")
 393       continue;
 394
 395     for (relocation_iterator i = si->begin_relocations(),
 396          e = si->end_relocations(); i != e;) {
 397       check(err);
 398
 399       // The R_PPC64_ADDR64 relocation indicates the first field
 400       // of a .opd entry
 401       uint64_t TypeFunc;
 402       check(i->getType(TypeFunc));
 403       if (TypeFunc != ELF::R_PPC64_ADDR64) {
 404         i.increment(err);
 405         continue;
 406       }
 407
 408       SymbolRef TargetSymbol;
 409       uint64_t TargetSymbolOffset;
 410       int64_t TargetAdditionalInfo;
 411       check(i->getSymbol(TargetSymbol));
 412       check(i->getOffset(TargetSymbolOffset));
 413       check(i->getAdditionalInfo(TargetAdditionalInfo));
 414
 415       i = i.increment(err);
 416       if (i == e)
 417         break;
 418       check(err);
 419
 420       // Just check if following relocation is a R_PPC64_TOC
 421       uint64_t TypeTOC;
 422       check(i->getType(TypeTOC));
 423       if (TypeTOC != ELF::R_PPC64_TOC)
 424         continue;
 425
 426       // Finally compares the Symbol value and the target symbol offset
 427       // to check if this .opd entry refers to the symbol the relocation
 428       // points to.
 429       if (Rel.Addend != (intptr_t)TargetSymbolOffset)
 430         continue;
 431
 432       section_iterator tsi(Obj.end_sections());
 433       check(TargetSymbol.getSection(tsi));
 434       Rel.SectionID = findOrEmitSection(Obj, (*tsi), true, LocalSections);
 435       Rel.Addend = (intptr_t)TargetAdditionalInfo;
 436       return;
 437     }
 438   }
 439   llvm_unreachable("Attempting to get address of ODP entry!");
 440 }
 441
 442 // Relocation masks following the #lo(value), #hi(value), #higher(value),
 443 // and #highest(value) macros defined in section 4.5.1. Relocation Types
 444 // in PPC-elf64abi document.
 445 //
 446 static inline
 447 uint16_t applyPPClo (uint64_t value)
 448 {
 449   return value & 0xffff;
 450 }
 451
 452 static inline
 453 uint16_t applyPPChi (uint64_t value)
 454 {
 455   return (value >> 16) & 0xffff;
 456 }
 457
 458 static inline
 459 uint16_t applyPPChigher (uint64_t value)
 460 {
 461   return (value >> 32) & 0xffff;
 462 }
 463
 464 static inline
 465 uint16_t applyPPChighest (uint64_t value)
 466 {
 467   return (value >> 48) & 0xffff;
 468 }
 469
 470 void RuntimeDyldELF::resolvePPC64Relocation(uint8_t *LocalAddress,
 471                                             uint64_t FinalAddress,
 472                                             uint64_t Value,
 473                                             uint32_t Type,
 474                                             int64_t Addend) {
 475   switch (Type) {
 476   default:
 477     llvm_unreachable("Relocation type not implemented yet!");
 478   break;
 479   case ELF::R_PPC64_ADDR16_LO :
 480     writeInt16BE(LocalAddress, applyPPClo (Value + Addend));
 481     break;
 482   case ELF::R_PPC64_ADDR16_HI :
 483     writeInt16BE(LocalAddress, applyPPChi (Value + Addend));
 484     break;
 485   case ELF::R_PPC64_ADDR16_HIGHER :
 486     writeInt16BE(LocalAddress, applyPPChigher (Value + Addend));
 487     break;
 488   case ELF::R_PPC64_ADDR16_HIGHEST :
 489     writeInt16BE(LocalAddress, applyPPChighest (Value + Addend));
 490     break;
 491   case ELF::R_PPC64_ADDR14 : {
 492     assert(((Value + Addend) & 3) == 0);
 493     // Preserve the AA/LK bits in the branch instruction
 494     uint8_t aalk = *(LocalAddress+3);
 495     writeInt16BE(LocalAddress + 2, (aalk & 3) | ((Value + Addend) & 0xfffc));
 496   } break;
 497   case ELF::R_PPC64_REL24 : {
 498     int32_t delta = static_cast<int32_t>(Value - FinalAddress + Addend);
 499     if (SignExtend32<24>(delta) != delta)
 500       llvm_unreachable("Relocation R_PPC64_REL24 overflow");
 501     // Generates a 'bl <address>' instruction
 502     writeInt32BE(LocalAddress, 0x48000001 | (delta & 0x03FFFFFC));
 503   } break;
 504   case ELF::R_PPC64_ADDR64 :
 505     writeInt64BE(LocalAddress, Value + Addend);
 506     break;
 507   case ELF::R_PPC64_TOC :
 508     writeInt64BE(LocalAddress, findPPC64TOC());
 509     break;
 510   case ELF::R_PPC64_TOC16 : {
 511     uint64_t TOCStart = findPPC64TOC();
 512     Value = applyPPClo((Value + Addend) - TOCStart);
 513     writeInt16BE(LocalAddress, applyPPClo(Value));
 514   } break;
 515   case ELF::R_PPC64_TOC16_DS : {
 516     uint64_t TOCStart = findPPC64TOC();
 517     Value = ((Value + Addend) - TOCStart);
 518     writeInt16BE(LocalAddress, applyPPClo(Value));
 519   } break;
 520   }
 521 }
 522
 523
 524 void RuntimeDyldELF::resolveRelocation(uint8_t *LocalAddress,
 525                                        uint64_t FinalAddress,
 526                                        uint64_t Value,
 527                                        uint32_t Type,
 528                                        int64_t Addend) {
 529   switch (Arch) {
 530   case Triple::x86_64:
 531     resolveX86_64Relocation(LocalAddress, FinalAddress, Value, Type, Addend);
 532     break;
 533   case Triple::x86:
 534     resolveX86Relocation(LocalAddress, (uint32_t)(FinalAddress & 0xffffffffL),
 535                          (uint32_t)(Value & 0xffffffffL), Type,
 536                          (uint32_t)(Addend & 0xffffffffL));
 537     break;
 538   case Triple::arm:    // Fall through.
 539   case Triple::thumb:
 540     resolveARMRelocation(LocalAddress, (uint32_t)(FinalAddress & 0xffffffffL),
 541                          (uint32_t)(Value & 0xffffffffL), Type,
 542                          (uint32_t)(Addend & 0xffffffffL));
 543     break;
 544   case Triple::mips:    // Fall through.
 545   case Triple::mipsel:
 546     resolveMIPSRelocation(LocalAddress, (uint32_t)(FinalAddress & 0xffffffffL),
 547                           (uint32_t)(Value & 0xffffffffL), Type,
 548                           (uint32_t)(Addend & 0xffffffffL));
 549     break;
 550   case Triple::ppc64:
 551     resolvePPC64Relocation(LocalAddress, FinalAddress, Value, Type, Addend);
 552     break;
 553   default: llvm_unreachable("Unsupported CPU type!");
 554   }
 555 }
 556
 557 void RuntimeDyldELF::processRelocationRef(const ObjRelocationInfo &Rel,
 558                                           ObjectImage &Obj,
 559                                           ObjSectionToIDMap &ObjSectionToID,
 560                                           const SymbolTableMap &Symbols,
 561                                           StubMap &Stubs) {
 562
 563   uint32_t RelType = (uint32_t)(Rel.Type & 0xffffffffL);
 564   intptr_t Addend = (intptr_t)Rel.AdditionalInfo;
 565   const SymbolRef &Symbol = Rel.Symbol;
 566
 567   // Obtain the symbol name which is referenced in the relocation
 568   StringRef TargetName;
 569   Symbol.getName(TargetName);
 570   DEBUG(dbgs() << "\t\tRelType: " << RelType
 571                << " Addend: " << Addend
 572                << " TargetName: " << TargetName
 573                << "\n");
 574   RelocationValueRef Value;
 575   // First search for the symbol in the local symbol table
 576   SymbolTableMap::const_iterator lsi = Symbols.find(TargetName.data());
 577   SymbolRef::Type SymType;
 578   Symbol.getType(SymType);
 579   if (lsi != Symbols.end()) {
 580     Value.SectionID = lsi->second.first;
 581     Value.Addend = lsi->second.second;
 582   } else {
 583     // Search for the symbol in the global symbol table
 584     SymbolTableMap::const_iterator gsi =
 585         GlobalSymbolTable.find(TargetName.data());
 586     if (gsi != GlobalSymbolTable.end()) {
 587       Value.SectionID = gsi->second.first;
 588       Value.Addend = gsi->second.second;
 589     } else {
 590       switch (SymType) {
 591         case SymbolRef::ST_Debug: {
 592           // TODO: Now ELF SymbolRef::ST_Debug = STT_SECTION, it's not obviously
 593           // and can be changed by another developers. Maybe best way is add
 594           // a new symbol type ST_Section to SymbolRef and use it.
 595           section_iterator si(Obj.end_sections());
 596           Symbol.getSection(si);
 597           if (si == Obj.end_sections())
 598             llvm_unreachable("Symbol section not found, bad object file format!");
 599           DEBUG(dbgs() << "\t\tThis is section symbol\n");
 600           // Default to 'true' in case isText fails (though it never does).
 601           bool isCode = true;
 602           si->isText(isCode);
 603           Value.SectionID = findOrEmitSection(Obj,
 604                                               (*si),
 605                                               isCode,
 606                                               ObjSectionToID);
 607           Value.Addend = Addend;
 608           break;
 609         }
 610         case SymbolRef::ST_Unknown: {
 611           Value.SymbolName = TargetName.data();
 612           Value.Addend = Addend;
 613           break;
 614         }
 615         default:
 616           llvm_unreachable("Unresolved symbol type!");
 617           break;
 618       }
 619     }
 620   }
 621   DEBUG(dbgs() << "\t\tRel.SectionID: " << Rel.SectionID
 622                << " Rel.Offset: " << Rel.Offset
 623                << "\n");
 624   if (Arch == Triple::arm &&
 625       (RelType == ELF::R_ARM_PC24 ||
 626        RelType == ELF::R_ARM_CALL ||
 627        RelType == ELF::R_ARM_JUMP24)) {
 628     // This is an ARM branch relocation, need to use a stub function.
 629     DEBUG(dbgs() << "\t\tThis is an ARM branch relocation.");
 630     SectionEntry &Section = Sections[Rel.SectionID];
 631     uint8_t *Target = Section.Address + Rel.Offset;
 632
 633     // Look for an existing stub.
 634     StubMap::const_iterator i = Stubs.find(Value);
 635     if (i != Stubs.end()) {
 636       resolveRelocation(Target, (uint64_t)Target, (uint64_t)Section.Address +
 637                         i->second, RelType, 0);
 638       DEBUG(dbgs() << " Stub function found\n");
 639     } else {
 640       // Create a new stub function.
 641       DEBUG(dbgs() << " Create a new stub function\n");
 642       Stubs[Value] = Section.StubOffset;
 643       uint8_t *StubTargetAddr = createStubFunction(Section.Address +
 644                                                    Section.StubOffset);
 645       RelocationEntry RE(Rel.SectionID, StubTargetAddr - Section.Address,
 646                          ELF::R_ARM_ABS32, Value.Addend);
 647       if (Value.SymbolName)
 648         addRelocationForSymbol(RE, Value.SymbolName);
 649       else
 650         addRelocationForSection(RE, Value.SectionID);
 651
 652       resolveRelocation(Target, (uint64_t)Target, (uint64_t)Section.Address +
 653                         Section.StubOffset, RelType, 0);
 654       Section.StubOffset += getMaxStubSize();
 655     }
 656   } else if (Arch == Triple::mipsel && RelType == ELF::R_MIPS_26) {
 657     // This is an Mips branch relocation, need to use a stub function.
 658     DEBUG(dbgs() << "\t\tThis is a Mips branch relocation.");
 659     SectionEntry &Section = Sections[Rel.SectionID];
 660     uint8_t *Target = Section.Address + Rel.Offset;
 661     uint32_t *TargetAddress = (uint32_t *)Target;
 662
 663     // Extract the addend from the instruction.
 664     uint32_t Addend = ((*TargetAddress) & 0x03ffffff) << 2;
 665
 666     Value.Addend += Addend;
 667
 668     //  Look up for existing stub.
 669     StubMap::const_iterator i = Stubs.find(Value);
 670     if (i != Stubs.end()) {
 671       resolveRelocation(Target, (uint64_t)Target,
 672                         (uint64_t)Section.Address +
 673                         i->second, RelType, 0);
 674       DEBUG(dbgs() << " Stub function found\n");
 675     } else {
 676       // Create a new stub function.
 677       DEBUG(dbgs() << " Create a new stub function\n");
 678       Stubs[Value] = Section.StubOffset;
 679       uint8_t *StubTargetAddr = createStubFunction(Section.Address +
 680                                                    Section.StubOffset);
 681
 682       // Creating Hi and Lo relocations for the filled stub instructions.
 683       RelocationEntry REHi(Rel.SectionID,
 684                            StubTargetAddr - Section.Address,
 685                            ELF::R_MIPS_HI16, Value.Addend);
 686       RelocationEntry RELo(Rel.SectionID,
 687                            StubTargetAddr - Section.Address + 4,
 688                            ELF::R_MIPS_LO16, Value.Addend);
 689
 690       if (Value.SymbolName) {
 691         addRelocationForSymbol(REHi, Value.SymbolName);
 692         addRelocationForSymbol(RELo, Value.SymbolName);
 693       } else {
 694         addRelocationForSection(REHi, Value.SectionID);
 695         addRelocationForSection(RELo, Value.SectionID);
 696       }
 697
 698       resolveRelocation(Target, (uint64_t)Target,
 699                         (uint64_t)Section.Address +
 700                         Section.StubOffset, RelType, 0);
 701       Section.StubOffset += getMaxStubSize();
 702     }
 703   } else if (Arch == Triple::ppc64) {
 704     if (RelType == ELF::R_PPC64_REL24) {
 705       // A PPC branch relocation will need a stub function if the target is
 706       // an external symbol (Symbol::ST_Unknown) or if the target address
 707       // is not within the signed 24-bits branch address.
 708       SectionEntry &Section = Sections[Rel.SectionID];
 709       uint8_t *Target = Section.Address + Rel.Offset;
 710       bool RangeOverflow = false;
 711       if (SymType != SymbolRef::ST_Unknown) {
 712         // A function call may points to the .opd entry, so the final symbol value
 713         // in calculated based in the relocation values in .opd section.
 714         findOPDEntrySection(Obj, ObjSectionToID, Value);
 715         uint8_t *RelocTarget = Sections[Value.SectionID].Address + Value.Addend;
 716         int32_t delta = static_cast<int32_t>(Target - RelocTarget);
 717         // If it is within 24-bits branch range, just set the branch target
 718         if (SignExtend32<24>(delta) == delta) {
 719           RelocationEntry RE(Rel.SectionID, Rel.Offset, RelType, Value.Addend);
 720           if (Value.SymbolName)
 721             addRelocationForSymbol(RE, Value.SymbolName);
 722           else
 723             addRelocationForSection(RE, Value.SectionID);
 724         } else {
 725           RangeOverflow = true;
 726         }
 727       }
 728       if (SymType == SymbolRef::ST_Unknown || RangeOverflow == true) {
 729         // It is an external symbol (SymbolRef::ST_Unknown) or within a range
 730         // larger than 24-bits.
 731         StubMap::const_iterator i = Stubs.find(Value);
 732         if (i != Stubs.end()) {
 733           // Symbol function stub already created, just relocate to it
 734           resolveRelocation(Target, (uint64_t)Target, (uint64_t)Section.Address
 735                             + i->second, RelType, 0);
 736           DEBUG(dbgs() << " Stub function found\n");
 737         } else {
 738           // Create a new stub function.
 739           DEBUG(dbgs() << " Create a new stub function\n");
 740           Stubs[Value] = Section.StubOffset;
 741           uint8_t *StubTargetAddr = createStubFunction(Section.Address +
 742                                                        Section.StubOffset);
 743           RelocationEntry RE(Rel.SectionID, StubTargetAddr - Section.Address,
 744                              ELF::R_PPC64_ADDR64, Value.Addend);
 745
 746           // Generates the 64-bits address loads as exemplified in section
 747           // 4.5.1 in PPC64 ELF ABI.
 748           RelocationEntry REhst(Rel.SectionID,
 749                                 StubTargetAddr - Section.Address + 2,
 750                                 ELF::R_PPC64_ADDR16_HIGHEST, Value.Addend);
 751           RelocationEntry REhr(Rel.SectionID,
 752                                StubTargetAddr - Section.Address + 6,
 753                                ELF::R_PPC64_ADDR16_HIGHER, Value.Addend);
 754           RelocationEntry REh(Rel.SectionID,
 755                               StubTargetAddr - Section.Address + 14,
 756                               ELF::R_PPC64_ADDR16_HI, Value.Addend);
 757           RelocationEntry REl(Rel.SectionID,
 758                               StubTargetAddr - Section.Address + 18,
 759                               ELF::R_PPC64_ADDR16_LO, Value.Addend);
 760
 761           if (Value.SymbolName) {
 762             addRelocationForSymbol(REhst, Value.SymbolName);
 763             addRelocationForSymbol(REhr,  Value.SymbolName);
 764             addRelocationForSymbol(REh,   Value.SymbolName);
 765             addRelocationForSymbol(REl,   Value.SymbolName);
 766           } else {
 767             addRelocationForSection(REhst, Value.SectionID);
 768             addRelocationForSection(REhr,  Value.SectionID);
 769             addRelocationForSection(REh,   Value.SectionID);
 770             addRelocationForSection(REl,   Value.SectionID);
 771           }
 772
 773           resolveRelocation(Target, (uint64_t)Target, (uint64_t)Section.Address
 774                             + Section.StubOffset, RelType, 0);
 775           if (SymType == SymbolRef::ST_Unknown)
 776             // Restore the TOC for external calls
 777             writeInt32BE(Target+4, 0xE8410028); // ld r2,40(r1)
 778           Section.StubOffset += getMaxStubSize();
 779         }
 780       }
 781     } else {
 782       RelocationEntry RE(Rel.SectionID, Rel.Offset, RelType, Value.Addend);
 783       // Extra check to avoid relocation againt empty symbols (usually
 784       // the R_PPC64_TOC).
 785       if (Value.SymbolName && !TargetName.empty())
 786         addRelocationForSymbol(RE, Value.SymbolName);
 787       else
 788         addRelocationForSection(RE, Value.SectionID);
 789     }
 790   } else {
 791     RelocationEntry RE(Rel.SectionID, Rel.Offset, RelType, Value.Addend);
 792     if (Value.SymbolName)
 793       addRelocationForSymbol(RE, Value.SymbolName);
 794     else
 795       addRelocationForSection(RE, Value.SectionID);
 796   }
 797 }
 798
 799 unsigned RuntimeDyldELF::getCommonSymbolAlignment(const SymbolRef &Sym) {
 800   // In ELF, the value of an SHN_COMMON symbol is its alignment requirement.
 801   uint64_t Align;
 802   Check(Sym.getValue(Align));
 803   return Align;
 804 }
 805
 806 bool RuntimeDyldELF::isCompatibleFormat(const ObjectBuffer *Buffer) const {
 807   if (Buffer->getBufferSize() < strlen(ELF::ElfMagic))
 808     return false;
 809   return (memcmp(Buffer->getBufferStart(), ELF::ElfMagic, strlen(ELF::ElfMagic))) == 0;
 810 }
 811 } // namespace llvm