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 template<support::endianness target_endianness, bool is64Bits>
  34 class DyldELFObject : public ELFObjectFile<target_endianness, is64Bits> {
  35   LLVM_ELF_IMPORT_TYPES(target_endianness, is64Bits)
  36
  37   typedef Elf_Shdr_Impl<target_endianness, is64Bits> Elf_Shdr;
  38   typedef Elf_Sym_Impl<target_endianness, is64Bits> Elf_Sym;
  39   typedef Elf_Rel_Impl<target_endianness, is64Bits, false> Elf_Rel;
  40   typedef Elf_Rel_Impl<target_endianness, is64Bits, true> Elf_Rela;
  41
  42   typedef Elf_Ehdr_Impl<target_endianness, is64Bits> Elf_Ehdr;
  43
  44   typedef typename ELFDataTypeTypedefHelper<
  45           target_endianness, is64Bits>::value_type addr_type;
  46
  47 public:
  48   DyldELFObject(MemoryBuffer *Wrapper, error_code &ec);
  49
  50   void updateSectionAddress(const SectionRef &Sec, uint64_t Addr);
  51   void updateSymbolAddress(const SymbolRef &Sym, uint64_t Addr);
  52
  53   // Methods for type inquiry through isa, cast and dyn_cast
  54   static inline bool classof(const Binary *v) {
  55     return (isa<ELFObjectFile<target_endianness, is64Bits> >(v)
  56             && classof(cast<ELFObjectFile<target_endianness, is64Bits> >(v)));
  57   }
  58   static inline bool classof(
  59       const ELFObjectFile<target_endianness, is64Bits> *v) {
  60     return v->isDyldType();
  61   }
  62   static inline bool classof(const DyldELFObject *v) {
  63     return true;
  64   }
  65 };
  66
  67 template<support::endianness target_endianness, bool is64Bits>
  68 class ELFObjectImage : public ObjectImageCommon {
  69   protected:
  70     DyldELFObject<target_endianness, is64Bits> *DyldObj;
  71     bool Registered;
  72
  73   public:
  74     ELFObjectImage(ObjectBuffer *Input,
  75                    DyldELFObject<target_endianness, is64Bits> *Obj)
  76     : ObjectImageCommon(Input, Obj),
  77       DyldObj(Obj),
  78       Registered(false) {}
  79
  80     virtual ~ELFObjectImage() {
  81       if (Registered)
  82         deregisterWithDebugger();
  83     }
  84
  85     // Subclasses can override these methods to update the image with loaded
  86     // addresses for sections and common symbols
  87     virtual void updateSectionAddress(const SectionRef &Sec, uint64_t Addr)
  88     {
  89       DyldObj->updateSectionAddress(Sec, Addr);
  90     }
  91
  92     virtual void updateSymbolAddress(const SymbolRef &Sym, uint64_t Addr)
  93     {
  94       DyldObj->updateSymbolAddress(Sym, Addr);
  95     }
  96
  97     virtual void registerWithDebugger()
  98     {
  99       JITRegistrar::getGDBRegistrar().registerObject(*Buffer);
 100       Registered = true;
 101     }
 102     virtual void deregisterWithDebugger()
 103     {
 104       JITRegistrar::getGDBRegistrar().deregisterObject(*Buffer);
 105     }
 106 };
 107
 108 // The MemoryBuffer passed into this constructor is just a wrapper around the
 109 // actual memory.  Ultimately, the Binary parent class will take ownership of
 110 // this MemoryBuffer object but not the underlying memory.
 111 template<support::endianness target_endianness, bool is64Bits>
 112 DyldELFObject<target_endianness, is64Bits>::DyldELFObject(MemoryBuffer *Wrapper,
 113                                                           error_code &ec)
 114   : ELFObjectFile<target_endianness, is64Bits>(Wrapper, ec) {
 115   this->isDyldELFObject = true;
 116 }
 117
 118 template<support::endianness target_endianness, bool is64Bits>
 119 void DyldELFObject<target_endianness, is64Bits>::updateSectionAddress(
 120                                                        const SectionRef &Sec,
 121                                                        uint64_t Addr) {
 122   DataRefImpl ShdrRef = Sec.getRawDataRefImpl();
 123   Elf_Shdr *shdr = const_cast<Elf_Shdr*>(
 124                           reinterpret_cast<const Elf_Shdr *>(ShdrRef.p));
 125
 126   // This assumes the address passed in matches the target address bitness
 127   // The template-based type cast handles everything else.
 128   shdr->sh_addr = static_cast<addr_type>(Addr);
 129 }
 130
 131 template<support::endianness target_endianness, bool is64Bits>
 132 void DyldELFObject<target_endianness, is64Bits>::updateSymbolAddress(
 133                                                        const SymbolRef &SymRef,
 134                                                        uint64_t Addr) {
 135
 136   Elf_Sym *sym = const_cast<Elf_Sym*>(
 137                                  ELFObjectFile<target_endianness, is64Bits>::
 138                                    getSymbol(SymRef.getRawDataRefImpl()));
 139
 140   // This assumes the address passed in matches the target address bitness
 141   // The template-based type cast handles everything else.
 142   sym->st_value = static_cast<addr_type>(Addr);
 143 }
 144
 145 } // namespace
 146
 147
 148 namespace llvm {
 149
 150 ObjectImage *RuntimeDyldELF::createObjectImage(ObjectBuffer *Buffer) {
 151   if (Buffer->getBufferSize() < ELF::EI_NIDENT)
 152     llvm_unreachable("Unexpected ELF object size");
 153   std::pair<unsigned char, unsigned char> Ident = std::make_pair(
 154                          (uint8_t)Buffer->getBufferStart()[ELF::EI_CLASS],
 155                          (uint8_t)Buffer->getBufferStart()[ELF::EI_DATA]);
 156   error_code ec;
 157
 158   if (Ident.first == ELF::ELFCLASS32 && Ident.second == ELF::ELFDATA2LSB) {
 159     DyldELFObject<support::little, false> *Obj =
 160            new DyldELFObject<support::little, false>(Buffer->getMemBuffer(), ec);
 161     return new ELFObjectImage<support::little, false>(Buffer, Obj);
 162   }
 163   else if (Ident.first == ELF::ELFCLASS32 && Ident.second == ELF::ELFDATA2MSB) {
 164     DyldELFObject<support::big, false> *Obj =
 165            new DyldELFObject<support::big, false>(Buffer->getMemBuffer(), ec);
 166     return new ELFObjectImage<support::big, false>(Buffer, Obj);
 167   }
 168   else if (Ident.first == ELF::ELFCLASS64 && Ident.second == ELF::ELFDATA2MSB) {
 169     DyldELFObject<support::big, true> *Obj =
 170            new DyldELFObject<support::big, true>(Buffer->getMemBuffer(), ec);
 171     return new ELFObjectImage<support::big, true>(Buffer, Obj);
 172   }
 173   else if (Ident.first == ELF::ELFCLASS64 && Ident.second == ELF::ELFDATA2LSB) {
 174     DyldELFObject<support::little, true> *Obj =
 175            new DyldELFObject<support::little, true>(Buffer->getMemBuffer(), ec);
 176     return new ELFObjectImage<support::little, true>(Buffer, Obj);
 177   }
 178   else
 179     llvm_unreachable("Unexpected ELF format");
 180 }
 181
 182 RuntimeDyldELF::~RuntimeDyldELF() {
 183 }
 184
 185 void RuntimeDyldELF::resolveX86_64Relocation(uint8_t *LocalAddress,
 186                                              uint64_t FinalAddress,
 187                                              uint64_t Value,
 188                                              uint32_t Type,
 189                                              int64_t Addend) {
 190   switch (Type) {
 191   default:
 192     llvm_unreachable("Relocation type not implemented yet!");
 193   break;
 194   case ELF::R_X86_64_64: {
 195     uint64_t *Target = (uint64_t*)(LocalAddress);
 196     *Target = Value + Addend;
 197     break;
 198   }
 199   case ELF::R_X86_64_32:
 200   case ELF::R_X86_64_32S: {
 201     Value += Addend;
 202     assert((Type == ELF::R_X86_64_32 && (Value <= UINT32_MAX)) ||
 203            (Type == ELF::R_X86_64_32S &&
 204              ((int64_t)Value <= INT32_MAX && (int64_t)Value >= INT32_MIN)));
 205     uint32_t TruncatedAddr = (Value & 0xFFFFFFFF);
 206     uint32_t *Target = reinterpret_cast<uint32_t*>(LocalAddress);
 207     *Target = TruncatedAddr;
 208     break;
 209   }
 210   case ELF::R_X86_64_PC32: {
 211     uint32_t *Placeholder = reinterpret_cast<uint32_t*>(LocalAddress);
 212     int64_t RealOffset = *Placeholder + Value + Addend - FinalAddress;
 213     assert(RealOffset <= INT32_MAX && RealOffset >= INT32_MIN);
 214     int32_t TruncOffset = (RealOffset & 0xFFFFFFFF);
 215     *Placeholder = TruncOffset;
 216     break;
 217   }
 218   }
 219 }
 220
 221 void RuntimeDyldELF::resolveX86Relocation(uint8_t *LocalAddress,
 222                                           uint32_t FinalAddress,
 223                                           uint32_t Value,
 224                                           uint32_t Type,
 225                                           int32_t Addend) {
 226   switch (Type) {
 227   case ELF::R_386_32: {
 228     uint32_t *Target = (uint32_t*)(LocalAddress);
 229     uint32_t Placeholder = *Target;
 230     *Target = Placeholder + Value + Addend;
 231     break;
 232   }
 233   case ELF::R_386_PC32: {
 234     uint32_t *Placeholder = reinterpret_cast<uint32_t*>(LocalAddress);
 235     uint32_t RealOffset = *Placeholder + Value + Addend - FinalAddress;
 236     *Placeholder = RealOffset;
 237     break;
 238     }
 239     default:
 240       // There are other relocation types, but it appears these are the
 241       // only ones currently used by the LLVM ELF object writer
 242       llvm_unreachable("Relocation type not implemented yet!");
 243       break;
 244   }
 245 }
 246
 247 void RuntimeDyldELF::resolveARMRelocation(uint8_t *LocalAddress,
 248                                           uint32_t FinalAddress,
 249                                           uint32_t Value,
 250                                           uint32_t Type,
 251                                           int32_t Addend) {
 252   // TODO: Add Thumb relocations.
 253   uint32_t* TargetPtr = (uint32_t*)LocalAddress;
 254   Value += Addend;
 255
 256   DEBUG(dbgs() << "resolveARMRelocation, LocalAddress: " << LocalAddress
 257                << " FinalAddress: " << format("%p",FinalAddress)
 258                << " Value: " << format("%x",Value)
 259                << " Type: " << format("%x",Type)
 260                << " Addend: " << format("%x",Addend)
 261                << "\n");
 262
 263   switch(Type) {
 264   default:
 265     llvm_unreachable("Not implemented relocation type!");
 266
 267   // Just write 32bit value to relocation address
 268   case ELF::R_ARM_ABS32 :
 269     *TargetPtr = Value;
 270     break;
 271
 272   // Write first 16 bit of 32 bit value to the mov instruction.
 273   // Last 4 bit should be shifted.
 274   case ELF::R_ARM_MOVW_ABS_NC :
 275     Value = Value & 0xFFFF;
 276     *TargetPtr |= Value & 0xFFF;
 277     *TargetPtr |= ((Value >> 12) & 0xF) << 16;
 278     break;
 279
 280   // Write last 16 bit of 32 bit value to the mov instruction.
 281   // Last 4 bit should be shifted.
 282   case ELF::R_ARM_MOVT_ABS :
 283     Value = (Value >> 16) & 0xFFFF;
 284     *TargetPtr |= Value & 0xFFF;
 285     *TargetPtr |= ((Value >> 12) & 0xF) << 16;
 286     break;
 287
 288   // Write 24 bit relative value to the branch instruction.
 289   case ELF::R_ARM_PC24 :    // Fall through.
 290   case ELF::R_ARM_CALL :    // Fall through.
 291   case ELF::R_ARM_JUMP24 :
 292     int32_t RelValue = static_cast<int32_t>(Value - FinalAddress - 8);
 293     RelValue = (RelValue & 0x03FFFFFC) >> 2;
 294     *TargetPtr &= 0xFF000000;
 295     *TargetPtr |= RelValue;
 296     break;
 297   }
 298 }
 299
 300 void RuntimeDyldELF::resolveMIPSRelocation(uint8_t *LocalAddress,
 301                                            uint32_t FinalAddress,
 302                                            uint32_t Value,
 303                                            uint32_t Type,
 304                                            int32_t Addend) {
 305   uint32_t* TargetPtr = (uint32_t*)LocalAddress;
 306   Value += Addend;
 307
 308   DEBUG(dbgs() << "resolveMipselocation, LocalAddress: " << LocalAddress
 309                << " FinalAddress: " << format("%p",FinalAddress)
 310                << " Value: " << format("%x",Value)
 311                << " Type: " << format("%x",Type)
 312                << " Addend: " << format("%x",Addend)
 313                << "\n");
 314
 315   switch(Type) {
 316   default:
 317     llvm_unreachable("Not implemented relocation type!");
 318     break;
 319   case ELF::R_MIPS_32:
 320     *TargetPtr = Value + (*TargetPtr);
 321     break;
 322   case ELF::R_MIPS_26:
 323     *TargetPtr = ((*TargetPtr) & 0xfc000000) | (( Value & 0x0fffffff) >> 2);
 324     break;
 325   case ELF::R_MIPS_HI16:
 326     // Get the higher 16-bits. Also add 1 if bit 15 is 1.
 327     Value += ((*TargetPtr) & 0x0000ffff) << 16;
 328     *TargetPtr = ((*TargetPtr) & 0xffff0000) |
 329                  (((Value + 0x8000) >> 16) & 0xffff);
 330     break;
 331    case ELF::R_MIPS_LO16:
 332     Value += ((*TargetPtr) & 0x0000ffff);
 333     *TargetPtr = ((*TargetPtr) & 0xffff0000) | (Value & 0xffff);
 334     break;
 335    }
 336 }
 337
 338 void RuntimeDyldELF::resolveRelocation(uint8_t *LocalAddress,
 339                                        uint64_t FinalAddress,
 340                                        uint64_t Value,
 341                                        uint32_t Type,
 342                                        int64_t Addend) {
 343   switch (Arch) {
 344   case Triple::x86_64:
 345     resolveX86_64Relocation(LocalAddress, FinalAddress, Value, Type, Addend);
 346     break;
 347   case Triple::x86:
 348     resolveX86Relocation(LocalAddress, (uint32_t)(FinalAddress & 0xffffffffL),
 349                          (uint32_t)(Value & 0xffffffffL), Type,
 350                          (uint32_t)(Addend & 0xffffffffL));
 351     break;
 352   case Triple::arm:    // Fall through.
 353   case Triple::thumb:
 354     resolveARMRelocation(LocalAddress, (uint32_t)(FinalAddress & 0xffffffffL),
 355                          (uint32_t)(Value & 0xffffffffL), Type,
 356                          (uint32_t)(Addend & 0xffffffffL));
 357     break;
 358   case Triple::mips:    // Fall through.
 359   case Triple::mipsel:
 360     resolveMIPSRelocation(LocalAddress, (uint32_t)(FinalAddress & 0xffffffffL),
 361                           (uint32_t)(Value & 0xffffffffL), Type,
 362                           (uint32_t)(Addend & 0xffffffffL));
 363     break;
 364   default: llvm_unreachable("Unsupported CPU type!");
 365   }
 366 }
 367
 368 void RuntimeDyldELF::processRelocationRef(const ObjRelocationInfo &Rel,
 369                                           ObjectImage &Obj,
 370                                           ObjSectionToIDMap &ObjSectionToID,
 371                                           const SymbolTableMap &Symbols,
 372                                           StubMap &Stubs) {
 373
 374   uint32_t RelType = (uint32_t)(Rel.Type & 0xffffffffL);
 375   intptr_t Addend = (intptr_t)Rel.AdditionalInfo;
 376   const SymbolRef &Symbol = Rel.Symbol;
 377
 378   // Obtain the symbol name which is referenced in the relocation
 379   StringRef TargetName;
 380   Symbol.getName(TargetName);
 381   DEBUG(dbgs() << "\t\tRelType: " << RelType
 382                << " Addend: " << Addend
 383                << " TargetName: " << TargetName
 384                << "\n");
 385   RelocationValueRef Value;
 386   // First search for the symbol in the local symbol table
 387   SymbolTableMap::const_iterator lsi = Symbols.find(TargetName.data());
 388   if (lsi != Symbols.end()) {
 389     Value.SectionID = lsi->second.first;
 390     Value.Addend = lsi->second.second;
 391   } else {
 392     // Search for the symbol in the global symbol table
 393     SymbolTableMap::const_iterator gsi =
 394         GlobalSymbolTable.find(TargetName.data());
 395     if (gsi != GlobalSymbolTable.end()) {
 396       Value.SectionID = gsi->second.first;
 397       Value.Addend = gsi->second.second;
 398     } else {
 399       SymbolRef::Type SymType;
 400       Symbol.getType(SymType);
 401       switch (SymType) {
 402         case SymbolRef::ST_Debug: {
 403           // TODO: Now ELF SymbolRef::ST_Debug = STT_SECTION, it's not obviously
 404           // and can be changed by another developers. Maybe best way is add
 405           // a new symbol type ST_Section to SymbolRef and use it.
 406           section_iterator si(Obj.end_sections());
 407           Symbol.getSection(si);
 408           if (si == Obj.end_sections())
 409             llvm_unreachable("Symbol section not found, bad object file format!");
 410           DEBUG(dbgs() << "\t\tThis is section symbol\n");
 411           Value.SectionID = findOrEmitSection(Obj, (*si), true, ObjSectionToID);
 412           Value.Addend = Addend;
 413           break;
 414         }
 415         case SymbolRef::ST_Unknown: {
 416           Value.SymbolName = TargetName.data();
 417           Value.Addend = Addend;
 418           break;
 419         }
 420         default:
 421           llvm_unreachable("Unresolved symbol type!");
 422           break;
 423       }
 424     }
 425   }
 426   DEBUG(dbgs() << "\t\tRel.SectionID: " << Rel.SectionID
 427                << " Rel.Offset: " << Rel.Offset
 428                << "\n");
 429   if (Arch == Triple::arm &&
 430       (RelType == ELF::R_ARM_PC24 ||
 431        RelType == ELF::R_ARM_CALL ||
 432        RelType == ELF::R_ARM_JUMP24)) {
 433     // This is an ARM branch relocation, need to use a stub function.
 434     DEBUG(dbgs() << "\t\tThis is an ARM branch relocation.");
 435     SectionEntry &Section = Sections[Rel.SectionID];
 436     uint8_t *Target = Section.Address + Rel.Offset;
 437
 438     //  Look up for existing stub.
 439     StubMap::const_iterator i = Stubs.find(Value);
 440     if (i != Stubs.end()) {
 441       resolveRelocation(Target, (uint64_t)Target, (uint64_t)Section.Address +
 442                         i->second, RelType, 0);
 443       DEBUG(dbgs() << " Stub function found\n");
 444     } else {
 445       // Create a new stub function.
 446       DEBUG(dbgs() << " Create a new stub function\n");
 447       Stubs[Value] = Section.StubOffset;
 448       uint8_t *StubTargetAddr = createStubFunction(Section.Address +
 449                                                    Section.StubOffset);
 450       RelocationEntry RE(Rel.SectionID, StubTargetAddr - Section.Address,
 451                          ELF::R_ARM_ABS32, Value.Addend);
 452       if (Value.SymbolName)
 453         addRelocationForSymbol(RE, Value.SymbolName);
 454       else
 455         addRelocationForSection(RE, Value.SectionID);
 456
 457       resolveRelocation(Target, (uint64_t)Target, (uint64_t)Section.Address +
 458                         Section.StubOffset, RelType, 0);
 459       Section.StubOffset += getMaxStubSize();
 460     }
 461   } else if (Arch == Triple::mipsel && RelType == ELF::R_MIPS_26) {
 462     // This is an Mips branch relocation, need to use a stub function.
 463     DEBUG(dbgs() << "\t\tThis is a Mips branch relocation.");
 464     SectionEntry &Section = Sections[Rel.SectionID];
 465     uint8_t *Target = Section.Address + Rel.Offset;
 466     uint32_t *TargetAddress = (uint32_t *)Target;
 467
 468     // Extract the addend from the instruction.
 469     uint32_t Addend = ((*TargetAddress) & 0x03ffffff) << 2;
 470
 471     Value.Addend += Addend;
 472
 473     //  Look up for existing stub.
 474     StubMap::const_iterator i = Stubs.find(Value);
 475     if (i != Stubs.end()) {
 476       resolveRelocation(Target, (uint64_t)Target,
 477                         (uint64_t)Section.Address +
 478                         i->second, RelType, 0);
 479       DEBUG(dbgs() << " Stub function found\n");
 480     } else {
 481       // Create a new stub function.
 482       DEBUG(dbgs() << " Create a new stub function\n");
 483       Stubs[Value] = Section.StubOffset;
 484       uint8_t *StubTargetAddr = createStubFunction(Section.Address +
 485                                                    Section.StubOffset);
 486
 487       // Creating Hi and Lo relocations for the filled stub instructions.
 488       RelocationEntry REHi(Rel.SectionID,
 489                            StubTargetAddr - Section.Address,
 490                            ELF::R_MIPS_HI16, Value.Addend);
 491       RelocationEntry RELo(Rel.SectionID,
 492                            StubTargetAddr - Section.Address + 4,
 493                            ELF::R_MIPS_LO16, Value.Addend);
 494
 495       if (Value.SymbolName) {
 496         addRelocationForSymbol(REHi, Value.SymbolName);
 497         addRelocationForSymbol(RELo, Value.SymbolName);
 498       } else {
 499         addRelocationForSection(REHi, Value.SectionID);
 500         addRelocationForSection(RELo, Value.SectionID);
 501       }
 502
 503       resolveRelocation(Target, (uint64_t)Target,
 504                         (uint64_t)Section.Address +
 505                         Section.StubOffset, RelType, 0);
 506       Section.StubOffset += getMaxStubSize();
 507     }
 508   } else {
 509     RelocationEntry RE(Rel.SectionID, Rel.Offset, RelType, Value.Addend);
 510     if (Value.SymbolName)
 511       addRelocationForSymbol(RE, Value.SymbolName);
 512     else
 513       addRelocationForSection(RE, Value.SectionID);
 514   }
 515 }
 516
 517 bool RuntimeDyldELF::isCompatibleFormat(const ObjectBuffer *Buffer) const {
 518   if (Buffer->getBufferSize() < strlen(ELF::ElfMagic))
 519     return false;
 520   return (memcmp(Buffer->getBufferStart(), ELF::ElfMagic, strlen(ELF::ElfMagic))) == 0;
 521 }
 522 } // namespace llvm