lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h

   1 //===-- RuntimeDyldImpl.h - Run-time dynamic linker for MC-JIT --*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // Interface for the implementations of runtime dynamic linker facilities.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #ifndef LLVM_LIB_EXECUTIONENGINE_RUNTIMEDYLD_RUNTIMEDYLDIMPL_H
  14 #define LLVM_LIB_EXECUTIONENGINE_RUNTIMEDYLD_RUNTIMEDYLDIMPL_H
  15
  16 #include "llvm/ADT/SmallVector.h"
  17 #include "llvm/ADT/StringMap.h"
  18 #include "llvm/ADT/Triple.h"
  19 #include "llvm/ExecutionEngine/RTDyldMemoryManager.h"
  20 #include "llvm/ExecutionEngine/RuntimeDyld.h"
  21 #include "llvm/ExecutionEngine/RuntimeDyldChecker.h"
  22 #include "llvm/Object/ObjectFile.h"
  23 #include "llvm/Support/Debug.h"
  24 #include "llvm/Support/ErrorHandling.h"
  25 #include "llvm/Support/Format.h"
  26 #include "llvm/Support/Host.h"
  27 #include "llvm/Support/Mutex.h"
  28 #include "llvm/Support/SwapByteOrder.h"
  29 #include <map>
  30 #include <system_error>
  31 #include <unordered_map>
  32
  33 using namespace llvm;
  34 using namespace llvm::object;
  35
  36 namespace llvm {
  37
  38 class Twine;
  39
  40 #define UNIMPLEMENTED_RELOC(RelType) \
  41   case RelType: \
  42     return make_error<RuntimeDyldError>("Unimplemented relocation: " #RelType)
  43
  44 /// SectionEntry - represents a section emitted into memory by the dynamic
  45 /// linker.
  46 class SectionEntry {
  47   /// Name - section name.
  48   std::string Name;
  49
  50   /// Address - address in the linker's memory where the section resides.
  51   uint8_t *Address;
  52
  53   /// Size - section size. Doesn't include the stubs.
  54   size_t Size;
  55
  56   /// LoadAddress - the address of the section in the target process's memory.
  57   /// Used for situations in which JIT-ed code is being executed in the address
  58   /// space of a separate process.  If the code executes in the same address
  59   /// space where it was JIT-ed, this just equals Address.
  60   uint64_t LoadAddress;
  61
  62   /// StubOffset - used for architectures with stub functions for far
  63   /// relocations (like ARM).
  64   uintptr_t StubOffset;
  65
  66   /// The total amount of space allocated for this section.  This includes the
  67   /// section size and the maximum amount of space that the stubs can occupy.
  68   size_t AllocationSize;
  69
  70   /// ObjAddress - address of the section in the in-memory object file.  Used
  71   /// for calculating relocations in some object formats (like MachO).
  72   uintptr_t ObjAddress;
  73
  74 public:
  75   SectionEntry(StringRef name, uint8_t *address, size_t size,
  76                size_t allocationSize, uintptr_t objAddress)
  77       : Name(name), Address(address), Size(size),
  78         LoadAddress(reinterpret_cast<uintptr_t>(address)), StubOffset(size),
  79         AllocationSize(allocationSize), ObjAddress(objAddress) {
  80     // AllocationSize is used only in asserts, prevent an "unused private field"
  81     // warning:
  82     (void)AllocationSize;
  83   }
  84
  85   StringRef getName() const { return Name; }
  86
  87   uint8_t *getAddress() const { return Address; }
  88
  89   /// Return the address of this section with an offset.
  90   uint8_t *getAddressWithOffset(unsigned OffsetBytes) const {
  91     assert(OffsetBytes <= AllocationSize && "Offset out of bounds!");
  92     return Address + OffsetBytes;
  93   }
  94
  95   size_t getSize() const { return Size; }
  96
  97   uint64_t getLoadAddress() const { return LoadAddress; }
  98   void setLoadAddress(uint64_t LA) { LoadAddress = LA; }
  99
 100   /// Return the load address of this section with an offset.
 101   uint64_t getLoadAddressWithOffset(unsigned OffsetBytes) const {
 102     assert(OffsetBytes <= AllocationSize && "Offset out of bounds!");
 103     return LoadAddress + OffsetBytes;
 104   }
 105
 106   uintptr_t getStubOffset() const { return StubOffset; }
 107
 108   void advanceStubOffset(unsigned StubSize) {
 109     StubOffset += StubSize;
 110     assert(StubOffset <= AllocationSize && "Not enough space allocated!");
 111   }
 112
 113   uintptr_t getObjAddress() const { return ObjAddress; }
 114 };
 115
 116 /// RelocationEntry - used to represent relocations internally in the dynamic
 117 /// linker.
 118 class RelocationEntry {
 119 public:
 120   /// SectionID - the section this relocation points to.
 121   unsigned SectionID;
 122
 123   /// Offset - offset into the section.
 124   uint64_t Offset;
 125
 126   /// RelType - relocation type.
 127   uint32_t RelType;
 128
 129   /// Addend - the relocation addend encoded in the instruction itself.  Also
 130   /// used to make a relocation section relative instead of symbol relative.
 131   int64_t Addend;
 132
 133   struct SectionPair {
 134       uint32_t SectionA;
 135       uint32_t SectionB;
 136   };
 137
 138   /// SymOffset - Section offset of the relocation entry's symbol (used for GOT
 139   /// lookup).
 140   union {
 141     uint64_t SymOffset;
 142     SectionPair Sections;
 143   };
 144
 145   /// True if this is a PCRel relocation (MachO specific).
 146   bool IsPCRel;
 147
 148   /// The size of this relocation (MachO specific).
 149   unsigned Size;
 150
 151   // ARM (MachO and COFF) specific.
 152   bool IsTargetThumbFunc = false;
 153
 154   RelocationEntry(unsigned id, uint64_t offset, uint32_t type, int64_t addend)
 155       : SectionID(id), Offset(offset), RelType(type), Addend(addend),
 156         SymOffset(0), IsPCRel(false), Size(0), IsTargetThumbFunc(false) {}
 157
 158   RelocationEntry(unsigned id, uint64_t offset, uint32_t type, int64_t addend,
 159                   uint64_t symoffset)
 160       : SectionID(id), Offset(offset), RelType(type), Addend(addend),
 161         SymOffset(symoffset), IsPCRel(false), Size(0),
 162         IsTargetThumbFunc(false) {}
 163
 164   RelocationEntry(unsigned id, uint64_t offset, uint32_t type, int64_t addend,
 165                   bool IsPCRel, unsigned Size)
 166       : SectionID(id), Offset(offset), RelType(type), Addend(addend),
 167         SymOffset(0), IsPCRel(IsPCRel), Size(Size), IsTargetThumbFunc(false) {}
 168
 169   RelocationEntry(unsigned id, uint64_t offset, uint32_t type, int64_t addend,
 170                   unsigned SectionA, uint64_t SectionAOffset, unsigned SectionB,
 171                   uint64_t SectionBOffset, bool IsPCRel, unsigned Size)
 172       : SectionID(id), Offset(offset), RelType(type),
 173         Addend(SectionAOffset - SectionBOffset + addend), IsPCRel(IsPCRel),
 174         Size(Size), IsTargetThumbFunc(false) {
 175     Sections.SectionA = SectionA;
 176     Sections.SectionB = SectionB;
 177   }
 178
 179   RelocationEntry(unsigned id, uint64_t offset, uint32_t type, int64_t addend,
 180                   unsigned SectionA, uint64_t SectionAOffset, unsigned SectionB,
 181                   uint64_t SectionBOffset, bool IsPCRel, unsigned Size,
 182                   bool IsTargetThumbFunc)
 183       : SectionID(id), Offset(offset), RelType(type),
 184         Addend(SectionAOffset - SectionBOffset + addend), IsPCRel(IsPCRel),
 185         Size(Size), IsTargetThumbFunc(IsTargetThumbFunc) {
 186     Sections.SectionA = SectionA;
 187     Sections.SectionB = SectionB;
 188   }
 189 };
 190
 191 class RelocationValueRef {
 192 public:
 193   unsigned SectionID;
 194   uint64_t Offset;
 195   int64_t Addend;
 196   const char *SymbolName;
 197   bool IsStubThumb = false;
 198   RelocationValueRef() : SectionID(0), Offset(0), Addend(0),
 199                          SymbolName(nullptr) {}
 200
 201   inline bool operator==(const RelocationValueRef &Other) const {
 202     return SectionID == Other.SectionID && Offset == Other.Offset &&
 203            Addend == Other.Addend && SymbolName == Other.SymbolName &&
 204            IsStubThumb == Other.IsStubThumb;
 205   }
 206   inline bool operator<(const RelocationValueRef &Other) const {
 207     if (SectionID != Other.SectionID)
 208       return SectionID < Other.SectionID;
 209     if (Offset != Other.Offset)
 210       return Offset < Other.Offset;
 211     if (Addend != Other.Addend)
 212       return Addend < Other.Addend;
 213     if (IsStubThumb != Other.IsStubThumb)
 214       return IsStubThumb < Other.IsStubThumb;
 215     return SymbolName < Other.SymbolName;
 216   }
 217 };
 218
 219 /// Symbol info for RuntimeDyld.
 220 class SymbolTableEntry {
 221 public:
 222   SymbolTableEntry() = default;
 223
 224   SymbolTableEntry(unsigned SectionID, uint64_t Offset, JITSymbolFlags Flags)
 225       : Offset(Offset), SectionID(SectionID), Flags(Flags) {}
 226
 227   unsigned getSectionID() const { return SectionID; }
 228   uint64_t getOffset() const { return Offset; }
 229   void setOffset(uint64_t NewOffset) { Offset = NewOffset; }
 230
 231   JITSymbolFlags getFlags() const { return Flags; }
 232
 233 private:
 234   uint64_t Offset = 0;
 235   unsigned SectionID = 0;
 236   JITSymbolFlags Flags = JITSymbolFlags::None;
 237 };
 238
 239 typedef StringMap<SymbolTableEntry> RTDyldSymbolTable;
 240
 241 class RuntimeDyldImpl {
 242   friend class RuntimeDyld::LoadedObjectInfo;
 243 protected:
 244   static const unsigned AbsoluteSymbolSection = ~0U;
 245
 246   // The MemoryManager to load objects into.
 247   RuntimeDyld::MemoryManager &MemMgr;
 248
 249   // The symbol resolver to use for external symbols.
 250   JITSymbolResolver &Resolver;
 251
 252   // A list of all sections emitted by the dynamic linker.  These sections are
 253   // referenced in the code by means of their index in this list - SectionID.
 254   typedef SmallVector<SectionEntry, 64> SectionList;
 255   SectionList Sections;
 256
 257   typedef unsigned SID; // Type for SectionIDs
 258 #define RTDYLD_INVALID_SECTION_ID ((RuntimeDyldImpl::SID)(-1))
 259
 260   // Keep a map of sections from object file to the SectionID which
 261   // references it.
 262   typedef std::map<SectionRef, unsigned> ObjSectionToIDMap;
 263
 264   // A global symbol table for symbols from all loaded modules.
 265   RTDyldSymbolTable GlobalSymbolTable;
 266
 267   // Keep a map of common symbols to their info pairs
 268   typedef std::vector<SymbolRef> CommonSymbolList;
 269
 270   // For each symbol, keep a list of relocations based on it. Anytime
 271   // its address is reassigned (the JIT re-compiled the function, e.g.),
 272   // the relocations get re-resolved.
 273   // The symbol (or section) the relocation is sourced from is the Key
 274   // in the relocation list where it's stored.
 275   typedef SmallVector<RelocationEntry, 64> RelocationList;
 276   // Relocations to sections already loaded. Indexed by SectionID which is the
 277   // source of the address. The target where the address will be written is
 278   // SectionID/Offset in the relocation itself.
 279   std::unordered_map<unsigned, RelocationList> Relocations;
 280
 281   // Relocations to external symbols that are not yet resolved.  Symbols are
 282   // external when they aren't found in the global symbol table of all loaded
 283   // modules.  This map is indexed by symbol name.
 284   StringMap<RelocationList> ExternalSymbolRelocations;
 285
 286
 287   typedef std::map<RelocationValueRef, uintptr_t> StubMap;
 288
 289   Triple::ArchType Arch;
 290   bool IsTargetLittleEndian;
 291   bool IsMipsO32ABI;
 292   bool IsMipsN32ABI;
 293   bool IsMipsN64ABI;
 294
 295   // True if all sections should be passed to the memory manager, false if only
 296   // sections containing relocations should be. Defaults to 'false'.
 297   bool ProcessAllSections;
 298
 299   // This mutex prevents simultaneously loading objects from two different
 300   // threads.  This keeps us from having to protect individual data structures
 301   // and guarantees that section allocation requests to the memory manager
 302   // won't be interleaved between modules.  It is also used in mapSectionAddress
 303   // and resolveRelocations to protect write access to internal data structures.
 304   //
 305   // loadObject may be called on the same thread during the handling of of
 306   // processRelocations, and that's OK.  The handling of the relocation lists
 307   // is written in such a way as to work correctly if new elements are added to
 308   // the end of the list while the list is being processed.
 309   sys::Mutex lock;
 310
 311   using NotifyStubEmittedFunction =
 312     RuntimeDyld::NotifyStubEmittedFunction;
 313   NotifyStubEmittedFunction NotifyStubEmitted;
 314
 315   virtual unsigned getMaxStubSize() const = 0;
 316   virtual unsigned getStubAlignment() = 0;
 317
 318   bool HasError;
 319   std::string ErrorStr;
 320
 321   void writeInt16BE(uint8_t *Addr, uint16_t Value) {
 322     if (IsTargetLittleEndian)
 323       sys::swapByteOrder(Value);
 324     *Addr       = (Value >> 8) & 0xFF;
 325     *(Addr + 1) = Value & 0xFF;
 326   }
 327
 328   void writeInt32BE(uint8_t *Addr, uint32_t Value) {
 329     if (IsTargetLittleEndian)
 330       sys::swapByteOrder(Value);
 331     *Addr       = (Value >> 24) & 0xFF;
 332     *(Addr + 1) = (Value >> 16) & 0xFF;
 333     *(Addr + 2) = (Value >> 8) & 0xFF;
 334     *(Addr + 3) = Value & 0xFF;
 335   }
 336
 337   void writeInt64BE(uint8_t *Addr, uint64_t Value) {
 338     if (IsTargetLittleEndian)
 339       sys::swapByteOrder(Value);
 340     *Addr       = (Value >> 56) & 0xFF;
 341     *(Addr + 1) = (Value >> 48) & 0xFF;
 342     *(Addr + 2) = (Value >> 40) & 0xFF;
 343     *(Addr + 3) = (Value >> 32) & 0xFF;
 344     *(Addr + 4) = (Value >> 24) & 0xFF;
 345     *(Addr + 5) = (Value >> 16) & 0xFF;
 346     *(Addr + 6) = (Value >> 8) & 0xFF;
 347     *(Addr + 7) = Value & 0xFF;
 348   }
 349
 350   virtual void setMipsABI(const ObjectFile &Obj) {
 351     IsMipsO32ABI = false;
 352     IsMipsN32ABI = false;
 353     IsMipsN64ABI = false;
 354   }
 355
 356   /// Endian-aware read Read the least significant Size bytes from Src.
 357   uint64_t readBytesUnaligned(uint8_t *Src, unsigned Size) const;
 358
 359   /// Endian-aware write. Write the least significant Size bytes from Value to
 360   /// Dst.
 361   void writeBytesUnaligned(uint64_t Value, uint8_t *Dst, unsigned Size) const;
 362
 363   /// Generate JITSymbolFlags from a libObject symbol.
 364   virtual Expected<JITSymbolFlags> getJITSymbolFlags(const SymbolRef &Sym);
 365
 366   /// Modify the given target address based on the given symbol flags.
 367   /// This can be used by subclasses to tweak addresses based on symbol flags,
 368   /// For example: the MachO/ARM target uses it to set the low bit if the target
 369   /// is a thumb symbol.
 370   virtual uint64_t modifyAddressBasedOnFlags(uint64_t Addr,
 371                                              JITSymbolFlags Flags) const {
 372     return Addr;
 373   }
 374
 375   /// Given the common symbols discovered in the object file, emit a
 376   /// new section for them and update the symbol mappings in the object and
 377   /// symbol table.
 378   Error emitCommonSymbols(const ObjectFile &Obj,
 379                           CommonSymbolList &CommonSymbols, uint64_t CommonSize,
 380                           uint32_t CommonAlign);
 381
 382   /// Emits section data from the object file to the MemoryManager.
 383   /// \param IsCode if it's true then allocateCodeSection() will be
 384   ///        used for emits, else allocateDataSection() will be used.
 385   /// \return SectionID.
 386   Expected<unsigned> emitSection(const ObjectFile &Obj,
 387                                  const SectionRef &Section,
 388                                  bool IsCode);
 389
 390   /// Find Section in LocalSections. If the secton is not found - emit
 391   ///        it and store in LocalSections.
 392   /// \param IsCode if it's true then allocateCodeSection() will be
 393   ///        used for emmits, else allocateDataSection() will be used.
 394   /// \return SectionID.
 395   Expected<unsigned> findOrEmitSection(const ObjectFile &Obj,
 396                                        const SectionRef &Section, bool IsCode,
 397                                        ObjSectionToIDMap &LocalSections);
 398
 399   // Add a relocation entry that uses the given section.
 400   void addRelocationForSection(const RelocationEntry &RE, unsigned SectionID);
 401
 402   // Add a relocation entry that uses the given symbol.  This symbol may
 403   // be found in the global symbol table, or it may be external.
 404   void addRelocationForSymbol(const RelocationEntry &RE, StringRef SymbolName);
 405
 406   /// Emits long jump instruction to Addr.
 407   /// \return Pointer to the memory area for emitting target address.
 408   uint8_t *createStubFunction(uint8_t *Addr, unsigned AbiVariant = 0);
 409
 410   /// Resolves relocations from Relocs list with address from Value.
 411   void resolveRelocationList(const RelocationList &Relocs, uint64_t Value);
 412
 413   /// A object file specific relocation resolver
 414   /// \param RE The relocation to be resolved
 415   /// \param Value Target symbol address to apply the relocation action
 416   virtual void resolveRelocation(const RelocationEntry &RE, uint64_t Value) = 0;
 417
 418   /// Parses one or more object file relocations (some object files use
 419   ///        relocation pairs) and stores it to Relocations or SymbolRelocations
 420   ///        (this depends on the object file type).
 421   /// \return Iterator to the next relocation that needs to be parsed.
 422   virtual Expected<relocation_iterator>
 423   processRelocationRef(unsigned SectionID, relocation_iterator RelI,
 424                        const ObjectFile &Obj, ObjSectionToIDMap &ObjSectionToID,
 425                        StubMap &Stubs) = 0;
 426
 427   void applyExternalSymbolRelocations(
 428       const StringMap<JITEvaluatedSymbol> ExternalSymbolMap);
 429
 430   /// Resolve relocations to external symbols.
 431   Error resolveExternalSymbols();
 432
 433   // Compute an upper bound of the memory that is required to load all
 434   // sections
 435   Error computeTotalAllocSize(const ObjectFile &Obj,
 436                               uint64_t &CodeSize, uint32_t &CodeAlign,
 437                               uint64_t &RODataSize, uint32_t &RODataAlign,
 438                               uint64_t &RWDataSize, uint32_t &RWDataAlign);
 439
 440   // Compute GOT size
 441   unsigned computeGOTSize(const ObjectFile &Obj);
 442
 443   // Compute the stub buffer size required for a section
 444   unsigned computeSectionStubBufSize(const ObjectFile &Obj,
 445                                      const SectionRef &Section);
 446
 447   // Implementation of the generic part of the loadObject algorithm.
 448   Expected<ObjSectionToIDMap> loadObjectImpl(const object::ObjectFile &Obj);
 449
 450   // Return size of Global Offset Table (GOT) entry
 451   virtual size_t getGOTEntrySize() { return 0; }
 452
 453   // Return true if the relocation R may require allocating a GOT entry.
 454   virtual bool relocationNeedsGot(const RelocationRef &R) const {
 455     return false;
 456   }
 457
 458   // Return true if the relocation R may require allocating a stub.
 459   virtual bool relocationNeedsStub(const RelocationRef &R) const {
 460     return true;    // Conservative answer
 461   }
 462
 463 public:
 464   RuntimeDyldImpl(RuntimeDyld::MemoryManager &MemMgr,
 465                   JITSymbolResolver &Resolver)
 466     : MemMgr(MemMgr), Resolver(Resolver),
 467       ProcessAllSections(false), HasError(false) {
 468   }
 469
 470   virtual ~RuntimeDyldImpl();
 471
 472   void setProcessAllSections(bool ProcessAllSections) {
 473     this->ProcessAllSections = ProcessAllSections;
 474   }
 475
 476   virtual std::unique_ptr<RuntimeDyld::LoadedObjectInfo>
 477   loadObject(const object::ObjectFile &Obj) = 0;
 478
 479   uint64_t getSectionLoadAddress(unsigned SectionID) const {
 480     return Sections[SectionID].getLoadAddress();
 481   }
 482
 483   uint8_t *getSectionAddress(unsigned SectionID) const {
 484     return Sections[SectionID].getAddress();
 485   }
 486
 487   StringRef getSectionContent(unsigned SectionID) const {
 488     return StringRef(reinterpret_cast<char *>(Sections[SectionID].getAddress()),
 489                      Sections[SectionID].getStubOffset() + getMaxStubSize());
 490   }
 491
 492   uint8_t* getSymbolLocalAddress(StringRef Name) const {
 493     // FIXME: Just look up as a function for now. Overly simple of course.
 494     // Work in progress.
 495     RTDyldSymbolTable::const_iterator pos = GlobalSymbolTable.find(Name);
 496     if (pos == GlobalSymbolTable.end())
 497       return nullptr;
 498     const auto &SymInfo = pos->second;
 499     // Absolute symbols do not have a local address.
 500     if (SymInfo.getSectionID() == AbsoluteSymbolSection)
 501       return nullptr;
 502     return getSectionAddress(SymInfo.getSectionID()) + SymInfo.getOffset();
 503   }
 504
 505   unsigned getSymbolSectionID(StringRef Name) const {
 506     auto GSTItr = GlobalSymbolTable.find(Name);
 507     if (GSTItr == GlobalSymbolTable.end())
 508       return ~0U;
 509     return GSTItr->second.getSectionID();
 510   }
 511
 512   JITEvaluatedSymbol getSymbol(StringRef Name) const {
 513     // FIXME: Just look up as a function for now. Overly simple of course.
 514     // Work in progress.
 515     RTDyldSymbolTable::const_iterator pos = GlobalSymbolTable.find(Name);
 516     if (pos == GlobalSymbolTable.end())
 517       return nullptr;
 518     const auto &SymEntry = pos->second;
 519     uint64_t SectionAddr = 0;
 520     if (SymEntry.getSectionID() != AbsoluteSymbolSection)
 521       SectionAddr = getSectionLoadAddress(SymEntry.getSectionID());
 522     uint64_t TargetAddr = SectionAddr + SymEntry.getOffset();
 523
 524     // FIXME: Have getSymbol should return the actual address and the client
 525     //        modify it based on the flags. This will require clients to be
 526     //        aware of the target architecture, which we should build
 527     //        infrastructure for.
 528     TargetAddr = modifyAddressBasedOnFlags(TargetAddr, SymEntry.getFlags());
 529     return JITEvaluatedSymbol(TargetAddr, SymEntry.getFlags());
 530   }
 531
 532   std::map<StringRef, JITEvaluatedSymbol> getSymbolTable() const {
 533     std::map<StringRef, JITEvaluatedSymbol> Result;
 534
 535     for (auto &KV : GlobalSymbolTable) {
 536       auto SectionID = KV.second.getSectionID();
 537       uint64_t SectionAddr = 0;
 538       if (SectionID != AbsoluteSymbolSection)
 539         SectionAddr = getSectionLoadAddress(SectionID);
 540       Result[KV.first()] =
 541         JITEvaluatedSymbol(SectionAddr + KV.second.getOffset(), KV.second.getFlags());
 542     }
 543
 544     return Result;
 545   }
 546
 547   void resolveRelocations();
 548
 549   void resolveLocalRelocations();
 550
 551   static void finalizeAsync(std::unique_ptr<RuntimeDyldImpl> This,
 552                             unique_function<void(Error)> OnEmitted,
 553                             std::unique_ptr<MemoryBuffer> UnderlyingBuffer);
 554
 555   void reassignSectionAddress(unsigned SectionID, uint64_t Addr);
 556
 557   void mapSectionAddress(const void *LocalAddress, uint64_t TargetAddress);
 558
 559   // Is the linker in an error state?
 560   bool hasError() { return HasError; }
 561
 562   // Mark the error condition as handled and continue.
 563   void clearError() { HasError = false; }
 564
 565   // Get the error message.
 566   StringRef getErrorString() { return ErrorStr; }
 567
 568   virtual bool isCompatibleFile(const ObjectFile &Obj) const = 0;
 569
 570   void setNotifyStubEmitted(NotifyStubEmittedFunction NotifyStubEmitted) {
 571     this->NotifyStubEmitted = std::move(NotifyStubEmitted);
 572   }
 573
 574   virtual void registerEHFrames();
 575
 576   void deregisterEHFrames();
 577
 578   virtual Error finalizeLoad(const ObjectFile &ObjImg,
 579                              ObjSectionToIDMap &SectionMap) {
 580     return Error::success();
 581   }
 582 };
 583
 584 } // end namespace llvm
 585
 586 #endif