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   friend class RuntimeDyldCheckerImpl;
 244 protected:
 245   static const unsigned AbsoluteSymbolSection = ~0U;
 246
 247   // The MemoryManager to load objects into.
 248   RuntimeDyld::MemoryManager &MemMgr;
 249
 250   // The symbol resolver to use for external symbols.
 251   JITSymbolResolver &Resolver;
 252
 253   // Attached RuntimeDyldChecker instance. Null if no instance attached.
 254   RuntimeDyldCheckerImpl *Checker;
 255
 256   // A list of all sections emitted by the dynamic linker.  These sections are
 257   // referenced in the code by means of their index in this list - SectionID.
 258   typedef SmallVector<SectionEntry, 64> SectionList;
 259   SectionList Sections;
 260
 261   typedef unsigned SID; // Type for SectionIDs
 262 #define RTDYLD_INVALID_SECTION_ID ((RuntimeDyldImpl::SID)(-1))
 263
 264   // Keep a map of sections from object file to the SectionID which
 265   // references it.
 266   typedef std::map<SectionRef, unsigned> ObjSectionToIDMap;
 267
 268   // A global symbol table for symbols from all loaded modules.
 269   RTDyldSymbolTable GlobalSymbolTable;
 270
 271   // Keep a map of common symbols to their info pairs
 272   typedef std::vector<SymbolRef> CommonSymbolList;
 273
 274   // For each symbol, keep a list of relocations based on it. Anytime
 275   // its address is reassigned (the JIT re-compiled the function, e.g.),
 276   // the relocations get re-resolved.
 277   // The symbol (or section) the relocation is sourced from is the Key
 278   // in the relocation list where it's stored.
 279   typedef SmallVector<RelocationEntry, 64> RelocationList;
 280   // Relocations to sections already loaded. Indexed by SectionID which is the
 281   // source of the address. The target where the address will be written is
 282   // SectionID/Offset in the relocation itself.
 283   std::unordered_map<unsigned, RelocationList> Relocations;
 284
 285   // Relocations to external symbols that are not yet resolved.  Symbols are
 286   // external when they aren't found in the global symbol table of all loaded
 287   // modules.  This map is indexed by symbol name.
 288   StringMap<RelocationList> ExternalSymbolRelocations;
 289
 290
 291   typedef std::map<RelocationValueRef, uintptr_t> StubMap;
 292
 293   Triple::ArchType Arch;
 294   bool IsTargetLittleEndian;
 295   bool IsMipsO32ABI;
 296   bool IsMipsN32ABI;
 297   bool IsMipsN64ABI;
 298
 299   // True if all sections should be passed to the memory manager, false if only
 300   // sections containing relocations should be. Defaults to 'false'.
 301   bool ProcessAllSections;
 302
 303   // This mutex prevents simultaneously loading objects from two different
 304   // threads.  This keeps us from having to protect individual data structures
 305   // and guarantees that section allocation requests to the memory manager
 306   // won't be interleaved between modules.  It is also used in mapSectionAddress
 307   // and resolveRelocations to protect write access to internal data structures.
 308   //
 309   // loadObject may be called on the same thread during the handling of of
 310   // processRelocations, and that's OK.  The handling of the relocation lists
 311   // is written in such a way as to work correctly if new elements are added to
 312   // the end of the list while the list is being processed.
 313   sys::Mutex lock;
 314
 315   virtual unsigned getMaxStubSize() = 0;
 316   virtual unsigned getStubAlignment() = 0;
 317
 318   bool HasError;
 319   std::string ErrorStr;
 320
 321   uint64_t getSectionLoadAddress(unsigned SectionID) const {
 322     return Sections[SectionID].getLoadAddress();
 323   }
 324
 325   uint8_t *getSectionAddress(unsigned SectionID) const {
 326     return Sections[SectionID].getAddress();
 327   }
 328
 329   void writeInt16BE(uint8_t *Addr, uint16_t Value) {
 330     if (IsTargetLittleEndian)
 331       sys::swapByteOrder(Value);
 332     *Addr       = (Value >> 8) & 0xFF;
 333     *(Addr + 1) = Value & 0xFF;
 334   }
 335
 336   void writeInt32BE(uint8_t *Addr, uint32_t Value) {
 337     if (IsTargetLittleEndian)
 338       sys::swapByteOrder(Value);
 339     *Addr       = (Value >> 24) & 0xFF;
 340     *(Addr + 1) = (Value >> 16) & 0xFF;
 341     *(Addr + 2) = (Value >> 8) & 0xFF;
 342     *(Addr + 3) = Value & 0xFF;
 343   }
 344
 345   void writeInt64BE(uint8_t *Addr, uint64_t Value) {
 346     if (IsTargetLittleEndian)
 347       sys::swapByteOrder(Value);
 348     *Addr       = (Value >> 56) & 0xFF;
 349     *(Addr + 1) = (Value >> 48) & 0xFF;
 350     *(Addr + 2) = (Value >> 40) & 0xFF;
 351     *(Addr + 3) = (Value >> 32) & 0xFF;
 352     *(Addr + 4) = (Value >> 24) & 0xFF;
 353     *(Addr + 5) = (Value >> 16) & 0xFF;
 354     *(Addr + 6) = (Value >> 8) & 0xFF;
 355     *(Addr + 7) = Value & 0xFF;
 356   }
 357
 358   virtual void setMipsABI(const ObjectFile &Obj) {
 359     IsMipsO32ABI = false;
 360     IsMipsN32ABI = false;
 361     IsMipsN64ABI = false;
 362   }
 363
 364   /// Endian-aware read Read the least significant Size bytes from Src.
 365   uint64_t readBytesUnaligned(uint8_t *Src, unsigned Size) const;
 366
 367   /// Endian-aware write. Write the least significant Size bytes from Value to
 368   /// Dst.
 369   void writeBytesUnaligned(uint64_t Value, uint8_t *Dst, unsigned Size) const;
 370
 371   /// Generate JITSymbolFlags from a libObject symbol.
 372   virtual Expected<JITSymbolFlags> getJITSymbolFlags(const SymbolRef &Sym);
 373
 374   /// Modify the given target address based on the given symbol flags.
 375   /// This can be used by subclasses to tweak addresses based on symbol flags,
 376   /// For example: the MachO/ARM target uses it to set the low bit if the target
 377   /// is a thumb symbol.
 378   virtual uint64_t modifyAddressBasedOnFlags(uint64_t Addr,
 379                                              JITSymbolFlags Flags) const {
 380     return Addr;
 381   }
 382
 383   /// Given the common symbols discovered in the object file, emit a
 384   /// new section for them and update the symbol mappings in the object and
 385   /// symbol table.
 386   Error emitCommonSymbols(const ObjectFile &Obj,
 387                           CommonSymbolList &CommonSymbols, uint64_t CommonSize,
 388                           uint32_t CommonAlign);
 389
 390   /// Emits section data from the object file to the MemoryManager.
 391   /// \param IsCode if it's true then allocateCodeSection() will be
 392   ///        used for emits, else allocateDataSection() will be used.
 393   /// \return SectionID.
 394   Expected<unsigned> emitSection(const ObjectFile &Obj,
 395                                  const SectionRef &Section,
 396                                  bool IsCode);
 397
 398   /// Find Section in LocalSections. If the secton is not found - emit
 399   ///        it and store in LocalSections.
 400   /// \param IsCode if it's true then allocateCodeSection() will be
 401   ///        used for emmits, else allocateDataSection() will be used.
 402   /// \return SectionID.
 403   Expected<unsigned> findOrEmitSection(const ObjectFile &Obj,
 404                                        const SectionRef &Section, bool IsCode,
 405                                        ObjSectionToIDMap &LocalSections);
 406
 407   // Add a relocation entry that uses the given section.
 408   void addRelocationForSection(const RelocationEntry &RE, unsigned SectionID);
 409
 410   // Add a relocation entry that uses the given symbol.  This symbol may
 411   // be found in the global symbol table, or it may be external.
 412   void addRelocationForSymbol(const RelocationEntry &RE, StringRef SymbolName);
 413
 414   /// Emits long jump instruction to Addr.
 415   /// \return Pointer to the memory area for emitting target address.
 416   uint8_t *createStubFunction(uint8_t *Addr, unsigned AbiVariant = 0);
 417
 418   /// Resolves relocations from Relocs list with address from Value.
 419   void resolveRelocationList(const RelocationList &Relocs, uint64_t Value);
 420
 421   /// A object file specific relocation resolver
 422   /// \param RE The relocation to be resolved
 423   /// \param Value Target symbol address to apply the relocation action
 424   virtual void resolveRelocation(const RelocationEntry &RE, uint64_t Value) = 0;
 425
 426   /// Parses one or more object file relocations (some object files use
 427   ///        relocation pairs) and stores it to Relocations or SymbolRelocations
 428   ///        (this depends on the object file type).
 429   /// \return Iterator to the next relocation that needs to be parsed.
 430   virtual Expected<relocation_iterator>
 431   processRelocationRef(unsigned SectionID, relocation_iterator RelI,
 432                        const ObjectFile &Obj, ObjSectionToIDMap &ObjSectionToID,
 433                        StubMap &Stubs) = 0;
 434
 435   void applyExternalSymbolRelocations(
 436       const StringMap<JITEvaluatedSymbol> ExternalSymbolMap);
 437
 438   /// Resolve relocations to external symbols.
 439   Error resolveExternalSymbols();
 440
 441   // Compute an upper bound of the memory that is required to load all
 442   // sections
 443   Error computeTotalAllocSize(const ObjectFile &Obj,
 444                               uint64_t &CodeSize, uint32_t &CodeAlign,
 445                               uint64_t &RODataSize, uint32_t &RODataAlign,
 446                               uint64_t &RWDataSize, uint32_t &RWDataAlign);
 447
 448   // Compute GOT size
 449   unsigned computeGOTSize(const ObjectFile &Obj);
 450
 451   // Compute the stub buffer size required for a section
 452   unsigned computeSectionStubBufSize(const ObjectFile &Obj,
 453                                      const SectionRef &Section);
 454
 455   // Implementation of the generic part of the loadObject algorithm.
 456   Expected<ObjSectionToIDMap> loadObjectImpl(const object::ObjectFile &Obj);
 457
 458   // Return size of Global Offset Table (GOT) entry
 459   virtual size_t getGOTEntrySize() { return 0; }
 460
 461   // Return true if the relocation R may require allocating a GOT entry.
 462   virtual bool relocationNeedsGot(const RelocationRef &R) const {
 463     return false;
 464   }
 465
 466   // Return true if the relocation R may require allocating a stub.
 467   virtual bool relocationNeedsStub(const RelocationRef &R) const {
 468     return true;    // Conservative answer
 469   }
 470
 471 public:
 472   RuntimeDyldImpl(RuntimeDyld::MemoryManager &MemMgr,
 473                   JITSymbolResolver &Resolver)
 474     : MemMgr(MemMgr), Resolver(Resolver), Checker(nullptr),
 475       ProcessAllSections(false), HasError(false) {
 476   }
 477
 478   virtual ~RuntimeDyldImpl();
 479
 480   void setProcessAllSections(bool ProcessAllSections) {
 481     this->ProcessAllSections = ProcessAllSections;
 482   }
 483
 484   void setRuntimeDyldChecker(RuntimeDyldCheckerImpl *Checker) {
 485     this->Checker = Checker;
 486   }
 487
 488   virtual std::unique_ptr<RuntimeDyld::LoadedObjectInfo>
 489   loadObject(const object::ObjectFile &Obj) = 0;
 490
 491   uint8_t* getSymbolLocalAddress(StringRef Name) const {
 492     // FIXME: Just look up as a function for now. Overly simple of course.
 493     // Work in progress.
 494     RTDyldSymbolTable::const_iterator pos = GlobalSymbolTable.find(Name);
 495     if (pos == GlobalSymbolTable.end())
 496       return nullptr;
 497     const auto &SymInfo = pos->second;
 498     // Absolute symbols do not have a local address.
 499     if (SymInfo.getSectionID() == AbsoluteSymbolSection)
 500       return nullptr;
 501     return getSectionAddress(SymInfo.getSectionID()) + SymInfo.getOffset();
 502   }
 503
 504   JITEvaluatedSymbol getSymbol(StringRef Name) const {
 505     // FIXME: Just look up as a function for now. Overly simple of course.
 506     // Work in progress.
 507     RTDyldSymbolTable::const_iterator pos = GlobalSymbolTable.find(Name);
 508     if (pos == GlobalSymbolTable.end())
 509       return nullptr;
 510     const auto &SymEntry = pos->second;
 511     uint64_t SectionAddr = 0;
 512     if (SymEntry.getSectionID() != AbsoluteSymbolSection)
 513       SectionAddr = getSectionLoadAddress(SymEntry.getSectionID());
 514     uint64_t TargetAddr = SectionAddr + SymEntry.getOffset();
 515
 516     // FIXME: Have getSymbol should return the actual address and the client
 517     //        modify it based on the flags. This will require clients to be
 518     //        aware of the target architecture, which we should build
 519     //        infrastructure for.
 520     TargetAddr = modifyAddressBasedOnFlags(TargetAddr, SymEntry.getFlags());
 521     return JITEvaluatedSymbol(TargetAddr, SymEntry.getFlags());
 522   }
 523
 524   std::map<StringRef, JITEvaluatedSymbol> getSymbolTable() const {
 525     std::map<StringRef, JITEvaluatedSymbol> Result;
 526
 527     for (auto &KV : GlobalSymbolTable) {
 528       auto SectionID = KV.second.getSectionID();
 529       uint64_t SectionAddr = 0;
 530       if (SectionID != AbsoluteSymbolSection)
 531         SectionAddr = getSectionLoadAddress(SectionID);
 532       Result[KV.first()] =
 533         JITEvaluatedSymbol(SectionAddr + KV.second.getOffset(), KV.second.getFlags());
 534     }
 535
 536     return Result;
 537   }
 538
 539   void resolveRelocations();
 540
 541   void resolveLocalRelocations();
 542
 543   static void finalizeAsync(std::unique_ptr<RuntimeDyldImpl> This,
 544                             std::function<void(Error)> OnEmitted,
 545                             std::unique_ptr<MemoryBuffer> UnderlyingBuffer);
 546
 547   void reassignSectionAddress(unsigned SectionID, uint64_t Addr);
 548
 549   void mapSectionAddress(const void *LocalAddress, uint64_t TargetAddress);
 550
 551   // Is the linker in an error state?
 552   bool hasError() { return HasError; }
 553
 554   // Mark the error condition as handled and continue.
 555   void clearError() { HasError = false; }
 556
 557   // Get the error message.
 558   StringRef getErrorString() { return ErrorStr; }
 559
 560   virtual bool isCompatibleFile(const ObjectFile &Obj) const = 0;
 561
 562   virtual void registerEHFrames();
 563
 564   void deregisterEHFrames();
 565
 566   virtual Error finalizeLoad(const ObjectFile &ObjImg,
 567                              ObjSectionToIDMap &SectionMap) {
 568     return Error::success();
 569   }
 570 };
 571
 572 } // end namespace llvm
 573
 574 #endif