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