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