LLVM  10.0.0svn
RuntimeDyldCOFFX86_64.h
Go to the documentation of this file.
1 //===-- RuntimeDyldCOFFX86_64.h --- COFF/X86_64 specific code ---*- 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 // COFF x86_x64 support for MC-JIT runtime dynamic linker.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #ifndef LLVM_LIB_EXECUTIONENGINE_RUNTIMEDYLD_TARGETS_RUNTIMEDYLDCOFF86_64_H
14 #define LLVM_LIB_EXECUTIONENGINE_RUNTIMEDYLD_TARGETS_RUNTIMEDYLDCOFF86_64_H
15 
16 #include "../RuntimeDyldCOFF.h"
17 #include "llvm/BinaryFormat/COFF.h"
18 #include "llvm/Object/COFF.h"
19 
20 #define DEBUG_TYPE "dyld"
21 
22 namespace llvm {
23 
25 
26 private:
27  // When a module is loaded we save the SectionID of the unwind
28  // sections in a table until we receive a request to register all
29  // unregisteredEH frame sections with the memory manager.
30  SmallVector<SID, 2> UnregisteredEHFrameSections;
31  SmallVector<SID, 2> RegisteredEHFrameSections;
32  uint64_t ImageBase;
33 
34  // Fake an __ImageBase pointer by returning the section with the lowest adress
35  uint64_t getImageBase() {
36  if (!ImageBase) {
38  for (const SectionEntry &Section : Sections)
39  // The Sections list may contain sections that weren't loaded for
40  // whatever reason: they may be debug sections, and ProcessAllSections
41  // is false, or they may be sections that contain 0 bytes. If the
42  // section isn't loaded, the load address will be 0, and it should not
43  // be included in the ImageBase calculation.
44  if (Section.getLoadAddress() != 0)
45  ImageBase = std::min(ImageBase, Section.getLoadAddress());
46  }
47  return ImageBase;
48  }
49 
50  void write32BitOffset(uint8_t *Target, int64_t Addend, uint64_t Delta) {
51  uint64_t Result = Addend + Delta;
52  assert(Result <= UINT32_MAX && "Relocation overflow");
53  writeBytesUnaligned(Result, Target, 4);
54  }
55 
56 public:
59  : RuntimeDyldCOFF(MM, Resolver), ImageBase(0) {}
60 
61  unsigned getStubAlignment() override { return 1; }
62 
63  // 2-byte jmp instruction + 32-bit relative address + 64-bit absolute jump
64  unsigned getMaxStubSize() const override { return 14; }
65 
66  // The target location for the relocation is described by RE.SectionID and
67  // RE.Offset. RE.SectionID can be used to find the SectionEntry. Each
68  // SectionEntry has three members describing its location.
69  // SectionEntry::Address is the address at which the section has been loaded
70  // into memory in the current (host) process. SectionEntry::LoadAddress is
71  // the address that the section will have in the target process.
72  // SectionEntry::ObjAddress is the address of the bits for this section in the
73  // original emitted object image (also in the current address space).
74  //
75  // Relocations will be applied as if the section were loaded at
76  // SectionEntry::LoadAddress, but they will be applied at an address based
77  // on SectionEntry::Address. SectionEntry::ObjAddress will be used to refer
78  // to Target memory contents if they are required for value calculations.
79  //
80  // The Value parameter here is the load address of the symbol for the
81  // relocation to be applied. For relocations which refer to symbols in the
82  // current object Value will be the LoadAddress of the section in which
83  // the symbol resides (RE.Addend provides additional information about the
84  // symbol location). For external symbols, Value will be the address of the
85  // symbol in the target address space.
86  void resolveRelocation(const RelocationEntry &RE, uint64_t Value) override {
88  uint8_t *Target = Section.getAddressWithOffset(RE.Offset);
89 
90  switch (RE.RelType) {
91 
98  uint64_t FinalAddress = Section.getLoadAddressWithOffset(RE.Offset);
99  // Delta is the distance from the start of the reloc to the end of the
100  // instruction with the reloc.
101  uint64_t Delta = 4 + (RE.RelType - COFF::IMAGE_REL_AMD64_REL32);
102  Value -= FinalAddress + Delta;
103  uint64_t Result = Value + RE.Addend;
104  assert(((int64_t)Result <= INT32_MAX) && "Relocation overflow");
105  assert(((int64_t)Result >= INT32_MIN) && "Relocation underflow");
106  writeBytesUnaligned(Result, Target, 4);
107  break;
108  }
109 
111  // ADDR32NB requires an offset less than 2GB from 'ImageBase'.
112  // The MemoryManager can make sure this is always true by forcing the
113  // memory layout to be: CodeSection < ReadOnlySection < ReadWriteSection.
114  const uint64_t ImageBase = getImageBase();
115  if (Value < ImageBase || ((Value - ImageBase) > UINT32_MAX)) {
116  llvm::errs() << "IMAGE_REL_AMD64_ADDR32NB relocation requires an"
117  << "ordered section layout.\n";
118  write32BitOffset(Target, 0, 0);
119  } else {
120  write32BitOffset(Target, RE.Addend, Value - ImageBase);
121  }
122  break;
123  }
124 
126  writeBytesUnaligned(Value + RE.Addend, Target, 8);
127  break;
128  }
129 
131  assert(static_cast<int64_t>(RE.Addend) <= INT32_MAX && "Relocation overflow");
132  assert(static_cast<int64_t>(RE.Addend) >= INT32_MIN && "Relocation underflow");
133  writeBytesUnaligned(RE.Addend, Target, 4);
134  break;
135  }
136 
137  default:
138  llvm_unreachable("Relocation type not implemented yet!");
139  break;
140  }
141  }
142 
143  std::tuple<uint64_t, uint64_t, uint64_t>
144  generateRelocationStub(unsigned SectionID, StringRef TargetName,
145  uint64_t Offset, uint64_t RelType, uint64_t Addend,
146  StubMap &Stubs) {
147  uintptr_t StubOffset;
148  SectionEntry &Section = Sections[SectionID];
149 
150  RelocationValueRef OriginalRelValueRef;
151  OriginalRelValueRef.SectionID = SectionID;
152  OriginalRelValueRef.Offset = Offset;
153  OriginalRelValueRef.Addend = Addend;
154  OriginalRelValueRef.SymbolName = TargetName.data();
155 
156  auto Stub = Stubs.find(OriginalRelValueRef);
157  if (Stub == Stubs.end()) {
158  LLVM_DEBUG(dbgs() << " Create a new stub function for "
159  << TargetName.data() << "\n");
160 
161  StubOffset = Section.getStubOffset();
162  Stubs[OriginalRelValueRef] = StubOffset;
163  createStubFunction(Section.getAddressWithOffset(StubOffset));
165  } else {
166  LLVM_DEBUG(dbgs() << " Stub function found for " << TargetName.data()
167  << "\n");
168  StubOffset = Stub->second;
169  }
170 
171  // FIXME: If RelType == COFF::IMAGE_REL_AMD64_ADDR32NB we should be able
172  // to ignore the __ImageBase requirement and just forward to the stub
173  // directly as an offset of this section:
174  // write32BitOffset(Section.getAddressWithOffset(Offset), 0, StubOffset);
175  // .xdata exception handler's aren't having this though.
176 
177  // Resolve original relocation to stub function.
178  const RelocationEntry RE(SectionID, Offset, RelType, Addend);
179  resolveRelocation(RE, Section.getLoadAddressWithOffset(StubOffset));
180 
181  // adjust relocation info so resolution writes to the stub function
182  Addend = 0;
183  Offset = StubOffset + 6;
185 
186  return std::make_tuple(Offset, RelType, Addend);
187  }
188 
190  processRelocationRef(unsigned SectionID,
192  const object::ObjectFile &Obj,
193  ObjSectionToIDMap &ObjSectionToID,
194  StubMap &Stubs) override {
195  // If possible, find the symbol referred to in the relocation,
196  // and the section that contains it.
197  object::symbol_iterator Symbol = RelI->getSymbol();
198  if (Symbol == Obj.symbol_end())
199  report_fatal_error("Unknown symbol in relocation");
200  auto SectionOrError = Symbol->getSection();
201  if (!SectionOrError)
202  return SectionOrError.takeError();
203  object::section_iterator SecI = *SectionOrError;
204  // If there is no section, this must be an external reference.
205  const bool IsExtern = SecI == Obj.section_end();
206 
207  // Determine the Addend used to adjust the relocation value.
208  uint64_t RelType = RelI->getType();
209  uint64_t Offset = RelI->getOffset();
210  uint64_t Addend = 0;
211  SectionEntry &Section = Sections[SectionID];
212  uintptr_t ObjTarget = Section.getObjAddress() + Offset;
213 
214  Expected<StringRef> TargetNameOrErr = Symbol->getName();
215  if (!TargetNameOrErr)
216  return TargetNameOrErr.takeError();
217  StringRef TargetName = *TargetNameOrErr;
218 
219  switch (RelType) {
220 
228  uint8_t *Displacement = (uint8_t *)ObjTarget;
229  Addend = readBytesUnaligned(Displacement, 4);
230 
231  if (IsExtern)
232  std::tie(Offset, RelType, Addend) = generateRelocationStub(
233  SectionID, TargetName, Offset, RelType, Addend, Stubs);
234 
235  break;
236  }
237 
239  uint8_t *Displacement = (uint8_t *)ObjTarget;
240  Addend = readBytesUnaligned(Displacement, 8);
241  break;
242  }
243 
244  default:
245  break;
246  }
247 
248  LLVM_DEBUG(dbgs() << "\t\tIn Section " << SectionID << " Offset " << Offset
249  << " RelType: " << RelType << " TargetName: "
250  << TargetName << " Addend " << Addend << "\n");
251 
252  if (IsExtern) {
253  RelocationEntry RE(SectionID, Offset, RelType, Addend);
254  addRelocationForSymbol(RE, TargetName);
255  } else {
256  bool IsCode = SecI->isText();
257  unsigned TargetSectionID;
258  if (auto TargetSectionIDOrErr =
259  findOrEmitSection(Obj, *SecI, IsCode, ObjSectionToID))
260  TargetSectionID = *TargetSectionIDOrErr;
261  else
262  return TargetSectionIDOrErr.takeError();
263  uint64_t TargetOffset = getSymbolOffset(*Symbol);
264  RelocationEntry RE(SectionID, Offset, RelType, TargetOffset + Addend);
265  addRelocationForSection(RE, TargetSectionID);
266  }
267 
268  return ++RelI;
269  }
270 
271  void registerEHFrames() override {
272  for (auto const &EHFrameSID : UnregisteredEHFrameSections) {
273  uint8_t *EHFrameAddr = Sections[EHFrameSID].getAddress();
274  uint64_t EHFrameLoadAddr = Sections[EHFrameSID].getLoadAddress();
275  size_t EHFrameSize = Sections[EHFrameSID].getSize();
276  MemMgr.registerEHFrames(EHFrameAddr, EHFrameLoadAddr, EHFrameSize);
277  RegisteredEHFrameSections.push_back(EHFrameSID);
278  }
279  UnregisteredEHFrameSections.clear();
280  }
281 
283  ObjSectionToIDMap &SectionMap) override {
284  // Look for and record the EH frame section IDs.
285  for (const auto &SectionPair : SectionMap) {
286  const object::SectionRef &Section = SectionPair.first;
287  Expected<StringRef> NameOrErr = Section.getName();
288  if (!NameOrErr)
289  return NameOrErr.takeError();
290 
291  // Note unwind info is stored in .pdata but often points to .xdata
292  // with an IMAGE_REL_AMD64_ADDR32NB relocation. Using a memory manager
293  // that keeps sections ordered in relation to __ImageBase is necessary.
294  if ((*NameOrErr) == ".pdata")
295  UnregisteredEHFrameSections.push_back(SectionPair.second);
296  }
297  return Error::success();
298  }
299 };
300 
301 } // end namespace llvm
302 
303 #undef DEBUG_TYPE
304 
305 #endif
RelocationEntry - used to represent relocations internally in the dynamic linker. ...
raw_ostream & errs()
This returns a reference to a raw_ostream for standard error.
LLVM_ATTRIBUTE_NORETURN void report_fatal_error(Error Err, bool gen_crash_diag=true)
Report a serious error, calling any installed error handler.
Definition: Error.cpp:139
This class represents lattice values for constants.
Definition: AllocatorList.h:23
Expected< StringRef > getName() const
Definition: ObjectFile.h:375
void push_back(const T &Elt)
Definition: SmallVector.h:211
uint64_t readBytesUnaligned(uint8_t *Src, unsigned Size) const
Endian-aware read Read the least significant Size bytes from Src.
uint64_t getLoadAddressWithOffset(unsigned OffsetBytes) const
Return the load address of this section with an offset.
RuntimeDyld::MemoryManager & MemMgr
This class is the base class for all object file types.
Definition: ObjectFile.h:221
uint64_t getSymbolOffset(const SymbolRef &Sym)
unsigned getMaxStubSize() const override
Error takeError()
Take ownership of the stored error.
Definition: Error.h:552
void writeBytesUnaligned(uint64_t Value, uint8_t *Dst, unsigned Size) const
Endian-aware write.
unsigned getStubAlignment() override
unsigned SectionID
SectionID - the section this relocation points to.
std::map< RelocationValueRef, uintptr_t > StubMap
Tagged union holding either a T or a Error.
Definition: yaml2obj.h:21
Expected< object::relocation_iterator > processRelocationRef(unsigned SectionID, object::relocation_iterator RelI, const object::ObjectFile &Obj, ObjSectionToIDMap &ObjSectionToID, StubMap &Stubs) override
Parses one or more object file relocations (some object files use relocation pairs) and stores it to ...
RuntimeDyldCOFFX86_64(RuntimeDyld::MemoryManager &MM, JITSymbolResolver &Resolver)
Expected< section_iterator > getSection() const
Get section this symbol is defined in reference to.
Definition: ObjectFile.h:395
void addRelocationForSymbol(const RelocationEntry &RE, StringRef SymbolName)
void addRelocationForSection(const RelocationEntry &RE, unsigned SectionID)
Interface for looking up the initializer for a variable name, used by Init::resolveReferences.
Definition: Record.h:1864
void resolveRelocation(const RelocationEntry &RE, uint64_t Value) override
A object file specific relocation resolver.
Symbol resolution interface.
Definition: JITSymbol.h:325
Error finalizeLoad(const object::ObjectFile &Obj, ObjSectionToIDMap &SectionMap) override
virtual basic_symbol_iterator symbol_end() const =0
uintptr_t getObjAddress() const
Expected< unsigned > findOrEmitSection(const ObjectFile &Obj, const SectionRef &Section, bool IsCode, ObjSectionToIDMap &LocalSections)
Find Section in LocalSections.
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
static ErrorSuccess success()
Create a success value.
Definition: Error.h:326
Align max(MaybeAlign Lhs, Align Rhs)
Definition: Alignment.h:390
int64_t Addend
Addend - the relocation addend encoded in the instruction itself.
uint32_t RelType
RelType - relocation type.
uint8_t * createStubFunction(uint8_t *Addr, unsigned AbiVariant=0)
Emits long jump instruction to Addr.
Expected< StringRef > getName() const
Definition: ObjectFile.h:432
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:132
Target - Wrapper for Target specific information.
uintptr_t getStubOffset() const
std::tuple< uint64_t, uint64_t, uint64_t > generateRelocationStub(unsigned SectionID, StringRef TargetName, uint64_t Offset, uint64_t RelType, uint64_t Addend, StubMap &Stubs)
uint64_t Offset
Offset - offset into the section.
virtual section_iterator section_end() const =0
std::map< SectionRef, unsigned > ObjSectionToIDMap
uint8_t * getAddressWithOffset(unsigned OffsetBytes) const
Return the address of this section with an offset.
SectionEntry - represents a section emitted into memory by the dynamic linker.
LLVM_NODISCARD const char * data() const
data - Get a pointer to the start of the string (which may not be null terminated).
Definition: StringRef.h:136
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
LLVM Value Representation.
Definition: Value.h:74
Lightweight error class with error context and mandatory checking.
Definition: Error.h:157
void advanceStubOffset(unsigned StubSize)
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:48
virtual void registerEHFrames(uint8_t *Addr, uint64_t LoadAddr, size_t Size)=0
Register the EH frames with the runtime so that c++ exceptions work.
#define LLVM_DEBUG(X)
Definition: Debug.h:122
This is a value type class that represents a single section in the list of sections in the object fil...
Definition: ObjectFile.h:81