LLVM  9.0.0svn
MCMachObjectWriter.h
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1 //===- llvm/MC/MCMachObjectWriter.h - Mach Object Writer --------*- 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 #ifndef LLVM_MC_MCMACHOBJECTWRITER_H
10 #define LLVM_MC_MCMACHOBJECTWRITER_H
11 
12 #include "llvm/ADT/DenseMap.h"
13 #include "llvm/ADT/StringRef.h"
15 #include "llvm/MC/MCExpr.h"
16 #include "llvm/MC/MCObjectWriter.h"
17 #include "llvm/MC/MCSection.h"
19 #include <cstdint>
20 #include <memory>
21 #include <string>
22 #include <vector>
23 
24 namespace llvm {
25 
26 class MachObjectWriter;
27 
29  const unsigned Is64Bit : 1;
30  const uint32_t CPUType;
31  const uint32_t CPUSubtype;
32  unsigned LocalDifference_RIT;
33 
34 protected:
35  MCMachObjectTargetWriter(bool Is64Bit_, uint32_t CPUType_,
36  uint32_t CPUSubtype_);
37 
39  LocalDifference_RIT = Type;
40  }
41 
42 public:
43  virtual ~MCMachObjectTargetWriter();
44 
45  virtual Triple::ObjectFormatType getFormat() const { return Triple::MachO; }
46  static bool classof(const MCObjectTargetWriter *W) {
47  return W->getFormat() == Triple::MachO;
48  }
49 
50  /// \name Lifetime Management
51  /// @{
52 
53  virtual void reset() {}
54 
55  /// @}
56 
57  /// \name Accessors
58  /// @{
59 
60  bool is64Bit() const { return Is64Bit; }
61  uint32_t getCPUType() const { return CPUType; }
62  uint32_t getCPUSubtype() const { return CPUSubtype; }
64  return LocalDifference_RIT;
65  }
66 
67  /// @}
68 
69  /// \name API
70  /// @{
71 
72  virtual void recordRelocation(MachObjectWriter *Writer, MCAssembler &Asm,
73  const MCAsmLayout &Layout,
74  const MCFragment *Fragment,
75  const MCFixup &Fixup, MCValue Target,
76  uint64_t &FixedValue) = 0;
77 
78  /// @}
79 };
80 
82  /// Helper struct for containing some precomputed information on symbols.
83  struct MachSymbolData {
84  const MCSymbol *Symbol;
85  uint64_t StringIndex;
86  uint8_t SectionIndex;
87 
88  // Support lexicographic sorting.
89  bool operator<(const MachSymbolData &RHS) const;
90  };
91 
92  /// The target specific Mach-O writer instance.
93  std::unique_ptr<MCMachObjectTargetWriter> TargetObjectWriter;
94 
95  /// \name Relocation Data
96  /// @{
97 
98  struct RelAndSymbol {
99  const MCSymbol *Sym;
101  RelAndSymbol(const MCSymbol *Sym, const MachO::any_relocation_info &MRE)
102  : Sym(Sym), MRE(MRE) {}
103  };
104 
107 
108  SectionAddrMap SectionAddress;
109 
110  /// @}
111  /// \name Symbol Table Data
112  /// @{
113 
115  std::vector<MachSymbolData> LocalSymbolData;
116  std::vector<MachSymbolData> ExternalSymbolData;
117  std::vector<MachSymbolData> UndefinedSymbolData;
118 
119  /// @}
120 
121  MachSymbolData *findSymbolData(const MCSymbol &Sym);
122 
123  void writeWithPadding(StringRef Str, uint64_t Size);
124 
125 public:
126  MachObjectWriter(std::unique_ptr<MCMachObjectTargetWriter> MOTW,
127  raw_pwrite_stream &OS, bool IsLittleEndian)
128  : TargetObjectWriter(std::move(MOTW)),
129  W(OS, IsLittleEndian ? support::little : support::big) {}
130 
132 
133  const MCSymbol &findAliasedSymbol(const MCSymbol &Sym) const;
134 
135  /// \name Lifetime management Methods
136  /// @{
137 
138  void reset() override;
139 
140  /// @}
141 
142  /// \name Utility Methods
143  /// @{
144 
145  bool isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind);
146 
147  SectionAddrMap &getSectionAddressMap() { return SectionAddress; }
148 
149  uint64_t getSectionAddress(const MCSection *Sec) const {
150  return SectionAddress.lookup(Sec);
151  }
152  uint64_t getSymbolAddress(const MCSymbol &S, const MCAsmLayout &Layout) const;
153 
154  uint64_t getFragmentAddress(const MCFragment *Fragment,
155  const MCAsmLayout &Layout) const;
156 
157  uint64_t getPaddingSize(const MCSection *SD, const MCAsmLayout &Layout) const;
158 
159  bool doesSymbolRequireExternRelocation(const MCSymbol &S);
160 
161  /// @}
162 
163  /// \name Target Writer Proxy Accessors
164  /// @{
165 
166  bool is64Bit() const { return TargetObjectWriter->is64Bit(); }
167  bool isX86_64() const {
168  uint32_t CPUType = TargetObjectWriter->getCPUType();
169  return CPUType == MachO::CPU_TYPE_X86_64;
170  }
171 
172  /// @}
173 
174  void writeHeader(MachO::HeaderFileType Type, unsigned NumLoadCommands,
175  unsigned LoadCommandsSize, bool SubsectionsViaSymbols);
176 
177  /// Write a segment load command.
178  ///
179  /// \param NumSections The number of sections in this segment.
180  /// \param SectionDataSize The total size of the sections.
181  void writeSegmentLoadCommand(StringRef Name, unsigned NumSections,
182  uint64_t VMAddr, uint64_t VMSize,
183  uint64_t SectionDataStartOffset,
184  uint64_t SectionDataSize, uint32_t MaxProt,
185  uint32_t InitProt);
186 
187  void writeSection(const MCAsmLayout &Layout, const MCSection &Sec,
188  uint64_t VMAddr, uint64_t FileOffset, unsigned Flags,
189  uint64_t RelocationsStart, unsigned NumRelocations);
190 
191  void writeSymtabLoadCommand(uint32_t SymbolOffset, uint32_t NumSymbols,
192  uint32_t StringTableOffset,
193  uint32_t StringTableSize);
194 
195  void writeDysymtabLoadCommand(
196  uint32_t FirstLocalSymbol, uint32_t NumLocalSymbols,
197  uint32_t FirstExternalSymbol, uint32_t NumExternalSymbols,
198  uint32_t FirstUndefinedSymbol, uint32_t NumUndefinedSymbols,
199  uint32_t IndirectSymbolOffset, uint32_t NumIndirectSymbols);
200 
201  void writeNlist(MachSymbolData &MSD, const MCAsmLayout &Layout);
202 
203  void writeLinkeditLoadCommand(uint32_t Type, uint32_t DataOffset,
204  uint32_t DataSize);
205 
206  void writeLinkerOptionsLoadCommand(const std::vector<std::string> &Options);
207 
208  // FIXME: We really need to improve the relocation validation. Basically, we
209  // want to implement a separate computation which evaluates the relocation
210  // entry as the linker would, and verifies that the resultant fixup value is
211  // exactly what the encoder wanted. This will catch several classes of
212  // problems:
213  //
214  // - Relocation entry bugs, the two algorithms are unlikely to have the same
215  // exact bug.
216  //
217  // - Relaxation issues, where we forget to relax something.
218  //
219  // - Input errors, where something cannot be correctly encoded. 'as' allows
220  // these through in many cases.
221 
222  // Add a relocation to be output in the object file. At the time this is
223  // called, the symbol indexes are not know, so if the relocation refers
224  // to a symbol it should be passed as \p RelSymbol so that it can be updated
225  // afterwards. If the relocation doesn't refer to a symbol, nullptr should be
226  // used.
227  void addRelocation(const MCSymbol *RelSymbol, const MCSection *Sec,
229  RelAndSymbol P(RelSymbol, MRE);
230  Relocations[Sec].push_back(P);
231  }
232 
233  void recordScatteredRelocation(const MCAssembler &Asm,
234  const MCAsmLayout &Layout,
235  const MCFragment *Fragment,
236  const MCFixup &Fixup, MCValue Target,
237  unsigned Log2Size, uint64_t &FixedValue);
238 
239  void recordTLVPRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
240  const MCFragment *Fragment, const MCFixup &Fixup,
241  MCValue Target, uint64_t &FixedValue);
242 
243  void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout,
244  const MCFragment *Fragment, const MCFixup &Fixup,
245  MCValue Target, uint64_t &FixedValue) override;
246 
247  void bindIndirectSymbols(MCAssembler &Asm);
248 
249  /// Compute the symbol table data.
250  void computeSymbolTable(MCAssembler &Asm,
251  std::vector<MachSymbolData> &LocalSymbolData,
252  std::vector<MachSymbolData> &ExternalSymbolData,
253  std::vector<MachSymbolData> &UndefinedSymbolData);
254 
255  void computeSectionAddresses(const MCAssembler &Asm,
256  const MCAsmLayout &Layout);
257 
258  void executePostLayoutBinding(MCAssembler &Asm,
259  const MCAsmLayout &Layout) override;
260 
261  bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
262  const MCSymbol &A,
263  const MCSymbol &B,
264  bool InSet) const override;
265 
266  bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
267  const MCSymbol &SymA,
268  const MCFragment &FB, bool InSet,
269  bool IsPCRel) const override;
270 
271  uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
272 };
273 
274 /// Construct a new Mach-O writer instance.
275 ///
276 /// This routine takes ownership of the target writer subclass.
277 ///
278 /// \param MOTW - The target specific Mach-O writer subclass.
279 /// \param OS - The stream to write to.
280 /// \returns The constructed object writer.
281 std::unique_ptr<MCObjectWriter>
282 createMachObjectWriter(std::unique_ptr<MCMachObjectTargetWriter> MOTW,
283  raw_pwrite_stream &OS, bool IsLittleEndian);
284 
285 } // end namespace llvm
286 
287 #endif // LLVM_MC_MCMACHOBJECTWRITER_H
Instances of this class represent a uniqued identifier for a section in the current translation unit...
Definition: MCSection.h:38
This class represents lattice values for constants.
Definition: AllocatorList.h:23
This represents an "assembler immediate".
Definition: MCValue.h:39
MCSymbol - Instances of this class represent a symbol name in the MC file, and MCSymbols are created ...
Definition: MCSymbol.h:41
amdgpu Simplify well known AMD library false FunctionCallee Value const Twine & Name
Defines the object file and target independent interfaces used by the assembler backend to write nati...
Encode information on a single operation to perform on a byte sequence (e.g., an encoded instruction)...
Definition: MCFixup.h:73
MachObjectWriter(std::unique_ptr< MCMachObjectTargetWriter > MOTW, raw_pwrite_stream &OS, bool IsLittleEndian)
support::endian::Writer W
Definition: BitVector.h:937
Encapsulates the layout of an assembly file at a particular point in time.
Definition: MCAsmLayout.h:28
HeaderFileType
Definition: MachO.h:36
virtual Triple::ObjectFormatType getFormat() const =0
void setLocalDifferenceRelocationType(unsigned Type)
Utility for building string tables with deduplicated suffixes.
void addRelocation(const MCSymbol *RelSymbol, const MCSection *Sec, MachO::any_relocation_info &MRE)
SectionAddrMap & getSectionAddressMap()
static bool classof(const MCObjectTargetWriter *W)
#define P(N)
static GCRegistry::Add< OcamlGC > B("ocaml", "ocaml 3.10-compatible GC")
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:45
PowerPC TLS Dynamic Call Fixup
virtual Triple::ObjectFormatType getFormat() const
unsigned getLocalDifferenceRelocationType() const
Target - Wrapper for Target specific information.
Adapter to write values to a stream in a particular byte order.
Definition: EndianStream.h:51
virtual void recordRelocation(MachObjectWriter *Writer, MCAssembler &Asm, const MCAsmLayout &Layout, const MCFragment *Fragment, const MCFixup &Fixup, MCValue Target, uint64_t &FixedValue)=0
std::unique_ptr< MCObjectWriter > createMachObjectWriter(std::unique_ptr< MCMachObjectTargetWriter > MOTW, raw_pwrite_stream &OS, bool IsLittleEndian)
Construct a new Mach-O writer instance.
uint32_t Size
Definition: Profile.cpp:46
Base class for classes that define behaviour that is specific to both the target and the object forma...
ValueT lookup(const_arg_type_t< KeyT > Val) const
lookup - Return the entry for the specified key, or a default constructed value if no such entry exis...
Definition: DenseMap.h:211
uint64_t getSectionAddress(const MCSection *Sec) const
An abstract base class for streams implementations that also support a pwrite operation.
Definition: raw_ostream.h:340
const unsigned Kind
ObjectFormatType
Definition: Triple.h:215
bool operator<(int64_t V1, const APSInt &V2)
Definition: APSInt.h:325
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:48
MCMachObjectTargetWriter(bool Is64Bit_, uint32_t CPUType_, uint32_t CPUSubtype_)