LLVM  12.0.0git
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"
20 #include <cstdint>
21 #include <memory>
22 #include <string>
23 #include <vector>
24 
25 namespace llvm {
26 
27 class MachObjectWriter;
28 
30  const unsigned Is64Bit : 1;
31  const uint32_t CPUType;
32 protected:
34 public:
36 
37 protected:
38  MCMachObjectTargetWriter(bool Is64Bit_, uint32_t CPUType_,
39  uint32_t CPUSubtype_);
40 
42  LocalDifference_RIT = Type;
43  }
44 
45 public:
46  virtual ~MCMachObjectTargetWriter();
47 
48  Triple::ObjectFormatType getFormat() const override { return Triple::MachO; }
49  static bool classof(const MCObjectTargetWriter *W) {
50  return W->getFormat() == Triple::MachO;
51  }
52 
53  /// \name Lifetime Management
54  /// @{
55 
56  virtual void reset() {}
57 
58  /// @}
59 
60  /// \name Accessors
61  /// @{
62 
63  bool is64Bit() const { return Is64Bit; }
64  uint32_t getCPUType() const { return CPUType; }
65  uint32_t getCPUSubtype() const { return CPUSubtype; }
67  return LocalDifference_RIT;
68  }
69 
70  /// @}
71 
72  /// \name API
73  /// @{
74 
75  virtual void recordRelocation(MachObjectWriter *Writer, MCAssembler &Asm,
76  const MCAsmLayout &Layout,
77  const MCFragment *Fragment,
78  const MCFixup &Fixup, MCValue Target,
79  uint64_t &FixedValue) = 0;
80 
81  /// @}
82 };
83 
85  /// Helper struct for containing some precomputed information on symbols.
86  struct MachSymbolData {
87  const MCSymbol *Symbol;
88  uint64_t StringIndex;
89  uint8_t SectionIndex;
90 
91  // Support lexicographic sorting.
92  bool operator<(const MachSymbolData &RHS) const;
93  };
94 
95  /// The target specific Mach-O writer instance.
96  std::unique_ptr<MCMachObjectTargetWriter> TargetObjectWriter;
97 
98  /// \name Relocation Data
99  /// @{
100 
101  struct RelAndSymbol {
102  const MCSymbol *Sym;
104  RelAndSymbol(const MCSymbol *Sym, const MachO::any_relocation_info &MRE)
105  : Sym(Sym), MRE(MRE) {}
106  };
107 
110 
111  SectionAddrMap SectionAddress;
112 
113  /// @}
114  /// \name Symbol Table Data
115  /// @{
116 
118  std::vector<MachSymbolData> LocalSymbolData;
119  std::vector<MachSymbolData> ExternalSymbolData;
120  std::vector<MachSymbolData> UndefinedSymbolData;
121 
122  /// @}
123 
124  MachSymbolData *findSymbolData(const MCSymbol &Sym);
125 
126  void writeWithPadding(StringRef Str, uint64_t Size);
127 
128 public:
129  MachObjectWriter(std::unique_ptr<MCMachObjectTargetWriter> MOTW,
130  raw_pwrite_stream &OS, bool IsLittleEndian)
131  : TargetObjectWriter(std::move(MOTW)),
132  W(OS, IsLittleEndian ? support::little : support::big) {}
133 
135 
136  const MCSymbol &findAliasedSymbol(const MCSymbol &Sym) const;
137 
138  /// \name Lifetime management Methods
139  /// @{
140 
141  void reset() override;
142 
143  /// @}
144 
145  /// \name Utility Methods
146  /// @{
147 
148  bool isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind);
149 
150  SectionAddrMap &getSectionAddressMap() { return SectionAddress; }
151 
152  uint64_t getSectionAddress(const MCSection *Sec) const {
153  return SectionAddress.lookup(Sec);
154  }
155  uint64_t getSymbolAddress(const MCSymbol &S, const MCAsmLayout &Layout) const;
156 
157  uint64_t getFragmentAddress(const MCFragment *Fragment,
158  const MCAsmLayout &Layout) const;
159 
160  uint64_t getPaddingSize(const MCSection *SD, const MCAsmLayout &Layout) const;
161 
162  bool doesSymbolRequireExternRelocation(const MCSymbol &S);
163 
164  /// @}
165 
166  /// \name Target Writer Proxy Accessors
167  /// @{
168 
169  bool is64Bit() const { return TargetObjectWriter->is64Bit(); }
170  bool isX86_64() const {
171  uint32_t CPUType = TargetObjectWriter->getCPUType();
172  return CPUType == MachO::CPU_TYPE_X86_64;
173  }
174 
175  /// @}
176 
177  void writeHeader(MachO::HeaderFileType Type, unsigned NumLoadCommands,
178  unsigned LoadCommandsSize, bool SubsectionsViaSymbols);
179 
180  /// Write a segment load command.
181  ///
182  /// \param NumSections The number of sections in this segment.
183  /// \param SectionDataSize The total size of the sections.
184  void writeSegmentLoadCommand(StringRef Name, unsigned NumSections,
185  uint64_t VMAddr, uint64_t VMSize,
186  uint64_t SectionDataStartOffset,
187  uint64_t SectionDataSize, uint32_t MaxProt,
188  uint32_t InitProt);
189 
190  void writeSection(const MCAsmLayout &Layout, const MCSection &Sec,
191  uint64_t VMAddr, uint64_t FileOffset, unsigned Flags,
192  uint64_t RelocationsStart, unsigned NumRelocations);
193 
194  void writeSymtabLoadCommand(uint32_t SymbolOffset, uint32_t NumSymbols,
195  uint32_t StringTableOffset,
196  uint32_t StringTableSize);
197 
198  void writeDysymtabLoadCommand(
199  uint32_t FirstLocalSymbol, uint32_t NumLocalSymbols,
200  uint32_t FirstExternalSymbol, uint32_t NumExternalSymbols,
201  uint32_t FirstUndefinedSymbol, uint32_t NumUndefinedSymbols,
202  uint32_t IndirectSymbolOffset, uint32_t NumIndirectSymbols);
203 
204  void writeNlist(MachSymbolData &MSD, const MCAsmLayout &Layout);
205 
206  void writeLinkeditLoadCommand(uint32_t Type, uint32_t DataOffset,
207  uint32_t DataSize);
208 
209  void writeLinkerOptionsLoadCommand(const std::vector<std::string> &Options);
210 
211  // FIXME: We really need to improve the relocation validation. Basically, we
212  // want to implement a separate computation which evaluates the relocation
213  // entry as the linker would, and verifies that the resultant fixup value is
214  // exactly what the encoder wanted. This will catch several classes of
215  // problems:
216  //
217  // - Relocation entry bugs, the two algorithms are unlikely to have the same
218  // exact bug.
219  //
220  // - Relaxation issues, where we forget to relax something.
221  //
222  // - Input errors, where something cannot be correctly encoded. 'as' allows
223  // these through in many cases.
224 
225  // Add a relocation to be output in the object file. At the time this is
226  // called, the symbol indexes are not know, so if the relocation refers
227  // to a symbol it should be passed as \p RelSymbol so that it can be updated
228  // afterwards. If the relocation doesn't refer to a symbol, nullptr should be
229  // used.
230  void addRelocation(const MCSymbol *RelSymbol, const MCSection *Sec,
232  RelAndSymbol P(RelSymbol, MRE);
233  Relocations[Sec].push_back(P);
234  }
235 
236  void recordScatteredRelocation(const MCAssembler &Asm,
237  const MCAsmLayout &Layout,
238  const MCFragment *Fragment,
239  const MCFixup &Fixup, MCValue Target,
240  unsigned Log2Size, uint64_t &FixedValue);
241 
242  void recordTLVPRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
243  const MCFragment *Fragment, const MCFixup &Fixup,
244  MCValue Target, uint64_t &FixedValue);
245 
246  void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout,
247  const MCFragment *Fragment, const MCFixup &Fixup,
248  MCValue Target, uint64_t &FixedValue) override;
249 
250  void bindIndirectSymbols(MCAssembler &Asm);
251 
252  /// Compute the symbol table data.
253  void computeSymbolTable(MCAssembler &Asm,
254  std::vector<MachSymbolData> &LocalSymbolData,
255  std::vector<MachSymbolData> &ExternalSymbolData,
256  std::vector<MachSymbolData> &UndefinedSymbolData);
257 
258  void computeSectionAddresses(const MCAssembler &Asm,
259  const MCAsmLayout &Layout);
260 
261  void executePostLayoutBinding(MCAssembler &Asm,
262  const MCAsmLayout &Layout) override;
263 
264  bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
265  const MCSymbol &A,
266  const MCSymbol &B,
267  bool InSet) const override;
268 
269  bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
270  const MCSymbol &SymA,
271  const MCFragment &FB, bool InSet,
272  bool IsPCRel) const override;
273 
274  uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
275 };
276 
277 /// Construct a new Mach-O writer instance.
278 ///
279 /// This routine takes ownership of the target writer subclass.
280 ///
281 /// \param MOTW - The target specific Mach-O writer subclass.
282 /// \param OS - The stream to write to.
283 /// \returns The constructed object writer.
284 std::unique_ptr<MCObjectWriter>
285 createMachObjectWriter(std::unique_ptr<MCMachObjectTargetWriter> MOTW,
286  raw_pwrite_stream &OS, bool IsLittleEndian);
287 
288 } // end namespace llvm
289 
290 #endif // LLVM_MC_MCMACHOBJECTWRITER_H
Instances of this class represent a uniqued identifier for a section in the current translation unit...
Definition: MCSection.h:39
This class represents lattice values for constants.
Definition: AllocatorList.h:23
This represents an "assembler immediate".
Definition: MCValue.h:37
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:82
MachObjectWriter(std::unique_ptr< MCMachObjectTargetWriter > MOTW, raw_pwrite_stream &OS, bool IsLittleEndian)
support::endian::Writer W
Definition: BitVector.h:959
Encapsulates the layout of an assembly file at a particular point in time.
Definition: MCAsmLayout.h:28
HeaderFileType
Definition: MachO.h:40
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:46
PowerPC TLS Dynamic Call Fixup
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
Triple::ObjectFormatType getFormat() const override
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:197
uint64_t getSectionAddress(const MCSection *Sec) const
An abstract base class for streams implementations that also support a pwrite operation.
Definition: raw_ostream.h:383
ObjectFormatType
Definition: Triple.h:225
bool operator<(int64_t V1, const APSInt &V2)
Definition: APSInt.h:343
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:57
MCMachObjectTargetWriter(bool Is64Bit_, uint32_t CPUType_, uint32_t CPUSubtype_)