1//===- llvm/MC/MCMachObjectWriter.h - Mach Object Writer --------*- 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#ifndef LLVM_MC_MCMACHOBJECTWRITER_H
11#define LLVM_MC_MCMACHOBJECTWRITER_H
12
13#include "llvm/ADT/DenseMap.h"
14#include "llvm/ADT/StringRef.h"
15#include "llvm/BinaryFormat/MachO.h"
16#include "llvm/MC/MCExpr.h"
17#include "llvm/MC/MCObjectWriter.h"
18#include "llvm/MC/MCSection.h"
19#include "llvm/MC/StringTableBuilder.h"
20#include <cstdint>
21#include <memory>
22#include <string>
23#include <vector>
24
25namespace llvm {
26
27class MachObjectWriter;
28
29class MCMachObjectTargetWriter {
30  const unsigned Is64Bit : 1;
31  const uint32_t CPUType;
32  const uint32_t CPUSubtype;
33  unsigned LocalDifference_RIT;
34
35protected:
36  MCMachObjectTargetWriter(bool Is64Bit_, uint32_t CPUType_,
37                           uint32_t CPUSubtype_);
38
39  void setLocalDifferenceRelocationType(unsigned Type) {
40    LocalDifference_RIT = Type;
41  }
42
43public:
44  virtual ~MCMachObjectTargetWriter();
45
46  /// \name Lifetime Management
47  /// @{
48
49  virtual void reset() {}
50
51  /// @}
52
53  /// \name Accessors
54  /// @{
55
56  bool is64Bit() const { return Is64Bit; }
57  uint32_t getCPUType() const { return CPUType; }
58  uint32_t getCPUSubtype() const { return CPUSubtype; }
59  unsigned getLocalDifferenceRelocationType() const {
60    return LocalDifference_RIT;
61  }
62
63  /// @}
64
65  /// \name API
66  /// @{
67
68  virtual void recordRelocation(MachObjectWriter *Writer, MCAssembler &Asm,
69                                const MCAsmLayout &Layout,
70                                const MCFragment *Fragment,
71                                const MCFixup &Fixup, MCValue Target,
72                                uint64_t &FixedValue) = 0;
73
74  /// @}
75};
76
77class MachObjectWriter : public MCObjectWriter {
78  /// Helper struct for containing some precomputed information on symbols.
79  struct MachSymbolData {
80    const MCSymbol *Symbol;
81    uint64_t StringIndex;
82    uint8_t SectionIndex;
83
84    // Support lexicographic sorting.
85    bool operator<(const MachSymbolData &RHS) const;
86  };
87
88  /// The target specific Mach-O writer instance.
89  std::unique_ptr<MCMachObjectTargetWriter> TargetObjectWriter;
90
91  /// \name Relocation Data
92  /// @{
93
94  struct RelAndSymbol {
95    const MCSymbol *Sym;
96    MachO::any_relocation_info MRE;
97    RelAndSymbol(const MCSymbol *Sym, const MachO::any_relocation_info &MRE)
98        : Sym(Sym), MRE(MRE) {}
99  };
100
101  DenseMap<const MCSection *, std::vector<RelAndSymbol>> Relocations;
102  DenseMap<const MCSection *, unsigned> IndirectSymBase;
103
104  SectionAddrMap SectionAddress;
105
106  /// @}
107  /// \name Symbol Table Data
108  /// @{
109
110  StringTableBuilder StringTable{StringTableBuilder::MachO};
111  std::vector<MachSymbolData> LocalSymbolData;
112  std::vector<MachSymbolData> ExternalSymbolData;
113  std::vector<MachSymbolData> UndefinedSymbolData;
114
115  /// @}
116
117  MachSymbolData *findSymbolData(const MCSymbol &Sym);
118
119public:
120  MachObjectWriter(std::unique_ptr<MCMachObjectTargetWriter> MOTW,
121                   raw_pwrite_stream &OS, bool IsLittleEndian)
122      : MCObjectWriter(OS, IsLittleEndian),
123        TargetObjectWriter(std::move(MOTW)) {}
124
125  const MCSymbol &findAliasedSymbol(const MCSymbol &Sym) const;
126
127  /// \name Lifetime management Methods
128  /// @{
129
130  void reset() override;
131
132  /// @}
133
134  /// \name Utility Methods
135  /// @{
136
137  bool isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind);
138
139  SectionAddrMap &getSectionAddressMap() { return SectionAddress; }
140
141  uint64_t getSectionAddress(const MCSection *Sec) const {
142    return SectionAddress.lookup(Sec);
143  }
144  uint64_t getSymbolAddress(const MCSymbol &S, const MCAsmLayout &Layout) const;
145
146  uint64_t getFragmentAddress(const MCFragment *Fragment,
147                              const MCAsmLayout &Layout) const;
148
149  uint64_t getPaddingSize(const MCSection *SD, const MCAsmLayout &Layout) const;
150
151  bool doesSymbolRequireExternRelocation(const MCSymbol &S);
152
153  /// @}
154
155  /// \name Target Writer Proxy Accessors
156  /// @{
157
158  bool is64Bit() const { return TargetObjectWriter->is64Bit(); }
159  bool isX86_64() const {
160    uint32_t CPUType = TargetObjectWriter->getCPUType();
161    return CPUType == MachO::CPU_TYPE_X86_64;
162  }
163
164  /// @}
165
166  void writeHeader(MachO::HeaderFileType Type, unsigned NumLoadCommands,
167                   unsigned LoadCommandsSize, bool SubsectionsViaSymbols);
168
169  /// Write a segment load command.
170  ///
171  /// \param NumSections The number of sections in this segment.
172  /// \param SectionDataSize The total size of the sections.
173  void writeSegmentLoadCommand(StringRef Name, unsigned NumSections,
174                               uint64_t VMAddr, uint64_t VMSize,
175                               uint64_t SectionDataStartOffset,
176                               uint64_t SectionDataSize, uint32_t MaxProt,
177                               uint32_t InitProt);
178
179  void writeSection(const MCAsmLayout &Layout, const MCSection &Sec,
180                    uint64_t VMAddr, uint64_t FileOffset, unsigned Flags,
181                    uint64_t RelocationsStart, unsigned NumRelocations);
182
183  void writeSymtabLoadCommand(uint32_t SymbolOffset, uint32_t NumSymbols,
184                              uint32_t StringTableOffset,
185                              uint32_t StringTableSize);
186
187  void writeDysymtabLoadCommand(
188      uint32_t FirstLocalSymbol, uint32_t NumLocalSymbols,
189      uint32_t FirstExternalSymbol, uint32_t NumExternalSymbols,
190      uint32_t FirstUndefinedSymbol, uint32_t NumUndefinedSymbols,
191      uint32_t IndirectSymbolOffset, uint32_t NumIndirectSymbols);
192
193  void writeNlist(MachSymbolData &MSD, const MCAsmLayout &Layout);
194
195  void writeLinkeditLoadCommand(uint32_t Type, uint32_t DataOffset,
196                                uint32_t DataSize);
197
198  void writeLinkerOptionsLoadCommand(const std::vector<std::string> &Options);
199
200  // FIXME: We really need to improve the relocation validation. Basically, we
201  // want to implement a separate computation which evaluates the relocation
202  // entry as the linker would, and verifies that the resultant fixup value is
203  // exactly what the encoder wanted. This will catch several classes of
204  // problems:
205  //
206  //  - Relocation entry bugs, the two algorithms are unlikely to have the same
207  //    exact bug.
208  //
209  //  - Relaxation issues, where we forget to relax something.
210  //
211  //  - Input errors, where something cannot be correctly encoded. 'as' allows
212  //    these through in many cases.
213
214  // Add a relocation to be output in the object file. At the time this is
215  // called, the symbol indexes are not know, so if the relocation refers
216  // to a symbol it should be passed as \p RelSymbol so that it can be updated
217  // afterwards. If the relocation doesn't refer to a symbol, nullptr should be
218  // used.
219  void addRelocation(const MCSymbol *RelSymbol, const MCSection *Sec,
220                     MachO::any_relocation_info &MRE) {
221    RelAndSymbol P(RelSymbol, MRE);
222    Relocations[Sec].push_back(P);
223  }
224
225  void recordScatteredRelocation(const MCAssembler &Asm,
226                                 const MCAsmLayout &Layout,
227                                 const MCFragment *Fragment,
228                                 const MCFixup &Fixup, MCValue Target,
229                                 unsigned Log2Size, uint64_t &FixedValue);
230
231  void recordTLVPRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
232                            const MCFragment *Fragment, const MCFixup &Fixup,
233                            MCValue Target, uint64_t &FixedValue);
234
235  void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout,
236                        const MCFragment *Fragment, const MCFixup &Fixup,
237                        MCValue Target, uint64_t &FixedValue) override;
238
239  void bindIndirectSymbols(MCAssembler &Asm);
240
241  /// Compute the symbol table data.
242  void computeSymbolTable(MCAssembler &Asm,
243                          std::vector<MachSymbolData> &LocalSymbolData,
244                          std::vector<MachSymbolData> &ExternalSymbolData,
245                          std::vector<MachSymbolData> &UndefinedSymbolData);
246
247  void computeSectionAddresses(const MCAssembler &Asm,
248                               const MCAsmLayout &Layout);
249
250  void executePostLayoutBinding(MCAssembler &Asm,
251                                const MCAsmLayout &Layout) override;
252
253  bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
254                                              const MCSymbol &A,
255                                              const MCSymbol &B,
256                                              bool InSet) const override;
257
258  bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
259                                              const MCSymbol &SymA,
260                                              const MCFragment &FB, bool InSet,
261                                              bool IsPCRel) const override;
262
263  void writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
264};
265
266/// Construct a new Mach-O writer instance.
267///
268/// This routine takes ownership of the target writer subclass.
269///
270/// \param MOTW - The target specific Mach-O writer subclass.
271/// \param OS - The stream to write to.
272/// \returns The constructed object writer.
273std::unique_ptr<MCObjectWriter>
274createMachObjectWriter(std::unique_ptr<MCMachObjectTargetWriter> MOTW,
275                       raw_pwrite_stream &OS, bool IsLittleEndian);
276
277} // end namespace llvm
278
279#endif // LLVM_MC_MCMACHOBJECTWRITER_H
280