ARMLDBackend.h revision 5f7f811840be89f5b7f0b5997054e6282a4a4196 
1//===- ARMLDBackend.h -----------------------------------------------------===//
2//
3//                     The MCLinker Project
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9#ifndef MCLD_ARM_LDBACKEND_H
10#define MCLD_ARM_LDBACKEND_H
11
12#include "ARMELFDynamic.h"
13#include "ARMGOT.h"
14#include "ARMPLT.h"
15#include <mcld/LD/LDSection.h>
16#include <mcld/Target/GNULDBackend.h>
17#include <mcld/Target/OutputRelocSection.h>
18
19namespace mcld {
20
21class MCLDInfo;
22class MCLinker;
23class Output;
24class SectionMap;
25
26
27//===----------------------------------------------------------------------===//
28/// ARMGNULDBackend - linker backend of ARM target of GNU ELF format
29///
30class ARMGNULDBackend : public GNULDBackend
31{
32public:
33  ARMGNULDBackend();
34  ~ARMGNULDBackend();
35public:
36  typedef std::vector<llvm::ELF::Elf32_Dyn*> ELF32DynList;
37
38  /** \enum ReservedEntryType
39   *  \brief The reserved entry type of reserved space in ResolveInfo.
40   *
41   *  This is used for sacnRelocation to record what kinds of entries are
42   *  reserved for this resolved symbol
43   *
44   *  In ARM, there are three kinds of entries, GOT, PLT, and dynamic reloction.
45   *  GOT may needs a corresponding relocation to relocate itself, so we
46   *  separate GOT to two situations: GOT and GOTRel. Besides, for the same
47   *  symbol, there might be two kinds of entries reserved for different location.
48   *  For example, reference to the same symbol, one may use GOT and the other may
49   *  use dynamic relocation.
50   *
51   *  bit:  3       2      1     0
52   *   | PLT | GOTRel | GOT | Rel |
53   *
54   *  value    Name         - Description
55   *
56   *  0000     None         - no reserved entry
57   *  0001     ReserveRel   - reserve an dynamic relocation entry
58   *  0010     ReserveGOT   - reserve an GOT entry
59   *  0011     GOTandRel    - For different relocation, we've reserved GOT and
60   *                          Rel for different location.
61   *  0100     GOTRel       - reserve an GOT entry and the corresponding Dyncamic
62   *                          relocation entry which relocate this GOT entry
63   *  0101     GOTRelandRel - For different relocation, we've reserved GOTRel
64   *                          and relocation entry for different location.
65   *  1000     ReservePLT   - reserve an PLT entry and the corresponding GOT,
66   *                          Dynamic relocation entries
67   *  1001     PLTandRel    - For different relocation, we've reserved PLT and
68   *                          Rel for different location.
69   */
70  enum ReservedEntryType {
71    None         = 0,
72    ReserveRel   = 1,
73    ReserveGOT   = 2,
74    GOTandRel    = 3,
75    GOTRel       = 4,
76    GOTRelandRel = 5,
77    ReservePLT   = 8,
78    PLTandRel    = 9
79  };
80
81public:
82  /// initTargetSectionMap - initialize target dependent section mapping
83  bool initTargetSectionMap(SectionMap& pSectionMap);
84
85  /// initTargetSections - initialize target dependent sections in output.
86  void initTargetSections(MCLinker& pLinker);
87
88  /// initTargetSymbols - initialize target dependent symbols in output.
89  void initTargetSymbols(MCLinker& pLinker);
90
91  /// initRelocFactory - create and initialize RelocationFactory
92  bool initRelocFactory(const MCLinker& pLinker);
93
94  /// getRelocFactory
95  RelocationFactory* getRelocFactory();
96
97  /// scanRelocation - determine the empty entries are needed or not and create
98  /// the empty entries if needed.
99  /// For ARM, following entries are check to create:
100  /// - GOT entry (for .got section)
101  /// - PLT entry (for .plt section)
102  /// - dynamin relocation entries (for .rel.plt and .rel.dyn sections)
103  void scanRelocation(Relocation& pReloc,
104                      const LDSymbol& pInputSym,
105                      MCLinker& pLinker,
106                      const MCLDInfo& pLDInfo,
107                      const Output& pOutput);
108
109  uint32_t machine() const
110  { return llvm::ELF::EM_ARM; }
111
112  /// OSABI - the value of e_ident[EI_OSABI]
113  virtual uint8_t OSABI() const
114  { return llvm::ELF::ELFOSABI_NONE; }
115
116  /// ABIVersion - the value of e_ident[EI_ABIVRESION]
117  virtual uint8_t ABIVersion() const
118  { return 0x0; }
119
120  /// flags - the value of ElfXX_Ehdr::e_flags
121  virtual uint64_t flags() const
122  { return (llvm::ELF::EF_ARM_EABIMASK & 0x05000000); }
123
124  bool isLittleEndian() const
125  { return true; }
126
127  unsigned int bitclass() const
128  { return 32; }
129
130  /// doPreLayout - Backend can do any needed modification before layout
131  void doPreLayout(const Output& pOutput,
132                   const MCLDInfo& pInfo,
133                   MCLinker& pLinker);
134
135  /// doPostLayout -Backend can do any needed modification after layout
136  void doPostLayout(const Output& pOutput,
137                    const MCLDInfo& pInfo,
138                    MCLinker& pLinker);
139
140  /// dynamic - the dynamic section of the target machine.
141  /// Use co-variant return type to return its own dynamic section.
142  ARMELFDynamic& dynamic();
143
144  /// dynamic - the dynamic section of the target machine.
145  /// Use co-variant return type to return its own dynamic section.
146  const ARMELFDynamic& dynamic() const;
147
148
149  /// emitSectionData - write out the section data into the memory region.
150  /// When writers get a LDSection whose kind is LDFileFormat::Target, writers
151  /// call back target backend to emit the data.
152  ///
153  /// Backends handle the target-special tables (plt, gp,...) by themselves.
154  /// Backend can put the data of the tables in MCSectionData directly
155  ///  - LDSection.getSectionData can get the section data.
156  /// Or, backend can put the data into special data structure
157  ///  - backend can maintain its own map<LDSection, table> to get the table
158  /// from given LDSection.
159  ///
160  /// @param pOutput - the output file
161  /// @param pSection - the given LDSection
162  /// @param pInfo - all options in the command line.
163  /// @param pRegion - the region to write out data
164  /// @return the size of the table in the file.
165  uint64_t emitSectionData(const Output& pOutput,
166                           const LDSection& pSection,
167                           const MCLDInfo& pInfo,
168                           MemoryRegion& pRegion) const;
169
170  ARMGOT& getGOT();
171
172  const ARMGOT& getGOT() const;
173
174  ARMPLT& getPLT();
175
176  const ARMPLT& getPLT() const;
177
178  OutputRelocSection& getRelDyn();
179
180  const OutputRelocSection& getRelDyn() const;
181
182  OutputRelocSection& getRelPLT();
183
184  const OutputRelocSection& getRelPLT() const;
185
186  /// getTargetSectionOrder - compute the layout order of ARM target sections
187  unsigned int getTargetSectionOrder(const Output& pOutput,
188                                     const LDSection& pSectHdr) const;
189
190  /// finalizeSymbol - finalize the symbol value
191  /// If the symbol's reserved field is not zero, MCLinker will call back this
192  /// function to ask the final value of the symbol
193  bool finalizeSymbol(LDSymbol& pSymbol) const;
194
195  /// allocateCommonSymbols - allocate common symbols in the corresponding
196  /// sections.
197  bool allocateCommonSymbols(const MCLDInfo& pLDInfo, MCLinker& pLinker) const;
198
199  /// readSection - read target dependent sections
200  bool readSection(Input& pInput,
201                   MCLinker& pLinker,
202                   LDSection& pInputSectHdr);
203
204public:
205  bool isSymbolPreemptible(const ResolveInfo& pSym,
206                           const MCLDInfo& pLDInfo,
207                           const Output& pOutput) const;
208
209  bool isPIC(const MCLDInfo& pLDInfo, const Output& pOutput) const;
210
211private:
212  void scanLocalReloc(Relocation& pReloc,
213                      const LDSymbol& pInputSym,
214                      MCLinker& pLinker,
215                      const MCLDInfo& pLDInfo,
216                      const Output& pOutput);
217
218  void scanGlobalReloc(Relocation& pReloc,
219                       const LDSymbol& pInputSym,
220                       MCLinker& pLinker,
221                       const MCLDInfo& pLDInfo,
222                       const Output& pOutput);
223
224  bool isSymbolNeedsPLT(const ResolveInfo& pSym,
225                        const MCLDInfo& pLDInfo,
226                        const Output& pOutput) const;
227
228  bool isSymbolNeedsDynRel(const ResolveInfo& pSym,
229                           const Output& pOutput,
230                           bool isAbsReloc) const;
231
232
233  void checkValidReloc(Relocation& pReloc,
234                       const MCLDInfo& pLDInfo,
235                       const Output& pOutput) const;
236
237  /// updateAddend - update addend value of the relocation if the
238  /// the target symbol is a section symbol. Addend is the offset
239  /// in the section. This value should be updated after section
240  /// merged.
241  void updateAddend(Relocation& pReloc,
242                    const LDSymbol& pInputSym,
243                    const Layout& pLayout) const;
244
245  void createARMGOT(MCLinker& pLinker, const Output& pOutput);
246
247  /// createARMPLTandRelPLT - create PLT and RELPLT sections.
248  /// Because in ELF sh_info in .rel.plt is the shndx of .plt, these two
249  /// sections should be create together.
250  void createARMPLTandRelPLT(MCLinker& pLinker, const Output& pOutput);
251
252  void createARMRelDyn(MCLinker& pLinker, const Output& pOutput);
253
254  ELFFileFormat* getOutputFormat(const Output& pOutput) const;
255
256private:
257  RelocationFactory* m_pRelocFactory;
258  ARMGOT* m_pGOT;
259  ARMPLT* m_pPLT;
260  /// m_RelDyn - dynamic relocation table of .rel.dyn
261  OutputRelocSection* m_pRelDyn;
262  /// m_RelPLT - dynamic relocation table of .rel.plt
263  OutputRelocSection* m_pRelPLT;
264
265  ARMELFDynamic* m_pDynamic;
266  LDSymbol* m_pGOTSymbol;
267
268  //     variable name           :  ELF
269  LDSection* m_pEXIDX;           // .ARM.exidx
270  LDSection* m_pEXTAB;           // .ARM.extab
271  LDSection* m_pAttributes;      // .ARM.attributes
272//  LDSection* m_pPreemptMap;      // .ARM.preemptmap
273//  LDSection* m_pDebugOverlay;    // .ARM.debug_overlay
274//  LDSection* m_pOverlayTable;    // .ARM.overlay_table
275};
276
277//===----------------------------------------------------------------------===//
278/// ARMMachOLDBackend - linker backend of ARM target of MachO format
279///
280/**
281class ARMMachOLDBackend : public DarwinARMLDBackend
282{
283public:
284  ARMMachOLDBackend();
285  ~ARMMachOLDBackend();
286
287private:
288  MCMachOTargetArchiveReader *createTargetArchiveReader() const;
289  MCMachOTargetObjectReader *createTargetObjectReader() const;
290  MCMachOTargetObjectWriter *createTargetObjectWriter() const;
291
292};
293**/
294} // namespace of mcld
295
296#endif
297