X86LDBackend.h revision d0fbbb227051be16931a1aa9b4a7722ac039c698 
1//===- X86LDBackend.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 X86_LDBACKEND_H
10#define X86_LDBACKEND_H
11
12#include "X86ELFDynamic.h"
13#include "X86GOT.h"
14#include "X86GOTPLT.h"
15#include "X86PLT.h"
16#include <mcld/LD/LDSection.h>
17#include <mcld/Target/GNULDBackend.h>
18#include <mcld/Target/OutputRelocSection.h>
19
20namespace mcld {
21
22class LinkerConfig;
23class X86GNUInfo;
24
25//===----------------------------------------------------------------------===//
26/// X86GNULDBackend - linker backend of X86 target of GNU ELF format
27///
28class X86GNULDBackend : public GNULDBackend
29{
30public:
31  /** \enum ReservedEntryType
32   *  \brief The reserved entry type of reserved space in ResolveInfo.
33   *
34   *  This is used for sacnRelocation to record what kinds of entries are
35   *  reserved for this resolved symbol
36   *
37   *  In X86, there are three kinds of entries, GOT, PLT, and dynamic reloction.
38   *  GOT may needs a corresponding relocation to relocate itself, so we
39   *  separate GOT to two situations: GOT and GOTRel. Besides, for the same
40   *  symbol, there might be two kinds of entries reserved for different location.
41   *  For example, reference to the same symbol, one may use GOT and the other may
42   *  use dynamic relocation.
43   *
44   *  bit:  3       2      1     0
45   *   | PLT | GOTRel | GOT | Rel |
46   *
47   *  value    Name         - Description
48   *
49   *  0000     None         - no reserved entry
50   *  0001     ReserveRel   - reserve an dynamic relocation entry
51   *  0010     ReserveGOT   - reserve an GOT entry
52   *  0011     GOTandRel    - For different relocation, we've reserved GOT and
53   *                          Rel for different location.
54   *  0100     GOTRel       - reserve an GOT entry and the corresponding Dyncamic
55   *                          relocation entry which relocate this GOT entry
56   *  0101     GOTRelandRel - For different relocation, we've reserved GOTRel
57   *                          and relocation entry for different location.
58   *  1000     ReservePLT   - reserve an PLT entry and the corresponding GOT,
59   *                          Dynamic relocation entries
60   *  1001     PLTandRel    - For different relocation, we've reserved PLT and
61   *                          Rel for different location.
62   */
63  enum ReservedEntryType {
64    None         = 0,
65    ReserveRel   = 1,
66    ReserveGOT   = 2,
67    GOTandRel    = 3,
68    GOTRel       = 4,
69    GOTRelandRel = 5,
70    ReservePLT   = 8,
71    PLTandRel    = 9
72  };
73
74public:
75  X86GNULDBackend(const LinkerConfig& pConfig, X86GNUInfo* pInfo);
76
77  ~X86GNULDBackend();
78
79  uint32_t machine() const;
80
81  X86GOT& getGOT();
82
83  const X86GOT& getGOT() const;
84
85  X86GOTPLT& getGOTPLT();
86
87  const X86GOTPLT& getGOTPLT() const;
88
89  X86PLT& getPLT();
90
91  const X86PLT& getPLT() const;
92
93  X86GOTEntry& getTLSModuleID();
94
95  /// preLayout - Backend can do any needed modification before layout
96  void doPreLayout(FragmentLinker& pLinker);
97
98  /// postLayout -Backend can do any needed modification after layout
99  void doPostLayout(Module& pModule, FragmentLinker& pLinker);
100
101  /// dynamic - the dynamic section of the target machine.
102  /// Use co-variant return type to return its own dynamic section.
103  X86ELFDynamic& dynamic();
104
105  /// dynamic - the dynamic section of the target machine.
106  /// Use co-variant return type to return its own dynamic section.
107  const X86ELFDynamic& dynamic() const;
108
109  /// emitSectionData - write out the section data into the memory region.
110  /// When writers get a LDSection whose kind is LDFileFormat::Target, writers
111  /// call back target backend to emit the data.
112  ///
113  /// Backends handle the target-special tables (plt, gp,...) by themselves.
114  /// Backend can put the data of the tables in MCSectionData directly
115  ///  - LDSection.getSectionData can get the section data.
116  /// Or, backend can put the data into special data structure
117  ///  - backend can maintain its own map<LDSection, table> to get the table
118  /// from given LDSection.
119  ///
120  /// @param pSection - the given LDSection
121  /// @param pLayout - for comouting the size of fragment
122  /// @param pRegion - the region to write out data
123  /// @return the size of the table in the file.
124  uint64_t emitSectionData(const LDSection& pSection,
125                           MemoryRegion& pRegion) const;
126
127  /// flags - the value of ElfXX_Ehdr::e_flags
128  /// FIXME
129  uint64_t flags() const
130  { return 0x0; }
131
132  uint64_t defaultTextSegmentAddr() const
133  { return 0x08048000; }
134
135  /// initRelocator - create and initialize Relocator.
136  bool initRelocator(const FragmentLinker& pLinker);
137
138  /// getRelocator - return relocator.
139  Relocator* getRelocator();
140
141  void initTargetSections(Module& pModule, ObjectBuilder& pBuilder);
142
143  void initTargetSymbols(FragmentLinker& pLinker);
144
145  /// scanRelocation - determine the empty entries are needed or not and create
146  /// the empty entries if needed.
147  /// For X86, following entries are check to create:
148  /// - GOT entry (for .got and .got.plt sections)
149  /// - PLT entry (for .plt section)
150  /// - dynamin relocation entries (for .rel.plt and .rel.dyn sections)
151  void scanRelocation(Relocation& pReloc,
152                      FragmentLinker& pLinker,
153                      Module& pModule,
154                      const LDSection& pSection);
155
156  OutputRelocSection& getRelDyn();
157
158  const OutputRelocSection& getRelDyn() const;
159
160  OutputRelocSection& getRelPLT();
161
162  const OutputRelocSection& getRelPLT() const;
163
164  /// getTargetSectionOrder - compute the layout order of X86 target sections
165  unsigned int getTargetSectionOrder(const LDSection& pSectHdr) const;
166
167  /// finalizeTargetSymbols - finalize the symbol value
168  bool finalizeTargetSymbols(FragmentLinker& pLinker);
169
170private:
171  void scanLocalReloc(Relocation& pReloc,
172                      FragmentLinker& pLinker,
173                      Module& pModule,
174                      const LDSection& pSection);
175
176  void scanGlobalReloc(Relocation& pReloc,
177                       FragmentLinker& pLinker,
178                       Module& pModule,
179                       const LDSection& pSection);
180
181  /// addCopyReloc - add a copy relocation into .rel.dyn for pSym
182  /// @param pSym - A resolved copy symbol that defined in BSS section
183  void addCopyReloc(ResolveInfo& pSym);
184
185  /// defineSymbolforCopyReloc - allocate a space in BSS section and
186  /// and force define the copy of pSym to BSS section
187  /// @return the output LDSymbol of the copy symbol
188  LDSymbol& defineSymbolforCopyReloc(FragmentLinker& pLinker,
189                                     const ResolveInfo& pSym);
190
191  void defineGOTSymbol(FragmentLinker& pLinker);
192
193  /// getRelEntrySize - the size in BYTE of rel type relocation
194  size_t getRelEntrySize()
195  { return 8; }
196
197  /// getRelEntrySize - the size in BYTE of rela type relocation
198  size_t getRelaEntrySize()
199  { return 12; }
200
201  /// doCreateProgramHdrs - backend can implement this function to create the
202  /// target-dependent segments
203  virtual void doCreateProgramHdrs(Module& pModule,
204                                   const FragmentLinker& pLinker);
205
206private:
207  Relocator* m_pRelocator;
208  X86GOT* m_pGOT;
209  X86PLT* m_pPLT;
210  X86GOTPLT* m_pGOTPLT;
211  /// m_RelDyn - dynamic relocation table of .rel.dyn
212  OutputRelocSection* m_pRelDyn;
213  /// m_RelPLT - dynamic relocation table of .rel.plt
214  OutputRelocSection* m_pRelPLT;
215
216  X86ELFDynamic* m_pDynamic;
217  LDSymbol* m_pGOTSymbol;
218};
219
220//===----------------------------------------------------------------------===//
221/// X86MachOLDBackend - linker backend of X86 target of MachO format
222///
223/**
224class X86MachOLDBackend : public DarwinX86LDBackend
225{
226public:
227  X86MachOLDBackend();
228  ~X86MachOLDBackend();
229
230private:
231  MCMachOTargetArchiveReader *createTargetArchiveReader() const;
232  MCMachOTargetObjectReader *createTargetObjectReader() const;
233  MCMachOTargetObjectWriter *createTargetObjectWriter() const;
234
235};
236**/
237} // namespace of mcld
238
239#endif
240
241