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      1 //===- GOT.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_GOT_H
     10 #define MCLD_GOT_H
     11 #ifdef ENABLE_UNITTEST
     12 #include <gtest.h>
     13 #endif
     14 
     15 #include <mcld/LD/LDSection.h>
     16 #include <mcld/MC/MCTargetFragment.h>
     17 
     18 namespace mcld
     19 {
     20 
     21 class GOT;
     22 class ResolveInfo;
     23 
     24 /** \class GOTEntry
     25  *  \brief The entry of Global Offset Table
     26  */
     27 class GOTEntry : public MCTargetFragment
     28 {
     29 public:
     30   explicit GOTEntry(uint64_t pContent, size_t pEntrySize,
     31                     llvm::MCSectionData* pParent);
     32 
     33   virtual ~GOTEntry();
     34 
     35   uint64_t& getContent()
     36   { return f_Content; }
     37 
     38   uint64_t getContent() const
     39   { return f_Content; }
     40 
     41   void setContent(uint64_t pValue)
     42   { f_Content = pValue; }
     43 
     44   static bool classof(const MCFragment *pFrag)
     45   { return pFrag->getKind() == llvm::MCFragment::FT_Target; }
     46 
     47   static bool classof(const GOTEntry* pFrag)
     48   { return true; }
     49 
     50   // Override pure virtual function
     51   size_t getSize() const
     52   { return m_EntrySize; }
     53 
     54 protected:
     55   uint64_t f_Content;
     56   size_t m_EntrySize;
     57 };
     58 
     59 /** \class GOT
     60  *  \brief The Global Offset Table
     61  */
     62 class GOT
     63 {
     64 protected:
     65   GOT(LDSection& pSection,
     66       llvm::MCSectionData& pSectionData,
     67       size_t pEntrySize);
     68 
     69 public:
     70   virtual ~GOT();
     71 
     72   /// entrySize - the number of bytes per entry
     73   size_t getEntrySize() const;
     74 
     75   const LDSection& getSection() const
     76   { return m_Section; }
     77 
     78   llvm::MCSectionData& getSectionData()
     79   { return m_SectionData; }
     80 
     81   const llvm::MCSectionData& getSectionData() const
     82   { return m_SectionData; }
     83 
     84 public:
     85   /// reserveEntry - reseve number of pNum of empty entries
     86   /// Before layout, we scan all relocations to determine if GOT entries are
     87   /// needed. If an entry is needed, the empty entry is reserved for layout
     88   /// to adjust the fragment offset. After that, we fill up the entries when
     89   /// applying relocations.
     90   virtual void reserveEntry(size_t pNum = 1) = 0;
     91 
     92   /// getEntry - get an empty entry or an exitsted filled entry with pSymbol.
     93   /// @param pSymbol - the target symbol
     94   /// @param pExist - ture if a filled entry with pSymbol existed, otherwise false.
     95   virtual GOTEntry* getEntry(const ResolveInfo& pSymbol, bool& pExist) = 0;
     96 
     97 protected:
     98   LDSection& m_Section;
     99   llvm::MCSectionData& m_SectionData;
    100   size_t f_EntrySize;
    101 };
    102 
    103 } // namespace of mcld
    104 
    105 #endif
    106 
    107