gold/target.h

   1 // target.h -- target support for gold   -*- C++ -*-
   2
   3 // The abstract class Target is the interface for target specific
   4 // support.  It defines abstract methods which each target must
   5 // implement.  Typically there will be one target per processor, but
   6 // in some cases it may be necessary to have subclasses.
   7
   8 // For speed and consistency we want to use inline functions to handle
   9 // relocation processing.  So besides implementations of the abstract
  10 // methods, each target is expected to define a template
  11 // specialization of the relocation functions.
  12
  13 #ifndef GOLD_TARGET_H
  14 #define GOLD_TARGET_H
  15
  16 #include <cassert>
  17
  18 #include "elfcpp.h"
  19
  20 namespace gold
  21 {
  22
  23 class General_options;
  24 class Object;
  25 template<int size, bool big_endian>
  26 class Sized_relobj;
  27 template<int size, bool big_endian>
  28 struct Relocate_info;
  29 class Symbol;
  30 template<int size>
  31 class Sized_symbol;
  32 class Symbol_table;
  33
  34 // The abstract class for target specific handling.
  35
  36 class Target
  37 {
  38  public:
  39   virtual ~Target()
  40   { }
  41
  42   // Return the bit size that this target implements.  This should
  43   // return 32 or 64.
  44   int
  45   get_size() const
  46   { return this->pti_->size; }
  47
  48   // Return whether this target is big-endian.
  49   bool
  50   is_big_endian() const
  51   { return this->pti_->is_big_endian; }
  52
  53   // Machine code to store in e_machine field of ELF header.
  54   elfcpp::EM
  55   machine_code() const
  56   { return this->pti_->machine_code; }
  57
  58   // Whether this target has a specific make_symbol function.
  59   bool
  60   has_make_symbol() const
  61   { return this->pti_->has_make_symbol; }
  62
  63   // Whether this target has a specific resolve function.
  64   bool
  65   has_resolve() const
  66   { return this->pti_->has_resolve; }
  67
  68   // Return the default name of the dynamic linker.
  69   const char*
  70   dynamic_linker() const
  71   { return this->pti_->dynamic_linker; }
  72
  73   // Return the default address to use for the text segment.
  74   uint64_t
  75   text_segment_address() const
  76   { return this->pti_->text_segment_address; }
  77
  78   // Return the ABI specified page size.
  79   uint64_t
  80   abi_pagesize() const
  81   { return this->pti_->abi_pagesize; }
  82
  83   // Return the common page size used on actual systems.
  84   uint64_t
  85   common_pagesize() const
  86   { return this->pti_->common_pagesize; }
  87
  88  protected:
  89   // This struct holds the constant information for a child class.  We
  90   // use a struct to avoid the overhead of virtual function calls for
  91   // simple information.
  92   struct Target_info
  93   {
  94     // Address size (32 or 64).
  95     int size;
  96     // Whether the target is big endian.
  97     bool is_big_endian;
  98     // The code to store in the e_machine field of the ELF header.
  99     elfcpp::EM machine_code;
 100     // Whether this target has a specific make_symbol function.
 101     bool has_make_symbol;
 102     // Whether this target has a specific resolve function.
 103     bool has_resolve;
 104     // The default dynamic linker name.
 105     const char* dynamic_linker;
 106     // The default text segment address.
 107     uint64_t text_segment_address;
 108     // The ABI specified page size.
 109     uint64_t abi_pagesize;
 110     // The common page size used by actual implementations.
 111     uint64_t common_pagesize;
 112   };
 113
 114   Target(const Target_info* pti)
 115     : pti_(pti)
 116   { }
 117
 118  private:
 119   Target(const Target&);
 120   Target& operator=(const Target&);
 121
 122   // The target information.
 123   const Target_info* pti_;
 124 };
 125
 126 // The abstract class for a specific size and endianness of target.
 127 // Each actual target implementation class should derive from an
 128 // instantiation of Sized_target.
 129
 130 template<int size, bool big_endian>
 131 class Sized_target : public Target
 132 {
 133  public:
 134   // Make a new symbol table entry for the target.  This should be
 135   // overridden by a target which needs additional information in the
 136   // symbol table.  This will only be called if has_make_symbol()
 137   // returns true.
 138   virtual Sized_symbol<size>*
 139   make_symbol()
 140   { abort(); }
 141
 142   // Resolve a symbol for the target.  This should be overridden by a
 143   // target which needs to take special action.  TO is the
 144   // pre-existing symbol.  SYM is the new symbol, seen in OBJECT.
 145   // This will only be called if has_resolve() returns true.
 146   virtual void
 147   resolve(Symbol*, const elfcpp::Sym<size, big_endian>&, Object*)
 148   { abort(); }
 149
 150   // Scan the relocs for a section, and record any information
 151   // required for the symbol.  OPTIONS is the command line options.
 152   // SYMTAB is the symbol table.  OBJECT is the object in which the
 153   // section appears.  SH_TYPE is the type of the relocation section,
 154   // SHT_REL or SHT_RELA.  PRELOCS points to the relocation data.
 155   // RELOC_COUNT is the number of relocs.  LOCAL_SYMBOL_COUNT is the
 156   // number of local symbols.  PLOCAL_SYMBOLS points to the local
 157   // symbol data from OBJECT.  GLOBAL_SYMBOLS is the array of pointers
 158   // to the global symbol table from OBJECT.
 159   virtual void
 160   scan_relocs(const General_options& options,
 161               Symbol_table* symtab,
 162               Layout* layout,
 163               Sized_relobj<size, big_endian>* object,
 164               unsigned int sh_type,
 165               const unsigned char* prelocs,
 166               size_t reloc_count,
 167               size_t local_symbol_count,
 168               const unsigned char* plocal_symbols,
 169               Symbol** global_symbols) = 0;
 170
 171   // Relocate section data.  SH_TYPE is the type of the relocation
 172   // section, SHT_REL or SHT_RELA.  PRELOCS points to the relocation
 173   // information.  RELOC_COUNT is the number of relocs.  VIEW is a
 174   // view into the output file holding the section contents,
 175   // VIEW_ADDRESS is the virtual address of the view, and VIEW_SIZE is
 176   // the size of the view.
 177   virtual void
 178   relocate_section(const Relocate_info<size, big_endian>*,
 179                    unsigned int sh_type,
 180                    const unsigned char* prelocs,
 181                    size_t reloc_count,
 182                    unsigned char* view,
 183                    typename elfcpp::Elf_types<size>::Elf_Addr view_address,
 184                    off_t view_size) = 0;
 185
 186  protected:
 187   Sized_target(const Target::Target_info* pti)
 188     : Target(pti)
 189   {
 190     assert(pti->size == size);
 191     assert(pti->is_big_endian ? big_endian : !big_endian);
 192   }
 193 };
 194
 195 } // End namespace gold.
 196
 197 #endif // !defined(GOLD_TARGET_H)