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 "elfcpp.h"
  17
  18 namespace gold
  19 {
  20
  21 class General_options;
  22 class Object;
  23 template<int size, bool big_endian>
  24 class Sized_relobj;
  25 template<int size, bool big_endian>
  26 struct Relocate_info;
  27 class Symbol;
  28 template<int size>
  29 class Sized_symbol;
  30 class Symbol_table;
  31
  32 // The abstract class for target specific handling.
  33
  34 class Target
  35 {
  36  public:
  37   virtual ~Target()
  38   { }
  39
  40   // Return the bit size that this target implements.  This should
  41   // return 32 or 64.
  42   int
  43   get_size() const
  44   { return this->pti_->size; }
  45
  46   // Return whether this target is big-endian.
  47   bool
  48   is_big_endian() const
  49   { return this->pti_->is_big_endian; }
  50
  51   // Machine code to store in e_machine field of ELF header.
  52   elfcpp::EM
  53   machine_code() const
  54   { return this->pti_->machine_code; }
  55
  56   // Whether this target has a specific make_symbol function.
  57   bool
  58   has_make_symbol() const
  59   { return this->pti_->has_make_symbol; }
  60
  61   // Whether this target has a specific resolve function.
  62   bool
  63   has_resolve() const
  64   { return this->pti_->has_resolve; }
  65
  66   // Return the default name of the dynamic linker.
  67   const char*
  68   dynamic_linker() const
  69   { return this->pti_->dynamic_linker; }
  70
  71   // Return the default address to use for the text segment.
  72   uint64_t
  73   text_segment_address() const
  74   { return this->pti_->text_segment_address; }
  75
  76   // Return the ABI specified page size.
  77   uint64_t
  78   abi_pagesize() const
  79   { return this->pti_->abi_pagesize; }
  80
  81   // Return the common page size used on actual systems.
  82   uint64_t
  83   common_pagesize() const
  84   { return this->pti_->common_pagesize; }
  85
  86  protected:
  87   // This struct holds the constant information for a child class.  We
  88   // use a struct to avoid the overhead of virtual function calls for
  89   // simple information.
  90   struct Target_info
  91   {
  92     // Address size (32 or 64).
  93     int size;
  94     // Whether the target is big endian.
  95     bool is_big_endian;
  96     // The code to store in the e_machine field of the ELF header.
  97     elfcpp::EM machine_code;
  98     // Whether this target has a specific make_symbol function.
  99     bool has_make_symbol;
 100     // Whether this target has a specific resolve function.
 101     bool has_resolve;
 102     // The default dynamic linker name.
 103     const char* dynamic_linker;
 104     // The default text segment address.
 105     uint64_t text_segment_address;
 106     // The ABI specified page size.
 107     uint64_t abi_pagesize;
 108     // The common page size used by actual implementations.
 109     uint64_t common_pagesize;
 110   };
 111
 112   Target(const Target_info* pti)
 113     : pti_(pti)
 114   { }
 115
 116  private:
 117   Target(const Target&);
 118   Target& operator=(const Target&);
 119
 120   // The target information.
 121   const Target_info* pti_;
 122 };
 123
 124 // The abstract class for a specific size and endianness of target.
 125 // Each actual target implementation class should derive from an
 126 // instantiation of Sized_target.
 127
 128 template<int size, bool big_endian>
 129 class Sized_target : public Target
 130 {
 131  public:
 132   // Make a new symbol table entry for the target.  This should be
 133   // overridden by a target which needs additional information in the
 134   // symbol table.  This will only be called if has_make_symbol()
 135   // returns true.
 136   virtual Sized_symbol<size>*
 137   make_symbol()
 138   { gold_unreachable(); }
 139
 140   // Resolve a symbol for the target.  This should be overridden by a
 141   // target which needs to take special action.  TO is the
 142   // pre-existing symbol.  SYM is the new symbol, seen in OBJECT.
 143   // This will only be called if has_resolve() returns true.
 144   virtual void
 145   resolve(Symbol*, const elfcpp::Sym<size, big_endian>&, Object*)
 146   { gold_unreachable(); }
 147
 148   // Scan the relocs for a section, and record any information
 149   // required for the symbol.  OPTIONS is the command line options.
 150   // SYMTAB is the symbol table.  OBJECT is the object in which the
 151   // section appears.  DATA_SHNDX is the section index that these
 152   // relocs apply to.  SH_TYPE is the type of the relocation section,
 153   // SHT_REL or SHT_RELA.  PRELOCS points to the relocation data.
 154   // RELOC_COUNT is the number of relocs.  LOCAL_SYMBOL_COUNT is the
 155   // number of local symbols.  PLOCAL_SYMBOLS points to the local
 156   // symbol data from OBJECT.  GLOBAL_SYMBOLS is the array of pointers
 157   // to the global symbol table from OBJECT.
 158   virtual void
 159   scan_relocs(const General_options& options,
 160               Symbol_table* symtab,
 161               Layout* layout,
 162               Sized_relobj<size, big_endian>* object,
 163               unsigned int data_shndx,
 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     gold_assert(pti->size == size);
 191     gold_assert(pti->is_big_endian ? big_endian : !big_endian);
 192   }
 193 };
 194
 195 } // End namespace gold.
 196
 197 #endif // !defined(GOLD_TARGET_H)