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   // Whether this target has a specific code fill function.
  67   bool
  68   has_code_fill() const
  69   { return this->pti_->has_code_fill; }
  70
  71   // Return the default name of the dynamic linker.
  72   const char*
  73   dynamic_linker() const
  74   { return this->pti_->dynamic_linker; }
  75
  76   // Return the default address to use for the text segment.
  77   uint64_t
  78   text_segment_address() const
  79   { return this->pti_->text_segment_address; }
  80
  81   // Return the ABI specified page size.
  82   uint64_t
  83   abi_pagesize() const
  84   { return this->pti_->abi_pagesize; }
  85
  86   // Return the common page size used on actual systems.
  87   uint64_t
  88   common_pagesize() const
  89   { return this->pti_->common_pagesize; }
  90
  91   // This is called to tell the target to complete any sections it is
  92   // handling.  After this all sections must have their final size.
  93   void
  94   finalize_sections(const General_options* options, Layout* layout)
  95   { return this->do_finalize_sections(options, layout); }
  96
  97   // Return a string to use to fill out a code section.  This is
  98   // basically one or more NOPS which must fill out the specified
  99   // length in bytes.
 100   std::string
 101   code_fill(off_t length)
 102   { return this->do_code_fill(length); }
 103
 104  protected:
 105   // This struct holds the constant information for a child class.  We
 106   // use a struct to avoid the overhead of virtual function calls for
 107   // simple information.
 108   struct Target_info
 109   {
 110     // Address size (32 or 64).
 111     int size;
 112     // Whether the target is big endian.
 113     bool is_big_endian;
 114     // The code to store in the e_machine field of the ELF header.
 115     elfcpp::EM machine_code;
 116     // Whether this target has a specific make_symbol function.
 117     bool has_make_symbol;
 118     // Whether this target has a specific resolve function.
 119     bool has_resolve;
 120     // Whether this target has a specific code fill function.
 121     bool has_code_fill;
 122     // The default dynamic linker name.
 123     const char* dynamic_linker;
 124     // The default text segment address.
 125     uint64_t text_segment_address;
 126     // The ABI specified page size.
 127     uint64_t abi_pagesize;
 128     // The common page size used by actual implementations.
 129     uint64_t common_pagesize;
 130   };
 131
 132   Target(const Target_info* pti)
 133     : pti_(pti)
 134   { }
 135
 136   // Virtual function which may be implemented by the child class.
 137   virtual void
 138   do_finalize_sections(const General_options*, Layout*)
 139   { }
 140
 141   // Virtual function which must be implemented by the child class if
 142   // needed.
 143   virtual std::string
 144   do_code_fill(off_t)
 145   { gold_unreachable(); }
 146
 147  private:
 148   Target(const Target&);
 149   Target& operator=(const Target&);
 150
 151   // The target information.
 152   const Target_info* pti_;
 153 };
 154
 155 // The abstract class for a specific size and endianness of target.
 156 // Each actual target implementation class should derive from an
 157 // instantiation of Sized_target.
 158
 159 template<int size, bool big_endian>
 160 class Sized_target : public Target
 161 {
 162  public:
 163   // Make a new symbol table entry for the target.  This should be
 164   // overridden by a target which needs additional information in the
 165   // symbol table.  This will only be called if has_make_symbol()
 166   // returns true.
 167   virtual Sized_symbol<size>*
 168   make_symbol() const
 169   { gold_unreachable(); }
 170
 171   // Resolve a symbol for the target.  This should be overridden by a
 172   // target which needs to take special action.  TO is the
 173   // pre-existing symbol.  SYM is the new symbol, seen in OBJECT.
 174   // VERSION is the version of SYM.  This will only be called if
 175   // has_resolve() returns true.
 176   virtual void
 177   resolve(Symbol*, const elfcpp::Sym<size, big_endian>&, Object*,
 178           const char*)
 179   { gold_unreachable(); }
 180
 181   // Scan the relocs for a section, and record any information
 182   // required for the symbol.  OPTIONS is the command line options.
 183   // SYMTAB is the symbol table.  OBJECT is the object in which the
 184   // section appears.  DATA_SHNDX is the section index that these
 185   // relocs apply to.  SH_TYPE is the type of the relocation section,
 186   // SHT_REL or SHT_RELA.  PRELOCS points to the relocation data.
 187   // RELOC_COUNT is the number of relocs.  LOCAL_SYMBOL_COUNT is the
 188   // number of local symbols.  PLOCAL_SYMBOLS points to the local
 189   // symbol data from OBJECT.  GLOBAL_SYMBOLS is the array of pointers
 190   // to the global symbol table from OBJECT.
 191   virtual void
 192   scan_relocs(const General_options& options,
 193               Symbol_table* symtab,
 194               Layout* layout,
 195               Sized_relobj<size, big_endian>* object,
 196               unsigned int data_shndx,
 197               unsigned int sh_type,
 198               const unsigned char* prelocs,
 199               size_t reloc_count,
 200               size_t local_symbol_count,
 201               const unsigned char* plocal_symbols,
 202               Symbol** global_symbols) = 0;
 203
 204   // Relocate section data.  SH_TYPE is the type of the relocation
 205   // section, SHT_REL or SHT_RELA.  PRELOCS points to the relocation
 206   // information.  RELOC_COUNT is the number of relocs.  VIEW is a
 207   // view into the output file holding the section contents,
 208   // VIEW_ADDRESS is the virtual address of the view, and VIEW_SIZE is
 209   // the size of the view.
 210   virtual void
 211   relocate_section(const Relocate_info<size, big_endian>*,
 212                    unsigned int sh_type,
 213                    const unsigned char* prelocs,
 214                    size_t reloc_count,
 215                    unsigned char* view,
 216                    typename elfcpp::Elf_types<size>::Elf_Addr view_address,
 217                    off_t view_size) = 0;
 218
 219  protected:
 220   Sized_target(const Target::Target_info* pti)
 221     : Target(pti)
 222   {
 223     gold_assert(pti->size == size);
 224     gold_assert(pti->is_big_endian ? big_endian : !big_endian);
 225   }
 226 };
 227
 228 } // End namespace gold.
 229
 230 #endif // !defined(GOLD_TARGET_H)