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