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 #include "symtab.h"
  20
  21 namespace gold
  22 {
  23
  24 class Object;
  25 template<int size, bool big_endian>
  26 class Sized_object;
  27
  28 // The abstract class for target specific handling.
  29
  30 class Target
  31 {
  32  public:
  33   virtual ~Target()
  34   { }
  35
  36   // Return the bit size that this target implements.  This should
  37   // return 32 or 64.
  38   int
  39   get_size() const
  40   { return this->pti_->size; }
  41
  42   // Return whether this target is big-endian.
  43   bool
  44   is_big_endian() const
  45   { return this->pti_->is_big_endian; }
  46
  47   // Machine code to store in e_machine field of ELF header.
  48   elfcpp::EM
  49   machine_code() const
  50   { return this->pti_->machine_code; }
  51
  52   // Whether this target has a specific make_symbol function.
  53   bool
  54   has_make_symbol() const
  55   { return this->pti_->has_make_symbol; }
  56
  57   // Whether this target has a specific resolve function.
  58   bool
  59   has_resolve() const
  60   { return this->pti_->has_resolve; }
  61
  62   // Return the default address to use for the text segment.
  63   uint64_t
  64   text_segment_address() const
  65   { return this->pti_->text_segment_address; }
  66
  67   // Return the ABI specified page size.
  68   uint64_t
  69   abi_pagesize() const
  70   { return this->pti_->abi_pagesize; }
  71
  72   // Return the common page size used on actual systems.
  73   uint64_t
  74   common_pagesize() const
  75   { return this->pti_->common_pagesize; }
  76
  77  protected:
  78   // This struct holds the constant information for a child class.  We
  79   // use a struct to avoid the overhead of virtual function calls for
  80   // simple information.
  81   struct Target_info
  82   {
  83     // Address size (32 or 64).
  84     int size;
  85     // Whether the target is big endian.
  86     bool is_big_endian;
  87     // The code to store in the e_machine field of the ELF header.
  88     elfcpp::EM machine_code;
  89     // Whether this target has a specific make_symbol function.
  90     bool has_make_symbol;
  91     // Whether this target has a specific resolve function.
  92     bool has_resolve;
  93     // The default text segment address.
  94     uint64_t text_segment_address;
  95     // The ABI specified page size.
  96     uint64_t abi_pagesize;
  97     // The common page size used by actual implementations.
  98     uint64_t common_pagesize;
  99   };
 100
 101   Target(const Target_info* pti)
 102     : pti_(pti)
 103   { }
 104
 105  private:
 106   Target(const Target&);
 107   Target& operator=(const Target&);
 108
 109   // The target information.
 110   const Target_info* pti_;
 111 };
 112
 113 // The abstract class for a specific size and endianness of target.
 114 // Each actual target implementation class should derive from an
 115 // instantiation of Sized_target.
 116
 117 template<int size, bool big_endian>
 118 class Sized_target : public Target
 119 {
 120  public:
 121   // Make a new symbol table entry for the target.  This should be
 122   // overridden by a target which needs additional information in the
 123   // symbol table.  This will only be called if has_make_symbol()
 124   // returns true.
 125   virtual Sized_symbol<size>*
 126   make_symbol()
 127   { abort(); }
 128
 129   // Resolve a symbol for the target.  This should be overridden by a
 130   // target which needs to take special action.  TO is the
 131   // pre-existing symbol.  SYM is the new symbol, seen in OBJECT.
 132   virtual void
 133   resolve(Symbol*, const elfcpp::Sym<size, big_endian>&, Object*)
 134   { abort(); }
 135
 136   // Relocate section data.  SYMTAB is the symbol table.  OBJECT is
 137   // the object in which the section appears.  SH_TYPE is the type of
 138   // the relocation section, SHT_REL or SHT_RELA.  PRELOCS points to
 139   // the relocation information.  RELOC_COUNT is the number of relocs.
 140   // LOCAL_COUNT is the number of local symbols.  The VALUES and
 141   // GLOBAL_SYMS have symbol table information.  VIEW is a view into
 142   // the output file holding the section contents, VIEW_ADDRESS is the
 143   // virtual address of the view, and VIEW_SIZE is the size of the
 144   // view.
 145   virtual void
 146   relocate_section(const Symbol_table*, // symtab
 147                    Sized_object<size, big_endian>*, // object
 148                    unsigned int, // sh_type
 149                    const unsigned char*, // prelocs
 150                    size_t, // reloc_count
 151                    unsigned int, // local_count
 152                    const typename elfcpp::Elf_types<size>::Elf_Addr*, // values
 153                    Symbol**, // global_syms
 154                    unsigned char*, // view
 155                    typename elfcpp::Elf_types<size>::Elf_Addr, // view_address
 156                    off_t) // view_size
 157   { abort(); }
 158
 159  protected:
 160   Sized_target(const Target::Target_info* pti)
 161     : Target(pti)
 162   {
 163     assert(pti->size == size);
 164     assert(pti->is_big_endian ? big_endian : !big_endian);
 165   }
 166 };
 167
 168 } // End namespace gold.
 169
 170 #endif // !defined(GOLD_TARGET_H)