gold/target.h

   1 // target.h -- target support for gold   -*- C++ -*-
   2
   3 // Copyright 2006, 2007 Free Software Foundation, Inc.
   4 // Written by Ian Lance Taylor <iant@google.com>.
   5
   6 // This file is part of gold.
   7
   8 // This program is free software; you can redistribute it and/or modify
   9 // it under the terms of the GNU General Public License as published by
  10 // the Free Software Foundation; either version 3 of the License, or
  11 // (at your option) any later version.
  12
  13 // This program is distributed in the hope that it will be useful,
  14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 // GNU General Public License for more details.
  17
  18 // You should have received a copy of the GNU General Public License
  19 // along with this program; if not, write to the Free Software
  20 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
  21 // MA 02110-1301, USA.
  22
  23 // The abstract class Target is the interface for target specific
  24 // support.  It defines abstract methods which each target must
  25 // implement.  Typically there will be one target per processor, but
  26 // in some cases it may be necessary to have subclasses.
  27
  28 // For speed and consistency we want to use inline functions to handle
  29 // relocation processing.  So besides implementations of the abstract
  30 // methods, each target is expected to define a template
  31 // specialization of the relocation functions.
  32
  33 #ifndef GOLD_TARGET_H
  34 #define GOLD_TARGET_H
  35
  36 #include "elfcpp.h"
  37
  38 namespace gold
  39 {
  40
  41 class General_options;
  42 class Object;
  43 template<int size, bool big_endian>
  44 class Sized_relobj;
  45 template<int size, bool big_endian>
  46 struct Relocate_info;
  47 class Symbol;
  48 template<int size>
  49 class Sized_symbol;
  50 class Symbol_table;
  51
  52 // The abstract class for target specific handling.
  53
  54 class Target
  55 {
  56  public:
  57   virtual ~Target()
  58   { }
  59
  60   // Return the bit size that this target implements.  This should
  61   // return 32 or 64.
  62   int
  63   get_size() const
  64   { return this->pti_->size; }
  65
  66   // Return whether this target is big-endian.
  67   bool
  68   is_big_endian() const
  69   { return this->pti_->is_big_endian; }
  70
  71   // Machine code to store in e_machine field of ELF header.
  72   elfcpp::EM
  73   machine_code() const
  74   { return this->pti_->machine_code; }
  75
  76   // Whether this target has a specific make_symbol function.
  77   bool
  78   has_make_symbol() const
  79   { return this->pti_->has_make_symbol; }
  80
  81   // Whether this target has a specific resolve function.
  82   bool
  83   has_resolve() const
  84   { return this->pti_->has_resolve; }
  85
  86   // Whether this target has a specific code fill function.
  87   bool
  88   has_code_fill() const
  89   { return this->pti_->has_code_fill; }
  90
  91   // Return the default name of the dynamic linker.
  92   const char*
  93   dynamic_linker() const
  94   { return this->pti_->dynamic_linker; }
  95
  96   // Return the default address to use for the text segment.
  97   uint64_t
  98   text_segment_address() const
  99   { return this->pti_->text_segment_address; }
 100
 101   // Return the ABI specified page size.
 102   uint64_t
 103   abi_pagesize() const
 104   { return this->pti_->abi_pagesize; }
 105
 106   // Return the common page size used on actual systems.
 107   uint64_t
 108   common_pagesize() const
 109   { return this->pti_->common_pagesize; }
 110
 111   // This is called to tell the target to complete any sections it is
 112   // handling.  After this all sections must have their final size.
 113   void
 114   finalize_sections(Layout* layout)
 115   { return this->do_finalize_sections(layout); }
 116
 117   // Return the value to use for a global symbol which needs a special
 118   // value in the dynamic symbol table.  This will only be called if
 119   // the backend first calls symbol->set_needs_dynsym_value().
 120   uint64_t
 121   dynsym_value(const Symbol* sym) const
 122   { return this->do_dynsym_value(sym); }
 123
 124   // Return a string to use to fill out a code section.  This is
 125   // basically one or more NOPS which must fill out the specified
 126   // length in bytes.
 127   std::string
 128   code_fill(off_t length)
 129   { return this->do_code_fill(length); }
 130
 131  protected:
 132   // This struct holds the constant information for a child class.  We
 133   // use a struct to avoid the overhead of virtual function calls for
 134   // simple information.
 135   struct Target_info
 136   {
 137     // Address size (32 or 64).
 138     int size;
 139     // Whether the target is big endian.
 140     bool is_big_endian;
 141     // The code to store in the e_machine field of the ELF header.
 142     elfcpp::EM machine_code;
 143     // Whether this target has a specific make_symbol function.
 144     bool has_make_symbol;
 145     // Whether this target has a specific resolve function.
 146     bool has_resolve;
 147     // Whether this target has a specific code fill function.
 148     bool has_code_fill;
 149     // The default dynamic linker name.
 150     const char* dynamic_linker;
 151     // The default text segment address.
 152     uint64_t text_segment_address;
 153     // The ABI specified page size.
 154     uint64_t abi_pagesize;
 155     // The common page size used by actual implementations.
 156     uint64_t common_pagesize;
 157   };
 158
 159   Target(const Target_info* pti)
 160     : pti_(pti)
 161   { }
 162
 163   // Virtual function which may be implemented by the child class.
 164   virtual void
 165   do_finalize_sections(Layout*)
 166   { }
 167
 168   // Virtual function which may be implemented by the child class.
 169   virtual uint64_t
 170   do_dynsym_value(const Symbol*) const
 171   { gold_unreachable(); }
 172
 173   // Virtual function which must be implemented by the child class if
 174   // needed.
 175   virtual std::string
 176   do_code_fill(off_t)
 177   { gold_unreachable(); }
 178
 179  private:
 180   Target(const Target&);
 181   Target& operator=(const Target&);
 182
 183   // The target information.
 184   const Target_info* pti_;
 185 };
 186
 187 // The abstract class for a specific size and endianness of target.
 188 // Each actual target implementation class should derive from an
 189 // instantiation of Sized_target.
 190
 191 template<int size, bool big_endian>
 192 class Sized_target : public Target
 193 {
 194  public:
 195   // Make a new symbol table entry for the target.  This should be
 196   // overridden by a target which needs additional information in the
 197   // symbol table.  This will only be called if has_make_symbol()
 198   // returns true.
 199   virtual Sized_symbol<size>*
 200   make_symbol() const
 201   { gold_unreachable(); }
 202
 203   // Resolve a symbol for the target.  This should be overridden by a
 204   // target which needs to take special action.  TO is the
 205   // pre-existing symbol.  SYM is the new symbol, seen in OBJECT.
 206   // VERSION is the version of SYM.  This will only be called if
 207   // has_resolve() returns true.
 208   virtual void
 209   resolve(Symbol*, const elfcpp::Sym<size, big_endian>&, Object*,
 210           const char*)
 211   { gold_unreachable(); }
 212
 213   // Scan the relocs for a section, and record any information
 214   // required for the symbol.  OPTIONS is the command line options.
 215   // SYMTAB is the symbol table.  OBJECT is the object in which the
 216   // section appears.  DATA_SHNDX is the section index that these
 217   // relocs apply to.  SH_TYPE is the type of the relocation section,
 218   // SHT_REL or SHT_RELA.  PRELOCS points to the relocation data.
 219   // RELOC_COUNT is the number of relocs.  LOCAL_SYMBOL_COUNT is the
 220   // number of local symbols.  PLOCAL_SYMBOLS points to the local
 221   // symbol data from OBJECT.  GLOBAL_SYMBOLS is the array of pointers
 222   // to the global symbol table from OBJECT.
 223   virtual void
 224   scan_relocs(const General_options& options,
 225               Symbol_table* symtab,
 226               Layout* layout,
 227               Sized_relobj<size, big_endian>* object,
 228               unsigned int data_shndx,
 229               unsigned int sh_type,
 230               const unsigned char* prelocs,
 231               size_t reloc_count,
 232               size_t local_symbol_count,
 233               const unsigned char* plocal_symbols,
 234               Symbol** global_symbols) = 0;
 235
 236   // Relocate section data.  SH_TYPE is the type of the relocation
 237   // section, SHT_REL or SHT_RELA.  PRELOCS points to the relocation
 238   // information.  RELOC_COUNT is the number of relocs.  VIEW is a
 239   // view into the output file holding the section contents,
 240   // VIEW_ADDRESS is the virtual address of the view, and VIEW_SIZE is
 241   // the size of the view.
 242   virtual void
 243   relocate_section(const Relocate_info<size, big_endian>*,
 244                    unsigned int sh_type,
 245                    const unsigned char* prelocs,
 246                    size_t reloc_count,
 247                    unsigned char* view,
 248                    typename elfcpp::Elf_types<size>::Elf_Addr view_address,
 249                    off_t view_size) = 0;
 250
 251  protected:
 252   Sized_target(const Target::Target_info* pti)
 253     : Target(pti)
 254   {
 255     gold_assert(pti->size == size);
 256     gold_assert(pti->is_big_endian ? big_endian : !big_endian);
 257   }
 258 };
 259
 260 } // End namespace gold.
 261
 262 #endif // !defined(GOLD_TARGET_H)