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 a string to use to fill out a code section.  This is
 118   // basically one or more NOPS which must fill out the specified
 119   // length in bytes.
 120   std::string
 121   code_fill(off_t length)
 122   { return this->do_code_fill(length); }
 123
 124  protected:
 125   // This struct holds the constant information for a child class.  We
 126   // use a struct to avoid the overhead of virtual function calls for
 127   // simple information.
 128   struct Target_info
 129   {
 130     // Address size (32 or 64).
 131     int size;
 132     // Whether the target is big endian.
 133     bool is_big_endian;
 134     // The code to store in the e_machine field of the ELF header.
 135     elfcpp::EM machine_code;
 136     // Whether this target has a specific make_symbol function.
 137     bool has_make_symbol;
 138     // Whether this target has a specific resolve function.
 139     bool has_resolve;
 140     // Whether this target has a specific code fill function.
 141     bool has_code_fill;
 142     // The default dynamic linker name.
 143     const char* dynamic_linker;
 144     // The default text segment address.
 145     uint64_t text_segment_address;
 146     // The ABI specified page size.
 147     uint64_t abi_pagesize;
 148     // The common page size used by actual implementations.
 149     uint64_t common_pagesize;
 150   };
 151
 152   Target(const Target_info* pti)
 153     : pti_(pti)
 154   { }
 155
 156   // Virtual function which may be implemented by the child class.
 157   virtual void
 158   do_finalize_sections(Layout*)
 159   { }
 160
 161   // Virtual function which must be implemented by the child class if
 162   // needed.
 163   virtual std::string
 164   do_code_fill(off_t)
 165   { gold_unreachable(); }
 166
 167  private:
 168   Target(const Target&);
 169   Target& operator=(const Target&);
 170
 171   // The target information.
 172   const Target_info* pti_;
 173 };
 174
 175 // The abstract class for a specific size and endianness of target.
 176 // Each actual target implementation class should derive from an
 177 // instantiation of Sized_target.
 178
 179 template<int size, bool big_endian>
 180 class Sized_target : public Target
 181 {
 182  public:
 183   // Make a new symbol table entry for the target.  This should be
 184   // overridden by a target which needs additional information in the
 185   // symbol table.  This will only be called if has_make_symbol()
 186   // returns true.
 187   virtual Sized_symbol<size>*
 188   make_symbol() const
 189   { gold_unreachable(); }
 190
 191   // Resolve a symbol for the target.  This should be overridden by a
 192   // target which needs to take special action.  TO is the
 193   // pre-existing symbol.  SYM is the new symbol, seen in OBJECT.
 194   // VERSION is the version of SYM.  This will only be called if
 195   // has_resolve() returns true.
 196   virtual void
 197   resolve(Symbol*, const elfcpp::Sym<size, big_endian>&, Object*,
 198           const char*)
 199   { gold_unreachable(); }
 200
 201   // Scan the relocs for a section, and record any information
 202   // required for the symbol.  OPTIONS is the command line options.
 203   // SYMTAB is the symbol table.  OBJECT is the object in which the
 204   // section appears.  DATA_SHNDX is the section index that these
 205   // relocs apply to.  SH_TYPE is the type of the relocation section,
 206   // SHT_REL or SHT_RELA.  PRELOCS points to the relocation data.
 207   // RELOC_COUNT is the number of relocs.  LOCAL_SYMBOL_COUNT is the
 208   // number of local symbols.  PLOCAL_SYMBOLS points to the local
 209   // symbol data from OBJECT.  GLOBAL_SYMBOLS is the array of pointers
 210   // to the global symbol table from OBJECT.
 211   virtual void
 212   scan_relocs(const General_options& options,
 213               Symbol_table* symtab,
 214               Layout* layout,
 215               Sized_relobj<size, big_endian>* object,
 216               unsigned int data_shndx,
 217               unsigned int sh_type,
 218               const unsigned char* prelocs,
 219               size_t reloc_count,
 220               size_t local_symbol_count,
 221               const unsigned char* plocal_symbols,
 222               Symbol** global_symbols) = 0;
 223
 224   // Relocate section data.  SH_TYPE is the type of the relocation
 225   // section, SHT_REL or SHT_RELA.  PRELOCS points to the relocation
 226   // information.  RELOC_COUNT is the number of relocs.  VIEW is a
 227   // view into the output file holding the section contents,
 228   // VIEW_ADDRESS is the virtual address of the view, and VIEW_SIZE is
 229   // the size of the view.
 230   virtual void
 231   relocate_section(const Relocate_info<size, big_endian>*,
 232                    unsigned int sh_type,
 233                    const unsigned char* prelocs,
 234                    size_t reloc_count,
 235                    unsigned char* view,
 236                    typename elfcpp::Elf_types<size>::Elf_Addr view_address,
 237                    off_t view_size) = 0;
 238
 239  protected:
 240   Sized_target(const Target::Target_info* pti)
 241     : Target(pti)
 242   {
 243     gold_assert(pti->size == size);
 244     gold_assert(pti->is_big_endian ? big_endian : !big_endian);
 245   }
 246 };
 247
 248 } // End namespace gold.
 249
 250 #endif // !defined(GOLD_TARGET_H)