gold/target-select.h

   1 // target-select.h -- select a target for an object file  -*- C++ -*-
   2
   3 // Copyright 2006, 2007, 2008, 2009, 2010, 2011, 2012
   4 // Free Software Foundation, Inc.
   5 // Written by Ian Lance Taylor <iant@google.com>.
   6
   7 // This file is part of gold.
   8
   9 // This program is free software; you can redistribute it and/or modify
  10 // it under the terms of the GNU General Public License as published by
  11 // the Free Software Foundation; either version 3 of the License, or
  12 // (at your option) any later version.
  13
  14 // This program is distributed in the hope that it will be useful,
  15 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  16 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17 // GNU General Public License for more details.
  18
  19 // You should have received a copy of the GNU General Public License
  20 // along with this program; if not, write to the Free Software
  21 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
  22 // MA 02110-1301, USA.
  23
  24 #ifndef GOLD_TARGET_SELECT_H
  25 #define GOLD_TARGET_SELECT_H
  26
  27 #include <vector>
  28
  29 #include "gold-threads.h"
  30
  31 namespace gold
  32 {
  33
  34 class Input_file;
  35 class Target;
  36 class Target_selector;
  37
  38 // Used to set the target only once.
  39
  40 class Set_target_once : public Once
  41 {
  42  public:
  43   Set_target_once(Target_selector* target_selector)
  44     : target_selector_(target_selector)
  45   { }
  46
  47  protected:
  48   void
  49   do_run_once(void*);
  50
  51  private:
  52   Target_selector* target_selector_;
  53 };
  54
  55 // We want to avoid a master list of targets, which implies using a
  56 // global constructor.  And we also want the program to start up as
  57 // quickly as possible, which implies avoiding global constructors.
  58 // We compromise on a very simple global constructor.  We use a target
  59 // selector, which specifies an ELF machine number and a recognition
  60 // function.  We use global constructors to build a linked list of
  61 // target selectors--a simple pointer list, not a std::list.
  62
  63 class Target_selector
  64 {
  65  public:
  66   // Create a target selector for a specific machine number, size (32
  67   // or 64), and endianness.  The machine number can be EM_NONE to
  68   // test for any machine number.  BFD_NAME is the name of the target
  69   // used by the GNU linker, for backward compatibility; it may be
  70   // NULL.  EMULATION is the name of the emulation used by the GNU
  71   // linker; it is similar to BFD_NAME.
  72   Target_selector(int machine, int size, bool is_big_endian,
  73                   const char* bfd_name, const char* emulation);
  74
  75   virtual ~Target_selector()
  76   { }
  77
  78   // If we can handle this target, return a pointer to a target
  79   // structure.  The size and endianness are known.
  80   Target*
  81   recognize(Input_file* input_file, off_t offset,
  82             int machine, int osabi, int abiversion)
  83   { return this->do_recognize(input_file, offset, machine, osabi, abiversion); }
  84
  85   // If NAME matches the target, return a pointer to a target
  86   // structure.
  87   Target*
  88   recognize_by_bfd_name(const char* name)
  89   { return this->do_recognize_by_bfd_name(name); }
  90
  91   // Push all supported BFD names onto the vector.  This is only used
  92   // for help output.
  93   void
  94   supported_bfd_names(std::vector<const char*>* names)
  95   { this->do_supported_bfd_names(names); }
  96
  97   // If NAME matches the target emulation, return a pointer to a
  98   // target structure.
  99   Target*
 100   recognize_by_emulation(const char* name)
 101   { return this->do_recognize_by_emulation(name); }
 102
 103   // Push all supported emulations onto the vector.  This is only used
 104   // for help output.
 105   void
 106   supported_emulations(std::vector<const char*>* names)
 107   { this->do_supported_emulations(names); }
 108
 109   // Return the next Target_selector in the linked list.
 110   Target_selector*
 111   next() const
 112   { return this->next_; }
 113
 114   // Return the machine number this selector is looking for.  This can
 115   // be EM_NONE to match any machine number, in which case the
 116   // do_recognize hook will be responsible for matching the machine
 117   // number.
 118   int
 119   machine() const
 120   { return this->machine_; }
 121
 122   // Return the size this is looking for (32 or 64).
 123   int
 124   get_size() const
 125   { return this->size_; }
 126
 127   // Return the endianness this is looking for.
 128   bool
 129   is_big_endian() const
 130   { return this->is_big_endian_; }
 131
 132   // Return the BFD name.  This may return NULL, in which case the
 133   // do_recognize_by_bfd_name hook will be responsible for matching
 134   // the BFD name.
 135   const char*
 136   bfd_name() const
 137   { return this->bfd_name_; }
 138
 139   // Return the emulation.  This may return NULL, in which case the
 140   // do_recognize_by_emulation hook will be responsible for matching
 141   // the emulation.
 142   const char*
 143   emulation() const
 144   { return this->emulation_; }
 145
 146   // The reverse mapping, for --print-output-format: if we
 147   // instantiated TARGET, return our BFD_NAME.  If we did not
 148   // instantiate it, return NULL.
 149   const char*
 150   target_bfd_name(const Target* target)
 151   { return this->do_target_bfd_name(target); }
 152
 153  protected:
 154   // Return an instance of the real target.  This must be implemented
 155   // by the child class.
 156   virtual Target*
 157   do_instantiate_target() = 0;
 158
 159   // Recognize an object file given a machine code, OSABI code, and
 160   // ELF version value.  When this is called we already know that they
 161   // match the machine_, size_, and is_big_endian_ fields.  The child
 162   // class may implement a different version of this to do additional
 163   // checks, or to check for multiple machine codes if the machine_
 164   // field is EM_NONE.
 165   virtual Target*
 166   do_recognize(Input_file*, off_t, int, int, int)
 167   { return this->instantiate_target(); }
 168
 169   // Recognize a target by name.  When this is called we already know
 170   // that the name matches (or that the bfd_name_ field is NULL).  The
 171   // child class may implement a different version of this to
 172   // recognize more than one name.
 173   virtual Target*
 174   do_recognize_by_bfd_name(const char*)
 175   { return this->instantiate_target(); }
 176
 177   // Return a list of supported BFD names.  The child class may
 178   // implement a different version of this to handle more than one
 179   // name.
 180   virtual void
 181   do_supported_bfd_names(std::vector<const char*>* names)
 182   {
 183     gold_assert(this->bfd_name_ != NULL);
 184     names->push_back(this->bfd_name_);
 185   }
 186
 187   // Recognize a target by emulation.  When this is called we already
 188   // know that the name matches (or that the emulation_ field is
 189   // NULL).  The child class may implement a different version of this
 190   // to recognize more than one emulation.
 191   virtual Target*
 192   do_recognize_by_emulation(const char*)
 193   { return this->instantiate_target(); }
 194
 195   // Return a list of supported emulations.  The child class may
 196   // implement a different version of this to handle more than one
 197   // emulation.
 198   virtual void
 199   do_supported_emulations(std::vector<const char*>* emulations)
 200   {
 201     gold_assert(this->emulation_ != NULL);
 202     emulations->push_back(this->emulation_);
 203   }
 204
 205   // Map from target to BFD name.
 206   virtual const char*
 207   do_target_bfd_name(const Target*);
 208
 209   // Instantiate the target and return it.
 210   Target*
 211   instantiate_target();
 212
 213   // Return whether TARGET is the target we instantiated.
 214   bool
 215   is_our_target(const Target* target)
 216   { return target == this->instantiated_target_; }
 217
 218  private:
 219   // Set the target.
 220   void
 221   set_target();
 222
 223   friend class Set_target_once;
 224
 225   // ELF machine code.
 226   const int machine_;
 227   // Target size--32 or 64.
 228   const int size_;
 229   // Whether the target is big endian.
 230   const bool is_big_endian_;
 231   // BFD name of target, for compatibility.
 232   const char* const bfd_name_;
 233   // GNU linker emulation for this target, for compatibility.
 234   const char* const emulation_;
 235   // Next entry in list built at global constructor time.
 236   Target_selector* next_;
 237   // The singleton Target structure--this points to an instance of the
 238   // real implementation.
 239   Target* instantiated_target_;
 240   // Used to set the target only once.
 241   Set_target_once set_target_once_;
 242 };
 243
 244 // Select the target for an ELF file.
 245
 246 extern Target*
 247 select_target(Input_file*, off_t,
 248               int machine, int size, bool big_endian, int osabi,
 249               int abiversion);
 250
 251 // Select a target using a BFD name.
 252
 253 extern Target*
 254 select_target_by_bfd_name(const char* name);
 255
 256 // Select a target using a GNU linker emulation.
 257
 258 extern Target*
 259 select_target_by_emulation(const char* name);
 260
 261 // Fill in a vector with the list of supported targets.  This returns
 262 // a list of BFD names.
 263
 264 extern void
 265 supported_target_names(std::vector<const char*>*);
 266
 267 // Fill in a vector with the list of supported emulations.
 268
 269 extern void
 270 supported_emulation_names(std::vector<const char*>*);
 271
 272 // Print the output format, for the --print-output-format option.
 273
 274 extern void
 275 print_output_format();
 276
 277 } // End namespace gold.
 278
 279 #endif // !defined(GOLD_TARGET_SELECT_H)