gold/target-select.h

   1 // target-select.h -- select a target for an object file  -*- C++ -*-
   2
   3 // Copyright 2006, 2007, 2008, 2009, 2010 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 #ifndef GOLD_TARGET_SELECT_H
  24 #define GOLD_TARGET_SELECT_H
  25
  26 #include <vector>
  27
  28 #include "gold-threads.h"
  29
  30 namespace gold
  31 {
  32
  33 class Target;
  34 class Target_selector;
  35
  36 // Used to set the target only once.
  37
  38 class Set_target_once : public Once
  39 {
  40  public:
  41   Set_target_once(Target_selector* target_selector)
  42     : target_selector_(target_selector)
  43   { }
  44
  45  protected:
  46   void
  47   do_run_once(void*);
  48
  49  private:
  50   Target_selector* target_selector_;
  51 };
  52
  53 // We want to avoid a master list of targets, which implies using a
  54 // global constructor.  And we also want the program to start up as
  55 // quickly as possible, which implies avoiding global constructors.
  56 // We compromise on a very simple global constructor.  We use a target
  57 // selector, which specifies an ELF machine number and a recognition
  58 // function.  We use global constructors to build a linked list of
  59 // target selectors--a simple pointer list, not a std::list.
  60
  61 class Target_selector
  62 {
  63  public:
  64   // Create a target selector for a specific machine number, size (32
  65   // or 64), and endianness.  The machine number can be EM_NONE to
  66   // test for any machine number.  BFD_NAME is the name of the target
  67   // used by the GNU linker, for backward compatibility; it may be
  68   // NULL.
  69   Target_selector(int machine, int size, bool is_big_endian,
  70                   const char* bfd_name);
  71
  72   virtual ~Target_selector()
  73   { }
  74
  75   // If we can handle this target, return a pointer to a target
  76   // structure.  The size and endianness are known.
  77   Target*
  78   recognize(int machine, int osabi, int abiversion)
  79   { return this->do_recognize(machine, osabi, abiversion); }
  80
  81   // If NAME matches the target, return a pointer to a target
  82   // structure.
  83   Target*
  84   recognize_by_name(const char* name)
  85   { return this->do_recognize_by_name(name); }
  86
  87   // Push all supported names onto the vector.  This is only used for
  88   // help output.
  89   void
  90   supported_names(std::vector<const char*>* names)
  91   { this->do_supported_names(names); }
  92
  93   // Return the next Target_selector in the linked list.
  94   Target_selector*
  95   next() const
  96   { return this->next_; }
  97
  98   // Return the machine number this selector is looking for.  This can
  99   // be EM_NONE to match any machine number, in which case the
 100   // do_recognize hook will be responsible for matching the machine
 101   // number.
 102   int
 103   machine() const
 104   { return this->machine_; }
 105
 106   // Return the size this is looking for (32 or 64).
 107   int
 108   get_size() const
 109   { return this->size_; }
 110
 111   // Return the endianness this is looking for.
 112   bool
 113   is_big_endian() const
 114   { return this->is_big_endian_; }
 115
 116   // Return the BFD name.  This may return NULL, in which case the
 117   // do_recognize_by_name hook will be responsible for matching the
 118   // BFD name.
 119   const char*
 120   bfd_name() const
 121   { return this->bfd_name_; }
 122
 123  protected:
 124   // Return an instance of the real target.  This must be implemented
 125   // by the child class.
 126   virtual Target*
 127   do_instantiate_target() = 0;
 128
 129   // Recognize an object file given a machine code, OSABI code, and
 130   // ELF version value.  When this is called we already know that they
 131   // match the machine_, size_, and is_big_endian_ fields.  The child
 132   // class may implement a different version of this to do additional
 133   // checks, or to check for multiple machine codes if the machine_
 134   // field is EM_NONE.
 135   virtual Target*
 136   do_recognize(int, int, int)
 137   { return this->instantiate_target(); }
 138
 139   // Recognize a target by name.  When this is called we already know
 140   // that the name matches (or that the bfd_name_ field is NULL).  The
 141   // child class may implement a different version of this to
 142   // recognize more than one name.
 143   virtual Target*
 144   do_recognize_by_name(const char*)
 145   { return this->instantiate_target(); }
 146
 147   // Return a list of supported BFD names.  The child class may
 148   // implement a different version of this to handle more than one
 149   // name.
 150   virtual void
 151   do_supported_names(std::vector<const char*>* names)
 152   {
 153     gold_assert(this->bfd_name_ != NULL);
 154     names->push_back(this->bfd_name_);
 155   }
 156
 157   // Instantiate the target and return it.
 158   Target*
 159   instantiate_target();
 160
 161  private:
 162   // Set the target.
 163   void
 164   set_target();
 165
 166   friend class Set_target_once;
 167
 168   // ELF machine code.
 169   const int machine_;
 170   // Target size--32 or 64.
 171   const int size_;
 172   // Whether the target is big endian.
 173   const bool is_big_endian_;
 174   // BFD name of target, for compatibility.
 175   const char* const bfd_name_;
 176   // Next entry in list built at global constructor time.
 177   Target_selector* next_;
 178   // The singleton Target structure--this points to an instance of the
 179   // real implementation.
 180   Target* instantiated_target_;
 181   // Used to set the target only once.
 182   Set_target_once set_target_once_;
 183 };
 184
 185 // Select the target for an ELF file.
 186
 187 extern Target*
 188 select_target(int machine, int size, bool big_endian, int osabi,
 189               int abiversion);
 190
 191 // Select a target using a BFD name.
 192
 193 extern Target*
 194 select_target_by_name(const char* name);
 195
 196 // Fill in a vector with the list of supported targets.  This returns
 197 // a list of BFD names.
 198
 199 extern void
 200 supported_target_names(std::vector<const char*>*);
 201
 202 } // End namespace gold.
 203
 204 #endif // !defined(GOLD_TARGET_SELECT_H)