gold/target-select.h

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