gold/merge.h

   1 // merge.h -- handle section merging 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 #ifndef GOLD_MERGE_H
  24 #define GOLD_MERGE_H
  25
  26 #include <climits>
  27
  28 #include "stringpool.h"
  29 #include "output.h"
  30
  31 namespace gold
  32 {
  33
  34 // A general class for SHF_MERGE data, to hold functions shared by
  35 // fixed-size constant data and string data.
  36
  37 class Output_merge_base : public Output_section_data
  38 {
  39  public:
  40   Output_merge_base(uint64_t entsize, uint64_t addralign)
  41     : Output_section_data(addralign), merge_map_(), entsize_(entsize)
  42   { }
  43
  44   // Return the output address for an input address.
  45   bool
  46   do_output_address(const Relobj* object, unsigned int shndx, off_t offset,
  47                     uint64_t output_section_address, uint64_t* poutput) const;
  48
  49  protected:
  50   // Return the entry size.
  51   uint64_t
  52   entsize() const
  53   { return this->entsize_; }
  54
  55   // Add a mapping from an OFFSET in input section SHNDX in object
  56   // OBJECT to an OUTPUT_OFFSET in the output section.
  57   void
  58   add_mapping(Relobj* object, unsigned int shndx, off_t offset,
  59               off_t output_offset);
  60
  61  private:
  62   // We build a mapping from OBJECT/SHNDX/OFFSET to an offset in the
  63   // output section.
  64   struct Merge_key
  65   {
  66     const Relobj* object;
  67     unsigned int shndx;
  68     off_t offset;
  69   };
  70
  71   struct Merge_key_less
  72   {
  73     bool
  74     operator()(const Merge_key&, const Merge_key&) const;
  75   };
  76
  77   typedef std::map<Merge_key, off_t, Merge_key_less> Merge_map;
  78
  79   // A mapping from input object/section/offset to offset in output
  80   // section.
  81   Merge_map merge_map_;
  82
  83   // The entry size.  For fixed-size constants, this is the size of
  84   // the constants.  For strings, this is the size of a character.
  85   uint64_t entsize_;
  86 };
  87
  88 // Handle SHF_MERGE sections with fixed-size constant data.
  89
  90 class Output_merge_data : public Output_merge_base
  91 {
  92  public:
  93   Output_merge_data(uint64_t entsize, uint64_t addralign)
  94     : Output_merge_base(entsize, addralign), p_(NULL), len_(0), alc_(0),
  95       hashtable_(128, Merge_data_hash(this), Merge_data_eq(this))
  96   { }
  97
  98   // Add an input section.
  99   bool
 100   do_add_input_section(Relobj* object, unsigned int shndx);
 101
 102   // Set the final data size.
 103   void
 104   do_set_address(uint64_t, off_t);
 105
 106   // Write the data to the file.
 107   void
 108   do_write(Output_file*);
 109
 110  private:
 111   // We build a hash table of the fixed-size constants.  Each constant
 112   // is stored as a pointer into the section data we are accumulating.
 113
 114   // A key in the hash table.  This is an offset in the section
 115   // contents we are building.
 116   typedef off_t Merge_data_key;
 117
 118   // Compute the hash code.  To do this we need a pointer back to the
 119   // object holding the data.
 120   class Merge_data_hash
 121   {
 122    public:
 123     Merge_data_hash(const Output_merge_data* pomd)
 124       : pomd_(pomd)
 125     { }
 126
 127     size_t
 128     operator()(Merge_data_key) const;
 129
 130    private:
 131     const Output_merge_data* pomd_;
 132   };
 133
 134   friend class Merge_data_hash;
 135
 136   // Compare two entries in the hash table for equality.  To do this
 137   // we need a pointer back to the object holding the data.  Note that
 138   // we now have a pointer to the object stored in two places in the
 139   // hash table.  Fixing this would require specializing the hash
 140   // table, which would be hard to do portably.
 141   class Merge_data_eq
 142   {
 143    public:
 144     Merge_data_eq(const Output_merge_data* pomd)
 145       : pomd_(pomd)
 146     { }
 147
 148     bool
 149     operator()(Merge_data_key k1, Merge_data_key k2) const;
 150
 151    private:
 152     const Output_merge_data* pomd_;
 153   };
 154
 155   friend class Merge_data_eq;
 156
 157   // The type of the hash table.
 158   typedef Unordered_set<Merge_data_key, Merge_data_hash, Merge_data_eq>
 159     Merge_data_hashtable;
 160
 161   // Given a hash table key, which is just an offset into the section
 162   // data, return a pointer to the corresponding constant.
 163   const unsigned char*
 164   constant(Merge_data_key k) const
 165   {
 166     gold_assert(k >= 0 && k < this->len_);
 167     return this->p_ + k;
 168   }
 169
 170   // Add a constant to the output.
 171   void
 172   add_constant(const unsigned char*);
 173
 174   // The accumulated data.
 175   unsigned char* p_;
 176   // The length of the accumulated data.
 177   off_t len_;
 178   // The size of the allocated buffer.
 179   size_t alc_;
 180   // The hash table.
 181   Merge_data_hashtable hashtable_;
 182 };
 183
 184 // Handle SHF_MERGE sections with string data.  This is a template
 185 // based on the type of the characters in the string.
 186
 187 template<typename Char_type>
 188 class Output_merge_string : public Output_merge_base
 189 {
 190  public:
 191   Output_merge_string(uint64_t addralign)
 192     : Output_merge_base(sizeof(Char_type), addralign), stringpool_(),
 193       merged_strings_()
 194   {
 195     gold_assert(addralign <= sizeof(Char_type));
 196     this->stringpool_.set_no_zero_null();
 197   }
 198
 199   // Add an input section.
 200   bool
 201   do_add_input_section(Relobj* object, unsigned int shndx);
 202
 203   // Set the final data size.
 204   void
 205   do_set_address(uint64_t, off_t);
 206
 207   // Write the data to the file.
 208   void
 209   do_write(Output_file*);
 210
 211  private:
 212   // As we see input sections, we build a mapping from object, section
 213   // index and offset to strings.
 214   struct Merged_string
 215   {
 216     // The input object where the string was found.
 217     Relobj* object;
 218     // The input section in the input object.
 219     unsigned int shndx;
 220     // The offset in the input section.
 221     off_t offset;
 222     // The string itself, a pointer into a Stringpool.
 223     const Char_type* string;
 224
 225     Merged_string(Relobj *objecta, unsigned int shndxa, off_t offseta,
 226                   const Char_type* stringa)
 227       : object(objecta), shndx(shndxa), offset(offseta), string(stringa)
 228     { }
 229   };
 230
 231   typedef std::vector<Merged_string> Merged_strings;
 232
 233   // As we see the strings, we add them to a Stringpool.
 234   Stringpool_template<Char_type> stringpool_;
 235   // Map from a location in an input object to an entry in the
 236   // Stringpool.
 237   Merged_strings merged_strings_;
 238 };
 239
 240 } // End namespace gold.
 241
 242 #endif // !defined(GOLD_MERGE_H)