gold/merge.cc

   1 // merge.cc -- handle section merging for gold
   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 #include "gold.h"
  24
  25 #include <cstdlib>
  26
  27 #include "merge.h"
  28
  29 namespace gold
  30 {
  31
  32 // Sort the entries in a merge mapping.  The key is an input object, a
  33 // section index in that object, and an offset in that section.
  34
  35 bool
  36 Output_merge_base::Merge_key_less::operator()(const Merge_key& mk1,
  37                                               const Merge_key& mk2) const
  38 {
  39   // The order of different objects and different sections doesn't
  40   // matter.  We want to get consistent results across links so we
  41   // don't use pointer comparison.
  42   if (mk1.object != mk2.object)
  43     return mk1.object->name() < mk2.object->name();
  44   if (mk1.shndx != mk2.shndx)
  45     return mk1.shndx < mk2.shndx;
  46   return mk1.offset < mk2.offset;
  47 }
  48
  49 // Add a mapping from an OFFSET in input section SHNDX in object
  50 // OBJECT to an OUTPUT_OFFSET in a merged output section.  This
  51 // manages the mapping used to resolve relocations against merged
  52 // sections.
  53
  54 void
  55 Output_merge_base::add_mapping(Relobj* object, unsigned int shndx,
  56                                off_t offset, off_t output_offset)
  57 {
  58   Merge_key mk;
  59   mk.object = object;
  60   mk.shndx = shndx;
  61   mk.offset = offset;
  62   std::pair<Merge_map::iterator, bool> ins =
  63     this->merge_map_.insert(std::make_pair(mk, output_offset));
  64   gold_assert(ins.second);
  65 }
  66
  67 // Return the output address for an input address.  The input address
  68 // is at offset OFFSET in section SHNDX in OBJECT.
  69 // OUTPUT_SECTION_ADDRESS is the address of the output section.  If we
  70 // know the address, set *POUTPUT and return true.  Otherwise return
  71 // false.
  72
  73 bool
  74 Output_merge_base::do_output_address(const Relobj* object, unsigned int shndx,
  75                                      off_t offset,
  76                                      uint64_t output_section_address,
  77                                      uint64_t* poutput) const
  78 {
  79   gold_assert(output_section_address == this->address());
  80
  81   Merge_key mk;
  82   mk.object = object;
  83   mk.shndx = shndx;
  84   mk.offset = offset;
  85   Merge_map::const_iterator p = this->merge_map_.lower_bound(mk);
  86
  87   // If MK is not in the map, lower_bound returns the next iterator
  88   // larger than it.
  89   if (p == this->merge_map_.end()
  90       || p->first.object != object
  91       || p->first.shndx != shndx
  92       || p->first.offset != offset)
  93     {
  94       if (p == this->merge_map_.begin())
  95         return false;
  96       --p;
  97     }
  98
  99   if (p->first.object != object || p->first.shndx != shndx)
 100     return false;
 101
 102   // Any input section is fully mapped: we don't need to know the size
 103   // of the range starting at P->FIRST.OFFSET.
 104   *poutput = output_section_address + p->second + (offset - p->first.offset);
 105   return true;
 106 }
 107
 108 // Compute the hash code for a fixed-size constant.
 109
 110 size_t
 111 Output_merge_data::Merge_data_hash::operator()(Merge_data_key k) const
 112 {
 113   const unsigned char* p = this->pomd_->constant(k);
 114   uint64_t entsize = this->pomd_->entsize();
 115
 116   // Fowler/Noll/Vo (FNV) hash (type FNV-1a).
 117   if (sizeof(size_t) == 8)
 118     {
 119       size_t result = static_cast<size_t>(14695981039346656037ULL);
 120       for (uint64_t i = 0; i < entsize; ++i)
 121         {
 122           result &= (size_t) *p++;
 123           result *= 1099511628211ULL;
 124         }
 125       return result;
 126     }
 127   else
 128     {
 129       size_t result = 2166136261UL;
 130       for (uint64_t i = 0; i < entsize; ++i)
 131         {
 132           result ^= (size_t) *p++;
 133           result *= 16777619UL;
 134         }
 135       return result;
 136     }
 137 }
 138
 139 // Return whether one hash table key equals another.
 140
 141 bool
 142 Output_merge_data::Merge_data_eq::operator()(Merge_data_key k1,
 143                                              Merge_data_key k2) const
 144 {
 145   const unsigned char* p1 = this->pomd_->constant(k1);
 146   const unsigned char* p2 = this->pomd_->constant(k2);
 147   return memcmp(p1, p2, this->pomd_->entsize()) == 0;
 148 }
 149
 150 // Add a constant to the end of the section contents.
 151
 152 void
 153 Output_merge_data::add_constant(const unsigned char* p)
 154 {
 155   uint64_t entsize = this->entsize();
 156   if (this->len_ + entsize > this->alc_)
 157     {
 158       if (this->alc_ == 0)
 159         this->alc_ = 128 * entsize;
 160       else
 161         this->alc_ *= 2;
 162       this->p_ = static_cast<unsigned char*>(realloc(this->p_, this->alc_));
 163       if (this->p_ == NULL)
 164         gold_fatal("out of memory", true);
 165     }
 166
 167   memcpy(this->p_ + this->len_, p, entsize);
 168   this->len_ += entsize;
 169 }
 170
 171 // Add the input section SHNDX in OBJECT to a merged output section
 172 // which holds fixed length constants.  Return whether we were able to
 173 // handle the section; if not, it will be linked as usual without
 174 // constant merging.
 175
 176 bool
 177 Output_merge_data::do_add_input_section(Relobj* object, unsigned int shndx)
 178 {
 179   off_t len;
 180   const unsigned char* p = object->section_contents(shndx, &len, false);
 181
 182   uint64_t entsize = this->entsize();
 183
 184   if (len % entsize != 0)
 185     return false;
 186
 187   for (off_t i = 0; i < len; i += entsize, p += entsize)
 188     {
 189       // Add the constant to the section contents.  If we find that it
 190       // is already in the hash table, we will remove it again.
 191       Merge_data_key k = this->len_;
 192       this->add_constant(p);
 193
 194       std::pair<Merge_data_hashtable::iterator, bool> ins =
 195         this->hashtable_.insert(k);
 196
 197       if (!ins.second)
 198         {
 199           // Key was already present.  Remove the copy we just added.
 200           this->len_ -= entsize;
 201           k = *ins.first;
 202         }
 203
 204       // Record the offset of this constant in the output section.
 205       this->add_mapping(object, shndx, i, k);
 206     }
 207
 208   return true;
 209 }
 210
 211 // Set the final data size in a merged output section with fixed size
 212 // constants.
 213
 214 void
 215 Output_merge_data::do_set_address(uint64_t, off_t)
 216 {
 217   // Release the memory we don't need.
 218   this->p_ = static_cast<unsigned char*>(realloc(this->p_, this->len_));
 219   gold_assert(this->p_ != NULL);
 220   this->set_data_size(this->len_);
 221 }
 222
 223 // Write the data of a merged output section with fixed size constants
 224 // to the file.
 225
 226 void
 227 Output_merge_data::do_write(Output_file* of)
 228 {
 229   of->write(this->offset(), this->p_, this->len_);
 230 }
 231
 232 // Add an input section to a merged string section.
 233
 234 template<typename Char_type>
 235 bool
 236 Output_merge_string<Char_type>::do_add_input_section(Relobj* object,
 237                                                      unsigned int shndx)
 238 {
 239   off_t len;
 240   const unsigned char* pdata = object->section_contents(shndx, &len, false);
 241
 242   const Char_type* p = reinterpret_cast<const Char_type*>(pdata);
 243
 244   if (len % sizeof(Char_type) != 0)
 245     {
 246       fprintf(stderr,
 247               _("%s: %s: mergeable string section length not multiple of "
 248                 "character size\n"),
 249               program_name, object->name().c_str());
 250       gold_exit(false);
 251     }
 252   len /= sizeof(Char_type);
 253
 254   off_t i = 0;
 255   while (i < len)
 256     {
 257       off_t plen = 0;
 258       for (const Char_type* pl = p; *pl != 0; ++pl)
 259         {
 260           ++plen;
 261           if (i + plen >= len)
 262             {
 263               fprintf(stderr,
 264                       _("%s: %s: entry in mergeable string section "
 265                         "not null terminated\n"),
 266                       program_name, object->name().c_str());
 267               gold_exit(false);
 268             }
 269         }
 270
 271       const Char_type* str = this->stringpool_.add(p, NULL);
 272
 273       this->merged_strings_.push_back(Merged_string(object, shndx, i, str));
 274
 275       p += plen + 1;
 276       i += plen + 1;
 277     }
 278
 279   return true;
 280 }
 281
 282 // Set the final data size of a merged string section.  This is where
 283 // we finalize the mappings from the input sections to the output
 284 // section.
 285
 286 template<typename Char_type>
 287 void
 288 Output_merge_string<Char_type>::do_set_address(uint64_t, off_t)
 289 {
 290   this->stringpool_.set_string_offsets();
 291
 292   for (typename Merged_strings::const_iterator p =
 293          this->merged_strings_.begin();
 294        p != this->merged_strings_.end();
 295        ++p)
 296     this->add_mapping(p->object, p->shndx, p->offset,
 297                       this->stringpool_.get_offset(p->string));
 298
 299   this->set_data_size(this->stringpool_.get_strtab_size());
 300
 301   // Save some memory.
 302   this->merged_strings_.clear();
 303 }
 304
 305 // Write out a merged string section.
 306
 307 template<typename Char_type>
 308 void
 309 Output_merge_string<Char_type>::do_write(Output_file* of)
 310 {
 311   this->stringpool_.write(of, this->offset());
 312 }
 313
 314 // Instantiate the templates we need.
 315
 316 template
 317 class Output_merge_string<char>;
 318
 319 template
 320 class Output_merge_string<uint16_t>;
 321
 322 template
 323 class Output_merge_string<uint32_t>;
 324
 325 } // End namespace gold.