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->first.object != object
  90       || p->first.shndx != shndx
  91       || p->first.offset != offset)
  92     {
  93       if (p == this->merge_map_.begin())
  94         return false;
  95       --p;
  96     }
  97
  98   if (p->first.object != object || p->first.shndx != shndx)
  99     return false;
 100
 101   // Any input section is fully mapped: we don't need to know the size
 102   // of the range starting at P->FIRST.OFFSET.
 103   *poutput = output_section_address + p->second + (offset - p->first.offset);
 104   return true;
 105 }
 106
 107 // Compute the hash code for a fixed-size constant.
 108
 109 size_t
 110 Output_merge_data::Merge_data_hash::operator()(Merge_data_key k) const
 111 {
 112   const unsigned char* p = this->pomd_->constant(k);
 113   uint64_t entsize = this->pomd_->entsize();
 114
 115   // Fowler/Noll/Vo (FNV) hash (type FNV-1a).
 116   if (sizeof(size_t) == 8)
 117     {
 118       size_t result = static_cast<size_t>(14695981039346656037ULL);
 119       for (uint64_t i = 0; i < entsize; ++i)
 120         {
 121           result &= (size_t) *p++;
 122           result *= 1099511628211ULL;
 123         }
 124       return result;
 125     }
 126   else
 127     {
 128       size_t result = 2166136261UL;
 129       for (uint64_t i = 0; i < entsize; ++i)
 130         {
 131           result ^= (size_t) *p++;
 132           result *= 16777619UL;
 133         }
 134       return result;
 135     }
 136 }
 137
 138 // Return whether one hash table key equals another.
 139
 140 bool
 141 Output_merge_data::Merge_data_eq::operator()(Merge_data_key k1,
 142                                              Merge_data_key k2) const
 143 {
 144   const unsigned char* p1 = this->pomd_->constant(k1);
 145   const unsigned char* p2 = this->pomd_->constant(k2);
 146   return memcmp(p1, p2, this->pomd_->entsize()) == 0;
 147 }
 148
 149 // Add a constant to the end of the section contents.
 150
 151 void
 152 Output_merge_data::add_constant(const unsigned char* p)
 153 {
 154   uint64_t entsize = this->entsize();
 155   if (this->len_ + entsize > this->alc_)
 156     {
 157       if (this->alc_ == 0)
 158         this->alc_ = 128 * entsize;
 159       else
 160         this->alc_ *= 2;
 161       this->p_ = static_cast<unsigned char*>(realloc(this->p_, this->alc_));
 162       if (this->p_ == NULL)
 163         gold_fatal("out of memory", true);
 164     }
 165
 166   memcpy(this->p_ + this->len_, p, entsize);
 167   this->len_ += entsize;
 168 }
 169
 170 // Add the input section SHNDX in OBJECT to a merged output section
 171 // which holds fixed length constants.  Return whether we were able to
 172 // handle the section; if not, it will be linked as usual without
 173 // constant merging.
 174
 175 bool
 176 Output_merge_data::do_add_input_section(Relobj* object, unsigned int shndx)
 177 {
 178   off_t len;
 179   const unsigned char* p = object->section_contents(shndx, &len);
 180
 181   uint64_t entsize = this->entsize();
 182
 183   if (len % entsize != 0)
 184     return false;
 185
 186   for (off_t i = 0; i < len; i += entsize, p += entsize)
 187     {
 188       // Add the constant to the section contents.  If we find that it
 189       // is already in the hash table, we will remove it again.
 190       Merge_data_key k = this->len_;
 191       this->add_constant(p);
 192
 193       std::pair<Merge_data_hashtable::iterator, bool> ins =
 194         this->hashtable_.insert(k);
 195
 196       if (!ins.second)
 197         {
 198           // Key was already present.  Remove the copy we just added.
 199           this->len_ -= entsize;
 200           k = *ins.first;
 201         }
 202
 203       // Record the offset of this constant in the output section.
 204       this->add_mapping(object, shndx, i, k);
 205     }
 206
 207   return true;
 208 }
 209
 210 // Set the final data size in a merged output section with fixed size
 211 // constants.
 212
 213 void
 214 Output_merge_data::do_set_address(uint64_t, off_t)
 215 {
 216   // Release the memory we don't need.
 217   this->p_ = static_cast<unsigned char*>(realloc(this->p_, this->len_));
 218   gold_assert(this->p_ != NULL);
 219   this->set_data_size(this->len_);
 220 }
 221
 222 // Write the data of a merged output section with fixed size constants
 223 // to the file.
 224
 225 void
 226 Output_merge_data::do_write(Output_file* of)
 227 {
 228   of->write(this->offset(), this->p_, this->len_);
 229 }
 230
 231 // Add an input section to a merged string section.
 232
 233 template<typename Char_type>
 234 bool
 235 Output_merge_string<Char_type>::do_add_input_section(Relobj* object,
 236                                                      unsigned int shndx)
 237 {
 238   off_t len;
 239   const unsigned char* pdata = object->section_contents(shndx, &len);
 240
 241   const Char_type* p = reinterpret_cast<const Char_type*>(pdata);
 242
 243   if (len % sizeof(Char_type) != 0)
 244     {
 245       fprintf(stderr,
 246               _("%s: %s: mergeable string section length not multiple of "
 247                 "character size\n"),
 248               program_name, object->name().c_str());
 249       gold_exit(false);
 250     }
 251   len /= sizeof(Char_type);
 252
 253   off_t i = 0;
 254   while (i < len)
 255     {
 256       off_t plen = 0;
 257       for (const Char_type* pl = p; *pl != 0; ++pl)
 258         {
 259           ++plen;
 260           if (i + plen >= len)
 261             {
 262               fprintf(stderr,
 263                       _("%s: %s: entry in mergeable string section "
 264                         "not null terminated\n"),
 265                       program_name, object->name().c_str());
 266               gold_exit(false);
 267             }
 268         }
 269
 270       const Char_type* str = this->stringpool_.add(p, NULL);
 271
 272       this->merged_strings_.push_back(Merged_string(object, shndx, i, str));
 273
 274       p += plen + 1;
 275       i += plen + 1;
 276     }
 277
 278   return true;
 279 }
 280
 281 // Set the final data size of a merged string section.  This is where
 282 // we finalize the mappings from the input sections to the output
 283 // section.
 284
 285 template<typename Char_type>
 286 void
 287 Output_merge_string<Char_type>::do_set_address(uint64_t, off_t)
 288 {
 289   this->stringpool_.set_string_offsets();
 290
 291   for (typename Merged_strings::const_iterator p =
 292          this->merged_strings_.begin();
 293        p != this->merged_strings_.end();
 294        ++p)
 295     this->add_mapping(p->object, p->shndx, p->offset,
 296                       this->stringpool_.get_offset(p->string));
 297
 298   this->set_data_size(this->stringpool_.get_strtab_size());
 299
 300   // Save some memory.
 301   this->merged_strings_.clear();
 302 }
 303
 304 // Write out a merged string section.
 305
 306 template<typename Char_type>
 307 void
 308 Output_merge_string<Char_type>::do_write(Output_file* of)
 309 {
 310   this->stringpool_.write(of, this->offset());
 311 }
 312
 313 // Instantiate the templates we need.
 314
 315 template
 316 class Output_merge_string<char>;
 317
 318 template
 319 class Output_merge_string<uint16_t>;
 320
 321 template
 322 class Output_merge_string<uint32_t>;
 323
 324 } // End namespace gold.