gold/merge.cc

   1 // merge.cc -- handle section merging for gold
   2
   3 #include "gold.h"
   4
   5 #include <cstdlib>
   6
   7 #include "merge.h"
   8
   9 namespace gold
  10 {
  11
  12 // Sort the entries in a merge mapping.  The key is an input object, a
  13 // section index in that object, and an offset in that section.
  14
  15 bool
  16 Output_merge_base::Merge_key_less::operator()(const Merge_key& mk1,
  17                                               const Merge_key& mk2) const
  18 {
  19   // The order of different objects and different sections doesn't
  20   // matter.  We want to get consistent results across links so we
  21   // don't use pointer comparison.
  22   if (mk1.object != mk2.object)
  23     return mk1.object->name() < mk2.object->name();
  24   if (mk1.shndx != mk2.shndx)
  25     return mk1.shndx < mk2.shndx;
  26   return mk1.offset < mk2.offset;
  27 }
  28
  29 // Add a mapping from an OFFSET in input section SHNDX in object
  30 // OBJECT to an OUTPUT_OFFSET in a merged output section.  This
  31 // manages the mapping used to resolve relocations against merged
  32 // sections.
  33
  34 void
  35 Output_merge_base::add_mapping(Relobj* object, unsigned int shndx,
  36                                off_t offset, off_t output_offset)
  37 {
  38   Merge_key mk;
  39   mk.object = object;
  40   mk.shndx = shndx;
  41   mk.offset = offset;
  42   std::pair<Merge_map::iterator, bool> ins =
  43     this->merge_map_.insert(std::make_pair(mk, output_offset));
  44   gold_assert(ins.second);
  45 }
  46
  47 // Return the output address for an input address.  The input address
  48 // is at offset OFFSET in section SHNDX in OBJECT.
  49 // OUTPUT_SECTION_ADDRESS is the address of the output section.  If we
  50 // know the address, set *POUTPUT and return true.  Otherwise return
  51 // false.
  52
  53 bool
  54 Output_merge_base::do_output_address(const Relobj* object, unsigned int shndx,
  55                                      off_t offset,
  56                                      uint64_t output_section_address,
  57                                      uint64_t* poutput) const
  58 {
  59   gold_assert(output_section_address == this->address());
  60
  61   Merge_key mk;
  62   mk.object = object;
  63   mk.shndx = shndx;
  64   mk.offset = offset;
  65   Merge_map::const_iterator p = this->merge_map_.lower_bound(mk);
  66
  67   // If MK is not in the map, lower_bound returns the next iterator
  68   // larger than it.
  69   if (p->first.object != object
  70       || p->first.shndx != shndx
  71       || p->first.offset != offset)
  72     {
  73       if (p == this->merge_map_.begin())
  74         return false;
  75       --p;
  76     }
  77
  78   if (p->first.object != object || p->first.shndx != shndx)
  79     return false;
  80
  81   // Any input section is fully mapped: we don't need to know the size
  82   // of the range starting at P->FIRST.OFFSET.
  83   *poutput = output_section_address + p->second + (offset - p->first.offset);
  84   return true;
  85 }
  86
  87 // Compute the hash code for a fixed-size constant.
  88
  89 size_t
  90 Output_merge_data::Merge_data_hash::operator()(Merge_data_key k) const
  91 {
  92   const unsigned char* p = this->pomd_->constant(k);
  93   uint64_t entsize = this->pomd_->entsize();
  94
  95   // Fowler/Noll/Vo (FNV) hash (type FNV-1a).
  96   if (sizeof(size_t) == 8)
  97     {
  98       size_t result = static_cast<size_t>(14695981039346656037ULL);
  99       for (uint64_t i = 0; i < entsize; ++i)
 100         {
 101           result &= (size_t) *p++;
 102           result *= 1099511628211ULL;
 103         }
 104       return result;
 105     }
 106   else
 107     {
 108       size_t result = 2166136261UL;
 109       for (uint64_t i = 0; i < entsize; ++i)
 110         {
 111           result ^= (size_t) *p++;
 112           result *= 16777619UL;
 113         }
 114       return result;
 115     }
 116 }
 117
 118 // Return whether one hash table key equals another.
 119
 120 bool
 121 Output_merge_data::Merge_data_eq::operator()(Merge_data_key k1,
 122                                              Merge_data_key k2) const
 123 {
 124   const unsigned char* p1 = this->pomd_->constant(k1);
 125   const unsigned char* p2 = this->pomd_->constant(k2);
 126   return memcmp(p1, p2, this->pomd_->entsize()) == 0;
 127 }
 128
 129 // Add a constant to the end of the section contents.
 130
 131 void
 132 Output_merge_data::add_constant(const unsigned char* p)
 133 {
 134   uint64_t entsize = this->entsize();
 135   if (this->len_ + entsize > this->alc_)
 136     {
 137       if (this->alc_ == 0)
 138         this->alc_ = 128 * entsize;
 139       else
 140         this->alc_ *= 2;
 141       this->p_ = static_cast<unsigned char*>(realloc(this->p_, this->alc_));
 142       if (this->p_ == NULL)
 143         gold_fatal("out of memory", true);
 144     }
 145
 146   memcpy(this->p_ + this->len_, p, entsize);
 147   this->len_ += entsize;
 148 }
 149
 150 // Add the input section SHNDX in OBJECT to a merged output section
 151 // which holds fixed length constants.  Return whether we were able to
 152 // handle the section; if not, it will be linked as usual without
 153 // constant merging.
 154
 155 bool
 156 Output_merge_data::do_add_input_section(Relobj* object, unsigned int shndx)
 157 {
 158   off_t len;
 159   const unsigned char* p = object->section_contents(shndx, &len);
 160
 161   uint64_t entsize = this->entsize();
 162
 163   if (len % entsize != 0)
 164     return false;
 165
 166   for (off_t i = 0; i < len; i += entsize, p += entsize)
 167     {
 168       // Add the constant to the section contents.  If we find that it
 169       // is already in the hash table, we will remove it again.
 170       Merge_data_key k = this->len_;
 171       this->add_constant(p);
 172
 173       std::pair<Merge_data_hashtable::iterator, bool> ins =
 174         this->hashtable_.insert(k);
 175
 176       if (!ins.second)
 177         {
 178           // Key was already present.  Remove the copy we just added.
 179           this->len_ -= entsize;
 180           k = *ins.first;
 181         }
 182
 183       // Record the offset of this constant in the output section.
 184       this->add_mapping(object, shndx, i, k);
 185     }
 186
 187   return true;
 188 }
 189
 190 // Set the final data size in a merged output section with fixed size
 191 // constants.
 192
 193 void
 194 Output_merge_data::do_set_address(uint64_t, off_t)
 195 {
 196   // Release the memory we don't need.
 197   this->p_ = static_cast<unsigned char*>(realloc(this->p_, this->len_));
 198   gold_assert(this->p_ != NULL);
 199   this->set_data_size(this->len_);
 200 }
 201
 202 // Write the data of a merged output section with fixed size constants
 203 // to the file.
 204
 205 void
 206 Output_merge_data::do_write(Output_file* of)
 207 {
 208   of->write(this->offset(), this->p_, this->len_);
 209 }
 210
 211 // Compute a hash code for a Merge_string_key, which is an object, a
 212 // section index, and an offset.
 213
 214 template<typename Char_type>
 215 size_t
 216 Output_merge_string<Char_type>::Merge_string_key_hash::operator()(
 217     const Merge_string_key& key) const
 218 {
 219   // This is a very simple minded hash code.  Fix it if it we get too
 220   // many collisions.
 221   const std::string& oname(key.object->name());
 222   return oname[0] + oname.length() + key.shndx + key.offset;
 223 }
 224
 225 // Compare two Merge_string_keys for equality.
 226
 227 template<typename Char_type>
 228 bool
 229 Output_merge_string<Char_type>::Merge_string_key_eq::operator()(
 230     const Merge_string_key& k1, const Merge_string_key& k2) const
 231 {
 232   return (k1.object == k2.object
 233           && k1.shndx == k2.shndx
 234           && k1.offset == k2.offset);
 235 }
 236
 237 // Add an input section to a merged string section.
 238
 239 template<typename Char_type>
 240 bool
 241 Output_merge_string<Char_type>::do_add_input_section(Relobj* object,
 242                                                      unsigned int shndx)
 243 {
 244   off_t len;
 245   const unsigned char* pdata = object->section_contents(shndx, &len);
 246
 247   const Char_type* p = reinterpret_cast<const Char_type*>(pdata);
 248
 249   if (len % sizeof(Char_type) != 0)
 250     {
 251       fprintf(stderr,
 252               _("%s: %s: mergeable string section length not multiple of "
 253                 "character size\n"),
 254               program_name, object->name().c_str());
 255       gold_exit(false);
 256     }
 257   len /= sizeof(Char_type);
 258
 259   off_t i = 0;
 260   while (i < len)
 261     {
 262       off_t plen = 0;
 263       for (const Char_type* pl = p; *pl != 0; ++pl)
 264         {
 265           ++plen;
 266           if (i + plen >= len)
 267             {
 268               fprintf(stderr,
 269                       _("%s: %s: entry in mergeable string section "
 270                         "not null terminated\n"),
 271                       program_name, object->name().c_str());
 272               gold_exit(false);
 273             }
 274         }
 275
 276       const Char_type* str = this->stringpool_.add(p, NULL);
 277
 278       Merge_string_key k(object, shndx, i);
 279       typename Merge_string_hashtable::value_type v(k, str);
 280       bool b = this->hashtable_.insert(v).second;
 281       gold_assert(b);
 282
 283       p += plen + 1;
 284       i += plen + 1;
 285     }
 286
 287   return true;
 288 }
 289
 290 // Set the final data size of a merged string section.  This is where
 291 // we finalize the mappings from the input sections to the output
 292 // section.
 293
 294 template<typename Char_type>
 295 void
 296 Output_merge_string<Char_type>::do_set_address(uint64_t, off_t)
 297 {
 298   this->stringpool_.set_string_offsets();
 299
 300   for (typename Merge_string_hashtable::const_iterator p =
 301          this->hashtable_.begin();
 302        p != this->hashtable_.end();
 303        ++p)
 304     this->add_mapping(p->first.object, p->first.shndx, p->first.offset,
 305                       this->stringpool_.get_offset(p->second));
 306
 307   this->set_data_size(this->stringpool_.get_strtab_size());
 308
 309   // Save some memory.
 310   this->hashtable_.clear();
 311 }
 312
 313 // Write out a merged string section.
 314
 315 template<typename Char_type>
 316 void
 317 Output_merge_string<Char_type>::do_write(Output_file* of)
 318 {
 319   this->stringpool_.write(of, this->offset());
 320 }
 321
 322 // Instantiate the templates we need.
 323
 324 template
 325 class Output_merge_string<char>;
 326
 327 template
 328 class Output_merge_string<uint16_t>;
 329
 330 template
 331 class Output_merge_string<uint32_t>;
 332
 333 } // End namespace gold.