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