gold/reduced_debug_output.cc

   1 // reduced_debug_output.cc -- output reduced debugging information to save space
   2
   3 // Copyright 2008 Free Software Foundation, Inc.
   4 // Written by Caleb Howe <cshowe@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 "parameters.h"
  26 #include "options.h"
  27 #include "dwarf.h"
  28 #include "dwarf_reader.h"
  29 #include "reduced_debug_output.h"
  30 #include "int_encoding.h"
  31
  32 #include <vector>
  33
  34 namespace gold
  35 {
  36
  37 // Given a pointer to the beginning of a die and the beginning of the associated
  38 // abbreviation fills in die_end with the end of the information entry.  If
  39 // successful returns true.  Get_die_end also takes a pointer to the end of the
  40 // buffer containing the die.  If die_end would be beyond the end of the
  41 // buffer, or if an unsupported dwarf form is encountered returns false.
  42 bool
  43 Output_reduced_debug_info_section::get_die_end(
  44     unsigned char* die, unsigned char* abbrev, unsigned char** die_end,
  45     unsigned char* buffer_end, int address_size, bool is64)
  46 {
  47   size_t LEB_size;
  48   uint64_t LEB_decoded;
  49   for(;;)
  50     {
  51       uint64_t attribute = read_unsigned_LEB_128(abbrev, &LEB_size);
  52       abbrev += LEB_size;
  53       elfcpp::DW_FORM form =
  54           static_cast<elfcpp::DW_FORM>(read_unsigned_LEB_128(abbrev,
  55                                                              &LEB_size));
  56       abbrev += LEB_size;
  57       if (!(attribute || form))
  58         break;
  59       if (die >= buffer_end)
  60         return false;
  61       switch(form)
  62         {
  63           case elfcpp::DW_FORM_null:
  64             break;
  65           case elfcpp::DW_FORM_strp:
  66             die += is64 ? 8 : 4;
  67             break;
  68           case elfcpp::DW_FORM_addr:
  69           case elfcpp::DW_FORM_ref_addr:
  70             die += address_size;
  71             break;
  72           case elfcpp::DW_FORM_block1:
  73             die += *die;
  74             die += 1;
  75             break;
  76           case elfcpp::DW_FORM_block2:
  77             {
  78               uint16_t block_size;
  79               block_size = read_from_pointer<16>(&die);
  80               die += block_size;
  81               break;
  82             }
  83           case elfcpp::DW_FORM_block4:
  84             {
  85               uint32_t block_size;
  86               block_size = read_from_pointer<32>(&die);
  87               die += block_size;
  88               break;
  89             }
  90           case elfcpp::DW_FORM_block:
  91             LEB_decoded = read_unsigned_LEB_128(die, &LEB_size);
  92             die += (LEB_decoded + LEB_size);
  93             break;
  94           case elfcpp::DW_FORM_data1:
  95           case elfcpp::DW_FORM_ref1:
  96           case elfcpp::DW_FORM_flag:
  97             die += 1;
  98             break;
  99           case elfcpp::DW_FORM_data2:
 100           case elfcpp::DW_FORM_ref2:
 101             die += 2;
 102             break;
 103           case elfcpp::DW_FORM_data4:
 104           case elfcpp::DW_FORM_ref4:
 105             die += 4;
 106             break;
 107           case elfcpp::DW_FORM_data8:
 108           case elfcpp::DW_FORM_ref8:
 109             die += 8;
 110             break;
 111           case elfcpp::DW_FORM_ref_udata:
 112           case elfcpp::DW_FORM_udata:
 113             read_unsigned_LEB_128(die, &LEB_size);
 114             die += LEB_size;
 115             break;
 116           case elfcpp::DW_FORM_string:
 117             {
 118               size_t length = strlen(reinterpret_cast<char*>(die));
 119               die += length + 1;
 120               break;
 121             }
 122           case elfcpp::DW_FORM_sdata:
 123           case elfcpp::DW_FORM_indirect:
 124             return false;
 125       }
 126     }
 127   *die_end = die;
 128   return true;
 129 }
 130
 131 void
 132 Output_reduced_debug_abbrev_section::set_final_data_size()
 133 {
 134   if (this->sized_ || this->failed_)
 135     return;
 136
 137   uint64_t abbrev_number;
 138   size_t LEB_size;
 139   unsigned char* abbrev_data = this->postprocessing_buffer();
 140   unsigned char* abbrev_end = this->postprocessing_buffer() +
 141                               this->postprocessing_buffer_size();
 142   this->write_to_postprocessing_buffer();
 143   while(abbrev_data < abbrev_end)
 144     {
 145       uint64_t abbrev_offset = abbrev_data - this->postprocessing_buffer();
 146       while((abbrev_number = read_unsigned_LEB_128(abbrev_data, &LEB_size)))
 147         {
 148           if (abbrev_data >= abbrev_end)
 149             {
 150               failed("Debug abbreviations extend beyond .debug_abbrev "
 151                      "section; failed to reduce debug abbreviations");
 152               return;
 153             }
 154           abbrev_data += LEB_size;
 155
 156           // Together with the abbreviation number these fields make up
 157           // the header for each abbreviation
 158           uint64_t abbrev_type = read_unsigned_LEB_128(abbrev_data, &LEB_size);
 159           abbrev_data += LEB_size;
 160
 161           // This would ordinarily be the has_children field of the
 162           // abbreviation.  But it's going to be false after reducting the
 163           // information, so there's no point in storing it
 164           abbrev_data++;
 165
 166           // Read to the end of the current abbreviation
 167           // This is indicated by two zero unsigned LEBs in a row.  We don't
 168           // need to parse the data yet, so we just scan through the data
 169           // looking for two consecutive 0 bytes indicating the end of the
 170           // abbreviation
 171           unsigned char* current_abbrev;
 172           for (current_abbrev = abbrev_data;
 173                current_abbrev[0] || current_abbrev[1];
 174                current_abbrev++)
 175             {
 176               if (current_abbrev >= abbrev_end)
 177                 {
 178                   this->failed(_("Debug abbreviations extend beyond "
 179                                  ".debug_abbrev section; failed to reduce "
 180                                  "debug abbreviations"));
 181                   return;
 182                 }
 183             }
 184           // Account for the two nulls and advance to the start of the
 185           // next abbreviation.
 186           current_abbrev += 2;
 187
 188           // We're eliminating every entry except for compile units, so we
 189           // only need to store abbreviations that describe them
 190           if (abbrev_type == elfcpp::DW_TAG_compile_unit)
 191             {
 192               write_unsigned_LEB_128(&this->data_, ++this->abbrev_count_);
 193               write_unsigned_LEB_128(&this->data_, abbrev_type);
 194               // has_children is false for all entries
 195               this->data_.push_back(0);
 196               this->abbrev_mapping_[std::make_pair(abbrev_offset,
 197                                                    abbrev_number)] =
 198                   std::make_pair(abbrev_count_, this->data_.size());
 199               this->data_.insert(this->data_.end(), abbrev_data,
 200                                  current_abbrev);
 201             }
 202           abbrev_data = current_abbrev;
 203         }
 204       gold_assert(LEB_size == 1);
 205       abbrev_data += LEB_size;
 206     }
 207   // Null terminate the list of abbreviations
 208   this->data_.push_back(0);
 209   this->set_data_size(data_.size());
 210   this->sized_ = true;
 211 }
 212
 213 void
 214 Output_reduced_debug_abbrev_section::do_write(Output_file* of)
 215 {
 216   off_t offset = this->offset();
 217   off_t data_size = this->data_size();
 218   unsigned char* view = of->get_output_view(offset, data_size);
 219   if (this->failed_)
 220     memcpy(view, this->postprocessing_buffer(),
 221            this->postprocessing_buffer_size());
 222   else
 223     memcpy(view, &this->data_.front(), data_size);
 224   of->write_output_view(offset, data_size, view);
 225 }
 226
 227 // Locates the abbreviation with abbreviation_number abbrev_number in the
 228 // abbreviation table at offset abbrev_offset.  abbrev_number is updated with
 229 // its new abbreviation number and a pointer to the beginning of the
 230 // abbreviation is returned.
 231 unsigned char*
 232 Output_reduced_debug_abbrev_section::get_new_abbrev(
 233   uint64_t* abbrev_number, uint64_t abbrev_offset)
 234 {
 235   set_final_data_size();
 236   std::pair<uint64_t, uint64_t> abbrev_info =
 237       this->abbrev_mapping_[std::make_pair(abbrev_offset, *abbrev_number)];
 238   *abbrev_number = abbrev_info.first;
 239   return &this->data_[abbrev_info.second];
 240 }
 241
 242 void Output_reduced_debug_info_section::set_final_data_size()
 243 {
 244   if (this->failed_)
 245     return;
 246   unsigned char* debug_info = this->postprocessing_buffer();
 247   unsigned char* debug_info_end = (this->postprocessing_buffer()
 248                                    + this->postprocessing_buffer_size());
 249   unsigned char* next_compile_unit;
 250   this->write_to_postprocessing_buffer();
 251
 252   while (debug_info < debug_info_end)
 253     {
 254       uint32_t compile_unit_start = read_from_pointer<32>(&debug_info);
 255       // The first 4 bytes of each compile unit determine whether or
 256       // not we're using dwarf32 or dwarf64.  This is not necessarily
 257       // related to whether the binary is 32 or 64 bits.
 258       if (compile_unit_start == 0xFFFFFFFF)
 259         {
 260           // Technically the size can be up to 96 bits.  Rather than handle
 261           // 96/128 bit integers we just truncate the size at 64 bits.
 262           if (0 != read_from_pointer<32>(&debug_info))
 263             {
 264               this->failed(_("Extremely large compile unit in debug info; "
 265                              "failed to reduce debug info"));
 266               return;
 267             }
 268           const int dwarf64_header_size = sizeof(uint64_t) + sizeof(uint16_t) +
 269                                           sizeof(uint64_t) + sizeof(uint8_t);
 270           if (debug_info + dwarf64_header_size >= debug_info_end)
 271             {
 272               this->failed(_("Debug info extends beyond .debug_info section;"
 273                              "failed to reduce debug info"));
 274               return;
 275             }
 276
 277           uint64_t compile_unit_size = read_from_pointer<64>(&debug_info);
 278           next_compile_unit = debug_info + compile_unit_size;
 279           uint16_t version = read_from_pointer<16>(&debug_info);
 280           uint64_t abbrev_offset = read_from_pointer<64>(&debug_info);
 281           uint8_t address_size = read_from_pointer<8>(&debug_info);
 282           size_t LEB_size;
 283           uint64_t abbreviation_number = read_unsigned_LEB_128(debug_info,
 284                                                                &LEB_size);
 285           debug_info += LEB_size;
 286           unsigned char* die_abbrev = this->associated_abbrev_->get_new_abbrev(
 287               &abbreviation_number, abbrev_offset);
 288           unsigned char* die_end;
 289           if (!this->get_die_end(debug_info, die_abbrev, &die_end,
 290                                  debug_info_end, address_size, true))
 291             {
 292               this->failed(_("Invalid DIE in debug info; "
 293                              "failed to reduce debug info"));
 294               return;
 295             }
 296
 297           insert_into_vector<32>(&this->data_, 0xFFFFFFFF);
 298           insert_into_vector<32>(&this->data_, 0);
 299           insert_into_vector<64>(
 300               &this->data_,
 301               (11 + get_length_as_unsigned_LEB_128(abbreviation_number)
 302                + die_end - debug_info));
 303           insert_into_vector<16>(&this->data_, version);
 304           insert_into_vector<64>(&this->data_, 0);
 305           insert_into_vector<8>(&this->data_, address_size);
 306           write_unsigned_LEB_128(&this->data_, abbreviation_number);
 307           this->data_.insert(this->data_.end(), debug_info, die_end);
 308         }
 309       else
 310         {
 311           const int dwarf32_header_size =
 312               sizeof(uint16_t) + sizeof(uint32_t) + sizeof(uint8_t);
 313           if (debug_info + dwarf32_header_size >= debug_info_end)
 314             {
 315               this->failed(_("Debug info extends beyond .debug_info section; "
 316                              "failed to reduce debug info"));
 317               return;
 318             }
 319           uint32_t compile_unit_size = compile_unit_start;
 320           next_compile_unit = debug_info + compile_unit_size;
 321           uint16_t version = read_from_pointer<16>(&debug_info);
 322           uint32_t abbrev_offset = read_from_pointer<32>(&debug_info);
 323           uint8_t address_size = read_from_pointer<8>(&debug_info);
 324           size_t LEB_size;
 325           uint64_t abbreviation_number = read_unsigned_LEB_128(debug_info,
 326                                                                &LEB_size);
 327           debug_info += LEB_size;
 328           unsigned char* die_abbrev = this->associated_abbrev_->get_new_abbrev(
 329               &abbreviation_number, abbrev_offset);
 330           unsigned char* die_end;
 331           if (!this->get_die_end(debug_info, die_abbrev, &die_end,
 332                                  debug_info_end, address_size, false))
 333             {
 334               this->failed(_("Invalid DIE in debug info; "
 335                              "failed to reduce debug info"));
 336               return;
 337             }
 338
 339           insert_into_vector<32>(
 340               &this->data_,
 341               (7 + get_length_as_unsigned_LEB_128(abbreviation_number)
 342                + die_end - debug_info));
 343           insert_into_vector<16>(&this->data_, version);
 344           insert_into_vector<32>(&this->data_, 0);
 345           insert_into_vector<8>(&this->data_, address_size);
 346           write_unsigned_LEB_128(&this->data_, abbreviation_number);
 347           this->data_.insert(this->data_.end(), debug_info, die_end);
 348         }
 349       debug_info = next_compile_unit;
 350     }
 351   this->set_data_size(data_.size());
 352 }
 353
 354 void Output_reduced_debug_info_section::do_write(Output_file* of)
 355 {
 356   off_t offset = this->offset();
 357   off_t data_size = this->data_size();
 358   unsigned char* view = of->get_output_view(offset, data_size);
 359   if (this->failed_)
 360     memcpy(view, this->postprocessing_buffer(),
 361            this->postprocessing_buffer_size());
 362   else
 363     memcpy(view, &this->data_.front(), data_size);
 364   of->write_output_view(offset, data_size, view);
 365 }
 366
 367 } // End namespace gold.