gold/incremental.cc

   1 // inremental.cc -- incremental linking support for gold
   2
   3 // Copyright 2009 Free Software Foundation, Inc.
   4 // Written by Mikolaj Zalewski <mikolajz@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 <cstdarg>
  26
  27 #include "elfcpp.h"
  28 #include "output.h"
  29 #include "incremental.h"
  30 #include "archive.h"
  31 #include "output.h"
  32 #include "target-select.h"
  33
  34 namespace gold {
  35
  36 // Version information. Will change frequently during the development, later
  37 // we could think about backward (and forward?) compatibility.
  38 const unsigned int INCREMENTAL_LINK_VERSION = 1;
  39
  40 // Inform the user why we don't do an incremental link.  Not called in
  41 // the obvious case of missing output file.  TODO: Is this helpful?
  42
  43 void
  44 vexplain_no_incremental(const char* format, va_list args)
  45 {
  46   char* buf = NULL;
  47   if (vasprintf(&buf, format, args) < 0)
  48     gold_nomem();
  49   gold_info(_("the link might take longer: "
  50               "cannot perform incremental link: %s"), buf);
  51   free(buf);
  52 }
  53
  54 void
  55 explain_no_incremental(const char* format, ...)
  56 {
  57   va_list args;
  58   va_start(args, format);
  59   vexplain_no_incremental(format, args);
  60   va_end(args);
  61 }
  62
  63 // Report an error.
  64
  65 void
  66 Incremental_binary::error(const char* format, ...) const
  67 {
  68   va_list args;
  69   va_start(args, format);
  70   // Current code only checks if the file can be used for incremental linking,
  71   // so errors shouldn't fail the build, but only result in a fallback to a
  72   // full build.
  73   // TODO: when we implement incremental editing of the file, we may need a
  74   // flag that will cause errors to be treated seriously.
  75   vexplain_no_incremental(format, args);
  76   va_end(args);
  77 }
  78
  79 template<int size, bool big_endian>
  80 bool
  81 Sized_incremental_binary<size, big_endian>::do_find_incremental_inputs_section(
  82     Location* location,
  83     unsigned int* strtab_shndx)
  84 {
  85   unsigned int shndx = this->elf_file_.find_section_by_type(
  86       elfcpp::SHT_GNU_INCREMENTAL_INPUTS);
  87   if (shndx == elfcpp::SHN_UNDEF)  // Not found.
  88     return false;
  89   *strtab_shndx = this->elf_file_.section_link(shndx);
  90   *location = this->elf_file_.section_contents(shndx);
  91   return true;
  92 }
  93
  94 template<int size, bool big_endian>
  95 bool
  96 Sized_incremental_binary<size, big_endian>::do_check_inputs(
  97     Incremental_inputs* incremental_inputs)
  98 {
  99   const int entry_size =
 100       Incremental_inputs_entry_write<size, big_endian>::data_size;
 101   const int header_size =
 102       Incremental_inputs_header_write<size, big_endian>::data_size;
 103
 104   unsigned int strtab_shndx;
 105   Location location;
 106
 107   if (!do_find_incremental_inputs_section(&location, &strtab_shndx))
 108     {
 109       explain_no_incremental(_("no incremental data from previous build"));
 110       return false;
 111     }
 112   if (location.data_size < header_size
 113       || strtab_shndx >= this->elf_file_.shnum()
 114       || this->elf_file_.section_type(strtab_shndx) != elfcpp::SHT_STRTAB)
 115     {
 116       explain_no_incremental(_("invalid incremental build data"));
 117       return false;
 118     }
 119
 120   Location strtab_location(this->elf_file_.section_contents(strtab_shndx));
 121   View data_view(view(location));
 122   View strtab_view(view(strtab_location));
 123   elfcpp::Elf_strtab strtab(strtab_view.data(), strtab_location.data_size);
 124   Incremental_inputs_header<size, big_endian> header(data_view.data());
 125
 126   if (header.get_version() != INCREMENTAL_LINK_VERSION)
 127     {
 128       explain_no_incremental(_("different version of incremental build data"));
 129       return false;
 130     }
 131
 132   const char* command_line;
 133   // We divide instead of multiplying to make sure there is no integer
 134   // overflow.
 135   size_t max_input_entries = (location.data_size - header_size) / entry_size;
 136   if (header.get_input_file_count() > max_input_entries
 137       || !strtab.get_c_string(header.get_command_line_offset(), &command_line))
 138     {
 139       explain_no_incremental(_("invalid incremental build data"));
 140       return false;
 141     }
 142
 143   if (incremental_inputs->command_line() != command_line)
 144     {
 145       explain_no_incremental(_("command line changed"));
 146       return false;
 147     }
 148
 149   // TODO: compare incremental_inputs->inputs() with entries in data_view.
 150   return true;
 151 }
 152
 153 namespace
 154 {
 155
 156 // Create a Sized_incremental_binary object of the specified size and
 157 // endianness. Fails if the target architecture is not supported.
 158
 159 template<int size, bool big_endian>
 160 Incremental_binary*
 161 make_sized_incremental_binary(Output_file* file,
 162                               const elfcpp::Ehdr<size, big_endian>& ehdr)
 163 {
 164   Target* target = select_target(ehdr.get_e_machine(), size, big_endian,
 165                                  ehdr.get_e_ident()[elfcpp::EI_OSABI],
 166                                  ehdr.get_e_ident()[elfcpp::EI_ABIVERSION]);
 167   if (target == NULL)
 168     {
 169       explain_no_incremental(_("unsupported ELF machine number %d"),
 170                ehdr.get_e_machine());
 171       return NULL;
 172     }
 173
 174   if (!parameters->target_valid())
 175     set_parameters_target(target);
 176   else if (target != &parameters->target())
 177     gold_error(_("%s: incompatible target"), file->filename());
 178
 179   return new Sized_incremental_binary<size, big_endian>(file, ehdr, target);
 180 }
 181
 182 }  // End of anonymous namespace.
 183
 184 // Create an Incremental_binary object for FILE. Returns NULL is this is not
 185 // possible, e.g. FILE is not an ELF file or has an unsupported target. FILE
 186 // should be opened.
 187
 188 Incremental_binary*
 189 open_incremental_binary(Output_file* file)
 190 {
 191   off_t filesize = file->filesize();
 192   int want = elfcpp::Elf_recognizer::max_header_size;
 193   if (filesize < want)
 194     want = filesize;
 195
 196   const unsigned char* p = file->get_input_view(0, want);
 197   if (!elfcpp::Elf_recognizer::is_elf_file(p, want))
 198     {
 199       explain_no_incremental(_("output is not an ELF file."));
 200       return NULL;
 201     }
 202
 203   int size = 0;
 204   bool big_endian = false;
 205   std::string error;
 206   if (!elfcpp::Elf_recognizer::is_valid_header(p, want, &size, &big_endian,
 207                                                &error))
 208     {
 209       explain_no_incremental(error.c_str());
 210       return NULL;
 211     }
 212
 213   Incremental_binary* result = NULL;
 214   if (size == 32)
 215     {
 216       if (big_endian)
 217         {
 218 #ifdef HAVE_TARGET_32_BIG
 219           result = make_sized_incremental_binary<32, true>(
 220               file, elfcpp::Ehdr<32, true>(p));
 221 #else
 222           explain_no_incremental(_("unsupported file: 32-bit, big-endian"));
 223 #endif
 224         }
 225       else
 226         {
 227 #ifdef HAVE_TARGET_32_LITTLE
 228           result = make_sized_incremental_binary<32, false>(
 229               file, elfcpp::Ehdr<32, false>(p));
 230 #else
 231           explain_no_incremental(_("unsupported file: 32-bit, little-endian"));
 232 #endif
 233         }
 234     }
 235   else if (size == 64)
 236     {
 237       if (big_endian)
 238         {
 239 #ifdef HAVE_TARGET_64_BIG
 240           result = make_sized_incremental_binary<64, true>(
 241               file, elfcpp::Ehdr<64, true>(p));
 242 #else
 243           explain_no_incremental(_("unsupported file: 64-bit, big-endian"));
 244 #endif
 245         }
 246       else
 247         {
 248 #ifdef HAVE_TARGET_64_LITTLE
 249           result = make_sized_incremental_binary<64, false>(
 250               file, elfcpp::Ehdr<64, false>(p));
 251 #else
 252           explain_no_incremental(_("unsupported file: 64-bit, little-endian"));
 253 #endif
 254         }
 255     }
 256   else
 257     gold_unreachable();
 258
 259   return result;
 260 }
 261
 262 // Analyzes the output file to check if incremental linking is possible and
 263 // (to be done) what files need to be relinked.
 264
 265 bool
 266 Incremental_checker::can_incrementally_link_output_file()
 267 {
 268   Output_file output(this->output_name_);
 269   if (!output.open_for_modification())
 270     return false;
 271   Incremental_binary* binary = open_incremental_binary(&output);
 272   if (binary == NULL)
 273     return false;
 274   return binary->check_inputs(this->incremental_inputs_);
 275 }
 276
 277 // Add the command line to the string table, setting
 278 // command_line_key_.  In incremental builds, the command line is
 279 // stored in .gnu_incremental_inputs so that the next linker run can
 280 // check if the command line options didn't change.
 281
 282 void
 283 Incremental_inputs::report_command_line(int argc, const char* const* argv)
 284 {
 285   // Always store 'gold' as argv[0] to avoid a full relink if the user used a
 286   // different path to the linker.
 287   std::string args("gold");
 288   // Copied from collect_argv in main.cc.
 289   for (int i = 1; i < argc; ++i)
 290     {
 291       // Adding/removing these options should result in a full relink.
 292       if (strcmp(argv[i], "--incremental-changed") == 0
 293           || strcmp(argv[i], "--incremental-unchanged") == 0
 294           || strcmp(argv[i], "--incremental-unknown") == 0)
 295         continue;
 296
 297       args.append(" '");
 298       // Now append argv[i], but with all single-quotes escaped
 299       const char* argpos = argv[i];
 300       while (1)
 301         {
 302           const int len = strcspn(argpos, "'");
 303           args.append(argpos, len);
 304           if (argpos[len] == '\0')
 305             break;
 306           args.append("'\"'\"'");
 307           argpos += len + 1;
 308         }
 309       args.append("'");
 310     }
 311
 312   this->command_line_ = args;
 313   this->strtab_->add(this->command_line_.c_str(), false,
 314                      &this->command_line_key_);
 315 }
 316
 317 // Record that the input argument INPUT is an achive ARCHIVE.  This is
 318 // called by Read_symbols after finding out the type of the file.
 319
 320 void
 321 Incremental_inputs::report_archive(const Input_argument* input,
 322                                    Archive* archive)
 323 {
 324   Hold_lock hl(*this->lock_);
 325
 326   Input_info info;
 327   info.type = INCREMENTAL_INPUT_ARCHIVE;
 328   info.archive = archive;
 329   info.mtime = archive->file().get_mtime();
 330   this->inputs_map_.insert(std::make_pair(input, info));
 331 }
 332
 333 // Record that the input argument INPUT is an object OBJ.  This is
 334 // called by Read_symbols after finding out the type of the file.
 335
 336 void
 337 Incremental_inputs::report_object(const Input_argument* input,
 338                                   Object* obj)
 339 {
 340   Hold_lock hl(*this->lock_);
 341
 342   Input_info info;
 343   info.type = (obj->is_dynamic()
 344                ? INCREMENTAL_INPUT_SHARED_LIBRARY
 345                : INCREMENTAL_INPUT_OBJECT);
 346   info.object = obj;
 347   info.mtime = obj->input_file()->file().get_mtime();
 348   this->inputs_map_.insert(std::make_pair(input, info));
 349 }
 350
 351 // Record that the input argument INPUT is an script SCRIPT.  This is
 352 // called by read_script after parsing the script and reading the list
 353 // of inputs added by this script.
 354
 355 void
 356 Incremental_inputs::report_script(const Input_argument* input,
 357                                   Timespec mtime,
 358                                   Script_info* script)
 359 {
 360   Hold_lock hl(*this->lock_);
 361
 362   Input_info info;
 363   info.type = INCREMENTAL_INPUT_SCRIPT;
 364   info.script = script;
 365   info.mtime = mtime;
 366   this->inputs_map_.insert(std::make_pair(input, info));
 367 }
 368
 369 // Compute indexes in the order in which the inputs should appear in
 370 // .gnu_incremental_inputs.  This needs to be done after all the
 371 // scripts are parsed.  The function is first called for the command
 372 // line inputs arguments and may call itself recursively for e.g. a
 373 // list of elements of a group or a list of inputs added by a script.
 374 // The [BEGIN; END) interval to analyze and *INDEX is the current
 375 // value of the index (that will be updated).
 376
 377 void
 378 Incremental_inputs::finalize_inputs(
 379     Input_argument_list::const_iterator begin,
 380     Input_argument_list::const_iterator end,
 381     unsigned int* index)
 382 {
 383   for (Input_argument_list::const_iterator p = begin; p != end; ++p)
 384     {
 385       if (p->is_group())
 386         {
 387           finalize_inputs(p->group()->begin(), p->group()->end(), index);
 388           continue;
 389         }
 390
 391       Inputs_info_map::iterator it = this->inputs_map_.find(&(*p));
 392       // TODO: turn it into an assert when the code will be more stable.
 393       if (it == this->inputs_map_.end())
 394         {
 395           gold_error("internal error: %s: incremental build info not provided",
 396                      (p->is_file() ? p->file().name() : "[group]"));
 397           continue;
 398         }
 399       Input_info* info = &it->second;
 400       info->index = *index;
 401       (*index)++;
 402       this->strtab_->add(p->file().name(), false, &info->filename_key);
 403       if (info->type == INCREMENTAL_INPUT_SCRIPT)
 404         {
 405           finalize_inputs(info->script->inputs()->begin(),
 406                           info->script->inputs()->end(),
 407                           index);
 408         }
 409     }
 410 }
 411
 412 // Finalize the incremental link information.  Called from
 413 // Layout::finalize.
 414
 415 void
 416 Incremental_inputs::finalize()
 417 {
 418   unsigned int index = 0;
 419   finalize_inputs(this->inputs_->begin(), this->inputs_->end(), &index);
 420
 421   // Sanity check.
 422   for (Inputs_info_map::const_iterator p = this->inputs_map_.begin();
 423        p != this->inputs_map_.end();
 424        ++p)
 425     {
 426       gold_assert(p->second.filename_key != 0);
 427     }
 428
 429   this->strtab_->set_string_offsets();
 430 }
 431
 432 // Create the content of the .gnu_incremental_inputs section.
 433
 434 Output_section_data*
 435 Incremental_inputs::create_incremental_inputs_section_data()
 436 {
 437   switch (parameters->size_and_endianness())
 438     {
 439 #ifdef HAVE_TARGET_32_LITTLE
 440     case Parameters::TARGET_32_LITTLE:
 441       return this->sized_create_inputs_section_data<32, false>();
 442 #endif
 443 #ifdef HAVE_TARGET_32_BIG
 444     case Parameters::TARGET_32_BIG:
 445       return this->sized_create_inputs_section_data<32, true>();
 446 #endif
 447 #ifdef HAVE_TARGET_64_LITTLE
 448     case Parameters::TARGET_64_LITTLE:
 449       return this->sized_create_inputs_section_data<64, false>();
 450 #endif
 451 #ifdef HAVE_TARGET_64_BIG
 452     case Parameters::TARGET_64_BIG:
 453       return this->sized_create_inputs_section_data<64, true>();
 454 #endif
 455     default:
 456       gold_unreachable();
 457     }
 458 }
 459
 460 // Sized creation of .gnu_incremental_inputs section.
 461
 462 template<int size, bool big_endian>
 463 Output_section_data*
 464 Incremental_inputs::sized_create_inputs_section_data()
 465 {
 466   const int entry_size =
 467       Incremental_inputs_entry_write<size, big_endian>::data_size;
 468   const int header_size =
 469       Incremental_inputs_header_write<size, big_endian>::data_size;
 470
 471   unsigned int sz = header_size + entry_size * this->inputs_map_.size();
 472   unsigned char* buffer = new unsigned char[sz];
 473   unsigned char* inputs_base = buffer + header_size;
 474
 475   Incremental_inputs_header_write<size, big_endian> header_writer(buffer);
 476   gold_assert(this->command_line_key_ > 0);
 477   int cmd_offset = this->strtab_->get_offset_from_key(this->command_line_key_);
 478
 479   header_writer.put_version(INCREMENTAL_LINK_VERSION);
 480   header_writer.put_input_file_count(this->inputs_map_.size());
 481   header_writer.put_command_line_offset(cmd_offset);
 482   header_writer.put_reserved(0);
 483
 484   for (Inputs_info_map::const_iterator it = this->inputs_map_.begin();
 485        it != this->inputs_map_.end();
 486        ++it)
 487     {
 488       gold_assert(it->second.index < this->inputs_map_.size());
 489
 490       unsigned char* entry_buffer =
 491           inputs_base + it->second.index * entry_size;
 492       Incremental_inputs_entry_write<size, big_endian> entry(entry_buffer);
 493       int filename_offset =
 494           this->strtab_->get_offset_from_key(it->second.filename_key);
 495       entry.put_filename_offset(filename_offset);
 496       switch (it->second.type)
 497         {
 498         case INCREMENTAL_INPUT_SCRIPT:
 499           entry.put_data_offset(0);
 500           break;
 501         case INCREMENTAL_INPUT_ARCHIVE:
 502         case INCREMENTAL_INPUT_OBJECT:
 503         case INCREMENTAL_INPUT_SHARED_LIBRARY:
 504           // TODO: add per input data.  Currently we store
 505           // an out-of-bounds offset for future version of gold to reject
 506           // such an incremental_inputs section.
 507           entry.put_data_offset(0xffffffff);
 508           break;
 509         default:
 510           gold_unreachable();
 511         }
 512       // TODO: add per input data and timestamp.  Currently we store
 513       // an out-of-bounds offset for future version of gold to reject
 514       // such an incremental_inputs section.
 515       entry.put_data_offset(0xffffffff);
 516       entry.put_timestamp_sec(it->second.mtime.seconds);
 517       entry.put_timestamp_nsec(it->second.mtime.nanoseconds);
 518       entry.put_input_type(it->second.type);
 519       entry.put_reserved(0);
 520     }
 521
 522   return new Output_data_const_buffer(buffer, sz, 8,
 523                                       "** incremental link inputs list");
 524 }
 525
 526 // Instantiate the templates we need.
 527
 528 #ifdef HAVE_TARGET_32_LITTLE
 529 template
 530 class Sized_incremental_binary<32, false>;
 531 #endif
 532
 533 #ifdef HAVE_TARGET_32_BIG
 534 template
 535 class Sized_incremental_binary<32, true>;
 536 #endif
 537
 538 #ifdef HAVE_TARGET_64_LITTLE
 539 template
 540 class Sized_incremental_binary<64, false>;
 541 #endif
 542
 543 #ifdef HAVE_TARGET_64_BIG
 544 template
 545 class Sized_incremental_binary<64, true>;
 546 #endif
 547
 548 } // End namespace gold.