gold/readsyms.cc

   1 // readsyms.cc -- read input file symbols 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 <cstring>
  26
  27 #include "elfcpp.h"
  28 #include "options.h"
  29 #include "dirsearch.h"
  30 #include "symtab.h"
  31 #include "object.h"
  32 #include "archive.h"
  33 #include "script.h"
  34 #include "readsyms.h"
  35
  36 namespace gold
  37 {
  38
  39 // If we fail to open the object, then we won't create an Add_symbols
  40 // task.  However, we still need to unblock the token, or else the
  41 // link won't proceed to generate more error messages.  We can only
  42 // unblock tokens when the workqueue lock is held, so we need a dummy
  43 // task to do that.  The dummy task has to maintain the right sequence
  44 // of blocks, so we need both this_blocker and next_blocker.
  45
  46 class Unblock_token : public Task
  47 {
  48  public:
  49   Unblock_token(Task_token* this_blocker, Task_token* next_blocker)
  50     : this_blocker_(this_blocker), next_blocker_(next_blocker)
  51   { }
  52
  53   ~Unblock_token()
  54   {
  55     if (this->this_blocker_ != NULL)
  56       delete this->this_blocker_;
  57   }
  58
  59   Task_token*
  60   is_runnable()
  61   {
  62     if (this->this_blocker_ != NULL && this->this_blocker_->is_blocked())
  63       return this->this_blocker_;
  64     return NULL;
  65   }
  66
  67   void
  68   locks(Task_locker* tl)
  69   { tl->add(this, this->next_blocker_); }
  70
  71   void
  72   run(Workqueue*)
  73   { }
  74
  75   std::string
  76   get_name() const
  77   { return "Unblock_token"; }
  78
  79  private:
  80   Task_token* this_blocker_;
  81   Task_token* next_blocker_;
  82 };
  83
  84 // Class read_symbols.
  85
  86 Read_symbols::~Read_symbols()
  87 {
  88   // The this_blocker_ and next_blocker_ pointers are passed on to the
  89   // Add_symbols task.
  90 }
  91
  92 // Return whether a Read_symbols task is runnable.  We can read an
  93 // ordinary input file immediately.  For an archive specified using
  94 // -l, we have to wait until the search path is complete.
  95
  96 Task_token*
  97 Read_symbols::is_runnable()
  98 {
  99   if (this->input_argument_->is_file()
 100       && this->input_argument_->file().may_need_search()
 101       && this->dirpath_->token()->is_blocked())
 102     return this->dirpath_->token();
 103
 104   return NULL;
 105 }
 106
 107 // Return a Task_locker for a Read_symbols task.  We don't need any
 108 // locks here.
 109
 110 void
 111 Read_symbols::locks(Task_locker*)
 112 {
 113 }
 114
 115 // Run a Read_symbols task.
 116
 117 void
 118 Read_symbols::run(Workqueue* workqueue)
 119 {
 120   // If we didn't queue a new task, then we need to explicitly unblock
 121   // the token.
 122   if (!this->do_read_symbols(workqueue))
 123     workqueue->queue_front(new Unblock_token(this->this_blocker_,
 124                                              this->next_blocker_));
 125 }
 126
 127 // Open the file and read the symbols.  Return true if a new task was
 128 // queued, false if that could not happen due to some error.
 129
 130 bool
 131 Read_symbols::do_read_symbols(Workqueue* workqueue)
 132 {
 133   if (this->input_argument_->is_group())
 134     {
 135       gold_assert(this->input_group_ == NULL);
 136       this->do_group(workqueue);
 137       return true;
 138     }
 139
 140   Input_file* input_file = new Input_file(&this->input_argument_->file());
 141   if (!input_file->open(this->options_, *this->dirpath_, this))
 142     return false;
 143
 144   // Read enough of the file to pick up the entire ELF header.
 145
 146   off_t filesize = input_file->file().filesize();
 147
 148   if (filesize == 0)
 149     {
 150       gold_error(_("%s: file is empty"),
 151                  input_file->file().filename().c_str());
 152       return false;
 153     }
 154
 155   unsigned char ehdr_buf[elfcpp::Elf_sizes<64>::ehdr_size];
 156
 157   int read_size = elfcpp::Elf_sizes<64>::ehdr_size;
 158   if (filesize < read_size)
 159     read_size = filesize;
 160
 161   input_file->file().read(0, read_size, ehdr_buf);
 162
 163   if (read_size >= 4)
 164     {
 165       static unsigned char elfmagic[4] =
 166         {
 167           elfcpp::ELFMAG0, elfcpp::ELFMAG1,
 168           elfcpp::ELFMAG2, elfcpp::ELFMAG3
 169         };
 170       if (memcmp(ehdr_buf, elfmagic, 4) == 0)
 171         {
 172           // This is an ELF object.
 173
 174           Object* obj = make_elf_object(input_file->filename(),
 175                                         input_file, 0, ehdr_buf, read_size);
 176           if (obj == NULL)
 177             return false;
 178
 179           Read_symbols_data* sd = new Read_symbols_data;
 180           obj->read_symbols(sd);
 181
 182           // Opening the file locked it, so now we need to unlock it.
 183           // We need to unlock it before queuing the Add_symbols task,
 184           // because the workqueue doesn't know about our lock on the
 185           // file.  If we queue the Add_symbols task first, it will be
 186           // stuck on the end of the file lock, but since the
 187           // workqueue doesn't know about that lock, it will never
 188           // release the Add_symbols task.
 189
 190           input_file->file().unlock(this);
 191
 192           workqueue->queue_front(new Add_symbols(this->input_objects_,
 193                                                  this->symtab_, this->layout_,
 194                                                  obj, sd,
 195                                                  this->this_blocker_,
 196                                                  this->next_blocker_));
 197
 198           return true;
 199         }
 200     }
 201
 202   if (read_size >= Archive::sarmag)
 203     {
 204       if (memcmp(ehdr_buf, Archive::armag, Archive::sarmag) == 0)
 205         {
 206           // This is an archive.
 207           Archive* arch = new Archive(this->input_argument_->file().name(),
 208                                       input_file);
 209           arch->setup(this);
 210
 211           workqueue->queue_front(new Add_archive_symbols(this->symtab_,
 212                                                          this->layout_,
 213                                                          this->input_objects_,
 214                                                          arch,
 215                                                          this->input_group_,
 216                                                          this->this_blocker_,
 217                                                          this->next_blocker_));
 218           return true;
 219         }
 220     }
 221
 222   // Try to parse this file as a script.
 223   if (read_input_script(workqueue, this->options_, this->symtab_,
 224                         this->layout_, this->dirpath_, this->input_objects_,
 225                         this->input_group_, this->input_argument_, input_file,
 226                         ehdr_buf, read_size, this->this_blocker_,
 227                         this->next_blocker_))
 228     return true;
 229
 230   // Here we have to handle any other input file types we need.
 231   gold_error(_("%s: not an object or archive"),
 232              input_file->file().filename().c_str());
 233
 234   return false;
 235 }
 236
 237 // Handle a group.  We need to walk through the arguments over and
 238 // over until we don't see any new undefined symbols.  We do this by
 239 // setting off Read_symbols Tasks as usual, but recording the archive
 240 // entries instead of deleting them.  We also start a Finish_group
 241 // Task which runs after we've read all the symbols.  In that task we
 242 // process the archives in a loop until we are done.
 243
 244 void
 245 Read_symbols::do_group(Workqueue* workqueue)
 246 {
 247   Input_group* input_group = new Input_group();
 248
 249   const Input_file_group* group = this->input_argument_->group();
 250   Task_token* this_blocker = this->this_blocker_;
 251
 252   for (Input_file_group::const_iterator p = group->begin();
 253        p != group->end();
 254        ++p)
 255     {
 256       const Input_argument* arg = &*p;
 257       gold_assert(arg->is_file());
 258
 259       Task_token* next_blocker = new Task_token(true);
 260       next_blocker->add_blocker();
 261       workqueue->queue(new Read_symbols(this->options_, this->input_objects_,
 262                                         this->symtab_, this->layout_,
 263                                         this->dirpath_, arg, input_group,
 264                                         this_blocker, next_blocker));
 265       this_blocker = next_blocker;
 266     }
 267
 268   const int saw_undefined = this->symtab_->saw_undefined();
 269   workqueue->queue(new Finish_group(this->input_objects_,
 270                                     this->symtab_,
 271                                     this->layout_,
 272                                     input_group,
 273                                     saw_undefined,
 274                                     this_blocker,
 275                                     this->next_blocker_));
 276 }
 277
 278 // Return a debugging name for a Read_symbols task.
 279
 280 std::string
 281 Read_symbols::get_name() const
 282 {
 283   if (!this->input_argument_->is_group())
 284     {
 285       std::string ret("Read_symbols ");
 286       if (this->input_argument_->file().is_lib())
 287         ret += "-l";
 288       ret += this->input_argument_->file().name();
 289       return ret;
 290     }
 291
 292   std::string ret("Read_symbols group (");
 293   bool add_space = false;
 294   const Input_file_group* group = this->input_argument_->group();
 295   for (Input_file_group::const_iterator p = group->begin();
 296        p != group->end();
 297        ++p)
 298     {
 299       if (add_space)
 300         ret += ' ';
 301       ret += p->file().name();
 302       add_space = true;
 303     }
 304   return ret + ')';
 305 }
 306
 307 // Class Add_symbols.
 308
 309 Add_symbols::~Add_symbols()
 310 {
 311   if (this->this_blocker_ != NULL)
 312     delete this->this_blocker_;
 313   // next_blocker_ is deleted by the task associated with the next
 314   // input file.
 315 }
 316
 317 // We are blocked by this_blocker_.  We block next_blocker_.  We also
 318 // lock the file.
 319
 320 Task_token*
 321 Add_symbols::is_runnable()
 322 {
 323   if (this->this_blocker_ != NULL && this->this_blocker_->is_blocked())
 324     return this->this_blocker_;
 325   if (this->object_->is_locked())
 326     return this->object_->token();
 327   return NULL;
 328 }
 329
 330 void
 331 Add_symbols::locks(Task_locker* tl)
 332 {
 333   tl->add(this, this->next_blocker_);
 334   tl->add(this, this->object_->token());
 335 }
 336
 337 // Add the symbols in the object to the symbol table.
 338
 339 void
 340 Add_symbols::run(Workqueue*)
 341 {
 342   if (!this->input_objects_->add_object(this->object_))
 343     {
 344       // FIXME: We need to close the descriptor here.
 345       delete this->object_;
 346     }
 347   else
 348     {
 349       this->object_->layout(this->symtab_, this->layout_, this->sd_);
 350       this->object_->add_symbols(this->symtab_, this->sd_);
 351       this->object_->release();
 352     }
 353   delete this->sd_;
 354   this->sd_ = NULL;
 355 }
 356
 357 // Class Finish_group.
 358
 359 Finish_group::~Finish_group()
 360 {
 361   if (this->this_blocker_ != NULL)
 362     delete this->this_blocker_;
 363   // next_blocker_ is deleted by the task associated with the next
 364   // input file following the group.
 365 }
 366
 367 // We need to wait for THIS_BLOCKER_ and unblock NEXT_BLOCKER_.
 368
 369 Task_token*
 370 Finish_group::is_runnable()
 371 {
 372   if (this->this_blocker_ != NULL && this->this_blocker_->is_blocked())
 373     return this->this_blocker_;
 374   return NULL;
 375 }
 376
 377 void
 378 Finish_group::locks(Task_locker* tl)
 379 {
 380   tl->add(this, this->next_blocker_);
 381 }
 382
 383 // Loop over the archives until there are no new undefined symbols.
 384
 385 void
 386 Finish_group::run(Workqueue*)
 387 {
 388   int saw_undefined = this->saw_undefined_;
 389   while (saw_undefined != this->symtab_->saw_undefined())
 390     {
 391       saw_undefined = this->symtab_->saw_undefined();
 392
 393       for (Input_group::const_iterator p = this->input_group_->begin();
 394            p != this->input_group_->end();
 395            ++p)
 396         {
 397           Task_lock_obj<Archive> tl(this, *p);
 398
 399           (*p)->add_symbols(this->symtab_, this->layout_,
 400                             this->input_objects_);
 401         }
 402     }
 403
 404   // Delete all the archives now that we no longer need them.
 405   for (Input_group::const_iterator p = this->input_group_->begin();
 406        p != this->input_group_->end();
 407        ++p)
 408     delete *p;
 409   delete this->input_group_;
 410 }
 411
 412 } // End namespace gold.