gold/gold.cc

   1 // gold.cc -- main linker functions
   2
   3 // Copyright 2006, 2007, 2008 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 #include <cstdio>
  27 #include <cstring>
  28 #include <unistd.h>
  29 #include <algorithm>
  30 #include "libiberty.h"
  31
  32 #include "options.h"
  33 #include "debug.h"
  34 #include "workqueue.h"
  35 #include "dirsearch.h"
  36 #include "readsyms.h"
  37 #include "symtab.h"
  38 #include "common.h"
  39 #include "object.h"
  40 #include "layout.h"
  41 #include "reloc.h"
  42 #include "defstd.h"
  43 #include "plugin.h"
  44
  45 namespace gold
  46 {
  47
  48 const char* program_name;
  49
  50 void
  51 gold_exit(bool status)
  52 {
  53   if (parameters != NULL
  54       && parameters->options_valid()
  55       && parameters->options().has_plugins())
  56     parameters->options().plugins()->cleanup();
  57   if (!status && parameters != NULL && parameters->options_valid())
  58     unlink_if_ordinary(parameters->options().output_file_name());
  59   exit(status ? EXIT_SUCCESS : EXIT_FAILURE);
  60 }
  61
  62 void
  63 gold_nomem()
  64 {
  65   // We are out of memory, so try hard to print a reasonable message.
  66   // Note that we don't try to translate this message, since the
  67   // translation process itself will require memory.
  68
  69   // LEN only exists to avoid a pointless warning when write is
  70   // declared with warn_use_result, as when compiling with
  71   // -D_USE_FORTIFY on GNU/Linux.  Casting to void does not appear to
  72   // work, at least not with gcc 4.3.0.
  73
  74   ssize_t len = write(2, program_name, strlen(program_name));
  75   if (len >= 0)
  76     {
  77       const char* const s = ": out of memory\n";
  78       len = write(2, s, strlen(s));
  79     }
  80   gold_exit(false);
  81 }
  82
  83 // Handle an unreachable case.
  84
  85 void
  86 do_gold_unreachable(const char* filename, int lineno, const char* function)
  87 {
  88   fprintf(stderr, _("%s: internal error in %s, at %s:%d\n"),
  89           program_name, function, filename, lineno);
  90   gold_exit(false);
  91 }
  92
  93 // This class arranges to run the functions done in the middle of the
  94 // link.  It is just a closure.
  95
  96 class Middle_runner : public Task_function_runner
  97 {
  98  public:
  99   Middle_runner(const General_options& options,
 100                 const Input_objects* input_objects,
 101                 Symbol_table* symtab,
 102                 Layout* layout, Mapfile* mapfile)
 103     : options_(options), input_objects_(input_objects), symtab_(symtab),
 104       layout_(layout), mapfile_(mapfile)
 105   { }
 106
 107   void
 108   run(Workqueue*, const Task*);
 109
 110  private:
 111   const General_options& options_;
 112   const Input_objects* input_objects_;
 113   Symbol_table* symtab_;
 114   Layout* layout_;
 115   Mapfile* mapfile_;
 116 };
 117
 118 void
 119 Middle_runner::run(Workqueue* workqueue, const Task* task)
 120 {
 121   queue_middle_tasks(this->options_, task, this->input_objects_, this->symtab_,
 122                      this->layout_, workqueue, this->mapfile_);
 123 }
 124
 125 // Queue up the initial set of tasks for this link job.
 126
 127 void
 128 queue_initial_tasks(const General_options& options,
 129                     Dirsearch& search_path,
 130                     const Command_line& cmdline,
 131                     Workqueue* workqueue, Input_objects* input_objects,
 132                     Symbol_table* symtab, Layout* layout, Mapfile* mapfile)
 133 {
 134   if (cmdline.begin() == cmdline.end())
 135     gold_fatal(_("no input files"));
 136
 137   int thread_count = options.thread_count_initial();
 138   if (thread_count == 0)
 139     thread_count = cmdline.number_of_input_files();
 140   workqueue->set_thread_count(thread_count);
 141
 142   // Read the input files.  We have to add the symbols to the symbol
 143   // table in order.  We do this by creating a separate blocker for
 144   // each input file.  We associate the blocker with the following
 145   // input file, to give us a convenient place to delete it.
 146   Task_token* this_blocker = NULL;
 147   for (Command_line::const_iterator p = cmdline.begin();
 148        p != cmdline.end();
 149        ++p)
 150     {
 151       Task_token* next_blocker = new Task_token(true);
 152       next_blocker->add_blocker();
 153       workqueue->queue(new Read_symbols(options, input_objects, symtab, layout,
 154                                         &search_path, mapfile, &*p, NULL,
 155                                         this_blocker, next_blocker));
 156       this_blocker = next_blocker;
 157     }
 158
 159   if (options.has_plugins())
 160     {
 161       Task_token* next_blocker = new Task_token(true);
 162       next_blocker->add_blocker();
 163       workqueue->queue(new Plugin_hook(options, input_objects, symtab, layout,
 164                                        &search_path, mapfile, this_blocker,
 165                                        next_blocker));
 166       this_blocker = next_blocker;
 167     }
 168
 169   workqueue->queue(new Task_function(new Middle_runner(options,
 170                                                        input_objects,
 171                                                        symtab,
 172                                                        layout,
 173                                                        mapfile),
 174                                      this_blocker,
 175                                      "Task_function Middle_runner"));
 176 }
 177
 178 // Queue up the middle set of tasks.  These are the tasks which run
 179 // after all the input objects have been found and all the symbols
 180 // have been read, but before we lay out the output file.
 181
 182 void
 183 queue_middle_tasks(const General_options& options,
 184                    const Task* task,
 185                    const Input_objects* input_objects,
 186                    Symbol_table* symtab,
 187                    Layout* layout,
 188                    Workqueue* workqueue,
 189                    Mapfile* mapfile)
 190 {
 191   // We have to support the case of not seeing any input objects, and
 192   // generate an empty file.  Existing builds depend on being able to
 193   // pass an empty archive to the linker and get an empty object file
 194   // out.  In order to do this we need to use a default target.
 195   if (input_objects->number_of_input_objects() == 0)
 196     set_parameters_target(&parameters->default_target());
 197
 198   int thread_count = options.thread_count_middle();
 199   if (thread_count == 0)
 200     thread_count = std::max(2, input_objects->number_of_input_objects());
 201   workqueue->set_thread_count(thread_count);
 202
 203   // Now we have seen all the input files.
 204   const bool doing_static_link = (!input_objects->any_dynamic()
 205                                   && !parameters->options().shared());
 206   set_parameters_doing_static_link(doing_static_link);
 207   if (!doing_static_link && options.is_static())
 208     {
 209       // We print out just the first .so we see; there may be others.
 210       gold_assert(input_objects->dynobj_begin() != input_objects->dynobj_end());
 211       gold_error(_("cannot mix -static with dynamic object %s"),
 212                  (*input_objects->dynobj_begin())->name().c_str());
 213     }
 214   if (!doing_static_link && parameters->options().relocatable())
 215     gold_error(_("cannot mix -r with dynamic object %s"),
 216                (*input_objects->dynobj_begin())->name().c_str());
 217   if (!doing_static_link
 218       && options.oformat_enum() != General_options::OBJECT_FORMAT_ELF)
 219     gold_fatal(_("cannot use non-ELF output format with dynamic object %s"),
 220                (*input_objects->dynobj_begin())->name().c_str());
 221
 222   if (is_debugging_enabled(DEBUG_SCRIPT))
 223     layout->script_options()->print(stderr);
 224
 225   // For each dynamic object, record whether we've seen all the
 226   // dynamic objects that it depends upon.
 227   input_objects->check_dynamic_dependencies();
 228
 229   // See if any of the input definitions violate the One Definition Rule.
 230   // TODO: if this is too slow, do this as a task, rather than inline.
 231   symtab->detect_odr_violations(task, options.output_file_name());
 232
 233   // Create any output sections required by any linker script.
 234   layout->create_script_sections();
 235
 236   // Define some sections and symbols needed for a dynamic link.  This
 237   // handles some cases we want to see before we read the relocs.
 238   layout->create_initial_dynamic_sections(symtab);
 239
 240   // Define symbols from any linker scripts.
 241   layout->define_script_symbols(symtab);
 242
 243   // Add any symbols named with -u options to the symbol table.
 244   symtab->add_undefined_symbols_from_command_line();
 245
 246   // Attach sections to segments.
 247   layout->attach_sections_to_segments();
 248
 249   if (!parameters->options().relocatable())
 250     {
 251       // Predefine standard symbols.
 252       define_standard_symbols(symtab, layout);
 253
 254       // Define __start and __stop symbols for output sections where
 255       // appropriate.
 256       layout->define_section_symbols(symtab);
 257     }
 258
 259   // Make sure we have symbols for any required group signatures.
 260   layout->define_group_signatures(symtab);
 261
 262   // Read the relocations of the input files.  We do this to find
 263   // which symbols are used by relocations which require a GOT and/or
 264   // a PLT entry, or a COPY reloc.  When we implement garbage
 265   // collection we will do it here by reading the relocations in a
 266   // breadth first search by references.
 267   //
 268   // We could also read the relocations during the first pass, and
 269   // mark symbols at that time.  That is how the old GNU linker works.
 270   // Doing that is more complex, since we may later decide to discard
 271   // some of the sections, and thus change our minds about the types
 272   // of references made to the symbols.
 273   Task_token* blocker = new Task_token(true);
 274   Task_token* symtab_lock = new Task_token(false);
 275   for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 276        p != input_objects->relobj_end();
 277        ++p)
 278     {
 279       // We can read and process the relocations in any order.  But we
 280       // only want one task to write to the symbol table at a time.
 281       // So we queue up a task for each object to read the
 282       // relocations.  That task will in turn queue a task to wait
 283       // until it can write to the symbol table.
 284       blocker->add_blocker();
 285       workqueue->queue(new Read_relocs(options, symtab, layout, *p,
 286                                        symtab_lock, blocker));
 287     }
 288
 289   // Allocate common symbols.  This requires write access to the
 290   // symbol table, but is independent of the relocation processing.
 291   if (parameters->options().define_common())
 292     {
 293       blocker->add_blocker();
 294       workqueue->queue(new Allocate_commons_task(symtab, layout, mapfile,
 295                                                  symtab_lock, blocker));
 296     }
 297
 298   // When all those tasks are complete, we can start laying out the
 299   // output file.
 300   // TODO(csilvers): figure out a more principled way to get the target
 301   Target* target = const_cast<Target*>(&parameters->target());
 302   workqueue->queue(new Task_function(new Layout_task_runner(options,
 303                                                             input_objects,
 304                                                             symtab,
 305                                                             target,
 306                                                             layout,
 307                                                             mapfile),
 308                                      blocker,
 309                                      "Task_function Layout_task_runner"));
 310 }
 311
 312 // Queue up the final set of tasks.  This is called at the end of
 313 // Layout_task.
 314
 315 void
 316 queue_final_tasks(const General_options& options,
 317                   const Input_objects* input_objects,
 318                   const Symbol_table* symtab,
 319                   Layout* layout,
 320                   Workqueue* workqueue,
 321                   Output_file* of)
 322 {
 323   int thread_count = options.thread_count_final();
 324   if (thread_count == 0)
 325     thread_count = std::max(2, input_objects->number_of_input_objects());
 326   workqueue->set_thread_count(thread_count);
 327
 328   bool any_postprocessing_sections = layout->any_postprocessing_sections();
 329
 330   // Use a blocker to wait until all the input sections have been
 331   // written out.
 332   Task_token* input_sections_blocker = NULL;
 333   if (!any_postprocessing_sections)
 334     input_sections_blocker = new Task_token(true);
 335
 336   // Use a blocker to block any objects which have to wait for the
 337   // output sections to complete before they can apply relocations.
 338   Task_token* output_sections_blocker = new Task_token(true);
 339
 340   // Use a blocker to block the final cleanup task.
 341   Task_token* final_blocker = new Task_token(true);
 342
 343   // Queue a task to write out the symbol table.
 344   final_blocker->add_blocker();
 345   workqueue->queue(new Write_symbols_task(layout,
 346                                           symtab,
 347                                           input_objects,
 348                                           layout->sympool(),
 349                                           layout->dynpool(),
 350                                           of,
 351                                           final_blocker));
 352
 353   // Queue a task to write out the output sections.
 354   output_sections_blocker->add_blocker();
 355   final_blocker->add_blocker();
 356   workqueue->queue(new Write_sections_task(layout, of, output_sections_blocker,
 357                                            final_blocker));
 358
 359   // Queue a task to write out everything else.
 360   final_blocker->add_blocker();
 361   workqueue->queue(new Write_data_task(layout, symtab, of, final_blocker));
 362
 363   // Queue a task for each input object to relocate the sections and
 364   // write out the local symbols.
 365   for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 366        p != input_objects->relobj_end();
 367        ++p)
 368     {
 369       if (input_sections_blocker != NULL)
 370         input_sections_blocker->add_blocker();
 371       final_blocker->add_blocker();
 372       workqueue->queue(new Relocate_task(options, symtab, layout, *p, of,
 373                                          input_sections_blocker,
 374                                          output_sections_blocker,
 375                                          final_blocker));
 376     }
 377
 378   // Queue a task to write out the output sections which depend on
 379   // input sections.  If there are any sections which require
 380   // postprocessing, then we need to do this last, since it may resize
 381   // the output file.
 382   if (!any_postprocessing_sections)
 383     {
 384       final_blocker->add_blocker();
 385       Task* t = new Write_after_input_sections_task(layout, of,
 386                                                     input_sections_blocker,
 387                                                     final_blocker);
 388       workqueue->queue(t);
 389     }
 390   else
 391     {
 392       Task_token *new_final_blocker = new Task_token(true);
 393       new_final_blocker->add_blocker();
 394       Task* t = new Write_after_input_sections_task(layout, of,
 395                                                     final_blocker,
 396                                                     new_final_blocker);
 397       workqueue->queue(t);
 398       final_blocker = new_final_blocker;
 399     }
 400
 401   // Queue a task to close the output file.  This will be blocked by
 402   // FINAL_BLOCKER.
 403   workqueue->queue(new Task_function(new Close_task_runner(&options, layout,
 404                                                            of),
 405                                      final_blocker,
 406                                      "Task_function Close_task_runner"));
 407 }
 408
 409 } // End namespace gold.