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