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