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