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