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() != 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   // Define some sections and symbols needed for a dynamic link.  This
 206   // handles some cases we want to see before we read the relocs.
 207   layout->create_initial_dynamic_sections(symtab);
 208
 209   // Define symbols from any linker scripts.
 210   layout->define_script_symbols(symtab);
 211
 212   if (!parameters->options().relocatable())
 213     {
 214       // Predefine standard symbols.
 215       define_standard_symbols(symtab, layout);
 216
 217       // Define __start and __stop symbols for output sections where
 218       // appropriate.
 219       layout->define_section_symbols(symtab);
 220     }
 221
 222   // Make sure we have symbols for any required group signatures.
 223   layout->define_group_signatures(symtab);
 224
 225   // Read the relocations of the input files.  We do this to find
 226   // which symbols are used by relocations which require a GOT and/or
 227   // a PLT entry, or a COPY reloc.  When we implement garbage
 228   // collection we will do it here by reading the relocations in a
 229   // breadth first search by references.
 230   //
 231   // We could also read the relocations during the first pass, and
 232   // mark symbols at that time.  That is how the old GNU linker works.
 233   // Doing that is more complex, since we may later decide to discard
 234   // some of the sections, and thus change our minds about the types
 235   // of references made to the symbols.
 236   Task_token* blocker = new Task_token(true);
 237   Task_token* symtab_lock = new Task_token(false);
 238   for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 239        p != input_objects->relobj_end();
 240        ++p)
 241     {
 242       // We can read and process the relocations in any order.  But we
 243       // only want one task to write to the symbol table at a time.
 244       // So we queue up a task for each object to read the
 245       // relocations.  That task will in turn queue a task to wait
 246       // until it can write to the symbol table.
 247       blocker->add_blocker();
 248       workqueue->queue(new Read_relocs(options, symtab, layout, *p,
 249                                        symtab_lock, blocker));
 250     }
 251
 252   // Allocate common symbols.  This requires write access to the
 253   // symbol table, but is independent of the relocation processing.
 254   // FIXME: We should have an option to do this even for a relocatable
 255   // link.
 256   if (!parameters->options().relocatable())
 257     {
 258       blocker->add_blocker();
 259       workqueue->queue(new Allocate_commons_task(options, symtab, layout,
 260                                                  symtab_lock, blocker));
 261     }
 262
 263   // When all those tasks are complete, we can start laying out the
 264   // output file.
 265   // TODO(csilvers): figure out a more principled way to get the target
 266   Target* target = const_cast<Target*>(&parameters->target());
 267   workqueue->queue(new Task_function(new Layout_task_runner(options,
 268                                                             input_objects,
 269                                                             symtab,
 270                                                             target,
 271                                                             layout),
 272                                      blocker,
 273                                      "Task_function Layout_task_runner"));
 274 }
 275
 276 // Queue up the final set of tasks.  This is called at the end of
 277 // Layout_task.
 278
 279 void
 280 queue_final_tasks(const General_options& options,
 281                   const Input_objects* input_objects,
 282                   const Symbol_table* symtab,
 283                   Layout* layout,
 284                   Workqueue* workqueue,
 285                   Output_file* of)
 286 {
 287   int thread_count = options.thread_count_final();
 288   if (thread_count == 0)
 289     thread_count = std::max(2, input_objects->number_of_input_objects());
 290   workqueue->set_thread_count(thread_count);
 291
 292   bool any_postprocessing_sections = layout->any_postprocessing_sections();
 293
 294   // Use a blocker to wait until all the input sections have been
 295   // written out.
 296   Task_token* input_sections_blocker = NULL;
 297   if (!any_postprocessing_sections)
 298     input_sections_blocker = new Task_token(true);
 299
 300   // Use a blocker to block any objects which have to wait for the
 301   // output sections to complete before they can apply relocations.
 302   Task_token* output_sections_blocker = new Task_token(true);
 303
 304   // Use a blocker to block the final cleanup task.
 305   Task_token* final_blocker = new Task_token(true);
 306
 307   // Queue a task to write out the symbol table.
 308   final_blocker->add_blocker();
 309   workqueue->queue(new Write_symbols_task(symtab,
 310                                           input_objects,
 311                                           layout->sympool(),
 312                                           layout->dynpool(),
 313                                           of,
 314                                           final_blocker));
 315
 316   // Queue a task to write out the output sections.
 317   output_sections_blocker->add_blocker();
 318   final_blocker->add_blocker();
 319   workqueue->queue(new Write_sections_task(layout, of, output_sections_blocker,
 320                                            final_blocker));
 321
 322   // Queue a task to write out everything else.
 323   final_blocker->add_blocker();
 324   workqueue->queue(new Write_data_task(layout, symtab, of, final_blocker));
 325
 326   // Queue a task for each input object to relocate the sections and
 327   // write out the local symbols.
 328   for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 329        p != input_objects->relobj_end();
 330        ++p)
 331     {
 332       if (input_sections_blocker != NULL)
 333         input_sections_blocker->add_blocker();
 334       final_blocker->add_blocker();
 335       workqueue->queue(new Relocate_task(options, symtab, layout, *p, of,
 336                                          input_sections_blocker,
 337                                          output_sections_blocker,
 338                                          final_blocker));
 339     }
 340
 341   // Queue a task to write out the output sections which depend on
 342   // input sections.  If there are any sections which require
 343   // postprocessing, then we need to do this last, since it may resize
 344   // the output file.
 345   if (!any_postprocessing_sections)
 346     {
 347       final_blocker->add_blocker();
 348       Task* t = new Write_after_input_sections_task(layout, of,
 349                                                     input_sections_blocker,
 350                                                     final_blocker);
 351       workqueue->queue(t);
 352     }
 353   else
 354     {
 355       Task_token *new_final_blocker = new Task_token(true);
 356       new_final_blocker->add_blocker();
 357       Task* t = new Write_after_input_sections_task(layout, of,
 358                                                     final_blocker,
 359                                                     new_final_blocker);
 360       workqueue->queue(t);
 361       final_blocker = new_final_blocker;
 362     }
 363
 364   // Queue a task to close the output file.  This will be blocked by
 365   // FINAL_BLOCKER.
 366   workqueue->queue(new Task_function(new Close_task_runner(&options, layout,
 367                                                            of),
 368                                      final_blocker,
 369                                      "Task_function Close_task_runner"));
 370 }
 371
 372 } // End namespace gold.