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 "libiberty.h"
  30
  31 #include "options.h"
  32 #include "debug.h"
  33 #include "workqueue.h"
  34 #include "dirsearch.h"
  35 #include "readsyms.h"
  36 #include "symtab.h"
  37 #include "common.h"
  38 #include "object.h"
  39 #include "layout.h"
  40 #include "reloc.h"
  41 #include "defstd.h"
  42
  43 namespace gold
  44 {
  45
  46 const char* program_name;
  47
  48 void
  49 gold_exit(bool status)
  50 {
  51   if (!status && parameters != NULL && parameters->options_valid())
  52     unlink_if_ordinary(parameters->output_file_name());
  53   exit(status ? EXIT_SUCCESS : EXIT_FAILURE);
  54 }
  55
  56 void
  57 gold_nomem()
  58 {
  59   // We are out of memory, so try hard to print a reasonable message.
  60   // Note that we don't try to translate this message, since the
  61   // translation process itself will require memory.
  62   write(2, program_name, strlen(program_name));
  63   const char* const s = ": out of memory\n";
  64   write(2, s, strlen(s));
  65   gold_exit(false);
  66 }
  67
  68 // Handle an unreachable case.
  69
  70 void
  71 do_gold_unreachable(const char* filename, int lineno, const char* function)
  72 {
  73   fprintf(stderr, _("%s: internal error in %s, at %s:%d\n"),
  74           program_name, function, filename, lineno);
  75   gold_exit(false);
  76 }
  77
  78 // This class arranges to run the functions done in the middle of the
  79 // link.  It is just a closure.
  80
  81 class Middle_runner : public Task_function_runner
  82 {
  83  public:
  84   Middle_runner(const General_options& options,
  85                 const Input_objects* input_objects,
  86                 Symbol_table* symtab,
  87                 Layout* layout)
  88     : options_(options), input_objects_(input_objects), symtab_(symtab),
  89       layout_(layout)
  90   { }
  91
  92   void
  93   run(Workqueue*, const Task*);
  94
  95  private:
  96   const General_options& options_;
  97   const Input_objects* input_objects_;
  98   Symbol_table* symtab_;
  99   Layout* layout_;
 100 };
 101
 102 void
 103 Middle_runner::run(Workqueue* workqueue, const Task* task)
 104 {
 105   queue_middle_tasks(this->options_, task, this->input_objects_, this->symtab_,
 106                      this->layout_, workqueue);
 107 }
 108
 109 // Queue up the initial set of tasks for this link job.
 110
 111 void
 112 queue_initial_tasks(const General_options& options,
 113                     Dirsearch& search_path,
 114                     const Command_line& cmdline,
 115                     Workqueue* workqueue, Input_objects* input_objects,
 116                     Symbol_table* symtab, Layout* layout)
 117 {
 118   if (cmdline.begin() == cmdline.end())
 119     gold_fatal(_("no input files"));
 120
 121   int thread_count = options.thread_count_initial();
 122   if (thread_count == 0)
 123     thread_count = cmdline.number_of_input_files();
 124   workqueue->set_thread_count(thread_count);
 125
 126   // Read the input files.  We have to add the symbols to the symbol
 127   // table in order.  We do this by creating a separate blocker for
 128   // each input file.  We associate the blocker with the following
 129   // input file, to give us a convenient place to delete it.
 130   Task_token* this_blocker = NULL;
 131   for (Command_line::const_iterator p = cmdline.begin();
 132        p != cmdline.end();
 133        ++p)
 134     {
 135       Task_token* next_blocker = new Task_token(true);
 136       next_blocker->add_blocker();
 137       workqueue->queue(new Read_symbols(options, input_objects, symtab, layout,
 138                                         &search_path, &*p, NULL, this_blocker,
 139                                         next_blocker));
 140       this_blocker = next_blocker;
 141     }
 142
 143   workqueue->queue(new Task_function(new Middle_runner(options,
 144                                                        input_objects,
 145                                                        symtab,
 146                                                        layout),
 147                                      this_blocker,
 148                                      "Task_function Middle_runner"));
 149 }
 150
 151 // Queue up the middle set of tasks.  These are the tasks which run
 152 // after all the input objects have been found and all the symbols
 153 // have been read, but before we lay out the output file.
 154
 155 void
 156 queue_middle_tasks(const General_options& options,
 157                    const Task* task,
 158                    const Input_objects* input_objects,
 159                    Symbol_table* symtab,
 160                    Layout* layout,
 161                    Workqueue* workqueue)
 162 {
 163   if (input_objects->number_of_input_objects() == 0)
 164     {
 165       // We had some input files, but we weren't able to open any of
 166       // them.
 167       gold_fatal(_("no input files"));
 168     }
 169
 170   int thread_count = options.thread_count_middle();
 171   if (thread_count == 0)
 172     thread_count = input_objects->number_of_input_objects();
 173   workqueue->set_thread_count(thread_count);
 174
 175   // Now we have seen all the input files.
 176   const bool doing_static_link = (!input_objects->any_dynamic()
 177                                   && !parameters->output_is_shared());
 178   set_parameters_doing_static_link(doing_static_link);
 179   if (!doing_static_link && options.is_static())
 180     {
 181       // We print out just the first .so we see; there may be others.
 182       gold_error(_("cannot mix -static with dynamic object %s"),
 183                  (*input_objects->dynobj_begin())->name().c_str());
 184     }
 185
 186   if (is_debugging_enabled(DEBUG_SCRIPT))
 187     layout->script_options()->print(stderr);
 188
 189   // For each dynamic object, record whether we've seen all the
 190   // dynamic objects that it depends upon.
 191   input_objects->check_dynamic_dependencies();
 192
 193   // See if any of the input definitions violate the One Definition Rule.
 194   // TODO: if this is too slow, do this as a task, rather than inline.
 195   symtab->detect_odr_violations(task, options.output_file_name());
 196
 197   // Define some sections and symbols needed for a dynamic link.  This
 198   // handles some cases we want to see before we read the relocs.
 199   layout->create_initial_dynamic_sections(symtab);
 200
 201   // Predefine standard symbols.  This should be fast, so we don't
 202   // bother to create a task for it.
 203   define_standard_symbols(symtab, layout);
 204
 205   // Define __start and __stop symbols for output sections where
 206   // appropriate.
 207   layout->define_section_symbols(symtab);
 208
 209   // Define symbols from any linker scripts.
 210   layout->define_script_symbols(symtab);
 211
 212   // Read the relocations of the input files.  We do this to find
 213   // which symbols are used by relocations which require a GOT and/or
 214   // a PLT entry, or a COPY reloc.  When we implement garbage
 215   // collection we will do it here by reading the relocations in a
 216   // breadth first search by references.
 217   //
 218   // We could also read the relocations during the first pass, and
 219   // mark symbols at that time.  That is how the old GNU linker works.
 220   // Doing that is more complex, since we may later decide to discard
 221   // some of the sections, and thus change our minds about the types
 222   // of references made to the symbols.
 223   Task_token* blocker = new Task_token(true);
 224   Task_token* symtab_lock = new Task_token(false);
 225   for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 226        p != input_objects->relobj_end();
 227        ++p)
 228     {
 229       // We can read and process the relocations in any order.  But we
 230       // only want one task to write to the symbol table at a time.
 231       // So we queue up a task for each object to read the
 232       // relocations.  That task will in turn queue a task to wait
 233       // until it can write to the symbol table.
 234       blocker->add_blocker();
 235       workqueue->queue(new Read_relocs(options, symtab, layout, *p,
 236                                        symtab_lock, blocker));
 237     }
 238
 239   // Allocate common symbols.  This requires write access to the
 240   // symbol table, but is independent of the relocation processing.
 241   blocker->add_blocker();
 242   workqueue->queue(new Allocate_commons_task(options, symtab, layout,
 243                                              symtab_lock, blocker));
 244
 245   // When all those tasks are complete, we can start laying out the
 246   // output file.
 247   workqueue->queue(new Task_function(new Layout_task_runner(options,
 248                                                             input_objects,
 249                                                             symtab,
 250                                                             layout),
 251                                      blocker,
 252                                      "Task_function Layout_task_runner"));
 253 }
 254
 255 // Queue up the final set of tasks.  This is called at the end of
 256 // Layout_task.
 257
 258 void
 259 queue_final_tasks(const General_options& options,
 260                   const Input_objects* input_objects,
 261                   const Symbol_table* symtab,
 262                   Layout* layout,
 263                   Workqueue* workqueue,
 264                   Output_file* of)
 265 {
 266   int thread_count = options.thread_count_final();
 267   if (thread_count == 0)
 268     thread_count = input_objects->number_of_input_objects();
 269   workqueue->set_thread_count(thread_count);
 270
 271   bool any_postprocessing_sections = layout->any_postprocessing_sections();
 272
 273   // Use a blocker to wait until all the input sections have been
 274   // written out.
 275   Task_token* input_sections_blocker = NULL;
 276   if (!any_postprocessing_sections)
 277     input_sections_blocker = new Task_token(true);
 278
 279   // Use a blocker to block any objects which have to wait for the
 280   // output sections to complete before they can apply relocations.
 281   Task_token* output_sections_blocker = new Task_token(true);
 282
 283   // Use a blocker to block the final cleanup task.
 284   Task_token* final_blocker = new Task_token(true);
 285
 286   // Queue a task to write out the symbol table.
 287   if (!options.strip_all())
 288     {
 289       final_blocker->add_blocker();
 290       workqueue->queue(new Write_symbols_task(symtab,
 291                                               input_objects,
 292                                               layout->sympool(),
 293                                               layout->dynpool(),
 294                                               of,
 295                                               final_blocker));
 296     }
 297
 298   // Queue a task to write out the output sections.
 299   output_sections_blocker->add_blocker();
 300   final_blocker->add_blocker();
 301   workqueue->queue(new Write_sections_task(layout, of, output_sections_blocker,
 302                                            final_blocker));
 303
 304   // Queue a task to write out everything else.
 305   final_blocker->add_blocker();
 306   workqueue->queue(new Write_data_task(layout, symtab, of, final_blocker));
 307
 308   // Queue a task for each input object to relocate the sections and
 309   // write out the local symbols.
 310   for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 311        p != input_objects->relobj_end();
 312        ++p)
 313     {
 314       if (input_sections_blocker != NULL)
 315         input_sections_blocker->add_blocker();
 316       final_blocker->add_blocker();
 317       workqueue->queue(new Relocate_task(options, symtab, layout, *p, of,
 318                                          input_sections_blocker,
 319                                          output_sections_blocker,
 320                                          final_blocker));
 321     }
 322
 323   // Queue a task to write out the output sections which depend on
 324   // input sections.  If there are any sections which require
 325   // postprocessing, then we need to do this last, since it may resize
 326   // the output file.
 327   if (!any_postprocessing_sections)
 328     {
 329       final_blocker->add_blocker();
 330       Task* t = new Write_after_input_sections_task(layout, of,
 331                                                     input_sections_blocker,
 332                                                     final_blocker);
 333       workqueue->queue(t);
 334     }
 335   else
 336     {
 337       Task_token *new_final_blocker = new Task_token(true);
 338       new_final_blocker->add_blocker();
 339       Task* t = new Write_after_input_sections_task(layout, of,
 340                                                     final_blocker,
 341                                                     new_final_blocker);
 342       workqueue->queue(t);
 343       final_blocker = new_final_blocker;
 344     }
 345
 346   // Queue a task to close the output file.  This will be blocked by
 347   // FINAL_BLOCKER.
 348   workqueue->queue(new Task_function(new Close_task_runner(of),
 349                                      final_blocker,
 350                                      "Task_function Close_task_runner"));
 351 }
 352
 353 } // End namespace gold.