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   // Define symbols from any linker scripts.
 202   layout->define_script_symbols(symtab);
 203
 204   // Predefine standard symbols.
 205   define_standard_symbols(symtab, layout);
 206
 207   // Define __start and __stop symbols for output sections where
 208   // appropriate.
 209   layout->define_section_symbols(symtab);
 210
 211   // Read the relocations of the input files.  We do this to find
 212   // which symbols are used by relocations which require a GOT and/or
 213   // a PLT entry, or a COPY reloc.  When we implement garbage
 214   // collection we will do it here by reading the relocations in a
 215   // breadth first search by references.
 216   //
 217   // We could also read the relocations during the first pass, and
 218   // mark symbols at that time.  That is how the old GNU linker works.
 219   // Doing that is more complex, since we may later decide to discard
 220   // some of the sections, and thus change our minds about the types
 221   // of references made to the symbols.
 222   Task_token* blocker = new Task_token(true);
 223   Task_token* symtab_lock = new Task_token(false);
 224   for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 225        p != input_objects->relobj_end();
 226        ++p)
 227     {
 228       // We can read and process the relocations in any order.  But we
 229       // only want one task to write to the symbol table at a time.
 230       // So we queue up a task for each object to read the
 231       // relocations.  That task will in turn queue a task to wait
 232       // until it can write to the symbol table.
 233       blocker->add_blocker();
 234       workqueue->queue(new Read_relocs(options, symtab, layout, *p,
 235                                        symtab_lock, blocker));
 236     }
 237
 238   // Allocate common symbols.  This requires write access to the
 239   // symbol table, but is independent of the relocation processing.
 240   blocker->add_blocker();
 241   workqueue->queue(new Allocate_commons_task(options, symtab, layout,
 242                                              symtab_lock, blocker));
 243
 244   // When all those tasks are complete, we can start laying out the
 245   // output file.
 246   workqueue->queue(new Task_function(new Layout_task_runner(options,
 247                                                             input_objects,
 248                                                             symtab,
 249                                                             layout),
 250                                      blocker,
 251                                      "Task_function Layout_task_runner"));
 252 }
 253
 254 // Queue up the final set of tasks.  This is called at the end of
 255 // Layout_task.
 256
 257 void
 258 queue_final_tasks(const General_options& options,
 259                   const Input_objects* input_objects,
 260                   const Symbol_table* symtab,
 261                   Layout* layout,
 262                   Workqueue* workqueue,
 263                   Output_file* of)
 264 {
 265   int thread_count = options.thread_count_final();
 266   if (thread_count == 0)
 267     thread_count = input_objects->number_of_input_objects();
 268   workqueue->set_thread_count(thread_count);
 269
 270   bool any_postprocessing_sections = layout->any_postprocessing_sections();
 271
 272   // Use a blocker to wait until all the input sections have been
 273   // written out.
 274   Task_token* input_sections_blocker = NULL;
 275   if (!any_postprocessing_sections)
 276     input_sections_blocker = new Task_token(true);
 277
 278   // Use a blocker to block any objects which have to wait for the
 279   // output sections to complete before they can apply relocations.
 280   Task_token* output_sections_blocker = new Task_token(true);
 281
 282   // Use a blocker to block the final cleanup task.
 283   Task_token* final_blocker = new Task_token(true);
 284
 285   // Queue a task to write out the symbol table.
 286   if (!options.strip_all())
 287     {
 288       final_blocker->add_blocker();
 289       workqueue->queue(new Write_symbols_task(symtab,
 290                                               input_objects,
 291                                               layout->sympool(),
 292                                               layout->dynpool(),
 293                                               of,
 294                                               final_blocker));
 295     }
 296
 297   // Queue a task to write out the output sections.
 298   output_sections_blocker->add_blocker();
 299   final_blocker->add_blocker();
 300   workqueue->queue(new Write_sections_task(layout, of, output_sections_blocker,
 301                                            final_blocker));
 302
 303   // Queue a task to write out everything else.
 304   final_blocker->add_blocker();
 305   workqueue->queue(new Write_data_task(layout, symtab, of, final_blocker));
 306
 307   // Queue a task for each input object to relocate the sections and
 308   // write out the local symbols.
 309   for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 310        p != input_objects->relobj_end();
 311        ++p)
 312     {
 313       if (input_sections_blocker != NULL)
 314         input_sections_blocker->add_blocker();
 315       final_blocker->add_blocker();
 316       workqueue->queue(new Relocate_task(options, symtab, layout, *p, of,
 317                                          input_sections_blocker,
 318                                          output_sections_blocker,
 319                                          final_blocker));
 320     }
 321
 322   // Queue a task to write out the output sections which depend on
 323   // input sections.  If there are any sections which require
 324   // postprocessing, then we need to do this last, since it may resize
 325   // the output file.
 326   if (!any_postprocessing_sections)
 327     {
 328       final_blocker->add_blocker();
 329       Task* t = new Write_after_input_sections_task(layout, of,
 330                                                     input_sections_blocker,
 331                                                     final_blocker);
 332       workqueue->queue(t);
 333     }
 334   else
 335     {
 336       Task_token *new_final_blocker = new Task_token(true);
 337       new_final_blocker->add_blocker();
 338       Task* t = new Write_after_input_sections_task(layout, of,
 339                                                     final_blocker,
 340                                                     new_final_blocker);
 341       workqueue->queue(t);
 342       final_blocker = new_final_blocker;
 343     }
 344
 345   // Queue a task to close the output file.  This will be blocked by
 346   // FINAL_BLOCKER.
 347   workqueue->queue(new Task_function(new Close_task_runner(of),
 348                                      final_blocker,
 349                                      "Task_function Close_task_runner"));
 350 }
 351
 352 } // End namespace gold.