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