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// gold.cc -- main linker functions

// Copyright 2006, 2007, 2008, 2009 Free Software Foundation, Inc.

// Written by Ian Lance Taylor <iant@google.com>.

// This file is part of gold.

// This program is free software; you can redistribute it and/or modify

// it under the terms of the GNU General Public License as published by

// the Free Software Foundation; either version 3 of the License, or

// (at your option) any later version.

// This program is distributed in the hope that it will be useful,

// but WITHOUT ANY WARRANTY; without even the implied warranty of

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License

// along with this program; if not, write to the Free Software

// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,

// MA 02110-1301, USA.

#include "gold.h"

#include <cstdlib>

#include <cstdio>

#include <cstring>

#include <unistd.h>

#include <algorithm>

#include "libiberty.h"

#include "options.h"

#include "debug.h"

#include "workqueue.h"

#include "dirsearch.h"

#include "readsyms.h"

#include "symtab.h"

#include "common.h"

#include "object.h"

#include "layout.h"

#include "reloc.h"

#include "defstd.h"

#include "plugin.h"

#include "gc.h"

#include "icf.h"

#include "incremental.h"

namespace gold

{

const char* program_name;

void

gold_exit(bool status)

{

  if (parameters != NULL

      && parameters->options_valid()

      && parameters->options().has_plugins())

    parameters->options().plugins()->cleanup();

  if (!status && parameters != NULL && parameters->options_valid())

    unlink_if_ordinary(parameters->options().output_file_name());

  exit(status ? EXIT_SUCCESS : EXIT_FAILURE);

}

void

gold_nomem()

{

  // We are out of memory, so try hard to print a reasonable message.

  // Note that we don't try to translate this message, since the

  // translation process itself will require memory.

  // LEN only exists to avoid a pointless warning when write is

  // declared with warn_use_result, as when compiling with

  // -D_USE_FORTIFY on GNU/Linux.  Casting to void does not appear to

  // work, at least not with gcc 4.3.0.

  ssize_t len = write(2, program_name, strlen(program_name));

  if (len >= 0)

    {

      const char* const s = ": out of memory\n";

      len = write(2, s, strlen(s));

    }

  gold_exit(false);

}

// Handle an unreachable case.

void

do_gold_unreachable(const char* filename, int lineno, const char* function)

{

  fprintf(stderr, _("%s: internal error in %s, at %s:%d\n"),

          program_name, function, filename, lineno);

  gold_exit(false);

}

// This class arranges to run the functions done in the middle of the

// link.  It is just a closure.

class Middle_runner : public Task_function_runner

{

 public:

  Middle_runner(const General_options& options,

                const Input_objects* input_objects,

                Symbol_table* symtab,

                Layout* layout, Mapfile* mapfile)

    : options_(options), input_objects_(input_objects), symtab_(symtab),

      layout_(layout), mapfile_(mapfile)

  { }

  void

  run(Workqueue*, const Task*);

 private:

  const General_options& options_;

  const Input_objects* input_objects_;

  Symbol_table* symtab_;

  Layout* layout_;

  Mapfile* mapfile_;

};

void

Middle_runner::run(Workqueue* workqueue, const Task* task)

{

  queue_middle_tasks(this->options_, task, this->input_objects_, this->symtab_,

                     this->layout_, workqueue, this->mapfile_);

}

// This class arranges the tasks to process the relocs for garbage collection.

class Gc_runner : public Task_function_runner

{

  public:

   Gc_runner(const General_options& options,

             const Input_objects* input_objects,

             Symbol_table* symtab,

             Layout* layout, Mapfile* mapfile)

    : options_(options), input_objects_(input_objects), symtab_(symtab),

      layout_(layout), mapfile_(mapfile)

   { }

  void

  run(Workqueue*, const Task*);

 private:

  const General_options& options_;

  const Input_objects* input_objects_;

  Symbol_table* symtab_;

  Layout* layout_;

  Mapfile* mapfile_;

};

void

Gc_runner::run(Workqueue* workqueue, const Task* task)

{

  queue_middle_gc_tasks(this->options_, task, this->input_objects_,

                        this->symtab_, this->layout_, workqueue,

                        this->mapfile_);

}

// Queue up the initial set of tasks for this link job.

void

queue_initial_tasks(const General_options& options,

                    Dirsearch& search_path,

                    const Command_line& cmdline,

                    Workqueue* workqueue, Input_objects* input_objects,

                    Symbol_table* symtab, Layout* layout, Mapfile* mapfile)

{

  if (cmdline.begin() == cmdline.end())

    {

      if (options.printed_version())

        gold_exit(true);

      gold_fatal(_("no input files"));

    }

  int thread_count = options.thread_count_initial();

  if (thread_count == 0)

    thread_count = cmdline.number_of_input_files();

  workqueue->set_thread_count(thread_count);

  if (cmdline.options().incremental())

    {

      Incremental_checker incremental_checker(

          parameters->options().output_file_name(),

          layout->incremental_inputs());

      if (incremental_checker.can_incrementally_link_output_file())

        {

          // TODO: remove when incremental linking implemented.

          printf("Incremental linking might be possible "

              "(not implemented yet)\n");

        }

      // TODO: If we decide on an incremental build, fewer tasks

      // should be scheduled.

    }

  // Read the input files.  We have to add the symbols to the symbol

  // table in order.  We do this by creating a separate blocker for

  // each input file.  We associate the blocker with the following

  // input file, to give us a convenient place to delete it.

  Task_token* this_blocker = NULL;

  for (Command_line::const_iterator p = cmdline.begin();

       p != cmdline.end();

       ++p)

    {

      Task_token* next_blocker = new Task_token(true);

      next_blocker->add_blocker();

      workqueue->queue(new Read_symbols(input_objects, symtab, layout,

                                        &search_path, 0, mapfile, &*p, NULL,

                                        this_blocker, next_blocker));

      this_blocker = next_blocker;

    }

  if (options.has_plugins())

    {

      Task_token* next_blocker = new Task_token(true);

      next_blocker->add_blocker();

      workqueue->queue(new Plugin_hook(options, input_objects, symtab, layout,

                                       &search_path, mapfile, this_blocker,

                                       next_blocker));

      this_blocker = next_blocker;

    }

  if (parameters->options().relocatable()

      && (parameters->options().gc_sections()

          || parameters->options().icf_enabled()))

    gold_error(_("cannot mix -r with --gc-sections or --icf"));

  if (parameters->options().gc_sections()

      || parameters->options().icf_enabled())

    {

      workqueue->queue(new Task_function(new Gc_runner(options,

                                                       input_objects,

                                                       symtab,

                                                       layout,

                                                       mapfile),

                                         this_blocker,

                                         "Task_function Gc_runner"));

    }

  else

    {

      workqueue->queue(new Task_function(new Middle_runner(options,

                                                           input_objects,

                                                           symtab,

                                                           layout,

                                                           mapfile),

                                         this_blocker,

                                         "Task_function Middle_runner"));

    }

}

// Queue up a set of tasks to be done before queueing the middle set

// of tasks.  This is only necessary when garbage collection

// (--gc-sections) of unused sections is desired.  The relocs are read

// and processed here early to determine the garbage sections before the

// relocs can be scanned in later tasks.

void

queue_middle_gc_tasks(const General_options& options,

                      const Task* ,

                      const Input_objects* input_objects,

                      Symbol_table* symtab,

                      Layout* layout,

                      Workqueue* workqueue,

                      Mapfile* mapfile)

{

  // Read_relocs for all the objects must be done and processed to find

  // unused sections before any scanning of the relocs can take place.

  Task_token* blocker = new Task_token(true);

  Task_token* symtab_lock = new Task_token(false);

  for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();

       p != input_objects->relobj_end();

       ++p)

    {

      // We can read and process the relocations in any order.  

      blocker->add_blocker();

      workqueue->queue(new Read_relocs(options, symtab, layout, *p,

                                       symtab_lock, blocker));

    }

  Task_token* this_blocker = new Task_token(true);

  workqueue->queue(new Task_function(new Middle_runner(options,

                                                       input_objects,

                                                       symtab,

                                                       layout,

                                                       mapfile),

                                     this_blocker,

                                     "Task_function Middle_runner"));

}

// Queue up the middle set of tasks.  These are the tasks which run

// after all the input objects have been found and all the symbols

// have been read, but before we lay out the output file.

void

queue_middle_tasks(const General_options& options,

                   const Task* task,

                   const Input_objects* input_objects,

                   Symbol_table* symtab,

                   Layout* layout,

                   Workqueue* workqueue,

                   Mapfile* mapfile)

{

  // Add any symbols named with -u options to the symbol table.

  symtab->add_undefined_symbols_from_command_line();

  // If garbage collection was chosen, relocs have been read and processed

  // at this point by pre_middle_tasks.  Layout can then be done for all 

  // objects.

  if (parameters->options().gc_sections())

    {

      // Find the start symbol if any.

      Symbol* start_sym;

      if (parameters->options().entry())

        start_sym = symtab->lookup(parameters->options().entry());

      else

        start_sym = symtab->lookup("_start");

      if (start_sym !=NULL)

        {

          bool is_ordinary;

          unsigned int shndx = start_sym->shndx(&is_ordinary);

          if (is_ordinary)

            {

              symtab->gc()->worklist().push(

                Section_id(start_sym->object(), shndx));

            }

        }

      // Symbols named with -u should not be considered garbage.

      symtab->gc_mark_undef_symbols();

      gold_assert(symtab->gc() != NULL);

      // Do a transitive closure on all references to determine the worklist.

      symtab->gc()->do_transitive_closure();

    }

  // If identical code folding (--icf) is chosen it makes sense to do it 

  // only after garbage collection (--gc-sections) as we do not want to 

  // be folding sections that will be garbage.

  if (parameters->options().icf_enabled())

    {

      symtab->icf()->find_identical_sections(input_objects, symtab);

    }

  // Call Object::layout for the second time to determine the 

  // output_sections for all referenced input sections.  When 

  // --gc-sections or --icf is turned on, Object::layout is 

  // called twice.  It is called the first time when the 

  // symbols are added.

  if (parameters->options().gc_sections()

      || parameters->options().icf_enabled())

    {

      for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();

           p != input_objects->relobj_end();

           ++p)

        {

          (*p)->layout(symtab, layout, NULL);

        }

    }

  // Layout deferred objects due to plugins.

  if (parameters->options().has_plugins())

    {

      Plugin_manager* plugins = parameters->options().plugins();

      gold_assert(plugins != NULL);

      plugins->layout_deferred_objects();

    }

  if (parameters->options().gc_sections()

      || parameters->options().icf_enabled())

    {

      for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();

           p != input_objects->relobj_end();

           ++p)

        {

          // Update the value of output_section stored in rd.

          Read_relocs_data *rd = (*p)->get_relocs_data();

          for (Read_relocs_data::Relocs_list::iterator q = rd->relocs.begin();

               q != rd->relocs.end();

               ++q)

            {

              q->output_section = (*p)->output_section(q->data_shndx);

              q->needs_special_offset_handling =

                      (*p)->is_output_section_offset_invalid(q->data_shndx);

            }

        }

    }

  // We have to support the case of not seeing any input objects, and

  // generate an empty file.  Existing builds depend on being able to

  // pass an empty archive to the linker and get an empty object file

  // out.  In order to do this we need to use a default target.

  if (input_objects->number_of_input_objects() == 0)

    parameters_force_valid_target();

  int thread_count = options.thread_count_middle();

  if (thread_count == 0)

    thread_count = std::max(2, input_objects->number_of_input_objects());

  workqueue->set_thread_count(thread_count);

  // Now we have seen all the input files.

  const bool doing_static_link =

    (!input_objects->any_dynamic()

     && !parameters->options().output_is_position_independent());

  set_parameters_doing_static_link(doing_static_link);

  if (!doing_static_link && options.is_static())

    {

      // We print out just the first .so we see; there may be others.

      gold_assert(input_objects->dynobj_begin() != input_objects->dynobj_end());

      gold_error(_("cannot mix -static with dynamic object %s"),

                 (*input_objects->dynobj_begin())->name().c_str());

    }

  if (!doing_static_link && parameters->options().relocatable())

    gold_fatal(_("cannot mix -r with dynamic object %s"),

               (*input_objects->dynobj_begin())->name().c_str());

  if (!doing_static_link

      && options.oformat_enum() != General_options::OBJECT_FORMAT_ELF)

    gold_fatal(_("cannot use non-ELF output format with dynamic object %s"),

               (*input_objects->dynobj_begin())->name().c_str());

  if (parameters->options().relocatable())

    {

      Input_objects::Relobj_iterator p = input_objects->relobj_begin();

      if (p != input_objects->relobj_end())

        {

          bool uses_split_stack = (*p)->uses_split_stack();

          for (++p; p != input_objects->relobj_end(); ++p)

            {

              if ((*p)->uses_split_stack() != uses_split_stack)

                gold_fatal(_("cannot mix split-stack '%s' and "

                             "non-split-stack '%s' when using -r"),

                           (*input_objects->relobj_begin())->name().c_str(),

                           (*p)->name().c_str());

            }

        }

    }

  if (is_debugging_enabled(DEBUG_SCRIPT))

    layout->script_options()->print(stderr);

  // For each dynamic object, record whether we've seen all the

  // dynamic objects that it depends upon.

  input_objects->check_dynamic_dependencies();

  // See if any of the input definitions violate the One Definition Rule.

  // TODO: if this is too slow, do this as a task, rather than inline.

  symtab->detect_odr_violations(task, options.output_file_name());

  // Create any automatic note sections.

  layout->create_notes();

  // Create any output sections required by any linker script.

  layout->create_script_sections();

  // Define some sections and symbols needed for a dynamic link.  This

  // handles some cases we want to see before we read the relocs.

  layout->create_initial_dynamic_sections(symtab);

  // Define symbols from any linker scripts.

  layout->define_script_symbols(symtab);

  // Attach sections to segments.

  layout->attach_sections_to_segments();

  if (!parameters->options().relocatable())

    {

      // Predefine standard symbols.

      define_standard_symbols(symtab, layout);

      // Define __start and __stop symbols for output sections where

      // appropriate.

      layout->define_section_symbols(symtab);

    }

  // Make sure we have symbols for any required group signatures.

  layout->define_group_signatures(symtab);

  Task_token* blocker = new Task_token(true);

  Task_token* symtab_lock = new Task_token(false);

  // If doing garbage collection, the relocations have already been read.

  // Otherwise, read and scan the relocations.

  if (parameters->options().gc_sections()

      || parameters->options().icf_enabled())

    {

      for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();

           p != input_objects->relobj_end();

           ++p)

        {

          blocker->add_blocker();

          workqueue->queue(new Scan_relocs(options, symtab, layout, *p,

                           (*p)->get_relocs_data(),symtab_lock, blocker));

        }

    }

  else

    {

      // Read the relocations of the input files.  We do this to find

      // which symbols are used by relocations which require a GOT and/or

      // a PLT entry, or a COPY reloc.  When we implement garbage

      // collection we will do it here by reading the relocations in a

      // breadth first search by references.

      //

      // We could also read the relocations during the first pass, and

      // mark symbols at that time.  That is how the old GNU linker works.

      // Doing that is more complex, since we may later decide to discard

      // some of the sections, and thus change our minds about the types

      // of references made to the symbols.

      for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();

           p != input_objects->relobj_end();

           ++p)

        {

          // We can read and process the relocations in any order.  But we

          // only want one task to write to the symbol table at a time.

          // So we queue up a task for each object to read the

          // relocations.  That task will in turn queue a task to wait

          // until it can write to the symbol table.

          blocker->add_blocker();

          workqueue->queue(new Read_relocs(options, symtab, layout, *p,

                   symtab_lock, blocker));

        }

    }

  // Allocate common symbols.  This requires write access to the

  // symbol table, but is independent of the relocation processing.

  if (parameters->options().define_common())

    {

      blocker->add_blocker();

      workqueue->queue(new Allocate_commons_task(symtab, layout, mapfile,

                                                 symtab_lock, blocker));

    }

  // When all those tasks are complete, we can start laying out the

  // output file.

  // TODO(csilvers): figure out a more principled way to get the target

  Target* target = const_cast<Target*>(&parameters->target());

  workqueue->queue(new Task_function(new Layout_task_runner(options,

                                                            input_objects,

                                                            symtab,

                                                            target,

                                                            layout,

                                                            mapfile),

                                     blocker,

                                     "Task_function Layout_task_runner"));

}

// Queue up the final set of tasks.  This is called at the end of

// Layout_task.

void

queue_final_tasks(const General_options& options,

                  const Input_objects* input_objects,

                  const Symbol_table* symtab,

                  Layout* layout,

                  Workqueue* workqueue,

                  Output_file* of)

{

  int thread_count = options.thread_count_final();

  if (thread_count == 0)

    thread_count = std::max(2, input_objects->number_of_input_objects());

  workqueue->set_thread_count(thread_count);

  bool any_postprocessing_sections = layout->any_postprocessing_sections();

  // Use a blocker to wait until all the input sections have been

  // written out.

  Task_token* input_sections_blocker = NULL;

  if (!any_postprocessing_sections)

    input_sections_blocker = new Task_token(true);

  // Use a blocker to block any objects which have to wait for the

  // output sections to complete before they can apply relocations.

  Task_token* output_sections_blocker = new Task_token(true);

  // Use a blocker to block the final cleanup task.

  Task_token* final_blocker = new Task_token(true);

  // Queue a task to write out the symbol table.

  final_blocker->add_blocker();

  workqueue->queue(new Write_symbols_task(layout,

                                          symtab,

                                          input_objects,

                                          layout->sympool(),

                                          layout->dynpool(),

                                          of,

                                          final_blocker));

  // Queue a task to write out the output sections.

  output_sections_blocker->add_blocker();

  final_blocker->add_blocker();

  workqueue->queue(new Write_sections_task(layout, of, output_sections_blocker,

                                           final_blocker));

  // Queue a task to write out everything else.

  final_blocker->add_blocker();

  workqueue->queue(new Write_data_task(layout, symtab, of, final_blocker));

  // Queue a task for each input object to relocate the sections and

  // write out the local symbols.

  for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();

       p != input_objects->relobj_end();

       ++p)

    {

      if (input_sections_blocker != NULL)

        input_sections_blocker->add_blocker();

      final_blocker->add_blocker();

      workqueue->queue(new Relocate_task(options, symtab, layout, *p, of,

                                         input_sections_blocker,

                                         output_sections_blocker,

                                         final_blocker));

    }

  // Queue a task to write out the output sections which depend on

  // input sections.  If there are any sections which require

  // postprocessing, then we need to do this last, since it may resize

  // the output file.

  if (!any_postprocessing_sections)

    {

      final_blocker->add_blocker();

      Task* t = new Write_after_input_sections_task(layout, of,

                                                    input_sections_blocker,

                                                    final_blocker);

      workqueue->queue(t);

    }

  else

    {

      Task_token *new_final_blocker = new Task_token(true);

      new_final_blocker->add_blocker();

      Task* t = new Write_after_input_sections_task(layout, of,

                                                    final_blocker,

                                                    new_final_blocker);

      workqueue->queue(t);

      final_blocker = new_final_blocker;

    }

  // Queue a task to close the output file.  This will be blocked by

  // FINAL_BLOCKER.

  workqueue->queue(new Task_function(new Close_task_runner(&options, layout,

                                                           of),

                                     final_blocker,

                                     "Task_function Close_task_runner"));

}

} // End namespace gold.