642 lines
22 KiB
C++
642 lines
22 KiB
C++
// gold.cc -- main linker functions
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// Copyright 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
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// Written by Ian Lance Taylor <iant@google.com>.
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// This file is part of gold.
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// This program is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 3 of the License, or
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// (at your option) any later version.
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
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// MA 02110-1301, USA.
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#include "gold.h"
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#include <cstdlib>
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#include <cstdio>
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#include <cstring>
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#include <unistd.h>
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#include <algorithm>
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#include "libiberty.h"
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#include "options.h"
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#include "debug.h"
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#include "workqueue.h"
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#include "dirsearch.h"
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#include "readsyms.h"
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#include "symtab.h"
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#include "common.h"
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#include "object.h"
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#include "layout.h"
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#include "reloc.h"
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#include "defstd.h"
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#include "plugin.h"
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#include "gc.h"
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#include "icf.h"
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#include "incremental.h"
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namespace gold
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{
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const char* program_name;
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void
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gold_exit(bool status)
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{
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if (parameters != NULL
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&& parameters->options_valid()
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&& parameters->options().has_plugins())
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parameters->options().plugins()->cleanup();
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if (!status && parameters != NULL && parameters->options_valid())
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unlink_if_ordinary(parameters->options().output_file_name());
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exit(status ? EXIT_SUCCESS : EXIT_FAILURE);
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}
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void
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gold_nomem()
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{
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// We are out of memory, so try hard to print a reasonable message.
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// Note that we don't try to translate this message, since the
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// translation process itself will require memory.
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// LEN only exists to avoid a pointless warning when write is
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// declared with warn_use_result, as when compiling with
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// -D_USE_FORTIFY on GNU/Linux. Casting to void does not appear to
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// work, at least not with gcc 4.3.0.
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ssize_t len = write(2, program_name, strlen(program_name));
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if (len >= 0)
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{
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const char* const s = ": out of memory\n";
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len = write(2, s, strlen(s));
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}
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gold_exit(false);
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}
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// Handle an unreachable case.
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void
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do_gold_unreachable(const char* filename, int lineno, const char* function)
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{
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fprintf(stderr, _("%s: internal error in %s, at %s:%d\n"),
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program_name, function, filename, lineno);
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gold_exit(false);
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}
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// This class arranges to run the functions done in the middle of the
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// link. It is just a closure.
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class Middle_runner : public Task_function_runner
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{
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public:
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Middle_runner(const General_options& options,
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const Input_objects* input_objects,
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Symbol_table* symtab,
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Layout* layout, Mapfile* mapfile)
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: options_(options), input_objects_(input_objects), symtab_(symtab),
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layout_(layout), mapfile_(mapfile)
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{ }
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void
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run(Workqueue*, const Task*);
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private:
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const General_options& options_;
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const Input_objects* input_objects_;
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Symbol_table* symtab_;
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Layout* layout_;
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Mapfile* mapfile_;
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};
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void
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Middle_runner::run(Workqueue* workqueue, const Task* task)
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{
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queue_middle_tasks(this->options_, task, this->input_objects_, this->symtab_,
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this->layout_, workqueue, this->mapfile_);
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}
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// This class arranges the tasks to process the relocs for garbage collection.
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class Gc_runner : public Task_function_runner
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{
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public:
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Gc_runner(const General_options& options,
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const Input_objects* input_objects,
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Symbol_table* symtab,
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Layout* layout, Mapfile* mapfile)
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: options_(options), input_objects_(input_objects), symtab_(symtab),
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layout_(layout), mapfile_(mapfile)
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{ }
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void
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run(Workqueue*, const Task*);
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private:
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const General_options& options_;
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const Input_objects* input_objects_;
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Symbol_table* symtab_;
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Layout* layout_;
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Mapfile* mapfile_;
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};
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void
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Gc_runner::run(Workqueue* workqueue, const Task* task)
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{
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queue_middle_gc_tasks(this->options_, task, this->input_objects_,
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this->symtab_, this->layout_, workqueue,
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this->mapfile_);
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}
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// Queue up the initial set of tasks for this link job.
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void
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queue_initial_tasks(const General_options& options,
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Dirsearch& search_path,
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const Command_line& cmdline,
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Workqueue* workqueue, Input_objects* input_objects,
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Symbol_table* symtab, Layout* layout, Mapfile* mapfile)
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{
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if (cmdline.begin() == cmdline.end())
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{
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if (options.printed_version())
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gold_exit(true);
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gold_fatal(_("no input files"));
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}
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int thread_count = options.thread_count_initial();
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if (thread_count == 0)
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thread_count = cmdline.number_of_input_files();
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workqueue->set_thread_count(thread_count);
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if (cmdline.options().incremental())
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{
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Incremental_checker incremental_checker(
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parameters->options().output_file_name(),
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layout->incremental_inputs());
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if (incremental_checker.can_incrementally_link_output_file())
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{
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// TODO: remove when incremental linking implemented.
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printf("Incremental linking might be possible "
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"(not implemented yet)\n");
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}
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// TODO: If we decide on an incremental build, fewer tasks
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// should be scheduled.
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}
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// Read the input files. We have to add the symbols to the symbol
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// table in order. We do this by creating a separate blocker for
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// each input file. We associate the blocker with the following
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// input file, to give us a convenient place to delete it.
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Task_token* this_blocker = NULL;
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for (Command_line::const_iterator p = cmdline.begin();
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p != cmdline.end();
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++p)
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{
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Task_token* next_blocker = new Task_token(true);
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next_blocker->add_blocker();
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workqueue->queue(new Read_symbols(input_objects, symtab, layout,
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&search_path, 0, mapfile, &*p, NULL,
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this_blocker, next_blocker));
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this_blocker = next_blocker;
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}
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if (options.has_plugins())
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{
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Task_token* next_blocker = new Task_token(true);
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next_blocker->add_blocker();
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workqueue->queue(new Plugin_hook(options, input_objects, symtab, layout,
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&search_path, mapfile, this_blocker,
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next_blocker));
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this_blocker = next_blocker;
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}
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if (parameters->options().relocatable()
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&& (parameters->options().gc_sections()
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|| parameters->options().icf_enabled()))
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gold_error(_("cannot mix -r with --gc-sections or --icf"));
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if (parameters->options().gc_sections()
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|| parameters->options().icf_enabled())
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{
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workqueue->queue(new Task_function(new Gc_runner(options,
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input_objects,
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symtab,
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layout,
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mapfile),
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this_blocker,
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"Task_function Gc_runner"));
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}
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else
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{
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workqueue->queue(new Task_function(new Middle_runner(options,
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input_objects,
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symtab,
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layout,
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mapfile),
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this_blocker,
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"Task_function Middle_runner"));
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}
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}
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// Queue up a set of tasks to be done before queueing the middle set
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// of tasks. This is only necessary when garbage collection
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// (--gc-sections) of unused sections is desired. The relocs are read
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// and processed here early to determine the garbage sections before the
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// relocs can be scanned in later tasks.
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void
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queue_middle_gc_tasks(const General_options& options,
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const Task* ,
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const Input_objects* input_objects,
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Symbol_table* symtab,
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Layout* layout,
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Workqueue* workqueue,
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Mapfile* mapfile)
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{
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// Read_relocs for all the objects must be done and processed to find
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// unused sections before any scanning of the relocs can take place.
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Task_token* blocker = new Task_token(true);
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Task_token* symtab_lock = new Task_token(false);
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for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
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p != input_objects->relobj_end();
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++p)
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{
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// We can read and process the relocations in any order.
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blocker->add_blocker();
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workqueue->queue(new Read_relocs(symtab, layout, *p, symtab_lock,
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blocker));
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}
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Task_token* this_blocker = new Task_token(true);
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workqueue->queue(new Task_function(new Middle_runner(options,
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input_objects,
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symtab,
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layout,
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mapfile),
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this_blocker,
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"Task_function Middle_runner"));
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}
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// Queue up the middle set of tasks. These are the tasks which run
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// after all the input objects have been found and all the symbols
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// have been read, but before we lay out the output file.
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void
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queue_middle_tasks(const General_options& options,
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const Task* task,
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const Input_objects* input_objects,
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Symbol_table* symtab,
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Layout* layout,
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Workqueue* workqueue,
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Mapfile* mapfile)
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{
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// Add any symbols named with -u options to the symbol table.
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symtab->add_undefined_symbols_from_command_line();
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// If garbage collection was chosen, relocs have been read and processed
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// at this point by pre_middle_tasks. Layout can then be done for all
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// objects.
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if (parameters->options().gc_sections())
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{
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// Find the start symbol if any.
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Symbol* start_sym;
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if (parameters->options().entry())
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start_sym = symtab->lookup(parameters->options().entry());
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else
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start_sym = symtab->lookup("_start");
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if (start_sym != NULL)
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{
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bool is_ordinary;
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unsigned int shndx = start_sym->shndx(&is_ordinary);
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if (is_ordinary)
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{
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symtab->gc()->worklist().push(
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Section_id(start_sym->object(), shndx));
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}
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}
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// Symbols named with -u should not be considered garbage.
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symtab->gc_mark_undef_symbols();
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gold_assert(symtab->gc() != NULL);
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// Do a transitive closure on all references to determine the worklist.
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symtab->gc()->do_transitive_closure();
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}
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// If identical code folding (--icf) is chosen it makes sense to do it
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// only after garbage collection (--gc-sections) as we do not want to
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// be folding sections that will be garbage.
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if (parameters->options().icf_enabled())
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{
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symtab->icf()->find_identical_sections(input_objects, symtab);
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}
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// Call Object::layout for the second time to determine the
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// output_sections for all referenced input sections. When
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// --gc-sections or --icf is turned on, Object::layout is
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// called twice. It is called the first time when the
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// symbols are added.
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if (parameters->options().gc_sections()
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|| parameters->options().icf_enabled())
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{
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for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
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p != input_objects->relobj_end();
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++p)
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{
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(*p)->layout(symtab, layout, NULL);
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}
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}
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// Layout deferred objects due to plugins.
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if (parameters->options().has_plugins())
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{
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Plugin_manager* plugins = parameters->options().plugins();
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gold_assert(plugins != NULL);
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plugins->layout_deferred_objects();
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}
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if (parameters->options().gc_sections()
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|| parameters->options().icf_enabled())
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{
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for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
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p != input_objects->relobj_end();
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++p)
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{
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// Update the value of output_section stored in rd.
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Read_relocs_data *rd = (*p)->get_relocs_data();
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for (Read_relocs_data::Relocs_list::iterator q = rd->relocs.begin();
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q != rd->relocs.end();
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++q)
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{
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q->output_section = (*p)->output_section(q->data_shndx);
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q->needs_special_offset_handling =
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(*p)->is_output_section_offset_invalid(q->data_shndx);
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}
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}
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}
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// We have to support the case of not seeing any input objects, and
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// generate an empty file. Existing builds depend on being able to
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// pass an empty archive to the linker and get an empty object file
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// out. In order to do this we need to use a default target.
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if (input_objects->number_of_input_objects() == 0)
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parameters_force_valid_target();
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int thread_count = options.thread_count_middle();
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if (thread_count == 0)
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thread_count = std::max(2, input_objects->number_of_input_objects());
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workqueue->set_thread_count(thread_count);
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// Now we have seen all the input files.
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const bool doing_static_link =
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(!input_objects->any_dynamic()
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&& !parameters->options().output_is_position_independent());
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set_parameters_doing_static_link(doing_static_link);
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if (!doing_static_link && options.is_static())
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{
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// We print out just the first .so we see; there may be others.
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gold_assert(input_objects->dynobj_begin() != input_objects->dynobj_end());
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gold_error(_("cannot mix -static with dynamic object %s"),
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(*input_objects->dynobj_begin())->name().c_str());
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}
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if (!doing_static_link && parameters->options().relocatable())
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gold_fatal(_("cannot mix -r with dynamic object %s"),
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(*input_objects->dynobj_begin())->name().c_str());
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if (!doing_static_link
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&& options.oformat_enum() != General_options::OBJECT_FORMAT_ELF)
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gold_fatal(_("cannot use non-ELF output format with dynamic object %s"),
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(*input_objects->dynobj_begin())->name().c_str());
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if (parameters->options().relocatable())
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{
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Input_objects::Relobj_iterator p = input_objects->relobj_begin();
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if (p != input_objects->relobj_end())
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{
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bool uses_split_stack = (*p)->uses_split_stack();
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for (++p; p != input_objects->relobj_end(); ++p)
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{
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if ((*p)->uses_split_stack() != uses_split_stack)
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gold_fatal(_("cannot mix split-stack '%s' and "
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"non-split-stack '%s' when using -r"),
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(*input_objects->relobj_begin())->name().c_str(),
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(*p)->name().c_str());
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}
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}
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}
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if (is_debugging_enabled(DEBUG_SCRIPT))
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layout->script_options()->print(stderr);
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// For each dynamic object, record whether we've seen all the
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// dynamic objects that it depends upon.
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input_objects->check_dynamic_dependencies();
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// See if any of the input definitions violate the One Definition Rule.
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// TODO: if this is too slow, do this as a task, rather than inline.
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symtab->detect_odr_violations(task, options.output_file_name());
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// Create any automatic note sections.
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layout->create_notes();
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// Create any output sections required by any linker script.
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layout->create_script_sections();
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// Define some sections and symbols needed for a dynamic link. This
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// handles some cases we want to see before we read the relocs.
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layout->create_initial_dynamic_sections(symtab);
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// Define symbols from any linker scripts.
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layout->define_script_symbols(symtab);
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// Attach sections to segments.
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layout->attach_sections_to_segments();
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if (!parameters->options().relocatable())
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{
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// Predefine standard symbols.
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define_standard_symbols(symtab, layout);
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// Define __start and __stop symbols for output sections where
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// appropriate.
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layout->define_section_symbols(symtab);
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}
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// Make sure we have symbols for any required group signatures.
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layout->define_group_signatures(symtab);
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Task_token* blocker = new Task_token(true);
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Task_token* symtab_lock = new Task_token(false);
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// If doing garbage collection, the relocations have already been read.
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// Otherwise, read and scan the relocations.
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if (parameters->options().gc_sections()
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|| parameters->options().icf_enabled())
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{
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for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
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p != input_objects->relobj_end();
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++p)
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{
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blocker->add_blocker();
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workqueue->queue(new Scan_relocs(symtab, layout, *p,
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(*p)->get_relocs_data(),
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symtab_lock, blocker));
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}
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}
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else
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{
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// Read the relocations of the input files. We do this to find
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// which symbols are used by relocations which require a GOT and/or
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// a PLT entry, or a COPY reloc. When we implement garbage
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// collection we will do it here by reading the relocations in a
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// breadth first search by references.
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//
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// We could also read the relocations during the first pass, and
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// mark symbols at that time. That is how the old GNU linker works.
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// Doing that is more complex, since we may later decide to discard
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// some of the sections, and thus change our minds about the types
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// of references made to the symbols.
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for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
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p != input_objects->relobj_end();
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++p)
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{
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// We can read and process the relocations in any order. But we
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// only want one task to write to the symbol table at a time.
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// So we queue up a task for each object to read the
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// relocations. That task will in turn queue a task to wait
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// until it can write to the symbol table.
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blocker->add_blocker();
|
|
workqueue->queue(new Read_relocs(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*>(¶meters->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(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.
|