old-cross-binutils/gold/gold.cc
2008-02-07 07:33:46 +00:00

378 lines
12 KiB
C++

// gold.cc -- main linker functions
// Copyright 2006, 2007, 2008 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 "target-select.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"
namespace gold
{
const char* program_name;
void
gold_exit(bool status)
{
if (!status && parameters != NULL && parameters->options_valid())
unlink_if_ordinary(parameters->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.
write(2, program_name, strlen(program_name));
const char* const s = ": out of memory\n";
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)
: options_(options), input_objects_(input_objects), symtab_(symtab),
layout_(layout)
{ }
void
run(Workqueue*, const Task*);
private:
const General_options& options_;
const Input_objects* input_objects_;
Symbol_table* symtab_;
Layout* layout_;
};
void
Middle_runner::run(Workqueue* workqueue, const Task* task)
{
queue_middle_tasks(this->options_, task, this->input_objects_, this->symtab_,
this->layout_, workqueue);
}
// 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)
{
if (cmdline.begin() == cmdline.end())
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);
// 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(options, input_objects, symtab, layout,
&search_path, &*p, NULL, this_blocker,
next_blocker));
this_blocker = next_blocker;
}
workqueue->queue(new Task_function(new Middle_runner(options,
input_objects,
symtab,
layout),
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)
{
// 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)
{
// The GOLD_xx macros are defined by the configure script.
Target* target = select_target(elfcpp::GOLD_DEFAULT_MACHINE,
GOLD_DEFAULT_SIZE,
GOLD_DEFAULT_BIG_ENDIAN,
0, 0);
gold_assert(target != NULL);
set_parameters_target(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->output_is_shared());
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_error(_("cannot mix -static with dynamic object %s"),
(*input_objects->dynobj_begin())->name().c_str());
}
if (!doing_static_link && parameters->output_is_object())
gold_error(_("cannot mix -r with dynamic object %s"),
(*input_objects->dynobj_begin())->name().c_str());
if (!doing_static_link
&& options.output_format() != General_options::OUTPUT_FORMAT_ELF)
gold_fatal(_("cannot use non-ELF output format with dynamic object %s"),
(*input_objects->dynobj_begin())->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());
// 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);
if (!parameters->output_is_object())
{
// 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);
// 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.
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. 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.
// FIXME: We should have an option to do this even for a relocatable
// link.
if (!parameters->output_is_object())
{
blocker->add_blocker();
workqueue->queue(new Allocate_commons_task(options, symtab, layout,
symtab_lock, blocker));
}
// When all those tasks are complete, we can start laying out the
// output file.
workqueue->queue(new Task_function(new Layout_task_runner(options,
input_objects,
symtab,
layout),
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(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.