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binutils-gdb/gold/gold.cc

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// gold.cc -- main linker functions
// Copyright 2006, 2007, 2008, 2009, 2010 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 (parameters->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,
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* this_blocker = NULL;
for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
p != input_objects->relobj_end();
++p)
{
Task_token* next_blocker = new Task_token(true);
next_blocker->add_blocker();
workqueue->queue(new Read_relocs(symtab, layout, *p, this_blocker,
next_blocker));
this_blocker = next_blocker;
}
// If we are given only archives in input, we have no regular
// objects and THIS_BLOCKER is NULL here. Create a dummy
// blocker here so that we can run the middle tasks immediately.
if (this_blocker == NULL)
{
gold_assert(input_objects->number_of_relobjs() == 0);
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(layout);
// 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(layout);
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)
{
Task_lock_obj<Object> tlo(task, *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());
// Do the --no-undefined-version check.
if (!parameters->options().undefined_version())
{
Script_options* so = layout->script_options();
so->version_script_info()->check_unmatched_names(symtab);
}
// 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* this_blocker = NULL;
// Allocate common symbols. We use a blocker to run this before the
// Scan_relocs tasks, because it writes to the symbol table just as
// they do.
if (parameters->options().define_common())
{
this_blocker = new Task_token(true);
this_blocker->add_blocker();
workqueue->queue(new Allocate_commons_task(symtab, layout, mapfile,
this_blocker));
}
// 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)
{
Task_token* next_blocker = new Task_token(true);
next_blocker->add_blocker();
workqueue->queue(new Scan_relocs(symtab, layout, *p,
(*p)->get_relocs_data(),
this_blocker, next_blocker));
this_blocker = next_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)
{
Task_token* next_blocker = new Task_token(true);
next_blocker->add_blocker();
workqueue->queue(new Read_relocs(symtab, layout, *p, this_blocker,
next_blocker));
this_blocker = next_blocker;
}
}
if (this_blocker == NULL)
{
if (input_objects->number_of_relobjs() == 0)
{
// If we are given only archives in input, we have no regular
// objects and THIS_BLOCKER is NULL here. Create a dummy
// blocker here so that we can run the layout task immediately.
this_blocker = new Task_token(true);
}
else
{
// If we failed to open any input files, it's possible for
// THIS_BLOCKER to be NULL here. There's no real point in
// continuing if that happens.
gold_assert(parameters->errors()->error_count() > 0);
gold_exit(false);
}
}
// 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),
this_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);
input_sections_blocker->add_blockers(input_objects->number_of_relobjs());
}
// 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);
output_sections_blocker->add_blocker();
// Use a blocker to block the final cleanup task.
Task_token* final_blocker = new Task_token(true);
// Write_symbols_task, Write_sections_task, Write_data_task,
// Relocate_tasks.
final_blocker->add_blockers(3);
final_blocker->add_blockers(input_objects->number_of_relobjs());
if (!any_postprocessing_sections)
final_blocker->add_blocker();
// Queue a task to write out the symbol table.
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.
workqueue->queue(new Write_sections_task(layout, of, output_sections_blocker,
final_blocker));
// Queue a task to write out everything else.
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)
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)
{
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.
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