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2009-01-20 Sriraman Tallam <tmsriram@google.com>

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* Makefile.am (CCFILES): Add gc.cc.
	(HFILES): Add gc.h.
	* Makefile.in: Regenerate.
	* gold.cc (Gc_runner): New class.
	(queue_initial_tasks): Call garbage collection related tasks
	when corresponding options are invoked.
	(queue_middle_gc_tasks): New function.
	(queue_middle_tasks): Reorder tasks to allow relocs to be read and
	processed early before laying out sections during garbage collection.
	* gold.h (queue_middle_gc_tasks): New function.
	(is_prefix_of): Move from "layout.cc".
	* i386.cc (Target_i386::gc_process_relocs): New function.
	* layout.cc (is_prefix_of): Remove. Move to "gold.h"
	* main.cc (main): Create object of class "Garbage_collection".
	* object.cc (Relobj::copy_symbols_data): New function.
	(Relobj::is_section_name_included): New function.
	(Sized_relobj::do_layout): Allow this function to be called twice
	during garbage collection and defer layout of section during the
	first call.
	* object.h (Relobj::get_symbols_data): New function.
	(Relobj::is_section_name_included): New function.
	(Relobj::copy_symbols_data): New function.
	(Relobj::set_symbols_data): New function.
	(Relobj::get_relocs_data): New function.
	(Relobj::set_relocs_data): New function.
	(Relobj::is_output_section_offset_invalid): New pure virtual function.
	(Relobj::gc_process_relocs): New function.
	(Relobj::do_gc_process_relocs): New pure virtual function.
	(Relobj::sd_): New data member.
	(Sized_relobj::is_output_section_offset_invalid): New function.
	(Sized_relobj::do_gc_process_relocs): New function.
	* options.h (General_options::gc_sections): Modify to not be a no-op.
	(General_options::print_gc_sections): New option.
	* plugin.cc (Plugin_finish::run): Remove function call to
	Plugin_manager::layout_deferred_objects.  Move it to "gold.cc".
	* powerpc.cc (Target_powerpc::gc_process_relocs): New function.
	* reloc.cc (Read_relocs::run): Add task to process relocs and
	determine unreferenced sections when doing garbage collection.
	(Gc_process_relocs): New class.
	(Sized_relobj::do_gc_process_relocs): New function.
	(Sized_relobj::do_scan_relocs): Don't try to scan the relocs for
	sections that are garbage collected.
	* reloc.h (Gc_process_relocs): New class.
	* sparc.cc (Target_sparc::gc_process_relocs): New function.
	* symtab.cc (Symbol::should_add_dynsym_entry): Do not add entries for
	symbols whose corresponding sections are garbage collected.
	(Symbol_table::Symbol_table): Add new parameter for the garbage
	collection object.
	(Symbol_table::gc_mark_undef_symbols): New function.
	(Symbol_table::gc_mark_symbol_for_shlib): New function.
	(Symbol_table::gc_mark_dyn_syms): New function.
	(Symbol_table::resolve): Do not treat symbols seen in dynamic objects
	as garbage.
	(Symbol_table::add_from_object): Likewise.
	(Symbol_table::add_from_relobj): When building shared objects, do not
	treat externally visible symbols as garbage.
	(Symbol_table::sized_finalize_symbol): Do not check dynamic symbol
	table information for static and relocatable links.
	* symtab.h (Symbol_table::set_gc): New function.
	(Symbol_table::gc): New function.
	(Symbol_table::gc_mark_undef_symbols): New function.
	(Symbol_table::gc_mark_symbol_for_shlib): New function.
	(Symbol_table::gc_mark_dyn_syms): New function.
	(Symbol_table::gc_): New data member.
	* target.h (Sized_target::gc_process_relocs): New pure virtual
	function.
	* x86_64.cc (Target_x86_64::gc_process_relocs): New function.
	* testsuite/testfile.cc (Target_test::gc_process_relocs): New function.
This commit is contained in:
Sriraman Tallam 2009-01-28 02:25:33 +00:00
parent 7df3ce4769
commit 6d03d481a0
23 changed files with 1497 additions and 140 deletions
Download patch file Download diff file Expand all files Collapse all files

230
gold/gold.cc
View file

@ -1,6 +1,6 @@
// gold.cc -- main linker functions
// Copyright 2006, 2007, 2008 Free Software Foundation, Inc.
// Copyright 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
// Written by Ian Lance Taylor <iant@google.com>.
// This file is part of gold.
@ -122,6 +122,38 @@ Middle_runner::run(Workqueue* workqueue, const Task* task)
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
@ -166,13 +198,69 @@ queue_initial_tasks(const General_options& options,
this_blocker = next_blocker;
}
if (parameters->options().relocatable()
&& parameters->options().gc_sections())
gold_error(_("cannot mix -r with garbage collection"));
if (parameters->options().gc_sections())
{
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"));
input_objects,
symtab,
layout,
mapfile),
this_blocker,
"Task_function Middle_runner"));
}
// Queue up the middle set of tasks. These are the tasks which run
@ -188,6 +276,70 @@ queue_middle_tasks(const General_options& options,
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();
// Call do_layout again to determine the output_sections for all
// referenced input sections.
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())
{
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
@ -240,9 +392,6 @@ queue_middle_tasks(const General_options& options,
// Define symbols from any linker scripts.
layout->define_script_symbols(symtab);
// Add any symbols named with -u options to the symbol table.
symtab->add_undefined_symbols_from_command_line();
// Attach sections to segments.
layout->attach_sections_to_segments();
@ -259,31 +408,48 @@ queue_middle_tasks(const General_options& options,
// 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)
// If doing garbage collection, the relocations have already been read.
// Otherwise, read and scan the relocations.
if (parameters->options().gc_sections())
{
// 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));
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