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// gc.h -- garbage collection of unused sections
// Copyright 2009 Free Software Foundation, Inc.
// Written by Sriraman Tallam <tmsriram@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.
#ifndef GOLD_GC_H
#define GOLD_GC_H
#include <queue>
#include <vector>
#include "elfcpp.h"
#include "symtab.h"
#include "icf.h"
namespace gold
{
class Object;
template<int size, bool big_endian>
class Sized_relobj;
template<int sh_type, int size, bool big_endian>
class Reloc_types;
class Output_section;
class General_options;
class Layout;
typedef std::pair<Object *, unsigned int> Section_id;
class Garbage_collection
{
struct Section_id_hash
{
size_t operator()(const Section_id& loc) const
{ return reinterpret_cast<uintptr_t>(loc.first) ^ loc.second; }
};
public:
typedef Unordered_set<Section_id, Section_id_hash> Sections_reachable;
typedef std::map<Section_id, Sections_reachable> Section_ref;
typedef std::queue<Section_id> Worklist_type;
Garbage_collection()
: is_worklist_ready_(false)
{ }
// Accessor methods for the private members.
Sections_reachable&
referenced_list()
{ return referenced_list_; }
Section_ref&
section_reloc_map()
{ return this->section_reloc_map_; }
Worklist_type&
worklist()
{ return this->work_list_; }
bool
is_worklist_ready()
{ return this->is_worklist_ready_; }
void
worklist_ready()
{ this->is_worklist_ready_ = true; }
void
do_transitive_closure();
bool
is_section_garbage(Object* obj, unsigned int shndx)
{ return (this->referenced_list().find(Section_id(obj, shndx))
== this->referenced_list().end()); }
private:
Worklist_type work_list_;
bool is_worklist_ready_;
Section_ref section_reloc_map_;
Sections_reachable referenced_list_;
};
// Data to pass between successive invocations of do_layout
// in object.cc while garbage collecting. This data structure
// is filled by using the data from Read_symbols_data.
struct Symbols_data
{
// Section headers.
unsigned char* section_headers_data;
// Section names.
unsigned char* section_names_data;
// Size of section name data in bytes.
section_size_type section_names_size;
// Symbol data.
unsigned char* symbols_data;
// Size of symbol data in bytes.
section_size_type symbols_size;
// Offset of external symbols within symbol data. This structure
// sometimes contains only external symbols, in which case this will
// be zero. Sometimes it contains all symbols.
section_offset_type external_symbols_offset;
// Symbol names.
unsigned char* symbol_names_data;
// Size of symbol name data in bytes.
section_size_type symbol_names_size;
};
// This function implements the generic part of reloc
// processing to map a section to all the sections it
// references through relocs. It is called only during
// garbage collection (--gc-sections) and identical code
// folding (--icf).
template<int size, bool big_endian, typename Target_type, int sh_type,
typename Scan>
inline void
gc_process_relocs(
Symbol_table* symtab,
Layout*,
Target_type* ,
Sized_relobj<size, big_endian>* src_obj,
unsigned int src_indx,
const unsigned char* prelocs,
size_t reloc_count,
Output_section*,
bool ,
size_t local_count,
const unsigned char* plocal_syms)
{
Object *dst_obj;
unsigned int dst_indx;
typedef typename Reloc_types<sh_type, size, big_endian>::Reloc Reltype;
const int reloc_size = Reloc_types<sh_type, size, big_endian>::reloc_size;
const int sym_size = elfcpp::Elf_sizes<size>::sym_size;
std::vector<Section_id>* secvec = NULL;
std::vector<Symbol*>* symvec = NULL;
std::vector<std::pair<long long, long long> >* addendvec = NULL;
bool is_icf_tracked = false;
if (parameters->options().icf_enabled()
&& is_prefix_of(".text.", (src_obj)->section_name(src_indx).c_str()))
{
is_icf_tracked = true;
Section_id src_id(src_obj, src_indx);
secvec = &symtab->icf()->section_reloc_list()[src_id];
symvec = &symtab->icf()->symbol_reloc_list()[src_id];
addendvec = &symtab->icf()->addend_reloc_list()[src_id];
}
for (size_t i = 0; i < reloc_count; ++i, prelocs += reloc_size)
{
Reltype reloc(prelocs);
typename elfcpp::Elf_types<size>::Elf_WXword r_info = reloc.get_r_info();
unsigned int r_sym = elfcpp::elf_r_sym<size>(r_info);
typename elfcpp::Elf_types<size>::Elf_Swxword addend =
Reloc_types<sh_type, size, big_endian>::get_reloc_addend_noerror(&reloc);
if (r_sym < local_count)
{
gold_assert(plocal_syms != NULL);
typename elfcpp::Sym<size, big_endian> lsym(plocal_syms
+ r_sym * sym_size);
unsigned int shndx = lsym.get_st_shndx();
bool is_ordinary;
shndx = src_obj->adjust_sym_shndx(r_sym, shndx, &is_ordinary);
if (!is_ordinary)
continue;
dst_obj = src_obj;
dst_indx = shndx;
Section_id dst_id(dst_obj, dst_indx);
if (is_icf_tracked)
{
(*secvec).push_back(dst_id);
(*symvec).push_back(NULL);
long long symvalue = static_cast<long long>(lsym.get_st_value());
(*addendvec).push_back(std::make_pair(symvalue,
static_cast<long long>(addend)));
}
if (shndx == src_indx)
continue;
}
else
{
Symbol* gsym = src_obj->global_symbol(r_sym);
gold_assert(gsym != NULL);
if (gsym->is_forwarder())
gsym = symtab->resolve_forwards(gsym);
if (gsym->source() != Symbol::FROM_OBJECT)
continue;
bool is_ordinary;
dst_obj = gsym->object();
dst_indx = gsym->shndx(&is_ordinary);
if (!is_ordinary)
continue;
Section_id dst_id(dst_obj, dst_indx);
if (is_icf_tracked)
{
(*secvec).push_back(dst_id);
(*symvec).push_back(gsym);
Sized_symbol<size>* sized_gsym =
static_cast<Sized_symbol<size>* >(gsym);
long long symvalue =
static_cast<long long>(sized_gsym->value());
(*addendvec).push_back(std::make_pair(symvalue,
static_cast<long long>(addend)));
}
}
if (parameters->options().gc_sections())
{
Section_id src_id(src_obj, src_indx);
Section_id dst_id(dst_obj, dst_indx);
Garbage_collection::Section_ref::iterator map_it;
map_it = symtab->gc()->section_reloc_map().find(src_id);
if (map_it == symtab->gc()->section_reloc_map().end())
{
symtab->gc()->section_reloc_map()[src_id].insert(dst_id);
}
else
{
Garbage_collection::Sections_reachable& v(map_it->second);
v.insert(dst_id);
}
}
}
return;
}
} // End of namespace gold.
#endif
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