// gc.h -- garbage collection of unused sections
-// Copyright 2009 Free Software Foundation, Inc.
+// Copyright 2009, 2010 Free Software Foundation, Inc.
// Written by Sriraman Tallam <tmsriram@google.com>.
// This file is part of gold.
#include "elfcpp.h"
#include "symtab.h"
+#include "object.h"
#include "icf.h"
namespace gold
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;
+ // This maps the name of the section which can be represented as a C
+ // identifier (cident) to the list of sections that have that name.
+ // Different object files can have cident sections with the same name.
+ typedef std::map<std::string, Sections_reachable> Cident_section_map;
Garbage_collection()
: is_worklist_ready_(false)
is_section_garbage(Object* obj, unsigned int shndx)
{ return (this->referenced_list().find(Section_id(obj, shndx))
== this->referenced_list().end()); }
+
+ Cident_section_map*
+ cident_sections()
+ { return &cident_sections_; }
+
+ void
+ add_cident_section(std::string section_name,
+ Section_id secn)
+ { this->cident_sections_[section_name].insert(secn); }
+
+ // Add a reference from the SRC_SHNDX-th section of SRC_OBJECT to
+ // DST_SHNDX-th section of DST_OBJECT.
+ void
+ add_reference(Object* src_object, unsigned int src_shndx,
+ Object* dst_object, unsigned int dst_shndx)
+ {
+ Section_id src_id(src_object, src_shndx);
+ Section_id dst_id(dst_object, dst_shndx);
+ Section_ref::iterator p = this->section_reloc_map_.find(src_id);
+ if (p == this->section_reloc_map_.end())
+ this->section_reloc_map_[src_id].insert(dst_id);
+ else
+ p->second.insert(dst_id);
+ }
+
private:
Worklist_type work_list_;
bool is_worklist_ready_;
Section_ref section_reloc_map_;
Sections_reachable referenced_list_;
+ Cident_section_map cident_sections_;
};
// Data to pass between successive invocations of do_layout
typename Scan>
inline void
gc_process_relocs(
- const General_options& ,
Symbol_table* symtab,
Layout*,
- Target_type* ,
+ Target_type* target,
Sized_relobj<size, big_endian>* src_obj,
unsigned int src_indx,
const unsigned char* prelocs,
size_t reloc_count,
Output_section*,
- bool ,
+ bool,
size_t local_count,
const unsigned char* plocal_syms)
{
Object *dst_obj;
unsigned int dst_indx;
+ Scan scan;
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;
+ Icf::Sections_reachable_info* secvec = NULL;
+ Icf::Symbol_info* symvec = NULL;
+ Icf::Addend_info* addendvec = NULL;
+ Icf::Offset_info* offsetvec = NULL;
bool is_icf_tracked = false;
+ const char* cident_section_name = NULL;
+
+ std::string src_section_name = (parameters->options().icf_enabled()
+ ? src_obj->section_name(src_indx)
+ : "");
+
+ bool check_section_for_function_pointers = false;
if (parameters->options().icf_enabled()
- && is_prefix_of(".text.", (src_obj)->section_name(src_indx).c_str()))
+ && is_section_foldable_candidate(src_section_name.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];
+ Icf::Reloc_info* reloc_info =
+ &symtab->icf()->reloc_info_list()[src_id];
+ secvec = &reloc_info->section_info;
+ symvec = &reloc_info->symbol_info;
+ addendvec = &reloc_info->addend_info;
+ offsetvec = &reloc_info->offset_info;
}
+ check_section_for_function_pointers =
+ symtab->icf()->check_section_for_function_pointers(src_section_name,
+ target);
+
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);
+ unsigned int r_type = elfcpp::elf_r_type<size>(r_info);
typename elfcpp::Elf_types<size>::Elf_Swxword addend =
Reloc_types<sh_type, size, big_endian>::get_reloc_addend_noerror(&reloc);
long long symvalue = static_cast<long long>(lsym.get_st_value());
(*addendvec).push_back(std::make_pair(symvalue,
static_cast<long long>(addend)));
+ uint64_t reloc_offset =
+ convert_to_section_size_type(reloc.get_r_offset());
+ (*offsetvec).push_back(reloc_offset);
}
+
+ // When doing safe folding, check to see if this relocation is that
+ // of a function pointer being taken.
+ if (check_section_for_function_pointers
+ && lsym.get_st_type() != elfcpp::STT_OBJECT
+ && scan.local_reloc_may_be_function_pointer(symtab, NULL, NULL,
+ src_obj, src_indx,
+ NULL, reloc, r_type,
+ lsym))
+ symtab->icf()->set_section_has_function_pointers(
+ src_obj, lsym.get_st_shndx());
+
if (shndx == src_indx)
continue;
}
bool is_ordinary;
dst_obj = gsym->object();
dst_indx = gsym->shndx(&is_ordinary);
+ Section_id dst_id(dst_obj, dst_indx);
+
+ // When doing safe folding, check to see if this relocation is that
+ // of a function pointer being taken.
+ if (check_section_for_function_pointers
+ && gsym->type() != elfcpp::STT_OBJECT
+ && (!is_ordinary
+ || scan.global_reloc_may_be_function_pointer(
+ symtab, NULL, NULL, src_obj, src_indx, NULL, reloc,
+ r_type, gsym)))
+ symtab->icf()->set_section_has_function_pointers(dst_obj, dst_indx);
+
if (!is_ordinary)
continue;
- Section_id dst_id(dst_obj, dst_indx);
+
+ // If the symbol name matches '__start_XXX' then the section with
+ // the C identifier like name 'XXX' should not be garbage collected.
+ // A similar treatment to symbols with the name '__stop_XXX'.
+ if (is_prefix_of(cident_section_start_prefix, gsym->name()))
+ {
+ cident_section_name = (gsym->name()
+ + strlen(cident_section_start_prefix));
+ }
+ else if (is_prefix_of(cident_section_stop_prefix, gsym->name()))
+ {
+ cident_section_name = (gsym->name()
+ + strlen(cident_section_stop_prefix));
+ }
if (is_icf_tracked)
{
(*secvec).push_back(dst_id);
static_cast<long long>(sized_gsym->value());
(*addendvec).push_back(std::make_pair(symvalue,
static_cast<long long>(addend)));
- }
+ uint64_t reloc_offset =
+ convert_to_section_size_type(reloc.get_r_offset());
+ (*offsetvec).push_back(reloc_offset);
+ }
}
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
+ symtab->gc()->add_reference(src_obj, src_indx, dst_obj, dst_indx);
+ if (cident_section_name != NULL)
{
- Garbage_collection::Sections_reachable& v(map_it->second);
- v.insert(dst_id);
+ Garbage_collection::Cident_section_map::iterator ele =
+ symtab->gc()->cident_sections()->find(std::string(cident_section_name));
+ if (ele == symtab->gc()->cident_sections()->end())
+ continue;
+ Section_id src_id(src_obj, src_indx);
+ Garbage_collection::Sections_reachable&
+ v(symtab->gc()->section_reloc_map()[src_id]);
+ Garbage_collection::Sections_reachable& cident_secn(ele->second);
+ for (Garbage_collection::Sections_reachable::iterator it_v
+ = cident_secn.begin();
+ it_v != cident_secn.end();
+ ++it_v)
+ {
+ v.insert(*it_v);
+ }
}
}
}