1 // gc.h -- garbage collection of unused sections
3 // Copyright 2009 Free Software Foundation, Inc.
4 // Written by Sriraman Tallam <tmsriram@google.com>.
6 // This file is part of gold.
8 // This program is free software; you can redistribute it and/or modify
9 // it under the terms of the GNU General Public License as published by
10 // the Free Software Foundation; either version 3 of the License, or
11 // (at your option) any later version.
13 // This program is distributed in the hope that it will be useful,
14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 // GNU General Public License for more details.
18 // You should have received a copy of the GNU General Public License
19 // along with this program; if not, write to the Free Software
20 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
21 // MA 02110-1301, USA.
38 template<int size
, bool big_endian
>
41 template<int sh_type
, int size
, bool big_endian
>
45 class General_options
;
48 typedef std::pair
<Object
*, unsigned int> Section_id
;
50 class Garbage_collection
52 struct Section_id_hash
54 size_t operator()(const Section_id
& loc
) const
55 { return reinterpret_cast<uintptr_t>(loc
.first
) ^ loc
.second
; }
60 typedef Unordered_set
<Section_id
, Section_id_hash
> Sections_reachable
;
61 typedef std::map
<Section_id
, Sections_reachable
> Section_ref
;
62 typedef std::queue
<Section_id
> Worklist_type
;
65 : is_worklist_ready_(false)
68 // Accessor methods for the private members.
72 { return referenced_list_
; }
76 { return this->section_reloc_map_
; }
80 { return this->work_list_
; }
84 { return this->is_worklist_ready_
; }
88 { this->is_worklist_ready_
= true; }
91 do_transitive_closure();
94 is_section_garbage(Object
* obj
, unsigned int shndx
)
95 { return (this->referenced_list().find(Section_id(obj
, shndx
))
96 == this->referenced_list().end()); }
99 Worklist_type work_list_
;
100 bool is_worklist_ready_
;
101 Section_ref section_reloc_map_
;
102 Sections_reachable referenced_list_
;
105 // Data to pass between successive invocations of do_layout
106 // in object.cc while garbage collecting. This data structure
107 // is filled by using the data from Read_symbols_data.
112 unsigned char* section_headers_data
;
114 unsigned char* section_names_data
;
115 // Size of section name data in bytes.
116 section_size_type section_names_size
;
118 unsigned char* symbols_data
;
119 // Size of symbol data in bytes.
120 section_size_type symbols_size
;
121 // Offset of external symbols within symbol data. This structure
122 // sometimes contains only external symbols, in which case this will
123 // be zero. Sometimes it contains all symbols.
124 section_offset_type external_symbols_offset
;
126 unsigned char* symbol_names_data
;
127 // Size of symbol name data in bytes.
128 section_size_type symbol_names_size
;
131 // This function implements the generic part of reloc
132 // processing to map a section to all the sections it
133 // references through relocs. It is called only during
134 // garbage collection (--gc-sections) and identical code
137 template<int size
, bool big_endian
, typename Target_type
, int sh_type
,
141 const General_options
& ,
142 Symbol_table
* symtab
,
145 Sized_relobj
<size
, big_endian
>* src_obj
,
146 unsigned int src_indx
,
147 const unsigned char* prelocs
,
152 const unsigned char* plocal_syms
)
155 unsigned int dst_indx
;
157 typedef typename Reloc_types
<sh_type
, size
, big_endian
>::Reloc Reltype
;
158 const int reloc_size
= Reloc_types
<sh_type
, size
, big_endian
>::reloc_size
;
159 const int sym_size
= elfcpp::Elf_sizes
<size
>::sym_size
;
161 std::vector
<Section_id
>* secvec
= NULL
;
162 std::vector
<Symbol
*>* symvec
= NULL
;
163 std::vector
<std::pair
<long long, long long> >* addendvec
= NULL
;
164 bool is_icf_tracked
= false;
166 if (parameters
->options().icf()
167 && is_prefix_of(".text.", (src_obj
)->section_name(src_indx
).c_str()))
169 is_icf_tracked
= true;
170 Section_id
src_id(src_obj
, src_indx
);
171 secvec
= &symtab
->icf()->section_reloc_list()[src_id
];
172 symvec
= &symtab
->icf()->symbol_reloc_list()[src_id
];
173 addendvec
= &symtab
->icf()->addend_reloc_list()[src_id
];
176 for (size_t i
= 0; i
< reloc_count
; ++i
, prelocs
+= reloc_size
)
178 Reltype
reloc(prelocs
);
179 typename
elfcpp::Elf_types
<size
>::Elf_WXword r_info
= reloc
.get_r_info();
180 unsigned int r_sym
= elfcpp::elf_r_sym
<size
>(r_info
);
181 typename
elfcpp::Elf_types
<size
>::Elf_Swxword addend
=
182 Reloc_types
<sh_type
, size
, big_endian
>::get_reloc_addend_noerror(&reloc
);
184 if (r_sym
< local_count
)
186 gold_assert(plocal_syms
!= NULL
);
187 typename
elfcpp::Sym
<size
, big_endian
> lsym(plocal_syms
189 unsigned int shndx
= lsym
.get_st_shndx();
191 shndx
= src_obj
->adjust_sym_shndx(r_sym
, shndx
, &is_ordinary
);
196 Section_id
dst_id(dst_obj
, dst_indx
);
199 (*secvec
).push_back(dst_id
);
200 (*symvec
).push_back(NULL
);
201 long long symvalue
= static_cast<long long>(lsym
.get_st_value());
202 (*addendvec
).push_back(std::make_pair(symvalue
,
203 static_cast<long long>(addend
)));
205 if (shndx
== src_indx
)
210 Symbol
* gsym
= src_obj
->global_symbol(r_sym
);
211 gold_assert(gsym
!= NULL
);
212 if (gsym
->is_forwarder())
213 gsym
= symtab
->resolve_forwards(gsym
);
214 if (gsym
->source() != Symbol::FROM_OBJECT
)
217 dst_obj
= gsym
->object();
218 dst_indx
= gsym
->shndx(&is_ordinary
);
221 Section_id
dst_id(dst_obj
, dst_indx
);
224 (*secvec
).push_back(dst_id
);
225 (*symvec
).push_back(gsym
);
226 Sized_symbol
<size
>* sized_gsym
=
227 static_cast<Sized_symbol
<size
>* >(gsym
);
229 static_cast<long long>(sized_gsym
->value());
230 (*addendvec
).push_back(std::make_pair(symvalue
,
231 static_cast<long long>(addend
)));
234 if (parameters
->options().gc_sections())
236 Section_id
src_id(src_obj
, src_indx
);
237 Section_id
dst_id(dst_obj
, dst_indx
);
238 Garbage_collection::Section_ref::iterator map_it
;
239 map_it
= symtab
->gc()->section_reloc_map().find(src_id
);
240 if (map_it
== symtab
->gc()->section_reloc_map().end())
242 symtab
->gc()->section_reloc_map()[src_id
].insert(dst_id
);
246 Garbage_collection::Sections_reachable
& v(map_it
->second
);
254 } // End of namespace gold.