1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
|
// 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"
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(
const General_options& ,
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()
&& 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
|
