File: copy-relocs.cc

package info (click to toggle)
binutils 2.28-5
  • links: PTS, VCS
  • area: main
  • in suites: stretch
  • size: 271,848 kB
  • sloc: ansic: 1,419,727; asm: 623,424; cpp: 125,042; exp: 64,226; makefile: 56,536; sh: 21,234; lisp: 15,206; yacc: 14,889; perl: 2,111; ada: 1,681; lex: 1,645; pascal: 1,438; cs: 879; sed: 195; python: 154; xml: 95; awk: 25
file content (292 lines) | stat: -rw-r--r-- 8,902 bytes parent folder | download
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
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
// copy-relocs.cc -- handle COPY relocations for gold.

// Copyright (C) 2006-2017 Free Software Foundation, Inc.
// Written by Ian Lance Taylor <iant@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.

#include "gold.h"

#include "symtab.h"
#include "copy-relocs.h"

namespace gold
{

// Copy_relocs methods.

// Handle a relocation against a symbol which may force us to generate
// a COPY reloc.

template<int sh_type, int size, bool big_endian>
void
Copy_relocs<sh_type, size, big_endian>::copy_reloc(
    Symbol_table* symtab,
    Layout* layout,
    Sized_symbol<size>* sym,
    Sized_relobj_file<size, big_endian>* object,
    unsigned int shndx,
    Output_section* output_section,
    unsigned int r_type,
    typename elfcpp::Elf_types<size>::Elf_Addr r_offset,
    typename elfcpp::Elf_types<size>::Elf_Swxword r_addend,
    Output_data_reloc<sh_type, true, size, big_endian>* reloc_section)
{
  if (this->need_copy_reloc(sym, object, shndx))
    this->make_copy_reloc(symtab, layout, sym, object, reloc_section);
  else
    {
      // We may not need a COPY relocation.  Save this relocation to
      // possibly be emitted later.
      this->save(sym, object, shndx, output_section,
		 r_type, r_offset, r_addend);
    }
}

// Return whether we need a COPY reloc for a relocation against SYM.
// The relocation is begin applied to section SHNDX in OBJECT.

template<int sh_type, int size, bool big_endian>
bool
Copy_relocs<sh_type, size, big_endian>::need_copy_reloc(
    Sized_symbol<size>* sym,
    Sized_relobj_file<size, big_endian>* object,
    unsigned int shndx) const
{
  if (!parameters->options().copyreloc())
    return false;

  if (sym->symsize() == 0)
    return false;

  // If this is a readonly section, then we need a COPY reloc.
  // Otherwise we can use a dynamic reloc.  Note that calling
  // section_flags here can be slow, as the information is not cached;
  // fortunately we shouldn't see too many potential COPY relocs.
  if ((object->section_flags(shndx) & elfcpp::SHF_WRITE) == 0)
    return true;

  return false;
}

// Emit a COPY relocation for SYM.

template<int sh_type, int size, bool big_endian>
void
Copy_relocs<sh_type, size, big_endian>::emit_copy_reloc(
    Symbol_table* symtab,
    Sized_symbol<size>* sym,
    Output_data* posd,
    off_t offset,
    Output_data_reloc<sh_type, true, size, big_endian>* reloc_section)
{
  // Define the symbol as being copied.
  symtab->define_with_copy_reloc(sym, posd, offset);

  // Add the COPY relocation to the dynamic reloc section.
  reloc_section->add_global_generic(sym, this->copy_reloc_type_, posd,
				    offset, 0);
}

// Make a COPY relocation for SYM and emit it.

template<int sh_type, int size, bool big_endian>
void
Copy_relocs<sh_type, size, big_endian>::make_copy_reloc(
    Symbol_table* symtab,
    Layout* layout,
    Sized_symbol<size>* sym,
    Sized_relobj_file<size, big_endian>* object,
    Output_data_reloc<sh_type, true, size, big_endian>* reloc_section)
{
  // We should not be here if -z nocopyreloc is given.
  gold_assert(parameters->options().copyreloc());

  gold_assert(sym->is_from_dynobj());

  // The symbol must not have protected visibility.
  if (sym->is_protected())
    {
      gold_error(_("%s: cannot make copy relocation for "
		   "protected symbol '%s', defined in %s"),
		 object->name().c_str(),
		 sym->name(),
		 sym->object()->name().c_str());
    }

  typename elfcpp::Elf_types<size>::Elf_WXword symsize = sym->symsize();

  // There is no defined way to determine the required alignment of
  // the symbol.  We know that the symbol is defined in a dynamic
  // object.  We start with the alignment of the section in which it
  // is defined; presumably we do not require an alignment larger than
  // that.  Then we reduce that alignment if the symbol is not aligned
  // within the section.
  bool is_ordinary;
  unsigned int shndx = sym->shndx(&is_ordinary);
  gold_assert(is_ordinary);
  typename elfcpp::Elf_types<size>::Elf_WXword addralign;
  bool is_readonly = false;

  {
    // Lock the object so we can read from it.  This is only called
    // single-threaded from scan_relocs, so it is OK to lock.
    // Unfortunately we have no way to pass in a Task token.
    const Task* dummy_task = reinterpret_cast<const Task*>(-1);
    Object* obj = sym->object();
    Task_lock_obj<Object> tl(dummy_task, obj);
    addralign = obj->section_addralign(shndx);
    if (parameters->options().relro())
      {
	if ((obj->section_flags(shndx) & elfcpp::SHF_WRITE) == 0)
	  is_readonly = true;
	else
	  {
	    // Symbols in .data.rel.ro should also be treated as read-only.
	    if (obj->section_name(shndx) == ".data.rel.ro")
	      is_readonly = true;
	  }
      }
  }

  typename Sized_symbol<size>::Value_type value = sym->value();
  while ((value & (addralign - 1)) != 0)
    addralign >>= 1;

  // Mark the dynamic object as needed for the --as-needed option.
  sym->object()->set_is_needed();

  Output_data_space* dynbss;

  if (is_readonly)
    {
      if (this->dynrelro_ == NULL)
	{
	  this->dynrelro_ = new Output_data_space(addralign, "** dynrelro");
	  layout->add_output_section_data(".data.rel.ro",
					  elfcpp::SHT_PROGBITS,
					  elfcpp::SHF_ALLOC | elfcpp::SHF_WRITE,
					  this->dynrelro_, ORDER_RELRO, false);
	}
      dynbss = this->dynrelro_;
    }
  else
    {
      if (this->dynbss_ == NULL)
	{
	  this->dynbss_ = new Output_data_space(addralign, "** dynbss");
	  layout->add_output_section_data(".bss",
					  elfcpp::SHT_NOBITS,
					  elfcpp::SHF_ALLOC | elfcpp::SHF_WRITE,
					  this->dynbss_, ORDER_BSS, false);
	}
      dynbss = this->dynbss_;
    }

  if (addralign > dynbss->addralign())
    dynbss->set_space_alignment(addralign);

  section_size_type dynbss_size =
    convert_to_section_size_type(dynbss->current_data_size());
  dynbss_size = align_address(dynbss_size, addralign);
  section_size_type offset = dynbss_size;
  dynbss->set_current_data_size(dynbss_size + symsize);

  this->emit_copy_reloc(symtab, sym, dynbss, offset, reloc_section);
}

// Save a relocation to possibly be emitted later.

template<int sh_type, int size, bool big_endian>
void
Copy_relocs<sh_type, size, big_endian>::save(
    Symbol* sym,
    Sized_relobj_file<size, big_endian>* object,
    unsigned int shndx,
    Output_section* output_section,
    unsigned int r_type,
    typename elfcpp::Elf_types<size>::Elf_Addr r_offset,
    typename elfcpp::Elf_types<size>::Elf_Swxword r_addend)
{
  this->entries_.push_back(Copy_reloc_entry(sym, r_type, object, shndx,
					    output_section, r_offset,
					    r_addend));
}

// Emit any saved relocs.

template<int sh_type, int size, bool big_endian>
void
Copy_relocs<sh_type, size, big_endian>::emit(
    Output_data_reloc<sh_type, true, size, big_endian>* reloc_section)
{
  for (typename Copy_reloc_entries::iterator p = this->entries_.begin();
       p != this->entries_.end();
       ++p)
    {
      Copy_reloc_entry& entry = *p;

      // If the symbol is no longer defined in a dynamic object, then we
      // emitted a COPY relocation, and we do not want to emit this
      // dynamic relocation.
      if (entry.sym_->is_from_dynobj())
        reloc_section->add_global_generic(entry.sym_, entry.reloc_type_,
                                          entry.output_section_, entry.relobj_,
                                          entry.shndx_, entry.address_,
                                          entry.addend_);
    }

  // We no longer need the saved information.
  this->entries_.clear();
}

// Instantiate the templates we need.

#ifdef HAVE_TARGET_32_LITTLE
template
class Copy_relocs<elfcpp::SHT_REL, 32, false>;

template
class Copy_relocs<elfcpp::SHT_RELA, 32, false>;
#endif

#ifdef HAVE_TARGET_32_BIG
template
class Copy_relocs<elfcpp::SHT_REL, 32, true>;

template
class Copy_relocs<elfcpp::SHT_RELA, 32, true>;
#endif

#ifdef HAVE_TARGET_64_LITTLE
template
class Copy_relocs<elfcpp::SHT_REL, 64, false>;

template
class Copy_relocs<elfcpp::SHT_RELA, 64, false>;
#endif

#ifdef HAVE_TARGET_64_BIG
template
class Copy_relocs<elfcpp::SHT_REL, 64, true>;

template
class Copy_relocs<elfcpp::SHT_RELA, 64, true>;
#endif

} // End namespace gold.