aboutsummaryrefslogtreecommitdiff
path: root/gold/target.h
blob: 218d9f757bbdb9d18737afa353c0e17d061c2ae6 (plain)
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
293
294
295
// target.h -- target support for gold   -*- C++ -*-

// Copyright 2006, 2007 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.

// The abstract class Target is the interface for target specific
// support.  It defines abstract methods which each target must
// implement.  Typically there will be one target per processor, but
// in some cases it may be necessary to have subclasses.

// For speed and consistency we want to use inline functions to handle
// relocation processing.  So besides implementations of the abstract
// methods, each target is expected to define a template
// specialization of the relocation functions.

#ifndef GOLD_TARGET_H
#define GOLD_TARGET_H

#include "elfcpp.h"

namespace gold
{

class General_options;
class Object;
template<int size, bool big_endian>
class Sized_relobj;
template<int size, bool big_endian>
class Relocate_info;
class Symbol;
template<int size>
class Sized_symbol;
class Symbol_table;
class Output_section;

// The abstract class for target specific handling.

class Target
{
 public:
  virtual ~Target()
  { }

  // Return the bit size that this target implements.  This should
  // return 32 or 64.
  int
  get_size() const
  { return this->pti_->size; }

  // Return whether this target is big-endian.
  bool
  is_big_endian() const
  { return this->pti_->is_big_endian; }

  // Machine code to store in e_machine field of ELF header.
  elfcpp::EM
  machine_code() const
  { return this->pti_->machine_code; }

  // Whether this target has a specific make_symbol function.
  bool
  has_make_symbol() const
  { return this->pti_->has_make_symbol; }

  // Whether this target has a specific resolve function.
  bool
  has_resolve() const
  { return this->pti_->has_resolve; }

  // Whether this target has a specific code fill function.
  bool
  has_code_fill() const
  { return this->pti_->has_code_fill; }

  // Return the default name of the dynamic linker.
  const char*
  dynamic_linker() const
  { return this->pti_->dynamic_linker; }

  // Return the default address to use for the text segment.
  uint64_t
  default_text_segment_address() const
  { return this->pti_->default_text_segment_address; }

  // Return the ABI specified page size.
  uint64_t
  abi_pagesize() const
  { return this->pti_->abi_pagesize; }

  // Return the common page size used on actual systems.
  uint64_t
  common_pagesize() const
  { return this->pti_->common_pagesize; }

  // If we see some object files with .note.GNU-stack sections, and
  // some objects files without them, this returns whether we should
  // consider the object files without them to imply that the stack
  // should be executable.
  bool
  is_default_stack_executable() const
  { return this->pti_->is_default_stack_executable; }

  // This is called to tell the target to complete any sections it is
  // handling.  After this all sections must have their final size.
  void
  finalize_sections(Layout* layout)
  { return this->do_finalize_sections(layout); }

  // Return the value to use for a global symbol which needs a special
  // value in the dynamic symbol table.  This will only be called if
  // the backend first calls symbol->set_needs_dynsym_value().
  uint64_t
  dynsym_value(const Symbol* sym) const
  { return this->do_dynsym_value(sym); }

  // Return a string to use to fill out a code section.  This is
  // basically one or more NOPS which must fill out the specified
  // length in bytes.
  std::string
  code_fill(section_size_type length)
  { return this->do_code_fill(length); }

  // Return whether SYM is known to be defined by the ABI.  This is
  // used to avoid inappropriate warnings about undefined symbols.
  bool
  is_defined_by_abi(Symbol* sym) const
  { return this->do_is_defined_by_abi(sym); }

 protected:
  // This struct holds the constant information for a child class.  We
  // use a struct to avoid the overhead of virtual function calls for
  // simple information.
  struct Target_info
  {
    // Address size (32 or 64).
    int size;
    // Whether the target is big endian.
    bool is_big_endian;
    // The code to store in the e_machine field of the ELF header.
    elfcpp::EM machine_code;
    // Whether this target has a specific make_symbol function.
    bool has_make_symbol;
    // Whether this target has a specific resolve function.
    bool has_resolve;
    // Whether this target has a specific code fill function.
    bool has_code_fill;
    // Whether an object file with no .note.GNU-stack sections implies
    // that the stack should be executable.
    bool is_default_stack_executable;
    // The default dynamic linker name.
    const char* dynamic_linker;
    // The default text segment address.
    uint64_t default_text_segment_address;
    // The ABI specified page size.
    uint64_t abi_pagesize;
    // The common page size used by actual implementations.
    uint64_t common_pagesize;
  };

  Target(const Target_info* pti)
    : pti_(pti)
  { }

  // Virtual function which may be implemented by the child class.
  virtual void
  do_finalize_sections(Layout*)
  { }

  // Virtual function which may be implemented by the child class.
  virtual uint64_t
  do_dynsym_value(const Symbol*) const
  { gold_unreachable(); }

  // Virtual function which must be implemented by the child class if
  // needed.
  virtual std::string
  do_code_fill(section_size_type)
  { gold_unreachable(); }

  // Virtual function which may be implemented by the child class.
  virtual bool
  do_is_defined_by_abi(Symbol*) const
  { return false; }

 private:
  Target(const Target&);
  Target& operator=(const Target&);

  // The target information.
  const Target_info* pti_;
};

// The abstract class for a specific size and endianness of target.
// Each actual target implementation class should derive from an
// instantiation of Sized_target.

template<int size, bool big_endian>
class Sized_target : public Target
{
 public:
  // Make a new symbol table entry for the target.  This should be
  // overridden by a target which needs additional information in the
  // symbol table.  This will only be called if has_make_symbol()
  // returns true.
  virtual Sized_symbol<size>*
  make_symbol() const
  { gold_unreachable(); }

  // Resolve a symbol for the target.  This should be overridden by a
  // target which needs to take special action.  TO is the
  // pre-existing symbol.  SYM is the new symbol, seen in OBJECT.
  // VERSION is the version of SYM.  This will only be called if
  // has_resolve() returns true.
  virtual void
  resolve(Symbol*, const elfcpp::Sym<size, big_endian>&, Object*,
	  const char*)
  { gold_unreachable(); }

  // Scan the relocs for a section, and record any information
  // required for the symbol.  OPTIONS is the command line options.
  // SYMTAB is the symbol table.  OBJECT is the object in which the
  // section appears.  DATA_SHNDX is the section index that these
  // relocs apply to.  SH_TYPE is the type of the relocation section,
  // SHT_REL or SHT_RELA.  PRELOCS points to the relocation data.
  // RELOC_COUNT is the number of relocs.  LOCAL_SYMBOL_COUNT is the
  // number of local symbols.  OUTPUT_SECTION is the output section.
  // NEEDS_SPECIAL_OFFSET_HANDLING is true if offsets to the output
  // sections are not mapped as usual.  PLOCAL_SYMBOLS points to the
  // local symbol data from OBJECT.  GLOBAL_SYMBOLS is the array of
  // pointers to the global symbol table from OBJECT.
  virtual void
  scan_relocs(const General_options& options,
	      Symbol_table* symtab,
	      Layout* layout,
	      Sized_relobj<size, big_endian>* object,
	      unsigned int data_shndx,
	      unsigned int sh_type,
	      const unsigned char* prelocs,
	      size_t reloc_count,
	      Output_section* output_section,
	      bool needs_special_offset_handling,
	      size_t local_symbol_count,
	      const unsigned char* plocal_symbols) = 0;

  // Relocate section data.  SH_TYPE is the type of the relocation
  // section, SHT_REL or SHT_RELA.  PRELOCS points to the relocation
  // information.  RELOC_COUNT is the number of relocs.
  // OUTPUT_SECTION is the output section.
  // NEEDS_SPECIAL_OFFSET_HANDLING is true if offsets must be mapped
  // to correspond to the output section.  VIEW is a view into the
  // output file holding the section contents, VIEW_ADDRESS is the
  // virtual address of the view, and VIEW_SIZE is the size of the
  // view.  If NEEDS_SPECIAL_OFFSET_HANDLING is true, the VIEW_xx
  // parameters refer to the complete output section data, not just
  // the input section data.
  virtual void
  relocate_section(const Relocate_info<size, big_endian>*,
		   unsigned int sh_type,
		   const unsigned char* prelocs,
		   size_t reloc_count,
		   Output_section* output_section,
		   bool needs_special_offset_handling,
		   unsigned char* view,
		   typename elfcpp::Elf_types<size>::Elf_Addr view_address,
		   section_size_type view_size) = 0;

 protected:
  Sized_target(const Target::Target_info* pti)
    : Target(pti)
  {
    gold_assert(pti->size == size);
    gold_assert(pti->is_big_endian ? big_endian : !big_endian);
  }
};

} // End namespace gold.

#endif // !defined(GOLD_TARGET_H)