aboutsummaryrefslogtreecommitdiff
path: root/gold/target.h
blob: 85af8d37c6706201f8a557cc5ac5ba3d57a2f3a9 (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
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
// target.h -- target support for gold   -*- C++ -*-

// Copyright 2006, 2007, 2008, 2009, 2010 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"
#include "options.h"
#include "parameters.h"
#include "debug.h"

namespace gold
{

class Object;
class Relobj;
template<int size, bool big_endian>
class Sized_relobj;
class Relocatable_relocs;
template<int size, bool big_endian>
class Relocate_info;
class Reloc_symbol_changes;
class Symbol;
template<int size>
class Sized_symbol;
class Symbol_table;
class Output_data;
class Output_section;
class Input_objects;
class Task;

// The abstract class for target specific handling.

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

  // Virtual function which is set to return true by a target if
  // it can use relocation types to determine if a function's
  // pointer is taken.
  virtual bool
  can_check_for_function_pointers() const
  { return false; }

  // This function is used in ICF (icf.cc).  This is set to true by
  // the target if a relocation to a merged section can be processed
  // to retrieve the contents of the merged section.
  virtual bool
  can_icf_inline_merge_sections () const
  { return false; }

  // Whether a section called SECTION_NAME may have function pointers to
  // sections not eligible for safe ICF folding.
  virtual bool
  section_may_have_icf_unsafe_pointers(const char* section_name) const
  {
    // We recognize sections for normal vtables, construction vtables and
    // EH frames.
    return (!is_prefix_of(".rodata._ZTV", section_name)
	    && !is_prefix_of(".data.rel.ro._ZTV", section_name)
	    && !is_prefix_of(".rodata._ZTC", section_name)
	    && !is_prefix_of(".data.rel.ro._ZTC", section_name)
	    && !is_prefix_of(".eh_frame", section_name));
  }

  // 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; }

  // Processor specific flags to store in e_flags field of ELF header.
  elfcpp::Elf_Word
  processor_specific_flags() const
  { return this->processor_specific_flags_; }

  // Whether processor specific flags are set at least once.
  bool
  are_processor_specific_flags_set() const
  { return this->are_processor_specific_flags_set_; }

  // 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
  {
    if (parameters->options().max_page_size() > 0)
      return parameters->options().max_page_size();
    else
      return this->pti_->abi_pagesize;
  }

  // Return the common page size used on actual systems.
  uint64_t
  common_pagesize() const
  {
    if (parameters->options().common_page_size() > 0)
      return std::min(parameters->options().common_page_size(),
		      this->abi_pagesize());
    else
      return std::min(this->pti_->common_pagesize,
		      this->abi_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; }

  // Return a character which may appear as a prefix for a wrap
  // symbol.  If this character appears, we strip it when checking for
  // wrapping and add it back when forming the final symbol name.
  // This should be '\0' if not special prefix is required, which is
  // the normal case.
  char
  wrap_char() const
  { return this->pti_->wrap_char; }

  // Return the special section index which indicates a small common
  // symbol.  This will return SHN_UNDEF if there are no small common
  // symbols.
  elfcpp::Elf_Half
  small_common_shndx() const
  { return this->pti_->small_common_shndx; }

  // Return values to add to the section flags for the section holding
  // small common symbols.
  elfcpp::Elf_Xword
  small_common_section_flags() const
  {
    gold_assert(this->pti_->small_common_shndx != elfcpp::SHN_UNDEF);
    return this->pti_->small_common_section_flags;
  }

  // Return the special section index which indicates a large common
  // symbol.  This will return SHN_UNDEF if there are no large common
  // symbols.
  elfcpp::Elf_Half
  large_common_shndx() const
  { return this->pti_->large_common_shndx; }

  // Return values to add to the section flags for the section holding
  // large common symbols.
  elfcpp::Elf_Xword
  large_common_section_flags() const
  {
    gold_assert(this->pti_->large_common_shndx != elfcpp::SHN_UNDEF);
    return this->pti_->large_common_section_flags;
  }

  // This hook is called when an output section is created.
  void
  new_output_section(Output_section* os) const
  { this->do_new_output_section(os); }

  // 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, const Input_objects* input_objects,
		    Symbol_table* symtab)
  { return this->do_finalize_sections(layout, input_objects, symtab); }

  // 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) const
  { 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(const Symbol* sym) const
  { return this->do_is_defined_by_abi(sym); }

  // Adjust the output file header before it is written out.  VIEW
  // points to the header in external form.  LEN is the length.
  void
  adjust_elf_header(unsigned char* view, int len) const
  { return this->do_adjust_elf_header(view, len); }

  // Return whether NAME is a local label name.  This is used to implement the
  // --discard-locals options.
  bool
  is_local_label_name(const char* name) const
  { return this->do_is_local_label_name(name); }

  // Get the symbol index to use for a target specific reloc.
  unsigned int
  reloc_symbol_index(void* arg, unsigned int type) const
  { return this->do_reloc_symbol_index(arg, type); }

  // Get the addend to use for a target specific reloc.
  uint64_t
  reloc_addend(void* arg, unsigned int type, uint64_t addend) const
  { return this->do_reloc_addend(arg, type, addend); }

  // Return the PLT section to use for a global symbol.  This is used
  // for STT_GNU_IFUNC symbols.
  Output_data*
  plt_section_for_global(const Symbol* sym) const
  { return this->do_plt_section_for_global(sym); }

  // Return the PLT section to use for a local symbol.  This is used
  // for STT_GNU_IFUNC symbols.
  Output_data*
  plt_section_for_local(const Relobj* object, unsigned int symndx) const
  { return this->do_plt_section_for_local(object, symndx); }

  // Return true if a reference to SYM from a reloc of type R_TYPE
  // means that the current function may call an object compiled
  // without -fsplit-stack.  SYM is known to be defined in an object
  // compiled without -fsplit-stack.
  bool
  is_call_to_non_split(const Symbol* sym, unsigned int r_type) const
  { return this->do_is_call_to_non_split(sym, r_type); }

  // A function starts at OFFSET in section SHNDX in OBJECT.  That
  // function was compiled with -fsplit-stack, but it refers to a
  // function which was compiled without -fsplit-stack.  VIEW is a
  // modifiable view of the section; VIEW_SIZE is the size of the
  // view.  The target has to adjust the function so that it allocates
  // enough stack.
  void
  calls_non_split(Relobj* object, unsigned int shndx,
		  section_offset_type fnoffset, section_size_type fnsize,
		  unsigned char* view, section_size_type view_size,
		  std::string* from, std::string* to) const
  {
    this->do_calls_non_split(object, shndx, fnoffset, fnsize, view, view_size,
			     from, to);
  }

  // Make an ELF object.
  template<int size, bool big_endian>
  Object*
  make_elf_object(const std::string& name, Input_file* input_file,
		  off_t offset, const elfcpp::Ehdr<size, big_endian>& ehdr)
  { return this->do_make_elf_object(name, input_file, offset, ehdr); }

  // Make an output section.
  Output_section*
  make_output_section(const char* name, elfcpp::Elf_Word type,
		      elfcpp::Elf_Xword flags)
  { return this->do_make_output_section(name, type, flags); }

  // Return true if target wants to perform relaxation.
  bool
  may_relax() const
  {
    // Run the dummy relaxation pass twice if relaxation debugging is enabled.
    if (is_debugging_enabled(DEBUG_RELAXATION))
      return true;

     return this->do_may_relax();
  }

  // Perform a relaxation pass.  Return true if layout may be changed.
  bool
  relax(int pass, const Input_objects* input_objects, Symbol_table* symtab,
	Layout* layout, const Task* task)
  {
    // Run the dummy relaxation pass twice if relaxation debugging is enabled.
    if (is_debugging_enabled(DEBUG_RELAXATION))
      return pass < 2;

    return this->do_relax(pass, input_objects, symtab, layout, task);
  } 

  // Return the target-specific name of attributes section.  This is
  // NULL if a target does not use attributes section or if it uses
  // the default section name ".gnu.attributes".
  const char*
  attributes_section() const
  { return this->pti_->attributes_section; }

  // Return the vendor name of vendor attributes.
  const char*
  attributes_vendor() const
  { return this->pti_->attributes_vendor; }

  // Whether a section called NAME is an attribute section.
  bool
  is_attributes_section(const char* name) const
  {
    return ((this->pti_->attributes_section != NULL
	     && strcmp(name, this->pti_->attributes_section) == 0)
	    || strcmp(name, ".gnu.attributes") == 0); 
  }

  // Return a bit mask of argument types for attribute with TAG.
  int
  attribute_arg_type(int tag) const
  { return this->do_attribute_arg_type(tag); }

  // Return the attribute tag of the position NUM in the list of fixed
  // attributes.  Normally there is no reordering and
  // attributes_order(NUM) == NUM.
  int
  attributes_order(int num) const
  { return this->do_attributes_order(num); }

  // When a target is selected as the default target, we call this method,
  // which may be used for expensive, target-specific initialization.
  void
  select_as_default_target()
  { this->do_select_as_default_target(); } 

 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;
    // Prefix character to strip when checking for wrapping.
    char wrap_char;
    // 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;
    // The special section index for small common symbols; SHN_UNDEF
    // if none.
    elfcpp::Elf_Half small_common_shndx;
    // The special section index for large common symbols; SHN_UNDEF
    // if none.
    elfcpp::Elf_Half large_common_shndx;
    // Section flags for small common section.
    elfcpp::Elf_Xword small_common_section_flags;
    // Section flags for large common section.
    elfcpp::Elf_Xword large_common_section_flags;
    // Name of attributes section if it is not ".gnu.attributes".
    const char* attributes_section;
    // Vendor name of vendor attributes.
    const char* attributes_vendor;
  };

  Target(const Target_info* pti)
    : pti_(pti), processor_specific_flags_(0),
      are_processor_specific_flags_set_(false)
  { }

  // Virtual function which may be implemented by the child class.
  virtual void
  do_new_output_section(Output_section*) const
  { }

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

  // 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) const
  { gold_unreachable(); }

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

  // Adjust the output file header before it is written out.  VIEW
  // points to the header in external form.  LEN is the length, and
  // will be one of the values of elfcpp::Elf_sizes<size>::ehdr_size.
  // By default, we do nothing.
  virtual void
  do_adjust_elf_header(unsigned char*, int) const
  { }

  // Virtual function which may be overridden by the child class.
  virtual bool
  do_is_local_label_name(const char*) const;

  // Virtual function that must be overridden by a target which uses
  // target specific relocations.
  virtual unsigned int
  do_reloc_symbol_index(void*, unsigned int) const
  { gold_unreachable(); }

  // Virtual function that must be overridden by a target which uses
  // target specific relocations.
  virtual uint64_t
  do_reloc_addend(void*, unsigned int, uint64_t) const
  { gold_unreachable(); }

  // Virtual functions that must be overridden by a target that uses
  // STT_GNU_IFUNC symbols.
  virtual Output_data*
  do_plt_section_for_global(const Symbol*) const
  { gold_unreachable(); }

  virtual Output_data*
  do_plt_section_for_local(const Relobj*, unsigned int) const
  { gold_unreachable(); }

  // Virtual function which may be overridden by the child class.  The
  // default implementation is that any function not defined by the
  // ABI is a call to a non-split function.
  virtual bool
  do_is_call_to_non_split(const Symbol* sym, unsigned int) const;

  // Virtual function which may be overridden by the child class.
  virtual void
  do_calls_non_split(Relobj* object, unsigned int, section_offset_type,
		     section_size_type, unsigned char*, section_size_type,
		     std::string*, std::string*) const;

  // make_elf_object hooks.  There are four versions of these for
  // different address sizes and endianness.

  // Set processor specific flags.
  void
  set_processor_specific_flags(elfcpp::Elf_Word flags)
  {
    this->processor_specific_flags_ = flags;
    this->are_processor_specific_flags_set_ = true;
  }
  
#ifdef HAVE_TARGET_32_LITTLE
  // Virtual functions which may be overridden by the child class.
  virtual Object*
  do_make_elf_object(const std::string&, Input_file*, off_t,
		     const elfcpp::Ehdr<32, false>&);
#endif

#ifdef HAVE_TARGET_32_BIG
  // Virtual functions which may be overridden by the child class.
  virtual Object*
  do_make_elf_object(const std::string&, Input_file*, off_t,
		     const elfcpp::Ehdr<32, true>&);
#endif

#ifdef HAVE_TARGET_64_LITTLE
  // Virtual functions which may be overridden by the child class.
  virtual Object*
  do_make_elf_object(const std::string&, Input_file*, off_t,
		     const elfcpp::Ehdr<64, false>& ehdr);
#endif

#ifdef HAVE_TARGET_64_BIG
  // Virtual functions which may be overridden by the child class.
  virtual Object*
  do_make_elf_object(const std::string& name, Input_file* input_file,
		     off_t offset, const elfcpp::Ehdr<64, true>& ehdr);
#endif

  // Virtual functions which may be overridden by the child class.
  virtual Output_section*
  do_make_output_section(const char* name, elfcpp::Elf_Word type,
			 elfcpp::Elf_Xword flags);

  // Virtual function which may be overridden by the child class.
  virtual bool
  do_may_relax() const
  { return parameters->options().relax(); }

  // Virtual function which may be overridden by the child class.
  virtual bool
  do_relax(int, const Input_objects*, Symbol_table*, Layout*, const Task*)
  { return false; }

  // A function for targets to call.  Return whether BYTES/LEN matches
  // VIEW/VIEW_SIZE at OFFSET.
  bool
  match_view(const unsigned char* view, section_size_type view_size,
	     section_offset_type offset, const char* bytes, size_t len) const;

  // Set the contents of a VIEW/VIEW_SIZE to nops starting at OFFSET
  // for LEN bytes.
  void
  set_view_to_nop(unsigned char* view, section_size_type view_size,
		  section_offset_type offset, size_t len) const;

  // This must be overridden by the child class if it has target-specific
  // attributes subsection in the attribute section. 
  virtual int
  do_attribute_arg_type(int) const
  { gold_unreachable(); }

  // This may be overridden by the child class.
  virtual int
  do_attributes_order(int num) const
  { return num; }

  // This may be overridden by the child class.
  virtual void
  do_select_as_default_target()
  { }

 private:
  // The implementations of the four do_make_elf_object virtual functions are
  // almost identical except for their sizes and endianness.  We use a template.
  // for their implementations.
  template<int size, bool big_endian>
  inline Object*
  do_make_elf_object_implementation(const std::string&, Input_file*, off_t,
				    const elfcpp::Ehdr<size, big_endian>&);

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

  // The target information.
  const Target_info* pti_;
  // Processor-specific flags.
  elfcpp::Elf_Word processor_specific_flags_;
  // Whether the processor-specific flags are set at least once.
  bool are_processor_specific_flags_set_;
};

// 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(); }

  // Process the relocs for a section, and record information of the
  // mapping from source to destination sections. This mapping is later
  // used to determine unreferenced garbage sections. This procedure is
  // only called during garbage collection.
  virtual void
  gc_process_relocs(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;

  // Scan the relocs for a section, and record any information
  // required for the symbol.  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(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,
		   const Reloc_symbol_changes*) = 0;

  // Scan the relocs during a relocatable link.  The parameters are
  // like scan_relocs, with an additional Relocatable_relocs
  // parameter, used to record the disposition of the relocs.
  virtual void
  scan_relocatable_relocs(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,
			  Relocatable_relocs*) = 0;

  // Relocate a section during a relocatable link.  The parameters are
  // like relocate_section, with additional parameters for the view of
  // the output reloc section.
  virtual void
  relocate_for_relocatable(const Relocate_info<size, big_endian>*,
			   unsigned int sh_type,
			   const unsigned char* prelocs,
			   size_t reloc_count,
			   Output_section* output_section,
			   off_t offset_in_output_section,
			   const Relocatable_relocs*,
			   unsigned char* view,
			   typename elfcpp::Elf_types<size>::Elf_Addr
			     view_address,
			   section_size_type view_size,
			   unsigned char* reloc_view,
			   section_size_type reloc_view_size) = 0;
 
  // Perform target-specific processing in a relocatable link.  This is
  // only used if we use the relocation strategy RELOC_SPECIAL.
  // RELINFO points to a Relocation_info structure. SH_TYPE is the relocation
  // section type. PRELOC_IN points to the original relocation.  RELNUM is
  // the index number of the relocation in the relocation section.
  // OUTPUT_SECTION is the output section to which the relocation is applied.
  // OFFSET_IN_OUTPUT_SECTION is the offset of the relocation input section
  // within the output section.  VIEW points to the output view of the
  // output section.  VIEW_ADDRESS is output address of the view.  VIEW_SIZE
  // is the size of the output view and PRELOC_OUT points to the new
  // relocation in the output object.
  //
  // A target only needs to override this if the generic code in
  // target-reloc.h cannot handle some relocation types.

  virtual void
  relocate_special_relocatable(const Relocate_info<size, big_endian>*
				/*relinfo */,
			       unsigned int /* sh_type */,
			       const unsigned char* /* preloc_in */,
			       size_t /* relnum */,
			       Output_section* /* output_section */,
			       off_t /* offset_in_output_section */,
			       unsigned char* /* view */,
			       typename elfcpp::Elf_types<size>::Elf_Addr
				 /* view_address */,
			       section_size_type /* view_size */,
			       unsigned char* /* preloc_out*/)
  { gold_unreachable(); }
 
  // Return the number of entries in the GOT.  This is only used for
  // laying out the incremental link info sections.  A target needs
  // to implement this to support incremental linking.

  virtual unsigned int
  got_entry_count() const
  { gold_unreachable(); }

  // Return the number of entries in the PLT.  This is only used for
  // laying out the incremental link info sections.  A target needs
  // to implement this to support incremental linking.

  virtual unsigned int
  plt_entry_count() const
  { gold_unreachable(); }

  // Return the offset of the first non-reserved PLT entry.  This is
  // only used for laying out the incremental link info sections.
  // A target needs to implement this to support incremental linking.

  virtual unsigned int
  first_plt_entry_offset() const
  { gold_unreachable(); }

  // Return the size of each PLT entry.  This is only used for
  // laying out the incremental link info sections.  A target needs
  // to implement this to support incremental linking.

  virtual unsigned int
  plt_entry_size() const
  { gold_unreachable(); }

 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)