1 // symtab.h -- the gold symbol table -*- C++ -*-
2
3 // Copyright (C) 2006-2023 Free Software Foundation, Inc.
4 // Written by Ian Lance Taylor <iant@google.com>.
5
6 // This file is part of gold.
7
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.
12
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.
17
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.
22
23 // Symbol_table
24 // The symbol table.
25
26 #ifndef GOLD_SYMTAB_H
27 #define GOLD_SYMTAB_H
28
29 #include <string>
30 #include <utility>
31 #include <vector>
32
33 #include "elfcpp.h"
34 #include "parameters.h"
35 #include "stringpool.h"
36 #include "object.h"
37
38 namespace gold
39 {
40
41 class Mapfile;
42 class Object;
43 class Relobj;
44 template<int size, bool big_endian>
45 class Sized_relobj_file;
46 template<int size, bool big_endian>
47 class Sized_pluginobj;
48 class Dynobj;
49 template<int size, bool big_endian>
50 class Sized_dynobj;
51 template<int size, bool big_endian>
52 class Sized_incrobj;
53 class Versions;
54 class Version_script_info;
55 class Input_objects;
56 class Output_data;
57 class Output_section;
58 class Output_segment;
59 class Output_file;
60 class Output_symtab_xindex;
61 class Garbage_collection;
62 class Icf;
63
64 // The base class of an entry in the symbol table. The symbol table
65 // can have a lot of entries, so we don't want this class too big.
66 // Size dependent fields can be found in the template class
67 // Sized_symbol. Targets may support their own derived classes.
68
69 class Symbol
70 {
71 public:
72 // Because we want the class to be small, we don't use any virtual
73 // functions. But because symbols can be defined in different
74 // places, we need to classify them. This enum is the different
75 // sources of symbols we support.
76 enum Source
77 {
78 // Symbol defined in a relocatable or dynamic input file--this is
79 // the most common case.
80 FROM_OBJECT,
81 // Symbol defined in an Output_data, a special section created by
82 // the target.
83 IN_OUTPUT_DATA,
84 // Symbol defined in an Output_segment, with no associated
85 // section.
86 IN_OUTPUT_SEGMENT,
87 // Symbol value is constant.
88 IS_CONSTANT,
89 // Symbol is undefined.
90 IS_UNDEFINED
91 };
92
93 // When the source is IN_OUTPUT_SEGMENT, we need to describe what
94 // the offset means.
95 enum Segment_offset_base
96 {
97 // From the start of the segment.
98 SEGMENT_START,
99 // From the end of the segment.
100 SEGMENT_END,
101 // From the filesz of the segment--i.e., after the loaded bytes
102 // but before the bytes which are allocated but zeroed.
103 SEGMENT_BSS
104 };
105
106 // Return the symbol name.
107 const char*
108 name() const
109 { return this->name_; }
110
111 // Return the (ANSI) demangled version of the name, if
112 // parameters.demangle() is true. Otherwise, return the name. This
113 // is intended to be used only for logging errors, so it's not
114 // super-efficient.
115 std::string
116 demangled_name() const;
117
118 // Return the symbol version. This will return NULL for an
119 // unversioned symbol.
120 const char*
121 version() const
122 { return this->version_; }
123
124 void
125 clear_version()
126 { this->version_ = NULL; }
127
128 // Return whether this version is the default for this symbol name
129 // (eg, "foo@@V2" is a default version; "foo@V1" is not). Only
130 // meaningful for versioned symbols.
131 bool
132 is_default() const
133 {
134 gold_assert(this->version_ != NULL);
135 return this->is_def_;
136 }
137
138 // Set that this version is the default for this symbol name.
139 void
140 set_is_default()
141 { this->is_def_ = true; }
142
143 // Set that this version is not the default for this symbol name.
144 void
145 set_is_not_default()
146 { this->is_def_ = false; }
147
148 // Return the symbol's name as name@version (or name@@version).
149 std::string
150 versioned_name() const;
151
152 // Return the symbol source.
153 Source
154 source() const
155 { return this->source_; }
156
157 // Return the object with which this symbol is associated.
158 Object*
159 object() const
160 {
161 gold_assert(this->source_ == FROM_OBJECT);
162 return this->u1_.object;
163 }
164
165 // Return the index of the section in the input relocatable or
166 // dynamic object file.
167 unsigned int
168 shndx(bool* is_ordinary) const
169 {
170 gold_assert(this->source_ == FROM_OBJECT);
171 *is_ordinary = this->is_ordinary_shndx_;
172 return this->u2_.shndx;
173 }
174
175 // Return the output data section with which this symbol is
176 // associated, if the symbol was specially defined with respect to
177 // an output data section.
178 Output_data*
179 output_data() const
180 {
181 gold_assert(this->source_ == IN_OUTPUT_DATA);
182 return this->u1_.output_data;
183 }
184
185 // If this symbol was defined with respect to an output data
186 // section, return whether the value is an offset from end.
187 bool
188 offset_is_from_end() const
189 {
190 gold_assert(this->source_ == IN_OUTPUT_DATA);
191 return this->u2_.offset_is_from_end;
192 }
193
194 // Return the output segment with which this symbol is associated,
195 // if the symbol was specially defined with respect to an output
196 // segment.
197 Output_segment*
198 output_segment() const
199 {
200 gold_assert(this->source_ == IN_OUTPUT_SEGMENT);
201 return this->u1_.output_segment;
202 }
203
204 // If this symbol was defined with respect to an output segment,
205 // return the offset base.
206 Segment_offset_base
207 offset_base() const
208 {
209 gold_assert(this->source_ == IN_OUTPUT_SEGMENT);
210 return this->u2_.offset_base;
211 }
212
213 // Return the symbol binding.
214 elfcpp::STB
215 binding() const
216 { return this->binding_; }
217
218 // Return the symbol type.
219 elfcpp::STT
220 type() const
221 { return this->type_; }
222
223 // Set the symbol type.
224 void
225 set_type(elfcpp::STT type)
226 { this->type_ = type; }
227
228 // Return true for function symbol.
229 bool
230 is_func() const
231 {
232 return (this->type_ == elfcpp::STT_FUNC
233 || this->type_ == elfcpp::STT_GNU_IFUNC);
234 }
235
236 // Return the symbol visibility.
237 elfcpp::STV
238 visibility() const
239 { return this->visibility_; }
240
241 // Set the visibility.
242 void
243 set_visibility(elfcpp::STV visibility)
244 { this->visibility_ = visibility; }
245
246 // Override symbol visibility.
247 void
248 override_visibility(elfcpp::STV);
249
250 // Set whether the symbol was originally a weak undef or a regular undef
251 // when resolved by a dynamic def or by a special symbol.
252 inline void
253 set_undef_binding(elfcpp::STB bind)
254 {
255 if (!this->undef_binding_set_ || this->undef_binding_weak_)
256 {
257 this->undef_binding_weak_ = bind == elfcpp::STB_WEAK;
258 this->undef_binding_set_ = true;
259 }
260 }
261
262 // Return TRUE if a weak undef was resolved by a dynamic def or
263 // by a special symbol.
264 inline bool
265 is_undef_binding_weak() const
266 { return this->undef_binding_weak_; }
267
268 // Return the non-visibility part of the st_other field.
269 unsigned char
270 nonvis() const
271 { return this->nonvis_; }
272
273 // Set the non-visibility part of the st_other field.
274 void
275 set_nonvis(unsigned int nonvis)
276 { this->nonvis_ = nonvis; }
277
278 // Return whether this symbol is a forwarder. This will never be
279 // true of a symbol found in the hash table, but may be true of
280 // symbol pointers attached to object files.
281 bool
282 is_forwarder() const
283 { return this->is_forwarder_; }
284
285 // Mark this symbol as a forwarder.
286 void
287 set_forwarder()
288 { this->is_forwarder_ = true; }
289
290 // Return whether this symbol has an alias in the weak aliases table
291 // in Symbol_table.
292 bool
293 has_alias() const
294 { return this->has_alias_; }
295
296 // Mark this symbol as having an alias.
297 void
298 set_has_alias()
299 { this->has_alias_ = true; }
300
301 // Return whether this symbol needs an entry in the dynamic symbol
302 // table.
303 bool
304 needs_dynsym_entry() const
305 {
306 return (this->needs_dynsym_entry_
307 || (this->in_reg()
308 && this->in_dyn()
309 && this->is_externally_visible()));
310 }
311
312 // Mark this symbol as needing an entry in the dynamic symbol table.
313 void
314 set_needs_dynsym_entry()
315 { this->needs_dynsym_entry_ = true; }
316
317 // Return whether this symbol should be added to the dynamic symbol
318 // table.
319 bool
320 should_add_dynsym_entry(Symbol_table*) const;
321
322 // Return whether this symbol has been seen in a regular object.
323 bool
324 in_reg() const
325 { return this->in_reg_; }
326
327 // Mark this symbol as having been seen in a regular object.
328 void
329 set_in_reg()
330 { this->in_reg_ = true; }
331
332 // Forget this symbol was seen in a regular object.
333 void
334 clear_in_reg()
335 { this->in_reg_ = false; }
336
337 // Return whether this symbol has been seen in a dynamic object.
338 bool
339 in_dyn() const
340 { return this->in_dyn_; }
341
342 // Mark this symbol as having been seen in a dynamic object.
343 void
344 set_in_dyn()
345 { this->in_dyn_ = true; }
346
347 // Return whether this symbol is defined in a dynamic object.
348 bool
349 from_dyn() const
350 { return this->source_ == FROM_OBJECT && this->object()->is_dynamic(); }
351
352 // Return whether this symbol has been seen in a real ELF object.
353 // (IN_REG will return TRUE if the symbol has been seen in either
354 // a real ELF object or an object claimed by a plugin.)
355 bool
356 in_real_elf() const
357 { return this->in_real_elf_; }
358
359 // Mark this symbol as having been seen in a real ELF object.
360 void
361 set_in_real_elf()
362 { this->in_real_elf_ = true; }
363
364 // Return whether this symbol was defined in a section that was
365 // discarded from the link. This is used to control some error
366 // reporting.
367 bool
368 is_defined_in_discarded_section() const
369 { return this->is_defined_in_discarded_section_; }
370
371 // Mark this symbol as having been defined in a discarded section.
372 void
373 set_is_defined_in_discarded_section()
374 { this->is_defined_in_discarded_section_ = true; }
375
376 // Return the index of this symbol in the output file symbol table.
377 // A value of -1U means that this symbol is not going into the
378 // output file. This starts out as zero, and is set to a non-zero
379 // value by Symbol_table::finalize. It is an error to ask for the
380 // symbol table index before it has been set.
381 unsigned int
382 symtab_index() const
383 {
384 gold_assert(this->symtab_index_ != 0);
385 return this->symtab_index_;
386 }
387
388 // Set the index of the symbol in the output file symbol table.
389 void
390 set_symtab_index(unsigned int index)
391 {
392 gold_assert(index != 0);
393 this->symtab_index_ = index;
394 }
395
396 // Return whether this symbol already has an index in the output
397 // file symbol table.
398 bool
399 has_symtab_index() const
400 { return this->symtab_index_ != 0; }
401
402 // Return the index of this symbol in the dynamic symbol table. A
403 // value of -1U means that this symbol is not going into the dynamic
404 // symbol table. This starts out as zero, and is set to a non-zero
405 // during Layout::finalize. It is an error to ask for the dynamic
406 // symbol table index before it has been set.
407 unsigned int
408 dynsym_index() const
409 {
410 gold_assert(this->dynsym_index_ != 0);
411 return this->dynsym_index_;
412 }
413
414 // Set the index of the symbol in the dynamic symbol table.
415 void
416 set_dynsym_index(unsigned int index)
417 {
418 gold_assert(index != 0);
419 this->dynsym_index_ = index;
420 }
421
422 // Return whether this symbol already has an index in the dynamic
423 // symbol table.
424 bool
425 has_dynsym_index() const
426 { return this->dynsym_index_ != 0; }
427
428 // Return whether this symbol has an entry in the GOT section.
429 // For a TLS symbol, this GOT entry will hold its tp-relative offset.
430 bool
431 has_got_offset(unsigned int got_type, uint64_t addend = 0) const
432 { return this->got_offsets_.get_offset(got_type, addend) != -1U; }
433
434 // Return the offset into the GOT section of this symbol.
435 unsigned int
436 got_offset(unsigned int got_type, uint64_t addend = 0) const
437 {
438 unsigned int got_offset = this->got_offsets_.get_offset(got_type, addend);
439 gold_assert(got_offset != -1U);
440 return got_offset;
441 }
442
443 // Set the GOT offset of this symbol.
444 void
445 set_got_offset(unsigned int got_type, unsigned int got_offset,
446 uint64_t addend = 0)
447 { this->got_offsets_.set_offset(got_type, got_offset, addend); }
448
449 // Return the GOT offset list.
450 const Got_offset_list*
451 got_offset_list() const
452 { return this->got_offsets_.get_list(); }
453
454 // Return whether this symbol has an entry in the PLT section.
455 bool
456 has_plt_offset() const
457 { return this->plt_offset_ != -1U; }
458
459 // Return the offset into the PLT section of this symbol.
460 unsigned int
461 plt_offset() const
462 {
463 gold_assert(this->has_plt_offset());
464 return this->plt_offset_;
465 }
466
467 // Set the PLT offset of this symbol.
468 void
469 set_plt_offset(unsigned int plt_offset)
470 {
471 gold_assert(plt_offset != -1U);
472 this->plt_offset_ = plt_offset;
473 }
474
475 // Return whether this dynamic symbol needs a special value in the
476 // dynamic symbol table.
477 bool
478 needs_dynsym_value() const
479 { return this->needs_dynsym_value_; }
480
481 // Set that this dynamic symbol needs a special value in the dynamic
482 // symbol table.
483 void
484 set_needs_dynsym_value()
485 {
486 gold_assert(this->object()->is_dynamic());
487 this->needs_dynsym_value_ = true;
488 }
489
490 // Return true if the final value of this symbol is known at link
491 // time.
492 bool
493 final_value_is_known() const;
494
495 // Return true if SHNDX represents a common symbol. This depends on
496 // the target.
497 static bool
498 is_common_shndx(unsigned int shndx);
499
500 // Return whether this is a defined symbol (not undefined or
501 // common).
502 bool
503 is_defined() const
504 {
505 bool is_ordinary;
506 if (this->source_ != FROM_OBJECT)
507 return this->source_ != IS_UNDEFINED;
508 unsigned int shndx = this->shndx(&is_ordinary);
509 return (is_ordinary
510 ? shndx != elfcpp::SHN_UNDEF
511 : !Symbol::is_common_shndx(shndx));
512 }
513
514 // Return true if this symbol is from a dynamic object.
515 bool
516 is_from_dynobj() const
517 {
518 return this->source_ == FROM_OBJECT && this->object()->is_dynamic();
519 }
520
521 // Return whether this is a placeholder symbol from a plugin object.
522 bool
523 is_placeholder() const
524 {
525 return this->source_ == FROM_OBJECT && this->object()->pluginobj() != NULL;
526 }
527
528 // Return whether this is an undefined symbol.
529 bool
530 is_undefined() const
531 {
532 bool is_ordinary;
533 return ((this->source_ == FROM_OBJECT
534 && this->shndx(&is_ordinary) == elfcpp::SHN_UNDEF
535 && is_ordinary)
536 || this->source_ == IS_UNDEFINED);
537 }
538
539 // Return whether this is a weak undefined symbol.
540 bool
541 is_weak_undefined() const
542 {
543 return (this->is_undefined()
544 && (this->binding() == elfcpp::STB_WEAK
545 || this->is_undef_binding_weak()
546 || parameters->options().weak_unresolved_symbols()));
547 }
548
549 // Return whether this is a strong undefined symbol.
550 bool
551 is_strong_undefined() const
552 {
553 return (this->is_undefined()
554 && this->binding() != elfcpp::STB_WEAK
555 && !this->is_undef_binding_weak()
556 && !parameters->options().weak_unresolved_symbols());
557 }
558
559 // Return whether this is an absolute symbol.
560 bool
561 is_absolute() const
562 {
563 bool is_ordinary;
564 return ((this->source_ == FROM_OBJECT
565 && this->shndx(&is_ordinary) == elfcpp::SHN_ABS
566 && !is_ordinary)
567 || this->source_ == IS_CONSTANT);
568 }
569
570 // Return whether this is a common symbol.
571 bool
572 is_common() const
573 {
574 if (this->source_ != FROM_OBJECT)
575 return false;
576 bool is_ordinary;
577 unsigned int shndx = this->shndx(&is_ordinary);
578 return !is_ordinary && Symbol::is_common_shndx(shndx);
579 }
580
581 // Return whether this symbol can be seen outside this object.
582 bool
583 is_externally_visible() const
584 {
585 return ((this->visibility_ == elfcpp::STV_DEFAULT
586 || this->visibility_ == elfcpp::STV_PROTECTED)
587 && !this->is_forced_local_);
588 }
589
590 // Return true if this symbol can be preempted by a definition in
591 // another link unit.
592 bool
593 is_preemptible() const
594 {
595 // It doesn't make sense to ask whether a symbol defined in
596 // another object is preemptible.
597 gold_assert(!this->is_from_dynobj());
598
599 // It doesn't make sense to ask whether an undefined symbol
600 // is preemptible.
601 gold_assert(!this->is_undefined());
602
603 // If a symbol does not have default visibility, it can not be
604 // seen outside this link unit and therefore is not preemptible.
605 if (this->visibility_ != elfcpp::STV_DEFAULT)
606 return false;
607
608 // If this symbol has been forced to be a local symbol by a
609 // version script, then it is not visible outside this link unit
610 // and is not preemptible.
611 if (this->is_forced_local_)
612 return false;
613
614 // If we are not producing a shared library, then nothing is
615 // preemptible.
616 if (!parameters->options().shared())
617 return false;
618
619 // If the symbol was named in a --dynamic-list script, it is preemptible.
620 if (parameters->options().in_dynamic_list(this->name()))
621 return true;
622
623 // If the user used -Bsymbolic, then nothing (else) is preemptible.
624 if (parameters->options().Bsymbolic())
625 return false;
626
627 // If the user used -Bsymbolic-functions, then functions are not
628 // preemptible. We explicitly check for not being STT_OBJECT,
629 // rather than for being STT_FUNC, because that is what the GNU
630 // linker does.
631 if (this->type() != elfcpp::STT_OBJECT
632 && parameters->options().Bsymbolic_functions())
633 return false;
634
635 // Otherwise the symbol is preemptible.
636 return true;
637 }
638
639 // Return true if this symbol is a function that needs a PLT entry.
640 bool
641 needs_plt_entry() const
642 {
643 // An undefined symbol from an executable does not need a PLT entry.
644 if (this->is_undefined() && !parameters->options().shared())
645 return false;
646
647 // An STT_GNU_IFUNC symbol always needs a PLT entry, even when
648 // doing a static link.
649 if (this->type() == elfcpp::STT_GNU_IFUNC)
650 return true;
651
652 // We only need a PLT entry for a function.
653 if (!this->is_func())
654 return false;
655
656 // If we're doing a static link or a -pie link, we don't create
657 // PLT entries.
658 if (parameters->doing_static_link()
659 || parameters->options().pie())
660 return false;
661
662 // We need a PLT entry if the function is defined in a dynamic
663 // object, or is undefined when building a shared object, or if it
664 // is subject to pre-emption.
665 return (this->is_from_dynobj()
666 || this->is_undefined()
667 || this->is_preemptible());
668 }
669
670 // When determining whether a reference to a symbol needs a dynamic
671 // relocation, we need to know several things about the reference.
672 // These flags may be or'ed together. 0 means that the symbol
673 // isn't referenced at all.
674 enum Reference_flags
675 {
676 // A reference to the symbol's absolute address. This includes
677 // references that cause an absolute address to be stored in the GOT.
678 ABSOLUTE_REF = 1,
679 // A reference that calculates the offset of the symbol from some
680 // anchor point, such as the PC or GOT.
681 RELATIVE_REF = 2,
682 // A TLS-related reference.
683 TLS_REF = 4,
684 // A reference that can always be treated as a function call.
685 FUNCTION_CALL = 8,
686 // When set, says that dynamic relocations are needed even if a
687 // symbol has a plt entry.
688 FUNC_DESC_ABI = 16,
689 };
690
691 // Given a direct absolute or pc-relative static relocation against
692 // the global symbol, this function returns whether a dynamic relocation
693 // is needed.
694
695 bool
696 needs_dynamic_reloc(int flags) const
697 {
698 // No dynamic relocations in a static link!
699 if (parameters->doing_static_link())
700 return false;
701
702 // A reference to an undefined symbol from an executable should be
703 // statically resolved to 0, and does not need a dynamic relocation.
704 // This matches gnu ld behavior.
705 if (this->is_undefined() && !parameters->options().shared())
706 return false;
707
708 // A reference to an absolute symbol does not need a dynamic relocation.
709 if (this->is_absolute())
710 return false;
711
712 // An absolute reference within a position-independent output file
713 // will need a dynamic relocation.
714 if ((flags & ABSOLUTE_REF)
715 && parameters->options().output_is_position_independent())
716 return true;
717
718 // A function call that can branch to a local PLT entry does not need
719 // a dynamic relocation.
720 if ((flags & FUNCTION_CALL) && this->has_plt_offset())
721 return false;
722
723 // A reference to any PLT entry in a non-position-independent executable
724 // does not need a dynamic relocation.
725 if (!(flags & FUNC_DESC_ABI)
726 && !parameters->options().output_is_position_independent()
727 && this->has_plt_offset())
728 return false;
729
730 // A reference to a symbol defined in a dynamic object or to a
731 // symbol that is preemptible will need a dynamic relocation.
732 if (this->is_from_dynobj()
733 || this->is_undefined()
734 || this->is_preemptible())
735 return true;
736
737 // For all other cases, return FALSE.
738 return false;
739 }
740
741 // Whether we should use the PLT offset associated with a symbol for
742 // a relocation. FLAGS is a set of Reference_flags.
743
744 bool
745 use_plt_offset(int flags) const
746 {
747 // If the symbol doesn't have a PLT offset, then naturally we
748 // don't want to use it.
749 if (!this->has_plt_offset())
750 return false;
751
752 // For a STT_GNU_IFUNC symbol we always have to use the PLT entry.
753 if (this->type() == elfcpp::STT_GNU_IFUNC)
754 return true;
755
756 // If we are going to generate a dynamic relocation, then we will
757 // wind up using that, so no need to use the PLT entry.
758 if (this->needs_dynamic_reloc(flags))
759 return false;
760
761 // If the symbol is from a dynamic object, we need to use the PLT
762 // entry.
763 if (this->is_from_dynobj())
764 return true;
765
766 // If we are generating a shared object, and this symbol is
767 // undefined or preemptible, we need to use the PLT entry.
768 if (parameters->options().shared()
769 && (this->is_undefined() || this->is_preemptible()))
770 return true;
771
772 // If this is a call to a weak undefined symbol, we need to use
773 // the PLT entry; the symbol may be defined by a library loaded
774 // at runtime.
775 if ((flags & FUNCTION_CALL) && this->is_weak_undefined())
776 return true;
777
778 // Otherwise we can use the regular definition.
779 return false;
780 }
781
782 // Given a direct absolute static relocation against
783 // the global symbol, where a dynamic relocation is needed, this
784 // function returns whether a relative dynamic relocation can be used.
785 // The caller must determine separately whether the static relocation
786 // is compatible with a relative relocation.
787
788 bool
789 can_use_relative_reloc(bool is_function_call) const
790 {
791 // A function call that can branch to a local PLT entry can
792 // use a RELATIVE relocation.
793 if (is_function_call && this->has_plt_offset())
794 return true;
795
796 // A reference to a symbol defined in a dynamic object or to a
797 // symbol that is preemptible can not use a RELATIVE relocation.
798 if (this->is_from_dynobj()
799 || this->is_undefined()
800 || this->is_preemptible())
801 return false;
802
803 // For all other cases, return TRUE.
804 return true;
805 }
806
807 // Return the output section where this symbol is defined. Return
808 // NULL if the symbol has an absolute value.
809 Output_section*
810 output_section() const;
811
812 // Set the symbol's output section. This is used for symbols
813 // defined in scripts. This should only be called after the symbol
814 // table has been finalized.
815 void
816 set_output_section(Output_section*);
817
818 // Set the symbol's output segment. This is used for pre-defined
819 // symbols whose segments aren't known until after layout is done
820 // (e.g., __ehdr_start).
821 void
822 set_output_segment(Output_segment*, Segment_offset_base);
823
824 // Set the symbol to undefined. This is used for pre-defined
825 // symbols whose segments aren't known until after layout is done
826 // (e.g., __ehdr_start).
827 void
828 set_undefined();
829
830 // Return whether there should be a warning for references to this
831 // symbol.
832 bool
833 has_warning() const
834 { return this->has_warning_; }
835
836 // Mark this symbol as having a warning.
837 void
838 set_has_warning()
839 { this->has_warning_ = true; }
840
841 // Return whether this symbol is defined by a COPY reloc from a
842 // dynamic object.
843 bool
844 is_copied_from_dynobj() const
845 { return this->is_copied_from_dynobj_; }
846
847 // Mark this symbol as defined by a COPY reloc.
848 void
849 set_is_copied_from_dynobj()
850 { this->is_copied_from_dynobj_ = true; }
851
852 // Return whether this symbol is forced to visibility STB_LOCAL
853 // by a "local:" entry in a version script.
854 bool
855 is_forced_local() const
856 { return this->is_forced_local_; }
857
858 // Mark this symbol as forced to STB_LOCAL visibility.
859 void
860 set_is_forced_local()
861 { this->is_forced_local_ = true; }
862
863 // Return true if this may need a COPY relocation.
864 // References from an executable object to non-function symbols
865 // defined in a dynamic object may need a COPY relocation.
866 bool
867 may_need_copy_reloc() const
868 {
869 return (parameters->options().copyreloc()
870 && this->is_from_dynobj()
871 && !this->is_func());
872 }
873
874 // Return true if this symbol was predefined by the linker.
875 bool
876 is_predefined() const
877 { return this->is_predefined_; }
878
879 // Return true if this is a C++ vtable symbol.
880 bool
881 is_cxx_vtable() const
882 { return is_prefix_of("_ZTV", this->name_); }
883
884 // Return true if this symbol is protected in a shared object.
885 // This is not the same as checking if visibility() == elfcpp::STV_PROTECTED,
886 // because the visibility_ field reflects the symbol's visibility from
887 // outside the shared object.
888 bool
889 is_protected() const
890 { return this->is_protected_; }
891
892 // Mark this symbol as protected in a shared object.
893 void
894 set_is_protected()
895 { this->is_protected_ = true; }
896
897 // Return state of PowerPC64 ELFv2 specific flag.
898 bool
899 non_zero_localentry() const
900 { return this->non_zero_localentry_; }
901
902 // Set PowerPC64 ELFv2 specific flag.
903 void
904 set_non_zero_localentry()
905 { this->non_zero_localentry_ = true; }
906
907 // Completely override existing symbol. Everything bar name_,
908 // version_, and is_forced_local_ flag are copied. version_ is
909 // cleared if from->version_ is clear. Returns true if this symbol
910 // should be forced local.
911 bool
912 clone(const Symbol* from);
913
914 protected:
915 // Instances of this class should always be created at a specific
916 // size.
917 Symbol()
918 { memset(static_cast<void*>(this), 0, sizeof *this); }
919
920 // Initialize the general fields.
921 void
922 init_fields(const char* name, const char* version,
923 elfcpp::STT type, elfcpp::STB binding,
924 elfcpp::STV visibility, unsigned char nonvis);
925
926 // Initialize fields from an ELF symbol in OBJECT. ST_SHNDX is the
927 // section index, IS_ORDINARY is whether it is a normal section
928 // index rather than a special code.
929 template<int size, bool big_endian>
930 void
931 init_base_object(const char* name, const char* version, Object* object,
932 const elfcpp::Sym<size, big_endian>&, unsigned int st_shndx,
933 bool is_ordinary);
934
935 // Initialize fields for an Output_data.
936 void
937 init_base_output_data(const char* name, const char* version, Output_data*,
938 elfcpp::STT, elfcpp::STB, elfcpp::STV,
939 unsigned char nonvis, bool offset_is_from_end,
940 bool is_predefined);
941
942 // Initialize fields for an Output_segment.
943 void
944 init_base_output_segment(const char* name, const char* version,
945 Output_segment* os, elfcpp::STT type,
946 elfcpp::STB binding, elfcpp::STV visibility,
947 unsigned char nonvis,
948 Segment_offset_base offset_base,
949 bool is_predefined);
950
951 // Initialize fields for a constant.
952 void
953 init_base_constant(const char* name, const char* version, elfcpp::STT type,
954 elfcpp::STB binding, elfcpp::STV visibility,
955 unsigned char nonvis, bool is_predefined);
956
957 // Initialize fields for an undefined symbol.
958 void
959 init_base_undefined(const char* name, const char* version, elfcpp::STT type,
960 elfcpp::STB binding, elfcpp::STV visibility,
961 unsigned char nonvis);
962
963 // Override existing symbol.
964 template<int size, bool big_endian>
965 void
966 override_base(const elfcpp::Sym<size, big_endian>&, unsigned int st_shndx,
967 bool is_ordinary, Object* object, const char* version);
968
969 // Override existing symbol with a special symbol.
970 void
971 override_base_with_special(const Symbol* from);
972
973 // Override symbol version.
974 void
975 override_version(const char* version);
976
977 // Allocate a common symbol by giving it a location in the output
978 // file.
979 void
980 allocate_base_common(Output_data*);
981
982 private:
983 Symbol(const Symbol&);
984 Symbol& operator=(const Symbol&);
985
986 // Symbol name (expected to point into a Stringpool).
987 const char* name_;
988 // Symbol version (expected to point into a Stringpool). This may
989 // be NULL.
990 const char* version_;
991
992 union
993 {
994 // This is used if SOURCE_ == FROM_OBJECT.
995 // Object in which symbol is defined, or in which it was first
996 // seen.
997 Object* object;
998
999 // This is used if SOURCE_ == IN_OUTPUT_DATA.
1000 // Output_data in which symbol is defined. Before
1001 // Layout::finalize the symbol's value is an offset within the
1002 // Output_data.
1003 Output_data* output_data;
1004
1005 // This is used if SOURCE_ == IN_OUTPUT_SEGMENT.
1006 // Output_segment in which the symbol is defined. Before
1007 // Layout::finalize the symbol's value is an offset.
1008 Output_segment* output_segment;
1009 } u1_;
1010
1011 union
1012 {
1013 // This is used if SOURCE_ == FROM_OBJECT.
1014 // Section number in object in which symbol is defined.
1015 unsigned int shndx;
1016
1017 // This is used if SOURCE_ == IN_OUTPUT_DATA.
1018 // True if the offset is from the end, false if the offset is
1019 // from the beginning.
1020 bool offset_is_from_end;
1021
1022 // This is used if SOURCE_ == IN_OUTPUT_SEGMENT.
1023 // The base to use for the offset before Layout::finalize.
1024 Segment_offset_base offset_base;
1025 } u2_;
1026
1027 // The index of this symbol in the output file. If the symbol is
1028 // not going into the output file, this value is -1U. This field
1029 // starts as always holding zero. It is set to a non-zero value by
1030 // Symbol_table::finalize.
1031 unsigned int symtab_index_;
1032
1033 // The index of this symbol in the dynamic symbol table. If the
1034 // symbol is not going into the dynamic symbol table, this value is
1035 // -1U. This field starts as always holding zero. It is set to a
1036 // non-zero value during Layout::finalize.
1037 unsigned int dynsym_index_;
1038
1039 // If this symbol has an entry in the PLT section, then this is the
1040 // offset from the start of the PLT section. This is -1U if there
1041 // is no PLT entry.
1042 unsigned int plt_offset_;
1043
1044 // The GOT section entries for this symbol. A symbol may have more
1045 // than one GOT offset (e.g., when mixing modules compiled with two
1046 // different TLS models), but will usually have at most one.
1047 Got_offset_list got_offsets_;
1048
1049 // Symbol type (bits 0 to 3).
1050 elfcpp::STT type_ : 4;
1051 // Symbol binding (bits 4 to 7).
1052 elfcpp::STB binding_ : 4;
1053 // Symbol visibility (bits 8 to 9).
1054 elfcpp::STV visibility_ : 2;
1055 // Rest of symbol st_other field (bits 10 to 15).
1056 unsigned int nonvis_ : 6;
1057 // The type of symbol (bits 16 to 18).
1058 Source source_ : 3;
1059 // True if this is the default version of the symbol (bit 19).
1060 bool is_def_ : 1;
1061 // True if this symbol really forwards to another symbol. This is
1062 // used when we discover after the fact that two different entries
1063 // in the hash table really refer to the same symbol. This will
1064 // never be set for a symbol found in the hash table, but may be set
1065 // for a symbol found in the list of symbols attached to an Object.
1066 // It forwards to the symbol found in the forwarders_ map of
1067 // Symbol_table (bit 20).
1068 bool is_forwarder_ : 1;
1069 // True if the symbol has an alias in the weak_aliases table in
1070 // Symbol_table (bit 21).
1071 bool has_alias_ : 1;
1072 // True if this symbol needs to be in the dynamic symbol table (bit
1073 // 22).
1074 bool needs_dynsym_entry_ : 1;
1075 // True if we've seen this symbol in a regular object (bit 23).
1076 bool in_reg_ : 1;
1077 // True if we've seen this symbol in a dynamic object (bit 24).
1078 bool in_dyn_ : 1;
1079 // True if this is a dynamic symbol which needs a special value in
1080 // the dynamic symbol table (bit 25).
1081 bool needs_dynsym_value_ : 1;
1082 // True if there is a warning for this symbol (bit 26).
1083 bool has_warning_ : 1;
1084 // True if we are using a COPY reloc for this symbol, so that the
1085 // real definition lives in a dynamic object (bit 27).
1086 bool is_copied_from_dynobj_ : 1;
1087 // True if this symbol was forced to local visibility by a version
1088 // script (bit 28).
1089 bool is_forced_local_ : 1;
1090 // True if the field u2_.shndx is an ordinary section
1091 // index, not one of the special codes from SHN_LORESERVE to
1092 // SHN_HIRESERVE (bit 29).
1093 bool is_ordinary_shndx_ : 1;
1094 // True if we've seen this symbol in a "real" ELF object (bit 30).
1095 // If the symbol has been seen in a relocatable, non-IR, object file,
1096 // it's known to be referenced from outside the IR. A reference from
1097 // a dynamic object doesn't count as a "real" ELF, and we'll simply
1098 // mark the symbol as "visible" from outside the IR. The compiler
1099 // can use this distinction to guide its handling of COMDAT symbols.
1100 bool in_real_elf_ : 1;
1101 // True if this symbol is defined in a section which was discarded
1102 // (bit 31).
1103 bool is_defined_in_discarded_section_ : 1;
1104 // True if UNDEF_BINDING_WEAK_ has been set (bit 32).
1105 bool undef_binding_set_ : 1;
1106 // True if this symbol was a weak undef resolved by a dynamic def
1107 // or by a special symbol (bit 33).
1108 bool undef_binding_weak_ : 1;
1109 // True if this symbol is a predefined linker symbol (bit 34).
1110 bool is_predefined_ : 1;
1111 // True if this symbol has protected visibility in a shared object (bit 35).
1112 // The visibility_ field will be STV_DEFAULT in this case because we
1113 // must treat it as such from outside the shared object.
1114 bool is_protected_ : 1;
1115 // Used by PowerPC64 ELFv2 to track st_other localentry (bit 36).
1116 bool non_zero_localentry_ : 1;
1117 };
1118
1119 // The parts of a symbol which are size specific. Using a template
1120 // derived class like this helps us use less space on a 32-bit system.
1121
1122 template<int size>
1123 class Sized_symbol : public Symbol
1124 {
1125 public:
1126 typedef typename elfcpp::Elf_types<size>::Elf_Addr Value_type;
1127 typedef typename elfcpp::Elf_types<size>::Elf_WXword Size_type;
1128
1129 Sized_symbol()
1130 { }
1131
1132 // Initialize fields from an ELF symbol in OBJECT. ST_SHNDX is the
1133 // section index, IS_ORDINARY is whether it is a normal section
1134 // index rather than a special code.
1135 template<bool big_endian>
1136 void
1137 init_object(const char* name, const char* version, Object* object,
1138 const elfcpp::Sym<size, big_endian>&, unsigned int st_shndx,
1139 bool is_ordinary);
1140
1141 // Initialize fields for an Output_data.
1142 void
1143 init_output_data(const char* name, const char* version, Output_data*,
1144 Value_type value, Size_type symsize, elfcpp::STT,
1145 elfcpp::STB, elfcpp::STV, unsigned char nonvis,
1146 bool offset_is_from_end, bool is_predefined);
1147
1148 // Initialize fields for an Output_segment.
1149 void
1150 init_output_segment(const char* name, const char* version, Output_segment*,
1151 Value_type value, Size_type symsize, elfcpp::STT,
1152 elfcpp::STB, elfcpp::STV, unsigned char nonvis,
1153 Segment_offset_base offset_base, bool is_predefined);
1154
1155 // Initialize fields for a constant.
1156 void
1157 init_constant(const char* name, const char* version, Value_type value,
1158 Size_type symsize, elfcpp::STT, elfcpp::STB, elfcpp::STV,
1159 unsigned char nonvis, bool is_predefined);
1160
1161 // Initialize fields for an undefined symbol.
1162 void
1163 init_undefined(const char* name, const char* version, Value_type value,
1164 elfcpp::STT, elfcpp::STB, elfcpp::STV, unsigned char nonvis);
1165
1166 // Override existing symbol.
1167 template<bool big_endian>
1168 void
1169 override(const elfcpp::Sym<size, big_endian>&, unsigned int st_shndx,
1170 bool is_ordinary, Object* object, const char* version);
1171
1172 // Override existing symbol with a special symbol.
1173 void
1174 override_with_special(const Sized_symbol<size>*);
1175
1176 // Return the symbol's value.
1177 Value_type
1178 value() const
1179 { return this->value_; }
1180
1181 // Return the symbol's size (we can't call this 'size' because that
1182 // is a template parameter).
1183 Size_type
1184 symsize() const
1185 { return this->symsize_; }
1186
1187 // Set the symbol size. This is used when resolving common symbols.
1188 void
1189 set_symsize(Size_type symsize)
1190 { this->symsize_ = symsize; }
1191
1192 // Set the symbol value. This is called when we store the final
1193 // values of the symbols into the symbol table.
1194 void
1195 set_value(Value_type value)
1196 { this->value_ = value; }
1197
1198 // Allocate a common symbol by giving it a location in the output
1199 // file.
1200 void
1201 allocate_common(Output_data*, Value_type value);
1202
1203 // Completely override existing symbol. Everything bar name_,
1204 // version_, and is_forced_local_ flag are copied. version_ is
1205 // cleared if from->version_ is clear. Returns true if this symbol
1206 // should be forced local.
1207 bool
1208 clone(const Sized_symbol<size>* from);
1209
1210 private:
1211 Sized_symbol(const Sized_symbol&);
1212 Sized_symbol& operator=(const Sized_symbol&);
1213
1214 // Symbol value. Before Layout::finalize this is the offset in the
1215 // input section. This is set to the final value during
1216 // Layout::finalize.
1217 Value_type value_;
1218 // Symbol size.
1219 Size_type symsize_;
1220 };
1221
1222 // A struct describing a symbol defined by the linker, where the value
1223 // of the symbol is defined based on an output section. This is used
1224 // for symbols defined by the linker, like "_init_array_start".
1225
1226 struct Define_symbol_in_section
1227 {
1228 // The symbol name.
1229 const char* name;
1230 // The name of the output section with which this symbol should be
1231 // associated. If there is no output section with that name, the
1232 // symbol will be defined as zero.
1233 const char* output_section;
1234 // The offset of the symbol within the output section. This is an
1235 // offset from the start of the output section, unless start_at_end
1236 // is true, in which case this is an offset from the end of the
1237 // output section.
1238 uint64_t value;
1239 // The size of the symbol.
1240 uint64_t size;
1241 // The symbol type.
1242 elfcpp::STT type;
1243 // The symbol binding.
1244 elfcpp::STB binding;
1245 // The symbol visibility.
1246 elfcpp::STV visibility;
1247 // The rest of the st_other field.
1248 unsigned char nonvis;
1249 // If true, the value field is an offset from the end of the output
1250 // section.
1251 bool offset_is_from_end;
1252 // If true, this symbol is defined only if we see a reference to it.
1253 bool only_if_ref;
1254 };
1255
1256 // A struct describing a symbol defined by the linker, where the value
1257 // of the symbol is defined based on a segment. This is used for
1258 // symbols defined by the linker, like "_end". We describe the
1259 // segment with which the symbol should be associated by its
1260 // characteristics. If no segment meets these characteristics, the
1261 // symbol will be defined as zero. If there is more than one segment
1262 // which meets these characteristics, we will use the first one.
1263
1264 struct Define_symbol_in_segment
1265 {
1266 // The symbol name.
1267 const char* name;
1268 // The segment type where the symbol should be defined, typically
1269 // PT_LOAD.
1270 elfcpp::PT segment_type;
1271 // Bitmask of segment flags which must be set.
1272 elfcpp::PF segment_flags_set;
1273 // Bitmask of segment flags which must be clear.
1274 elfcpp::PF segment_flags_clear;
1275 // The offset of the symbol within the segment. The offset is
1276 // calculated from the position set by offset_base.
1277 uint64_t value;
1278 // The size of the symbol.
1279 uint64_t size;
1280 // The symbol type.
1281 elfcpp::STT type;
1282 // The symbol binding.
1283 elfcpp::STB binding;
1284 // The symbol visibility.
1285 elfcpp::STV visibility;
1286 // The rest of the st_other field.
1287 unsigned char nonvis;
1288 // The base from which we compute the offset.
1289 Symbol::Segment_offset_base offset_base;
1290 // If true, this symbol is defined only if we see a reference to it.
1291 bool only_if_ref;
1292 };
1293
1294 // Specify an object/section/offset location. Used by ODR code.
1295
1296 struct Symbol_location
1297 {
1298 // Object where the symbol is defined.
1299 Object* object;
1300 // Section-in-object where the symbol is defined.
1301 unsigned int shndx;
1302 // For relocatable objects, offset-in-section where the symbol is defined.
1303 // For dynamic objects, address where the symbol is defined.
1304 off_t offset;
1305 bool operator==(const Symbol_location& that) const
1306 {
1307 return (this->object == that.object
1308 && this->shndx == that.shndx
1309 && this->offset == that.offset);
1310 }
1311 };
1312
1313 // A map from symbol name (as a pointer into the namepool) to all
1314 // the locations the symbols is (weakly) defined (and certain other
1315 // conditions are met). This map will be used later to detect
1316 // possible One Definition Rule (ODR) violations.
1317 struct Symbol_location_hash
1318 {
1319 size_t operator()(const Symbol_location& loc) const
1320 { return reinterpret_cast<uintptr_t>(loc.object) ^ loc.offset ^ loc.shndx; }
1321 };
1322
1323 // This class manages warnings. Warnings are a GNU extension. When
1324 // we see a section named .gnu.warning.SYM in an object file, and if
1325 // we wind using the definition of SYM from that object file, then we
1326 // will issue a warning for any relocation against SYM from a
1327 // different object file. The text of the warning is the contents of
1328 // the section. This is not precisely the definition used by the old
1329 // GNU linker; the old GNU linker treated an occurrence of
1330 // .gnu.warning.SYM as defining a warning symbol. A warning symbol
1331 // would trigger a warning on any reference. However, it was
1332 // inconsistent in that a warning in a dynamic object only triggered
1333 // if there was no definition in a regular object. This linker is
1334 // different in that we only issue a warning if we use the symbol
1335 // definition from the same object file as the warning section.
1336
1337 class Warnings
1338 {
1339 public:
1340 Warnings()
1341 : warnings_()
1342 { }
1343
1344 // Add a warning for symbol NAME in object OBJ. WARNING is the text
1345 // of the warning.
1346 void
1347 add_warning(Symbol_table* symtab, const char* name, Object* obj,
1348 const std::string& warning);
1349
1350 // For each symbol for which we should give a warning, make a note
1351 // on the symbol.
1352 void
1353 note_warnings(Symbol_table* symtab);
1354
1355 // Issue a warning for a reference to SYM at RELINFO's location.
1356 template<int size, bool big_endian>
1357 void
1358 issue_warning(const Symbol* sym, const Relocate_info<size, big_endian>*,
1359 size_t relnum, off_t reloffset) const;
1360
1361 private:
1362 Warnings(const Warnings&);
1363 Warnings& operator=(const Warnings&);
1364
1365 // What we need to know to get the warning text.
1366 struct Warning_location
1367 {
1368 // The object the warning is in.
1369 Object* object;
1370 // The warning text.
1371 std::string text;
1372
1373 Warning_location()
1374 : object(NULL), text()
1375 { }
1376
1377 void
1378 set(Object* o, const std::string& t)
1379 {
1380 this->object = o;
1381 this->text = t;
1382 }
1383 };
1384
1385 // A mapping from warning symbol names (canonicalized in
1386 // Symbol_table's namepool_ field) to warning information.
1387 typedef Unordered_map<const char*, Warning_location> Warning_table;
1388
1389 Warning_table warnings_;
1390 };
1391
1392 // The main linker symbol table.
1393
1394 class Symbol_table
1395 {
1396 public:
1397 // The different places where a symbol definition can come from.
1398 enum Defined
1399 {
1400 // Defined in an object file--the normal case.
1401 OBJECT,
1402 // Defined for a COPY reloc.
1403 COPY,
1404 // Defined on the command line using --defsym.
1405 DEFSYM,
1406 // Defined (so to speak) on the command line using -u.
1407 UNDEFINED,
1408 // Defined in a linker script.
1409 SCRIPT,
1410 // Predefined by the linker.
1411 PREDEFINED,
1412 // Defined by the linker during an incremental base link, but not
1413 // a predefined symbol (e.g., common, defined in script).
1414 INCREMENTAL_BASE,
1415 };
1416
1417 // The order in which we sort common symbols.
1418 enum Sort_commons_order
1419 {
1420 SORT_COMMONS_BY_SIZE_DESCENDING,
1421 SORT_COMMONS_BY_ALIGNMENT_DESCENDING,
1422 SORT_COMMONS_BY_ALIGNMENT_ASCENDING
1423 };
1424
1425 // COUNT is an estimate of how many symbols will be inserted in the
1426 // symbol table. It's ok to put 0 if you don't know; a correct
1427 // guess will just save some CPU by reducing hashtable resizes.
1428 Symbol_table(unsigned int count, const Version_script_info& version_script);
1429
1430 ~Symbol_table();
1431
1432 void
1433 set_icf(Icf* icf)
1434 { this->icf_ = icf;}
1435
1436 Icf*
1437 icf() const
1438 { return this->icf_; }
1439
1440 // Returns true if ICF determined that this is a duplicate section.
1441 bool
1442 is_section_folded(Relobj* obj, unsigned int shndx) const;
1443
1444 void
1445 set_gc(Garbage_collection* gc)
1446 { this->gc_ = gc; }
1447
1448 Garbage_collection*
1449 gc() const
1450 { return this->gc_; }
1451
1452 // During garbage collection, this keeps undefined symbols.
1453 void
1454 gc_mark_undef_symbols(Layout*);
1455
1456 // This tells garbage collection that this symbol is referenced.
1457 void
1458 gc_mark_symbol(Symbol* sym);
1459
1460 // During garbage collection, this keeps sections that correspond to
1461 // symbols seen in dynamic objects.
1462 inline void
1463 gc_mark_dyn_syms(Symbol* sym);
1464
1465 // Add COUNT external symbols from the relocatable object RELOBJ to
1466 // the symbol table. SYMS is the symbols, SYMNDX_OFFSET is the
1467 // offset in the symbol table of the first symbol, SYM_NAMES is
1468 // their names, SYM_NAME_SIZE is the size of SYM_NAMES. This sets
1469 // SYMPOINTERS to point to the symbols in the symbol table. It sets
1470 // *DEFINED to the number of defined symbols.
1471 template<int size, bool big_endian>
1472 void
1473 add_from_relobj(Sized_relobj_file<size, big_endian>* relobj,
1474 const unsigned char* syms, size_t count,
1475 size_t symndx_offset, const char* sym_names,
1476 size_t sym_name_size,
1477 typename Sized_relobj_file<size, big_endian>::Symbols*,
1478 size_t* defined);
1479
1480 // Add one external symbol from the plugin object OBJ to the symbol table.
1481 // Returns a pointer to the resolved symbol in the symbol table.
1482 template<int size, bool big_endian>
1483 Symbol*
1484 add_from_pluginobj(Sized_pluginobj<size, big_endian>* obj,
1485 const char* name, const char* ver,
1486 elfcpp::Sym<size, big_endian>* sym);
1487
1488 // Add COUNT dynamic symbols from the dynamic object DYNOBJ to the
1489 // symbol table. SYMS is the symbols. SYM_NAMES is their names.
1490 // SYM_NAME_SIZE is the size of SYM_NAMES. The other parameters are
1491 // symbol version data.
1492 template<int size, bool big_endian>
1493 void
1494 add_from_dynobj(Sized_dynobj<size, big_endian>* dynobj,
1495 const unsigned char* syms, size_t count,
1496 const char* sym_names, size_t sym_name_size,
1497 const unsigned char* versym, size_t versym_size,
1498 const std::vector<const char*>*,
1499 typename Sized_relobj_file<size, big_endian>::Symbols*,
1500 size_t* defined);
1501
1502 // Add one external symbol from the incremental object OBJ to the symbol
1503 // table. Returns a pointer to the resolved symbol in the symbol table.
1504 template<int size, bool big_endian>
1505 Sized_symbol<size>*
1506 add_from_incrobj(Object* obj, const char* name,
1507 const char* ver, elfcpp::Sym<size, big_endian>* sym);
1508
1509 // Define a special symbol based on an Output_data. It is a
1510 // multiple definition error if this symbol is already defined.
1511 Symbol*
1512 define_in_output_data(const char* name, const char* version, Defined,
1513 Output_data*, uint64_t value, uint64_t symsize,
1514 elfcpp::STT type, elfcpp::STB binding,
1515 elfcpp::STV visibility, unsigned char nonvis,
1516 bool offset_is_from_end, bool only_if_ref);
1517
1518 // Define a special symbol based on an Output_segment. It is a
1519 // multiple definition error if this symbol is already defined.
1520 Symbol*
1521 define_in_output_segment(const char* name, const char* version, Defined,
1522 Output_segment*, uint64_t value, uint64_t symsize,
1523 elfcpp::STT type, elfcpp::STB binding,
1524 elfcpp::STV visibility, unsigned char nonvis,
1525 Symbol::Segment_offset_base, bool only_if_ref);
1526
1527 // Define a special symbol with a constant value. It is a multiple
1528 // definition error if this symbol is already defined.
1529 Symbol*
1530 define_as_constant(const char* name, const char* version, Defined,
1531 uint64_t value, uint64_t symsize, elfcpp::STT type,
1532 elfcpp::STB binding, elfcpp::STV visibility,
1533 unsigned char nonvis, bool only_if_ref,
1534 bool force_override);
1535
1536 // Define a set of symbols in output sections. If ONLY_IF_REF is
1537 // true, only define them if they are referenced.
1538 void
1539 define_symbols(const Layout*, int count, const Define_symbol_in_section*,
1540 bool only_if_ref);
1541
1542 // Define a set of symbols in output segments. If ONLY_IF_REF is
1543 // true, only defined them if they are referenced.
1544 void
1545 define_symbols(const Layout*, int count, const Define_symbol_in_segment*,
1546 bool only_if_ref);
1547
1548 // Add a target-specific global symbol.
1549 // (Used by SPARC backend to add STT_SPARC_REGISTER symbols.)
1550 void
1551 add_target_global_symbol(Symbol* sym)
1552 { this->target_symbols_.push_back(sym); }
1553
1554 // Define SYM using a COPY reloc. POSD is the Output_data where the
1555 // symbol should be defined--typically a .dyn.bss section. VALUE is
1556 // the offset within POSD.
1557 template<int size>
1558 void
1559 define_with_copy_reloc(Sized_symbol<size>* sym, Output_data* posd,
1560 typename elfcpp::Elf_types<size>::Elf_Addr);
1561
1562 // Look up a symbol.
1563 Symbol*
1564 lookup(const char*, const char* version = NULL) const;
1565
1566 // Return the real symbol associated with the forwarder symbol FROM.
1567 Symbol*
1568 resolve_forwards(const Symbol* from) const;
1569
1570 // Return the sized version of a symbol in this table.
1571 template<int size>
1572 Sized_symbol<size>*
1573 get_sized_symbol(Symbol*) const;
1574
1575 template<int size>
1576 const Sized_symbol<size>*
1577 get_sized_symbol(const Symbol*) const;
1578
1579 // Return the count of undefined symbols seen.
1580 size_t
1581 saw_undefined() const
1582 { return this->saw_undefined_; }
1583
1584 void
1585 set_has_gnu_output()
1586 { this->has_gnu_output_ = true; }
1587
1588 // Allocate the common symbols
1589 void
1590 allocate_commons(Layout*, Mapfile*);
1591
1592 // Add a warning for symbol NAME in object OBJ. WARNING is the text
1593 // of the warning.
1594 void
1595 add_warning(const char* name, Object* obj, const std::string& warning)
1596 { this->warnings_.add_warning(this, name, obj, warning); }
1597
1598 // Canonicalize a symbol name for use in the hash table.
1599 const char*
1600 canonicalize_name(const char* name)
1601 { return this->namepool_.add(name, true, NULL); }
1602
1603 // Possibly issue a warning for a reference to SYM at LOCATION which
1604 // is in OBJ.
1605 template<int size, bool big_endian>
1606 void
1607 issue_warning(const Symbol* sym,
1608 const Relocate_info<size, big_endian>* relinfo,
1609 size_t relnum, off_t reloffset) const
1610 { this->warnings_.issue_warning(sym, relinfo, relnum, reloffset); }
1611
1612 // Check candidate_odr_violations_ to find symbols with the same name
1613 // but apparently different definitions (different source-file/line-no).
1614 void
1615 detect_odr_violations(const Task*, const char* output_file_name) const;
1616
1617 // Add any undefined symbols named on the command line to the symbol
1618 // table.
1619 void
1620 add_undefined_symbols_from_command_line(Layout*);
1621
1622 // SYM is defined using a COPY reloc. Return the dynamic object
1623 // where the original definition was found.
1624 Dynobj*
1625 get_copy_source(const Symbol* sym) const;
1626
1627 // Set the dynamic symbol indexes. INDEX is the index of the first
1628 // global dynamic symbol. Return the count of forced-local symbols in
1629 // *PFORCED_LOCAL_COUNT. Pointers to the symbols are stored into
1630 // the vector. The names are stored into the Stringpool. This
1631 // returns an updated dynamic symbol index.
1632 unsigned int
1633 set_dynsym_indexes(unsigned int index, unsigned int* pforced_local_count,
1634 std::vector<Symbol*>*, Stringpool*, Versions*);
1635
1636 // Finalize the symbol table after we have set the final addresses
1637 // of all the input sections. This sets the final symbol indexes,
1638 // values and adds the names to *POOL. *PLOCAL_SYMCOUNT is the
1639 // index of the first global symbol. OFF is the file offset of the
1640 // global symbol table, DYNOFF is the offset of the globals in the
1641 // dynamic symbol table, DYN_GLOBAL_INDEX is the index of the first
1642 // global dynamic symbol, and DYNCOUNT is the number of global
1643 // dynamic symbols. This records the parameters, and returns the
1644 // new file offset. It updates *PLOCAL_SYMCOUNT if it created any
1645 // local symbols.
1646 off_t
1647 finalize(off_t off, off_t dynoff, size_t dyn_global_index, size_t dyncount,
1648 Stringpool* pool, unsigned int* plocal_symcount);
1649
1650 // Set the final file offset of the symbol table.
1651 void
1652 set_file_offset(off_t off)
1653 { this->offset_ = off; }
1654
1655 // Status code of Symbol_table::compute_final_value.
1656 enum Compute_final_value_status
1657 {
1658 // No error.
1659 CFVS_OK,
1660 // Unsupported symbol section.
1661 CFVS_UNSUPPORTED_SYMBOL_SECTION,
1662 // No output section.
1663 CFVS_NO_OUTPUT_SECTION
1664 };
1665
1666 // Compute the final value of SYM and store status in location PSTATUS.
1667 // During relaxation, this may be called multiple times for a symbol to
1668 // compute its would-be final value in each relaxation pass.
1669
1670 template<int size>
1671 typename Sized_symbol<size>::Value_type
1672 compute_final_value(const Sized_symbol<size>* sym,
1673 Compute_final_value_status* pstatus) const;
1674
1675 // Return the index of the first global symbol.
1676 unsigned int
1677 first_global_index() const
1678 { return this->first_global_index_; }
1679
1680 // Return the total number of symbols in the symbol table.
1681 unsigned int
1682 output_count() const
1683 { return this->output_count_; }
1684
1685 // Write out the global symbols.
1686 void
1687 write_globals(const Stringpool*, const Stringpool*,
1688 Output_symtab_xindex*, Output_symtab_xindex*,
1689 Output_file*) const;
1690
1691 // Write out a section symbol. Return the updated offset.
1692 void
1693 write_section_symbol(const Output_section*, Output_symtab_xindex*,
1694 Output_file*, off_t) const;
1695
1696 // Loop over all symbols, applying the function F to each.
1697 template<int size, typename F>
1698 void
1699 for_all_symbols(F f) const
1700 {
1701 for (Symbol_table_type::const_iterator p = this->table_.begin();
1702 p != this->table_.end();
1703 ++p)
1704 {
1705 Sized_symbol<size>* sym = static_cast<Sized_symbol<size>*>(p->second);
1706 f(sym);
1707 }
1708 }
1709
1710 // Dump statistical information to stderr.
1711 void
1712 print_stats() const;
1713
1714 // Return the version script information.
1715 const Version_script_info&
1716 version_script() const
1717 { return version_script_; }
1718
1719 // Completely override existing symbol.
1720 template<int size>
1721 void
1722 clone(Sized_symbol<size>* to, const Sized_symbol<size>* from)
1723 {
1724 if (to->clone(from))
1725 this->force_local(to);
1726 }
1727
1728 private:
1729 Symbol_table(const Symbol_table&);
1730 Symbol_table& operator=(const Symbol_table&);
1731
1732 // The type of the list of common symbols.
1733 typedef std::vector<Symbol*> Commons_type;
1734
1735 // The type of the symbol hash table.
1736
1737 typedef std::pair<Stringpool::Key, Stringpool::Key> Symbol_table_key;
1738
1739 // The hash function. The key values are Stringpool keys.
1740 struct Symbol_table_hash
1741 {
1742 inline size_t
1743 operator()(const Symbol_table_key& key) const
1744 {
1745 return key.first ^ key.second;
1746 }
1747 };
1748
1749 struct Symbol_table_eq
1750 {
1751 bool
1752 operator()(const Symbol_table_key&, const Symbol_table_key&) const;
1753 };
1754
1755 typedef Unordered_map<Symbol_table_key, Symbol*, Symbol_table_hash,
1756 Symbol_table_eq> Symbol_table_type;
1757
1758 typedef Unordered_map<const char*,
1759 Unordered_set<Symbol_location, Symbol_location_hash> >
1760 Odr_map;
1761
1762 // Make FROM a forwarder symbol to TO.
1763 void
1764 make_forwarder(Symbol* from, Symbol* to);
1765
1766 // Add a symbol.
1767 template<int size, bool big_endian>
1768 Sized_symbol<size>*
1769 add_from_object(Object*, const char* name, Stringpool::Key name_key,
1770 const char* version, Stringpool::Key version_key,
1771 bool def, const elfcpp::Sym<size, big_endian>& sym,
1772 unsigned int st_shndx, bool is_ordinary,
1773 unsigned int orig_st_shndx);
1774
1775 // Define a default symbol.
1776 template<int size, bool big_endian>
1777 void
1778 define_default_version(Sized_symbol<size>*, bool,
1779 Symbol_table_type::iterator);
1780
1781 // Resolve symbols.
1782 template<int size, bool big_endian>
1783 void
1784 resolve(Sized_symbol<size>* to,
1785 const elfcpp::Sym<size, big_endian>& sym,
1786 unsigned int st_shndx, bool is_ordinary,
1787 unsigned int orig_st_shndx,
1788 Object*, const char* version,
1789 bool is_default_version);
1790
1791 template<int size, bool big_endian>
1792 void
1793 resolve(Sized_symbol<size>* to, const Sized_symbol<size>* from);
1794
1795 // Record that a symbol is forced to be local by a version script or
1796 // by visibility.
1797 void
1798 force_local(Symbol*);
1799
1800 // Adjust NAME and *NAME_KEY for wrapping.
1801 const char*
1802 wrap_symbol(const char* name, Stringpool::Key* name_key);
1803
1804 // Whether we should override a symbol, based on flags in
1805 // resolve.cc.
1806 static bool
1807 should_override(const Symbol*, unsigned int, elfcpp::STT, Defined,
1808 Object*, bool*, bool*, bool);
1809
1810 // Report a problem in symbol resolution.
1811 static void
1812 report_resolve_problem(bool is_error, const char* msg, const Symbol* to,
1813 Defined, Object* object);
1814
1815 // Override a symbol.
1816 template<int size, bool big_endian>
1817 void
1818 override(Sized_symbol<size>* tosym,
1819 const elfcpp::Sym<size, big_endian>& fromsym,
1820 unsigned int st_shndx, bool is_ordinary,
1821 Object* object, const char* version);
1822
1823 // Whether we should override a symbol with a special symbol which
1824 // is automatically defined by the linker.
1825 static bool
1826 should_override_with_special(const Symbol*, elfcpp::STT, Defined);
1827
1828 // Override a symbol with a special symbol.
1829 template<int size>
1830 void
1831 override_with_special(Sized_symbol<size>* tosym,
1832 const Sized_symbol<size>* fromsym);
1833
1834 // Record all weak alias sets for a dynamic object.
1835 template<int size>
1836 void
1837 record_weak_aliases(std::vector<Sized_symbol<size>*>*);
1838
1839 // Define a special symbol.
1840 template<int size, bool big_endian>
1841 Sized_symbol<size>*
1842 define_special_symbol(const char** pname, const char** pversion,
1843 bool only_if_ref, elfcpp::STV visibility,
1844 Sized_symbol<size>** poldsym,
1845 bool* resolve_oldsym, bool is_forced_local);
1846
1847 // Define a symbol in an Output_data, sized version.
1848 template<int size>
1849 Sized_symbol<size>*
1850 do_define_in_output_data(const char* name, const char* version, Defined,
1851 Output_data*,
1852 typename elfcpp::Elf_types<size>::Elf_Addr value,
1853 typename elfcpp::Elf_types<size>::Elf_WXword ssize,
1854 elfcpp::STT type, elfcpp::STB binding,
1855 elfcpp::STV visibility, unsigned char nonvis,
1856 bool offset_is_from_end, bool only_if_ref);
1857
1858 // Define a symbol in an Output_segment, sized version.
1859 template<int size>
1860 Sized_symbol<size>*
1861 do_define_in_output_segment(
1862 const char* name, const char* version, Defined, Output_segment* os,
1863 typename elfcpp::Elf_types<size>::Elf_Addr value,
1864 typename elfcpp::Elf_types<size>::Elf_WXword ssize,
1865 elfcpp::STT type, elfcpp::STB binding,
1866 elfcpp::STV visibility, unsigned char nonvis,
1867 Symbol::Segment_offset_base offset_base, bool only_if_ref);
1868
1869 // Define a symbol as a constant, sized version.
1870 template<int size>
1871 Sized_symbol<size>*
1872 do_define_as_constant(
1873 const char* name, const char* version, Defined,
1874 typename elfcpp::Elf_types<size>::Elf_Addr value,
1875 typename elfcpp::Elf_types<size>::Elf_WXword ssize,
1876 elfcpp::STT type, elfcpp::STB binding,
1877 elfcpp::STV visibility, unsigned char nonvis,
1878 bool only_if_ref, bool force_override);
1879
1880 // Add any undefined symbols named on the command line to the symbol
1881 // table, sized version.
1882 template<int size>
1883 void
1884 do_add_undefined_symbols_from_command_line(Layout*);
1885
1886 // Add one undefined symbol.
1887 template<int size>
1888 void
1889 add_undefined_symbol_from_command_line(const char* name);
1890
1891 // Types of common symbols.
1892
1893 enum Commons_section_type
1894 {
1895 COMMONS_NORMAL,
1896 COMMONS_TLS,
1897 COMMONS_SMALL,
1898 COMMONS_LARGE
1899 };
1900
1901 // Allocate the common symbols, sized version.
1902 template<int size>
1903 void
1904 do_allocate_commons(Layout*, Mapfile*, Sort_commons_order);
1905
1906 // Allocate the common symbols from one list.
1907 template<int size>
1908 void
1909 do_allocate_commons_list(Layout*, Commons_section_type, Commons_type*,
1910 Mapfile*, Sort_commons_order);
1911
1912 // Returns all of the lines attached to LOC, not just the one the
1913 // instruction actually came from. This helps the ODR checker avoid
1914 // false positives.
1915 static std::vector<std::string>
1916 linenos_from_loc(const Task* task, const Symbol_location& loc);
1917
1918 // Implement detect_odr_violations.
1919 template<int size, bool big_endian>
1920 void
1921 sized_detect_odr_violations() const;
1922
1923 // Finalize symbols specialized for size.
1924 template<int size>
1925 off_t
1926 sized_finalize(off_t, Stringpool*, unsigned int*);
1927
1928 // Finalize a symbol. Return whether it should be added to the
1929 // symbol table.
1930 template<int size>
1931 bool
1932 sized_finalize_symbol(Symbol*);
1933
1934 // Add a symbol the final symtab by setting its index.
1935 template<int size>
1936 void
1937 add_to_final_symtab(Symbol*, Stringpool*, unsigned int* pindex, off_t* poff);
1938
1939 // Write globals specialized for size and endianness.
1940 template<int size, bool big_endian>
1941 void
1942 sized_write_globals(const Stringpool*, const Stringpool*,
1943 Output_symtab_xindex*, Output_symtab_xindex*,
1944 Output_file*) const;
1945
1946 // Write out a symbol to P.
1947 template<int size, bool big_endian>
1948 void
1949 sized_write_symbol(Sized_symbol<size>*,
1950 typename elfcpp::Elf_types<size>::Elf_Addr value,
1951 unsigned int shndx, elfcpp::STB,
1952 const Stringpool*, unsigned char* p) const;
1953
1954 // Possibly warn about an undefined symbol from a dynamic object.
1955 void
1956 warn_about_undefined_dynobj_symbol(Symbol*) const;
1957
1958 // Write out a section symbol, specialized for size and endianness.
1959 template<int size, bool big_endian>
1960 void
1961 sized_write_section_symbol(const Output_section*, Output_symtab_xindex*,
1962 Output_file*, off_t) const;
1963
1964 // The type of the list of symbols which have been forced local.
1965 typedef std::vector<Symbol*> Forced_locals;
1966
1967 // A map from symbols with COPY relocs to the dynamic objects where
1968 // they are defined.
1969 typedef Unordered_map<const Symbol*, Dynobj*> Copied_symbol_dynobjs;
1970
1971 // We increment this every time we see a new undefined symbol, for
1972 // use in archive groups.
1973 size_t saw_undefined_;
1974 // The index of the first global symbol in the output file.
1975 unsigned int first_global_index_;
1976 // The file offset within the output symtab section where we should
1977 // write the table.
1978 off_t offset_;
1979 // The number of global symbols we want to write out.
1980 unsigned int output_count_;
1981 // The file offset of the global dynamic symbols, or 0 if none.
1982 off_t dynamic_offset_;
1983 // The index of the first global dynamic symbol (including
1984 // forced-local symbols).
1985 unsigned int first_dynamic_global_index_;
1986 // The number of global dynamic symbols (including forced-local symbols),
1987 // or 0 if none.
1988 unsigned int dynamic_count_;
1989 // Set if a STT_GNU_IFUNC or STB_GNU_UNIQUE symbol will be output.
1990 bool has_gnu_output_;
1991 // The symbol hash table.
1992 Symbol_table_type table_;
1993 // A pool of symbol names. This is used for all global symbols.
1994 // Entries in the hash table point into this pool.
1995 Stringpool namepool_;
1996 // Forwarding symbols.
1997 Unordered_map<const Symbol*, Symbol*> forwarders_;
1998 // Weak aliases. A symbol in this list points to the next alias.
1999 // The aliases point to each other in a circular list.
2000 Unordered_map<Symbol*, Symbol*> weak_aliases_;
2001 // We don't expect there to be very many common symbols, so we keep
2002 // a list of them. When we find a common symbol we add it to this
2003 // list. It is possible that by the time we process the list the
2004 // symbol is no longer a common symbol. It may also have become a
2005 // forwarder.
2006 Commons_type commons_;
2007 // This is like the commons_ field, except that it holds TLS common
2008 // symbols.
2009 Commons_type tls_commons_;
2010 // This is for small common symbols.
2011 Commons_type small_commons_;
2012 // This is for large common symbols.
2013 Commons_type large_commons_;
2014 // A list of symbols which have been forced to be local. We don't
2015 // expect there to be very many of them, so we keep a list of them
2016 // rather than walking the whole table to find them.
2017 Forced_locals forced_locals_;
2018 // Manage symbol warnings.
2019 Warnings warnings_;
2020 // Manage potential One Definition Rule (ODR) violations.
2021 Odr_map candidate_odr_violations_;
2022
2023 // When we emit a COPY reloc for a symbol, we define it in an
2024 // Output_data. When it's time to emit version information for it,
2025 // we need to know the dynamic object in which we found the original
2026 // definition. This maps symbols with COPY relocs to the dynamic
2027 // object where they were defined.
2028 Copied_symbol_dynobjs copied_symbol_dynobjs_;
2029 // Information parsed from the version script, if any.
2030 const Version_script_info& version_script_;
2031 Garbage_collection* gc_;
2032 Icf* icf_;
2033 // Target-specific symbols, if any.
2034 std::vector<Symbol*> target_symbols_;
2035 };
2036
2037 // We inline get_sized_symbol for efficiency.
2038
2039 template<int size>
2040 Sized_symbol<size>*
2041 Symbol_table::get_sized_symbol(Symbol* sym) const
2042 {
2043 gold_assert(size == parameters->target().get_size());
2044 return static_cast<Sized_symbol<size>*>(sym);
2045 }
2046
2047 template<int size>
2048 const Sized_symbol<size>*
2049 Symbol_table::get_sized_symbol(const Symbol* sym) const
2050 {
2051 gold_assert(size == parameters->target().get_size());
2052 return static_cast<const Sized_symbol<size>*>(sym);
2053 }
2054
2055 } // End namespace gold.
2056
2057 #endif // !defined(GOLD_SYMTAB_H)