1 // symtab.h -- the gold symbol table -*- C++ -*-
3 // Copyright 2006, 2007, 2008 Free Software Foundation, Inc.
4 // Written by Ian Lance Taylor <iant@google.com>.
6 // This file is part of gold.
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.
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.
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.
31 #include "parameters.h"
32 #include "stringpool.h"
44 template<int size, bool big_endian>
47 template<int size, bool big_endian>
50 class Version_script_info;
56 class Output_symtab_xindex;
58 // The base class of an entry in the symbol table. The symbol table
59 // can have a lot of entries, so we don't want this class to big.
60 // Size dependent fields can be found in the template class
61 // Sized_symbol. Targets may support their own derived classes.
66 // Because we want the class to be small, we don't use any virtual
67 // functions. But because symbols can be defined in different
68 // places, we need to classify them. This enum is the different
69 // sources of symbols we support.
72 // Symbol defined in a relocatable or dynamic input file--this is
73 // the most common case.
75 // Symbol defined in an Output_data, a special section created by
78 // Symbol defined in an Output_segment, with no associated
81 // Symbol value is constant.
83 // Symbol is undefined.
87 // When the source is IN_OUTPUT_SEGMENT, we need to describe what
89 enum Segment_offset_base
91 // From the start of the segment.
93 // From the end of the segment.
95 // From the filesz of the segment--i.e., after the loaded bytes
96 // but before the bytes which are allocated but zeroed.
100 // Return the symbol name.
103 { return this->name_; }
105 // Return the (ANSI) demangled version of the name, if
106 // parameters.demangle() is true. Otherwise, return the name. This
107 // is intended to be used only for logging errors, so it's not
110 demangled_name() const;
112 // Return the symbol version. This will return NULL for an
113 // unversioned symbol.
116 { return this->version_; }
118 // Return whether this version is the default for this symbol name
119 // (eg, "foo@@V2" is a default version; "foo@V1" is not). Only
120 // meaningful for versioned symbols.
124 gold_assert(this->version_ != NULL);
125 return this->is_def_;
128 // Set that this version is the default for this symbol name.
131 { this->is_def_ = true; }
133 // Return the symbol source.
136 { return this->source_; }
138 // Return the object with which this symbol is associated.
142 gold_assert(this->source_ == FROM_OBJECT);
143 return this->u_.from_object.object;
146 // Return the index of the section in the input relocatable or
147 // dynamic object file.
149 shndx(bool* is_ordinary) const
151 gold_assert(this->source_ == FROM_OBJECT);
152 *is_ordinary = this->is_ordinary_shndx_;
153 return this->u_.from_object.shndx;
156 // Return the output data section with which this symbol is
157 // associated, if the symbol was specially defined with respect to
158 // an output data section.
162 gold_assert(this->source_ == IN_OUTPUT_DATA);
163 return this->u_.in_output_data.output_data;
166 // If this symbol was defined with respect to an output data
167 // section, return whether the value is an offset from end.
169 offset_is_from_end() const
171 gold_assert(this->source_ == IN_OUTPUT_DATA);
172 return this->u_.in_output_data.offset_is_from_end;
175 // Return the output segment with which this symbol is associated,
176 // if the symbol was specially defined with respect to an output
179 output_segment() const
181 gold_assert(this->source_ == IN_OUTPUT_SEGMENT);
182 return this->u_.in_output_segment.output_segment;
185 // If this symbol was defined with respect to an output segment,
186 // return the offset base.
190 gold_assert(this->source_ == IN_OUTPUT_SEGMENT);
191 return this->u_.in_output_segment.offset_base;
194 // Return the symbol binding.
197 { return this->binding_; }
199 // Return the symbol type.
202 { return this->type_; }
204 // Return the symbol visibility.
207 { return this->visibility_; }
209 // Return the non-visibility part of the st_other field.
212 { return this->nonvis_; }
214 // Return whether this symbol is a forwarder. This will never be
215 // true of a symbol found in the hash table, but may be true of
216 // symbol pointers attached to object files.
219 { return this->is_forwarder_; }
221 // Mark this symbol as a forwarder.
224 { this->is_forwarder_ = true; }
226 // Return whether this symbol has an alias in the weak aliases table
230 { return this->has_alias_; }
232 // Mark this symbol as having an alias.
235 { this->has_alias_ = true; }
237 // Return whether this symbol needs an entry in the dynamic symbol
240 needs_dynsym_entry() const
242 return (this->needs_dynsym_entry_
243 || (this->in_reg() && this->in_dyn()));
246 // Mark this symbol as needing an entry in the dynamic symbol table.
248 set_needs_dynsym_entry()
249 { this->needs_dynsym_entry_ = true; }
251 // Return whether this symbol should be added to the dynamic symbol
254 should_add_dynsym_entry() const;
256 // Return whether this symbol has been seen in a regular object.
259 { return this->in_reg_; }
261 // Mark this symbol as having been seen in a regular object.
264 { this->in_reg_ = true; }
266 // Return whether this symbol has been seen in a dynamic object.
269 { return this->in_dyn_; }
271 // Mark this symbol as having been seen in a dynamic object.
274 { this->in_dyn_ = true; }
276 // Return the index of this symbol in the output file symbol table.
277 // A value of -1U means that this symbol is not going into the
278 // output file. This starts out as zero, and is set to a non-zero
279 // value by Symbol_table::finalize. It is an error to ask for the
280 // symbol table index before it has been set.
284 gold_assert(this->symtab_index_ != 0);
285 return this->symtab_index_;
288 // Set the index of the symbol in the output file symbol table.
290 set_symtab_index(unsigned int index)
292 gold_assert(index != 0);
293 this->symtab_index_ = index;
296 // Return whether this symbol already has an index in the output
297 // file symbol table.
299 has_symtab_index() const
300 { return this->symtab_index_ != 0; }
302 // Return the index of this symbol in the dynamic symbol table. A
303 // value of -1U means that this symbol is not going into the dynamic
304 // symbol table. This starts out as zero, and is set to a non-zero
305 // during Layout::finalize. It is an error to ask for the dynamic
306 // symbol table index before it has been set.
310 gold_assert(this->dynsym_index_ != 0);
311 return this->dynsym_index_;
314 // Set the index of the symbol in the dynamic symbol table.
316 set_dynsym_index(unsigned int index)
318 gold_assert(index != 0);
319 this->dynsym_index_ = index;
322 // Return whether this symbol already has an index in the dynamic
325 has_dynsym_index() const
326 { return this->dynsym_index_ != 0; }
328 // Return whether this symbol has an entry in the GOT section.
329 // For a TLS symbol, this GOT entry will hold its tp-relative offset.
331 has_got_offset(unsigned int got_type) const
332 { return this->got_offsets_.get_offset(got_type) != -1U; }
334 // Return the offset into the GOT section of this symbol.
336 got_offset(unsigned int got_type) const
338 unsigned int got_offset = this->got_offsets_.get_offset(got_type);
339 gold_assert(got_offset != -1U);
343 // Set the GOT offset of this symbol.
345 set_got_offset(unsigned int got_type, unsigned int got_offset)
346 { this->got_offsets_.set_offset(got_type, got_offset); }
348 // Return whether this symbol has an entry in the PLT section.
350 has_plt_offset() const
351 { return this->has_plt_offset_; }
353 // Return the offset into the PLT section of this symbol.
357 gold_assert(this->has_plt_offset());
358 return this->plt_offset_;
361 // Set the PLT offset of this symbol.
363 set_plt_offset(unsigned int plt_offset)
365 this->has_plt_offset_ = true;
366 this->plt_offset_ = plt_offset;
369 // Return whether this dynamic symbol needs a special value in the
370 // dynamic symbol table.
372 needs_dynsym_value() const
373 { return this->needs_dynsym_value_; }
375 // Set that this dynamic symbol needs a special value in the dynamic
378 set_needs_dynsym_value()
380 gold_assert(this->object()->is_dynamic());
381 this->needs_dynsym_value_ = true;
384 // Return true if the final value of this symbol is known at link
387 final_value_is_known() const;
389 // Return whether this is a defined symbol (not undefined or
395 if (this->source_ != FROM_OBJECT)
396 return this->source_ != IS_UNDEFINED;
397 unsigned int shndx = this->shndx(&is_ordinary);
399 ? shndx != elfcpp::SHN_UNDEF
400 : shndx != elfcpp::SHN_COMMON);
403 // Return true if this symbol is from a dynamic object.
405 is_from_dynobj() const
407 return this->source_ == FROM_OBJECT && this->object()->is_dynamic();
410 // Return whether this is an undefined symbol.
415 return ((this->source_ == FROM_OBJECT
416 && this->shndx(&is_ordinary) == elfcpp::SHN_UNDEF
418 || this->source_ == IS_UNDEFINED);
421 // Return whether this is a weak undefined symbol.
423 is_weak_undefined() const
424 { return this->is_undefined() && this->binding() == elfcpp::STB_WEAK; }
426 // Return whether this is an absolute symbol.
431 return ((this->source_ == FROM_OBJECT
432 && this->shndx(&is_ordinary) == elfcpp::SHN_ABS
434 || this->source_ == IS_CONSTANT);
437 // Return whether this is a common symbol.
442 return (this->source_ == FROM_OBJECT
443 && ((this->shndx(&is_ordinary) == elfcpp::SHN_COMMON
445 || this->type_ == elfcpp::STT_COMMON));
448 // Return whether this symbol can be seen outside this object.
450 is_externally_visible() const
452 return (this->visibility_ == elfcpp::STV_DEFAULT
453 || this->visibility_ == elfcpp::STV_PROTECTED);
456 // Return true if this symbol can be preempted by a definition in
457 // another link unit.
459 is_preemptible() const
461 // It doesn't make sense to ask whether a symbol defined in
462 // another object is preemptible.
463 gold_assert(!this->is_from_dynobj());
465 // It doesn't make sense to ask whether an undefined symbol
467 gold_assert(!this->is_undefined());
469 // If a symbol does not have default visibility, it can not be
470 // seen outside this link unit and therefore is not preemptible.
471 if (this->visibility_ != elfcpp::STV_DEFAULT)
474 // If this symbol has been forced to be a local symbol by a
475 // version script, then it is not visible outside this link unit
476 // and is not preemptible.
477 if (this->is_forced_local_)
480 // If we are not producing a shared library, then nothing is
482 if (!parameters->options().shared())
485 // If the user used -Bsymbolic, then nothing is preemptible.
486 if (parameters->options().Bsymbolic())
489 // If the user used -Bsymbolic-functions, then functions are not
490 // preemptible. We explicitly check for not being STT_OBJECT,
491 // rather than for being STT_FUNC, because that is what the GNU
493 if (this->type() != elfcpp::STT_OBJECT
494 && parameters->options().Bsymbolic_functions())
497 // Otherwise the symbol is preemptible.
501 // Return true if this symbol is a function that needs a PLT entry.
502 // If the symbol is defined in a dynamic object or if it is subject
503 // to pre-emption, we need to make a PLT entry. If we're doing a
504 // static link, we don't create PLT entries.
506 needs_plt_entry() const
508 return (!parameters->doing_static_link()
509 && this->type() == elfcpp::STT_FUNC
510 && (this->is_from_dynobj()
511 || this->is_undefined()
512 || this->is_preemptible()));
515 // When determining whether a reference to a symbol needs a dynamic
516 // relocation, we need to know several things about the reference.
517 // These flags may be or'ed together.
520 // Reference to the symbol's absolute address.
522 // A non-PIC reference.
528 // Given a direct absolute or pc-relative static relocation against
529 // the global symbol, this function returns whether a dynamic relocation
533 needs_dynamic_reloc(int flags) const
535 // No dynamic relocations in a static link!
536 if (parameters->doing_static_link())
539 // A reference to a weak undefined symbol from an executable should be
540 // statically resolved to 0, and does not need a dynamic relocation.
541 // This matches gnu ld behavior.
542 if (this->is_weak_undefined() && !parameters->options().shared())
545 // A reference to an absolute symbol does not need a dynamic relocation.
546 if (this->is_absolute())
549 // An absolute reference within a position-independent output file
550 // will need a dynamic relocation.
551 if ((flags & ABSOLUTE_REF)
552 && parameters->options().output_is_position_independent())
555 // A function call that can branch to a local PLT entry does not need
556 // a dynamic relocation. A non-pic pc-relative function call in a
557 // shared library cannot use a PLT entry.
558 if ((flags & FUNCTION_CALL)
559 && this->has_plt_offset()
560 && !((flags & NON_PIC_REF) && parameters->options().shared()))
563 // A reference to any PLT entry in a non-position-independent executable
564 // does not need a dynamic relocation.
565 if (!parameters->options().output_is_position_independent()
566 && this->has_plt_offset())
569 // A reference to a symbol defined in a dynamic object or to a
570 // symbol that is preemptible will need a dynamic relocation.
571 if (this->is_from_dynobj()
572 || this->is_undefined()
573 || this->is_preemptible())
576 // For all other cases, return FALSE.
580 // Given a direct absolute static relocation against
581 // the global symbol, where a dynamic relocation is needed, this
582 // function returns whether a relative dynamic relocation can be used.
583 // The caller must determine separately whether the static relocation
584 // is compatible with a relative relocation.
587 can_use_relative_reloc(bool is_function_call) const
589 // A function call that can branch to a local PLT entry can
590 // use a RELATIVE relocation.
591 if (is_function_call && this->has_plt_offset())
594 // A reference to a symbol defined in a dynamic object or to a
595 // symbol that is preemptible can not use a RELATIVE relocaiton.
596 if (this->is_from_dynobj()
597 || this->is_undefined()
598 || this->is_preemptible())
601 // For all other cases, return TRUE.
605 // Return the output section where this symbol is defined. Return
606 // NULL if the symbol has an absolute value.
608 output_section() const;
610 // Set the symbol's output section. This is used for symbols
611 // defined in scripts. This should only be called after the symbol
612 // table has been finalized.
614 set_output_section(Output_section*);
616 // Return whether there should be a warning for references to this
620 { return this->has_warning_; }
622 // Mark this symbol as having a warning.
625 { this->has_warning_ = true; }
627 // Return whether this symbol is defined by a COPY reloc from a
630 is_copied_from_dynobj() const
631 { return this->is_copied_from_dynobj_; }
633 // Mark this symbol as defined by a COPY reloc.
635 set_is_copied_from_dynobj()
636 { this->is_copied_from_dynobj_ = true; }
638 // Return whether this symbol is forced to visibility STB_LOCAL
639 // by a "local:" entry in a version script.
641 is_forced_local() const
642 { return this->is_forced_local_; }
644 // Mark this symbol as forced to STB_LOCAL visibility.
646 set_is_forced_local()
647 { this->is_forced_local_ = true; }
650 // Instances of this class should always be created at a specific
653 { memset(this, 0, sizeof *this); }
655 // Initialize the general fields.
657 init_fields(const char* name, const char* version,
658 elfcpp::STT type, elfcpp::STB binding,
659 elfcpp::STV visibility, unsigned char nonvis);
661 // Initialize fields from an ELF symbol in OBJECT. ST_SHNDX is the
662 // section index, IS_ORDINARY is whether it is a normal section
663 // index rather than a special code.
664 template<int size, bool big_endian>
666 init_base_object(const char *name, const char* version, Object* object,
667 const elfcpp::Sym<size, big_endian>&, unsigned int st_shndx,
670 // Initialize fields for an Output_data.
672 init_base_output_data(const char* name, const char* version, Output_data*,
673 elfcpp::STT, elfcpp::STB, elfcpp::STV,
674 unsigned char nonvis, bool offset_is_from_end);
676 // Initialize fields for an Output_segment.
678 init_base_output_segment(const char* name, const char* version,
679 Output_segment* os, elfcpp::STT type,
680 elfcpp::STB binding, elfcpp::STV visibility,
681 unsigned char nonvis,
682 Segment_offset_base offset_base);
684 // Initialize fields for a constant.
686 init_base_constant(const char* name, const char* version, elfcpp::STT type,
687 elfcpp::STB binding, elfcpp::STV visibility,
688 unsigned char nonvis);
690 // Initialize fields for an undefined symbol.
692 init_base_undefined(const char* name, const char* version, elfcpp::STT type,
693 elfcpp::STB binding, elfcpp::STV visibility,
694 unsigned char nonvis);
696 // Override existing symbol.
697 template<int size, bool big_endian>
699 override_base(const elfcpp::Sym<size, big_endian>&, unsigned int st_shndx,
700 bool is_ordinary, Object* object, const char* version);
702 // Override existing symbol with a special symbol.
704 override_base_with_special(const Symbol* from);
706 // Override symbol version.
708 override_version(const char* version);
710 // Allocate a common symbol by giving it a location in the output
713 allocate_base_common(Output_data*);
716 Symbol(const Symbol&);
717 Symbol& operator=(const Symbol&);
719 // Symbol name (expected to point into a Stringpool).
721 // Symbol version (expected to point into a Stringpool). This may
723 const char* version_;
727 // This struct is used if SOURCE_ == FROM_OBJECT.
730 // Object in which symbol is defined, or in which it was first
733 // Section number in object_ in which symbol is defined.
737 // This struct is used if SOURCE_ == IN_OUTPUT_DATA.
740 // Output_data in which symbol is defined. Before
741 // Layout::finalize the symbol's value is an offset within the
743 Output_data* output_data;
744 // True if the offset is from the end, false if the offset is
745 // from the beginning.
746 bool offset_is_from_end;
749 // This struct is used if SOURCE_ == IN_OUTPUT_SEGMENT.
752 // Output_segment in which the symbol is defined. Before
753 // Layout::finalize the symbol's value is an offset.
754 Output_segment* output_segment;
755 // The base to use for the offset before Layout::finalize.
756 Segment_offset_base offset_base;
760 // The index of this symbol in the output file. If the symbol is
761 // not going into the output file, this value is -1U. This field
762 // starts as always holding zero. It is set to a non-zero value by
763 // Symbol_table::finalize.
764 unsigned int symtab_index_;
766 // The index of this symbol in the dynamic symbol table. If the
767 // symbol is not going into the dynamic symbol table, this value is
768 // -1U. This field starts as always holding zero. It is set to a
769 // non-zero value during Layout::finalize.
770 unsigned int dynsym_index_;
772 // If this symbol has an entry in the GOT section (has_got_offset_
773 // is true), this holds the offset from the start of the GOT section.
774 // A symbol may have more than one GOT offset (e.g., when mixing
775 // modules compiled with two different TLS models), but will usually
777 Got_offset_list got_offsets_;
779 // If this symbol has an entry in the PLT section (has_plt_offset_
780 // is true), then this is the offset from the start of the PLT
782 unsigned int plt_offset_;
784 // Symbol type (bits 0 to 3).
785 elfcpp::STT type_ : 4;
786 // Symbol binding (bits 4 to 7).
787 elfcpp::STB binding_ : 4;
788 // Symbol visibility (bits 8 to 9).
789 elfcpp::STV visibility_ : 2;
790 // Rest of symbol st_other field (bits 10 to 15).
791 unsigned int nonvis_ : 6;
792 // The type of symbol (bits 16 to 18).
794 // True if this symbol always requires special target-specific
795 // handling (bit 19).
796 bool is_target_special_ : 1;
797 // True if this is the default version of the symbol (bit 20).
799 // True if this symbol really forwards to another symbol. This is
800 // used when we discover after the fact that two different entries
801 // in the hash table really refer to the same symbol. This will
802 // never be set for a symbol found in the hash table, but may be set
803 // for a symbol found in the list of symbols attached to an Object.
804 // It forwards to the symbol found in the forwarders_ map of
805 // Symbol_table (bit 21).
806 bool is_forwarder_ : 1;
807 // True if the symbol has an alias in the weak_aliases table in
808 // Symbol_table (bit 22).
810 // True if this symbol needs to be in the dynamic symbol table (bit
812 bool needs_dynsym_entry_ : 1;
813 // True if we've seen this symbol in a regular object (bit 24).
815 // True if we've seen this symbol in a dynamic object (bit 25).
817 // True if the symbol has an entry in the PLT section (bit 26).
818 bool has_plt_offset_ : 1;
819 // True if this is a dynamic symbol which needs a special value in
820 // the dynamic symbol table (bit 27).
821 bool needs_dynsym_value_ : 1;
822 // True if there is a warning for this symbol (bit 28).
823 bool has_warning_ : 1;
824 // True if we are using a COPY reloc for this symbol, so that the
825 // real definition lives in a dynamic object (bit 29).
826 bool is_copied_from_dynobj_ : 1;
827 // True if this symbol was forced to local visibility by a version
829 bool is_forced_local_ : 1;
830 // True if the field u_.from_object.shndx is an ordinary section
831 // index, not one of the special codes from SHN_LORESERVE to
833 bool is_ordinary_shndx_ : 1;
836 // The parts of a symbol which are size specific. Using a template
837 // derived class like this helps us use less space on a 32-bit system.
840 class Sized_symbol : public Symbol
843 typedef typename elfcpp::Elf_types<size>::Elf_Addr Value_type;
844 typedef typename elfcpp::Elf_types<size>::Elf_WXword Size_type;
849 // Initialize fields from an ELF symbol in OBJECT. ST_SHNDX is the
850 // section index, IS_ORDINARY is whether it is a normal section
851 // index rather than a special code.
852 template<bool big_endian>
854 init_object(const char *name, const char* version, Object* object,
855 const elfcpp::Sym<size, big_endian>&, unsigned int st_shndx,
858 // Initialize fields for an Output_data.
860 init_output_data(const char* name, const char* version, Output_data*,
861 Value_type value, Size_type symsize, elfcpp::STT,
862 elfcpp::STB, elfcpp::STV, unsigned char nonvis,
863 bool offset_is_from_end);
865 // Initialize fields for an Output_segment.
867 init_output_segment(const char* name, const char* version, Output_segment*,
868 Value_type value, Size_type symsize, elfcpp::STT,
869 elfcpp::STB, elfcpp::STV, unsigned char nonvis,
870 Segment_offset_base offset_base);
872 // Initialize fields for a constant.
874 init_constant(const char* name, const char* version, Value_type value,
875 Size_type symsize, elfcpp::STT, elfcpp::STB, elfcpp::STV,
876 unsigned char nonvis);
878 // Initialize fields for an undefined symbol.
880 init_undefined(const char* name, const char* version, elfcpp::STT,
881 elfcpp::STB, elfcpp::STV, unsigned char nonvis);
883 // Override existing symbol.
884 template<bool big_endian>
886 override(const elfcpp::Sym<size, big_endian>&, unsigned int st_shndx,
887 bool is_ordinary, Object* object, const char* version);
889 // Override existing symbol with a special symbol.
891 override_with_special(const Sized_symbol<size>*);
893 // Return the symbol's value.
896 { return this->value_; }
898 // Return the symbol's size (we can't call this 'size' because that
899 // is a template parameter).
902 { return this->symsize_; }
904 // Set the symbol size. This is used when resolving common symbols.
906 set_symsize(Size_type symsize)
907 { this->symsize_ = symsize; }
909 // Set the symbol value. This is called when we store the final
910 // values of the symbols into the symbol table.
912 set_value(Value_type value)
913 { this->value_ = value; }
915 // Allocate a common symbol by giving it a location in the output
918 allocate_common(Output_data*, Value_type value);
921 Sized_symbol(const Sized_symbol&);
922 Sized_symbol& operator=(const Sized_symbol&);
924 // Symbol value. Before Layout::finalize this is the offset in the
925 // input section. This is set to the final value during
932 // A struct describing a symbol defined by the linker, where the value
933 // of the symbol is defined based on an output section. This is used
934 // for symbols defined by the linker, like "_init_array_start".
936 struct Define_symbol_in_section
940 // The name of the output section with which this symbol should be
941 // associated. If there is no output section with that name, the
942 // symbol will be defined as zero.
943 const char* output_section;
944 // The offset of the symbol within the output section. This is an
945 // offset from the start of the output section, unless start_at_end
946 // is true, in which case this is an offset from the end of the
949 // The size of the symbol.
953 // The symbol binding.
955 // The symbol visibility.
956 elfcpp::STV visibility;
957 // The rest of the st_other field.
958 unsigned char nonvis;
959 // If true, the value field is an offset from the end of the output
961 bool offset_is_from_end;
962 // If true, this symbol is defined only if we see a reference to it.
966 // A struct describing a symbol defined by the linker, where the value
967 // of the symbol is defined based on a segment. This is used for
968 // symbols defined by the linker, like "_end". We describe the
969 // segment with which the symbol should be associated by its
970 // characteristics. If no segment meets these characteristics, the
971 // symbol will be defined as zero. If there is more than one segment
972 // which meets these characteristics, we will use the first one.
974 struct Define_symbol_in_segment
978 // The segment type where the symbol should be defined, typically
980 elfcpp::PT segment_type;
981 // Bitmask of segment flags which must be set.
982 elfcpp::PF segment_flags_set;
983 // Bitmask of segment flags which must be clear.
984 elfcpp::PF segment_flags_clear;
985 // The offset of the symbol within the segment. The offset is
986 // calculated from the position set by offset_base.
988 // The size of the symbol.
992 // The symbol binding.
994 // The symbol visibility.
995 elfcpp::STV visibility;
996 // The rest of the st_other field.
997 unsigned char nonvis;
998 // The base from which we compute the offset.
999 Symbol::Segment_offset_base offset_base;
1000 // If true, this symbol is defined only if we see a reference to it.
1004 // This class manages warnings. Warnings are a GNU extension. When
1005 // we see a section named .gnu.warning.SYM in an object file, and if
1006 // we wind using the definition of SYM from that object file, then we
1007 // will issue a warning for any relocation against SYM from a
1008 // different object file. The text of the warning is the contents of
1009 // the section. This is not precisely the definition used by the old
1010 // GNU linker; the old GNU linker treated an occurrence of
1011 // .gnu.warning.SYM as defining a warning symbol. A warning symbol
1012 // would trigger a warning on any reference. However, it was
1013 // inconsistent in that a warning in a dynamic object only triggered
1014 // if there was no definition in a regular object. This linker is
1015 // different in that we only issue a warning if we use the symbol
1016 // definition from the same object file as the warning section.
1025 // Add a warning for symbol NAME in object OBJ. WARNING is the text
1028 add_warning(Symbol_table* symtab, const char* name, Object* obj,
1029 const std::string& warning);
1031 // For each symbol for which we should give a warning, make a note
1034 note_warnings(Symbol_table* symtab);
1036 // Issue a warning for a reference to SYM at RELINFO's location.
1037 template<int size, bool big_endian>
1039 issue_warning(const Symbol* sym, const Relocate_info<size, big_endian>*,
1040 size_t relnum, off_t reloffset) const;
1043 Warnings(const Warnings&);
1044 Warnings& operator=(const Warnings&);
1046 // What we need to know to get the warning text.
1047 struct Warning_location
1049 // The object the warning is in.
1051 // The warning text.
1055 : object(NULL), text()
1059 set(Object* o, const std::string& t)
1066 // A mapping from warning symbol names (canonicalized in
1067 // Symbol_table's namepool_ field) to warning information.
1068 typedef Unordered_map<const char*, Warning_location> Warning_table;
1070 Warning_table warnings_;
1073 // The main linker symbol table.
1078 // COUNT is an estimate of how many symbosl will be inserted in the
1079 // symbol table. It's ok to put 0 if you don't know; a correct
1080 // guess will just save some CPU by reducing hashtable resizes.
1081 Symbol_table(unsigned int count, const Version_script_info& version_script);
1085 // Add COUNT external symbols from the relocatable object RELOBJ to
1086 // the symbol table. SYMS is the symbols, SYMNDX_OFFSET is the
1087 // offset in the symbol table of the first symbol, SYM_NAMES is
1088 // their names, SYM_NAME_SIZE is the size of SYM_NAMES. This sets
1089 // SYMPOINTERS to point to the symbols in the symbol table. It sets
1090 // *DEFINED to the number of defined symbols.
1091 template<int size, bool big_endian>
1093 add_from_relobj(Sized_relobj<size, big_endian>* relobj,
1094 const unsigned char* syms, size_t count,
1095 size_t symndx_offset, const char* sym_names,
1096 size_t sym_name_size,
1097 typename Sized_relobj<size, big_endian>::Symbols*,
1100 // Add COUNT dynamic symbols from the dynamic object DYNOBJ to the
1101 // symbol table. SYMS is the symbols. SYM_NAMES is their names.
1102 // SYM_NAME_SIZE is the size of SYM_NAMES. The other parameters are
1103 // symbol version data.
1104 template<int size, bool big_endian>
1106 add_from_dynobj(Sized_dynobj<size, big_endian>* dynobj,
1107 const unsigned char* syms, size_t count,
1108 const char* sym_names, size_t sym_name_size,
1109 const unsigned char* versym, size_t versym_size,
1110 const std::vector<const char*>*,
1111 typename Sized_relobj<size, big_endian>::Symbols*,
1114 // Define a special symbol based on an Output_data. It is a
1115 // multiple definition error if this symbol is already defined.
1117 define_in_output_data(const char* name, const char* version,
1118 Output_data*, uint64_t value, uint64_t symsize,
1119 elfcpp::STT type, elfcpp::STB binding,
1120 elfcpp::STV visibility, unsigned char nonvis,
1121 bool offset_is_from_end, bool only_if_ref);
1123 // Define a special symbol based on an Output_segment. It is a
1124 // multiple definition error if this symbol is already defined.
1126 define_in_output_segment(const char* name, const char* version,
1127 Output_segment*, uint64_t value, uint64_t symsize,
1128 elfcpp::STT type, elfcpp::STB binding,
1129 elfcpp::STV visibility, unsigned char nonvis,
1130 Symbol::Segment_offset_base, bool only_if_ref);
1132 // Define a special symbol with a constant value. It is a multiple
1133 // definition error if this symbol is already defined.
1135 define_as_constant(const char* name, const char* version,
1136 uint64_t value, uint64_t symsize, elfcpp::STT type,
1137 elfcpp::STB binding, elfcpp::STV visibility,
1138 unsigned char nonvis, bool only_if_ref,
1139 bool force_override);
1141 // Define a set of symbols in output sections. If ONLY_IF_REF is
1142 // true, only define them if they are referenced.
1144 define_symbols(const Layout*, int count, const Define_symbol_in_section*,
1147 // Define a set of symbols in output segments. If ONLY_IF_REF is
1148 // true, only defined them if they are referenced.
1150 define_symbols(const Layout*, int count, const Define_symbol_in_segment*,
1153 // Define SYM using a COPY reloc. POSD is the Output_data where the
1154 // symbol should be defined--typically a .dyn.bss section. VALUE is
1155 // the offset within POSD.
1158 define_with_copy_reloc(Sized_symbol<size>* sym, Output_data* posd,
1159 typename elfcpp::Elf_types<size>::Elf_Addr);
1161 // Look up a symbol.
1163 lookup(const char*, const char* version = NULL) const;
1165 // Return the real symbol associated with the forwarder symbol FROM.
1167 resolve_forwards(const Symbol* from) const;
1169 // Return the sized version of a symbol in this table.
1172 get_sized_symbol(Symbol*) const;
1175 const Sized_symbol<size>*
1176 get_sized_symbol(const Symbol*) const;
1178 // Return the count of undefined symbols seen.
1180 saw_undefined() const
1181 { return this->saw_undefined_; }
1183 // Allocate the common symbols
1185 allocate_commons(Layout*, Mapfile*);
1187 // Add a warning for symbol NAME in object OBJ. WARNING is the text
1190 add_warning(const char* name, Object* obj, const std::string& warning)
1191 { this->warnings_.add_warning(this, name, obj, warning); }
1193 // Canonicalize a symbol name for use in the hash table.
1195 canonicalize_name(const char* name)
1196 { return this->namepool_.add(name, true, NULL); }
1198 // Possibly issue a warning for a reference to SYM at LOCATION which
1200 template<int size, bool big_endian>
1202 issue_warning(const Symbol* sym,
1203 const Relocate_info<size, big_endian>* relinfo,
1204 size_t relnum, off_t reloffset) const
1205 { this->warnings_.issue_warning(sym, relinfo, relnum, reloffset); }
1207 // Check candidate_odr_violations_ to find symbols with the same name
1208 // but apparently different definitions (different source-file/line-no).
1210 detect_odr_violations(const Task*, const char* output_file_name) const;
1212 // Add any undefined symbols named on the command line to the symbol
1215 add_undefined_symbols_from_command_line();
1217 // SYM is defined using a COPY reloc. Return the dynamic object
1218 // where the original definition was found.
1220 get_copy_source(const Symbol* sym) const;
1222 // Set the dynamic symbol indexes. INDEX is the index of the first
1223 // global dynamic symbol. Pointers to the symbols are stored into
1224 // the vector. The names are stored into the Stringpool. This
1225 // returns an updated dynamic symbol index.
1227 set_dynsym_indexes(unsigned int index, std::vector<Symbol*>*,
1228 Stringpool*, Versions*);
1230 // Finalize the symbol table after we have set the final addresses
1231 // of all the input sections. This sets the final symbol indexes,
1232 // values and adds the names to *POOL. *PLOCAL_SYMCOUNT is the
1233 // index of the first global symbol. OFF is the file offset of the
1234 // global symbol table, DYNOFF is the offset of the globals in the
1235 // dynamic symbol table, DYN_GLOBAL_INDEX is the index of the first
1236 // global dynamic symbol, and DYNCOUNT is the number of global
1237 // dynamic symbols. This records the parameters, and returns the
1238 // new file offset. It updates *PLOCAL_SYMCOUNT if it created any
1241 finalize(off_t off, off_t dynoff, size_t dyn_global_index, size_t dyncount,
1242 Stringpool* pool, unsigned int *plocal_symcount);
1244 // Write out the global symbols.
1246 write_globals(const Input_objects*, const Stringpool*, const Stringpool*,
1247 Output_symtab_xindex*, Output_symtab_xindex*,
1248 Output_file*) const;
1250 // Write out a section symbol. Return the updated offset.
1252 write_section_symbol(const Output_section*, Output_symtab_xindex*,
1253 Output_file*, off_t) const;
1255 // Dump statistical information to stderr.
1257 print_stats() const;
1259 // Return the version script information.
1260 const Version_script_info&
1261 version_script() const
1262 { return version_script_; }
1265 Symbol_table(const Symbol_table&);
1266 Symbol_table& operator=(const Symbol_table&);
1268 // The type of the list of common symbols.
1269 typedef std::vector<Symbol*> Commons_type;
1271 // Make FROM a forwarder symbol to TO.
1273 make_forwarder(Symbol* from, Symbol* to);
1276 template<int size, bool big_endian>
1278 add_from_object(Object*, const char *name, Stringpool::Key name_key,
1279 const char *version, Stringpool::Key version_key,
1280 bool def, const elfcpp::Sym<size, big_endian>& sym,
1281 unsigned int st_shndx, bool is_ordinary,
1282 unsigned int orig_st_shndx);
1285 template<int size, bool big_endian>
1287 resolve(Sized_symbol<size>* to,
1288 const elfcpp::Sym<size, big_endian>& sym,
1289 unsigned int st_shndx, bool is_ordinary,
1290 unsigned int orig_st_shndx,
1291 Object*, const char* version);
1293 template<int size, bool big_endian>
1295 resolve(Sized_symbol<size>* to, const Sized_symbol<size>* from);
1297 // Record that a symbol is forced to be local by a version script.
1299 force_local(Symbol*);
1301 // Adjust NAME and *NAME_KEY for wrapping.
1303 wrap_symbol(Object* object, const char*, Stringpool::Key* name_key);
1305 // Whether we should override a symbol, based on flags in
1308 should_override(const Symbol*, unsigned int, Object*, bool*);
1310 // Override a symbol.
1311 template<int size, bool big_endian>
1313 override(Sized_symbol<size>* tosym,
1314 const elfcpp::Sym<size, big_endian>& fromsym,
1315 unsigned int st_shndx, bool is_ordinary,
1316 Object* object, const char* version);
1318 // Whether we should override a symbol with a special symbol which
1319 // is automatically defined by the linker.
1321 should_override_with_special(const Symbol*);
1323 // Override a symbol with a special symbol.
1326 override_with_special(Sized_symbol<size>* tosym,
1327 const Sized_symbol<size>* fromsym);
1329 // Record all weak alias sets for a dynamic object.
1332 record_weak_aliases(std::vector<Sized_symbol<size>*>*);
1334 // Define a special symbol.
1335 template<int size, bool big_endian>
1337 define_special_symbol(const char** pname, const char** pversion,
1338 bool only_if_ref, Sized_symbol<size>** poldsym);
1340 // Define a symbol in an Output_data, sized version.
1343 do_define_in_output_data(const char* name, const char* version, Output_data*,
1344 typename elfcpp::Elf_types<size>::Elf_Addr value,
1345 typename elfcpp::Elf_types<size>::Elf_WXword ssize,
1346 elfcpp::STT type, elfcpp::STB binding,
1347 elfcpp::STV visibility, unsigned char nonvis,
1348 bool offset_is_from_end, bool only_if_ref);
1350 // Define a symbol in an Output_segment, sized version.
1353 do_define_in_output_segment(
1354 const char* name, const char* version, Output_segment* os,
1355 typename elfcpp::Elf_types<size>::Elf_Addr value,
1356 typename elfcpp::Elf_types<size>::Elf_WXword ssize,
1357 elfcpp::STT type, elfcpp::STB binding,
1358 elfcpp::STV visibility, unsigned char nonvis,
1359 Symbol::Segment_offset_base offset_base, bool only_if_ref);
1361 // Define a symbol as a constant, sized version.
1364 do_define_as_constant(
1365 const char* name, const char* version,
1366 typename elfcpp::Elf_types<size>::Elf_Addr value,
1367 typename elfcpp::Elf_types<size>::Elf_WXword ssize,
1368 elfcpp::STT type, elfcpp::STB binding,
1369 elfcpp::STV visibility, unsigned char nonvis,
1370 bool only_if_ref, bool force_override);
1372 // Add any undefined symbols named on the command line to the symbol
1373 // table, sized version.
1376 do_add_undefined_symbols_from_command_line();
1378 // Allocate the common symbols, sized version.
1381 do_allocate_commons(Layout*, Mapfile*);
1383 // Allocate the common symbols from one list.
1386 do_allocate_commons_list(Layout*, bool is_tls, Commons_type*, Mapfile*);
1388 // Implement detect_odr_violations.
1389 template<int size, bool big_endian>
1391 sized_detect_odr_violations() const;
1393 // Finalize symbols specialized for size.
1396 sized_finalize(off_t, Stringpool*, unsigned int*);
1398 // Finalize a symbol. Return whether it should be added to the
1402 sized_finalize_symbol(Symbol*);
1404 // Add a symbol the final symtab by setting its index.
1407 add_to_final_symtab(Symbol*, Stringpool*, unsigned int* pindex, off_t* poff);
1409 // Write globals specialized for size and endianness.
1410 template<int size, bool big_endian>
1412 sized_write_globals(const Input_objects*, const Stringpool*,
1413 const Stringpool*, Output_symtab_xindex*,
1414 Output_symtab_xindex*, Output_file*) const;
1416 // Write out a symbol to P.
1417 template<int size, bool big_endian>
1419 sized_write_symbol(Sized_symbol<size>*,
1420 typename elfcpp::Elf_types<size>::Elf_Addr value,
1422 const Stringpool*, unsigned char* p) const;
1424 // Possibly warn about an undefined symbol from a dynamic object.
1426 warn_about_undefined_dynobj_symbol(const Input_objects*, Symbol*) const;
1428 // Write out a section symbol, specialized for size and endianness.
1429 template<int size, bool big_endian>
1431 sized_write_section_symbol(const Output_section*, Output_symtab_xindex*,
1432 Output_file*, off_t) const;
1434 // The type of the symbol hash table.
1436 typedef std::pair<Stringpool::Key, Stringpool::Key> Symbol_table_key;
1438 struct Symbol_table_hash
1441 operator()(const Symbol_table_key&) const;
1444 struct Symbol_table_eq
1447 operator()(const Symbol_table_key&, const Symbol_table_key&) const;
1450 typedef Unordered_map<Symbol_table_key, Symbol*, Symbol_table_hash,
1451 Symbol_table_eq> Symbol_table_type;
1453 // The type of the list of symbols which have been forced local.
1454 typedef std::vector<Symbol*> Forced_locals;
1456 // A map from symbols with COPY relocs to the dynamic objects where
1457 // they are defined.
1458 typedef Unordered_map<const Symbol*, Dynobj*> Copied_symbol_dynobjs;
1460 // A map from symbol name (as a pointer into the namepool) to all
1461 // the locations the symbols is (weakly) defined (and certain other
1462 // conditions are met). This map will be used later to detect
1463 // possible One Definition Rule (ODR) violations.
1464 struct Symbol_location
1466 Object* object; // Object where the symbol is defined.
1467 unsigned int shndx; // Section-in-object where the symbol is defined.
1468 off_t offset; // Offset-in-section where the symbol is defined.
1469 bool operator==(const Symbol_location& that) const
1471 return (this->object == that.object
1472 && this->shndx == that.shndx
1473 && this->offset == that.offset);
1477 struct Symbol_location_hash
1479 size_t operator()(const Symbol_location& loc) const
1480 { return reinterpret_cast<uintptr_t>(loc.object) ^ loc.offset ^ loc.shndx; }
1483 typedef Unordered_map<const char*,
1484 Unordered_set<Symbol_location, Symbol_location_hash> >
1487 // We increment this every time we see a new undefined symbol, for
1488 // use in archive groups.
1490 // The index of the first global symbol in the output file.
1491 unsigned int first_global_index_;
1492 // The file offset within the output symtab section where we should
1495 // The number of global symbols we want to write out.
1496 unsigned int output_count_;
1497 // The file offset of the global dynamic symbols, or 0 if none.
1498 off_t dynamic_offset_;
1499 // The index of the first global dynamic symbol.
1500 unsigned int first_dynamic_global_index_;
1501 // The number of global dynamic symbols, or 0 if none.
1502 unsigned int dynamic_count_;
1503 // The symbol hash table.
1504 Symbol_table_type table_;
1505 // A pool of symbol names. This is used for all global symbols.
1506 // Entries in the hash table point into this pool.
1507 Stringpool namepool_;
1508 // Forwarding symbols.
1509 Unordered_map<const Symbol*, Symbol*> forwarders_;
1510 // Weak aliases. A symbol in this list points to the next alias.
1511 // The aliases point to each other in a circular list.
1512 Unordered_map<Symbol*, Symbol*> weak_aliases_;
1513 // We don't expect there to be very many common symbols, so we keep
1514 // a list of them. When we find a common symbol we add it to this
1515 // list. It is possible that by the time we process the list the
1516 // symbol is no longer a common symbol. It may also have become a
1518 Commons_type commons_;
1519 // This is like the commons_ field, except that it holds TLS common
1521 Commons_type tls_commons_;
1522 // A list of symbols which have been forced to be local. We don't
1523 // expect there to be very many of them, so we keep a list of them
1524 // rather than walking the whole table to find them.
1525 Forced_locals forced_locals_;
1526 // Manage symbol warnings.
1528 // Manage potential One Definition Rule (ODR) violations.
1529 Odr_map candidate_odr_violations_;
1531 // When we emit a COPY reloc for a symbol, we define it in an
1532 // Output_data. When it's time to emit version information for it,
1533 // we need to know the dynamic object in which we found the original
1534 // definition. This maps symbols with COPY relocs to the dynamic
1535 // object where they were defined.
1536 Copied_symbol_dynobjs copied_symbol_dynobjs_;
1537 // Information parsed from the version script, if any.
1538 const Version_script_info& version_script_;
1541 // We inline get_sized_symbol for efficiency.
1545 Symbol_table::get_sized_symbol(Symbol* sym) const
1547 gold_assert(size == parameters->target().get_size());
1548 return static_cast<Sized_symbol<size>*>(sym);
1552 const Sized_symbol<size>*
1553 Symbol_table::get_sized_symbol(const Symbol* sym) const
1555 gold_assert(size == parameters->target().get_size());
1556 return static_cast<const Sized_symbol<size>*>(sym);
1559 } // End namespace gold.
1561 #endif // !defined(GOLD_SYMTAB_H)