1 // symtab.h -- the gold symbol table -*- C++ -*-
3 // Copyright 2006, 2007, 2008, 2009 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.
33 #include "parameters.h"
34 #include "stringpool.h"
46 template<int size, bool big_endian>
48 template<int size, bool big_endian>
49 class Sized_pluginobj;
51 template<int size, bool big_endian>
54 class Version_script_info;
60 class Output_symtab_xindex;
61 class Garbage_collection;
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 to big.
66 // Size dependent fields can be found in the template class
67 // Sized_symbol. Targets may support their own derived classes.
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.
78 // Symbol defined in a relocatable or dynamic input file--this is
79 // the most common case.
81 // Symbol defined in an Output_data, a special section created by
84 // Symbol defined in an Output_segment, with no associated
87 // Symbol value is constant.
89 // Symbol is undefined.
93 // When the source is IN_OUTPUT_SEGMENT, we need to describe what
95 enum Segment_offset_base
97 // From the start of the segment.
99 // From the end of the segment.
101 // From the filesz of the segment--i.e., after the loaded bytes
102 // but before the bytes which are allocated but zeroed.
106 // Return the symbol name.
109 { return this->name_; }
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
116 demangled_name() const;
118 // Return the symbol version. This will return NULL for an
119 // unversioned symbol.
122 { return this->version_; }
124 // Return whether this version is the default for this symbol name
125 // (eg, "foo@@V2" is a default version; "foo@V1" is not). Only
126 // meaningful for versioned symbols.
130 gold_assert(this->version_ != NULL);
131 return this->is_def_;
134 // Set that this version is the default for this symbol name.
137 { this->is_def_ = true; }
139 // Return the symbol source.
142 { return this->source_; }
144 // Return the object with which this symbol is associated.
148 gold_assert(this->source_ == FROM_OBJECT);
149 return this->u_.from_object.object;
152 // Return the index of the section in the input relocatable or
153 // dynamic object file.
155 shndx(bool* is_ordinary) const
157 gold_assert(this->source_ == FROM_OBJECT);
158 *is_ordinary = this->is_ordinary_shndx_;
159 return this->u_.from_object.shndx;
162 // Return the output data section with which this symbol is
163 // associated, if the symbol was specially defined with respect to
164 // an output data section.
168 gold_assert(this->source_ == IN_OUTPUT_DATA);
169 return this->u_.in_output_data.output_data;
172 // If this symbol was defined with respect to an output data
173 // section, return whether the value is an offset from end.
175 offset_is_from_end() const
177 gold_assert(this->source_ == IN_OUTPUT_DATA);
178 return this->u_.in_output_data.offset_is_from_end;
181 // Return the output segment with which this symbol is associated,
182 // if the symbol was specially defined with respect to an output
185 output_segment() const
187 gold_assert(this->source_ == IN_OUTPUT_SEGMENT);
188 return this->u_.in_output_segment.output_segment;
191 // If this symbol was defined with respect to an output segment,
192 // return the offset base.
196 gold_assert(this->source_ == IN_OUTPUT_SEGMENT);
197 return this->u_.in_output_segment.offset_base;
200 // Return the symbol binding.
203 { return this->binding_; }
205 // Return the symbol type.
208 { return this->type_; }
210 // Return the symbol visibility.
213 { return this->visibility_; }
215 // Set the visibility.
217 set_visibility(elfcpp::STV visibility)
218 { this->visibility_ = visibility; }
220 // Override symbol visibility.
222 override_visibility(elfcpp::STV);
224 // Return the non-visibility part of the st_other field.
227 { return this->nonvis_; }
229 // Return whether this symbol is a forwarder. This will never be
230 // true of a symbol found in the hash table, but may be true of
231 // symbol pointers attached to object files.
234 { return this->is_forwarder_; }
236 // Mark this symbol as a forwarder.
239 { this->is_forwarder_ = true; }
241 // Return whether this symbol has an alias in the weak aliases table
245 { return this->has_alias_; }
247 // Mark this symbol as having an alias.
250 { this->has_alias_ = true; }
252 // Return whether this symbol needs an entry in the dynamic symbol
255 needs_dynsym_entry() const
257 return (this->needs_dynsym_entry_
258 || (this->in_reg() && this->in_dyn()));
261 // Mark this symbol as needing an entry in the dynamic symbol table.
263 set_needs_dynsym_entry()
264 { this->needs_dynsym_entry_ = true; }
266 // Return whether this symbol should be added to the dynamic symbol
269 should_add_dynsym_entry() const;
271 // Return whether this symbol has been seen in a regular object.
274 { return this->in_reg_; }
276 // Mark this symbol as having been seen in a regular object.
279 { this->in_reg_ = true; }
281 // Return whether this symbol has been seen in a dynamic object.
284 { return this->in_dyn_; }
286 // Mark this symbol as having been seen in a dynamic object.
289 { this->in_dyn_ = true; }
291 // Return whether this symbol has been seen in a real ELF object.
292 // (IN_REG will return TRUE if the symbol has been seen in either
293 // a real ELF object or an object claimed by a plugin.)
296 { return this->in_real_elf_; }
298 // Mark this symbol as having been seen in a real ELF object.
301 { this->in_real_elf_ = true; }
303 // Return the index of this symbol in the output file symbol table.
304 // A value of -1U means that this symbol is not going into the
305 // output file. This starts out as zero, and is set to a non-zero
306 // value by Symbol_table::finalize. It is an error to ask for the
307 // symbol table index before it has been set.
311 gold_assert(this->symtab_index_ != 0);
312 return this->symtab_index_;
315 // Set the index of the symbol in the output file symbol table.
317 set_symtab_index(unsigned int index)
319 gold_assert(index != 0);
320 this->symtab_index_ = index;
323 // Return whether this symbol already has an index in the output
324 // file symbol table.
326 has_symtab_index() const
327 { return this->symtab_index_ != 0; }
329 // Return the index of this symbol in the dynamic symbol table. A
330 // value of -1U means that this symbol is not going into the dynamic
331 // symbol table. This starts out as zero, and is set to a non-zero
332 // during Layout::finalize. It is an error to ask for the dynamic
333 // symbol table index before it has been set.
337 gold_assert(this->dynsym_index_ != 0);
338 return this->dynsym_index_;
341 // Set the index of the symbol in the dynamic symbol table.
343 set_dynsym_index(unsigned int index)
345 gold_assert(index != 0);
346 this->dynsym_index_ = index;
349 // Return whether this symbol already has an index in the dynamic
352 has_dynsym_index() const
353 { return this->dynsym_index_ != 0; }
355 // Return whether this symbol has an entry in the GOT section.
356 // For a TLS symbol, this GOT entry will hold its tp-relative offset.
358 has_got_offset(unsigned int got_type) const
359 { return this->got_offsets_.get_offset(got_type) != -1U; }
361 // Return the offset into the GOT section of this symbol.
363 got_offset(unsigned int got_type) const
365 unsigned int got_offset = this->got_offsets_.get_offset(got_type);
366 gold_assert(got_offset != -1U);
370 // Set the GOT offset of this symbol.
372 set_got_offset(unsigned int got_type, unsigned int got_offset)
373 { this->got_offsets_.set_offset(got_type, got_offset); }
375 // Return whether this symbol has an entry in the PLT section.
377 has_plt_offset() const
378 { return this->has_plt_offset_; }
380 // Return the offset into the PLT section of this symbol.
384 gold_assert(this->has_plt_offset());
385 return this->plt_offset_;
388 // Set the PLT offset of this symbol.
390 set_plt_offset(unsigned int plt_offset)
392 this->has_plt_offset_ = true;
393 this->plt_offset_ = plt_offset;
396 // Return whether this dynamic symbol needs a special value in the
397 // dynamic symbol table.
399 needs_dynsym_value() const
400 { return this->needs_dynsym_value_; }
402 // Set that this dynamic symbol needs a special value in the dynamic
405 set_needs_dynsym_value()
407 gold_assert(this->object()->is_dynamic());
408 this->needs_dynsym_value_ = true;
411 // Return true if the final value of this symbol is known at link
414 final_value_is_known() const;
416 // Return true if SHNDX represents a common symbol. This depends on
419 is_common_shndx(unsigned int shndx);
421 // Return whether this is a defined symbol (not undefined or
427 if (this->source_ != FROM_OBJECT)
428 return this->source_ != IS_UNDEFINED;
429 unsigned int shndx = this->shndx(&is_ordinary);
431 ? shndx != elfcpp::SHN_UNDEF
432 : !Symbol::is_common_shndx(shndx));
435 // Return true if this symbol is from a dynamic object.
437 is_from_dynobj() const
439 return this->source_ == FROM_OBJECT && this->object()->is_dynamic();
442 // Return whether this is an undefined symbol.
447 return ((this->source_ == FROM_OBJECT
448 && this->shndx(&is_ordinary) == elfcpp::SHN_UNDEF
450 || this->source_ == IS_UNDEFINED);
453 // Return whether this is a weak undefined symbol.
455 is_weak_undefined() const
456 { return this->is_undefined() && this->binding() == elfcpp::STB_WEAK; }
458 // Return whether this is an absolute symbol.
463 return ((this->source_ == FROM_OBJECT
464 && this->shndx(&is_ordinary) == elfcpp::SHN_ABS
466 || this->source_ == IS_CONSTANT);
469 // Return whether this is a common symbol.
473 if (this->type_ == elfcpp::STT_COMMON)
475 if (this->source_ != FROM_OBJECT)
478 unsigned int shndx = this->shndx(&is_ordinary);
479 return !is_ordinary && Symbol::is_common_shndx(shndx);
482 // Return whether this symbol can be seen outside this object.
484 is_externally_visible() const
486 return (this->visibility_ == elfcpp::STV_DEFAULT
487 || this->visibility_ == elfcpp::STV_PROTECTED);
490 // Return true if this symbol can be preempted by a definition in
491 // another link unit.
493 is_preemptible() const
495 // It doesn't make sense to ask whether a symbol defined in
496 // another object is preemptible.
497 gold_assert(!this->is_from_dynobj());
499 // It doesn't make sense to ask whether an undefined symbol
501 gold_assert(!this->is_undefined());
503 // If a symbol does not have default visibility, it can not be
504 // seen outside this link unit and therefore is not preemptible.
505 if (this->visibility_ != elfcpp::STV_DEFAULT)
508 // If this symbol has been forced to be a local symbol by a
509 // version script, then it is not visible outside this link unit
510 // and is not preemptible.
511 if (this->is_forced_local_)
514 // If we are not producing a shared library, then nothing is
516 if (!parameters->options().shared())
519 // If the user used -Bsymbolic, then nothing is preemptible.
520 if (parameters->options().Bsymbolic())
523 // If the user used -Bsymbolic-functions, then functions are not
524 // preemptible. We explicitly check for not being STT_OBJECT,
525 // rather than for being STT_FUNC, because that is what the GNU
527 if (this->type() != elfcpp::STT_OBJECT
528 && parameters->options().Bsymbolic_functions())
531 // Otherwise the symbol is preemptible.
535 // Return true if this symbol is a function that needs a PLT entry.
536 // If the symbol is defined in a dynamic object or if it is subject
537 // to pre-emption, we need to make a PLT entry. If we're doing a
538 // static link, we don't create PLT entries.
540 needs_plt_entry() const
542 // An undefined symbol from an executable does not need a PLT entry.
543 if (this->is_undefined() && !parameters->options().shared())
546 return (!parameters->doing_static_link()
547 && this->type() == elfcpp::STT_FUNC
548 && (this->is_from_dynobj()
549 || this->is_undefined()
550 || this->is_preemptible()));
553 // When determining whether a reference to a symbol needs a dynamic
554 // relocation, we need to know several things about the reference.
555 // These flags may be or'ed together.
558 // Reference to the symbol's absolute address.
560 // A non-PIC reference.
566 // Given a direct absolute or pc-relative static relocation against
567 // the global symbol, this function returns whether a dynamic relocation
571 needs_dynamic_reloc(int flags) const
573 // No dynamic relocations in a static link!
574 if (parameters->doing_static_link())
577 // A reference to an undefined symbol from an executable should be
578 // statically resolved to 0, and does not need a dynamic relocation.
579 // This matches gnu ld behavior.
580 if (this->is_undefined() && !parameters->options().shared())
583 // A reference to an absolute symbol does not need a dynamic relocation.
584 if (this->is_absolute())
587 // An absolute reference within a position-independent output file
588 // will need a dynamic relocation.
589 if ((flags & ABSOLUTE_REF)
590 && parameters->options().output_is_position_independent())
593 // A function call that can branch to a local PLT entry does not need
594 // a dynamic relocation. A non-pic pc-relative function call in a
595 // shared library cannot use a PLT entry.
596 if ((flags & FUNCTION_CALL)
597 && this->has_plt_offset()
598 && !((flags & NON_PIC_REF) && parameters->options().shared()))
601 // A reference to any PLT entry in a non-position-independent executable
602 // does not need a dynamic relocation.
603 if (!parameters->options().output_is_position_independent()
604 && this->has_plt_offset())
607 // A reference to a symbol defined in a dynamic object or to a
608 // symbol that is preemptible will need a dynamic relocation.
609 if (this->is_from_dynobj()
610 || this->is_undefined()
611 || this->is_preemptible())
614 // For all other cases, return FALSE.
618 // Whether we should use the PLT offset associated with a symbol for
619 // a relocation. IS_NON_PIC_REFERENCE is true if this is a non-PIC
620 // reloc--the same set of relocs for which we would pass NON_PIC_REF
621 // to the needs_dynamic_reloc function.
624 use_plt_offset(bool is_non_pic_reference) const
626 // If the symbol doesn't have a PLT offset, then naturally we
627 // don't want to use it.
628 if (!this->has_plt_offset())
631 // If we are going to generate a dynamic relocation, then we will
632 // wind up using that, so no need to use the PLT entry.
633 if (this->needs_dynamic_reloc(FUNCTION_CALL
634 | (is_non_pic_reference
639 // If the symbol is from a dynamic object, we need to use the PLT
641 if (this->is_from_dynobj())
644 // If we are generating a shared object, and this symbol is
645 // undefined or preemptible, we need to use the PLT entry.
646 if (parameters->options().shared()
647 && (this->is_undefined() || this->is_preemptible()))
650 // If this is a weak undefined symbol, we need to use the PLT
651 // entry; the symbol may be defined by a library loaded at
653 if (this->is_weak_undefined())
656 // Otherwise we can use the regular definition.
660 // Given a direct absolute static relocation against
661 // the global symbol, where a dynamic relocation is needed, this
662 // function returns whether a relative dynamic relocation can be used.
663 // The caller must determine separately whether the static relocation
664 // is compatible with a relative relocation.
667 can_use_relative_reloc(bool is_function_call) const
669 // A function call that can branch to a local PLT entry can
670 // use a RELATIVE relocation.
671 if (is_function_call && this->has_plt_offset())
674 // A reference to a symbol defined in a dynamic object or to a
675 // symbol that is preemptible can not use a RELATIVE relocaiton.
676 if (this->is_from_dynobj()
677 || this->is_undefined()
678 || this->is_preemptible())
681 // For all other cases, return TRUE.
685 // Return the output section where this symbol is defined. Return
686 // NULL if the symbol has an absolute value.
688 output_section() const;
690 // Set the symbol's output section. This is used for symbols
691 // defined in scripts. This should only be called after the symbol
692 // table has been finalized.
694 set_output_section(Output_section*);
696 // Return whether there should be a warning for references to this
700 { return this->has_warning_; }
702 // Mark this symbol as having a warning.
705 { this->has_warning_ = true; }
707 // Return whether this symbol is defined by a COPY reloc from a
710 is_copied_from_dynobj() const
711 { return this->is_copied_from_dynobj_; }
713 // Mark this symbol as defined by a COPY reloc.
715 set_is_copied_from_dynobj()
716 { this->is_copied_from_dynobj_ = true; }
718 // Return whether this symbol is forced to visibility STB_LOCAL
719 // by a "local:" entry in a version script.
721 is_forced_local() const
722 { return this->is_forced_local_; }
724 // Mark this symbol as forced to STB_LOCAL visibility.
726 set_is_forced_local()
727 { this->is_forced_local_ = true; }
729 // Return true if this may need a COPY relocation.
730 // References from an executable object to non-function symbols
731 // defined in a dynamic object may need a COPY relocation.
733 may_need_copy_reloc() const
735 return (!parameters->options().shared()
736 && parameters->options().copyreloc()
737 && this->is_from_dynobj()
738 && this->type() != elfcpp::STT_FUNC);
742 // Instances of this class should always be created at a specific
745 { memset(this, 0, sizeof *this); }
747 // Initialize the general fields.
749 init_fields(const char* name, const char* version,
750 elfcpp::STT type, elfcpp::STB binding,
751 elfcpp::STV visibility, unsigned char nonvis);
753 // Initialize fields from an ELF symbol in OBJECT. ST_SHNDX is the
754 // section index, IS_ORDINARY is whether it is a normal section
755 // index rather than a special code.
756 template<int size, bool big_endian>
758 init_base_object(const char *name, const char* version, Object* object,
759 const elfcpp::Sym<size, big_endian>&, unsigned int st_shndx,
762 // Initialize fields for an Output_data.
764 init_base_output_data(const char* name, const char* version, Output_data*,
765 elfcpp::STT, elfcpp::STB, elfcpp::STV,
766 unsigned char nonvis, bool offset_is_from_end);
768 // Initialize fields for an Output_segment.
770 init_base_output_segment(const char* name, const char* version,
771 Output_segment* os, elfcpp::STT type,
772 elfcpp::STB binding, elfcpp::STV visibility,
773 unsigned char nonvis,
774 Segment_offset_base offset_base);
776 // Initialize fields for a constant.
778 init_base_constant(const char* name, const char* version, elfcpp::STT type,
779 elfcpp::STB binding, elfcpp::STV visibility,
780 unsigned char nonvis);
782 // Initialize fields for an undefined symbol.
784 init_base_undefined(const char* name, const char* version, elfcpp::STT type,
785 elfcpp::STB binding, elfcpp::STV visibility,
786 unsigned char nonvis);
788 // Override existing symbol.
789 template<int size, bool big_endian>
791 override_base(const elfcpp::Sym<size, big_endian>&, unsigned int st_shndx,
792 bool is_ordinary, Object* object, const char* version);
794 // Override existing symbol with a special symbol.
796 override_base_with_special(const Symbol* from);
798 // Override symbol version.
800 override_version(const char* version);
802 // Allocate a common symbol by giving it a location in the output
805 allocate_base_common(Output_data*);
808 Symbol(const Symbol&);
809 Symbol& operator=(const Symbol&);
811 // Symbol name (expected to point into a Stringpool).
813 // Symbol version (expected to point into a Stringpool). This may
815 const char* version_;
819 // This struct is used if SOURCE_ == FROM_OBJECT.
822 // Object in which symbol is defined, or in which it was first
825 // Section number in object_ in which symbol is defined.
829 // This struct is used if SOURCE_ == IN_OUTPUT_DATA.
832 // Output_data in which symbol is defined. Before
833 // Layout::finalize the symbol's value is an offset within the
835 Output_data* output_data;
836 // True if the offset is from the end, false if the offset is
837 // from the beginning.
838 bool offset_is_from_end;
841 // This struct is used if SOURCE_ == IN_OUTPUT_SEGMENT.
844 // Output_segment in which the symbol is defined. Before
845 // Layout::finalize the symbol's value is an offset.
846 Output_segment* output_segment;
847 // The base to use for the offset before Layout::finalize.
848 Segment_offset_base offset_base;
852 // The index of this symbol in the output file. If the symbol is
853 // not going into the output file, this value is -1U. This field
854 // starts as always holding zero. It is set to a non-zero value by
855 // Symbol_table::finalize.
856 unsigned int symtab_index_;
858 // The index of this symbol in the dynamic symbol table. If the
859 // symbol is not going into the dynamic symbol table, this value is
860 // -1U. This field starts as always holding zero. It is set to a
861 // non-zero value during Layout::finalize.
862 unsigned int dynsym_index_;
864 // If this symbol has an entry in the GOT section (has_got_offset_
865 // is true), this holds the offset from the start of the GOT section.
866 // A symbol may have more than one GOT offset (e.g., when mixing
867 // modules compiled with two different TLS models), but will usually
869 Got_offset_list got_offsets_;
871 // If this symbol has an entry in the PLT section (has_plt_offset_
872 // is true), then this is the offset from the start of the PLT
874 unsigned int plt_offset_;
876 // Symbol type (bits 0 to 3).
877 elfcpp::STT type_ : 4;
878 // Symbol binding (bits 4 to 7).
879 elfcpp::STB binding_ : 4;
880 // Symbol visibility (bits 8 to 9).
881 elfcpp::STV visibility_ : 2;
882 // Rest of symbol st_other field (bits 10 to 15).
883 unsigned int nonvis_ : 6;
884 // The type of symbol (bits 16 to 18).
886 // True if this symbol always requires special target-specific
887 // handling (bit 19).
888 bool is_target_special_ : 1;
889 // True if this is the default version of the symbol (bit 20).
891 // True if this symbol really forwards to another symbol. This is
892 // used when we discover after the fact that two different entries
893 // in the hash table really refer to the same symbol. This will
894 // never be set for a symbol found in the hash table, but may be set
895 // for a symbol found in the list of symbols attached to an Object.
896 // It forwards to the symbol found in the forwarders_ map of
897 // Symbol_table (bit 21).
898 bool is_forwarder_ : 1;
899 // True if the symbol has an alias in the weak_aliases table in
900 // Symbol_table (bit 22).
902 // True if this symbol needs to be in the dynamic symbol table (bit
904 bool needs_dynsym_entry_ : 1;
905 // True if we've seen this symbol in a regular object (bit 24).
907 // True if we've seen this symbol in a dynamic object (bit 25).
909 // True if the symbol has an entry in the PLT section (bit 26).
910 bool has_plt_offset_ : 1;
911 // True if this is a dynamic symbol which needs a special value in
912 // the dynamic symbol table (bit 27).
913 bool needs_dynsym_value_ : 1;
914 // True if there is a warning for this symbol (bit 28).
915 bool has_warning_ : 1;
916 // True if we are using a COPY reloc for this symbol, so that the
917 // real definition lives in a dynamic object (bit 29).
918 bool is_copied_from_dynobj_ : 1;
919 // True if this symbol was forced to local visibility by a version
921 bool is_forced_local_ : 1;
922 // True if the field u_.from_object.shndx is an ordinary section
923 // index, not one of the special codes from SHN_LORESERVE to
924 // SHN_HIRESERVE (bit 31).
925 bool is_ordinary_shndx_ : 1;
926 // True if we've seen this symbol in a real ELF object.
927 bool in_real_elf_ : 1;
930 // The parts of a symbol which are size specific. Using a template
931 // derived class like this helps us use less space on a 32-bit system.
934 class Sized_symbol : public Symbol
937 typedef typename elfcpp::Elf_types<size>::Elf_Addr Value_type;
938 typedef typename elfcpp::Elf_types<size>::Elf_WXword Size_type;
943 // Initialize fields from an ELF symbol in OBJECT. ST_SHNDX is the
944 // section index, IS_ORDINARY is whether it is a normal section
945 // index rather than a special code.
946 template<bool big_endian>
948 init_object(const char *name, const char* version, Object* object,
949 const elfcpp::Sym<size, big_endian>&, unsigned int st_shndx,
952 // Initialize fields for an Output_data.
954 init_output_data(const char* name, const char* version, Output_data*,
955 Value_type value, Size_type symsize, elfcpp::STT,
956 elfcpp::STB, elfcpp::STV, unsigned char nonvis,
957 bool offset_is_from_end);
959 // Initialize fields for an Output_segment.
961 init_output_segment(const char* name, const char* version, Output_segment*,
962 Value_type value, Size_type symsize, elfcpp::STT,
963 elfcpp::STB, elfcpp::STV, unsigned char nonvis,
964 Segment_offset_base offset_base);
966 // Initialize fields for a constant.
968 init_constant(const char* name, const char* version, Value_type value,
969 Size_type symsize, elfcpp::STT, elfcpp::STB, elfcpp::STV,
970 unsigned char nonvis);
972 // Initialize fields for an undefined symbol.
974 init_undefined(const char* name, const char* version, elfcpp::STT,
975 elfcpp::STB, elfcpp::STV, unsigned char nonvis);
977 // Override existing symbol.
978 template<bool big_endian>
980 override(const elfcpp::Sym<size, big_endian>&, unsigned int st_shndx,
981 bool is_ordinary, Object* object, const char* version);
983 // Override existing symbol with a special symbol.
985 override_with_special(const Sized_symbol<size>*);
987 // Return the symbol's value.
990 { return this->value_; }
992 // Return the symbol's size (we can't call this 'size' because that
993 // is a template parameter).
996 { return this->symsize_; }
998 // Set the symbol size. This is used when resolving common symbols.
1000 set_symsize(Size_type symsize)
1001 { this->symsize_ = symsize; }
1003 // Set the symbol value. This is called when we store the final
1004 // values of the symbols into the symbol table.
1006 set_value(Value_type value)
1007 { this->value_ = value; }
1009 // Allocate a common symbol by giving it a location in the output
1012 allocate_common(Output_data*, Value_type value);
1015 Sized_symbol(const Sized_symbol&);
1016 Sized_symbol& operator=(const Sized_symbol&);
1018 // Symbol value. Before Layout::finalize this is the offset in the
1019 // input section. This is set to the final value during
1020 // Layout::finalize.
1026 // A struct describing a symbol defined by the linker, where the value
1027 // of the symbol is defined based on an output section. This is used
1028 // for symbols defined by the linker, like "_init_array_start".
1030 struct Define_symbol_in_section
1034 // The name of the output section with which this symbol should be
1035 // associated. If there is no output section with that name, the
1036 // symbol will be defined as zero.
1037 const char* output_section;
1038 // The offset of the symbol within the output section. This is an
1039 // offset from the start of the output section, unless start_at_end
1040 // is true, in which case this is an offset from the end of the
1043 // The size of the symbol.
1047 // The symbol binding.
1048 elfcpp::STB binding;
1049 // The symbol visibility.
1050 elfcpp::STV visibility;
1051 // The rest of the st_other field.
1052 unsigned char nonvis;
1053 // If true, the value field is an offset from the end of the output
1055 bool offset_is_from_end;
1056 // If true, this symbol is defined only if we see a reference to it.
1060 // A struct describing a symbol defined by the linker, where the value
1061 // of the symbol is defined based on a segment. This is used for
1062 // symbols defined by the linker, like "_end". We describe the
1063 // segment with which the symbol should be associated by its
1064 // characteristics. If no segment meets these characteristics, the
1065 // symbol will be defined as zero. If there is more than one segment
1066 // which meets these characteristics, we will use the first one.
1068 struct Define_symbol_in_segment
1072 // The segment type where the symbol should be defined, typically
1074 elfcpp::PT segment_type;
1075 // Bitmask of segment flags which must be set.
1076 elfcpp::PF segment_flags_set;
1077 // Bitmask of segment flags which must be clear.
1078 elfcpp::PF segment_flags_clear;
1079 // The offset of the symbol within the segment. The offset is
1080 // calculated from the position set by offset_base.
1082 // The size of the symbol.
1086 // The symbol binding.
1087 elfcpp::STB binding;
1088 // The symbol visibility.
1089 elfcpp::STV visibility;
1090 // The rest of the st_other field.
1091 unsigned char nonvis;
1092 // The base from which we compute the offset.
1093 Symbol::Segment_offset_base offset_base;
1094 // If true, this symbol is defined only if we see a reference to it.
1098 // This class manages warnings. Warnings are a GNU extension. When
1099 // we see a section named .gnu.warning.SYM in an object file, and if
1100 // we wind using the definition of SYM from that object file, then we
1101 // will issue a warning for any relocation against SYM from a
1102 // different object file. The text of the warning is the contents of
1103 // the section. This is not precisely the definition used by the old
1104 // GNU linker; the old GNU linker treated an occurrence of
1105 // .gnu.warning.SYM as defining a warning symbol. A warning symbol
1106 // would trigger a warning on any reference. However, it was
1107 // inconsistent in that a warning in a dynamic object only triggered
1108 // if there was no definition in a regular object. This linker is
1109 // different in that we only issue a warning if we use the symbol
1110 // definition from the same object file as the warning section.
1119 // Add a warning for symbol NAME in object OBJ. WARNING is the text
1122 add_warning(Symbol_table* symtab, const char* name, Object* obj,
1123 const std::string& warning);
1125 // For each symbol for which we should give a warning, make a note
1128 note_warnings(Symbol_table* symtab);
1130 // Issue a warning for a reference to SYM at RELINFO's location.
1131 template<int size, bool big_endian>
1133 issue_warning(const Symbol* sym, const Relocate_info<size, big_endian>*,
1134 size_t relnum, off_t reloffset) const;
1137 Warnings(const Warnings&);
1138 Warnings& operator=(const Warnings&);
1140 // What we need to know to get the warning text.
1141 struct Warning_location
1143 // The object the warning is in.
1145 // The warning text.
1149 : object(NULL), text()
1153 set(Object* o, const std::string& t)
1160 // A mapping from warning symbol names (canonicalized in
1161 // Symbol_table's namepool_ field) to warning information.
1162 typedef Unordered_map<const char*, Warning_location> Warning_table;
1164 Warning_table warnings_;
1167 // The main linker symbol table.
1172 // COUNT is an estimate of how many symbosl will be inserted in the
1173 // symbol table. It's ok to put 0 if you don't know; a correct
1174 // guess will just save some CPU by reducing hashtable resizes.
1175 Symbol_table(unsigned int count, const Version_script_info& version_script);
1181 { this->icf_ = icf;}
1185 { return this->icf_; }
1187 // Returns true if ICF determined that this is a duplicate section.
1189 is_section_folded(Object* obj, unsigned int shndx) const;
1192 set_gc(Garbage_collection* gc)
1197 { return this->gc_; }
1199 // During garbage collection, this keeps undefined symbols.
1201 gc_mark_undef_symbols();
1203 // During garbage collection, this ensures externally visible symbols
1204 // are not treated as garbage while building shared objects.
1206 gc_mark_symbol_for_shlib(Symbol* sym);
1208 // During garbage collection, this keeps sections that correspond to
1209 // symbols seen in dynamic objects.
1211 gc_mark_dyn_syms(Symbol* sym);
1213 // Add COUNT external symbols from the relocatable object RELOBJ to
1214 // the symbol table. SYMS is the symbols, SYMNDX_OFFSET is the
1215 // offset in the symbol table of the first symbol, SYM_NAMES is
1216 // their names, SYM_NAME_SIZE is the size of SYM_NAMES. This sets
1217 // SYMPOINTERS to point to the symbols in the symbol table. It sets
1218 // *DEFINED to the number of defined symbols.
1219 template<int size, bool big_endian>
1221 add_from_relobj(Sized_relobj<size, big_endian>* relobj,
1222 const unsigned char* syms, size_t count,
1223 size_t symndx_offset, const char* sym_names,
1224 size_t sym_name_size,
1225 typename Sized_relobj<size, big_endian>::Symbols*,
1228 // Add one external symbol from the plugin object OBJ to the symbol table.
1229 // Returns a pointer to the resolved symbol in the symbol table.
1230 template<int size, bool big_endian>
1232 add_from_pluginobj(Sized_pluginobj<size, big_endian>* obj,
1233 const char* name, const char* ver,
1234 elfcpp::Sym<size, big_endian>* sym);
1236 // Add COUNT dynamic symbols from the dynamic object DYNOBJ to the
1237 // symbol table. SYMS is the symbols. SYM_NAMES is their names.
1238 // SYM_NAME_SIZE is the size of SYM_NAMES. The other parameters are
1239 // symbol version data.
1240 template<int size, bool big_endian>
1242 add_from_dynobj(Sized_dynobj<size, big_endian>* dynobj,
1243 const unsigned char* syms, size_t count,
1244 const char* sym_names, size_t sym_name_size,
1245 const unsigned char* versym, size_t versym_size,
1246 const std::vector<const char*>*,
1247 typename Sized_relobj<size, big_endian>::Symbols*,
1250 // Define a special symbol based on an Output_data. It is a
1251 // multiple definition error if this symbol is already defined.
1253 define_in_output_data(const char* name, const char* version,
1254 Output_data*, uint64_t value, uint64_t symsize,
1255 elfcpp::STT type, elfcpp::STB binding,
1256 elfcpp::STV visibility, unsigned char nonvis,
1257 bool offset_is_from_end, bool only_if_ref);
1259 // Define a special symbol based on an Output_segment. It is a
1260 // multiple definition error if this symbol is already defined.
1262 define_in_output_segment(const char* name, const char* version,
1263 Output_segment*, uint64_t value, uint64_t symsize,
1264 elfcpp::STT type, elfcpp::STB binding,
1265 elfcpp::STV visibility, unsigned char nonvis,
1266 Symbol::Segment_offset_base, bool only_if_ref);
1268 // Define a special symbol with a constant value. It is a multiple
1269 // definition error if this symbol is already defined.
1271 define_as_constant(const char* name, const char* version,
1272 uint64_t value, uint64_t symsize, elfcpp::STT type,
1273 elfcpp::STB binding, elfcpp::STV visibility,
1274 unsigned char nonvis, bool only_if_ref,
1275 bool force_override);
1277 // Define a set of symbols in output sections. If ONLY_IF_REF is
1278 // true, only define them if they are referenced.
1280 define_symbols(const Layout*, int count, const Define_symbol_in_section*,
1283 // Define a set of symbols in output segments. If ONLY_IF_REF is
1284 // true, only defined them if they are referenced.
1286 define_symbols(const Layout*, int count, const Define_symbol_in_segment*,
1289 // Define SYM using a COPY reloc. POSD is the Output_data where the
1290 // symbol should be defined--typically a .dyn.bss section. VALUE is
1291 // the offset within POSD.
1294 define_with_copy_reloc(Sized_symbol<size>* sym, Output_data* posd,
1295 typename elfcpp::Elf_types<size>::Elf_Addr);
1297 // Look up a symbol.
1299 lookup(const char*, const char* version = NULL) const;
1301 // Return the real symbol associated with the forwarder symbol FROM.
1303 resolve_forwards(const Symbol* from) const;
1305 // Return the sized version of a symbol in this table.
1308 get_sized_symbol(Symbol*) const;
1311 const Sized_symbol<size>*
1312 get_sized_symbol(const Symbol*) const;
1314 // Return the count of undefined symbols seen.
1316 saw_undefined() const
1317 { return this->saw_undefined_; }
1319 // Allocate the common symbols
1321 allocate_commons(Layout*, Mapfile*);
1323 // Add a warning for symbol NAME in object OBJ. WARNING is the text
1326 add_warning(const char* name, Object* obj, const std::string& warning)
1327 { this->warnings_.add_warning(this, name, obj, warning); }
1329 // Canonicalize a symbol name for use in the hash table.
1331 canonicalize_name(const char* name)
1332 { return this->namepool_.add(name, true, NULL); }
1334 // Possibly issue a warning for a reference to SYM at LOCATION which
1336 template<int size, bool big_endian>
1338 issue_warning(const Symbol* sym,
1339 const Relocate_info<size, big_endian>* relinfo,
1340 size_t relnum, off_t reloffset) const
1341 { this->warnings_.issue_warning(sym, relinfo, relnum, reloffset); }
1343 // Check candidate_odr_violations_ to find symbols with the same name
1344 // but apparently different definitions (different source-file/line-no).
1346 detect_odr_violations(const Task*, const char* output_file_name) const;
1348 // Add any undefined symbols named on the command line to the symbol
1351 add_undefined_symbols_from_command_line();
1353 // SYM is defined using a COPY reloc. Return the dynamic object
1354 // where the original definition was found.
1356 get_copy_source(const Symbol* sym) const;
1358 // Set the dynamic symbol indexes. INDEX is the index of the first
1359 // global dynamic symbol. Pointers to the symbols are stored into
1360 // the vector. The names are stored into the Stringpool. This
1361 // returns an updated dynamic symbol index.
1363 set_dynsym_indexes(unsigned int index, std::vector<Symbol*>*,
1364 Stringpool*, Versions*);
1366 // Finalize the symbol table after we have set the final addresses
1367 // of all the input sections. This sets the final symbol indexes,
1368 // values and adds the names to *POOL. *PLOCAL_SYMCOUNT is the
1369 // index of the first global symbol. OFF is the file offset of the
1370 // global symbol table, DYNOFF is the offset of the globals in the
1371 // dynamic symbol table, DYN_GLOBAL_INDEX is the index of the first
1372 // global dynamic symbol, and DYNCOUNT is the number of global
1373 // dynamic symbols. This records the parameters, and returns the
1374 // new file offset. It updates *PLOCAL_SYMCOUNT if it created any
1377 finalize(off_t off, off_t dynoff, size_t dyn_global_index, size_t dyncount,
1378 Stringpool* pool, unsigned int *plocal_symcount);
1380 // Status code of Symbol_table::compute_final_value.
1381 enum Compute_final_value_status
1385 // Unspported symbol section.
1386 CFVS_UNSUPPORTED_SYMBOL_SECTION,
1387 // No output section.
1388 CFVS_NO_OUTPUT_SECTION
1391 // Compute the final value of SYM and store status in location PSTATUS.
1392 // During relaxation, this may be called multiple times for a symbol to
1393 // compute its would-be final value in each relaxation pass.
1396 typename Sized_symbol<size>::Value_type
1397 compute_final_value(const Sized_symbol<size>* sym,
1398 Compute_final_value_status* pstatus) const;
1400 // Write out the global symbols.
1402 write_globals(const Stringpool*, const Stringpool*,
1403 Output_symtab_xindex*, Output_symtab_xindex*,
1404 Output_file*) const;
1406 // Write out a section symbol. Return the updated offset.
1408 write_section_symbol(const Output_section*, Output_symtab_xindex*,
1409 Output_file*, off_t) const;
1411 // Dump statistical information to stderr.
1413 print_stats() const;
1415 // Return the version script information.
1416 const Version_script_info&
1417 version_script() const
1418 { return version_script_; }
1421 Symbol_table(const Symbol_table&);
1422 Symbol_table& operator=(const Symbol_table&);
1424 // The type of the list of common symbols.
1425 typedef std::vector<Symbol*> Commons_type;
1427 // The type of the symbol hash table.
1429 typedef std::pair<Stringpool::Key, Stringpool::Key> Symbol_table_key;
1431 struct Symbol_table_hash
1434 operator()(const Symbol_table_key&) const;
1437 struct Symbol_table_eq
1440 operator()(const Symbol_table_key&, const Symbol_table_key&) const;
1443 typedef Unordered_map<Symbol_table_key, Symbol*, Symbol_table_hash,
1444 Symbol_table_eq> Symbol_table_type;
1446 // Make FROM a forwarder symbol to TO.
1448 make_forwarder(Symbol* from, Symbol* to);
1451 template<int size, bool big_endian>
1453 add_from_object(Object*, const char *name, Stringpool::Key name_key,
1454 const char *version, Stringpool::Key version_key,
1455 bool def, const elfcpp::Sym<size, big_endian>& sym,
1456 unsigned int st_shndx, bool is_ordinary,
1457 unsigned int orig_st_shndx);
1459 // Define a default symbol.
1460 template<int size, bool big_endian>
1462 define_default_version(Sized_symbol<size>*, bool,
1463 Symbol_table_type::iterator);
1466 template<int size, bool big_endian>
1468 resolve(Sized_symbol<size>* to,
1469 const elfcpp::Sym<size, big_endian>& sym,
1470 unsigned int st_shndx, bool is_ordinary,
1471 unsigned int orig_st_shndx,
1472 Object*, const char* version);
1474 template<int size, bool big_endian>
1476 resolve(Sized_symbol<size>* to, const Sized_symbol<size>* from);
1478 // Record that a symbol is forced to be local by a version script or
1481 force_local(Symbol*);
1483 // Adjust NAME and *NAME_KEY for wrapping.
1485 wrap_symbol(const char* name, Stringpool::Key* name_key);
1487 // Whether we should override a symbol, based on flags in
1490 should_override(const Symbol*, unsigned int, Object*, bool*);
1492 // Override a symbol.
1493 template<int size, bool big_endian>
1495 override(Sized_symbol<size>* tosym,
1496 const elfcpp::Sym<size, big_endian>& fromsym,
1497 unsigned int st_shndx, bool is_ordinary,
1498 Object* object, const char* version);
1500 // Whether we should override a symbol with a special symbol which
1501 // is automatically defined by the linker.
1503 should_override_with_special(const Symbol*);
1505 // Override a symbol with a special symbol.
1508 override_with_special(Sized_symbol<size>* tosym,
1509 const Sized_symbol<size>* fromsym);
1511 // Record all weak alias sets for a dynamic object.
1514 record_weak_aliases(std::vector<Sized_symbol<size>*>*);
1516 // Define a special symbol.
1517 template<int size, bool big_endian>
1519 define_special_symbol(const char** pname, const char** pversion,
1520 bool only_if_ref, Sized_symbol<size>** poldsym,
1521 bool* resolve_oldsym);
1523 // Define a symbol in an Output_data, sized version.
1526 do_define_in_output_data(const char* name, const char* version, Output_data*,
1527 typename elfcpp::Elf_types<size>::Elf_Addr value,
1528 typename elfcpp::Elf_types<size>::Elf_WXword ssize,
1529 elfcpp::STT type, elfcpp::STB binding,
1530 elfcpp::STV visibility, unsigned char nonvis,
1531 bool offset_is_from_end, bool only_if_ref);
1533 // Define a symbol in an Output_segment, sized version.
1536 do_define_in_output_segment(
1537 const char* name, const char* version, Output_segment* os,
1538 typename elfcpp::Elf_types<size>::Elf_Addr value,
1539 typename elfcpp::Elf_types<size>::Elf_WXword ssize,
1540 elfcpp::STT type, elfcpp::STB binding,
1541 elfcpp::STV visibility, unsigned char nonvis,
1542 Symbol::Segment_offset_base offset_base, bool only_if_ref);
1544 // Define a symbol as a constant, sized version.
1547 do_define_as_constant(
1548 const char* name, const char* version,
1549 typename elfcpp::Elf_types<size>::Elf_Addr value,
1550 typename elfcpp::Elf_types<size>::Elf_WXword ssize,
1551 elfcpp::STT type, elfcpp::STB binding,
1552 elfcpp::STV visibility, unsigned char nonvis,
1553 bool only_if_ref, bool force_override);
1555 // Add any undefined symbols named on the command line to the symbol
1556 // table, sized version.
1559 do_add_undefined_symbols_from_command_line();
1561 // Types of common symbols.
1563 enum Commons_section_type
1571 // Allocate the common symbols, sized version.
1574 do_allocate_commons(Layout*, Mapfile*);
1576 // Allocate the common symbols from one list.
1579 do_allocate_commons_list(Layout*, Commons_section_type, Commons_type*,
1582 // Implement detect_odr_violations.
1583 template<int size, bool big_endian>
1585 sized_detect_odr_violations() const;
1587 // Finalize symbols specialized for size.
1590 sized_finalize(off_t, Stringpool*, unsigned int*);
1592 // Finalize a symbol. Return whether it should be added to the
1596 sized_finalize_symbol(Symbol*);
1598 // Add a symbol the final symtab by setting its index.
1601 add_to_final_symtab(Symbol*, Stringpool*, unsigned int* pindex, off_t* poff);
1603 // Write globals specialized for size and endianness.
1604 template<int size, bool big_endian>
1606 sized_write_globals(const Stringpool*, const Stringpool*,
1607 Output_symtab_xindex*, Output_symtab_xindex*,
1608 Output_file*) const;
1610 // Write out a symbol to P.
1611 template<int size, bool big_endian>
1613 sized_write_symbol(Sized_symbol<size>*,
1614 typename elfcpp::Elf_types<size>::Elf_Addr value,
1616 const Stringpool*, unsigned char* p) const;
1618 // Possibly warn about an undefined symbol from a dynamic object.
1620 warn_about_undefined_dynobj_symbol(Symbol*) const;
1622 // Write out a section symbol, specialized for size and endianness.
1623 template<int size, bool big_endian>
1625 sized_write_section_symbol(const Output_section*, Output_symtab_xindex*,
1626 Output_file*, off_t) const;
1628 // The type of the list of symbols which have been forced local.
1629 typedef std::vector<Symbol*> Forced_locals;
1631 // A map from symbols with COPY relocs to the dynamic objects where
1632 // they are defined.
1633 typedef Unordered_map<const Symbol*, Dynobj*> Copied_symbol_dynobjs;
1635 // A map from symbol name (as a pointer into the namepool) to all
1636 // the locations the symbols is (weakly) defined (and certain other
1637 // conditions are met). This map will be used later to detect
1638 // possible One Definition Rule (ODR) violations.
1639 struct Symbol_location
1641 Object* object; // Object where the symbol is defined.
1642 unsigned int shndx; // Section-in-object where the symbol is defined.
1643 off_t offset; // Offset-in-section where the symbol is defined.
1644 bool operator==(const Symbol_location& that) const
1646 return (this->object == that.object
1647 && this->shndx == that.shndx
1648 && this->offset == that.offset);
1652 struct Symbol_location_hash
1654 size_t operator()(const Symbol_location& loc) const
1655 { return reinterpret_cast<uintptr_t>(loc.object) ^ loc.offset ^ loc.shndx; }
1658 typedef Unordered_map<const char*,
1659 Unordered_set<Symbol_location, Symbol_location_hash> >
1662 // We increment this every time we see a new undefined symbol, for
1663 // use in archive groups.
1665 // The index of the first global symbol in the output file.
1666 unsigned int first_global_index_;
1667 // The file offset within the output symtab section where we should
1670 // The number of global symbols we want to write out.
1671 unsigned int output_count_;
1672 // The file offset of the global dynamic symbols, or 0 if none.
1673 off_t dynamic_offset_;
1674 // The index of the first global dynamic symbol.
1675 unsigned int first_dynamic_global_index_;
1676 // The number of global dynamic symbols, or 0 if none.
1677 unsigned int dynamic_count_;
1678 // The symbol hash table.
1679 Symbol_table_type table_;
1680 // A pool of symbol names. This is used for all global symbols.
1681 // Entries in the hash table point into this pool.
1682 Stringpool namepool_;
1683 // Forwarding symbols.
1684 Unordered_map<const Symbol*, Symbol*> forwarders_;
1685 // Weak aliases. A symbol in this list points to the next alias.
1686 // The aliases point to each other in a circular list.
1687 Unordered_map<Symbol*, Symbol*> weak_aliases_;
1688 // We don't expect there to be very many common symbols, so we keep
1689 // a list of them. When we find a common symbol we add it to this
1690 // list. It is possible that by the time we process the list the
1691 // symbol is no longer a common symbol. It may also have become a
1693 Commons_type commons_;
1694 // This is like the commons_ field, except that it holds TLS common
1696 Commons_type tls_commons_;
1697 // This is for small common symbols.
1698 Commons_type small_commons_;
1699 // This is for large common symbols.
1700 Commons_type large_commons_;
1701 // A list of symbols which have been forced to be local. We don't
1702 // expect there to be very many of them, so we keep a list of them
1703 // rather than walking the whole table to find them.
1704 Forced_locals forced_locals_;
1705 // Manage symbol warnings.
1707 // Manage potential One Definition Rule (ODR) violations.
1708 Odr_map candidate_odr_violations_;
1710 // When we emit a COPY reloc for a symbol, we define it in an
1711 // Output_data. When it's time to emit version information for it,
1712 // we need to know the dynamic object in which we found the original
1713 // definition. This maps symbols with COPY relocs to the dynamic
1714 // object where they were defined.
1715 Copied_symbol_dynobjs copied_symbol_dynobjs_;
1716 // Information parsed from the version script, if any.
1717 const Version_script_info& version_script_;
1718 Garbage_collection* gc_;
1722 // We inline get_sized_symbol for efficiency.
1726 Symbol_table::get_sized_symbol(Symbol* sym) const
1728 gold_assert(size == parameters->target().get_size());
1729 return static_cast<Sized_symbol<size>*>(sym);
1733 const Sized_symbol<size>*
1734 Symbol_table::get_sized_symbol(const Symbol* sym) const
1736 gold_assert(size == parameters->target().get_size());
1737 return static_cast<const Sized_symbol<size>*>(sym);
1740 } // End namespace gold.
1742 #endif // !defined(GOLD_SYMTAB_H)