// object.h -- support for an object file for linking in gold -*- C++ -*- // Copyright 2006, 2007 Free Software Foundation, Inc. // Written by Ian Lance Taylor <iant@google.com>. // This file is part of gold. // This program is free software; you can redistribute it and/or modify // it under the terms of the GNU General Public License as published by // the Free Software Foundation; either version 3 of the License, or // (at your option) any later version. // This program is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU General Public License for more details. // You should have received a copy of the GNU General Public License // along with this program; if not, write to the Free Software // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, // MA 02110-1301, USA. #ifndef GOLD_OBJECT_H #define GOLD_OBJECT_H #include <string> #include <vector> #include "elfcpp.h" #include "elfcpp_file.h" #include "fileread.h" #include "target.h" namespace gold { class General_options; class Layout; class Output_section; class Output_file; class Dynobj; template<typename Stringpool_char> class Stringpool_template; // Data to pass from read_symbols() to add_symbols(). struct Read_symbols_data { // Section headers. File_view* section_headers; // Section names. File_view* section_names; // Size of section name data in bytes. off_t section_names_size; // Symbol data. File_view* symbols; // Size of symbol data in bytes. off_t symbols_size; // Symbol names. File_view* symbol_names; // Size of symbol name data in bytes. off_t symbol_names_size; // Version information. This is only used on dynamic objects. // Version symbol data (from SHT_GNU_versym section). File_view* versym; off_t versym_size; // Version definition data (from SHT_GNU_verdef section). File_view* verdef; off_t verdef_size; unsigned int verdef_info; // Needed version data (from SHT_GNU_verneed section). File_view* verneed; off_t verneed_size; unsigned int verneed_info; }; // Information used to print error messages. struct Symbol_location_info { std::string source_file; std::string enclosing_symbol_name; int line_number; }; // Data about a single relocation section. This is read in // read_relocs and processed in scan_relocs. struct Section_relocs { // Index of reloc section. unsigned int reloc_shndx; // Index of section that relocs apply to. unsigned int data_shndx; // Contents of reloc section. File_view* contents; // Reloc section type. unsigned int sh_type; // Number of reloc entries. size_t reloc_count; }; // Relocations in an object file. This is read in read_relocs and // processed in scan_relocs. struct Read_relocs_data { typedef std::vector<Section_relocs> Relocs_list; // The relocations. Relocs_list relocs; // The local symbols. File_view* local_symbols; }; // Object is an abstract base class which represents either a 32-bit // or a 64-bit input object. This can be a regular object file // (ET_REL) or a shared object (ET_DYN). class Object { public: // NAME is the name of the object as we would report it to the user // (e.g., libfoo.a(bar.o) if this is in an archive. INPUT_FILE is // used to read the file. OFFSET is the offset within the input // file--0 for a .o or .so file, something else for a .a file. Object(const std::string& name, Input_file* input_file, bool is_dynamic, off_t offset = 0) : name_(name), input_file_(input_file), offset_(offset), shnum_(-1U), is_dynamic_(is_dynamic), target_(NULL) { } virtual ~Object() { } // Return the name of the object as we would report it to the tuser. const std::string& name() const { return this->name_; } // Get the offset into the file. off_t offset() const { return this->offset_; } // Return whether this is a dynamic object. bool is_dynamic() const { return this->is_dynamic_; } // Return the target structure associated with this object. Target* target() const { return this->target_; } // Lock the underlying file. void lock() { this->input_file_->file().lock(); } // Unlock the underlying file. void unlock() { this->input_file_->file().unlock(); } // Return whether the underlying file is locked. bool is_locked() const { return this->input_file_->file().is_locked(); } // Return the sized target structure associated with this object. // This is like the target method but it returns a pointer of // appropriate checked type. template<int size, bool big_endian> Sized_target<size, big_endian>* sized_target(ACCEPT_SIZE_ENDIAN_ONLY); // Get the number of sections. unsigned int shnum() const { return this->shnum_; } // Return a view of the contents of a section. Set *PLEN to the // size. CACHE is a hint as in File_read::get_view. const unsigned char* section_contents(unsigned int shndx, off_t* plen, bool cache); // Return the name of a section given a section index. This is only // used for error messages. std::string section_name(unsigned int shndx) { return this->do_section_name(shndx); } // Return the section flags given a section index. uint64_t section_flags(unsigned int shndx) { return this->do_section_flags(shndx); } // Return the section link field given a section index. unsigned int section_link(unsigned int shndx) { return this->do_section_link(shndx); } // Read the symbol information. void read_symbols(Read_symbols_data* sd) { return this->do_read_symbols(sd); } // Pass sections which should be included in the link to the Layout // object, and record where the sections go in the output file. void layout(Symbol_table* symtab, Layout* layout, Read_symbols_data* sd) { this->do_layout(symtab, layout, sd); } // Add symbol information to the global symbol table. void add_symbols(Symbol_table* symtab, Read_symbols_data* sd) { this->do_add_symbols(symtab, sd); } // Functions and types for the elfcpp::Elf_file interface. This // permit us to use Object as the File template parameter for // elfcpp::Elf_file. // The View class is returned by view. It must support a single // method, data(). This is trivial, because get_view does what we // need. class View { public: View(const unsigned char* p) : p_(p) { } const unsigned char* data() const { return this->p_; } private: const unsigned char* p_; }; // Return a View. View view(off_t file_offset, off_t data_size) { return View(this->get_view(file_offset, data_size, true)); } // Report an error. void error(const char* format, ...) const ATTRIBUTE_PRINTF_2; // A location in the file. struct Location { off_t file_offset; off_t data_size; Location(off_t fo, off_t ds) : file_offset(fo), data_size(ds) { } }; // Get a View given a Location. View view(Location loc) { return View(this->get_view(loc.file_offset, loc.data_size, true)); } protected: // Read the symbols--implemented by child class. virtual void do_read_symbols(Read_symbols_data*) = 0; // Lay out sections--implemented by child class. virtual void do_layout(Symbol_table*, Layout*, Read_symbols_data*) = 0; // Add symbol information to the global symbol table--implemented by // child class. virtual void do_add_symbols(Symbol_table*, Read_symbols_data*) = 0; // Return the location of the contents of a section. Implemented by // child class. virtual Location do_section_contents(unsigned int shndx) = 0; // Get the name of a section--implemented by child class. virtual std::string do_section_name(unsigned int shndx) = 0; // Get section flags--implemented by child class. virtual uint64_t do_section_flags(unsigned int shndx) = 0; // Get section link field--implemented by child class. virtual unsigned int do_section_link(unsigned int shndx) = 0; // Get the file. Input_file* input_file() const { return this->input_file_; } // Get a view into the underlying file. const unsigned char* get_view(off_t start, off_t size, bool cache) { return this->input_file_->file().get_view(start + this->offset_, size, cache); } // Get a lasting view into the underlying file. File_view* get_lasting_view(off_t start, off_t size, bool cache) { return this->input_file_->file().get_lasting_view(start + this->offset_, size, cache); } // Read data from the underlying file. void read(off_t start, off_t size, void* p) { this->input_file_->file().read(start + this->offset_, size, p); } // Set the target. void set_target(int machine, int size, bool big_endian, int osabi, int abiversion); // Set the number of sections. void set_shnum(int shnum) { this->shnum_ = shnum; } // Functions used by both Sized_relobj and Sized_dynobj. // Read the section data into a Read_symbols_data object. template<int size, bool big_endian> void read_section_data(elfcpp::Elf_file<size, big_endian, Object>*, Read_symbols_data*); // If NAME is the name of a special .gnu.warning section, arrange // for the warning to be issued. SHNDX is the section index. // Return whether it is a warning section. bool handle_gnu_warning_section(const char* name, unsigned int shndx, Symbol_table*); private: // This class may not be copied. Object(const Object&); Object& operator=(const Object&); // Name of object as printed to user. std::string name_; // For reading the file. Input_file* input_file_; // Offset within the file--0 for an object file, non-0 for an // archive. off_t offset_; // Number of input sections. unsigned int shnum_; // Whether this is a dynamic object. bool is_dynamic_; // Target functions--may be NULL if the target is not known. Target* target_; }; // Implement sized_target inline for efficiency. This approach breaks // static type checking, but is made safe using asserts. template<int size, bool big_endian> inline Sized_target<size, big_endian>* Object::sized_target(ACCEPT_SIZE_ENDIAN_ONLY) { gold_assert(this->target_->get_size() == size); gold_assert(this->target_->is_big_endian() ? big_endian : !big_endian); return static_cast<Sized_target<size, big_endian>*>(this->target_); } // A regular object (ET_REL). This is an abstract base class itself. // The implementation is the template class Sized_relobj. class Relobj : public Object { public: Relobj(const std::string& name, Input_file* input_file, off_t offset = 0) : Object(name, input_file, false, offset) { } // Read the relocs. void read_relocs(Read_relocs_data* rd) { return this->do_read_relocs(rd); } // Scan the relocs and adjust the symbol table. void scan_relocs(const General_options& options, Symbol_table* symtab, Layout* layout, Read_relocs_data* rd) { return this->do_scan_relocs(options, symtab, layout, rd); } // Initial local symbol processing: set the offset where local // symbol information will be stored; add local symbol names to // *POOL; return the new local symbol index. unsigned int finalize_local_symbols(unsigned int index, off_t off, Stringpool_template<char>* pool) { return this->do_finalize_local_symbols(index, off, pool); } // Relocate the input sections and write out the local symbols. void relocate(const General_options& options, const Symbol_table* symtab, const Layout* layout, Output_file* of) { return this->do_relocate(options, symtab, layout, of); } // Return whether an input section is being included in the link. bool is_section_included(unsigned int shndx) const { gold_assert(shndx < this->map_to_output_.size()); return this->map_to_output_[shndx].output_section != NULL; } // Given a section index, return the corresponding Output_section // (which will be NULL if the section is not included in the link) // and set *POFF to the offset within that section. inline Output_section* output_section(unsigned int shndx, off_t* poff) const; // Set the offset of an input section within its output section. void set_section_offset(unsigned int shndx, off_t off) { gold_assert(shndx < this->map_to_output_.size()); this->map_to_output_[shndx].offset = off; } protected: // What we need to know to map an input section to an output // section. We keep an array of these, one for each input section, // indexed by the input section number. struct Map_to_output { // The output section. This is NULL if the input section is to be // discarded. Output_section* output_section; // The offset within the output section. This is -1 if the // section requires special handling. off_t offset; }; // Read the relocs--implemented by child class. virtual void do_read_relocs(Read_relocs_data*) = 0; // Scan the relocs--implemented by child class. virtual void do_scan_relocs(const General_options&, Symbol_table*, Layout*, Read_relocs_data*) = 0; // Finalize local symbols--implemented by child class. virtual unsigned int do_finalize_local_symbols(unsigned int, off_t, Stringpool_template<char>*) = 0; // Relocate the input sections and write out the local // symbols--implemented by child class. virtual void do_relocate(const General_options& options, const Symbol_table* symtab, const Layout*, Output_file* of) = 0; // Return the vector mapping input sections to output sections. std::vector<Map_to_output>& map_to_output() { return this->map_to_output_; } const std::vector<Map_to_output>& map_to_output() const { return this->map_to_output_; } private: // Mapping from input sections to output section. std::vector<Map_to_output> map_to_output_; }; // Implement Object::output_section inline for efficiency. inline Output_section* Relobj::output_section(unsigned int shndx, off_t* poff) const { gold_assert(shndx < this->map_to_output_.size()); const Map_to_output& mo(this->map_to_output_[shndx]); *poff = mo.offset; return mo.output_section; } // This POD class is holds the value of a symbol. This is used for // local symbols, and for all symbols during relocation processing. // In order to process relocs we need to be able to handle SHF_MERGE // sections correctly. template<int size> class Symbol_value { public: typedef typename elfcpp::Elf_types<size>::Elf_Addr Value; Symbol_value() : output_symtab_index_(0), input_shndx_(0), is_section_symbol_(false), needs_output_address_(false), value_(0) { } // Get the value of this symbol. OBJECT is the object in which this // symbol is defined, and ADDEND is an addend to add to the value. template<bool big_endian> Value value(const Sized_relobj<size, big_endian>* object, Value addend) const { if (!this->needs_output_address_) return this->value_ + addend; return object->local_value(this->input_shndx_, this->value_, this->is_section_symbol_, addend); } // Set the value of this symbol in the output symbol table. void set_output_value(Value value) { this->value_ = value; this->needs_output_address_ = false; } // If this symbol is mapped to an output section which requires // special handling to determine the output value, we store the // value of the symbol in the input file. This is used for // SHF_MERGE sections. void set_input_value(Value value) { this->value_ = value; this->needs_output_address_ = true; } // Return whether this symbol should go into the output symbol // table. bool needs_output_symtab_entry() const { gold_assert(this->output_symtab_index_ != 0); return this->output_symtab_index_ != -1U; } // Return the index in the output symbol table. unsigned int output_symtab_index() const { gold_assert(this->output_symtab_index_ != 0); return this->output_symtab_index_; } // Set the index in the output symbol table. void set_output_symtab_index(unsigned int i) { gold_assert(this->output_symtab_index_ == 0); this->output_symtab_index_ = i; } // Record that this symbol should not go into the output symbol // table. void set_no_output_symtab_entry() { gold_assert(this->output_symtab_index_ == 0); this->output_symtab_index_ = -1U; } // Set the index of the input section in the input file. void set_input_shndx(unsigned int i) { this->input_shndx_ = i; } // Record that this is a section symbol. void set_is_section_symbol() { this->is_section_symbol_ = true; } private: // The index of this local symbol in the output symbol table. This // will be -1 if the symbol should not go into the symbol table. unsigned int output_symtab_index_; // The section index in the input file in which this symbol is // defined. unsigned int input_shndx_ : 30; // Whether this is a STT_SECTION symbol. bool is_section_symbol_ : 1; // Whether getting the value of this symbol requires calling an // Output_section method. For example, this will be true of a // symbol in a SHF_MERGE section. bool needs_output_address_ : 1; // The value of the symbol. If !needs_output_address_, this is the // value in the output file. If needs_output_address_, this is the // value in the input file. Value value_; }; // A regular object file. This is size and endian specific. template<int size, bool big_endian> class Sized_relobj : public Relobj { public: typedef typename elfcpp::Elf_types<size>::Elf_Addr Address; typedef std::vector<Symbol_value<size> > Local_values; Sized_relobj(const std::string& name, Input_file* input_file, off_t offset, const typename elfcpp::Ehdr<size, big_endian>&); ~Sized_relobj(); // Set up the object file based on the ELF header. void setup(const typename elfcpp::Ehdr<size, big_endian>&); // Return the index of local symbol SYM in the ordinary symbol // table. A value of -1U means that the symbol is not being output. unsigned int symtab_index(unsigned int sym) const { gold_assert(sym < this->local_values_.size()); return this->local_values_[sym].output_symtab_index(); } // Return the appropriate Sized_target structure. Sized_target<size, big_endian>* sized_target() { return this->Object::sized_target SELECT_SIZE_ENDIAN_NAME(size, big_endian) ( SELECT_SIZE_ENDIAN_ONLY(size, big_endian)); } // Return the value of the local symbol symndx. Address local_symbol_value(unsigned int symndx) const; // Return the value of a local symbol defined in input section // SHNDX, with value VALUE, adding addend ADDEND. IS_SECTION_SYMBOL // indicates whether the symbol is a section symbol. This handles // SHF_MERGE sections. Address local_value(unsigned int shndx, Address value, bool is_section_symbol, Address addend) const; // Return whether the local symbol SYMNDX has a GOT offset. bool local_has_got_offset(unsigned int symndx) const { return (this->local_got_offsets_.find(symndx) != this->local_got_offsets_.end()); } // Return the GOT offset of the local symbol SYMNDX. unsigned int local_got_offset(unsigned int symndx) const { Local_got_offsets::const_iterator p = this->local_got_offsets_.find(symndx); gold_assert(p != this->local_got_offsets_.end()); return p->second; } // Set the GOT offset of the local symbol SYMNDX to GOT_OFFSET. void set_local_got_offset(unsigned int symndx, unsigned int got_offset) { std::pair<Local_got_offsets::iterator, bool> ins = this->local_got_offsets_.insert(std::make_pair(symndx, got_offset)); gold_assert(ins.second); } // Return the name of the symbol that spans the given offset in the // specified section in this object. This is used only for error // messages and is not particularly efficient. bool get_symbol_location_info(unsigned int shndx, off_t offset, Symbol_location_info* info); // Read the symbols. void do_read_symbols(Read_symbols_data*); // Lay out the input sections. void do_layout(Symbol_table*, Layout*, Read_symbols_data*); // Add the symbols to the symbol table. void do_add_symbols(Symbol_table*, Read_symbols_data*); // Read the relocs. void do_read_relocs(Read_relocs_data*); // Scan the relocs and adjust the symbol table. void do_scan_relocs(const General_options&, Symbol_table*, Layout*, Read_relocs_data*); // Finalize the local symbols. unsigned int do_finalize_local_symbols(unsigned int, off_t, Stringpool_template<char>*); // Relocate the input sections and write out the local symbols. void do_relocate(const General_options& options, const Symbol_table* symtab, const Layout*, Output_file* of); // Get the name of a section. std::string do_section_name(unsigned int shndx) { return this->elf_file_.section_name(shndx); } // Return the location of the contents of a section. Object::Location do_section_contents(unsigned int shndx) { return this->elf_file_.section_contents(shndx); } // Return section flags. uint64_t do_section_flags(unsigned int shndx) { return this->elf_file_.section_flags(shndx); } // Return the section link field. unsigned int do_section_link(unsigned int shndx) { return this->elf_file_.section_link(shndx); } private: // For convenience. typedef Sized_relobj<size, big_endian> This; static const int ehdr_size = elfcpp::Elf_sizes<size>::ehdr_size; static const int shdr_size = elfcpp::Elf_sizes<size>::shdr_size; static const int sym_size = elfcpp::Elf_sizes<size>::sym_size; typedef elfcpp::Shdr<size, big_endian> Shdr; // Find the SHT_SYMTAB section, given the section headers. void find_symtab(const unsigned char* pshdrs); // Whether to include a section group in the link. bool include_section_group(Layout*, unsigned int, const elfcpp::Shdr<size, big_endian>&, std::vector<bool>*); // Whether to include a linkonce section in the link. bool include_linkonce_section(Layout*, const char*, const elfcpp::Shdr<size, big_endian>&); // Views and sizes when relocating. struct View_size { unsigned char* view; typename elfcpp::Elf_types<size>::Elf_Addr address; off_t offset; off_t view_size; }; typedef std::vector<View_size> Views; // Write section data to the output file. Record the views and // sizes in VIEWS for use when relocating. void write_sections(const unsigned char* pshdrs, Output_file*, Views*); // Relocate the sections in the output file. void relocate_sections(const General_options& options, const Symbol_table*, const Layout*, const unsigned char* pshdrs, Views*); // Write out the local symbols. void write_local_symbols(Output_file*, const Stringpool_template<char>*); // The GOT offsets of local symbols. typedef Unordered_map<unsigned int, unsigned int> Local_got_offsets; // General access to the ELF file. elfcpp::Elf_file<size, big_endian, Object> elf_file_; // Index of SHT_SYMTAB section. unsigned int symtab_shndx_; // The number of local symbols. unsigned int local_symbol_count_; // The number of local symbols which go into the output file. unsigned int output_local_symbol_count_; // The entries in the symbol table for the external symbols. Symbol** symbols_; // File offset for local symbols. off_t local_symbol_offset_; // Values of local symbols. Local_values local_values_; // GOT offsets for local symbols, indexed by symbol number. Local_got_offsets local_got_offsets_; }; // A class to manage the list of all objects. class Input_objects { public: Input_objects() : relobj_list_(), dynobj_list_(), target_(NULL), sonames_() { } // The type of the list of input relocateable objects. typedef std::vector<Relobj*> Relobj_list; typedef Relobj_list::const_iterator Relobj_iterator; // The type of the list of input dynamic objects. typedef std::vector<Dynobj*> Dynobj_list; typedef Dynobj_list::const_iterator Dynobj_iterator; // Add an object to the list. Return true if all is well, or false // if this object should be ignored. bool add_object(Object*); // Get the target we should use for the output file. Target* target() const { return this->target_; } // Iterate over all regular objects. Relobj_iterator relobj_begin() const { return this->relobj_list_.begin(); } Relobj_iterator relobj_end() const { return this->relobj_list_.end(); } // Iterate over all dynamic objects. Dynobj_iterator dynobj_begin() const { return this->dynobj_list_.begin(); } Dynobj_iterator dynobj_end() const { return this->dynobj_list_.end(); } // Return whether we have seen any dynamic objects. bool any_dynamic() const { return !this->dynobj_list_.empty(); } // Return the number of input objects. int number_of_input_objects() const { return this->relobj_list_.size() + this->dynobj_list_.size(); } private: Input_objects(const Input_objects&); Input_objects& operator=(const Input_objects&); // The list of ordinary objects included in the link. Relobj_list relobj_list_; // The list of dynamic objects included in the link. Dynobj_list dynobj_list_; // The target. Target* target_; // SONAMEs that we have seen. Unordered_set<std::string> sonames_; }; // Some of the information we pass to the relocation routines. We // group this together to avoid passing a dozen different arguments. template<int size, bool big_endian> struct Relocate_info { // Command line options. const General_options* options; // Symbol table. const Symbol_table* symtab; // Layout. const Layout* layout; // Object being relocated. Sized_relobj<size, big_endian>* object; // Number of local symbols. unsigned int local_symbol_count; // Values of local symbols. const typename Sized_relobj<size, big_endian>::Local_values* local_values; // Global symbols. const Symbol* const * symbols; // Section index of relocation section. unsigned int reloc_shndx; // Section index of section being relocated. unsigned int data_shndx; // Return a string showing the location of a relocation. This is // only used for error messages. std::string location(size_t relnum, off_t reloffset) const; }; // Return an Object appropriate for the input file. P is BYTES long, // and holds the ELF header. extern Object* make_elf_object(const std::string& name, Input_file*, off_t offset, const unsigned char* p, off_t bytes); } // end namespace gold #endif // !defined(GOLD_OBJECT_H)