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Diffstat (limited to 'gold/object.h')
-rw-r--r-- | gold/object.h | 820 |
1 files changed, 820 insertions, 0 deletions
diff --git a/gold/object.h b/gold/object.h new file mode 100644 index 000000000000..2027f8e97dff --- /dev/null +++ b/gold/object.h @@ -0,0 +1,820 @@ +// object.h -- support for an object file for linking in gold -*- C++ -*- + +#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; +}; + +// 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_; } + + // 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. + const unsigned char* + section_contents(unsigned int shndx, off_t* plen); + + // 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); } + + // 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(const General_options& options, Symbol_table* symtab, + Layout* layout, Read_symbols_data* sd) + { this->do_layout(options, 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)); } + + // Report an error. + void + error(const char* format, ...) 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)); } + + 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(const General_options&, 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 the file. + Input_file* + input_file() const + { return this->input_file_; } + + // Get the offset into the file. + off_t + offset() const + { return this->offset_; } + + // Get a view into the underlying file. + const unsigned char* + get_view(off_t start, off_t size) + { return this->input_file_->file().get_view(start + this->offset_, size); } + + // Get a lasting view into the underlying file. + File_view* + get_lasting_view(off_t start, off_t size) + { + return this->input_file_->file().get_lasting_view(start + this->offset_, + size); + } + + // 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), 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_, 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; } + + 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_ : 31; + // Whether getting the value of this symbol requires calling an + // Output_section method. For example, this will be true of a + // STT_SECTION 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(); + } + + // Read the symbols. + void + do_read_symbols(Read_symbols_data*); + + // Lay out the input sections. + void + do_layout(const General_options&, 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 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 a local symbol define in input section SHNDX, + // with value VALUE, adding addend ADDEND. This handles SHF_MERGE + // sections. + Address + local_value(unsigned int shndx, Address value, Address addend) const; + + 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>*); + + // 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_; +}; + +// 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(); } + + 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) |