// layout.h -- lay out output file sections for gold -*- C++ -*- // Copyright 2006, 2007, 2008 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_LAYOUT_H #define GOLD_LAYOUT_H #include <cstring> #include <list> #include <string> #include <utility> #include <vector> #include "script.h" #include "workqueue.h" #include "object.h" #include "dynobj.h" #include "stringpool.h" namespace gold { class General_options; class Input_objects; class Mapfile; class Symbol_table; class Output_section_data; class Output_section; class Output_section_headers; class Output_segment; class Output_data; class Output_data_dynamic; class Output_symtab_xindex; class Output_reduced_debug_abbrev_section; class Output_reduced_debug_info_section; class Eh_frame; class Target; // This task function handles mapping the input sections to output // sections and laying them out in memory. class Layout_task_runner : public Task_function_runner { public: // OPTIONS is the command line options, INPUT_OBJECTS is the list of // input objects, SYMTAB is the symbol table, LAYOUT is the layout // object. Layout_task_runner(const General_options& options, const Input_objects* input_objects, Symbol_table* symtab, Target* target, Layout* layout, Mapfile* mapfile) : options_(options), input_objects_(input_objects), symtab_(symtab), target_(target), layout_(layout), mapfile_(mapfile) { } // Run the operation. void run(Workqueue*, const Task*); private: Layout_task_runner(const Layout_task_runner&); Layout_task_runner& operator=(const Layout_task_runner&); const General_options& options_; const Input_objects* input_objects_; Symbol_table* symtab_; Target* target_; Layout* layout_; Mapfile* mapfile_; }; // This class handles the details of laying out input sections. class Layout { public: Layout(const General_options& options, Script_options*); // Given an input section SHNDX, named NAME, with data in SHDR, from // the object file OBJECT, return the output section where this // input section should go. RELOC_SHNDX is the index of a // relocation section which applies to this section, or 0 if none, // or -1U if more than one. RELOC_TYPE is the type of the // relocation section if there is one. Set *OFFSET to the offset // within the output section. template<int size, bool big_endian> Output_section* layout(Sized_relobj<size, big_endian> *object, unsigned int shndx, const char* name, const elfcpp::Shdr<size, big_endian>& shdr, unsigned int reloc_shndx, unsigned int reloc_type, off_t* offset); // Layout an input reloc section when doing a relocatable link. The // section is RELOC_SHNDX in OBJECT, with data in SHDR. // DATA_SECTION is the reloc section to which it refers. RR is the // relocatable information. template<int size, bool big_endian> Output_section* layout_reloc(Sized_relobj<size, big_endian>* object, unsigned int reloc_shndx, const elfcpp::Shdr<size, big_endian>& shdr, Output_section* data_section, Relocatable_relocs* rr); // Layout a group section when doing a relocatable link. template<int size, bool big_endian> void layout_group(Symbol_table* symtab, Sized_relobj<size, big_endian>* object, unsigned int group_shndx, const char* group_section_name, const char* signature, const elfcpp::Shdr<size, big_endian>& shdr, elfcpp::Elf_Word flags, std::vector<unsigned int>* shndxes); // Like layout, only for exception frame sections. OBJECT is an // object file. SYMBOLS is the contents of the symbol table // section, with size SYMBOLS_SIZE. SYMBOL_NAMES is the contents of // the symbol name section, with size SYMBOL_NAMES_SIZE. SHNDX is a // .eh_frame section in OBJECT. SHDR is the section header. // RELOC_SHNDX is the index of a relocation section which applies to // this section, or 0 if none, or -1U if more than one. RELOC_TYPE // is the type of the relocation section if there is one. This // returns the output section, and sets *OFFSET to the offset. template<int size, bool big_endian> Output_section* layout_eh_frame(Sized_relobj<size, big_endian>* object, const unsigned char* symbols, off_t symbols_size, const unsigned char* symbol_names, off_t symbol_names_size, unsigned int shndx, const elfcpp::Shdr<size, big_endian>& shdr, unsigned int reloc_shndx, unsigned int reloc_type, off_t* offset); // Handle a GNU stack note. This is called once per input object // file. SEEN_GNU_STACK is true if the object file has a // .note.GNU-stack section. GNU_STACK_FLAGS is the section flags // from that section if there was one. void layout_gnu_stack(bool seen_gnu_stack, uint64_t gnu_stack_flags); // Add an Output_section_data to the layout. This is used for // special sections like the GOT section. Output_section* add_output_section_data(const char* name, elfcpp::Elf_Word type, elfcpp::Elf_Xword flags, Output_section_data*); // Create dynamic sections if necessary. void create_initial_dynamic_sections(Symbol_table*); // Define __start and __stop symbols for output sections. void define_section_symbols(Symbol_table*); // Create sections for linker scripts. void create_script_sections() { this->script_options_->create_script_sections(this); } // Define symbols from any linker script. void define_script_symbols(Symbol_table* symtab) { this->script_options_->add_symbols_to_table(symtab); } // Define symbols for group signatures. void define_group_signatures(Symbol_table*); // Return the Stringpool used for symbol names. const Stringpool* sympool() const { return &this->sympool_; } // Return the Stringpool used for dynamic symbol names and dynamic // tags. const Stringpool* dynpool() const { return &this->dynpool_; } // Return the symtab_xindex section used to hold large section // indexes for the normal symbol table. Output_symtab_xindex* symtab_xindex() const { return this->symtab_xindex_; } // Return the dynsym_xindex section used to hold large section // indexes for the dynamic symbol table. Output_symtab_xindex* dynsym_xindex() const { return this->dynsym_xindex_; } // Return whether a section is a .gnu.linkonce section, given the // section name. static inline bool is_linkonce(const char* name) { return strncmp(name, ".gnu.linkonce", sizeof(".gnu.linkonce") - 1) == 0; } // Return true if a section is a debugging section. static inline bool is_debug_info_section(const char* name) { // Debugging sections can only be recognized by name. return (strncmp(name, ".debug", sizeof(".debug") - 1) == 0 || strncmp(name, ".gnu.linkonce.wi.", sizeof(".gnu.linkonce.wi.") - 1) == 0 || strncmp(name, ".line", sizeof(".line") - 1) == 0 || strncmp(name, ".stab", sizeof(".stab") - 1) == 0); } // Record the signature of a comdat section, and return whether to // include it in the link. The GROUP parameter is true for a // section group signature, false for a signature derived from a // .gnu.linkonce section. bool add_comdat(Relobj*, unsigned int, const std::string&, bool group); // Find the given comdat signature, and return the object and section // index of the kept group. Relobj* find_kept_object(const std::string&, unsigned int*) const; // Finalize the layout after all the input sections have been added. off_t finalize(const Input_objects*, Symbol_table*, Target*, const Task*); // Return whether any sections require postprocessing. bool any_postprocessing_sections() const { return this->any_postprocessing_sections_; } // Return the size of the output file. off_t output_file_size() const { return this->output_file_size_; } // Return the TLS segment. This will return NULL if there isn't // one. Output_segment* tls_segment() const { return this->tls_segment_; } // Return the normal symbol table. Output_section* symtab_section() const { gold_assert(this->symtab_section_ != NULL); return this->symtab_section_; } // Return the dynamic symbol table. Output_section* dynsym_section() const { gold_assert(this->dynsym_section_ != NULL); return this->dynsym_section_; } // Return the dynamic tags. Output_data_dynamic* dynamic_data() const { return this->dynamic_data_; } // Write out the output sections. void write_output_sections(Output_file* of) const; // Write out data not associated with an input file or the symbol // table. void write_data(const Symbol_table*, Output_file*) const; // Write out output sections which can not be written until all the // input sections are complete. void write_sections_after_input_sections(Output_file* of); // Return an output section named NAME, or NULL if there is none. Output_section* find_output_section(const char* name) const; // Return an output segment of type TYPE, with segment flags SET set // and segment flags CLEAR clear. Return NULL if there is none. Output_segment* find_output_segment(elfcpp::PT type, elfcpp::Elf_Word set, elfcpp::Elf_Word clear) const; // Return the number of segments we expect to produce. size_t expected_segment_count() const; // Set a flag to indicate that an object file uses the static TLS model. void set_has_static_tls() { this->has_static_tls_ = true; } // Return true if any object file uses the static TLS model. bool has_static_tls() const { return this->has_static_tls_; } // Return the options which may be set by a linker script. Script_options* script_options() { return this->script_options_; } const Script_options* script_options() const { return this->script_options_; } // Compute and write out the build ID if needed. void write_build_id(Output_file*) const; // Rewrite output file in binary format. void write_binary(Output_file* in) const; // Print output sections to the map file. void print_to_mapfile(Mapfile*) const; // Dump statistical information to stderr. void print_stats() const; // A list of segments. typedef std::vector<Output_segment*> Segment_list; // A list of sections. typedef std::vector<Output_section*> Section_list; // The list of information to write out which is not attached to // either a section or a segment. typedef std::vector<Output_data*> Data_list; // Store the allocated sections into the section list. This is used // by the linker script code. void get_allocated_sections(Section_list*) const; // Make a section for a linker script to hold data. Output_section* make_output_section_for_script(const char* name); // Make a segment. This is used by the linker script code. Output_segment* make_output_segment(elfcpp::Elf_Word type, elfcpp::Elf_Word flags); // Return the number of segments. size_t segment_count() const { return this->segment_list_.size(); } // Map from section flags to segment flags. static elfcpp::Elf_Word section_flags_to_segment(elfcpp::Elf_Xword flags); // Attach sections to segments. void attach_sections_to_segments(); private: Layout(const Layout&); Layout& operator=(const Layout&); // Mapping from .gnu.linkonce section names to output section names. struct Linkonce_mapping { const char* from; int fromlen; const char* to; int tolen; }; static const Linkonce_mapping linkonce_mapping[]; static const int linkonce_mapping_count; // During a relocatable link, a list of group sections and // signatures. struct Group_signature { // The group section. Output_section* section; // The signature. const char* signature; Group_signature() : section(NULL), signature(NULL) { } Group_signature(Output_section* sectiona, const char* signaturea) : section(sectiona), signature(signaturea) { } }; typedef std::vector<Group_signature> Group_signatures; // Create a .note section, filling in the header. Output_section* create_note(const char* name, int note_type, size_t descsz, bool allocate, size_t* trailing_padding); // Create a .note section for gold. void create_gold_note(); // Record whether the stack must be executable. void create_executable_stack_info(const Target*); // Create a build ID note if needed. void create_build_id(); // Find the first read-only PT_LOAD segment, creating one if // necessary. Output_segment* find_first_load_seg(); // Count the local symbols in the regular symbol table and the dynamic // symbol table, and build the respective string pools. void count_local_symbols(const Task*, const Input_objects*); // Create the output sections for the symbol table. void create_symtab_sections(const Input_objects*, Symbol_table*, unsigned int, off_t*); // Create the .shstrtab section. Output_section* create_shstrtab(); // Create the section header table. void create_shdrs(const Output_section* shstrtab_section, off_t*); // Create the dynamic symbol table. void create_dynamic_symtab(const Input_objects*, Symbol_table*, Output_section** pdynstr, unsigned int* plocal_dynamic_count, std::vector<Symbol*>* pdynamic_symbols, Versions* versions); // Assign offsets to each local portion of the dynamic symbol table. void assign_local_dynsym_offsets(const Input_objects*); // Finish the .dynamic section and PT_DYNAMIC segment. void finish_dynamic_section(const Input_objects*, const Symbol_table*); // Create the .interp section and PT_INTERP segment. void create_interp(const Target* target); // Create the version sections. void create_version_sections(const Versions*, const Symbol_table*, unsigned int local_symcount, const std::vector<Symbol*>& dynamic_symbols, const Output_section* dynstr); template<int size, bool big_endian> void sized_create_version_sections(const Versions* versions, const Symbol_table*, unsigned int local_symcount, const std::vector<Symbol*>& dynamic_symbols, const Output_section* dynstr); // Return whether to include this section in the link. template<int size, bool big_endian> bool include_section(Sized_relobj<size, big_endian>* object, const char* name, const elfcpp::Shdr<size, big_endian>&); // Return the output section name to use given an input section // name. Set *PLEN to the length of the name. *PLEN must be // initialized to the length of NAME. static const char* output_section_name(const char* name, size_t* plen); // Return the output section name to use for a linkonce section // name. PLEN is as for output_section_name. static const char* linkonce_output_name(const char* name, size_t* plen); // Return the number of allocated output sections. size_t allocated_output_section_count() const; // Return the output section for NAME, TYPE and FLAGS. Output_section* get_output_section(const char* name, Stringpool::Key name_key, elfcpp::Elf_Word type, elfcpp::Elf_Xword flags); // Choose the output section for NAME in RELOBJ. Output_section* choose_output_section(const Relobj* relobj, const char* name, elfcpp::Elf_Word type, elfcpp::Elf_Xword flags, bool is_input_section); // Create a new Output_section. Output_section* make_output_section(const char* name, elfcpp::Elf_Word type, elfcpp::Elf_Xword flags); // Attach a section to a segment. void attach_section_to_segment(Output_section*); // Attach an allocated section to a segment. void attach_allocated_section_to_segment(Output_section*); // Set the final file offsets of all the segments. off_t set_segment_offsets(const Target*, Output_segment*, unsigned int* pshndx); // Set the file offsets of the sections when doing a relocatable // link. off_t set_relocatable_section_offsets(Output_data*, unsigned int* pshndx); // Set the final file offsets of all the sections not associated // with a segment. We set section offsets in three passes: the // first handles all allocated sections, the second sections that // require postprocessing, and the last the late-bound STRTAB // sections (probably only shstrtab, which is the one we care about // because it holds section names). enum Section_offset_pass { BEFORE_INPUT_SECTIONS_PASS, POSTPROCESSING_SECTIONS_PASS, STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS }; off_t set_section_offsets(off_t, Section_offset_pass pass); // Set the final section indexes of all the sections not associated // with a segment. Returns the next unused index. unsigned int set_section_indexes(unsigned int pshndx); // Set the section addresses when using a script. Output_segment* set_section_addresses_from_script(Symbol_table*); // Return whether SEG1 comes before SEG2 in the output file. static bool segment_precedes(const Output_segment* seg1, const Output_segment* seg2); // A mapping used for group signatures. struct Kept_section { Kept_section() : object_(NULL), shndx_(0), group_(false) { } Kept_section(Relobj* object, unsigned int shndx, bool group) : object_(object), shndx_(shndx), group_(group) { } Relobj* object_; unsigned int shndx_; bool group_; }; typedef Unordered_map<std::string, Kept_section> Signatures; // Mapping from input section name/type/flags to output section. We // use canonicalized strings here. typedef std::pair<Stringpool::Key, std::pair<elfcpp::Elf_Word, elfcpp::Elf_Xword> > Key; struct Hash_key { size_t operator()(const Key& k) const; }; typedef Unordered_map<Key, Output_section*, Hash_key> Section_name_map; // A comparison class for segments. struct Compare_segments { bool operator()(const Output_segment* seg1, const Output_segment* seg2) { return Layout::segment_precedes(seg1, seg2); } }; // A reference to the options on the command line. const General_options& options_; // Information set by scripts or by command line options. Script_options* script_options_; // The output section names. Stringpool namepool_; // The output symbol names. Stringpool sympool_; // The dynamic strings, if needed. Stringpool dynpool_; // The list of group sections and linkonce sections which we have seen. Signatures signatures_; // The mapping from input section name/type/flags to output sections. Section_name_map section_name_map_; // The list of output segments. Segment_list segment_list_; // The list of output sections. Section_list section_list_; // The list of output sections which are not attached to any output // segment. Section_list unattached_section_list_; // Whether we have attached the sections to the segments. bool sections_are_attached_; // The list of unattached Output_data objects which require special // handling because they are not Output_sections. Data_list special_output_list_; // The section headers. Output_section_headers* section_headers_; // A pointer to the PT_TLS segment if there is one. Output_segment* tls_segment_; // A pointer to the PT_GNU_RELRO segment if there is one. Output_segment* relro_segment_; // The SHT_SYMTAB output section. Output_section* symtab_section_; // The SHT_SYMTAB_SHNDX for the regular symbol table if there is one. Output_symtab_xindex* symtab_xindex_; // The SHT_DYNSYM output section if there is one. Output_section* dynsym_section_; // The SHT_SYMTAB_SHNDX for the dynamic symbol table if there is one. Output_symtab_xindex* dynsym_xindex_; // The SHT_DYNAMIC output section if there is one. Output_section* dynamic_section_; // The dynamic data which goes into dynamic_section_. Output_data_dynamic* dynamic_data_; // The exception frame output section if there is one. Output_section* eh_frame_section_; // The exception frame data for eh_frame_section_. Eh_frame* eh_frame_data_; // Whether we have added eh_frame_data_ to the .eh_frame section. bool added_eh_frame_data_; // The exception frame header output section if there is one. Output_section* eh_frame_hdr_section_; // The space for the build ID checksum if there is one. Output_section_data* build_id_note_; // The output section containing dwarf abbreviations Output_reduced_debug_abbrev_section* debug_abbrev_; // The output section containing the dwarf debug info tree Output_reduced_debug_info_section* debug_info_; // A list of group sections and their signatures. Group_signatures group_signatures_; // The size of the output file. off_t output_file_size_; // Whether we have seen an object file marked to require an // executable stack. bool input_requires_executable_stack_; // Whether we have seen at least one object file with an executable // stack marker. bool input_with_gnu_stack_note_; // Whether we have seen at least one object file without an // executable stack marker. bool input_without_gnu_stack_note_; // Whether we have seen an object file that uses the static TLS model. bool has_static_tls_; // Whether any sections require postprocessing. bool any_postprocessing_sections_; }; // This task handles writing out data in output sections which is not // part of an input section, or which requires special handling. When // this is done, it unblocks both output_sections_blocker and // final_blocker. class Write_sections_task : public Task { public: Write_sections_task(const Layout* layout, Output_file* of, Task_token* output_sections_blocker, Task_token* final_blocker) : layout_(layout), of_(of), output_sections_blocker_(output_sections_blocker), final_blocker_(final_blocker) { } // The standard Task methods. Task_token* is_runnable(); void locks(Task_locker*); void run(Workqueue*); std::string get_name() const { return "Write_sections_task"; } private: class Write_sections_locker; const Layout* layout_; Output_file* of_; Task_token* output_sections_blocker_; Task_token* final_blocker_; }; // This task handles writing out data which is not part of a section // or segment. class Write_data_task : public Task { public: Write_data_task(const Layout* layout, const Symbol_table* symtab, Output_file* of, Task_token* final_blocker) : layout_(layout), symtab_(symtab), of_(of), final_blocker_(final_blocker) { } // The standard Task methods. Task_token* is_runnable(); void locks(Task_locker*); void run(Workqueue*); std::string get_name() const { return "Write_data_task"; } private: const Layout* layout_; const Symbol_table* symtab_; Output_file* of_; Task_token* final_blocker_; }; // This task handles writing out the global symbols. class Write_symbols_task : public Task { public: Write_symbols_task(const Layout* layout, const Symbol_table* symtab, const Input_objects* input_objects, const Stringpool* sympool, const Stringpool* dynpool, Output_file* of, Task_token* final_blocker) : layout_(layout), symtab_(symtab), input_objects_(input_objects), sympool_(sympool), dynpool_(dynpool), of_(of), final_blocker_(final_blocker) { } // The standard Task methods. Task_token* is_runnable(); void locks(Task_locker*); void run(Workqueue*); std::string get_name() const { return "Write_symbols_task"; } private: const Layout* layout_; const Symbol_table* symtab_; const Input_objects* input_objects_; const Stringpool* sympool_; const Stringpool* dynpool_; Output_file* of_; Task_token* final_blocker_; }; // This task handles writing out data in output sections which can't // be written out until all the input sections have been handled. // This is for sections whose contents is based on the contents of // other output sections. class Write_after_input_sections_task : public Task { public: Write_after_input_sections_task(Layout* layout, Output_file* of, Task_token* input_sections_blocker, Task_token* final_blocker) : layout_(layout), of_(of), input_sections_blocker_(input_sections_blocker), final_blocker_(final_blocker) { } // The standard Task methods. Task_token* is_runnable(); void locks(Task_locker*); void run(Workqueue*); std::string get_name() const { return "Write_after_input_sections_task"; } private: Layout* layout_; Output_file* of_; Task_token* input_sections_blocker_; Task_token* final_blocker_; }; // This task function handles closing the file. class Close_task_runner : public Task_function_runner { public: Close_task_runner(const General_options* options, const Layout* layout, Output_file* of) : options_(options), layout_(layout), of_(of) { } // Run the operation. void run(Workqueue*, const Task*); private: const General_options* options_; const Layout* layout_; Output_file* of_; }; // A small helper function to align an address. inline uint64_t align_address(uint64_t address, uint64_t addralign) { if (addralign != 0) address = (address + addralign - 1) &~ (addralign - 1); return address; } } // End namespace gold. #endif // !defined(GOLD_LAYOUT_H)