// target.h -- target support for gold -*- C++ -*- // Copyright 2006, 2007, 2008, 2009 Free Software Foundation, Inc. // Written by Ian Lance Taylor . // 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. // The abstract class Target is the interface for target specific // support. It defines abstract methods which each target must // implement. Typically there will be one target per processor, but // in some cases it may be necessary to have subclasses. // For speed and consistency we want to use inline functions to handle // relocation processing. So besides implementations of the abstract // methods, each target is expected to define a template // specialization of the relocation functions. #ifndef GOLD_TARGET_H #define GOLD_TARGET_H #include "elfcpp.h" #include "options.h" #include "parameters.h" #include "debug.h" namespace gold { class General_options; class Object; class Relobj; template class Sized_relobj; class Relocatable_relocs; template class Relocate_info; class Reloc_symbol_changes; class Symbol; template class Sized_symbol; class Symbol_table; class Output_section; // The abstract class for target specific handling. class Target { public: virtual ~Target() { } // Return the bit size that this target implements. This should // return 32 or 64. int get_size() const { return this->pti_->size; } // Return whether this target is big-endian. bool is_big_endian() const { return this->pti_->is_big_endian; } // Machine code to store in e_machine field of ELF header. elfcpp::EM machine_code() const { return this->pti_->machine_code; } // Whether this target has a specific make_symbol function. bool has_make_symbol() const { return this->pti_->has_make_symbol; } // Whether this target has a specific resolve function. bool has_resolve() const { return this->pti_->has_resolve; } // Whether this target has a specific code fill function. bool has_code_fill() const { return this->pti_->has_code_fill; } // Return the default name of the dynamic linker. const char* dynamic_linker() const { return this->pti_->dynamic_linker; } // Return the default address to use for the text segment. uint64_t default_text_segment_address() const { return this->pti_->default_text_segment_address; } // Return the ABI specified page size. uint64_t abi_pagesize() const { if (parameters->options().max_page_size() > 0) return parameters->options().max_page_size(); else return this->pti_->abi_pagesize; } // Return the common page size used on actual systems. uint64_t common_pagesize() const { if (parameters->options().common_page_size() > 0) return std::min(parameters->options().common_page_size(), this->abi_pagesize()); else return std::min(this->pti_->common_pagesize, this->abi_pagesize()); } // If we see some object files with .note.GNU-stack sections, and // some objects files without them, this returns whether we should // consider the object files without them to imply that the stack // should be executable. bool is_default_stack_executable() const { return this->pti_->is_default_stack_executable; } // Return a character which may appear as a prefix for a wrap // symbol. If this character appears, we strip it when checking for // wrapping and add it back when forming the final symbol name. // This should be '\0' if not special prefix is required, which is // the normal case. char wrap_char() const { return this->pti_->wrap_char; } // Return the special section index which indicates a small common // symbol. This will return SHN_UNDEF if there are no small common // symbols. elfcpp::Elf_Half small_common_shndx() const { return this->pti_->small_common_shndx; } // Return values to add to the section flags for the section holding // small common symbols. elfcpp::Elf_Xword small_common_section_flags() const { gold_assert(this->pti_->small_common_shndx != elfcpp::SHN_UNDEF); return this->pti_->small_common_section_flags; } // Return the special section index which indicates a large common // symbol. This will return SHN_UNDEF if there are no large common // symbols. elfcpp::Elf_Half large_common_shndx() const { return this->pti_->large_common_shndx; } // Return values to add to the section flags for the section holding // large common symbols. elfcpp::Elf_Xword large_common_section_flags() const { gold_assert(this->pti_->large_common_shndx != elfcpp::SHN_UNDEF); return this->pti_->large_common_section_flags; } // This hook is called when an output section is created. void new_output_section(Output_section* os) const { this->do_new_output_section(os); } // This is called to tell the target to complete any sections it is // handling. After this all sections must have their final size. void finalize_sections(Layout* layout) { return this->do_finalize_sections(layout); } // Return the value to use for a global symbol which needs a special // value in the dynamic symbol table. This will only be called if // the backend first calls symbol->set_needs_dynsym_value(). uint64_t dynsym_value(const Symbol* sym) const { return this->do_dynsym_value(sym); } // Return a string to use to fill out a code section. This is // basically one or more NOPS which must fill out the specified // length in bytes. std::string code_fill(section_size_type length) const { return this->do_code_fill(length); } // Return whether SYM is known to be defined by the ABI. This is // used to avoid inappropriate warnings about undefined symbols. bool is_defined_by_abi(const Symbol* sym) const { return this->do_is_defined_by_abi(sym); } // Adjust the output file header before it is written out. VIEW // points to the header in external form. LEN is the length. void adjust_elf_header(unsigned char* view, int len) const { return this->do_adjust_elf_header(view, len); } // Return whether NAME is a local label name. This is used to implement the // --discard-locals options. bool is_local_label_name(const char* name) const { return this->do_is_local_label_name(name); } // A function starts at OFFSET in section SHNDX in OBJECT. That // function was compiled with -fsplit-stack, but it refers to a // function which was compiled without -fsplit-stack. VIEW is a // modifiable view of the section; VIEW_SIZE is the size of the // view. The target has to adjust the function so that it allocates // enough stack. void calls_non_split(Relobj* object, unsigned int shndx, section_offset_type fnoffset, section_size_type fnsize, unsigned char* view, section_size_type view_size, std::string* from, std::string* to) const { this->do_calls_non_split(object, shndx, fnoffset, fnsize, view, view_size, from, to); } // Make an ELF object. template Object* make_elf_object(const std::string& name, Input_file* input_file, off_t offset, const elfcpp::Ehdr& ehdr) { return this->do_make_elf_object(name, input_file, offset, ehdr); } // Make an output section. Output_section* make_output_section(const char* name, elfcpp::Elf_Word type, elfcpp::Elf_Xword flags) { return this->do_make_output_section(name, type, flags); } // Return true if target wants to perform relaxation. bool may_relax() const { // Run the dummy relaxation pass twice if relaxation debugging is enabled. if (is_debugging_enabled(DEBUG_RELAXATION)) return true; return this->do_may_relax(); } // Perform a relaxation pass. Return true if layout may be changed. bool relax(int pass, const Input_objects* input_objects, Symbol_table* symtab, Layout* layout) { // Run the dummy relaxation pass twice if relaxation debugging is enabled. if (is_debugging_enabled(DEBUG_RELAXATION)) return pass < 2; return this->do_relax(pass, input_objects, symtab, layout); } protected: // This struct holds the constant information for a child class. We // use a struct to avoid the overhead of virtual function calls for // simple information. struct Target_info { // Address size (32 or 64). int size; // Whether the target is big endian. bool is_big_endian; // The code to store in the e_machine field of the ELF header. elfcpp::EM machine_code; // Whether this target has a specific make_symbol function. bool has_make_symbol; // Whether this target has a specific resolve function. bool has_resolve; // Whether this target has a specific code fill function. bool has_code_fill; // Whether an object file with no .note.GNU-stack sections implies // that the stack should be executable. bool is_default_stack_executable; // Prefix character to strip when checking for wrapping. char wrap_char; // The default dynamic linker name. const char* dynamic_linker; // The default text segment address. uint64_t default_text_segment_address; // The ABI specified page size. uint64_t abi_pagesize; // The common page size used by actual implementations. uint64_t common_pagesize; // The special section index for small common symbols; SHN_UNDEF // if none. elfcpp::Elf_Half small_common_shndx; // The special section index for large common symbols; SHN_UNDEF // if none. elfcpp::Elf_Half large_common_shndx; // Section flags for small common section. elfcpp::Elf_Xword small_common_section_flags; // Section flags for large common section. elfcpp::Elf_Xword large_common_section_flags; }; Target(const Target_info* pti) : pti_(pti) { } // Virtual function which may be implemented by the child class. virtual void do_new_output_section(Output_section*) const { } // Virtual function which may be implemented by the child class. virtual void do_finalize_sections(Layout*) { } // Virtual function which may be implemented by the child class. virtual uint64_t do_dynsym_value(const Symbol*) const { gold_unreachable(); } // Virtual function which must be implemented by the child class if // needed. virtual std::string do_code_fill(section_size_type) const { gold_unreachable(); } // Virtual function which may be implemented by the child class. virtual bool do_is_defined_by_abi(const Symbol*) const { return false; } // Adjust the output file header before it is written out. VIEW // points to the header in external form. LEN is the length, and // will be one of the values of elfcpp::Elf_sizes::ehdr_size. // By default, we do nothing. virtual void do_adjust_elf_header(unsigned char*, int) const { } // Virtual function which may be overriden by the child class. virtual bool do_is_local_label_name(const char*) const; // Virtual function which may be overridden by the child class. virtual void do_calls_non_split(Relobj* object, unsigned int, section_offset_type, section_size_type, unsigned char*, section_size_type, std::string*, std::string*) const; // make_elf_object hooks. There are four versions of these for // different address sizes and endianities. #ifdef HAVE_TARGET_32_LITTLE // Virtual functions which may be overriden by the child class. virtual Object* do_make_elf_object(const std::string&, Input_file*, off_t, const elfcpp::Ehdr<32, false>&); #endif #ifdef HAVE_TARGET_32_BIG // Virtual functions which may be overriden by the child class. virtual Object* do_make_elf_object(const std::string&, Input_file*, off_t, const elfcpp::Ehdr<32, true>&); #endif #ifdef HAVE_TARGET_64_LITTLE // Virtual functions which may be overriden by the child class. virtual Object* do_make_elf_object(const std::string&, Input_file*, off_t, const elfcpp::Ehdr<64, false>& ehdr); #endif #ifdef HAVE_TARGET_64_BIG // Virtual functions which may be overriden by the child class. virtual Object* do_make_elf_object(const std::string& name, Input_file* input_file, off_t offset, const elfcpp::Ehdr<64, true>& ehdr); #endif // Virtual functions which may be overriden by the child class. virtual Output_section* do_make_output_section(const char* name, elfcpp::Elf_Word type, elfcpp::Elf_Xword flags); // Virtual function which may be overriden by the child class. virtual bool do_may_relax() const { return parameters->options().relax(); } // Virtual function which may be overriden by the child class. virtual bool do_relax(int, const Input_objects*, Symbol_table*, Layout*) { return false; } // A function for targets to call. Return whether BYTES/LEN matches // VIEW/VIEW_SIZE at OFFSET. bool match_view(const unsigned char* view, section_size_type view_size, section_offset_type offset, const char* bytes, size_t len) const; // Set the contents of a VIEW/VIEW_SIZE to nops starting at OFFSET // for LEN bytes. void set_view_to_nop(unsigned char* view, section_size_type view_size, section_offset_type offset, size_t len) const; private: // The implementations of the four do_make_elf_object virtual functions are // almost identical except for their sizes and endianity. We use a template. // for their implementations. template inline Object* do_make_elf_object_implementation(const std::string&, Input_file*, off_t, const elfcpp::Ehdr&); Target(const Target&); Target& operator=(const Target&); // The target information. const Target_info* pti_; }; // The abstract class for a specific size and endianness of target. // Each actual target implementation class should derive from an // instantiation of Sized_target. template class Sized_target : public Target { public: // Make a new symbol table entry for the target. This should be // overridden by a target which needs additional information in the // symbol table. This will only be called if has_make_symbol() // returns true. virtual Sized_symbol* make_symbol() const { gold_unreachable(); } // Resolve a symbol for the target. This should be overridden by a // target which needs to take special action. TO is the // pre-existing symbol. SYM is the new symbol, seen in OBJECT. // VERSION is the version of SYM. This will only be called if // has_resolve() returns true. virtual void resolve(Symbol*, const elfcpp::Sym&, Object*, const char*) { gold_unreachable(); } // Process the relocs for a section, and record information of the // mapping from source to destination sections. This mapping is later // used to determine unreferenced garbage sections. This procedure is // only called during garbage collection. virtual void gc_process_relocs(const General_options& options, Symbol_table* symtab, Layout* layout, Sized_relobj* object, unsigned int data_shndx, unsigned int sh_type, const unsigned char* prelocs, size_t reloc_count, Output_section* output_section, bool needs_special_offset_handling, size_t local_symbol_count, const unsigned char* plocal_symbols) = 0; // Scan the relocs for a section, and record any information // required for the symbol. OPTIONS is the command line options. // SYMTAB is the symbol table. OBJECT is the object in which the // section appears. DATA_SHNDX is the section index that these // relocs apply to. SH_TYPE is the type of the relocation section, // SHT_REL or SHT_RELA. PRELOCS points to the relocation data. // RELOC_COUNT is the number of relocs. LOCAL_SYMBOL_COUNT is the // number of local symbols. OUTPUT_SECTION is the output section. // NEEDS_SPECIAL_OFFSET_HANDLING is true if offsets to the output // sections are not mapped as usual. PLOCAL_SYMBOLS points to the // local symbol data from OBJECT. GLOBAL_SYMBOLS is the array of // pointers to the global symbol table from OBJECT. virtual void scan_relocs(const General_options& options, Symbol_table* symtab, Layout* layout, Sized_relobj* object, unsigned int data_shndx, unsigned int sh_type, const unsigned char* prelocs, size_t reloc_count, Output_section* output_section, bool needs_special_offset_handling, size_t local_symbol_count, const unsigned char* plocal_symbols) = 0; // Relocate section data. SH_TYPE is the type of the relocation // section, SHT_REL or SHT_RELA. PRELOCS points to the relocation // information. RELOC_COUNT is the number of relocs. // OUTPUT_SECTION is the output section. // NEEDS_SPECIAL_OFFSET_HANDLING is true if offsets must be mapped // to correspond to the output section. VIEW is a view into the // output file holding the section contents, VIEW_ADDRESS is the // virtual address of the view, and VIEW_SIZE is the size of the // view. If NEEDS_SPECIAL_OFFSET_HANDLING is true, the VIEW_xx // parameters refer to the complete output section data, not just // the input section data. virtual void relocate_section(const Relocate_info*, unsigned int sh_type, const unsigned char* prelocs, size_t reloc_count, Output_section* output_section, bool needs_special_offset_handling, unsigned char* view, typename elfcpp::Elf_types::Elf_Addr view_address, section_size_type view_size, const Reloc_symbol_changes*) = 0; // Scan the relocs during a relocatable link. The parameters are // like scan_relocs, with an additional Relocatable_relocs // parameter, used to record the disposition of the relocs. virtual void scan_relocatable_relocs(const General_options& options, Symbol_table* symtab, Layout* layout, Sized_relobj* object, unsigned int data_shndx, unsigned int sh_type, const unsigned char* prelocs, size_t reloc_count, Output_section* output_section, bool needs_special_offset_handling, size_t local_symbol_count, const unsigned char* plocal_symbols, Relocatable_relocs*) = 0; // Relocate a section during a relocatable link. The parameters are // like relocate_section, with additional parameters for the view of // the output reloc section. virtual void relocate_for_relocatable(const Relocate_info*, unsigned int sh_type, const unsigned char* prelocs, size_t reloc_count, Output_section* output_section, off_t offset_in_output_section, const Relocatable_relocs*, unsigned char* view, typename elfcpp::Elf_types::Elf_Addr view_address, section_size_type view_size, unsigned char* reloc_view, section_size_type reloc_view_size) = 0; protected: Sized_target(const Target::Target_info* pti) : Target(pti) { gold_assert(pti->size == size); gold_assert(pti->is_big_endian ? big_endian : !big_endian); } }; } // End namespace gold. #endif // !defined(GOLD_TARGET_H)