| // target.h -- target support for gold -*- C++ -*- |
| |
| // Copyright 2006, 2007, 2008, 2009 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. |
| |
| // 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<int size, bool big_endian> |
| class Sized_relobj; |
| class Relocatable_relocs; |
| template<int size, bool big_endian> |
| class Relocate_info; |
| class Reloc_symbol_changes; |
| class Symbol; |
| template<int size> |
| 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<int size, bool big_endian> |
| Object* |
| make_elf_object(const std::string& name, Input_file* input_file, |
| off_t offset, const elfcpp::Ehdr<size, big_endian>& 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<size>::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<int size, bool big_endian> |
| inline Object* |
| do_make_elf_object_implementation(const std::string&, Input_file*, off_t, |
| const elfcpp::Ehdr<size, big_endian>&); |
| |
| 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<int size, bool big_endian> |
| 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<size>* |
| 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<size, big_endian>&, 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<size, big_endian>* 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<size, big_endian>* 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<size, big_endian>*, |
| 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<size>::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<size, big_endian>* 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<size, big_endian>*, |
| 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<size>::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) |