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Diffstat (limited to 'binutils-2.20.1/gold/target.h')
| -rw-r--r-- | binutils-2.20.1/gold/target.h | 739 |
1 files changed, 739 insertions, 0 deletions
diff --git a/binutils-2.20.1/gold/target.h b/binutils-2.20.1/gold/target.h new file mode 100644 index 00000000..48b11b2c --- /dev/null +++ b/binutils-2.20.1/gold/target.h @@ -0,0 +1,739 @@ +// 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 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; +class Input_objects; + +// The abstract class for target specific handling. + +class Target +{ + public: + virtual ~Target() + { } + + // Virtual function which is set to return true by a target if + // it can use relocation types to determine if a function's + // pointer is taken. + virtual bool + can_check_for_function_pointers() const + { return false; } + + // This function is used in ICF (icf.cc). This is set to true by + // the target if a relocation to a merged section can be processed + // to retrieve the contents of the merged section. + virtual bool + can_icf_inline_merge_sections () const + { return false; } + + // Whether a section called SECTION_NAME may have function pointers to + // sections not eligible for safe ICF folding. + virtual bool + section_may_have_icf_unsafe_pointers(const char* section_name) const + { + // We recognize sections for normal vtables, construction vtables and + // EH frames. + return (!is_prefix_of(".rodata._ZTV", section_name) + && !is_prefix_of(".data.rel.ro._ZTV", section_name) + && !is_prefix_of(".rodata._ZTC", section_name) + && !is_prefix_of(".data.rel.ro._ZTC", section_name) + && !is_prefix_of(".eh_frame", section_name)); + } + + // 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; } + + // Processor specific flags to store in e_flags field of ELF header. + elfcpp::Elf_Word + processor_specific_flags() const + { return this->processor_specific_flags_; } + + // Whether processor specific flags are set at least once. + bool + are_processor_specific_flags_set() const + { return this->are_processor_specific_flags_set_; } + + // 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, const Input_objects* input_objects, + Symbol_table* symtab) + { return this->do_finalize_sections(layout, input_objects, symtab); } + + // 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); } + + // Get the symbol index to use for a target specific reloc. + unsigned int + reloc_symbol_index(void* arg, unsigned int type) const + { return this->do_reloc_symbol_index(arg, type); } + + // Get the addend to use for a target specific reloc. + uint64_t + reloc_addend(void* arg, unsigned int type, uint64_t addend) const + { return this->do_reloc_addend(arg, type, addend); } + + // 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); + } + + // Return the target-specific name of attributes section. This is + // NULL if a target does not use attributes section or if it uses + // the default section name ".gnu.attributes". + const char* + attributes_section() const + { return this->pti_->attributes_section; } + + // Return the vendor name of vendor attributes. + const char* + attributes_vendor() const + { return this->pti_->attributes_vendor; } + + // Whether a section called NAME is an attribute section. + bool + is_attributes_section(const char* name) const + { + return ((this->pti_->attributes_section != NULL + && strcmp(name, this->pti_->attributes_section) == 0) + || strcmp(name, ".gnu.attributes") == 0); + } + + // Return a bit mask of argument types for attribute with TAG. + int + attribute_arg_type(int tag) const + { return this->do_attribute_arg_type(tag); } + + // Return the attribute tag of the position NUM in the list of fixed + // attributes. Normally there is no reordering and + // attributes_order(NUM) == NUM. + int + attributes_order(int num) const + { return this->do_attributes_order(num); } + + // When a target is selected as the default target, we call this method, + // which may be used for expensive, target-specific initialization. + void + select_as_default_target() + { this->do_select_as_default_target(); } + + 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; + // Name of attributes section if it is not ".gnu.attributes". + const char* attributes_section; + // Vendor name of vendor attributes. + const char* attributes_vendor; + }; + + Target(const Target_info* pti) + : pti_(pti), processor_specific_flags_(0), + are_processor_specific_flags_set_(false) + { } + + // 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*, const Input_objects*, Symbol_table*) + { } + + // 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 that must be overridden by a target which uses + // target specific relocations. + virtual unsigned int + do_reloc_symbol_index(void*, unsigned int) const + { gold_unreachable(); } + + // Virtual function that must be overidden by a target which uses + // target specific relocations. + virtual uint64_t + do_reloc_addend(void*, unsigned int, uint64_t) const + { gold_unreachable(); } + + // 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 endianness. + + // Set processor specific flags. + void + set_processor_specific_flags(elfcpp::Elf_Word flags) + { + this->processor_specific_flags_ = flags; + this->are_processor_specific_flags_set_ = true; + } + +#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; + + // This must be overriden by the child class if it has target-specific + // attributes subsection in the attribute section. + virtual int + do_attribute_arg_type(int) const + { gold_unreachable(); } + + // This may be overridden by the child class. + virtual int + do_attributes_order(int num) const + { return num; } + + // This may be overridden by the child class. + virtual void + do_select_as_default_target() + { } + + private: + // The implementations of the four do_make_elf_object virtual functions are + // almost identical except for their sizes and endianness. 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_; + // Processor-specific flags. + elfcpp::Elf_Word processor_specific_flags_; + // Whether the processor-specific flags are set at least once. + bool are_processor_specific_flags_set_; +}; + +// 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(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. 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(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(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; + + // Perform target-specific processing in a relocatable link. This is + // only used if we use the relocation strategy RELOC_SPECIAL. + // RELINFO points to a Relocation_info structure. SH_TYPE is the relocation + // section type. PRELOC_IN points to the original relocation. RELNUM is + // the index number of the relocation in the relocation section. + // OUTPUT_SECTION is the output section to which the relocation is applied. + // OFFSET_IN_OUTPUT_SECTION is the offset of the relocation input section + // within the output section. VIEW points to the output view of the + // output section. VIEW_ADDRESS is output address of the view. VIEW_SIZE + // is the size of the output view and PRELOC_OUT points to the new + // relocation in the output object. + // + // A target only needs to override this if the generic code in + // target-reloc.h cannot handle some relocation types. + + virtual void + relocate_special_relocatable(const Relocate_info<size, big_endian>* + /*relinfo */, + unsigned int /* sh_type */, + const unsigned char* /* preloc_in */, + size_t /* relnum */, + Output_section* /* output_section */, + off_t /* offset_in_output_section */, + unsigned char* /* view */, + typename elfcpp::Elf_types<size>::Elf_Addr + /* view_address */, + section_size_type /* view_size */, + unsigned char* /* preloc_out*/) + { gold_unreachable(); } + + 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) |