1 // target.h -- target support for gold -*- C++ -*-
3 // Copyright (C) 2006-2018 Free Software Foundation, Inc.
4 // Written by Ian Lance Taylor <iant@google.com>.
6 // This file is part of gold.
8 // This program is free software; you can redistribute it and/or modify
9 // it under the terms of the GNU General Public License as published by
10 // the Free Software Foundation; either version 3 of the License, or
11 // (at your option) any later version.
13 // This program is distributed in the hope that it will be useful,
14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 // GNU General Public License for more details.
18 // You should have received a copy of the GNU General Public License
19 // along with this program; if not, write to the Free Software
20 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
21 // MA 02110-1301, USA.
23 // The abstract class Target is the interface for target specific
24 // support. It defines abstract methods which each target must
25 // implement. Typically there will be one target per processor, but
26 // in some cases it may be necessary to have subclasses.
28 // For speed and consistency we want to use inline functions to handle
29 // relocation processing. So besides implementations of the abstract
30 // methods, each target is expected to define a template
31 // specialization of the relocation functions.
38 #include "parameters.h"
39 #include "stringpool.h"
47 template<int size, bool big_endian>
49 template<int size, bool big_endian>
50 class Sized_relobj_file;
51 class Relocatable_relocs;
52 template<int size, bool big_endian>
54 class Reloc_symbol_changes;
60 class Output_data_got_base;
64 struct Symbol_location;
67 // The abstract class for target specific handling.
75 // Return the bit size that this target implements. This should
79 { return this->pti_->size; }
81 // Return whether this target is big-endian.
84 { return this->pti_->is_big_endian; }
86 // Machine code to store in e_machine field of ELF header.
89 { return this->pti_->machine_code; }
91 // Processor specific flags to store in e_flags field of ELF header.
93 processor_specific_flags() const
94 { return this->processor_specific_flags_; }
96 // Whether processor specific flags are set at least once.
98 are_processor_specific_flags_set() const
99 { return this->are_processor_specific_flags_set_; }
101 // Whether this target has a specific make_symbol function.
103 has_make_symbol() const
104 { return this->pti_->has_make_symbol; }
106 // Whether this target has a specific resolve function.
109 { return this->pti_->has_resolve; }
111 // Whether this target has a specific code fill function.
113 has_code_fill() const
114 { return this->pti_->has_code_fill; }
116 // Return the default name of the dynamic linker.
118 dynamic_linker() const
119 { return this->pti_->dynamic_linker; }
121 // Return the default address to use for the text segment.
122 // If a -z max-page-size argument has set the ABI page size
123 // to a value larger than the default starting address,
124 // bump the starting address up to the page size, to avoid
125 // misaligning the text segment in the file.
127 default_text_segment_address() const
129 uint64_t addr = this->pti_->default_text_segment_address;
130 uint64_t pagesize = this->abi_pagesize();
136 // Return the ABI specified page size.
140 if (parameters->options().max_page_size() > 0)
141 return parameters->options().max_page_size();
143 return this->pti_->abi_pagesize;
146 // Return the common page size used on actual systems.
148 common_pagesize() const
150 if (parameters->options().common_page_size() > 0)
151 return std::min(parameters->options().common_page_size(),
152 this->abi_pagesize());
154 return std::min(this->pti_->common_pagesize,
155 this->abi_pagesize());
158 // Return whether PF_X segments must contain nothing but the contents of
159 // SHF_EXECINSTR sections (no non-executable data, no headers).
161 isolate_execinstr() const
162 { return this->pti_->isolate_execinstr; }
165 rosegment_gap() const
166 { return this->pti_->rosegment_gap; }
168 // If we see some object files with .note.GNU-stack sections, and
169 // some objects files without them, this returns whether we should
170 // consider the object files without them to imply that the stack
171 // should be executable.
173 is_default_stack_executable() const
174 { return this->pti_->is_default_stack_executable; }
176 // Return a character which may appear as a prefix for a wrap
177 // symbol. If this character appears, we strip it when checking for
178 // wrapping and add it back when forming the final symbol name.
179 // This should be '\0' if not special prefix is required, which is
183 { return this->pti_->wrap_char; }
185 // Return the special section index which indicates a small common
186 // symbol. This will return SHN_UNDEF if there are no small common
189 small_common_shndx() const
190 { return this->pti_->small_common_shndx; }
192 // Return values to add to the section flags for the section holding
193 // small common symbols.
195 small_common_section_flags() const
197 gold_assert(this->pti_->small_common_shndx != elfcpp::SHN_UNDEF);
198 return this->pti_->small_common_section_flags;
201 // Return the special section index which indicates a large common
202 // symbol. This will return SHN_UNDEF if there are no large common
205 large_common_shndx() const
206 { return this->pti_->large_common_shndx; }
208 // Return values to add to the section flags for the section holding
209 // large common symbols.
211 large_common_section_flags() const
213 gold_assert(this->pti_->large_common_shndx != elfcpp::SHN_UNDEF);
214 return this->pti_->large_common_section_flags;
217 // This hook is called when an output section is created.
219 new_output_section(Output_section* os) const
220 { this->do_new_output_section(os); }
222 // This is called to tell the target to complete any sections it is
223 // handling. After this all sections must have their final size.
225 finalize_sections(Layout* layout, const Input_objects* input_objects,
226 Symbol_table* symtab)
227 { return this->do_finalize_sections(layout, input_objects, symtab); }
229 // Return the value to use for a global symbol which needs a special
230 // value in the dynamic symbol table. This will only be called if
231 // the backend first calls symbol->set_needs_dynsym_value().
233 dynsym_value(const Symbol* sym) const
234 { return this->do_dynsym_value(sym); }
236 // Return a string to use to fill out a code section. This is
237 // basically one or more NOPS which must fill out the specified
240 code_fill(section_size_type length) const
241 { return this->do_code_fill(length); }
243 // Return whether SYM is known to be defined by the ABI. This is
244 // used to avoid inappropriate warnings about undefined symbols.
246 is_defined_by_abi(const Symbol* sym) const
247 { return this->do_is_defined_by_abi(sym); }
249 // Adjust the output file header before it is written out. VIEW
250 // points to the header in external form. LEN is the length.
252 adjust_elf_header(unsigned char* view, int len)
253 { return this->do_adjust_elf_header(view, len); }
255 // Return address and size to plug into eh_frame FDEs associated with a PLT.
257 plt_fde_location(const Output_data* plt, unsigned char* oview,
258 uint64_t* address, off_t* len) const
259 { return this->do_plt_fde_location(plt, oview, address, len); }
261 // Return whether NAME is a local label name. This is used to implement the
262 // --discard-locals options.
264 is_local_label_name(const char* name) const
265 { return this->do_is_local_label_name(name); }
267 // Get the symbol index to use for a target specific reloc.
269 reloc_symbol_index(void* arg, unsigned int type) const
270 { return this->do_reloc_symbol_index(arg, type); }
272 // Get the addend to use for a target specific reloc.
274 reloc_addend(void* arg, unsigned int type, uint64_t addend) const
275 { return this->do_reloc_addend(arg, type, addend); }
277 // Return the PLT address to use for a global symbol.
279 plt_address_for_global(const Symbol* sym) const
280 { return this->do_plt_address_for_global(sym); }
282 // Return the PLT address to use for a local symbol.
284 plt_address_for_local(const Relobj* object, unsigned int symndx) const
285 { return this->do_plt_address_for_local(object, symndx); }
287 // Return the offset to use for the GOT_INDX'th got entry which is
288 // for a local tls symbol specified by OBJECT, SYMNDX.
290 tls_offset_for_local(const Relobj* object,
292 unsigned int got_indx) const
293 { return do_tls_offset_for_local(object, symndx, got_indx); }
295 // Return the offset to use for the GOT_INDX'th got entry which is
296 // for global tls symbol GSYM.
298 tls_offset_for_global(Symbol* gsym, unsigned int got_indx) const
299 { return do_tls_offset_for_global(gsym, got_indx); }
301 // For targets that use function descriptors, if LOC is the location
302 // of a function, modify it to point at the function entry location.
304 function_location(Symbol_location* loc) const
305 { return do_function_location(loc); }
307 // Return whether this target can use relocation types to determine
308 // if a function's address is taken.
310 can_check_for_function_pointers() const
311 { return this->do_can_check_for_function_pointers(); }
313 // Return whether a relocation to a merged section can be processed
314 // to retrieve the contents.
316 can_icf_inline_merge_sections () const
317 { return this->pti_->can_icf_inline_merge_sections; }
319 // Whether a section called SECTION_NAME may have function pointers to
320 // sections not eligible for safe ICF folding.
322 section_may_have_icf_unsafe_pointers(const char* section_name) const
323 { return this->do_section_may_have_icf_unsafe_pointers(section_name); }
325 // Return the base to use for the PC value in an FDE when it is
326 // encoded using DW_EH_PE_datarel. This does not appear to be
327 // documented anywhere, but it is target specific. Any use of
328 // DW_EH_PE_datarel in gcc requires defining a special macro
329 // (ASM_MAYBE_OUTPUT_ENCODED_ADDR_RTX) to output the value.
331 ehframe_datarel_base() const
332 { return this->do_ehframe_datarel_base(); }
334 // Return true if a reference to SYM from a reloc at *PRELOC
335 // means that the current function may call an object compiled
336 // without -fsplit-stack. SYM is known to be defined in an object
337 // compiled without -fsplit-stack.
339 is_call_to_non_split(const Symbol* sym, const unsigned char* preloc,
340 const unsigned char* view,
341 section_size_type view_size) const
342 { return this->do_is_call_to_non_split(sym, preloc, view, view_size); }
344 // A function starts at OFFSET in section SHNDX in OBJECT. That
345 // function was compiled with -fsplit-stack, but it refers to a
346 // function which was compiled without -fsplit-stack. VIEW is a
347 // modifiable view of the section; VIEW_SIZE is the size of the
348 // view. The target has to adjust the function so that it allocates
351 calls_non_split(Relobj* object, unsigned int shndx,
352 section_offset_type fnoffset, section_size_type fnsize,
353 const unsigned char* prelocs, size_t reloc_count,
354 unsigned char* view, section_size_type view_size,
355 std::string* from, std::string* to) const
357 this->do_calls_non_split(object, shndx, fnoffset, fnsize,
358 prelocs, reloc_count, view, view_size,
362 // Make an ELF object.
363 template<int size, bool big_endian>
365 make_elf_object(const std::string& name, Input_file* input_file,
366 off_t offset, const elfcpp::Ehdr<size, big_endian>& ehdr)
367 { return this->do_make_elf_object(name, input_file, offset, ehdr); }
369 // Make an output section.
371 make_output_section(const char* name, elfcpp::Elf_Word type,
372 elfcpp::Elf_Xword flags)
373 { return this->do_make_output_section(name, type, flags); }
375 // Return true if target wants to perform relaxation.
379 // Run the dummy relaxation pass twice if relaxation debugging is enabled.
380 if (is_debugging_enabled(DEBUG_RELAXATION))
383 return this->do_may_relax();
386 // Perform a relaxation pass. Return true if layout may be changed.
388 relax(int pass, const Input_objects* input_objects, Symbol_table* symtab,
389 Layout* layout, const Task* task)
391 // Run the dummy relaxation pass twice if relaxation debugging is enabled.
392 if (is_debugging_enabled(DEBUG_RELAXATION))
395 return this->do_relax(pass, input_objects, symtab, layout, task);
398 // Return the target-specific name of attributes section. This is
399 // NULL if a target does not use attributes section or if it uses
400 // the default section name ".gnu.attributes".
402 attributes_section() const
403 { return this->pti_->attributes_section; }
405 // Return the vendor name of vendor attributes.
407 attributes_vendor() const
408 { return this->pti_->attributes_vendor; }
410 // Whether a section called NAME is an attribute section.
412 is_attributes_section(const char* name) const
414 return ((this->pti_->attributes_section != NULL
415 && strcmp(name, this->pti_->attributes_section) == 0)
416 || strcmp(name, ".gnu.attributes") == 0);
419 // Return a bit mask of argument types for attribute with TAG.
421 attribute_arg_type(int tag) const
422 { return this->do_attribute_arg_type(tag); }
424 // Return the attribute tag of the position NUM in the list of fixed
425 // attributes. Normally there is no reordering and
426 // attributes_order(NUM) == NUM.
428 attributes_order(int num) const
429 { return this->do_attributes_order(num); }
431 // When a target is selected as the default target, we call this method,
432 // which may be used for expensive, target-specific initialization.
434 select_as_default_target()
435 { this->do_select_as_default_target(); }
437 // Return the value to store in the EI_OSABI field in the ELF
441 { return this->osabi_; }
443 // Set the value to store in the EI_OSABI field in the ELF header.
445 set_osabi(elfcpp::ELFOSABI osabi)
446 { this->osabi_ = osabi; }
448 // Define target-specific standard symbols.
450 define_standard_symbols(Symbol_table* symtab, Layout* layout)
451 { this->do_define_standard_symbols(symtab, layout); }
453 // Return the output section name to use given an input section
454 // name, or NULL if no target specific name mapping is required.
455 // Set *PLEN to the length of the name if returning non-NULL.
457 output_section_name(const Relobj* relobj,
460 { return this->do_output_section_name(relobj, name, plen); }
462 // Add any special sections for this symbol to the gc work list.
464 gc_mark_symbol(Symbol_table* symtab, Symbol* sym) const
465 { this->do_gc_mark_symbol(symtab, sym); }
467 // Return the name of the entry point symbol.
469 entry_symbol_name() const
470 { return this->pti_->entry_symbol_name; }
472 // Return the size in bits of SHT_HASH entry.
474 hash_entry_size() const
475 { return this->pti_->hash_entry_size; }
477 // Return the section type to use for unwind sections.
479 unwind_section_type() const
480 { return this->pti_->unwind_section_type; }
482 // Whether the target has a custom set_dynsym_indexes method.
484 has_custom_set_dynsym_indexes() const
485 { return this->do_has_custom_set_dynsym_indexes(); }
487 // Custom set_dynsym_indexes method for a target.
489 set_dynsym_indexes(std::vector<Symbol*>* dyn_symbols, unsigned int index,
490 std::vector<Symbol*>* syms, Stringpool* dynpool,
491 Versions* versions, Symbol_table* symtab) const
493 return this->do_set_dynsym_indexes(dyn_symbols, index, syms, dynpool,
497 // Get the custom dynamic tag value.
499 dynamic_tag_custom_value(elfcpp::DT tag) const
500 { return this->do_dynamic_tag_custom_value(tag); }
502 // Adjust the value written to the dynamic symbol table.
504 adjust_dyn_symbol(const Symbol* sym, unsigned char* view) const
505 { this->do_adjust_dyn_symbol(sym, view); }
507 // Return whether to include the section in the link.
509 should_include_section(elfcpp::Elf_Word sh_type) const
510 { return this->do_should_include_section(sh_type); }
512 // Merge a target-specific program property in the .note.gnu.properties
515 merge_gnu_property(int note_type,
517 size_t new_pr_datasz,
518 const unsigned char* new_pr_data,
519 size_t old_pr_datasz,
520 unsigned char* old_pr_data,
521 const Object* object) const
523 return this->do_merge_gnu_property(note_type, pr_type,
524 new_pr_datasz, new_pr_data,
525 old_pr_datasz, old_pr_data,
530 // This struct holds the constant information for a child class. We
531 // use a struct to avoid the overhead of virtual function calls for
532 // simple information.
535 // Address size (32 or 64).
537 // Whether the target is big endian.
539 // The code to store in the e_machine field of the ELF header.
540 elfcpp::EM machine_code;
541 // Whether this target has a specific make_symbol function.
542 bool has_make_symbol;
543 // Whether this target has a specific resolve function.
545 // Whether this target has a specific code fill function.
547 // Whether an object file with no .note.GNU-stack sections implies
548 // that the stack should be executable.
549 bool is_default_stack_executable;
550 // Whether a relocation to a merged section can be processed to
551 // retrieve the contents.
552 bool can_icf_inline_merge_sections;
553 // Prefix character to strip when checking for wrapping.
555 // The default dynamic linker name.
556 const char* dynamic_linker;
557 // The default text segment address.
558 uint64_t default_text_segment_address;
559 // The ABI specified page size.
560 uint64_t abi_pagesize;
561 // The common page size used by actual implementations.
562 uint64_t common_pagesize;
563 // Whether PF_X segments must contain nothing but the contents of
564 // SHF_EXECINSTR sections (no non-executable data, no headers).
565 bool isolate_execinstr;
566 // If nonzero, distance from the text segment to the read-only segment.
567 uint64_t rosegment_gap;
568 // The special section index for small common symbols; SHN_UNDEF
570 elfcpp::Elf_Half small_common_shndx;
571 // The special section index for large common symbols; SHN_UNDEF
573 elfcpp::Elf_Half large_common_shndx;
574 // Section flags for small common section.
575 elfcpp::Elf_Xword small_common_section_flags;
576 // Section flags for large common section.
577 elfcpp::Elf_Xword large_common_section_flags;
578 // Name of attributes section if it is not ".gnu.attributes".
579 const char* attributes_section;
580 // Vendor name of vendor attributes.
581 const char* attributes_vendor;
582 // Name of the main entry point to the program.
583 const char* entry_symbol_name;
584 // Size (in bits) of SHT_HASH entry. Always equal to 32, except for
586 const int hash_entry_size;
587 // Processor-specific section type for ".eh_frame" (unwind) sections.
588 // SHT_PROGBITS if there is no special section type.
589 const unsigned int unwind_section_type;
592 Target(const Target_info* pti)
593 : pti_(pti), processor_specific_flags_(0),
594 are_processor_specific_flags_set_(false), osabi_(elfcpp::ELFOSABI_NONE)
597 // Virtual function which may be implemented by the child class.
599 do_new_output_section(Output_section*) const
602 // Virtual function which may be implemented by the child class.
604 do_finalize_sections(Layout*, const Input_objects*, Symbol_table*)
607 // Virtual function which may be implemented by the child class.
609 do_dynsym_value(const Symbol*) const
610 { gold_unreachable(); }
612 // Virtual function which must be implemented by the child class if
615 do_code_fill(section_size_type) const
616 { gold_unreachable(); }
618 // Virtual function which may be implemented by the child class.
620 do_is_defined_by_abi(const Symbol*) const
623 // Adjust the output file header before it is written out. VIEW
624 // points to the header in external form. LEN is the length, and
625 // will be one of the values of elfcpp::Elf_sizes<size>::ehdr_size.
626 // By default, we set the EI_OSABI field if requested (in
629 do_adjust_elf_header(unsigned char*, int) = 0;
631 // Return address and size to plug into eh_frame FDEs associated with a PLT.
633 do_plt_fde_location(const Output_data* plt, unsigned char* oview,
634 uint64_t* address, off_t* len) const;
636 // Virtual function which may be overridden by the child class.
638 do_is_local_label_name(const char*) const;
640 // Virtual function that must be overridden by a target which uses
641 // target specific relocations.
643 do_reloc_symbol_index(void*, unsigned int) const
644 { gold_unreachable(); }
646 // Virtual function that must be overridden by a target which uses
647 // target specific relocations.
649 do_reloc_addend(void*, unsigned int, uint64_t) const
650 { gold_unreachable(); }
652 // Virtual functions that must be overridden by a target that uses
653 // STT_GNU_IFUNC symbols.
655 do_plt_address_for_global(const Symbol*) const
656 { gold_unreachable(); }
659 do_plt_address_for_local(const Relobj*, unsigned int) const
660 { gold_unreachable(); }
663 do_tls_offset_for_local(const Relobj*, unsigned int, unsigned int) const
664 { gold_unreachable(); }
667 do_tls_offset_for_global(Symbol*, unsigned int) const
668 { gold_unreachable(); }
671 do_function_location(Symbol_location*) const = 0;
673 // Virtual function which may be overriden by the child class.
675 do_can_check_for_function_pointers() const
678 // Virtual function which may be overridden by the child class. We
679 // recognize some default sections for which we don't care whether
680 // they have function pointers.
682 do_section_may_have_icf_unsafe_pointers(const char* section_name) const
684 // We recognize sections for normal vtables, construction vtables and
686 return (!is_prefix_of(".rodata._ZTV", section_name)
687 && !is_prefix_of(".data.rel.ro._ZTV", section_name)
688 && !is_prefix_of(".rodata._ZTC", section_name)
689 && !is_prefix_of(".data.rel.ro._ZTC", section_name)
690 && !is_prefix_of(".eh_frame", section_name));
694 do_ehframe_datarel_base() const
695 { gold_unreachable(); }
697 // Virtual function which may be overridden by the child class. The
698 // default implementation is that any function not defined by the
699 // ABI is a call to a non-split function.
701 do_is_call_to_non_split(const Symbol* sym, const unsigned char*,
702 const unsigned char*, section_size_type) const;
704 // Virtual function which may be overridden by the child class.
706 do_calls_non_split(Relobj* object, unsigned int, section_offset_type,
707 section_size_type, const unsigned char*, size_t,
708 unsigned char*, section_size_type,
709 std::string*, std::string*) const;
711 // make_elf_object hooks. There are four versions of these for
712 // different address sizes and endianness.
714 // Set processor specific flags.
716 set_processor_specific_flags(elfcpp::Elf_Word flags)
718 this->processor_specific_flags_ = flags;
719 this->are_processor_specific_flags_set_ = true;
722 #ifdef HAVE_TARGET_32_LITTLE
723 // Virtual functions which may be overridden by the child class.
725 do_make_elf_object(const std::string&, Input_file*, off_t,
726 const elfcpp::Ehdr<32, false>&);
729 #ifdef HAVE_TARGET_32_BIG
730 // Virtual functions which may be overridden by the child class.
732 do_make_elf_object(const std::string&, Input_file*, off_t,
733 const elfcpp::Ehdr<32, true>&);
736 #ifdef HAVE_TARGET_64_LITTLE
737 // Virtual functions which may be overridden by the child class.
739 do_make_elf_object(const std::string&, Input_file*, off_t,
740 const elfcpp::Ehdr<64, false>& ehdr);
743 #ifdef HAVE_TARGET_64_BIG
744 // Virtual functions which may be overridden by the child class.
746 do_make_elf_object(const std::string& name, Input_file* input_file,
747 off_t offset, const elfcpp::Ehdr<64, true>& ehdr);
750 // Virtual functions which may be overridden by the child class.
751 virtual Output_section*
752 do_make_output_section(const char* name, elfcpp::Elf_Word type,
753 elfcpp::Elf_Xword flags);
755 // Virtual function which may be overridden by the child class.
758 { return parameters->options().relax(); }
760 // Virtual function which may be overridden by the child class.
762 do_relax(int, const Input_objects*, Symbol_table*, Layout*, const Task*)
765 // A function for targets to call. Return whether BYTES/LEN matches
766 // VIEW/VIEW_SIZE at OFFSET.
768 match_view(const unsigned char* view, section_size_type view_size,
769 section_offset_type offset, const char* bytes, size_t len) const;
771 // Set the contents of a VIEW/VIEW_SIZE to nops starting at OFFSET
774 set_view_to_nop(unsigned char* view, section_size_type view_size,
775 section_offset_type offset, size_t len) const;
777 // This must be overridden by the child class if it has target-specific
778 // attributes subsection in the attribute section.
780 do_attribute_arg_type(int) const
781 { gold_unreachable(); }
783 // This may be overridden by the child class.
785 do_attributes_order(int num) const
788 // This may be overridden by the child class.
790 do_select_as_default_target()
793 // This may be overridden by the child class.
795 do_define_standard_symbols(Symbol_table*, Layout*)
798 // This may be overridden by the child class.
800 do_output_section_name(const Relobj*, const char*, size_t*) const
803 // This may be overridden by the child class.
805 do_gc_mark_symbol(Symbol_table*, Symbol*) const
808 // This may be overridden by the child class.
810 do_has_custom_set_dynsym_indexes() const
813 // This may be overridden by the child class.
815 do_set_dynsym_indexes(std::vector<Symbol*>*, unsigned int,
816 std::vector<Symbol*>*, Stringpool*, Versions*,
818 { gold_unreachable(); }
820 // This may be overridden by the child class.
822 do_dynamic_tag_custom_value(elfcpp::DT) const
823 { gold_unreachable(); }
825 // This may be overridden by the child class.
827 do_adjust_dyn_symbol(const Symbol*, unsigned char*) const
830 // This may be overridden by the child class.
832 do_should_include_section(elfcpp::Elf_Word) const
835 // Merge a target-specific program property in the .note.gnu.properties
838 do_merge_gnu_property(int, int, size_t, const unsigned char*,
839 size_t, unsigned char*, const Object*) const
843 // The implementations of the four do_make_elf_object virtual functions are
844 // almost identical except for their sizes and endianness. We use a template.
845 // for their implementations.
846 template<int size, bool big_endian>
848 do_make_elf_object_implementation(const std::string&, Input_file*, off_t,
849 const elfcpp::Ehdr<size, big_endian>&);
851 Target(const Target&);
852 Target& operator=(const Target&);
854 // The target information.
855 const Target_info* pti_;
856 // Processor-specific flags.
857 elfcpp::Elf_Word processor_specific_flags_;
858 // Whether the processor-specific flags are set at least once.
859 bool are_processor_specific_flags_set_;
860 // If not ELFOSABI_NONE, the value to put in the EI_OSABI field of
861 // the ELF header. This is handled at this level because it is
862 // OS-specific rather than processor-specific.
863 elfcpp::ELFOSABI osabi_;
866 // The abstract class for a specific size and endianness of target.
867 // Each actual target implementation class should derive from an
868 // instantiation of Sized_target.
870 template<int size, bool big_endian>
871 class Sized_target : public Target
874 // Make a new symbol table entry for the target. This should be
875 // overridden by a target which needs additional information in the
876 // symbol table. This will only be called if has_make_symbol()
878 virtual Sized_symbol<size>*
879 make_symbol(const char*, elfcpp::STT, Object*, unsigned int, uint64_t)
880 { gold_unreachable(); }
882 // Resolve a symbol for the target. This should be overridden by a
883 // target which needs to take special action. TO is the
884 // pre-existing symbol. SYM is the new symbol, seen in OBJECT.
885 // VERSION is the version of SYM. This will only be called if
886 // has_resolve() returns true.
888 resolve(Symbol*, const elfcpp::Sym<size, big_endian>&, Object*,
890 { gold_unreachable(); }
892 // Process the relocs for a section, and record information of the
893 // mapping from source to destination sections. This mapping is later
894 // used to determine unreferenced garbage sections. This procedure is
895 // only called during garbage collection.
897 gc_process_relocs(Symbol_table* symtab,
899 Sized_relobj_file<size, big_endian>* object,
900 unsigned int data_shndx,
901 unsigned int sh_type,
902 const unsigned char* prelocs,
904 Output_section* output_section,
905 bool needs_special_offset_handling,
906 size_t local_symbol_count,
907 const unsigned char* plocal_symbols) = 0;
909 // Scan the relocs for a section, and record any information
910 // required for the symbol. SYMTAB is the symbol table. OBJECT is
911 // the object in which the section appears. DATA_SHNDX is the
912 // section index that these relocs apply to. SH_TYPE is the type of
913 // the relocation section, SHT_REL or SHT_RELA. PRELOCS points to
914 // the relocation data. RELOC_COUNT is the number of relocs.
915 // LOCAL_SYMBOL_COUNT is the number of local symbols.
916 // OUTPUT_SECTION is the output section.
917 // NEEDS_SPECIAL_OFFSET_HANDLING is true if offsets to the output
918 // sections are not mapped as usual. PLOCAL_SYMBOLS points to the
919 // local symbol data from OBJECT. GLOBAL_SYMBOLS is the array of
920 // pointers to the global symbol table from OBJECT.
922 scan_relocs(Symbol_table* symtab,
924 Sized_relobj_file<size, big_endian>* object,
925 unsigned int data_shndx,
926 unsigned int sh_type,
927 const unsigned char* prelocs,
929 Output_section* output_section,
930 bool needs_special_offset_handling,
931 size_t local_symbol_count,
932 const unsigned char* plocal_symbols) = 0;
934 // Relocate section data. SH_TYPE is the type of the relocation
935 // section, SHT_REL or SHT_RELA. PRELOCS points to the relocation
936 // information. RELOC_COUNT is the number of relocs.
937 // OUTPUT_SECTION is the output section.
938 // NEEDS_SPECIAL_OFFSET_HANDLING is true if offsets must be mapped
939 // to correspond to the output section. VIEW is a view into the
940 // output file holding the section contents, VIEW_ADDRESS is the
941 // virtual address of the view, and VIEW_SIZE is the size of the
942 // view. If NEEDS_SPECIAL_OFFSET_HANDLING is true, the VIEW_xx
943 // parameters refer to the complete output section data, not just
944 // the input section data.
946 relocate_section(const Relocate_info<size, big_endian>*,
947 unsigned int sh_type,
948 const unsigned char* prelocs,
950 Output_section* output_section,
951 bool needs_special_offset_handling,
953 typename elfcpp::Elf_types<size>::Elf_Addr view_address,
954 section_size_type view_size,
955 const Reloc_symbol_changes*) = 0;
957 // Scan the relocs during a relocatable link. The parameters are
958 // like scan_relocs, with an additional Relocatable_relocs
959 // parameter, used to record the disposition of the relocs.
961 scan_relocatable_relocs(Symbol_table* symtab,
963 Sized_relobj_file<size, big_endian>* object,
964 unsigned int data_shndx,
965 unsigned int sh_type,
966 const unsigned char* prelocs,
968 Output_section* output_section,
969 bool needs_special_offset_handling,
970 size_t local_symbol_count,
971 const unsigned char* plocal_symbols,
972 Relocatable_relocs*) = 0;
974 // Scan the relocs for --emit-relocs. The parameters are
975 // like scan_relocatable_relocs.
977 emit_relocs_scan(Symbol_table* symtab,
979 Sized_relobj_file<size, big_endian>* object,
980 unsigned int data_shndx,
981 unsigned int sh_type,
982 const unsigned char* prelocs,
984 Output_section* output_section,
985 bool needs_special_offset_handling,
986 size_t local_symbol_count,
987 const unsigned char* plocal_syms,
988 Relocatable_relocs* rr) = 0;
990 // Emit relocations for a section during a relocatable link, and for
991 // --emit-relocs. The parameters are like relocate_section, with
992 // additional parameters for the view of the output reloc section.
994 relocate_relocs(const Relocate_info<size, big_endian>*,
995 unsigned int sh_type,
996 const unsigned char* prelocs,
998 Output_section* output_section,
999 typename elfcpp::Elf_types<size>::Elf_Off
1000 offset_in_output_section,
1001 unsigned char* view,
1002 typename elfcpp::Elf_types<size>::Elf_Addr view_address,
1003 section_size_type view_size,
1004 unsigned char* reloc_view,
1005 section_size_type reloc_view_size) = 0;
1007 // Perform target-specific processing in a relocatable link. This is
1008 // only used if we use the relocation strategy RELOC_SPECIAL.
1009 // RELINFO points to a Relocation_info structure. SH_TYPE is the relocation
1010 // section type. PRELOC_IN points to the original relocation. RELNUM is
1011 // the index number of the relocation in the relocation section.
1012 // OUTPUT_SECTION is the output section to which the relocation is applied.
1013 // OFFSET_IN_OUTPUT_SECTION is the offset of the relocation input section
1014 // within the output section. VIEW points to the output view of the
1015 // output section. VIEW_ADDRESS is output address of the view. VIEW_SIZE
1016 // is the size of the output view and PRELOC_OUT points to the new
1017 // relocation in the output object.
1019 // A target only needs to override this if the generic code in
1020 // target-reloc.h cannot handle some relocation types.
1023 relocate_special_relocatable(const Relocate_info<size, big_endian>*
1025 unsigned int /* sh_type */,
1026 const unsigned char* /* preloc_in */,
1027 size_t /* relnum */,
1028 Output_section* /* output_section */,
1029 typename elfcpp::Elf_types<size>::Elf_Off
1030 /* offset_in_output_section */,
1031 unsigned char* /* view */,
1032 typename elfcpp::Elf_types<size>::Elf_Addr
1034 section_size_type /* view_size */,
1035 unsigned char* /* preloc_out*/)
1036 { gold_unreachable(); }
1038 // Return the number of entries in the GOT. This is only used for
1039 // laying out the incremental link info sections. A target needs
1040 // to implement this to support incremental linking.
1042 virtual unsigned int
1043 got_entry_count() const
1044 { gold_unreachable(); }
1046 // Return the number of entries in the PLT. This is only used for
1047 // laying out the incremental link info sections. A target needs
1048 // to implement this to support incremental linking.
1050 virtual unsigned int
1051 plt_entry_count() const
1052 { gold_unreachable(); }
1054 // Return the offset of the first non-reserved PLT entry. This is
1055 // only used for laying out the incremental link info sections.
1056 // A target needs to implement this to support incremental linking.
1058 virtual unsigned int
1059 first_plt_entry_offset() const
1060 { gold_unreachable(); }
1062 // Return the size of each PLT entry. This is only used for
1063 // laying out the incremental link info sections. A target needs
1064 // to implement this to support incremental linking.
1066 virtual unsigned int
1067 plt_entry_size() const
1068 { gold_unreachable(); }
1070 // Return the size of each GOT entry. This is only used for
1071 // laying out the incremental link info sections. A target needs
1072 // to implement this if its GOT size is different.
1074 virtual unsigned int
1075 got_entry_size() const
1076 { return size / 8; }
1078 // Create the GOT and PLT sections for an incremental update.
1079 // A target needs to implement this to support incremental linking.
1081 virtual Output_data_got_base*
1082 init_got_plt_for_update(Symbol_table*,
1084 unsigned int /* got_count */,
1085 unsigned int /* plt_count */)
1086 { gold_unreachable(); }
1088 // Reserve a GOT entry for a local symbol, and regenerate any
1089 // necessary dynamic relocations.
1091 reserve_local_got_entry(unsigned int /* got_index */,
1092 Sized_relobj<size, big_endian>* /* obj */,
1093 unsigned int /* r_sym */,
1094 unsigned int /* got_type */)
1095 { gold_unreachable(); }
1097 // Reserve a GOT entry for a global symbol, and regenerate any
1098 // necessary dynamic relocations.
1100 reserve_global_got_entry(unsigned int /* got_index */, Symbol* /* gsym */,
1101 unsigned int /* got_type */)
1102 { gold_unreachable(); }
1104 // Register an existing PLT entry for a global symbol.
1105 // A target needs to implement this to support incremental linking.
1108 register_global_plt_entry(Symbol_table*, Layout*,
1109 unsigned int /* plt_index */,
1111 { gold_unreachable(); }
1113 // Force a COPY relocation for a given symbol.
1114 // A target needs to implement this to support incremental linking.
1117 emit_copy_reloc(Symbol_table*, Symbol*, Output_section*, off_t)
1118 { gold_unreachable(); }
1120 // Apply an incremental relocation.
1123 apply_relocation(const Relocate_info<size, big_endian>* /* relinfo */,
1124 typename elfcpp::Elf_types<size>::Elf_Addr /* r_offset */,
1125 unsigned int /* r_type */,
1126 typename elfcpp::Elf_types<size>::Elf_Swxword /* r_addend */,
1127 const Symbol* /* gsym */,
1128 unsigned char* /* view */,
1129 typename elfcpp::Elf_types<size>::Elf_Addr /* address */,
1130 section_size_type /* view_size */)
1131 { gold_unreachable(); }
1133 // Handle target specific gc actions when adding a gc reference from
1134 // SRC_OBJ, SRC_SHNDX to a location specified by DST_OBJ, DST_SHNDX
1137 gc_add_reference(Symbol_table* symtab,
1139 unsigned int src_shndx,
1141 unsigned int dst_shndx,
1142 typename elfcpp::Elf_types<size>::Elf_Addr dst_off) const
1144 this->do_gc_add_reference(symtab, src_obj, src_shndx,
1145 dst_obj, dst_shndx, dst_off);
1148 // Return the r_sym field from a relocation.
1149 // Most targets can use the default version of this routine,
1150 // but some targets have a non-standard r_info field, and will
1151 // need to provide a target-specific version.
1152 virtual unsigned int
1153 get_r_sym(const unsigned char* preloc) const
1155 // Since REL and RELA relocs share the same structure through
1156 // the r_info field, we can just use REL here.
1157 elfcpp::Rel<size, big_endian> rel(preloc);
1158 return elfcpp::elf_r_sym<size>(rel.get_r_info());
1162 Sized_target(const Target::Target_info* pti)
1165 gold_assert(pti->size == size);
1166 gold_assert(pti->is_big_endian ? big_endian : !big_endian);
1169 // Set the EI_OSABI field if requested.
1171 do_adjust_elf_header(unsigned char*, int);
1173 // Handle target specific gc actions when adding a gc reference.
1175 do_gc_add_reference(Symbol_table*, Relobj*, unsigned int,
1176 Relobj*, unsigned int,
1177 typename elfcpp::Elf_types<size>::Elf_Addr) const
1181 do_function_location(Symbol_location*) const
1185 } // End namespace gold.
1187 #endif // !defined(GOLD_TARGET_H)