1 // target.h -- target support for gold -*- C++ -*- 2 3 // Copyright (C) 2006-2016 Free Software Foundation, Inc. 4 // Written by Ian Lance Taylor <iant@google.com>. 5 6 // This file is part of gold. 7 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. 12 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. 17 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. 22 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. 27 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. 32 33 #ifndef GOLD_TARGET_H 34 #define GOLD_TARGET_H 35 36 #include "elfcpp.h" 37 #include "options.h" 38 #include "parameters.h" 39 #include "stringpool.h" 40 #include "debug.h" 41 42 namespace gold 43 { 44 45 class Object; 46 class Relobj; 47 template<int size, bool big_endian> 48 class Sized_relobj; 49 template<int size, bool big_endian> 50 class Sized_relobj_file; 51 class Relocatable_relocs; 52 template<int size, bool big_endian> 53 struct Relocate_info; 54 class Reloc_symbol_changes; 55 class Symbol; 56 template<int size> 57 class Sized_symbol; 58 class Symbol_table; 59 class Output_data; 60 class Output_data_got_base; 61 class Output_section; 62 class Input_objects; 63 class Task; 64 struct Symbol_location; 65 class Versions; 66 67 // The abstract class for target specific handling. 68 69 class Target 70 { 71 public: 72 virtual ~Target() 73 { } 74 75 // Return the bit size that this target implements. This should 76 // return 32 or 64. 77 int 78 get_size() const 79 { return this->pti_->size; } 80 81 // Return whether this target is big-endian. 82 bool 83 is_big_endian() const 84 { return this->pti_->is_big_endian; } 85 86 // Machine code to store in e_machine field of ELF header. 87 elfcpp::EM 88 machine_code() const 89 { return this->pti_->machine_code; } 90 91 // Processor specific flags to store in e_flags field of ELF header. 92 elfcpp::Elf_Word 93 processor_specific_flags() const 94 { return this->processor_specific_flags_; } 95 96 // Whether processor specific flags are set at least once. 97 bool 98 are_processor_specific_flags_set() const 99 { return this->are_processor_specific_flags_set_; } 100 101 // Whether this target has a specific make_symbol function. 102 bool 103 has_make_symbol() const 104 { return this->pti_->has_make_symbol; } 105 106 // Whether this target has a specific resolve function. 107 bool 108 has_resolve() const 109 { return this->pti_->has_resolve; } 110 111 // Whether this target has a specific code fill function. 112 bool 113 has_code_fill() const 114 { return this->pti_->has_code_fill; } 115 116 // Return the default name of the dynamic linker. 117 const char* 118 dynamic_linker() const 119 { return this->pti_->dynamic_linker; } 120 121 // Return the default address to use for the text segment. 122 uint64_t 123 default_text_segment_address() const 124 { return this->pti_->default_text_segment_address; } 125 126 // Return the ABI specified page size. 127 uint64_t 128 abi_pagesize() const 129 { 130 if (parameters->options().max_page_size() > 0) 131 return parameters->options().max_page_size(); 132 else 133 return this->pti_->abi_pagesize; 134 } 135 136 // Return the common page size used on actual systems. 137 uint64_t 138 common_pagesize() const 139 { 140 if (parameters->options().common_page_size() > 0) 141 return std::min(parameters->options().common_page_size(), 142 this->abi_pagesize()); 143 else 144 return std::min(this->pti_->common_pagesize, 145 this->abi_pagesize()); 146 } 147 148 // Return whether PF_X segments must contain nothing but the contents of 149 // SHF_EXECINSTR sections (no non-executable data, no headers). 150 bool 151 isolate_execinstr() const 152 { return this->pti_->isolate_execinstr; } 153 154 uint64_t 155 rosegment_gap() const 156 { return this->pti_->rosegment_gap; } 157 158 // If we see some object files with .note.GNU-stack sections, and 159 // some objects files without them, this returns whether we should 160 // consider the object files without them to imply that the stack 161 // should be executable. 162 bool 163 is_default_stack_executable() const 164 { return this->pti_->is_default_stack_executable; } 165 166 // Return a character which may appear as a prefix for a wrap 167 // symbol. If this character appears, we strip it when checking for 168 // wrapping and add it back when forming the final symbol name. 169 // This should be '\0' if not special prefix is required, which is 170 // the normal case. 171 char 172 wrap_char() const 173 { return this->pti_->wrap_char; } 174 175 // Return the special section index which indicates a small common 176 // symbol. This will return SHN_UNDEF if there are no small common 177 // symbols. 178 elfcpp::Elf_Half 179 small_common_shndx() const 180 { return this->pti_->small_common_shndx; } 181 182 // Return values to add to the section flags for the section holding 183 // small common symbols. 184 elfcpp::Elf_Xword 185 small_common_section_flags() const 186 { 187 gold_assert(this->pti_->small_common_shndx != elfcpp::SHN_UNDEF); 188 return this->pti_->small_common_section_flags; 189 } 190 191 // Return the special section index which indicates a large common 192 // symbol. This will return SHN_UNDEF if there are no large common 193 // symbols. 194 elfcpp::Elf_Half 195 large_common_shndx() const 196 { return this->pti_->large_common_shndx; } 197 198 // Return values to add to the section flags for the section holding 199 // large common symbols. 200 elfcpp::Elf_Xword 201 large_common_section_flags() const 202 { 203 gold_assert(this->pti_->large_common_shndx != elfcpp::SHN_UNDEF); 204 return this->pti_->large_common_section_flags; 205 } 206 207 // This hook is called when an output section is created. 208 void 209 new_output_section(Output_section* os) const 210 { this->do_new_output_section(os); } 211 212 // This is called to tell the target to complete any sections it is 213 // handling. After this all sections must have their final size. 214 void 215 finalize_sections(Layout* layout, const Input_objects* input_objects, 216 Symbol_table* symtab) 217 { return this->do_finalize_sections(layout, input_objects, symtab); } 218 219 // Return the value to use for a global symbol which needs a special 220 // value in the dynamic symbol table. This will only be called if 221 // the backend first calls symbol->set_needs_dynsym_value(). 222 uint64_t 223 dynsym_value(const Symbol* sym) const 224 { return this->do_dynsym_value(sym); } 225 226 // Return a string to use to fill out a code section. This is 227 // basically one or more NOPS which must fill out the specified 228 // length in bytes. 229 std::string 230 code_fill(section_size_type length) const 231 { return this->do_code_fill(length); } 232 233 // Return whether SYM is known to be defined by the ABI. This is 234 // used to avoid inappropriate warnings about undefined symbols. 235 bool 236 is_defined_by_abi(const Symbol* sym) const 237 { return this->do_is_defined_by_abi(sym); } 238 239 // Adjust the output file header before it is written out. VIEW 240 // points to the header in external form. LEN is the length. 241 void 242 adjust_elf_header(unsigned char* view, int len) 243 { return this->do_adjust_elf_header(view, len); } 244 245 // Return address and size to plug into eh_frame FDEs associated with a PLT. 246 void 247 plt_fde_location(const Output_data* plt, unsigned char* oview, 248 uint64_t* address, off_t* len) const 249 { return this->do_plt_fde_location(plt, oview, address, len); } 250 251 // Return whether NAME is a local label name. This is used to implement the 252 // --discard-locals options. 253 bool 254 is_local_label_name(const char* name) const 255 { return this->do_is_local_label_name(name); } 256 257 // Get the symbol index to use for a target specific reloc. 258 unsigned int 259 reloc_symbol_index(void* arg, unsigned int type) const 260 { return this->do_reloc_symbol_index(arg, type); } 261 262 // Get the addend to use for a target specific reloc. 263 uint64_t 264 reloc_addend(void* arg, unsigned int type, uint64_t addend) const 265 { return this->do_reloc_addend(arg, type, addend); } 266 267 // Return the PLT address to use for a global symbol. 268 uint64_t 269 plt_address_for_global(const Symbol* sym) const 270 { return this->do_plt_address_for_global(sym); } 271 272 // Return the PLT address to use for a local symbol. 273 uint64_t 274 plt_address_for_local(const Relobj* object, unsigned int symndx) const 275 { return this->do_plt_address_for_local(object, symndx); } 276 277 // Return the offset to use for the GOT_INDX'th got entry which is 278 // for a local tls symbol specified by OBJECT, SYMNDX. 279 int64_t 280 tls_offset_for_local(const Relobj* object, 281 unsigned int symndx, 282 unsigned int got_indx) const 283 { return do_tls_offset_for_local(object, symndx, got_indx); } 284 285 // Return the offset to use for the GOT_INDX'th got entry which is 286 // for global tls symbol GSYM. 287 int64_t 288 tls_offset_for_global(Symbol* gsym, unsigned int got_indx) const 289 { return do_tls_offset_for_global(gsym, got_indx); } 290 291 // For targets that use function descriptors, if LOC is the location 292 // of a function, modify it to point at the function entry location. 293 void 294 function_location(Symbol_location* loc) const 295 { return do_function_location(loc); } 296 297 // Return whether this target can use relocation types to determine 298 // if a function's address is taken. 299 bool 300 can_check_for_function_pointers() const 301 { return this->do_can_check_for_function_pointers(); } 302 303 // Return whether a relocation to a merged section can be processed 304 // to retrieve the contents. 305 bool 306 can_icf_inline_merge_sections () const 307 { return this->pti_->can_icf_inline_merge_sections; } 308 309 // Whether a section called SECTION_NAME may have function pointers to 310 // sections not eligible for safe ICF folding. 311 virtual bool 312 section_may_have_icf_unsafe_pointers(const char* section_name) const 313 { return this->do_section_may_have_icf_unsafe_pointers(section_name); } 314 315 // Return the base to use for the PC value in an FDE when it is 316 // encoded using DW_EH_PE_datarel. This does not appear to be 317 // documented anywhere, but it is target specific. Any use of 318 // DW_EH_PE_datarel in gcc requires defining a special macro 319 // (ASM_MAYBE_OUTPUT_ENCODED_ADDR_RTX) to output the value. 320 uint64_t 321 ehframe_datarel_base() const 322 { return this->do_ehframe_datarel_base(); } 323 324 // Return true if a reference to SYM from a reloc at *PRELOC 325 // means that the current function may call an object compiled 326 // without -fsplit-stack. SYM is known to be defined in an object 327 // compiled without -fsplit-stack. 328 bool 329 is_call_to_non_split(const Symbol* sym, const unsigned char* preloc, 330 const unsigned char* view, 331 section_size_type view_size) const 332 { return this->do_is_call_to_non_split(sym, preloc, view, view_size); } 333 334 // A function starts at OFFSET in section SHNDX in OBJECT. That 335 // function was compiled with -fsplit-stack, but it refers to a 336 // function which was compiled without -fsplit-stack. VIEW is a 337 // modifiable view of the section; VIEW_SIZE is the size of the 338 // view. The target has to adjust the function so that it allocates 339 // enough stack. 340 void 341 calls_non_split(Relobj* object, unsigned int shndx, 342 section_offset_type fnoffset, section_size_type fnsize, 343 const unsigned char* prelocs, size_t reloc_count, 344 unsigned char* view, section_size_type view_size, 345 std::string* from, std::string* to) const 346 { 347 this->do_calls_non_split(object, shndx, fnoffset, fnsize, 348 prelocs, reloc_count, view, view_size, 349 from, to); 350 } 351 352 // Make an ELF object. 353 template<int size, bool big_endian> 354 Object* 355 make_elf_object(const std::string& name, Input_file* input_file, 356 off_t offset, const elfcpp::Ehdr<size, big_endian>& ehdr) 357 { return this->do_make_elf_object(name, input_file, offset, ehdr); } 358 359 // Make an output section. 360 Output_section* 361 make_output_section(const char* name, elfcpp::Elf_Word type, 362 elfcpp::Elf_Xword flags) 363 { return this->do_make_output_section(name, type, flags); } 364 365 // Return true if target wants to perform relaxation. 366 bool 367 may_relax() const 368 { 369 // Run the dummy relaxation pass twice if relaxation debugging is enabled. 370 if (is_debugging_enabled(DEBUG_RELAXATION)) 371 return true; 372 373 return this->do_may_relax(); 374 } 375 376 // Perform a relaxation pass. Return true if layout may be changed. 377 bool 378 relax(int pass, const Input_objects* input_objects, Symbol_table* symtab, 379 Layout* layout, const Task* task) 380 { 381 // Run the dummy relaxation pass twice if relaxation debugging is enabled. 382 if (is_debugging_enabled(DEBUG_RELAXATION)) 383 return pass < 2; 384 385 return this->do_relax(pass, input_objects, symtab, layout, task); 386 } 387 388 // Return the target-specific name of attributes section. This is 389 // NULL if a target does not use attributes section or if it uses 390 // the default section name ".gnu.attributes". 391 const char* 392 attributes_section() const 393 { return this->pti_->attributes_section; } 394 395 // Return the vendor name of vendor attributes. 396 const char* 397 attributes_vendor() const 398 { return this->pti_->attributes_vendor; } 399 400 // Whether a section called NAME is an attribute section. 401 bool 402 is_attributes_section(const char* name) const 403 { 404 return ((this->pti_->attributes_section != NULL 405 && strcmp(name, this->pti_->attributes_section) == 0) 406 || strcmp(name, ".gnu.attributes") == 0); 407 } 408 409 // Return a bit mask of argument types for attribute with TAG. 410 int 411 attribute_arg_type(int tag) const 412 { return this->do_attribute_arg_type(tag); } 413 414 // Return the attribute tag of the position NUM in the list of fixed 415 // attributes. Normally there is no reordering and 416 // attributes_order(NUM) == NUM. 417 int 418 attributes_order(int num) const 419 { return this->do_attributes_order(num); } 420 421 // When a target is selected as the default target, we call this method, 422 // which may be used for expensive, target-specific initialization. 423 void 424 select_as_default_target() 425 { this->do_select_as_default_target(); } 426 427 // Return the value to store in the EI_OSABI field in the ELF 428 // header. 429 elfcpp::ELFOSABI 430 osabi() const 431 { return this->osabi_; } 432 433 // Set the value to store in the EI_OSABI field in the ELF header. 434 void 435 set_osabi(elfcpp::ELFOSABI osabi) 436 { this->osabi_ = osabi; } 437 438 // Define target-specific standard symbols. 439 void 440 define_standard_symbols(Symbol_table* symtab, Layout* layout) 441 { this->do_define_standard_symbols(symtab, layout); } 442 443 // Return the output section name to use given an input section 444 // name, or NULL if no target specific name mapping is required. 445 // Set *PLEN to the length of the name if returning non-NULL. 446 const char* 447 output_section_name(const Relobj* relobj, 448 const char* name, 449 size_t* plen) const 450 { return this->do_output_section_name(relobj, name, plen); } 451 452 // Add any special sections for this symbol to the gc work list. 453 void 454 gc_mark_symbol(Symbol_table* symtab, Symbol* sym) const 455 { this->do_gc_mark_symbol(symtab, sym); } 456 457 // Return the name of the entry point symbol. 458 const char* 459 entry_symbol_name() const 460 { return this->pti_->entry_symbol_name; } 461 462 // Return the size in bits of SHT_HASH entry. 463 int 464 hash_entry_size() const 465 { return this->pti_->hash_entry_size; } 466 467 // Whether the target has a custom set_dynsym_indexes method. 468 bool 469 has_custom_set_dynsym_indexes() const 470 { return this->do_has_custom_set_dynsym_indexes(); } 471 472 // Custom set_dynsym_indexes method for a target. 473 unsigned int 474 set_dynsym_indexes(std::vector<Symbol*>* dyn_symbols, unsigned int index, 475 std::vector<Symbol*>* syms, Stringpool* dynpool, 476 Versions* versions, Symbol_table* symtab) const 477 { 478 return this->do_set_dynsym_indexes(dyn_symbols, index, syms, dynpool, 479 versions, symtab); 480 } 481 482 // Get the custom dynamic tag value. 483 unsigned int 484 dynamic_tag_custom_value(elfcpp::DT tag) const 485 { return this->do_dynamic_tag_custom_value(tag); } 486 487 // Adjust the value written to the dynamic symbol table. 488 void 489 adjust_dyn_symbol(const Symbol* sym, unsigned char* view) const 490 { this->do_adjust_dyn_symbol(sym, view); } 491 492 // Return whether to include the section in the link. 493 bool 494 should_include_section(elfcpp::Elf_Word sh_type) const 495 { return this->do_should_include_section(sh_type); } 496 497 protected: 498 // This struct holds the constant information for a child class. We 499 // use a struct to avoid the overhead of virtual function calls for 500 // simple information. 501 struct Target_info 502 { 503 // Address size (32 or 64). 504 int size; 505 // Whether the target is big endian. 506 bool is_big_endian; 507 // The code to store in the e_machine field of the ELF header. 508 elfcpp::EM machine_code; 509 // Whether this target has a specific make_symbol function. 510 bool has_make_symbol; 511 // Whether this target has a specific resolve function. 512 bool has_resolve; 513 // Whether this target has a specific code fill function. 514 bool has_code_fill; 515 // Whether an object file with no .note.GNU-stack sections implies 516 // that the stack should be executable. 517 bool is_default_stack_executable; 518 // Whether a relocation to a merged section can be processed to 519 // retrieve the contents. 520 bool can_icf_inline_merge_sections; 521 // Prefix character to strip when checking for wrapping. 522 char wrap_char; 523 // The default dynamic linker name. 524 const char* dynamic_linker; 525 // The default text segment address. 526 uint64_t default_text_segment_address; 527 // The ABI specified page size. 528 uint64_t abi_pagesize; 529 // The common page size used by actual implementations. 530 uint64_t common_pagesize; 531 // Whether PF_X segments must contain nothing but the contents of 532 // SHF_EXECINSTR sections (no non-executable data, no headers). 533 bool isolate_execinstr; 534 // If nonzero, distance from the text segment to the read-only segment. 535 uint64_t rosegment_gap; 536 // The special section index for small common symbols; SHN_UNDEF 537 // if none. 538 elfcpp::Elf_Half small_common_shndx; 539 // The special section index for large common symbols; SHN_UNDEF 540 // if none. 541 elfcpp::Elf_Half large_common_shndx; 542 // Section flags for small common section. 543 elfcpp::Elf_Xword small_common_section_flags; 544 // Section flags for large common section. 545 elfcpp::Elf_Xword large_common_section_flags; 546 // Name of attributes section if it is not ".gnu.attributes". 547 const char* attributes_section; 548 // Vendor name of vendor attributes. 549 const char* attributes_vendor; 550 // Name of the main entry point to the program. 551 const char* entry_symbol_name; 552 // Size (in bits) of SHT_HASH entry. Always equal to 32, except for 553 // 64-bit S/390. 554 const int hash_entry_size; 555 }; 556 557 Target(const Target_info* pti) 558 : pti_(pti), processor_specific_flags_(0), 559 are_processor_specific_flags_set_(false), osabi_(elfcpp::ELFOSABI_NONE) 560 { } 561 562 // Virtual function which may be implemented by the child class. 563 virtual void 564 do_new_output_section(Output_section*) const 565 { } 566 567 // Virtual function which may be implemented by the child class. 568 virtual void 569 do_finalize_sections(Layout*, const Input_objects*, Symbol_table*) 570 { } 571 572 // Virtual function which may be implemented by the child class. 573 virtual uint64_t 574 do_dynsym_value(const Symbol*) const 575 { gold_unreachable(); } 576 577 // Virtual function which must be implemented by the child class if 578 // needed. 579 virtual std::string 580 do_code_fill(section_size_type) const 581 { gold_unreachable(); } 582 583 // Virtual function which may be implemented by the child class. 584 virtual bool 585 do_is_defined_by_abi(const Symbol*) const 586 { return false; } 587 588 // Adjust the output file header before it is written out. VIEW 589 // points to the header in external form. LEN is the length, and 590 // will be one of the values of elfcpp::Elf_sizes<size>::ehdr_size. 591 // By default, we set the EI_OSABI field if requested (in 592 // Sized_target). 593 virtual void 594 do_adjust_elf_header(unsigned char*, int) = 0; 595 596 // Return address and size to plug into eh_frame FDEs associated with a PLT. 597 virtual void 598 do_plt_fde_location(const Output_data* plt, unsigned char* oview, 599 uint64_t* address, off_t* len) const; 600 601 // Virtual function which may be overridden by the child class. 602 virtual bool 603 do_is_local_label_name(const char*) const; 604 605 // Virtual function that must be overridden by a target which uses 606 // target specific relocations. 607 virtual unsigned int 608 do_reloc_symbol_index(void*, unsigned int) const 609 { gold_unreachable(); } 610 611 // Virtual function that must be overridden by a target which uses 612 // target specific relocations. 613 virtual uint64_t 614 do_reloc_addend(void*, unsigned int, uint64_t) const 615 { gold_unreachable(); } 616 617 // Virtual functions that must be overridden by a target that uses 618 // STT_GNU_IFUNC symbols. 619 virtual uint64_t 620 do_plt_address_for_global(const Symbol*) const 621 { gold_unreachable(); } 622 623 virtual uint64_t 624 do_plt_address_for_local(const Relobj*, unsigned int) const 625 { gold_unreachable(); } 626 627 virtual int64_t 628 do_tls_offset_for_local(const Relobj*, unsigned int, unsigned int) const 629 { gold_unreachable(); } 630 631 virtual int64_t 632 do_tls_offset_for_global(Symbol*, unsigned int) const 633 { gold_unreachable(); } 634 635 virtual void 636 do_function_location(Symbol_location*) const = 0; 637 638 // Virtual function which may be overriden by the child class. 639 virtual bool 640 do_can_check_for_function_pointers() const 641 { return false; } 642 643 // Virtual function which may be overridden by the child class. We 644 // recognize some default sections for which we don't care whether 645 // they have function pointers. 646 virtual bool 647 do_section_may_have_icf_unsafe_pointers(const char* section_name) const 648 { 649 // We recognize sections for normal vtables, construction vtables and 650 // EH frames. 651 return (!is_prefix_of(".rodata._ZTV", section_name) 652 && !is_prefix_of(".data.rel.ro._ZTV", section_name) 653 && !is_prefix_of(".rodata._ZTC", section_name) 654 && !is_prefix_of(".data.rel.ro._ZTC", section_name) 655 && !is_prefix_of(".eh_frame", section_name)); 656 } 657 658 virtual uint64_t 659 do_ehframe_datarel_base() const 660 { gold_unreachable(); } 661 662 // Virtual function which may be overridden by the child class. The 663 // default implementation is that any function not defined by the 664 // ABI is a call to a non-split function. 665 virtual bool 666 do_is_call_to_non_split(const Symbol* sym, const unsigned char*, 667 const unsigned char*, section_size_type) const; 668 669 // Virtual function which may be overridden by the child class. 670 virtual void 671 do_calls_non_split(Relobj* object, unsigned int, section_offset_type, 672 section_size_type, const unsigned char*, size_t, 673 unsigned char*, section_size_type, 674 std::string*, std::string*) const; 675 676 // make_elf_object hooks. There are four versions of these for 677 // different address sizes and endianness. 678 679 // Set processor specific flags. 680 void 681 set_processor_specific_flags(elfcpp::Elf_Word flags) 682 { 683 this->processor_specific_flags_ = flags; 684 this->are_processor_specific_flags_set_ = true; 685 } 686 687 #ifdef HAVE_TARGET_32_LITTLE 688 // Virtual functions which may be overridden by the child class. 689 virtual Object* 690 do_make_elf_object(const std::string&, Input_file*, off_t, 691 const elfcpp::Ehdr<32, false>&); 692 #endif 693 694 #ifdef HAVE_TARGET_32_BIG 695 // Virtual functions which may be overridden by the child class. 696 virtual Object* 697 do_make_elf_object(const std::string&, Input_file*, off_t, 698 const elfcpp::Ehdr<32, true>&); 699 #endif 700 701 #ifdef HAVE_TARGET_64_LITTLE 702 // Virtual functions which may be overridden by the child class. 703 virtual Object* 704 do_make_elf_object(const std::string&, Input_file*, off_t, 705 const elfcpp::Ehdr<64, false>& ehdr); 706 #endif 707 708 #ifdef HAVE_TARGET_64_BIG 709 // Virtual functions which may be overridden by the child class. 710 virtual Object* 711 do_make_elf_object(const std::string& name, Input_file* input_file, 712 off_t offset, const elfcpp::Ehdr<64, true>& ehdr); 713 #endif 714 715 // Virtual functions which may be overridden by the child class. 716 virtual Output_section* 717 do_make_output_section(const char* name, elfcpp::Elf_Word type, 718 elfcpp::Elf_Xword flags); 719 720 // Virtual function which may be overridden by the child class. 721 virtual bool 722 do_may_relax() const 723 { return parameters->options().relax(); } 724 725 // Virtual function which may be overridden by the child class. 726 virtual bool 727 do_relax(int, const Input_objects*, Symbol_table*, Layout*, const Task*) 728 { return false; } 729 730 // A function for targets to call. Return whether BYTES/LEN matches 731 // VIEW/VIEW_SIZE at OFFSET. 732 bool 733 match_view(const unsigned char* view, section_size_type view_size, 734 section_offset_type offset, const char* bytes, size_t len) const; 735 736 // Set the contents of a VIEW/VIEW_SIZE to nops starting at OFFSET 737 // for LEN bytes. 738 void 739 set_view_to_nop(unsigned char* view, section_size_type view_size, 740 section_offset_type offset, size_t len) const; 741 742 // This must be overridden by the child class if it has target-specific 743 // attributes subsection in the attribute section. 744 virtual int 745 do_attribute_arg_type(int) const 746 { gold_unreachable(); } 747 748 // This may be overridden by the child class. 749 virtual int 750 do_attributes_order(int num) const 751 { return num; } 752 753 // This may be overridden by the child class. 754 virtual void 755 do_select_as_default_target() 756 { } 757 758 // This may be overridden by the child class. 759 virtual void 760 do_define_standard_symbols(Symbol_table*, Layout*) 761 { } 762 763 // This may be overridden by the child class. 764 virtual const char* 765 do_output_section_name(const Relobj*, const char*, size_t*) const 766 { return NULL; } 767 768 // This may be overridden by the child class. 769 virtual void 770 do_gc_mark_symbol(Symbol_table*, Symbol*) const 771 { } 772 773 // This may be overridden by the child class. 774 virtual bool 775 do_has_custom_set_dynsym_indexes() const 776 { return false; } 777 778 // This may be overridden by the child class. 779 virtual unsigned int 780 do_set_dynsym_indexes(std::vector<Symbol*>*, unsigned int, 781 std::vector<Symbol*>*, Stringpool*, Versions*, 782 Symbol_table*) const 783 { gold_unreachable(); } 784 785 // This may be overridden by the child class. 786 virtual unsigned int 787 do_dynamic_tag_custom_value(elfcpp::DT) const 788 { gold_unreachable(); } 789 790 // This may be overridden by the child class. 791 virtual void 792 do_adjust_dyn_symbol(const Symbol*, unsigned char*) const 793 { } 794 795 // This may be overridden by the child class. 796 virtual bool 797 do_should_include_section(elfcpp::Elf_Word) const 798 { return true; } 799 800 private: 801 // The implementations of the four do_make_elf_object virtual functions are 802 // almost identical except for their sizes and endianness. We use a template. 803 // for their implementations. 804 template<int size, bool big_endian> 805 inline Object* 806 do_make_elf_object_implementation(const std::string&, Input_file*, off_t, 807 const elfcpp::Ehdr<size, big_endian>&); 808 809 Target(const Target&); 810 Target& operator=(const Target&); 811 812 // The target information. 813 const Target_info* pti_; 814 // Processor-specific flags. 815 elfcpp::Elf_Word processor_specific_flags_; 816 // Whether the processor-specific flags are set at least once. 817 bool are_processor_specific_flags_set_; 818 // If not ELFOSABI_NONE, the value to put in the EI_OSABI field of 819 // the ELF header. This is handled at this level because it is 820 // OS-specific rather than processor-specific. 821 elfcpp::ELFOSABI osabi_; 822 }; 823 824 // The abstract class for a specific size and endianness of target. 825 // Each actual target implementation class should derive from an 826 // instantiation of Sized_target. 827 828 template<int size, bool big_endian> 829 class Sized_target : public Target 830 { 831 public: 832 // Make a new symbol table entry for the target. This should be 833 // overridden by a target which needs additional information in the 834 // symbol table. This will only be called if has_make_symbol() 835 // returns true. 836 virtual Sized_symbol<size>* 837 make_symbol(const char*, elfcpp::STT, Object*, unsigned int, uint64_t) 838 { gold_unreachable(); } 839 840 // Resolve a symbol for the target. This should be overridden by a 841 // target which needs to take special action. TO is the 842 // pre-existing symbol. SYM is the new symbol, seen in OBJECT. 843 // VERSION is the version of SYM. This will only be called if 844 // has_resolve() returns true. 845 virtual void 846 resolve(Symbol*, const elfcpp::Sym<size, big_endian>&, Object*, 847 const char*) 848 { gold_unreachable(); } 849 850 // Process the relocs for a section, and record information of the 851 // mapping from source to destination sections. This mapping is later 852 // used to determine unreferenced garbage sections. This procedure is 853 // only called during garbage collection. 854 virtual void 855 gc_process_relocs(Symbol_table* symtab, 856 Layout* layout, 857 Sized_relobj_file<size, big_endian>* object, 858 unsigned int data_shndx, 859 unsigned int sh_type, 860 const unsigned char* prelocs, 861 size_t reloc_count, 862 Output_section* output_section, 863 bool needs_special_offset_handling, 864 size_t local_symbol_count, 865 const unsigned char* plocal_symbols) = 0; 866 867 // Scan the relocs for a section, and record any information 868 // required for the symbol. SYMTAB is the symbol table. OBJECT is 869 // the object in which the section appears. DATA_SHNDX is the 870 // section index that these relocs apply to. SH_TYPE is the type of 871 // the relocation section, SHT_REL or SHT_RELA. PRELOCS points to 872 // the relocation data. RELOC_COUNT is the number of relocs. 873 // LOCAL_SYMBOL_COUNT is the number of local symbols. 874 // OUTPUT_SECTION is the output section. 875 // NEEDS_SPECIAL_OFFSET_HANDLING is true if offsets to the output 876 // sections are not mapped as usual. PLOCAL_SYMBOLS points to the 877 // local symbol data from OBJECT. GLOBAL_SYMBOLS is the array of 878 // pointers to the global symbol table from OBJECT. 879 virtual void 880 scan_relocs(Symbol_table* symtab, 881 Layout* layout, 882 Sized_relobj_file<size, big_endian>* object, 883 unsigned int data_shndx, 884 unsigned int sh_type, 885 const unsigned char* prelocs, 886 size_t reloc_count, 887 Output_section* output_section, 888 bool needs_special_offset_handling, 889 size_t local_symbol_count, 890 const unsigned char* plocal_symbols) = 0; 891 892 // Relocate section data. SH_TYPE is the type of the relocation 893 // section, SHT_REL or SHT_RELA. PRELOCS points to the relocation 894 // information. RELOC_COUNT is the number of relocs. 895 // OUTPUT_SECTION is the output section. 896 // NEEDS_SPECIAL_OFFSET_HANDLING is true if offsets must be mapped 897 // to correspond to the output section. VIEW is a view into the 898 // output file holding the section contents, VIEW_ADDRESS is the 899 // virtual address of the view, and VIEW_SIZE is the size of the 900 // view. If NEEDS_SPECIAL_OFFSET_HANDLING is true, the VIEW_xx 901 // parameters refer to the complete output section data, not just 902 // the input section data. 903 virtual void 904 relocate_section(const Relocate_info<size, big_endian>*, 905 unsigned int sh_type, 906 const unsigned char* prelocs, 907 size_t reloc_count, 908 Output_section* output_section, 909 bool needs_special_offset_handling, 910 unsigned char* view, 911 typename elfcpp::Elf_types<size>::Elf_Addr view_address, 912 section_size_type view_size, 913 const Reloc_symbol_changes*) = 0; 914 915 // Scan the relocs during a relocatable link. The parameters are 916 // like scan_relocs, with an additional Relocatable_relocs 917 // parameter, used to record the disposition of the relocs. 918 virtual void 919 scan_relocatable_relocs(Symbol_table* symtab, 920 Layout* layout, 921 Sized_relobj_file<size, big_endian>* object, 922 unsigned int data_shndx, 923 unsigned int sh_type, 924 const unsigned char* prelocs, 925 size_t reloc_count, 926 Output_section* output_section, 927 bool needs_special_offset_handling, 928 size_t local_symbol_count, 929 const unsigned char* plocal_symbols, 930 Relocatable_relocs*) = 0; 931 932 // Scan the relocs for --emit-relocs. The parameters are 933 // like scan_relocatable_relocs. 934 virtual void 935 emit_relocs_scan(Symbol_table* symtab, 936 Layout* layout, 937 Sized_relobj_file<size, big_endian>* object, 938 unsigned int data_shndx, 939 unsigned int sh_type, 940 const unsigned char* prelocs, 941 size_t reloc_count, 942 Output_section* output_section, 943 bool needs_special_offset_handling, 944 size_t local_symbol_count, 945 const unsigned char* plocal_syms, 946 Relocatable_relocs* rr) = 0; 947 948 // Emit relocations for a section during a relocatable link, and for 949 // --emit-relocs. The parameters are like relocate_section, with 950 // additional parameters for the view of the output reloc section. 951 virtual void 952 relocate_relocs(const Relocate_info<size, big_endian>*, 953 unsigned int sh_type, 954 const unsigned char* prelocs, 955 size_t reloc_count, 956 Output_section* output_section, 957 typename elfcpp::Elf_types<size>::Elf_Off 958 offset_in_output_section, 959 unsigned char* view, 960 typename elfcpp::Elf_types<size>::Elf_Addr view_address, 961 section_size_type view_size, 962 unsigned char* reloc_view, 963 section_size_type reloc_view_size) = 0; 964 965 // Perform target-specific processing in a relocatable link. This is 966 // only used if we use the relocation strategy RELOC_SPECIAL. 967 // RELINFO points to a Relocation_info structure. SH_TYPE is the relocation 968 // section type. PRELOC_IN points to the original relocation. RELNUM is 969 // the index number of the relocation in the relocation section. 970 // OUTPUT_SECTION is the output section to which the relocation is applied. 971 // OFFSET_IN_OUTPUT_SECTION is the offset of the relocation input section 972 // within the output section. VIEW points to the output view of the 973 // output section. VIEW_ADDRESS is output address of the view. VIEW_SIZE 974 // is the size of the output view and PRELOC_OUT points to the new 975 // relocation in the output object. 976 // 977 // A target only needs to override this if the generic code in 978 // target-reloc.h cannot handle some relocation types. 979 980 virtual void 981 relocate_special_relocatable(const Relocate_info<size, big_endian>* 982 /*relinfo */, 983 unsigned int /* sh_type */, 984 const unsigned char* /* preloc_in */, 985 size_t /* relnum */, 986 Output_section* /* output_section */, 987 typename elfcpp::Elf_types<size>::Elf_Off 988 /* offset_in_output_section */, 989 unsigned char* /* view */, 990 typename elfcpp::Elf_types<size>::Elf_Addr 991 /* view_address */, 992 section_size_type /* view_size */, 993 unsigned char* /* preloc_out*/) 994 { gold_unreachable(); } 995 996 // Return the number of entries in the GOT. This is only used for 997 // laying out the incremental link info sections. A target needs 998 // to implement this to support incremental linking. 999 1000 virtual unsigned int 1001 got_entry_count() const 1002 { gold_unreachable(); } 1003 1004 // Return the number of entries in the PLT. This is only used for 1005 // laying out the incremental link info sections. A target needs 1006 // to implement this to support incremental linking. 1007 1008 virtual unsigned int 1009 plt_entry_count() const 1010 { gold_unreachable(); } 1011 1012 // Return the offset of the first non-reserved PLT entry. This is 1013 // only used for laying out the incremental link info sections. 1014 // A target needs to implement this to support incremental linking. 1015 1016 virtual unsigned int 1017 first_plt_entry_offset() const 1018 { gold_unreachable(); } 1019 1020 // Return the size of each PLT entry. This is only used for 1021 // laying out the incremental link info sections. A target needs 1022 // to implement this to support incremental linking. 1023 1024 virtual unsigned int 1025 plt_entry_size() const 1026 { gold_unreachable(); } 1027 1028 // Return the size of each GOT entry. This is only used for 1029 // laying out the incremental link info sections. A target needs 1030 // to implement this if its GOT size is different. 1031 1032 virtual unsigned int 1033 got_entry_size() const 1034 { return size / 8; } 1035 1036 // Create the GOT and PLT sections for an incremental update. 1037 // A target needs to implement this to support incremental linking. 1038 1039 virtual Output_data_got_base* 1040 init_got_plt_for_update(Symbol_table*, 1041 Layout*, 1042 unsigned int /* got_count */, 1043 unsigned int /* plt_count */) 1044 { gold_unreachable(); } 1045 1046 // Reserve a GOT entry for a local symbol, and regenerate any 1047 // necessary dynamic relocations. 1048 virtual void 1049 reserve_local_got_entry(unsigned int /* got_index */, 1050 Sized_relobj<size, big_endian>* /* obj */, 1051 unsigned int /* r_sym */, 1052 unsigned int /* got_type */) 1053 { gold_unreachable(); } 1054 1055 // Reserve a GOT entry for a global symbol, and regenerate any 1056 // necessary dynamic relocations. 1057 virtual void 1058 reserve_global_got_entry(unsigned int /* got_index */, Symbol* /* gsym */, 1059 unsigned int /* got_type */) 1060 { gold_unreachable(); } 1061 1062 // Register an existing PLT entry for a global symbol. 1063 // A target needs to implement this to support incremental linking. 1064 1065 virtual void 1066 register_global_plt_entry(Symbol_table*, Layout*, 1067 unsigned int /* plt_index */, 1068 Symbol*) 1069 { gold_unreachable(); } 1070 1071 // Force a COPY relocation for a given symbol. 1072 // A target needs to implement this to support incremental linking. 1073 1074 virtual void 1075 emit_copy_reloc(Symbol_table*, Symbol*, Output_section*, off_t) 1076 { gold_unreachable(); } 1077 1078 // Apply an incremental relocation. 1079 1080 virtual void 1081 apply_relocation(const Relocate_info<size, big_endian>* /* relinfo */, 1082 typename elfcpp::Elf_types<size>::Elf_Addr /* r_offset */, 1083 unsigned int /* r_type */, 1084 typename elfcpp::Elf_types<size>::Elf_Swxword /* r_addend */, 1085 const Symbol* /* gsym */, 1086 unsigned char* /* view */, 1087 typename elfcpp::Elf_types<size>::Elf_Addr /* address */, 1088 section_size_type /* view_size */) 1089 { gold_unreachable(); } 1090 1091 // Handle target specific gc actions when adding a gc reference from 1092 // SRC_OBJ, SRC_SHNDX to a location specified by DST_OBJ, DST_SHNDX 1093 // and DST_OFF. 1094 void 1095 gc_add_reference(Symbol_table* symtab, 1096 Relobj* src_obj, 1097 unsigned int src_shndx, 1098 Relobj* dst_obj, 1099 unsigned int dst_shndx, 1100 typename elfcpp::Elf_types<size>::Elf_Addr dst_off) const 1101 { 1102 this->do_gc_add_reference(symtab, src_obj, src_shndx, 1103 dst_obj, dst_shndx, dst_off); 1104 } 1105 1106 // Return the r_sym field from a relocation. 1107 // Most targets can use the default version of this routine, 1108 // but some targets have a non-standard r_info field, and will 1109 // need to provide a target-specific version. 1110 virtual unsigned int 1111 get_r_sym(const unsigned char* preloc) const 1112 { 1113 // Since REL and RELA relocs share the same structure through 1114 // the r_info field, we can just use REL here. 1115 elfcpp::Rel<size, big_endian> rel(preloc); 1116 return elfcpp::elf_r_sym<size>(rel.get_r_info()); 1117 } 1118 1119 protected: 1120 Sized_target(const Target::Target_info* pti) 1121 : Target(pti) 1122 { 1123 gold_assert(pti->size == size); 1124 gold_assert(pti->is_big_endian ? big_endian : !big_endian); 1125 } 1126 1127 // Set the EI_OSABI field if requested. 1128 virtual void 1129 do_adjust_elf_header(unsigned char*, int); 1130 1131 // Handle target specific gc actions when adding a gc reference. 1132 virtual void 1133 do_gc_add_reference(Symbol_table*, Relobj*, unsigned int, 1134 Relobj*, unsigned int, 1135 typename elfcpp::Elf_types<size>::Elf_Addr) const 1136 { } 1137 1138 virtual void 1139 do_function_location(Symbol_location*) const 1140 { } 1141 }; 1142 1143 } // End namespace gold. 1144 1145 #endif // !defined(GOLD_TARGET_H) 1146