1 // script.h -- handle linker scripts for gold -*- C++ -*- 2 3 // Copyright (C) 2006-2020 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 // We implement a subset of the original GNU ld linker script language 24 // for compatibility. The goal is not to implement the entire 25 // language. It is merely to implement enough to handle common uses. 26 // In particular we need to handle /usr/lib/libc.so on a typical 27 // GNU/Linux system, and we want to handle linker scripts used by the 28 // Linux kernel build. 29 30 #ifndef GOLD_SCRIPT_H 31 #define GOLD_SCRIPT_H 32 33 #include <cstdio> 34 #include <string> 35 #include <vector> 36 37 #include "elfcpp.h" 38 #include "script-sections.h" 39 40 namespace gold 41 { 42 43 class General_options; 44 class Command_line; 45 class Symbol_table; 46 class Layout; 47 class Mapfile; 48 class Input_argument; 49 class Input_arguments; 50 class Input_objects; 51 class Input_group; 52 class Input_file; 53 class Output_segment; 54 class Task_token; 55 class Workqueue; 56 struct Version_dependency_list; 57 struct Version_expression_list; 58 struct Version_tree; 59 struct Version_expression; 60 class Lazy_demangler; 61 class Incremental_script_entry; 62 63 // This class represents an expression in a linker script. 64 65 class Expression 66 { 67 protected: 68 // These should only be created by child classes. 69 Expression() 70 { } 71 72 public: 73 virtual ~Expression() 74 { } 75 76 // Return the value of the expression which is not permitted to 77 // refer to the dot symbol. CHECK_ASSERTIONS is true if we should 78 // check whether assertions are true. 79 uint64_t 80 eval(const Symbol_table*, const Layout*, bool check_assertions); 81 82 // Return the value of an expression which is permitted to refer to 83 // the dot symbol. DOT_VALUE is the absolute value of the dot 84 // symbol. DOT_SECTION is the section in which dot is defined; it 85 // should be NULL if the dot symbol has an absolute value (e.g., is 86 // defined in a SECTIONS clause outside of any output section 87 // definition). This sets *RESULT_SECTION to indicate where the 88 // value is defined. If the value is absolute *RESULT_SECTION will 89 // be NULL. Note that the returned value is still an absolute 90 // value; to get a section relative value the caller must subtract 91 // the section address. If RESULT_ALIGNMENT is not NULL, this sets 92 // *RESULT_ALIGNMENT to the alignment of the value of that alignment 93 // is larger than *RESULT_ALIGNMENT; this will only be non-zero if 94 // this is an ALIGN expression. If IS_SECTION_DOT_ASSIGMENT is true, 95 // we are evaluating an assignment to dot within an output section, 96 // and an absolute value should be interpreted as an offset within 97 // the section. 98 uint64_t 99 eval_with_dot(const Symbol_table*, const Layout*, bool check_assertions, 100 uint64_t dot_value, Output_section* dot_section, 101 Output_section** result_section, uint64_t* result_alignment, 102 bool is_section_dot_assignment); 103 104 // Return the value of an expression which may or may not be 105 // permitted to refer to the dot symbol, depending on 106 // is_dot_available. If IS_SECTION_DOT_ASSIGMENT is true, 107 // we are evaluating an assignment to dot within an output section, 108 // and an absolute value should be interpreted as an offset within 109 // the section. 110 uint64_t 111 eval_maybe_dot(const Symbol_table*, const Layout*, bool check_assertions, 112 bool is_dot_available, uint64_t dot_value, 113 Output_section* dot_section, 114 Output_section** result_section, uint64_t* result_alignment, 115 elfcpp::STT* type, elfcpp::STV* vis, unsigned char* nonvis, 116 bool is_section_dot_assignment, bool* is_valid_pointer); 117 118 // Print the expression to the FILE. This is for debugging. 119 virtual void 120 print(FILE*) const = 0; 121 122 protected: 123 struct Expression_eval_info; 124 125 public: 126 // Compute the value of the expression (implemented by child class). 127 // This is public rather than protected because it is called 128 // directly by children of Expression on other Expression objects. 129 virtual uint64_t 130 value(const Expression_eval_info*) = 0; 131 132 // Sets all symbols used in expressions as seen in a real ELF object. 133 virtual void 134 set_expr_sym_in_real_elf(Symbol_table*) const 135 { return; } 136 137 private: 138 // May not be copied. 139 Expression(const Expression&); 140 Expression& operator=(const Expression&); 141 }; 142 143 // Version_script_info stores information parsed from the version 144 // script, either provided by --version-script or as part of a linker 145 // script. A single Version_script_info object per target is owned by 146 // Script_options. 147 148 class Version_script_info 149 { 150 public: 151 // The languages which can be specified in a versionn script. 152 enum Language 153 { 154 LANGUAGE_C, // No demangling. 155 LANGUAGE_CXX, // C++ demangling. 156 LANGUAGE_JAVA, // Java demangling. 157 LANGUAGE_COUNT 158 }; 159 160 Version_script_info(); 161 162 ~Version_script_info(); 163 164 // Clear everything. 165 void 166 clear(); 167 168 // Finalize the version control information. 169 void 170 finalize(); 171 172 // Return whether the information is finalized. 173 bool 174 is_finalized() const 175 { return this->is_finalized_; } 176 177 // Return whether any version were defined in the version script. 178 bool 179 empty() const 180 { return this->version_trees_.empty(); } 181 182 // If there is a version associated with SYMBOL, return true, and 183 // set *VERSION to the version, and *IS_GLOBAL to whether the symbol 184 // should be global. Otherwise, return false. 185 bool 186 get_symbol_version(const char* symbol, std::string* version, 187 bool* is_global) const; 188 189 // Return whether this symbol matches the local: section of some 190 // version. 191 bool 192 symbol_is_local(const char* symbol) const 193 { 194 bool is_global; 195 return (this->get_symbol_version(symbol, NULL, &is_global) 196 && !is_global); 197 } 198 199 // Return the names of versions defined in the version script. 200 std::vector<std::string> 201 get_versions() const; 202 203 // Return the list of dependencies for this version. 204 std::vector<std::string> 205 get_dependencies(const char* version) const; 206 207 // The following functions should only be used by the bison helper 208 // functions. They allocate new structs whose memory belongs to 209 // Version_script_info. The bison functions copy the information 210 // from the version script into these structs. 211 struct Version_dependency_list* 212 allocate_dependency_list(); 213 214 struct Version_expression_list* 215 allocate_expression_list(); 216 217 struct Version_tree* 218 allocate_version_tree(); 219 220 // Build the lookup tables after all data have been read. 221 void 222 build_lookup_tables(); 223 224 // Give an error if there are any unmatched names in the version 225 // script. 226 void 227 check_unmatched_names(const Symbol_table*) const; 228 229 // Print contents to the FILE. This is for debugging. 230 void 231 print(FILE*) const; 232 233 private: 234 void 235 print_expression_list(FILE* f, const Version_expression_list*) const; 236 237 bool 238 get_symbol_version_helper(const char* symbol, 239 bool check_global, 240 std::string* pversion) const; 241 242 // Fast lookup information for a given language. 243 244 // We map from exact match strings to Version_tree's. Historically 245 // version scripts sometimes have the same symbol multiple times, 246 // which is ambiguous. We warn about that case by storing the 247 // second Version_tree we see. 248 struct Version_tree_match 249 { 250 Version_tree_match(const Version_tree* r, bool ig, 251 const Version_expression* e) 252 : real(r), is_global(ig), expression(e), ambiguous(NULL) 253 { } 254 255 // The Version_tree that we return. 256 const Version_tree* real; 257 // True if this is a global match for the REAL member, false if it 258 // is a local match. 259 bool is_global; 260 // Point back to the Version_expression for which we created this 261 // match. 262 const Version_expression* expression; 263 // If not NULL, another Version_tree that defines the symbol. 264 const Version_tree* ambiguous; 265 }; 266 267 // Map from an exact match string to a Version_tree. 268 269 typedef Unordered_map<std::string, Version_tree_match> Exact; 270 271 // Fast lookup information for a glob pattern. 272 struct Glob 273 { 274 Glob() 275 : expression(NULL), version(NULL), is_global(false) 276 { } 277 278 Glob(const Version_expression* e, const Version_tree* v, bool ig) 279 : expression(e), version(v), is_global(ig) 280 { } 281 282 // A pointer to the version expression holding the pattern to 283 // match and the language to use for demangling the symbol before 284 // doing the match. 285 const Version_expression* expression; 286 // The Version_tree we use if this pattern matches. 287 const Version_tree* version; 288 // True if this is a global symbol. 289 bool is_global; 290 }; 291 292 typedef std::vector<Glob> Globs; 293 294 bool 295 unquote(std::string*) const; 296 297 void 298 add_exact_match(const std::string&, const Version_tree*, bool is_global, 299 const Version_expression*, Exact*); 300 301 void 302 build_expression_list_lookup(const Version_expression_list*, 303 const Version_tree*, bool); 304 305 const char* 306 get_name_to_match(const char*, int, 307 Lazy_demangler*, Lazy_demangler*) const; 308 309 // All the version dependencies we allocate. 310 std::vector<Version_dependency_list*> dependency_lists_; 311 // All the version expressions we allocate. 312 std::vector<Version_expression_list*> expression_lists_; 313 // The list of versions. 314 std::vector<Version_tree*> version_trees_; 315 // Exact matches for global symbols, by language. 316 Exact* exact_[LANGUAGE_COUNT]; 317 // A vector of glob patterns mapping to Version_trees. 318 Globs globs_; 319 // The default version to use, if there is one. This is from a 320 // pattern of "*". 321 const Version_tree* default_version_; 322 // True if the default version is global. 323 bool default_is_global_; 324 // Whether this has been finalized. 325 bool is_finalized_; 326 }; 327 328 // This class manages assignments to symbols. These can appear in 329 // three different locations in scripts: outside of a SECTIONS clause, 330 // within a SECTIONS clause, and within an output section definition 331 // within a SECTIONS clause. This can also appear on the command line 332 // via the --defsym command line option. 333 334 class Symbol_assignment 335 { 336 public: 337 Symbol_assignment(const char* name, size_t namelen, bool is_defsym, 338 Expression* val, bool provide, bool hidden) 339 : name_(name, namelen), val_(val), is_defsym_(is_defsym), 340 provide_(provide), hidden_(hidden), sym_(NULL) 341 { } 342 343 // Add the symbol to the symbol table. 344 void 345 add_to_table(Symbol_table*); 346 347 // Finalize the symbol value. 348 void 349 finalize(Symbol_table*, const Layout*); 350 351 bool 352 is_defsym() const 353 { return is_defsym_; } 354 355 Expression * 356 value() const 357 { return val_; } 358 359 // Finalize the symbol value when it can refer to the dot symbol. 360 void 361 finalize_with_dot(Symbol_table*, const Layout*, uint64_t dot_value, 362 Output_section* dot_section); 363 364 // Set the symbol value, but only if the value is absolute or relative to 365 // DOT_SECTION. This is used while processing a SECTIONS clause. 366 // We assume that dot is an absolute value here. We do not check assertions. 367 void 368 set_if_absolute(Symbol_table*, const Layout*, bool is_dot_available, 369 uint64_t dot_value, Output_section* dot_section); 370 371 const std::string& 372 name() const 373 { return this->name_; } 374 375 // Print the assignment to the FILE. This is for debugging. 376 void 377 print(FILE*) const; 378 379 private: 380 // Shared by finalize and finalize_with_dot. 381 void 382 finalize_maybe_dot(Symbol_table*, const Layout*, bool is_dot_available, 383 uint64_t dot_value, Output_section* dot_section); 384 385 // Sized version of finalize. 386 template<int size> 387 void 388 sized_finalize(Symbol_table*, const Layout*, bool is_dot_available, 389 uint64_t dot_value, Output_section*); 390 391 // Symbol name. 392 std::string name_; 393 // Expression to assign to symbol. 394 Expression* val_; 395 // True if this symbol is defined by a --defsym, false if it is 396 // defined in a linker script. 397 bool is_defsym_; 398 // Whether the assignment should be provided (only set if there is 399 // an undefined reference to the symbol. 400 bool provide_; 401 // Whether the assignment should be hidden. 402 bool hidden_; 403 // The entry in the symbol table. 404 Symbol* sym_; 405 }; 406 407 // This class manages assertions in linker scripts. These can appear 408 // in all the places where a Symbol_assignment can appear. 409 410 class Script_assertion 411 { 412 public: 413 Script_assertion(Expression* check, const char* message, 414 size_t messagelen) 415 : check_(check), message_(message, messagelen) 416 { } 417 418 // Check the assertion. 419 void 420 check(const Symbol_table*, const Layout*); 421 422 // Print the assertion to the FILE. This is for debugging. 423 void 424 print(FILE*) const; 425 426 private: 427 // The expression to check. 428 Expression* check_; 429 // The message to issue if the expression fails. 430 std::string message_; 431 }; 432 433 // We can read a linker script in two different contexts: when 434 // initially parsing the command line, and when we find an input file 435 // which is actually a linker script. Also some of the data which can 436 // be set by a linker script can also be set via command line options 437 // like -e and --defsym. This means that we have a type of data which 438 // can be set both during command line option parsing and while 439 // reading input files. We store that data in an instance of this 440 // object. We will keep pointers to that instance in both the 441 // Command_line and Layout objects. 442 443 class Script_options 444 { 445 public: 446 Script_options(); 447 448 // Add a symbol to be defined. 449 void 450 add_symbol_assignment(const char* name, size_t length, bool is_defsym, 451 Expression* value, bool provide, bool hidden); 452 453 // Look for an assigned symbol. 454 bool 455 is_pending_assignment(const char* name); 456 457 // Add a reference to a symbol. 458 void 459 add_symbol_reference(const char* name, size_t length); 460 461 // Add an assertion. 462 void 463 add_assertion(Expression* check, const char* message, size_t messagelen); 464 465 // Define a symbol from the command line. 466 bool 467 define_symbol(const char* definition); 468 469 // Populates the set with symbol names used in LHS of defsym. 470 void 471 find_defsym_defs(Unordered_set<std::string>&); 472 473 // Set symbols used in defsym expressions as seen in a real ELF object. 474 void set_defsym_uses_in_real_elf(Symbol_table*) const; 475 476 // Create sections required by any linker scripts. 477 void 478 create_script_sections(Layout*); 479 480 // Add all symbol definitions to the symbol table. 481 void 482 add_symbols_to_table(Symbol_table*); 483 484 // Used to iterate over symbols which are referenced in expressions 485 // but not defined. 486 typedef Unordered_set<std::string>::const_iterator referenced_const_iterator; 487 488 referenced_const_iterator 489 referenced_begin() const 490 { return this->symbol_references_.begin(); } 491 492 referenced_const_iterator 493 referenced_end() const 494 { return this->symbol_references_.end(); } 495 496 // Return whether a symbol is referenced but not defined. 497 bool 498 is_referenced(const std::string& name) const 499 { 500 return (this->symbol_references_.find(name) 501 != this->symbol_references_.end()); 502 } 503 504 // Return whether there are any symbols which were referenced but 505 // not defined. 506 bool 507 any_unreferenced() const 508 { return !this->symbol_references_.empty(); } 509 510 // Finalize the symbol values. Also check assertions. 511 void 512 finalize_symbols(Symbol_table*, const Layout*); 513 514 // Version information parsed from a version script. Everything 515 // else has a pointer to this object. 516 Version_script_info* 517 version_script_info() 518 { return &this->version_script_info_; } 519 520 const Version_script_info* 521 version_script_info() const 522 { return &this->version_script_info_; } 523 524 // A SECTIONS clause parsed from a linker script. Everything else 525 // has a pointer to this object. 526 Script_sections* 527 script_sections() 528 { return &this->script_sections_; } 529 530 const Script_sections* 531 script_sections() const 532 { return &this->script_sections_; } 533 534 // Whether we saw a SECTIONS clause. 535 bool 536 saw_sections_clause() const 537 { return this->script_sections_.saw_sections_clause(); } 538 539 // Whether we saw a PHDRS clause. 540 bool 541 saw_phdrs_clause() const 542 { return this->script_sections_.saw_phdrs_clause(); } 543 544 // Set section addresses using a SECTIONS clause. Return the 545 // segment which should hold the file header and segment headers; 546 // this may return NULL, in which case the headers are not in a 547 // loadable segment. 548 Output_segment* 549 set_section_addresses(Symbol_table*, Layout*); 550 551 // Print the script to the FILE. This is for debugging. 552 void 553 print(FILE*) const; 554 555 private: 556 // We keep a list of symbol assignments which occur outside of a 557 // SECTIONS clause. 558 typedef std::vector<Symbol_assignment*> Symbol_assignments; 559 560 // We keep a list of all assertions which occur outside of a 561 // SECTIONS clause. 562 typedef std::vector<Script_assertion*> Assertions; 563 564 // The entry address. This will be empty if not set. 565 std::string entry_; 566 // Symbols to set. 567 Symbol_assignments symbol_assignments_; 568 // Symbols defined in an expression, for faster lookup. 569 Unordered_set<std::string> symbol_definitions_; 570 // Symbols referenced in an expression. 571 Unordered_set<std::string> symbol_references_; 572 // Assertions to check. 573 Assertions assertions_; 574 // Version information parsed from a version script. 575 Version_script_info version_script_info_; 576 // Information from any SECTIONS clauses. 577 Script_sections script_sections_; 578 }; 579 580 // FILE was found as an argument on the command line, but was not 581 // recognized as an ELF file. Try to read it as a script. Return 582 // true if the file was handled. This has to handle /usr/lib/libc.so 583 // on a GNU/Linux system. *USED_NEXT_BLOCKER is set to indicate 584 // whether the function took over NEXT_BLOCKER. 585 586 bool 587 read_input_script(Workqueue*, Symbol_table*, Layout*, Dirsearch*, int, 588 Input_objects*, Mapfile*, Input_group*, 589 const Input_argument*, Input_file*, 590 Task_token* next_blocker, bool* used_next_blocker); 591 592 // FILE was found as an argument to --script (-T). 593 // Read it as a script, and execute its contents immediately. 594 595 bool 596 read_commandline_script(const char* filename, Command_line* cmdline); 597 598 // FILE was found as an argument to --version-script. Read it as a 599 // version script, and store its contents in 600 // cmdline->script_options()->version_script_info(). 601 602 bool 603 read_version_script(const char* filename, Command_line* cmdline); 604 605 // FILENAME was found as an argument to --dynamic-list. Read it as a 606 // version script (actually, a versym_node from a version script), and 607 // store its contents in DYNAMIC_LIST. 608 609 bool 610 read_dynamic_list(const char* filename, Command_line* cmdline, 611 Script_options* dynamic_list); 612 613 } // End namespace gold. 614 615 #endif // !defined(GOLD_SCRIPT_H) 616