lld/wasm/Driver.cpp

   1 //===- Driver.cpp ---------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "lld/Common/Driver.h"
  10 #include "Config.h"
  11 #include "InputChunks.h"
  12 #include "InputElement.h"
  13 #include "MarkLive.h"
  14 #include "SymbolTable.h"
  15 #include "Writer.h"
  16 #include "lld/Common/Args.h"
  17 #include "lld/Common/ErrorHandler.h"
  18 #include "lld/Common/Filesystem.h"
  19 #include "lld/Common/Memory.h"
  20 #include "lld/Common/Reproduce.h"
  21 #include "lld/Common/Strings.h"
  22 #include "lld/Common/Version.h"
  23 #include "llvm/ADT/Twine.h"
  24 #include "llvm/Config/llvm-config.h"
  25 #include "llvm/Object/Wasm.h"
  26 #include "llvm/Option/Arg.h"
  27 #include "llvm/Option/ArgList.h"
  28 #include "llvm/Support/CommandLine.h"
  29 #include "llvm/Support/Host.h"
  30 #include "llvm/Support/Parallel.h"
  31 #include "llvm/Support/Path.h"
  32 #include "llvm/Support/Process.h"
  33 #include "llvm/Support/TarWriter.h"
  34 #include "llvm/Support/TargetSelect.h"
  35
  36 #define DEBUG_TYPE "lld"
  37
  38 using namespace llvm;
  39 using namespace llvm::object;
  40 using namespace llvm::sys;
  41 using namespace llvm::wasm;
  42
  43 namespace lld {
  44 namespace wasm {
  45 Configuration *config;
  46
  47 namespace {
  48
  49 // Create enum with OPT_xxx values for each option in Options.td
  50 enum {
  51   OPT_INVALID = 0,
  52 #define OPTION(_1, _2, ID, _4, _5, _6, _7, _8, _9, _10, _11, _12) OPT_##ID,
  53 #include "Options.inc"
  54 #undef OPTION
  55 };
  56
  57 // This function is called on startup. We need this for LTO since
  58 // LTO calls LLVM functions to compile bitcode files to native code.
  59 // Technically this can be delayed until we read bitcode files, but
  60 // we don't bother to do lazily because the initialization is fast.
  61 static void initLLVM() {
  62   InitializeAllTargets();
  63   InitializeAllTargetMCs();
  64   InitializeAllAsmPrinters();
  65   InitializeAllAsmParsers();
  66 }
  67
  68 class LinkerDriver {
  69 public:
  70   void linkerMain(ArrayRef<const char *> argsArr);
  71
  72 private:
  73   void createFiles(opt::InputArgList &args);
  74   void addFile(StringRef path);
  75   void addLibrary(StringRef name);
  76
  77   // True if we are in --whole-archive and --no-whole-archive.
  78   bool inWholeArchive = false;
  79
  80   std::vector<InputFile *> files;
  81 };
  82 } // anonymous namespace
  83
  84 bool link(ArrayRef<const char *> args, llvm::raw_ostream &stdoutOS,
  85           llvm::raw_ostream &stderrOS, bool exitEarly, bool disableOutput) {
  86   // This driver-specific context will be freed later by lldMain().
  87   auto *ctx = new CommonLinkerContext;
  88
  89   ctx->e.initialize(stdoutOS, stderrOS, exitEarly, disableOutput);
  90   ctx->e.logName = args::getFilenameWithoutExe(args[0]);
  91   ctx->e.errorLimitExceededMsg = "too many errors emitted, stopping now (use "
  92                                  "-error-limit=0 to see all errors)";
  93
  94   config = make<Configuration>();
  95   symtab = make<SymbolTable>();
  96
  97   initLLVM();
  98   LinkerDriver().linkerMain(args);
  99
 100   return errorCount() == 0;
 101 }
 102
 103 // Create prefix string literals used in Options.td
 104 #define PREFIX(NAME, VALUE) const char *const NAME[] = VALUE;
 105 #include "Options.inc"
 106 #undef PREFIX
 107
 108 // Create table mapping all options defined in Options.td
 109 static const opt::OptTable::Info optInfo[] = {
 110 #define OPTION(X1, X2, ID, KIND, GROUP, ALIAS, X7, X8, X9, X10, X11, X12)      \
 111   {X1, X2, X10,         X11,         OPT_##ID, opt::Option::KIND##Class,       \
 112    X9, X8, OPT_##GROUP, OPT_##ALIAS, X7,       X12},
 113 #include "Options.inc"
 114 #undef OPTION
 115 };
 116
 117 namespace {
 118 class WasmOptTable : public llvm::opt::OptTable {
 119 public:
 120   WasmOptTable() : OptTable(optInfo) {}
 121   opt::InputArgList parse(ArrayRef<const char *> argv);
 122 };
 123 } // namespace
 124
 125 // Set color diagnostics according to -color-diagnostics={auto,always,never}
 126 // or -no-color-diagnostics flags.
 127 static void handleColorDiagnostics(opt::InputArgList &args) {
 128   auto *arg = args.getLastArg(OPT_color_diagnostics, OPT_color_diagnostics_eq,
 129                               OPT_no_color_diagnostics);
 130   if (!arg)
 131     return;
 132   if (arg->getOption().getID() == OPT_color_diagnostics) {
 133     lld::errs().enable_colors(true);
 134   } else if (arg->getOption().getID() == OPT_no_color_diagnostics) {
 135     lld::errs().enable_colors(false);
 136   } else {
 137     StringRef s = arg->getValue();
 138     if (s == "always")
 139       lld::errs().enable_colors(true);
 140     else if (s == "never")
 141       lld::errs().enable_colors(false);
 142     else if (s != "auto")
 143       error("unknown option: --color-diagnostics=" + s);
 144   }
 145 }
 146
 147 static cl::TokenizerCallback getQuotingStyle(opt::InputArgList &args) {
 148   if (auto *arg = args.getLastArg(OPT_rsp_quoting)) {
 149     StringRef s = arg->getValue();
 150     if (s != "windows" && s != "posix")
 151       error("invalid response file quoting: " + s);
 152     if (s == "windows")
 153       return cl::TokenizeWindowsCommandLine;
 154     return cl::TokenizeGNUCommandLine;
 155   }
 156   if (Triple(sys::getProcessTriple()).isOSWindows())
 157     return cl::TokenizeWindowsCommandLine;
 158   return cl::TokenizeGNUCommandLine;
 159 }
 160
 161 // Find a file by concatenating given paths.
 162 static Optional<std::string> findFile(StringRef path1, const Twine &path2) {
 163   SmallString<128> s;
 164   path::append(s, path1, path2);
 165   if (fs::exists(s))
 166     return std::string(s);
 167   return None;
 168 }
 169
 170 opt::InputArgList WasmOptTable::parse(ArrayRef<const char *> argv) {
 171   SmallVector<const char *, 256> vec(argv.data(), argv.data() + argv.size());
 172
 173   unsigned missingIndex;
 174   unsigned missingCount;
 175
 176   // We need to get the quoting style for response files before parsing all
 177   // options so we parse here before and ignore all the options but
 178   // --rsp-quoting.
 179   opt::InputArgList args = this->ParseArgs(vec, missingIndex, missingCount);
 180
 181   // Expand response files (arguments in the form of @<filename>)
 182   // and then parse the argument again.
 183   cl::ExpandResponseFiles(saver(), getQuotingStyle(args), vec);
 184   args = this->ParseArgs(vec, missingIndex, missingCount);
 185
 186   handleColorDiagnostics(args);
 187   for (auto *arg : args.filtered(OPT_UNKNOWN))
 188     error("unknown argument: " + arg->getAsString(args));
 189   return args;
 190 }
 191
 192 // Currently we allow a ".imports" to live alongside a library. This can
 193 // be used to specify a list of symbols which can be undefined at link
 194 // time (imported from the environment.  For example libc.a include an
 195 // import file that lists the syscall functions it relies on at runtime.
 196 // In the long run this information would be better stored as a symbol
 197 // attribute/flag in the object file itself.
 198 // See: https://github.com/WebAssembly/tool-conventions/issues/35
 199 static void readImportFile(StringRef filename) {
 200   if (Optional<MemoryBufferRef> buf = readFile(filename))
 201     for (StringRef sym : args::getLines(*buf))
 202       config->allowUndefinedSymbols.insert(sym);
 203 }
 204
 205 // Returns slices of MB by parsing MB as an archive file.
 206 // Each slice consists of a member file in the archive.
 207 std::vector<MemoryBufferRef> static getArchiveMembers(MemoryBufferRef mb) {
 208   std::unique_ptr<Archive> file =
 209       CHECK(Archive::create(mb),
 210             mb.getBufferIdentifier() + ": failed to parse archive");
 211
 212   std::vector<MemoryBufferRef> v;
 213   Error err = Error::success();
 214   for (const Archive::Child &c : file->children(err)) {
 215     MemoryBufferRef mbref =
 216         CHECK(c.getMemoryBufferRef(),
 217               mb.getBufferIdentifier() +
 218                   ": could not get the buffer for a child of the archive");
 219     v.push_back(mbref);
 220   }
 221   if (err)
 222     fatal(mb.getBufferIdentifier() +
 223           ": Archive::children failed: " + toString(std::move(err)));
 224
 225   // Take ownership of memory buffers created for members of thin archives.
 226   for (std::unique_ptr<MemoryBuffer> &mb : file->takeThinBuffers())
 227     make<std::unique_ptr<MemoryBuffer>>(std::move(mb));
 228
 229   return v;
 230 }
 231
 232 void LinkerDriver::addFile(StringRef path) {
 233   Optional<MemoryBufferRef> buffer = readFile(path);
 234   if (!buffer.hasValue())
 235     return;
 236   MemoryBufferRef mbref = *buffer;
 237
 238   switch (identify_magic(mbref.getBuffer())) {
 239   case file_magic::archive: {
 240     SmallString<128> importFile = path;
 241     path::replace_extension(importFile, ".imports");
 242     if (fs::exists(importFile))
 243       readImportFile(importFile.str());
 244
 245     // Handle -whole-archive.
 246     if (inWholeArchive) {
 247       for (MemoryBufferRef &m : getArchiveMembers(mbref)) {
 248         auto *object = createObjectFile(m, path);
 249         // Mark object as live; object members are normally not
 250         // live by default but -whole-archive is designed to treat
 251         // them as such.
 252         object->markLive();
 253         files.push_back(object);
 254       }
 255
 256       return;
 257     }
 258
 259     std::unique_ptr<Archive> file =
 260         CHECK(Archive::create(mbref), path + ": failed to parse archive");
 261
 262     if (!file->isEmpty() && !file->hasSymbolTable()) {
 263       error(mbref.getBufferIdentifier() +
 264             ": archive has no index; run ranlib to add one");
 265     }
 266
 267     files.push_back(make<ArchiveFile>(mbref));
 268     return;
 269   }
 270   case file_magic::bitcode:
 271   case file_magic::wasm_object:
 272     files.push_back(createObjectFile(mbref));
 273     break;
 274   default:
 275     error("unknown file type: " + mbref.getBufferIdentifier());
 276   }
 277 }
 278
 279 // Add a given library by searching it from input search paths.
 280 void LinkerDriver::addLibrary(StringRef name) {
 281   for (StringRef dir : config->searchPaths) {
 282     if (Optional<std::string> s = findFile(dir, "lib" + name + ".a")) {
 283       addFile(*s);
 284       return;
 285     }
 286   }
 287
 288   error("unable to find library -l" + name);
 289 }
 290
 291 void LinkerDriver::createFiles(opt::InputArgList &args) {
 292   for (auto *arg : args) {
 293     switch (arg->getOption().getID()) {
 294     case OPT_l:
 295       addLibrary(arg->getValue());
 296       break;
 297     case OPT_INPUT:
 298       addFile(arg->getValue());
 299       break;
 300     case OPT_whole_archive:
 301       inWholeArchive = true;
 302       break;
 303     case OPT_no_whole_archive:
 304       inWholeArchive = false;
 305       break;
 306     }
 307   }
 308   if (files.empty() && errorCount() == 0)
 309     error("no input files");
 310 }
 311
 312 static StringRef getEntry(opt::InputArgList &args) {
 313   auto *arg = args.getLastArg(OPT_entry, OPT_no_entry);
 314   if (!arg) {
 315     if (args.hasArg(OPT_relocatable))
 316       return "";
 317     if (args.hasArg(OPT_shared))
 318       return "__wasm_call_ctors";
 319     return "_start";
 320   }
 321   if (arg->getOption().getID() == OPT_no_entry)
 322     return "";
 323   return arg->getValue();
 324 }
 325
 326 // Determines what we should do if there are remaining unresolved
 327 // symbols after the name resolution.
 328 static UnresolvedPolicy getUnresolvedSymbolPolicy(opt::InputArgList &args) {
 329   UnresolvedPolicy errorOrWarn = args.hasFlag(OPT_error_unresolved_symbols,
 330                                               OPT_warn_unresolved_symbols, true)
 331                                      ? UnresolvedPolicy::ReportError
 332                                      : UnresolvedPolicy::Warn;
 333
 334   if (auto *arg = args.getLastArg(OPT_unresolved_symbols)) {
 335     StringRef s = arg->getValue();
 336     if (s == "ignore-all")
 337       return UnresolvedPolicy::Ignore;
 338     if (s == "import-dynamic")
 339       return UnresolvedPolicy::ImportDynamic;
 340     if (s == "report-all")
 341       return errorOrWarn;
 342     error("unknown --unresolved-symbols value: " + s);
 343   }
 344
 345   return errorOrWarn;
 346 }
 347
 348 // Initializes Config members by the command line options.
 349 static void readConfigs(opt::InputArgList &args) {
 350   config->bsymbolic = args.hasArg(OPT_Bsymbolic);
 351   config->checkFeatures =
 352       args.hasFlag(OPT_check_features, OPT_no_check_features, true);
 353   config->compressRelocations = args.hasArg(OPT_compress_relocations);
 354   config->demangle = args.hasFlag(OPT_demangle, OPT_no_demangle, true);
 355   config->disableVerify = args.hasArg(OPT_disable_verify);
 356   config->emitRelocs = args.hasArg(OPT_emit_relocs);
 357   config->experimentalPic = args.hasArg(OPT_experimental_pic);
 358   config->entry = getEntry(args);
 359   config->exportAll = args.hasArg(OPT_export_all);
 360   config->exportTable = args.hasArg(OPT_export_table);
 361   config->growableTable = args.hasArg(OPT_growable_table);
 362   config->importMemory = args.hasArg(OPT_import_memory);
 363   config->sharedMemory = args.hasArg(OPT_shared_memory);
 364   config->importTable = args.hasArg(OPT_import_table);
 365   config->importUndefined = args.hasArg(OPT_import_undefined);
 366   config->ltoo = args::getInteger(args, OPT_lto_O, 2);
 367   config->ltoPartitions = args::getInteger(args, OPT_lto_partitions, 1);
 368   config->ltoNewPassManager = args.hasFlag(OPT_no_lto_legacy_pass_manager,
 369                                            OPT_lto_legacy_pass_manager, true);
 370   config->ltoDebugPassManager = args.hasArg(OPT_lto_debug_pass_manager);
 371   config->mapFile = args.getLastArgValue(OPT_Map);
 372   config->optimize = args::getInteger(args, OPT_O, 1);
 373   config->outputFile = args.getLastArgValue(OPT_o);
 374   config->relocatable = args.hasArg(OPT_relocatable);
 375   config->gcSections =
 376       args.hasFlag(OPT_gc_sections, OPT_no_gc_sections, !config->relocatable);
 377   config->mergeDataSegments =
 378       args.hasFlag(OPT_merge_data_segments, OPT_no_merge_data_segments,
 379                    !config->relocatable);
 380   config->pie = args.hasFlag(OPT_pie, OPT_no_pie, false);
 381   config->printGcSections =
 382       args.hasFlag(OPT_print_gc_sections, OPT_no_print_gc_sections, false);
 383   config->saveTemps = args.hasArg(OPT_save_temps);
 384   config->searchPaths = args::getStrings(args, OPT_L);
 385   config->shared = args.hasArg(OPT_shared);
 386   config->stripAll = args.hasArg(OPT_strip_all);
 387   config->stripDebug = args.hasArg(OPT_strip_debug);
 388   config->stackFirst = args.hasArg(OPT_stack_first);
 389   config->trace = args.hasArg(OPT_trace);
 390   config->thinLTOCacheDir = args.getLastArgValue(OPT_thinlto_cache_dir);
 391   config->thinLTOCachePolicy = CHECK(
 392       parseCachePruningPolicy(args.getLastArgValue(OPT_thinlto_cache_policy)),
 393       "--thinlto-cache-policy: invalid cache policy");
 394   config->unresolvedSymbols = getUnresolvedSymbolPolicy(args);
 395   errorHandler().verbose = args.hasArg(OPT_verbose);
 396   LLVM_DEBUG(errorHandler().verbose = true);
 397
 398   config->initialMemory = args::getInteger(args, OPT_initial_memory, 0);
 399   config->globalBase = args::getInteger(args, OPT_global_base, 1024);
 400   config->maxMemory = args::getInteger(args, OPT_max_memory, 0);
 401   config->zStackSize =
 402       args::getZOptionValue(args, OPT_z, "stack-size", WasmPageSize);
 403
 404   // Default value of exportDynamic depends on `-shared`
 405   config->exportDynamic =
 406       args.hasFlag(OPT_export_dynamic, OPT_no_export_dynamic, config->shared);
 407
 408   // Parse wasm32/64.
 409   if (auto *arg = args.getLastArg(OPT_m)) {
 410     StringRef s = arg->getValue();
 411     if (s == "wasm32")
 412       config->is64 = false;
 413     else if (s == "wasm64")
 414       config->is64 = true;
 415     else
 416       error("invalid target architecture: " + s);
 417   }
 418
 419   // --threads= takes a positive integer and provides the default value for
 420   // --thinlto-jobs=.
 421   if (auto *arg = args.getLastArg(OPT_threads)) {
 422     StringRef v(arg->getValue());
 423     unsigned threads = 0;
 424     if (!llvm::to_integer(v, threads, 0) || threads == 0)
 425       error(arg->getSpelling() + ": expected a positive integer, but got '" +
 426             arg->getValue() + "'");
 427     parallel::strategy = hardware_concurrency(threads);
 428     config->thinLTOJobs = v;
 429   }
 430   if (auto *arg = args.getLastArg(OPT_thinlto_jobs))
 431     config->thinLTOJobs = arg->getValue();
 432
 433   if (auto *arg = args.getLastArg(OPT_features)) {
 434     config->features =
 435         llvm::Optional<std::vector<std::string>>(std::vector<std::string>());
 436     for (StringRef s : arg->getValues())
 437       config->features->push_back(std::string(s));
 438   }
 439
 440   // Legacy --allow-undefined flag which is equivalent to
 441   // --unresolve-symbols=ignore + --import-undefined
 442   if (args.hasArg(OPT_allow_undefined)) {
 443     config->importUndefined = true;
 444     config->unresolvedSymbols = UnresolvedPolicy::Ignore;
 445   }
 446
 447   if (args.hasArg(OPT_print_map))
 448     config->mapFile = "-";
 449 }
 450
 451 // Some Config members do not directly correspond to any particular
 452 // command line options, but computed based on other Config values.
 453 // This function initialize such members. See Config.h for the details
 454 // of these values.
 455 static void setConfigs() {
 456   config->isPic = config->pie || config->shared;
 457
 458   if (config->isPic) {
 459     if (config->exportTable)
 460       error("-shared/-pie is incompatible with --export-table");
 461     config->importTable = true;
 462   }
 463
 464   if (config->relocatable) {
 465     if (config->exportTable)
 466       error("--relocatable is incompatible with --export-table");
 467     if (config->growableTable)
 468       error("--relocatable is incompatible with --growable-table");
 469     // Ignore any --import-table, as it's redundant.
 470     config->importTable = true;
 471   }
 472
 473   if (config->shared) {
 474     config->importMemory = true;
 475     config->importUndefined = true;
 476   }
 477 }
 478
 479 // Some command line options or some combinations of them are not allowed.
 480 // This function checks for such errors.
 481 static void checkOptions(opt::InputArgList &args) {
 482   if (!config->stripDebug && !config->stripAll && config->compressRelocations)
 483     error("--compress-relocations is incompatible with output debug"
 484           " information. Please pass --strip-debug or --strip-all");
 485
 486   if (config->ltoo > 3)
 487     error("invalid optimization level for LTO: " + Twine(config->ltoo));
 488   if (config->ltoPartitions == 0)
 489     error("--lto-partitions: number of threads must be > 0");
 490   if (!get_threadpool_strategy(config->thinLTOJobs))
 491     error("--thinlto-jobs: invalid job count: " + config->thinLTOJobs);
 492
 493   if (config->pie && config->shared)
 494     error("-shared and -pie may not be used together");
 495
 496   if (config->outputFile.empty())
 497     error("no output file specified");
 498
 499   if (config->importTable && config->exportTable)
 500     error("--import-table and --export-table may not be used together");
 501
 502   if (config->relocatable) {
 503     if (!config->entry.empty())
 504       error("entry point specified for relocatable output file");
 505     if (config->gcSections)
 506       error("-r and --gc-sections may not be used together");
 507     if (config->compressRelocations)
 508       error("-r -and --compress-relocations may not be used together");
 509     if (args.hasArg(OPT_undefined))
 510       error("-r -and --undefined may not be used together");
 511     if (config->pie)
 512       error("-r and -pie may not be used together");
 513     if (config->sharedMemory)
 514       error("-r and --shared-memory may not be used together");
 515   }
 516
 517   // To begin to prepare for Module Linking-style shared libraries, start
 518   // warning about uses of `-shared` and related flags outside of Experimental
 519   // mode, to give anyone using them a heads-up that they will be changing.
 520   //
 521   // Also, warn about flags which request explicit exports.
 522   if (!config->experimentalPic) {
 523     // -shared will change meaning when Module Linking is implemented.
 524     if (config->shared) {
 525       warn("creating shared libraries, with -shared, is not yet stable");
 526     }
 527
 528     // -pie will change meaning when Module Linking is implemented.
 529     if (config->pie) {
 530       warn("creating PIEs, with -pie, is not yet stable");
 531     }
 532
 533     if (config->unresolvedSymbols == UnresolvedPolicy::ImportDynamic) {
 534       warn("dynamic imports are not yet stable "
 535            "(--unresolved-symbols=import-dynamic)");
 536     }
 537   }
 538
 539   if (config->bsymbolic && !config->shared) {
 540     warn("-Bsymbolic is only meaningful when combined with -shared");
 541   }
 542 }
 543
 544 // Force Sym to be entered in the output. Used for -u or equivalent.
 545 static Symbol *handleUndefined(StringRef name) {
 546   Symbol *sym = symtab->find(name);
 547   if (!sym)
 548     return nullptr;
 549
 550   // Since symbol S may not be used inside the program, LTO may
 551   // eliminate it. Mark the symbol as "used" to prevent it.
 552   sym->isUsedInRegularObj = true;
 553
 554   if (auto *lazySym = dyn_cast<LazySymbol>(sym))
 555     lazySym->fetch();
 556
 557   return sym;
 558 }
 559
 560 static void handleLibcall(StringRef name) {
 561   Symbol *sym = symtab->find(name);
 562   if (!sym)
 563     return;
 564
 565   if (auto *lazySym = dyn_cast<LazySymbol>(sym)) {
 566     MemoryBufferRef mb = lazySym->getMemberBuffer();
 567     if (isBitcode(mb))
 568       lazySym->fetch();
 569   }
 570 }
 571
 572 static UndefinedGlobal *
 573 createUndefinedGlobal(StringRef name, llvm::wasm::WasmGlobalType *type) {
 574   auto *sym = cast<UndefinedGlobal>(symtab->addUndefinedGlobal(
 575       name, None, None, WASM_SYMBOL_UNDEFINED, nullptr, type));
 576   config->allowUndefinedSymbols.insert(sym->getName());
 577   sym->isUsedInRegularObj = true;
 578   return sym;
 579 }
 580
 581 static InputGlobal *createGlobal(StringRef name, bool isMutable) {
 582   llvm::wasm::WasmGlobal wasmGlobal;
 583   bool is64 = config->is64.getValueOr(false);
 584   wasmGlobal.Type = {uint8_t(is64 ? WASM_TYPE_I64 : WASM_TYPE_I32), isMutable};
 585   wasmGlobal.InitExpr = intConst(0, is64);
 586   wasmGlobal.SymbolName = name;
 587   return make<InputGlobal>(wasmGlobal, nullptr);
 588 }
 589
 590 static GlobalSymbol *createGlobalVariable(StringRef name, bool isMutable) {
 591   InputGlobal *g = createGlobal(name, isMutable);
 592   return symtab->addSyntheticGlobal(name, WASM_SYMBOL_VISIBILITY_HIDDEN, g);
 593 }
 594
 595 static GlobalSymbol *createOptionalGlobal(StringRef name, bool isMutable) {
 596   InputGlobal *g = createGlobal(name, isMutable);
 597   return symtab->addOptionalGlobalSymbol(name, g);
 598 }
 599
 600 // Create ABI-defined synthetic symbols
 601 static void createSyntheticSymbols() {
 602   if (config->relocatable)
 603     return;
 604
 605   static WasmSignature nullSignature = {{}, {}};
 606   static WasmSignature i32ArgSignature = {{}, {ValType::I32}};
 607   static WasmSignature i64ArgSignature = {{}, {ValType::I64}};
 608   static llvm::wasm::WasmGlobalType globalTypeI32 = {WASM_TYPE_I32, false};
 609   static llvm::wasm::WasmGlobalType globalTypeI64 = {WASM_TYPE_I64, false};
 610   static llvm::wasm::WasmGlobalType mutableGlobalTypeI32 = {WASM_TYPE_I32,
 611                                                             true};
 612   static llvm::wasm::WasmGlobalType mutableGlobalTypeI64 = {WASM_TYPE_I64,
 613                                                             true};
 614   WasmSym::callCtors = symtab->addSyntheticFunction(
 615       "__wasm_call_ctors", WASM_SYMBOL_VISIBILITY_HIDDEN,
 616       make<SyntheticFunction>(nullSignature, "__wasm_call_ctors"));
 617
 618     bool is64 = config->is64.getValueOr(false);
 619
 620   if (config->isPic) {
 621     WasmSym::stackPointer =
 622         createUndefinedGlobal("__stack_pointer", config->is64.getValueOr(false)
 623                                                      ? &mutableGlobalTypeI64
 624                                                      : &mutableGlobalTypeI32);
 625     // For PIC code, we import two global variables (__memory_base and
 626     // __table_base) from the environment and use these as the offset at
 627     // which to load our static data and function table.
 628     // See:
 629     // https://github.com/WebAssembly/tool-conventions/blob/main/DynamicLinking.md
 630     auto *globalType = is64 ? &globalTypeI64 : &globalTypeI32;
 631     WasmSym::memoryBase = createUndefinedGlobal("__memory_base", globalType);
 632     WasmSym::tableBase = createUndefinedGlobal("__table_base", globalType);
 633     WasmSym::memoryBase->markLive();
 634     WasmSym::tableBase->markLive();
 635     if (is64) {
 636       WasmSym::tableBase32 =
 637           createUndefinedGlobal("__table_base32", &globalTypeI32);
 638       WasmSym::tableBase32->markLive();
 639     } else {
 640       WasmSym::tableBase32 = nullptr;
 641     }
 642   } else {
 643     // For non-PIC code
 644     WasmSym::stackPointer = createGlobalVariable("__stack_pointer", true);
 645     WasmSym::stackPointer->markLive();
 646   }
 647
 648   if (config->sharedMemory) {
 649     WasmSym::tlsBase = createGlobalVariable("__tls_base", true);
 650     WasmSym::tlsSize = createGlobalVariable("__tls_size", false);
 651     WasmSym::tlsAlign = createGlobalVariable("__tls_align", false);
 652     WasmSym::initTLS = symtab->addSyntheticFunction(
 653         "__wasm_init_tls", WASM_SYMBOL_VISIBILITY_HIDDEN,
 654         make<SyntheticFunction>(
 655             is64 ? i64ArgSignature : i32ArgSignature,
 656             "__wasm_init_tls"));
 657   }
 658 }
 659
 660 static void createOptionalSymbols() {
 661   if (config->relocatable)
 662     return;
 663
 664   WasmSym::dsoHandle = symtab->addOptionalDataSymbol("__dso_handle");
 665
 666   if (!config->shared)
 667     WasmSym::dataEnd = symtab->addOptionalDataSymbol("__data_end");
 668
 669   if (!config->isPic) {
 670     WasmSym::globalBase = symtab->addOptionalDataSymbol("__global_base");
 671     WasmSym::heapBase = symtab->addOptionalDataSymbol("__heap_base");
 672     WasmSym::definedMemoryBase = symtab->addOptionalDataSymbol("__memory_base");
 673     WasmSym::definedTableBase = symtab->addOptionalDataSymbol("__table_base");
 674     if (config->is64.getValueOr(false))
 675       WasmSym::definedTableBase32 =
 676           symtab->addOptionalDataSymbol("__table_base32");
 677   }
 678
 679   // For non-shared memory programs we still need to define __tls_base since we
 680   // allow object files built with TLS to be linked into single threaded
 681   // programs, and such object files can contain references to this symbol.
 682   //
 683   // However, in this case __tls_base is immutable and points directly to the
 684   // start of the `.tdata` static segment.
 685   //
 686   // __tls_size and __tls_align are not needed in this case since they are only
 687   // needed for __wasm_init_tls (which we do not create in this case).
 688   if (!config->sharedMemory)
 689     WasmSym::tlsBase = createOptionalGlobal("__tls_base", false);
 690 }
 691
 692 // Reconstructs command line arguments so that so that you can re-run
 693 // the same command with the same inputs. This is for --reproduce.
 694 static std::string createResponseFile(const opt::InputArgList &args) {
 695   SmallString<0> data;
 696   raw_svector_ostream os(data);
 697
 698   // Copy the command line to the output while rewriting paths.
 699   for (auto *arg : args) {
 700     switch (arg->getOption().getID()) {
 701     case OPT_reproduce:
 702       break;
 703     case OPT_INPUT:
 704       os << quote(relativeToRoot(arg->getValue())) << "\n";
 705       break;
 706     case OPT_o:
 707       // If -o path contains directories, "lld @response.txt" will likely
 708       // fail because the archive we are creating doesn't contain empty
 709       // directories for the output path (-o doesn't create directories).
 710       // Strip directories to prevent the issue.
 711       os << "-o " << quote(sys::path::filename(arg->getValue())) << "\n";
 712       break;
 713     default:
 714       os << toString(*arg) << "\n";
 715     }
 716   }
 717   return std::string(data.str());
 718 }
 719
 720 // The --wrap option is a feature to rename symbols so that you can write
 721 // wrappers for existing functions. If you pass `-wrap=foo`, all
 722 // occurrences of symbol `foo` are resolved to `wrap_foo` (so, you are
 723 // expected to write `wrap_foo` function as a wrapper). The original
 724 // symbol becomes accessible as `real_foo`, so you can call that from your
 725 // wrapper.
 726 //
 727 // This data structure is instantiated for each -wrap option.
 728 struct WrappedSymbol {
 729   Symbol *sym;
 730   Symbol *real;
 731   Symbol *wrap;
 732 };
 733
 734 static Symbol *addUndefined(StringRef name) {
 735   return symtab->addUndefinedFunction(name, None, None, WASM_SYMBOL_UNDEFINED,
 736                                       nullptr, nullptr, false);
 737 }
 738
 739 // Handles -wrap option.
 740 //
 741 // This function instantiates wrapper symbols. At this point, they seem
 742 // like they are not being used at all, so we explicitly set some flags so
 743 // that LTO won't eliminate them.
 744 static std::vector<WrappedSymbol> addWrappedSymbols(opt::InputArgList &args) {
 745   std::vector<WrappedSymbol> v;
 746   DenseSet<StringRef> seen;
 747
 748   for (auto *arg : args.filtered(OPT_wrap)) {
 749     StringRef name = arg->getValue();
 750     if (!seen.insert(name).second)
 751       continue;
 752
 753     Symbol *sym = symtab->find(name);
 754     if (!sym)
 755       continue;
 756
 757     Symbol *real = addUndefined(saver().save("__real_" + name));
 758     Symbol *wrap = addUndefined(saver().save("__wrap_" + name));
 759     v.push_back({sym, real, wrap});
 760
 761     // We want to tell LTO not to inline symbols to be overwritten
 762     // because LTO doesn't know the final symbol contents after renaming.
 763     real->canInline = false;
 764     sym->canInline = false;
 765
 766     // Tell LTO not to eliminate these symbols.
 767     sym->isUsedInRegularObj = true;
 768     wrap->isUsedInRegularObj = true;
 769     real->isUsedInRegularObj = false;
 770   }
 771   return v;
 772 }
 773
 774 // Do renaming for -wrap by updating pointers to symbols.
 775 //
 776 // When this function is executed, only InputFiles and symbol table
 777 // contain pointers to symbol objects. We visit them to replace pointers,
 778 // so that wrapped symbols are swapped as instructed by the command line.
 779 static void wrapSymbols(ArrayRef<WrappedSymbol> wrapped) {
 780   DenseMap<Symbol *, Symbol *> map;
 781   for (const WrappedSymbol &w : wrapped) {
 782     map[w.sym] = w.wrap;
 783     map[w.real] = w.sym;
 784   }
 785
 786   // Update pointers in input files.
 787   parallelForEach(symtab->objectFiles, [&](InputFile *file) {
 788     MutableArrayRef<Symbol *> syms = file->getMutableSymbols();
 789     for (size_t i = 0, e = syms.size(); i != e; ++i)
 790       if (Symbol *s = map.lookup(syms[i]))
 791         syms[i] = s;
 792   });
 793
 794   // Update pointers in the symbol table.
 795   for (const WrappedSymbol &w : wrapped)
 796     symtab->wrap(w.sym, w.real, w.wrap);
 797 }
 798
 799 static void splitSections() {
 800   // splitIntoPieces needs to be called on each MergeInputChunk
 801   // before calling finalizeContents().
 802   LLVM_DEBUG(llvm::dbgs() << "splitSections\n");
 803   parallelForEach(symtab->objectFiles, [](ObjFile *file) {
 804     for (InputChunk *seg : file->segments) {
 805       if (auto *s = dyn_cast<MergeInputChunk>(seg))
 806         s->splitIntoPieces();
 807     }
 808     for (InputChunk *sec : file->customSections) {
 809       if (auto *s = dyn_cast<MergeInputChunk>(sec))
 810         s->splitIntoPieces();
 811     }
 812   });
 813 }
 814
 815 static bool isKnownZFlag(StringRef s) {
 816   // For now, we only support a very limited set of -z flags
 817   return s.startswith("stack-size=");
 818 }
 819
 820 // Report a warning for an unknown -z option.
 821 static void checkZOptions(opt::InputArgList &args) {
 822   for (auto *arg : args.filtered(OPT_z))
 823     if (!isKnownZFlag(arg->getValue()))
 824       warn("unknown -z value: " + StringRef(arg->getValue()));
 825 }
 826
 827 void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
 828   WasmOptTable parser;
 829   opt::InputArgList args = parser.parse(argsArr.slice(1));
 830
 831   // Interpret these flags early because error()/warn() depend on them.
 832   errorHandler().errorLimit = args::getInteger(args, OPT_error_limit, 20);
 833   errorHandler().fatalWarnings =
 834       args.hasFlag(OPT_fatal_warnings, OPT_no_fatal_warnings, false);
 835   checkZOptions(args);
 836
 837   // Handle --help
 838   if (args.hasArg(OPT_help)) {
 839     parser.printHelp(lld::outs(),
 840                      (std::string(argsArr[0]) + " [options] file...").c_str(),
 841                      "LLVM Linker", false);
 842     return;
 843   }
 844
 845   // Handle --version
 846   if (args.hasArg(OPT_version) || args.hasArg(OPT_v)) {
 847     lld::outs() << getLLDVersion() << "\n";
 848     return;
 849   }
 850
 851   // Handle --reproduce
 852   if (auto *arg = args.getLastArg(OPT_reproduce)) {
 853     StringRef path = arg->getValue();
 854     Expected<std::unique_ptr<TarWriter>> errOrWriter =
 855         TarWriter::create(path, path::stem(path));
 856     if (errOrWriter) {
 857       tar = std::move(*errOrWriter);
 858       tar->append("response.txt", createResponseFile(args));
 859       tar->append("version.txt", getLLDVersion() + "\n");
 860     } else {
 861       error("--reproduce: " + toString(errOrWriter.takeError()));
 862     }
 863   }
 864
 865   // Parse and evaluate -mllvm options.
 866   std::vector<const char *> v;
 867   v.push_back("wasm-ld (LLVM option parsing)");
 868   for (auto *arg : args.filtered(OPT_mllvm))
 869     v.push_back(arg->getValue());
 870   cl::ResetAllOptionOccurrences();
 871   cl::ParseCommandLineOptions(v.size(), v.data());
 872
 873   readConfigs(args);
 874
 875   createFiles(args);
 876   if (errorCount())
 877     return;
 878
 879   setConfigs();
 880   checkOptions(args);
 881   if (errorCount())
 882     return;
 883
 884   if (auto *arg = args.getLastArg(OPT_allow_undefined_file))
 885     readImportFile(arg->getValue());
 886
 887   // Fail early if the output file or map file is not writable. If a user has a
 888   // long link, e.g. due to a large LTO link, they do not wish to run it and
 889   // find that it failed because there was a mistake in their command-line.
 890   if (auto e = tryCreateFile(config->outputFile))
 891     error("cannot open output file " + config->outputFile + ": " + e.message());
 892   if (auto e = tryCreateFile(config->mapFile))
 893     error("cannot open map file " + config->mapFile + ": " + e.message());
 894   if (errorCount())
 895     return;
 896
 897   // Handle --trace-symbol.
 898   for (auto *arg : args.filtered(OPT_trace_symbol))
 899     symtab->trace(arg->getValue());
 900
 901   for (auto *arg : args.filtered(OPT_export_if_defined))
 902     config->exportedSymbols.insert(arg->getValue());
 903
 904   for (auto *arg : args.filtered(OPT_export)) {
 905     config->exportedSymbols.insert(arg->getValue());
 906     config->requiredExports.push_back(arg->getValue());
 907   }
 908
 909   createSyntheticSymbols();
 910
 911   // Add all files to the symbol table. This will add almost all
 912   // symbols that we need to the symbol table.
 913   for (InputFile *f : files)
 914     symtab->addFile(f);
 915   if (errorCount())
 916     return;
 917
 918   // Handle the `--undefined <sym>` options.
 919   for (auto *arg : args.filtered(OPT_undefined))
 920     handleUndefined(arg->getValue());
 921
 922   // Handle the `--export <sym>` options
 923   // This works like --undefined but also exports the symbol if its found
 924   for (auto &iter : config->exportedSymbols)
 925     handleUndefined(iter.first());
 926
 927   Symbol *entrySym = nullptr;
 928   if (!config->relocatable && !config->entry.empty()) {
 929     entrySym = handleUndefined(config->entry);
 930     if (entrySym && entrySym->isDefined())
 931       entrySym->forceExport = true;
 932     else
 933       error("entry symbol not defined (pass --no-entry to suppress): " +
 934             config->entry);
 935   }
 936
 937   // If the user code defines a `__wasm_call_dtors` function, remember it so
 938   // that we can call it from the command export wrappers. Unlike
 939   // `__wasm_call_ctors` which we synthesize, `__wasm_call_dtors` is defined
 940   // by libc/etc., because destructors are registered dynamically with
 941   // `__cxa_atexit` and friends.
 942   if (!config->relocatable && !config->shared &&
 943       !WasmSym::callCtors->isUsedInRegularObj &&
 944       WasmSym::callCtors->getName() != config->entry &&
 945       !config->exportedSymbols.count(WasmSym::callCtors->getName())) {
 946     if (Symbol *callDtors = handleUndefined("__wasm_call_dtors")) {
 947       if (auto *callDtorsFunc = dyn_cast<DefinedFunction>(callDtors)) {
 948         if (callDtorsFunc->signature &&
 949             (!callDtorsFunc->signature->Params.empty() ||
 950              !callDtorsFunc->signature->Returns.empty())) {
 951           error("__wasm_call_dtors must have no argument or return values");
 952         }
 953         WasmSym::callDtors = callDtorsFunc;
 954       } else {
 955         error("__wasm_call_dtors must be a function");
 956       }
 957     }
 958   }
 959
 960   if (errorCount())
 961     return;
 962
 963   // Create wrapped symbols for -wrap option.
 964   std::vector<WrappedSymbol> wrapped = addWrappedSymbols(args);
 965
 966   // If any of our inputs are bitcode files, the LTO code generator may create
 967   // references to certain library functions that might not be explicit in the
 968   // bitcode file's symbol table. If any of those library functions are defined
 969   // in a bitcode file in an archive member, we need to arrange to use LTO to
 970   // compile those archive members by adding them to the link beforehand.
 971   //
 972   // We only need to add libcall symbols to the link before LTO if the symbol's
 973   // definition is in bitcode. Any other required libcall symbols will be added
 974   // to the link after LTO when we add the LTO object file to the link.
 975   if (!symtab->bitcodeFiles.empty())
 976     for (auto *s : lto::LTO::getRuntimeLibcallSymbols())
 977       handleLibcall(s);
 978   if (errorCount())
 979     return;
 980
 981   // Do link-time optimization if given files are LLVM bitcode files.
 982   // This compiles bitcode files into real object files.
 983   symtab->compileBitcodeFiles();
 984   if (errorCount())
 985     return;
 986
 987   createOptionalSymbols();
 988
 989   // Resolve any variant symbols that were created due to signature
 990   // mismatchs.
 991   symtab->handleSymbolVariants();
 992   if (errorCount())
 993     return;
 994
 995   // Apply symbol renames for -wrap.
 996   if (!wrapped.empty())
 997     wrapSymbols(wrapped);
 998
 999   for (auto &iter : config->exportedSymbols) {
1000     Symbol *sym = symtab->find(iter.first());
1001     if (sym && sym->isDefined())
1002       sym->forceExport = true;
1003   }
1004
1005   if (!config->relocatable && !config->isPic) {
1006     // Add synthetic dummies for weak undefined functions.  Must happen
1007     // after LTO otherwise functions may not yet have signatures.
1008     symtab->handleWeakUndefines();
1009   }
1010
1011   if (entrySym)
1012     entrySym->setHidden(false);
1013
1014   if (errorCount())
1015     return;
1016
1017   // Split WASM_SEG_FLAG_STRINGS sections into pieces in preparation for garbage
1018   // collection.
1019   splitSections();
1020
1021   // Do size optimizations: garbage collection
1022   markLive();
1023
1024   // Provide the indirect function table if needed.
1025   WasmSym::indirectFunctionTable =
1026       symtab->resolveIndirectFunctionTable(/*required =*/false);
1027
1028   if (errorCount())
1029     return;
1030
1031   // Write the result to the file.
1032   writeResult();
1033 }
1034
1035 } // namespace wasm
1036 } // namespace lld