1 //===- lib/MC/WasmObjectWriter.cpp - Wasm File Writer ---------------------===// 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 // This file implements Wasm object file writer information. 10 // 11 //===----------------------------------------------------------------------===// 12 13 #include "llvm/ADT/STLExtras.h" 14 #include "llvm/ADT/SmallPtrSet.h" 15 #include "llvm/BinaryFormat/Wasm.h" 16 #include "llvm/BinaryFormat/WasmTraits.h" 17 #include "llvm/Config/llvm-config.h" 18 #include "llvm/MC/MCAsmBackend.h" 19 #include "llvm/MC/MCAsmLayout.h" 20 #include "llvm/MC/MCAssembler.h" 21 #include "llvm/MC/MCContext.h" 22 #include "llvm/MC/MCExpr.h" 23 #include "llvm/MC/MCFixupKindInfo.h" 24 #include "llvm/MC/MCObjectWriter.h" 25 #include "llvm/MC/MCSectionWasm.h" 26 #include "llvm/MC/MCSymbolWasm.h" 27 #include "llvm/MC/MCValue.h" 28 #include "llvm/MC/MCWasmObjectWriter.h" 29 #include "llvm/Support/Casting.h" 30 #include "llvm/Support/Debug.h" 31 #include "llvm/Support/EndianStream.h" 32 #include "llvm/Support/ErrorHandling.h" 33 #include "llvm/Support/LEB128.h" 34 #include "llvm/Support/StringSaver.h" 35 #include <vector> 36 37 using namespace llvm; 38 39 #define DEBUG_TYPE "mc" 40 41 namespace { 42 43 // When we create the indirect function table we start at 1, so that there is 44 // and empty slot at 0 and therefore calling a null function pointer will trap. 45 static const uint32_t InitialTableOffset = 1; 46 47 // For patching purposes, we need to remember where each section starts, both 48 // for patching up the section size field, and for patching up references to 49 // locations within the section. 50 struct SectionBookkeeping { 51 // Where the size of the section is written. 52 uint64_t SizeOffset; 53 // Where the section header ends (without custom section name). 54 uint64_t PayloadOffset; 55 // Where the contents of the section starts. 56 uint64_t ContentsOffset; 57 uint32_t Index; 58 }; 59 60 // A wasm data segment. A wasm binary contains only a single data section 61 // but that can contain many segments, each with their own virtual location 62 // in memory. Each MCSection data created by llvm is modeled as its own 63 // wasm data segment. 64 struct WasmDataSegment { 65 MCSectionWasm *Section; 66 StringRef Name; 67 uint32_t InitFlags; 68 uint64_t Offset; 69 uint32_t Alignment; 70 uint32_t LinkerFlags; 71 SmallVector<char, 4> Data; 72 }; 73 74 // A wasm function to be written into the function section. 75 struct WasmFunction { 76 uint32_t SigIndex; 77 const MCSymbolWasm *Sym; 78 }; 79 80 // A wasm global to be written into the global section. 81 struct WasmGlobal { 82 wasm::WasmGlobalType Type; 83 uint64_t InitialValue; 84 }; 85 86 // Information about a single item which is part of a COMDAT. For each data 87 // segment or function which is in the COMDAT, there is a corresponding 88 // WasmComdatEntry. 89 struct WasmComdatEntry { 90 unsigned Kind; 91 uint32_t Index; 92 }; 93 94 // Information about a single relocation. 95 struct WasmRelocationEntry { 96 uint64_t Offset; // Where is the relocation. 97 const MCSymbolWasm *Symbol; // The symbol to relocate with. 98 int64_t Addend; // A value to add to the symbol. 99 unsigned Type; // The type of the relocation. 100 const MCSectionWasm *FixupSection; // The section the relocation is targeting. 101 102 WasmRelocationEntry(uint64_t Offset, const MCSymbolWasm *Symbol, 103 int64_t Addend, unsigned Type, 104 const MCSectionWasm *FixupSection) 105 : Offset(Offset), Symbol(Symbol), Addend(Addend), Type(Type), 106 FixupSection(FixupSection) {} 107 108 bool hasAddend() const { return wasm::relocTypeHasAddend(Type); } 109 110 void print(raw_ostream &Out) const { 111 Out << wasm::relocTypetoString(Type) << " Off=" << Offset 112 << ", Sym=" << *Symbol << ", Addend=" << Addend 113 << ", FixupSection=" << FixupSection->getName(); 114 } 115 116 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) 117 LLVM_DUMP_METHOD void dump() const { print(dbgs()); } 118 #endif 119 }; 120 121 static const uint32_t InvalidIndex = -1; 122 123 struct WasmCustomSection { 124 125 StringRef Name; 126 MCSectionWasm *Section; 127 128 uint32_t OutputContentsOffset; 129 uint32_t OutputIndex; 130 131 WasmCustomSection(StringRef Name, MCSectionWasm *Section) 132 : Name(Name), Section(Section), OutputContentsOffset(0), 133 OutputIndex(InvalidIndex) {} 134 }; 135 136 #if !defined(NDEBUG) 137 raw_ostream &operator<<(raw_ostream &OS, const WasmRelocationEntry &Rel) { 138 Rel.print(OS); 139 return OS; 140 } 141 #endif 142 143 // Write X as an (unsigned) LEB value at offset Offset in Stream, padded 144 // to allow patching. 145 template <int W> 146 void writePatchableLEB(raw_pwrite_stream &Stream, uint64_t X, uint64_t Offset) { 147 uint8_t Buffer[W]; 148 unsigned SizeLen = encodeULEB128(X, Buffer, W); 149 assert(SizeLen == W); 150 Stream.pwrite((char *)Buffer, SizeLen, Offset); 151 } 152 153 // Write X as an signed LEB value at offset Offset in Stream, padded 154 // to allow patching. 155 template <int W> 156 void writePatchableSLEB(raw_pwrite_stream &Stream, int64_t X, uint64_t Offset) { 157 uint8_t Buffer[W]; 158 unsigned SizeLen = encodeSLEB128(X, Buffer, W); 159 assert(SizeLen == W); 160 Stream.pwrite((char *)Buffer, SizeLen, Offset); 161 } 162 163 // Write X as a plain integer value at offset Offset in Stream. 164 static void patchI32(raw_pwrite_stream &Stream, uint32_t X, uint64_t Offset) { 165 uint8_t Buffer[4]; 166 support::endian::write32le(Buffer, X); 167 Stream.pwrite((char *)Buffer, sizeof(Buffer), Offset); 168 } 169 170 static void patchI64(raw_pwrite_stream &Stream, uint64_t X, uint64_t Offset) { 171 uint8_t Buffer[8]; 172 support::endian::write64le(Buffer, X); 173 Stream.pwrite((char *)Buffer, sizeof(Buffer), Offset); 174 } 175 176 bool isDwoSection(const MCSection &Sec) { 177 return Sec.getName().endswith(".dwo"); 178 } 179 180 class WasmObjectWriter : public MCObjectWriter { 181 support::endian::Writer *W; 182 183 /// The target specific Wasm writer instance. 184 std::unique_ptr<MCWasmObjectTargetWriter> TargetObjectWriter; 185 186 // Relocations for fixing up references in the code section. 187 std::vector<WasmRelocationEntry> CodeRelocations; 188 // Relocations for fixing up references in the data section. 189 std::vector<WasmRelocationEntry> DataRelocations; 190 191 // Index values to use for fixing up call_indirect type indices. 192 // Maps function symbols to the index of the type of the function 193 DenseMap<const MCSymbolWasm *, uint32_t> TypeIndices; 194 // Maps function symbols to the table element index space. Used 195 // for TABLE_INDEX relocation types (i.e. address taken functions). 196 DenseMap<const MCSymbolWasm *, uint32_t> TableIndices; 197 // Maps function/global/table symbols to the 198 // function/global/table/event/section index space. 199 DenseMap<const MCSymbolWasm *, uint32_t> WasmIndices; 200 DenseMap<const MCSymbolWasm *, uint32_t> GOTIndices; 201 // Maps data symbols to the Wasm segment and offset/size with the segment. 202 DenseMap<const MCSymbolWasm *, wasm::WasmDataReference> DataLocations; 203 204 // Stores output data (index, relocations, content offset) for custom 205 // section. 206 std::vector<WasmCustomSection> CustomSections; 207 std::unique_ptr<WasmCustomSection> ProducersSection; 208 std::unique_ptr<WasmCustomSection> TargetFeaturesSection; 209 // Relocations for fixing up references in the custom sections. 210 DenseMap<const MCSectionWasm *, std::vector<WasmRelocationEntry>> 211 CustomSectionsRelocations; 212 213 // Map from section to defining function symbol. 214 DenseMap<const MCSection *, const MCSymbol *> SectionFunctions; 215 216 DenseMap<wasm::WasmSignature, uint32_t> SignatureIndices; 217 SmallVector<wasm::WasmSignature, 4> Signatures; 218 SmallVector<WasmDataSegment, 4> DataSegments; 219 unsigned NumFunctionImports = 0; 220 unsigned NumGlobalImports = 0; 221 unsigned NumTableImports = 0; 222 unsigned NumEventImports = 0; 223 uint32_t SectionCount = 0; 224 225 enum class DwoMode { 226 AllSections, 227 NonDwoOnly, 228 DwoOnly, 229 }; 230 bool IsSplitDwarf = false; 231 raw_pwrite_stream *OS = nullptr; 232 raw_pwrite_stream *DwoOS = nullptr; 233 234 // TargetObjectWriter wranppers. 235 bool is64Bit() const { return TargetObjectWriter->is64Bit(); } 236 bool isEmscripten() const { return TargetObjectWriter->isEmscripten(); } 237 238 void startSection(SectionBookkeeping &Section, unsigned SectionId); 239 void startCustomSection(SectionBookkeeping &Section, StringRef Name); 240 void endSection(SectionBookkeeping &Section); 241 242 public: 243 WasmObjectWriter(std::unique_ptr<MCWasmObjectTargetWriter> MOTW, 244 raw_pwrite_stream &OS_) 245 : TargetObjectWriter(std::move(MOTW)), OS(&OS_) {} 246 247 WasmObjectWriter(std::unique_ptr<MCWasmObjectTargetWriter> MOTW, 248 raw_pwrite_stream &OS_, raw_pwrite_stream &DwoOS_) 249 : TargetObjectWriter(std::move(MOTW)), IsSplitDwarf(true), OS(&OS_), 250 DwoOS(&DwoOS_) {} 251 252 private: 253 void reset() override { 254 CodeRelocations.clear(); 255 DataRelocations.clear(); 256 TypeIndices.clear(); 257 WasmIndices.clear(); 258 GOTIndices.clear(); 259 TableIndices.clear(); 260 DataLocations.clear(); 261 CustomSections.clear(); 262 ProducersSection.reset(); 263 TargetFeaturesSection.reset(); 264 CustomSectionsRelocations.clear(); 265 SignatureIndices.clear(); 266 Signatures.clear(); 267 DataSegments.clear(); 268 SectionFunctions.clear(); 269 NumFunctionImports = 0; 270 NumGlobalImports = 0; 271 NumTableImports = 0; 272 MCObjectWriter::reset(); 273 } 274 275 void writeHeader(const MCAssembler &Asm); 276 277 void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout, 278 const MCFragment *Fragment, const MCFixup &Fixup, 279 MCValue Target, uint64_t &FixedValue) override; 280 281 void executePostLayoutBinding(MCAssembler &Asm, 282 const MCAsmLayout &Layout) override; 283 void prepareImports(SmallVectorImpl<wasm::WasmImport> &Imports, 284 MCAssembler &Asm, const MCAsmLayout &Layout); 285 uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override; 286 287 uint64_t writeOneObject(MCAssembler &Asm, const MCAsmLayout &Layout, 288 DwoMode Mode); 289 290 void writeString(const StringRef Str) { 291 encodeULEB128(Str.size(), W->OS); 292 W->OS << Str; 293 } 294 295 void writeI32(int32_t val) { 296 char Buffer[4]; 297 support::endian::write32le(Buffer, val); 298 W->OS.write(Buffer, sizeof(Buffer)); 299 } 300 301 void writeI64(int64_t val) { 302 char Buffer[8]; 303 support::endian::write64le(Buffer, val); 304 W->OS.write(Buffer, sizeof(Buffer)); 305 } 306 307 void writeValueType(wasm::ValType Ty) { W->OS << static_cast<char>(Ty); } 308 309 void writeTypeSection(ArrayRef<wasm::WasmSignature> Signatures); 310 void writeImportSection(ArrayRef<wasm::WasmImport> Imports, uint64_t DataSize, 311 uint32_t NumElements); 312 void writeFunctionSection(ArrayRef<WasmFunction> Functions); 313 void writeExportSection(ArrayRef<wasm::WasmExport> Exports); 314 void writeElemSection(ArrayRef<uint32_t> TableElems); 315 void writeDataCountSection(); 316 uint32_t writeCodeSection(const MCAssembler &Asm, const MCAsmLayout &Layout, 317 ArrayRef<WasmFunction> Functions); 318 uint32_t writeDataSection(const MCAsmLayout &Layout); 319 void writeEventSection(ArrayRef<wasm::WasmEventType> Events); 320 void writeGlobalSection(ArrayRef<wasm::WasmGlobal> Globals); 321 void writeTableSection(ArrayRef<wasm::WasmTable> Tables); 322 void writeRelocSection(uint32_t SectionIndex, StringRef Name, 323 std::vector<WasmRelocationEntry> &Relocations); 324 void writeLinkingMetaDataSection( 325 ArrayRef<wasm::WasmSymbolInfo> SymbolInfos, 326 ArrayRef<std::pair<uint16_t, uint32_t>> InitFuncs, 327 const std::map<StringRef, std::vector<WasmComdatEntry>> &Comdats); 328 void writeCustomSection(WasmCustomSection &CustomSection, 329 const MCAssembler &Asm, const MCAsmLayout &Layout); 330 void writeCustomRelocSections(); 331 332 uint64_t getProvisionalValue(const WasmRelocationEntry &RelEntry, 333 const MCAsmLayout &Layout); 334 void applyRelocations(ArrayRef<WasmRelocationEntry> Relocations, 335 uint64_t ContentsOffset, const MCAsmLayout &Layout); 336 337 uint32_t getRelocationIndexValue(const WasmRelocationEntry &RelEntry); 338 uint32_t getFunctionType(const MCSymbolWasm &Symbol); 339 uint32_t getEventType(const MCSymbolWasm &Symbol); 340 void registerFunctionType(const MCSymbolWasm &Symbol); 341 void registerEventType(const MCSymbolWasm &Symbol); 342 }; 343 344 } // end anonymous namespace 345 346 // Write out a section header and a patchable section size field. 347 void WasmObjectWriter::startSection(SectionBookkeeping &Section, 348 unsigned SectionId) { 349 LLVM_DEBUG(dbgs() << "startSection " << SectionId << "\n"); 350 W->OS << char(SectionId); 351 352 Section.SizeOffset = W->OS.tell(); 353 354 // The section size. We don't know the size yet, so reserve enough space 355 // for any 32-bit value; we'll patch it later. 356 encodeULEB128(0, W->OS, 5); 357 358 // The position where the section starts, for measuring its size. 359 Section.ContentsOffset = W->OS.tell(); 360 Section.PayloadOffset = W->OS.tell(); 361 Section.Index = SectionCount++; 362 } 363 364 void WasmObjectWriter::startCustomSection(SectionBookkeeping &Section, 365 StringRef Name) { 366 LLVM_DEBUG(dbgs() << "startCustomSection " << Name << "\n"); 367 startSection(Section, wasm::WASM_SEC_CUSTOM); 368 369 // The position where the section header ends, for measuring its size. 370 Section.PayloadOffset = W->OS.tell(); 371 372 // Custom sections in wasm also have a string identifier. 373 writeString(Name); 374 375 // The position where the custom section starts. 376 Section.ContentsOffset = W->OS.tell(); 377 } 378 379 // Now that the section is complete and we know how big it is, patch up the 380 // section size field at the start of the section. 381 void WasmObjectWriter::endSection(SectionBookkeeping &Section) { 382 uint64_t Size = W->OS.tell(); 383 // /dev/null doesn't support seek/tell and can report offset of 0. 384 // Simply skip this patching in that case. 385 if (!Size) 386 return; 387 388 Size -= Section.PayloadOffset; 389 if (uint32_t(Size) != Size) 390 report_fatal_error("section size does not fit in a uint32_t"); 391 392 LLVM_DEBUG(dbgs() << "endSection size=" << Size << "\n"); 393 394 // Write the final section size to the payload_len field, which follows 395 // the section id byte. 396 writePatchableLEB<5>(static_cast<raw_pwrite_stream &>(W->OS), Size, 397 Section.SizeOffset); 398 } 399 400 // Emit the Wasm header. 401 void WasmObjectWriter::writeHeader(const MCAssembler &Asm) { 402 W->OS.write(wasm::WasmMagic, sizeof(wasm::WasmMagic)); 403 W->write<uint32_t>(wasm::WasmVersion); 404 } 405 406 void WasmObjectWriter::executePostLayoutBinding(MCAssembler &Asm, 407 const MCAsmLayout &Layout) { 408 // As a stopgap measure until call_indirect instructions start explicitly 409 // referencing the indirect function table via TABLE_NUMBER relocs, ensure 410 // that the indirect function table import makes it to the output if anything 411 // in the compilation unit has caused it to be present. 412 if (auto *Sym = Asm.getContext().lookupSymbol("__indirect_function_table")) 413 Asm.registerSymbol(*Sym); 414 415 // Build a map of sections to the function that defines them, for use 416 // in recordRelocation. 417 for (const MCSymbol &S : Asm.symbols()) { 418 const auto &WS = static_cast<const MCSymbolWasm &>(S); 419 if (WS.isDefined() && WS.isFunction() && !WS.isVariable()) { 420 const auto &Sec = static_cast<const MCSectionWasm &>(S.getSection()); 421 auto Pair = SectionFunctions.insert(std::make_pair(&Sec, &S)); 422 if (!Pair.second) 423 report_fatal_error("section already has a defining function: " + 424 Sec.getName()); 425 } 426 } 427 } 428 429 void WasmObjectWriter::recordRelocation(MCAssembler &Asm, 430 const MCAsmLayout &Layout, 431 const MCFragment *Fragment, 432 const MCFixup &Fixup, MCValue Target, 433 uint64_t &FixedValue) { 434 // The WebAssembly backend should never generate FKF_IsPCRel fixups 435 assert(!(Asm.getBackend().getFixupKindInfo(Fixup.getKind()).Flags & 436 MCFixupKindInfo::FKF_IsPCRel)); 437 438 const auto &FixupSection = cast<MCSectionWasm>(*Fragment->getParent()); 439 uint64_t C = Target.getConstant(); 440 uint64_t FixupOffset = Layout.getFragmentOffset(Fragment) + Fixup.getOffset(); 441 MCContext &Ctx = Asm.getContext(); 442 443 if (const MCSymbolRefExpr *RefB = Target.getSymB()) { 444 // To get here the A - B expression must have failed evaluateAsRelocatable. 445 // This means either A or B must be undefined and in WebAssembly we can't 446 // support either of those cases. 447 const auto &SymB = cast<MCSymbolWasm>(RefB->getSymbol()); 448 Ctx.reportError( 449 Fixup.getLoc(), 450 Twine("symbol '") + SymB.getName() + 451 "': unsupported subtraction expression used in relocation."); 452 return; 453 } 454 455 // We either rejected the fixup or folded B into C at this point. 456 const MCSymbolRefExpr *RefA = Target.getSymA(); 457 const auto *SymA = cast<MCSymbolWasm>(&RefA->getSymbol()); 458 459 // The .init_array isn't translated as data, so don't do relocations in it. 460 if (FixupSection.getName().startswith(".init_array")) { 461 SymA->setUsedInInitArray(); 462 return; 463 } 464 465 if (SymA->isVariable()) { 466 const MCExpr *Expr = SymA->getVariableValue(); 467 if (const auto *Inner = dyn_cast<MCSymbolRefExpr>(Expr)) 468 if (Inner->getKind() == MCSymbolRefExpr::VK_WEAKREF) 469 llvm_unreachable("weakref used in reloc not yet implemented"); 470 } 471 472 // Put any constant offset in an addend. Offsets can be negative, and 473 // LLVM expects wrapping, in contrast to wasm's immediates which can't 474 // be negative and don't wrap. 475 FixedValue = 0; 476 477 unsigned Type = TargetObjectWriter->getRelocType(Target, Fixup); 478 479 // Absolute offset within a section or a function. 480 // Currently only supported for for metadata sections. 481 // See: test/MC/WebAssembly/blockaddress.ll 482 if (Type == wasm::R_WASM_FUNCTION_OFFSET_I32 || 483 Type == wasm::R_WASM_FUNCTION_OFFSET_I64 || 484 Type == wasm::R_WASM_SECTION_OFFSET_I32) { 485 if (!FixupSection.getKind().isMetadata()) 486 report_fatal_error("relocations for function or section offsets are " 487 "only supported in metadata sections"); 488 489 const MCSymbol *SectionSymbol = nullptr; 490 const MCSection &SecA = SymA->getSection(); 491 if (SecA.getKind().isText()) 492 SectionSymbol = SectionFunctions.find(&SecA)->second; 493 else 494 SectionSymbol = SecA.getBeginSymbol(); 495 if (!SectionSymbol) 496 report_fatal_error("section symbol is required for relocation"); 497 498 C += Layout.getSymbolOffset(*SymA); 499 SymA = cast<MCSymbolWasm>(SectionSymbol); 500 } 501 502 if (Type == wasm::R_WASM_TABLE_INDEX_REL_SLEB || 503 Type == wasm::R_WASM_TABLE_INDEX_SLEB || 504 Type == wasm::R_WASM_TABLE_INDEX_SLEB64 || 505 Type == wasm::R_WASM_TABLE_INDEX_I32 || 506 Type == wasm::R_WASM_TABLE_INDEX_I64) { 507 // TABLE_INDEX relocs implicitly use the default indirect function table. 508 auto TableName = "__indirect_function_table"; 509 MCSymbolWasm *Sym = cast_or_null<MCSymbolWasm>(Ctx.lookupSymbol(TableName)); 510 if (Sym) { 511 if (!Sym->isFunctionTable()) 512 Ctx.reportError( 513 Fixup.getLoc(), 514 "symbol '__indirect_function_table' is not a function table"); 515 } else { 516 Sym = cast<MCSymbolWasm>(Ctx.getOrCreateSymbol(TableName)); 517 Sym->setFunctionTable(); 518 // The default function table is synthesized by the linker. 519 Sym->setUndefined(); 520 } 521 Sym->setUsedInReloc(); 522 Asm.registerSymbol(*Sym); 523 } 524 525 // Relocation other than R_WASM_TYPE_INDEX_LEB are required to be 526 // against a named symbol. 527 if (Type != wasm::R_WASM_TYPE_INDEX_LEB) { 528 if (SymA->getName().empty()) 529 report_fatal_error("relocations against un-named temporaries are not yet " 530 "supported by wasm"); 531 532 SymA->setUsedInReloc(); 533 } 534 535 if (RefA->getKind() == MCSymbolRefExpr::VK_GOT) 536 SymA->setUsedInGOT(); 537 538 WasmRelocationEntry Rec(FixupOffset, SymA, C, Type, &FixupSection); 539 LLVM_DEBUG(dbgs() << "WasmReloc: " << Rec << "\n"); 540 541 if (FixupSection.isWasmData()) { 542 DataRelocations.push_back(Rec); 543 } else if (FixupSection.getKind().isText()) { 544 CodeRelocations.push_back(Rec); 545 } else if (FixupSection.getKind().isMetadata()) { 546 CustomSectionsRelocations[&FixupSection].push_back(Rec); 547 } else { 548 llvm_unreachable("unexpected section type"); 549 } 550 } 551 552 // Compute a value to write into the code at the location covered 553 // by RelEntry. This value isn't used by the static linker; it just serves 554 // to make the object format more readable and more likely to be directly 555 // useable. 556 uint64_t 557 WasmObjectWriter::getProvisionalValue(const WasmRelocationEntry &RelEntry, 558 const MCAsmLayout &Layout) { 559 if ((RelEntry.Type == wasm::R_WASM_GLOBAL_INDEX_LEB || 560 RelEntry.Type == wasm::R_WASM_GLOBAL_INDEX_I32) && 561 !RelEntry.Symbol->isGlobal()) { 562 assert(GOTIndices.count(RelEntry.Symbol) > 0 && "symbol not found in GOT index space"); 563 return GOTIndices[RelEntry.Symbol]; 564 } 565 566 switch (RelEntry.Type) { 567 case wasm::R_WASM_TABLE_INDEX_REL_SLEB: 568 case wasm::R_WASM_TABLE_INDEX_SLEB: 569 case wasm::R_WASM_TABLE_INDEX_SLEB64: 570 case wasm::R_WASM_TABLE_INDEX_I32: 571 case wasm::R_WASM_TABLE_INDEX_I64: { 572 // Provisional value is table address of the resolved symbol itself 573 const MCSymbolWasm *Base = 574 cast<MCSymbolWasm>(Layout.getBaseSymbol(*RelEntry.Symbol)); 575 assert(Base->isFunction()); 576 if (RelEntry.Type == wasm::R_WASM_TABLE_INDEX_REL_SLEB) 577 return TableIndices[Base] - InitialTableOffset; 578 else 579 return TableIndices[Base]; 580 } 581 case wasm::R_WASM_TYPE_INDEX_LEB: 582 // Provisional value is same as the index 583 return getRelocationIndexValue(RelEntry); 584 case wasm::R_WASM_FUNCTION_INDEX_LEB: 585 case wasm::R_WASM_GLOBAL_INDEX_LEB: 586 case wasm::R_WASM_GLOBAL_INDEX_I32: 587 case wasm::R_WASM_EVENT_INDEX_LEB: 588 case wasm::R_WASM_TABLE_NUMBER_LEB: 589 // Provisional value is function/global/event Wasm index 590 assert(WasmIndices.count(RelEntry.Symbol) > 0 && "symbol not found in wasm index space"); 591 return WasmIndices[RelEntry.Symbol]; 592 case wasm::R_WASM_FUNCTION_OFFSET_I32: 593 case wasm::R_WASM_FUNCTION_OFFSET_I64: 594 case wasm::R_WASM_SECTION_OFFSET_I32: { 595 const auto &Section = 596 static_cast<const MCSectionWasm &>(RelEntry.Symbol->getSection()); 597 return Section.getSectionOffset() + RelEntry.Addend; 598 } 599 case wasm::R_WASM_MEMORY_ADDR_LEB: 600 case wasm::R_WASM_MEMORY_ADDR_LEB64: 601 case wasm::R_WASM_MEMORY_ADDR_SLEB: 602 case wasm::R_WASM_MEMORY_ADDR_SLEB64: 603 case wasm::R_WASM_MEMORY_ADDR_REL_SLEB: 604 case wasm::R_WASM_MEMORY_ADDR_REL_SLEB64: 605 case wasm::R_WASM_MEMORY_ADDR_I32: 606 case wasm::R_WASM_MEMORY_ADDR_I64: 607 case wasm::R_WASM_MEMORY_ADDR_TLS_SLEB: { 608 // Provisional value is address of the global plus the offset 609 const MCSymbolWasm *Base = 610 cast<MCSymbolWasm>(Layout.getBaseSymbol(*RelEntry.Symbol)); 611 // For undefined symbols, use zero 612 if (!Base->isDefined()) 613 return 0; 614 const wasm::WasmDataReference &BaseRef = DataLocations[Base], 615 &SymRef = DataLocations[RelEntry.Symbol]; 616 const WasmDataSegment &Segment = DataSegments[BaseRef.Segment]; 617 // Ignore overflow. LLVM allows address arithmetic to silently wrap. 618 return Segment.Offset + BaseRef.Offset + SymRef.Offset + RelEntry.Addend; 619 } 620 default: 621 llvm_unreachable("invalid relocation type"); 622 } 623 } 624 625 static void addData(SmallVectorImpl<char> &DataBytes, 626 MCSectionWasm &DataSection) { 627 LLVM_DEBUG(errs() << "addData: " << DataSection.getName() << "\n"); 628 629 DataBytes.resize(alignTo(DataBytes.size(), DataSection.getAlignment())); 630 631 for (const MCFragment &Frag : DataSection) { 632 if (Frag.hasInstructions()) 633 report_fatal_error("only data supported in data sections"); 634 635 if (auto *Align = dyn_cast<MCAlignFragment>(&Frag)) { 636 if (Align->getValueSize() != 1) 637 report_fatal_error("only byte values supported for alignment"); 638 // If nops are requested, use zeros, as this is the data section. 639 uint8_t Value = Align->hasEmitNops() ? 0 : Align->getValue(); 640 uint64_t Size = 641 std::min<uint64_t>(alignTo(DataBytes.size(), Align->getAlignment()), 642 DataBytes.size() + Align->getMaxBytesToEmit()); 643 DataBytes.resize(Size, Value); 644 } else if (auto *Fill = dyn_cast<MCFillFragment>(&Frag)) { 645 int64_t NumValues; 646 if (!Fill->getNumValues().evaluateAsAbsolute(NumValues)) 647 llvm_unreachable("The fill should be an assembler constant"); 648 DataBytes.insert(DataBytes.end(), Fill->getValueSize() * NumValues, 649 Fill->getValue()); 650 } else if (auto *LEB = dyn_cast<MCLEBFragment>(&Frag)) { 651 const SmallVectorImpl<char> &Contents = LEB->getContents(); 652 llvm::append_range(DataBytes, Contents); 653 } else { 654 const auto &DataFrag = cast<MCDataFragment>(Frag); 655 const SmallVectorImpl<char> &Contents = DataFrag.getContents(); 656 llvm::append_range(DataBytes, Contents); 657 } 658 } 659 660 LLVM_DEBUG(dbgs() << "addData -> " << DataBytes.size() << "\n"); 661 } 662 663 uint32_t 664 WasmObjectWriter::getRelocationIndexValue(const WasmRelocationEntry &RelEntry) { 665 if (RelEntry.Type == wasm::R_WASM_TYPE_INDEX_LEB) { 666 if (!TypeIndices.count(RelEntry.Symbol)) 667 report_fatal_error("symbol not found in type index space: " + 668 RelEntry.Symbol->getName()); 669 return TypeIndices[RelEntry.Symbol]; 670 } 671 672 return RelEntry.Symbol->getIndex(); 673 } 674 675 // Apply the portions of the relocation records that we can handle ourselves 676 // directly. 677 void WasmObjectWriter::applyRelocations( 678 ArrayRef<WasmRelocationEntry> Relocations, uint64_t ContentsOffset, 679 const MCAsmLayout &Layout) { 680 auto &Stream = static_cast<raw_pwrite_stream &>(W->OS); 681 for (const WasmRelocationEntry &RelEntry : Relocations) { 682 uint64_t Offset = ContentsOffset + 683 RelEntry.FixupSection->getSectionOffset() + 684 RelEntry.Offset; 685 686 LLVM_DEBUG(dbgs() << "applyRelocation: " << RelEntry << "\n"); 687 auto Value = getProvisionalValue(RelEntry, Layout); 688 689 switch (RelEntry.Type) { 690 case wasm::R_WASM_FUNCTION_INDEX_LEB: 691 case wasm::R_WASM_TYPE_INDEX_LEB: 692 case wasm::R_WASM_GLOBAL_INDEX_LEB: 693 case wasm::R_WASM_MEMORY_ADDR_LEB: 694 case wasm::R_WASM_EVENT_INDEX_LEB: 695 case wasm::R_WASM_TABLE_NUMBER_LEB: 696 writePatchableLEB<5>(Stream, Value, Offset); 697 break; 698 case wasm::R_WASM_MEMORY_ADDR_LEB64: 699 writePatchableLEB<10>(Stream, Value, Offset); 700 break; 701 case wasm::R_WASM_TABLE_INDEX_I32: 702 case wasm::R_WASM_MEMORY_ADDR_I32: 703 case wasm::R_WASM_FUNCTION_OFFSET_I32: 704 case wasm::R_WASM_SECTION_OFFSET_I32: 705 case wasm::R_WASM_GLOBAL_INDEX_I32: 706 patchI32(Stream, Value, Offset); 707 break; 708 case wasm::R_WASM_TABLE_INDEX_I64: 709 case wasm::R_WASM_MEMORY_ADDR_I64: 710 case wasm::R_WASM_FUNCTION_OFFSET_I64: 711 patchI64(Stream, Value, Offset); 712 break; 713 case wasm::R_WASM_TABLE_INDEX_SLEB: 714 case wasm::R_WASM_TABLE_INDEX_REL_SLEB: 715 case wasm::R_WASM_MEMORY_ADDR_SLEB: 716 case wasm::R_WASM_MEMORY_ADDR_REL_SLEB: 717 case wasm::R_WASM_MEMORY_ADDR_TLS_SLEB: 718 writePatchableSLEB<5>(Stream, Value, Offset); 719 break; 720 case wasm::R_WASM_TABLE_INDEX_SLEB64: 721 case wasm::R_WASM_MEMORY_ADDR_SLEB64: 722 case wasm::R_WASM_MEMORY_ADDR_REL_SLEB64: 723 writePatchableSLEB<10>(Stream, Value, Offset); 724 break; 725 default: 726 llvm_unreachable("invalid relocation type"); 727 } 728 } 729 } 730 731 void WasmObjectWriter::writeTypeSection( 732 ArrayRef<wasm::WasmSignature> Signatures) { 733 if (Signatures.empty()) 734 return; 735 736 SectionBookkeeping Section; 737 startSection(Section, wasm::WASM_SEC_TYPE); 738 739 encodeULEB128(Signatures.size(), W->OS); 740 741 for (const wasm::WasmSignature &Sig : Signatures) { 742 W->OS << char(wasm::WASM_TYPE_FUNC); 743 encodeULEB128(Sig.Params.size(), W->OS); 744 for (wasm::ValType Ty : Sig.Params) 745 writeValueType(Ty); 746 encodeULEB128(Sig.Returns.size(), W->OS); 747 for (wasm::ValType Ty : Sig.Returns) 748 writeValueType(Ty); 749 } 750 751 endSection(Section); 752 } 753 754 void WasmObjectWriter::writeImportSection(ArrayRef<wasm::WasmImport> Imports, 755 uint64_t DataSize, 756 uint32_t NumElements) { 757 if (Imports.empty()) 758 return; 759 760 uint64_t NumPages = (DataSize + wasm::WasmPageSize - 1) / wasm::WasmPageSize; 761 762 SectionBookkeeping Section; 763 startSection(Section, wasm::WASM_SEC_IMPORT); 764 765 encodeULEB128(Imports.size(), W->OS); 766 for (const wasm::WasmImport &Import : Imports) { 767 writeString(Import.Module); 768 writeString(Import.Field); 769 W->OS << char(Import.Kind); 770 771 switch (Import.Kind) { 772 case wasm::WASM_EXTERNAL_FUNCTION: 773 encodeULEB128(Import.SigIndex, W->OS); 774 break; 775 case wasm::WASM_EXTERNAL_GLOBAL: 776 W->OS << char(Import.Global.Type); 777 W->OS << char(Import.Global.Mutable ? 1 : 0); 778 break; 779 case wasm::WASM_EXTERNAL_MEMORY: 780 encodeULEB128(Import.Memory.Flags, W->OS); 781 encodeULEB128(NumPages, W->OS); // initial 782 break; 783 case wasm::WASM_EXTERNAL_TABLE: 784 W->OS << char(Import.Table.ElemType); 785 encodeULEB128(0, W->OS); // flags 786 encodeULEB128(NumElements, W->OS); // initial 787 break; 788 case wasm::WASM_EXTERNAL_EVENT: 789 encodeULEB128(Import.Event.Attribute, W->OS); 790 encodeULEB128(Import.Event.SigIndex, W->OS); 791 break; 792 default: 793 llvm_unreachable("unsupported import kind"); 794 } 795 } 796 797 endSection(Section); 798 } 799 800 void WasmObjectWriter::writeFunctionSection(ArrayRef<WasmFunction> Functions) { 801 if (Functions.empty()) 802 return; 803 804 SectionBookkeeping Section; 805 startSection(Section, wasm::WASM_SEC_FUNCTION); 806 807 encodeULEB128(Functions.size(), W->OS); 808 for (const WasmFunction &Func : Functions) 809 encodeULEB128(Func.SigIndex, W->OS); 810 811 endSection(Section); 812 } 813 814 void WasmObjectWriter::writeEventSection(ArrayRef<wasm::WasmEventType> Events) { 815 if (Events.empty()) 816 return; 817 818 SectionBookkeeping Section; 819 startSection(Section, wasm::WASM_SEC_EVENT); 820 821 encodeULEB128(Events.size(), W->OS); 822 for (const wasm::WasmEventType &Event : Events) { 823 encodeULEB128(Event.Attribute, W->OS); 824 encodeULEB128(Event.SigIndex, W->OS); 825 } 826 827 endSection(Section); 828 } 829 830 void WasmObjectWriter::writeGlobalSection(ArrayRef<wasm::WasmGlobal> Globals) { 831 if (Globals.empty()) 832 return; 833 834 SectionBookkeeping Section; 835 startSection(Section, wasm::WASM_SEC_GLOBAL); 836 837 encodeULEB128(Globals.size(), W->OS); 838 for (const wasm::WasmGlobal &Global : Globals) { 839 encodeULEB128(Global.Type.Type, W->OS); 840 W->OS << char(Global.Type.Mutable); 841 W->OS << char(Global.InitExpr.Opcode); 842 switch (Global.Type.Type) { 843 case wasm::WASM_TYPE_I32: 844 encodeSLEB128(0, W->OS); 845 break; 846 case wasm::WASM_TYPE_I64: 847 encodeSLEB128(0, W->OS); 848 break; 849 case wasm::WASM_TYPE_F32: 850 writeI32(0); 851 break; 852 case wasm::WASM_TYPE_F64: 853 writeI64(0); 854 break; 855 case wasm::WASM_TYPE_EXTERNREF: 856 writeValueType(wasm::ValType::EXTERNREF); 857 break; 858 default: 859 llvm_unreachable("unexpected type"); 860 } 861 W->OS << char(wasm::WASM_OPCODE_END); 862 } 863 864 endSection(Section); 865 } 866 867 void WasmObjectWriter::writeTableSection(ArrayRef<wasm::WasmTable> Tables) { 868 if (Tables.empty()) 869 return; 870 871 SectionBookkeeping Section; 872 startSection(Section, wasm::WASM_SEC_TABLE); 873 874 encodeULEB128(Tables.size(), W->OS); 875 for (const wasm::WasmTable &Table : Tables) { 876 encodeULEB128(Table.Type.ElemType, W->OS); 877 encodeULEB128(Table.Type.Limits.Flags, W->OS); 878 encodeULEB128(Table.Type.Limits.Initial, W->OS); 879 if (Table.Type.Limits.Flags & wasm::WASM_LIMITS_FLAG_HAS_MAX) 880 encodeULEB128(Table.Type.Limits.Maximum, W->OS); 881 } 882 endSection(Section); 883 } 884 885 void WasmObjectWriter::writeExportSection(ArrayRef<wasm::WasmExport> Exports) { 886 if (Exports.empty()) 887 return; 888 889 SectionBookkeeping Section; 890 startSection(Section, wasm::WASM_SEC_EXPORT); 891 892 encodeULEB128(Exports.size(), W->OS); 893 for (const wasm::WasmExport &Export : Exports) { 894 writeString(Export.Name); 895 W->OS << char(Export.Kind); 896 encodeULEB128(Export.Index, W->OS); 897 } 898 899 endSection(Section); 900 } 901 902 void WasmObjectWriter::writeElemSection(ArrayRef<uint32_t> TableElems) { 903 if (TableElems.empty()) 904 return; 905 906 SectionBookkeeping Section; 907 startSection(Section, wasm::WASM_SEC_ELEM); 908 909 encodeULEB128(1, W->OS); // number of "segments" 910 encodeULEB128(0, W->OS); // the table index 911 912 // init expr for starting offset 913 W->OS << char(wasm::WASM_OPCODE_I32_CONST); 914 encodeSLEB128(InitialTableOffset, W->OS); 915 W->OS << char(wasm::WASM_OPCODE_END); 916 917 encodeULEB128(TableElems.size(), W->OS); 918 for (uint32_t Elem : TableElems) 919 encodeULEB128(Elem, W->OS); 920 921 endSection(Section); 922 } 923 924 void WasmObjectWriter::writeDataCountSection() { 925 if (DataSegments.empty()) 926 return; 927 928 SectionBookkeeping Section; 929 startSection(Section, wasm::WASM_SEC_DATACOUNT); 930 encodeULEB128(DataSegments.size(), W->OS); 931 endSection(Section); 932 } 933 934 uint32_t WasmObjectWriter::writeCodeSection(const MCAssembler &Asm, 935 const MCAsmLayout &Layout, 936 ArrayRef<WasmFunction> Functions) { 937 if (Functions.empty()) 938 return 0; 939 940 SectionBookkeeping Section; 941 startSection(Section, wasm::WASM_SEC_CODE); 942 943 encodeULEB128(Functions.size(), W->OS); 944 945 for (const WasmFunction &Func : Functions) { 946 auto &FuncSection = static_cast<MCSectionWasm &>(Func.Sym->getSection()); 947 948 int64_t Size = 0; 949 if (!Func.Sym->getSize()->evaluateAsAbsolute(Size, Layout)) 950 report_fatal_error(".size expression must be evaluatable"); 951 952 encodeULEB128(Size, W->OS); 953 FuncSection.setSectionOffset(W->OS.tell() - Section.ContentsOffset); 954 Asm.writeSectionData(W->OS, &FuncSection, Layout); 955 } 956 957 // Apply fixups. 958 applyRelocations(CodeRelocations, Section.ContentsOffset, Layout); 959 960 endSection(Section); 961 return Section.Index; 962 } 963 964 uint32_t WasmObjectWriter::writeDataSection(const MCAsmLayout &Layout) { 965 if (DataSegments.empty()) 966 return 0; 967 968 SectionBookkeeping Section; 969 startSection(Section, wasm::WASM_SEC_DATA); 970 971 encodeULEB128(DataSegments.size(), W->OS); // count 972 973 for (const WasmDataSegment &Segment : DataSegments) { 974 encodeULEB128(Segment.InitFlags, W->OS); // flags 975 if (Segment.InitFlags & wasm::WASM_DATA_SEGMENT_HAS_MEMINDEX) 976 encodeULEB128(0, W->OS); // memory index 977 if ((Segment.InitFlags & wasm::WASM_DATA_SEGMENT_IS_PASSIVE) == 0) { 978 W->OS << char(Segment.Offset > INT32_MAX ? wasm::WASM_OPCODE_I64_CONST 979 : wasm::WASM_OPCODE_I32_CONST); 980 encodeSLEB128(Segment.Offset, W->OS); // offset 981 W->OS << char(wasm::WASM_OPCODE_END); 982 } 983 encodeULEB128(Segment.Data.size(), W->OS); // size 984 Segment.Section->setSectionOffset(W->OS.tell() - Section.ContentsOffset); 985 W->OS << Segment.Data; // data 986 } 987 988 // Apply fixups. 989 applyRelocations(DataRelocations, Section.ContentsOffset, Layout); 990 991 endSection(Section); 992 return Section.Index; 993 } 994 995 void WasmObjectWriter::writeRelocSection( 996 uint32_t SectionIndex, StringRef Name, 997 std::vector<WasmRelocationEntry> &Relocs) { 998 // See: https://github.com/WebAssembly/tool-conventions/blob/master/Linking.md 999 // for descriptions of the reloc sections. 1000 1001 if (Relocs.empty()) 1002 return; 1003 1004 // First, ensure the relocations are sorted in offset order. In general they 1005 // should already be sorted since `recordRelocation` is called in offset 1006 // order, but for the code section we combine many MC sections into single 1007 // wasm section, and this order is determined by the order of Asm.Symbols() 1008 // not the sections order. 1009 llvm::stable_sort( 1010 Relocs, [](const WasmRelocationEntry &A, const WasmRelocationEntry &B) { 1011 return (A.Offset + A.FixupSection->getSectionOffset()) < 1012 (B.Offset + B.FixupSection->getSectionOffset()); 1013 }); 1014 1015 SectionBookkeeping Section; 1016 startCustomSection(Section, std::string("reloc.") + Name.str()); 1017 1018 encodeULEB128(SectionIndex, W->OS); 1019 encodeULEB128(Relocs.size(), W->OS); 1020 for (const WasmRelocationEntry &RelEntry : Relocs) { 1021 uint64_t Offset = 1022 RelEntry.Offset + RelEntry.FixupSection->getSectionOffset(); 1023 uint32_t Index = getRelocationIndexValue(RelEntry); 1024 1025 W->OS << char(RelEntry.Type); 1026 encodeULEB128(Offset, W->OS); 1027 encodeULEB128(Index, W->OS); 1028 if (RelEntry.hasAddend()) 1029 encodeSLEB128(RelEntry.Addend, W->OS); 1030 } 1031 1032 endSection(Section); 1033 } 1034 1035 void WasmObjectWriter::writeCustomRelocSections() { 1036 for (const auto &Sec : CustomSections) { 1037 auto &Relocations = CustomSectionsRelocations[Sec.Section]; 1038 writeRelocSection(Sec.OutputIndex, Sec.Name, Relocations); 1039 } 1040 } 1041 1042 void WasmObjectWriter::writeLinkingMetaDataSection( 1043 ArrayRef<wasm::WasmSymbolInfo> SymbolInfos, 1044 ArrayRef<std::pair<uint16_t, uint32_t>> InitFuncs, 1045 const std::map<StringRef, std::vector<WasmComdatEntry>> &Comdats) { 1046 SectionBookkeeping Section; 1047 startCustomSection(Section, "linking"); 1048 encodeULEB128(wasm::WasmMetadataVersion, W->OS); 1049 1050 SectionBookkeeping SubSection; 1051 if (SymbolInfos.size() != 0) { 1052 startSection(SubSection, wasm::WASM_SYMBOL_TABLE); 1053 encodeULEB128(SymbolInfos.size(), W->OS); 1054 for (const wasm::WasmSymbolInfo &Sym : SymbolInfos) { 1055 encodeULEB128(Sym.Kind, W->OS); 1056 encodeULEB128(Sym.Flags, W->OS); 1057 switch (Sym.Kind) { 1058 case wasm::WASM_SYMBOL_TYPE_FUNCTION: 1059 case wasm::WASM_SYMBOL_TYPE_GLOBAL: 1060 case wasm::WASM_SYMBOL_TYPE_EVENT: 1061 case wasm::WASM_SYMBOL_TYPE_TABLE: 1062 encodeULEB128(Sym.ElementIndex, W->OS); 1063 if ((Sym.Flags & wasm::WASM_SYMBOL_UNDEFINED) == 0 || 1064 (Sym.Flags & wasm::WASM_SYMBOL_EXPLICIT_NAME) != 0) 1065 writeString(Sym.Name); 1066 break; 1067 case wasm::WASM_SYMBOL_TYPE_DATA: 1068 writeString(Sym.Name); 1069 if ((Sym.Flags & wasm::WASM_SYMBOL_UNDEFINED) == 0) { 1070 encodeULEB128(Sym.DataRef.Segment, W->OS); 1071 encodeULEB128(Sym.DataRef.Offset, W->OS); 1072 encodeULEB128(Sym.DataRef.Size, W->OS); 1073 } 1074 break; 1075 case wasm::WASM_SYMBOL_TYPE_SECTION: { 1076 const uint32_t SectionIndex = 1077 CustomSections[Sym.ElementIndex].OutputIndex; 1078 encodeULEB128(SectionIndex, W->OS); 1079 break; 1080 } 1081 default: 1082 llvm_unreachable("unexpected kind"); 1083 } 1084 } 1085 endSection(SubSection); 1086 } 1087 1088 if (DataSegments.size()) { 1089 startSection(SubSection, wasm::WASM_SEGMENT_INFO); 1090 encodeULEB128(DataSegments.size(), W->OS); 1091 for (const WasmDataSegment &Segment : DataSegments) { 1092 writeString(Segment.Name); 1093 encodeULEB128(Segment.Alignment, W->OS); 1094 encodeULEB128(Segment.LinkerFlags, W->OS); 1095 } 1096 endSection(SubSection); 1097 } 1098 1099 if (!InitFuncs.empty()) { 1100 startSection(SubSection, wasm::WASM_INIT_FUNCS); 1101 encodeULEB128(InitFuncs.size(), W->OS); 1102 for (auto &StartFunc : InitFuncs) { 1103 encodeULEB128(StartFunc.first, W->OS); // priority 1104 encodeULEB128(StartFunc.second, W->OS); // function index 1105 } 1106 endSection(SubSection); 1107 } 1108 1109 if (Comdats.size()) { 1110 startSection(SubSection, wasm::WASM_COMDAT_INFO); 1111 encodeULEB128(Comdats.size(), W->OS); 1112 for (const auto &C : Comdats) { 1113 writeString(C.first); 1114 encodeULEB128(0, W->OS); // flags for future use 1115 encodeULEB128(C.second.size(), W->OS); 1116 for (const WasmComdatEntry &Entry : C.second) { 1117 encodeULEB128(Entry.Kind, W->OS); 1118 encodeULEB128(Entry.Index, W->OS); 1119 } 1120 } 1121 endSection(SubSection); 1122 } 1123 1124 endSection(Section); 1125 } 1126 1127 void WasmObjectWriter::writeCustomSection(WasmCustomSection &CustomSection, 1128 const MCAssembler &Asm, 1129 const MCAsmLayout &Layout) { 1130 SectionBookkeeping Section; 1131 auto *Sec = CustomSection.Section; 1132 startCustomSection(Section, CustomSection.Name); 1133 1134 Sec->setSectionOffset(W->OS.tell() - Section.ContentsOffset); 1135 Asm.writeSectionData(W->OS, Sec, Layout); 1136 1137 CustomSection.OutputContentsOffset = Section.ContentsOffset; 1138 CustomSection.OutputIndex = Section.Index; 1139 1140 endSection(Section); 1141 1142 // Apply fixups. 1143 auto &Relocations = CustomSectionsRelocations[CustomSection.Section]; 1144 applyRelocations(Relocations, CustomSection.OutputContentsOffset, Layout); 1145 } 1146 1147 uint32_t WasmObjectWriter::getFunctionType(const MCSymbolWasm &Symbol) { 1148 assert(Symbol.isFunction()); 1149 assert(TypeIndices.count(&Symbol)); 1150 return TypeIndices[&Symbol]; 1151 } 1152 1153 uint32_t WasmObjectWriter::getEventType(const MCSymbolWasm &Symbol) { 1154 assert(Symbol.isEvent()); 1155 assert(TypeIndices.count(&Symbol)); 1156 return TypeIndices[&Symbol]; 1157 } 1158 1159 void WasmObjectWriter::registerFunctionType(const MCSymbolWasm &Symbol) { 1160 assert(Symbol.isFunction()); 1161 1162 wasm::WasmSignature S; 1163 1164 if (auto *Sig = Symbol.getSignature()) { 1165 S.Returns = Sig->Returns; 1166 S.Params = Sig->Params; 1167 } 1168 1169 auto Pair = SignatureIndices.insert(std::make_pair(S, Signatures.size())); 1170 if (Pair.second) 1171 Signatures.push_back(S); 1172 TypeIndices[&Symbol] = Pair.first->second; 1173 1174 LLVM_DEBUG(dbgs() << "registerFunctionType: " << Symbol 1175 << " new:" << Pair.second << "\n"); 1176 LLVM_DEBUG(dbgs() << " -> type index: " << Pair.first->second << "\n"); 1177 } 1178 1179 void WasmObjectWriter::registerEventType(const MCSymbolWasm &Symbol) { 1180 assert(Symbol.isEvent()); 1181 1182 // TODO Currently we don't generate imported exceptions, but if we do, we 1183 // should have a way of infering types of imported exceptions. 1184 wasm::WasmSignature S; 1185 if (auto *Sig = Symbol.getSignature()) { 1186 S.Returns = Sig->Returns; 1187 S.Params = Sig->Params; 1188 } 1189 1190 auto Pair = SignatureIndices.insert(std::make_pair(S, Signatures.size())); 1191 if (Pair.second) 1192 Signatures.push_back(S); 1193 TypeIndices[&Symbol] = Pair.first->second; 1194 1195 LLVM_DEBUG(dbgs() << "registerEventType: " << Symbol << " new:" << Pair.second 1196 << "\n"); 1197 LLVM_DEBUG(dbgs() << " -> type index: " << Pair.first->second << "\n"); 1198 } 1199 1200 static bool isInSymtab(const MCSymbolWasm &Sym) { 1201 if (Sym.isUsedInReloc() || Sym.isUsedInInitArray()) 1202 return true; 1203 1204 if (Sym.isComdat() && !Sym.isDefined()) 1205 return false; 1206 1207 if (Sym.isTemporary()) 1208 return false; 1209 1210 if (Sym.isSection()) 1211 return false; 1212 1213 return true; 1214 } 1215 1216 void WasmObjectWriter::prepareImports( 1217 SmallVectorImpl<wasm::WasmImport> &Imports, MCAssembler &Asm, 1218 const MCAsmLayout &Layout) { 1219 // For now, always emit the memory import, since loads and stores are not 1220 // valid without it. In the future, we could perhaps be more clever and omit 1221 // it if there are no loads or stores. 1222 wasm::WasmImport MemImport; 1223 MemImport.Module = "env"; 1224 MemImport.Field = "__linear_memory"; 1225 MemImport.Kind = wasm::WASM_EXTERNAL_MEMORY; 1226 MemImport.Memory.Flags = is64Bit() ? wasm::WASM_LIMITS_FLAG_IS_64 1227 : wasm::WASM_LIMITS_FLAG_NONE; 1228 Imports.push_back(MemImport); 1229 1230 // Populate SignatureIndices, and Imports and WasmIndices for undefined 1231 // symbols. This must be done before populating WasmIndices for defined 1232 // symbols. 1233 for (const MCSymbol &S : Asm.symbols()) { 1234 const auto &WS = static_cast<const MCSymbolWasm &>(S); 1235 1236 // Register types for all functions, including those with private linkage 1237 // (because wasm always needs a type signature). 1238 if (WS.isFunction()) { 1239 const auto *BS = Layout.getBaseSymbol(S); 1240 if (!BS) 1241 report_fatal_error(Twine(S.getName()) + 1242 ": absolute addressing not supported!"); 1243 registerFunctionType(*cast<MCSymbolWasm>(BS)); 1244 } 1245 1246 if (WS.isEvent()) 1247 registerEventType(WS); 1248 1249 if (WS.isTemporary()) 1250 continue; 1251 1252 // If the symbol is not defined in this translation unit, import it. 1253 if (!WS.isDefined() && !WS.isComdat()) { 1254 if (WS.isFunction()) { 1255 wasm::WasmImport Import; 1256 Import.Module = WS.getImportModule(); 1257 Import.Field = WS.getImportName(); 1258 Import.Kind = wasm::WASM_EXTERNAL_FUNCTION; 1259 Import.SigIndex = getFunctionType(WS); 1260 Imports.push_back(Import); 1261 assert(WasmIndices.count(&WS) == 0); 1262 WasmIndices[&WS] = NumFunctionImports++; 1263 } else if (WS.isGlobal()) { 1264 if (WS.isWeak()) 1265 report_fatal_error("undefined global symbol cannot be weak"); 1266 1267 wasm::WasmImport Import; 1268 Import.Field = WS.getImportName(); 1269 Import.Kind = wasm::WASM_EXTERNAL_GLOBAL; 1270 Import.Module = WS.getImportModule(); 1271 Import.Global = WS.getGlobalType(); 1272 Imports.push_back(Import); 1273 assert(WasmIndices.count(&WS) == 0); 1274 WasmIndices[&WS] = NumGlobalImports++; 1275 } else if (WS.isEvent()) { 1276 if (WS.isWeak()) 1277 report_fatal_error("undefined event symbol cannot be weak"); 1278 1279 wasm::WasmImport Import; 1280 Import.Module = WS.getImportModule(); 1281 Import.Field = WS.getImportName(); 1282 Import.Kind = wasm::WASM_EXTERNAL_EVENT; 1283 Import.Event.Attribute = wasm::WASM_EVENT_ATTRIBUTE_EXCEPTION; 1284 Import.Event.SigIndex = getEventType(WS); 1285 Imports.push_back(Import); 1286 assert(WasmIndices.count(&WS) == 0); 1287 WasmIndices[&WS] = NumEventImports++; 1288 } else if (WS.isTable()) { 1289 if (WS.isWeak()) 1290 report_fatal_error("undefined table symbol cannot be weak"); 1291 1292 wasm::WasmImport Import; 1293 Import.Module = WS.getImportModule(); 1294 Import.Field = WS.getImportName(); 1295 Import.Kind = wasm::WASM_EXTERNAL_TABLE; 1296 wasm::ValType ElemType = WS.getTableType(); 1297 Import.Table.ElemType = uint8_t(ElemType); 1298 // FIXME: Extend table type to include limits? For now we don't specify 1299 // a min or max which does not place any restrictions on the size of the 1300 // imported table. 1301 Import.Table.Limits = {wasm::WASM_LIMITS_FLAG_NONE, 0, 0}; 1302 Imports.push_back(Import); 1303 assert(WasmIndices.count(&WS) == 0); 1304 WasmIndices[&WS] = NumTableImports++; 1305 } 1306 } 1307 } 1308 1309 // Add imports for GOT globals 1310 for (const MCSymbol &S : Asm.symbols()) { 1311 const auto &WS = static_cast<const MCSymbolWasm &>(S); 1312 if (WS.isUsedInGOT()) { 1313 wasm::WasmImport Import; 1314 if (WS.isFunction()) 1315 Import.Module = "GOT.func"; 1316 else 1317 Import.Module = "GOT.mem"; 1318 Import.Field = WS.getName(); 1319 Import.Kind = wasm::WASM_EXTERNAL_GLOBAL; 1320 Import.Global = {wasm::WASM_TYPE_I32, true}; 1321 Imports.push_back(Import); 1322 assert(GOTIndices.count(&WS) == 0); 1323 GOTIndices[&WS] = NumGlobalImports++; 1324 } 1325 } 1326 } 1327 1328 uint64_t WasmObjectWriter::writeObject(MCAssembler &Asm, 1329 const MCAsmLayout &Layout) { 1330 support::endian::Writer MainWriter(*OS, support::little); 1331 W = &MainWriter; 1332 if (IsSplitDwarf) { 1333 uint64_t TotalSize = writeOneObject(Asm, Layout, DwoMode::NonDwoOnly); 1334 assert(DwoOS); 1335 support::endian::Writer DwoWriter(*DwoOS, support::little); 1336 W = &DwoWriter; 1337 return TotalSize + writeOneObject(Asm, Layout, DwoMode::DwoOnly); 1338 } else { 1339 return writeOneObject(Asm, Layout, DwoMode::AllSections); 1340 } 1341 } 1342 1343 uint64_t WasmObjectWriter::writeOneObject(MCAssembler &Asm, 1344 const MCAsmLayout &Layout, 1345 DwoMode Mode) { 1346 uint64_t StartOffset = W->OS.tell(); 1347 SectionCount = 0; 1348 CustomSections.clear(); 1349 1350 LLVM_DEBUG(dbgs() << "WasmObjectWriter::writeObject\n"); 1351 1352 // Collect information from the available symbols. 1353 SmallVector<WasmFunction, 4> Functions; 1354 SmallVector<uint32_t, 4> TableElems; 1355 SmallVector<wasm::WasmImport, 4> Imports; 1356 SmallVector<wasm::WasmExport, 4> Exports; 1357 SmallVector<wasm::WasmEventType, 1> Events; 1358 SmallVector<wasm::WasmGlobal, 1> Globals; 1359 SmallVector<wasm::WasmTable, 1> Tables; 1360 SmallVector<wasm::WasmSymbolInfo, 4> SymbolInfos; 1361 SmallVector<std::pair<uint16_t, uint32_t>, 2> InitFuncs; 1362 std::map<StringRef, std::vector<WasmComdatEntry>> Comdats; 1363 uint64_t DataSize = 0; 1364 if (Mode != DwoMode::DwoOnly) { 1365 prepareImports(Imports, Asm, Layout); 1366 } 1367 1368 // Populate DataSegments and CustomSections, which must be done before 1369 // populating DataLocations. 1370 for (MCSection &Sec : Asm) { 1371 auto &Section = static_cast<MCSectionWasm &>(Sec); 1372 StringRef SectionName = Section.getName(); 1373 1374 if (Mode == DwoMode::NonDwoOnly && isDwoSection(Sec)) 1375 continue; 1376 if (Mode == DwoMode::DwoOnly && !isDwoSection(Sec)) 1377 continue; 1378 1379 LLVM_DEBUG(dbgs() << "Processing Section " << SectionName << " group " 1380 << Section.getGroup() << "\n";); 1381 1382 // .init_array sections are handled specially elsewhere. 1383 if (SectionName.startswith(".init_array")) 1384 continue; 1385 1386 // Code is handled separately 1387 if (Section.getKind().isText()) 1388 continue; 1389 1390 if (Section.isWasmData()) { 1391 uint32_t SegmentIndex = DataSegments.size(); 1392 DataSize = alignTo(DataSize, Section.getAlignment()); 1393 DataSegments.emplace_back(); 1394 WasmDataSegment &Segment = DataSegments.back(); 1395 Segment.Name = SectionName; 1396 Segment.InitFlags = Section.getPassive() 1397 ? (uint32_t)wasm::WASM_DATA_SEGMENT_IS_PASSIVE 1398 : 0; 1399 Segment.Offset = DataSize; 1400 Segment.Section = &Section; 1401 addData(Segment.Data, Section); 1402 Segment.Alignment = Log2_32(Section.getAlignment()); 1403 Segment.LinkerFlags = 0; 1404 DataSize += Segment.Data.size(); 1405 Section.setSegmentIndex(SegmentIndex); 1406 1407 if (const MCSymbolWasm *C = Section.getGroup()) { 1408 Comdats[C->getName()].emplace_back( 1409 WasmComdatEntry{wasm::WASM_COMDAT_DATA, SegmentIndex}); 1410 } 1411 } else { 1412 // Create custom sections 1413 assert(Sec.getKind().isMetadata()); 1414 1415 StringRef Name = SectionName; 1416 1417 // For user-defined custom sections, strip the prefix 1418 if (Name.startswith(".custom_section.")) 1419 Name = Name.substr(strlen(".custom_section.")); 1420 1421 MCSymbol *Begin = Sec.getBeginSymbol(); 1422 if (Begin) { 1423 assert(WasmIndices.count(cast<MCSymbolWasm>(Begin)) == 0); 1424 WasmIndices[cast<MCSymbolWasm>(Begin)] = CustomSections.size(); 1425 } 1426 1427 // Separate out the producers and target features sections 1428 if (Name == "producers") { 1429 ProducersSection = std::make_unique<WasmCustomSection>(Name, &Section); 1430 continue; 1431 } 1432 if (Name == "target_features") { 1433 TargetFeaturesSection = 1434 std::make_unique<WasmCustomSection>(Name, &Section); 1435 continue; 1436 } 1437 1438 // Custom sections can also belong to COMDAT groups. In this case the 1439 // decriptor's "index" field is the section index (in the final object 1440 // file), but that is not known until after layout, so it must be fixed up 1441 // later 1442 if (const MCSymbolWasm *C = Section.getGroup()) { 1443 Comdats[C->getName()].emplace_back( 1444 WasmComdatEntry{wasm::WASM_COMDAT_SECTION, 1445 static_cast<uint32_t>(CustomSections.size())}); 1446 } 1447 1448 CustomSections.emplace_back(Name, &Section); 1449 } 1450 } 1451 1452 if (Mode != DwoMode::DwoOnly) { 1453 // Populate WasmIndices and DataLocations for defined symbols. 1454 for (const MCSymbol &S : Asm.symbols()) { 1455 // Ignore unnamed temporary symbols, which aren't ever exported, imported, 1456 // or used in relocations. 1457 if (S.isTemporary() && S.getName().empty()) 1458 continue; 1459 1460 const auto &WS = static_cast<const MCSymbolWasm &>(S); 1461 LLVM_DEBUG( 1462 dbgs() << "MCSymbol: " << toString(WS.getType()) << " '" << S << "'" 1463 << " isDefined=" << S.isDefined() << " isExternal=" 1464 << S.isExternal() << " isTemporary=" << S.isTemporary() 1465 << " isWeak=" << WS.isWeak() << " isHidden=" << WS.isHidden() 1466 << " isVariable=" << WS.isVariable() << "\n"); 1467 1468 if (WS.isVariable()) 1469 continue; 1470 if (WS.isComdat() && !WS.isDefined()) 1471 continue; 1472 1473 if (WS.isFunction()) { 1474 unsigned Index; 1475 if (WS.isDefined()) { 1476 if (WS.getOffset() != 0) 1477 report_fatal_error( 1478 "function sections must contain one function each"); 1479 1480 if (WS.getSize() == nullptr) 1481 report_fatal_error( 1482 "function symbols must have a size set with .size"); 1483 1484 // A definition. Write out the function body. 1485 Index = NumFunctionImports + Functions.size(); 1486 WasmFunction Func; 1487 Func.SigIndex = getFunctionType(WS); 1488 Func.Sym = &WS; 1489 assert(WasmIndices.count(&WS) == 0); 1490 WasmIndices[&WS] = Index; 1491 Functions.push_back(Func); 1492 1493 auto &Section = static_cast<MCSectionWasm &>(WS.getSection()); 1494 if (const MCSymbolWasm *C = Section.getGroup()) { 1495 Comdats[C->getName()].emplace_back( 1496 WasmComdatEntry{wasm::WASM_COMDAT_FUNCTION, Index}); 1497 } 1498 1499 if (WS.hasExportName()) { 1500 wasm::WasmExport Export; 1501 Export.Name = WS.getExportName(); 1502 Export.Kind = wasm::WASM_EXTERNAL_FUNCTION; 1503 Export.Index = Index; 1504 Exports.push_back(Export); 1505 } 1506 } else { 1507 // An import; the index was assigned above. 1508 Index = WasmIndices.find(&WS)->second; 1509 } 1510 1511 LLVM_DEBUG(dbgs() << " -> function index: " << Index << "\n"); 1512 1513 } else if (WS.isData()) { 1514 if (!isInSymtab(WS)) 1515 continue; 1516 1517 if (!WS.isDefined()) { 1518 LLVM_DEBUG(dbgs() << " -> segment index: -1" 1519 << "\n"); 1520 continue; 1521 } 1522 1523 if (!WS.getSize()) 1524 report_fatal_error("data symbols must have a size set with .size: " + 1525 WS.getName()); 1526 1527 int64_t Size = 0; 1528 if (!WS.getSize()->evaluateAsAbsolute(Size, Layout)) 1529 report_fatal_error(".size expression must be evaluatable"); 1530 1531 auto &DataSection = static_cast<MCSectionWasm &>(WS.getSection()); 1532 if (!DataSection.isWasmData()) 1533 report_fatal_error("data symbols must live in a data section: " + 1534 WS.getName()); 1535 1536 // For each data symbol, export it in the symtab as a reference to the 1537 // corresponding Wasm data segment. 1538 wasm::WasmDataReference Ref = wasm::WasmDataReference{ 1539 DataSection.getSegmentIndex(), Layout.getSymbolOffset(WS), 1540 static_cast<uint64_t>(Size)}; 1541 assert(DataLocations.count(&WS) == 0); 1542 DataLocations[&WS] = Ref; 1543 LLVM_DEBUG(dbgs() << " -> segment index: " << Ref.Segment << "\n"); 1544 1545 } else if (WS.isGlobal()) { 1546 // A "true" Wasm global (currently just __stack_pointer) 1547 if (WS.isDefined()) { 1548 wasm::WasmGlobal Global; 1549 Global.Type = WS.getGlobalType(); 1550 Global.Index = NumGlobalImports + Globals.size(); 1551 switch (Global.Type.Type) { 1552 case wasm::WASM_TYPE_I32: 1553 Global.InitExpr.Opcode = wasm::WASM_OPCODE_I32_CONST; 1554 break; 1555 case wasm::WASM_TYPE_I64: 1556 Global.InitExpr.Opcode = wasm::WASM_OPCODE_I64_CONST; 1557 break; 1558 case wasm::WASM_TYPE_F32: 1559 Global.InitExpr.Opcode = wasm::WASM_OPCODE_F32_CONST; 1560 break; 1561 case wasm::WASM_TYPE_F64: 1562 Global.InitExpr.Opcode = wasm::WASM_OPCODE_F64_CONST; 1563 break; 1564 case wasm::WASM_TYPE_EXTERNREF: 1565 Global.InitExpr.Opcode = wasm::WASM_OPCODE_REF_NULL; 1566 break; 1567 default: 1568 llvm_unreachable("unexpected type"); 1569 } 1570 assert(WasmIndices.count(&WS) == 0); 1571 WasmIndices[&WS] = Global.Index; 1572 Globals.push_back(Global); 1573 } else { 1574 // An import; the index was assigned above 1575 LLVM_DEBUG(dbgs() << " -> global index: " 1576 << WasmIndices.find(&WS)->second << "\n"); 1577 } 1578 } else if (WS.isTable()) { 1579 if (WS.isDefined()) { 1580 wasm::WasmTable Table; 1581 Table.Index = NumTableImports + Tables.size(); 1582 Table.Type.ElemType = static_cast<uint8_t>(WS.getTableType()); 1583 // FIXME: Work on custom limits is ongoing 1584 Table.Type.Limits = {wasm::WASM_LIMITS_FLAG_NONE, 0, 0}; 1585 assert(WasmIndices.count(&WS) == 0); 1586 WasmIndices[&WS] = Table.Index; 1587 Tables.push_back(Table); 1588 } 1589 LLVM_DEBUG(dbgs() << " -> table index: " 1590 << WasmIndices.find(&WS)->second << "\n"); 1591 } else if (WS.isEvent()) { 1592 // C++ exception symbol (__cpp_exception) 1593 unsigned Index; 1594 if (WS.isDefined()) { 1595 Index = NumEventImports + Events.size(); 1596 wasm::WasmEventType Event; 1597 Event.SigIndex = getEventType(WS); 1598 Event.Attribute = wasm::WASM_EVENT_ATTRIBUTE_EXCEPTION; 1599 assert(WasmIndices.count(&WS) == 0); 1600 WasmIndices[&WS] = Index; 1601 Events.push_back(Event); 1602 } else { 1603 // An import; the index was assigned above. 1604 assert(WasmIndices.count(&WS) > 0); 1605 } 1606 LLVM_DEBUG(dbgs() << " -> event index: " 1607 << WasmIndices.find(&WS)->second << "\n"); 1608 1609 } else { 1610 assert(WS.isSection()); 1611 } 1612 } 1613 1614 // Populate WasmIndices and DataLocations for aliased symbols. We need to 1615 // process these in a separate pass because we need to have processed the 1616 // target of the alias before the alias itself and the symbols are not 1617 // necessarily ordered in this way. 1618 for (const MCSymbol &S : Asm.symbols()) { 1619 if (!S.isVariable()) 1620 continue; 1621 1622 assert(S.isDefined()); 1623 1624 const auto *BS = Layout.getBaseSymbol(S); 1625 if (!BS) 1626 report_fatal_error(Twine(S.getName()) + 1627 ": absolute addressing not supported!"); 1628 const MCSymbolWasm *Base = cast<MCSymbolWasm>(BS); 1629 1630 // Find the target symbol of this weak alias and export that index 1631 const auto &WS = static_cast<const MCSymbolWasm &>(S); 1632 LLVM_DEBUG(dbgs() << WS.getName() << ": weak alias of '" << *Base 1633 << "'\n"); 1634 1635 if (Base->isFunction()) { 1636 assert(WasmIndices.count(Base) > 0); 1637 uint32_t WasmIndex = WasmIndices.find(Base)->second; 1638 assert(WasmIndices.count(&WS) == 0); 1639 WasmIndices[&WS] = WasmIndex; 1640 LLVM_DEBUG(dbgs() << " -> index:" << WasmIndex << "\n"); 1641 } else if (Base->isData()) { 1642 auto &DataSection = static_cast<MCSectionWasm &>(WS.getSection()); 1643 uint64_t Offset = Layout.getSymbolOffset(S); 1644 int64_t Size = 0; 1645 // For data symbol alias we use the size of the base symbol as the 1646 // size of the alias. When an offset from the base is involved this 1647 // can result in a offset + size goes past the end of the data section 1648 // which out object format doesn't support. So we must clamp it. 1649 if (!Base->getSize()->evaluateAsAbsolute(Size, Layout)) 1650 report_fatal_error(".size expression must be evaluatable"); 1651 const WasmDataSegment &Segment = 1652 DataSegments[DataSection.getSegmentIndex()]; 1653 Size = 1654 std::min(static_cast<uint64_t>(Size), Segment.Data.size() - Offset); 1655 wasm::WasmDataReference Ref = wasm::WasmDataReference{ 1656 DataSection.getSegmentIndex(), 1657 static_cast<uint32_t>(Layout.getSymbolOffset(S)), 1658 static_cast<uint32_t>(Size)}; 1659 DataLocations[&WS] = Ref; 1660 LLVM_DEBUG(dbgs() << " -> index:" << Ref.Segment << "\n"); 1661 } else { 1662 report_fatal_error("don't yet support global/event aliases"); 1663 } 1664 } 1665 } 1666 1667 // Finally, populate the symbol table itself, in its "natural" order. 1668 for (const MCSymbol &S : Asm.symbols()) { 1669 const auto &WS = static_cast<const MCSymbolWasm &>(S); 1670 if (!isInSymtab(WS)) { 1671 WS.setIndex(InvalidIndex); 1672 continue; 1673 } 1674 if (WS.isTable() && WS.getName() == "__indirect_function_table") { 1675 // For the moment, don't emit table symbols -- wasm-ld can't handle them. 1676 continue; 1677 } 1678 LLVM_DEBUG(dbgs() << "adding to symtab: " << WS << "\n"); 1679 1680 uint32_t Flags = 0; 1681 if (WS.isWeak()) 1682 Flags |= wasm::WASM_SYMBOL_BINDING_WEAK; 1683 if (WS.isHidden()) 1684 Flags |= wasm::WASM_SYMBOL_VISIBILITY_HIDDEN; 1685 if (!WS.isExternal() && WS.isDefined()) 1686 Flags |= wasm::WASM_SYMBOL_BINDING_LOCAL; 1687 if (WS.isUndefined()) 1688 Flags |= wasm::WASM_SYMBOL_UNDEFINED; 1689 if (WS.isNoStrip()) { 1690 Flags |= wasm::WASM_SYMBOL_NO_STRIP; 1691 if (isEmscripten()) { 1692 Flags |= wasm::WASM_SYMBOL_EXPORTED; 1693 } 1694 } 1695 if (WS.hasImportName()) 1696 Flags |= wasm::WASM_SYMBOL_EXPLICIT_NAME; 1697 if (WS.hasExportName()) 1698 Flags |= wasm::WASM_SYMBOL_EXPORTED; 1699 1700 wasm::WasmSymbolInfo Info; 1701 Info.Name = WS.getName(); 1702 Info.Kind = WS.getType(); 1703 Info.Flags = Flags; 1704 if (!WS.isData()) { 1705 assert(WasmIndices.count(&WS) > 0); 1706 Info.ElementIndex = WasmIndices.find(&WS)->second; 1707 } else if (WS.isDefined()) { 1708 assert(DataLocations.count(&WS) > 0); 1709 Info.DataRef = DataLocations.find(&WS)->second; 1710 } 1711 WS.setIndex(SymbolInfos.size()); 1712 SymbolInfos.emplace_back(Info); 1713 } 1714 1715 { 1716 auto HandleReloc = [&](const WasmRelocationEntry &Rel) { 1717 // Functions referenced by a relocation need to put in the table. This is 1718 // purely to make the object file's provisional values readable, and is 1719 // ignored by the linker, which re-calculates the relocations itself. 1720 if (Rel.Type != wasm::R_WASM_TABLE_INDEX_I32 && 1721 Rel.Type != wasm::R_WASM_TABLE_INDEX_I64 && 1722 Rel.Type != wasm::R_WASM_TABLE_INDEX_SLEB && 1723 Rel.Type != wasm::R_WASM_TABLE_INDEX_SLEB64 && 1724 Rel.Type != wasm::R_WASM_TABLE_INDEX_REL_SLEB) 1725 return; 1726 assert(Rel.Symbol->isFunction()); 1727 const MCSymbolWasm *Base = 1728 cast<MCSymbolWasm>(Layout.getBaseSymbol(*Rel.Symbol)); 1729 uint32_t FunctionIndex = WasmIndices.find(Base)->second; 1730 uint32_t TableIndex = TableElems.size() + InitialTableOffset; 1731 if (TableIndices.try_emplace(Base, TableIndex).second) { 1732 LLVM_DEBUG(dbgs() << " -> adding " << Base->getName() 1733 << " to table: " << TableIndex << "\n"); 1734 TableElems.push_back(FunctionIndex); 1735 registerFunctionType(*Base); 1736 } 1737 }; 1738 1739 for (const WasmRelocationEntry &RelEntry : CodeRelocations) 1740 HandleReloc(RelEntry); 1741 for (const WasmRelocationEntry &RelEntry : DataRelocations) 1742 HandleReloc(RelEntry); 1743 } 1744 1745 // Translate .init_array section contents into start functions. 1746 for (const MCSection &S : Asm) { 1747 const auto &WS = static_cast<const MCSectionWasm &>(S); 1748 if (WS.getName().startswith(".fini_array")) 1749 report_fatal_error(".fini_array sections are unsupported"); 1750 if (!WS.getName().startswith(".init_array")) 1751 continue; 1752 if (WS.getFragmentList().empty()) 1753 continue; 1754 1755 // init_array is expected to contain a single non-empty data fragment 1756 if (WS.getFragmentList().size() != 3) 1757 report_fatal_error("only one .init_array section fragment supported"); 1758 1759 auto IT = WS.begin(); 1760 const MCFragment &EmptyFrag = *IT; 1761 if (EmptyFrag.getKind() != MCFragment::FT_Data) 1762 report_fatal_error(".init_array section should be aligned"); 1763 1764 IT = std::next(IT); 1765 const MCFragment &AlignFrag = *IT; 1766 if (AlignFrag.getKind() != MCFragment::FT_Align) 1767 report_fatal_error(".init_array section should be aligned"); 1768 if (cast<MCAlignFragment>(AlignFrag).getAlignment() != (is64Bit() ? 8 : 4)) 1769 report_fatal_error(".init_array section should be aligned for pointers"); 1770 1771 const MCFragment &Frag = *std::next(IT); 1772 if (Frag.hasInstructions() || Frag.getKind() != MCFragment::FT_Data) 1773 report_fatal_error("only data supported in .init_array section"); 1774 1775 uint16_t Priority = UINT16_MAX; 1776 unsigned PrefixLength = strlen(".init_array"); 1777 if (WS.getName().size() > PrefixLength) { 1778 if (WS.getName()[PrefixLength] != '.') 1779 report_fatal_error( 1780 ".init_array section priority should start with '.'"); 1781 if (WS.getName().substr(PrefixLength + 1).getAsInteger(10, Priority)) 1782 report_fatal_error("invalid .init_array section priority"); 1783 } 1784 const auto &DataFrag = cast<MCDataFragment>(Frag); 1785 const SmallVectorImpl<char> &Contents = DataFrag.getContents(); 1786 for (const uint8_t * 1787 P = (const uint8_t *)Contents.data(), 1788 *End = (const uint8_t *)Contents.data() + Contents.size(); 1789 P != End; ++P) { 1790 if (*P != 0) 1791 report_fatal_error("non-symbolic data in .init_array section"); 1792 } 1793 for (const MCFixup &Fixup : DataFrag.getFixups()) { 1794 assert(Fixup.getKind() == 1795 MCFixup::getKindForSize(is64Bit() ? 8 : 4, false)); 1796 const MCExpr *Expr = Fixup.getValue(); 1797 auto *SymRef = dyn_cast<MCSymbolRefExpr>(Expr); 1798 if (!SymRef) 1799 report_fatal_error("fixups in .init_array should be symbol references"); 1800 const auto &TargetSym = cast<const MCSymbolWasm>(SymRef->getSymbol()); 1801 if (TargetSym.getIndex() == InvalidIndex) 1802 report_fatal_error("symbols in .init_array should exist in symtab"); 1803 if (!TargetSym.isFunction()) 1804 report_fatal_error("symbols in .init_array should be for functions"); 1805 InitFuncs.push_back( 1806 std::make_pair(Priority, TargetSym.getIndex())); 1807 } 1808 } 1809 1810 // Write out the Wasm header. 1811 writeHeader(Asm); 1812 1813 uint32_t CodeSectionIndex, DataSectionIndex; 1814 if (Mode != DwoMode::DwoOnly) { 1815 writeTypeSection(Signatures); 1816 writeImportSection(Imports, DataSize, TableElems.size()); 1817 writeFunctionSection(Functions); 1818 writeTableSection(Tables); 1819 // Skip the "memory" section; we import the memory instead. 1820 writeEventSection(Events); 1821 writeGlobalSection(Globals); 1822 writeExportSection(Exports); 1823 writeElemSection(TableElems); 1824 writeDataCountSection(); 1825 1826 CodeSectionIndex = writeCodeSection(Asm, Layout, Functions); 1827 DataSectionIndex = writeDataSection(Layout); 1828 } 1829 1830 // The Sections in the COMDAT list have placeholder indices (their index among 1831 // custom sections, rather than among all sections). Fix them up here. 1832 for (auto &Group : Comdats) { 1833 for (auto &Entry : Group.second) { 1834 if (Entry.Kind == wasm::WASM_COMDAT_SECTION) { 1835 Entry.Index += SectionCount; 1836 } 1837 } 1838 } 1839 for (auto &CustomSection : CustomSections) 1840 writeCustomSection(CustomSection, Asm, Layout); 1841 1842 if (Mode != DwoMode::DwoOnly) { 1843 writeLinkingMetaDataSection(SymbolInfos, InitFuncs, Comdats); 1844 1845 writeRelocSection(CodeSectionIndex, "CODE", CodeRelocations); 1846 writeRelocSection(DataSectionIndex, "DATA", DataRelocations); 1847 } 1848 writeCustomRelocSections(); 1849 if (ProducersSection) 1850 writeCustomSection(*ProducersSection, Asm, Layout); 1851 if (TargetFeaturesSection) 1852 writeCustomSection(*TargetFeaturesSection, Asm, Layout); 1853 1854 // TODO: Translate the .comment section to the output. 1855 return W->OS.tell() - StartOffset; 1856 } 1857 1858 std::unique_ptr<MCObjectWriter> 1859 llvm::createWasmObjectWriter(std::unique_ptr<MCWasmObjectTargetWriter> MOTW, 1860 raw_pwrite_stream &OS) { 1861 return std::make_unique<WasmObjectWriter>(std::move(MOTW), OS); 1862 } 1863 1864 std::unique_ptr<MCObjectWriter> 1865 llvm::createWasmDwoObjectWriter(std::unique_ptr<MCWasmObjectTargetWriter> MOTW, 1866 raw_pwrite_stream &OS, 1867 raw_pwrite_stream &DwoOS) { 1868 return std::make_unique<WasmObjectWriter>(std::move(MOTW), OS, DwoOS); 1869 } 1870