| //===- lib/MC/WasmObjectWriter.cpp - Wasm File Writer ---------------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file implements Wasm object file writer information. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/ADT/STLExtras.h" |
| #include "llvm/ADT/SmallPtrSet.h" |
| #include "llvm/BinaryFormat/Wasm.h" |
| #include "llvm/BinaryFormat/WasmTraits.h" |
| #include "llvm/Config/llvm-config.h" |
| #include "llvm/MC/MCAsmBackend.h" |
| #include "llvm/MC/MCAsmLayout.h" |
| #include "llvm/MC/MCAssembler.h" |
| #include "llvm/MC/MCContext.h" |
| #include "llvm/MC/MCExpr.h" |
| #include "llvm/MC/MCFixupKindInfo.h" |
| #include "llvm/MC/MCObjectWriter.h" |
| #include "llvm/MC/MCSectionWasm.h" |
| #include "llvm/MC/MCSymbolWasm.h" |
| #include "llvm/MC/MCValue.h" |
| #include "llvm/MC/MCWasmObjectWriter.h" |
| #include "llvm/Support/Casting.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/EndianStream.h" |
| #include "llvm/Support/ErrorHandling.h" |
| #include "llvm/Support/LEB128.h" |
| #include "llvm/Support/StringSaver.h" |
| #include <vector> |
| |
| using namespace llvm; |
| |
| #define DEBUG_TYPE "mc" |
| |
| namespace { |
| |
| // When we create the indirect function table we start at 1, so that there is |
| // and empty slot at 0 and therefore calling a null function pointer will trap. |
| static const uint32_t InitialTableOffset = 1; |
| |
| // For patching purposes, we need to remember where each section starts, both |
| // for patching up the section size field, and for patching up references to |
| // locations within the section. |
| struct SectionBookkeeping { |
| // Where the size of the section is written. |
| uint64_t SizeOffset; |
| // Where the section header ends (without custom section name). |
| uint64_t PayloadOffset; |
| // Where the contents of the section starts. |
| uint64_t ContentsOffset; |
| uint32_t Index; |
| }; |
| |
| // A wasm data segment. A wasm binary contains only a single data section |
| // but that can contain many segments, each with their own virtual location |
| // in memory. Each MCSection data created by llvm is modeled as its own |
| // wasm data segment. |
| struct WasmDataSegment { |
| MCSectionWasm *Section; |
| StringRef Name; |
| uint32_t InitFlags; |
| uint64_t Offset; |
| uint32_t Alignment; |
| uint32_t LinkingFlags; |
| SmallVector<char, 4> Data; |
| }; |
| |
| // A wasm function to be written into the function section. |
| struct WasmFunction { |
| uint32_t SigIndex; |
| const MCSymbolWasm *Sym; |
| }; |
| |
| // A wasm global to be written into the global section. |
| struct WasmGlobal { |
| wasm::WasmGlobalType Type; |
| uint64_t InitialValue; |
| }; |
| |
| // Information about a single item which is part of a COMDAT. For each data |
| // segment or function which is in the COMDAT, there is a corresponding |
| // WasmComdatEntry. |
| struct WasmComdatEntry { |
| unsigned Kind; |
| uint32_t Index; |
| }; |
| |
| // Information about a single relocation. |
| struct WasmRelocationEntry { |
| uint64_t Offset; // Where is the relocation. |
| const MCSymbolWasm *Symbol; // The symbol to relocate with. |
| int64_t Addend; // A value to add to the symbol. |
| unsigned Type; // The type of the relocation. |
| const MCSectionWasm *FixupSection; // The section the relocation is targeting. |
| |
| WasmRelocationEntry(uint64_t Offset, const MCSymbolWasm *Symbol, |
| int64_t Addend, unsigned Type, |
| const MCSectionWasm *FixupSection) |
| : Offset(Offset), Symbol(Symbol), Addend(Addend), Type(Type), |
| FixupSection(FixupSection) {} |
| |
| bool hasAddend() const { return wasm::relocTypeHasAddend(Type); } |
| |
| void print(raw_ostream &Out) const { |
| Out << wasm::relocTypetoString(Type) << " Off=" << Offset |
| << ", Sym=" << *Symbol << ", Addend=" << Addend |
| << ", FixupSection=" << FixupSection->getName(); |
| } |
| |
| #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) |
| LLVM_DUMP_METHOD void dump() const { print(dbgs()); } |
| #endif |
| }; |
| |
| static const uint32_t InvalidIndex = -1; |
| |
| struct WasmCustomSection { |
| |
| StringRef Name; |
| MCSectionWasm *Section; |
| |
| uint32_t OutputContentsOffset; |
| uint32_t OutputIndex; |
| |
| WasmCustomSection(StringRef Name, MCSectionWasm *Section) |
| : Name(Name), Section(Section), OutputContentsOffset(0), |
| OutputIndex(InvalidIndex) {} |
| }; |
| |
| #if !defined(NDEBUG) |
| raw_ostream &operator<<(raw_ostream &OS, const WasmRelocationEntry &Rel) { |
| Rel.print(OS); |
| return OS; |
| } |
| #endif |
| |
| // Write X as an (unsigned) LEB value at offset Offset in Stream, padded |
| // to allow patching. |
| template <int W> |
| void writePatchableLEB(raw_pwrite_stream &Stream, uint64_t X, uint64_t Offset) { |
| uint8_t Buffer[W]; |
| unsigned SizeLen = encodeULEB128(X, Buffer, W); |
| assert(SizeLen == W); |
| Stream.pwrite((char *)Buffer, SizeLen, Offset); |
| } |
| |
| // Write X as an signed LEB value at offset Offset in Stream, padded |
| // to allow patching. |
| template <int W> |
| void writePatchableSLEB(raw_pwrite_stream &Stream, int64_t X, uint64_t Offset) { |
| uint8_t Buffer[W]; |
| unsigned SizeLen = encodeSLEB128(X, Buffer, W); |
| assert(SizeLen == W); |
| Stream.pwrite((char *)Buffer, SizeLen, Offset); |
| } |
| |
| // Write X as a plain integer value at offset Offset in Stream. |
| static void patchI32(raw_pwrite_stream &Stream, uint32_t X, uint64_t Offset) { |
| uint8_t Buffer[4]; |
| support::endian::write32le(Buffer, X); |
| Stream.pwrite((char *)Buffer, sizeof(Buffer), Offset); |
| } |
| |
| static void patchI64(raw_pwrite_stream &Stream, uint64_t X, uint64_t Offset) { |
| uint8_t Buffer[8]; |
| support::endian::write64le(Buffer, X); |
| Stream.pwrite((char *)Buffer, sizeof(Buffer), Offset); |
| } |
| |
| bool isDwoSection(const MCSection &Sec) { |
| return Sec.getName().endswith(".dwo"); |
| } |
| |
| class WasmObjectWriter : public MCObjectWriter { |
| support::endian::Writer *W; |
| |
| /// The target specific Wasm writer instance. |
| std::unique_ptr<MCWasmObjectTargetWriter> TargetObjectWriter; |
| |
| // Relocations for fixing up references in the code section. |
| std::vector<WasmRelocationEntry> CodeRelocations; |
| // Relocations for fixing up references in the data section. |
| std::vector<WasmRelocationEntry> DataRelocations; |
| |
| // Index values to use for fixing up call_indirect type indices. |
| // Maps function symbols to the index of the type of the function |
| DenseMap<const MCSymbolWasm *, uint32_t> TypeIndices; |
| // Maps function symbols to the table element index space. Used |
| // for TABLE_INDEX relocation types (i.e. address taken functions). |
| DenseMap<const MCSymbolWasm *, uint32_t> TableIndices; |
| // Maps function/global/table symbols to the |
| // function/global/table/tag/section index space. |
| DenseMap<const MCSymbolWasm *, uint32_t> WasmIndices; |
| DenseMap<const MCSymbolWasm *, uint32_t> GOTIndices; |
| // Maps data symbols to the Wasm segment and offset/size with the segment. |
| DenseMap<const MCSymbolWasm *, wasm::WasmDataReference> DataLocations; |
| |
| // Stores output data (index, relocations, content offset) for custom |
| // section. |
| std::vector<WasmCustomSection> CustomSections; |
| std::unique_ptr<WasmCustomSection> ProducersSection; |
| std::unique_ptr<WasmCustomSection> TargetFeaturesSection; |
| // Relocations for fixing up references in the custom sections. |
| DenseMap<const MCSectionWasm *, std::vector<WasmRelocationEntry>> |
| CustomSectionsRelocations; |
| |
| // Map from section to defining function symbol. |
| DenseMap<const MCSection *, const MCSymbol *> SectionFunctions; |
| |
| DenseMap<wasm::WasmSignature, uint32_t> SignatureIndices; |
| SmallVector<wasm::WasmSignature, 4> Signatures; |
| SmallVector<WasmDataSegment, 4> DataSegments; |
| unsigned NumFunctionImports = 0; |
| unsigned NumGlobalImports = 0; |
| unsigned NumTableImports = 0; |
| unsigned NumTagImports = 0; |
| uint32_t SectionCount = 0; |
| |
| enum class DwoMode { |
| AllSections, |
| NonDwoOnly, |
| DwoOnly, |
| }; |
| bool IsSplitDwarf = false; |
| raw_pwrite_stream *OS = nullptr; |
| raw_pwrite_stream *DwoOS = nullptr; |
| |
| // TargetObjectWriter wranppers. |
| bool is64Bit() const { return TargetObjectWriter->is64Bit(); } |
| bool isEmscripten() const { return TargetObjectWriter->isEmscripten(); } |
| |
| void startSection(SectionBookkeeping &Section, unsigned SectionId); |
| void startCustomSection(SectionBookkeeping &Section, StringRef Name); |
| void endSection(SectionBookkeeping &Section); |
| |
| public: |
| WasmObjectWriter(std::unique_ptr<MCWasmObjectTargetWriter> MOTW, |
| raw_pwrite_stream &OS_) |
| : TargetObjectWriter(std::move(MOTW)), OS(&OS_) {} |
| |
| WasmObjectWriter(std::unique_ptr<MCWasmObjectTargetWriter> MOTW, |
| raw_pwrite_stream &OS_, raw_pwrite_stream &DwoOS_) |
| : TargetObjectWriter(std::move(MOTW)), IsSplitDwarf(true), OS(&OS_), |
| DwoOS(&DwoOS_) {} |
| |
| private: |
| void reset() override { |
| CodeRelocations.clear(); |
| DataRelocations.clear(); |
| TypeIndices.clear(); |
| WasmIndices.clear(); |
| GOTIndices.clear(); |
| TableIndices.clear(); |
| DataLocations.clear(); |
| CustomSections.clear(); |
| ProducersSection.reset(); |
| TargetFeaturesSection.reset(); |
| CustomSectionsRelocations.clear(); |
| SignatureIndices.clear(); |
| Signatures.clear(); |
| DataSegments.clear(); |
| SectionFunctions.clear(); |
| NumFunctionImports = 0; |
| NumGlobalImports = 0; |
| NumTableImports = 0; |
| MCObjectWriter::reset(); |
| } |
| |
| void writeHeader(const MCAssembler &Asm); |
| |
| void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout, |
| const MCFragment *Fragment, const MCFixup &Fixup, |
| MCValue Target, uint64_t &FixedValue) override; |
| |
| void executePostLayoutBinding(MCAssembler &Asm, |
| const MCAsmLayout &Layout) override; |
| void prepareImports(SmallVectorImpl<wasm::WasmImport> &Imports, |
| MCAssembler &Asm, const MCAsmLayout &Layout); |
| uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override; |
| |
| uint64_t writeOneObject(MCAssembler &Asm, const MCAsmLayout &Layout, |
| DwoMode Mode); |
| |
| void writeString(const StringRef Str) { |
| encodeULEB128(Str.size(), W->OS); |
| W->OS << Str; |
| } |
| |
| void writeStringWithAlignment(const StringRef Str, unsigned Alignment); |
| |
| void writeI32(int32_t val) { |
| char Buffer[4]; |
| support::endian::write32le(Buffer, val); |
| W->OS.write(Buffer, sizeof(Buffer)); |
| } |
| |
| void writeI64(int64_t val) { |
| char Buffer[8]; |
| support::endian::write64le(Buffer, val); |
| W->OS.write(Buffer, sizeof(Buffer)); |
| } |
| |
| void writeValueType(wasm::ValType Ty) { W->OS << static_cast<char>(Ty); } |
| |
| void writeTypeSection(ArrayRef<wasm::WasmSignature> Signatures); |
| void writeImportSection(ArrayRef<wasm::WasmImport> Imports, uint64_t DataSize, |
| uint32_t NumElements); |
| void writeFunctionSection(ArrayRef<WasmFunction> Functions); |
| void writeExportSection(ArrayRef<wasm::WasmExport> Exports); |
| void writeElemSection(const MCSymbolWasm *IndirectFunctionTable, |
| ArrayRef<uint32_t> TableElems); |
| void writeDataCountSection(); |
| uint32_t writeCodeSection(const MCAssembler &Asm, const MCAsmLayout &Layout, |
| ArrayRef<WasmFunction> Functions); |
| uint32_t writeDataSection(const MCAsmLayout &Layout); |
| void writeTagSection(ArrayRef<uint32_t> TagTypes); |
| void writeGlobalSection(ArrayRef<wasm::WasmGlobal> Globals); |
| void writeTableSection(ArrayRef<wasm::WasmTable> Tables); |
| void writeRelocSection(uint32_t SectionIndex, StringRef Name, |
| std::vector<WasmRelocationEntry> &Relocations); |
| void writeLinkingMetaDataSection( |
| ArrayRef<wasm::WasmSymbolInfo> SymbolInfos, |
| ArrayRef<std::pair<uint16_t, uint32_t>> InitFuncs, |
| const std::map<StringRef, std::vector<WasmComdatEntry>> &Comdats); |
| void writeCustomSection(WasmCustomSection &CustomSection, |
| const MCAssembler &Asm, const MCAsmLayout &Layout); |
| void writeCustomRelocSections(); |
| |
| uint64_t getProvisionalValue(const WasmRelocationEntry &RelEntry, |
| const MCAsmLayout &Layout); |
| void applyRelocations(ArrayRef<WasmRelocationEntry> Relocations, |
| uint64_t ContentsOffset, const MCAsmLayout &Layout); |
| |
| uint32_t getRelocationIndexValue(const WasmRelocationEntry &RelEntry); |
| uint32_t getFunctionType(const MCSymbolWasm &Symbol); |
| uint32_t getTagType(const MCSymbolWasm &Symbol); |
| void registerFunctionType(const MCSymbolWasm &Symbol); |
| void registerTagType(const MCSymbolWasm &Symbol); |
| }; |
| |
| } // end anonymous namespace |
| |
| // Write out a section header and a patchable section size field. |
| void WasmObjectWriter::startSection(SectionBookkeeping &Section, |
| unsigned SectionId) { |
| LLVM_DEBUG(dbgs() << "startSection " << SectionId << "\n"); |
| W->OS << char(SectionId); |
| |
| Section.SizeOffset = W->OS.tell(); |
| |
| // The section size. We don't know the size yet, so reserve enough space |
| // for any 32-bit value; we'll patch it later. |
| encodeULEB128(0, W->OS, 5); |
| |
| // The position where the section starts, for measuring its size. |
| Section.ContentsOffset = W->OS.tell(); |
| Section.PayloadOffset = W->OS.tell(); |
| Section.Index = SectionCount++; |
| } |
| |
| // Write a string with extra paddings for trailing alignment |
| // TODO: support alignment at asm and llvm level? |
| void WasmObjectWriter::writeStringWithAlignment(const StringRef Str, |
| unsigned Alignment) { |
| |
| // Calculate the encoded size of str length and add pads based on it and |
| // alignment. |
| raw_null_ostream NullOS; |
| uint64_t StrSizeLength = encodeULEB128(Str.size(), NullOS); |
| uint64_t Offset = W->OS.tell() + StrSizeLength + Str.size(); |
| uint64_t Paddings = offsetToAlignment(Offset, Align(Alignment)); |
| Offset += Paddings; |
| |
| // LEB128 greater than 5 bytes is invalid |
| assert((StrSizeLength + Paddings) <= 5 && "too long string to align"); |
| |
| encodeSLEB128(Str.size(), W->OS, StrSizeLength + Paddings); |
| W->OS << Str; |
| |
| assert(W->OS.tell() == Offset && "invalid padding"); |
| } |
| |
| void WasmObjectWriter::startCustomSection(SectionBookkeeping &Section, |
| StringRef Name) { |
| LLVM_DEBUG(dbgs() << "startCustomSection " << Name << "\n"); |
| startSection(Section, wasm::WASM_SEC_CUSTOM); |
| |
| // The position where the section header ends, for measuring its size. |
| Section.PayloadOffset = W->OS.tell(); |
| |
| // Custom sections in wasm also have a string identifier. |
| if (Name != "__clangast") { |
| writeString(Name); |
| } else { |
| // The on-disk hashtable in clangast needs to be aligned by 4 bytes. |
| writeStringWithAlignment(Name, 4); |
| } |
| |
| // The position where the custom section starts. |
| Section.ContentsOffset = W->OS.tell(); |
| } |
| |
| // Now that the section is complete and we know how big it is, patch up the |
| // section size field at the start of the section. |
| void WasmObjectWriter::endSection(SectionBookkeeping &Section) { |
| uint64_t Size = W->OS.tell(); |
| // /dev/null doesn't support seek/tell and can report offset of 0. |
| // Simply skip this patching in that case. |
| if (!Size) |
| return; |
| |
| Size -= Section.PayloadOffset; |
| if (uint32_t(Size) != Size) |
| report_fatal_error("section size does not fit in a uint32_t"); |
| |
| LLVM_DEBUG(dbgs() << "endSection size=" << Size << "\n"); |
| |
| // Write the final section size to the payload_len field, which follows |
| // the section id byte. |
| writePatchableLEB<5>(static_cast<raw_pwrite_stream &>(W->OS), Size, |
| Section.SizeOffset); |
| } |
| |
| // Emit the Wasm header. |
| void WasmObjectWriter::writeHeader(const MCAssembler &Asm) { |
| W->OS.write(wasm::WasmMagic, sizeof(wasm::WasmMagic)); |
| W->write<uint32_t>(wasm::WasmVersion); |
| } |
| |
| void WasmObjectWriter::executePostLayoutBinding(MCAssembler &Asm, |
| const MCAsmLayout &Layout) { |
| // Some compilation units require the indirect function table to be present |
| // but don't explicitly reference it. This is the case for call_indirect |
| // without the reference-types feature, and also function bitcasts in all |
| // cases. In those cases the __indirect_function_table has the |
| // WASM_SYMBOL_NO_STRIP attribute. Here we make sure this symbol makes it to |
| // the assembler, if needed. |
| if (auto *Sym = Asm.getContext().lookupSymbol("__indirect_function_table")) { |
| const auto *WasmSym = static_cast<const MCSymbolWasm *>(Sym); |
| if (WasmSym->isNoStrip()) |
| Asm.registerSymbol(*Sym); |
| } |
| |
| // Build a map of sections to the function that defines them, for use |
| // in recordRelocation. |
| for (const MCSymbol &S : Asm.symbols()) { |
| const auto &WS = static_cast<const MCSymbolWasm &>(S); |
| if (WS.isDefined() && WS.isFunction() && !WS.isVariable()) { |
| const auto &Sec = static_cast<const MCSectionWasm &>(S.getSection()); |
| auto Pair = SectionFunctions.insert(std::make_pair(&Sec, &S)); |
| if (!Pair.second) |
| report_fatal_error("section already has a defining function: " + |
| Sec.getName()); |
| } |
| } |
| } |
| |
| void WasmObjectWriter::recordRelocation(MCAssembler &Asm, |
| const MCAsmLayout &Layout, |
| const MCFragment *Fragment, |
| const MCFixup &Fixup, MCValue Target, |
| uint64_t &FixedValue) { |
| // The WebAssembly backend should never generate FKF_IsPCRel fixups |
| assert(!(Asm.getBackend().getFixupKindInfo(Fixup.getKind()).Flags & |
| MCFixupKindInfo::FKF_IsPCRel)); |
| |
| const auto &FixupSection = cast<MCSectionWasm>(*Fragment->getParent()); |
| uint64_t C = Target.getConstant(); |
| uint64_t FixupOffset = Layout.getFragmentOffset(Fragment) + Fixup.getOffset(); |
| MCContext &Ctx = Asm.getContext(); |
| bool IsLocRel = false; |
| |
| if (const MCSymbolRefExpr *RefB = Target.getSymB()) { |
| |
| const auto &SymB = cast<MCSymbolWasm>(RefB->getSymbol()); |
| |
| if (FixupSection.getKind().isText()) { |
| Ctx.reportError(Fixup.getLoc(), |
| Twine("symbol '") + SymB.getName() + |
| "' unsupported subtraction expression used in " |
| "relocation in code section."); |
| return; |
| } |
| |
| if (SymB.isUndefined()) { |
| Ctx.reportError(Fixup.getLoc(), |
| Twine("symbol '") + SymB.getName() + |
| "' can not be undefined in a subtraction expression"); |
| return; |
| } |
| const MCSection &SecB = SymB.getSection(); |
| if (&SecB != &FixupSection) { |
| Ctx.reportError(Fixup.getLoc(), |
| Twine("symbol '") + SymB.getName() + |
| "' can not be placed in a different section"); |
| return; |
| } |
| IsLocRel = true; |
| C += FixupOffset - Layout.getSymbolOffset(SymB); |
| } |
| |
| // We either rejected the fixup or folded B into C at this point. |
| const MCSymbolRefExpr *RefA = Target.getSymA(); |
| const auto *SymA = cast<MCSymbolWasm>(&RefA->getSymbol()); |
| |
| // The .init_array isn't translated as data, so don't do relocations in it. |
| if (FixupSection.getName().startswith(".init_array")) { |
| SymA->setUsedInInitArray(); |
| return; |
| } |
| |
| if (SymA->isVariable()) { |
| const MCExpr *Expr = SymA->getVariableValue(); |
| if (const auto *Inner = dyn_cast<MCSymbolRefExpr>(Expr)) |
| if (Inner->getKind() == MCSymbolRefExpr::VK_WEAKREF) |
| llvm_unreachable("weakref used in reloc not yet implemented"); |
| } |
| |
| // Put any constant offset in an addend. Offsets can be negative, and |
| // LLVM expects wrapping, in contrast to wasm's immediates which can't |
| // be negative and don't wrap. |
| FixedValue = 0; |
| |
| unsigned Type = |
| TargetObjectWriter->getRelocType(Target, Fixup, FixupSection, IsLocRel); |
| |
| // Absolute offset within a section or a function. |
| // Currently only supported for for metadata sections. |
| // See: test/MC/WebAssembly/blockaddress.ll |
| if ((Type == wasm::R_WASM_FUNCTION_OFFSET_I32 || |
| Type == wasm::R_WASM_FUNCTION_OFFSET_I64 || |
| Type == wasm::R_WASM_SECTION_OFFSET_I32) && |
| SymA->isDefined()) { |
| // SymA can be a temp data symbol that represents a function (in which case |
| // it needs to be replaced by the section symbol), [XXX and it apparently |
| // later gets changed again to a func symbol?] or it can be a real |
| // function symbol, in which case it can be left as-is. |
| |
| if (!FixupSection.getKind().isMetadata()) |
| report_fatal_error("relocations for function or section offsets are " |
| "only supported in metadata sections"); |
| |
| const MCSymbol *SectionSymbol = nullptr; |
| const MCSection &SecA = SymA->getSection(); |
| if (SecA.getKind().isText()) { |
| auto SecSymIt = SectionFunctions.find(&SecA); |
| if (SecSymIt == SectionFunctions.end()) |
| report_fatal_error("section doesn\'t have defining symbol"); |
| SectionSymbol = SecSymIt->second; |
| } else { |
| SectionSymbol = SecA.getBeginSymbol(); |
| } |
| if (!SectionSymbol) |
| report_fatal_error("section symbol is required for relocation"); |
| |
| C += Layout.getSymbolOffset(*SymA); |
| SymA = cast<MCSymbolWasm>(SectionSymbol); |
| } |
| |
| if (Type == wasm::R_WASM_TABLE_INDEX_REL_SLEB || |
| Type == wasm::R_WASM_TABLE_INDEX_REL_SLEB64 || |
| Type == wasm::R_WASM_TABLE_INDEX_SLEB || |
| Type == wasm::R_WASM_TABLE_INDEX_SLEB64 || |
| Type == wasm::R_WASM_TABLE_INDEX_I32 || |
| Type == wasm::R_WASM_TABLE_INDEX_I64) { |
| // TABLE_INDEX relocs implicitly use the default indirect function table. |
| // We require the function table to have already been defined. |
| auto TableName = "__indirect_function_table"; |
| MCSymbolWasm *Sym = cast_or_null<MCSymbolWasm>(Ctx.lookupSymbol(TableName)); |
| if (!Sym) { |
| report_fatal_error("missing indirect function table symbol"); |
| } else { |
| if (!Sym->isFunctionTable()) |
| report_fatal_error("__indirect_function_table symbol has wrong type"); |
| // Ensure that __indirect_function_table reaches the output. |
| Sym->setNoStrip(); |
| Asm.registerSymbol(*Sym); |
| } |
| } |
| |
| // Relocation other than R_WASM_TYPE_INDEX_LEB are required to be |
| // against a named symbol. |
| if (Type != wasm::R_WASM_TYPE_INDEX_LEB) { |
| if (SymA->getName().empty()) |
| report_fatal_error("relocations against un-named temporaries are not yet " |
| "supported by wasm"); |
| |
| SymA->setUsedInReloc(); |
| } |
| |
| switch (RefA->getKind()) { |
| case MCSymbolRefExpr::VK_GOT: |
| case MCSymbolRefExpr::VK_WASM_GOT_TLS: |
| SymA->setUsedInGOT(); |
| break; |
| default: |
| break; |
| } |
| |
| WasmRelocationEntry Rec(FixupOffset, SymA, C, Type, &FixupSection); |
| LLVM_DEBUG(dbgs() << "WasmReloc: " << Rec << "\n"); |
| |
| if (FixupSection.isWasmData()) { |
| DataRelocations.push_back(Rec); |
| } else if (FixupSection.getKind().isText()) { |
| CodeRelocations.push_back(Rec); |
| } else if (FixupSection.getKind().isMetadata()) { |
| CustomSectionsRelocations[&FixupSection].push_back(Rec); |
| } else { |
| llvm_unreachable("unexpected section type"); |
| } |
| } |
| |
| // Compute a value to write into the code at the location covered |
| // by RelEntry. This value isn't used by the static linker; it just serves |
| // to make the object format more readable and more likely to be directly |
| // useable. |
| uint64_t |
| WasmObjectWriter::getProvisionalValue(const WasmRelocationEntry &RelEntry, |
| const MCAsmLayout &Layout) { |
| if ((RelEntry.Type == wasm::R_WASM_GLOBAL_INDEX_LEB || |
| RelEntry.Type == wasm::R_WASM_GLOBAL_INDEX_I32) && |
| !RelEntry.Symbol->isGlobal()) { |
| assert(GOTIndices.count(RelEntry.Symbol) > 0 && "symbol not found in GOT index space"); |
| return GOTIndices[RelEntry.Symbol]; |
| } |
| |
| switch (RelEntry.Type) { |
| case wasm::R_WASM_TABLE_INDEX_REL_SLEB: |
| case wasm::R_WASM_TABLE_INDEX_REL_SLEB64: |
| case wasm::R_WASM_TABLE_INDEX_SLEB: |
| case wasm::R_WASM_TABLE_INDEX_SLEB64: |
| case wasm::R_WASM_TABLE_INDEX_I32: |
| case wasm::R_WASM_TABLE_INDEX_I64: { |
| // Provisional value is table address of the resolved symbol itself |
| const MCSymbolWasm *Base = |
| cast<MCSymbolWasm>(Layout.getBaseSymbol(*RelEntry.Symbol)); |
| assert(Base->isFunction()); |
| if (RelEntry.Type == wasm::R_WASM_TABLE_INDEX_REL_SLEB || |
| RelEntry.Type == wasm::R_WASM_TABLE_INDEX_REL_SLEB64) |
| return TableIndices[Base] - InitialTableOffset; |
| else |
| return TableIndices[Base]; |
| } |
| case wasm::R_WASM_TYPE_INDEX_LEB: |
| // Provisional value is same as the index |
| return getRelocationIndexValue(RelEntry); |
| case wasm::R_WASM_FUNCTION_INDEX_LEB: |
| case wasm::R_WASM_GLOBAL_INDEX_LEB: |
| case wasm::R_WASM_GLOBAL_INDEX_I32: |
| case wasm::R_WASM_TAG_INDEX_LEB: |
| case wasm::R_WASM_TABLE_NUMBER_LEB: |
| // Provisional value is function/global/tag Wasm index |
| assert(WasmIndices.count(RelEntry.Symbol) > 0 && "symbol not found in wasm index space"); |
| return WasmIndices[RelEntry.Symbol]; |
| case wasm::R_WASM_FUNCTION_OFFSET_I32: |
| case wasm::R_WASM_FUNCTION_OFFSET_I64: |
| case wasm::R_WASM_SECTION_OFFSET_I32: { |
| if (!RelEntry.Symbol->isDefined()) |
| return 0; |
| const auto &Section = |
| static_cast<const MCSectionWasm &>(RelEntry.Symbol->getSection()); |
| return Section.getSectionOffset() + RelEntry.Addend; |
| } |
| case wasm::R_WASM_MEMORY_ADDR_LEB: |
| case wasm::R_WASM_MEMORY_ADDR_LEB64: |
| case wasm::R_WASM_MEMORY_ADDR_SLEB: |
| case wasm::R_WASM_MEMORY_ADDR_SLEB64: |
| case wasm::R_WASM_MEMORY_ADDR_REL_SLEB: |
| case wasm::R_WASM_MEMORY_ADDR_REL_SLEB64: |
| case wasm::R_WASM_MEMORY_ADDR_I32: |
| case wasm::R_WASM_MEMORY_ADDR_I64: |
| case wasm::R_WASM_MEMORY_ADDR_TLS_SLEB: |
| case wasm::R_WASM_MEMORY_ADDR_TLS_SLEB64: |
| case wasm::R_WASM_MEMORY_ADDR_LOCREL_I32: { |
| // Provisional value is address of the global plus the offset |
| // For undefined symbols, use zero |
| if (!RelEntry.Symbol->isDefined()) |
| return 0; |
| const wasm::WasmDataReference &SymRef = DataLocations[RelEntry.Symbol]; |
| const WasmDataSegment &Segment = DataSegments[SymRef.Segment]; |
| // Ignore overflow. LLVM allows address arithmetic to silently wrap. |
| return Segment.Offset + SymRef.Offset + RelEntry.Addend; |
| } |
| default: |
| llvm_unreachable("invalid relocation type"); |
| } |
| } |
| |
| static void addData(SmallVectorImpl<char> &DataBytes, |
| MCSectionWasm &DataSection) { |
| LLVM_DEBUG(errs() << "addData: " << DataSection.getName() << "\n"); |
| |
| DataBytes.resize(alignTo(DataBytes.size(), DataSection.getAlignment())); |
| |
| for (const MCFragment &Frag : DataSection) { |
| if (Frag.hasInstructions()) |
| report_fatal_error("only data supported in data sections"); |
| |
| if (auto *Align = dyn_cast<MCAlignFragment>(&Frag)) { |
| if (Align->getValueSize() != 1) |
| report_fatal_error("only byte values supported for alignment"); |
| // If nops are requested, use zeros, as this is the data section. |
| uint8_t Value = Align->hasEmitNops() ? 0 : Align->getValue(); |
| uint64_t Size = |
| std::min<uint64_t>(alignTo(DataBytes.size(), Align->getAlignment()), |
| DataBytes.size() + Align->getMaxBytesToEmit()); |
| DataBytes.resize(Size, Value); |
| } else if (auto *Fill = dyn_cast<MCFillFragment>(&Frag)) { |
| int64_t NumValues; |
| if (!Fill->getNumValues().evaluateAsAbsolute(NumValues)) |
| llvm_unreachable("The fill should be an assembler constant"); |
| DataBytes.insert(DataBytes.end(), Fill->getValueSize() * NumValues, |
| Fill->getValue()); |
| } else if (auto *LEB = dyn_cast<MCLEBFragment>(&Frag)) { |
| const SmallVectorImpl<char> &Contents = LEB->getContents(); |
| llvm::append_range(DataBytes, Contents); |
| } else { |
| const auto &DataFrag = cast<MCDataFragment>(Frag); |
| const SmallVectorImpl<char> &Contents = DataFrag.getContents(); |
| llvm::append_range(DataBytes, Contents); |
| } |
| } |
| |
| LLVM_DEBUG(dbgs() << "addData -> " << DataBytes.size() << "\n"); |
| } |
| |
| uint32_t |
| WasmObjectWriter::getRelocationIndexValue(const WasmRelocationEntry &RelEntry) { |
| if (RelEntry.Type == wasm::R_WASM_TYPE_INDEX_LEB) { |
| if (!TypeIndices.count(RelEntry.Symbol)) |
| report_fatal_error("symbol not found in type index space: " + |
| RelEntry.Symbol->getName()); |
| return TypeIndices[RelEntry.Symbol]; |
| } |
| |
| return RelEntry.Symbol->getIndex(); |
| } |
| |
| // Apply the portions of the relocation records that we can handle ourselves |
| // directly. |
| void WasmObjectWriter::applyRelocations( |
| ArrayRef<WasmRelocationEntry> Relocations, uint64_t ContentsOffset, |
| const MCAsmLayout &Layout) { |
| auto &Stream = static_cast<raw_pwrite_stream &>(W->OS); |
| for (const WasmRelocationEntry &RelEntry : Relocations) { |
| uint64_t Offset = ContentsOffset + |
| RelEntry.FixupSection->getSectionOffset() + |
| RelEntry.Offset; |
| |
| LLVM_DEBUG(dbgs() << "applyRelocation: " << RelEntry << "\n"); |
| auto Value = getProvisionalValue(RelEntry, Layout); |
| |
| switch (RelEntry.Type) { |
| case wasm::R_WASM_FUNCTION_INDEX_LEB: |
| case wasm::R_WASM_TYPE_INDEX_LEB: |
| case wasm::R_WASM_GLOBAL_INDEX_LEB: |
| case wasm::R_WASM_MEMORY_ADDR_LEB: |
| case wasm::R_WASM_TAG_INDEX_LEB: |
| case wasm::R_WASM_TABLE_NUMBER_LEB: |
| writePatchableLEB<5>(Stream, Value, Offset); |
| break; |
| case wasm::R_WASM_MEMORY_ADDR_LEB64: |
| writePatchableLEB<10>(Stream, Value, Offset); |
| break; |
| case wasm::R_WASM_TABLE_INDEX_I32: |
| case wasm::R_WASM_MEMORY_ADDR_I32: |
| case wasm::R_WASM_FUNCTION_OFFSET_I32: |
| case wasm::R_WASM_SECTION_OFFSET_I32: |
| case wasm::R_WASM_GLOBAL_INDEX_I32: |
| case wasm::R_WASM_MEMORY_ADDR_LOCREL_I32: |
| patchI32(Stream, Value, Offset); |
| break; |
| case wasm::R_WASM_TABLE_INDEX_I64: |
| case wasm::R_WASM_MEMORY_ADDR_I64: |
| case wasm::R_WASM_FUNCTION_OFFSET_I64: |
| patchI64(Stream, Value, Offset); |
| break; |
| case wasm::R_WASM_TABLE_INDEX_SLEB: |
| case wasm::R_WASM_TABLE_INDEX_REL_SLEB: |
| case wasm::R_WASM_MEMORY_ADDR_SLEB: |
| case wasm::R_WASM_MEMORY_ADDR_REL_SLEB: |
| case wasm::R_WASM_MEMORY_ADDR_TLS_SLEB: |
| writePatchableSLEB<5>(Stream, Value, Offset); |
| break; |
| case wasm::R_WASM_TABLE_INDEX_SLEB64: |
| case wasm::R_WASM_TABLE_INDEX_REL_SLEB64: |
| case wasm::R_WASM_MEMORY_ADDR_SLEB64: |
| case wasm::R_WASM_MEMORY_ADDR_REL_SLEB64: |
| case wasm::R_WASM_MEMORY_ADDR_TLS_SLEB64: |
| writePatchableSLEB<10>(Stream, Value, Offset); |
| break; |
| default: |
| llvm_unreachable("invalid relocation type"); |
| } |
| } |
| } |
| |
| void WasmObjectWriter::writeTypeSection( |
| ArrayRef<wasm::WasmSignature> Signatures) { |
| if (Signatures.empty()) |
| return; |
| |
| SectionBookkeeping Section; |
| startSection(Section, wasm::WASM_SEC_TYPE); |
| |
| encodeULEB128(Signatures.size(), W->OS); |
| |
| for (const wasm::WasmSignature &Sig : Signatures) { |
| W->OS << char(wasm::WASM_TYPE_FUNC); |
| encodeULEB128(Sig.Params.size(), W->OS); |
| for (wasm::ValType Ty : Sig.Params) |
| writeValueType(Ty); |
| encodeULEB128(Sig.Returns.size(), W->OS); |
| for (wasm::ValType Ty : Sig.Returns) |
| writeValueType(Ty); |
| } |
| |
| endSection(Section); |
| } |
| |
| void WasmObjectWriter::writeImportSection(ArrayRef<wasm::WasmImport> Imports, |
| uint64_t DataSize, |
| uint32_t NumElements) { |
| if (Imports.empty()) |
| return; |
| |
| uint64_t NumPages = (DataSize + wasm::WasmPageSize - 1) / wasm::WasmPageSize; |
| |
| SectionBookkeeping Section; |
| startSection(Section, wasm::WASM_SEC_IMPORT); |
| |
| encodeULEB128(Imports.size(), W->OS); |
| for (const wasm::WasmImport &Import : Imports) { |
| writeString(Import.Module); |
| writeString(Import.Field); |
| W->OS << char(Import.Kind); |
| |
| switch (Import.Kind) { |
| case wasm::WASM_EXTERNAL_FUNCTION: |
| encodeULEB128(Import.SigIndex, W->OS); |
| break; |
| case wasm::WASM_EXTERNAL_GLOBAL: |
| W->OS << char(Import.Global.Type); |
| W->OS << char(Import.Global.Mutable ? 1 : 0); |
| break; |
| case wasm::WASM_EXTERNAL_MEMORY: |
| encodeULEB128(Import.Memory.Flags, W->OS); |
| encodeULEB128(NumPages, W->OS); // initial |
| break; |
| case wasm::WASM_EXTERNAL_TABLE: |
| W->OS << char(Import.Table.ElemType); |
| encodeULEB128(0, W->OS); // flags |
| encodeULEB128(NumElements, W->OS); // initial |
| break; |
| case wasm::WASM_EXTERNAL_TAG: |
| W->OS << char(0); // Reserved 'attribute' field |
| encodeULEB128(Import.SigIndex, W->OS); |
| break; |
| default: |
| llvm_unreachable("unsupported import kind"); |
| } |
| } |
| |
| endSection(Section); |
| } |
| |
| void WasmObjectWriter::writeFunctionSection(ArrayRef<WasmFunction> Functions) { |
| if (Functions.empty()) |
| return; |
| |
| SectionBookkeeping Section; |
| startSection(Section, wasm::WASM_SEC_FUNCTION); |
| |
| encodeULEB128(Functions.size(), W->OS); |
| for (const WasmFunction &Func : Functions) |
| encodeULEB128(Func.SigIndex, W->OS); |
| |
| endSection(Section); |
| } |
| |
| void WasmObjectWriter::writeTagSection(ArrayRef<uint32_t> TagTypes) { |
| if (TagTypes.empty()) |
| return; |
| |
| SectionBookkeeping Section; |
| startSection(Section, wasm::WASM_SEC_TAG); |
| |
| encodeULEB128(TagTypes.size(), W->OS); |
| for (uint32_t Index : TagTypes) { |
| W->OS << char(0); // Reserved 'attribute' field |
| encodeULEB128(Index, W->OS); |
| } |
| |
| endSection(Section); |
| } |
| |
| void WasmObjectWriter::writeGlobalSection(ArrayRef<wasm::WasmGlobal> Globals) { |
| if (Globals.empty()) |
| return; |
| |
| SectionBookkeeping Section; |
| startSection(Section, wasm::WASM_SEC_GLOBAL); |
| |
| encodeULEB128(Globals.size(), W->OS); |
| for (const wasm::WasmGlobal &Global : Globals) { |
| encodeULEB128(Global.Type.Type, W->OS); |
| W->OS << char(Global.Type.Mutable); |
| W->OS << char(Global.InitExpr.Opcode); |
| switch (Global.Type.Type) { |
| case wasm::WASM_TYPE_I32: |
| encodeSLEB128(0, W->OS); |
| break; |
| case wasm::WASM_TYPE_I64: |
| encodeSLEB128(0, W->OS); |
| break; |
| case wasm::WASM_TYPE_F32: |
| writeI32(0); |
| break; |
| case wasm::WASM_TYPE_F64: |
| writeI64(0); |
| break; |
| case wasm::WASM_TYPE_EXTERNREF: |
| writeValueType(wasm::ValType::EXTERNREF); |
| break; |
| default: |
| llvm_unreachable("unexpected type"); |
| } |
| W->OS << char(wasm::WASM_OPCODE_END); |
| } |
| |
| endSection(Section); |
| } |
| |
| void WasmObjectWriter::writeTableSection(ArrayRef<wasm::WasmTable> Tables) { |
| if (Tables.empty()) |
| return; |
| |
| SectionBookkeeping Section; |
| startSection(Section, wasm::WASM_SEC_TABLE); |
| |
| encodeULEB128(Tables.size(), W->OS); |
| for (const wasm::WasmTable &Table : Tables) { |
| encodeULEB128(Table.Type.ElemType, W->OS); |
| encodeULEB128(Table.Type.Limits.Flags, W->OS); |
| encodeULEB128(Table.Type.Limits.Minimum, W->OS); |
| if (Table.Type.Limits.Flags & wasm::WASM_LIMITS_FLAG_HAS_MAX) |
| encodeULEB128(Table.Type.Limits.Maximum, W->OS); |
| } |
| endSection(Section); |
| } |
| |
| void WasmObjectWriter::writeExportSection(ArrayRef<wasm::WasmExport> Exports) { |
| if (Exports.empty()) |
| return; |
| |
| SectionBookkeeping Section; |
| startSection(Section, wasm::WASM_SEC_EXPORT); |
| |
| encodeULEB128(Exports.size(), W->OS); |
| for (const wasm::WasmExport &Export : Exports) { |
| writeString(Export.Name); |
| W->OS << char(Export.Kind); |
| encodeULEB128(Export.Index, W->OS); |
| } |
| |
| endSection(Section); |
| } |
| |
| void WasmObjectWriter::writeElemSection( |
| const MCSymbolWasm *IndirectFunctionTable, ArrayRef<uint32_t> TableElems) { |
| if (TableElems.empty()) |
| return; |
| |
| assert(IndirectFunctionTable); |
| |
| SectionBookkeeping Section; |
| startSection(Section, wasm::WASM_SEC_ELEM); |
| |
| encodeULEB128(1, W->OS); // number of "segments" |
| |
| assert(WasmIndices.count(IndirectFunctionTable)); |
| uint32_t TableNumber = WasmIndices.find(IndirectFunctionTable)->second; |
| uint32_t Flags = 0; |
| if (TableNumber) |
| Flags |= wasm::WASM_ELEM_SEGMENT_HAS_TABLE_NUMBER; |
| encodeULEB128(Flags, W->OS); |
| if (Flags & wasm::WASM_ELEM_SEGMENT_HAS_TABLE_NUMBER) |
| encodeULEB128(TableNumber, W->OS); // the table number |
| |
| // init expr for starting offset |
| W->OS << char(wasm::WASM_OPCODE_I32_CONST); |
| encodeSLEB128(InitialTableOffset, W->OS); |
| W->OS << char(wasm::WASM_OPCODE_END); |
| |
| if (Flags & wasm::WASM_ELEM_SEGMENT_MASK_HAS_ELEM_KIND) { |
| // We only write active function table initializers, for which the elem kind |
| // is specified to be written as 0x00 and interpreted to mean "funcref". |
| const uint8_t ElemKind = 0; |
| W->OS << ElemKind; |
| } |
| |
| encodeULEB128(TableElems.size(), W->OS); |
| for (uint32_t Elem : TableElems) |
| encodeULEB128(Elem, W->OS); |
| |
| endSection(Section); |
| } |
| |
| void WasmObjectWriter::writeDataCountSection() { |
| if (DataSegments.empty()) |
| return; |
| |
| SectionBookkeeping Section; |
| startSection(Section, wasm::WASM_SEC_DATACOUNT); |
| encodeULEB128(DataSegments.size(), W->OS); |
| endSection(Section); |
| } |
| |
| uint32_t WasmObjectWriter::writeCodeSection(const MCAssembler &Asm, |
| const MCAsmLayout &Layout, |
| ArrayRef<WasmFunction> Functions) { |
| if (Functions.empty()) |
| return 0; |
| |
| SectionBookkeeping Section; |
| startSection(Section, wasm::WASM_SEC_CODE); |
| |
| encodeULEB128(Functions.size(), W->OS); |
| |
| for (const WasmFunction &Func : Functions) { |
| auto &FuncSection = static_cast<MCSectionWasm &>(Func.Sym->getSection()); |
| |
| int64_t Size = 0; |
| if (!Func.Sym->getSize()->evaluateAsAbsolute(Size, Layout)) |
| report_fatal_error(".size expression must be evaluatable"); |
| |
| encodeULEB128(Size, W->OS); |
| FuncSection.setSectionOffset(W->OS.tell() - Section.ContentsOffset); |
| Asm.writeSectionData(W->OS, &FuncSection, Layout); |
| } |
| |
| // Apply fixups. |
| applyRelocations(CodeRelocations, Section.ContentsOffset, Layout); |
| |
| endSection(Section); |
| return Section.Index; |
| } |
| |
| uint32_t WasmObjectWriter::writeDataSection(const MCAsmLayout &Layout) { |
| if (DataSegments.empty()) |
| return 0; |
| |
| SectionBookkeeping Section; |
| startSection(Section, wasm::WASM_SEC_DATA); |
| |
| encodeULEB128(DataSegments.size(), W->OS); // count |
| |
| for (const WasmDataSegment &Segment : DataSegments) { |
| encodeULEB128(Segment.InitFlags, W->OS); // flags |
| if (Segment.InitFlags & wasm::WASM_DATA_SEGMENT_HAS_MEMINDEX) |
| encodeULEB128(0, W->OS); // memory index |
| if ((Segment.InitFlags & wasm::WASM_DATA_SEGMENT_IS_PASSIVE) == 0) { |
| W->OS << char(is64Bit() ? wasm::WASM_OPCODE_I64_CONST |
| : wasm::WASM_OPCODE_I32_CONST); |
| encodeSLEB128(Segment.Offset, W->OS); // offset |
| W->OS << char(wasm::WASM_OPCODE_END); |
| } |
| encodeULEB128(Segment.Data.size(), W->OS); // size |
| Segment.Section->setSectionOffset(W->OS.tell() - Section.ContentsOffset); |
| W->OS << Segment.Data; // data |
| } |
| |
| // Apply fixups. |
| applyRelocations(DataRelocations, Section.ContentsOffset, Layout); |
| |
| endSection(Section); |
| return Section.Index; |
| } |
| |
| void WasmObjectWriter::writeRelocSection( |
| uint32_t SectionIndex, StringRef Name, |
| std::vector<WasmRelocationEntry> &Relocs) { |
| // See: https://github.com/WebAssembly/tool-conventions/blob/main/Linking.md |
| // for descriptions of the reloc sections. |
| |
| if (Relocs.empty()) |
| return; |
| |
| // First, ensure the relocations are sorted in offset order. In general they |
| // should already be sorted since `recordRelocation` is called in offset |
| // order, but for the code section we combine many MC sections into single |
| // wasm section, and this order is determined by the order of Asm.Symbols() |
| // not the sections order. |
| llvm::stable_sort( |
| Relocs, [](const WasmRelocationEntry &A, const WasmRelocationEntry &B) { |
| return (A.Offset + A.FixupSection->getSectionOffset()) < |
| (B.Offset + B.FixupSection->getSectionOffset()); |
| }); |
| |
| SectionBookkeeping Section; |
| startCustomSection(Section, std::string("reloc.") + Name.str()); |
| |
| encodeULEB128(SectionIndex, W->OS); |
| encodeULEB128(Relocs.size(), W->OS); |
| for (const WasmRelocationEntry &RelEntry : Relocs) { |
| uint64_t Offset = |
| RelEntry.Offset + RelEntry.FixupSection->getSectionOffset(); |
| uint32_t Index = getRelocationIndexValue(RelEntry); |
| |
| W->OS << char(RelEntry.Type); |
| encodeULEB128(Offset, W->OS); |
| encodeULEB128(Index, W->OS); |
| if (RelEntry.hasAddend()) |
| encodeSLEB128(RelEntry.Addend, W->OS); |
| } |
| |
| endSection(Section); |
| } |
| |
| void WasmObjectWriter::writeCustomRelocSections() { |
| for (const auto &Sec : CustomSections) { |
| auto &Relocations = CustomSectionsRelocations[Sec.Section]; |
| writeRelocSection(Sec.OutputIndex, Sec.Name, Relocations); |
| } |
| } |
| |
| void WasmObjectWriter::writeLinkingMetaDataSection( |
| ArrayRef<wasm::WasmSymbolInfo> SymbolInfos, |
| ArrayRef<std::pair<uint16_t, uint32_t>> InitFuncs, |
| const std::map<StringRef, std::vector<WasmComdatEntry>> &Comdats) { |
| SectionBookkeeping Section; |
| startCustomSection(Section, "linking"); |
| encodeULEB128(wasm::WasmMetadataVersion, W->OS); |
| |
| SectionBookkeeping SubSection; |
| if (SymbolInfos.size() != 0) { |
| startSection(SubSection, wasm::WASM_SYMBOL_TABLE); |
| encodeULEB128(SymbolInfos.size(), W->OS); |
| for (const wasm::WasmSymbolInfo &Sym : SymbolInfos) { |
| encodeULEB128(Sym.Kind, W->OS); |
| encodeULEB128(Sym.Flags, W->OS); |
| switch (Sym.Kind) { |
| case wasm::WASM_SYMBOL_TYPE_FUNCTION: |
| case wasm::WASM_SYMBOL_TYPE_GLOBAL: |
| case wasm::WASM_SYMBOL_TYPE_TAG: |
| case wasm::WASM_SYMBOL_TYPE_TABLE: |
| encodeULEB128(Sym.ElementIndex, W->OS); |
| if ((Sym.Flags & wasm::WASM_SYMBOL_UNDEFINED) == 0 || |
| (Sym.Flags & wasm::WASM_SYMBOL_EXPLICIT_NAME) != 0) |
| writeString(Sym.Name); |
| break; |
| case wasm::WASM_SYMBOL_TYPE_DATA: |
| writeString(Sym.Name); |
| if ((Sym.Flags & wasm::WASM_SYMBOL_UNDEFINED) == 0) { |
| encodeULEB128(Sym.DataRef.Segment, W->OS); |
| encodeULEB128(Sym.DataRef.Offset, W->OS); |
| encodeULEB128(Sym.DataRef.Size, W->OS); |
| } |
| break; |
| case wasm::WASM_SYMBOL_TYPE_SECTION: { |
| const uint32_t SectionIndex = |
| CustomSections[Sym.ElementIndex].OutputIndex; |
| encodeULEB128(SectionIndex, W->OS); |
| break; |
| } |
| default: |
| llvm_unreachable("unexpected kind"); |
| } |
| } |
| endSection(SubSection); |
| } |
| |
| if (DataSegments.size()) { |
| startSection(SubSection, wasm::WASM_SEGMENT_INFO); |
| encodeULEB128(DataSegments.size(), W->OS); |
| for (const WasmDataSegment &Segment : DataSegments) { |
| writeString(Segment.Name); |
| encodeULEB128(Segment.Alignment, W->OS); |
| encodeULEB128(Segment.LinkingFlags, W->OS); |
| } |
| endSection(SubSection); |
| } |
| |
| if (!InitFuncs.empty()) { |
| startSection(SubSection, wasm::WASM_INIT_FUNCS); |
| encodeULEB128(InitFuncs.size(), W->OS); |
| for (auto &StartFunc : InitFuncs) { |
| encodeULEB128(StartFunc.first, W->OS); // priority |
| encodeULEB128(StartFunc.second, W->OS); // function index |
| } |
| endSection(SubSection); |
| } |
| |
| if (Comdats.size()) { |
| startSection(SubSection, wasm::WASM_COMDAT_INFO); |
| encodeULEB128(Comdats.size(), W->OS); |
| for (const auto &C : Comdats) { |
| writeString(C.first); |
| encodeULEB128(0, W->OS); // flags for future use |
| encodeULEB128(C.second.size(), W->OS); |
| for (const WasmComdatEntry &Entry : C.second) { |
| encodeULEB128(Entry.Kind, W->OS); |
| encodeULEB128(Entry.Index, W->OS); |
| } |
| } |
| endSection(SubSection); |
| } |
| |
| endSection(Section); |
| } |
| |
| void WasmObjectWriter::writeCustomSection(WasmCustomSection &CustomSection, |
| const MCAssembler &Asm, |
| const MCAsmLayout &Layout) { |
| SectionBookkeeping Section; |
| auto *Sec = CustomSection.Section; |
| startCustomSection(Section, CustomSection.Name); |
| |
| Sec->setSectionOffset(W->OS.tell() - Section.ContentsOffset); |
| Asm.writeSectionData(W->OS, Sec, Layout); |
| |
| CustomSection.OutputContentsOffset = Section.ContentsOffset; |
| CustomSection.OutputIndex = Section.Index; |
| |
| endSection(Section); |
| |
| // Apply fixups. |
| auto &Relocations = CustomSectionsRelocations[CustomSection.Section]; |
| applyRelocations(Relocations, CustomSection.OutputContentsOffset, Layout); |
| } |
| |
| uint32_t WasmObjectWriter::getFunctionType(const MCSymbolWasm &Symbol) { |
| assert(Symbol.isFunction()); |
| assert(TypeIndices.count(&Symbol)); |
| return TypeIndices[&Symbol]; |
| } |
| |
| uint32_t WasmObjectWriter::getTagType(const MCSymbolWasm &Symbol) { |
| assert(Symbol.isTag()); |
| assert(TypeIndices.count(&Symbol)); |
| return TypeIndices[&Symbol]; |
| } |
| |
| void WasmObjectWriter::registerFunctionType(const MCSymbolWasm &Symbol) { |
| assert(Symbol.isFunction()); |
| |
| wasm::WasmSignature S; |
| |
| if (auto *Sig = Symbol.getSignature()) { |
| S.Returns = Sig->Returns; |
| S.Params = Sig->Params; |
| } |
| |
| auto Pair = SignatureIndices.insert(std::make_pair(S, Signatures.size())); |
| if (Pair.second) |
| Signatures.push_back(S); |
| TypeIndices[&Symbol] = Pair.first->second; |
| |
| LLVM_DEBUG(dbgs() << "registerFunctionType: " << Symbol |
| << " new:" << Pair.second << "\n"); |
| LLVM_DEBUG(dbgs() << " -> type index: " << Pair.first->second << "\n"); |
| } |
| |
| void WasmObjectWriter::registerTagType(const MCSymbolWasm &Symbol) { |
| assert(Symbol.isTag()); |
| |
| // TODO Currently we don't generate imported exceptions, but if we do, we |
| // should have a way of infering types of imported exceptions. |
| wasm::WasmSignature S; |
| if (auto *Sig = Symbol.getSignature()) { |
| S.Returns = Sig->Returns; |
| S.Params = Sig->Params; |
| } |
| |
| auto Pair = SignatureIndices.insert(std::make_pair(S, Signatures.size())); |
| if (Pair.second) |
| Signatures.push_back(S); |
| TypeIndices[&Symbol] = Pair.first->second; |
| |
| LLVM_DEBUG(dbgs() << "registerTagType: " << Symbol << " new:" << Pair.second |
| << "\n"); |
| LLVM_DEBUG(dbgs() << " -> type index: " << Pair.first->second << "\n"); |
| } |
| |
| static bool isInSymtab(const MCSymbolWasm &Sym) { |
| if (Sym.isUsedInReloc() || Sym.isUsedInInitArray()) |
| return true; |
| |
| if (Sym.isComdat() && !Sym.isDefined()) |
| return false; |
| |
| if (Sym.isTemporary()) |
| return false; |
| |
| if (Sym.isSection()) |
| return false; |
| |
| if (Sym.omitFromLinkingSection()) |
| return false; |
| |
| return true; |
| } |
| |
| void WasmObjectWriter::prepareImports( |
| SmallVectorImpl<wasm::WasmImport> &Imports, MCAssembler &Asm, |
| const MCAsmLayout &Layout) { |
| // For now, always emit the memory import, since loads and stores are not |
| // valid without it. In the future, we could perhaps be more clever and omit |
| // it if there are no loads or stores. |
| wasm::WasmImport MemImport; |
| MemImport.Module = "env"; |
| MemImport.Field = "__linear_memory"; |
| MemImport.Kind = wasm::WASM_EXTERNAL_MEMORY; |
| MemImport.Memory.Flags = is64Bit() ? wasm::WASM_LIMITS_FLAG_IS_64 |
| : wasm::WASM_LIMITS_FLAG_NONE; |
| Imports.push_back(MemImport); |
| |
| // Populate SignatureIndices, and Imports and WasmIndices for undefined |
| // symbols. This must be done before populating WasmIndices for defined |
| // symbols. |
| for (const MCSymbol &S : Asm.symbols()) { |
| const auto &WS = static_cast<const MCSymbolWasm &>(S); |
| |
| // Register types for all functions, including those with private linkage |
| // (because wasm always needs a type signature). |
| if (WS.isFunction()) { |
| const auto *BS = Layout.getBaseSymbol(S); |
| if (!BS) |
| report_fatal_error(Twine(S.getName()) + |
| ": absolute addressing not supported!"); |
| registerFunctionType(*cast<MCSymbolWasm>(BS)); |
| } |
| |
| if (WS.isTag()) |
| registerTagType(WS); |
| |
| if (WS.isTemporary()) |
| continue; |
| |
| // If the symbol is not defined in this translation unit, import it. |
| if (!WS.isDefined() && !WS.isComdat()) { |
| if (WS.isFunction()) { |
| wasm::WasmImport Import; |
| Import.Module = WS.getImportModule(); |
| Import.Field = WS.getImportName(); |
| Import.Kind = wasm::WASM_EXTERNAL_FUNCTION; |
| Import.SigIndex = getFunctionType(WS); |
| Imports.push_back(Import); |
| assert(WasmIndices.count(&WS) == 0); |
| WasmIndices[&WS] = NumFunctionImports++; |
| } else if (WS.isGlobal()) { |
| if (WS.isWeak()) |
| report_fatal_error("undefined global symbol cannot be weak"); |
| |
| wasm::WasmImport Import; |
| Import.Field = WS.getImportName(); |
| Import.Kind = wasm::WASM_EXTERNAL_GLOBAL; |
| Import.Module = WS.getImportModule(); |
| Import.Global = WS.getGlobalType(); |
| Imports.push_back(Import); |
| assert(WasmIndices.count(&WS) == 0); |
| WasmIndices[&WS] = NumGlobalImports++; |
| } else if (WS.isTag()) { |
| if (WS.isWeak()) |
| report_fatal_error("undefined tag symbol cannot be weak"); |
| |
| wasm::WasmImport Import; |
| Import.Module = WS.getImportModule(); |
| Import.Field = WS.getImportName(); |
| Import.Kind = wasm::WASM_EXTERNAL_TAG; |
| Import.SigIndex = getTagType(WS); |
| Imports.push_back(Import); |
| assert(WasmIndices.count(&WS) == 0); |
| WasmIndices[&WS] = NumTagImports++; |
| } else if (WS.isTable()) { |
| if (WS.isWeak()) |
| report_fatal_error("undefined table symbol cannot be weak"); |
| |
| wasm::WasmImport Import; |
| Import.Module = WS.getImportModule(); |
| Import.Field = WS.getImportName(); |
| Import.Kind = wasm::WASM_EXTERNAL_TABLE; |
| Import.Table = WS.getTableType(); |
| Imports.push_back(Import); |
| assert(WasmIndices.count(&WS) == 0); |
| WasmIndices[&WS] = NumTableImports++; |
| } |
| } |
| } |
| |
| // Add imports for GOT globals |
| for (const MCSymbol &S : Asm.symbols()) { |
| const auto &WS = static_cast<const MCSymbolWasm &>(S); |
| if (WS.isUsedInGOT()) { |
| wasm::WasmImport Import; |
| if (WS.isFunction()) |
| Import.Module = "GOT.func"; |
| else |
| Import.Module = "GOT.mem"; |
| Import.Field = WS.getName(); |
| Import.Kind = wasm::WASM_EXTERNAL_GLOBAL; |
| Import.Global = {wasm::WASM_TYPE_I32, true}; |
| Imports.push_back(Import); |
| assert(GOTIndices.count(&WS) == 0); |
| GOTIndices[&WS] = NumGlobalImports++; |
| } |
| } |
| } |
| |
| uint64_t WasmObjectWriter::writeObject(MCAssembler &Asm, |
| const MCAsmLayout &Layout) { |
| support::endian::Writer MainWriter(*OS, support::little); |
| W = &MainWriter; |
| if (IsSplitDwarf) { |
| uint64_t TotalSize = writeOneObject(Asm, Layout, DwoMode::NonDwoOnly); |
| assert(DwoOS); |
| support::endian::Writer DwoWriter(*DwoOS, support::little); |
| W = &DwoWriter; |
| return TotalSize + writeOneObject(Asm, Layout, DwoMode::DwoOnly); |
| } else { |
| return writeOneObject(Asm, Layout, DwoMode::AllSections); |
| } |
| } |
| |
| uint64_t WasmObjectWriter::writeOneObject(MCAssembler &Asm, |
| const MCAsmLayout &Layout, |
| DwoMode Mode) { |
| uint64_t StartOffset = W->OS.tell(); |
| SectionCount = 0; |
| CustomSections.clear(); |
| |
| LLVM_DEBUG(dbgs() << "WasmObjectWriter::writeObject\n"); |
| |
| // Collect information from the available symbols. |
| SmallVector<WasmFunction, 4> Functions; |
| SmallVector<uint32_t, 4> TableElems; |
| SmallVector<wasm::WasmImport, 4> Imports; |
| SmallVector<wasm::WasmExport, 4> Exports; |
| SmallVector<uint32_t, 2> TagTypes; |
| SmallVector<wasm::WasmGlobal, 1> Globals; |
| SmallVector<wasm::WasmTable, 1> Tables; |
| SmallVector<wasm::WasmSymbolInfo, 4> SymbolInfos; |
| SmallVector<std::pair<uint16_t, uint32_t>, 2> InitFuncs; |
| std::map<StringRef, std::vector<WasmComdatEntry>> Comdats; |
| uint64_t DataSize = 0; |
| if (Mode != DwoMode::DwoOnly) { |
| prepareImports(Imports, Asm, Layout); |
| } |
| |
| // Populate DataSegments and CustomSections, which must be done before |
| // populating DataLocations. |
| for (MCSection &Sec : Asm) { |
| auto &Section = static_cast<MCSectionWasm &>(Sec); |
| StringRef SectionName = Section.getName(); |
| |
| if (Mode == DwoMode::NonDwoOnly && isDwoSection(Sec)) |
| continue; |
| if (Mode == DwoMode::DwoOnly && !isDwoSection(Sec)) |
| continue; |
| |
| LLVM_DEBUG(dbgs() << "Processing Section " << SectionName << " group " |
| << Section.getGroup() << "\n";); |
| |
| // .init_array sections are handled specially elsewhere. |
| if (SectionName.startswith(".init_array")) |
| continue; |
| |
| // Code is handled separately |
| if (Section.getKind().isText()) |
| continue; |
| |
| if (Section.isWasmData()) { |
| uint32_t SegmentIndex = DataSegments.size(); |
| DataSize = alignTo(DataSize, Section.getAlignment()); |
| DataSegments.emplace_back(); |
| WasmDataSegment &Segment = DataSegments.back(); |
| Segment.Name = SectionName; |
| Segment.InitFlags = Section.getPassive() |
| ? (uint32_t)wasm::WASM_DATA_SEGMENT_IS_PASSIVE |
| : 0; |
| Segment.Offset = DataSize; |
| Segment.Section = &Section; |
| addData(Segment.Data, Section); |
| Segment.Alignment = Log2_32(Section.getAlignment()); |
| Segment.LinkingFlags = Section.getSegmentFlags(); |
| DataSize += Segment.Data.size(); |
| Section.setSegmentIndex(SegmentIndex); |
| |
| if (const MCSymbolWasm *C = Section.getGroup()) { |
| Comdats[C->getName()].emplace_back( |
| WasmComdatEntry{wasm::WASM_COMDAT_DATA, SegmentIndex}); |
| } |
| } else { |
| // Create custom sections |
| assert(Sec.getKind().isMetadata()); |
| |
| StringRef Name = SectionName; |
| |
| // For user-defined custom sections, strip the prefix |
| if (Name.startswith(".custom_section.")) |
| Name = Name.substr(strlen(".custom_section.")); |
| |
| MCSymbol *Begin = Sec.getBeginSymbol(); |
| if (Begin) { |
| assert(WasmIndices.count(cast<MCSymbolWasm>(Begin)) == 0); |
| WasmIndices[cast<MCSymbolWasm>(Begin)] = CustomSections.size(); |
| } |
| |
| // Separate out the producers and target features sections |
| if (Name == "producers") { |
| ProducersSection = std::make_unique<WasmCustomSection>(Name, &Section); |
| continue; |
| } |
| if (Name == "target_features") { |
| TargetFeaturesSection = |
| std::make_unique<WasmCustomSection>(Name, &Section); |
| continue; |
| } |
| |
| // Custom sections can also belong to COMDAT groups. In this case the |
| // decriptor's "index" field is the section index (in the final object |
| // file), but that is not known until after layout, so it must be fixed up |
| // later |
| if (const MCSymbolWasm *C = Section.getGroup()) { |
| Comdats[C->getName()].emplace_back( |
| WasmComdatEntry{wasm::WASM_COMDAT_SECTION, |
| static_cast<uint32_t>(CustomSections.size())}); |
| } |
| |
| CustomSections.emplace_back(Name, &Section); |
| } |
| } |
| |
| if (Mode != DwoMode::DwoOnly) { |
| // Populate WasmIndices and DataLocations for defined symbols. |
| for (const MCSymbol &S : Asm.symbols()) { |
| // Ignore unnamed temporary symbols, which aren't ever exported, imported, |
| // or used in relocations. |
| if (S.isTemporary() && S.getName().empty()) |
| continue; |
| |
| const auto &WS = static_cast<const MCSymbolWasm &>(S); |
| LLVM_DEBUG(dbgs() |
| << "MCSymbol: " |
| << toString(WS.getType().getValueOr(wasm::WASM_SYMBOL_TYPE_DATA)) |
| << " '" << S << "'" |
| << " isDefined=" << S.isDefined() << " isExternal=" |
| << S.isExternal() << " isTemporary=" << S.isTemporary() |
| << " isWeak=" << WS.isWeak() << " isHidden=" << WS.isHidden() |
| << " isVariable=" << WS.isVariable() << "\n"); |
| |
| if (WS.isVariable()) |
| continue; |
| if (WS.isComdat() && !WS.isDefined()) |
| continue; |
| |
| if (WS.isFunction()) { |
| unsigned Index; |
| if (WS.isDefined()) { |
| if (WS.getOffset() != 0) |
| report_fatal_error( |
| "function sections must contain one function each"); |
| |
| if (WS.getSize() == nullptr) |
| report_fatal_error( |
| "function symbols must have a size set with .size"); |
| |
| // A definition. Write out the function body. |
| Index = NumFunctionImports + Functions.size(); |
| WasmFunction Func; |
| Func.SigIndex = getFunctionType(WS); |
| Func.Sym = &WS; |
| assert(WasmIndices.count(&WS) == 0); |
| WasmIndices[&WS] = Index; |
| Functions.push_back(Func); |
| |
| auto &Section = static_cast<MCSectionWasm &>(WS.getSection()); |
| if (const MCSymbolWasm *C = Section.getGroup()) { |
| Comdats[C->getName()].emplace_back( |
| WasmComdatEntry{wasm::WASM_COMDAT_FUNCTION, Index}); |
| } |
| |
| if (WS.hasExportName()) { |
| wasm::WasmExport Export; |
| Export.Name = WS.getExportName(); |
| Export.Kind = wasm::WASM_EXTERNAL_FUNCTION; |
| Export.Index = Index; |
| Exports.push_back(Export); |
| } |
| } else { |
| // An import; the index was assigned above. |
| Index = WasmIndices.find(&WS)->second; |
| } |
| |
| LLVM_DEBUG(dbgs() << " -> function index: " << Index << "\n"); |
| |
| } else if (WS.isData()) { |
| if (!isInSymtab(WS)) |
| continue; |
| |
| if (!WS.isDefined()) { |
| LLVM_DEBUG(dbgs() << " -> segment index: -1" |
| << "\n"); |
| continue; |
| } |
| |
| if (!WS.getSize()) |
| report_fatal_error("data symbols must have a size set with .size: " + |
| WS.getName()); |
| |
| int64_t Size = 0; |
| if (!WS.getSize()->evaluateAsAbsolute(Size, Layout)) |
| report_fatal_error(".size expression must be evaluatable"); |
| |
| auto &DataSection = static_cast<MCSectionWasm &>(WS.getSection()); |
| if (!DataSection.isWasmData()) |
| report_fatal_error("data symbols must live in a data section: " + |
| WS.getName()); |
| |
| // For each data symbol, export it in the symtab as a reference to the |
| // corresponding Wasm data segment. |
| wasm::WasmDataReference Ref = wasm::WasmDataReference{ |
| DataSection.getSegmentIndex(), Layout.getSymbolOffset(WS), |
| static_cast<uint64_t>(Size)}; |
| assert(DataLocations.count(&WS) == 0); |
| DataLocations[&WS] = Ref; |
| LLVM_DEBUG(dbgs() << " -> segment index: " << Ref.Segment << "\n"); |
| |
| } else if (WS.isGlobal()) { |
| // A "true" Wasm global (currently just __stack_pointer) |
| if (WS.isDefined()) { |
| wasm::WasmGlobal Global; |
| Global.Type = WS.getGlobalType(); |
| Global.Index = NumGlobalImports + Globals.size(); |
| switch (Global.Type.Type) { |
| case wasm::WASM_TYPE_I32: |
| Global.InitExpr.Opcode = wasm::WASM_OPCODE_I32_CONST; |
| break; |
| case wasm::WASM_TYPE_I64: |
| Global.InitExpr.Opcode = wasm::WASM_OPCODE_I64_CONST; |
| break; |
| case wasm::WASM_TYPE_F32: |
| Global.InitExpr.Opcode = wasm::WASM_OPCODE_F32_CONST; |
| break; |
| case wasm::WASM_TYPE_F64: |
| Global.InitExpr.Opcode = wasm::WASM_OPCODE_F64_CONST; |
| break; |
| case wasm::WASM_TYPE_EXTERNREF: |
| Global.InitExpr.Opcode = wasm::WASM_OPCODE_REF_NULL; |
| break; |
| default: |
| llvm_unreachable("unexpected type"); |
| } |
| assert(WasmIndices.count(&WS) == 0); |
| WasmIndices[&WS] = Global.Index; |
| Globals.push_back(Global); |
| } else { |
| // An import; the index was assigned above |
| LLVM_DEBUG(dbgs() << " -> global index: " |
| << WasmIndices.find(&WS)->second << "\n"); |
| } |
| } else if (WS.isTable()) { |
| if (WS.isDefined()) { |
| wasm::WasmTable Table; |
| Table.Index = NumTableImports + Tables.size(); |
| Table.Type = WS.getTableType(); |
| assert(WasmIndices.count(&WS) == 0); |
| WasmIndices[&WS] = Table.Index; |
| Tables.push_back(Table); |
| } |
| LLVM_DEBUG(dbgs() << " -> table index: " |
| << WasmIndices.find(&WS)->second << "\n"); |
| } else if (WS.isTag()) { |
| // C++ exception symbol (__cpp_exception) or longjmp symbol |
| // (__c_longjmp) |
| unsigned Index; |
| if (WS.isDefined()) { |
| Index = NumTagImports + TagTypes.size(); |
| uint32_t SigIndex = getTagType(WS); |
| assert(WasmIndices.count(&WS) == 0); |
| WasmIndices[&WS] = Index; |
| TagTypes.push_back(SigIndex); |
| } else { |
| // An import; the index was assigned above. |
| assert(WasmIndices.count(&WS) > 0); |
| } |
| LLVM_DEBUG(dbgs() << " -> tag index: " << WasmIndices.find(&WS)->second |
| << "\n"); |
| |
| } else { |
| assert(WS.isSection()); |
| } |
| } |
| |
| // Populate WasmIndices and DataLocations for aliased symbols. We need to |
| // process these in a separate pass because we need to have processed the |
| // target of the alias before the alias itself and the symbols are not |
| // necessarily ordered in this way. |
| for (const MCSymbol &S : Asm.symbols()) { |
| if (!S.isVariable()) |
| continue; |
| |
| assert(S.isDefined()); |
| |
| const auto *BS = Layout.getBaseSymbol(S); |
| if (!BS) |
| report_fatal_error(Twine(S.getName()) + |
| ": absolute addressing not supported!"); |
| const MCSymbolWasm *Base = cast<MCSymbolWasm>(BS); |
| |
| // Find the target symbol of this weak alias and export that index |
| const auto &WS = static_cast<const MCSymbolWasm &>(S); |
| LLVM_DEBUG(dbgs() << WS.getName() << ": weak alias of '" << *Base |
| << "'\n"); |
| |
| if (Base->isFunction()) { |
| assert(WasmIndices.count(Base) > 0); |
| uint32_t WasmIndex = WasmIndices.find(Base)->second; |
| assert(WasmIndices.count(&WS) == 0); |
| WasmIndices[&WS] = WasmIndex; |
| LLVM_DEBUG(dbgs() << " -> index:" << WasmIndex << "\n"); |
| } else if (Base->isData()) { |
| auto &DataSection = static_cast<MCSectionWasm &>(WS.getSection()); |
| uint64_t Offset = Layout.getSymbolOffset(S); |
| int64_t Size = 0; |
| // For data symbol alias we use the size of the base symbol as the |
| // size of the alias. When an offset from the base is involved this |
| // can result in a offset + size goes past the end of the data section |
| // which out object format doesn't support. So we must clamp it. |
| if (!Base->getSize()->evaluateAsAbsolute(Size, Layout)) |
| report_fatal_error(".size expression must be evaluatable"); |
| const WasmDataSegment &Segment = |
| DataSegments[DataSection.getSegmentIndex()]; |
| Size = |
| std::min(static_cast<uint64_t>(Size), Segment.Data.size() - Offset); |
| wasm::WasmDataReference Ref = wasm::WasmDataReference{ |
| DataSection.getSegmentIndex(), |
| static_cast<uint32_t>(Layout.getSymbolOffset(S)), |
| static_cast<uint32_t>(Size)}; |
| DataLocations[&WS] = Ref; |
| LLVM_DEBUG(dbgs() << " -> index:" << Ref.Segment << "\n"); |
| } else { |
| report_fatal_error("don't yet support global/tag aliases"); |
| } |
| } |
| } |
| |
| // Finally, populate the symbol table itself, in its "natural" order. |
| for (const MCSymbol &S : Asm.symbols()) { |
| const auto &WS = static_cast<const MCSymbolWasm &>(S); |
| if (!isInSymtab(WS)) { |
| WS.setIndex(InvalidIndex); |
| continue; |
| } |
| LLVM_DEBUG(dbgs() << "adding to symtab: " << WS << "\n"); |
| |
| uint32_t Flags = 0; |
| if (WS.isWeak()) |
| Flags |= wasm::WASM_SYMBOL_BINDING_WEAK; |
| if (WS.isHidden()) |
| Flags |= wasm::WASM_SYMBOL_VISIBILITY_HIDDEN; |
| if (!WS.isExternal() && WS.isDefined()) |
| Flags |= wasm::WASM_SYMBOL_BINDING_LOCAL; |
| if (WS.isUndefined()) |
| Flags |= wasm::WASM_SYMBOL_UNDEFINED; |
| if (WS.isNoStrip()) { |
| Flags |= wasm::WASM_SYMBOL_NO_STRIP; |
| if (isEmscripten()) { |
| Flags |= wasm::WASM_SYMBOL_EXPORTED; |
| } |
| } |
| if (WS.hasImportName()) |
| Flags |= wasm::WASM_SYMBOL_EXPLICIT_NAME; |
| if (WS.hasExportName()) |
| Flags |= wasm::WASM_SYMBOL_EXPORTED; |
| if (WS.isTLS()) |
| Flags |= wasm::WASM_SYMBOL_TLS; |
| |
| wasm::WasmSymbolInfo Info; |
| Info.Name = WS.getName(); |
| Info.Kind = WS.getType().getValueOr(wasm::WASM_SYMBOL_TYPE_DATA); |
| Info.Flags = Flags; |
| if (!WS.isData()) { |
| assert(WasmIndices.count(&WS) > 0); |
| Info.ElementIndex = WasmIndices.find(&WS)->second; |
| } else if (WS.isDefined()) { |
| assert(DataLocations.count(&WS) > 0); |
| Info.DataRef = DataLocations.find(&WS)->second; |
| } |
| WS.setIndex(SymbolInfos.size()); |
| SymbolInfos.emplace_back(Info); |
| } |
| |
| { |
| auto HandleReloc = [&](const WasmRelocationEntry &Rel) { |
| // Functions referenced by a relocation need to put in the table. This is |
| // purely to make the object file's provisional values readable, and is |
| // ignored by the linker, which re-calculates the relocations itself. |
| if (Rel.Type != wasm::R_WASM_TABLE_INDEX_I32 && |
| Rel.Type != wasm::R_WASM_TABLE_INDEX_I64 && |
| Rel.Type != wasm::R_WASM_TABLE_INDEX_SLEB && |
| Rel.Type != wasm::R_WASM_TABLE_INDEX_SLEB64 && |
| Rel.Type != wasm::R_WASM_TABLE_INDEX_REL_SLEB && |
| Rel.Type != wasm::R_WASM_TABLE_INDEX_REL_SLEB64) |
| return; |
| assert(Rel.Symbol->isFunction()); |
| const MCSymbolWasm *Base = |
| cast<MCSymbolWasm>(Layout.getBaseSymbol(*Rel.Symbol)); |
| uint32_t FunctionIndex = WasmIndices.find(Base)->second; |
| uint32_t TableIndex = TableElems.size() + InitialTableOffset; |
| if (TableIndices.try_emplace(Base, TableIndex).second) { |
| LLVM_DEBUG(dbgs() << " -> adding " << Base->getName() |
| << " to table: " << TableIndex << "\n"); |
| TableElems.push_back(FunctionIndex); |
| registerFunctionType(*Base); |
| } |
| }; |
| |
| for (const WasmRelocationEntry &RelEntry : CodeRelocations) |
| HandleReloc(RelEntry); |
| for (const WasmRelocationEntry &RelEntry : DataRelocations) |
| HandleReloc(RelEntry); |
| } |
| |
| // Translate .init_array section contents into start functions. |
| for (const MCSection &S : Asm) { |
| const auto &WS = static_cast<const MCSectionWasm &>(S); |
| if (WS.getName().startswith(".fini_array")) |
| report_fatal_error(".fini_array sections are unsupported"); |
| if (!WS.getName().startswith(".init_array")) |
| continue; |
| if (WS.getFragmentList().empty()) |
| continue; |
| |
| // init_array is expected to contain a single non-empty data fragment |
| if (WS.getFragmentList().size() != 3) |
| report_fatal_error("only one .init_array section fragment supported"); |
| |
| auto IT = WS.begin(); |
| const MCFragment &EmptyFrag = *IT; |
| if (EmptyFrag.getKind() != MCFragment::FT_Data) |
| report_fatal_error(".init_array section should be aligned"); |
| |
| IT = std::next(IT); |
| const MCFragment &AlignFrag = *IT; |
| if (AlignFrag.getKind() != MCFragment::FT_Align) |
| report_fatal_error(".init_array section should be aligned"); |
| if (cast<MCAlignFragment>(AlignFrag).getAlignment() != (is64Bit() ? 8 : 4)) |
| report_fatal_error(".init_array section should be aligned for pointers"); |
| |
| const MCFragment &Frag = *std::next(IT); |
| if (Frag.hasInstructions() || Frag.getKind() != MCFragment::FT_Data) |
| report_fatal_error("only data supported in .init_array section"); |
| |
| uint16_t Priority = UINT16_MAX; |
| unsigned PrefixLength = strlen(".init_array"); |
| if (WS.getName().size() > PrefixLength) { |
| if (WS.getName()[PrefixLength] != '.') |
| report_fatal_error( |
| ".init_array section priority should start with '.'"); |
| if (WS.getName().substr(PrefixLength + 1).getAsInteger(10, Priority)) |
| report_fatal_error("invalid .init_array section priority"); |
| } |
| const auto &DataFrag = cast<MCDataFragment>(Frag); |
| const SmallVectorImpl<char> &Contents = DataFrag.getContents(); |
| for (const uint8_t * |
| P = (const uint8_t *)Contents.data(), |
| *End = (const uint8_t *)Contents.data() + Contents.size(); |
| P != End; ++P) { |
| if (*P != 0) |
| report_fatal_error("non-symbolic data in .init_array section"); |
| } |
| for (const MCFixup &Fixup : DataFrag.getFixups()) { |
| assert(Fixup.getKind() == |
| MCFixup::getKindForSize(is64Bit() ? 8 : 4, false)); |
| const MCExpr *Expr = Fixup.getValue(); |
| auto *SymRef = dyn_cast<MCSymbolRefExpr>(Expr); |
| if (!SymRef) |
| report_fatal_error("fixups in .init_array should be symbol references"); |
| const auto &TargetSym = cast<const MCSymbolWasm>(SymRef->getSymbol()); |
| if (TargetSym.getIndex() == InvalidIndex) |
| report_fatal_error("symbols in .init_array should exist in symtab"); |
| if (!TargetSym.isFunction()) |
| report_fatal_error("symbols in .init_array should be for functions"); |
| InitFuncs.push_back( |
| std::make_pair(Priority, TargetSym.getIndex())); |
| } |
| } |
| |
| // Write out the Wasm header. |
| writeHeader(Asm); |
| |
| uint32_t CodeSectionIndex, DataSectionIndex; |
| if (Mode != DwoMode::DwoOnly) { |
| writeTypeSection(Signatures); |
| writeImportSection(Imports, DataSize, TableElems.size()); |
| writeFunctionSection(Functions); |
| writeTableSection(Tables); |
| // Skip the "memory" section; we import the memory instead. |
| writeTagSection(TagTypes); |
| writeGlobalSection(Globals); |
| writeExportSection(Exports); |
| const MCSymbol *IndirectFunctionTable = |
| Asm.getContext().lookupSymbol("__indirect_function_table"); |
| writeElemSection(cast_or_null<const MCSymbolWasm>(IndirectFunctionTable), |
| TableElems); |
| writeDataCountSection(); |
| |
| CodeSectionIndex = writeCodeSection(Asm, Layout, Functions); |
| DataSectionIndex = writeDataSection(Layout); |
| } |
| |
| // The Sections in the COMDAT list have placeholder indices (their index among |
| // custom sections, rather than among all sections). Fix them up here. |
| for (auto &Group : Comdats) { |
| for (auto &Entry : Group.second) { |
| if (Entry.Kind == wasm::WASM_COMDAT_SECTION) { |
| Entry.Index += SectionCount; |
| } |
| } |
| } |
| for (auto &CustomSection : CustomSections) |
| writeCustomSection(CustomSection, Asm, Layout); |
| |
| if (Mode != DwoMode::DwoOnly) { |
| writeLinkingMetaDataSection(SymbolInfos, InitFuncs, Comdats); |
| |
| writeRelocSection(CodeSectionIndex, "CODE", CodeRelocations); |
| writeRelocSection(DataSectionIndex, "DATA", DataRelocations); |
| } |
| writeCustomRelocSections(); |
| if (ProducersSection) |
| writeCustomSection(*ProducersSection, Asm, Layout); |
| if (TargetFeaturesSection) |
| writeCustomSection(*TargetFeaturesSection, Asm, Layout); |
| |
| // TODO: Translate the .comment section to the output. |
| return W->OS.tell() - StartOffset; |
| } |
| |
| std::unique_ptr<MCObjectWriter> |
| llvm::createWasmObjectWriter(std::unique_ptr<MCWasmObjectTargetWriter> MOTW, |
| raw_pwrite_stream &OS) { |
| return std::make_unique<WasmObjectWriter>(std::move(MOTW), OS); |
| } |
| |
| std::unique_ptr<MCObjectWriter> |
| llvm::createWasmDwoObjectWriter(std::unique_ptr<MCWasmObjectTargetWriter> MOTW, |
| raw_pwrite_stream &OS, |
| raw_pwrite_stream &DwoOS) { |
| return std::make_unique<WasmObjectWriter>(std::move(MOTW), OS, DwoOS); |
| } |