| //==- WebAssemblyDisassembler.cpp - Disassembler for WebAssembly -*- C++ -*-==// |
| // |
| // 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 |
| // |
| //===----------------------------------------------------------------------===// |
| /// |
| /// \file |
| /// This file is part of the WebAssembly Disassembler. |
| /// |
| /// It contains code to translate the data produced by the decoder into |
| /// MCInsts. |
| /// |
| //===----------------------------------------------------------------------===// |
| |
| #include "MCTargetDesc/WebAssemblyMCExpr.h" |
| #include "MCTargetDesc/WebAssemblyMCTypeUtilities.h" |
| #include "TargetInfo/WebAssemblyTargetInfo.h" |
| #include "llvm/BinaryFormat/Wasm.h" |
| #include "llvm/MC/MCContext.h" |
| #include "llvm/MC/MCDisassembler/MCDisassembler.h" |
| #include "llvm/MC/MCInst.h" |
| #include "llvm/MC/MCInstrInfo.h" |
| #include "llvm/MC/MCSubtargetInfo.h" |
| #include "llvm/MC/MCSymbol.h" |
| #include "llvm/MC/MCSymbolWasm.h" |
| #include "llvm/MC/TargetRegistry.h" |
| #include "llvm/Support/Casting.h" |
| #include "llvm/Support/Endian.h" |
| #include "llvm/Support/LEB128.h" |
| |
| using namespace llvm; |
| |
| #define DEBUG_TYPE "wasm-disassembler" |
| |
| using DecodeStatus = MCDisassembler::DecodeStatus; |
| |
| #include "WebAssemblyGenDisassemblerTables.inc" |
| |
| static constexpr int WebAssemblyInstructionTableSize = 256; |
| |
| namespace { |
| class WebAssemblyDisassembler final : public MCDisassembler { |
| std::unique_ptr<const MCInstrInfo> MCII; |
| |
| DecodeStatus getInstruction(MCInst &Instr, uint64_t &Size, |
| ArrayRef<uint8_t> Bytes, uint64_t Address, |
| raw_ostream &CStream) const override; |
| |
| Expected<bool> onSymbolStart(SymbolInfoTy &Symbol, uint64_t &Size, |
| ArrayRef<uint8_t> Bytes, |
| uint64_t Address) const override; |
| |
| public: |
| WebAssemblyDisassembler(const MCSubtargetInfo &STI, MCContext &Ctx, |
| std::unique_ptr<const MCInstrInfo> MCII) |
| : MCDisassembler(STI, Ctx), MCII(std::move(MCII)) {} |
| }; |
| } // end anonymous namespace |
| |
| static MCDisassembler *createWebAssemblyDisassembler(const Target &T, |
| const MCSubtargetInfo &STI, |
| MCContext &Ctx) { |
| std::unique_ptr<const MCInstrInfo> MCII(T.createMCInstrInfo()); |
| return new WebAssemblyDisassembler(STI, Ctx, std::move(MCII)); |
| } |
| |
| extern "C" LLVM_EXTERNAL_VISIBILITY void |
| LLVMInitializeWebAssemblyDisassembler() { |
| // Register the disassembler for each target. |
| TargetRegistry::RegisterMCDisassembler(getTheWebAssemblyTarget32(), |
| createWebAssemblyDisassembler); |
| TargetRegistry::RegisterMCDisassembler(getTheWebAssemblyTarget64(), |
| createWebAssemblyDisassembler); |
| } |
| |
| static int nextByte(ArrayRef<uint8_t> Bytes, uint64_t &Size) { |
| if (Size >= Bytes.size()) |
| return -1; |
| auto V = Bytes[Size]; |
| Size++; |
| return V; |
| } |
| |
| static bool nextLEB(int64_t &Val, ArrayRef<uint8_t> Bytes, uint64_t &Size, |
| bool Signed) { |
| unsigned N = 0; |
| const char *Error = nullptr; |
| Val = Signed ? decodeSLEB128(Bytes.data() + Size, &N, |
| Bytes.data() + Bytes.size(), &Error) |
| : static_cast<int64_t>(decodeULEB128(Bytes.data() + Size, &N, |
| Bytes.data() + Bytes.size(), |
| &Error)); |
| if (Error) |
| return false; |
| Size += N; |
| return true; |
| } |
| |
| static bool parseLEBImmediate(MCInst &MI, uint64_t &Size, |
| ArrayRef<uint8_t> Bytes, bool Signed) { |
| int64_t Val; |
| if (!nextLEB(Val, Bytes, Size, Signed)) |
| return false; |
| MI.addOperand(MCOperand::createImm(Val)); |
| return true; |
| } |
| |
| template <typename T> |
| bool parseImmediate(MCInst &MI, uint64_t &Size, ArrayRef<uint8_t> Bytes) { |
| if (Size + sizeof(T) > Bytes.size()) |
| return false; |
| T Val = |
| support::endian::read<T, llvm::endianness::little>(Bytes.data() + Size); |
| Size += sizeof(T); |
| if (std::is_floating_point<T>::value) { |
| MI.addOperand( |
| MCOperand::createDFPImm(bit_cast<uint64_t>(static_cast<double>(Val)))); |
| } else { |
| MI.addOperand(MCOperand::createImm(static_cast<int64_t>(Val))); |
| } |
| return true; |
| } |
| |
| Expected<bool> WebAssemblyDisassembler::onSymbolStart(SymbolInfoTy &Symbol, |
| uint64_t &Size, |
| ArrayRef<uint8_t> Bytes, |
| uint64_t Address) const { |
| Size = 0; |
| if (Symbol.Type == wasm::WASM_SYMBOL_TYPE_SECTION) { |
| // Start of a code section: we're parsing only the function count. |
| int64_t FunctionCount; |
| if (!nextLEB(FunctionCount, Bytes, Size, false)) |
| return false; |
| outs() << " # " << FunctionCount << " functions in section."; |
| } else { |
| // Parse the start of a single function. |
| int64_t BodySize, LocalEntryCount; |
| if (!nextLEB(BodySize, Bytes, Size, false) || |
| !nextLEB(LocalEntryCount, Bytes, Size, false)) |
| return false; |
| if (LocalEntryCount) { |
| outs() << " .local "; |
| for (int64_t I = 0; I < LocalEntryCount; I++) { |
| int64_t Count, Type; |
| if (!nextLEB(Count, Bytes, Size, false) || |
| !nextLEB(Type, Bytes, Size, false)) |
| return false; |
| for (int64_t J = 0; J < Count; J++) { |
| if (I || J) |
| outs() << ", "; |
| outs() << WebAssembly::anyTypeToString(Type); |
| } |
| } |
| } |
| } |
| outs() << "\n"; |
| return true; |
| } |
| |
| MCDisassembler::DecodeStatus WebAssemblyDisassembler::getInstruction( |
| MCInst &MI, uint64_t &Size, ArrayRef<uint8_t> Bytes, uint64_t /*Address*/, |
| raw_ostream &CS) const { |
| CommentStream = &CS; |
| Size = 0; |
| int Opc = nextByte(Bytes, Size); |
| if (Opc < 0) |
| return MCDisassembler::Fail; |
| const auto *WasmInst = &InstructionTable0[Opc]; |
| // If this is a prefix byte, indirect to another table. |
| if (WasmInst->ET == ET_Prefix) { |
| WasmInst = nullptr; |
| // Linear search, so far only 4 entries. |
| for (const auto &[Prefix, Table] : PrefixTable) { |
| if (Prefix == Opc) { |
| WasmInst = Table; |
| break; |
| } |
| } |
| if (!WasmInst) |
| return MCDisassembler::Fail; |
| int64_t PrefixedOpc; |
| if (!nextLEB(PrefixedOpc, Bytes, Size, false)) |
| return MCDisassembler::Fail; |
| if (PrefixedOpc < 0 || PrefixedOpc >= WebAssemblyInstructionTableSize) |
| return MCDisassembler::Fail; |
| WasmInst += PrefixedOpc; |
| } |
| if (WasmInst->ET == ET_Unused) |
| return MCDisassembler::Fail; |
| // At this point we must have a valid instruction to decode. |
| assert(WasmInst->ET == ET_Instruction); |
| MI.setOpcode(WasmInst->Opcode); |
| // Parse any operands. |
| for (uint8_t OPI = 0; OPI < WasmInst->NumOperands; OPI++) { |
| auto OT = OperandTable[WasmInst->OperandStart + OPI]; |
| switch (OT) { |
| // ULEB operands: |
| case WebAssembly::OPERAND_BASIC_BLOCK: |
| case WebAssembly::OPERAND_LOCAL: |
| case WebAssembly::OPERAND_GLOBAL: |
| case WebAssembly::OPERAND_FUNCTION32: |
| case WebAssembly::OPERAND_TABLE: |
| case WebAssembly::OPERAND_OFFSET32: |
| case WebAssembly::OPERAND_OFFSET64: |
| case WebAssembly::OPERAND_P2ALIGN: |
| case WebAssembly::OPERAND_TYPEINDEX: |
| case WebAssembly::OPERAND_TAG: |
| case MCOI::OPERAND_IMMEDIATE: { |
| if (!parseLEBImmediate(MI, Size, Bytes, false)) |
| return MCDisassembler::Fail; |
| break; |
| } |
| // SLEB operands: |
| case WebAssembly::OPERAND_I32IMM: |
| case WebAssembly::OPERAND_I64IMM: { |
| if (!parseLEBImmediate(MI, Size, Bytes, true)) |
| return MCDisassembler::Fail; |
| break; |
| } |
| // block_type operands: |
| case WebAssembly::OPERAND_SIGNATURE: { |
| int64_t Val; |
| uint64_t PrevSize = Size; |
| if (!nextLEB(Val, Bytes, Size, true)) |
| return MCDisassembler::Fail; |
| if (Val < 0) { |
| // Negative values are single septet value types or empty types |
| if (Size != PrevSize + 1) { |
| MI.addOperand( |
| MCOperand::createImm(int64_t(WebAssembly::BlockType::Invalid))); |
| } else { |
| MI.addOperand(MCOperand::createImm(Val & 0x7f)); |
| } |
| } else { |
| // We don't have access to the signature, so create a symbol without one |
| MCSymbol *Sym = getContext().createTempSymbol("typeindex", true); |
| auto *WasmSym = cast<MCSymbolWasm>(Sym); |
| WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION); |
| const MCExpr *Expr = MCSymbolRefExpr::create( |
| WasmSym, WebAssembly::S_TYPEINDEX, getContext()); |
| MI.addOperand(MCOperand::createExpr(Expr)); |
| } |
| break; |
| } |
| // FP operands. |
| case WebAssembly::OPERAND_F32IMM: { |
| if (!parseImmediate<float>(MI, Size, Bytes)) |
| return MCDisassembler::Fail; |
| break; |
| } |
| case WebAssembly::OPERAND_F64IMM: { |
| if (!parseImmediate<double>(MI, Size, Bytes)) |
| return MCDisassembler::Fail; |
| break; |
| } |
| // Vector lane operands (not LEB encoded). |
| case WebAssembly::OPERAND_VEC_I8IMM: { |
| if (!parseImmediate<uint8_t>(MI, Size, Bytes)) |
| return MCDisassembler::Fail; |
| break; |
| } |
| case WebAssembly::OPERAND_VEC_I16IMM: { |
| if (!parseImmediate<uint16_t>(MI, Size, Bytes)) |
| return MCDisassembler::Fail; |
| break; |
| } |
| case WebAssembly::OPERAND_VEC_I32IMM: { |
| if (!parseImmediate<uint32_t>(MI, Size, Bytes)) |
| return MCDisassembler::Fail; |
| break; |
| } |
| case WebAssembly::OPERAND_VEC_I64IMM: { |
| if (!parseImmediate<uint64_t>(MI, Size, Bytes)) |
| return MCDisassembler::Fail; |
| break; |
| } |
| case WebAssembly::OPERAND_BRLIST: { |
| int64_t TargetTableLen; |
| if (!nextLEB(TargetTableLen, Bytes, Size, false)) |
| return MCDisassembler::Fail; |
| for (int64_t I = 0; I < TargetTableLen; I++) { |
| if (!parseLEBImmediate(MI, Size, Bytes, false)) |
| return MCDisassembler::Fail; |
| } |
| // Default case. |
| if (!parseLEBImmediate(MI, Size, Bytes, false)) |
| return MCDisassembler::Fail; |
| break; |
| } |
| case WebAssembly::OPERAND_CATCH_LIST: { |
| if (!parseLEBImmediate(MI, Size, Bytes, false)) |
| return MCDisassembler::Fail; |
| int64_t NumCatches = MI.getOperand(MI.getNumOperands() - 1).getImm(); |
| for (int64_t I = 0; I < NumCatches; I++) { |
| if (!parseImmediate<uint8_t>(MI, Size, Bytes)) |
| return MCDisassembler::Fail; |
| int64_t CatchOpcode = MI.getOperand(MI.getNumOperands() - 1).getImm(); |
| if (CatchOpcode == wasm::WASM_OPCODE_CATCH || |
| CatchOpcode == wasm::WASM_OPCODE_CATCH_REF) { |
| if (!parseLEBImmediate(MI, Size, Bytes, false)) // tag index |
| return MCDisassembler::Fail; |
| } |
| if (!parseLEBImmediate(MI, Size, Bytes, false)) // destination |
| return MCDisassembler::Fail; |
| } |
| break; |
| } |
| case MCOI::OPERAND_REGISTER: |
| // The tablegen header currently does not have any register operands since |
| // we use only the stack (_S) instructions. |
| // If you hit this that probably means a bad instruction definition in |
| // tablegen. |
| llvm_unreachable("Register operand in WebAssemblyDisassembler"); |
| default: |
| llvm_unreachable("Unknown operand type in WebAssemblyDisassembler"); |
| } |
| } |
| return MCDisassembler::Success; |
| } |
