1 //===-- WebAssemblyWasmObjectWriter.cpp - WebAssembly Wasm 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 /// \file 10 /// This file handles Wasm-specific object emission, converting LLVM's 11 /// internal fixups into the appropriate relocations. 12 /// 13 //===----------------------------------------------------------------------===// 14 15 #include "MCTargetDesc/WebAssemblyFixupKinds.h" 16 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h" 17 #include "llvm/BinaryFormat/Wasm.h" 18 #include "llvm/MC/MCAsmBackend.h" 19 #include "llvm/MC/MCFixup.h" 20 #include "llvm/MC/MCFixupKindInfo.h" 21 #include "llvm/MC/MCObjectWriter.h" 22 #include "llvm/MC/MCSectionWasm.h" 23 #include "llvm/MC/MCSymbolWasm.h" 24 #include "llvm/MC/MCValue.h" 25 #include "llvm/MC/MCWasmObjectWriter.h" 26 #include "llvm/Support/Casting.h" 27 #include "llvm/Support/ErrorHandling.h" 28 29 using namespace llvm; 30 31 namespace { 32 class WebAssemblyWasmObjectWriter final : public MCWasmObjectTargetWriter { 33 public: 34 explicit WebAssemblyWasmObjectWriter(bool Is64Bit, bool IsEmscripten); 35 36 private: 37 unsigned getRelocType(const MCValue &Target, const MCFixup &Fixup, 38 const MCSectionWasm &FixupSection, 39 bool IsLocRel) const override; 40 }; 41 } // end anonymous namespace 42 43 WebAssemblyWasmObjectWriter::WebAssemblyWasmObjectWriter(bool Is64Bit, 44 bool IsEmscripten) 45 : MCWasmObjectTargetWriter(Is64Bit, IsEmscripten) {} 46 47 static const MCSection *getTargetSection(const MCExpr *Expr) { 48 if (auto SyExp = dyn_cast<MCSymbolRefExpr>(Expr)) { 49 if (SyExp->getSymbol().isInSection()) 50 return &SyExp->getSymbol().getSection(); 51 return nullptr; 52 } 53 54 if (auto BinOp = dyn_cast<MCBinaryExpr>(Expr)) { 55 auto SectionLHS = getTargetSection(BinOp->getLHS()); 56 auto SectionRHS = getTargetSection(BinOp->getRHS()); 57 return SectionLHS == SectionRHS ? nullptr : SectionLHS; 58 } 59 60 if (auto UnOp = dyn_cast<MCUnaryExpr>(Expr)) 61 return getTargetSection(UnOp->getSubExpr()); 62 63 return nullptr; 64 } 65 66 unsigned WebAssemblyWasmObjectWriter::getRelocType( 67 const MCValue &Target, const MCFixup &Fixup, 68 const MCSectionWasm &FixupSection, bool IsLocRel) const { 69 const MCSymbolRefExpr *RefA = Target.getSymA(); 70 assert(RefA); 71 auto& SymA = cast<MCSymbolWasm>(RefA->getSymbol()); 72 73 MCSymbolRefExpr::VariantKind Modifier = Target.getAccessVariant(); 74 75 switch (Modifier) { 76 case MCSymbolRefExpr::VK_GOT: 77 return wasm::R_WASM_GLOBAL_INDEX_LEB; 78 case MCSymbolRefExpr::VK_WASM_TBREL: 79 assert(SymA.isFunction()); 80 return is64Bit() ? wasm::R_WASM_TABLE_INDEX_REL_SLEB64 81 : wasm::R_WASM_TABLE_INDEX_REL_SLEB; 82 case MCSymbolRefExpr::VK_WASM_TLSREL: 83 return is64Bit() ? wasm::R_WASM_MEMORY_ADDR_TLS_SLEB64 84 : wasm::R_WASM_MEMORY_ADDR_TLS_SLEB; 85 case MCSymbolRefExpr::VK_WASM_MBREL: 86 assert(SymA.isData()); 87 return is64Bit() ? wasm::R_WASM_MEMORY_ADDR_REL_SLEB64 88 : wasm::R_WASM_MEMORY_ADDR_REL_SLEB; 89 case MCSymbolRefExpr::VK_WASM_TYPEINDEX: 90 return wasm::R_WASM_TYPE_INDEX_LEB; 91 default: 92 break; 93 } 94 95 switch (unsigned(Fixup.getKind())) { 96 case WebAssembly::fixup_sleb128_i32: 97 if (SymA.isFunction()) 98 return wasm::R_WASM_TABLE_INDEX_SLEB; 99 return wasm::R_WASM_MEMORY_ADDR_SLEB; 100 case WebAssembly::fixup_sleb128_i64: 101 if (SymA.isFunction()) 102 return wasm::R_WASM_TABLE_INDEX_SLEB64; 103 return wasm::R_WASM_MEMORY_ADDR_SLEB64; 104 case WebAssembly::fixup_uleb128_i32: 105 if (SymA.isGlobal()) 106 return wasm::R_WASM_GLOBAL_INDEX_LEB; 107 if (SymA.isFunction()) 108 return wasm::R_WASM_FUNCTION_INDEX_LEB; 109 if (SymA.isTag()) 110 return wasm::R_WASM_TAG_INDEX_LEB; 111 if (SymA.isTable()) 112 return wasm::R_WASM_TABLE_NUMBER_LEB; 113 return wasm::R_WASM_MEMORY_ADDR_LEB; 114 case WebAssembly::fixup_uleb128_i64: 115 assert(SymA.isData()); 116 return wasm::R_WASM_MEMORY_ADDR_LEB64; 117 case FK_Data_4: 118 if (SymA.isFunction()) { 119 if (FixupSection.getKind().isMetadata()) 120 return wasm::R_WASM_FUNCTION_OFFSET_I32; 121 assert(FixupSection.isWasmData()); 122 return wasm::R_WASM_TABLE_INDEX_I32; 123 } 124 if (SymA.isGlobal()) 125 return wasm::R_WASM_GLOBAL_INDEX_I32; 126 if (auto Section = static_cast<const MCSectionWasm *>( 127 getTargetSection(Fixup.getValue()))) { 128 if (Section->getKind().isText()) 129 return wasm::R_WASM_FUNCTION_OFFSET_I32; 130 else if (!Section->isWasmData()) 131 return wasm::R_WASM_SECTION_OFFSET_I32; 132 } 133 return IsLocRel ? wasm::R_WASM_MEMORY_ADDR_LOCREL_I32 134 : wasm::R_WASM_MEMORY_ADDR_I32; 135 case FK_Data_8: 136 if (SymA.isFunction()) { 137 if (FixupSection.getKind().isMetadata()) 138 return wasm::R_WASM_FUNCTION_OFFSET_I64; 139 return wasm::R_WASM_TABLE_INDEX_I64; 140 } 141 if (SymA.isGlobal()) 142 llvm_unreachable("unimplemented R_WASM_GLOBAL_INDEX_I64"); 143 if (auto Section = static_cast<const MCSectionWasm *>( 144 getTargetSection(Fixup.getValue()))) { 145 if (Section->getKind().isText()) 146 return wasm::R_WASM_FUNCTION_OFFSET_I64; 147 else if (!Section->isWasmData()) 148 llvm_unreachable("unimplemented R_WASM_SECTION_OFFSET_I64"); 149 } 150 assert(SymA.isData()); 151 return wasm::R_WASM_MEMORY_ADDR_I64; 152 default: 153 llvm_unreachable("unimplemented fixup kind"); 154 } 155 } 156 157 std::unique_ptr<MCObjectTargetWriter> 158 llvm::createWebAssemblyWasmObjectWriter(bool Is64Bit, bool IsEmscripten) { 159 return std::make_unique<WebAssemblyWasmObjectWriter>(Is64Bit, IsEmscripten); 160 } 161