1 //===-- WebAssemblyELFObjectWriter.cpp - WebAssembly ELF Writer -----------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 /// 10 /// \file 11 /// \brief This file handles ELF-specific object emission, converting LLVM's 12 /// internal fixups into the appropriate relocations. 13 /// 14 //===----------------------------------------------------------------------===// 15 16 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h" 17 #include "llvm/MC/MCELFObjectWriter.h" 18 #include "llvm/MC/MCFixup.h" 19 #include "llvm/Support/ErrorHandling.h" 20 using namespace llvm; 21 22 namespace { 23 class WebAssemblyELFObjectWriter final : public MCELFObjectTargetWriter { 24 public: 25 WebAssemblyELFObjectWriter(bool Is64Bit, uint8_t OSABI); 26 27 protected: 28 unsigned getRelocType(MCContext &Ctx, const MCValue &Target, 29 const MCFixup &Fixup, bool IsPCRel) const override; 30 }; 31 } // end anonymous namespace 32 WebAssemblyELFObjectWriter(bool Is64Bit,uint8_t OSABI)33 WebAssemblyELFObjectWriter::WebAssemblyELFObjectWriter(bool Is64Bit, 34 uint8_t OSABI) 35 : MCELFObjectTargetWriter(Is64Bit, OSABI, ELF::EM_WEBASSEMBLY, 36 /*HasRelocationAddend=*/false) {} 37 getRelocType(MCContext & Ctx,const MCValue & Target,const MCFixup & Fixup,bool IsPCRel) const38 unsigned WebAssemblyELFObjectWriter::getRelocType(MCContext &Ctx, 39 const MCValue &Target, 40 const MCFixup &Fixup, 41 bool IsPCRel) const { 42 // WebAssembly functions are not allocated in the address space. To resolve a 43 // pointer to a function, we must use a special relocation type. 44 if (const MCSymbolRefExpr *SyExp = 45 dyn_cast<MCSymbolRefExpr>(Fixup.getValue())) 46 if (SyExp->getKind() == MCSymbolRefExpr::VK_WebAssembly_FUNCTION) 47 return ELF::R_WEBASSEMBLY_FUNCTION; 48 49 switch (Fixup.getKind()) { 50 case FK_Data_4: 51 assert(!is64Bit() && "4-byte relocations only supported on wasm32"); 52 return ELF::R_WEBASSEMBLY_DATA; 53 case FK_Data_8: 54 assert(is64Bit() && "8-byte relocations only supported on wasm64"); 55 return ELF::R_WEBASSEMBLY_DATA; 56 default: 57 llvm_unreachable("unimplemented fixup kind"); 58 } 59 } 60 createWebAssemblyELFObjectWriter(raw_pwrite_stream & OS,bool Is64Bit,uint8_t OSABI)61 MCObjectWriter *llvm::createWebAssemblyELFObjectWriter(raw_pwrite_stream &OS, 62 bool Is64Bit, 63 uint8_t OSABI) { 64 MCELFObjectTargetWriter *MOTW = 65 new WebAssemblyELFObjectWriter(Is64Bit, OSABI); 66 return createELFObjectWriter(MOTW, OS, /*IsLittleEndian=*/true); 67 } 68