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" 20using namespace llvm; 21 22namespace { 23class WebAssemblyELFObjectWriter final : public MCELFObjectTargetWriter { 24public: 25 WebAssemblyELFObjectWriter(bool Is64Bit, uint8_t OSABI); 26 27protected: 28 unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup, 29 bool IsPCRel) const override; 30}; 31} // end anonymous namespace 32 33WebAssemblyELFObjectWriter::WebAssemblyELFObjectWriter(bool Is64Bit, 34 uint8_t OSABI) 35 : MCELFObjectTargetWriter(Is64Bit, OSABI, ELF::EM_WEBASSEMBLY, 36 /*HasRelocationAddend=*/false) {} 37 38unsigned WebAssemblyELFObjectWriter::GetRelocType(const MCValue &Target, 39 const MCFixup &Fixup, 40 bool IsPCRel) const { 41 // WebAssembly functions are not allocated in the address space. To resolve a 42 // pointer to a function, we must use a special relocation type. 43 if (const MCSymbolRefExpr *SyExp = 44 dyn_cast<MCSymbolRefExpr>(Fixup.getValue())) 45 if (SyExp->getKind() == MCSymbolRefExpr::VK_WebAssembly_FUNCTION) 46 return ELF::R_WEBASSEMBLY_FUNCTION; 47 48 switch (Fixup.getKind()) { 49 case FK_Data_4: 50 assert(!is64Bit() && "4-byte relocations only supported on wasm32"); 51 return ELF::R_WEBASSEMBLY_DATA; 52 case FK_Data_8: 53 assert(is64Bit() && "8-byte relocations only supported on wasm64"); 54 return ELF::R_WEBASSEMBLY_DATA; 55 default: 56 llvm_unreachable("unimplemented fixup kind"); 57 } 58} 59 60MCObjectWriter *llvm::createWebAssemblyELFObjectWriter(raw_pwrite_stream &OS, 61 bool Is64Bit, 62 uint8_t OSABI) { 63 MCELFObjectTargetWriter *MOTW = 64 new WebAssemblyELFObjectWriter(Is64Bit, OSABI); 65 return createELFObjectWriter(MOTW, OS, /*IsLittleEndian=*/true); 66} 67