1 //===-- X86TargetObjectFile.cpp - X86 Object Info -------------------------===// 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 #include "X86TargetObjectFile.h" 11 #include "llvm/IR/Mangler.h" 12 #include "llvm/IR/Operator.h" 13 #include "llvm/MC/MCContext.h" 14 #include "llvm/MC/MCExpr.h" 15 #include "llvm/MC/MCSectionELF.h" 16 #include "llvm/Support/Dwarf.h" 17 #include "llvm/Target/TargetLowering.h" 18 19 using namespace llvm; 20 using namespace dwarf; 21 22 const MCExpr *X86_64MachoTargetObjectFile::getTTypeGlobalReference( 23 const GlobalValue *GV, unsigned Encoding, Mangler &Mang, 24 const TargetMachine &TM, MachineModuleInfo *MMI, 25 MCStreamer &Streamer) const { 26 27 // On Darwin/X86-64, we can reference dwarf symbols with foo@GOTPCREL+4, which 28 // is an indirect pc-relative reference. 29 if ((Encoding & DW_EH_PE_indirect) && (Encoding & DW_EH_PE_pcrel)) { 30 const MCSymbol *Sym = TM.getSymbol(GV, Mang); 31 const MCExpr *Res = 32 MCSymbolRefExpr::Create(Sym, MCSymbolRefExpr::VK_GOTPCREL, getContext()); 33 const MCExpr *Four = MCConstantExpr::Create(4, getContext()); 34 return MCBinaryExpr::CreateAdd(Res, Four, getContext()); 35 } 36 37 return TargetLoweringObjectFileMachO::getTTypeGlobalReference( 38 GV, Encoding, Mang, TM, MMI, Streamer); 39 } 40 41 MCSymbol *X86_64MachoTargetObjectFile::getCFIPersonalitySymbol( 42 const GlobalValue *GV, Mangler &Mang, const TargetMachine &TM, 43 MachineModuleInfo *MMI) const { 44 return TM.getSymbol(GV, Mang); 45 } 46 47 void 48 X86LinuxTargetObjectFile::Initialize(MCContext &Ctx, const TargetMachine &TM) { 49 TargetLoweringObjectFileELF::Initialize(Ctx, TM); 50 InitializeELF(TM.Options.UseInitArray); 51 } 52 53 const MCExpr * 54 X86LinuxTargetObjectFile::getDebugThreadLocalSymbol( 55 const MCSymbol *Sym) const { 56 return MCSymbolRefExpr::Create(Sym, MCSymbolRefExpr::VK_DTPOFF, getContext()); 57 } 58 59 const MCExpr *X86WindowsTargetObjectFile::getExecutableRelativeSymbol( 60 const ConstantExpr *CE, Mangler &Mang, const TargetMachine &TM) const { 61 // We are looking for the difference of two symbols, need a subtraction 62 // operation. 63 const SubOperator *Sub = dyn_cast<SubOperator>(CE); 64 if (!Sub) 65 return nullptr; 66 67 // Symbols must first be numbers before we can subtract them, we need to see a 68 // ptrtoint on both subtraction operands. 69 const PtrToIntOperator *SubLHS = 70 dyn_cast<PtrToIntOperator>(Sub->getOperand(0)); 71 const PtrToIntOperator *SubRHS = 72 dyn_cast<PtrToIntOperator>(Sub->getOperand(1)); 73 if (!SubLHS || !SubRHS) 74 return nullptr; 75 76 // Our symbols should exist in address space zero, cowardly no-op if 77 // otherwise. 78 if (SubLHS->getPointerAddressSpace() != 0 || 79 SubRHS->getPointerAddressSpace() != 0) 80 return nullptr; 81 82 // Both ptrtoint instructions must wrap global variables: 83 // - Only global variables are eligible for image relative relocations. 84 // - The subtrahend refers to the special symbol __ImageBase, a global. 85 const GlobalVariable *GVLHS = 86 dyn_cast<GlobalVariable>(SubLHS->getPointerOperand()); 87 const GlobalVariable *GVRHS = 88 dyn_cast<GlobalVariable>(SubRHS->getPointerOperand()); 89 if (!GVLHS || !GVRHS) 90 return nullptr; 91 92 // We expect __ImageBase to be a global variable without a section, externally 93 // defined. 94 // 95 // It should look something like this: @__ImageBase = external constant i8 96 if (GVRHS->isThreadLocal() || GVRHS->getName() != "__ImageBase" || 97 !GVRHS->hasExternalLinkage() || GVRHS->hasInitializer() || 98 GVRHS->hasSection()) 99 return nullptr; 100 101 // An image-relative, thread-local, symbol makes no sense. 102 if (GVLHS->isThreadLocal()) 103 return nullptr; 104 105 return MCSymbolRefExpr::Create(TM.getSymbol(GVLHS, Mang), 106 MCSymbolRefExpr::VK_COFF_IMGREL32, 107 getContext()); 108 } 109
