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
getTTypeGlobalReference(const GlobalValue * GV,unsigned Encoding,Mangler & Mang,const TargetMachine & TM,MachineModuleInfo * MMI,MCStreamer & Streamer) const22 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
getCFIPersonalitySymbol(const GlobalValue * GV,Mangler & Mang,const TargetMachine & TM,MachineModuleInfo * MMI) const41 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
Initialize(MCContext & Ctx,const TargetMachine & TM)48 X86LinuxTargetObjectFile::Initialize(MCContext &Ctx, const TargetMachine &TM) {
49 TargetLoweringObjectFileELF::Initialize(Ctx, TM);
50 InitializeELF(TM.Options.UseInitArray);
51 }
52
53 const MCExpr *
getDebugThreadLocalSymbol(const MCSymbol * Sym) const54 X86LinuxTargetObjectFile::getDebugThreadLocalSymbol(
55 const MCSymbol *Sym) const {
56 return MCSymbolRefExpr::Create(Sym, MCSymbolRefExpr::VK_DTPOFF, getContext());
57 }
58
getExecutableRelativeSymbol(const ConstantExpr * CE,Mangler & Mang,const TargetMachine & TM) const59 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