1 //===-- SystemZMCObjectWriter.cpp - SystemZ 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 #include "MCTargetDesc/SystemZMCTargetDesc.h"
11 #include "MCTargetDesc/SystemZMCFixups.h"
12 #include "llvm/MC/MCELFObjectWriter.h"
13 #include "llvm/MC/MCExpr.h"
14 #include "llvm/MC/MCValue.h"
15 
16 using namespace llvm;
17 
18 namespace {
19 class SystemZObjectWriter : public MCELFObjectTargetWriter {
20 public:
21   SystemZObjectWriter(uint8_t OSABI);
22 
23   virtual ~SystemZObjectWriter();
24 
25 protected:
26   // Override MCELFObjectTargetWriter.
27   unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
28                         bool IsPCRel) const override;
29   const MCSymbol *ExplicitRelSym(const MCAssembler &Asm, const MCValue &Target,
30                                  const MCFragment &F, const MCFixup &Fixup,
31                                  bool IsPCRel) const override;
32 };
33 } // end anonymous namespace
34 
35 SystemZObjectWriter::SystemZObjectWriter(uint8_t OSABI)
36   : MCELFObjectTargetWriter(/*Is64Bit=*/true, OSABI, ELF::EM_S390,
37                             /*HasRelocationAddend=*/ true) {}
38 
39 SystemZObjectWriter::~SystemZObjectWriter() {
40 }
41 
42 // Return the relocation type for an absolute value of MCFixupKind Kind.
43 static unsigned getAbsoluteReloc(unsigned Kind) {
44   switch (Kind) {
45   case FK_Data_1: return ELF::R_390_8;
46   case FK_Data_2: return ELF::R_390_16;
47   case FK_Data_4: return ELF::R_390_32;
48   case FK_Data_8: return ELF::R_390_64;
49   }
50   llvm_unreachable("Unsupported absolute address");
51 }
52 
53 // Return the relocation type for a PC-relative value of MCFixupKind Kind.
54 static unsigned getPCRelReloc(unsigned Kind) {
55   switch (Kind) {
56   case FK_Data_2:                return ELF::R_390_PC16;
57   case FK_Data_4:                return ELF::R_390_PC32;
58   case FK_Data_8:                return ELF::R_390_PC64;
59   case SystemZ::FK_390_PC16DBL:  return ELF::R_390_PC16DBL;
60   case SystemZ::FK_390_PC32DBL:  return ELF::R_390_PC32DBL;
61   case SystemZ::FK_390_PLT16DBL: return ELF::R_390_PLT16DBL;
62   case SystemZ::FK_390_PLT32DBL: return ELF::R_390_PLT32DBL;
63   }
64   llvm_unreachable("Unsupported PC-relative address");
65 }
66 
67 // Return the R_390_TLS_LE* relocation type for MCFixupKind Kind.
68 static unsigned getTLSLEReloc(unsigned Kind) {
69   switch (Kind) {
70   case FK_Data_4: return ELF::R_390_TLS_LE32;
71   case FK_Data_8: return ELF::R_390_TLS_LE64;
72   }
73   llvm_unreachable("Unsupported absolute address");
74 }
75 
76 // Return the PLT relocation counterpart of MCFixupKind Kind.
77 static unsigned getPLTReloc(unsigned Kind) {
78   switch (Kind) {
79   case SystemZ::FK_390_PC16DBL: return ELF::R_390_PLT16DBL;
80   case SystemZ::FK_390_PC32DBL: return ELF::R_390_PLT32DBL;
81   }
82   llvm_unreachable("Unsupported absolute address");
83 }
84 
85 unsigned SystemZObjectWriter::GetRelocType(const MCValue &Target,
86                                            const MCFixup &Fixup,
87                                            bool IsPCRel) const {
88   MCSymbolRefExpr::VariantKind Modifier = Fixup.getAccessVariant();
89   unsigned Kind = Fixup.getKind();
90   switch (Modifier) {
91   case MCSymbolRefExpr::VK_None:
92     if (IsPCRel)
93       return getPCRelReloc(Kind);
94     return getAbsoluteReloc(Kind);
95 
96   case MCSymbolRefExpr::VK_NTPOFF:
97     assert(!IsPCRel && "NTPOFF shouldn't be PC-relative");
98     return getTLSLEReloc(Kind);
99 
100   case MCSymbolRefExpr::VK_GOT:
101     if (IsPCRel && Kind == SystemZ::FK_390_PC32DBL)
102       return ELF::R_390_GOTENT;
103     llvm_unreachable("Only PC-relative GOT accesses are supported for now");
104 
105   case MCSymbolRefExpr::VK_PLT:
106     assert(IsPCRel && "@PLT shouldt be PC-relative");
107     return getPLTReloc(Kind);
108 
109   default:
110     llvm_unreachable("Modifier not supported");
111   }
112 }
113 
114 const MCSymbol *SystemZObjectWriter::ExplicitRelSym(const MCAssembler &Asm,
115                                                     const MCValue &Target,
116                                                     const MCFragment &F,
117                                                     const MCFixup &Fixup,
118                                                     bool IsPCRel) const {
119   // The addend in a PC-relative R_390_* relocation is always applied to
120   // the PC-relative part of the address.  If some kind of indirection
121   // is applied to the symbol first, we can't use an addend there too.
122   if (!Target.isAbsolute() &&
123       Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None &&
124       IsPCRel)
125     return &Target.getSymA()->getSymbol().AliasedSymbol();
126   return NULL;
127 }
128 
129 MCObjectWriter *llvm::createSystemZObjectWriter(raw_ostream &OS,
130                                                 uint8_t OSABI) {
131   MCELFObjectTargetWriter *MOTW = new SystemZObjectWriter(OSABI);
132   return createELFObjectWriter(MOTW, OS, /*IsLittleEndian=*/false);
133 }
134