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, bool IsRelocWithSymbol,
29                         int64_t Addend) const override;
30   const MCSymbol *ExplicitRelSym(const MCAssembler &Asm, const MCValue &Target,
31                                  const MCFragment &F, const MCFixup &Fixup,
32                                  bool IsPCRel) const override;
33 };
34 } // end anonymous namespace
35 
36 SystemZObjectWriter::SystemZObjectWriter(uint8_t OSABI)
37   : MCELFObjectTargetWriter(/*Is64Bit=*/true, OSABI, ELF::EM_S390,
38                             /*HasRelocationAddend=*/ true) {}
39 
40 SystemZObjectWriter::~SystemZObjectWriter() {
41 }
42 
43 // Return the relocation type for an absolute value of MCFixupKind Kind.
44 static unsigned getAbsoluteReloc(unsigned Kind) {
45   switch (Kind) {
46   case FK_Data_1: return ELF::R_390_8;
47   case FK_Data_2: return ELF::R_390_16;
48   case FK_Data_4: return ELF::R_390_32;
49   case FK_Data_8: return ELF::R_390_64;
50   }
51   llvm_unreachable("Unsupported absolute address");
52 }
53 
54 // Return the relocation type for a PC-relative value of MCFixupKind Kind.
55 static unsigned getPCRelReloc(unsigned Kind) {
56   switch (Kind) {
57   case FK_Data_2:                return ELF::R_390_PC16;
58   case FK_Data_4:                return ELF::R_390_PC32;
59   case FK_Data_8:                return ELF::R_390_PC64;
60   case SystemZ::FK_390_PC16DBL:  return ELF::R_390_PC16DBL;
61   case SystemZ::FK_390_PC32DBL:  return ELF::R_390_PC32DBL;
62   case SystemZ::FK_390_PLT16DBL: return ELF::R_390_PLT16DBL;
63   case SystemZ::FK_390_PLT32DBL: return ELF::R_390_PLT32DBL;
64   }
65   llvm_unreachable("Unsupported PC-relative address");
66 }
67 
68 // Return the R_390_TLS_LE* relocation type for MCFixupKind Kind.
69 static unsigned getTLSLEReloc(unsigned Kind) {
70   switch (Kind) {
71   case FK_Data_4: return ELF::R_390_TLS_LE32;
72   case FK_Data_8: return ELF::R_390_TLS_LE64;
73   }
74   llvm_unreachable("Unsupported absolute address");
75 }
76 
77 // Return the PLT relocation counterpart of MCFixupKind Kind.
78 static unsigned getPLTReloc(unsigned Kind) {
79   switch (Kind) {
80   case SystemZ::FK_390_PC16DBL: return ELF::R_390_PLT16DBL;
81   case SystemZ::FK_390_PC32DBL: return ELF::R_390_PLT32DBL;
82   }
83   llvm_unreachable("Unsupported absolute address");
84 }
85 
86 unsigned SystemZObjectWriter::GetRelocType(const MCValue &Target,
87                                            const MCFixup &Fixup,
88                                            bool IsPCRel,
89                                            bool IsRelocWithSymbol,
90                                            int64_t Addend) const {
91   MCSymbolRefExpr::VariantKind Modifier = (Target.isAbsolute() ?
92                                            MCSymbolRefExpr::VK_None :
93                                            Target.getSymA()->getKind());
94   unsigned Kind = Fixup.getKind();
95   switch (Modifier) {
96   case MCSymbolRefExpr::VK_None:
97     if (IsPCRel)
98       return getPCRelReloc(Kind);
99     return getAbsoluteReloc(Kind);
100 
101   case MCSymbolRefExpr::VK_NTPOFF:
102     assert(!IsPCRel && "NTPOFF shouldn't be PC-relative");
103     return getTLSLEReloc(Kind);
104 
105   case MCSymbolRefExpr::VK_GOT:
106     if (IsPCRel && Kind == SystemZ::FK_390_PC32DBL)
107       return ELF::R_390_GOTENT;
108     llvm_unreachable("Only PC-relative GOT accesses are supported for now");
109 
110   case MCSymbolRefExpr::VK_PLT:
111     assert(IsPCRel && "@PLT shouldt be PC-relative");
112     return getPLTReloc(Kind);
113 
114   default:
115     llvm_unreachable("Modifier not supported");
116   }
117 }
118 
119 const MCSymbol *SystemZObjectWriter::ExplicitRelSym(const MCAssembler &Asm,
120                                                     const MCValue &Target,
121                                                     const MCFragment &F,
122                                                     const MCFixup &Fixup,
123                                                     bool IsPCRel) const {
124   // The addend in a PC-relative R_390_* relocation is always applied to
125   // the PC-relative part of the address.  If some kind of indirection
126   // is applied to the symbol first, we can't use an addend there too.
127   if (!Target.isAbsolute() &&
128       Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None &&
129       IsPCRel)
130     return &Target.getSymA()->getSymbol().AliasedSymbol();
131   return NULL;
132 }
133 
134 MCObjectWriter *llvm::createSystemZObjectWriter(raw_ostream &OS,
135                                                 uint8_t OSABI) {
136   MCELFObjectTargetWriter *MOTW = new SystemZObjectWriter(OSABI);
137   return createELFObjectWriter(MOTW, OS, /*IsLittleEndian=*/false);
138 }
139