1 //===-- X86ELFObjectWriter.cpp - X86 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/X86FixupKinds.h"
11 #include "MCTargetDesc/X86MCTargetDesc.h"
12 #include "llvm/MC/MCELFObjectWriter.h"
13 #include "llvm/MC/MCExpr.h"
14 #include "llvm/MC/MCValue.h"
15 #include "llvm/Support/ELF.h"
16 #include "llvm/Support/ErrorHandling.h"
17 
18 using namespace llvm;
19 
20 namespace {
21   class X86ELFObjectWriter : public MCELFObjectTargetWriter {
22   public:
23     X86ELFObjectWriter(bool IsELF64, uint8_t OSABI, uint16_t EMachine);
24 
25     ~X86ELFObjectWriter() override;
26 
27   protected:
28     unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
29                           bool IsPCRel) const override;
30   };
31 }
32 
X86ELFObjectWriter(bool IsELF64,uint8_t OSABI,uint16_t EMachine)33 X86ELFObjectWriter::X86ELFObjectWriter(bool IsELF64, uint8_t OSABI,
34                                        uint16_t EMachine)
35   : MCELFObjectTargetWriter(IsELF64, OSABI, EMachine,
36                             // Only i386 uses Rel instead of RelA.
37                             /*HasRelocationAddend*/ EMachine != ELF::EM_386) {}
38 
~X86ELFObjectWriter()39 X86ELFObjectWriter::~X86ELFObjectWriter()
40 {}
41 
42 enum X86_64RelType { RT64_64, RT64_32, RT64_32S, RT64_16, RT64_8 };
43 
getType64(unsigned Kind,MCSymbolRefExpr::VariantKind & Modifier,bool & IsPCRel)44 static X86_64RelType getType64(unsigned Kind,
45                                MCSymbolRefExpr::VariantKind &Modifier,
46                                bool &IsPCRel) {
47   switch (Kind) {
48   default:
49     llvm_unreachable("Unimplemented");
50   case X86::reloc_global_offset_table8:
51     Modifier = MCSymbolRefExpr::VK_GOT;
52     IsPCRel = true;
53     return RT64_64;
54   case FK_Data_8:
55     return RT64_64;
56   case X86::reloc_signed_4byte:
57     if (Modifier == MCSymbolRefExpr::VK_None && !IsPCRel)
58       return RT64_32S;
59     return RT64_32;
60   case X86::reloc_global_offset_table:
61     Modifier = MCSymbolRefExpr::VK_GOT;
62     IsPCRel = true;
63     return RT64_32;
64   case FK_Data_4:
65   case FK_PCRel_4:
66   case X86::reloc_riprel_4byte:
67   case X86::reloc_riprel_4byte_movq_load:
68     return RT64_32;
69   case FK_Data_2:
70     return RT64_16;
71   case FK_PCRel_1:
72   case FK_Data_1:
73     return RT64_8;
74   }
75 }
76 
getRelocType64(MCSymbolRefExpr::VariantKind Modifier,X86_64RelType Type,bool IsPCRel)77 static unsigned getRelocType64(MCSymbolRefExpr::VariantKind Modifier,
78                                X86_64RelType Type, bool IsPCRel) {
79   switch (Modifier) {
80   default:
81     llvm_unreachable("Unimplemented");
82   case MCSymbolRefExpr::VK_None:
83     switch (Type) {
84     case RT64_64:
85       return IsPCRel ? ELF::R_X86_64_PC64 : ELF::R_X86_64_64;
86     case RT64_32:
87       return IsPCRel ? ELF::R_X86_64_PC32 : ELF::R_X86_64_32;
88     case RT64_32S:
89       return ELF::R_X86_64_32S;
90     case RT64_16:
91       return IsPCRel ? ELF::R_X86_64_PC16 : ELF::R_X86_64_16;
92     case RT64_8:
93       return IsPCRel ? ELF::R_X86_64_PC8 : ELF::R_X86_64_8;
94     }
95   case MCSymbolRefExpr::VK_GOT:
96     switch (Type) {
97     case RT64_64:
98       return IsPCRel ? ELF::R_X86_64_GOTPC64 : ELF::R_X86_64_GOT64;
99     case RT64_32:
100       return IsPCRel ? ELF::R_X86_64_GOTPC32 : ELF::R_X86_64_GOT32;
101     case RT64_32S:
102     case RT64_16:
103     case RT64_8:
104       llvm_unreachable("Unimplemented");
105     }
106   case MCSymbolRefExpr::VK_GOTOFF:
107     assert(Type == RT64_64);
108     assert(!IsPCRel);
109     return ELF::R_X86_64_GOTOFF64;
110   case MCSymbolRefExpr::VK_TPOFF:
111     assert(!IsPCRel);
112     switch (Type) {
113     case RT64_64:
114       return ELF::R_X86_64_TPOFF64;
115     case RT64_32:
116       return ELF::R_X86_64_TPOFF32;
117     case RT64_32S:
118     case RT64_16:
119     case RT64_8:
120       llvm_unreachable("Unimplemented");
121     }
122   case MCSymbolRefExpr::VK_DTPOFF:
123     assert(!IsPCRel);
124     switch (Type) {
125     case RT64_64:
126       return ELF::R_X86_64_DTPOFF64;
127     case RT64_32:
128       return ELF::R_X86_64_DTPOFF32;
129     case RT64_32S:
130     case RT64_16:
131     case RT64_8:
132       llvm_unreachable("Unimplemented");
133     }
134   case MCSymbolRefExpr::VK_SIZE:
135     assert(!IsPCRel);
136     switch (Type) {
137     case RT64_64:
138       return ELF::R_X86_64_SIZE64;
139     case RT64_32:
140       return ELF::R_X86_64_SIZE32;
141     case RT64_32S:
142     case RT64_16:
143     case RT64_8:
144       llvm_unreachable("Unimplemented");
145     }
146   case MCSymbolRefExpr::VK_TLSGD:
147     assert(Type == RT64_32);
148     return ELF::R_X86_64_TLSGD;
149   case MCSymbolRefExpr::VK_GOTTPOFF:
150     assert(Type == RT64_32);
151     return ELF::R_X86_64_GOTTPOFF;
152   case MCSymbolRefExpr::VK_TLSLD:
153     assert(Type == RT64_32);
154     return ELF::R_X86_64_TLSLD;
155   case MCSymbolRefExpr::VK_PLT:
156     assert(Type == RT64_32);
157     return ELF::R_X86_64_PLT32;
158   case MCSymbolRefExpr::VK_GOTPCREL:
159     assert(Type == RT64_32);
160     return ELF::R_X86_64_GOTPCREL;
161   }
162 }
163 
164 enum X86_32RelType { RT32_32, RT32_16, RT32_8 };
165 
getType32(X86_64RelType T)166 static X86_32RelType getType32(X86_64RelType T) {
167   switch (T) {
168   case RT64_64:
169     llvm_unreachable("Unimplemented");
170   case RT64_32:
171   case RT64_32S:
172     return RT32_32;
173   case RT64_16:
174     return RT32_16;
175   case RT64_8:
176     return RT32_8;
177   }
178   llvm_unreachable("unexpected relocation type!");
179 }
180 
getRelocType32(MCSymbolRefExpr::VariantKind Modifier,X86_32RelType Type,bool IsPCRel)181 static unsigned getRelocType32(MCSymbolRefExpr::VariantKind Modifier,
182                                X86_32RelType Type, bool IsPCRel) {
183   switch (Modifier) {
184   default:
185     llvm_unreachable("Unimplemented");
186   case MCSymbolRefExpr::VK_None:
187     switch (Type) {
188     case RT32_32:
189       return IsPCRel ? ELF::R_386_PC32 : ELF::R_386_32;
190     case RT32_16:
191       return IsPCRel ? ELF::R_386_PC16 : ELF::R_386_16;
192     case RT32_8:
193       return IsPCRel ? ELF::R_386_PC8 : ELF::R_386_8;
194     }
195   case MCSymbolRefExpr::VK_GOT:
196     assert(Type == RT32_32);
197     return IsPCRel ? ELF::R_386_GOTPC : ELF::R_386_GOT32;
198   case MCSymbolRefExpr::VK_GOTOFF:
199     assert(Type == RT32_32);
200     assert(!IsPCRel);
201     return ELF::R_386_GOTOFF;
202   case MCSymbolRefExpr::VK_TPOFF:
203     assert(Type == RT32_32);
204     assert(!IsPCRel);
205     return ELF::R_386_TLS_LE_32;
206   case MCSymbolRefExpr::VK_DTPOFF:
207     assert(Type == RT32_32);
208     assert(!IsPCRel);
209     return ELF::R_386_TLS_LDO_32;
210   case MCSymbolRefExpr::VK_TLSGD:
211     assert(Type == RT32_32);
212     assert(!IsPCRel);
213     return ELF::R_386_TLS_GD;
214   case MCSymbolRefExpr::VK_GOTTPOFF:
215     assert(Type == RT32_32);
216     assert(!IsPCRel);
217     return ELF::R_386_TLS_IE_32;
218   case MCSymbolRefExpr::VK_PLT:
219     assert(Type == RT32_32);
220     return ELF::R_386_PLT32;
221   case MCSymbolRefExpr::VK_INDNTPOFF:
222     assert(Type == RT32_32);
223     assert(!IsPCRel);
224     return ELF::R_386_TLS_IE;
225   case MCSymbolRefExpr::VK_NTPOFF:
226     assert(Type == RT32_32);
227     assert(!IsPCRel);
228     return ELF::R_386_TLS_LE;
229   case MCSymbolRefExpr::VK_GOTNTPOFF:
230     assert(Type == RT32_32);
231     assert(!IsPCRel);
232     return ELF::R_386_TLS_GOTIE;
233   case MCSymbolRefExpr::VK_TLSLDM:
234     assert(Type == RT32_32);
235     assert(!IsPCRel);
236     return ELF::R_386_TLS_LDM;
237   }
238 }
239 
GetRelocType(const MCValue & Target,const MCFixup & Fixup,bool IsPCRel) const240 unsigned X86ELFObjectWriter::GetRelocType(const MCValue &Target,
241                                           const MCFixup &Fixup,
242                                           bool IsPCRel) const {
243   MCSymbolRefExpr::VariantKind Modifier = Target.getAccessVariant();
244   X86_64RelType Type = getType64(Fixup.getKind(), Modifier, IsPCRel);
245   if (getEMachine() == ELF::EM_X86_64)
246     return getRelocType64(Modifier, Type, IsPCRel);
247 
248   assert(getEMachine() == ELF::EM_386 && "Unsupported ELF machine type.");
249   return getRelocType32(Modifier, getType32(Type), IsPCRel);
250 }
251 
createX86ELFObjectWriter(raw_pwrite_stream & OS,bool IsELF64,uint8_t OSABI,uint16_t EMachine)252 MCObjectWriter *llvm::createX86ELFObjectWriter(raw_pwrite_stream &OS,
253                                                bool IsELF64, uint8_t OSABI,
254                                                uint16_t EMachine) {
255   MCELFObjectTargetWriter *MOTW =
256     new X86ELFObjectWriter(IsELF64, OSABI, EMachine);
257   return createELFObjectWriter(MOTW, OS,  /*IsLittleEndian=*/true);
258 }
259