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/MCAsmInfo.h" 13 #include "llvm/MC/MCContext.h" 14 #include "llvm/MC/MCELFObjectWriter.h" 15 #include "llvm/MC/MCExpr.h" 16 #include "llvm/MC/MCValue.h" 17 #include "llvm/Support/ELF.h" 18 #include "llvm/Support/ErrorHandling.h" 19 20 using namespace llvm; 21 22 namespace { 23 class X86ELFObjectWriter : public MCELFObjectTargetWriter { 24 public: 25 X86ELFObjectWriter(bool IsELF64, uint8_t OSABI, uint16_t EMachine); 26 27 ~X86ELFObjectWriter() override; 28 29 protected: 30 unsigned getRelocType(MCContext &Ctx, const MCValue &Target, 31 const MCFixup &Fixup, bool IsPCRel) const override; 32 }; 33 } 34 35 X86ELFObjectWriter::X86ELFObjectWriter(bool IsELF64, uint8_t OSABI, 36 uint16_t EMachine) 37 : MCELFObjectTargetWriter(IsELF64, OSABI, EMachine, 38 // Only i386 and IAMCU use Rel instead of RelA. 39 /*HasRelocationAddend*/ 40 (EMachine != ELF::EM_386) && 41 (EMachine != ELF::EM_IAMCU)) {} 42 43 X86ELFObjectWriter::~X86ELFObjectWriter() 44 {} 45 46 enum X86_64RelType { RT64_64, RT64_32, RT64_32S, RT64_16, RT64_8 }; 47 48 static X86_64RelType getType64(unsigned Kind, 49 MCSymbolRefExpr::VariantKind &Modifier, 50 bool &IsPCRel) { 51 switch (Kind) { 52 default: 53 llvm_unreachable("Unimplemented"); 54 case X86::reloc_global_offset_table8: 55 Modifier = MCSymbolRefExpr::VK_GOT; 56 IsPCRel = true; 57 return RT64_64; 58 case FK_Data_8: 59 return RT64_64; 60 case X86::reloc_signed_4byte: 61 case X86::reloc_signed_4byte_relax: 62 if (Modifier == MCSymbolRefExpr::VK_None && !IsPCRel) 63 return RT64_32S; 64 return RT64_32; 65 case X86::reloc_global_offset_table: 66 Modifier = MCSymbolRefExpr::VK_GOT; 67 IsPCRel = true; 68 return RT64_32; 69 case FK_Data_4: 70 case FK_PCRel_4: 71 case X86::reloc_riprel_4byte: 72 case X86::reloc_riprel_4byte_relax: 73 case X86::reloc_riprel_4byte_relax_rex: 74 case X86::reloc_riprel_4byte_movq_load: 75 return RT64_32; 76 case FK_PCRel_2: 77 case FK_Data_2: 78 return RT64_16; 79 case FK_PCRel_1: 80 case FK_Data_1: 81 return RT64_8; 82 } 83 } 84 85 static void checkIs32(MCContext &Ctx, SMLoc Loc, X86_64RelType Type) { 86 if (Type != RT64_32) 87 Ctx.reportError(Loc, 88 "32 bit reloc applied to a field with a different size"); 89 } 90 91 static unsigned getRelocType64(MCContext &Ctx, SMLoc Loc, 92 MCSymbolRefExpr::VariantKind Modifier, 93 X86_64RelType Type, bool IsPCRel, 94 unsigned Kind) { 95 switch (Modifier) { 96 default: 97 llvm_unreachable("Unimplemented"); 98 case MCSymbolRefExpr::VK_None: 99 switch (Type) { 100 case RT64_64: 101 return IsPCRel ? ELF::R_X86_64_PC64 : ELF::R_X86_64_64; 102 case RT64_32: 103 return IsPCRel ? ELF::R_X86_64_PC32 : ELF::R_X86_64_32; 104 case RT64_32S: 105 return ELF::R_X86_64_32S; 106 case RT64_16: 107 return IsPCRel ? ELF::R_X86_64_PC16 : ELF::R_X86_64_16; 108 case RT64_8: 109 return IsPCRel ? ELF::R_X86_64_PC8 : ELF::R_X86_64_8; 110 } 111 case MCSymbolRefExpr::VK_GOT: 112 switch (Type) { 113 case RT64_64: 114 return IsPCRel ? ELF::R_X86_64_GOTPC64 : ELF::R_X86_64_GOT64; 115 case RT64_32: 116 return IsPCRel ? ELF::R_X86_64_GOTPC32 : ELF::R_X86_64_GOT32; 117 case RT64_32S: 118 case RT64_16: 119 case RT64_8: 120 llvm_unreachable("Unimplemented"); 121 } 122 case MCSymbolRefExpr::VK_GOTOFF: 123 assert(Type == RT64_64); 124 assert(!IsPCRel); 125 return ELF::R_X86_64_GOTOFF64; 126 case MCSymbolRefExpr::VK_TPOFF: 127 assert(!IsPCRel); 128 switch (Type) { 129 case RT64_64: 130 return ELF::R_X86_64_TPOFF64; 131 case RT64_32: 132 return ELF::R_X86_64_TPOFF32; 133 case RT64_32S: 134 case RT64_16: 135 case RT64_8: 136 llvm_unreachable("Unimplemented"); 137 } 138 case MCSymbolRefExpr::VK_DTPOFF: 139 assert(!IsPCRel); 140 switch (Type) { 141 case RT64_64: 142 return ELF::R_X86_64_DTPOFF64; 143 case RT64_32: 144 return ELF::R_X86_64_DTPOFF32; 145 case RT64_32S: 146 case RT64_16: 147 case RT64_8: 148 llvm_unreachable("Unimplemented"); 149 } 150 case MCSymbolRefExpr::VK_SIZE: 151 assert(!IsPCRel); 152 switch (Type) { 153 case RT64_64: 154 return ELF::R_X86_64_SIZE64; 155 case RT64_32: 156 return ELF::R_X86_64_SIZE32; 157 case RT64_32S: 158 case RT64_16: 159 case RT64_8: 160 llvm_unreachable("Unimplemented"); 161 } 162 case MCSymbolRefExpr::VK_TLSCALL: 163 return ELF::R_X86_64_TLSDESC_CALL; 164 case MCSymbolRefExpr::VK_TLSDESC: 165 return ELF::R_X86_64_GOTPC32_TLSDESC; 166 case MCSymbolRefExpr::VK_TLSGD: 167 checkIs32(Ctx, Loc, Type); 168 return ELF::R_X86_64_TLSGD; 169 case MCSymbolRefExpr::VK_GOTTPOFF: 170 checkIs32(Ctx, Loc, Type); 171 return ELF::R_X86_64_GOTTPOFF; 172 case MCSymbolRefExpr::VK_TLSLD: 173 checkIs32(Ctx, Loc, Type); 174 return ELF::R_X86_64_TLSLD; 175 case MCSymbolRefExpr::VK_PLT: 176 checkIs32(Ctx, Loc, Type); 177 return ELF::R_X86_64_PLT32; 178 case MCSymbolRefExpr::VK_GOTPCREL: 179 checkIs32(Ctx, Loc, Type); 180 // Older versions of ld.bfd/ld.gold/lld 181 // do not support GOTPCRELX/REX_GOTPCRELX, 182 // and we want to keep back-compatibility. 183 if (!Ctx.getAsmInfo()->canRelaxRelocations()) 184 return ELF::R_X86_64_GOTPCREL; 185 switch (Kind) { 186 default: 187 return ELF::R_X86_64_GOTPCREL; 188 case X86::reloc_riprel_4byte_relax: 189 return ELF::R_X86_64_GOTPCRELX; 190 case X86::reloc_riprel_4byte_relax_rex: 191 case X86::reloc_riprel_4byte_movq_load: 192 return ELF::R_X86_64_REX_GOTPCRELX; 193 } 194 } 195 } 196 197 enum X86_32RelType { RT32_32, RT32_16, RT32_8 }; 198 199 static X86_32RelType getType32(X86_64RelType T) { 200 switch (T) { 201 case RT64_64: 202 llvm_unreachable("Unimplemented"); 203 case RT64_32: 204 case RT64_32S: 205 return RT32_32; 206 case RT64_16: 207 return RT32_16; 208 case RT64_8: 209 return RT32_8; 210 } 211 llvm_unreachable("unexpected relocation type!"); 212 } 213 214 static unsigned getRelocType32(MCContext &Ctx, 215 MCSymbolRefExpr::VariantKind Modifier, 216 X86_32RelType Type, bool IsPCRel, 217 unsigned Kind) { 218 switch (Modifier) { 219 default: 220 llvm_unreachable("Unimplemented"); 221 case MCSymbolRefExpr::VK_None: 222 switch (Type) { 223 case RT32_32: 224 return IsPCRel ? ELF::R_386_PC32 : ELF::R_386_32; 225 case RT32_16: 226 return IsPCRel ? ELF::R_386_PC16 : ELF::R_386_16; 227 case RT32_8: 228 return IsPCRel ? ELF::R_386_PC8 : ELF::R_386_8; 229 } 230 case MCSymbolRefExpr::VK_GOT: 231 assert(Type == RT32_32); 232 if (IsPCRel) 233 return ELF::R_386_GOTPC; 234 // Older versions of ld.bfd/ld.gold/lld do not support R_386_GOT32X and we 235 // want to maintain compatibility. 236 if (!Ctx.getAsmInfo()->canRelaxRelocations()) 237 return ELF::R_386_GOT32; 238 239 return Kind == X86::reloc_signed_4byte_relax ? ELF::R_386_GOT32X 240 : ELF::R_386_GOT32; 241 case MCSymbolRefExpr::VK_GOTOFF: 242 assert(Type == RT32_32); 243 assert(!IsPCRel); 244 return ELF::R_386_GOTOFF; 245 case MCSymbolRefExpr::VK_TPOFF: 246 assert(Type == RT32_32); 247 assert(!IsPCRel); 248 return ELF::R_386_TLS_LE_32; 249 case MCSymbolRefExpr::VK_DTPOFF: 250 assert(Type == RT32_32); 251 assert(!IsPCRel); 252 return ELF::R_386_TLS_LDO_32; 253 case MCSymbolRefExpr::VK_TLSGD: 254 assert(Type == RT32_32); 255 assert(!IsPCRel); 256 return ELF::R_386_TLS_GD; 257 case MCSymbolRefExpr::VK_GOTTPOFF: 258 assert(Type == RT32_32); 259 assert(!IsPCRel); 260 return ELF::R_386_TLS_IE_32; 261 case MCSymbolRefExpr::VK_PLT: 262 assert(Type == RT32_32); 263 return ELF::R_386_PLT32; 264 case MCSymbolRefExpr::VK_INDNTPOFF: 265 assert(Type == RT32_32); 266 assert(!IsPCRel); 267 return ELF::R_386_TLS_IE; 268 case MCSymbolRefExpr::VK_NTPOFF: 269 assert(Type == RT32_32); 270 assert(!IsPCRel); 271 return ELF::R_386_TLS_LE; 272 case MCSymbolRefExpr::VK_GOTNTPOFF: 273 assert(Type == RT32_32); 274 assert(!IsPCRel); 275 return ELF::R_386_TLS_GOTIE; 276 case MCSymbolRefExpr::VK_TLSLDM: 277 assert(Type == RT32_32); 278 assert(!IsPCRel); 279 return ELF::R_386_TLS_LDM; 280 } 281 } 282 283 unsigned X86ELFObjectWriter::getRelocType(MCContext &Ctx, const MCValue &Target, 284 const MCFixup &Fixup, 285 bool IsPCRel) const { 286 MCSymbolRefExpr::VariantKind Modifier = Target.getAccessVariant(); 287 unsigned Kind = Fixup.getKind(); 288 X86_64RelType Type = getType64(Kind, Modifier, IsPCRel); 289 if (getEMachine() == ELF::EM_X86_64) 290 return getRelocType64(Ctx, Fixup.getLoc(), Modifier, Type, IsPCRel, Kind); 291 292 assert((getEMachine() == ELF::EM_386 || getEMachine() == ELF::EM_IAMCU) && 293 "Unsupported ELF machine type."); 294 return getRelocType32(Ctx, Modifier, getType32(Type), IsPCRel, Kind); 295 } 296 297 MCObjectWriter *llvm::createX86ELFObjectWriter(raw_pwrite_stream &OS, 298 bool IsELF64, uint8_t OSABI, 299 uint16_t EMachine) { 300 MCELFObjectTargetWriter *MOTW = 301 new X86ELFObjectWriter(IsELF64, OSABI, EMachine); 302 return createELFObjectWriter(MOTW, OS, /*IsLittleEndian=*/true); 303 } 304
