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