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