1 //===-- X86MachObjectWriter.cpp - X86 Mach-O 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/X86MCTargetDesc.h" 11 #include "MCTargetDesc/X86FixupKinds.h" 12 #include "llvm/ADT/Twine.h" 13 #include "llvm/MC/MCAsmInfo.h" 14 #include "llvm/MC/MCAsmLayout.h" 15 #include "llvm/MC/MCAssembler.h" 16 #include "llvm/MC/MCContext.h" 17 #include "llvm/MC/MCMachObjectWriter.h" 18 #include "llvm/MC/MCSectionMachO.h" 19 #include "llvm/MC/MCValue.h" 20 #include "llvm/Support/ErrorHandling.h" 21 #include "llvm/Support/Format.h" 22 #include "llvm/Support/MachO.h" 23 24 using namespace llvm; 25 26 namespace { 27 class X86MachObjectWriter : public MCMachObjectTargetWriter { 28 bool RecordScatteredRelocation(MachObjectWriter *Writer, 29 const MCAssembler &Asm, 30 const MCAsmLayout &Layout, 31 const MCFragment *Fragment, 32 const MCFixup &Fixup, 33 MCValue Target, 34 unsigned Log2Size, 35 uint64_t &FixedValue); 36 void RecordTLVPRelocation(MachObjectWriter *Writer, 37 const MCAssembler &Asm, 38 const MCAsmLayout &Layout, 39 const MCFragment *Fragment, 40 const MCFixup &Fixup, 41 MCValue Target, 42 uint64_t &FixedValue); 43 44 void RecordX86Relocation(MachObjectWriter *Writer, 45 const MCAssembler &Asm, 46 const MCAsmLayout &Layout, 47 const MCFragment *Fragment, 48 const MCFixup &Fixup, 49 MCValue Target, 50 uint64_t &FixedValue); 51 void RecordX86_64Relocation(MachObjectWriter *Writer, MCAssembler &Asm, 52 const MCAsmLayout &Layout, 53 const MCFragment *Fragment, const MCFixup &Fixup, 54 MCValue Target, uint64_t &FixedValue); 55 56 public: 57 X86MachObjectWriter(bool Is64Bit, uint32_t CPUType, 58 uint32_t CPUSubtype) 59 : MCMachObjectTargetWriter(Is64Bit, CPUType, CPUSubtype, 60 /*UseAggressiveSymbolFolding=*/Is64Bit) {} 61 62 void RecordRelocation(MachObjectWriter *Writer, MCAssembler &Asm, 63 const MCAsmLayout &Layout, const MCFragment *Fragment, 64 const MCFixup &Fixup, MCValue Target, 65 uint64_t &FixedValue) override { 66 if (Writer->is64Bit()) 67 RecordX86_64Relocation(Writer, Asm, Layout, Fragment, Fixup, Target, 68 FixedValue); 69 else 70 RecordX86Relocation(Writer, Asm, Layout, Fragment, Fixup, Target, 71 FixedValue); 72 } 73 }; 74 } 75 76 static bool isFixupKindRIPRel(unsigned Kind) { 77 return Kind == X86::reloc_riprel_4byte || 78 Kind == X86::reloc_riprel_4byte_movq_load; 79 } 80 81 static unsigned getFixupKindLog2Size(unsigned Kind) { 82 switch (Kind) { 83 default: 84 llvm_unreachable("invalid fixup kind!"); 85 case FK_PCRel_1: 86 case FK_Data_1: return 0; 87 case FK_PCRel_2: 88 case FK_Data_2: return 1; 89 case FK_PCRel_4: 90 // FIXME: Remove these!!! 91 case X86::reloc_riprel_4byte: 92 case X86::reloc_riprel_4byte_movq_load: 93 case X86::reloc_signed_4byte: 94 case FK_Data_4: return 2; 95 case FK_Data_8: return 3; 96 } 97 } 98 99 void X86MachObjectWriter::RecordX86_64Relocation( 100 MachObjectWriter *Writer, MCAssembler &Asm, const MCAsmLayout &Layout, 101 const MCFragment *Fragment, const MCFixup &Fixup, MCValue Target, 102 uint64_t &FixedValue) { 103 unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind()); 104 unsigned IsRIPRel = isFixupKindRIPRel(Fixup.getKind()); 105 unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind()); 106 107 // See <reloc.h>. 108 uint32_t FixupOffset = 109 Layout.getFragmentOffset(Fragment) + Fixup.getOffset(); 110 uint32_t FixupAddress = 111 Writer->getFragmentAddress(Fragment, Layout) + Fixup.getOffset(); 112 int64_t Value = 0; 113 unsigned Index = 0; 114 unsigned IsExtern = 0; 115 unsigned Type = 0; 116 const MCSymbolData *RelSymbol = nullptr; 117 118 Value = Target.getConstant(); 119 120 if (IsPCRel) { 121 // Compensate for the relocation offset, Darwin x86_64 relocations only have 122 // the addend and appear to have attempted to define it to be the actual 123 // expression addend without the PCrel bias. However, instructions with data 124 // following the relocation are not accommodated for (see comment below 125 // regarding SIGNED{1,2,4}), so it isn't exactly that either. 126 Value += 1LL << Log2Size; 127 } 128 129 if (Target.isAbsolute()) { // constant 130 // SymbolNum of 0 indicates the absolute section. 131 Type = MachO::X86_64_RELOC_UNSIGNED; 132 133 // FIXME: I believe this is broken, I don't think the linker can understand 134 // it. I think it would require a local relocation, but I'm not sure if that 135 // would work either. The official way to get an absolute PCrel relocation 136 // is to use an absolute symbol (which we don't support yet). 137 if (IsPCRel) { 138 IsExtern = 1; 139 Type = MachO::X86_64_RELOC_BRANCH; 140 } 141 } else if (Target.getSymB()) { // A - B + constant 142 const MCSymbol *A = &Target.getSymA()->getSymbol(); 143 if (A->isTemporary()) 144 A = &A->AliasedSymbol(); 145 const MCSymbolData &A_SD = Asm.getSymbolData(*A); 146 const MCSymbolData *A_Base = Asm.getAtom(&A_SD); 147 148 const MCSymbol *B = &Target.getSymB()->getSymbol(); 149 if (B->isTemporary()) 150 B = &B->AliasedSymbol(); 151 const MCSymbolData &B_SD = Asm.getSymbolData(*B); 152 const MCSymbolData *B_Base = Asm.getAtom(&B_SD); 153 154 // Neither symbol can be modified. 155 if (Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None || 156 Target.getSymB()->getKind() != MCSymbolRefExpr::VK_None) 157 report_fatal_error("unsupported relocation of modified symbol", false); 158 159 // We don't support PCrel relocations of differences. Darwin 'as' doesn't 160 // implement most of these correctly. 161 if (IsPCRel) 162 report_fatal_error("unsupported pc-relative relocation of difference", 163 false); 164 165 // The support for the situation where one or both of the symbols would 166 // require a local relocation is handled just like if the symbols were 167 // external. This is certainly used in the case of debug sections where the 168 // section has only temporary symbols and thus the symbols don't have base 169 // symbols. This is encoded using the section ordinal and non-extern 170 // relocation entries. 171 172 // Darwin 'as' doesn't emit correct relocations for this (it ends up with a 173 // single SIGNED relocation); reject it for now. Except the case where both 174 // symbols don't have a base, equal but both NULL. 175 if (A_Base == B_Base && A_Base) 176 report_fatal_error("unsupported relocation with identical base", false); 177 178 // A subtraction expression where either symbol is undefined is a 179 // non-relocatable expression. 180 if (A->isUndefined() || B->isUndefined()) { 181 StringRef Name = A->isUndefined() ? A->getName() : B->getName(); 182 Asm.getContext().FatalError(Fixup.getLoc(), 183 "unsupported relocation with subtraction expression, symbol '" + 184 Name + "' can not be undefined in a subtraction expression"); 185 } 186 187 Value += Writer->getSymbolAddress(&A_SD, Layout) - 188 (!A_Base ? 0 : Writer->getSymbolAddress(A_Base, Layout)); 189 Value -= Writer->getSymbolAddress(&B_SD, Layout) - 190 (!B_Base ? 0 : Writer->getSymbolAddress(B_Base, Layout)); 191 192 if (!A_Base) 193 Index = A_SD.getFragment()->getParent()->getOrdinal() + 1; 194 Type = MachO::X86_64_RELOC_UNSIGNED; 195 196 MachO::any_relocation_info MRE; 197 MRE.r_word0 = FixupOffset; 198 MRE.r_word1 = 199 (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28); 200 Writer->addRelocation(A_Base, Fragment->getParent(), MRE); 201 202 if (B_Base) 203 RelSymbol = B_Base; 204 else 205 Index = B_SD.getFragment()->getParent()->getOrdinal() + 1; 206 Type = MachO::X86_64_RELOC_SUBTRACTOR; 207 } else { 208 const MCSymbol *Symbol = &Target.getSymA()->getSymbol(); 209 if (Symbol->isTemporary() && Value) { 210 const MCSection &Sec = Symbol->getSection(); 211 if (!Asm.getContext().getAsmInfo()->isSectionAtomizableBySymbols(Sec)) 212 Asm.addLocalUsedInReloc(*Symbol); 213 } 214 const MCSymbolData &SD = Asm.getSymbolData(*Symbol); 215 RelSymbol = Asm.getAtom(&SD); 216 217 // Relocations inside debug sections always use local relocations when 218 // possible. This seems to be done because the debugger doesn't fully 219 // understand x86_64 relocation entries, and expects to find values that 220 // have already been fixed up. 221 if (Symbol->isInSection()) { 222 const MCSectionMachO &Section = static_cast<const MCSectionMachO&>( 223 Fragment->getParent()->getSection()); 224 if (Section.hasAttribute(MachO::S_ATTR_DEBUG)) 225 RelSymbol = nullptr; 226 } 227 228 // x86_64 almost always uses external relocations, except when there is no 229 // symbol to use as a base address (a local symbol with no preceding 230 // non-local symbol). 231 if (RelSymbol) { 232 // Add the local offset, if needed. 233 if (RelSymbol != &SD) 234 Value += 235 Layout.getSymbolOffset(&SD) - Layout.getSymbolOffset(RelSymbol); 236 } else if (Symbol->isInSection() && !Symbol->isVariable()) { 237 // The index is the section ordinal (1-based). 238 Index = SD.getFragment()->getParent()->getOrdinal() + 1; 239 Value += Writer->getSymbolAddress(&SD, Layout); 240 241 if (IsPCRel) 242 Value -= FixupAddress + (1 << Log2Size); 243 } else if (Symbol->isVariable()) { 244 const MCExpr *Value = Symbol->getVariableValue(); 245 int64_t Res; 246 bool isAbs = Value->EvaluateAsAbsolute(Res, Layout, 247 Writer->getSectionAddressMap()); 248 if (isAbs) { 249 FixedValue = Res; 250 return; 251 } else { 252 report_fatal_error("unsupported relocation of variable '" + 253 Symbol->getName() + "'", false); 254 } 255 } else { 256 report_fatal_error("unsupported relocation of undefined symbol '" + 257 Symbol->getName() + "'", false); 258 } 259 260 MCSymbolRefExpr::VariantKind Modifier = Target.getSymA()->getKind(); 261 if (IsPCRel) { 262 if (IsRIPRel) { 263 if (Modifier == MCSymbolRefExpr::VK_GOTPCREL) { 264 // x86_64 distinguishes movq foo@GOTPCREL so that the linker can 265 // rewrite the movq to an leaq at link time if the symbol ends up in 266 // the same linkage unit. 267 if (unsigned(Fixup.getKind()) == X86::reloc_riprel_4byte_movq_load) 268 Type = MachO::X86_64_RELOC_GOT_LOAD; 269 else 270 Type = MachO::X86_64_RELOC_GOT; 271 } else if (Modifier == MCSymbolRefExpr::VK_TLVP) { 272 Type = MachO::X86_64_RELOC_TLV; 273 } else if (Modifier != MCSymbolRefExpr::VK_None) { 274 report_fatal_error("unsupported symbol modifier in relocation", 275 false); 276 } else { 277 Type = MachO::X86_64_RELOC_SIGNED; 278 279 // The Darwin x86_64 relocation format has a problem where it cannot 280 // encode an address (L<foo> + <constant>) which is outside the atom 281 // containing L<foo>. Generally, this shouldn't occur but it does 282 // happen when we have a RIPrel instruction with data following the 283 // relocation entry (e.g., movb $012, L0(%rip)). Even with the PCrel 284 // adjustment Darwin x86_64 uses, the offset is still negative and the 285 // linker has no way to recognize this. 286 // 287 // To work around this, Darwin uses several special relocation types 288 // to indicate the offsets. However, the specification or 289 // implementation of these seems to also be incomplete; they should 290 // adjust the addend as well based on the actual encoded instruction 291 // (the additional bias), but instead appear to just look at the final 292 // offset. 293 switch (-(Target.getConstant() + (1LL << Log2Size))) { 294 case 1: Type = MachO::X86_64_RELOC_SIGNED_1; break; 295 case 2: Type = MachO::X86_64_RELOC_SIGNED_2; break; 296 case 4: Type = MachO::X86_64_RELOC_SIGNED_4; break; 297 } 298 } 299 } else { 300 if (Modifier != MCSymbolRefExpr::VK_None) 301 report_fatal_error("unsupported symbol modifier in branch " 302 "relocation", false); 303 304 Type = MachO::X86_64_RELOC_BRANCH; 305 } 306 } else { 307 if (Modifier == MCSymbolRefExpr::VK_GOT) { 308 Type = MachO::X86_64_RELOC_GOT; 309 } else if (Modifier == MCSymbolRefExpr::VK_GOTPCREL) { 310 // GOTPCREL is allowed as a modifier on non-PCrel instructions, in which 311 // case all we do is set the PCrel bit in the relocation entry; this is 312 // used with exception handling, for example. The source is required to 313 // include any necessary offset directly. 314 Type = MachO::X86_64_RELOC_GOT; 315 IsPCRel = 1; 316 } else if (Modifier == MCSymbolRefExpr::VK_TLVP) { 317 report_fatal_error("TLVP symbol modifier should have been rip-rel", 318 false); 319 } else if (Modifier != MCSymbolRefExpr::VK_None) 320 report_fatal_error("unsupported symbol modifier in relocation", false); 321 else { 322 Type = MachO::X86_64_RELOC_UNSIGNED; 323 unsigned Kind = Fixup.getKind(); 324 if (Kind == X86::reloc_signed_4byte) 325 report_fatal_error("32-bit absolute addressing is not supported in " 326 "64-bit mode", false); 327 } 328 } 329 } 330 331 // x86_64 always writes custom values into the fixups. 332 FixedValue = Value; 333 334 // struct relocation_info (8 bytes) 335 MachO::any_relocation_info MRE; 336 MRE.r_word0 = FixupOffset; 337 MRE.r_word1 = (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | 338 (IsExtern << 27) | (Type << 28); 339 Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE); 340 } 341 342 bool X86MachObjectWriter::RecordScatteredRelocation(MachObjectWriter *Writer, 343 const MCAssembler &Asm, 344 const MCAsmLayout &Layout, 345 const MCFragment *Fragment, 346 const MCFixup &Fixup, 347 MCValue Target, 348 unsigned Log2Size, 349 uint64_t &FixedValue) { 350 uint64_t OriginalFixedValue = FixedValue; 351 uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset(); 352 unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind()); 353 unsigned Type = MachO::GENERIC_RELOC_VANILLA; 354 355 // See <reloc.h>. 356 const MCSymbol *A = &Target.getSymA()->getSymbol(); 357 const MCSymbolData *A_SD = &Asm.getSymbolData(*A); 358 359 if (!A_SD->getFragment()) 360 report_fatal_error("symbol '" + A->getName() + 361 "' can not be undefined in a subtraction expression", 362 false); 363 364 uint32_t Value = Writer->getSymbolAddress(A_SD, Layout); 365 uint64_t SecAddr = Writer->getSectionAddress(A_SD->getFragment()->getParent()); 366 FixedValue += SecAddr; 367 uint32_t Value2 = 0; 368 369 if (const MCSymbolRefExpr *B = Target.getSymB()) { 370 const MCSymbolData *B_SD = &Asm.getSymbolData(B->getSymbol()); 371 372 if (!B_SD->getFragment()) 373 report_fatal_error("symbol '" + B->getSymbol().getName() + 374 "' can not be undefined in a subtraction expression", 375 false); 376 377 // Select the appropriate difference relocation type. 378 // 379 // Note that there is no longer any semantic difference between these two 380 // relocation types from the linkers point of view, this is done solely for 381 // pedantic compatibility with 'as'. 382 Type = A_SD->isExternal() ? (unsigned)MachO::GENERIC_RELOC_SECTDIFF : 383 (unsigned)MachO::GENERIC_RELOC_LOCAL_SECTDIFF; 384 Value2 = Writer->getSymbolAddress(B_SD, Layout); 385 FixedValue -= Writer->getSectionAddress(B_SD->getFragment()->getParent()); 386 } 387 388 // Relocations are written out in reverse order, so the PAIR comes first. 389 if (Type == MachO::GENERIC_RELOC_SECTDIFF || 390 Type == MachO::GENERIC_RELOC_LOCAL_SECTDIFF) { 391 // If the offset is too large to fit in a scattered relocation, 392 // we're hosed. It's an unfortunate limitation of the MachO format. 393 if (FixupOffset > 0xffffff) { 394 char Buffer[32]; 395 format("0x%x", FixupOffset).print(Buffer, sizeof(Buffer)); 396 Asm.getContext().FatalError(Fixup.getLoc(), 397 Twine("Section too large, can't encode " 398 "r_address (") + Buffer + 399 ") into 24 bits of scattered " 400 "relocation entry."); 401 llvm_unreachable("fatal error returned?!"); 402 } 403 404 MachO::any_relocation_info MRE; 405 MRE.r_word0 = ((0 << 0) | // r_address 406 (MachO::GENERIC_RELOC_PAIR << 24) | // r_type 407 (Log2Size << 28) | 408 (IsPCRel << 30) | 409 MachO::R_SCATTERED); 410 MRE.r_word1 = Value2; 411 Writer->addRelocation(nullptr, Fragment->getParent(), MRE); 412 } else { 413 // If the offset is more than 24-bits, it won't fit in a scattered 414 // relocation offset field, so we fall back to using a non-scattered 415 // relocation. This is a bit risky, as if the offset reaches out of 416 // the block and the linker is doing scattered loading on this 417 // symbol, things can go badly. 418 // 419 // Required for 'as' compatibility. 420 if (FixupOffset > 0xffffff) { 421 FixedValue = OriginalFixedValue; 422 return false; 423 } 424 } 425 426 MachO::any_relocation_info MRE; 427 MRE.r_word0 = ((FixupOffset << 0) | 428 (Type << 24) | 429 (Log2Size << 28) | 430 (IsPCRel << 30) | 431 MachO::R_SCATTERED); 432 MRE.r_word1 = Value; 433 Writer->addRelocation(nullptr, Fragment->getParent(), MRE); 434 return true; 435 } 436 437 void X86MachObjectWriter::RecordTLVPRelocation(MachObjectWriter *Writer, 438 const MCAssembler &Asm, 439 const MCAsmLayout &Layout, 440 const MCFragment *Fragment, 441 const MCFixup &Fixup, 442 MCValue Target, 443 uint64_t &FixedValue) { 444 assert(Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP && 445 !is64Bit() && 446 "Should only be called with a 32-bit TLVP relocation!"); 447 448 unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind()); 449 uint32_t Value = Layout.getFragmentOffset(Fragment)+Fixup.getOffset(); 450 unsigned IsPCRel = 0; 451 452 // Get the symbol data. 453 const MCSymbolData *SD_A = &Asm.getSymbolData(Target.getSymA()->getSymbol()); 454 455 // We're only going to have a second symbol in pic mode and it'll be a 456 // subtraction from the picbase. For 32-bit pic the addend is the difference 457 // between the picbase and the next address. For 32-bit static the addend is 458 // zero. 459 if (Target.getSymB()) { 460 // If this is a subtraction then we're pcrel. 461 uint32_t FixupAddress = 462 Writer->getFragmentAddress(Fragment, Layout) + Fixup.getOffset(); 463 const MCSymbolData *SD_B = 464 &Asm.getSymbolData(Target.getSymB()->getSymbol()); 465 IsPCRel = 1; 466 FixedValue = (FixupAddress - Writer->getSymbolAddress(SD_B, Layout) + 467 Target.getConstant()); 468 FixedValue += 1ULL << Log2Size; 469 } else { 470 FixedValue = 0; 471 } 472 473 // struct relocation_info (8 bytes) 474 MachO::any_relocation_info MRE; 475 MRE.r_word0 = Value; 476 MRE.r_word1 = 477 (IsPCRel << 24) | (Log2Size << 25) | (MachO::GENERIC_RELOC_TLV << 28); 478 Writer->addRelocation(SD_A, Fragment->getParent(), MRE); 479 } 480 481 void X86MachObjectWriter::RecordX86Relocation(MachObjectWriter *Writer, 482 const MCAssembler &Asm, 483 const MCAsmLayout &Layout, 484 const MCFragment *Fragment, 485 const MCFixup &Fixup, 486 MCValue Target, 487 uint64_t &FixedValue) { 488 unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind()); 489 unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind()); 490 491 // If this is a 32-bit TLVP reloc it's handled a bit differently. 492 if (Target.getSymA() && 493 Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP) { 494 RecordTLVPRelocation(Writer, Asm, Layout, Fragment, Fixup, Target, 495 FixedValue); 496 return; 497 } 498 499 // If this is a difference or a defined symbol plus an offset, then we need a 500 // scattered relocation entry. Differences always require scattered 501 // relocations. 502 if (Target.getSymB()) { 503 RecordScatteredRelocation(Writer, Asm, Layout, Fragment, Fixup, 504 Target, Log2Size, FixedValue); 505 return; 506 } 507 508 // Get the symbol data, if any. 509 const MCSymbolData *SD = nullptr; 510 if (Target.getSymA()) 511 SD = &Asm.getSymbolData(Target.getSymA()->getSymbol()); 512 513 // If this is an internal relocation with an offset, it also needs a scattered 514 // relocation entry. 515 uint32_t Offset = Target.getConstant(); 516 if (IsPCRel) 517 Offset += 1 << Log2Size; 518 // Try to record the scattered relocation if needed. Fall back to non 519 // scattered if necessary (see comments in RecordScatteredRelocation() 520 // for details). 521 if (Offset && SD && !Writer->doesSymbolRequireExternRelocation(SD) && 522 RecordScatteredRelocation(Writer, Asm, Layout, Fragment, Fixup, 523 Target, Log2Size, FixedValue)) 524 return; 525 526 // See <reloc.h>. 527 uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset(); 528 unsigned Index = 0; 529 unsigned Type = 0; 530 const MCSymbolData *RelSymbol = nullptr; 531 532 if (Target.isAbsolute()) { // constant 533 // SymbolNum of 0 indicates the absolute section. 534 // 535 // FIXME: Currently, these are never generated (see code below). I cannot 536 // find a case where they are actually emitted. 537 Type = MachO::GENERIC_RELOC_VANILLA; 538 } else { 539 // Resolve constant variables. 540 if (SD->getSymbol().isVariable()) { 541 int64_t Res; 542 if (SD->getSymbol().getVariableValue()->EvaluateAsAbsolute( 543 Res, Layout, Writer->getSectionAddressMap())) { 544 FixedValue = Res; 545 return; 546 } 547 } 548 549 // Check whether we need an external or internal relocation. 550 if (Writer->doesSymbolRequireExternRelocation(SD)) { 551 RelSymbol = SD; 552 // For external relocations, make sure to offset the fixup value to 553 // compensate for the addend of the symbol address, if it was 554 // undefined. This occurs with weak definitions, for example. 555 if (!SD->getSymbol().isUndefined()) 556 FixedValue -= Layout.getSymbolOffset(SD); 557 } else { 558 // The index is the section ordinal (1-based). 559 const MCSectionData &SymSD = Asm.getSectionData( 560 SD->getSymbol().getSection()); 561 Index = SymSD.getOrdinal() + 1; 562 FixedValue += Writer->getSectionAddress(&SymSD); 563 } 564 if (IsPCRel) 565 FixedValue -= Writer->getSectionAddress(Fragment->getParent()); 566 567 Type = MachO::GENERIC_RELOC_VANILLA; 568 } 569 570 // struct relocation_info (8 bytes) 571 MachO::any_relocation_info MRE; 572 MRE.r_word0 = FixupOffset; 573 MRE.r_word1 = 574 (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28); 575 Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE); 576 } 577 578 MCObjectWriter *llvm::createX86MachObjectWriter(raw_ostream &OS, 579 bool Is64Bit, 580 uint32_t CPUType, 581 uint32_t CPUSubtype) { 582 return createMachObjectWriter(new X86MachObjectWriter(Is64Bit, 583 CPUType, 584 CPUSubtype), 585 OS, /*IsLittleEndian=*/true); 586 } 587