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, uint32_t CPUSubtype) 58 : MCMachObjectTargetWriter(Is64Bit, CPUType, CPUSubtype) {} 59 60 void recordRelocation(MachObjectWriter *Writer, MCAssembler &Asm, 61 const MCAsmLayout &Layout, const MCFragment *Fragment, 62 const MCFixup &Fixup, MCValue Target, 63 uint64_t &FixedValue) override { 64 if (Writer->is64Bit()) 65 RecordX86_64Relocation(Writer, Asm, Layout, Fragment, Fixup, Target, 66 FixedValue); 67 else 68 RecordX86Relocation(Writer, Asm, Layout, Fragment, Fixup, Target, 69 FixedValue); 70 } 71 }; 72 } 73 74 static bool isFixupKindRIPRel(unsigned Kind) { 75 return Kind == X86::reloc_riprel_4byte || 76 Kind == X86::reloc_riprel_4byte_movq_load; 77 } 78 79 static unsigned getFixupKindLog2Size(unsigned Kind) { 80 switch (Kind) { 81 default: 82 llvm_unreachable("invalid fixup kind!"); 83 case FK_PCRel_1: 84 case FK_Data_1: return 0; 85 case FK_PCRel_2: 86 case FK_Data_2: return 1; 87 case FK_PCRel_4: 88 // FIXME: Remove these!!! 89 case X86::reloc_riprel_4byte: 90 case X86::reloc_riprel_4byte_movq_load: 91 case X86::reloc_signed_4byte: 92 case FK_Data_4: return 2; 93 case FK_Data_8: return 3; 94 } 95 } 96 97 void X86MachObjectWriter::RecordX86_64Relocation( 98 MachObjectWriter *Writer, MCAssembler &Asm, const MCAsmLayout &Layout, 99 const MCFragment *Fragment, const MCFixup &Fixup, MCValue Target, 100 uint64_t &FixedValue) { 101 unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind()); 102 unsigned IsRIPRel = isFixupKindRIPRel(Fixup.getKind()); 103 unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind()); 104 105 // See <reloc.h>. 106 uint32_t FixupOffset = 107 Layout.getFragmentOffset(Fragment) + Fixup.getOffset(); 108 uint32_t FixupAddress = 109 Writer->getFragmentAddress(Fragment, Layout) + Fixup.getOffset(); 110 int64_t Value = 0; 111 unsigned Index = 0; 112 unsigned IsExtern = 0; 113 unsigned Type = 0; 114 const MCSymbol *RelSymbol = nullptr; 115 116 Value = Target.getConstant(); 117 118 if (IsPCRel) { 119 // Compensate for the relocation offset, Darwin x86_64 relocations only have 120 // the addend and appear to have attempted to define it to be the actual 121 // expression addend without the PCrel bias. However, instructions with data 122 // following the relocation are not accommodated for (see comment below 123 // regarding SIGNED{1,2,4}), so it isn't exactly that either. 124 Value += 1LL << Log2Size; 125 } 126 127 if (Target.isAbsolute()) { // constant 128 // SymbolNum of 0 indicates the absolute section. 129 Type = MachO::X86_64_RELOC_UNSIGNED; 130 131 // FIXME: I believe this is broken, I don't think the linker can understand 132 // it. I think it would require a local relocation, but I'm not sure if that 133 // would work either. The official way to get an absolute PCrel relocation 134 // is to use an absolute symbol (which we don't support yet). 135 if (IsPCRel) { 136 IsExtern = 1; 137 Type = MachO::X86_64_RELOC_BRANCH; 138 } 139 } else if (Target.getSymB()) { // A - B + constant 140 const MCSymbol *A = &Target.getSymA()->getSymbol(); 141 if (A->isTemporary()) 142 A = &Writer->findAliasedSymbol(*A); 143 const MCSymbol *A_Base = Asm.getAtom(*A); 144 145 const MCSymbol *B = &Target.getSymB()->getSymbol(); 146 if (B->isTemporary()) 147 B = &Writer->findAliasedSymbol(*B); 148 const MCSymbol *B_Base = Asm.getAtom(*B); 149 150 // Neither symbol can be modified. 151 if (Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None || 152 Target.getSymB()->getKind() != MCSymbolRefExpr::VK_None) { 153 Asm.getContext().reportError(Fixup.getLoc(), 154 "unsupported relocation of modified symbol"); 155 return; 156 } 157 158 // We don't support PCrel relocations of differences. Darwin 'as' doesn't 159 // implement most of these correctly. 160 if (IsPCRel) { 161 Asm.getContext().reportError( 162 Fixup.getLoc(), "unsupported pc-relative relocation of difference"); 163 return; 164 } 165 166 // The support for the situation where one or both of the symbols would 167 // require a local relocation is handled just like if the symbols were 168 // external. This is certainly used in the case of debug sections where the 169 // section has only temporary symbols and thus the symbols don't have base 170 // symbols. This is encoded using the section ordinal and non-extern 171 // relocation entries. 172 173 // Darwin 'as' doesn't emit correct relocations for this (it ends up with a 174 // single SIGNED relocation); reject it for now. Except the case where both 175 // symbols don't have a base, equal but both NULL. 176 if (A_Base == B_Base && A_Base) { 177 Asm.getContext().reportError( 178 Fixup.getLoc(), "unsupported relocation with identical base"); 179 return; 180 } 181 182 // A subtraction expression where either symbol is undefined is a 183 // non-relocatable expression. 184 if (A->isUndefined() || B->isUndefined()) { 185 StringRef Name = A->isUndefined() ? A->getName() : B->getName(); 186 Asm.getContext().reportError(Fixup.getLoc(), 187 "unsupported relocation with subtraction expression, symbol '" + 188 Name + "' can not be undefined in a subtraction expression"); 189 return; 190 } 191 192 Value += Writer->getSymbolAddress(*A, Layout) - 193 (!A_Base ? 0 : Writer->getSymbolAddress(*A_Base, Layout)); 194 Value -= Writer->getSymbolAddress(*B, Layout) - 195 (!B_Base ? 0 : Writer->getSymbolAddress(*B_Base, Layout)); 196 197 if (!A_Base) 198 Index = A->getFragment()->getParent()->getOrdinal() + 1; 199 Type = MachO::X86_64_RELOC_UNSIGNED; 200 201 MachO::any_relocation_info MRE; 202 MRE.r_word0 = FixupOffset; 203 MRE.r_word1 = 204 (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28); 205 Writer->addRelocation(A_Base, Fragment->getParent(), MRE); 206 207 if (B_Base) 208 RelSymbol = B_Base; 209 else 210 Index = B->getFragment()->getParent()->getOrdinal() + 1; 211 Type = MachO::X86_64_RELOC_SUBTRACTOR; 212 } else { 213 const MCSymbol *Symbol = &Target.getSymA()->getSymbol(); 214 if (Symbol->isTemporary() && Value) { 215 const MCSection &Sec = Symbol->getSection(); 216 if (!Asm.getContext().getAsmInfo()->isSectionAtomizableBySymbols(Sec)) 217 Symbol->setUsedInReloc(); 218 } 219 RelSymbol = Asm.getAtom(*Symbol); 220 221 // Relocations inside debug sections always use local relocations when 222 // possible. This seems to be done because the debugger doesn't fully 223 // understand x86_64 relocation entries, and expects to find values that 224 // have already been fixed up. 225 if (Symbol->isInSection()) { 226 const MCSectionMachO &Section = 227 static_cast<const MCSectionMachO &>(*Fragment->getParent()); 228 if (Section.hasAttribute(MachO::S_ATTR_DEBUG)) 229 RelSymbol = nullptr; 230 } 231 232 // x86_64 almost always uses external relocations, except when there is no 233 // symbol to use as a base address (a local symbol with no preceding 234 // non-local symbol). 235 if (RelSymbol) { 236 // Add the local offset, if needed. 237 if (RelSymbol != Symbol) 238 Value += Layout.getSymbolOffset(*Symbol) - 239 Layout.getSymbolOffset(*RelSymbol); 240 } else if (Symbol->isInSection() && !Symbol->isVariable()) { 241 // The index is the section ordinal (1-based). 242 Index = Symbol->getFragment()->getParent()->getOrdinal() + 1; 243 Value += Writer->getSymbolAddress(*Symbol, Layout); 244 245 if (IsPCRel) 246 Value -= FixupAddress + (1 << Log2Size); 247 } else if (Symbol->isVariable()) { 248 const MCExpr *Value = Symbol->getVariableValue(); 249 int64_t Res; 250 bool isAbs = Value->evaluateAsAbsolute(Res, Layout, 251 Writer->getSectionAddressMap()); 252 if (isAbs) { 253 FixedValue = Res; 254 return; 255 } else { 256 Asm.getContext().reportError(Fixup.getLoc(), 257 "unsupported relocation of variable '" + 258 Symbol->getName() + "'"); 259 return; 260 } 261 } else { 262 Asm.getContext().reportError( 263 Fixup.getLoc(), "unsupported relocation of undefined symbol '" + 264 Symbol->getName() + "'"); 265 return; 266 } 267 268 MCSymbolRefExpr::VariantKind Modifier = Target.getSymA()->getKind(); 269 if (IsPCRel) { 270 if (IsRIPRel) { 271 if (Modifier == MCSymbolRefExpr::VK_GOTPCREL) { 272 // x86_64 distinguishes movq foo@GOTPCREL so that the linker can 273 // rewrite the movq to an leaq at link time if the symbol ends up in 274 // the same linkage unit. 275 if (unsigned(Fixup.getKind()) == X86::reloc_riprel_4byte_movq_load) 276 Type = MachO::X86_64_RELOC_GOT_LOAD; 277 else 278 Type = MachO::X86_64_RELOC_GOT; 279 } else if (Modifier == MCSymbolRefExpr::VK_TLVP) { 280 Type = MachO::X86_64_RELOC_TLV; 281 } else if (Modifier != MCSymbolRefExpr::VK_None) { 282 Asm.getContext().reportError( 283 Fixup.getLoc(), "unsupported symbol modifier in relocation"); 284 return; 285 } else { 286 Type = MachO::X86_64_RELOC_SIGNED; 287 288 // The Darwin x86_64 relocation format has a problem where it cannot 289 // encode an address (L<foo> + <constant>) which is outside the atom 290 // containing L<foo>. Generally, this shouldn't occur but it does 291 // happen when we have a RIPrel instruction with data following the 292 // relocation entry (e.g., movb $012, L0(%rip)). Even with the PCrel 293 // adjustment Darwin x86_64 uses, the offset is still negative and the 294 // linker has no way to recognize this. 295 // 296 // To work around this, Darwin uses several special relocation types 297 // to indicate the offsets. However, the specification or 298 // implementation of these seems to also be incomplete; they should 299 // adjust the addend as well based on the actual encoded instruction 300 // (the additional bias), but instead appear to just look at the final 301 // offset. 302 switch (-(Target.getConstant() + (1LL << Log2Size))) { 303 case 1: Type = MachO::X86_64_RELOC_SIGNED_1; break; 304 case 2: Type = MachO::X86_64_RELOC_SIGNED_2; break; 305 case 4: Type = MachO::X86_64_RELOC_SIGNED_4; break; 306 } 307 } 308 } else { 309 if (Modifier != MCSymbolRefExpr::VK_None) { 310 Asm.getContext().reportError( 311 Fixup.getLoc(), 312 "unsupported symbol modifier in branch relocation"); 313 return; 314 } 315 316 Type = MachO::X86_64_RELOC_BRANCH; 317 } 318 } else { 319 if (Modifier == MCSymbolRefExpr::VK_GOT) { 320 Type = MachO::X86_64_RELOC_GOT; 321 } else if (Modifier == MCSymbolRefExpr::VK_GOTPCREL) { 322 // GOTPCREL is allowed as a modifier on non-PCrel instructions, in which 323 // case all we do is set the PCrel bit in the relocation entry; this is 324 // used with exception handling, for example. The source is required to 325 // include any necessary offset directly. 326 Type = MachO::X86_64_RELOC_GOT; 327 IsPCRel = 1; 328 } else if (Modifier == MCSymbolRefExpr::VK_TLVP) { 329 Asm.getContext().reportError( 330 Fixup.getLoc(), "TLVP symbol modifier should have been rip-rel"); 331 return; 332 } else if (Modifier != MCSymbolRefExpr::VK_None) { 333 Asm.getContext().reportError( 334 Fixup.getLoc(), "unsupported symbol modifier in relocation"); 335 return; 336 } else { 337 Type = MachO::X86_64_RELOC_UNSIGNED; 338 unsigned Kind = Fixup.getKind(); 339 if (Kind == X86::reloc_signed_4byte) { 340 Asm.getContext().reportError( 341 Fixup.getLoc(), 342 "32-bit absolute addressing is not supported in 64-bit mode"); 343 return; 344 } 345 } 346 } 347 } 348 349 // x86_64 always writes custom values into the fixups. 350 FixedValue = Value; 351 352 // struct relocation_info (8 bytes) 353 MachO::any_relocation_info MRE; 354 MRE.r_word0 = FixupOffset; 355 MRE.r_word1 = (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | 356 (IsExtern << 27) | (Type << 28); 357 Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE); 358 } 359 360 bool X86MachObjectWriter::recordScatteredRelocation(MachObjectWriter *Writer, 361 const MCAssembler &Asm, 362 const MCAsmLayout &Layout, 363 const MCFragment *Fragment, 364 const MCFixup &Fixup, 365 MCValue Target, 366 unsigned Log2Size, 367 uint64_t &FixedValue) { 368 uint64_t OriginalFixedValue = FixedValue; 369 uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset(); 370 unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind()); 371 unsigned Type = MachO::GENERIC_RELOC_VANILLA; 372 373 // See <reloc.h>. 374 const MCSymbol *A = &Target.getSymA()->getSymbol(); 375 376 if (!A->getFragment()) { 377 Asm.getContext().reportError( 378 Fixup.getLoc(), 379 "symbol '" + A->getName() + 380 "' can not be undefined in a subtraction expression"); 381 return false; 382 } 383 384 uint32_t Value = Writer->getSymbolAddress(*A, Layout); 385 uint64_t SecAddr = Writer->getSectionAddress(A->getFragment()->getParent()); 386 FixedValue += SecAddr; 387 uint32_t Value2 = 0; 388 389 if (const MCSymbolRefExpr *B = Target.getSymB()) { 390 const MCSymbol *SB = &B->getSymbol(); 391 392 if (!SB->getFragment()) { 393 Asm.getContext().reportError( 394 Fixup.getLoc(), 395 "symbol '" + B->getSymbol().getName() + 396 "' can not be undefined in a subtraction expression"); 397 return false; 398 } 399 400 // Select the appropriate difference relocation type. 401 // 402 // Note that there is no longer any semantic difference between these two 403 // relocation types from the linkers point of view, this is done solely for 404 // pedantic compatibility with 'as'. 405 Type = A->isExternal() ? (unsigned)MachO::GENERIC_RELOC_SECTDIFF 406 : (unsigned)MachO::GENERIC_RELOC_LOCAL_SECTDIFF; 407 Value2 = Writer->getSymbolAddress(B->getSymbol(), Layout); 408 FixedValue -= Writer->getSectionAddress(SB->getFragment()->getParent()); 409 } 410 411 // Relocations are written out in reverse order, so the PAIR comes first. 412 if (Type == MachO::GENERIC_RELOC_SECTDIFF || 413 Type == MachO::GENERIC_RELOC_LOCAL_SECTDIFF) { 414 // If the offset is too large to fit in a scattered relocation, 415 // we're hosed. It's an unfortunate limitation of the MachO format. 416 if (FixupOffset > 0xffffff) { 417 char Buffer[32]; 418 format("0x%x", FixupOffset).print(Buffer, sizeof(Buffer)); 419 Asm.getContext().reportError(Fixup.getLoc(), 420 Twine("Section too large, can't encode " 421 "r_address (") + Buffer + 422 ") into 24 bits of scattered " 423 "relocation entry."); 424 return false; 425 } 426 427 MachO::any_relocation_info MRE; 428 MRE.r_word0 = ((0 << 0) | // r_address 429 (MachO::GENERIC_RELOC_PAIR << 24) | // r_type 430 (Log2Size << 28) | 431 (IsPCRel << 30) | 432 MachO::R_SCATTERED); 433 MRE.r_word1 = Value2; 434 Writer->addRelocation(nullptr, Fragment->getParent(), MRE); 435 } else { 436 // If the offset is more than 24-bits, it won't fit in a scattered 437 // relocation offset field, so we fall back to using a non-scattered 438 // relocation. This is a bit risky, as if the offset reaches out of 439 // the block and the linker is doing scattered loading on this 440 // symbol, things can go badly. 441 // 442 // Required for 'as' compatibility. 443 if (FixupOffset > 0xffffff) { 444 FixedValue = OriginalFixedValue; 445 return false; 446 } 447 } 448 449 MachO::any_relocation_info MRE; 450 MRE.r_word0 = ((FixupOffset << 0) | 451 (Type << 24) | 452 (Log2Size << 28) | 453 (IsPCRel << 30) | 454 MachO::R_SCATTERED); 455 MRE.r_word1 = Value; 456 Writer->addRelocation(nullptr, Fragment->getParent(), MRE); 457 return true; 458 } 459 460 void X86MachObjectWriter::recordTLVPRelocation(MachObjectWriter *Writer, 461 const MCAssembler &Asm, 462 const MCAsmLayout &Layout, 463 const MCFragment *Fragment, 464 const MCFixup &Fixup, 465 MCValue Target, 466 uint64_t &FixedValue) { 467 assert(Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP && 468 !is64Bit() && 469 "Should only be called with a 32-bit TLVP relocation!"); 470 471 unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind()); 472 uint32_t Value = Layout.getFragmentOffset(Fragment)+Fixup.getOffset(); 473 unsigned IsPCRel = 0; 474 475 // We're only going to have a second symbol in pic mode and it'll be a 476 // subtraction from the picbase. For 32-bit pic the addend is the difference 477 // between the picbase and the next address. For 32-bit static the addend is 478 // zero. 479 if (Target.getSymB()) { 480 // If this is a subtraction then we're pcrel. 481 uint32_t FixupAddress = 482 Writer->getFragmentAddress(Fragment, Layout) + Fixup.getOffset(); 483 IsPCRel = 1; 484 FixedValue = 485 FixupAddress - 486 Writer->getSymbolAddress(Target.getSymB()->getSymbol(), Layout) + 487 Target.getConstant(); 488 FixedValue += 1ULL << Log2Size; 489 } else { 490 FixedValue = 0; 491 } 492 493 // struct relocation_info (8 bytes) 494 MachO::any_relocation_info MRE; 495 MRE.r_word0 = Value; 496 MRE.r_word1 = 497 (IsPCRel << 24) | (Log2Size << 25) | (MachO::GENERIC_RELOC_TLV << 28); 498 Writer->addRelocation(&Target.getSymA()->getSymbol(), Fragment->getParent(), 499 MRE); 500 } 501 502 void X86MachObjectWriter::RecordX86Relocation(MachObjectWriter *Writer, 503 const MCAssembler &Asm, 504 const MCAsmLayout &Layout, 505 const MCFragment *Fragment, 506 const MCFixup &Fixup, 507 MCValue Target, 508 uint64_t &FixedValue) { 509 unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind()); 510 unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind()); 511 512 // If this is a 32-bit TLVP reloc it's handled a bit differently. 513 if (Target.getSymA() && 514 Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP) { 515 recordTLVPRelocation(Writer, Asm, Layout, Fragment, Fixup, Target, 516 FixedValue); 517 return; 518 } 519 520 // If this is a difference or a defined symbol plus an offset, then we need a 521 // scattered relocation entry. Differences always require scattered 522 // relocations. 523 if (Target.getSymB()) { 524 recordScatteredRelocation(Writer, Asm, Layout, Fragment, Fixup, 525 Target, Log2Size, FixedValue); 526 return; 527 } 528 529 // Get the symbol data, if any. 530 const MCSymbol *A = nullptr; 531 if (Target.getSymA()) 532 A = &Target.getSymA()->getSymbol(); 533 534 // If this is an internal relocation with an offset, it also needs a scattered 535 // relocation entry. 536 uint32_t Offset = Target.getConstant(); 537 if (IsPCRel) 538 Offset += 1 << Log2Size; 539 // Try to record the scattered relocation if needed. Fall back to non 540 // scattered if necessary (see comments in recordScatteredRelocation() 541 // for details). 542 if (Offset && A && !Writer->doesSymbolRequireExternRelocation(*A) && 543 recordScatteredRelocation(Writer, Asm, Layout, Fragment, Fixup, Target, 544 Log2Size, FixedValue)) 545 return; 546 547 // See <reloc.h>. 548 uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset(); 549 unsigned Index = 0; 550 unsigned Type = 0; 551 const MCSymbol *RelSymbol = nullptr; 552 553 if (Target.isAbsolute()) { // constant 554 // SymbolNum of 0 indicates the absolute section. 555 // 556 // FIXME: Currently, these are never generated (see code below). I cannot 557 // find a case where they are actually emitted. 558 Type = MachO::GENERIC_RELOC_VANILLA; 559 } else { 560 // Resolve constant variables. 561 if (A->isVariable()) { 562 int64_t Res; 563 if (A->getVariableValue()->evaluateAsAbsolute( 564 Res, Layout, Writer->getSectionAddressMap())) { 565 FixedValue = Res; 566 return; 567 } 568 } 569 570 // Check whether we need an external or internal relocation. 571 if (Writer->doesSymbolRequireExternRelocation(*A)) { 572 RelSymbol = A; 573 // For external relocations, make sure to offset the fixup value to 574 // compensate for the addend of the symbol address, if it was 575 // undefined. This occurs with weak definitions, for example. 576 if (!A->isUndefined()) 577 FixedValue -= Layout.getSymbolOffset(*A); 578 } else { 579 // The index is the section ordinal (1-based). 580 const MCSection &Sec = A->getSection(); 581 Index = Sec.getOrdinal() + 1; 582 FixedValue += Writer->getSectionAddress(&Sec); 583 } 584 if (IsPCRel) 585 FixedValue -= Writer->getSectionAddress(Fragment->getParent()); 586 587 Type = MachO::GENERIC_RELOC_VANILLA; 588 } 589 590 // struct relocation_info (8 bytes) 591 MachO::any_relocation_info MRE; 592 MRE.r_word0 = FixupOffset; 593 MRE.r_word1 = 594 (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28); 595 Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE); 596 } 597 598 MCObjectWriter *llvm::createX86MachObjectWriter(raw_pwrite_stream &OS, 599 bool Is64Bit, uint32_t CPUType, 600 uint32_t CPUSubtype) { 601 return createMachObjectWriter(new X86MachObjectWriter(Is64Bit, 602 CPUType, 603 CPUSubtype), 604 OS, /*IsLittleEndian=*/true); 605 } 606