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/X86FixupKinds.h" 11 #include "MCTargetDesc/X86MCTargetDesc.h" 12 #include "llvm/ADT/Twine.h" 13 #include "llvm/BinaryFormat/MachO.h" 14 #include "llvm/MC/MCAsmInfo.h" 15 #include "llvm/MC/MCAsmLayout.h" 16 #include "llvm/MC/MCAssembler.h" 17 #include "llvm/MC/MCContext.h" 18 #include "llvm/MC/MCMachObjectWriter.h" 19 #include "llvm/MC/MCSectionMachO.h" 20 #include "llvm/MC/MCValue.h" 21 #include "llvm/Support/ErrorHandling.h" 22 #include "llvm/Support/Format.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 Kind == X86::reloc_riprel_4byte_relax || 78 Kind == X86::reloc_riprel_4byte_relax_rex; 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_relax: 93 case X86::reloc_riprel_4byte_relax_rex: 94 case X86::reloc_riprel_4byte_movq_load: 95 case X86::reloc_signed_4byte: 96 case X86::reloc_signed_4byte_relax: 97 case X86::reloc_branch_4byte_pcrel: 98 case FK_Data_4: return 2; 99 case FK_Data_8: return 3; 100 } 101 } 102 103 void X86MachObjectWriter::RecordX86_64Relocation( 104 MachObjectWriter *Writer, MCAssembler &Asm, const MCAsmLayout &Layout, 105 const MCFragment *Fragment, const MCFixup &Fixup, MCValue Target, 106 uint64_t &FixedValue) { 107 unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind()); 108 unsigned IsRIPRel = isFixupKindRIPRel(Fixup.getKind()); 109 unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind()); 110 111 // See <reloc.h>. 112 uint32_t FixupOffset = 113 Layout.getFragmentOffset(Fragment) + Fixup.getOffset(); 114 uint32_t FixupAddress = 115 Writer->getFragmentAddress(Fragment, Layout) + Fixup.getOffset(); 116 int64_t Value = 0; 117 unsigned Index = 0; 118 unsigned IsExtern = 0; 119 unsigned Type = 0; 120 const MCSymbol *RelSymbol = nullptr; 121 122 Value = Target.getConstant(); 123 124 if (IsPCRel) { 125 // Compensate for the relocation offset, Darwin x86_64 relocations only have 126 // the addend and appear to have attempted to define it to be the actual 127 // expression addend without the PCrel bias. However, instructions with data 128 // following the relocation are not accommodated for (see comment below 129 // regarding SIGNED{1,2,4}), so it isn't exactly that either. 130 Value += 1LL << Log2Size; 131 } 132 133 if (Target.isAbsolute()) { // constant 134 // SymbolNum of 0 indicates the absolute section. 135 Type = MachO::X86_64_RELOC_UNSIGNED; 136 137 // FIXME: I believe this is broken, I don't think the linker can understand 138 // it. I think it would require a local relocation, but I'm not sure if that 139 // would work either. The official way to get an absolute PCrel relocation 140 // is to use an absolute symbol (which we don't support yet). 141 if (IsPCRel) { 142 IsExtern = 1; 143 Type = MachO::X86_64_RELOC_BRANCH; 144 } 145 } else if (Target.getSymB()) { // A - B + constant 146 const MCSymbol *A = &Target.getSymA()->getSymbol(); 147 if (A->isTemporary()) 148 A = &Writer->findAliasedSymbol(*A); 149 const MCSymbol *A_Base = Asm.getAtom(*A); 150 151 const MCSymbol *B = &Target.getSymB()->getSymbol(); 152 if (B->isTemporary()) 153 B = &Writer->findAliasedSymbol(*B); 154 const MCSymbol *B_Base = Asm.getAtom(*B); 155 156 // Neither symbol can be modified. 157 if (Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None) { 158 Asm.getContext().reportError(Fixup.getLoc(), 159 "unsupported relocation of modified symbol"); 160 return; 161 } 162 163 // We don't support PCrel relocations of differences. Darwin 'as' doesn't 164 // implement most of these correctly. 165 if (IsPCRel) { 166 Asm.getContext().reportError( 167 Fixup.getLoc(), "unsupported pc-relative relocation of difference"); 168 return; 169 } 170 171 // The support for the situation where one or both of the symbols would 172 // require a local relocation is handled just like if the symbols were 173 // external. This is certainly used in the case of debug sections where the 174 // section has only temporary symbols and thus the symbols don't have base 175 // symbols. This is encoded using the section ordinal and non-extern 176 // relocation entries. 177 178 // Darwin 'as' doesn't emit correct relocations for this (it ends up with a 179 // single SIGNED relocation); reject it for now. Except the case where both 180 // symbols don't have a base, equal but both NULL. 181 if (A_Base == B_Base && A_Base) { 182 Asm.getContext().reportError( 183 Fixup.getLoc(), "unsupported relocation with identical base"); 184 return; 185 } 186 187 // A subtraction expression where either symbol is undefined is a 188 // non-relocatable expression. 189 if (A->isUndefined() || B->isUndefined()) { 190 StringRef Name = A->isUndefined() ? A->getName() : B->getName(); 191 Asm.getContext().reportError(Fixup.getLoc(), 192 "unsupported relocation with subtraction expression, symbol '" + 193 Name + "' can not be undefined in a subtraction expression"); 194 return; 195 } 196 197 Value += Writer->getSymbolAddress(*A, Layout) - 198 (!A_Base ? 0 : Writer->getSymbolAddress(*A_Base, Layout)); 199 Value -= Writer->getSymbolAddress(*B, Layout) - 200 (!B_Base ? 0 : Writer->getSymbolAddress(*B_Base, Layout)); 201 202 if (!A_Base) 203 Index = A->getFragment()->getParent()->getOrdinal() + 1; 204 Type = MachO::X86_64_RELOC_UNSIGNED; 205 206 MachO::any_relocation_info MRE; 207 MRE.r_word0 = FixupOffset; 208 MRE.r_word1 = 209 (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28); 210 Writer->addRelocation(A_Base, Fragment->getParent(), MRE); 211 212 if (B_Base) 213 RelSymbol = B_Base; 214 else 215 Index = B->getFragment()->getParent()->getOrdinal() + 1; 216 Type = MachO::X86_64_RELOC_SUBTRACTOR; 217 } else { 218 const MCSymbol *Symbol = &Target.getSymA()->getSymbol(); 219 if (Symbol->isTemporary() && Value) { 220 const MCSection &Sec = Symbol->getSection(); 221 if (!Asm.getContext().getAsmInfo()->isSectionAtomizableBySymbols(Sec)) 222 Symbol->setUsedInReloc(); 223 } 224 RelSymbol = Asm.getAtom(*Symbol); 225 226 // Relocations inside debug sections always use local relocations when 227 // possible. This seems to be done because the debugger doesn't fully 228 // understand x86_64 relocation entries, and expects to find values that 229 // have already been fixed up. 230 if (Symbol->isInSection()) { 231 const MCSectionMachO &Section = 232 static_cast<const MCSectionMachO &>(*Fragment->getParent()); 233 if (Section.hasAttribute(MachO::S_ATTR_DEBUG)) 234 RelSymbol = nullptr; 235 } 236 237 // x86_64 almost always uses external relocations, except when there is no 238 // symbol to use as a base address (a local symbol with no preceding 239 // non-local symbol). 240 if (RelSymbol) { 241 // Add the local offset, if needed. 242 if (RelSymbol != Symbol) 243 Value += Layout.getSymbolOffset(*Symbol) - 244 Layout.getSymbolOffset(*RelSymbol); 245 } else if (Symbol->isInSection() && !Symbol->isVariable()) { 246 // The index is the section ordinal (1-based). 247 Index = Symbol->getFragment()->getParent()->getOrdinal() + 1; 248 Value += Writer->getSymbolAddress(*Symbol, Layout); 249 250 if (IsPCRel) 251 Value -= FixupAddress + (1 << Log2Size); 252 } else if (Symbol->isVariable()) { 253 const MCExpr *Value = Symbol->getVariableValue(); 254 int64_t Res; 255 bool isAbs = Value->evaluateAsAbsolute(Res, Layout, 256 Writer->getSectionAddressMap()); 257 if (isAbs) { 258 FixedValue = Res; 259 return; 260 } else { 261 Asm.getContext().reportError(Fixup.getLoc(), 262 "unsupported relocation of variable '" + 263 Symbol->getName() + "'"); 264 return; 265 } 266 } else { 267 Asm.getContext().reportError( 268 Fixup.getLoc(), "unsupported relocation of undefined symbol '" + 269 Symbol->getName() + "'"); 270 return; 271 } 272 273 MCSymbolRefExpr::VariantKind Modifier = Target.getSymA()->getKind(); 274 if (IsPCRel) { 275 if (IsRIPRel) { 276 if (Modifier == MCSymbolRefExpr::VK_GOTPCREL) { 277 // x86_64 distinguishes movq foo@GOTPCREL so that the linker can 278 // rewrite the movq to an leaq at link time if the symbol ends up in 279 // the same linkage unit. 280 if (unsigned(Fixup.getKind()) == X86::reloc_riprel_4byte_movq_load) 281 Type = MachO::X86_64_RELOC_GOT_LOAD; 282 else 283 Type = MachO::X86_64_RELOC_GOT; 284 } else if (Modifier == MCSymbolRefExpr::VK_TLVP) { 285 Type = MachO::X86_64_RELOC_TLV; 286 } else if (Modifier != MCSymbolRefExpr::VK_None) { 287 Asm.getContext().reportError( 288 Fixup.getLoc(), "unsupported symbol modifier in relocation"); 289 return; 290 } else { 291 Type = MachO::X86_64_RELOC_SIGNED; 292 293 // The Darwin x86_64 relocation format has a problem where it cannot 294 // encode an address (L<foo> + <constant>) which is outside the atom 295 // containing L<foo>. Generally, this shouldn't occur but it does 296 // happen when we have a RIPrel instruction with data following the 297 // relocation entry (e.g., movb $012, L0(%rip)). Even with the PCrel 298 // adjustment Darwin x86_64 uses, the offset is still negative and the 299 // linker has no way to recognize this. 300 // 301 // To work around this, Darwin uses several special relocation types 302 // to indicate the offsets. However, the specification or 303 // implementation of these seems to also be incomplete; they should 304 // adjust the addend as well based on the actual encoded instruction 305 // (the additional bias), but instead appear to just look at the final 306 // offset. 307 switch (-(Target.getConstant() + (1LL << Log2Size))) { 308 case 1: Type = MachO::X86_64_RELOC_SIGNED_1; break; 309 case 2: Type = MachO::X86_64_RELOC_SIGNED_2; break; 310 case 4: Type = MachO::X86_64_RELOC_SIGNED_4; break; 311 } 312 } 313 } else { 314 if (Modifier != MCSymbolRefExpr::VK_None) { 315 Asm.getContext().reportError( 316 Fixup.getLoc(), 317 "unsupported symbol modifier in branch relocation"); 318 return; 319 } 320 321 Type = MachO::X86_64_RELOC_BRANCH; 322 } 323 } else { 324 if (Modifier == MCSymbolRefExpr::VK_GOT) { 325 Type = MachO::X86_64_RELOC_GOT; 326 } else if (Modifier == MCSymbolRefExpr::VK_GOTPCREL) { 327 // GOTPCREL is allowed as a modifier on non-PCrel instructions, in which 328 // case all we do is set the PCrel bit in the relocation entry; this is 329 // used with exception handling, for example. The source is required to 330 // include any necessary offset directly. 331 Type = MachO::X86_64_RELOC_GOT; 332 IsPCRel = 1; 333 } else if (Modifier == MCSymbolRefExpr::VK_TLVP) { 334 Asm.getContext().reportError( 335 Fixup.getLoc(), "TLVP symbol modifier should have been rip-rel"); 336 return; 337 } else if (Modifier != MCSymbolRefExpr::VK_None) { 338 Asm.getContext().reportError( 339 Fixup.getLoc(), "unsupported symbol modifier in relocation"); 340 return; 341 } else { 342 Type = MachO::X86_64_RELOC_UNSIGNED; 343 unsigned Kind = Fixup.getKind(); 344 if (Kind == X86::reloc_signed_4byte) { 345 Asm.getContext().reportError( 346 Fixup.getLoc(), 347 "32-bit absolute addressing is not supported in 64-bit mode"); 348 return; 349 } 350 } 351 } 352 } 353 354 // x86_64 always writes custom values into the fixups. 355 FixedValue = Value; 356 357 // struct relocation_info (8 bytes) 358 MachO::any_relocation_info MRE; 359 MRE.r_word0 = FixupOffset; 360 MRE.r_word1 = (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | 361 (IsExtern << 27) | (Type << 28); 362 Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE); 363 } 364 365 bool X86MachObjectWriter::recordScatteredRelocation(MachObjectWriter *Writer, 366 const MCAssembler &Asm, 367 const MCAsmLayout &Layout, 368 const MCFragment *Fragment, 369 const MCFixup &Fixup, 370 MCValue Target, 371 unsigned Log2Size, 372 uint64_t &FixedValue) { 373 uint64_t OriginalFixedValue = FixedValue; 374 uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset(); 375 unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind()); 376 unsigned Type = MachO::GENERIC_RELOC_VANILLA; 377 378 // See <reloc.h>. 379 const MCSymbol *A = &Target.getSymA()->getSymbol(); 380 381 if (!A->getFragment()) { 382 Asm.getContext().reportError( 383 Fixup.getLoc(), 384 "symbol '" + A->getName() + 385 "' can not be undefined in a subtraction expression"); 386 return false; 387 } 388 389 uint32_t Value = Writer->getSymbolAddress(*A, Layout); 390 uint64_t SecAddr = Writer->getSectionAddress(A->getFragment()->getParent()); 391 FixedValue += SecAddr; 392 uint32_t Value2 = 0; 393 394 if (const MCSymbolRefExpr *B = Target.getSymB()) { 395 const MCSymbol *SB = &B->getSymbol(); 396 397 if (!SB->getFragment()) { 398 Asm.getContext().reportError( 399 Fixup.getLoc(), 400 "symbol '" + SB->getName() + 401 "' can not be undefined in a subtraction expression"); 402 return false; 403 } 404 405 // Select the appropriate difference relocation type. 406 // 407 // Note that there is no longer any semantic difference between these two 408 // relocation types from the linkers point of view, this is done solely for 409 // pedantic compatibility with 'as'. 410 Type = A->isExternal() ? (unsigned)MachO::GENERIC_RELOC_SECTDIFF 411 : (unsigned)MachO::GENERIC_RELOC_LOCAL_SECTDIFF; 412 Value2 = Writer->getSymbolAddress(*SB, Layout); 413 FixedValue -= Writer->getSectionAddress(SB->getFragment()->getParent()); 414 } 415 416 // Relocations are written out in reverse order, so the PAIR comes first. 417 if (Type == MachO::GENERIC_RELOC_SECTDIFF || 418 Type == MachO::GENERIC_RELOC_LOCAL_SECTDIFF) { 419 // If the offset is too large to fit in a scattered relocation, 420 // we're hosed. It's an unfortunate limitation of the MachO format. 421 if (FixupOffset > 0xffffff) { 422 char Buffer[32]; 423 format("0x%x", FixupOffset).print(Buffer, sizeof(Buffer)); 424 Asm.getContext().reportError(Fixup.getLoc(), 425 Twine("Section too large, can't encode " 426 "r_address (") + Buffer + 427 ") into 24 bits of scattered " 428 "relocation entry."); 429 return false; 430 } 431 432 MachO::any_relocation_info MRE; 433 MRE.r_word0 = ((0 << 0) | // r_address 434 (MachO::GENERIC_RELOC_PAIR << 24) | // r_type 435 (Log2Size << 28) | 436 (IsPCRel << 30) | 437 MachO::R_SCATTERED); 438 MRE.r_word1 = Value2; 439 Writer->addRelocation(nullptr, Fragment->getParent(), MRE); 440 } else { 441 // If the offset is more than 24-bits, it won't fit in a scattered 442 // relocation offset field, so we fall back to using a non-scattered 443 // relocation. This is a bit risky, as if the offset reaches out of 444 // the block and the linker is doing scattered loading on this 445 // symbol, things can go badly. 446 // 447 // Required for 'as' compatibility. 448 if (FixupOffset > 0xffffff) { 449 FixedValue = OriginalFixedValue; 450 return false; 451 } 452 } 453 454 MachO::any_relocation_info MRE; 455 MRE.r_word0 = ((FixupOffset << 0) | 456 (Type << 24) | 457 (Log2Size << 28) | 458 (IsPCRel << 30) | 459 MachO::R_SCATTERED); 460 MRE.r_word1 = Value; 461 Writer->addRelocation(nullptr, Fragment->getParent(), MRE); 462 return true; 463 } 464 465 void X86MachObjectWriter::recordTLVPRelocation(MachObjectWriter *Writer, 466 const MCAssembler &Asm, 467 const MCAsmLayout &Layout, 468 const MCFragment *Fragment, 469 const MCFixup &Fixup, 470 MCValue Target, 471 uint64_t &FixedValue) { 472 const MCSymbolRefExpr *SymA = Target.getSymA(); 473 assert(SymA->getKind() == MCSymbolRefExpr::VK_TLVP && !is64Bit() && 474 "Should only be called with a 32-bit TLVP relocation!"); 475 476 unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind()); 477 uint32_t Value = Layout.getFragmentOffset(Fragment)+Fixup.getOffset(); 478 unsigned IsPCRel = 0; 479 480 // We're only going to have a second symbol in pic mode and it'll be a 481 // subtraction from the picbase. For 32-bit pic the addend is the difference 482 // between the picbase and the next address. For 32-bit static the addend is 483 // zero. 484 if (auto *SymB = Target.getSymB()) { 485 // If this is a subtraction then we're pcrel. 486 uint32_t FixupAddress = 487 Writer->getFragmentAddress(Fragment, Layout) + Fixup.getOffset(); 488 IsPCRel = 1; 489 FixedValue = FixupAddress - 490 Writer->getSymbolAddress(SymB->getSymbol(), Layout) + 491 Target.getConstant(); 492 FixedValue += 1ULL << Log2Size; 493 } else { 494 FixedValue = 0; 495 } 496 497 // struct relocation_info (8 bytes) 498 MachO::any_relocation_info MRE; 499 MRE.r_word0 = Value; 500 MRE.r_word1 = 501 (IsPCRel << 24) | (Log2Size << 25) | (MachO::GENERIC_RELOC_TLV << 28); 502 Writer->addRelocation(&SymA->getSymbol(), Fragment->getParent(), MRE); 503 } 504 505 void X86MachObjectWriter::RecordX86Relocation(MachObjectWriter *Writer, 506 const MCAssembler &Asm, 507 const MCAsmLayout &Layout, 508 const MCFragment *Fragment, 509 const MCFixup &Fixup, 510 MCValue Target, 511 uint64_t &FixedValue) { 512 unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind()); 513 unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind()); 514 515 // If this is a 32-bit TLVP reloc it's handled a bit differently. 516 if (Target.getSymA() && 517 Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP) { 518 recordTLVPRelocation(Writer, Asm, Layout, Fragment, Fixup, Target, 519 FixedValue); 520 return; 521 } 522 523 // If this is a difference or a defined symbol plus an offset, then we need a 524 // scattered relocation entry. Differences always require scattered 525 // relocations. 526 if (Target.getSymB()) { 527 recordScatteredRelocation(Writer, Asm, Layout, Fragment, Fixup, 528 Target, Log2Size, FixedValue); 529 return; 530 } 531 532 // Get the symbol data, if any. 533 const MCSymbol *A = nullptr; 534 if (Target.getSymA()) 535 A = &Target.getSymA()->getSymbol(); 536 537 // If this is an internal relocation with an offset, it also needs a scattered 538 // relocation entry. 539 uint32_t Offset = Target.getConstant(); 540 if (IsPCRel) 541 Offset += 1 << Log2Size; 542 // Try to record the scattered relocation if needed. Fall back to non 543 // scattered if necessary (see comments in recordScatteredRelocation() 544 // for details). 545 if (Offset && A && !Writer->doesSymbolRequireExternRelocation(*A) && 546 recordScatteredRelocation(Writer, Asm, Layout, Fragment, Fixup, Target, 547 Log2Size, FixedValue)) 548 return; 549 550 // See <reloc.h>. 551 uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset(); 552 unsigned Index = 0; 553 unsigned Type = 0; 554 const MCSymbol *RelSymbol = nullptr; 555 556 if (Target.isAbsolute()) { // constant 557 // SymbolNum of 0 indicates the absolute section. 558 // 559 // FIXME: Currently, these are never generated (see code below). I cannot 560 // find a case where they are actually emitted. 561 Type = MachO::GENERIC_RELOC_VANILLA; 562 } else { 563 // Resolve constant variables. 564 if (A->isVariable()) { 565 int64_t Res; 566 if (A->getVariableValue()->evaluateAsAbsolute( 567 Res, Layout, Writer->getSectionAddressMap())) { 568 FixedValue = Res; 569 return; 570 } 571 } 572 573 // Check whether we need an external or internal relocation. 574 if (Writer->doesSymbolRequireExternRelocation(*A)) { 575 RelSymbol = A; 576 // For external relocations, make sure to offset the fixup value to 577 // compensate for the addend of the symbol address, if it was 578 // undefined. This occurs with weak definitions, for example. 579 if (!A->isUndefined()) 580 FixedValue -= Layout.getSymbolOffset(*A); 581 } else { 582 // The index is the section ordinal (1-based). 583 const MCSection &Sec = A->getSection(); 584 Index = Sec.getOrdinal() + 1; 585 FixedValue += Writer->getSectionAddress(&Sec); 586 } 587 if (IsPCRel) 588 FixedValue -= Writer->getSectionAddress(Fragment->getParent()); 589 590 Type = MachO::GENERIC_RELOC_VANILLA; 591 } 592 593 // struct relocation_info (8 bytes) 594 MachO::any_relocation_info MRE; 595 MRE.r_word0 = FixupOffset; 596 MRE.r_word1 = 597 (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28); 598 Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE); 599 } 600 601 std::unique_ptr<MCObjectWriter> 602 llvm::createX86MachObjectWriter(raw_pwrite_stream &OS, bool Is64Bit, 603 uint32_t CPUType, uint32_t CPUSubtype) { 604 return createMachObjectWriter( 605 llvm::make_unique<X86MachObjectWriter>(Is64Bit, CPUType, CPUSubtype), OS, 606 /*IsLittleEndian=*/true); 607 } 608