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 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 FK_Data_4: return 2; 98 case FK_Data_8: return 3; 99 } 100 } 101 102 void X86MachObjectWriter::RecordX86_64Relocation( 103 MachObjectWriter *Writer, MCAssembler &Asm, const MCAsmLayout &Layout, 104 const MCFragment *Fragment, const MCFixup &Fixup, MCValue Target, 105 uint64_t &FixedValue) { 106 unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind()); 107 unsigned IsRIPRel = isFixupKindRIPRel(Fixup.getKind()); 108 unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind()); 109 110 // See <reloc.h>. 111 uint32_t FixupOffset = 112 Layout.getFragmentOffset(Fragment) + Fixup.getOffset(); 113 uint32_t FixupAddress = 114 Writer->getFragmentAddress(Fragment, Layout) + Fixup.getOffset(); 115 int64_t Value = 0; 116 unsigned Index = 0; 117 unsigned IsExtern = 0; 118 unsigned Type = 0; 119 const MCSymbol *RelSymbol = nullptr; 120 121 Value = Target.getConstant(); 122 123 if (IsPCRel) { 124 // Compensate for the relocation offset, Darwin x86_64 relocations only have 125 // the addend and appear to have attempted to define it to be the actual 126 // expression addend without the PCrel bias. However, instructions with data 127 // following the relocation are not accommodated for (see comment below 128 // regarding SIGNED{1,2,4}), so it isn't exactly that either. 129 Value += 1LL << Log2Size; 130 } 131 132 if (Target.isAbsolute()) { // constant 133 // SymbolNum of 0 indicates the absolute section. 134 Type = MachO::X86_64_RELOC_UNSIGNED; 135 136 // FIXME: I believe this is broken, I don't think the linker can understand 137 // it. I think it would require a local relocation, but I'm not sure if that 138 // would work either. The official way to get an absolute PCrel relocation 139 // is to use an absolute symbol (which we don't support yet). 140 if (IsPCRel) { 141 IsExtern = 1; 142 Type = MachO::X86_64_RELOC_BRANCH; 143 } 144 } else if (Target.getSymB()) { // A - B + constant 145 const MCSymbol *A = &Target.getSymA()->getSymbol(); 146 if (A->isTemporary()) 147 A = &Writer->findAliasedSymbol(*A); 148 const MCSymbol *A_Base = Asm.getAtom(*A); 149 150 const MCSymbol *B = &Target.getSymB()->getSymbol(); 151 if (B->isTemporary()) 152 B = &Writer->findAliasedSymbol(*B); 153 const MCSymbol *B_Base = Asm.getAtom(*B); 154 155 // Neither symbol can be modified. 156 if (Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None || 157 Target.getSymB()->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 '" + B->getSymbol().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(B->getSymbol(), 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 assert(Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP && 473 !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 (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 = 490 FixupAddress - 491 Writer->getSymbolAddress(Target.getSymB()->getSymbol(), Layout) + 492 Target.getConstant(); 493 FixedValue += 1ULL << Log2Size; 494 } else { 495 FixedValue = 0; 496 } 497 498 // struct relocation_info (8 bytes) 499 MachO::any_relocation_info MRE; 500 MRE.r_word0 = Value; 501 MRE.r_word1 = 502 (IsPCRel << 24) | (Log2Size << 25) | (MachO::GENERIC_RELOC_TLV << 28); 503 Writer->addRelocation(&Target.getSymA()->getSymbol(), Fragment->getParent(), 504 MRE); 505 } 506 507 void X86MachObjectWriter::RecordX86Relocation(MachObjectWriter *Writer, 508 const MCAssembler &Asm, 509 const MCAsmLayout &Layout, 510 const MCFragment *Fragment, 511 const MCFixup &Fixup, 512 MCValue Target, 513 uint64_t &FixedValue) { 514 unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind()); 515 unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind()); 516 517 // If this is a 32-bit TLVP reloc it's handled a bit differently. 518 if (Target.getSymA() && 519 Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP) { 520 recordTLVPRelocation(Writer, Asm, Layout, Fragment, Fixup, Target, 521 FixedValue); 522 return; 523 } 524 525 // If this is a difference or a defined symbol plus an offset, then we need a 526 // scattered relocation entry. Differences always require scattered 527 // relocations. 528 if (Target.getSymB()) { 529 recordScatteredRelocation(Writer, Asm, Layout, Fragment, Fixup, 530 Target, Log2Size, FixedValue); 531 return; 532 } 533 534 // Get the symbol data, if any. 535 const MCSymbol *A = nullptr; 536 if (Target.getSymA()) 537 A = &Target.getSymA()->getSymbol(); 538 539 // If this is an internal relocation with an offset, it also needs a scattered 540 // relocation entry. 541 uint32_t Offset = Target.getConstant(); 542 if (IsPCRel) 543 Offset += 1 << Log2Size; 544 // Try to record the scattered relocation if needed. Fall back to non 545 // scattered if necessary (see comments in recordScatteredRelocation() 546 // for details). 547 if (Offset && A && !Writer->doesSymbolRequireExternRelocation(*A) && 548 recordScatteredRelocation(Writer, Asm, Layout, Fragment, Fixup, Target, 549 Log2Size, FixedValue)) 550 return; 551 552 // See <reloc.h>. 553 uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset(); 554 unsigned Index = 0; 555 unsigned Type = 0; 556 const MCSymbol *RelSymbol = nullptr; 557 558 if (Target.isAbsolute()) { // constant 559 // SymbolNum of 0 indicates the absolute section. 560 // 561 // FIXME: Currently, these are never generated (see code below). I cannot 562 // find a case where they are actually emitted. 563 Type = MachO::GENERIC_RELOC_VANILLA; 564 } else { 565 // Resolve constant variables. 566 if (A->isVariable()) { 567 int64_t Res; 568 if (A->getVariableValue()->evaluateAsAbsolute( 569 Res, Layout, Writer->getSectionAddressMap())) { 570 FixedValue = Res; 571 return; 572 } 573 } 574 575 // Check whether we need an external or internal relocation. 576 if (Writer->doesSymbolRequireExternRelocation(*A)) { 577 RelSymbol = A; 578 // For external relocations, make sure to offset the fixup value to 579 // compensate for the addend of the symbol address, if it was 580 // undefined. This occurs with weak definitions, for example. 581 if (!A->isUndefined()) 582 FixedValue -= Layout.getSymbolOffset(*A); 583 } else { 584 // The index is the section ordinal (1-based). 585 const MCSection &Sec = A->getSection(); 586 Index = Sec.getOrdinal() + 1; 587 FixedValue += Writer->getSectionAddress(&Sec); 588 } 589 if (IsPCRel) 590 FixedValue -= Writer->getSectionAddress(Fragment->getParent()); 591 592 Type = MachO::GENERIC_RELOC_VANILLA; 593 } 594 595 // struct relocation_info (8 bytes) 596 MachO::any_relocation_info MRE; 597 MRE.r_word0 = FixupOffset; 598 MRE.r_word1 = 599 (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28); 600 Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE); 601 } 602 603 MCObjectWriter *llvm::createX86MachObjectWriter(raw_pwrite_stream &OS, 604 bool Is64Bit, uint32_t CPUType, 605 uint32_t CPUSubtype) { 606 return createMachObjectWriter(new X86MachObjectWriter(Is64Bit, 607 CPUType, 608 CPUSubtype), 609 OS, /*IsLittleEndian=*/true); 610 } 611
