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/MCAsmLayout.h" 14 #include "llvm/MC/MCAssembler.h" 15 #include "llvm/MC/MCContext.h" 16 #include "llvm/MC/MCMachObjectWriter.h" 17 #include "llvm/MC/MCSectionMachO.h" 18 #include "llvm/MC/MCValue.h" 19 #include "llvm/Support/ErrorHandling.h" 20 #include "llvm/Support/Format.h" 21 #include "llvm/Support/MachO.h" 22 23 using namespace llvm; 24 25 namespace { 26 class X86MachObjectWriter : public MCMachObjectTargetWriter { 27 bool RecordScatteredRelocation(MachObjectWriter *Writer, 28 const MCAssembler &Asm, 29 const MCAsmLayout &Layout, 30 const MCFragment *Fragment, 31 const MCFixup &Fixup, 32 MCValue Target, 33 unsigned Log2Size, 34 uint64_t &FixedValue); 35 void RecordTLVPRelocation(MachObjectWriter *Writer, 36 const MCAssembler &Asm, 37 const MCAsmLayout &Layout, 38 const MCFragment *Fragment, 39 const MCFixup &Fixup, 40 MCValue Target, 41 uint64_t &FixedValue); 42 43 void RecordX86Relocation(MachObjectWriter *Writer, 44 const MCAssembler &Asm, 45 const MCAsmLayout &Layout, 46 const MCFragment *Fragment, 47 const MCFixup &Fixup, 48 MCValue Target, 49 uint64_t &FixedValue); 50 void RecordX86_64Relocation(MachObjectWriter *Writer, 51 const MCAssembler &Asm, 52 const MCAsmLayout &Layout, 53 const MCFragment *Fragment, 54 const MCFixup &Fixup, 55 MCValue Target, 56 uint64_t &FixedValue); 57 public: 58 X86MachObjectWriter(bool Is64Bit, uint32_t CPUType, 59 uint32_t CPUSubtype) 60 : MCMachObjectTargetWriter(Is64Bit, CPUType, CPUSubtype, 61 /*UseAggressiveSymbolFolding=*/Is64Bit) {} 62 63 void RecordRelocation(MachObjectWriter *Writer, 64 const MCAssembler &Asm, const MCAsmLayout &Layout, 65 const MCFragment *Fragment, const MCFixup &Fixup, 66 MCValue Target, uint64_t &FixedValue) override { 67 if (Writer->is64Bit()) 68 RecordX86_64Relocation(Writer, Asm, Layout, Fragment, Fixup, Target, 69 FixedValue); 70 else 71 RecordX86Relocation(Writer, Asm, Layout, Fragment, Fixup, Target, 72 FixedValue); 73 } 74 }; 75 } 76 77 static bool isFixupKindRIPRel(unsigned Kind) { 78 return Kind == X86::reloc_riprel_4byte || 79 Kind == X86::reloc_riprel_4byte_movq_load; 80 } 81 82 static unsigned getFixupKindLog2Size(unsigned Kind) { 83 switch (Kind) { 84 default: 85 llvm_unreachable("invalid fixup kind!"); 86 case FK_PCRel_1: 87 case FK_Data_1: return 0; 88 case FK_PCRel_2: 89 case FK_Data_2: return 1; 90 case FK_PCRel_4: 91 // FIXME: Remove these!!! 92 case X86::reloc_riprel_4byte: 93 case X86::reloc_riprel_4byte_movq_load: 94 case X86::reloc_signed_4byte: 95 case FK_Data_4: return 2; 96 case FK_Data_8: return 3; 97 } 98 } 99 100 void X86MachObjectWriter::RecordX86_64Relocation(MachObjectWriter *Writer, 101 const MCAssembler &Asm, 102 const MCAsmLayout &Layout, 103 const MCFragment *Fragment, 104 const MCFixup &Fixup, 105 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; 120 121 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 Index = 0; 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 = &A->AliasedSymbol(); 149 const MCSymbolData &A_SD = Asm.getSymbolData(*A); 150 const MCSymbolData *A_Base = Asm.getAtom(&A_SD); 151 152 const MCSymbol *B = &Target.getSymB()->getSymbol(); 153 if (B->isTemporary()) 154 B = &B->AliasedSymbol(); 155 const MCSymbolData &B_SD = Asm.getSymbolData(*B); 156 const MCSymbolData *B_Base = Asm.getAtom(&B_SD); 157 158 // Neither symbol can be modified. 159 if (Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None || 160 Target.getSymB()->getKind() != MCSymbolRefExpr::VK_None) 161 report_fatal_error("unsupported relocation of modified symbol", false); 162 163 // We don't support PCrel relocations of differences. Darwin 'as' doesn't 164 // implement most of these correctly. 165 if (IsPCRel) 166 report_fatal_error("unsupported pc-relative relocation of difference", 167 false); 168 169 // The support for the situation where one or both of the symbols would 170 // require a local relocation is handled just like if the symbols were 171 // external. This is certainly used in the case of debug sections where the 172 // section has only temporary symbols and thus the symbols don't have base 173 // symbols. This is encoded using the section ordinal and non-extern 174 // relocation entries. 175 176 // Darwin 'as' doesn't emit correct relocations for this (it ends up with a 177 // single SIGNED relocation); reject it for now. Except the case where both 178 // symbols don't have a base, equal but both NULL. 179 if (A_Base == B_Base && A_Base) 180 report_fatal_error("unsupported relocation with identical base", false); 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().FatalError(Fixup.getLoc(), 187 "unsupported relocation with subtraction expression, symbol '" + 188 Name + "' can not be undefined in a subtraction expression"); 189 } 190 191 Value += Writer->getSymbolAddress(&A_SD, Layout) - 192 (!A_Base ? 0 : Writer->getSymbolAddress(A_Base, Layout)); 193 Value -= Writer->getSymbolAddress(&B_SD, Layout) - 194 (!B_Base ? 0 : Writer->getSymbolAddress(B_Base, Layout)); 195 196 if (A_Base) { 197 Index = A_Base->getIndex(); 198 IsExtern = 1; 199 } 200 else { 201 Index = A_SD.getFragment()->getParent()->getOrdinal() + 1; 202 IsExtern = 0; 203 } 204 Type = MachO::X86_64_RELOC_UNSIGNED; 205 206 MachO::any_relocation_info MRE; 207 MRE.r_word0 = FixupOffset; 208 MRE.r_word1 = ((Index << 0) | 209 (IsPCRel << 24) | 210 (Log2Size << 25) | 211 (IsExtern << 27) | 212 (Type << 28)); 213 Writer->addRelocation(Fragment->getParent(), MRE); 214 215 if (B_Base) { 216 Index = B_Base->getIndex(); 217 IsExtern = 1; 218 } 219 else { 220 Index = B_SD.getFragment()->getParent()->getOrdinal() + 1; 221 IsExtern = 0; 222 } 223 Type = MachO::X86_64_RELOC_SUBTRACTOR; 224 } else { 225 const MCSymbol *Symbol = &Target.getSymA()->getSymbol(); 226 const MCSymbolData &SD = Asm.getSymbolData(*Symbol); 227 const MCSymbolData *Base = Asm.getAtom(&SD); 228 229 // Relocations inside debug sections always use local relocations when 230 // possible. This seems to be done because the debugger doesn't fully 231 // understand x86_64 relocation entries, and expects to find values that 232 // have already been fixed up. 233 if (Symbol->isInSection()) { 234 const MCSectionMachO &Section = static_cast<const MCSectionMachO&>( 235 Fragment->getParent()->getSection()); 236 if (Section.hasAttribute(MachO::S_ATTR_DEBUG)) 237 Base = nullptr; 238 } 239 240 // x86_64 almost always uses external relocations, except when there is no 241 // symbol to use as a base address (a local symbol with no preceding 242 // non-local symbol). 243 if (Base) { 244 Index = Base->getIndex(); 245 IsExtern = 1; 246 247 // Add the local offset, if needed. 248 if (Base != &SD) 249 Value += Layout.getSymbolOffset(&SD) - Layout.getSymbolOffset(Base); 250 } else if (Symbol->isInSection() && !Symbol->isVariable()) { 251 // The index is the section ordinal (1-based). 252 Index = SD.getFragment()->getParent()->getOrdinal() + 1; 253 IsExtern = 0; 254 Value += Writer->getSymbolAddress(&SD, Layout); 255 256 if (IsPCRel) 257 Value -= FixupAddress + (1 << Log2Size); 258 } else if (Symbol->isVariable()) { 259 const MCExpr *Value = Symbol->getVariableValue(); 260 int64_t Res; 261 bool isAbs = Value->EvaluateAsAbsolute(Res, Layout, 262 Writer->getSectionAddressMap()); 263 if (isAbs) { 264 FixedValue = Res; 265 return; 266 } else { 267 report_fatal_error("unsupported relocation of variable '" + 268 Symbol->getName() + "'", false); 269 } 270 } else { 271 report_fatal_error("unsupported relocation of undefined symbol '" + 272 Symbol->getName() + "'", false); 273 } 274 275 MCSymbolRefExpr::VariantKind Modifier = Target.getSymA()->getKind(); 276 if (IsPCRel) { 277 if (IsRIPRel) { 278 if (Modifier == MCSymbolRefExpr::VK_GOTPCREL) { 279 // x86_64 distinguishes movq foo@GOTPCREL so that the linker can 280 // rewrite the movq to an leaq at link time if the symbol ends up in 281 // the same linkage unit. 282 if (unsigned(Fixup.getKind()) == X86::reloc_riprel_4byte_movq_load) 283 Type = MachO::X86_64_RELOC_GOT_LOAD; 284 else 285 Type = MachO::X86_64_RELOC_GOT; 286 } else if (Modifier == MCSymbolRefExpr::VK_TLVP) { 287 Type = MachO::X86_64_RELOC_TLV; 288 } else if (Modifier != MCSymbolRefExpr::VK_None) { 289 report_fatal_error("unsupported symbol modifier in relocation", 290 false); 291 } else { 292 Type = MachO::X86_64_RELOC_SIGNED; 293 294 // The Darwin x86_64 relocation format has a problem where it cannot 295 // encode an address (L<foo> + <constant>) which is outside the atom 296 // containing L<foo>. Generally, this shouldn't occur but it does 297 // happen when we have a RIPrel instruction with data following the 298 // relocation entry (e.g., movb $012, L0(%rip)). Even with the PCrel 299 // adjustment Darwin x86_64 uses, the offset is still negative and the 300 // linker has no way to recognize this. 301 // 302 // To work around this, Darwin uses several special relocation types 303 // to indicate the offsets. However, the specification or 304 // implementation of these seems to also be incomplete; they should 305 // adjust the addend as well based on the actual encoded instruction 306 // (the additional bias), but instead appear to just look at the final 307 // offset. 308 switch (-(Target.getConstant() + (1LL << Log2Size))) { 309 case 1: Type = MachO::X86_64_RELOC_SIGNED_1; break; 310 case 2: Type = MachO::X86_64_RELOC_SIGNED_2; break; 311 case 4: Type = MachO::X86_64_RELOC_SIGNED_4; break; 312 } 313 } 314 } else { 315 if (Modifier != MCSymbolRefExpr::VK_None) 316 report_fatal_error("unsupported symbol modifier in branch " 317 "relocation", false); 318 319 Type = MachO::X86_64_RELOC_BRANCH; 320 } 321 } else { 322 if (Modifier == MCSymbolRefExpr::VK_GOT) { 323 Type = MachO::X86_64_RELOC_GOT; 324 } else if (Modifier == MCSymbolRefExpr::VK_GOTPCREL) { 325 // GOTPCREL is allowed as a modifier on non-PCrel instructions, in which 326 // case all we do is set the PCrel bit in the relocation entry; this is 327 // used with exception handling, for example. The source is required to 328 // include any necessary offset directly. 329 Type = MachO::X86_64_RELOC_GOT; 330 IsPCRel = 1; 331 } else if (Modifier == MCSymbolRefExpr::VK_TLVP) { 332 report_fatal_error("TLVP symbol modifier should have been rip-rel", 333 false); 334 } else if (Modifier != MCSymbolRefExpr::VK_None) 335 report_fatal_error("unsupported symbol modifier in relocation", false); 336 else { 337 Type = MachO::X86_64_RELOC_UNSIGNED; 338 unsigned Kind = Fixup.getKind(); 339 if (Kind == X86::reloc_signed_4byte) 340 report_fatal_error("32-bit absolute addressing is not supported in " 341 "64-bit mode", false); 342 } 343 } 344 } 345 346 // x86_64 always writes custom values into the fixups. 347 FixedValue = Value; 348 349 // struct relocation_info (8 bytes) 350 MachO::any_relocation_info MRE; 351 MRE.r_word0 = FixupOffset; 352 MRE.r_word1 = ((Index << 0) | 353 (IsPCRel << 24) | 354 (Log2Size << 25) | 355 (IsExtern << 27) | 356 (Type << 28)); 357 Writer->addRelocation(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 const MCSymbolData *A_SD = &Asm.getSymbolData(*A); 376 377 if (!A_SD->getFragment()) 378 report_fatal_error("symbol '" + A->getName() + 379 "' can not be undefined in a subtraction expression", 380 false); 381 382 uint32_t Value = Writer->getSymbolAddress(A_SD, Layout); 383 uint64_t SecAddr = Writer->getSectionAddress(A_SD->getFragment()->getParent()); 384 FixedValue += SecAddr; 385 uint32_t Value2 = 0; 386 387 if (const MCSymbolRefExpr *B = Target.getSymB()) { 388 const MCSymbolData *B_SD = &Asm.getSymbolData(B->getSymbol()); 389 390 if (!B_SD->getFragment()) 391 report_fatal_error("symbol '" + B->getSymbol().getName() + 392 "' can not be undefined in a subtraction expression", 393 false); 394 395 // Select the appropriate difference relocation type. 396 // 397 // Note that there is no longer any semantic difference between these two 398 // relocation types from the linkers point of view, this is done solely for 399 // pedantic compatibility with 'as'. 400 Type = A_SD->isExternal() ? (unsigned)MachO::GENERIC_RELOC_SECTDIFF : 401 (unsigned)MachO::GENERIC_RELOC_LOCAL_SECTDIFF; 402 Value2 = Writer->getSymbolAddress(B_SD, Layout); 403 FixedValue -= Writer->getSectionAddress(B_SD->getFragment()->getParent()); 404 } 405 406 // Relocations are written out in reverse order, so the PAIR comes first. 407 if (Type == MachO::GENERIC_RELOC_SECTDIFF || 408 Type == MachO::GENERIC_RELOC_LOCAL_SECTDIFF) { 409 // If the offset is too large to fit in a scattered relocation, 410 // we're hosed. It's an unfortunate limitation of the MachO format. 411 if (FixupOffset > 0xffffff) { 412 char Buffer[32]; 413 format("0x%x", FixupOffset).print(Buffer, sizeof(Buffer)); 414 Asm.getContext().FatalError(Fixup.getLoc(), 415 Twine("Section too large, can't encode " 416 "r_address (") + Buffer + 417 ") into 24 bits of scattered " 418 "relocation entry."); 419 llvm_unreachable("fatal error returned?!"); 420 } 421 422 MachO::any_relocation_info MRE; 423 MRE.r_word0 = ((0 << 0) | // r_address 424 (MachO::GENERIC_RELOC_PAIR << 24) | // r_type 425 (Log2Size << 28) | 426 (IsPCRel << 30) | 427 MachO::R_SCATTERED); 428 MRE.r_word1 = Value2; 429 Writer->addRelocation(Fragment->getParent(), MRE); 430 } else { 431 // If the offset is more than 24-bits, it won't fit in a scattered 432 // relocation offset field, so we fall back to using a non-scattered 433 // relocation. This is a bit risky, as if the offset reaches out of 434 // the block and the linker is doing scattered loading on this 435 // symbol, things can go badly. 436 // 437 // Required for 'as' compatibility. 438 if (FixupOffset > 0xffffff) { 439 FixedValue = OriginalFixedValue; 440 return false; 441 } 442 } 443 444 MachO::any_relocation_info MRE; 445 MRE.r_word0 = ((FixupOffset << 0) | 446 (Type << 24) | 447 (Log2Size << 28) | 448 (IsPCRel << 30) | 449 MachO::R_SCATTERED); 450 MRE.r_word1 = Value; 451 Writer->addRelocation(Fragment->getParent(), MRE); 452 return true; 453 } 454 455 void X86MachObjectWriter::RecordTLVPRelocation(MachObjectWriter *Writer, 456 const MCAssembler &Asm, 457 const MCAsmLayout &Layout, 458 const MCFragment *Fragment, 459 const MCFixup &Fixup, 460 MCValue Target, 461 uint64_t &FixedValue) { 462 assert(Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP && 463 !is64Bit() && 464 "Should only be called with a 32-bit TLVP relocation!"); 465 466 unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind()); 467 uint32_t Value = Layout.getFragmentOffset(Fragment)+Fixup.getOffset(); 468 unsigned IsPCRel = 0; 469 470 // Get the symbol data. 471 const MCSymbolData *SD_A = &Asm.getSymbolData(Target.getSymA()->getSymbol()); 472 unsigned Index = SD_A->getIndex(); 473 474 // We're only going to have a second symbol in pic mode and it'll be a 475 // subtraction from the picbase. For 32-bit pic the addend is the difference 476 // between the picbase and the next address. For 32-bit static the addend is 477 // zero. 478 if (Target.getSymB()) { 479 // If this is a subtraction then we're pcrel. 480 uint32_t FixupAddress = 481 Writer->getFragmentAddress(Fragment, Layout) + Fixup.getOffset(); 482 const MCSymbolData *SD_B = 483 &Asm.getSymbolData(Target.getSymB()->getSymbol()); 484 IsPCRel = 1; 485 FixedValue = (FixupAddress - Writer->getSymbolAddress(SD_B, Layout) + 486 Target.getConstant()); 487 FixedValue += 1ULL << Log2Size; 488 } else { 489 FixedValue = 0; 490 } 491 492 // struct relocation_info (8 bytes) 493 MachO::any_relocation_info MRE; 494 MRE.r_word0 = Value; 495 MRE.r_word1 = ((Index << 0) | 496 (IsPCRel << 24) | 497 (Log2Size << 25) | 498 (1 << 27) | // r_extern 499 (MachO::GENERIC_RELOC_TLV << 28)); // r_type 500 Writer->addRelocation(Fragment->getParent(), MRE); 501 } 502 503 void X86MachObjectWriter::RecordX86Relocation(MachObjectWriter *Writer, 504 const MCAssembler &Asm, 505 const MCAsmLayout &Layout, 506 const MCFragment *Fragment, 507 const MCFixup &Fixup, 508 MCValue Target, 509 uint64_t &FixedValue) { 510 unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind()); 511 unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind()); 512 513 // If this is a 32-bit TLVP reloc it's handled a bit differently. 514 if (Target.getSymA() && 515 Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP) { 516 RecordTLVPRelocation(Writer, Asm, Layout, Fragment, Fixup, Target, 517 FixedValue); 518 return; 519 } 520 521 // If this is a difference or a defined symbol plus an offset, then we need a 522 // scattered relocation entry. Differences always require scattered 523 // relocations. 524 if (Target.getSymB()) { 525 RecordScatteredRelocation(Writer, Asm, Layout, Fragment, Fixup, 526 Target, Log2Size, FixedValue); 527 return; 528 } 529 530 // Get the symbol data, if any. 531 const MCSymbolData *SD = nullptr; 532 if (Target.getSymA()) 533 SD = &Asm.getSymbolData(Target.getSymA()->getSymbol()); 534 535 // If this is an internal relocation with an offset, it also needs a scattered 536 // relocation entry. 537 uint32_t Offset = Target.getConstant(); 538 if (IsPCRel) 539 Offset += 1 << Log2Size; 540 // Try to record the scattered relocation if needed. Fall back to non 541 // scattered if necessary (see comments in RecordScatteredRelocation() 542 // for details). 543 if (Offset && SD && !Writer->doesSymbolRequireExternRelocation(SD) && 544 RecordScatteredRelocation(Writer, Asm, Layout, Fragment, Fixup, 545 Target, Log2Size, FixedValue)) 546 return; 547 548 // See <reloc.h>. 549 uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset(); 550 unsigned Index = 0; 551 unsigned IsExtern = 0; 552 unsigned Type = 0; 553 554 if (Target.isAbsolute()) { // constant 555 // SymbolNum of 0 indicates the absolute section. 556 // 557 // FIXME: Currently, these are never generated (see code below). I cannot 558 // find a case where they are actually emitted. 559 Type = MachO::GENERIC_RELOC_VANILLA; 560 } else { 561 // Resolve constant variables. 562 if (SD->getSymbol().isVariable()) { 563 int64_t Res; 564 if (SD->getSymbol().getVariableValue()->EvaluateAsAbsolute( 565 Res, Layout, Writer->getSectionAddressMap())) { 566 FixedValue = Res; 567 return; 568 } 569 } 570 571 // Check whether we need an external or internal relocation. 572 if (Writer->doesSymbolRequireExternRelocation(SD)) { 573 IsExtern = 1; 574 Index = SD->getIndex(); 575 // For external relocations, make sure to offset the fixup value to 576 // compensate for the addend of the symbol address, if it was 577 // undefined. This occurs with weak definitions, for example. 578 if (!SD->getSymbol().isUndefined()) 579 FixedValue -= Layout.getSymbolOffset(SD); 580 } else { 581 // The index is the section ordinal (1-based). 582 const MCSectionData &SymSD = Asm.getSectionData( 583 SD->getSymbol().getSection()); 584 Index = SymSD.getOrdinal() + 1; 585 FixedValue += Writer->getSectionAddress(&SymSD); 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 = ((Index << 0) | 597 (IsPCRel << 24) | 598 (Log2Size << 25) | 599 (IsExtern << 27) | 600 (Type << 28)); 601 Writer->addRelocation(Fragment->getParent(), MRE); 602 } 603 604 MCObjectWriter *llvm::createX86MachObjectWriter(raw_ostream &OS, 605 bool Is64Bit, 606 uint32_t CPUType, 607 uint32_t CPUSubtype) { 608 return createMachObjectWriter(new X86MachObjectWriter(Is64Bit, 609 CPUType, 610 CPUSubtype), 611 OS, /*IsLittleEndian=*/true); 612 } 613