1 //===- lib/MC/MachObjectWriter.cpp - Mach-O File Writer -------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 #include "llvm/MC/MCMachObjectWriter.h"
11 #include "llvm/ADT/StringMap.h"
12 #include "llvm/ADT/Twine.h"
13 #include "llvm/MC/MCAsmBackend.h"
14 #include "llvm/MC/MCAsmLayout.h"
15 #include "llvm/MC/MCAssembler.h"
16 #include "llvm/MC/MCExpr.h"
17 #include "llvm/MC/MCFixupKindInfo.h"
18 #include "llvm/MC/MCMachOSymbolFlags.h"
19 #include "llvm/MC/MCObjectWriter.h"
20 #include "llvm/MC/MCSectionMachO.h"
21 #include "llvm/MC/MCSymbol.h"
22 #include "llvm/MC/MCValue.h"
23 #include "llvm/Support/Debug.h"
24 #include "llvm/Support/ErrorHandling.h"
25 #include "llvm/Support/MachO.h"
26 #include "llvm/Support/raw_ostream.h"
30 #define DEBUG_TYPE "mc"
32 void MachObjectWriter::reset() {
34 IndirectSymBase.clear();
36 LocalSymbolData.clear();
37 ExternalSymbolData.clear();
38 UndefinedSymbolData.clear();
39 MCObjectWriter::reset();
42 bool MachObjectWriter::
43 doesSymbolRequireExternRelocation(const MCSymbolData *SD) {
44 // Undefined symbols are always extern.
45 if (SD->getSymbol().isUndefined())
48 // References to weak definitions require external relocation entries; the
49 // definition may not always be the one in the same object file.
50 if (SD->getFlags() & SF_WeakDefinition)
53 // Otherwise, we can use an internal relocation.
57 bool MachObjectWriter::
58 MachSymbolData::operator<(const MachSymbolData &RHS) const {
59 return SymbolData->getSymbol().getName() <
60 RHS.SymbolData->getSymbol().getName();
63 bool MachObjectWriter::isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind) {
64 const MCFixupKindInfo &FKI = Asm.getBackend().getFixupKindInfo(
67 return FKI.Flags & MCFixupKindInfo::FKF_IsPCRel;
70 uint64_t MachObjectWriter::getFragmentAddress(const MCFragment *Fragment,
71 const MCAsmLayout &Layout) const {
72 return getSectionAddress(Fragment->getParent()) +
73 Layout.getFragmentOffset(Fragment);
76 uint64_t MachObjectWriter::getSymbolAddress(const MCSymbolData* SD,
77 const MCAsmLayout &Layout) const {
78 const MCSymbol &S = SD->getSymbol();
80 // If this is a variable, then recursively evaluate now.
82 if (const MCConstantExpr *C =
83 dyn_cast<const MCConstantExpr>(S.getVariableValue()))
88 if (!S.getVariableValue()->EvaluateAsRelocatable(Target, &Layout, nullptr))
89 report_fatal_error("unable to evaluate offset for variable '" +
92 // Verify that any used symbols are defined.
93 if (Target.getSymA() && Target.getSymA()->getSymbol().isUndefined())
94 report_fatal_error("unable to evaluate offset to undefined symbol '" +
95 Target.getSymA()->getSymbol().getName() + "'");
96 if (Target.getSymB() && Target.getSymB()->getSymbol().isUndefined())
97 report_fatal_error("unable to evaluate offset to undefined symbol '" +
98 Target.getSymB()->getSymbol().getName() + "'");
100 uint64_t Address = Target.getConstant();
101 if (Target.getSymA())
102 Address += getSymbolAddress(&Layout.getAssembler().getSymbolData(
103 Target.getSymA()->getSymbol()), Layout);
104 if (Target.getSymB())
105 Address += getSymbolAddress(&Layout.getAssembler().getSymbolData(
106 Target.getSymB()->getSymbol()), Layout);
110 return getSectionAddress(SD->getFragment()->getParent()) +
111 Layout.getSymbolOffset(SD);
114 uint64_t MachObjectWriter::getPaddingSize(const MCSectionData *SD,
115 const MCAsmLayout &Layout) const {
116 uint64_t EndAddr = getSectionAddress(SD) + Layout.getSectionAddressSize(SD);
117 unsigned Next = SD->getLayoutOrder() + 1;
118 if (Next >= Layout.getSectionOrder().size())
121 const MCSectionData &NextSD = *Layout.getSectionOrder()[Next];
122 if (NextSD.getSection().isVirtualSection())
124 return OffsetToAlignment(EndAddr, NextSD.getAlignment());
127 void MachObjectWriter::WriteHeader(unsigned NumLoadCommands,
128 unsigned LoadCommandsSize,
129 bool SubsectionsViaSymbols) {
132 if (SubsectionsViaSymbols)
133 Flags |= MachO::MH_SUBSECTIONS_VIA_SYMBOLS;
135 // struct mach_header (28 bytes) or
136 // struct mach_header_64 (32 bytes)
138 uint64_t Start = OS.tell();
141 Write32(is64Bit() ? MachO::MH_MAGIC_64 : MachO::MH_MAGIC);
143 Write32(TargetObjectWriter->getCPUType());
144 Write32(TargetObjectWriter->getCPUSubtype());
146 Write32(MachO::MH_OBJECT);
147 Write32(NumLoadCommands);
148 Write32(LoadCommandsSize);
151 Write32(0); // reserved
153 assert(OS.tell() - Start ==
154 (is64Bit()?sizeof(MachO::mach_header_64): sizeof(MachO::mach_header)));
157 /// WriteSegmentLoadCommand - Write a segment load command.
159 /// \param NumSections The number of sections in this segment.
160 /// \param SectionDataSize The total size of the sections.
161 void MachObjectWriter::WriteSegmentLoadCommand(unsigned NumSections,
163 uint64_t SectionDataStartOffset,
164 uint64_t SectionDataSize) {
165 // struct segment_command (56 bytes) or
166 // struct segment_command_64 (72 bytes)
168 uint64_t Start = OS.tell();
171 unsigned SegmentLoadCommandSize =
172 is64Bit() ? sizeof(MachO::segment_command_64):
173 sizeof(MachO::segment_command);
174 Write32(is64Bit() ? MachO::LC_SEGMENT_64 : MachO::LC_SEGMENT);
175 Write32(SegmentLoadCommandSize +
176 NumSections * (is64Bit() ? sizeof(MachO::section_64) :
177 sizeof(MachO::section)));
181 Write64(0); // vmaddr
182 Write64(VMSize); // vmsize
183 Write64(SectionDataStartOffset); // file offset
184 Write64(SectionDataSize); // file size
186 Write32(0); // vmaddr
187 Write32(VMSize); // vmsize
188 Write32(SectionDataStartOffset); // file offset
189 Write32(SectionDataSize); // file size
192 Write32(MachO::VM_PROT_READ | MachO::VM_PROT_WRITE | MachO::VM_PROT_EXECUTE);
194 Write32(MachO::VM_PROT_READ | MachO::VM_PROT_WRITE | MachO::VM_PROT_EXECUTE);
195 Write32(NumSections);
198 assert(OS.tell() - Start == SegmentLoadCommandSize);
201 void MachObjectWriter::WriteSection(const MCAssembler &Asm,
202 const MCAsmLayout &Layout,
203 const MCSectionData &SD,
205 uint64_t RelocationsStart,
206 unsigned NumRelocations) {
207 uint64_t SectionSize = Layout.getSectionAddressSize(&SD);
209 // The offset is unused for virtual sections.
210 if (SD.getSection().isVirtualSection()) {
211 assert(Layout.getSectionFileSize(&SD) == 0 && "Invalid file size!");
215 // struct section (68 bytes) or
216 // struct section_64 (80 bytes)
218 uint64_t Start = OS.tell();
221 const MCSectionMachO &Section = cast<MCSectionMachO>(SD.getSection());
222 WriteBytes(Section.getSectionName(), 16);
223 WriteBytes(Section.getSegmentName(), 16);
225 Write64(getSectionAddress(&SD)); // address
226 Write64(SectionSize); // size
228 Write32(getSectionAddress(&SD)); // address
229 Write32(SectionSize); // size
233 unsigned Flags = Section.getTypeAndAttributes();
234 if (SD.hasInstructions())
235 Flags |= MachO::S_ATTR_SOME_INSTRUCTIONS;
237 assert(isPowerOf2_32(SD.getAlignment()) && "Invalid alignment!");
238 Write32(Log2_32(SD.getAlignment()));
239 Write32(NumRelocations ? RelocationsStart : 0);
240 Write32(NumRelocations);
242 Write32(IndirectSymBase.lookup(&SD)); // reserved1
243 Write32(Section.getStubSize()); // reserved2
245 Write32(0); // reserved3
247 assert(OS.tell() - Start == (is64Bit() ? sizeof(MachO::section_64) :
248 sizeof(MachO::section)));
251 void MachObjectWriter::WriteSymtabLoadCommand(uint32_t SymbolOffset,
253 uint32_t StringTableOffset,
254 uint32_t StringTableSize) {
255 // struct symtab_command (24 bytes)
257 uint64_t Start = OS.tell();
260 Write32(MachO::LC_SYMTAB);
261 Write32(sizeof(MachO::symtab_command));
262 Write32(SymbolOffset);
264 Write32(StringTableOffset);
265 Write32(StringTableSize);
267 assert(OS.tell() - Start == sizeof(MachO::symtab_command));
270 void MachObjectWriter::WriteDysymtabLoadCommand(uint32_t FirstLocalSymbol,
271 uint32_t NumLocalSymbols,
272 uint32_t FirstExternalSymbol,
273 uint32_t NumExternalSymbols,
274 uint32_t FirstUndefinedSymbol,
275 uint32_t NumUndefinedSymbols,
276 uint32_t IndirectSymbolOffset,
277 uint32_t NumIndirectSymbols) {
278 // struct dysymtab_command (80 bytes)
280 uint64_t Start = OS.tell();
283 Write32(MachO::LC_DYSYMTAB);
284 Write32(sizeof(MachO::dysymtab_command));
285 Write32(FirstLocalSymbol);
286 Write32(NumLocalSymbols);
287 Write32(FirstExternalSymbol);
288 Write32(NumExternalSymbols);
289 Write32(FirstUndefinedSymbol);
290 Write32(NumUndefinedSymbols);
291 Write32(0); // tocoff
293 Write32(0); // modtaboff
294 Write32(0); // nmodtab
295 Write32(0); // extrefsymoff
296 Write32(0); // nextrefsyms
297 Write32(IndirectSymbolOffset);
298 Write32(NumIndirectSymbols);
299 Write32(0); // extreloff
300 Write32(0); // nextrel
301 Write32(0); // locreloff
302 Write32(0); // nlocrel
304 assert(OS.tell() - Start == sizeof(MachO::dysymtab_command));
307 MachObjectWriter::MachSymbolData *
308 MachObjectWriter::findSymbolData(const MCSymbol &Sym) {
309 for (auto &Entry : LocalSymbolData)
310 if (&Entry.SymbolData->getSymbol() == &Sym)
313 for (auto &Entry : ExternalSymbolData)
314 if (&Entry.SymbolData->getSymbol() == &Sym)
317 for (auto &Entry : UndefinedSymbolData)
318 if (&Entry.SymbolData->getSymbol() == &Sym)
324 const MCSymbol &MachObjectWriter::findAliasedSymbol(const MCSymbol &Sym) const {
325 const MCSymbol *S = &Sym;
326 while (S->isVariable()) {
327 const MCExpr *Value = S->getVariableValue();
328 const auto *Ref = dyn_cast<MCSymbolRefExpr>(Value);
331 S = &Ref->getSymbol();
336 void MachObjectWriter::WriteNlist(MachSymbolData &MSD,
337 const MCAsmLayout &Layout) {
338 MCSymbolData &Data = *MSD.SymbolData;
339 const MCSymbol *Symbol = &Data.getSymbol();
340 const MCSymbol *AliasedSymbol = &findAliasedSymbol(*Symbol);
341 uint8_t SectionIndex = MSD.SectionIndex;
343 uint16_t Flags = Data.getFlags();
344 uint64_t Address = 0;
345 bool IsAlias = Symbol != AliasedSymbol;
347 MachSymbolData *AliaseeInfo;
349 AliaseeInfo = findSymbolData(*AliasedSymbol);
351 SectionIndex = AliaseeInfo->SectionIndex;
352 Symbol = AliasedSymbol;
355 // Set the N_TYPE bits. See <mach-o/nlist.h>.
357 // FIXME: Are the prebound or indirect fields possible here?
358 if (IsAlias && Symbol->isUndefined())
359 Type = MachO::N_INDR;
360 else if (Symbol->isUndefined())
361 Type = MachO::N_UNDF;
362 else if (Symbol->isAbsolute())
365 Type = MachO::N_SECT;
367 // FIXME: Set STAB bits.
369 if (Data.isPrivateExtern())
370 Type |= MachO::N_PEXT;
373 if (Data.isExternal() || (!IsAlias && Symbol->isUndefined()))
374 Type |= MachO::N_EXT;
376 // Compute the symbol address.
377 if (IsAlias && Symbol->isUndefined())
378 Address = AliaseeInfo->StringIndex;
379 else if (Symbol->isDefined())
380 Address = getSymbolAddress(&Data, Layout);
381 else if (Data.isCommon()) {
382 // Common symbols are encoded with the size in the address
383 // field, and their alignment in the flags.
384 Address = Data.getCommonSize();
386 // Common alignment is packed into the 'desc' bits.
387 if (unsigned Align = Data.getCommonAlignment()) {
388 unsigned Log2Size = Log2_32(Align);
389 assert((1U << Log2Size) == Align && "Invalid 'common' alignment!");
391 report_fatal_error("invalid 'common' alignment '" +
392 Twine(Align) + "' for '" + Symbol->getName() + "'",
394 // FIXME: Keep this mask with the SymbolFlags enumeration.
395 Flags = (Flags & 0xF0FF) | (Log2Size << 8);
399 if (Layout.getAssembler().isThumbFunc(Symbol))
400 Flags |= SF_ThumbFunc;
402 // struct nlist (12 bytes)
404 Write32(MSD.StringIndex);
406 Write8(SectionIndex);
408 // The Mach-O streamer uses the lowest 16-bits of the flags for the 'desc'
417 void MachObjectWriter::WriteLinkeditLoadCommand(uint32_t Type,
420 uint64_t Start = OS.tell();
424 Write32(sizeof(MachO::linkedit_data_command));
428 assert(OS.tell() - Start == sizeof(MachO::linkedit_data_command));
431 static unsigned ComputeLinkerOptionsLoadCommandSize(
432 const std::vector<std::string> &Options, bool is64Bit)
434 unsigned Size = sizeof(MachO::linker_option_command);
435 for (unsigned i = 0, e = Options.size(); i != e; ++i)
436 Size += Options[i].size() + 1;
437 return RoundUpToAlignment(Size, is64Bit ? 8 : 4);
440 void MachObjectWriter::WriteLinkerOptionsLoadCommand(
441 const std::vector<std::string> &Options)
443 unsigned Size = ComputeLinkerOptionsLoadCommandSize(Options, is64Bit());
444 uint64_t Start = OS.tell();
447 Write32(MachO::LC_LINKER_OPTION);
449 Write32(Options.size());
450 uint64_t BytesWritten = sizeof(MachO::linker_option_command);
451 for (unsigned i = 0, e = Options.size(); i != e; ++i) {
452 // Write each string, including the null byte.
453 const std::string &Option = Options[i];
454 WriteBytes(Option.c_str(), Option.size() + 1);
455 BytesWritten += Option.size() + 1;
458 // Pad to a multiple of the pointer size.
459 WriteBytes("", OffsetToAlignment(BytesWritten, is64Bit() ? 8 : 4));
461 assert(OS.tell() - Start == Size);
464 void MachObjectWriter::RecordRelocation(MCAssembler &Asm,
465 const MCAsmLayout &Layout,
466 const MCFragment *Fragment,
467 const MCFixup &Fixup, MCValue Target,
468 bool &IsPCRel, uint64_t &FixedValue) {
469 TargetObjectWriter->RecordRelocation(this, Asm, Layout, Fragment, Fixup,
473 void MachObjectWriter::BindIndirectSymbols(MCAssembler &Asm) {
474 // This is the point where 'as' creates actual symbols for indirect symbols
475 // (in the following two passes). It would be easier for us to do this sooner
476 // when we see the attribute, but that makes getting the order in the symbol
477 // table much more complicated than it is worth.
479 // FIXME: Revisit this when the dust settles.
481 // Report errors for use of .indirect_symbol not in a symbol pointer section
483 for (MCAssembler::indirect_symbol_iterator it = Asm.indirect_symbol_begin(),
484 ie = Asm.indirect_symbol_end(); it != ie; ++it) {
485 const MCSectionMachO &Section =
486 cast<MCSectionMachO>(it->SectionData->getSection());
488 if (Section.getType() != MachO::S_NON_LAZY_SYMBOL_POINTERS &&
489 Section.getType() != MachO::S_LAZY_SYMBOL_POINTERS &&
490 Section.getType() != MachO::S_SYMBOL_STUBS) {
491 MCSymbol &Symbol = *it->Symbol;
492 report_fatal_error("indirect symbol '" + Symbol.getName() +
493 "' not in a symbol pointer or stub section");
497 // Bind non-lazy symbol pointers first.
498 unsigned IndirectIndex = 0;
499 for (MCAssembler::indirect_symbol_iterator it = Asm.indirect_symbol_begin(),
500 ie = Asm.indirect_symbol_end(); it != ie; ++it, ++IndirectIndex) {
501 const MCSectionMachO &Section =
502 cast<MCSectionMachO>(it->SectionData->getSection());
504 if (Section.getType() != MachO::S_NON_LAZY_SYMBOL_POINTERS)
507 // Initialize the section indirect symbol base, if necessary.
508 IndirectSymBase.insert(std::make_pair(it->SectionData, IndirectIndex));
510 Asm.getOrCreateSymbolData(*it->Symbol);
513 // Then lazy symbol pointers and symbol stubs.
515 for (MCAssembler::indirect_symbol_iterator it = Asm.indirect_symbol_begin(),
516 ie = Asm.indirect_symbol_end(); it != ie; ++it, ++IndirectIndex) {
517 const MCSectionMachO &Section =
518 cast<MCSectionMachO>(it->SectionData->getSection());
520 if (Section.getType() != MachO::S_LAZY_SYMBOL_POINTERS &&
521 Section.getType() != MachO::S_SYMBOL_STUBS)
524 // Initialize the section indirect symbol base, if necessary.
525 IndirectSymBase.insert(std::make_pair(it->SectionData, IndirectIndex));
527 // Set the symbol type to undefined lazy, but only on construction.
529 // FIXME: Do not hardcode.
531 MCSymbolData &Entry = Asm.getOrCreateSymbolData(*it->Symbol, &Created);
533 Entry.setFlags(Entry.getFlags() | 0x0001);
537 /// ComputeSymbolTable - Compute the symbol table data
538 void MachObjectWriter::ComputeSymbolTable(
539 MCAssembler &Asm, std::vector<MachSymbolData> &LocalSymbolData,
540 std::vector<MachSymbolData> &ExternalSymbolData,
541 std::vector<MachSymbolData> &UndefinedSymbolData) {
542 // Build section lookup table.
543 DenseMap<const MCSection*, uint8_t> SectionIndexMap;
545 for (MCAssembler::iterator it = Asm.begin(),
546 ie = Asm.end(); it != ie; ++it, ++Index)
547 SectionIndexMap[&it->getSection()] = Index;
548 assert(Index <= 256 && "Too many sections!");
550 // Build the string table.
551 for (MCSymbolData &SD : Asm.symbols()) {
552 const MCSymbol &Symbol = SD.getSymbol();
553 if (!Asm.isSymbolLinkerVisible(Symbol))
556 StringTable.add(Symbol.getName());
558 StringTable.finalize(StringTableBuilder::MachO);
560 // Build the symbol arrays but only for non-local symbols.
562 // The particular order that we collect and then sort the symbols is chosen to
563 // match 'as'. Even though it doesn't matter for correctness, this is
564 // important for letting us diff .o files.
565 for (MCSymbolData &SD : Asm.symbols()) {
566 const MCSymbol &Symbol = SD.getSymbol();
568 // Ignore non-linker visible symbols.
569 if (!Asm.isSymbolLinkerVisible(Symbol))
572 if (!SD.isExternal() && !Symbol.isUndefined())
576 MSD.SymbolData = &SD;
577 MSD.StringIndex = StringTable.getOffset(Symbol.getName());
579 if (Symbol.isUndefined()) {
580 MSD.SectionIndex = 0;
581 UndefinedSymbolData.push_back(MSD);
582 } else if (Symbol.isAbsolute()) {
583 MSD.SectionIndex = 0;
584 ExternalSymbolData.push_back(MSD);
586 MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
587 assert(MSD.SectionIndex && "Invalid section index!");
588 ExternalSymbolData.push_back(MSD);
592 // Now add the data for local symbols.
593 for (MCSymbolData &SD : Asm.symbols()) {
594 const MCSymbol &Symbol = SD.getSymbol();
596 // Ignore non-linker visible symbols.
597 if (!Asm.isSymbolLinkerVisible(Symbol))
600 if (SD.isExternal() || Symbol.isUndefined())
604 MSD.SymbolData = &SD;
605 MSD.StringIndex = StringTable.getOffset(Symbol.getName());
607 if (Symbol.isAbsolute()) {
608 MSD.SectionIndex = 0;
609 LocalSymbolData.push_back(MSD);
611 MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
612 assert(MSD.SectionIndex && "Invalid section index!");
613 LocalSymbolData.push_back(MSD);
617 // External and undefined symbols are required to be in lexicographic order.
618 std::sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
619 std::sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end());
621 // Set the symbol indices.
623 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
624 LocalSymbolData[i].SymbolData->setIndex(Index++);
625 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
626 ExternalSymbolData[i].SymbolData->setIndex(Index++);
627 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
628 UndefinedSymbolData[i].SymbolData->setIndex(Index++);
630 for (const MCSectionData &SD : Asm) {
631 std::vector<RelAndSymbol> &Relocs = Relocations[&SD];
632 for (RelAndSymbol &Rel : Relocs) {
636 // Set the Index and the IsExtern bit.
637 unsigned Index = Rel.Sym->getIndex();
638 assert(isInt<24>(Index));
640 Rel.MRE.r_word1 = (Rel.MRE.r_word1 & (-1 << 24)) | Index | (1 << 27);
642 Rel.MRE.r_word1 = (Rel.MRE.r_word1 & 0xff) | Index << 8 | (1 << 4);
647 void MachObjectWriter::computeSectionAddresses(const MCAssembler &Asm,
648 const MCAsmLayout &Layout) {
649 uint64_t StartAddress = 0;
650 const SmallVectorImpl<MCSectionData*> &Order = Layout.getSectionOrder();
651 for (int i = 0, n = Order.size(); i != n ; ++i) {
652 const MCSectionData *SD = Order[i];
653 StartAddress = RoundUpToAlignment(StartAddress, SD->getAlignment());
654 SectionAddress[SD] = StartAddress;
655 StartAddress += Layout.getSectionAddressSize(SD);
657 // Explicitly pad the section to match the alignment requirements of the
658 // following one. This is for 'gas' compatibility, it shouldn't
659 /// strictly be necessary.
660 StartAddress += getPaddingSize(SD, Layout);
664 void MachObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm,
665 const MCAsmLayout &Layout) {
666 computeSectionAddresses(Asm, Layout);
668 // Create symbol data for any indirect symbols.
669 BindIndirectSymbols(Asm);
672 bool MachObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(
673 const MCAssembler &Asm, const MCSymbolData &DataA, const MCFragment &FB,
674 bool InSet, bool IsPCRel) const {
678 // The effective address is
679 // addr(atom(A)) + offset(A)
680 // - addr(atom(B)) - offset(B)
681 // and the offsets are not relocatable, so the fixup is fully resolved when
682 // addr(atom(A)) - addr(atom(B)) == 0.
683 const MCSymbolData *A_Base = nullptr, *B_Base = nullptr;
685 const MCSymbol &SA = findAliasedSymbol(DataA.getSymbol());
686 const MCSection &SecA = SA.getSection();
687 const MCSection &SecB = FB.getParent()->getSection();
690 // The simple (Darwin, except on x86_64) way of dealing with this was to
691 // assume that any reference to a temporary symbol *must* be a temporary
692 // symbol in the same atom, unless the sections differ. Therefore, any PCrel
693 // relocation to a temporary symbol (in the same section) is fully
694 // resolved. This also works in conjunction with absolutized .set, which
695 // requires the compiler to use .set to absolutize the differences between
696 // symbols which the compiler knows to be assembly time constants, so we
697 // don't need to worry about considering symbol differences fully resolved.
699 // If the file isn't using sub-sections-via-symbols, we can make the
700 // same assumptions about any symbol that we normally make about
703 bool hasReliableSymbolDifference = isX86_64();
704 if (!hasReliableSymbolDifference) {
705 if (!SA.isInSection() || &SecA != &SecB ||
706 (!SA.isTemporary() &&
707 FB.getAtom() != Asm.getSymbolData(SA).getFragment()->getAtom() &&
708 Asm.getSubsectionsViaSymbols()))
712 // For Darwin x86_64, there is one special case when the reference IsPCRel.
713 // If the fragment with the reference does not have a base symbol but meets
714 // the simple way of dealing with this, in that it is a temporary symbol in
715 // the same atom then it is assumed to be fully resolved. This is needed so
716 // a relocation entry is not created and so the static linker does not
717 // mess up the reference later.
718 else if(!FB.getAtom() &&
719 SA.isTemporary() && SA.isInSection() && &SecA == &SecB){
723 if (!TargetObjectWriter->useAggressiveSymbolFolding())
727 // If they are not in the same section, we can't compute the diff.
731 const MCFragment *FA = Asm.getSymbolData(SA).getFragment();
733 // Bail if the symbol has no fragment.
737 A_Base = FA->getAtom();
738 B_Base = FB.getAtom();
740 // If the atoms are the same, they are guaranteed to have the same address.
741 if (A_Base == B_Base)
744 // Otherwise, we can't prove this is fully resolved.
748 void MachObjectWriter::WriteObject(MCAssembler &Asm,
749 const MCAsmLayout &Layout) {
750 // Compute symbol table information and bind symbol indices.
751 ComputeSymbolTable(Asm, LocalSymbolData, ExternalSymbolData,
752 UndefinedSymbolData);
754 unsigned NumSections = Asm.size();
755 const MCAssembler::VersionMinInfoType &VersionInfo =
756 Layout.getAssembler().getVersionMinInfo();
758 // The section data starts after the header, the segment load command (and
759 // section headers) and the symbol table.
760 unsigned NumLoadCommands = 1;
761 uint64_t LoadCommandsSize = is64Bit() ?
762 sizeof(MachO::segment_command_64) + NumSections * sizeof(MachO::section_64):
763 sizeof(MachO::segment_command) + NumSections * sizeof(MachO::section);
765 // Add the deployment target version info load command size, if used.
766 if (VersionInfo.Major != 0) {
768 LoadCommandsSize += sizeof(MachO::version_min_command);
771 // Add the data-in-code load command size, if used.
772 unsigned NumDataRegions = Asm.getDataRegions().size();
773 if (NumDataRegions) {
775 LoadCommandsSize += sizeof(MachO::linkedit_data_command);
778 // Add the loh load command size, if used.
779 uint64_t LOHRawSize = Asm.getLOHContainer().getEmitSize(*this, Layout);
780 uint64_t LOHSize = RoundUpToAlignment(LOHRawSize, is64Bit() ? 8 : 4);
783 LoadCommandsSize += sizeof(MachO::linkedit_data_command);
786 // Add the symbol table load command sizes, if used.
787 unsigned NumSymbols = LocalSymbolData.size() + ExternalSymbolData.size() +
788 UndefinedSymbolData.size();
790 NumLoadCommands += 2;
791 LoadCommandsSize += (sizeof(MachO::symtab_command) +
792 sizeof(MachO::dysymtab_command));
795 // Add the linker option load commands sizes.
796 const std::vector<std::vector<std::string> > &LinkerOptions =
797 Asm.getLinkerOptions();
798 for (unsigned i = 0, e = LinkerOptions.size(); i != e; ++i) {
800 LoadCommandsSize += ComputeLinkerOptionsLoadCommandSize(LinkerOptions[i],
804 // Compute the total size of the section data, as well as its file size and vm
806 uint64_t SectionDataStart = (is64Bit() ? sizeof(MachO::mach_header_64) :
807 sizeof(MachO::mach_header)) + LoadCommandsSize;
808 uint64_t SectionDataSize = 0;
809 uint64_t SectionDataFileSize = 0;
811 for (MCAssembler::const_iterator it = Asm.begin(),
812 ie = Asm.end(); it != ie; ++it) {
813 const MCSectionData &SD = *it;
814 uint64_t Address = getSectionAddress(&SD);
815 uint64_t Size = Layout.getSectionAddressSize(&SD);
816 uint64_t FileSize = Layout.getSectionFileSize(&SD);
817 FileSize += getPaddingSize(&SD, Layout);
819 VMSize = std::max(VMSize, Address + Size);
821 if (SD.getSection().isVirtualSection())
824 SectionDataSize = std::max(SectionDataSize, Address + Size);
825 SectionDataFileSize = std::max(SectionDataFileSize, Address + FileSize);
828 // The section data is padded to 4 bytes.
830 // FIXME: Is this machine dependent?
831 unsigned SectionDataPadding = OffsetToAlignment(SectionDataFileSize, 4);
832 SectionDataFileSize += SectionDataPadding;
834 // Write the prolog, starting with the header and load command...
835 WriteHeader(NumLoadCommands, LoadCommandsSize,
836 Asm.getSubsectionsViaSymbols());
837 WriteSegmentLoadCommand(NumSections, VMSize,
838 SectionDataStart, SectionDataSize);
840 // ... and then the section headers.
841 uint64_t RelocTableEnd = SectionDataStart + SectionDataFileSize;
842 for (MCAssembler::const_iterator it = Asm.begin(),
843 ie = Asm.end(); it != ie; ++it) {
844 std::vector<RelAndSymbol> &Relocs = Relocations[it];
845 unsigned NumRelocs = Relocs.size();
846 uint64_t SectionStart = SectionDataStart + getSectionAddress(it);
847 WriteSection(Asm, Layout, *it, SectionStart, RelocTableEnd, NumRelocs);
848 RelocTableEnd += NumRelocs * sizeof(MachO::any_relocation_info);
851 // Write out the deployment target information, if it's available.
852 if (VersionInfo.Major != 0) {
853 assert(VersionInfo.Update < 256 && "unencodable update target version");
854 assert(VersionInfo.Minor < 256 && "unencodable minor target version");
855 assert(VersionInfo.Major < 65536 && "unencodable major target version");
856 uint32_t EncodedVersion = VersionInfo.Update | (VersionInfo.Minor << 8) |
857 (VersionInfo.Major << 16);
858 Write32(VersionInfo.Kind == MCVM_OSXVersionMin ? MachO::LC_VERSION_MIN_MACOSX :
859 MachO::LC_VERSION_MIN_IPHONEOS);
860 Write32(sizeof(MachO::version_min_command));
861 Write32(EncodedVersion);
862 Write32(0); // reserved.
865 // Write the data-in-code load command, if used.
866 uint64_t DataInCodeTableEnd = RelocTableEnd + NumDataRegions * 8;
867 if (NumDataRegions) {
868 uint64_t DataRegionsOffset = RelocTableEnd;
869 uint64_t DataRegionsSize = NumDataRegions * 8;
870 WriteLinkeditLoadCommand(MachO::LC_DATA_IN_CODE, DataRegionsOffset,
874 // Write the loh load command, if used.
875 uint64_t LOHTableEnd = DataInCodeTableEnd + LOHSize;
877 WriteLinkeditLoadCommand(MachO::LC_LINKER_OPTIMIZATION_HINT,
878 DataInCodeTableEnd, LOHSize);
880 // Write the symbol table load command, if used.
882 unsigned FirstLocalSymbol = 0;
883 unsigned NumLocalSymbols = LocalSymbolData.size();
884 unsigned FirstExternalSymbol = FirstLocalSymbol + NumLocalSymbols;
885 unsigned NumExternalSymbols = ExternalSymbolData.size();
886 unsigned FirstUndefinedSymbol = FirstExternalSymbol + NumExternalSymbols;
887 unsigned NumUndefinedSymbols = UndefinedSymbolData.size();
888 unsigned NumIndirectSymbols = Asm.indirect_symbol_size();
889 unsigned NumSymTabSymbols =
890 NumLocalSymbols + NumExternalSymbols + NumUndefinedSymbols;
891 uint64_t IndirectSymbolSize = NumIndirectSymbols * 4;
892 uint64_t IndirectSymbolOffset = 0;
894 // If used, the indirect symbols are written after the section data.
895 if (NumIndirectSymbols)
896 IndirectSymbolOffset = LOHTableEnd;
898 // The symbol table is written after the indirect symbol data.
899 uint64_t SymbolTableOffset = LOHTableEnd + IndirectSymbolSize;
901 // The string table is written after symbol table.
902 uint64_t StringTableOffset =
903 SymbolTableOffset + NumSymTabSymbols * (is64Bit() ?
904 sizeof(MachO::nlist_64) :
905 sizeof(MachO::nlist));
906 WriteSymtabLoadCommand(SymbolTableOffset, NumSymTabSymbols,
907 StringTableOffset, StringTable.data().size());
909 WriteDysymtabLoadCommand(FirstLocalSymbol, NumLocalSymbols,
910 FirstExternalSymbol, NumExternalSymbols,
911 FirstUndefinedSymbol, NumUndefinedSymbols,
912 IndirectSymbolOffset, NumIndirectSymbols);
915 // Write the linker options load commands.
916 for (unsigned i = 0, e = LinkerOptions.size(); i != e; ++i) {
917 WriteLinkerOptionsLoadCommand(LinkerOptions[i]);
920 // Write the actual section data.
921 for (MCAssembler::const_iterator it = Asm.begin(),
922 ie = Asm.end(); it != ie; ++it) {
923 Asm.writeSectionData(it, Layout);
925 uint64_t Pad = getPaddingSize(it, Layout);
929 // Write the extra padding.
930 WriteZeros(SectionDataPadding);
932 // Write the relocation entries.
933 for (MCAssembler::const_iterator it = Asm.begin(),
934 ie = Asm.end(); it != ie; ++it) {
935 // Write the section relocation entries, in reverse order to match 'as'
936 // (approximately, the exact algorithm is more complicated than this).
937 std::vector<RelAndSymbol> &Relocs = Relocations[it];
938 for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
939 Write32(Relocs[e - i - 1].MRE.r_word0);
940 Write32(Relocs[e - i - 1].MRE.r_word1);
944 // Write out the data-in-code region payload, if there is one.
945 for (MCAssembler::const_data_region_iterator
946 it = Asm.data_region_begin(), ie = Asm.data_region_end();
948 const DataRegionData *Data = &(*it);
950 getSymbolAddress(&Layout.getAssembler().getSymbolData(*Data->Start),
953 getSymbolAddress(&Layout.getAssembler().getSymbolData(*Data->End),
955 DEBUG(dbgs() << "data in code region-- kind: " << Data->Kind
956 << " start: " << Start << "(" << Data->Start->getName() << ")"
957 << " end: " << End << "(" << Data->End->getName() << ")"
958 << " size: " << End - Start
961 Write16(End - Start);
965 // Write out the loh commands, if there is one.
968 unsigned Start = OS.tell();
970 Asm.getLOHContainer().Emit(*this, Layout);
971 // Pad to a multiple of the pointer size.
972 WriteBytes("", OffsetToAlignment(LOHRawSize, is64Bit() ? 8 : 4));
973 assert(OS.tell() - Start == LOHSize);
976 // Write the symbol table data, if used.
978 // Write the indirect symbol entries.
979 for (MCAssembler::const_indirect_symbol_iterator
980 it = Asm.indirect_symbol_begin(),
981 ie = Asm.indirect_symbol_end(); it != ie; ++it) {
982 // Indirect symbols in the non-lazy symbol pointer section have some
984 const MCSectionMachO &Section =
985 static_cast<const MCSectionMachO&>(it->SectionData->getSection());
986 if (Section.getType() == MachO::S_NON_LAZY_SYMBOL_POINTERS) {
987 // If this symbol is defined and internal, mark it as such.
988 if (it->Symbol->isDefined() &&
989 !Asm.getSymbolData(*it->Symbol).isExternal()) {
990 uint32_t Flags = MachO::INDIRECT_SYMBOL_LOCAL;
991 if (it->Symbol->isAbsolute())
992 Flags |= MachO::INDIRECT_SYMBOL_ABS;
998 Write32(Asm.getSymbolData(*it->Symbol).getIndex());
1001 // FIXME: Check that offsets match computed ones.
1003 // Write the symbol table entries.
1004 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
1005 WriteNlist(LocalSymbolData[i], Layout);
1006 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
1007 WriteNlist(ExternalSymbolData[i], Layout);
1008 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
1009 WriteNlist(UndefinedSymbolData[i], Layout);
1011 // Write the string table.
1012 OS << StringTable.data();
1016 MCObjectWriter *llvm::createMachObjectWriter(MCMachObjectTargetWriter *MOTW,
1017 raw_pwrite_stream &OS,
1018 bool IsLittleEndian) {
1019 return new MachObjectWriter(MOTW, OS, IsLittleEndian);