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"
29 #define DEBUG_TYPE "mc"
31 void MachObjectWriter::reset() {
33 IndirectSymBase.clear();
35 LocalSymbolData.clear();
36 ExternalSymbolData.clear();
37 UndefinedSymbolData.clear();
38 MCObjectWriter::reset();
41 bool MachObjectWriter::
42 doesSymbolRequireExternRelocation(const MCSymbolData *SD) {
43 // Undefined symbols are always extern.
44 if (SD->Symbol->isUndefined())
47 // References to weak definitions require external relocation entries; the
48 // definition may not always be the one in the same object file.
49 if (SD->getFlags() & SF_WeakDefinition)
52 // Otherwise, we can use an internal relocation.
56 bool MachObjectWriter::
57 MachSymbolData::operator<(const MachSymbolData &RHS) const {
58 return SymbolData->getSymbol().getName() <
59 RHS.SymbolData->getSymbol().getName();
62 bool MachObjectWriter::isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind) {
63 const MCFixupKindInfo &FKI = Asm.getBackend().getFixupKindInfo(
66 return FKI.Flags & MCFixupKindInfo::FKF_IsPCRel;
69 uint64_t MachObjectWriter::getFragmentAddress(const MCFragment *Fragment,
70 const MCAsmLayout &Layout) const {
71 return getSectionAddress(Fragment->getParent()) +
72 Layout.getFragmentOffset(Fragment);
75 uint64_t MachObjectWriter::getSymbolAddress(const MCSymbolData* SD,
76 const MCAsmLayout &Layout) const {
77 const MCSymbol &S = SD->getSymbol();
79 // If this is a variable, then recursively evaluate now.
81 if (const MCConstantExpr *C =
82 dyn_cast<const MCConstantExpr>(S.getVariableValue()))
87 if (!S.getVariableValue()->EvaluateAsRelocatable(Target, &Layout, nullptr))
88 report_fatal_error("unable to evaluate offset for variable '" +
91 // Verify that any used symbols are defined.
92 if (Target.getSymA() && Target.getSymA()->getSymbol().isUndefined())
93 report_fatal_error("unable to evaluate offset to undefined symbol '" +
94 Target.getSymA()->getSymbol().getName() + "'");
95 if (Target.getSymB() && Target.getSymB()->getSymbol().isUndefined())
96 report_fatal_error("unable to evaluate offset to undefined symbol '" +
97 Target.getSymB()->getSymbol().getName() + "'");
99 uint64_t Address = Target.getConstant();
100 if (Target.getSymA())
101 Address += getSymbolAddress(&Layout.getAssembler().getSymbolData(
102 Target.getSymA()->getSymbol()), Layout);
103 if (Target.getSymB())
104 Address += getSymbolAddress(&Layout.getAssembler().getSymbolData(
105 Target.getSymB()->getSymbol()), Layout);
109 return getSectionAddress(SD->getFragment()->getParent()) +
110 Layout.getSymbolOffset(SD);
113 uint64_t MachObjectWriter::getPaddingSize(const MCSectionData *SD,
114 const MCAsmLayout &Layout) const {
115 uint64_t EndAddr = getSectionAddress(SD) + Layout.getSectionAddressSize(SD);
116 unsigned Next = SD->getLayoutOrder() + 1;
117 if (Next >= Layout.getSectionOrder().size())
120 const MCSectionData &NextSD = *Layout.getSectionOrder()[Next];
121 if (NextSD.getSection().isVirtualSection())
123 return OffsetToAlignment(EndAddr, NextSD.getAlignment());
126 void MachObjectWriter::WriteHeader(unsigned NumLoadCommands,
127 unsigned LoadCommandsSize,
128 bool SubsectionsViaSymbols) {
131 if (SubsectionsViaSymbols)
132 Flags |= MachO::MH_SUBSECTIONS_VIA_SYMBOLS;
134 // struct mach_header (28 bytes) or
135 // struct mach_header_64 (32 bytes)
137 uint64_t Start = OS.tell();
140 Write32(is64Bit() ? MachO::MH_MAGIC_64 : MachO::MH_MAGIC);
142 Write32(TargetObjectWriter->getCPUType());
143 Write32(TargetObjectWriter->getCPUSubtype());
145 Write32(MachO::MH_OBJECT);
146 Write32(NumLoadCommands);
147 Write32(LoadCommandsSize);
150 Write32(0); // reserved
152 assert(OS.tell() - Start ==
153 (is64Bit()?sizeof(MachO::mach_header_64): sizeof(MachO::mach_header)));
156 /// WriteSegmentLoadCommand - Write a segment load command.
158 /// \param NumSections The number of sections in this segment.
159 /// \param SectionDataSize The total size of the sections.
160 void MachObjectWriter::WriteSegmentLoadCommand(unsigned NumSections,
162 uint64_t SectionDataStartOffset,
163 uint64_t SectionDataSize) {
164 // struct segment_command (56 bytes) or
165 // struct segment_command_64 (72 bytes)
167 uint64_t Start = OS.tell();
170 unsigned SegmentLoadCommandSize =
171 is64Bit() ? sizeof(MachO::segment_command_64):
172 sizeof(MachO::segment_command);
173 Write32(is64Bit() ? MachO::LC_SEGMENT_64 : MachO::LC_SEGMENT);
174 Write32(SegmentLoadCommandSize +
175 NumSections * (is64Bit() ? sizeof(MachO::section_64) :
176 sizeof(MachO::section)));
180 Write64(0); // vmaddr
181 Write64(VMSize); // vmsize
182 Write64(SectionDataStartOffset); // file offset
183 Write64(SectionDataSize); // file size
185 Write32(0); // vmaddr
186 Write32(VMSize); // vmsize
187 Write32(SectionDataStartOffset); // file offset
188 Write32(SectionDataSize); // file size
191 Write32(MachO::VM_PROT_READ | MachO::VM_PROT_WRITE | MachO::VM_PROT_EXECUTE);
193 Write32(MachO::VM_PROT_READ | MachO::VM_PROT_WRITE | MachO::VM_PROT_EXECUTE);
194 Write32(NumSections);
197 assert(OS.tell() - Start == SegmentLoadCommandSize);
200 void MachObjectWriter::WriteSection(const MCAssembler &Asm,
201 const MCAsmLayout &Layout,
202 const MCSectionData &SD,
204 uint64_t RelocationsStart,
205 unsigned NumRelocations) {
206 uint64_t SectionSize = Layout.getSectionAddressSize(&SD);
208 // The offset is unused for virtual sections.
209 if (SD.getSection().isVirtualSection()) {
210 assert(Layout.getSectionFileSize(&SD) == 0 && "Invalid file size!");
214 // struct section (68 bytes) or
215 // struct section_64 (80 bytes)
217 uint64_t Start = OS.tell();
220 const MCSectionMachO &Section = cast<MCSectionMachO>(SD.getSection());
221 WriteBytes(Section.getSectionName(), 16);
222 WriteBytes(Section.getSegmentName(), 16);
224 Write64(getSectionAddress(&SD)); // address
225 Write64(SectionSize); // size
227 Write32(getSectionAddress(&SD)); // address
228 Write32(SectionSize); // size
232 unsigned Flags = Section.getTypeAndAttributes();
233 if (SD.hasInstructions())
234 Flags |= MachO::S_ATTR_SOME_INSTRUCTIONS;
236 assert(isPowerOf2_32(SD.getAlignment()) && "Invalid alignment!");
237 Write32(Log2_32(SD.getAlignment()));
238 Write32(NumRelocations ? RelocationsStart : 0);
239 Write32(NumRelocations);
241 Write32(IndirectSymBase.lookup(&SD)); // reserved1
242 Write32(Section.getStubSize()); // reserved2
244 Write32(0); // reserved3
246 assert(OS.tell() - Start == (is64Bit() ? sizeof(MachO::section_64) :
247 sizeof(MachO::section)));
250 void MachObjectWriter::WriteSymtabLoadCommand(uint32_t SymbolOffset,
252 uint32_t StringTableOffset,
253 uint32_t StringTableSize) {
254 // struct symtab_command (24 bytes)
256 uint64_t Start = OS.tell();
259 Write32(MachO::LC_SYMTAB);
260 Write32(sizeof(MachO::symtab_command));
261 Write32(SymbolOffset);
263 Write32(StringTableOffset);
264 Write32(StringTableSize);
266 assert(OS.tell() - Start == sizeof(MachO::symtab_command));
269 void MachObjectWriter::WriteDysymtabLoadCommand(uint32_t FirstLocalSymbol,
270 uint32_t NumLocalSymbols,
271 uint32_t FirstExternalSymbol,
272 uint32_t NumExternalSymbols,
273 uint32_t FirstUndefinedSymbol,
274 uint32_t NumUndefinedSymbols,
275 uint32_t IndirectSymbolOffset,
276 uint32_t NumIndirectSymbols) {
277 // struct dysymtab_command (80 bytes)
279 uint64_t Start = OS.tell();
282 Write32(MachO::LC_DYSYMTAB);
283 Write32(sizeof(MachO::dysymtab_command));
284 Write32(FirstLocalSymbol);
285 Write32(NumLocalSymbols);
286 Write32(FirstExternalSymbol);
287 Write32(NumExternalSymbols);
288 Write32(FirstUndefinedSymbol);
289 Write32(NumUndefinedSymbols);
290 Write32(0); // tocoff
292 Write32(0); // modtaboff
293 Write32(0); // nmodtab
294 Write32(0); // extrefsymoff
295 Write32(0); // nextrefsyms
296 Write32(IndirectSymbolOffset);
297 Write32(NumIndirectSymbols);
298 Write32(0); // extreloff
299 Write32(0); // nextrel
300 Write32(0); // locreloff
301 Write32(0); // nlocrel
303 assert(OS.tell() - Start == sizeof(MachO::dysymtab_command));
306 MachObjectWriter::MachSymbolData *
307 MachObjectWriter::findSymbolData(const MCSymbol &Sym) {
308 for (auto &Entry : LocalSymbolData)
309 if (&Entry.SymbolData->getSymbol() == &Sym)
312 for (auto &Entry : ExternalSymbolData)
313 if (&Entry.SymbolData->getSymbol() == &Sym)
316 for (auto &Entry : UndefinedSymbolData)
317 if (&Entry.SymbolData->getSymbol() == &Sym)
323 void MachObjectWriter::WriteNlist(MachSymbolData &MSD,
324 const MCAsmLayout &Layout) {
325 MCSymbolData &Data = *MSD.SymbolData;
326 const MCSymbol *Symbol = &Data.getSymbol();
327 const MCSymbol *AliasedSymbol = &Symbol->AliasedSymbol();
328 uint8_t SectionIndex = MSD.SectionIndex;
330 uint16_t Flags = Data.getFlags();
331 uint64_t Address = 0;
332 bool IsAlias = Symbol != AliasedSymbol;
334 MachSymbolData *AliaseeInfo;
336 AliaseeInfo = findSymbolData(*AliasedSymbol);
338 SectionIndex = AliaseeInfo->SectionIndex;
339 Symbol = AliasedSymbol;
342 // Set the N_TYPE bits. See <mach-o/nlist.h>.
344 // FIXME: Are the prebound or indirect fields possible here?
345 if (IsAlias && Symbol->isUndefined())
346 Type = MachO::N_INDR;
347 else if (Symbol->isUndefined())
348 Type = MachO::N_UNDF;
349 else if (Symbol->isAbsolute())
352 Type = MachO::N_SECT;
354 // FIXME: Set STAB bits.
356 if (Data.isPrivateExtern())
357 Type |= MachO::N_PEXT;
360 if (Data.isExternal() || (!IsAlias && Symbol->isUndefined()))
361 Type |= MachO::N_EXT;
363 // Compute the symbol address.
364 if (IsAlias && Symbol->isUndefined())
365 Address = AliaseeInfo->StringIndex;
366 else if (Symbol->isDefined())
367 Address = getSymbolAddress(&Data, Layout);
368 else if (Data.isCommon()) {
369 // Common symbols are encoded with the size in the address
370 // field, and their alignment in the flags.
371 Address = Data.getCommonSize();
373 // Common alignment is packed into the 'desc' bits.
374 if (unsigned Align = Data.getCommonAlignment()) {
375 unsigned Log2Size = Log2_32(Align);
376 assert((1U << Log2Size) == Align && "Invalid 'common' alignment!");
378 report_fatal_error("invalid 'common' alignment '" +
379 Twine(Align) + "' for '" + Symbol->getName() + "'",
381 // FIXME: Keep this mask with the SymbolFlags enumeration.
382 Flags = (Flags & 0xF0FF) | (Log2Size << 8);
386 if (Layout.getAssembler().isThumbFunc(Symbol))
387 Flags |= SF_ThumbFunc;
389 // struct nlist (12 bytes)
391 Write32(MSD.StringIndex);
393 Write8(SectionIndex);
395 // The Mach-O streamer uses the lowest 16-bits of the flags for the 'desc'
404 void MachObjectWriter::WriteLinkeditLoadCommand(uint32_t Type,
407 uint64_t Start = OS.tell();
411 Write32(sizeof(MachO::linkedit_data_command));
415 assert(OS.tell() - Start == sizeof(MachO::linkedit_data_command));
418 static unsigned ComputeLinkerOptionsLoadCommandSize(
419 const std::vector<std::string> &Options, bool is64Bit)
421 unsigned Size = sizeof(MachO::linker_options_command);
422 for (unsigned i = 0, e = Options.size(); i != e; ++i)
423 Size += Options[i].size() + 1;
424 return RoundUpToAlignment(Size, is64Bit ? 8 : 4);
427 void MachObjectWriter::WriteLinkerOptionsLoadCommand(
428 const std::vector<std::string> &Options)
430 unsigned Size = ComputeLinkerOptionsLoadCommandSize(Options, is64Bit());
431 uint64_t Start = OS.tell();
434 Write32(MachO::LC_LINKER_OPTIONS);
436 Write32(Options.size());
437 uint64_t BytesWritten = sizeof(MachO::linker_options_command);
438 for (unsigned i = 0, e = Options.size(); i != e; ++i) {
439 // Write each string, including the null byte.
440 const std::string &Option = Options[i];
441 WriteBytes(Option.c_str(), Option.size() + 1);
442 BytesWritten += Option.size() + 1;
445 // Pad to a multiple of the pointer size.
446 WriteBytes("", OffsetToAlignment(BytesWritten, is64Bit() ? 8 : 4));
448 assert(OS.tell() - Start == Size);
452 void MachObjectWriter::RecordRelocation(const MCAssembler &Asm,
453 const MCAsmLayout &Layout,
454 const MCFragment *Fragment,
455 const MCFixup &Fixup,
458 uint64_t &FixedValue) {
459 TargetObjectWriter->RecordRelocation(this, Asm, Layout, Fragment, Fixup,
463 void MachObjectWriter::BindIndirectSymbols(MCAssembler &Asm) {
464 // This is the point where 'as' creates actual symbols for indirect symbols
465 // (in the following two passes). It would be easier for us to do this sooner
466 // when we see the attribute, but that makes getting the order in the symbol
467 // table much more complicated than it is worth.
469 // FIXME: Revisit this when the dust settles.
471 // Report errors for use of .indirect_symbol not in a symbol pointer section
473 for (MCAssembler::indirect_symbol_iterator it = Asm.indirect_symbol_begin(),
474 ie = Asm.indirect_symbol_end(); it != ie; ++it) {
475 const MCSectionMachO &Section =
476 cast<MCSectionMachO>(it->SectionData->getSection());
478 if (Section.getType() != MachO::S_NON_LAZY_SYMBOL_POINTERS &&
479 Section.getType() != MachO::S_LAZY_SYMBOL_POINTERS &&
480 Section.getType() != MachO::S_SYMBOL_STUBS) {
481 MCSymbol &Symbol = *it->Symbol;
482 report_fatal_error("indirect symbol '" + Symbol.getName() +
483 "' not in a symbol pointer or stub section");
487 // Bind non-lazy symbol pointers first.
488 unsigned IndirectIndex = 0;
489 for (MCAssembler::indirect_symbol_iterator it = Asm.indirect_symbol_begin(),
490 ie = Asm.indirect_symbol_end(); it != ie; ++it, ++IndirectIndex) {
491 const MCSectionMachO &Section =
492 cast<MCSectionMachO>(it->SectionData->getSection());
494 if (Section.getType() != MachO::S_NON_LAZY_SYMBOL_POINTERS)
497 // Initialize the section indirect symbol base, if necessary.
498 IndirectSymBase.insert(std::make_pair(it->SectionData, IndirectIndex));
500 Asm.getOrCreateSymbolData(*it->Symbol);
503 // Then lazy symbol pointers and symbol stubs.
505 for (MCAssembler::indirect_symbol_iterator it = Asm.indirect_symbol_begin(),
506 ie = Asm.indirect_symbol_end(); it != ie; ++it, ++IndirectIndex) {
507 const MCSectionMachO &Section =
508 cast<MCSectionMachO>(it->SectionData->getSection());
510 if (Section.getType() != MachO::S_LAZY_SYMBOL_POINTERS &&
511 Section.getType() != MachO::S_SYMBOL_STUBS)
514 // Initialize the section indirect symbol base, if necessary.
515 IndirectSymBase.insert(std::make_pair(it->SectionData, IndirectIndex));
517 // Set the symbol type to undefined lazy, but only on construction.
519 // FIXME: Do not hardcode.
521 MCSymbolData &Entry = Asm.getOrCreateSymbolData(*it->Symbol, &Created);
523 Entry.setFlags(Entry.getFlags() | 0x0001);
527 /// ComputeSymbolTable - Compute the symbol table data
528 void MachObjectWriter::ComputeSymbolTable(
529 MCAssembler &Asm, std::vector<MachSymbolData> &LocalSymbolData,
530 std::vector<MachSymbolData> &ExternalSymbolData,
531 std::vector<MachSymbolData> &UndefinedSymbolData) {
532 // Build section lookup table.
533 DenseMap<const MCSection*, uint8_t> SectionIndexMap;
535 for (MCAssembler::iterator it = Asm.begin(),
536 ie = Asm.end(); it != ie; ++it, ++Index)
537 SectionIndexMap[&it->getSection()] = Index;
538 assert(Index <= 256 && "Too many sections!");
540 // Build the string table.
541 for (MCSymbolData &SD : Asm.symbols()) {
542 const MCSymbol &Symbol = SD.getSymbol();
543 if (!Asm.isSymbolLinkerVisible(Symbol))
546 StringTable.add(Symbol.getName());
548 StringTable.finalize(StringTableBuilder::MachO);
550 // Build the symbol arrays but only for non-local symbols.
552 // The particular order that we collect and then sort the symbols is chosen to
553 // match 'as'. Even though it doesn't matter for correctness, this is
554 // important for letting us diff .o files.
555 for (MCSymbolData &SD : Asm.symbols()) {
556 const MCSymbol &Symbol = SD.getSymbol();
558 // Ignore non-linker visible symbols.
559 if (!Asm.isSymbolLinkerVisible(Symbol))
562 if (!SD.isExternal() && !Symbol.isUndefined())
566 MSD.SymbolData = &SD;
567 MSD.StringIndex = StringTable.getOffset(Symbol.getName());
569 if (Symbol.isUndefined()) {
570 MSD.SectionIndex = 0;
571 UndefinedSymbolData.push_back(MSD);
572 } else if (Symbol.isAbsolute()) {
573 MSD.SectionIndex = 0;
574 ExternalSymbolData.push_back(MSD);
576 MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
577 assert(MSD.SectionIndex && "Invalid section index!");
578 ExternalSymbolData.push_back(MSD);
582 // Now add the data for local symbols.
583 for (MCSymbolData &SD : Asm.symbols()) {
584 const MCSymbol &Symbol = SD.getSymbol();
586 // Ignore non-linker visible symbols.
587 if (!Asm.isSymbolLinkerVisible(Symbol))
590 if (SD.isExternal() || Symbol.isUndefined())
594 MSD.SymbolData = &SD;
595 MSD.StringIndex = StringTable.getOffset(Symbol.getName());
597 if (Symbol.isAbsolute()) {
598 MSD.SectionIndex = 0;
599 LocalSymbolData.push_back(MSD);
601 MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
602 assert(MSD.SectionIndex && "Invalid section index!");
603 LocalSymbolData.push_back(MSD);
607 // External and undefined symbols are required to be in lexicographic order.
608 std::sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
609 std::sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end());
611 // Set the symbol indices.
613 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
614 LocalSymbolData[i].SymbolData->setIndex(Index++);
615 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
616 ExternalSymbolData[i].SymbolData->setIndex(Index++);
617 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
618 UndefinedSymbolData[i].SymbolData->setIndex(Index++);
621 void MachObjectWriter::computeSectionAddresses(const MCAssembler &Asm,
622 const MCAsmLayout &Layout) {
623 uint64_t StartAddress = 0;
624 const SmallVectorImpl<MCSectionData*> &Order = Layout.getSectionOrder();
625 for (int i = 0, n = Order.size(); i != n ; ++i) {
626 const MCSectionData *SD = Order[i];
627 StartAddress = RoundUpToAlignment(StartAddress, SD->getAlignment());
628 SectionAddress[SD] = StartAddress;
629 StartAddress += Layout.getSectionAddressSize(SD);
631 // Explicitly pad the section to match the alignment requirements of the
632 // following one. This is for 'gas' compatibility, it shouldn't
633 /// strictly be necessary.
634 StartAddress += getPaddingSize(SD, Layout);
638 void MachObjectWriter::markAbsoluteVariableSymbols(MCAssembler &Asm,
639 const MCAsmLayout &Layout) {
640 for (MCSymbolData &SD : Asm.symbols()) {
641 if (!SD.getSymbol().isVariable())
644 // Is the variable is a symbol difference (SA - SB + C) expression,
645 // and neither symbol is external, mark the variable as absolute.
646 const MCExpr *Expr = SD.getSymbol().getVariableValue();
648 if (Expr->EvaluateAsRelocatable(Value, &Layout, nullptr)) {
649 if (Value.getSymA() && Value.getSymB())
650 const_cast<MCSymbol*>(&SD.getSymbol())->setAbsolute();
655 void MachObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm,
656 const MCAsmLayout &Layout) {
657 computeSectionAddresses(Asm, Layout);
659 // Create symbol data for any indirect symbols.
660 BindIndirectSymbols(Asm);
662 // Mark symbol difference expressions in variables (from .set or = directives)
664 markAbsoluteVariableSymbols(Asm, Layout);
666 // Compute symbol table information and bind symbol indices.
667 ComputeSymbolTable(Asm, LocalSymbolData, ExternalSymbolData,
668 UndefinedSymbolData);
671 bool MachObjectWriter::
672 IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
673 const MCSymbolData &DataA,
674 const MCFragment &FB,
676 bool IsPCRel) const {
680 // The effective address is
681 // addr(atom(A)) + offset(A)
682 // - addr(atom(B)) - offset(B)
683 // and the offsets are not relocatable, so the fixup is fully resolved when
684 // addr(atom(A)) - addr(atom(B)) == 0.
685 const MCSymbolData *A_Base = nullptr, *B_Base = nullptr;
687 const MCSymbol &SA = DataA.getSymbol().AliasedSymbol();
688 const MCSection &SecA = SA.getSection();
689 const MCSection &SecB = FB.getParent()->getSection();
692 // The simple (Darwin, except on x86_64) way of dealing with this was to
693 // assume that any reference to a temporary symbol *must* be a temporary
694 // symbol in the same atom, unless the sections differ. Therefore, any PCrel
695 // relocation to a temporary symbol (in the same section) is fully
696 // resolved. This also works in conjunction with absolutized .set, which
697 // requires the compiler to use .set to absolutize the differences between
698 // symbols which the compiler knows to be assembly time constants, so we
699 // don't need to worry about considering symbol differences fully resolved.
701 // If the file isn't using sub-sections-via-symbols, we can make the
702 // same assumptions about any symbol that we normally make about
705 bool hasReliableSymbolDifference = isX86_64();
706 if (!hasReliableSymbolDifference) {
707 if (!SA.isInSection() || &SecA != &SecB ||
708 (!SA.isTemporary() &&
709 FB.getAtom() != Asm.getSymbolData(SA).getFragment()->getAtom() &&
710 Asm.getSubsectionsViaSymbols()))
714 // For Darwin x86_64, there is one special case when the reference IsPCRel.
715 // If the fragment with the reference does not have a base symbol but meets
716 // the simple way of dealing with this, in that it is a temporary symbol in
717 // the same atom then it is assumed to be fully resolved. This is needed so
718 // a relocation entry is not created and so the static linker does not
719 // mess up the reference later.
720 else if(!FB.getAtom() &&
721 SA.isTemporary() && SA.isInSection() && &SecA == &SecB){
725 if (!TargetObjectWriter->useAggressiveSymbolFolding())
729 const MCFragment *FA = Asm.getSymbolData(SA).getFragment();
731 // Bail if the symbol has no fragment.
735 A_Base = FA->getAtom();
739 B_Base = FB.getAtom();
743 // If the atoms are the same, they are guaranteed to have the same address.
744 if (A_Base == B_Base)
747 // Otherwise, we can't prove this is fully resolved.
751 void MachObjectWriter::WriteObject(MCAssembler &Asm,
752 const MCAsmLayout &Layout) {
753 unsigned NumSections = Asm.size();
754 const MCAssembler::VersionMinInfoType &VersionInfo =
755 Layout.getAssembler().getVersionMinInfo();
757 // The section data starts after the header, the segment load command (and
758 // section headers) and the symbol table.
759 unsigned NumLoadCommands = 1;
760 uint64_t LoadCommandsSize = is64Bit() ?
761 sizeof(MachO::segment_command_64) + NumSections * sizeof(MachO::section_64):
762 sizeof(MachO::segment_command) + NumSections * sizeof(MachO::section);
764 // Add the deployment target version info load command size, if used.
765 if (VersionInfo.Major != 0) {
767 LoadCommandsSize += sizeof(MachO::version_min_command);
770 // Add the data-in-code load command size, if used.
771 unsigned NumDataRegions = Asm.getDataRegions().size();
772 if (NumDataRegions) {
774 LoadCommandsSize += sizeof(MachO::linkedit_data_command);
777 // Add the loh load command size, if used.
778 uint64_t LOHRawSize = Asm.getLOHContainer().getEmitSize(*this, Layout);
779 uint64_t LOHSize = RoundUpToAlignment(LOHRawSize, is64Bit() ? 8 : 4);
782 LoadCommandsSize += sizeof(MachO::linkedit_data_command);
785 // Add the symbol table load command sizes, if used.
786 unsigned NumSymbols = LocalSymbolData.size() + ExternalSymbolData.size() +
787 UndefinedSymbolData.size();
789 NumLoadCommands += 2;
790 LoadCommandsSize += (sizeof(MachO::symtab_command) +
791 sizeof(MachO::dysymtab_command));
794 // Add the linker option load commands sizes.
795 const std::vector<std::vector<std::string> > &LinkerOptions =
796 Asm.getLinkerOptions();
797 for (unsigned i = 0, e = LinkerOptions.size(); i != e; ++i) {
799 LoadCommandsSize += ComputeLinkerOptionsLoadCommandSize(LinkerOptions[i],
803 // Compute the total size of the section data, as well as its file size and vm
805 uint64_t SectionDataStart = (is64Bit() ? sizeof(MachO::mach_header_64) :
806 sizeof(MachO::mach_header)) + LoadCommandsSize;
807 uint64_t SectionDataSize = 0;
808 uint64_t SectionDataFileSize = 0;
810 for (MCAssembler::const_iterator it = Asm.begin(),
811 ie = Asm.end(); it != ie; ++it) {
812 const MCSectionData &SD = *it;
813 uint64_t Address = getSectionAddress(&SD);
814 uint64_t Size = Layout.getSectionAddressSize(&SD);
815 uint64_t FileSize = Layout.getSectionFileSize(&SD);
816 FileSize += getPaddingSize(&SD, Layout);
818 VMSize = std::max(VMSize, Address + Size);
820 if (SD.getSection().isVirtualSection())
823 SectionDataSize = std::max(SectionDataSize, Address + Size);
824 SectionDataFileSize = std::max(SectionDataFileSize, Address + FileSize);
827 // The section data is padded to 4 bytes.
829 // FIXME: Is this machine dependent?
830 unsigned SectionDataPadding = OffsetToAlignment(SectionDataFileSize, 4);
831 SectionDataFileSize += SectionDataPadding;
833 // Write the prolog, starting with the header and load command...
834 WriteHeader(NumLoadCommands, LoadCommandsSize,
835 Asm.getSubsectionsViaSymbols());
836 WriteSegmentLoadCommand(NumSections, VMSize,
837 SectionDataStart, SectionDataSize);
839 // ... and then the section headers.
840 uint64_t RelocTableEnd = SectionDataStart + SectionDataFileSize;
841 for (MCAssembler::const_iterator it = Asm.begin(),
842 ie = Asm.end(); it != ie; ++it) {
843 std::vector<MachO::any_relocation_info> &Relocs = Relocations[it];
844 unsigned NumRelocs = Relocs.size();
845 uint64_t SectionStart = SectionDataStart + getSectionAddress(it);
846 WriteSection(Asm, Layout, *it, SectionStart, RelocTableEnd, NumRelocs);
847 RelocTableEnd += NumRelocs * sizeof(MachO::any_relocation_info);
850 // Write out the deployment target information, if it's available.
851 if (VersionInfo.Major != 0) {
852 assert(VersionInfo.Update < 256 && "unencodable update target version");
853 assert(VersionInfo.Minor < 256 && "unencodable minor target version");
854 assert(VersionInfo.Major < 65536 && "unencodable major target version");
855 uint32_t EncodedVersion = VersionInfo.Update | (VersionInfo.Minor << 8) |
856 (VersionInfo.Major << 16);
857 Write32(VersionInfo.Kind == MCVM_OSXVersionMin ? MachO::LC_VERSION_MIN_MACOSX :
858 MachO::LC_VERSION_MIN_IPHONEOS);
859 Write32(sizeof(MachO::version_min_command));
860 Write32(EncodedVersion);
861 Write32(0); // reserved.
864 // Write the data-in-code load command, if used.
865 uint64_t DataInCodeTableEnd = RelocTableEnd + NumDataRegions * 8;
866 if (NumDataRegions) {
867 uint64_t DataRegionsOffset = RelocTableEnd;
868 uint64_t DataRegionsSize = NumDataRegions * 8;
869 WriteLinkeditLoadCommand(MachO::LC_DATA_IN_CODE, DataRegionsOffset,
873 // Write the loh load command, if used.
874 uint64_t LOHTableEnd = DataInCodeTableEnd + LOHSize;
876 WriteLinkeditLoadCommand(MachO::LC_LINKER_OPTIMIZATION_HINT,
877 DataInCodeTableEnd, LOHSize);
879 // Write the symbol table load command, if used.
881 unsigned FirstLocalSymbol = 0;
882 unsigned NumLocalSymbols = LocalSymbolData.size();
883 unsigned FirstExternalSymbol = FirstLocalSymbol + NumLocalSymbols;
884 unsigned NumExternalSymbols = ExternalSymbolData.size();
885 unsigned FirstUndefinedSymbol = FirstExternalSymbol + NumExternalSymbols;
886 unsigned NumUndefinedSymbols = UndefinedSymbolData.size();
887 unsigned NumIndirectSymbols = Asm.indirect_symbol_size();
888 unsigned NumSymTabSymbols =
889 NumLocalSymbols + NumExternalSymbols + NumUndefinedSymbols;
890 uint64_t IndirectSymbolSize = NumIndirectSymbols * 4;
891 uint64_t IndirectSymbolOffset = 0;
893 // If used, the indirect symbols are written after the section data.
894 if (NumIndirectSymbols)
895 IndirectSymbolOffset = LOHTableEnd;
897 // The symbol table is written after the indirect symbol data.
898 uint64_t SymbolTableOffset = LOHTableEnd + IndirectSymbolSize;
900 // The string table is written after symbol table.
901 uint64_t StringTableOffset =
902 SymbolTableOffset + NumSymTabSymbols * (is64Bit() ?
903 sizeof(MachO::nlist_64) :
904 sizeof(MachO::nlist));
905 WriteSymtabLoadCommand(SymbolTableOffset, NumSymTabSymbols,
906 StringTableOffset, StringTable.data().size());
908 WriteDysymtabLoadCommand(FirstLocalSymbol, NumLocalSymbols,
909 FirstExternalSymbol, NumExternalSymbols,
910 FirstUndefinedSymbol, NumUndefinedSymbols,
911 IndirectSymbolOffset, NumIndirectSymbols);
914 // Write the linker options load commands.
915 for (unsigned i = 0, e = LinkerOptions.size(); i != e; ++i) {
916 WriteLinkerOptionsLoadCommand(LinkerOptions[i]);
919 // Write the actual section data.
920 for (MCAssembler::const_iterator it = Asm.begin(),
921 ie = Asm.end(); it != ie; ++it) {
922 Asm.writeSectionData(it, Layout);
924 uint64_t Pad = getPaddingSize(it, Layout);
925 for (unsigned int i = 0; i < Pad; ++i)
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<MachO::any_relocation_info> &Relocs = Relocations[it];
938 for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
939 Write32(Relocs[e - i - 1].r_word0);
940 Write32(Relocs[e - i - 1].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,
1018 bool IsLittleEndian) {
1019 return new MachObjectWriter(MOTW, OS, IsLittleEndian);