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::doesSymbolRequireExternRelocation(const MCSymbol &S) {
43 // Undefined symbols are always extern.
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 (S.getFlags() & SF_WeakDefinition)
52 // Otherwise, we can use an internal relocation.
56 bool MachObjectWriter::
57 MachSymbolData::operator<(const MachSymbolData &RHS) const {
58 return Symbol->getName() < RHS.Symbol->getName();
61 bool MachObjectWriter::isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind) {
62 const MCFixupKindInfo &FKI = Asm.getBackend().getFixupKindInfo(
65 return FKI.Flags & MCFixupKindInfo::FKF_IsPCRel;
68 uint64_t MachObjectWriter::getFragmentAddress(const MCFragment *Fragment,
69 const MCAsmLayout &Layout) const {
70 return getSectionAddress(Fragment->getParent()) +
71 Layout.getFragmentOffset(Fragment);
74 uint64_t MachObjectWriter::getSymbolAddress(const MCSymbol &S,
75 const MCAsmLayout &Layout) const {
76 // If this is a variable, then recursively evaluate now.
78 if (const MCConstantExpr *C =
79 dyn_cast<const MCConstantExpr>(S.getVariableValue()))
84 if (!S.getVariableValue()->evaluateAsRelocatable(Target, &Layout, nullptr))
85 report_fatal_error("unable to evaluate offset for variable '" +
88 // Verify that any used symbols are defined.
89 if (Target.getSymA() && Target.getSymA()->getSymbol().isUndefined())
90 report_fatal_error("unable to evaluate offset to undefined symbol '" +
91 Target.getSymA()->getSymbol().getName() + "'");
92 if (Target.getSymB() && Target.getSymB()->getSymbol().isUndefined())
93 report_fatal_error("unable to evaluate offset to undefined symbol '" +
94 Target.getSymB()->getSymbol().getName() + "'");
96 uint64_t Address = Target.getConstant();
98 Address += getSymbolAddress(Target.getSymA()->getSymbol(), Layout);
100 Address += getSymbolAddress(Target.getSymB()->getSymbol(), Layout);
104 return getSectionAddress(S.getFragment()->getParent()) +
105 Layout.getSymbolOffset(S);
108 uint64_t MachObjectWriter::getPaddingSize(const MCSection *Sec,
109 const MCAsmLayout &Layout) const {
110 uint64_t EndAddr = getSectionAddress(Sec) + Layout.getSectionAddressSize(Sec);
111 unsigned Next = Sec->getLayoutOrder() + 1;
112 if (Next >= Layout.getSectionOrder().size())
115 const MCSection &NextSec = *Layout.getSectionOrder()[Next];
116 if (NextSec.isVirtualSection())
118 return OffsetToAlignment(EndAddr, NextSec.getAlignment());
121 void MachObjectWriter::WriteHeader(unsigned NumLoadCommands,
122 unsigned LoadCommandsSize,
123 bool SubsectionsViaSymbols) {
126 if (SubsectionsViaSymbols)
127 Flags |= MachO::MH_SUBSECTIONS_VIA_SYMBOLS;
129 // struct mach_header (28 bytes) or
130 // struct mach_header_64 (32 bytes)
132 uint64_t Start = OS.tell();
135 Write32(is64Bit() ? MachO::MH_MAGIC_64 : MachO::MH_MAGIC);
137 Write32(TargetObjectWriter->getCPUType());
138 Write32(TargetObjectWriter->getCPUSubtype());
140 Write32(MachO::MH_OBJECT);
141 Write32(NumLoadCommands);
142 Write32(LoadCommandsSize);
145 Write32(0); // reserved
147 assert(OS.tell() - Start ==
148 (is64Bit()?sizeof(MachO::mach_header_64): sizeof(MachO::mach_header)));
151 /// WriteSegmentLoadCommand - Write a segment load command.
153 /// \param NumSections The number of sections in this segment.
154 /// \param SectionDataSize The total size of the sections.
155 void MachObjectWriter::WriteSegmentLoadCommand(unsigned NumSections,
157 uint64_t SectionDataStartOffset,
158 uint64_t SectionDataSize) {
159 // struct segment_command (56 bytes) or
160 // struct segment_command_64 (72 bytes)
162 uint64_t Start = OS.tell();
165 unsigned SegmentLoadCommandSize =
166 is64Bit() ? sizeof(MachO::segment_command_64):
167 sizeof(MachO::segment_command);
168 Write32(is64Bit() ? MachO::LC_SEGMENT_64 : MachO::LC_SEGMENT);
169 Write32(SegmentLoadCommandSize +
170 NumSections * (is64Bit() ? sizeof(MachO::section_64) :
171 sizeof(MachO::section)));
175 Write64(0); // vmaddr
176 Write64(VMSize); // vmsize
177 Write64(SectionDataStartOffset); // file offset
178 Write64(SectionDataSize); // file size
180 Write32(0); // vmaddr
181 Write32(VMSize); // vmsize
182 Write32(SectionDataStartOffset); // file offset
183 Write32(SectionDataSize); // file size
186 Write32(MachO::VM_PROT_READ | MachO::VM_PROT_WRITE | MachO::VM_PROT_EXECUTE);
188 Write32(MachO::VM_PROT_READ | MachO::VM_PROT_WRITE | MachO::VM_PROT_EXECUTE);
189 Write32(NumSections);
192 assert(OS.tell() - Start == SegmentLoadCommandSize);
195 void MachObjectWriter::WriteSection(const MCAssembler &Asm,
196 const MCAsmLayout &Layout,
197 const MCSection &Sec, uint64_t FileOffset,
198 uint64_t RelocationsStart,
199 unsigned NumRelocations) {
200 uint64_t SectionSize = Layout.getSectionAddressSize(&Sec);
201 const MCSectionMachO &Section = cast<MCSectionMachO>(Sec);
203 // The offset is unused for virtual sections.
204 if (Section.isVirtualSection()) {
205 assert(Layout.getSectionFileSize(&Sec) == 0 && "Invalid file size!");
209 // struct section (68 bytes) or
210 // struct section_64 (80 bytes)
212 uint64_t Start = OS.tell();
215 WriteBytes(Section.getSectionName(), 16);
216 WriteBytes(Section.getSegmentName(), 16);
218 Write64(getSectionAddress(&Sec)); // address
219 Write64(SectionSize); // size
221 Write32(getSectionAddress(&Sec)); // address
222 Write32(SectionSize); // size
226 unsigned Flags = Section.getTypeAndAttributes();
227 if (Section.hasInstructions())
228 Flags |= MachO::S_ATTR_SOME_INSTRUCTIONS;
230 assert(isPowerOf2_32(Section.getAlignment()) && "Invalid alignment!");
231 Write32(Log2_32(Section.getAlignment()));
232 Write32(NumRelocations ? RelocationsStart : 0);
233 Write32(NumRelocations);
235 Write32(IndirectSymBase.lookup(&Sec)); // reserved1
236 Write32(Section.getStubSize()); // reserved2
238 Write32(0); // reserved3
240 assert(OS.tell() - Start == (is64Bit() ? sizeof(MachO::section_64) :
241 sizeof(MachO::section)));
244 void MachObjectWriter::WriteSymtabLoadCommand(uint32_t SymbolOffset,
246 uint32_t StringTableOffset,
247 uint32_t StringTableSize) {
248 // struct symtab_command (24 bytes)
250 uint64_t Start = OS.tell();
253 Write32(MachO::LC_SYMTAB);
254 Write32(sizeof(MachO::symtab_command));
255 Write32(SymbolOffset);
257 Write32(StringTableOffset);
258 Write32(StringTableSize);
260 assert(OS.tell() - Start == sizeof(MachO::symtab_command));
263 void MachObjectWriter::WriteDysymtabLoadCommand(uint32_t FirstLocalSymbol,
264 uint32_t NumLocalSymbols,
265 uint32_t FirstExternalSymbol,
266 uint32_t NumExternalSymbols,
267 uint32_t FirstUndefinedSymbol,
268 uint32_t NumUndefinedSymbols,
269 uint32_t IndirectSymbolOffset,
270 uint32_t NumIndirectSymbols) {
271 // struct dysymtab_command (80 bytes)
273 uint64_t Start = OS.tell();
276 Write32(MachO::LC_DYSYMTAB);
277 Write32(sizeof(MachO::dysymtab_command));
278 Write32(FirstLocalSymbol);
279 Write32(NumLocalSymbols);
280 Write32(FirstExternalSymbol);
281 Write32(NumExternalSymbols);
282 Write32(FirstUndefinedSymbol);
283 Write32(NumUndefinedSymbols);
284 Write32(0); // tocoff
286 Write32(0); // modtaboff
287 Write32(0); // nmodtab
288 Write32(0); // extrefsymoff
289 Write32(0); // nextrefsyms
290 Write32(IndirectSymbolOffset);
291 Write32(NumIndirectSymbols);
292 Write32(0); // extreloff
293 Write32(0); // nextrel
294 Write32(0); // locreloff
295 Write32(0); // nlocrel
297 assert(OS.tell() - Start == sizeof(MachO::dysymtab_command));
300 MachObjectWriter::MachSymbolData *
301 MachObjectWriter::findSymbolData(const MCSymbol &Sym) {
302 for (auto &Entry : LocalSymbolData)
303 if (Entry.Symbol == &Sym)
306 for (auto &Entry : ExternalSymbolData)
307 if (Entry.Symbol == &Sym)
310 for (auto &Entry : UndefinedSymbolData)
311 if (Entry.Symbol == &Sym)
317 const MCSymbol &MachObjectWriter::findAliasedSymbol(const MCSymbol &Sym) const {
318 const MCSymbol *S = &Sym;
319 while (S->isVariable()) {
320 const MCExpr *Value = S->getVariableValue();
321 const auto *Ref = dyn_cast<MCSymbolRefExpr>(Value);
324 S = &Ref->getSymbol();
329 void MachObjectWriter::WriteNlist(MachSymbolData &MSD,
330 const MCAsmLayout &Layout) {
331 const MCSymbol *Symbol = MSD.Symbol;
332 const MCSymbol &Data = *Symbol;
333 const MCSymbol *AliasedSymbol = &findAliasedSymbol(*Symbol);
334 uint8_t SectionIndex = MSD.SectionIndex;
336 uint16_t Flags = Symbol->getFlags();
337 uint64_t Address = 0;
338 bool IsAlias = Symbol != AliasedSymbol;
340 const MCSymbol &OrigSymbol = *Symbol;
341 MachSymbolData *AliaseeInfo;
343 AliaseeInfo = findSymbolData(*AliasedSymbol);
345 SectionIndex = AliaseeInfo->SectionIndex;
346 Symbol = AliasedSymbol;
347 // FIXME: Should this update Data as well? Do we need OrigSymbol at all?
350 // Set the N_TYPE bits. See <mach-o/nlist.h>.
352 // FIXME: Are the prebound or indirect fields possible here?
353 if (IsAlias && Symbol->isUndefined())
354 Type = MachO::N_INDR;
355 else if (Symbol->isUndefined())
356 Type = MachO::N_UNDF;
357 else if (Symbol->isAbsolute())
360 Type = MachO::N_SECT;
362 // FIXME: Set STAB bits.
364 if (Data.isPrivateExtern())
365 Type |= MachO::N_PEXT;
368 if (Data.isExternal() || (!IsAlias && Symbol->isUndefined()))
369 Type |= MachO::N_EXT;
371 // Compute the symbol address.
372 if (IsAlias && Symbol->isUndefined())
373 Address = AliaseeInfo->StringIndex;
374 else if (Symbol->isDefined())
375 Address = getSymbolAddress(OrigSymbol, Layout);
376 else if (Symbol->isCommon()) {
377 // Common symbols are encoded with the size in the address
378 // field, and their alignment in the flags.
379 Address = Symbol->getCommonSize();
381 // Common alignment is packed into the 'desc' bits.
382 if (unsigned Align = Symbol->getCommonAlignment()) {
383 unsigned Log2Size = Log2_32(Align);
384 assert((1U << Log2Size) == Align && "Invalid 'common' alignment!");
386 report_fatal_error("invalid 'common' alignment '" +
387 Twine(Align) + "' for '" + Symbol->getName() + "'",
389 // FIXME: Keep this mask with the SymbolFlags enumeration.
390 Flags = (Flags & 0xF0FF) | (Log2Size << 8);
394 if (Layout.getAssembler().isThumbFunc(Symbol))
395 Flags |= SF_ThumbFunc;
397 // struct nlist (12 bytes)
399 Write32(MSD.StringIndex);
401 Write8(SectionIndex);
403 // The Mach-O streamer uses the lowest 16-bits of the flags for the 'desc'
412 void MachObjectWriter::WriteLinkeditLoadCommand(uint32_t Type,
415 uint64_t Start = OS.tell();
419 Write32(sizeof(MachO::linkedit_data_command));
423 assert(OS.tell() - Start == sizeof(MachO::linkedit_data_command));
426 static unsigned ComputeLinkerOptionsLoadCommandSize(
427 const std::vector<std::string> &Options, bool is64Bit)
429 unsigned Size = sizeof(MachO::linker_option_command);
430 for (unsigned i = 0, e = Options.size(); i != e; ++i)
431 Size += Options[i].size() + 1;
432 return RoundUpToAlignment(Size, is64Bit ? 8 : 4);
435 void MachObjectWriter::WriteLinkerOptionsLoadCommand(
436 const std::vector<std::string> &Options)
438 unsigned Size = ComputeLinkerOptionsLoadCommandSize(Options, is64Bit());
439 uint64_t Start = OS.tell();
442 Write32(MachO::LC_LINKER_OPTION);
444 Write32(Options.size());
445 uint64_t BytesWritten = sizeof(MachO::linker_option_command);
446 for (unsigned i = 0, e = Options.size(); i != e; ++i) {
447 // Write each string, including the null byte.
448 const std::string &Option = Options[i];
449 WriteBytes(Option.c_str(), Option.size() + 1);
450 BytesWritten += Option.size() + 1;
453 // Pad to a multiple of the pointer size.
454 WriteBytes("", OffsetToAlignment(BytesWritten, is64Bit() ? 8 : 4));
456 assert(OS.tell() - Start == Size);
459 void MachObjectWriter::RecordRelocation(MCAssembler &Asm,
460 const MCAsmLayout &Layout,
461 const MCFragment *Fragment,
462 const MCFixup &Fixup, MCValue Target,
463 bool &IsPCRel, uint64_t &FixedValue) {
464 TargetObjectWriter->RecordRelocation(this, Asm, Layout, Fragment, Fixup,
468 void MachObjectWriter::BindIndirectSymbols(MCAssembler &Asm) {
469 // This is the point where 'as' creates actual symbols for indirect symbols
470 // (in the following two passes). It would be easier for us to do this sooner
471 // when we see the attribute, but that makes getting the order in the symbol
472 // table much more complicated than it is worth.
474 // FIXME: Revisit this when the dust settles.
476 // Report errors for use of .indirect_symbol not in a symbol pointer section
478 for (MCAssembler::indirect_symbol_iterator it = Asm.indirect_symbol_begin(),
479 ie = Asm.indirect_symbol_end(); it != ie; ++it) {
480 const MCSectionMachO &Section = cast<MCSectionMachO>(*it->Section);
482 if (Section.getType() != MachO::S_NON_LAZY_SYMBOL_POINTERS &&
483 Section.getType() != MachO::S_LAZY_SYMBOL_POINTERS &&
484 Section.getType() != MachO::S_SYMBOL_STUBS) {
485 MCSymbol &Symbol = *it->Symbol;
486 report_fatal_error("indirect symbol '" + Symbol.getName() +
487 "' not in a symbol pointer or stub section");
491 // Bind non-lazy symbol pointers first.
492 unsigned IndirectIndex = 0;
493 for (MCAssembler::indirect_symbol_iterator it = Asm.indirect_symbol_begin(),
494 ie = Asm.indirect_symbol_end(); it != ie; ++it, ++IndirectIndex) {
495 const MCSectionMachO &Section = cast<MCSectionMachO>(*it->Section);
497 if (Section.getType() != MachO::S_NON_LAZY_SYMBOL_POINTERS)
500 // Initialize the section indirect symbol base, if necessary.
501 IndirectSymBase.insert(std::make_pair(it->Section, IndirectIndex));
503 Asm.registerSymbol(*it->Symbol);
506 // Then lazy symbol pointers and symbol stubs.
508 for (MCAssembler::indirect_symbol_iterator it = Asm.indirect_symbol_begin(),
509 ie = Asm.indirect_symbol_end(); it != ie; ++it, ++IndirectIndex) {
510 const MCSectionMachO &Section = cast<MCSectionMachO>(*it->Section);
512 if (Section.getType() != MachO::S_LAZY_SYMBOL_POINTERS &&
513 Section.getType() != MachO::S_SYMBOL_STUBS)
516 // Initialize the section indirect symbol base, if necessary.
517 IndirectSymBase.insert(std::make_pair(it->Section, IndirectIndex));
519 // Set the symbol type to undefined lazy, but only on construction.
521 // FIXME: Do not hardcode.
523 Asm.registerSymbol(*it->Symbol, &Created);
525 it->Symbol->setFlags(it->Symbol->getFlags() | 0x0001);
529 /// ComputeSymbolTable - Compute the symbol table data
530 void MachObjectWriter::ComputeSymbolTable(
531 MCAssembler &Asm, std::vector<MachSymbolData> &LocalSymbolData,
532 std::vector<MachSymbolData> &ExternalSymbolData,
533 std::vector<MachSymbolData> &UndefinedSymbolData) {
534 // Build section lookup table.
535 DenseMap<const MCSection*, uint8_t> SectionIndexMap;
537 for (MCAssembler::iterator it = Asm.begin(),
538 ie = Asm.end(); it != ie; ++it, ++Index)
539 SectionIndexMap[&*it] = Index;
540 assert(Index <= 256 && "Too many sections!");
542 // Build the string table.
543 for (const MCSymbol &Symbol : Asm.symbols()) {
544 if (!Asm.isSymbolLinkerVisible(Symbol))
547 StringTable.add(Symbol.getName());
549 StringTable.finalize(StringTableBuilder::MachO);
551 // Build the symbol arrays but only for non-local symbols.
553 // The particular order that we collect and then sort the symbols is chosen to
554 // match 'as'. Even though it doesn't matter for correctness, this is
555 // important for letting us diff .o files.
556 for (const MCSymbol &Symbol : Asm.symbols()) {
557 // Ignore non-linker visible symbols.
558 if (!Asm.isSymbolLinkerVisible(Symbol))
561 if (!Symbol.isExternal() && !Symbol.isUndefined())
565 MSD.Symbol = &Symbol;
566 MSD.StringIndex = StringTable.getOffset(Symbol.getName());
568 if (Symbol.isUndefined()) {
569 MSD.SectionIndex = 0;
570 UndefinedSymbolData.push_back(MSD);
571 } else if (Symbol.isAbsolute()) {
572 MSD.SectionIndex = 0;
573 ExternalSymbolData.push_back(MSD);
575 MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
576 assert(MSD.SectionIndex && "Invalid section index!");
577 ExternalSymbolData.push_back(MSD);
581 // Now add the data for local symbols.
582 for (const MCSymbol &Symbol : Asm.symbols()) {
583 // Ignore non-linker visible symbols.
584 if (!Asm.isSymbolLinkerVisible(Symbol))
587 if (Symbol.isExternal() || Symbol.isUndefined())
591 MSD.Symbol = &Symbol;
592 MSD.StringIndex = StringTable.getOffset(Symbol.getName());
594 if (Symbol.isAbsolute()) {
595 MSD.SectionIndex = 0;
596 LocalSymbolData.push_back(MSD);
598 MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
599 assert(MSD.SectionIndex && "Invalid section index!");
600 LocalSymbolData.push_back(MSD);
604 // External and undefined symbols are required to be in lexicographic order.
605 std::sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
606 std::sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end());
608 // Set the symbol indices.
610 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
611 LocalSymbolData[i].Symbol->setIndex(Index++);
612 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
613 ExternalSymbolData[i].Symbol->setIndex(Index++);
614 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
615 UndefinedSymbolData[i].Symbol->setIndex(Index++);
617 for (const MCSection &Section : Asm) {
618 std::vector<RelAndSymbol> &Relocs = Relocations[&Section];
619 for (RelAndSymbol &Rel : Relocs) {
623 // Set the Index and the IsExtern bit.
624 unsigned Index = Rel.Sym->getIndex();
625 assert(isInt<24>(Index));
627 Rel.MRE.r_word1 = (Rel.MRE.r_word1 & (~0U << 24)) | Index | (1 << 27);
629 Rel.MRE.r_word1 = (Rel.MRE.r_word1 & 0xff) | Index << 8 | (1 << 4);
634 void MachObjectWriter::computeSectionAddresses(const MCAssembler &Asm,
635 const MCAsmLayout &Layout) {
636 uint64_t StartAddress = 0;
637 const SmallVectorImpl<MCSection *> &Order = Layout.getSectionOrder();
638 for (int i = 0, n = Order.size(); i != n ; ++i) {
639 const MCSection *Sec = Order[i];
640 StartAddress = RoundUpToAlignment(StartAddress, Sec->getAlignment());
641 SectionAddress[Sec] = StartAddress;
642 StartAddress += Layout.getSectionAddressSize(Sec);
644 // Explicitly pad the section to match the alignment requirements of the
645 // following one. This is for 'gas' compatibility, it shouldn't
646 /// strictly be necessary.
647 StartAddress += getPaddingSize(Sec, Layout);
651 void MachObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm,
652 const MCAsmLayout &Layout) {
653 computeSectionAddresses(Asm, Layout);
655 // Create symbol data for any indirect symbols.
656 BindIndirectSymbols(Asm);
659 bool MachObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(
660 const MCAssembler &Asm, const MCSymbol &SymA, const MCFragment &FB,
661 bool InSet, bool IsPCRel) const {
665 // The effective address is
666 // addr(atom(A)) + offset(A)
667 // - addr(atom(B)) - offset(B)
668 // and the offsets are not relocatable, so the fixup is fully resolved when
669 // addr(atom(A)) - addr(atom(B)) == 0.
670 const MCSymbol &SA = findAliasedSymbol(SymA);
671 const MCSection &SecA = SA.getSection();
672 const MCSection &SecB = *FB.getParent();
675 // The simple (Darwin, except on x86_64) way of dealing with this was to
676 // assume that any reference to a temporary symbol *must* be a temporary
677 // symbol in the same atom, unless the sections differ. Therefore, any PCrel
678 // relocation to a temporary symbol (in the same section) is fully
679 // resolved. This also works in conjunction with absolutized .set, which
680 // requires the compiler to use .set to absolutize the differences between
681 // symbols which the compiler knows to be assembly time constants, so we
682 // don't need to worry about considering symbol differences fully resolved.
684 // If the file isn't using sub-sections-via-symbols, we can make the
685 // same assumptions about any symbol that we normally make about
688 bool hasReliableSymbolDifference = isX86_64();
689 if (!hasReliableSymbolDifference) {
690 if (!SA.isInSection() || &SecA != &SecB ||
691 (!SA.isTemporary() && FB.getAtom() != SA.getFragment()->getAtom() &&
692 Asm.getSubsectionsViaSymbols()))
696 // For Darwin x86_64, there is one special case when the reference IsPCRel.
697 // If the fragment with the reference does not have a base symbol but meets
698 // the simple way of dealing with this, in that it is a temporary symbol in
699 // the same atom then it is assumed to be fully resolved. This is needed so
700 // a relocation entry is not created and so the static linker does not
701 // mess up the reference later.
702 else if(!FB.getAtom() &&
703 SA.isTemporary() && SA.isInSection() && &SecA == &SecB){
708 // If they are not in the same section, we can't compute the diff.
712 const MCFragment *FA = SA.getFragment();
714 // Bail if the symbol has no fragment.
718 // If the atoms are the same, they are guaranteed to have the same address.
719 if (FA->getAtom() == FB.getAtom())
722 // Otherwise, we can't prove this is fully resolved.
726 void MachObjectWriter::WriteObject(MCAssembler &Asm,
727 const MCAsmLayout &Layout) {
728 // Compute symbol table information and bind symbol indices.
729 ComputeSymbolTable(Asm, LocalSymbolData, ExternalSymbolData,
730 UndefinedSymbolData);
732 unsigned NumSections = Asm.size();
733 const MCAssembler::VersionMinInfoType &VersionInfo =
734 Layout.getAssembler().getVersionMinInfo();
736 // The section data starts after the header, the segment load command (and
737 // section headers) and the symbol table.
738 unsigned NumLoadCommands = 1;
739 uint64_t LoadCommandsSize = is64Bit() ?
740 sizeof(MachO::segment_command_64) + NumSections * sizeof(MachO::section_64):
741 sizeof(MachO::segment_command) + NumSections * sizeof(MachO::section);
743 // Add the deployment target version info load command size, if used.
744 if (VersionInfo.Major != 0) {
746 LoadCommandsSize += sizeof(MachO::version_min_command);
749 // Add the data-in-code load command size, if used.
750 unsigned NumDataRegions = Asm.getDataRegions().size();
751 if (NumDataRegions) {
753 LoadCommandsSize += sizeof(MachO::linkedit_data_command);
756 // Add the loh load command size, if used.
757 uint64_t LOHRawSize = Asm.getLOHContainer().getEmitSize(*this, Layout);
758 uint64_t LOHSize = RoundUpToAlignment(LOHRawSize, is64Bit() ? 8 : 4);
761 LoadCommandsSize += sizeof(MachO::linkedit_data_command);
764 // Add the symbol table load command sizes, if used.
765 unsigned NumSymbols = LocalSymbolData.size() + ExternalSymbolData.size() +
766 UndefinedSymbolData.size();
768 NumLoadCommands += 2;
769 LoadCommandsSize += (sizeof(MachO::symtab_command) +
770 sizeof(MachO::dysymtab_command));
773 // Add the linker option load commands sizes.
774 const std::vector<std::vector<std::string> > &LinkerOptions =
775 Asm.getLinkerOptions();
776 for (unsigned i = 0, e = LinkerOptions.size(); i != e; ++i) {
778 LoadCommandsSize += ComputeLinkerOptionsLoadCommandSize(LinkerOptions[i],
782 // Compute the total size of the section data, as well as its file size and vm
784 uint64_t SectionDataStart = (is64Bit() ? sizeof(MachO::mach_header_64) :
785 sizeof(MachO::mach_header)) + LoadCommandsSize;
786 uint64_t SectionDataSize = 0;
787 uint64_t SectionDataFileSize = 0;
789 for (const MCSection &Sec : Asm) {
790 uint64_t Address = getSectionAddress(&Sec);
791 uint64_t Size = Layout.getSectionAddressSize(&Sec);
792 uint64_t FileSize = Layout.getSectionFileSize(&Sec);
793 FileSize += getPaddingSize(&Sec, Layout);
795 VMSize = std::max(VMSize, Address + Size);
797 if (Sec.isVirtualSection())
800 SectionDataSize = std::max(SectionDataSize, Address + Size);
801 SectionDataFileSize = std::max(SectionDataFileSize, Address + FileSize);
804 // The section data is padded to 4 bytes.
806 // FIXME: Is this machine dependent?
807 unsigned SectionDataPadding = OffsetToAlignment(SectionDataFileSize, 4);
808 SectionDataFileSize += SectionDataPadding;
810 // Write the prolog, starting with the header and load command...
811 WriteHeader(NumLoadCommands, LoadCommandsSize,
812 Asm.getSubsectionsViaSymbols());
813 WriteSegmentLoadCommand(NumSections, VMSize,
814 SectionDataStart, SectionDataSize);
816 // ... and then the section headers.
817 uint64_t RelocTableEnd = SectionDataStart + SectionDataFileSize;
818 for (const MCSection &Sec : Asm) {
819 std::vector<RelAndSymbol> &Relocs = Relocations[&Sec];
820 unsigned NumRelocs = Relocs.size();
821 uint64_t SectionStart = SectionDataStart + getSectionAddress(&Sec);
822 WriteSection(Asm, Layout, Sec, SectionStart, RelocTableEnd, NumRelocs);
823 RelocTableEnd += NumRelocs * sizeof(MachO::any_relocation_info);
826 // Write out the deployment target information, if it's available.
827 if (VersionInfo.Major != 0) {
828 assert(VersionInfo.Update < 256 && "unencodable update target version");
829 assert(VersionInfo.Minor < 256 && "unencodable minor target version");
830 assert(VersionInfo.Major < 65536 && "unencodable major target version");
831 uint32_t EncodedVersion = VersionInfo.Update | (VersionInfo.Minor << 8) |
832 (VersionInfo.Major << 16);
833 Write32(VersionInfo.Kind == MCVM_OSXVersionMin ? MachO::LC_VERSION_MIN_MACOSX :
834 MachO::LC_VERSION_MIN_IPHONEOS);
835 Write32(sizeof(MachO::version_min_command));
836 Write32(EncodedVersion);
837 Write32(0); // reserved.
840 // Write the data-in-code load command, if used.
841 uint64_t DataInCodeTableEnd = RelocTableEnd + NumDataRegions * 8;
842 if (NumDataRegions) {
843 uint64_t DataRegionsOffset = RelocTableEnd;
844 uint64_t DataRegionsSize = NumDataRegions * 8;
845 WriteLinkeditLoadCommand(MachO::LC_DATA_IN_CODE, DataRegionsOffset,
849 // Write the loh load command, if used.
850 uint64_t LOHTableEnd = DataInCodeTableEnd + LOHSize;
852 WriteLinkeditLoadCommand(MachO::LC_LINKER_OPTIMIZATION_HINT,
853 DataInCodeTableEnd, LOHSize);
855 // Write the symbol table load command, if used.
857 unsigned FirstLocalSymbol = 0;
858 unsigned NumLocalSymbols = LocalSymbolData.size();
859 unsigned FirstExternalSymbol = FirstLocalSymbol + NumLocalSymbols;
860 unsigned NumExternalSymbols = ExternalSymbolData.size();
861 unsigned FirstUndefinedSymbol = FirstExternalSymbol + NumExternalSymbols;
862 unsigned NumUndefinedSymbols = UndefinedSymbolData.size();
863 unsigned NumIndirectSymbols = Asm.indirect_symbol_size();
864 unsigned NumSymTabSymbols =
865 NumLocalSymbols + NumExternalSymbols + NumUndefinedSymbols;
866 uint64_t IndirectSymbolSize = NumIndirectSymbols * 4;
867 uint64_t IndirectSymbolOffset = 0;
869 // If used, the indirect symbols are written after the section data.
870 if (NumIndirectSymbols)
871 IndirectSymbolOffset = LOHTableEnd;
873 // The symbol table is written after the indirect symbol data.
874 uint64_t SymbolTableOffset = LOHTableEnd + IndirectSymbolSize;
876 // The string table is written after symbol table.
877 uint64_t StringTableOffset =
878 SymbolTableOffset + NumSymTabSymbols * (is64Bit() ?
879 sizeof(MachO::nlist_64) :
880 sizeof(MachO::nlist));
881 WriteSymtabLoadCommand(SymbolTableOffset, NumSymTabSymbols,
882 StringTableOffset, StringTable.data().size());
884 WriteDysymtabLoadCommand(FirstLocalSymbol, NumLocalSymbols,
885 FirstExternalSymbol, NumExternalSymbols,
886 FirstUndefinedSymbol, NumUndefinedSymbols,
887 IndirectSymbolOffset, NumIndirectSymbols);
890 // Write the linker options load commands.
891 for (unsigned i = 0, e = LinkerOptions.size(); i != e; ++i) {
892 WriteLinkerOptionsLoadCommand(LinkerOptions[i]);
895 // Write the actual section data.
896 for (const MCSection &Sec : Asm) {
897 Asm.writeSectionData(&Sec, Layout);
899 uint64_t Pad = getPaddingSize(&Sec, Layout);
903 // Write the extra padding.
904 WriteZeros(SectionDataPadding);
906 // Write the relocation entries.
907 for (const MCSection &Sec : Asm) {
908 // Write the section relocation entries, in reverse order to match 'as'
909 // (approximately, the exact algorithm is more complicated than this).
910 std::vector<RelAndSymbol> &Relocs = Relocations[&Sec];
911 for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
912 Write32(Relocs[e - i - 1].MRE.r_word0);
913 Write32(Relocs[e - i - 1].MRE.r_word1);
917 // Write out the data-in-code region payload, if there is one.
918 for (MCAssembler::const_data_region_iterator
919 it = Asm.data_region_begin(), ie = Asm.data_region_end();
921 const DataRegionData *Data = &(*it);
922 uint64_t Start = getSymbolAddress(*Data->Start, Layout);
923 uint64_t End = getSymbolAddress(*Data->End, Layout);
924 DEBUG(dbgs() << "data in code region-- kind: " << Data->Kind
925 << " start: " << Start << "(" << Data->Start->getName() << ")"
926 << " end: " << End << "(" << Data->End->getName() << ")"
927 << " size: " << End - Start
930 Write16(End - Start);
934 // Write out the loh commands, if there is one.
937 unsigned Start = OS.tell();
939 Asm.getLOHContainer().emit(*this, Layout);
940 // Pad to a multiple of the pointer size.
941 WriteBytes("", OffsetToAlignment(LOHRawSize, is64Bit() ? 8 : 4));
942 assert(OS.tell() - Start == LOHSize);
945 // Write the symbol table data, if used.
947 // Write the indirect symbol entries.
948 for (MCAssembler::const_indirect_symbol_iterator
949 it = Asm.indirect_symbol_begin(),
950 ie = Asm.indirect_symbol_end(); it != ie; ++it) {
951 // Indirect symbols in the non-lazy symbol pointer section have some
953 const MCSectionMachO &Section =
954 static_cast<const MCSectionMachO &>(*it->Section);
955 if (Section.getType() == MachO::S_NON_LAZY_SYMBOL_POINTERS) {
956 // If this symbol is defined and internal, mark it as such.
957 if (it->Symbol->isDefined() && !it->Symbol->isExternal()) {
958 uint32_t Flags = MachO::INDIRECT_SYMBOL_LOCAL;
959 if (it->Symbol->isAbsolute())
960 Flags |= MachO::INDIRECT_SYMBOL_ABS;
966 Write32(it->Symbol->getIndex());
969 // FIXME: Check that offsets match computed ones.
971 // Write the symbol table entries.
972 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
973 WriteNlist(LocalSymbolData[i], Layout);
974 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
975 WriteNlist(ExternalSymbolData[i], Layout);
976 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
977 WriteNlist(UndefinedSymbolData[i], Layout);
979 // Write the string table.
980 OS << StringTable.data();
984 MCObjectWriter *llvm::createMachObjectWriter(MCMachObjectTargetWriter *MOTW,
985 raw_pwrite_stream &OS,
986 bool IsLittleEndian) {
987 return new MachObjectWriter(MOTW, OS, IsLittleEndian);