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/Object/MachOFormat.h"
24 #include "llvm/Support/Debug.h"
25 #include "llvm/Support/ErrorHandling.h"
28 using namespace llvm::object;
30 bool MachObjectWriter::
31 doesSymbolRequireExternRelocation(const MCSymbolData *SD) {
32 // Undefined symbols are always extern.
33 if (SD->Symbol->isUndefined())
36 // References to weak definitions require external relocation entries; the
37 // definition may not always be the one in the same object file.
38 if (SD->getFlags() & SF_WeakDefinition)
41 // Otherwise, we can use an internal relocation.
45 bool MachObjectWriter::
46 MachSymbolData::operator<(const MachSymbolData &RHS) const {
47 return SymbolData->getSymbol().getName() <
48 RHS.SymbolData->getSymbol().getName();
51 bool MachObjectWriter::isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind) {
52 const MCFixupKindInfo &FKI = Asm.getBackend().getFixupKindInfo(
55 return FKI.Flags & MCFixupKindInfo::FKF_IsPCRel;
58 uint64_t MachObjectWriter::getFragmentAddress(const MCFragment *Fragment,
59 const MCAsmLayout &Layout) const {
60 return getSectionAddress(Fragment->getParent()) +
61 Layout.getFragmentOffset(Fragment);
64 uint64_t MachObjectWriter::getSymbolAddress(const MCSymbolData* SD,
65 const MCAsmLayout &Layout) const {
66 const MCSymbol &S = SD->getSymbol();
68 // If this is a variable, then recursively evaluate now.
70 if (const MCConstantExpr *C =
71 dyn_cast<const MCConstantExpr>(S.getVariableValue()))
76 if (!S.getVariableValue()->EvaluateAsRelocatable(Target, Layout))
77 report_fatal_error("unable to evaluate offset for variable '" +
80 // Verify that any used symbols are defined.
81 if (Target.getSymA() && Target.getSymA()->getSymbol().isUndefined())
82 report_fatal_error("unable to evaluate offset to undefined symbol '" +
83 Target.getSymA()->getSymbol().getName() + "'");
84 if (Target.getSymB() && Target.getSymB()->getSymbol().isUndefined())
85 report_fatal_error("unable to evaluate offset to undefined symbol '" +
86 Target.getSymB()->getSymbol().getName() + "'");
88 uint64_t Address = Target.getConstant();
90 Address += getSymbolAddress(&Layout.getAssembler().getSymbolData(
91 Target.getSymA()->getSymbol()), Layout);
93 Address += getSymbolAddress(&Layout.getAssembler().getSymbolData(
94 Target.getSymB()->getSymbol()), Layout);
98 return getSectionAddress(SD->getFragment()->getParent()) +
99 Layout.getSymbolOffset(SD);
102 uint64_t MachObjectWriter::getPaddingSize(const MCSectionData *SD,
103 const MCAsmLayout &Layout) const {
104 uint64_t EndAddr = getSectionAddress(SD) + Layout.getSectionAddressSize(SD);
105 unsigned Next = SD->getLayoutOrder() + 1;
106 if (Next >= Layout.getSectionOrder().size())
109 const MCSectionData &NextSD = *Layout.getSectionOrder()[Next];
110 if (NextSD.getSection().isVirtualSection())
112 return OffsetToAlignment(EndAddr, NextSD.getAlignment());
115 void MachObjectWriter::WriteHeader(unsigned NumLoadCommands,
116 unsigned LoadCommandsSize,
117 bool SubsectionsViaSymbols) {
120 if (SubsectionsViaSymbols)
121 Flags |= macho::HF_SubsectionsViaSymbols;
123 // struct mach_header (28 bytes) or
124 // struct mach_header_64 (32 bytes)
126 uint64_t Start = OS.tell();
129 Write32(is64Bit() ? macho::HM_Object64 : macho::HM_Object32);
131 Write32(TargetObjectWriter->getCPUType());
132 Write32(TargetObjectWriter->getCPUSubtype());
134 Write32(macho::HFT_Object);
135 Write32(NumLoadCommands);
136 Write32(LoadCommandsSize);
139 Write32(0); // reserved
141 assert(OS.tell() - Start ==
142 (is64Bit() ? macho::Header64Size : macho::Header32Size));
145 /// WriteSegmentLoadCommand - Write a segment load command.
147 /// \param NumSections The number of sections in this segment.
148 /// \param SectionDataSize The total size of the sections.
149 void MachObjectWriter::WriteSegmentLoadCommand(unsigned NumSections,
151 uint64_t SectionDataStartOffset,
152 uint64_t SectionDataSize) {
153 // struct segment_command (56 bytes) or
154 // struct segment_command_64 (72 bytes)
156 uint64_t Start = OS.tell();
159 unsigned SegmentLoadCommandSize =
160 is64Bit() ? macho::SegmentLoadCommand64Size:
161 macho::SegmentLoadCommand32Size;
162 Write32(is64Bit() ? macho::LCT_Segment64 : macho::LCT_Segment);
163 Write32(SegmentLoadCommandSize +
164 NumSections * (is64Bit() ? macho::Section64Size :
165 macho::Section32Size));
169 Write64(0); // vmaddr
170 Write64(VMSize); // vmsize
171 Write64(SectionDataStartOffset); // file offset
172 Write64(SectionDataSize); // file size
174 Write32(0); // vmaddr
175 Write32(VMSize); // vmsize
176 Write32(SectionDataStartOffset); // file offset
177 Write32(SectionDataSize); // file size
179 Write32(0x7); // maxprot
180 Write32(0x7); // initprot
181 Write32(NumSections);
184 assert(OS.tell() - Start == SegmentLoadCommandSize);
187 void MachObjectWriter::WriteSection(const MCAssembler &Asm,
188 const MCAsmLayout &Layout,
189 const MCSectionData &SD,
191 uint64_t RelocationsStart,
192 unsigned NumRelocations) {
193 uint64_t SectionSize = Layout.getSectionAddressSize(&SD);
195 // The offset is unused for virtual sections.
196 if (SD.getSection().isVirtualSection()) {
197 assert(Layout.getSectionFileSize(&SD) == 0 && "Invalid file size!");
201 // struct section (68 bytes) or
202 // struct section_64 (80 bytes)
204 uint64_t Start = OS.tell();
207 const MCSectionMachO &Section = cast<MCSectionMachO>(SD.getSection());
208 WriteBytes(Section.getSectionName(), 16);
209 WriteBytes(Section.getSegmentName(), 16);
211 Write64(getSectionAddress(&SD)); // address
212 Write64(SectionSize); // size
214 Write32(getSectionAddress(&SD)); // address
215 Write32(SectionSize); // size
219 unsigned Flags = Section.getTypeAndAttributes();
220 if (SD.hasInstructions())
221 Flags |= MCSectionMachO::S_ATTR_SOME_INSTRUCTIONS;
223 assert(isPowerOf2_32(SD.getAlignment()) && "Invalid alignment!");
224 Write32(Log2_32(SD.getAlignment()));
225 Write32(NumRelocations ? RelocationsStart : 0);
226 Write32(NumRelocations);
228 Write32(IndirectSymBase.lookup(&SD)); // reserved1
229 Write32(Section.getStubSize()); // reserved2
231 Write32(0); // reserved3
233 assert(OS.tell() - Start == (is64Bit() ? macho::Section64Size :
234 macho::Section32Size));
237 void MachObjectWriter::WriteSymtabLoadCommand(uint32_t SymbolOffset,
239 uint32_t StringTableOffset,
240 uint32_t StringTableSize) {
241 // struct symtab_command (24 bytes)
243 uint64_t Start = OS.tell();
246 Write32(macho::LCT_Symtab);
247 Write32(macho::SymtabLoadCommandSize);
248 Write32(SymbolOffset);
250 Write32(StringTableOffset);
251 Write32(StringTableSize);
253 assert(OS.tell() - Start == macho::SymtabLoadCommandSize);
256 void MachObjectWriter::WriteDysymtabLoadCommand(uint32_t FirstLocalSymbol,
257 uint32_t NumLocalSymbols,
258 uint32_t FirstExternalSymbol,
259 uint32_t NumExternalSymbols,
260 uint32_t FirstUndefinedSymbol,
261 uint32_t NumUndefinedSymbols,
262 uint32_t IndirectSymbolOffset,
263 uint32_t NumIndirectSymbols) {
264 // struct dysymtab_command (80 bytes)
266 uint64_t Start = OS.tell();
269 Write32(macho::LCT_Dysymtab);
270 Write32(macho::DysymtabLoadCommandSize);
271 Write32(FirstLocalSymbol);
272 Write32(NumLocalSymbols);
273 Write32(FirstExternalSymbol);
274 Write32(NumExternalSymbols);
275 Write32(FirstUndefinedSymbol);
276 Write32(NumUndefinedSymbols);
277 Write32(0); // tocoff
279 Write32(0); // modtaboff
280 Write32(0); // nmodtab
281 Write32(0); // extrefsymoff
282 Write32(0); // nextrefsyms
283 Write32(IndirectSymbolOffset);
284 Write32(NumIndirectSymbols);
285 Write32(0); // extreloff
286 Write32(0); // nextrel
287 Write32(0); // locreloff
288 Write32(0); // nlocrel
290 assert(OS.tell() - Start == macho::DysymtabLoadCommandSize);
293 void MachObjectWriter::WriteNlist(MachSymbolData &MSD,
294 const MCAsmLayout &Layout) {
295 MCSymbolData &Data = *MSD.SymbolData;
296 const MCSymbol &Symbol = Data.getSymbol();
298 uint16_t Flags = Data.getFlags();
299 uint64_t Address = 0;
301 // Set the N_TYPE bits. See <mach-o/nlist.h>.
303 // FIXME: Are the prebound or indirect fields possible here?
304 if (Symbol.isUndefined())
305 Type = macho::STT_Undefined;
306 else if (Symbol.isAbsolute())
307 Type = macho::STT_Absolute;
309 Type = macho::STT_Section;
311 // FIXME: Set STAB bits.
313 if (Data.isPrivateExtern())
314 Type |= macho::STF_PrivateExtern;
317 if (Data.isExternal() || Symbol.isUndefined())
318 Type |= macho::STF_External;
320 // Compute the symbol address.
321 if (Symbol.isDefined()) {
322 Address = getSymbolAddress(&Data, Layout);
323 } else if (Data.isCommon()) {
324 // Common symbols are encoded with the size in the address
325 // field, and their alignment in the flags.
326 Address = Data.getCommonSize();
328 // Common alignment is packed into the 'desc' bits.
329 if (unsigned Align = Data.getCommonAlignment()) {
330 unsigned Log2Size = Log2_32(Align);
331 assert((1U << Log2Size) == Align && "Invalid 'common' alignment!");
333 report_fatal_error("invalid 'common' alignment '" +
335 // FIXME: Keep this mask with the SymbolFlags enumeration.
336 Flags = (Flags & 0xF0FF) | (Log2Size << 8);
340 // struct nlist (12 bytes)
342 Write32(MSD.StringIndex);
344 Write8(MSD.SectionIndex);
346 // The Mach-O streamer uses the lowest 16-bits of the flags for the 'desc'
355 void MachObjectWriter::WriteLinkeditLoadCommand(uint32_t Type,
358 uint64_t Start = OS.tell();
362 Write32(macho::LinkeditLoadCommandSize);
366 assert(OS.tell() - Start == macho::LinkeditLoadCommandSize);
370 void MachObjectWriter::RecordRelocation(const MCAssembler &Asm,
371 const MCAsmLayout &Layout,
372 const MCFragment *Fragment,
373 const MCFixup &Fixup,
375 uint64_t &FixedValue) {
376 TargetObjectWriter->RecordRelocation(this, Asm, Layout, Fragment, Fixup,
380 void MachObjectWriter::BindIndirectSymbols(MCAssembler &Asm) {
381 // This is the point where 'as' creates actual symbols for indirect symbols
382 // (in the following two passes). It would be easier for us to do this sooner
383 // when we see the attribute, but that makes getting the order in the symbol
384 // table much more complicated than it is worth.
386 // FIXME: Revisit this when the dust settles.
388 // Bind non lazy symbol pointers first.
389 unsigned IndirectIndex = 0;
390 for (MCAssembler::indirect_symbol_iterator it = Asm.indirect_symbol_begin(),
391 ie = Asm.indirect_symbol_end(); it != ie; ++it, ++IndirectIndex) {
392 const MCSectionMachO &Section =
393 cast<MCSectionMachO>(it->SectionData->getSection());
395 if (Section.getType() != MCSectionMachO::S_NON_LAZY_SYMBOL_POINTERS)
398 // Initialize the section indirect symbol base, if necessary.
399 IndirectSymBase.insert(std::make_pair(it->SectionData, IndirectIndex));
401 Asm.getOrCreateSymbolData(*it->Symbol);
404 // Then lazy symbol pointers and symbol stubs.
406 for (MCAssembler::indirect_symbol_iterator it = Asm.indirect_symbol_begin(),
407 ie = Asm.indirect_symbol_end(); it != ie; ++it, ++IndirectIndex) {
408 const MCSectionMachO &Section =
409 cast<MCSectionMachO>(it->SectionData->getSection());
411 if (Section.getType() != MCSectionMachO::S_LAZY_SYMBOL_POINTERS &&
412 Section.getType() != MCSectionMachO::S_SYMBOL_STUBS)
415 // Initialize the section indirect symbol base, if necessary.
416 IndirectSymBase.insert(std::make_pair(it->SectionData, IndirectIndex));
418 // Set the symbol type to undefined lazy, but only on construction.
420 // FIXME: Do not hardcode.
422 MCSymbolData &Entry = Asm.getOrCreateSymbolData(*it->Symbol, &Created);
424 Entry.setFlags(Entry.getFlags() | 0x0001);
428 /// ComputeSymbolTable - Compute the symbol table data
430 /// \param StringTable [out] - The string table data.
431 /// \param StringIndexMap [out] - Map from symbol names to offsets in the
433 void MachObjectWriter::
434 ComputeSymbolTable(MCAssembler &Asm, SmallString<256> &StringTable,
435 std::vector<MachSymbolData> &LocalSymbolData,
436 std::vector<MachSymbolData> &ExternalSymbolData,
437 std::vector<MachSymbolData> &UndefinedSymbolData) {
438 // Build section lookup table.
439 DenseMap<const MCSection*, uint8_t> SectionIndexMap;
441 for (MCAssembler::iterator it = Asm.begin(),
442 ie = Asm.end(); it != ie; ++it, ++Index)
443 SectionIndexMap[&it->getSection()] = Index;
444 assert(Index <= 256 && "Too many sections!");
446 // Index 0 is always the empty string.
447 StringMap<uint64_t> StringIndexMap;
448 StringTable += '\x00';
450 // Build the symbol arrays and the string table, but only for non-local
453 // The particular order that we collect the symbols and create the string
454 // table, then sort the symbols is chosen to match 'as'. Even though it
455 // doesn't matter for correctness, this is important for letting us diff .o
457 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
458 ie = Asm.symbol_end(); it != ie; ++it) {
459 const MCSymbol &Symbol = it->getSymbol();
461 // Ignore non-linker visible symbols.
462 if (!Asm.isSymbolLinkerVisible(it->getSymbol()))
465 if (!it->isExternal() && !Symbol.isUndefined())
468 uint64_t &Entry = StringIndexMap[Symbol.getName()];
470 Entry = StringTable.size();
471 StringTable += Symbol.getName();
472 StringTable += '\x00';
477 MSD.StringIndex = Entry;
479 if (Symbol.isUndefined()) {
480 MSD.SectionIndex = 0;
481 UndefinedSymbolData.push_back(MSD);
482 } else if (Symbol.isAbsolute()) {
483 MSD.SectionIndex = 0;
484 ExternalSymbolData.push_back(MSD);
486 MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
487 assert(MSD.SectionIndex && "Invalid section index!");
488 ExternalSymbolData.push_back(MSD);
492 // Now add the data for local symbols.
493 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
494 ie = Asm.symbol_end(); it != ie; ++it) {
495 const MCSymbol &Symbol = it->getSymbol();
497 // Ignore non-linker visible symbols.
498 if (!Asm.isSymbolLinkerVisible(it->getSymbol()))
501 if (it->isExternal() || Symbol.isUndefined())
504 uint64_t &Entry = StringIndexMap[Symbol.getName()];
506 Entry = StringTable.size();
507 StringTable += Symbol.getName();
508 StringTable += '\x00';
513 MSD.StringIndex = Entry;
515 if (Symbol.isAbsolute()) {
516 MSD.SectionIndex = 0;
517 LocalSymbolData.push_back(MSD);
519 MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
520 assert(MSD.SectionIndex && "Invalid section index!");
521 LocalSymbolData.push_back(MSD);
525 // External and undefined symbols are required to be in lexicographic order.
526 std::sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
527 std::sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end());
529 // Set the symbol indices.
531 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
532 LocalSymbolData[i].SymbolData->setIndex(Index++);
533 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
534 ExternalSymbolData[i].SymbolData->setIndex(Index++);
535 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
536 UndefinedSymbolData[i].SymbolData->setIndex(Index++);
538 // The string table is padded to a multiple of 4.
539 while (StringTable.size() % 4)
540 StringTable += '\x00';
543 void MachObjectWriter::computeSectionAddresses(const MCAssembler &Asm,
544 const MCAsmLayout &Layout) {
545 uint64_t StartAddress = 0;
546 const SmallVectorImpl<MCSectionData*> &Order = Layout.getSectionOrder();
547 for (int i = 0, n = Order.size(); i != n ; ++i) {
548 const MCSectionData *SD = Order[i];
549 StartAddress = RoundUpToAlignment(StartAddress, SD->getAlignment());
550 SectionAddress[SD] = StartAddress;
551 StartAddress += Layout.getSectionAddressSize(SD);
553 // Explicitly pad the section to match the alignment requirements of the
554 // following one. This is for 'gas' compatibility, it shouldn't
555 /// strictly be necessary.
556 StartAddress += getPaddingSize(SD, Layout);
560 void MachObjectWriter::markAbsoluteVariableSymbols(MCAssembler &Asm,
561 const MCAsmLayout &Layout) {
562 for (MCAssembler::symbol_iterator i = Asm.symbol_begin(),
563 e = Asm.symbol_end();
565 MCSymbolData &SD = *i;
566 if (!SD.getSymbol().isVariable())
569 // Is the variable is a symbol difference (SA - SB + C) expression,
570 // and neither symbol is external, mark the variable as absolute.
571 const MCExpr *Expr = SD.getSymbol().getVariableValue();
573 if (Expr->EvaluateAsRelocatable(Value, Layout)) {
574 if (Value.getSymA() && Value.getSymB())
575 const_cast<MCSymbol*>(&SD.getSymbol())->setAbsolute();
580 void MachObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm,
581 const MCAsmLayout &Layout) {
582 computeSectionAddresses(Asm, Layout);
584 // Create symbol data for any indirect symbols.
585 BindIndirectSymbols(Asm);
587 // Mark symbol difference expressions in variables (from .set or = directives)
589 markAbsoluteVariableSymbols(Asm, Layout);
591 // Compute symbol table information and bind symbol indices.
592 ComputeSymbolTable(Asm, StringTable, LocalSymbolData, ExternalSymbolData,
593 UndefinedSymbolData);
596 bool MachObjectWriter::
597 IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
598 const MCSymbolData &DataA,
599 const MCFragment &FB,
601 bool IsPCRel) const {
605 // The effective address is
606 // addr(atom(A)) + offset(A)
607 // - addr(atom(B)) - offset(B)
608 // and the offsets are not relocatable, so the fixup is fully resolved when
609 // addr(atom(A)) - addr(atom(B)) == 0.
610 const MCSymbolData *A_Base = 0, *B_Base = 0;
612 const MCSymbol &SA = DataA.getSymbol().AliasedSymbol();
613 const MCSection &SecA = SA.getSection();
614 const MCSection &SecB = FB.getParent()->getSection();
617 // The simple (Darwin, except on x86_64) way of dealing with this was to
618 // assume that any reference to a temporary symbol *must* be a temporary
619 // symbol in the same atom, unless the sections differ. Therefore, any PCrel
620 // relocation to a temporary symbol (in the same section) is fully
621 // resolved. This also works in conjunction with absolutized .set, which
622 // requires the compiler to use .set to absolutize the differences between
623 // symbols which the compiler knows to be assembly time constants, so we
624 // don't need to worry about considering symbol differences fully resolved.
626 // If the file isn't using sub-sections-via-symbols, we can make the
627 // same assumptions about any symbol that we normally make about
630 if (!Asm.getBackend().hasReliableSymbolDifference()) {
631 if (!SA.isInSection() || &SecA != &SecB ||
632 (!SA.isTemporary() &&
633 FB.getAtom() != Asm.getSymbolData(SA).getFragment()->getAtom() &&
634 Asm.getSubsectionsViaSymbols()))
638 // For Darwin x86_64, there is one special case when the reference IsPCRel.
639 // If the fragment with the reference does not have a base symbol but meets
640 // the simple way of dealing with this, in that it is a temporary symbol in
641 // the same atom then it is assumed to be fully resolved. This is needed so
642 // a relocation entry is not created and so the static linker does not
643 // mess up the reference later.
644 else if(!FB.getAtom() &&
645 SA.isTemporary() && SA.isInSection() && &SecA == &SecB){
649 if (!TargetObjectWriter->useAggressiveSymbolFolding())
653 const MCFragment *FA = Asm.getSymbolData(SA).getFragment();
655 // Bail if the symbol has no fragment.
659 A_Base = FA->getAtom();
663 B_Base = FB.getAtom();
667 // If the atoms are the same, they are guaranteed to have the same address.
668 if (A_Base == B_Base)
671 // Otherwise, we can't prove this is fully resolved.
675 void MachObjectWriter::WriteObject(MCAssembler &Asm,
676 const MCAsmLayout &Layout) {
677 unsigned NumSections = Asm.size();
679 // The section data starts after the header, the segment load command (and
680 // section headers) and the symbol table.
681 unsigned NumLoadCommands = 1;
682 uint64_t LoadCommandsSize = is64Bit() ?
683 macho::SegmentLoadCommand64Size + NumSections * macho::Section64Size :
684 macho::SegmentLoadCommand32Size + NumSections * macho::Section32Size;
686 // Add the symbol table load command sizes, if used.
687 unsigned NumSymbols = LocalSymbolData.size() + ExternalSymbolData.size() +
688 UndefinedSymbolData.size();
690 NumLoadCommands += 2;
691 LoadCommandsSize += (macho::SymtabLoadCommandSize +
692 macho::DysymtabLoadCommandSize);
695 // Add the data-in-code load command size, if used.
696 unsigned NumDataRegions = Asm.getDataRegions().size();
697 if (NumDataRegions) {
699 LoadCommandsSize += macho::LinkeditLoadCommandSize;
702 // Compute the total size of the section data, as well as its file size and vm
704 uint64_t SectionDataStart = (is64Bit() ? macho::Header64Size :
705 macho::Header32Size) + LoadCommandsSize;
706 uint64_t SectionDataSize = 0;
707 uint64_t SectionDataFileSize = 0;
709 for (MCAssembler::const_iterator it = Asm.begin(),
710 ie = Asm.end(); it != ie; ++it) {
711 const MCSectionData &SD = *it;
712 uint64_t Address = getSectionAddress(&SD);
713 uint64_t Size = Layout.getSectionAddressSize(&SD);
714 uint64_t FileSize = Layout.getSectionFileSize(&SD);
715 FileSize += getPaddingSize(&SD, Layout);
717 VMSize = std::max(VMSize, Address + Size);
719 if (SD.getSection().isVirtualSection())
722 SectionDataSize = std::max(SectionDataSize, Address + Size);
723 SectionDataFileSize = std::max(SectionDataFileSize, Address + FileSize);
726 // The section data is padded to 4 bytes.
728 // FIXME: Is this machine dependent?
729 unsigned SectionDataPadding = OffsetToAlignment(SectionDataFileSize, 4);
730 SectionDataFileSize += SectionDataPadding;
732 // Write the prolog, starting with the header and load command...
733 WriteHeader(NumLoadCommands, LoadCommandsSize,
734 Asm.getSubsectionsViaSymbols());
735 WriteSegmentLoadCommand(NumSections, VMSize,
736 SectionDataStart, SectionDataSize);
738 // ... and then the section headers.
739 uint64_t RelocTableEnd = SectionDataStart + SectionDataFileSize;
740 for (MCAssembler::const_iterator it = Asm.begin(),
741 ie = Asm.end(); it != ie; ++it) {
742 std::vector<macho::RelocationEntry> &Relocs = Relocations[it];
743 unsigned NumRelocs = Relocs.size();
744 uint64_t SectionStart = SectionDataStart + getSectionAddress(it);
745 WriteSection(Asm, Layout, *it, SectionStart, RelocTableEnd, NumRelocs);
746 RelocTableEnd += NumRelocs * macho::RelocationInfoSize;
749 // Write the data-in-code load command, if used.
750 uint64_t DataInCodeTableEnd = RelocTableEnd + NumDataRegions * 8;
751 if (NumDataRegions) {
752 uint64_t DataRegionsOffset = RelocTableEnd;
753 uint64_t DataRegionsSize = NumDataRegions * 8;
754 WriteLinkeditLoadCommand(macho::LCT_DataInCode, DataRegionsOffset,
758 // Write the symbol table load command, if used.
760 unsigned FirstLocalSymbol = 0;
761 unsigned NumLocalSymbols = LocalSymbolData.size();
762 unsigned FirstExternalSymbol = FirstLocalSymbol + NumLocalSymbols;
763 unsigned NumExternalSymbols = ExternalSymbolData.size();
764 unsigned FirstUndefinedSymbol = FirstExternalSymbol + NumExternalSymbols;
765 unsigned NumUndefinedSymbols = UndefinedSymbolData.size();
766 unsigned NumIndirectSymbols = Asm.indirect_symbol_size();
767 unsigned NumSymTabSymbols =
768 NumLocalSymbols + NumExternalSymbols + NumUndefinedSymbols;
769 uint64_t IndirectSymbolSize = NumIndirectSymbols * 4;
770 uint64_t IndirectSymbolOffset = 0;
772 // If used, the indirect symbols are written after the section data.
773 if (NumIndirectSymbols)
774 IndirectSymbolOffset = DataInCodeTableEnd;
776 // The symbol table is written after the indirect symbol data.
777 uint64_t SymbolTableOffset = DataInCodeTableEnd + IndirectSymbolSize;
779 // The string table is written after symbol table.
780 uint64_t StringTableOffset =
781 SymbolTableOffset + NumSymTabSymbols * (is64Bit() ? macho::Nlist64Size :
783 WriteSymtabLoadCommand(SymbolTableOffset, NumSymTabSymbols,
784 StringTableOffset, StringTable.size());
786 WriteDysymtabLoadCommand(FirstLocalSymbol, NumLocalSymbols,
787 FirstExternalSymbol, NumExternalSymbols,
788 FirstUndefinedSymbol, NumUndefinedSymbols,
789 IndirectSymbolOffset, NumIndirectSymbols);
792 // Write the actual section data.
793 for (MCAssembler::const_iterator it = Asm.begin(),
794 ie = Asm.end(); it != ie; ++it) {
795 Asm.writeSectionData(it, Layout);
797 uint64_t Pad = getPaddingSize(it, Layout);
798 for (unsigned int i = 0; i < Pad; ++i)
802 // Write the extra padding.
803 WriteZeros(SectionDataPadding);
805 // Write the relocation entries.
806 for (MCAssembler::const_iterator it = Asm.begin(),
807 ie = Asm.end(); it != ie; ++it) {
808 // Write the section relocation entries, in reverse order to match 'as'
809 // (approximately, the exact algorithm is more complicated than this).
810 std::vector<macho::RelocationEntry> &Relocs = Relocations[it];
811 for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
812 Write32(Relocs[e - i - 1].Word0);
813 Write32(Relocs[e - i - 1].Word1);
817 // Write out the data-in-code region payload, if there is one.
818 for (MCAssembler::const_data_region_iterator
819 it = Asm.data_region_begin(), ie = Asm.data_region_end();
821 const DataRegionData *Data = &(*it);
823 getSymbolAddress(&Layout.getAssembler().getSymbolData(*Data->Start),
826 getSymbolAddress(&Layout.getAssembler().getSymbolData(*Data->End),
828 DEBUG(dbgs() << "data in code region-- kind: " << Data->Kind
829 << " start: " << Start << "(" << Data->Start->getName() << ")"
830 << " end: " << End << "(" << Data->End->getName() << ")"
831 << " size: " << End - Start
834 Write16(End - Start);
838 // Write the symbol table data, if used.
840 // Write the indirect symbol entries.
841 for (MCAssembler::const_indirect_symbol_iterator
842 it = Asm.indirect_symbol_begin(),
843 ie = Asm.indirect_symbol_end(); it != ie; ++it) {
844 // Indirect symbols in the non lazy symbol pointer section have some
846 const MCSectionMachO &Section =
847 static_cast<const MCSectionMachO&>(it->SectionData->getSection());
848 if (Section.getType() == MCSectionMachO::S_NON_LAZY_SYMBOL_POINTERS) {
849 // If this symbol is defined and internal, mark it as such.
850 if (it->Symbol->isDefined() &&
851 !Asm.getSymbolData(*it->Symbol).isExternal()) {
852 uint32_t Flags = macho::ISF_Local;
853 if (it->Symbol->isAbsolute())
854 Flags |= macho::ISF_Absolute;
860 Write32(Asm.getSymbolData(*it->Symbol).getIndex());
863 // FIXME: Check that offsets match computed ones.
865 // Write the symbol table entries.
866 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
867 WriteNlist(LocalSymbolData[i], Layout);
868 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
869 WriteNlist(ExternalSymbolData[i], Layout);
870 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
871 WriteNlist(UndefinedSymbolData[i], Layout);
873 // Write the string table.
874 OS << StringTable.str();
878 MCObjectWriter *llvm::createMachObjectWriter(MCMachObjectTargetWriter *MOTW,
880 bool IsLittleEndian) {
881 return new MachObjectWriter(MOTW, OS, IsLittleEndian);