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/MachObjectWriter.h"
11 #include "llvm/ADT/StringMap.h"
12 #include "llvm/ADT/Twine.h"
13 #include "llvm/MC/MCAssembler.h"
14 #include "llvm/MC/MCAsmLayout.h"
15 #include "llvm/MC/MCExpr.h"
16 #include "llvm/MC/MCObjectWriter.h"
17 #include "llvm/MC/MCSectionMachO.h"
18 #include "llvm/MC/MCSymbol.h"
19 #include "llvm/MC/MCValue.h"
20 #include "llvm/Support/ErrorHandling.h"
21 #include "llvm/Support/MachO.h"
22 #include "llvm/Target/TargetAsmBackend.h"
25 #include "../Target/X86/X86FixupKinds.h"
30 static unsigned getFixupKindLog2Size(unsigned Kind) {
32 default: llvm_unreachable("invalid fixup kind!");
33 case X86::reloc_pcrel_1byte:
34 case FK_Data_1: return 0;
35 case FK_Data_2: return 1;
36 case X86::reloc_pcrel_4byte:
37 case X86::reloc_riprel_4byte:
38 case X86::reloc_riprel_4byte_movq_load:
39 case FK_Data_4: return 2;
40 case FK_Data_8: return 3;
44 static bool isFixupKindPCRel(unsigned Kind) {
48 case X86::reloc_pcrel_1byte:
49 case X86::reloc_pcrel_4byte:
50 case X86::reloc_riprel_4byte:
51 case X86::reloc_riprel_4byte_movq_load:
56 static bool isFixupKindRIPRel(unsigned Kind) {
57 return Kind == X86::reloc_riprel_4byte ||
58 Kind == X86::reloc_riprel_4byte_movq_load;
63 class MachObjectWriterImpl {
64 // See <mach-o/loader.h>.
66 Header_Magic32 = 0xFEEDFACE,
67 Header_Magic64 = 0xFEEDFACF
73 SegmentLoadCommand32Size = 56,
74 SegmentLoadCommand64Size = 72,
77 SymtabLoadCommandSize = 24,
78 DysymtabLoadCommandSize = 80,
81 RelocationInfoSize = 8
89 HF_SubsectionsViaSymbols = 0x2000
92 enum LoadCommandType {
99 // See <mach-o/nlist.h>.
100 enum SymbolTypeType {
101 STT_Undefined = 0x00,
106 enum SymbolTypeFlags {
107 // If any of these bits are set, then the entry is a stab entry number (see
108 // <mach-o/stab.h>. Otherwise the other masks apply.
109 STF_StabsEntryMask = 0xe0,
113 STF_PrivateExtern = 0x10
116 /// IndirectSymbolFlags - Flags for encoding special values in the indirect
118 enum IndirectSymbolFlags {
119 ISF_Local = 0x80000000,
120 ISF_Absolute = 0x40000000
123 /// RelocationFlags - Special flags for addresses.
124 enum RelocationFlags {
125 RF_Scattered = 0x80000000
128 enum RelocationInfoType {
132 RIT_PreboundLazyPointer = 3,
133 RIT_LocalDifference = 4
136 /// X86_64 uses its own relocation types.
137 enum RelocationInfoTypeX86_64 {
138 RIT_X86_64_Unsigned = 0,
139 RIT_X86_64_Signed = 1,
140 RIT_X86_64_Branch = 2,
141 RIT_X86_64_GOTLoad = 3,
143 RIT_X86_64_Subtractor = 5,
144 RIT_X86_64_Signed1 = 6,
145 RIT_X86_64_Signed2 = 7,
146 RIT_X86_64_Signed4 = 8
149 /// MachSymbolData - Helper struct for containing some precomputed information
151 struct MachSymbolData {
152 MCSymbolData *SymbolData;
153 uint64_t StringIndex;
154 uint8_t SectionIndex;
156 // Support lexicographic sorting.
157 bool operator<(const MachSymbolData &RHS) const {
158 const std::string &Name = SymbolData->getSymbol().getName();
159 return Name < RHS.SymbolData->getSymbol().getName();
163 /// @name Relocation Data
166 struct MachRelocationEntry {
171 llvm::DenseMap<const MCSectionData*,
172 std::vector<MachRelocationEntry> > Relocations;
175 /// @name Symbol Table Data
178 SmallString<256> StringTable;
179 std::vector<MachSymbolData> LocalSymbolData;
180 std::vector<MachSymbolData> ExternalSymbolData;
181 std::vector<MachSymbolData> UndefinedSymbolData;
185 MachObjectWriter *Writer;
189 unsigned Is64Bit : 1;
192 MachObjectWriterImpl(MachObjectWriter *_Writer, bool _Is64Bit)
193 : Writer(_Writer), OS(Writer->getStream()), Is64Bit(_Is64Bit) {
196 void Write8(uint8_t Value) { Writer->Write8(Value); }
197 void Write16(uint16_t Value) { Writer->Write16(Value); }
198 void Write32(uint32_t Value) { Writer->Write32(Value); }
199 void Write64(uint64_t Value) { Writer->Write64(Value); }
200 void WriteZeros(unsigned N) { Writer->WriteZeros(N); }
201 void WriteBytes(StringRef Str, unsigned ZeroFillSize = 0) {
202 Writer->WriteBytes(Str, ZeroFillSize);
205 void WriteHeader(unsigned NumLoadCommands, unsigned LoadCommandsSize,
206 bool SubsectionsViaSymbols) {
209 if (SubsectionsViaSymbols)
210 Flags |= HF_SubsectionsViaSymbols;
212 // struct mach_header (28 bytes) or
213 // struct mach_header_64 (32 bytes)
215 uint64_t Start = OS.tell();
218 Write32(Is64Bit ? Header_Magic64 : Header_Magic32);
220 // FIXME: Support cputype.
221 Write32(Is64Bit ? MachO::CPUTypeX86_64 : MachO::CPUTypeI386);
222 // FIXME: Support cpusubtype.
223 Write32(MachO::CPUSubType_I386_ALL);
225 Write32(NumLoadCommands); // Object files have a single load command, the
227 Write32(LoadCommandsSize);
230 Write32(0); // reserved
232 assert(OS.tell() - Start == Is64Bit ? Header64Size : Header32Size);
235 /// WriteSegmentLoadCommand - Write a segment load command.
237 /// \arg NumSections - The number of sections in this segment.
238 /// \arg SectionDataSize - The total size of the sections.
239 void WriteSegmentLoadCommand(unsigned NumSections,
241 uint64_t SectionDataStartOffset,
242 uint64_t SectionDataSize) {
243 // struct segment_command (56 bytes) or
244 // struct segment_command_64 (72 bytes)
246 uint64_t Start = OS.tell();
249 unsigned SegmentLoadCommandSize = Is64Bit ? SegmentLoadCommand64Size :
250 SegmentLoadCommand32Size;
251 Write32(Is64Bit ? LCT_Segment64 : LCT_Segment);
252 Write32(SegmentLoadCommandSize +
253 NumSections * (Is64Bit ? Section64Size : Section32Size));
257 Write64(0); // vmaddr
258 Write64(VMSize); // vmsize
259 Write64(SectionDataStartOffset); // file offset
260 Write64(SectionDataSize); // file size
262 Write32(0); // vmaddr
263 Write32(VMSize); // vmsize
264 Write32(SectionDataStartOffset); // file offset
265 Write32(SectionDataSize); // file size
267 Write32(0x7); // maxprot
268 Write32(0x7); // initprot
269 Write32(NumSections);
272 assert(OS.tell() - Start == SegmentLoadCommandSize);
275 void WriteSection(const MCAssembler &Asm, const MCAsmLayout &Layout,
276 const MCSectionData &SD, uint64_t FileOffset,
277 uint64_t RelocationsStart, unsigned NumRelocations) {
278 uint64_t SectionSize = Layout.getSectionSize(&SD);
280 // The offset is unused for virtual sections.
281 if (Asm.getBackend().isVirtualSection(SD.getSection())) {
282 assert(Layout.getSectionFileSize(&SD) == 0 && "Invalid file size!");
286 // struct section (68 bytes) or
287 // struct section_64 (80 bytes)
289 uint64_t Start = OS.tell();
292 // FIXME: cast<> support!
293 const MCSectionMachO &Section =
294 static_cast<const MCSectionMachO&>(SD.getSection());
295 WriteBytes(Section.getSectionName(), 16);
296 WriteBytes(Section.getSegmentName(), 16);
298 Write64(Layout.getSectionAddress(&SD)); // address
299 Write64(SectionSize); // size
301 Write32(Layout.getSectionAddress(&SD)); // address
302 Write32(SectionSize); // size
306 unsigned Flags = Section.getTypeAndAttributes();
307 if (SD.hasInstructions())
308 Flags |= MCSectionMachO::S_ATTR_SOME_INSTRUCTIONS;
310 assert(isPowerOf2_32(SD.getAlignment()) && "Invalid alignment!");
311 Write32(Log2_32(SD.getAlignment()));
312 Write32(NumRelocations ? RelocationsStart : 0);
313 Write32(NumRelocations);
315 Write32(0); // reserved1
316 Write32(Section.getStubSize()); // reserved2
318 Write32(0); // reserved3
320 assert(OS.tell() - Start == Is64Bit ? Section64Size : Section32Size);
323 void WriteSymtabLoadCommand(uint32_t SymbolOffset, uint32_t NumSymbols,
324 uint32_t StringTableOffset,
325 uint32_t StringTableSize) {
326 // struct symtab_command (24 bytes)
328 uint64_t Start = OS.tell();
332 Write32(SymtabLoadCommandSize);
333 Write32(SymbolOffset);
335 Write32(StringTableOffset);
336 Write32(StringTableSize);
338 assert(OS.tell() - Start == SymtabLoadCommandSize);
341 void WriteDysymtabLoadCommand(uint32_t FirstLocalSymbol,
342 uint32_t NumLocalSymbols,
343 uint32_t FirstExternalSymbol,
344 uint32_t NumExternalSymbols,
345 uint32_t FirstUndefinedSymbol,
346 uint32_t NumUndefinedSymbols,
347 uint32_t IndirectSymbolOffset,
348 uint32_t NumIndirectSymbols) {
349 // struct dysymtab_command (80 bytes)
351 uint64_t Start = OS.tell();
354 Write32(LCT_Dysymtab);
355 Write32(DysymtabLoadCommandSize);
356 Write32(FirstLocalSymbol);
357 Write32(NumLocalSymbols);
358 Write32(FirstExternalSymbol);
359 Write32(NumExternalSymbols);
360 Write32(FirstUndefinedSymbol);
361 Write32(NumUndefinedSymbols);
362 Write32(0); // tocoff
364 Write32(0); // modtaboff
365 Write32(0); // nmodtab
366 Write32(0); // extrefsymoff
367 Write32(0); // nextrefsyms
368 Write32(IndirectSymbolOffset);
369 Write32(NumIndirectSymbols);
370 Write32(0); // extreloff
371 Write32(0); // nextrel
372 Write32(0); // locreloff
373 Write32(0); // nlocrel
375 assert(OS.tell() - Start == DysymtabLoadCommandSize);
378 void WriteNlist(MachSymbolData &MSD, const MCAsmLayout &Layout) {
379 MCSymbolData &Data = *MSD.SymbolData;
380 const MCSymbol &Symbol = Data.getSymbol();
382 uint16_t Flags = Data.getFlags();
383 uint32_t Address = 0;
385 // Set the N_TYPE bits. See <mach-o/nlist.h>.
387 // FIXME: Are the prebound or indirect fields possible here?
388 if (Symbol.isUndefined())
389 Type = STT_Undefined;
390 else if (Symbol.isAbsolute())
395 // FIXME: Set STAB bits.
397 if (Data.isPrivateExtern())
398 Type |= STF_PrivateExtern;
401 if (Data.isExternal() || Symbol.isUndefined())
402 Type |= STF_External;
404 // Compute the symbol address.
405 if (Symbol.isDefined()) {
406 if (Symbol.isAbsolute()) {
407 llvm_unreachable("FIXME: Not yet implemented!");
409 Address = Layout.getSymbolAddress(&Data);
411 } else if (Data.isCommon()) {
412 // Common symbols are encoded with the size in the address
413 // field, and their alignment in the flags.
414 Address = Data.getCommonSize();
416 // Common alignment is packed into the 'desc' bits.
417 if (unsigned Align = Data.getCommonAlignment()) {
418 unsigned Log2Size = Log2_32(Align);
419 assert((1U << Log2Size) == Align && "Invalid 'common' alignment!");
421 report_fatal_error("invalid 'common' alignment '" +
423 // FIXME: Keep this mask with the SymbolFlags enumeration.
424 Flags = (Flags & 0xF0FF) | (Log2Size << 8);
428 // struct nlist (12 bytes)
430 Write32(MSD.StringIndex);
432 Write8(MSD.SectionIndex);
434 // The Mach-O streamer uses the lowest 16-bits of the flags for the 'desc'
443 // FIXME: We really need to improve the relocation validation. Basically, we
444 // want to implement a separate computation which evaluates the relocation
445 // entry as the linker would, and verifies that the resultant fixup value is
446 // exactly what the encoder wanted. This will catch several classes of
449 // - Relocation entry bugs, the two algorithms are unlikely to have the same
452 // - Relaxation issues, where we forget to relax something.
454 // - Input errors, where something cannot be correctly encoded. 'as' allows
455 // these through in many cases.
457 void RecordX86_64Relocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
458 const MCFragment *Fragment,
459 const MCAsmFixup &Fixup, MCValue Target,
460 uint64_t &FixedValue) {
461 unsigned IsPCRel = isFixupKindPCRel(Fixup.Kind);
462 unsigned IsRIPRel = isFixupKindRIPRel(Fixup.Kind);
463 unsigned Log2Size = getFixupKindLog2Size(Fixup.Kind);
466 uint32_t Address = Layout.getFragmentOffset(Fragment) + Fixup.Offset;
469 unsigned IsExtern = 0;
472 Value = Target.getConstant();
475 // Compensate for the relocation offset, Darwin x86_64 relocations only
476 // have the addend and appear to have attempted to define it to be the
477 // actual expression addend without the PCrel bias. However, instructions
478 // with data following the relocation are not accomodated for (see comment
479 // below regarding SIGNED{1,2,4}), so it isn't exactly that either.
480 Value += 1LL << Log2Size;
483 if (Target.isAbsolute()) { // constant
484 // SymbolNum of 0 indicates the absolute section.
485 Type = RIT_X86_64_Unsigned;
488 // FIXME: I believe this is broken, I don't think the linker can
489 // understand it. I think it would require a local relocation, but I'm not
490 // sure if that would work either. The official way to get an absolute
491 // PCrel relocation is to use an absolute symbol (which we don't support
495 Type = RIT_X86_64_Branch;
497 } else if (Target.getSymB()) { // A - B + constant
498 const MCSymbol *A = &Target.getSymA()->getSymbol();
499 MCSymbolData &A_SD = Asm.getSymbolData(*A);
500 const MCSymbolData *A_Base = Asm.getAtom(Layout, &A_SD);
502 const MCSymbol *B = &Target.getSymB()->getSymbol();
503 MCSymbolData &B_SD = Asm.getSymbolData(*B);
504 const MCSymbolData *B_Base = Asm.getAtom(Layout, &B_SD);
506 // Neither symbol can be modified.
507 if (Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None ||
508 Target.getSymB()->getKind() != MCSymbolRefExpr::VK_None)
509 report_fatal_error("unsupported relocation of modified symbol");
511 // We don't support PCrel relocations of differences. Darwin 'as' doesn't
512 // implement most of these correctly.
514 report_fatal_error("unsupported pc-relative relocation of difference");
516 // We don't currently support any situation where one or both of the
517 // symbols would require a local relocation. This is almost certainly
518 // unused and may not be possible to encode correctly.
519 if (!A_Base || !B_Base)
520 report_fatal_error("unsupported local relocations in difference");
522 // Darwin 'as' doesn't emit correct relocations for this (it ends up with
523 // a single SIGNED relocation); reject it for now.
524 if (A_Base == B_Base)
525 report_fatal_error("unsupported relocation with identical base");
527 Value += Layout.getSymbolAddress(&A_SD) - Layout.getSymbolAddress(A_Base);
528 Value -= Layout.getSymbolAddress(&B_SD) - Layout.getSymbolAddress(B_Base);
530 Index = A_Base->getIndex();
532 Type = RIT_X86_64_Unsigned;
534 MachRelocationEntry MRE;
536 MRE.Word1 = ((Index << 0) |
541 Relocations[Fragment->getParent()].push_back(MRE);
543 Index = B_Base->getIndex();
545 Type = RIT_X86_64_Subtractor;
547 const MCSymbol *Symbol = &Target.getSymA()->getSymbol();
548 MCSymbolData &SD = Asm.getSymbolData(*Symbol);
549 const MCSymbolData *Base = Asm.getAtom(Layout, &SD);
551 // x86_64 almost always uses external relocations, except when there is no
552 // symbol to use as a base address (a local symbol with no preceeding
553 // non-local symbol).
555 Index = Base->getIndex();
558 // Add the local offset, if needed.
560 Value += Layout.getSymbolAddress(&SD) - Layout.getSymbolAddress(Base);
562 // The index is the section ordinal (1-based).
563 Index = SD.getFragment()->getParent()->getOrdinal() + 1;
565 Value += Layout.getSymbolAddress(&SD);
568 Value -= Address + (1 << Log2Size);
571 MCSymbolRefExpr::VariantKind Modifier = Target.getSymA()->getKind();
574 if (Modifier == MCSymbolRefExpr::VK_GOTPCREL) {
575 // x86_64 distinguishes movq foo@GOTPCREL so that the linker can
576 // rewrite the movq to an leaq at link time if the symbol ends up in
577 // the same linkage unit.
578 if (unsigned(Fixup.Kind) == X86::reloc_riprel_4byte_movq_load)
579 Type = RIT_X86_64_GOTLoad;
581 Type = RIT_X86_64_GOT;
582 } else if (Modifier != MCSymbolRefExpr::VK_None)
583 report_fatal_error("unsupported symbol modifier in relocation");
585 Type = RIT_X86_64_Signed;
587 if (Modifier != MCSymbolRefExpr::VK_None)
588 report_fatal_error("unsupported symbol modifier in branch "
591 Type = RIT_X86_64_Branch;
594 // The Darwin x86_64 relocation format has a problem where it cannot
595 // encode an address (L<foo> + <constant>) which is outside the atom
596 // containing L<foo>. Generally, this shouldn't occur but it does happen
597 // when we have a RIPrel instruction with data following the relocation
598 // entry (e.g., movb $012, L0(%rip)). Even with the PCrel adjustment
599 // Darwin x86_64 uses, the offset is still negative and the linker has
600 // no way to recognize this.
602 // To work around this, Darwin uses several special relocation types to
603 // indicate the offsets. However, the specification or implementation of
604 // these seems to also be incomplete; they should adjust the addend as
605 // well based on the actual encoded instruction (the additional bias),
606 // but instead appear to just look at the final offset.
608 switch (-(Target.getConstant() + (1LL << Log2Size))) {
609 case 1: Type = RIT_X86_64_Signed1; break;
610 case 2: Type = RIT_X86_64_Signed2; break;
611 case 4: Type = RIT_X86_64_Signed4; break;
615 if (Modifier == MCSymbolRefExpr::VK_GOT) {
616 Type = RIT_X86_64_GOT;
617 } else if (Modifier == MCSymbolRefExpr::VK_GOTPCREL) {
618 // GOTPCREL is allowed as a modifier on non-PCrel instructions, in
619 // which case all we do is set the PCrel bit in the relocation entry;
620 // this is used with exception handling, for example. The source is
621 // required to include any necessary offset directly.
622 Type = RIT_X86_64_GOT;
624 } else if (Modifier != MCSymbolRefExpr::VK_None)
625 report_fatal_error("unsupported symbol modifier in relocation");
627 Type = RIT_X86_64_Unsigned;
631 // x86_64 always writes custom values into the fixups.
634 // struct relocation_info (8 bytes)
635 MachRelocationEntry MRE;
637 MRE.Word1 = ((Index << 0) |
642 Relocations[Fragment->getParent()].push_back(MRE);
645 void RecordScatteredRelocation(const MCAssembler &Asm,
646 const MCAsmLayout &Layout,
647 const MCFragment *Fragment,
648 const MCAsmFixup &Fixup, MCValue Target,
649 uint64_t &FixedValue) {
650 uint32_t Address = Layout.getFragmentOffset(Fragment) + Fixup.Offset;
651 unsigned IsPCRel = isFixupKindPCRel(Fixup.Kind);
652 unsigned Log2Size = getFixupKindLog2Size(Fixup.Kind);
653 unsigned Type = RIT_Vanilla;
656 const MCSymbol *A = &Target.getSymA()->getSymbol();
657 MCSymbolData *A_SD = &Asm.getSymbolData(*A);
659 if (!A_SD->getFragment())
660 report_fatal_error("symbol '" + A->getName() +
661 "' can not be undefined in a subtraction expression");
663 uint32_t Value = Layout.getSymbolAddress(A_SD);
666 if (const MCSymbolRefExpr *B = Target.getSymB()) {
667 MCSymbolData *B_SD = &Asm.getSymbolData(B->getSymbol());
669 if (!B_SD->getFragment())
670 report_fatal_error("symbol '" + B->getSymbol().getName() +
671 "' can not be undefined in a subtraction expression");
673 // Select the appropriate difference relocation type.
675 // Note that there is no longer any semantic difference between these two
676 // relocation types from the linkers point of view, this is done solely
677 // for pedantic compatibility with 'as'.
678 Type = A_SD->isExternal() ? RIT_Difference : RIT_LocalDifference;
679 Value2 = Layout.getSymbolAddress(B_SD);
682 // Relocations are written out in reverse order, so the PAIR comes first.
683 if (Type == RIT_Difference || Type == RIT_LocalDifference) {
684 MachRelocationEntry MRE;
685 MRE.Word0 = ((0 << 0) |
691 Relocations[Fragment->getParent()].push_back(MRE);
694 MachRelocationEntry MRE;
695 MRE.Word0 = ((Address << 0) |
701 Relocations[Fragment->getParent()].push_back(MRE);
704 void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
705 const MCFragment *Fragment, const MCAsmFixup &Fixup,
706 MCValue Target, uint64_t &FixedValue) {
708 RecordX86_64Relocation(Asm, Layout, Fragment, Fixup, Target, FixedValue);
712 unsigned IsPCRel = isFixupKindPCRel(Fixup.Kind);
713 unsigned Log2Size = getFixupKindLog2Size(Fixup.Kind);
715 // If this is a difference or a defined symbol plus an offset, then we need
716 // a scattered relocation entry.
717 uint32_t Offset = Target.getConstant();
719 Offset += 1 << Log2Size;
720 if (Target.getSymB() ||
721 (Target.getSymA() && !Target.getSymA()->getSymbol().isUndefined() &&
723 RecordScatteredRelocation(Asm, Layout, Fragment, Fixup,Target,FixedValue);
728 uint32_t Address = Layout.getFragmentOffset(Fragment) + Fixup.Offset;
731 unsigned IsExtern = 0;
734 if (Target.isAbsolute()) { // constant
735 // SymbolNum of 0 indicates the absolute section.
737 // FIXME: Currently, these are never generated (see code below). I cannot
738 // find a case where they are actually emitted.
742 const MCSymbol *Symbol = &Target.getSymA()->getSymbol();
743 MCSymbolData *SD = &Asm.getSymbolData(*Symbol);
745 if (Symbol->isUndefined()) {
747 Index = SD->getIndex();
750 // The index is the section ordinal (1-based).
751 Index = SD->getFragment()->getParent()->getOrdinal() + 1;
752 Value = Layout.getSymbolAddress(SD);
758 // struct relocation_info (8 bytes)
759 MachRelocationEntry MRE;
761 MRE.Word1 = ((Index << 0) |
766 Relocations[Fragment->getParent()].push_back(MRE);
769 void BindIndirectSymbols(MCAssembler &Asm) {
770 // This is the point where 'as' creates actual symbols for indirect symbols
771 // (in the following two passes). It would be easier for us to do this
772 // sooner when we see the attribute, but that makes getting the order in the
773 // symbol table much more complicated than it is worth.
775 // FIXME: Revisit this when the dust settles.
777 // Bind non lazy symbol pointers first.
778 for (MCAssembler::indirect_symbol_iterator it = Asm.indirect_symbol_begin(),
779 ie = Asm.indirect_symbol_end(); it != ie; ++it) {
780 // FIXME: cast<> support!
781 const MCSectionMachO &Section =
782 static_cast<const MCSectionMachO&>(it->SectionData->getSection());
784 if (Section.getType() != MCSectionMachO::S_NON_LAZY_SYMBOL_POINTERS)
787 Asm.getOrCreateSymbolData(*it->Symbol);
790 // Then lazy symbol pointers and symbol stubs.
791 for (MCAssembler::indirect_symbol_iterator it = Asm.indirect_symbol_begin(),
792 ie = Asm.indirect_symbol_end(); it != ie; ++it) {
793 // FIXME: cast<> support!
794 const MCSectionMachO &Section =
795 static_cast<const MCSectionMachO&>(it->SectionData->getSection());
797 if (Section.getType() != MCSectionMachO::S_LAZY_SYMBOL_POINTERS &&
798 Section.getType() != MCSectionMachO::S_SYMBOL_STUBS)
801 // Set the symbol type to undefined lazy, but only on construction.
803 // FIXME: Do not hardcode.
805 MCSymbolData &Entry = Asm.getOrCreateSymbolData(*it->Symbol, &Created);
807 Entry.setFlags(Entry.getFlags() | 0x0001);
811 /// ComputeSymbolTable - Compute the symbol table data
813 /// \param StringTable [out] - The string table data.
814 /// \param StringIndexMap [out] - Map from symbol names to offsets in the
816 void ComputeSymbolTable(MCAssembler &Asm, SmallString<256> &StringTable,
817 std::vector<MachSymbolData> &LocalSymbolData,
818 std::vector<MachSymbolData> &ExternalSymbolData,
819 std::vector<MachSymbolData> &UndefinedSymbolData) {
820 // Build section lookup table.
821 DenseMap<const MCSection*, uint8_t> SectionIndexMap;
823 for (MCAssembler::iterator it = Asm.begin(),
824 ie = Asm.end(); it != ie; ++it, ++Index)
825 SectionIndexMap[&it->getSection()] = Index;
826 assert(Index <= 256 && "Too many sections!");
828 // Index 0 is always the empty string.
829 StringMap<uint64_t> StringIndexMap;
830 StringTable += '\x00';
832 // Build the symbol arrays and the string table, but only for non-local
835 // The particular order that we collect the symbols and create the string
836 // table, then sort the symbols is chosen to match 'as'. Even though it
837 // doesn't matter for correctness, this is important for letting us diff .o
839 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
840 ie = Asm.symbol_end(); it != ie; ++it) {
841 const MCSymbol &Symbol = it->getSymbol();
843 // Ignore non-linker visible symbols.
844 if (!Asm.isSymbolLinkerVisible(it))
847 if (!it->isExternal() && !Symbol.isUndefined())
850 uint64_t &Entry = StringIndexMap[Symbol.getName()];
852 Entry = StringTable.size();
853 StringTable += Symbol.getName();
854 StringTable += '\x00';
859 MSD.StringIndex = Entry;
861 if (Symbol.isUndefined()) {
862 MSD.SectionIndex = 0;
863 UndefinedSymbolData.push_back(MSD);
864 } else if (Symbol.isAbsolute()) {
865 MSD.SectionIndex = 0;
866 ExternalSymbolData.push_back(MSD);
868 MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
869 assert(MSD.SectionIndex && "Invalid section index!");
870 ExternalSymbolData.push_back(MSD);
874 // Now add the data for local symbols.
875 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
876 ie = Asm.symbol_end(); it != ie; ++it) {
877 const MCSymbol &Symbol = it->getSymbol();
879 // Ignore non-linker visible symbols.
880 if (!Asm.isSymbolLinkerVisible(it))
883 if (it->isExternal() || Symbol.isUndefined())
886 uint64_t &Entry = StringIndexMap[Symbol.getName()];
888 Entry = StringTable.size();
889 StringTable += Symbol.getName();
890 StringTable += '\x00';
895 MSD.StringIndex = Entry;
897 if (Symbol.isAbsolute()) {
898 MSD.SectionIndex = 0;
899 LocalSymbolData.push_back(MSD);
901 MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
902 assert(MSD.SectionIndex && "Invalid section index!");
903 LocalSymbolData.push_back(MSD);
907 // External and undefined symbols are required to be in lexicographic order.
908 std::sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
909 std::sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end());
911 // Set the symbol indices.
913 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
914 LocalSymbolData[i].SymbolData->setIndex(Index++);
915 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
916 ExternalSymbolData[i].SymbolData->setIndex(Index++);
917 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
918 UndefinedSymbolData[i].SymbolData->setIndex(Index++);
920 // The string table is padded to a multiple of 4.
921 while (StringTable.size() % 4)
922 StringTable += '\x00';
925 void ExecutePostLayoutBinding(MCAssembler &Asm) {
926 // Create symbol data for any indirect symbols.
927 BindIndirectSymbols(Asm);
929 // Compute symbol table information and bind symbol indices.
930 ComputeSymbolTable(Asm, StringTable, LocalSymbolData, ExternalSymbolData,
931 UndefinedSymbolData);
934 void WriteObject(const MCAssembler &Asm, const MCAsmLayout &Layout) {
935 unsigned NumSections = Asm.size();
937 // The section data starts after the header, the segment load command (and
938 // section headers) and the symbol table.
939 unsigned NumLoadCommands = 1;
940 uint64_t LoadCommandsSize = Is64Bit ?
941 SegmentLoadCommand64Size + NumSections * Section64Size :
942 SegmentLoadCommand32Size + NumSections * Section32Size;
944 // Add the symbol table load command sizes, if used.
945 unsigned NumSymbols = LocalSymbolData.size() + ExternalSymbolData.size() +
946 UndefinedSymbolData.size();
948 NumLoadCommands += 2;
949 LoadCommandsSize += SymtabLoadCommandSize + DysymtabLoadCommandSize;
952 // Compute the total size of the section data, as well as its file size and
954 uint64_t SectionDataStart = (Is64Bit ? Header64Size : Header32Size)
956 uint64_t SectionDataSize = 0;
957 uint64_t SectionDataFileSize = 0;
959 for (MCAssembler::const_iterator it = Asm.begin(),
960 ie = Asm.end(); it != ie; ++it) {
961 const MCSectionData &SD = *it;
962 uint64_t Address = Layout.getSectionAddress(&SD);
963 uint64_t Size = Layout.getSectionSize(&SD);
964 uint64_t FileSize = Layout.getSectionFileSize(&SD);
966 VMSize = std::max(VMSize, Address + Size);
968 if (Asm.getBackend().isVirtualSection(SD.getSection()))
971 SectionDataSize = std::max(SectionDataSize, Address + Size);
972 SectionDataFileSize = std::max(SectionDataFileSize, Address + FileSize);
975 // The section data is padded to 4 bytes.
977 // FIXME: Is this machine dependent?
978 unsigned SectionDataPadding = OffsetToAlignment(SectionDataFileSize, 4);
979 SectionDataFileSize += SectionDataPadding;
981 // Write the prolog, starting with the header and load command...
982 WriteHeader(NumLoadCommands, LoadCommandsSize,
983 Asm.getSubsectionsViaSymbols());
984 WriteSegmentLoadCommand(NumSections, VMSize,
985 SectionDataStart, SectionDataSize);
987 // ... and then the section headers.
988 uint64_t RelocTableEnd = SectionDataStart + SectionDataFileSize;
989 for (MCAssembler::const_iterator it = Asm.begin(),
990 ie = Asm.end(); it != ie; ++it) {
991 std::vector<MachRelocationEntry> &Relocs = Relocations[it];
992 unsigned NumRelocs = Relocs.size();
993 uint64_t SectionStart = SectionDataStart + Layout.getSectionAddress(it);
994 WriteSection(Asm, Layout, *it, SectionStart, RelocTableEnd, NumRelocs);
995 RelocTableEnd += NumRelocs * RelocationInfoSize;
998 // Write the symbol table load command, if used.
1000 unsigned FirstLocalSymbol = 0;
1001 unsigned NumLocalSymbols = LocalSymbolData.size();
1002 unsigned FirstExternalSymbol = FirstLocalSymbol + NumLocalSymbols;
1003 unsigned NumExternalSymbols = ExternalSymbolData.size();
1004 unsigned FirstUndefinedSymbol = FirstExternalSymbol + NumExternalSymbols;
1005 unsigned NumUndefinedSymbols = UndefinedSymbolData.size();
1006 unsigned NumIndirectSymbols = Asm.indirect_symbol_size();
1007 unsigned NumSymTabSymbols =
1008 NumLocalSymbols + NumExternalSymbols + NumUndefinedSymbols;
1009 uint64_t IndirectSymbolSize = NumIndirectSymbols * 4;
1010 uint64_t IndirectSymbolOffset = 0;
1012 // If used, the indirect symbols are written after the section data.
1013 if (NumIndirectSymbols)
1014 IndirectSymbolOffset = RelocTableEnd;
1016 // The symbol table is written after the indirect symbol data.
1017 uint64_t SymbolTableOffset = RelocTableEnd + IndirectSymbolSize;
1019 // The string table is written after symbol table.
1020 uint64_t StringTableOffset =
1021 SymbolTableOffset + NumSymTabSymbols * (Is64Bit ? Nlist64Size :
1023 WriteSymtabLoadCommand(SymbolTableOffset, NumSymTabSymbols,
1024 StringTableOffset, StringTable.size());
1026 WriteDysymtabLoadCommand(FirstLocalSymbol, NumLocalSymbols,
1027 FirstExternalSymbol, NumExternalSymbols,
1028 FirstUndefinedSymbol, NumUndefinedSymbols,
1029 IndirectSymbolOffset, NumIndirectSymbols);
1032 // Write the actual section data.
1033 for (MCAssembler::const_iterator it = Asm.begin(),
1034 ie = Asm.end(); it != ie; ++it)
1035 Asm.WriteSectionData(it, Layout, Writer);
1037 // Write the extra padding.
1038 WriteZeros(SectionDataPadding);
1040 // Write the relocation entries.
1041 for (MCAssembler::const_iterator it = Asm.begin(),
1042 ie = Asm.end(); it != ie; ++it) {
1043 // Write the section relocation entries, in reverse order to match 'as'
1044 // (approximately, the exact algorithm is more complicated than this).
1045 std::vector<MachRelocationEntry> &Relocs = Relocations[it];
1046 for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
1047 Write32(Relocs[e - i - 1].Word0);
1048 Write32(Relocs[e - i - 1].Word1);
1052 // Write the symbol table data, if used.
1054 // Write the indirect symbol entries.
1055 for (MCAssembler::const_indirect_symbol_iterator
1056 it = Asm.indirect_symbol_begin(),
1057 ie = Asm.indirect_symbol_end(); it != ie; ++it) {
1058 // Indirect symbols in the non lazy symbol pointer section have some
1059 // special handling.
1060 const MCSectionMachO &Section =
1061 static_cast<const MCSectionMachO&>(it->SectionData->getSection());
1062 if (Section.getType() == MCSectionMachO::S_NON_LAZY_SYMBOL_POINTERS) {
1063 // If this symbol is defined and internal, mark it as such.
1064 if (it->Symbol->isDefined() &&
1065 !Asm.getSymbolData(*it->Symbol).isExternal()) {
1066 uint32_t Flags = ISF_Local;
1067 if (it->Symbol->isAbsolute())
1068 Flags |= ISF_Absolute;
1074 Write32(Asm.getSymbolData(*it->Symbol).getIndex());
1077 // FIXME: Check that offsets match computed ones.
1079 // Write the symbol table entries.
1080 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
1081 WriteNlist(LocalSymbolData[i], Layout);
1082 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
1083 WriteNlist(ExternalSymbolData[i], Layout);
1084 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
1085 WriteNlist(UndefinedSymbolData[i], Layout);
1087 // Write the string table.
1088 OS << StringTable.str();
1095 MachObjectWriter::MachObjectWriter(raw_ostream &OS,
1097 bool IsLittleEndian)
1098 : MCObjectWriter(OS, IsLittleEndian)
1100 Impl = new MachObjectWriterImpl(this, Is64Bit);
1103 MachObjectWriter::~MachObjectWriter() {
1104 delete (MachObjectWriterImpl*) Impl;
1107 void MachObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm) {
1108 ((MachObjectWriterImpl*) Impl)->ExecutePostLayoutBinding(Asm);
1111 void MachObjectWriter::RecordRelocation(const MCAssembler &Asm,
1112 const MCAsmLayout &Layout,
1113 const MCFragment *Fragment,
1114 const MCAsmFixup &Fixup, MCValue Target,
1115 uint64_t &FixedValue) {
1116 ((MachObjectWriterImpl*) Impl)->RecordRelocation(Asm, Layout, Fragment, Fixup,
1117 Target, FixedValue);
1120 void MachObjectWriter::WriteObject(const MCAssembler &Asm,
1121 const MCAsmLayout &Layout) {
1122 ((MachObjectWriterImpl*) Impl)->WriteObject(Asm, Layout);