1 //===- tools/dsymutil/DwarfLinker.cpp - Dwarf debug info linker -----------===//
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 #include "BinaryHolder.h"
13 #include "llvm/CodeGen/AsmPrinter.h"
14 #include "llvm/CodeGen/DIE.h"
15 #include "llvm/DebugInfo/DWARF/DWARFContext.h"
16 #include "llvm/DebugInfo/DWARF/DWARFDebugInfoEntry.h"
17 #include "llvm/DebugInfo/DWARF/DWARFFormValue.h"
18 #include "llvm/MC/MCAsmBackend.h"
19 #include "llvm/MC/MCAsmInfo.h"
20 #include "llvm/MC/MCContext.h"
21 #include "llvm/MC/MCCodeEmitter.h"
22 #include "llvm/MC/MCInstrInfo.h"
23 #include "llvm/MC/MCObjectFileInfo.h"
24 #include "llvm/MC/MCRegisterInfo.h"
25 #include "llvm/MC/MCStreamer.h"
26 #include "llvm/Object/MachO.h"
27 #include "llvm/Support/Dwarf.h"
28 #include "llvm/Support/LEB128.h"
29 #include "llvm/Support/TargetRegistry.h"
30 #include "llvm/Target/TargetMachine.h"
31 #include "llvm/Target/TargetOptions.h"
39 void warn(const Twine &Warning, const Twine &Context) {
40 errs() << Twine("while processing ") + Context + ":\n";
41 errs() << Twine("warning: ") + Warning + "\n";
44 bool error(const Twine &Error, const Twine &Context) {
45 errs() << Twine("while processing ") + Context + ":\n";
46 errs() << Twine("error: ") + Error + "\n";
50 /// \brief Stores all information relating to a compile unit, be it in
51 /// its original instance in the object file to its brand new cloned
52 /// and linked DIE tree.
55 /// \brief Information gathered about a DIE in the object file.
57 uint64_t Address; ///< Linked address of the described entity.
58 uint32_t ParentIdx; ///< The index of this DIE's parent.
59 bool Keep; ///< Is the DIE part of the linked output?
60 bool InDebugMap; ///< Was this DIE's entity found in the map?
63 CompileUnit(DWARFUnit &OrigUnit) : OrigUnit(OrigUnit) {
64 Info.resize(OrigUnit.getNumDIEs());
67 // Workaround MSVC not supporting implicit move ops
68 CompileUnit(CompileUnit &&RHS)
69 : OrigUnit(RHS.OrigUnit), Info(std::move(RHS.Info)),
70 CUDie(std::move(RHS.CUDie)), StartOffset(RHS.StartOffset),
71 NextUnitOffset(RHS.NextUnitOffset) {}
73 DWARFUnit &getOrigUnit() const { return OrigUnit; }
75 DIE *getOutputUnitDIE() const { return CUDie.get(); }
76 void setOutputUnitDIE(DIE *Die) { CUDie.reset(Die); }
78 DIEInfo &getInfo(unsigned Idx) { return Info[Idx]; }
79 const DIEInfo &getInfo(unsigned Idx) const { return Info[Idx]; }
81 uint64_t getStartOffset() const { return StartOffset; }
82 uint64_t getNextUnitOffset() const { return NextUnitOffset; }
84 /// \brief Set the start and end offsets for this unit. Must be
85 /// called after the CU's DIEs have been cloned. The unit start
86 /// offset will be set to \p DebugInfoSize.
87 /// \returns the next unit offset (which is also the current
88 /// debug_info section size).
89 uint64_t computeOffsets(uint64_t DebugInfoSize);
93 std::vector<DIEInfo> Info; ///< DIE info indexed by DIE index.
94 std::unique_ptr<DIE> CUDie; ///< Root of the linked DIE tree.
97 uint64_t NextUnitOffset;
100 uint64_t CompileUnit::computeOffsets(uint64_t DebugInfoSize) {
101 StartOffset = DebugInfoSize;
102 NextUnitOffset = StartOffset + 11 /* Header size */;
103 // The root DIE might be null, meaning that the Unit had nothing to
104 // contribute to the linked output. In that case, we will emit the
105 // unit header without any actual DIE.
107 NextUnitOffset += CUDie->getSize();
108 return NextUnitOffset;
111 /// \brief A string table that doesn't need relocations.
113 /// We are doing a final link, no need for a string table that
114 /// has relocation entries for every reference to it. This class
115 /// provides this ablitity by just associating offsets with
117 class NonRelocatableStringpool {
119 /// \brief Entries are stored into the StringMap and simply linked
120 /// together through the second element of this pair in order to
121 /// keep track of insertion order.
122 typedef StringMap<std::pair<uint32_t, StringMapEntryBase *>, BumpPtrAllocator>
125 NonRelocatableStringpool()
126 : CurrentEndOffset(0), Sentinel(0), Last(&Sentinel) {
127 // Legacy dsymutil puts an empty string at the start of the line
132 /// \brief Get the offset of string \p S in the string table. This
133 /// can insert a new element or return the offset of a preexisitng
135 uint32_t getStringOffset(StringRef S);
137 /// \brief Get permanent storage for \p S (but do not necessarily
138 /// emit \p S in the output section).
139 /// \returns The StringRef that points to permanent storage to use
140 /// in place of \p S.
141 StringRef internString(StringRef S);
143 // \brief Return the first entry of the string table.
144 const MapTy::MapEntryTy *getFirstEntry() const {
145 return getNextEntry(&Sentinel);
148 // \brief Get the entry following \p E in the string table or null
149 // if \p E was the last entry.
150 const MapTy::MapEntryTy *getNextEntry(const MapTy::MapEntryTy *E) const {
151 return static_cast<const MapTy::MapEntryTy *>(E->getValue().second);
154 uint64_t getSize() { return CurrentEndOffset; }
158 uint32_t CurrentEndOffset;
159 MapTy::MapEntryTy Sentinel, *Last;
162 /// \brief Get the offset of string \p S in the string table. This
163 /// can insert a new element or return the offset of a preexisitng
165 uint32_t NonRelocatableStringpool::getStringOffset(StringRef S) {
166 if (S.empty() && !Strings.empty())
169 std::pair<uint32_t, StringMapEntryBase *> Entry(0, nullptr);
173 // A non-empty string can't be at offset 0, so if we have an entry
174 // with a 0 offset, it must be a previously interned string.
175 std::tie(It, Inserted) = Strings.insert(std::make_pair(S, Entry));
176 if (Inserted || It->getValue().first == 0) {
177 // Set offset and chain at the end of the entries list.
178 It->getValue().first = CurrentEndOffset;
179 CurrentEndOffset += S.size() + 1; // +1 for the '\0'.
180 Last->getValue().second = &*It;
183 return It->getValue().first;
186 /// \brief Put \p S into the StringMap so that it gets permanent
187 /// storage, but do not actually link it in the chain of elements
188 /// that go into the output section. A latter call to
189 /// getStringOffset() with the same string will chain it though.
190 StringRef NonRelocatableStringpool::internString(StringRef S) {
191 std::pair<uint32_t, StringMapEntryBase *> Entry(0, nullptr);
192 auto InsertResult = Strings.insert(std::make_pair(S, Entry));
193 return InsertResult.first->getKey();
196 /// \brief The Dwarf streaming logic
198 /// All interactions with the MC layer that is used to build the debug
199 /// information binary representation are handled in this class.
200 class DwarfStreamer {
201 /// \defgroup MCObjects MC layer objects constructed by the streamer
203 std::unique_ptr<MCRegisterInfo> MRI;
204 std::unique_ptr<MCAsmInfo> MAI;
205 std::unique_ptr<MCObjectFileInfo> MOFI;
206 std::unique_ptr<MCContext> MC;
207 MCAsmBackend *MAB; // Owned by MCStreamer
208 std::unique_ptr<MCInstrInfo> MII;
209 std::unique_ptr<MCSubtargetInfo> MSTI;
210 MCCodeEmitter *MCE; // Owned by MCStreamer
211 MCStreamer *MS; // Owned by AsmPrinter
212 std::unique_ptr<TargetMachine> TM;
213 std::unique_ptr<AsmPrinter> Asm;
216 /// \brief the file we stream the linked Dwarf to.
217 std::unique_ptr<raw_fd_ostream> OutFile;
220 /// \brief Actually create the streamer and the ouptut file.
222 /// This could be done directly in the constructor, but it feels
223 /// more natural to handle errors through return value.
224 bool init(Triple TheTriple, StringRef OutputFilename);
226 /// \brief Dump the file to the disk.
229 AsmPrinter &getAsmPrinter() const { return *Asm; }
231 /// \brief Set the current output section to debug_info and change
232 /// the MC Dwarf version to \p DwarfVersion.
233 void switchToDebugInfoSection(unsigned DwarfVersion);
235 /// \brief Emit the compilation unit header for \p Unit in the
236 /// debug_info section.
238 /// As a side effect, this also switches the current Dwarf version
239 /// of the MC layer to the one of U.getOrigUnit().
240 void emitCompileUnitHeader(CompileUnit &Unit);
242 /// \brief Recursively emit the DIE tree rooted at \p Die.
243 void emitDIE(DIE &Die);
245 /// \brief Emit the abbreviation table \p Abbrevs to the
246 /// debug_abbrev section.
247 void emitAbbrevs(const std::vector<DIEAbbrev *> &Abbrevs);
249 /// \brief Emit the string table described by \p Pool.
250 void emitStrings(const NonRelocatableStringpool &Pool);
253 bool DwarfStreamer::init(Triple TheTriple, StringRef OutputFilename) {
254 std::string ErrorStr;
255 std::string TripleName;
256 StringRef Context = "dwarf streamer init";
259 const Target *TheTarget =
260 TargetRegistry::lookupTarget(TripleName, TheTriple, ErrorStr);
262 return error(ErrorStr, Context);
263 TripleName = TheTriple.getTriple();
265 // Create all the MC Objects.
266 MRI.reset(TheTarget->createMCRegInfo(TripleName));
268 return error(Twine("no register info for target ") + TripleName, Context);
270 MAI.reset(TheTarget->createMCAsmInfo(*MRI, TripleName));
272 return error("no asm info for target " + TripleName, Context);
274 MOFI.reset(new MCObjectFileInfo);
275 MC.reset(new MCContext(MAI.get(), MRI.get(), MOFI.get()));
276 MOFI->InitMCObjectFileInfo(TripleName, Reloc::Default, CodeModel::Default,
279 MAB = TheTarget->createMCAsmBackend(*MRI, TripleName, "");
281 return error("no asm backend for target " + TripleName, Context);
283 MII.reset(TheTarget->createMCInstrInfo());
285 return error("no instr info info for target " + TripleName, Context);
287 MSTI.reset(TheTarget->createMCSubtargetInfo(TripleName, "", ""));
289 return error("no subtarget info for target " + TripleName, Context);
291 MCE = TheTarget->createMCCodeEmitter(*MII, *MRI, *MSTI, *MC);
293 return error("no code emitter for target " + TripleName, Context);
295 // Create the output file.
298 llvm::make_unique<raw_fd_ostream>(OutputFilename, EC, sys::fs::F_None);
300 return error(Twine(OutputFilename) + ": " + EC.message(), Context);
302 MS = TheTarget->createMCObjectStreamer(TripleName, *MC, *MAB, *OutFile, MCE,
305 return error("no object streamer for target " + TripleName, Context);
307 // Finally create the AsmPrinter we'll use to emit the DIEs.
308 TM.reset(TheTarget->createTargetMachine(TripleName, "", "", TargetOptions()));
310 return error("no target machine for target " + TripleName, Context);
312 Asm.reset(TheTarget->createAsmPrinter(*TM, std::unique_ptr<MCStreamer>(MS)));
314 return error("no asm printer for target " + TripleName, Context);
319 bool DwarfStreamer::finish() {
324 /// \brief Set the current output section to debug_info and change
325 /// the MC Dwarf version to \p DwarfVersion.
326 void DwarfStreamer::switchToDebugInfoSection(unsigned DwarfVersion) {
327 MS->SwitchSection(MOFI->getDwarfInfoSection());
328 MC->setDwarfVersion(DwarfVersion);
331 /// \brief Emit the compilation unit header for \p Unit in the
332 /// debug_info section.
334 /// A Dwarf scetion header is encoded as:
335 /// uint32_t Unit length (omiting this field)
337 /// uint32_t Abbreviation table offset
338 /// uint8_t Address size
340 /// Leading to a total of 11 bytes.
341 void DwarfStreamer::emitCompileUnitHeader(CompileUnit &Unit) {
342 unsigned Version = Unit.getOrigUnit().getVersion();
343 switchToDebugInfoSection(Version);
345 // Emit size of content not including length itself. The size has
346 // already been computed in CompileUnit::computeOffsets(). Substract
347 // 4 to that size to account for the length field.
348 Asm->EmitInt32(Unit.getNextUnitOffset() - Unit.getStartOffset() - 4);
349 Asm->EmitInt16(Version);
350 // We share one abbreviations table across all units so it's always at the
351 // start of the section.
353 Asm->EmitInt8(Unit.getOrigUnit().getAddressByteSize());
356 /// \brief Emit the \p Abbrevs array as the shared abbreviation table
357 /// for the linked Dwarf file.
358 void DwarfStreamer::emitAbbrevs(const std::vector<DIEAbbrev *> &Abbrevs) {
359 MS->SwitchSection(MOFI->getDwarfAbbrevSection());
360 Asm->emitDwarfAbbrevs(Abbrevs);
363 /// \brief Recursively emit the DIE tree rooted at \p Die.
364 void DwarfStreamer::emitDIE(DIE &Die) {
365 MS->SwitchSection(MOFI->getDwarfInfoSection());
366 Asm->emitDwarfDIE(Die);
369 /// \brief Emit the debug_str section stored in \p Pool.
370 void DwarfStreamer::emitStrings(const NonRelocatableStringpool &Pool) {
371 Asm->OutStreamer.SwitchSection(MOFI->getDwarfStrSection());
372 for (auto *Entry = Pool.getFirstEntry(); Entry;
373 Entry = Pool.getNextEntry(Entry))
374 Asm->OutStreamer.EmitBytes(
375 StringRef(Entry->getKey().data(), Entry->getKey().size() + 1));
378 /// \brief The core of the Dwarf linking logic.
380 /// The link of the dwarf information from the object files will be
381 /// driven by the selection of 'root DIEs', which are DIEs that
382 /// describe variables or functions that are present in the linked
383 /// binary (and thus have entries in the debug map). All the debug
384 /// information that will be linked (the DIEs, but also the line
385 /// tables, ranges, ...) is derived from that set of root DIEs.
387 /// The root DIEs are identified because they contain relocations that
388 /// correspond to a debug map entry at specific places (the low_pc for
389 /// a function, the location for a variable). These relocations are
390 /// called ValidRelocs in the DwarfLinker and are gathered as a very
391 /// first step when we start processing a DebugMapObject.
394 DwarfLinker(StringRef OutputFilename, const LinkOptions &Options)
395 : OutputFilename(OutputFilename), Options(Options),
396 BinHolder(Options.Verbose) {}
399 for (auto *Abbrev : Abbreviations)
403 /// \brief Link the contents of the DebugMap.
404 bool link(const DebugMap &);
407 /// \brief Called at the start of a debug object link.
408 void startDebugObject(DWARFContext &);
410 /// \brief Called at the end of a debug object link.
411 void endDebugObject();
413 /// \defgroup FindValidRelocations Translate debug map into a list
414 /// of relevant relocations
421 const DebugMapObject::DebugMapEntry *Mapping;
423 ValidReloc(uint32_t Offset, uint32_t Size, uint64_t Addend,
424 const DebugMapObject::DebugMapEntry *Mapping)
425 : Offset(Offset), Size(Size), Addend(Addend), Mapping(Mapping) {}
427 bool operator<(const ValidReloc &RHS) const { return Offset < RHS.Offset; }
430 /// \brief The valid relocations for the current DebugMapObject.
431 /// This vector is sorted by relocation offset.
432 std::vector<ValidReloc> ValidRelocs;
434 /// \brief Index into ValidRelocs of the next relocation to
435 /// consider. As we walk the DIEs in acsending file offset and as
436 /// ValidRelocs is sorted by file offset, keeping this index
437 /// uptodate is all we have to do to have a cheap lookup during the
438 /// root DIE selection.
439 unsigned NextValidReloc;
441 bool findValidRelocsInDebugInfo(const object::ObjectFile &Obj,
442 const DebugMapObject &DMO);
444 bool findValidRelocs(const object::SectionRef &Section,
445 const object::ObjectFile &Obj,
446 const DebugMapObject &DMO);
448 void findValidRelocsMachO(const object::SectionRef &Section,
449 const object::MachOObjectFile &Obj,
450 const DebugMapObject &DMO);
453 /// \defgroup FindRootDIEs Find DIEs corresponding to debug map entries.
456 /// \brief Recursively walk the \p DIE tree and look for DIEs to
457 /// keep. Store that information in \p CU's DIEInfo.
458 void lookForDIEsToKeep(const DWARFDebugInfoEntryMinimal &DIE,
459 const DebugMapObject &DMO, CompileUnit &CU,
462 /// \brief Flags passed to DwarfLinker::lookForDIEsToKeep
464 TF_Keep = 1 << 0, ///< Mark the traversed DIEs as kept.
465 TF_InFunctionScope = 1 << 1, ///< Current scope is a fucntion scope.
466 TF_DependencyWalk = 1 << 2, ///< Walking the dependencies of a kept DIE.
467 TF_ParentWalk = 1 << 3, ///< Walking up the parents of a kept DIE.
470 /// \brief Mark the passed DIE as well as all the ones it depends on
472 void keepDIEAndDenpendencies(const DWARFDebugInfoEntryMinimal &DIE,
473 CompileUnit::DIEInfo &MyInfo,
474 const DebugMapObject &DMO, CompileUnit &CU,
477 unsigned shouldKeepDIE(const DWARFDebugInfoEntryMinimal &DIE,
478 CompileUnit &Unit, CompileUnit::DIEInfo &MyInfo,
481 unsigned shouldKeepVariableDIE(const DWARFDebugInfoEntryMinimal &DIE,
483 CompileUnit::DIEInfo &MyInfo, unsigned Flags);
485 unsigned shouldKeepSubprogramDIE(const DWARFDebugInfoEntryMinimal &DIE,
487 CompileUnit::DIEInfo &MyInfo,
490 bool hasValidRelocation(uint32_t StartOffset, uint32_t EndOffset,
491 CompileUnit::DIEInfo &Info);
494 /// \defgroup Linking Methods used to link the debug information
497 /// \brief Recursively clone \p InputDIE into an tree of DIE objects
498 /// where useless (as decided by lookForDIEsToKeep()) bits have been
499 /// stripped out and addresses have been rewritten according to the
502 /// \param OutOffset is the offset the cloned DIE in the output
505 /// \returns the root of the cloned tree.
506 DIE *cloneDIE(const DWARFDebugInfoEntryMinimal &InputDIE, CompileUnit &U,
509 typedef DWARFAbbreviationDeclaration::AttributeSpec AttributeSpec;
511 /// \brief Helper for cloneDIE.
512 unsigned cloneAttribute(DIE &Die, const DWARFDebugInfoEntryMinimal &InputDIE,
513 CompileUnit &U, const DWARFFormValue &Val,
514 const AttributeSpec AttrSpec, unsigned AttrSize);
516 /// \brief Helper for cloneDIE.
517 unsigned cloneStringAttribute(DIE &Die, AttributeSpec AttrSpec,
518 const DWARFFormValue &Val, const DWARFUnit &U);
520 /// \brief Helper for cloneDIE.
521 unsigned cloneDieReferenceAttribute(DIE &Die, AttributeSpec AttrSpec,
524 /// \brief Helper for cloneDIE.
525 unsigned cloneBlockAttribute(DIE &Die, AttributeSpec AttrSpec,
526 const DWARFFormValue &Val, unsigned AttrSize);
528 /// \brief Helper for cloneDIE.
529 unsigned cloneScalarAttribute(DIE &Die,
530 const DWARFDebugInfoEntryMinimal &InputDIE,
531 const DWARFUnit &U, AttributeSpec AttrSpec,
532 const DWARFFormValue &Val, unsigned AttrSize);
534 /// \brief Assign an abbreviation number to \p Abbrev
535 void AssignAbbrev(DIEAbbrev &Abbrev);
537 /// \brief FoldingSet that uniques the abbreviations.
538 FoldingSet<DIEAbbrev> AbbreviationsSet;
539 /// \brief Storage for the unique Abbreviations.
540 /// This is passed to AsmPrinter::emitDwarfAbbrevs(), thus it cannot
541 /// be changed to a vecot of unique_ptrs.
542 std::vector<DIEAbbrev *> Abbreviations;
544 /// \brief DIELoc objects that need to be destructed (but not freed!).
545 std::vector<DIELoc *> DIELocs;
546 /// \brief DIEBlock objects that need to be destructed (but not freed!).
547 std::vector<DIEBlock *> DIEBlocks;
548 /// \brief Allocator used for all the DIEValue objects.
549 BumpPtrAllocator DIEAlloc;
552 /// \defgroup Helpers Various helper methods.
555 const DWARFDebugInfoEntryMinimal *
556 resolveDIEReference(DWARFFormValue &RefValue, const DWARFUnit &Unit,
557 const DWARFDebugInfoEntryMinimal &DIE,
558 CompileUnit *&ReferencedCU);
560 CompileUnit *getUnitForOffset(unsigned Offset);
562 void reportWarning(const Twine &Warning, const DWARFUnit *Unit = nullptr,
563 const DWARFDebugInfoEntryMinimal *DIE = nullptr);
565 bool createStreamer(Triple TheTriple, StringRef OutputFilename);
569 std::string OutputFilename;
571 BinaryHolder BinHolder;
572 std::unique_ptr<DwarfStreamer> Streamer;
574 /// The units of the current debug map object.
575 std::vector<CompileUnit> Units;
577 /// The debug map object curently under consideration.
578 DebugMapObject *CurrentDebugObject;
580 /// \brief The Dwarf string pool
581 NonRelocatableStringpool StringPool;
584 /// \brief Similar to DWARFUnitSection::getUnitForOffset(), but
585 /// returning our CompileUnit object instead.
586 CompileUnit *DwarfLinker::getUnitForOffset(unsigned Offset) {
588 std::upper_bound(Units.begin(), Units.end(), Offset,
589 [](uint32_t LHS, const CompileUnit &RHS) {
590 return LHS < RHS.getOrigUnit().getNextUnitOffset();
592 return CU != Units.end() ? &*CU : nullptr;
595 /// \brief Resolve the DIE attribute reference that has been
596 /// extracted in \p RefValue. The resulting DIE migh be in another
597 /// CompileUnit which is stored into \p ReferencedCU.
598 /// \returns null if resolving fails for any reason.
599 const DWARFDebugInfoEntryMinimal *DwarfLinker::resolveDIEReference(
600 DWARFFormValue &RefValue, const DWARFUnit &Unit,
601 const DWARFDebugInfoEntryMinimal &DIE, CompileUnit *&RefCU) {
602 assert(RefValue.isFormClass(DWARFFormValue::FC_Reference));
603 uint64_t RefOffset = *RefValue.getAsReference(&Unit);
605 if ((RefCU = getUnitForOffset(RefOffset)))
606 if (const auto *RefDie = RefCU->getOrigUnit().getDIEForOffset(RefOffset))
609 reportWarning("could not find referenced DIE", &Unit, &DIE);
613 /// \brief Report a warning to the user, optionaly including
614 /// information about a specific \p DIE related to the warning.
615 void DwarfLinker::reportWarning(const Twine &Warning, const DWARFUnit *Unit,
616 const DWARFDebugInfoEntryMinimal *DIE) {
617 StringRef Context = "<debug map>";
618 if (CurrentDebugObject)
619 Context = CurrentDebugObject->getObjectFilename();
620 warn(Warning, Context);
622 if (!Options.Verbose || !DIE)
625 errs() << " in DIE:\n";
626 DIE->dump(errs(), const_cast<DWARFUnit *>(Unit), 0 /* RecurseDepth */,
630 bool DwarfLinker::createStreamer(Triple TheTriple, StringRef OutputFilename) {
631 if (Options.NoOutput)
634 Streamer = llvm::make_unique<DwarfStreamer>();
635 return Streamer->init(TheTriple, OutputFilename);
638 /// \brief Recursive helper to gather the child->parent relationships in the
639 /// original compile unit.
640 static void gatherDIEParents(const DWARFDebugInfoEntryMinimal *DIE,
641 unsigned ParentIdx, CompileUnit &CU) {
642 unsigned MyIdx = CU.getOrigUnit().getDIEIndex(DIE);
643 CU.getInfo(MyIdx).ParentIdx = ParentIdx;
645 if (DIE->hasChildren())
646 for (auto *Child = DIE->getFirstChild(); Child && !Child->isNULL();
647 Child = Child->getSibling())
648 gatherDIEParents(Child, MyIdx, CU);
651 static bool dieNeedsChildrenToBeMeaningful(uint32_t Tag) {
655 case dwarf::DW_TAG_subprogram:
656 case dwarf::DW_TAG_lexical_block:
657 case dwarf::DW_TAG_subroutine_type:
658 case dwarf::DW_TAG_structure_type:
659 case dwarf::DW_TAG_class_type:
660 case dwarf::DW_TAG_union_type:
663 llvm_unreachable("Invalid Tag");
666 void DwarfLinker::startDebugObject(DWARFContext &Dwarf) {
667 Units.reserve(Dwarf.getNumCompileUnits());
671 void DwarfLinker::endDebugObject() {
675 for (auto *Block : DIEBlocks)
677 for (auto *Loc : DIELocs)
685 /// \brief Iterate over the relocations of the given \p Section and
686 /// store the ones that correspond to debug map entries into the
687 /// ValidRelocs array.
688 void DwarfLinker::findValidRelocsMachO(const object::SectionRef &Section,
689 const object::MachOObjectFile &Obj,
690 const DebugMapObject &DMO) {
692 Section.getContents(Contents);
693 DataExtractor Data(Contents, Obj.isLittleEndian(), 0);
695 for (const object::RelocationRef &Reloc : Section.relocations()) {
696 object::DataRefImpl RelocDataRef = Reloc.getRawDataRefImpl();
697 MachO::any_relocation_info MachOReloc = Obj.getRelocation(RelocDataRef);
698 unsigned RelocSize = 1 << Obj.getAnyRelocationLength(MachOReloc);
700 if ((RelocSize != 4 && RelocSize != 8) || Reloc.getOffset(Offset64)) {
701 reportWarning(" unsupported relocation in debug_info section.");
704 uint32_t Offset = Offset64;
705 // Mach-o uses REL relocations, the addend is at the relocation offset.
706 uint64_t Addend = Data.getUnsigned(&Offset, RelocSize);
708 auto Sym = Reloc.getSymbol();
709 if (Sym != Obj.symbol_end()) {
710 StringRef SymbolName;
711 if (Sym->getName(SymbolName)) {
712 reportWarning("error getting relocation symbol name.");
715 if (const auto *Mapping = DMO.lookupSymbol(SymbolName))
716 ValidRelocs.emplace_back(Offset64, RelocSize, Addend, Mapping);
717 } else if (const auto *Mapping = DMO.lookupObjectAddress(Addend)) {
718 // Do not store the addend. The addend was the address of the
719 // symbol in the object file, the address in the binary that is
720 // stored in the debug map doesn't need to be offseted.
721 ValidRelocs.emplace_back(Offset64, RelocSize, 0, Mapping);
726 /// \brief Dispatch the valid relocation finding logic to the
727 /// appropriate handler depending on the object file format.
728 bool DwarfLinker::findValidRelocs(const object::SectionRef &Section,
729 const object::ObjectFile &Obj,
730 const DebugMapObject &DMO) {
731 // Dispatch to the right handler depending on the file type.
732 if (auto *MachOObj = dyn_cast<object::MachOObjectFile>(&Obj))
733 findValidRelocsMachO(Section, *MachOObj, DMO);
735 reportWarning(Twine("unsupported object file type: ") + Obj.getFileName());
737 if (ValidRelocs.empty())
740 // Sort the relocations by offset. We will walk the DIEs linearly in
741 // the file, this allows us to just keep an index in the relocation
742 // array that we advance during our walk, rather than resorting to
743 // some associative container. See DwarfLinker::NextValidReloc.
744 std::sort(ValidRelocs.begin(), ValidRelocs.end());
748 /// \brief Look for relocations in the debug_info section that match
749 /// entries in the debug map. These relocations will drive the Dwarf
750 /// link by indicating which DIEs refer to symbols present in the
752 /// \returns wether there are any valid relocations in the debug info.
753 bool DwarfLinker::findValidRelocsInDebugInfo(const object::ObjectFile &Obj,
754 const DebugMapObject &DMO) {
755 // Find the debug_info section.
756 for (const object::SectionRef &Section : Obj.sections()) {
757 StringRef SectionName;
758 Section.getName(SectionName);
759 SectionName = SectionName.substr(SectionName.find_first_not_of("._"));
760 if (SectionName != "debug_info")
762 return findValidRelocs(Section, Obj, DMO);
767 /// \brief Checks that there is a relocation against an actual debug
768 /// map entry between \p StartOffset and \p NextOffset.
770 /// This function must be called with offsets in strictly ascending
771 /// order because it never looks back at relocations it already 'went past'.
772 /// \returns true and sets Info.InDebugMap if it is the case.
773 bool DwarfLinker::hasValidRelocation(uint32_t StartOffset, uint32_t EndOffset,
774 CompileUnit::DIEInfo &Info) {
775 assert(NextValidReloc == 0 ||
776 StartOffset > ValidRelocs[NextValidReloc - 1].Offset);
777 if (NextValidReloc >= ValidRelocs.size())
780 uint64_t RelocOffset = ValidRelocs[NextValidReloc].Offset;
782 // We might need to skip some relocs that we didn't consider. For
783 // example the high_pc of a discarded DIE might contain a reloc that
784 // is in the list because it actually corresponds to the start of a
785 // function that is in the debug map.
786 while (RelocOffset < StartOffset && NextValidReloc < ValidRelocs.size() - 1)
787 RelocOffset = ValidRelocs[++NextValidReloc].Offset;
789 if (RelocOffset < StartOffset || RelocOffset >= EndOffset)
792 const auto &ValidReloc = ValidRelocs[NextValidReloc++];
794 outs() << "Found valid debug map entry: " << ValidReloc.Mapping->getKey()
795 << " " << format("\t%016" PRIx64 " => %016" PRIx64,
796 ValidReloc.Mapping->getValue().ObjectAddress,
797 ValidReloc.Mapping->getValue().BinaryAddress);
800 ValidReloc.Mapping->getValue().BinaryAddress + ValidReloc.Addend;
801 Info.InDebugMap = true;
805 /// \brief Get the starting and ending (exclusive) offset for the
806 /// attribute with index \p Idx descibed by \p Abbrev. \p Offset is
807 /// supposed to point to the position of the first attribute described
809 /// \return [StartOffset, EndOffset) as a pair.
810 static std::pair<uint32_t, uint32_t>
811 getAttributeOffsets(const DWARFAbbreviationDeclaration *Abbrev, unsigned Idx,
812 unsigned Offset, const DWARFUnit &Unit) {
813 DataExtractor Data = Unit.getDebugInfoExtractor();
815 for (unsigned i = 0; i < Idx; ++i)
816 DWARFFormValue::skipValue(Abbrev->getFormByIndex(i), Data, &Offset, &Unit);
818 uint32_t End = Offset;
819 DWARFFormValue::skipValue(Abbrev->getFormByIndex(Idx), Data, &End, &Unit);
821 return std::make_pair(Offset, End);
824 /// \brief Check if a variable describing DIE should be kept.
825 /// \returns updated TraversalFlags.
826 unsigned DwarfLinker::shouldKeepVariableDIE(
827 const DWARFDebugInfoEntryMinimal &DIE, CompileUnit &Unit,
828 CompileUnit::DIEInfo &MyInfo, unsigned Flags) {
829 const auto *Abbrev = DIE.getAbbreviationDeclarationPtr();
831 // Global variables with constant value can always be kept.
832 if (!(Flags & TF_InFunctionScope) &&
833 Abbrev->findAttributeIndex(dwarf::DW_AT_const_value) != -1U) {
834 MyInfo.InDebugMap = true;
835 return Flags | TF_Keep;
838 uint32_t LocationIdx = Abbrev->findAttributeIndex(dwarf::DW_AT_location);
839 if (LocationIdx == -1U)
842 uint32_t Offset = DIE.getOffset() + getULEB128Size(Abbrev->getCode());
843 const DWARFUnit &OrigUnit = Unit.getOrigUnit();
844 uint32_t LocationOffset, LocationEndOffset;
845 std::tie(LocationOffset, LocationEndOffset) =
846 getAttributeOffsets(Abbrev, LocationIdx, Offset, OrigUnit);
848 // See if there is a relocation to a valid debug map entry inside
849 // this variable's location. The order is important here. We want to
850 // always check in the variable has a valid relocation, so that the
851 // DIEInfo is filled. However, we don't want a static variable in a
852 // function to force us to keep the enclosing function.
853 if (!hasValidRelocation(LocationOffset, LocationEndOffset, MyInfo) ||
854 (Flags & TF_InFunctionScope))
858 DIE.dump(outs(), const_cast<DWARFUnit *>(&OrigUnit), 0, 8 /* Indent */);
860 return Flags | TF_Keep;
863 /// \brief Check if a function describing DIE should be kept.
864 /// \returns updated TraversalFlags.
865 unsigned DwarfLinker::shouldKeepSubprogramDIE(
866 const DWARFDebugInfoEntryMinimal &DIE, CompileUnit &Unit,
867 CompileUnit::DIEInfo &MyInfo, unsigned Flags) {
868 const auto *Abbrev = DIE.getAbbreviationDeclarationPtr();
870 Flags |= TF_InFunctionScope;
872 uint32_t LowPcIdx = Abbrev->findAttributeIndex(dwarf::DW_AT_low_pc);
876 uint32_t Offset = DIE.getOffset() + getULEB128Size(Abbrev->getCode());
877 const DWARFUnit &OrigUnit = Unit.getOrigUnit();
878 uint32_t LowPcOffset, LowPcEndOffset;
879 std::tie(LowPcOffset, LowPcEndOffset) =
880 getAttributeOffsets(Abbrev, LowPcIdx, Offset, OrigUnit);
883 DIE.getAttributeValueAsAddress(&OrigUnit, dwarf::DW_AT_low_pc, -1ULL);
884 assert(LowPc != -1ULL && "low_pc attribute is not an address.");
885 if (LowPc == -1ULL ||
886 !hasValidRelocation(LowPcOffset, LowPcEndOffset, MyInfo))
890 DIE.dump(outs(), const_cast<DWARFUnit *>(&OrigUnit), 0, 8 /* Indent */);
892 return Flags | TF_Keep;
895 /// \brief Check if a DIE should be kept.
896 /// \returns updated TraversalFlags.
897 unsigned DwarfLinker::shouldKeepDIE(const DWARFDebugInfoEntryMinimal &DIE,
899 CompileUnit::DIEInfo &MyInfo,
901 switch (DIE.getTag()) {
902 case dwarf::DW_TAG_constant:
903 case dwarf::DW_TAG_variable:
904 return shouldKeepVariableDIE(DIE, Unit, MyInfo, Flags);
905 case dwarf::DW_TAG_subprogram:
906 return shouldKeepSubprogramDIE(DIE, Unit, MyInfo, Flags);
907 case dwarf::DW_TAG_module:
908 case dwarf::DW_TAG_imported_module:
909 case dwarf::DW_TAG_imported_declaration:
910 case dwarf::DW_TAG_imported_unit:
911 // We always want to keep these.
912 return Flags | TF_Keep;
918 /// \brief Mark the passed DIE as well as all the ones it depends on
921 /// This function is called by lookForDIEsToKeep on DIEs that are
922 /// newly discovered to be needed in the link. It recursively calls
923 /// back to lookForDIEsToKeep while adding TF_DependencyWalk to the
924 /// TraversalFlags to inform it that it's not doing the primary DIE
926 void DwarfLinker::keepDIEAndDenpendencies(const DWARFDebugInfoEntryMinimal &DIE,
927 CompileUnit::DIEInfo &MyInfo,
928 const DebugMapObject &DMO,
929 CompileUnit &CU, unsigned Flags) {
930 const DWARFUnit &Unit = CU.getOrigUnit();
933 // First mark all the parent chain as kept.
934 unsigned AncestorIdx = MyInfo.ParentIdx;
935 while (!CU.getInfo(AncestorIdx).Keep) {
936 lookForDIEsToKeep(*Unit.getDIEAtIndex(AncestorIdx), DMO, CU,
937 TF_ParentWalk | TF_Keep | TF_DependencyWalk);
938 AncestorIdx = CU.getInfo(AncestorIdx).ParentIdx;
941 // Then we need to mark all the DIEs referenced by this DIE's
942 // attributes as kept.
943 DataExtractor Data = Unit.getDebugInfoExtractor();
944 const auto *Abbrev = DIE.getAbbreviationDeclarationPtr();
945 uint32_t Offset = DIE.getOffset() + getULEB128Size(Abbrev->getCode());
947 // Mark all DIEs referenced through atttributes as kept.
948 for (const auto &AttrSpec : Abbrev->attributes()) {
949 DWARFFormValue Val(AttrSpec.Form);
951 if (!Val.isFormClass(DWARFFormValue::FC_Reference)) {
952 DWARFFormValue::skipValue(AttrSpec.Form, Data, &Offset, &Unit);
956 Val.extractValue(Data, &Offset, &Unit);
957 CompileUnit *ReferencedCU;
958 if (const auto *RefDIE = resolveDIEReference(Val, Unit, DIE, ReferencedCU))
959 lookForDIEsToKeep(*RefDIE, DMO, *ReferencedCU,
960 TF_Keep | TF_DependencyWalk);
964 /// \brief Recursively walk the \p DIE tree and look for DIEs to
965 /// keep. Store that information in \p CU's DIEInfo.
967 /// This function is the entry point of the DIE selection
968 /// algorithm. It is expected to walk the DIE tree in file order and
969 /// (though the mediation of its helper) call hasValidRelocation() on
970 /// each DIE that might be a 'root DIE' (See DwarfLinker class
972 /// While walking the dependencies of root DIEs, this function is
973 /// also called, but during these dependency walks the file order is
974 /// not respected. The TF_DependencyWalk flag tells us which kind of
975 /// traversal we are currently doing.
976 void DwarfLinker::lookForDIEsToKeep(const DWARFDebugInfoEntryMinimal &DIE,
977 const DebugMapObject &DMO, CompileUnit &CU,
979 unsigned Idx = CU.getOrigUnit().getDIEIndex(&DIE);
980 CompileUnit::DIEInfo &MyInfo = CU.getInfo(Idx);
981 bool AlreadyKept = MyInfo.Keep;
983 // If the Keep flag is set, we are marking a required DIE's
984 // dependencies. If our target is already marked as kept, we're all
986 if ((Flags & TF_DependencyWalk) && AlreadyKept)
989 // We must not call shouldKeepDIE while called from keepDIEAndDenpendencies,
990 // because it would screw up the relocation finding logic.
991 if (!(Flags & TF_DependencyWalk))
992 Flags = shouldKeepDIE(DIE, CU, MyInfo, Flags);
994 // If it is a newly kept DIE mark it as well as all its dependencies as kept.
995 if (!AlreadyKept && (Flags & TF_Keep))
996 keepDIEAndDenpendencies(DIE, MyInfo, DMO, CU, Flags);
998 // The TF_ParentWalk flag tells us that we are currently walking up
999 // the parent chain of a required DIE, and we don't want to mark all
1000 // the children of the parents as kept (consider for example a
1001 // DW_TAG_namespace node in the parent chain). There are however a
1002 // set of DIE types for which we want to ignore that directive and still
1003 // walk their children.
1004 if (dieNeedsChildrenToBeMeaningful(DIE.getTag()))
1005 Flags &= ~TF_ParentWalk;
1007 if (!DIE.hasChildren() || (Flags & TF_ParentWalk))
1010 for (auto *Child = DIE.getFirstChild(); Child && !Child->isNULL();
1011 Child = Child->getSibling())
1012 lookForDIEsToKeep(*Child, DMO, CU, Flags);
1015 /// \brief Assign an abbreviation numer to \p Abbrev.
1017 /// Our DIEs get freed after every DebugMapObject has been processed,
1018 /// thus the FoldingSet we use to unique DIEAbbrevs cannot refer to
1019 /// the instances hold by the DIEs. When we encounter an abbreviation
1020 /// that we don't know, we create a permanent copy of it.
1021 void DwarfLinker::AssignAbbrev(DIEAbbrev &Abbrev) {
1022 // Check the set for priors.
1023 FoldingSetNodeID ID;
1026 DIEAbbrev *InSet = AbbreviationsSet.FindNodeOrInsertPos(ID, InsertToken);
1028 // If it's newly added.
1030 // Assign existing abbreviation number.
1031 Abbrev.setNumber(InSet->getNumber());
1033 // Add to abbreviation list.
1034 Abbreviations.push_back(
1035 new DIEAbbrev(Abbrev.getTag(), Abbrev.hasChildren()));
1036 for (const auto &Attr : Abbrev.getData())
1037 Abbreviations.back()->AddAttribute(Attr.getAttribute(), Attr.getForm());
1038 AbbreviationsSet.InsertNode(Abbreviations.back(), InsertToken);
1039 // Assign the unique abbreviation number.
1040 Abbrev.setNumber(Abbreviations.size());
1041 Abbreviations.back()->setNumber(Abbreviations.size());
1045 /// \brief Clone a string attribute described by \p AttrSpec and add
1047 /// \returns the size of the new attribute.
1048 unsigned DwarfLinker::cloneStringAttribute(DIE &Die, AttributeSpec AttrSpec,
1049 const DWARFFormValue &Val,
1050 const DWARFUnit &U) {
1051 // Switch everything to out of line strings.
1052 const char *String = *Val.getAsCString(&U);
1053 unsigned Offset = StringPool.getStringOffset(String);
1054 Die.addValue(dwarf::Attribute(AttrSpec.Attr), dwarf::DW_FORM_strp,
1055 new (DIEAlloc) DIEInteger(Offset));
1059 /// \brief Clone an attribute referencing another DIE and add
1061 /// \returns the size of the new attribute.
1062 unsigned DwarfLinker::cloneDieReferenceAttribute(DIE &Die,
1063 AttributeSpec AttrSpec,
1064 unsigned AttrSize) {
1065 // FIXME: Handle DIE references.
1066 Die.addValue(dwarf::Attribute(AttrSpec.Attr), dwarf::Form(AttrSpec.Form),
1067 new (DIEAlloc) DIEInteger(0));
1071 /// \brief Clone an attribute of block form (locations, constants) and add
1073 /// \returns the size of the new attribute.
1074 unsigned DwarfLinker::cloneBlockAttribute(DIE &Die, AttributeSpec AttrSpec,
1075 const DWARFFormValue &Val,
1076 unsigned AttrSize) {
1079 DIELoc *Loc = nullptr;
1080 DIEBlock *Block = nullptr;
1081 // Just copy the block data over.
1082 if (AttrSpec.Attr == dwarf::DW_FORM_exprloc) {
1083 Loc = new (DIEAlloc) DIELoc();
1084 DIELocs.push_back(Loc);
1086 Block = new (DIEAlloc) DIEBlock();
1087 DIEBlocks.push_back(Block);
1089 Attr = Loc ? static_cast<DIE *>(Loc) : static_cast<DIE *>(Block);
1090 Value = Loc ? static_cast<DIEValue *>(Loc) : static_cast<DIEValue *>(Block);
1091 ArrayRef<uint8_t> Bytes = *Val.getAsBlock();
1092 for (auto Byte : Bytes)
1093 Attr->addValue(static_cast<dwarf::Attribute>(0), dwarf::DW_FORM_data1,
1094 new (DIEAlloc) DIEInteger(Byte));
1095 // FIXME: If DIEBlock and DIELoc just reuses the Size field of
1096 // the DIE class, this if could be replaced by
1097 // Attr->setSize(Bytes.size()).
1100 Loc->ComputeSize(&Streamer->getAsmPrinter());
1102 Block->ComputeSize(&Streamer->getAsmPrinter());
1104 Die.addValue(dwarf::Attribute(AttrSpec.Attr), dwarf::Form(AttrSpec.Form),
1109 /// \brief Clone a scalar attribute and add it to \p Die.
1110 /// \returns the size of the new attribute.
1111 unsigned DwarfLinker::cloneScalarAttribute(
1112 DIE &Die, const DWARFDebugInfoEntryMinimal &InputDIE, const DWARFUnit &U,
1113 AttributeSpec AttrSpec, const DWARFFormValue &Val, unsigned AttrSize) {
1115 if (AttrSpec.Form == dwarf::DW_FORM_sec_offset)
1116 Value = *Val.getAsSectionOffset();
1117 else if (AttrSpec.Form == dwarf::DW_FORM_sdata)
1118 Value = *Val.getAsSignedConstant();
1119 else if (AttrSpec.Form == dwarf::DW_FORM_addr)
1120 Value = *Val.getAsAddress(&U);
1121 else if (auto OptionalValue = Val.getAsUnsignedConstant())
1122 Value = *OptionalValue;
1124 reportWarning("Unsupported scalar attribute form. Dropping attribute.", &U,
1128 Die.addValue(dwarf::Attribute(AttrSpec.Attr), dwarf::Form(AttrSpec.Form),
1129 new (DIEAlloc) DIEInteger(Value));
1133 /// \brief Clone \p InputDIE's attribute described by \p AttrSpec with
1134 /// value \p Val, and add it to \p Die.
1135 /// \returns the size of the cloned attribute.
1136 unsigned DwarfLinker::cloneAttribute(DIE &Die,
1137 const DWARFDebugInfoEntryMinimal &InputDIE,
1139 const DWARFFormValue &Val,
1140 const AttributeSpec AttrSpec,
1141 unsigned AttrSize) {
1142 const DWARFUnit &U = Unit.getOrigUnit();
1144 switch (AttrSpec.Form) {
1145 case dwarf::DW_FORM_strp:
1146 case dwarf::DW_FORM_string:
1147 return cloneStringAttribute(Die, AttrSpec, Val, U);
1148 case dwarf::DW_FORM_ref_addr:
1149 case dwarf::DW_FORM_ref1:
1150 case dwarf::DW_FORM_ref2:
1151 case dwarf::DW_FORM_ref4:
1152 case dwarf::DW_FORM_ref8:
1153 return cloneDieReferenceAttribute(Die, AttrSpec, AttrSize);
1154 case dwarf::DW_FORM_block:
1155 case dwarf::DW_FORM_block1:
1156 case dwarf::DW_FORM_block2:
1157 case dwarf::DW_FORM_block4:
1158 case dwarf::DW_FORM_exprloc:
1159 return cloneBlockAttribute(Die, AttrSpec, Val, AttrSize);
1160 case dwarf::DW_FORM_addr:
1161 case dwarf::DW_FORM_data1:
1162 case dwarf::DW_FORM_data2:
1163 case dwarf::DW_FORM_data4:
1164 case dwarf::DW_FORM_data8:
1165 case dwarf::DW_FORM_udata:
1166 case dwarf::DW_FORM_sdata:
1167 case dwarf::DW_FORM_sec_offset:
1168 case dwarf::DW_FORM_flag:
1169 case dwarf::DW_FORM_flag_present:
1170 return cloneScalarAttribute(Die, InputDIE, U, AttrSpec, Val, AttrSize);
1172 reportWarning("Unsupported attribute form in cloneAttribute. Dropping.", &U,
1179 /// \brief Recursively clone \p InputDIE's subtrees that have been
1180 /// selected to appear in the linked output.
1182 /// \param OutOffset is the Offset where the newly created DIE will
1183 /// lie in the linked compile unit.
1185 /// \returns the cloned DIE object or null if nothing was selected.
1186 DIE *DwarfLinker::cloneDIE(const DWARFDebugInfoEntryMinimal &InputDIE,
1187 CompileUnit &Unit, uint32_t OutOffset) {
1188 DWARFUnit &U = Unit.getOrigUnit();
1189 unsigned Idx = U.getDIEIndex(&InputDIE);
1191 // Should the DIE appear in the output?
1192 if (!Unit.getInfo(Idx).Keep)
1195 uint32_t Offset = InputDIE.getOffset();
1197 DIE *Die = new DIE(static_cast<dwarf::Tag>(InputDIE.getTag()));
1198 Die->setOffset(OutOffset);
1200 // Extract and clone every attribute.
1201 DataExtractor Data = U.getDebugInfoExtractor();
1202 const auto *Abbrev = InputDIE.getAbbreviationDeclarationPtr();
1203 Offset += getULEB128Size(Abbrev->getCode());
1205 for (const auto &AttrSpec : Abbrev->attributes()) {
1206 DWARFFormValue Val(AttrSpec.Form);
1207 uint32_t AttrSize = Offset;
1208 Val.extractValue(Data, &Offset, &U);
1209 AttrSize = Offset - AttrSize;
1211 OutOffset += cloneAttribute(*Die, InputDIE, Unit, Val, AttrSpec, AttrSize);
1214 DIEAbbrev &NewAbbrev = Die->getAbbrev();
1215 // If a scope DIE is kept, we must have kept at least one child. If
1216 // it's not the case, we'll just be emitting one wasteful end of
1217 // children marker, but things won't break.
1218 if (InputDIE.hasChildren())
1219 NewAbbrev.setChildrenFlag(dwarf::DW_CHILDREN_yes);
1220 // Assign a permanent abbrev number
1221 AssignAbbrev(Die->getAbbrev());
1223 // Add the size of the abbreviation number to the output offset.
1224 OutOffset += getULEB128Size(Die->getAbbrevNumber());
1226 if (!Abbrev->hasChildren()) {
1228 Die->setSize(OutOffset - Die->getOffset());
1232 // Recursively clone children.
1233 for (auto *Child = InputDIE.getFirstChild(); Child && !Child->isNULL();
1234 Child = Child->getSibling()) {
1235 if (DIE *Clone = cloneDIE(*Child, Unit, OutOffset)) {
1236 Die->addChild(std::unique_ptr<DIE>(Clone));
1237 OutOffset = Clone->getOffset() + Clone->getSize();
1241 // Account for the end of children marker.
1242 OutOffset += sizeof(int8_t);
1244 Die->setSize(OutOffset - Die->getOffset());
1248 bool DwarfLinker::link(const DebugMap &Map) {
1250 if (Map.begin() == Map.end()) {
1251 errs() << "Empty debug map.\n";
1255 if (!createStreamer(Map.getTriple(), OutputFilename))
1258 // Size of the DIEs (and headers) generated for the linked output.
1259 uint64_t OutputDebugInfoSize = 0;
1261 for (const auto &Obj : Map.objects()) {
1262 CurrentDebugObject = Obj.get();
1264 if (Options.Verbose)
1265 outs() << "DEBUG MAP OBJECT: " << Obj->getObjectFilename() << "\n";
1266 auto ErrOrObj = BinHolder.GetObjectFile(Obj->getObjectFilename());
1267 if (std::error_code EC = ErrOrObj.getError()) {
1268 reportWarning(Twine(Obj->getObjectFilename()) + ": " + EC.message());
1272 // Look for relocations that correspond to debug map entries.
1273 if (!findValidRelocsInDebugInfo(*ErrOrObj, *Obj)) {
1274 if (Options.Verbose)
1275 outs() << "No valid relocations found. Skipping.\n";
1279 // Setup access to the debug info.
1280 DWARFContextInMemory DwarfContext(*ErrOrObj);
1281 startDebugObject(DwarfContext);
1283 // In a first phase, just read in the debug info and store the DIE
1284 // parent links that we will use during the next phase.
1285 for (const auto &CU : DwarfContext.compile_units()) {
1286 auto *CUDie = CU->getCompileUnitDIE(false);
1287 if (Options.Verbose) {
1288 outs() << "Input compilation unit:";
1289 CUDie->dump(outs(), CU.get(), 0);
1291 Units.emplace_back(*CU);
1292 gatherDIEParents(CUDie, 0, Units.back());
1295 // Then mark all the DIEs that need to be present in the linked
1296 // output and collect some information about them. Note that this
1297 // loop can not be merged with the previous one becaue cross-cu
1298 // references require the ParentIdx to be setup for every CU in
1299 // the object file before calling this.
1300 for (auto &CurrentUnit : Units)
1301 lookForDIEsToKeep(*CurrentUnit.getOrigUnit().getCompileUnitDIE(), *Obj,
1304 // Construct the output DIE tree by cloning the DIEs we chose to
1305 // keep above. If there are no valid relocs, then there's nothing
1307 if (!ValidRelocs.empty())
1308 for (auto &CurrentUnit : Units) {
1309 const auto *InputDIE = CurrentUnit.getOrigUnit().getCompileUnitDIE();
1311 cloneDIE(*InputDIE, CurrentUnit, 11 /* Unit Header size */);
1312 CurrentUnit.setOutputUnitDIE(OutputDIE);
1313 OutputDebugInfoSize = CurrentUnit.computeOffsets(OutputDebugInfoSize);
1316 // Emit all the compile unit's debug information.
1317 if (!ValidRelocs.empty() && !Options.NoOutput)
1318 for (auto &CurrentUnit : Units) {
1319 Streamer->emitCompileUnitHeader(CurrentUnit);
1320 if (!CurrentUnit.getOutputUnitDIE())
1322 Streamer->emitDIE(*CurrentUnit.getOutputUnitDIE());
1325 // Clean-up before starting working on the next object.
1329 // Emit everything that's global.
1330 if (!Options.NoOutput) {
1331 Streamer->emitAbbrevs(Abbreviations);
1332 Streamer->emitStrings(StringPool);
1335 return Options.NoOutput ? true : Streamer->finish();
1339 bool linkDwarf(StringRef OutputFilename, const DebugMap &DM,
1340 const LinkOptions &Options) {
1341 DwarfLinker Linker(OutputFilename, Options);
1342 return Linker.link(DM);