1 //===-- llvm-dwp.cpp - Split DWARF merging tool for llvm ------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // A utility for merging DWARF 5 Split DWARF .dwo files into .dwp (DWARF
10 // package files).
11 //
12 //===----------------------------------------------------------------------===//
13 #include "DWPError.h"
14 #include "DWPStringPool.h"
15 #include "llvm/ADT/MapVector.h"
16 #include "llvm/ADT/Optional.h"
17 #include "llvm/ADT/STLExtras.h"
18 #include "llvm/DebugInfo/DWARF/DWARFContext.h"
19 #include "llvm/DebugInfo/DWARF/DWARFFormValue.h"
20 #include "llvm/DebugInfo/DWARF/DWARFUnitIndex.h"
21 #include "llvm/MC/MCAsmBackend.h"
22 #include "llvm/MC/MCAsmInfo.h"
23 #include "llvm/MC/MCCodeEmitter.h"
24 #include "llvm/MC/MCContext.h"
25 #include "llvm/MC/MCInstrInfo.h"
26 #include "llvm/MC/MCObjectFileInfo.h"
27 #include "llvm/MC/MCObjectWriter.h"
28 #include "llvm/MC/MCRegisterInfo.h"
29 #include "llvm/MC/MCStreamer.h"
30 #include "llvm/MC/MCTargetOptionsCommandFlags.h"
31 #include "llvm/Object/Decompressor.h"
32 #include "llvm/Object/ObjectFile.h"
33 #include "llvm/Support/DataExtractor.h"
34 #include "llvm/Support/Error.h"
35 #include "llvm/Support/FileSystem.h"
36 #include "llvm/Support/InitLLVM.h"
37 #include "llvm/Support/MathExtras.h"
38 #include "llvm/Support/MemoryBuffer.h"
39 #include "llvm/Support/Path.h"
40 #include "llvm/Support/TargetRegistry.h"
41 #include "llvm/Support/TargetSelect.h"
42 #include "llvm/Support/ToolOutputFile.h"
43 #include "llvm/Support/WithColor.h"
44 #include "llvm/Support/raw_ostream.h"
45 
46 using namespace llvm;
47 using namespace llvm::object;
48 
49 static mc::RegisterMCTargetOptionsFlags MCTargetOptionsFlags;
50 
51 cl::OptionCategory DwpCategory("Specific Options");
52 static cl::list<std::string> InputFiles(cl::Positional, cl::ZeroOrMore,
53                                         cl::desc("<input files>"),
54                                         cl::cat(DwpCategory));
55 
56 static cl::list<std::string> ExecFilenames(
57     "e", cl::ZeroOrMore,
58     cl::desc("Specify the executable/library files to get the list of *.dwo from"),
59     cl::value_desc("filename"), cl::cat(DwpCategory));
60 
61 static cl::opt<std::string> OutputFilename(cl::Required, "o",
62                                            cl::desc("Specify the output file."),
63                                            cl::value_desc("filename"),
64                                            cl::cat(DwpCategory));
65 
66 static void writeStringsAndOffsets(MCStreamer &Out, DWPStringPool &Strings,
67                                    MCSection *StrOffsetSection,
68                                    StringRef CurStrSection,
69                                    StringRef CurStrOffsetSection) {
70   // Could possibly produce an error or warning if one of these was non-null but
71   // the other was null.
72   if (CurStrSection.empty() || CurStrOffsetSection.empty())
73     return;
74 
75   DenseMap<uint64_t, uint32_t> OffsetRemapping;
76 
77   DataExtractor Data(CurStrSection, true, 0);
78   uint64_t LocalOffset = 0;
79   uint64_t PrevOffset = 0;
80   while (const char *s = Data.getCStr(&LocalOffset)) {
81     OffsetRemapping[PrevOffset] =
82         Strings.getOffset(s, LocalOffset - PrevOffset);
83     PrevOffset = LocalOffset;
84   }
85 
86   Data = DataExtractor(CurStrOffsetSection, true, 0);
87 
88   Out.SwitchSection(StrOffsetSection);
89 
90   uint64_t Offset = 0;
91   uint64_t Size = CurStrOffsetSection.size();
92   while (Offset < Size) {
93     auto OldOffset = Data.getU32(&Offset);
94     auto NewOffset = OffsetRemapping[OldOffset];
95     Out.emitIntValue(NewOffset, 4);
96   }
97 }
98 
99 static uint64_t getCUAbbrev(StringRef Abbrev, uint64_t AbbrCode) {
100   uint64_t CurCode;
101   uint64_t Offset = 0;
102   DataExtractor AbbrevData(Abbrev, true, 0);
103   while ((CurCode = AbbrevData.getULEB128(&Offset)) != AbbrCode) {
104     // Tag
105     AbbrevData.getULEB128(&Offset);
106     // DW_CHILDREN
107     AbbrevData.getU8(&Offset);
108     // Attributes
109     while (AbbrevData.getULEB128(&Offset) | AbbrevData.getULEB128(&Offset))
110       ;
111   }
112   return Offset;
113 }
114 
115 struct CompileUnitIdentifiers {
116   uint64_t Signature = 0;
117   const char *Name = "";
118   const char *DWOName = "";
119 };
120 
121 static Expected<const char *>
122 getIndexedString(dwarf::Form Form, DataExtractor InfoData,
123                  uint64_t &InfoOffset, StringRef StrOffsets, StringRef Str) {
124   if (Form == dwarf::DW_FORM_string)
125     return InfoData.getCStr(&InfoOffset);
126   if (Form != dwarf::DW_FORM_GNU_str_index)
127     return make_error<DWPError>(
128         "string field encoded without DW_FORM_string or DW_FORM_GNU_str_index");
129   auto StrIndex = InfoData.getULEB128(&InfoOffset);
130   DataExtractor StrOffsetsData(StrOffsets, true, 0);
131   uint64_t StrOffsetsOffset = 4 * StrIndex;
132   uint64_t StrOffset = StrOffsetsData.getU32(&StrOffsetsOffset);
133   DataExtractor StrData(Str, true, 0);
134   return StrData.getCStr(&StrOffset);
135 }
136 
137 static Expected<CompileUnitIdentifiers> getCUIdentifiers(StringRef Abbrev,
138                                                          StringRef Info,
139                                                          StringRef StrOffsets,
140                                                          StringRef Str) {
141   uint64_t Offset = 0;
142   DataExtractor InfoData(Info, true, 0);
143   dwarf::DwarfFormat Format = dwarf::DwarfFormat::DWARF32;
144   uint64_t Length = InfoData.getU32(&Offset);
145   CompileUnitIdentifiers ID;
146   Optional<uint64_t> Signature = None;
147   // If the length is 0xffffffff, then this indictes that this is a DWARF 64
148   // stream and the length is actually encoded into a 64 bit value that follows.
149   if (Length == 0xffffffffU) {
150     Format = dwarf::DwarfFormat::DWARF64;
151     Length = InfoData.getU64(&Offset);
152   }
153   uint16_t Version = InfoData.getU16(&Offset);
154   if (Version >= 5) {
155     auto UnitType = InfoData.getU8(&Offset);
156     if (UnitType != dwarf::DW_UT_split_compile)
157       return make_error<DWPError>(
158           std::string("unit type DW_UT_split_compile type not found in "
159                       "debug_info header. Unexpected unit type 0x" +
160                       utostr(UnitType) + " found"));
161   }
162   InfoData.getU32(&Offset); // Abbrev offset (should be zero)
163   uint8_t AddrSize = InfoData.getU8(&Offset);
164   if (Version >= 5)
165     Signature = InfoData.getU64(&Offset);
166   uint32_t AbbrCode = InfoData.getULEB128(&Offset);
167 
168   DataExtractor AbbrevData(Abbrev, true, 0);
169   uint64_t AbbrevOffset = getCUAbbrev(Abbrev, AbbrCode);
170   auto Tag = static_cast<dwarf::Tag>(AbbrevData.getULEB128(&AbbrevOffset));
171   if (Tag != dwarf::DW_TAG_compile_unit)
172     return make_error<DWPError>("top level DIE is not a compile unit");
173   // DW_CHILDREN
174   AbbrevData.getU8(&AbbrevOffset);
175   uint32_t Name;
176   dwarf::Form Form;
177   while ((Name = AbbrevData.getULEB128(&AbbrevOffset)) |
178          (Form = static_cast<dwarf::Form>(AbbrevData.getULEB128(&AbbrevOffset))) &&
179          (Name != 0 || Form != 0)) {
180     switch (Name) {
181     case dwarf::DW_AT_name: {
182       Expected<const char *> EName =
183           getIndexedString(Form, InfoData, Offset, StrOffsets, Str);
184       if (!EName)
185         return EName.takeError();
186       ID.Name = *EName;
187       break;
188     }
189     case dwarf::DW_AT_GNU_dwo_name:
190     case dwarf::DW_AT_dwo_name: {
191       Expected<const char *> EName =
192           getIndexedString(Form, InfoData, Offset, StrOffsets, Str);
193       if (!EName)
194         return EName.takeError();
195       ID.DWOName = *EName;
196       break;
197     }
198     case dwarf::DW_AT_GNU_dwo_id:
199       Signature = InfoData.getU64(&Offset);
200       break;
201     default:
202       DWARFFormValue::skipValue(Form, InfoData, &Offset,
203                                 dwarf::FormParams({Version, AddrSize, Format}));
204     }
205   }
206   if (!Signature)
207     return make_error<DWPError>("compile unit missing dwo_id");
208   ID.Signature = *Signature;
209   return ID;
210 }
211 
212 struct UnitIndexEntry {
213   DWARFUnitIndex::Entry::SectionContribution Contributions[8];
214   std::string Name;
215   std::string DWOName;
216   StringRef DWPName;
217 };
218 
219 // Convert an internal section identifier into the index to use with
220 // UnitIndexEntry::Contributions.
221 static unsigned getContributionIndex(DWARFSectionKind Kind) {
222   // Assuming the pre-standard DWP format.
223   assert(serializeSectionKind(Kind, 2) >= DW_SECT_INFO);
224   return serializeSectionKind(Kind, 2) - DW_SECT_INFO;
225 }
226 
227 // Convert a UnitIndexEntry::Contributions index to the corresponding on-disk
228 // value of the section identifier.
229 static unsigned getOnDiskSectionId(unsigned Index) {
230   return Index + DW_SECT_INFO;
231 }
232 
233 static StringRef getSubsection(StringRef Section,
234                                const DWARFUnitIndex::Entry &Entry,
235                                DWARFSectionKind Kind) {
236   const auto *Off = Entry.getContribution(Kind);
237   if (!Off)
238     return StringRef();
239   return Section.substr(Off->Offset, Off->Length);
240 }
241 
242 static void addAllTypesFromDWP(
243     MCStreamer &Out, MapVector<uint64_t, UnitIndexEntry> &TypeIndexEntries,
244     const DWARFUnitIndex &TUIndex, MCSection *OutputTypes, StringRef Types,
245     const UnitIndexEntry &TUEntry, uint32_t &TypesOffset) {
246   Out.SwitchSection(OutputTypes);
247   for (const DWARFUnitIndex::Entry &E : TUIndex.getRows()) {
248     auto *I = E.getContributions();
249     if (!I)
250       continue;
251     auto P = TypeIndexEntries.insert(std::make_pair(E.getSignature(), TUEntry));
252     if (!P.second)
253       continue;
254     auto &Entry = P.first->second;
255     // Zero out the debug_info contribution
256     Entry.Contributions[0] = {};
257     for (auto Kind : TUIndex.getColumnKinds()) {
258       auto &C = Entry.Contributions[getContributionIndex(Kind)];
259       C.Offset += I->Offset;
260       C.Length = I->Length;
261       ++I;
262     }
263     unsigned TypesIndex = getContributionIndex(DW_SECT_EXT_TYPES);
264     auto &C = Entry.Contributions[TypesIndex];
265     Out.emitBytes(Types.substr(
266         C.Offset - TUEntry.Contributions[TypesIndex].Offset, C.Length));
267     C.Offset = TypesOffset;
268     TypesOffset += C.Length;
269   }
270 }
271 
272 static void addAllTypes(MCStreamer &Out,
273                         MapVector<uint64_t, UnitIndexEntry> &TypeIndexEntries,
274                         MCSection *OutputTypes,
275                         const std::vector<StringRef> &TypesSections,
276                         const UnitIndexEntry &CUEntry, uint32_t &TypesOffset) {
277   for (StringRef Types : TypesSections) {
278     Out.SwitchSection(OutputTypes);
279     uint64_t Offset = 0;
280     DataExtractor Data(Types, true, 0);
281     while (Data.isValidOffset(Offset)) {
282       UnitIndexEntry Entry = CUEntry;
283       // Zero out the debug_info contribution
284       Entry.Contributions[0] = {};
285       auto &C = Entry.Contributions[getContributionIndex(DW_SECT_EXT_TYPES)];
286       C.Offset = TypesOffset;
287       auto PrevOffset = Offset;
288       // Length of the unit, including the 4 byte length field.
289       C.Length = Data.getU32(&Offset) + 4;
290 
291       Data.getU16(&Offset); // Version
292       Data.getU32(&Offset); // Abbrev offset
293       Data.getU8(&Offset);  // Address size
294       auto Signature = Data.getU64(&Offset);
295       Offset = PrevOffset + C.Length;
296 
297       auto P = TypeIndexEntries.insert(std::make_pair(Signature, Entry));
298       if (!P.second)
299         continue;
300 
301       Out.emitBytes(Types.substr(PrevOffset, C.Length));
302       TypesOffset += C.Length;
303     }
304   }
305 }
306 
307 static void
308 writeIndexTable(MCStreamer &Out, ArrayRef<unsigned> ContributionOffsets,
309                 const MapVector<uint64_t, UnitIndexEntry> &IndexEntries,
310                 uint32_t DWARFUnitIndex::Entry::SectionContribution::*Field) {
311   for (const auto &E : IndexEntries)
312     for (size_t i = 0; i != array_lengthof(E.second.Contributions); ++i)
313       if (ContributionOffsets[i])
314         Out.emitIntValue(E.second.Contributions[i].*Field, 4);
315 }
316 
317 static void
318 writeIndex(MCStreamer &Out, MCSection *Section,
319            ArrayRef<unsigned> ContributionOffsets,
320            const MapVector<uint64_t, UnitIndexEntry> &IndexEntries) {
321   if (IndexEntries.empty())
322     return;
323 
324   unsigned Columns = 0;
325   for (auto &C : ContributionOffsets)
326     if (C)
327       ++Columns;
328 
329   std::vector<unsigned> Buckets(NextPowerOf2(3 * IndexEntries.size() / 2));
330   uint64_t Mask = Buckets.size() - 1;
331   size_t i = 0;
332   for (const auto &P : IndexEntries) {
333     auto S = P.first;
334     auto H = S & Mask;
335     auto HP = ((S >> 32) & Mask) | 1;
336     while (Buckets[H]) {
337       assert(S != IndexEntries.begin()[Buckets[H] - 1].first &&
338              "Duplicate unit");
339       H = (H + HP) & Mask;
340     }
341     Buckets[H] = i + 1;
342     ++i;
343   }
344 
345   Out.SwitchSection(Section);
346   Out.emitIntValue(2, 4);                   // Version
347   Out.emitIntValue(Columns, 4);             // Columns
348   Out.emitIntValue(IndexEntries.size(), 4); // Num Units
349   Out.emitIntValue(Buckets.size(), 4);      // Num Buckets
350 
351   // Write the signatures.
352   for (const auto &I : Buckets)
353     Out.emitIntValue(I ? IndexEntries.begin()[I - 1].first : 0, 8);
354 
355   // Write the indexes.
356   for (const auto &I : Buckets)
357     Out.emitIntValue(I, 4);
358 
359   // Write the column headers (which sections will appear in the table)
360   for (size_t i = 0; i != ContributionOffsets.size(); ++i)
361     if (ContributionOffsets[i])
362       Out.emitIntValue(getOnDiskSectionId(i), 4);
363 
364   // Write the offsets.
365   writeIndexTable(Out, ContributionOffsets, IndexEntries,
366                   &DWARFUnitIndex::Entry::SectionContribution::Offset);
367 
368   // Write the lengths.
369   writeIndexTable(Out, ContributionOffsets, IndexEntries,
370                   &DWARFUnitIndex::Entry::SectionContribution::Length);
371 }
372 
373 std::string buildDWODescription(StringRef Name, StringRef DWPName, StringRef DWOName) {
374   std::string Text = "\'";
375   Text += Name;
376   Text += '\'';
377   if (!DWPName.empty()) {
378     Text += " (from ";
379     if (!DWOName.empty()) {
380       Text += '\'';
381       Text += DWOName;
382       Text += "' in ";
383     }
384     Text += '\'';
385     Text += DWPName;
386     Text += "')";
387   }
388   return Text;
389 }
390 
391 static Error createError(StringRef Name, Error E) {
392   return make_error<DWPError>(
393       ("failure while decompressing compressed section: '" + Name + "', " +
394        llvm::toString(std::move(E)))
395           .str());
396 }
397 
398 static Error
399 handleCompressedSection(std::deque<SmallString<32>> &UncompressedSections,
400                         StringRef &Name, StringRef &Contents) {
401   if (!Decompressor::isGnuStyle(Name))
402     return Error::success();
403 
404   Expected<Decompressor> Dec =
405       Decompressor::create(Name, Contents, false /*IsLE*/, false /*Is64Bit*/);
406   if (!Dec)
407     return createError(Name, Dec.takeError());
408 
409   UncompressedSections.emplace_back();
410   if (Error E = Dec->resizeAndDecompress(UncompressedSections.back()))
411     return createError(Name, std::move(E));
412 
413   Name = Name.substr(2); // Drop ".z"
414   Contents = UncompressedSections.back();
415   return Error::success();
416 }
417 
418 static Error handleSection(
419     const StringMap<std::pair<MCSection *, DWARFSectionKind>> &KnownSections,
420     const MCSection *StrSection, const MCSection *StrOffsetSection,
421     const MCSection *TypesSection, const MCSection *CUIndexSection,
422     const MCSection *TUIndexSection, const SectionRef &Section, MCStreamer &Out,
423     std::deque<SmallString<32>> &UncompressedSections,
424     uint32_t (&ContributionOffsets)[8], UnitIndexEntry &CurEntry,
425     StringRef &CurStrSection, StringRef &CurStrOffsetSection,
426     std::vector<StringRef> &CurTypesSection, StringRef &InfoSection,
427     StringRef &AbbrevSection, StringRef &CurCUIndexSection,
428     StringRef &CurTUIndexSection) {
429   if (Section.isBSS())
430     return Error::success();
431 
432   if (Section.isVirtual())
433     return Error::success();
434 
435   Expected<StringRef> NameOrErr = Section.getName();
436   if (!NameOrErr)
437     return NameOrErr.takeError();
438   StringRef Name = *NameOrErr;
439 
440   Expected<StringRef> ContentsOrErr = Section.getContents();
441   if (!ContentsOrErr)
442     return ContentsOrErr.takeError();
443   StringRef Contents = *ContentsOrErr;
444 
445   if (auto Err = handleCompressedSection(UncompressedSections, Name, Contents))
446     return Err;
447 
448   Name = Name.substr(Name.find_first_not_of("._"));
449 
450   auto SectionPair = KnownSections.find(Name);
451   if (SectionPair == KnownSections.end())
452     return Error::success();
453 
454   if (DWARFSectionKind Kind = SectionPair->second.second) {
455     auto Index = getContributionIndex(Kind);
456     if (Kind != DW_SECT_EXT_TYPES) {
457       CurEntry.Contributions[Index].Offset = ContributionOffsets[Index];
458       ContributionOffsets[Index] +=
459           (CurEntry.Contributions[Index].Length = Contents.size());
460     }
461 
462     switch (Kind) {
463     case DW_SECT_INFO:
464       InfoSection = Contents;
465       break;
466     case DW_SECT_ABBREV:
467       AbbrevSection = Contents;
468       break;
469     default:
470       break;
471     }
472   }
473 
474   MCSection *OutSection = SectionPair->second.first;
475   if (OutSection == StrOffsetSection)
476     CurStrOffsetSection = Contents;
477   else if (OutSection == StrSection)
478     CurStrSection = Contents;
479   else if (OutSection == TypesSection)
480     CurTypesSection.push_back(Contents);
481   else if (OutSection == CUIndexSection)
482     CurCUIndexSection = Contents;
483   else if (OutSection == TUIndexSection)
484     CurTUIndexSection = Contents;
485   else {
486     Out.SwitchSection(OutSection);
487     Out.emitBytes(Contents);
488   }
489   return Error::success();
490 }
491 
492 static Error
493 buildDuplicateError(const std::pair<uint64_t, UnitIndexEntry> &PrevE,
494                     const CompileUnitIdentifiers &ID, StringRef DWPName) {
495   return make_error<DWPError>(
496       std::string("duplicate DWO ID (") + utohexstr(PrevE.first) + ") in " +
497       buildDWODescription(PrevE.second.Name, PrevE.second.DWPName,
498                           PrevE.second.DWOName) +
499       " and " + buildDWODescription(ID.Name, DWPName, ID.DWOName));
500 }
501 
502 static Expected<SmallVector<std::string, 16>>
503 getDWOFilenames(StringRef ExecFilename) {
504   auto ErrOrObj = object::ObjectFile::createObjectFile(ExecFilename);
505   if (!ErrOrObj)
506     return ErrOrObj.takeError();
507 
508   const ObjectFile &Obj = *ErrOrObj.get().getBinary();
509   std::unique_ptr<DWARFContext> DWARFCtx = DWARFContext::create(Obj);
510 
511   SmallVector<std::string, 16> DWOPaths;
512   for (const auto &CU : DWARFCtx->compile_units()) {
513     const DWARFDie &Die = CU->getUnitDIE();
514     std::string DWOName = dwarf::toString(
515         Die.find({dwarf::DW_AT_dwo_name, dwarf::DW_AT_GNU_dwo_name}), "");
516     if (DWOName.empty())
517       continue;
518     std::string DWOCompDir =
519         dwarf::toString(Die.find(dwarf::DW_AT_comp_dir), "");
520     if (!DWOCompDir.empty()) {
521       SmallString<16> DWOPath;
522       sys::path::append(DWOPath, DWOCompDir, DWOName);
523       DWOPaths.emplace_back(DWOPath.data(), DWOPath.size());
524     } else {
525       DWOPaths.push_back(std::move(DWOName));
526     }
527   }
528   return std::move(DWOPaths);
529 }
530 
531 static Error write(MCStreamer &Out, ArrayRef<std::string> Inputs) {
532   const auto &MCOFI = *Out.getContext().getObjectFileInfo();
533   MCSection *const StrSection = MCOFI.getDwarfStrDWOSection();
534   MCSection *const StrOffsetSection = MCOFI.getDwarfStrOffDWOSection();
535   MCSection *const TypesSection = MCOFI.getDwarfTypesDWOSection();
536   MCSection *const CUIndexSection = MCOFI.getDwarfCUIndexSection();
537   MCSection *const TUIndexSection = MCOFI.getDwarfTUIndexSection();
538   const StringMap<std::pair<MCSection *, DWARFSectionKind>> KnownSections = {
539       {"debug_info.dwo", {MCOFI.getDwarfInfoDWOSection(), DW_SECT_INFO}},
540       {"debug_types.dwo", {MCOFI.getDwarfTypesDWOSection(), DW_SECT_EXT_TYPES}},
541       {"debug_str_offsets.dwo", {StrOffsetSection, DW_SECT_STR_OFFSETS}},
542       {"debug_str.dwo", {StrSection, static_cast<DWARFSectionKind>(0)}},
543       {"debug_loc.dwo", {MCOFI.getDwarfLocDWOSection(), DW_SECT_EXT_LOC}},
544       {"debug_line.dwo", {MCOFI.getDwarfLineDWOSection(), DW_SECT_LINE}},
545       {"debug_abbrev.dwo", {MCOFI.getDwarfAbbrevDWOSection(), DW_SECT_ABBREV}},
546       {"debug_cu_index", {CUIndexSection, static_cast<DWARFSectionKind>(0)}},
547       {"debug_tu_index", {TUIndexSection, static_cast<DWARFSectionKind>(0)}}};
548 
549   MapVector<uint64_t, UnitIndexEntry> IndexEntries;
550   MapVector<uint64_t, UnitIndexEntry> TypeIndexEntries;
551 
552   uint32_t ContributionOffsets[8] = {};
553 
554   DWPStringPool Strings(Out, StrSection);
555 
556   SmallVector<OwningBinary<object::ObjectFile>, 128> Objects;
557   Objects.reserve(Inputs.size());
558 
559   std::deque<SmallString<32>> UncompressedSections;
560 
561   for (const auto &Input : Inputs) {
562     auto ErrOrObj = object::ObjectFile::createObjectFile(Input);
563     if (!ErrOrObj)
564       return ErrOrObj.takeError();
565 
566     auto &Obj = *ErrOrObj->getBinary();
567     Objects.push_back(std::move(*ErrOrObj));
568 
569     UnitIndexEntry CurEntry = {};
570 
571     StringRef CurStrSection;
572     StringRef CurStrOffsetSection;
573     std::vector<StringRef> CurTypesSection;
574     StringRef InfoSection;
575     StringRef AbbrevSection;
576     StringRef CurCUIndexSection;
577     StringRef CurTUIndexSection;
578 
579     for (const auto &Section : Obj.sections())
580       if (auto Err = handleSection(
581               KnownSections, StrSection, StrOffsetSection, TypesSection,
582               CUIndexSection, TUIndexSection, Section, Out,
583               UncompressedSections, ContributionOffsets, CurEntry,
584               CurStrSection, CurStrOffsetSection, CurTypesSection, InfoSection,
585               AbbrevSection, CurCUIndexSection, CurTUIndexSection))
586         return Err;
587 
588     if (InfoSection.empty())
589       continue;
590 
591     writeStringsAndOffsets(Out, Strings, StrOffsetSection, CurStrSection,
592                            CurStrOffsetSection);
593 
594     if (CurCUIndexSection.empty()) {
595       Expected<CompileUnitIdentifiers> EID = getCUIdentifiers(
596           AbbrevSection, InfoSection, CurStrOffsetSection, CurStrSection);
597       if (!EID)
598         return createFileError(Input, EID.takeError());
599       const auto &ID = *EID;
600       auto P = IndexEntries.insert(std::make_pair(ID.Signature, CurEntry));
601       if (!P.second)
602         return buildDuplicateError(*P.first, ID, "");
603       P.first->second.Name = ID.Name;
604       P.first->second.DWOName = ID.DWOName;
605       addAllTypes(Out, TypeIndexEntries, TypesSection, CurTypesSection,
606                   CurEntry,
607                   ContributionOffsets[getContributionIndex(DW_SECT_EXT_TYPES)]);
608       continue;
609     }
610 
611     DWARFUnitIndex CUIndex(DW_SECT_INFO);
612     DataExtractor CUIndexData(CurCUIndexSection, Obj.isLittleEndian(), 0);
613     if (!CUIndex.parse(CUIndexData))
614       return make_error<DWPError>("failed to parse cu_index");
615 
616     for (const DWARFUnitIndex::Entry &E : CUIndex.getRows()) {
617       auto *I = E.getContributions();
618       if (!I)
619         continue;
620       auto P = IndexEntries.insert(std::make_pair(E.getSignature(), CurEntry));
621       Expected<CompileUnitIdentifiers> EID = getCUIdentifiers(
622           getSubsection(AbbrevSection, E, DW_SECT_ABBREV),
623           getSubsection(InfoSection, E, DW_SECT_INFO),
624           getSubsection(CurStrOffsetSection, E, DW_SECT_STR_OFFSETS),
625           CurStrSection);
626       if (!EID)
627         return createFileError(Input, EID.takeError());
628       const auto &ID = *EID;
629       if (!P.second)
630         return buildDuplicateError(*P.first, ID, Input);
631       auto &NewEntry = P.first->second;
632       NewEntry.Name = ID.Name;
633       NewEntry.DWOName = ID.DWOName;
634       NewEntry.DWPName = Input;
635       for (auto Kind : CUIndex.getColumnKinds()) {
636         auto &C = NewEntry.Contributions[getContributionIndex(Kind)];
637         C.Offset += I->Offset;
638         C.Length = I->Length;
639         ++I;
640       }
641     }
642 
643     if (!CurTypesSection.empty()) {
644       if (CurTypesSection.size() != 1)
645         return make_error<DWPError>("multiple type unit sections in .dwp file");
646       DWARFUnitIndex TUIndex(DW_SECT_EXT_TYPES);
647       DataExtractor TUIndexData(CurTUIndexSection, Obj.isLittleEndian(), 0);
648       if (!TUIndex.parse(TUIndexData))
649         return make_error<DWPError>("failed to parse tu_index");
650       addAllTypesFromDWP(
651           Out, TypeIndexEntries, TUIndex, TypesSection, CurTypesSection.front(),
652           CurEntry,
653           ContributionOffsets[getContributionIndex(DW_SECT_EXT_TYPES)]);
654     }
655   }
656 
657   // Lie about there being no info contributions so the TU index only includes
658   // the type unit contribution
659   ContributionOffsets[0] = 0;
660   writeIndex(Out, MCOFI.getDwarfTUIndexSection(), ContributionOffsets,
661              TypeIndexEntries);
662 
663   // Lie about the type contribution
664   ContributionOffsets[getContributionIndex(DW_SECT_EXT_TYPES)] = 0;
665   // Unlie about the info contribution
666   ContributionOffsets[0] = 1;
667 
668   writeIndex(Out, MCOFI.getDwarfCUIndexSection(), ContributionOffsets,
669              IndexEntries);
670 
671   return Error::success();
672 }
673 
674 static int error(const Twine &Error, const Twine &Context) {
675   errs() << Twine("while processing ") + Context + ":\n";
676   errs() << Twine("error: ") + Error + "\n";
677   return 1;
678 }
679 
680 int main(int argc, char **argv) {
681   InitLLVM X(argc, argv);
682 
683   cl::ParseCommandLineOptions(argc, argv, "merge split dwarf (.dwo) files\n");
684 
685   llvm::InitializeAllTargetInfos();
686   llvm::InitializeAllTargetMCs();
687   llvm::InitializeAllTargets();
688   llvm::InitializeAllAsmPrinters();
689 
690   std::string ErrorStr;
691   StringRef Context = "dwarf streamer init";
692 
693   Triple TheTriple("x86_64-linux-gnu");
694 
695   // Get the target.
696   const Target *TheTarget =
697       TargetRegistry::lookupTarget("", TheTriple, ErrorStr);
698   if (!TheTarget)
699     return error(ErrorStr, Context);
700   std::string TripleName = TheTriple.getTriple();
701 
702   // Create all the MC Objects.
703   std::unique_ptr<MCRegisterInfo> MRI(TheTarget->createMCRegInfo(TripleName));
704   if (!MRI)
705     return error(Twine("no register info for target ") + TripleName, Context);
706 
707   MCTargetOptions MCOptions = llvm::mc::InitMCTargetOptionsFromFlags();
708   std::unique_ptr<MCAsmInfo> MAI(
709       TheTarget->createMCAsmInfo(*MRI, TripleName, MCOptions));
710   if (!MAI)
711     return error("no asm info for target " + TripleName, Context);
712 
713   MCObjectFileInfo MOFI;
714   MCContext MC(MAI.get(), MRI.get(), &MOFI);
715   MOFI.InitMCObjectFileInfo(TheTriple, /*PIC*/ false, MC);
716 
717   std::unique_ptr<MCSubtargetInfo> MSTI(
718       TheTarget->createMCSubtargetInfo(TripleName, "", ""));
719   if (!MSTI)
720     return error("no subtarget info for target " + TripleName, Context);
721 
722   MCTargetOptions Options;
723   auto MAB = TheTarget->createMCAsmBackend(*MSTI, *MRI, Options);
724   if (!MAB)
725     return error("no asm backend for target " + TripleName, Context);
726 
727   std::unique_ptr<MCInstrInfo> MII(TheTarget->createMCInstrInfo());
728   if (!MII)
729     return error("no instr info info for target " + TripleName, Context);
730 
731   MCCodeEmitter *MCE = TheTarget->createMCCodeEmitter(*MII, *MRI, MC);
732   if (!MCE)
733     return error("no code emitter for target " + TripleName, Context);
734 
735   // Create the output file.
736   std::error_code EC;
737   ToolOutputFile OutFile(OutputFilename, EC, sys::fs::OF_None);
738   Optional<buffer_ostream> BOS;
739   raw_pwrite_stream *OS;
740   if (EC)
741     return error(Twine(OutputFilename) + ": " + EC.message(), Context);
742   if (OutFile.os().supportsSeeking()) {
743     OS = &OutFile.os();
744   } else {
745     BOS.emplace(OutFile.os());
746     OS = BOS.getPointer();
747   }
748 
749   std::unique_ptr<MCStreamer> MS(TheTarget->createMCObjectStreamer(
750       TheTriple, MC, std::unique_ptr<MCAsmBackend>(MAB),
751       MAB->createObjectWriter(*OS), std::unique_ptr<MCCodeEmitter>(MCE), *MSTI,
752       MCOptions.MCRelaxAll, MCOptions.MCIncrementalLinkerCompatible,
753       /*DWARFMustBeAtTheEnd*/ false));
754   if (!MS)
755     return error("no object streamer for target " + TripleName, Context);
756 
757   std::vector<std::string> DWOFilenames = InputFiles;
758   for (const auto &ExecFilename : ExecFilenames) {
759     auto DWOs = getDWOFilenames(ExecFilename);
760     if (!DWOs) {
761       logAllUnhandledErrors(DWOs.takeError(), WithColor::error());
762       return 1;
763     }
764     DWOFilenames.insert(DWOFilenames.end(),
765                         std::make_move_iterator(DWOs->begin()),
766                         std::make_move_iterator(DWOs->end()));
767   }
768 
769   if (auto Err = write(*MS, DWOFilenames)) {
770     logAllUnhandledErrors(std::move(Err), WithColor::error());
771     return 1;
772   }
773 
774   MS->Finish();
775   OutFile.keep();
776   return 0;
777 }
778