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