1 //===-- LLVMSymbolize.cpp -------------------------------------------------===//
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 // Implementation for LLVM symbolization library.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "llvm/DebugInfo/Symbolize/Symbolize.h"
14 
15 #include "llvm/ADT/STLExtras.h"
16 #include "llvm/BinaryFormat/COFF.h"
17 #include "llvm/Config/config.h"
18 #include "llvm/DebugInfo/DWARF/DWARFContext.h"
19 #include "llvm/DebugInfo/PDB/PDB.h"
20 #include "llvm/DebugInfo/PDB/PDBContext.h"
21 #include "llvm/DebugInfo/Symbolize/DIFetcher.h"
22 #include "llvm/DebugInfo/Symbolize/SymbolizableObjectFile.h"
23 #include "llvm/Demangle/Demangle.h"
24 #include "llvm/Object/COFF.h"
25 #include "llvm/Object/MachO.h"
26 #include "llvm/Object/MachOUniversal.h"
27 #include "llvm/Support/CRC.h"
28 #include "llvm/Support/Casting.h"
29 #include "llvm/Support/Compression.h"
30 #include "llvm/Support/DataExtractor.h"
31 #include "llvm/Support/Errc.h"
32 #include "llvm/Support/FileSystem.h"
33 #include "llvm/Support/MemoryBuffer.h"
34 #include "llvm/Support/Path.h"
35 #include <algorithm>
36 #include <cassert>
37 #include <cstring>
38 
39 namespace llvm {
40 namespace symbolize {
41 
42 template <typename T>
43 Expected<DILineInfo>
44 LLVMSymbolizer::symbolizeCodeCommon(const T &ModuleSpecifier,
45                                     object::SectionedAddress ModuleOffset) {
46 
47   auto InfoOrErr = getOrCreateModuleInfo(ModuleSpecifier);
48   if (!InfoOrErr)
49     return InfoOrErr.takeError();
50 
51   SymbolizableModule *Info = *InfoOrErr;
52 
53   // A null module means an error has already been reported. Return an empty
54   // result.
55   if (!Info)
56     return DILineInfo();
57 
58   // If the user is giving us relative addresses, add the preferred base of the
59   // object to the offset before we do the query. It's what DIContext expects.
60   if (Opts.RelativeAddresses)
61     ModuleOffset.Address += Info->getModulePreferredBase();
62 
63   DILineInfo LineInfo = Info->symbolizeCode(
64       ModuleOffset, DILineInfoSpecifier(Opts.PathStyle, Opts.PrintFunctions),
65       Opts.UseSymbolTable);
66   if (Opts.Demangle)
67     LineInfo.FunctionName = DemangleName(LineInfo.FunctionName, Info);
68   return LineInfo;
69 }
70 
71 Expected<DILineInfo>
72 LLVMSymbolizer::symbolizeCode(const ObjectFile &Obj,
73                               object::SectionedAddress ModuleOffset) {
74   return symbolizeCodeCommon(Obj, ModuleOffset);
75 }
76 
77 Expected<DILineInfo>
78 LLVMSymbolizer::symbolizeCode(const std::string &ModuleName,
79                               object::SectionedAddress ModuleOffset) {
80   return symbolizeCodeCommon(ModuleName, ModuleOffset);
81 }
82 
83 template <typename T>
84 Expected<DIInliningInfo> LLVMSymbolizer::symbolizeInlinedCodeCommon(
85     const T &ModuleSpecifier, object::SectionedAddress ModuleOffset) {
86   auto InfoOrErr = getOrCreateModuleInfo(ModuleSpecifier);
87   if (!InfoOrErr)
88     return InfoOrErr.takeError();
89 
90   SymbolizableModule *Info = *InfoOrErr;
91 
92   // A null module means an error has already been reported. Return an empty
93   // result.
94   if (!Info)
95     return DIInliningInfo();
96 
97   // If the user is giving us relative addresses, add the preferred base of the
98   // object to the offset before we do the query. It's what DIContext expects.
99   if (Opts.RelativeAddresses)
100     ModuleOffset.Address += Info->getModulePreferredBase();
101 
102   DIInliningInfo InlinedContext = Info->symbolizeInlinedCode(
103       ModuleOffset, DILineInfoSpecifier(Opts.PathStyle, Opts.PrintFunctions),
104       Opts.UseSymbolTable);
105   if (Opts.Demangle) {
106     for (int i = 0, n = InlinedContext.getNumberOfFrames(); i < n; i++) {
107       auto *Frame = InlinedContext.getMutableFrame(i);
108       Frame->FunctionName = DemangleName(Frame->FunctionName, Info);
109     }
110   }
111   return InlinedContext;
112 }
113 
114 Expected<DIInliningInfo>
115 LLVMSymbolizer::symbolizeInlinedCode(const ObjectFile &Obj,
116                                      object::SectionedAddress ModuleOffset) {
117   return symbolizeInlinedCodeCommon(Obj, ModuleOffset);
118 }
119 
120 Expected<DIInliningInfo>
121 LLVMSymbolizer::symbolizeInlinedCode(const std::string &ModuleName,
122                                      object::SectionedAddress ModuleOffset) {
123   return symbolizeInlinedCodeCommon(ModuleName, ModuleOffset);
124 }
125 
126 template <typename T>
127 Expected<DIGlobal>
128 LLVMSymbolizer::symbolizeDataCommon(const T &ModuleSpecifier,
129                                     object::SectionedAddress ModuleOffset) {
130 
131   auto InfoOrErr = getOrCreateModuleInfo(ModuleSpecifier);
132   if (!InfoOrErr)
133     return InfoOrErr.takeError();
134 
135   SymbolizableModule *Info = *InfoOrErr;
136   // A null module means an error has already been reported. Return an empty
137   // result.
138   if (!Info)
139     return DIGlobal();
140 
141   // If the user is giving us relative addresses, add the preferred base of
142   // the object to the offset before we do the query. It's what DIContext
143   // expects.
144   if (Opts.RelativeAddresses)
145     ModuleOffset.Address += Info->getModulePreferredBase();
146 
147   DIGlobal Global = Info->symbolizeData(ModuleOffset);
148   if (Opts.Demangle)
149     Global.Name = DemangleName(Global.Name, Info);
150   return Global;
151 }
152 
153 Expected<DIGlobal>
154 LLVMSymbolizer::symbolizeData(const ObjectFile &Obj,
155                               object::SectionedAddress ModuleOffset) {
156   return symbolizeDataCommon(Obj, ModuleOffset);
157 }
158 
159 Expected<DIGlobal>
160 LLVMSymbolizer::symbolizeData(const std::string &ModuleName,
161                               object::SectionedAddress ModuleOffset) {
162   return symbolizeDataCommon(ModuleName, ModuleOffset);
163 }
164 
165 template <typename T>
166 Expected<std::vector<DILocal>>
167 LLVMSymbolizer::symbolizeFrameCommon(const T &ModuleSpecifier,
168                                      object::SectionedAddress ModuleOffset) {
169   auto InfoOrErr = getOrCreateModuleInfo(ModuleSpecifier);
170   if (!InfoOrErr)
171     return InfoOrErr.takeError();
172 
173   SymbolizableModule *Info = *InfoOrErr;
174   // A null module means an error has already been reported. Return an empty
175   // result.
176   if (!Info)
177     return std::vector<DILocal>();
178 
179   // If the user is giving us relative addresses, add the preferred base of
180   // the object to the offset before we do the query. It's what DIContext
181   // expects.
182   if (Opts.RelativeAddresses)
183     ModuleOffset.Address += Info->getModulePreferredBase();
184 
185   return Info->symbolizeFrame(ModuleOffset);
186 }
187 
188 Expected<std::vector<DILocal>>
189 LLVMSymbolizer::symbolizeFrame(const ObjectFile &Obj,
190                                object::SectionedAddress ModuleOffset) {
191   return symbolizeFrameCommon(Obj, ModuleOffset);
192 }
193 
194 Expected<std::vector<DILocal>>
195 LLVMSymbolizer::symbolizeFrame(const std::string &ModuleName,
196                                object::SectionedAddress ModuleOffset) {
197   return symbolizeFrameCommon(ModuleName, ModuleOffset);
198 }
199 
200 void LLVMSymbolizer::flush() {
201   ObjectForUBPathAndArch.clear();
202   BinaryForPath.clear();
203   ObjectPairForPathArch.clear();
204   Modules.clear();
205 }
206 
207 namespace {
208 
209 // For Path="/path/to/foo" and Basename="foo" assume that debug info is in
210 // /path/to/foo.dSYM/Contents/Resources/DWARF/foo.
211 // For Path="/path/to/bar.dSYM" and Basename="foo" assume that debug info is in
212 // /path/to/bar.dSYM/Contents/Resources/DWARF/foo.
213 std::string getDarwinDWARFResourceForPath(const std::string &Path,
214                                           const std::string &Basename) {
215   SmallString<16> ResourceName = StringRef(Path);
216   if (sys::path::extension(Path) != ".dSYM") {
217     ResourceName += ".dSYM";
218   }
219   sys::path::append(ResourceName, "Contents", "Resources", "DWARF");
220   sys::path::append(ResourceName, Basename);
221   return std::string(ResourceName.str());
222 }
223 
224 bool checkFileCRC(StringRef Path, uint32_t CRCHash) {
225   ErrorOr<std::unique_ptr<MemoryBuffer>> MB =
226       MemoryBuffer::getFileOrSTDIN(Path);
227   if (!MB)
228     return false;
229   return CRCHash == llvm::crc32(arrayRefFromStringRef(MB.get()->getBuffer()));
230 }
231 
232 bool getGNUDebuglinkContents(const ObjectFile *Obj, std::string &DebugName,
233                              uint32_t &CRCHash) {
234   if (!Obj)
235     return false;
236   for (const SectionRef &Section : Obj->sections()) {
237     StringRef Name;
238     consumeError(Section.getName().moveInto(Name));
239 
240     Name = Name.substr(Name.find_first_not_of("._"));
241     if (Name == "gnu_debuglink") {
242       Expected<StringRef> ContentsOrErr = Section.getContents();
243       if (!ContentsOrErr) {
244         consumeError(ContentsOrErr.takeError());
245         return false;
246       }
247       DataExtractor DE(*ContentsOrErr, Obj->isLittleEndian(), 0);
248       uint64_t Offset = 0;
249       if (const char *DebugNameStr = DE.getCStr(&Offset)) {
250         // 4-byte align the offset.
251         Offset = (Offset + 3) & ~0x3;
252         if (DE.isValidOffsetForDataOfSize(Offset, 4)) {
253           DebugName = DebugNameStr;
254           CRCHash = DE.getU32(&Offset);
255           return true;
256         }
257       }
258       break;
259     }
260   }
261   return false;
262 }
263 
264 bool darwinDsymMatchesBinary(const MachOObjectFile *DbgObj,
265                              const MachOObjectFile *Obj) {
266   ArrayRef<uint8_t> dbg_uuid = DbgObj->getUuid();
267   ArrayRef<uint8_t> bin_uuid = Obj->getUuid();
268   if (dbg_uuid.empty() || bin_uuid.empty())
269     return false;
270   return !memcmp(dbg_uuid.data(), bin_uuid.data(), dbg_uuid.size());
271 }
272 
273 template <typename ELFT>
274 Optional<ArrayRef<uint8_t>> getBuildID(const ELFFile<ELFT> &Obj) {
275   auto PhdrsOrErr = Obj.program_headers();
276   if (!PhdrsOrErr) {
277     consumeError(PhdrsOrErr.takeError());
278     return {};
279   }
280   for (const auto &P : *PhdrsOrErr) {
281     if (P.p_type != ELF::PT_NOTE)
282       continue;
283     Error Err = Error::success();
284     for (auto N : Obj.notes(P, Err))
285       if (N.getType() == ELF::NT_GNU_BUILD_ID &&
286           N.getName() == ELF::ELF_NOTE_GNU)
287         return N.getDesc();
288     consumeError(std::move(Err));
289   }
290   return {};
291 }
292 
293 Optional<ArrayRef<uint8_t>> getBuildID(const ELFObjectFileBase *Obj) {
294   Optional<ArrayRef<uint8_t>> BuildID;
295   if (auto *O = dyn_cast<ELFObjectFile<ELF32LE>>(Obj))
296     BuildID = getBuildID(O->getELFFile());
297   else if (auto *O = dyn_cast<ELFObjectFile<ELF32BE>>(Obj))
298     BuildID = getBuildID(O->getELFFile());
299   else if (auto *O = dyn_cast<ELFObjectFile<ELF64LE>>(Obj))
300     BuildID = getBuildID(O->getELFFile());
301   else if (auto *O = dyn_cast<ELFObjectFile<ELF64BE>>(Obj))
302     BuildID = getBuildID(O->getELFFile());
303   else
304     llvm_unreachable("unsupported file format");
305   return BuildID;
306 }
307 
308 } // end anonymous namespace
309 
310 ObjectFile *LLVMSymbolizer::lookUpDsymFile(const std::string &ExePath,
311                                            const MachOObjectFile *MachExeObj,
312                                            const std::string &ArchName) {
313   // On Darwin we may find DWARF in separate object file in
314   // resource directory.
315   std::vector<std::string> DsymPaths;
316   StringRef Filename = sys::path::filename(ExePath);
317   DsymPaths.push_back(
318       getDarwinDWARFResourceForPath(ExePath, std::string(Filename)));
319   for (const auto &Path : Opts.DsymHints) {
320     DsymPaths.push_back(
321         getDarwinDWARFResourceForPath(Path, std::string(Filename)));
322   }
323   for (const auto &Path : DsymPaths) {
324     auto DbgObjOrErr = getOrCreateObject(Path, ArchName);
325     if (!DbgObjOrErr) {
326       // Ignore errors, the file might not exist.
327       consumeError(DbgObjOrErr.takeError());
328       continue;
329     }
330     ObjectFile *DbgObj = DbgObjOrErr.get();
331     if (!DbgObj)
332       continue;
333     const MachOObjectFile *MachDbgObj = dyn_cast<const MachOObjectFile>(DbgObj);
334     if (!MachDbgObj)
335       continue;
336     if (darwinDsymMatchesBinary(MachDbgObj, MachExeObj))
337       return DbgObj;
338   }
339   return nullptr;
340 }
341 
342 ObjectFile *LLVMSymbolizer::lookUpDebuglinkObject(const std::string &Path,
343                                                   const ObjectFile *Obj,
344                                                   const std::string &ArchName) {
345   std::string DebuglinkName;
346   uint32_t CRCHash;
347   std::string DebugBinaryPath;
348   if (!getGNUDebuglinkContents(Obj, DebuglinkName, CRCHash))
349     return nullptr;
350   if (!findDebugBinary(Path, DebuglinkName, CRCHash, DebugBinaryPath))
351     return nullptr;
352   auto DbgObjOrErr = getOrCreateObject(DebugBinaryPath, ArchName);
353   if (!DbgObjOrErr) {
354     // Ignore errors, the file might not exist.
355     consumeError(DbgObjOrErr.takeError());
356     return nullptr;
357   }
358   return DbgObjOrErr.get();
359 }
360 
361 ObjectFile *LLVMSymbolizer::lookUpBuildIDObject(const std::string &Path,
362                                                 const ELFObjectFileBase *Obj,
363                                                 const std::string &ArchName) {
364   auto BuildID = getBuildID(Obj);
365   if (!BuildID)
366     return nullptr;
367   if (BuildID->size() < 2)
368     return nullptr;
369   std::string DebugBinaryPath;
370   if (!findDebugBinary(*BuildID, DebugBinaryPath))
371     return nullptr;
372   auto DbgObjOrErr = getOrCreateObject(DebugBinaryPath, ArchName);
373   if (!DbgObjOrErr) {
374     consumeError(DbgObjOrErr.takeError());
375     return nullptr;
376   }
377   return DbgObjOrErr.get();
378 }
379 
380 bool LLVMSymbolizer::findDebugBinary(const std::string &OrigPath,
381                                      const std::string &DebuglinkName,
382                                      uint32_t CRCHash, std::string &Result) {
383   SmallString<16> OrigDir(OrigPath);
384   llvm::sys::path::remove_filename(OrigDir);
385   SmallString<16> DebugPath = OrigDir;
386   // Try relative/path/to/original_binary/debuglink_name
387   llvm::sys::path::append(DebugPath, DebuglinkName);
388   if (checkFileCRC(DebugPath, CRCHash)) {
389     Result = std::string(DebugPath.str());
390     return true;
391   }
392   // Try relative/path/to/original_binary/.debug/debuglink_name
393   DebugPath = OrigDir;
394   llvm::sys::path::append(DebugPath, ".debug", DebuglinkName);
395   if (checkFileCRC(DebugPath, CRCHash)) {
396     Result = std::string(DebugPath.str());
397     return true;
398   }
399   // Make the path absolute so that lookups will go to
400   // "/usr/lib/debug/full/path/to/debug", not
401   // "/usr/lib/debug/to/debug"
402   llvm::sys::fs::make_absolute(OrigDir);
403   if (!Opts.FallbackDebugPath.empty()) {
404     // Try <FallbackDebugPath>/absolute/path/to/original_binary/debuglink_name
405     DebugPath = Opts.FallbackDebugPath;
406   } else {
407 #if defined(__NetBSD__)
408     // Try /usr/libdata/debug/absolute/path/to/original_binary/debuglink_name
409     DebugPath = "/usr/libdata/debug";
410 #else
411     // Try /usr/lib/debug/absolute/path/to/original_binary/debuglink_name
412     DebugPath = "/usr/lib/debug";
413 #endif
414   }
415   llvm::sys::path::append(DebugPath, llvm::sys::path::relative_path(OrigDir),
416                           DebuglinkName);
417   if (checkFileCRC(DebugPath, CRCHash)) {
418     Result = std::string(DebugPath.str());
419     return true;
420   }
421   return false;
422 }
423 
424 bool LLVMSymbolizer::findDebugBinary(const ArrayRef<uint8_t> BuildID,
425                                      std::string &Result) {
426   Optional<std::string> Path;
427   Path = LocalDIFetcher(Opts.DebugFileDirectory).fetchBuildID(BuildID);
428   if (Path) {
429     Result = std::move(*Path);
430     return true;
431   }
432 
433   // Try caller-provided debug info fetchers.
434   for (const std::unique_ptr<DIFetcher> &Fetcher : DIFetchers) {
435     Path = Fetcher->fetchBuildID(BuildID);
436     if (Path) {
437       Result = std::move(*Path);
438       return true;
439     }
440   }
441 
442   return false;
443 }
444 
445 Expected<LLVMSymbolizer::ObjectPair>
446 LLVMSymbolizer::getOrCreateObjectPair(const std::string &Path,
447                                       const std::string &ArchName) {
448   auto I = ObjectPairForPathArch.find(std::make_pair(Path, ArchName));
449   if (I != ObjectPairForPathArch.end())
450     return I->second;
451 
452   auto ObjOrErr = getOrCreateObject(Path, ArchName);
453   if (!ObjOrErr) {
454     ObjectPairForPathArch.emplace(std::make_pair(Path, ArchName),
455                                   ObjectPair(nullptr, nullptr));
456     return ObjOrErr.takeError();
457   }
458 
459   ObjectFile *Obj = ObjOrErr.get();
460   assert(Obj != nullptr);
461   ObjectFile *DbgObj = nullptr;
462 
463   if (auto MachObj = dyn_cast<const MachOObjectFile>(Obj))
464     DbgObj = lookUpDsymFile(Path, MachObj, ArchName);
465   else if (auto ELFObj = dyn_cast<const ELFObjectFileBase>(Obj))
466     DbgObj = lookUpBuildIDObject(Path, ELFObj, ArchName);
467   if (!DbgObj)
468     DbgObj = lookUpDebuglinkObject(Path, Obj, ArchName);
469   if (!DbgObj)
470     DbgObj = Obj;
471   ObjectPair Res = std::make_pair(Obj, DbgObj);
472   ObjectPairForPathArch.emplace(std::make_pair(Path, ArchName), Res);
473   return Res;
474 }
475 
476 Expected<ObjectFile *>
477 LLVMSymbolizer::getOrCreateObject(const std::string &Path,
478                                   const std::string &ArchName) {
479   Binary *Bin;
480   auto Pair = BinaryForPath.emplace(Path, OwningBinary<Binary>());
481   if (!Pair.second) {
482     Bin = Pair.first->second.getBinary();
483   } else {
484     Expected<OwningBinary<Binary>> BinOrErr = createBinary(Path);
485     if (!BinOrErr)
486       return BinOrErr.takeError();
487     Pair.first->second = std::move(BinOrErr.get());
488     Bin = Pair.first->second.getBinary();
489   }
490 
491   if (!Bin)
492     return static_cast<ObjectFile *>(nullptr);
493 
494   if (MachOUniversalBinary *UB = dyn_cast_or_null<MachOUniversalBinary>(Bin)) {
495     auto I = ObjectForUBPathAndArch.find(std::make_pair(Path, ArchName));
496     if (I != ObjectForUBPathAndArch.end())
497       return I->second.get();
498 
499     Expected<std::unique_ptr<ObjectFile>> ObjOrErr =
500         UB->getMachOObjectForArch(ArchName);
501     if (!ObjOrErr) {
502       ObjectForUBPathAndArch.emplace(std::make_pair(Path, ArchName),
503                                      std::unique_ptr<ObjectFile>());
504       return ObjOrErr.takeError();
505     }
506     ObjectFile *Res = ObjOrErr->get();
507     ObjectForUBPathAndArch.emplace(std::make_pair(Path, ArchName),
508                                    std::move(ObjOrErr.get()));
509     return Res;
510   }
511   if (Bin->isObject()) {
512     return cast<ObjectFile>(Bin);
513   }
514   return errorCodeToError(object_error::arch_not_found);
515 }
516 
517 Expected<SymbolizableModule *>
518 LLVMSymbolizer::createModuleInfo(const ObjectFile *Obj,
519                                  std::unique_ptr<DIContext> Context,
520                                  StringRef ModuleName) {
521   auto InfoOrErr = SymbolizableObjectFile::create(Obj, std::move(Context),
522                                                   Opts.UntagAddresses);
523   std::unique_ptr<SymbolizableModule> SymMod;
524   if (InfoOrErr)
525     SymMod = std::move(*InfoOrErr);
526   auto InsertResult = Modules.insert(
527       std::make_pair(std::string(ModuleName), std::move(SymMod)));
528   assert(InsertResult.second);
529   if (!InfoOrErr)
530     return InfoOrErr.takeError();
531   return InsertResult.first->second.get();
532 }
533 
534 Expected<SymbolizableModule *>
535 LLVMSymbolizer::getOrCreateModuleInfo(const std::string &ModuleName) {
536   auto I = Modules.find(ModuleName);
537   if (I != Modules.end())
538     return I->second.get();
539 
540   std::string BinaryName = ModuleName;
541   std::string ArchName = Opts.DefaultArch;
542   size_t ColonPos = ModuleName.find_last_of(':');
543   // Verify that substring after colon form a valid arch name.
544   if (ColonPos != std::string::npos) {
545     std::string ArchStr = ModuleName.substr(ColonPos + 1);
546     if (Triple(ArchStr).getArch() != Triple::UnknownArch) {
547       BinaryName = ModuleName.substr(0, ColonPos);
548       ArchName = ArchStr;
549     }
550   }
551   auto ObjectsOrErr = getOrCreateObjectPair(BinaryName, ArchName);
552   if (!ObjectsOrErr) {
553     // Failed to find valid object file.
554     Modules.emplace(ModuleName, std::unique_ptr<SymbolizableModule>());
555     return ObjectsOrErr.takeError();
556   }
557   ObjectPair Objects = ObjectsOrErr.get();
558 
559   std::unique_ptr<DIContext> Context;
560   // If this is a COFF object containing PDB info, use a PDBContext to
561   // symbolize. Otherwise, use DWARF.
562   if (auto CoffObject = dyn_cast<COFFObjectFile>(Objects.first)) {
563     const codeview::DebugInfo *DebugInfo;
564     StringRef PDBFileName;
565     auto EC = CoffObject->getDebugPDBInfo(DebugInfo, PDBFileName);
566     if (!EC && DebugInfo != nullptr && !PDBFileName.empty()) {
567       using namespace pdb;
568       std::unique_ptr<IPDBSession> Session;
569 
570       PDB_ReaderType ReaderType =
571           Opts.UseDIA ? PDB_ReaderType::DIA : PDB_ReaderType::Native;
572       if (auto Err = loadDataForEXE(ReaderType, Objects.first->getFileName(),
573                                     Session)) {
574         Modules.emplace(ModuleName, std::unique_ptr<SymbolizableModule>());
575         // Return along the PDB filename to provide more context
576         return createFileError(PDBFileName, std::move(Err));
577       }
578       Context.reset(new PDBContext(*CoffObject, std::move(Session)));
579     }
580   }
581   if (!Context)
582     Context = DWARFContext::create(
583         *Objects.second, DWARFContext::ProcessDebugRelocations::Process,
584         nullptr, Opts.DWPName);
585   return createModuleInfo(Objects.first, std::move(Context), ModuleName);
586 }
587 
588 Expected<SymbolizableModule *>
589 LLVMSymbolizer::getOrCreateModuleInfo(const ObjectFile &Obj) {
590   StringRef ObjName = Obj.getFileName();
591   auto I = Modules.find(ObjName);
592   if (I != Modules.end())
593     return I->second.get();
594 
595   std::unique_ptr<DIContext> Context = DWARFContext::create(Obj);
596   // FIXME: handle COFF object with PDB info to use PDBContext
597   return createModuleInfo(&Obj, std::move(Context), ObjName);
598 }
599 
600 namespace {
601 
602 // Undo these various manglings for Win32 extern "C" functions:
603 // cdecl       - _foo
604 // stdcall     - _foo@12
605 // fastcall    - @foo@12
606 // vectorcall  - foo@@12
607 // These are all different linkage names for 'foo'.
608 StringRef demanglePE32ExternCFunc(StringRef SymbolName) {
609   // Remove any '_' or '@' prefix.
610   char Front = SymbolName.empty() ? '\0' : SymbolName[0];
611   if (Front == '_' || Front == '@')
612     SymbolName = SymbolName.drop_front();
613 
614   // Remove any '@[0-9]+' suffix.
615   if (Front != '?') {
616     size_t AtPos = SymbolName.rfind('@');
617     if (AtPos != StringRef::npos &&
618         all_of(drop_begin(SymbolName, AtPos + 1), isDigit))
619       SymbolName = SymbolName.substr(0, AtPos);
620   }
621 
622   // Remove any ending '@' for vectorcall.
623   if (SymbolName.endswith("@"))
624     SymbolName = SymbolName.drop_back();
625 
626   return SymbolName;
627 }
628 
629 } // end anonymous namespace
630 
631 std::string
632 LLVMSymbolizer::DemangleName(const std::string &Name,
633                              const SymbolizableModule *DbiModuleDescriptor) {
634   std::string Result;
635   if (nonMicrosoftDemangle(Name.c_str(), Result))
636     return Result;
637 
638   if (!Name.empty() && Name.front() == '?') {
639     // Only do MSVC C++ demangling on symbols starting with '?'.
640     int status = 0;
641     char *DemangledName = microsoftDemangle(
642         Name.c_str(), nullptr, nullptr, nullptr, &status,
643         MSDemangleFlags(MSDF_NoAccessSpecifier | MSDF_NoCallingConvention |
644                         MSDF_NoMemberType | MSDF_NoReturnType));
645     if (status != 0)
646       return Name;
647     Result = DemangledName;
648     free(DemangledName);
649     return Result;
650   }
651 
652   if (DbiModuleDescriptor && DbiModuleDescriptor->isWin32Module())
653     return std::string(demanglePE32ExternCFunc(Name));
654   return Name;
655 }
656 
657 } // namespace symbolize
658 } // namespace llvm
659