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