xref: /freebsd/contrib/llvm-project/llvm/lib/DebugInfo/Symbolize/Symbolize.cpp (revision c66ec88fed842fbaad62c30d510644ceb7bd2d71) 
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(
55       ModuleOffset, DILineInfoSpecifier(Opts.PathStyle, Opts.PrintFunctions),
56       Opts.UseSymbolTable);
57   if (Opts.Demangle)
58     LineInfo.FunctionName = DemangleName(LineInfo.FunctionName, Info);
59   return LineInfo;
60 }
61 
62 Expected<DILineInfo>
63 LLVMSymbolizer::symbolizeCode(const ObjectFile &Obj,
64                               object::SectionedAddress ModuleOffset) {
65   StringRef ModuleName = Obj.getFileName();
66   auto I = Modules.find(ModuleName);
67   if (I != Modules.end())
68     return symbolizeCodeCommon(I->second.get(), ModuleOffset);
69 
70   std::unique_ptr<DIContext> Context = DWARFContext::create(Obj);
71   Expected<SymbolizableModule *> InfoOrErr =
72                      createModuleInfo(&Obj, std::move(Context), ModuleName);
73   if (!InfoOrErr)
74     return InfoOrErr.takeError();
75   return symbolizeCodeCommon(*InfoOrErr, ModuleOffset);
76 }
77 
78 Expected<DILineInfo>
79 LLVMSymbolizer::symbolizeCode(const std::string &ModuleName,
80                               object::SectionedAddress ModuleOffset) {
81   Expected<SymbolizableModule *> InfoOrErr = getOrCreateModuleInfo(ModuleName);
82   if (!InfoOrErr)
83     return InfoOrErr.takeError();
84   return symbolizeCodeCommon(*InfoOrErr, ModuleOffset);
85 }
86 
87 Expected<DIInliningInfo>
88 LLVMSymbolizer::symbolizeInlinedCode(const std::string &ModuleName,
89                                      object::SectionedAddress ModuleOffset) {
90   SymbolizableModule *Info;
91   if (auto InfoOrErr = getOrCreateModuleInfo(ModuleName))
92     Info = InfoOrErr.get();
93   else
94     return InfoOrErr.takeError();
95 
96   // A null module means an error has already been reported. Return an empty
97   // result.
98   if (!Info)
99     return DIInliningInfo();
100 
101   // If the user is giving us relative addresses, add the preferred base of the
102   // object to the offset before we do the query. It's what DIContext expects.
103   if (Opts.RelativeAddresses)
104     ModuleOffset.Address += Info->getModulePreferredBase();
105 
106   DIInliningInfo InlinedContext = Info->symbolizeInlinedCode(
107       ModuleOffset, DILineInfoSpecifier(Opts.PathStyle, Opts.PrintFunctions),
108       Opts.UseSymbolTable);
109   if (Opts.Demangle) {
110     for (int i = 0, n = InlinedContext.getNumberOfFrames(); i < n; i++) {
111       auto *Frame = InlinedContext.getMutableFrame(i);
112       Frame->FunctionName = DemangleName(Frame->FunctionName, Info);
113     }
114   }
115   return InlinedContext;
116 }
117 
118 Expected<DIGlobal>
119 LLVMSymbolizer::symbolizeData(const std::string &ModuleName,
120                               object::SectionedAddress ModuleOffset) {
121   SymbolizableModule *Info;
122   if (auto InfoOrErr = getOrCreateModuleInfo(ModuleName))
123     Info = InfoOrErr.get();
124   else
125     return InfoOrErr.takeError();
126 
127   // A null module means an error has already been reported. Return an empty
128   // result.
129   if (!Info)
130     return DIGlobal();
131 
132   // If the user is giving us relative addresses, add the preferred base of
133   // the object to the offset before we do the query. It's what DIContext
134   // expects.
135   if (Opts.RelativeAddresses)
136     ModuleOffset.Address += Info->getModulePreferredBase();
137 
138   DIGlobal Global = Info->symbolizeData(ModuleOffset);
139   if (Opts.Demangle)
140     Global.Name = DemangleName(Global.Name, Info);
141   return Global;
142 }
143 
144 Expected<std::vector<DILocal>>
145 LLVMSymbolizer::symbolizeFrame(const std::string &ModuleName,
146                                object::SectionedAddress ModuleOffset) {
147   SymbolizableModule *Info;
148   if (auto InfoOrErr = getOrCreateModuleInfo(ModuleName))
149     Info = InfoOrErr.get();
150   else
151     return InfoOrErr.takeError();
152 
153   // A null module means an error has already been reported. Return an empty
154   // result.
155   if (!Info)
156     return std::vector<DILocal>();
157 
158   // If the user is giving us relative addresses, add the preferred base of
159   // the object to the offset before we do the query. It's what DIContext
160   // expects.
161   if (Opts.RelativeAddresses)
162     ModuleOffset.Address += Info->getModulePreferredBase();
163 
164   return Info->symbolizeFrame(ModuleOffset);
165 }
166 
167 void LLVMSymbolizer::flush() {
168   ObjectForUBPathAndArch.clear();
169   BinaryForPath.clear();
170   ObjectPairForPathArch.clear();
171   Modules.clear();
172 }
173 
174 namespace {
175 
176 // For Path="/path/to/foo" and Basename="foo" assume that debug info is in
177 // /path/to/foo.dSYM/Contents/Resources/DWARF/foo.
178 // For Path="/path/to/bar.dSYM" and Basename="foo" assume that debug info is in
179 // /path/to/bar.dSYM/Contents/Resources/DWARF/foo.
180 std::string getDarwinDWARFResourceForPath(
181     const std::string &Path, const std::string &Basename) {
182   SmallString<16> ResourceName = StringRef(Path);
183   if (sys::path::extension(Path) != ".dSYM") {
184     ResourceName += ".dSYM";
185   }
186   sys::path::append(ResourceName, "Contents", "Resources", "DWARF");
187   sys::path::append(ResourceName, Basename);
188   return std::string(ResourceName.str());
189 }
190 
191 bool checkFileCRC(StringRef Path, uint32_t CRCHash) {
192   ErrorOr<std::unique_ptr<MemoryBuffer>> MB =
193       MemoryBuffer::getFileOrSTDIN(Path);
194   if (!MB)
195     return false;
196   return CRCHash == llvm::crc32(arrayRefFromStringRef(MB.get()->getBuffer()));
197 }
198 
199 bool findDebugBinary(const std::string &OrigPath,
200                      const std::string &DebuglinkName, uint32_t CRCHash,
201                      const std::string &FallbackDebugPath,
202                      std::string &Result) {
203   SmallString<16> OrigDir(OrigPath);
204   llvm::sys::path::remove_filename(OrigDir);
205   SmallString<16> DebugPath = OrigDir;
206   // Try relative/path/to/original_binary/debuglink_name
207   llvm::sys::path::append(DebugPath, DebuglinkName);
208   if (checkFileCRC(DebugPath, CRCHash)) {
209     Result = std::string(DebugPath.str());
210     return true;
211   }
212   // Try relative/path/to/original_binary/.debug/debuglink_name
213   DebugPath = OrigDir;
214   llvm::sys::path::append(DebugPath, ".debug", DebuglinkName);
215   if (checkFileCRC(DebugPath, CRCHash)) {
216     Result = std::string(DebugPath.str());
217     return true;
218   }
219   // Make the path absolute so that lookups will go to
220   // "/usr/lib/debug/full/path/to/debug", not
221   // "/usr/lib/debug/to/debug"
222   llvm::sys::fs::make_absolute(OrigDir);
223   if (!FallbackDebugPath.empty()) {
224     // Try <FallbackDebugPath>/absolute/path/to/original_binary/debuglink_name
225     DebugPath = FallbackDebugPath;
226   } else {
227 #if defined(__NetBSD__)
228     // Try /usr/libdata/debug/absolute/path/to/original_binary/debuglink_name
229     DebugPath = "/usr/libdata/debug";
230 #else
231     // Try /usr/lib/debug/absolute/path/to/original_binary/debuglink_name
232     DebugPath = "/usr/lib/debug";
233 #endif
234   }
235   llvm::sys::path::append(DebugPath, llvm::sys::path::relative_path(OrigDir),
236                           DebuglinkName);
237   if (checkFileCRC(DebugPath, CRCHash)) {
238     Result = std::string(DebugPath.str());
239     return true;
240   }
241   return false;
242 }
243 
244 bool getGNUDebuglinkContents(const ObjectFile *Obj, std::string &DebugName,
245                              uint32_t &CRCHash) {
246   if (!Obj)
247     return false;
248   for (const SectionRef &Section : Obj->sections()) {
249     StringRef Name;
250     if (Expected<StringRef> NameOrErr = Section.getName())
251       Name = *NameOrErr;
252     else
253       consumeError(NameOrErr.takeError());
254 
255     Name = Name.substr(Name.find_first_not_of("._"));
256     if (Name == "gnu_debuglink") {
257       Expected<StringRef> ContentsOrErr = Section.getContents();
258       if (!ContentsOrErr) {
259         consumeError(ContentsOrErr.takeError());
260         return false;
261       }
262       DataExtractor DE(*ContentsOrErr, Obj->isLittleEndian(), 0);
263       uint64_t Offset = 0;
264       if (const char *DebugNameStr = DE.getCStr(&Offset)) {
265         // 4-byte align the offset.
266         Offset = (Offset + 3) & ~0x3;
267         if (DE.isValidOffsetForDataOfSize(Offset, 4)) {
268           DebugName = DebugNameStr;
269           CRCHash = DE.getU32(&Offset);
270           return true;
271         }
272       }
273       break;
274     }
275   }
276   return false;
277 }
278 
279 bool darwinDsymMatchesBinary(const MachOObjectFile *DbgObj,
280                              const MachOObjectFile *Obj) {
281   ArrayRef<uint8_t> dbg_uuid = DbgObj->getUuid();
282   ArrayRef<uint8_t> bin_uuid = Obj->getUuid();
283   if (dbg_uuid.empty() || bin_uuid.empty())
284     return false;
285   return !memcmp(dbg_uuid.data(), bin_uuid.data(), dbg_uuid.size());
286 }
287 
288 template <typename ELFT>
289 Optional<ArrayRef<uint8_t>> getBuildID(const ELFFile<ELFT> *Obj) {
290   if (!Obj)
291     return {};
292   auto PhdrsOrErr = Obj->program_headers();
293   if (!PhdrsOrErr) {
294     consumeError(PhdrsOrErr.takeError());
295     return {};
296   }
297   for (const auto &P : *PhdrsOrErr) {
298     if (P.p_type != ELF::PT_NOTE)
299       continue;
300     Error Err = Error::success();
301     for (auto N : Obj->notes(P, Err))
302       if (N.getType() == ELF::NT_GNU_BUILD_ID && N.getName() == ELF::ELF_NOTE_GNU)
303         return N.getDesc();
304     consumeError(std::move(Err));
305   }
306   return {};
307 }
308 
309 Optional<ArrayRef<uint8_t>> getBuildID(const ELFObjectFileBase *Obj) {
310   Optional<ArrayRef<uint8_t>> BuildID;
311   if (auto *O = dyn_cast<ELFObjectFile<ELF32LE>>(Obj))
312     BuildID = getBuildID(O->getELFFile());
313   else if (auto *O = dyn_cast<ELFObjectFile<ELF32BE>>(Obj))
314     BuildID = getBuildID(O->getELFFile());
315   else if (auto *O = dyn_cast<ELFObjectFile<ELF64LE>>(Obj))
316     BuildID = getBuildID(O->getELFFile());
317   else if (auto *O = dyn_cast<ELFObjectFile<ELF64BE>>(Obj))
318     BuildID = getBuildID(O->getELFFile());
319   else
320     llvm_unreachable("unsupported file format");
321   return BuildID;
322 }
323 
324 bool findDebugBinary(const std::vector<std::string> &DebugFileDirectory,
325                      const ArrayRef<uint8_t> BuildID,
326                      std::string &Result) {
327   auto getDebugPath = [&](StringRef Directory) {
328     SmallString<128> Path{Directory};
329     sys::path::append(Path, ".build-id",
330                       llvm::toHex(BuildID[0], /*LowerCase=*/true),
331                       llvm::toHex(BuildID.slice(1), /*LowerCase=*/true));
332     Path += ".debug";
333     return Path;
334   };
335   if (DebugFileDirectory.empty()) {
336     SmallString<128> Path = getDebugPath(
337 #if defined(__NetBSD__)
338       // Try /usr/libdata/debug/.build-id/../...
339       "/usr/libdata/debug"
340 #else
341       // Try /usr/lib/debug/.build-id/../...
342       "/usr/lib/debug"
343 #endif
344     );
345     if (llvm::sys::fs::exists(Path)) {
346       Result = std::string(Path.str());
347       return true;
348     }
349   } else {
350     for (const auto &Directory : DebugFileDirectory) {
351       // Try <debug-file-directory>/.build-id/../...
352       SmallString<128> Path = getDebugPath(Directory);
353       if (llvm::sys::fs::exists(Path)) {
354         Result = std::string(Path.str());
355         return true;
356       }
357     }
358   }
359   return false;
360 }
361 
362 } // end anonymous namespace
363 
364 ObjectFile *LLVMSymbolizer::lookUpDsymFile(const std::string &ExePath,
365     const MachOObjectFile *MachExeObj, const std::string &ArchName) {
366   // On Darwin we may find DWARF in separate object file in
367   // resource directory.
368   std::vector<std::string> DsymPaths;
369   StringRef Filename = sys::path::filename(ExePath);
370   DsymPaths.push_back(
371       getDarwinDWARFResourceForPath(ExePath, std::string(Filename)));
372   for (const auto &Path : Opts.DsymHints) {
373     DsymPaths.push_back(
374         getDarwinDWARFResourceForPath(Path, std::string(Filename)));
375   }
376   for (const auto &Path : DsymPaths) {
377     auto DbgObjOrErr = getOrCreateObject(Path, ArchName);
378     if (!DbgObjOrErr) {
379       // Ignore errors, the file might not exist.
380       consumeError(DbgObjOrErr.takeError());
381       continue;
382     }
383     ObjectFile *DbgObj = DbgObjOrErr.get();
384     if (!DbgObj)
385       continue;
386     const MachOObjectFile *MachDbgObj = dyn_cast<const MachOObjectFile>(DbgObj);
387     if (!MachDbgObj)
388       continue;
389     if (darwinDsymMatchesBinary(MachDbgObj, MachExeObj))
390       return DbgObj;
391   }
392   return nullptr;
393 }
394 
395 ObjectFile *LLVMSymbolizer::lookUpDebuglinkObject(const std::string &Path,
396                                                   const ObjectFile *Obj,
397                                                   const std::string &ArchName) {
398   std::string DebuglinkName;
399   uint32_t CRCHash;
400   std::string DebugBinaryPath;
401   if (!getGNUDebuglinkContents(Obj, DebuglinkName, CRCHash))
402     return nullptr;
403   if (!findDebugBinary(Path, DebuglinkName, CRCHash, Opts.FallbackDebugPath,
404                        DebugBinaryPath))
405     return nullptr;
406   auto DbgObjOrErr = getOrCreateObject(DebugBinaryPath, ArchName);
407   if (!DbgObjOrErr) {
408     // Ignore errors, the file might not exist.
409     consumeError(DbgObjOrErr.takeError());
410     return nullptr;
411   }
412   return DbgObjOrErr.get();
413 }
414 
415 ObjectFile *LLVMSymbolizer::lookUpBuildIDObject(const std::string &Path,
416                                                 const ELFObjectFileBase *Obj,
417                                                 const std::string &ArchName) {
418   auto BuildID = getBuildID(Obj);
419   if (!BuildID)
420     return nullptr;
421   if (BuildID->size() < 2)
422     return nullptr;
423   std::string DebugBinaryPath;
424   if (!findDebugBinary(Opts.DebugFileDirectory, *BuildID, DebugBinaryPath))
425     return nullptr;
426   auto DbgObjOrErr = getOrCreateObject(DebugBinaryPath, ArchName);
427   if (!DbgObjOrErr) {
428     consumeError(DbgObjOrErr.takeError());
429     return nullptr;
430   }
431   return DbgObjOrErr.get();
432 }
433 
434 Expected<LLVMSymbolizer::ObjectPair>
435 LLVMSymbolizer::getOrCreateObjectPair(const std::string &Path,
436                                       const std::string &ArchName) {
437   auto I = ObjectPairForPathArch.find(std::make_pair(Path, ArchName));
438   if (I != ObjectPairForPathArch.end())
439     return I->second;
440 
441   auto ObjOrErr = getOrCreateObject(Path, ArchName);
442   if (!ObjOrErr) {
443     ObjectPairForPathArch.emplace(std::make_pair(Path, ArchName),
444                                   ObjectPair(nullptr, nullptr));
445     return ObjOrErr.takeError();
446   }
447 
448   ObjectFile *Obj = ObjOrErr.get();
449   assert(Obj != nullptr);
450   ObjectFile *DbgObj = nullptr;
451 
452   if (auto MachObj = dyn_cast<const MachOObjectFile>(Obj))
453     DbgObj = lookUpDsymFile(Path, MachObj, ArchName);
454   else if (auto ELFObj = dyn_cast<const ELFObjectFileBase>(Obj))
455     DbgObj = lookUpBuildIDObject(Path, ELFObj, ArchName);
456   if (!DbgObj)
457     DbgObj = lookUpDebuglinkObject(Path, Obj, ArchName);
458   if (!DbgObj)
459     DbgObj = Obj;
460   ObjectPair Res = std::make_pair(Obj, DbgObj);
461   ObjectPairForPathArch.emplace(std::make_pair(Path, ArchName), Res);
462   return Res;
463 }
464 
465 Expected<ObjectFile *>
466 LLVMSymbolizer::getOrCreateObject(const std::string &Path,
467                                   const std::string &ArchName) {
468   Binary *Bin;
469   auto Pair = BinaryForPath.emplace(Path, OwningBinary<Binary>());
470   if (!Pair.second) {
471     Bin = Pair.first->second.getBinary();
472   } else {
473     Expected<OwningBinary<Binary>> BinOrErr = createBinary(Path);
474     if (!BinOrErr)
475       return BinOrErr.takeError();
476     Pair.first->second = std::move(BinOrErr.get());
477     Bin = Pair.first->second.getBinary();
478   }
479 
480   if (!Bin)
481     return static_cast<ObjectFile *>(nullptr);
482 
483   if (MachOUniversalBinary *UB = dyn_cast_or_null<MachOUniversalBinary>(Bin)) {
484     auto I = ObjectForUBPathAndArch.find(std::make_pair(Path, ArchName));
485     if (I != ObjectForUBPathAndArch.end())
486       return I->second.get();
487 
488     Expected<std::unique_ptr<ObjectFile>> ObjOrErr =
489         UB->getMachOObjectForArch(ArchName);
490     if (!ObjOrErr) {
491       ObjectForUBPathAndArch.emplace(std::make_pair(Path, ArchName),
492                                      std::unique_ptr<ObjectFile>());
493       return ObjOrErr.takeError();
494     }
495     ObjectFile *Res = ObjOrErr->get();
496     ObjectForUBPathAndArch.emplace(std::make_pair(Path, ArchName),
497                                    std::move(ObjOrErr.get()));
498     return Res;
499   }
500   if (Bin->isObject()) {
501     return cast<ObjectFile>(Bin);
502   }
503   return errorCodeToError(object_error::arch_not_found);
504 }
505 
506 Expected<SymbolizableModule *>
507 LLVMSymbolizer::createModuleInfo(const ObjectFile *Obj,
508                                  std::unique_ptr<DIContext> Context,
509                                  StringRef ModuleName) {
510   auto InfoOrErr = SymbolizableObjectFile::create(Obj, std::move(Context),
511                                                   Opts.UntagAddresses);
512   std::unique_ptr<SymbolizableModule> SymMod;
513   if (InfoOrErr)
514     SymMod = std::move(*InfoOrErr);
515   auto InsertResult = Modules.insert(
516       std::make_pair(std::string(ModuleName), std::move(SymMod)));
517   assert(InsertResult.second);
518   if (!InfoOrErr)
519     return InfoOrErr.takeError();
520   return InsertResult.first->second.get();
521 }
522 
523 Expected<SymbolizableModule *>
524 LLVMSymbolizer::getOrCreateModuleInfo(const std::string &ModuleName) {
525   auto I = Modules.find(ModuleName);
526   if (I != Modules.end())
527     return I->second.get();
528 
529   std::string BinaryName = ModuleName;
530   std::string ArchName = Opts.DefaultArch;
531   size_t ColonPos = ModuleName.find_last_of(':');
532   // Verify that substring after colon form a valid arch name.
533   if (ColonPos != std::string::npos) {
534     std::string ArchStr = ModuleName.substr(ColonPos + 1);
535     if (Triple(ArchStr).getArch() != Triple::UnknownArch) {
536       BinaryName = ModuleName.substr(0, ColonPos);
537       ArchName = ArchStr;
538     }
539   }
540   auto ObjectsOrErr = getOrCreateObjectPair(BinaryName, ArchName);
541   if (!ObjectsOrErr) {
542     // Failed to find valid object file.
543     Modules.emplace(ModuleName, std::unique_ptr<SymbolizableModule>());
544     return ObjectsOrErr.takeError();
545   }
546   ObjectPair Objects = ObjectsOrErr.get();
547 
548   std::unique_ptr<DIContext> Context;
549   // If this is a COFF object containing PDB info, use a PDBContext to
550   // symbolize. Otherwise, use DWARF.
551   if (auto CoffObject = dyn_cast<COFFObjectFile>(Objects.first)) {
552     const codeview::DebugInfo *DebugInfo;
553     StringRef PDBFileName;
554     auto EC = CoffObject->getDebugPDBInfo(DebugInfo, PDBFileName);
555     if (!EC && DebugInfo != nullptr && !PDBFileName.empty()) {
556 #if 0
557       using namespace pdb;
558       std::unique_ptr<IPDBSession> Session;
559       PDB_ReaderType ReaderType = Opts.UseNativePDBReader
560                                       ? PDB_ReaderType::Native
561                                       : PDB_ReaderType::DIA;
562       if (auto Err = loadDataForEXE(ReaderType, Objects.first->getFileName(),
563                                     Session)) {
564         Modules.emplace(ModuleName, std::unique_ptr<SymbolizableModule>());
565         // Return along the PDB filename to provide more context
566         return createFileError(PDBFileName, std::move(Err));
567       }
568       Context.reset(new PDBContext(*CoffObject, std::move(Session)));
569 #else
570       return make_error<StringError>(
571           "PDB support not compiled in",
572           std::make_error_code(std::errc::not_supported));
573 #endif
574     }
575   }
576   if (!Context)
577     Context = DWARFContext::create(*Objects.second, nullptr, Opts.DWPName);
578   return createModuleInfo(Objects.first, std::move(Context), ModuleName);
579 }
580 
581 namespace {
582 
583 // Undo these various manglings for Win32 extern "C" functions:
584 // cdecl       - _foo
585 // stdcall     - _foo@12
586 // fastcall    - @foo@12
587 // vectorcall  - foo@@12
588 // These are all different linkage names for 'foo'.
589 StringRef demanglePE32ExternCFunc(StringRef SymbolName) {
590   // Remove any '_' or '@' prefix.
591   char Front = SymbolName.empty() ? '\0' : SymbolName[0];
592   if (Front == '_' || Front == '@')
593     SymbolName = SymbolName.drop_front();
594 
595   // Remove any '@[0-9]+' suffix.
596   if (Front != '?') {
597     size_t AtPos = SymbolName.rfind('@');
598     if (AtPos != StringRef::npos &&
599         std::all_of(SymbolName.begin() + AtPos + 1, SymbolName.end(),
600                     [](char C) { return C >= '0' && C <= '9'; })) {
601       SymbolName = SymbolName.substr(0, AtPos);
602     }
603   }
604 
605   // Remove any ending '@' for vectorcall.
606   if (SymbolName.endswith("@"))
607     SymbolName = SymbolName.drop_back();
608 
609   return SymbolName;
610 }
611 
612 } // end anonymous namespace
613 
614 std::string
615 LLVMSymbolizer::DemangleName(const std::string &Name,
616                              const SymbolizableModule *DbiModuleDescriptor) {
617   // We can spoil names of symbols with C linkage, so use an heuristic
618   // approach to check if the name should be demangled.
619   if (Name.substr(0, 2) == "_Z") {
620     int status = 0;
621     char *DemangledName = itaniumDemangle(Name.c_str(), nullptr, nullptr, &status);
622     if (status != 0)
623       return Name;
624     std::string Result = DemangledName;
625     free(DemangledName);
626     return Result;
627   }
628 
629   if (!Name.empty() && Name.front() == '?') {
630     // Only do MSVC C++ demangling on symbols starting with '?'.
631     int status = 0;
632     char *DemangledName = microsoftDemangle(
633         Name.c_str(), nullptr, nullptr, nullptr, &status,
634         MSDemangleFlags(MSDF_NoAccessSpecifier | MSDF_NoCallingConvention |
635                         MSDF_NoMemberType | MSDF_NoReturnType));
636     if (status != 0)
637       return Name;
638     std::string Result = DemangledName;
639     free(DemangledName);
640     return Result;
641   }
642 
643   if (DbiModuleDescriptor && DbiModuleDescriptor->isWin32Module())
644     return std::string(demanglePE32ExternCFunc(Name));
645   return Name;
646 }
647 
648 } // namespace symbolize
649 } // namespace llvm
650