2 files changed, 107 insertions, 2 deletions

diff --git a/llvm/lib/DebugInfo/Symbolize/DIPrinter.cpp b/llvm/lib/DebugInfo/Symbolize/DIPrinter.cpp
index b1a80cbc4580..2f3a2500c293 100644
--- a/llvm/lib/DebugInfo/Symbolize/DIPrinter.cpp
+++ b/llvm/lib/DebugInfo/Symbolize/DIPrinter.cpp
@@ -118,21 +118,32 @@ DIPrinter &DIPrinter::operator<<(const DIGlobal &Global) {
 }
 
 DIPrinter &DIPrinter::operator<<(const DILocal &Local) {
-  OS << Local.FunctionName << '\n';
-  OS << Local.Name << '\n';
+  if (Local.FunctionName.empty())
+    OS << "??\n";
+  else
+    OS << Local.FunctionName << '\n';
+
+  if (Local.Name.empty())
+    OS << "??\n";
+  else
+    OS << Local.Name << '\n';
+
   if (Local.DeclFile.empty())
     OS << "??";
   else
     OS << Local.DeclFile;
   OS << ':' << Local.DeclLine << '\n';
+
   if (Local.FrameOffset)
     OS << *Local.FrameOffset << ' ';
   else
     OS << "?? ";
+
   if (Local.Size)
     OS << *Local.Size << ' ';
   else
     OS << "?? ";
+
   if (Local.TagOffset)
     OS << *Local.TagOffset << '\n';
   else
diff --git a/llvm/lib/DebugInfo/Symbolize/Symbolize.cpp b/llvm/lib/DebugInfo/Symbolize/Symbolize.cpp
index be79d9e637c1..35e3ead6317b 100644
--- a/llvm/lib/DebugInfo/Symbolize/Symbolize.cpp
+++ b/llvm/lib/DebugInfo/Symbolize/Symbolize.cpp
@@ -284,6 +284,79 @@ bool darwinDsymMatchesBinary(const MachOObjectFile *DbgObj,
   return !memcmp(dbg_uuid.data(), bin_uuid.data(), dbg_uuid.size());
 }
 
+template <typename ELFT>
+Optional<ArrayRef<uint8_t>> getBuildID(const ELFFile<ELFT> *Obj) {
+  if (!Obj)
+    return {};
+  auto PhdrsOrErr = Obj->program_headers();
+  if (!PhdrsOrErr) {
+    consumeError(PhdrsOrErr.takeError());
+    return {};
+  }
+  for (const auto &P : *PhdrsOrErr) {
+    if (P.p_type != ELF::PT_NOTE)
+      continue;
+    Error Err = Error::success();
+    for (auto N : Obj->notes(P, Err))
+      if (N.getType() == ELF::NT_GNU_BUILD_ID && N.getName() == ELF::ELF_NOTE_GNU)
+        return N.getDesc();
+  }
+  return {};
+}
+
+Optional<ArrayRef<uint8_t>> getBuildID(const ELFObjectFileBase *Obj) {
+  Optional<ArrayRef<uint8_t>> BuildID;
+  if (auto *O = dyn_cast<ELFObjectFile<ELF32LE>>(Obj))
+    BuildID = getBuildID(O->getELFFile());
+  else if (auto *O = dyn_cast<ELFObjectFile<ELF32BE>>(Obj))
+    BuildID = getBuildID(O->getELFFile());
+  else if (auto *O = dyn_cast<ELFObjectFile<ELF64LE>>(Obj))
+    BuildID = getBuildID(O->getELFFile());
+  else if (auto *O = dyn_cast<ELFObjectFile<ELF64BE>>(Obj))
+    BuildID = getBuildID(O->getELFFile());
+  else
+    llvm_unreachable("unsupported file format");
+  return BuildID;
+}
+
+bool findDebugBinary(const std::vector<std::string> &DebugFileDirectory,
+                     const ArrayRef<uint8_t> BuildID,
+                     std::string &Result) {
+  auto getDebugPath = [&](StringRef Directory) {
+    SmallString<128> Path{Directory};
+    sys::path::append(Path, ".build-id",
+                      llvm::toHex(BuildID[0], /*LowerCase=*/true),
+                      llvm::toHex(BuildID.slice(1), /*LowerCase=*/true));
+    Path += ".debug";
+    return Path;
+  };
+  if (DebugFileDirectory.empty()) {
+    SmallString<128> Path = getDebugPath(
+#if defined(__NetBSD__)
+      // Try /usr/libdata/debug/.build-id/../...
+      "/usr/libdata/debug"
+#else
+      // Try /usr/lib/debug/.build-id/../...
+      "/usr/lib/debug"
+#endif
+    );
+    if (llvm::sys::fs::exists(Path)) {
+      Result = Path.str();
+      return true;
+    }
+  } else {
+    for (const auto &Directory : DebugFileDirectory) {
+      // Try <debug-file-directory>/.build-id/../...
+      SmallString<128> Path = getDebugPath(Directory);
+      if (llvm::sys::fs::exists(Path)) {
+        Result = Path.str();
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
 } // end anonymous namespace
 
 ObjectFile *LLVMSymbolizer::lookUpDsymFile(const std::string &ExePath,
@@ -335,6 +408,25 @@ ObjectFile *LLVMSymbolizer::lookUpDebuglinkObject(const std::string &Path,
   return DbgObjOrErr.get();
 }
 
+ObjectFile *LLVMSymbolizer::lookUpBuildIDObject(const std::string &Path,
+                                                const ELFObjectFileBase *Obj,
+                                                const std::string &ArchName) {
+  auto BuildID = getBuildID(Obj);
+  if (!BuildID)
+    return nullptr;
+  if (BuildID->size() < 2)
+    return nullptr;
+  std::string DebugBinaryPath;
+  if (!findDebugBinary(Opts.DebugFileDirectory, *BuildID, DebugBinaryPath))
+    return nullptr;
+  auto DbgObjOrErr = getOrCreateObject(DebugBinaryPath, ArchName);
+  if (!DbgObjOrErr) {
+    consumeError(DbgObjOrErr.takeError());
+    return nullptr;
+  }
+  return DbgObjOrErr.get();
+}
+
 Expected<LLVMSymbolizer::ObjectPair>
 LLVMSymbolizer::getOrCreateObjectPair(const std::string &Path,
                                       const std::string &ArchName) {
@@ -355,6 +447,8 @@ LLVMSymbolizer::getOrCreateObjectPair(const std::string &Path,
 
   if (auto MachObj = dyn_cast<const MachOObjectFile>(Obj))
     DbgObj = lookUpDsymFile(Path, MachObj, ArchName);
+  else if (auto ELFObj = dyn_cast<const ELFObjectFileBase>(Obj))
+    DbgObj = lookUpBuildIDObject(Path, ELFObj, ArchName);
   if (!DbgObj)
     DbgObj = lookUpDebuglinkObject(Path, Obj, ArchName);
   if (!DbgObj)