[Object] Move llvm-nm's symbol version utility to ELFObjectFile::readDynsymVersions

[MaskRay]

Summary

The utility can be reused by llvm-objdump -T.

[jhenderson]

I've not looked too carefully to make sure the moved code is essentially the same before and after. I assume it is, and if so, LGTM. If not, please point out anything that's changed.

[MaskRay]

SymbolVersion has been replaced by VersionEntry defined in include/llvm/Object.

if (!VerSec)
  return std::vector<VersionEntry>();

has been added so that llvm-objdump can know whether the version sections exist or not. llvm-nm code already does if (!SymbolVersions.empty() ... so llvm-nm doesn't need a change.

[jhenderson]

Thanks. Sounds good.

llvm/include/llvm/Object/ELFObjectFile.h

public:
   void setARMSubArch(Triple &TheTriple) const override;
 
   virtual uint16_t getEType() const = 0;
 
   virtual uint16_t getEMachine() const = 0;
 
   std::vector<std::pair<Optional<DataRefImpl>, uint64_t>>
   getPltAddresses() const;
+
+  /// Returns a vector containing a symbol version for each dynamic symbol.
+  /// Returns an empty vector if version sections do not exist.
+  Expected<std::vector<VersionEntry>> readDynsymVersions() const;
 };
 
 class ELFSectionRef : public SectionRef {
 public:
   ELFSectionRef(const SectionRef &B) : SectionRef(B) {
     assert(isa<ELFObjectFileBase>(SectionRef::getObject()));
   }
 

llvm/lib/Object/ELFObjectFile.cpp

if (PltEntryIter != GotToPlt.end()) {
       if (Sym == symbol_end())
         Result.emplace_back(None, PltEntryIter->second);
       else
         Result.emplace_back(Sym->getRawDataRefImpl(), PltEntryIter->second);
     }
   }
   return Result;
 }
+
+template <class ELFT>
+static Expected<std::vector<VersionEntry>>
+readDynsymVersionsImpl(const ELFFile<ELFT> &EF,
+                       ELFObjectFileBase::elf_symbol_iterator_range Symbols) {
+  using Elf_Shdr = typename ELFT::Shdr;
+  const Elf_Shdr *VerSec = nullptr;
+  const Elf_Shdr *VerNeedSec = nullptr;
+  const Elf_Shdr *VerDefSec = nullptr;
+  // The user should ensure sections() can't fail here.
+  for (const Elf_Shdr &Sec : cantFail(EF.sections())) {
+    if (Sec.sh_type == ELF::SHT_GNU_versym)
+      VerSec = &Sec;
+    else if (Sec.sh_type == ELF::SHT_GNU_verdef)
+      VerDefSec = &Sec;
+    else if (Sec.sh_type == ELF::SHT_GNU_verneed)
+      VerNeedSec = &Sec;
+  }
+  if (!VerSec)
+    return std::vector<VersionEntry>();
+
+  Expected<SmallVector<Optional<VersionEntry>, 0>> MapOrErr =
+      EF.loadVersionMap(VerNeedSec, VerDefSec);
+  if (!MapOrErr)
+    return MapOrErr.takeError();
+
+  std::vector<VersionEntry> Ret;
+  size_t I = 0;
+  for (auto It = Symbols.begin(), E = Symbols.end(); It != E; ++It) {
+    ++I;
+    Expected<const typename ELFT::Versym *> VerEntryOrErr =
+        EF.template getEntry<typename ELFT::Versym>(*VerSec, I);
+    if (!VerEntryOrErr)
+      return createError("unable to read an entry with index " + Twine(I) +
+                         " from " + describe(EF, *VerSec) + ": " +
+                         toString(VerEntryOrErr.takeError()));
+
+    Expected<uint32_t> FlagsOrErr = It->getFlags();
+    if (!FlagsOrErr)
+      return createError("unable to read flags for symbol with index " +
+                         Twine(I) + ": " + toString(FlagsOrErr.takeError()));
+
+    bool IsDefault;
+    Expected<StringRef> VerOrErr = EF.getSymbolVersionByIndex(
+        (*VerEntryOrErr)->vs_index, IsDefault, *MapOrErr,
+        (*FlagsOrErr) & SymbolRef::SF_Undefined);
+    if (!VerOrErr)
+      return createError("unable to get a version for entry " + Twine(I) +
+                         " of " + describe(EF, *VerSec) + ": " +
+                         toString(VerOrErr.takeError()));
+
+    Ret.push_back({(*VerOrErr).str(), IsDefault});
+  }
+
+  return Ret;
+}
+
+Expected<std::vector<VersionEntry>>
+ELFObjectFileBase::readDynsymVersions() const {
+  elf_symbol_iterator_range Symbols = getDynamicSymbolIterators();
+  if (const auto *Obj = dyn_cast<ELF32LEObjectFile>(this))
+    return readDynsymVersionsImpl(Obj->getELFFile(), Symbols);
+  if (const auto *Obj = dyn_cast<ELF32BEObjectFile>(this))
+    return readDynsymVersionsImpl(Obj->getELFFile(), Symbols);
+  if (const auto *Obj = dyn_cast<ELF64LEObjectFile>(this))
+    return readDynsymVersionsImpl(Obj->getELFFile(), Symbols);
+  return readDynsymVersionsImpl(cast<ELF64BEObjectFile>(this)->getELFFile(),
+                                Symbols);
+}

llvm/tools/llvm-nm/llvm-nm.cpp

if (FunctionStartsAdded) {
           Q += strlen(Q) + 1;
         }
         I++;
       }
     }
   }
 }
 
-namespace {
-struct SymbolVersion {
-  std::string Name;
-  bool IsDefault;
-};
-} // namespace
-
-template <class ELFT>
-static Expected<std::vector<SymbolVersion>>
-readSymbolVersionsELF(const ELFFile<ELFT> &Obj, StringRef FileName,
-                      ELFObjectFileBase::elf_symbol_iterator_range Symbols) {
-  using Elf_Shdr = typename ELFT::Shdr;
-
-  // We called sections() earlier, so can't fail here.
-  typename ELFT::ShdrRange SectionsOrErr = cantFail(Obj.sections());
-  const Elf_Shdr *SymVerSec = nullptr;
-  const Elf_Shdr *SymVerNeedSec = nullptr;
-  const Elf_Shdr *SymVerDefSec = nullptr;
-  for (const Elf_Shdr &Sec : SectionsOrErr) {
-    if (Sec.sh_type == ELF::SHT_GNU_versym)
-      SymVerSec = &Sec;
-    else if (Sec.sh_type == ELF::SHT_GNU_verdef)
-      SymVerDefSec = &Sec;
-    else if (Sec.sh_type == ELF::SHT_GNU_verneed)
-      SymVerNeedSec = &Sec;
-  }
-
-  if (!SymVerSec)
-    return std::vector<SymbolVersion>{};
-
-  Expected<SmallVector<Optional<VersionEntry>, 0>> MapOrErr =
-      Obj.loadVersionMap(SymVerNeedSec, SymVerDefSec);
-  if (!MapOrErr)
-    return MapOrErr.takeError();
-
-  std::vector<SymbolVersion> Ret;
-  size_t I = 0;
-  for (auto It = Symbols.begin(), E = Symbols.end(); It != E; ++It) {
-    ++I;
-    Expected<const typename ELFT::Versym *> VerEntryOrErr =
-        Obj.template getEntry<typename ELFT::Versym>(*SymVerSec, I);
-    if (!VerEntryOrErr)
-      return createError("unable to read an entry with index " + Twine(I) +
-                         " from " + describe(Obj, *SymVerSec) + ": " +
-                         toString(VerEntryOrErr.takeError()));
-
-    Expected<uint32_t> FlagsOrErr = It->getFlags();
-    if (!FlagsOrErr)
-      return createError("unable to read flags for symbol with index " +
-                         Twine(I) + ": " + toString(FlagsOrErr.takeError()));
-
-    bool IsDefault;
-    Expected<StringRef> VerOrErr = Obj.getSymbolVersionByIndex(
-        (*VerEntryOrErr)->vs_index, IsDefault, *MapOrErr,
-        (*FlagsOrErr) & SymbolRef::SF_Undefined);
-    if (!VerOrErr)
-      return createError("unable to get a version for entry " + Twine(I) +
-                         " of " + describe(Obj, *SymVerSec) + ": " +
-                         toString(VerOrErr.takeError()));
-
-    Ret.push_back({(*VerOrErr).str(), IsDefault});
-  }
-
-  return Ret;
-}
-
-static Expected<std::vector<SymbolVersion>>
-readSymbolVersionsELF(const ELFObjectFileBase &Obj,
-                      ELFObjectFileBase::elf_symbol_iterator_range Symbols) {
-  if (const auto *ELF = dyn_cast<ELF32LEObjectFile>(&Obj))
-    return readSymbolVersionsELF(ELF->getELFFile(), Obj.getFileName(), Symbols);
-  else if (const auto *ELF = dyn_cast<ELF32BEObjectFile>(&Obj))
-    return readSymbolVersionsELF(ELF->getELFFile(), Obj.getFileName(), Symbols);
-  else if (const auto *ELF = dyn_cast<ELF64LEObjectFile>(&Obj))
-    return readSymbolVersionsELF(ELF->getELFFile(), Obj.getFileName(), Symbols);
-  return readSymbolVersionsELF(cast<ELF64BEObjectFile>(&Obj)->getELFFile(),
-                               Obj.getFileName(), Symbols);
-}
-
 static void dumpSymbolNamesFromObject(SymbolicFile &Obj, bool printName,
                                       StringRef ArchiveName = {},
                                       StringRef ArchitectureName = {}) {
   auto Symbols = Obj.symbols();
-  std::vector<SymbolVersion> SymbolVersions;
+  std::vector<VersionEntry> SymbolVersions;
   if (DynamicSyms) {
     const auto *E = dyn_cast<ELFObjectFileBase>(&Obj);
     if (!E) {
       error("File format has no dynamic symbol table", Obj.getFileName());
       return;
     }
     Symbols = E->getDynamicSymbolIterators();
 
-    if (Expected<std::vector<SymbolVersion>> VersionsOrErr =
-            readSymbolVersionsELF(*E, Symbols))
+    if (Expected<std::vector<VersionEntry>> VersionsOrErr =
+            E->readDynsymVersions())
       SymbolVersions = std::move(*VersionsOrErr);
     else
       WithColor::warning(errs(), ToolName)
           << "unable to read symbol versions: "
           << toString(VersionsOrErr.takeError()) << "\n";
   }
 
   // If a "-s segname sectname" option was specified and this is a Mach-O
for (BasicSymbolRef Sym : Symbols) {
         if (MachO) {
           OS << "bad string index";
           consumeError(std::move(E));
         } else
           error(std::move(E), Obj.getFileName());
       }
       if (!SymbolVersions.empty() && !SymbolVersions[I].Name.empty())
         S.Name +=
-            (SymbolVersions[I].IsDefault ? "@@" : "@") + SymbolVersions[I].Name;
+            (SymbolVersions[I].IsVerDef ? "@@" : "@") + SymbolVersions[I].Name;
 
       S.Sym = Sym;
       SymbolList.push_back(S);
     }
   }
 
   // If this is a Mach-O file where the nlist symbol table is out of sync
   // with the dyld export trie then look through exports and fake up symbols