Support reading GNU symbol versions in ELFObjectFile

* Add enums and structures for GNU version information.
* Implement extraction of that information on a per-symbol basis (ELFObjectFile::getSymbolVersion).
* Implement a generic interface, GetELFSymbolVersion(), for getting the symbol version from the ObjectFile (hides the templating).
* Have llvm-readobj print out the version, when available.
* Add a test for the new feature: readobj-elf-versioning.test



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@152436 91177308-0d34-0410-b5e6-96231b3b80d8

8 files changed, 470 insertions, 19 deletions

diff --git a/include/llvm/Object/ELF.h b/include/llvm/Object/ELF.h
index e27a23edeb..d33f317c6b 100644
--- a/include/llvm/Object/ELF.h
+++ b/include/llvm/Object/ELF.h
@@ -18,6 +18,7 @@
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/PointerIntPair.h"
 #include "llvm/Object/ObjectFile.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/ELF.h"
@@ -176,7 +177,72 @@ struct Elf_Sym_Impl : Elf_Sym_Base<target_endianness, is64Bits> {
   }
 };
 
-// Elf_Dyn: Entry in the dynamic table
+/// Elf_Versym: This is the structure of entries in the SHT_GNU_versym section
+/// (.gnu.version). This structure is identical for ELF32 and ELF64.
+template<support::endianness target_endianness, bool is64Bits>
+struct Elf_Versym_Impl {
+  LLVM_ELF_IMPORT_TYPES(target_endianness, is64Bits)
+  Elf_Half vs_index;   // Version index with flags (e.g. VERSYM_HIDDEN)
+};
+
+template<support::endianness target_endianness, bool is64Bits>
+struct Elf_Verdaux_Impl;
+
+/// Elf_Verdef: This is the structure of entries in the SHT_GNU_verdef section
+/// (.gnu.version_d). This structure is identical for ELF32 and ELF64.
+template<support::endianness target_endianness, bool is64Bits>
+struct Elf_Verdef_Impl {
+  LLVM_ELF_IMPORT_TYPES(target_endianness, is64Bits)
+  typedef Elf_Verdaux_Impl<target_endianness, is64Bits> Elf_Verdaux;
+  Elf_Half vd_version; // Version of this structure (e.g. VER_DEF_CURRENT)
+  Elf_Half vd_flags;   // Bitwise flags (VER_DEF_*)
+  Elf_Half vd_ndx;     // Version index, used in .gnu.version entries
+  Elf_Half vd_cnt;     // Number of Verdaux entries
+  Elf_Word vd_hash;    // Hash of name
+  Elf_Word vd_aux;     // Offset to the first Verdaux entry (in bytes)
+  Elf_Word vd_next;    // Offset to the next Verdef entry (in bytes)
+
+  /// Get the first Verdaux entry for this Verdef.
+  const Elf_Verdaux *getAux() const {
+    return reinterpret_cast<const Elf_Verdaux*>((const char*)this + vd_aux);
+  }
+};
+
+/// Elf_Verdaux: This is the structure of auxilary data in the SHT_GNU_verdef
+/// section (.gnu.version_d). This structure is identical for ELF32 and ELF64.
+template<support::endianness target_endianness, bool is64Bits>
+struct Elf_Verdaux_Impl {
+  LLVM_ELF_IMPORT_TYPES(target_endianness, is64Bits)
+  Elf_Word vda_name; // Version name (offset in string table)
+  Elf_Word vda_next; // Offset to next Verdaux entry (in bytes)
+};
+
+/// Elf_Verneed: This is the structure of entries in the SHT_GNU_verneed
+/// section (.gnu.version_r). This structure is identical for ELF32 and ELF64.
+template<support::endianness target_endianness, bool is64Bits>
+struct Elf_Verneed_Impl {
+  LLVM_ELF_IMPORT_TYPES(target_endianness, is64Bits)
+  Elf_Half vn_version; // Version of this structure (e.g. VER_NEED_CURRENT)
+  Elf_Half vn_cnt;     // Number of associated Vernaux entries
+  Elf_Word vn_file;    // Library name (string table offset)
+  Elf_Word vn_aux;     // Offset to first Vernaux entry (in bytes)
+  Elf_Word vn_next;    // Offset to next Verneed entry (in bytes)
+};
+
+/// Elf_Vernaux: This is the structure of auxiliary data in SHT_GNU_verneed
+/// section (.gnu.version_r). This structure is identical for ELF32 and ELF64.
+template<support::endianness target_endianness, bool is64Bits>
+struct Elf_Vernaux_Impl {
+  LLVM_ELF_IMPORT_TYPES(target_endianness, is64Bits)
+  Elf_Word vna_hash;  // Hash of dependency name
+  Elf_Half vna_flags; // Bitwise Flags (VER_FLAG_*)
+  Elf_Half vna_other; // Version index, used in .gnu.version entries
+  Elf_Word vna_name;  // Dependency name
+  Elf_Word vna_next;  // Offset to next Vernaux entry (in bytes)
+};
+
+/// Elf_Dyn_Base: This structure matches the form of entries in the dynamic
+///               table section (.dynamic) look like.
 template<support::endianness target_endianness, bool is64Bits>
 struct Elf_Dyn_Base;
 
@@ -200,6 +266,7 @@ struct Elf_Dyn_Base<target_endianness, true> {
   } d_un;
 };
 
+/// Elf_Dyn_Impl: This inherits from Elf_Dyn_Base, adding getters and setters.
 template<support::endianness target_endianness, bool is64Bits>
 struct Elf_Dyn_Impl : Elf_Dyn_Base<target_endianness, is64Bits> {
   using Elf_Dyn_Base<target_endianness, is64Bits>::d_tag;
@@ -323,6 +390,11 @@ class ELFObjectFile : public ObjectFile {
   typedef Elf_Dyn_Impl<target_endianness, is64Bits> Elf_Dyn;
   typedef Elf_Rel_Impl<target_endianness, is64Bits, false> Elf_Rel;
   typedef Elf_Rel_Impl<target_endianness, is64Bits, true> Elf_Rela;
+  typedef Elf_Verdef_Impl<target_endianness, is64Bits> Elf_Verdef;
+  typedef Elf_Verdaux_Impl<target_endianness, is64Bits> Elf_Verdaux;
+  typedef Elf_Verneed_Impl<target_endianness, is64Bits> Elf_Verneed;
+  typedef Elf_Vernaux_Impl<target_endianness, is64Bits> Elf_Vernaux;
+  typedef Elf_Versym_Impl<target_endianness, is64Bits> Elf_Versym;
   typedef DynRefImpl<target_endianness, is64Bits> DynRef;
   typedef content_iterator<DynRef> dyn_iterator;
 
@@ -364,15 +436,48 @@ private:
   const Elf_Shdr *dot_shstrtab_sec; // Section header string table.
   const Elf_Shdr *dot_strtab_sec;   // Symbol header string table.
   const Elf_Shdr *dot_dynstr_sec;   // Dynamic symbol string table.
+
+  // SymbolTableSections[0] always points to the dynamic string table section
+  // header, or NULL if there is no dynamic string table.
   Sections_t SymbolTableSections;
   IndexMap_t SymbolTableSectionsIndexMap;
   DenseMap<const Elf_Sym*, ELF::Elf64_Word> ExtendedSymbolTable;
 
-  const Elf_Shdr *dot_dynamic_sec; // .dynamic
+  const Elf_Shdr *dot_dynamic_sec;       // .dynamic
+  const Elf_Shdr *dot_gnu_version_sec;   // .gnu.version
+  const Elf_Shdr *dot_gnu_version_r_sec; // .gnu.version_r
+  const Elf_Shdr *dot_gnu_version_d_sec; // .gnu.version_d
+
   // Pointer to SONAME entry in dynamic string table
   // This is set the first time getLoadName is called.
   mutable const char *dt_soname;
 
+  // Records for each version index the corresponding Verdef or Vernaux entry.
+  // This is filled the first time LoadVersionMap() is called.
+  class VersionMapEntry : public PointerIntPair<const void*, 1> {
+    public:
+    // If the integer is 0, this is an Elf_Verdef*.
+    // If the integer is 1, this is an Elf_Vernaux*.
+    VersionMapEntry() : PointerIntPair<const void*, 1>(NULL, 0) { }
+    VersionMapEntry(const Elf_Verdef *verdef)
+        : PointerIntPair<const void*, 1>(verdef, 0) { }
+    VersionMapEntry(const Elf_Vernaux *vernaux)
+        : PointerIntPair<const void*, 1>(vernaux, 1) { }
+    bool isNull() const { return getPointer() == NULL; }
+    bool isVerdef() const { return !isNull() && getInt() == 0; }
+    bool isVernaux() const { return !isNull() && getInt() == 1; }
+    const Elf_Verdef *getVerdef() const {
+      return isVerdef() ? (const Elf_Verdef*)getPointer() : NULL;
+    }
+    const Elf_Vernaux *getVernaux() const {
+      return isVernaux() ? (const Elf_Vernaux*)getPointer() : NULL;
+    }
+  };
+  mutable SmallVector<VersionMapEntry, 16> VersionMap;
+  void LoadVersionDefs(const Elf_Shdr *sec) const;
+  void LoadVersionNeeds(const Elf_Shdr *ec) const;
+  void LoadVersionMap() const;
+
   /// @brief Map sections to an array of relocation sections that reference
   ///        them sorted by section index.
   RelocMap_t SectionRelocMap;
@@ -396,6 +501,10 @@ private:
   error_code      getSymbolName(const Elf_Shdr *section,
                                 const Elf_Sym *Symb,
                                 StringRef &Res) const;
+  error_code      getSymbolVersion(const Elf_Shdr *section,
+                                   const Elf_Sym *Symb,
+                                   StringRef &Version,
+                                   bool &IsDefault) const;
   void VerifyStrTab(const Elf_Shdr *sh) const;
 
 protected:
@@ -404,7 +513,8 @@ protected:
 
 public:
   const Elf_Dyn  *getDyn(DataRefImpl DynData) const;
-
+  error_code getSymbolVersion(SymbolRef Symb, StringRef &Version,
+                              bool &IsDefault) const;
 protected:
   virtual error_code getSymbolNext(DataRefImpl Symb, SymbolRef &Res) const;
   virtual error_code getSymbolName(DataRefImpl Symb, StringRef &Res) const;
@@ -473,6 +583,7 @@ public:
 
   virtual uint8_t getBytesInAddress() const;
   virtual StringRef getFileFormatName() const;
+  virtual StringRef getObjectType() const { return "ELF"; }
   virtual unsigned getArch() const;
   virtual StringRef getLoadName() const;
 
@@ -490,6 +601,89 @@ public:
   static inline bool classof(const ELFObjectFile *v) { return true; }
 };
 
+// Iterate through the version definitions, and place each Elf_Verdef
+// in the VersionMap according to its index.
+template<support::endianness target_endianness, bool is64Bits>
+void ELFObjectFile<target_endianness, is64Bits>::
+                  LoadVersionDefs(const Elf_Shdr *sec) const {
+  unsigned vd_size = sec->sh_size; // Size of section in bytes
+  unsigned vd_count = sec->sh_info; // Number of Verdef entries
+  const char *sec_start = (const char*)base() + sec->sh_offset;
+  const char *sec_end = sec_start + vd_size;
+  // The first Verdef entry is at the start of the section.
+  const char *p = sec_start;
+  for (unsigned i = 0; i < vd_count; i++) {
+    if (p + sizeof(Elf_Verdef) > sec_end)
+      report_fatal_error("Section ended unexpectedly while scanning "
+                         "version definitions.");
+    const Elf_Verdef *vd = reinterpret_cast<const Elf_Verdef *>(p);
+    if (vd->vd_version != ELF::VER_DEF_CURRENT)
+      report_fatal_error("Unexpected verdef version");
+    size_t index = vd->vd_ndx & ELF::VERSYM_VERSION;
+    if (index >= VersionMap.size())
+      VersionMap.resize(index+1);
+    VersionMap[index] = VersionMapEntry(vd);
+    p += vd->vd_next;
+  }
+}
+
+// Iterate through the versions needed section, and place each Elf_Vernaux
+// in the VersionMap according to its index.
+template<support::endianness target_endianness, bool is64Bits>
+void ELFObjectFile<target_endianness, is64Bits>::
+                  LoadVersionNeeds(const Elf_Shdr *sec) const {
+  unsigned vn_size = sec->sh_size; // Size of section in bytes
+  unsigned vn_count = sec->sh_info; // Number of Verneed entries
+  const char *sec_start = (const char*)base() + sec->sh_offset;
+  const char *sec_end = sec_start + vn_size;
+  // The first Verneed entry is at the start of the section.
+  const char *p = sec_start;
+  for (unsigned i = 0; i < vn_count; i++) {
+    if (p + sizeof(Elf_Verneed) > sec_end)
+      report_fatal_error("Section ended unexpectedly while scanning "
+                         "version needed records.");
+    const Elf_Verneed *vn = reinterpret_cast<const Elf_Verneed *>(p);
+    if (vn->vn_version != ELF::VER_NEED_CURRENT)
+      report_fatal_error("Unexpected verneed version");
+    // Iterate through the Vernaux entries
+    const char *paux = p + vn->vn_aux;
+    for (unsigned j = 0; j < vn->vn_cnt; j++) {
+      if (paux + sizeof(Elf_Vernaux) > sec_end)
+        report_fatal_error("Section ended unexpected while scanning auxiliary "
+                           "version needed records.");
+      const Elf_Vernaux *vna = reinterpret_cast<const Elf_Vernaux *>(paux);
+      size_t index = vna->vna_other & ELF::VERSYM_VERSION;
+      if (index >= VersionMap.size())
+        VersionMap.resize(index+1);
+      VersionMap[index] = VersionMapEntry(vna);
+      paux += vna->vna_next;
+    }
+    p += vn->vn_next;
+  }
+}
+
+template<support::endianness target_endianness, bool is64Bits>
+void ELFObjectFile<target_endianness, is64Bits>::LoadVersionMap() const {
+  // If there is no dynamic symtab or version table, there is nothing to do.
+  if (SymbolTableSections[0] == NULL || dot_gnu_version_sec == NULL)
+    return;
+
+  // Has the VersionMap already been loaded?
+  if (VersionMap.size() > 0)
+    return;
+
+  // The first two version indexes are reserved.
+  // Index 0 is LOCAL, index 1 is GLOBAL.
+  VersionMap.push_back(VersionMapEntry());
+  VersionMap.push_back(VersionMapEntry());
+
+  if (dot_gnu_version_d_sec)
+    LoadVersionDefs(dot_gnu_version_d_sec);
+
+  if (dot_gnu_version_r_sec)
+    LoadVersionNeeds(dot_gnu_version_r_sec);
+}
+
 template<support::endianness target_endianness, bool is64Bits>
 void ELFObjectFile<target_endianness, is64Bits>
                   ::validateSymbol(DataRefImpl Symb) const {
@@ -547,6 +741,18 @@ error_code ELFObjectFile<target_endianness, is64Bits>
 }
 
 template<support::endianness target_endianness, bool is64Bits>
+error_code ELFObjectFile<target_endianness, is64Bits>
+                        ::getSymbolVersion(SymbolRef SymRef,
+                                           StringRef &Version,
+                                           bool &IsDefault) const {
+  DataRefImpl Symb = SymRef.getRawDataRefImpl();
+  validateSymbol(Symb);
+  const Elf_Sym *symb = getSymbol(Symb);
+  return getSymbolVersion(SymbolTableSections[Symb.d.b], symb,
+                          Version, IsDefault);
+}
+
+template<support::endianness target_endianness, bool is64Bits>
 ELF::Elf64_Word ELFObjectFile<target_endianness, is64Bits>
                       ::getSymbolTableIndex(const Elf_Sym *symb) const {
   if (symb->st_shndx == ELF::SHN_XINDEX)
@@ -1266,7 +1472,11 @@ ELFObjectFile<target_endianness, is64Bits>::ELFObjectFile(MemoryBuffer *Object
   , dot_strtab_sec(0)
   , dot_dynstr_sec(0)
   , dot_dynamic_sec(0)
-  , dt_soname(0) {
+  , dot_gnu_version_sec(0)
+  , dot_gnu_version_r_sec(0)
+  , dot_gnu_version_d_sec(0)
+  , dt_soname(0)
+ {
 
   const uint64_t FileSize = Data->getBufferSize();
 
@@ -1302,31 +1512,60 @@ ELFObjectFile<target_endianness, is64Bits>::ELFObjectFile(MemoryBuffer *Object
   SymbolTableSections.push_back(NULL);
 
   for (uint64_t i = 0, e = getNumSections(); i != e; ++i) {
-    if (sh->sh_type == ELF::SHT_SYMTAB_SHNDX) {
+    switch (sh->sh_type) {
+    case ELF::SHT_SYMTAB_SHNDX: {
       if (SymbolTableSectionHeaderIndex)
         // FIXME: Proper error handling.
         report_fatal_error("More than one .symtab_shndx!");
       SymbolTableSectionHeaderIndex = sh;
+      break;
     }
-    if (sh->sh_type == ELF::SHT_SYMTAB) {
+    case ELF::SHT_SYMTAB: {
       SymbolTableSectionsIndexMap[i] = SymbolTableSections.size();
       SymbolTableSections.push_back(sh);
+      break;
     }
-    if (sh->sh_type == ELF::SHT_DYNSYM) {
+    case ELF::SHT_DYNSYM: {
       if (SymbolTableSections[0] != NULL)
         // FIXME: Proper error handling.
         report_fatal_error("More than one .dynsym!");
       SymbolTableSectionsIndexMap[i] = 0;
       SymbolTableSections[0] = sh;
+      break;
     }
-    if (sh->sh_type == ELF::SHT_REL || sh->sh_type == ELF::SHT_RELA) {
+    case ELF::SHT_REL:
+    case ELF::SHT_RELA: {
       SectionRelocMap[getSection(sh->sh_info)].push_back(i);
+      break;
     }
-    if (sh->sh_type == ELF::SHT_DYNAMIC) {
+    case ELF::SHT_DYNAMIC: {
       if (dot_dynamic_sec != NULL)
         // FIXME: Proper error handling.
         report_fatal_error("More than one .dynamic!");
       dot_dynamic_sec = sh;
+      break;
+    }
+    case ELF::SHT_GNU_versym: {
+      if (dot_gnu_version_sec != NULL)
+        // FIXME: Proper error handling.
+        report_fatal_error("More than one .gnu.version section!");
+      dot_gnu_version_sec = sh;
+      break;
+    }
+    case ELF::SHT_GNU_verdef: {
+      if (dot_gnu_version_d_sec != NULL)
+        // FIXME: Proper error handling.
+        report_fatal_error("More than one .gnu.version_d section!");
+      dot_gnu_version_d_sec = sh;
+      break;
+    }
+    case ELF::SHT_GNU_verneed: {
+      if (dot_gnu_version_r_sec != NULL)
+        // FIXME: Proper error handling.
+        report_fatal_error("More than one .gnu.version_r section!");
+      dot_gnu_version_r_sec = sh;
+      break;
+    }
     }
     ++sh;
   }
@@ -1776,6 +2015,89 @@ error_code ELFObjectFile<target_endianness, is64Bits>
 }
 
 template<support::endianness target_endianness, bool is64Bits>
+error_code ELFObjectFile<target_endianness, is64Bits>
+                        ::getSymbolVersion(const Elf_Shdr *section,
+                                           const Elf_Sym *symb,
+                                           StringRef &Version,
+                                           bool &IsDefault) const {
+  // Handle non-dynamic symbols.
+  if (section != SymbolTableSections[0]) {
+    // Non-dynamic symbols can have versions in their names
+    // A name of the form 'foo@V1' indicates version 'V1', non-default.
+    // A name of the form 'foo@@V2' indicates version 'V2', default version.
+    StringRef Name;
+    error_code ec = getSymbolName(section, symb, Name);
+    if (ec != object_error::success)
+      return ec;
+    size_t atpos = Name.find('@');
+    if (atpos == StringRef::npos) {
+      Version = "";
+      IsDefault = false;
+      return object_error::success;
+    }
+    ++atpos;
+    if (atpos < Name.size() && Name[atpos] == '@') {
+      IsDefault = true;
+      ++atpos;
+    } else {
+      IsDefault = false;
+    }
+    Version = Name.substr(atpos);
+    return object_error::success;
+  }
+
+  // This is a dynamic symbol. Look in the GNU symbol version table.
+  if (dot_gnu_version_sec == NULL) {
+    // No version table.
+    Version = "";
+    IsDefault = false;
+    return object_error::success;
+  }
+
+  // Determine the position in the symbol table of this entry.
+  const char *sec_start = (const char*)base() + section->sh_offset;
+  size_t entry_index = ((const char*)symb - sec_start)/section->sh_entsize;
+
+  // Get the corresponding version index entry
+  const Elf_Versym *vs = getEntry<Elf_Versym>(dot_gnu_version_sec, entry_index);
+  size_t version_index = vs->vs_index & ELF::VERSYM_VERSION;
+
+  // Special markers for unversioned symbols.
+  if (version_index == ELF::VER_NDX_LOCAL ||
+      version_index == ELF::VER_NDX_GLOBAL) {
+    Version = "";
+    IsDefault = false;
+    return object_error::success;
+  }
+
+  // Lookup this symbol in the version table
+  LoadVersionMap();
+  if (version_index >= VersionMap.size() || VersionMap[version_index].isNull())
+    report_fatal_error("Symbol has version index without corresponding "
+                       "define or reference entry");
+  const VersionMapEntry &entry = VersionMap[version_index];
+
+  // Get the version name string
+  size_t name_offset;
+  if (entry.isVerdef()) {
+    // The first Verdaux entry holds the name.
+    name_offset = entry.getVerdef()->getAux()->vda_name;
+  } else {
+    name_offset = entry.getVernaux()->vna_name;
+  }
+  Version = getString(dot_dynstr_sec, name_offset);
+
+  // Set IsDefault
+  if (entry.isVerdef()) {
+    IsDefault = !(vs->vs_index & ELF::VERSYM_HIDDEN);
+  } else {
+    IsDefault = false;
+  }
+
+  return object_error::success;
+}
+
+template<support::endianness target_endianness, bool is64Bits>
 inline DynRefImpl<target_endianness, is64Bits>
                  ::DynRefImpl(DataRefImpl DynP, const OwningType *Owner)
   : DynPimpl(DynP)
@@ -1823,6 +2145,35 @@ inline DataRefImpl DynRefImpl<target_endianness, is64Bits>
   return DynPimpl;
 }
 
+/// This is a generic interface for retrieving GNU symbol version
+/// information from an ELFObjectFile.
+static inline error_code GetELFSymbolVersion(const ObjectFile *Obj,
+                                             const SymbolRef &Sym,
+                                             StringRef &Version,
+                                             bool &IsDefault) {
+  // Little-endian 32-bit
+  if (const ELFObjectFile<support::little, false> *ELFObj =
+          dyn_cast<ELFObjectFile<support::little, false> >(Obj))
+    return ELFObj->getSymbolVersion(Sym, Version, IsDefault);
+
+  // Big-endian 32-bit
+  if (const ELFObjectFile<support::big, false> *ELFObj =
+          dyn_cast<ELFObjectFile<support::big, false> >(Obj))
+    return ELFObj->getSymbolVersion(Sym, Version, IsDefault);
+
+  // Little-endian 64-bit
+  if (const ELFObjectFile<support::little, true> *ELFObj =
+          dyn_cast<ELFObjectFile<support::little, true> >(Obj))
+    return ELFObj->getSymbolVersion(Sym, Version, IsDefault);
+
+  // Big-endian 64-bit
+  if (const ELFObjectFile<support::big, true> *ELFObj =
+          dyn_cast<ELFObjectFile<support::big, true> >(Obj))
+    return ELFObj->getSymbolVersion(Sym, Version, IsDefault);
+
+  llvm_unreachable("Object passed to GetELFSymbolVersion() is not ELF");
+}
+
 }
 }
 
diff --git a/include/llvm/Support/ELF.h b/include/llvm/Support/ELF.h
index 6dd76ea170..052fc5135f 100644
--- a/include/llvm/Support/ELF.h
+++ b/include/llvm/Support/ELF.h
@@ -734,6 +734,9 @@ enum {
   SHT_GROUP         = 17, // Section group.
   SHT_SYMTAB_SHNDX  = 18, // Indices for SHN_XINDEX entries.
   SHT_LOOS          = 0x60000000, // Lowest operating system-specific type.
+  SHT_GNU_verdef    = 0x6ffffffd, // GNU version definitions.
+  SHT_GNU_verneed   = 0x6ffffffe, // GNU version references.
+  SHT_GNU_versym    = 0x6fffffff, // GNU symbol versions table.
   SHT_HIOS          = 0x6fffffff, // Highest operating system-specific type.
   SHT_LOPROC        = 0x70000000, // Lowest processor architecture-specific type.
   // Fixme: All this is duplicated in MCSectionELF. Why??
@@ -1102,6 +1105,33 @@ enum {
   DF_STATIC_TLS = 0x10  // Reject attempts to load dynamically.
 };
 
+// ElfXX_VerDef structure version (GNU versioning)
+enum {
+  VER_DEF_NONE    = 0,
+  VER_DEF_CURRENT = 1
+};
+
+// VerDef Flags (ElfXX_VerDef::vd_flags)
+enum {
+  VER_FLG_BASE = 0x1,
+  VER_FLG_WEAK = 0x2,
+  VER_FLG_INFO = 0x4
+};
+
+// Special constants for the version table. (SHT_GNU_versym/.gnu.version)
+enum {
+  VER_NDX_LOCAL  = 0,      // Unversioned local symbol
+  VER_NDX_GLOBAL = 1,      // Unversioned global symbol
+  VERSYM_VERSION = 0x7fff, // Version Index mask
+  VERSYM_HIDDEN  = 0x8000  // Hidden bit (non-default version)
+};
+
+// ElfXX_VerNeed structure version (GNU versioning)
+enum {
+  VER_NEED_NONE = 0,
+  VER_NEED_CURRENT = 1
+};
+
 } // end namespace ELF
 
 } // end namespace llvm
diff --git a/test/Object/Inputs/elf-versioning-test.i386 b/test/Object/Inputs/elf-versioning-test.i386
new file mode 100755
index 0000000000..c7c1eac497
--- /dev/null
+++ b/test/Object/Inputs/elf-versioning-test.i386
diff --git a/test/Object/Inputs/elf-versioning-test.x86_64 b/test/Object/Inputs/elf-versioning-test.x86_64
new file mode 100755
index 0000000000..cba79baeb4
--- /dev/null
+++ b/test/Object/Inputs/elf-versioning-test.x86_64
diff --git a/test/Object/Inputs/elfver.S b/test/Object/Inputs/elfver.S
new file mode 100644
index 0000000000..ba63279c7a
--- /dev/null
+++ b/test/Object/Inputs/elfver.S
@@ -0,0 +1,31 @@
+# Compile with:
+#   ARGS="-shared -nostdlib -Wl,--version-script=elfver.script"
+#   clang $ARGS -m32 elfver.S -lc -o elf-versioning-test.i386
+#   clang $ARGS -m64 elfver.S -lc -o elf-versioning-test.x86_64
+
+# Also, strip off non-dynamic symbols:
+#   strip elf-versioning-test.i386
+#   strip elf-versioning-test.x86_64
+
+#ifdef __i386__
+.symver _puts, puts@GLIBC_2.0
+#else
+.symver _puts, puts@GLIBC_2.2.5
+#endif
+call _puts@PLT
+
+.symver foo1, foo@VER1
+.globl foo1
+.type foo1, @function
+foo1:
+  ret
+
+.symver foo2, foo@@VER2
+.globl foo2
+.type foo2, @function
+foo2:
+  ret
+
+.globl unversioned_define
+.type unversioned_define, @function
+unversioned_define:
diff --git a/test/Object/Inputs/elfver.script b/test/Object/Inputs/elfver.script
new file mode 100644
index 0000000000..1316fcb84c
--- /dev/null
+++ b/test/Object/Inputs/elfver.script
@@ -0,0 +1,10 @@
+VER1 {
+  global:
+    foo;
+};
+
+VER2 {
+  global:
+    foo;
+} VER1;
+
diff --git a/test/Object/readobj-elf-versioning.test b/test/Object/readobj-elf-versioning.test
new file mode 100644
index 0000000000..0906f344e2
--- /dev/null
+++ b/test/Object/readobj-elf-versioning.test
@@ -0,0 +1,15 @@
+RUN: llvm-readobj %p/Inputs/elf-versioning-test.i386 \
+RUN:         | FileCheck %s -check-prefix ELF
+RUN: llvm-readobj %p/Inputs/elf-versioning-test.i386 \
+RUN:         | FileCheck %s -check-prefix ELF32
+RUN: llvm-readobj %p/Inputs/elf-versioning-test.x86_64 \
+RUN:         | FileCheck %s -check-prefix ELF
+RUN: llvm-readobj %p/Inputs/elf-versioning-test.x86_64 \
+RUN:         | FileCheck %s -check-prefix ELF64
+
+ELF: foo@@VER2          FUNC  {{[0-9a-f]+}} {{[0-9a-f]+}} {{[0-9a-f]+}} global
+ELF: foo@VER1           FUNC  {{[0-9a-f]+}} {{[0-9a-f]+}} {{[0-9a-f]+}} global
+ELF: unversioned_define FUNC  {{[0-9a-f]+}} {{[0-9a-f]+}} {{[0-9a-f]+}} global
+
+ELF32: puts@GLIBC_2.0   FUNC {{[0-9a-f]+}} {{[0-9a-f]+}} {{[0-9a-f]+}} undef,global
+ELF64: puts@GLIBC_2.2.5 FUNC {{[0-9a-f]+}} {{[0-9a-f]+}} {{[0-9a-f]+}} undef,global
diff --git a/tools/llvm-readobj/llvm-readobj.cpp b/tools/llvm-readobj/llvm-readobj.cpp
index 3f8789dc17..0c58fb3fb4 100644
--- a/tools/llvm-readobj/llvm-readobj.cpp
+++ b/tools/llvm-readobj/llvm-readobj.cpp
@@ -17,6 +17,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Object/ObjectFile.h"
+#include "llvm/Object/ELF.h"
 #include "llvm/Analysis/Verifier.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/Support/Format.h"
@@ -78,22 +79,35 @@ std::string GetFlagStr(uint32_t Flags) {
   return result;
 }
 
-void DumpSymbol(const SymbolRef &sym) {
+void DumpSymbol(const SymbolRef &Sym, const ObjectFile *obj, bool IsDynamic) {
     StringRef Name;
     SymbolRef::Type Type;
     uint32_t Flags;
     uint64_t Address;
     uint64_t Size;
     uint64_t FileOffset;
-    sym.getName(Name);
-    sym.getAddress(Address);
-    sym.getSize(Size);
-    sym.getFileOffset(FileOffset);
-    sym.getType(Type);
-    sym.getFlags(Flags);
+    Sym.getName(Name);
+    Sym.getAddress(Address);
+    Sym.getSize(Size);
+    Sym.getFileOffset(FileOffset);
+    Sym.getType(Type);
+    Sym.getFlags(Flags);
+    std::string FullName = Name;
+
+    // If this is a dynamic symbol from an ELF object, append
+    // the symbol's version to the name.
+    if (IsDynamic && obj->isELF()) {
+      StringRef Version;
+      bool IsDefault;
+      GetELFSymbolVersion(obj, Sym, Version, IsDefault);
+      if (!Version.empty()) {
+        FullName += (IsDefault ? "@@" : "@");
+        FullName += Version;
+      }
+    }
 
     // format() can't handle StringRefs
-    outs() << format("  %-32s", Name.str().c_str())
+    outs() << format("  %-32s", FullName.c_str())
            << format("  %-4s", GetTypeStr(Type))
            << format("  %16"PRIx64, Address)
            << format("  %16"PRIx64, Size)
@@ -111,7 +125,7 @@ void DumpSymbols(const ObjectFile *obj) {
   symbol_iterator it = obj->begin_symbols();
   symbol_iterator ie = obj->end_symbols();
   while (it != ie) {
-    DumpSymbol(*it);
+    DumpSymbol(*it, obj, false);
     it.increment(ec);
     if (ec)
       report_fatal_error("Symbol iteration failed");
@@ -128,7 +142,7 @@ void DumpDynamicSymbols(const ObjectFile *obj) {
   symbol_iterator it = obj->begin_dynamic_symbols();
   symbol_iterator ie = obj->end_dynamic_symbols();
   while (it != ie) {
-    DumpSymbol(*it);
+    DumpSymbol(*it, obj, true);
     it.increment(ec);
     if (ec)
       report_fatal_error("Symbol iteration failed");