ENH: Add ELF file parsing

  - Enabled when system provides elf.h
  - Introduce cmELF class to parse ELF files
  - Use in cmSystemTools::GuessLibrarySOName to really get soname

5 files changed, 718 insertions, 0 deletions

diff --git a/Source/CMakeLists.txt b/Source/CMakeLists.txt
index 987e908..39c0731 100644
--- a/Source/CMakeLists.txt
+++ b/Source/CMakeLists.txt
@@ -1,3 +1,11 @@
+# Check if we can build support for ELF parsing.
+CHECK_INCLUDE_FILE("elf.h" HAVE_ELF_H)
+IF(HAVE_ELF_H)
+  SET(CMAKE_USE_ELF_PARSER 1)
+ELSE(HAVE_ELF_H)
+  SET(CMAKE_USE_ELF_PARSER)
+ENDIF(HAVE_ELF_H)
+
 # configure the .h file
 CONFIGURE_FILE(
   "${CMake_SOURCE_DIR}/Source/cmConfigure.cmake.h.in"
@@ -75,6 +83,12 @@ IF(CMAKE_REGENERATE_YACCLEX)
   ENDIF(FLEX_EXECUTABLE)
 
 ENDIF(CMAKE_REGENERATE_YACCLEX)
+
+# Check if we can build the ELF parser.
+IF(CMAKE_USE_ELF_PARSER)
+  SET(ELF_SRCS cmELF.h cmELF.cxx)
+ENDIF(CMAKE_USE_ELF_PARSER)
+
 #
 # Sources for CMakeLib
 #
@@ -123,6 +137,7 @@ SET(SRCS
   cmDocumentVariables.cxx
   cmDynamicLoader.cxx
   cmDynamicLoader.h
+  ${ELF_SRCS}
   cmExprLexer.cxx
   cmExprParser.cxx
   cmExprParserHelper.cxx
diff --git a/Source/cmConfigure.cmake.h.in b/Source/cmConfigure.cmake.h.in
index dd03627..ba4a6c9 100644
--- a/Source/cmConfigure.cmake.h.in
+++ b/Source/cmConfigure.cmake.h.in
@@ -20,6 +20,7 @@
 #cmakedefine CMAKE_NO_ANSI_FOR_SCOPE
 #cmakedefine HAVE_ENVIRON_NOT_REQUIRE_PROTOTYPE
 #cmakedefine HAVE_UNSETENV
+#cmakedefine CMAKE_USE_ELF_PARSER
 #cmakedefine CMAKE_STRICT
 #define  CMAKE_ROOT_DIR "${CMake_SOURCE_DIR}"
 #define  CMAKE_BUILD_DIR "${CMake_BINARY_DIR}"
diff --git a/Source/cmELF.cxx b/Source/cmELF.cxx
new file mode 100644
index 0000000..36ac61f
--- /dev/null
+++ b/Source/cmELF.cxx
@@ -0,0 +1,612 @@
+/*=========================================================================
+
+  Program:   CMake - Cross-Platform Makefile Generator
+  Module:    $RCSfile$
+  Language:  C++
+  Date:      $Date$
+  Version:   $Revision$
+
+  Copyright (c) 2002 Kitware, Inc., Insight Consortium.  All rights reserved.
+  See Copyright.txt or http://www.cmake.org/HTML/Copyright.html for details.
+
+     This software is distributed WITHOUT ANY WARRANTY; without even
+     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+     PURPOSE.  See the above copyright notices for more information.
+
+=========================================================================*/
+#include "cmStandardIncludes.h" // to get CMAKE_USE_ELF_PARSER first
+#include "cmELF.h"
+
+#include <cmsys/auto_ptr.hxx>
+
+// Need the native byte order of the running CPU.
+#include <cmsys/CPU.h>
+
+// Include the ELF format information system header.
+#include <elf.h>
+
+//----------------------------------------------------------------------------
+// Low-level byte swapping implementation.
+template <size_t s> struct cmELFByteSwapSize {};
+void cmELFByteSwap(char*, cmELFByteSwapSize<1> const&)
+{
+}
+void cmELFByteSwap(char* data, cmELFByteSwapSize<2> const&)
+{
+  char one_byte;
+  one_byte = data[0]; data[0] = data[1]; data[1] = one_byte;
+}
+void cmELFByteSwap(char* data, cmELFByteSwapSize<4> const&)
+{
+  char one_byte;
+  one_byte = data[0]; data[0] = data[3]; data[3] = one_byte;
+  one_byte = data[1]; data[1] = data[2]; data[2] = one_byte;
+}
+void cmELFByteSwap(char* data, cmELFByteSwapSize<8> const&)
+{
+  char one_byte;
+  one_byte = data[0]; data[0] = data[7]; data[7] = one_byte;
+  one_byte = data[1]; data[1] = data[6]; data[6] = one_byte;
+  one_byte = data[2]; data[2] = data[5]; data[5] = one_byte;
+  one_byte = data[3]; data[3] = data[4]; data[4] = one_byte;
+}
+
+// Low-level byte swapping interface.
+template <typename T>
+void cmELFByteSwap(T& x)
+{
+  cmELFByteSwap(reinterpret_cast<char*>(&x), cmELFByteSwapSize<sizeof(T)>());
+}
+
+//----------------------------------------------------------------------------
+class cmELFInternal
+{
+public:
+  enum ByteOrderType { ByteOrderMSB, ByteOrderLSB };
+
+  // Construct and take ownership of the file stream object.
+  cmELFInternal(cmELF* external,
+                cmsys::auto_ptr<std::ifstream>& fin,
+                ByteOrderType order):
+    External(external),
+    Stream(*fin.release()),
+    ByteOrder(order),
+    ELFType(cmELF::FileTypeInvalid)
+    {
+    // Decide whether we need to byte swap fields.
+#if cmsys_CPU_ENDIAN_ID == cmsys_CPU_ENDIAN_ID_LITTLE
+    this->NeedSwap = (this->ByteOrder == ByteOrderMSB);
+#elif cmsys_CPU_ENDIAN_ID == cmsys_CPU_ENDIAN_ID_BIG
+    this->NeedSwap = (this->ByteOrder == ByteOrderLSB);
+#endif
+
+    // We have not yet loaded the section info.
+    this->DynamicSectionIndex = -1;
+    }
+
+  // Destruct and delete the file stream object.
+  ~cmELFInternal()
+    {
+    delete &this->Stream;
+    }
+
+  // Forward to the per-class implementation.
+  virtual unsigned int GetNumberOfSections() const = 0;
+  virtual bool GetSOName(std::string& soname) = 0;
+  virtual void PrintInfo(std::ostream& os) const = 0;
+
+  // Return the recorded ELF type.
+  cmELF::FileType GetFileType() const { return this->ELFType; }
+protected:
+  // Data common to all ELF class implementations.
+
+  // The external cmELF object.
+  cmELF* External;
+
+  // The stream from which to read.
+  std::istream& Stream;
+
+  // The byte order of the ELF file.
+  ByteOrderType ByteOrder;
+
+  // The ELF file type.
+  cmELF::FileType ELFType;
+
+  // Whether we need to byte-swap structures read from the stream.
+  bool NeedSwap;
+
+  // The section header index of the DYNAMIC section (-1 if none).
+  int DynamicSectionIndex;
+
+  // Helper methods for subclasses.
+  void SetErrorMessage(const char* msg)
+    {
+    this->External->ErrorMessage = msg;
+    this->ELFType = cmELF::FileTypeInvalid;
+    }
+};
+
+//----------------------------------------------------------------------------
+// Configure the implementation template for 32-bit ELF files.
+struct cmELFTypes32
+{
+  typedef Elf32_Ehdr ELF_Ehdr;
+  typedef Elf32_Shdr ELF_Shdr;
+  typedef Elf32_Dyn  ELF_Dyn;
+  typedef Elf32_Half ELF_Half;
+  static const char* GetName() { return "32-bit"; }
+};
+
+// Configure the implementation template for 32-bit ELF files.
+struct cmELFTypes64
+{
+  typedef Elf64_Ehdr ELF_Ehdr;
+  typedef Elf64_Shdr ELF_Shdr;
+  typedef Elf64_Dyn  ELF_Dyn;
+  typedef Elf64_Half ELF_Half;
+  static const char* GetName() { return "64-bit"; }
+};
+
+//----------------------------------------------------------------------------
+// Parser implementation template.
+template <class Types>
+class cmELFInternalImpl: public cmELFInternal
+{
+public:
+  // Copy the ELF file format types from our configuration parameter.
+  typedef typename Types::ELF_Ehdr ELF_Ehdr;
+  typedef typename Types::ELF_Shdr ELF_Shdr;
+  typedef typename Types::ELF_Dyn  ELF_Dyn;
+  typedef typename Types::ELF_Half ELF_Half;
+
+  // Construct with a stream and byte swap indicator.
+  cmELFInternalImpl(cmELF* external,
+                    cmsys::auto_ptr<std::ifstream>& fin,
+                    ByteOrderType order);
+
+  // Return the number of sections as specified by the ELF header.
+  virtual unsigned int GetNumberOfSections() const
+    {
+    return static_cast<unsigned int>(this->ELFHeader.e_shnum);
+    }
+
+  // Lookup the SONAME in the DYNAMIC section.
+  virtual bool GetSOName(std::string& soname);
+
+  // Print information about the ELF file.
+  virtual void PrintInfo(std::ostream& os) const
+    {
+    os << "ELF " << Types::GetName();
+    if(this->ByteOrder == ByteOrderMSB)
+      {
+      os << " MSB";
+      }
+    else if(this->ByteOrder == ByteOrderLSB)
+      {
+      os << " LSB";
+      }
+    switch(this->ELFType)
+      {
+      case cmELF::FileTypeRelocatableObject:
+        os << " relocatable object";
+        break;
+      case cmELF::FileTypeExecutable:
+        os << " executable";
+        break;
+      case cmELF::FileTypeSharedLibrary:
+        os << " shared library";
+        break;
+      case cmELF::FileTypeCore:
+        os << " core file";
+        break;
+      }
+    os << "\n";
+    }
+
+private:
+  void ByteSwap(ELF_Ehdr& elf_header)
+    {
+    cmELFByteSwap(elf_header.e_type);
+    cmELFByteSwap(elf_header.e_machine);
+    cmELFByteSwap(elf_header.e_version);
+    cmELFByteSwap(elf_header.e_entry);
+    cmELFByteSwap(elf_header.e_phoff);
+    cmELFByteSwap(elf_header.e_shoff);
+    cmELFByteSwap(elf_header.e_flags);
+    cmELFByteSwap(elf_header.e_ehsize);
+    cmELFByteSwap(elf_header.e_phentsize);
+    cmELFByteSwap(elf_header.e_phnum);
+    cmELFByteSwap(elf_header.e_shentsize);
+    cmELFByteSwap(elf_header.e_shnum);
+    cmELFByteSwap(elf_header.e_shstrndx);
+    }
+
+  void ByteSwap(ELF_Shdr& sec_header)
+    {
+    cmELFByteSwap(sec_header.sh_name);
+    cmELFByteSwap(sec_header.sh_type);
+    cmELFByteSwap(sec_header.sh_flags);
+    cmELFByteSwap(sec_header.sh_addr);
+    cmELFByteSwap(sec_header.sh_offset);
+    cmELFByteSwap(sec_header.sh_size);
+    cmELFByteSwap(sec_header.sh_link);
+    cmELFByteSwap(sec_header.sh_info);
+    cmELFByteSwap(sec_header.sh_addralign);
+    cmELFByteSwap(sec_header.sh_entsize);
+    }
+
+  void ByteSwap(ELF_Dyn& dyn)
+    {
+    cmELFByteSwap(dyn.d_tag);
+    switch (dyn.d_tag)
+      {
+      case DT_NULL:     /* dyn.d_un ignored */         break;
+      case DT_NEEDED:   cmELFByteSwap(dyn.d_un.d_val); break;
+      case DT_PLTRELSZ: cmELFByteSwap(dyn.d_un.d_val); break;
+      case DT_PLTGOT:   cmELFByteSwap(dyn.d_un.d_ptr); break;
+      case DT_HASH:     cmELFByteSwap(dyn.d_un.d_ptr); break;
+      case DT_STRTAB:   cmELFByteSwap(dyn.d_un.d_ptr); break;
+      case DT_SYMTAB:   cmELFByteSwap(dyn.d_un.d_ptr); break;
+      case DT_RELA:     cmELFByteSwap(dyn.d_un.d_ptr); break;
+      case DT_RELASZ:   cmELFByteSwap(dyn.d_un.d_val); break;
+      case DT_RELAENT:  cmELFByteSwap(dyn.d_un.d_val); break;
+      case DT_STRSZ:    cmELFByteSwap(dyn.d_un.d_val); break;
+      case DT_SYMENT:   cmELFByteSwap(dyn.d_un.d_val); break;
+      case DT_INIT:     cmELFByteSwap(dyn.d_un.d_ptr); break;
+      case DT_FINI:     cmELFByteSwap(dyn.d_un.d_ptr); break;
+      case DT_SONAME:   cmELFByteSwap(dyn.d_un.d_val); break;
+      case DT_RPATH:    cmELFByteSwap(dyn.d_un.d_val); break;
+      case DT_SYMBOLIC: /* dyn.d_un ignored */         break;
+      case DT_REL:      cmELFByteSwap(dyn.d_un.d_ptr); break;
+      case DT_RELSZ:    cmELFByteSwap(dyn.d_un.d_val); break;
+      case DT_RELENT:   cmELFByteSwap(dyn.d_un.d_val); break;
+      case DT_PLTREL:   cmELFByteSwap(dyn.d_un.d_val); break;
+      case DT_DEBUG:    cmELFByteSwap(dyn.d_un.d_ptr); break;
+      case DT_TEXTREL:  /* dyn.d_un ignored */         break;
+      case DT_JMPREL:   cmELFByteSwap(dyn.d_un.d_ptr); break;
+      }
+    }
+
+  bool Read(ELF_Ehdr& x)
+    {
+    if(this->Stream.read(reinterpret_cast<char*>(&x), sizeof(x)) &&
+       this->NeedSwap)
+      {
+      ByteSwap(x);
+      }
+    return this->Stream? true:false;
+    }
+  bool Read(ELF_Shdr& x)
+    {
+    if(this->Stream.read(reinterpret_cast<char*>(&x), sizeof(x)) &&
+       this->NeedSwap)
+      {
+      ByteSwap(x);
+      }
+    return this->Stream? true:false;
+    }
+  bool Read(ELF_Dyn& x)
+    {
+    if(this->Stream.read(reinterpret_cast<char*>(&x), sizeof(x)) &&
+       this->NeedSwap)
+      {
+      ByteSwap(x);
+      }
+    return this->Stream? true:false;
+    }
+
+  bool LoadSectionHeader(ELF_Half i)
+    {
+    // Read the section header from the file.
+    this->Stream.seekg(this->ELFHeader.e_shoff +
+                       this->ELFHeader.e_shentsize * i);
+    if(!this->Read(this->SectionHeaders[i]))
+      {
+      return false;
+      }
+
+    // Identify some important sections.
+    if(this->SectionHeaders[i].sh_type == SHT_DYNAMIC)
+      {
+      this->DynamicSectionIndex = i;
+      }
+    return true;
+    }
+
+  bool LoadDynamicSection();
+
+  // Store the main ELF header.
+  ELF_Ehdr ELFHeader;
+
+  // Store all the section headers.
+  std::vector<ELF_Shdr> SectionHeaders;
+
+  // Store all entries of the DYNAMIC section.
+  std::vector<ELF_Dyn> DynamicSectionEntries;
+
+  // Store the SOName if it has been loaded.
+  std::string SOName;
+  bool SONameChecked;
+};
+
+//----------------------------------------------------------------------------
+template <class Types>
+cmELFInternalImpl<Types>
+::cmELFInternalImpl(cmELF* external,
+                    cmsys::auto_ptr<std::ifstream>& fin,
+                    ByteOrderType order):
+  cmELFInternal(external, fin, order)
+{
+  // Initialize state.
+  this->SONameChecked = false;
+
+  // Read the main header.
+  if(!this->Read(this->ELFHeader))
+    {
+    return;
+    }
+
+  // Determine the ELF file type.
+  switch(this->ELFHeader.e_type)
+    {
+    case 1:
+      this->ELFType = cmELF::FileTypeRelocatableObject;
+      break;
+    case 2:
+      this->ELFType = cmELF::FileTypeExecutable;
+      break;
+    case 3:
+      this->ELFType = cmELF::FileTypeSharedLibrary;
+      break;
+    case 4:
+      this->ELFType = cmELF::FileTypeCore;
+      break;
+    default:
+      return;
+    }
+
+  // Load the section headers.
+  this->SectionHeaders.resize(this->ELFHeader.e_shnum);
+  for(ELF_Half i=0; i < this->ELFHeader.e_shnum; ++i)
+    {
+    if(!this->LoadSectionHeader(i))
+      {
+      this->ELFType = cmELF::FileTypeInvalid;
+      return;
+      }
+    }
+}
+
+//----------------------------------------------------------------------------
+template <class Types>
+bool cmELFInternalImpl<Types>::LoadDynamicSection()
+{
+  // If there is no dynamic section we are done.
+  if(this->DynamicSectionIndex < 0)
+    {
+    return false;
+    }
+
+  // If the section was already loaded we are done.
+  if(!this->DynamicSectionEntries.empty())
+    {
+    return true;
+    }
+
+  // Allocate the dynamic section entries.
+  ELF_Shdr const& sec = this->SectionHeaders[this->DynamicSectionIndex];
+  int n = sec.sh_size / sec.sh_entsize;
+  this->DynamicSectionEntries.resize(n);
+
+  // Read each entry.
+  for(int j=0; j < n; ++j)
+    {
+    // Seek to the beginning of the section entry.
+    this->Stream.seekg(sec.sh_offset + sec.sh_entsize*j);
+    ELF_Dyn& dyn = this->DynamicSectionEntries[j];
+
+    // Try reading the entry.
+    if(!this->Read(dyn))
+      {
+      this->SetErrorMessage("Error reading entry from DYNAMIC section.");
+      this->DynamicSectionIndex = -1;
+      return false;
+      }
+    }
+  return true;
+}
+
+//----------------------------------------------------------------------------
+template <class Types>
+bool cmELFInternalImpl<Types>::GetSOName(std::string& soname)
+{
+  // Short-circuit if already checked.
+  if(this->SONameChecked)
+    {
+    soname = this->SOName;
+    return !soname.empty();
+    }
+  this->SONameChecked = true;
+
+  // Try reading the dynamic section.
+  if(!this->LoadDynamicSection())
+    {
+    return false;
+    }
+
+  // Get the string table referenced by the DYNAMIC section.
+  ELF_Shdr const& sec = this->SectionHeaders[this->DynamicSectionIndex];
+  if(sec.sh_link >= this->SectionHeaders.size())
+    {
+    this->SetErrorMessage("Section DYNAMIC has invalid string table index.");
+    return false;
+    }
+  ELF_Shdr const& strtab = this->SectionHeaders[sec.sh_link];
+
+  // Look for the soname entry.
+  for(typename std::vector<ELF_Dyn>::iterator
+        di = this->DynamicSectionEntries.begin();
+      di != this->DynamicSectionEntries.end(); ++di)
+    {
+    ELF_Dyn& dyn = *di;
+    if(dyn.d_tag == DT_SONAME)
+      {
+      this->Stream.seekg(strtab.sh_offset + dyn.d_un.d_val);
+      char c;
+      while(this->Stream.get(c) && c != 0)
+        {
+        this->SOName += c;
+        }
+      if(!this->Stream)
+        {
+        this->SetErrorMessage("Dynamic section specifies unreadable SONAME.");
+        this->SOName = "";
+        return false;
+        }
+      soname = this->SOName;
+      return true;
+      }
+    }
+  return false;
+}
+
+//============================================================================
+// External class implementation.
+
+//----------------------------------------------------------------------------
+cmELF::cmELF(const char* fname): Internal(0)
+{
+  // Try to open the file.
+  cmsys::auto_ptr<std::ifstream> fin(new std::ifstream(fname));
+
+  // Quit now if the file could not be opened.
+  if(!fin.get() || !*fin)
+    {
+    this->ErrorMessage = "Error opening input file.";
+    return;
+    }
+
+  // Read the ELF identification block.
+  char ident[EI_NIDENT];
+  if(!fin->read(ident, EI_NIDENT))
+    {
+    this->ErrorMessage = "Error reading ELF identification.";
+    return;
+    }
+  if(!fin->seekg(0))
+    {
+    this->ErrorMessage = "Error seeking to beginning of file.";
+    return;
+    }
+
+  // Verify the ELF identification.
+  if(!(ident[EI_MAG0] == ELFMAG0 &&
+       ident[EI_MAG1] == ELFMAG1 &&
+       ident[EI_MAG2] == ELFMAG2 &&
+       ident[EI_MAG3] == ELFMAG3))
+    {
+    this->ErrorMessage = "File does not have a valid ELF identification.";
+    return;
+    }
+
+  // Check the byte order in which the rest of the file is encoded.
+  cmELFInternal::ByteOrderType order;
+  if(ident[EI_DATA] == ELFDATA2LSB)
+    {
+    // File is LSB.
+    order =  cmELFInternal::ByteOrderLSB;
+    }
+  else if(ident[EI_DATA] == ELFDATA2MSB)
+    {
+    // File is MSB.
+    order =  cmELFInternal::ByteOrderMSB;
+    }
+  else
+    {
+    this->ErrorMessage = "ELF file is not LSB or MSB encoded.";
+    return;
+    }
+
+  // Check the class of the file and construct the corresponding
+  // parser implementation.
+  if(ident[EI_CLASS] == ELFCLASS32)
+    {
+    // 32-bit ELF
+    this->Internal = new cmELFInternalImpl<cmELFTypes32>(this, fin, order);
+    }
+  else if(ident[EI_CLASS] == ELFCLASS64)
+    {
+    // 64-bit ELF
+    this->Internal = new cmELFInternalImpl<cmELFTypes64>(this, fin, order);
+    }
+  else
+    {
+    this->ErrorMessage = "ELF file class is not 32-bit or 64-bit.";
+    return;
+    }
+}
+
+//----------------------------------------------------------------------------
+cmELF::~cmELF()
+{
+  delete this->Internal;
+}
+
+//----------------------------------------------------------------------------
+bool cmELF::Valid() const
+{
+  return this->Internal && this->Internal->GetFileType() != FileTypeInvalid;
+}
+
+//----------------------------------------------------------------------------
+cmELF::FileType cmELF::GetFileType() const
+{
+  if(this->Valid())
+    {
+    return this->Internal->GetFileType();
+    }
+  else
+    {
+    return FileTypeInvalid;
+    }
+}
+
+//----------------------------------------------------------------------------
+unsigned int cmELF::GetNumberOfSections() const
+{
+  if(this->Valid())
+    {
+    return this->Internal->GetNumberOfSections();
+    }
+  else
+    {
+    return 0;
+    }
+}
+
+//----------------------------------------------------------------------------
+bool cmELF::GetSOName(std::string& soname)
+{
+  if(this->Valid() &&
+     this->Internal->GetFileType() == cmELF::FileTypeSharedLibrary)
+    {
+    return this->Internal->GetSOName(soname);
+    }
+  else
+    {
+    return false;
+    }
+}
+
+//----------------------------------------------------------------------------
+void cmELF::PrintInfo(std::ostream& os) const
+{
+  if(this->Valid())
+    {
+    this->Internal->PrintInfo(os);
+    }
+  else
+    {
+    os << "Not a valid ELF file.\n";
+    }
+}
diff --git a/Source/cmELF.h b/Source/cmELF.h
new file mode 100644
index 0000000..11bf354
--- /dev/null
+++ b/Source/cmELF.h
@@ -0,0 +1,76 @@
+/*=========================================================================
+
+  Program:   CMake - Cross-Platform Makefile Generator
+  Module:    $RCSfile$
+  Language:  C++
+  Date:      $Date$
+  Version:   $Revision$
+
+  Copyright (c) 2002 Kitware, Inc., Insight Consortium.  All rights reserved.
+  See Copyright.txt or http://www.cmake.org/HTML/Copyright.html for details.
+
+     This software is distributed WITHOUT ANY WARRANTY; without even
+     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+     PURPOSE.  See the above copyright notices for more information.
+
+=========================================================================*/
+#ifndef cmELF_h
+#define cmELF_h
+
+#if !defined(CMAKE_USE_ELF_PARSER)
+# error "This file may be included only if CMAKE_USE_ELF_PARSER is enabled."
+#endif
+
+class cmELFInternal;
+
+/** \class cmELF
+ * \brief Executable and Link Format (ELF) parser.
+ */
+class cmELF
+{
+public:
+  /** Construct with the name of the ELF input file to parse.  */
+  cmELF(const char* fname);
+
+  /** Destruct.   */
+  ~cmELF();
+
+  /** Get the error message if any.  */
+  std::string const& GetErrorMessage() const
+    {
+    return this->ErrorMessage;
+    }
+
+  /** Boolean conversion.  True if the ELF file is valid.  */
+  operator bool() const { return this->Valid(); }
+
+  /** Enumeration of ELF file types.  */
+  enum FileType
+  {
+    FileTypeInvalid,
+    FileTypeRelocatableObject,
+    FileTypeExecutable,
+    FileTypeSharedLibrary,
+    FileTypeCore
+  };
+
+  /** Get the type of the file opened.  */
+  FileType GetFileType() const;
+
+  /** Get the number of ELF sections present.  */
+  unsigned int GetNumberOfSections() const;
+
+  /** Get the SONAME field if any.  */
+  bool GetSOName(std::string& soname);
+
+  /** Print human-readable information about the ELF file.  */
+  void PrintInfo(std::ostream& os) const;
+
+private:
+  friend class cmELFInternal;
+  bool Valid() const;
+  cmELFInternal* Internal;
+  std::string ErrorMessage;
+};
+
+#endif
diff --git a/Source/cmSystemTools.cxx b/Source/cmSystemTools.cxx
index 8d13e11..aa4d1c2 100644
--- a/Source/cmSystemTools.cxx
+++ b/Source/cmSystemTools.cxx
@@ -52,6 +52,10 @@
 #  include <cmsys/MD5.h>
 #endif
 
+#if defined(CMAKE_USE_ELF_PARSER)
+# include "cmELF.h"
+#endif
+
 #if defined(__sgi) && !defined(__GNUC__)
 # pragma set woff 1375 /* base class destructor not virtual */
 #endif
@@ -2155,6 +2159,16 @@ void cmSystemTools::MakefileColorEcho(int color, const char* message,
 bool cmSystemTools::GuessLibrarySOName(std::string const& fullPath,
                                        std::string& soname)
 {
+  // For ELF shared libraries use a real parser to get the correct
+  // soname.
+#if defined(CMAKE_USE_ELF_PARSER)
+  cmELF elf(fullPath.c_str());
+  if(elf)
+    {
+    return elf.GetSOName(soname);
+    }
+#endif
+
   // If the file is not a symlink we have no guess for its soname.
   if(!cmSystemTools::FileIsSymlink(fullPath.c_str()))
     {