Source/cmELF.cxx

   1 /*=========================================================================
   2
   3   Program:   CMake - Cross-Platform Makefile Generator
   4   Module:    $RCSfile: cmELF.cxx,v $
   5   Language:  C++
   6   Date:      $Date: 2008-08-04 13:38:38 $
   7   Version:   $Revision: 1.13 $
   8
   9   Copyright (c) 2002 Kitware, Inc., Insight Consortium.  All rights reserved.
  10   See Copyright.txt or http://www.cmake.org/HTML/Copyright.html for details.
  11
  12      This software is distributed WITHOUT ANY WARRANTY; without even
  13      the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
  14      PURPOSE.  See the above copyright notices for more information.
  15
  16 =========================================================================*/
  17 #include "cmStandardIncludes.h" // to get CMAKE_USE_ELF_PARSER first
  18 #include "cmELF.h"
  19
  20 #include <cmsys/auto_ptr.hxx>
  21
  22 // Need the native byte order of the running CPU.
  23 #define cmsys_CPU_UNKNOWN_OKAY // We can decide at runtime if not known.
  24 #include <cmsys/CPU.h>
  25
  26 // Include the ELF format information system header.
  27 #include <elf.h>
  28 #if defined(__sun)
  29 # include <sys/link.h> // For dynamic section information
  30 #endif
  31
  32 //----------------------------------------------------------------------------
  33 // Low-level byte swapping implementation.
  34 template <size_t s> struct cmELFByteSwapSize {};
  35 void cmELFByteSwap(char*, cmELFByteSwapSize<1> const&)
  36 {
  37 }
  38 void cmELFByteSwap(char* data, cmELFByteSwapSize<2> const&)
  39 {
  40   char one_byte;
  41   one_byte = data[0]; data[0] = data[1]; data[1] = one_byte;
  42 }
  43 void cmELFByteSwap(char* data, cmELFByteSwapSize<4> const&)
  44 {
  45   char one_byte;
  46   one_byte = data[0]; data[0] = data[3]; data[3] = one_byte;
  47   one_byte = data[1]; data[1] = data[2]; data[2] = one_byte;
  48 }
  49 void cmELFByteSwap(char* data, cmELFByteSwapSize<8> const&)
  50 {
  51   char one_byte;
  52   one_byte = data[0]; data[0] = data[7]; data[7] = one_byte;
  53   one_byte = data[1]; data[1] = data[6]; data[6] = one_byte;
  54   one_byte = data[2]; data[2] = data[5]; data[5] = one_byte;
  55   one_byte = data[3]; data[3] = data[4]; data[4] = one_byte;
  56 }
  57
  58 // Low-level byte swapping interface.
  59 template <typename T>
  60 void cmELFByteSwap(T& x)
  61 {
  62   cmELFByteSwap(reinterpret_cast<char*>(&x), cmELFByteSwapSize<sizeof(T)>());
  63 }
  64
  65 //----------------------------------------------------------------------------
  66 class cmELFInternal
  67 {
  68 public:
  69   typedef cmELF::StringEntry StringEntry;
  70   enum ByteOrderType { ByteOrderMSB, ByteOrderLSB };
  71
  72   // Construct and take ownership of the file stream object.
  73   cmELFInternal(cmELF* external,
  74                 cmsys::auto_ptr<std::ifstream>& fin,
  75                 ByteOrderType order):
  76     External(external),
  77     Stream(*fin.release()),
  78     ByteOrder(order),
  79     ELFType(cmELF::FileTypeInvalid)
  80     {
  81     // In most cases the processor-specific byte order will match that
  82     // of the target execution environment.  If we choose wrong here
  83     // it is fixed when the header is read.
  84 #if cmsys_CPU_ENDIAN_ID == cmsys_CPU_ENDIAN_ID_LITTLE
  85     this->NeedSwap = (this->ByteOrder == ByteOrderMSB);
  86 #elif cmsys_CPU_ENDIAN_ID == cmsys_CPU_ENDIAN_ID_BIG
  87     this->NeedSwap = (this->ByteOrder == ByteOrderLSB);
  88 #else
  89     this->NeedSwap = false; // Final decision is at runtime anyway.
  90 #endif
  91
  92     // We have not yet loaded the section info.
  93     this->DynamicSectionIndex = -1;
  94     }
  95
  96   // Destruct and delete the file stream object.
  97   virtual ~cmELFInternal()
  98     {
  99     delete &this->Stream;
 100     }
 101
 102   // Forward to the per-class implementation.
 103   virtual unsigned int GetNumberOfSections() const = 0;
 104   virtual unsigned int GetDynamicEntryCount() = 0;
 105   virtual unsigned long GetDynamicEntryPosition(int j) = 0;
 106   virtual StringEntry const* GetDynamicSectionString(int tag) = 0;
 107   virtual void PrintInfo(std::ostream& os) const = 0;
 108
 109   bool ReadBytes(unsigned long pos, unsigned long size, char* buf)
 110     {
 111     this->Stream.seekg(pos);
 112     this->Stream.read(buf, size);
 113     return this->Stream?true:false;
 114     }
 115
 116   // Lookup the SONAME in the DYNAMIC section.
 117   StringEntry const* GetSOName()
 118     {
 119     return this->GetDynamicSectionString(DT_SONAME);
 120     }
 121
 122   // Lookup the RPATH in the DYNAMIC section.
 123   StringEntry const* GetRPath()
 124     {
 125     return this->GetDynamicSectionString(DT_RPATH);
 126     }
 127
 128   // Lookup the RUNPATH in the DYNAMIC section.
 129   StringEntry const* GetRunPath()
 130     {
 131 #if defined(DT_RUNPATH)
 132     return this->GetDynamicSectionString(DT_RUNPATH);
 133 #else
 134     return 0;
 135 #endif
 136     }
 137
 138   // Return the recorded ELF type.
 139   cmELF::FileType GetFileType() const { return this->ELFType; }
 140 protected:
 141   // Data common to all ELF class implementations.
 142
 143   // The external cmELF object.
 144   cmELF* External;
 145
 146   // The stream from which to read.
 147   std::istream& Stream;
 148
 149   // The byte order of the ELF file.
 150   ByteOrderType ByteOrder;
 151
 152   // The ELF file type.
 153   cmELF::FileType ELFType;
 154
 155   // Whether we need to byte-swap structures read from the stream.
 156   bool NeedSwap;
 157
 158   // The section header index of the DYNAMIC section (-1 if none).
 159   int DynamicSectionIndex;
 160
 161   // Helper methods for subclasses.
 162   void SetErrorMessage(const char* msg)
 163     {
 164     this->External->ErrorMessage = msg;
 165     this->ELFType = cmELF::FileTypeInvalid;
 166     }
 167
 168   // Store string table entry states.
 169   std::map<int, StringEntry> DynamicSectionStrings;
 170 };
 171
 172 //----------------------------------------------------------------------------
 173 // Configure the implementation template for 32-bit ELF files.
 174 struct cmELFTypes32
 175 {
 176   typedef Elf32_Ehdr ELF_Ehdr;
 177   typedef Elf32_Shdr ELF_Shdr;
 178   typedef Elf32_Dyn  ELF_Dyn;
 179   typedef Elf32_Half ELF_Half;
 180   static const char* GetName() { return "32-bit"; }
 181 };
 182
 183 // Configure the implementation template for 32-bit ELF files.
 184 struct cmELFTypes64
 185 {
 186   typedef Elf64_Ehdr ELF_Ehdr;
 187   typedef Elf64_Shdr ELF_Shdr;
 188   typedef Elf64_Dyn  ELF_Dyn;
 189   typedef Elf64_Half ELF_Half;
 190   static const char* GetName() { return "64-bit"; }
 191 };
 192
 193 //----------------------------------------------------------------------------
 194 // Parser implementation template.
 195 template <class Types>
 196 class cmELFInternalImpl: public cmELFInternal
 197 {
 198 public:
 199   // Copy the ELF file format types from our configuration parameter.
 200   typedef typename Types::ELF_Ehdr ELF_Ehdr;
 201   typedef typename Types::ELF_Shdr ELF_Shdr;
 202   typedef typename Types::ELF_Dyn  ELF_Dyn;
 203   typedef typename Types::ELF_Half ELF_Half;
 204
 205   // Construct with a stream and byte swap indicator.
 206   cmELFInternalImpl(cmELF* external,
 207                     cmsys::auto_ptr<std::ifstream>& fin,
 208                     ByteOrderType order);
 209
 210   // Return the number of sections as specified by the ELF header.
 211   virtual unsigned int GetNumberOfSections() const
 212     {
 213     return static_cast<unsigned int>(this->ELFHeader.e_shnum);
 214     }
 215
 216   // Get the file position and size of a dynamic section entry.
 217   virtual unsigned int GetDynamicEntryCount();
 218   virtual unsigned long GetDynamicEntryPosition(int j);
 219
 220   // Lookup a string from the dynamic section with the given tag.
 221   virtual StringEntry const* GetDynamicSectionString(int tag);
 222
 223   // Print information about the ELF file.
 224   virtual void PrintInfo(std::ostream& os) const
 225     {
 226     os << "ELF " << Types::GetName();
 227     if(this->ByteOrder == ByteOrderMSB)
 228       {
 229       os << " MSB";
 230       }
 231     else if(this->ByteOrder == ByteOrderLSB)
 232       {
 233       os << " LSB";
 234       }
 235     switch(this->ELFType)
 236       {
 237       case cmELF::FileTypeInvalid:
 238         os << " invalid file";
 239         break;
 240       case cmELF::FileTypeRelocatableObject:
 241         os << " relocatable object";
 242         break;
 243       case cmELF::FileTypeExecutable:
 244         os << " executable";
 245         break;
 246       case cmELF::FileTypeSharedLibrary:
 247         os << " shared library";
 248         break;
 249       case cmELF::FileTypeCore:
 250         os << " core file";
 251         break;
 252       case cmELF::FileTypeSpecificOS:
 253         os << " os-specific type";
 254         break;
 255       case cmELF::FileTypeSpecificProc:
 256         os << " processor-specific type";
 257         break;
 258       }
 259     os << "\n";
 260     }
 261
 262 private:
 263   void ByteSwap(ELF_Ehdr& elf_header)
 264     {
 265     cmELFByteSwap(elf_header.e_type);
 266     cmELFByteSwap(elf_header.e_machine);
 267     cmELFByteSwap(elf_header.e_version);
 268     cmELFByteSwap(elf_header.e_entry);
 269     cmELFByteSwap(elf_header.e_phoff);
 270     cmELFByteSwap(elf_header.e_shoff);
 271     cmELFByteSwap(elf_header.e_flags);
 272     cmELFByteSwap(elf_header.e_ehsize);
 273     cmELFByteSwap(elf_header.e_phentsize);
 274     cmELFByteSwap(elf_header.e_phnum);
 275     cmELFByteSwap(elf_header.e_shentsize);
 276     cmELFByteSwap(elf_header.e_shnum);
 277     cmELFByteSwap(elf_header.e_shstrndx);
 278     }
 279
 280   void ByteSwap(ELF_Shdr& sec_header)
 281     {
 282     cmELFByteSwap(sec_header.sh_name);
 283     cmELFByteSwap(sec_header.sh_type);
 284     cmELFByteSwap(sec_header.sh_flags);
 285     cmELFByteSwap(sec_header.sh_addr);
 286     cmELFByteSwap(sec_header.sh_offset);
 287     cmELFByteSwap(sec_header.sh_size);
 288     cmELFByteSwap(sec_header.sh_link);
 289     cmELFByteSwap(sec_header.sh_info);
 290     cmELFByteSwap(sec_header.sh_addralign);
 291     cmELFByteSwap(sec_header.sh_entsize);
 292     }
 293
 294   void ByteSwap(ELF_Dyn& dyn)
 295     {
 296     cmELFByteSwap(dyn.d_tag);
 297     switch (dyn.d_tag)
 298       {
 299       case DT_NULL:     /* dyn.d_un ignored */         break;
 300       case DT_NEEDED:   cmELFByteSwap(dyn.d_un.d_val); break;
 301       case DT_PLTRELSZ: cmELFByteSwap(dyn.d_un.d_val); break;
 302       case DT_PLTGOT:   cmELFByteSwap(dyn.d_un.d_ptr); break;
 303       case DT_HASH:     cmELFByteSwap(dyn.d_un.d_ptr); break;
 304       case DT_STRTAB:   cmELFByteSwap(dyn.d_un.d_ptr); break;
 305       case DT_SYMTAB:   cmELFByteSwap(dyn.d_un.d_ptr); break;
 306       case DT_RELA:     cmELFByteSwap(dyn.d_un.d_ptr); break;
 307       case DT_RELASZ:   cmELFByteSwap(dyn.d_un.d_val); break;
 308       case DT_RELAENT:  cmELFByteSwap(dyn.d_un.d_val); break;
 309       case DT_STRSZ:    cmELFByteSwap(dyn.d_un.d_val); break;
 310       case DT_SYMENT:   cmELFByteSwap(dyn.d_un.d_val); break;
 311       case DT_INIT:     cmELFByteSwap(dyn.d_un.d_ptr); break;
 312       case DT_FINI:     cmELFByteSwap(dyn.d_un.d_ptr); break;
 313       case DT_SONAME:   cmELFByteSwap(dyn.d_un.d_val); break;
 314       case DT_RPATH:    cmELFByteSwap(dyn.d_un.d_val); break;
 315       case DT_SYMBOLIC: /* dyn.d_un ignored */         break;
 316       case DT_REL:      cmELFByteSwap(dyn.d_un.d_ptr); break;
 317       case DT_RELSZ:    cmELFByteSwap(dyn.d_un.d_val); break;
 318       case DT_RELENT:   cmELFByteSwap(dyn.d_un.d_val); break;
 319       case DT_PLTREL:   cmELFByteSwap(dyn.d_un.d_val); break;
 320       case DT_DEBUG:    cmELFByteSwap(dyn.d_un.d_ptr); break;
 321       case DT_TEXTREL:  /* dyn.d_un ignored */         break;
 322       case DT_JMPREL:   cmELFByteSwap(dyn.d_un.d_ptr); break;
 323 #ifdef T_BIND_NOW
 324       case T_BIND_NOW:         /* dyn.d_un ignored */         break;
 325 #endif
 326 #ifdef DT_INIT_ARRAY
 327       case DT_INIT_ARRAY:      cmELFByteSwap(dyn.d_un.d_ptr); break;
 328 #endif
 329 #ifdef DT_FINI_ARRAY
 330       case DT_FINI_ARRAY:      cmELFByteSwap(dyn.d_un.d_ptr); break;
 331 #endif
 332 #ifdef DT_INIT_ARRAYSZ
 333       case DT_INIT_ARRAYSZ:    cmELFByteSwap(dyn.d_un.d_val); break;
 334 #endif
 335 #ifdef DT_FINI_ARRAYSZ
 336       case DT_FINI_ARRAYSZ:    cmELFByteSwap(dyn.d_un.d_val); break;
 337 #endif
 338 #ifdef DT_RUNPATH
 339       case DT_RUNPATH:         cmELFByteSwap(dyn.d_un.d_val); break;
 340 #endif
 341 #ifdef DT_FLAGS
 342       case DT_FLAGS:           cmELFByteSwap(dyn.d_un.d_val); break;
 343 #endif
 344 #ifdef DT_PREINIT_ARRAY
 345       case DT_PREINIT_ARRAY:   cmELFByteSwap(dyn.d_un.d_ptr); break;
 346 #endif
 347 #ifdef DT_PREINIT_ARRAYSZ
 348       case DT_PREINIT_ARRAYSZ: cmELFByteSwap(dyn.d_un.d_val); break;
 349 #endif
 350       }
 351     }
 352
 353   bool FileTypeValid(ELF_Half et)
 354     {
 355     unsigned int eti = static_cast<unsigned int>(et);
 356     if(eti == ET_NONE || eti == ET_REL || eti == ET_EXEC ||
 357        eti == ET_DYN || eti == ET_CORE)
 358       {
 359       return true;
 360       }
 361 #if defined(ET_LOOS) && defined(ET_HIOS)
 362     if(eti >= ET_LOOS && eti <= ET_HIOS)
 363       {
 364       return true;
 365       }
 366 #endif
 367 #if defined(ET_LOPROC) && defined(ET_HIPROC)
 368     if(eti >= ET_LOPROC && eti <= ET_HIPROC)
 369       {
 370       return true;
 371       }
 372 #endif
 373     return false;
 374     }
 375
 376   bool Read(ELF_Ehdr& x)
 377     {
 378     // Read the header from the file.
 379     if(!this->Stream.read(reinterpret_cast<char*>(&x), sizeof(x)))
 380       {
 381       return false;
 382       }
 383
 384     // The byte order of ELF header fields may not match that of the
 385     // processor-specific data.  The header fields are ordered to
 386     // match the target execution environment, so we may need to
 387     // memorize the order of all platforms based on the e_machine
 388     // value.  As a heuristic, if the type is invalid but its
 389     // swapped value is okay then flip our swap mode.
 390     ELF_Half et = x.e_type;
 391     if(this->NeedSwap)
 392       {
 393       cmELFByteSwap(et);
 394       }
 395     if(!this->FileTypeValid(et))
 396       {
 397       cmELFByteSwap(et);
 398       if(this->FileTypeValid(et))
 399         {
 400         // The previous byte order guess was wrong.  Flip it.
 401         this->NeedSwap = !this->NeedSwap;
 402         }
 403       }
 404
 405     // Fix the byte order of the header.
 406     if(this->NeedSwap)
 407       {
 408       ByteSwap(x);
 409       }
 410     return true;
 411     }
 412   bool Read(ELF_Shdr& x)
 413     {
 414     if(this->Stream.read(reinterpret_cast<char*>(&x), sizeof(x)) &&
 415        this->NeedSwap)
 416       {
 417       ByteSwap(x);
 418       }
 419     return this->Stream? true:false;
 420     }
 421   bool Read(ELF_Dyn& x)
 422     {
 423     if(this->Stream.read(reinterpret_cast<char*>(&x), sizeof(x)) &&
 424        this->NeedSwap)
 425       {
 426       ByteSwap(x);
 427       }
 428     return this->Stream? true:false;
 429     }
 430
 431   bool LoadSectionHeader(ELF_Half i)
 432     {
 433     // Read the section header from the file.
 434     this->Stream.seekg(this->ELFHeader.e_shoff +
 435                        this->ELFHeader.e_shentsize * i);
 436     if(!this->Read(this->SectionHeaders[i]))
 437       {
 438       return false;
 439       }
 440
 441     // Identify some important sections.
 442     if(this->SectionHeaders[i].sh_type == SHT_DYNAMIC)
 443       {
 444       this->DynamicSectionIndex = i;
 445       }
 446     return true;
 447     }
 448
 449   bool LoadDynamicSection();
 450
 451   // Store the main ELF header.
 452   ELF_Ehdr ELFHeader;
 453
 454   // Store all the section headers.
 455   std::vector<ELF_Shdr> SectionHeaders;
 456
 457   // Store all entries of the DYNAMIC section.
 458   std::vector<ELF_Dyn> DynamicSectionEntries;
 459 };
 460
 461 //----------------------------------------------------------------------------
 462 template <class Types>
 463 cmELFInternalImpl<Types>
 464 ::cmELFInternalImpl(cmELF* external,
 465                     cmsys::auto_ptr<std::ifstream>& fin,
 466                     ByteOrderType order):
 467   cmELFInternal(external, fin, order)
 468 {
 469   // Read the main header.
 470   if(!this->Read(this->ELFHeader))
 471     {
 472     this->SetErrorMessage("Failed to read main ELF header.");
 473     return;
 474     }
 475
 476   // Determine the ELF file type.
 477   switch(this->ELFHeader.e_type)
 478     {
 479     case ET_NONE:
 480       this->SetErrorMessage("ELF file type is NONE.");
 481       return;
 482     case ET_REL:
 483       this->ELFType = cmELF::FileTypeRelocatableObject;
 484       break;
 485     case ET_EXEC:
 486       this->ELFType = cmELF::FileTypeExecutable;
 487       break;
 488     case ET_DYN:
 489       this->ELFType = cmELF::FileTypeSharedLibrary;
 490       break;
 491     case ET_CORE:
 492       this->ELFType = cmELF::FileTypeCore;
 493       break;
 494     default:
 495       {
 496       unsigned int eti = static_cast<unsigned int>(this->ELFHeader.e_type);
 497 #if defined(ET_LOOS) && defined(ET_HIOS)
 498       if(eti >= ET_LOOS && eti <= ET_HIOS)
 499         {
 500         this->ELFType = cmELF::FileTypeSpecificOS;
 501         break;
 502         }
 503 #endif
 504 #if defined(ET_LOPROC) && defined(ET_HIPROC)
 505       if(eti >= ET_LOPROC && eti <= ET_HIPROC)
 506         {
 507         this->ELFType = cmELF::FileTypeSpecificProc;
 508         break;
 509         }
 510 #endif
 511       cmOStringStream e;
 512       e << "Unknown ELF file type " << eti;
 513       this->SetErrorMessage(e.str().c_str());
 514       return;
 515       }
 516     }
 517
 518   // Load the section headers.
 519   this->SectionHeaders.resize(this->ELFHeader.e_shnum);
 520   for(ELF_Half i=0; i < this->ELFHeader.e_shnum; ++i)
 521     {
 522     if(!this->LoadSectionHeader(i))
 523       {
 524       this->SetErrorMessage("Failed to load section headers.");
 525       return;
 526       }
 527     }
 528 }
 529
 530 //----------------------------------------------------------------------------
 531 template <class Types>
 532 bool cmELFInternalImpl<Types>::LoadDynamicSection()
 533 {
 534   // If there is no dynamic section we are done.
 535   if(this->DynamicSectionIndex < 0)
 536     {
 537     return false;
 538     }
 539
 540   // If the section was already loaded we are done.
 541   if(!this->DynamicSectionEntries.empty())
 542     {
 543     return true;
 544     }
 545
 546   // Allocate the dynamic section entries.
 547   ELF_Shdr const& sec = this->SectionHeaders[this->DynamicSectionIndex];
 548   int n = sec.sh_size / sec.sh_entsize;
 549   this->DynamicSectionEntries.resize(n);
 550
 551   // Read each entry.
 552   for(int j=0; j < n; ++j)
 553     {
 554     // Seek to the beginning of the section entry.
 555     this->Stream.seekg(sec.sh_offset + sec.sh_entsize*j);
 556     ELF_Dyn& dyn = this->DynamicSectionEntries[j];
 557
 558     // Try reading the entry.
 559     if(!this->Read(dyn))
 560       {
 561       this->SetErrorMessage("Error reading entry from DYNAMIC section.");
 562       this->DynamicSectionIndex = -1;
 563       return false;
 564       }
 565     }
 566   return true;
 567 }
 568
 569 //----------------------------------------------------------------------------
 570 template <class Types>
 571 unsigned int cmELFInternalImpl<Types>::GetDynamicEntryCount()
 572 {
 573   if(!this->LoadDynamicSection())
 574     {
 575     return 0;
 576     }
 577   for(unsigned int i = 0; i < this->DynamicSectionEntries.size(); ++i)
 578     {
 579     if(this->DynamicSectionEntries[i].d_tag == DT_NULL)
 580       {
 581       return i;
 582       }
 583     }
 584   return this->DynamicSectionEntries.size();
 585 }
 586
 587 //----------------------------------------------------------------------------
 588 template <class Types>
 589 unsigned long cmELFInternalImpl<Types>::GetDynamicEntryPosition(int j)
 590 {
 591   if(!this->LoadDynamicSection())
 592     {
 593     return 0;
 594     }
 595   if(j < 0 || j >= static_cast<int>(this->DynamicSectionEntries.size()))
 596     {
 597     return 0;
 598     }
 599   ELF_Shdr const& sec = this->SectionHeaders[this->DynamicSectionIndex];
 600   return sec.sh_offset + sec.sh_entsize*j;
 601 }
 602
 603 //----------------------------------------------------------------------------
 604 template <class Types>
 605 cmELF::StringEntry const*
 606 cmELFInternalImpl<Types>::GetDynamicSectionString(int tag)
 607 {
 608   // Short-circuit if already checked.
 609   std::map<int, StringEntry>::iterator dssi =
 610     this->DynamicSectionStrings.find(tag);
 611   if(dssi != this->DynamicSectionStrings.end())
 612     {
 613     if(dssi->second.Position > 0)
 614       {
 615       return &dssi->second;
 616       }
 617     return 0;
 618     }
 619
 620   // Create an entry for this tag.  Assume it is missing until found.
 621   StringEntry& se = this->DynamicSectionStrings[tag];
 622   se.Position = 0;
 623   se.Size = 0;
 624   se.IndexInSection = -1;
 625
 626   // Try reading the dynamic section.
 627   if(!this->LoadDynamicSection())
 628     {
 629     return 0;
 630     }
 631
 632   // Get the string table referenced by the DYNAMIC section.
 633   ELF_Shdr const& sec = this->SectionHeaders[this->DynamicSectionIndex];
 634   if(sec.sh_link >= this->SectionHeaders.size())
 635     {
 636     this->SetErrorMessage("Section DYNAMIC has invalid string table index.");
 637     return 0;
 638     }
 639   ELF_Shdr const& strtab = this->SectionHeaders[sec.sh_link];
 640
 641   // Look for the requested entry.
 642   for(typename std::vector<ELF_Dyn>::iterator
 643         di = this->DynamicSectionEntries.begin();
 644       di != this->DynamicSectionEntries.end(); ++di)
 645     {
 646     ELF_Dyn& dyn = *di;
 647     if(dyn.d_tag == tag)
 648       {
 649       // We found the tag requested.
 650       // Make sure the position given is within the string section.
 651       if(dyn.d_un.d_val >= strtab.sh_size)
 652         {
 653         this->SetErrorMessage("Section DYNAMIC references string beyond "
 654                               "the end of its string section.");
 655         return 0;
 656         }
 657
 658       // Seek to the position reported by the entry.
 659       unsigned long first = static_cast<unsigned long>(dyn.d_un.d_val);
 660       unsigned long last = first;
 661       unsigned long end = static_cast<unsigned long>(strtab.sh_size);
 662       this->Stream.seekg(strtab.sh_offset + first);
 663
 664       // Read the string.  It may be followed by more than one NULL
 665       // terminator.  Count the total size of the region allocated to
 666       // the string.  This assumes that the next string in the table
 667       // is non-empty, but the "chrpath" tool makes the same
 668       // assumption.
 669       bool terminated = false;
 670       char c;
 671       while(last != end && this->Stream.get(c) && !(terminated && c))
 672         {
 673         ++last;
 674         if(c)
 675           {
 676           se.Value += c;
 677           }
 678         else
 679           {
 680           terminated = true;
 681           }
 682         }
 683
 684       // Make sure the whole value was read.
 685       if(!this->Stream)
 686         {
 687         this->SetErrorMessage("Dynamic section specifies unreadable RPATH.");
 688         se.Value = "";
 689         return 0;
 690         }
 691
 692       // The value has been read successfully.  Report it.
 693       se.Position = static_cast<unsigned long>(strtab.sh_offset + first);
 694       se.Size = last - first;
 695       se.IndexInSection = di - this->DynamicSectionEntries.begin();
 696       return &se;
 697       }
 698     }
 699   return 0;
 700 }
 701
 702 //============================================================================
 703 // External class implementation.
 704
 705 //----------------------------------------------------------------------------
 706 cmELF::cmELF(const char* fname): Internal(0)
 707 {
 708   // Try to open the file.
 709   cmsys::auto_ptr<std::ifstream> fin(new std::ifstream(fname));
 710
 711   // Quit now if the file could not be opened.
 712   if(!fin.get() || !*fin)
 713     {
 714     this->ErrorMessage = "Error opening input file.";
 715     return;
 716     }
 717
 718   // Read the ELF identification block.
 719   char ident[EI_NIDENT];
 720   if(!fin->read(ident, EI_NIDENT))
 721     {
 722     this->ErrorMessage = "Error reading ELF identification.";
 723     return;
 724     }
 725   if(!fin->seekg(0))
 726     {
 727     this->ErrorMessage = "Error seeking to beginning of file.";
 728     return;
 729     }
 730
 731   // Verify the ELF identification.
 732   if(!(ident[EI_MAG0] == ELFMAG0 &&
 733        ident[EI_MAG1] == ELFMAG1 &&
 734        ident[EI_MAG2] == ELFMAG2 &&
 735        ident[EI_MAG3] == ELFMAG3))
 736     {
 737     this->ErrorMessage = "File does not have a valid ELF identification.";
 738     return;
 739     }
 740
 741   // Check the byte order in which the rest of the file is encoded.
 742   cmELFInternal::ByteOrderType order;
 743   if(ident[EI_DATA] == ELFDATA2LSB)
 744     {
 745     // File is LSB.
 746     order =  cmELFInternal::ByteOrderLSB;
 747     }
 748   else if(ident[EI_DATA] == ELFDATA2MSB)
 749     {
 750     // File is MSB.
 751     order =  cmELFInternal::ByteOrderMSB;
 752     }
 753   else
 754     {
 755     this->ErrorMessage = "ELF file is not LSB or MSB encoded.";
 756     return;
 757     }
 758
 759   // Check the class of the file and construct the corresponding
 760   // parser implementation.
 761   if(ident[EI_CLASS] == ELFCLASS32)
 762     {
 763     // 32-bit ELF
 764     this->Internal = new cmELFInternalImpl<cmELFTypes32>(this, fin, order);
 765     }
 766   else if(ident[EI_CLASS] == ELFCLASS64)
 767     {
 768     // 64-bit ELF
 769     this->Internal = new cmELFInternalImpl<cmELFTypes64>(this, fin, order);
 770     }
 771   else
 772     {
 773     this->ErrorMessage = "ELF file class is not 32-bit or 64-bit.";
 774     return;
 775     }
 776 }
 777
 778 //----------------------------------------------------------------------------
 779 cmELF::~cmELF()
 780 {
 781   delete this->Internal;
 782 }
 783
 784 //----------------------------------------------------------------------------
 785 bool cmELF::Valid() const
 786 {
 787   return this->Internal && this->Internal->GetFileType() != FileTypeInvalid;
 788 }
 789
 790 //----------------------------------------------------------------------------
 791 cmELF::FileType cmELF::GetFileType() const
 792 {
 793   if(this->Valid())
 794     {
 795     return this->Internal->GetFileType();
 796     }
 797   else
 798     {
 799     return FileTypeInvalid;
 800     }
 801 }
 802
 803 //----------------------------------------------------------------------------
 804 unsigned int cmELF::GetNumberOfSections() const
 805 {
 806   if(this->Valid())
 807     {
 808     return this->Internal->GetNumberOfSections();
 809     }
 810   else
 811     {
 812     return 0;
 813     }
 814 }
 815
 816 //----------------------------------------------------------------------------
 817 unsigned int cmELF::GetDynamicEntryCount() const
 818 {
 819   if(this->Valid())
 820     {
 821     return this->Internal->GetDynamicEntryCount();
 822     }
 823   else
 824     {
 825     return 0;
 826     }
 827 }
 828
 829 //----------------------------------------------------------------------------
 830 unsigned long cmELF::GetDynamicEntryPosition(int index) const
 831 {
 832   if(this->Valid())
 833     {
 834     return this->Internal->GetDynamicEntryPosition(index);
 835     }
 836   else
 837     {
 838     return 0;
 839     }
 840 }
 841
 842 //----------------------------------------------------------------------------
 843 bool cmELF::ReadBytes(unsigned long pos, unsigned long size, char* buf) const
 844 {
 845   if(this->Valid())
 846     {
 847     return this->Internal->ReadBytes(pos, size, buf);
 848     }
 849   else
 850     {
 851     return false;
 852     }
 853 }
 854
 855 //----------------------------------------------------------------------------
 856 bool cmELF::GetSOName(std::string& soname)
 857 {
 858   if(StringEntry const* se = this->GetSOName())
 859     {
 860     soname = se->Value;
 861     return true;
 862     }
 863   else
 864     {
 865     return false;
 866     }
 867 }
 868
 869 //----------------------------------------------------------------------------
 870 cmELF::StringEntry const* cmELF::GetSOName()
 871 {
 872   if(this->Valid() &&
 873      this->Internal->GetFileType() == cmELF::FileTypeSharedLibrary)
 874     {
 875     return this->Internal->GetSOName();
 876     }
 877   else
 878     {
 879     return 0;
 880     }
 881 }
 882
 883 //----------------------------------------------------------------------------
 884 cmELF::StringEntry const* cmELF::GetRPath()
 885 {
 886   if(this->Valid() &&
 887      (this->Internal->GetFileType() == cmELF::FileTypeExecutable ||
 888       this->Internal->GetFileType() == cmELF::FileTypeSharedLibrary))
 889     {
 890     return this->Internal->GetRPath();
 891     }
 892   else
 893     {
 894     return 0;
 895     }
 896 }
 897
 898 //----------------------------------------------------------------------------
 899 cmELF::StringEntry const* cmELF::GetRunPath()
 900 {
 901   if(this->Valid() &&
 902      (this->Internal->GetFileType() == cmELF::FileTypeExecutable ||
 903       this->Internal->GetFileType() == cmELF::FileTypeSharedLibrary))
 904     {
 905     return this->Internal->GetRunPath();
 906     }
 907   else
 908     {
 909     return 0;
 910     }
 911 }
 912
 913 //----------------------------------------------------------------------------
 914 void cmELF::PrintInfo(std::ostream& os) const
 915 {
 916   if(this->Valid())
 917     {
 918     this->Internal->PrintInfo(os);
 919     }
 920   else
 921     {
 922     os << "Not a valid ELF file.\n";
 923     }
 924 }