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 // Copyright (c) 2011 Google Inc.

 // All rights reserved.

 //

 // Redistribution and use in source and binary forms, with or without

 // modification, are permitted provided that the following conditions are

 // met:

 //

 //     * Redistributions of source code must retain the above copyright

 // notice, this list of conditions and the following disclaimer.

 //     * Redistributions in binary form must reproduce the above

 // copyright notice, this list of conditions and the following disclaimer

 // in the documentation and/or other materials provided with the

 // distribution.

 //     * Neither the name of Google Inc. nor the names of its

 // contributors may be used to endorse or promote products derived from

 // this software without specific prior written permission.

 //

 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 // Restructured in 2009 by: Jim Blandy <jimb@mozilla.com> <jimb@red-bean.com>

 // dump_symbols.cc: implement google_breakpad::WriteSymbolFile:

 // Find all the debugging info in a file and dump it as a Breakpad symbol file.

 #include "common/linux/dump_symbols.h"

 #include <assert.h>

 #include <elf.h>

 #include <errno.h>

 #include <fcntl.h>

 #include <link.h>

 #include <stdio.h>

 #include <stdlib.h>

 #include <string.h>

 #include <sys/mman.h>

 #include <sys/stat.h>

 #include <unistd.h>

 #include <iostream>

 #include <set>

 #include <string>

 #include <utility>

 #include <vector>

 #include "common/arm_ex_reader.h"

 #include "common/dwarf/bytereader-inl.h"

 #include "common/dwarf/dwarf2diehandler.h"

 #include "common/dwarf_cfi_to_module.h"

 #include "common/dwarf_cu_to_module.h"

 #include "common/dwarf_line_to_module.h"

 #include "common/linux/elfutils.h"

 #include "common/linux/elfutils-inl.h"

 #include "common/linux/elf_symbols_to_module.h"

 #include "common/linux/file_id.h"

 #include "common/module.h"

 #include "common/scoped_ptr.h"

 #ifndef NO_STABS_SUPPORT

 #include "common/stabs_reader.h"

 #include "common/stabs_to_module.h"

 #endif

 #include "common/using_std_string.h"

 #include "common/logging.h"

 #ifndef SHT_ARM_EXIDX

 // bionic and older glibc don't define it

 # define SHT_ARM_EXIDX (SHT_LOPROC + 1)

 #endif

 // This namespace contains helper functions.

 namespace {

 using google_breakpad::DwarfCFIToModule;

 using google_breakpad::DwarfCUToModule;

 using google_breakpad::DwarfLineToModule;

 using google_breakpad::ElfClass;

 using google_breakpad::ElfClass32;

 using google_breakpad::ElfClass64;

 using google_breakpad::FindElfSectionByName;

 using google_breakpad::GetOffset;

 using google_breakpad::IsValidElf;

 using google_breakpad::Module;

 #ifndef NO_STABS_SUPPORT

 using google_breakpad::StabsToModule;

 #endif

 using google_breakpad::UniqueString;

 using google_breakpad::scoped_ptr;

 //

 // FDWrapper

 //

 // Wrapper class to make sure opened file is closed.

 //

 class FDWrapper {

  public:

   explicit FDWrapper(int fd) :

     fd_(fd) {}

   ~FDWrapper() {

     if (fd_ != -1)

       close(fd_);

   }

   int get() {

     return fd_;

   }

   int release() {

     int fd = fd_;

     fd_ = -1;

     return fd;

   }

  private:

   int fd_;

 };

 //

 // MmapWrapper

 //

 // Wrapper class to make sure mapped regions are unmapped.

 //

 class MmapWrapper {

  public:

   MmapWrapper() : is_set_(false) {}

   ~MmapWrapper() {

     if (is_set_ && base_ != NULL) {

       assert(size_ > 0);

       munmap(base_, size_);

     }

   }

   void set(void *mapped_address, size_t mapped_size) {

     is_set_ = true;

     base_ = mapped_address;

     size_ = mapped_size;

   }

   void release() {

     assert(is_set_);

     is_set_ = false;

     base_ = NULL;

     size_ = 0;

   }

  private:

   bool is_set_;

   void *base_;

   size_t size_;

 };

 // Find the preferred loading address of the binary.

 template<typename ElfClass>

 typename ElfClass::Addr GetLoadingAddress(

     const typename ElfClass::Phdr* program_headers,

     int nheader) {

   typedef typename ElfClass::Phdr Phdr;

   for (int i = 0; i < nheader; ++i) {

     const Phdr& header = program_headers[i];

     // For executable, it is the PT_LOAD segment with offset to zero.

     if (header.p_type == PT_LOAD &&

         header.p_offset == 0)

       return header.p_vaddr;

   }

   // For other types of ELF, return 0.

   return 0;

 }

 #ifndef NO_STABS_SUPPORT

 template<typename ElfClass>

 bool LoadStabs(const typename ElfClass::Ehdr* elf_header,

                const typename ElfClass::Shdr* stab_section,

                const typename ElfClass::Shdr* stabstr_section,

                const bool big_endian,

                Module* module) {

   // A callback object to handle data from the STABS reader.

   StabsToModule handler(module);

   // Find the addresses of the STABS data, and create a STABS reader object.

   // On Linux, STABS entries always have 32-bit values, regardless of the

   // address size of the architecture whose code they're describing, and

   // the strings are always "unitized".

   const uint8_t* stabs =

       GetOffset<ElfClass, uint8_t>(elf_header, stab_section->sh_offset);

   const uint8_t* stabstr =

       GetOffset<ElfClass, uint8_t>(elf_header, stabstr_section->sh_offset);

   google_breakpad::StabsReader reader(stabs, stab_section->sh_size,

                                       stabstr, stabstr_section->sh_size,

                                       big_endian, 4, true, &handler);

   // Read the STABS data, and do post-processing.

   if (!reader.Process())

     return false;

   handler.Finalize();

   return true;

 }

 #endif  // NO_STABS_SUPPORT

 // A line-to-module loader that accepts line number info parsed by

 // dwarf2reader::LineInfo and populates a Module and a line vector

 // with the results.

 class DumperLineToModule: public DwarfCUToModule::LineToModuleHandler {

  public:

   // Create a line-to-module converter using BYTE_READER.

   explicit DumperLineToModule(dwarf2reader::ByteReader *byte_reader)

       : byte_reader_(byte_reader) { }

   void StartCompilationUnit(const string& compilation_dir) {

     compilation_dir_ = compilation_dir;

   }

   void ReadProgram(const char *program, uint64 length,

                    Module *module, std::vector<Module::Line> *lines) {

     DwarfLineToModule handler(module, compilation_dir_, lines);

     dwarf2reader::LineInfo parser(program, length, byte_reader_, &handler);

     parser.Start();

   }

  private:

   string compilation_dir_;

   dwarf2reader::ByteReader *byte_reader_;

 };

 template<typename ElfClass>

 bool LoadDwarf(const string& dwarf_filename,

                const typename ElfClass::Ehdr* elf_header,

                const bool big_endian,

                Module* module) {

   typedef typename ElfClass::Shdr Shdr;

   const dwarf2reader::Endianness endianness = big_endian ?

       dwarf2reader::ENDIANNESS_BIG : dwarf2reader::ENDIANNESS_LITTLE;

   dwarf2reader::ByteReader byte_reader(endianness);

   // Construct a context for this file.

   DwarfCUToModule::FileContext file_context(dwarf_filename, module);

   // Build a map of the ELF file's sections.

   const Shdr* sections =

       GetOffset<ElfClass, Shdr>(elf_header, elf_header->e_shoff);

   int num_sections = elf_header->e_shnum;

   const Shdr* section_names = sections + elf_header->e_shstrndx;

   for (int i = 0; i < num_sections; i++) {

     const Shdr* section = &sections[i];

     string name = GetOffset<ElfClass, char>(elf_header,

                                             section_names->sh_offset) +

                   section->sh_name;

     const char* contents = GetOffset<ElfClass, char>(elf_header,

                                                      section->sh_offset);

     uint64 length = section->sh_size;

     file_context.section_map[name] = std::make_pair(contents, length);

   }

   // Parse all the compilation units in the .debug_info section.

   DumperLineToModule line_to_module(&byte_reader);

   std::pair<const char *, uint64> debug_info_section

       = file_context.section_map[".debug_info"];

   // This should never have been called if the file doesn't have a

   // .debug_info section.

   assert(debug_info_section.first);

   uint64 debug_info_length = debug_info_section.second;

   for (uint64 offset = 0; offset < debug_info_length;) {

     // Make a handler for the root DIE that populates MODULE with the

     // data that was found.

     DwarfCUToModule::WarningReporter reporter(dwarf_filename, offset);

     DwarfCUToModule root_handler(&file_context, &line_to_module, &reporter);

     // Make a Dwarf2Handler that drives the DIEHandler.

     dwarf2reader::DIEDispatcher die_dispatcher(&root_handler);

     // Make a DWARF parser for the compilation unit at OFFSET.

     dwarf2reader::CompilationUnit reader(file_context.section_map,

                                          offset,

                                          &byte_reader,

                                          &die_dispatcher);

     // Process the entire compilation unit; get the offset of the next.

     offset += reader.Start();

   }

   return true;

 }

 // Fill REGISTER_NAMES with the register names appropriate to the

 // machine architecture given in HEADER, indexed by the register

 // numbers used in DWARF call frame information. Return true on

 // success, or false if HEADER's machine architecture is not

 // supported.

 template<typename ElfClass>

 bool DwarfCFIRegisterNames(const typename ElfClass::Ehdr* elf_header,

                            std::vector<const UniqueString*>* register_names) {

   switch (elf_header->e_machine) {

     case EM_386:

       *register_names = DwarfCFIToModule::RegisterNames::I386();

       return true;

     case EM_ARM:

       *register_names = DwarfCFIToModule::RegisterNames::ARM();

       return true;

     case EM_X86_64:

       *register_names = DwarfCFIToModule::RegisterNames::X86_64();

       return true;

     default:

       return false;

   }

 }

 template<typename ElfClass>

 bool LoadDwarfCFI(const string& dwarf_filename,

                   const typename ElfClass::Ehdr* elf_header,

                   const char* section_name,

                   const typename ElfClass::Shdr* section,

                   const bool eh_frame,

                   const typename ElfClass::Shdr* got_section,

                   const typename ElfClass::Shdr* text_section,

                   const bool big_endian,

                   Module* module) {

   // Find the appropriate set of register names for this file's

   // architecture.

   std::vector<const UniqueString*> register_names;

   if (!DwarfCFIRegisterNames<ElfClass>(elf_header, &register_names)) {

     fprintf(stderr, "%s: unrecognized ELF machine architecture '%d';"

             " cannot convert DWARF call frame information\n",

             dwarf_filename.c_str(), elf_header->e_machine);

     return false;

   }

   const dwarf2reader::Endianness endianness = big_endian ?

       dwarf2reader::ENDIANNESS_BIG : dwarf2reader::ENDIANNESS_LITTLE;

   // Find the call frame information and its size.

   const char* cfi =

       GetOffset<ElfClass, char>(elf_header, section->sh_offset);

   size_t cfi_size = section->sh_size;

   // Plug together the parser, handler, and their entourages.

   DwarfCFIToModule::Reporter module_reporter(dwarf_filename, section_name);

   DwarfCFIToModule handler(module, register_names, &module_reporter);

   dwarf2reader::ByteReader byte_reader(endianness);

   byte_reader.SetAddressSize(ElfClass::kAddrSize);

   // Provide the base addresses for .eh_frame encoded pointers, if

   // possible.

   byte_reader.SetCFIDataBase(section->sh_addr, cfi);

   if (got_section)

     byte_reader.SetDataBase(got_section->sh_addr);

   if (text_section)

     byte_reader.SetTextBase(text_section->sh_addr);

   dwarf2reader::CallFrameInfo::Reporter dwarf_reporter(dwarf_filename,

                                                        section_name);

   dwarf2reader::CallFrameInfo parser(cfi, cfi_size,

                                      &byte_reader, &handler, &dwarf_reporter,

                                      eh_frame);

   parser.Start();

   return true;

 }

 template<typename ElfClass>

 bool LoadARMexidx(const typename ElfClass::Ehdr* elf_header,

                   const typename ElfClass::Shdr* exidx_section,

                   const typename ElfClass::Shdr* extab_section,

                   uint32_t loading_addr,

                   Module* module) {

   // To do this properly we need to know:

   // * the bounds of the .ARM.exidx section in the mapped image

   // * the bounds of the .ARM.extab section in the mapped image

   // * the vma of the last byte in the text section associated with the .exidx

   // The first two are easy.  The third is a bit tricky.  If we can't

   // figure out what it is, just pass in zero.

   const char *exidx_img

     = GetOffset<ElfClass, char>(elf_header, exidx_section->sh_offset);

   size_t exidx_size = exidx_section->sh_size;

   const char *extab_img

     = GetOffset<ElfClass, char>(elf_header, extab_section->sh_offset);

   size_t extab_size = extab_section->sh_size;

   // The sh_link field of the exidx section gives the section number

   // for the associated text section.

   uint32_t exidx_text_last_svma = 0;

   int exidx_text_sno = exidx_section->sh_link;

   typedef typename ElfClass::Shdr Shdr;

   // |sections| points to the section header table

   const Shdr* sections

     = GetOffset<ElfClass, Shdr>(elf_header, elf_header->e_shoff);

   const int num_sections = elf_header->e_shnum;

   if (exidx_text_sno >= 0 && exidx_text_sno < num_sections) {

     const Shdr* exidx_text_shdr = &sections[exidx_text_sno];

     if (exidx_text_shdr->sh_size > 0) {

       exidx_text_last_svma

         = exidx_text_shdr->sh_addr + exidx_text_shdr->sh_size - 1;

     }

   }

   arm_ex_to_module::ARMExToModule handler(module);

   arm_ex_reader::ExceptionTableInfo

     parser(exidx_img, exidx_size, extab_img, extab_size, exidx_text_last_svma,

            &handler,

            reinterpret_cast<const char*>(elf_header),

            loading_addr);

   parser.Start();

   return true;

 }

 bool LoadELF(const string& obj_file, MmapWrapper* map_wrapper,

              void** elf_header) {

   int obj_fd = open(obj_file.c_str(), O_RDONLY);

   if (obj_fd < 0) {

     fprintf(stderr, "Failed to open ELF file '%s': %s\n",

             obj_file.c_str(), strerror(errno));

     return false;

   }

   FDWrapper obj_fd_wrapper(obj_fd);

   struct stat st;

   if (fstat(obj_fd, &st) != 0 && st.st_size <= 0) {

     fprintf(stderr, "Unable to fstat ELF file '%s': %s\n",

             obj_file.c_str(), strerror(errno));

     return false;

   }

   void *obj_base = mmap(NULL, st.st_size,

                         PROT_READ | PROT_WRITE, MAP_PRIVATE, obj_fd, 0);

   if (obj_base == MAP_FAILED) {

     fprintf(stderr, "Failed to mmap ELF file '%s': %s\n",

             obj_file.c_str(), strerror(errno));

     return false;

   }

   map_wrapper->set(obj_base, st.st_size);

   *elf_header = obj_base;

   if (!IsValidElf(*elf_header)) {

     fprintf(stderr, "Not a valid ELF file: %s\n", obj_file.c_str());

     return false;

   }

   return true;

 }

 // Get the endianness of ELF_HEADER. If it's invalid, return false.

 template<typename ElfClass>

 bool ElfEndianness(const typename ElfClass::Ehdr* elf_header,

                    bool* big_endian) {

   if (elf_header->e_ident[EI_DATA] == ELFDATA2LSB) {

     *big_endian = false;

     return true;

   }

   if (elf_header->e_ident[EI_DATA] == ELFDATA2MSB) {

     *big_endian = true;

     return true;

   }

   fprintf(stderr, "bad data encoding in ELF header: %d\n",

           elf_header->e_ident[EI_DATA]);

   return false;

 }

 // Read the .gnu_debuglink and get the debug file name. If anything goes

 // wrong, return an empty string.

 template<typename ElfClass>

 string ReadDebugLink(const char* debuglink,

                      size_t debuglink_size,

                      const string& obj_file,

                      const std::vector<string>& debug_dirs) {

   size_t debuglink_len = strlen(debuglink) + 5;  // '\0' + CRC32.

   debuglink_len = 4 * ((debuglink_len + 3) / 4);  // Round to nearest 4 bytes.

   // Sanity check.

   if (debuglink_len != debuglink_size) {

     fprintf(stderr, "Mismatched .gnu_debuglink string / section size: "

             "%zx %zx\n", debuglink_len, debuglink_size);

     return "";

   }

   bool found = false;

   int debuglink_fd = -1;

   string debuglink_path;

   std::vector<string>::const_iterator it;

   for (it = debug_dirs.begin(); it < debug_dirs.end(); ++it) {

     const string& debug_dir = *it;

     debuglink_path = debug_dir + "/" + debuglink;

     debuglink_fd = open(debuglink_path.c_str(), O_RDONLY);

     if (debuglink_fd >= 0) {

       found = true;

       break;

     }

   }

   if (!found) {

     fprintf(stderr, "Failed to find debug ELF file for '%s' after trying:\n",

             obj_file.c_str());

     for (it = debug_dirs.begin(); it < debug_dirs.end(); ++it) {

       const string debug_dir = *it;

       fprintf(stderr, "  %s/%s\n", debug_dir.c_str(), debuglink);

     }

     return "";

   }

   FDWrapper debuglink_fd_wrapper(debuglink_fd);

   // TODO(thestig) check the CRC-32 at the end of the .gnu_debuglink

   // section.

   return debuglink_path;

 }

 //

 // LoadSymbolsInfo

 //

 // Holds the state between the two calls to LoadSymbols() in case it's necessary

 // to follow the .gnu_debuglink section and load debug information from a

 // different file.

 //

 template<typename ElfClass>

 class LoadSymbolsInfo {

  public:

   typedef typename ElfClass::Addr Addr;

   explicit LoadSymbolsInfo(const std::vector<string>& dbg_dirs) :

     debug_dirs_(dbg_dirs),

     has_loading_addr_(false) {}

   // Keeps track of which sections have been loaded so sections don't

   // accidentally get loaded twice from two different files.

   void LoadedSection(const string &section) {

     if (loaded_sections_.count(section) == 0) {

       loaded_sections_.insert(section);

     } else {

       fprintf(stderr, "Section %s has already been loaded.\n",

               section.c_str());

     }

   }

   // The ELF file and linked debug file are expected to have the same preferred

   // loading address.

   void set_loading_addr(Addr addr, const string &filename) {

     if (!has_loading_addr_) {

       loading_addr_ = addr;

       loaded_file_ = filename;

       return;

     }

     if (addr != loading_addr_) {

       fprintf(stderr,

               "ELF file '%s' and debug ELF file '%s' "

               "have different load addresses.\n",

               loaded_file_.c_str(), filename.c_str());

       assert(false);

     }

   }

   // Setters and getters

   const std::vector<string>& debug_dirs() const {

     return debug_dirs_;

   }

   string debuglink_file() const {

     return debuglink_file_;

   }

   void set_debuglink_file(string file) {

     debuglink_file_ = file;

   }

  private:

   const std::vector<string>& debug_dirs_; // Directories in which to

                                           // search for the debug ELF file.

   string debuglink_file_;  // Full path to the debug ELF file.

   bool has_loading_addr_;  // Indicate if LOADING_ADDR_ is valid.

   Addr loading_addr_;  // Saves the preferred loading address from the

                        // first call to LoadSymbols().

   string loaded_file_;  // Name of the file loaded from the first call to

                         // LoadSymbols().

   std::set<string> loaded_sections_;  // Tracks the Loaded ELF sections

                                       // between calls to LoadSymbols().

 };

 template<typename ElfClass>

 bool LoadSymbols(const string& obj_file,

                  const bool big_endian,

                  const typename ElfClass::Ehdr* elf_header,

                  const bool read_gnu_debug_link,

                  LoadSymbolsInfo<ElfClass>* info,

                  SymbolData symbol_data,

                  Module* module) {

   typedef typename ElfClass::Addr Addr;

   typedef typename ElfClass::Phdr Phdr;

   typedef typename ElfClass::Shdr Shdr;

   BPLOG(INFO) << "";

   BPLOG(INFO) << "LoadSymbols: BEGIN   " << obj_file;

   Addr loading_addr = GetLoadingAddress<ElfClass>(

       GetOffset<ElfClass, Phdr>(elf_header, elf_header->e_phoff),

       elf_header->e_phnum);

   module->SetLoadAddress(loading_addr);

   info->set_loading_addr(loading_addr, obj_file);

   const Shdr* sections =

       GetOffset<ElfClass, Shdr>(elf_header, elf_header->e_shoff);

   const Shdr* section_names = sections + elf_header->e_shstrndx;

   const char* names =

       GetOffset<ElfClass, char>(elf_header, section_names->sh_offset);

   const char *names_end = names + section_names->sh_size;

   bool found_debug_info_section = false;

   bool found_usable_info = false;

   if (symbol_data != ONLY_CFI) {

 #ifndef NO_STABS_SUPPORT

     // Look for STABS debugging information, and load it if present.

     const Shdr* stab_section =

       FindElfSectionByName<ElfClass>(".stab", SHT_PROGBITS,

                                      sections, names, names_end,

                                      elf_header->e_shnum);

     if (stab_section) {

       const Shdr* stabstr_section = stab_section->sh_link + sections;

       if (stabstr_section) {

         found_debug_info_section = true;

         found_usable_info = true;

         info->LoadedSection(".stab");

         if (!LoadStabs<ElfClass>(elf_header, stab_section, stabstr_section,

                                  big_endian, module)) {

           fprintf(stderr, "%s: \".stab\" section found, but failed to load"

                   " STABS debugging information\n", obj_file.c_str());

         }

       }

     }

 #endif  // NO_STABS_SUPPORT

     // Look for DWARF debugging information, and load it if present.

     const Shdr* dwarf_section =

       FindElfSectionByName<ElfClass>(".debug_info", SHT_PROGBITS,

                                      sections, names, names_end,

                                      elf_header->e_shnum);

     if (dwarf_section) {

       found_debug_info_section = true;

       found_usable_info = true;

       info->LoadedSection(".debug_info");

       if (!LoadDwarf<ElfClass>(obj_file, elf_header, big_endian, module))

         fprintf(stderr, "%s: \".debug_info\" section found, but failed to load "

                 "DWARF debugging information\n", obj_file.c_str());

     }

   }

   if (symbol_data != NO_CFI) {

     // Dwarf Call Frame Information (CFI) is actually independent from

     // the other DWARF debugging information, and can be used alone.

     const Shdr* dwarf_cfi_section =

         FindElfSectionByName<ElfClass>(".debug_frame", SHT_PROGBITS,

                                        sections, names, names_end,

                                        elf_header->e_shnum);

     if (dwarf_cfi_section) {

       // Ignore the return value of this function; even without call frame

       // information, the other debugging information could be perfectly

       // useful.

       info->LoadedSection(".debug_frame");

       bool result =

           LoadDwarfCFI<ElfClass>(obj_file, elf_header, ".debug_frame",

                                  dwarf_cfi_section, false, 0, 0, big_endian,

                                  module);

       found_usable_info = found_usable_info || result;

       if (result)

         BPLOG(INFO) << "LoadSymbols:   read CFI from .debug_frame";

     }

     // Linux C++ exception handling information can also provide

     // unwinding data.

     const Shdr* eh_frame_section =

         FindElfSectionByName<ElfClass>(".eh_frame", SHT_PROGBITS,

                                        sections, names, names_end,

                                        elf_header->e_shnum);

     if (eh_frame_section) {

       // Pointers in .eh_frame data may be relative to the base addresses of

       // certain sections. Provide those sections if present.

       const Shdr* got_section =

           FindElfSectionByName<ElfClass>(".got", SHT_PROGBITS,

                                          sections, names, names_end,

                                          elf_header->e_shnum);

       const Shdr* text_section =

           FindElfSectionByName<ElfClass>(".text", SHT_PROGBITS,

                                          sections, names, names_end,

                                          elf_header->e_shnum);

       info->LoadedSection(".eh_frame");

       // As above, ignore the return value of this function.

       bool result =

           LoadDwarfCFI<ElfClass>(obj_file, elf_header, ".eh_frame",

                                  eh_frame_section, true,

                                  got_section, text_section, big_endian, module);

       found_usable_info = found_usable_info || result;

       if (result)

         BPLOG(INFO) << "LoadSymbols:   read CFI from .eh_frame";

     }

   }

   // ARM has special unwind tables that can be used.

   const Shdr* arm_exidx_section =

       FindElfSectionByName<ElfClass>(".ARM.exidx", SHT_ARM_EXIDX,

                                      sections, names, names_end,

                                      elf_header->e_shnum);

   const Shdr* arm_extab_section =

       FindElfSectionByName<ElfClass>(".ARM.extab", SHT_PROGBITS,

                                      sections, names, names_end,

                                      elf_header->e_shnum);

   // Only load information from this section if there isn't a .debug_info

   // section.

   if (!found_debug_info_section

       && arm_exidx_section && arm_extab_section && symbol_data != NO_CFI) {

     info->LoadedSection(".ARM.exidx");

     info->LoadedSection(".ARM.extab");

     bool result = LoadARMexidx<ElfClass>(elf_header,

                                          arm_exidx_section, arm_extab_section,

                                          loading_addr, module);

     found_usable_info = found_usable_info || result;

     if (result)

       BPLOG(INFO) << "LoadSymbols:   read EXIDX from .ARM.{exidx,extab}";

   }

   if (!found_debug_info_section && symbol_data != ONLY_CFI) {

     fprintf(stderr, "%s: file contains no debugging information"

             " (no \".stab\" or \".debug_info\" sections)\n",

             obj_file.c_str());

     // Failed, but maybe there's a .gnu_debuglink section?

     if (read_gnu_debug_link) {

       const Shdr* gnu_debuglink_section

           = FindElfSectionByName<ElfClass>(".gnu_debuglink", SHT_PROGBITS,

                                            sections, names,

                                            names_end, elf_header->e_shnum);

       if (gnu_debuglink_section) {

         if (!info->debug_dirs().empty()) {

           const char* debuglink_contents =

               GetOffset<ElfClass, char>(elf_header,

                                         gnu_debuglink_section->sh_offset);

           string debuglink_file

               = ReadDebugLink<ElfClass>(debuglink_contents,

                                         gnu_debuglink_section->sh_size,

                                         obj_file, info->debug_dirs());

           info->set_debuglink_file(debuglink_file);

         } else {

           fprintf(stderr, ".gnu_debuglink section found in '%s', "

                   "but no debug path specified.\n", obj_file.c_str());

         }

       } else {

         fprintf(stderr, "%s does not contain a .gnu_debuglink section.\n",

                 obj_file.c_str());

       }

     } else {

       if (symbol_data != ONLY_CFI) {

         // The caller doesn't want to consult .gnu_debuglink.

         // See if there are export symbols available.

         const Shdr* dynsym_section =

           FindElfSectionByName<ElfClass>(".dynsym", SHT_DYNSYM,

                                          sections, names, names_end,

                                          elf_header->e_shnum);

         const Shdr* dynstr_section =

           FindElfSectionByName<ElfClass>(".dynstr", SHT_STRTAB,

                                          sections, names, names_end,

                                          elf_header->e_shnum);

         if (dynsym_section && dynstr_section) {

           info->LoadedSection(".dynsym");

           const uint8_t* dynsyms =

               GetOffset<ElfClass, uint8_t>(elf_header,

                                            dynsym_section->sh_offset);

           const uint8_t* dynstrs =

               GetOffset<ElfClass, uint8_t>(elf_header,

                                            dynstr_section->sh_offset);

           bool result =

               ELFSymbolsToModule(dynsyms,

                                  dynsym_section->sh_size,

                                  dynstrs,

                                  dynstr_section->sh_size,

                                  big_endian,

                                  ElfClass::kAddrSize,

                                  module);

           found_usable_info = found_usable_info || result;

         }

       }

       // Return true if some usable information was found, since

       // the caller doesn't want to use .gnu_debuglink.

       BPLOG(INFO) << "LoadSymbols: " 

                   << (found_usable_info ? "SUCCESS " : "FAILURE ")

                   << obj_file;

       return found_usable_info;

     }

     // No debug info was found, let the user try again with .gnu_debuglink

     // if present.

     BPLOG(INFO) << "LoadSymbols: FAILURE " << obj_file;

     return false;

   }

   BPLOG(INFO) << "LoadSymbols: SUCCESS " << obj_file;

   return true;

 }

 // Return the breakpad symbol file identifier for the architecture of

 // ELF_HEADER.

 template<typename ElfClass>

 const char* ElfArchitecture(const typename ElfClass::Ehdr* elf_header) {

   typedef typename ElfClass::Half Half;

   Half arch = elf_header->e_machine;

   switch (arch) {

     case EM_386:        return "x86";

     case EM_ARM:        return "arm";

     case EM_MIPS:       return "mips";

     case EM_PPC64:      return "ppc64";

     case EM_PPC:        return "ppc";

     case EM_S390:       return "s390";

     case EM_SPARC:      return "sparc";

     case EM_SPARCV9:    return "sparcv9";

     case EM_X86_64:     return "x86_64";

     default: return NULL;

   }

 }

 // Format the Elf file identifier in IDENTIFIER as a UUID with the

 // dashes removed.

 string FormatIdentifier(unsigned char identifier[16]) {

   char identifier_str[40];

   google_breakpad::FileID::ConvertIdentifierToString(

       identifier,

       identifier_str,

       sizeof(identifier_str));

   string id_no_dash;

   for (int i = 0; identifier_str[i] != '\0'; ++i)

     if (identifier_str[i] != '-')

       id_no_dash += identifier_str[i];

   // Add an extra "0" by the end.  PDB files on Windows have an 'age'

   // number appended to the end of the file identifier; this isn't

   // really used or necessary on other platforms, but be consistent.

   id_no_dash += '0';

   return id_no_dash;

 }

 // Return the non-directory portion of FILENAME: the portion after the

 // last slash, or the whole filename if there are no slashes.

 string BaseFileName(const string &filename) {

   // Lots of copies!  basename's behavior is less than ideal.

   char *c_filename = strdup(filename.c_str());

   string base = basename(c_filename);

   free(c_filename);

   return base;

 }

 template<typename ElfClass>

 bool ReadSymbolDataElfClass(const typename ElfClass::Ehdr* elf_header,

                              const string& obj_filename,

                              const std::vector<string>& debug_dirs,

                              SymbolData symbol_data,

                              Module** out_module) {

   typedef typename ElfClass::Ehdr Ehdr;

   typedef typename ElfClass::Shdr Shdr;

   *out_module = NULL;

   unsigned char identifier[16];

   if (!google_breakpad::FileID::ElfFileIdentifierFromMappedFile(elf_header,

                                                                 identifier)) {

     fprintf(stderr, "%s: unable to generate file identifier\n",

             obj_filename.c_str());

     return false;

   }

   const char *architecture = ElfArchitecture<ElfClass>(elf_header);

   if (!architecture) {

     fprintf(stderr, "%s: unrecognized ELF machine architecture: %d\n",

             obj_filename.c_str(), elf_header->e_machine);

     return false;

   }

   // Figure out what endianness this file is.

   bool big_endian;

   if (!ElfEndianness<ElfClass>(elf_header, &big_endian))

     return false;

   string name = BaseFileName(obj_filename);

   string os = "Linux";

   string id = FormatIdentifier(identifier);

   LoadSymbolsInfo<ElfClass> info(debug_dirs);

   scoped_ptr<Module> module(new Module(name, os, architecture, id));

   if (!LoadSymbols<ElfClass>(obj_filename, big_endian, elf_header,

                              !debug_dirs.empty(), &info,

                              symbol_data, module.get())) {

     const string debuglink_file = info.debuglink_file();

     if (debuglink_file.empty())

       return false;

     // Load debuglink ELF file.

     fprintf(stderr, "Found debugging info in %s\n", debuglink_file.c_str());

     MmapWrapper debug_map_wrapper;

     Ehdr* debug_elf_header = NULL;

     if (!LoadELF(debuglink_file, &debug_map_wrapper,

                  reinterpret_cast<void**>(&debug_elf_header)))

       return false;

     // Sanity checks to make sure everything matches up.

     const char *debug_architecture =

         ElfArchitecture<ElfClass>(debug_elf_header);

     if (!debug_architecture) {

       fprintf(stderr, "%s: unrecognized ELF machine architecture: %d\n",

               debuglink_file.c_str(), debug_elf_header->e_machine);

       return false;

     }

     if (strcmp(architecture, debug_architecture)) {

       fprintf(stderr, "%s with ELF machine architecture %s does not match "

               "%s with ELF architecture %s\n",

               debuglink_file.c_str(), debug_architecture,

               obj_filename.c_str(), architecture);

       return false;

     }

     bool debug_big_endian;

     if (!ElfEndianness<ElfClass>(debug_elf_header, &debug_big_endian))

       return false;

     if (debug_big_endian != big_endian) {

       fprintf(stderr, "%s and %s does not match in endianness\n",

               obj_filename.c_str(), debuglink_file.c_str());

       return false;

     }

     if (!LoadSymbols<ElfClass>(debuglink_file, debug_big_endian,

                                debug_elf_header, false, &info,

                                symbol_data, module.get())) {

       return false;

     }

   }

   *out_module = module.release();

   return true;

 }

 }  // namespace

 namespace google_breakpad {

 // Not explicitly exported, but not static so it can be used in unit tests.

 bool ReadSymbolDataInternal(const uint8_t* obj_file,

                             const string& obj_filename,

                             const std::vector<string>& debug_dirs,

                             SymbolData symbol_data,

                             Module** module) {

   if (!IsValidElf(obj_file)) {

     fprintf(stderr, "Not a valid ELF file: %s\n", obj_filename.c_str());

     return false;

   }

   int elfclass = ElfClass(obj_file);

   if (elfclass == ELFCLASS32) {

     return ReadSymbolDataElfClass<ElfClass32>(

         reinterpret_cast<const Elf32_Ehdr*>(obj_file), obj_filename, debug_dirs,

         symbol_data, module);

   }

   if (elfclass == ELFCLASS64) {

     return ReadSymbolDataElfClass<ElfClass64>(

         reinterpret_cast<const Elf64_Ehdr*>(obj_file), obj_filename, debug_dirs,

         symbol_data, module);

   }

   return false;

 }

 bool WriteSymbolFile(const string &obj_file,

                      const std::vector<string>& debug_dirs,

                      SymbolData symbol_data,

                      std::ostream &sym_stream) {

   Module* module;

   if (!ReadSymbolData(obj_file, debug_dirs, symbol_data, &module))

     return false;

   bool result = module->Write(sym_stream, symbol_data);

   delete module;

   return result;

 }

 bool ReadSymbolData(const string& obj_file,

                     const std::vector<string>& debug_dirs,

                     SymbolData symbol_data,

                     Module** module) {

   MmapWrapper map_wrapper;

   void* elf_header = NULL;

   if (!LoadELF(obj_file, &map_wrapper, &elf_header))

     return false;

   return ReadSymbolDataInternal(reinterpret_cast<uint8_t*>(elf_header),

                                 obj_file, debug_dirs, symbol_data, module);

 }

 }  // namespace google_breakpad