Rework dump_symbols.cc using templates and traits classes to handle cross-word-size symbol dumping

R=mark at https://breakpad.appspot.com/393002/

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@987 4c0a9323-5329-0410-9bdc-e9ce6186880e

5 files changed, 371 insertions, 253 deletions

diff --git a/src/common/linux/dump_symbols.cc b/src/common/linux/dump_symbols.cc
index 019a3a6c..8ed78a87 100644
--- a/src/common/linux/dump_symbols.cc
+++ b/src/common/linux/dump_symbols.cc
@@ -57,6 +57,8 @@
 #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"
@@ -70,6 +72,12 @@ 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;
 using google_breakpad::StabsToModule;
 
@@ -130,24 +138,15 @@ class MmapWrapper {
   size_t size_;
 };
 
-
-// Fix offset into virtual address by adding the mapped base into offsets.
-// Make life easier when want to find something by offset.
-static void FixAddress(void *obj_base) {
-  ElfW(Addr) base = reinterpret_cast<ElfW(Addr)>(obj_base);
-  ElfW(Ehdr) *elf_header = static_cast<ElfW(Ehdr) *>(obj_base);
-  elf_header->e_phoff += base;
-  elf_header->e_shoff += base;
-  ElfW(Shdr) *sections = reinterpret_cast<ElfW(Shdr) *>(elf_header->e_shoff);
-  for (int i = 0; i < elf_header->e_shnum; ++i)
-    sections[i].sh_offset += base;
-}
-
 // Find the preferred loading address of the binary.
-static ElfW(Addr) GetLoadingAddress(const ElfW(Phdr) *program_headers,
-                                    int nheader) {
+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 ElfW(Phdr) &header = program_headers[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)
@@ -157,57 +156,22 @@ static ElfW(Addr) GetLoadingAddress(const ElfW(Phdr) *program_headers,
   return 0;
 }
 
-static bool IsValidElf(const ElfW(Ehdr) *elf_header) {
-  return memcmp(elf_header, ELFMAG, SELFMAG) == 0;
-}
-
-static const ElfW(Shdr) *FindSectionByName(const char *name,
-                                           const ElfW(Shdr) *sections,
-                                           const ElfW(Shdr) *section_names,
-                                           int nsection) {
-  assert(name != NULL);
-  assert(sections != NULL);
-  assert(nsection > 0);
-
-  int name_len = strlen(name);
-  if (name_len == 0)
-    return NULL;
-
-  // Find the end of the section name section, to make sure that
-  // comparisons don't run off the end of the section.
-  const char *names_end =
-    reinterpret_cast<char*>(section_names->sh_offset + section_names->sh_size);
-
-  for (int i = 0; i < nsection; ++i) {
-    const char *section_name =
-      reinterpret_cast<char*>(section_names->sh_offset + sections[i].sh_name);
-    if (names_end - section_name >= name_len + 1 &&
-        strcmp(name, section_name) == 0) {
-      if (sections[i].sh_type == SHT_NOBITS) {
-        fprintf(stderr,
-                "Section %s found, but ignored because type=SHT_NOBITS.\n",
-                name);
-        return NULL;
-      }
-      return sections + i;
-    }
-  }
-  return NULL;
-}
-
-static bool LoadStabs(const ElfW(Ehdr) *elf_header,
-                      const ElfW(Shdr) *stab_section,
-                      const ElfW(Shdr) *stabstr_section,
-                      const bool big_endian,
-                      Module *module) {
+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".
-  uint8_t *stabs = reinterpret_cast<uint8_t *>(stab_section->sh_offset);
-  uint8_t *stabstr = reinterpret_cast<uint8_t *>(stabstr_section->sh_offset);
+  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);
@@ -236,10 +200,13 @@ class DumperLineToModule: public DwarfCUToModule::LineToModuleFunctor {
   dwarf2reader::ByteReader *byte_reader_;
 };
 
-static bool LoadDwarf(const string &dwarf_filename,
-                      const ElfW(Ehdr) *elf_header,
-                      const bool big_endian,
-                      Module *module) {
+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);
@@ -248,15 +215,17 @@ static bool LoadDwarf(const string &dwarf_filename,
   DwarfCUToModule::FileContext file_context(dwarf_filename, module);
 
   // Build a map of the ELF file's sections.
-  const ElfW(Shdr) *sections
-      = reinterpret_cast<ElfW(Shdr) *>(elf_header->e_shoff);
+  const Shdr* sections =
+      GetOffset<ElfClass, Shdr>(elf_header, elf_header->e_shoff);
   int num_sections = elf_header->e_shnum;
-  const ElfW(Shdr) *section_names = sections + elf_header->e_shstrndx;
+  const Shdr* section_names = sections + elf_header->e_shstrndx;
   for (int i = 0; i < num_sections; i++) {
-    const ElfW(Shdr) *section = &sections[i];
-    string name = reinterpret_cast<const char *>(section_names->sh_offset +
-                                                 section->sh_name);
-    const char *contents = reinterpret_cast<const char *>(section->sh_offset);
+    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);
   }
@@ -265,16 +234,16 @@ static bool LoadDwarf(const string &dwarf_filename,
   DumperLineToModule line_to_module(&byte_reader);
   std::pair<const char *, uint64> debug_info_section
       = file_context.section_map[".debug_info"];
-  // We should never have been called if the file doesn't have a
+  // 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 we find.
+    // data that was found.
     DwarfCUToModule::WarningReporter reporter(dwarf_filename, offset);
     DwarfCUToModule root_handler(&file_context, &line_to_module, &reporter);
-    // Make a Dwarf2Handler that drives our DIEHandler.
+    // 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,
@@ -290,10 +259,11 @@ static bool LoadDwarf(const string &dwarf_filename,
 // 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 we don't recognize HEADER's machine
-// architecture.
-static bool DwarfCFIRegisterNames(const ElfW(Ehdr) *elf_header,
-                                  std::vector<string> *register_names) {
+// success, or false if HEADER's machine architecture is not
+// supported.
+template<typename ElfClass>
+bool DwarfCFIRegisterNames(const typename ElfClass::Ehdr* elf_header,
+                           std::vector<string>* register_names) {
   switch (elf_header->e_machine) {
     case EM_386:
       *register_names = DwarfCFIToModule::RegisterNames::I386();
@@ -309,19 +279,20 @@ static bool DwarfCFIRegisterNames(const ElfW(Ehdr) *elf_header,
   }
 }
 
-static bool LoadDwarfCFI(const string &dwarf_filename,
-                         const ElfW(Ehdr) *elf_header,
-                         const char *section_name,
-                         const ElfW(Shdr) *section,
-                         const bool eh_frame,
-                         const ElfW(Shdr) *got_section,
-                         const ElfW(Shdr) *text_section,
-                         const bool big_endian,
-                         Module *module) {
+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<string> register_names;
-  if (!DwarfCFIRegisterNames(elf_header, &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);
@@ -332,25 +303,17 @@ static bool LoadDwarfCFI(const string &dwarf_filename,
       dwarf2reader::ENDIANNESS_BIG : dwarf2reader::ENDIANNESS_LITTLE;
 
   // Find the call frame information and its size.
-  const char *cfi = reinterpret_cast<const char *>(section->sh_offset);
+  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);
-  // Since we're using the ElfW macro, we're not actually capable of
-  // processing both ELF32 and ELF64 files with the same program; that
-  // would take a bit more work. But this will work out well enough.
-  if (elf_header->e_ident[EI_CLASS] == ELFCLASS32)
-    byte_reader.SetAddressSize(4);
-  else if (elf_header->e_ident[EI_CLASS] == ELFCLASS64)
-    byte_reader.SetAddressSize(8);
-  else {
-    fprintf(stderr, "%s: bad file class in ELF header: %d\n",
-            dwarf_filename.c_str(), elf_header->e_ident[EI_CLASS]);
-    return false;
-  }
+
+  byte_reader.SetAddressSize(ElfClass::kAddrSize);
+
   // Provide the base addresses for .eh_frame encoded pointers, if
   // possible.
   byte_reader.SetCFIDataBase(section->sh_addr, cfi);
@@ -368,8 +331,8 @@ static bool LoadDwarfCFI(const string &dwarf_filename,
   return true;
 }
 
-bool LoadELF(const string &obj_file, MmapWrapper* map_wrapper,
-             ElfW(Ehdr) **elf_header) {
+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",
@@ -391,7 +354,7 @@ bool LoadELF(const string &obj_file, MmapWrapper* map_wrapper,
     return false;
   }
   map_wrapper->set(obj_base, st.st_size);
-  *elf_header = reinterpret_cast<ElfW(Ehdr) *>(obj_base);
+  *elf_header = obj_base;
   if (!IsValidElf(*elf_header)) {
     fprintf(stderr, "Not a valid ELF file: %s\n", obj_file.c_str());
     return false;
@@ -400,7 +363,9 @@ bool LoadELF(const string &obj_file, MmapWrapper* map_wrapper,
 }
 
 // Get the endianness of ELF_HEADER. If it's invalid, return false.
-bool ElfEndianness(const ElfW(Ehdr) *elf_header, bool *big_endian) {
+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;
@@ -417,17 +382,18 @@ bool ElfEndianness(const ElfW(Ehdr) *elf_header, bool *big_endian) {
 
 // Read the .gnu_debuglink and get the debug file name. If anything goes
 // wrong, return an empty string.
-static string ReadDebugLink(const ElfW(Shdr) *debuglink_section,
-                            const string &obj_file,
-                            const string &debug_dir) {
-  char *debuglink = reinterpret_cast<char *>(debuglink_section->sh_offset);
+template<typename ElfClass>
+string ReadDebugLink(const char* debuglink,
+                     size_t debuglink_size,
+                     const string& obj_file,
+                     const string& debug_dir) {
   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_section->sh_size) {
+  if (debuglink_len != debuglink_size) {
     fprintf(stderr, "Mismatched .gnu_debuglink string / section size: "
-            "%zx %zx\n", debuglink_len, debuglink_section->sh_size);
+            "%zx %zx\n", debuglink_len, debuglink_size);
     return "";
   }
 
@@ -448,18 +414,21 @@ static string ReadDebugLink(const ElfW(Shdr) *debuglink_section,
 //
 // LoadSymbolsInfo
 //
-// Holds the state between the two calls to LoadSymbols() in case we have to
-// follow the .gnu_debuglink section and load debug information from a
+// 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 string &dbg_dir) :
     debug_dir_(dbg_dir),
     has_loading_addr_(false) {}
 
-  // Keeps track of which sections have been loaded so we don't accidentally
-  // load it twice from two different files.
+  // 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);
@@ -469,9 +438,9 @@ class LoadSymbolsInfo {
     }
   }
 
-  // We expect the ELF file and linked debug file to have the same preferred
+  // The ELF file and linked debug file are expected to have the same preferred
   // loading address.
-  void set_loading_addr(ElfW(Addr) addr, const string &filename) {
+  void set_loading_addr(Addr addr, const string &filename) {
     if (!has_loading_addr_) {
       loading_addr_ = addr;
       loaded_file_ = filename;
@@ -506,48 +475,55 @@ class LoadSymbolsInfo {
 
   bool has_loading_addr_;  // Indicate if LOADING_ADDR_ is valid.
 
-  ElfW(Addr) loading_addr_;  // Saves the preferred loading address from the
-                             // first call to LoadSymbols().
+  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().
+                        // LoadSymbols().
 
   std::set<string> loaded_sections_;  // Tracks the Loaded ELF sections
-                                           // between calls to LoadSymbols().
+                                      // between calls to LoadSymbols().
 };
 
-static bool LoadSymbols(const string &obj_file,
-                        const bool big_endian,
-                        ElfW(Ehdr) *elf_header,
-                        const bool read_gnu_debug_link,
-                        LoadSymbolsInfo *info,
-                        Module *module) {
-  // Translate all offsets in section headers into address.
-  FixAddress(elf_header);
-  ElfW(Addr) loading_addr = GetLoadingAddress(
-      reinterpret_cast<ElfW(Phdr) *>(elf_header->e_phoff),
+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,
+                 Module* module) {
+  typedef typename ElfClass::Addr Addr;
+  typedef typename ElfClass::Phdr Phdr;
+  typedef typename ElfClass::Shdr Shdr;
+
+  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 ElfW(Shdr) *sections =
-      reinterpret_cast<ElfW(Shdr) *>(elf_header->e_shoff);
-  const ElfW(Shdr) *section_names = sections + elf_header->e_shstrndx;
+  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;
 
   // Look for STABS debugging information, and load it if present.
-  const ElfW(Shdr) *stab_section
-      = FindSectionByName(".stab", sections, section_names,
-                          elf_header->e_shnum);
+  const Shdr* stab_section =
+      FindElfSectionByName<ElfClass>(".stab", SHT_PROGBITS,
+                                     sections, names, names_end,
+                                     elf_header->e_shnum);
   if (stab_section) {
-    const ElfW(Shdr) *stabstr_section = stab_section->sh_link + sections;
+    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(elf_header, stab_section, stabstr_section, big_endian,
-                     module)) {
+      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());
       }
@@ -555,52 +531,60 @@ static bool LoadSymbols(const string &obj_file,
   }
 
   // Look for DWARF debugging information, and load it if present.
-  const ElfW(Shdr) *dwarf_section
-      = FindSectionByName(".debug_info", sections, section_names,
-                          elf_header->e_shnum);
+  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(obj_file, elf_header, big_endian, module))
+    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());
   }
 
   // Dwarf Call Frame Information (CFI) is actually independent from
   // the other DWARF debugging information, and can be used alone.
-  const ElfW(Shdr) *dwarf_cfi_section =
-      FindSectionByName(".debug_frame", sections, section_names,
-                          elf_header->e_shnum);
+  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(obj_file, elf_header, ".debug_frame",
-                   dwarf_cfi_section, false, 0, 0, big_endian, module);
+        LoadDwarfCFI<ElfClass>(obj_file, elf_header, ".debug_frame",
+                               dwarf_cfi_section, false, 0, 0, big_endian,
+                               module);
     found_usable_info = found_usable_info || result;
   }
 
   // Linux C++ exception handling information can also provide
   // unwinding data.
-  const ElfW(Shdr) *eh_frame_section =
-      FindSectionByName(".eh_frame", sections, section_names,
-                        elf_header->e_shnum);
+  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 ElfW(Shdr) *got_section =
-      FindSectionByName(".got", sections, section_names, elf_header->e_shnum);
-    const ElfW(Shdr) *text_section =
-      FindSectionByName(".text", sections, section_names,
-                        elf_header->e_shnum);
+    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(obj_file, elf_header, ".eh_frame", eh_frame_section, true,
-                   got_section, text_section, big_endian, module);
+        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;
   }
 
@@ -609,15 +593,21 @@ static bool LoadSymbols(const string &obj_file,
             " (no \".stab\" or \".debug_info\" sections)\n",
             obj_file.c_str());
 
-    // Failed, but maybe we can find a .gnu_debuglink section?
+    // Failed, but maybe there's a .gnu_debuglink section?
     if (read_gnu_debug_link) {
-      const ElfW(Shdr) *gnu_debuglink_section
-          = FindSectionByName(".gnu_debuglink", sections, section_names,
-                              elf_header->e_shnum);
+      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_dir().empty()) {
-          string debuglink_file =
-              ReadDebugLink(gnu_debuglink_section, obj_file, info->debug_dir());
+          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_dir());
           info->set_debuglink_file(debuglink_file);
         } else {
           fprintf(stderr, ".gnu_debuglink section found in '%s', "
@@ -630,31 +620,29 @@ static bool LoadSymbols(const string &obj_file,
     } else {
       // The caller doesn't want to consult .gnu_debuglink.
       // See if there are export symbols available.
-      const ElfW(Shdr) *dynsym_section =
-        FindSectionByName(".dynsym", sections, section_names,
-                          elf_header->e_shnum);
-      const ElfW(Shdr) *dynstr_section =
-        FindSectionByName(".dynstr", sections, section_names,
-                          elf_header->e_shnum);
+      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");
-        fprintf(stderr, "Have .dynsym + .dynstr\n");
 
-        uint8_t* dynsyms =
-          reinterpret_cast<uint8_t*>(dynsym_section->sh_offset);
-        uint8_t* dynstrs =
-          reinterpret_cast<uint8_t*>(dynstr_section->sh_offset);
+        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,
-                             // This could change to something more useful
-                             // when support for dumping cross-architecture
-                             // symbols is finished.
-                             sizeof(ElfW(Addr)),
-                             module);
+            ELFSymbolsToModule(dynsyms,
+                               dynsym_section->sh_size,
+                               dynstrs,
+                               dynstr_section->sh_size,
+                               big_endian,
+                               ElfClass::kAddrSize,
+                               module);
         found_usable_info = found_usable_info || result;
       }
 
@@ -673,8 +661,10 @@ static bool LoadSymbols(const string &obj_file,
 
 // Return the breakpad symbol file identifier for the architecture of
 // ELF_HEADER.
-const char *ElfArchitecture(const ElfW(Ehdr) *elf_header) {
-  ElfW(Half) arch = elf_header->e_machine;
+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";
@@ -703,8 +693,7 @@ string FormatIdentifier(unsigned char identifier[16]) {
       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 let's preserve
-  // the pattern.
+  // really used or necessary on other platforms, but be consistent.
   id_no_dash += '0';
   return id_no_dash;
 }
@@ -719,24 +708,14 @@ string BaseFileName(const string &filename) {
   return base;
 }
 
-}  // namespace
-
-namespace google_breakpad {
-
-// Not explicitly exported, but not static so it can be used in unit tests.
-// Ideally obj_file would be const, but internally this code does write
-// to some ELF header fields to make its work simpler.
-bool WriteSymbolFileInternal(uint8_t* obj_file,
-                             const string &obj_filename,
-                             const string &debug_dir,
+template<typename ElfClass>
+bool WriteSymbolFileElfClass(const typename ElfClass::Ehdr* elf_header,
+                             const string& obj_filename,
+                             const string& debug_dir,
                              bool cfi,
-                             std::ostream &sym_stream) {
-  ElfW(Ehdr) *elf_header = reinterpret_cast<ElfW(Ehdr) *>(obj_file);
-
-  if (!IsValidElf(elf_header)) {
-    fprintf(stderr, "Not a valid ELF file: %s\n", obj_filename.c_str());
-    return false;
-  }
+                             std::ostream& sym_stream) {
+  typedef typename ElfClass::Ehdr Ehdr;
+  typedef typename ElfClass::Shdr Shdr;
 
   unsigned char identifier[16];
   if (!google_breakpad::FileID::ElfFileIdentifierFromMappedFile(elf_header,
@@ -746,7 +725,7 @@ bool WriteSymbolFileInternal(uint8_t* obj_file,
     return false;
   }
 
-  const char *architecture = ElfArchitecture(elf_header);
+  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);
@@ -755,17 +734,17 @@ bool WriteSymbolFileInternal(uint8_t* obj_file,
 
   // Figure out what endianness this file is.
   bool big_endian;
-  if (!ElfEndianness(elf_header, &big_endian))
+  if (!ElfEndianness<ElfClass>(elf_header, &big_endian))
     return false;
 
   string name = BaseFileName(obj_filename);
   string os = "Linux";
   string id = FormatIdentifier(identifier);
 
-  LoadSymbolsInfo info(debug_dir);
+  LoadSymbolsInfo<ElfClass> info(debug_dir);
   Module module(name, os, architecture, id);
-  if (!LoadSymbols(obj_filename, big_endian, elf_header, !debug_dir.empty(),
-                   &info, &module)) {
+  if (!LoadSymbols<ElfClass>(obj_filename, big_endian, elf_header,
+                             !debug_dir.empty(), &info, &module)) {
     const string debuglink_file = info.debuglink_file();
     if (debuglink_file.empty())
       return false;
@@ -773,11 +752,13 @@ bool WriteSymbolFileInternal(uint8_t* obj_file,
     // Load debuglink ELF file.
     fprintf(stderr, "Found debugging info in %s\n", debuglink_file.c_str());
     MmapWrapper debug_map_wrapper;
-    ElfW(Ehdr) *debug_elf_header = NULL;
-    if (!LoadELF(debuglink_file, &debug_map_wrapper, &debug_elf_header))
+    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(debug_elf_header);
+    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);
@@ -792,7 +773,7 @@ bool WriteSymbolFileInternal(uint8_t* obj_file,
     }
 
     bool debug_big_endian;
-    if (!ElfEndianness(debug_elf_header, &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",
@@ -800,8 +781,8 @@ bool WriteSymbolFileInternal(uint8_t* obj_file,
       return false;
     }
 
-    if (!LoadSymbols(debuglink_file, debug_big_endian, debug_elf_header,
-                     false, &info, &module)) {
+    if (!LoadSymbols<ElfClass>(debuglink_file, debug_big_endian,
+                               debug_elf_header, false, &info, &module)) {
       return false;
     }
   }
@@ -811,12 +792,43 @@ bool WriteSymbolFileInternal(uint8_t* obj_file,
   return true;
 }
 
+}  // namespace
+
+namespace google_breakpad {
+
+// Not explicitly exported, but not static so it can be used in unit tests.
+bool WriteSymbolFileInternal(const uint8_t* obj_file,
+                             const string& obj_filename,
+                             const string& debug_dir,
+                             bool cfi,
+                             std::ostream& sym_stream) {
+
+  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 WriteSymbolFileElfClass<ElfClass32>(
+        reinterpret_cast<const Elf32_Ehdr*>(obj_file), obj_filename, debug_dir,
+        cfi, sym_stream);
+  }
+  if (elfclass == ELFCLASS64) {
+    return WriteSymbolFileElfClass<ElfClass64>(
+        reinterpret_cast<const Elf64_Ehdr*>(obj_file), obj_filename, debug_dir,
+        cfi, sym_stream);
+  }
+
+  return false;
+}
+
 bool WriteSymbolFile(const string &obj_file,
                      const string &debug_dir,
                      bool cfi,
                      std::ostream &sym_stream) {
   MmapWrapper map_wrapper;
-  ElfW(Ehdr) *elf_header = NULL;
+  void* elf_header = NULL;
   if (!LoadELF(obj_file, &map_wrapper, &elf_header))
     return false;
 
diff --git a/src/common/linux/dump_symbols_unittest.cc b/src/common/linux/dump_symbols_unittest.cc
index 2c4f0e65..aec6720c 100644
--- a/src/common/linux/dump_symbols_unittest.cc
+++ b/src/common/linux/dump_symbols_unittest.cc
@@ -45,7 +45,7 @@
 #include "common/using_std_string.h"
 
 namespace google_breakpad {
-bool WriteSymbolFileInternal(uint8_t* obj_file,
+bool WriteSymbolFileInternal(const uint8_t* obj_file,
                              const string &obj_filename,
                              const string &debug_dir,
                              bool cfi,
@@ -89,9 +89,6 @@ TEST_F(DumpSymbols, Invalid) {
                                        s));
 }
 
-// TODO(ted): Fix the dump_symbols code to deal with cross-word-size
-// ELF files.
-#if __ELF_NATIVE_CLASS == 32
 TEST_F(DumpSymbols, SimplePublic32) {
   ELF elf(EM_386, ELFCLASS32, kLittleEndian);
   // Zero out text section for simplicity.
@@ -126,9 +123,7 @@ TEST_F(DumpSymbols, SimplePublic32) {
             "PUBLIC 1000 0 superfunc\n",
             s.str());
 }
-#endif
 
-#if __ELF_NATIVE_CLASS == 64
 TEST_F(DumpSymbols, SimplePublic64) {
   ELF elf(EM_X86_64, ELFCLASS64, kLittleEndian);
   // Zero out text section for simplicity.
@@ -163,4 +158,3 @@ TEST_F(DumpSymbols, SimplePublic64) {
             "PUBLIC 1000 0 superfunc\n",
             s.str());
 }
-#endif
diff --git a/src/common/linux/elfutils-inl.h b/src/common/linux/elfutils-inl.h
new file mode 100644
index 00000000..e56b37a9
--- /dev/null
+++ b/src/common/linux/elfutils-inl.h
@@ -0,0 +1,74 @@
+// Copyright (c) 2012, 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.
+
+#ifndef COMMON_LINUX_ELFUTILS_INL_H__
+#define COMMON_LINUX_ELFUTILS_INL_H__
+
+#include "common/linux/linux_libc_support.h"
+#include "elfutils.h"
+
+namespace google_breakpad {
+
+template<typename ElfClass, typename T>
+const T* GetOffset(const typename ElfClass::Ehdr* elf_header,
+                   typename ElfClass::Off offset) {
+  return reinterpret_cast<const T*>(reinterpret_cast<uintptr_t>(elf_header) +
+                                    offset);
+}
+
+template<typename ElfClass>
+const typename ElfClass::Shdr* FindElfSectionByName(
+    const char* name,
+    typename ElfClass::Word section_type,
+    const typename ElfClass::Shdr* sections,
+    const char* section_names,
+    const char* names_end,
+    int nsection) {
+  assert(name != NULL);
+  assert(sections != NULL);
+  assert(nsection > 0);
+
+  int name_len = my_strlen(name);
+  if (name_len == 0)
+    return NULL;
+
+  for (int i = 0; i < nsection; ++i) {
+    const char* section_name = section_names + sections[i].sh_name;
+    if (sections[i].sh_type == section_type &&
+        names_end - section_name >= name_len + 1 &&
+        my_strcmp(name, section_name) == 0) {
+      return sections + i;
+    }
+  }
+  return NULL;
+}
+
+}  // namespace google_breakpad
+
+#endif  // COMMON_LINUX_ELFUTILS_INL_H__
diff --git a/src/common/linux/elfutils.cc b/src/common/linux/elfutils.cc
index 2fd5c1ff..ee2f4ac0 100644
--- a/src/common/linux/elfutils.cc
+++ b/src/common/linux/elfutils.cc
@@ -33,6 +33,7 @@
 #include <string.h>
 
 #include "common/linux/linux_libc_support.h"
+#include "common/linux/elfutils-inl.h"
 
 namespace google_breakpad {
 
@@ -41,7 +42,7 @@ namespace {
 template<typename ElfClass>
 void FindElfClassSection(const char *elf_base,
                          const char *section_name,
-                         uint32_t section_type,
+                         typename ElfClass::Word section_type,
                          const void **section_start,
                          int *section_size) {
   typedef typename ElfClass::Ehdr Ehdr;
@@ -53,27 +54,21 @@ void FindElfClassSection(const char *elf_base,
 
   assert(my_strncmp(elf_base, ELFMAG, SELFMAG) == 0);
 
-  int name_len = my_strlen(section_name);
-
   const Ehdr* elf_header = reinterpret_cast<const Ehdr*>(elf_base);
   assert(elf_header->e_ident[EI_CLASS] == ElfClass::kClass);
 
   const Shdr* sections =
-      reinterpret_cast<const Shdr*>(elf_base + elf_header->e_shoff);
-  const Shdr* string_section = sections + elf_header->e_shstrndx;
-
-  const Shdr* section = NULL;
-  for (int i = 0; i < elf_header->e_shnum; ++i) {
-    if (sections[i].sh_type == section_type) {
-      const char* current_section_name = (char*)(elf_base +
-                                                 string_section->sh_offset +
-                                                 sections[i].sh_name);
-      if (!my_strncmp(current_section_name, section_name, name_len)) {
-        section = &sections[i];
-        break;
-      }
-    }
-  }
+    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;
+
+  const Shdr* section =
+    FindElfSectionByName<ElfClass>(section_name, section_type,
+                                   sections, names, names_end,
+                                   elf_header->e_shnum);
+
   if (section != NULL && section->sh_size > 0) {
     *section_start = elf_base + section->sh_offset;
     *section_size = section->sh_size;
@@ -82,6 +77,18 @@ void FindElfClassSection(const char *elf_base,
 
 }  // namespace
 
+bool IsValidElf(const void* elf_base) {
+  return my_strncmp(reinterpret_cast<const char*>(elf_base),
+                    ELFMAG, SELFMAG) == 0;
+}
+
+int ElfClass(const void* elf_base) {
+  const ElfW(Ehdr)* elf_header =
+    reinterpret_cast<const ElfW(Ehdr)*>(elf_base);
+
+  return elf_header->e_ident[EI_CLASS];
+}
+
 bool FindElfSection(const void *elf_mapped_base,
                     const char *section_name,
                     uint32_t section_type,
@@ -95,22 +102,22 @@ bool FindElfSection(const void *elf_mapped_base,
   *section_start = NULL;
   *section_size = 0;
 
-  const char* elf_base =
-    static_cast<const char*>(elf_mapped_base);
-  const ElfW(Ehdr)* elf_header =
-    reinterpret_cast<const ElfW(Ehdr)*>(elf_base);
-  if (my_strncmp(elf_base, ELFMAG, SELFMAG) != 0)
+  if (!IsValidElf(elf_mapped_base))
     return false;
 
+  int cls = ElfClass(elf_mapped_base);
   if (elfclass) {
-    *elfclass = elf_header->e_ident[EI_CLASS];
+    *elfclass = cls;
   }
 
-  if (elf_header->e_ident[EI_CLASS] == ELFCLASS32) {
+  const char* elf_base =
+    static_cast<const char*>(elf_mapped_base);
+
+  if (cls == ELFCLASS32) {
     FindElfClassSection<ElfClass32>(elf_base, section_name, section_type,
                                     section_start, section_size);
     return *section_start != NULL;
-  } else if (elf_header->e_ident[EI_CLASS] == ELFCLASS64) {
+  } else if (cls == ELFCLASS64) {
     FindElfClassSection<ElfClass64>(elf_base, section_name, section_type,
                                     section_start, section_size);
     return *section_start != NULL;
diff --git a/src/common/linux/elfutils.h b/src/common/linux/elfutils.h
index 30f2af3f..95105966 100644
--- a/src/common/linux/elfutils.h
+++ b/src/common/linux/elfutils.h
@@ -52,7 +52,11 @@ struct ElfClass32 {
   typedef Elf32_Nhdr Nhdr;
   typedef Elf32_Phdr Phdr;
   typedef Elf32_Shdr Shdr;
+  typedef Elf32_Half Half;
+  typedef Elf32_Off Off;
+  typedef Elf32_Word Word;
   static const int kClass = ELFCLASS32;
+  static const size_t kAddrSize = sizeof(Elf32_Addr);
 };
 
 struct ElfClass64 {
@@ -61,9 +65,16 @@ struct ElfClass64 {
   typedef Elf64_Nhdr Nhdr;
   typedef Elf64_Phdr Phdr;
   typedef Elf64_Shdr Shdr;
+  typedef Elf64_Half Half;
+  typedef Elf64_Off Off;
+  typedef Elf64_Word Word;
   static const int kClass = ELFCLASS64;
+  static const size_t kAddrSize = sizeof(Elf64_Addr);
 };
 
+bool IsValidElf(const void* elf_header);
+int ElfClass(const void* elf_base);
+
 // Attempt to find a section named |section_name| of type |section_type|
 // in the ELF binary data at |elf_mapped_base|. On success, returns true
 // and sets |*section_start| to point to the start of the section data,
@@ -76,6 +87,26 @@ bool FindElfSection(const void *elf_mapped_base,
                     int *section_size,
                     int *elfclass);
 
+// Internal helper method, exposed for convenience for callers
+// that already have more info.
+template<typename ElfClass>
+const typename ElfClass::Shdr*
+FindElfSectionByName(const char* name,
+                     typename ElfClass::Word section_type,
+                     const typename ElfClass::Shdr* sections,
+                     const char* section_names,
+                     const char* names_end,
+                     int nsection);
+
+// Convert an offset from an Elf header into a pointer to the mapped
+// address in the current process. Takes an extra template parameter
+// to specify the return type to avoid having to dynamic_cast the
+// result.
+template<typename ElfClass, typename T>
+const T*
+GetOffset(const typename ElfClass::Ehdr* elf_header,
+          typename ElfClass::Off offset);
+
 }  // namespace google_breakpad
 
 #endif  // COMMON_LINUX_ELFUTILS_H__