Fork breakpad's dump_syms and related code. Generate XOR of first page of mem...

breakpad/linux/dump_symbols.cc

+// Copyright (c) 2006, 2009, 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.
+
+#include "breakpad/linux/dump_symbols.h"
+
+#include <a.out.h>
+#include <assert.h>
+#include <cxxabi.h>
+#include <elf.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <link.h>
+#include <stab.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <algorithm>
+#include <cstdarg>
+#include <cstdio>
+#include <cstdlib>
+#include <functional>
+#include <list>
+#include <vector>
+
+#include "breakpad/linux/file_id.h"
+#include "common/linux/guid_creator.h"
+
+// This namespace contains helper functions.
+namespace {
+
+// Infomation of a line.
+struct LineInfo {
+  // The index into string table for the name of the source file which
+  // this line belongs to.
+  // Load from stab symbol.
+  uint32_t source_name_index;
+  // Offset from start of the function.
+  // Load from stab symbol.
+  ElfW(Off) rva_to_func;
+  // Offset from base of the loading binary.
+  ElfW(Off) rva_to_base;
+  // Size of the line.
+  // It is the difference of the starting address of the line and starting
+  // address of the next N_SLINE, N_FUN or N_SO.
+  uint32_t size;
+  // Line number.
+  uint32_t line_num;
+  // Id of the source file for this line.
+  int source_id;
+};
+
+typedef std::list<struct LineInfo> LineInfoList;
+
+// Information of a function.
+struct FuncInfo {
+  // Name of the function.
+  const char* name;
+  // Offset from the base of the loading address.
+  ElfW(Off) rva_to_base;
+  // Virtual address of the function.
+  // Load from stab symbol.
+  ElfW(Addr) addr;
+  // Size of the function.
+  // It is the difference of the starting address of the function and starting
+  // address of the next N_FUN or N_SO.
+  uint32_t size;
+  // Total size of stack parameters.
+  uint32_t stack_param_size;
+  // Is there any lines included from other files?
+  bool has_sol;
+  // Line information array.
+  LineInfoList line_info;
+};
+
+typedef std::list<struct FuncInfo> FuncInfoList;
+
+// Information of a source file.
+struct SourceFileInfo {
+  // Name string index into the string table.
+  uint32_t name_index;
+  // Name of the source file.
+  const char* name;
+  // Starting address of the source file.
+  ElfW(Addr) addr;
+  // Id of the source file.
+  int source_id;
+  // Functions information.
+  FuncInfoList func_info;
+};
+
+typedef std::list<struct SourceFileInfo> SourceFileInfoList;
+
+// Information of a symbol table.
+// This is the root of all types of symbol.
+struct SymbolInfo {
+  SourceFileInfoList source_file_info;
+
+  // The next source id for newly found source file.
+  int next_source_id;
+};
+
+// Stab section name.
+static const char* kStabName = ".stab";
+
+// Demangle using abi call.
+// Older GCC may not support it.
+static std::string Demangle(const char* mangled) {
+  int status = 0;
+  char* demangled = abi::__cxa_demangle(mangled, NULL, NULL, &status);
+  if (status == 0 && demangled != NULL) {
+    std::string str(demangled);
+    free(demangled);
+    return str;
+  }
+  return std::string(mangled);
+}
+
+// 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(Word) base = reinterpret_cast<ElfW(Word)>(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 prefered loading address of the binary.
+static ElfW(Addr) GetLoadingAddress(const ElfW(Phdr)* program_headers,
+                                    int nheader) {
+  for (int i = 0; i < nheader; ++i) {
+    const ElfW(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;
+}
+
+static bool WriteFormat(int fd, const char* fmt, ...) {
+  va_list list;
+  char buffer[4096];
+  ssize_t expected, written;
+  va_start(list, fmt);
+  vsnprintf(buffer, sizeof(buffer), fmt, list);
+  expected = strlen(buffer);
+  written = write(fd, buffer, strlen(buffer));
+  va_end(list);
+  return expected == written;
+}
+
+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)* strtab,
+                                           int nsection) {
+  assert(name != NULL);
+  assert(sections != NULL);
+  assert(nsection > 0);
+
+  int name_len = strlen(name);
+  if (name_len == 0)
+    return NULL;
+
+  for (int i = 0; i < nsection; ++i) {
+    const char* section_name =
+      reinterpret_cast<char*>(strtab->sh_offset + sections[i].sh_name);
+    if (!strncmp(name, section_name, name_len))
+      return sections + i;
+  }
+  return NULL;
+}
+
+// TODO(liuli): Computer the stack parameter size.
+// Expect parameter variables are immediately following the N_FUN symbol.
+// Will need to parse the type information to get a correct size.
+static int LoadStackParamSize(struct nlist* list,
+                              struct nlist* list_end,
+                              struct FuncInfo* func_info) {
+  struct nlist* cur_list = list;
+  assert(cur_list->n_type == N_FUN);
+  ++cur_list;
+  int step = 1;
+  while (cur_list < list_end && cur_list->n_type == N_PSYM) {
+    ++cur_list;
+    ++step;
+  }
+  func_info->stack_param_size = 0;
+  return step;
+}
+
+static int LoadLineInfo(struct nlist* list,
+                        struct nlist* list_end,
+                        const struct SourceFileInfo& source_file_info,
+                        struct FuncInfo* func_info) {
+  struct nlist* cur_list = list;
+  func_info->has_sol = false;
+  // Records which source file the following lines belongs. Default
+  // to the file we are handling. This helps us handling inlined source.
+  // When encountering N_SOL, we will change this to the source file
+  // specified by N_SOL.
+  int current_source_name_index = source_file_info.name_index;
+  do {
+    // Skip non line information.
+    while (cur_list < list_end && cur_list->n_type != N_SLINE) {
+      // Only exit when got another function, or source file.
+      if (cur_list->n_type == N_FUN || cur_list->n_type == N_SO)
+        return cur_list - list;
+      // N_SOL means source lines following it will be from
+      // another source file.
+      if (cur_list->n_type == N_SOL) {
+        func_info->has_sol = true;
+
+        if (cur_list->n_un.n_strx > 0 &&
+            cur_list->n_un.n_strx != current_source_name_index) {
+          // The following lines will be from this source file.
+          current_source_name_index = cur_list->n_un.n_strx;
+        }
+      }
+      ++cur_list;
+    }
+    struct LineInfo line;
+    while (cur_list < list_end && cur_list->n_type == N_SLINE) {
+      line.source_name_index = current_source_name_index;
+      line.rva_to_func = cur_list->n_value;
+      // n_desc is a signed short
+      line.line_num = (unsigned short)cur_list->n_desc;
+      // Don't set it here.
+      // Will be processed in later pass.
+      line.source_id = -1;
+      func_info->line_info.push_back(line);
+      ++cur_list;
+    }
+  } while (list < list_end);
+
+  return cur_list - list;
+}
+
+static int LoadFuncSymbols(struct nlist* list,
+                           struct nlist* list_end,
+                           const ElfW(Shdr)* stabstr_section,
+                           struct SourceFileInfo* source_file_info) {
+  struct nlist* cur_list = list;
+  assert(cur_list->n_type == N_SO);
+  ++cur_list;
+  source_file_info->func_info.clear();
+  while (cur_list < list_end) {
+    // Go until the function symbol.
+    while (cur_list < list_end && cur_list->n_type != N_FUN) {
+      if (cur_list->n_type == N_SO) {
+        return cur_list - list;
+      }
+      ++cur_list;
+      continue;
+    }
+    if (cur_list->n_type == N_FUN) {
+      struct FuncInfo func_info;
+      func_info.name =
+        reinterpret_cast<char* >(cur_list->n_un.n_strx +
+                                 stabstr_section->sh_offset);
+      func_info.addr = cur_list->n_value;
+      func_info.rva_to_base = 0;
+      func_info.size = 0;
+      func_info.stack_param_size = 0;
+      func_info.has_sol = 0;
+
+      // Stack parameter size.
+      cur_list += LoadStackParamSize(cur_list, list_end, &func_info);
+      // Line info.
+      cur_list += LoadLineInfo(cur_list,
+                               list_end,
+                               *source_file_info,
+                               &func_info);
+
+      // Functions in this module should have address bigger than the module
+      // startring address.
+      // There maybe a lot of duplicated entry for a function in the symbol,
+      // only one of them can met this.
+      if (func_info.addr >= source_file_info->addr) {
+        source_file_info->func_info.push_back(func_info);
+      }
+    }
+  }
+  return cur_list - list;
+}
+
+// Comapre the address.
+// The argument should have a memeber named "addr"
+template<class T1, class T2>
+static bool CompareAddress(T1* a, T2* b) {
+  return a->addr < b->addr;
+}
+
+// Sort the array into increasing ordered array based on the virtual address.
+// Return vector of pointers to the elements in the incoming array. So caller
+// should make sure the returned vector lives longer than the incoming vector.
+template<class Container>
+static std::vector<typename Container::value_type* > SortByAddress(
+    Container* container) {
+  typedef typename Container::iterator It;
+  typedef typename Container::value_type T;
+  std::vector<T* > sorted_array_ptr;
+  sorted_array_ptr.reserve(container->size());
+  for (It it = container->begin(); it != container->end(); it++)
+    sorted_array_ptr.push_back(&(*it));
+  std::sort(sorted_array_ptr.begin(),
+            sorted_array_ptr.end(),
+            std::ptr_fun(CompareAddress<T, T>));
+
+  return sorted_array_ptr;
+}
+
+// Find the address of the next function or source file symbol in the symbol
+// table. The address should be bigger than the current function's address.
+static ElfW(Addr) NextAddress(
+    std::vector<struct FuncInfo* >* sorted_functions,
+    std::vector<struct SourceFileInfo* >* sorted_files,
+    const struct FuncInfo& func_info) {
+  std::vector<struct FuncInfo* >::iterator next_func_iter =
+    std::find_if(sorted_functions->begin(),
+                 sorted_functions->end(),
+                 std::bind1st(
+                     std::ptr_fun(
+                         CompareAddress<struct FuncInfo,
+                                        struct FuncInfo>),
+                     &func_info));
+  if (next_func_iter != sorted_functions->end())
+    return (*next_func_iter)->addr;
+
+  std::vector<struct SourceFileInfo* >::iterator next_file_iter =
+    std::find_if(sorted_files->begin(),
+                 sorted_files->end(),
+                 std::bind1st(
+                     std::ptr_fun(
+                         CompareAddress<struct FuncInfo,
+                                        struct SourceFileInfo>),
+                     &func_info));
+  if (next_file_iter != sorted_files->end()) {
+    return (*next_file_iter)->addr;
+  }
+  return 0;
+}
+
+static int FindFileByNameIdx(uint32_t name_index,
+                             SourceFileInfoList& files) {
+  for (SourceFileInfoList::iterator it = files.begin();
+       it != files.end(); it++) {
+    if (it->name_index == name_index)
+      return it->source_id;
+  }
+
+  return -1;
+}
+
+// Add included file information.
+// Also fix the source id for the line info.
+static void AddIncludedFiles(struct SymbolInfo* symbols,
+                             const ElfW(Shdr)* stabstr_section) {
+  for (SourceFileInfoList::iterator source_file_it =
+         symbols->source_file_info.begin();
+       source_file_it != symbols->source_file_info.end();
+       ++source_file_it) {
+    struct SourceFileInfo& source_file = *source_file_it;
+
+    for (FuncInfoList::iterator func_info_it = source_file.func_info.begin();
+         func_info_it != source_file.func_info.end();
+         ++func_info_it) {
+      struct FuncInfo& func_info = *func_info_it;
+
+      for (LineInfoList::iterator line_info_it = func_info.line_info.begin();
+           line_info_it != func_info.line_info.end(); ++line_info_it) {
+        struct LineInfo& line_info = *line_info_it;
+
+        assert(line_info.source_name_index > 0);
+        assert(source_file.name_index > 0);
+
+        // Check if the line belongs to the source file by comparing the
+        // name index into string table.
+        if (line_info.source_name_index != source_file.name_index) {
+          // This line is not from the current source file, check if this
+          // source file has been added before.
+          int found_source_id = FindFileByNameIdx(line_info.source_name_index,
+                                                  symbols->source_file_info);
+          if (found_source_id < 0) {
+            // Got a new included file.
+            // Those included files don't have address or line information.
+            SourceFileInfo new_file;
+            new_file.name_index = line_info.source_name_index;
+            new_file.name =
+                reinterpret_cast<char* >(new_file.name_index +
+                                         stabstr_section->sh_offset);
+            new_file.addr = 0;
+            new_file.source_id = symbols->next_source_id++;
+            line_info.source_id = new_file.source_id;
+            symbols->source_file_info.push_back(new_file);
+          } else {
+            // The file has been added.
+            line_info.source_id = found_source_id;
+          }
+        } else {
+          // The line belongs to the file.
+          line_info.source_id = source_file.source_id;
+        }
+      }  // for each line.
+    }  // for each function.
+  }  // for each source file.
+}
+
+// Compute size and rva information based on symbols loaded from stab section.
+static bool ComputeSizeAndRVA(ElfW(Addr) loading_addr,
+                              struct SymbolInfo* symbols) {
+  std::vector<struct SourceFileInfo* > sorted_files =
+    SortByAddress(&(symbols->source_file_info));
+  for (size_t i = 0; i < sorted_files.size(); ++i) {
+    struct SourceFileInfo& source_file =* sorted_files[i];
+    std::vector<struct FuncInfo* > sorted_functions =
+      SortByAddress(&(source_file.func_info));
+    for (size_t j = 0; j < sorted_functions.size(); ++j) {
+      struct FuncInfo& func_info = *sorted_functions[j];
+      assert(func_info.addr >= loading_addr);
+      func_info.rva_to_base = func_info.addr - loading_addr;
+      func_info.size = 0;
+      ElfW(Addr) next_addr = NextAddress(&sorted_functions,
+                                         &sorted_files,
+                                         func_info);
+      // I've noticed functions with an address bigger than any other functions
+      // and source files modules, this is probably the last function in the
+      // module, due to limitions of Linux stab symbol, it is impossible to get
+      // the exact size of this kind of function, thus we give it a default
+      // very big value. This should be safe since this is the last function.
+      // But it is a ugly hack.....
+      // The following code can reproduce the case:
+      // template<class T>
+      // void Foo(T value) {
+      // }
+      //
+      // int main(void) {
+      //   Foo(10);
+      //   Foo(std::string("hello"));
+      //   return 0;
+      // }
+      // TODO(liuli): Find a better solution.
+      static const int kDefaultSize = 0x10000000;
+      static int no_next_addr_count = 0;
+      if (next_addr != 0) {
+        func_info.size = next_addr - func_info.addr;
+      } else {
+        if (no_next_addr_count > 1) {
+          fprintf(stderr, "Got more than one function without the following ");
+          fprintf(stderr, "symbol. Ignore this function.\n");
+          fprintf(stderr, "The dumped symbol may not correct.\n");
+          assert(!"This should not happen!\n");
+          func_info.size = 0;
+          continue;
+        }
+
+        no_next_addr_count++;
+        func_info.size = kDefaultSize;
+      }
+      // Compute line size.
+      for (LineInfoList::iterator line_info_it = func_info.line_info.begin();
+           line_info_it != func_info.line_info.end(); line_info_it++) {
+        struct LineInfo& line_info = *line_info_it;
+        LineInfoList::iterator next_line_info_it = line_info_it;
+        next_line_info_it++;
+        line_info.size = 0;
+        if (next_line_info_it != func_info.line_info.end()) {
+          line_info.size =
+            next_line_info_it->rva_to_func - line_info.rva_to_func;
+        } else {
+          // The last line in the function.
+          // If we can find a function or source file symbol immediately
+          // following the line, we can get the size of the line by computing
+          // the difference of the next address to the starting address of this
+          // line.
+          // Otherwise, we need to set a default big enough value. This occurs
+          // mostly because the this function is the last one in the module.
+          if (next_addr != 0) {
+            ElfW(Off) next_addr_offset = next_addr - func_info.addr;
+            line_info.size = next_addr_offset - line_info.rva_to_func;
+          } else {
+            line_info.size = kDefaultSize;
+          }
+        }
+        line_info.rva_to_base = line_info.rva_to_func + func_info.rva_to_base;
+      }  // for each line.
+    }  // for each function.
+  }  // for each source file.
+  return true;
+}
+
+static bool LoadSymbols(const ElfW(Shdr)* stab_section,
+                        const ElfW(Shdr)* stabstr_section,
+                        ElfW(Addr) loading_addr,
+                        struct SymbolInfo* symbols) {
+  if (stab_section == NULL || stabstr_section == NULL)
+    return false;
+
+  struct nlist* lists =
+    reinterpret_cast<struct nlist* >(stab_section->sh_offset);
+  int nstab = stab_section->sh_size / sizeof(struct nlist);
+  // First pass, load all symbols from the object file.
+  for (int i = 0; i < nstab;) {
+    int step = 1;
+    struct nlist* cur_list = lists + i;
+    if (cur_list->n_type == N_SO) {
+      // FUNC <address> <length> <param_stack_size> <function>
+      struct SourceFileInfo source_file_info;
+      source_file_info.name_index = cur_list->n_un.n_strx;
+      source_file_info.name = reinterpret_cast<char* >(cur_list->n_un.n_strx +
+                                 stabstr_section->sh_offset);
+      source_file_info.addr = cur_list->n_value;
+      if (strchr(source_file_info.name, '.'))
+        source_file_info.source_id = symbols->next_source_id++;
+      else
+        source_file_info.source_id = -1;
+      step = LoadFuncSymbols(cur_list, lists + nstab,
+                             stabstr_section, &source_file_info);
+      symbols->source_file_info.push_back(source_file_info);
+    }
+    i += step;
+  }
+
+  // Second pass, compute the size of functions and lines.
+  if (ComputeSizeAndRVA(loading_addr, symbols)) {
+    // Third pass, check for included source code, especially for header files.
+    // Until now, we only have compiling unit information, but they can
+    // have code from include files, add them here.
+    AddIncludedFiles(symbols, stabstr_section);
+    return true;
+  }
+  return false;
+}
+
+static bool LoadSymbols(ElfW(Ehdr)* elf_header, struct SymbolInfo* symbols) {
+  // Translate all offsets in section headers into address.
+  FixAddress(elf_header);
+  ElfW(Addr) loading_addr = GetLoadingAddress(
+      reinterpret_cast<ElfW(Phdr)* >(elf_header->e_phoff),
+      elf_header->e_phnum);
+
+  const ElfW(Shdr)* sections =
+    reinterpret_cast<ElfW(Shdr)* >(elf_header->e_shoff);
+  const ElfW(Shdr)* strtab = sections + elf_header->e_shstrndx;
+  const ElfW(Shdr)* stab_section =
+    FindSectionByName(kStabName, sections, strtab, elf_header->e_shnum);
+  if (stab_section == NULL) {
+    fprintf(stderr, "Stab section not found.\n");
+    return false;
+  }
+  const ElfW(Shdr)* stabstr_section = stab_section->sh_link + sections;
+
+  // Load symbols.
+  return LoadSymbols(stab_section, stabstr_section, loading_addr, symbols);
+}
+
+static bool WriteModuleInfo(int fd,
+                            ElfW(Half) arch,
+                            const std::string& obj_file) {
+  const char* arch_name = NULL;
+  if (arch == EM_386)
+    arch_name = "x86";
+  else if (arch == EM_X86_64)
+    arch_name = "x86_64";
+  else
+    return false;
+
+  uint8_t identifier[google_breakpad::kMDGUIDSize];
+  google_breakpad::FileID file_id(obj_file.c_str());
+  if (file_id.ElfFileIdentifier(identifier)) {
+    char identifier_str[40];
+    file_id.ConvertIdentifierToString(identifier,
+                                      identifier_str, sizeof(identifier_str));
+    char id_no_dash[40];
+    int id_no_dash_len = 0;
+    memset(id_no_dash, 0, sizeof(id_no_dash));
+    for (int i = 0; identifier_str[i] != '\0'; ++i)
+      if (identifier_str[i] != '-')
+        id_no_dash[id_no_dash_len++] = identifier_str[i];
+    // Add an extra "0" by the end.
+    id_no_dash[id_no_dash_len++] = '0';
+    std::string filename = obj_file;
+    size_t slash_pos = obj_file.find_last_of("/");
+    if (slash_pos != std::string::npos)
+      filename = obj_file.substr(slash_pos + 1);
+    return WriteFormat(fd, "MODULE Linux %s %s %s\n", arch_name,
+                       id_no_dash, filename.c_str());
+  }
+  return false;
+}
+
+static bool WriteSourceFileInfo(int fd, const struct SymbolInfo& symbols) {
+  for (SourceFileInfoList::const_iterator it =
+         symbols.source_file_info.begin();
+       it != symbols.source_file_info.end(); it++) {
+    if (it->source_id != -1) {
+      const char* name = it->name;
+      if (!WriteFormat(fd, "FILE %d %s\n", it->source_id, name))
+        return false;
+    }
+  }
+  return true;
+}
+
+static bool WriteOneFunction(int fd,
+                             const struct FuncInfo& func_info) {
+  // Discard the ending part of the name.
+  std::string func_name(func_info.name);
+  std::string::size_type last_colon = func_name.find_last_of(':');
+  if (last_colon != std::string::npos)
+    func_name = func_name.substr(0, last_colon);
+  func_name = Demangle(func_name.c_str());
+
+  if (func_info.size <= 0)
+    return true;
+
+  if (WriteFormat(fd, "FUNC %lx %lx %d %s\n",
+                  func_info.rva_to_base,
+                  func_info.size,
+                  func_info.stack_param_size,
+                  func_name.c_str())) {
+    for (LineInfoList::const_iterator it = func_info.line_info.begin();
+         it != func_info.line_info.end(); it++) {
+      const struct LineInfo& line_info =* it;
+      if (!WriteFormat(fd, "%lx %lx %d %d\n",
+                       line_info.rva_to_base,
+                       line_info.size,
+                       line_info.line_num,
+                       line_info.source_id))
+        return false;
+    }
+    return true;
+  }
+  return false;
+}
+
+static bool WriteFunctionInfo(int fd, const struct SymbolInfo& symbols) {
+  for (SourceFileInfoList::const_iterator it =
+         symbols.source_file_info.begin();
+       it != symbols.source_file_info.end(); it++) {
+    const struct SourceFileInfo& file_info =* it;
+    for (FuncInfoList::const_iterator fiIt = file_info.func_info.begin();
+         fiIt != file_info.func_info.end(); fiIt++) {
+      const struct FuncInfo& func_info =* fiIt;
+      if (!WriteOneFunction(fd, func_info))
+        return false;
+    }
+  }
+  return true;
+}
+
+static bool DumpStabSymbols(int fd, const struct SymbolInfo& symbols) {
+  return WriteSourceFileInfo(fd, symbols) &&
+    WriteFunctionInfo(fd, symbols);
+}
+
+//
+// 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(void* mapped_address, size_t mapped_size) :
+    base_(mapped_address), size_(mapped_size) {
+    }
+  ~MmapWrapper() {
+    if (base_ != NULL) {
+      assert(size_ > 0);
+      munmap(base_, size_);
+    }
+  }
+  void release() {
+    base_ = NULL;
+    size_ = 0;
+  }
+
+ private:
+  void* base_;
+  size_t size_;
+};
+
+}  // namespace
+
+namespace google_breakpad {
+
+bool DumpSymbols::WriteSymbolFile(const std::string& obj_file,
+                                  int sym_fd) {
+  int obj_fd = open(obj_file.c_str(), O_RDONLY);
+  if (obj_fd < 0)
+    return false;
+  FDWrapper obj_fd_wrapper(obj_fd);
+  struct stat st;
+  if (fstat(obj_fd, &st) != 0 && st.st_size <= 0)
+    return false;
+  void* obj_base = mmap(NULL, st.st_size,
+                        PROT_READ | PROT_WRITE, MAP_PRIVATE, obj_fd, 0);
+  if (obj_base == MAP_FAILED)
+    return false;
+  MmapWrapper map_wrapper(obj_base, st.st_size);
+  ElfW(Ehdr)* elf_header = reinterpret_cast<ElfW(Ehdr)* >(obj_base);
+  if (!IsValidElf(elf_header))
+    return false;
+  struct SymbolInfo symbols;
+  symbols.next_source_id = 0;
+
+  if (!LoadSymbols(elf_header, &symbols))
+     return false;
+  // Write to symbol file.
+  if (WriteModuleInfo(sym_fd, elf_header->e_machine, obj_file) &&
+      DumpStabSymbols(sym_fd, symbols))
+    return true;
+
+  return false;
+}
+
+}  // namespace google_breakpad