lib/sanitizer_common/sanitizer_symbolizer.cc - platform/external/compiler-rt - Git at Google

 //===-- sanitizer_symbolizer.cc -------------------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file is shared between AddressSanitizer and ThreadSanitizer
 // run-time libraries. See sanitizer_symbolizer.h for details.
 //===----------------------------------------------------------------------===//

 #include "sanitizer_common.h"
 #include "sanitizer_placement_new.h"
 #include "sanitizer_procmaps.h"
 #include "sanitizer_symbolizer.h"

 namespace __sanitizer {

 void AddressInfo::Clear() {
   InternalFree(module);
   InternalFree(function);
   InternalFree(file);
   internal_memset(this, 0, sizeof(AddressInfo));
 }

 LoadedModule::LoadedModule(const char *module_name, uptr base_address) {
   full_name_ = internal_strdup(module_name);
   base_address_ = base_address;
   n_ranges_ = 0;
 }

 void LoadedModule::addAddressRange(uptr beg, uptr end) {
   CHECK_LT(n_ranges_, kMaxNumberOfAddressRanges);
   ranges_[n_ranges_].beg = beg;
   ranges_[n_ranges_].end = end;
   n_ranges_++;
 }

 bool LoadedModule::containsAddress(uptr address) const {
   for (uptr i = 0; i < n_ranges_; i++) {
     if (ranges_[i].beg <= address && address < ranges_[i].end)
       return true;
   }
   return false;
 }

 // Extracts the prefix of "str" that consists of any characters not
 // present in "delims" string, and copies this prefix to "result", allocating
 // space for it.
 // Returns a pointer to "str" after skipping extracted prefix and first
 // delimiter char.
 static const char *ExtractToken(const char *str, const char *delims,
                                 char **result) {
   uptr prefix_len = internal_strcspn(str, delims);
   *result = (char*)InternalAlloc(prefix_len + 1);
   internal_memcpy(*result, str, prefix_len);
   (*result)[prefix_len] = '\0';
   const char *prefix_end = str + prefix_len;
   if (*prefix_end != '\0') prefix_end++;
   return prefix_end;
 }

 // Same as ExtractToken, but converts extracted token to integer.
 static const char *ExtractInt(const char *str, const char *delims,
                               int *result) {
   char *buff;
   const char *ret = ExtractToken(str, delims, &buff);
   if (buff != 0) {
     *result = (int)internal_atoll(buff);
   }
   InternalFree(buff);
   return ret;
 }

 static const char *ExtractUptr(const char *str, const char *delims,
                                uptr *result) {
   char *buff;
   const char *ret = ExtractToken(str, delims, &buff);
   if (buff != 0) {
     *result = (uptr)internal_atoll(buff);
   }
   InternalFree(buff);
   return ret;
 }

 // ExternalSymbolizer encapsulates communication between the tool and
 // external symbolizer program, running in a different subprocess,
 // For now we assume the following protocol:
 // For each request of the form
 //   <module_name> <module_offset>
 // passed to STDIN, external symbolizer prints to STDOUT response:
 //   <function_name>
 //   <file_name>:<line_number>:<column_number>
 //   <function_name>
 //   <file_name>:<line_number>:<column_number>
 //   ...
 //   <empty line>
 class ExternalSymbolizer {
  public:
   ExternalSymbolizer(const char *path, int input_fd, int output_fd)
       : path_(path),
         input_fd_(input_fd),
         output_fd_(output_fd),
         times_restarted_(0) {
     CHECK(path_);
     CHECK_NE(input_fd_, kInvalidFd);
     CHECK_NE(output_fd_, kInvalidFd);
   }

   char *SendCommand(bool is_data, const char *module_name, uptr module_offset) {
     CHECK(module_name);
     internal_snprintf(buffer_, kBufferSize, "%s%s 0x%zx\n",
                       is_data ? "DATA " : "", module_name, module_offset);
     if (!writeToSymbolizer(buffer_, internal_strlen(buffer_)))
       return 0;
     if (!readFromSymbolizer(buffer_, kBufferSize))
       return 0;
     return buffer_;
   }

   bool Restart() {
     if (times_restarted_ >= kMaxTimesRestarted) return false;
     times_restarted_++;
     internal_close(input_fd_);
     internal_close(output_fd_);
     return StartSymbolizerSubprocess(path_, &input_fd_, &output_fd_);
   }

  private:
   bool readFromSymbolizer(char *buffer, uptr max_length) {
     if (max_length == 0)
       return true;
     uptr read_len = 0;
     while (true) {
       uptr just_read = internal_read(input_fd_, buffer + read_len,
                                      max_length - read_len);
       // We can't read 0 bytes, as we don't expect external symbolizer to close
       // its stdout.
       if (just_read == 0 || just_read == (uptr)-1) {
         Report("WARNING: Can't read from symbolizer at fd %d\n", input_fd_);
         return false;
       }
       read_len += just_read;
       // Empty line marks the end of symbolizer output.
       if (read_len >= 2 && buffer[read_len - 1] == '\n' &&
                            buffer[read_len - 2] == '\n') {
         break;
       }
     }
     return true;
   }

   bool writeToSymbolizer(const char *buffer, uptr length) {
     if (length == 0)
       return true;
     uptr write_len = internal_write(output_fd_, buffer, length);
     if (write_len == 0 || write_len == (uptr)-1) {
       Report("WARNING: Can't write to symbolizer at fd %d\n", output_fd_);
       return false;
     }
     return true;
   }

   const char *path_;
   int input_fd_;
   int output_fd_;

   static const uptr kBufferSize = 16 * 1024;
   char buffer_[kBufferSize];

   static const uptr kMaxTimesRestarted = 5;
   uptr times_restarted_;
 };

 static LowLevelAllocator symbolizer_allocator;  // Linker initialized.

 #if SANITIZER_SUPPORTS_WEAK_HOOKS
 extern "C" {
 SANITIZER_WEAK_ATTRIBUTE SANITIZER_INTERFACE_ATTRIBUTE
 bool __sanitizer_symbolize_code(const char *ModuleName, u64 ModuleOffset,
                                 char *Buffer, int MaxLength);
 SANITIZER_WEAK_ATTRIBUTE SANITIZER_INTERFACE_ATTRIBUTE
 bool __sanitizer_symbolize_data(const char *ModuleName, u64 ModuleOffset,
                                 char *Buffer, int MaxLength);
 }  // extern "C"

 class InternalSymbolizer {
  public:
   typedef bool (*SanitizerSymbolizeFn)(const char*, u64, char*, int);
   static InternalSymbolizer *get() {
     if (__sanitizer_symbolize_code != 0 &&
         __sanitizer_symbolize_data != 0) {
       void *mem = symbolizer_allocator.Allocate(sizeof(InternalSymbolizer));
       return new(mem) InternalSymbolizer();
     }
     return 0;
   }
   char *SendCommand(bool is_data, const char *module_name, uptr module_offset) {
     SanitizerSymbolizeFn symbolize_fn = is_data ? __sanitizer_symbolize_data
                                                 : __sanitizer_symbolize_code;
     if (symbolize_fn(module_name, module_offset, buffer_, kBufferSize))
       return buffer_;
     return 0;
   }

  private:
   InternalSymbolizer() { }

   static const int kBufferSize = 16 * 1024;
   char buffer_[kBufferSize];
 };
 #else  // SANITIZER_SUPPORTS_WEAK_HOOKS

 class InternalSymbolizer {
  public:
   static InternalSymbolizer *get() { return 0; }
   char *SendCommand(bool is_data, const char *module_name, uptr module_offset) {
     return 0;
   }
 };

 #endif  // SANITIZER_SUPPORTS_WEAK_HOOKS

 class Symbolizer {
  public:
   uptr SymbolizeCode(uptr addr, AddressInfo *frames, uptr max_frames) {
     if (max_frames == 0)
       return 0;
     LoadedModule *module = FindModuleForAddress(addr);
     if (module == 0)
       return 0;
     const char *module_name = module->full_name();
     uptr module_offset = addr - module->base_address();
     const char *str = SendCommand(false, module_name, module_offset);
     if (str == 0) {
       // External symbolizer was not initialized or failed. Fill only data
       // about module name and offset.
       AddressInfo *info = &frames[0];
       info->Clear();
       info->FillAddressAndModuleInfo(addr, module_name, module_offset);
       return 1;
     }
     uptr frame_id = 0;
     for (frame_id = 0; frame_id < max_frames; frame_id++) {
       AddressInfo *info = &frames[frame_id];
       char *function_name = 0;
       str = ExtractToken(str, "\n", &function_name);
       CHECK(function_name);
       if (function_name[0] == '\0') {
         // There are no more frames.
         break;
       }
       info->Clear();
       info->FillAddressAndModuleInfo(addr, module_name, module_offset);
       info->function = function_name;
       // Parse <file>:<line>:<column> buffer.
       char *file_line_info = 0;
       str = ExtractToken(str, "\n", &file_line_info);
       CHECK(file_line_info);
       const char *line_info = ExtractToken(file_line_info, ":", &info->file);
       line_info = ExtractInt(line_info, ":", &info->line);
       line_info = ExtractInt(line_info, "", &info->column);
       InternalFree(file_line_info);

       // Functions and filenames can be "??", in which case we write 0
       // to address info to mark that names are unknown.
       if (0 == internal_strcmp(info->function, "??")) {
         InternalFree(info->function);
         info->function = 0;
       }
       if (0 == internal_strcmp(info->file, "??")) {
         InternalFree(info->file);
         info->file = 0;
       }
     }
     if (frame_id == 0) {
       // Make sure we return at least one frame.
       AddressInfo *info = &frames[0];
       info->Clear();
       info->FillAddressAndModuleInfo(addr, module_name, module_offset);
       frame_id = 1;
     }
     return frame_id;
   }

   bool SymbolizeData(uptr addr, DataInfo *info) {
     LoadedModule *module = FindModuleForAddress(addr);
     if (module == 0)
       return false;
     const char *module_name = module->full_name();
     uptr module_offset = addr - module->base_address();
     internal_memset(info, 0, sizeof(*info));
     info->address = addr;
     info->module = internal_strdup(module_name);
     info->module_offset = module_offset;
     const char *str = SendCommand(true, module_name, module_offset);
     if (str == 0)
       return true;
     str = ExtractToken(str, "\n", &info->name);
     str = ExtractUptr(str, " ", &info->start);
     str = ExtractUptr(str, "\n", &info->size);
     info->start += module->base_address();
     return true;
   }

   bool InitializeExternalSymbolizer(const char *path_to_symbolizer) {
     int input_fd, output_fd;
     if (!StartSymbolizerSubprocess(path_to_symbolizer, &input_fd, &output_fd))
       return false;
     void *mem = symbolizer_allocator.Allocate(sizeof(ExternalSymbolizer));
     external_symbolizer_ = new(mem) ExternalSymbolizer(path_to_symbolizer,
                                                        input_fd, output_fd);
     return true;
   }

   bool IsSymbolizerAvailable() {
     if (internal_symbolizer_ == 0)
       internal_symbolizer_ = InternalSymbolizer::get();
     return internal_symbolizer_ || external_symbolizer_;
   }

  private:
   char *SendCommand(bool is_data, const char *module_name, uptr module_offset) {
     // First, try to use internal symbolizer.
     if (!IsSymbolizerAvailable()) {
       return 0;
     }
     if (internal_symbolizer_) {
       return internal_symbolizer_->SendCommand(is_data, module_name,
                                                module_offset);
     }
     // Otherwise, fall back to external symbolizer.
     if (external_symbolizer_ == 0) {
       ReportExternalSymbolizerError(
           "WARNING: Trying to symbolize code, but external "
           "symbolizer is not initialized!\n");
       return 0;
     }
     for (;;) {
       char *reply = external_symbolizer_->SendCommand(is_data, module_name,
           module_offset);
       if (reply)
         return reply;
       // Try to restart symbolizer subprocess. If we don't succeed, forget
       // about it and don't try to use it later.
       if (!external_symbolizer_->Restart()) {
         ReportExternalSymbolizerError(
             "WARNING: Failed to use and restart external symbolizer!\n");
         external_symbolizer_ = 0;
         return 0;
       }
     }
   }

   LoadedModule *FindModuleForAddress(uptr address) {
     if (modules_ == 0) {
       modules_ = (LoadedModule*)(symbolizer_allocator.Allocate(
           kMaxNumberOfModuleContexts * sizeof(LoadedModule)));
       CHECK(modules_);
       n_modules_ = GetListOfModules(modules_, kMaxNumberOfModuleContexts);
       // FIXME: Return this check when GetListOfModules is implemented on Mac.
       // CHECK_GT(n_modules_, 0);
       CHECK_LT(n_modules_, kMaxNumberOfModuleContexts);
     }
     for (uptr i = 0; i < n_modules_; i++) {
       if (modules_[i].containsAddress(address)) {
         return &modules_[i];
       }
     }
     return 0;
   }
   void ReportExternalSymbolizerError(const char *msg) {
     // Don't use atomics here for now, as SymbolizeCode can't be called
     // from multiple threads anyway.
     static bool reported;
     if (!reported) {
       Report(msg);
       reported = true;
     }
   }

   // 16K loaded modules should be enough for everyone.
   static const uptr kMaxNumberOfModuleContexts = 1 << 14;
   LoadedModule *modules_;  // Array of module descriptions is leaked.
   uptr n_modules_;

   ExternalSymbolizer *external_symbolizer_;  // Leaked.
   InternalSymbolizer *internal_symbolizer_;  // Leaked.
 };

 static Symbolizer symbolizer;  // Linker initialized.

 uptr SymbolizeCode(uptr address, AddressInfo *frames, uptr max_frames) {
   return symbolizer.SymbolizeCode(address, frames, max_frames);
 }

 bool SymbolizeData(uptr address, DataInfo *info) {
   return symbolizer.SymbolizeData(address, info);
 }

 bool InitializeExternalSymbolizer(const char *path_to_symbolizer) {
   return symbolizer.InitializeExternalSymbolizer(path_to_symbolizer);
 }

 bool IsSymbolizerAvailable() {
   return symbolizer.IsSymbolizerAvailable();
 }

 }  // namespace __sanitizer
	//===-- sanitizer_symbolizer.cc -------------------------------------------===//
	//
	// The LLVM Compiler Infrastructure
	//
	// This file is distributed under the University of Illinois Open Source
	// License. See LICENSE.TXT for details.
	//
	//===----------------------------------------------------------------------===//
	//
	// This file is shared between AddressSanitizer and ThreadSanitizer
	// run-time libraries. See sanitizer_symbolizer.h for details.
	//===----------------------------------------------------------------------===//

	#include "sanitizer_common.h"
	#include "sanitizer_placement_new.h"
	#include "sanitizer_procmaps.h"
	#include "sanitizer_symbolizer.h"

	namespace __sanitizer {

	void AddressInfo::Clear() {
	InternalFree(module);
	InternalFree(function);
	InternalFree(file);
	internal_memset(this, 0, sizeof(AddressInfo));
	}

	LoadedModule::LoadedModule(const char *module_name, uptr base_address) {
	full_name_ = internal_strdup(module_name);
	base_address_ = base_address;
	n_ranges_ = 0;
	}

	void LoadedModule::addAddressRange(uptr beg, uptr end) {
	CHECK_LT(n_ranges_, kMaxNumberOfAddressRanges);
	ranges_[n_ranges_].beg = beg;
	ranges_[n_ranges_].end = end;
	n_ranges_++;
	}

	bool LoadedModule::containsAddress(uptr address) const {
	for (uptr i = 0; i < n_ranges_; i++) {
	if (ranges_[i].beg <= address && address < ranges_[i].end)
	return true;
	}
	return false;
	}

	// Extracts the prefix of "str" that consists of any characters not
	// present in "delims" string, and copies this prefix to "result", allocating
	// space for it.
	// Returns a pointer to "str" after skipping extracted prefix and first
	// delimiter char.
	static const char ExtractToken(const char str, const char *delims,
	char **result) {
	uptr prefix_len = internal_strcspn(str, delims);
	result = (char)InternalAlloc(prefix_len + 1);
	internal_memcpy(*result, str, prefix_len);
	(*result)[prefix_len] = '\0';
	const char *prefix_end = str + prefix_len;
	if (*prefix_end != '\0') prefix_end++;
	return prefix_end;
	}

	// Same as ExtractToken, but converts extracted token to integer.
	static const char ExtractInt(const char str, const char *delims,
	int *result) {
	char *buff;
	const char *ret = ExtractToken(str, delims, &buff);
	if (buff != 0) {
	*result = (int)internal_atoll(buff);
	}
	InternalFree(buff);
	return ret;
	}

	static const char ExtractUptr(const char str, const char *delims,
	uptr *result) {
	char *buff;
	const char *ret = ExtractToken(str, delims, &buff);
	if (buff != 0) {
	*result = (uptr)internal_atoll(buff);
	}
	InternalFree(buff);
	return ret;
	}

	// ExternalSymbolizer encapsulates communication between the tool and
	// external symbolizer program, running in a different subprocess,
	// For now we assume the following protocol:
	// For each request of the form
	// <module_name> <module_offset>
	// passed to STDIN, external symbolizer prints to STDOUT response:
	// <function_name>
	// <file_name>:<line_number>:<column_number>
	// <function_name>
	// <file_name>:<line_number>:<column_number>
	// ...
	// <empty line>
	class ExternalSymbolizer {
	public:
	ExternalSymbolizer(const char *path, int input_fd, int output_fd)
	: path_(path),
	input_fd_(input_fd),
	output_fd_(output_fd),
	times_restarted_(0) {
	CHECK(path_);
	CHECK_NE(input_fd_, kInvalidFd);
	CHECK_NE(output_fd_, kInvalidFd);
	}

	char SendCommand(bool is_data, const char module_name, uptr module_offset) {
	CHECK(module_name);
	internal_snprintf(buffer_, kBufferSize, "%s%s 0x%zx\n",
	is_data ? "DATA " : "", module_name, module_offset);
	if (!writeToSymbolizer(buffer_, internal_strlen(buffer_)))
	return 0;
	if (!readFromSymbolizer(buffer_, kBufferSize))
	return 0;
	return buffer_;
	}

	bool Restart() {
	if (times_restarted_ >= kMaxTimesRestarted) return false;
	times_restarted_++;
	internal_close(input_fd_);
	internal_close(output_fd_);
	return StartSymbolizerSubprocess(path_, &input_fd_, &output_fd_);
	}

	private:
	bool readFromSymbolizer(char *buffer, uptr max_length) {
	if (max_length == 0)
	return true;
	uptr read_len = 0;
	while (true) {
	uptr just_read = internal_read(input_fd_, buffer + read_len,
	max_length - read_len);
	// We can't read 0 bytes, as we don't expect external symbolizer to close
	// its stdout.
	if (just_read == 0 \|\| just_read == (uptr)-1) {
	Report("WARNING: Can't read from symbolizer at fd %d\n", input_fd_);
	return false;
	}
	read_len += just_read;
	// Empty line marks the end of symbolizer output.
	if (read_len >= 2 && buffer[read_len - 1] == '\n' &&
	buffer[read_len - 2] == '\n') {
	break;
	}
	}
	return true;
	}

	bool writeToSymbolizer(const char *buffer, uptr length) {
	if (length == 0)
	return true;
	uptr write_len = internal_write(output_fd_, buffer, length);
	if (write_len == 0 \|\| write_len == (uptr)-1) {
	Report("WARNING: Can't write to symbolizer at fd %d\n", output_fd_);
	return false;
	}
	return true;
	}

	const char *path_;
	int input_fd_;
	int output_fd_;

	static const uptr kBufferSize = 16 * 1024;
	char buffer_[kBufferSize];

	static const uptr kMaxTimesRestarted = 5;
	uptr times_restarted_;
	};

	static LowLevelAllocator symbolizer_allocator; // Linker initialized.

	#if SANITIZER_SUPPORTS_WEAK_HOOKS
	extern "C" {
	SANITIZER_WEAK_ATTRIBUTE SANITIZER_INTERFACE_ATTRIBUTE
	bool __sanitizer_symbolize_code(const char *ModuleName, u64 ModuleOffset,
	char *Buffer, int MaxLength);
	SANITIZER_WEAK_ATTRIBUTE SANITIZER_INTERFACE_ATTRIBUTE
	bool __sanitizer_symbolize_data(const char *ModuleName, u64 ModuleOffset,
	char *Buffer, int MaxLength);
	} // extern "C"

	class InternalSymbolizer {
	public:
	typedef bool (SanitizerSymbolizeFn)(const char, u64, char*, int);
	static InternalSymbolizer *get() {
	if (__sanitizer_symbolize_code != 0 &&
	__sanitizer_symbolize_data != 0) {
	void *mem = symbolizer_allocator.Allocate(sizeof(InternalSymbolizer));
	return new(mem) InternalSymbolizer();
	}
	return 0;
	}
	char SendCommand(bool is_data, const char module_name, uptr module_offset) {
	SanitizerSymbolizeFn symbolize_fn = is_data ? __sanitizer_symbolize_data
	: __sanitizer_symbolize_code;
	if (symbolize_fn(module_name, module_offset, buffer_, kBufferSize))
	return buffer_;
	return 0;
	}

	private:
	InternalSymbolizer() { }

	static const int kBufferSize = 16 * 1024;
	char buffer_[kBufferSize];
	};
	#else // SANITIZER_SUPPORTS_WEAK_HOOKS

	class InternalSymbolizer {
	public:
	static InternalSymbolizer *get() { return 0; }
	char SendCommand(bool is_data, const char module_name, uptr module_offset) {
	return 0;
	}
	};

	#endif // SANITIZER_SUPPORTS_WEAK_HOOKS

	class Symbolizer {
	public:
	uptr SymbolizeCode(uptr addr, AddressInfo *frames, uptr max_frames) {
	if (max_frames == 0)
	return 0;
	LoadedModule *module = FindModuleForAddress(addr);
	if (module == 0)
	return 0;
	const char *module_name = module->full_name();
	uptr module_offset = addr - module->base_address();
	const char *str = SendCommand(false, module_name, module_offset);
	if (str == 0) {
	// External symbolizer was not initialized or failed. Fill only data
	// about module name and offset.
	AddressInfo *info = &frames[0];
	info->Clear();
	info->FillAddressAndModuleInfo(addr, module_name, module_offset);
	return 1;
	}
	uptr frame_id = 0;
	for (frame_id = 0; frame_id < max_frames; frame_id++) {
	AddressInfo *info = &frames[frame_id];
	char *function_name = 0;
	str = ExtractToken(str, "\n", &function_name);
	CHECK(function_name);
	if (function_name[0] == '\0') {
	// There are no more frames.
	break;
	}
	info->Clear();
	info->FillAddressAndModuleInfo(addr, module_name, module_offset);
	info->function = function_name;
	// Parse <file>:<line>:<column> buffer.
	char *file_line_info = 0;
	str = ExtractToken(str, "\n", &file_line_info);
	CHECK(file_line_info);
	const char *line_info = ExtractToken(file_line_info, ":", &info->file);
	line_info = ExtractInt(line_info, ":", &info->line);
	line_info = ExtractInt(line_info, "", &info->column);
	InternalFree(file_line_info);

	// Functions and filenames can be "??", in which case we write 0
	// to address info to mark that names are unknown.
	if (0 == internal_strcmp(info->function, "??")) {
	InternalFree(info->function);
	info->function = 0;
	}
	if (0 == internal_strcmp(info->file, "??")) {
	InternalFree(info->file);
	info->file = 0;
	}
	}
	if (frame_id == 0) {
	// Make sure we return at least one frame.
	AddressInfo *info = &frames[0];
	info->Clear();
	info->FillAddressAndModuleInfo(addr, module_name, module_offset);
	frame_id = 1;
	}
	return frame_id;
	}

	bool SymbolizeData(uptr addr, DataInfo *info) {
	LoadedModule *module = FindModuleForAddress(addr);
	if (module == 0)
	return false;
	const char *module_name = module->full_name();
	uptr module_offset = addr - module->base_address();
	internal_memset(info, 0, sizeof(*info));
	info->address = addr;
	info->module = internal_strdup(module_name);
	info->module_offset = module_offset;
	const char *str = SendCommand(true, module_name, module_offset);
	if (str == 0)
	return true;
	str = ExtractToken(str, "\n", &info->name);
	str = ExtractUptr(str, " ", &info->start);
	str = ExtractUptr(str, "\n", &info->size);
	info->start += module->base_address();
	return true;
	}

	bool InitializeExternalSymbolizer(const char *path_to_symbolizer) {
	int input_fd, output_fd;
	if (!StartSymbolizerSubprocess(path_to_symbolizer, &input_fd, &output_fd))
	return false;
	void *mem = symbolizer_allocator.Allocate(sizeof(ExternalSymbolizer));
	external_symbolizer_ = new(mem) ExternalSymbolizer(path_to_symbolizer,
	input_fd, output_fd);
	return true;
	}

	bool IsSymbolizerAvailable() {
	if (internal_symbolizer_ == 0)
	internal_symbolizer_ = InternalSymbolizer::get();
	return internal_symbolizer_ \|\| external_symbolizer_;
	}

	private:
	char SendCommand(bool is_data, const char module_name, uptr module_offset) {
	// First, try to use internal symbolizer.
	if (!IsSymbolizerAvailable()) {
	return 0;
	}
	if (internal_symbolizer_) {
	return internal_symbolizer_->SendCommand(is_data, module_name,
	module_offset);
	}
	// Otherwise, fall back to external symbolizer.
	if (external_symbolizer_ == 0) {
	ReportExternalSymbolizerError(
	"WARNING: Trying to symbolize code, but external "
	"symbolizer is not initialized!\n");
	return 0;
	}
	for (;;) {
	char *reply = external_symbolizer_->SendCommand(is_data, module_name,
	module_offset);
	if (reply)
	return reply;
	// Try to restart symbolizer subprocess. If we don't succeed, forget
	// about it and don't try to use it later.
	if (!external_symbolizer_->Restart()) {
	ReportExternalSymbolizerError(
	"WARNING: Failed to use and restart external symbolizer!\n");
	external_symbolizer_ = 0;
	return 0;
	}
	}
	}

	LoadedModule *FindModuleForAddress(uptr address) {
	if (modules_ == 0) {
	modules_ = (LoadedModule*)(symbolizer_allocator.Allocate(
	kMaxNumberOfModuleContexts * sizeof(LoadedModule)));
	CHECK(modules_);
	n_modules_ = GetListOfModules(modules_, kMaxNumberOfModuleContexts);
	// FIXME: Return this check when GetListOfModules is implemented on Mac.
	// CHECK_GT(n_modules_, 0);
	CHECK_LT(n_modules_, kMaxNumberOfModuleContexts);
	}
	for (uptr i = 0; i < n_modules_; i++) {
	if (modules_[i].containsAddress(address)) {
	return &modules_[i];
	}
	}
	return 0;
	}
	void ReportExternalSymbolizerError(const char *msg) {
	// Don't use atomics here for now, as SymbolizeCode can't be called
	// from multiple threads anyway.
	static bool reported;
	if (!reported) {
	Report(msg);
	reported = true;
	}
	}

	// 16K loaded modules should be enough for everyone.
	static const uptr kMaxNumberOfModuleContexts = 1 << 14;
	LoadedModule *modules_; // Array of module descriptions is leaked.
	uptr n_modules_;

	ExternalSymbolizer *external_symbolizer_; // Leaked.
	InternalSymbolizer *internal_symbolizer_; // Leaked.
	};

	static Symbolizer symbolizer; // Linker initialized.

	uptr SymbolizeCode(uptr address, AddressInfo *frames, uptr max_frames) {
	return symbolizer.SymbolizeCode(address, frames, max_frames);
	}

	bool SymbolizeData(uptr address, DataInfo *info) {
	return symbolizer.SymbolizeData(address, info);
	}

	bool InitializeExternalSymbolizer(const char *path_to_symbolizer) {
	return symbolizer.InitializeExternalSymbolizer(path_to_symbolizer);
	}

	bool IsSymbolizerAvailable() {
	return symbolizer.IsSymbolizerAvailable();
	}

	} // namespace __sanitizer