src/client/windows/handler/exception_handler.h

// Copyright (c) 2006, 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.

// ExceptionHandler can write a minidump file when an exception occurs,
// or when WriteMinidump() is called explicitly by your program.
//
// To have the exception handler write minidumps when an uncaught exception
// (crash) occurs, you should create an instance early in the execution
// of your program, and keep it around for the entire time you want to
// have crash handling active (typically, until shutdown).
//
// If you want to write minidumps without installing the exception handler,
// you can create an ExceptionHandler with install_handler set to false,
// then call WriteMinidump.  You can also use this technique if you want to
// use different minidump callbacks for different call sites.
//
// In either case, a callback function is called when a minidump is written,
// which receives the unqiue id of the minidump.  The caller can use this
// id to collect and write additional application state, and to launch an
// external crash-reporting application.
//
// It is important that creation and destruction of ExceptionHandler objects
// be nested cleanly, when using install_handler = true.
// Avoid the following pattern:
//   ExceptionHandler *e = new ExceptionHandler(...);
//   ExceptionHandler *f = new ExceptionHandler(...);
//   delete e;
// This will put the exception filter stack into an inconsistent state.
//
// To use this library in your project, you will need to link against
// ole32.lib.

#ifndef CLIENT_WINDOWS_HANDLER_EXCEPTION_HANDLER_H__
#define CLIENT_WINDOWS_HANDLER_EXCEPTION_HANDLER_H__

#include <Windows.h>
#include <DbgHelp.h>

#pragma warning( push )
// Disable exception handler warnings.
#pragma warning( disable : 4530 ) 

#include <string>
#include <vector>

namespace google_airbag {

using std::vector;
using std::wstring;

class ExceptionHandler {
 public:
  // A callback function to run before Airbag performs any substantial
  // processing of an exception.  A FilterCallback is called before writing
  // a minidump.  context is the parameter supplied by the user as
  // callback_context when the handler was created.
  //
  // If a FilterCallback returns true, Airbag will continue processing,
  // attempting to write a minidump.  If a FilterCallback returns false, Airbag
  // will immediately report the exception as unhandled without writing a
  // minidump, allowing another handler the opportunity to handle it.
  typedef bool (*FilterCallback)(void *context);

  // A callback function to run after the minidump has been written.
  // minidump_id is a unique id for the dump, so the minidump
  // file is <dump_path>\<minidump_id>.dmp.  context is the parameter supplied
  // by the user as callback_context when the handler was created.  succeeded
  // indicates whether a minidump file was successfully written.
  //
  // If an exception occurred and the callback returns true, Airbag will treat
  // the exception as fully-handled, suppressing any other handlers from being
  // notified of the exception.  If the callback returns false, Airbag will
  // treat the exception as unhandled, and allow another handler to handle it.
  // If there are no other handlers, Airbag will report the exception to the
  // system as unhandled, allowing a debugger or native crash dialog the
  // opportunity to handle the exception.  Most callback implementations
  // should normally return the value of |succeeded|, or when they wish to
  // not report an exception of handled, false.  Callbacks will rarely want to
  // return true directly (unless |succeeded| is true).
  typedef bool (*MinidumpCallback)(const wchar_t *dump_path,
                                   const wchar_t *minidump_id,
                                   void *context,
                                   bool succeeded);

  // Creates a new ExceptionHandler instance to handle writing minidumps.
  // Before writing a minidump, the optional filter callback will be called.
  // Its return value determines whether or not Airbag should write a minidump.
  // Minidump files will be written to dump_path, and the optional callback
  // is called after writing the dump file, as described above.
  // If install_handler is true, then a minidump will be written whenever
  // an unhandled exception occurs.  If it is false, minidumps will only
  // be written when WriteMinidump is called.
  ExceptionHandler(const wstring &dump_path,
                   FilterCallback filter, MinidumpCallback callback,
                   void *callback_context, bool install_handler);
  ~ExceptionHandler();

  // Get and set the minidump path.
  wstring dump_path() const { return dump_path_; }
  void set_dump_path(const wstring &dump_path) {
    dump_path_ = dump_path;
    dump_path_c_ = dump_path_.c_str();
    UpdateNextID();  // Necessary to put dump_path_ in next_minidump_path_.
  }

  // Writes a minidump immediately.  This can be used to capture the
  // execution state independently of a crash.  Returns true on success.
  bool WriteMinidump();

  // Convenience form of WriteMinidump which does not require an
  // ExceptionHandler instance.
  static bool WriteMinidump(const wstring &dump_path,
                            MinidumpCallback callback, void *callback_context);

 private:
  // Function pointer type for MiniDumpWriteDump, which is looked up
  // dynamically.
  typedef BOOL (WINAPI *MiniDumpWriteDump_type)(
      HANDLE hProcess,
      DWORD dwPid,
      HANDLE hFile,
      MINIDUMP_TYPE DumpType,
      CONST PMINIDUMP_EXCEPTION_INFORMATION ExceptionParam,
      CONST PMINIDUMP_USER_STREAM_INFORMATION UserStreamParam,
      CONST PMINIDUMP_CALLBACK_INFORMATION CallbackParam);

  // Runs the main loop for the exception handler thread.
  static DWORD WINAPI ExceptionHandlerThreadMain(void *lpParameter);

  // Called on the exception thread when an unhandled exception occurs.
  // Signals the exception handler thread to handle the exception.
  static LONG WINAPI HandleException(EXCEPTION_POINTERS *exinfo);

  // This is called on the exception thread or on another thread that
  // the user wishes to produce a dump from.  It calls
  // WriteMinidumpWithException on the handler thread, avoiding stack
  // overflows and inconsistent dumps due to writing the dump from
  // the exception thread.  If the dump is requested as a result of an
  // exception, exinfo contains exception information, otherwise, it
  // is NULL.
  bool WriteMinidumpOnHandlerThread(EXCEPTION_POINTERS *exinfo);

  // This function does the actual writing of a minidump.  It is called
  // on the handler thread.  requesting_thread_id is the ID of the thread
  // that requested the dump.  If the dump is requested as a result of
  // an exception, exinfo contains exception information, otherwise,
  // it is NULL.
  bool WriteMinidumpWithException(DWORD requesting_thread_id,
                                  EXCEPTION_POINTERS *exinfo);

  // Generates a new ID and stores it in next_minidump_id_, and stores the
  // path of the next minidump to be written in next_minidump_path_.
  void UpdateNextID();

  FilterCallback filter_;
  MinidumpCallback callback_;
  void *callback_context_;

  // The directory in which a minidump will be written, set by the dump_path
  // argument to the constructor, or set_dump_path.
  wstring dump_path_;

  // The basename of the next minidump to be written, without the extension.
  wstring next_minidump_id_;

  // The full pathname of the next minidump to be written, including the file
  // extension.
  wstring next_minidump_path_;

  // Pointers to C-string representations of the above.  These are set when
  // the above wstring versions are set in order to avoid calling c_str during
  // an exception, as c_str may attempt to allocate heap memory.  These
  // pointers are not owned by the ExceptionHandler object, but their lifetimes
  // should be equivalent to the lifetimes of the associated wstring, provided
  // that the wstrings are not altered.
  const wchar_t *dump_path_c_;
  const wchar_t *next_minidump_id_c_;
  const wchar_t *next_minidump_path_c_;

  HMODULE dbghelp_module_;
  MiniDumpWriteDump_type minidump_write_dump_;

  // True if the ExceptionHandler installed an unhandled exception filter
  // when created (with an install_handler parameter set to true).
  bool installed_handler_;

  // When installed_handler_ is true, previous_filter_ is the unhandled
  // exception filter that was set prior to installing ExceptionHandler as
  // the unhandled exception filter and pointing it to |this|.  NULL indicates
  // that there is no previous unhandled exception filter.
  LPTOP_LEVEL_EXCEPTION_FILTER previous_filter_;

  // The exception handler thread.
  HANDLE handler_thread_;

  // The critical section enforcing the requirement that only one exception be
  // handled by a handler at a time.
  CRITICAL_SECTION handler_critical_section_;

  // Semaphores used to move exception handling between the exception thread
  // and the handler thread.  handler_start_semaphore_ is signalled by the
  // exception thread to wake up the handler thread when an exception occurs.
  // handler_finish_semaphore_ is signalled by the handler thread to wake up
  // the exception thread when handling is complete.
  HANDLE handler_start_semaphore_;
  HANDLE handler_finish_semaphore_;

  // The next 2 fields contain data passed from the requesting thread to
  // the handler thread.

  // The thread ID of the thread requesting the dump (either the exception
  // thread or any other thread that called WriteMinidump directly).
  DWORD requesting_thread_id_;

  // The exception info passed to the exception handler on the exception
  // thread, if an exception occurred.  NULL for user-requested dumps.
  EXCEPTION_POINTERS *exception_info_;

  // The return value of the handler, passed from the handler thread back to
  // the requesting thread.
  bool handler_return_value_;

  // A stack of ExceptionHandler objects that have installed unhandled
  // exception filters.  This vector is used by HandleException to determine
  // which ExceptionHandler object to route an exception to.  When an
  // ExceptionHandler is created with install_handler true, it will append
  // itself to this list.
  static vector<ExceptionHandler *> *handler_stack_;

  // The index of the ExceptionHandler in handler_stack_ that will handle the
  // next exception.  Note that 0 means the last entry in handler_stack_, 1
  // means the next-to-last entry, and so on.  This is used by HandleException
  // to support multiple stacked Airbag handlers.
  static LONG handler_stack_index_;

  // handler_stack_critical_section_ guards operations on handler_stack_ and
  // handler_stack_index_.
  static CRITICAL_SECTION handler_stack_critical_section_;

  // True when handler_stack_critical_section_ has been initialized.
  static bool handler_stack_critical_section_initialized_;

  // disallow copy ctor and operator=
  explicit ExceptionHandler(const ExceptionHandler &);
  void operator=(const ExceptionHandler &);
};

}  // namespace google_airbag

#pragma warning( pop )

#endif  // CLIENT_WINDOWS_HANDLER_EXCEPTION_HANDLER_H__