キーボードリマッパーから見る Mac OS X のカーネル拡張の作り方

• Kernel Extension Concepts: Introduction to Kernel Extension Concepts
• Kernel Extension Concepts: Hello I/O Kit: Creating a Device Driver With Xcode

1. カーネル拡張本体の開発
2. (必要があれば) ローダスクリプト等のユーティリティの作成
3. パッケージング
4. 公開

% xcodebuild clean
% xcodebuild build

% /Developer/Applications/Utilities/PackageMaker.app/Contents/MacOS/PackageMaker --help

• C++ 言語を使う場合 STL とか使えません。 mem_fun_ref とかは諦めましょう。
• コードにバグがあると、まずクラッシュします。 カーネル拡張の種類によっては Darwin/x86 とかを仮想マシンに用意して作業したほうが楽だと思います。 仮想マシンが無理な場合には、テスト用ハードウェアを別途用意したほうが良いでしょう。

• 処理が比較的簡潔になる。
• アプリケーションレイヤに近いレイヤでの処理になる。
• 他のソフトウェアでの実績がある。

// IOHIKeyboard.h

class IOHIKeyboard : public IOHIDevice
{
...
    OSObject *                 _keyboardEventTarget;
    KeyboardEventAction        _keyboardEventAction;
    OSObject *                 _keyboardSpecialEventTarget;
    KeyboardSpecialEventAction _keyboardSpecialEventAction;
    OSObject *                 _updateEventFlagsTarget;
    UpdateEventFlagsAction     _updateEventFlagsAction;
...
}

// IOHIKeyboard.cpp

bool IOHIKeyboard::open(...
                        KeyboardEventCallback        keCallback,
                        ...)
{
    ...
    _keyboardEventAction        = (KeyboardEventAction)keCallback;
    ...
}

// IOHIKeyboard.cpp

void IOHIKeyboard::_keyboardEvent(...)
{
    KeyboardEventCallback       keCallback;
    keCallback = (KeyboardEventCallback)self->_keyboardEventAction;

    if ( !keCallback )
        return;

    (*keCallback)(...);
}

• IOHIDSystem の getProviderIterator で取得する。
• Notification Methods を利用する。

// KeyRemap4MacBook.cpp

bool
org_pqrs_driver_KeyRemap4MacBook::start(IOService *provider)
{
  keyboardNotifier = addNotification(gIOMatchedNotification,
                                     serviceMatching("IOHIKeyboard"),
                                     ((IOServiceNotificationHandler)&(org_pqrs_driver_KeyRemap4MacBook::notifier_hookKeyboard)),
                                     this, NULL, 0);
}

bool
org_pqrs_driver_KeyRemap4MacBook::notifier_hookKeyboard(org_pqrs_driver_KeyRemap4MacBook *self, void *ref, IOService *newService)
{
  IOLog("KeyRemap4MacBook::notifier_hookKeyboard\n");

  IOHIKeyboard *kbd = OSDynamicCast(IOHIKeyboard, newService);
  return replaceKeyboardEvent(kbd);
}

bool
org_pqrs_driver_KeyRemap4MacBook::replaceKeyboardEvent(IOHIKeyboard *kbd)
{
  if (kbd) {
    const char *name = kbd->getName();
    IOLog("KeyRemap4MacBook::replaceKeyboardEvent name = %s\n", name);

    if (strcmp(name, "IOHIDKeyboard") == 0) {
      HookedKeyboard *p = new_hookedKeyboard();
      if (p) {
        IOLog("KeyRemap4MacBook::replaceKeyboardEvent 0x%x (%x)\n", kbd, kbd->_keyboardEventAction);
        p->kbd = kbd;
        p->origEventAction = kbd->_keyboardEventAction;

        kbd->_keyboardEventAction = reinterpret_cast<KeyboardEventAction>(org_pqrs_driver_KeyRemap4MacBook::keyboardEventCallBack);
      }
    }
    return true;
  }
  return false;
}

// KeyRemap4MacBook.cpp

void
org_pqrs_driver_KeyRemap4MacBook::keyboardEventCallBack(OSObject *target,
                                                        unsigned eventType,
                                                        unsigned flags,
                                                        unsigned key,
                                                        unsigned charCode,
                                                        unsigned charSet,
                                                        unsigned origCharCode,
                                                        unsigned origCharSet,
                                                        unsigned keyboardType,
                                                        bool repeat,
                                                        AbsoluteTime ts,
                                                        OSObject *sender,
                                                        void *refcon)
{
  IOHIKeyboard *kbd = OSDynamicCast(IOHIKeyboard, sender);
  if (kbd) {
    HookedKeyboard *p = search_hookedKeyboard(kbd);
    if (p) {
      remap(&eventType, &flags, &key, &charCode, &charSet,
            &origCharCode, &origCharSet, &keyboardType);

      p->origEventAction(target, eventType, flags, key, charCode,
                         charSet, origCharCode, origCharSet, keyboardType, repeat, ts);
    }
  }
}

// IOHIKeyboard.h

typedef void (*KeyboardEventAction)(       OSObject * target,
                    /* eventFlags  */      unsigned   eventType,
                    /* flags */            unsigned   flags,
                    /* keyCode */          unsigned   key,
                    /* charCode */         unsigned   charCode,
                    /* charSet */          unsigned   charSet,
                    /* originalCharCode */ unsigned   origCharCode,
                    /* originalCharSet */  unsigned   origCharSet,
                    /* keyboardType */     unsigned   keyboardType,
                    /* repeat */           bool       repeat,
                    /* atTime */           AbsoluteTime ts);

1. とりあえず、最初に見つかった IOHIKeyboard インスタンスを信じて使う。
2. keyboardEventGated によろしく頼む。
3. _keyboardEventAction は実際には KeyboardEventCallback 型として処理されていることを利用する。

// IOHIKeyboard.h

typedef void (*KeyboardEventCallback)(
                    /* target */           OSObject * target,
                    /* eventFlags  */      unsigned   eventType,
                    /* flags */            unsigned   flags,
                    /* keyCode */          unsigned   key,
                    /* charCode */         unsigned   charCode,
                    /* charSet */          unsigned   charSet,
                    /* originalCharCode */ unsigned   origCharCode,
                    /* originalCharSet */  unsigned   origCharSet,
                    /* keyboardType */     unsigned   keyboardType,
                    /* repeat */           bool       repeat,
                    /* atTime */           AbsoluteTime ts,
                    /* sender */           OSObject * sender,
                    /* refcon */           void *     refcon);

    <key>OSBundleLibraries</key>
    <dict>
      ...
      <key>com.apple.kpi.bsd</key>
      <string>8.0.0</string>
      ...
    </dict>
  </dict>

• SYSCTL_INT や SYSCTL_STRING で宣言を行う。
• sysctl_register_oid で登録 & sysctl_unregister_oid で登録解除を行う。

// KeyRemap4MacBook.cpp

SYSCTL_DECL(_keyremap4macbook);
SYSCTL_NODE(, OID_AUTO, keyremap4macbook, CTLFLAG_RW, 0, "KeyRemap4MacBook");

SYSCTL_INT(_keyremap4macbook, OID_AUTO, return2option, CTLFLAG_RW,
            &(org_pqrs_driver_KeyRemap4MacBook::config_return2option),
           0,
           "Remap 'Return Key' as 'Command Key'");

SYSCTL_INT(_keyremap4macbook, OID_AUTO, shift2escape, CTLTYPE_INT|CTLFLAG_RW,
           &(org_pqrs_driver_KeyRemap4MacBook::config_shift2escape),
           0,
           "Remap 'ShiftR Key' as 'Escape Key'");

SYSCTL_INT(_keyremap4macbook, OID_AUTO, shift2escape, CTLTYPE_INT|CTLFLAG_RW,
           &(org_pqrs_driver_KeyRemap4MacBook::config_shift2escape),
           0,
           "Remap 'ShiftR Key' as 'Escape Key'");

SYSCTL_INT(_keyremap4macbook, OID_AUTO, debug, CTLTYPE_INT|CTLFLAG_RW,
           &(org_pqrs_driver_KeyRemap4MacBook::config_debug),
           0,
           "Output Debug Messages");

SYSCTL_STRING(_keyremap4macbook, OID_AUTO, version, CTLFLAG_RD,
              org_pqrs_driver_KeyRemap4MacBook::config_version,
              0,
              "Output Version");

// KeyRemap4MacBook.cpp

bool
org_pqrs_driver_KeyRemap4MacBook::init(OSDictionary *dict)
{
  ...
  sysctl_register_oid(&sysctl__keyremap4macbook);
  sysctl_register_oid(&sysctl__keyremap4macbook_return2option);
  sysctl_register_oid(&sysctl__keyremap4macbook_shift2escape);
  sysctl_register_oid(&sysctl__keyremap4macbook_debug);
  sysctl_register_oid(&sysctl__keyremap4macbook_version);
  ...
}

void
org_pqrs_driver_KeyRemap4MacBook::free(void)
{
  ...
  sysctl_unregister_oid(&sysctl__keyremap4macbook);
  sysctl_unregister_oid(&sysctl__keyremap4macbook_return2option);
  sysctl_unregister_oid(&sysctl__keyremap4macbook_shift2escape);
  sysctl_unregister_oid(&sysctl__keyremap4macbook_debug);
  sysctl_unregister_oid(&sysctl__keyremap4macbook_version);
  ...
}