cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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notifier.rst (1874B)

      1=================
      2Keyboard notifier
      3=================
      4
      5One can use register_keyboard_notifier to get called back on keyboard
      6events (see kbd_keycode() function for details).  The passed structure is
      7keyboard_notifier_param (see <linux/keyboard.h>):
      8
      9- 'vc' always provide the VC for which the keyboard event applies;
     10- 'down' is 1 for a key press event, 0 for a key release;
     11- 'shift' is the current modifier state, mask bit indexes are KG_*;
     12- 'ledstate' is the current LED state;
     13- 'value' depends on the type of event.
     14
     15- KBD_KEYCODE events are always sent before other events, value is the keycode.
     16- KBD_UNBOUND_KEYCODE events are sent if the keycode is not bound to a keysym.
     17  value is the keycode.
     18- KBD_UNICODE events are sent if the keycode -> keysym translation produced a
     19  unicode character. value is the unicode value.
     20- KBD_KEYSYM events are sent if the keycode -> keysym translation produced a
     21  non-unicode character. value is the keysym.
     22- KBD_POST_KEYSYM events are sent after the treatment of non-unicode keysyms.
     23  That permits one to inspect the resulting LEDs for instance.
     24
     25For each kind of event but the last, the callback may return NOTIFY_STOP in
     26order to "eat" the event: the notify loop is stopped and the keyboard event is
     27dropped.
     28
     29In a rough C snippet, we have::
     30
     31    kbd_keycode(keycode) {
     32	...
     33	params.value = keycode;
     34	if (notifier_call_chain(KBD_KEYCODE,&params) == NOTIFY_STOP)
     35	    || !bound) {
     36		notifier_call_chain(KBD_UNBOUND_KEYCODE,&params);
     37		return;
     38	}
     39
     40	if (unicode) {
     41		param.value = unicode;
     42		if (notifier_call_chain(KBD_UNICODE,&params) == NOTIFY_STOP)
     43			return;
     44		emit unicode;
     45		return;
     46	}
     47
     48	params.value = keysym;
     49	if (notifier_call_chain(KBD_KEYSYM,&params) == NOTIFY_STOP)
     50		return;
     51	apply keysym;
     52	notifier_call_chain(KBD_POST_KEYSYM,&params);
     53    }
     54
     55.. note:: This notifier is usually called from interrupt context.