[PATCH v3] i8042: Add debug_kbd option

[cpaul@redhat.com]

From: Stephen Chandler Paul <cpaul@redhat.com>

A big problem with the current i8042 debugging option is that it outputs
data going to and from the keyboard by default. As a result, many dmesg
logs uploaded by users will unintentionally contain sensitive information
such as their password, as such it's probably a good idea not to output
data coming from the keyboard unless specifically enabled by the user.

Signed-off-by: Stephen Chandler Paul <cpaul@redhat.com>
---
That patch was not working at all like I thought it was, the results on the
machine I tested it on were very misleading so I apologize for any trouble that
may have caused! I've done more thorough testing of this, and it should work
perfectly on any machine.

				    Changes
* Bus structs are shared between devices, whoops. Now when the notifier goes
  off we check two things:
    * That the device actually belongs to the i8042 platform driver. This is
      something that's difficult to reproduce, since devices on the i8042 bus
      are usually handled by the plaform driver. If they don't happen to be
      however (which currently I've only seen with ps2emu, a kernel module I'm
      working on to replay PS/2 devices in the kernel), then we make the false
      assumption the port_data variable points to an i8042_port struct, and
      very likely crash the machine or worse.
    * That the IRQ of the port is equivalent to that of the KBD port, so that
      we only mask the interrupts coming from the keyboard.

 Documentation/kernel-parameters.txt |  3 ++
 drivers/input/serio/i8042.c         | 64 +++++++++++++++++++++++++++++++++----
 drivers/input/serio/i8042.h         | 13 ++++++++
 3 files changed, 74 insertions(+), 6 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index ae44749..a9d2b19 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1304,6 +1304,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			     <bus_id>,<clkrate>
 
 	i8042.debug	[HW] Toggle i8042 debug mode
+	i8042.debug_kbd [HW] Enable printing of interrupt data from the KBD port
+			     (disabled by default, requires that i8042.debug=1
+			     be enabled)
 	i8042.direct	[HW] Put keyboard port into non-translated mode
 	i8042.dumbkbd	[HW] Pretend that controller can only read data from
 			     keyboard and cannot control its state
diff --git a/drivers/input/serio/i8042.c b/drivers/input/serio/i8042.c
index cb5ece7..0e17bdd 100644
--- a/drivers/input/serio/i8042.c
+++ b/drivers/input/serio/i8042.c
@@ -88,6 +88,10 @@ MODULE_PARM_DESC(nopnp, "Do not use PNP to detect controller settings");
 static bool i8042_debug;
 module_param_named(debug, i8042_debug, bool, 0600);
 MODULE_PARM_DESC(debug, "Turn i8042 debugging mode on and off");
+
+static bool i8042_debug_kbd;
+module_param_named(debug_kbd, i8042_debug_kbd, bool, 0600);
+MODULE_PARM_DESC(i8042_kbd, "Turn i8042 kbd debugging output on or off (requires i8042.debug=1)");
 #endif
 
 static bool i8042_bypass_aux_irq_test;
@@ -116,6 +120,9 @@ struct i8042_port {
 	struct serio *serio;
 	int irq;
 	bool exists;
+#ifdef DEBUG
+	bool filter_dbg;
+#endif
 	signed char mux;
 };
 
@@ -133,6 +140,9 @@ static bool i8042_kbd_irq_registered;
 static bool i8042_aux_irq_registered;
 static unsigned char i8042_suppress_kbd_ack;
 static struct platform_device *i8042_platform_device;
+#ifdef DEBUG
+static struct notifier_block i8042_kbd_bind_notifier_block;
+#endif
 
 static irqreturn_t i8042_interrupt(int irq, void *dev_id);
 static bool (*i8042_platform_filter)(unsigned char data, unsigned char str,
@@ -528,10 +538,10 @@ static irqreturn_t i8042_interrupt(int irq, void *dev_id)
 	port = &i8042_ports[port_no];
 	serio = port->exists ? port->serio : NULL;
 
-	dbg("%02x <- i8042 (interrupt, %d, %d%s%s)\n",
-	    data, port_no, irq,
-	    dfl & SERIO_PARITY ? ", bad parity" : "",
-	    dfl & SERIO_TIMEOUT ? ", timeout" : "");
+	filter_dbg(port->filter_dbg, data, "<- i8042 (interrupt, %d, %d%s%s)\n",
+		   port_no, irq,
+		   dfl & SERIO_PARITY ? ", bad parity" : "",
+		   dfl & SERIO_TIMEOUT ? ", timeout" : "");
 
 	filtered = i8042_filter(data, str, serio);
 
@@ -1329,6 +1339,13 @@ static void __init i8042_register_ports(void)
 				i8042_ports[i].irq);
 			serio_register_port(serio);
 			device_set_wakeup_capable(&serio->dev, true);
+#ifdef DEBUG
+			if (i == I8042_KBD_PORT_NO) {
+				bus_register_notifier(
+					serio->dev.bus,
+					&i8042_kbd_bind_notifier_block);
+			}
+#endif
 		}
 	}
 }
@@ -1338,8 +1355,17 @@ static void i8042_unregister_ports(void)
 	int i;
 
 	for (i = 0; i < I8042_NUM_PORTS; i++) {
-		if (i8042_ports[i].serio) {
-			serio_unregister_port(i8042_ports[i].serio);
+		struct serio *serio = i8042_ports[i].serio;
+
+		if (serio) {
+#ifdef DEBUG
+			if (i == I8042_KBD_PORT_NO) {
+				bus_unregister_notifier(
+					serio->dev.bus,
+					&i8042_kbd_bind_notifier_block);
+			}
+#endif
+			serio_unregister_port(serio);
 			i8042_ports[i].serio = NULL;
 		}
 	}
@@ -1438,6 +1464,26 @@ static int __init i8042_setup_kbd(void)
 	return error;
 }
 
+#ifdef DEBUG
+static int i8042_kbd_bind_notifier(struct notifier_block *nb,
+				   unsigned long action, void *data)
+{
+	struct device *dev = data;
+	struct i8042_port *port = to_serio_port(dev)->port_data;
+
+	if (dev->parent != &i8042_platform_device->dev ||
+	    port->irq != I8042_KBD_IRQ)
+		return 0;
+
+	if (action == BUS_NOTIFY_BOUND_DRIVER)
+		port->filter_dbg = true;
+	else if (action == BUS_NOTIFY_UNBOUND_DRIVER)
+		port->filter_dbg = false;
+
+	return 0;
+}
+#endif
+
 static int __init i8042_probe(struct platform_device *dev)
 {
 	int error;
@@ -1507,6 +1553,12 @@ static struct platform_driver i8042_driver = {
 	.shutdown	= i8042_shutdown,
 };
 
+#ifdef DEBUG
+static struct notifier_block i8042_kbd_bind_notifier_block = {
+	.notifier_call = i8042_kbd_bind_notifier,
+};
+#endif
+
 static int __init i8042_init(void)
 {
 	struct platform_device *pdev;
diff --git a/drivers/input/serio/i8042.h b/drivers/input/serio/i8042.h
index fc080be..a198f0d 100644
--- a/drivers/input/serio/i8042.h
+++ b/drivers/input/serio/i8042.h
@@ -73,6 +73,17 @@ static unsigned long i8042_start_time;
 			printk(KERN_DEBUG KBUILD_MODNAME ": [%d] " format,	\
 			       (int) (jiffies - i8042_start_time), ##arg);	\
 	} while (0)
+
+#define filter_dbg(filter, data, format, args...)		\
+	do {							\
+		if (!i8042_debug)				\
+			break;					\
+								\
+		if (!filter || i8042_debug_kbd)			\
+			dbg("%02x " format, data, ##args);	\
+		else						\
+			dbg("** " format, ##args);		\
+	} while (0)
 #else
 #define dbg_init() do { } while (0)
 #define dbg(format, arg...)							\
@@ -80,6 +91,8 @@ static unsigned long i8042_start_time;
 		if (0)								\
 			printk(KERN_DEBUG pr_fmt(format), ##arg);		\
 	} while (0)
+
+#define filter_dbg(filter, data, format, args...) do { } while (0)
 #endif
 
 #endif /* _I8042_H */
-- 
2.4.3