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Date: Fri, 26 Jun 2015 16:24:37 -0700
From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
To: Stephen Chandler Paul <cpaul@redhat.com>
Cc: Benjamin Tissoires <benjamin.tissoires@redhat.com>,
        linux-kernel@vger.kernel.org, linux-input@vger.kernel.org,
        Hans de Goede <hdegoede@redhat.com>
Subject: Re: [PATCH v3] i8042: Add debug_kbd option
Message-ID: <20150626232437.GA23364@dtor-ws>
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On Fri, Jun 26, 2015 at 07:21:47PM -0400, Stephen Chandler Paul wrote:
> On Fri, 2015-06-26 at 16:05 -0700, Dmitry Torokhov wrote:
> > Hi Stephen,
> > 
> > On Fri, Jun 26, 2015 at 06:28:18PM -0400, cpaul@redhat.com wrote:
> > > 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
> > 
> > Could we call it "driver_bound" and drop #ifdef DEBUG? In fact, I'd
> > rager we dropped the #ifdef DEBUG arounf all bus notifier code.
> > 
> > >  	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_b
> > > lock);
> > > +			}
> > 
> > 
> > Umm, let's export serio_bus and register the notifier when we load 
> > the
> > module.
> > 
> 
> Sorry, but would you mind clarifying what you mean by "export
> serio_bus"?

Right now in serio.c we have:

static struct bus_type serio_bus;

and that is why you have to go by serio->dev.bus to access it. If you
export the symbol you can use it directly, before you allocate any
serio ports.

Thanks.

-- 
Dmitry
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