serial/mxs-auart: Unable to get interrupt counter from user space

serial/mxs-auart: Unable to get interrupt counter from user space

[Stefan Wahren]

Hello,

i'm using Linux 2.6.35 at ARM and i experience the following issue with 
the mxs-auart (App UART). If i transmit and receive data over the serial 
port (using mxs-auart), all the interrupt counter (RX, TX, frame, 
parity, break) accessed from user space (ioctl with TIOCGICOUNT or 
/proc/tty/driver/auart) are zero.

Here is the scenario to reproduce the problem:

1. echoing some characters to the uart device
2. fetch the statistics from proc-Filesystem

Expected results: transmit counter greater than zero

Observed results: transmit counter is always zero

The same szenario on the mxs-duart (Debug UART) doesn't show this problem.

Is this a bug in mxs-auart or just not implemented?


Best Regards
Stefan

Re: serial/mxs-auart: Unable to get interrupt counter from user space

[Greg KH]

On Sat, Jun 23, 2012 at 09:19:40PM +0200, Stefan Wahren wrote:
> Hello,
> 
> i'm using Linux 2.6.35 at ARM and i experience the following issue
> with the mxs-auart (App UART). If i transmit and receive data over
> the serial port (using mxs-auart), all the interrupt counter (RX,
> TX, frame, parity, break) accessed from user space (ioctl with
> TIOCGICOUNT or /proc/tty/driver/auart) are zero.
> 
> Here is the scenario to reproduce the problem:
> 
> 1. echoing some characters to the uart device
> 2. fetch the statistics from proc-Filesystem
> 
> Expected results: transmit counter greater than zero
> 
> Observed results: transmit counter is always zero
> 
> The same szenario on the mxs-duart (Debug UART) doesn't show this problem.
> 
> Is this a bug in mxs-auart or just not implemented?

We disabled the transmit counter from being displayed a while ago for
security reasons, perhaps that is what you are seeing?

Also, you do realize just how old 2.6.35 really is, right?

thanks,

greg k-h

Re: serial/mxs-auart: Unable to get interrupt counter from user space

[Stefan Wahren]

Hi,

Am 24.06.2012 04:25, schrieb Greg KH:
> On Sat, Jun 23, 2012 at 09:19:40PM +0200, Stefan Wahren wrote:
>> Hello,
>>
>> i'm using Linux 2.6.35 at ARM and i experience the following issue
>> with the mxs-auart (App UART). If i transmit and receive data over
>> the serial port (using mxs-auart), all the interrupt counter (RX,
>> TX, frame, parity, break) accessed from user space (ioctl with
>> TIOCGICOUNT or /proc/tty/driver/auart) are zero.
>>
>> Here is the scenario to reproduce the problem:
>>
>> 1. echoing some characters to the uart device
>> 2. fetch the statistics from proc-Filesystem
>>
>> Expected results: transmit counter greater than zero
>>
>> Observed results: transmit counter is always zero
>>
>> The same szenario on the mxs-duart (Debug UART) doesn't show this problem.
>>
>> Is this a bug in mxs-auart or just not implemented?
>
> We disabled the transmit counter from being displayed a while ago for
> security reasons, perhaps that is what you are seeing?

Does this security fix affect serial_core or only mxs-auart?

Prevent this security fix from reading all counter (TX, RX, frame erros, 
parity errors, breaks)?

Do you mean this security issue ( 
https://bugzilla.redhat.com/show_bug.cgi?id=648660 ) ?

>
> Also, you do realize just how old 2.6.35 really is, right?

Unfortunaley yes, Freescale the vendor delivers the Board Support 
Package only with 2.6.35.

>
> thanks,
>
> greg k-h
>

Thanks

Stefan

Re: serial/mxs-auart: Unable to get interrupt counter from user space

[Greg KH]

On Sun, Jun 24, 2012 at 11:14:49AM +0200, Stefan Wahren wrote:
> Hi,
> 
> Am 24.06.2012 04:25, schrieb Greg KH:
> >On Sat, Jun 23, 2012 at 09:19:40PM +0200, Stefan Wahren wrote:
> >>Hello,
> >>
> >>i'm using Linux 2.6.35 at ARM and i experience the following issue
> >>with the mxs-auart (App UART). If i transmit and receive data over
> >>the serial port (using mxs-auart), all the interrupt counter (RX,
> >>TX, frame, parity, break) accessed from user space (ioctl with
> >>TIOCGICOUNT or /proc/tty/driver/auart) are zero.
> >>
> >>Here is the scenario to reproduce the problem:
> >>
> >>1. echoing some characters to the uart device
> >>2. fetch the statistics from proc-Filesystem
> >>
> >>Expected results: transmit counter greater than zero
> >>
> >>Observed results: transmit counter is always zero
> >>
> >>The same szenario on the mxs-duart (Debug UART) doesn't show this problem.
> >>
> >>Is this a bug in mxs-auart or just not implemented?
> >
> >We disabled the transmit counter from being displayed a while ago for
> >security reasons, perhaps that is what you are seeing?
> 
> Does this security fix affect serial_core or only mxs-auart?

I do not recall, sorry.

> Prevent this security fix from reading all counter (TX, RX, frame
> erros, parity errors, breaks)?
> 
> Do you mean this security issue (
> https://bugzilla.redhat.com/show_bug.cgi?id=648660 ) ?

Nope, a different one.

> >Also, you do realize just how old 2.6.35 really is, right?
> 
> Unfortunaley yes, Freescale the vendor delivers the Board Support
> Package only with 2.6.35.

I suggest you contact Freescale for support for this issue then, as
there's nothing we can do about that old kernel version, sorry.

good luck,

greg k-h