linux-kernel - Re: [PATCH v3] i2c: core-smbus: don't trace smbus

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Date:   Wed, 13 Feb 2019 08:50:54 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     John Sperbeck <jsperbeck@...gle.com>
Cc:     wsa@...-dreams.de, linux-i2c@...r.kernel.org,
        linux-kernel@...r.kernel.org, mingo@...hat.com
Subject: Re: [PATCH v3] i2c: core-smbus: don't trace smbus_reply data on
 errors

On Tue, 12 Feb 2019 19:40:57 -0800
John Sperbeck <jsperbeck@...gle.com> wrote:

> If an smbus transfer fails, there's no guarantee that the output
> buffer was written.  So, avoid trying to show the output buffer when
> tracing after an error.  This was 'mostly harmless', but would trip
> up kasan checking if left-over cruft in byte 0 is a large length,
> causing us to read from unwritten memory.

>From a tracing viewpoint:

 Reviewed-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

-- Steve

> 
> Signed-off-by: John Sperbeck <jsperbeck@...gle.com>
> ---
>  drivers/i2c/i2c-core-smbus.c | 2 +-
>  include/trace/events/smbus.h | 6 +++---
>  2 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/i2c/i2c-core-smbus.c b/drivers/i2c/i2c-core-smbus.c
> index 9cd66cabb84f..132119112596 100644
> --- a/drivers/i2c/i2c-core-smbus.c
> +++ b/drivers/i2c/i2c-core-smbus.c
> @@ -585,7 +585,7 @@ s32 __i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr,
>  trace:
>  	/* If enabled, the reply tracepoint is conditional on read_write. */
>  	trace_smbus_reply(adapter, addr, flags, read_write,
> -			  command, protocol, data);
> +			  command, protocol, data, res);
>  	trace_smbus_result(adapter, addr, flags, read_write,
>  			   command, protocol, res);
>  
> diff --git a/include/trace/events/smbus.h b/include/trace/events/smbus.h
> index d2fb6e1d3e10..a4892a187842 100644
> --- a/include/trace/events/smbus.h
> +++ b/include/trace/events/smbus.h
> @@ -138,9 +138,9 @@ TRACE_EVENT_CONDITION(smbus_reply,
>  	TP_PROTO(const struct i2c_adapter *adap,
>  		 u16 addr, unsigned short flags,
>  		 char read_write, u8 command, int protocol,
> -		 const union i2c_smbus_data *data),
> -	TP_ARGS(adap, addr, flags, read_write, command, protocol, data),
> -	TP_CONDITION(read_write == I2C_SMBUS_READ),
> +		 const union i2c_smbus_data *data, int res),
> +	TP_ARGS(adap, addr, flags, read_write, command, protocol, data, res),
> +	TP_CONDITION(res >= 0 && read_write == I2C_SMBUS_READ),
>  	TP_STRUCT__entry(
>  		__field(int,	adapter_nr		)
>  		__field(__u16,	addr			)