Re: [PATCHv2 4/4] coresight: etm3x: Add support to exclude kernel mode tracing

[Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>]

On 2021-03-02 04:13, Doug Anderson wrote:
> Hi,
> 
> On Mon, Mar 1, 2021 at 11:05 AM Sai Prakash Ranjan
> <saiprakash.ranjan@codeaurora.org> wrote:
>> 
>> On production systems with ETMs enabled, it is preferred to exclude
>> kernel mode(NS EL1) tracing for security concerns and support only
>> userspace(NS EL0) tracing. Perf subsystem interface uses the newly
>> introduced kernel config CONFIG_EXCLUDE_KERNEL_PMU_TRACE to exclude
>> kernel mode tracing, but there is an additional interface
>> via sysfs for ETMs which also needs to be handled to exclude kernel
>> mode tracing. So we use this same generic kernel config to handle
>> the sysfs mode of tracing. This config is disabled by default and
>> would not affect the current configuration which has both kernel and
>> userspace tracing enabled by default.
>> 
>> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
>> ---
>>  drivers/hwtracing/coresight/coresight-etm3x-core.c  | 3 +++
>>  drivers/hwtracing/coresight/coresight-etm3x-sysfs.c | 6 ++++++
>>  2 files changed, 9 insertions(+)
> 
> Reviewed-by: Douglas Anderson <dianders@chromium.org>
> 

Thanks.

> 
>> diff --git a/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c 
>> b/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c
>> index e8c7649f123e..f522fc2e01b3 100644
>> --- a/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c
>> +++ b/drivers/hwtracing/coresight/coresight-etm3x-sysfs.c
>> @@ -116,6 +116,12 @@ static ssize_t mode_store(struct device *dev,
>>         if (ret)
>>                 return ret;
>> 
>> +       if (IS_ENABLED(CONFIG_EXCLUDE_KERNEL_PMU_TRACE) && (!(val & 
>> ETM_MODE_EXCL_KERN))) {
>> +               dev_warn(dev,
>> +                       "Kernel mode tracing is not allowed, check 
>> your kernel config\n");
> 
> Same nit as in patch #3 that the above string should be indented by 1
> more space.
> 

Will fix this up as well in v3.

Thanks,
Sai

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