Re: [PATCH RFC 3/3] kfence: Make test case compatible with run time set sample interval

["liupeng (DM)" <liupeng256@huawei.com>]

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On 2022/1/24 16:25, Marco Elver wrote:
> On Mon, 24 Jan 2022 at 03:37, 'Peng Liu' via kasan-dev
> <kasan-dev@googlegroups.com>  wrote:
>> The parameter kfence_sample_interval can be set via boot parameter
>> and late shell command. However, KFENCE test case just use compile
>> time CONFIG_KFENCE_SAMPLE_INTERVAL, this will make KFENCE test case
>> not run as user desired. This patch will make KFENCE test case
>> compatible with run-time-set sample interval.
>>
>> Signed-off-by: Peng Liu<liupeng256@huawei.com>
>> ---
>>   include/linux/kfence.h  | 2 ++
>>   mm/kfence/core.c        | 3 ++-
>>   mm/kfence/kfence_test.c | 8 ++++----
>>   3 files changed, 8 insertions(+), 5 deletions(-)
>>
>> diff --git a/include/linux/kfence.h b/include/linux/kfence.h
>> index bf91b76b87ee..0fc913a7f017 100644
>> --- a/include/linux/kfence.h
>> +++ b/include/linux/kfence.h
>> @@ -19,6 +19,8 @@
>>
>>   extern bool kfence_enabled;
>>   extern unsigned long kfence_num_objects;
>> +extern unsigned long kfence_sample_interval;
>> +
>>   /*
>>    * We allocate an even number of pages, as it simplifies calculations to map
>>    * address to metadata indices; effectively, the very first page serves as an
>> diff --git a/mm/kfence/core.c b/mm/kfence/core.c
>> index 2301923182b8..e2fcae34cc84 100644
>> --- a/mm/kfence/core.c
>> +++ b/mm/kfence/core.c
>> @@ -50,7 +50,8 @@
>>
>>   bool kfence_enabled __read_mostly;
>>
>> -static unsigned long kfence_sample_interval __read_mostly = CONFIG_KFENCE_SAMPLE_INTERVAL;
>> +unsigned long kfence_sample_interval __read_mostly = CONFIG_KFENCE_SAMPLE_INTERVAL;
>> +EXPORT_SYMBOL(kfence_sample_interval); /* Export for test modules. */
> While it would make some situations more convenient, I've wanted to
> avoid exporting a new symbol just for the test. And in most cases it
> only makes sense to run the test on a custom debug kernel.
>
> Why do you need this?

To automatically do more tests.

>
> Should you really need this, I suggest at least using
> EXPORT_SYMBOL_GPL. Should you want it, you can resend this patch
> standalone detached from the rest.
>
> Thanks,
> -- Marco
> .

When KFENCE pool size can be adjusted by boot parameters(assumption),
automatically test and train KFENCE may be useful. So far, exporting
kfence.sample_interval is not necessary.

Thanks,
-- Peng Liu
.

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