Re: [PATCH v3] kfence: Make test case compatible with run time set sample interval

[Marco Elver <elver@google.com>]

On Mon, 7 Feb 2022 at 04:29, '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, which is convenient for automated tests and
> KFENCE parameter optimization. However, KFENCE test case just uses
> compile-time CONFIG_KFENCE_SAMPLE_INTERVAL, which will make KFENCE
> test case not run as users desired. Export kfence_sample_interval,
> so that KFENCE test case can use run-time-set sample interval.
>
> Signed-off-by: Peng Liu <liupeng256@huawei.com>

Reviewed-by: Marco Elver <elver@google.com>

Thank you.

> ---
> v2->v3:
> - Revise change log description
> v1->v2:
> - Use EXPORT_SYMBOL_GPL replace EXPORT_SYMBOL
>
>  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 4b5e3679a72c..f49e64222628 100644
> --- a/include/linux/kfence.h
> +++ b/include/linux/kfence.h
> @@ -17,6 +17,8 @@
>  #include <linux/atomic.h>
>  #include <linux/static_key.h>
>
> +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 5ad40e3add45..13128fa13062 100644
> --- a/mm/kfence/core.c
> +++ b/mm/kfence/core.c
> @@ -47,7 +47,8 @@
>
>  static 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_GPL(kfence_sample_interval); /* Export for test modules. */
>
>  #ifdef MODULE_PARAM_PREFIX
>  #undef MODULE_PARAM_PREFIX
> diff --git a/mm/kfence/kfence_test.c b/mm/kfence/kfence_test.c
> index a22b1af85577..50dbb815a2a8 100644
> --- a/mm/kfence/kfence_test.c
> +++ b/mm/kfence/kfence_test.c
> @@ -268,13 +268,13 @@ static void *test_alloc(struct kunit *test, size_t size, gfp_t gfp, enum allocat
>          * 100x the sample interval should be more than enough to ensure we get
>          * a KFENCE allocation eventually.
>          */
> -       timeout = jiffies + msecs_to_jiffies(100 * CONFIG_KFENCE_SAMPLE_INTERVAL);
> +       timeout = jiffies + msecs_to_jiffies(100 * kfence_sample_interval);
>         /*
>          * Especially for non-preemption kernels, ensure the allocation-gate
>          * timer can catch up: after @resched_after, every failed allocation
>          * attempt yields, to ensure the allocation-gate timer is scheduled.
>          */
> -       resched_after = jiffies + msecs_to_jiffies(CONFIG_KFENCE_SAMPLE_INTERVAL);
> +       resched_after = jiffies + msecs_to_jiffies(kfence_sample_interval);
>         do {
>                 if (test_cache)
>                         alloc = kmem_cache_alloc(test_cache, gfp);
> @@ -608,7 +608,7 @@ static void test_gfpzero(struct kunit *test)
>         int i;
>
>         /* Skip if we think it'd take too long. */
> -       KFENCE_TEST_REQUIRES(test, CONFIG_KFENCE_SAMPLE_INTERVAL <= 100);
> +       KFENCE_TEST_REQUIRES(test, kfence_sample_interval <= 100);
>
>         setup_test_cache(test, size, 0, NULL);
>         buf1 = test_alloc(test, size, GFP_KERNEL, ALLOCATE_ANY);
> @@ -739,7 +739,7 @@ static void test_memcache_alloc_bulk(struct kunit *test)
>          * 100x the sample interval should be more than enough to ensure we get
>          * a KFENCE allocation eventually.
>          */
> -       timeout = jiffies + msecs_to_jiffies(100 * CONFIG_KFENCE_SAMPLE_INTERVAL);
> +       timeout = jiffies + msecs_to_jiffies(100 * kfence_sample_interval);
>         do {
>                 void *objects[100];
>                 int i, num = kmem_cache_alloc_bulk(test_cache, GFP_ATOMIC, ARRAY_SIZE(objects),
> --
> 2.18.0.huawei.25
>
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