Re: [PATCH v2 sl-b 2/5] mm: Make mem_dump_obj() handle NULL and zero-sized pointers

Vlastimil Babka
2020-12-09T17:48:53Z

On 12/9/20 2:13 AM, paulmck@kernel.org wrote:
> From: "Paul E. McKenney" <paulmck@kernel.org>
>
> This commit makes mem_dump_obj() call out NULL and zero-sized pointers
> specially instead of classifying them as non-paged memory.
>
> Cc: Christoph Lameter <cl@linux.com>
> Cc: Pekka Enberg <penberg@kernel.org>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: <linux-mm@kvack.org>
> Reported-by: Andrii Nakryiko <andrii@kernel.org>
> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> ---
> mm/util.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/mm/util.c b/mm/util.c
> index d0e60d2..8c2449f 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -985,7 +985,12 @@ int __weak memcmp_pages(struct page *page1, struct page *page2)
> void mem_dump_obj(void *object)
> {
> if (!virt_addr_valid(object)) {
> - pr_cont(" non-paged (local) memory.\n");
> + if (object == NULL)
> + pr_cont(" NULL pointer.\n");
> + else if (object == ZERO_SIZE_PTR)
> + pr_cont(" zero-size pointer.\n");
> + else
> + pr_cont(" non-paged (local) memory.\n");
> return;
> }
> if (kmem_valid_obj(object)) {
>