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

[Vlastimil Babka]

On 12/9/20 2:13 AM, paulmck@xxxxxxxxxx wrote:
> From: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
> 
> 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@xxxxxxxxx>
> Cc: Pekka Enberg <penberg@xxxxxxxxxx>
> Cc: David Rientjes <rientjes@xxxxxxxxxx>
> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: <linux-mm@xxxxxxxxx>
> Reported-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>

Acked-by: Vlastimil Babka <vbabka@xxxxxxx>

> ---
>  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)) {
>