[tip: core/rcu] mm: Make mem_dump_obj() handle NULL and zero-sized pointers

[tip-bot2 for Paul E. McKenney]

The following commit has been merged into the core/rcu branch of tip:

Commit-ID:     b70fa3b12fc8d2b870d1ac7fd44da89271eb8705
Gitweb:        https://git.kernel.org/tip/b70fa3b12fc8d2b870d1ac7fd44da89271eb8705
Author:        Paul E. McKenney <paulmck@xxxxxxxxxx>
AuthorDate:    Tue, 08 Dec 2020 15:26:22 -08:00
Committer:     Paul E. McKenney <paulmck@xxxxxxxxxx>
CommitterDate: Fri, 22 Jan 2021 15:23:57 -08:00

mm: Make mem_dump_obj() handle NULL and zero-sized pointers

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>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Tested-by: Naresh Kamboju <naresh.kamboju@xxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
---
 mm/util.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/mm/util.c b/mm/util.c
index da46f9d..92f23d2 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -997,7 +997,12 @@ 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)) {