[v2,bpf-next,4/4] selftests/bpf: Test bpf_kptr_xchg stashing into local kptr

Commit Message

Amery Hung Aug. 3, 2024, 12:11 a.m. UTC

From: Dave Marchevsky <[e-mail]>

Test stashing a referenced kptr in to a local kptr.

Acked-by: Martin KaFai Lau <[e-mail]>
Signed-off-by: Dave Marchevsky <[e-mail]>
Signed-off-by: Amery Hung <[e-mail]>
---
 .../selftests/bpf/progs/local_kptr_stash.c    | 22 +++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

Comments

Hou Tao Aug. 5, 2024, 2:47 a.m. UTC | #1

Hi,

On 8/3/2024 8:11 AM, Amery Hung wrote:
> From: Dave Marchevsky <[e-mail]>
>
> Test stashing a referenced kptr in to a local kptr.
>
> Acked-by: Martin KaFai Lau <[e-mail]>
> Signed-off-by: Dave Marchevsky <[e-mail]>
> Signed-off-by: Amery Hung <[e-mail]>
> ---
>  .../selftests/bpf/progs/local_kptr_stash.c    | 22 +++++++++++++++++--
>  1 file changed, 20 insertions(+), 2 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/progs/local_kptr_stash.c b/tools/testing/selftests/bpf/progs/local_kptr_stash.c
> index 75043ffc5dad..a0d784e8a05b 100644
> --- a/tools/testing/selftests/bpf/progs/local_kptr_stash.c
> +++ b/tools/testing/selftests/bpf/progs/local_kptr_stash.c
> @@ -11,6 +11,7 @@
>  struct node_data {
>  	long key;
>  	long data;
> +	struct prog_test_ref_kfunc __kptr *stashed_in_node;
>  	struct bpf_rb_node node;
>  };

Because prog_test_ref_kfunc is a module btf, so the btf_get() in
btf_parse_kptr() will not be invoked. I would like to suggest to add a
user-defined type kptr in node_data to exercise the btf_get() in
btf_parse_kptr().
>  
> @@ -85,18 +86,35 @@ static bool less(struct bpf_rb_node *a, const struct bpf_rb_node *b)
>  
>  static int create_and_stash(int idx, int val)
>  {
> +	struct prog_test_ref_kfunc *inner;
>  	struct map_value *mapval;
>  	struct node_data *res;
> +	unsigned long dummy;
>  
>  	mapval = bpf_map_lookup_elem(&some_nodes, &idx);
>  	if (!mapval)
>  		return 1;
>  
> +	dummy = 0;
> +	inner = bpf_kfunc_call_test_acquire(&dummy);
> +	if (!inner)
> +		return 2;
> +
>  	res = bpf_obj_new(typeof(*res));
> -	if (!res)
> -		return 1;
> +	if (!res) {
> +		bpf_kfunc_call_test_release(inner);
> +		return 3;
> +	}
>  	res->key = val;
>  
> +	inner = bpf_kptr_xchg(&res->stashed_in_node, inner);
> +	if (inner) {
> +		/* Should never happen, we just obj_new'd res */
> +		bpf_kfunc_call_test_release(inner);
> +		bpf_obj_drop(res);
> +		return 4;
> +	}
> +
>  	res = bpf_kptr_xchg(&mapval->node, res);
>  	if (res)
>  		bpf_obj_drop(res);

Patch

diff --git a/tools/testing/selftests/bpf/progs/local_kptr_stash.c b/tools/testing/selftests/bpf/progs/local_kptr_stash.c
index 75043ffc5dad..a0d784e8a05b 100644
--- a/tools/testing/selftests/bpf/progs/local_kptr_stash.c
+++ b/tools/testing/selftests/bpf/progs/local_kptr_stash.c
@@ -11,6 +11,7 @@ 
 struct node_data {
 	long key;
 	long data;
+	struct prog_test_ref_kfunc __kptr *stashed_in_node;
 	struct bpf_rb_node node;
 };
 
@@ -85,18 +86,35 @@  static bool less(struct bpf_rb_node *a, const struct bpf_rb_node *b)
 
 static int create_and_stash(int idx, int val)
 {
+	struct prog_test_ref_kfunc *inner;
 	struct map_value *mapval;
 	struct node_data *res;
+	unsigned long dummy;
 
 	mapval = bpf_map_lookup_elem(&some_nodes, &idx);
 	if (!mapval)
 		return 1;
 
+	dummy = 0;
+	inner = bpf_kfunc_call_test_acquire(&dummy);
+	if (!inner)
+		return 2;
+
 	res = bpf_obj_new(typeof(*res));
-	if (!res)
-		return 1;
+	if (!res) {
+		bpf_kfunc_call_test_release(inner);
+		return 3;
+	}
 	res->key = val;
 
+	inner = bpf_kptr_xchg(&res->stashed_in_node, inner);
+	if (inner) {
+		/* Should never happen, we just obj_new'd res */
+		bpf_kfunc_call_test_release(inner);
+		bpf_obj_drop(res);
+		return 4;
+	}
+
 	res = bpf_kptr_xchg(&mapval->node, res);
 	if (res)
 		bpf_obj_drop(res);