netdev - Re: [RFC PATCH bpf-next 10/12] selftests/bpf: Add test for bpf_list

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Message-ID: <CAP01T76heQ9rV1sNdssBQ_mSeDk_yxwP-Binh_j-AfTtXFVPdw@mail.gmail.com>
Date: Tue, 22 Apr 2025 05:08:21 +0200
From: Kumar Kartikeya Dwivedi <memxor@...il.com>
To: Martin KaFai Lau <martin.lau@...ux.dev>
Cc: bpf@...r.kernel.org, Alexei Starovoitov <ast@...nel.org>, 
	Andrii Nakryiko <andrii@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, netdev@...r.kernel.org, 
	kernel-team@...a.com, Amery Hung <ameryhung@...il.com>
Subject: Re: [RFC PATCH bpf-next 10/12] selftests/bpf: Add test for bpf_list_{front,back}

On Sat, 19 Apr 2025 at 00:48, Martin KaFai Lau <martin.lau@...ux.dev> wrote:
>
> From: Martin KaFai Lau <martin.lau@...nel.org>
>
> This patch adds a test for the new bpf_list_{front,back} kfunc.
>
> It also adds a test to ensure the non-owning node pointer cannot
> be used after unlock.
>
> Signed-off-by: Martin KaFai Lau <martin.lau@...nel.org>
> ---
>  .../selftests/bpf/prog_tests/linked_list.c    |   2 +
>  .../selftests/bpf/progs/linked_list_peek.c    | 104 ++++++++++++++++++
>  2 files changed, 106 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/progs/linked_list_peek.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/linked_list.c b/tools/testing/selftests/bpf/prog_tests/linked_list.c
> index 77d07e0a4a55..559f45239a83 100644
> --- a/tools/testing/selftests/bpf/prog_tests/linked_list.c
> +++ b/tools/testing/selftests/bpf/prog_tests/linked_list.c
> @@ -7,6 +7,7 @@
>
>  #include "linked_list.skel.h"
>  #include "linked_list_fail.skel.h"
> +#include "linked_list_peek.skel.h"
>
>  static char log_buf[1024 * 1024];
>
> @@ -804,4 +805,5 @@ void test_linked_list(void)
>         test_linked_list_success(LIST_IN_LIST, false);
>         test_linked_list_success(LIST_IN_LIST, true);
>         test_linked_list_success(TEST_ALL, false);
> +       RUN_TESTS(linked_list_peek);
>  }
> diff --git a/tools/testing/selftests/bpf/progs/linked_list_peek.c b/tools/testing/selftests/bpf/progs/linked_list_peek.c
> new file mode 100644
> index 000000000000..26c978091e5b
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/linked_list_peek.c
> @@ -0,0 +1,104 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */
> +
> +#include <vmlinux.h>
> +#include <bpf/bpf_helpers.h>
> +#include "bpf_misc.h"
> +#include "bpf_experimental.h"
> +
> +struct node_data {
> +       struct bpf_list_node l;
> +       int key;
> +};
> +
> +#define private(name) SEC(".data." #name) __hidden __attribute__((aligned(8)))
> +private(A) struct bpf_spin_lock glock;
> +private(A) struct bpf_list_head ghead __contains(node_data, l);
> +
> +#define list_entry(ptr, type, member) container_of(ptr, type, member)
> +#define NR_NODES 32
> +
> +int zero = 0;
> +
> +SEC("syscall")
> +__failure __msg("invalid mem access 'scalar'")
> +long list_peek_unlock_scalar_node(void *ctx)
> +{
> +       struct bpf_list_node *l_n;
> +       struct node_data *n;
> +
> +       bpf_spin_lock(&glock);
> +       l_n = bpf_list_front(&ghead);
> +       bpf_spin_unlock(&glock);
> +
> +       if (l_n) {
> +               n = list_entry(l_n, struct node_data, l);
> +               if (n->key == 0)
> +                       return __LINE__;
> +       }
> +
> +       return 0;
> +}

Would be good to have tests explicitly asserting the type is
non-owning ref (even though we indirectly do that by touching it after
unlock, relying on invalidation logic.).

> +
> [...]
>