linux-kernel - Re: [RESEND PATCH bpf-next v3 2/2] selftests/bpf: Add testcase for xdp attaching failure tracepoint

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Date:   Wed, 26 Jul 2023 14:52:45 -0700
From:   Martin KaFai Lau <martin.lau@...ux.dev>
To:     Leon Hwang <hffilwlqm@...il.com>
Cc:     ast@...nel.org, daniel@...earbox.net, john.fastabend@...il.com,
        andrii@...nel.org, song@...nel.org, yhs@...com, kpsingh@...nel.org,
        sdf@...gle.com, haoluo@...gle.com, jolsa@...nel.org,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, hawk@...nel.org, tangyeechou@...il.com,
        kernel-patches-bot@...com, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [RESEND PATCH bpf-next v3 2/2] selftests/bpf: Add testcase for
 xdp attaching failure tracepoint

On 7/20/23 8:52 AM, Leon Hwang wrote:
> Add a test case for the tracepoint of xdp attaching failure by bpf
> tracepoint when attach XDP to a device with invalid flags option.
> 
> The bpf tracepoint retrieves error message from the tracepoint, and
> then put the error message to a perf buffer. The testing code receives
> error message from perf buffer, and then ASSERT "Invalid XDP flags for
> BPF link attachment".
> 
> Signed-off-by: Leon Hwang <hffilwlqm@...il.com>
> ---
>   .../selftests/bpf/prog_tests/xdp_attach.c     | 65 +++++++++++++++++++
>   .../bpf/progs/test_xdp_attach_fail.c          | 52 +++++++++++++++
>   2 files changed, 117 insertions(+)
>   create mode 100644 tools/testing/selftests/bpf/progs/test_xdp_attach_fail.c
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_attach.c b/tools/testing/selftests/bpf/prog_tests/xdp_attach.c
> index fa3cac5488f5d..99f8d03f3c8bd 100644
> --- a/tools/testing/selftests/bpf/prog_tests/xdp_attach.c
> +++ b/tools/testing/selftests/bpf/prog_tests/xdp_attach.c
> @@ -1,5 +1,6 @@
>   // SPDX-License-Identifier: GPL-2.0
>   #include <test_progs.h>
> +#include "test_xdp_attach_fail.skel.h"
>   
>   #define IFINDEX_LO 1
>   #define XDP_FLAGS_REPLACE		(1U << 4)
> @@ -85,10 +86,74 @@ static void test_xdp_attach(const char *file)
>   	bpf_object__close(obj1);
>   }
>   
> +struct xdp_errmsg {
> +	char msg[64];
> +};
> +
> +static void on_xdp_errmsg(void *ctx, int cpu, void *data, __u32 size)
> +{
> +	struct xdp_errmsg *ctx_errmg = ctx, *tp_errmsg = data;
> +
> +	memcpy(&ctx_errmg->msg, &tp_errmsg->msg, size);
> +}
> +
> +static const char tgt_errmsg[] = "Invalid XDP flags for BPF link attachment";
> +
> +static void test_xdp_attach_fail(const char *file)

The test crashed: 
https://github.com/kernel-patches/bpf/actions/runs/5672753995/job/15373384795#step:6:8037

Please monitor the CI test result in the future.

> +{
> +	__u32 duration = 0;
> +	int err, fd_xdp, fd_link_xdp;
> +	struct bpf_object *obj = NULL;
> +	struct test_xdp_attach_fail *skel = NULL;
> +	struct bpf_link *link = NULL;
> +	struct perf_buffer *pb = NULL;
> +	struct xdp_errmsg errmsg = {};
> +
> +	LIBBPF_OPTS(bpf_link_create_opts, opts);
> +
> +	skel = test_xdp_attach_fail__open_and_load();
> +	if (!ASSERT_OK_PTR(skel, "test_xdp_attach_fail_skel"))
> +		goto out_close;
> +
> +	link = bpf_program__attach_tracepoint(skel->progs.tp__xdp__bpf_xdp_link_attach_failed,
> +					      "xdp", "bpf_xdp_link_attach_failed");
> +	if (!ASSERT_OK_PTR(link, "attach_tp"))
> +		goto out_close;
> +
> +	/* set up perf buffer */
> +	pb = perf_buffer__new(bpf_map__fd(skel->maps.xdp_errmsg_pb), 1,
> +			      on_xdp_errmsg, NULL, &errmsg, NULL);
> +
> +	err = bpf_prog_test_load(file, BPF_PROG_TYPE_XDP, &obj, &fd_xdp);
> +	if (CHECK_FAIL(err))
> +		goto out_close;
> +
> +	opts.flags = 0xFF; // invalid flags to fail to attach XDP prog
> +	fd_link_xdp = bpf_link_create(fd_xdp, IFINDEX_LO, BPF_XDP, &opts);
> +	if (CHECK(fd_link_xdp != -22, "bpf_link_create_failed",

Please stay with the ASSERT_* macro.

-- 
pw-bot: cr