netdev - Re: [PATCH v4 bpf-next 2/2] selftests/bpf: add tests for BPF_F_PRESERVE

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Message-ID: <6EE9333C-93C8-47EC-AF4B-F4924177CF99@fb.com>
Date:   Wed, 30 Sep 2020 22:46:47 +0000
From:   Song Liu <songliubraving@...com>
To:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>
CC:     Kernel Team <Kernel-team@...com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        John Fastabend <john.fastabend@...il.com>,
        "kpsingh@...omium.org" <kpsingh@...omium.org>
Subject: Re: [PATCH v4 bpf-next 2/2] selftests/bpf: add tests for
 BPF_F_PRESERVE_ELEMS



> On Sep 30, 2020, at 2:28 PM, Song Liu <songliubraving@...com> wrote:
> 
> Add tests for perf event array with and without BPF_F_PRESERVE_ELEMS.
> 
> Add a perf event to array via fd mfd. Without BPF_F_PRESERVE_ELEMS, the
> perf event is removed when mfd is closed. With BPF_F_PRESERVE_ELEMS, the
> perf event is removed when the map is freed.
> 
> Signed-off-by: Song Liu <songliubraving@...com>
> ---
> .../bpf/prog_tests/pe_preserve_elems.c        | 66 +++++++++++++++++++
> .../bpf/progs/test_pe_preserve_elems.c        | 44 +++++++++++++
> 2 files changed, 110 insertions(+)
> create mode 100644 tools/testing/selftests/bpf/prog_tests/pe_preserve_elems.c
> create mode 100644 tools/testing/selftests/bpf/progs/test_pe_preserve_elems.c
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/pe_preserve_elems.c b/tools/testing/selftests/bpf/prog_tests/pe_preserve_elems.c
> new file mode 100644
> index 0000000000000..673d38395253b
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/pe_preserve_elems.c
> @@ -0,0 +1,66 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/* Copyright (c) 2019 Facebook */
> +#include <test_progs.h>
> +#include <linux/bpf.h>
> +#include "test_pe_preserve_elems.skel.h"
> +
> +static int duration;
> +
> +static void test_one_map(struct bpf_map *map, struct bpf_program *prog,
> +			 bool has_share_pe)
> +{
> +	int err, key = 0, pfd = -1, mfd = bpf_map__fd(map);
> +	DECLARE_LIBBPF_OPTS(bpf_test_run_opts, opts);
> +	struct perf_event_attr attr = {
> +		.size = sizeof(struct perf_event_attr),
> +		.type = PERF_TYPE_SOFTWARE,
> +		.config = PERF_COUNT_SW_CPU_CLOCK,
> +	};
> +
> +	pfd = syscall(__NR_perf_event_open, &attr, 0 /* pid */,
> +		      -1 /* cpu 0 */, -1 /* group id */, 0 /* flags */);
> +	if (CHECK(pfd < 0, "perf_event_open", "failed\n"))
> +		return;
> +
> +	err = bpf_map_update_elem(mfd, &key, &pfd, BPF_ANY);
> +	close(pfd);
> +	if (CHECK(err < 0, "bpf_map_update_elem", "failed\n"))
> +		return;
> +
> +	err = bpf_prog_test_run_opts(bpf_program__fd(prog), &opts);
> +	if (CHECK(err < 0, "bpf_prog_test_run_opts", "failed\n"))
> +		return;
> +	if (CHECK(opts.retval != 0, "bpf_perf_event_read_value",
> +		  "failed with %d\n", opts.retval))
> +		return;
> +
> +	/* closing mfd, prog still holds a reference on map */
> +	close(mfd);
> +
> +	err = bpf_prog_test_run_opts(bpf_program__fd(prog), &opts);
> +	if (CHECK(err < 0, "bpf_prog_test_run_opts", "failed\n"))
> +		return;
> +
> +	if (has_share_pe) {
> +		CHECK(opts.retval != 0, "bpf_perf_event_read_value",
> +		      "failed with %d\n", opts.retval);
> +	} else {
> +		CHECK(opts.retval != -ENOENT, "bpf_perf_event_read_value",
> +		      "should have failed with %d, but got %d\n", -ENOENT,
> +		      opts.retval);
> +	}
> +}
> +
> +void test_pe_preserve_elems(void)
> +{
> +	struct test_pe_preserve_elems *skel;
> +
> +	skel = test_pe_preserve_elems__open_and_load();
> +	if (CHECK(!skel, "skel_open", "failed to open skeleton\n"))
> +		return;
> +
> +	test_one_map(skel->maps.array_1, skel->progs.read_array_1, false);
> +	test_one_map(skel->maps.array_2, skel->progs.read_array_2, true);
> +
> +	test_pe_preserve_elems__destroy(skel);
> +}
> diff --git a/tools/testing/selftests/bpf/progs/test_pe_preserve_elems.c b/tools/testing/selftests/bpf/progs/test_pe_preserve_elems.c
> new file mode 100644
> index 0000000000000..dc77e406de41f
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_pe_preserve_elems.c
> @@ -0,0 +1,44 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// Copyright (c) 2020 Facebook
> +#include "vmlinux.h"
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_tracing.h>
> +
> +struct {
> +	__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
> +	__uint(max_entries, 1);
> +	__uint(key_size, sizeof(int));
> +	__uint(value_size, sizeof(int));
> +} array_1 SEC(".maps");
> +
> +struct {
> +	__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
> +	__uint(max_entries, 1);
> +	__uint(key_size, sizeof(int));
> +	__uint(value_size, sizeof(int));
> +	__uint(map_flags, BPF_F_PRESERVE_ELEMS);
> +} array_2 SEC(".maps");
> +
> +SEC("raw_tp/sched_switch")
> +int BPF_PROG(read_array_1)
> +{
> +	struct bpf_perf_event_value val;
> +	long ret;
> +
> +	ret = bpf_perf_event_read_value(&array_1, 0, &val, sizeof(val));
> +	bpf_printk("read_array_1 returns %ld", ret);

Oops, I didn't do amend... Please ignore this version..

I am so sorry for the problem...

Song

> +	return ret;
> +}
> +
> +SEC("raw_tp/task_rename")
> +int BPF_PROG(read_array_2)
> +{
> +	struct bpf_perf_event_value val;
> +	long ret;
> +
> +	ret = bpf_perf_event_read_value(&array_2, 0, &val, sizeof(val));
> +	bpf_printk("read_array_2 returns %ld", ret);
> +	return ret;
> +}
> +
> +char LICENSE[] SEC("license") = "GPL";
> -- 
> 2.24.1
>