Date:   Mon, 28 Oct 2019 11:43:11 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Toke Høiland-Jørgensen <toke@...hat.com>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        David Miller <davem@...emloft.net>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf-next v3 4/4] selftests: Add tests for automatic map pinning

On Sun, Oct 27, 2019 at 1:53 PM Toke Høiland-Jørgensen <toke@...hat.com> wrote:
>
> From: Toke Høiland-Jørgensen <toke@...hat.com>
>
> This adds a new BPF selftest to exercise the new automatic map pinning
> code.
>
> Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
> ---
>  tools/testing/selftests/bpf/prog_tests/pinning.c |   91 ++++++++++++++++++++++
>  tools/testing/selftests/bpf/progs/test_pinning.c |   29 +++++++
>  2 files changed, 120 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/pinning.c
>  create mode 100644 tools/testing/selftests/bpf/progs/test_pinning.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/pinning.c b/tools/testing/selftests/bpf/prog_tests/pinning.c
> new file mode 100644
> index 000000000000..d4a63de72f5a
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/pinning.c
> @@ -0,0 +1,91 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <sys/types.h>
> +#include <sys/stat.h>
> +#include <unistd.h>
> +#include <test_progs.h>
> +
> +__u32 get_map_id(struct bpf_object *obj, const char *name)
> +{
> +       __u32 map_info_len, duration, retval;
> +       struct bpf_map_info map_info = {};
> +       struct bpf_map *map;
> +       int err;
> +
> +       map_info_len = sizeof(map_info);
> +
> +       map = bpf_object__find_map_by_name(obj, name);
> +       if (!CHECK(!map, "find map", "NULL map")) {

please follow the pattern of "if (CHECK()) { return or goto cleanup
}". There is literally zero cases where we have `if (!CHECK())` in
selftests.

> +               err = bpf_obj_get_info_by_fd(bpf_map__fd(map),
> +                                            &map_info, &map_info_len);
> +               CHECK(err, "get map info", "err %d errno %d", err, errno);
> +               return map_info.id;
> +       }
> +       return 0;
> +}
> +
> +void test_pinning(void)
> +{
> +       __u32 duration, retval, size, map_id, map_id2;
> +       const char *custpinpath = "/sys/fs/bpf/custom/pinmap";
> +       const char *nopinpath = "/sys/fs/bpf/nopinmap";
> +       const char *custpath = "/sys/fs/bpf/custom";
> +       const char *pinpath = "/sys/fs/bpf/pinmap";
> +       const char *file = "./test_pinning.o";
> +       struct stat statbuf = {};
> +       struct bpf_object *obj;
> +       DECLARE_LIBBPF_OPTS(bpf_object_open_opts, opts,
> +               .auto_pin_path = custpath,
> +       );
> +
> +       int err;
> +       obj = bpf_object__open_file(file, NULL);
> +       if (CHECK_FAIL(libbpf_get_error(obj)))
> +               return;
> +
> +       err = bpf_object__load(obj);
> +       CHECK(err, "default load", "err %d errno %d\n", err, errno);

cleanup and exit, you don't have a valid set up to proceed with
testing. Same for almost every check below.

> +
> +       /* check that pinmap was pinned */
> +       err = stat(pinpath, &statbuf);
> +       CHECK(err, "stat pinpath", "err %d errno %d\n", err, errno);
> +
> +        /* check that nopinmap was *not* pinned */
> +       err = stat(nopinpath, &statbuf);
> +       CHECK(errno != ENOENT, "stat nopinpath", "err %d errno %d\n", err, errno);

if previous stat succeeded, errno might be from other syscall, you
have to check both

> +
> +        map_id = get_map_id(obj, "pinmap");

formatting? check that get_map_id succeeded?

> +       bpf_object__close(obj);
> +
> +       obj = bpf_object__open_file(file, NULL);
> +       if (CHECK_FAIL(libbpf_get_error(obj)))
> +               return;
> +
> +       err = bpf_object__load(obj);
> +       CHECK(err, "default load", "err %d errno %d\n", err, errno);
> +
> +       /* check that same map ID was reused for second load */
> +       map_id2 = get_map_id(obj, "pinmap");
> +       CHECK(map_id != map_id2, "check reuse",
> +             "err %d errno %d id %d id2 %d\n", err, errno, map_id, map_id2);
> +       unlink(pinpath);
> +       bpf_object__close(obj);
> +
> +       err = mkdir(custpath, 0700);
> +       CHECK(err, "mkdir custpath",  "err %d errno %d\n", err, errno);
> +
> +       obj = bpf_object__open_file(file, &opts);
> +       if (CHECK_FAIL(libbpf_get_error(obj)))
> +               return;
> +
> +       err = bpf_object__load(obj);
> +       CHECK(err, "custom load", "err %d errno %d\n", err, errno);
> +
> +       /* check that pinmap was pinned at the custom path */
> +       err = stat(custpinpath, &statbuf);
> +       CHECK(err, "stat custpinpath", "err %d errno %d\n", err, errno);
> +
> +       unlink(custpinpath);
> +       rmdir(custpath);
> +       bpf_object__close(obj);
> +}
> diff --git a/tools/testing/selftests/bpf/progs/test_pinning.c b/tools/testing/selftests/bpf/progs/test_pinning.c
> new file mode 100644
> index 000000000000..ff2d7447777e
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_pinning.c
> @@ -0,0 +1,29 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/bpf.h>
> +#include "bpf_helpers.h"
> +
> +int _version SEC("version") = 1;
> +
> +struct {
> +       __uint(type, BPF_MAP_TYPE_ARRAY);
> +       __uint(max_entries, 1);
> +       __type(key, __u32);
> +       __type(value, __u64);
> +       __uint(pinning, LIBBPF_PIN_BY_NAME);
> +} pinmap SEC(".maps");
> +
> +struct {
> +       __uint(type, BPF_MAP_TYPE_ARRAY);
> +       __uint(max_entries, 1);
> +       __type(key, __u32);
> +       __type(value, __u64);
> +} nopinmap SEC(".maps");
> +
> +SEC("xdp_prog")
> +int _xdp_prog(struct xdp_md *xdp)
> +{
> +       return XDP_PASS;
> +}
> +
> +char _license[] SEC("license") = "GPL";
>

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