Re: [PATCH bpf-next v4 5/5] selftests: Add tests for automatic map pinning

Andrii Nakryiko [off-list ref] writes:

On Tue, Oct 29, 2019 at 12:39 PM Toke Høiland-Jørgensen [off-list ref] wrote:

quoted

From: Toke Høiland-Jørgensen <redacted>

This adds a new BPF selftest to exercise the new automatic map pinning
code.

Signed-off-by: Toke Høiland-Jørgensen <redacted>
---
 tools/testing/selftests/bpf/prog_tests/pinning.c |  157 ++++++++++++++++++++++
 tools/testing/selftests/bpf/progs/test_pinning.c |   29 ++++
 2 files changed, 186 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..71f7dc51edc7
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/pinning.c

@@ -0,0 +1,157 @@
+// 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"))
+               return 0;
+
+       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;
+}
+
+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";

Should this test mount/unmount (if necessary) /sys/fs/bpf? They will
all fail if BPF FS is not mounted, right?

Yeah; I was kinda expecting that the test harness takes care of this. Is
it really a good idea for a selftest to mess with mount()?

quoted

+       const char *pinpath = "/sys/fs/bpf/pinmap";
+       const char *file = "./test_pinning.o";
+       struct stat statbuf = {};
+       struct bpf_object *obj;
+       struct bpf_map *map;
+       DECLARE_LIBBPF_OPTS(bpf_object_open_opts, opts,
+               .pin_root_path = custpath,
+       );
+
+       int err;
+       obj = bpf_object__open_file(file, NULL);
+       if (CHECK_FAIL(libbpf_get_error(obj)))
+               return;
+
+       err = bpf_object__load(obj);
+       if (CHECK(err, "default load", "err %d errno %d\n", err, errno))
+               goto out;
+
+       /* check that pinmap was pinned */
+       err = stat(pinpath, &statbuf);
+       if (CHECK(err, "stat pinpath", "err %d errno %d\n", err, errno))
+               goto out;
+
+        /* check that nopinmap was *not* pinned */
+       err = stat(nopinpath, &statbuf);
+       if (CHECK(!err || errno != ENOENT, "stat nopinpath",
+                 "err %d errno %d\n", err, errno))
+               goto out;
+
+        map_id = get_map_id(obj, "pinmap");

something wrong with whitespaces here? can you please run
scripts/checkpatch.pl to double-check?

Yup, some space got in where a tab should be

quoted

+       if (!map_id)
+               goto out;
+
+       bpf_object__close(obj);
+
+       obj = bpf_object__open_file(file, NULL);
+       if (CHECK_FAIL(libbpf_get_error(obj)))

obj = NULL here before you go to out

Yup

quoted

+               goto out;
+
+       err = bpf_object__load(obj);
+       if (CHECK(err, "default load", "err %d errno %d\n", err, errno))
+               goto out;
+

[...]

quoted

+       err = rmdir(custpath);
+       if (CHECK(err, "rmdir custpindir", "err %d errno %d\n", err, errno))
+               goto out;
+
+       bpf_object__close(obj);
+
+       /* test auto-pinning at custom path with open opt */
+       obj = bpf_object__open_file(file, &opts);
+       if (CHECK_FAIL(libbpf_get_error(obj)))
+               return;

obj = NULL; goto out; to ensure pinpath is unlinked?

Yeah.

quoted

+
+       err = bpf_object__load(obj);
+       if (CHECK(err, "custom load", "err %d errno %d\n", err, errno))
+               goto out;
+
+       /* check that pinmap was pinned at the custom path */
+       err = stat(custpinpath, &statbuf);
+       if (CHECK(err, "stat custpinpath", "err %d errno %d\n", err, errno))
+               goto out;
+
+out:
+       unlink(pinpath);
+       unlink(nopinpath);
+       unlink(custpinpath);
+       rmdir(custpath);
+       if (obj)
+               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");

would be nice to ensure that __uint(pinning, LIBBPF_PIN_NONE) also
works as expected, do you mind adding one extra map?

Sure, can do...

quoted

+
+SEC("xdp_prog")
+int _xdp_prog(struct xdp_md *xdp)
+{
+       return XDP_PASS;
+}
+
+char _license[] SEC("license") = "GPL";