selftests/bpf: Add tests for BPF_F_PRESERVE_ELEMS

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@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200930224927.1936644-3-songliubraving@fb.com

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 (file)
index 0000000..673d383
--- /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 (file)
index 0000000..fb22de7
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_pe_preserve_elems.c
@@ -0,0 +1,38 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2020 Facebook
+#include <linux/bpf.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;
+
+       return bpf_perf_event_read_value(&array_1, 0, &val, sizeof(val));
+}
+
+SEC("raw_tp/task_rename")
+int BPF_PROG(read_array_2)
+{
+       struct bpf_perf_event_value val;
+
+       return bpf_perf_event_read_value(&array_2, 0, &val, sizeof(val));
+}
+
+char LICENSE[] SEC("license") = "GPL";