selftests/bpf: Add link pinning selftests

Add selftests validating link pinning/unpinning and associated BPF link
(attachment) lifetime.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200303043159.323675-4-andriin@fb.com

diff --git a/tools/testing/selftests/bpf/prog_tests/link_pinning.c b/tools/testing/selftests/bpf/prog_tests/link_pinning.c
new file mode 100644 (file)
index 0000000..a743288
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/link_pinning.c
@@ -0,0 +1,105 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Facebook */
+
+#include <test_progs.h>
+#include <sys/stat.h>
+
+#include "test_link_pinning.skel.h"
+
+static int duration = 0;
+
+void test_link_pinning_subtest(struct bpf_program *prog,
+                              struct test_link_pinning__bss *bss)
+{
+       const char *link_pin_path = "/sys/fs/bpf/pinned_link_test";
+       struct stat statbuf = {};
+       struct bpf_link *link;
+       int err, i;
+
+       link = bpf_program__attach(prog);
+       if (CHECK(IS_ERR(link), "link_attach", "err: %ld\n", PTR_ERR(link)))
+               goto cleanup;
+
+       bss->in = 1;
+       usleep(1);
+       CHECK(bss->out != 1, "res_check1", "exp %d, got %d\n", 1, bss->out);
+
+       /* pin link */
+       err = bpf_link__pin(link, link_pin_path);
+       if (CHECK(err, "link_pin", "err: %d\n", err))
+               goto cleanup;
+
+       CHECK(strcmp(link_pin_path, bpf_link__pin_path(link)), "pin_path1",
+             "exp %s, got %s\n", link_pin_path, bpf_link__pin_path(link));
+
+       /* check that link was pinned */
+       err = stat(link_pin_path, &statbuf);
+       if (CHECK(err, "stat_link", "err %d errno %d\n", err, errno))
+               goto cleanup;
+
+       bss->in = 2;
+       usleep(1);
+       CHECK(bss->out != 2, "res_check2", "exp %d, got %d\n", 2, bss->out);
+
+       /* destroy link, pinned link should keep program attached */
+       bpf_link__destroy(link);
+       link = NULL;
+
+       bss->in = 3;
+       usleep(1);
+       CHECK(bss->out != 3, "res_check3", "exp %d, got %d\n", 3, bss->out);
+
+       /* re-open link from BPFFS */
+       link = bpf_link__open(link_pin_path);
+       if (CHECK(IS_ERR(link), "link_open", "err: %ld\n", PTR_ERR(link)))
+               goto cleanup;
+
+       CHECK(strcmp(link_pin_path, bpf_link__pin_path(link)), "pin_path2",
+             "exp %s, got %s\n", link_pin_path, bpf_link__pin_path(link));
+
+       /* unpin link from BPFFS, program still attached */
+       err = bpf_link__unpin(link);
+       if (CHECK(err, "link_unpin", "err: %d\n", err))
+               goto cleanup;
+
+       /* still active, as we have FD open now */
+       bss->in = 4;
+       usleep(1);
+       CHECK(bss->out != 4, "res_check4", "exp %d, got %d\n", 4, bss->out);
+
+       bpf_link__destroy(link);
+       link = NULL;
+
+       /* Validate it's finally detached.
+        * Actual detachment might get delayed a bit, so there is no reliable
+        * way to validate it immediately here, let's count up for long enough
+        * and see if eventually output stops being updated
+        */
+       for (i = 5; i < 10000; i++) {
+               bss->in = i;
+               usleep(1);
+               if (bss->out == i - 1)
+                       break;
+       }
+       CHECK(i == 10000, "link_attached", "got to iteration #%d\n", i);
+
+cleanup:
+       if (!IS_ERR(link))
+               bpf_link__destroy(link);
+}
+
+void test_link_pinning(void)
+{
+       struct test_link_pinning* skel;
+
+       skel = test_link_pinning__open_and_load();
+       if (CHECK(!skel, "skel_open", "failed to open skeleton\n"))
+               return;
+
+       if (test__start_subtest("pin_raw_tp"))
+               test_link_pinning_subtest(skel->progs.raw_tp_prog, skel->bss);
+       if (test__start_subtest("pin_tp_btf"))
+               test_link_pinning_subtest(skel->progs.tp_btf_prog, skel->bss);
+
+       test_link_pinning__destroy(skel);
+}

diff --git a/tools/testing/selftests/bpf/progs/test_link_pinning.c b/tools/testing/selftests/bpf/progs/test_link_pinning.c
new file mode 100644 (file)
index 0000000..bbf2a52
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_link_pinning.c
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Facebook */
+
+#include <stdbool.h>
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+int in = 0;
+int out = 0;
+
+SEC("raw_tp/sys_enter")
+int raw_tp_prog(const void *ctx)
+{
+       out = in;
+       return 0;
+}
+
+SEC("tp_btf/sys_enter")
+int tp_btf_prog(const void *ctx)
+{
+       out = in;
+       return 0;
+}
+
+char _license[] SEC("license") = "GPL";