[PATCH bpf-next v4 5/7] selftests/bpf: test struct_ops with epoll

Kui-Feng Lee
2024-05-21T22:53:08Z

Verify whether a user space program is informed through epoll with EPOLLHUP
when a struct_ops object is detached.

The BPF code in selftests/bpf/progs/struct_ops_module.c has become
complex. Therefore, struct_ops_detach.c has been added to segregate the BPF
code for detachment tests from the BPF code for other tests based on the
recommendation of Andrii Nakryiko.

Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
---
.../bpf/prog_tests/test_struct_ops_module.c | 57 +++++++++++++++++++
.../selftests/bpf/progs/struct_ops_detach.c | 9 +++
2 files changed, 66 insertions(+)
create mode 100644 tools/testing/selftests/bpf/progs/struct_ops_detach.c

diff --git a/tools/testing/selftests/bpf/prog_tests/test_struct_ops_module.c b/tools/testing/selftests/bpf/prog_tests/test_struct_ops_module.c
index 29e183a80f49..bbcf12696a6b 100644
--- a/tools/testing/selftests/bpf/prog_tests/test_struct_ops_module.c
+++ b/tools/testing/selftests/bpf/prog_tests/test_struct_ops_module.c
@@ -3,9 +3,12 @@
#include <test_progs.h>
#include <time.h>

+#include <sys/epoll.h>
+
#include "struct_ops_module.skel.h"
#include "struct_ops_nulled_out_cb.skel.h"
#include "struct_ops_forgotten_cb.skel.h"
+#include "struct_ops_detach.skel.h"

static void check_map_info(struct bpf_map_info *info)
{
@@ -242,6 +245,58 @@ static void test_struct_ops_forgotten_cb(void)
struct_ops_forgotten_cb__destroy(skel);
}

+/* Detach a link from a user space program */
+static void test_detach_link(void)
+{
+ struct epoll_event ev, events[2];
+ struct struct_ops_detach *skel;
+ struct bpf_link *link = NULL;
+ int fd, epollfd = -1, nfds;
+ int err;
+
+ skel = struct_ops_detach__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "struct_ops_detach__open_and_load"))
+ return;
+
+ link = bpf_map__attach_struct_ops(skel->maps.testmod_do_detach);
+ if (!ASSERT_OK_PTR(link, "attach_struct_ops"))
+ goto cleanup;
+
+ fd = bpf_link__fd(link);
+ if (!ASSERT_GE(fd, 0, "link_fd"))
+ goto cleanup;
+
+ epollfd = epoll_create1(0);
+ if (!ASSERT_GE(epollfd, 0, "epoll_create1"))
+ goto cleanup;
+
+ ev.events = EPOLLHUP;
+ ev.data.fd = fd;
+ err = epoll_ctl(epollfd, EPOLL_CTL_ADD, fd, &ev);
+ if (!ASSERT_OK(err, "epoll_ctl"))
+ goto cleanup;
+
+ err = bpf_link__detach(link);
+ if (!ASSERT_OK(err, "detach_link"))
+ goto cleanup;
+
+ /* Wait for EPOLLHUP */
+ nfds = epoll_wait(epollfd, events, 2, 500);
+ if (!ASSERT_EQ(nfds, 1, "epoll_wait"))
+ goto cleanup;
+
+ if (!ASSERT_EQ(events[0].data.fd, fd, "epoll_wait_fd"))
+ goto cleanup;
+ if (!ASSERT_TRUE(events[0].events & EPOLLHUP, "events[0].events"))
+ goto cleanup;
+
+cleanup:
+ if (epollfd >= 0)
+ close(epollfd);
+ bpf_link__destroy(link);
+ struct_ops_detach__destroy(skel);
+}
+
void serial_test_struct_ops_module(void)
{
if (test__start_subtest("struct_ops_load"))
@@ -254,5 +309,7 @@ void serial_test_struct_ops_module(void)
test_struct_ops_nulled_out_cb();
if (test__start_subtest("struct_ops_forgotten_cb"))
test_struct_ops_forgotten_cb();
+ if (test__start_subtest("test_detach_link"))
+ test_detach_link();
}

diff --git a/tools/testing/selftests/bpf/progs/struct_ops_detach.c b/tools/testing/selftests/bpf/progs/struct_ops_detach.c
new file mode 100644
index 000000000000..45eacc2ca657
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/struct_ops_detach.c
@@ -0,0 +1,9 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */
+#include <vmlinux.h>
+#include "../bpf_testmod/bpf_testmod.h"
+
+char _license[] SEC("license") = "GPL";
+
+SEC(".struct_ops.link")
+struct bpf_testmod_ops testmod_do_detach;
--
2.34.1