[PATCH bpf-next 6/6] selftests/bpf: test detaching struct_ops links.

[Kui-Feng Lee <thinker.li@gmail.com>]

Verify whether a user space program is informed through epoll with EPOLLHUP
when a struct_ops object is detached or unregistered using the function
bpf_struct_ops_kvalue_unreg() or BPF_LINK_DETACH.

Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
---
 .../selftests/bpf/bpf_testmod/bpf_testmod.c   |  18 ++-
 .../selftests/bpf/bpf_testmod/bpf_testmod.h   |   1 +
 .../bpf/prog_tests/test_struct_ops_module.c   | 104 ++++++++++++++++++
 .../selftests/bpf/progs/struct_ops_module.c   |   7 ++
 4 files changed, 126 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
index 39ad96a18123..e526ccfad8bf 100644
--- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
@@ -539,16 +539,20 @@ static int bpf_testmod_ops_init_member(const struct btf_type *t,
 				       const struct btf_member *member,
 				       void *kdata, const void *udata)
 {
+	struct bpf_testmod_ops *ops = kdata;
+
 	if (member->offset == offsetof(struct bpf_testmod_ops, data) * 8) {
 		/* For data fields, this function has to copy it and return
 		 * 1 to indicate that the data has been handled by the
 		 * struct_ops type, or the verifier will reject the map if
 		 * the value of the data field is not zero.
 		 */
-		((struct bpf_testmod_ops *)kdata)->data = ((struct bpf_testmod_ops *)udata)->data;
-		return 1;
-	}
-	return 0;
+		ops->data = ((struct bpf_testmod_ops *)udata)->data;
+	} else if (member->offset == offsetof(struct bpf_testmod_ops, do_unreg) * 8) {
+		ops->do_unreg = ((struct bpf_testmod_ops *)udata)->do_unreg;
+	} else
+		return 0;
+	return 1;
 }
 
 static const struct btf_kfunc_id_set bpf_testmod_kfunc_set = {
@@ -572,6 +576,12 @@ static int bpf_dummy_reg(void *kdata)
 	if (ops->test_2)
 		ops->test_2(4, ops->data);
 
+	if (ops->do_unreg) {
+		rcu_read_lock();
+		bpf_struct_ops_kvalue_unreg(kdata);
+		rcu_read_unlock();
+	}
+
 	return 0;
 }
 
diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h
index 23fa1872ee67..ee8d4a2cd187 100644
--- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h
+++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h
@@ -43,6 +43,7 @@ struct bpf_testmod_ops {
 		int b;
 	} unsupported;
 	int data;
+	bool do_unreg;
 
 	/* The following pointers are used to test the maps having multiple
 	 * pages of trampolines.
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 7cf2b9ddd3e1..b4d3b29114ca 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
@@ -3,6 +3,8 @@
 #include <test_progs.h>
 #include <time.h>
 
+#include <sys/epoll.h>
+
 #include "struct_ops_module.skel.h"
 
 static void check_map_info(struct bpf_map_info *info)
@@ -160,6 +162,104 @@ static void test_struct_ops_incompatible(void)
 	struct_ops_module__destroy(skel);
 }
 
+static void test_detach_link(void)
+{
+	struct epoll_event ev, events[2];
+	struct struct_ops_module *skel;
+	struct bpf_link *link = NULL;
+	int fd, epollfd = -1, nfds;
+	int err;
+
+	skel = struct_ops_module__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "open_and_load"))
+		return;
+
+	link = bpf_map__attach_struct_ops(skel->maps.testmod_1);
+	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;
+
+	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:
+	close(epollfd);
+	bpf_link__destroy(link);
+	struct_ops_module__destroy(skel);
+}
+
+/* Test bpf_struct_ops_kvalue_unreg() */
+static void test_do_unreg(void)
+{
+	struct epoll_event ev, events[2];
+	struct struct_ops_module *skel;
+	struct bpf_link *link = NULL;
+	int fd, epollfd = -1, nfds;
+	int err;
+
+	skel = struct_ops_module__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "open_and_load"))
+		return;
+
+	/* bpf_testmod will unregister this map immediately through the
+	 * function bpf_struct_ops_kvalue_unreg() since "do_unreg" is true.
+	 */
+	link = bpf_map__attach_struct_ops(skel->maps.testmod_do_unreg);
+	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;
+
+	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:
+	close(epollfd);
+	bpf_link__destroy(link);
+	struct_ops_module__destroy(skel);
+}
+
 void serial_test_struct_ops_module(void)
 {
 	if (test__start_subtest("test_struct_ops_load"))
@@ -168,5 +268,9 @@ void serial_test_struct_ops_module(void)
 		test_struct_ops_not_zeroed();
 	if (test__start_subtest("test_struct_ops_incompatible"))
 		test_struct_ops_incompatible();
+	if (test__start_subtest("test_detach_link"))
+		test_detach_link();
+	if (test__start_subtest("test_do_unreg"))
+		test_do_unreg();
 }
 
diff --git a/tools/testing/selftests/bpf/progs/struct_ops_module.c b/tools/testing/selftests/bpf/progs/struct_ops_module.c
index 63b065dae002..7a697a7dd0ac 100644
--- a/tools/testing/selftests/bpf/progs/struct_ops_module.c
+++ b/tools/testing/selftests/bpf/progs/struct_ops_module.c
@@ -81,3 +81,10 @@ struct bpf_testmod_ops___incompatible testmod_incompatible = {
 	.test_2 = (void *)test_2,
 	.data = 3,
 };
+
+SEC(".struct_ops.link")
+struct bpf_testmod_ops testmod_do_unreg = {
+	.test_1 = (void *)test_1,
+	.test_2 = (void *)test_2,
+	.do_unreg = true,
+};
-- 
2.34.1