This patch adds a selftest for the `bpf_task_get_cgroup` kfunc. The test
focuses on the use case of obtaining the cgroup ID of the previous task
in a `sched_switch` tracepoint.
The selftest involves creating a test cgroup, attaching a BPF program
that utilizes the `bpf_task_get_cgroup` during a `sched_switch`
tracepoint, and validating that the obtained cgroup ID for the previous
task matches the expected cgroup ID.
Signed-off-by: Jose Fernandez <josef@xxxxxxxxxxx>
Reviewed-by: Tycho Andersen <tycho@tycho.pizza>
---
V1 -> V2: Refactor test to work with a cgroup pointer instead of the ID
.../bpf/prog_tests/task_get_cgroup.c | 58 +++++++++++++++++++
.../bpf/progs/test_task_get_cgroup.c | 37 ++++++++++++
2 files changed, 95 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/task_get_cgroup.c
create mode 100644 tools/testing/selftests/bpf/progs/test_task_get_cgroup.c
diff --git a/tools/testing/selftests/bpf/prog_tests/task_get_cgroup.c b/tools/testing/selftests/bpf/prog_tests/task_get_cgroup.c
new file mode 100644
index 000000000000..67ed65d0c461
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/task_get_cgroup.c
@@ -0,0 +1,58 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright 2024 Netflix, Inc.
+
+#include <test_progs.h>
+#include <cgroup_helpers.h>
+#include "test_task_get_cgroup.skel.h"
+#include <unistd.h>
+
+#define TEST_CGROUP "/test-task-get-cgroup/"
+
+void test_task_get_cgroup(void)
+{
+ struct test_task_get_cgroup *skel;
+ int err, fd;
+ pid_t pid;
+ __u64 cgroup_id, expected_cgroup_id;
+ const struct timespec req = {
+ .tv_sec = 1,
+ .tv_nsec = 0,
+ };
+
+ fd = test__join_cgroup(TEST_CGROUP);
+ if (!ASSERT_OK(fd < 0, "test_join_cgroup_TEST_CGROUP"))
+ return;
+
+ skel = test_task_get_cgroup__open();
+ if (!ASSERT_OK_PTR(skel, "test_task_get_cgroup__open"))
+ goto cleanup;
+
+ err = test_task_get_cgroup__load(skel);
+ if (!ASSERT_OK(err, "test_task_get_cgroup__load"))
+ goto cleanup;
+
+ err = test_task_get_cgroup__attach(skel);
+ if (!ASSERT_OK(err, "test_task_get_cgroup__attach"))
+ goto cleanup;
+
+ pid = getpid();
+ expected_cgroup_id = get_cgroup_id(TEST_CGROUP);
+ if (!ASSERT_GT(expected_cgroup_id, 0, "get_cgroup_id"))
+ goto cleanup;
+
+ /* Trigger nanosleep to enter the sched_switch tracepoint */
+ /* The previous task should be this process */
+ syscall(__NR_nanosleep, &req, NULL);
+
+ err = bpf_map_lookup_elem(bpf_map__fd(skel->maps.pid_to_cgid_map), &pid,
+ &cgroup_id);
+
+ if (!ASSERT_OK(err, "bpf_map_lookup_elem"))
+ goto cleanup;
+
+ ASSERT_EQ(cgroup_id, expected_cgroup_id, "cgroup_id");
+
+cleanup:
+ test_task_get_cgroup__destroy(skel);
+ close(fd);
+}
diff --git a/tools/testing/selftests/bpf/progs/test_task_get_cgroup.c b/tools/testing/selftests/bpf/progs/test_task_get_cgroup.c
new file mode 100644
index 000000000000..580f8f0657d5
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_task_get_cgroup.c
@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright 2024 Netflix, Inc.
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+struct cgroup *bpf_task_get_cgroup(struct task_struct *task) __ksym;
+void bpf_cgroup_release(struct cgroup *cgrp) __ksym;
+
+struct {
+ __uint(type, BPF_MAP_TYPE_HASH);
+ __uint(max_entries, 4096);
+ __type(key, __u32);
+ __type(value, __u64);
+} pid_to_cgid_map SEC(".maps");
+
+SEC("tp_btf/sched_switch")
+int BPF_PROG(sched_switch, bool preempt, struct task_struct *prev,
+ struct task_struct *next)
+{
+ struct cgroup *cgrp;
+ u64 cgroup_id;
+ u32 pid;
+
+ cgrp = bpf_task_get_cgroup(prev);
+ if (cgrp == NULL)
+ return 0;
+ cgroup_id = cgrp->kn->id;
+ pid = prev->pid;
+ bpf_map_update_elem(&pid_to_cgid_map, &pid, &cgroup_id, BPF_ANY);
+
+ bpf_cgroup_release(cgrp);
+ return 0;
+}
+
+char _license[] SEC("license") = "GPL";
--
2.40.1
