[PATCH v3 bpf-next 06/11] bpf: Add a new kfunc for cgroup1 hierarchy

[Yafang Shao <laoar.shao@gmail.com>]

A new kfunc is added to acquire cgroup1 of a task:

- bpf_task_get_cgroup1
  Acquires the associated cgroup of a task whithin a specific cgroup1
  hierarchy. The cgroup1 hierarchy is identified by its hierarchy ID.

This new kfunc enables the tracing of tasks within a designated
container or cgroup directory in BPF programs.

Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
 kernel/bpf/helpers.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 61f51de..f4cdeae 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2222,6 +2222,25 @@ __bpf_kfunc long bpf_task_under_cgroup(struct task_struct *task,
 	rcu_read_unlock();
 	return ret;
 }
+
+/**
+ * bpf_task_get_cgroup1 - Acquires the associated cgroup of a task within a
+ * specific cgroup1 hierarchy. The cgroup1 hierarchy is identified by its
+ * hierarchy ID.
+ * @task: The target task
+ * @hierarchy_id: The ID of a cgroup1 hierarchy
+ *
+ * On success, the cgroup is returen. On failure, NULL is returned.
+ */
+__bpf_kfunc struct cgroup *
+bpf_task_get_cgroup1(struct task_struct *task, int hierarchy_id)
+{
+	struct cgroup *cgrp = task_get_cgroup1(task, hierarchy_id);
+
+	if (IS_ERR(cgrp))
+		return NULL;
+	return cgrp;
+}
 #endif /* CONFIG_CGROUPS */
 
 /**
@@ -2528,6 +2547,7 @@ __bpf_kfunc void bpf_throw(u64 cookie)
 BTF_ID_FLAGS(func, bpf_cgroup_ancestor, KF_ACQUIRE | KF_RCU | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_cgroup_from_id, KF_ACQUIRE | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_task_under_cgroup, KF_RCU)
+BTF_ID_FLAGS(func, bpf_task_get_cgroup1, KF_ACQUIRE | KF_RCU | KF_RET_NULL)
 #endif
 BTF_ID_FLAGS(func, bpf_task_from_pid, KF_ACQUIRE | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_throw)
-- 
1.8.3.1