[RFC PATCH bpf-next v2 4/9] bpf: Add a new kfunc for cgroup1 hierarchy

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

A new kfunc is added to acquire cgroup1:

- bpf_task_get_cgroup1_within_hierarchy
  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.

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 62a53ebfedf9..a682b47d3b97 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2217,6 +2217,25 @@ __bpf_kfunc long bpf_task_under_cgroup(struct task_struct *task,
 {
 	return task_under_cgroup_hierarchy(task, ancestor);
 }
+
+/**
+ * bpf_task_get_cgroup_within_hierarchy - 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_within_hierarchy(struct task_struct *task, int hierarchy_id)
+{
+	struct cgroup *cgrp = task_get_cgroup1_within_hierarchy(task, hierarchy_id);
+
+	if (IS_ERR(cgrp))
+		return NULL;
+	return cgrp;
+}
 #endif /* CONFIG_CGROUPS */
 
 /**
@@ -2523,6 +2542,7 @@ BTF_ID_FLAGS(func, bpf_cgroup_release, KF_RELEASE)
 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_within_hierarchy, 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)
-- 
2.30.1 (Apple Git-130)