netdev - [PATCH bpf-next v7 1/2] bpf: Add bpf_task_under

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Message-Id: <20230506031545.35991-2-zhoufeng.zf@bytedance.com>
Date: Sat,  6 May 2023 11:15:44 +0800
From: Feng zhou <zhoufeng.zf@...edance.com>
To: martin.lau@...ux.dev,
	ast@...nel.org,
	daniel@...earbox.net,
	andrii@...nel.org,
	song@...nel.org,
	yhs@...com,
	john.fastabend@...il.com,
	kpsingh@...nel.org,
	sdf@...gle.com,
	haoluo@...gle.com,
	jolsa@...nel.org,
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	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	mykolal@...com,
	shuah@...nel.org
Cc: bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	yangzhenze@...edance.com,
	wangdongdong.6@...edance.com,
	zhoufeng.zf@...edance.com
Subject: [PATCH bpf-next v7 1/2] bpf: Add bpf_task_under_cgroup() kfunc

From: Feng Zhou <zhoufeng.zf@...edance.com>

Add a kfunc that's similar to the bpf_current_task_under_cgroup.
The difference is that it is a designated task.

When hook sched related functions, sometimes it is necessary to
specify a task instead of the current task.

Signed-off-by: Feng Zhou <zhoufeng.zf@...edance.com>
Acked-by: Yonghong Song <yhs@...com>
---
 kernel/bpf/helpers.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index bb6b4637ebf2..a128fe0ab2d0 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2149,6 +2149,22 @@ __bpf_kfunc struct cgroup *bpf_cgroup_from_id(u64 cgid)
 		return NULL;
 	return cgrp;
 }
+
+/**
+ * bpf_task_under_cgroup - wrap task_under_cgroup_hierarchy() as a kfunc, test
+ * task's membership of cgroup ancestry.
+ * @task: the task to be tested
+ * @ancestor: possible ancestor of @task's cgroup
+ *
+ * Tests whether @task's default cgroup hierarchy is a descendant of @ancestor.
+ * It follows all the same rules as cgroup_is_descendant, and only applies
+ * to the default hierarchy.
+ */
+__bpf_kfunc long bpf_task_under_cgroup(struct task_struct *task,
+				       struct cgroup *ancestor)
+{
+	return task_under_cgroup_hierarchy(task, ancestor);
+}
 #endif /* CONFIG_CGROUPS */
 
 /**
@@ -2400,6 +2416,7 @@ BTF_ID_FLAGS(func, bpf_cgroup_acquire, KF_ACQUIRE | KF_RCU | KF_RET_NULL)
 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)
 #endif
 BTF_ID_FLAGS(func, bpf_task_from_pid, KF_ACQUIRE | KF_RET_NULL)
 BTF_SET8_END(generic_btf_ids)
-- 
2.20.1