linux-kernel - [PATCH bpf-next v5 1/2] bpf: Add bpf_task_under

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Message-Id: <20230504031513.13749-2-zhoufeng.zf@bytedance.com>
Date:   Thu,  4 May 2023 11:15:11 +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, davem@...emloft.net,
        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 v5 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>
---
 kernel/bpf/helpers.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index bb6b4637ebf2..453cbd312366 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2149,6 +2149,25 @@ __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)
+{
+	if (unlikely(!ancestor || !task))
+		return -EINVAL;
+
+	return task_under_cgroup_hierarchy(task, ancestor);
+}
 #endif /* CONFIG_CGROUPS */
 
 /**
@@ -2400,6 +2419,7 @@ 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