Re: [PATCH net-next v3 1/2] bpf: Add bpf_current_task_in_cgroup helper
From: Tejun Heo <tj@kernel.org>
Date: 2016-08-11 21:58:59
Hello, Sargun. On Thu, Aug 11, 2016 at 11:51:42AM -0700, Sargun Dhillon wrote:
This adds a bpf helper that's similar to the skb_in_cgroup helper to check whether the probe is currently executing in the context of a specific subset of the cgroupsv2 hierarchy. It does this based on membership test for a cgroup arraymap. It is invalid to call this in an interrupt, and it'll return an error. The helper is primarily to be used in debugging activities for containers, where you may have multiple programs running in a given top-level "container". This patch also genericizes some of the arraymap fetching logic between the skb_in_cgroup helper and this new helper.
I think it'd be better to put the changes into separate patches.
quoted hunk ↗ jump to hunk
@@ -319,4 +319,26 @@ extern const struct bpf_func_proto bpf_get_stackid_proto; void bpf_user_rnd_init_once(void); u64 bpf_user_rnd_u32(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5); +/* Helper to fetch a cgroup pointer based on index.
/** *
+ * @map: a cgroup arraymap + * @idx: index of the item you want to fetch + * + * Returns pointer on success, + * Error code if item not found, or out-of-bounds access + */ +static inline struct cgroup *fetch_arraymap_ptr(struct bpf_map *map, int idx)
...
quoted hunk ↗ jump to hunk
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 984f73b..d4e173d 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h@@ -497,6 +497,23 @@ static inline bool cgroup_is_descendant(struct cgroup *cgrp, return cgrp->ancestor_ids[ancestor->level] == ancestor->id; } +/** + * task_in_cgroup_hierarchy - 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. + */ +static inline bool task_in_cgroup_hierarchy(struct task_struct *task, + struct cgroup *ancestor)
Maybe task_is_under_cgroup() is a better name?
quoted hunk ↗ jump to hunk
@@ -574,6 +592,11 @@ static inline void cgroup_free(struct task_struct *p) {} static inline int cgroup_init_early(void) { return 0; } static inline int cgroup_init(void) { return 0; } +static inline bool task_in_cgroup_hierarchy(struct task_struct *task, + struct cgroup *ancestor) +{ + return false; +}
If cgroup is not enabled, all tasks are in the root cgroup, so the test should always return true.
quoted hunk ↗ jump to hunk
--- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h@@ -375,6 +375,17 @@ enum bpf_func_id { */ BPF_FUNC_probe_write_user, + /** + * bpf_current_task_in_cgroup(map, index) - Check cgroup2 membership of current task + * @map: pointer to bpf_map in BPF_MAP_TYPE_CGROUP_ARRAY type + * @index: index of the cgroup in the bpf_map + * Return: + * == 0 current failed the cgroup2 descendant test + * == 1 current succeeded the cgroup2 descendant test + * < 0 error + */ + BPF_FUNC_current_task_in_cgroup,
I think "under" would be better than "in" here. Thanks. -- tejun