Re: [External] Re: [PATCH bpf-next 1/2] bpf: Add bpf_task_under_cgroup helper

[Feng Zhou]

在 2023/4/21 02:22, Alexei Starovoitov 写道:
> On Thu, Apr 20, 2023 at 12:27 AM Feng zhou <zhoufeng.zf@xxxxxxxxxxxxx> wrote:
> > From: Feng Zhou <zhoufeng.zf@xxxxxxxxxxxxx>
> >
> > This adds a bpf helper 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@xxxxxxxxxxxxx>
> > ---
> >   include/uapi/linux/bpf.h       | 13 +++++++++++++
> >   kernel/bpf/verifier.c          |  4 +++-
> >   kernel/trace/bpf_trace.c       | 31 +++++++++++++++++++++++++++++++
> >   tools/include/uapi/linux/bpf.h | 13 +++++++++++++
> >   4 files changed, 60 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index 4b20a7269bee..3d31ddb39e10 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -5550,6 +5550,18 @@ union bpf_attr {
> >    *             0 on success.
> >    *
> >    *             **-ENOENT** if the bpf_local_storage cannot be found.
> > + *
> > + * long bpf_task_under_cgroup(struct bpf_map *map, struct task_struct *task, u32 index)
> > + *     Description
> > + *             Check whether the probe is being run is the context of a given
> > + *             subset of the cgroup2 hierarchy. The cgroup2 to test is held by
> > + *             *map* of type **BPF_MAP_TYPE_CGROUP_ARRAY**, at *index*.
> > + *     Return
> > + *             The return value depends on the result of the test, and can be:
> > + *
> > + *             * 1, if assigned task belongs to the cgroup2.
> > + *             * 0, if assigned task does not belong to the cgroup2.
> > + *             * A negative error code, if an error occurred.
> >    */
> >   #define ___BPF_FUNC_MAPPER(FN, ctx...)                 \
> >          FN(unspec, 0, ##ctx)                            \
> > @@ -5764,6 +5776,7 @@ union bpf_attr {
> >          FN(user_ringbuf_drain, 209, ##ctx)              \
> >          FN(cgrp_storage_get, 210, ##ctx)                \
> >          FN(cgrp_storage_delete, 211, ##ctx)             \
> > +       FN(task_under_cgroup, 212, ##ctx)               \
> >          /* */
> >
> >   /* backwards-compatibility macros for users of __BPF_FUNC_MAPPER that don't
> > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > index 1e05355facdc..1e2c3c3e8d5f 100644
> > --- a/kernel/bpf/verifier.c
> > +++ b/kernel/bpf/verifier.c
> > @@ -7771,7 +7771,8 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env,
> >                  break;
> >          case BPF_MAP_TYPE_CGROUP_ARRAY:
> >                  if (func_id != BPF_FUNC_skb_under_cgroup &&
> > -                   func_id != BPF_FUNC_current_task_under_cgroup)
> > +                   func_id != BPF_FUNC_current_task_under_cgroup &&
> > +                   func_id != BPF_FUNC_task_under_cgroup)
> >                          goto error;
> >                  break;
> >          case BPF_MAP_TYPE_CGROUP_STORAGE:
> > @@ -7902,6 +7903,7 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env,
> >                          goto error;
> >                  break;
> >          case BPF_FUNC_current_task_under_cgroup:
> > +       case BPF_FUNC_task_under_cgroup:
> >          case BPF_FUNC_skb_under_cgroup:
> >                  if (map->map_type != BPF_MAP_TYPE_CGROUP_ARRAY)
> >                          goto error;
> > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> > index bcf91bc7bf71..b02a04768824 100644
> > --- a/kernel/trace/bpf_trace.c
> > +++ b/kernel/trace/bpf_trace.c
> > @@ -814,6 +814,35 @@ static const struct bpf_func_proto bpf_current_task_under_cgroup_proto = {
> >          .arg2_type      = ARG_ANYTHING,
> >   };
> >
> > +BPF_CALL_3(bpf_task_under_cgroup, struct bpf_map *, map, struct task_struct *,
> > +          task, u32, idx)
> > +{
> > +       struct bpf_array *array = container_of(map, struct bpf_array, map);
> > +       struct cgroup *cgrp;
> > +
> > +       if (unlikely(!task))
> > +               return -ENOENT;
> > +
> > +       if (unlikely(idx >= array->map.max_entries))
> > +               return -E2BIG;
> > +
> > +       cgrp = READ_ONCE(array->ptrs[idx]);
> > +       if (unlikely(!cgrp))
> > +               return -EAGAIN;
> > +
> > +       return task_under_cgroup_hierarchy(task, cgrp);
> We don't add helpers anymore.
> Please wrap task_under_cgroup_hierarchy() as a kfunc
> that takes two TRUSTED pointers task and cgroup.
Will do, thanks.