linux-kernel - Re: [PATCH] sched_ext: Fix the incorrect bpf

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Message-ID: <9c9498a0-342f-4ade-8310-b5a9aaa485b0@bytedance.com>
Date: Wed, 12 Feb 2025 15:30:20 +0800
From: Chuyi Zhou <zhouchuyi@...edance.com>
To: tj@...nel.org, void@...ifault.com, arighi@...dia.com, changwoo@...lia.com
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched_ext: Fix the incorrect bpf_list kfunc API in
 common.bpf.h.



在 2025/2/12 15:19, Chuyi Zhou 写道:
> Now BPF only supports bpf_list_push_{front,back}_impl kfunc, not bpf_list_
> push_{front,back}.
> 
> This patch fix this issue. Without this patch, if we use bpf_list kfunc
> in scx, the BPF verifier would complain:
> 
> libbpf: extern (func ksym) 'bpf_list_push_back': not found in kernel or
> module BTFs
> libbpf: failed to load object 'scx_foo'
> libbpf: failed to load BPF skeleton 'scx_foo': -EINVAL
> 
> With this patch, the bpf list kfunc will work as expected.
> 

Sorry, I missed the Fixes tag.

Fixes: 2a52ca7c98960 ("sched_ext: Add scx_simple and scx_example_qmap 
example schedulers")

> Signed-off-by: Chuyi Zhou <zhouchuyi@...edance.com>
> ---
>   tools/sched_ext/include/scx/common.bpf.h | 12 ++++++++++--
>   1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/sched_ext/include/scx/common.bpf.h b/tools/sched_ext/include/scx/common.bpf.h
> index d72b60a0c582..7849405614b1 100644
> --- a/tools/sched_ext/include/scx/common.bpf.h
> +++ b/tools/sched_ext/include/scx/common.bpf.h
> @@ -270,8 +270,16 @@ void bpf_obj_drop_impl(void *kptr, void *meta) __ksym;
>   #define bpf_obj_new(type) ((type *)bpf_obj_new_impl(bpf_core_type_id_local(type), NULL))
>   #define bpf_obj_drop(kptr) bpf_obj_drop_impl(kptr, NULL)
>   
> -void bpf_list_push_front(struct bpf_list_head *head, struct bpf_list_node *node) __ksym;
> -void bpf_list_push_back(struct bpf_list_head *head, struct bpf_list_node *node) __ksym;
> +int bpf_list_push_front_impl(struct bpf_list_head *head,
> +				    struct bpf_list_node *node,
> +				    void *meta, __u64 off) __ksym;
> +#define bpf_list_push_front(head, node) bpf_list_push_front_impl(head, node, NULL, 0)
> +
> +int bpf_list_push_back_impl(struct bpf_list_head *head,
> +				   struct bpf_list_node *node,
> +				   void *meta, __u64 off) __ksym;
> +#define bpf_list_push_back(head, node) bpf_list_push_back_impl(head, node, NULL, 0)
> +
>   struct bpf_list_node *bpf_list_pop_front(struct bpf_list_head *head) __ksym;
>   struct bpf_list_node *bpf_list_pop_back(struct bpf_list_head *head) __ksym;
>   struct bpf_rb_node *bpf_rbtree_remove(struct bpf_rb_root *root,