linux-kernel - Re: [PATCH] selftests: bpf: Add missing symbol declarations to common header

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Message-ID: <49f21df7-5505-4ce4-9bde-4431bf97831e@linux.dev>
Date: Thu, 31 Jul 2025 20:08:51 -0700
From: Yonghong Song <yonghong.song@...ux.dev>
To: chenyuan_fl@....com, ast@...nel.org, daniel@...earbox.net,
 andrii@...nel.org
Cc: bpf@...r.kernel.org, linux-kselftest@...r.kernel.org,
 linux-kernel@...r.kernel.org, Yuan Chen <chenyuan@...inos.cn>
Subject: Re: [PATCH] selftests: bpf: Add missing symbol declarations to common
 header



On 7/31/25 7:52 PM, chenyuan_fl@....com wrote:
> From: Yuan Chen <chenyuan@...inos.cn>
>
> Fix implicit function declaration errors in bpf_qdisc_xxx.c by adding
> the required kernel symbol declarations to the shared header file
> bpf_qdisc_common.h. This ensures all qdisc BPF programs can properly
> resolve these kernel functions.
>
> The added declarations include:
> - bpf_qdisc_skb_drop
> - bpf_qdisc_bstats_update
> - bpf_kfree_skb
> - bpf_skb_get_hash
> - bpf_qdisc_watchdog_schedule
>
> Using a common header prevents duplication and ensures consistency
> across different qdisc implementations.

If you have proper and recent vmlinux.h (with recent pahole as well during
kernel build), all the above declarations should be in vmlinux.h.
How did you generate your vmlinux.h? Can you just generate a better one
based on recent kernel/pahole?

>
> Signed-off-by: Yuan Chen <chenyuan@...inos.cn>
> ---
>   tools/testing/selftests/bpf/progs/bpf_qdisc_common.h | 9 +++++++++
>   1 file changed, 9 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/progs/bpf_qdisc_common.h b/tools/testing/selftests/bpf/progs/bpf_qdisc_common.h
> index 3754f581b328..4c896b3e0f65 100644
> --- a/tools/testing/selftests/bpf/progs/bpf_qdisc_common.h
> +++ b/tools/testing/selftests/bpf/progs/bpf_qdisc_common.h
> @@ -14,6 +14,15 @@
>   
>   struct bpf_sk_buff_ptr;
>   
> +extern void bpf_qdisc_skb_drop(struct sk_buff *skb,
> +			       struct bpf_sk_buff_ptr *to_free_list) __ksym;
> +extern void bpf_qdisc_bstats_update(struct Qdisc *sch,
> +				    const struct sk_buff *skb) __ksym;
> +extern void bpf_kfree_skb(struct sk_buff *skb) __ksym;
> +extern u32 bpf_skb_get_hash(struct sk_buff *skb) __ksym;
> +extern void bpf_qdisc_watchdog_schedule(struct Qdisc *sch, u64 expire,
> +					u64 delta_ns) __ksym;
> +
>   static struct qdisc_skb_cb *qdisc_skb_cb(const struct sk_buff *skb)
>   {
>   	return (struct qdisc_skb_cb *)skb->cb;