linux-kernel - Re: [PATCH RFC bpf-next v3 06/16] bpf/helpers: introduce bpf_timer_set_sleepable

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Date: Fri, 23 Feb 2024 17:10:52 +0200
From: Eduard Zingerman <eddyz87@...il.com>
To: Benjamin Tissoires <bentiss@...nel.org>, Alexei Starovoitov
 <ast@...nel.org>,  Daniel Borkmann <daniel@...earbox.net>, John Fastabend
 <john.fastabend@...il.com>, Andrii Nakryiko <andrii@...nel.org>, Martin
 KaFai Lau <martin.lau@...ux.dev>, Song Liu <song@...nel.org>, Yonghong Song
 <yonghong.song@...ux.dev>, KP Singh <kpsingh@...nel.org>, Stanislav
 Fomichev <sdf@...gle.com>, Hao Luo <haoluo@...gle.com>, Jiri Olsa
 <jolsa@...nel.org>, Jiri Kosina <jikos@...nel.org>,  Benjamin Tissoires
 <benjamin.tissoires@...hat.com>, Jonathan Corbet <corbet@....net>, Shuah
 Khan <shuah@...nel.org>
Cc: bpf@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-input@...r.kernel.org, linux-doc@...r.kernel.org, 
	linux-kselftest@...r.kernel.org
Subject: Re: [PATCH RFC bpf-next v3 06/16] bpf/helpers: introduce
 bpf_timer_set_sleepable_cb() kfunc

On Wed, 2024-02-21 at 17:25 +0100, Benjamin Tissoires wrote:

[...]

> @@ -12120,6 +12137,16 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
>  		}
>  	}
>  
> +	if (is_async_callback_calling_kfunc(meta.func_id)) {

I think that it's better to check specific kfunc id here:

  meta.func_id == special_kfunc_list[KF_bpf_timer_set_sleepable_cb_impl]

In case if some new async callback calling kfunc would be added,
for which set_timer_callback_state() won't be correct.

> +		err = push_callback_call(env, insn, insn_idx, meta.subprogno,
> +					 set_timer_callback_state);
> +		if (err) {
> +			verbose(env, "kfunc %s#%d failed callback verification\n",
> +				func_name, meta.func_id);
> +			return err;
> +		}
> +	}
> +
>  	rcu_lock = is_kfunc_bpf_rcu_read_lock(&meta);
>  	rcu_unlock = is_kfunc_bpf_rcu_read_unlock(&meta);
>  
>