netdev - Re: [PATCH bpf-next v4 05/10] bpf: Add reference tracking support to kfunc

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Date:   Sat, 18 Dec 2021 18:22:48 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Kumar Kartikeya Dwivedi <memxor@...il.com>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org,
        netfilter-devel@...r.kernel.org,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        Maxim Mikityanskiy <maximmi@...dia.com>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Florian Westphal <fw@...len.de>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Toke Høiland-Jørgensen <toke@...hat.com>
Subject: Re: [PATCH bpf-next v4 05/10] bpf: Add reference tracking support to
 kfunc

On Fri, Dec 17, 2021 at 07:20:26AM +0530, Kumar Kartikeya Dwivedi wrote:
> 
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 965fffaf0308..015cb633838b 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -521,6 +521,9 @@ struct bpf_verifier_ops {
>  				 enum bpf_access_type atype,
>  				 u32 *next_btf_id);
>  	bool (*check_kfunc_call)(u32 kfunc_btf_id, struct module *owner);
> +	bool (*is_acquire_kfunc)(u32 kfunc_btf_id, struct module *owner);
> +	bool (*is_release_kfunc)(u32 kfunc_btf_id, struct module *owner);
> +	bool (*is_kfunc_ret_type_null)(u32 kfunc_btf_id, struct module *owner);

Same feedback as before...

Those callbacks are not necessary.
The existing check_kfunc_call() is just as inconvenient.
When module's BTF comes in could you add it to mod's info instead of
introducing callbacks for every kind of data the module has.
Those callbacks don't server any purpose other than passing the particular
data set back. The verifier side should access those data sets directly.