linux-kernel - Re: per st_ops kfunc allow/deny mask. Was: [PATCH bpf-next v6 4/5] bpf: Make fs kfuncs available for SYSCALL program type

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Message-ID:
 <AM6PR03MB5080AC3D309A9072196E6C4D991C2@AM6PR03MB5080.eurprd03.prod.outlook.com>
Date: Fri, 10 Jan 2025 20:50:09 +0000
From: Juntong Deng <juntong.deng@...look.com>
To: Tejun Heo <tj@...nel.org>, Song Liu <song@...nel.org>
Cc: Alexei Starovoitov <alexei.starovoitov@...il.com>,
 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>, Eddy Z <eddyz87@...il.com>,
 Yonghong Song <yonghong.song@...ux.dev>, KP Singh <kpsingh@...nel.org>,
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>,
 Jiri Olsa <jolsa@...nel.org>, Kumar Kartikeya Dwivedi <memxor@...il.com>,
 snorcht@...il.com, Christian Brauner <brauner@...nel.org>,
 bpf <bpf@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
 Linux-Fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: per st_ops kfunc allow/deny mask. Was: [PATCH bpf-next v6 4/5]
 bpf: Make fs kfuncs available for SYSCALL program type

On 2025/1/10 20:19, Tejun Heo wrote:
> Hello,
> 
> On Thu, Jan 09, 2025 at 12:49:39PM -0800, Song Liu wrote:
> ...
>> Shall we move some of these logics from verifier core to
>> btf_kfunc_id_set.filter()? IIUC, this would avoid using extra
>> KF_* bits. To make the filter functions more capable, we
>> probably need to pass bpf_verifier_env into the filter() function.
> 
> FWIW, doing this through callbacks (maybe with predefined helpers and
> conventions) seems like the better approach to me given that this policy is
> closely tied to specific subsystem (sched_ext here). e.g. If sched_ext want
> to introduce new kfunc groups or rules, the changes being contained within
> sched_ext implementation would be nicer.
> 
> Thanks.
> 

I think so, it would be better to use callback functions and keep
this part decoupled from bpf core.