linux-kernel - Re: [PATCH bpf-next v3 3/6] resolve_btfids: Introduce enum btf_id

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4daf5253-685b-4047-8e2a-06ed2c72c830@linux.dev>
Date: Mon, 15 Dec 2025 18:52:17 -0800
From: Ihor Solodrai <ihor.solodrai@...ux.dev>
To: Eduard Zingerman <eddyz87@...il.com>, Alexei Starovoitov
 <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
 Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau
 <martin.lau@...ux.dev>, Song Liu <song@...nel.org>,
 Yonghong Song <yonghong.song@...ux.dev>,
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>,
 Jiri Olsa <jolsa@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>,
 Nathan Chancellor <nathan@...nel.org>, Nicolas Schier <nsc@...nel.org>,
 Tejun Heo <tj@...nel.org>, David Vernet <void@...ifault.com>,
 Andrea Righi <arighi@...dia.com>, Changwoo Min <changwoo@...lia.com>,
 Shuah Khan <shuah@...nel.org>,
 Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
 Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>,
 Alan Maguire <alan.maguire@...cle.com>, Donglin Peng <dolinux.peng@...il.com>
Cc: bpf@...r.kernel.org, dwarves@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org
Subject: Re: [PATCH bpf-next v3 3/6] resolve_btfids: Introduce enum
 btf_id_kind

On 12/15/25 6:38 PM, Eduard Zingerman wrote:
> On Mon, 2025-12-15 at 18:31 -0800, Ihor Solodrai wrote:
>> On 12/11/25 11:09 PM, Eduard Zingerman wrote:
>>> On Fri, 2025-12-05 at 14:30 -0800, Ihor Solodrai wrote:
>>>> Instead of using multiple flags, make struct btf_id tagged with an
>>>> enum value indicating its kind in the context of resolve_btfids.
>>>>
>>>> Signed-off-by: Ihor Solodrai <ihor.solodrai@...ux.dev>
>>>> ---
>>>
>>> Acked-by: Eduard Zingerman <eddyz87@...il.com>
>>>
>>> (But see a question below).
>>>
>>>> @@ -213,14 +218,19 @@ btf_id__add(struct rb_root *root, char *name, bool unique)
>>>>  			p = &(*p)->rb_left;
>>>>  		else if (cmp > 0)
>>>>  			p = &(*p)->rb_right;
>>>> -		else
>>>> -			return unique ? NULL : id;
>>>> +		else if (kind == BTF_ID_KIND_SYM && id->kind == BTF_ID_KIND_SYM)
>>>
>>> Nit: I'd keep the 'unique' parameter alongside 'kind' and resolve this
>>>      condition on the function callsite.
>>
>> I don't like the boolean args, they're always opaque on the callsite.
>>
>> We want to allow duplicates for _KIND_SYM and forbid for other kinds.
>> Since we are passing the kind from outside, I think it makes sense to
>> check for this inside the function. It makes the usage simpler.
> 
> On the contrary, the callsite knows exactly what it wants:
> unique or non-unique entries. Here you need additional logic
> to figure out the intent.
> 
> Arguably the uniqueness is associated not with entry type,
> but with a particular tree the entry is added to.
> And that is a property of the callsite.

You're right that the uniqueness is associated with a tree.
This means we could even check the kind of the root...

I'm thinking maybe it's cleaner to have btf_id__add() and
btf_id__add_unique(). It can even be a wrapper around btf_id__add()
with a boolean.  wdyt?

> 
>>>
>>> [...]
>>>