linux-kernel - Re: [PATCH v2 1/3] rust: helpers: Add list helpers for C linked list operations

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Message-ID: <b79fc5fe-3682-4439-b669-663e234943b5@nvidia.com>
Date: Sat, 29 Nov 2025 14:44:20 -0800
From: John Hubbard <jhubbard@...dia.com>
To: Joel Fernandes <joelagnelf@...dia.com>,
 Alexandre Courbot <acourbot@...dia.com>
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Subject: Re: [PATCH v2 1/3] rust: helpers: Add list helpers for C linked list
 operations

On 11/28/25 1:49 PM, Joel Fernandes wrote:
> On 11/27/2025 8:46 AM, Alexandre Courbot wrote:
>> On Thu Nov 27, 2025 at 2:10 PM JST, Joel Fernandes wrote:
...
>> There is also at least one precedent: the Rust `page_align()` does not
>> call a C helper that wraps `PAGE_ALIGN()`, it just reimplements it. I
>> think `list_head` is a quite similar situation, but ultimately that's
>> for the core team to say.
> 
> I don't think a one size/rule fits all will apply for this. We need carefully do

Case-by-case is certainly a good way to evaluate these things, yes.

> it on a case-by-case basis, for example - if we implement list_add directly in
> rust, we'd miss out on CONFIG_LIST_HARDENED. So for that, I will still use the
> bindings. For INIT_LIST_HEAD and iteration, it should be Ok, though. So I'll add
> that directly in Rust without bindings.

Here, I'm not so sure that even this case is a solid one. Because
CONFIG_LIST_HARDENED is a way for C code to help protect against
list corruption--which is generally going to come from the C side,
not the Rust side, for the most part.

Let the C code have its extra checks, but on the Rust side we can
either add them, or skip them--but I don't think we need to *invoke*
them via the C code.



thanks,
-- 
John Hubbard