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From:   Alice Ryhl <aliceryhl@google.com>
Date:   Wed, 6 Dec 2023 13:57:52 +0100
Message-ID: <CAH5fLgh+0G85Acf4-zqr_9COB5DUtt6ifVpZP-9V06hjJgd_jQ@mail.gmail.com>
Subject: Re: [PATCH v2 5/7] rust: file: add `Kuid` wrapper
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Miguel Ojeda <ojeda@kernel.org>,
        Alex Gaynor <alex.gaynor@gmail.com>,
        Wedson Almeida Filho <wedsonaf@gmail.com>,
        Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>,
        =?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= <bjorn3_gh@protonmail.com>,
        Benno Lossin <benno.lossin@proton.me>,
        Andreas Hindborg <a.hindborg@samsung.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Christian Brauner <brauner@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        =?UTF-8?B?QXJ2ZSBIasO4bm5ldsOlZw==?= <arve@android.com>,
        Todd Kjos <tkjos@android.com>,
        Martijn Coenen <maco@android.com>,
        Joel Fernandes <joel@joelfernandes.org>,
        Carlos Llamas <cmllamas@google.com>,
        Suren Baghdasaryan <surenb@google.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Kees Cook <keescook@chromium.org>,
        Matthew Wilcox <willy@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Daniel Xu <dxu@dxuuu.xyz>, linux-kernel@vger.kernel.org,
        rust-for-linux@vger.kernel.org, linux-fsdevel@vger.kernel.org
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On Wed, Dec 6, 2023 at 1:34=E2=80=AFPM Peter Zijlstra <peterz@infradead.org=
> wrote:
>
> On Wed, Dec 06, 2023 at 11:59:50AM +0000, Alice Ryhl wrote:
>
> > diff --git a/rust/helpers.c b/rust/helpers.c
> > index fd633d9db79a..58e3a9dff349 100644
> > --- a/rust/helpers.c
> > +++ b/rust/helpers.c
> > @@ -142,6 +142,51 @@ void rust_helper_put_task_struct(struct task_struc=
t *t)
> >  }
> >  EXPORT_SYMBOL_GPL(rust_helper_put_task_struct);
> >
> > +kuid_t rust_helper_task_uid(struct task_struct *task)
> > +{
> > +     return task_uid(task);
> > +}
> > +EXPORT_SYMBOL_GPL(rust_helper_task_uid);
> > +
> > +kuid_t rust_helper_task_euid(struct task_struct *task)
> > +{
> > +     return task_euid(task);
> > +}
> > +EXPORT_SYMBOL_GPL(rust_helper_task_euid);
>
> So I still object to these on the ground that they're obvious and
> trivial speculation gadgets.
>
> We should not have (exported) functions that are basically a single
> dereference of a pointer argument.
>
> And I do not appreciate my feedback on the previous round being ignored.

I'm sorry about that. I barely know what speculation gadgets are, so I
didn't really know what to respond. But I should have responded by
saying that.

I can reimplement these specific functions as inline Rust functions,
but I don't think I can give you a general solution to the
rust_helper_* problem in this patch series.

Alice