linux-kernel - Re: [PATCH v8 4/6] rust: debugfs: Support arbitrary owned backing for File

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: <CAGSQo00C9b0KA7QLEeR6EYWhn288LWTm5h3O_ko3GO=naMQsiw@mail.gmail.com>
Date: Mon, 30 Jun 2025 10:36:34 -0700
From: Matthew Maurer <mmaurer@...gle.com>
To: Danilo Krummrich <dakr@...nel.org>
Cc: Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>, 
	Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, 
	Björn Roy Baron <bjorn3_gh@...tonmail.com>, 
	Andreas Hindborg <a.hindborg@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>, 
	Trevor Gross <tmgross@...ch.edu>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	"Rafael J. Wysocki" <rafael@...nel.org>, Sami Tolvanen <samitolvanen@...gle.com>, 
	Timur Tabi <ttabi@...dia.com>, Benno Lossin <lossin@...nel.org>, linux-kernel@...r.kernel.org, 
	rust-for-linux@...r.kernel.org, Dirk Behme <dirk.behme@...bosch.com>
Subject: Re: [PATCH v8 4/6] rust: debugfs: Support arbitrary owned backing for File

On Mon, Jun 30, 2025 at 10:34 AM Matthew Maurer <mmaurer@...gle.com> wrote:
>
> On Mon, Jun 30, 2025 at 10:30 AM Danilo Krummrich <dakr@...nel.org> wrote:
> >
> > On 6/28/25 1:18 AM, Matthew Maurer wrote:
> > > +    fn create_file<D: ForeignOwnable>(&self, _name: &CStr, data: D) -> File
> > > +    where
> > > +        for<'a> D::Borrowed<'a>: Display,
> > > +    {
> > > +        File {
> > > +            _foreign: ForeignHolder::new(data),
> > > +        }
> > >       }
> >
> > What's the motivation for the ForeignHolder abstraction? Why not just make it
> > File<D> and store data directly?
>
> 1. A `File<D>` can't be held in collection data structures as easily
> unless all your files contain the *same* backing type.
> 2. None of the APIs or potential APIs for `File` care about which type
> it's wrapping, nor are they supposed to. If nothing you can do with a
> `File` is different depending on the backing type, making it
> polymorphic is just needlessly confusing.

If it helps, effectively what I'm doing is adding a `dyn*
ForeignOwnable`, but `dyn*` isn't available, so writing this without
`ForeignHolder` would involve an unnecessary `Box` to hide the `dyn`.