linux-kernel - Re: [PATCH v2 16/19] gendwarfksyms: Add support for reserved structure fields

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: <CABCJKue-YtCQWinad2GW7uJuVN-ZSUmRYttK_PUurJOR51Urgg@mail.gmail.com>
Date: Thu, 12 Sep 2024 13:58:25 -0700
From: Sami Tolvanen <samitolvanen@...gle.com>
To: Benno Lossin <benno.lossin@...ton.me>
Cc: Petr Pavlu <petr.pavlu@...e.com>, Miroslav Benes <mbenes@...e.cz>, 
	Masahiro Yamada <masahiroy@...nel.org>, Luis Chamberlain <mcgrof@...nel.org>, 
	Miguel Ojeda <ojeda@...nel.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Matthew Maurer <mmaurer@...gle.com>, Alex Gaynor <alex.gaynor@...il.com>, 
	Wedson Almeida Filho <wedsonaf@...il.com>, Gary Guo <gary@...yguo.net>, Neal Gompa <neal@...pa.dev>, 
	Hector Martin <marcan@...can.st>, Janne Grunau <j@...nau.net>, Asahi Linux <asahi@...ts.linux.dev>, 
	linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-modules@...r.kernel.org, rust-for-linux@...r.kernel.org
Subject: Re: [PATCH v2 16/19] gendwarfksyms: Add support for reserved
 structure fields

Hi Benno,

On Thu, Sep 12, 2024 at 11:08 AM Benno Lossin <benno.lossin@...ton.me> wrote:
>
> On 12.09.24 18:06, Sami Tolvanen wrote:
> >
> > I thought about this a bit and I wonder if we need a separate
> > mechanism for that, or is it sufficient to just #define any additional
> > hidden values you want to add instead of including them in the enum?
> >
> >   enum e {
> >       A,
> >       B,
> >   #define C (B + 1)
> >   #define D (C + 1)
> >   };
> >
> >
> > Do you see any issues with this approach? I think Clang would complain
> > about this with -Wassign-enum, but I'm not sure if we even enable that
> > in the kernel, and as long as you don't overflow the underlying type,
> > which is a requirement for not breaking the ABI anyway, it should be
> > fine.
>
> Rust has problems with `#define`-style enums, because bindgen (the tool
> that generates definitions for Rust to be able to call C code) isn't
> able to convert them to Rust enums.
>
> So if you can come up with an approach that allows you to continue to
> use C enums instead of `#define`, we would appreciate that, since it
> would make our lives a lot easier.

That's an interesting point. Is the problem that you cannot assign
arbitrary values to the Rust enum that bindgen generates, or is using
a #define the problem? We could probably just make the hidden enum
values visible to bindgen only if needed.

Sami