linux-kernel - Re: module parameters permission

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Date:   Thu, 29 Apr 2021 12:25:43 +0200
From:   Fabio Aiuto <fabioaiuto83@...il.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: module parameters permission

On Thu, Apr 29, 2021 at 12:05:08PM +0200, Greg KH wrote:
> On Thu, Apr 29, 2021 at 11:58:20AM +0200, Fabio Aiuto wrote:
> > Hi all,
> > 
> > I'm trying to declare module parameters this way:
> > 
> > 
> >    params: {
> >         scull_major: i32 {
> >             default: 0,
> >             permissions: bindings::S_IRUGO as i32,
> >             description: b"Major number",
> >         },
> >         scull_minor: i32 {
> >             default: 0,
> >             permissions: bindings::S_IRUGO as i32,
> >             description: b"Minor number",
> >         },
> > 
> > i.e. using S_IRUGO macro exposed by bindgen. But I have the
> > following compiler error:
> > 
> > error: proc macro panicked
> >   --> samples/rust/rust_scull.rs:12:1
> >    |
> > 12 | / module! {
> > 13 | |     type: RustScull,
> > 14 | |     name: b"rust_scull",
> > 15 | |     author: b"Alessandro Rubini, Jonathan Corbet",
> > ...  |
> > 44 | |     },
> > 45 | | }
> >    | |_^
> >    |
> >    = help: message: Expected Literal
> > 
> > the same if I remove as i32 casts.
> > 
> > if I write permissions as in samples/rust/rust_module_parameters.rs
> > 
> >     params: {
> >         my_bool: bool {
> >             default: true,
> >             permissions: 0,
> >             description: b"Example of bool",
> >         },
> >         my_i32: i32 {
> >             default: 42,
> >             permissions: 0o644, <-------
> >             description: b"Example of i32",
> >         },
> > 
> > I get no error.
> > 
> > What's the right way to use S_I*UGO macros?
> 
> Not at all, use the octal values instead please.
> 
> That's the way that we have declared a while ago, and I think
> checkpatch.pl will even catch if you try to do this in any new code.
> Please don't force us to deal with S_* defines in rust code as well.
> 
> thanks,
> 
> greg k-h

thank you I didn't know that. I will use octal than.

Anyway I'd like to know what was the matter with those bindings...

fabio