Re: [PATCH v2] rust: place generated init_module() function in .init.text

[Greg KH <greg@kroah.com>]

On Tue, Feb 06, 2024 at 11:29:05AM +0100, Alice Ryhl wrote:
> On Tue, Feb 6, 2024 at 11:01 AM Greg KH <greg@kroah.com> wrote:
> >
> > On Mon, Feb 05, 2024 at 06:25:35PM -0700, Thomas Bertschinger wrote:
> > >              // Loadable modules need to export the `{{init,cleanup}}_module` identifiers.
> > > +            /// # Safety
> > > +            /// This function must only be called once, during module initialization, because it
> > > +            /// may be freed after it returns.
> >
> > Oh, and the compiler will catch this if you get it wrong, correct?
> >
> > If not, you all should work on that, as it is caught in C code :)
> 
> Based on the commit message, it sounds like the warning that C uses to
> catch this happens a link-time, which means that it is also triggered
> on Rust code:
> 
> > If a Rust `init_module()` function (that lives in `.text`) calls a C
> > function annotated with `__init`, then a warning is generated because
> > the C function lives in `.init.text`.

Cool, but has anyone tested it?

> I suggested that we make this function unsafe too, to make it even
> harder to call incorrectly.

It's not "unsafe" at all!  It's totally normal, and "safe" and should be
used for many types of modules.  If you get it "wrong" the linker will
catch the issue, so what is unsafe?

> But I think for the more general case of this problem, it makes sense
> to rely on the existing warning for this.

If the linker catches this, yes.

thanks,

greg k-h