Re: [PATCH 5/5] types: Add standard __ob_trap and __ob_wrap scalar types

[Linus Torvalds]

On Tue, 31 Mar 2026 at 13:03, Kees Cook <kees@xxxxxxxxxx> wrote:
>
> Mark Rutland had strong reservations about function-level annotations,
> but I wonder if the combination of new type _and_ function-level
> annotation could get us something near what would be palatable:

Yes, if we had some way to specify the label, that actually looks
really nice to me.

So with _this_ kind of interface, all my reservations about it go away.

And as long as the compiler actually requires that label to exist when
trapping arithmetic is done, I don't think people will use it without
having fixups.

> Or we could make the label a global part of the language itself so it
> wouldn't need to be a function annotation, but rather a _required_
> element of any function that uses a trapping type?

Yes, I'd be ok with that too, because I think in practice you
typically only ever have one, and I guess you could use local labels -
or multiple functions - if you really needed to have different
targets.

We have a few years of experience with "unsafe_get_user()" and
friends, and a few hundred places that use it, and while it's common
to have several cases in one function, I can't think of a single case
where we actually had more than one error target.

I tried a quick grep, and nothing jumped out at me.

(And a lot of them use "Efault" or "efault" as the target name, so it
probably would have been fine with a default name)

            Linus