Re: [PATCH v6 11/11] arm64: annotate user pointers casts detected by sparse

Al Viro
2018-08-31T17:50:35Z

On Fri, Aug 31, 2018 at 10:11:24AM +0200, Luc Van Oostenryck wrote:
> On Thu, Aug 30, 2018 at 01:41:16PM +0200, Andrey Konovalov wrote:
> > This patch adds __force annotations for __user pointers casts detected by
> > sparse with the -Wcast-from-as flag enabled (added in [1]).
> >
> > [1] https://github.com/lucvoo/sparse-dev/commit/5f960cb10f56ec2017c128ef9d16060e0145f292
>
> Hi,
>
> It would be nice to have some explanation for why these added __force
> are useful.

It would be even more useful if that series would either deal with
the noise for real ("that's what we intend here, that's what we intend there,
here's a primitive for such-and-such kind of cases, here we actually
ought to pass __user pointer instead of unsigned long", etc.) or left it
unmasked.

As it is, __force says only one thing: "I know the code is doing
the right thing here". That belongs in primitives, and I do *not* mean the
#define cast_to_ulong(x) ((__force unsigned long)(x))
kind.

Folks, if you don't want to deal with that - leave the warnings be.
They do carry more information than "someone has slapped __force in that place".

Al, very annoyed by that kind of information-hiding crap...