Re: endian bitshift defects [ was: staging: fusb302: don't bitshift __le16 type ]

[Julia Lawall <julia.lawall@lip6.fr>]

On Sat, 24 Jun 2017, Frans Klaver wrote:

> Hm. For some reason the great mail filtering scheme decided to push
> this past my inbox :-/
>
> On Sat, Jun 17, 2017 at 12:44 AM, Joe Perches <joe@perches.com> wrote:
> > On Fri, 2017-06-16 at 19:45 +0200, Frans Klaver wrote:
> >> The header field in struct pd_message is declared as an __le16 type. The
> >> data in the message is supposed to be little endian. This means we don't
> >> have to go and shift the individual bytes into position when we're
> >> filling the buffer, we can just copy the contents right away. As an
> >> added benefit we don't get fishy results on big endian systems anymore.
> >
> > Thanks for pointing this out.
> >
> > There are several instances of this class of error.
>
> There are other smells around __(le|be) types that show up in staging
> that might be worth checking in the rest of the kernel as well. e.g.
> converting to cpu and storing it back into itself (possibly with its
> bytes reversed), direct assignments without conversion and what else
> you might have. sparse obviously already flags anything fishy going on
> with these types, but cannot distinguish between the classes of
> errors. I'll need to acquaint myself with spatch a bit more to be able
> to track that down.

If you have concrete code examples, even fake ones, illustrating a class
of problem, then that would be great.

thanks,
julia