Re: [PATCH 1/2] x86: unify copy_from_user() size checking

From: Ingo Molnar
Date: Tue Oct 29 2013 - 06:13:06 EST



* Jan Beulich <JBeulich@xxxxxxxx> wrote:

> >>> On 29.10.13 at 10:54, Ingo Molnar <mingo@xxxxxxxxxx> wrote:
>
> > * Jan Beulich <JBeulich@xxxxxxxx> wrote:
> >
> >> >>> On 26.10.13 at 12:31, Ingo Molnar <mingo@xxxxxxxxxx> wrote:
> >> > * Jan Beulich <JBeulich@xxxxxxxx> wrote:
> >> >> I'd like to point out though that with __compiletime_object_size()
> >> >> being restricted to gcc before 4.6, the whole construct is going to
> >> >> become more and more pointless going forward. I would question
> >> >> however that commit 2fb0815c9ee6b9ac50e15dd8360ec76d9fa46a2 ("gcc4:
> >> >> disable __compiletime_object_size for GCC 4.6+") was really necessary,
> >> >> and instead this should have been dealt with as is done here from the
> >> >> beginning.
> >> >
> >> > Can we now revert 2fb0815c9ee6?
> >>
> >> Actually I'm afraid parisc would first need to follow the changes
> >> done on x86 here, or else they'd run into (compile time) issues
> >> (s390 and tile only emit warnings, i.e. would at worst suffer
> >> cosmetically unless subtrees putting -Werror in place are
> >> affected).
> >
> > Given how trivial __compiletime_object_size() is, we could replicate
> > a (differently named) copy of that in x86 uaccess.h?
>
> I would never have dared to suggest something like that...
>
> But if you're fine with that, I can certainly do so. I'd then even
> wonder whether we shouldn't re-use the same name,
> #undef-ing the one we got from compiler*.h - after all the
> goal would be for compiler-gcc4.h to change in exactly that way.

Yeah, I think that would work.

> > This is something that would be pretty platform dependent
> > anyway.
>
> Why do you think so? That's entirely a compiler construct.

Yeah, what I mean is that the progress of kernel support here is
done on a per platform manner anyway, the 'generic' piece in
compiler.h and compiler-gcc4.h is tiny and more of a hindrance than
a useful generalization/sharing of code...

Thanks,

Ingo
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