linux-kernel - Re: [PATCH 1/2] x86: unify copy_from

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Date:	Tue, 29 Oct 2013 10:08:15 +0000
From:	"Jan Beulich" <JBeulich@...e.com>
To:	"Ingo Molnar" <mingo@...nel.org>
Cc:	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>, <mingo@...e.hu>,
	<tglx@...utronix.de>, "Andrew Morton" <akpm@...ux-foundation.org>,
	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	<arjan@...ux.intel.com>, <linux@...ck-us.net>,
	<linux-kernel@...r.kernel.org>, <hpa@...or.com>
Subject: Re: [PATCH 1/2] x86: unify copy_from_user() size checking

>>> On 29.10.13 at 10:54, Ingo Molnar <mingo@...nel.org> wrote:

> * Jan Beulich <JBeulich@...e.com> wrote:
> 
>> >>> On 26.10.13 at 12:31, Ingo Molnar <mingo@...nel.org> wrote:
>> > * Jan Beulich <JBeulich@...e.com> 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.

> This is something that would be pretty platform dependent anyway.

Why do you think so? That's entirely a compiler construct.

Jan

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