linux-kernel - Re: [PATCH 3/5] exec: unify compat_do

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Message-ID: <20110226174408.GA17442@redhat.com>
Date:	Sat, 26 Feb 2011 18:44:08 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>, pageexec@...email.hu,
	Solar Designer <solar@...nwall.com>,
	Eugene Teo <eteo@...hat.com>,
	Brad Spengler <spender@...ecurity.net>,
	Roland McGrath <roland@...hat.com>,
	Milton Miller <miltonm@....com>
Subject: Re: [PATCH 3/5] exec: unify compat_do_execve() code

On 02/26, Linus Torvalds wrote:
>
> On Sat, Feb 26, 2011 at 4:37 AM, Oleg Nesterov <oleg@...hat.com> wrote:
> >>
> > Otherwise, get_arg_ptr() should return conditional_user_ptr_t as well,
>
> No it shouldn't.

(Yes I am stupid, see the next email).

> and notice how it gets the types right, and it even has one line LESS
> than your version, exactly because it gets the types right and doesn't
> need that implied cast in your
>
>      compat_uptr_t *a = argv;
>
> (in fact, I think your version needs an _explicit_ cast in order to
> not get a warning: you can't just cast "void **" to something else).

Yes, and get_user(argv) in the !compat case doesn't look nice, I agree.

> See? The advantage of the union is that the types are correct, which
> means that the casts are unnecessary.

My point was, apart from the trivial get_arg_ptr() helper, nobody else
uses this argv/envp, so I thought it is OK to drop the type info and
use "void *".

But as I said, I won't insist. I'll redo/resend.

Thanks.

Oleg.

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