linux-kernel - Re: [patch cr 2/4] [RFC] syscalls, x86: Add __NR

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Message-ID: <20120203092823.GE1968@moon>
Date:	Fri, 3 Feb 2012 13:28:23 +0400
From:	Cyrill Gorcunov <gorcunov@...nvz.org>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>
Cc:	linux-kernel@...r.kernel.org,
	Pavel Emelyanov <xemul@...allels.com>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Kees Cook <keescook@...omium.org>, Tejun Heo <tj@...nel.org>,
	Andrew Vagin <avagin@...nvz.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Andi Kleen <andi@...stfloor.org>,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Glauber Costa <glommer@...allels.com>,
	Matt Helsley <matthltc@...ibm.com>,
	Pekka Enberg <penberg@...nel.org>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Vasiliy Kulikov <segoon@...nwall.com>, Valdis.Kletnieks@...edu
Subject: Re: [patch cr 2/4] [RFC] syscalls, x86: Add __NR_kcmp syscall v7

On Fri, Feb 03, 2012 at 01:22:41AM -0800, Andrew Morton wrote:
> On Fri, 3 Feb 2012 10:09:29 +0100 Ingo Molnar <mingo@...e.hu> wrote:
> 
> > 
> > * Cyrill Gorcunov <gorcunov@...nvz.org> wrote:
> > 
> > > > > +			get_random_bytes(&cookies[i][j],
> > > > > +					 sizeof(cookies[i][j]));
> > > > 
> > > > ugly line break.
> > > > 
> > > 
> > > Why? Looks pretty good to me. But sure I'll change it.
> > 
> > It's ugly because it serves no purpose other than pacifying 
> > checkpatch and makes the code *uglier*.
> 
> No it doesn't.  For 80-col displays the code is *already wrapped*.  And
> that wrapping to column 0 is vastly worse than the above.
> 
> If we want to increase the standard to (say) 96 cols then fine, I'd be
> happy with that.  But until we do that we should not create such a
> gruesome mess for those who use 80 cols.
> 
> > It's a disease. When checkpatch tells you "this line is too 
> > long" then consider it a code cleanliness warning!
> 
> Well yes, if it can be fixed by other means then great.
> 

Guys, I simply made it as

static __init int kcmp_cookie_init(void)
{
	int i, j;

	for (i = 0; i < KCMP_TYPES; i++) {
		for (j = 0; j < 2; j++)
			get_random_bytes(&cookies[i][j], sizeof(long));
		cookies[i][1] |= (~(~0UL >>  1) | 1);
	}

	return 0;
}

I thought in first place that sizeof(cookies[i][j]) would allow me
to change type of cookies in one place (ie at declaration) but
if cookies type will be changed -- the code will need careful review
anway, so sizeof(long) will be enough I think.

On the other hands, maybe more clean variant will be

static __init int kcmp_cookie_init(void)
{
	const int size = sizeof(cookies[0][0]);
	int i, j;

	for (i = 0; i < KCMP_TYPES; i++) {
		for (j = 0; j < 2; j++)
			get_random_bytes(&cookies[i][j], size);
		cookies[i][1] |= (~(~0UL >>  1) | 1);
	}

	return 0;
}

Hm?

	Cyrill
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