linux-kernel - Re: [RFC] syscalls, x86: Add __NR

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Date:	Fri, 20 Jan 2012 08:57:11 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Cyrill Gorcunov <gorcunov@...il.com>
CC:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Pavel Emelyanov <xemul@...allels.com>,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>, david@...g.hm,
	Alexey Dobriyan <adobriyan@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrey Vagin <avagin@...nvz.org>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Glauber Costa <glommer@...allels.com>,
	Andi Kleen <andi@...stfloor.org>, Tejun Heo <tj@...nel.org>,
	Matt Helsley <matthltc@...ibm.com>,
	Pekka Enberg <penberg@...nel.org>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Vasiliy Kulikov <segoon@...nwall.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Valdis.Kletnieks@...edu
Subject: Re: [RFC] syscalls, x86: Add __NR_kcmp syscall

On 01/20/2012 08:29 AM, Cyrill Gorcunov wrote:
>
> We've had kind of emergency pool before which were used in such cases.
> These legitime cases can happen not that frequently, so I guess -- can
> we use it again?
>
> 	if (cookies[i][j])
> 		continue;
> 	else
> 		cookies[i][j] = some-value;
>
> One wont know which exactly values we were using.
>

I would not worry about get_random_bytes() returning nothing... if so, a 
lot of other places in the kernel would be broken.

>> The other thing is that for the multiplicative cookie you should OR in
>> the value (~(~0UL>>  1) | 1) in order to make sure that the value is (a)
>> large and (b) odd.
>>
>
> I see, i'll update (at first, I occasionally translated odd as 'even' which
> made me really scratching the head, until I realized it's 'odd'! :)
>
> 	Cyrill

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