netdev - Re: [PATCH net] bpf: do not use reciprocal divide

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Date:	Wed, 15 Jan 2014 16:10:08 +0100
From:	Heiko Carstens <heiko.carstens@...ibm.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	netdev@...r.kernel.org, dborkman@...hat.com,
	darkjames-ws@...kjames.pl, Mircea Gherzan <mgherzan@...il.com>,
	Russell King <rmk+kernel@....linux.org.uk>,
	Matt Evans <matt@...abs.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: Re: [PATCH net] bpf: do not use reciprocal divide

On Wed, Jan 15, 2014 at 06:16:38AM -0800, Eric Dumazet wrote:
> On Wed, 2014-01-15 at 09:00 +0100, Heiko Carstens wrote:
> > Are you sure you want to remove the k == 0 check? Is there something
> > else that would prevent a division by zero?
> 
> This is done by factoring the two cases, modulo and divide :
> 
>  vi +553 net/core/filter.c 
> 
>                 /* Some instructions need special checks */
>                 switch (code) {
>                 case BPF_S_ALU_DIV_K:
>                 case BPF_S_ALU_MOD_K:
>                         /* check for division by zero */
>                         if (ftest->k == 0)
>                                 return -EINVAL;
>                         break;

Oh, sorry. I missed the fallthrough.

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