From: Hagen Paul Pfeifer <hagen@jauu.net>
To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: <eric.dumazet@gmail.com>, <mjt@tls.msk.ru>, <davem@davemloft.net>,
<drosenberg@vsecurity.com>, <xiaosuo@gmail.com>,
<netdev@vger.kernel.org>
Subject: Re: [PATCH v3] filter: Optimize instruction revalidation code.
Date: Wed, 17 Nov 2010 10:01:56 +0100 [thread overview]
Message-ID: <fb1f2f80c2a0663226799d4fa345d0f8@localhost> (raw)
In-Reply-To: <201011170806.oAH86AdI013337@www262.sakura.ne.jp>
On Wed, 17 Nov 2010 17:06:10 +0900, Tetsuo Handawrote:
> If compilers can generate better code for continuous case values
> than discontinuous case values, then keeping BPF_S_* makes sense.
Yes, this is crucial. A compiler cannot generate a jump table of O(1) for
dense labels. The BPF_S_* translation was done to convert to a dense label
construct. So this "optimization" is a no-go.
Look at the log and read my comment for a detailed explanation.
Anyway: "code--" increments the _copied_ value, not the value in the
evaluated opcode itself. I will validate the patch!
Hagen
next prev parent reply other threads:[~2010-11-17 9:01 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-10 18:18 [PATCH] Prevent reading uninitialized memory with socketfilters Dan Rosenberg
2010-11-10 18:21 ` David Miller
2010-11-10 18:33 ` Eric Dumazet
2010-11-10 18:38 ` David Miller
2010-11-16 13:08 ` [PATCH] filter: Optimize instruction revalidation code Tetsuo Handa
2010-11-16 13:11 ` Michael Tokarev
2010-11-16 13:44 ` Eric Dumazet
2010-11-16 14:31 ` [PATCH v2] " Tetsuo Handa
2010-11-16 16:30 ` Eric Dumazet
2010-11-17 1:19 ` [PATCH v3] " Tetsuo Handa
2010-11-17 7:48 ` Eric Dumazet
2010-11-17 7:54 ` Changli Gao
2010-11-17 8:18 ` Eric Dumazet
2010-11-17 8:06 ` Tetsuo Handa
2010-11-17 9:01 ` Hagen Paul Pfeifer [this message]
2010-11-18 18:58 ` David Miller
2010-11-16 22:13 ` [PATCH] " Hagen Paul Pfeifer
2010-11-16 23:31 ` Changli Gao
2010-11-16 23:45 ` Hagen Paul Pfeifer
2010-11-16 23:24 ` Changli Gao
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