linux-kernel - Re: [PATCH net-next 0/2] bpf: add search pruning optimization and tests

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Message-Id: <20141001.213110.1976557946620505084.davem@davemloft.net>
Date:	Wed, 01 Oct 2014 21:31:10 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	ast@...mgrid.com
Cc:	mingo@...nel.org, torvalds@...ux-foundation.org,
	luto@...capital.net, dborkman@...hat.com,
	hannes@...essinduktion.org, chema@...gle.com, edumazet@...gle.com,
	a.p.zijlstra@...llo.nl, pablo@...filter.org, hpa@...or.com,
	akpm@...ux-foundation.org, keescook@...omium.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 0/2] bpf: add search pruning optimization and
 tests

From: Alexei Starovoitov <ast@...mgrid.com>
Date: Mon, 29 Sep 2014 18:50:00 -0700

> patch #1 commit log explains why eBPF verifier has to examine some
> instructions multiple times and describes the search pruning optimization
> that improves verification speed for branchy programs and allows more
> complex programs to be verified successfully.
> This patch completes the core verifier logic.
> 
> patch #2 adds more verifier tests related to branches and search pruning
> 
> I'm still working on Andy's 'bitmask for stack slots' suggestion. It will be
> done on top of this patch.
> 
> The current verifier algorithm is brute force depth first search with
> state pruning. If anyone can come up with another algorithm that demonstrates
> better results, we'll replace the algorithm without affecting user space.
> 
> Note verifier doesn't guarantee that all possible valid programs are accepted.
> Overly complex programs may still be rejected.
> Verifier improvements/optimizations will guarantee that if a program
> was passing verification in the past, it will still be passing.

Series applied, thanks.
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