netdev - Re: [PATCH net-next] ebpf: remove self-assignment in interpreter's tail call

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Message-Id: <20150713.131216.1152635752338498540.davem@davemloft.net>
Date:	Mon, 13 Jul 2015 13:12:16 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	daniel@...earbox.net
Cc:	ast@...mgrid.com, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] ebpf: remove self-assignment in interpreter's
 tail call

From: Daniel Borkmann <daniel@...earbox.net>
Date: Mon, 13 Jul 2015 20:49:32 +0200

> ARG1 = BPF_R1 as it stands, evaluates to regs[BPF_REG_1] = regs[BPF_REG_1]
> and thus has no effect. Add a comment instead, explaining what happens and
> why it's okay to just remove it. Since from user space side, a tail call is
> invoked as a pseudo helper function via bpf_tail_call_proto, the verifier
> checks the arguments just like with any other helper function and makes
> sure that the first argument (regs[BPF_REG_1])'s type is ARG_PTR_TO_CTX.
> 
> Signed-off-by: Daniel Borkmann <daniel@...earbox.net>

Applied, thanks Daniel.
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