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

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Message-ID: <55A40947.2000706@plumgrid.com>
Date:	Mon, 13 Jul 2015 11:53:59 -0700
From:	Alexei Starovoitov <ast@...mgrid.com>
To:	Daniel Borkmann <daniel@...earbox.net>, davem@...emloft.net
CC:	netdev@...r.kernel.org
Subject: Re: [PATCH net-next] ebpf: remove self-assignment in interpreter's
 tail call

On 7/13/15 11:49 AM, Daniel Borkmann wrote:
> 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>

Thanks!
Acked-by: Alexei Starovoitov <ast@...mgrid.com>

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