netdev - Re: [PATCH net-next 1/9] bpf: add BPF

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Message-ID: <598B3FCA.7060904@iogearbox.net>
Date:   Wed, 09 Aug 2017 19:00:58 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     David Miller <davem@...emloft.net>
CC:     ast@...com, holzheu@...ux.vnet.ibm.com,
        naveen.n.rao@...ux.vnet.ibm.com, jakub.kicinski@...ronome.com,
        netdev@...r.kernel.org
Subject: Re: [PATCH net-next 1/9] bpf: add BPF_J{LT,LE,SLT,SLE} instructions

On 08/09/2017 06:55 PM, David Miller wrote:
> From: Daniel Borkmann <daniel@...earbox.net>
> Date: Wed,  9 Aug 2017 12:23:53 +0200
>
>>    [1] https://github.com/borkmann/llvm/tree/bpf-insns
>
> How is this "backwards compatible"?
>
> If someone takes a new LLVM and tries to load those programs
> into an older kernel they will be rejected.
>
> There appears to be no effort to make things work cleanly in
> that situation at all.

No, that was just the patch I used for LLVM to enable the
insns, so not the final one that will be submitted there
officially where we have a switch to enable/disable this
functionality.