netdev - Re: [RFC PATCH net-next 1/2] bpf: Save original ebpf instructions

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Message-ID: <5894F19A.60305@iogearbox.net>
Date:   Fri, 03 Feb 2017 22:09:46 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     David Ahern <dsa@...ulusnetworks.com>, netdev@...r.kernel.org,
        alexei.starovoitov@...il.com
CC:     roopa@...ulusnetworks.com
Subject: Re: [RFC PATCH net-next 1/2] bpf: Save original ebpf instructions

On 02/03/2017 09:38 PM, David Ahern wrote:
> Similar to classic bpf, support saving original ebpf instructions
>
> Signed-off-by: David Ahern <dsa@...ulusnetworks.com>

Not convinced that this is in the right direction, this not only *significantly*
increases mem footprint for each and every program, but also when you dump this,
then map references from relocs inside the insns are meaningless (f.e. what about
prog arrays used in tail calls?), so things like criu also won't be able to use
this kind of interface for dump and restore. If it's just for debugging, then
why not extend the existing tracing infrastructure around bpf that was started
with intention to gain more visibility.

Thanks,
Daniel