netdev - Re: [PATCH net-next] bpf: add show

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Date:	Thu, 19 Nov 2015 10:45:07 -0800
From:	Alexei Starovoitov <alexei.starovoitov@...il.com>
To:	Daniel Borkmann <daniel@...earbox.net>
Cc:	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] bpf: add show_fdinfo handler for maps

On Thu, Nov 19, 2015 at 07:36:10PM +0100, Daniel Borkmann wrote:
> On 11/19/2015 07:19 PM, Hannes Frederic Sowa wrote:
> >On Thu, Nov 19, 2015, at 11:56, Daniel Borkmann wrote:
> >>Add a handler for show_fdinfo() to be used by the anon-inodes
> >>backend for eBPF maps, and dump the map specification there. Not
> >>only useful for admins, but also it provides a minimal way to
> >>compare specs from ELF vs pinned object.
> >>
> >>Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
> >
> >Acked-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
> >
> >Does it make sense to include bpf_htab->count in case of a hashmap?
> 
> It would give a sort-of only volatile view, e.g. like the map's
> refcount. It would be possible to show it, but only as kind of
> informative to an admin, have no strong opinion on it, though.
> 
> I think this goes rather into the direction of better debugging
> interfaces for eBPF, probably makes sense think about it wrt a
> general debugging/introspection framework and better dump it
> there ...

refcnt to userspace?! nack.
I'm strongly against such 'debugging' that can only be misused
if exposed to user space. Regardless whether it's admin or not.

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