netdev - Re: [PATCH bpf-next v2 4/4] selftest: bpf: Test copying a sockmap and sockhash

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Date:   Tue, 29 Sep 2020 10:21:05 +0100
From:   Lorenz Bauer <lmb@...udflare.com>
To:     Martin KaFai Lau <kafai@...com>
Cc:     Shuah Khan <shuah@...nel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        kernel-team <kernel-team@...udflare.com>,
        linux-kselftest@...r.kernel.org,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next v2 4/4] selftest: bpf: Test copying a sockmap and sockhash

On Tue, 29 Sep 2020 at 07:06, Martin KaFai Lau <kafai@...com> wrote:

...

> > +     /* We need a temporary buffer on the stack, since the verifier doesn't
> > +      * let us use the pointer from the context as an argument to the helper.
> Is it something that can be improved later?
>
> others LGTM.

Yeah, I think so. We'd need to do something similar to your
sock_common work for PTR_TO_RDONLY_BUF_OR_NULL. The fact that the
pointer is read only makes it a bit more difficult I think. After
that, a user could just plug the key into map_update_elem directly.
Alternatively, allow specialising map_ops per context.

-- 
Lorenz Bauer  |  Systems Engineer
6th Floor, County Hall/The Riverside Building, SE1 7PB, UK

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