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

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Message-ID: <20200929172340.hogj6zficvhkpibx@kafai-mbp.dhcp.thefacebook.com>
Date:   Tue, 29 Sep 2020 10:23:40 -0700
From:   Martin KaFai Lau <kafai@...com>
To:     Lorenz Bauer <lmb@...udflare.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, Sep 29, 2020 at 10:21:05AM +0100, Lorenz Bauer wrote:
> 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
I thought the key arg should be used as read-only in the map's helper.
or there is map type's helper that modifies the key?

> that, a user could just plug the key into map_update_elem directly.
> Alternatively, allow specialising map_ops per context.