linux-kernel - Re: [PATCH 3/5] bpf: Add bpf_user_ringbuf

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Message-ID: <YvWYYhHfvEQ34wEv@maniforge.dhcp.thefacebook.com>
Date:   Thu, 11 Aug 2022 19:01:38 -0500
From:   David Vernet <void@...ifault.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     bpf@...r.kernel.org, ast@...nel.org, daniel@...earbox.net,
        andrii@...nel.org, john.fastabend@...il.com, martin.lau@...ux.dev,
        song@...nel.org, yhs@...com, kpsingh@...nel.org, sdf@...gle.com,
        haoluo@...gle.com, jolsa@...nel.org, tj@...nel.org,
        joannelkoong@...il.com, linux-kernel@...r.kernel.org,
        Kernel-team@...com
Subject: Re: [PATCH 3/5] bpf: Add bpf_user_ringbuf_drain() helper

On Thu, Aug 11, 2022 at 04:22:43PM -0700, Andrii Nakryiko wrote:
> On Mon, Aug 8, 2022 at 8:54 AM David Vernet <void@...ifault.com> wrote:
> >
> > Now that we have a BPF_MAP_TYPE_USER_RINGBUF map type, we need to add a
> > helper function that allows BPF programs to drain samples from the ring
> > buffer, and invoke a callback for each. This patch adds a new
> > bpf_user_ringbuf_drain() helper that provides this abstraction.
> >
> > In order to support this, we needed to also add a new PTR_TO_DYNPTR
> > register type to reflect a dynptr that was allocated by a helper function
> > and passed to a BPF program. The verifier currently only supports
> > PTR_TO_DYNPTR registers that are also DYNPTR_TYPE_LOCAL and MEM_ALLOC.
> 
> This commit message is a bit too laconic. There is a lot of
> implications of various parts of this patch, it would be great to
> highlight most important ones. Please consider elaborating a bit more.

Not a problem, I'll do this in v3.