Re: [RFC PATCH 00/11] bpf, trace, dtrace: DTrace BPF program type implementation and sample use

Alexei Starovoitov
2019-05-21T17:56:22Z

On Mon, May 20, 2019 at 11:47:00PM +0000, Kris Van Hees wrote:
>
> 2. bpf: add BPF_PROG_TYPE_DTRACE
>
> This patch adds BPF_PROG_TYPE_DTRACE as a new BPF program type, without
> actually providing an implementation. The actual implementation is
> added in patch 4 (see below). We do it this way because the
> implementation is being added to the tracing subsystem as a component
> that I would be happy to maintain (if merged) whereas the declaration
> of the program type must be in the bpf subsystem. Since the two
> subsystems are maintained by different people, we split the
> implementing patches across maintainer boundaries while ensuring that
> the kernel remains buildable between patches.

None of these kernel patches are necessary for what you want to achieve.
Feel free to add tools/dtrace/ directory and maintain it though.

The new dtrace_buffer doesn't need to replicate existing bpf+kernel functionality
and no changes are necessary in kernel/events/ring_buffer.c either.
tools/dtrace/ user space component can use either per-cpu array map
or hash map as a buffer to store arbitrary data into and use
existing bpf_perf_event_output() to send it to user space via perf ring buffer.

See, for example, how bpftrace does that.