netdev - Re: [PATCH v2 bpf-next 04/17] libbpf: Add support to attach to fentry/fexit tracing progs

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Date:   Thu, 7 Nov 2019 23:13:15 +0000
From:   Song Liu <songliubraving@...com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
CC:     Alexei Starovoitov <ast@...nel.org>,
        David Miller <davem@...emloft.net>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "x86@...nel.org" <x86@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        Kernel Team <Kernel-team@...com>
Subject: Re: [PATCH v2 bpf-next 04/17] libbpf: Add support to attach to
 fentry/fexit tracing progs



> On Nov 7, 2019, at 3:07 PM, Alexei Starovoitov <alexei.starovoitov@...il.com> wrote:
> 
> On Thu, Nov 07, 2019 at 10:51:41PM +0000, Song Liu wrote:
>> 
>> 
>>> On Nov 6, 2019, at 9:46 PM, Alexei Starovoitov <ast@...nel.org> wrote:
>>> 
>>> Teach libbpf to recognize tracing programs types and attach them to
>>> fentry/fexit.
>>> 
>>> Signed-off-by: Alexei Starovoitov <ast@...nel.org>
>> 
>> Acked-by: Song Liu <songliubraving@...com>
>> 
>> With nit below:
>> 
>>> ---
>>> tools/include/uapi/linux/bpf.h |  2 ++
>>> tools/lib/bpf/libbpf.c         | 61 +++++++++++++++++++++++++++++-----
>>> tools/lib/bpf/libbpf.h         |  5 +++
>>> tools/lib/bpf/libbpf.map       |  2 ++
>>> 4 files changed, 61 insertions(+), 9 deletions(-)
>>> 
>> 
>> [...]
>> 
>>> 
>>> /* Accessors of bpf_program */
>>> struct bpf_program;
>>> @@ -248,6 +251,8 @@ LIBBPF_API struct bpf_link *
>>> bpf_program__attach_raw_tracepoint(struct bpf_program *prog,
>>> 				   const char *tp_name);
>>> 
>>> +LIBBPF_API struct bpf_link *
>>> +bpf_program__attach_trace(struct bpf_program *prog);
>>> struct bpf_insn;
>> 
>> attach_trace is not very clear. I guess we cannot call it 
>> attach_ftrace? Maybe we call it attach_fentry and attach_fexit
>> (two names pointing to same function)? 
> 
> bpf_program__attach_trace() can attach all BPF_PROG_TYPE_TRACING.
> Which today are:
>        BPF_TRACE_RAW_TP,
>        BPF_TRACE_FENTRY,
>        BPF_TRACE_FEXIT,
> There will be more BPF_TRACE_* enum bpf_attach_type in the future.
> I considered naming it bpf_program__attach_tracing(), but it's uglier
> and longer.

I see. Thanks for the explanation. 

Song