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Date:   Mon, 6 Feb 2023 12:37:14 -0800
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Subject: Re: [PATCH v2 bpf-next] Add support for tracing programs in
 BPF_PROG_RUN
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To:     Grant Seltzer Richman <grantseltzer@gmail.com>
Cc:     andrii@kernel.org, kpsingh@kernel.org, bpf@vger.kernel.org
References: <20230203182812.20657-1-grantseltzer@gmail.com>
 <6433db0e-5cc6-8acc-b92f-eb5e17f032d6@linux.dev>
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From:   Martin KaFai Lau <martin.lau@linux.dev>
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On 2/5/23 9:29 AM, Grant Seltzer Richman wrote:
> On Sat, Feb 4, 2023 at 1:58 AM Martin KaFai Lau <martin.lau@linux.dev> wrote:
>>
>> On 2/3/23 10:28 AM, Grant Seltzer wrote:
>>> This patch changes the behavior of how BPF_PROG_RUN treats tracing
>>> (fentry/fexit) programs. Previously only a return value is injected
>>> but the actual program was not run.
>>
>> hmm... I don't understand this. The actual program is run by attaching to the
>> bpf_fentry_test{1,2,3...}. eg. The test in fentry_test.c
> 
> I'm not sure what you mean. Are you saying in order to use the
> BPF_PROG_RUN bpf syscall command the user must first attach to
> `bpf_fentry_test1` (or any 1-8), and then execute the BPF_PROG_RUN?

It is how the fentry/fexit/fmod_ret...BPF_PROG_TYPE_TRACIN_xxx prog is setup to 
run now in test_run. afaik, these tracing progs require the trampoline setup 
before calling the bpf prog, so don't understand how __bpf_prog_test_run_tracing 
will work safely.

A selftest will help how this will work without the traompline but may be first 
need to understand what it is trying to solve.