linux-kernel - Re: [PATCH bpf-next v3 1/3] libbpf: Refactor libbpf_probe_bpf

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Message-ID: <a043941b-f7d0-4f5a-a2aa-4f47c58370b2@gmail.com>
Date: Sat, 25 Jan 2025 22:52:03 +0800
From: Tao Chen <chen.dylane@...il.com>
To: Jiri Olsa <olsajiri@...il.com>
Cc: ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
 eddyz87@...il.com, haoluo@...gle.com, qmo@...nel.org, bpf@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH bpf-next v3 1/3] libbpf: Refactor libbpf_probe_bpf_helper

在 2025/1/25 00:26, Jiri Olsa 写道:
> On Fri, Jan 24, 2025 at 10:44:09PM +0800, Tao Chen wrote:
>> Extract the common part as probe_func_comm, which will be used in
>> both libbpf_probe_bpf_{helper, kfunc}
>>
>> Signed-off-by: Tao Chen <chen.dylane@...il.com>
>> ---
>>   tools/lib/bpf/libbpf_probes.c | 38 ++++++++++++++++++++++++-----------
>>   1 file changed, 26 insertions(+), 12 deletions(-)
>>
>> diff --git a/tools/lib/bpf/libbpf_probes.c b/tools/lib/bpf/libbpf_probes.c
>> index 9dfbe7750f56..b73345977b4e 100644
>> --- a/tools/lib/bpf/libbpf_probes.c
>> +++ b/tools/lib/bpf/libbpf_probes.c
>> @@ -413,22 +413,20 @@ int libbpf_probe_bpf_map_type(enum bpf_map_type map_type, const void *opts)
>>   	return libbpf_err(ret);
>>   }
>>   
>> -int libbpf_probe_bpf_helper(enum bpf_prog_type prog_type, enum bpf_func_id helper_id,
>> -			    const void *opts)
>> +static int probe_func_comm(enum bpf_prog_type prog_type, struct bpf_insn insn,
>> +			   char *accepted_msgs, size_t msgs_size)
>>   {
>>   	struct bpf_insn insns[] = {
>> -		BPF_EMIT_CALL((__u32)helper_id),
>> +		BPF_EXIT_INSN(),
>>   		BPF_EXIT_INSN(),
> 
> I'd just keep above in libbpf_probe_bpf_helper and pass insns to probe_func_comm,
> seems easier
> 
> jirka
> 

Hi jiri,
Thank you for your review, your suggestion seems better, i will
send it in v4.

>>   	};
>>   	const size_t insn_cnt = ARRAY_SIZE(insns);
>> -	char buf[4096];
>> -	int ret;
>> +	int err;
>>   
>> -	if (opts)
>> -		return libbpf_err(-EINVAL);
>> +	insns[0] = insn;
>>   
>>   	/* we can't successfully load all prog types to check for BPF helper
>> -	 * support, so bail out with -EOPNOTSUPP error
>> +	 * and kfunc support, so bail out with -EOPNOTSUPP error
>>   	 */
>>   	switch (prog_type) {
>>   	case BPF_PROG_TYPE_TRACING:
>> @@ -440,10 +438,26 @@ int libbpf_probe_bpf_helper(enum bpf_prog_type prog_type, enum bpf_func_id helpe
>>   		break;
>>   	}
>>   
>> -	buf[0] = '\0';
>> -	ret = probe_prog_load(prog_type, insns, insn_cnt, buf, sizeof(buf));
>> -	if (ret < 0)
>> -		return libbpf_err(ret);
>> +	accepted_msgs[0] = '\0';
>> +	err = probe_prog_load(prog_type, insns, insn_cnt, accepted_msgs, msgs_size);
>> +	if (err < 0)
>> +		return libbpf_err(err);
>> +
>> +	return 0;
>> +}
>> +
>> +int libbpf_probe_bpf_helper(enum bpf_prog_type prog_type, enum bpf_func_id helper_id,
>> +			    const void *opts)
>> +{
>> +	char buf[4096];
>> +	int ret;
>> +
>> +	if (opts)
>> +		return libbpf_err(-EINVAL);
>> +
>> +	ret = probe_func_comm(prog_type, BPF_EMIT_CALL((__u32)helper_id), buf, sizeof(buf));
>> +	if (ret)
>> +		return ret;
>>   
>>   	/* If BPF verifier doesn't recognize BPF helper ID (enum bpf_func_id)
>>   	 * at all, it will emit something like "invalid func unknown#181".
>> -- 
>> 2.43.0
>>


-- 
Best Regards
Dylane Chen