Re: [PATCH bpf-next v3 1/3] libbpf: Refactor libbpf_probe_bpf_helper

[Jiri Olsa <olsajiri@gmail.com>]

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@gmail.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

>  	};
>  	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
>