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Thu, 23 Jan 2025 17:34:09 -0800 (PST) Message-ID: <8d286a6b2a5f481e1eb23466c199a1b05ec81a88.camel@gmail.com> Subject: Re: [PATCH bpf-next v2 1/2] libbpf: Add libbpf_probe_bpf_kfunc API From: Eduard Zingerman To: Tao Chen , ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, haoluo@google.com, jolsa@kernel.org, qmo@kernel.org Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org Date: Thu, 23 Jan 2025 17:34:04 -0800 In-Reply-To: <20250123170555.291896-2-chen.dylane@gmail.com> References: <20250123170555.291896-1-chen.dylane@gmail.com> <20250123170555.291896-2-chen.dylane@gmail.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.54.2 (3.54.2-1.fc41) Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Fri, 2025-01-24 at 01:05 +0800, Tao Chen wrote: [...] > +int libbpf_probe_bpf_kfunc(enum bpf_prog_type prog_type, int kfunc_id, > + __s16 off, const void *opts) ^^^ Nit: maybe name this btf_fd? > +{ In v2 function looks identical to libbpf_probe_bpf_helper, do we want to copy-paste it or introduce a utility: static int probe_insn(enum bpf_prog_type prog_type, struct bpf_insn insn, const char **accepted_msgs) And call it from both libbpf_probe_bpf_{helper,kfunc}? > + struct bpf_insn insns[] =3D { > + BPF_EXIT_INSN(), > + BPF_EXIT_INSN(), > + }; > + const size_t insn_cnt =3D ARRAY_SIZE(insns); > + int err; > + char buf[4096]; > + > + if (opts) > + return libbpf_err(-EINVAL); > + > + /* Same logic as probe_bpf_helper check */ > + switch (prog_type) { > + case BPF_PROG_TYPE_TRACING: > + case BPF_PROG_TYPE_EXT: > + case BPF_PROG_TYPE_LSM: > + case BPF_PROG_TYPE_STRUCT_OPS: > + return -EOPNOTSUPP; > + default: > + break; > + } > + > + insns[0].code =3D BPF_JMP | BPF_CALL; > + insns[0].src_reg =3D BPF_PSEUDO_KFUNC_CALL; > + insns[0].imm =3D kfunc_id; > + insns[0].off =3D off; > + > + buf[0] =3D '\0'; > + err =3D probe_prog_load(prog_type, insns, insn_cnt, buf, sizeof(buf)); > + if (err < 0) > + return libbpf_err(err); > + > + /* If BPF verifier recognizes BPF kfunc but it's not supported for > + * given BPF program type, it will emit "calling kernel function > + * bpf_cpumask_create is not allowed", if the kfunc id is invalid, > + * it will emit "kernel btf_id 4294967295 is not a function" > + */ > + if (err =3D=3D 0 && (strstr(buf, "not allowed") || strstr(buf, "not a f= unction"))) > + return 0; > + > + return 1; /* assume supported */ > +} > + > int libbpf_probe_bpf_helper(enum bpf_prog_type prog_type, enum bpf_func_= id helper_id, > const void *opts) > {