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Thu, 23 Jan 2025 19:25:47 -0800 (PST) Message-ID: <26e2e47f-4c95-4874-969f-c497aadbb5f0@gmail.com> Date: Fri, 24 Jan 2025 11:25:42 +0800 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH bpf-next v2 1/2] libbpf: Add libbpf_probe_bpf_kfunc API To: Eduard Zingerman , 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 References: <20250123170555.291896-1-chen.dylane@gmail.com> <20250123170555.291896-2-chen.dylane@gmail.com> <8d286a6b2a5f481e1eb23466c199a1b05ec81a88.camel@gmail.com> From: Tao Chen In-Reply-To: <8d286a6b2a5f481e1eb23466c199a1b05ec81a88.camel@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 在 2025/1/24 09:34, Eduard Zingerman 写道: > 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? Hi Eduard, thank you for your guidance, ack, i will send it in v3. > >> +{ > > 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}? Yes, it seems much more concise. I will send it in v3. Thanks. > >> + struct bpf_insn insns[] = { >> + BPF_EXIT_INSN(), >> + BPF_EXIT_INSN(), >> + }; >> + const size_t insn_cnt = 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 = BPF_JMP | BPF_CALL; >> + insns[0].src_reg = BPF_PSEUDO_KFUNC_CALL; >> + insns[0].imm = kfunc_id; >> + insns[0].off = off; >> + >> + buf[0] = '\0'; >> + err = 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 == 0 && (strstr(buf, "not allowed") || strstr(buf, "not a function"))) >> + 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) >> { > > -- Best Regards Dylane Chen