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Mon, 10 Feb 2025 07:19:19 -0800 (PST) Message-ID: <4914fa43-650c-403e-b2a5-b5ec66d02101@gmail.com> Date: Mon, 10 Feb 2025 23:19:13 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH bpf-next v5 3/4] libbpf: Add libbpf_probe_bpf_kfunc API To: Jiri Olsa Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, haoluo@google.com, qmo@kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, Tao Chen References: <20250210055945.27192-1-chen.dylane@gmail.com> <20250210055945.27192-4-chen.dylane@gmail.com> From: Tao Chen In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 在 2025/2/10 21:47, Jiri Olsa 写道: > On Mon, Feb 10, 2025 at 01:59:44PM +0800, Tao Chen wrote: > > SNIP > >> diff --git a/tools/lib/bpf/libbpf_probes.c b/tools/lib/bpf/libbpf_probes.c >> index e142130cb83c..53f1196394bf 100644 >> --- a/tools/lib/bpf/libbpf_probes.c >> +++ b/tools/lib/bpf/libbpf_probes.c >> @@ -433,6 +433,54 @@ static bool can_probe_prog_type(enum bpf_prog_type prog_type) >> return true; >> } >> >> +int libbpf_probe_bpf_kfunc(enum bpf_prog_type prog_type, int kfunc_id, int btf_fd, >> + const void *opts) >> +{ >> + struct bpf_insn insns[] = { >> + BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, BPF_PSEUDO_KFUNC_CALL, 1, kfunc_id), >> + BPF_EXIT_INSN(), >> + }; >> + const size_t insn_cnt = ARRAY_SIZE(insns); >> + char buf[4096]; >> + int fd_array[2] = {-1}; >> + int ret; >> + >> + if (opts) >> + return libbpf_err(-EINVAL); >> + >> + if (!can_probe_prog_type(prog_type)) >> + return -EOPNOTSUPP; >> + >> + if (btf_fd >= 0) { >> + fd_array[1] = btf_fd; >> + } else if (btf_fd == -1) { >> + /* insn.off = 0, means vmlinux btf */ >> + insns[0].off = 0; >> + } else { >> + return libbpf_err(-EINVAL); >> + } >> + >> + buf[0] = '\0'; >> + ret = probe_prog_load(prog_type, insns, insn_cnt, btf_fd >= 0 ? fd_array : NULL, >> + 0, buf, sizeof(buf)); > > hum, you pass fd_array_cnt as 0, which IIUC will work properly > > but I guess then we don't need to have fd_array_cnt argument in > probe_prog_load if all callers pass 0 ? > > jirka > Hi, jiri In fact, 0 is indeed used everywhere here. I was just thinking about whether we might need it in the future. Anyway, it seems better to remove it. I'll make the modifications in the next version. >> + if (ret < 0) >> + return libbpf_err(ret); >> + >> + /* 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 btf fd >> + * invalid in module btf, it will emit "invalid module BTF fd specified" or >> + * "negative offset disallowed for kernel module function call" >> + */ >> + if (ret == 0 && (strstr(buf, "not allowed") || strstr(buf, "not a function") || >> + (strstr(buf, "invalid module BTF fd")) || >> + (strstr(buf, "negative offset disallowed")))) >> + 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) >> { >> -- >> 2.43.0 >> -- Best Regards Dylane Chen