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Sun, 09 Feb 2025 22:00:12 -0800 (PST) Received: from localhost ([111.229.209.227]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-730789aee96sm3209182b3a.96.2025.02.09.22.00.11 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Sun, 09 Feb 2025 22:00:12 -0800 (PST) From: Tao Chen To: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, haoluo@google.com, jolsa@kernel.org, qmo@kernel.org Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, chen.dylane@gmail.com, Tao Chen Subject: [PATCH bpf-next v5 3/4] libbpf: Add libbpf_probe_bpf_kfunc API Date: Mon, 10 Feb 2025 13:59:44 +0800 Message-Id: <20250210055945.27192-4-chen.dylane@gmail.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20250210055945.27192-1-chen.dylane@gmail.com> References: <20250210055945.27192-1-chen.dylane@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Similarly to libbpf_probe_bpf_helper, the libbpf_probe_bpf_kfunc used to test the availability of the different eBPF kfuncs on the current system. Cc: Tao Chen Signed-off-by: Tao Chen --- tools/lib/bpf/libbpf.h | 19 +++++++++++++- tools/lib/bpf/libbpf.map | 1 + tools/lib/bpf/libbpf_probes.c | 48 +++++++++++++++++++++++++++++++++++ 3 files changed, 67 insertions(+), 1 deletion(-) diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index 3020ee45303a..e796e38cf255 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -1680,7 +1680,24 @@ LIBBPF_API int libbpf_probe_bpf_map_type(enum bpf_ma= p_type map_type, const void */ LIBBPF_API int libbpf_probe_bpf_helper(enum bpf_prog_type prog_type, enum bpf_func_id helper_id, const void *opts); - +/** + * @brief **libbpf_probe_bpf_kfunc()** detects if host kernel supports the + * use of a given BPF kfunc from specified BPF program type. + * @param prog_type BPF program type used to check the support of BPF kfunc + * @param kfunc_id The btf ID of BPF kfunc to check support for + * @param btf_fd The module BTF FD, if kfunc is defined in kernel module, + * btf_fd is used to point to module's BTF, which is >=3D 0, and -1 means = kfunc + * defined in vmlinux. + * @param opts reserved for future extensibility, should be NULL + * @return 1, if given combination of program type and kfunc is supported;= 0, + * if the combination is not supported; negative error code if feature + * detection for provided input arguments failed or can't be performed + * + * Make sure the process has required set of CAP_* permissions (or runs as + * root) when performing feature checking. + */ +LIBBPF_API int libbpf_probe_bpf_kfunc(enum bpf_prog_type prog_type, + int kfunc_id, int btf_fd, const void *opts); /** * @brief **libbpf_num_possible_cpus()** is a helper function to get the * number of possible CPUs that the host kernel supports and expects. diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index b5a838de6f47..3bbfe13aeb6a 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map @@ -438,4 +438,5 @@ LIBBPF_1.6.0 { bpf_linker__new_fd; btf__add_decl_attr; btf__add_type_attr; + libbpf_probe_bpf_kfunc; } LIBBPF_1.5.0; 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 pro= g_type) return true; } =20 +int libbpf_probe_bpf_kfunc(enum bpf_prog_type prog_type, int kfunc_id, int= btf_fd, + const void *opts) +{ + struct bpf_insn insns[] =3D { + BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, BPF_PSEUDO_KFUNC_CALL, 1, kfunc_id), + BPF_EXIT_INSN(), + }; + const size_t insn_cnt =3D ARRAY_SIZE(insns); + char buf[4096]; + int fd_array[2] =3D {-1}; + int ret; + + if (opts) + return libbpf_err(-EINVAL); + + if (!can_probe_prog_type(prog_type)) + return -EOPNOTSUPP; + + if (btf_fd >=3D 0) { + fd_array[1] =3D btf_fd; + } else if (btf_fd =3D=3D -1) { + /* insn.off =3D 0, means vmlinux btf */ + insns[0].off =3D 0; + } else { + return libbpf_err(-EINVAL); + } + + buf[0] =3D '\0'; + ret =3D probe_prog_load(prog_type, insns, insn_cnt, btf_fd >=3D 0 ? fd_ar= ray : NULL, + 0, buf, sizeof(buf)); + 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 =3D=3D 0 && (strstr(buf, "not allowed") || strstr(buf, "not a fun= ction") || + (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) { --=20 2.43.0