From patchwork Fri Feb 21 16:33:34 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tao Chen X-Patchwork-Id: 13985952 X-Patchwork-Delegate: bpf@iogearbox.net Received: from out-177.mta1.migadu.com (out-177.mta1.migadu.com [95.215.58.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 614CD20F08F for ; Fri, 21 Feb 2025 16:36:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.177 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740155794; cv=none; b=G3H/gv2EvYa4t8oZTvVKUCboCoYJmC53jRDAgezM1UQnxcOglf0PGdlwq+xaTcK0Q6sIhB1n43p0t7dQduIS/Co9vXPScFkoap4QdnfKpuqQBOgIOCCksryHuHUsEmQHUzzui/myQSnH53/fEN2f4kEWzJqZvWApj6v+xza9KVQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740155794; c=relaxed/simple; bh=pWXtRo6gHo4DEJYISY33x6GfcFgrTWBD7e3ZWdUBELE=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=rqj+yOsD2G9UJ2zbVgNZZKDA0u3CRJh13ETlLD9csXHMm1230ZQ3Qahg6OrtjSswtUxuc7pQzCvT2poqav/3TnivYzq2/yWFwbhekDZsI9js2SFzMdFlm4onWJOSz8M3GhUmDYeoMqG6qK/4Sg8Ki0U9SXVgLc38zKoR/eKw3Eg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=kDCLDEcF; arc=none smtp.client-ip=95.215.58.177 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="kDCLDEcF" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1740155789; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=vB83pcYOlAu6TvcgZccjSdqVZZ3UtGjDlwpT4jeGmb0=; b=kDCLDEcFzNmdb93Nm5TYmHvhLUoeyk70BPC12DJ75fHQSkmqpW/CvtrD0z0NTJBcSAKB+m GG72WyeMITRgC0dTq3RnT14bobqFvGdZe6N5jophG4izfinGCV9hs74j7+A9S/kb1LZ6AN QAx026QBlwhel5knRCgUjGlH4QrB7xE= 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 , Tao Chen Subject: [PATCH bpf-next v8 3/4] libbpf: Add libbpf_probe_bpf_kfunc API Date: Sat, 22 Feb 2025 00:33:34 +0800 Message-Id: <20250221163335.262143-4-chen.dylane@linux.dev> In-Reply-To: <20250221163335.262143-1-chen.dylane@linux.dev> References: <20250221163335.262143-1-chen.dylane@linux.dev> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Migadu-Flow: FLOW_OUT X-Patchwork-Delegate: bpf@iogearbox.net 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 Reviewed-by: Jiri Olsa Reviewed-by: Eduard Zingerman Signed-off-by: Tao Chen --- tools/lib/bpf/libbpf.h | 19 ++++++++++++- tools/lib/bpf/libbpf.map | 1 + tools/lib/bpf/libbpf_probes.c | 51 +++++++++++++++++++++++++++++++++++ 3 files changed, 70 insertions(+), 1 deletion(-) diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index 3020ee45303a..c79b4475b956 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_map_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 >= 0, and < 0 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 de2b1205b436..8efebc18a215 100644 --- a/tools/lib/bpf/libbpf_probes.c +++ b/tools/lib/bpf/libbpf_probes.c @@ -431,6 +431,57 @@ 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 libbpf_err(-EOPNOTSUPP); + + if (btf_fd >= 0) + fd_array[1] = btf_fd; + else + /* insn.off = 0, means vmlinux btf */ + insns[0].off = 0; + + buf[0] = '\0'; + ret = probe_prog_load(prog_type, insns, insn_cnt, btf_fd >= 0 ? fd_array : NULL, + buf, sizeof(buf)); + if (ret < 0) + return libbpf_err(ret); + + if (ret > 0) + return 1; /* assume supported */ + + /* If BPF verifier recognizes BPF kfunc but it's not supported for + * given BPF program type, it will emit "calling kernel function + * is not allowed". If the kfunc id is invalid, + * it will emit "kernel btf_id 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 + * kfunc prog not dev buound, it will emit "metadata kfuncs require + * device-bound program". + */ + if (strstr(buf, "not allowed") || strstr(buf, "not a function") || + strstr(buf, "invalid module BTF fd") || + strstr(buf, "negative offset disallowed") || + strstr(buf, "device-bound program")) + return 0; + + return 1; +} + int libbpf_probe_bpf_helper(enum bpf_prog_type prog_type, enum bpf_func_id helper_id, const void *opts) {