From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-182.mta0.migadu.com (out-182.mta0.migadu.com [91.218.175.182]) (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 DFCD2318B8A for ; Fri, 23 Jan 2026 01:42:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.182 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769132539; cv=none; b=rc7dP55kCuRf7awcoibtnwLaHmPFj+jpQ7tbLY4LY6Z4tsn6529eOdDF5yqloqxEvV3q0AGxpZ1binlk15QH7hWPEkeO3ps039/sLq9K/m4Mkju1sT++ndD69GQ0ph8E8YBiZOeILPmdJNJ+OWmPgs3w5rvMVEsvSKJiD1tDQj4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769132539; c=relaxed/simple; bh=1jYCfNu2E99u9MI+Zrtb1OeT/4uF24Ygozh31Z2W9Lo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=rZk1XSIMXynGZWNI3CPTR5t2TniBvT3n6uxJZRE8mpvNBMfH6NnqWgGg0rbPD588z1gNL1tsvZv+8bw/F3IbiPRM5IjpDcY51agReufoyM68QDZBiRQCutwaMNOfrstsst2taYeGJutvt20Aqqs7mo8HRruCOK16ghDXFjc8nIM= 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=dVi5OMKZ; arc=none smtp.client-ip=91.218.175.182 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="dVi5OMKZ" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1769132514; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=iGfcUAaWbMDiu8CMjALaFc9nVb/oZtC296G14BPTQ8A=; b=dVi5OMKZnN2En7ntGYp3qS0caDqEIYvqTphe3/sn0O/6gZuDkrOON6x7HgsoWD0jNsfpqz nY2Taz8iZn++LOsX49O3LO4I9yG+BA+fHUYPHgGiJ7JF40NxOBbjWm8h+2ML5vJ5pfvhLu FfQokaE1/T4ZFe5L/FnUYq/dDhcLujo= Date: Fri, 23 Jan 2026 09:41:38 +0800 Precedence: bulk X-Mailing-List: linux-api@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [RESEND PATCH bpf-next v6 2/9] libbpf: Add support for extended bpf syscall Content-Language: en-US To: Andrii Nakryiko Cc: bpf@vger.kernel.org, Alexei Starovoitov , Daniel Borkmann , John Fastabend , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Shuah Khan , Christian Brauner , Seth Forshee , Yuichiro Tsuji , Andrey Albershteyn , Willem de Bruijn , Jason Xing , Tao Chen , Mykyta Yatsenko , Kumar Kartikeya Dwivedi , Anton Protopopov , Amery Hung , Rong Tao , linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, linux-kselftest@vger.kernel.org, kernel-patches-bot@fb.com References: <20260120152424.40766-1-leon.hwang@linux.dev> <20260120152424.40766-3-leon.hwang@linux.dev> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Leon Hwang In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT On 23/1/26 08:53, Andrii Nakryiko wrote: > On Tue, Jan 20, 2026 at 7:26 AM Leon Hwang wrote: >> >> To support the extended BPF syscall introduced in the previous commit, >> introduce the following internal APIs: >> >> * 'sys_bpf_ext()' >> * 'sys_bpf_ext_fd()' >> They wrap the raw 'syscall()' interface to support passing extended >> attributes. >> * 'probe_sys_bpf_ext()' >> Check whether current kernel supports the BPF syscall common attributes. >> >> Signed-off-by: Leon Hwang >> --- >> tools/lib/bpf/bpf.c | 32 ++++++++++++++++++++++++++++++++ >> tools/lib/bpf/features.c | 8 ++++++++ >> tools/lib/bpf/libbpf_internal.h | 3 +++ >> 3 files changed, 43 insertions(+) >> >> diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c >> index 21b57a629916..ed9c6eaeb656 100644 >> --- a/tools/lib/bpf/bpf.c >> +++ b/tools/lib/bpf/bpf.c >> @@ -69,6 +69,38 @@ static inline __u64 ptr_to_u64(const void *ptr) >> return (__u64) (unsigned long) ptr; >> } >> >> +static inline int sys_bpf_ext(enum bpf_cmd cmd, union bpf_attr *attr, >> + unsigned int size, >> + struct bpf_common_attr *attr_common, >> + unsigned int size_common) >> +{ >> + cmd = attr_common ? (cmd | BPF_COMMON_ATTRS) : (cmd & ~BPF_COMMON_ATTRS); >> + return syscall(__NR_bpf, cmd, attr, size, attr_common, size_common); >> +} >> + >> +static inline int sys_bpf_ext_fd(enum bpf_cmd cmd, union bpf_attr *attr, >> + unsigned int size, >> + struct bpf_common_attr *attr_common, >> + unsigned int size_common) >> +{ >> + int fd; >> + >> + fd = sys_bpf_ext(cmd, attr, size, attr_common, size_common); >> + return ensure_good_fd(fd); >> +} >> + >> +int probe_sys_bpf_ext(void) >> +{ >> + const size_t attr_sz = offsetofend(union bpf_attr, prog_token_fd); >> + union bpf_attr attr; >> + >> + memset(&attr, 0, attr_sz); >> + /* This syscall() will return error always. */ > > I'll cite myself from the last review: > >> But fd should really not be >= 0, and if it is -- it's some problem, >> so I'd return an error in that case to keep us aware, which is why I'm >> saying I'd just return inside if (fd >= 0) { } > > I didn't say let's just ignore syscall return with (void) cast and > happily check errno no matter what, did I? Drop the comment, and > handle fd >= 0 case explicitly, please. > My mistake — sorry for the misunderstanding. You’re right; the return value should not be ignored. In the next revision, I’ll handle the fd >= 0 case explicitly and drop the comment. The logic will be updated along the lines of: fd = syscall(__NR_bpf, BPF_PROG_LOAD | BPF_COMMON_ATTRS, &attr, attr_sz, NULL, sizeof(struct bpf_common_attr)); if (fd >= 0) { close(fd); return 0; } return errno == EFAULT; Thanks, Leon