From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-178.mta0.migadu.com (out-178.mta0.migadu.com [91.218.175.178]) (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 50B063B8943; Mon, 30 Mar 2026 09:07:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.178 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774861666; cv=none; b=OeY0eXiLoDx11SVFw+bKRvXvclHuZfduR+kwrGwxD6A/YWN6vkTqUgyO5VBD0fzOXFz2DLT3GiLLh03tHKTlhSjqjgmJ9+M42k6phV8WLh9eVRumI/6SNR/xk0nzI0fN5T4YJmywac2FczWs/5xeWwMiYuEKnc7JGMOrXSjMqOQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774861666; c=relaxed/simple; bh=B6PZfVeG7snpqwW2Dj2BcofsI5G8BWCMHmjYcpSMZ8I=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=KS1Bv7rRHj6k7iLoDTM1BPChwT/EA8nW1MKOpBJAFXKjLGvjP0GZTK5WAEJ8E1vTAYgdWejMp7wedUKlP8H6slki/OI3RpqgPXyHN4nYkLy1o4zYjwd2MxsAlimGN5rcxUPTtIUz5eObJtEGgNZLV3kR/qMqcTJLk+fVK0SkSfY= 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=wKcebj5x; arc=none smtp.client-ip=91.218.175.178 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="wKcebj5x" Message-ID: <4b0e7341-f2e2-4ad2-8c9e-b482a1b1cbfb@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1774861662; 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=eedqsRaw3mwJSZ/9l+mCaxc+9OYTIiN/zRg8cpwfdus=; b=wKcebj5xfXxM1Fw495xOyB2jzCiJKB9ou6uzKzTaLVi9/bz6ODPm2dfB2gI90j2p/qzLPv 6BHDPN/DWoFGuFswV1e/BU/ctuwpx5ObQtV/ktCTdan0S29tEqbOFV/B6Eo06i9McyJQB8 TE4AWlgw0sHXvx7QGwN9qFajMww6L0Y= Date: Mon, 30 Mar 2026 17:07:34 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH bpf-next 1/2] bpf, x86: patch tail-call fentry slot on non-IBT JITs Content-Language: en-US To: Takeru Hayasaka , Alexei Starovoitov Cc: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , bpf , X86 ML , "open list:KERNEL SELFTEST FRAMEWORK" , LKML References: <20260327141616.1961457-1-hayatake396@gmail.com> <20260327141616.1961457-2-hayatake396@gmail.com> 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: 7bit X-Migadu-Flow: FLOW_OUT On 28/3/26 00:30, Takeru Hayasaka wrote: >> see how cilium did it. with pwru tool, etc. > > Thank you for the suggestion. > As for pwru, I had thought it was not able to capture packet data such as pcap, > and understood it more as a tool to trace where a specific packet > enters the processing path and how it is handled. > > For example, in an environment where systems are already > interconnected and running, I sometimes want to capture the actual > packets being sent for real processing. > On the other hand, if the goal is simply to observe processing safely > in a development environment, I think tools such as ipftrace2 or pwru > can be very useful. > Sounds like you are developing/maintaining an XDP project. If so, and the kernel carries the patches in https://lore.kernel.org/all/20230912150442.2009-1-hffilwlqm@gmail.com/, recommend modifying the XDP project using dispatcher like libxdp [1]. Then, you are able to trace the subprogs which aim to run tail calls; meanwhile, you are able to filter packets using pcap-filter, and to output packets using bpf_xdp_output() helper. [1] https://github.com/xdp-project/xdp-tools/blob/main/lib/libxdp/xdp-dispatcher.c.in Thanks, Leon