From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from pdx-out-007.esa.us-west-2.outbound.mail-perimeter.amazon.com (pdx-out-007.esa.us-west-2.outbound.mail-perimeter.amazon.com [52.34.181.151]) (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 51F7F46F4A7; Thu, 1 Oct 2026 23:53:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=52.34.181.151 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790898815; cv=none; b=uSK/Pqp+uDn5obRiRsaXySLeVoMReHci3Fzjay1stNUURx5pD9xWMLIT0TBP3w/W7weJ0QmWfkY1IPRwWSsZtGtHWW+Snzjd8q/DUrfIeNojKieMtr3H93GyDFW23aXxPUMWulEyLpGboCflasHYP12tlosVoT+Tu/hkKJgoOZY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790898815; c=relaxed/simple; bh=sxgzWa7Pg4Vu0QV7HUff5HmJa7L8rhf32QKppY3kv4k=; h=From:To:CC:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=OrXpwWOHgbI6jShMVXqPo0jj2t6jv9/GlUY6i+BhGCE/DsZlnIYfCPP3abXqBMgWY1pqbE6+Lh7PdJ3c5QVp+9DFYEcPFLIQ6EY6MKMaST85m+mEmoGPAcgGa4Um2KCVhlUOeniDN9D7ctwkvUuS9yViQhUKqxPWvvLAWuQx9Zk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.com; spf=pass smtp.mailfrom=amazon.com; dkim=pass (2048-bit key) header.d=amazon.com header.i=@amazon.com header.b=s71rMD84; arc=none smtp.client-ip=52.34.181.151 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=amazon.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=amazon.com header.i=@amazon.com header.b="s71rMD84" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazoncorp2; t=1790898814; x=1822434814; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=aKYNDJBaF/a+oEVTdroRmzbc+8LBZqR2cnhVz8NN1Ws=; b=s71rMD84CQ5rDgVgCGSOdYE4S42eN2FwBQYpn107AxEPWjjzWkOHLhlw kJ0VEhrL10StCtGiV8FXgN9/Ewfs0ZmlMT4jeCHBNriUxMfRtyjb1phfu DDMQOzrkRXDLvxv2/ma4iUtspdnxOu2+vSt4hZAAWGbhq/P9qhCU2827E qaEKZxmvgqX04N8guw00xXF3g4/h/fACKhPWjS5u3l72NION/0hauNJFk bj7yQFi/S4V7OCt0U6NS1Irzu+/nU3GRP3L+5xCn7LjLKDdv74c2YIRNo fBb3CfdN5GQ8QXNDcNgzZg/dhpowpkCLn3mI8sw7UdNTiwhHJnj68Hg5S g==; X-CSE-ConnectionGUID: Scd1Ez1gQp2utnFTzEvrxw== X-CSE-MsgGUID: rtNnwBb8RneFt1wqoso4Og== X-IronPort-AV: E=Sophos;i="6.27,135,1787011200"; d="scan'208";a="30178142" Received: from ip-10-5-0-115.us-west-2.compute.internal (HELO smtpout.naws.us-west-2.prod.farcaster.email.amazon.dev) ([10.5.0.115]) by internal-pdx-out-007.esa.us-west-2.outbound.mail-perimeter.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Oct 2026 23:53:34 +0000 Received: from EX19MTAUWA002.ant.amazon.com [205.251.233.234:19497] by smtpin.naws.us-west-2.prod.farcaster.email.amazon.dev [10.0.47.21:2525] with esmtp (Farcaster) id edbeb6ac-af33-4878-a212-0ac95593aed5; Thu, 1 Oct 2026 23:53:33 +0000 (UTC) X-Farcaster-Flow-ID: edbeb6ac-af33-4878-a212-0ac95593aed5 Received: from EX19D001UWA001.ant.amazon.com (10.13.138.214) by EX19MTAUWA002.ant.amazon.com (10.250.64.202) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.49; Thu, 1 Oct 2026 23:53:33 +0000 Received: from dev-dsk-wanjay-2c-d25651b4.us-west-2.amazon.com (172.19.198.4) by EX19D001UWA001.ant.amazon.com (10.13.138.214) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.49; Thu, 1 Oct 2026 23:53:33 +0000 From: Jay Wang To: , , , , , , CC: , , , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH bpf-next v3 9/9] kbuild, bpf: allow building the vmlinux BTF as a module Date: Thu, 1 Oct 2026 23:53:32 +0000 Message-ID: <20261001235332.8074-1-wanjay@amazon.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <6e565a3c5689de1d5ba05904e3d7f477373bca8e10be75fea4b6adc048ab6ac4@mail.kernel.org> References: <6e565a3c5689de1d5ba05904e3d7f477373bca8e10be75fea4b6adc048ab6ac4@mail.kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: EX19D039UWB004.ant.amazon.com (10.13.138.57) To EX19D001UWA001.ant.amazon.com (10.13.138.214) All three are addressed in v4: https://lore.kernel.org/bpf/20261001225214.12351-1-wanjay@amazon.com/ - The ftrace argument printer is a real problem: it can run from ftrace_dump() with interrupts disabled. print_function_args() now only prints the arguments if the vmlinux BTF is already loaded (bpf_peek_btf_vmlinux(), patch 5/12), like bpf_snprintf_btf(); in v4 the lookup it uses would not load the BTF anyway. Tested with func-args on and sysrq-z as the first thing touching BTF after boot, on a kernel with CONFIG_DEBUG_ATOMIC_SLEEP. - The opening of the changelog now names the exceptions: BPF_PRELOAD, users of kernel types that run before btf_vmlinux.ko can be loaded, and code that assumes the vmlinux BTF has id 1. - btf.rst now lists the requests that load the BTF, including struct_ops maps, kprobe events with BTF arguments, tracepoint btf_ids files and bpffs delegate_* options. PROBE_EVENTS_BTF_ARGS and FUNCTION_TRACE_ARGS do stay enabled with =m, which is intended: creating a probe with BTF arguments loads the BTF, in process context, and the argument printer uses it once it is there. Jay