From patchwork Tue Aug 2 17:39:12 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Paul E. McKenney" X-Patchwork-Id: 12934923 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DA350C19F28 for ; Tue, 2 Aug 2022 17:39:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231928AbiHBRjS (ORCPT ); Tue, 2 Aug 2022 13:39:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34226 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229690AbiHBRjQ (ORCPT ); Tue, 2 Aug 2022 13:39:16 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2D7ED4B0D8; Tue, 2 Aug 2022 10:39:16 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id B610561237; Tue, 2 Aug 2022 17:39:15 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0F530C433D7; Tue, 2 Aug 2022 17:39:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1659461955; bh=FoyrG1ZSgKJnTOrE1VYOwsrWEx1RrK04H5tFHcdUZVQ=; h=From:To:Cc:Subject:Date:From; b=TUu4iDrz3DrUo8FNNO8C4m/cOmNQjCSLfHHDce2HS8xmXDvyJ0cnuqkYwXmfQUWS/ tZSBxAwGWPvOGIZzqYajSRjmwILqxtCfegWY0V7JwkNLxrwpw3xmDQdQujnfZnal7e Vo7y8JaxgvRQ/J74Jgku27zQtrGL0nVQvlZNpIpPuei8U5dC4gjy7b62OIDCJ+q9lJ TcaAsO6hEmNDHgZ/RKpsmX/FQTOU66UJfNkZdsQa1mmtALo+6ccDhPUwwbJGa//jnt cCl+moQlsJe187WTXds2JG9vBJeN75DmFjP1fmCepjDcQ4B0/TtxeyYZZcP/zj7548 PEJedS7AJdWyg== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id B52515C0155; Tue, 2 Aug 2022 10:39:14 -0700 (PDT) From: "Paul E. McKenney" To: bpf@vger.kernel.org, netdev@vger.kernel.org, linux-doc@vger.kernel.org Cc: corbet@lwn.net, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, kafai@fb.com, songliubraving@fb.com, yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org, kernel-team@fb.com, "Paul E. McKenney" Subject: [PATCH v3 bpf 2/3] bpf: Update bpf_design_QA.rst to clarify that attaching to functions is not ABI Date: Tue, 2 Aug 2022 10:39:12 -0700 Message-Id: <20220802173913.4170192-2-paulmck@kernel.org> X-Mailer: git-send-email 2.31.1.189.g2e36527f23 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net This patch updates bpf_design_QA.rst to clarify that the ability to attach a BPF program to an arbitrary function in the kernel does not make that function become part of the Linux kernel's ABI. [ paulmck: Apply Daniel Borkmann feedback. ] Signed-off-by: Paul E. McKenney --- Documentation/bpf/bpf_design_QA.rst | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/Documentation/bpf/bpf_design_QA.rst b/Documentation/bpf/bpf_design_QA.rst index 2ed9128cfbec8..a06ae8a828e3d 100644 --- a/Documentation/bpf/bpf_design_QA.rst +++ b/Documentation/bpf/bpf_design_QA.rst @@ -279,3 +279,15 @@ cc (congestion-control) implementations. If any of these kernel functions has changed, both the in-tree and out-of-tree kernel tcp cc implementations have to be changed. The same goes for the bpf programs and they have to be adjusted accordingly. + +Q: Attaching to arbitrary kernel functions is an ABI? +----------------------------------------------------- +Q: BPF programs can be attached to many kernel functions. Do these +kernel functions become part of the ABI? + +A: NO. + +The kernel function prototypes will change, and BPF programs attaching to +them will need to change. The BPF compile-once-run-everywhere (CO-RE) +should be used in order to make it easier to adapt your BPF programs to +different versions of the kernel.