From mboxrd@z Thu Jan 1 00:00:00 1970 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 EAEEDC77B7E for ; Mon, 29 May 2023 08:37:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229669AbjE2Ihb (ORCPT ); Mon, 29 May 2023 04:37:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44560 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229556AbjE2Ihb (ORCPT ); Mon, 29 May 2023 04:37:31 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F3D44A7; Mon, 29 May 2023 01:37:29 -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 8209F611E4; Mon, 29 May 2023 08:37:29 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 70462C433EF; Mon, 29 May 2023 08:37:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1685349448; bh=CCUPziSkCzOqPqywzNs2qZ9qhrttdWy8eSJClG82XbI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=NH/TNk+FaUKdryMnaUVwo560jZ2kmTBlw4OUah1VnPKtBqjxmavJqh7kjdIAkHuU5 dA2fN0+JEwl1NvmDMjm87muL9Ya/wsgdzCT1oV6+nwCzz5Os5pezyf1tRDi7uTpzP3 A/+DX+3mYdjq91TkjDPKjk7Z+6Umu/808sLJZkoo= Date: Mon, 29 May 2023 09:37:26 +0100 From: Greg KH To: Jiri Olsa Cc: stable@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, Masami Hiramatsu , Tsahee Zidenberg , Andrii Nakryiko , Christoph Hellwig , Daniel Borkmann , Thomas Gleixner , =?iso-8859-1?Q?Mah=E9?= Tardy , linux-arm-kernel@lists.infradead.org Subject: Re: [RFC PATCH stable 5.4 0/8] bpf: Fix bpf_probe_read/bpf_probe_read_str helpers Message-ID: <2023052947-jubilance-driven-31d8@gregkh> References: <20230522203352.738576-1-jolsa@kernel.org> <2023052646-magnetize-equate-2b24@gregkh> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Sun, May 28, 2023 at 10:02:49PM +0200, Jiri Olsa wrote: > On Fri, May 26, 2023 at 07:54:17PM +0100, Greg KH wrote: > > On Mon, May 22, 2023 at 10:33:44PM +0200, Jiri Olsa wrote: > > > hi, > > > we see broken access to user space with bpf_probe_read/bpf_probe_read_str > > > helpers on arm64 with 5.4 kernel. The problem is that both helpers try to > > > read user memory by calling probe_kernel_read, which seems to work on x86 > > > but fails on arm64. > > > > Has this ever worked on arm64 for the 5.4 kernel tree? If not, it's not > > really a regression, and so, why not use a newer kernel that has this > > new feature added to it there? > > > > In other words, what requires you to use the 5.4.y tree and requires > > feature parity across architectures? > > we have a customer running ok on x86 v5.4, but arm64 is broken with > the same bpf/user space code Again why can they not use a newer kernel version? What forces this customer to be stuck with a specific kernel version that spans different processor types? > upgrade is an option of course, but it's not a big change and we can > have 5.4 working on arm64 as well For loads of other reasons, I'd recommend 5.15 or newer for arm64, so why not use that? > I can send out the change that will be closer to upstream changes, > if that's a concern.. with adding the new probe helpers, which I > guess is not a problem, because it does not change current API You are trying to add features to a stable kernel that are not regression fixes, which is something that we generally do not accept into stable kernels. thnaks, greg k-h