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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: X-Rspamd-Queue-Id: A2C6220013 X-Rspam-User: X-Stat-Signature: w7q1bzgw11adm6dqncouso5e6no4fstm X-Rspamd-Server: rspam03 X-HE-Tag: 1685349450-886051 X-HE-Meta: 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 6zewkWLs c5IFyRLhRQoOa+x4eKpwxzU+v5D8mKNmGfrE8Br0p8jxWJQ8T7q1wnxVYKGvL8qGx3/5wZGbr2VAxBhFhB0Y1W7PdD4LrahflwGQfLRU7mHbrSYLBqdOVwM9DIUEkr6qYMu8w14USSDW1BGq9mQqOTub60H7iA94+tG18D87CEyo6fNPVHOsGQgIKesI9f8XK2uqcBlQujfJ8GSDegVShUho+WKevP8ILQwUmIt/PwuUwe5ZI306BdiPm+fUnlanNFESZGfYm0Q/GvFHFQq9sdJHqTfu5vN5ACreCYNfszszN1l4E4V8vVKogPKaoYCbE3Stni2RtOcRoR5gvOQCrn3JfwVTYKYM/TK+MJV2GGL6I/8c= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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