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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 2B0A6C433EF for ; Wed, 8 Jun 2022 23:57:33 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4LJPKl2KbMz3dt2 for ; Thu, 9 Jun 2022 09:57:31 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=f+5uNDkm; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kernel.org (client-ip=139.178.84.217; helo=dfw.source.kernel.org; envelope-from=mhiramat@kernel.org; receiver=) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=f+5uNDkm; dkim-atps=neutral Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4LJ8YK4rTKz308m for ; Thu, 9 Jun 2022 00:21:41 +1000 (AEST) 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 CF57461B1C; Wed, 8 Jun 2022 14:21:37 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 33A51C34116; Wed, 8 Jun 2022 14:21:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1654698097; bh=1qpAEjSAq5djkkmLyIM6rUzEBFpBwb5S8o8YQ4yPKWA=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=f+5uNDkmztVja1h70Kf8HEKtlvbSFHPe7GufnVlMvMkA7EPZj1hNREAoLZkLn4yMZ 6bQ50bNMEBhe4ElBm12ffDV3hbaNZWOfcPkkH6bD1GJ7qTD49z3ahsgnNBTvpURWx5 rrvu5QDBi4lRbKEy6EZew4PC7oAb8cDKq8Fbm+3bojZb/vbBuJ9tfwqhpbvZdjxTl3 y+uNV/KGl545f2ZW+p6SVfNeUdQ8cwc6SLEJ01DZ+ERUPHKg87AJa/IPMGV7vQAvac xZpWEpxQFIZUDnAYuJHwAFDjwTFYVd/DGOvZKjhTQTx1jhQ+TBRkABL3RxqqFRF6Ed MNrXttwyxlWig== Date: Wed, 8 Jun 2022 23:21:15 +0900 From: Masami Hiramatsu (Google) To: Jarkko Sakkinen Subject: Re: [PATCH] kprobes: Enable tracing for mololithic kernel images Message-Id: <20220608232115.ccd4399f4a1d133e9b65c2a9@kernel.org> In-Reply-To: References: <20220608000014.3054333-1-jarkko@profian.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Mailman-Approved-At: Thu, 09 Jun 2022 09:55:19 +1000 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Dan Li , Heiko Stuebner , Linus Walleij , Guo Ren , Alexander Gordeev , Javier Martinez Canillas , Geert Uytterhoeven , Catalin Marinas , Christian Borntraeger , Guenter Roeck , =?UTF-8?B?QW5kcsOp?= Almeida , Michael Roth , Nicholas Piggin , Thomas Gleixner , Andrey Konovalov , Nick Desaulniers , Linux Kernel Mailing List , Luis Chamberlain , Masami Hiramatsu , Wu Caize , Paul Mackerras , Andrew Morton , Mark Rutland , Luis Machado , Atsushi Nemoto < anemo@mba.ocn.ne.jp>, Dave Hansen , Joey Gouly , "James E.J. Bottomley" , Song Liu , linux-s390 , Ilya Leoshkevich , Anup Patel , Helge Deller , Anil S Keshavamurthy , Sven Schnelle , Tom Lendacky , Vasily Gorbik , Philipp Tomsich , Dave Anglin , Linux ARM , Daniel Axtens , Nicolas Pitre , "Eric W. Biederman" , "Aneesh Kumar K.V" , Daniel Bristot de Oliveira , Kefeng Wang , Emil Renner Berthing , Jordan Niethe , Atish Patra , Ale xei Starovoitov , Will Deacon , Masahiro Yamada , Jarkko Sakkinen , Sami Tolvanen , "Naveen N. Rao" , Marco Elver , Kees Cook , Steven Rostedt , Nathan Chancellor , "Russell King \(Oracle\)" , Mark Brown , Borislav Petkov , Alexander Egorenkov , Thomas Bogendoerfer , Parisc List , Nathaniel McCallum , Dmitry Torokhov , "David S. Miller" , "Kirill A. Shutemov" , Tobias Huschle , "Peter Zijlstra \(Intel\)" , "H. Peter Anvin" , sparclinux , Tiezhu Yang , Miroslav Benes , Chen Zhongjin , Ard Biesheuvel , the arch/x86 maintainers , Russell King , linux-riscv , Ingo Molnar , Aaron Tomlin , Albert Ou , Heiko Carstens , Liao Chang , Paul Walmsley , Josh Poimboeuf , Thomas Richter , "open list:BROADCOM NVRAM DRIVER" , Changbin Du , Palmer Dabbelt , linuxppc-dev , linux-modules@vger.kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Hi Jarkko, On Wed, 8 Jun 2022 08:25:38 +0300 Jarkko Sakkinen wrote: > On Wed, Jun 08, 2022 at 10:35:42AM +0800, Guo Ren wrote: > > . > > > > On Wed, Jun 8, 2022 at 8:02 AM Jarkko Sakkinen wrote: > > > > > > Tracing with kprobes while running a monolithic kernel is currently > > > impossible because CONFIG_KPROBES is dependent of CONFIG_MODULES. This > > > dependency is a result of kprobes code using the module allocator for the > > > trampoline code. > > > > > > Detaching kprobes from modules helps to squeeze down the user space, > > > e.g. when developing new core kernel features, while still having all > > > the nice tracing capabilities. > > > > > > For kernel/ and arch/*, move module_alloc() and module_memfree() to > > > module_alloc.c, and compile as part of vmlinux when either CONFIG_MODULES > > > or CONFIG_KPROBES is enabled. In addition, flag kernel module specific > > > code with CONFIG_MODULES. > > > > > > As the result, kprobes can be used with a monolithic kernel. > > It's strange when MODULES is n, but vmlinux still obtains module_alloc. > > > > Maybe we need a kprobe_alloc, right? > > Perhaps not the best name but at least it documents the fact that > they use the same allocator. > > Few years ago I carved up something "half-way there" for kprobes, > and I used the name text_alloc() [*]. > > [*] https://lore.kernel.org/all/20200724050553.1724168-1-jarkko.sakkinen@linux.intel.com/ Yeah, I remember that. Thank you for updating your patch! I think the idea (split module_alloc() from CONFIG_MODULE) is good to me. If module support maintainers think this name is not good, you may be able to rename it as text_alloc() and make the module_alloc() as a wrapper of it. Acked-by: Masami Hiramatsu (Google) for kprobe side. Thank you, -- Masami Hiramatsu (Google)