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 5F62AC433EF for ; Thu, 9 Jun 2022 00:22:39 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4LJPtj4DQ9z3hX3 for ; Thu, 9 Jun 2022 10:22:37 +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=irtsjIpR; 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=song@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=irtsjIpR; 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 4LJFsp4R73z307B for ; Thu, 9 Jun 2022 04:21:18 +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 C1A3461C01 for ; Wed, 8 Jun 2022 18:21:16 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 40E95C341D1 for ; Wed, 8 Jun 2022 18:21:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1654712475; bh=tnKw98gSFfcp7IeTy3/rsQTZtNfF844s9r6khIEQFqc=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=irtsjIpRsHz95M7/Br69jkU/el6Euka6pz8QbkiyfxAGuuX/C14ulDJ5rxSFQdTQ7 wZmQnG+5kZ1N4zDACMrhVdh8N1lIAQcTyjhQEx/UZAyriQAWTfWq2iXIz8TlzKHkRZ n2pYPB98p0EkCVoZ5eaO9iB+TrowElP2u+A71qJOmZWpHP2PUqJ7hp0POqVpmhuU53 Lh8rcUMQKhpMpfRyOYxIWnNXxRQTCXBtL5cAGt6juZqp3GqLiQVgaZ+Tx6KP9eyqQA jmFM0+2W+9KKQB2OgG1tubg70tpLYx98T96K4bUlCS+6hsnhS0mgNGYeYhLS9J69TN MTrYJfs+yokrQ== Received: by mail-yb1-f174.google.com with SMTP id l204so37878825ybf.10 for ; Wed, 08 Jun 2022 11:21:15 -0700 (PDT) X-Gm-Message-State: AOAM531FuHkmIw9AvHl0OfwTW58lFGgOuuKXDYxiqPEd7TuAuXi8HpWT +YJVHTJwfXiU4sadlhSSF1hMjYjOWJOFMnzoOjE= X-Google-Smtp-Source: ABdhPJzq98NOqo/VCRPluNkAkEsBsSfWL/uWjG/p7ZIu0au9GHRqptIRFE98zq1/+bCu49t4PTpXeJwRmf8/7KNbQ00= X-Received: by 2002:a0d:eb4d:0:b0:30c:9849:27a1 with SMTP id u74-20020a0deb4d000000b0030c984927a1mr37988780ywe.472.1654712463961; Wed, 08 Jun 2022 11:21:03 -0700 (PDT) MIME-Version: 1.0 References: <20220608000014.3054333-1-jarkko@profian.com> <20220608232115.ccd4399f4a1d133e9b65c2a9@kernel.org> In-Reply-To: From: Song Liu Date: Wed, 8 Jun 2022 11:20:53 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] kprobes: Enable tracing for mololithic kernel images To: Masami Hiramatsu Content-Type: text/plain; charset="UTF-8" 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?Q?Andr=C3=A9_Almeida?= , Michael Roth , Nicholas Piggin , Thomas Gleixner , Andrey Konovalov , Nick Desaulniers , Linux Kernel Mailing List , Luis Chamberlain , Sven Schnelle , Wu Caize , Paul Mackerras , Andrew Morton , Mark Rutland , Luis Machado , Atsushi Nemoto , Dave Hansen , Joey Gouly , "James E.J. Bottomley" , linux-s390 , Ilya Leoshkevich , Anup Patel , Helge Deller , Anil S Keshavamurthy , Tom Lendacky , Vasily Gorbik , Philipp Tomsich , Dave Anglin , Linux ARM , Daniel Axtens , Nicolas Pitre , Jarkko Sakkinen , "Eric W. Biederman" , "Aneesh Kumar K.V" , Daniel Bristot de Oliveira , Kefeng Wang , Emil Renner Berthing , Jordan Niethe , Atish Patra , Alexei Starovoitov , Will Deacon , Masahiro Yamada < masahiroy@kernel.org>, 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" On Wed, Jun 8, 2022 at 9:12 AM Song Liu wrote: > > On Wed, Jun 8, 2022 at 7:21 AM Masami Hiramatsu wrote: > > > > 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. > > IIUC, most users of module_alloc() use it to allocate memory for text, except > that module code uses it for both text and data. Therefore, I guess calling it > text_alloc() is not 100% accurate until we change the module code (to use > a different API to allocate memory for data). Git history showed me 7a0e27b2a0ce mm: remove vmalloc_exec I guess we are somehow going back in time... Song > > Thanks, > Song > > > > > Acked-by: Masami Hiramatsu (Google) > > for kprobe side. > > > > Thank you, > > > > -- > > Masami Hiramatsu (Google)