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 X-Spam-Level: X-Spam-Status: No, score=-10.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 51F56C433ED for ; Sat, 17 Apr 2021 13:32:49 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id E1BA761207 for ; Sat, 17 Apr 2021 13:32:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E1BA761207 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=csgroup.eu Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4FMvCL4MwWz3c0l for ; Sat, 17 Apr 2021 23:32:46 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=csgroup.eu (client-ip=93.17.236.30; helo=pegase1.c-s.fr; envelope-from=christophe.leroy@csgroup.eu; receiver=) Received: from pegase1.c-s.fr (pegase1.c-s.fr [93.17.236.30]) (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 4FMmBX20vpz2xZK for ; Sat, 17 Apr 2021 18:16:32 +1000 (AEST) Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 4FMmBL3J3fz9vBnF; Sat, 17 Apr 2021 10:16:26 +0200 (CEST) X-Virus-Scanned: Debian amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [192.168.12.234]) (amavisd-new, port 10024) with ESMTP id wonQJcvXPfFi; Sat, 17 Apr 2021 10:16:26 +0200 (CEST) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 4FMmBL1x8Xz9vBn9; Sat, 17 Apr 2021 10:16:26 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 3776F8B778; Sat, 17 Apr 2021 10:16:27 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id eGIdiAD4X9M2; Sat, 17 Apr 2021 10:16:27 +0200 (CEST) Received: from [192.168.4.90] (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 3BFFF8B75B; Sat, 17 Apr 2021 10:16:24 +0200 (CEST) Subject: Re: [PATCH bpf-next 1/2] bpf: Remove bpf_jit_enable=2 debugging mode To: Alexei Starovoitov , Quentin Monnet References: <20210415093250.3391257-1-Jianlin.Lv@arm.com> <9c4a78d2-f73c-832a-e6e2-4b4daa729e07@iogearbox.net> From: Christophe Leroy Message-ID: <0dea05ba-9467-0d84-4515-b8766f60318e@csgroup.eu> Date: Sat, 17 Apr 2021 10:16:22 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr Content-Transfer-Encoding: 8bit X-Mailman-Approved-At: Sat, 17 Apr 2021 23:32:25 +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: Ian Rogers , Song Liu , "open list:DOCUMENTATION" , Zi Shen Lim , Alexei Starovoitov , Russell King , "David S. Miller" , Paul Mackerras , Sandipan Das , "H. Peter Anvin" , sparclinux@vger.kernel.org, Shubham Bansal , Mahesh Bandewar , Will Deacon , linux-riscv , linux-s390 , Ilya Leoshkevich , paulburton@kernel.org, Jonathan Corbet , Mauro Carvalho Chehab , Masahiro Yamada , X86 ML , John Fastabend , Andrii Nakryiko , Christian Borntraeger , Ingo Molnar , Dmitry Vyukov , Catalin Marinas , "Naveen N . Rao" , Jakub Kicinski , Tobias Klauser , grantseltzer@gmail.com, Xi Wang , Albert Ou , Kees Cook , Vasily Gorbik , Luke Nelson , Heiko Carstens , KP Singh , iecedge@gmail.com, Simon Horman , Borislav Petkov , Alexander Viro , Paul Walmsley , Jianlin Lv , Nicolas Dichtel , Palmer Dabbelt , linux-arm-kernel , Wang YanQing , tsbogend@alpha.franken.de, Daniel Borkmann , Hideaki YOSHIFUJI , Network Development , David Ahern , linux-mips@vger.kernel.org, LKML , Yonghong Song , =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= , Thomas Gleixner , bpf , ppc-dev , Martin KaFai Lau Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Le 16/04/2021 à 01:49, Alexei Starovoitov a écrit : > On Thu, Apr 15, 2021 at 8:41 AM Quentin Monnet wrote: >> >> 2021-04-15 16:37 UTC+0200 ~ Daniel Borkmann >>> On 4/15/21 11:32 AM, Jianlin Lv wrote: >>>> For debugging JITs, dumping the JITed image to kernel log is discouraged, >>>> "bpftool prog dump jited" is much better way to examine JITed dumps. >>>> This patch get rid of the code related to bpf_jit_enable=2 mode and >>>> update the proc handler of bpf_jit_enable, also added auxiliary >>>> information to explain how to use bpf_jit_disasm tool after this change. >>>> >>>> Signed-off-by: Jianlin Lv >> >> Hello, >> >> For what it's worth, I have already seen people dump the JIT image in >> kernel logs in Qemu VMs running with just a busybox, not for kernel >> development, but in a context where buiding/using bpftool was not >> possible. > > If building/using bpftool is not possible then majority of selftests won't > be exercised. I don't think such environment is suitable for any kind > of bpf development. Much so for JIT debugging. > While bpf_jit_enable=2 is nothing but the debugging tool for JIT developers. > I'd rather nuke that code instead of carrying it from kernel to kernel. > When I implemented JIT for PPC32, it was extremely helpfull. As far as I understand, for the time being bpftool is not usable in my environment because it doesn't support cross compilation when the target's endianess differs from the building host endianess, see discussion at https://lore.kernel.org/bpf/21e66a09-514f-f426-b9e2-13baab0b938b@csgroup.eu/ That's right that selftests can't be exercised because they don't build. The question might be candid as I didn't investigate much about the replacement of "bpf_jit_enable=2 debugging mode" by bpftool, how do we use bpftool exactly for that ? Especially when using the BPF test module ?