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=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 77D5AC43600 for ; Thu, 15 Apr 2021 09:33:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 56BC1613B4 for ; Thu, 15 Apr 2021 09:33:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232165AbhDOJeE (ORCPT ); Thu, 15 Apr 2021 05:34:04 -0400 Received: from foss.arm.com ([217.140.110.172]:41266 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231960AbhDOJeD (ORCPT ); Thu, 15 Apr 2021 05:34:03 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 58113106F; Thu, 15 Apr 2021 02:33:40 -0700 (PDT) Received: from net-arm-thunderx2-02.shanghai.arm.com (net-arm-thunderx2-02.shanghai.arm.com [10.169.208.215]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 225E33F694; Thu, 15 Apr 2021 02:33:22 -0700 (PDT) From: Jianlin Lv To: bpf@vger.kernel.org Cc: corbet@lwn.net, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, kafai@fb.com, songliubraving@fb.com, yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org, davem@davemloft.net, kuba@kernel.org, illusionist.neo@gmail.com, linux@armlinux.org.uk, zlim.lnx@gmail.com, catalin.marinas@arm.com, will@kernel.org, paulburton@kernel.org, tsbogend@alpha.franken.de, naveen.n.rao@linux.ibm.com, sandipan@linux.ibm.com, mpe@ellerman.id.au, benh@kernel.crashing.org, paulus@samba.org, luke.r.nels@gmail.com, xi.wang@gmail.com, bjorn@kernel.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, iii@linux.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com, borntraeger@de.ibm.com, yoshfuji@linux-ipv6.org, dsahern@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, udknight@gmail.com, mchehab+huawei@kernel.org, dvyukov@google.com, maheshb@google.com, horms@verge.net.au, nicolas.dichtel@6wind.com, viro@zeniv.linux.org.uk, masahiroy@kernel.org, keescook@chromium.org, quentin@isovalent.com, tklauser@distanz.ch, grantseltzer@gmail.com, irogers@google.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, Jianlin.Lv@arm.com, iecedge@gmail.com Subject: [PATCH bpf-next 2/2] docs: bpf: bpf_jit_enable mode changed Date: Thu, 15 Apr 2021 17:32:50 +0800 Message-Id: <20210415093250.3391257-2-Jianlin.Lv@arm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210415093250.3391257-1-Jianlin.Lv@arm.com> References: <20210415093250.3391257-1-Jianlin.Lv@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Remove information about bpf_jit_enable=2 mode and added description for how to use the bpf_jit_disasm tool after get rid of =2 mode. Signed-off-by: Jianlin Lv --- Documentation/admin-guide/sysctl/net.rst | 1 - Documentation/networking/filter.rst | 25 ++++++------------------ 2 files changed, 6 insertions(+), 20 deletions(-) diff --git a/Documentation/admin-guide/sysctl/net.rst b/Documentation/admin-guide/sysctl/net.rst index c941b214e0b7..a39f99deac38 100644 --- a/Documentation/admin-guide/sysctl/net.rst +++ b/Documentation/admin-guide/sysctl/net.rst @@ -86,7 +86,6 @@ Values: - 0 - disable the JIT (default value) - 1 - enable the JIT - - 2 - enable the JIT and ask the compiler to emit traces on kernel log. bpf_jit_harden -------------- diff --git a/Documentation/networking/filter.rst b/Documentation/networking/filter.rst index 251c6bd73d15..86954f922168 100644 --- a/Documentation/networking/filter.rst +++ b/Documentation/networking/filter.rst @@ -504,25 +504,12 @@ been previously enabled by root:: echo 1 > /proc/sys/net/core/bpf_jit_enable -For JIT developers, doing audits etc, each compile run can output the generated -opcode image into the kernel log via:: - - echo 2 > /proc/sys/net/core/bpf_jit_enable - -Example output from dmesg:: - - [ 3389.935842] flen=6 proglen=70 pass=3 image=ffffffffa0069c8f - [ 3389.935847] JIT code: 00000000: 55 48 89 e5 48 83 ec 60 48 89 5d f8 44 8b 4f 68 - [ 3389.935849] JIT code: 00000010: 44 2b 4f 6c 4c 8b 87 d8 00 00 00 be 0c 00 00 00 - [ 3389.935850] JIT code: 00000020: e8 1d 94 ff e0 3d 00 08 00 00 75 16 be 17 00 00 - [ 3389.935851] JIT code: 00000030: 00 e8 28 94 ff e0 83 f8 01 75 07 b8 ff ff 00 00 - [ 3389.935852] JIT code: 00000040: eb 02 31 c0 c9 c3 - -When CONFIG_BPF_JIT_ALWAYS_ON is enabled, bpf_jit_enable is permanently set to 1 and -setting any other value than that will return in failure. This is even the case for -setting bpf_jit_enable to 2, since dumping the final JIT image into the kernel log -is discouraged and introspection through bpftool (under tools/bpf/bpftool/) is the -generally recommended approach instead. +When CONFIG_BPF_JIT_ALWAYS_ON is enabled, bpf_jit_enable is permanently set +to 1 and setting any other value than that will return in failure. +For debugging JITs, the introspection through bpftool (tools/bpf/bpftool/) +is the generally recommended approach instead. For JIT developers, doing +audits etc, you can insert bpf_jit_dump() and recompile the kernel to +output the generated opcode image into the kernel log. In the kernel source tree under tools/bpf/, there's bpf_jit_disasm for generating disassembly out of the kernel log's hexdump:: -- 2.25.1