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Thu, 15 Apr 2021 08:41:25 -0700 (PDT) Subject: Re: [PATCH bpf-next 1/2] bpf: Remove bpf_jit_enable=2 debugging mode To: Daniel Borkmann , Jianlin Lv , bpf@vger.kernel.org Cc: corbet@lwn.net, ast@kernel.org, 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, 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, iecedge@gmail.com References: <20210415093250.3391257-1-Jianlin.Lv@arm.com> <9c4a78d2-f73c-832a-e6e2-4b4daa729e07@iogearbox.net> From: Quentin Monnet Message-ID: Date: Thu, 15 Apr 2021 16:41:23 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.9.1 MIME-Version: 1.0 In-Reply-To: <9c4a78d2-f73c-832a-e6e2-4b4daa729e07@iogearbox.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org 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. Maybe not a common case, but still, removing the debugging mode will make that impossible. Is there a particular incentive to remove the feature? Best regards, Quentin