From patchwork Thu Apr 15 09:32:49 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jianlin Lv X-Patchwork-Id: 12204815 X-Patchwork-Delegate: bpf@iogearbox.net 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 C59BCC433B4 for ; Thu, 15 Apr 2021 09:33:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A543F613BB for ; Thu, 15 Apr 2021 09:33:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231415AbhDOJdn (ORCPT ); Thu, 15 Apr 2021 05:33:43 -0400 Received: from foss.arm.com ([217.140.110.172]:41198 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230260AbhDOJdm (ORCPT ); Thu, 15 Apr 2021 05:33:42 -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 6837612FC; Thu, 15 Apr 2021 02:33:19 -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 2ACE53F694; Thu, 15 Apr 2021 02:33:01 -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 1/2] bpf: Remove bpf_jit_enable=2 debugging mode Date: Thu, 15 Apr 2021 17:32:49 +0800 Message-Id: <20210415093250.3391257-1-Jianlin.Lv@arm.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net 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 --- arch/arm/net/bpf_jit_32.c | 4 ---- arch/arm64/net/bpf_jit_comp.c | 4 ---- arch/mips/net/bpf_jit.c | 4 ---- arch/mips/net/ebpf_jit.c | 4 ---- arch/powerpc/net/bpf_jit_comp.c | 10 ---------- arch/powerpc/net/bpf_jit_comp64.c | 11 ----------- arch/riscv/net/bpf_jit_core.c | 3 --- arch/s390/net/bpf_jit_comp.c | 4 ---- arch/sparc/net/bpf_jit_comp_32.c | 3 --- arch/sparc/net/bpf_jit_comp_64.c | 13 ------------- arch/x86/net/bpf_jit_comp.c | 3 --- arch/x86/net/bpf_jit_comp32.c | 3 --- net/core/sysctl_net_core.c | 14 +++----------- tools/bpf/bpf_jit_disasm.c | 2 +- tools/bpf/bpftool/feature.c | 3 --- 15 files changed, 4 insertions(+), 81 deletions(-) diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c index 897634d0a67c..92d669c0b2d3 100644 --- a/arch/arm/net/bpf_jit_32.c +++ b/arch/arm/net/bpf_jit_32.c @@ -1997,10 +1997,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) } flush_icache_range((u32)header, (u32)(ctx.target + ctx.idx)); - if (bpf_jit_enable > 1) - /* there are 2 passes here */ - bpf_jit_dump(prog->len, image_size, 2, ctx.target); - bpf_jit_binary_lock_ro(header); prog->bpf_func = (void *)ctx.target; prog->jited = 1; diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index f7b194878a99..a13b83ac4ca8 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -1090,10 +1090,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) goto out_off; } - /* And we're done. */ - if (bpf_jit_enable > 1) - bpf_jit_dump(prog->len, prog_size, 2, ctx.image); - bpf_flush_icache(header, ctx.image + ctx.idx); if (!prog->is_func || extra_pass) { diff --git a/arch/mips/net/bpf_jit.c b/arch/mips/net/bpf_jit.c index 0af88622c619..b5221282dd88 100644 --- a/arch/mips/net/bpf_jit.c +++ b/arch/mips/net/bpf_jit.c @@ -1250,10 +1250,6 @@ void bpf_jit_compile(struct bpf_prog *fp) /* Update the icache */ flush_icache_range((ptr)ctx.target, (ptr)(ctx.target + ctx.idx)); - if (bpf_jit_enable > 1) - /* Dump JIT code */ - bpf_jit_dump(fp->len, alloc_size, 2, ctx.target); - fp->bpf_func = (void *)ctx.target; fp->jited = 1; diff --git a/arch/mips/net/ebpf_jit.c b/arch/mips/net/ebpf_jit.c index 939dd06764bc..dac5a1fc2462 100644 --- a/arch/mips/net/ebpf_jit.c +++ b/arch/mips/net/ebpf_jit.c @@ -1910,10 +1910,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) flush_icache_range((unsigned long)ctx.target, (unsigned long)&ctx.target[ctx.idx]); - if (bpf_jit_enable > 1) - /* Dump JIT code */ - bpf_jit_dump(prog->len, image_size, 2, ctx.target); - bpf_jit_binary_lock_ro(header); prog->bpf_func = (void *)ctx.target; prog->jited = 1; diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c index e809cb5a1631..ebca629de2d1 100644 --- a/arch/powerpc/net/bpf_jit_comp.c +++ b/arch/powerpc/net/bpf_jit_comp.c @@ -646,18 +646,8 @@ void bpf_jit_compile(struct bpf_prog *fp) bpf_jit_build_prologue(fp, code_base, &cgctx); bpf_jit_build_body(fp, code_base, &cgctx, addrs); bpf_jit_build_epilogue(code_base, &cgctx); - - if (bpf_jit_enable > 1) - pr_info("Pass %d: shrink = %d, seen = 0x%x\n", pass, - proglen - (cgctx.idx * 4), cgctx.seen); } - if (bpf_jit_enable > 1) - /* Note that we output the base address of the code_base - * rather than image, since opcodes are in code_base. - */ - bpf_jit_dump(flen, proglen, pass, code_base); - bpf_flush_icache(code_base, code_base + (proglen/4)); #ifdef CONFIG_PPC64 diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c index aaf1a887f653..26243399ef2e 100644 --- a/arch/powerpc/net/bpf_jit_comp64.c +++ b/arch/powerpc/net/bpf_jit_comp64.c @@ -1215,20 +1215,9 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp) bpf_jit_build_prologue(code_base, &cgctx); bpf_jit_build_body(fp, code_base, &cgctx, addrs, extra_pass); bpf_jit_build_epilogue(code_base, &cgctx); - - if (bpf_jit_enable > 1) - pr_info("Pass %d: shrink = %d, seen = 0x%x\n", pass, - proglen - (cgctx.idx * 4), cgctx.seen); } skip_codegen_passes: - if (bpf_jit_enable > 1) - /* - * Note that we output the base address of the code_base - * rather than image, since opcodes are in code_base. - */ - bpf_jit_dump(flen, proglen, pass, code_base); - #ifdef PPC64_ELF_ABI_v1 /* Function descriptor nastiness: Address + TOC */ ((u64 *)image)[0] = (u64)code_base; diff --git a/arch/riscv/net/bpf_jit_core.c b/arch/riscv/net/bpf_jit_core.c index 3630d447352c..856b84fb3947 100644 --- a/arch/riscv/net/bpf_jit_core.c +++ b/arch/riscv/net/bpf_jit_core.c @@ -142,9 +142,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) } bpf_jit_build_epilogue(ctx); - if (bpf_jit_enable > 1) - bpf_jit_dump(prog->len, image_size, pass, ctx->insns); - prog->bpf_func = (void *)ctx->insns; prog->jited = 1; prog->jited_len = image_size; diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c index 63cae0476bb4..aa8b94ba694f 100644 --- a/arch/s390/net/bpf_jit_comp.c +++ b/arch/s390/net/bpf_jit_comp.c @@ -1842,10 +1842,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp) fp = orig_fp; goto free_addrs; } - if (bpf_jit_enable > 1) { - bpf_jit_dump(fp->len, jit.size, pass, jit.prg_buf); - print_fn_code(jit.prg_buf, jit.size_prg); - } if (!fp->is_func || extra_pass) { bpf_jit_binary_lock_ro(header); } else { diff --git a/arch/sparc/net/bpf_jit_comp_32.c b/arch/sparc/net/bpf_jit_comp_32.c index b1dbf2fa8c0a..cb4c55422730 100644 --- a/arch/sparc/net/bpf_jit_comp_32.c +++ b/arch/sparc/net/bpf_jit_comp_32.c @@ -743,9 +743,6 @@ cond_branch: f_offset = addrs[i + filter[i].jf]; oldproglen = proglen; } - if (bpf_jit_enable > 1) - bpf_jit_dump(flen, proglen, pass + 1, image); - if (image) { fp->bpf_func = (void *)image; fp->jited = 1; diff --git a/arch/sparc/net/bpf_jit_comp_64.c b/arch/sparc/net/bpf_jit_comp_64.c index 4b8d3c65d266..09ebd48c4f1b 100644 --- a/arch/sparc/net/bpf_jit_comp_64.c +++ b/arch/sparc/net/bpf_jit_comp_64.c @@ -1546,16 +1546,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) } build_epilogue(&ctx); - if (bpf_jit_enable > 1) - pr_info("Pass %d: size = %u, seen = [%c%c%c%c%c%c]\n", pass, - ctx.idx * 4, - ctx.tmp_1_used ? '1' : ' ', - ctx.tmp_2_used ? '2' : ' ', - ctx.tmp_3_used ? '3' : ' ', - ctx.saw_frame_pointer ? 'F' : ' ', - ctx.saw_call ? 'C' : ' ', - ctx.saw_tail_call ? 'T' : ' '); - if (ctx.idx * 4 == prev_image_size) break; prev_image_size = ctx.idx * 4; @@ -1593,9 +1583,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) goto out_off; } - if (bpf_jit_enable > 1) - bpf_jit_dump(prog->len, image_size, pass, ctx.image); - bpf_flush_icache(header, (u8 *)header + (header->pages * PAGE_SIZE)); if (!prog->is_func || extra_pass) { diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index 9eead60f0301..0a511f42a2a7 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -2311,9 +2311,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) cond_resched(); } - if (bpf_jit_enable > 1) - bpf_jit_dump(prog->len, proglen, pass + 1, image); - if (image) { if (!prog->is_func || extra_pass) { bpf_tail_call_direct_fixup(prog); diff --git a/arch/x86/net/bpf_jit_comp32.c b/arch/x86/net/bpf_jit_comp32.c index 0a7a2870f111..8d36b4658076 100644 --- a/arch/x86/net/bpf_jit_comp32.c +++ b/arch/x86/net/bpf_jit_comp32.c @@ -2566,9 +2566,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) cond_resched(); } - if (bpf_jit_enable > 1) - bpf_jit_dump(prog->len, proglen, pass + 1, image); - if (image) { bpf_jit_binary_lock_ro(header); prog->bpf_func = (void *)image; diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c index c8496c1142c9..990b1720c7a4 100644 --- a/net/core/sysctl_net_core.c +++ b/net/core/sysctl_net_core.c @@ -273,16 +273,8 @@ static int proc_dointvec_minmax_bpf_enable(struct ctl_table *table, int write, tmp.data = &jit_enable; ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos); - if (write && !ret) { - if (jit_enable < 2 || - (jit_enable == 2 && bpf_dump_raw_ok(current_cred()))) { - *(int *)table->data = jit_enable; - if (jit_enable == 2) - pr_warn("bpf_jit_enable = 2 was set! NEVER use this in production, only for JIT debugging!\n"); - } else { - ret = -EPERM; - } - } + if (write && !ret) + *(int *)table->data = jit_enable; return ret; } @@ -389,7 +381,7 @@ static struct ctl_table net_core_table[] = { .extra2 = SYSCTL_ONE, # else .extra1 = SYSCTL_ZERO, - .extra2 = &two, + .extra2 = SYSCTL_ONE, # endif }, # ifdef CONFIG_HAVE_EBPF_JIT diff --git a/tools/bpf/bpf_jit_disasm.c b/tools/bpf/bpf_jit_disasm.c index c8ae95804728..efa4b17ae016 100644 --- a/tools/bpf/bpf_jit_disasm.c +++ b/tools/bpf/bpf_jit_disasm.c @@ -7,7 +7,7 @@ * * To get the disassembly of the JIT code, do the following: * - * 1) `echo 2 > /proc/sys/net/core/bpf_jit_enable` + * 1) Insert bpf_jit_dump() and recompile the kernel to output JITed image into log * 2) Load a BPF filter (e.g. `tcpdump -p -n -s 0 -i eth1 host 192.168.20.0/24`) * 3) Run e.g. `bpf_jit_disasm -o` to read out the last JIT code * diff --git a/tools/bpf/bpftool/feature.c b/tools/bpf/bpftool/feature.c index 40a88df275f9..98c7eec2923f 100644 --- a/tools/bpf/bpftool/feature.c +++ b/tools/bpf/bpftool/feature.c @@ -203,9 +203,6 @@ static void probe_jit_enable(void) case 1: printf("JIT compiler is enabled\n"); break; - case 2: - printf("JIT compiler is enabled with debugging traces in kernel logs\n"); - break; case -1: printf("Unable to retrieve JIT-compiler status\n"); break; From patchwork Thu Apr 15 09:32:50 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jianlin Lv X-Patchwork-Id: 12204817 X-Patchwork-Delegate: bpf@iogearbox.net 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 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net 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::