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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D1FC4C4332F for ; Fri, 13 May 2022 15:01:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1357931AbiEMPBX (ORCPT ); Fri, 13 May 2022 11:01:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57354 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1381863AbiEMPBJ (ORCPT ); Fri, 13 May 2022 11:01:09 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 14A7340A37; Fri, 13 May 2022 08:00:06 -0700 (PDT) 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 6EE8F113E; Fri, 13 May 2022 08:00:06 -0700 (PDT) Received: from lakrids (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9DAC83F73D; Fri, 13 May 2022 08:00:01 -0700 (PDT) Date: Fri, 13 May 2022 15:59:59 +0100 From: Mark Rutland To: Xu Kuohai Cc: bpf@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-kselftest@vger.kernel.org, Catalin Marinas , Will Deacon , Steven Rostedt , Ingo Molnar , Daniel Borkmann , Alexei Starovoitov , Zi Shen Lim , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , "David S . Miller" , Hideaki YOSHIFUJI , David Ahern , Thomas Gleixner , Borislav Petkov , Dave Hansen , x86@kernel.org, hpa@zytor.com, Shuah Khan , Jakub Kicinski , Jesper Dangaard Brouer , Pasha Tatashin , Ard Biesheuvel , Daniel Kiss , Steven Price , Sudeep Holla , Marc Zyngier , Peter Collingbourne , Mark Brown , Delyan Kratunov , Kumar Kartikeya Dwivedi Subject: Re: [PATCH bpf-next v3 4/7] bpf, arm64: Impelment bpf_arch_text_poke() for arm64 Message-ID: References: <20220424154028.1698685-1-xukuohai@huawei.com> <20220424154028.1698685-5-xukuohai@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220424154028.1698685-5-xukuohai@huawei.com> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Sun, Apr 24, 2022 at 11:40:25AM -0400, Xu Kuohai wrote: > Impelment bpf_arch_text_poke() for arm64, so bpf trampoline code can use > it to replace nop with jump, or replace jump with nop. > > Signed-off-by: Xu Kuohai > Acked-by: Song Liu > --- > arch/arm64/net/bpf_jit_comp.c | 63 +++++++++++++++++++++++++++++++++++ > 1 file changed, 63 insertions(+) > > diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c > index 8ab4035dea27..3f9bdfec54c4 100644 > --- a/arch/arm64/net/bpf_jit_comp.c > +++ b/arch/arm64/net/bpf_jit_comp.c > @@ -9,6 +9,7 @@ > > #include > #include > +#include > #include > #include > #include > @@ -18,6 +19,7 @@ > #include > #include > #include > +#include > #include > > #include "bpf_jit.h" > @@ -1529,3 +1531,64 @@ void bpf_jit_free_exec(void *addr) > { > return vfree(addr); > } > + > +static int gen_branch_or_nop(enum aarch64_insn_branch_type type, void *ip, > + void *addr, u32 *insn) > +{ > + if (!addr) > + *insn = aarch64_insn_gen_nop(); > + else > + *insn = aarch64_insn_gen_branch_imm((unsigned long)ip, > + (unsigned long)addr, > + type); > + > + return *insn != AARCH64_BREAK_FAULT ? 0 : -EFAULT; > +} > + > +int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type poke_type, > + void *old_addr, void *new_addr) > +{ > + int ret; > + u32 old_insn; > + u32 new_insn; > + u32 replaced; > + enum aarch64_insn_branch_type branch_type; > + > + if (!is_bpf_text_address((long)ip)) > + /* Only poking bpf text is supported. Since kernel function > + * entry is set up by ftrace, we reply on ftrace to poke kernel > + * functions. For kernel funcitons, bpf_arch_text_poke() is only > + * called after a failed poke with ftrace. In this case, there > + * is probably something wrong with fentry, so there is nothing > + * we can do here. See register_fentry, unregister_fentry and > + * modify_fentry for details. > + */ > + return -EINVAL; If you rely on ftrace to poke functions, why do you need to patch text at all? Why does the rest of this function exist? I really don't like having another piece of code outside of ftrace patching the ftrace patch-site; this needs a much better explanation. > + > + if (poke_type == BPF_MOD_CALL) > + branch_type = AARCH64_INSN_BRANCH_LINK; > + else > + branch_type = AARCH64_INSN_BRANCH_NOLINK; > + > + if (gen_branch_or_nop(branch_type, ip, old_addr, &old_insn) < 0) > + return -EFAULT; > + > + if (gen_branch_or_nop(branch_type, ip, new_addr, &new_insn) < 0) > + return -EFAULT; > + > + mutex_lock(&text_mutex); > + if (aarch64_insn_read(ip, &replaced)) { > + ret = -EFAULT; > + goto out; > + } > + > + if (replaced != old_insn) { > + ret = -EFAULT; > + goto out; > + } > + > + ret = aarch64_insn_patch_text_nosync((void *)ip, new_insn); ... and where does the actual synchronization come from in this case? Thanks, Mark. > +out: > + mutex_unlock(&text_mutex); > + return ret; > +} > -- > 2.30.2 >