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=-3.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 5D99EC34022 for ; Wed, 19 Feb 2020 09:01:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3E4842176D for ; Wed, 19 Feb 2020 09:01:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726480AbgBSJBj (ORCPT ); Wed, 19 Feb 2020 04:01:39 -0500 Received: from Galois.linutronix.de ([193.142.43.55]:37615 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726202AbgBSJBi (ORCPT ); Wed, 19 Feb 2020 04:01:38 -0500 Received: from p5de0bf0b.dip0.t-ipconnect.de ([93.224.191.11] helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1j4LE1-0000bh-BZ; Wed, 19 Feb 2020 10:00:57 +0100 Received: by nanos.tec.linutronix.de (Postfix, from userid 1000) id 6083A100F56; Wed, 19 Feb 2020 10:00:56 +0100 (CET) From: Thomas Gleixner To: Vinicius Costa Gomes , LKML Cc: David Miller , bpf@vger.kernel.org, netdev@vger.kernel.org, Alexei Starovoitov , Daniel Borkmann , Sebastian Sewior , Peter Zijlstra , Clark Williams , Steven Rostedt , Juri Lelli , Ingo Molnar , Kees Cook , Will Drewry , Andy Lutomirski Subject: Re: [RFC patch 09/19] bpf: Use BPF_PROG_RUN_PIN_ON_CPU() at simple call sites. In-Reply-To: <87a75ftkwu.fsf@linux.intel.com> References: <20200214133917.304937432@linutronix.de> <20200214161503.804093748@linutronix.de> <87a75ftkwu.fsf@linux.intel.com> Date: Wed, 19 Feb 2020 10:00:56 +0100 Message-ID: <875zg3q7cn.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Vinicius Costa Gomes writes: Cc+: seccomp folks > Thomas Gleixner writes: > >> From: David Miller Leaving content for reference >> All of these cases are strictly of the form: >> >> preempt_disable(); >> BPF_PROG_RUN(...); >> preempt_enable(); >> >> Replace this with BPF_PROG_RUN_PIN_ON_CPU() which wraps BPF_PROG_RUN() >> with: >> >> migrate_disable(); >> BPF_PROG_RUN(...); >> migrate_enable(); >> >> On non RT enabled kernels this maps to preempt_disable/enable() and on RT >> enabled kernels this solely prevents migration, which is sufficient as >> there is no requirement to prevent reentrancy to any BPF program from a >> preempting task. The only requirement is that the program stays on the same >> CPU. >> >> Therefore, this is a trivially correct transformation. >> >> [ tglx: Converted to BPF_PROG_RUN_PIN_ON_CPU() ] >> >> Signed-off-by: David S. Miller >> Signed-off-by: Thomas Gleixner >> >> --- >> include/linux/filter.h | 4 +--- >> kernel/seccomp.c | 4 +--- >> net/core/flow_dissector.c | 4 +--- >> net/core/skmsg.c | 8 ++------ >> net/kcm/kcmsock.c | 4 +--- >> 5 files changed, 6 insertions(+), 18 deletions(-) >> >> --- a/include/linux/filter.h >> +++ b/include/linux/filter.h >> @@ -713,9 +713,7 @@ static inline u32 bpf_prog_run_clear_cb( >> if (unlikely(prog->cb_access)) >> memset(cb_data, 0, BPF_SKB_CB_LEN); >> >> - preempt_disable(); >> - res = BPF_PROG_RUN(prog, skb); >> - preempt_enable(); >> + res = BPF_PROG_RUN_PIN_ON_CPU(prog, skb); >> return res; >> } >> >> --- a/kernel/seccomp.c >> +++ b/kernel/seccomp.c >> @@ -268,16 +268,14 @@ static u32 seccomp_run_filters(const str >> * All filters in the list are evaluated and the lowest BPF return >> * value always takes priority (ignoring the DATA). >> */ >> - preempt_disable(); >> for (; f; f = f->prev) { >> - u32 cur_ret = BPF_PROG_RUN(f->prog, sd); >> + u32 cur_ret = BPF_PROG_RUN_PIN_ON_CPU(f->prog, sd); >> > > More a question really, isn't the behavior changing here? i.e. shouldn't > migrate_disable()/migrate_enable() be moved to outside the loop? Or is > running seccomp filters on different cpus not a problem? In my understanding this is a list of filters and they are independent of each other. Kees, Will. Andy? Thanks, tglx