From patchwork Thu Sep 22 22:56:23 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Martin KaFai Lau X-Patchwork-Id: 12985917 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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0A7F2C54EE9 for ; Thu, 22 Sep 2022 22:56:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230021AbiIVW4i (ORCPT ); Thu, 22 Sep 2022 18:56:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55834 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230255AbiIVW4f (ORCPT ); Thu, 22 Sep 2022 18:56:35 -0400 Received: from mx0a-00082601.pphosted.com (mx0a-00082601.pphosted.com [67.231.145.42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AA31D10FE3B for ; Thu, 22 Sep 2022 15:56:33 -0700 (PDT) Received: from pps.filterd (m0044012.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.17.1.5/8.17.1.5) with ESMTP id 28MKigCt027103 for ; Thu, 22 Sep 2022 15:56:33 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : content-type; s=facebook; bh=h9D6nJwYPmU+FeFh90ooVRJBT3lkdMbR7mCWzwU2vow=; b=RWExcF7eM2xD1o0K3Tql+RHe1dZU48s4X4zvtK4K+T2aPDo1nExvddwYSauXJ6CYOMUu byLitfMaiw2VzS4zS6ck6UCwEky4WWrZzY25+izjoqwJrI7OpxuJ4HVbibS6kDu6Ts+x jiPgRrjD2dNPjTdCY3SiQRCVYNY7HfxR43Q= Received: from maileast.thefacebook.com ([163.114.130.16]) by mx0a-00082601.pphosted.com (PPS) with ESMTPS id 3jrenwfgb9-4 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Thu, 22 Sep 2022 15:56:33 -0700 Received: from twshared5413.23.frc3.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:82::c) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Thu, 22 Sep 2022 15:56:29 -0700 Received: by devbig933.frc1.facebook.com (Postfix, from userid 6611) id ACE27999DAFA; Thu, 22 Sep 2022 15:56:23 -0700 (PDT) From: Martin KaFai Lau To: CC: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , , , Martin KaFai Lau Subject: [PATCH bpf-next 1/5] bpf: Add __bpf_prog_{enter,exit}_struct_ops for struct_ops trampoline Date: Thu, 22 Sep 2022 15:56:23 -0700 Message-ID: <20220922225623.3055902-1-kafai@fb.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220922225616.3054840-1-kafai@fb.com> References: <20220922225616.3054840-1-kafai@fb.com> MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-GUID: dREilJCYBTl_3OCvKbpwMxb5iJVCrVKP X-Proofpoint-ORIG-GUID: dREilJCYBTl_3OCvKbpwMxb5iJVCrVKP X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.895,Hydra:6.0.528,FMLib:17.11.122.1 definitions=2022-09-22_15,2022-09-22_02,2022-06-22_01 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net From: Martin KaFai Lau The struct_ops prog is to allow using bpf to implement the functions in a struct (eg. kernel module). The current usage is to implement the tcp_congestion. The kernel does not call the tcp-cc's ops (ie. the bpf prog) in a recursive way. The struct_ops is sharing the tracing-trampoline's enter/exit function which tracks prog->active to avoid recursion. It is needed for tracing prog. However, it turns out the struct_ops bpf prog will hit this prog->active and unnecessarily skipped running the struct_ops prog. eg. The '.ssthresh' may run in_task() and then interrupted by softirq that runs the same '.ssthresh'. Skip running the '.ssthresh' will end up returning random value to the caller. The patch adds __bpf_prog_{enter,exit}_struct_ops for the struct_ops trampoline. They do not track the prog->active to detect recursion. One exception is when the tcp_congestion's '.init' ops is doing bpf_setsockopt(TCP_CONGESTION) and then recurs to the same '.init' ops. This will be addressed in the following patches. Fixes: ca06f55b9002 ("bpf: Add per-program recursion prevention mechanism") Signed-off-by: Martin KaFai Lau --- arch/x86/net/bpf_jit_comp.c | 3 +++ include/linux/bpf.h | 4 ++++ kernel/bpf/trampoline.c | 23 +++++++++++++++++++++++ 3 files changed, 30 insertions(+) diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index ae89f4143eb4..58a131dec954 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -1836,6 +1836,9 @@ static int invoke_bpf_prog(const struct btf_func_model *m, u8 **pprog, if (p->aux->sleepable) { enter = __bpf_prog_enter_sleepable; exit = __bpf_prog_exit_sleepable; + } else if (p->type == BPF_PROG_TYPE_STRUCT_OPS) { + enter = __bpf_prog_enter_struct_ops; + exit = __bpf_prog_exit_struct_ops; } else if (p->expected_attach_type == BPF_LSM_CGROUP) { enter = __bpf_prog_enter_lsm_cgroup; exit = __bpf_prog_exit_lsm_cgroup; diff --git a/include/linux/bpf.h b/include/linux/bpf.h index edd43edb27d6..6fdbc1398b8a 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -864,6 +864,10 @@ u64 notrace __bpf_prog_enter_lsm_cgroup(struct bpf_prog *prog, struct bpf_tramp_run_ctx *run_ctx); void notrace __bpf_prog_exit_lsm_cgroup(struct bpf_prog *prog, u64 start, struct bpf_tramp_run_ctx *run_ctx); +u64 notrace __bpf_prog_enter_struct_ops(struct bpf_prog *prog, + struct bpf_tramp_run_ctx *run_ctx); +void notrace __bpf_prog_exit_struct_ops(struct bpf_prog *prog, u64 start, + struct bpf_tramp_run_ctx *run_ctx); void notrace __bpf_tramp_enter(struct bpf_tramp_image *tr); void notrace __bpf_tramp_exit(struct bpf_tramp_image *tr); diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c index 41b67eb83ab3..e6551e4a6064 100644 --- a/kernel/bpf/trampoline.c +++ b/kernel/bpf/trampoline.c @@ -976,6 +976,29 @@ void notrace __bpf_prog_exit_sleepable(struct bpf_prog *prog, u64 start, rcu_read_unlock_trace(); } +u64 notrace __bpf_prog_enter_struct_ops(struct bpf_prog *prog, + struct bpf_tramp_run_ctx *run_ctx) + __acquires(RCU) +{ + rcu_read_lock(); + migrate_disable(); + + run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx); + + return bpf_prog_start_time(); +} + +void notrace __bpf_prog_exit_struct_ops(struct bpf_prog *prog, u64 start, + struct bpf_tramp_run_ctx *run_ctx) + __releases(RCU) +{ + bpf_reset_run_ctx(run_ctx->saved_run_ctx); + + update_prog_stats(prog, start); + migrate_enable(); + rcu_read_unlock(); +} + void notrace __bpf_tramp_enter(struct bpf_tramp_image *tr) { percpu_ref_get(&tr->pcref);