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=-4.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT 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 389E3C47404 for ; Sat, 5 Oct 2019 05:03:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0FD5520873 for ; Sat, 5 Oct 2019 05:03:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570251836; bh=/+g3BxhQpqNYKyuCms+42GKclcwMF/8/43rg7GPOfss=; h=From:To:CC:Subject:Date:List-ID:From; b=xstWxH+/4WkHsxvQuu4biAsMf5RdKhmuovRYWpDIHc5IQEiUFudRh+UKO4f1hHH35 5SMt5NEHpEhHHN0iKPfsM9j8TQhwJ/XT2t4PcqyxPby/Df+zLHCz7Gebh0ozCyeTHs yGN3MbHWBtrg6JyZMa2Ghlrv03+Ch0jyRJsKsLFE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727184AbfJEFDz convert rfc822-to-8bit (ORCPT ); Sat, 5 Oct 2019 01:03:55 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:32862 "EHLO mx0b-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727117AbfJEFDy (ORCPT ); Sat, 5 Oct 2019 01:03:54 -0400 Received: from pps.filterd (m0109332.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id x954xZID015206 for ; Fri, 4 Oct 2019 22:03:53 -0700 Received: from maileast.thefacebook.com ([163.114.130.16]) by mx0a-00082601.pphosted.com with ESMTP id 2ve548c1nf-17 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Fri, 04 Oct 2019 22:03:53 -0700 Received: from 2401:db00:2120:80e1:face:0:29:0 (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:83::4) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1713.5; Fri, 4 Oct 2019 22:03:20 -0700 Received: by devbig007.ftw2.facebook.com (Postfix, from userid 572438) id 65DC176091D; Fri, 4 Oct 2019 22:03:14 -0700 (PDT) Smtp-Origin-Hostprefix: devbig From: Alexei Starovoitov Smtp-Origin-Hostname: devbig007.ftw2.facebook.com To: CC: , , , , Smtp-Origin-Cluster: ftw2c04 Subject: [PATCH bpf-next 00/10] bpf: revolutionize bpf tracing Date: Fri, 4 Oct 2019 22:03:04 -0700 Message-ID: <20191005050314.1114330-1-ast@kernel.org> X-Mailer: git-send-email 2.20.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT X-FB-Internal: Safe Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.95,1.0.8 definitions=2019-10-05_02:2019-10-03,2019-10-05 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 priorityscore=1501 impostorscore=0 mlxscore=0 bulkscore=0 mlxlogscore=999 adultscore=0 lowpriorityscore=0 malwarescore=0 suspectscore=1 spamscore=0 clxscore=1015 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1908290000 definitions=main-1910050044 X-FB-Internal: deliver Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Revolutionize bpf tracing and bpf C programming. C language allows any pointer to be typecasted to any other pointer or convert integer to a pointer. Though bpf verifier is operating at assembly level it has strict type checking for fixed number of types. Known types are defined in 'enum bpf_reg_type'. For example: PTR_TO_FLOW_KEYS is a pointer to 'struct bpf_flow_keys' PTR_TO_SOCKET is a pointer to 'struct bpf_sock', and so on. When it comes to bpf tracing there are no types to track. bpf+kprobe receives 'struct pt_regs' as input. bpf+raw_tracepoint receives raw kernel arguments as an array of u64 values. It was up to bpf program to interpret these integers. Typical tracing program looks like: int bpf_prog(struct pt_regs *ctx) { struct net_device *dev; struct sk_buff *skb; int ifindex; skb = (struct sk_buff *) ctx->di; bpf_probe_read(&dev, sizeof(dev), &skb->dev); bpf_probe_read(&ifindex, sizeof(ifindex), &dev->ifindex); } Addressing mistakes will not be caught by C compiler or by the verifier. The program above could have typecasted ctx->si to skb and page faulted on every bpf_probe_read(). bpf_probe_read() allows reading any address and suppresses page faults. Typical program has hundreds of bpf_probe_read() calls to walk kernel data structures. Not only tracing program would be slow, but there was always a risk that bpf_probe_read() would read mmio region of memory and cause unpredictable hw behavior. With introduction of Compile Once Run Everywhere technology in libbpf and in LLVM and BPF Type Format (BTF) the verifier is finally ready for the next step in program verification. Now it can use in-kernel BTF to type check bpf assembly code. Equivalent program will look like: struct trace_kfree_skb { struct sk_buff *skb; void *location; }; SEC("raw_tracepoint/kfree_skb") int trace_kfree_skb(struct trace_kfree_skb* ctx) { struct sk_buff *skb = ctx->skb; struct net_device *dev; int ifindex; __builtin_preserve_access_index(({ dev = skb->dev; ifindex = dev->ifindex; })); } These patches teach bpf verifier to recognize kfree_skb's first argument as 'struct sk_buff *' because this is what kernel C code is doing. The bpf program cannot 'cheat' and say that the first argument to kfree_skb raw_tracepoint is some other type. The verifier will catch such type mismatch between bpf program assumption of kernel code and the actual type in the kernel. Furthermore skb->dev access is type tracked as well. The verifier can see which field of skb is being read in bpf assembly. It will match offset to type. If bpf program has code: struct net_device *dev = (void *)skb->len; C compiler will not complain and generate bpf assembly code, but the verifier will recognize that integer 'len' field is being accessed at offsetof(struct sk_buff, len) and will reject further dereference of 'dev' variable because it contains integer value instead of a pointer. Such sophisticated type tracking allows calling networking bpf helpers from tracing programs. This patchset allows calling bpf_skb_event_output() that dumps skb data into perf ring buffer. It greatly improves observability. Now users can not only see packet lenth of the skb about to be freed in kfree_skb() kernel function, but can dump it to user space via perf ring buffer using bpf helper that was previously available only to TC and socket filters. See patch 10 for full example. The end result is safer and faster bpf tracing. Safer - because direct calls to bpf_probe_read() are disallowed and arbitrary addresses cannot be read. Faster - because normal loads are used to walk kernel data structures instead of bpf_probe_read() calls. Note that such loads can page fault and are supported by hidden bpf_probe_read() in interpreter and via exception table if program is JITed. See patches for details. Alexei Starovoitov (10): bpf: add typecast to raw_tracepoints to help BTF generation bpf: add typecast to bpf helpers to help BTF generation bpf: process in-kernel BTF libbpf: auto-detect btf_id of raw_tracepoint bpf: implement accurate raw_tp context access via BTF bpf: add support for BTF pointers to interpreter bpf: add support for BTF pointers to x86 JIT bpf: check types of arguments passed into helpers bpf: disallow bpf_probe_read[_str] helpers selftests/bpf: add kfree_skb raw_tp test arch/x86/net/bpf_jit_comp.c | 96 +++++- include/linux/bpf.h | 21 +- include/linux/bpf_verifier.h | 6 +- include/linux/btf.h | 1 + include/linux/extable.h | 10 + include/linux/filter.h | 6 +- include/trace/bpf_probe.h | 3 +- include/uapi/linux/bpf.h | 3 +- kernel/bpf/btf.c | 318 ++++++++++++++++++ kernel/bpf/core.c | 39 ++- kernel/bpf/verifier.c | 125 ++++++- kernel/extable.c | 2 + kernel/trace/bpf_trace.c | 10 +- net/core/filter.c | 15 +- tools/include/uapi/linux/bpf.h | 3 +- tools/lib/bpf/libbpf.c | 16 + tools/testing/selftests/bpf/bpf_helpers.h | 4 + .../selftests/bpf/prog_tests/kfree_skb.c | 90 +++++ tools/testing/selftests/bpf/progs/kfree_skb.c | 76 +++++ 19 files changed, 828 insertions(+), 16 deletions(-) create mode 100644 tools/testing/selftests/bpf/prog_tests/kfree_skb.c create mode 100644 tools/testing/selftests/bpf/progs/kfree_skb.c -- 2.20.0