From patchwork Fri Aug 7 21:06:26 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrii Nakryiko X-Patchwork-Id: 262644 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=-13.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=unavailable 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 8EE90C433E3 for ; Fri, 7 Aug 2020 21:06:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5F5652177B for ; Fri, 7 Aug 2020 21:06:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=fb.com header.i=@fb.com header.b="Rdpl88pE" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726910AbgHGVGt (ORCPT ); Fri, 7 Aug 2020 17:06:49 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:30904 "EHLO mx0b-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726825AbgHGVGq (ORCPT ); Fri, 7 Aug 2020 17:06:46 -0400 Received: from pps.filterd (m0109331.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 077Ku8DN000508 for ; Fri, 7 Aug 2020 14:06:45 -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=n+JELzjK3JaJE2mrP8GcRwWHFGwRMDRrATAS1ZE54nk=; b=Rdpl88pEbjRCLthUWjcB5U+FfHNghPN8vwpY4uYdnrmcxaVpVSX9BYyGd1xna59pWUH9 F/dQRAKenKjXdKikJPAEdkxKM7WWyyiByyVfLQzS8dLeNWyZ4puRhVSRGB0h1toMJlyr +5ymxdzbAND2DOLq2I/WX4tuOo8z/r74RpQ= Received: from mail.thefacebook.com ([163.114.132.120]) by mx0a-00082601.pphosted.com with ESMTP id 32rvwf4g96-3 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Fri, 07 Aug 2020 14:06:45 -0700 Received: from intmgw005.03.ash8.facebook.com (2620:10d:c085:208::11) by mail.thefacebook.com (2620:10d:c085:21d::6) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1979.3; Fri, 7 Aug 2020 14:06:43 -0700 Received: by devbig012.ftw2.facebook.com (Postfix, from userid 137359) id 39B992EC5494; Fri, 7 Aug 2020 14:06:41 -0700 (PDT) Smtp-Origin-Hostprefix: devbig From: Andrii Nakryiko Smtp-Origin-Hostname: devbig012.ftw2.facebook.com To: , , , CC: , , Andrii Nakryiko Smtp-Origin-Cluster: ftw2c04 Subject: [RFC PATCH bpf-next 4/7] libbpf: sanitize BPF program code for bpf_probe_read_{kernel, user}[_str] Date: Fri, 7 Aug 2020 14:06:26 -0700 Message-ID: <20200807210629.394335-5-andriin@fb.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200807210629.394335-1-andriin@fb.com> References: <20200807210629.394335-1-andriin@fb.com> MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235, 18.0.687 definitions=2020-08-07_20:2020-08-06,2020-08-07 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 spamscore=0 impostorscore=0 mlxscore=0 lowpriorityscore=0 clxscore=1015 bulkscore=0 adultscore=0 malwarescore=0 phishscore=0 mlxlogscore=999 priorityscore=1501 suspectscore=8 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2008070147 X-FB-Internal: deliver Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Add BPF program code sanitization pass, replacing calls to BPF bpf_probe_read_{kernel,user}[_str]() helpers with bpf_probe_read[_str](), if libbpf detects that kernel doesn't support new variants. Signed-off-by: Andrii Nakryiko --- tools/lib/bpf/libbpf.c | 80 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 80 insertions(+) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 24c806559867..32c71a3b3aef 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -180,6 +180,8 @@ enum kern_feature_id { FEAT_ARRAY_MMAP, /* kernel support for expected_attach_type in BPF_PROG_LOAD */ FEAT_EXP_ATTACH_TYPE, + /* bpf_probe_read_{kernel,user}[_str] helpers */ + FEAT_PROBE_READ_KERN, __FEAT_CNT, }; @@ -3586,6 +3588,27 @@ static int probe_kern_exp_attach_type(void) return probe_fd(bpf_load_program_xattr(&attr, NULL, 0)); } +static int probe_kern_probe_read_kernel(void) +{ + struct bpf_load_program_attr attr; + struct bpf_insn insns[] = { + BPF_MOV64_REG(BPF_REG_1, BPF_REG_10), /* r1 = r10 (fp) */ + BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -8), /* r1 += -8 */ + BPF_MOV64_IMM(BPF_REG_2, 8), /* r2 = 8 */ + BPF_MOV64_IMM(BPF_REG_3, 0), /* r3 = 0 */ + BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_probe_read_kernel), + BPF_EXIT_INSN(), + }; + + memset(&attr, 0, sizeof(attr)); + attr.prog_type = BPF_PROG_TYPE_KPROBE; + attr.insns = insns; + attr.insns_cnt = ARRAY_SIZE(insns); + attr.license = "GPL"; + + return probe_fd(bpf_load_program_xattr(&attr, NULL, 0)); +} + enum kern_feature_result { FEAT_UNKNOWN = 0, FEAT_SUPPORTED = 1, @@ -3621,6 +3644,9 @@ static struct kern_feature_desc { "BPF_PROG_LOAD expected_attach_type attribute", probe_kern_exp_attach_type, }, + [FEAT_PROBE_READ_KERN] = { + "bpf_probe_read_kernel() helper", probe_kern_probe_read_kernel, + } }; static bool kernel_supports(enum kern_feature_id feat_id) @@ -5326,6 +5352,53 @@ static int bpf_object__collect_reloc(struct bpf_object *obj) return 0; } +static bool insn_is_helper_call(struct bpf_insn *insn, enum bpf_func_id *func_id) +{ + __u8 class = BPF_CLASS(insn->code); + + if ((class == BPF_JMP || class == BPF_JMP32) && + BPF_OP(insn->code) == BPF_CALL && + BPF_SRC(insn->code) == BPF_K && + insn->src_reg == 0 && insn->dst_reg == 0) { + if (func_id) + *func_id = insn->imm; + return true; + } + return false; +} + +static int bpf_object__sanitize_prog(struct bpf_object* obj, struct bpf_program *prog) +{ + struct bpf_insn *insn = prog->insns; + enum bpf_func_id func_id; + int i; + + for (i = 0; i < prog->insns_cnt; i++, insn++) { + if (!insn_is_helper_call(insn, &func_id)) + continue; + + /* on kernels that don't yet support + * bpf_probe_read_{kernel,user}[_str] helpers, fall back + * to bpf_probe_read() which works well for old kernels + */ + switch (func_id) { + case BPF_FUNC_probe_read_kernel: + case BPF_FUNC_probe_read_user: + if (!kernel_supports(FEAT_PROBE_READ_KERN)) + insn->imm = BPF_FUNC_probe_read; + break; + case BPF_FUNC_probe_read_kernel_str: + case BPF_FUNC_probe_read_user_str: + if (!kernel_supports(FEAT_PROBE_READ_KERN)) + insn->imm = BPF_FUNC_probe_read_str; + break; + default: + break; + } + } + return 0; +} + static int load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt, char *license, __u32 kern_version, int *pfd) @@ -5540,6 +5613,13 @@ bpf_object__load_progs(struct bpf_object *obj, int log_level) size_t i; int err; + for (i = 0; i < obj->nr_programs; i++) { + prog = &obj->programs[i]; + err = bpf_object__sanitize_prog(obj, prog); + if (err) + return err; + } + for (i = 0; i < obj->nr_programs; i++) { prog = &obj->programs[i]; if (bpf_program__is_function_storage(prog, obj))